Adipocyte triglyceride lipase expression in human obesity

Increased serum carboxylesterase-1 levels are associated with metabolic dysfunction associated steatotic liver disease and metabolic syndrome in children with obesity

BACKGROUND

Carboxylesterase 1(CES1) is expressed mainly in the liver and adipose tissue and is highly hypothesized to play an essential role in metabolism. Our study aimed to investigate the association between CES1 and metabolic syndrome (MetS) and metabolic dysfunction associated steatotic liver disease (MASLD) in children with obesity in China.

METHODS

This study included 72 children with obesity aged 6-13years (including 25(35%) diagnosed as MetS and 36(50%) diagnosed as MASLD). All subjects were measured in anthropometry, serum level of biochemical parameters related to obesity, circumstance levels of insulin-like growth factor1, adipokines (adiponectin, leptin and growth differentiation factor 15) and CES1.

RESULTS

Higher serum CES1 level were found in the MetS group (P = 0.004) and the MASLD group (P < 0.001) of children with obesity. Serum CES1 levels were positively correlated with alanine aminotransferase, aspartate aminotransferase, triglyceride, cholesterol, low-density lipoprotein cholesterol, GDF15, Leptin and negatively correlated with high-density lipoprotein cholesterol, adiponectin and IGF1. We also found a multivariable logistic regression analysis of MASLD and MetS predicted by CES1 significantly (MASLD P < 0.01, MetS P < 0.05). The combination of CES1, sex, age and BMI Z-score showed a sensitivity and specificity of 92.7% for the identification of MASLD and 78.6% for the identification of MetS. The cutoff for CES1 of MASLD is 56.30 ng/mL and of MetS is 97.79 ng/mL.

CONCLUSIONS

CES1 is associated with an increasing risk of MetS and MASLD and can be established as a biomarker for metabolic syndrome and MASLD of children with obesity.

Glycerol Handling in Paired Visceral and Subcutaneous Adipose Tissues in Women with Normal Weight and Upper-Body Obesity

In adipose tissue, reduced expression of the glycerol channel aquaporin 7 (AQP7) has been associated with increased accumulation of triglyceride. The present study determines the relative protein abundances of lipolytic enzymes, AQP7, and cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) in paired mesenteric and omental visceral adipose tissue (VAT) and abdominal and femoral subcutaneous adipose tissue (SAT) in women with either normal weight or upper-body obesity. No differences in the expression of hormone-sensitive lipase (HSL) or AQP7 were found between the two groups in the four depots. The expression of adipocyte triglyceride lipase (ATGL) and HSL were higher in omental VAT and femoral SAT than in mesenteric VAT in both groups of women. Similarly, AQP7 expression was higher in omental VAT than in mesenteric VAT. The expression of PEPCK-C was lower in omental VAT than in femoral SAT. No correlation between the expression of AQP7 and the mean adipocyte size was observed; however, the expression of PEPCK-C positively correlated with the mean adipocyte size. In conclusion, a depot-specific protein expression pattern was found for ATGL, HSL, AQP7, and PEPCK-C. The expression pattern supports that the regulation of AQP7 protein expression is at least in part linked to the lipolytic rate. Furthermore, the results support that the synthesis of glycerol-3-phosphate via glyceroneogenesis contributes to regulating triglyceride accumulation in white adipose tissue in women.

Anti-Obesity Properties of Blackberries Fermented with L. plantarum JBMI F5 via Suppression of Adipogenesis Signaling Mechanisms

Blackberries (Rubus fruticosus), which are known to include a variety of bioactive substances, have been extensively studied for their antioxidant properties. Blackberries possess multiple health beneficial effects, including anti-inflammation, anti-atherosclerosis, anti-tumor and immunomodulatory activity. However, the potential biological effects and precise molecular mechanisms of the fermented extracts remain largely unexplored. In this research, we demonstrate the effect of blackberries fermented with Lactobacillus for addressing obesity. We investigated the effect of blackberries fermented by Lactobacillus on mice fed a high-fat (60% kcal) diet for 12 weeks. Fermented blackberry administration reduced the body weight and epididymal fat caused by a high-fat diet compared to the obese group. The triglyceride and total cholesterol, which are blood lipid indicators, and the levels of leptin, which is an insulin resistance indicator, were significantly increased in the obese group but were significantly decreased in the fermented blackberries-treated group. Additionally, the expression of adipogenesis marker proteins, such as CEBPα, PPAR-γ and SREBP-1, was significantly increased in the obese group, whereas it was decreased in the fermented blackberries-treated group. These results suggest that fermented blackberries have a protective effect against high-fat-diet-induced obesity by inhibiting adipogenesis and are a potential candidate for the treatment of obesity.

Role of carboxylesterase and arylacetamide deacetylase in drug metabolism, physiology, and pathology

Carboxylesterases (CES1 and CES2) and arylacetamide deacetylase (AADAC), which are expressed primarily in the liver and/or gastrointestinal tract, hydrolyze drugs containing ester and amide bonds in their chemical structure. These enzymes often catalyze the conversion of prodrugs, including the COVID-19 drugs remdesivir and molnupiravir, to their pharmacologically active forms. Information on the substrate specificity and inhibitory properties of these enzymes, which would be useful for drug development and toxicity avoidance, has accumulated. Recently,in vitroandin vivostudies have shown that these enzymes are involved not only in drug hydrolysis but also in lipid metabolism. CES1 and CES2 are capable of hydrolyzing triacylglycerol, and the deletion of their orthologous genes in mice has been associated with impaired lipid metabolism and hepatic steatosis. Adeno-associated virus-mediated human CES overexpression decreases hepatic triacylglycerol levels and increases fatty acid oxidation in mice. It has also been shown that overexpression of CES enzymes or AADAC in cultured cells suppresses the intracellular accumulation of triacylglycerol. Recent reports indicate that AADAC can be up- or downregulated in tumors of various organs, and its varied expression is associated with poor prognosis in patients with cancer. Thus, CES and AADAC not only determine drug efficacy and toxicity but are also involved in pathophysiology. This review summarizes recent findings on the roles of CES and AADAC in drug metabolism, physiology, and pathology.

PNPLA-mediated lipid hydrolysis and transacylation - At the intersection of catabolism and anabolism

Patatin-like phospholipase domain containing proteins (PNPLAs) play diverse roles in lipid metabolism. In this review, we focus on the enzymatic properties and predicted 3D structures of PNPLA1-5. PNPLA2-4 exert both catabolic and anabolic functions. Whereas PNPLA1 is predominantly expressed in the epidermis and involved in sphingolipid biosynthesis, PNPLA2 and 4 are ubiquitously expressed and exhibit several enzymatic activities, including hydrolysis and transacylation of various (glycero-)lipid species. This review summarizes known biological roles for PNPLA-mediated hydrolysis and transacylation reactions and highlights open questions concerning their physiological function.

