Abstract
Adipose tissue is a primary site of obesity-induced inflammation, which has been emerging as an important contributor to obesity associated disorders. The factors influencing adipose tissue-induced inflammation and the resulting pathophysiological events remain poorly understood. However, dietary fiber consumptions appear to be protective. Short-chain fatty acids such as propionic acid (PA) are the principal products of the dietary fiber fermentation by microbiota. Therefore, we aim to investigate the influence of PA on inflammation, lipogenesis and glucose uptake markers from human subcutaneous adipose tissue (SAT). We showed that the treatment of SAT with PA resulted in a significant downregulation of inflammatory parameters (e.g. TNF-α and IP-10) and macrophage markers (e.g. CD163 and MMP-9). The expression levels of PA receptors (i.e. G protein coupled receptor-41 and -43) in human primary adipocytes were very low in comparison with SAT and macrophages. Upon PA treatment, no anti-inflammatory effect was observed in human adipocytes. PA significantly upregulated the expression of lipoprotein lipase (LPL), sterol regulatory-element-binding protein-1c (SREBP-1c) and glucose transporter 4 (GLUT-4), which are associated with lipogenesis and glucose uptake. We also showed that the observed anti-inflammatory effects of PA on SAT were partly mediated by Gi/o protein coupled receptor. Our data suggests that PA anti-inflammatory effects on SAT are mediated partly via Gi/o proteins, leading to the improved expression of factors associated with lipogenesis and glucose uptake. These responses appeared to be not mediated by adipocytes; but most probably by macrophages. The current study provides new knowledge, which can be used as a potential new avenue for drug development in preventing obesity-related inflammation and metabolic disorders in future.Graphical abstractSchematic presentation of study flow and the components of the investigation. In this study the effect of propionic acid (PA) on inflammation investigated in human subcutaneous adipose tissue (SAT), human primary adipocytes and the expression of a few hallmark inflammatory components produced by SAT and human adipocytes.
Highlights
Obesity has reached epidemic proportions and is still escalating at an alarming rate worldwide
Obesity is associated with chronic activation of low-grade inflammation [3], which is implicated in the pathogenesis of obesity-associated diseases including insulin resistance, type-2 diabetes (T2D) [4, 5] and cardiovascular disease [6, 7]
A numerous of studies has been shown that shortchain fatty acids (SCFAs) inhibit inflammation with focus on butyrate and to a lesser extent on acetate and Propionic Acid (PA), [16]
Summary
Obesity has reached epidemic proportions and is still escalating at an alarming rate worldwide. In Palestine the prevalence of obesity has been shown to be approximately 4. The etiology of obesity and low-grade inflammation is complex and involves intrinsic and extrinsic factors. The colonization of germ-free mice with microbiota derived from obese mice results in significantly greater adiposity than colonization with microbiota from lean mice [12]. Prebiotic diets such as fructans [13] are associated with general better health, including the decrease in body weight, fat mass and the severity of T2D [14,15,16]. The factors that influence the composition and metabolism of intestinal
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