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Blood Glucose, Curcumin, Sugar, And Coffee

October 2017

Coffee

Habitual coffee consumption and risk of cognitive decline/dementia: A systematic review and meta-analysis of prospective cohort studies.

OBJECTIVE: Findings from epidemiologic studies of coffee consumption and risk for cognitive decline or dementia are inconclusive. The aim of this study was to conduct a meta-analysis of prospective studies to assess the association between coffee consumption and the risk for cognitive decline and dementia. METHODS: Relevant studies were identified by searching PubMed and Embase databases between 1966 and December 2014. Prospective cohorts that reported relative risk (RRs) and 95% confidence intervals (CIs) for the association of coffee consumption with dementia incidence or cognitive changing were eligible. Study-specific RRs were combined by using a random-effects model. RESULTS: Eleven prospective studies, including 29,155 participants, were included in the meta-analysis. The combined RR indicated that high coffee consumption was not associated with the different measures of cognitive decline or dementia (summary RR, 0.97; 95% CI, 0.84-1.11). Subgroup analyses suggested a significant inverse association between highest coffee consumption and the risk for Alzheimer disease (summary RR, 0.73; 95% CI, 0.55-0.97). The dose-response analysis, including eight studies, did not show an association between the increment of coffee intake and cognitive decline or dementia risk (an increment of 1 cup/d of coffee consumed; summary RR, 1.00; 95% CI, 0.98-1.02). CONCLUSIONS: The present study suggests that higher coffee consumption is associated with reduced risk for Alzheimer disease. Further randomized controlled trials or well-designed cohort studies are needed to determine the association between coffee consumption and cognitive decline or dementia.

Nutrition. 2016 Jun;32(6):628-36.

Coffee consumption and prostate cancer risk: a meta-analysis of cohort studies.

This meta-analysis was conducted to assess the association between coffee consumption and prostate cancer risk. Thirteen cohort studies with 34,105 cases and 539,577 participants were included in the meta-analysis. The summary relative risks (RRs) with 95% confidence intervals (CIs) for different coffee intake levels were calculated. Dose-response relationship was assessed using generalized least square trend estimation. The pooled RR for the highest vs. lowest coffee intake was 0.90 (95% CI: 0.85-0.95), with no significant heterogeneity across studies (P = 0.267; I(2) = 17.5%). The dose-response analysis showed a lower cancer risk decreased by 2.5% (RR = 0.975; 95% CI: 0.957-0.995) for every 2 cups/day increment in coffee consumption. Stratifying by geographic region, there was a statistically significant protective influence of coffee on prostate cancer risk among European populations. In subgroup analysis of prostate cancer grade, the summary RRs were 0.89 (95% CI: 0.83-0.96) for nonadvanced, 0.82 (95% CI: 0.61-1.10) for advanced and 0.76 (95% CI: 0.55-1.06) for fatal diseases. Our findings suggest that coffee consumption may be associated with a reduced risk of prostate cancer and it also has an inverse association with nonadvanced prostate cancer. Because of the limited number of studies, more prospective studies with large sample size are needed to confirm this association.

Nutr Cancer. 2015;67(3):392-400.

Effects of chlorogenic acid on voltage-gated potassium channels of trigeminal ganglion neurons in an inflammatory environment.

Chlorogenic acid (CGA) composed of coffee acid and quinic acid is an effective ingredient of many foods and medicines and widely exhibits biological effects. Recently, it is reported to have analgesic effect. However, little is known about the analgesic mechanism of CGA. In this study, whole-cell patch-clamp recordings were performed on two main subtypes (IK,A and IK,V channels) of voltage-gated potassium (KV) channels in small-diameter(<30µm) trigemianl ganglion neurons to analyze the effects of CGA in an inflammatory environment created by Prostaglandin E2 (PGE2). On one hand, the activation and inactivation V1/2 values of IK,A and IK,V channels showed an elevation towards a depolarizing shift caused by PGE2. On the other hand, the activation and inactivation V1/2 values of the two channels had a reduction towards a hyperpolarizing shift caused by CGA under PGE2 pretreatment. Our results demonstrated that CGA may exhibited an analgesic effect by promoting KV channels activation and inactivation under inflammatory condition, which provided a novel molecular and ionic mechanism underlying anti-inflammatory pain of CGA.

Brain Res Bull. 2016 Oct;127:119-125.

Neuroprotection comparison of chlorogenic acid and its metabolites against mechanistically distinct cell death-inducing agents in cultured cerebellar granule neurons.

