Background & objectives: Folate deficiency is a public health problem and is the most notable for its association with neural tube defect in developing embryo, megaloblastic anaemia, cancers and cardiovascular diseases. The mechanisms of the intestinal folate uptake process have been earlier characterized. However, much less is known about regulation. In this study we evaluated the mechanistic insights of folate absorption in an in vivo model of folate deficiency.
Methods: Male Wistar rats were fed folate-containing diet (2 mg/kg folic acid) or a folic acid-free diet over 3 months and folate transport was studied in intestinal brush border membrane vesicles (BBMV).
Results: The characterization of the folate transport system in intestinal brush border membrane (BBM) suggested it to be a carrier mediated, acidic pH stimulated, and Na⁺ independent. Folate deficiency increased the folate transport by altering the Vmax without changing the Km of folate transport process. The increased transport efficiency of the BBM was associated with upregulation of folate transporters at both mRNA and protein level.
Interpretation & conclusions: Folate deficiency resulted in significant upregulation of intestinal folate uptake, by increasing number of transporters without any change in specificity of transporters towards its substrate. The observed upregulation was associated with significant increase in reduced folate carrier (RFC) and proton coupled folate transporter (PCFT) expressions, suggesting the transcriptional and translational regulation of folate uptake during folate deficiency.