Dynamic changes in DICER levels in adipose tissue control metabolic adaptations to exercise.

DICER is a key enzyme in microRNA (miRNA) biogenesis. Here we show that aerobic exercise training up-regulates DICER in adipose tissue of mice and humans. This can be mimicked by infusion of serum from exercised mice into sedentary mice and depends on AMPK-mediated signaling in both muscle and adipocytes. Adipocyte DICER is required for whole-body metabolic adaptations to aerobic exercise training, in part, by allowing controlled substrate utilization in adipose tissue, which, in turn, supports skeletal muscle function. Exercise training increases overall miRNA expression in adipose tissue, and up-regulation of miR-203-3p limits glycolysis in adipose under conditions of metabolic stress. We propose that exercise training-induced DICER-miR-203-3p up-regulation in adipocytes is a key adaptive response that coordinates signals from working muscle to promote whole-body metabolic adaptations.

The transition of total elbow arthroplasty into the outpatient theater.

BACKGROUND: Outpatient total joint arthroplasty is increasing in frequency as reimbursement models change. Potential benefits include same-day surgery for patients and decreased exposure to nosocomial pathogens. This study aims to determine if total elbow arthroplasty (TEA) is also trending toward an outpatient setting, and if there is any impact on complication rates as a result. METHODS: A retrospective chart review of the American College of Surgeons National Surgical Quality Improvement Program was performed. Specifically, the database was queried for all patients with CPT code 24363 from 2010-2017. The percentage of TEAs performed each year as an outpatient was trended from 2010-2017. Additionally, the complication rate between the inpatient and outpatient cohorts was compared. RESULTS: A total of 524 TEAs were analyzed. Of these, 111 procedures (21.2%) were performed as an outpatient. There was a statistically significant increase in the percentage of outpatient TEAs from 2010-2017 (P = .0016). In 2010, 2.4% of TEAs were outpatient, compared with 34.5% in 2017. The total complication rate trended toward being lower in the outpatient group, but this difference was not statistically significant (P = .08). CONCLUSIONS: There is a significant trend toward TEA being performed as an outpatient procedure, with more than one-third currently being performed in this manner. In our study, there was no difference in the complication rate between inpatient and outpatient TEAs; in fact, outpatient TEAs trended toward having a lower complication rate than inpatient TEAs. Taken together, the outpatient setting comprises an ever-increasing segment of TEA without an increase in morbidity to patients.

In Vivo Analysis of Troponin C Knock-In (A8V) Mice: Evidence that TNNC1 Is a Hypertrophic Cardiomyopathy Susceptibility Gene.

BACKGROUND: Mutations in thin-filament proteins have been linked to hypertrophic cardiomyopathy, but it has never been demonstrated that variants identified in the TNNC1 (gene encoding troponin C) can evoke cardiac remodeling in vivo. The goal of this study was to determine whether TNNC1 can be categorized as an hypertrophic cardiomyopathy susceptibility gene, such that a mouse model can recapitulate the clinical presentation of the proband. METHODS AND RESULTS: The TNNC1-A8V proband diagnosed with severe obstructive hypertrophic cardiomyopathy at 34 years of age exhibited mild-to-moderate thickening in left and right ventricular walls, decreased left ventricular dimensions, left atrial enlargement, and hyperdynamic left ventricular systolic function. Genetically engineered knock-in (KI) mice containing the A8V mutation (heterozygote=KI-TnC-A8V(+/-); homozygote=KI-TnC-A8V(+/+)) were characterized by echocardiography and pressure-volume studies. Three-month-old KI-TnC-A8V(+/+) mice displayed decreased ventricular dimensions, mild diastolic dysfunction, and enhanced systolic function, whereas KI-TnC-A8V(+/-) mice displayed cardiac restriction at 14 months of age. KI hearts exhibited atrial enlargement, papillary muscle hypertrophy, and fibrosis. Liquid chromatography-mass spectroscopy was used to determine incorporation of mutant cardiac troponin C (≈ 21%) into the KI-TnC-A8V(+/-) cardiac myofilament. Reduced diastolic sarcomeric length, increased shortening, and prolonged Ca(2+) and contractile transients were recorded in intact KI-TnC-A8V(+/-) and KI-TnC-A8V(+/+) cardiomyocytes. Ca(2+) sensitivity of contraction in skinned fibers increased with mutant gene dose: KI-TnC-A8V(+/+)>KI-TnC-A8V(+/-)>wild-type, whereas KI-TnC-A8V(+/+) relaxed more slowly on flash photolysis of diazo-2. CONCLUSIONS: The TNNC1-A8V mutant increases the Ca(2+)-binding affinity of the thin filament and elicits changes in Ca(2+) homeostasis and cellular remodeling, which leads to diastolic dysfunction. These in vivo alterations further implicate the role of TNNC1 mutations in the development of cardiomyopathy.

