Riboflavin supplementation alters global and gene-specific DNA methylation in adults with the MTHFR 677 TT genotype.

DNA methylation is important in regulating gene expression and genomic stability while aberrant DNA methylation is associated with disease. Riboflavin (FAD) is a cofactor for methylenetetrahydrofolate reductase (MTHFR), a critical enzyme in folate recycling, which generates methyl groups for homocysteine remethylation to methionine, the pre-cursor to the universal methyl donor S-adenosylmethionine (SAM). A polymorphism (C677T) in MTHFR results in decreased MTHFR activity and increased homocysteine concentration. Previous studies demonstrated that riboflavin modulates this phenotype in homozygous adults (MTHFR 677 TT genotype), however, DNA methylation was not considered. This study examined DNA methylation, globally and at key MTHFR regulatory sites, in adults stratified by MTHFR genotype and the effect of riboflavin supplementation on DNA methylation in individuals with the 677 TT genotype. Samples were accessed from participants, screened for the MTHFR C677T polymorphism, who participated in observational (n = 80) and targeted riboflavin (1.6 mg/day) RCTs (n = 80). DNA methylation at LINE-1 and key regulatory regions of the MTHFR locus were analysed by pyrosequencing in peripheral blood leukocytes. LINE-1 (+1.6%; p = 0.011) and MTHFR south shelf (+4.7%, p < 0.001) were significantly hypermethylated in individuals with the MTHFR 677 TT compared to CC genotype. Riboflavin supplementation resulted in decreased global methylation, albeit only significant at one CpG. A significant reduction in DNA methylation at the MTHFR north shore (-1.2%, p < 0.001) was also observed in TT adults following intervention with riboflavin. This provides the first RCT evidence that DNA methylation may be modulated by riboflavin in adults with the MTHFR 677 TT genotype.

Recurrent posterior circulatory emboli from a mildly stenosed bicuspid aortic valve.

Bicuspid aortic valve (BAV) is a common condition but is only rarely associated with embolic complications. We describe a 42-year-old man with recurrent posterior circulatory ischemic strokes that resulted in ataxia and cognitive impairment. Transesophageal echocardiography demonstrated a BAV with mild stenosis, moderate calcification, and a dilated ascending aorta. The degree of calcification and the valve phenotype might be important factors implicating the BAV as a rare cause of ischemic stroke.

Don't stop at two.

An asymptomatic 35-year-old woman with history of coarctation repair underwent routine echo. This showed a bicuspid aortic valve with a significant gradient in the left ventricular outflow tract (LVOT). The anterior mitral valve leaflet appeared redundant. Transoesophageal echo showed thickened chordae tendineae from both mitral valve leaflets inserted into a single postero-medial papillary muscle-a parachute mitral valve. During systole, there was anterior motion of redundant mitral chordae into the LVOT producing significant obstruction. A diagnosis of partial Shone complex was made. She was referred for mitral (and possibly aortic) valve surgery. The combination of aortic coarctation with bicuspid aortic valve should stimulate a search for other levels of systemic obstruction-don't stop at two!