Apolipoprotein M

Risk factors for cardiovascular diseases in patients with vitiligo: an analysis of current evidence

OBJECTIVE

The relationship between vitiligo and cardiovascular diseases remains controversial. This study aimed to systematically review the evidence comparing cardiovascular disease risk factors between patients with vitiligo and controls and to perform a meta-analysis of the results.

DATA SOURCES

A comprehensive database search was performed for all studies in PubMed, EMBASE, and Cochrane Central Register databases from inception to November, 2023. The main keywords used were vitiligo, hypertension, diabetes, hyperlipidemia, metabolic syndrome, obesity, smoking, alcohol consumption, C-reactive protein, and homocysteine.

STUDY SELECTION

Only observational studies and no randomized controlled trials were included. Of the 1269 studies initially selected, the full texts of 108 were assessed for eligibility, and 74 were ultimately included in the analysis.

DATA EXTRACTION AND SYNTHESIS

Three reviewers independently extracted the following data: study design, number and characteristics of participants, inclusion indicators, and disease duration. A meta-analysis of the single-group rates was performed for the diabetes, hypertension, hyperlipidemia, and obesity groups. Random-effects or fixed-effects models were used to calculate the sample-size weighted averages for the indicators included in the studies.

MAIN OUTCOMES AND MEASURES

The primary outcomes were co-morbidity analysis and co-morbidity rates of vitiligo with metabolic syndrome, obesity, hyperlipidemia, hypertension, and diabetes mellitus. Secondary outcomes were factors associated with vitiligo and cardiovascular disease.

RESULTS

This meta-analysis concluded that comorbidities in patients with vitiligo included metabolic syndrome, diabetes, obesity, hyperlipidemia, and hypertension, with comorbidity rates of 28.3%, 6.0%, 38.5%, 43.0%, and 15.8%, respectively. Simultaneously, we showed that the vitiligo group differed significantly from the control group in the following aspects: fasting blood glucose, insulin, systolic and diastolic blood pressure, total cholesterol, triglycerides, low-density lipoprotein, high-density lipoprotein, homocysteine, C-reactive protein, smoking, and alcohol consumption. However, no significant differences were observed between the vitiligo and control groups in terms of waist circumference, body mass index, or phospholipid levels.

LIMITATIONS

The vast majority of the studies were from Eastern countries; therefore, extrapolation of these results to Western populations is questionable. The significant heterogeneity may be due to different protocols, doses, durations, center settings, population registries, etc., which severely compromise the validity of the results.

CONCLUSION

This study summarized not only the factors associated with, but also those not associated with, cardiovascular disease in patients with vitiligo. This study provides a foundation for the prevention and treatment of cardiovascular disease in patients with vitiligo.

Apolipoprotein M supports S1P production and conservation and mediates prolonged Akt activation via S1PR1 and S1PR3

Sphingosine 1-phosphate (S1P) is one of the lipid mediators involved in diverse physiological functions. S1P circulates in blood and lymph bound to carrier proteins. Three S1P carrier proteins have been reported, albumin, apolipoprotein M (ApoM) and apolipoprotein A4 (ApoA4). The carrier-bound S1P exerts its functions via specific S1P receptors (S1PR1-5) on target cells. Previous studies showed several differences in physiological functions between albumin-bound S1P and ApoM-bound S1P. However, molecular mechanisms underlying the carrier-dependent differences have not been clarified. In addition, ApoA4 is a recently identified S1P carrier protein, and its functional differences from albumin and ApoM have not been addressed. Here, we compared the three carrier proteins in the processes of S1P degradation, release from S1P-producing cells and receptor activation. ApoM retained S1P more stable than albumin and ApoA4 in the cell culture medium when compared in the equimolar amounts. ApoM facilitated theS1P release from endothelial cells most efficiently. Furthermore, ApoM-bound S1P showed a tendency to induce prolonged activation of Akt via S1PR1 and S1PR3. These results suggest that the carrier-dependent functional differences of S1P are partly ascribed to the differences in the S1P stability, S1P-releasing efficiency and signaling duration.

ApoM suppresses kidney renal clear cell carcinoma growth and metastasis via the Hippo-YAP signaling pathway

Renal cell carcinoma is one of the most common malignancies worldwide, and kidney renal clear cell carcinoma (KIRC) is the most common histopathological type of renal cell carcinoma. However, the mechanism of KIRC progression remains poorly understood. Apolipoprotein M (ApoM) is a plasma apolipoprotein and a member of the lipid transport protein superfamily. Lipid metabolism is essential for tumor progression, and its related proteins can be used as therapeutic targets for tumors. ApoM influences the development of several cancers, but its relationship with KIRC remains unclear. In this study, we aimed to investigate the biological function of ApoM in KIRC and to reveal its potential molecular mechanisms. We found that ApoM expression was significantly reduced in KIRC and was strongly correlated with patient prognosis. ApoM overexpression significantly inhibited KIRC cell proliferation in vitro, suppressed the epithelial mesenchymal transition (EMT) of KIRC cells, and decreased their metastatic capacity. Additionally, the growth of KIRC cells was inhibited by ApoM overexpression in vivo. In addition, we found that overexpression of ApoM in KIRC attenuated Hippo-YAP protein expression and YAP stability and thus inhibited KIRC growth and progression. Therefore, ApoM may be a potential target for the treatment of KIRC.

