Discovery of a New Role of Human Resistin in Hepatocyte Low-Density Lipoprotein Receptor Suppression Mediated in Part by Proprotein Convertase Subtilisin/Kexin Type 9

The role of PCSK9 in heart failure and other cardiovascular diseases-mechanisms of action beyond its effect on LDL cholesterol

Proprotein convertase subtilisin/kexin type-9 (PCSK9) is a protein that regulates low-density lipoprotein (LDL) cholesterol metabolism by binding to the hepatic LDL receptor (LDLR), ultimately leading to its lysosomal degradation and an increase in LDL cholesterol (LDLc) levels. Treatment strategies have been developed based on blocking PCSK9 with specific antibodies (alirocumab, evolocumab) and on blocking its production with small regulatory RNA (siRNA) (inclisiran). Clinical trials evaluating these drugs have confirmed their high efficacy in reducing serum LDLc levels and improving the prognosis in patients with atherosclerotic cardiovascular diseases. Most studies have focused on the action of PCSK9 on LDLRs and the subsequent increase in LDLc concentrations. Increasing evidence suggests that the adverse cardiovascular effects of PCSK9, particularly its atherosclerotic effects on the vascular wall, may also result from mechanisms independent of its effects on lipid metabolism. PCSK9 induces the expression of pro-inflammatory cytokines contributing to inflammation within the vascular wall and promotes apoptosis, pyroptosis, and ferroptosis of cardiomyocytes and is thus involved in the development and progression of heart failure. The elimination of PCSK9 may, therefore, not only be a treatment for hypercholesterolaemia but also for atherosclerosis and other cardiovascular diseases. The mechanisms of action of PCSK9 in the cardiovascular system are not yet fully understood. This article reviews the current understanding of the mechanisms of PCSK9 action in the cardiovascular system and its contribution to cardiovascular diseases. Knowledge of these mechanisms may contribute to the wider use of PCSK9 inhibitors in the treatment of cardiovascular diseases.

Proprotein convertase subtisilin/kexin 9 levels decline with hepatitis C virus therapy in people with HIV/hepatitis C virus and correlate with inflammation

BACKGROUND

Proprotein convertase subtisilin/kexin 9 (PCSK9) raises low-density lipoprotein cholesterol (LDL-C) levels and is associated with inflammation, which is elevated in HIV and hepatitis C virus (HCV) infection. We compared PCSK9 levels in people with co-occurring HIV and HCV (HIV/HCV) vs. HIV alone, and evaluated the impact of HCV direct-acting antiviral (DAA) therapy on PCSK9.

DESIGN

A prospective, observational cohort study.

METHODS

Thirty-five adults with HIV/HCV and 37 with HIV alone were evaluated, all with HIV virologic suppression and without documented cardiovascular disease. Circulating PCSK9 and inflammatory biomarkers were measured at baseline and following HCV treatment or at week 52 (for HIV alone) and compared using Wilcoxon tests and Spearman correlations.

RESULTS

At baseline, PCSK9 trended higher in HIV/HCV vs. HIV alone (307 vs. 284 ng/ml, P  = 0.06). Twenty-nine participants with HIV/HCV completed DAA therapy with sustained virologic response. PCSK9 declined from baseline to posttreatment 1 (median 7.3 weeks after end of therapy [EOT]) and posttreatment 2 (median 43.5 weeks after EOT), reaching levels similar to HIV alone; median within-person reduction was -60.5 ng/ml ( P  = 0.003) and -55.6 ng/ml ( P  = 0.02), respectively. Decline in PCSK9 correlated with decline in soluble (s)E-selectin and sCD163 ( r  = 0.64, P  = 0.002; r  = 0.58, P  = 0.008, respectively), but not with changes in LDL-C or other biomarkers. No significant change in PCSK9 occurred in the HIV alone group over 52 weeks.

CONCLUSION

PCSK9 declined with DAA therapy in participants with HIV/HCV, correlating with declines in several inflammatory biomarkers but not LDL-C. Elevated PCSK9 with HCV may be linked to particular HCV-associated inflammatory pathways more so than cholesterol homeostasis.

Resistin Contribution to Cardiovascular Risk in Chronic Kidney Disease Male Patients

BACKGROUND

Resistin is a molecule that belongs to the Resistin-Like Molecules family (RELMs), the group of proteins taking part in inflammatory processes. Increased resistin concentrations are observed in cardiovascular complications. Resistin contributes to the onset of atherosclerosis and intensifies the atherosclerotic processes. The aim of this study was to investigate the relationship between resistin and cardiovascular (CV) risk in men with chronic kidney disease (CKD) not treated with dialysis.

MATERIALS AND METHODS

One hundred and forty-two men were included in the study: 99 men with eGFR lower than 60 mL/min/1.73 m² and 43 men with eGFR ≥ 60 mL/min/1.73 m². CV risk was assessed. Serum resistin, tumor necrosis factor-alpha (TNF-alpha) and plasminogen activator inhibitor-1 (PAI-1) were measured among other biochemical parameters.

RESULTS

We observed that resistin concentrations were significantly higher in patients with CKD compared to individuals with eGFR ≥ 60 mL/min/1.73 m² (p = 0.003). In CKD, after estimating the general linear model (GLM), we found that resistin is associated with CV risk (p = 0.026) and PAI-1 serum concentrations (0.012). The relationship of PAI-1 with resistin depends on the level of CV risk in CKD (p = 0.048).

CONCLUSIONS

Resistin concentrations rise with the increase of CV risk in CKD patients and thus resistin may contribute to the progression of cardiovascular risk in this group of patients. The relationship between resistin and CV risk is modified by PAI-1 concentrations.

Resistin impairs mitochondrial homeostasis via cyclase-associated protein 1-mediated fission, leading to obesity-induced metabolic diseases

OBJECTIVE

One of the suggested mechanisms of obesity-induced insulin resistance is mitochondrial dysfunction in target tissues such as skeletal muscle. In our study, we examined whether resistin, an adipokine associated with obesity-mediated insulin resistance, induced metabolic disorders by impairing mitochondrial homeostasis.

METHODS

The morphology and function of mitochondria of skeletal muscle were examined in resistin-knockout and humanized resistin mice that were subjected to high-fat diet for 3 months. Morphology was examined by transmission electron microscopy. Mitochondria bioenergetics of skeletal muscle were evaluated using a Seahorse XF96 analyzer. Human skeletal myoblasts were used for in vitro studies on signaling mechanisms in responses to resistin.

RESULTS

A high-fat diet in humanized resistin mice increased fragmented and shorter mitochondria in the skeletal muscle, whereas resistin-knockout mice had healthy normal mitochondria. In vitro studies showed that human resistin treatment impaired mitochondrial homeostasis by inducing mitochondrial fission, leading to a decrease in ATP production and mitochondrial dysfunction. Induction of mitochondrial fission by resistin was accompanied by increased formation of mitochondria-associated ER membranes (MAM). At the same time, resistin induced up-regulation of the protein kinase A (PKA) pathway. This activation of PKA induced phosphorylation of Drp1 at serine 616, leading to Drp1 activation and subsequent induction of mitochondrial fission. The key molecule that mediated human resistin-induced mitochondrial fission was adenylyl cyclase-associated protein 1 (CAP1), which was reported as a bona fide receptor for human resistin. Moreover, our newly developed biomimetic selective blocking peptide could repress human resistin-mediated mitochondrial dysfunction. High-fat diet-fed mice showed lower exercise capacity and higher insulin resistance, which was prevented by a novel peptide to block the binding of resistin to CAP1 or in the CAP1-knockdown mice.

CONCLUSIONS

Our study demonstrated that human resistin induces mitochondrial dysfunction by inducing abnormal mitochondrial fission. This result suggests that the resistin-CAP1 complex could be a potential therapeutic target for the treatment of obesity-related metabolic diseases such as diabetes and cardiometabolic diseases.

Physical activity to reduce PCSK9 levels

The amount of physical activity (PA) people practice everyday has been reducing in the last decades. Sedentary subjects tend to have an impaired lipid plasma profile with a higher risk of atherosclerosis and related cardio- and cerebrovascular events. Regular PA helps in both primary and secondary cardiovascular prevention because of its beneficial effect on the whole metabolism. Several studies reported lower levels of plasma lipids in trained subjects, but the precise mechanisms by which PA modulates lipoproteins remain only partially described. Thereupon, proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serin protease whose main function is to reduce the amount of low-density lipoprotein cholesterol (LDL-C) receptors, with the direct consequence of reducing LDL-C uptake by the liver and increasing its circulating pool. Accordingly, recently developed PCSK9 inhibitors improved cardiovascular prevention and are increasingly used to reach LDL-C goals in patients at high CV risk. Whether PA can modulate the levels of PCSK9 remains partially explored. Recent studies suggest PA as a negative modulator of such a deleterious CV mediator. Yet the level of evidence is limited. The aim of this review is to summarize the recent reports concerning the regulatory role of PA on PCSK9 plasma levels, highlighting the beneficial role of regular exercise on the prevention of atherosclerosis and overall CV health.

