Modified Dark Matter in Galaxies and Galaxy Clusters

Modified Dark Matter (MDM) is a phenomenological model of dark matter, inspired by gravitational thermodynamics, that naturally accounts for the universal acceleration constant observed in galactic rotation curve data; a critical acceleration related to the cosmological constant, $\Lambda$, appears as a phenomenological manifestation of MDM. We show that the resulting mass profiles, which are sensitve to $\Lambda$, are consistent with observations at the galactic and galaxy cluster scales. Our results suggest that dark matter mass profiles contain information about the cosmological constant in a non-trivial way.Comment: To be published in the Proceedings of the Bahamas Advanced Study Institute and Conferences (BASIC

Variation in extracellular matrix genes is associated with weight regain after weight loss in a sex-specific manner

The extracellular matrix (ECM) of adipocytes is important for body weight regulation. Here, we investigated whether genetic variation in ECM-related genes is associated with weight regain among participants of the European DiOGenes study. Overweight and obese subjects (n = 469, 310 females, 159 males) were on an 8-week low-calorie diet with a 6-month follow-up. Body weight was measured before and after the diet, and after follow-up. Weight maintenance scores (WMS, regained weight as percentage of lost weight) were calculated based on the weight data. Genotype data were retrieved for 2903 SNPs corresponding to 124 ECM-related genes. Regression analyses provided us with six significant SNPs associated with the WMS in males: 3 SNPs in the POSTN gene and a SNP in the LAMB1, COL23A1, and FBLN5 genes. For females, 1 SNP was found in the FN1 gene. The risk of weight regain was increased by: the C/C genotype for POSTN in a co-dominant model (OR 8.25, 95 % CI 2.85-23.88) and the T/C-C/C genotype in a dominant model (OR 4.88, 95 % CI 2.35-10.16); the A/A genotype for LAMB1 both in a co-dominant model (OR 18.43, 95 % CI 2.35-144.63) and in a recessive model (OR 16.36, 95 % CI 2.14-124.9); the G/A genotype for COL23A1 in a co-dominant model (OR 3.94, 95 % CI 1.28-12.10), or the A-allele in a dominant model (OR 2.86, 95 % CI 1.10-7.49); the A/A genotype for FBLN5 in a co-dominant model (OR 13.00, 95 % CI 1.61-104.81); and the A/A genotype for FN1 in a recessive model (OR 2.81, 95 % CI 1.40-5.63). Concluding, variants of ECM genes are associated with weight regain after weight loss in a sex-specific manner

A computational model of postprandial adipose tissue lipid metabolism derived using human arteriovenous stable isotope tracer data

Given the association of disturbances in non-esterified fatty acid (NEFA) metabolism with the development of Type 2 Diabetes and Non-Alcoholic Fatty Liver Disease, computational models of glucose-insulin dynamics have been extended to account for the interplay with NEFA. In this study, we use arteriovenous measurement across the subcutaneous adipose tissue during a mixed meal challenge test to evaluate the performance and underlying assumptions of three existing models of adipose tissue metabolism and construct a new, refined model of adipose tissue metabolism. Our model introduces new terms, explicitly accounting for the conversion of glucose to glyceraldehye-3-phosphate, the postprandial influx of glycerol into the adipose tissue, and several physiologically relevant delays in insulin signalling in order to better describe the measured adipose tissues fluxes. We then applied our refined model to human adipose tissue flux data collected before and after a diet intervention as part of the Yoyo study, to quantify the effects of caloric restriction on postprandial adipose tissue metabolism. Significant increases were observed in the model parameters describing the rate of uptake and release of both glycerol and NEFA. Additionally, decreases in the model’s delay in insulin signalling parameters indicates there is an improvement in adipose tissue insulin sensitivity following caloric restriction.</p

Increased circulating IgG levels, myocardial immune cells and IgG deposits support a role for an immune response in pre- and end-stage heart failure