Predicting late-stage age-related macular degeneration by integrating marginally weak SNPs in GWA studies

Introduction: Age-related macular degeneration (AMD) is a progressive neurodegenerative disease and the leading cause of blindness in developed countries. Current genome-wide association studies (GWAS) for late-stage age-related macular degeneration are mainly single-marker-based approaches, which investigate one Single-Nucleotide Polymorphism (SNP) at a time and postpone the integration of inter-marker Linkage-disequilibrium (LD) information in the downstream fine mappings. Recent studies showed that directly incorporating inter-marker connection/correlation into variants detection can help discover novel marginally weak single-nucleotide polymorphisms, which are often missed in conventional genome-wide association studies, and can also help improve disease prediction accuracy. Methods: Single-marker analysis is performed first to detect marginally strong single-nucleotide polymorphisms. Then the whole-genome linkage-disequilibrium spectrum is explored and used to search for high-linkage-disequilibrium connected single-nucleotide polymorphism clusters for each strong single-nucleotide polymorphism detected. Marginally weak single-nucleotide polymorphisms are selected via a joint linear discriminant model with the detected single-nucleotide polymorphism clusters. Prediction is made based on the selected strong and weak single-nucleotide polymorphisms. Results: Several previously identified late-stage age-related macular degeneration susceptibility genes, for example, BTBD16, C3, CFH, CFHR3, HTARA1, are confirmed. Novel genes DENND1B, PLK5, ARHGAP45, and BAG6 are discovered as marginally weak signals. Overall prediction accuracy of 76.8% and 73.2% was achieved with and without the inclusion of the identified marginally weak signals, respectively. Conclusion: Marginally weak single-nucleotide polymorphisms, detected from integrating inter-marker linkage-disequilibrium information, may have strong predictive effects on age-related macular degeneration. Detecting and integrating such marginally weak signals can help with a better understanding of the underlying disease-development mechanisms for age-related macular degeneration and more accurate prognostics.

Apolipoproteins: New players in cancers

Apolipoproteins (APOs), the primary protein moiety of lipoproteins, are known for their crucial role in lipid traffic and metabolism. Despite extensive exploration of APOs in cardiovascular diseases, their roles in cancers did not attract enough attention. Recently, research focusing on the roles of APOs in cancers has flourished. Multiple studies demonstrate the interaction of APOs with classical pathways of tumorigenesis. Besides, the dysregulation of APOs may indicate cancer occurrence and progression, thus serving as potential biomarkers for cancer patients. Herein, we summarize the mechanisms of APOs involved in the development of various cancers, their applications as cancer biomarkers and their genetic polymorphism associated with cancer risk. Additionally, we also discuss the potential anti-cancer therapies by virtue of APOs. The comprehensive review of APOs in cancers may advance the understanding of the roles of APOs in cancers and their potential mechanisms. We hope that it will provide novel clues and new therapeutic strategies for cancers.

Protective properties of sardine and chickpea protein hydrolysates against lipoprotein oxidative damages and some inflammation markers in hypercholesterolemic rats

OBJECTIVE: This study evaluated the effect of sardine (SPH) and chickpea protein hydrolysates (CPH) on oxidant stress and inflammatory profile in cholesterol-fed rats. METHODS: The experiment was undertaken for thirty days on 18 cholesterol-fed Wistar rats (220±10 g) divided into three groups and receiving 1 g/kg of body weight either chickpea protein hydrolysate (CPH), sardine protein hydrolysate (SPH) or casein in water (CG). RESULTS: Compared to CG, SPH and CPH treatment reduced cholesterol, hydroperoxide and malondialdehyde contents in serum, lipoproteins, erythrocytes and aorta. These same treated groups showed also lower serum isoprostane levels. However, serum paraoxonase activity and HDL-antioxidant property were improved only by CPH compared to CG. SOD activity of aorta and erythrocytes was higher in CPH but in SPH group, SOD activity was lower in these tissues and remained unchanged in serum. Furthermore, CPH and SPH stimulated glutathione peroxidase and catalase activities of aorta and erythrocytes. In CPH group, nitric oxide levels of serum, erythrocytes and aorta were increased by respectively 1.4- to 1.8-fold compared to CG and SPH. In addition, among the three groups, CPH exhibited the best anti-inflammatory effect by lowering serum C reactive protein, uric acid and albumin concentrations. CONCLUSIONS: SPH and particularly CPH possess antioxidant and anti-inflammatory properties and could be useful as nutraceuticals for health improving and preventing numerous disorders such as cardiovascular diseases.

The apoM/S1P Complex-A Mediator in Kidney Biology and Disease?

Kidney disease affects more than 10% of the population, can be both acute and chronic, and is linked to other diseases such as cardiovascular disease, diabetes, and sepsis. Despite the detrimental consequences for patients, no good treatment options directly targeting the kidney are available. Thus, a better understanding of the pathology and new treatment modalities are required. Accumulating evidence suggests that the apolipoprotein M/sphingosine-1-phosphate (apoM/S1P) axis is a likely drug target, but significant gaps in our knowledge remain. In this review, we present what has so far been elucidated about the role of apoM in normal kidney biology and describe how changes in the apoM/S1P axis are thought to affect the development of kidney disease. ApoM is primarily produced in the liver and kidneys. From the liver, apoM is secreted into circulation, where it is attached to lipoproteins (primarily HDL). Importantly, apoM is a carrier of the bioactive lipid S1P. S1P acts by binding to five different receptors. Together, apoM/S1P plays a role in several biological mechanisms, such as inflammation, endothelial cell permeability, and lipid turnover. In the kidney, apoM is primarily expressed in the proximal tubular cells. S1P can be produced locally in the kidney, and several of the five S1P receptors are present in the kidney. The functional role of kidney-derived apoM as well as plasma-derived apoM is far from elucidated and will be discussed based on both experimental and clinical studies. In summary, the current studies provide evidence that support a role for the apoM/S1P axis in kidney disease; however, additional pre-clinical and clinical studies are needed to reveal the mechanisms and target potential in the treatment of patients.

New insights into the emerging effects of inflammatory response on HDL particles structure and function

According to the increasing results, it has been well-demonstrated that the chronic inflammatory response, including systemic lupus erythematosus, rheumatoid arthritis, and inflammatory bowel disease are associated with an increased risk of atherosclerotic cardiovascular disease. The mechanism whereby inflammatory response up-regulates the risk of cardio-metabolic disorder disease is multifactorial; furthermore, the alterations in high density lipoprotein (HDL) structure and function which occur under the inflammatory response could play an important modulatory function. On the other hand, the serum concentrations of HDL cholesterol (HDL-C) have been shown to be reduced significantly under inflammatory status with remarked alterations in HDL particles. Nevertheless, the potential mechanism whereby the inflammatory response reduces serum HDL-C levels is not simply defined but reduces apolipoprotein A1 production. The alterations in HDL structure mediated by the inflammatory response has been also confirmed to decrease the ability of HDL particle to play an important role in reverse cholesterol transport and protect the LDL particles from oxidation. Recently, it has been shown that under the inflammatory condition, diverse alterations in HDL structure could be observed which lead to changes in HDL function. In the current review, the emerging effects of inflammatory response on HDL particles structure and function are well-summarized to elucidate the potential mechanism whereby different inflammatory status modulates the pathogenic development of dyslipidemia.

