INS and diabetes mellitus: The LEA rats exhibit several distinctive diabetes-related characteristics: (1) onset of diabetes is observed only in male rats, not in female, at over 6 months of age; (2) the early-phase insulin secretion is impaired at 2 months of age; (3) the progressive fibrosis in islet in an age-dependent manner; (4) a normal glycaemic response to exogenous insulin; (5) nonobese.