Metabolic features of diet-induced obesity without hyperphagia in young rats.
Diet-induced obesity (DIO) developed in 1-mo-old male Sprague-Dawley rats over an 8-wk period on a relatively high-fat (16%) high-calorie (4.6 kcal/g) diet (DIO diet). Percent carcass lipid (56%) and body weight gain (15%) were greater, whereas food intake was decreased over the first 3-5 wk in DIO diet-compared with chow-fed controls. Overall, 8-wk body weight gain (15%), percent carcass lipid (26%), and feed efficiency (15%) were greater, but food intake was not increased. Norepinephrine (NE) turnover rate, indicative of organ sympathetic activity, increased in interscapular brown adipose tissue (IBAT; 57-218%), heart (21-44%), and pancreas (25%) during the first 3 wk and remained elevated for the entire 8 wk. IBAT weight (51%) and in vitro lipolytic capacity (68%) increased by 1 wk and brown adipocyte size (43%) by 3 wk; IBAT thermogenic capacity (maximal NE-stimulated in vitro O2 consumption) increased by 5 wk (39%). Plasma insulin levels were similar in both diet groups over the entire 8-wk period. Why DIO diet-fed rats had increased metabolic efficiency is unknown, but activation of IBAT metabolism and thermogenesis failed to prevent the development of DIO.
D002001:Adipose Tissue, Brown / Q000378:metabolism; D000818:Animals; D001835:Body Weight; D004032:Diet; D004435:Eating; D007328:Insulin / Q000097:blood; D008297:Male; D009638:Norepinephrine / Q000378:metabolism; D009765:Obesity / Q000097:blood / Q000209:etiology / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D007328:Insulin; D009638:Norepinephrine