Curcumin nicotinate decreases serum LDL cholesterol through LDL receptor-mediated mechanism

Curcumin nicotinate (Curtn) is a synthesized ester derivative of curcumin and niacin. Our previous study has shown that Curtn lowers serum low-density lipoprotein cholesterol (LDL-C) levels in apoE^-/- mice and promotes LDL-C uptake into HepG2 cells in vitro. The present study was to test the hypothesis that Curtn decreases serum LDL-C levels through decreased expression of pro-protein convertase subtilisin/kexin type 9 (PCSK9) and subsequent increase in LDL receptor expression. Male Wistar rats on high-fat diet (HFD) were treated with Curtn or rosuvastatin. Curtn or rosuvastatin treatment significantly decreased serum levels of total cholesterol (TC) and LDL-C in rats on HFD with increased liver LDL receptor expression. LDL-C-lowering effect of Curtn was not observed in LDL receptor deficient (LDLR^-/-) mice on HFD, while rosuvastatin still decreased serum lipid levels in LDLR^-/- mice, indicating that the reduction of serum LDL-C levels by Curtn treatment was LDL receptor-dependent. Curtn treatment also significantly decreased the protein expression of PCSK9 in Wistar rats and LDLR^-/- mice. In HepG2 cells with overexpression of human PCSK9, Curtn treatment significantly increased LDL-C uptakes into hepatocytes, and increased LDL receptor distribution on cell surface in association with decreased PCSK9 protein expression. RNAi-LDLR significantly attenuated the effect of Curtn on LDLR distribution on cell surface. These data indicates that Curtn would decrease serum LDL-C level at least partially through inhibition of PCSK9 expression, and subsequent increase in LDL receptor expression and distribution in hepatocytes, serving as a potential novel compound to treat hyperlipidemia.

Expanding Biology of PCSK9: Roles in Atherosclerosis and Beyond

Purpose of Review

Since the discovery of PCSK9 in 2003, this proprotein convertase was shown to target specific receptors for degradation in endosomes/lysosomes, including LDLR and other family members and hence to enhance the levels of circulating LDL-cholesterol (LDLc). Accordingly, inhibitors of PCSK9, including monoclonal antibodies blocking its circulating activity and siRNA silencers of its hepatic expression, are now used in clinics worldwide to treat hypercholesterolemia patients effectively and safely in combination with statins and/or ezetimibe. These powerful treatments reduce the incidence of atherosclerosis by at least 20%. Since 2008, novel targets of PCSK9 began to be defined, thereby expanding its roles beyond LDLc regulation into the realm of inflammation, pathogen infections and cellular proliferation in various cancers and associated metastases.

Recent Findings

Some pathogens such as dengue virus exploit the ability of PCSK9 to target the LDLR for degradation to enhance their ability to infect cells. Aside from increasing the degradation of the LDLR and its family members VLDLR, ApoER2 and LRP1, circulating PCSK9 also reduces the levels of other receptors such as CD36 (implicated in fatty acid uptake), oxidized LDLR receptor (that clears oxidized LDLc) as well as major histocompatibility class-I (MHC-I) receptors (implicated in the immune response to antigens). Thus, these novel targets provided links between PCSK9 and inflammation/atherosclerosis, viral infections and cancer/metastasis. The functional activities of PCSK9, accelerated the development of novel therapies to inhibit PCSK9 functions, including small molecular inhibitors, long-term vaccines, and possibly CRISPR-based silencing of hepatic expression of PCSK9.

Summary

The future of inhibitors/silencers of PCSK9 function or expression looks bright, as these are expected to provide a modern armamentarium to treat various pathologies beyond hypercholesterolemia and its effects on atherosclerosis.

Resistin Modulates Low-Density Lipoprotein Cholesterol Uptake in Human Placental Explants via PCSK9

Maternal metabolic status influences pregnancy and, consequently, the perinatal outcome. Resistin is a pro-inflammatory adipokine predominantly expressed and secreted by mononuclear cells, adipose tissue, and placental trophoblastic cells during pregnancy. Recently, we reported an inverse association between maternal resistin levels and fetal low-density lipoprotein cholesterol (LDL-C). Then, in this work, we used a human placental explant model and the trophoblast cell line JEG-3 to evaluate whether resistin affects placental LDL-C uptake. Resistin exposure induced the transcription factor SREBP-2, LDLR, and PCSK9 mRNA expression, and changes at the protein level were confirmed by immunohistochemistry and Western blot. However, for LDLR, the changes were not consistent between mRNA and protein levels. Using a labeled LDL-cholesterol (BODIPY FL LDL), uptake assay demonstrated that the LDL-C was significantly decreased in placental explants exposed to a high dose of resistin and a lesser extent in JEG-3 cells. In summary, resistin induces PCSK9 expression in placental explants and JEG-3 cells, which could be related to negative regulation of the LDLR by lysosomal degradation. These findings suggest that resistin may significantly regulate the LDL-C uptake and transport from the maternal circulation to the fetus, affecting its growth and lipid profile.

Effects of PCSK9 Targeting: Alleviating Oxidation, Inflammation, and Atherosclerosis

Characterized as a chronic inflammatory disease of the large arteries, atherosclerosis is the primary cause of cardiovascular disease, the leading contributor of morbidity and mortality worldwide. Elevated plasma cholesterol levels and chronic inflammation within the arterial plaque are major mediators of plaque initiation, progression, and instability. In 2003, the protein PCSK9 (proprotein convertase subtilisin/kexin 9) was discovered to play a critical role in cholesterol regulation, thus becoming a key player in the mechanisms behind atherosclerotic plaque development. Emerging evidence suggests that PCSK9 could potentially have effects on atherosclerosis that are independent of cholesterol levels. The objective of this review was to discuss the role on PCSK9 in oxidation, inflammation, and atherosclerosis. This function activates proinflammatory cytokine production and affects oxidative modifications within atherosclerotic lesions, revealing its more significant role in atherosclerosis. Although a variety of evidence demonstrates that PCSK9 plays a role in atherosclerotic inflammation, the direct mechanism of involvement is still unknown, driving a gap in knowledge to such a predominant player in cardiovascular disease. Investigation of proteins structurally related to PCSK9 may interestingly be the link in unveiling the mechanistic role of this protein’s involvement in oxidation and inflammation. Importantly, the unique structure of PCSK9 bears structural homology to a one‐of‐a‐kind domain found in the metabolic protein resistin, which is responsible for many of the same inflammatory outcomes as PCSK9. Closing this gap in knowledge of PCSK9`s role in atherosclerotic oxidation and inflammation will provide fundamental information for understanding, preventing, and treating cardiovascular disease.

Measurement of Plasma Resistin Concentrations in Horses with Metabolic and Inflammatory Disorders

Simple Summary

Obesity and its associated complications, such as metabolic syndrome, are an increasing problem in both humans and horses in the developed world. Adipose tissue is a key endocrine organ that communicates with other organs by multiple endocrine substances called adipokines. There is evidence to suggest that adipokines may contribute to the regulation of biological processes, such as metabolism, immunity, and inflammation. The aim of this study was to investigate the usefulness of one of these adipokines in horses, resistin, and its relationship with insulin dysregulation (ID) and inflammation. Seventy-two horses, included in one of the four following groups, were studied: healthy controls, horses with inflammatory conditions, horses with mild, and horses with severe ID. Plasma resistin concentrations were significantly different between groups, and the highest values were recorded in the inflammatory and severe ID groups. The lack of correlation of resistin with basal insulin concentration and the significant correlation of resistin with the inflammatory marker serum amyloid A suggest that, as is the case in humans, plasma resistin concentrations in horses are predominantly related to inflammatory conditions and not to ID.

Abstract

Obesity and its associated complications, such as metabolic syndrome, are an increasing problem in both humans and horses in the developed world. The expression patterns of resistin differ considerably between species. In rodents, resistin is expressed by adipocytes and is related to obesity and ID. In humans, resistin is predominantly produced by inflammatory cells, and resistin concentrations do not reflect the degree of obesity, although they may predict cardiovascular outcomes. The aim of this study was to investigate the usefulness of resistin and its relationship with ID and selected indicators of inflammation in horses. Seventy-two horses, included in one of the four following groups, were studied: healthy controls (C, n = 14), horses with inflammatory conditions (I, n = 21), horses with mild ID (ID1, n = 18), and horses with severe ID (ID2, n = 19). Plasma resistin concentrations were significantly different between groups and the higher values were recorded in the I and ID2 groups (C: 2.38 ± 1.69 ng/mL; I: 6.85 ± 8.38 ng/mL; ID1: 2.41 ± 2.70 ng/mL; ID2: 4.49 ± 3.08 ng/mL). Plasma resistin was not correlated with basal insulin concentrations. A significant (r = 0.336, p = 0.002) correlation was found between resistin and serum amyloid A. Our results show that, as is the case in humans, plasma resistin concentrations in horses are predominantly related to inflammatory conditions and not to ID. Horses with severe ID showed an elevation in resistin that may be secondary to the inflammatory status associated with metabolic syndrome.

