Glutamine supplementation improves contractile function of regenerating soleus muscles from rats.

This study evaluated the effects of glutamine supplementation immediately after freezing injury on morphological and contractile function of regenerating soleus muscles from rats. Young male Wistar rats were subjected to cryolesion of soleus muscles, and immediately after received a daily supplementation of glutamine (1 g/kg/day). The muscles were evaluated on post-injury days 3 and 10. Glutamine-supplemented injured muscles had a lower number of CD11b positive immune cells and higher mRNA levels of IL-4 compared to those from the cryolesioned muscles analyzed on post-injury day 3. The mRNA and protein expression levels of the myogenic transcription factor MyoD were also higher in glutamine-supplemented injured muscles than in injured muscles examined on post-cryolesion day 3. In addition, glutamine-supplemented injured muscles had a higher size of their regenerating myofibers, attenuated decline in maximum tetanic strength and improved fatigue resistance compared to those from injured muscles evaluated on post-cryolesion day 10. No effect was observed in uninjured muscles supplemented with glutamine. Our results suggest that glutamine supplementation improves the resolution of inflammation, as well as the size and functional recovery of regenerating myofibers from soleus muscles by accelerating the up-regulation of IL-4 and MyoD expression. Future non-pharmacological rehabilitation studies are warranted to investigate the effect of glutamine supplementation on the outcome of injured skeletal muscles.

Beta-hydroxy-beta-methylbutyrate associated with low-intensity exercise training improves skeletal muscle regeneration through the IGF-Akt pathway.

The effect of beta-hydroxy-beta-methylbutyrate (HMB) supplementation associated with exercise training at different intensities and frequencies on skeletal muscle regeneration of muscle-injured rats was investigated. Male Wistar rats were divided into sedentary and trained groups. The sedentary groups were subdivided into non-injured (SED-Ct), non-injured supplemented with HMB (SED-Ct-HMB), injured (SED), and injured with HMB (SED-HMB), and the trained groups were injured, supplemented with HMB, and then divided into training three times a week without load (HT3) or with load (HT3L) and training five times a week without load (HT5) and with load (HT5L). The rats received a daily dose of HMB associated with 60 min of swimming with or without 5% body mass load for 14 days. On the 15th day, cryoinjury was performed in the right tibialis anterior muscle (TA), and 48 h later, supplementation and training continued for 15 days. After the last session, the TA was dissected and a cross-sectional area (CSA) of muscle fibers was used to determine the percentage of CSA fibers and connective tissue (%CT), as well as the total and phosphorylated protein contents. SED-HMB showed increased CSA and decreased %CT and TGF-ß when compared to SED. HT3 showed increased CSA and reduced %CT accompanied by increased IGF-1/Akt, myogenin, and MuRF1, and decreased TGF-ß. The CSA of HT5L also increased, but at the cost of a higher %CT compared to the other groups. Our results demonstrated that HMB associated with training without load and with lower frequency per week may be a valuable strategy for skeletal muscle regeneration.

Dietary supplementation with inosine-5'-monophosphate improves the functional, energetic, and antioxidant status of liver and muscle growth in pigs.

Inosine 5'-monophosphate (5'-IMP) is an essential nucleotide for de novo nucleotide biosynthesis and metabolism of energy, proteins, and antioxidants. Nucleotides are conditionally essential, as they cannot be produced sufficiently rapidly to meet the needs of the body in situations of oxidative stress or rapid muscle growth. A deficient intake of nucleotides can result in decreased ATP and GTP synthesis and impaired metabolism. We demonstrated that supplementation of finishing pig diets with 5'-IMP reduces the relative weight of the liver, and increases oxygen consumption during mitochondrial respiration without changing the ADP/O ratio, indicating an increase in the respiratory efficiency of liver mitochondria. We also observed a reduction in liver lipid peroxidation and an increase in muscle creatine. Moreover, 5'IMP supplementation increases slaughter weight, lean meat yield, sarcomere length, and backfat thickness in finishing barrows, demonstrating influence on protein metabolism. We suggest that 5'-IMP supplementation increase the mitochondrial respiratory capacity when the liver metabolic activity is stimulated, enhances antioxidant defense, and promotes muscle growth in finishing barrows.

