Is the gut microbiota dysbiotic in patients with classical homocystinuria

Abstract Classical homocystinuria (HCU) is characterized by increased plasma levels of total homocysteine (tHcy) and methionine (Met). Treatment may involve supplementation of B vitamins and essential amino acids, as well as restricted Met intake. Dysbiosis has been described in some inborn errors of metabolism, but has not been investigated in HCU. The aim of this study was to investigate the gut microbiota of HCU patients on treatment. Six unrelated HCU patients (males= 5, median age= 25.5 years) and six age-and-sex-matched healthy controls (males= 5, median age= 24.5 years) had their fecal microbiota characterized through partial 16S rRNA gene sequencing. Fecal pH, a 3-day dietary record, medical history, and current medications were recorded for both groups. All patients were on a Met-restricted diet and presented with high tHcy. Oral supplementation of folate (n=6) and pyridoxine (n=5), oral intake of betaine (n=4), and IM vitamin B12 supplementation (n=4), were reported only in the HCU group. Patients had decreased daily intake of fat, cholesterol, vitamin D, and selenium compared to controls (p