Leucine Group Research Articles

Leucine improves thiram-induced tibial dyschondroplasia and gut microbiota dysbiosis in broilers

Thiram, a commonly used agricultural insecticide and fungicide, has been found to cause tibial dyschondroplasia (TD) in broilers, leading to substantial economic losses in the poultry industry. In this study, we aimed to investigate the mechanism of action of leucine in mitigating thiram-induced TD and leucine effects on gut microbial diversity. Broiler chickens were randomly divided into five equal groups: control group (standard diet), thiram-induced group (thiram 80 mg/kg from day 3 to day 7), and different concentrations of leucine groups (0.3%, 0.6%, 0.9% leucine from day 8 to day 18). Performance indicator analysis and tibial parameter analysis showed that leucine positively affected thiram-induced TD broilers. Additionally, mRNA expressions and protein levels of HIF-1α/VEGFA and Ihh/PTHrP genes were determined via quantitative real-time polymerase chain reaction and western blot. The results showed that leucine recovered lameness disorder by downregulating the expression of HIF-1α, VEGFA, and PTHrP while upregulating the expression of Ihh. Moreover, the 16 S rRNA sequencing revealed that the leucine group demonstrated a decrease in the abundance of harmful bacteria compared to the TD group, with an enrichment of beneficial bacteria responsible for producing short-chain fatty acids, including Alistipes, Paludicola, CHKCI002, Lactobacillus, and Erysipelatoclostridium. In summary, the current study suggests that leucine could improve the symptoms of thiram-induced TD and maintain gut microbiota homeostasis.

Leucine improves the growth performance, carcass traits, and lipid nutritional quality of pork in Shaziling pigs

Leucine is involved in promoting fatty acid oxidation and lipolysis, mediating lipid metabolism and energy homeostasis, thus it has been widely used in livestock production. However, the effects of leucine on fat deposition and nutrition in Shaziling pigs remain unclear. A total of 72 Shaziling pigs (150 days old, weight 35.00 ± 1.00 kg) were randomly divided into 2 groups and fed with basal diet (control group) or basal diet containing 1% leucine (leucine group) for 60 days. The results showed that leucine significantly increased the average daily feed intake but decreased the ratio of feed to gain (P < 0.05), increased the loin muscle area and serum glucose content (P < 0.05) of Shaziling pigs. Besides, leucine regulated the re-distribution of fatty acids from adipose tissue to muscle as it significantly increased the contents of C18:1n-9 and C22:6n-3 (DHA) in the longissimus thoracis while decreased the contents of C22:5n-3 (DPA), C20:5n-3 (EPA), and DHA in the adipose tissue of Shaziling pigs (P < 0.05). Lipidomic analysis showed that the contents of phosphatidylethanolamines (PEs), cardiolipins (CLs), and phosphatidylglycerols (PGs) in the longissimus thoracis and the contents of lysophosphatidylethanolamines (LPEs), ceramides (Cers), phosphatidylinositols (PIs) in adipose tissue of Shaziling pigs were decreased in leucine group (P < 0.05). Collectively, this study clarified that dietary addition of 1% leucine have a better effect on growth performance and the deposition of beneficial fatty acids in the muscle of Shaziling pigs, which is conductive to the production of high quality and healthy pork. In addition, leucine altered the lipid composition of muscle and fat in Shaziling pigs. The related results provide a theoretical basis and application guidance for regulating fat deposition in Shaziling pigs, which is important for the healthy breeding of Shaziling pigs.

Leucine improves dietary protein use efficiency by regulating protein synthesis by activating amino acid transporters and the mTORC1 pathways in Chinese mitten crab (Eriocheir sinensis)

