MUSCLE EXTRACELLULAR MEMBRANE IMMUNOFLUORESCENCE AND HLA AS POSSIBLE MARKERS OF PREDIABETES

Abstract

Markers for prediabetes were sought in a study of 29 non-diabetic sibs of patients with insulin-dependent diabetes, 18 of whom were HLA-identical, and 11 non-HLA identical, to their diabetic sibs, and 47 controls. HLA-identical sibs had higher mean plasma glucose levels than controls at 60, 90, and 120 min during oral glucose tolerance tests (GTT). Similarly, mean serum insulin levels were higher in HLA-identical sibs than in controls at 60 and 90 min during the GTT. Non-HLA-identical sibs had higher glucose and insulin levels only at 60 min when compared to controls, but they were not different from HLA-identical sibs at any time during the GTT. HLA-identical sibs had significantly more intense immunofluorescent (IF) staining of albumin in the skeletal muscle extracellular membrane than either non-HLA-identical sibs or controls. IF staining for IgG in the skeletal muscle extracellular membrane was significantly more intense in both sib groups than in the controls. Muscle capillary basement thickness was normal in both sib groups. There were no significant differences among the three groups for glycosylated hæmoglobin and cytoplasmic islet-cell antibodies. Since HLA identity with the proband is likely to be a marker for prediabetes in diabetic families, the abnormal IF staining of muscle extracellular membrane for protein is likely to be an expression of the prediabetic state and may be related to mild, possibly intermittent, glucose intolerance.