Histological Influences of Food Restriction on Brown Adipose Tissue in Young OLETF Rats

Abstract

Whitening of brown adipose tissue (BAT) promotes obesity and causes obesity‐related health problems. It has been suggested that food restriction can prevent BAT whitening and inhibit the decline of BAT function with obesity. However, details of the histological feature remain unknown. The purpose of the present study was to investigate the influences of food restriction during childhood on histological features of BAT in Otsuka Long‐Evans Tokushima fatty (OLETF) rats.Male OLETF rats and Long‐Evans Tokushima Otsuka (LETO) rats were used as models of obesity and non‐obesity, respectively. OLETF rats were divided into the food restriction and ad libitum feeding groups. OLETF rats with food restriction were received the daily average amount of food consumed by same‐age LETO rats. The others were fed ad libitum with standard laboratory rodent chow from 4‐ to 20‐week‐old. At 20‐week‐old, the BAT was collected from the interscapular region and the sections were stained with hematoxylin and eosin for histological observation. This study was approved by the Institutional Animal Care and Use Committee of Hiroshima University (A19‐163) and conducted in accordance with the Hiroshima University Regulations for Animal Experimentation. All experiments complied with the National Institute of Health Guidelines for the Care and Use of Laboratory Animals.Body weight of OLETF rats ad libitum feeding was significantly higher than those of LETO rats and OLETF rats with food restriction at 20‐week‐old. Enlarged unilocular adipocytes were often located in the peripheral area of the adipose lobule, the number appeared to be higher in OLETF rats ad libitum feeding than in LETO rats. Although the number of whitened unilocular adipocytes located in the central area was significantly lower in OLETF rats with food restriction than in OLETF rats ad libitum feeding, the number of enlarged unilocular adipocytes located in the peripheral area was a bit less in OLETF rats with food restriction.These results suggest that BAT whitening in young OLETF rats is started from the peripheral area of the adipose lobule, adipocytes located in the central area of the lobule translate from multilocular to unilocular with the progression of hyperphagia‐induced obesity.