Acute heat exposure improves microvascular function in skeletal muscle of aged adults.

Acute heat exposure improves microvascular function in aged adults as assessed using reactive hyperemia. The cutaneous and skeletal muscle microcirculations are thought to contribute to this response, but this has never been confirmed due to the methodological challenges associated with differentiating blood flow between these vascular beds. We hypothesized that acute hot water immersion would improve endothelial-dependent, but not endothelial-independent vasodilation in the microcirculation of the vastus lateralis muscle in healthy aged adults. Participants (70 ± 5 yr) were immersed for 60 min in thermoneutral (36°C) or hot (40°C) water. Ninety minutes following immersion, skeletal muscle microdialysis was used to bypass the cutaneous circulation and directly assess endothelial-dependent and endothelial-independent vasodilation by measuring the local hyperemic response to graded infusions of acetylcholine (ACh, 27.5 and 55.0 mM) and sodium nitroprusside (SNP, 21 and 42 mM), respectively. The hyperemic response to 27.5 mM ACh did not differ between thermal conditions (P = 0.9). However, the hyperemic response to 55.0 mM ACh was increased with prior hot water immersion (thermoneutral immersion, 43.9 ± 23.2 mL/min/100 g vs. hot water immersion, 66.5 ± 25.5 mL/min/100 g; P < 0.01). Similarly, the hyperemic response to 21 mM SNP did not differ between thermal conditions (P = 0.3) but was increased following hot water immersion with the infusion of 42 mM SNP (thermoneutral immersion, 48.8 ± 25.6 mL/min/100 g vs. hot water immersion, 90.7 ± 53.5 mL/min/100 g; P < 0.01). These data suggest that acute heat exposure improves microvascular function in skeletal muscle of aged humans.NEW & NOTEWORTHY Acute heat exposure improves microvascular function in aged adults as assessed using reactive hyperemia. The cutaneous and skeletal muscle microcirculations are thought to contribute to this response, but this has never been confirmed due to the methodological challenges associated with differentiating blood flow between these vascular beds. Using the microdialysis technique to bypass the cutaneous circulation, we demonstrated that heat exposure improves endothelial-dependent and endothelial-independent vasodilation in the microcirculation of skeletal muscle in aged humans.

Carcass characteristics and meat evaluation of cattle finished in temperate pasture and supplemented with natural additive containing clove, cashew oil, castor oils, and a microencapsulated blend of eugenol, thymol, and vanillin.

BACKGROUND: Forty crossbred steers were supplemented with different doses (from 0 control to 6000 mg/animal/day) of natural additive blend containing clove essential oil, cashew oil, castor oil, and a microencapsulated blend of eugenol, thymol, and vanillin for 80 days. Carcass characteristics, drip loss, and antioxidant activity were evaluated 24 h post mortem on longissimus thoracis, and the effects of aging (until 14 days) were evaluated for water losses (thawing/aging and cooking), texture, color, and lipid oxidation. RESULTS: The use of the natural additive blend did not modify (P > 0.05) carcass characteristics but did, however, modify body composition (P < 0.05). Drip losses were unaffected by the treatments tested (P > 0.05). There was an observed quadratic effect (P < 0.05) on losses from thawing/aging on the first day of storage. Regarding the effects of natural additives on cooking losses, there was a quadratic effect (P < 0.05) among the treatments on day 7 of aging. Differences between days of aging were only observed with control treatment. Shear force was similar among treatments on days 1 and 7 of aging. On day 14 a linear effect (P < 0.05) was observed. Also, a linear effect (P < 0.05) appeared on meat lightness, meat from the control group being clearer on day 1. No changes were observed in redness among treatments or days of storage (P > 0.05). Yellowness was not modified by the treatments (P > 0.05)but only by the days of storage in control and the lowest dosage used. CONCLUSION: The blend of natural additives has potential use in pasture feeding and could improve meat quality. However, doses should be adjusted. © 2021 Society of Chemical Industry.