The Role of Adipokines in Cardiovascular Pathology

The recent decades saw a steady growth of obesity incidence worldwide. Obesity is an independent risk factor for cardiovascular diseases (CVDs) and type 2 diabetes mellitus and is also associated with a shorter life expectancy. Not only hemodynamic but also hormone metabolic processes, arising from excessive accumulation of adipose tissue in human body, underlie the development of CVDs. Adipose tissue has now been proved to be a hormone-active substrate. Studies of the influence of adipokines will bring us closer to understanding cardiovascular pathogenesis and help personalize prophylactic strategies.

Regulation of PCSK9 Expression and Function: Mechanisms and Therapeutic Implications

Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes degradation of low-density lipoprotein receptor (LDLR) and plays a central role in regulating plasma levels of LDL cholesterol levels, lipoprotein(a) and triglyceride-rich lipoproteins, increasing the risk of cardiovascular disease. Additionally, PCSK9 promotes degradation of major histocompatibility protein class I and reduces intratumoral infiltration of cytotoxic T cells. Inhibition of PCSK9 increases expression of LDLR, thereby reducing plasma levels of lipoproteins and the risk of cardiovascular disease. PCSK9 inhibition also increases cell surface levels of major histocompatibility protein class I in cancer cells and suppresses tumor growth. Therefore, PCSK9 plays a vital role in the pathogenesis of cardiovascular disease and cancer, the top two causes of morbidity and mortality worldwide. Monoclonal anti-PCSK9 antibody-based therapy is currently the only available treatment that can effectively reduce plasma LDL-C levels and suppress tumor growth. However, high expenses limit their widespread use. PCSK9 promotes lysosomal degradation of its substrates, but the detailed molecular mechanism by which PCSK9 promotes degradation of its substrates is not completely understood, impeding the development of more cost-effective alternative strategies to inhibit PCSK9. Here, we review our current understanding of PCSK9 and focus on the regulation of its expression and functions.

Differential prognostic value of resistin for cardiac death in patients with coronary artery disease according to the presence of metabolic syndrome

Resistin is associated with atherosclerosis progression by affecting inflammation and insulin resistance. There are controversial data regarding the prognostic value of resistin in stable coronary artery disease (CAD) patients. We prospectively investigated the long-term prognostic value of resistin in patients with stable CAD. A total 741 consecutive patients with stable CAD were followed for a median of 5.5 years. Serum resistin, lipids, high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6) levels were measured at baseline. Primary endpoints were cardiac death and secondary hospitalizations for acute coronary syndrome, arrhythmic event or ischemic stroke. Follow-up data were obtained from 703 patients of whom 79 had a cardiac death (11.2%) and 205 (29.2%) met the secondary endpoints. Resistin was positively correlated with hsCRP (r = 0.159, p < 0.001) and IL-6 (r = 0.165, p = 0.002), and negatively with high-density lipoprotein-cholesterol (r = - 0.176, p < 0.001). Resistin levels could not predict cardiac death [HR 1.044; 95% CI 0.994-1.096; p = 0.087] neither secondary endpoints [HR 1.025; 95% CI 0.983-1.068; p = 0.250). Among 298 patients (42.4%) with metabolic syndrome (MS) resistin levels were independently associated with cardiac death after adjustment for conventional risk factors [HR 1.121; 95% CI 1.045-1.204; p = 0.002). Further adjustment for ejection fraction of left ventricle (LVEF) did not change the association (HR 1.145; 95% CI 1.057-1.240; p = 0.001). Patients with resistin values ≥ 7.6 ng/mL (median level) had 2.8 times higher risk of cardiac death compared to those with resistin levels < 7.6 ng/mL after adjustment for traditional risk factors and LVEF (HR 2.882; 95% CI 1.311-6.336; p = 0.008). Resistin is independently associated with cardiac death in patients with stable CAD and MS.

Salmon peptides limit obesity-associated metabolic disorders by modulating a gut-liver axis in vitamin D-deficient mice

OBJECTIVE

This study investigated the effects of a low-dose salmon peptide fraction (SPF) and vitamin D₃ (VitD₃ ) in obese and VitD₃ -deficient mice at risk of metabolic syndrome (MetS).

METHODS

Obese and VitD₃ -deficient low-density lipoprotein receptor (LDLr)^-/- /apolipoprotein B100 (ApoB)^100/100 mice were treated with high-fat high-sucrose diets, with 25% of dietary proteins replaced by SPF or a nonfish protein mix (MP). The SPF and MP groups received a VitD₃ -deficient diet or a supplementation of 15,000 IU of VitD₃ per kilogram of diet. Glucose homeostasis, atherosclerosis, nonalcoholic fatty liver disease, and gut health were assessed.

RESULTS

VitD₃ supplementation increased plasma 25-hydroxyvitamin D to optimal status whereas the VitD₃ -deficient diet maintained moderate deficiency. SPF-treated groups spent more energy and accumulated less visceral fat in association with an improved adipokine profile. SPF lowered homeostatic model assessment of insulin resistance compared with MP, suggesting that SPF can improve insulin sensitivity. SPF alone blunted hepatic and colonic inflammation, whereas VitD₃ supplementation attenuated ileal inflammation. These effects were associated with changes in gut microbiota such as increased Mogibacterium and Muribaculaceae.

CONCLUSIONS

SPF treatment improves MetS by modulating hepatic and gut inflammation along with gut microbiota, suggesting that SPF operates through a gut-liver axis. VitD₃ supplementation has limited influence on MetS in this model.

Is resistin the master link between inflammation and inflammation-related chronic diseases?

Resistin has been firstly discovered in mice and was identified as an adipose tissue-secreted hormone or adipokine linking obesity and insulin resistance. In humans, resistin has been characterized as a hormone expressed and secreted by Immune cells especially by macrophages, and was linked to many inflammatory responses including inflammation of adipose tissue due to macrophages' infiltration. Human and mouse resistin display sequence and structural similarities and also dissimilarities that could explain their different expression pattern. In mice, strong pieces of evidence clearly associated high resistin plasma levels to obesity and insulin resistance suggesting that resistin could play an important role in the onset and progression of obesity and insulin resistance via resistin-induced inflammation. In humans, the link between resistin and obesity/insulin resistance is still a matter of debate and needs more epidemiological studies. Also, resistin has been linked to other chronic diseases such as cardiovascular diseases and cancers where resistin has been proposed in many studies as a biological marker.

Resistin: A journey from metabolism to cancer

•

Resistin levels have been associated with several pathological disorders such as metabolic disorders, cancers etc.

•

Resistin exists in three isoforms namely RELM-α, β and γ.

•

High resistin level activates inflammatory pathways, promotes metabolic disorders and is associated with carcinogenesis.

•

Increase in the resistin level impairs the therapeutic response by inducing stemness or resistance, in cancer cells.

•

Conventional drugs which alter resistin level could have therapeutic implications in several pathological disorders.

Resistin, a small secretory molecule, has been implicated to play an important role in the development of insulin resistance under obese condition. For the past few decades, it has been linked to various cellular and metabolic functions. It has been associated with diseases like metabolic disorders, cardiovascular diseases and cancers. Numerous clinical studies have indicated an increased serum resistin level in pathological disorders which have been reported to increase mortality rate in comparison to low resistin expressing subjects. Various molecular studies suggest resistin plays a pivotal role in proliferation, metastasis, angiogenesis, inflammation as well as in regulating metabolism in cancer cells. Therefore, understanding the role of resistin and elucidating its’ associated molecular mechanism will give a better insight into the management of these disorders. In this article, we summarize the diverse roles of resistin in pathological disorders based on the available literature, clinicopathological data, and a compiled study from various databases. The article mainly provides comprehensive information of its role as a target in different treatment modalities in pre as well as post-clinical studies.

