ppGpp is a dual-role regulator involved in balancing iron absorption and prodiginine biosynthesis in Pseudoalteromonas.

Iron is an essential element for microbial survival and secondary metabolism. However, excess iron availability and overloaded secondary metabolites can hinder microbial growth and survival. Microorganisms must tightly control iron homeostasis and secondary metabolism. Our previous studies have found that the stringent starvation protein A (SspA) positively regulates prodiginine biosynthesis by activating iron uptake in Pseudoalteromonas sp. strain R3. It is believed that the interaction between SspA and the small nucleotide ppGpp is important for iron to exert regulation functions. However, the roles of ppGpp in iron absorption and prodiginine biosynthesis, and the underlying relationship between ppGpp and SspA in strain R3 remain unclear. In this study, we found that ppGpp accumulation in strain R3 could be induced by limiting iron. In addition, ppGpp not only positively regulated iron uptake and prodiginine biosynthesis via increasing the SspA level but also directly repressed iron uptake and prodiginine biosynthesis independent of SspA, highlighting the finding that ppGpp can stabilize both iron levels and prodiginine production. Notably, the abolishment of ppGpp significantly increased prodiginine production, thus providing a theoretical basis for manipulating prodiginine production in the future. This dynamic ppGpp-mediated interaction between iron uptake and prodiginine biosynthesis has significant implications for understanding the roles of nutrient uptake and secondary metabolism for the survival of bacteria in unfavorable environments.

Enhanced exclusive enteral nutrition delivery during the first 7 days is associated with decreased 28-day mortality in critically ill patients with normal lactate level: a post hoc analysis of a multicenter randomized trial.

BACKGROUND AND AIMS: Exclusive enteral nutrition (EN) is often observed during the first week of ICU admission because of the extra costs and safety considerations for early parenteral nutrition. This study aimed to assess the association between nutrition intake and 28-day mortality in critically ill patients receiving exclusive EN. METHODS: This is a post hoc analysis of a cluster-randomized clinical trial that assesses the effect of implementing a feeding protocol on mortality in critically ill patients. Patients who stayed in the ICUs for at least 7 days and received exclusive EN were included in this analysis. Multivariable Cox hazard regression models and restricted cubic spline models were used to assess the relationship between the different doses of EN delivery and 28-day mortality. Subgroups with varying lactate levels at enrollment were additionally analyzed to address the potential confounding effect brought in by the presence of shock-related hypoperfusion. RESULTS: Overall, 1322 patients were included in the analysis. The median (interquartile range) daily energy and protein delivery during the first week of enrollment were 14.6 (10.3-19.6) kcal/kg and 0.6 (0.4-0.8) g/kg, respectively. An increase of 5 kcal/kg energy delivery was associated with a significant reduction (approximately 14%) in 28-day mortality (adjusted hazard ratio [HR] = 0.865, 95% confidence interval [CI]: 0.768-0.974, P = 0.016). For protein intake, a 0.2 g/kg increase was associated with a similar mortality reduction with an adjusted HR of 0.868 (95% CI 0.770-0.979). However, the benefits associated with enhanced nutrition delivery could be observed in patients with lactate concentration ≤ 2 mmol/L (adjusted HR = 0.804 (95% CI 0.674-0.960) for energy delivery and adjusted HR = 0.804 (95% CI 0.672-0.962) for protein delivery, respectively), but not in those > 2 mmol/L. CONCLUSIONS: During the first week of critical illness, enhanced nutrition delivery is associated with reduced mortality in critically ill patients receiving exclusive EN, only for those with lactate concentration ≤ 2 mmol/L. TRIAL REGISTRATION: ISRCTN12233792, registered on November 24, 2017.

Modulation of sarcopenia phenotypes by glutathione peroxidase 4 overexpression in mice.

