AGE-RELATED DIFFERENCES IN THE PANCREATIC ??-CELL RESPONSE TO HYPERGLYCEMIA FOLLOWING ECCENTRIC EXERCISE

Abstract

136 Eccentric exercise results in delayed muscle soreness, muscle damage, insulin resistance, and increased insulin secretion in young individuals. The purpose of this investigation was to determine if older subjects differ from young subjects, in the pancreatic β-cell response to glucose following eccentric exercise. Hyperglycemic clamps (180 min, 10.0 mM) were performed on 8 young (age, 22 ± 1 yrs; body mass index, BMI, 23.4 ± 1.9 kg·m-2.; waist-to-hip ratio, WHR, 0.83 ± 0.02) and 8 older (age, 66 ± 2; BMI, 25.5 ± 1.2; WHR, 0.91 ± 0.01) sedentary healthy men with normal glucose tolerance, without exercise (CON) and 48 h after a single bout of eccentric exercise (ECC; leg extension and chest press, 10 sets X 10 reps, 100% 3-RM). ECC resulted in a 3-to-7-fold increase in muscle soreness ratings at 36 h in all subjects, and elevated (P< 0.02) plasma creatine kinase (CK) concentrations 48 h after ECC in young(1179 ± 480 vs. 58 ± 17 IU·I-1.; ECC vs. CON) and older subjects (629 ± 418 vs. 49 ± 15). Pancreatic β-cell secretion was similar in all subjects during CON clamps. When ECC was compared to CON, the first phase (0-10 min) C-peptide area under the curve (AUC) increased (P < 0.05) in young (4.2 ± 0.4 vs. 3.7 ± 0.6 nmol·I-1·min), but not among older subjects (3.2 ± 0.7 vs. 3.5 ± 0.7). The first phase C-peptide AUC response to ECC was significantly different (P < 0.02) between young and older subjects. Individual peak C-peptide concentrations were lower (P < 0.05) after ECC in older subjects (0.93 ± 0.16 vs. 1.12 ± 0.11 nmol·I-1), suggesting reduced first phase pancreatic β-cell secretion. In addition, first phase insulin-to-C-peptide molar ratios suggest opposite trends (P = 0.05) in insulin and/or C-peptide clearance for young and older subjects. Furthermore, the C-peptide AUC response to ECC was inversely related to WHR (r = -0.62, P < 0.02 and r = -0.66, P < 0.0006; first and second (10-180 min) phase, respectively). In conclusion, although all subjects experienced muscle soreness and apparent muscle damage after eccentric exercise, older subjects did not exhibit the increase in pancreaticβ-cell response to hyperglycemia that was observed among young subjects. Furthermore, abdominal adiposity may account for some of the age-related differences in pancreatic β-cell secretion following eccentric exercise.