Leucine plays a critical role in protein metabolism and energy homeostasis. This study determines whether leucine supplementation increases body protein synthesis in juvenile E. sinensis while consuming less protein than their requirements. It also investigates the effects of leucine on molecular mechanisms regulating protein synthesis. The 8-week growth trial included three dietary protein levels (22%, 30% or 38%) crossing three leucine levels (1.1, 2.5 or 5.0%). In the trial, 1440 crabs (0.40 ± 0.05 g) were allocated to a 3 × 3 factorial experiment with four replicates of 40 crabs each. The WG and SGR of the NP group were significantly higher than those of the LLP group when the diet contained 1.1% leucine (P < 0.05). The WG, SGR and whole-body protein content of the LP group were significantly higher than those of the LLP group with 2.5% leucine added to the diet (P < 0.05) but not significantly different from those of the NP group (P > 0.05). However, when 5% leucine was added to the diet, the whole-body protein content of the LP group was significantly higher than that of the LLP group (P < 0.05). Dietary leucine supplementation significantly improved growth performance, increased crude protein and decreased crude lipids in the crabs. When the diet contained 30% crude protein, the highest WG, SGR, PER and PRR appeared in the LP-2.5 group (P > 0.05). The PER and PRR of the NP-2.5 group were significantly higher than those of the NP-1.1 group (P < 0.05) and were not significantly different from those of the NP-5.0 group (P > 0.05). In addition, the whole-body protein content of the NP-2.5 group was significantly higher than that of the NP-1.1 and NP-5.0 groups (P < 0.05). Growth hormone and ecdysterone significantly increased with dietary protein levels. The highest growth hormone and ecdysterone in the hemolymph occurred in the 2.5% leucine groups. Moreover, leucine supplementation significantly increased lipase and amylase activity in the hepatopancreas (P < 0.05). The 2.5% leucine supplementation significantly increased CAT activity and decreased MDA in the hepatopancreas. Dietary leucine significantly increased hemocyanin in the hemolymph, and the expression of amino acid transporter genes was significantly increased with dietary leucine supplementation. The crabs fed 2.5% leucine supplementation had the highest gene expression of the mTOR pathway, indicating that dietary leucine significantly promotes amino acid transport and protein synthesis in the hepatopancreas and muscles. This study suggests that a low-protein diet can inhibit animal protein synthesis and decrease energy accumulation and growth. The 2.5% leucine supplementation in the 30% protein diet effectively could promote protein synthesis and utilization and improve crabs growth and protein utlization.

Can Leucine Supplementation Improve Frailty Index Scores?

Sarcopenia and frailty are important conditions that become increasingly prevalent with age. There is partial overlap between the two conditions, especially in terms of the physical aspects of the frailty phenotype: low grip strength, gait speed, and muscle mass. This study examined whether administration of the essential branched-chain amino acid leucine, besides improving sarcopenia, may reduce frailty assessed by frailty index (FI) in older institutionalized people living in nursing homes. We conducted a secondary analysis of a placebo-controlled, randomized, double-blind design study (ClinicalTrials.gov NCT03831399). The study included fifty males and females aged 65 and over who were living in nursing homes and did not have dementia. The participants were randomized to a parallel group intervention of 13 weeks' duration, with a daily intake of leucine (6 g/day) or placebo (lactose, 6 g/day). The outcome of this study was to evaluate whether there was a change in the level of a 95 item FI compared to the baseline and to compare the effect of the leucine group versus the placebo group. A significant inverse correlation was found between FI and performance of the activities of daily life, cognitive function, gait and balance, muscle function parameters, and nutritional status (p < 0.001 in all cases). There were no statistically significant differences in FI levels at baseline (placebo group FI 0.27 ± 0.08 and leucine group FI 0.27 ± 0.10) and at the 13 week follow-up (placebo group FI 0.28 ± 0.10 and leucine group FI 0.28 ± 0.09). There were also no significant differences between the leucine and placebo groups in the mean FI difference between baseline and follow-up (p = 0.316, Cohen's d: 0.04). This pilot study showed that a nutritional supplementation with leucine did not significantly modify the frailty index in older nursing home residents.

Effects of dietary leucine on growth, antioxidant capacity, immune response, and inflammation in juvenile yellow catfish Pelteobagrus fulvidraco.

The experiment was conducted to investigate the effects of dietary leucine on growth, antioxidant capacity, immune response, and inflammation in juvenile yellow catfish. Five diets were formulated to contain five dietary leucine levels: 12.00 (control), 19.00, 26.00, 33.00, and 40.00gkg-1. Each diet was randomly assigned to triplicate groups of 30 juvenile fish (5.02 ± 0.15g) twice daily to apparent satiation for 56days. Weight gain rate, specific growth rate, and activities of liver superoxide dismutase, glutathione peroxidase, and serum lysozyme, as well as immunoglobulin M content, significantly increased with increase in dietary leucine levels up to 26.00gkg-1, but those values decreased significantly with a further increase in dietary leucine. On the contrary, the lowest malondialdehyde content was found in 26.00 and 33.00gkg-1 leucine groups. The expression levels of IGF 1 and MYF 5 genes in muscle were significantly upregulated with increase in dietary leucine levels up to 26.00gkg-1, but the expression of MSTN level showed the opposite trend. The lowest expression levels of IL 8 and TNFɑ genes in the liver were found in 26.00gkg-1 leucine groups. The quadratic regression analysis on weight gain, specific growth rate, and feed conversion ratio against dietary leucine levels indicated that the optimal dietary leucine requirement was estimated to be 26.84-27.00gkg-1of the dry diet.

