Gene expression pattern of glucose transporters in the skeletal muscles of newly hatched chicks

Intracellular Calcium Overload and Activation of CaMKK/AMPK Signaling Are Related to the Acceleration of Muscle Glycolysis of Broiler Chickens Subjected to Acute Stress

The current study investigated the effect of preslaughter transport on stress response and meat quality of broilers and explored the underlying mechanisms involved in the regulation of muscle glycolysis through calcium/calmodulin-dependent protein kinase kinase (CaMKK)/AMP-activated protein kinase (AMPK) signaling. Results suggested that transport induced stress responses of broilers and caused PSE-like syndrome of pectoralis major muscle. Preslaughter transport enhanced the mRNA expressions of glycogen phosphorylase and glucose transporters, as well as the activities of glycolytic enzymes, which accelerated the breakdown of glycolytic substrates and the accumulation of lactic acid. In addition, acute stress induced abnormal intracellular calcium homeostasis by disrupting calcium channels on the cell membrane and sarcoplasmic reticulum, which led to the activation of CaMKK and promoted AMPK phosphorylation. This study provides evidence that the intracellular calcium overload and the enhancement of CaMKK/AMPK signaling are related to the accelerated muscle glycolysis of broiler chickens subjected to acute stress.

Revisiting glucose regulation in birds - A negative model of diabetes complications

Birds naturally have blood glucose concentrations that are nearly double levels measured for mammals of similar body size and studies have shown that birds are resistant to insulin-mediated glucose uptake into tissues. While a combination of high blood glucose and insulin resistance is associated with diabetes-related pathologies in mammals, birds do not develop such complications. Moreover, studies have shown that birds are resistant to oxidative stress and protein glycation and in fact, live longer than similar-sized mammals. This review seeks to explore how birds regulate blood glucose as well as various theories that might explain their apparent resistance to insulin-mediated glucose uptake and adaptations that enable them to thrive in a state of relative hyperglycemia.

Early Growth and Protein-Energy Metabolism in Chicken Lines Divergently Selected on Ultimate pH

In chickens, a divergent selection on the Pectoralis major pHu allowed the creation of the pHu+ and pHu− lines, which represent a unique model for studying the biological control of carbohydrate storage in muscle. The present study aimed to describe the early mechanisms involved in the establishment of pHu+ and pHu− phenotypes. At hatching, pHu+ chicks were slightly heavier but exhibited lower plasma glucose and triglyceride and higher uric acid. After 5 days, pHu+ chicks exhibited higher breast meat yield compared to pHu− while their body weight was no different. At both ages, in vivo muscle glycogen content was lower in pHu+ than in pHu− muscles. The lower ability of pHu+ chicks to store carbohydrate in their muscle was associated with the increased expression of SLC2A1 and SLC2A3 genes coding glucose transporters 1 and 3, and of CS and LDHα coding key enzymes of oxidative and glycolytic pathways, respectively. Reduced muscle glycogen content at hatching of the pHu+ was concomitant with higher activation by phosphorylation of S6 kinase 1/ribosomal protein S6 pathway, known to activate protein synthesis in chicken muscle. In conclusion, differences observed in muscle at slaughter age in the pHu+ and pHu− lines are already present at hatching. They are associated with several changes related to both carbohydrate and protein metabolism, which are likely to affect their ability to use eggs or exogenous nutrients for muscle growth or energy storage.

