Individual severity of dietary obesity in unselected Wistar rats: relationship with hyperphagia.
We investigated the relative importance of overeating, thermogenesis, and uncoupling protein (UCP) expression in determining the severity of obesity in male Wistar rats fed a highly palatable diet. After 2 wk of feeding, body weight did not differ significantly from controls (248 +/- 4 vs. 229 +/- 3 g; P > 0.3), but rectal temperature, brown adipose tissue (BAT) mass, UCP3 expression in gastrocnemius muscle, and UCP2 expression in white adipose tissue (WAT) were all elevated in diet-fed animals. In a further study, rats fed a palatable diet for 8 wk exhibited higher energy intake and rectal temperature than controls. Dietary-obese rats were divided into high (427-490 g; n = 8) and low (313-410 g; n = 10) weight gainers. The high gainers ate significantly more than the low gainers, and energy intake was positively correlated with weight gain (r(2) = 0.72, P < 0.01). UCP2 and UCP3 mRNA levels in gastrocnemius muscle were significantly increased above lean controls in all diet-fed animals, whereas UCPs in WAT and BAT did not differ significantly from controls. Whereas rats fed palatable food exhibited a thermogenic response, there was no significant difference in core temperature between high and low gain groups (37. 5 +/- 0.1 vs. 37.6 +/- 0.1 degrees C; P > 0.5). We conclude that a higher energy intake is the critical factor determining susceptibility to dietary obesity in unselected Wistar rats.
Diabetes and Endocrinology Research Group, Department of Medicine, University of Liverpool, Liverpool L69 3GA, United Kingdom. harrold@liverpool.ac.uk
J A
JA
Harrold
P S
PS
Widdowson
J C
JC
Clapham
G
G
Williams
D002001:Adipose Tissue, Brown / Q000502:physiology; D000818:Animals; D001823:Body Composition / Q000502:physiology; D001831:Body Temperature / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D002352:Carrier Proteins / Q000096:biosynthesis; D004032:Diet; D002149:Energy Intake / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000032:analysis / Q000097:blood; D006153:Guanosine Diphosphate / Q000378:metabolism; D006963:Hyperphagia / Q000378:metabolism*; D007328:Insulin / Q000097:blood; D007473:Ion Channels; D020738:Leptin / Q000097:blood; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis; D026901:Membrane Transport Proteins; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins; D018482:Muscle, Skeletal / Q000737:chemistry; D009765:Obesity / Q000097:blood / Q000209:etiology / Q000378:metabolism*; D014176:Protein Biosynthesis; D051381:Rats; D017208:Rats, Wistar; D014280:Triglycerides / Q000032:analysis / Q000097:blood; D000071256:Uncoupling Protein 1; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3
D002352:Carrier Proteins; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D007473:Ion Channels; D020738:Leptin; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D014280:Triglycerides; C000604391:Ucp2 protein, rat; C000604394:Ucp3 protein, rat; D000071256:Uncoupling Protein 1; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3; D006153:Guanosine Diphosphate