Functional high-intensity training improves pancreatic β-cell function in adults with type 2 diabetes

Abstract

Type 2 diabetes (T2D) is characterized by reductions in β-cell function and insulin secretion on the background of elevated insulin resistance. Aerobic exercise has been shown to improve β-cell function, despite a subset of T2D patients displaying "exercise resistance." Further investigations into the effectiveness of alternate forms of exercise on β-cell function in the T2D patient population are needed. We examined the effect of a novel, 6-wk CrossFit functional high-intensity training (F-HIT) intervention on β-cell function in 12 sedentary adults with clinically diagnosed T2D (54 ± 2 yr, 166 ± 16 mg/dl fasting glucose). Supervised training was completed 3 days/wk, comprising functional movements performed at a high intensity in a variety of 10- to 20-min sessions. All subjects completed an oral glucose tolerance test and anthropometric measures at baseline and following the intervention. The mean disposition index, a validated measure of β-cell function, was significantly increased (PRE: 8.4 ± 3.1, POST: 11.5 ± 3.5, P = 0.02) after the intervention. Insulin processing inefficiency in the β-cell, expressed as the fasting proinsulin-to-insulin ratio, was also reduced (PRE: 2.40 ± 0.37, POST: 1.78 ± 0.30, P = 0.04). Increased β-cell function during the early-phase response to glucose correlated significantly with reductions in abdominal body fat (R² = 0.56, P = 0.005) and fasting plasma alkaline phosphatase (R² = 0.55, P = 0.006). Mean total body-fat percentage decreased significantly (Δ: -1.17 0.30%, P = 0.003), whereas lean body mass was preserved (Δ: +0.05 ± 0.68 kg, P = 0.94). We conclude that F-HIT is an effective exercise strategy for improving β-cell function in adults with T2D.

Keywords: exercise; insulin secretion; obesity; pancreas; type 2 diabetes.

Fig. 1.

A: early-phase pancreatic cell function PRE to POST intervention, presented as the mean disposition index. B: insulin-processing inefficiency expressed as the ratio between fasting proinsulin and insulin. C: individual changes with means ± SE. DI change with individuals with changes below the mean are indicated with crossed circles; DI change with individuals with changes above the mean are indicated with filled circles. Individual changes in secretion (D) and sensitivity (E), keeping the same individual demarcations used in C. *P < 0.05; n = 12.

Fig. 2.

Correlations of changes in early-phase β-cell function (A and C) and secretion (B and D) vs. abdominal fat percentage (A and B) and fasting ALP (C and D). Linear regression is shown with a 95% confidence interval with Pearson correlation coefficient of determination (R²) and significant P value; n = 12.