Impact of dietary fat on Th1/Th2 cytokine gene expression in the pancreas and gut of diabetes-prone BB rats.

The effect of dietary n-3 or n-6 polyunsaturated fatty acids on the development of autoimmune insulitis was analysed in diabetes-prone BB rats. Litter-matched groups of rats received a standard open formula NIH-07 (National Institutes of Health, NIH) diet enriched with 10% fish oil, 10% flaxseed oil or with 10% palm oil plus 2% cholesterol during the period of insulitis onset (50-70 days of age). Analysis of cytokine gene expression in pancreatic RNA revealed an increase of IFN-gamma and a decrease of IL-10 mRNA with onset of insulitis. When compared to unsupplemented NIH, none of the three fat-enriched diets depressed the rise of IFN-gamma gene expression or the influx of leukocytes into islets. However, all of the fat-enriched diets led to significantly higher IL-10 mRNA levels. Although a specific anti-inflammatory effect of fish oil was not seen in the pancreas, a clear shift of the Th1/Th2 cytokine mRNA ratio towards Th2 was seen in the gut-associated immune system. We conclude that diets high in fat support IL-10 without suppressing IFN-gamma gene expression in islet inflammation. A special anti-inflammatory effect of fish oil was not seen in pancreatic lesions of BB rats, although there was strong modulation of the IFN-gamma/IL-10 mRNA ratio in the gut associated immune system.