mRNA Expression Of Amino Acid Transporters Research Articles

Standardized ileal digestible tryptophan to lysine ratios affect performance and regulate intestinal mRNA expression of amino acid transporters in weaning pigs fed a low crude protein diet

The objective of this study was to estimate the effect of standardized ileal digestible (SID) tryptophan (Trp) to lysine (Lys) ratios on growth performance and jejunal expression of amino acid transporters in weaning pigs. A total of 240 hybrid [(Duroc, male) x (Large White x Landrace, female)] piglets (6.52 ± 0.42 kg) were used in a 28-day growth trial and randomly allotted to one of four diets providing SID Trp to Lys ratios of 0.15, 0.18, 0.21, or 0.24 and were allocated in 6 pens per treatment with 10 pigs per pen. The average daily gain (ADG), average daily feed intake (ADFI), and serum levels of Trp, serine, isoleucine and leucine in pigs significantly increased when the SID Trp to Lys ratios increased from 0.15 to 0.18, 0.21, or 0.24 (P < 0.05). The pigs fed the diet with the 0.24 ratio had a reduced serum urea nitrogen (SUN) concentration compared with the pigs fed the 0.15 ratio diet (P < 0.05). The villus heights of the duodenum and jejunum in pigs fed the diet with a 0.21 ratio were greater than those of pigs fed the 0.15 ratio diet (P < 0.05). The increase in the SID Trp to Lys ratio from 0.15 to 0.18 decreased the intestinal ASCT2 mRNA level in weaning pigs (P < 0.05). The increase in the SID Trp to Lys ratio from 0.15 to 0.21 or 0.24 increased the mRNA abundance of intestinal B°AT1 (P < 0.05). The increase in the SID Trp to Lys ratio from 0.15 to 0.18 increased the mRNA abundances of intestinal CAT-1 and rBAT (P < 0.05). The intestinal b0,+AT mRNA level in the pigs fed the 0.21 ratio diet was higher than that in pigs in other three treatments (P < 0.05). The mRNA abundances of y+LAT1 and 4F2hc in the pigs fed the 0.15 ratio diet were lower than those in pigs in other three treatments (P < 0.05). The intestinal PepT-1 mRNA level in the pigs fed the 0.15 or 0.24 ratio diet was lower than that of the pigs fed the 0.21 ratio diet (P < 0.05). In conclusion, the optimal SID Trp to Lys ratio was determined to be 0.18 for weaning pigs that were fed a low crude protein diet using ADG and jejunal amino acid transporter mRNA expression as the response criteria.

Plasma citrulline correlates with basolateral amino acid transporter LAT4 expression in human small intestine

Background & aimsPlasma citrulline, a non-protein amino acid, is a biochemical marker of small intestine enterocyte mass in humans. Indeed, citrulline is highly correlated with residual bowel length in patients with short bowel syndrome. It is known to be synthesised in epithelial cells of the small intestine from other amino acids (precursors). Citrulline is then released into systemic circulation and interconverted into arginine in kidneys. If plasma citrulline concentration depends on abundance of intestinal amino acid transporters is not known. The aim of the present study was to explore whether plasma citrulline concentration correlates with the expression of intestinal amino acid transporters. Furthermore, we assessed if arginine in urine correlates with plasma citrulline.MethodsDuodenal samples, blood plasma and urine were collected from 43 subjects undergoing routine gastroduodenoscopy. mRNA expression of seven basolateral membrane amino acid transporters/transporter subunits were assessed by real-time PCR. Plasma and urine amino acid concentrations of citrulline, its precursors and other amino acids were analysed using High Performance Liquid Chromatography measurements. Amino acid transporter mRNA expression was correlated with blood plasma and urine levels of citrulline and its precursors using Spearman's rank correlation. Likewise, urine arginine was correlated with plasma citrulline.ResultsPlasma citrulline correlated with the mRNA expression of basolateral amino acid transporter LAT4 (Spearman's r = 0.467, p = 0.028) in small intestine. None of the other basolateral membrane transporters/transporter subunits assessed correlated with plasma citrulline. Plasma citrulline correlated with urinary arginine, (Spearman's r = 0.419, p = 0.017), but not with urinary citrulline or other proteinogenic amino acids in the urine.ConclusionsIn this study, we showed for the first time that small intestinal basolateral LAT4 expression correlates with plasma citrulline concentration. This finding indicates that LAT4 has an important function in mediating citrulline efflux from enterocytes. Furthermore, urine arginine correlated with plasma citrulline, indicating arginine in the urine as possible additional marker for small intestine enterocyte mass. Finally, basolateral LAT4 expression along the human small intestine was shown for the first time.