Our laboratory previously showed lipid hydroperoxides and oxylipin levels are elevated in response to loss of skeletal muscle innervation and are associated with muscle pathologies. To elucidate the pathological impact of lipid hydroperoxides, we overexpressed glutathione peroxidase 4 (GPx4), an enzyme that targets reduction of lipid hydroperoxides in membranes, in adult CuZn superoxide dismutase knockout (Sod1KO) mice that show accelerated muscle atrophy associated with loss of innervation. The gastrocnemius muscle from Sod1KO mice shows reduced mitochondrial respiration and elevated oxidative stress (F2 -isoprostanes and hydroperoxides) compared to wild-type (WT) mice. Overexpression of GPx4 improved mitochondrial respiration and reduced hydroperoxide generation in Sod1KO mice, but did not attenuate the muscle loss that occurs in Sod1KO mice. In contrast, contractile force generation is reduced in EDL muscle in Sod1KO mice relative to WT mice, and overexpression of GPx4 restored force generation to WT levels in Sod1KO mice. GPx4 overexpression also prevented loss of muscle contractility at the single fibre level in fast-twitch fibres from Sod1KO mice. Muscle fibres from Sod1KO mice were less sensitive to both depolarization and calcium at the single fibre level and exhibited a reduced activation by S-glutathionylation. GPx4 overexpression in Sod1KO mice rescued the deficits in both membrane excitability and calcium sensitivity of fast-twitch muscle fibres. Overexpression of GPx4 also restored the sarco/endoplasmic reticulum Ca2+ -ATPase activity in Sod1KO gastrocnemius muscles. These data suggest that GPx4 plays an important role in preserving excitation-contraction coupling function and Ca2+ homeostasis, and in maintaining muscle and mitochondrial function in oxidative stress-induced sarcopenia. KEY POINTS: Knockout of CuZn superoxide dismutase (Sod1KO) induces elevated oxidative stress with accelerated muscle atrophy and weakness. Glutathione peroxidase 4 (GPx4) plays a fundamental role in the reduction of lipid hydroperoxides in membranes, and overexpression of GPx4 improves mitochondrial respiration and reduces hydroperoxide generation in Sod1KO mice. Muscle contractile function deficits in Sod1KO mice are alleviated by the overexpression of GPx4. GPx4 overexpression in Sod1KO mice rescues the impaired muscle membrane excitability of fast-twitch muscle fibres and improves their calcium sensitivity. Sarco/endoplasmic reticulum Ca2+ -ATPase activity in Sod1KO muscles is decreased, and it is restored by the overexpression of GPx4. Our results confirm that GPx4 plays an important role in preserving excitation-contraction coupling function and Ca2+ homeostasis, and maintaining muscle and mitochondrial function in oxidative stress-induced sarcopenia.

Association between weight-adjusted-waist index and chronic kidney disease: a cross-sectional study.

AIMS: We aimed to investigate the potential association between weight-adjusted-waist index (WWI) and chronic kidney disease (CKD). DESIGN AND METHODS: This research examined data collected from the National Health and Nutrition Examination Survey (NHANES) spanning from 1999 to 2020. CKD was defined as the low estimated glomerular filtration rate (eGFR) or the existence of albuminuria (urinary albumin-to-creatinine ratio (ACR) ≥ 30mg/g). Low-eGFR was described as eGFR < 60 mL/min/1.73m2. The associations between WWI with CKD, albuminuria, and low-eGFR were examined using generalized additive models and weighted multivariable logistic regression models. We also analyzed the associations of other obesity indicators with CKD, albuminuria, and low-eGFR, including body mass index (BMI), waist-to-height ratio (WHtR), waist circumference(WC), height, and weight. The receiver operating characteristic (ROC) curves were used to assess and compare their diagnostic abilities. RESULTS: Males made up 48.26% of the total 40,421 individuals that were recruited. The prevalences of CKD, albuminuria, and low-eGFR were 16.71%, 10.97%, and 7.63%, respectively. WWI was found to be positively linked with CKD (OR = 1.42; 95% CI: 1.26, 1.60). A nonlinear connection between WWI and CKD was found using smooth curve fitting. Additionally, a higher prevalence of albuminuria is linked to a higher level of WWI (OR = 1.60; 95% CI: 1.40, 1.82). Different stratifications did not substantially influence the connection between WWI and CKD, albuminuria, and low-eGFR, according to subgroup analysis and interaction tests. We observed higher height was related to higher low-eGFR prevalence (OR = 1.05; 95% CI: 1.03, 1.06). ROC analysis revealed that WWI had the best discrimination and accuracy for predicting CKD and albuminuria compared to other obesity indicators (BMI, WHTR, WC, height and weight). In addition, height had the highest area under the curve (AUC) value for predicting low-eGFR. CONCLUSION: WWI is the best obesity indicator to predict CKD and albuminuria compared to other obesity indicators (BMI, WHTR, WC, height, and weight). WWI and CKD and albuminuria were found to be positively correlated. Furthermore, height had the strongest ability to predict low-eGFR. Therefore, the importance of WWI and height in assessing kidney health in US adults should be emphasized.

