Functional Characteristics of the Human Ortholog of Riboflavin Transporter 2 and Riboflavin-Responsive Expression of Its Rat Ortholog in the Small Intestine Indicate Its Involvement in Riboflavin Absorption , ,

Abstract

Riboflavin transporter (RFT) 2 has recently been identified as a transporter that may be, mainly based on the functional characteristics of its rat ortholog (rRFT2), involved in the intestinal absorption of riboflavin. The present study was conducted to further examine such a possible role of RFT2, focusing on the functional characteristics of its human ortholog (hRFT2) and the response of rRFT2 expression in the small intestine to deprivation of dietary riboflavin. When transiently expressed in human embryonic kidney 293 cells, hRFT2 could transport riboflavin efficiently in a pH-sensitive manner, favoring acidic pH and without requiring Na(+). Riboflavin transport by hRFT2 was saturable with a Michaelis constant of 0.77 μmol/L at pH 6.0, and inhibited by some riboflavin derivatives, such as lumiflavin. It was also inhibited, to a lesser extent, by some cationic compounds, such as ethidium. Thus, hRFT2 was suggested to, together with a finding that its mRNA is highly expressed in the small intestine, have characteristics as an intestinal RFT. Furthermore, feeding rats a riboflavin-deficient diet caused an upregulation of the expression of rRFT2 mRNA in the small intestine, presumably as an adaptive response to enhance riboflavin absorption, which would involve rRFT2, and its apically localized characteristic was suggested by the observation of rRFT2 tagged with green fluorescent protein stably expressed in polarized Madin-Darby canine kidney II cells. All these results combined indicate that RFT2 is a transporter involved in the epithelial uptake of riboflavin in the small intestine for its nutritional utilization.

Involvement of riboflavin transporter RFVT2/Slc52a2 in hepatic homeostasis of riboflavin in mice

“…The riboflavin contents in the control and deficient diet were 6.5070.42 and 0.3070.05 mg/kg, respectively. The composition of the AIM-93M diet has been reported previously (Fujimura et al, 2010).…”

The Functional SNP rs3746804 in C20orf54 Modifies Susceptibility to Esophageal Squamous Cell Carcinoma

“…The protein is believed to play an important role in intestinal riboflavin absorption [2,3]. Riboflavin deficiency has been shown to be an important risk factor for ESCC [4,5].…”

Intestinal immune function, antioxidant status and tight junction proteins mRNA expression in young grass carp ( Ctenopharyngodon idella ) fed riboflavin deficient diet

“…However, no studies have investigated the relationship between riboflavin and intestinal health of fish. In human and rats, the intestine has developed riboflavin transporter to transport and absorb riboflavin [6]. Meanwhile, it was reported that dietary riboflavin deficiency could reduce iron absorption and increase gastrointestinal iron loss in rats [7].…”