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Saturday, June 10, 2006

 

antiaging effect of acipimox and once-weekly fasting

[Acipimox may aid, and glutamine may hinder the anti-aging effect of once-weekly fasting.]

Exp Gerontol. 2004 Jul;39(7):1061-7 Anti-aging effects of anti-lipolytic drugs. Genetic disruption of insulin and insulin-like signaling pathways may extend lifespan. Hyperinsulinemia and insulin resistance may accelerate aging. The hypothesis was tested that a once-a-week life-long inhibition of insulin secretion by the administration of anti-lipolytic drugs might have anti-aging effects. Groups of 3-month-old male Sprague-Dawley rats were (a) given standard laboratory food ad libitum (AL); (b) fed AL 6 days and fasted 1 day every week (FW); (c) fed AL every other day (EOD), (d) fed like FW and given Acipimox (50 mg/kg b.w.) on the day of fasting (FWA) by the gastric tube. The AL, FW and EOD groups received saline intragastrically. Treatment with ACIPIMOX transiently decreased plasma free fatty acids, glucos! e and insulin and increased valine plasma levels, and had no long-term effect on food consumption and body weight. By age 6, 12 and 24 months subgroups were taken and the age-related changes in liver dolichol and autophagic proteolysis--which are correlated with life-expectancy--were measured. Liver dolichol levels increased and autophagic proteolysis decreased in mature and older AL rats; EOD and FWA fully counteracted these changes; FW rats had significant but smaller beneficial effects. It is concluded that life-long weekly-repeated transient inhibition of insulin secretion by antilipolytic drugs may have an anti-aging effect, additive to the anti-aging effect of a milder caloric restriction. Speculation is that transiently lower plasma insulin levels might stimulate the anti-aging cell-repair mechanism autophagy, which has longer lasting effects on cell housekeeping.

Proc Natl Acad Sci U S A. 2003 May 13;100(10):6216-20. Epub 2003 Apr 30. Intermitten! t fasting dissociates beneficial effects of dietary restriction on gl ucose metabolism and neuronal resistance to injury from calorie intake. Dietary restriction has been shown to have several health benefits including increased insulin sensitivity, stress resistance, reduced morbidity, and increased life span. The mechanism remains unknown, but the need for a long-term reduction in caloric intake to achieve these benefits has been assumed. We report that when C57BL6 mice are maintained on an intermittent fasting (alternate-day fasting) dietary-restriction regimen their overall food intake is not decreased and their body weight is maintained. Nevertheless, intermittent fasting resulted in beneficial effects that met or exceeded those of caloric restriction including reduced serum glucose and insulin levels and increased resistance of neurons in the brain to excitotoxic stress. Intermittent fasting therefore has beneficial effects on glucose regulation and neuronal resistance to injury in these mice that are independent of calori! c intake.

Exp Gerontol. 2003 May;38(5):519-27 Ageing-related changes in the in vivo function of rat liver macroautophagy and proteolysis. Autophagy is a universal, highly regulated mechanism responsible for the degradation of long-lived proteins, cytomembranes and organelles during fasting and may be the cell repair mechanism that mediates the anti-ageing effects of calorie restriction (Bergamini and Gori, 1995). The function of autophagy was studied in vivo on male Sprague Dawley rats fed ad libitum or 40% food restricted. Autophagy was induced in overnight fasted rats by the injection of an anti-lipolytic agent and was investigated by electron microscopy. Changes in regulatory plasma nutrients and hormones were assessed and rate of proteolysis was calculated from the release of 14C(6)-valine from pre-labelled resident proteins. Results in rats fed ad libitum showed that autophagic-proteolytic response to antilypolitic agents was paramount in one month-o! ld rats; was high but delayed in 2 month-old rats, decreased remarkab ly in 6 month-old rats and almost negligible at older age. Parallel ageing-related changes were observed in the effects of treatment lowering glucose and insulin plasma levels. Calorie restriction prevented all changes. In view of the known suppressive effects of insulin, it may be concluded that the age-changes of autophagy are secondary to the ageing-related alteration in glucose metabolism and hormone levels, whose appearance is delayed by calorie restriction. Data may support the hypothesis that ad libitum feeding accelerates the rate of ageing by raising insulin plasma levels and suppressing autophagy and membrane maintenance, and that calorie restriction may break this vicious circle.

