Endocrine Abstracts

Propionate upregulates leptin synthesis through the G protein-coupled receptor 41 (GPR41) in mice. In contrast to monogastric mammals, ruminants almost entirely depend on short chain fatty acids as energy source, but the reports about the physiological relevance of propionate for leptin secretion in these species are controversial and the importance of the GPR41 for its regulation is not yet clarified. Here we characterise the effects of intravenously infused propionate on the leptin system and on GPR41 mRNA in goats. Castrated male goats (Deutsche-Edelziege, 10 to 12 months old) were allocated to infusions through jugular catheters after an over-night fast. They received propionate infusion (96 μmol/kg*min; n=8) or NaCl-solution of the equivalent Na-concentration (n=5). After recording leptin baseline concentrations for 1 h, infusions were carried out for 260 minutes. Blood samples were collected in 10 to 15 min intervals and analyzed for leptin by ELISA. The mRNA of leptin, leptin receptor (long form) and GPR41 from subcutanous adipose tissue (SAT) and perirenal adipose tissue (PAT) were quantified by real-time PCR after euthanasia (propionate group: n=4; NaCl group: n=5). Repeated measurement analysis of serum leptin values showed an increase in the propionate versus the control group (P<0.05). Estimation of the mRNA expression data indicated a tendency for an increase of leptin mRNA in PAT (P=0.081) but not in SAT (P=0.106). The leptin receptor mRNA decreased in PAT (P=0.042) and in SAT, the latter decrease, however, did not reach the level of significance (P=0.286). GPR41 mRNA was elevated in SAT (P=0.029) but not in PAT (P=0.756). The differential response of GPR41 mRNA in SAT versus PAT towards propionate might be involved in the regulation of the leptin system whereby the decrease of leptin receptor mRNA might be attributable to the increasing serum concentrations of leptin.