Non-cell-autonomous regulation of germline proteostasis by insulin/IGF-1 signaling-induced dietary peptide uptake via PEPT-1.

Gametogenesis involves active protein synthesis and is proposed to rely on proteostasis. Our previous work in C. elegans indicates that germline development requires coordinated activities of insulin/IGF-1 signaling (IIS) and HSF-1, the central regulator of the heat shock response. However, the downstream mechanisms were not identified. Here, we show that depletion of HSF-1 from germ cells impairs chaperone gene expression, causing protein degradation and aggregation and, consequently, reduced fecundity and gamete quality. Conversely, reduced IIS confers germ cell resilience to HSF-1 depletion-induced protein folding defects and various proteotoxic stresses. Surprisingly, this effect was not mediated by an enhanced stress response, which underlies longevity in low IIS conditions, but by reduced ribosome biogenesis and translation rate. We found that IIS activates the expression of intestinal peptide transporter PEPT-1 by alleviating its repression by FOXO/DAF-16, allowing dietary proteins to be efficiently incorporated into an amino acid pool that fuels germline protein synthesis. Our data suggest this non-cell-autonomous pathway is critical for proteostasis regulation during gametogenesis.

The sugar transporter ZmSUGCAR1 of the nitrate transporter 1/peptide transporter family is critical for maize grain filling.

Maternal-to-filial nutrition transfer is central to grain development and yield. nitrate transporter 1/peptide transporter (NRT1-PTR)-type transporters typically transport nitrate, peptides, and ions. Here, we report the identification of a maize (Zea mays) NRT1-PTR-type transporter that transports sucrose and glucose. The activity of this sugar transporter, named Sucrose and Glucose Carrier 1 (SUGCAR1), was systematically verified by tracer-labeled sugar uptake and serial electrophysiological studies including two-electrode voltage-clamp, non-invasive microelectrode ion flux estimation assays in Xenopus laevis oocytes and patch clamping in HEK293T cells. ZmSUGCAR1 is specifically expressed in the basal endosperm transfer layer and loss-of-function mutation of ZmSUGCAR1 caused significantly decreased sucrose and glucose contents and subsequent shrinkage of maize kernels. Notably, the ZmSUGCAR1 orthologs SbSUGCAR1 (from Sorghum bicolor) and TaSUGCAR1 (from Triticum aestivum) displayed similar sugar transport activities in oocytes, supporting the functional conservation of SUGCAR1 in closely related cereal species. Thus, the discovery of ZmSUGCAR1 uncovers a type of sugar transporter essential for grain development and opens potential avenues for genetic improvement of seed-filling and yield in maize and other grain crops.

Short-peptide-based enteral nutrition affects rats MDP translocation and protects against gut-lung injury via the PepT1-NOD2-beclin-1 pathway in vivo.

BACKGROUND: Peptide transporter 1 (PepT1) transports bacterial oligopeptide products and induces inflammation of the bowel. Nutritional peptides compete for the binding of intestinal bacterial products to PepT1. We investigated the mechanism of short-peptide-based enteral nutrition (SPEN) on the damage to the gut caused by the bacterial oligopeptide product muramyl dipeptide (MDP), which is transported by PepT1. The gut-lung axis is a shared mucosal immune system, and immune responses and disorders can affect the gut-respiratory relationship. METHODS AND RESULTS: Sprague-Dawley rats were gavaged with solutions containing MDP, MDP + SPEN, MDP + intact-protein-based enteral nutrition (IPEN), glucose as a control, or glucose with GSK669 (a NOD2 antagonist). Inflammation, mitochondrial damage, autophagy, and apoptosis were explored to determine the role of the PepT1-nucleotide-binding oligomerization domain-containing protein 2 (NOD2)-beclin-1 signaling pathway in the small intestinal mucosa. MDP and proinflammatory factors of lung tissue were explored to determine that MDP can migrate to lung tissue and cause inflammation. Induction of proinflammatory cell accumulation and intestinal damage in MDP gavage rats was associated with increased NOD2 and Beclin-1 mRNA expression. IL-6 and TNF-α expression and apoptosis were increased, and mitochondrial damage was severe, as indicated by increased mtDNA in the MDP group compared with controls. MDP levels and expression of proinflammatory factors in lung tissue increased in the MDP group compared with the control group. SPEN, but not IPEN, eliminated these impacts. CONCLUSIONS: Gavage of MDP to rats resulted in damage to the gut-lung axis. SPEN reverses the adverse effects of MDP. The PepT1-NOD2-beclin-1 pathway plays a role in small intestinal inflammation, mitochondrial damage, autophagy, and apoptosis.

