This review deals with the age- and diet-related metabolic and functional anomalies found in BB rats, currently considered as an animal model of type 1 diabetes mellitus. The metabolism of nutrients, the secretion of insulin, the production of NO, the effects of IL-1β and the activity of the mitochondrial FAD-linked glycerophosphate dehydrogenase in pancreatic islets are first considered. The metabolism and mitotic activity in Peyers patch cells and both mesenteric and pancreatic lymph node cells are then evoked. The occurrence of intestinal dysfunction is mentioned, with emphasis on recent findings made in BB rats before weaning. The participation of zonulins and mucins in the perturbation of gut permeability are also discussed. Last, attention is drawn to the perturbation of the anomeric specificity of glucose-induced insulin release, considered as a manifestation of pancreatic islet beta-cell glucotoxicity.