High intensity intermittent exercise improves cardiac structure and function and reduces liver fat in patients with type 2 diabetes: a randomised controlled trial

Aims/hypothesis Cardiac disease remains the leading cause of mortality in type 2 diabetes, yet few strategies to target cardiac dysfunction have been developed. This randomised controlled trial aimed to investigate high intensity intermittent training (HIIT) as a potential therapy to improve cardiac structure and function in type 2 diabetes. The impact of HIIT on liver fat and metabolic control was also investigated. Methods Using an online random allocation sequence, 28 patients with type 2 diabetes (metformin and diet controlled) were randomised to 12 weeks of HIIT (n = 14) or standard care (n = 14). Cardiac structure and function were measured by 3.0 T MRI and tagging. Liver fat was determined by H-1-magnetic resonance spectroscopy and glucose control by an OGTT. MRI analysis was performed by an observer blinded to group allocation. All study procedures took place in Newcastle upon Tyne, UK. Results Five patients did not complete the study and were therefore excluded from analysis: this left 12 HIIT and 11 control patients for the intention-to-treat analysis. Compared with controls, HIIT improved cardiac structure (left ventricular wall mass 104 +/- 17 g to 116 +/- 20 g vs 107 +/- 25 g to 105 +/- 25 g, p < 0.05) and systolic function (stroke volume 76 +/- 16 ml to 87 +/- 19 ml vs 79 +/- 14 ml to 75 +/- 15 ml, p < 0.01). Early diastolic filling rates increased (241 +/- 84 ml/s to 299 +/- 89 ml/s vs 250 +/- 44 ml/s to 251 +/- 47 ml/s, p < 0.05) and peak torsion decreased (8.1 +/- 1.8 degrees to 6.9 +/- 1.6 degrees vs 7.1 A +/- 2.2 degrees to 7.6 +/- 1.9 degrees, p < 0.05) in the treatment group. Following HIIT, there was a 39% relative reduction in liver fat (p < 0.05) and a reduction in HbA(1c) (7.1 +/- 1.0% [54.5 mmol/mol] to 6.8 +/- 0.9% [51.3 mmol/mol] vs 7.2 +/- 0.5% [54.9 mmol/mol] to 7.4 +/- 0.7% [57.0 mmol/mol], p < 0.05). Changes in liver fat correlated with changes in HbA(1c) (r = 0.70, p < 0.000) and 2 h glucose (r = 0.57, p < 0.004). No adverse events were recorded. Conclusions/interpretation This is the first study to demonstrate improvements in cardiac structure and function, along with the greatest reduction in liver fat, to be recorded following an exercise intervention in type 2 diabetes. HIIT should be considered by clinical care teams as a therapy to improve cardiometabolic risk in patients with type 2 diabetes.