Effects of Polyphenols on Diet-Induced Lipid Accumulation and Insulin Sensitivity in Skeletal Muscles of Rodent Models: Systematic Review and Meta-Analysis

Abstract

Background Excess lipid accumulation in skeletal muscles has been closely linked to increased insulin resistance, and both conditions are identified as features of Metabolic Syndrome (MetS). Recently, dietary polyphenols have been the subject of great interest for their potential benefits in the prevention of various clinical conditions including MetS, through improving lipid metabolism and insulin action. This systematic review and meta-analysis aimed to determine the effects of polyphenols on diet-induced intramuscular lipid deposition and subsequently insulin sensitivity in rodents. Methods We searched PubMed and Web of Science databases to identify preclinical studies that assessed the effects of polyphenol supplementation on lipid concertation in skeletal muscles of rodents. Two researchers selected the studies, extracted the data, and assessed the quality of studies. The meta-analysis was performed using RevMan. Results 11 studies were included in the systematic review and 10 studies with 17 matched groups in the meta-analysis. Overall results showed that polyphenolic compounds significantly lowered lipid content in skeletal muscles [SMD: −0.87; 95% confidence interval: −1.13, 0.60], and improved measures of insulin sensitivity, HOMA-IR [SMD: −0.95; −1.31, −0.60), and glucose area under the curve (AUC) [SMD = −1.09; −1.54, −0.64] when compared to control groups. Discussion and Implications The reported therapeutic effects of polyphenols in the present review appear to be dose- dependent, as more significant improvements were seen with higher doses. The observed results might be associated with the tested compounds’ ability to stimulate AMP-activated protein kinase (AMPK) mediated signal pathways which promoted fatty acid oxidation and improved insulin sensitivity. The promising findings of this review demonstrate the potential role of polyphenols in ameliorating two major features of MetS. Preclinical trials contribute significantly to our understanding of disease mechanisms and provide essential evidence for developing novel and effective treatments.