Structure-Based Analysis of Cefaclor Pharmacokinetic Diversity According to Human Peptide Transporter-1 Genetic Polymorphism.

Cefaclor is a substrate of human-peptide-transporter-1 (PEPT1), and the impact of inter-individual pharmacokinetic variation due to genetic polymorphisms of solute-carrier-family-15-member-1 (SLC15A1) has been a topic of great debate. The main objective of this study was to analyze and interpret cefaclor pharmacokinetic variations according to genetic polymorphisms in SLC15A1 exons 5 and 16. The previous cefaclor bioequivalence results were integrated with additional SLC15A1 exons 5 and 16 genotyping results. An analysis of the structure-based functional impact of SLC15A1 exons 5 and 16 genetic polymorphisms was recently performed using a PEPT1 molecular modeling approach. In cefaclor pharmacokinetic analysis results according to SLC15A1 exons 5 and 16 genetic polymorphisms, no significant differences were identified between genotype groups. Furthermore, in the population pharmacokinetic modeling, genetic polymorphisms in SLC15A1 exons 5 and 16 were not established as effective covariates. PEPT1 molecular modeling results also confirmed that SLC15A1 exons 5 and 16 genetic polymorphisms did not have a significant effect on substrate interaction with cefaclor and did not have a major effect in terms of structural stability. This was determined by comprehensively considering the insignificant change in energy values related to cefaclor docking due to point mutations in SLC15A1 exons 5 and 16, the structural change in conformations confirmed to be less than 0.05 Å, and the relative stabilization of molecular dynamic simulation energy values. As a result, molecular structure-based analysis recently suggested that SLC15A1 exons 5 and 16 genetic polymorphisms of PEPT1 were limited to being the main focus in interpreting the pharmacokinetic diversity of cefaclor.

Irinotecan-induced gastrointestinal damage alters the expression of peptide transporter 1 and absorption of cephalexin in rats.

Irinotecan causes severe gastrointestinal damage, which may affect the expression of intestinal transporters. However, neither the expression of peptide transporter 1 (Pept1) nor the pharmacokinetics of Pept1 substrate drugs has been investigated under irinotecan-induced gastrointestinal damage. Therefore, the present study quantitatively investigated the effects of irinotecan-induced gastrointestinal damage on the intestinal expression of Pept1 and absorption of cephalexin (CEX), a typical Pept1 substrate, in rats. Irinotecan was administered intravenously to rats for 4 days to induce gastrointestinal damage. The expression of Pept1 mRNA and the Pept1 protein in the upper, middle, and lower segments of the small intestine of irinotecan-treated rats was assessed by quantitative real-time polymerase chain reaction (PCR) and western blotting, respectively. The pharmacokinetic profile of CEX was examined after its oral or intravenous administration (10 mg/kg). In irinotecan-treated rats, ∼2-fold increases in Pept1 protein levels were observed in all three segments, whereas mRNA levels remained unchanged. The oral bioavailability of CEX significantly decreased to 76% of that in control rats. The decrease in passive diffusion caused by intestinal damage may have overcome the increase in Pept1-mediated uptake. In conclusion, irinotecan may decrease the intestinal absorption of Pept1 substrate drugs; however, it increased the expression of intestinal Pept1.