Impact of delayed veno-venous extracorporeal membrane oxygenation weaning on postoperative rehabilitation of lung transplantation: a single-center comparative study.

Veno-venous extracorporeal membrane oxygenation (VV-ECMO) is a reliable and effective extracorporeal life support during lung transplantation (LTx). However, the clinical benefit of delayed VV-ECMO weaning remains unclear. The current study aims to investigate whether delayed weaning of VV-ECMO is more beneficial to the rehabilitation for lung transplant patients. Patients who underwent LTx with VV-ECMO between January 2017 and January 2019 were included. Enrollment of patients was suitable for weaning off ECMO immediately after surgery. Randomization was performed in the operating room. Postoperative outcomes were compared between the two groups. Besides, univariate and multivariable logistic regressions were performed to estimate risk of postoperative complications. Compared to VV-ECMO weaning immediately after LTx, delayed weaning was associated with shorter hospital length of stay (days, 31 vs. 46; P < 0.05), lower incidence of noninvasive ventilation (4.3% vs. 24.4%; P < 0.05), primary graft dysfunction (PGD) (6.4% vs. 29.3%; P < 0.05), atrial fibrillation (AF) (4.3% vs. 22%, P < 0.05), and respiratory failure (4.3% vs. 19.5%; P < 0.05). Multivariable logistic regressions revealed that VV-ECMO weaning after LTx was independently correlated with increased risk of developing PGD [odds ratio (OR), 5.97, 95% CI 1.16-30.74], AF (OR, 6.87, 95% CI 1.66-28.47) and respiratory failure (OR, 6.02, 95% CI 1.12-32.49) by comparison of delayed VV-ECMO weaning. Patients with delayed VV-ECMO weaning are associated with lower complications and short hospital length of stay, while it relates to longer mechanical ventilation. These findings suggest that delayed VV-ECMO after LTx can facilitate rehabilitation.

Concurrent chemoradiotherapy versus radiotherapy alone for stage II nasopharyngeal carcinoma in the era of intensity-modulated radiotherapy.

BACKGROUND: Concurrent chemoradiotherapy has long been a standardized therapy for localized advanced nasopharyngeal cancer. It is widely used in clinical applications. In contrast, NCCN guidelines highlight that the efficacy of concurrent chemoradiotherapy for stage II nasopharyngeal cancer in the new era of intensity-modulated radiotherapy has not been defined. Thus, we systematically reviewed the significance of concurrent chemoradiotherapy for stage II nasopharyngeal cancer. METHODS: We searched the relevant literature in PubMed, EMBASE, and Cochrane, extracting relevant data from the searched literature. The main items extracted were hazard ratios (HRs), risk ratios (RRs) and 95% confidence intervals (CIs). When the HR could not be extracted from the literature, we used Engauge Digitizer software for extraction. Data analysis was accomplished using the Review Manager 5.4 tool. RESULTS: Our study included seven articles involving 1633 cases of stage II nasopharyngeal cancer. The survival outcomes were overall survival (OS) (HR = 1.03, 95% CI (0.71-1.49), P = 0.87), progression-free survival (PFS) (HR = 0.91, 95% CI (0.59-1.39), P = 0.66), distant metastasis-free survival (DMFS) (HR = 1.05, 95% CI (0.57-1.93), P = 0.87), local recurrence-free survival (LRFS) (HR = 0.87, 95% CI (0.41-1.84), P = 0.71, P > 0.05), and locoregional failure-free survival (LFFS) (HR = 1.18, 95% CI (0.52-2.70), P = 0.69). CONCLUSIONS: In the era of intensity-modulated radiotherapy, concurrent chemoradiotherapy and radiotherapy alone have the same survival benefits, and concurrent chemoradiotherapy increases acute hematological toxicity. Subgroup analysis showed that for people with N1 nasopharyngeal cancer at risk of distant metastases, concurrent chemoradiotherapy and radiotherapy alone also had equal survival benefits.

Associations of genetic risk, BMI trajectories, and the risk of non-small cell lung cancer: a population-based cohort study.