An aminopeptidase N-based color-convertible fluorescent nano-probe for cancer diagnosis.

Specific cancer diagnosis at an early stage plays a significant role in preventing cancer metastasis and reducing cancer mortality. Thus, exploring specific and sensitive fluorescent probes to realize early cancer diagnosis is an urgent need in clinic. Aminopeptidase N (APN/CD13), overexpressed in numerous malignant tumors, is an important tumor biomarker associated with cancer progression, invasion, and metastasis. In this study, a novel fluorescent molecule APN-SUB, capable of monitoring APN in real time, is encapsulated in a pH-responsive block copolymer (termed APN-SUB nanoprobe) for cancer diagnosis. APN-SUB contains a fluorophore center and a trigger moiety (leucine group), which is covalently conjugated on the fluorophore with an amide bond. The hydrolysis of the amide bond in APN-SUB activated by APN leads to a red shift of maximum fluorescence emission wavelength from 495 nm to 600 nm, realizing dual-color transformation from green to red. Moreover, the APN-SUB nanoprobe with pH-responsiveness is prepared to improve the accumulation and the release rate in the tumor region. It is worth noting that the APN-SUB nanoprobe exhibits good performance for APN imaging, namely, superior limit of detection (0.14 nU mL-1), excellent selectivity and strong photostability. More importantly, the APN-SUB nanoprobe can be successfully employed as a color-convertible fluorescent probe for cancer diagnosis by tracking the activity of APN with high specificity and sensitivity in vivo, demonstrating its potential value for cancer diagnosis.

Regulation of skeletal muscle protein synthesis in the preterm pig by intermittent leucine pulses during continuous parenteral feeding.

Extrauterine growth restriction is a common complication of preterm birth. Leucine (Leu) is an agonist for the mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) signaling pathway that regulates translation initiation and protein synthesis in skeletal muscle. Previously, we showed that intermittent intravenous pulses of Leu to neonatal pigs born at term receiving continuous enteral nutrition increases muscle protein synthesis and lean mass accretion. Our objective was to determine the impact of intermittent intravenous pulses of Leu on muscle protein anabolism in preterm neonatal pigs administered continuous parenteral nutrition. Following preterm delivery (on day 105 of 115 gestation), pigs were fitted with umbilical artery and jugular vein catheters and provided continuous parenteral nutrition. Four days after birth, pigs were assigned to receive intermittent Leu (1600 µmol kg-1 h-1 ; n = 8) or alanine (1600 µmol kg-1 h-1 ; n = 8) parenteral pulses every 4 h for 28 h. Anabolic signaling and fractional protein synthesis were determined in skeletal muscle. Leu concentration in the longissimus dorsi and gastrocnemius muscles increased in the leucine (LEU) group compared with the alanine (ALA) group (P < 0.0001). Despite the Leu-induced disruption of the Sestrin2·GATOR2 complex, which inhibits mTORC1 activation, in these muscles (P < 0.01), the abundance of mTOR·RagA and mTOR·RagC was not different. Accordingly, mTORC1-dependent activation of 4EBP1, S6K1, eIF4E·eIF4G, and protein synthesis were not different in any muscle between the LEU and ALA groups. Intermittent pulses of Leu do not enhance muscle protein anabolism in preterm pigs supplied continuous parenteral nutrition.

Effects of dietary L-leucine supplementation on testicular development and semen quality in boars.

