Dietary leucine supplementation alters energy metabolism and induces slow-to-fast transitions in longissimus dorsi muscle of weanling piglets

Dietary short-term supplementation of grape seed proanthocyanidin extract improves pork quality and promotes skeletal muscle fiber type conversion in finishing pigs

Plant extracts are commonly used as feed additives to improve pork quality. However, due to their high cost, shortening the duration of supplement use can help reduce production costs. In this study, we aimed to investigate the effects of grape seed proanthocyanidin extract (GSPE) on meat quality and muscle fiber characteristics of finishing pigs during the late stage of fattening, which was 30 days in our experimental design. The results indicated that short-term dietary supplementation of GSPE significantly reduced backfat thickness, but increased loin eye area and improved meat color and tenderness. Moreover, GSPE increased slow myosin heavy chain (MyHC) expression and malate dehydrogenase (MDH) activity, while decreasing fast MyHC expression and lactate dehydrogenase (LDH) activity in the Longissimus thoracis (LT) muscle. Additionally, GSPE increased the expression of Sirt1 and PGC-1α proteins in the LT muscle of finishing pigs and upregulated AMP-activated protein kinase α 1 (AMPKα1), AMPKα2, nuclear respiratory factor 1 (NRF1), and calcium/calmodulin-dependent protein kinase kinase β (CaMKKβ) mRNA expression levels. These findings suggest that even during the late stage of fattening, GSPE treatment can regulate skeletal muscle fiber type transformation through the AMPK signaling pathway, thereby affecting the muscle quality of finishing pigs. Therefore, by incorporating GSPE into the diet of pigs during the late stage of fattening, producers can enhance pork quality while reducing production costs.

From stability to reliability: Unveiling the un-biased reference genes in porcine ovarian granulosa cells under different conditions

Selection of optimal reference genes (RGs) is fundamental for functional genomics studies and gene expression analysis, which are two main approaches to identify functional genes and their expression patterns. However, no systematic study has identified the suitable RGs in porcine ovarian granulosa cells (GCs) which are essential for follicle fate and sow fertility. In this study, the expression profiles of 12 widely-used RGs (GAPDH, RPLP0, ACTB, TUBA1B, EIF3K, PPIA, ATP5F1, B2M, HPRT1, UBC, RPS3, and EEF1A1) in porcine GCs during follicular development and under different abiotic stresses were systematically investigated. Expression stability of the candidate RGs were comprehensively accessed by five statistical algorithms including ΔCt, NormFinder, BestKeeper, geNorm, and RefFinder, indicating that RPS3 and PPIA are the optimal RGs during follicular development, EEF1A1 and RPLP0 are most stable under oxidative stress and inflammation, while ATP5F1, B2M, and RPS3 have higher stability under starvation and heat stress. Notably, the most commonly used RGs (ACTB, GAPDH, and TUBA1B) exhibited low stability in GCs. Reliability of stable RGs was verified by RT-qPCR and showed that selection of the stable RGs significantly improved the detection accuracy of qPCR, which confirms once again that the stability of RGs should not be taken for granted. Our findings identified optimal RG sets in porcine GCs under different conditions, which is helpful in future studies to accurately identify the key regulators and their expression patterns during follicular development in sows.

Effects of Microbial Fermented Feed on Serum Biochemical Profile, Carcass Traits, Meat Amino Acid and Fatty Acid Profile, and Gut Microbiome Composition of Finishing Pigs

Microbial fermented feed is an important part of feed industry, while little research has focused on the solid-state fermentation of complete feed. Herein, the purpose of the present study was to investigate the effects of fermented complete feed (FCF) on the growth performance, biochemical profile, carcass traits, meat proximate composition, meat amino acid and fatty acid profile, and gut microbiome composition of finishing pigs, thereby providing references for the application of FCF in animal production. Twenty Duroc × Landrace × Yorkshire pigs with an average body weight (BW) of 48.74 ± 1.49 kg were divided randomly into control group (pigs received a basal diet, CN, n = 10) and FCF group (pigs fed with FCF, n = 10). The experiment lasted for 60 days. FCF improved the growth performance, which was indicated by a significantly increased final BW, average daily gain and average daily feed intake, and a significantly decreased feed-to-gain ratio. FCF improved biochemical profile, which was indicated by a higher alkaline phosphatase, glucose, immunoglobulin G, immunoglobulin M, superoxide dismutase, and total antioxidant capacity content. Pigs that received FCF had better carcass traits and meat quality than did pigs that received basal diet, which was indicated by a higher carcass length, crude protein content, lysine content, Glu content, C18:ln9c, C18:2n6c, C20:4n6, and unsaturated fatty acid content and a lower average back-fat thickness, C18:0, and saturated fatty acids. FCF significantly reduced the relative abundances of presumably pathogenic bacteria of phylum Proteobacteria and genus Escherichia–Shigella and enhanced the relative abundances of likely beneficial bacteria of phylum Firmicutes and genus Clostridium. In summary, FCF had a certain effect on the improvement of growth performance, serum biochemical profile, carcass traits, meat proximate composition, amino acid and fatty acid profile, and gut microbiome composition of finishing pigs.

