Modification of RXRalpha expression according to the duration of a cafeteria diet

PPAR-γ2 Expression in Response to Cafeteria Diet: Gender- and Depot-Specific Effects

OBJECTIVE

To investigate the effects of short-term cafeteria (CAF) diet feeding on the expression of adipogenic transcription factors and their association with adiposity.

RESEARCH METHODS AND PROCEDURES

Four-week-old male and female Wistar rats were fed CAF diet or standard chow for 2 weeks. Body weight, energy intake, tissue weights, and serum parameters were determined. Peroxisome proliferator-activated receptor (PPAR)-gamma2, PPARalpha, CCAAT enhancer-binding protein-alpha, and adipocyte differentiation and determination factor 1 mRNAs in gonadal white adipose tissue (gWAT) (visceral depot) and inguinal white adipose tissue (iWAT) (subcutaneous depot) and in interscapular brown adipose tissue were measured by reverse transcription-polymerase chain reaction.

RESULTS

Short-term CAF diet feeding resulted in increases in body weight, adipose tissue weights, and lipid serum levels. Increased adiposity was more related to an increase in visceral fat than an increase in subcutaneous fat. This difference was associated with a higher expression of key adipogenic transcription factors (mainly PPARgamma2 and CCAAT enhancer-binding protein-alpha) in gWAT when compared with iWAT. Higher hypertrophy of gWAT was found in females, whereas males showed a higher hypertrophy of iWAT. Differential gender and depot response to CAF diet could be explained by depot and gender differential expression of key adipogenic transcription factors, especially PPARgamma2. Hence, reduced hypertrophy of female iWAT and defective thermogenesis in interscapular brown adipose tissue in response to CAF diet were related to decreased PPARgamma2 mRNA levels, whereas increased hypertrophy in male iWAT and gWAT and in female gWAT was related to a tendency toward increased PPARgamma2 mRNA levels in response to overfeeding.

DISCUSSION

Our results suggest the involvement of PPARgamma2 in gender- and depot-specific effects of CAF diet on development and function in adipose tissues.

Serum and gene expression levels of leptin and adiponectin in rats susceptible or resistant to diet-induced obesity

The aim of the present study was to identify the role of leptin and adiponectin in the development of resistance or susceptibility to diet-induced obesity in rats. For this purpose, male Wistar rats were fed with standard laboratory diet (control group) or cafeteria diet. After 15 days, two groups of rats with different response respect to the cafeteria diet were identified, and were assigned as diet-induced obesity (DIO) and diet resistant (DR) rats. The high-fat diet induced a very significant increase in both body and fat mass weight in DIO group. However, DR rats, gained even less weight than control-fed animals. Food intake was increased in cafeteria-fed rats (both DIO and DR) in comparison to control group; but hyperphagia was higher in DIO rats. In addition, feed efficiency (the ratio of weight gained to calories consumed) was significantly decreased in DR as compared to DIO rats. Regarding leptin, a significant increase in both adipose tissue gene expression and serum levels was observed in DIO rats in comparison with other groups (control and DR). A significant increase in both adiponectin circulating levels and adipose tissue mRNA expression was also observed in DIO animals as compared with the other groups. These data suggest that the susceptibility to obesity of DIO rats might be secondary, at least in part, to an earlier development of leptin resistance, which could lead to alterations in food intake (hyperphagia) and energetic metabolism. However, neither changes in leptin or adiponectin seem to be involved in the adaptive mechanisms that confer resistance to high fat intake.