Предсказание торсионных углов в аминокислотных последовательностях белков на основе байесовской процедуры распознавания на цепях Маркова

Запропоновано процедуру розпізнавання торсіонних кутів, утворених C^α атомами чотирьох сусідніх амінокислотних залишків. Отримана послідовність кутів використовується для побудови просторової структури білка на решітці Z³.Torsion angles defined on C^α atoms of four neighbouring residues are predicted using Bayesian pattern recognition procedure on non-stationary Markov chains. The predicted sequence of torsion angles is used for constructing protein 3-dimensional structure on Z³

Loss of hepatic SMLR1 causes hepatosteatosis and protects against atherosclerosis due to decreased hepatic VLDL secretion

The assembly and secretion of VLDL from the liver, a pathway that affects hepatic and plasma lipids, remains incompletely understood. We set out to identify players in the VLDL biogenesis pathway by identifying genes that are co-expressed with the MTTP gene that encodes for microsomal triglyceride transfer protein, key to the lipidation of apolipoprotein B, the core protein of VLDL. Using human and murine transcriptomic data sets, we identified small leucine-rich protein 1 (SMLR1), encoding for small leucine-rich protein 1, a protein of unknown function that is exclusively expressed in liver and small intestine. To assess the role of SMLR1 in the liver, we used somatic CRISPR/CRISPR-associated protein 9 gene editing to silence murine Smlr1 in hepatocytes (Smlr1-LKO). When fed a chow diet, male and female mice show hepatic steatosis, reduced plasma apolipoprotein B and triglycerides, and reduced VLDL secretion without affecting microsomal triglyceride transfer protein activity. Immunofluorescence studies show that SMLR1 is in the endoplasmic reticulum and Cis-Golgi complex. The loss of hepatic SMLR1 in female mice protects against diet-induced hyperlipidemia and atherosclerosis but causes NASH. On a high-fat, high-cholesterol diet, insulin and glucose tolerance tests did not reveal differences in male Smlr1-LKO mice versus controls. We propose a role for SMLR1 in the trafficking of VLDL from the endoplasmic reticulum to the Cis-Golgi complex. While this study uncovers SMLR1 as a player in the VLDL assembly, trafficking, and secretion pathway, it also shows that NASH can occur with undisturbed glucose homeostasis and atheroprotection.Medicinal Chemistr

Cholesterol-induced hepatic inflammation does not underlie the predisposition to insulin resistance in dyslipidemic female LDL receptor knockout mice.

Contains fulltext : 154761.pdf (publisher's version ) (Open Access)Chronic inflammation is considered a causal risk factor predisposing to insulin resistance. However, evidence is accumulating that inflammation confined to the liver may not be causal to metabolic dysfunction. To investigate this, we assessed if hepatic inflammation explains the predisposition towards insulin resistance in low-density lipoprotein receptor knock-out (Ldlr (-/-)) mice. For this, wild type (WT) and Ldlr (-/-) mice were fed a chow diet, a high fat (HF) diet, or a high fat, high cholesterol (HFC) diet for 2 weeks. Plasma lipid levels were elevated in chow-fed Ldlr (-/-) mice compared to WT mice. Although short-term HF or HFC feeding did not result in body weight gain and adipose tissue inflammation, dyslipidemia was worsened in Ldlr (-/-) mice compared to WT mice. In addition, dyslipidemic HF-fed Ldlr (-/-) mice had a higher hepatic glucose production rate than HF-fed WT mice, while peripheral insulin resistance was unaffected. This suggests that HF-fed Ldlr (-/-) mice suffered from hepatic insulin resistance. While HFC-fed Ldlr (-/-) mice displayed the anticipated increased hepatic inflammation, this did neither exacerbate systemic nor hepatic insulin resistance. Therefore, our results show that hepatic insulin resistance is unrelated to cholesterol-induced hepatic inflammation in Ldlr (-/-) mice, indicating that hepatic inflammation may not contribute to metabolic dysfunction per se

Mirabegron-induced brown fat activation does not exacerbate atherosclerosis in mice with a functional hepatic ApoE-LDLR pathway.

