Polyol pathway metabolites in human cataracts. Correlation of circulating glycosylated hemoglobin content and fasting blood glucose levels.

Circulating glycosylated hemoglobin (Hb A1) and/or fasting blood glucose (FBG) levels, measures of the extent to which diabetes is clinically controlled, were correlated with the contents of fructose, sorbitol, glucose, and inositol in 27 cataracts removed by intracapsular extraction. In the series of patients studied, Hb A1 levels ranged from 6.0% to 15.5% of the total hemoglobin value. The levels of fructose and sorbitol (micromoles per gram of lens) in their cataracts ranged from 0 to 8.4 and 0 to 10.2 mumole/g, respectively, with correlation coefficients greater than .8. Similar correlations were noted with FBG. The Hb A1 correlated with lens glucose (r = .58) and not with inositol. However, FBG had no correlation with either lens glucose or inositol. The observed correlation of the polyol pathway metabolites with both Hb A1 and FBG suggests that the lens can synthesize substantial quantities of sorbitol and fructose in response to the excess glucose available to lenses of human diabetics. A synergistic role of the polyol pathway in the cause of senile cataracts is thus possible.