Sperm and seminal plasma are rich in leucine, and leucine can promote the protein synthesis. This property makes it an interesting amino acid to increase sperm quality of human and livestock spermatogenesis. The goal of this study was to explore the effects of dietary leucine supplementation on testicular development and semen quality in boars from weaning to 10 months of age. 30 pure-bred, weaned Duroc boars (8.0 ± 1.0 kg) were randomly divided into two groups: control group (CON; fed the basal diet) and leucine group (LEU; fed the basal diet supplemented with 1.2% leucine); then, their body weight and testicular volume were recorded every 4 weeks. Testes were collected for histological and genes expression analysis from 150-day-old boars. Semen was collected and analyzed. Amino acids contents of blood plasma, seminal plasma, sperm, and testes were determined. Dietary supplementation with leucine increased the testicular volume and weight of boars, compared with CON. Sperm viability, sperm count per ejaculation, and average curve speed of sperm in leucine-supplemented boars were increased. Furthermore, leucine supplementation increased the blood plasma and seminal plasma leucine concentrations, and enhanced the gene expressions of branch chain amino acid transaminase, protein kinase B, mammalian target of rapamycin (mTOR), and cyclinb1 in the testes. Interestingly, the expressions of the p-mTOR and mTOR proteins in the testes were also upregulated. Thus, dietary leucine supplementation increased leucine absorption and utilization in the testes, promoted testicular development, and improved semen quality of boars, partly through the mTOR signaling pathway.

Effects of leucine-rich protein supplements in older adults with sarcopenia: A systematic review and meta-analysis of randomized controlled trials

ObjectivesThis study examined whether leucine-rich protein supplements improve muscle strength, mass, and performance in sarcopenic older adults. MethodsWe searched PubMed-Medline, Embase, and Cochrane Library databases for randomized controlled trials comparing leucine-rich protein supplements with a control intervention in sarcopenic older adults. A pairwise meta-analysis using a fixed-effects model was performed. The primary outcome of interest was muscle strength regardless of the measures used. Effect sizes were computed as standardized mean differences (SMDs) with 95% confidence intervals (CIs). ResultsSix randomized controlled trials including a total of 699 participants were retrieved. Leucine-rich protein supplements improved participants’ overall muscle strength, mass, and performance compared to the control group (SMD = 0.939; 95% CI, 0.440–1.438; P < 0.001). As the primary outcome, muscle strength improved significantly in the leucine group (SMD = 0.794; 95% CI, 0.104–1.485; P = 0.024). ConclusionLeucine-rich protein supplements improve muscle strength in sarcopenic older adults. They may be suggested in nutritional treatment of sarcopenia.

Effect of Citrulline and Leucine Intake with Exercises on Body Composition, Physical Activity, and Amino Acid Concentration in Older Women: A Randomized Double-Blind Placebo-Controlled Study.

The combined intake of citrulline (CIT) and leucine (LEU) can stimulate protein synthesis. Therefore, this study aimed to investigate the effect of combined intake of CIT and LEU accompanied by exercise for 20 weeks on body composition, physical activity (PA), and amino acid concentrations in older Japanese women with low body mass index (BMI) (16 to 21 kg/m2) using a randomized, double-blind, placebo-controlled design. The supplement was administered twice a day for 20 weeks (Ex (exercise) + CIT·LEU group, n = 10: mainly 0.8 g CIT and 1.6 g LEU; Ex + Placebo group, n = 13: mainly 3.5 g carbohydrate). Additionally, both groups exercised (weight-bearing exercise, square stepping exercise) once a week for 75 min. Body composition, PA, and amino acid concentrations in the plasma were measured. Body weight, BMI, body mass, household PA, total PA, and phenylalanine significantly increased in the Ex + CIT·LEU group (p < 0.05) post intervention. This study suggests that the combined intake of CIT and LEU accompanied by exercise can improve body weight, BMI, body mass, and PA in older women with low BMI, which may prevent sarcopenia and frailty.

Responses to graded levels of leucine and branched-chain amino acid imbalance in tiger puffer Takifugu rubripes