Diagnostic Power of Circulatory Metabolic Biomarkers as Metabolic Syndrome Risk Predictors in Community-Dwelling Older Adults in Northwest of England (A Feasibility Study)

Background: Metabolic Syndrome (MetS) is a cluster of risk factors for diabetes and cardiovascular diseases with pathophysiology strongly linked to aging. A range of circulatory metabolic biomarkers such as inflammatory adipokines have been associated with MetS; however, the diagnostic power of these markers as MetS risk correlates in elderly has yet to be elucidated. This cross-sectional study investigated the diagnostic power of circulatory metabolic biomarkers as MetS risk correlates in older adults. Methods: Hundred community dwelling older adults (mean age: 68.7 years) were recruited in a study, where their blood pressure, body composition and Pulse Wave Velocity (PWV) were measured; and their fasting capillary and venous blood were collected. The components of the MetS; and the serum concentrations of Interleukin-6 (IL-6), Tumor Necrosis Factor-α (TNF-α), Plasminogen Activator Inhibitor-I (PAI-I), Leptin, Adiponectin, Resistin, Cystatin-C, C-Reactive Protein (CRP), insulin and ferritin were measured within the laboratory, and the HOMA1-IR and Atherogenic Index of Plasma (AIP) were calculated. Results: Apart from other markers which were related with some cardiometabolic (CM) risk, after Bonferroni correction insulin had significant association with all components of Mets and AIP. These associations also remained significant in multivariate regression. The multivariate odds ratio (OR with 95% confidence interval (CI)) showed a statistically significant association between IL-6 (OR: 1.32 (1.06–1.64)), TNF-α (OR: 1.37 (1.02–1.84)), Resistin (OR: 1.27 (1.04–1.54)) and CRP (OR: 1.29 (1.09–1.54)) with MetS risk; however, these associations were not found when the model was adjusted for age, dietary intake and adiposity. In unadjusted models, insulin was consistently statistically associated with at least two CM risk factors (OR: 1.33 (1.16–1.53)) and MetS risk (OR: 1.24 (1.12–1.37)) and in adjusted models it was found to be associated with at least two CM risk factors and MetS risk (OR: 1.87 (1.24–2.83) and OR: 1.25 (1.09–1.43)) respectively. Area under curve (AUC) for receiver operating characteristics (ROC) demonstrated a good discriminatory diagnostics power of insulin with AUC: 0.775 (0.683–0.866) and 0.785 by cross validation and bootstrapping samples for at least two CM risk factors and AUC: 0.773 (0.653–0.893) and 0.783 by cross validation and bootstrapping samples for MetS risk. This was superior to all other AUC reported from the ROC analysis of other biomarkers. Area under precision-recall curve for insulin was also superior to all other markers (0.839 and 0.586 for at least two CM risk factors and MetS, respectively). Conclusion: Fasting serum insulin concentration was statistically linked with MetS and its risk, and this link is stronger than all other biomarkers. Our ROC analysis confirmed the discriminatory diagnostic power of insulin as CM and MetS risk correlate in older adults.

Role of Mcpip1 in obesity-induced hepatic steatosis as determined by myeloid and liver-specific conditional knockouts

Monocyte chemoattractant protein-induced protein 1 (MCPIP1, alias Regnase 1) is a negative regulator of inflammation, acting through cleavage of transcripts coding for proinflammatory cytokines and by inhibition of NFκB activity. Moreover, it was demonstrated that MCPIP1 regulates lipid metabolism both in adipose tissue and in hepatocytes. In this study, we investigated the effects of tissue-specific Mcpip1 deletion on the regulation of hepatic metabolism and development of nonalcoholic fatty liver disease (NAFLD). We used control Mcpip1^fl/fl mice and animals with deletion of Mcpip1 in myeloid leukocytes (Mcpip1^fl/fl LysM^Cre ) and in hepatocytes (Mcpip1^fl/fl Alb^Cre ), which were fed chow or a high-fat diet (HFD) for 12 weeks. Mcpip1^fl/fl LysM^Cre mice fed a chow diet were characterized by a significantly reduced hepatic expression of genes regulating lipid and glucose metabolism, which subsequently resulted in low plasma glucose level and dyslipidemia. These animals also displayed systemic inflammation, demonstrated by increased concentrations of cytokines in the plasma and high Tnfa, Il6, IL1b mRNA levels in the liver and brown adipose tissue (BAT). Proinflammatory leukocyte infiltration into BAT, together with low expression of Ucp1 and Ppargc1a, resulted in hypothermia of 22-week-old Mcpip1^fl/fl LysM^Cre mice. On the other hand, there were no significant changes in phenotype in Mcpip1^fl/fl Alb^Cre mice. Although we detected a reduced hepatic expression of genes regulating glucose metabolism and β-oxidation in these mice, they remained asymptomatic. Upon feeding with a HFD, Mcpip1^fl/fl LysM^Cre mice did not develop obesity, glucose intolerance, nor hepatic steatosis, but were characterized by low plasma glucose level and dyslipidemia, along with proinflammatory phenotype. Mcpip1^fl/fl Alb^Cre animals, following a HFD, became hypercholesterolemic, but accumulated lipids in the liver at the same level as Mcpip1^fl/fl mice, and no changes in the level of soluble factors tested in the plasma were detected. We have demonstrated that Mcpip1 protein plays an important role in the liver homeostasis. Depletion of Mcpip1 in myeloid leukocytes, followed by systemic inflammation, has a more pronounced effect on controlling liver metabolism and homeostasis than the depletion of Mcpip1 in hepatocytes.

Proprotein Convertase Subtilisin/Kexin Type 9: A View beyond the Canonical Cholesterol-Lowering Impact

Proprotein convertase subtilisin/kexin type 9 (PCSK9), mainly synthetized and released by the liver, represents one of the key regulators of low-density lipoprotein cholesterol. Although genetic and interventional studies have demonstrated that lowering PCSK9 levels corresponds to a cardiovascular benefit, identification of non-cholesterol-related processes has emerged since its discovery. Besides liver, PCSK9 is also expressed in many tissues (eg, intestine, endocrine pancreas, and brain). The aim of the present review is to describe and discuss PCSK9 pathophysiology and possible non-lipid-lowering effects whether already extensively characterized (eg, inflammatory burden of atherosclerosis, triglyceride-rich lipoprotein metabolism, and platelet activation), or to be unraveled (eg, in adipose tissue). The identification of novel transcriptional factors in the promoter region of human PCSK9 (eg, ChREBP) characterizes new mechanisms explaining how controlling intrahepatic glucose may be a therapeutic strategy to reduce cardiovascular risk in type 2 diabetes. Finally, the evidence describing PCSK9 as involved in cell proliferation and apoptosis raises the possibility of this protein being involved in cancer risk.

Familial combined hyperlipidaemia/polygenic mixed hyperlipidaemia

Familial combined hyperlipidaemia (FCH) is the most prevalent form of familial hyperlipidaemia with a multigenic origin and a complex pattern of inheritance. In this respect, FCH is an oligogenic primary lipid disorder due to interaction of genetic variants and mutations with environmental factors. Patients with FCH are at increased risk of cardiovascular disease and often have other associated metabolic conditions. Despite its relevance in cardiovascular prevention, FCH is frequently underdiagnosed and very often undertreated. In this review, emphasis is placed on the most recent advances in FCH, in order to increase its awareness and ultimately contribute to improving its clinical control.

PCSK9: Associated with cardiac diseases and their risk factors?

PCSK9 plays a critical role in cholesterol metabolism via the PCSK9-LDLR axis. Liver-derived, circulating PCSK9 has become a novel drug target in lipid-lowering therapy. Accumulative evidence supports the possible association between PCSK9 and cardiac diseases and their risk factors. PCSK9 exerts various effects in the heart independently of LDL-cholesterol regulation. Acute myocardial infarction (AMI) induces local and systemic inflammation and reactive oxygen species generation, resulting in increased PCSK9 expression in hepatocytes and cardiomyocytes. PCSK9 upregulation promotes excessive autophagy and apoptosis in cardiomyocytes, thereby contributing to cardiac insufficiency. PCSK9 might also participate in the pathophysiology of heart failure by regulating fatty acid metabolism and cardiomyocyte contractility. It also promotes platelet activation and coagulation in patients with atrial fibrillation. PCSK9 is an independent predictor of aortic valve calcification and accelerates calcific aortic valve disease by regulating lipoprotein(a) catabolism. Accordingly, the use of PCSK9 inhibitors significantly reduced infarct sizes and arrhythmia and improves cardiac contractile function in a rat model of AMI. Circulating PCSK9 levels are positively correlated with age, diabetes mellitus, obesity, and hypertension. Here, we reviewed recent clinical and experimental studies exploring the association between PCSK9, cardiac diseases, and their related risk factors and aiming to identify possible underlying mechanisms.

Resistin: Potential biomarker and therapeutic target in atherosclerosis

Resistin, a cysteine-rich secretory protein, has a pleiotropic role in humans. Resistin usually presents as trimer or hexamer in plasma, and targets specific receptors Toll Like Receptor 4 (TLR4) or Adenylyl Cyclase-Associated Protein 1 (CAP1). Upon binding to TLR4 and CAP1, resistin can trigger various intracellular signal transduction pathways to induce vascular inflammation, lipid accumulation, and plaque vulnerability. These pro-atherosclerotic effects of resistin appear in various cell types, including endothelial cells, vessel smooth muscle cells and macrophages, which cause diverse damages to cardiovascular system from dyslipidemia, atherosclerosis rupture and ventricular remodeling. In this review, we gather recent evidence about the pro- atherosclerotic effects of resistin and highlight it as a candidate therapeutic or diagnostic target for cardiovascular disease.

