Abstract
BackgroundIn mammals, calories ingested in excess of those used are stored primarily as fat in adipose tissue; consistent ingestion of excess calories requires an enlargement of the adipose tissue mass. Thus, a dysfunction in adipose tissue growth may be a key factor in insulin resistance due to imbalanced fat storage and disrupted insulin action. Adipose tissue growth requires the recruitment and then the development of adipose precursor cells, but little is known about these processes in vivo.MethodologyIn this study, adipose cell-size probability distributions were measured in two Zucker fa/fa rats over a period of 151 and 163 days, from four weeks of age, using micro-biopsies to obtain subcutaneous (inguinal) fat tissue from the animals. These longitudinal probability distributions were analyzed to assess the probability of periodic phenomena.ConclusionsAdipose tissue growth in this strain of rat exhibits a striking temporal periodicity of approximately days. A simple model is proposed for the periodicity, with PPAR signaling driven by a deficit in lipid uptake capacity leading to the periodic recruitment of new adipocytes. This model predicts that the observed period will be diet-dependent.
Highlights
The functional character of adipose tissue is of topical interest, given the marked increase in obesity that has been noted in much of the developed world
A simple model is proposed for the periodicity, with PPAR signaling driven by a deficit in lipid uptake capacity leading to the periodic recruitment of new adipocytes
While the causes and consequences of this increase in obesity are the subject of debate, it is incontrovertible that obesity is an enlargement of adipose tissue to store excess energy intake
Summary
The functional character of adipose tissue is of topical interest, given the marked increase in obesity that has been noted in much of the developed world. Adipose tissue obesity phenotypes are influenced by developmental stage, diet, and genetics, as well as by their interactions [4,5,6,7,8,9,10,11,12,13]. Much of this literature draws conclusions from studies of the mean sizes or other averaged characteristics of adipose cells. Adipose tissue growth requires the recruitment and the development of adipose precursor cells, but little is known about these processes in vivo
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