Dietary Supplementation with Lauric Acid Improves Aerobic Endurance in Sedentary Mice via Enhancing Fat Mobilization and Glyconeogenesis.

BACKGROUND: Lauric acid (LA), a major, natural, medium-chain fatty acid, is considered an efficient energy substrate for intense exercise and in patients with long-chain fatty acid ß-oxidation disorders. However, few studies have focused on the role of LA in exercise performance and related glucolipid metabolism in vivo. OBJECTIVES: We aimed to investigate the effect of dietary supplementation with LA on exercise performance and related metabolic mechanisms. METHODS: Male C57BL/6N mice (14 wk old) were fed a basal diet or a diet containing 1% LA, and a series of exercise tests, including a high-speed treadmill test, aerobic endurance exercises, a 4-limb hanging test, and acute aerobic exercises, were performed. RESULTS: Dietary supplementation with 1.0% LA accelerated the recovery from fatigue after explosive exercise (P < 0.05) and improved aerobic endurance and muscle strength in sedentary mice (P = 0.039). Lauric acid intake not only changed muscle fatty acid profiles, including increases in C12:0 and n-6/n-3 PUFAs (P < 0.001) and reductions in C18:0, C20:4n-6, C22:6n-3, and n-3 PUFAs (P < 0.05) but also enhanced fat mobilization from adipose tissue and fatty acid oxidation in the liver, at least partly via the AMP-activated protein kinase-acetyl CoA carboxylase pathway (P < 0.05). Likewise, LA supplementation promoted liver glyconeogenesis and conserved muscular glycogen during acute aerobic exercise (P < 0.05), which was accompanied by an increase in the mitochondrial DNA copy number and Krebs cycle activity in skeletal muscle (P < 0.05). CONCLUSIONS: Dietary supplemental LA serves as an efficient energy substrate for sedentary mice to improve aerobic exercise endurance and muscle strength through regulation of glucolipid metabolism. These findings imply that LA supplementation might be a promising nutritional strategy to improve aerobic exercise performance in sedentary people.

Maternal transfer of florfenicol impacts development and disrupts metabolic pathways in F1 offspring zebrafish by destroying mitochondria.

Maternal exposure to antibiotics existing in the environment is a predisposing factor for developmental malformation with metabolic disorders in offspring. In this study, female zebrafish (3 months) were exposed to 0.05 mg/L and 0.5 mg/L florfenicol (FF) for 28 days. After pairing and spawning with healthy male fish, F1 embryos were collected and developed to 5 d post-fertilization (dpf) in clear water. And the adverse effects on the F1 generation were examined thoroughly. The fecundity of F0 female fish and the hatchability, mortality, and body length of F1 larvae significantly decreased in the treatment group. Meanwhile, multi-malformation types were found in the exposure group, including delayed yolk sac absorption, lack of swim bladder, and spinal curvature. Metabolomic and transcriptomic results revealed alterations in metabolism with dysregulation in tricarboxylase acid cycle, amino acid metabolism, and disordered lipid metabolism with elevated levels of glycerophospholipid and sphingolipid. Accompanying these metabolic derangements, decreased levels of ATP and disordered oxidative-redox state were observed. These results were consistent with the damaged mitochondrial membrane potential and respiratory chain function, suggesting that the developmental toxicity and perturbed metabolic signaling in the F1 generation were related to the mitochondrial injury after exposing F0 female zebrafish to FF. Our findings highlighted the potential toxicity of FF to offspring generations even though they were not directly exposed to environmental contaminants.

Effect of iron and phosphorus on the microalgae growth in co-culture.

Iron and phosphorus (P) are the important micro- and macro-nutrient for microalgae growth, respectively. However, the effect of iron and P on microalgae growth in co-culture associating with the formation of dominate algae has not been investigated before. In the current study, Anabaene flos-aquae, Chlorella vulgaris and Melosira sp. were co-cultivated under the addition of different initial iron and P to reveal the effect of iron and phosphorus on the growth of microalgae. The results showed that the mean growth rate of A. flos-aquae, C. vulgaris and Melosira was 0.270, 0.261 and 0.062, respectively, indicating that the A. flos-aquae and C. vulgaris algae are liable to be the dominant algae while the growth of Melosira was restrained when co-cultured. The ratio of Fe to P has a significant impact on the growth of microalgae and could be regarded as an indicator of algae growth. Microalgae showed a much more obvious uptake of iron compared to that of P. The information obtained in the current study was useful for the forecast of water quality and the control of microalgae bloom.

