Impact of leucine on energy balance

The impact of leucine supplementation on body composition and glucose tolerance following energy restriction: an 8-week RCT in adults at risk of the metabolic syndrome

BACKGROUND

L-Leucine (Leu) supplementation may benefit fat-free mass (FFM) per se and glucose metabolism.

OBJECTIVES

To determine whether Leu supplementation during energy restriction blunted the loss of FFM, enhanced the loss of fat mass (FM) and improved glucose tolerance.

DESIGN

Thirty-seven adults, aged 20-65 years, with increased waist circumference and at least one other metabolic syndrome (MetS) component, were selected. We employed a two-arm parallel, double blind, randomized control trial (RCT) design. Participants were randomly assigned to an intervention group (leucine - 3 g/d) or placebo (lactose - 2.67 g/d), while following an individualised energy restricted diet for an 8-week period. Detailed body composition (DEXA), oral glucose tolerance test (OGTT), insulin and components of MetS were measured before and after the trial. Analysis of covariance (ANCOVA) assessed the effect of Leu on an intention-to-treat (ITT) principle. Bootstrapping method with 1000 bootstrap samples was used to derive parameter estimates, standard errors, p-values, and 95% confidence intervals for all outcomes.

RESULTS

Adjusted for baseline values and other covariates, FFM (p = 0.045) and lean tissue mass (LTM) (p = 0.050) were significantly higher following Leu. These outcomes were modified by a significant treatment x sex interaction that indicated Leu had the greater effect in men. However, on adjustment for body composition changes, there was no difference in insulin sensitivity, oral glucose tolerance, or change in MetS components following Leu.

CONCLUSION

Short-term leucine supplementation during energy restriction resulted in a greater preservation of FFM and LTM particularly in men, but did not impact glucose metabolism.

Research progress in the role and mechanism of Leucine in regulating animal growth and development

Leucine, a branched-chain amino acid, is essential in regulating animal growth and development. Recent research has uncovered the mechanisms underlying Leucine's anabolic effects on muscle and other tissues, including its ability to stimulate protein synthesis by activating the mTORC1 signaling pathway. The co-ingestion of carbohydrates and essential amino acids enhances Leucine's anabolic effects. Moreover, Leucine has been shown to benefit lipid metabolism, and insulin sensitivity, making it a promising strategy for preventing and treating metabolic diseases, including type 2 diabetes and obesity. While emerging evidence indicates that epigenetic mechanisms may mediate Leucine's effects on growth and development, more research is needed to elucidate its mechanisms of action fully. Specific studies have demonstrated that Leucine promotes muscle growth and metabolic health in animals and humans, making it a promising therapeutic agent. However, it is essential to note that Leucine supplementation may cause digestive issues or interact with certain medications, and More study is required to determine definitively optimal dosages. Therefore, it is important to understand how Leucine interacts with other nutrients, dietary factors, and lifestyle habits to maximize its benefits. Overall, Leucine's importance in human nutrition is far-reaching, and its potential to prevent muscle loss and enhance athletic performance warrants further investigation.

Branched-chain amino acid modulation of lipid metabolism, gluconeogenesis, and inflammation in a finishing pig model: targeting leucine and valine

Branched-chain amino acids (BCAAs) play a regulatory role in adipogenesis and energy balance. Therefore, this study aimed to investigate the impact of BCAA supplements, especially leucine (Leu) and valine (Val) supplementation, on lipid metabolism and related disorders in a finishing pig model. The results demonstrated that Leu (1%) and Val decreased serum as well as hepatic lipid accumulation. Moreover, metabolomics and lipidomics analyses revealed that Leu and Val markedly downregulated the level of various lipid species in the liver. This outcome may be explained by Leu and Val promoting cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA)/hormone-sensitive triglyceride lipase (HSL) signaling pathways. Leu and Val altered the fatty acid composition in distinct adipose tissues and decreased the levels of inflammatory factors. Additionally, they significantly decreased back fat thickness, and the results of the fatty acid profiles demonstrated that Leu and Val significantly increased the levels of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) while decreasing those of saturated fatty acids (SFAs), especially in back fat and abdominal fat. Besides, Leu and Val restored glucose homeostasis by suppressing gluconeogenesis through the serine/threonine protein kinase (AKT)/transcription factor forkhead box O1 (FOXO1) signaling pathway in the liver and back fat. In summary, these results suggest that Leu and Val may serve as key regulators for modulating lipid metabolism and steatosis.