Adipose triglyceride lipase gene expression in peripheral blood mononuclear cells of subjects with obesity and its association with insulin resistance, inflammation and lipid accumulation in liver

Introduction

Adipose triglyceride lipase (ATGL) is a crucial enzyme responsible for the release of fatty acids from various tissues. The expression of ATGL is regulated by insulin and this enzyme is linked to Insulin resistance (IR). On the other hand, ATGL-mediated lipolysis is connected to macrophage function and thus, ATGL is involved in inflammation and the pathogenesis of lipid-related disorders. This study aimed to investigate the correlation between ATGL, obesity, Metabolic Syndrome (MetS), and inflammation.

Methods

A total of 100 participants, including 50 individuals with obesity and 50 healthy participants, were recruited for this study and underwent comprehensive clinical evaluations. Blood samples were collected to measure plasma lipid profiles, glycemic indices, and liver function tests. Additionally, peripheral blood mononuclear cells (PBMCs) were isolated and used for the assessment of the gene expression of ATGL, using real-time PCR. Furthermore, PBMCs were cultured and exposed to lipopolysaccharides (LPS) with simultaneous ATGL inhibition, and the gene expression of inflammatory cytokines, along with the secretion of prostaglandin E2 (PGE2), were measured.

Results

The gene expression of ATGL was significantly elevated in PBMCs obtained from participants with obesity and was particularly higher in those diagnosed with MetS. It exhibited a correlation with insulin levels and Homeostatic Model Assessment for IR (HOMA-IR), and it was associated with lipid accumulation in the liver. Stimulation with LPS increased ATGL expression in PBMCs, while inhibition of ATGL attenuated the inflammatory responses induced by LPS.

Conclusions

Obesity and MetS were associated with dysregulation of ATGL. ATGL might play a role in the upregulation of inflammatory cytokines and act as a significant contributor to the development of metabolic abnormalities related to obesity.

Anti-Obesity Effects of SPY Fermented with Lactobacillus rhamnosus BST-L.601 via Suppression of Adipogenesis and Lipogenesis in High-Fat Diet-Induced Obese Mice

In this research, the potential anti-obesity efficacy of Lactobacillus rhamnosus BST-L.601 and its fermented product (named SPY) with mashed sweet potato paste were investigated using 3T3-L1 preadipocytes and high-fat diet (HD)-induced obese mice. SPY (0-0.5 mg/mL) dose-dependently and significantly reduced lipid accumulation and TG content and the expression of adipogenic markers (C/EBPα, PPAR-γ, and aP2) and fatty acid synthetic pathway proteins (ACC and FAS) in 3T3-L1 adipocytes, demonstrating that SPY suppresses adipocyte differentiation and lipogenesis. Oral administration of SPY (4 × 10⁷ CFU/kg body weight) to HD-induced obese mice for 12 weeks significantly reduced the body and liver weight, the size of adipocytes, and the weight of epididymal, visceral, and subcutaneous fat tissues. SPY was more effective in decreasing body weight gain in HD mice than in treatment with BST-L.601 alone. Administration of SPY or BST-L.601 also reduced the serum level of total cholesterol and LDL cholesterol and leptin secretion at a similar level. These results revealed that both SPY and BST-L.601 effectively suppress HD-induced adipogenesis and lipogenesis, suggesting that these materials would be useful in the functional foods industry to ameliorate and/or prevent obesity.

Genome-wide association study of a lipedema phenotype among women in the UK Biobank identifies multiple genetic risk factors

Lipedema is a common disorder characterized by excessive deposition of subcutaneous adipose tissue (SAT) in the legs, hips, and buttocks, mainly occurring in adult women. Although it appears to be heritable, no specific genes have yet been identified. To identify potential genetic risk factors for lipedema, we used bioelectrical impedance analysis and anthropometric data from the UK Biobank to identify women with and without a lipedema phenotype. Specifically, we identified women with both a high percentage of fat in the lower limbs and a relatively small waist, adjusting for hip circumference. We performed a genome-wide association study (GWAS) for this phenotype, and performed multiple sensitivity GWAS. In an independent case/control study of lipedema based on strict clinical criteria, we attempted to replicate our top hits. We identified 18 significant loci (p < 5 × 10-9), several of which have previously been identified in GWAS of waist-to-hip ratio with larger effects in women. Two loci (VEGFA and GRB14-COBLL1) were significantly associated with lipedema in the independent replication study. Follow-up analyses suggest an enrichment of genes expressed in blood vessels and adipose tissue, among other tissues. Our findings provide a starting point towards better understanding the genetic and physiological basis of lipedema.

FABP4 Expression in Subcutaneous Adipose Tissue Is Independently Associated with Circulating Triglycerides in Obesity

Hypertriglyceridemia (HTG) has been associated with an increased risk of pancreatitis and cardiovascular disease. Adipose tissue plays a major role in lipid metabolism, mobilization and distribution. We have compared the histological and transcriptomic profiles of the subcutaneous (SAT) and visceral (VAT) adipose tissues from subjects with severe obesity undergoing bariatric surgery with (Ob-HTG, n = 37) and without HTG (Ob-NTG, n = 67). Mean age and BMI were 51.87 ± 11.21 years, 45.78 ± 6.96 kg/m² and 50.03 ± 10.17 years, 44.04 ± 4.69 kg/m², respectively. The Ob-HTG group showed higher levels of glycosylated hemoglobin, fasting plasma glucose, high-sensitivity C-reactive protein and prevalence of hypertension. The degree of fibrosis was increased by 14% in SAT from the Ob-HTG group (p = 0.028), while adipocyte size distribution was comparable. Twenty genes were found differentially expressed in SAT and VAT between study groups. Among them, only SAT expression of FABP4 resulted significantly associated with circulating triglyceride levels after adjusting for other covariates and independently explained 5% of the variance in triglyceride levels in the combined model. This relationship was not found in the cohort of lean or overweight patients with normotriglyceridemia (non-Ob, n = 21). These results emphasize the contribution of SAT to triglyceride concentrations in obesity and indicate that FABP4 may be a potential drug target for the treatment of HTG.

