The Effects of Propionate and Valerate on Insulin Responsiveness for Glucose Uptake in 3T3-L1 Adipocytes and C2C12 Myotubes via G Protein-Coupled Receptor 41

Abstract

Since insulin resistance can lead to hyperglycemia, improving glucose uptake into target tissues is critical for regulating blood glucose levels. Among the free fatty acid receptor (FFAR) family of G protein-coupled receptors, GPR41 is known to be the Gαi/o-coupled receptor for short-chain fatty acids (SCFAs) such as propionic acid (C3) and valeric acid (C5). This study aimed to investigate the role of GPR41 in modulating basal and insulin-stimulated glucose uptake in insulin-sensitive cells including adipocytes and skeletal muscle cells. Expression of GPR41 mRNA and protein was increased with maximal expression at differentiation day 8 for 3T3-L1 adipocytes and day 6 for C2C12 myotubes. GPR41 protein was also expressed in adipose tissues and skeletal muscle. After analyzing dose-response relationship, 300 µM propionic acid or 500 µM valeric acid for 30 min incubation was used for the measurement of glucose uptake. Both propionic acid and valeric acid increased insulin-stimulated glucose uptake in 3T3-L1 adipocyte, which did not occur in cells transfected with siRNA for GPR41 (siGPR41). In C2C12 myotubes, these SCFAs increased basal glucose uptake, but did not potentiate insulin-stimulated glucose uptake, and siGPR41 treatment reduced valerate-stimulated basal glucose uptake. Therefore, these findings indicate that GPR41 plays a role in insulin responsiveness enhanced by both propionic and valeric acids on glucose uptake in 3T3-L1 adipocytes and C2C12 myotubes, and in valerate-induced increase in basal glucose uptake in C2C12 myotubes.

IL-1β and TNFα inhibit GPR120 (FFAR4) and stimulate GPR84 (EX33) and GPR41 (FFAR3) fatty acid receptor expression in human adipocytes: implications for the anti-inflammatory action of n-3 fatty acids

“…Although a signal for GPR41 was consistently observed in the present work using real-time PCR, the mRNA was not detected in the study on macrophage-conditioned medium which utilised human Oligo microarrays (O'Hara et al, 2009). Studies on murine adipose tissue have also reported a lack of GPR41 expression (Zaibi et al, 2010), although some other reports have observed clear signals together with functional responses associated with this receptor (Xiong et al, 2004;Han et al, 2014). GPR41, for which the main ligands are short chain fatty acids Ulven & Christiansen, 2015), is less well-characterised than the other GPCR fatty acid receptors, but it was reported to mediate the stimulation of leptin secretion from adipocytes by propionate and butyrate (Xiong et al, 2004).…”

Complex Pharmacology of Free Fatty Acid Receptors

“…229−234 Expression of both FFA2 and FFA3 has also been described in pancreatic β-cells, 235 and interest has been increasing recently in the role of these receptors in regulating insulin secretion. 236−238 Expression of both FFA2 and FFA3 in adipose tissue has also been reported, 239,240 although the expression of FFA3 has been contentious, with many studies finding only FFA2. 227,241,242 FFA3 only appears to be expressed highly in the neurons present in both sympathetic ganglia and the enteric nervous system.…”

“…Finally, SCFAs have also been reported to regulate glucose uptake in adipocytes, in particular, enhancing insulin-stimulated glucose uptake. 239,265 One study has found that these effects are reduced by transfection of FFA3 siRNA, suggesting a role for the FFA3 receptor. 239 However, this study did not assess the effects of FFA2.…”

“…239,265 One study has found that these effects are reduced by transfection of FFA3 siRNA, suggesting a role for the FFA3 receptor. 239 However, this study did not assess the effects of FFA2. It has, however, also been suggested in a nonpeer-reviewed patent application that FFA2 activation may modestly stimulate glucose uptake.…”

Cross-talk between α7 nAChR-mediated cholinergic pathway and acylation stimulating protein signaling in 3T3-L1 adipocytes: role of NFκB and STAT3

“…The target sense sequence of siRNA for STAT3 used was: 5=-GAGUUGAAU-UAUCAGCUUAUU-3=, the sense sequence of scrambled siRNA was: 5=-CCUCGUGCCGUUCCAUCAGGUAGUU-3=. The 3T3-L1 cells were transfected with 100 nmol/L chemically synthesized siRNA using Lipofectamine RNAimax (Invitrogen), as previously described (Han et al 2014). After overnight incubation, the medium was replaced with growth medium as mentioned above.…”