Developmental changes and the impact of isoflavones on mRNA expression of IGF-I receptor, EGF receptor and related growth factors in porcine skeletal muscle cell cultures

Production of Proliferation- and Differentiation-Competent Porcine Myoblasts for Preclinical Studies in a Porcine Large Animal Model of Muscular Insufficiency

Muscular insufficiency is observed in many conditions after injury, chronic inflammation, and especially in elderly populations. Causative cell therapies for muscle deficiencies are not state of the art. Animal models to study the therapy efficacy are, therefore, needed. We developed an improved protocol to produce myoblasts suitable for pre-clinical muscle therapy studies in a large animal model. Myoblasts were isolated from the striated muscle, expanded by employing five different protocols, and characterized on transcript and protein expression levels to determine procedures that yielded optimized regeneration-competent myoblasts and multi-nucleated myotubes. We report that swine skeletal myoblasts proliferated well under improved conditions without signs of cellular senescence, and expressed significant levels of myogenic markers including Pax7, MyoD1, Myf5, MyoG, Des, Myf6, CD56 (p ≤ 0.05 each). Upon terminal differentiation, myoblasts ceased proliferation and generated multi-nucleated myotubes. Injection of such myoblasts into the urethral sphincter complex of pigs with sphincter muscle insufficiency yielded an enhanced functional regeneration of this muscle (81.54% of initial level) when compared to the spontaneous regeneration in the sham controls without myoblast injection (67.03% of initial level). We conclude that the optimized production of porcine myoblasts yields cells that seem suitable for preclinical studies of cell therapy in a porcine large animal model of muscle insufficiency.

Cell Therapy by Mesenchymal Stromal Cells Versus Myoblasts in a Pig Model of Urinary Incontinence

The leading cause of stress urinary incontinence (SUI) in women is the urethral sphincter muscle deficiency caused by mechanical stress during pregnancy and vaginal delivery. In men, prostate cancer surgery and injury of local nerves and muscles are associated with incontinence. Current treatment often fails to satisfy the patient's needs. Cell therapy may improve the situation. We therefore investigated the regeneration potential of cells in ameliorating sphincter muscle deficiency and UI in a large animal model. Urethral sphincter deficiency was induced surgically in gilts by electrocautery and balloon dilatation. Adipose tissue-derived stromal cells (ADSCs) and myoblasts from Musculus semitendinosus were isolated from male littermates, expanded, characterized in depth for expression of marker genes and in vitro differentiation, and labeled. The cells were injected into the deficient sphincter complex of the incontinent female littermates. Incontinent gilts receiving no cell therapy served as controls. Sphincter deficiency and functional regeneration were recorded by monitoring the urethral wall pressure during follow-up by two independent methods. Cells injected were detected in vivo during follow-up by transurethral fluorimetry, ex vivo by fluorescence imaging, and in cryosections of tissues targeted by immunofluorescence and by polymerase chain reaction of the sex-determining region Y (SRY) gene. Partial spontaneous regeneration of sphincter muscle function was recorded in control gilts, but the sphincter function remained significantly below levels measured before induction of incontinence (67.03% ± 14.00%, n = 6, p < 0.05). Injection of myoblasts yielded an improved sphincter regeneration within 5 weeks of follow-up but did not reach significance compared to control gilts (81.54% ± 25.40%, n = 5). A significant and full recovery of the urethral sphincter function was observed upon injection of ADSCs within 5 weeks of follow-up (100.4% ± 23.13%, n = 6, p < 0.05). Injection of stromal cells provoked slightly stronger infiltration of CD45pos leukocytes compared to myoblasts injections and controls. The data of this exploratory study indicate that ADSCs inherit a significant potential to regenerate the function of the urethral sphincter muscle.

Effect of muscle fibre types and carnosine levels on the expression of carnosine-related genes in pig skeletal muscle

It is generally accepted that carnosine (β-alanyl-L-histidine) content is higher in glycolytic than in oxidative muscle fibres, but the underlying mechanisms responsible for this difference remain to be elucidated. A first study to better understand potential mechanisms involved was undertaken (1) to determine whether differences in the expression of carnosine-related enzymes (CARNS1, CNDP2) and transporters (SLC6A6, SLC15A3, SLC15A4, SLC36A1) exist between oxidative and glycolytic myofibres and (2) to study the effect of carnosine on myoblast proliferative growth and on carnosine-related gene expression in cultured myoblasts isolated from glycolytic and oxidative muscles. Immunohistochemistry analyses were conducted to determine the cellular localization of carnosine-related proteins. Laser-capture microdissection and qPCR analyses were performed to measure the expression of carnosine-related genes in different myofibres isolated from the longissimus dorsi muscle of ten crossbred pigs. Myogenic cells originating from glycolytic and oxidative muscles were cultured to assess the effect of carnosine (0, 10, 25 and 50 mM) on their proliferative growth and on carnosine-related gene expression. The mRNA abundance of CNDP2 and of the studied carnosine transporters was higher in oxidative than in glycolytic myofibres. Since carnosine synthase (CARNS1) mRNA abundance was not affected by either the fibre type or the addition of carnosine to myoblasts, its transcriptional regulation would not be the main process by which carnosine content differences are determined in oxidative and glycolytic muscles. The addition of carnosine to myoblasts leading to a dose-dependent increase in SLC15A3 transcripts, however, suggests a role for this transporter in carnosine uptake and/or efflux to maintain cellular homeostasis.