BACKGROUND: Body mass index (BMI) has been found to be associated with a decreased risk of non-small cell lung cancer (NSCLC); however, the effect of BMI trajectories and potential interactions with genetic variants on NSCLC risk remain unknown. METHODS: Cox proportional hazards regression model was applied to assess the association between BMI trajectory and NSCLC risk in a cohort of 138,110 participants from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. One-sample Mendelian randomization (MR) analysis was further used to access the causality between BMI trajectories and NSCLC risk. Additionally, polygenic risk score (PRS) and genome-wide interaction analysis (GWIA) were used to evaluate the multiplicative interaction between BMI trajectories and genetic variants in NSCLC risk. RESULTS: Compared with individuals maintaining a stable normal BMI (n = 47,982, 34.74%), BMI trajectories from normal to overweight (n = 64,498, 46.70%), from normal to obese (n = 21,259, 15.39%), and from overweight to obese (n = 4,371, 3.16%) were associated with a decreased risk of NSCLC (hazard ratio [HR] for trend = 0.78, P < 2×10-16). An MR study using BMI trajectory associated with genetic variants revealed no significant association between BMI trajectories and NSCLC risk. Further analysis of PRS showed that a higher GWAS-identified PRS (PRSGWAS) was associated with an increased risk of NSCLC, while the interaction between BMI trajectories and PRSGWAS with the NSCLC risk was not significant (PsPRS= 0.863 and PwPRS= 0.704). In GWIA analysis, four independent susceptibility loci (P < 1×10-6) were found to be associated with BMI trajectories on NSCLC risk, including rs79297227 (12q14.1, located in SLC16A7, Pinteraction = 1.01×10-7), rs2336652 (3p22.3, near CLASP2, Pinteraction = 3.92×10-7), rs16018 (19p13.2, in CACNA1A, Pinteraction = 3.92×10-7), and rs4726760 (7q34, near BRAF, Pinteraction = 9.19×10-7). Functional annotation demonstrated that these loci may be involved in the development of NSCLC by regulating cell growth, differentiation, and inflammation. CONCLUSIONS: Our study has shown an association between BMI trajectories, genetic factors, and NSCLC risk. Interestingly, four novel genetic loci were identified to interact with BMI trajectories on NSCLC risk, providing more support for the aetiology research of NSCLC. TRIAL REGISTRATION: http://www. CLINICALTRIALS: gov , NCT01696968 .

Salidroside Activates the AMP-Activated Protein Kinase Pathway to Suppress Nonalcoholic Steatohepatitis in Mice.

BACKGROUND AND AIMS: NASH is becoming a leading cause of liver cirrhosis and HCC. Salidroside (p-hydroxyphenethyl-ß-D-glucoside; SAL) has various biological and pharmacological activities, including anti-inflammatory, -oxidant, and -cancer activities. However, the therapeutic effect and underlying molecular mechanism of SAL in NASH remain to be further clarified. METHODS AND RESULTS: In this study, we found that SAL alleviated lipid accumulation and inflammatory response in primary hepatocytes after palmitic acid/oleic acid (PO) stimulation. In addition, SAL effectively prevented high-fat/high-cholesterol (HFHC)-diet-induced NASH progression by regulating glucose metabolism dysregulation, insulin resistance, lipid accumulation, inflammation, and fibrosis. Mechanistically, integrated RNA-sequencing and bioinformatic analysis showed that SAL promoted AMPK-signaling pathway activation in vitro and in vivo, and this finding was further verified by determining the phosphorylation levels of AMPK. Furthermore, the protective effects of SAL on lipid accumulation and inflammation in hepatocytes and livers induced by PO or HFHC stimulation were blocked by AMPK interruption. CONCLUSIONS: Our studies demonstrate that SAL protects against metabolic-stress-induced NASH progression through activation of AMPK signaling, indicating that SAL could be a potential drug component for NASH therapy.

Phosphorus equivalency of phytase with various evaluation indicators of duck in starter.

This study was conducted to evaluate phosphorus (P) equivalency of phytase with various evaluation indicators of ducks in starter (0-14 days). Three hundred and twenty 1-day-old Cherry Valley ducks were randomly assigned to eight groups. The dietary treatments were four levels of available phosphorus (aP) with 0.25%, 0.32%, 0.39%, and 0.46% (treatments I-IV) and four levels of phytase added to low-aP basal diet (treatment I) with 300, 600, 900, and 1200 units (U) per kg (treatments V-VIII). The results were that compared to treatment I, increasing aP and supplementary phytase significantly (p < 0.05) improved body weight (BW), BW gain (BWG), feed intake (FI), live BW, carcass weight, semieviscerated weight, eviscerated weight, leg muscle weight, and decreased feed conversion ratio (FCR). Treatments V and VI did not significantly increase tibia ash, tibia calcium, and tibia P of 14-day-old ducks (p > 0.05). Following the increase of aP level (treatments I-IV), apparent utilization of Ca and P of ducks increased with varying degrees. With the increase of dietary phytase level (treatments V-VIII), the apparent utilization of Ca and P showed no significant difference (p > 0.05) but an increasing trend. Serum P reached the highest level when adding 600 U/kg phytase (treatment VI). Serum Ca and serum alkaline phosphatase activity showed no significant difference among treatments V-VIII (p > 0.05). Based on corn-soybean-rapeseed meal diet, with the evaluation indexes of FI, BWG, tibia ash, tibia Ca, tibia P, and apparent utilization of Ca and P, the addition of 500 U/kg phytase could release aP of 0.03%, 0.04%, 0.02%, 0.01%, 0.02%, 0.08%, and 0.07%, respectively. On the same way, the addition of 1000 U/kg phytase could release aP of 0.07%, 0.09%, 0.06%, 0.02%, 0.07%, 0.09%, and 0.09%, respectively.