Preliminary insights on the metabolomics of Trichinella zimbabwensis infection in Sprague Dawley rats using GCxGC-TOF-MS (untargeted approach)

Trichinella infections have been documented globally and have been detected in wild and/or domestic animals except Antarctica. There is paucity of information in the metabolic responses of hosts during Trichinella infections and biomarkers for infection that can be used in the diagnosis of the disease. The current study aimed to apply a non-targeted metabolomic approach to identify Trichinella zimbabwensis biomarkers including metabolic response from sera of infected Sprague-Dawley rats. Fifty-four male Sprague-Dawley rats were randomly assigned into T. zimbabwensis infected group (n = 36) and the non-infected control (n = 18). Results from the study showed that the metabolic signature of T. zimbabwensis infection consists of enriched methyl histidine metabolism, disturbance of the liver urea cycle, impeded TCA cycle, and upregulation of gluconeogenesis metabolism. The observed disturbance in the metabolic pathways was attributed to the effects caused by the parasite during its migration to the muscles resulting in downregulation of amino acids intermediates in the Trichinella-infected animals, and therefore affecting energy production and degradation of biomolecules. It was concluded that T. zimbabwensis infection caused an upregulation of amino acids; pipecolic acid, histidine, and urea, and upregulation of glucose and meso-Erythritol. Moreover, T. zimbabwensis infection caused upregulation of the fatty acids, retinoic acid, and acetic acid. These findings highlight the potential of metabolomics as a novel approach for fundamental investigations of host-pathogen interactions as well as for disease progression and prognosis.

Metabolic profiling of liver and faeces in mice infected with echinococcosis

Background

Echinococcosis is a severe zoonotic parasitic disease which severely affects the health of the hosts. The diagnosis of echinococcosis depends mainly on imaging examination. However, the patient is often in the late stage of the disease when the symptoms appear, thus limiting the early diagnosis of echinococcosis. The treatment and prognosis of the patients are hampered because of long-term asymptomatic latency. Metabolomics is a new discipline developed in the late 1990s. It reflects a series of biological responses in pathophysiological processes by demonstrating the changes in metabolism under the influence of internal and external factors. When the organism is invaded by pathogens, the alteration in the characteristics of metabolites in cells becomes extremely sensitive. Here, we used a metabolomics approach involving liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) to determine the molecular mechanism of cystic echinococcosis (CE) and to develop an effective method for CE diagnosis.

Methods

Twenty 8-week-old female BALB/c mice were divided into normal and Echinococcus granulosus infection groups. To develop the E. granulosus infection model, mice were infected with protoscoleces. Six weeks later, the abdomens of the mice showed significant bulging. An LC–MS/MS system-based metabolomics approach was used to analyse the liver and faeces to reveal the metabolic profiles of mice with echinococcosis.

Results

We found that the metabolism of nucleotides, alkaloids, amino acids, amides, and organic acids in mice is closely interrelated with E. granulosus infection. In the liver, the metabolic pathways of tyrosine and tryptophan biosynthesis; phenylalanine, valine, leucine and isoleucine biosynthesis; and phenylalanine metabolism were notably associated with the occurrence and development of hydatid disease, and in the faeces, pantothenate and CoA biosynthesis are thought to be closely associated with the development of CE.

Conclusion

The metabolomics approach used in this study provides a reference for a highly sensitive and specific diagnostic and screening method for echinococcosis.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04807-1.

A fifty percent leucine-restricted diet reduces fat mass and improves glucose regulation

Background

Leucine deprivation modulates the dietary amino acid composition, reducing the fat content and improving the glucose tolerance, thus protecting the organism against obesity. However, a complete deprivation of leucine can lead to an extremely rapid fat loss in mice, accompanied by prolonged adverse effects such as weakness and mental fatigue. Therefore, in this study we aimed to seek the optimal concentration of dietary leucine that can reduce fat mass and improve the metabolism without the onset of severe effects.

Methods

To investigate whether there is a better concentration of diet leucine restriction (LR), based on the diet we conducted (A10021B), that can reduce fat mass and improve metabolism status without taking many negative effects, we fed 8 weeks old male C57Bl/6J mice with increasing degrees of leucine restriction diet 0% LR (control group), 25% LR, 50% LR, and 75% LR groups (4–6 mice each group). Fat mass and blood glucose levels were measured. The expression levels of genes involved in lipid metabolism in white adipose tissue (WAT) and liver, and proteins in insulin signaling were assessed in WAT, liver and muscle.