[Prevalence and the relevant factors of type 2 diabetes mellitus among adults in Guizhou Province in 2010-2012].

OBJECTIVE: To investigate the prevalence and relevant factors of type 2 diabetes mellitus among urban and rural residents over 18 years old in Guizhou Province in 2010-2012. METHODS: A total of 3073 residents over 18 years old were sampled by multi-stage and stratified random cluster sampling in Guizhou Province from"2010-2012 Chinese nutrition and health surveillance", including 1576 people in urban areas and 1497 people in rural areas, 1362 males and 1711 females. The participants were investigated for their basic conditions, lifestyle and behavior, and physical indicators, blood pressure, blood glucose, TC, and TG were also measured, and then the prevalence was calculated. Multivariate analysis was performed using an unconditional logistic regression model. RESULTS: Among the 3073 residents aged 18 years and over in Guizhou Province, 151 were diagnosed with type 2 diabetes mellitus, with a prevalence of4. 9%, among which 80 were urban residents and 71 were rural residents, with a prevalence of 5. 1% and 4. 7%, respectively. There was no statistically significant difference between urban and rural areas( χ~2= 0. 183, P = 0. 669). Age was associated with type 2 diabetes mellitus, and the prevalence increased with age( χ_()~2= 55. 478, P =0. 001). The result of multivariate Logistic regression analysis showed that family history, abdominal obesity, hypertension, abnormal TC and abnormal TG all had statistically significant influences on the prevalence of type 2 diabetes mellitus( OR values were2. 377, 1. 721, 1. 666, 1. 619 and 1. 982, respectively, all P <0. 05). CONCLUSION: The prevalence of type 2 diabetes mellitus in residents aged 18 and over in Guizhou Province was lower than the national average level. The prevention of type 2 diabetes in Guizhou residents should be targeted at middle-aged and elderly people, people with family history, people with abdominal obesity, people with hypertension and dyslipidemia.

Effect of limitation of iron and manganese on microalgae growth in fresh water.

Eutrophication is caused by the rapid growth of microalgae. Iron and manganese are important micronutrients for microalgae growth. However, the effect of the limitation of iron and manganese on microalgae growth in fresh water has not been well understood. In this study, natural mixed algae, Anabaena flosaquae and Scenedesmus quadricanda, were cultivated under different quotas of iron and manganese to reveal the effect of the limitation of iron and manganese on the growth of microalgae in fresh water. The results showed that the growth rate of algae is influenced more by iron than by manganese. However, the effect of manganese cannot be overlooked: when the initial manganese quota was replete, i.e. 0.6-0.8 mg l-1, manganese was able to relieve the effect of iron limitation on microalgae growth in fresh water. We further found that the microalgae showed an uptake preference for iron over manganese. Iron had a competitive effect on manganese uptake, while manganese had less impact on iron uptake by microalgae. The information obtained in the current study is useful for the provision of water quality warnings and for the control of microalgae bloom in fresh water.

Recurrence and metastasis of pseudomyxoma peritonei: A rare case report.

Pseudomyxoma peritonei (PMP) is a relatively uncommon condition primarily associated with neoplasms of the appendiceal epithelium. It is characterized by non-specific clinical manifestations, leading to a high rate of misdiagnosis. This report describes the case of a 62-year-old male patient with recurrent and metastatic PMP. The patient first experienced unexplained epigastric pain and paroxysmal abdominal pain accompanied by distension over 8 years ago. He underwent surgical interventions for the condition in other hospitals in 2015 and 2018, respectively.

Synergistic developmental effects of zebrafish exposed to combined perfluorooctanoic acid and atrazine.

