Exercise Training and Glucose Metabolism in Aging

Not Applicable

Completed

Conditions: Type 2 Diabetes Mellitus
Impaired Glucose Tolerance (Prediabetes)

Interventions: Behavioral: Aerobic exercise training
Behavioral: Detraining (cessation of exercise)

Brief Summary: Diabetes and its associated complications affect more than 20 million Americans, and the prevalence of type 2 diabetes and impaired glucose tolerance rises dramatically with age such that 40% of Americans over age 60 are affected. In older adults, glucose metabolism may be affected by reduced skeletal muscle capillary supply, which limits insulin, glucose, and oxygen delivery to skeletal muscle. Reduced capillary supply to skeletal muscle is found in older individuals with impaired glucose tolerance and we hypothesize that this is due to reduced vascular growth factor expression, and chronic inflammation. Further, we hypothesize that reversal of a sedentary lifestyle through aerobic exercise training will increase insulin signaling and vascular growth factor expression, as well as decrease inflammation, to increase capillary supply to skeletal muscle, which contributes to improved glucose metabolism in older adults. This study will: 1) Determine the mechanisms underlying reduced skeletal muscle capillarization in older adults with impaired glucose tolerance; and 2) Determine the effect of aerobic exercise training-induced increases in skeletal muscle capillarization on glucose metabolism in older adults.

Recruitment & Eligibility

Inclusion Criteria

Exclusion Criteria

History of CAD or cerebrovascular disease that would preclude exercise
Implantable defibrillator
Active cancer
Chronic pulmonary, thyroid, renal, liver, or hematological disease
HIV positive or prone to malnutrition
Sickle cell anemia
Type 1 diabetes, or currently on medication to treat type 2 diabetes
Poorly-controlled type 2 diabetes
Poorly-controlled hypertension
Taking medications including: beta-blockers, oral steroids, warfarin, certain statins, hormone replacement therapy (HRT), oral contraceptives (OCP), thiazolidinediones (TZD), or chronic steroids or nonsteroidal analgesics (NSAIDS) that may not be safely discontinued temporarily for specific procedures (i.e. for 72 hours prior)
Allergic to lidocaine or heparin
Recent weight change (>5kg in 3 months)
Currently pregnant or nursing
Physical impairment limiting exercise
Dementia or unstable clinical depression

Arm && Interventions

Group	Intervention	Description
Arm 1	Aerobic exercise training	Older adults, normal glucose tolerance
Arm 1	Detraining (cessation of exercise)	Older adults, normal glucose tolerance
Arm 2	Aerobic exercise training	Older adults, impaired glucose tolerance
Arm 2	Detraining (cessation of exercise)	Older adults, impaired glucose tolerance

Primary Outcome Measures

Name	Time	Method
Baseline Glucose Utilization	baseline	Insulin-stimulated glucose uptake
Glucose Utilization (Pre/Post Intervention)	baseline, 24 weeks, 26 weeks	Insulin-stimulated glucose uptake
Baseline Skeletal Muscle Capillarization	baseline
Skeletal Muscle Capillarization (Pre/Post Intervention)	baseline, 24 weeks, 26 weeks

Secondary Outcome Measures

Name	Time	Method
Baseline 2-hour Postprandial Glucose	baseline
Baseline Cardiorespiratory Fitness	baseline	maximal oxygen consumption
Cardiorespiratory Fitness	baseline, 24 weeks, 26 weeks	Maximal oxygen consumption
Body Composition (%Fat)	baseline, 24 weeks
2-hr Post-prandial Plasma Glucose Level	baseline, 24 weeks, 26 weeks