Dietary triggers of insulin-dependent diabetes in the BB rat.

Environmental "triggers" (including viruses, toxins and dietary factors) have been implicated in the pathogenesis of insulin-dependent diabetes mellitus. Data have suggested a possible role for cow's milk protein (CMP) as a trigger of diabetes. To study this further, 86 BB rats were divided into 2 groups during the weaning period (days 13-25): Group A received rat chow without CMP; Group B, rat chow with 1% CMP added. Each group was subdivided afterwards into 2: Groups A1 and B1 received chow without CMP; Groups A2 and B2, chow with CMP. Animals weaned with chow containing CMP (B1 and B2) had a higher incidence of diabetes (66%) than those weaned without (A1 and A2; 29%, p less than 0.001). The incidence in both B1 and B2 was significantly greater than in either A1 or A2 (p less than 0.05). The highest incidence of diabetes occurred in male rats weaned on rat chow with CMP (90%), the incidence being significantly higher than female rats weaned with (43%) or without CMP (18%) and males weaned without CMP (39%). Thus, it appears that (a) the presence of cow's milk protein in the diet increases the incidence of diabetes in the BB rat; (b) the critical time for exposure to CMP appears to be the weaning period; and (c) male rats appear to be more susceptible to the development of diabetes than female rats, when exposed to this trigger. This supports the hypothesis that dietary triggers may play an important role in the expression of diabetes in the susceptible host and that its prevalent action occurs early in life.