Correlation Between Apolipoprotein M and Inflammatory Factors in Obese Patients

The adipocyte apolipoprotein M is negatively associated with inflammation

Obesity is associated with the development of local adipose tissue (AT) and systemic inflammation. Most adipokines are upregulated with obesity and have pro-inflammatory properties. Few are downregulated and possess beneficial anti-inflammatory effects. The apolipoprotein M (APOM) is an adipokine whose expression is low during obesity and associated with a metabolically healthy AT. Here, the role of adipose-derived APOM on obesity-associated AT inflammation was investigated by measuring the expression of pro-inflammatory genes in human and mouse models. In 300 individuals with obesity, AT APOM mRNA level was negatively associated with plasma hs-CRP. The inflammatory profile was assessed in Apom-/- and WT mice fed a normal chow diet (NCD), or a high-fat diet (HFD) to induce AT inflammation. After HFD, mice had a higher inflammatory profile in AT and liver, and a 50% lower Apom gene expression compared with NCD-fed mice. Apom deficiency was associated with a higher inflammatory signature in AT compared with WT mice but not in the liver. Adeno-associated viruses encoding human APOM were used to induce APOM overexpression: in vivo, in WT mice AT prior to HFD; in vitro, in human adipocytes which conditioned media was applied to ThP-1 macrophages. The murine AT overexpressing APOM gene had a reduced inflammatory profile. The macrophages treated with APOM-enriched media from adipocytes exhibited lower IL6 and MCP1 gene expression compared with macrophages treated with control media, independently of S1P. Our study highlights the protective role of adipocyte APOM against obesity-induced AT inflammation.

Effects of dietary interventions and intermittent fasting on HDL function in obese individuals with T2DM: a randomized controlled trial

BACKGROUND

Cardiovascular disease represents a significant risk factor for mortality in individuals with type 2 diabetes mellitus (T2DM). High-density lipoprotein (HDL) is believed to play a crucial role in maintaining cardiovascular health through its multifaceted atheroprotective effects and its capacity to enhance glycemic control. The impact of dietary interventions and intermittent fasting (IF) on HDL functionality remains uncertain. The objective of this study was to assess the effects of dietary interventions and IF as a strategy to safely improve glycemic control and reduce body weight on functional parameters of HDL in individuals with T2DM.

METHODS

Before the 12-week intervention, all participants (n = 41) of the INTERFAST-2 study were standardized to a uniform basal insulin regimen and randomized to an IF or non-IF group. Additionally, all participants were advised to adhere to dietary recommendations that promoted healthy eating patterns. The IF group (n = 19) followed an alternate-day fasting routine, reducing their calorie intake by 75% on fasting days. The participants' glucose levels were continuously monitored. Other parameters were measured following the intervention: Lipoprotein composition and subclass distribution were measured by nuclear magnetic resonance spectroscopy. HDL cholesterol efflux capacity, paraoxonase 1 (PON1) activity, lecithin cholesterol acyltransferase (LCAT) activity, and cholesterol ester transfer protein (CETP) activity were assessed using cell-based assays and commercially available kits. Apolipoprotein M (apoM) levels were determined by ELISA.

RESULTS

Following the 12-week intervention, the IF regimen significantly elevated serum apoM levels (p = 0.0144), whereas no increase was observed in the non-IF group (p = 0.9801). ApoM levels correlated with weight loss and fasting glucose levels in the IF group. Both groups exhibited a robust enhancement in HDL cholesterol efflux capacity (p < 0.0001, p = 0.0006) after 12 weeks. Notably, only the non-IF group exhibited significantly elevated activity of PON1 (p = 0.0455) and LCAT (p = 0.0117) following the 12-week intervention. In contrast, the changes observed in the IF group did not reach statistical significance.

CONCLUSIONS

A balanced diet combined with meticulous insulin management improves multiple metrics of HDL function. While additional IF increases apoM levels, it does not further enhance other aspects of HDL functionality.

TRIAL REGISTRATION

The study was registered at the German Clinical Trial Register (DRKS) on 3 September 2019 under the number DRKS00018070.

