Endogenous glycogen prevents Ca2+ overload and hypercontracture in harp seal myocardial cells during simulated ischemia

The purpose of this study was to determine if elevated myocardial glycogen content could obviate Ca(2+) overload and subsequent myocardial injury in the setting of low oxygen and diminished exogenous substrate supplies. Isolated harp seal cardiomyocytes, recognized as having large glycogen stores, were incubated under conditions simulating ischemia (oxygen and substrate deprivation) for 1 h. Rat cardiomyocytes were used for comparison. Freshly isolated seal cardiomyocytes contained approximately 10 times more glycogen than those from rats (479 +/- 39 vs. 48 +/- 5 nmol glucose/mg dry weight (dry wt), mean +/- S.E., n = 6), and during ischemia lactate production was significantly greater in seal compared to rat cardiomyocytes (660 +/- 99 vs. 97 +/- 14 nmol/mg dry wt), while glycogen content decreased both in seal (from 479 +/- 39 to 315 +/- 58 nmol glucose/mg dry wt) and rat cardiomyocytes (from 48 +/- 5 to 18 +/- 5 nmol glucose/mg dry wt). Cellular ATP was well maintained in ischemic seal cardiomyocytes, whereas it showed a 65% decline (from 31 +/- 3 to 11 +/- 1 nmol ATP/mg dry wt) in rat cardiomyocytes. Similarly, total seal cardiomyocyte Ca(2+) content was not affected by ischemia, while Ca(2+) increased from 8.5 +/- 2.0 to 13.3 +/- 2.0 nmol/mg dry wt in ischemic rat myocytes. Rat cardiomyocytes also showed a notable decline in the percentage of rod-shaped cells in response to ischemia (from 66 +/- 4% to 30 +/- 3%), and cell morphology was unaffected in seal incubations. Addition of iodoacetate (IAA, an inhibitor of glycolysis) to seal cardiomyocytes, on top of substrate and oxygen deprivation, reduced the cellular content of ATP by 52.9 +/- 4.4% (from 25 +/- 4 to 11 +/- 2 nmol ATP/mg dry wt) and the percentage of rod-shaped myocytes from 51 +/- 3% to 28 +/- 4%, while total Ca(2+) content was unchanged by these conditions. Seal cardiomyocytes thus tolerate low oxygen conditions better than rat cardiomyocytes. This finding is most likely due to a higher glycolysis rate in seals, fueled by larger myocardial glycogen stores.     

Human skeletal muscle fiber type percentage and area after reduced muscle use: A systematic review and meta-analysis

The main objective of this systematic review was to examine the effect of reduced muscle activity on the relative number of type 1 muscle fibers (%) in the human vastus lateralis muscle. Other objectives were changes in type 2A and 2X percentages and muscle fiber cross-sectional area. We conducted systematic literature searches in eight databases and included studies assessing type 1 fiber percentage visualized by ATPase or immunohistochemical staining before and after a period (≥14 days) of reduced muscle activity. The reduced muscle activity models were detraining, leg unloading, and bed rest. Forty-two studies comprising 451 participants were included. Effect sizes were calculated as the mean difference between baseline and follow-up and Generic Inverse Variance tests with random-effects models were used for the weighted summary effect size. Overall, the mean type 1 muscle fiber percentage was significantly reduced after interventions (−1.94%-points, 95% CI [−3.37, −0.51], P = .008), with no significant differences between intervention models (P = .86). Meta-regression showed no effect of study duration on type 1 fiber percentage (P = .98). Conversely, the overall type 2X fiber percentage increased after reduced muscle activity (P < .001). The CSA of the muscle fiber types decreased after the study period (all P-values < 0.001) with greater reductions in type 2 than type 1 fibers (P < .001). The result of this meta-analysis display that the type 1 muscle fiber percentage decrease as a result of reduced muscle activity, although the effect size is relatively small.     

Very Low Levels of Atherogenic Lipoproteins and the Risk for Cardiovascular Events : A Meta-Analysis of Statin Trials

Background

Levels of atherogenic lipoproteins achieved with statin therapy are highly variable, but the consequence of this variability for cardiovascular disease risk is not well-documented.

Objectives

The aim of this meta-analysis was to evaluate: 1) the interindividual variability of reductions in low-density lipoprotein cholesterol (LDL-C), non–high-density lipoprotein cholesterol (non-HDL-C), or apolipoprotein B (apoB) levels achieved with statin therapy; 2) the proportion of patients not reaching guideline-recommended lipid levels on high-dose statin therapy; and 3) the association between very low levels of atherogenic lipoproteins achieved with statin therapy and cardiovascular disease risk.

Methods

This meta-analysis used individual patient data from 8 randomized controlled statin trials, in which conventional lipids and apolipoproteins were determined in all study participants at baseline and at 1-year follow-up.

