Life Extension Magazine®

Issue: Nov 2014

Endothelial Defense Skin Ceramides Longevity And Nicotinamide Riboside

Endothelial Defense Skin Ceramides Longevity And Nicotinamide Riboside

By Life Extension.

Endothelial defense

Recognizing global burden of cardiovascular disease and related chronic diseases.

Cardiovascular disease is the leading cause of death worldwide, affecting not only high-income but also low- and middle-income countries. Nearly 80 percent of all estimated cardiovascular disease-related deaths worldwide now occur in low- and middle-income countries, where nearly 30 percent of all deaths are attributable to cardiovascular disease. The health burden of cardiovascular disease and other chronic diseases is also accompanied by a significant deleterious economic impact at the level of both national economies and households. The global trends in the health and economic burden of cardiovascular disease provide a compelling argument in support of prioritizing urgent yet carefully planned efforts to prevent and control cardiovascular disease worldwide-and especially in low- and middle-income countries. After decades of escalating efforts to draw attention to the high burden of cardiovascular disease and other chronic diseases, this critically important issue is now emerging as a more central part of the global health and development agenda. The breadth of behavioral, biological, social, environmental, and systems-level factors that contribute to cardiovascular disease necessitates multisectoral approaches across the lifecourse that promote healthful lifestyles, reduce risk, and reduce cardiovascular-disease morbidity and mortality through the delivery of quality health care services. Given that the complex interactions among the determinants of cardiovascular disease vary in different contexts, real progress in control efforts will come through approaches that are driven by a country’s disease burden and risk profile, capacities, resources, and priorities-approaches that are led by a country’s key decision-makers and stakeholders, including governments, civil society, the private sector, and communities. Many countries are already establishing efforts to address chronic diseases. In addition to these locally driven efforts, success will require active engagement and sustained action from a wide array of stakeholders operating at global and regional levels.

Mt Sinai J Med. 2012 Nov-Dec;79(6):632-40

The role of nutrition and nutraceutical supplements in the treatment of hypertension.

Vascular biology, endothelial and vascular smooth muscle and cardiac dysfunction play a primary role in the initiation and perpetuation of hypertension, cardiovascular disease and target organ damage. Nutrient-gene interactions and epigenetics are predominant factors in promoting beneficial or detrimental effects in cardiovascular health and hypertension. Macronutrients and micronutrients can prevent, control and treat hypertension through numerous mechanisms related to vascular biology. Oxidative stress, inflammation and autoimmune dysfunction initiate and propagate hypertension and cardiovascular disease. There is a role for the selected use of single and component nutraceutical supplements, vitamins, antioxidants and minerals in the treatment of hypertension based on scientifically controlled studies which complement optimal nutrition, coupled with other lifestyle modifications.

World J Cardiol. 2014 Feb 26;6(2):38-66

Introduction to endothelial cell biology.

Vascular endothelial cells form a monocellular layer on blood vessel walls with an estimated mass of 1.5 kg. One of the roles of endothelial cells is to control the hemodynamics through various metabolic activities affecting homeostasis, vascular tonus, blood fluidity, coagulating properties and blood cell adhesion. In other respects thousands of studies have underlined the crucial role of local blood flow conditions on their properties. However, the hemodynamic forces are different according to the anatomical site and to the type of blood vessels (arteries, veins, venules, ...). In microcirculation, the endothelial cells in the venules are particularly active and constitute the physiological site of liquid exchange (permeability) and above all cellular transit. During critical ischemia, the post-capillary venules are deeply involved. In other respects the properties of endothelial cells may be impaired in many diseases as atherosclerosis, hypertension, inflammation and metabolic diseases.

Clin Hemorheol Microcirc. 2007;37(1-2):5-8

Pomegranate juice supplementation to atherosclerotic mice reduces macrophage lipid peroxidation, cellular cholesterol accumulation and development of atherosclerosis.

Inhibition of lipid peroxidation contributes to the attenuation of macrophage cholesterol accumulation, foam-cell formation and atherosclerosis. Evidence suggests that nutritional antioxidants such as pomegranate juice (PJ) can contribute to the reduction of oxidative stress and atherogenesis. The goals of the present study were to determine whether such beneficial effects of PJ exist when supplemented to apolipoprotein E-deficient (E(0)) mice with advanced atherosclerosis and to analyze the antiatherosclerotic activity of a tannin-fraction isolated from PJ. Mice (4-mo-old) were supplemented with PJ in their drinking water for 2 mo and compared with age-matched placebo-treated mice, as well as to young (4-mo-old) control mice, for their mouse peritoneal macrophage (MPM) oxidative state, cholesterol flux and mice atherosclerotic lesion size. PJ supplementation reduced each of the proatherogenic variables determined in the present study compared with age-matched placebo-treated mice. It significantly induced serum paraoxonase activity and reduced MPM lipid peroxide content compared with placebo-treated mice and control mice. PJ administration to E(0) mice significantly reduced the oxidized (Ox)-LDL MPM uptake by 31% and MPM cholesterol esterification and increased macrophage cholesterol efflux by 39% compared with age-matched, placebo-treated mice. PJ consumption reduced macrophage Ox-LDL uptake and cholesterol esterification to levels lower than those in 4-mo-old, unsupplemented controls. PJ supplementation to E(0) mice with advanced atherosclerosis reduced the lesion size by 17% compared with placebo-treated mice. In a separate study, supplementation of young (2-mo-old) E(0) mice for 2 mo with a tannin fraction isolated from PJ reduced their atherosclerotic lesion size, paralleled by reduced plasma lipid peroxidation and decreased Ox-LDL MPM uptake. PJ supplementation to mice with advanced atherosclerosis reduced their macrophage oxidative stress, their macrophage cholesterol flux and even attenuated the development of atherosclerosis. Moreover, a tannin-fraction isolated from PJ had a significant antiatherosclerotic activity.

J Nutr. 2001 Aug;131(8):2082-9

Pomegranate juice (PJ) consumption antioxidative properties on mouse macrophages, but not PJ beneficial effects on macrophage cholesterol and triglyceride metabolism, are mediated via PJ-induced stimulation of macrophage PON2.