Identification of circulating apolipoprotein M as a new determinant of insulin sensitivity and relationship with adiponectin

BACKGROUND

The adiponectin is one of the rare adipokines down-regulated with obesity and protects against obesity-related disorders. Similarly, the apolipoprotein M (apoM) is expressed in adipocytes and its expression in adipose tissue is associated with metabolic health. We compared circulating apoM with adiponectin regarding their relationship with metabolic parameters and insulin sensitivity and examined their gene expression patterns in adipocytes and in the adipose tissue.

METHODS

Circulating apoM and adiponectin were examined in 169 men with overweight in a cross-sectional study, and 13 patients with obesity during a surgery-induced slimming program. Correlations with clinical parameters including the insulin resistance index (HOMA-IR) were analyzed. Multiple regression analyses were performed on HOMA-IR. The APOM and ADIPOQ gene expression were measured in the adipose tissue from 267 individuals with obesity and a human adipocyte cell line.

RESULTS

Participants with type 2 diabetes had lower circulating adiponectin and apoM, while apoM was higher in individuals with dyslipidemia. Similar to adiponectin, apoM showed negative associations with HOMA-IR and hs-CRP (r < -0.2), and positive correlations with HDL markers (HDL-C and apoA-I, r > 0.3). Unlike adiponectin, apoM was positively associated with LDL markers (LDL-C and apoB100, r < 0.20) and negatively correlated with insulin and age (r < -0.2). The apoM was the sole negative determinant of HOMA-IR in multiple regression models, while adiponectin not contributing significantly. After surgery, the change in HOMA-IR was negatively associated with the change in circulating apoM (r = -0.71), but not with the change in adiponectin. The APOM and ADIPOQ gene expression positively correlated in adipose tissue (r > 0.44) as well as in adipocytes (r > 0.81). In adipocytes, APOM was downregulated by inflammatory factors and upregulated by adiponectin.

CONCLUSIONS

The apoM rises as a new partner of adiponectin regarding insulin sensitivity. At the adipose tissue level, the adiponectin may be supported by apoM to promote a healthy adipose tissue.

TRIAL REGISTRATION

NCT01277068, registered 13 January 2011; NCT02332434, registered 5 January 2015; and NCT00390637, registered 20 October 2006.

Could Tumor Necrosis Factor Serve as a Marker for Cardiovascular Risk Factors and Left Ventricular Hypertrophy in Patients with Early-Onset Coronary Artery Disease?

Introduction: Tumor necrosis factor (TNF), a pro-inflammatory cytokine, can be produced by cardiomyocytes, leading to metabolic disorders in the myocardium. The objective of this study was to assess the relationship between plasma levels of the TNF cytokine and the presence of known biochemical and clinical risk factors for cardiovascular disease, along with the parameters of cardiac morphology in patients diagnosed with coronary artery disease (CAD) at a young age. Materials and Methods: The study group included 75 men aged up to 50 years and 25 women aged up to 55 years. The plasma TNF concentration was measured by use of the ELISA assay. Echocardiography and electrocardiographic examinations were performed in all patients. Results: We observed positive correlations for TNF with the BMI ratio, weight, waist and hip circumference. We also found negative correlations for TNF with HDL levels and ApoA concentrations, and positive correlations with the ApoB/ApoA1 ratio, Apo B, IL6, LDL and TG concentrations. These results suggest an association between higher plasma TNF concentrations and components of metabolic syndrome, including dyslipidemia. TNF may be a potential risk factor for impaired diastolic function. Conclusions: While TNF may be useful for diagnosing certain risks in CAD patients, the TNF measurement cannot be used as a surrogate test for echocardiography.

High density lipoprotein-associated proteins in non-obese women with and without polycystic ovary syndrome

Introduction

Dyslipidemia frequently occurs in women with polycystic ovary syndrome (PCOS), but it is unclear whether dyslipidemia is due to obesity and insulin resistance (IR) or is inherent to PCOS. To address this, proteomic analysis of proteins important in lipid metabolism, particularly for high-density lipoprotein cholesterol (HDL-C), was performed in non-obese, non-insulin resistant PCOS women compared to matched controls.

