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Increased skeletal muscle capillarization after aerobic exercise training and weight loss improves insulin sensitivity in adults with IGT.

ABSTRACT: Transcapillary transport of insulin is one determinant of glucose uptake by skeletal muscle; thus, a reduction in capillary density (CD) may worsen insulin sensitivity. Skeletal muscle CD is lower in older adults with impaired glucose tolerance (IGT) compared with those with normal glucose tolerance and may be modifiable through aerobic exercise training and weight loss (AEX+WL). We tested the hypothesis that 6-month AEX+WL would increase CD to improve insulin sensitivity and glucose tolerance in older adults with IGT.Sixteen sedentary, overweight-obese (BMI 27-35 kg/m2), older (63 ± 2 years) men and women with IGT underwent hyperinsulinemic-euglycemic clamps to measure insulin sensitivity, oral glucose tolerance tests, exercise and body composition testing, and vastus lateralis muscle biopsies to determine CD before and after 6-month AEX+WL.Insulin sensitivity (M) and 120-min postprandial glucose (G120) correlated with CD at baseline (r = 0.58 and r = -0.60, respectively, P < 0.05). AEX+WL increased maximal oxygen consumption (VO2max) 18% (P = 0.02) and reduced weight and fat mass 8% (P < 0.02). CD increased 15% (264 ± 11 vs. 304 ± 14 capillaries/mm(2), P = 0.01), M increased 21% (42.4 ± 4.0 vs. 51.4 ± 4.3 µmol/kg FFM/min, P < 0.05), and G120 decreased 16% (9.35 ± 0.5 vs. 7.85 ± 0.5 mmol/L, P = 0.008) after AEX+WL. Regression analyses showed that the AEX+WL-induced increase in CD independently predicted the increase in M (r = 0.74, P < 0.01) as well as the decrease in G120 (r = -0.55, P < 0.05).Six-month AEX+WL increases skeletal muscle CD in older adults with IGT. This represents one mechanism by which AEX+WL improves insulin sensitivity in older adults with IGT.

SUBMITTER: Prior SJ

PROVIDER: S-EPMC3994928 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Increased skeletal muscle capillarization after aerobic exercise training and weight loss improves insulin sensitivity in adults with IGT.

Prior Steven J SJ Blumenthal Jacob B JB Katzel Leslie I LI Goldberg Andrew P AP Ryan Alice S AS

Diabetes care 20140304 5

<h4>Objective</h4>Transcapillary transport of insulin is one determinant of glucose uptake by skeletal muscle; thus, a reduction in capillary density (CD) may worsen insulin sensitivity. Skeletal muscle CD is lower in older adults with impaired glucose tolerance (IGT) compared with those with normal glucose tolerance and may be modifiable through aerobic exercise training and weight loss (AEX+WL). We tested the hypothesis that 6-month AEX+WL would increase CD to improve insulin sensitivity and g ...[more]

PMID: 24595633

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Project description:OBJECTIVES:Adequate muscle perfusion supports the transport of nutrients, oxygen and hormones into muscle fibers. Aging is associated with a substantial decrease in skeletal muscle capillarization, fiber size and oxidative capacity, which may be improved with regular physical activity. The aim of this study was to investigate the relationship between muscle capillarization and indices of muscle hypertrophy (i.e. lean mass; fiber cross sectional area (CSA)) in older adults before and after 12?weeks of progressive resistance exercise training (RET). DESIGN:Interventional study SETTING AND PARTICIPANTS: 19 subjects (10 male and 9 female; 71.1?±?4.3?years; 27.6?±?3.2 BMI) were enrolled in the study and performed a whole body RET program for 12?weeks. Subjects where then retrospectively divided into a LOW or HIGH group, based on their pre-RET capillary-to-fiber perimeter exchange index (CFPE). Physical activity level, indices of capillarization (capillaries-to-fiber ratio, C:Fi; CFPE index and capillary-to-fiber interface, LC-PF index), muscle hypertrophy, muscle protein turnover and mitochondrial function were assessed before and after RET. RESULTS:Basal capillarization (C:Fi; CFPE and LP-CF index) correlates with daily physical activity level (C:Fi, r?=?0.57, p?=?0.019; CFPE index, r?=?0.55, p?=?0.024; LC-PF index, r?=?0.56, p?=?0.022) and CFPE and LC-PF indices were also positively associated with oxidative capacity (respectively r?=?0.45, p?=?0.06; r?=?0.67, p?=?0.004). Following RET, subjects in the HIGH group underwent hypertrophy with significant improvements in muscle protein synthesis and muscle fiber CSA (p?<?0.05). However, RET did not promote muscle hypertrophy in the LOW group, but RET significantly increased muscle capillary density (p?<?0.05). CONCLUSION/IMPLICATIONS:Muscle fiber capillarization before starting an exercise training program may be predictive of the muscle hypertrophic response to RET in older adults. Increases in muscle fiber size following RET appear to be blunted when muscle capillarization is low, suggesting that an adequate initial capillarization is critical to achieve a meaningful degree of muscle adaptation to RET.

Project description:To examine the relationships between plasma and tissue markers of systemic and vascular inflammation and obesity and insulin resistance and determine the effects of aerobic exercise training plus weight loss (AEX+WL) and weight loss (WL) alone on these biomarkers.Prospective controlled study.Veterans Affairs Medical Center and University research setting.Overweight and obese sedentary postmenopausal women (N = 77).Six months, 3 d/wk AEX+WL (n = 37) or WL (n = 40).Total-body dual-energy X-ray absorptiometry, abdominal computed tomography, hyperinsulinemic-euglycemic clamps (a criterion standard method of assessing insulin sensitivity), adipose tissue biopsies (n = 28), and blood for homeostasis model assessment-insulin resistance, and soluble forms of intracellular adhesion molecule 1 (sICAM-1) and vascular cell adhesion molecule 1 (sVCAM-1), C-reactive protein (CRP), and serum amyloid A (SAA).Body weight (P < .001), percentage of fat (P < .001), visceral fat (P < .005), triglyceride levels (P < .001), and systolic blood pressure decreased comparably after WL and AEX+WL (P = .04). Maximal oxygen consumption increased 16% after AEX+WL (P < .001). Insulin resistance decreased in both groups (P = .005). Glucose utilization according to the clamp increased 10% (P = .04) with AEX+WL and 8% with WL (P = .07). AEX+WL decreased CRP by 29% (P < .001) and WL by 21% (P = .02). SAA levels decreased twice as much after AEX+WL (-19%, P = .02) as after WL (-9%, P = .08). Plasma sICAM-1 and sVCAM-1 levels did not change, but women with the greatest reduction in plasma sICAM-1 levels had the greatest reductions in fasting glucose (P = .02), insulin (P = .02), and insulin resistance (P = .004). Gluteal ICAM messenger ribonucleic acid levels decreased 27% after AEX+WL (P = .02) and did not change after WL.Obesity and insulin resistance worsen markers of systemic and vascular inflammation. A reduction in plasma sICAM-1 is important to improve insulin sensitivity. CRP, SAA, and tissue ICAM decrease with exercise and weight loss, suggesting that exercise training is a necessary component of lifestyle modification in obese postmenopausal women.

Dataset Information

Increased skeletal muscle capillarization after aerobic exercise training and weight loss improves insulin sensitivity in adults with IGT.

Publications

Increased skeletal muscle capillarization after aerobic exercise training and weight loss improves insulin sensitivity in adults with IGT.

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