Long-term programming of skeletal muscle and liver lipid and energy metabolism by resveratrol supplementation to suckling mice.

Metabolic programming by dietary chemicals consumed in early life stages is receiving increasing attention. We here studied long-term effects of mild resveratrol (RSV) supplementation during lactation on muscular and hepatic lipid metabolism in adulthood. Newborn male mice received RSV or vehicle from day 2-20 of age, were weaned onto a chow diet on day 21, and were assigned to either a high-fat diet (HFD) or a normal-fat diet on day 90 of age for 10 weeks. RSV-treated mice showed in adulthood protection against HFD-induced triacylglycerol accumulation in skeletal muscle, enhanced muscular capacities for fat oxidation and mitochondria activity, signs of enhanced sirtuin 1 and AMP-dependent protein kinase signaling in muscle, and increased fat oxidation capacities and a decreased capacity for lipogenesis in liver compared with controls. Thus, RSV supplementation in early postnatal life may help preventing later diet-related disorders linked to ectopic lipid accumulation in muscle and liver tissues.

Ascorbic Acid Supplementation Improves Skeletal Muscle Growth in Pacu (Piaractus mesopotamicus) Juveniles: In Vivo and In Vitro Studies.

In fish, fasting leads to loss of muscle mass. This condition triggers oxidative stress, and therefore, antioxidants can be an alternative to muscle recovery. We investigated the effects of antioxidant ascorbic acid (AA) on the morphology, antioxidant enzyme activity, and gene expression in the skeletal muscle of pacu (Piaractus mesopotamicus) following fasting, using in vitro and in vivo strategies. Isolated muscle cells of the pacu were subjected to 72 h of nutrient restriction, followed by 24 h of incubation with nutrients or nutrients and AA (200 µM). Fish were fasted for 15 days, followed by 6 h and 15 and 30 days of refeeding with 100, 200, and 400 mg/kg of AA supplementation. AA addition increased cell diameter and the expression of anabolic and cell proliferation genes in vitro. In vivo, 400 mg/kg of AA increased anabolic and proliferative genes expression at 6 h of refeeding, the fiber diameter and the expression of genes related to cell proliferation at 15 days, and the expression of catabolic and oxidative metabolism genes at 30 days. Catalase activity remained low in the higher supplementation group. In conclusion, AA directly affected the isolated muscle cells, and the higher AA supplementation positively influenced muscle growth after fasting.

The Effect of a Multi-ingredient Supplement on Resistance Training-induced Adaptations.

INTRODUCTION: Resistance exercise training (RET) induces muscle hypertrophy that, when combined with co-temporal protein ingestion, is enhanced. However, fewer studies have been conducted when RET is combined with multi-ingredient supplements. PURPOSE: We aimed to determine the effect of a high-quality multi-ingredient nutritional supplement (SUPP) versus an isonitrogenous (lower protein quality), isoenergetic placebo (PL) on RET-induced gains in lean body mass (LBM), muscle thickness, and muscle cross-sectional area (CSA). We hypothesized that RET-induced gains in LBM and muscle CSA would be greater in SUPP versus PL. METHODS: In a double-blind randomized controlled trial, 26 (13 male, 13 female) healthy young adults (mean ± SD, 22 ± 2 yr) were randomized to either the SUPP group (n = 13; 20 g whey protein, 2 g leucine, 2.5 g creatine monohydrate, 300 mg calcium citrate, 1000 IU vitamin D) or the PL group (n = 13; 20 g collagen peptides, 1.4 g alanine, 0.6 g glycine) groups, ingesting their respective supplements twice daily. Measurements were obtained before and after a 10-wk linear progressive RET program. RESULTS: Greater increases in LBM were observed for SUPP versus PL (SUPP: +4.1 ± 1.3 kg, PL: +2.8 ± 1.7 kg, P < 0.05). No additive effect of the supplement could be detected on vastus lateralis muscle CSA, but SUPP did result in increased biceps brachii muscle CSA and thickness (P < 0.05). CONCLUSIONS: We conclude that when combined with RET, the consumption of SUPP increased LBM and upper-body CSA and thickness to a greater extent than to that observed in the PL group of healthy young adults.