Approaches to Measuring the Activity of Major Lipolytic and Lipogenic Enzymes In Vitro and Ex Vivo

Since the 1950s, one of the goals of adipose tissue research has been to determine lipolytic and lipogenic activity as the primary metabolic pathways affecting adipocyte health and size and thus representing potential therapeutic targets for the treatment of obesity and associated diseases. Nowadays, there is a relatively large number of methods to measure the activity of these pathways and involved enzymes, but their applicability to different biological samples is variable. Here, we review the characteristics of mean lipogenic and lipolytic enzymes, their inhibitors, and available methodologies for assessing their activity, and comment on the advantages and disadvantages of these methodologies and their applicability in vivo, ex vivo, and in vitro, i.e., in cells, organs and their respective extracts, with the emphasis on adipocytes and adipose tissue.

Emerging role of carboxylesterases in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is increasingly recognized as a global public health problem. Carboxylesterases (CESs), as potential influencing factors of NAFLD, are very important to improve clinical outcomes. This review aims to deeply understand the role of CESs in the progression of NAFLD and proposes that CESs can be used as potential targets for NAFLD treatment. We first introduced CESs and analyzed the relationship between CESs and hepatic lipid metabolism and inflammation. Then, we further reviewed the regulation of nuclear receptors on CESs, including PXR, CAR, PPARα, HNF4α and FXR, which may influence the progression of NAFLD. Finally, we evaluated the advantages and disadvantages of existing NAFLD animal models and summarized the application of CES-related animal models in NAFLD research. In general, this review provides an overview of the relationship between CESs and NAFLD and discusses the role and potential value of CESs in the treatment and prevention of NAFLD.

α-Linolenic acid rich-chia seed modulates visceral adipose tissue collagen deposition, lipolytic enzymes expression, insulin signaling and GLUT-4 levels in a diet-induced adiposity rodent model

Given obesity and its associated metabolic disorders have reached epidemic proportions, the study of therapeutic strategies targeting white adipose tissue (WAT) are of main research interest. We previously shown that α-linolenic acid-rich chia seed was able to ameliorate a wide range of metabolic disorders including body fat accretion in sucrose-rich diet (SRD)-fed rats, an experimental model of visceral adiposity and insulin resistance. However, the mechanisms involved are not fully clarified. The aim of this study was to evaluate the effect of chia seed administration upon WAT remodeling and key enzymes that controls lipolysis, insulin signaling (tAKT, pAKT), and GLUT-4 levels in different visceral fat pad depots (epididymal -eWAT- and retroperitoneal -rWAT- adipose tissues) of SRD-fed rats. Results showed that chia seed reduces adipocytes hypertrophy, the increased lipid content and collagen deposition in both WAT. These changes were accompanied by a significant reduction of HSL and ATGL protein levels in eWAT and HSL protein levels in rWAT. Moreover, chia seed restored the altered expression pattern of the pAKT observed in SRD-fed rats, and modulated GLUT-4 levels. Chia seed could be a dietary intervention of great relevance with potential beneficial effects in the management of body fat excess and WAT function.

Copy Number Variation Analysis Increases the Number of Candidate Loci Associated with Pediatric Obesity

BACKGROUND/AIMS

Obesity is a multifactorial disease caused by the interaction of genetic, environmental, and behavioral factors. Currently, only a small number of obese children undergo genetic analysis, usually when obesity is associated with dysmorphic features. The aim of this study was to identify genomic rearrangement causing obesity.

METHODS

We analyzed the DNA of children and adolescents by single-nucleotide polymorphism-array (platform CytoScan HD, Affymetrix). Patients included in this study were obese with dysmorphic features and/or intellectual disabilities and/or neuropsychomotor signs.

RESULTS

Ninety-four children and adolescents with obesity (9.25 ± 4.04 years old, 60 males) were enrolled in the study. Dysmorphic features were found in 64 out of 94 subjects (68.1%), intellectual disability was found in 23 subjects (24.5%), and other neuropsychomotor signs in 31 (32.9%). Copy number variations (CNVs) were identified in 43 out of 94 patients (45.7%): among these 14 subjects showed at least 1 deletion, 22 duplication, whereas 7 patients showed both deletion and duplication. In 20 subjects (13 males), CNVs were linked or possibly related with obesity; in 23 subjects, this correlation cannot be inferred.

CONCLUSION

A genetic origin of obesity was detected in about half of our obese children and adolescents with associated dysmorphic features and/or intellectual disability and/or neuropsychomotor signs. In these children, array-CGH analysis can be useful to identify causative genetic mutations, with consequent advantage in therapeutic management and follow-up of these patients.

Elevated S-adenosylhomocysteine induces adipocyte dysfunction to promote alcohol-associated liver steatosis

It has been previously shown that chronic ethanol administration-induced increase in adipose tissue lipolysis and reduction in the secretion of protective adipokines collectively contribute to alcohol-associated liver disease (ALD) pathogenesis. Further studies have revealed that increased adipose S-adenosylhomocysteine (SAH) levels generate methylation defects that promote lipolysis. Here, we hypothesized that increased intracellular SAH alone causes additional related pathological changes in adipose tissue as seen with alcohol administration. To test this, we used 3-deazaadenosine (DZA), which selectively elevates intracellular SAH levels by blocking its hydrolysis. Fully differentiated 3T3-L1 adipocytes were treated in vitro for 48 h with DZA and analysed for lipolysis, adipokine release and differentiation status. DZA treatment enhanced adipocyte lipolysis, as judged by lower levels of intracellular triglycerides, reduced lipid droplet sizes and higher levels of glycerol and free fatty acids released into the culture medium. These findings coincided with activation of both adipose triglyceride lipase and hormone sensitive lipase. DZA treatment also significantly reduced adipocyte differentiation factors, impaired adiponectin and leptin secretion but increased release of pro-inflammatory cytokines, IL-6, TNF and MCP-1. Together, our results demonstrate that elevation of intracellular SAH alone by DZA treatment of 3T3-L1 adipocytes induces lipolysis and dysregulates adipokine secretion. Selective elevation of intracellular SAH by DZA treatment mimics ethanol's effects and induces adipose dysfunction. We conclude that alcohol-induced elevations in adipose SAH levels contribute to the pathogenesis and progression of ALD.

Copy number variation in the CES1 gene and the risk of non-alcoholic fatty liver in a Chinese Han population

A recent genome-wide copy number variations (CNVs) scan identified a 16q12.2 deletion that included the carboxylesterase 1 (CES1) gene, which is important in the metabolism of fatty acids and cholesterol. We aimed to investigate whether CES1 CNVs was associated with susceptibility to non-alcoholic fatty liver disease (NAFLD) in a Chinese Han population. A case-control study was conducted among 303 patients diagnosed with NAFLD and 303 age (± 5) and sex-matched controls from the Affiliated Nanping First Hospital of Fujian Medical University in China. The copy numbers of CES1 were measured using TaqMan quantitative real-time polymerase chain reaction (qPCR) and serum CES1 was measured using enzyme-linked immunosorbent assays. The Chi-squared test and a logistic regression model were used to evaluate the association between CES1 CNVs and NAFLD susceptibility. The distribution of CES1 CNVs showed a higher frequency of CNVs loss (< 2) among patients; however, the difference was not significant (P = 0.05). After controlling for other known or suspected risk factors for NAFLD, CES1 CNVs loss was significantly associated with greater risk of NAFLD (adjusted OR = 2.75, 95% CI 1.30-5.85, P = 0.01); while CES1 CNVs gain (> 2) was not. There was a suggestion of an association between increased CES1 serum protein levels and CNVs losses among cases, although this was not statistically significant (P = 0.07). Copy number losses (< 2) of CES1 contribute to susceptibility to NAFLD in the Chinese Han population.

