Muscle Mitochondrial Capacity and Endurance in Adults with Type 1 Diabetes

Abstract

15ABSTRACT 16 The impact of type 1 diabetes (T1D) on muscle endurance and oxidative capacity is 17 currently unknown. Purpose: Measure muscle endurance and oxidative capacity of adults 18 with T1D compared to controls. Methods: A cross-sectional study design with a control 19 group was used. Subjects (19-37 years old) with T1D (n=17) and controls (n=17) were 20 assessed with hemoglobin A1c (HbA1c) and casual glucose. Muscle endurance was21 measured with an accelerometer at stimulation frequencies of 2, 4, and 6 Hz for a total of 22 nine minutes. Mitochondrial capacity was measured using near-infrared spectroscopy after 23 exercise as the rate constant of the rate of recovery of oxygen consumption. Results: T1D 24 and control groups were similar in age, sex, height, and race. The T1D group had slightly 25 higher BMI values and adipose tissue thickness over the forearm muscles. Casual glucose 26 was 150+70 mg/dL for T1D and 98+16 mg/dL for controls (P=0.006). HbA1c of T1D 27 subjects was 7.1+0.9% and 5.0+0.4% for controls (P<0.01). Endurance indexes at 2, 4, 28 and 6 Hz were 94.5+5.2%, 81.8+8.4%, and 68.6+13.5% for T1D and 94.6+4.1%, 29 85.9+6.3%, and 68.7+15.4% for controls (p = 0.97, 0.12, 0.99, respectively). There were 30 no differences between groups in mitochondrial capacity (T1D= 1.9+0.5 min -1 and 31 control=1.8+0.4 min -1 , P=0.29) or reperfusion rate (T1D= 8.8+2.8s and control=10.3+3.0s, 32 P=0.88). There were no significant correlations between HbA1c and either muscle 33 endurance, mitochondrial capacity or reperfusion rate. Conclusions: Adults with T1D did 34 not have reduced oxidative capacity, muscle endurance or muscle reperfusion rates 35 compared to controls. HbA1c also did not correlate with muscle endurance, mitochondrial 36 capacity or reperfusion rates. Future studies should extend these measurements to older 37 people or people with poorly-controlled T1D. 38 3 39