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9. Does the absolute HbA1c improve the genotype-phenotype association in Type 2 Diabetes?

Does the absolute HbA1c improve the genotype-phenotype association in Type 2 Diabetes?
Pages 60-63
Alexandra Fiott, N. Pace, R. Galdies, J. Vassallo and A.E. Felice


HbA1c is a measure of the mean blood glucose levels for the prior 90 - 120 days, the mean lifetime of red blood cells. However, factors that influence the erythrocyte turnover or the biochemical structure of haemoglobin (Hb) might complicate the interpretation of results. With a frequency of haemoglobinopathies of around 5% in the Maltese population, an alternative biomarker should be considered. The aim of this study was to determine whether the absolute HbA1c could improve the genotype-phenotype association in Type 2 Diabetes Mellitus (T2DM) and whether it could thus be an alternative measure.

Ion-exchange high performance liquid chromatography (HPLC) and polymerase chain reaction (PCR) were used to genotype and phenotype five different groups of subjects: haematologically normal adult controls, anaemics Hb <10g/dL), beta-thalassaemics, normal pregnant women and type 2 diabetics (controlling their diabetes either by diet alone, or using metformin for up to six months). The single nucleotide polymorphisms (SNPs) selected were in the ADRB2, LEP, FABP2, TCF7L2, MIF, IL6 and UCP1 genes.

Statistical analysis showed that the absolute HbA1c did not improve the genotype-phenotype association, as it showed the same trends as the relative HbA1c. The difference between the HbF and HbA1cis due to the homogenous distribution of HbA1c among erythrocytes, unlike HbF. \textit{In vitro} glycation showed that Hb Beta-Valletta, found in 1.8% of Maltese adults, does not influence glycation and thus the HbA1c is not influenced by this variant in heterozygotes/homozygotes.

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