Effects of voluntary wheel running on mitochondrial content and dynamics in rat skeletal muscle.

This study reports that in rat skeletal muscle the proteins specifically responsible for mitochondrial dynamics, mitofusin-2 (MFN2) and mitochondrial dynamics protein 49 (MiD49), are higher (p < 0.05) in oxidative soleus (SOL) muscle compared with predominantly glycolytic extensor digitorum longus (EDL) muscle, but not seen for optic atrophy 1 (OPA1; p = 0.06). Markers of mitochondrial content, complex I component, NADH:Ubiquinone oxidoreductase subunit A9 (NDUFA9) and complex IV protein, cytochrome C oxidase subunit IV (COXIV; p < 0.05) were also higher in SOL compared with EDL muscle; however, there was no difference in mitochondrial content between muscles, as measured using a citrate synthase assay (p > 0.05). SOL and EDL muscles were compared between age-matched sedentary rats that were housed individually with (RUN) or without (SED) free-access to a running wheel for 12 weeks and showed no change in mitochondrial content, as examined by the abundances of NDUFA9 and COXIV proteins, as well as citrate synthase activity, in either muscle (p > 0.05). Compared to SED animals, MiD49 and OPA1 were not different in either EDL or SOL muscles, and MFN2 was higher in SOL muscles from RUN rats (p < 0.05). Overall, these findings reveal that voluntary wheel running is an insufficient stimulus to result in a significantly higher abundance of most markers of mitochondrial content or dynamics, and it is likely that a greater stimulus, such as either adding resistance to the wheel or an increase in running volume by using a treadmill, is required for mitochondrial adaptation in rat skeletal muscle.

Nutritional practice in critically ill COVID-19 patients: A multicenter ambidirectional cohort study in Wuhan and Jingzhou.

BACKGROUND AND OBJECTIVES: The novel coronavirus disease (COVID-19) epidemic is spreading all over the world. With the number of cases increasing rapidly, the epidemiological data on the nutritional practice is scarce. In this study, we aim to describe the clinical characteristics and nutritional practice in a cohort of critically ill COVID-19 patients. METHODS AND STUDY DESIGN: This is a multicenter, ambidirectional cohort study conducted at 11 hospitals in Hubei Province, China. All eligible critical COVID-19 patients in the study hospital intensive care units at 00:00, March 6th, 2020, were included. Data collection was performed via written case report forms. RESULTS: A total of 44 patients were identified and enrolled, of whom eight died during the 28-day outcome follow- up period. The median interval between hospital admission and the study day was 24 (interquartile range, 13- 26) days and 52.2% (23 of 44) of patients were on invasive mechanical ventilation. The median nutrition risk in critically ill (mNUTRIC) score was 3 (interquartile range, 2-5) on the study day. During the enrolment day, 68.2% (30 of 44) of patients received enteral nutrition (EN), while 6.8% (3 of 44) received parenteral nutrition (PN) alone. Nausea and aspiration were uncommon, with a prevalence of 11.4% (5 of 44) and 6.8% (3 of 44), respectively. As for energy delivery, 69.7% (23 of 33) of patients receiving EN and/or PN were achieving their prescribed targets. CONCLUSIONS: The study showed that EN was frequently applied in critical COVID-19 patients. Energy delivery may be suboptimal in this study requiring more attention.

Elevated MMP2 abundance and activity in mdx mice are alleviated by prenatal taurine supplementation.