Transcriptomic analysis for pork color – the ham halo effect in biceps femoris

Pork color is a major indicator of product quality that guides consumerpurchasing decisions. Recently, industry has received an increase in consumercomplaints about the lightness and non-uniformity of ham color, primarilylighter color in the periphery termed “ham halo” that is not caused bymanufacturing procedures. This effect is seen in fresh and processed hams andthe outer, lighter muscle is associated with lower myoglobin concentration, pHand type I fibers. The objective of this study was to identify differences ingene expression profiles between light and normal colored portions of biceps femoris muscle from pork hams.RNA-sequencing was performed for paired light and normal colored muscle samplesfrom 10 animals showing the ham halo effect. Over 50 million paired-end reads(2x75bp) per library were obtained. An average of 99.74% of trimmed high-qualityreads were mapped to the Sscrofa 11.1 genome assembly. Differentially expressedgenes (DEGs) were identified using both the DESeq2 and GFOLD software packages.A total of 14,049 genes were expressed in bicepsfemoris; 13,907 were expressed in both light and normal muscle, while 56and 86 genes were only expressed in light and normal muscle, respectively. Analysiswith DESeq2 identified 392 DEGs with 359 genes being more highly expressed innormal colored muscle. A total of 61 DEGs were identified in the DESeq2analysis and also were identified in at least 7 of the 10 individual animalanalyses. All 61 of these DEGs were up-regulated in normal colored muscle. Geneontology (GO) enrichment analysis of DEGs identified the transition betweenfast and slow fibers, and skeletal muscle adaptation and contraction as themost significant biological process terms. The evaluation of gene expression byRNA-Seq identified DEGs between regions of the biceps femoris with the ham halo effect that are associated with thevariation in pork color.

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, but not isoleucine or valine, affects serum lipid profiles and browning of WAT in mice

Branched chain amino acids (BCAA), especially leucine (Leu), have been reported to decrease fat deposition. However, opposite effects of BCAA on lipid metabolism have been observed. To determine the role of BCAA in lipid metabolism, an amino acid-defined diet was formulated and C57BL/6J mice were assigned into the following groups: amino acid-defined control diet and control diet supplemented with Leu, isoleucine, or valine. Nitrogen was balanced by proportionally mixed amino acids except BCAA. Results showed that dietary Leu supplementation significantly increased the levels of serum triglycerides, total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol and urea nitrogen. Metabolomics showed that biosynthesis of unsaturated fatty acids was altered by Leu supplementation. Leu treatment up-regulated the expression of genes related to fat synthesis and down-regulated the expression of genes related to fatty acid synthesis. Furthermore, the genes and proteins of selective markers involved in browning of white adipose tissue (WAT) were up-regulated by dietary supplementation with Leu. This study indicated that dietary supplementation with Leu, but not isoleucine or valine, significantly affected lipid metabolism by regulating lipid metabolism-related genes and serum fatty acid concentration, providing a new tool in the management of obesity and metabolic disorders.

PGC-1α-Targeted Therapeutic Approaches to Enhance Muscle Recovery in Aging

Impaired muscle recovery (size and strength) following a disuse period commonly occurs in older adults. Many of these individuals are not able to adequately exercise due to pain and logistic barriers. Thus, nutritional and pharmacological therapeutics, that are translatable, are needed to promote muscle recovery following disuse in older individuals. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) may be a suitable therapeutic target due to pleiotropic regulation of skeletal muscle. This review focuses on nutritional and pharmacological interventions that target PGC-1α and related Sirtuin 1 (SIRT1) and 5' AMP-activated protein kinase (AMPKα) signaling in muscle and thus may be rapidly translated to prevent muscle disuse atrophy and promote recovery. In this review, we present several therapeutics that target PGC-1α in skeletal muscle such as leucine, β-hydroxy-β-methylbuyrate (HMB), arginine, resveratrol, metformin and combination therapies that may have future application to conditions of disuse and recovery in humans.

