Lipase maturation factor 1 (LMF1) is a chaperone for lipoprotein lipase (LPL) and critically required for the enzyme to attain lipase activity. LMF1 has been identified as a canonical gene affected in Familial Chylomicronemia Syndrome (FCS) and it has also been extensively analyzed in Multifactorial Chylomicronemia Syndrome (MCS), the polygenic form of severe hypertriglyceridemia (hTG). While recent genetic studies resulted in an explosion in the number of hTG-associated LMF1 variants in different populations, their functional significance remains largely unknown. Here, we present a second-generation LMF1 activity assay allowing the streamlined quantitative functional analysis of LMF1 variants. The assay is based on the reconstitution of lipase maturation in transfected LMF1-deficient cells and fluorescence-based measurement of LPL activity in the culture medium. The use of Gaussia luciferase (GLuc)-LMF1 fusion constructs allows the assessment of LMF1 protein expression and the calculation of LMF1 specific activity. Several variants previously reported as neutral resulted in loss of LMF1 function in the new assay demonstrating increased sensitivity to detect variants of modest effect sizes. Furthermore, the functional analysis of 14 hTG-associated missense mutations identified 12 loss-of-function (LOF) variants. To gain initial insights into the structural determinants of LMF1 function, we analyzed the domain distribution of 73 hTG-associated missense variants and identified Loop C as a critical region in lipase maturation. In conclusion, we developed a simple, non-radioactive and sensitive quantitative assay of LMF1 activity to facilitate the functional analysis of hyperlipidemia-associated genetic variants and structure-function studies.

Impaired triglyceride (TG) metabolism is associated with metabolic diseases. Non-steady state dynamics make studying postprandial lipid metabolism challenging. We already introduced a mathematical model to estimate cholesteryl ester transfer protein (CETP)-mediated TG net flux in the fasting state. Here, we expand this model to chylomicrons (CMs) and the dynamics of postprandial lipemia. Blood samples of normolipidemic, hypertriglyceridemic, and hyperchylomicronemic volunteers were drawn at fasting and postprandial state. We separated lipoprotein classes via classical sequential ultracentrifugation. To address CMs, we developed a novel method based on Airfuge® ultracentrifugation. We studied postprandial changes of lipoproteins and their components. CETP-mediated TG redistribution was modeled based on the surface and composition data of respective lipoprotein fractions and validated by corresponding measured values. Our model estimated CETP-mediated TG flux in the fasting and postprandial state with high accuracy. Even in the postprandial condition, TG net flux to LDL/HDL is dominated by VLDL. Separating CM from VLDL and modeling both fractions instead of just using the combined CM + VLDL fraction did only improve the model's accuracy slightly (by less than 7%). The proportion of ApoC3 redistributed from HDL to VLDL in postprandial lipemia is highly correlated with the change of ApoA1 in HDL2b. Our basic model is able to estimate TG redistribution via CETP among lipoproteins in postprandial lipemia of healthy and hypertriglyceridemic subjects. An additional separation of VLDL and CM is not strictly necessary to model postprandial TG flux. Our model makes postprandial lipoprotein metabolism more tangible and may help to study lipoprotein-associated pathologies.

Aims: Sirtuin 4 (SIRT4) is a mitochondrially-localized stress-responsive NAD+-dependent deacetylase predominantly regulating energy metabolism and reactive oxygen species (ROS) homeostasis. Overexpression of SIRT4 aggravates angiotensin-induced cardiac hypertrophy, however underlying mechanisms remain incompletely elucidated. To current study was designed to explore mechanisms underlying adverse effects of increased SIRT4 levels in the heart following pressure overload. Methods and results: Mice with cardiomyocyte-specific overexpression of Sirt4 (cSirt4-Tg) or non-transgenic controls underwent transverse aortic constriction (TAC) or sham procedure. Cardiac structure, function and energy metabolism were assessed by echocardiography and working heart perfusions. Transcriptome analysis was performed using RNA sequencing. Nine weeks following TAC and thereafter, cSirt4-Tg mice displayed exacerbated cardiac dilation, dysfunction, and fibrosis compared to non-transgenic controls. This aggravation was accompanied by impaired rates of glycolysis and a blunted increase of mitochondrial respiratory capacity. More importantly, expression of numerous genes encoding collagens and profibrotic regulators was elevated. This profibrotic signaling was reversed by mitochondria-targeted antioxidant treatment using MitoQ, along with attenuation of cardiac dysfunction and reversal of structural remodeling. SIRT4 may drive oxidative stress and fibrotic signaling via increased NOX4 expression (>7-fold), and/or direct modulation of potential SIRT4 targets newly identified by Human Protein Microarray, including calcitonin gene-related peptide receptor component protein, cyclophilin A, and interleukin-2 receptor β. Conclusions: SIRT4 overexpression accelerates heart failure development in response to pressure overload, predominantly by ROS-mediated enhancement of profibrotic transcriptional signaling.