Perfluorooctanoic acid (PFOA) and atrazine are two endocrine disruptors that are widely found in waters. Negative effects of PFOA and atrazine have been studied individually, but few data have focused on their combined effects. Here, zebrafish embryos were used as model to investigate the combined toxicity of PFOA and atrazine. The acute toxicity of atrazine (11.9 mg/L) to zebrafish embryos was much higher than that of perfluorooctanoic acid (224.6 mg/L) as shown by the 120h-LC50 value. Developmental effects, including delayed yolk sac absorption, spinal curvature, and liver abnormalities, were observed in both one- and two-component exposures. Notably, the rate of embryonic malformations in the co-exposure group was more than twice as high as that of single component exposure in the concentration range of 1/8-1/2 EC50, which indicated a synergistic effect of the binary mixture. The synergistic effect of PFOA-atrazine was further validated by combinatorial index (CI) modeling. In addition, changes of amino acid metabolites, reactive oxygen species and superoxide dismutase indicated that oxidative stress might be the main pathway for enhanced toxicity under co-exposure condition. Overall, co-exposure of PFOA and atrazine resulted in stronger developmental effects and more complicated amino acid metabolic response toward zebrafish, compared with single component exposure.

Carcass and meat quality traits and their relationships in Duroc × Landrace × Yorkshire barrows slaughtered at various seasons.

To understand characteristics of carcass traits and meat quality in pig population, 22 indicators of carcass characteristics and meat quality traits were measured on 278 Duroc × Landrace × Yorkshire barrows that were slaughtered in different seasons (spring, summer, autumn and winter). The effects of body weight and season on carcass characteristics and meat quality were analyzed by GLM procedure, followed the Bonferroni multiple test. The phenotypic correlations among those traits were calculated by employing the CORR procedure. In addition, the linear regression equations were constructed by stepwise regression model in REG procedure. The results showed that pigs slaughtered in spring had the heaviest body weight among the four seasons (P < 0.05), pigs slaughtered in summer had the lowest backfat depth and shear force (P < 0.05), and pigs slaughtered in winter had the lowest drip loss (P < 0.05). The results showed more variation in backfat depth, drip loss, intramuscular fat content, and shear force, compared with other indicators across pigs. Body weight had a significant association with loin eye area, average backfat depth and L⁎24 h (P < 0.05). Furthermore, regression equations for drip loss, cooking loss, shear force, and intramuscular fat content were constructed using more accessible indicators. Collectively, this study provided an overall view of carcass and meat quality traits in a commercial pig population in China, and illustrated that season significantly affected carcass characteristics and meat quality traits independently of body weight.

Maternal consumption of l-malic acid enriched diets improves antioxidant capacity and glucose metabolism in offspring by regulating the gut microbiota.

Maternal diets during pregnancy and lactation are key determinants that regulate the development of metabolic syndrome (MetS) in offspring. l-malic acid (MA) was previously reported to improve antioxidant capacity and aerobic metabolism. However, the effects of maternal MA consumption on the metabolic features of offspring remain largely unexplored. Herein, through pig models consuming MA-enriched diets during late pregnancy and lactation, we found that maternal MA consumption potentiated the anti-inflammatory and antioxidant capacity of sows, thereby improving their reproductive performance and the growth performance of piglets. Maternal MA consumption also induced a transition of slow-twitch to fast-twitch fibers in the early life of offspring. Along with muscle growth and fiber-type transition, insulin sensitivity and glucose metabolism, including aerobic metabolism and glycolysis, were improved in the skeletal muscle of offspring. An untargeted metabolomic analysis further revealed the contribution of modified amino acid metabolism to the improved aerobic metabolism. Mechanistically, maternal MA consumption remodeled colonic microbiota of their offspring. Briefly, the abundance of Colidextribacter, Romboutsia, and Family_XIII_AD3011_group increased, which were positively associated with the antioxidant capacity and glucose metabolism of skeletal muscles. A decreased abundance of Prevotella, Blautia, Prevotellaceae_NK3B31_group, and Collinsella was also detected, which were involved in less insulin sensitivity. Notably, milk metabolites, such as ascorbic acid (AA) and granisetron (GS), were found as key effectors regulating the gut microbiota composition of piglets. The properties of AA and GS in alleviating insulin resistance, inflammation, and oxidative stress were further verified through mice treated with high-fat diets. Overall, this study revealed that maternal MA consumption could modulate the inflammatory response, antioxidant capacity, and glucose metabolism by regulating the gut microbiota of offspring through the vertical transmission of milk metabolites. These findings suggest the potential of MA in the prevention and treatment of MetS in early life.

Dietary supplementation of laminarin improves the reproductive performance of sows and the growth of suckling piglets.