PCSK9 regulates pyroptosis via mtDNA damage in chronic myocardial ischemia

Proprotein convertase subtilisin/Kexin type 9 (PCSK9) and pyroptosis both play important roles in myocardial infarction. This study was designed to test the hypothesis that PCSK9 regulates pyroptosis in cardiomyocytes during chronic myocardial ischemia. Primary cardiomyocytes were isolated from WT and PCSK9^-/- mice. HL-1 cardiomyocytes were used to set up PCSK9-deficient (PCSK9^-/-) and PCSK9-upregulated (PCSK9^CRISPRa) cardiomyocyte cell line with CRISPR/Cas9 knockout or activation plasmid. Additional studies were performed with chronic myocardial ischemia in WT and PCSK9^-/- mice. We observed that PCSK9 initiates mitochondrial DNA (mtDNA) damage, activates NLRP3 inflammasome signaling (NLRP3, ASC, Caspase-1, IL-1β, and IL-18), and subsequently induces Caspase-1-dependent pyroptosis. There was an intense expression of PCSK9 and pyroptosis marker, GSDMD-NT, in the zone bordering the infarct area. PCSK9^-/- significantly suppressed expression of NLRP3 inflammasome signaling, GSDMD-NT, and LDH release. Furthermore, serum levels of PCSK9, NLPR3 inflammasome signaling, and pyroptosis (GSDMD and LDH release) were significantly elevated in patients with chronic myocardial ischemia as compared to those in age-matched healthy subjects. Human hearts with recent infarcts also showed high expression of PCSK9 and GSDMD-NT in the border zone similar to that in the infarcted mouse heart. These observations provide compelling evidence for the role of PCSK9 in regulating Caspase-1-dependent pyroptosis via mtDNA damage and may qualify pro-inflammatory cytokines and pyroptosis as potential targets to treat PCSK9-related cardiovascular diseases.

PCSK9 and inflammation: role of shear stress, pro-inflammatory cytokines, and LOX-1

PCSK9 degrades low-density lipoprotein cholesterol (LDL) receptors and subsequently increases serum LDL cholesterol. Clinical trials show that inhibition of PCSK9 efficiently lowers LDL cholesterol levels and reduces cardiovascular events. PCSK9 inhibitors also reduce the extent of atherosclerosis. Recent studies show that PCSK9 is secreted by vascular endothelial cells, smooth muscle cells, and macrophages. PCSK9 induces secretion of pro-inflammatory cytokines in macrophages, liver cells, and in a variety of tissues. PCSK9 regulates toll-like receptor 4 expression and NF-κB activation as well as development of apoptosis and autophagy. PCSK9 also interacts with oxidized-LDL receptor-1 (LOX-1) in a mutually facilitative fashion. These observations suggest that PCSK9 is inter-twined with inflammation with implications in atherosclerosis and its major consequence-myocardial ischaemia. This relationship provides a basis for the use of PCSK9 inhibitors in prevention of atherosclerosis and related clinical events.

An Update on the Role of PCSK9 in Atherosclerosis

Atherosclerosis is initiated by functional changes in the endothelium accompanied by accumulation, oxidation, and glycation of LDL-cholesterol in the inner layer of the arterial wall and continues with the expression of adhesion molecules and release of chemoattractants. PCSK9 is a proprotein convertase that increases circulating LDL levels by directing hepatic LDL receptors into lysosomes for degradation. The effects of PCSK9 on hepatic LDL receptors and contribution to atherosclerosis via the induction of hyperlipidemia are well defined. Monoclonal PCSK9 antibodies that block the effects of PCSK9 on LDL receptors demonstrated beneficial results in cardiovascular outcome trials. In recent years, extrahepatic functions of PCSK9, particularly its direct effects on atherosclerotic plaques have received increasing attention. Experimental trials have revealed that PCSK9 plays a significant role in every step of atherosclerotic plaque formation. It contributes to foam cell formation by increasing the uptake of LDL by macrophages via scavenger receptors and inhibiting cholesterol efflux from macrophages. It induces the expression of inflammatory cytokines, adhesion molecules, and chemoattractants, thereby increasing monocyte recruitment, inflammatory cell adhesion, and inflammation at the atherosclerotic vascular wall. Moreover, low shear stress is associated with increased PCSK9 expression. PCSK9 may induce endothelial cell apoptosis and autophagy and stimulate the differentiation of smooth muscle cells from the contractile phenotype to synthetic phenotype. Increasing evidence indicates that PCSK9 is a molecular target in the development of novel approaches toward the prevention and treatment of atherosclerosis. This review focuses on the molecular roles of PCSK9 in atherosclerotic plaque formation.

Leptin, Resistin, and Proprotein Convertase Subtilisin/Kexin Type 9: The Role of STAT3

In a condition of dysfunctional visceral fat depots, as in the case of obesity, alterations in adipokine levels may be detrimental for the cardiovascular system. The proinflammatory leptin and resistin adipokines have been described as possible links between obesity and atherosclerosis. The present study was aimed at evaluating whether proprotein convertase subtilisin/kexin type 9 (PCSK9), a key regulator of low-density lipoprotein metabolism, is induced by leptin and resistin through the involvement of the inflammatory pathway of STAT3. In HepG2 cells, leptin and resistin up-regulated PCSK9 gene and protein expression, as well as the phosphorylation of STAT3. Upon STAT3 silencing, leptin and resistin lost their ability to activate PCSK9. The knockdown of STAT3 did not affect the expression of leptin and resistin receptors or that of PCSK9. The analysis of the human PCSK9 promoter region showed that the two adipokines raised PCSK9 promoter activity via the involvement of a sterol regulatory element motif. In healthy males, a positive association between circulating leptin and PCSK9 levels was found only when the body mass index was <25 kg/m². In conclusion, this study identified STAT3 as one of the molecular regulators of leptin- and resistin-mediated transcriptional induction of PCSK9.

Are anti-inflammatory agents and nutraceuticals - novel inhibitors of PCSK9?

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protease which increases the lysosomal degradation of low density lipoprotein receptor (LDLR) resulting in elevated serum LDL-cholesterol levels. Elevated LDL-cholesterol is the main risk factor for cardiovascular disease (CVD). Antibodies to PCSK9 decrease LDL-cholesterol. Recent studies have suggested a direct relationship between PCSK9 and inflammation and the potential inhibitory effects of anti-inflammatory agents against this enzyme. Nutraceuticals are natural compounds, which have numerous anti-inflammatory and lipid-lowering effects. In this review we focus on anti-inflammatory substances and nutraceuticals, which are beneficial in treatment of dyslipidemia. We also reviewed the recent findings concerning the role of PCSK9 as the main target for molecular mechanisms of these substances.

Metabolic cross-talk between skeletal muscle and adipose tissue in high-intensity interval training vs. moderate-intensity continuous training by regulation of PGC-1α

PURPOSE

An imbalance in the production of adipokines and myokines impairs the energy expenditure, increases adipocyte and develops metabolic pathologies. Physical exercise is able to regulate the secretion of myokines and adipokines. The present study considers the metabolic cross talk between skeletal muscle and adipose tissue in high-intensity interval training vs. moderate-intensity continuous training by regulation of PGC-1α.

METHODS

A sample of 32 male Wistar rats (8 weeks old with mean weight 250 ± 55 g) were divided into four groups randomly: control of base (CO), control of 8 weeks (CO8w), moderate-intensity continuous training (MICT), and high-intensity interval training (HIIT). The rats were fed with standard chow diet. The CO group was killed at the start of the study and the CO8w group was kept alive for the same time as the experimental groups, but did not participate in any exercise. MICT and HIIT groups for 8 weeks were placed under the moderate-intensity continuous training (15-60 min, with speed of 15-30 m/min) and high-intensity interval training (8-4 intense period for 1 min, with speed of 28-55 m/min, with 3-7 slow-intensity period for 1 min, with a speed of 12-30 m/min) for 8 weeks, respectively. To measure the levels of serum irisin, nesfatin, and resistin the ELISA method was used and real-time PCR method was used to evaluate the relative expression of soleus PGC-1α gene mRNA.

RESULTS

The levels of irisin and nesfatin significantly increased in the HIIT compared with control groups (p = 0.001). Resistin values in both training groups showed a significant decrease compared to the control groups (p = 0.005). The level of PGC-1α gene expression in both HIIT and MICT groups was significantly increased in comparison with the control groups (p = 0.001).

DISCUSSION

The results showed that HIIT and MICT increase the transcription of the PGC-1α gene and possibly the increased expression of this gene after HIIT and MICT plays a central role in the secretion of skeletal muscle myokines and adipokines of adipose tissue.

LEVEL OF EVIDENCE

No Level of evidence: Animal study.

