Effects of Traffic-Related Diesel Exhaust Exposure and Moderate Exercise on Obesity, Metabolic Dysfunction, and Inflammatory Responses in Rats

Objective: Traffic-related air pollution is recognised as a significant environmental risk factor associated with obesity and metabolic dysfunction. Although the positive effects of regular exercise on metabolic health are well established, its protective role against traffic-related air-pollution-induced metabolic dysfunction has not been fully elucidated. This study was conducted to investigate the effects of diesel exhaust exposure and moderate exercise on the development of obesity, metabolic changes, adipokine profile, and inflammatory response in rats. Materials and Methods: In this randomised controlled experimental study, 48 female Wistar Albino rats were randomised into six experimental groups. The animals were exposed to diesel exhaust simulating traffic-related air pollution (average 300 μg PM2.5/m3) for 2 or 4 h daily over an eight-week period. Rats in the exercise groups underwent moderate-intensity treadmill exercise for 30 min at a speed of 15 m/min, five days a week, over the same period. At the end of the study, obesity indicators, serum lipid profile, glucose metabolism parameters, adipokines and inflammation markers were assessed. Results: Diesel exhaust exposure caused a significant increase in final body weight, BMI, Lee index and VAI values (p < 0.001). Furthermore, levels of LDL cholesterol, total cholesterol, triglycerides, glucose, adiponectin, leptin, CRP, IL-37, IL-1β, IL-6 and TNF-α increased significantly, whilst HDL cholesterol and insulin levels decreased significantly (p < 0.001). The most pronounced metabolic and inflammatory changes were observed in the 4 h exhaust gas exposure group. Elevations in pro-inflammatory cytokines, accompanied by increased visceral adiposity, supported the development of systemic metabolic inflammation. Exercise significantly reduced weight gain, visceral adiposity, dyslipidaemia, hyperglycaemia, adipokine imbalance and the inflammatory response (p < 0.001). However, exercise could not fully reverse all the changes associated with long-term diesel exhaust exposure. Conclusions: Traffic-related diesel exhaust exposure led to metabolic disorders in rats, characterised by visceral adiposity, dyslipidaemia, impaired glucose homeostasis, adipokine imbalance and chronic low-grade inflammation. Regular moderate-intensity exercise significantly reduced these adverse effects but could not eliminate them entirely. The findings suggest that traffic-related air pollution may contribute to the development of obesity via inflammation-mediated metabolic mechanisms, and that regular physical activity may serve as an important protective strategy in limiting these effects.