Effects of dietary ferulic acid supplementation on growth performance and skeletal muscle fiber type conversion in weaned piglets.

BACKGROUND: Ferulic acid (FA) is a common polyphenolic compound. The purpose of this study was to explore the effect of dietary FA supplementation on growth performance and muscle fiber type conversion in weaned piglets. In this study, eighteen 21-day-old DLY (Duroc × Landrace × Yorkshire) weaned piglets were randomly divided into control, 0.05% FA, and 0.45% FA groups. RESULTS: Our study showed that dietary FA supplementation had no effect on growth performance, but it could upregulate the expression of slow myosin heavy chain (MyHC) protein, increase the activities of succinic dehydrogenase and malate dehydrogenase, and downregulate the expression of fast MyHC protein. Dietary FA supplementation also increased the expression levels of phosphorylated AMP-activated protein kinase, sirtuin 1 (Sirt1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), myocyte enhancer factor 2C, and troponin I-SS, increased the proportion of slow-twitch fiber, and decreased the proportion of fast-twitch fiber. In addition, our results showed that dietary FA supplementation increased the messenger RNA abundance of mitochondrial nuclear transcription genes, including ATP synthase membrane subunit c locus 1, cytochrome oxidase subunit 1, nuclear respiratory factor 1, mitochondrial transcription factor A, mitochondrial transcription factor B1, and cytochrome c. CONCLUSION: We provided the first evidence that FA could promote muscle fiber type conversion from fast-twitch to slow-twitch via the Sirt1/AMP-activated protein kinase/PGC-1α signaling pathway and could improve the mitochondrial function in weaned piglets. This means that FA can be used as a dietary supplement to improve the quality of pork. © 2021 Society of Chemical Industry.

Dietary taurine supplementation ameliorates muscle loss in chronic heat stressed broilers via suppressing the perk signaling and reversing endoplasmic reticulum-stress-induced apoptosis.

BACKGROUND: Heat stress seriously affects animal health and induces enormous financial losses in poultry production. Exploring the appropriate means for ameliorating unfavorable effects caused by heat stress is essential. We investigated whether taurine supplementation could attenuate breast muscle loss in chronic heat-stressed broilers, as well as its mechanism. We designed three groups: a normal control group (22 °C), a heat stress group (32 °C) and a taurine treatment group (32 °C, basal diet + 5 g·kg-1 taurine). RESULTS: We found that taurine significantly moderated the decreases of breast muscle mass and yield, as well as the increases of serum aspartate aminotransferase activity and serum urine acid level in chronic heat-stressed broilers. Additionally, supplementary taurine significantly alleviated elevations of the cytoplasm Ca2+ concentration, protein expressions of GRP78 and p-PERK, mRNA expressions of Ca2+ channels (RyR1, IP3R3) and endoplasmic reticulum (ER) stress factors (GRP78, GRP94, PERK, EIF2α, ATF4, IRE1, XBP1, ATF6 and CHOP), apoptosis (Caspase-3 and TUNEL), protein catabolism, and the reduction of taurine transporter (TauT) mRNA expression in the breast muscle induced by chronic heat stress. CONCLUSION: Supplementary taurine could attenuate chronic heat stress-induced breast muscle loss via reversing ER stress-induced apoptosis and suppressing protein catabolism. © 2020 Society of Chemical Industry.

Effect of dietary l-arginine of broiler breeder hens on embryonic development, apparent metabolism, and immunity of offspring.