Results

Among 38,153 patients allocated to statin therapy, a total of 6,286 major cardiovascular events occurred in 5,387 study participants during follow-up. There was large interindividual variability in the reductions of LDL-C, non-HDL-C, and apoB achieved with a fixed statin dose. More than 40% of trial participants assigned to high-dose statin therapy did not reach an LDL-C target <70 mg/dl. Compared with patients who achieved an LDL-C >175 mg/dl, those who reached an LDL-C 75 to <100 mg/dl, 50 to <75 mg/dl, and <50 mg/dl had adjusted hazard ratios for major cardiovascular events of 0.56 (95% confidence interval [CI]: 0.46 to 0.67), 0.51 (95% CI: 0.42 to 0.62), and 0.44 (95% CI: 0.35 to 0.55), respectively. Similar associations were observed for non-HDL-C and apoB.

Conclusions

The reductions of LDL-C, non-HDL-C, and apoB levels achieved with statin therapy displayed large interindividual variation. Among trial participants treated with high-dose statin therapy, >40% did not reach an LDL-C target <70 mg/dl. Patients who achieve very low LDL-C levels have a lower risk for major cardiovascular events than do those achieving moderately low levels.     

The acetabulum in Perthes’ disease: Inter-observer agreement and reliability of radiographic measurements

Background and purpose

Perthes’ disease leads to radiographic changes in both the femoral head and the acetabulum. We investigated the inter-observer agreement and reliability of 4 radiographic measurements assessing the acetabular changes.

Patients and methods

We included 123 children with unilateral involvement, femoral head necrosis of more than 50%, and age at diagnosis of 6 years or older. Radiographs were taken at onset, and 1 year and 5 years after diagnosis. Sharp’s angle, acetabular depth-width ratio (ADR), lateral acetabular inclination (LAI), and acetabular retroversion (ischial spine sign, ISS) were measured by 3 observers. Before measuring, 2 of the observers had a consensus meeting.

Results

We found good agreement and moderate to excellent reliability for Sharp’s angle for all observers (intra-class correlation coefficient (ICC) > 0.80 with consensus, ICC = 0.46–0.57 without consensus). There was good agreement and substantial reliability for ADR between the observers who had had a consensus meeting (ICC = 0.62–0.89). Low levels of agreement and poor reliability were found for observers who had not had a consensus meeting. LAI showed fair agreement throughout the course of the disease (kappa = 0.28–0.52). The agreement between observations for ISS ranged from fair to good (kappa = 0.20–0.76).

Interpretation

Sharp’s angle showed the highest reliability and agreement throughout the course of the disease. ADR was only reliable and showed good agreement between the observers when landmarks were clarified before measuring the radiographs. Thus, we recommend both parameters in clinical practice, provided a consensus is established for ADR. The observations for LAI had only fair agreement and ISS showed inconclusive agreement in our study. Thus, LAI and ISS can hardly be recommended in clinical practice.Perthes’ disease leads to typical radiographic changes of the femoral head. Several authors have described simultaneous changes of the acetabular anatomy, such as hypertrophy, bicompartmental development, retroversion, and dysplastic changes (Yngve and Roberts 1985, Joseph 1989, Ezoe et al. 2006).Most measurements describing the radiographic changes of the acetabulum on anteroposterior (AP) pelvic radiographs have been validated in children with hip dysplasia. As the hip pathology and the morphological changes in Perthes’ disease are different from those in hip dysplasia, we wanted to assess inter-observer reliability and agreement of 4 commonly used acetabular measurements at the different stages of skeletal maturity in Perthes’ disease.     

Mediastinitis after coronary artery bypass grafting: the effect of vacuum‐assisted closure versus traditional closed drainage on survival and re‐infection rate

Mediastinitis is treated with either vacuum‐assisted closure (VAC) or traditional closed drainage (TCD) with irrigation. The aim of the study was to determine the effect of the two treatments on mortality and re‐infection rate in a source population, using 21 314 consecutive patients undergoing isolated coronary artery bypass grafting (CABG) from January 1997 to October 2010. Median observation time was 2·9 years in the VAC group and 8·0 years in the TCD group. The epidemiological design was of an exposed (VAC, n = 64) versus non‐exposed (TCD, n = 66) cohort with two endpoints: (1) mortality and (2) failure of sternal wound healing or re‐infection. The crude effect of treatment technique versus endpoint was estimated by univariate analysis. Stratification analysis by the Mantel–Haenszel method was performed to quantify confounders and to pinpoint effect modifiers. Adjustment for confounders was performed using Cox regression analysis. Mediastinitis was diagnosed 6–105 (median 14) days after primary operation in the VAC group and 13 (5–29) days in the TCD group. There was no difference between groups in long‐term survival. Failure of sternal wound healing or re‐infection occurred less frequently in the VAC group (6%) than in the TCD group (21%; relative risk = 0·29, 95% CI = 0·06–0·88, P = 0·01). There are concerns for increase in right ventricle rupture in VAC compared with TCD. There was no difference in survival after VAC therapy and TCD therapy of post‐CABG mediastinitis. Failure of sternal wound healing or re‐infection was more common after TCD therapy.     