OBJECTIVE: To examine whether the beneficial effects of PJ consumption by mice on their macrophages are mediated via PJ-induced increment in serum paraoxonase 1 (PON1) activity and/or in macrophage PON2 expression. METHODS AND RESULTS: We performed studies in peritoneal macrophages (MPM) from C57BL/6 control mice, or from PON1KO mice, or from PON2KO mice that consumed PJ (200 microg of gallic acid equivalents/mouse/day, for 1 month period). PJ consumption by C57BL/6 mice resulted in a significant increment, by 36% in serum PON1 catalytic activities, and upregulated MPM PON2 expression. In MPM from C57BL/6 or from PON1KO mice that consumed PJ, the extent of cell-mediated LDL oxidation was decreased by 22%, and that of cellular superoxide release by 20-26%. In contrast, PJ consumption by PON2KO mice resulted in a minimal inhibitory effect on macrophage oxidative stress by only 4-9%. Unlike PJ antioxidative effects in MPM, PJ anti-atherogenic effects on MPM cholesterol and triglyceride metabolism were similar in all mice groups that consumed PJ. After PJ consumption, cellular cholesterol content was decreased by 14-19%, and this could be attributed to a significant inhibition in MPM cholesterol biosynthesis rate by 20-32%, and/or to stimulation of HDL-mediated cholesterol efflux from the cells by 22-37%. Similarly, MPM triglyceride content and triglyceride biosynthesis rate were both significantly decreased after PJ consumption, by 16-27% and by 22-28%, respectively. CONCLUSION: PJ consumption antioxidative properties on mouse macrophages, but not PJ beneficial effects on macrophage cholesterol and triglyceride metabolism, are mediated via PJ-induced stimulation of macrophage PON2 expression. Serum PON1 stimulation by PJ consumption, however, was not involved in PJ-induced effects on macrophages.

Atherosclerosis. 2010 Sep;212(1):86-92

Pomegranate for your cardiovascular health.

Pomegranate is a source of some very potent antioxidants (tannins, anthocyanins) which are considered to be also potent anti-atherogenic agents. The combination of the above unique various types of pomegranate polyphenols provides a much wider spectrum of action against several types of free radicals. Indeed, pomegranate is superior in comparison to other antioxidants in protecting low-density lipoprotein (LDL, “the bad cholesterol”) and high-density lipoprotein (HDL, “the good cholesterol”) from oxidation, and as a result it attenuates atherosclerosis development and its consequent cardiovascular events. Pomegranate antioxidants are not free, but are attached to the pomegranate sugars, and hence were shown to be beneficial even in diabetic patients. Furthermore, pomegranate antioxidants are unique in their ability to increase the activity of the HDL-associated paraoxonase 1 (PON1), which breaks down harmful oxidized lipids in lipoproteins, in macrophages, and in atherosclerotic plaques. Finally, unique pomegranate antioxidants beneficially decrease blood pressure. All the above beneficial characteristics make the pomegranate a uniquely healthy fruit.

Rambam Maimonides Med J. 2013 Apr 30;4(2):e0013

Pomegranate juice consumption for 3 years by patients with carotid artery stenosis reduces common carotid intima-media thickness, blood pressure and LDL oxidation.

Dietary supplementation with polyphenolic antioxidants to animals was shown to be associated with inhibition of LDL oxidation and macrophage foam cell formation, and attenuation of atherosclerosis development. We investigated the effects of pomegranate juice (PJ, which contains potent tannins and anthocyanins) consumption by atherosclerotic patients with carotid artery stenosis (CAS) on the progression of carotid lesions and changes in oxidative stress and blood pressure. Ten patients were supplemented with PJ for 1 year and five of them continued for up to 3 years. Blood samples were collected before treatment and during PJ consumption. In the control group that did not consume PJ, common carotid intima-media thickness (IMT) increased by 9% during 1 year, whereas, PJ consumption resulted in a significant IMT reduction, by up to 30%, after 1 year. The patients’ serum paraoxonase 1 (PON 1) activity was increased by 83%, whereas serum LDL basal oxidative state and LDL susceptibility to copper ion-induced oxidation were both significantly reduced, by 90% and 59%, respectively, after 12 months of PJ consumption, compared to values obtained before PJ consumption. Furthermore, serum levels of antibodies against oxidized LDL were decreased by 19%, and in parallel serum total antioxidant status (TAS) was increased by 130% after 1 year of PJ consumption. Systolic blood pressure was reduced after 1 year of PJ consumption by 12% [corrected] and was not further reduced along 3 years of PJ consumption. For all studied parameters, the maximal effects were observed after 1 year of PJ consumption. Further consumption of PJ, for up to 3 years, had no additional beneficial effects on IMT and serum PON1 activity, whereas serum lipid peroxidation was further reduced by up to 16% after 3 years of PJ consumption. The results of the present study thus suggest that PJ consumption by patients with CAS decreases carotid IMT and systolic blood pressure and these effects could be related to the potent antioxidant characteristics of PJ polyphenols.

Clin Nutr. 2004 Jun;23(3):423-33

Clinical evaluation of blood pressure lowering, endothelial function improving, hypolipidemic and anti-inflammatory effects of pomegranate juice in hypertensive subjects.

Pomegranate (Punica granatum L.) juice (PJ) contains different types of antioxidants and bioactive polyphenols and has been reported to promote cardiovascular health through several mechanisms. The present study aimed to examine the effects of 2-week intake of fresh PJ on blood pressure, flow-mediated dilatation (FMD), serum lipid profile and concentrations of inflammatory and endothelial function biomarkers. Twenty-one hypertensive patients (aged 30-67 years) were recruited into the trial and assigned to receive either PJ (150 ml/day in a single occasion between lunch and dinner; n = 11) or the same amount of water (n = 10) for a period of 2 weeks. Systolic (SBP) and diastolic (DBP) pressures together with FMD and serum concentrations of lipid profile parameters, apolipoproteins A and B, intracellular adhesion molecule-1 (ICAM-1), vascular endothelial adhesion molecule 1 (VCAM-1), E-selectin, high-sensitivity C-reactive protein (hs-CRP) and interleukin-6 (IL-6) were measured at baseline and at the end of trial. PJ consumption was associated with significant reductions in SBP (p = 0.002) and DBP (p = 0.038) but not FMD (p > 0.05). Serum levels of VCAM-1 (p = 0.008) were significantly reduced by PJ while those of E-selectin were elevated (p = 0.039). However, no significant effect was observed from PJ on serum levels of ICAM-1, hs-CRP, lipid profile parameters, apolipoproteins and IL-6 in any of the study groups (p > 0.05). Consumption of PJ for 2 weeks has effective hypotensive effects, and may improve endothelial function by decreasing serum concentrations of VCAM-1. These findings suggest PJ as a beneficial cardioprotective supplement for hypertensive subjects.

Phytother Res. 2014 Feb;28(2):193-9

Effects of consumption of pomegranate juice on carotid intima-media thickness in men and women at moderate risk for coronary heart disease.

This randomized, double-blind, parallel trial assessed the influence of pomegranate juice consumption on anterior and posterior carotid intima-media thickness (CIMT) progression rates in subjects at moderate risk for coronary heart disease. Subjects were men (45 to 74 years old) and women (55 to 74 years old) with > or =1 major coronary heart disease risk factor and baseline posterior wall CIMT 0.7 to 2.0 mm, without significant stenosis. Participants consumed 240 ml/day of pomegranate juice (n = 146) or a control beverage (n = 143) for up to 18 months. No significant difference in overall CIMT progression rate was observed between pomegranate juice and control treatments. In exploratory analyses, in subjects in the most adverse tertiles for baseline serum lipid peroxides, triglycerides (TGs), high-density lipoprotein (HDL) cholesterol, TGs/HDL cholesterol, total cholesterol/HDL cholesterol, and apolipoprotein-B100, those in the pomegranate juice group had significantly less anterior wall and/or composite CIMT progression versus control subjects. In conclusion, these results suggest that in subjects at moderate coronary heart disease risk, pomegranate juice consumption had no significant effect on overall CIMT progression rate but may have slowed CIMT progression in subjects with increased oxidative stress and disturbances in the TG-rich lipoprotein/HDL axis.