The chronic inflammatory response plays an important role in adverse cardiac remodelling and the development of heart failure (HF). There is also evidence that in the pathogenesis of several cardiovascular diseases, chronic inflammation is accompanied by antibody and complement deposits in the heart, suggestive of a true autoimmune response. However, the role of antibody-mediated immune responses in HF progression is less clear. We assessed whether immune cell infiltration and immunoglobulin levels are associated with HF type and disease stage, taking sex differences into account. We found IgG deposits and increased infiltration of immune cells in the affected myocardium of patients with end-stage HF with reduced ejection fraction (HFrEF, n = 20). Circulating levels of IgG1 and IgG3 were elevated in these patients. Furthermore, the percentage of transitional/regulatory B cells was decreased (from 6.9% to 2.4%) compared with healthy controls (n = 5). Similarly, increased levels of circulating IgG1 and IgG3 were observed in men with left ventricular diastolic dysfunction (LVDD, n = 5), possibly an early stage of HF with preserved EF (HFpEF). In conclusion, IgG deposits and infiltrates of immune cells are present in end-stage HFrEF. In addition, both LVDD patients and end-stage HFrEF patients show elevated levels of circulating IgG1 and IgG3, suggesting an antibody-mediated immune response upon cardiac remodelling, which in the early phase of remodelling appear to differ between men and women. These immunoglobulin subclasses might be used as marker for pre-stage HF and its progression. Future identification of auto-antigens might open possibilities for new therapeutic interventions

Lithium carbonate in amyotrophic lateral sclerosis patients homozygous for the C-allele at SNP rs12608932 in UNC13A: protocol for a confirmatory, randomized, group-sequential, event-driven, double-blind, placebo-controlled trial

BackgroundGiven the large genetic heterogeneity in amyotrophic lateral sclerosis (ALS), it seems likely that genetic subgroups may benefit differently from treatment. An exploratory meta-analysis identified that patients homozygous for the C-allele at SNP rs12608932, a single nucleotide polymorphism in the gene UNC13A, had a statistically significant survival benefit when treated with lithium carbonate. We aim to confirm the efficacy of lithium carbonate on the time to death or respiratory insufficiency in patients with ALS homozygous for the C-allele at SNP rs12608932 in UNC13A. MethodsA randomized, group-sequential, event-driven, double-blind, placebo-controlled trial will be conducted in 15 sites across Europe and Australia. Patients will be genotyped for UNC13A; those homozygous for the C-allele at SNP rs12608932 will be eligible. Patients must have a diagnosis of ALS according to the revised El Escorial criteria, and a TRICALS risk-profile score between -6.0 and -2.0. An expected number of 1200 patients will be screened in order to enroll a target sample size of 171 patients. Patients will be randomly allocated in a 2:1 ratio to lithium carbonate or matching placebo, and treated for a maximum duration of 24 months. The primary endpoint is the time to death or respiratory insufficiency, whichever occurs first. Key secondary endpoints include functional decline, respiratory function, quality of life, tolerability, and safety. An interim analysis for futility and efficacy will be conducted after the occurrence of 41 events. DiscussionLithium carbonate has been proven to be safe and well-tolerated in patients with ALS. Given the favorable safety profile, the potential benefits are considered to outweigh the burden and risks associated with study participation. This study may provide conclusive evidence about the life-prolonging potential of lithium carbonate in a genetic ALS subgroup

H3K27ac acetylome signatures reveal the epigenomic reorganization in remodeled non-failing human hearts

BACKGROUND: H3K27ac histone acetylome changes contribute to the phenotypic response in heart diseases, particularly in end-stage heart failure. However, such epigenetic alterations have not been systematically investigated in remodeled non-failing human hearts. Therefore, valuable insight into cardiac dysfunction in early remodeling is lacking. This study aimed to reveal the acetylation changes of chromatin regions in response to myocardial remodeling and their correlations to transcriptional changes of neighboring genes. RESULTS: We detected chromatin regions with differential acetylation activity (DARs; Padj. < 0.05) between remodeled non-failing patient hearts and healthy donor hearts. The acetylation level of the chromatin region correlated with its RNA polymerase II occupancy level and the mRNA expression level of its adjacent gene per sample. Annotated genes from DARs were enriched in disease-related pathways, including fibrosis and cell metabolism regulation. DARs that change in the same direction have a tendency to cluster together, suggesting the well-reorganized chromatin architecture that facilitates the interactions of regulatory domains in response to myocardial remodeling. We further show the differences between the acetylation level and the mRNA expression level of cell-type-specific markers for cardiomyocytes and 11 non-myocyte cell types. Notably, we identified transcriptome factor (TF) binding motifs that were enriched in DARs and defined TFs that were predicted to bind to these motifs. We further showed 64 genes coding for these TFs that were differentially expressed in remodeled myocardium when compared with controls. CONCLUSIONS: Our study reveals extensive novel insight on myocardial remodeling at the DNA regulatory level. Differences between the acetylation level and the transcriptional level of cell-type-specific markers suggest additional mechanism(s) between acetylome and transcriptome. By integrating these two layers of epigenetic profiles, we further provide promising TF-encoding genes that could serve as master regulators of myocardial remodeling. Combined, our findings highlight the important role of chromatin regulatory signatures in understanding disease etiology

