Muscle Atrophy F-box mRNA Expression Research Articles

Metformin attenuates angiotensin II‑induced cardiomyocyte hypertrophy by upregulating the MuRF1 and MAFbx pathway

Pathological cardiac hypertrophy induced by aging and neurohumoral activation, such as angiotensin II (Ang II) activation, is an independent risk factor for heart failure. The muscle really interesting new gene-finger protein-1 (MuRF1) and muscle atrophy F-box (MAFbx) pathway has been previously reported to be an important mechanism underlying the pathogenesis of cardiac hypertrophy. Metformin is currently the first-line blood glucose-lowering agent that can be useful for the treatment of cardiovascular diseases. However, the potential role of metformin in the modulation of MuRF1 and MAFbx in cardiomyocyte hypertrophy remains poorly understood. The present study used H9c2 cells, a cardiomyocyte cell model. The surface area of cultured rat H9c2 myoblasts was measured and the expression levels of MuRF1 and MAFbx were quantified using western blot or reverse transcription-quantitative PCR. H9c2 cells were transfected with MuRF1 and MAFbx small interfering (si) RNA. The present study revealed that Ang II treatment significantly increased the cell surface area of model cardiomyocytes. Additionally, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) mRNA and protein expression was increased following this treatment. Ang II also downregulated MuRF1 and MAFbx protein and mRNA expression. In the H9C2, treatment with metformin attenuated hypertrophic remodeling. In addition, expression of ANP and BNP was significantly reduced in metformin-treated H9C2 cells. The results indicated that metformin increased the activity of MuRF1 and MAFbx and upregulated their expression, the knockdown of which resulted in deteriorative Ang II-induced cell hypertrophy, even following treatment with metformin. Taken together, data from the present study suggest that metformin can prevent cardiac hypertrophy through the MuRF1 and MAFbx pathways.

Effects of electroacupuncture on proangiogenesis process and protein turnover in a mouse model of sarcopenia

To observe the effect of electroacupuncture(EA) on proangiogenesis process and protein turn-over in a mouse model of sarcopenia, so as to explore its potential molecular mechanism anti-aging. Fourteen 30-week-old male SAMP8 mice were randomly divided into a model group (n=7) and an EA group (n=7). Seven anti-rapidly aging SAMR1 mice of the same age were used as the control group (n=7). EA (1 mA, 4 Hz) was applied to bilateral "Zusanli"(ST36) and "Yanglingquan"(GB34) for 20 minutes each time once a day, 6 times a week for 4 weeks. The exhausted running platform was used to test the sports function. Gastrocnemius muscle mass and relative ratio of gastrocnemius muscle mass to body mass were measured. HE staining and transmission electron microscope were used to observe the morphology, and the cross-sectional area of gastrocnemius muscle was calculated. Relative protein expressions of protein kinase B (AKT) , phosphorylated (p) -AKT, mammalian target of rapamycin (mTOR) , p-mTOR, p70 ribosomal protein S6 kinase (p70S6K) , p-p70S6K,hypoxia inducible factor-1α (HIF-1α) and relative mRNA expressions of HIF-1α, vascular endothelial growth factor A (VEGF-A) , muscle RING finger-1 (MuRF-1) and muscle atrophy F-box (MAFbx) were detected by Western blot and real-time fluorescence quantitative PCR, seperatively. Compared with the control group, the running time and distance, body mass and gastrocnemius mass, and the ratio of gastrocnemius mass to body mass decreased(P<0.01, P<0.05), cross-sectional area of gastrocnemius, related protein expression of p-AKT,p-mTOR, p-p70S6K and HIF-1α, mRNA expression of HIF-1α and VEGF-A decreased (P<0.01), while mRNA expression of MuRF1 and MAFbx increased (P<0.01) in the model group. Following EA intervention, the running time and distance, body mass and gastrocnemius mass and the ratio of gastrocnemius mass to body mass increased (P<0.05), cross-sectional area of gastrocnemius, related protein expression of p-AKT,p-mTOR, p-p70S6K and HIF-1α, mRNA expression of HIF-1α and VEGF-A were significantly up-regulated (P<0.01), mRNA expression of MuRF1 and MAFbx down-regulated (P<0.01, P<0.05) in the EA group compared with the model group. EA may delay the aging muscle atrophy in mice by regulating the gastrocnemius muscle's proangiogenesis process and protein turnover.