Activation of brown adipose tissue (BAT) with the β3-adrenergic receptor agonist CL316,243 protects mice from atherosclerosis development, and the presence of metabolically active BAT is associated with cardiometabolic health in humans. In contrast, exposure to cold or treatment with the clinically used β3-adrenergic receptor agonist mirabegron to activate BAT exacerbates atherosclerosis in apolipoprotein E (ApoE)- and low-density lipoprotein receptor (LDLR)-deficient mice, both lacking a functional ApoE-LDLR pathway crucial for lipoprotein remnant clearance. We, therefore, investigated the effects of mirabegron treatment on dyslipidemia and atherosclerosis development in APOE*3-Leiden.CETP mice, a humanized lipoprotein metabolism model with a functional ApoE-LDLR clearance pathway. Mirabegron activated BAT and induced white adipose tissue (WAT) browning, accompanied by selectively increased fat oxidation and attenuated fat mass gain. Mirabegron increased the uptake of fatty acids derived from triglyceride (TG)-rich lipoproteins by BAT and WAT, which was coupled to increased hepatic uptake of the generated cholesterol-enriched core remnants. Mirabegron also promoted hepatic very low-density lipoprotein (VLDL) production, likely due to an increased flux of fatty acids from WAT to the liver, and resulted in transient elevation in plasma TG levels followed by a substantial decrease in plasma TGs. These effects led to a trend toward lower plasma cholesterol levels and reduced atherosclerosis. We conclude that BAT activation by mirabegron leads to substantial metabolic benefits in APOE*3-Leiden.CETP mice, and mirabegron treatment is certainly not atherogenic. These data underscore the importance of the choice of experimental models when investigating the effect of BAT activation on lipoprotein metabolism and atherosclerosis

Cholesterol-induced hepatic inflammation does not contribute to the development of insulin resistance in male LDL receptor knockout mice.

Item does not contain fulltextOBJECTIVE: It is generally assumed that hepatic inflammation in obesity is linked to the pathogenesis of insulin resistance. Several recent studies have shed doubt on this view, which questions the causality of this association. This study focuses on Kupffer cell-mediated hepatic inflammation as a possible driver of insulin resistance in the absence and presence of obesity. METHODS: We used male mice deficient for the low-density lipoprotein receptor (Ldlr(-/-)) and susceptible to cholesterol-induced hepatic inflammation. Whole body and hepatic insulin resistance was measured in mice fed 4 diets for 2 and 15 weeks, i.e., chow, high-fat (HF), HF-cholesterol (HFC; 0.2% cholesterol) and HF without cholesterol (HFnC). Biochemical parameters in plasma and liver were measured and inflammation was determined using immunohistochemistry and RT-PCR. RESULTS: At 2 weeks, we did not find significant metabolic effects in either diet group, except for the mice fed a HFC diet which showed pronounced hepatic inflammation (p HF, HFnC; p < 0.05) insulin resistance in mice fed HFC was no worse compared to mice on a HFnC and HF diet. CONCLUSION: These data show that cholesterol-induced hepatic inflammation does not contribute to the development of insulin resistance in male Ldlr(-/-) mice. This study suggests that Kupffer cell-driven hepatic inflammation is a consequence, not a cause, of metabolic dysfunction in obesity.1 februari 201

Cargo-specific role for retriever subunit VPS26C in hepatocyte lipoprotein receptor recycling to control postprandial triglyceride-rich lipoproteins.

BACKGROUND: The coiled-coil domain containing 22/coiled-coil domain containing 93/copper metabolism MURR1 domains (CCC) complex is required for the transport of low-density lipoprotein receptor (LDLR) and LRP1 (LDLR-related protein 1) from endosomes to the cell surface of hepatocytes. Impaired functioning of hepatocytic CCC causes hypercholesterolemia in mice, dogs, and humans. Retriever, a protein complex consisting of subunits VPS26C, VPS35L, and VPS29, is associated with CCC, but its role in endosomal lipoprotein receptor transport is unclear. We here investigated the contribution of retriever to hepatocytic lipoprotein receptor recycling and plasma lipids regulation. METHODS: Using somatic CRISPR/Cas9 gene editing, we generated liver-specific VPS35L or VPS26C-deficient mice. We determined total and surface levels of LDLR and LRP1 and plasma lipids. In addition, we studied the protein levels and composition of CCC and retriever. RESULTS: Hepatocyte VPS35L deficiency reduced VPS26C levels but had minimal impact on CCC composition. VPS35L deletion decreased hepatocytic surface expression of LDLR and LRP1, accompanied by a 21% increase in plasma cholesterol levels. Hepatic VPS26C ablation affected neither levels of VPS35L and CCC subunits, nor plasma lipid concentrations. However, VPS26C deficiency increased hepatic LDLR protein levels by 2-fold, probably compensating for reduced LRP1 functioning, as we showed in VPS26C-deficient hepatoma cells. Upon PCSK9 (proprotein convertase subtilisin/kexin type 9)-mediated LDLR elimination, VPS26C ablation delayed postprandial triglyceride clearance and increased plasma TG levels by 26%. CONCLUSIONS: Our study suggests that VPS35L is shared between retriever and CCC to facilitate LDLR and LRP1 transport from endosomes to the cell surface. Conversely, retriever subunit VPS26C selectively transports LRP1, but not LDLR, and thereby may control hepatic uptake of postprandial TG-rich lipoprotein remnants

High-fat diet induced obesity primes inflammation in adipose tissue prior to liver in C57BL/6j mice.