Methods

Weight and aged-matched non-obese subjects with PCOS (n=24) and without IR were compared with control women (n=24). 19 proteins were measured by Somalogic proteomic analysis: alpha-1-antichymotrypsin, alpha-1-antitrypsin, apolipoproteins A-1, B, D, E, E2, E3, E4, L1, M, clusterin, complement C3, hemopexin, heparin cofactor-II (HCFII), kininogen-1, serum amyloid A-1, amyloid beta A-4 and paraoxonase-1.

Results

Women with PCOS had a higher free androgen index (FAI) (p<0.001) and anti-Mullerian hormone (AMH) (p<0.001), but IR and C-reactive protein (CRP), a marker of inflammation, did not differ from controls (p>0.05). The triglyceride:HDL-cholesterol ratio was elevated (p=0.03) in PCOS. Alpha-1-antitrypsin levels were lower (p<0.05) and complement C3 levels were higher (p=0.001) in PCOS. C3 correlated with body mass index (BMI) (r=0.59, p=0.001), IR (r=0.63, p=0.0005) and CRP (r=0.42, p=0.04) in women with PCOS, though no correlations of these parameters with alpha-1-antitrypsin were found. Total cholesterol, triglycerides, HDL-cholesterol, LDL-cholesterol and levels of the other 17 lipoprotein metabolism-associated proteins did not differ between the two groups (p>0.05). However, in PCOS, alpha-1-antichymotrypsin correlated negatively with BMI (r=-0.40, p<0.04) and HOMA-IR (r=-0.42, p<0.03), apoM correlated positively with CRP (r=0.36, p<0.04) and HCFII correlated negatively with BMI (r=-0.34, p<0.04).

Conclusion

In PCOS subjects, when obesity, IR and inflammation confounders were absent, alpha-1-antitrypsin was lower and complement C3 was higher than in non-PCOS women, suggesting increased cardiovascular risk; however, subsequent obesity related IR/inflammation likely stimulates other HDL-associated protein abnormalities, thus increasing cardiovascular risk further.

An association between adropin hormone and total testosterone in obese men: a case-control study

BACKGROUND

Obesity is associated with low testosterone levels that could be caused by many mechanisms. Adropin, a peptide hormone, its levels are decreased in obesity and its receptors are expressed in the hypothalamus, the pituitary gland, and the testis. Adropin association to total testosterone in obese men is not detected yet. This study tries to find out possible associations between serum levels of adropin, adiponectin, total testosterone, and lipid profile in obese men.

METHODS

Serum levels of adropin, adiponectin, total testosterone, and lipid profile parameters were measured in 43 obese men and 40 age-matched normal-weight men.

RESULTS

Adropin, adiponectin, and testosterone levels were significantly lower in obese men versus normal-weight men. In all participants, positive correlations between adropin, adiponectin, and total testosterone were detected. Adropin is considered a predictor risk factor for testosterone.

CONCLUSIONS

This study suggests a possible causal relationship between adropin and total testosterone which needs further investigation.

TRIAL REGISTRATION

Clincialtrials.gov NCT03724825 , registered October 30th, 2018.

Proteome-wide associations with short- and long-term weight loss and regain after Roux-en-Y gastric bypass surgery

OBJECTIVE

Gastric bypass surgery results in long-term weight loss. Small studies have examined protein changes during rapid weight loss (up to 1 or 2 years post surgery). This study tested whether short-term changes were maintained after 12 years.

METHODS

A 12-year follow-up, protein-wide association study of 1,297 SomaLogic aptamer-based plasma proteins compared short- (2-year) and long-term (12-year) protein changes in 234 individuals who had gastric bypass surgery with 144 nonintervened individuals with severe obesity.

