We previously found that rapid declines in food intake and body weight were accompanied by significant cold-exposed hypothermia in aging male F344 rats In this study, we tested the hypothesis that the thermogenic responses of isolated brown adipocytes would be significantly decreased in older rats showing rapid weight loss vs. those that did not. Male and female F344 rats were obtained at 23 mo of age and body weights measured every 2-3 days up to 26 mo. Rats showing rapid declines in body weight (loss of 0.9-4.5% of baseline body weight/day; median loss = 1.4% per day) were killed for brown adipocyte isolations (total weight loss ranged from 7-20%). The age at which this rapid weight loss began ranged from 23-26 months. Brown adipocytes were also isolated from 26 mo old rats that were weight-stable. Rates of oxygen consumption were measured polarigraphically in response to norepinephrine (NE) and CL 316,243 (a specific β3-agonist) Interscapular BAT weight (mg BAT/g body weight) of rapid weight loss rats was 33% lower in males and 59% lower in females compared with their weight-stable 26 mo counterparts. Similarly, maximal rates of NE- and CL 316,243-stimulated respiration of brown adipocytes from rats with rapid weight loss were 33-40% less than those of adipocytes from weight-stable 26 mo rats, with no apparent gender differences. Maximal rates of NE-stimulated respiration (nmol O2/min/106 cells) for females: 351 ±47 (rapid weight loss), 579 ±26 (weight stable); and for males: 467 ± 124 (rapid weight loss), 689 ±44 (weight stable). These data indicate that attenuated cold-exposed thermoregulatory ability of older rats with rapid weight loss involves altered metabolic properties of brown adipocytes themselves.
|Original language||English (US)|
|State||Published - 1996|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology