Maternal perinatal undernutrition programs a "brown-like" phenotype of gonadal white fat in male rat at weaning

Several studies indicate that maternal undernutrition sensitizes the offspring to the development of metabolic disorders, such as obesity. Using a model of perinatal maternal 50% food-restricted diet (FR50), we recently reported that rat neonates from undernourished mothers exhibit decreased leptin plasma levels associated with alterations of hypothalamic proopiomelanocortin system. The present study aimed at examining the consequences of FR50 on the brain-adipose axis in male rat neonates. Using quantitative RT-PCR array containing 84 obesity-related genes, we demonstrated that most of the genes involved in energy metabolism regulation are expressed in rat gonadal white adipose tissue (WAT) and are sensitive to maternal perinatal undernutrition (MPU). In contrast, hypothalamic gene expression was not substantially affected by MPU. Gene expression of uncoupling protein 1 (UCP1), a marker of brown adipocytes, showed an almost 400-fold stimulation in postnatal day 21 (PND21) FR50 animals, suggesting that their gonadal WAT possesses a brown-like phenotype. This was confirmed by histological and immunoshistochemical procedures, which demonstrated that PND21 FR50 gonadal adipocytes are multilocular, resembling those present in interscapular brown adipose tissue, and exhibit an overexpression of UCP1 and neuropeptide Y (NPY) at the protein level. Control animals contained almost exclusively "classical" unilocular white adipocytes that did not show high UCP1 and NPY labeling. After weaning, FR50 animals exhibited a transient hyperphagia that was associated with the disappearance of brown-like fat pads in PND30 WAT. Our results demonstrate that MPU delays the maturation of gonadal WAT during critical developmental time windows, suggesting that it could have long-term consequences on body weight regulation in the offspring.