RESULTS

There were 51 replicated 12-year protein changes that differed between the surgery and nonsurgery groups. Adjusting for change in BMI, only 12 proteins remained significant, suggesting that BMI change was the primary reason for most protein changes and not non-BMI-related surgical effects. Protein changes were related to BMI changes during both weight-loss and weight-regain periods. The significant proteins were associated primarily with lipid, uric acid, or resting energy expenditure clinical variables and metabolic pathways. Eight protein changes were associated with 12-year diabetes remission, including apolipoprotein M, sex hormone binding globulin, and adiponectin (p < 3.5 × 10^-5 ).

CONCLUSIONS

This study showed that most short-term postsurgical changes in proteins were maintained at 12 years. Systemic protection pathways, including inflammation, complement, lipid, and adipocyte pathways, were related to the long-term benefits of gastric bypass surgery.

Revealing the Role of High-Density Lipoprotein in Colorectal Cancer

Colorectal cancer (CRC) is a highly prevalent malignancy with multifactorial etiology, which includes metabolic alterations as contributors to disease development. Studies have shown that lipid status disorders are involved in colorectal carcinogenesis. In line with this, previous studies have also suggested that the serum high-density lipoprotein cholesterol (HDL-C) level decreases in patients with CRC, but more recently, the focus of investigations has shifted toward the exploration of qualitative properties of HDL in this malignancy. Herein, a comprehensive overview of available evidences regarding the putative role of HDL in CRC will be presented. We will analyze existing findings regarding alterations of HDL-C levels but also HDL particle structure and distribution in CRC. In addition, changes in HDL functionality in this malignancy will be discussed. Moreover, we will focus on the genetic regulation of HDL metabolism, as well as the involvement of HDL in disturbances of cholesterol trafficking in CRC. Finally, possible therapeutic implications related to HDL will be presented. Given the available evidence, future studies are needed to resolve all raised issues concerning the suggested protective role of HDL in CRC, its presumed function as a biomarker, and eventual therapeutic approaches based on HDL.

YKL-40 as a novel biomarker in cardio-metabolic disorders and inflammatory diseases

Dyslipidaemia is associated with numerous health problems that include the combination of insulin resistance, hypertension and obesity, ie, metabolic syndrome. Although the use of statins to decrease serum low density lipoprotein cholesterol (LDL-C) has been an effective therapeutic in treating atherosclerosis, the persistence of high atherosclerotic risk, ie, residual risk, is notable and is not simply explained as a phenomenon of dyslipidaemia. As such, it is imperative that we identify new biomarkers to monitor treatment and more accurately predict future cardiovascular events. This athero-protective strategy includes the assessment of novel inflammatory biomarkers such as YKL-40. Recent evidence has implicated YKL-40 in patients with inflammatory diseases and cardio-metabolic disorders, making it potentially useful to evaluate disease severity, prognosis and survival. In this review, we summarize role of YKL-40 in the pathogenesis of cardio-metabolic disorders and explore its use as a novel biomarker for monitoring athero-protective therapy.

Berberine reduces gut-vascular barrier permeability via modulation of ApoM/S1P pathway in a model of polymicrobial sepsis

AIMS

The hyperpermeability of gut-vascular barrier (GVB) plays a role in gut-derived sepsis. The goal of this study was to evaluate if berberine might improve hepatic apolipoprotein M (ApoM) generation and raise plasma ApoM level to protect the compromised GVB.

MATERIALS AND METHODS

The compromised GVB was induced by sepsis. Hepatic ApoM mRNA and phosphoenolpyruvate carboxykinase (PEPCK) mRNA and plasma ApoM level were assayed by qRT-PCR and ELISA, respectively. The permeability of intestinal capillary in vivo and of rat intestinal microvascular endothelial cells (RIMECs) in vitro was assayed by FITC-dextran. The blood glucose was detected by a glucometer. Plasma insulin, TNF-α and IL-1β were assayed by ELISA. The plasmalemma vesicle-associated protein-1 (PV1), β-catenin and occludin in RIMECs were assayed by Western blot.