The effects of temperature and donor piglet age on the transcriptomic profile and energy metabolism of myoblasts

Rapid climate change is associated with frequent extreme heat events and the resulting thermal stress has consequences for the health, welfare, and growth of farm animals. The aim of this study was to characterize the transcriptional changes and the effects on energy metabolism in proliferating porcine myoblasts derived from piglets of different ages, representing differences in thermoregulatory abilities, and cultivated below (35°C) and above (39°C, 41°C) the standard cultivation temperature (37°C). Satellite cells originating from Musculus rhomboideus of piglets isolated on days 5 (P5, thermolabile) and 20 (P20, thermostable) of age were used. Our expression analyses highlighted differentially expressed genes in porcine myoblasts cultures under heat or cold induced stress. These gene sets showed enrichment for biological processes and pathways related to organelle fission, cell cycle, chromosome organization, and DNA replication. Culture at 35°C resulted in increased metabolic flux as well as a greater abundance of transcripts of the cold shock protein-encoding gene RBM3 and those of genes related to biological processes and signaling pathways, especially those involving the immune system (cytokine–cytokine receptor interaction, TNF and IL-17 signaling pathways). For cultivation at 39°C, differences in the expression of genes related to DNA replication and cell growth were identified. The highest glutathione index ratio was also found under 39°C. Meanwhile, cultivation at 41°C induced a heat stress response, including the upregulation of HSP70 expression and the downregulation of many biological processes and signaling pathways related to proliferative ability. Our analysis also identified differentially expressed genes between cells of donors with a not yet (P5) and already fully developed (P20) capacity for thermoregulation at different cultivation temperatures. When comparing P5 and P20, most of the changes in gene expression were detected at 37°C. At this optimal temperature, muscle cells can develop to their full capacity. Therefore, the most diverse molecular signaling pathways, including PI3K-Akt signaling, Wnt signaling, and EGFR tyrosine kinase inhibitor, were found and are more pronounced in muscle cells from 20-day-old piglets. These results contribute to a better understanding of the mechanisms underlying the adaptation of skeletal muscle cells to temperature stress in terms of their thermoregulatory ability.

Replacing Needle Injection by a Novel Waterjet Technology Grants Improved Muscle Cell Delivery in Target Tissues

Current regimen to treat patients suffering from stress urinary incontinence often seems not to yield satisfactory improvement or may come with severe side effects. To overcome these hurdles, preclinical studies and clinical feasibility studies explored the potential of cell therapies successfully and raised high hopes for better outcome. However, other studies were rather disappointing. We therefore developed a novel cell injection technology to deliver viable cells in the urethral sphincter complex by waterjet instead of using injection needles. We hypothesized that the risk of tissue injury and loss of cells could be reduced by a needle-free injection technology. Muscle-derived cells were obtained from young male piglets and characterized. Upon expansion and fluorescent labeling, cells were injected into cadaveric tissue samples by either waterjet or injection needle. In other experiments, labeled cells were injected by waterjet in the urethra of living pigs and incubated for up to 7 days of follow-up. The analyses documented that the cells injected by waterjet in vitro were viable and proliferated well. Upon injection in live animals, cells appeared undamaged, showed defined cellular somata with distinct nuclei, and contained intact chromosomal DNA. Most importantly, by in vivo waterjet injections, a significantly wider cell distribution was observed when compared with needle injections (P < .05, n ≥ 12 samples). The success rates of waterjet cell application in living animals were significantly higher (≥95%, n = 24) when compared with needle injections, and the injection depth of cells in the urethra could be adapted to the need by adjusting waterjet pressures. We conclude that the novel waterjet technology injects viable muscle cells in tissues at distinct and predetermined depth depending on the injection pressure employed. After waterjet injection, loss of cells by full penetration or injury of the tissue targeted was reduced significantly in comparison with our previous studies employing needle injections.