This study investigated the effects of supplemented l-arginine (l-Arg) in broiler breeder hens' diets on the embryonic development and physiological changes of offspring during the hatching period. A total of 480 35-wk-old healthy female Arbor Acres broiler breeders were randomly divided into 6 groups and fed a corn and soybean meal diet with 6 digestible Arg levels (0.96%, 1.16%, 1.35%, 1.55%, 1.74%, and 1.93%). After a 10-wk experiment, eggs were collected for incubation. At embryonic day (E) 11 to E21, eggs, embryos, and organs (liver, breast muscle, and thigh muscle) were weighed. Total protein, urea nitrogen, creatinine, cholesterol, and triglyceride in plasma, were measured. Plasma level of immunoglobulin G (IgG), immunoglobulin M (IgM), and nitric oxide synthase (NOS) were measured at E13, E17, and E21. Messenger RNA expression of carbamoyl phosphate synthase I (CPS1), ornithine transcarbamylase (OTC), and argininosuccinate synthase (ASS) in liver and breast muscle tissues was assessed at E13, E17, and E21. The results showed that 1.16% Arg in maternal diet increased egg weight (P < 0.05). The level of Arg in maternal diet has a significant effect on organ index and embryo weight of multiple embryonic days (P < 0.05). Embryonic plasma total protein concentration was significantly affected by maternal dietary Arg level (P < 0.05) and exhibited quadratic responses at E11, E15, E17, and E21 (P < 0.01). Plasma urea nitrogen, creatinine, triglyceride, and cholesterol level were also significantly affected by the level of maternal Arg at different embryonic ages (P < 0.05). Dietary digestible Arg levels quadratically influenced plasma urea nitrogen level at E21 (P < 0.05) and cholesterol concentration at E17 and E19 (P < 0.01). L-Arg supplementation in maternal diet significantly improved the IgG level at E17 and E21 (1.16%, 1.35%, 1.55%, and 1.74%; P < 0.05), the IgM level at E13 (1.35%, 1.55%, 1.74%, and 1.93%) and E17 (P < 0.05) and the NOS level at E13, E17, and E21 (P < 0.05). Maternal dietary L-Arg supplementation significantly improved the expression of CPS1 gene, OTC gene (1.16%, 1.35%, and 1.55%), and ASS gene (1.35% and 1.55%) in the liver (P < 0.05), and also enhanced the CPS1 gene (except 1.35%) and OTC gene (1.55% and 1.74%) expression in the breast muscle (P < 0.05). In conclusion, maternal Arg level affected the embryonic development of offspring and regulated the apparent metabolic programming and immunity state of the embryo. Arginine level of 1.55% in hens' diet was beneficial to the protein synthesis and immunity of the offspring in the embryonic period, and it was recommended to obtain healthy offspring.

The Effect of Orally Supplemented Melatonin on Larval Performance and Skeletal Deformities in Farmed Gilthead Seabream (Sparus aurata).

The gilthead seabream larval rearing in continuous light is common in most Mediterranean hatcheries to stimulate larval length growth and increase food consumption. Several studies have shown that continuous light affects larval development and increases the prevalence of skeletal deformities. Melatonin is a crucial pineal neurohormone that displays daily secretion patterns, stimulates cell proliferation and embryonic development in Atlantic salmon and zebrafish, and improves osseointegration in mice and humans. However, no studies have examined the effects of orally supplemented melatonin on skeletal deformities in Sparus aurata larvae. We administered exogenous melatonin to gilthead seabream larvae via enriched rotifers and nauplii of Artemia. Exogenous melatonin induced bone deformities and stimulated parathyroid hormone-related protein-coding gene (PTHrP) mRNA expression. In addition to the melatonin-induced PTHrP high expression level, the recorded non coordinated function of skeletal muscle and bone during growth can be the fountainhead of bone deformities. Both myosin light chain 2 (mlc2) and bone gamma-carboxyglutamate protein-coding gene (bglap) expression levels were significantly affected by melatonin administration in an inverse dose-response manner during the exogenous melatonin administration. This is the first study to report the effect of inducing melatonin bone deformities on Sparus aurata larvae reared under ordinary hatchery conditions.