Pig Liver Esterases Hydrolyze Endocannabinoids and Promote Inflammatory Response

Endocannabinoids are endogenous ligands of cannabinoid receptors and activation of these receptors has strong physiological and pathological significance. Structurally, endocannabinoids are esters (e.g., 2-arachidonoylglycerol, 2-AG) or amides (e.g., N-arachidonoylethanolamine, AEA). Hydrolysis of these compounds yields arachidonic acid (AA), a major precursor of proinflammatory mediators such as prostaglandin E₂. Carboxylesterases are known to hydrolyze esters and amides with high efficiency. CES1, a human carboxylesterase, has been shown to hydrolyze 2-AG, and shares a high sequence identity with pig carboxylesterases: PLE1 and PLE6 (pig liver esterase). The present study was designed to test the hypothesis that PLE1 and PLE6 hydrolyze endocannabinoids and promote inflammatory response. Consistent with the hypothesis, purified PLE1 and PLE6 efficaciously hydrolyzed 2-AG and AEA. PLE6 was 40-fold and 3-fold as active as PLE1 towards 2-AG and AEA, respectively. In addition, both PLE1 and PLE6 were highly sensitive to bis(4-nitrophenyl) phosphate (BNPP), an aryl phosphodiester known to predominately inhibit carboxylesterases. Based on the study with BNPP, PLEs contributed to the hydrolysis of 2-AG by 53.4 to 88.4% among various organs and cells. Critically, exogenous addition or transfection of PLE6 increased the expression and secretion of proinflammatory cytokines in response to the immunostimulant lipopolysaccharide (LPS). This increase was recapitulated in cocultured alveolar macrophages and PLE6 transfected cells in transwells. Finally, BNPP reduced inflammation trigged by LPS accompanied by reduced formation of AA and proinflammatory mediators. These findings define an innovative connection: PLE-endocannabinoid-inflammation. This mechanistic connection signifies critical roles of carboxylesterases in pathophysiological processes related to the metabolism of endocannabinoids.

Chemoproteomics-Enabled De Novo Discovery of Photoswitchable Carboxylesterase Inhibitors for Optically Controlled Drug Metabolism

Herein, we report arylazopyrazole ureas and sulfones as a novel class of photoswitchable serine hydrolase inhibitors and present a chemoproteomic platform for rapid discovery of optically controlled serine hydrolase targets in complex proteomes. Specifically, we identify highly potent and selective photoswitchable inhibitors of the drug-metabolizing enzymes carboxylesterases 1 and 2 and demonstrate their pharmacological application by optically controlling the metabolism of the immunosuppressant drug mycophenolate mofetil. Collectively, this proof-of-concept study provides a first example of photopharmacological tools to optically control drug metabolism by modulating the activity of a metabolizing enzyme. Our arylazopyrazole ureas and sulfones offer synthetically accessible scaffolds that can be expanded to identify specific photoswitchable inhibitors for other serine hydrolases, including lipases, peptidases, and proteases. Our chemoproteomic platform can be applied to other photoswitches and scaffolds to achieve optical control over diverse protein classes.

CD10 marks non-canonical PPARγ-independent adipocyte maturation and browning potential of adipose-derived stem cells

BACKGROUND

Effective stem cell therapy is dependent on the stem cell quality that is determined by their differentiation potential, impairment of which leads to poor engraftment and survival into the target cells. However, limitations in our understanding and the lack of reliable markers that can predict their maturation efficacies have hindered the development of stem cells as an effective therapeutic strategy. Our previous study identified CD10, a pro-adipogenic, depot-specific prospective cell surface marker of human adipose-derived stem cells (ASCs). Here, we aim to determine if CD10 can be used as a prospective marker to predict mature adipocyte quality and play a direct role in adipocyte maturation.

METHODS

We first generated 14 primary human subject-derived ASCs and stable immortalized CD10 knockdown and overexpression lines for 4 subjects by the lentiviral transduction system. To evaluate the role of CD10 in adipogenesis, the adipogenic potential of the human subject samples were scored against their respective CD10 transcript levels. Assessment of UCP1 expression levels was performed to correlate CD10 levels to the browning potential of mature ASCs. Quantitative polymerase chain reaction (qPCR) and Western blot analysis were performed to determine CD10-dependent regulation of various targets. Seahorse analysis of oxidative metabolism and lipolysis assay were studied. Lastly, as a proof-of-concept study, we used CD10 as a prospective marker for screening nuclear receptor ligands library.

RESULTS

We identified intrinsic CD10 levels as a positive determinant of adipocyte maturation as well as browning potential of ASCs. Interestingly, CD10 regulates ASC's adipogenic maturation non-canonically by modulating endogenous lipolysis without affecting the classical peroxisome proliferator-activated receptor gamma (PPARγ)-dependent adipogenic pathways. Furthermore, our CD10-mediated screening analysis identified dexamethasone and retinoic acid as stimulator and inhibitor of adipogenesis, respectively, indicating CD10 as a useful biomarker for pro-adipogenic drug screening.

CONCLUSION

Overall, we establish CD10 as a functionally relevant ASC biomarker, which may be a prerequisite to identify high-quality cell populations for improving metabolic diseases.