AIM:Sirtuin 5 (SIRT5), a mitochondrial NAD+-dependent deacylase, regulates fundamental cellular pathways, including energy substrate metabolism. The current study is designed to better elucidate the role of SIRT5 in the development of heart failure (HF). METHODS:Mice with cardiomyocyte-specific deletion (cSirt5-/-) or overexpression (cSirt5-Tg) of SIRT5 were generated and subjected to chronic pressure overload by transverse aortic constriction (TAC) or Sham surgery. Cardiac structure and function were assessed by echocardiography, isolated heart perfusions, and histology. MS-based metabolomics and bulk RNA sequencing were used to explore metabolic and molecular signatures. RESULTS:cSirt5-Tg mice had similar cardiac structure and function compared to control mice, whereas cSirt5-/- mice displayed exacerbated cardiac dilation and dysfunction following TAC, measured both in vivo by echocardiography and ex vivo in isolated heart perfusions. Metabolomics revealed accumulation of inosine and hypoxanthine, and depletion of adenosine, adenine, AMP, and ADP in cSirt5-/- hearts and following TAC, indicating dysregulation of purine metabolism. RNA-sequencing uncovered upregulation of purine-nucleoside phosphorylase and 5' nucleotidase, and downregulation of adenosine kinase (ADK) in cSirt5-/- hearts following TAC, indicating dysregulation at the interface of adenosine nucleotide salvage and purine degradation in the absence of SIRT5. Analyses of left ventricular tissue of patients with HF revealed reduced SIRT5 expression correlating with reduced ADK expression. CONCLUSION:Loss of SIRT5 in cardiomyocytes aggravates cardiac remodeling and dysfunction in response to chronic pressure overload, involving ATP precursor depletion due to transcriptional dysregulation of cardiac purine metabolism.

Other Supporting Colleagues from Clinical Predictors for Germline Mutations in Head and Neck Paraganglioma Patients: Cost Reduction Strategy in Genetic Diagnostic Process as Fall-Out

Supplementary Table 2 from Clinical Predictors for Germline Mutations in Head and Neck Paraganglioma Patients: Cost Reduction Strategy in Genetic Diagnostic Process as Fall-Out

Aims Apolipoprotein C-II (ApoC-II) is thought to activate lipoprotein lipase (LPL) and is therefore a possible target for treating hypertriglyceridemia. Its relationship with cardiovascular risk has not been investigated in large-scale epidemiologic studies, particularly allowing for apolipoprotein C-III (ApoC-III), an LPL antagonist. Furthermore, the exact mechanism of ApoC-II-mediated LPL activation is unclear. Methods and results ApoC-II was measured in 3141 LURIC participants of which 590 died from cardiovascular diseases during a median (inter-quartile range) follow-up of 9.9 (8.7-10.7) years. Apolipoprotein C-II-mediated activation of the glycosylphosphatidylinositol high-density lipoprotein binding protein 1 (GPIHBP1)-LPL complex was studied using enzymatic activity assays with fluorometric lipase and very low-density lipoprotein (VLDL) substrates. The mean ApoC-II concentration was 4.5 (2.4) mg/dL. The relationship of ApoC-II quintiles with cardiovascular mortality exhibited a trend toward an inverse J-shape, with the highest risk in the first (lowest) quintile and lowest risk in the middle quintile. Compared with the first quintile, all other quintiles were associated with decreased cardiovascular mortality after multivariate adjustments including ApoC-III as a covariate (all P < 0.05). In experiments using fluorometric substrate-based lipase assays, there was a bell-shaped relationship for the effect of ApoC-II on GPIHBP1-LPL activity when exogenous ApoC-II was added. In ApoC-II-containing VLDL substrate-based lipase assays, GPIHBP1-LPL enzymatic activity was almost completely blocked by a neutralizing anti-ApoC-II antibody. Conclusion The present epidemiologic data suggest that increasing low circulating ApoC-II levels may reduce cardiovascular risk. This conclusion is supported by the observation that optimal ApoC-II concentrations are required for maximal GPIHBP1-LPL enzymatic activity.