Effects of temperature on proliferation of myoblasts from donor piglets with different thermoregulatory maturities

Background

Climate change and the associated risk for the occurrence of extreme temperature events or permanent changes in ambient temperature are important in the husbandry of farm animals. The aim of our study was to investigate the effects of permanent cultivation temperatures below (35 °C) and above (39 °C, 41 °C) the standard cultivation temperature (37 °C) on porcine muscle development. Therefore, we used our porcine primary muscle cell culture derived from satellite cells as an in vitro model. Neonatal piglets have limited thermoregulatory stability, and several days after birth are required to maintain their body temperature. To consider this developmental step, we used myoblasts originating from thermolabile (five days of age) and thermostable piglets (twenty days of age).

Results

The efficiency of myoblast proliferation using real-time monitoring via electrical impedance was comparable at all temperatures with no difference in the cell index, slope or doubling time. Both temperatures of 37 °C and 39 °C led to similar biochemical growth properties and cell viability. Only differences in the mRNA expression of myogenesis-associated genes were found at 39 °C compared to 37 °C with less MYF5, MYOD and MSTN and more MYH3 mRNA. Myoblasts grown at 35 °C are smaller, exhibit higher DNA synthesis and express higher amounts of the satellite cell marker PAX7, muscle growth inhibitor MSTN and metabolic coactivator PPARGC1A. Only permanent cultivation at 41 °C resulted in higher HSP expression at the mRNA and protein levels. Interactions between the temperature and donor age showed that MYOD, MYOG, MYH3 and SMPX mRNAs were temperature-dependently expressed in myoblasts of thermolabile but not thermostable piglets.

Conclusions

We conclude that 37 °C to 39 °C is the best physiological temperature range for adequate porcine myoblast development. Corresponding to the body temperatures of piglets, it is therefore possible to culture primary muscle cells at 39 °C. Only the highest temperature of 41 °C acts as a thermal stressor for myoblasts with increased HSP expression, but it also accelerates myogenic development. Cultivation at 35 °C, however, leads to less differentiated myoblasts with distinct thermogenetic activity. The adaptive behavior of derived primary muscle cells to different cultivation temperatures seems to be determined by the thermoregulatory stability of the donor piglets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-021-00376-4.

Establishment and validation of cell pools using primary muscle cells derived from satellite cells of pig skeletal muscle

Primary cell cultures derived from satellite cells of skeletal muscle provide an appropriate in vitro model for proliferating myoblasts and differentiating myotubes for muscle biological research. These cell cultures may consist of harvested cells per animal or of a cell pool made of cells from several animals. However, cell pooling reduces the biological variability of the different cell donors. On the other hand, the use of cell pools offers an opportunity to use less donor tissue and to perform long-term projects with a broad spectrum of analysis and replications. In the literature, information about the donors of cell pools, the procedure used for pooling, and the characterization/validation of cell pools is often lacking. In this study, we established three cell pools consisting of M. rhomboideus or M. longissimus from ten or six piglets, each with one gender and medium birth weight. Real-time impedimetric monitoring was used to evaluate the proliferative growth behavior of myoblasts for the cell pools in comparison to their corresponding unpooled cells over a period of 72 h, with a measurement being taken every 30 min. For each of the tested cell pools, cell index, slope, and doubling time did not differ between the cell pool and the unpooled cells of the donor animals. Differentiation capacity and mRNA expression of PAX7, MYOD and MYOG remained unchanged between the cell pool and the unpooled cells. Current results support that the use of cell pools is an appropriate method to reflect the average proliferative growth behavior of unpooled cells.

Soy Isoflavone Improved Female Sexual Dysfunction of Mice Via Endothelial Nitric Oxide Synthase Pathway

Introduction

Female sexual dysfunction (FSD) is a common endocrine disease that impairs the quality of life for many women. The existing therapy strategies still have many disadvantages. It is necessary to explore new pharmacologic treatments that are effective and safe.

Aim

The aim of this study was to explore the effects of soy isoflavone (SI) on FSD in mice and the underlying mechanisms.

Methods and Main Outcome Measures

Laser Doppler flowmetry was used to determine vaginal blood flow. Serum hormone levels and histologic changes of the vagina were analyzed by enzyme-linked immunosorbent assay (ELISA) and by hematoxylin and eosin (H&E) and Masson’s trichome staining. The mRNA and protein expression of endothelial nitric oxide synthase (eNOS) was then evaluated by quantitative real-time polymerase chain reaction and western blot assays.

Results

Vaginal blood flow was found to be remarkably lower in adult mice, and SI was shown to increase vaginal blood flow in a dose-dependent manner (P < .05). The results of ELISA and H&E and Masson’s trichome staining suggest that SI had a positive effect on FSD, as evidenced by the levels of hormones in serum and histologic changes of the vagina, which changed consistently. In addition, the level of eNOS was positively correlated with the concentration of SI, and eNOS inhibitor was able to reverse the improvement in sexual function induced by SI.

Conclusion

Our study demonstrated that SI could improve sexual function by upregulating the eNOS pathway. Therefore, SI might serve as a promising candidate for the treatment of sexual dysfunction.