Optimal branched-chain amino acid ratio improves cell proliferation and protein metabolism of porcine enterocytesin in vivo and in vitro.

The aim of this study was to investigate the effects of different branched-chain amino acid (BCAA) ratios on intestinal cell proliferation and protein metabolism. This in vivo study was conducted in growing pigs (average initial body weight = 9.85 ± 0.35 kg) exposed to different leucine, isoleucine, and valine (Leu:Ile:Val) ratios (1:1:1, 1:0.75:0.75, 1:0.51:0.63, and 1:0.25:0.25) in 17% crude protein (CP) diets for 45 d to determine intestinal morphology, cell proliferation, and amino acid transporter mRNA expression. This in vitro study was performed in porcine jejunal epithelial cell line to investigate the effects of different BCAA ratios (0, 1:0.25:0.25, 1:0.5:0.5, and 1:1:1) on cell proliferation, AA transporter expression. and protein turnover. Relative to the positive control (Leu:Ile:Val = 1:0.51:0.63, 20% CP), the 1:0.75:0.75 group (17% CP) significantly increased the jejunal villus height, the percentage of proliferating cell nuclear antigen-positive cells and decreased the ileal crypt depth (P <0.05). Moreover, most AA concentrations and AA transporter expression in the jejunal and ileal mucosa in 17% CP diets were increased to the levels similar to those in the positive control. Additionally, this in vitro study showed that the BCAA ratio of 1:0.25:0.25 significantly increased intestinal cell proliferation, mRNA expression of AA transporters, AA concentrations, and protein turnover (P <0.05). These findings suggest that optimal BCAA ratio (in vivo = 1:0.75:0.75; in vitro = 1:0.25:0.25) would improve intestinal morphology and cell proliferation, increase intestinal AA absorption through mediating expression of intestinal AA transporters, and promote intestinal protein turnover. The findings yield new insights into the use of BCAAs in humans and animals.

Large Reduction in Adiponectin During Pregnancy Is Associated With Large-for-Gestational-Age Newborns.

Fetuses exposed to an obese intrauterine environment are more likely to be born large-for-gestational age (LGA) and are at increased risk of obesity in childhood and cardiovascular disease and/or type 2 diabetes mellitus as adults, but which factors that influence the intrauterine environment is less clear. To investigate the association between circulating levels of leptin and adiponectin, measured multiple times during pregnancy, and birth weight and prevalence of LGA or small-for-gestational-age infants. The association between birth weight and messenger RNA (mRNA) expression of adiponectin receptors and genes involved in nutrient transport in the placenta was also investigated. Population-based prospective cohort [substudy of the STORK study (STORe barn og Komplikasjoner, translated as Large Babies and Complications)] from 2001 to 2008. University hospital. Patients or other participants: 300 women. Oral glucose tolerance test was performed twice along with adiponectin and leptin levels measured four times during pregnancy. Circulating adiponectin was lower in mothers who gave birth to LGA offspring or had fetuses with high intrauterine abdominal circumference late in pregnancy. Adiponectin decreased most from early to late pregnancy in mothers who gave birth to LGA offspring, and the decrease was an independent predictor of birth weight. Adiponectin receptor 2 and system A amino acid transporter mRNA expression in placentas was negatively correlated with birth weight and was lower in placentas from LGA infants. Our findings suggest that maternal adiponectin may be an important predictor of fetal growth and birth weight, independent of body mass index and insulin resistance.

The relationship between gene expression of cationic and neutral amino acid transporters in the small intestine of chick embryos and chick breed, development, sex, and egg amino acid concentration