Multifaceted Interaction Between Hepatitis B Virus Infection and Lipid Metabolism in Hepatocytes: A Potential Target of Antiviral Therapy for Chronic Hepatitis B

Hepatitis B virus (HBV) is considered a “metabolic virus” and affects many hepatic metabolic pathways. However, how HBV affects lipid metabolism in hepatocytes remains uncertain yet. Accumulating clinical studies suggested that compared to non-HBV-infected controls, chronic HBV infection was associated with lower levels of serum total cholesterol and triglycerides and a lower prevalence of hepatic steatosis. In patients with chronic HBV infection, high ALT level, high body mass index, male gender, or old age was found to be positively correlated with hepatic steatosis. Furthermore, mechanisms of how HBV infection affected hepatic lipid metabolism had also been explored in a number of studies based on cell lines and mouse models. These results demonstrated that HBV replication or expression induced extensive and diverse changes in hepatic lipid metabolism, by not only activating expression of some critical lipogenesis and cholesterolgenesis-related proteins but also upregulating fatty acid oxidation and bile acid synthesis. Moreover, increasing studies found some potential targets to inhibit HBV replication or expression by decreasing or enhancing certain lipid metabolism-related proteins or metabolites. Therefore, in this article, we comprehensively reviewed these publications and revealed the connections between clinical observations and experimental findings to better understand the interaction between hepatic lipid metabolism and HBV infection. However, the available data are far from conclusive, and there is still a long way to go before clarifying the complex interaction between HBV infection and hepatic lipid metabolism.

Recent advances in the regulation of ABCA1 and ABCG1 by lncRNAs

Coronary heart disease (CHD) with atherosclerosis is the leading cause of death worldwide. ABCA1 and ABCG1 promote cholesterol efflux to suppress foam cell generation and reduce atherosclerosis development. Long noncoding RNAs (lncRNAs) are emerging as a unique group of RNA transcripts that longer than 200 nucleotides and have no protein-coding potential. Many studies have found that lncRNAs regulate cholesterol efflux to influence atherosclerosis development. ABCA1 is regulated by different lncRNAs, including MeXis, GAS5, TUG1, MEG3, MALAT1, Lnc-HC, RP5-833A20.1, LOXL1-AS1, CHROME, DAPK1-IT1, SIRT1 AS lncRNA, DYNLRB2-2, DANCR, LeXis, LOC286367, and LncOR13C9. ABCG1 is also regulated by different lncRNAs, including TUG1, GAS5, RP5-833A20.1, DYNLRB2-2, ENST00000602558.1, and AC096664.3. Thus, various lncRNAs are associated with the roles of ABCA1 and ABCG1 on cholesterol efflux in atherosclerosis regulation. However, some lncRNAs play dual roles in ABCA1 expression and atherosclerosis, and the functions of some lncRNAs in atherosclerosis have not been investigated in vivo. In this article, we review the roles of lncRNAs in atherosclerosis and focus on new insights into lncRNAs associated with the roles of ABCA1 and ABCG1 on cholesterol efflux and the potential of these lncRNAs as novel therapeutic targets in atherosclerosis.

High-Density Lipoprotein Modifications: A Pathological Consequence or Cause of Disease Progression?

High-density lipoprotein (HDL) is well-known for its cardioprotective effects, as it possesses anti-inflammatory, anti-oxidative, anti-thrombotic, and cytoprotective properties. Traditionally, studies and therapeutic approaches have focused on raising HDL cholesterol levels. Recently, it became evident that, not HDL cholesterol, but HDL composition and functionality, is probably a more fruitful target. In disorders, such as chronic kidney disease or cardiovascular diseases, it has been observed that HDL is modified and becomes dysfunctional. There are different modification that can occur, such as serum amyloid, an enrichment and oxidation, carbamylation, and glycation of key proteins. Additionally, the composition of HDL can be affected by changes to enzymes such as cholesterol ester transfer protein (CETP), lecithin-cholesterol acyltransferase (LCAT), and phospholipid transfer protein (PLTP) or by modification to other important components. This review will highlight some main modifications to HDL and discuss whether these modifications are purely a consequential result of pathology or are actually involved in the pathology itself and have a causal role. Therefore, HDL composition may present a molecular target for the amelioration of certain diseases, but more information is needed to determine to what extent HDL modifications play a causal role in disease development.

Interaction between high-density lipoproteins and inflammation: Function matters more than concentration!

High-density lipoprotein (HDL) plays an important role in lipid metabolism and especially contributes to the reverse cholesterol transport pathway. Over recent years it has become clear that the effect of HDL on immune-modulation is not only dependent on HDL concentration but also and perhaps even more so on HDL function. This review will provide a concise general introduction to HDL followed by an overview of post-translational modifications of HDL and a detailed overview of the role of HDL in inflammatory diseases. The clinical potential of HDL and its main apolipoprotein constituent, apoA-I, is also addressed in this context. Finally, some conclusions and remarks that are important for future HDL-based research and further development of HDL-focused therapies are discussed.

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.

Identification of Differentially Expressed Proteins in Serum of Obese Patients by Isobaric Tags for Relative and Absolute Quantification (iTRAQ)-Coupled 2D LC-MS

BACKGROUND The aim of this study was to identify the differentially expressed proteins of obese patients compared with normal participants and to provide a potential target for future investigation of obesity. MATERIAL AND METHODS We enrolled 10 obese male adults and 10 matched normal subjects. Serum samples were collected to get total protein extraction, denaturation, deoxidation, and enzymatic hydrolysis. Differentially expressed proteins were distinguished with mass spectrometry after samples were labeled with iTRAQ. RESULTS A total of 9622 differentially expressed peptides were identified, corresponding to 733 proteins; 118 proteins of these showed significant differential expression, with 15 upregulated and 103 downregulated. CONCLUSIONS iTRAQ is an effective technique to identify differentially expressed proteins in obese patients. The development of obesity is correlated with a series of complex elements and mutual effects. The proteins identified in this study may provide novel directions and targets for future pathological studies of obesity.

