Objectives: White adipose tissue (WAT) expands through hypertrophy (increased adipocyte size) and/or hyperplasia (increased adipocyte number). Hypertrophy has been associated with insulin resistance and dyslipidemia independently of body composition and fat distribution. In contrast, hyperplasia protects against metabolic alterations. Proanthocyanidins, which are the most abundant flavonoids in the human diet, improve metabolic disturbances associated with diet-induced obesity without reducing body weight or adiposity. The aim of this study was to determine whether grape seed proanthocyanidin extract (GSPE) can modulate WAT expandability. Because GSPE also contains gallic acid, we also studied the capacity of gallic acid to remodel WAT.
Design: Male Wistar rats were fed a standard chow diet (n=6) or a cafeteria diet (CAF) for 11 weeks. After 8 weeks, the CAF-fed animals were supplemented with 25 mg GSPE/kg body weight (n=6), 7 mg gallic acid/kg body weight (n=6) or the vehicle (n=6) for 3 weeks. Histological analyses were performed in the retroperitoneal (rWAT) and inguinal (iWAT) WAT to determine adipocyte size and number. Specific markers for adipogenesis and WAT functionality were analysed in rWAT using quantitative RT-PCR.
Results: GSPE or gallic acid supplementation did not reduce weight gain or reverse and adiposity. However, GSPE reduced adipocyte size significantly in rWAT and moderately in iWAT and tripled the adipocyte number in rWAT. Gallic acid slightly reduced adipocyte size in rWAT and iWAT and doubled the adipocyte number in both WATs. In accordance with this adipogenic activity, Pref-1 and PPARγ tended to be overexpressed in rWAT of rats supplemented with GSPE. Moreover, GSPE supplementation increased Plin1 and Fabp4 expression and restored adiponectin expression completely, indicating a better functionality of visceral WAT.
Conclusions: GSPE supplementation has anti-hypertrophic and hyperplasic activities in rats with established obesity, mainly in visceral WAT inducing a healthier expansion of WAT to match the surplus energy provided by the cafeteria diet.