Analysis of antennary fucose as a routine diagnostics of HNF1A-MODY
Our recent genome wide association study (GWAS) of human glycome has shown that the nuclear factor HNF1A is a key regulator of antennary fucose on human plasma proteins (Lauc et al, PLOS Genetics 6(12): e1001256, 2010). Inactivating mutations in HNF1A are the cause for a subtype of diabetes named HNF1A-MODY (Maturity onset diabetes of the young). HNF1A-MODY represents around 0.5% of all diabetes cases (around 400 cases per one million inhabitants) nevertheless, majority of cases remain unrecognized due to absence of adequate diagnostic methods. Accurate and early diagnosis of HNF1A-MODY is of crucial importance because, in contrast to other types of diabetes which are commonly treated with insulin, HNF1A-MODY can successfully be treated with low doses of sulfonylurea based medications thus significantly increasing the quality of patients’ life and at the same time, decreasing expenses of treatment.
In collaboration with the Oxford Centre for Diabetes, Endocrinology, and Metabolism, we performed a high-throughput HPLC glycan analysis in plasma of 600 patients with different types of diabetes. Within the analysis, we have shown that determination of antennary fucose level on plasma proteins by means of HPLC method can well differentiate HNF1A-MODY from other diabetes subtypes. In this study, we also discovered two new patients with HNF1A-MODY who had inaccurately been diagnosed as Type-1 and Type-2 diabetes patients. The new diagnosis, HNF1A-MODY, was confirmed by additional sequencing of HNF1A gene, therefore the capability of HPLC glycan analysis in plasma to recognize undiagnosed HNF1A-MODY patients was efficiently demonstrated.
Since HPLC glycan analysis is not suitable for execution of the expected one million analyses per year due to its price as well as due to the fact that HPLC devices are not part of routine laboratory equipment, it is necessary to demonstrate technical feasibility of performing antennary fucose analysis as a routine diagnostic procedure for recognizing HNF1A-MODY. In this project, we will test technical executability of two quantification options: (i) ELISA technique with specific lectins that recognize antennary fucose and (ii) quantification of antennary fucose released by means of specific exoglycosidases.
The selected method will be validated by means of an analysis of 500 patients who were diagnosed with diabetes before 45years of age and who have frequency of HNF1A-MODY up to even 5%. Confirmation of HNF1A-MODY diagnosis will be carried out by sequencing of HNF1A gene in collaboration with the Oxford Centre for Diabetes, Endocrinology, and Metabolism and they will also co-finance part of expenses for the glycan analysis.
At the moment, the best technique for recognizing HNF1A-MODY is the analysis of CRP in plasma (recognizing about 80% of patients) and according to our results, quantification of protein antennary fucosylation is significantly better and recognizes up to 95% of patients. If we succeed in showing technical feasibility of antennary fucose analysis with methods that are suitable for routine biochemical laboratories, it can be expected that this procedure will be implemented in routine diagnostic algorithms of all diabetes cases diagnosed before 45 years of age and those with suspicion of an inherited type of diabetes.