Supplementary Table 1 from Clinical Predictors for Germline Mutations in Head and Neck Paraganglioma Patients: Cost Reduction Strategy in Genetic Diagnostic Process as Fall-Out

Apolipoprotein-CIII (apoC-III) is mainly synthesized in the liver and found on the surface of very low-density lipoproteins (VLDLs), low-density lipoproteins (LDLs), and high-density lipoproteins. The main functions of apoC-III in lipoprotein metabolism are (i) inhibition of the clearance of apolipoprotein B (apoB) containing lipoproteins from the circulation, (ii) inhibition of lipoprotein lipase, and (iii) promotion of VLDL assembly and secretion by the liver.1 Since apoC-III is a key regulator of triglyceride-rich lipoprotein metabolism, it represents a potential therapeutic target to reduce cardiovascular risk. Therefore, epidemiologic studies have investigated the relationships of circulating apoC-III with cardiovascular events. However, most of these studies had a relatively low sample size, a cross-sectional design, or did not thoroughly allow for potential confounding.2 We aimed to precisely analyse the associations of circulating apoC-III with cardiovascular mortality in 3141 participants of the LUdwigshafen RIsk and Cardiovascular health (LURIC) study.3,4 They were...

BACKGROUND AND AIMS:Very rare loss-of-function mutations in the apolipoprotein C3 (APOC3) gene have been associated with low circulating apoC-III, low triglycerides, and reduced cardiovascular risk. We aimed to analyze the impact of common APOC3 variants on key parameters of lipid metabolism and coronary artery disease in the largest sample so far. METHODS:Common variants in APOC3 were tested for associations with circulating apoC-III, lipids, and apolipoprotein B (apoB) in 3041 participants of the LUdwigshafen RIsk and Cardiovascular health study (LURIC). These variants were then tested for associations with coronary artery disease in a meta-analysis comprising up to 332,389 participants of the CARDIOGRAMplusC4D consortium and the UK Biobank. RESULTS:The mean (standard deviation) apoC-III concentration was 14.6 (5.1) mg/dl. Seven common variants in APOC3 (rs734104, rs4520, rs5142, rs5141, rs5130, rs5128, and rs4225) were associated with circulating apoC-III (all p < 0.05). The alleles that modestly raised apoC-III were also associated with markedly higher total triglycerides and very low density lipoprotein (VLDL) triglycerides and cholesterol (all p < 0.05), but not with low density lipoprotein (LDL) cholesterol and total apoB (all p > 0.05). These variants were not associated with coronary artery disease in the CARDIOGRAMplusC4D consortium and the UK Biobank (all p > 0.1). CONCLUSIONS:Modest, genetically caused elevations of apoC-III are associated with a marked increase of triglyceride-rich lipoproteins but not with an increase of LDL cholesterol, total apoB, and coronary artery disease. Whether effective inhibition of apoC-III production with antisense oligomers will be instrumental to reduce cardiovascular risk remains to be demonstrated.