Hypertension alters the function and expression profile of the peptide cotransporters PEPT1 and PEPT2 in the rodent renal proximal tubule.

Hypertension is a major risk factor for kidney and cardiovascular disease. The treatment of hypertensive individuals by selected ACE inhibitors and certain di-and tripeptides halts the progression of renal deterioration and extends life-span. Renal reabsorption of these low molecular weight substrates are mediated by the PEPT1 and PEPT2 cotransporters. This study aims to investigate whether hypertension and ageing affects renal PEPT cotransporters at gene, protein expression and distribution as well as function in the superficial cortex and the outer medulla of the kidney. Membrane vesicles from the brush border (BBMV) and outer medulla (OMMV) were isolated from the kidneys of young Wistar Kyoto (Y-WKY), young spontaneously hypertensive (Y-SHR), and middle aged SHR (M-SHR) rats. Transport activity was measured using the substrate, ß-Ala-Lys (AMCA). Gene expression levels of PEPT genes were assessed with qRT-PCR while renal localisation of PEPT cotransporters was examined by immunohistochemistry with Western Blot validation. The Km and Vmax of renal PEPT1 were decreased significantly in SHR compared to WKY BBMV, whilst the Vmax of PEPT2 showed differences between SHR and WKY. By contrast to the reported cortical distribution of PEPT1, PEPT1-staining was detected in the outer medulla, whilst PEPT2 was expressed primarily in the cortex of all SHR; PEPT1 was significantly upregulated in the cortex of Y-SHR. These outcomes are indicative of a redistribution of PEPT1 and PEPT2 in the kidney proximal tubule under hypertensive conditions that has potential repercussions for nutrient handling and the therapeutic use of ACE inhibitors in hypertensive individuals.

Expression, purification and characterization of human proton-coupled oligopeptide transporter 1 hPEPT1.

The human peptide transporter hPEPT1 (SLC15A1) is responsible for uptake of dietary di- and tripeptides and a number of drugs from the small intestine by utilizing the proton electrochemical gradient, and hence an important target for peptide-like drug design and drug delivery. hPEPT1 belongs to the ubiquitous major facilitator superfamily that all contain a 12TM core structure, with global conformational changes occurring during the transport cycle. Several bacterial homologues of these transporters have been characterized, providing valuable insight into the transport mechanism of this family. Here we report the overexpression and purification of recombinant hPEPT1 in a detergent-solubilized state. Thermostability profiling of hPEPT1 at different pH values revealed that hPEPT1 is more stable at pH 6 as compared to pH 7 and 8. Micro-scale thermophoresis (MST) confirmed that the purified hPEPT1 was able to bind di- and tripeptides respectively. To assess the in-solution oligomeric state of hPEPT1, negative stain electron microscopy was performed, demonstrating a predominantly monomeric state.

PEPT1 is essential for the growth of pancreatic cancer cells: a viable drug target.

PEPT1 is a proton-coupled peptide transporter that is up-regulated in PDAC cell lines and PDXs, with little expression in the normal pancreas. However, the relevance of this up-regulation to cancer progression and the mechanism of up-regulation have not been investigated. Herein, we show that PEPT1 is not just up-regulated in a large panel of PDAC cell lines and PDXs but is also functional and transport-competent. PEPT2, another proton-coupled peptide transporter, is also overexpressed in PDAC cell lines and PDXs, but is not functional due to its intracellular localization. Using glibenclamide as a pharmacological inhibitor of PEPT1, we demonstrate in cell lines in vitro and mouse xenografts in vivo that inhibition of PEPT1 reduces the proliferation of the cancer cells. These findings are supported by genetic knockdown of PEPT1 with shRNA, wherein the absence of the transporter significantly attenuates the growth of cancer cells, both in vitro and in vivo, suggesting that PEPT1 is critical for the survival of cancer cells. We also establish that the tumor-derived lactic acid (Warburg effect) in the tumor microenvironment supports the transport function of PEPT1 in the maintenance of amino acid nutrition in cancer cells by inducing MMPs and DPPIV to generate peptide substrates for PEPT1 and by generating a H+ gradient across the plasma membrane to energize PEPT1. Taken collectively, these studies demonstrate a functional link between PEPT1 and extracellular protein breakdown in the tumor microenvironment as a key determinant of pancreatic cancer growth, thus identifying PEPT1 as a potential therapeutic target for PDAC.

