Effects of Exercise Training on Inflammatory and Cardiometabolic Risk Biomarkers in Patients With Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background The interaction between type 2 diabetes mellitus (T2DM) and cardiometabolic morbidity and mortality stems from the progressive nature of inflammation underpinning both diseases. Exercise training is considered an effective treatment strategy for T2DM and cardiometabolic diseases. Objective The current systematic review and meta-analysis investigated the effects of exercise training on inflammatory and cardiometabolic risk biomarkers in patients with T2DM. Data sources Electronic databases (PubMed/Medline, Embase, Cochrane Library, CINAHL, Google Scholar, Scopus, and Web of Science) were searched for randomized controlled trials (RCTs) from inception to January 2022. We used random effects models to estimate weighted mean differences with 95% confidence intervals. Study selection Twenty-five RCTs were included (N = 1257 participants; mean age = 52 years). Included studies had moderate to good overall methodological quality (TESTEX = 9 (range 7-13). Results Meta-analysis indicated that exercise training significantly increased adiponectin and decreased fasting insulin, homeostatic model assessment for insulin resistance, tumor necrosis factor-alpha, interleukin-6, and C-reactive protein (ps <= 0.05). Subgroup analysis by type of training indicated that aerobic exercise had the most consistent beneficial effects as compared to other types of exercise training; however, there was high heterogeneity among studies. Conclusion Different types of exercise training increase adiponectin levels and decrease pro-inflammatory cytokines such as TNF-alpha, IL-6, and CRP, as well as fasting insulin and insulin resistance markers in patients with T2DM. However, these effects were not beneficial for more commonly measured cardiometabolic risk factors (i.e., lipid profiles). Additional relevant clinical trials are required to confirm these results.