Lipoproteins and lipids in cardiovascular disease: from mechanistic insights to therapeutic targeting

With cardiovascular disease being the leading cause of morbidity and mortality worldwide, effective and cost-efficient therapies to reduce cardiovascular risk are highly needed. Lipids and lipoprotein particles crucially contribute to atherosclerosis as underlying pathology of cardiovascular disease and influence inflammatory processes as well as function of leukocytes, vascular and cardiac cells, thereby impacting on vessels and heart. Statins form the first-line therapy with the aim to block cholesterol synthesis, but additional lipid-lowering drugs are sometimes needed to achieve low-density lipoprotein (LDL) cholesterol target values. Furthermore, beyond LDL cholesterol, also other lipid mediators contribute to cardiovascular risk. This review comprehensively discusses low- and high-density lipoprotein cholesterol, lipoprotein (a), triglycerides as well as fatty acids and derivatives in the context of cardiovascular disease, providing mechanistic insights into their role in pathological processes impacting on cardiovascular disease. Also, an overview of applied as well as emerging therapeutic strategies to reduce lipid-induced cardiovascular burden is provided.

Glomerular endothelial cell heterogeneity in Alport syndrome

Glomerular endothelial cells (GEC) are a crucial component of the glomerular physiology and their damage contributes to the progression of chronic kidney diseases. How GEC affect the pathology of Alport syndrome (AS) however, is unclear. We characterized GEC from wild type (WT) and col4α5 knockout AS mice, a hereditary disorder characterized by progressive renal failure. We used endothelial-specific Tek-tdTomato reporter mice to isolate GEC by FACS and performed transcriptome analysis on them from WT and AS mice, followed by in vitro functional assays and confocal and intravital imaging studies. Biopsies from patients with chronic kidney disease, including AS were compared with our findings in mice. We identified two subpopulations of GEC (dim^tdT and bright^tdT) based on the fluorescence intensity of the Tek^tdT signal. In AS mice, the bright^tdT cell number increased and presented differential expression of endothelial markers compared to WT. RNA-seq analysis revealed differences in the immune and metabolic signaling pathways. In AS mice, dim^tdT and bright^tdT cells had different expression profiles of matrix-associated genes (Svep1, Itgβ6), metabolic activity (Apom, Pgc1α) and immune modulation (Apelin, Icam1) compared to WT mice. We confirmed a new pro-inflammatory role of Apelin in AS mice and in cultured human GEC. Gene modulations were identified comparable to the biopsies from patients with AS and focal segmental glomerulosclerosis, possibly indicating that the same mechanisms apply to humans. We report the presence of two GEC subpopulations that differ between AS and healthy mice or humans. This finding paves the way to a better understanding of the pathogenic role of GEC in AS progression and could lead to novel therapeutic targets.

Comparison of Omega-3 Eicosapentaenoic Acid Versus Docosahexaenoic Acid-Rich Fish Oil Supplementation on Plasma Lipids and Lipoproteins in Normolipidemic Adults

Background: Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have both shared and different cardiovascular effects, and commonly used fish oil supplements have considerably varied EPA/DHA ratios. Aims: We compared the effects of fish oil supplements with different EPA/DHA ratios on lipoprotein metabolism. Methods: In a double-blind, randomized cross-over study, normolipidemic adults (n = 30) consumed 12 g/day of EPA-rich (EPA/DHA: 2.3) or DHA-rich (EPA/DHA: 0.3) fish oil for 8-weeks, separated by an 8-week washout period. Results: Both fish oil supplements similarly lowered plasma TG levels and TG-related NMR parameters versus baseline (p < 0.05). There were no changes in plasma cholesterol-related parameters due to either fish oil, although on-treatment levels for LDL particle number were slightly higher for DHA-rich oil compared with EPA-rich oil (p < 0.05). Both fish oil supplements similarly altered HDL subclass profile and proteome, and down regulated HDL proteins related to inflammation, with EPA-rich oil to a greater extent. Furthermore, EPA-rich oil increased apoM abundance versus DHA-rich oil (p < 0.05). Conclusions: Overall, fish oil supplements with varied EPA/DHA ratios had similar effects on total lipids/lipoproteins, but differences were observed in lipoprotein subfraction composition and distribution, which could impact on the use of EPA versus DHA for improving cardiovascular health.

Apolipoprotein M, identified as a novel hepatitis C virus (HCV) particle associated protein, contributes to HCV assembly and interacts with E2 protein

Hepatitis C virus (HCV) infection is a major cause of chronic liver diseases such as steatosis, cirrhosis, and hepatocellular carcinoma. HCV particles have been found to associate with apolipoproteins, and apolipoproteins not only participate in the HCV life cycle, but also help HCV escape recognition by the host immune system, which pose challenges for the development of both HCV treatments and vaccines. However, no study has reported on the comprehensive identification of apolipoprotein associations with HCV particles. In the present study, we performed proteome analysis by affinity purification coupled with mass spectrometry (AP-MS) to comprehensively identify the apolipoprotein associations with HCV particles, and ApoM was first identified by AP-MS besides the previously reported ApoE, ApoB, ApoA-I and ApoC-I. Additionally, three assays further confirmed that ApoM was a novel virus particle associated protein. We also showed that ApoM was required for HCV production, especially for the assembly/release step of HCV life cycle. Furthermore, ApoM interacted with the HCV E2 protein. Finally, HCV infection reduced ApoM expression both in vitro and in vivo. Collectively, our study demonstrates that ApoM, identified as a novel HCV particle associated protein, contributes to HCV assembly/release and interacts with HCV E2 protein. It provides new insights on how HCV and the host apolipoproteins are reciprocally influenced and lays a basis for research in developing innovative antiviral strategies.

Insulin Resistance in Apolipoprotein M Knockout Mice is Mediated by the Protein Kinase Akt Signaling Pathway

BACKGROUND

Previous clinical studies have suggested that apolipoprotein M (apoM) is involved in glucose metabolism and plays a causative role in insulin sensitivity.

OBJECTIVE

The potential mechanism of apoM on modulating glucose homeostasis is explored and differentially expressed genes are analyzed by employing ApoM deficient (ApoM-/- ) and wild type (WT) mice.

