Low-glycemic diet seen to reverse diastolic dysfunction of diabetes

Vienna, Austria - A diet that was short on carbohydrates and long on protein, given to diabetic patients engaged in a supervised exercise and weight-loss program, appeared not only to cut proinsulin levels and postprandial glucose and triglyceride levels, it seemed to improve LV diastolic function [1].

In the study that compared the "low-carb" diet to a traditionally recommended low-fat diet, the one designed to flatten out resulting insulin and glucose curves also allowed them to take far fewer oral diabetes medications and apparently cut both systolic and diastolic pressures. The low-fat diet had no apparent effect on diastolic function or med use or on blood pressures.

Prof Helene von Bibra

On the other hand, the two diets led to about the same declines in weight and waist circumference and lipoprotein-cholesterol levels, reported Prof Helene von Bibra (Technical University Munich, Germany) here at the Prediabetes and the Metabolic Syndrome 2013 Congress.

Many patients with insulin resistance, diabetes, or both have subclinical diastolic dysfunction, with severe prognostic implications if it becomes symptomatic, von Bibra reminded heartwire. About 65% of the 32 patients in the study had abnormal diastolic function as defined echocardiographically by low early diastolic myocardial velocity. That measure in most cases nearly normalized after the low-carb diet, but not after the low-fat diet, she said.

Of 32 overweight or obese diabetic patients (mean body-mass index, 34) without cardiac disease who were engaged in a "rehabilitation program in order to lose weight" that included two hours of supervised aerobic exercise per day, half followed a low-glycemic diet (25% carbohydrate, 45% fat, 30% protein) and the other half a low-fat diet (55% carbohydrate, 25% fat, and 20% protein) for three weeks. The diets provided the same amount of calories. Those on the low-fat diet then switched to the low-glycemic diet for an additional two weeks. Cardiac function by echo and metabolic parameters were assessed daily before and after a 400-kcal breakfast.

From baseline to three weeks, patients on the low-carb diet reduced their use of conventional oral antidiabetic medication by 86%. Those on the low-fat diet reduced them by only 6% by the end of three weeks, but intake went down another 57% by the end of their two-week low-glycemic diet phase. "And still they had improvements in glucose," von Bibra said. Medications other than oral ones for diabetes, such as antihypertensive drugs, were not changed in anyone during the study.

Laboratory and echo changes in overweight/obese diabetic patients assigned to low-glycemic (n=16) and low-fat (n=16) diets

Initial assigned diet	Baseline	3 wk	2 wk after crossover to low-carb	p
Low-glycemic
Triglycerides (mg/dL)	150	111	—	<0 .005="" br="">
Postprandial glucose (mg/dL)	141	125	—	<0 .04="" br="">
E' (cm/s)	9.5	10.4	—	<0 .03="" br="">
Low-fat
Triglycerides (mg/dL)	208	194	138	<0 .003="" 3="" baseline="" br="" vs="" wk="">
Postprandial glucose (mg/dL)	168	137	127	<0 .008="" baseline="" br="" vs="">
E' (cm/s)	10.8	10.7	11.4	<0 .02="" 3="" br="" vs="" wk="">

E'=early diastolic myocardial velocity by tissue-Doppler echocardiography

The gains in diastolic function probably were not independently related to the associated blood-pressure reductions; rather, she proposed, they reflected improvements in myocardial energy utilization on the low-glycemic diet. Insulin resistance can lead to diastolic dysfunction via several pathways, she noted, but the most prominent seems to be myocardial energy deficiency secondary to microvascular dysregulation and mitochondrial imbalances of glucose vs fat oxidation.

APRIL 22, 2013 Steve Stiles