Duchenne muscular dystrophy (DMD) is a severe, progressive muscle-wasting disorder that leads to early death. The mdx mouse is a naturally occurring mutant model for DMD. It lacks dystrophin and displays peak muscle cell necrosis at ~28 days (D28), but in contrast to DMD, mdx mice experience muscle regeneration by D70. We hypothesized that matrix metalloproteinase-2 (MMP2) and/or MMP9 play key roles in the degeneration/regeneration phases in mdx mice. MMP2 abundance in muscle homogenates, measured by calibrated Western blotting, and activity, measured by zymogram, were lower at D70 compared with D28 in both mdx and wild-type (WT) mice. Importantly, MMP2 abundance was higher in both D28 and D70 mdx mice than in age-matched WT mice. The higher MMP2 abundance was not due to infiltrating macrophages, because MMP2 content was still higher in isolated muscle fibers where most macrophages had been removed. Prenatal supplementation with the amino acid taurine, which improved muscle strength in D28 mdx mice, produced approximately twofold lower MMP2 activity, indicating that increased MMP2 abundance is not required when muscle damage is attenuated. There was no difference in MMP9 abundance between age-matched WT and mdx mice (P > 0.05). WT mice displayed decreased MMP9 abundance as they aged. While MMP9 may have a role during age-related skeletal muscle growth, it does not appear essential for degeneration/regeneration cycles in the mdx mouse. Our findings indicate that MMP2 plays a more active role than MMP9 in the degenerative phases of muscle fibers in D28 mdx mice.

Universal Adaptive Neural Network Predictive Algorithm for Remotely Piloted Unmanned Combat Aerial Vehicle in Wireless Sensor Network.

Remotely piloted unmanned combat aerial vehicle (UCAV) will be a prospective mode of air fight in the future, which can remove the physical restraint of the pilot, maximize the performance of the fighter and effectively reduce casualties. However, it has two difficulties in this mode: (1) There is greater time delay in the network of pilot-wireless sensor-UCAV, which can degrade the piloting performance. (2) Designing of a universal predictive method is very important to pilot different UCAVs remotely, even if the model of the control augmentation system of the UCAV is totally unknown. Considering these two issues, this paper proposes a novel universal modeling method, and establishes a universal nonlinear uncertain model which uses the pilot's remotely piloted command as input and the states of the UCAV with a control augmentation system as output. To deal with the nonlinear uncertainty of the model, a neural network observer is proposed to identify the nonlinear dynamics model online. Meanwhile, to guarantee the stability of the overall observer system, an adaptive law is designed to adjust the neural network weights. To solve the greater transmission time delay existing in the pilot-wireless sensor-UCAV closed-loop system, a time-varying delay state predictor is designed based on the identified nonlinear dynamics model to predict the time delay states. Moreover, the overall observer-predictor system is proved to be uniformly ultimately bounded (UUB). Finally, two simulations verify the effectiveness and universality of the proposed method. The results indicate that the proposed method has desirable performance of accurately compensating the time delay and has universality of remotely piloting two different UCAVs.

Restoration of Sarcoplasmic Reticulum Ca2+ ATPase (SERCA) Activity Prevents Age-Related Muscle Atrophy and Weakness in Mice.

Sarcopenia has a significant negative impact on healthspan in the elderly and effective pharmacologic interventions remain elusive. We have previously demonstrated that sarcopenia is associated with reduced activity of the sarcoplasmic reticulum Ca2+ ATPase (SERCA) pump. We asked whether restoring SERCA activity using pharmacologic activation in aging mice could mitigate the sarcopenia phenotype. We treated 16-month male C57BL/6J mice with vehicle or CDN1163, an allosteric SERCA activator, for 10 months. At 26 months, maximal SERCA activity was reduced 41% in gastrocnemius muscle in vehicle-treated mice but maintained in old CDN1163 treated mice. Reductions in gastrocnemius mass (9%) and in vitro specific force generation in extensor digitorum longus muscle (11%) in 26 versus 16-month-old wild-type mice were also reversed by CDN1163. CDN1163 administered by intra-peritoneal injection also prevented the increase in mitochondrial ROS production in gastrocnemius muscles of aged mice. Transcriptomic analysis revealed that these effects are at least in part mediated by enhanced cellular energetics by activation of PGC1-α, UCP1, HSF1, and APMK and increased regenerative capacity by suppression of MEF2C and p38 MAPK signaling. Together, these exciting findings are the first to support that pharmacological targeting of SERCA can be an effective therapy to counter age-related muscle dysfunction.

Mitochondrial content is preserved throughout disease progression in the mdx mouse model of Duchenne muscular dystrophy, regardless of taurine supplementation.