METHODS

The metabolism of glucose in the hepatic tissues of high-fat diet ApoM-/- and WT mice was measured by a glycomics approach. Bioinformatic analysis was applied for analyzing the levels of differentially expressed mRNAs in the liver tissues of these mice. The insulin sensitivity of ApoM-/- and WT mice was compared using the insulin tolerance test and the phosphorylation levels of protein kinase Akt (AKT) and insulin stimulation in different tissues were examined by Western blot.

RESULTS

The majority of the hepatic glucose metabolites exhibited lower concentration levels in the ApoM-/- mice compared with those of the WT mice. Gene Ontology (GO) classification and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that ApoM deficiency affected the genes associated with the metabolism of glucose. The insulin tolerance test suggested that insulin sensitivity was impaired in ApoM-/- mice. The phosphorylation levels of AKT in muscle and adipose tissues of ApoM-/- mice were significantly diminished in response to insulin stimulation compared with those noted in WT mice.

CONCLUSION

ApoM deficiency led to the disorders of glucose metabolism and altered genes related to glucose metabolism in mice liver. In vivo data indicated that apoM might augment insulin sensitivity by AKT-dependent mechanism.

Effects of Replacing Dietary Monounsaturated Fat With Carbohydrate on HDL (High-Density Lipoprotein) Protein Metabolism and Proteome Composition in Humans

OBJECTIVE

Clinical evidence has linked low HDL (high-density lipoprotein) cholesterol levels with high cardiovascular disease risk; however, its significance as a therapeutic target remains unestablished. We hypothesize that HDLs functional heterogeneity is comprised of metabolically distinct proteins, each on distinct HDL sizes and that are affected by diet. Approach and Results: Twelve participants were placed on 2 healthful diets high in monounsaturated fat or carbohydrate. After 4 weeks on each diet, participants completed a metabolic tracer study. HDL was isolated by Apo (apolipoprotein) A1 immunopurification and separated into 5 sizes. Tracer enrichment and metabolic rates for 8 HDL proteins-ApoA1, ApoA2, ApoC3, ApoE, ApoJ, ApoL1, ApoM, and LCAT (lecithin-cholesterol acyltransferase)-were determined by parallel reaction monitoring and compartmental modeling, respectively. Each protein had a unique, size-specific distribution that was not altered by diet. However, carbohydrate, when replacing fat, increased the fractional catabolic rate of ApoA1 and ApoA2 on alpha3 HDL; ApoE on alpha3 and alpha1 HDL; and ApoM on alpha2 HDL. Additionally, carbohydrate increased the production of ApoC3 on alpha3 HDL and ApoJ and ApoL1 on the largest alpha0 HDL. LCAT was the only protein studied that diet did not affect. Finally, global proteomics showed that diet did not alter the distribution of the HDL proteome across HDL sizes.

CONCLUSIONS

This study demonstrates that HDL in humans is composed of a complex system of proteins, each with its own unique size distribution, metabolism, and diet regulation. The carbohydrate-induced hypercatabolic state of HDL proteins may represent mechanisms by which carbohydrate alters the cardioprotective properties of HDL.

Apolipoprotein M: a novel adipokine decreasing with obesity and upregulated by calorie restriction

BACKGROUND

The adipose tissue (AT) is a secretory organ producing a wide variety of factors that participate in the genesis of metabolic disorders linked to excess fat mass. Weight loss improves obesity-related disorders.

OBJECTIVES

Transcriptomic studies on human AT, and a combination of analyses of transcriptome and proteome profiling of conditioned media from adipocytes and stromal cells isolated from human AT, have led to the identification of apolipoprotein M (apoM) as a putative adipokine. We aimed to validate apoM as novel adipokine, investigate the relation of AT APOM expression with metabolic syndrome and insulin sensitivity, and study the regulation of its expression in AT and secretion during calorie restriction-induced weight loss.

METHODS

We examined APOM mRNA level and secretion in AT from 485 individuals enrolled in 5 independent clinical trials, and in vitro in human multipotent adipose-derived stem cell adipocytes. APOM expression and secretion were measured during dieting.

RESULTS

APOM was expressed in human subcutaneous and visceral AT, mainly by adipocytes. ApoM was released into circulation from AT, and plasma apoM concentrations correlate with AT APOM mRNA levels. In AT, APOM expression inversely correlated with adipocyte size, was lower in obese compared to lean individuals, and reduced in subjects with metabolic syndrome and type 2 diabetes. Regardless of fat depot, there was a positive relation between AT APOM expression and systemic insulin sensitivity, independently of fat mass and plasma HDL cholesterol. In human multipotent adipose-derived stem cell adipocytes, APOM expression was enhanced by insulin-sensitizing peroxisome proliferator-activated receptor agonists and inhibited by tumor necrosis factor α, a cytokine that causes insulin resistance. In obese individuals, calorie restriction increased AT APOM expression and secretion.

CONCLUSIONS

ApoM is a novel adipokine, the expression of which is a hallmark of healthy AT and is upregulated by calorie restriction. AT apoM deserves further investigation as a potential biomarker of risk for diabetes and cardiovascular diseases.

Apolipoprotein M could inhibit growth and metastasis of SMMC7721 cells via vitamin D receptor signaling

Objective: Hepatocellular carcinoma (HCC) is one of the most common malignant tumors with high mortality-to-incidence ratios. Apolipoprotein M (ApoM), a member of the apolipoprotein family, is mainly synthesized in the liver, whereas its role in HCC has not been elucidated. Here, we examined the effect of ApoM on the biological behavior of HCC cells and the possible mechanisms. Methods: We used CRISPR/Cas9 technology to knock out ApoM in SMMC7721 cells. Differentially expressed genes before and after ApoM knockout (KO) were analyzed by GeneChip microarrays and confirmed by qRT-PCR. Cell assays of proliferation, apoptosis, migration and invasion were performed in SMMC7721 cells, and the expression of epithelial-mesenchymal transition (EMT) markers was performed by western blot. And we performed functional recovery experiments by overexpressing vitamin D receptor (VDR) in SMMC7721. Results: The ApoM-KO SMMC7721 cell line was successfully constructed using the CRISPR/Cas9 technology. Our results showed that silencing ApoM suppressed apoptosis and promoted proliferation, migration, invasion and EMT of SMMC7721 cells. The microarray data revealed that a total of 1,868 differentially expressed genes were identified, including VDR. The qRT-PCR and western blot verification results demonstrated that knocking out ApoM could significantly reduce the expression of VDR. The functional recovery experiments indicated that VDR overexpression could offset the inhibition of cell apoptosis and the promotion of cell proliferation, migration, invasion and EMT caused by knocking out ApoM in SMMC7721 cells. Conclusion: ApoM could function as a tumor suppressor to inhibit the growth and metastasis of SMMC7721 cells via VDR signaling in HCC.

