Correlation between residual beta-cell function and age at onset of spontaneous diabetes in Long Evans Tokushima lean rats.

We studied the natural course of disease in spontaneously diabetic rats, Long Evans Tokushima Lean (LETL) rats, to determine whether it showed similar pathogenetic heterogeneity to that of patients with insulin-dependent diabetes mellitus (IDDM) with regard to the relationships between age at onset, rapidity of disease progress, and degree of beta-cell function at the time of its manifestation. Type 1 diabetes developed in 35 rats (6.3%) between 40 and 140 days of age. Eight rats that became diabetic at age 69 days or less were more severely ketotic at the time of first detection of glycosuria and showed more rapid deterioration than seven rats that became diabetic later after birth (mean plasma 3-hydroxybutyrate levels, 4,707 +/- 1,215 pmol/L v 1,390 +/- 859 pmol/L; mean +/- SEM, P < .01). The mean plasma levels and pancreatic content of immunoreactive insulin (IRI) of the early onset rats, 47 +/- 13 pmol/L and 19 +/- 12 pmol/g tissue weight, were significantly lower (P < .01) than the corresponding values of the late-onset rats, 262 +/- 52 pmol/L and 348 +/- 87 pmol/g tissue weight, respectively. Both values were markedly lower than the mean values of 25 nondiabetic LETL rats, 976 +/- 122 pmol/L and 3,488 +/- 628 pmol/g tissue weight. Plasma immunoreactive glucagon (IRG) levels were significantly increased in the diabetic groups (early onset, 57 +/- 13 pmol/L; late-onset, 51 +/- 12 pmol/L; nondiabetic, 18 +/- 1 pmol/L; P < .01). These changes in pancreatic hormone levels of the early onset and late-onset rats were compatible with the histological features of their pancreatic islets.(ABSTRACT TRUNCATED AT 250 WORDS)