Mitochondrial dysfunction is a pathological feature of Duchenne muscular dystrophy (DMD), a debilitating and fatal neuromuscular disorder characterized by progressive muscle wasting and weakness. Mitochondria are a source of cellular ATP involved in Ca2+ regulation and apoptotic signaling. Ameliorating aberrant mitochondrial function has therapeutic potential for reducing DMD disease severity. The dystrophic mdx mouse exhibits peak muscle damage at 21-28 days, which stabilizes after 8 wk. The amino acid taurine is implicated in mitochondrial health and function, with endogenous concentrations low when measured during the cycle of peak muscle damage in mdx mice. Using whole soleus and extensor digitorum longus (EDL) muscle homogenates from 28- and 70-day mdx mice, we found that there was no change in native state mitochondrial complexes using blue native-PAGE. NADH:ubiquinone oxidotreductase subunit-A9 (NDUFA9) protein abundance was lower in soleus muscle of 28- and 70-day mdx mice and EDL muscle of 70-day mdx mice compared with same muscles in WT (C57/BL10ScSn) animals. There were age-dependent increases in both NDUFA9 protein abundance and citrate synthase activity in soleus muscles of mdx and wild-type mice. There was no change in abundances of mitochondrial dynamics proteins mitofusin 2 (Mfn2) and mitochondrial dynamics protein 49 (MiD49). Taurine administration essentially did not affect any measurements of mitochondria. Collectively, these findings suggest mitochondrial content and dynamics are not reduced in the mdx mouse regardless of disease severity. We also elucidate that taurine affords no significant benefit to mitochondrial content or dynamics in the mdx mouse at either 28 or 70 days.

A probabilistic method for testing and estimating selection differences between populations.

Human populations around the world encounter various environmental challenges and, consequently, develop genetic adaptations to different selection forces. Identifying the differences in natural selection between populations is critical for understanding the roles of specific genetic variants in evolutionary adaptation. Although numerous methods have been developed to detect genetic loci under recent directional selection, a probabilistic solution for testing and quantifying selection differences between populations is lacking. Here we report the development of a probabilistic method for testing and estimating selection differences between populations. By use of a probabilistic model of genetic drift and selection, we showed that logarithm odds ratios of allele frequencies provide estimates of the differences in selection coefficients between populations. The estimates approximate a normal distribution, and variance can be estimated using genome-wide variants. This allows us to quantify differences in selection coefficients and to determine the confidence intervals of the estimate. Our work also revealed the link between genetic association testing and hypothesis testing of selection differences. It therefore supplies a solution for hypothesis testing of selection differences. This method was applied to a genome-wide data analysis of Han and Tibetan populations. The results confirmed that both the EPAS1 and EGLN1 genes are under statistically different selection in Han and Tibetan populations. We further estimated differences in the selection coefficients for genetic variants involved in melanin formation and determined their confidence intervals between continental population groups. Application of the method to empirical data demonstrated the outstanding capability of this novel approach for testing and quantifying differences in natural selection.

Physiological and biochemical characteristics of skeletal muscles in sedentary and active rats.

Laboratory rats are sedentary if housed in conditions where activity is limited. Changes in muscle characteristics with chronic inactivity were investigated by comparing sedentary rats with rats undertaking voluntary wheel running for either 6 or 12 weeks. EDL (type II fibers) and soleus (SOL) muscles (predominantly type I fibers) were examined. When measured within 1-2 h post-running, calcium sensitivity of the contractile apparatus was increased, but only in type II fibers. This increase disappeared when fibers were treated with DTT, indicative of oxidative regulation of the contractile apparatus, and was absent in fibers from rats that had ceased running 24 h prior to experiments. Specific force production was ~ 10 to 25% lower in muscle fibers of sedentary compared to active rats, and excitability of skinned fibers was decreased. Muscle glycogen content was ~ 30% lower and glycogen synthase content ~ 50% higher in SOL of sedentary rats, and in EDL glycogenin was 30% lower. Na+, K+-ATPase α1 subunit density was ~ 20% lower in both EDL and SOL in sedentary rats, and GAPDH content in SOL ~ 35% higher. There were no changes in content of the calcium handling proteins calsequestrin and SERCA, but the content of CSQ-like protein was increased in active rats (by ~ 20% in EDL and 60% in SOL). These findings show that voluntary exercise elicits an acute oxidation-induced increase in Ca2+ sensitivity in type II fibers, and also that there are substantial changes in skeletal muscle characteristics and biochemical processes in sedentary rats.

