a b s t r a c t GPR41 is reportedly expressed in murine adipose tissue and mediates short chain fatty acid (SCFA)-stimulated leptin secretion by activating Ga i . Here, we agree with a contradictory report in finding no expression of GPR41 in murine adipose tissue. Nevertheless, in the presence of adenosine deaminase to minimise Ga i signalling via the adenosine A1 receptor, SCFA stimulated leptin secretion by adipocytes from wild-type but not GPR41 knockout mice. Expression of GPR43 was reduced in GPR41 knockout mice. Acetate but not butyrate stimulated leptin secretion in wild-type mesenteric adipocytes, consistent with mediation of the response by GPR43 rather than GPR41. Pertussis toxin prevented stimulation of leptin secretion by propionate in epididymal adipocytes, implicating Ga i signalling mediated by GPR43 in SCFA-stimulated leptin secretion.

Background-Although there is strong evidence that plasma HDL levels correlate inversely with the incidence of coronary artery disease, the precise mechanism(s) for the protective effect of HDLs remains unclear. We recently showed that HDLs inhibit endothelial cell expression of cytokine-induced leukocyte adhesion molecules in vitro. Our study therefore sought to test the hypothesis that elevating the level of circulating HDLs would inhibit endothelial cell activation in vivo. Methods and Results-We used a porcine model of inflammation previously established in our laboratory, in which the level of vascular endothelial cell expression of E-selectin in interleukin (IL)-1␣-induced skin lesions was measured by the uptake of a radiolabeled anti-E-selectin antibody (1.2B6). Porcine plasma HDL levels were elevated by use of a bolus injection of reconstituted discoidal HDL (recHDL). These particles resemble nascent HDL particles in shape and contain apolipoprotein A-I as the sole protein and soybean phosphatidylcholine as the sole phospholipid. We found that recHDLs inhibited the expression of IL-1␣-induced E-selectin by porcine aortic endothelial cells in vitro, confirming that the inhibitory effect is conserved with synthetic HDLs and demonstrating that the phenomenon is not restricted to human endothelial cells. In vivo, elevating the circulating level of HDLs Ϸ2-fold led to significant inhibition of basal and IL-1␣-induced E-selectin expression by porcine microvascular endothelial cells. Conclusions-These observations demonstrate the potential anti-inflammatory action of HDLs and provide support for the further investigation of the mechanisms underlying the inhibitory effects of HDLs on endothelial cell activation.

Here we demonstrate for the first time that plasma chemerin levels are significantly heritable and identified a novel role for chemerin as a stimulator of angiogenesis.