Maturity-onset diabetes of the young (MODY) mutation in type 2 diabetes and latent autoimmune diabetes of the adult

Onset of type 1 diabetes mellitus in two patients with maturity onset diabetes of the young

The association between maturity onset diabetes of the young (MODY) and type 1 diabetes mellitus (T1DM) has been rarely described. We report two patients affected by MODY who developed T1DM. Case 1: a 4-yr-old girl referred for glycosuria presented hemoglobin A1c (HbA1c) of 6.6%. Islet cell antibodies (ICA) and anti-glutamic acid decarboxylase (GADA) were initially negative. As her father, uncle and grandmother showed mild hyperglycemia, they were screened for MODY 2. A novel mutation in glucokinase gene was found in the family. Few months later, her glycemic control worsened consistently and she required insulin treatment. A high titer of GADA and ICA was then detected. Six years afterwards insulin requirement is 0.8 U/kg and HbA1c 6.7%. Case 2: a 15-yr-old boy treated for growth hormone deficiency was found with a blood glucose level of 106 mg/dL. HbA1c was 7.2%, ICA and GADA were negative. Family history was positive for autoimmune diseases and type 2 diabetes mellitus. The patient was investigated for MODY 2 and MODY 3, and a mutation of hepatocyte nuclear factor-1 alpha gene was found. The same mutation was found in the mother who had never been referred for hyperglycemia. After 1 yr, due to an unjustified worsening of the metabolic control, autoimmunity was again investigated and a mild positivity was found. He then required insulin therapy and after 5 yr current HbA1c was 8.2%. The diagnosis of MODY does not exclude the risk of developing T1DM. Therefore autoimmunity should be investigated when ordinary treatments fail and metabolic control unexpectedly worsens.

Hypertriglyceridemia: phenomics and genomics

Hypertriglyceridemia is a common complex metabolic trait that is associated with increased atherosclerosis risk, presence of the metabolic syndrome and, with extreme elevation, increased risk of pancreatitis. Hierarchical cluster analysis using clinical and biochemical features of the Frederickson hyperlipoproteinemia types can generate hypotheses for molecular genetic studies. High throughput resequencing of individuals at the extremes of plasma triglyceride concentration has shown that both rare genetic variants with large effects and common genetic variants with moderate effects explain a relatively large proportion of variation. Very recent progress using high-density sets of genome-wide markers have identified additional genetic determinants of plasma triglyceride concentrations, albeit within largely normolipidemic subjects and with small effect sizes. Phenomic evaluation of patients with hypertriglyceridemia might help to clarify genotype-phenotype correlations and responses to interventions.

Genetic determinants of plasma lipoproteins

The search for common genetic determinants of plasma lipoproteins began in the early 1980s. Despite some exceptions, these efforts have not yet yielded a set of biological markers that can be used in clinical practice. By contrast, successes in defining the molecular basis of rare single-gene disorders, such as familial hypoalphalipoproteinemia, have shown the value of experimental designs that focus on genomic analysis of individuals within the tails of Gaussian distributions of quantitative lipoprotein traits. For example, this strategy showed that a small but relevant proportion of individuals within the <5% tail of plasma HDL-cholesterol distribution have mutations in genes that cause familial hypoalphalipoproteinemia. The value of clinical testing for genomic variants as an adjunct to a biochemical measurement of plasma lipoproteins, however, is at best questionable. A more direct impact of genetic studies is that definitions of 'common' and 'large genetic effects' have become more tempered, reflecting perhaps the biological reality that plasma lipoproteins are probably determined by the aggregate of numerous modest and occasional large genetic effects in addition to environmental factors. Here, we review recent progress on genomic variants and cholesterol metabolism, and discuss the impact these genetic studies will have on clinical cardiology.