A role for leukocyte integrins and extracellular matrix remodeling of adipose tissue in the risk of weight regain after weight loss

Background: Weight loss (WL) is often followed by weight regain after an energy-restricted dietary intervention (DI). When people are following a diet, the volume of an adipocyte decreases by loss of triglycerides, which creates stress between the cell contents and the surrounding extracellular matrix (ECM). Previously, we observed that genetic variations in ECM genes are associated with an increased risk of weight regain. Objective: We investigated the relation between the expression of ECM genes during WL and a period of weight stabilization (WS) and the risk of weight regain. Design: In this randomized controlled trial, 61 healthy overweight or obese participants followed either a 5-wk very-low-calorie diet (VLCD; 500 kcal/d) or a 12-wk low-calorie diet (1250 kcal/d) (WL period) with a subsequent 4-wk WS period and a 9-mo follow-up. The WL and WS periods combined were considered the DI. Abdominal subcutaneous adipose tissue biopsy samples were collected for microarray analysis. Gene expression changes for a broad set of ECM-related genes were correlated with the weight-regain percentage (WR%). Results: A total of 26 of the 277 genes were significantly correlated with WR% during WL, WS, or the DI periods. Most correlations were observed in the VLCD group during the WS period. Four genes code for leukocyte-specific receptors. These and other genes belong to a group of 26 genes, among which the expression changes were highly correlated (r ≥ 0.7, P ≤ 0.001). This group could be divided into 3 subclusters linking to 2 biological processes-leukocyte integrin gene activity and ECM remodeling-and a link to insulin sensitivity was also apparent. Conclusions: Our present findings indicate the importance of adipose tissue leukocytes for the risk of weight regain. ECM modification also seems to be involved, and we observed a link to insulin sensitivity. This trial was registered at clinicaltrials.gov as NCT01559415.</p

A role for leukocyte integrins and extracellular matrix remodeling of adipose tissue in the risk of weight regain after weight loss

Background: Weight loss (WL) is often followed by weight regain after an energy-restricted dietary intervention (DI). When people are following a diet, the volume of an adipocyte decreases by loss of triglycerides, which creates stress between the cell contents and the surrounding extracellular matrix (ECM). Previously, we observed that genetic variations in ECM genes are associated with an increased risk of weight regain. Objective: We investigated the relation between the expression of ECM genes during WL and a period of weight stabilization (WS) and the risk of weight regain. Design: In this randomized controlled trial, 61 healthy overweight or obese participants followed either a 5-wk very-low-calorie diet (VLCD; 500 kcal/d) or a 12-wk low-calorie diet (1250 kcal/d) (WL period) with a subsequent 4-wk WS period and a 9-mo follow-up. The WL and WS periods combined were considered the DI. Abdominal subcutaneous adipose tissue biopsy samples were collected for microarray analysis. Gene expression changes for a broad set of ECM-related genes were correlated with the weight-regain percentage (WR%). Results: A total of 26 of the 277 genes were significantly correlated with WR% during WL, WS, or the DI periods. Most correlations were observed in the VLCD group during the WS period. Four genes code for leukocyte-specific receptors. These and other genes belong to a group of 26 genes, among which the expression changes were highly correlated (r ≥ 0.7, P ≤ 0.001). This group could be divided into 3 subclusters linking to 2 biological processes-leukocyte integrin gene activity and ECM remodeling-and a link to insulin sensitivity was also apparent. Conclusions: Our present findings indicate the importance of adipose tissue leukocytes for the risk of weight regain. ECM modification also seems to be involved, and we observed a link to insulin sensitivity. This trial was registered at clinicaltrials.gov as NCT01559415.</p