Am J Cardiol. 2009 Oct 1;104(7):936-42

Molecular aspects of atherogenesis: new insights and unsolved questions.

The development of atherosclerotic disease results from the interaction between environment and genetic make up. A key factor in atherogenesis is the oxidative modification of lipids, which is involved in the recruitment of mononuclear leukocytes to the arterial intima--a process regulated by several groups of adhesion molecules and cytokines. Activated leukocytes, as well as endothelial mitochondria, can produce reactive oxygen species (ROS) that are associated with endothelial dysfunction, a cause of reduced nitric oxide (NO) bioactivity and further ROS production. Peroxisome proliferator-activated receptors (PPAR) and liver X receptors (LXR) are nuclear receptors significantly involved in the control of lipid metabolism, inflammation and insulin sensitivity. Also, an emerging role has been suggested for G protein coupled receptors and for the small Ras and Rho GTPases in the regulation of the expression of endothelial NO synthase (eNOS) and of tissue factor, which are involved in thrombus formation and modulation of vascular tone. Further, the interactions among eNOS, cholesterol, oxidated LDL and caveola membranes are probably involved in some molecular changes observed in vascular diseases. Despite the relevance of oxidative processes in atherogenesis, anti-oxidants have failed to significantly improve atherosclerosis (ATS) prevention, while statins have proved to be the most successful drugs.

J Biomed Sci. 2005 Dec;12(6):839-53

Skin ceramides

Stratum corneum lipids: the effect of ageing and the seasons.

Stratum corneum lipids play a predominant role in maintaining the water barrier of the skin. In order to understand the biological variation in the levels and composition of ceramides, ceramide 1 subtypes, cholesterol and fatty acids, stratum corneum lipids collected from tape strippings from three body sites (face, hand, leg) of female Caucasians of different age groups were analysed. In addition, we studied the influence of seasonal variation on the lipid composition of stratum corneum from the same body sites. The main lipid species were quantified using high-performance thin-layer chromatography and individual fatty acids using gas chromatography. Our findings demonstrated significantly decreased levels of all major lipid species, in particular ceramides, with increasing age. Similarly, the stratum corneum lipid levels of all the body sites examined were dramatically depleted in winter compared with spring and summer. The relative levels of ceramide 1 linoleate were also depleted in winter and in aged skin whereas ceramide 1 oleate levels increased. The other fatty acid levels remained fairly constant with both season and age, apart from lignoceric and heptadecanoic acid which showed a decrease in winter compared with summer. The decrease in the mass levels of intercellular lipids and the altered ratios of fatty acids esterified to ceramide 1, are likely to contribute to the increased susceptibility of aged skin to perturbation of barrier function and xerosis, particularly during the winter months.

Arch Dermatol Res. 1996 Nov;288(12):765-70

Age- and sex-dependent change in stratum corneum sphingolipids.

We measured six stratum corneum sphingolipid species (ceramides 1-6) in 26 males and 27 females, and found a significant change in their percentage composition only among female subjects of different age groups. There was a significant increase in ceramide 1 and 2 with a corresponding decrease in ceramide 3 and 6 from prepubertal age to adulthood. Thereafter the ratio of ceramide 2 to total sphingolipids decreased with age in contrast to ceramide 3 which showed an increase. Such a pattern of change in the aging population is different from that observed in scaly skin experimentally induced by tape stripping. The present results suggest a significant influence of female hormones on the composition of stratum corneum sphingolipids. Moreover, the different patterns of change in sphingolipid composition of stratum corneum lipids between scales from inflammatory skin and those from aged skin also suggest that epidermal biosynthesis of sphingolipids is influenced by epidermal proliferative activity.

Arch Dermatol Res. 1993;285(7):415-7

Age-dependent changes in stratum corneum barrier function.

BACKGROUND/PURPOSE: The Stratum Corneum (SC) barrier function mainly depends on the SC structure at the tissue level, its composition, and the organization of intercellular lipidic cement at the molecular level. The goal of this study was to assess the age-dependent changes of the SC barrier function and the associated physiological parameters. METHODS: This study was conducted on 40 French women divided into four groups of age. Measurements were done on three sites: cheek, protected, and exposed arm sites. SC composition (water, lipid/protein ratio, cholesterol, and ceramides) was measured using Raman confocal microspectroscopy, skin surface hydration using skin conductance, and barrier function through transepidermal water loss (TEWL) measurements. RESULTS: Transepidermal water loss decreases slightly with age, which is partially explained by the age-dependent increase in SC thickness. This decrease is faster for the face compared to both arm sites. The lipid to protein ratio and lipid compactness decrease significantly with age only for the arm sites. Water concentration profiles only decrease very close to the skin surface. At all ages tested, the SC on the cheek showed significantly higher TEWL, water and lipid content and less thickness compared to the arm sites. Comparison of the exposed to unexposed arm site showed difference only for the lipid compactness at the older group studied. CONCLUSION: Skin aging, body site and environmental exposure can affect the SC barrier function, its structure, and its lipid content. The thickening of the SC with age compensates for the decrease of the quantity and ordering of the lipidic cement.

Skin Res Technol. 2014 Feb 12

Decreased level of ceramides in stratum corneum of atopic dermatitis: an etiologic factor in atopic dry skin?

Stratum corneum lipids are an important determinant for both water-retention function and permeability-barrier function in the stratum corneum. However, their major constituent, ceramides, have not been analyzed in detail in skin diseases such as atopic dermatitis that show defective water-retention and permeability-barrier function. In an attempt to assess the quantity of ceramides per unit mass of the stratum corneum in atopic dermatitis, stratum corneum sheet was removed from the forearm skin by stripping with cyanoacrylate resin and placed in hexane/ethanol extraction to yield stratum corneum lipids. The stratum corneum was dispersed by solubilization of cyanoacrylate resin with dimethylformamide, and after membrane filtration, the weight of the stratum corneum mass was measured. The ceramides were quantified by thin-layer chromatography and evaluated as microgram/mg stratum corneum. In the forearm skin of healthy individuals (n = 65), the total ceramide content significantly declined with increasing age. In atopic dermatitis (n = 32-35), there was a marked reduction in the amount of ceramides in the lesional forearm skin compared with those of healthy individuals of the same age. Interestingly, the non-lesional skin also exhibited a similar and significant decrease of ceramides. Among six ceramide fractions, ceramide 1 was most significantly reduced in both lesional and non-lesional skin. These findings suggest that an insufficiency of ceramides in the stratum corneum is an etiologic factor in atopic dry skin.

