Effects of restricted feeding, low-energy diet, and implantation of trenbolone acetate plus estradiol on growth, carcass traits, and circulating concentrations of insulin-like growth factor (IGF)-I and IGF-binding protein-3 in finishing barrows.
Effects of restricted feeding (80% ad libitum), feeding a low-energy diet containing 84% DE (2.95 Mcal/kg) of the control diet, and implantation of Revalor H (140 mg trenbolone acetate plus 14 mg estradiol-17beta) on growth, carcass traits, and serum concentrations of insulin-like growth factor (IGF)-I and IGFbinding protein-3 (IGFBP-3) were studied in crossbred finishing barrows beginning from 59 +/- 0.9 kg of body weight. Blood samples were taken every three week and the animals were slaughtered at approximately 105 kg body weight. Restricted feeding caused a decrease (P < 0.01) in ADG; feeding the low-energy diet was effective in reducing backfat thickness but decreased gain:feed; the implantation caused a decrease in ADG, feed intake, and backfat thickness and increased gain:feed. Overall pork quality based on pH, drip loss, and the lightness in color of longissimus muscle was not affected by any of the treatments. Serum IGF-I concentration increased following the implantation but did not change (P > 0.05) due to other treatments. Immunoreactive IGFBP-3 concentration was not changed by any of the treatments. Overall ADG was positively correlated with early-stage (d 21) IGF-I and IGFBP-3 concentrations only in unimplanted barrows, whereas backfat thickness was negatively correlated with d-42 IGF-I concentration in all but unimplanted barrows with ad libitum intake. A strong positive correlation (P < 0.01) between IGF-I and IGFBP-3 concentrations was apparent with increasing age of the animals. Results suggest that growth rate and backfat thickness are decreased by a moderate restriction of feed or energy intake with no accompanying changes in circulating IGF-I and IGFBP-3 concentrations and that the beneficial effect of Revalor H implantation on feed efficiency may be mediated, in part, by IGF-I. Moreover, both IGF-I and IGFBP-3 concentrations may be useful as growth indices in pigs.
Anim Sci. 2002 Jan;80(1):84-93
Molecular targets for green tea in prostate cancer prevention.
Prostate cancer (PCa) is the most frequently diagnosed malignancy and the second leading cause of cancer-related deaths in American males. For these reasons, it is necessary to intensify our efforts for better understanding and development of novel treatment and chemopreventive approaches for this disease. In recent years, green tea has gained considerable attention as an agent that could reduce the risk of several cancer types. The cancer-chemopreventive effects of green tea appear to be mediated by the polyphenolic constituents present therein. Based on geographical observations that suggest that the incidence of PCa is lower in Japanese and Chinese populations that consume green tea on a regular basis, we hypothesized that green tea and/or its constituents could be effective for chemoprevention of PCa. To investigate this hypothesis, we initiated a program for the chemoprevention of PCa by green tea. In cell-culture systems that employ human PCa cells DU145 (androgen insensitive) and LNCaP (androgen sensitive), we found that the major polyphenolic constituent (-)-epigallocatechin-3-gallate (EGCG) of green tea induces 1) apoptosis, 2) cell-growth inhibition, and 3) cyclin kinase inhibitor WAF-1/p21-mediated cell-cycle dysregulation. More recently, using a cDNA microarray, we found that EGCG treatment of LNCaP cells results in 1) induction of genes that functionally exhibit growth-inhibitory effects, and 2) repression of genes that belong to the G-protein signaling network. In animal studies that employ a transgenic adenocarcinoma of the mouse prostate (TRAMP), which is a model that mimics progressive forms of human prostatic disease, we observed that oral infusion of a polyphenolic fraction isolated from green tea (GTP) at a human achievable dose (equivalent to 6 cups of green tea/d) significantly inhibits PCa development and metastasis. We extended these studies and more recently observed increased expression of genes related to angiogenesis such as vascular endothelial growth factor (VEGF) and those related to metastasis such as matrix metalloproteinases (MMP)-2 and MMP-9 in prostate cancer of TRAMP mice. Oral feeding of GTP as the sole source of drinking fluid to TRAMP mice results in significant inhibition of VEGF, MMP-2 and MMP-9. These data suggest that there are multiple targets for PCa chemoprevention by green tea and highlight the need for further studies to identify novel pathways that may be modulated by green tea or its polyphenolic constituents that could be further exploited for prevention and/or treatment of PCa.
J Nutr. 2003 Jul;133(7 Suppl):2417S-2424S
Melatonin as a chronobiotic/anticancer agent: cellular, biochemical, and molecular mechanisms of action and their implications for circadian-based cancer therapy.