Effects of passive heating intervention on muscle hypertrophy and neuromuscular function: A preliminary systematic review with meta-analysis.

Passive heating has been therapeutically used to treat a range of health conditions. Further, this intervention presents as a potential exercise mimetic strategy showing acute and chronic effects on skeletal muscle adaptation and neuromuscular systems. This systematic review and meta-analysis aimed to synthesise the existing evidence on the effects of passive heating on muscle hypertrophy and neuromuscular function. Seven databases were searched (i.e., PubMed, Web of Science, Scopus, CINAHL, EMBASE, Cochrane, and SPORTDiscus) from 1937 to October 2019. Eligible studies included original papers using healthy animals or human samples (≥18 years; both sexes) that have used a control group or condition. Ten original articles were included in this review and four in the meta-analysis. The meta-analysis detected an increase in muscle mass in animal samples seven days after passive heating (I2 = 65%, P < 0.01). The systematic review showed preliminary evidence that repeated passive heating exposures may promote muscle hypertrophy in animals and humans. Moreover, augmented muscle strength (involuntary and voluntary) may be observed after long-term passive heating (animals and humans) and increases in corticospinal excitability in humans after a single passive heating session. Passive heating has shown some potential benefits for skeletal muscle mass gain and muscle force improvement. Therefore, it is plausible to suggest that passive heating might be a worthwhile alternative to be recommended as an exercise mimetic for those people who lack or are unable to complete sufficient exercise.

Lysine inhibits apoptosis in satellite cells to govern skeletal muscle growth via the JAK2-STAT3 pathway.

Apoptosis is programmed cell death that can be stimulated by external stress or nutrition restrictions. However, the precise mechanism of apoptosis in skeletal muscle remains unknown. The objective of this study was to investigate whether apoptosis could be regulated by lysine (Lys) supplementation and the potential mechanism. In this study, an isobaric tag for relative and absolute quantification (iTRAQ) proteomics analysis of the longissimus dorsi muscle from piglets showed that the Janus family tyrosine kinase (JAK)-signal transducer and activator of transcription (STAT) pathway was involved in Lys deficiency-induced apoptosis and inhibited skeletal muscle growth. Meanwhile, western blotting results demonstrated that Lys deficiency led to apoptosis in the longissimus dorsi muscle with the JAK2-STAT3 pathway inhibition. Interestingly, apoptosis was suppressed, and the JAK2-STAT3 pathway was reactivated after Lys re-supplementation. In addition, the results showed that Lys deficiency-induced apoptosis in satellite cells (SCs) was mediated by the JAK2-STAT3 pathway inhibition. Moreover, the JAK2-STAT3 pathway was reactivated by Lys re-supplementation and suppressed cell apoptosis, and this effect was inhibited after treatment with Tyrphostin B42 (AG 490). In conclusion, we found that Lys inhibits apoptosis in SCs to govern skeletal muscle growth via the JAK2-STAT3 pathway.

mTORC1-Mediated Satellite Cell Differentiation Is Required for Lysine-Induced Skeletal Muscle Growth.

Skeletal muscle is the primary source of protein for humans. However, the mechanisms of skeletal muscle growth, such as nutrition control, remain unknown. Moreover, the function of lysine (Lys) in controling skeletal muscle growth has gradually demonstrated that Lys is not only substantial for protein synthesis but also a signaling molecule for satellite cell (SC) activation. In the current work, the number of differentiated SCs in the longissimus thoracis muscle and the fusion index of SCs were both governed by Lys supplementation. Meanwhile, the myogenic regulatory factors and the mammalian target of rapamycin complex 1 (mTORC1) pathway showed the same tendencies of changes as the differentiation of SCs. After Lys was resupplemented with rapamycin, the mTORC1 pathway was inhibited and the differentiation ability of SCs was suppressed. Collectively, the results showed that the mTORC1-pathway-mediated SC differentiation was required for Lys-promoted skeletal muscle growth.

Effects of copper hydroxychloride on growth performance and abundance of genes involved in lipid metabolism of growing pigs.

