Improved endothelial function following a 14-month resistance exercise training program in adults with type 2 diabetes

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Abstract

Objective

We examined the effect of a 14-month progressive resistance training (PRT) program on endothelial function in both a supervised training (Center) group and non-supervised training (Home) group of patients with type 2 diabetes. We studied 28 men and women with type 2 diabetes who participated in a 14-month PRT involving an initial 2-month supervised program and a 12-month maintenance program.

Methods

Endothelial function testing was performed through laser doppler flow responses in the skin microcirculation to iontophoresis of acetylcholine (ACh) and sodium nitroprusside (NaNP) and doses of 4, 8 and 16 mC were used. Measurements of vascular response (VR), HbA1c, weight and blood pressure were performed at 0, 2 and 14 months.

Results

VR to ACh and NaNP was significantly increased at 14 months compared with baseline in both the Center and Home groups. However, no between-group differences were observed. A significant correlation was observed between HbA1c and VR to ACh at baseline and 8 weeks using 8 mC dose of ACh. There was a strong correlation between HbA1c at baseline and VR at 14 months using all three doses of ACh (4 mC:r = −0.546, p = 0.003, 8 mC:r = −0.470, p = 0.002, 16 mC:r = −0.547, p = 0.006).

Conclusions/interpretation

Endothelial function is improved following 14 months of PRT in type 2 diabetes both in a supervised and non-supervised program. Strong correlations with HbA1c including initial HbA1c levels suggest that glycemic control may be an important factor in long-term regulation of endothelial function.

Introduction

Type 2 diabetes is associated with a two- to three-fold increased risk of cardiovascular disease compared to the normal population. This increased risk is not fully explained by traditional cardiovascular risk factors. Endothelial dysfunction has been demonstrated in patients with clinical coronary artery disease [1] and in conditions predisposing to coronary artery disease including hypertension, obesity and dyslipidemia [2], [3], [4], [5], [6]. The attenuation or reversal of endothelial dysfunction may be important for the prevention of cardiovascular morbidity and mortality in diabetes.

Impaired endothelial function (EF) has been demonstrated in both type 1 and type 2 diabetes and this may be due to many factors including hyperglycemia, oxidative stress, insulin resistance and obesity [7], [8], [9]. Improved glycemic control associated with oral hypoglycemic agents and insulin therapy has been shown to improve EF in some studies [2], [10], [11], [12]. Furthermore, weight loss and physical activity have been shown to improve EF in obesity [2], [13], [14]. However, few studies have examined the effect of exercise training on EF in type 2 diabetes [15].

We have previously shown that high-intensity progressive resistance training (PRT) leads to improved glycemic control, muscle strength and well-being in adults with type 2 diabetes [16]. In an extension to this work, we have now examined the efficacy of PRT in the community fitness and recreation center setting for the maintenance of glycemic control [17]. The main trial was designed to assess the feasibility and effectiveness of long-term (12-months) PRT in the community fitness and recreation center and home-based settings in overweight adults with type 2 diabetes who had completed an initial 2-month period of supervised laboratory-based PRT. We now report on a sub-study nested within the main trial which examined the effects of PRT on vascular response (VR), a measure of endothelial function. We also assessed the relationship between changes in VR and HbA1c, BMI and measures of exercise adherence.

Section snippets

Patients

This study was a sub-study of a larger clinical trial in which individuals with type 2 diabetes were recruited from the clinics of the International Diabetes Institute and a local advertising campaign to measure the effects of a 14-month resistance exercise training program. Full details have been previously described in a recent publication in which 57 individuals were studied [17]. Recruitment for endothelial function testing began after recruitment for the main study and 31 of the 57

Results

Thirty-one people were initially recruited for this sub-study. Of these, two participants, from the Home group were unavailable for follow up at 14 months. One of the Home group did not attend for endothelial testing but did attend for pathology and physical examination. Thirteen females and sixteen males with mean age 60.5 ± 7.6 years completed the trial. There were no differences at baseline for HbA1c, BMI or age, between Center and Home groups (Table 1). Analysis of pooled data (both groups

Discussion

Our results demonstrate that a strength training program in adults with type 2 diabetes is associated with an improvement in endothelial dependent vasodilatation at 14 months but not at 2 months. This is the first long-term study of resistance training and endothelial function in type 2 diabetes. The improvement in vascular response was marked compared with modest improvements in glycemic control, weight and blood pressure. There was some improvement also in endothelial independent

Summary

This study suggests that a prolonged resistance training program may improve endothelial function in a previously sedentary population of patients with type 2 diabetes. The improvement demonstrated was marked despite only modest gains in glycemic control and body weight. There were no changes observed after 2 months of exercise suggesting more prolonged exercise is required to benefit endothelial function. Our findings may have important implications for the treatment of type 2 diabetes,

Conflict of interest

The authors state that they have no conflict of interest.

Acknowledgement

This study was financially supported by a grant from the Victorian Health Promotion Foundation (VicHealth).

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