Impact of Graded Exercise Intensity on Irisin Secretion, Lipid Profile, and Stress in a Prediabetic Population

Abstract

Background: Prediabetes is a growing global health concern characterized by impaired metabolic regulation and elevated risk of progression to type 2 diabetes mellitus. Exercise is a cornerstone of non-pharmacological management; however, the acute physiological effects of varying exercise intensities on metabolic and psychological markers in prediabetic individuals remain inadequately defined. This study evaluates the influence of progressively increasing exercise intensity on cholesterol levels, circulating Irisin concentrations, and perceived stress. Methods: Twenty-two sedentary adults with prediabetes completed four laboratory visits involving treadmill exercise at 50%, 60%, 70%, and 80% of predicted maximum heart rate (PMHR). Exercise duration was fixed at 40 minutes for Visits 1 and 2, and adjusted according to tolerance for Visits 3 and 4. Blood samples were collected pre- and post-exercise to assess total cholesterol and Irisin concentrations. Perceived Stress Scale (PSS-10) scores were recorded before and after each session. Paired t-tests compared pre–post changes across visits. Results: Cholesterol levels decreased significantly after all four exercise intensities (Visit 1: −17.5 mg/dL, p = 0.002; Visit 2: −14.5 mg/dL, p = 0.006; Visit 3: −12.5 mg/dL, p = 0.009; Visit 4: −15.9 mg/dL, p < 0.001). Irisin concentrations increased following each session, with significant elevations in Visits 1–3 (p < 0.05) and a positive, non-significant trend at Visit 4 (p = 0.051). Higher intensities elicited larger Irisin responses despite shorter tolerated durations. PSS scores showed no significant quantitative change (p > 0.05), although participants reported subjective improvements in mood and relaxation. Conclusion: Increasing exercise intensity elicits acute and clinically meaningful improvements in cholesterol and stimulates Irisin release in adults with prediabetes, even when higher intensities limit exercise duration. While perceived stress scores remained statistically unchanged, subjective well-being improved across sessions. These findings highlight the metabolic value of tailored intensity-based exercise prescriptions in prediabetes management.