BACKGROUND: Maternal nutrition is essential in keeping a highly efficient production system in the pig industry. Laminarin has been shown to improve antioxidant capacity, reduce the inflammatory response, and favor the homeostasis of intestinal microbiota. However, the effect of dietary supplementation of laminarin on the reproductive performance of sows and the growth of suckling offspring remains unknown. METHODS: A total of 40 Landrace × Yorkshire multiparous sows on d 85 of gestation, similar in age, body weight (BW), parity and reproductive performance, were randomly divided into four dietary treatments with 10 sows per treatment, receiving a control diet (basal pregnancy or lactating diets) and a basal diet supplemented with 0.025%, 0.05% and 0.10% laminarin, respectively. The experiment lasted from d 85 of gestation to d 21 of lactation. RESULTS: Laminarin supplementation linearly increased number born alive per litter (P = 0.03), average daily feed intake (ADFI, P < 0.01), and total milk yield of sows during the lactation of 1-21 d (P = 0.02). Furthermore, maternal laminarin supplementation increased the average daily gain (ADG) of piglets while tending to reduce the culling and death rate before weaning. In addition, alterations to the composition of colostrum and milk, as well as to serum inflammatory cytokines and immunoglobulins of sows were observed. The fecal microbiota profile of sows supported the improvement of reproductive performance in sows and the growth performance in suckling offspring. CONCLUSIONS: Dietary supplementation of laminarin during late pregnancy and lactation could significantly improve reproductive performance of sows and growth performance of piglets.

Multi-omics analysis of a drug-induced model of bipolar disorder in zebrafish.

Emerging studies demonstrate that inflammation plays a crucial role in the pathogenesis of bipolar disorder (BD), but the underlying mechanism remains largely unclear. Given the complexity of BD pathogenesis, we performed high-throughput multi-omic profiling (metabolomics, lipidomics, and transcriptomics) of the BD zebrafish brain to comprehensively unravel the molecular mechanism. Our research proved that in BD zebrafish, JNK-mediated neuroinflammation altered metabolic pathways involved in neurotransmission. On one hand, disturbed metabolism of tryptophan and tyrosine limited the participation of the monoamine neurotransmitters serotonin and dopamine in synaptic vesicle recycling. On the other hand, dysregulated metabolism of the membrane lipids sphingomyelin and glycerophospholipids altered the synaptic membrane structure and neurotransmitter receptors (chrnα7, htr1b, drd5b, and gabra1) activity. Our findings revealed that disturbance of serotonergic and dopaminergic synaptic transmission mediated by the JNK inflammatory cascade was the key pathogenic mechanism in a zebrafish model of BD, provides critical biological insights into the pathogenesis of BD.

Lack of adipocyte IP3R1 reduces diet-induced obesity and greatly improves whole-body glucose homeostasis.

The normal function of skeletal muscle and adipose tissue ensures whole-body glucose homeostasis. Ca2+ release channel inositol 1,4,5-trisphosphate receptor 1 (IP3R1) plays a vital role in regulating diet-induced obesity and disorders, but its functions in peripheral tissue regulating glucose homeostasis remain unexplored. In this study, mice with Ip3r1 specific knockout in skeletal muscle or adipocytes were used for investigating the mediatory role of IP3R1 on whole-body glucose homeostasis under normal or high-fat diet. We reported that IP3R1 expression levels were increased in the white adipose tissue and skeletal muscle of diet-induced obese mice. Ip3r1 knockout in skeletal muscle improved glucose tolerance and insulin sensitivity of mice on a normal chow diet, but worsened insulin resistance in diet-induced obese mice. These changes were associated with the reduced muscle weight and compromised Akt signaling activation. Importantly, Ip3r1 deletion in adipocytes protected mice from diet-induced obesity and glucose intolerance, mainly due to the enhanced lipolysis and AMPK signaling pathway in the visceral fat. In conclusion, our study demonstrates that IP3R1 in skeletal muscle and adipocytes exerts divergent effects on systemic glucose homeostasis, and characterizes adipocyte IP3R1 as a promising target for treating obesity and type 2 diabetes.

Ryanodine receptor RyR1-mediated elevation of Ca2+ concentration is required for the late stage of myogenic differentiation and fusion.