PepT1-knockout mice harbor a protective metabolome beneficial for intestinal wound healing.

Genetic knockout (KO) of peptide transporter-1 (PepT1) protein is known to provide resistance to acute colitis and colitis-associated cancer (CAC) in mouse models. However, it was unclear which molecule(s) or pathway(s) formed the basis for these protective effects. Recently, we demonstrated that the PepT1-/- microbiota is sufficient to protect against colitis and CAC. Given that PepT1 KO alters the gut microbiome and thereby changes the intestinal metabolites that are ultimately reflected in the feces, we investigated the fecal metabolites of our PepT1 KO mice. Using a liquid chromatography-mass spectrometry (LC-MS)-based untargeted-metabolomics technique, we found that the fecal metabolites were significantly different between the KO and normal wild-type (WT) mice. Among the altered fecal metabolites, tuberonic acid (TA) was sevenfold higher in KO mouse feces than in WT mouse feces. Accordingly, we studied whether the increased TA could direct an anti-inflammatory effect. Using in vitro models, we discovered that TA not only prevented lipopolysaccharide (LPS)-induced inflammation in macrophages but also improved the epithelial cell healing processes. Our results suggest that TA, and possibly other fecal metabolites, play a crucial role in the pathway(s) associated with the anticolitis effects of PepT1 KO.NEW & NOTEWORTHY Fecal metabolites were significantly different between the KO and normal wild-type (WT) mice. One fecal metabolite, tuberonic acid (TA), was sevenfold higher in KO mouse feces than in WT mouse feces. TA prevented lipopolysaccharide (LPS)-induced inflammation in macrophages and improved the epithelial cell healing process.

Protonation State of a Histidine Residue in Human Oligopeptide Transporter 1 (hPEPT1) Regulates hPEPT1-Mediated Efflux Activity.

To clarify the role of an amino acid residue in the pH-dependent efflux process in Chinese hamster ovary (CHO) cells expressing the human oligopeptide transporter hPEPT1 (CHO/hPEPT1), we determined the effect of extracellular pH on the hPEPT1-mediated efflux process. The efflux of glycylsarcosine (Gly-Sar), a typical substrate for hPEPT1, was determined using an infinite dilution method after cells were preloaded with [3H]-Gly-Sar. The efflux of [3H]-Gly-Sar was stimulated by 5 mM unlabeled hPEPT1 substrates in the medium. This trans-stimulation phenomenon showed that hPEPT1 mediated the efflux of [3H]-Gly-Sar from CHO/hPEPT1 and that hPEPT1 is a bi-directional transporter. We then determined the effect of extracellular pH (varying from 8.0 to 3.5) on the efflux activity. The efflux activity by hPEPT1 decreased with the decrease in extracellular pH. The Henderson-Hasselbälch-type equation, which fitted well to the pH-profile of efflux activity, indicated that a single amino acid residue with a pKa value of approximately 5.7 regulates the efflux activity. The pH-profile of the efflux activity remained almost unchanged irrespective of the proton gradient across the plasma membrane. In addition, the chemical modification of the histidine residue with diethylpyrocarbonate completely abolished the efflux activity from cells, which could be prevented by the presence of 10 mM Gly-Sar. These data indicate that the efflux process of hPEPT1 is also regulated in a pH-dependent manner by the protonation state of a histidine residue located at or near the substrate recognition site facing the extracellular space.

