Rapeseed protein inhibits the initiation of insulin resistance by a high-saturated fat, high-sucrose diet in rats.

In contrast to the quality of carbohydrates and lipids, little is known on the influence of the type of dietary protein on the development of the metabolic or insulin resistance syndrome. Cysteine intake has been recently documented to impact insulin sensitivity. The aim of this study was to determine whether rapeseed protein, an emergent cysteine-rich protein, could inhibit the onset of the metabolic syndrome. For 9 weeks, rats were fed a diet rich in saturated fats and sucrose, which also included 20 % protein either as milk protein ('Induction' diet I) or rapeseed protein (diet R). A third, control group received an isoenergetic diet containing milk protein but polyunsaturated fats and starch ('Prudent' diet P). Plasma glucose, insulin, TAG and cholesterol, and blood pressure were monitored during the study, glucose tolerance was tested at week 7 and body composition determined at week 9. Plasma glucose, insulin and TAG increased during the experiment and, at week 9, plasma insulin was significantly 34 % lower in the R group and 56 % lower in P group as compared with the I group. The insulin peak after the glucose load was significantly 28-30 % lower in R and P than in I and the insulin sensitivity index was significantly higher in R than in I. Unexpectedly, peripheral fat deposition was slightly higher in R than in I. In this model, substituting rapeseed protein for milk protein had preventive effects on the early onset of insulin resistance, similar to those achieved by manipulating the types of dietary fat and carbohydrates.

The poor digestibility of rapeseed protein is balanced by its very high metabolic utilization in humans.

Rapeseed protein (RP, Brassica napus) is used in only animal feed despite its high nutritional potential for human nutrition. We sought to assess the nutritional quality of rapeseed by measuring its real ileal digestibility (RID) and net postprandial protein utilization (NPPU) in humans fed (15)N-RP. Volunteers equipped with an intestinal tube at the jejunal (n = 5) or ileal level (n = 7) ingested a mixed meal containing 27.3 g (15)N-RP and a total energy content of 700 kcal (2.93 MJ). Dietary N kinetics was quantified in intestinal fluid, urine, and blood sampled at regular intervals during the postprandial period. The RID of RP was 84.0 +/- 8.8%. Dietary N at the ileal level was mostly in the form of undigested protein from both 12S and 2S rapeseed fractions. Aminoacidemia was not significantly increased by meal ingestion. The postprandial distribution of dietary N was 5.4 +/- 1.8% in urinary urea and ammonia, 8.2 +/- 3.4% in body urea, and 7.7 +/- 2.0% in plasma protein 8 h after the meal. The NPPU of RP amounted to 70.5 +/- 9.6% and the postprandial biological value (PBV) was high at 83.8 +/- 4.6%. RP has a low RID in humans compared with other plant proteins but also exhibits a very low deamination rate. Thus, the PBV of RP is excellent in humans, being as high as that of milk protein. We conclude that RP has a high nutritional potential for human nutrition.