Cardiovascular Risk Factors and Differential Transcriptomic Profile of the Subcutaneous and Visceral Adipose Tissue and Their Resident Stem Cells

Background: The increase in the incidence of obesity and obesity-related cardiovascular risk factors (CVRFs) over the last decades has brought attention on adipose tissue (AT) pathobiology. The expansion of AT is associated with the development of new vasculature needed to perfuse the tissue; however, not all fat depots have the same ability to induce angiogenesis that requires recruitment of their own endothelial cells. In this study we have investigated the effect of different CVRFs, on the angiogenic capacity of the subcutaneous (SAT) and visceral (VAT) adipose tissue and on the function of their mesenchymal cell reservoir. Methods: A transcriptomic approach was used to compare the different angiogenic and inflammatory profiles of the subcutaneous and visceral fat depots from individuals with obesity, as well as their resident stem cells (ASCs). Influence of other risk factors on fat composition was also measured. Finally, the microvesicles (MVs) released by ASCs were isolated and their regenerative potential analyzed by molecular and cellular methodologies. Results: Obesity decreases the angiogenic capacity of AT. There are differences between SAT and VAT; from the 21 angiogenic-related genes analyzed, only three were decreased in SAT compared with those decreased in VAT. ASCs isolated from both fat depots showed significant differences; there was a significant up-regulation of the VEGF-pathway on visceral derived ASCs. ASCs release MVs that stimulate endothelial cell migration and angiogenic capacity. Conclusions: In patients with obesity, SAT expresses a greater number of angiogenic molecules than VAT, independent of the presence of other CVRFs.

Inhibition of miR-27b Regulates Lipid Metabolism in Skeletal Muscle of Obese Rats During Hypoxic Exercise by Increasing PPARγ Expression

Hypoxic exercise may represent a novel therapeutic strategy to reduce and prevent obesity through the regulation of lipid metabolism. During hypoxic exercise, the targeting of peroxisome proliferator-activated receptor gamma (PPARγ) by miR-27b has been proposed to be one of the mechanisms involved in the modulation of lipid metabolism. We have previously shown that miR-27b can repress PPARγ and lipid metabolism-associated factors, thereby affecting lipid metabolism during hypoxic exercise in a rat model of obesity. In the current study, we aimed to confirm the role of miR-27b in the regulation of lipid metabolism. First, miR-27b expression was either upregulated or downregulated through the injection of adeno-associated virus (AAV) 9 containing a miR-27b expression cassette or miR-27b-3p inhibitor, respectively, into the right gastrocnemius muscle of obese rats. The rats were then subjected to a 4-week program of hypoxic exercise, and a series of parameters related to lipid metabolism were systematically evaluated, including body composition, blood lipid levels, miR-27b RNA levels, and mRNA and protein levels of PPARγ and those of its downstream lipid metabolism-associated factors. No significant differences were found in body composition between rats expressing different levels of miR-27b. However, regarding blood lipids, miR-27b overexpression led to increased concentrations of triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and free fatty acids (FFAs), while inhibition of miR-27b decreased the total cholesterol (TC) level and increased that of high-density lipoprotein cholesterol (HDL-C). At the mRNA level, miR-27b overexpression downregulated the expression of Pparγ, but upregulated that of lipid metabolism-associated factors such as heart-type fatty acid-binding protein (H-FABP), fatty acid transport protein 1 (FATP1), adipose triglyceride lipase (ATGL), and lipoprotein lipase (LPL), whereas miR-27b inhibition elicited the opposite effect; however, inhibition of miR-27b led to elevated cholesterol 7 alpha-hydroxylase (CYP7A1) and fatty acid translocase 36 (CD36) levels. Similarly, at the protein level, miR-27b overexpression promoted a decrease in the concentration of PPARγ, whereas miR-27b inhibition led to an increase in PPARγ levels, as well as those of CYP7A1, CD36, ATGL, and LPL. Overall, our results indicated that hypoxic exercise regulates lipid metabolism via the miR-27b/PPARγ pathway and modulates ATGL and LPL expression through inducing their post-transcriptional modifications.

Assessment of Periprostatic and Subcutaneous Adipose Tissue Lipolysis and Adipocyte Size from Men with Localized Prostate Cancer

The prostate is surrounded by periprostatic adipose tissue (PPAT), the thickness of which has been associated with more aggressive prostate cancer (PCa). There are limited data regarding the functional characteristics of PPAT, how it compares to subcutaneous adipose tissue (SAT), and whether in a setting of localized PCa, these traits are altered by obesity or disease aggressiveness. PPAT and SAT were collected from 60 men (age: 42–78 years, BMI: 21.3–35.6 kg/m²) undergoing total prostatectomy for PCa. Compared to SAT, adipocytes in PPAT were smaller, had the same basal rates of fatty acid release (lipolysis) yet released less polyunsaturated fatty acid species, and were more sensitive to isoproterenol-stimulated lipolysis. Basal lipolysis of PPAT was increased in men diagnosed with less aggressive PCa (Gleason score (GS) ≤ 3 + 4) compared to men with more aggressive PCa (GS ≥ 4 + 3) but no other measured adipocyte parameters related to PCa aggressiveness. Likewise, there was no difference in PPAT lipid biology between lean and obese men. In conclusion, lipid biological features of PPAT do differ from SAT; however, we did not observe any meaningful difference in ex vivo PPAT biology that is associated with PCa aggressiveness or obesity. As such, our findings do not support a relationship between altered PCa behavior in obese men and the metabolic reprogramming of PPAT.

Iron deficiency attenuates catecholamine‑stimulated lipolysis via downregulation of lipolysis‑related proteins and glucose utilization in 3T3‑L1 adipocytes

Iron deficiency has been associated with obesity and related metabolic disorders. The aim of the present study was to evaluate the effect of iron deficiency on fat metabolism, particularly regarding the lipolytic activity, lipolysis‑related protein expression, and glucose utilization of adipocytes. Differentiated 3T3‑L1 adipocytes were incubated with an iron chelator, deferoxamine mesylate (DFO), for 48 h. Subsequently, basal and isoproterenol‑stimulated lipolytic activities, the proteins involved in lipolysis and glucose utilization were compared with a control (CON). The results revealed that treatment with DFO significantly decreased the free iron content but did not affect total protein and lipid contents in adipocytes. Iron deprivation caused a significant reduction in isoproterenol‑stimulated lipolysis, but not basal lipolysis. Lipolysis‑related proteins, including perilipin A, adipose triglyceride lipase, hormone sensitive lipase and comparative gene identification‑58, were decreased in the DFO compared with the CON group. Furthermore, glucose utilization, a major precursor of 3‑glycerol phosphate for micro‑lipid droplet synthesis during lipolysis and the expression of glucose transporter (GLUT) 4 were significantly lower in the DFO group when compared with the CON group. However, hypoxia‑inducible factor‑1α and GLUT1 expressions were upregulated in DFO‑treated adipocytes. In conclusion, the results indicated that low iron availability attenuated catecholamine‑stimulated lipolysis by downregulating lipolytic enzymes and glucose utilization in 3T3‑L1 adipocytes.