Onset of nutrient consumption during early life stage digestive system development of two tuna species (Thunnus orientalis and Thunnus albacares).

To specify the timing of exogenous nutrient consumption in the larvae of two commercially important tuna species, the Pacific bluefin tuna (PBF) Thunnus orientalis and the yellowfin tuna (YFT) Thunnus albacares, the gene expressions of peptide transporter 1 (PEPT1) were examined. The mRNA expressions of PEPT1 first occurred at 2 days post hatching (dph) in PBF larvae and 3 dph for the YFT, and PEPT1 was found to only be expressed in the intestinal tract. The histological changes of the digestive tract of the YFT larvae were observed and compared to PBF larvae from a previous study. The intestines were developed at the hatching day for both species. It was found that the developmental timing of internal organs differed between the species, with the YFT showing an approximately one-day delay. The major organs such as liver, pancreas and gall bladder that excrete digestive enzymes appeared at 1 dph for PBF and 2 dph for YFT. The development of external morphological features was similar to organ development timings, with mouth-opening and first feeding starting at 2 dph for PBF, and 3 dph for YFT. Growth during the first month is rapid and variable for both species, ranging from 1.06 to 1.56 mm/d. Our findings provide new information about the early onset of feeding and larval development for the two species which would contribute to future aquaculture.

Identification and characterization of the Atlantic salmon peptide transporter 1a.

Peptide transporter 1 (PepT1) mediates the uptake of dietary di-/tripeptides in vertebrates. However, in teleost fish gut, more than one PepT1-type transporter might operate, because of teleost-specific whole gen(om)e duplication event(s) that occurred during evolution. Here, we describe a novel teleost di-/tripeptide transporter, i.e., the Atlantic salmon (Salmo salar) peptide transporter 1a [PepT1a; or solute carrier family 15 member 1a (Slc15a1a)], which is a paralog (77% similarity and 64% identity at the amino acid level) of the well-described Atlantic salmon peptide transporter 1b [PepT1b, alias PepT1; or solute carrier family 15 member 1b (Slc15a1b)]. Comparative analysis and evolutionary relationships of gene/protein sequences were conducted after ad hoc database mining. Tissue mRNA expression analysis was performed by quantitative real-time PCR, whereas transport function analysis was accomplished by heterologous expression in Xenopus laevis oocytes and two-electrode voltage-clamp measurements. Atlantic salmon pept1a is highly expressed in the proximal intestine (pyloric ceca ≈ anterior midgut > midgut >> posterior midgut), in the same gut regions as pept1b but notably ~5-fold less abundant. Like PepT1b, Atlantic salmon PepT1a is a low-affinity/high-capacity system. Functional analysis showed electrogenic, Na+-independent/pH-dependent transport and apparent substrate affinity (K0.5) values for Gly-Gln of 1.593 mmol/L at pH 7.6 and 0.076 mmol/L at pH 6.5. In summary, we show that a piscine PepT1a-type transporter is functional. Defining the role of Atlantic salmon PepT1a in the gut will help to understand the evolutionary and functional relationships among peptide transporters. Its functional characterization will contribute to elucidate the relevance of peptide transporters in Atlantic salmon nutritional physiology.

Alternate expression of PEPT1 and PEPT2 in epidermal differentiation is required for NOD2 immune responses by bacteria-derived muramyl dipeptide.