Results

We found that the 50% LR group is the most proper group here at the lowest leucine effective concentration, which reduced fat mass (p < 0.05) and improved glucose regulation in mice over a 90 days feeding. Further studies revealed that lipid synthesis pathway (Fas, Scd1and Srebp1, p < 0.05) was downregulated and lipolysis (Atgl, p < 0.05) was upregulated in WAT in 50% LR group, compared to that in control group. Furthermore, glucose regulation (glucose tolerance test, p < 0.05) was also improved, and insulin signaling (p < 0.05) in the muscle was enhanced in 50% LR group while in WAT and liver were not changed.

Conclusions

Collectively, a 50% LR in mice reduced fat mass and improved glucose regulation, which may function through modulating lipid synthesis and lipolysis pathway in adipose tissue as well as enhancing insulin signaling in muscle. So far, we provide a further consideration for carrying out the diet of leucine restriction to reduce fat and improve metabolism status before clinical study.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-021-00564-1.

Analysis of plasma metabolic profile, characteristics and enzymes in the progression from chronic hepatitis B to hepatocellular carcinoma

Hepatitis B virus (HBV) infection is an important factor causing hepatocellular carcinoma (HCC). The aim of this study was to investigate the metabolic characteristics and related metabolic enzyme changes during the progression from chronic hepatitis B (CHB) to liver cirrhosis (LC) and, ultimately, to HCC. An untargeted metabolomics assay was performed in plasma from 50 healthy volunteers, 43 CHB patients, 67 LC patients, and 39 HCC patients. A total of 24 differential metabolites (DMs) were identified. Joint pathway analysis suggested striking changes in amino acid metabolism and lipid metabolism from CHB to HCC. The panel of L-serine, creatine and glycine distinguished LC from CHB, and L-serine, cystathionine, creatine and linoleic acid distinguished HCC from LC. Bioinformatic analysis of publicly available data showed that differential metabolite profile-associated enzyme genes, including alanine-glyoxylate aminotransferase-2 (AGXT2), D-amino-acid oxidase (DAO), and cystathionine gamma-lyase (CTH), were downregulated, while bisphosphoglycerate mutase (BPGM), cystathionine-β-synthase (CBS), phosphoserine phosphatase (PSPH) and acyl-CoA thioesterase 7 (ACOT7) were upregulated, in HCC, all of which correlated with a poor prognosis for HCC patients. Our results indicated that serum metabolites and related enzymes are of considerable significance for the diagnosis and prognosis of HCC and can provide a theoretical basis and therapeutic index for future diagnosis and treatment.

Screening and Identification of Differentially Expressed and Adipose Growth-Related Protein-Coding Genes During the Deposition of Perirenal Adipose Tissue in Rabbits

BACKGROUND

Rabbit is a good model for genetic and medical studies in other livestock species. The rabbit shows low adipose tissue deposition, and the phenomena indicates that there is some specificity of adipose deposition during the rabbit growth. However, little is known about genes that regulate the growth of adipose tissue in rabbits.

MATERIALS AND METHODS

Deep RNA-seq and comprehensive bioinformatics analyses were used to characterize the genes of rabbit visceral adipose tissue (VAT) at 35, 85 and 120 days after birth. Differentially expressed genes (DEGs) were identified at the three growth stages by DESeq. To explore the function of the candidate genes, Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed. Six DEGs were randomly selected, and their expression profiles were validated by q-PCR.

RESULTS

A total of 20,303 known transcripts and 99,199 new transcripts from 8 RNA sequencing libraries were identified, and 34 differentially expressed genes (DEGs) were screened. GO enrichment and KEGG pathway analyses revealed that the DEGs were mainly involved in lipid metabolism regulation including acylglycerol metabolic process and mobilization, and decomposition of lipids to generate ATP in adipocytes and fatty acid metabolism, included LOC100342322 and LOC100342572. In addition, 133 protein-coding genes that play a role in adipose growth and development were screened, including acyl-CoA synthetase long-chain family member 5 (ACSL5) and fatty acid-binding protein 2 (FABP2). The validation results of six DEGs by q-PCR showed similar trends with the results of RNA-seq.

