Impact of a Longer-Term Physical Activity Intervention on Inflammatory and Oxidative Stress Biomarkers in Older People with Metabolic Syndrome

Metabolic syndrome (MetS) is characterised by cardiometabolic risk factors and is closely associated with increased oxidative stress and chronic low-grade inflammation. MetS is largely driven by adverse lifestyle behaviours, particularly physical inactivity, and regular physical activity is recognised as a central strategy for its prevention and management. This study aimed to assess the long-term impact of a five-year follow-up period of physical activity on oxidative stress, inflammatory biomarkers, and cardiometabolic health in adults with MetS. Forty participants diagnosed with MetS (50% men, aged 55-75 years) were selected and stratified into two groups: those who increased their physical activity and those who reduced it during the intervention. Physical activity was assessed using metabolic equivalent task minutes per week (MET·min/week), and evaluations were performed at baseline, 3 years, and 5 years. Participants who increased physical activity showed a progressive reduction in reactive oxygen species (ROS) produced by peripheral blood mononuclear cells (PBMCs), together with a decrease in plasma malondialdehyde (MDA). Antioxidant enzyme activities, including catalase and superoxide dismutase, exhibited a favourable long-term profile, with recovery or maintenance of higher activity levels by the end of follow-up, reflecting enhanced endogenous antioxidant defence. Inflammatory status improved and was characterised by a reduction in myeloperoxidase (MPO) activity and a sustained increase in plasma interleukin-15 (IL-15). These participants also showed reductions in body weight, body mass index (BMI), waist circumference, fasting glucose, and glycosylated haemoglobin A1c (HbA1c), consistent with improved insulin sensitivity and metabolic control. Participants who reduced physical activity tended to show unfavourable trajectories in several biomarkers. Increasing physical activity over time is associated with substantial improvements in redox balance, inflammatory status, and cardiometabolic health in adults with MetS. These findings reinforce the central role of physical activity as a fundamental therapeutic component within lifestyle interventions aimed at mitigating metabolic dysfunction and preventing MetS progression.