Low-carbohydrate/high-protein diet improves diastolic cardiac function and the metabolic syndrome in overweight-obese patients with type 2 diabetes

Background: Diastolic dysfunction/heart failure in the metabolic syndrome and type 2 diabetes (T2D) is an epidemic without evidence-based treatment strategies. While improved glycemic control/insulin sensitivity has been associated with augmented cardiac function in pharmacologic studies, studies on dietary intervention are scarce. Low-carbohydrate nutrition (LC) improves postprandial glucose control and insulin resistance more than standard low-fat diet (LF). We tested the hypothesis, that LC improves cardiac function in overweight-obese patients with T2D more than LF. Methods: Two matched groups of 16 T2D patients without overt heart disease (52 ± 7 years, BMI 34 ± 6 kg/m2) were studied in a parallel and partial cross-over design during a 3-week rehabilitation programme with either LC or LF followed by 2 weeks LC. Cardiac function was assessed as myocardial velocity during systole and early diastole (E′) using Doppler tissue imaging and metabolic control before and after a standardised breakfast. Results: In the parallel groups, both diets induced similar and significant reductions of weight, HbA1c and cholesterol. LC considerably improved insulin resistance, fasting and postmeal triglycerides, blood pressure and diastolic cardiac function E′ (by 0.9 ± 1.4 cm/s, p = 0.023). None of these variables changed on LF, but all of them improved significantly after subsequent LC (E′ by 0.9 ± 1.1 cm/s, p = 0.023). Postprandial intact proinsulin was unchanged on LF but decreased with subsequent LC (p = 0.032). Conclusions: These data indicate, that a low-glycaemic/high-protein but not a low-fat/high-carbohydrate nutrition modulates diastolic dysfunction in overweight T2D patients, improves insulin resistance and may prevent or delay the onset of diabetic cardiomyopathy and the metabolic syndrome