CONCLUSION

In summary, this study provides the first report of the coding genes profiles of rabbit adipose tissue during different growth stages. These data allow for the identification of candidate genes for subsequent studies on rabbit genetics and regulation of adipose cells, and provide an animal model for studying obesity in humans.

Branched-Chain amino acids intake is negatively related to body adiposity in individuals at cardiometabolic risk

ABSTRACT Objective To assess the relationship between branched-chain amino acids intake in the current diet and the metabolic and body adiposity markers in a population at cardiovascular risk. Methods This is a cross-sectional study with 282 adults and elderly people from the Cardiovascular Health Care Program of the Universidade Federal de Viçosa. Sociodemographic, anthropometric and body composition data, as well as metabolic biomarkers were collected using standardized protocols. Dietary intake of branched amino acids was assessed using a 24-hour recall. Results Individuals with a higher branched-chain amino acids intake (≥2.6g/day, median value) had lower body fat (29.6 vs 32.2%; p=0.019), and higher serum ferritin (113.2 vs. 60.1mg/dL; p=0.006) and uric acid concentrations (4.4 vs. 4.0; p=0.023). In addition, a lower prevalence of overweight and excessive abdominal fat (p<0.05) was found in the individuals with higher branched-chain amino acids intake. They also had a higher daily intake of fiber, copper, zinc, magnesium, and iron, as well as a lower intake of total lipids. Conclusion In the present study, the intake of branched amino acids is negatively related to total and central adiposity, but more studies are needed to fully elucidate this possible relationship. (Brazilian Registry of Clinical Trials, code RBR-5n4y2g).

Inhibitory effect of high leucine concentration on α-amylase secretion by pancreatic acinar cells: possible key factor of proteasome

The present study aimed to investigate whether leucine affects the pancreatic exocrine by controlling the antisecretory factor (AF) and cholecystokinin receptor (CCKR) expression as well as the proteasome activity in pancreatic acinar cells of dairy calves. The pancreatic acinar cells were isolated from newborn Holstein bull calves and cultured using the Dulbecco’s modified Eagle’s medium/nutrient mixture F12 Ham’s liquid (DMEM/F12). There were six treatments of leucine dosage including 0 (control), 0.23, 0.45, 1.35, 4.05, and 12.15 mM, respectively. After culture for 3 h, the samples were collected for subsequent analysis. As the leucine concentration increased from 0 to 1.35 mM, the α-amylase activity in media decreased significantly (P<0.05), while further increase in leucine concentration did not show any decrease in α-amylase activity. Addition of leucine inhibited (P<0.05) the expression of AF and CCKR, and decreased the activity of proteasome (P<0.05) by 76%, 63%, 24%, 7%, and 9%, respectively. Correlation analysis results showed α-amylase secretion was negatively correlated with leucine concentration (P<0.01), and positively correlated with proteasome activity (P<0.01) and the expression of CCK1R (P<0.01) and AF (P<0.05). The biggest regression coefficient was showed between α-amylase activity and proteasome (0.7699, P<0.001). After inhibition of proteasome by MG-132, low dosage leucine decreased (P<0.05) the activity of proteasome and α-amylase, as well as the expression of CCK1R. In conclusion, we demonstrated that the high-concentration leucine induced decrease in α-amylase release was mainly by decreasing proteasome activity.

Metabolomic Study to Determine the Mechanism Underlying the Effects of Sagittaria sagittifolia Polysaccharide on Isoniazid- and Rifampicin-Induced Hepatotoxicity in Mice

In this study, a non-targeted metabolic profiling method based on ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) was used to characterize the plasma metabolic profile associated with the protective effects of the Sagittaria sagittifolia polysaccharide (SSP) on isoniazid (INH)—and rifampicin (RFP)-induced hepatotoxicity in mice. Fourteen potential biomarkers were identified from the plasma of SSP-treated mice. The protective effects of SSP on hepatotoxicity caused by the combination of INH and RFP (INH/RFP) were further elucidated by investigating the related metabolic pathways. INH/RFP was found to disrupt fatty acid metabolism, the tricarboxylic acid cycle, amino acid metabolism, taurine metabolism, and the ornithine cycle. The results of the metabolomics study showed that SSP provided protective effects against INH/RFP-induced liver injury by partially regulating perturbed metabolic pathways.