Zhang J, Zhu Y, Pan L, et al. Soy Isoflavone Improved Female Sexual Dysfunction of Mice Via Endothelial Nitric Oxide Synthase Pathway. Sex Med 2019; 7:345–351.

Immunomodulatory potential of dietary soybean-derived isoflavones and saponins in pigs

In this review, the potential for use of soy-derived bioactive compounds as immunomodulatory feed additives in pigs is discussed. Soy is a major component of the modern U.S. swine diet in today's commercial industry, providing the bulk of dietary AA necessary for growth and production. However, soy use has generally been limited in early growth phases, during which the risks of immunological insult and disease are among the highest. Improvements of soybean processing and development of soy protein products with little to no antinutritional factors have made soy more appropriate for use in young pigs but additional processing may affect bioactive compound levels in the feed. The bioactive compounds of interest for this review are soy isoflavones and soy saponins. Soy isoflavones are flavonoid compounds with a range of biological activity including moderate estrogenic effects at low biological concentrations. Although estrogenic effects are of more interest in human medical research, isoflavones are also known for their anti-inflammatory, antioxidative properties at cellular levels, engaging several receptors and pathways including inhibition of NF-κB activation and inducible-nitric oxide synthase enzymes, thereby ascribing antiviral properties. Saponins, amphipathic glycoside compounds, also engage anti-inflammatory pathways, though their biological activity in pigs has not been well investigated and seem to mainly be observed on the mucous membrane in the gastrointestinal tract. Regarding use as an immunomodulatory feed additive, supplemental soy isoflavones have been shown to improve immunological status of pigs and produce mild improvements of growth performance under certain disease challenges including porcine reproductive and respiratory syndrome virus. Although more in vivo research in pigs is needed to fully understand biological activity of these compounds in the live animal, soy-derived bioactive compounds show great potential as a health promoting feed additive for the modern swine industry.

Transcriptomics-Related Mechanisms of Supplementing Laying Broiler Breeder Hens with Dietary Daidzein to Improve the Immune Function and Growth Performance of Offspring

Daidzein (DA) is an isoflavone that is primarily extracted from soy plants. This study evaluated the effects of supplementing laying broiler breeder hens with dietary DA on the immune function and growth performance of their offspring and the underlying mechanism. A total of 720 breeders were divided into three treatment groups that were fed either a control diet (CON), a DA-low-supplemented diet (DLS, CON+20 mg/kg DA), or a DA-high-supplemented diet (DHS, CON+100 mg/kg DA) for 8 weeks, and eggs were collected for hatching during the final week. The broiler offspring received a basal diet for 42 days, and blood, livers, and immune organs were collected at 21 and 42 days of age. DLS treatment promoted embryonic development and increased growth hormone levels, body weight, feed intake, and carcass traits on days 21 and 42 of broilers. Additionally, the IgA and IgG concentrations, antibody titers, and antioxidant capacity of broilers were increased at 21 days of age, and B lymphocyte differentiation was increased at 42 days. Besides, DLS treatment upregulated the expression of genes related to embryonic and muscle development in offspring and regulated mitogen-activated protein kinase (MAPK), transforming growth factor beta (TGF-β), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and Toll-like receptor signaling. DHS treatment decreased the percentage of abdominal fat in the broilers at 42 days, but it did not significantly affect embryonic development, growth performance, or IgA and IgG concentrations. In summary, providing dietary DA supplementation at 20 mg/kg to broiler breeders can improve their immune function and growth performance.

Voluntary locomotor activity promotes myogenic growth potential in domestic pigs

Self-determined physical activity is an essential behavioural need and can vary considerably between individuals of a given species. Although locomotion is suggested as a prerequisite for adequate function of skeletal muscle, domestic pigs are usually reared under limited space allowance. The aim of our study was to investigate if a different voluntary locomotor activity leads to altered properties in the muscle structure, biochemistry and mRNA expression of selected genes involved in myogenesis and skeletal muscle metabolism. Based on a video tracking method, we assigned pigs to three categories according to their total distances walked over five observed time points: long distance, medium distance, and short distance. The microstructure and biochemistry parameters of the M. semitendinosus were unaffected by the distance categories. However, we found distance-dependent differences in the mRNA expression of the genes encoding growth (IGF2, EGF, MSTN) and transcription factors (MRF4, MYOD). In particular, the IGF2/MSTN ratio appears to be a sensitive indicator, at the molecular level, for the locomotor activity of individuals. Our results indicate that the myogenic growth potential of pigs under standard rearing conditions is triggered by their displayed voluntary locomotor activity, but the covered distances are insufficient to induce adaptive changes at the tissue level.