Peptide transporters 1 and 2 (PEPT1 and PEPT2) are proton-coupled oligopeptide transporter members of the solute carrier 15 family and play a role in the cellular uptake of di/tri-peptides and peptidomimetics. Our previous work showed that PEPT2 is predominantly expressed within undifferentiated keratinocytes. Here we show that PEPT2 expression decreases as keratinocyte differentiation progresses and that PEPT1 alternately is expressed at later stages. Absolute quantification using quantitative polymerase chain reaction revealed that the expression level of PEPT1 is about 17 times greater than that of PEPT2. Immunohistochemical study of human skin provided evidence of PEPT1 in the epidermis. The uptake of glycylsarcosine into keratinocytes was significantly blocked by PEPT inhibitors, including nateglinide and glibenclamide. Moreover, we found that PEPT1 knockdown in differentiated keratinocytes significantly suppressed the influence of a bacterial-derived peptide, muramyl dipeptide (MDP), on the production of proinflammatory cytokine interleukin-8, implying that bacteria-derived oligopeptides can be transported by PEPT1 in advanced differentiated keratinocytes. Taken together, PEPT1 and PEPT2 may concertedly play an important role in MDP-NOD2 signaling in the epidermis, which provides new insight into the mechanisms of skin homeostasis against microbial pathogens.

Transport Characteristics of 5-Aminosalicylic Acid Derivatives Conjugated with Amino Acids via Human H+-Coupled Oligopeptide Transporter PEPT1.

5-Aminosalicylic acid (5-ASA) is used as first line therapy for symptom remission and maintenance of inflammatory bowel disease (IBD). Because 5-ASA is well absorbed from the small intestine when orally administered, several 5-ASA formulations for selective delivery to the colon have been developed and used in clinical practice. However, its delivery efficiency to local inflamed colonic sites remains low. Intestinal H+-coupled oligopeptide transporter 1 (PEPT1) expression in the colon is low, whereas its expression is induced in the colon under chronic inflammation conditions, such as IBD. Therefore, we considered that PEPT1 would be a target transporter to improve 5-ASA delivery efficiency to local colonic lesions. We evaluated the transport characteristics of dipeptide-like 5-ASA derivatives, which were coupling glycine (Gly), lysine, glutamic acid (Glu), valine (Val) and tyrosine to amino or carboxyl group of 5-ASA, in Caco-2 cells. [3H]Glycylsarcosine (Gly-Sar) uptake into Caco-2 cells was inhibited by all 5-ASA derivatives. In addition, 5-ASA derivatives (Gly-ASA, Glu-ASA and Val-ASA), which were coupled by glycine, glutamic acid and valine to amino group of 5-ASA, were taken up in a pH- and concentration-dependent manner and their uptake was inhibited by excess Gly-Sar. Two-electrode voltage-clamp experiment using human PEPT1 expressing Xenopus oocytes showed that Gly-ASA, Glu-ASA and Val-ASA induced marked currents at pH 6.0. Taken together, these results showed that these 5-ASA derivatives are transportable substrates for PEPT1.

In Silico Prediction of the Absorption and Disposition of Cefadroxil in Humans using an Intestinal Permeability Method Scaled from Humanized PepT1 Mice.

It is difficult to predict the pharmacokinetics and plasma concentration-time profiles of new chemical entities in humans based on animal data. Some pharmacokinetic parameters, such as clearance and volume of distribution, can be scaled allometrically from rodents, mammals, and nonhuman primates with good success. However, it is far more challenging to predict the oral pharmacokinetics of experimental drug candidates. In the present study, we used in situ estimates of intestinal permeability, obtained in silico and from rat, wild-type (WT), and humanized PepT1 (huPepT1) mice, to predict the systemic exposure of cefadroxil, an orally administered model compound, under a variety of conditions. Using the GastroPlus simulation software program (Simulations Plus, Lancaster, CA), we found that the C max and area under the plasma concentration-time curve from time zero to the last measurable concentration of cefadroxil were better predicted using intestinal permeability estimates (both segmental and jejunal) from huPepT1 than from WT mice, and that intestinal permeabilities based on in silico and rat estimates gave worse predictions. We also observed that accurate predictions were possible for cefadroxil during oral dose escalation (i.e., 5, 15, and 30 mg/kg cefadroxil), a drug-drug interaction study (i.e., 5 mg/kg oral cefadroxil plus 45 mg/kg oral cephalexin), and an oral multiple dose study [i.e., 500 mg (6.7 mg/kg) cefadroxil every 6 hours]. Finally, the greatest amount of cefadroxil was absorbed in duodenal and jejunal segments of the small intestine after a 5 mg/kg oral dose. Thus, by combining a humanized mouse model and in silico software, the present study offers a novel strategy for better translating preclinical pharmacokinetic data to oral drug exposure during first-in-human studies.

