title: Folate malabsorption is associated with down-regulation of folate transporter expression and function at colon basolateral membrane in rats.
abstract: Folates, an essential component (important B vitamin) in the human diet, are involved in many metabolic pathways, mainly in carbon transfer reactions such as purine and pyrimidine biosynthesis and amino acid interconversions. Deficiency of this micronutrient leads to the disruption of folate-dependent metabolic pathways that lead to the development of clinical abnormalities ranging from anaemia to growth retardation. Folate deficiency due to alcohol ingestion is quite common, primarily due to malabsorption. The present study dealt with the mechanistic insights of folate malabsorption in colonic basolateral membrane (BLM). Wistar rats (n 12) were fed 1 g/kg body weight per d ethanol (20 %) solution orally for 3 months and folate transport was studied in the isolated colonic BLM. The folate exit across colon BLM shows characteristics of carrier-mediated process with the major involvement of reduced folate carrier (RFC). The chronic ethanol ingestion decreased the uptake by decreasing the affinity by 46 % (P < 0·01) and the number of transport molecules by 43 % (P < 0·001) at the colon BLM. The decreased uptake was associated with down-regulation of proton-coupled folate transporter (PCFT) and RFC expression at mRNA and protein levels. The extent of decrease was 44 % (P < 0·01) and 24 % (P < 0·05) for PCFT and 23 % (P < 0·01) and 57 % (P < 0·01) for RFC at mRNA and protein levels, respectively. Moreover, folate transporters were associated with lipid rafts (LR) of colon BLM, and chronic alcoholism decreased the association of these transporters with LR.
authors.affiliation: Department of Biochemistry, Postgraduate Institute of Medical Education and Research, Chandigarh 160 012, India.
authors.forename: Nissar Ahmad
authors.initials: NA
authors.lastname: Wani
authors.forename: Abid
authors.initials: A
authors.lastname: Hamid
authors.forename: Krishan Lal
authors.initials: KL
authors.lastname: Khanduja
authors.forename: Jyotdeep
authors.initials: J
authors.lastname: Kaur
mesh_terms: D000437:Alcoholism / Q000503:physiopathology; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003106:Colon / Q000378:metabolism* / Q000473:pathology; D015536:Down-Regulation; D005492:Folic Acid / Q000378:metabolism*; D005494:Folic Acid Deficiency / Q000209:etiology; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000473:pathology; D007700:Kinetics; D008286:Malabsorption Syndromes / Q000209:etiology / Q000378:metabolism*; D008297:Male; D021962:Membrane Microdomains / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D015778:Minor Histocompatibility Antigens; D058979:Proton-Coupled Folate Transporter / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D058978:Reduced Folate Carrier Protein / Q000235:genetics / Q000378:metabolism*; D013763:Tetrahydrofolates / Q000378:metabolism
chemical_list: D026901:Membrane Transport Proteins; D015778:Minor Histocompatibility Antigens; D058979:Proton-Coupled Folate Transporter; D012333:RNA, Messenger; D058978:Reduced Folate Carrier Protein; C043408:Slc19a1 protein, rat; C525126:Slc46a1 protein, rat; D013763:Tetrahydrofolates; D005492:Folic Acid; C005984:5-methyltetrahydrofolate