Exp Mol Pathol. 1987 Feb;46(1):114-22. Increased degradation in rat liver induced by antilipolytic agents: a model for studying autophagy and protein degradation in liver? A dramatic increase in the plasma glucagon/insulin ratio can be induced by treating fasted rats wi! th antilipolytic drugs (e.g., with 3,5-dimethylpyrazole, 12 mg/kg body wt). These hormone changes are the physiologically appropriate response to a rapid decrease in free fatty acids and glucose plasma levels. Under this experimental condition, many vacuolated lysosomes can be observed at the electron microscopic level as early as 30 min and autophagic vacuoles are detectable in the liver cells 1 hr after the administration of the drug. By 1 hr and 45 min, vacuoles often contain recognizable peroxisomes. At the biochemical level, liver proteolysis in vitro is increased significantly. Very interestingly, changes in peroxisomal (but not mitochondrial or reticulum or cytosolic) enzyme activities are detected that are preventable by the administration of glutamine (i.e., of an inhibitor of proteolysis in vivo) but not by an isocaloric amount of glycine or alanine. It is concluded that the administration of antilipolytic agents to fasted animals may provide a conve! nient (i.e., an inexpensive, highly reproducible and timable) physiol ogic model to study hormone-induced autophagy in liver cells.

J Nutr Biochem. 2005 Mar;16(3):129-37. Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. Intermittent fasting (IF; reduced meal frequency) and caloric restriction (CR) extend lifespan and increase resistance to age-related diseases in rodents and monkeys and improve the health of overweight humans. Both IF and CR enhance cardiovascular and brain functions and improve several risk factors for coronary artery disease and stroke including a reduction in blood pressure and increased insulin sensitivity. Cardiovascular stress adaptation is improved and heart rate variability is increased in rodents maintained on an IF or a CR diet. Moreover, rodents maintained on an IF regimen exhibit increased resistance of heart and brain cells to ischemic injury in experimental models of myocardial infarction and stroke. The beneficial effects of ! IF and CR result from at least two mechanisms--reduced oxidative damage and increased cellular stress resistance. Recent findings suggest that some of the beneficial effects of IF on both the cardiovascular system and the brain are mediated by brain-derived neurotrophic factor signaling in the brain. Interestingly, cellular and molecular effects of IF and CR on the cardiovascular system and the brain are similar to those of regular physical exercise, suggesting shared mechanisms. A better understanding of the cellular and molecular mechanisms by which IF and CR affect the blood vessels and heart and brain cells will likely lead to novel preventative and therapeutic strategies for extending health span.

Biochim Biophys Acta. 1985 Mar 29;839(1):96-104 Effects of antilipolytic agents on rat liver peroxisomes and peroxisomal oxidative activities. The mechanisms involved in the inhibitory effects of antilipolytic agents on rat liver peroxisomal fatty acid oxida! tive activity have been explored. Treatment of fasting rats with anti lipolytic drugs (either 3,5-dimethylpyrazole (12 mg/kg body weight) or Acipimox (25 mg/kg body weight] resulted in a decrease in free fatty acid and glucose plasma levels within 5-10 and in a significant increase in the plasma glucagon to insulin ratio within 15. Changes in the fatty acid oxidative activity appeared with a 2.5-3 h delay and were then very rapid (a 30-40% decrease in the activity occurred in additional 2 h). Many peroxisomal enzyme activities (including non-beta-oxidative activities such as uricase and D-amino acid oxidase) exhibited similar changes with the same delay. Simultaneously with the enzyme changes, at the electron microscope level many autophagic vacuoles were detected in the liver cells, often containing peroxisomal structures. Glutamine, an inhibitor of proteolysis in vivo, prevented the decrease in enzyme activities. It was concluded that the decrease in peroxisomal enzyme activities may be the consequence of enhanced peroxisome de! gradation due to the stimulation of autophagic processes in liver cells.


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