Glycosylated Hemoglobin in Normal Subjects and Subjects with Maturity-onset Diabetes Evidence for a Saturable System in Man

Concentrations of glycosylated hemoglobin (GHb) are elevated in diabetes mellitus and are believed to reflect previous metabolic control. To better define possible determinants of GHb in man, we investigated the relationship between GHb and both fasting plasma glucose (FPG) and basal insulin (IRI) in 42 normal subjects and 29 patients with maturity-onset diabetes. Concentrations of GHb in diabetic subjects (12.7 ± 3.4, x ± S.D., per cent total hemoglobin) were significantly higher than in normal subjects (8.2 ± 1.2, p < 0.001). In normal subjects, FPG (r = 0.52) and GHb (r = 0.58) (both p < 0.001) correlated with age. GHb did not correlate with IRI in either group. However, GHb was closely associated with FPG in both normal (r = 0.60, p < 0.001) and diabetic (r = 0.85, p < 0.001) subjects. Linear regression analysis of the data for the two groups combined was highly significant (r = 0.91, p < 0.001). However, the slope of the regression line for GHb versus FPG seen in normal subjects was significantly steeper than that of diabetic patients (p < 0.005). A curve describing a nonenzymatic saturable model was also found to fit the data of the two groups combined (r = 0.85, p < 0.001), suggesting the possible existence of a saturable system for glycosylation in man.