Heat stress alters muscle protein and amino acid metabolism and accelerates liver gluconeogenesis for energy supply in broilers

Heat stress impairs growth performance and alters body protein and amino acid metabolism. This study was investigated to explore how body protein and amino acid metabolism changed under heat stress (HS) and the stress adaptation mechanism. A total of 144 broilers (28 d old) were divided into 3 treatment groups for 1 wk: HS group (32°C), normal control group (22°C), and pair-feeding group (22°C). We found that HS elevated the feed-to-gain ratio, reduced the ADFI and ADG, decreased breast muscle mass and plasma levels of several amino acids (glycine, lysine, threonine, and tyrosine), and increased serum glutamic oxaloacetic transaminase (GOT) activity and corticosterone (CORT) level and liver GOT and glutamic pyruvic transaminase activities. Heat stress elevated muscle atrophy F-box mRNA expression and reduced mRNA expression of the 70-kD ribosomal protein S6 kinase in the breast muscle of broilers. Broilers in the HS group exhibited striking increases of mRNA expressions of solute carrier family 1 member 1, family 3 member 1, family 7 member 1, and family 7 member-like in the liver and liver gluconeogenesis genes (PCKc, PCKm, PC, and FBP1) in comparison with the other 2 groups. In conclusion, HS increased the circulating CORT level and subsequently caused muscle protein breakdown to provide amino acid substrates to liver gluconeogenesis responsible for energy supply.

GW24-e2121 Adenosine monophosphate-activated protein kinase attenuates cardiomyocyte hypertrophy through regulation of FOXO3a/MAFbx signalling pathway

ObjectivesTo examine the inhibitory effects of adenosine monophosphate-activated protein kinase (AMPK) activation on cardiomyocyte hypertrophy in vitro and to investigate the underlying molecular mechanisms.MethodsCultured neonatal rat cardiomyocytes were treated with...

Effect of Prehabilitation on the Outcome of Anterior Cruciate Ligament Reconstruction

Background: Prehabilitation is defined as preparing an individual to withstand a stressful event through enhancement of functional capacity. Hypothesis: We hypothesized that a preoperative exercise program would enhance postoperative outcomes after anterior cruciate ligament reconstruction (ACLR). Study Design: Randomized controlled clinical trial; Level of evidence, 1. Methods: Twenty volunteers awaiting ACLR were randomly assigned to a control or exercise intervention group. The exercise group completed a 6-week gym- and home-based exercise program. Assessments include single-legged hop test; quadriceps and hamstring peak torque and magnetic resonance imaging cross-sectional area (CSA); Modified Cincinnati Knee Rating System score; and muscle biopsy of the vastus lateralis muscle completed at baseline, preoperatively, and 12 weeks postoperatively. Myosin heavy chain (MHC) isoforms protein and messenger RNA (mRNA) expression were determined with SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) and RT-PCR (real-time polymerase chain reaction), respectively; IGF-1 (insulin-like growth factor 1), MuRF-1 (muscle RING-finger protein-1), and MAFbx (muscle atrophy f-box) mRNA expression were determined with quantitative RT-PCR. Results: Following 6 weeks of exercise intervention, the single-legged hop test results improved significantly in the exercise-injured limb compared with baseline (P = .001). Quadriceps peak torque in the injured limb improved with similar gains in CSA compared with baseline (P = .001). However, this was not significantly increased compared with the control group. Quadriceps and vastus medialis CSA were also larger in the exercise group than in controls (P = .0024 and P = .015, respectively). The modified Cincinnati score was better in the exercise-injured limb compared with baseline. At 12 weeks postoperatively, the rate of decline in the single-legged hop test was reduced in the exercise group compared with controls (P = .001). Similar trends were not seen for quadriceps peak torque and CSA. The vastus medialis CSA had regressed to similar levels as the control group (P = .008). The modified Cincinnati score continued to increase in the exercise group compared with controls (P = .004). The expression of the hypertrophic IGF-1 gene was significantly increased after the exercise intervention (P = .028), with a decrease back to baseline 12 weeks postoperatively (P = .012). Atrophic MuRF-1 gene expression was decreased after intervention compared with baseline (P = .05) but increased again at 12 weeks postoperatively (P = .03). The MAFbx levels did not change significantly in either group and within each time point. On the mRNA level, there was a shift from MHC-IIx isoform to MHC-IIa after exercise, with significant changes compared with control preoperatively (P = .028). Protein testing was able to reproduce this increase for MHC-IIa isoform expression only. Conclusion: The 6-week progressive prehabilitation program for subjects undergoing ACLR led to improved knee function based on the single-legged hop test and self-reported assessment using the modified Cincinnati score. These effects were sustained at 12 weeks postoperatively. This study supports prehabilitation as a consideration for patients awaiting ACLR; however, further studies are warranted.

