L-Arginine enriched biscuits improve endothelial function and glucose metabolism : a pilot study in healthy subjects and a cross-over study in subjects with impaired glucose tolerance and metabolic syndrome

Objective. The aim of this study was to evaluate the effects of a new L-rginine-enriched biscuit on endothelial function, insulin sensitivity/secretion and body composition. Materials/Methods. The project was composed of two studies. The first study was an acute pilot postprandial study in 7 healthy subjects that evaluated bio-availability and vascular effects of L-arginine-enriched biscuits that contained 6.6gL-arginine, 21.9g carbohydrates, 3.6g protein, 7.5g fat and 4.3g dietary fiber compared with placebo biscuits and 6.6g powdered L-arginine. Subjects underwent the tests in random order, in at least 14-day intervals. The second study was a double-blind crossover study in 15 obese subjects with IGT and MS. These subjects consumed 6.6g of L-arginine-enriched biscuits or placebo biscuits in a 1600kcal diet. Each study period lasted 2weeks with a 2-week washout in between.Endothelial function, glucose tolerance, insulin sensitivity and insulin secretion were evaluated at the end of each intervention period. Results. In the first study, the groups that received the L-arginine-enriched biscuits and the powdered L-arginine had similarly increased L-arginine, NOx and cGMP levels and postischemic blood flow (PI-BF). In both cases, these levels were significantly higher than those in the placebo biscuit recipient group. In the second study, the L-arginine-enriched biscuit recipient group displayed increased L-arginine, NOx, cGMP, PI-BF, and Matsuda index levels, whereas their circulating glucose, proinsulin/insulin ratio and fat mass were decreased compared with the placebo biscuit recipient group. Conclusions. L-Arginine-enriched biscuits with low sugar and protein content enhance endothelial function and improve glucose metabolism, insulin sensitivity and insulin secretion in subjects with IGT and MS.