Item does not contain fulltextMetabolic inflammation in adipose tissue and the liver is frequently observed as a result of diet-induced obesity in human and rodent studies. Although the adipose tissue and the liver are both prone to become chronically inflamed with prolonged obesity, their individual contribution to the development of metabolic inflammation remains speculative. Thus, we aimed to elucidate the sequence of inflammatory events in adipose and hepatic tissues to determine their contribution to the development of metabolic inflammation and insulin resistance (IR) in diet-induced obesity. To confirm our hypothesis that adipose tissue (AT) inflammation is initiated prior to hepatic inflammation, C57BL/6J male mice were fed a low-fat diet (LFD; 10% kcal fat) or high-fat diet (HFD; 45% kcal fat) for either 24, 40 or 52 weeks. Lipid accumulation and inflammation was measured in AT and liver. Glucose tolerance was assessed and plasma levels of glucose, insulin, leptin and adiponectin were measured at various time points throughout the study. With HFD, C57BL/6j mice developed a progressive obese phenotype, accompanied by IR at 24 and 40 weeks of HFD, but IR was attenuated after 52 weeks of HFD. AT inflammation was present after 24 weeks of HFD, as indicated by the increased presence of crown-like structures and up-regulation of pro-inflammatory genes Tnf, Il1beta, Mcp1 and F4/80. As hepatic inflammation was not detected until 40 weeks of HFD, we show that AT inflammation is established prior to the development of hepatic inflammation. Thus, AT inflammation is likely to have a greater contribution to the development of IR compared to hepatic inflammation.1 april 201

A cell-type-specific role for murine Commd1 in liver inflammation

The transcription factor NF-kappaB plays a critical role in the inflammatory response and it has been implicated in various diseases, including non-alcoholic fatty liver disease (NAFLD). Although transient NF-kappaB activation may protect tissues from stress, a prolonged NF-kappaB activation can have a detrimental effect on tissue homeostasis and therefore accurate termination is crucial. Copper Metabolism MURR1 Domain-containing 1 (COMMD1), a protein with functions in multiple pathways, has been shown to suppress NF-kappaB activity. However, its action in controlling liver inflammation has not yet been investigated. To determine the cell-type-specific contribution of Commd1 to liver inflammation, we used hepatocyte and myeloid-specific Commd1-deficient mice. We also used a mouse model of NAFLD to study low-grade chronic liver inflammation: we fed the mice a high fat, high cholesterol (HFC) diet, which results in hepatic lipid accumulation accompanied by liver inflammation. Depletion of hepatocyte Commd1 resulted in elevated levels of the NF-kappaB transactivation subunit p65 (RelA) but, surprisingly, the level of liver inflammation was not aggravated. In contrast, deficiency of myeloid Commd1 exacerbated diet-induced liver inflammation. Unexpectedly we observed that hepatic and myeloid Commd1 deficiency in the mice both augmented hepatic lipid accumulation. The elevated levels of proinflammatory cytokines in myeloid Commd1-deficient mice might be responsible for the increased level of steatosis. This increase was not seen in hepatocyte Commd1-deficient mice, in which increased lipid accumulation appeared to be independent of inflammation. Our mouse models demonstrate a cell-type-specific role for Commd1 in suppressing liver inflammation and in the progression of NAFLD

Apolipoprotein F is reduced in humans with steatosis and controls plasma triglyceride-rich lipoprotein metabolism

Background: NAFLD affects nearly 25% of the global population. Cardiovascular disease (CVD) is the most common cause of death among patients with NAFLD, in line with highly prevalent dyslipidemia in this population. Increased plasma triglyceride (TG)-rich lipoprotein (TRL) concentrations, an important risk factor for CVD, are closely linked with hepatic TG content. Therefore, it is of great interest to identify regulatory mechanisms of hepatic TRL production and remnant uptake in the setting of hepatic steatosis.Approach and Results: To identify liver-regulated pathways linking intrahepatic and plasma TG metabolism, we performed transcriptomic analysis of liver biopsies from two independent cohorts of obese patients. Hepatic encoding apolipoprotein F (APOF) expression showed the fourth-strongest negatively correlation with hepatic steatosis and the strongest negative correlation with plasma TG levels. The effects of adenoviral-mediated human ApoF (hApoF) overexpression on plasma and hepatic TG were assessed in C57BL6/J mice. Surprisingly, hApoF overexpression increased both hepatic very low density lipoprotein (VLDL)-TG secretion and hepatic lipoprotein remnant clearance, associated a similar to 25% reduction in plasma TG levels. Conversely, reducing endogenous ApoF expression reduced VLDL secretion in vivo, and reduced hepatocyte VLDL uptake by similar to 15% in vitro. Transcriptomic analysis of APOF-overexpressing mouse livers revealed a gene signature related to enhanced ApoB-lipoprotein clearance, including increased expression of Ldlr and Lrp1, among others.Conclusion: These data reveal a previously undescribed role for ApoF in the control of plasma and hepatic lipoprotein metabolism by favoring VLDL-TG secretion and hepatic lipoprotein remnant particle clearance.Diabetes mellitus: pathophysiological changes and therap