In fish, it has been debatable whether branched-chain amino acid (BCAA) imbalance will show antagonistic effects on the growth and the concentrations of plasma or tissue BCAAs. The objective of this study were to investigate the effects of incremental levels of dietary leucine on the growth (trial 1) and potential antagonistic effects between BCAAs (trial 2) in tiger puffer. This study was composed of two separate trials. In trial 1, six experimental diets were prepared by the basal diet containing incremental levels of leucine (19.3, 24.9, 28.6, 32.6, 36.3 and 40.7 g kg−1 of dry diet). In trial 2, five experimental diets were formulated to contain a proper amount of leucine (29.0 g kg−1 of dry diet), a deficiency of leucine (12.6 g kg−1 of dry diet), an excess of leucine (55.9 g kg−1 of dry diet), an excess of isoleucine (43.2 g kg−1 of dry diet) and an excess of valine (49.6 g kg−1 of dry diet). All diets in two trials were fed to fish in triplicate net cages and polyethylene tanks, respectively. In trial 1, growth increase relative to initial body weight was 206.2–227.5%, while growth performance and body condition indices were not significantly affected by different levels of dietary leucine and did not show significantly linear or quadratic relationships with incremental levels of dietary leucine. In trial 2, growth performance also did not exhibit significant differences in fish fed imbalanced BCAAs diets. Compared with a proper amount of leucine group, the activities of branched-chain α-keto acid dehydrogenase enzyme complex (BCKDH) and BCKDH kinase increased in the leucine or valine excessive diet. The expressions of amino acid transporters (B0AT1 and y+LAT2) and peptide transporter 1 (PepT1) were down-regulated by excessive dietary leucine, isoleucine or valine. Free valine concentration in plasma and muscle increased in the leucine deficient diet compared to a proper amount and an excess of leucine in diets. In conclusion, the growth of tiger puffer was not affected by the diets containing 12.6–55.9 g kg−1 leucine. An excess of dietary leucine, isoleucine or valine possibly resulted in antagonism between BCAAs based on the activities of enzymes related to BCAA catabolism and the expressions of amino acid transporters, although the growth was not significantly depressed by one excessive BCAA when the other two BCAAs met the requirements for tiger puffer. In addition, plasma and muscle valine levels indicated that the antagonism of valine to leucine were observed in the leucine deficient diet, but not in the leucine excessive diet.

Effect of dietary leucine supplementation on skeletal muscle fiber type transformation in weaning piglets

To investigate the effects of dietary leucine supplementation on muscle fiber type transformation in weaning piglets, 54 21-day-old male DLY (Duroc × Landrace × Yorkshire) weaned piglets were randomly divided into control, 0.25% and 0.5% leucine groups. The experiment lasted for 42 d. The results showed that dietary supplementation of 0.25% leucine significantly increased the protein expressions of slow MyHC, myoglobin and Troponin I-SS and the mRNA expressions of MyHC I, MyHC IIa, Tnni1, Tnnc1, Tnnt1 and myoglobin, while decreased the protein level of fast MyHC and the mRNA level of MyHC IIb in longissimus dorsi (LD) muscle. Furthermore, 0.25% leucine significantly increased succinic dehydrogenase (SDH) activity and decreased lactate dehydrogenase (LDH) activity. In addition, our data found that 0.25% leucine significantly increased serum adiponectin (AdipoQ) concentration, and the protein levels of AdipoQ, adiponectin receptor 1 (AdipoR1), phosphorylated AMP-activated protein kinase (p-AMPK) and PPAR-γ coactivator-1α (PGC-1α) and the mRNA levels of AdipoQ, AdipoR1 and AMPKα2. Together, our findings indicate that leucine promotes porcine skeletal muscle fiber type transformation from fast-twitch to slow-twitch, and the effect may be mediated by AdipoQ-AMPK-PGC-1α signaling pathway.

Leucine Supplementation Increases Muscle Strength and Volume, Reduces Inflammation, and Affects Wellbeing in Adults and Adolescents with Cerebral Palsy

BackgroundSpastic cerebral palsy (CP) is characterized by muscle weakness owing, in part, to a blunted muscle protein synthetic response. This might be normalized by long-term leucine supplementation. ObjectivesThe study assessed the effects of 10 wk leucine supplementation in adolescents and adults with CP. MethodsThe study was a single-center randomized controlled trial. Twenty-four participants were randomly assigned to a control group (n = 12) or a leucine group (n = 12). l-Leucine (192 mg/kg body mass) was dissolved in water and administered daily for 10 wk. The primary outcome measures of elbow flexor muscle strength and muscle volume (measured by 3D ultrasound technique) and inflammation [C-reactive protein (CRP) concentration] were assessed before and after the 10 wk, alongside the secondary outcomes of body composition (measured by CP-specific skinfold assessment), metabolic rate (measured by indirect calorimetry), and wellbeing (measured by a self-reported daily questionnaire). Data were compared via a series of 2-factor mixed ANOVAs. ResultsTwenty-one participants completed the intervention (control group: n = 11, mean ± SD age: 18.3 ± 2.8 y, body mass: 48.8 ± 11.9 kg, 45% male; leucine group: n = 10, age: 18.6 ± 1.7 y, body mass: 58.3 ± 20.2 kg, 70% male). After 10 wk, there was a 25.4% increase in strength (P = 0.019) and a 3.6% increase in muscle volume (P = 0.001) in the leucine group, with no changes in the control group. This was accompanied by a 59.1% reduction in CRP (P = 0.045) and improved perceptions of wellbeing (P = 0.006) in the leucine group. No changes in metabolism or body composition were observed in either group (P > 0.05). ConclusionsImprovements in muscle strength and volume with leucine supplementation might provide important functional changes for adults and adolescents with CP and could be partly explained by reduced inflammation. The improved wellbeing highlights its capacity to improve the quality of daily living. This trial was registered at http://www.clinicaltrials.gov as NCT03668548.

