Exercise better than diet to combat early heart changes in type 2 diabetes
medwireNews: The results of a small randomized trial suggest exercise is more helpful than diet for combating early cardiac dysfunction associated with type 2 diabetes, although both may be beneficial.
“It is possible that the best approach for improving stage B heart failure in people with [type 2 diabetes] is a combination of exercise and dietary restriction to achieve weight loss, given the different effects of these interventions on diastolic function and cardiac remodeling in our study,” say Gerry McCann (University of Leicester, UK) and study co-authors.
The researchers believe that the 87 people with type 2 diabetes enrolled to their study were in the early stages of heart failure, having had diabetes for a median of 56 months at an average age of 50 years.
For example, compared with 36 healthy control participants, the people with diabetes had a significantly lower ratio of left ventricular (LV) mass to volume, a reduced early diastolic to late filling ratio (E/A), and an increased LV filling pressure (E/e’).
“Diastolic dysfunction and concentric LV remodeling are typically the earliest manifestations of diabetic cardiomyopathy and precursors to the onset of clinical heart failure,” write McCann and team in Diabetes Care.
The trial’s primary endpoint of LV peak early diastolic strain rate, which indicates the speed of myocardial relaxation, was also significantly lower in people with than without diabetes, at 1.01 versus 1.10 s-1.
However, this endpoint improved in the 22 people with diabetes who successfully completed 12 weeks of supervised, moderate-intensity aerobic exercise sessions three times weekly, improving from 0.92 to 1.02 s-1 compared with decreases from 1.00 to 0.96 s-1 in the 24 people with diabetes who completed a 12-week low-calorie meal-replacement plan and from 1.02 to 0.98 s-1 in the 30 who received usual care.
This suggests that “supervised aerobic exercise training may improve the earliest functional consequence of [type 2 diabetes] on the myocardium,” say the researchers, adding that “beneficial effects on diastolic function were observed even when only accompanied by small improvements in fitness.”
E/A and E/e’ “tended to improve in both intervention arms,” says the team, and they note that these measurements “may have been confounded by relatively poor image quality in this obese cohort where 20% had inadequate windows for complete assessment.”
The diet group had large improvements in weight, blood pressure, and glucose metabolism. Although there were no significant changes in cardiac variables, the researchers did find “modest” improvements in LV mass, indexed LV end-diastolic volume, concentric LV remodeling, and aortic distensibility, which they say “may indicate favorable long-term effects of the dietary restriction or weight loss on the structural manifestations of heart failure in [type 2 diabetes].”
There was also a 4.54% reduction in LV ejection fraction, which they believe may “reflect normalization of hyperdynamic LV function with weight loss.”
Nevertheless, McCann and colleagues conclude that diastolic dysfunction is likely not reversible purely by improving glucose dysregulation.
They say: “Further trials are needed to assess the cardiovascular effects of combined exercise with dietary restriction and weight loss in people with [type 2 diabetes] and for longer durations.”
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