Examination of the Effects of a Sphingolipid-Enriched Lipid Fraction from Wheat Gluten on the Incidence of Diabetes in BBdp Rats
This study was designed to examine if a sphingolipid-enriched lipid fraction from wheat gluten could affect the incidence of type I diabetes in BioBreeding diabetes prone (BBdp) rats. Wheat gluten was extracted with a chloroform-methanol (CM) mixture to isolate most of the lipids. Isolated lipids were subjected to silica gel column chromatography and saponification to remove most of neutral lipids and phospholipids, leaving behind a lipid fraction enriched in sphingolipids. This sphingolipid-enriched lipid fraction was used in a BBdp rat feeding study. BBdp rats were fed with one of five diets from weaning at 23 days of age until 125 days of age: a hydrolyzed casein based diet (HC), a NTP-2000 standard rodent diet (NTP-2000), a wheat gluten based diet (WG), a sphingolipid-free wheat gluten based diet (WGSLF), and a hydrolyzed casein plus sphingolipid-enriched lipid fraction diet (HC+SL).
The yield of sphingolipid-enriched lipid fraction was about 0.62% of wheat gluten. The content of glycosylceramide in sphingolipid-enriched lipid fraction was increased more than five fold compared to that in total isolated lipids. Rats fed the NTP-2000 diet had the highest incidence of diabetes; while rats on the HC diet had the lowest diabetes incidence. There was no significant difference with regard to the onset age of diabetes among rats in the five diet groups. The addition of sphingolipid-enriched fraction to the HC diet caused a significant increase in the incidence of diabetes in BBdp rats in the first 80 days of the study. However, the ultimate diabetes incidence at day 125 was not changed. The removal of lipids from wheat gluten did not change the diabetes incidence in BBdp rats at any stages of the feeding study. These findings suggest that the sphingolipid-enriched fraction from wheat gluten acted as a possible promoter but not as a trigger of the development of type I diabetes in BBdp rats. There must be something that remains in wheat gluten after chloroform-methanol extraction that serves as a trigger for type I diabetes in these rodents. Type I diabetes in this animal model for the human disease seems to be caused by multiple factors, most likely, by the interaction of sphingolipids and some other unknown substances in wheat gluten.