Deconstructing the traditional Japanese medicine "Kampo": compounds, metabolites and pharmacological profile of maoto, a remedy for flu-like symptoms

Pharmacological activities of the traditional Japanese herbal medicine (Kampo) are putatively mediated by complex interactions between multiple herbal compounds and host factors, which are difficult to characterize via the reductive approach of purifying major bioactive compounds and elucidating their mechanisms by conventional pharmacology. Here, we performed comprehensive compound, pharmacological and metabolomic analyses of maoto, a pharmaceutical-grade Kampo prescribed for flu-like symptoms, in normal and polyI:C-injected rats, the latter suffering from acute inflammation via Toll-like receptor 3 activation. In total, 352 chemical composition-determined compounds (CCDs) were detected in maoto extract by mass spectrometric analysis. After maoto treatment, 113 CCDs were newly detected in rat plasma. Of these CCDs, 19 were present in maoto extract, while 94 were presumed to be metabolites generated from maoto compounds or endogenous substances such as phospholipids. At the phenotypic level, maoto ameliorated the polyI:C-induced decrease in locomotor activity and body weight; however, body weight was not affected by individual maoto components in isolation. In accordance with symptom relief, maoto suppressed TNF-α and IL-1β, increased IL-10, and altered endogenous metabolites related to sympathetic activation and energy expenditure. Furthermore, maoto decreased inflammatory prostaglandins and leukotrienes, and increased anti-inflammatory eicosapentaenoic acid and hydroxyl-eicosapentaenoic acids, suggesting that it has differential effects on eicosanoid metabolic pathways involving cyclooxygenases, lipoxygenases and cytochrome P450s. Collectively, these data indicate that extensive profiling of compounds, metabolites and pharmacological phenotypes is essential for elucidating the mechanisms of herbal medicines, whose vast array of constituents induce a wide range of changes in xenobiotic and endogenous metabolism.

Pharmacological activities of Kampo, or traditional Japanese herbal medicine, are putatively mediated by complex interactions between the plant-derived compounds and endogenous molecules. To elucidate these properties, we performed comprehensive phytochemical profiling, and pharmacological and metabolomic analyses of maoto, an herbal remedy for flu-like symptoms. In the plasma of maoto-treated rats, we detected maoto-derived compounds, metabolites produced from the chemical transformation of maoto compounds by host metabolism and gut microbes, and endogenous metabolites that were appeared following maoto administration. In an acute inflammatory rat model, maoto ameliorated symptoms of sickness behavior, suppressed inflammatory cytokines, and extensively affected common metabolites and lipid mediators. These data suggest that the diverse chemical composition of Kampo broadly affects the host’s endogenous metabolism and exerts specific pharmacological effects.

Amino acid supplements and metabolic health: a potential interplay between intestinal microbiota and systems control

Dietary supplementation of essential amino acids (EAAs) has been shown to promote healthspan. EAAs regulate, in fact, glucose and lipid metabolism and energy balance, increase mitochondrial biogenesis, and maintain immune homeostasis. Basic science and epidemiological results indicate that dietary macronutrient composition affects healthspan through multiple and integrated mechanisms, and their effects are closely related to the metabolic status to which they act. In particular, EAA supplementation can trigger different and even opposite effects depending on the catabolic and anabolic states of the organisms. Among others, gut-associated microbial communities (referred to as gut microbiota) emerged as a major regulator of the host metabolism. Diet and host health influence gut microbiota, and composition of gut microbiota, in turn, controls many aspects of host health, including nutrient metabolism, resistance to infection, and immune signals. Altered communication between the innate immune system and the gut microbiota might contribute to complex diseases. Furthermore, gut microbiota and its impact to host health change largely during different life phases such as lactation, weaning, and aging. Here we will review the accumulating body of knowledge on the impact of dietary EAA supplementation on the host metabolic health and healthspan from a holistic perspective. Moreover, we will focus on the current efforts to establish causal relationships among dietary EAAs, gut microbiota, and health during human development.

