Retraction Note: Identification of a novel Na+-coupled Fe3+-citrate transport system, distinct from mammalian INDY, for uptake of citrate in mammalian cells.

This paper has been retracted at the request of the authors

The amino acid transporter SLC6A14 in cancer and its potential use in chemotherapy

Tumor cells have an increased demand for glucose and amino acids to support their rapid growth, and also exhibit alterations in biochemical pathways that metabolize these nutrients. Transport across the plasma membrane is essential to feed glucose and amino acids into these tumor cell-selective metabolic pathways. Transfer of amino acids across biological membranes occurs via a multitude of transporters; tumor cells must upregulate one or more of these transporters to satisfy their increased demand for amino acids. Among the amino acid transporters, SLC6A14 stands out with specific functional features uniquely suited for the biological needs of the tumor cells. This transporter is indeed upregulated in tumors of epithelial origin, including colon cancer, cervical cancer, breast cancer, and pancreatic cancer. Since normal cells express this transporter only at low levels, blockade of this transporter should lead to amino acid starvation selectively in tumor cells, thus having little effect on normal cells. This offers a novel, yet logical, strategy for the treatment of cancers that are associated with upregulation of SLC6A14. In addition, a variety of amino acid-based prodrugs are recognized as substrates by SLC6A14, thus raising the possibility that anticancer drugs can be delivered into tumor cells selectively via this transporter in the form of amino acid prodrugs. This strategy allows exposure of SLC6A14-positive tumor cells to chemotherapy with minimal off-target effects. In conclusion, the amino acid transporter SLC6A14 holds great potential not only as a direct drug target for cancer therapy but also for tumor cell-selective delivery of anticancer drugs

RETRACTED ARTICLE: Identification of a novel Na+-coupled Fe3+-citrate transport system, distinct from mammalian INDY, for uptake of citrate in mammalian cells

Abstract NaCT is a Na+-coupled transporter for citrate expressed in hepatocytes and neurons. It is the mammalian ortholog of INDY (I’m Not Dead Yet), a transporter which modifies lifespan in Drosophila. Here we describe a hitherto unknown transport system for citrate in mammalian cells. When liver and mammary epithelial cells were pretreated with the iron supplement ferric ammonium citrate (FAC), uptake of citrate increased >10-fold. Iron chelators abrogated the stimulation of citrate uptake in FAC-treated cells. The iron exporter ferroportin had no role in this process. The stimulation of citrate uptake also occurred when Fe3+ was added during uptake without pretreatment. Similarly, uptake of Fe3+ was enhanced by citrate. The Fe3+-citrate uptake was coupled to Na+. This transport system was detectable in primary hepatocytes and neuronal cell lines. The functional features of this citrate transport system distinguish it from NaCT. Loss-of-function mutations in NaCT cause early-onset epilepsy and encephalopathy; the newly discovered Na+-coupled Fe3+-citrate transport system might offer a novel treatment strategy for these patients to deliver citrate into affected neurons independent of NaCT. It also has implications to iron-overload conditions where circulating free iron increases, which would stimulate cellular uptake of citrate and consequently affect multiple metabolic pathways

Retraction Note: Identification of a novel Na+-coupled Fe3+-citrate transport system, distinct from mammalian INDY, for uptake of citrate in mammalian cells.

This paper has been retracted at the request of the authors

Cuminaldehyde ameliorates hyperglycemia in diabetic mice

Background: Animal-fats are rich in long-chain saturated fatty-acids, well known to induct diabetic distress among ingested insulin-insensitive individuals. In the current-study, bovine-fat was fed to selective mice breeds highly sensitized to heavy dietary lipid load. Methods: The later high fat diet (HFD) group indeed undergone diabetic-onset within weeks with a drastically altered feed-behavior pattern. It consumed more food, gained body mass, elevated homeostatic model assessment value and extensively glycosylated Hb transporters. Results: However, the hypothetical test drug (Cuminaldehyde or CA) with known therapeutic-potential worked-well to balance food efficiency-ratio and Hb- counts closer to control. The fat-soluble phytochemical mono-terpenoid (CA) promoted constitutive mono-hexose (glucose) consuming catabolic-cycles via mono-glycoprotein (insulin) signal-transduction. It resolved diabetogenic-upsurge of gluconeogenic-enzymes, reduced non-sugar (amino/fatty acids) utilization by restricting transamination/dephosphorylation and restored liver-glycogen reserves near to normal-group effectively at 10 mg/kg b.w dose. Conclusions: Hence, the nutraceutical-potential (anti-diabetes/transaminitis ability) of administered exogenous redox-active agent CA can be entertained for evoking therapeutic-heath in diabetic human-community

Transport via SLC5A8 (SMCT1) Is Obligatory for 2-Oxothiazolidine-4-Carboxylate to Enhance Glutathione Production in Retinal Pigment Epithelial Cells

The present study describes the role of the sodium-dependent monocarboxylate transporter SLC5A8 (SMCT1) in the transport of the cysteine prodrug 2-oxothiazolidine-4-carboxylate (OTC), and the resultant augmentation of glutathione production in RPE cells. Given the key causative role oxidative damage to RPE plays in the pathogenesis of AMD, the present study is critically important and highly clinically relevant

Nutrient Transporter Expression in the Jejunum in Relation to Body Mass Index in Patients Undergoing Bariatric Surgery

Nutrient tranters (NT) facilitate nutrient absorption and contribute to the regulation of circulating nutrients. In this cross-sectional study, we determined the associations between the level of obesity; mRNA abundance for NTs; and serum concentrations of amino acids, short-chain fatty acids, and glucose in patients with morbid obesity undergoing a Roux-en-Y gastric bypass. Proximal jejunal samples were obtained at the time of surgery from 42 patients (90% female, age = 42.6 ± 11.9 years, pre-operative body mass index (BMI) = 55.5 ± 11.3 kg/m2) undergoing a Roux-en-Y gastric bypass. RNA was extracted from the jejunal mucosa and quantitative real-time–PCR was performed for the NTs studied. BMI negatively correlated with jejunal mRNA abundance of the amino acid NTs TauT (r = −0.625, p < 0.0001), ASCT2 (r = −0.320, p = 0.039), LAT1 (r = −0.304, p = 0.05). BMI positively correlated with jejunal mRNA abundance of the lactate/short-chain fatty acid NT SMCT1 (r = 0.543, p = 0.0002). Serum concentrations of the short-chain fatty acids, butyric, valeric, and isocaproic acid correlated positively with BMI (n = 30) (r = 0.45, r = 0.44, r = 0.36, p ≤ 0.05; respectively). Lower jejunal mRNA abundance for the amino acid NTs TauT, ASCT2, and LAT1 could protect against further obesity-related elevations in circulating amino acids. The positive correlation between BMI and the jejunal mRNA abundance of the high-affinity short-chain fatty acid/monocarboxylate transporter SMCT1 is intriguing and requires further investigation