Assignment of the Ile, Leu, Val, Met and Ala methyl group resonances of the DEAD-box RNA helicase DbpA from E. coli

ATP-dependent DEAD-box helicases constitute one of the largest families of RNA helicases and are important regulators of most RNA-dependent cellular processes. The functional core of these enzymes consists of two RecA-like domains. Changes in the interdomain orientation of these domains upon ATP and RNA binding result in the unwinding of double-stranded RNA. The DEAD-box helicase DbpA from E. coli is involved in ribosome maturation. It possesses a C-terminal RNA recognition motif (RRM) in addition to the canonical RecA-like domains. The RRM recruits DbpA to nascent ribosomes by binding to hairpin 92 of the 23S rRNA. To follow the conformational changes of Dbpa during the catalytic cycle we initiated solution state NMR studies. We use a divide and conquer approach to obtain an almost complete resonance assignment of the isoleucine, leucine, valine, methionine and alanine methyl group signals of full length DbpA (49 kDa). In addition, we also report the backbone resonance assignments of two fragments of DbpA that were used in the course of the methyl group assignment. These assignments are the first step towards a better understanding of the molecular mechanism behind the ATP-dependent RNA unwinding process catalyzed by DEAD-box helicases.

Effects of dietary leucine levels on intestinal antioxidant status and immune response for juvenile golden pompano (Trachinotus ovatus) involved in Nrf2 and NF-κB signaling pathway

The aim of the study was to evaluate the effects of dietary leucine level on growth performance, intestinal antioxidant status and immune response involved in Nrf2 and NF-κB signaling pathway in juvenile golden pompano (Trachinotus ovatus). A total of 450 juvenile golden pompano (9.15 ± 0.04 g) were fed three isonitrogenous diets with graded leucine levels [1.25% (control), 2.77% and 5.84%] for 8 weeks. The results showed that, compared with the control group, the WG was significantly improved in fish fed with 2.77% of dietary leucine (P < 0.05), and the 5.84% dietary leucine group had a tendency to increase. Compared to control group, 5.84% dietary leucine group significantly decreased the moisture and ash contents of whole body (P < 0.05), meanwhile, 2.77% dietary leucine group significantly decreased moisture content of whole body, but significantly improved the whole body crude lipid content (P < 0.05). Compared with the control group, the ALP level was significantly improved in fish fed with 2.77% of dietary leucine (P < 0.05). Inversely, the AST and ALT activities were significantly decreased in fish fed with 2.77% dietary leucine level (P < 0.05). Compared with the control group, GPx, T-AOC, SOD activities in group of 2.77% dietary arginine level were significantly increased (P < 0.05). However, MDA level showed a reverse trend, which was significantly decreased in fish fed with 2.77% dietary leucine level (P < 0.05). 2.77% dietary leucine levels significantly increased the relative expressions of Nrf2, HO-1, Cu/Zn-SOD, Mn-SOD and CAT (P < 0.05). In contrast, the relative expression of Keap1 showed a converse trend. Compared with the control group, the relative expressions of NF-κB, TNF-α and IL1-β were significantly lowered in fish fed with 2.77% of dietary leucine (P < 0.05). Additionally, 2.77% dietary leucine level significantly improved the relative expressions of TGF-β and IL-10 (P < 0.05). The 2.77% dietary leucine level significantly increased the muscular thickness compared with 5.84% dietary leucine level (P < 0.05). Furthermore, compared with the control group, the villus height and goblet cell counts were significantly improved in fish fed with 2.77% of dietary leucine (P < 0.05). These results indicated that the optimum dietary leucine plays an important role in promoting growth, enhancing antioxidant and immunity to maintain the intestinal health status of juvenile golden pompano.