While the number of patients diagnosed with neurodegenerative disorders like Alzheimer's disease, amyotrophic lateral sclerosis, and Parkinson's disease is increasing, there are currently no effective treatments that significantly limit the neuronal cell death underlying these diseases. Chlorogenic acid (CGA), a polyphenolic compound found in high concentration in coffee, is known to possess antioxidant and free radical scavenging activity. In this study, we investigated the neuroprotective effects of CGA and its major metabolites in primary cultures of rat cerebellar granule neurons. We show that CGA and caffeic acid displayed a dramatic protective effect against the nitric oxide donor, sodium nitroprusside. In marked contrast, ferulic acid and quinic acid had no protective effect against this nitrosative stress. While CGA and quinic acid had no protective effect against glutamate-induced cell death, caffeic acid and ferulic acid significantly protected neurons from excitotoxicity. Finally, caffeic acid was the only compound to display significant protective activity against hydrogen peroxide, proteasome inhibition, caspase-dependent intrinsic apoptosis, and endoplasmic reticulum stress. These results indicate that caffeic acid displays a much broader profile of neuroprotection against a diverse range of stressors than its parent polyphenol, CGA, or the other major metabolites, ferulic acid and quinic acid. We conclude that caffeic acid is a promising candidate for testing in pre-clinical models of neurodegeneration.

Brain Res. 2016 Oct 1;1648(Pt A):69-80.

Chronic coffee and caffeine ingestion effects on the cognitive function and antioxidant system of rat brains.

Coffee is a popular beverage consumed worldwide and its effect on health protection has been well studied throughout literature. This study investigates the effect of chronic coffee and caffeine ingestion on cognitive behavior and the antioxidant system of rat brains. The paradigms of open field and object recognition were used to assess locomotor and exploratory activities, as well as learning and memory. The antioxidant system was evaluated by determining the activities of glutathione reductase (GR), glutathione peroxidase (GPx) and superoxide dismutase (SOD), as well as the lipid peroxidation and reduced glutathione content. Five groups of male rats were fed for approximately 80 days with different diets: control diet (CD), fed a control diet; 3% coffee diet (3%Co) and 6% coffee diet (6%Co), both fed a diet containing brewed coffee; 0.04% caffeine diet (0.04%Ca) and 0.08% caffeine diet (0.08%Ca), both fed a control diet supplemented with caffeine. The estimated caffeine intake was approximately 20 and 40 mg/kg per day, for the 3%Co-0.04%Ca and 6%Co-0.08%Ca treatments, respectively. At 90 days of life, the animals were subjected to the behavioral tasks and then sacrificed. The results indicated that the intake of coffee, similar to caffeine, improved long-term memory when tested with object recognition; however, this was not accompanied by an increase in locomotor and exploratory activities. In addition, chronic coffee and caffeine ingestion reduced the lipid peroxidation of brain membranes and increased the concentration of reduced-glutathione. The activities of the GR and SOD were similarly increased, but no change in GPx activity could be observed. Thus, besides improving cognitive function, our data show that chronic coffee consumption modulates the endogenous antioxidant system in the brain. Therefore, chronic coffee ingestion, through the protection of the antioxidant system, may play an important role in preventing age-associated decline in the cognitive function.

Pharmacol Biochem Behav. 2011 Oct;99(4): 659-64.

Protective Effects of Chlorogenic Acid and its Metabolites on Hydrogen Peroxide-Induced Alterations in Rat Brain Slices: A Comparative Study with Resveratrol.

The effectiveness of chlorogenic acid and its main metabolites, caffeic and quinic acids, against oxidative stress was investigated. Resveratrol, another natural phenolic compound, was also tested for comparison. Rat cortical slices were incubated with 200 µM H2O2 for 1 h, and alterations in oxidative stress parameters, such as 2, 3, 5-triphenyltetrazolium chloride (TTC) staining and the production of both malondialdehyde (MDA) and reactive oxygen species (ROS), were assayed in the absence or presence of phenolic compounds. Additionally, the effectiveness of chlorogenic acid and other compounds on H2O2-induced increases in fluorescence intensities were also compared in slice-free incubation medium. Although quinic acid failed, chlorogenic and caffeic acids significantly ameliorated the H2O2-induced decline in TTC staining intensities. Although resveratrol also caused an increase in staining intensity, its effect was not dose-dependent; the high concentrations of resveratrol tested in the present study (10 and 100 µM) further lessened the staining of the slices. Additionally, all phenolic compounds significantly attenuated the H2O2-induced increases in MDA and ROS levels in cortical slices. When the IC50 values were compared to H2O2-induced alterations, chlorogenic acid was more potent than either its metabolites or resveratrol for all parameters studied under these experimental conditions. In slice-free experimental conditions, on the other hand, chlorogenic and caffeic acids significantly attenuated the fluorescence emission enhanced by H2O2 with a similar order of potency to that obtained in slice-containing physiological medium. These results indicate that chlorogenic acid is a more potent phenolic compound than resveratrol and its main metabolites caffeic and quinic acids against H2O2-induced alterations in oxidative stress parameters in rat cortical slices.

Neurochem Res. 2016 Aug;41(8):2075-85.