Body condition of late pregnant gilts affects the expression of selected adipokines and their receptors in mammary fat and backfat tissues

The impact of body condition in late gestating gilts on gene expression of selected adipokines and their receptors in backfat and mammary fat tissues was studied. The presence of associations between mammary gland composition variables and the mRNA abundance of selected genes and serum concentrations of adiponectin and leptin was also investigated. A total of 45 gilts were selected at mating based on their backfat depth and were allocated to three groups: (1) low backfat (LBF; 12-15 mm; n = 14), (2) medium backfat (MBF; 17-19 mm; n = 15), and (3) high backfat (HBF; 22-26 mm; n = 16). Gilts were fed different amounts of a conventional diet to maintain differences in backfat depth throughout the gestation period. Blood samples were collected at day 109 of gestation to measure adiponectin and leptin serum concentrations. Gilts were slaughtered on day 110 of gestation, and mammary glands were collected to determine mammary composition. Mammary fat and backfat tissues were also sampled to measure the mRNA abundance of selected genes. In mammary fat tissue, there was an effect of body condition on the prolactin (PRL; P = 0.01), adiponutrin (PNPLA3; P < 0.10), and prolactin receptor long form (PRLR-LF; P < 0.10) genes. There was a greater PRL mRNA abundance in mammary fat tissue from HBF than LBF or MBF gilts (P < 0.05). The PNPLA3 mRNA abundance was lower in HBF than in MBF gilts (P < 0.05), and that of PRLR-LF was lower in LBF than in HBF gilts (P < 0.05). In backfat, body condition affected the mRNA abundance of leptin (P < 0.05) and PNPLA3 (P < 0.01), with the greatest expression levels being observed in HBF gilts for both genes. Association analyses suggest a detrimental effect of high circulating leptin concentrations on gilts mammary development, as reflected by the negative correlations between serum leptin and protein percent (r = -0.66, P < 0.01), and concentrations of DNA (r = -0.62, P < 0.01) and RNA (r = -0.60, P < 0.01) in mammary parenchyma. Current results show that body condition of gilts at the end of gestation can affect the expression of adipokines in mammary fat and backfat tissues, with a different regulation of transcript abundance being observed in these two fat depots. Results also suggest that circulating leptin is strongly associated with mammary gland composition of late pregnant gilts, whereas locally synthesized leptin from mammary fat tissue is not.

Genome-Wide and Abdominal MRI Data Provide Evidence That a Genetically Determined Favorable Adiposity Phenotype Is Characterized by Lower Ectopic Liver Fat and Lower Risk of Type 2 Diabetes, Heart Disease, and Hypertension

Recent genetic studies have identified alleles associated with opposite effects on adiposity and risk of type 2 diabetes. We aimed to identify more of these variants and test the hypothesis that such favorable adiposity alleles are associated with higher subcutaneous fat and lower ectopic fat. We combined MRI data with genome-wide association studies of body fat percentage (%) and metabolic traits. We report 14 alleles, including 7 newly characterized alleles, associated with higher adiposity but a favorable metabolic profile. Consistent with previous studies, individuals carrying more favorable adiposity alleles had higher body fat % and higher BMI but lower risk of type 2 diabetes, heart disease, and hypertension. These individuals also had higher subcutaneous fat but lower liver fat and a lower visceral-to-subcutaneous adipose tissue ratio. Individual alleles associated with higher body fat % but lower liver fat and lower risk of type 2 diabetes included those in PPARG, GRB14, and IRS1, whereas the allele in ANKRD55 was paradoxically associated with higher visceral fat but lower risk of type 2 diabetes. Most identified favorable adiposity alleles are associated with higher subcutaneous and lower liver fat, a mechanism consistent with the beneficial effects of storing excess triglycerides in metabolically low-risk depots.

Update on the synergistic effect of HSL and insulin in the treatment of metabolic disorders

Hormone-sensitive lipase (HSL) is one of the three lipases in adipose tissue present during periods of energy demand. HSL is tightly controlled by insulin regulation via the central and peripheral systems. The suppressive effects of insulin on HSL are also associated with complex crosstalk with other pathways in the metabolic network. Because impaired insulin action is the driving force behind the pathogenesis of diabetes and other metabolic complications, elucidation of the intricate relationships between HSL and insulin may provide an in-depth understanding of these pandemic diseases and potentially identify strategies to inhibit disease development. Insulin not only differentially regulates HSL isoform transcription but also post-transcriptionally affects HSL phosphorylation by stimulating PKA and endothelin (ET-1), and controls its expression indirectly via regulating the activity of growth hormone (GH). In addition, a rapid elevation of HSL levels was detected after insulin injection in patients, which suggests that the inhibitory effects of insulin on HSL can be overridden by insulin-induced hypoglycemia. Conversely, individuals with hereditary HSL deficiency, and animals with experimental HSL deletion, showed major disruptions in mRNA/protein expression in insulin signaling pathways, ultimately leading to insulin resistance, diabetes, and fatty liver. Notably, HSL inactivation could cause insulin-independent fatty liver, while insulin resistance induced by HSL deficiency may further aggravate disease progression. The common beliefs that HSL is the overall rate-limiting enzyme in lipolysis and that insulin is an inhibitor of HSL have been challenged by recent discoveries; therefore, a renewed examination of their relationships is required. In this review, by analyzing current data related to the role of, and mutual regulation between, HSL and insulin and discussing unanswered questions and disparities in different lines of studies, the authors intend to shed light on our understanding of lipid metabolism and provide a rational basis for future research in drug development.

Structural and chemical biology of deacetylases for carbohydrates, proteins, small molecules and histones

Deacetylation is the removal of an acetyl group and occurs on a plethora of targets and for a wide range of biological reasons. Several pathogens deacetylate their surface carbohydrates to evade immune response or to support biofilm formation. Furthermore, dynamic acetylation/deacetylation cycles govern processes from chromatin remodeling to posttranslational modifications that compete with phosphorylation. Acetylation usually occurs on nitrogen and oxygen atoms and are referred to as N- and O-acetylation, respectively. This review discusses the structural prerequisites that enzymes must have to catalyze the deacetylation reaction, and how they adapted by formation of specific substrate and metal binding sites.

Microcephaly/Trigonocephaly, Intellectual Disability, Autism Spectrum Disorder, and Atypical Dysmorphic Features in a Boy with Xp22.31 Duplication

The Xp22.31 segment of the short arm of the human X chromosome is a region of high instability with frequent rearrangement. The duplication of this region has been found in healthy people as well as in individuals with varying degrees of neurological impairment. The incidence has been reported in a range of 0.4-0.44% of the patients with neurological impairment. Moreover, there is evidence that Xp22.31 duplication may cause a common phenotype including developmental delay, intellectual disability, feeding difficulty, autistic spectrum disorders, hypotonia, seizures, and talipes. We report on a patient with microcephaly and trigonocephaly, moderate intellectual disability, speech and language delay, and poor social interaction in addition to minor but atypical dysmorphic features. This report provides further insight into the pathogenicity of the Xp22.31 duplication by extending knowledge of its clinical features. This case, in association with those reported in the literature, indicates that the Xp22.31 duplication may contribute to cause pathological phenotypes with minor facial dysmorphisms, microcephaly, and intellectual disability as main features.