Atorvastatin upregulates apolipoprotein M expression via attenuating LXRα expression in hyperlipidemic apoE-deficient mice

Apolipoprotein M (apoM) is a recently identified human apolipoprotein that is associated with the formation of high-density lipoprotein (HDL). Studies have demonstrated that statins may affect the expression of apoM; however, the regulatory effects of statins on apoM are controversial. Furthermore, the underlying mechanisms by which statins regulate apoM remain unclear. In the present study, in vivo and in vitro models were used to investigate whether the anti-atherosclerotic effects of statins are associated with its apoM-regulating effects and the underlying mechanism. Hyperlipidemia was induced by in apolipoprotein E-deficient mice by providing a high-fat diet. Atorvastatin was administered to hyperlipidemic mice and HepG2 cells to investigate its effect on apoM expression. The liver X receptor α (LXRα) agonist T0901317 was also administered together with atorvastatin to hyperlipidemic mice and HepG2 cells. The results revealed that atorvastatin increased apoM expression, which was accompanied with decreased expression of LXRα in the liver of hyperlipidemic apolipoprotein E-deficient mice and HepG2 cells. Additionally, apoM upregulation was inhibited following treatment with T0901317. In summary, atorvastatin exhibited anti-atherosclerotic effects by upregulating apoM expression in hyperlipidemic mice, which may be mediated by the inhibition of LXRα.

The role of sphingosine 1 phosphate in coronary artery disease and ischemia reperfusion injury

Coronary artery disease (CAD) is a common cause of morbidity and mortality worldwide. Atherosclerotic plaques, as a hallmark of CAD, cause chronic narrowing of coronary arteries over time and could also result in acute myocardial infarction (AMI). The standard treatments for ameliorating AMI are reperfusion strategies, which paradoxically result in ischemic reperfusion (I/R) injury. Sphingosine 1 phosphate (S1P), as a potent lysophospholipid, plays an important role in various organs, including immune and cardiovascular systems. In addition, high-density lipoprotein, as a negative predictor of atherosclerosis and CAD, is a major carrier of S1P in blood circulation. S1P mediates its effects through binding to specific G protein-coupled receptors, and its signaling contributes to a variety of responses, including cardiac inflammation, dysfunction, and I/R injury protection. In this review, we will focus on the role of S1P in CAD and I/R injury as a potential therapeutic target.

Deletion of ApoM gene induces apoptosis in mouse kidney via mitochondrial and endoplasmic reticulum stress pathways

Apolipoprotein M (ApoM) is involved in lipid metabolism, and especially is involved in reverse cholesterol transport. However, the relationship between ApoM and apoptosis has been rarely reported. This study aimed to investigate the effect of ApoM on apoptosis using an ApoM gene-deficient mice (ApoM^-/-) model and a mouse mesangial cell model with suppressed ApoM gene expression. First, we observed by transmission electron microscopy that mitochondrial damage and endoplasmic reticulum stress were abnormally altered in the kidneys of ApoM^-/- mice compared with wild-type mice, showing mitochondrial swelling, vacuolization, myeloid changes, and expansion of the rough endoplasmic reticulum. At the molecular level, the expression of pro-apoptotic related proteins such as AIF, Bax, chop, clever-caspase 3, clever-caspase 7, clever-caspase 9, and clever-caspase 12 increased, and the expression of anti-apoptotic protein Bcl-2 decreased. Secondly, by interfering with the expression of the ApoM gene in mouse mesangial cells, we found that, compared with the control group (NC-si), the cells of the experimental group (siApoM) showed decreased cell viability, nuclear chromatin condensation, nuclear lysis, and an increased proportion of early apoptotic cells. The results in cells at the molecular level were consistent with those at the tissue level. These data indicated that the deletion of the ApoM gene led to upregulation of apoptosis in mouse kidney tissues and mesangial cells through the mitochondrial and endoplasmic reticulum pathways.

Proteomic Toolbox To Standardize the Separation of Extracellular Vesicles and Lipoprotein Particles

Circulating in blood, extracellular vesicles (EVs) and lipoprotein particles (LPs) have diagnostic and prognostic value. To unambiguously define their functions, separation protocols need to be developed. However, because of their similar size and density, traditional approaches to separate EVs and LPs often fail to provide the required resolution. Further development and standardization of affinity-based protocols is necessary, and a quantitative method is needed to assess the efficiency of LP depletion from EV samples. In the present study, we propose the simultaneous quantification of three groups of proteins by mass spectrometry as a toolbox to evaluate prospective separation protocols. We generated ¹⁵N-labeled internal standards for quantification of (i) EV-specific proteins, (ii) all classes and subclasses of apolipoproteins constituting LPs, and (iii) several major serum proteins. These standards were then used in multiple reaction monitoring assay to evaluate the performance of size-exclusion chromatography, heparin-Sepharose, lipopolysaccharide-Sepharose, (2-hydroxypropyl)-β-cyclodextrin-Sepharose, and concanavalin A-Sepharose in separating serum EVs and LPs. The efficiency of a resin to separate EVs from non-EV substances could be jeopardized by simultaneous EV aggregation. Therefore, dynamic light scattering analysis was used in this study in addition to the proteomic toolbox when making a recommendation to use particular resin for EV isolation. On the basis of our measurements, we concluded that none of the individual separation protocols used in this study resulted in LP-free EVs, and the combination of two protocols may be complex due to low EV yield. Overall, this further points to the importance of proposed proteomic toolbox for the future evaluation of EV separation protocols.

