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-arginine-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 post-ischemic 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.