title: Age-related differences in the pancreatic beta-cell response to hyperglycemia after eccentric exercise.
abstract: Eccentric exercise (ECC) causes muscle damage, insulin resistance, and increased pancreatic beta-cell secretion in young individuals. However, the effects of age on the pancreatic beta-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 beta-cell secretion observed among young individuals after ECC. Thus, with increasing age, the pancreatic beta-cell may be less responsive to the physiological stress associated with ECC.
authors.affiliation: Noll Physiological Research Center and the General Clinical Research Center, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: R K
authors.initials: RK
authors.lastname: Krishnan
authors.forename: J M
authors.initials: JM
authors.lastname: Hernandez
authors.forename: D L
authors.initials: DL
authors.lastname: Williamson
authors.forename: D J
authors.initials: DJ
authors.lastname: O'Gorman
authors.forename: W J
authors.initials: WJ
authors.lastname: Evans
authors.forename: J P
authors.initials: JP
authors.lastname: Kirwan
mesh_terms: D000204:Activity Cycles; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001786:Blood Glucose / Q000502:physiology; D001824:Body Constitution; D015992:Body Mass Index; D001835:Body Weight; D002096:C-Peptide / Q000097:blood / Q000378:metabolism*; D003402:Creatine Kinase / Q000097:blood; D015444:Exercise / Q000502:physiology*; D015309:Glucose Clamp Technique; D006801:Humans; D006943:Hyperglycemia / Q000503:physiopathology*; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000254:growth & development / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue; D005082:Physical Exertion / Q000502:physiology*; D012044:Regression Analysis
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D003402:Creatine Kinase