A single dose of sodium nitrate does not improve oral glucose tolerance in patients with type 2 diabetes mellitus

Abstract

Dietary nitrate supplementation has been proposed as an emerging treatment strategy for type 2 diabetes. We hypothesized that ingestion of a single bolus of dietary nitrate ingestion improves oral glucose tolerance in patients with type 2 diabetes. Seventeen men with type 2 diabetes (HbA1c: 7.3±0.2%) participated in a randomized crossover experiment. Subjects ingested a glucose beverage 2.5 h after consuming either sodium nitrate (0.15 mmol NaNO3-·kg-1) or a placebo solution. Venous blood samples were collected before ingestion of the glucose beverage and every 30 min thereafter during a 2-h period to assess postprandial plasma glucose and insulin concentrations. The results show that plasma nitrate and nitrite levels were increased after sodium nitrate as opposed to placebo ingestion (treatment-effect: P=0.001). Despite the elevated plasma nitrate and nitrite levels, ingestion of sodium nitrate did not attenuate the postprandial rise in plasma glucose and insulin concentrations (time x treatment interaction: P=0.41 for glucose, P=0.93 for insulin). Despite the lack of effect on oral glucose tolerance, basal plasma glucose concentrations measured 2.5 h after sodium nitrate ingestion were lower when compared with the placebo treatment (7.5±0.4 vs 8.3±0.4 mmol/L, respectively; P=0.04). We conclude that ingestion of a single dose of dietary nitrate does not improve subsequent oral glucose tolerance in patients with type 2 diabetes.