It has recently been discovered that G protein-coupled receptors (GPCR) 41 and 43 are characterized by having the short chain fatty acids acetate and propionate as their ligands. The objective of this study was to investigate the involvement of GPCR41, GPCR43, and their ligands in the process of adipogenesis. We measured the levels of GPCR41 and GPCR43 mRNA in both adipose and other tissues of the mouse. GRP43 mRNA expression was higher in four types of adipose tissue than in other tissues, whereas GPCR41 mRNA was not detected in any adipose tissues. A high level of GPCR43 expression was found in isolated adipocytes, but expression level was very low in stromal-vascular cells. Expression of GPCR43 was up-regulated in adipose tissues of mice fed a high-fat diet compared with those fed a normal-fat diet. GPCR43 mRNA could not be detected in confluent and undifferentiated 3T3-L1 adipocytes; however, the levels rose with time after the initiation of differentiation. GPCR41 expression was not detected in confluent and differentiated adipocytes. Acetate and propionate treatments increased lipids present as multiple droplets in 3T3-L1 adipocytes. Propionate significantly elevated the level of GPCR43 expression during adipose differentiation, with up-regulation of PPAR-gamma2. Small interfering RNA mediated a reduction of GPCR43 mRNA in 3T3-L1 cells and blocked the process of adipocyte differentiation. In addition, both acetate and propionate inhibited isoproterenol-induced lipolysis in a dose-dependent manner. We conclude that acetate and propionate short chain fatty acids may have important physiological roles in adipogenesis through GPCR43, but not through GPCR41.

Our results suggest that the bone mineral distribution of the proximal tibia is directly affected but lumbar BMD is not influenced by the local mechanical stress around the knee with medial compartment OA.

The kinetic and kinematic effects of wearing of lateral wedged insoles were significant in Kellgren-Lawrence grades I and II knee OA. The results support the recommendation of use of lateral wedged insoles for patients with early and mild knee OA.

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