Effects of food restriction on peroxisome proliferator-activated receptor-gamma and glucocorticoid receptor signaling in adipose tissues of normal rats.
In adipocytes, peroxisome proliferator-activated receptor (PPAR)-gamma activates adipocyte differentiation and glucocorticoid (GC) stimulates the expression of PPAR-gamma mRNA. The local tissue concentrations of GC, in turn, are modulated by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). To clarify the change of energy metabolism in condition of reduced energy intake, we investigated whether food restriction alters the adipocyte size and levels of PPAR-gamma, GC receptor (GR), and 11beta-HSD1 mRNA expression in the white adipose tissues of normal rats. Male Wistar rats weighing 340 g were housed under free feeding or 20% reduction of food intake for 2 or 14 days. We found that 2-day food restriction did not cause any change in the mean size or number of adipocytes in the omentum, while 14-day food restriction decreased the size and increased the number of adipocytes. In addition, the levels of PPAR-gamma2, GR, and 11beta-HSD1 mRNA expression in the omentum were lower in the food-restricted rats after 2 days, while they did not differ after 14 days. Also, after both 2 and 14 days, plasma concentrations of free fatty acid (FFA) were higher in the food-restricted rats than in control rats. Finally, plasma concentrations of adrenocorticotropin (ACTH) and corticosterone were the same in the both groups after 2 days, although they were higher in the food-restricted rats after 14 days. These results suggest that adipocyte differentiation in the omentum of food-restricted rats is attenuated after 2 days but recovers after 14 days, resulting in an increase in the number of small adipocytes. It is also likely that lipolysis induced during the 14-day period of food restriction decreased the size of adipocytes. Further, food restriction may affect the efficiency of local GC effects by altering GR and 11beta-HSD1 mRNA expression. Also, higher levels of plasma GC and recovery of GR and 11beta-HSD1 mRNA expression may contribute to the recovery of the levels of PPAR-gamma2 mRNA expression in the omentum and result in the recovery of adipocyte differentiation.
Arai
Keiko
K
Department of Physiology, Nippon Medical School, Tokyo, Japan.
Soga
Tomoko
T
Ohata
Hisayuki
H
Otagiri
Asuka
A
Shibasaki
Tamotsu
T
D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1 / Q000235:genetics; D017667:Adipocytes / Q000166:cytology; D000273:Adipose Tissue / Q000033:anatomy & histology / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D001835:Body Weight; D002452:Cell Count; D048429:Cell Size; D003345:Corticosterone / Q000097:blood; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005508:Food Deprivation / Q000502:physiology*; D008297:Male; D009852:Omentum; D009929:Organ Size; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000502:physiology*; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
D005230:Fatty Acids, Nonesterified; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D011965:Receptors, Glucocorticoid; D014157:Transcription Factors; D000324:Adrenocorticotropic Hormone; D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1; D003345:Corticosterone