Substrate Availability and Utilization During Sub-maximal Exercise in the Elderly
Aging is associated with a decline in physiological capacity and metabolic function, leading to increased risk for chronic conditions such as insulin resistance and diabetes. Reduced ability to utilize fatty acids in the elderly has been linked to increased fat deposition within skeletal muscle. However, intramuscular triglyceride (IMTG) content and its relation to substrate oxidation has not been clearly established in older individuals. The two main purposes of the present investigation were 1.) to compare IMTG stores in the elderly with a younger group of men and women and 2.) to examine the relationship between substrate content and utilization during an acute sub-maximal bout of exercise in the elderly. A total of thirteen sedentary, healthy older men (5) and women (8) aged 67 + 3 yrs were matched for gender and percent body fat with a younger, control group (age=39 + 6 yrs) for IMTG comparison. Fat free mass (FFM), body mass index (BMI), weight, and height were not significantly different between the old and young and ORO staining from vastus lateralis muscle obtained by percutaneous needle biopsy revealed no statistically significant differences between the two groups. Sixteen sedentary elderly men (5) and women (11) were given constant infusions of 13C palmitate and d2 glucose during 60 minutes of cycle ergometry exercise at ~58% VO2peak to assess substrate utilization during exercise. There was a significant negative correlation between IMTG content by Oil Red O staining and total fatty acid oxidation (rho= -0.5989; p=0.03) and IMTG content and oxidative capacity of muscle (rho= -0.6485; p=0.04) induced by sub-maximal exercise. Oxidative capacity of muscle was not associated with rates of NPFA oxidation during sub-maximal exercise. Fitness was marginally correlated with fasting insulin levels (rho= -0.4857; p=0.056) and HOMA IR (rho= -0.4441; p=0.085). In summary, IMTG content was not higher in this group of sedentary elderly compared to younger individuals, but higher IMTG content was associated with decreased fat oxidation during sub-maximal exercise in this group. In addition, higher fitness predicted more favorable trends for markers of insulin resistance.
Advisor:Bret H. Goodpaster, PhD; Robert J. Robertson, PhD; David E. Kelley, MD; Deborah J. Aaron, PhD; Elizabeth Nagle-Stilley, PhD
School:University of Pittsburgh
School Location:USA - Pennsylvania
Source Type:Master's Thesis
Keywords:health physical and recreation education
Date of Publication:12/23/2004