Role of Complement and Complement-Related Adipokines in Regulation of Energy Metabolism and Fat Storage

Adipose tissue releases many cytokines and inflammatory factors described as adipokines. In obesity, adipokines released from expanding adipose tissue are implicated in disease progression and metabolic dysfunction. However, mechanisms controlling the progression of adiposity and metabolic complications are not fully understood. It has been suggested that expanding fat mass and sustained release of inflammatory adipokines in adipose tissue lead to hypoxia, oxidative stress, apoptosis, and cellular damage. These changes trigger an immune response involving infiltration of adipose tissue with immune cells, complement activation and generation of factors involved in opsonization and clearance of damaged cells. Abundant evidence now indicates that adipose tissue is an active secretory source of complement and complement-related adipokines that, in addition to their inflammatory role, contribute to the regulation of metabolic function. This article highlights advances in knowledge regarding the role of these adipokines in energy regulation of adipose tissue through modulating lipogenic and lipolytic pathways. Several adipokines will be discussed including adipsin, Factor H, properdin, C3a, Acylation-Stimulating Protein, C1q/TNF-related proteins, and response gene to complement-32 (RGC-32). Interactions between these factors will be described considering their immune-metabolic roles in the adipose tissue microenvironment and their potential contribution to progression of adiposity and metabolic dysfunction. The differential expression and the role of complement factors in gender-related fat partitioning will also be addressed. Identifying lipogenic adipokines and their specific autocrine/paracrine roles may provide means for adipose-tissue-targeted therapeutic interventions that may disrupt the vicious circle of adiposity and disease progression. © 2019 American Physiological Society. Compr Physiol 9:1411-1429, 2019.

Associations of Circulating Protein Levels With Lipid Fractions in the General Population

Objective- Revealing patterns of associations between circulating protein and lipid levels could improve biological understanding of cardiovascular disease (CVD). In this study, we investigated the associations between proteins related to CVD and triglyceride (TG), total cholesterol, LDL (low-density lipoprotein), and HDL (high-density lipoprotein) cholesterol levels in individuals from the general population. Approach and Results- We measured plasma protein levels using the Olink ProSeek CVD I or II+III arrays and analyzed 57 proteins available in 3 population-based cohorts: EpiHealth (n=2029; 52% women; median age, 61 years), PIVUS (Prospective Study of the Vasculature in Uppsala Seniors; n=790; 51% women; all aged 70 years), and ULSAM (Uppsala Longitudinal Study of Adult Men; n=551; all men aged 77 years). A discovery analysis was performed in EpiHealth in a regression framework (adjusted for sex, age, body mass index, smoking, glucose levels, systolic blood pressure, blood pressure medication, diabetes mellitus medication, and CVD history), and associations with false discovery rate <0.05 were further tested in PIVUS and ULSAM, where a P value of 0.05 was considered a successful replication (validation false discovery rate of 0.1%). We used summary statistics from a genome-wide association study on each protein biomarker (meta-analysis of EpiHealth, PIVUS, ULSAM, and IMPROVE [Carotid Intima-Media Thickness and IMT-Progression as Predictors of Vascular Events in a High-Risk European Population]) and publicly available data from Global Lipids Genetics Consortium to perform Mendelian randomization analyses to address possible causality of protein levels. Of 57 tested proteins, 42 demonstrated an association with at least 1 lipid fraction; 35 were associated with TG, 15 with total cholesterol, 9 with LDL cholesterol, and 24 with HDL cholesterol. Among these associations, we found KIM-1 (kidney injury molecule-1), TNFR (TNF [tumor necrosis factor] receptor) 1 and 2, TRAIL-R2 (TRAIL [TNF-related apoptosis-inducing ligand] receptor 2), and RETN (resistin) to be associated with all 4 lipid fractions. Further, 15 proteins were related to both TG and HDL cholesterol in a consistent and biologically expected manner, that is, higher TG and lower HDL cholesterol or vice versa. Another common pattern of associations was concomitantly higher TG, total cholesterol, and LDL cholesterol, which is associated with higher CVD risk. We did not find evidence of causal links for protein levels. Conclusions- Our comprehensive analysis of plasma proteins and lipid fractions of 3370 individuals from the general population provides new information about lipid metabolism.

Angiotensin-(1-7), Adipokines and Inflammation

Nowadays the adipose tissue is recognized as one of the most critical endocrine organs releasing many adipokines that regulate metabolism, inflammation and body homeostasis. There are several described adipokines, including the renin-angiotensin system (RAS) components that are especially activated in some diseases with increased production of angiotensin II and several pro-inflammatory hormones. On the other hand, RAS also expresses angiotensin-(1-7), which is now recognized as the main peptide on counteracting Ang II effects. New studies have shown that increased activation of ACE2/Ang-(1-7)/MasR arm can revert and prevent local and systemic dysfunctions improving lipid profile and insulin resistance by modulating insulin actions, and reducing inflammation. In this context, the present review shows the interaction and relevance of Ang-(1-7) effects on regulating adipokines, and as one adipokine itself, modulating body homeostasis, with emphasis on its anti-inflammatory properties, especially in the context of metabolic disorders with focus on obesity and type 2 diabetes mellitus pandemic.

Obesity and dyslipidemia

Obesity, a pandemic of the modern world, is intimately associated with dyslipidemia, which is mainly driven by the effects of insulin resistance and pro-inflammatory adipokines. However, recent evidence suggests that obesity-induced dyslipidemia is not a unique pathophysiological entity, but rather has distinct characteristics depending on many individual factors. In line with that, in a subgroup of metabolically healthy obese (MHO) individuals, dyslipidemia is less prominent or even absent. In this review, we will address the main characteristics of dyslipidemia and mechanisms that induce its development in obesity. The fields, which should be further investigated to expand our knowledge on obesity-related dyslipidemia and potentially yield new strategies for prevention and management of cardiometabolic risk, will be highlighted. Also, we will discuss recent findings on novel lipid biomarkers in obesity, in particular proprotein convertase subtilisin/kexin type 9 (PCSK9), as the key molecule that regulates metabolism of low-density lipoproteins (LDL), and sphingosine-1-phosphate (S1P), as one of the most important mediators of high-density lipoprotein (HDL) particles function. Special attention will be given to microRNAs and their potential use as biomarkers of obesity-associated dyslipidemia.

Metabolic Syndrome and Skin Diseases

The increasing prevalence of Metabolic syndrome (MetS) is a worldwide health problem, and the association between MetS and skin diseases has recently attracted growing attention. In this review, we summarize the associations between MetS and skin diseases, such as psoriasis, acne vulgaris, hidradenitis suppurativa, androgenetic alopecia, acanthosis nigricans, and atopic dermatitis. To discuss the potential common mechanisms underlying MetS and skin diseases, we focus on insulin signaling and insulin resistance, as well as chronic inflammation including adipokines and proinflammatory cytokines related to molecular mechanisms. A better understanding of the relationship between MetS and skin diseases contributes to early diagnosis and prevention, as well as providing clues for developing novel therapeutic strategies.

Association between serum resistin, adiposity measures and inflammatory makers in women without cardiovascular diseases

AIMS

The convergence of obesity and inflammation in the pathogenesis of cardiovascular diseases (CVD) has been recognized over the past decade. Resistin has emerged as a novel secreted protein with links to both insulin resistance and inflammation. We aimed to investigate the relationship between changes in serum resistin levels with metabolic parameters, including obesity and inflammatory markers in women free of CVD.

METHODS AND RESULTS

A total of 200 apparently healthy women were consecutively recruited from the Out-patients Clinics at King Abdulaziz university Hospital in Jeddah, Saudi Arabia. They were classified into 4 groups based on quartile for serum resistin. Anthropometric variables were measured in all study subjects. Fasting blood samples were collected for measurement of lipid profile, blood glucose and inflammatory markers. Study subjects within the upper quartile (Q4) had significantly higher body height (p < 0.0001), waist and hip circumferences (p < 0.05) and inflammatory markers (p < 0.0001) values than those in the lower quartile (Q1). Significant correlations were found between circulating resistin levels and systolic blood pressure, some anthropometric measures as well as inflammatory markers.

CONCLUSION

Serum resistin levels were found to be increased in overweight and obese women. Resistin was also independently associated with hs-CRP in women free of CVD, suggesting that resistin may be related to low-grade inflammation among obese subjects in the absence of overt CVD.

Potentiation of Psoriasis-Like Inflammation by PCSK9

Psoriasis is a systemic inflammatory disease, associated with metabolic disorders, including high level of low-density lipoprotein. PCSK9, which promotes the degradation of low-density lipoprotein receptors and, therefore, the increased concentration of circulating low-density lipoprotein, is also involved in inflammation. This study aims to examine the role of PCSK9 in psoriasis and to investigate the potential of topically applying small interfering RNA targeting Pcsk9 as a psoriasis treatment. We investigated the expression of PCSK9 in lesions of psoriasis patients and imiquimod-induced psoriatic reactions in Pcsk9-knockout and Pcsk9 small interfering RNA-treated mice, and we also used cultured human keratinocytes to investigate the role of PCSK9 in regulating cell proliferation and apoptosis. We found that PCSK9 is overexpressed in psoriatic lesions and that suppressing Pcsk9 can decrease the inflammatory reaction induced by imiquimod treatment and inhibit hyperproliferation of keratinocytes. We also found that suppressing PCSK9 can significantly alter the cell cycle and induce apoptosis of human keratinocytes. Taken together, our findings indicate that PCSK9 plays an important role in psoriasis and may be a therapeutic target.

PCSK9: A novel inflammation modulator in atherosclerosis?