An experiment was conducted to test the hypothesis that copper (Cu) hydroxychloride improves growth performance by upregulating the mRNA transcription of genes involved in lipid metabolism of pigs fed a diet based on corn, soybean meal (SBM), and distillers dried grains with solubles (DDGS). Thirty-two pigs (15.05 ± 0.98 kg) were allotted to 2 dietary treatments with 2 pigs per pen for a total of 8 replicate pens per treatment. Pigs were fed a corn-SBM-DDGS control diet that included Cu to meet the requirement. A second diet was formulated by adding 150 mg Cu/kg from copper hydroxychloride to the control diet. On the last day of the experiment, one pig per pen was sacrificed, and samples from liver, skeletal muscle, and subcutaneous adipose tissue were collected to analyze relative mRNA abundance of genes involved in lipid metabolism. Results indicated that overall ADG and G:F were greater (P < 0.05) for pigs fed the diet containing copper hydroxychloride compared with pigs fed the control diet. Pigs fed the diet supplemented with copper hydroxychloride also had increased (P < 0.05) abundance of cluster of differentiation 36 in the liver and increased (P < 0.05) abundance of fatty acid-binding protein 4 and lipoprotein lipase in subcutaneous adipose tissue. Inclusion of copper hydroxychloride also tended to increase (P < 0.10) the abundance of fatty acid-binding protein 1, peroxisome proliferator-activated receptor α, and carnitine palmitoyltransferase 1B in the liver, skeletal muscle, and subcutaneous adipose tissue, respectively. This indicates that dietary Cu may affect signaling pathways associated with lipid metabolism by improving the uptake, transport, and utilization of fatty acids. In conclusion, supplementation of copper hydroxychloride to the control diet improved growth performance and upregulated the abundance of some genes involved in postabsorptive metabolism of lipids.

Variable impacts of L-arginine or L-NAME during early life on molecular and cellular markers of muscle growth mechanisms in rainbow trout.

Two experiments were conducted to test if manipulations of the Arginine-Nitric oxide pathway during the early life of rainbow trout would act on its early myogenic process. In experiment 1, trout embryos were immersed at 72° days post-fertilization (°dpf) or 104°dpf in water alone (control treatment, C) or containing 2 mM/L L-Arg (treatment A) or 1 mM/L of L-NAME, a NOS inhibitor (treatment N). We observed the beginning of expression of myf5 and fmhc genes at 72°dpf and 96°dpf, respectively. "A" treatment doubled the free Arg content of eggs but did not affect either the pattern of expression of myf5 and fmhc, nor white muscle cross-sectional area and number of white muscle fibres at hatching, nor embryo survival and fry growth. "N" treatment also did not affect these markers. In experiment 2, trout fry were fed from first feeding onwards and during 20 days either a control diet (C) or the same diet supplemented with L-NAME (0.1 g/100 g diet, N-diet). In C-fed fry, distribution of a single meal after overnight fasting induced changes in pcna, myod1, myog, fmhc, inos, nnos and ctsd gene expressions. N-feeding decreased fry growth but did not change their growth trajectory or survival. Twenty days of N-feeding led, compared to C-feeding, to changes in kinetics of transcription of pcna, myod1, myog, fmhc, inos, nnos, ctsd genes and to decreased white muscle cross-sectional area, total number of white muscle fibres, and number of large muscle fibres. L-NAME feeding thus decreased fry muscle growth by altering both hyperplasia and hypertrophy.

Dietary supplementation with pioglitazone hydrochloride improves intramuscular fat, fatty acid profile, and antioxidant ability of thigh muscle in yellow-feathered chickens.