Branched-chain amino acids differently modulate catabolic and anabolic states in mammals: a pharmacological point of view

Substantial evidence has been accumulated suggesting that branched-chain amino acid (BCAA) supplementation or BCAA-rich diets have a positive effect on the regulation of body weight, muscle protein synthesis, glucose homeostasis, the ageing process and extend healthspan. Despite these beneficial effects, epidemiological studies have shown that BCAA plasma concentrations and BCAA metabolism are altered in several metabolic disorders, including type 2 diabetes mellitus and cardiovascular diseases. In this review article, we present an overview of the current literature on the different effects of BCAAs in health and disease. We also highlight the results showing the most promising therapeutic effects of dietary BCAA supplementation and discuss how BCAAs can trigger different and even opposite effects, depending on the catabolic and anabolic states of the organisms. Moreover, we consider the effects of BCAAs when metabolism is abnormal, in the presence of a mixture of different anabolic and catabolic signals. These unique pharmacodynamic properties may partially explain some of the markedly different effects found in BCAA supplementation studies. To predict accurately these effects, the overall catabolic/anabolic status of patients should be carefully considered. In wider terms, a correct modulation of metabolic disorders would make nutraceutical interventions with BCAAs more effective.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

Chronic leucine supplementation improves lipid metabolism in C57BL/6J mice fed with a high-fat/cholesterol diet

Background

Leucine supplementation has been reported to improve lipid metabolism. However, lipid metabolism in adipose tissues and liver has not been extensively studied for leucine supplementation in mice fed with a high-fat/cholesterol diet (HFCD).

Design

C57BL/6J mice were fed a chow diet, HFCD, HFCD supplemented with 1.5% leucine (HFCD+1.5% Leu group) or 3% leucine (HFCD+3% Leu group) for 24 weeks. The body weight, peritoneal adipose weight, total cholesterol (TC), triglyceride in serum and liver, and serum adipokines were analyzed. In addition, expression levels of proteins associated with hepatic lipogenesis, adipocyte lipolysis, and white adipose tissue (WAT) browning were determined.

Results

Mice in the HFCD group developed obesity and deteriorated lipid metabolism. Compared with HFCD, leucine supplementation lowered weight gain and TC levels in circulation and the liver without changing energy intake. The decrease in body fat was supported by histological examination in the WAT and liver. Furthermore, serum levels of proinflammatory adipokines, such as leptin, IL-6, and tumor necrosis factor-alpha, were significantly decreased by supplemented leucine. At the protein level, leucine potently decreased the hepatic lipogenic enzymes (fatty acid synthase and acetyl-coenzyme A carboxylase) and corresponding upstream proteins. In epididymal WAT, the reduced expression levels of two major lipases by HFCD, namely phosphorylated hormone-sensitive lipase and adipose triglyceride lipase, were reversed when leucine was supplemented. Uncoupling protein 1, β3 adrenergic receptors, peroxisome proliferator-activated receptor g coactivator-1α, and fibroblast growth factor 21 were involved in the thermogenic program and WAT browning. Leucine additionally upregulated their protein expression in both WAT and interscapular brown adipose tissue.

Conclusion

This study demonstrated that chronic leucine supplementation reduced the body weight and improved the lipid profile of mice fed with a HFCD. This beneficial effect was ascribed to hepatic lipogenesis, adipocyte lipolysis, and WAT browning.

Branched-chain amino acids are associated with cardiometabolic risk profiles found already in lean, overweight and obese young

Cardiovascular risk is increased in obese subjects. Nevertheless, some overweight and obese remain cardiometabolically healthy (CMH), and normal-weight persons develop cardiovascular disease (CVD). Herein, we investigate the potential of branched-chain amino acids (BCAAs) to identify an increased CVD risk in a cross-sectional study of 666 adults and juveniles (age 25.3±12.8years), classified as lean, overweight or obese. Cardiometabolic groups were defined by cutoffs of systolic blood pressure<130mmHg, diastolic blood pressure<85mmHg, glucose<125mg/dl, triglycerides<150mg/dl, HDL-cholesterol>40mg/dl (males), HDL-cholesterol>50mg/dl (females) and HOMA-IR<5. CMH had ≤1 cutoff, and cardiometabolically abnormal (CMA) had ≥2 cutoffs. Amino acids were measured by high-pressure lipid chromatography after precipitation of serum with perchloric acid and derivatization with o-phthalaldehyde. Valine correlated with 5, leucine correlated with 3 and isoleucine correlated with 5 of the cardiac risk classification factors. Valine and leucine were significantly higher in the obese (P<.001, P=.015, respectively), overweight (P<.001, P=.015, respectively) and lean (P=.024, P=.012, respectively) CMA compared to CMH subjects. Isoleucine showed except of the lean group the same results. Taken together, BCAAs, especially valine and leucine, are proposed as a cardiometabolic risk marker independent of body mass index (BMI) category.