BACKGROUND: Cytosolic Ca2+ plays vital roles in myogenesis and muscle development. As a major Ca2+ release channel of endoplasmic reticulum (ER), ryanodine receptor 1 (RyR1) key mutations are main causes of severe congenital myopathies. The role of RyR1 in myogenic differentiation has attracted intense research interest but remains unclear. RESULTS: In the present study, both RyR1-knockdown myoblasts and CRISPR/Cas9-based RyR1-knockout myoblasts were employed to explore the role of RyR1 in myogenic differentiation, myotube formation as well as the potential mechanism of RyR1-related myopathies. We observed that RyR1 expression was dramatically increased during the late stage of myogenic differentiation, accompanied by significantly elevated cytoplasmic Ca2+ concentration. Inhibition of RyR1 by siRNA-mediated knockdown or chemical inhibitor, dantrolene, significantly reduced cytosolic Ca2+ and blocked multinucleated myotube formation. The elevation of cytoplasmic Ca2+ concentration can effectively relieve myogenic differentiation stagnation by RyR1 inhibition, demonstrating that RyR1 modulates myogenic differentiation via regulation of Ca2+ release channel. However, RyR1-knockout-induced Ca2+ leakage led to the severe ER stress and excessive unfolded protein response, and drove myoblasts into apoptosis. CONCLUSIONS: Therefore, we concluded that Ca2+ release mediated by dramatic increase in RyR1 expression is required for the late stage of myogenic differentiation and fusion. This study contributes to a novel understanding of the role of RyR1 in myogenic differentiation and related congenital myopathies, and provides a potential target for regulation of muscle characteristics and meat quality.

Identifying a novel serum microRNA biomarker panel for the diagnosis of childhood asthma.

The pathological mechanism of childhood asthma is complex, and timely diagnosis is the key to effective prevention and control of childhood asthma. We collected 170 serum samples from 95 children with asthma and 75 healthy children. Serum miRNA biomarkers were analyzed by Illumina sequencing for childhood asthma. Differentially serum miRNAs were confirmed with quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay. The Illumina sequencing data showed the differential expression of 111 serum miRNAs among asthmatic and healthy children. After confirmation of miRNAs expression through qRT-PCR, four of them (namely hsa-miR-106a-5p, hsa-miR-18a-5p, hsa-miR-144-3p, and hsa-miR-375) manifested significant differential expression between asthmatic children and healthy controls. The biomarkers classification tree model created with these four miRNAs using the Biomarker Patterns Software could effectively separate childhood asthma and healthy children, with a specificity of 88.3%, a sensitivity of 95.0%, and an area under the curve (AUC) value of 0.942. The regulatory networks containing miRNAs and their gene targets suggested that the four miRNAs might have gene targets implicated in inflammation, immunity, and transcriptional efficiency. Taken together, this four-serum-miRNA panel is a promising biomarker to diagnose childhood asthma noninvasively.

Effects of Dietary Yeast ß-Glucan Supplementation on Meat Quality, Antioxidant Capacity and Gut Microbiota of Finishing Pigs.

Yeast ß-glucan is a natural antioxidant and has been reported to improve growth performance of piglets, but its application in improving pork quality is limited. This study investigated the effects of dietary yeast ß-glucan supplementation on meat quality, antioxidant capacity and gut microbiota of finishing pigs. In a 40-day experiment, ninety finishing pigs (Duroc × Landrace × Yorkshire, 70.47 ± 0.04 kg) were randomly allocated into five treatments including a basal diet supplemented with 0, 50, 100, 200 and 400 mg/kg yeast ß-glucan. Results showed that yeast ß-glucan significantly increased pH45 min (linear and quadratic, p < 0.01) and a*45 min (linear, p < 0.05), and reduced cooking loss (linear, p < 0.05) and drip loss (quadratic, p < 0.05) of meat in finishing pigs. Importantly, the 200 mg/kg group exhibited the highest values of pH45 min (p < 0.01) and the lowest values of drip loss (p < 0.05), accompanied by a decreased lactate content (p < 0.05) and glycolytic potential (p < 0.05). Dietary supplementation of 200 mg/kg yeast ß-glucan markedly increased catalase (CAT) (p < 0.05), superoxide dismutase (SOD) (p < 0.05) and total antioxidant capacity (T-AOC) (p < 0.01) activities in skeletal muscle. Moreover, WPS-2 abundance was decreased significantly in colonic digesta by 200 mg/kg yeast ß-glucan and exhibited a positive association with muscle lactate content and drip loss. Together, dietary 200 mg/kg yeast ß-glucan supplementation effectively improved pH value and the water-holding capacity of fresh meat through reducing muscle postmortem glycolysis, increasing antioxidant capacity and altering the gut microbiota composition of finishing pigs.