Differential regulation of protein synthesis by skeletal muscle type in chickens

In mammalian skeletal muscles, protein synthesis rates vary according to fiber types. We herein demonstrated differences in the regulatory mechanism underlying the protein synthesis in the pectoralis major (a glycolytic twitch muscle), adductor superficialis (an oxidative twitch muscle), and adductor profound (a tonic muscle) muscles of 14-day-old chickens. Under ad libitum feeding conditions, protein synthesis is significantly higher in the adductor superficialis muscle than in the pectoralis major muscle, suggesting that protein synthesis is upregulated in oxidative muscles in chickens, similar to that in mammals. In the pectoralis major muscle, fasting significantly inhibited the Akt/S6 pathway and protein synthesis with a corresponding decrease in plasma insulin concentration. Conversely, the insulin like growth factor-1 (IGF-1) mRNA levels significantly increased. These findings suggest that the insulin/Akt/S6 pathway plays an important role in the regulation of protein synthesis in the pectoralis major muscle. Interestingly, protein synthesis in the adductor superficialis muscle appears to be regulated in an Akt-independent manner, because fasting significantly decreased S6 phosphorylation and protein synthesis without affecting Akt phosphorylation. In the adductor profound muscle, IGF-1 expression, phosphorylation of Akt and S6, and protein synthesis were decreased by fasting, suggesting that insulin and/or skeletal IGF-1 appear contribute to protein synthesis via the Akt/S6 pathway. These findings revealed the differential regulation of protein synthesis depending on skeletal muscle types in chickens.

Prediction of hub genes associated with intramuscular fat content in Nelore cattle

BACKGROUND

The aim of this study was to use transcriptome RNA-Seq data from longissimus thoracis muscle of uncastrated Nelore males to identify hub genes based on co-expression network obtained from differentially expressed genes (DEGs) associated with intramuscular fat content.

RESULTS

A total of 30 transcriptomics datasets (RNA-Seq) obtained from longissimus thoracis muscle were selected based on the phenotypic value of divergent intramuscular fat content: 15 with the highest intramuscular fat content (HIF) and 15 with the lowest intramuscular fat content (LIF). The transcriptomics datasets were aligned with a reference genome and 65 differentially expressed genes (DEGs) were identified, including 21 upregulated and 44 downregulated genes in HIF animals. The normalized count data from DEGs was then used for co-expression network construction. From the co-expression network, four modules were identified. The topological properties of the network were analyzed; those genes engaging in the most interactions (maximal clique centrality method) with other DEGs were predicted to be hub genes (PDE4D, KLHL30 and IL1RAP), which consequently may play a role in cellular and/or systemic lipid biology in Nelore cattle. Top modules screened from the gene co-expression network were identify. The two candidate modules had clear associated biological pathways related to fat development, cell adhesion, and muscle differentiation, immune system, among others. The hub genes belonged in top modules and were downregulated in HIF animals. PDE4D and IL1RAP have known effects on lipid metabolism and the immune system through the regulation of cAMP signaling. Given that cAMP is known to play a role in lipid systems, PDE4D and IL1RAP downregulation may contribute to increased levels of intracellular cAMP and thus may have effects on IF content differences in Nelore cattle. KLHL30 may have effects on muscle metabolism. Klhl protein families play a role in protein degradation. However, the downregulation of this gene and its role in lipid metabolism has not yet been clarified.

CONCLUSIONS

The results reported in this study indicate candidate genes and molecular mechanisms involved in IF content difference in Nelore cattle.

In Ovo Feeding of Creatine Pyruvate Increases the Glycolysis Pathway, Glucose Transporter Gene Expression, and AMPK Phosphorylation in Breast Muscle of Neonatal Broilers

This study aims to investigate in ovo feeding (IOF) of creatine pyruvate (CrPyr) on glucose metabolism, hormone concentration, and the 5'-AMP-activated protein kinase (AMPK) pathway in breast muscle of embryos and neonatal broilers. The three treatments were noninjected control, 0.75% NaCl treatment, and 12 mg CrPyr/egg treatment. The solution was injected on the 17.5 day of incubation. At hatch, 120 male broilers from each treatment were chosen for a 7 day feeding trial. Compared with other treatments, CrPyr treated broilers enhanced insulin and thyroxine levels in plasma, adenosine triphosphate (ATP) concentration, hexokinase and pyruvate kinase activities, glucose transporter protein mRNA expressions, as well as protein abundances of phosphor-liver kinase B1 and phosphor-AMPK in breast muscle at hatch. In conclusion, IOF of CrPyr improved the energy status, increased the gene expression of glucose transporter proteins, and facilitated glycolysis in breast muscle, which may be associated with the activated AMPK pathway.