J Invest Dermatol. 1991 Apr;96(4):523-6

Liposomal ursolic acid (merotaine) increases ceramides and collagen in human skin.

Skin wrinkling and xerosis associated with aging result from decreases of dermal collagen and stratum corneum ceramide content. This study demonstrates that ursolic acid incorporated into liposomes (Merotaine) increases both the ceramide content of cultured normal human epidermal keratinocytes and the collagen content of cultured normal human dermal fibroblasts. In clinical tests, Merotaine increased the ceramide content in human skin over an 11-day period. Merotaine has effects on keratinocyte differentiation and dermal fibroblast collagen synthesis similar to retinoids. However, unlike retinoids, Merotaine increases ceramide content of human keratinocytes. Ursolic acid may bind to members of the glucocorticoid receptor family to initiate changes in keratinocyte gene transcription.

Horm Res. 2000;54(5-6):318-21

Ceramide composition of the psoriatic scale.

This paper investigates the ceramide composition of the psoriatic scale compared with that of normal human SC. A method was optimalized, based on TLC separation followed by densitometry, allowing the provision of good resolution and quantification of ceramide fractions from both normal and pathological specimens. Seven ceramide fractions were isolated and submitted to compositional analysis. The obtained results suggested a revisitation of previous ceramide designation. Therefore a simple classification is suggested, based on grouping ceramides carrying structural similarities under common codes. According to these rules, ceramides were grouped into five classes designated as: (1) Cer[EOS], which contains ester-linked fatty acids, omega-OH fatty acids and sphingosines; (2) Cer[NS], which contains non-OH fatty acids and sphingosines; (3) Cer[NP], which contains non-OH fatty acids and phytosphingosines; (4) Cer[AS], which contains alpha-OH fatty acids and sphingosines; (5) Cer[AP], which contains alpha-OH fatty acids and phytosphingosines. Analysis of ceramides from the psoriatic scale, compared to those from normal human SC, resulted in an impairment of the Cer[EOS] content as well as of the ceramides containing phytosphingosine, with concurrent increase in ceramides containing sphingosine, being the total amount maintained identical. Since one of the suggested pathways for phytosphingosine biosynthesis involves the water addition to the corresponding sphingosine double bond, we can speculate that the observed alteration is due to a deranged water bioavailability, associated with psoriasis.

Biochim Biophys Acta. 1993 Sep 8;1182(2):147-51

Delayed ERK activation by ceramide reduces melanin synthesis in human melanocytes.

Sphingolipid metabolites regulate many aspects of cell growth and differentiation. However, the effects of sphingolipids on the growth and melanogenesis of human melanocytes are not known. In the present study, we investigated the effects of sphingolipid metabolites and the possible signalling pathways involved in human melanocytes. Our data show that C(2)-ceramide inhibits cell growth in a dose-dependent manner, whereas sphingosine-1-phosphate (SPP) has no effect. Moreover, we observed that the melanin content of the cells was significantly decreased by C(2)-ceramide. The pigmentation-inhibiting effect of C(2)-ceramide at 1-10 microM was stronger than that of kojic acid, tested at 1-100 microM. The tyrosinase activity of cell extracts was reduced by C(2)-ceramide treatment. However, in the cell-free system, C(2)-ceramide could not suppress tyrosinase, whereas kojic acid directly inhibited tyrosinase. These results suggest that C(2)-ceramide decreases the pigmentation of melanocytes indirectly regulating tyrosinase. Furthermore, we found that C(2)-ceramide decreased the protein expression of microphthalmia-associated transcription factor (MITF), which is required for tyrosinase expression. To identify the signalling pathway of ceramide, we studied the ability of C(2)-ceramide to influence extracellular signal-regulated protein kinase (ERK) and Akt/protein kinase B (PKB) activation. C(2)-ceramide induced a delayed activation of ERK ( > 1 h) and a much later activation of Akt/PKB ( > 3 h) in human melanocytes. In addition, the specific inhibition of the ERK and the Akt signalling pathways by PD98059 and LY294002, respectively, increased melanin synthesis. Thus, it seems that sustained ERK and Akt activation may lead to the suppression of cell growth and melanogenesis.

Cell Signal. 2002 Sep;14(9):779-85

Ceramide PC102 inhibits melanin synthesis via proteasomal degradation of microphthalmia-associated transcription factor and tyrosinase.

A few types of ceramide are reported to decrease melanin synthesis. In the present study, we examined the effects of an artificial ceramide analog, PC102, on melanogenesis using a spontaneously immortalized melanocyte cell line (Mel-Ab). PC102 is currently used as a moisturizing additive in a variety of cosmetics. Our data showed that PC102 inhibited melanin production and tyrosinase activity in a dose-dependent manner, but did not directly affect tyrosinase activity. Microphthalmia-associated transcription factor (MITF), tyrosinase, and b-catenin protein levels decreased after 48 h of PC102 treatment. In contrast, PC102 did not decrease MITF, tyrosinase, and b-catenin mRNA levels. Therefore, we investigated whether the decrease in MITF and tyrosinase by PC102 is due to proteasomal degradation. MG132, a proteasomal inhibitor, completely abolished tyrosinase downregulation due to PC102 and partially reduced the downregulation of MITF and b-catenin due to PC102. Moreover, MG132 abrogated the inhibition of melanin synthesis by PC102. Taken together, our data suggest that PC102 may inhibit melanin synthesis through MITF and tyrosinase degradation.

Mol Cell Biochem. 2013 Mar;375(1-2):81-7

Ceramides and skin function.

Ceramides are the major lipid constituent of lamellar sheets present in the intercellular spaces of the stratum corneum. These lamellar sheets are thought to provide the barrier property of the epidermis. It is generally accepted that the intercellular lipid domain is composed of approximately equimolar concentrations of free fatty acids, cholesterol, and ceramides. Ceramides are a structurally heterogeneous and complex group of sphingolipids containing derivatives of sphingosine bases in amide linkage with a variety of fatty acids. Differences in chain length, type and extent of hydroxylation, saturation etc. are responsible for the heterogeneity of the epidermal sphingolipids. It is well known that ceramides play an essential role in structuring and maintaining the water permeability barrier function of the skin. In conjunction with the other stratum corneum lipids, they form ordered structures. An essential factor is the physical state of the lipid chains in the nonpolar regions of the bilayers. The stratum corneum intercellular lipid lamellae, the aliphatic chains in the ceramides and the fatty acids are mostly straight long-chain saturated compounds with a high melting point and a small polar head group. This means that at physiological temperatures, the lipid chains are mostly in a solid crystalline or gel state, which exhibits low lateral diffusional properties and is less permeable than the state of liquid crystalline membranes, which are present at higher temperatures. The link between skin disorders and changes in barrier lipid composition, especially in ceramides, is difficult to prove because of the many variables involved. However, most skin disorders that have a diminished barrier function present a decrease in total ceramide content with some differences in the ceramide pattern. Formulations containing lipids identical to those in skin and, in particular, some ceramide supplementation could improve disturbed skin conditions. Incomplete lipid mixtures yield abnormal lamellar body contents, and disorder intercellular lamellae, whereas complete lipid mixtures result in normal lamellar bodies and intercellular bilayers. The utilization of physiological lipids according to these parameters have potential as new forms of topical therapy for dermatoses. An alternative strategy to improving barrier function by topical application of the various mature lipid species is to enhance the natural lipid-synthetic capability of the epidermis through the topical delivery of lipid precursors.

