Effect of Comparable Carbon Chain Length Short- and Branched-Chain Fatty Acids on Adipokine Secretion from Normoxic and Hypoxic Lipopolysaccharide-Stimulated 3T3-L1 Adipocytes.

Abstract

Background: Microbial fermentation of non-digestible carbohydrates and/or protein produces short-chain fatty acids (SCFA), whereas branched-chain fatty acids (BCFA) are produced from protein fermentation. The effects of individual SCFA and BCFA of comparable carbon chain length on adipocyte inflammation have not been investigated. Objective: To compare the effects of SCFA and BCFA on inflammatory mediator secretion in an adipocyte cell culture model designed to recapitulate obesity-associated adipocyte inflammation under normoxic and hypoxic conditions. Methods: The 3T3-L1 adipocytes were cultured (24 h) without (Control, Con) and with 1 mmol/L of SCFA (butyric acid (But) or valeric acid (Val)) or 1 mmol/L of BCFA (isobutyric acid (IsoBut) or isovaleric acid (IsoVal)) and were unstimulated (cells alone, n = 6/treatment), or stimulated with 10 ng/mL lipopolysaccharide (LPS, inflammatory stimulus, n = 8/treatment) or 10 ng/mL LPS + 100 µmol/L of the hypoxia memetic cobalt chloride (LPS/CC, inflammatory/hypoxic stimulus, n = 8/treatment). Results: Compared to Con + LPS, But + LPS reduced secreted protein levels of interleukin (IL)-1β, IL-6, macrophage chemoattractant protein (MCP)-1/chemokine ligand (CCL)2, MCP3/CCL7, macrophage inflammatory protein (MIP)-1α/CCL3 and regulated upon activation, normal T cell expressed, and secreted (RANTES)/CCL5 and decreased intracellular protein expression of the ratio of phosphorylated to total signal transducer and activator of transcription 3 (STAT3) and nuclear factor kappa B (NFκB) p65 (p < 0.05). Val + LPS reduced IL-6 secretion and increased MCP-1/CCL2 secretion compared to Con + LPS and exhibited a different inflammatory mediator secretory profile from But + LPS (p < 0.05), indicating that individual SCFA exert individual effects. There were no differences in the secretory profile of the BCFA IsoBut + LPS and IsoVal + LPS (p > 0.05). Alternatively, under inflammatory hypoxic conditions (LPS/CC) Val, IsoVal, and IsoBut all increased secretion of IL-6, MCP-1/CCL2 and MIP-1α/CCL3 compared to Con (p < 0.05), whereas mediator secretion did not differ between But and Con (p > 0.05), indicating that the proinflammatory effects of SCFA and BCFA was attenuated by But. Interestingly, But + LPS/CC decreased STAT3 activation versus Con + LPS/CC (p < 0.05). Conclusions: The decreased secretion of inflammatory mediators that is attributable to But highlights the fact that individual SCFA and BCFA exert differential effects on adipocyte inflammation under normoxic and hypoxic conditions.