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-cell response to
hyperglycemia after eccentric exercise
Noll Physiological Research Center and the General Clinical Research Center, The Pennsylvania State University, University Park, Pennsylvania 16802
Eccentric exercise
(ECC) causes muscle damage, insulin resistance, and increased
pancreatic 
-cell secretion in young individuals. However, the
effects of age on the pancreatic -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 -cell
secretion observed among young individuals after ECC. Thus, with
increasing age, the pancreatic -cell may be less responsive to the
physiological stress associated with ECC.
hyperglycemic clamp; C-peptide; insulin; exercise-induced muscle damage; abdominal adiposity
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