Bone morphogenetic protein-focused strategies to induce cytotoxicity in lung cancer cells.

BACKGROUND: High bone morphogenetic protein (BMP)-2 expression in lung carcinoma correlates with poor patient prognosis. The present study explored strategies to repress BMP signaling. MATERIALS AND METHODS: The cytotoxicity of BMP2-knockdown, dorsomorphin derivatives, and microRNAs was tested in transformed and non-transformed lung cells. Microarray analyses of 1,145 microRNAs in A549 lung adenocarcinoma cells and two other transformed lung cell types relative to BEAS-2B bronchial epithelial cells were performed. RESULTS: Reduced BMP2 synthesis inhibited A549 cell growth. The dorsomorphin derivative LDN-193189, but not DMH1 or DMH4, was strongly cytotoxic towards A549 cells, but not towards BEAS-2B cells. Microarray analysis revealed that 106 miRNAs were down-regulated and 69 miRNAs were up-regulated in the three transformed lines. Three down-regulated miRNAs, hsa-mir-34b, hsa-mir-34c-3p, and hsa-miR-486-3p, repressed a BMP2 reporter gene and were cytotoxic in A549 cells, but not towards BEAS-2B cells. CONCLUSION: The observed cytotoxicity suggests that reducing BMP signaling is a useful line of attack for therapy of lung cancer.

Reciprocal amplification of ROS and Ca(2+) signals in stressed mdx dystrophic skeletal muscle fibers.

Muscular dystrophies are among the most severe inherited muscle diseases. The genetic defect is a mutation in the gene for dystrophin, a cytoskeletal protein which protects muscle cells from mechanical damage. Mechanical stress, applied as osmotic shock, elicits an abnormal surge of Ca(2+) spark-like events in skeletal muscle fibers from dystrophin deficient (mdx) mice. Previous studies suggested a link between changes in the intracellular redox environment and appearance of Ca(2+) sparks in normal mammalian skeletal muscle. Here, we tested whether the exaggerated Ca(2+) responses in mdx fibers are related to oxidative stress. Localized intracellular and mitochondrial Ca(2+) transients, as well as ROS production, were assessed with confocal microscopy. The rate of basal cellular but not mitochondrial ROS generation was significantly higher in mdx cells. This difference was abolished by pre-incubation of mdx fibers with an inhibitor of NAD(P)H oxidase. In addition, immunoblotting showed a significantly stronger expression of NAD(P)H oxidase in mdx muscle, suggesting a major contribution of this enzyme to oxidative stress in mdx fibers. Osmotic shock produced an abnormal and persistent Ca(2+) spark activity, which was suppressed by ROS-reducing agents and by inhibitors of NAD(P)H oxidase. These Ca(2+) signals resulted in mitochondrial Ca(2+) accumulation in mdx fibers and an additional boost in cellular and mitochondrial ROS production. Taken together, our results indicate that the excessive ROS production and the simultaneous activation of abnormal Ca(2+) signals amplify each other, finally culminating in a vicious cycle of damaging events, which may contribute to the abnormal stress sensitivity in dystrophic skeletal muscle.

Dystrophic cardiomyopathy: amplification of cellular damage by Ca2+ signalling and reactive oxygen species-generating pathways.

AIMS: Cardiac myopathies are the second leading cause of death in patients with Duchenne and Becker muscular dystrophy, the two most common and severe forms of a disabling striated muscle disease. Although the genetic defect has been identified as mutations of the dystrophin gene, very little is known about the molecular and cellular events leading to progressive cardiac muscle damage. Dystrophin is a protein linking the cytoskeleton to a complex of transmembrane proteins that interact with the extracellular matrix. The fragility of the cell membrane resulting from the lack of dystrophin is thought to cause an excessive susceptibility to mechanical stress. Here, we examined cellular mechanisms linking the initial membrane damage to the dysfunction of dystrophic heart. METHODS AND RESULTS: Cardiac ventricular myocytes were enzymatically isolated from 5- to 9-month-old dystrophic mdx and wild-type (WT) mice. Cells were exposed to mechanical stress, applied as osmotic shock. Stress-induced cytosolic and mitochondrial Ca(2+) signals, production of reactive oxygen species (ROS), and mitochondrial membrane potential were monitored with confocal microscopy and fluorescent indicators. Pharmacological tools were used to scavenge ROS and to identify their possible sources. Osmotic shock triggered excessive cytosolic Ca(2+) signals, often lasting for several minutes, in 82% of mdx cells. In contrast, only 47% of the WT cardiomyocytes responded with transient and moderate intracellular Ca(2+) signals. On average, the reaction was 6-fold larger in mdx cells. Removal of extracellular Ca(2+) abolished these responses, implicating Ca(2+) influx as a trigger for abnormal Ca(2+) signalling. Our further experiments revealed that osmotic stress in mdx cells produced an increase in ROS production and mitochondrial Ca(2+) overload. The latter was followed by collapse of the mitochondrial membrane potential, an early sign of cell death. CONCLUSION: Overall, our findings reveal that excessive intracellular Ca(2+) signals and ROS generation link the initial sarcolemmal injury to mitochondrial dysfunctions. The latter possibly contribute to the loss of functional cardiac myocytes and heart failure in dystrophy. Understanding the sequence of events of dystrophic cell damage and the deleterious amplification systems involved, including several positive feed-back loops, may allow for a rational development of novel therapeutic strategies.