Molecular changes to the rat renal cotransporters PEPT1 and PEPT2 due to ageing.

Renal PEPT1 and PEPT2 cotransporters play an important role in the balance of circulating body oligopeptides and selected peptidomimetic drugs. We aim to comprehensively characterise age-related changes of the renal PEPT cotransporters at the gene, protein, and functional level. Brush border membrane vesicles (BBMV) and outer medulla membrane vesicles (OMMV) were isolated from the kidneys of young, middle-aged and old rats. The protein expression of PEPT1 was not only increased in BBMV from old rats, but PEPT1 also appeared in OMMV from middle-aged and old rats. SLC15A1 gene expression in the renal cortex increased in middle-aged group. PEPT2 protein expression was not only increased with ageing, but PEPT2 also was found in BBMV from middle-aged and old groups. SLC15A2 gene expression in the renal outer medulla increased in the old group. These changes in the expressions and localisations of PEPT1 and PEPT2 could explain the changes to transport activity in BBMV and OMMV. These findings provide novel insights that would be useful for maintaining protein nutrition and optimising the delivery of some peptidomimetic drugs in elderly individuals.

Boron delivery for boron neutron capture therapy targeting a cancer-upregulated oligopeptide transporter.

Boron neutron capture therapy (BNCT) is a radiotherapy utilizing the neutron capture and nuclear fission reaction of 10B taken up into tumor cells. The most commonly used boron agent in BNCT, p-borono-l-phenylalanine (BPA), is accumulated in tumors by amino acid transporters upregulated in tumor cells. Here, by using dipeptides of BPA and tyrosine (BPA-Tyr and Tyr-BPA), we propose a novel strategy of selective boron delivery into tumor cells via oligopeptide transporter PEPT1 upregulated in various cancers. Kinetic analyses indicated that BPA-Tyr and Tyr-BPA are transported by oligopeptide transporters, PEPT1 and PEPT2. The intrinsic oligopeptide transport activity in tumor cells clearly correlated with PEPT1 protein expression level but not with PEPT2, suggesting that PEPT1 is the predominant oligopeptide transporter at least in tumor cell lines. Furthermore, using BPA-Tyr and Tyr-BPA, boron was successfully delivered into PEPT1-expressing pancreatic cancer AsPC-1 cells via a PEPT1-mediated mechanism. Intravenous administration of BPA-Tyr into the mice bearing AsPC-1 xenograft tumors resulted in significant boron accumulation in the tumors. It is proposed that the oligopeptide transporters, especially PEPT1, are promising candidates for molecular targets of boron delivery in BNCT. The BPA-containing dipeptides would have a potential for the development of novel boron carriers targeting PEPT1.

Association of SLC15A1 polymorphisms with susceptibility to dyslipidaemia in a Chinese Han population.