Effects of fetal calf serum on cGMP pathway and oocyte lipid metabolism in vitro

Intracellular levels of cyclic nucleotides, such as cGMP, are involved in the regulation of adipocyte lipolysis. Cumulus-oocyte complexes (COCs) express enzymes that both synthesise (guanylate cyclase) and degrade (phosphodiesterase (PDE) 5A) cGMP. Because serum interferes with lipid metabolism, its effects on the cGMP pathway and lipid content in bovine COCs were examined. COCs were matured in medium containing fetal calf serum (FCS; 2% or 10%) or 0.4% bovine serum albumin (BSA; control). At both 2% and 10%, FCS decreased cGMP levels in COCs compared with BSA (0.64 and 1.04 vs 9.46 fmol per COC respectively; P<0.05) and decreased transcript levels of guanylate cyclase 1, soluble, beta 3 (GUCY1B3), whereas PDE5A levels were increased. FCS also affected the expression of genes related to lipolysis, increasing relative expression of perilipin 2 (PLIN2) and carnitine palmitoyltransferase 1B (CPT1B) in cumulus cells. Effects of FCS and cGMP on the lipid content of oocytes and embryos were evaluated by Nile red staining. COCs were matured with 10% FCS, FCS+10^-5 M sildenafil (SDF), a PDE5 inhibitor, or 0.4% BSA. The lipid content was increased in oocytes matured in FCS compared with BSA (fluorescence intensity 20.1 vs 17.61 respectively; P<0.05), whereas the lipid content in oocytes matured in FCS+SDF (fluorescence intensity 16.33) was similar to that in the BSA-treated group (P>0.05). In addition, lipid content was higher in embryos from oocytes matured with FCS than BSA (fluorescence intensity 31.12 vs 22.31 respectively; P<0.05), but was increased even further in the FCS+SDF-treated group (fluorescence intensity 40.35; P<0.05), possibly due to a compensatory mechanism during embryo culture without SDF for the reduction in lipid content during IVM. The present study provides, for the first time, evidence that the cGMP pathway may be involved in lipid metabolism in bovine COCs and that this pathway is affected by FCS.

Exome sequencing identified a de novo mutation of PURA gene in a patient with familial Xp22.31 microduplication

The clinical significance of Xp22.31 microduplication is controversial as it is reported in subjects with developmental delay (DD), their unaffected relatives and unrelated controls. We performed multifaceted studies in a family of a boy with hypotonia, dysmorphic features and DD who carried a 600 Kb Xp22.31 microduplication (7515787-8123310bp, hg19) containing two genes, VCX and PNPLA4. The duplication was transmitted from his cognitively normal maternal grandfather. We found no evidence of the duplication causing the proband's DD and congenital anomalies based on unaltered expression of PNPLA4 in the proband and his mother in comparison to controls and preferential activation of the paternal chromosome X with Xp22.31 duplication in proband's mother. However, a de novo, previously reported deleterious, missense mutation in Pur-alpha gene (PURA) (5q31.2), with a role in neuronal differentiation was detected in the proband by exome sequencing. We propose that the variability in the phenotype in carriers of Xp22.31 microduplication can be due to a second and more deleterious genetic mutation in more severely affected carriers. Widespread use of whole genome next generation sequencing in families with Xp22.31 CNV could help identify such cases.

Lactic acid bacteria-fermented product of green tea and Houttuynia cordata leaves exerts anti-adipogenic and anti-obesity effects

Obesity is associated with higher risks of developing diabetes and cardiovascular disease. Green tea, rich in polyphenolic compounds such as epigallocatechin gallate (EGCG) and epigallocatechin (EGC), has been shown to display anti-obesity effects. Houttuynia cordata leaves have also been shown to exhibit anti-obesity effects due to their chlorogenic acid content. Lactic acid bacteria are able to increase the production of polyphenolic compounds. This study aims to develop a novel anti-obesity fermentation product by combining H. cordata leaf tea with green tea, using Lactobacillus paracasei subsp. paracasei NTU 101 (NTU 101) for fermentation due to the advantages of bioconverting the poly-phenolic compounds. The regulation of adipogenesis factors and the anti-obesity effect of the NTU 101-fermented tea were evaluated in an in vitro 3T3-L1 pre-adipocyte model and an in vivo obese rat model, respectively. The results show that the NTU 101-fermented tea, which contained higher EGCG, EGC, and chlorogenic acid levels than unfermented tea, was able to inhibit the lipogenesis of mature 3T3-L1 adipocytes by the stimulation of lipolysis. Furthermore, the body weight gain, body fat pad, and feeding efficiency of obese rats, induced with a high fat diet, were decreased by the oral administration of NTU 101-fermented tea. The significant anti-obesity effect was probably due to lipolysis. However, NTU 101 bacteria cells and EGCG may also act as functional ingredients to contribute to the anti-obesity effects of NTU 101-fermented products.

Lyplal1 is dispensable for normal fat deposition in mice

Genome-wide association studies (GWAS) have detected association between variants in or near the Lysophospholipase-like 1 (LYPLAL1) locus and metabolic traits, including central obesity, fatty liver and waist-to-hip ratio. LYPLAL1 is also known to be upregulated in the adipose tissue of obese patients. However, the physiological role of LYPLAL1 is not understood. To investigate the function of Lyplal1 in vivo we investigated the phenotype of the Lyplal1^{tm1a(KOMP)Wtsi} homozygous mouse. Body composition was unaltered in Lyplal1 knockout mice as assessed by dual-energy X-ray absorptiometry (DEXA) scanning, both on normal chow and on a high-fat diet. Adipose tissue distribution between visceral and subcutaneous fat depots was unaltered, with no change in adipocyte cell size. The response to both insulin and glucose dosing was normal in Lyplal1^{tm1a(KOMP)Wtsi} homozygous mice, with normal fasting blood glucose concentrations. RNAseq analysis of liver, muscle and adipose tissue confirmed that Lyplal1 expression was ablated with minimal additional changes in gene expression. These results suggest that Lyplal1 is dispensable for normal mouse metabolic physiology and that despite having been maintained through evolution Lyplal1 is not an essential gene, suggesting possible functional redundancy. Further studies will be required to clarify its physiological role.