Am J Clin Dermatol. 2003;4(2):107-29

Ceramide synthesis in the epidermis.

The epidermis and in particular its outermost layer the stratum corneum provides terrestrial vertebrates with a pivotal defensive barrier against water loss, xenobiotics and harmful pathogens. A vital demand for this epidermal permeability barrier is the lipid-enriched lamellar matrix that embeds the enucleated corneocytes. Ceramides are the major components of these highly ordered intercellular lamellar structures, in which linoleic acid- and protein-esterified ceramides are crucial for structuring and maintaining skin barrier integrity. In this review, we describe the fascinating diversity of epidermal ceramides including 1-O-acylceramides. We focus on epidermal ceramide biosynthesis emphasizing its metabolic and topological requirements and discuss enzymes that may be involved in a- and w-hydroxylation. Finally, we turn to epidermal ceramide regulation, highlighting transcription factors and liposensors recently described to play crucial roles in modulating skin lipid metabolism and epidermal barrier homeostasis. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier.

Biochim Biophys Acta. 2014 Mar;1841(3):422-34

Longevity

Serum N-glycan profile shift during human ageing.

Biomarkers indicating biological age are of significant interest for prevention, diagnosis and monitoring (and the treatment) of age-related diseases. We previously reported an alteration of serum N-glycan profile in old humans using “DNA Sequencer Adapted-Fluorophore Assisted Carbohydrate Electrophoresis” (DSA-FACE). To validate the shift in serum N-glycan profile during ageing, we studied serum N-glycan profiles in different age groups of healthy volunteers, patients with dementia, and patients with Cockayne syndrome, a genetic DNA repair disorder involving neurodegeneration and premature ageing. We found that the log of the ratio of two glycans (NGA2F and NA2F), named GlycoAgeTest, remained steady up to the age of 40years and thereafter gradually increased to reach its highest level in nonagenarians. Patients with dementia or Cockayne syndrome had a higher GlycoAgeTest level than age-matched healthy individuals. We thus demonstrate that the value of GlycoAgeTest is better than chronological age for estimating the physiological age of a human individual, and that it could be used as an ageing biomarker for healthy humans. Our data indicate that the GlycoAgeTest could be used as a non-invasive surrogate marker for general health, for forecasting disease progression during ageing, and for monitoring the efficacy of anti-ageing food compounds.

Exp Gerontol. 2010 Oct;45(10):738-43

Effects of aging, body mass index, plasma lipid profiles, and smoking on human plasma N-glycans.

Protein glycosylation affects nearly all molecular interactions at the cell surface and in the intercellular space. Many of the physiological variations which are part of homeostatic mechanisms influence glycosylation. However, a comprehensive overview of changes in glycosylation caused by aging and common lifestyle parameters is still lacking. After analyzing N-glycans in the plasma of 1914 individuals from the Croatian islands of Vis and Korcula, we performed a comprehensive analysis of the dependence of different glycosylation features (position of fucose, level of galactosylation, sialylation and branching) on aging, smoking, body fat and plasma lipid status. A number of statistically significant associations were observed. Glycosylation changes with aging were especially evident in females, mostly in association with the transition from pre-menopausal to post-menopausal age. Levels of core-fucosylated, non-galactosylated, digalactosylated and disialylated biantennary glycans were shown to be mainly age dependent, but the level of branching and higher levels of galactosylation were found to correlate with lipid status. For the majority of glycans which we analyzed, all examined parameters explained up to 5% of the variance. The only notable exception were non-galactosylated glycans where 20% of the variance was explained mostly by age and blood pressure. In general, only a small fraction of the variability in glycan levels observed in a population was explained by age and other measured parameters, indicating that even in the absence of a genetic template, glycan levels are mostly determined by genetic background and/or specific pathophysiological processes.

Glycobiology. 2010 Aug;20(8):959-69

N-glycomic biomarkers of biological aging and longevity: a link with inflammaging.

Glycosylation is a frequent co/post-translational modification of proteins which modulates a variety of biological functions. The analysis of N-glycome, i.e. the sugar chains N-linked to asparagine, identified new candidate biomarkers of aging such as N-glycans devoid of galactose residues on their branches, in a variety of human and experimental model systems, such as healthy old people, centenarians and their offspring and caloric restricted mice. These agalactosylated biantennary structures mainly decorate Asn297 of Fc portion of IgG (IgG-G0), and are present also in patients affected by progeroid syndromes and a variety of autoimmune/inflammatory diseases. IgG-G0 exert a pro-inflammatory effect through different mechanisms, including the lectin pathway of complement, binding to Fcg receptors and formation of autoantibody aggregates. The age-related accumulation of IgG-G0 can contribute to inflammaging, the low-grade pro-inflammatory status that characterizes elderly, by creating a vicious loop in which inflammation is responsible for the production of aberrantly glycosylated IgG which, in turn, would activate the immune system, exacerbating inflammation. Moreover, recent data suggest that the N-glycomic shift observed in aging could be related not only to inflammation but also to alteration of important metabolic pathways. Thus, altered N-glycans are both powerful markers of aging and possible contributors to its pathogenesis.

Ageing Res Rev. 2013 Mar;12(2):685-98

Methylation of ELOVL2 gene as a new epigenetic marker of age.

The discovery of biomarkers able to predict biological age of individuals is a crucial goal in aging research. Recently, researchers’ attention has turn toward epigenetic markers of aging. Using the Illumina Infinium HumanMethylation450 BeadChip on whole blood DNA from a small cohort of 64 subjects of different ages, we identified 3 regions, the CpG islands of ELOVL2, FHL2, and PENK genes, whose methylation level strongly correlates with age. These results were confirmed by the Sequenom’s EpiTYPER assay on a larger cohort of 501 subjects from 9 to 99 years, including 7 cord blood samples. Among the 3 genes, ELOVL2 shows a progressive increase in methylation that begins since the very first stage of life (Spearman’s correlation coefficient = 0.92) and appears to be a very promising biomarker of aging.

Aging Cell. 2012 Dec;11(6):1132-4

Metabolic signatures of extreme longevity in northern Italian centenarians reveal a complex remodeling of lipids, amino acids, and gut microbiota metabolism.