Proprotein convertase subtilisin/kexin 9 (PCSK9) is the ninth member of the secretory serine protease family. It binds to low-density lipoprotein receptor (LDLR) for endocytosis and lysosome degradation in the liver, resulting in an increasing in circulating LDL-cholesterol (LDL-c) level. Since a PCSK9 induced increase in plasma LDL-c contributes to atherosclerosis, PCSK9 inhibition has become a new strategy in preventing and treating atherosclerosis. However, in addition to the effect of PCSK9 on elevating blood LDL-c levels, accumulating evidence shows that PCSK9 plays an important role in inflammation, likely representing another major mechanism for PCSK9 to promote atherosclerosis. In this review, we discuss the association of PCSK9 and inflammation, and highlight the specific effects of PCSK9 on different vascular cellular components involved in the atherosclerotic inflammation. We also discuss the clinical evidence for the association between PCSK9 and inflammation in atherosclerotic cardiovascular disease. A better understanding of the direct association of PCSK9 with atherosclerotic inflammation might help establish a new role for PCSK9 in vascular biology and identify a novel molecular mechanism for PCSK9 therapy.

Hyperhomocysteinemia and hyperandrogenemia share PCSK9-LDLR pathway to disrupt lipid homeostasis in PCOS

Women with polycystic ovary syndrome (PCOS) are at increased risk of cardiovascular diseases (CVD); however, the independent role of PCOS in the incident CVD remains unknown. There are reports that hyperhomocysteinemia (HHcy), a potential cause of CVD, is frequently associated with PCOS. The present study investigates the independent attributes of hyperandrogenemia (HA), the integral associate of PCOS, and HHcy in causing atherogenic dyslipidemia. Twenty-five-day old rats were treated with homocysteine (Hcy) at 50 mg/kg/day dose level for 12 weeks. The HepG2 cell lines transfected with siRNA directed to PCSK9 were challenged with Hcy, homocysteine thiolactone (HTL), testosterone, 5α-dihydroxytestosterone (5α-DHT), or estradiol for 24 h. Rats administered with Hcy developed HHcy and displayed PCOS-like phenotypes with adversely altered lipid homeostasis and attenuated PI3K-AKT and Wnt signalling cascade. Overexpression of steroidogenic acute regulatory protein (StAR) and down-regulated expression of Aromatase together with elevated testosterone level marked the state of HA. In culture, the HepG2 cells responded independently to Hcy, HTL, testosterone, and 5α-DHT by an overt expression of PCSK9 and down-regulated expression of LDLR. The effect was magnified under the combined influence of Hcy and androgen(s). Estradiol, by contrast, exhibited the reverse effect. The findings suggest that HA may independently attribute to an increased cardiovascular risk in PCOS; however, the coexistence of HHcy catalyzes the risk further.

Role of PCSK9 in lipid metabolism and atherosclerosis

Elevated plasma low-density lipoprotein cholesterol (LDL-C) is an important risk factor for cardiovascular diseases. Statins are the most widely used therapy for patients with hyperlipidemia. However, a significant residual cardiovascular risk remains in some patients even after maximally tolerated statin therapy. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a new pharmacologically therapeutic target for decreasing LDL-C. PCSK9 reduces LDL intake from circulation by enhancing LDLR degradation and preventing LDLR recirculation to the cell surface. Moreover, PCSK9 inhibitors have been approved for patients with either familial hypercholesterolemia or atherosclerotic cardiovascular disease, who require additional reduction of LDL-C. In addition, PCSK9 inhibition combined with statins has been used as a new approach to help reduce LDL-C levels in patients with either statin intolerance or unattainable LDL goal. This review will discuss the emerging anti-PCSK9 therapies in the regulation of cholesterol metabolism and atherosclerosis.

Proprotein Convertase Subtilisin-Kexin type-9 (PCSK9) and triglyceride-rich lipoprotein metabolism: Facts and gaps

After more than a decade of intense investigation, Pro-protein Convertase Subtilisin-Kexin type 9 (PCSK9) remains a hot topic of research both at experimental and clinical level. Interestingly PCSK9 is expressed in different tissues suggesting the existence of additional function(s) beyond the modulation of the Low-Density Lipoprotein (LDL) receptor in the liver. Emerging data suggest that PCSK9 might play a role in the modulation of triglyceride-rich lipoprotein (TGRL) metabolism, mainly Very Low-Density Lipoproteins (VLDL) and their remnants. In vitro, PCSK9 affects TGRLs production by intestinal cells as well as the catabolism of LDL receptor homologous and non-homologous targets such as VLDL receptor, CD36 and ApoE2R. However, the in vivo relevance of these findings is still debated. This review aims at critically discussing the role of PCSK9 on TGRLs metabolism with a major focus on the impact of its genetic and pharmacological modulation on circulating lipids and lipoproteins beyond LDL.

Effects of Sex Hormone Treatment on the Metabolic Syndrome in Transgender Individuals: Focus on Metabolic Cytokines

CONTEXT

Hormonal treatment in transgender persons affects many components of the metabolic syndrome (MS).

OBJECTIVE

To determine the role of direct hormonal effects, changes in metabolic cytokines, and body composition on metabolic outcomes.

DESIGN, SETTING, AND PARTICIPANTS

24 transwomen and 45 transmen from the European Network for the Investigation of Gender Incongruence were investigated at baseline and after 12 months of hormonal therapy.

OUTCOME MEASURES

Best predictors for changes in components of MS, applying least absolute shrinkage and selection operator regression.

RESULTS

In transwomen, a decrease in triglyceride levels was best explained by a decrease in fat mass and an increase in fibroblast growth factor 21 (FGF-21); the decrease in total and low-density lipoprotein cholesterol levels was principally due to a decrease in resistin. A decrease in high-density lipoprotein cholesterol depended on an inverse association with fat mass. In contrast, in transmen, an increase in low-density lipoprotein cholesterol was predicted by a decrease in FGF-21 and an increase in the waist/hip ratio; a decrease in the high-density lipoprotein/total cholesterol ratio depended on a decline in adiponectin levels. In transwomen, worsened insulin resistance and increased early insulin response seemed to be due to a direct treatment effect; however, improvements in hepatic insulin sensitivity in transmen were best predicted by a positive association with chemerin, resistin, and FGF-21 and were inversely related to changes in the waist/hip ratio and leptin and adipocyte fatty acid-binding protein levels.

CONCLUSIONS

The effects of hormonal therapy on different components of the MS are sex-specific and involve a complex interplay of direct hormonal effects, changes in body composition, and metabolic cytokine secretion.

The Combined Effects of Exercise, Diet, and a Multi-Ingredient Dietary Supplement on Body Composition and Adipokine Changes in Overweight Adults

BACKGROUND

Very few weight and fat loss supplements undergo finished-product research to examine efficacy. The purpose of this study was to determine the effects of an 8-week diet and exercise program on body composition, hip and waist girth, and adipokines and evaluate whether a dietary supplement containing raspberry ketone, capsaicin, caffeine, garlic, and Citrus aurantium enhanced outcomes.

METHODS

Overweight men and women completed this randomized, placebo-controlled, double-blind study. Participants consumed 4 capsules/d of supplement (EXP; n = 18) or placebo (PLA; n = 18). Participants underwent 8 weeks of daily supplementation, calorie restriction (500 kcal < RMR [resting metabolic rate] × 1.2), and supervised progressive exercise training 3 times a week. Body composition, girth, and adipokines were assessed at baseline and postintervention (T1 and T2).

RESULTS

Significant decreases in weight (-2.6 ± 0.57 kg, p < 0.001), fat mass (-1.8 ± 0.20 kg; p < 0.001), and percentage body fat (-3.7% ± 0.29%, p < 0.001) and a significant increase in lean body mass (LBM; 1.5 ± 0.26 kg; p < 0.001) were seen from T1 to T2 in both groups. For men, only those in the EXP group increased LBM from T1 to T2 (1.3 ± 0.38 kg; p < 0.05). Hip girth was also reduced, with the women in the EXP group (-10.7 ± 2.15 cm, p < 0.001) having a greater reduction. There was a time by group interaction, with significant decreases in leptin (p < 0.001) and significant increases in adiponectin (p < 0.05) in the EXP group.

CONCLUSIONS

Significant improvements in adipokines and leptin support the utility of exercise, diet, and fat loss for impacting inflammatory biomarkers. The improvement in adiponectin with EXP may suggest a unique health mechanism.

Acute and Chronic Impact of Bariatric Surgery on Plasma LDL Cholesterol and PCSK9 Levels in Patients With Severe Obesity

CONTEXT

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key regulator of low-density lipoprotein cholesterol (LDL-C) concentrations. In patients with severe obesity, biliopancreatic diversion with duodenal switch (BPD-DS) surgery induces substantial weight loss and influences lipoprotein metabolism. The effect of BPD-DS on PCSK9 levels is unknown.

OBJECTIVES

To determine the acute and chronic impact of BPD-DS on PCSK9 levels and whether the acute impact of BPD-DS could be explained by BPD-DS-associated caloric restriction (CR).