This study was conducted to investigate the gene expression of cationic and neutral amino acid (AA) transporters in the small intestine of chick embryos with different genetic backgrounds [Wenshi Yellow-Feathered chick (WYFC) and White Recessive Rock chick (WRRC)]. The study also investigated the correlation between the abundance of AA transporter mRNA and the AA content of fertilized eggs. Intestinal samples were collected on embryonic d 9, 12, 14, 17, and 19 and the day of hatch. The results showed that, before incubation, the AA content of WRRC eggs was lower (P < 0.05) than the AA content of WYFC eggs. In WYFC, the mRNA abundance of CAT-1 [solute carrier (SLC) family 7 member 1], CAT-4 (SLC family 7 member 4), rBAT (SLC family 3 member 1), y(+)LAT-1 (SLC family 7 member 7), y(+)LAT-2 (SLC family 7 member 6), LAT-4 (SLC family 43 member 2), and SNAT-2 (SLC family 38 member 2), as detected by real-time reverse transcriptase PCR, was greater (P < 0.05) than the mRNA abundance detected in the WRRC samples. The mRNA abundance of all measured AA transporters was affected (P < 0.05) by embryonic age. Sex had the largest effect (P < 0.05) on the mRNA expression of CAT-1, CAT-4, y(+)LAT-2, and LAT-4 in WYFC and on CAT-4 and B(0)AT-1 (SLC family 6 member 19) mRNA expression in WRRC. In WYFC, only CAT-1 mRNA expression was negatively correlated (r = -0.68 to -0.84, P < 0.05) with all AA content. However, few correlations were detected between AA content and the mRNA expression of multiple transporters in WRRC. These findings provide a comprehensive profile of the temporal and spatial mRNA expression of AA transporters in the small intestine of chick embryos. Few correlations were detected between the AA content of the eggs and mRNA expression of specific AA transporters in the small intestine.

High levels of leucine are required for the upregulation of amino acid transporters in human skeletal muscle following essential amino acid ingestion

The goal of this study was to determine whether the upregulation of select amino acid transporters in human skeletal muscle is dependent upon the amount of leucine in an essential amino acid (EAA) solution. Young, healthy individuals ingested 10g of EAA with either a leucine concentration similar to high quality protein (CTRL; 1.8g leucine [n=6]) or an increased leucine concentration (LEU; 3.5g leucine [n=7]). Muscle biopsies were obtained prior to and at 1 and 2h following EAA ingestion to examine select amino acid transporter mRNA expression. Following EAA ingestion, CTRL had little change in amino acid transporter mRNA expression, whereas at 1h post ingestion LEU experienced an increase in L-type (LAT1), sodium-coupled neutral (SNAT2), and proton-coupled (PAT1) amino acid transporter mRNA expression. These data highlight an important role for leucine availability in the upregulation of select amino acid transporters. Furthermore, additional leucine may sensitize the muscle cell to subsequent feedings by increasing the availability of amino acid transporters. Funding: NIH/NIAMS R01 AR049877, NIA P30AG024832, NIH 1UL1RR029876-01

Skeletal Muscle Amino Acid Transporter mRNA Expression Is Increased In Young And Older Humans Following Resistance Exercise

INTRODUCTION: Amino acid availability is important for increasing muscle protein synthesis. However, for amino acids to be taken up and utilized by the cell, adequate transport of amino acids must occur. Interestingly, amino acid transporters have been linked to mTOR cellular signaling- a major regulator of muscle protein synthesis. PURPOSE: Therefore, we evaluated the expression levels of select amino acid transporters in young and older humans following a single bout of heavy resistance exercise. METHODS: Young (n=5) and Older (n=5) male subjects participated in a single bout of resistance exercise. Muscle biopsies were sampled at Basal, 6 and 24h post exercise. Muscle biopsies were analyzed for LAT1/SLC7A5, CD98/SLC3A2, SNAT2/SLC38A2 and PAT1/SLC36A1 mRNA expression utilizing real-time PCR. RESULTS: LAT1, CD98 and PAT1 mRNA expression were significantly elevated at 6h post in young and older subjects. However, LAT1 response was greater and was prolonged (24h) for the older subjects. Additionally, SNAT2 mRNA expression was elevated at 6 and 24h post in the older while unchanged for the younger subjects. CONCLUSIONS: These data support a rapid upregulation of amino acid transporters gene expression which may support enhanced protein synthesis following a bout of exercise. However, the robust and sustained transporter expression in the old may reflect a greater export of amino acids due to accelerated protein breakdown and muscle remodeling. Supported by ACSM Research Endowment Grant (MJD), P30 AG-024832 (MJD) and NIH/NIAMS grant R01 AR049877 (BBR)

Cationic amino acid transporter mRNA expression in rat kidney and liver

Expression of rat cationic amino acid transporter 2 (r-CAT-2) mRNA was studied in kidney and liver using Northern blot analysis and nonradioactive in situ hybridization with a probe identifying both the r-CAT-2alpha and -2beta splice variants. Expression of r-CAT-2 mRNA was higher in the liver than in the kidney. Within the kidney, r-CAT-2 mRNA was more abundant in the outer and inner medulla than in the cortex. In the liver lobule, the intensity of the hybridization signal in hepatocytes decreased between the portal area and the central vein. In the kidney, hybridization signals were detected in parietal cells of Bowman's capsule, various tubule cells of outer and inner medulla, in endothelial and interstitial cells of inner medulla, and in papillary epithelial cells.