Efficacy of L-Leucine Supplementation Coupled with a Calorie-Restricted Diet to Promote Weight Loss in Mid-Life Women

Objective This study evaluated the effect of leucine supplementation coupled with a calorie-restricted diet over a 12-week period in mid-life overweight and obese women on body composition and resting metabolic rate (RMR). Method This study was a randomized, single-blind, placebo-controlled trial in which 34 women were randomly assigned to either 10 g leucine (LEU) or placebo daily, while following a calorie-restricted diet A dual energy x-ray absorptiometry (DXA) analysis, metabolic rate assessment via a BodyGem® and anthropometrics were performed at baseline and after the 12-week study to determine changes in fat mass, lean mass and RMR. Main variables were analyzed using 2 (condition) by 2 (time) mixed design ANOVAs with repeated measures. Odds ratio was calculated by counting the number of individuals gaining or maintaining lean mass (p ≤ .05). Results Both groups lost a significant amount of weight due to both fat and lean mass loss, but there was no significant difference between groups, with RMR remaining unchanged over the course of the study and not significantly different between groups. The loss in lean mass was noticeably less, though not statistically significant (p = 0.644) for the women in the LEU group, with 38% vs. 6%, gaining or retaining lean mass during the intervention relative to the placebo. Conclusions Our findings demonstrate that a greater proportion of mid-life overweight or obese women taking LEU supplements gained or maintained lean mass during intentional weight loss, though it did not reach a level of statistical significance.

MTOR - Mediated protein synthesis by inhibiting protein catabolism in Chinese perch (Siniperca chuatsi)

Activation of the mechanistic target of rapamycin (mTOR) pathway is known to promote protein synthesis by enhancing mRNA translation. However, there have been few literatures on the effect of mTOR on protein metabolism in non-mammals. The main source of ammonia in fish comes from protein catabolism. The key step of protein catabolism involves the deamination and/or transamination of amino acids. This study is aimed to explore the mechanism underlying mTOR pathway influencing protein retention from the perspective of protein catabolism. Chinese perch were fasted for 24 h and divided into 4 groups randomly before intracerebroventricular (ICV) injection: (1) control group for leucine; (2) leucine group; (3) control group for leucine and rapamycin; (4) leucine and rapamycin group. Food intake was equivalent between each control and treatment groups at each time point (0.5, 4, 12 and 24 h post-injection). Ammonia-N excretion rate, blood glucose, S6 phosphorylation level, and expression of relative genes of protein catabolism (GDH, AMPD, AST, ALT) were determined. The results indicated that the pS6 level was increased, and that the ammonia-N excretion rate, blood glucose, and mRNA level of protein catabolism genes (GDH and AMPD) were significantly decreased after injection with leucine, while those changes were reversed after injection with leucine and rapamycin. Our study not only reveals the mechanism by which mTOR mediates protein synthesis by inhibiting protein catabolism in Chinese perch, but also provides reference for improving the utilization of feed protein.

The effects of leucine and whey protein supplementation with eight weeks of resistance training on strength and body composition.

In past few decades, supplementation has become very popular within professional and recreational athletes. Most interested among supplements are protein and amino acids. Therefore, the purpose of this study was to examine the effects of leucine supplementation in comparison to whey protein supplementation with placebo group on strength and body composition during 8 weeks of resistance training program. Thirty male college athletes (mean age±SD =23.92±1.54 years) participated in this investigation and were randomly assigned to one of three groups: whey protein (WP, N.=10), leucine (LEU, N.=10) or placebo (PLA, N.=10). The WP, LEU and PLA performed resistance training for 8 weeks. Strength (1RM bench press, squat, shoulder press) and maximum pull-ups and body composition has been assessed and data was analyzed with mixed-design analysis of variance (P≤0.01). The WP group achieved significantly greater (P≤0.01) increases in 1RM bench press than the LEU and PLA groups (+16 kg for WP; + 7.5 kg for LEU and + 5 kg for PLA). The LEU group achieved significantly greater gains (P≤0.01) in fat free mass, muscle mass and significantly decreases (P≤0.01) in fat mass compared to WP and PLA groups. Whey protein supplementation in male collegiate athletes during resistance training achieved greater increase in strength than leucine and placebo groups, and leucine group achieved significantly greater improvement in body composition than whey protein and placebo groups.

