1,5-Anhydroglucitol (1,5-Ag) and its Usefulness in Clinical Practice

1,5-anhydroglucitol (1,5-AG) is a major polyol in human serum, structurally similar to D-glucose. The 1,5-AG pool can be determined by the balance between oral intake and urinary excretion. It is derived mainly from dietary sources with a half-life of about 1-2 weeks. 1,5-AG is not metabolized, whereas it is excreted in urine and nearly 99.9% of it is reabsorbed by the kidneys. When serum glucose level exceeds the renal threshold for glucosuria, urinary glucose suppresses tubular reabsorbing of 1,5-AG, leading to a loss of it in the urine and a rapid reduction of this polyol in serum levels. Therefore, the plasma 1,5-AG concentration indirectly reflects episodes of hyperglycaemia. This marker can be measured in serum, EDTA or in plasma using enzymatic assays or chromatography techniques which are also helpful to detect 1,5-AG in urine. In clinical practice, 1,5-AG is a good marker of short-term episodes of hyperglycaemia such as postprandial hyperglycaemia and other short term glycaemia excursions, for example during pregnancy or in pre-conception, before operations and after glycaemia-related therapeutic changes. It has been also reported as a marker of first-ever cardiovascular disease, a clinical test to differentiate subtypes of diabetes and to monitor type 1 diabetes in children. Despite small limitations such as end-stage renal disease or liver cirrhosis, which should be taken into consideration when interpreting levels of 1,5-AG, it seems to be a useful and sensitive marker of acute and postprandial hyperglycaemia episodes in diabetology or cardiodiabetology.