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.
Harrold
J A
JA
Diabetes and Endocrinology Research Group, Department of Medicine, University of Liverpool, Liverpool L69 3GA, United Kingdom. harrold@liverpool.ac.uk
Widdowson
P S
PS
Clapham
J C
JC
Williams
G
G
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