Adenosine monophosphate-activated protein kinase attenuates cardiomyocyte hypertrophy through regulation of FOXO3a/MAFbx signalling pathway

AimTo examine the inhibitory effects of adenosine monophosphate-activated protein kinase (AMPK) activation on cardiomyocytes hypertrophy and explore the underlying molecular mechanisms.MethodsCultured neonatal rat cardiomyocytes were treated with specific AMPK activator...

No muscle atrophy without GSK-3β. Focus on “Glycogen synthase kinase-3β is required for the induction of skeletal muscle atrophy”

skeletal muscle atrophy is driven by an imbalance of protein synthesis and degradation, generally in favor of the latter. The ubiquitin-proteasome system (UPS) is commonly regarded as the major proteolytic system involved in breakdown of muscle protein under atrophy-inducing conditions ([6][1]), and

Muscle protein breakdown has a minor role in the protein anabolic response to essential amino acid and carbohydrate intake following resistance exercise

Muscle protein breakdown (MPB) is increased following resistance exercise, but ingestion of carbohydrate during postexercise recovery can decrease MPB with no effect on muscle protein synthesis (MPS). We sought to determine whether a combination of essential amino acids (EAA) with low carbohydrate or high carbohydrate could effectively reduce MPB following resistance exercise and improve muscle protein net balance (NB). We hypothesized that higher levels of carbohydrate and resulting increases in circulating insulin would inhibit MPB and associated signaling, resulting in augmented NB. Thirteen male subjects were assigned to one of two groups receiving equivalent amounts of EAA (approximately 20 g) but differing carbohydrate levels (low = 30, high = 90 g). Groups ingested nutrients 1 h after an acute bout of leg resistance exercise. Leg phenylalanine kinetics (e.g., MPB, MPS, NB), signaling proteins, and mRNA expression were assessed on successive muscle biopsies using stable isotopic techniques, immunoblotting, and real-time quantitative PCR, respectively. MPB tended to decrease (P < 0.1) and MPS increased (P < 0.05) similarly in both groups following nutrient ingestion. No group differences were observed, but muscle ring finger 1 (MuRF1) protein content and MuRF1 mRNA expression increased following resistance exercise and remained elevated following nutrient ingestion, while autophagy marker (light-chain 3B-II) decreased after nutrient ingestion (P < 0.05). Forkhead box-O3a phosphorylation, total muscle atrophy F-box (MAFbx) protein, and MAFbx and caspase-3 mRNA expression were unchanged. We conclude that the enhanced muscle protein anabolic response detected when EAA+carbohydrate are ingested postresistance exercise is primarily due to an increase in MPS with minor changes in MPB, regardless of carbohydrate dose or circulating insulin level.