Effects of Dietary L-malic Acid Supplementation on Meat Quality, Antioxidant Capacity and Muscle Fiber Characteristics of Finishing Pigs.

L-malic acid is a vital intermediate in the citric acid cycle and has been reported to improve the antioxidant capacity and aerobic oxidation of weaned piglets; however, its application in finishing pigs is limited at present. This study explored the effects of dietary L-malic acid supplementation on the carcass traits and meat quality of finishing pigs. In a 45-day experiment, 192 Duroc × Landrace × Yorkshire pigs (75.01 ± 0.51 kg) were divided into four treatments, i.e., a basal diet supplemented with 0, 0.5%, 1%, and 2% L-malic acid complex. The results showed that L-malic acid supplementation had no effects on the growth performance of finishing pigs. Importantly, L-malic acid significantly increased redness (a*) value at 24-h postmortem (quadratic, p < 0.05) and tended to increase the proportion of oxymyoglobin (OMb) (quadratic, p = 0.10), as well as the total antioxidant capacity (T-AOC) activity (quadratic, p = 0.08) in the longissimus dorsi (LD) muscle. Further, dietary supplementation of 1% L-malic acid markedly increased the protein expression level of slow skeletal myosin heavy chain (MyHC) in the LD muscle (p < 0.05). Moreover, 0.5% and 2% L-malic acid supplementation significantly increased carcass length and loin eye area (p < 0.05). In conclusion, dietary L-malic acid could effectively improve the meat color and carcass traits of finishing pigs.

Dietary guanidinoacetic acid supplementation improves water holding capacity and lowers free amino acid concentration of fresh meat in finishing pigs fed with various dietary protein levels.

The current study was carried out to detect the effect of dietary guanidinoacetic acid (GAA) supplementation on carcass characteristics and meat quality in finishing pigs fed different dietary crude protein (CP) levels. Sixty-four barrows with an initial body weight of 73.05 ± 2.34 kg were randomly allocated into 1 of 4 dietary treatments in a 2 (100% vs. 125% NRC CP level) × 2 (0 vs. 300 mg/kg GAA) factorial arrangement (n = 7). The feeding trial lasted for 49 d. GAA supplementation significantly reduced drip loss (P = 0.01), free water distribution (T 23 peak area ratio) (P = 0.05) and the concentrations of free alanine, threonine, methionine and isoleucine (P < 0.05); but increased total glycine content (P = 0.03) in the longissimus dorsi muscle of finishing pigs regardless of the dietary CP levels. Furthermore, primary myogenic cell differentiation system was employed to investigate the influence of inclusion of GAA on free amino acid concentrations in myotubes (n = 4) and validate the finding in the animal feeding trial. We found that GAA inclusion in culture medium also decreased intracellular concentrations of free alanine, threonine, methionine, isoleucine, valine and proline in differentiated primary myogenic cells in vitro (P < 0.05). Meanwhile, relative to diets with 100% NRC CP level, the intake of diets with 125% NRC CP level improved sarcoplasmic protein solubility, increased the contents of carnosine and total free amino acids as well as flavor amino acids in the longissimus dorsi muscle and decreased backfat thickness at the 6-7th ribs in pigs (P < 0.05). In addition, we observed that the impact of dietary GAA supplementation on the last rib fat thickness, shear force, and free lysine content in the longissimus dorsi muscle was dependent on dietary CP levels (P < 0.05). Collectively, dietary GAA supplementation can reduce drip loss, decrease the concentrations of free amino acids and flavor amino acids of fresh meat independent of dietary CP levels.

Dietary Valine/Isoleucine Ratio Impact Carcass Characteristics, Meat Edible Quality and Nutritional Values in Finishing Crossbred Duroc × Landrace × Yorkshire Pigs With Different Slaughter Weights.