Moderate high or low maternal protein diets change gene expression but not the phenotype of skeletal muscle from porcine fetuses

The aim of our study was to characterize the immediate phenotypic and adaptive regulatory responses of fetuses to different in utero conditions reflecting inadequate maternal protein supply during gestation. The gilts fed high- (250% above control) or low- (50% under control) protein diets isoenergetically adjusted at the expense of carbohydrates from the day of insemination until the fetuses were collected at day 64 or 94 of gestation. We analyzed body composition, histomorphology, biochemistry, and messenger RNA (mRNA) expression of fetal skeletal muscle. Both diets had only marginal effects on body composition and muscular cellularity of fetuses including an unchanged total number of myofibers. However, mRNA expression of myogenic regulatory factors (MYOG, MRF4, P ≤ 0.1), IGF system (IGF1, IGF1R, P ≤ 0.05) and myostatin antagonist FST (P = 0.6, in males only) was reduced in the fetal muscle exposed to a maternal low-protein diet. As a result of excess protein, MYOD, MYOG, IGF1R, and IGFBP5 mRNA expression (P ≤ 0.05) was upregulated in fetal muscle. Differences in muscular mRNA expression indicate in utero regulatory adaptive responses to maternal diet. Modulation of gene expression immediately contributes to the maintenance of an appropriate fetal phenotype that would be similar to that observed in the control fetuses. Moreover, we suggest that the modified gene expression in fetal skeletal muscle can be viewed as the origin of developmental muscular plasticity involved in the concept of fetal programming.

Exogenous genistein in late gestation: effects on fetal development and sow and piglet performance

Due to their functional similarity to estradiol, phytoestrogens could prove to be beneficial in late gestating sows. The goal of this study was to determine the impact of providing the phytoestrogen genistein during late pregnancy on the performance of sows and their litters. In total, 56 gilts were equally divided into the two following groups on day 90 of gestation: (1) controls (CTL); and (2) two daily i.m. injections of 220 mg of genistein (GEN). Treatments were carried out until farrowing. Jugular blood samples were collected from 16 gilts/treatment on days 89 and 110 of gestation, and on days 3 and 21 of lactation. Milk samples were also obtained from those sows on day 3 of lactation. A male piglet from 16 CTL and 15 GEN litters was slaughtered at 24 h postpartum and a blood sample was obtained. The liver, heart and visceral organs were weighed and the semitendinosus (ST) muscle was collected and carcass composition was determined. The treatment increased (P0.1) on weight or backfat loss of sows during lactation, milk composition or weights of piglets. The pre-weaning mortality rate of piglets was very low (0.1). However, carcasses from GEN litters contained more fat than those from CTL litters (9.63% v. 8.34%, P0.1). In conclusion, injecting gilts with 440 mg/day of genistein in late gestation increased IGF1 concentrations in gilts and carcass fat in neonatal piglets, but had minimal effect on muscle development of piglets at birth and on the performance of lactating sows and their litters.

Effects of leptin and adiponectin on the growth of porcine myoblasts are associated with changes in p44/42 MAPK signaling

We hypothesized that both adiponectin and leptin affect the growth of porcine skeletal muscle cells, with fatty acids acting as modifiers in adipokine action and that both adipokines influence the gene expression of their receptors. Therefore, the objective of this study was to investigate the effects of recombinant adiponectin and leptin on cell number (DNA) and DNA synthesis rate with and without oleic acid supplementation, on cell death, and on key intracellular signaling molecules of proliferating porcine myoblasts in vitro. Moreover, the mRNA expression of genes encoding for the leptin and adiponectin receptors (LEPR, ADIPOR1, ADIPOR2) as affected by leptin or adiponectin was examined. Recombinant porcine adiponectin (40 μg/mL) and leptin (20 ng/mL) increased DNA synthesis rate, measured as [(3)H]-thymidine incorporation (P < 0.01), reduced cell viability in terms of lactate dehydrogenase release (P < 0.05), or lowered DNA content after 24 h (P < 0.05). In adiponectin-treated cultures, oleic acid supplementation increased DNA synthesis rate and reduced cell number in a dose-dependent manner (P < 0.05). Both adiponectin (P = 0.07) and leptin (P < 0.05) induced a transient activation of p44/42 mitogen-activated protein kinase (MAPK) after 15 min, followed by decreases after 60 and 180 min (P < 0.05). Adiponectin tended to increase c-fos activation (P = 0.08) and decreased p53 activation at 180 min (P = 0.03). Both adiponectin and leptin down-regulated the abundance of ADIPOR2 mRNA and, transiently, of LEPR mRNA (P < 0.05). In conclusion, adiponectin and leptin may adversely affect the growth of porcine myoblasts, which is related to p44/42 MAPK signaling and associated with changes in ligand receptor gene expression.