Effect of androgen deprivation therapy on the contractile properties of type I and type II skeletal muscle fibres in men with non-metastatic prostate cancer.

The contractile properties of vastus lateralis muscle fibres were examined in prostate cancer (PrCa) patients undergoing androgen deprivation therapy (ADT) and in age- and activity-matched healthy male subjects (Control). Mechanically-skinned muscle fibres were exposed to a sequence of heavily Ca2+ -buffered solutions at progressively higher free [Ca2+ ] to determine their force-Ca2+ relationship. Ca2+ -sensitivity was decreased in both type I and type II muscle fibres of ADT subjects relative to Controls (by -0.05 and -0.04 pCa units, respectively, P < .02), and specific force was around 13% lower in type I fibres of ADT subjects than in Controls (P = .02), whereas there was no significant difference in type II fibres. Treatment with the reducing agent dithiothreitol slightly increased specific force in type I and type II fibres of ADT subjects (by ~2%-3%, P < .05) but not in Controls. Pure type IIx fibres were found frequently in muscle from ADT subjects but not in Controls, and the overall percentage of myosin heavy chain IIx in muscle samples was 2.5 times higher in ADT subjects (P < .01). The findings suggest that testosterone suppression can negatively impact the contractile properties by (i) reducing Ca2+ -sensitivity in both type I and type II fibres and (ii) reducing maximum specific force in type I fibres.

Changes in contractile and metabolic parameters of skeletal muscle as rats age from 3 to 12 months.

Laboratory rats are considered mature at 3 months despite that musculoskeletal growth is still occurring. Changes in muscle physiological and biochemical characteristics during development from 3 months, however, are not well understood. Whole muscles and single skinned fibres from fast-twitch extensor digitorum longus (EDL) and predominantly slow-twitch soleus (SOL) muscles were examined from male Sprague-Dawley rats (3, 6, 9, 12 months). Ca2+ sensitivity of contractile apparatus decreased with age in both fast- (~ 0.04 pCa units) and slow-twitch (~ 0.07 pCa units) muscle fibres, and specific force increased (by ~ 50% and ~ 25%, respectively). Myosin heavy chain composition of EDL and SOL muscles altered to a small extent with age (decrease in MHCIIa proportion after 3 months). Glycogen content increased with age (~ 80% in EDL and 25% in SOL) and GLUT4 protein density decreased (~ 35 and 20%, respectively), whereas the glycogen-related enzymes were little changed. GAPDH protein content was relatively constant in both muscle types, but COXIV protein decreased ~ 40% in SOL muscle. Calsequestrin (CSQ) and SERCA densities remained relatively constant with age, whereas there was a progressive ~ 2-3 fold increase in CSQ-like proteins, though their role and importance remain unclear. There was also ~ 40% decrease in the density of the Na+, K+-ATPase (NKA) α1 subunit in EDL and the α2 subunit in SOL. These findings emphasise there are substantial changes in skeletal muscle function and the density of key proteins during early to mid-adulthood in rats, which need to be considered in the design and interpretation of experiments.

When phosphorylated at Thr148, the ß2-subunit of AMP-activated kinase does not associate with glycogen in skeletal muscle.

The 5'-AMP-activated protein kinase (AMPK), a heterotrimeric complex that functions as an intracellular fuel sensor that affects metabolism, is activated in skeletal muscle in response to exercise and utilization of stored energy. The diffusibility properties of α- and ß-AMPK were examined in isolated skeletal muscle fiber segments dissected from rat fast-twitch extensor digitorum longus and oxidative soleus muscles from which the surface membranes were removed by mechanical dissection. After the muscle segments were washed for 1 and 10 min, ∼60% and 75%, respectively, of the total AMPK pools were found in the diffusible fraction. After in vitro stimulation of the muscle, which resulted in an ∼80% decline in maximal force, 20% of the diffusible pool became bound in the fiber. This bound pool was not associated with glycogen, as determined by addition of a wash step containing amylase. Stimulation of extensor digitorum longus muscles resulted in 28% glycogen utilization and a 40% increase in phosphorylation of the downstream AMPK target acetyl carboxylase-CoA. This, however, had no effect on the proportion of total ß2-AMPK that was phosphorylated in whole muscle homogenates measured by immunoprecipitation. These findings suggest that, in rat skeletal muscle, ß2-AMPK is not associated with glycogen and that activation of AMPK by muscle contraction does not dephosphorylate ß2-AMPK. These findings question the physiological relevance of the carbohydrate-binding function of ß2-AMPK in skeletal muscle.