Update on the laboratory investigation of dyslipidemias

The role of the clinical laboratory is evolving to provide more information to clinicians to assess cardiovascular disease (CVD) risk and target therapy more effectively. Current routine methods to measure LDL-cholesterol (LDL-C), the Friedewald calculation, ultracentrifugation, electrophoresis and homogeneous direct methods have established limitations. Studies suggest that LDL and HDL size or particle concentration are alternative methods to predict future CVD risk. At this time there is no consensus role for lipoprotein particle or subclasses in CVD risk assessment. LDL and HDL particle concentration are measured by several methods, namely gradient gel electrophoresis, ultracentrifugation-vertical auto profile, nuclear magnetic resonance and ion mobility. It has been suggested that HDL functional assays may be better predictors of CVD risk. To assess the issue of lipoprotein subclasses/particles and HDL function as potential CVD risk markers robust, simple, validated analytical methods are required. In patients with small dense LDL particles, even a perfect measure of LDL-C will not reflect LDL particle concentration. Non-HDL-C is an alternative measurement and includes VLDL and CM remnant cholesterol and LDL-C. However, apolipoprotein B measurement may more accurately reflect LDL particle numbers. Non-fasting lipid measurements have many practical advantages. Defining thresholds for treatment with new measurements of CVD risk remain a challenge. In families with genetic variants, ApoCIII and lipoprotein (a) may be additional risk factors. Recognition of familial causes of dyslipidemias and diagnosis in childhood will result in early treatment. This review discusses the limitations in current laboratory technologies to predict CVD risk and reviews the evidence for emergent approaches using newer biomarkers in clinical practice.

Stable Isotope Kinetic Study of ApoM (Apolipoprotein M)

OBJECTIVE

ApoM (apolipoprotein M) binds primarily to high-density lipoprotein before to be exchanged with apoB (apolipoprotein B)-containing lipoproteins. Low-density lipoprotein (LDL) receptor-mediated clearance of apoB-containing particles could influence plasma apoM kinetics and decrease its antiatherogenic properties. In humans, we aimed to describe the interaction of apoM kinetics with other components of lipid metabolism to better define its potential benefit on atherosclerosis.

APPROACH AND RESULTS

Fourteen male subjects received a primed infusion of ²H₃-leucine for 14 hours, and analyses were performed by liquid chromatography-tandem mass spectrometry from the hourly plasma samples. Fractional catabolic rates and production rates within lipoproteins were calculated using compartmental models. ApoM was found not only in high-density lipoprotein (59%) and LDL (4%) but also in a non-lipoprotein-related compartment (37%). The apoM distribution was heterogeneous within LDL and non-lipoprotein-related compartments according to plasma triglycerides (r=0.86; P<0.001). The relationships between sphingosine-1-phosphate and apoM were confirmed in all compartments (r range, 0.55-0.89; P<0.05). ApoM fractional catabolic rates and production rates were 0.16±0.07 pool/d and 0.14±0.06 mg/kg per day in high-density lipoprotein and 0.56±0.10 pool/d and 0.03±0.01 mg/kg per day in LDL, respectively. Fractional catabolic rates of LDL-apoM and LDL-apoB100 were correlated (r=0.55; P=0.042). Significant correlations were found between triglycerides and production rates of LDL-apoM (r=0.73; P<0.004).

CONCLUSIONS

In humans, LDL kinetics play a key role in apoM turnover. Plasma triglycerides act on both apoM and sphingosine-1-phosphate distributions between lipoproteins. These results confirmed that apoM could be bound to high-density lipoprotein after secretion and then quickly exchanged with a non-lipoprotein-related compartment and to LDL to be slowly catabolized.

Evaluation of Expression Level of Apolipoprotein M as a Diagnostic Marker for Primary Venous Thromboembolism

Recently, decreased levels of apolipoprotein M (ApoM) were shown to be associated with higher risk of recurrent venous thromboembolism (VTE) in male patients. However, the role of ApoM in primary VTE is unknown. We aimed in our study to analyze the plasma levels of ApoM in patients with VTE in order to evaluate the diagnostic importance of ApoM in primary VTE. A total of 357 patients with suspected first episode of VTE were recruited prospectively in the SCORE study. Plasma samples from 307 patients were available for quantifying the plasma levels of ApoM in patients with VTE using sandwich enzyme-linked immunosorbent assay method. Among the whole population, plasma levels (mean [standard deviation]) of ApoM were not significantly different between patients with VTE (0.72 [0.20]) and non-VTE patients (0.72 [0.16]), P = .99. Similarly, in regression analyses, no significant association of ApoM plasma levels with the risk of VTE was found on univariate (odds ratio [OR] =1.0, 95% confidence interval [CI] 0.21-4.84, P = .99) and multivariate analysis (OR = 1.25, 95% CI = 0.19-8.34, P = .819) after adjusting for age, body mass index, and smoking. Moreover, results did not differ significantly after stratification of data according to sex ( P > .05). In this study, our results do not suggest a diagnostic role for ApoM plasma levels in patients with primary VTE. Moreover, the current study suggests that role of ApoM as a risk factor may differ for primary VTE and recurrent VTE in male patients.

A Novel Perspective on the ApoM-S1P Axis, Highlighting the Metabolism of ApoM and Its Role in Liver Fibrosis and Neuroinflammation

Hepatocytes, renal proximal tubule cells as well as the highly specialized endothelium of the blood brain barrier (BBB) express and secrete apolipoprotein M (apoM). ApoM is a typical lipocalin containing a hydrophobic binding pocket predominantly carrying Sphingosine-1-Phosphate (S1P). The small signaling molecule S1P is associated with several physiological as well as pathological pathways whereas the role of apoM is less explored. Hepatic apoM acts as a chaperone to transport S1P through the circulation and kidney derived apoM seems to play a role in S1P recovery to prevent urinal loss. Finally, polarized endothelial cells constituting the lining of the BBB express apoM and secrete the protein to the brain as well as to the blood compartment. The review will provide novel insights on apoM and S1P, and its role in hepatic fibrosis, neuroinflammation and BBB integrity.

Low sphingosine-1-phosphate plasma levels are predictive for increased mortality in patients with liver cirrhosis

Background & aim

The association of circulating sphingosine-1-phosphate (S1P), a bioactive lipid involved in various cellular processes, and related metabolites such as sphinganine-1-phosphate (SA1P) and sphingosine (SPH) with mortality in patients with end-stage liver disease is investigated in the presented study. S1P as a bioactive lipid mediator, is involved in several cellular processes, however, in end-stage liver disease its role is not understood.