Predicted high-performing piglets exhibit more and larger skeletal muscle fibers

Postnatal (muscle) growth potential in pigs depends on the total number and hypertrophy of myofibers in skeletal muscle tissue. In a previous study an algorithm was developed to predict piglet BW at the end of the nursery period (10 wk of age) on the basis of BW at birth, at weaning, and at 6 wk of age. The objective of this study was to determine whether the differences in growth performance between poor (PP) and high (HP) performing piglets could be the result of different skeletal muscle properties. Therefore, from a total of 368 piglets (offspring from Hypor sows bred to TOPIGS sires) 2 groups with a divergent growth performance were selected at 6 wk of age: HP (n = 20, predicted BW at 10 wk of age 26.8-30.9 kg) and PP (n = 20, predicted BW at 10 wk of age 16.0-22.9 kg). Piglets were euthanized at 10 wk of age, and samples of the semitendinosus muscle (STN) were collected for histochemistry and gene expression analysis using quantitative PCR (qPCR). At 10 wk of age, realized BW did not differ from predicted BW in either group (P > 0.880). The HP piglets exhibited greater ADG and ADFI from 6 to 10 wk and greater BW at birth and 6 and 10 wk of age (P ≤ 0.002) compared with the PP piglets, whereas G:F ratio was similar (P = 0.417). Superior growth performance of HP piglets was associated with a 1.27-fold higher IGF1 plasma concentration at 10 wk compared with the PP piglets (P = 0.044). The greater weight and muscle cross-sectional area of STN in HP piglets was due to a 1.20-fold increase in total muscle fiber number (TFN; P = 0.009) and 1.34-fold increase in fiber cross-sectional area (FCSA; P = 0.004) compared with the PP piglets. The number of myonuclei per red and intermediate fiber was greater in HP piglets (P ≤ 0.097), but the nucleus-to-cytoplasm ratio was unaffected by the performance group (P = 0.861). The mRNA expression of proliferating cell nuclear antigen (PCNA), paired box 7 (PAX7), myogenic factor 5 (MYF5), and myogenic differentiation factor (MYOD) did not differ between groups (P ≥ 0.327). However, IGF2-specific mRNA expression was numerically higher in the HP piglets (P = 0.101). The greater myofiber number, the higher degree of myofiber hypertrophy, and the increased muscular mRNA expression of IGF2 indicate that HP piglets exhibit a greater capacity for lean accretion and may grow faster until market weight. In summary, pigs that were selected for predicted high BW at 10 wk of age using a complex selection model had a superior muscularity in terms of greater TFN and FCSA, which may be of advantage for lean mass accretion in later life and for meat quality.

Soy isoflavones modulate adipokines and myokines to regulate lipid metabolism in adipose tissue, skeletal muscle and liver of male Huanjiang mini-pigs

Although a growing body of evidence suggests that soy isoflavones help regulate lipid metabolism, the underlying mechanism has not yet been thoroughly clarified. The present study was undertaken to determine the effects of soy isoflavones on the expression of genes involved in lipid metabolism in different adipose tissue depots, skeletal muscle and liver of male Huanjiang mini-pigs, as well as the expression of adipokines and myokines. A total of 36 male Huanjiang mini-pigs were fed basal diet (control, Con), low-dose soy isoflavones (LSI) and high-dose soy isoflavones (HSI). The results showed that LSI and HSI regulated the expression of genes involved in the anabolism and catabolism of fatty acids in dorsal subcutaneous (DSA), abdominal subcutaneous (ASA) and perirenal (PRA) adipose tissue depots, as well as longissimus dorsi muscle (LDM) and liver. LSI and HSI also regulated the expression of adipokines in DSA, ASA and PRA, and the expression of myokines in LDM in male Huanjiang mini-pigs. In addition, soy isoflavones regulated plasma glucose, leptin and adiponectin contents after treatment for two months. Our results indicate that soy isoflavones, by regulating the expression of adipokines and myokines, may regulate the metabolism of lipids and could have potential therapeutic applications in lipid abnormalities.

The cannabinoid receptor inverse agonist AM251 regulates the expression of the EGF receptor and its ligands via destabilization of oestrogen-related receptor α protein

BACKGROUND AND PURPOSE

AM251 is an inverse agonist of the cannabinoid 1 receptor (CB(1)R) that can exert 'off-target' effects in vitro and in CB(1)R knock-out mice. AM251 is also potent at modulating tumour cell growth, suggesting that growth factor-mediated oncogenic signalling could be regulated by AM251. Since dysregulation of the EGF receptor has been associated with carcinogenesis, we examined AM251 regulation of EGF receptor (EGFR) expression and function.

EXPERIMENTAL APPROACH

The various biological functions of AM251 were measured in CB(1)R-negative human cancer cells. Pharmacological and genetic approaches were used to validate the data.