Reactive oxygen species contribute to Ca2+ signals produced by osmotic stress in mouse skeletal muscle fibres.

Ca(2+) sparks, localized elevations in cytosolic [Ca(2+)], are rarely detected in intact adult mammalian skeletal muscle under physiological conditions. However, they have been observed in permeabilized cells and in intact fibres subjected to stresses, such as osmotic shock and strenuous exercise. Our previous studies indicated that an excess in cellular reactive oxygen species (ROS) generation over the ROS scavenging capabilities could be one of the up-stream causes of Ca(2+) spark appearance in permeabilized muscle fibres. Here we tested whether the cytosolic ROS balance is compromised in intact skeletal muscle fibres that underwent osmotic shock and whether this misbalance contributes to unmasking Ca(2+) sparks. Spontaneous Ca(2+) sparks and the rate of ROS generation were assessed with single photon confocal microscopy and fluorescent indicators fluo-4, CM-H(2)DCFDA and MitoSOX Red. Osmotic shock produced spontaneous Ca(2+) sparks and a concomitant significant increase in ROS production. Preincubation of muscle cells with ROS scavengers (e.g. MnTBAP, Mn-cpx 3, TIRON) nearly eliminated Ca(2+) sparks. In addition, inhibitors of NAD(P)H oxidase (DPI and apocynin) significantly reduced ROS production and suppressed the appearance of Ca(2+) sparks. Taken together, the data suggest that ROS contribute to the abnormal Ca(2+) spark activity in mammalian skeletal muscle subjected to osmotic stress and also indicate that NAD(P)H oxidase is a possible source of ROS. We propose that ROS-dependent Ca(2+) sparks are an important component of adaptive/maladaptive muscle responses under various pathological conditions such as eccentric stretch, osmotic changes during ischaemia and reperfusion, and some muscle diseases.

Hypertension and exercise training differentially affect oxytocin and oxytocin receptor expression in the brain.

We have previously shown that exercise training activates nucleus tractus solitarii (NTS) oxytocinergic projections, resulting in blunted exercise tachycardia. The objective of this study was to determine the effects of hypertension and training on oxytocin (OT) and OT receptor expression in the hypothalamic paraventricular nucleus (PVN) and projection areas (dorsal brain stem [DBS]). Male, normotensive, Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats were trained (55% maximal exercise capacity, 3 months) or kept sedentary, and pressure was measured weekly. DBS sections were processed for immunohistochemistry (polyclonal guinea pig anti-OT) or in situ hybridization for OT and OT receptor (35S-oligonucleotide probes). Other groups of rats had brains removed and frozen to isolate the DBS and PVN; samples were processed for OT and OT receptor cDNA reverse transcription-polymerase chain reaction amplification with beta-actin as the housekeeping gene. Training was equally effective in improving running distance in both groups, with pressure reduction only in SHR (-10%, P<0.05). In trained WKY, baseline bradycardia (P<0.05) occurred simultaneously with increased NTS OT immunostaining and mRNA expression (+3.5-fold), without any change in OT receptor mRNA expression. PVN OT mRNA and DBS OT receptor mRNA expressions were significantly lower in SHR versus WKY (-39% and -56%, respectively). Training did not alter DBS OT receptor density in the SHR group but increased OT mRNA in both PVN and DBS areas (+78% and +45%, respectively). Our results show a marked hypertension-induced reduction in OT receptor mRNA expression, not altered by training. In contrast, training increased OT mRNA expression in sedentary and hypertensive rats, which may facilitate training-induced cardiac performance.