Abstract

Introduction: The mass of adipose tissue expands during weight gain mostly because of an increase in fat cell diameter, which is one of the most important determinants of tissue metabolism. The aim of this study was to examine the effects of aging associated with weight gain on cell size and heterogeneity of adipocytes at different fat depots. Materials and Methods: Adipose tissues were harvested from subcutaneous (SC), retroperitoneal (RP), perirenal (PR), proximal epididymal (PE) and distal epididymal (DE) regions of two groups of rats with a 30-day difference in age and 36% increase in body weight. Diameters of fat cells were measured using a microscope equipped with a calibrated micrometer. Cell size heterogeneity was deduced from coefficient of variation. Results: In both groups, no significant regional differences were observed in diameter of adipocytes in various fat depots. With the exception of the RP depot, the weight gain caused a significant increase in diameter of adipocytes in all other depots. The highest and the lowest increase were seen in PR and RP adipocyte diameter, respectively. The degree of heterogeneity of fat depots was not significantly altered by weight gain. Conclusion: Aging associated with weight gain leads to fat cell hypertrophy in a depot specific manner, and cells at depots close to survival organs such as kidney and gonads are more affected than those of the other depots. The results of this study can enhance current knowledge on adipose tissue mass expansion and its related health complications such as cardiovascular diseases and diabetes.