KEY RESULTS

The mRNA levels for EGFR and its associated ligands, including HB-EGF, were induced several fold in PANC-1 and HCT116 cells in response to AM251. This event was associated with enhanced expression of EGFR on the cell surface with concomitant increase in EGF-induced cellular responses in AM251-treated cells. Exposure to XCT790, a synthetic inverse agonist of the orphan nuclear oestrogen-related receptor α (ERRα), also induced EGFR and HB-EGF expression to the same extent as AM251, whereas pretreatment with the ERRα-selective agonist, biochanin A, blunted AM251 actions. AM251 promoted the degradation of ERRα protein without loss of the corresponding mRNA. Knock-down of ERRα by siRNA-based approach led to constitutive induction of EGFR and HB-EGF levels, and eliminated the biological responses of AM251 and XCT790. Finally, AM251 displaced diethylstilbestrol prebound to the ligand-binding domain of ERRα.

CONCLUSIONS AND IMPLICATIONS

AM251 up-regulates EGFR expression and signalling via a novel non-CB(1)R-mediated pathway involving destabilization of ERRα protein in selected cancer cell lines.

Effects of limited and excess protein intakes of pregnant gilts on carcass quality and cellular properties of skeletal muscle and subcutaneous adipose tissue in fattening pigs

The aim of this study was to investigate whether dietary protein intake of gilts during gestation below (50%) or above (250%) recommendations affects body composition, carcass and meat quality, and properties of skeletal muscle and subcutaneous adipose tissue (SCAT) in offspring at d 83 and 188 of age. German Landrace gilts were fed isoenergetic gestation diets (~13.7 MJ of ME/kg) containing a low (LP, 6.5%; n = 18), an adequate (AP, 12.1%; n = 20), or a high (HP, 30%; n = 16) protein content from mating until farrowing. Within 48 h of birth, offspring were cross-fostered to sows fed a standard diet. On d 83 of age, no effects of the LP diet on BW and body composition were detected, whereas HP pigs showed a slight growth delay (P = 0.06) associated with increased relative weights of small intestine (P < 0.01) and brain (P = 0.08), and reduced relative thymus weight (P < 0.01). On d 188 of age, BW was not different among the dietary groups. However, the carcass of LP pigs contained less (P = 0.01) lean and more (P = 0.07) fat compared with AP and HP pigs, which was only pronounced in pigs originating from large litters (P < 0.05). Like skeletal muscles (P = 0.06), the heart muscle weighed less (P = 0.02) in LP than AP pigs. Compared with AP pigs, LP pigs exhibited a fewer (P = 0.09) total number of myofibers in semitendinosus muscle plus LM both at d 83 and 188 of age, whereas total muscular DNA was less (P = 0.02) at d 188 only. The mRNA abundance of IGF2 measured on d 188 was reduced in SCAT (P = 0.03) and LM (P = 0.07) of LP compared with AP pigs. No changes in muscular fiber type frequency, capillary density, or creatine kinase activity, as well as SCAT adipocyte size and number, were observed at either stages of age. Meat quality characteristics remained unchanged at d 83, whereas Warner-Bratzler shear force value in LM was decreased (P = 0.03) in LP compared with AP pigs on d 188 of age. The results suggest that the maternal LP diet impairs prenatal myofiber formation, reduces the potential of postnatal lean growth related to reduced IGF2 mRNA expression and myonuclear accumulation, and consequently changes carcass quality toward reduced lean proportion and improved tenderness at market weight. In contrast, except for a slight transient growth delay, excess dietary protein during gestation seems to have little effect on the fetal programming of postnatal muscle and adipose tissue phenotype of the progeny.

Study of the differential transcription in liver of growth hormone receptor (GHR), insulin-like growth factors (IGF1, IGF2) and insulin-like growth factor receptor (IGF1R) genes at different postnatal developmental ages in pig breeds

The objective of this study was to determine hepatic expression levels of GHR, IGF1R, IGF1 and IGF2 genes in young growing gilts at different developmental ages (60-210 days) in five pig breeds: Polish Large White (PLW), Polish Landrace (PL), Pulawska (Pul), Duroc (Dur) and Pietrain (Pie). We studied the differences among pig breeds as well as within each breed for pigs in different developmental ages. Obtained results revealed major differences among breeds in hepatic gene expression of porcine GHR, IGF1R, IGF1 and IGF2 genes in different developmental ages. The differences among breeds of GHR expression were significantly higher in PLW, PL at the age of 60, 90, 120 days as compared to Pul, Dur and Pie. In turn, the highest level of IGF1R expression was observed in PL at age of 150, 180 and 210 days, whereas in case of IGF1 the highest level was recorded in Pie gilts at the age of 60 and 90 days. Moreover trait associated study revealed highly significant correlations between hepatic expressions of IGF1R and IGF2 genes and carcass composition traits (P < 0.01) The results of study suggest that porcine GHR, IGF1R, IGF1 and IGF2 genes may be potential candidate genes for postnatal growth and carcass composition traits. Therefore, the implementation of the hepatic expression of GH/IGF genes into the pig breeding and gene assisted selection program in different pig breeds should be considered. However, further population wide study is needed to clarify the hepatic expression association with economic traits, such as body growth, meat quality and carcass composition traits.