KEY FINDINGS

Sepsis decreased hepatic ApoM mRNA and plasma ApoM level, but raised hepatic PEPCK mRNA and plasma glucose, insulin, TNF-α, and IL-1β levels. The increased vascular endothelial permeability was abrogated by recombinant rat ApoM in vivo or ApoM-bound S1P in vitro. ApoM-bound S1P decreased PV1 but increased occludin and β-catenin expression in LPS-treated RIMECs. Berberine in a dose-dependent manner raised hepatic ApoM mRNA and plasma ApoM level, but decreased septic hyperglycemia, insulin resistance and plasma TNF-α and IL-1β levels. Berberine reduced sepsis-induced PEPCK and TLR4 mRNA overexpression in the liver.

SIGNIFICANCE

This study demonstrated berberine inhibited TLR4-mediated hyperglycemia, insulin resistance and proinflammatory molecule production, thereby increasing ApoM gene expression and plasma ApoM. Berberine protected the damaged GVB via modulation of ApoM/S1P pathway.

Increased expression levels of inflammatory cytokines and adhesion molecules in lipopolysaccharide‑induced acute inflammatory apoM‑/‑ mice

Apolipoprotein M (apoM) may serve a protective role in the development of inflammation. Nuclear factor-κB (NF-κB) and its downstream factors (including a number of inflammatory cytokines and adhesion molecules) are essential for the regulation of inflammatory processes. In the present study, the importance of apoM in lipopolysaccharide (LPS)-induced acute inflammation and its potential underlying mechanisms, were investigated using an apoM-knockout mouse model. The levels of inducible nitric oxide synthase (iNOS), NF-κB, interleukin (IL)-1β, intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion protein 1 (VCAM-1) were detected using reverse transcription-quantitative PCR and western blotting. The serum levels of IL-6 and IL-10 were detected using Luminex technology. The results demonstrated that the protein levels of iNOS, NF-κB, IL-1β, ICAM-1 and VCAM-1 were significantly increased in apoM^−/− mice compared with those in apoM^+/+ mice. In addition, two-way ANOVA revealed that the interaction between apoM and LPS had a statistically significant effect on a number of factors, including the mRNA expression levels of hepatic iNOS, NF-κB, IL-1β, ICAM-1 and VCAM-1. Notably, the effects of apoM and 10 mg/kg LPS on the levels of IL-6 and IL-10 were the opposite of those induced by 5 mg/kg LPS, which could be associated with the dual anti- and pro-inflammatory effects of IL-6 and IL-10. Collectively, the results of the present study revealed that apoM is an important regulator of inflammatory cytokine and adhesion molecule production in LPS-induced inflammation, which may consequently be associated with the severity of inflammation. These findings indicated that the anti-inflammatory effects of apoM may partly result from the inhibition of the NF-κB pathway.

Apolipoprotein M: new connections with diet, adipose tissue and metabolic syndrome

PURPOSE OF REVIEW

To focus on state-of-the-art knowledge on the apolipoprotein M (ApoM) physiology and physiopathology regarding metabolism.

RECENT FINDINGS

In humans, the ApoM was recently described as secreted by adipocytes. Obesity, metabolic syndrome and type 2 diabetes are associated with low circulating ApoM and adipose tissue APOM expression. Dieting-induced weight loss enhances adipose tissue expression and secretion, and exercise training increases plasma ApoM. The ApoM is a chaperone for the bioactive sphingolipid, sphingosine-1-phosphate (S1P), which has a specific role in inflammation. Its association with S1P in the inhibition of brown adipose tissue activity and subsequent insulin sensitivity was reported with the model of ApoM-deficient mouse.

SUMMARY

The adipose tissue is an endocrine organ responsible for obesity-related comorbidities. Obesity and dieting impact the adipose tissue secretory profile. The recent demonstration of ApoM being secreted by healthy adipocytes questions about the possible role of this adipose production in metabolic diseases. Low-circulating ApoM is associated with unhealthy metabolic phenotype. The lower circulating apoM during metabolic syndrome might be a cause of obesity-related comorbidities. Lifestyle interventions enhance ApoM production. Whether it acts in combination to S1P or other small lipidic molecules deserves further investigations.