Mediastinitis after coronary artery bypass grafting increases the incidence of left internal mammary artery obstruction

Mediastinitis after coronary artery bypass grafting (CABG) gives a longstanding chronic inflammation and has a detrimental negative effect on long‐term survival. For this reason, we aimed to study the effect of mediastinitis on graft patency after CABG. The epidemiologic design was of an exposed (mediastinitis, n = 41) versus non‐exposed (non‐mediastinitis, controls, n = 41) cohort with two endpoints: (i) obstruction of saphenous vein grafts (SVG) and (ii) obstruction of the internal mammary artery (IMA) grafts. The graft patency was evaluated with coronary CT‐angiography examination at a median follow‐up of 2·7 years. The number of occluded SVG in the mediastinitis group was 18·9% versus 15·5% in the control group. Using generalized estimating equations model with exchangeable matrix, and confounding effect of ischaemic time and patients age, we found no significant association between presence of mediastinitis and SVG obstruction [rate ratio (RR) = 0·96, 95% CI (0·52–2·67), P = 0·697]. The number of occluded IMA grafts was 10·5% in the mediastinitis group and 2·4% in the control group. Using the Poisson regression model, we estimated RR = 5·48, 95% CI (1·43–21·0) and P = 0·013. There was a significant association between mediastinitis and IMA graft obstruction, when controlling for the confounding effect of ischaemic time, body mass index, presence of diabetes mellitus and the number of diseased vessels. Presence of mediastinitis increases the risk of IMA graft obstruction. This may confirm the importance of inflammation as a major contributor to the pathogenesis of atherosclerosis and explain the negative effect of mediastinitis on a long‐term survival.     

Altered mitochondrial metabolism in the insulin‐resistant heart

Obesity‐induced insulin resistance and type 2 diabetes mellitus can ultimately result in various complications, including diabetic cardiomyopathy. In this case, cardiac dysfunction is characterized by metabolic disturbances such as impaired glucose oxidation and an increased reliance on fatty acid (FA) oxidation. Mitochondrial dysfunction has often been associated with the altered metabolic function in the diabetic heart, and may result from FA‐induced lipotoxicity and uncoupling of oxidative phosphorylation. In this review, we address the metabolic changes in the diabetic heart, focusing on the loss of metabolic flexibility and cardiac mitochondrial function. We consider the alterations observed in mitochondrial substrate utilization, bioenergetics and dynamics, and highlight new areas of research which may improve our understanding of the cause and effect of cardiac mitochondrial dysfunction in diabetes. Finally, we explore how lifestyle (nutrition and exercise) and pharmacological interventions can prevent and treat metabolic and mitochondrial dysfunction in diabetes.     

Molecular characterisation of TP53 mutated squamous cell carcinomas of the lung to identify putative targets for therapy

Personalised cancer treatment depends on identification of therapeutically relevant biological subgroups of patients for assessing effect of treatment and to discover new therapeutic options. By analyses in heterogeneous patient populations, the effects may be lost in noise. Squamous cell carcinoma of the lung is a major killer worldwide. Despite recent advances, mortality is high and response to therapies varies greatly from patient to patient. Target search in biologically relevant subgroups may identify treatment options not so far discovered. A total of 198 patients undergoing surgery for squamous cell carcinomas of the lung were included in the study. The tumours were analysed for copy number alterations (n = 152) and gene expression from tumour (n = 188) and normal lung (n = 21), with both data levels present in 140 patients. We studied alterations in tumours harbouring mutations in TP53 and in previously published gene expression subtypes. Genes with consistent alterations in both genomic levels were identified as putative biomarkers. Results were validated in TCGA. The most convincing biomarker in TP53 mutated squamous cell carcinomas of the lung was BIRC5 with amplification in 36% of mutated samples, 5% in wild-type samples and a 17%-fold change of expression between TP53 mutated tumours and normal lung tissue. BIRC5 was significantly altered in the classical and primitive subtypes. We suggest BIRC5 as a putative predictive biomarker and putative druggable target in squamous cell lung carcinomas harbouring TP53 mutation or classified as classical and primitive subtypes.     

Natural History of Mild and of Moderate Aortic Stenosis—New Insights From a Large Prospective European Study

Increased life expectancy has led to a higher prevalence of calcific aortic valve disease. Both ends of the disease spectrum—sclerosis of the aortic valve without hemodynamic obstruction and the late stage of aortic valve stenosis (AS)—have been associated with increased morbidity and mortality. This raises the question of the prognostic contribution of atherosclerotic diseases and other comorbidities as opposed to the hemodynamic effect of obstructive AS. Hence, the evaluation of asymptomatic patients with mild or moderate AS without comorbidities is of major interest. In the Simvastatin and Ezetimibe in Aortic Stenosis study, with the exception of hypertension, comorbidities were excluded, thus allowing an analysis of the effect of pure AS as well as the effect of hypertension on the progression and outcome of AS.