Brown Adipose Tissue Reduction and Overfeeding Impact on Adipose Cellularity

Abstract

Cafeteria overfeeding of normally lean rats during early postweaning growth results in hyperplasia and increased thermogenesis in Brown Adipose Tissue (BAT). Most studies have focused on the Interscapular BAT depot, which represents approximately one third of the total BAT in lean rats. To determine the effects of overnutrition via a Café overfeeding regimen combined with removal of the thermogenic potential of the Interscapular Brown Adipose Tissue (IBAT) depot on Adipose Tissue (AT) cellularity, groups (n=6 rats/group) of normally lean 4-week-old Sprague-Dawley rats were maintained on a Purina Chow diet (CHOW) or offered a cafeteria diet (Café) supplement for 52 days during postweaning growth and development. An additional group of the Café diet groups was subjected to surgical removal of their IBAT at 4 weeks of age and continued on the Café diet regimen (Café-IBAT). Measures of body weight (BW) and biometry were obtained at periodic intervals. At the end of the study, abdominal and subcutaneous adipose tissue depots were dissected in their entirety and measures of adipose tissue cellularity determined. BW of Café > CHOW and BW of Café were similar to Café-IBAT. Torso length was similar in all groups, but mid-abdominal girth and Girth to Torso ratios were similarly increases in Café and Café-IBAT. The mass of Epididymal (EPI), Retroperitoneal (RP), Mesenteric (MES), Dorsal (DOR) and Inguinal (ING) fat pads of Café- >>CHOW-fed rats, with further increases in DOR, ING and total fat pad mass in the Cafe IBAT group. The AT cell number of Café > CHOW in DOR, ING and RP and unchanged by diet regimen in EPI. Adipocyte lipid content of Café >CHOW in all depots and increased further in DOR, EPI and RP, while differences in cell diameter were similar to the measures of cell lipid content. In addition, surgical reduction of IBAT resulted in further increases in the mass, cell size and cell lipid content of the ING subcutaneous depot. These results indicate that overfeeding results in greater adiposity characterized by differential cellular effects in abdominal and subcutaneous depots, with the greatest increase in diet induced adipocyte hyperplasia in the inguinal, dorsal and retroperitoneal depots. In conclusion, while adipocyte hypertrophy occurred in all depots studied, the partial reduction of BAT mass following IBAT removal resulted in an only modest additional impact on overall adiposity during overfeeding, with the greatest impact in the ING subcutaneous depot and thereby consistent with potential thermogenic compensation in other BAT depots to minimize the impact of the Café feeding regimen on developing adiposity.