Limited and excess protein intake of pregnant gilts differently affects body composition and cellularity of skeletal muscle and subcutaneous adipose tissue of newborn and weanling piglets

AIM

This study investigated whether dietary protein intake less (50%) or greater (250%) than requirements throughout gestation differently affects offspring body composition and cellular properties of skeletal muscle and subcutaneous adipose tissue (SCAT).

METHODS

Primiparous gilts were fed iso-energetic diets containing adequate (22 AP), high (21 HP), or low (19 LP) protein contents. Newborn (n = 166) and weanling piglets cross-fostered to sows fed a standard diet (day 28; n = 83) were examined by morphological, biochemical, histological, and molecular analyses of the body, SCAT, and semitendinosus, longissimus, biceps femoris muscles.

RESULTS

Lowered birth weight (BW) in response to the HP and LP diets (p < 0.01) resulted from decreases in all body constituents in LP, and mainly from reduced body fat in HP piglets (p < 0.05). In the light BW class within litters, HP piglets exhibited a greater percentage of muscle tissue (p < 0.05) than LP piglets. Less SCAT mass in HP and LP piglets resulted from reduced (p < 0.05) number, but not the size of adipocytes. The LP diet adversely affected myogenesis and muscular differentiation derived from less (p < 0.01) primary and secondary myofibers, lower creatine kinase activity (p < 0.05), less IGF2 mRNA (p < 0.10), and greater expression of the embryonic myosin heavy chain isoform (p < 0.01). Catch-up growth of LP but not HP pigs until day 28 increased body fat (p = 0.01). Despite compensated muscle growth in LP piglets, the deficit in myofiber number remained.

CONCLUSION

Poor intrauterine environment by limited and excess protein supply retards fetal growth, but only limited protein supply impairs myogenesis, persistently restricts muscle growth potential, and favors obesity at infancy.

Dose-dependent effects of genistein and daidzein on protein metabolism in porcine myotube cultures

This study was conducted to investigate whether the isoflavones genistein and daidzein, which are components of soy-based diets, and the estrogen 17beta-estradiol affect differentiation and protein metabolism of porcine skeletal muscle cells in vitro. Serum-free porcine myotube cultures expressing the estrogen receptors ERalpha and ERbeta were treated with various concentrations of genistein, daidzein, or 17beta-estradiol for 26 h. The degree of differentiation by creatine phosphokinase activity was not altered by treatment. At 100 micromol/L both genistein and daidzein caused decreases in protein amount due to cell loss. In addition, 100 micromol/L genistein reduced protein synthesis rate of the surviving cells (P < 0.05) measured as [3H]-phenylalanine incorporation. Interestingly, genistein (0.1 micromol/L), daidzein (10, 100 micromol/L), and 17beta-estradiol (0.1, 1 nmol/L) slightly reduced protein degradation (P < 0.05). The results suggest that both genistein and daidzein affect protein metabolism in a dose-dependent manner and that estrogenic actions may play a role in decreasing protein degradation in porcine skeletal muscle.

IGF-I- and EGF-dependent DNA synthesis of porcine myoblasts is influenced by the dietary isoflavones genistein and daidzein

Soy-derived isoflavones have been reported to be specific inhibitors of protein tyrosine kinases like the type 1 insulin-like growth factor receptor (IGF-1R) and the epidermal growth factor receptor (EGFR). This study was conducted to investigate, whether IGF-I and EGF stimulate porcine myoblast growth and whether the responses are influenced by isoflavones. Satellite cell-born myoblasts derived from the semimembranosus muscle of newborn piglets were treated for 26 h with IGF-I or EGF alone and in combination with genistein or daidzein. The DNA amount was measured and DNA synthesis was recorded as 6 h-[(3)H]thymidine incorporation during exponential growth in serum-free basal medium. IGF-I and EGF synergistically stimulated DNA synthesis of porcine myoblast with EGF causing a greater response. Genistein (100 micromol/l) effectively reduced the growth factor-mediated DNA synthesis, which was associated with an inhibition of growth factor receptor protein expression. In response to daidzein no reduction in growth factor-mediated DNA synthesis was found. Daidzein (1; 10 micromol/l) combined with IGF-I caused even a slight increase in DNA amount compared with the untreated control. The expression of the IGF-1R precursor protein was reduced with 10 and 100 micromol/l daidzein, whereas the EGFR expression remained unchanged with daidzein. The results suggest that dietary isoflavones may interact with growth factor-induced stimulation of pig skeletal muscle growth.