Myostatin, a member of the transforming growth factor-β (TGF-β) superfamily, has been shown to be a negative regulator of myogenesis. Here we show that myostatin functions by controlling the proliferation of muscle precursor cells. When C2C12 myoblasts were incubated with myostatin, proliferation of myoblasts decreased with increasing levels of myostatin. Fluorescence-activated cell sorting analysis revealed that myostatin prevented the progression of myoblasts from the G1- to S-phase of the cell cycle. Western analysis indicated that myostatin specifically up-regulated p21Waf1, Cip1, a cyclin-dependent kinase inhibitor, and decreased the levels and activity of Cdk2 protein in myoblasts. Furthermore, we also observed that in myoblasts treated with myostatin protein, Rb was predominately present in the hypophosphorylated form. These results suggests that, in response to myostatin signaling, there is an increase in p21 expression and a decrease in Cdk2 protein and activity thus resulting in an accumulation of hypophosphorylated Rb protein. This, in turn, leads to the arrest of myoblasts in G1-phase of cell cycle. Thus, we propose that the generalized muscular hyperplasia phenotype observed in animals that lack functional myostatin could be as a result of deregulated myoblast proliferation.

Myostatin, a negative regulator of muscle growth, functions by inhibiting myoblast proliferation.

https://gcris.iyte.edu.tr/bitstream/11147/7059/1/7059.pdf

The Importance of Boron in Biological Systems

Boron is an essential mineral that plays an important role in several biological processes. Boron is required for growth of plants, animals, and humans. There are increasing evidences of this nutrient showing a variety of pleiotropic effects, ranging from anti-inflammatory and antioxidant effects to the modulation of different body systems. In the past few years, the trials showed disease-related polymorphisms of boron in different species, which has drawn attention of scientists to the significance of boron to health. Low boron profile has been related with poor immune function, increased risk of mortality, osteoporosis, and cognitive deterioration. High boron status revealed injury to cell and toxicity in different animals and humans. Some studies have shown some benefits of higher boron status, but findings have been generally mixed, which perhaps accentuates the fact that dietary intake will benefit only if supplemental amount is appropriate. The health benefits of boron are numerous in animals and humans; for instance, it affects the growth at safe intake. Central nervous system shows improvement and immune organs exhibit enhanced immunity with boron supplementation. Hepatic metabolism also shows positive changes in response to dietary boron intake. Furthermore, animals and human fed diets supplemented with boron reveal improved bone density and other benefits including embryonic development, wound healing, and cancer therapy. It has also been reported that boron affects the metabolism of several enzymes and minerals. In the background of these health benefits, low or high boron status is giving cause for concern. Additionally, researches are needed to further elucidate the mechanisms of boron effects, and determine the requirements in different species.

The Physiological Role of Boron on Health.

Farm-animal species play crucial roles in satisfying demands for meat on a global scale, and they are genetically being developed to enhance the efficiency of meat production. In particular, one of the important breeders' aims is to increase skeletal muscle growth in farm animals. The enhancement of muscle development and growth is crucial to meet consumers' demands regarding meat quality. Fetal skeletal muscle development involves myogenesis (with myoblast proliferation, differentiation, and fusion), fibrogenesis, and adipogenesis. Typically, myogenesis is regulated by a convoluted network of intrinsic and extrinsic factors monitored by myogenic regulatory factor genes in two or three phases, as well as genes that code for kinases. Marker-assisted selection relies on candidate genes related positively or negatively to muscle development and can be a strong supplement to classical selection strategies in farm animals. This comprehensive review covers important (candidate) genes that regulate muscle development and growth in farm animals (cattle, sheep, chicken, and pig). The identification of these genes is an important step toward the goal of increasing meat yields and improves meat quality.

https://www.mdpi.com/2076-2615/11/3/835/pdf

Key Genes Regulating Skeletal Muscle Development and Growth in Farm Animals.

The vital roles of boron in animal health and production: a comprehensive review.

In order to determine the relationship between boron and development of the spleen, especially in the promoting biological effects, we examined the effects of different levels of boron on weight, organ index, microstructure, and antioxidative activities of the spleen in rats. Sprague-Dawley (SD) rats were selected and treated with different concentrations of boron, and then, the organs were resected and weighed. One half of the tissue was fixed and embedded in paraffin to observe tissue structure changes. The other half of the tissue was homogenated for determining the antioxidant activities. The results showed that 40 mg/L of boron could increase weight, organ indexes, and antioxidant capacity of spleens and improve the spleen tissue structure, while the boron concentration above 80 mg/L could decrease weight, organ indexes, and antioxidant capacity of spleens and damage the spleen tissue structure. The higher the concentration, the more serious the damage was. Especially at the concentration of 640 mg/L, it could significantly inhibit the development of the spleen and even exhibit toxic effect. Hence, low boron concentration played a protective role in the development of the spleen, while high boron concentration could damage the organs and even produce toxic effect.

