RESISTANCE TO AGING-ASSOCIATED OBESITY IN CAPSAICIN-DESENSITIZED RATSONE-YEAR AFTER TREATMENT

Previous studies demonstrated reduced weight of abdominal white adipos e tissue depots and of carcass fat in capsaicin-desensitized (Cap-Des) rats up to 8 months after treatment, The objective of the present stu dy was to find out whether aging-associated obesity and hyperplasia of retroperitoneal white adipose tissue was prevented in older (13.5 mon th old) Cap-Des rats, one year after treatment with Cap (done when the y were 1.5 months old), The prevalence of obesity is known to increase in rats by this age, Abdominal white adipose tissue depots weighed le ss in old Cap-Des rats, both epididymal (9% less) and retroperitoneal (30% less), The number of mature white adipocytes was 28% less in the retroperitoneal depot but was not significantly different in the epidi dymal depot, Adipocyte size was not different, Carcass fat was less, b oth total and as percent of body weight, Food intake was normal for th eir reduced body size, The exponential increase in retroperitoneal whi te adipose tissue weight characteristic of aging rats that are becomin g obese was virtually absent in Cap-Des rats, We conclude that lack of function of capsaicin-sensitive afferent autonomic nerves, known to b e destroyed in Cap-Des rats, results in an alteration in energy balanc e conducive to leanness, We suggest that the attenuated age-associated increase in circulating CGRP (derived mainly from capsaicin-sensitive nerves) in the Cap-Des rat results in a lower degree of aging-associa ted insulin-resistance, hence in a lesser degree of obesity.