Methods

The study cohort consisted of 95 patients with end-stage liver disease and available information on one-year outcome. The median MELD (Model for end-stage liver disease) score was 12.41 (Range 6.43–39.63). The quantification of sphingolipids in citrated plasma specimen was performed after methanolic protein precipitation followed by hydrophilic interaction liquid chromatography and tandem mass spectrometric detection.

Results

S1P and SA1P displayed significant correlations with the MELD score. Patients with circulating S1P levels below the lowest tertile (110.68 ng/ml) showed the poorest one-year survival rate of only 57.1%, whereas one-year survival rate in patients with S1P plasma levels above 165.67 ng/ml was 93.8%. In a multivariate cox regression analysis including platelet counts, concentrations of hemoglobin and MELD score, S1P remained a significant predictor for three-month and one-year mortality.

Conclusions

Low plasma S1P concentrations are highly significantly associated with prognosis in end-stage liver disease. This association is independent of the stage of liver disease. Further studies should be performed to investigate S1P, its role in the pathophysiology of liver diseases and its potential for therapeutic interventions.

TGF-β Down-regulates Apolipoprotein M Expression through the TAK-1-JNK-c-Jun Pathway in HepG2 Cells

Apolipoprotein M (apoM) is a relatively novel apolipoprotein that plays pivotal roles in many dyslipidemia-associated diseases; however, its regulatory mechanisms are poorly understood. Many cytokines have been identified that down-regulate apoM expression in HepG2 cells, among which transforming growth factor-β (TGF-β) exerts the most potent effects. In addition, c-Jun, a member of the activated protein 1 (AP-1) family whose activity is modulated by c-Jun N-terminal kinase (JNK), decreases apoM expression at the transcriptional level by binding to the regulatory element in the proximal apoM promoter. In this study, we investigated the molecular mechanisms through which TGF-β decreases the apoM level in HepG2 cells. The results revealed that TGF-β inhibited apoM expression at both the mRNA and protein levels in a dose- and time-dependent manner and that it suppressed apoM secretion. These effects were attenuated by treatment of cells with either SP600125 (JNK inhibitor) or c-Jun siRNA. 5Z-7-oxozeaenol [(a TGF-β-activated kinase 1 (TAK-1) inhibitor)] also attenuated the TGF-β-mediated inhibition of apoM expression and suppressed the activation of JNK and c-Jun. These results have demonstrated that TGF-β suppresses apoM expression through the TAK-1-JNK-c-Jun pathway in HepG2 cells.

Effect of inflammation on HDL structure and function

PURPOSE OF REVIEW

Studies have shown that chronic inflammatory disorders, such as rheumatoid arthritis, systemic lupus erythematosus, and psoriasis are associated with an increased risk of atherosclerotic cardiovascular disease. The mechanism by which inflammation increases cardiovascular disease is likely multifactorial but changes in HDL structure and function that occur during inflammation could play a role.

RECENT FINDINGS

HDL levels decrease with inflammation and there are marked changes in HDL-associated proteins. Serum amyloid A markedly increases whereas apolipoprotein A-I, lecithin:cholesterol acyltransferase, cholesterol ester transfer protein, paraoxonase 1, and apolipoprotein M decrease. The exact mechanism by which inflammation decreases HDL levels is not defined but decreases in apolipoprotein A-I production, increases in serum amyloid A, increases in endothelial lipase and secretory phospholipase A2 activity, and decreases in lecithin:cholesterol acyltransferase activity could all contribute. The changes in HDL induced by inflammation reduce the ability of HDL to participate in reverse cholesterol transport and protect LDL from oxidation.

SUMMARY

During inflammation multiple changes in HDL structure occur leading to alterations in HDL function. In the short term, these changes may be beneficial resulting in an increase in cholesterol in peripheral cells to improve host defense and repair but over the long term these changes may increase the risk of atherosclerosis.

Human plasma lipocalins and serum albumin: Plasma alternative carriers?

Lipocalins are an evolutionarily conserved family of proteins that bind and transport a variety of exogenous and endogenous ligands. Lipocalins share a conserved eight anti-parallel β-sheet structure. Among the different lipocalins identified in humans, α-1-acid glycoprotein (AGP), apolipoprotein D (apoD), apolipoprotein M (apoM), α1-microglobulin (α1-m) and retinol-binding protein (RBP) are plasma proteins. In particular, AGP is the most important transporter for basic and neutral drugs, apoD, apoM, and RBP mainly bind endogenous molecules such as progesterone, pregnenolone, bilirubin, sphingosine-1-phosphate, and retinol, while α1-m binds the heme. Human serum albumin (HSA) is a monomeric all-α protein that binds endogenous and exogenous molecules like fatty acids, heme, and acidic drugs. Changes in the plasmatic levels of lipocalins and HSA are responsible for the onset of pathological conditions associated with an altered drug transport and delivery. This, however, does not necessary result in potential adverse effects in patients because many drugs can bind both HSA and lipocalins, and therefore mutual compensatory binding mechanisms can be hypothesized. Here, molecular and clinical aspects of ligand transport by plasma lipocalins and HSA are reviewed, with special attention to their role as alterative carriers in health and disease.

The role of bile acids in metabolic regulation

Bile acids (BA), long believed to only have lipid-digestive functions, have emerged as novel metabolic modulators. They have important endocrine effects through multiple cytoplasmic as well as nuclear receptors in various organs and tissues. BA affect multiple functions to control energy homeostasis, as well as glucose and lipid metabolism, predominantly by activating the nuclear farnesoid X receptor and the cytoplasmic G protein-coupled BA receptor TGR5 in a variety of tissues. However, BA also are aimed at many other cellular targets in a wide array of organs and cell compartments. Their role in the pathogenesis of diabetes, obesity and other 'diseases of civilization' becomes even more clear. They also interact with the gut microbiome, with important clinical implications, further extending the complexity of their biological functions. Therefore, it is not surprising that BA metabolism is substantially modulated by bariatric surgery, a phenomenon contributing favorably to the therapeutic effects of these surgical procedures. Based on these data, several therapeutic approaches to ameliorate obesity and diabetes have been proposed to affect the cellular targets of BA.