Abstract Sirtuin 4 (SIRT4) is a mitochondrial NAD+-dependent deacylase which inhibits the oxidation of glucose and fatty acids, and has been implicated in the regulation of oxidative stress. Given the importance of cardiac energy depletion and ROS during heart failure development, we aimed to define the role of SIRT4 in the development of heart failure. Mice with deletion (SIRT4−/−) or overexpression (SIRT4 TG) of SIRT4 were subjected to transverse aortic constriction (TAC) for 12 weeks or underwent sham procedures. Using echocardiography, ejection fraction (EF) was not different between SIRT4 TG and WT mice subjected to sham operations. In contrast, TAC induced a more pronounced decrease in EF (35% vs. 51%; p<0.05), and a more pronounced increase in LV endsystolic diameter (4.5mm vs. 3.6mm; p<0.05) and myocardial fibrosis (2.2-fold; p<0.05) in SIRT4 TG mice compared to WT mice. Myocardial levels of the lipid peroxidation product 4-hydroxynonenal were increased in WT mice following TAC and were synergistically increased in SIRT4 TG mice following TAC (+66% vs. WT TAC; p<0.05). Administration of the mitochondria-targeted antioxidant MitoQ normalized 4-hydroxynonenal levels, markedly attenuated the decline in EF and almost normalized endsystolic LV diameter in SIRT4 TG mice following TAC. Cardiac function and morphology were unaffected in SIRT4−/− mice during normal or increased workload conditions. Thus, while SIRT4 is not required to maintain cardiac function even in response to increased energy demands, increased expression of SIRT4 accelerates the development of heart failure following TAC, at least in part due to increased mitochondrial oxidative stress. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): German Research Foundation

Background: Sepsis-induced cardiomyopathy contributes to the high mortality of septic shock in critically ill patients. Since the underlying mechanisms are incompletely understood, we hypothesized that sepsis-induced impairment of sirtuin 3 (SIRT3) activity contributes to the development of septic cardiomyopathy. Methods and results: Treatment of mice with lipopolysaccharide (LPS) for 6 h resulted in myocardial NAD(+) depletion and increased mitochondrial protein acetylation, indicating impaired myocardial SIRT3 activity due to NAD(+) depletion. LPS treatment also resulted in impaired cardiac output in isolated working hearts, indicating endotoxemia-induced cardiomyopathy. Maintaining normal myocardial NAD(+) levels in LPS-treated mice by Poly(ADP-ribose)polymerase 1 (PARP1) deletion prevented cardiac dysfunction, whereas additional SIRT3 deficiency blunted this beneficial effect, indicating that impaired SIRT3 activity contributes to cardiac dysfunction in endotoxemia. Measurements of mitochondrial ATP synthesis suggest that LPS-induced contractile dysfunction may result from cardiac energy depletion due to impaired SIRT3 activity. Pharmacological inhibition of mitochondrial calpains using MDL28170 normalized LPS-induced cleavage of the ATP5A1 subunit of ATP synthase and normalized contractile dysfunction, suggesting that cardiac energy depletion may result from calpain-mediated cleavage of ATP5A1. These beneficial effects were completely blunted by SIRT3 deficiency. Finally, a gene set enrichment analysis of hearts of patients with septic, ischemic or dilated cardiomyopathy revealed a sepsis-specific suppression of SIRT3 deacetylation targets, including ATP5A1, indicating a functional relevance of SIRT3-dependent pathways in human sepsis. Conclusions: Impaired SIRT3 activity may mediate cardiac dysfunction in endotoxemia by facilitating calpain-mediated disruption of ATP synthesis, suggesting SIRT3 activation as a potential therapeutic strategy to treat septic cardiomyopathy.