The aging phenotype in humans has been thoroughly studied but a detailed metabolic profiling capable of shading light on the underpinning biological processes of longevity is still missing. Here using a combined metabonomics approach compromising holistic (1)H-NMR profiling and targeted MS approaches, we report for the first time the metabolic phenotype of longevity in a well characterized human aging cohort compromising mostly female centenarians, elderly, and young individuals. With increasing age, targeted MS profiling of blood serum displayed a marked decrease in tryptophan concentration, while an unique alteration of specific glycerophospholipids and sphingolipids are seen in the longevity phenotype. We hypothesized that the overall lipidome changes specific to longevity putatively reflect centenarians’ unique capacity to adapt/respond to the accumulating oxidative and chronic inflammatory conditions characteristic of their extreme aging phenotype. Our data in centenarians support promotion of cellular detoxification mechanisms through specific modulation of the arachidonic acid metabolic cascade as we underpinned increased concentration of 8,9-EpETrE, suggesting enhanced cytochrome P450 (CYP) enzyme activity. Such effective mechanism might result in the activation of an anti-oxidative response, as displayed by decreased circulating levels of 9-HODE and 9-oxoODE, markers of lipid peroxidation and oxidative products of linoleic acid. Lastly, we also revealed that the longevity process deeply affects the structure and composition of the human gut microbiota as shown by the increased extrection of phenylacetylglutamine (PAG) and p-cresol sulfate (PCS) in urine of centenarians. Together, our novel approach in this representative Italian longevity cohort support the hypothesis that a complex remodeling of lipid, amino acid metabolism, and of gut microbiota functionality are key regulatory processes marking exceptional longevity in humans.

PLoS One. 2013;8(3):e56564

Serum profiling of healthy aging identifies phospho- and sphingolipid species as markers of human longevity.

As centenarians well represent the model of healthy aging, there are many important implications in revealing the underlying molecular mechanisms behind such successful aging. By combining NMR metabonomics and shot-gun lipidomics in serum we analyzed metabolome and lipidome composition of a group of centenarians with respect to elderly individuals. Specifically, NMR metabonomics profiling of serum revealed that centenarians are characterized by a metabolic phenotype distinct from that of elderly subjects, in particular regarding amino acids and lipid species. Shot- gun lipidomics approach displays unique changes in lipids biosynthesis in centenarians, with 41 differently abundant lipid species with respect to elderly subjects. These findings reveal phospho/sphingolipids as putative markers and biological modulators of healthy aging, in humans. Considering the particular actions of these metabolites, these data are suggestive of a better counteractive antioxidant capacity and a well-developed membrane lipid remodelling process in the healthy aging phenotype.

Aging (Albany NY). 2014 Jan;6(1):9-25

Intestinal microbial metabolism of phosphatidylcholine and cardiovascular risk.

BACKGROUND: Recent studies in animals have shown a mechanistic link between intestinal microbial metabolism of the choline moiety in dietary phosphatidylcholine (lecithin) and coronary artery disease through the production of a proatherosclerotic metabolite, trimethylamine-N-oxide (TMAO). We investigated the relationship among intestinal microbiota-dependent metabolism of dietary phosphatidylcholine, TMAO levels, and adverse cardiovascular events in humans. METHODS: We quantified plasma and urinary levels of TMAO and plasma choline and betaine levels by means of liquid chromatography and online tandem mass spectrometry after a phosphatidylcholine challenge (ingestion of two hard-boiled eggs and deuterium [d9]-labeled phosphatidylcholine) in healthy participants before and after the suppression of intestinal microbiota with oral broad-spectrum antibiotics. We further examined the relationship between fasting plasma levels of TMAO and incident major adverse cardiovascular events (death, myocardial infarction, or stroke) during 3 years of follow-up in 4007 patients undergoing elective coronary angiography. RESULTS: Time-dependent increases in levels of both TMAO and its d9 isotopologue, as well as other choline metabolites, were detected after the phosphatidylcholine challenge. Plasma levels of TMAO were markedly suppressed after the administration of antibiotics and then reappeared after withdrawal of antibiotics. Increased plasma levels of TMAO were associated with an increased risk of a major adverse cardiovascular event (hazard ratio for highest vs. lowest TMAO quartile, 2.54; 95% confidence interval, 1.96 to 3.28; P<0.001). An elevated TMAO level predicted an increased risk of major adverse cardiovascular events after adjustment for traditional risk factors (P<0.001), as well as in lower-risk subgroups. CONCLUSIONS: The production of TMAO from dietary phosphatidylcholine is dependent on metabolism by the intestinal microbiota. Increased TMAO levels are associated with an increased risk of incident major adverse cardiovascular events.

N Engl J Med. 2013 Apr 25;368(17):1575-84

A global clinical measure of fitness and frailty in elderly people.

BACKGROUND: There is no single generally accepted clinical definition of frailty. Previously developed tools to assess frailty that have been shown to be predictive of death or need for entry into an institutional facility have not gained acceptance among practising clinicians. We aimed to develop a tool that would be both predictive and easy to use. METHODS: We developed the 7-point Clinical Frailty Scale and applied it and other established tools that measure frailty to 2305 elderly patients who participated in the second stage of the Canadian Study of Health and Aging (CSHA). We followed this cohort prospectively; after 5 years, we determined the ability of the Clinical Frailty Scale to predict death or need for institutional care, and correlated the results with those obtained from other established tools. RESULTS: The CSHA Clinical Frailty Scale was highly correlated (r = 0.80) with the Frailty Index. Each 1-category increment of our scale significantly increased the medium-term risks of death (21.2% within about 70 mo, 95% confidence interval [CI] 12.5%-30.6%) and entry into an institution (23.9%, 95% CI 8.8%-41.2%) in multivariable models that adjusted for age, sex and education. Analyses of receiver operating characteristic curves showed that our Clinical Frailty Scale performed better than measures of cognition, function or comorbidity in assessing risk for death (area under the curve 0.77 for 18-month and 0.70 for 70-month mortality). INTERPRETATION: Frailty is a valid and clinically important construct that is recognizable by physicians. Clinical judgments about frailty can yield useful predictive information.

CMAJ. 2005 Aug 30;173(5):489-95

Identifying the genomic determinants of aging and longevity in human population studies: progress and challenges.

Human lifespan variation is mainly determined by environmental factors, whereas the genetic contribution is 25-30% and expected to be polygenic. Two complementary fields go hand in hand in order to unravel the mechanisms of biological aging: genomic and biomarker research. Explorative and candidate gene studies of the human genome by genetic, transcriptomic, and epigenomic approaches have resulted in the identification of a limited number of interesting positive linkage regions, genes, and pathways that contribute to lifespan variation. The possibilities to further exploit these findings are rapidly increasing through the use of novel technologies, such as next-generation sequencing. Genomic research is progressively being integrated with biomarker studies on aging, including the application of (noninvasive) deep phenotyping and omics data - generated using novel technologies - in a wealth of studies in human populations. Hence, these studies may assist in obtaining a more holistic perspective on the role of the genome in aging and lifespan regulation.

Bioessays. 2013 Apr;35(4):386-96

Frailty and migration in middle-aged and older Europeans.

