Abstract
Aims/hypothesisIt remains unclear whether and which modality of exercise training as a component of lifestyle intervention may exert favourable effects on somatosensory and autonomic nerve tests in people with type 2 diabetes.MethodsCardiovascular autonomic and somatosensory nerve function as well as intraepidermal nerve fibre density (IENFD) were assessed in overweight men with type 2 diabetes (type 2 diabetes, n = 20) and male glucose-tolerant individuals (normal glucose tolerance [NGT], n = 23), comparable in age and BMI and serving as a control group, before and after a supervised high-intensity interval training (HIIT) intervention programme over 12 weeks. Study endpoints included clinical scores, nerve conduction studies, quantitative sensory testing, IENFD, heart rate variability, postural change in systolic blood pressure and spontaneous baroreflex sensitivity (BRS).ResultsAfter 12 weeks of HIIT, resting heart rate decreased in both groups ([mean ± SD] baseline/12 weeks: NGT: 65.1 ± 8.2/60.2 ± 9.0 beats per min; type 2 diabetes: 68.8 ± 10.1/63.4 ± 7.8 beats per min), while three BRS indices increased (sequence analysis BRS: 8.82 ± 4.89/14.6 ± 11.7 ms2/mmHg; positive sequences BRS: 7.19 ± 5.43/15.4 ± 15.9 ms2/mmHg; negative sequences BRS: 12.8 ± 5.4/14.6 ± 8.7 ms2/mmHg) and postural change in systolic blood pressure decreased (−13.9 ± 11.6/−9.35 ± 9.76 mmHg) in participants with type 2 diabetes, and two heart rate variability indices increased in the NGT group (standard deviation of R–R intervals: 36.1 ± 11.8/55.3 ± 41.3 ms; coefficient of R–R interval variation: 3.84 ± 1.21/5.17 ± 3.28) (all p<0.05). In contrast, BMI, clinical scores, nerve conduction studies, quantitative sensory testing, IENFD and the prevalence rates of diabetic sensorimotor polyneuropathy and cardiovascular autonomic neuropathy remained unchanged in both groups. In the entire cohort, correlations between the changes in two BRS indices and changes in dot{V}{mathrm{O}}_{2max } over 12 weeks of HIIT (e.g. sequence analysis BRS: r = 0.528, p=0.017) were observed.Conclusions/interpretationIn male overweight individuals with type 2 diabetes, BRS, resting heart rate and orthostatic blood pressure regulation improved in the absence of weight loss after 12 weeks of supervised HIIT. Since no favourable effects on somatic nerve function and structure were observed, cardiovascular autonomic function appears to be more amenable to this short-term intervention, possibly due to improved cardiorespiratory fitness.Graphical abstract
Highlights
Diabetic sensorimotor polyneuropathy (DSPN) and cardiovascular autonomic neuropathy (CAN) are substantial contributors to an increased morbidity and mortality risk and reduced quality of life in people with diabetes [1]
The results of this study demonstrate an improvement in spontaneous baroreflex sensitivity (BRS) and orthostatic blood pressure regulation after
While several exercise interventions showed that physical activity may improve cardiovascular autonomic regulation in type 2 diabetes [35], studies assessing the effects of high-intensity interval training (HIIT) on cardiovascular autonomic nerve function in patients with diabetes are scarce
Summary
Diabetic sensorimotor polyneuropathy (DSPN) and cardiovascular autonomic neuropathy (CAN) are substantial contributors to an increased morbidity and mortality risk and reduced quality of life in people with diabetes [1]. 30% of individuals with diabetes are affected by DSPN [2]. The prevalence of CAN in individuals with diabetes has been estimated to vary between 16% and 31% depending on the diagnostic criteria used [2]. CAN is characterised by reduced, predominantly vagally mediated, heart rate variability (HRV), increasing the risk of clinical features such as resting tachycardia, orthostatic hypotension, exercise intolerance and silent myocardial ischaemia [3]. Both DSPN and CAN may develop insidiously with a considerable heterogeneity of clinical features and complications, while the complex multifactorial pathogenesis remains incompletely understood [3]
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