Regional muscle glucose uptake remains elevated one week after cessation of resistance training independent of altered insulin sensitivity response in older adults with type 2 diabetes

Abstract

Background: Aging is associated with a decline in skeletal muscle size.Muscle is critical both for mobility and glucose disposal. While resistance exercise (RE) increases muscle mass and function in the elderly, its role in improving glucose utilization is less clear.

Aims: To investigate whether muscle size was linked with insulin sensitivity (IS) in elders with diabetes following RE and if regional muscle glucose uptake differed from systemic glucose utilization.

Methods: Seven (68.4 ± 5.9 yr) adults with diabetes participated. After 16 weeks of RE, within 24 h (post 1) and after 1 week of no exercise (post 2), lean tissue cross-sectional area (CSA) and IS via glucose infusion rate (GIR) were assessed along with a standardized 18-F fluorodeoxyglucose (FDG)-positron emission tomography uptake value (SUV).

Results: CSA increased between pre-test (108.5 ± 35.3 cm2) and post 1 (116.8 ± 40.9 cm2), p=0.02 and did not differ at post 2 (116.0 ± 39.3 cm2). GIR during the 40 mU/m2/min insulin clamp differed between pretest (22.0 ± 15.8 mg/kg/min) and post 1 (67.9 ± 72.8 mg/kg/min), and post 1 and post 2 (25.0 ± 27.2 mg/kg/min) but not between pre-test and post 2. GIR results during the 200 mU/m2/min insulin clamps also differed between pre-test and post 1, and post 1 and post 2 but not between pre-test and post 2. FDG-SUV increased between pre-test (1.1 ± 0.2) and post 1 (1.4 ± 0.3), and remained stable between post 1 and post 2 (1.4 ± 0.4).

Conclusion: RE that increased muscle size and FDG-SUV improved IS 24 h but not 1 week after exercise training.

Fig. 1

Experimental design. Timeline and data collection points for the study. Post-test 1 was performed within 24 h of the final exercise session, post-test 2 was performed 7 days after post-test 1. Each testing session included a hyperinsulinemic-euglycemic clamp, 18-F fluorodeoxyglucose-position emission totmography (PET) scan, vastus lateralis muscle biopsy, and thigh magnetic resonance imaging (MRI) and was preceded by a 3-day prepared diet.

Fig. 2

Representative pre- (A) and post 1 (B) magnetic resonance imaging (MRI) images.

Fig. 3

Muscle glucose transporter 4 (GLUT4) content. Western analysis of the glucose transporter GLUT4. Graph represents fluorescent values determined as outlined in methods corrected to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and normalized to pre-samples (=1.0). Data are mean±SEM. no.=7, p<0.02 vs pre-test.