Method development for the determination of D- and L-isomers of leucine in human plasma by high-performance liquid chromatography tandem mass spectrometry and its application to animal plasma samples

We developed a highly sensitive and specific high-performance liquid chromatography tandem mass spectrometry method with an electrospray ionization for the determination of D- and L-isomers of leucine in human plasma. Phosphate-buffered saline was used as the surrogate matrix for preparation of calibration curves and quality control samples. The extraction of D- and L-leucine in plasma samples (100 μL) was performed using cationic exchange solid-phase extraction. The enantiomer separation of D- and L-leucine was successfully achieved without derivatization using a CHIRALPAK ZWIX(-) with an isocratic mobile phase comprised of methanol/acetonitrile/1 mol/L ammonium formate/formic acid (500:500:25:2, v/v/v/v) at a flow rate of 0.5 mL/min. In addition, the discrimination of DL-leucine from structural isomers DL-isoleucine and DL-allo-isoleucine was performed using the unique precursor and product ion pair transition of DL-leucine (m/z 132.1 > 43.0) and DL-leucine-d 7 (m/z 139.2 > 93.0) in positive electrospray ionization mode. The standard curves were linear throughout the calibration range from 0.001 to 1 μg/mL for D-leucine and from 1 to 1000 μg/mL for L-leucine, respectively, with acceptable intra- and inter-day precision and accuracy. The stability of D- and L-leucine in human plasma and solvents was confirmed. The endogenous level of D- and L-leucine in human plasma was 0.00197~0.00591 and 9.63~24.7 μg/mL, respectively. This method was also successfully applied to investigate the species difference in the ratios of D-leucine to total leucine from individual plasma concentrations in humans and various animals. The plasma D-leucine concentrations or their ratio to total leucine in rodents was much higher than that in humans.

Consumption of Branched-Chain Amino Acids Is Inversely Associated with Central Obesity and Cardiometabolic Features in a Population of Brazilian Middle-Aged Men: Potential Role of Leucine Intake

OBJECTIVE

To assess the potential associations of branched-chain amino acids (BCAA) consumption with central obesity (CObesity) and cardiometabolic risk factors in a population of Brazilian middle-aged men. Special attention was given to leucine intake.

DESIGN

Cross-sectional study.

SETTING

Universidade Federal de Viçosa, Viçosa, Brazil.

PARTICIPANTS

Two-hundred ninety-six middle-aged men (Age: 50.5 ± 5.0 years; Body mass index: 25.8 ± 3.5 kg/m2).

MEASUREMENTS

Anthropometry, lifestyle features, blood biochemical parameters were assessed and dietary intake was estimated by a food frequency questionnaire. Participants were classified by the occurrence of CObesity, hypertriglyceridemia (HTG), hypertriglyceridemic waist phenotype (HWP) and metabolic syndrome (MetS).

RESULTS

Subjects in the BCAA highest tertile (≥0.17 g/kg/d) presented lower occurrence of CObesity (36.0% vs 72.4%, P<0.01, z=-5.10), HTG (17.0% vs 30.6% P<0.032, z=-2.32), HWP (23.0% vs 46.9%, P<0.01, z=-3.57) and MetS (19.0% vs 34.7%, P<0.01, z=-2.57). They also exhibited lower values for Castelli index (total cholesterol:HDL-c) and triglycerides: HDL-c ratio than those in the first tertile, regardless of interfering factors (i.e. habitual physical activity, work position, smoking habit, and energy intake). Interestingly, leucine consumption showed similar associations with cardiometabolic risk factors, as compared to BCAA consumption (P<0.05).

CONCLUSION

BCAA consumption was cross-sectionally and negatively associated with relevant cardiometabolic risk factors in a population of Brazilian middle-aged men. The content of leucine in BCAA consumption may have contributed to such relationship.

Leucine supplementation improves leptin sensitivity in high-fat diet fed rats

Background

Several studies have reported the favorable effect of leucine supplementation on insulin resistance or insulin sensitivity. However, whether or not leucine supplementation improves leptin sensitivity remains unclear.

Design

Forty-eight male Sprague-Dawley rats were fed with either a high-fat diet (HFD) or HFD supplemented with 1.5, 3.0, and 4.5% leucine for 16 weeks. At the end of the experiment, serum leptin level was measured by ELISA, and leptin receptor (ObR) in the hypothalamus was examined by immunohistochemistry. The protein expressions of ObR and leptin-signaling pathway in adipose tissues were detected by western blot.