Short telomeres and B vitamin deficiencies have been proposed as risk factors for age-related diseases and mortality that interact through oxidative stress and inflammation. However, available data to support this concept are insufficient. We aimed to investigate the predictive role of B vitamins and homocysteine (HCY) for mortality in cardiovascular patients. We explored potential relationships between HCY, B vitamins, relative telomere length (RTL), and indices of inflammation. Vitamin B6, HCY, interleukin-6 (IL-6), high-sensitive-C-reactive protein (hs-CRP), and RTL were measured in participants of the Ludwigshafen Risk and Cardiovascular Health Study. Death events were recorded over a median follow-up of 9.9 years. All-cause mortality increased with higher concentrations of HCY and lower vitamin B6. Patients in the 4th quartile of HCY and vitamin B6 had hazard ratios (HR) for all-cause mortality of 2.77 (95% CI 2.28–3.37) and 0.41(95% CI 0.33–0.49), respectively, and for cardiovascular mortality of 2.78 (95% CI 2.29–3.39) and 0.40 (95% CI 0.33–0.49), respectively, compared to those in the 1st quartile. Multiple adjustments for confounders did not change these results. HCY and vitamin B6 correlated with age-corrected RTL (r = − 0.086, p < 0.001; r = 0.04, p = 0.031, respectively), IL-6 (r = 0.148, p < 0.001; r = − 0.249, p < 0.001, respectively), and hs-CRP (r = 0.101, p < 0.001; r = − 0.320, p < 0.001, respectively). Subjects with the longest telomeres had a significantly higher concentration of vitamin B6, but lower concentrations of HCY, IL-6, and hs-CRP. Multiple regression analyses identified HCY as an independent negative predictor of age-corrected RTL. In conclusion, hyperhomocysteinemia and vitamin B6 deficiency are risk factors for death from any cause. Hyperhomocysteinemia and vitamin B6 deficiency correlate with increased mortality. This correlation might, at least partially, be explained by accelerated telomere shortening induced by oxidative stress and systemic inflammation in these circumstances.

Background and Aims: Very rare loss-of-function mutations in the apolipoprotein C3 (APOC3) gene have been associated with low circulating apoC-III, low triglycerides, and reduced cardiovascular risk. However, these very rare mutations have also been related to low LDL cholesterol. We aimed to precisely analyze the impact of common APOC3 variants on circulating apoC-III, lipids, and on coronary artery disease in the largest sample so far.

BackgroundCholesterylester transfer protein (CETP) modulates the composition of various lipoproteins associated with cardiovascular disease. Despite its central role in lipoprotein metabolism, its mode of action is still not fully understood. Here we present a simple way to estimate CETP-mediated lipid fluxes between different lipoprotein fractions.ResultsThe model derived adequately describes the observed findings, especially regarding low- and high dense lipoproteins (LDL and HDL), delivering correlation coefficients of R-2=0.567 (p<0.001) and R-2=0.466 (p<0.001), respectively. These estimated fluxes correlate best among all other measured concentrations and lipid per lipoprotein' ratios to the observed fluxes.ConclusionOur model approach is independent of CETP-action's exact mechanistic mode. It is simple and easy to apply, and may be a useful tool in revealing CETP's ambiguous role in lipid metabolism. The model mirrors a diffusion-like exchange of triglycerides between lipoproteins. Cholesteryl ester and triglyceride concentrations measured in HDL, LDL and VLDL are sufficient to apply the model on a plasma sample.

Decreased serum adiponectin levels in type 2 diabetes has been linked to the onset of mitochondrial dysfunction in diabetic complications by impairing AMPK-SIRT1-PGC-1α signaling via impaired adiponectin receptor 1 (AdipoR1) signaling. Here, we aimed to characterize the previously undefined role of disrupted AdipoR1 signaling on the mitochondrial protein composition of cardiac, renal, and hepatic tissues as three organs principally associated with diabetic complications. Comparative proteomics were performed in mitochondria isolated from the heart, kidneys and liver of Adipor1−/− mice. A total of 790, 1,573, and 1,833 proteins were identified in cardiac, renal and hepatic mitochondria, respectively. While 121, 98, and 78 proteins were differentially regulated in cardiac, renal, and hepatic tissue of Adipor1−/− mice, respectively; only 15 proteins were regulated in the same direction across all investigated tissues. Enrichment analysis of differentially expressed proteins revealed disproportionate representation of proteins involved in oxidative phosphorylation conserved across tissue types. Curated pathway analysis identified HNF4, NRF1, LONP, RICTOR, SURF1, insulin receptor, and PGC-1α as candidate upstream regulators. In high fat-fed non-transgenic mice with obesity and insulin resistance, AdipoR1 gene expression was markedly reduced in heart (−70%), kidney (−80%), and liver (−90%) (all P < 0.05) as compared to low fat-fed mice. NRF1 was the only upstream regulator downregulated both in Adipor1−/− mice and in high fat-fed mice, suggesting common mechanisms of regulation. Thus, AdipoR1 signaling regulates mitochondrial protein composition across all investigated tissues in a functionally conserved, yet molecularly distinct, manner. The biological significance and potential implications of impaired AdipoR1 signaling are discussed.