Melatonin, as a new member of an expanding group of regulatory factors that control cell proliferation and loss, is the only known chronobiotic, hormonal regulator of neoplastic cell growth. At physiological circulating concentrations, this indoleamine is cytostatic and inhibits cancer cell proliferation in vitro via specific cell cycle effects. At pharmacological concentrations, melatonin exhibits cytotoxic activity in cancer cells. At both physiological and pharmacological concentrations, melatonin acts as a differentiating agent in some cancer cells and lowers their invasive and metastatic status through alterations in adhesion molecules and maintenance of gap junctional intercellular communication. In other cancer cell types, melatonin, either alone or in combination with other agents, induces apoptotic cell death. Biochemical and molecular mechanisms of melatonin's oncostatic action may include regulation of estrogen receptor expression and transactivation, calcium/calmodulin activity, protein kinase C activity, cytoskeletal architecture and function, intracellular redox status, melatonin receptor-mediated signal transduction cascades, and fatty acid transport and metabolism. A major mechanism mediating melatonin's circadian stage-dependent tumor growth inhibitory action is the suppression of epidermal growth factor receptor (EGFR)/mitogen-activated protein kinase (MAPK) activity. This occurs via melatonin receptor-mediated blockade of tumor linoleic acid uptake and its conversion to 13-hydroxyoctadecadienoic acid (13-HODE) which normally activates EGFR/MAPK mitogenic signaling. This represents a potentially unifying model for the chronobiological inhibitory regulation of cancer growth by melatonin in the maintenance of the host/cancer balance. It also provides the first biological explanation of melatonin-induced enhancement of the efficacy and reduced toxicity of chemo- and radiotherapy in cancer patients.
Curr Top Med Chem. 2002 Feb;2(2):113-32
Five years survival in metastatic non-small cell lung cancer patients treated with chemotherapy alone or chemotherapy and melatonin: a randomized trial.
Numerous experimental data have documented the oncostatic properties of melatonin. In addition to its potential direct antitumor activity, melatonin has proved to modulate the effects of cancer chemotherapy, by enhancing its therapeutic efficacy and reducing its toxicity. The increase in chemotherapeutic efficacy by melatonin may depend on two main mechanisms, namely prevention of chemotherapy-induced lymphocyte damage and its antioxidant effect, which has been proved to amplify cytotoxic actions of the chemotherapeutic agents against cancer cells. However, the clinical results available at present with melatonin and chemotherapy in the treatment of human neoplasms are generally limited to the evaluation of 1-year survival in patients with very advanced disease. Thus, the present study was performed to assess the 5-year survival results in metastatic non-small cell lung cancer patients obtained with a chemotherapeutic regimen consisting of cisplatin and etoposide, with or without the concomitant administration of melatonin (20 mg/day orally in the evening). The study included 100 consecutive patients who were randomized to receive chemotherapy alone or chemotherapy and melatonin. Both the overall tumor regression rate and the 5-year survival results were significantly higher in patients concomitantly treated with melatonin. In particular, no patient treated with chemotherapy alone was alive after 2 years, whereas a 5-year survival was achieved in three of 49 (6%) patients treated with chemotherapy and melatonin. Moreover, chemotherapy was better tolerated in patients treated with melatonin. This study confirms, in a considerable number of patients and for a long follow-up period, the possibility to improve the efficacy of chemotherapy in terms of both survival and quality of life by a concomitant administration of melatonin. This suggests a new biochemotherapeutic strategy in the treatment of human neoplasms.
J Pineal Res. 2003 Aug;35(1):12-5
Role of melatonin in the regulation of human circadian rhythms and sleep.
The circadian rhythm of pineal melatonin is the best marker of internal time under low ambient light levels. The endogenous melatonin rhythm exhibits a close association with the endogenous circadian component of the sleep propensity rhythm. This has led to the idea that melatonin is an internal sleep "facilitator" in humans, and therefore useful in the treatment of insomnia and the readjustment of circadian rhythms. There is evidence that administration of melatonin is able: (i) to induce sleep when the homeostatic drive to sleep is insufficient; (ii) to inhibit the drive for wakefulness emanating from the circadian pacemaker; and (iii) induce phase shifts in the circadian clock such that the circadian phase of increased sleep propensity occurs at a new, desired time. Therefore, exogenous melatonin can act as soporific agent, a chronohypnotic, and/or a chronobiotic. We describe the role of melatonin in the regulation of sleep, and the use of exogenous melatonin to treat sleep or circadian rhythm disorders.
J Neuroendocrinol. 2003 Apr;15(4):432-7
Cancer anorexia-cachexia syndrome: current issues in research and management.
