To measure the effects of cyclosporin A (CyA) with no insulin therapy on glucose tolerance and β-cell function in the preclinical phase of insulin-dependent diabetes mellitus (IDDM).
β-cell responses to the intravenous glucose tolerance test (IVGTT), hyperglycemic clamp, intravenous arginine, and intravenous glucagon were evaluated before and after a 6-month course of CyA in seven patients (mean age 19.6 years) with asymptomatic IDDM.
Initial insulin secretory responses were severely decreased when the patients were compared with eight healthy control subjects: IVGTT (1 + 3 min): 106 ± 16 vs. 884 ± 190 pmol/l (P < 0.001); hyperglycemic clamp: 102 ± 16 vs. 310 ± 42 pmol/l (P < 0.001); intravenous arginine: 346 ± 72 vs. 1104 ± 168 pmol/l (P < 0.01); and intravenous glucagon: 170 ± 37 vs. 247 ± 35 pmol/l (NS). The β-cell responses remained markedly abnormal after 6 months of CyA, although the response to intravenous glucose and oral glucose tolerance tests improved in three subjects. All the patients became insulin-dependent after 5–36 months.
CyA alone is not a suitable treatment for asymptomatic IDDM. Earlier identification of subjects with substantial β-cell secretory capacity and newer nontoxic intervention strategies are required for the prevention of IDDM.
