Age-related differences in the pancreatic β-cell response to hyperglycemia after eccentric exercise.

Eccentric exercise (ECC) causes muscle damage, insulin resistance, and increased pancreatic β-cell secretion in young individuals. However, the effects of age on the pancreatic β-cell response to glucose after ECC are unknown. Hyperglycemic clamps (180 min, 10.0 mM) were performed on eight young (age 22 ± 1 yr) and eight older (age 66 ± 2 yr) healthy sedentary males without exercise (CONT) and 48 h after ECC. ECC increased ( P < 0.02) muscle soreness ratings and plasma creatine kinase concentrations in both groups. Insulin and C-peptide secretions were similar between young and older subjects during CONT clamps. ECC increased ( P < 0.05) first-phase (0-10 min) C-peptide area under the curve in young (4.2 ± 0.4 vs. 3.7 ± 0.6 nM ⋅ min; ECC vs. CONT, respectively) but not in older subjects (3.2 ± 0.7 vs. 3.5 ± 0.7 nM ⋅ min; ECC vs. CONT), with significant group differences ( P < 0.02). Indeed, ECC repressed ( P < 0.05) first-phase peak C-peptide concentrations in older subjects (0.93 ± 0.16 vs. 1.12 ± 0.11 nM; ECC vs. CONT). Moreover, first-phase C-peptide-to-insulin molar ratios suggest age-related differences ( P < 0.05) in insulin/C-peptide clearance after ECC. Furthermore, the observed C-peptide response after ECC was related to abdominal adiposity [ r = -0.62, P < 0.02, and r = -0.66, P < 0.006, for first and second (10-180 min) phases, respectively]. In conclusion, older individuals did not exhibit the compensatory increase in β-cell secretion observed among young individuals after ECC. Thus, with increasing age, the pancreatic β-cell may be less responsive to the physiological stress associated with ECC.