Circadian Neuroendocrine Role in Age-Related Changes in Body Fat Stores and Insulin Sensitivity of the Male Sprague-Dawley Rat |
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Authors: | Anthony H Cincotta Bradford C Schiller Roger J Landry Stephen J Herbert Wendell R Miers Albert H Meier |
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Institution: |
a The Wellman Laboratories of Photomedicine, Maxsachusetts General Hospital,
b The Department of Dermatology, Harvard Medical School, Boston, Massachusetts
c The Department of Zoology and Physiology, Louisiana Stale University, Baton Rouge, Louisiana, USA |
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Abstract: | A role for circadian neuroendocrine rhythms in the age-related development of obesity and insulin resistance was investigated in the male Sprague-Dawley rat. The phases and amplitudes of the plasma rhythms of several metabolic hormones (i.e. corticosterone, prolactin, insulin, and triiodothyronine) differed in lean, insulin-sensitive (3-week-old rats). insulin-resistant (8-week-old rats) and obese, insulin-resistant (44-week-old rats) animals. Simulation of the daily rhythms of endogenous corticosterone and prolactin by daily injections of the hormones at times corresponding to the peak levels found in 3-week-old rats reversed age-related increases in insulin resistance and body fat in older (5-6-month-old) rats. Ten such daily injections of corticosterone and prolactin in 12-14-week-old rats produced long-term reductions in body fat stores (30%). plasma insulin concentration (40%'). and insulin resistance (60%) (determined by a glucose tolerance test) measured 11-14 weeks after the treatment. Alterations in circadian neuroendocrine rhythms may account for age-related changes in carbohydrate and lipid metabolism in the male Sprague-Dawley rat, and resetting of these rhythms by appropriately timed daily injections of corticosterone and prolactin may help maintain metabolism characteristic of younger animals. |
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Keywords: | Circadian rhythms Insulin resistance Metabolism Prolactin Corticosterone Obesity Aging |
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