Influence of hormone replacement therapy on eccentric exercise induced myogenic gene expression in postmenopausal women

Hormone replacement therapy (HRT) is used in postmenopausal women to relieve symptoms of menopause and prevent osteoporosis. We sought to evaluate changes in mRNA expression of key myogenic factors in postmenopausal women taking and not taking HRT following a high-intensity eccentric resistance exercise. Fourteen postmenopausal women were studied and included 6 control women not using HRT (59 +/- 4 years, 63 +/- 17 kg) and 8 women using traditional HRT (59 +/- 4 yr, 89 +/- 24 kg). Both groups performed 10 sets of 10 maximal eccentric repetitions of single-leg extension on a Cybex dynamometer at 60 degrees /s. Muscle biopsies of the vastus lateralis were obtained from the exercised leg at baseline and 4 h after the exercise bout. Gene expression was determined using RT-PCR for follistatin, forkhead box 3A (FOXO3A), muscle atrophy F-box (MAFbx), muscle ring finger-1 (MuRF-1), myogenic differentiation factor (MyoD), myogenin, myostatin, myogenic factor 5 (Myf5), and muscle regulatory factor 4 (MRF4). At rest, the HRT group expressed higher levels of MyoD, myogenin, Myf5, MRF4, and follistatin (P < 0.05). In response to eccentric exercise, follistatin, MyoD, myogenin, Myf5, and MRF4 were significantly increased (P <or= 0.05) and FOXO3A, MAFbx, MuRF-1, and myostatin were significantly decreased in the control and HRT groups (P <or= 0.05). Significantly greater changes in mRNA expression of follistatin, FOXO3A, MAFbx, MuRF-1, MyoD, myogenin, myostatin, Myf5, and MRF4 (p<or=0.05) occurred in the HRT group than in the control group after exercise. These data suggest that postmenopausal women using HRT express higher myogenic regulatory factor gene expression, which may reflect an attempt to preserve muscle mass. Furthermore, postmenopausal women using HRT experienced a greater myogenic response to maximal eccentric exercise.

MAFbx and MuRF1 mRNA expression and its relationship with muscular contractility following free muscle transfer

To study muscle atrophy F-box (MAFbx) and muscle ring finger 1 (MuRF1) mRNA expression and its relationship with muscular contraction following free muscle transfer. The gracilis muscle was orthotopic transferred in adult rat to establish the animal model. The muscle at the unoperated side was used as control. The expression of MAFbx and MuRF1 mRNA, the muscle contraction and muscle function were measured by real-time PCR and multiple function physiological device. The relationship among the expression of MAFbx and MuRF1 mRNA, the muscle contraction and muscle function was analyzed. After muscle free transfer, muscle wet weight reservation, the maximum contraction and tetanus strength reduce first and increased later, but still lower than those at control side. The expression of MAFbx and MuRF1 mRNA reached peak level 3 - 4 weeks after muscle transfer which was 7.1 and 4.1 times as that at control side. It decreased later, but still higher than that at control side, showing a significant difference between them (P< 0. 05). Persistent over-expression of MAFbx and MuRF1 mRNA after muscle transfer has a close relationship with muscle atrophy and muscle dysfunction. MAFbx and MuRF1 can be used as markers for early muscle atrophy, and also as potential target for drug treatment of muscle atrophy.

Decreased muscle atrophy F‐box (MAFbx) expression in regenerating muscle after muscle‐damaging exercise

A muscle-specific ubiquitin ligase, Muscle Atrophy F-box (MAFbx), is known to mediate the degradation of muscle-specific transcription factor MyoD in vitro. Its regulation in regenerating skeletal muscle, however, has not been clarified. We looked for evidence of MAFbx downregulation in the course of regeneration after muscle damaging exercise. The soleus and gastrocnemius muscles of mice were subjected to forced eccentric contraction by electrical stimulation to induce muscle damage. The expression of developmental myosin heavy chain (MHCd) suggested that muscle regeneration took place from Day 3 after exercise. mRNA and protein expression of MAFbx decreased on Days 3, 5, and 7, while MyoD protein increased on Days 3, 5, and 7. Although further study is required to establish the causal relationships, downregulation of MAFbx may have reduced MyoD degradation in favor of muscle regeneration.