Leucine-rich diet induces a shift in tumour metabolism from glycolytic towards oxidative phosphorylation, reducing glucose consumption and metastasis in Walker-256 tumour-bearing rats

Leucine can stimulate protein synthesis in skeletal muscle, and recent studies have shown an increase in leucine-related mitochondrial biogenesis and oxidative phosphorylation capacity in muscle cells. However, leucine-related effects in tumour tissues are still poorly understood. Thus, we described the effects of leucine in both in vivo and in vitro models of a Walker-256 tumour. Tumour-bearing Wistar rats were randomly distributed into a control group (W; normoprotein diet) and leucine group (LW; leucine-rich diet [normoprotein + 3% leucine]). After 20 days of tumour evolution, the animals underwent 18-fludeoxyglucose positron emission computed tomography (18F-FDG PET-CT) imaging, and after euthanasia, fresh tumour biopsy samples were taken for oxygen consumption rate measurements (Oroboros Oxygraph), electron microscopy analysis and RNA and protein extraction. Our main results from the LW group showed no tumour size change, lower tumour glucose (18F-FDG) uptake, and reduced metastatic sites. Furthermore, leucine stimulated a shift in tumour metabolism from glycolytic towards oxidative phosphorylation, higher mRNA and protein expression of oxidative phosphorylation components, and enhanced mitochondrial density/area even though the leucine-treated tumour had a higher number of apoptotic nuclei with increased oxidative stress. In summary, a leucine-rich diet directed Walker-256 tumour metabolism to a less glycolytic phenotype profile in which these metabolic alterations were associated with a decrease in tumour aggressiveness and reduction in the number of metastatic sites in rats fed a diet supplemented with this branched-chain amino acid.

Preliminary study: Leucine Supplementation Exacerbates Muscle Wasting Independent of the Ubiquitin-Proteasome System

Cancer Cachexia is a devastating syndrome that affects around 50-80% of cancer patients and is characterized by a rapid, drastic fat and muscle mass loss. The APCMin/+ mouse strain is a well-studied mouse model of human colorectal cancer and cancer cachexia. The branched-chain amino acid leucine is known to stimulate muscle growth/maintenance through activation of mTOR and protein synthesis. PURPOSE: To examine the effects of chronic leucine supplementation on cancer cachexia development in APCMin/+ mice. METHODS: 7 APCMin/+ mice (APC) and 11 wild-type (WT) were used for this study. The animals were assigned to the following groups: WT no leucine (WTNL, n=5), WT leucine (WTL, n=5), APCMin/+ no leucine (APCNL, n=5) and APCMin/+ leucine (APCL, n=2). Mice were given ad libitum access to food and water. Mice in the leucine groups received 1.5% leucine-rich water. Plantaris muscles and tibias were excised at 20 weeks of age. Tissue was immediately frozen for morphology and gene expression analysis using RT- qPCR. RESULTS: The number of polyps increased in APCMin/+ compared to WT (46.57 ± 2.44 vs 0.00 ± 0.00). The number of polyps < 1 mm was increased (14.33 ± 1.45 vs. 7.75 ± 2.05) in APCL compared to APCNL (p<.05). There was a main effect for APCMin/+ to have lower body mass than WT (p<.0001). There was a main effect of genotype to decrease plantaris weight/tibia length in APCMin/+ mice vs. WT mice (p<.0001) and a main effect of leucine to decrease plantaris weight/tibia length in APCMin/+ mice (p<.05), which appeared to be driven by the APC (interaction p=.0841). There was an ~8-fold increase in atrogin-1 gene expression in APCNL compared to WTNL (p<.05). Atrogin-1 gene expression was ~7-fold lower in APCL compared to APCNL (p<.05). There was a main effect of genotype to increase MuRF1 expression in APCMin/+ mice compared to WT (p<. 05) and a main effect of leucine to decrease MuRF1 expression (p<.05), which appeared to be driven by the APC genotype (interaction p=.0560). No difference was found in MyoD or Myogenin gene expression. CONCLUSION: The preliminary data suggest deletory effects of leucine in cancer cachexia, which need to be affirmed by further studies. Based on gene expression of the E3 ubiquitin ligases, this loss in muscle mass may be independent of protein degradation. Supported by the Arkansas Biosciences Institute