Pea-derived peptides, VLP, LLP, VA, and LL, improve insulin resistance in HepG2 cells via activating IRS-1/PI3K/AKT and blocking ROS-mediated p38MAPK signaling

This study evaluated the effect of four peptides, VLP, LLP, LL, and LL from pea on regulating glucose metabolism and antioxidant through IRS-1/PI3K/AKT and p38MAPK signal pathway in IR-HepG2 cell induced by 10-6 M insulin. The genes expression of PEPCK, G6Pase, GLUT2, and IRS-1 and proteins of IRS-1, p(Ser307)-IRS-1, AKT, p(Ser473)-AKT, p38MAPK, and p-p38MAPK were determined by RT-PCR and western blotting, respectively. Results show that they displayed highly potent on stimulation glucose metabolism and relief oxidative stress in IR-HepG2 cells. VLP, LLP, VA, and LL reduced Ser307 phosphorylation of IRS-1 and promoted Ser473 phosphorylation of AKT. Among them, LLP, VA, and LL increased the expression both gene and protein of GLUT2, and VLP and LL reduced p38MAPK phosphorylation showing strong antioxidant capacity. Therefore, pea oligopeptides have considerable potential for reversing the metabolic abnormalities associated with type 2 diabetes. PRACTICAL APPLICATIONS: This paper examined the intervention effect of VLP, LLP, VA, and LL that from pea on insulin resistance, and the mechanisms were detected by western blotting. The results provide a theoretical knowledge for the prevention of insulin resistance in T2D of pea-derived peptides and lay the foundation for the development of functional products and drugs in the future.

Fermented Feed Modulates Meat Quality and Promotes the Growth of Longissimus Thoracis of Late-Finishing Pigs

This study investigated the effect of fermented diet on growth performance, carcass traits, meat quality and growth of longissimus thoracis (LT) of finishing pigs. A total of 48 finishing pigs [Duroc × (Landrace × Large White), male, 126 ± 5-d-old] weighing 98.76 ± 1.27 kg were randomly assigned to two treatments (eight pens per treatment and three pigs per pen) for a 28-d feeding trial, including control diet and fermented diet. Fermented diet significantly increased the loin eye area and lean mass percentage, decreased backfat thickness and improved meat quality of LT by decreasing the shear force and drip loss at 48 h post slaughter and improving meat sensory characteristics compared with control diet. A fermented diet also significantly increased the abundance of insulin, insulin receptor (IR), myoblast determination protein (MyoD) and myosin heavy chain-I (MyHC-I) transcripts, and the phosphorylation levels of AKT, mTORC1, 4EBP1 and S6K1 in LT, while decreasing the expression of muscle atrophy F-box (MAFbx) and forkhead Box O1 (Foxo1) mRNA transcripts. Moreover, proteomic analysis revealed that differentially expressed proteins predominantly involved in protein synthesis and muscle development were modulated by fermented diet. Our results indicated that a fermented diet improved meat quality and enhanced LT growth of finishing pigs by increasing insulin/AKT/mTORC1 protein synthesis cascade and activating the Foxo1/MAFbx pathway, along with the regulation of ribosomal protein and proteins involved in muscle contraction and muscle hypertrophy.

Leucine Supplementation: A Novel Strategy for Modulating Lipid Metabolism and Energy Homeostasis

Lipid metabolism is an important and complex biochemical process involved in the storage of energy and maintenance of normal biological functions. Leucine, a branched amino acid, has anti-obesity effects on glucose tolerance, lipid metabolism, and insulin sensitivity. Leucine also modulates mitochondrial dysfunction, representing a new strategy to target aging, neurodegenerative disease, obesity, diabetes, and cardiovascular disease. Although various studies have been carried out, much uncertainty still exists and further studies are required to fully elucidate the relationship between leucine and lipid metabolism. This review offers an up-to-date report on leucine, as key roles in both lipid metabolism and energy homeostasis in vivo and in vitro by acceleration of fatty acid oxidation, lipolysis, activation of the adenosine 5'-monophosphate-activated protein kinase (AMPK)-silent information regulator of transcription 1 (SIRT1)-proliferator-activated receptor γ coactivator-1α (PGC-1α) pathway, synthesis, and/or secretion of adipokines and stability of the gut microbiota.