We evaluated life course influences on health by investigating potential differences in levels of frailty between middle-aged and older European immigrants born in low- and middle-income countries (LMICs), immigrants born in high income countries (HICs), and their native-born European peers. Using data from the Survey of Health, Ageing, and Retirement in Europe (SHARE), we constructed a frailty index from 70 age-related health measures for 33,745 participants aged 50+ (mean=64.9 ± 10.2 years; 54% women) in 14 European countries. Participants were grouped as native-born or as immigrants born in LMICs or in HICs, and further by current residence in Northern/Western or Southern/Eastern Europe. Seven percent of participants (n=2369) were immigrants (mean=64.4 ± 10.2 years; 56% women; LMIC-born=3.4%, HIC-born=3.6%). In Northern/Western Europe, after adjustment for age, gender, and education, LMIC-born immigrants demonstrated higher frailty index scores (mean=0.18, 95% confidence interval=0.17-0.19) than both HIC-born immigrants (0.16, 0.16-0.17) and native-born participants (0.15, 0.14-0.15 both p<0.001). In Southern/Eastern Europe, frailty index scores did not differ between groups (p=0.2). Time since migration explained significant variance in frailty index scores only in HIC-born immigrants to Southern/Eastern Europe (4.3%, p=0.03). Despite differences in frailty, survival did not differ between groups (p=0.2). LMIC-born immigrants demonstrated higher levels of frailty in Northern/Western Europe, but not Southern/Eastern Europe. Country of birth and current country of residence were each associated with frailty. Life course influences are demonstrable, but complex.

Arch Gerontol Geriatr. 2014 Jan-Feb;58(1):63-8

Nicotinamide riboside

NAD+ and vitamin B3: from metabolism to therapies.

The role of NAD(+) metabolism in health and disease is of increased interest as the use of niacin (nicotinic acid) has emerged as a major therapy for treatment of hyperlipidemias and with the recognition that nicotinamide can protect tissues and NAD(+) metabolism in a variety of disease states, including ischemia/reperfusion. In addition, a growing body of evidence supports the view that NAD(+) metabolism regulates important biological effects, including lifespan. NAD(+) exerts potent effects through the poly(ADP-ribose) polymerases, mono-ADP-ribosyltransferases, and the recently characterized sirtuin enzymes. These enzymes catalyze protein modifications, such as ADP-ribosylation and deacetylation, leading to changes in protein function. These enzymes regulate apoptosis, DNA repair, stress resistance, metabolism, and endocrine signaling, suggesting that these enzymes and/or NAD(+) metabolism could be targeted for therapeutic benefit. This review considers current knowledge of NAD(+) metabolism in humans and microbes, including new insights into mechanisms that regulate NAD(+) biosynthetic pathways, current use of nicotinamide and nicotinic acid as pharmacological agents, and opportunities for drug design that are directed at modulation of NAD(+) biosynthesis for treatment of human disorders and infections.

J Pharmacol Exp Ther. 2008 Mar;324(3):883-93

Nicotinamide riboside promotes Sir2 silencing and extends lifespan via Nrk and Urh1/Pnp1/Meu1 pathways to NAD+.

Although NAD(+) biosynthesis is required for Sir2 functions and replicative lifespan in yeast, alterations in NAD(+) precursors have been reported to accelerate aging but not to extend lifespan. In eukaryotes, nicotinamide riboside is a newly discovered NAD(+) precursor that is converted to nicotinamide mononucleotide by specific nicotinamide riboside kinases, Nrk1 and Nrk2. In this study, we discovered that exogenous nicotinamide riboside promotes Sir2-dependent repression of recombination, improves gene silencing, and extends lifespan without calorie restriction. The mechanism of action of nicotinamide riboside is totally dependent on increased net NAD(+) synthesis through two pathways, the Nrk1 pathway and the Urh1/Pnp1/Meu1 pathway, which is Nrk1 independent. Additionally, the two nicotinamide riboside salvage pathways contribute to NAD(+) metabolism in the absence of nicotinamide-riboside supplementation. Thus, like calorie restriction in the mouse, nicotinamide riboside elevates NAD(+) and increases Sir2 function.

Cell. 2007 May 4;129(3):473-84

Transcriptional silencing and longevity protein Sir2 is an NAD-dependent histone deacetylase.

Yeast Sir2 is a heterochromatin component that silences transcription at silent mating loci, telomeres and the ribosomal DNA, and that also suppresses recombination in the rDNA and extends replicative life span. Mutational studies indicate that lysine 16 in the amino-terminal tail of histone H4 and lysines 9, 14 and 18 in H3 are critically important in silencing, whereas lysines 5, 8 and 12 of H4 have more redundant functions. Lysines 9 and 14 of histone H3 and lysines 5, 8 and 16 of H4 are acetylated in active chromatin and hypoacetylated in silenced chromatin, and overexpression of Sir2 promotes global deacetylation of histones, indicating that Sir2 may be a histone deacetylase. Deacetylation of lysine 16 of H4 is necessary for binding the silencing protein, Sir3. Here we show that yeast and mouse Sir2 proteins are nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylases, which deacetylate lysines 9 and 14 of H3 and specifically lysine 16 of H4. Our analysis of two SIR2 mutations supports the idea that this deacetylase activity accounts for silencing, recombination suppression and extension of life span in vivo. These findings provide a molecular framework of NAD-dependent histone deacetylation that connects metabolism, genomic silencing and ageing in yeast and, perhaps, in higher eukaryotes.

Nature. 2000 Feb 17;403(6771):795-800

Declining NAD(+) induces a pseudohypoxic state disrupting nuclear-mitochondrial communication during aging.

Ever since eukaryotes subsumed the bacterial ancestor of mitochondria, the nuclear and mitochondrial genomes have had to closely coordinate their activities, as each encode different subunits of the oxidative phosphorylation (OXPHOS) system. Mitochondrial dysfunction is a hallmark of aging, but its causes are debated. We show that, during aging, there is a specific loss of mitochondrial, but not nuclear, encoded OXPHOS subunits. We trace the cause to an alternate PGC-1a/b-independent pathway of nuclear-mitochondrial communication that is induced by a decline in nuclear NAD(+) and the accumulation of HIF-1a under normoxic conditions, with parallels to Warburg reprogramming. Deleting SIRT1 accelerates this process, whereas raising NAD(+) levels in old mice restores mitochondrial function to that of a young mouse in a SIRT1-dependent manner. Thus, a pseudohypoxic state that disrupts PGC-1a/b-independent nuclear-mitochondrial communication contributes to the decline in mitochondrial function with age, a process that is apparently reversible.

Cell. 2013 Dec 19;155(7):1624-38

NAD(+)-dependent repair of damaged DNA by human cell extracts.

