The anti-inflammatory effects of aerobic exercise training in patients with type 2 diabetes: A systematic review and meta-analysis

Background: Type 2 diabetes mellitus (T2DM) is a low-grade, chronic inflammatory disease, associated with increased cardiovascular risk. The purpose of this systematic review/ meta-analysis was to evaluate the effects of aerobic exercise training (AET) on inflammatory markers in T2DM patients.Methods: The literature search was conducted utilizing PubMed, Web of Science, Embase, and the Cochrane Library from their inception up to April 2022. We screened only for randomized controlled trials (RCTs) investigating the effects of AET on C-reactive protein (CRP) and adipokines: adiponectin, resistin, interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-a), along with changes in anthropometric indices and glycemic control in adult T2DM patients. Pooled post-exercise weighted mean differences (WMDs) with 95% Confidence Intervals (CIs) were calculated for all outcomes of interest between exercise-treated patients and controls.Results: Twenty-six RCTs involving 1239 T2DM patients were retrieved from the databases for meta-analysis. The cumulative results showed that post-AET inflammatory markers were lower in exercise-treated patients compared to controls regarding CRP (mg/L): WMD:-0.91; 95%CIs:-1.43,-0.40; p < 0.001 resistin (mg/ml): (WMD:-2.08; 95%CIs:-3.32,-0.84; p < 0.001); TNF-a (pg/ml): (WMD:-2.70; 95%CIs:-4.26,-1.14; p < 0.001), and IL-6 (pg/ml): (WMD:-1.05; 95%CIs:-1.68,-0.43; p < 0.001). Those effects were accompanied by significant amelioration of fasting glucose (mg/dl) (WMD:-13.02; 95%CIs:-25.39,-0.66; p = 0.04), HbA1c (%) (WMD:-0.51; 95%CIs:-0.73,-0.28, p < 0.001), and fat mass (%) (WMD:-3.14; 95%CI:-4.71,-1.58; p < 0.001). Our meta-analysis demonstrated less-consistent results for adiponectin (mu g/ml), (WMD: 1.00; 95%CI:-0.12, 2.12; p = 0.08) and body-mass index (kg/m2) (WMD:-1.34; 95%CI:-2.76, 0.08; p = 0.06) tending to differ between AET and control group.Conclusions: AET can significantly reduce the inflammatory burden in T2DM patients. by ameliorating the circulating levels of CRP, resistin, TNF-a and IL-6, even without accompanied significant weight-loss. The clinical impact of those anti-inflammatory effects of AET needs to be determined.