Leucine improves α-amylase secretion through the general secretory signaling pathway in pancreatic acinar cells of dairy calves

The present study aimed to elucidate the mechanisms by which leucine impacts the secretion of pancreatic enzymes, especially amylase, by studying the proteomics profiles of pancreatic acinar (PA) cells from dairy cows. PA cells, the experimental model, were treated with four concentrations of leucine (0, 0.23, 0.45, and 0.90 mM). The abundance of different proteins in the four leucine treatment groups was detected. Label-free proteomic analysis enabled the identification of 1,906 proteins in all four treatment groups, and 1,350 of these proteins showed common expression across the groups. The primary effects of leucine supplementation were increased (P < 0.05) citrate synthase and ATPase activity, which enlarged the cytosolic ATP pool, and the upregulation of secretory protein 61 (Sec61) expression, which promoted protein secretion. In summary, these results suggest that leucine increases citrate synthase in the TCA cycle and ATPase activity and promotes the Sec signaling pathway to increase the exocrine function of PA cells.

Proteomic Analysis of Beef Tenderloin and Flank Assessed Using an Isobaric Tag for Relative and Absolute Quantitation (iTRAQ)

Simple Summary

Amino acid composition is among the important indexes of the nutritional composition of meat nutrients. In this study, we performed a proteomic analysis of tenderloin and flank steaks from Simmental cattle using isobaric tags for a relative and absolute quantification (iTRAQ) approach. Seventeen amino acids were detected in tenderloin and flank steaks, including seven essential amino acids and 10 non-essential amino acids. A comparison of the expression patterns in steaks revealed 128 differentially expressed proteins (DEPs). Furthermore, 27 DEPs (p < 0.05) were subjected to Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis.

Abstract

Herein, we performed a proteomic analysis of tenderloin and flank steaks from Simmental cattle using the isobaric tags for a relative and absolute quantification (iTRAQ) approach. We identified 17 amino acids in both steaks, and Gly, Cys, Ile, Lys, and Pro differed most in abundance between the steak types (p < 0.05). A comparison of the expression patterns in steaks revealed 128 differentially expressed proteins (DEPs), of which 44 were up-regulated and 84 were down-regulated. Furthermore, 27 DEPs (p < 0.05) were subjected to gene ontology (GO) analysis, and many were found to be related to oxidation-reduction, metabolism, hydrogen ion transmembrane transport, transport, the tricarboxylic acid (TCA) cycle, mitochondrial electron transport, and the conversion of nicotinamide adenine dinucleotide (NADH) to ubiquinone. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis also implicated these DEPs in various signalling pathways, including oxidative phosphorylation, cardiac muscle contraction, the TCA cycle, biosynthesis, and the metabolism. These findings provide a new insight into key proteins involved in the determination of amino acid composition in beef.

β-Hydroxy-β-methylbutyrate-Induced Upregulation of miR-199a-3p Contributes to Slow-To-Fast Muscle Fiber Type Conversion in Mice and C2C12 Cells

The influence of β-hydroxy-β-methylbutyrate (HMB) on proliferation and differentiation of myogenic cells has been well-studied. However, the role of HMB in myofiber specification and potential mechanisms is largely unknown. Thus, the objective of this research was to explore the role of HMB supplementation in myofiber specification. Results showed that HMB treatment significantly increased the fast MyHC protein level (mice: 1.59 ± 0.08, P < 0.01; C2C12: 2.26 ± 0.11, P < 0.001), decreased the slow MyHC protein level (mice: 0.76 ± 0.05, P < 0.05; C2C12: 0.52 ± 0.02, P < 0.001), and increased the miR-199a-3p level (mice: 4.93 ± 0.37, P < 0.001; C2C12: 11.25 ± 0.57, P < 0.001). Besides, we also observed that HMB promoted the activity of glycolysis-related enzymes and reduced the activities of oxidation-related enzymes in mice and C2C12 cells. Overexpression of miR-199a-3p downregulated the slow MyHC protein level (0.71 ± 0.02, P < 0.01) and upregulated the fast MyHC protein level (2.13 ± 0.09, P < 0.001), while repression of miR-199a-3p exhibited the opposite effect. Target identification results verified that miR-199a-3p targets the 3'UTR of the TEA domain family member 1 (TEAD1) to cause its post-transcriptional inhibition (0.41 ± 0.07, P < 0.01). Knockdown of TEAD1 exhibited a similar effect with miR-199a-3p on myofiber specification. Moreover, suppression of miR-199a-3p blocked slow-to-fast myofiber type transition induced by HMB. Together, our finding revealed that miR-199-3p is induced by HMB and contributes to the action of HMB on slow-to-fast myofiber type conversion via targeting TEAD1.