Effects of Boron on Structure and Antioxidative Activities of Spleen in Rats

This study demonstrated the mechanisms of boron effects in a rat model and provided a scientific basis for the rational of boron use. These findings were achieved by investigating the effects of boron (10, 20, 40, 80, 160, 320, and 640 mg/L in drinking water or 1.5, 3, 6, 12, 24, 48, and 96 mg/kg BW) on rat serum immunoglobulins (IgGs), splenic cytokines, lymphocyte subsets, as well as on lymphocyte proliferation and apoptosis. Addition of 20 (3) and 40 (6) mg/L (mg/kg BW) of boron to drinking water significantly increased rat serum IgG concentrations, splenic IFN-γ and IL-4 expression as well as the number of splenic CD3+, CD4+ and proliferating cell nuclear antigen (PCNA)+ cells. Supplementation of drinking water with 40 mg/L (6 mg/kg BW) boron also markedly increased splenic IL-2 expression and the CD4+/CD8+ cell ratio and reduced splenic CD8+ cell number. Supplementation with 80 mg/L (12 mg/kg BW) boron significantly increased CD3+ and PCNA+ cell numbers (P < 0.05) and decreased the IL-10 expression in the spleen. Addition of 320 (48) and 640 (96) mg/L (mg/kg BW) boron markedly reduced the serum IgG concentrations; splenic IL-2 and IL-10 expression; the number of CD3+, CD4+ and PCNA+ cells; and increased the number of splenic CD8+ and caspase-3+ cells and promoted caspase-3 expression in CD3+ cells. In conclusion, these findings suggest that the supplementation of rat drinking water with 20(3) and 40(6) mg/L (mg/kg BW) boron can markedly enhance humoral and cellular immune functions, while boron concentrations above 320 mg/L (48 mg/kg BW) can have an inhibitory effect or even toxicity on immune functions. These results exhibit a U-shaped response characteristic of low and high doses of boron supplementation on immune function and imply that proper boron supplementation in food for humans and animals could be used as an immunity regulator.

Boron Affects Immune Function Through Modulation of Splenic T Lymphocyte Subsets, Cytokine Secretion, and Lymphocyte Proliferation and Apoptosis in Rats

Intramuscular fat (IMF) content is an important trait closely related to meat quality, which is highly variable among pig breeds from diverse genetic backgrounds. High-throughput sequencing has become a powerful technique for analyzing the whole transcription profiles of organisms. In order to elucidate the molecular mechanism underlying porcine meat quality, we adopted RNA sequencing to detect transcriptome in the longissimus dorsi muscle of Wei pigs (a Chinese indigenous breed) and Yorkshire pigs (a Western lean-type breed) with different IMF content. For the Wei and Yorkshire pig libraries, over 57 and 64 million clean reads were generated by transcriptome sequencing, respectively. A total of 717 differentially expressed genes (DEGs) were identified in our study (false discovery rate   2), with 323 up-regulated and 394 down-regulated genes in Wei pigs compared with Yorkshire pigs. Gene Ontology analysis showed that DEGs significantly related to skeletal muscle cell differentiation, phospholipid catabolic process, and extracellular matrix structural constituent. Pathway analysis revealed that DEGs were involved in fatty acid metabolism, steroid biosynthesis, glycerophospholipid metabolism, and protein digestion and absorption. Quantitative real time PCR confirmed the differential expression of 11 selected DEGs in both pig breeds. The results provide useful information to investigate the transcriptional profiling in skeletal muscle of different pig breeds with divergent phenotypes, and several DEGs can be taken as functional candidate genes related to lipid metabolism (ACSL1, FABP3, UCP3 and PDK4) and skeletal muscle development (ASB2, MSTN, ANKRD1 and ANKRD2).

Identification of differentially expressed genes in longissimus dorsi muscle between Wei and Yorkshire pigs using RNA sequencing

Boron is an essential trace element in animals. Appropriate boron supplementation can promote thymus development; however, a high dose of boron can lead to adverse effects and cause toxicity. The influencing mechanism of boron on the animal body remains unclear. In this study, we examined the effect of boron on cytokine expression, thymosin and thymopoietin secretion, antioxidant function, cell proliferation and apoptosis, and extracellular signal-regulated kinases 1 and 2 (ERK1/2) pathway in the thymus of rats. We found that supplementation with 10 and 20 mg/L boron to the drinking water significantly elevated levels of interleukin 2 (IL-2), interferon γ (IFN-γ), interleukin 4 (IL-4), and thymosin α1 in the thymus of rats (p < 0.05), increased the number of positive proliferating cell nuclear antigen (PCNA+) cells and concentrations of glutathione peroxidase (GSH-Px) and phosphorylated extracellular signal-regulated kinase (p-ERK) (p < 0.05), and promoted mRNA expression of PCNA and ERK1/2 in thymocytes ...

Effect of Boron on Thymic Cytokine Expression, Hormone Secretion, Antioxidant Functions, Cell Proliferation, and Apoptosis Potential via the Extracellular Signal-Regulated Kinases 1 and 2 Signaling Pathway

This study was performed to investigate changes in growth performance, immune organs weight and microstructure of broilers fed different levels of boron (0, 100, 200 and 400 mg/L) in drinking water for 6 weeks. A total of 240 newly-hatched Gushi chickens [body weight (BW)=34±2 kg; male: female=1:1] were equally divided into 4 treatments with 5 pens each (n=12 per pen). The birds were weighed after fasting for 12 h every two weeks until the end of experiment. The thymus, bursa and spleen samples were collected every two weeks and fixed in 4% paraformaldehyde phosphate buffer at room temperature (25°C). Results showed that BW and average daily gain significantly reduced by addition of 200 and 400 mg/L boron to drinking water compared to control group (P200 mg/L) could significantly inhibit the growth of immune organs and even exhibit toxic effects.

Youfang Gu

Papers

Effects of Boron on Structure and Antioxidative Activities of Spleen in Rats

Boron Affects Immune Function Through Modulation of Splenic T Lymphocyte Subsets, Cytokine Secretion, and Lymphocyte Proliferation and Apoptosis in Rats

Identification of differentially expressed genes in longissimus dorsi muscle between Wei and Yorkshire pigs using RNA sequencing

Effect of Boron on Thymic Cytokine Expression, Hormone Secretion, Antioxidant Functions, Cell Proliferation, and Apoptosis Potential via the Extracellular Signal-Regulated Kinases 1 and 2 Signaling Pathway

Effect of supplementation of drinking water with different levels of boron on performance and immune organ parameters of broilers