The aim of this study was to investigate effects of dietary ratio of valine to isoleucine [R(V/I)] on carcass characteristics and meat quality of finishing pigs and whether slaughter weight influence the effect. We carried out a 2 × 3 factorial trial with two slaughter weight (105 vs. 130 kg) and three R(V/I) (0.58, 1.23, and 2.60 at 75-100 kg body weight, and 0.70, 1.24, and 2.39 at 100-135 kg body weight for L-, N- and H-R (V/I), respectively). Data show that increasing slaughter weight significantly increased meat color (a*45 min and b*45 min), drip loss and shear force (P < 0.05). Meanwhile, increasing slaughter weight reduced sarcomere length, the proportion of protein-bound water, and most kinds of muscular total amino acid contents except for tryptophan and arginine, while increased contents of muscular free lysine, tryptophan, leucine, isoleucine, valine, alanine, and arginine in the M. longissimus thoracis (P < 0.05). Health lipid indices based on fatty acid composition of intramuscular lipid were improved as the slaughter weight increased (P < 0.05). Notably, pigs received N-R (V/I) diet improved carcass traits in terms of thinner backfat thickness and higher fat-free lean index, as well as increased meat flavor-contributing amino acids at the cost of reduced intramuscular fat content and increased shear force of cooked meat compared with the pigs fed L-R (V/I) and H-R(V/I) diets (P < 0.05). H-R (V/I) diet decreased ultimate pH value and sarcomere length of the skeletal muscle but increased the proportion of free water (T 23), consequently, increased drip loss and cooking loss of fresh meat in pigs (P < 0.05). In conclusion, both slaughter weight and dietary ratio of valine to isoleucine exerted significant impacts on carcass characteristics, meat quality and nutrition values. In particular, carcass traits and meat color of lighter pigs were more susceptible to the influence of dietary R (V/I) relative to heavier pigs.

Arginine promotes myogenic differentiation and myotube formation through the elevation of cytoplasmic calcium concentration.

This study aimed to explore the mechanism underlying arginine-promoted myogenesis of myoblasts. C2C12 cells were cultured with a medium containing 0.1, 0.4, 0.8, or 1.2 mmol/L arginine, respectively. Cell proliferation, viability, differentiation indexes, cytoplasmic Ca2+ concentration, and relative mRNA expression levels of myogenic regulatory factors (MRF) and key Ca2+ channels were measured in the absence or presence of 2 chemical inhibitors, dantrolene (DAN, 10 µmol/L) and nisoldipine (NIS, 10 µmol/L), respectively. Results demonstrated that arginine promoted myogenic differentiation and myotube formation. Compared with the control (0.4 mmol/L arginine), 1.2 mmol/L arginine upregulated the relative mRNA expression levels of myogenin (MyoG) and Myomaker at d 2 during myogenic induction (P < 0.05). Cytoplasmic Ca2+ concentrations were significantly elevated by arginine supplementation at d 2 and 4 (P < 0.05). Relative mRNA expression levels of Ca2+ channels including the type 1 ryanodine receptor (RyR1) and voltage-gated Ca2+ channel (Cav1.1) were upregulated by 1.2 mmol/L arginine during 2-d myogenic induction (P < 0.01). However, arginine-promoted myogenic potential of myoblasts was remarkably compromised by DAN and NIS, respectively (P < 0.05). These findings evidenced that the supplementation of arginine promoted myogenic differentiation and myotube formation through increasing cytoplasmic Ca2+ concentration from both extracellular and sarcoplasmic reticulum Ca2+.

Impacts of Selected Dietary Nutrient Intakes on Skeletal Muscle Insulin Sensitivity and Applications to Early Prevention of Type 2 Diabetes.

As the largest tissue in the body, skeletal muscle not only plays key roles in movement and glucose uptake and utilization but also mediates insulin sensitivity in the body by myokines. Insulin resistance in the skeletal muscle is a major feature of type 2 diabetes (T2D). A weakened response to insulin could lead to muscle mass loss and dysfunction. Increasing evidence in skeletal muscle cells, rodents, nonhuman primates, and humans has shown that restriction of caloric or protein intake positively mediates insulin sensitivity. Restriction of essential or nonessential amino acids was reported to facilitate glucose utilization and regulate protein turnover in skeletal muscle under certain conditions. Furthermore, some minerals, such as zinc, chromium, vitamins, and some natural phytochemicals such as curcumin, resveratrol, berberine, astragalus polysaccharide, emodin, and genistein, have been shown recently to protect skeletal muscle cells, mice, or humans with or without diabetes from insulin resistance. In this review, we discuss the roles of nutritional interventions in the regulation of skeletal muscle insulin sensitivity. A comprehensive understanding of the nutritional regulation of insulin signaling would contribute to the development of tools and treatment programs for improving skeletal muscle health and for preventing T2D.