Overcoming nature’s paradox in skeletal muscle to optimise animal production

Nature’s paradox in skeletal muscle describes the seemingly mutually exclusive relationship between muscle fibre size and oxidative capacity. In mammals, there is a constraint on the size at which mitochondria-rich, high O2-dependent oxidative fibres can attain before they become anoxic or adapt to a glycolytic phenotype, being less reliant on O2. This implies that a muscle fibre can hypertrophy at the expense of its endurance capacity. Adaptations to activity (exercise) generally obey this relationship, with optimal muscle endurance generally being linked to an enhanced proportion of small, slow oxidative fibres and muscle strength (force and/or power) being linked to an enhanced proportion of large, fast glycolytic fibres. This relationship generally constrains not only the physiological limits of performance (e.g. speed and endurance), but also the capacity to manipulate muscle attributes such as fibre size and composition, with important relevance to the livestock and aquaculture industries for producing specific muscle traits such as (flesh) quality, texture and taste. Highly glycolytic (white) muscles have different traits than do highly oxidative (red) muscles and so the ability to manipulate muscle attributes to produce flesh with specific traits has important implications for optimising meat production and quality. Understanding the biological regulation of muscle size, and phenotype and the capacity to manipulate signalling pathways to produce specific attributes, has important implications for promoting ethically sustainable and profitable commercial livestock and aquaculture practices and for developing alternative food sources, including ‘laboratory meat’ or ‘clean meat’. This review describes the exciting potential of manipulating muscle attributes relevant to animal production, through traditional nutritional and pharmacological approaches and through viral-mediated strategies that could theoretically push the limits of muscle fibre growth, adaptation and plasticity.

Lactobacillus gasseri LA39 Activates the Oxidative Phosphorylation Pathway in Porcine Intestinal Epithelial Cells

Intestinal microbial interactions with the host epithelium have important roles in host health. Our previous data have suggested that Lactobacillus gasseri LA39 is the predominant intestinal Lactobacillus in weaned piglets. However, the regulatory role of L. gasseri LA39 in the intestinal epithelial protein expression in piglets remains unclear. In the present study, we conducted comparative proteomics approach to investigate the intestinal epithelial protein profile alteration caused by L. gasseri LA39 in piglets. The expressions of 15 proteins significantly increased, whereas the expressions of 13 proteins significantly decreased in the IPEC-J2 cells upon L. gasseri LA39 treatment. Bioinformatics analyses, including COG function annotation, GO annotation, and KEGG pathway analysis for the differentially expressed proteins revealed that the oxidative phosphorylation (OXPHOS) pathway in IPEC-J2 cells was significantly activated by L. gasseri LA39 treatment. Further data indicated that two differentially expressed proteins UQCRC2 and TCIRG1, associated with the OXPHOS pathway, and cellular ATP levels in IPEC-J2 cells were significantly up-regulated by L. gasseri LA39 treatment. Importantly, the in vivo data indicated that oral gavage of L. gasseri LA39 significantly increased the expression of UQCRC2 and TCIRG1 and the cellular ATP levels in the intestinal epithelial cells of weaned piglets. Our results, both in vitro and in vivo, reveal that L. gasseri LA39 activates the OXPHOS pathway and increases the energy production in porcine intestinal epithelial cells. These findings suggest that L. gasseri LA39 may be a potential probiotics candidate for intestinal energy production promotion and confers health-promoting functions in mammals.

Cooperative and Independent Functions of the miR-23a~27a~24-2 Cluster in Bovine Adipocyte Adipogenesis

The miR-23a~27a~24-2 cluster is an important regulator in cell metabolism. However, the cooperative and independent functions of this cluster in bovine adipocyte adipogenesis have not been elucidated. In this study, we found that expression of the miR-23a~27a~24-2 cluster was induced during adipogenesis and this cluster acted as a negative regulator of adipogenesis. miR-27a and miR-24-2 were shown to inhibit adipogenesis by directly targeting glycerol-3-phosphate acyltransferase, mitochondrial (GPAM) and diacylglycerol O-acyltransferase 2 (DGAT2), both of which promoted adipogenesis. Meanwhile, miR-23a and miR-24-2 were shown to target decorin (DCN), glucose-6-phosphate dehydrogenase (G6PD), and lipoprotein lipase (LPL), all of which repressed adipogenesis in this study. Thus, the miR-23a~27a~24-2 cluster exhibits a non-canonical regulatory role in bovine adipocyte adipogenesis. To determine how the miR-23a~27a~24-2 cluster inhibits adipogenesis while targeting anti-adipogenic genes, we identified another target gene, fibroblast growth factor 11 (FGF11), a positive regulator of adipogenesis, that was commonly targeted by the entire miR-23a~27a~24-2 cluster. Our findings suggest that the miR-23a~27a~24-2 cluster fine-tunes the regulation of adipogenesis by targeting two types of genes with pro- or anti-adipogenic effects. This balanced regulatory role of miR-23a~27a~24-2 cluster finally repressed adipogenesis.