DESIGN, SETTINGS, AND PARTICIPANTS

PCSK9 levels were measured in 20 men and 49 women (age, 41.5 ± 11.1 years) with severe obesity before, 24 hours, 5 days, and 6 and 12 months after BPD-DS and in a comparable control group (n = 31) at baseline and at 6 and 12 months. PCSK9 levels were also measured during 3-day CR in patients (n = 7) with severe obesity and type 2 diabetes.

RESULTS

PCSK9 levels increased 13.4% after 24 hours (248.7 ± 64.8 to 269.7 ± 63.8 ng/mL; P = 0,02) and decreased 9.5% at 12 months compared with baseline (217.6 ± 43.0 ng/mL; P < 0,0001). LDL-C levels decreased 36.2% after 24 hours (2.6 ± 0.7 to 1.7 ± 0.6 mmol/L; P < 0.0001) and 30% at 12 months compared with baseline (1.7 ± 0.5 mmol/L; P < 0.0001). Compared with baseline levels, PCSK9 levels were lower at day 2 but not at day 1 or 3 after CR.

CONCLUSION

BPD-DS is associated with acute increases in PCSK9 levels that do not appear to be explained by CR but may be due to an acute response following surgery. BPD-DS induces chronic reductions in both PCSK9 and LDL-C levels.

PCSK9 Mutations in Familial Hypercholesterolemia: from a Groundbreaking Discovery to Anti-PCSK9 Therapies

PURPOSE OF REVIEW

In 2003, Abifadel et al. (Nat. Genet. 34:154-156, 2003) identified PCSK9, encoding proprotein convertase subtilisin/kexin type 9, as the third causal gene for autosomal dominant hypercholesterolemia. This review focuses on the main steps from this major breakthrough in familial hypercholesterolemia (FH) to the latest clinical trials with the anti-PCSK9 antibodies.

RECENT FINDINGS

The year 2015 was remarkable in cardiovascular disease through the field of cholesterol. Nearly 30 years after the discovery of statins, a new class of effective lipid-lowering drugs has emerged: the anti-PCSK9 antibodies. The discovery of the first gain-of-function mutations of PCSK9 in FH rapidly became the center of interest of researchers worldwide. Preclinical and clinical studies launched by pharmaceutical companies led to the first three anti-PCSK9 antibodies, two of which (evolocumab and alirocumab) reduce LDL cholesterol levels by 50-60% and received FDA and European Medicines Agency approvals in 2015 on top of statin therapy. Recently, results of the Further Cardiovascular Outcomes Research With PCSK9 Inhibition in Subjects With Elevated Risk (FOURIER) trial, the outcome trial of evolocumab over 2.2 years, showed a reduction of 15-20% in the risk of major cardiovascular outcomes in high-risk patients receiving statin therapy. Results of ODYSSEY OUTCOMES trial, evaluating the effect of alirocumab in 18,000 patients with established CVD are also eagerly awaited in 2018. The evolution of research on PCSK9, starting from the discovery of the first set of mutations in PCSK9 in FH in 2003, is an amazing example of successful translational research. It shows how rigorous and powered genetic analyses can lead to the discovery of a new class of lipid-lowering drugs that give hope in fighting high cholesterol levels and their cardiovascular complications.

Dietary coconut water vinegar for improvement of obesity-associated inflammation in high-fat-diet-treated mice

Obesity has become a serious health problem worldwide. Various types of healthy food, including vinegar, have been proposed to manage obesity. However, different types of vinegar may have different bioactivities. This study was performed to evaluate the anti-obesity and anti-inflammatory effects of coconut water vinegar on high-fat-diet (HFD)-induced obese mice. Changes in the gut microbiota of the mice were also evaluated. To induce obesity, C57/BL mice were continuously fed an HFD for 33 weeks. Coconut water vinegar (0.08 and 2 ml/kg body weight) was fed to the obese mice from early in week 24 to the end of week 33. Changes in the body weight, fat-pad weight, serum lipid profile, expression of adipogenesis-related genes and adipokines in the fat pad, expression of inflammatory-related genes, and nitric oxide levels in the livers of the untreated and coconut water vinegar-treated mice were evaluated. Faecal samples from the untreated and coconut water vinegar-treated mice (2 ml/kg body weight) were subjected to 16S metagenomic analysis to compare their gut microbiota. The oral intake of coconut water vinegar significantly (p < 0.05) reduced the body weight, fat-pad weight, and serum lipid profile of the HFD-induced obese mice in a dose-dependent manner. We also observed up-regulation of adiponectin and down-regulation of sterol regulatory element-binding protein-1, retinol-binding protein-4, and resistin expression. The coconut water vinegar also reduced HFD-induced inflammation by down-regulating nuclear factor-κB and inducible nitric oxide synthase expression, which consequently reduced the nitric oxide level in the liver. Alterations in the gut microbiota due to an increase in the populations of the Bacteroides and Akkermansia genera by the coconut water vinegar may have helped to overcome the obesity and inflammation caused by the HFD. These results provide valuable insights into coconut water vinegar as a potential food ingredient with anti-obesity and anti-inflammatory effects.

Adipokines in Liver Cirrhosis

Liver fibrosis can progress to cirrhosis, which is considered a serious disease. The Child-Pugh score and the model of end-stage liver disease score have been established to assess residual liver function in patients with liver cirrhosis. The development of portal hypertension contributes to ascites, variceal bleeding and further complications in these patients. A transjugular intrahepatic portosystemic shunt (TIPS) is used to lower portal pressure, which represents a major improvement in the treatment of patients. Adipokines are proteins released from adipose tissue and modulate hepatic fibrogenesis. These proteins affect various biological processes that are involved in liver function, including angiogenesis, vasodilation, inflammation and deposition of extracellular matrix proteins. The best studied adipokines are adiponectin and leptin. Adiponectin protects against hepatic inflammation and fibrogenesis, and leptin functions as a profibrogenic factor. These and other adipokines are supposed to modulate disease severity in patients with liver cirrhosis. Consequently, circulating levels of these proteins have been analyzed to identify associations with parameters of hepatic function, portal hypertension and its associated complications in patients with liver cirrhosis. This review article briefly addresses the role of adipokines in hepatitis and liver fibrosis. Here, studies having analyzed these proteins in systemic blood in cirrhotic patients are listed to identify adipokines that are comparably changed in the different cohorts of patients with liver cirrhosis. Some studies measured these proteins in systemic, hepatic and portal vein blood or after TIPS to specify the tissues contributing to circulating levels of these proteins and the effect of portal hypertension, respectively.

Translating the biology of adipokines in atherosclerosis and cardiovascular diseases: Gaps and open questions

AIM

Critically discuss the available data, to identify the current gaps and to provide key concepts that will help clinicians in translating the biology of adipokines in the context of atherosclerosis and cardio-metabolic diseases.

DATA SYNTHESIS

Adipose tissue is nowadays recognized as an active endocrine organ, a function related to the ability to secrete adipokines (such as leptin and adiponectin) and pro-inflammatory cytokines (tumor necrosis factor alpha and resistin). Studies in vitro and in animal models have observed that obesity status presents a chronic low-grade inflammation as the consequence of the immune cells infiltrating the adipose tissue as well as adipocytes. This inflammatory signature is often related to the presence of cardiovascular diseases, including atherosclerosis and thrombosis. These links are less clear in humans, where the role of adipokines as prognostic marker and/or player in cardiovascular diseases is not as clear as that observed in experimental models. Moreover, plasma adipokine levels might reflect a condition of adipokine-resistance in which adipokine redundancy occurs. The investigation of the cardio-metabolic phenotype of carriers of single nucleotide polymorphisms affecting the levels or function of a specific adipokine might help determine their relevance in humans. Thus, the aim of the present review is to critically discuss the available data, identify the current gaps and provide key concepts that will help clinicians translate the biology of adipokines in the context of atherosclerosis and cardio-metabolic diseases.

Physiological and therapeutic regulation of PCSK9 activity in cardiovascular disease

Ischemic heart disease is the main cause of death worldwide and is accelerated by increased levels of low-density lipoprotein cholesterol (LDL-C). Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a potent circulating regulator of LDL-C through its ability to induce degradation of the LDL receptor (LDLR) in the lysosome of hepatocytes. Only in the last few years, a number of breakthroughs in the understanding of PCSK9 biology have been reported illustrating how PCSK9 activity is tightly regulated at several levels by factors influencing its transcription, secretion, or by extracellular inactivation and clearance. Two humanized antibodies directed against the LDLR-binding site in PCSK9 received approval by the European and US authorities and additional PCSK9 directed therapeutics are climbing up the phases of clinical trials. The first outcome data of the PCSK9 inhibitor evolocumab reported a significant reduction in the composite endpoint (cardiovascular death, myocardial infarction, or stroke) and further outcome data are awaited. Meanwhile, it became evident that PCSK9 has (patho)physiological roles in several cardiovascular cells. In this review, we summarize and discuss the recent biological and clinical data on PCSK9, the regulation of PCSK9, its extra-hepatic activities focusing on cardiovascular cells, molecular concepts to target PCSK9, and finally briefly summarize the data of recent clinical studies.