WHAT IS KNOWN AND OBJECTIVE: Dyslipidaemia is an increasingly serious clinical and public health issue. In this study, we aim to explore the association of genetic polymorphisms in solute carrier transporter (SLC) 15A1 with the risk of dyslipidaemia in a Chinese Han population. METHODS: Three single nucleotide polymorphisms (SNPs) in SLC15A1 (rs2297322, rs4646234 and rs1289389) were selected using bioinformatics in a Chinese Han population with 530 participants. Genotyping was conducted with Sequenom MassARRAY. A logistic regression model was used for the analysis of the association between genotypes and dyslipidaemia. SHEsis software was applied to the haplotype analysis. RESULTS AND DISCUSSION: The SLC15A1 rs2297322 TT genotype was associated with a lower risk of hypertriglyceridaemia compared with the CC genotype (OR = 0.44, 95% CI = 0.21-0.93, P = .032). The carriers of the SLC15A1 rs1289389 T allele were found to be significantly associated with a lower risk of hypertriglyceridaemia compared with the C allele (OR = 0.54, 95% CI = 0.33-0.88, P = .013). In the recessive model, the carriers of the SLC15A1 rs4646234 CC genotype showed a significantly reduced risk of hypercholesterolaemia (OR = 2.29, 95% CI = 1.23-4.28, P = .009). Haplotype analysis showed that the CTC haplotype composed of SLC15A1 rs2297322, rs4646234 and rs1289389 was associated with a lower risk of hypertriglyceridaemia (OR = 1.58, 95% CI = 1.12-2.24, P = .009), whereas the TTC haplotype was associated with a significantly reduced risk of hypertriglyceridaemia (OR = 0.63, 95% CI = 0.40-0.99, P = .045). WHAT IS NEW AND CONCLUSION: SLC15A1 rs2297322 and rs1289389 polymorphisms were associated with alterations in the risk of dyslipidaemia in a Chinese Han population.

Effects of methionine partially replaced by methionyl-methionine dipeptide on intestinal function in methionine-deficient pregnant mice.

This study was to compare the effects of parenteral supplementation of methionyl-methionine (Met-Met) or Met on intestinal barrier function in Met-deficient pregnant mice. Pregnant mice were randomly divided into three groups. The Control group was provided a diet containing Met and received i.p. injection of saline. The Met group was fed the same diet but without Met and received daily i.p. injection of 35% of the Met contained in the control diet. The Met-Met group was treated the same as the Met group, except that 25% of the Met injected was replaced with Met-Met. Met-Met promoted villus surface area in ileum compared with Met alone. In addition, the mRNA abundance of amino acid and glucose transporters in the small intestine was altered with Met-Met. Moreover, Met-Met increased tight junction protein and decreased apoptosis-related proteins expression in the jejunum and ileum. These results suggest that Met-Met can promote intestinal function over Met alone in Met-deficient mice.

Soybean glycinin decreased growth performance, impaired intestinal health, and amino acid absorption capacity of juvenile grass carp (Ctenopharyngodon idella).

The present study evaluated the influence of dietary soybean glycinin on growth performance, intestinal morphology, free intestinal amino acid (AA) content, and intestinal AA transporter (AAT) mRNA levels in juvenile grass carp (Ctenopharyngodon idella). Results were displayed as follows: (1) 8% dietary glycinin decreased growth performance, inhibited intestinal growth, and caused intestinal histology damage of grass carp; (2) dietary glycinin decreased the content of free neutral AAs including Val, Ser, Tyr, Ala, Pro, and Gln in all intestinal segments, and Thr, Ile, Leu, Phe, and Gly in the MI and DI while downregulated the mRNA levels of corresponding transporters including SLC38A2, SLC6A19b, and SLC6A14 in all intestinal segments, and SLC7A5, SLC7A8, and SLC1A5 in the MI and DI. Dietary glycinin decreased the content of free basic AAs including Arg in the MI and DI and His in all intestinal segments while downregulated cationic AAT SLC7A1 mRNA levels in the MI and DI. Dietary glycinin decreased the content of free acidic AAs including Glu in all intestinal segments and Asp in the MI and DI while decreased mRNA levels of corresponding transporters including SLC1A2a in all intestinal segments and SLC1A3 in the MI and DI; (3) the digestion trial showed that basic subunits of glycinin was hard to digest in the intestine of grass carp; (4) co-administration of glutamine with glycinin partially alleviated the negative effects. Overall, glycinin decreased intestinal AA absorption capacity partly contributed by decreased AATs' mRNA levels and the indigestibility of glycinin.