Cachexia is among the most debilitating and life-threatening aspects of cancer. Associated with anorexia, fat and muscle tissue wasting, psychological distress, and a lower quality of life, cachexia arises from a complex interaction between the cancer and the host. This process includes cytokine production, release of lipid-mobilizing and proteolysis-inducing factors, and alterations in intermediary metabolism. Cachexia should be suspected in patients with cancer if an involuntary weight loss of greater than five percent of premorbid weight occurs within a six-month period. The two major options for pharmacological therapy have been either progestational agents, such as megestrol acetate, or corticosteroids. However, knowledge of the mechanisms of cancer anorexia-cachexia syndrome has led to, and continues to lead to, effective therapeutic interventions for several aspects of the syndrome. These include antiserotonergic drugs, gastroprokinetic agents, branched-chain amino acids, eicosapentanoic acid, cannabinoids, melatonin, and thalidomide--all of which act on the feeding-regulatory circuitry to increase appetite and inhibit tumor-derived catabolic factors to antagonize tissue wasting and/or host cytokine release. Because weight loss shortens the survival time of cancer patients and decreases performance status, effective therapy would extend patient survival and improve quality of life.
CA Cancer J Clin. 2002 Mar-Apr;52(2):72-91
Extrapineal melatonin in pathology: new perspectives for diagnosis, prognosis and treatment of illness.
During the last decade, attention was concentrated on melatonin -- one of the hormones of the diffuse neuroendocrine system, which has been considered only as a hormone of the pineal gland, for many years. Currently, melatonin has been identified not only in the pineal gland, but also in extrapineal tissues -- retina, harderian gland, gut mucosa, cerebellum, airway epithelium, liver, kidney, adrenals, thymus, thyroid, pancreas, ovary, carotid body, placenta and endometrium as well as in non-neuroendocrine cells like mast cells, natural killer cells, eosinophilic leukocytes, platelets and endothelial cells. The above list of the cells storing melatonin indicates that melatonin has a unique position among the hormones of the diffuse neuroendocrine system, which is present in practically all organ systems. Functionally, melatonin-producing cells are certain to be part and parcel of the diffuse neuroendocrine system as a universal system of response, control and organism protection. Taking into account the large number of melatonin-producing cells in many organs, the wide spectrum of biological activities of melatonin and especially its main property as a universal regulator of biological rhythms, it should be possible to consider extrapineal melatonin as a key paracrine signal molecule for the local coordination of intercellular relationships. Analysis of our long-term clinical investigations shows the direct participation and active role of extrapineal melatonin in the pathogenesis of tumor growth and many other non-tumor pathologies such as gastric ulcer, immune diseases, neurodegenerative processes, radiation disorders, etc. The modification of antitumor and other specific therapy by the activation or inhibition of extrapineal melatonin activity could be useful for the improvement of the treatment of illness.
Neuroendocrinol Lett. 2002 Apr;23 Suppl 1:92-6
Gastrointestinal melatonin: localization, function, and clinical relevance.
The gastrointestinal tract of vertebrate species is a rich source of extrapineal melatonin. The concentration of melatonin in the gastrointestinal tissues surpasses blood levels by 10-100 times and there is at least 400x more melatonin in the gastrointestinal tract than in the pineal gland. The gastrointestinal tract contributes significantly to circulating concentrations of melatonin, especially during the daytime and melatonin may serve as an endocrine, paracrine, or autocrine hormone influencing the regeneration and function of epithelium, enhancing the immune system of the gut, and reducing the tone of gastrointestinal muscles. As binding sites for melatonin exhibit circadian variation in various species, it has been hypothesized that some melatonin found in the gastrointestinal tract might be of pineal origin. Unlike the photoperiodically regulated production of melatonin in the pineal, the release of gastrointestinal melatonin seems to be related to the periodicity of food intake. Phylogenetically, melatonin and its binding sites were detected in the gastrointestinal tract of lower vertebrates, birds, and mammals. Melatonin was found also in large quantities in the embryonic tissue of the mammalian and avian gastrointestinal tract. Food intake and, paradoxically, also longterm food deprivation resulted in an increase of tissue and plasma concentrations of melatonin. Melatonin release may have a direct effect on many gastrointestinal tissues but may also well influence the digestive tract indirectly, via the central nervous system and the sympathetic and parasympathetic nerves. Melatonin prevents ulcerations of gastrointestinal mucosa by an antioxidant action, reduction of secretion of hydrochloric acid, stimulation of the immune system, fostering epithelial regeneration, and increasing microcirculation. Because of its unique properties, melatonin could be considered for prevention or treatment of colorectal cancer, ulcerative colitis, gastric ulcers, irritable bowel syndrome, and childhood colic.
Dig Dis Sci. 2002 Oct;47(10):2336-48