Results

No significant differences in body weight and food/energy intake existed among the four groups. Serum leptin levels were significantly lower, and ObR expression in the hypothalamus and adipose tissues was significantly higher in the three leucine groups than in the control group. These phenomena suggested that leptin sensitivity was improved in the leucine groups. Furthermore, the expressions of JAK2 and STAT3 (activated by ObR) were significantly higher, and that of SOCS3 (inhibits leptin signaling) was significantly lower in the three leucine groups than in the control group.

Conclusions

Leucine supplementation improves leptin sensitivity in rats on HFD likely by promoting leptin signaling.

Protein quality and the protein to carbohydrate ratio within a high fat diet influences energy balance and the gut microbiota in C57BL/6J mice

Macronutrient quality and composition are important determinants of energy balance and the gut microbiota. Here, we investigated how changes to protein quality (casein versus whey protein isolate; WPI) and the protein to carbohydrate (P/C) ratio within a high fat diet (HFD) impacts on these parameters. Mice were fed a low fat diet (10% kJ) or a high fat diet (HFD; 45% kJ) for 21 weeks with either casein (20% kJ, HFD) or WPI at 20%, 30% or 40% kJ. In comparison to casein, WPI at a similar energy content normalised energy intake, increased lean mass and caused a trend towards a reduction in fat mass (P = 0.08), but the protein challenge did not alter oxygen consumption or locomotor activity. WPI reduced HFD-induced plasma leptin and liver triacylglycerol, and partially attenuated the reduction in adipose FASN mRNA in HFD-fed mice. High throughput sequence-based analysis of faecal microbial populations revealed microbiota in the HFD-20% WPI group clustering closely with HFD controls, although WPI specifically increased Lactobacillaceae/Lactobacillus and decreased Clostridiaceae/Clostridium in HFD-fed mice. There was no effect of increasing the P/C ratio on energy intake, but the highest ratio reduced HFD-induced weight gain, fat mass and plasma triacylglycerol, non-esterified fatty acids, glucose and leptin levels, while it increased lean mass and oxygen consumption. Similar effects were observed on adipose mRNA expression, where the highest ratio reduced HFD-associated expression of UCP-2, TNFα and CD68 and increased the diet-associated expression of β3-AR, LPL, IR, IRS-1 and GLUT4. The P/C ratio also impacted on gut microbiota, with populations in the 30/40% WPI groups clustering together and away from the 20% WPI group. Taken together, our data show that increasing the P/C ratio has a dramatic effect on energy balance and the composition of gut microbiota, which is distinct from that caused by changes to protein quality.

Whey protein isolate counteracts the effects of a high-fat diet on energy intake and hypothalamic and adipose tissue expression of energy balance-related genes

The intake of whey protein isolate (WPI) is known to reduce high-fat diet (HFD)-induced body-weight gain and adiposity. However, the molecular mechanisms are not fully understood. To this end, we fed C57BL/6J mice for 8 weeks with diets containing 10 % energy as fat (low-fat diet, LFD) or 45 % energy as fat (HFD) enriched with either 20 % energy as casein (LFD and HFD) or WPI (high-fat WPI). Metabolic parameters and the hypothalamic and epididymal adipose tissue expression of energy balance-related genes were investigated. The HFD increased fat mass and plasma leptin levels and decreased the dark-phase energy intake, meal number, RER, and metabolic (VO₂ and heat) and locomotor activities compared with the LFD. The HFD increased the hypothalamic tissue mRNA expression of the leptin receptor, insulin receptor (INSR) and carnitine palmitoyltransferase 1b (CPT1b). The HFD also reduced the adipose tissue mRNA expression of GLUT4 and INSR. In contrast, WPI reduced fat mass, normalised dark-phase energy intake and increased meal size in HFD-fed mice. The dietary protein did not have an impact on plasma leptin, insulin, glucose or glucagon-like peptide 1 levels, but increased plasma TAG levels in HFD-fed mice. At a cellular level, WPI significantly reduced the HFD-associated increase in the hypothalamic tissue mRNA expression of the leptin receptor, INSR and CPT1b. Also, WPI prevented the HFD-induced reduction in the adipose tissue mRNA expression of INSR and GLUT4. In comparison with casein, the effects of WPI on energy intake and hypothalamic and adipose tissue gene expression may thus represent a state of reduced susceptibility to weight gain on a HFD.