Abstract
Forty-two non-diabetics whose glycated haemoglobin levels could not be explained by their levels of fasting glycaemia or glucose tolerance were identified as part of the Islington Diabetes Survey. Mean glycated haemoglobin levels that were high relative to their blood glucose levels (HIGH GLYCATORS) were found in 22 subjects whilst 20 subjects had low relative levels (LOW GLYCATORS). A repeat glucose tolerance test in 13 of the 42 subjects (7 high and 6 low glycators) showed that they remained categorised in the two groups four years after the discrepancy was identified. Mean blood glucose levels calculated from two 5-point diurnal profiles also failed to explain the glycated haemoglobin levels in the two groups. Further biochemical and haematological tests revealed that glycated albumin showed a better relationship with blood glucose levels than did glycated haemoglobin. Intra-erythrocyte glucose concentrations were significantly lower than the plasma glucose in the low glycators, whilst the levels of erythrocyte 2,3-diphosphoglycerate (a known catalyst of glycation) were significantly higher in the high glycators. These findings may partially explain the original discovery of low and high glycators. The effects of high fibre/low glucose and high glucose/low fibre diets on glycated proteins were studied in normal subjects. Only glycated albumin levels changed significantly, probably due to small changes in plasma glucose occurring on each diet, which were not mirrored by similar changes in the erythrocyte. When another group of normal subjects received 1 g vitamin C daily for three months, significant reductions in glycated albumin and glycated haemoglobin were observed, with the former being reduced to a greater extent. This suggests that vitamin C has the potential of being used therapeutically to reduce glycation. In conclusion, for normal subjects, glycated albumin is a more reliable indicator of blood glucose control than glycated haemoglobin.