BACKGROUND: Muscle fat content and fatty acid composition play an important role in poultry flavor and taste. To investigate the effects of pioglitazone hydrochloride (PGZ) on growth performance and thigh muscle quality in yellow-feathered chickens, 360 female chickens were randomly divided into three groups and treated with three doses of PGZ (0, 7.5, and 15 mg kg-1 ) for 28 days. Each group had six replicates of 20 chickens. RESULTS: The results showed that dietary supplementation with 15 mg kg-1 PGZ increased average daily feed intake (ADFI) and the average daily gain (ADG) from 0 to 14 days. Furthermore, the triglyceride (TG) level was decreased by 15 mg kg-1 PGZ, whereas the eviscerated yield was increased. The relative weight of the heart and kidneys showed a linear increase with dietary PGZ supplementation, and the drip loss of the thigh muscle was significantly decreased by 15 mg kg-1 PGZ supplementation. Moreover, a* value, intramuscular fat (IMF), and polyunsaturated fatty acids (PUFAs) showed a linear increase, and pH24 h and drip loss showed a quadratic influence with the levels of PGZ supplementation. In particular, the PUFA proportion was increased by 7.63% and 9.14% in the 7.5 mg kg-1 PGZ and 15 mg kg-1 PGZ groups, respectively. Additionally, 15 mg kg-1 of PGZ increased the total antioxidant capacity (T-AOC) and glutathione peroxidase (GSH-PX ) activity. CONCLUSION: In summary, 15 mg kg-1 PGZ has substantial effects on growth performance and meat quality, particularly by decreasing drip loss and increasing IMF content, PUFA proportions, and antioxidant ability. © 2019 Society of Chemical Industry.

mTORC1 Mediates Lysine-Induced Satellite Cell Activation to Promote Skeletal Muscle Growth.

As the first limiting amino acid, lysine (Lys) has been thought to promote muscle fiber hypertrophy by increasing protein synthesis. However, the functions of Lys seem far more complex than that. Despite the fact that satellite cells (SCs) play an important role in skeletal muscle growth, the communication between Lys and SCs remains unclear. In this study, we investigated whether SCs participate directly in Lys-induced skeletal muscle growth and whether the mammalian target of rapamycin complex 1 (mTORC1) pathway was activated both in vivo and in vitro to mediate SC functions in response to Lys supplementation. Subsequently, the skeletal muscle growth of piglets was controlled by dietary Lys supplementation. Isobaric tag for relative and absolute quantitation (iTRAQ) analysis showed activated SCs were required for longissimus dorsi muscle growth, and this effect was accompanied by mTORC1 pathway upregulation. Furthermore, SC proliferation was governed by medium Lys concentrations, and the mTORC1 pathway was significantly enhanced in vitro. After verifying that rapamycin inhibits the mTORC1 pathway and suppresses SC proliferation, we conclude that Lys is not only a molecular building block for protein synthesis but also a signal that activates SCs to manipulate muscle growth via the mTORC1 pathway.

Effects of maternal dietary supplementation of phytosterol esters during gestation on muscle development of offspring in mice.

The development of muscle in the embryo, which is crucial for postnatal skeletal muscle growth, has been investigated widely. Much has been learned during the past several decades about the role of maternal nutrition in the outcome of pregnancy. Protein and carbohydrate levels during pregnancy have been shown to be important in the development of offspring, especially muscle development. However, the maternal effects of steroids were still not clear. Phytosterol esters (PEs) are produced by the esterification of phytosterols and fatty acids and have many beneficial functions, such as anti-inflammation and hypolipemic functions. Through the effect of regulation on lipid metabolism, can pregnant mice fed with PEs show any programming effect on the muscle development of offspring? In our study, PEs were supplied to the maternal diet, and changes in maternal lipid metabolism and the development of offspring skeletal muscle were detected. As a result, the amniotic fluid total bile acid (TBA) and total cholesterol (TC) levels were decreased; the growth of offspring was significantly faster than that of the control group until 6 weeks of age. Adult offspring had a higher lean mass index and grip strength. In skeletal muscle, the proportion of myosin heavy chain (MHC) 1 was significantly decreased, while the proportion of MHC 2 b was increased. In conclusion, maternal PEs significantly reduced sterols in the amniotic fluid, while skeletal muscle development was promoted in the offspring.