Rejoining of DNA single-strand breaks generated by treatment of plasmids with gamma-rays, neocarzinostatin, or bleomycin was catalyzed inefficiently by human cell extracts. The reaction was strongly promoted by the addition of NAD+, which was employed for rapid and transient synthesis of poly(ADP-ribose). The DNA rejoining reaction was accompanied by DNA repair replication, apparently due to replacement of damaged residues at termini. Selective depletion of poly(ADP-ribose) polymerase from cell extracts improved the repair of DNA exposed to a variety of DNA-damaging agents by removing the NAD+ dependence of the repair reaction. NAD(+)-promoted DNA repair by soluble cell extracts also occurred with alkylated DNA as substrate and was suppressed by 3-aminobenzamide. A similar stimulatory effect by NAD+ was observed for repair of ultraviolet-irradiated DNA, and this could be ascribed to the presence of pyrimidine hydrates as minor radiation-induced DNA lesions. No effect was observed on the sealing of gamma-irradiated DNA by supplementation of cell extracts with purified mammalian DNA ligase I or DNA ligase II. The results indicate that poly(ADP-ribose) polymerase interferes with base excision-repair processes because bound enzyme molecules block DNA strand interruptions. Release of bound poly-(ADP-ribose) polymerase following automodification, or physical removal of the protein from reaction mixtures, facilitates DNA repair.

J Biol Chem. 1993 Mar 15;268(8):5480-7

Manipulation of a nuclear NAD+ salvage pathway delays aging without altering steady-state NAD+ levels.

Yeast deprived of nutrients exhibit a marked life span extension that requires the activity of the NAD(+)-dependent histone deacetylase, Sir2p. Here we show that increased dosage of NPT1, encoding a nicotinate phosphoribosyltransferase critical for the NAD(+) salvage pathway, increases Sir2-dependent silencing, stabilizes the rDNA locus, and extends yeast replicative life span by up to 60%. Both NPT1 and SIR2 provide resistance against heat shock, demonstrating that these genes act in a more general manner to promote cell survival. We show that Npt1 and a previously uncharacterized salvage pathway enzyme, Nma2, are both concentrated in the nucleus, indicating that a significant amount of NAD(+) is regenerated in this organelle. Additional copies of the salvage pathway genes, PNC1, NMA1, and NMA2, increase telomeric and rDNA silencing, implying that multiple steps affect the rate of the pathway. Although SIR2-dependent processes are enhanced by additional NPT1, steady-state NAD(+) levels and NAD(+)/NADH ratios remain unaltered. This finding suggests that yeast life span extension may be facilitated by an increase in the availability of NAD(+) to Sir2, although not through a simple increase in steady-state levels. We propose a model in which increased flux through the NAD(+) salvage pathway is responsible for the Sir2-dependent extension of life span.

J Biol Chem. 2002 May 24;277(21):18881-90

Nicotinamide riboside restores cognition through an upregulation of proliferator-activated receptor-g coactivator 1a regulated b-secretase 1 degradation and mitochondrial gene expression in Alzheimer’s mouse models.

Nicotinamide adenine dinucleotide (NAD)(+), a coenzyme involved in redox activities in the mitochondrial electron transport chain, has been identified as a key regulator of the lifespan-extending effects, and the activation of NAD(+) expression has been linked with a decrease in beta-amyloid (Ab) toxicity in Alzheimer’s disease (AD). Nicotinamide riboside (NR) is a NAD(+) precursor, it promotes peroxisome proliferator-activated receptor-g coactivator 1 (PGC)-1a expression in the brain. Evidence has shown that PGC-1a is a crucial regulator of Ab generation because it affects b-secretase (BACE1) degradation. In this study we tested the hypothesis that NR treatment in an AD mouse model could attenuate Ab toxicity through the activation of PGC-1a-mediated BACE1 degradation. Using the Tg2576 AD mouse model, using in vivo behavioral analyses, biochemistry assays, small hairpin RNA (shRNA) gene silencing and electrophysiological recording, we found (1) dietary treatment of Tg2576 mice with 250 mg/kg/day of NR for 3 months significantly attenuates cognitive deterioration in Tg2576 mice and coincides with an increase in the steady-state levels of NAD(+) in the cerebral cortex; (2) application of NR to hippocampal slices (10 µM) for 4 hours abolishes the deficits in long-term potentiation recorded in the CA1 region of Tg2576 mice; (3) NR treatment promotes PGC-1a expression in the brain coinciding with enhanced degradation of BACE1 and the reduction of Ab production in Tg2576 mice. Further in vitro studies confirmed that BACE1 protein content is decreased by NR treatment in primary neuronal cultures derived from Tg2576 embryos, in which BACE1 degradation was prevented by PGC-1a-shRNA gene silencing; and (4) NR treatment and PGC-1a overexpression enhance BACE1 ubiquitination and proteasomal degradation. Our studies suggest that dietary treatment with NR might benefit AD cognitive function and synaptic plasticity, in part by promoting PGC-1a-mediated BACE1 ubiquitination and degradation, thus preventing Ab production in the brain.

Neurobiol Aging. 2013 Jun;34(6):1581-8

NAD+ and sirtuins in aging and disease.

Nicotinamide adenine dinucleotide (NAD+) is a classical coenzyme mediating many redox reactions. NAD+ also plays an important role in the regulation of NAD+-consuming enzymes, including sirtuins, poly-ADP-ribose polymerases (PARPs), and CD38/157 ectoenzymes. NAD+ biosynthesis, particularly mediated by nicotinamide phosphoribosyltransferase (NAMPT), and SIRT1 function together to regulate metabolism and circadian rhythm. NAD+ levels decline during the aging process and may be an Achilles’ heel, causing defects in nuclear and mitochondrial functions and resulting in many age-associated pathologies. Restoring NAD+ by supplementing NAD+ intermediates can dramatically ameliorate these age-associated functional defects, counteracting many diseases of aging, including neurodegenerative diseases. Thus, the combination of sirtuin activation and NAD+ intermediate supplementation may be an effective antiaging intervention, providing hope to aging societies worldwide.

Trends Cell Biol. 2014 Aug;24(8):464-471

NAD+ deficiency in age-related mitochondrial dysfunction.

Homologs of the chromatin-bound yeast silent information regulator 2 (SIR2) protein are found in organisms from all biological kingdoms. SIR2 itself was originally discovered to influence mating-type control in haploid cells by locus-specific transcriptional silencing. Since then, SIR2 and its homologs have been suggested to play additional roles in suppression of recombination, chromosomal stability, metabolic regulation, meiosis, and aging. Considering the far-ranging nature of these functions, a major experimental goal has been to understand the molecular mechanism(s) by which this family of proteins acts. We report here that members of the SIR2 family catalyze an NAD-nicotinamide exchange reaction that requires the presence of acetylated lysines such as those found in the N termini of histones. Significantly, these enzymes also catalyze histone deacetylation in a reaction that absolutely requires NAD, thereby distinguishing them from previously characterized deacetylases. The enzymes are active on histone substrates that have been acetylated by both chromatin assembly-linked and transcription-related acetyltransferases. Contrary to a recent report, we find no evidence that these proteins ADP-ribosylate histones. Discovery of an intrinsic deacetylation activity for the conserved SIR2 family provides a mechanism for modifying histones and other proteins to regulate transcription and diverse biological processes.

Cell Metab. 2014 Feb 4;19(2):178-80

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