The long-term objectives of this renewal application continue to focus on investigating the cell/molecular physiology and pathophysiology of the intestinal vitamin B2 (riboflavin; RF) uptake process and of the factors that affect and interfere with the event. RF is essential for normal human health due to the key roles it plays in biological oxidation-reduction reactions involving lipid, carbohydrate and amino acid metabolism, and in the conversion of vitamin B6 and folate into their active forms. Recent findings have uncovered additional roles for RF in normal immune function, as an anti-inflammatory and anti-oxidant agent, and in the maintenance of normal intestinal homeostasis. Humans (mammals) cannot synthesize RF, and thus, must obtain the vitamin from exogenous sources via intestinal absorption. Studies from our laboratory and others have characterized different aspects of intestinal RF absorption and shown the process is specific and carrier-mediated; also all the three recently cloned RFVTs (RFVT-1, -2 & -3; products of the SLC52A1, SLC52A2 & SLC52A3 genes, respectively) are expressed in the intestine. In studies performed during the current funding period, we used an in vitro gene-silencing (siRNA) approach to show that the apically expressed RFVT-3 plays a major role in intestinal RF uptake. In new preliminary studies aimed at establishing the role of RFVT-3 in intestinal RF absorption in native intestine in vivo, we generated a conditional (intestinal-specific) SLC52A3 knockout (KO) mouse model and plan to use it to confirm and extend our in vitro findings. In other new preliminary studies, we have identified (via homology modeling/ligand docking analyses) putative structural features in the RFVT-3 protein that may be important for its function, obtained evidence implicating microRNAs (miRNAs) in post-transcriptional regulation of intestinal RF uptake, and have identified several potential interactig partners with RFVT-3 in intestinal epithelial cells. We also obtained evidence showing that infection of intestinal epithelial cells with S. Typhimurium, and exposure to pro-inflammatory cytokines and to bacterial LPS significantly lead to inhibition in intestinal RF uptake. Finally, w obtained new preliminary evidence suggesting possible involvement of epigenetic mechanism(s) in the inhibitory effect of chronic alcohol feeding on intestinal/colonic RF uptake that we observed during the current funding period. Based on our published studies and new preliminary findings, our working hypotheses in this proposal are that: 1) the RFVT-3 plays an important role in RF absorption in native intestine in vivo; that the transporter is post-transcriptionally regulated by microRNA; and that it has interacting partner(s) that may influence its physiology/cell biology; 2) Salmonella infection, and exposure to pro-inflammatory cytokines and to bacterial LPS inhibits intestinal RF uptake; and 3) the inhibitory effect of chronic alcohol exposure on SLC52A3 transcription in the intestine is mediated, at least in part, via epigenetic/molecular mechanism(s).
Three specific aims are proposed to test these hypotheses and will utilize state-of-the-art in vivo and in vitro physiological, cellular, and molecular approaches. Results of these studies should continue to provide novel and valuable information regarding the cell/molecular physiology and pathophysiology of intestinal RF uptake and of external factors that affect and interfere with the process. This should ultimately assist us in th designing of effective strategies to optimize RF body homeostasis, especially in conditions associated with RF deficiency and sub-optimal levels.

Public Health Relevance

Riboflavin (RF; vitamin B2) is essential for normal human health and its deficiency leads to a variety of clinical abnormalities. Humans cannot synthesize RF and obtain it from exogenous sources via intestinal absorption. Thus, the gut plays a central role in regulating and normal RF body level. The objectives of this renewal application continue to focus on investigating the physiology and pathophysiology of the intestinal/colonic RF uptake process and of the factors that affect and interfere with the event (e. g., infection with enteric pathogens, pro-inflammatory factors, chronic alcohol exposure). Results of these investigations should provide valuable information regarding the cell/molecular physiology and pathophysiology of intestinal RF absorption and how external factors interfere with the event. This should ultimately assist us in the designing of effective strategies to optimize RF body homeostasis, especially in conditions of RF deficiency and sub-optimal levels. 1

Agency
National Institute of Health (NIH)
Institute
Veterans Affairs (VA)
Type
Non-HHS Research Projects (I01)
Project #
5I01BX001142-07
Application #
9553448
Study Section
Gastroenterology (GAST)
Project Start
2012-07-01
Project End
2020-06-30
Budget Start
2018-07-01
Budget End
2019-06-30
Support Year
7
Fiscal Year
2018
Total Cost
Indirect Cost
Name
Veterans Health Administration
Department
Type
DUNS #
625399951
City
Long Beach
State
CA
Country
United States
Zip Code
90822
Subramanian, Veedamali S; Sabui, Subrata; Moradi, Hamid et al. (2018) Inhibition of intestinal ascorbic acid uptake by lipopolysaccharide is mediated via transcriptional mechanisms. Biochim Biophys Acta Biomembr 1860:556-565
Elahi, Asif; Sabui, Subrata; Narasappa, Nell N et al. (2018) Biotin Deficiency Induces Th1- and Th17-Mediated Proinflammatory Responses in Human CD4+ T Lymphocytes via Activation of the mTOR Signaling Pathway. J Immunol 200:2563-2570
Lakhan, Ram; Subramanian, Veedamali S; Said, Hamid M (2017) Role of MicroRNA-423-5p in posttranscriptional regulation of the intestinal riboflavin transporter-3. Am J Physiol Gastrointest Liver Physiol 313:G589-G598
Subramanian, Veedamali S; Srinivasan, Padmanabhan; Wildman, Alexis J et al. (2017) Molecular mechanism(s) involved in differential expression of vitamin C transporters along the intestinal tract. Am J Physiol Gastrointest Liver Physiol 312:G340-G347
Sabui, Subrata; Subramanian, Veedamali S; Kapadia, Rubina et al. (2017) Adaptive regulation of pancreatic acinar mitochondrial thiamin pyrophosphate uptake process: possible involvement of epigenetic mechanism(s). Am J Physiol Gastrointest Liver Physiol 313:G448-G455
Lakhan, Ram; Said, Hamid M (2017) Lipopolysaccharide inhibits colonic biotin uptake via interference with membrane expression of its transporter: a role for a casein kinase 2-mediated pathway. Am J Physiol Cell Physiol 312:C376-C384
Subramanian, Veedamali S; Constantinescu, Alexandru R; Benke, Paul J et al. (2017) Mutations in SLC5A6 associated with brain, immune, bone, and intestinal dysfunction in a young child. Hum Genet 136:253-261
Anandam, Kasin Yadunandam; Srinivasan, Padmanabhan; Subramanian, Veedamali S et al. (2017) Molecular mechanisms involved in the adaptive regulation of the colonic thiamin pyrophosphate uptake process. Am J Physiol Cell Physiol 313:C655-C663
Subramanian, Veedamali S; Sabui, Subrata; Teafatiller, Trevor et al. (2017) Structure/functional aspects of the human riboflavin transporter-3 (SLC52A3): role of the predicted glycosylation and substrate-interacting sites. Am J Physiol Cell Physiol 313:C228-C238
Subramanian, Veedamali S; Lambrecht, Nils; Lytle, Christian et al. (2016) Conditional (intestinal-specific) knockout of the riboflavin transporter-3 (RFVT-3) impairs riboflavin absorption. Am J Physiol Gastrointest Liver Physiol 310:G285-93

Showing the most recent 10 out of 19 publications