Genetic factors are known to modulate cardiac susceptibility to ventricular hypertrophy and failure. To determine how strain influences the transcriptional response to pressure overload-induced heart failure (HF) and which of these changes accurately reflect the human disease, we analyzed the myocardial transcriptional profile of mouse strains with high (C57BL/6J) and low (129S1/SvImJ) susceptibility for HF development, which we compared to that of human failing hearts. Following transverse aortic constriction (TAC), C57BL/6J mice developed overt HF while 129S1/SvImJ did not. Despite a milder aortic constriction, impairment of ejection fraction and ventricular remodeling (dilation, fibrosis) was more pronounced in C57BL/6J mice. Similarly, changes in myocardial gene expression were more robust in C57BL/6J (461 genes) compared to 129S1/SvImJ mice (71 genes). When comparing these patterns to human dilated cardiomyopathy (1344 genes), C57BL/6J mice tightly grouped to human hearts. Overlay and bioinformatic analysis of the transcriptional profiles of C57BL/6J mice and human failing hearts identified six co-regulated genes (POSTN, CTGF, FN1, LOX, NOX4, TGFB2) with established link to HF development. Pathway enrichment analysis identified angiotensin and IGF-1 signaling as most enriched putative upstream regulator and pathway, respectively, shared between TAC-induced HF in C57BL/6J mice and in human failing hearts. TAC-induced heart failure in C57BL/6J mice more closely reflects the gene expression pattern of human dilated cardiomyopathy compared to 129S1/SvImJ mice. Unbiased as well as targeted gene expression and pathway analyses identified periostin, angiotensin signaling, and IGF-1 signaling as potential causes of increased HF susceptibility in C57BL/6J mice and as potentially useful drug targets for HF treatment.

Background: Nanoscale drug delivery systems accumulate in solid tumors preferentially by the enhanced permeation and retention effect (EPR-effect). Nevertheless, only a miniscule fraction of a given dosage reaches the tumor, while >90% of the given drug ends up in otherwise healthy tissues, leading to the severe toxic reactions observed during chemotherapy. Once accumulation in the tumor has reached its maximum, extracorporeal elimination of circulating nanoparticles by plasmapheresis can diminish toxicities. Objective: In this study, we investigated the effect of dosing and plasmapheresis timing on adverse events and antitumor efficacy in a syngeneic rat tumor model. Methods: MAT-B-III cells transfected with a luciferase reporter plasmid were inoculated into female Fisher rats, and pegylated liposomal doxorubicin (PLD) was used for treatment. Plasmapheresis was performed in a discontinuous manner via centrifugation and subsequent filtration of isolated plasma. Results: Bioluminescence measurements of tumor growth could not substitute caliper measurements of tumor size. In the control group, raising the dosage above 9 mg PLD/kg body weight did not increase therapeutic efficacy in our fully immunocompetent animal model. Plasmapheresis was best done 36 h after injecting PLD, leading to similar antitumor efficacy with significantly less toxicity. Plasmapheresis 24 h after injection interfered with therapeutic efficacy, while plasmapheresis after 48 h led to fewer side effects but also to increased weight loss. Conclusion: Long-circulating nanoparticles offer the unique possibility to eliminate the excess of circulating particles after successful accumulation in tumors by EPR, thereby reducing toxicities and likely toxicity-related therapeutic limitations.

Purpose of Review Today, statins are the first choice to lower LDL cholesterol and concomitantly the risk of atherosclerotic cardiovascular disease. There is a significant minority of statin-treated patients who are more susceptible to occasionally serious side effects that may increase morbidity and lead to compliance problems or the discontinuation of therapy. This review addresses the question of whether genetics can provide meaningful insights into the risk of statin side effects or therapy success. Recent Findings The use of genome-wide association studies has significantly reduced the number of predictive genetic markers for statin effects, and the isolated effect of the surviving markers is low; more promising are approaches to stratify patients with genetic risk scores. Summary Patients reveal a pronounced individual response to the administration of statins. The idea of being able to adequately describe this variability with single genetic markers has failed, genetic risk scores will be the method of choice.