Comparative Assessment of Serum Adipokines Zinc-α2-glycoprotein and Adipose Triglyceride Lipase, and Cardiovascular Risk Factors Between Normal Weight and Obese Patients with Hemodialysis

BACKGROUND

Little is known about the potential relationship of obesity, adipose tissue and novel adipokines with cardiometabolic risk factors in end-stage renal disease. Zinc-α2-glycoprotein (ZAG) and adipose triglyceride lipase (ATGL) are novel adipokines with proposed desirable effects on inflammation, and lipid and glucose metabolism. The aim of this study was to investigate serum concentrations of ZAG and ATGL, and the relationship of these adipokines with cardiovascular risk factors in normal weight (NW) and obese (OB) patients undergoing hemodialysis.

METHODS

Patients with regular hemodialysis including 44 normal weight (18.5<BMI<25 kg/m²) and 44 obese (BMI≥30 kg/m²) were enrolled. Serum lipid profile, high-sensitivity C-reactive protein (hsCRP) and nitric oxide metabolites along with ZAG and ATGL concentrations were assessed.

RESULTS

ZAG concentrations were significantly lower in OB compared to NW group (100 ± 34 vs. 106 ± 31 ng/ml; p = 0.007). No significant difference was observed in ATGL between the two groups. A significant inverse correlation between ZAG and HDL (r = ‒0.236, p = 0.048) and a marginal inverse correlation between ATGL and HDL (r = ‒0.211, p = 0.078) were observed in all patients. ZAG had positive correlations with triglyceride/HDL (r = 0.279, p = 0.019), cholesterol/HDL (r = 0.319, p = 0.007), and LDL/HDL (r = 0.26, p = 0.029) ratios. Among cardiovascular risk factors, only LDL/HDL ratio and hsCRP were significantly higher in OB patients (p = 0.009 and p = 0.038, respectively).

CONCLUSIONS

Serum concentrations of ZAG, but not ATGL, were significantly lower in the OB group. It appears that obesity overrides the role of hemodialysis in determining ZAG concentration. In contrast, uremic condition might overshadow the role of obesity in determining levels of traditional cardiovascular risk factors.

Reduced expression of adipose triglyceride lipase decreases arachidonic acid release and prostacyclin secretion in human aortic endothelial cells

BACKGROUND

Vascular endothelial cells represent an important source of arachidonic acid (AA)-derived mediators involved in the generation of anti- or proatherogenic environments. Evidence emerged (in mast cells), that in addition to phospholipases, neutral lipid hydrolases as adipose triglyceride lipase (ATGL) also participate in this process.

OBJECTIVE

To examine the impact of ATGL on AA-release from cellular phospholipids (PL) and on prostacyclin secretion in human aortic endothelial cells (HAEC).

METHODS AND RESULTS

siRNA-mediated silencing of ATGL promoted lipid droplet formation and TG accumulation in HAEC (nile red stain). ATGL knockdown decreased the basal and A23187 (calcium ionophore)-induced release of ¹⁴C-AA from (¹⁴C-AA-labeled) HAEC. In A23187-stimulated ATGL silenced cells, this was accompanied by a decreased content of ¹⁴C-AA in cellular PL and a decreased secretion of prostacyclin (determined by 6-keto PGF1α EIA).

CONCLUSIONS

In vascular endothelial cells, the efficiency of stimulus-induced AA release and prostacyclin secretion is dependent on ATGL.

Two obesity susceptibility loci in LYPLAL1 and ETV5 independently associated with childhood hypertension in Chinese population

AIMS

Genome-wide association studies have identified novel obesity-associated susceptibility loci. Associations of these variants with childhood obesity have been studied in our previous research. The purpose of this study is to investigate if these loci are associated with hypertension being independent of obesity in Chinese children and adolescents.

METHODS

Nineteen candidate SNPs were genotyped using Sequenom MassARRAY platform among Chinese children (N=2954, 514 hypertension and 2440 controls, aged 7-17years). Dietary behaviors were assessed through face to face investigations.

RESULTS

Of the nineteen obese related SNPs, ten SNPs were found to be associated with systolic blood pressure (SBP) or diastolic blood pressure (DBP) in Chinese children. After adjusting for age, sex and WHtR, rs2605100 in LYPLAL1was found to be associated with high blood pressure (HBP) under dominant model (P=0.024) with the OR of 1.274 (95% CI =1.033-1.572, effect genotype=GG). The distribution of genotype of rs7647305 in ETV5 showed significant difference between HBP and non-HBP subjects under dominant model (P=0.011) with the OR of 0.654 (95% CI=0.471-0.909, effect genotype=CC). Using rs2605100 and rs7647305, the genetic risk score (GRS) analysis showed that, after adjusted for age, sex and WHtR, subjects carrying one or two risk alleles had the risks of hypertension with the ORs 1.797 (95% CI, 1.168-2.765), 2.149 (95% CI, 1.375-3.357) comparing with the subjects with non-risk-allele.

CONCLUSIONS

Genetic variations of obesity-associated loci, LYPLAL1 rs2605100 and ETV5 rs7647305 independently associate with the risk of childhood hypertension in China.

Carboxylesterases in lipid metabolism: from mouse to human

Mammalian carboxylesterases hydrolyze a wide range of xenobiotic and endogenous compounds, including lipid esters. Physiological functions of carboxylesterases in lipid metabolism and energy homeostasis in vivo have been demonstrated by genetic manipulations and chemical inhibition in mice, and in vitro through (over)expression, knockdown of expression, and chemical inhibition in a variety of cells. Recent research advances have revealed the relevance of carboxylesterases to metabolic diseases such as obesity and fatty liver disease, suggesting these enzymes might be potential targets for treatment of metabolic disorders. In order to translate pre-clinical studies in cellular and mouse models to humans, differences and similarities of carboxylesterases between mice and human need to be elucidated. This review presents and discusses the research progress in structure and function of mouse and human carboxylesterases, and the role of these enzymes in lipid metabolism and metabolic disorders.

Crystal structure of Pelagibacterium halotolerans PE8: New insight into its substrate-binding pattern

Lysophospholipase_carboxylesterase (LPCE) has highly conserved homologs in many diverse species ranging from bacteria to humans, as well as substantial biological significance and potential therapeutic implications. However, its biological function and catalytic mechanism remain minimally investigated because of the lack of structural information. Here, we report the crystal structure of a bacterial esterase PE8 belonging to the LPCE family. The crystal structure of PE8 was solved with a high resolution of 1.66 Å. Compared with other homologs in the family, significant differences were observed in the amino acid sequence, three-dimensional structure, and substrate-binding pattern. Residue Arg79 undergoes configuration switching when binding to the substrate and forms a unique wall, leading to a relatively closed cavity in the substrate-binding pocket compared with the relatively more open and longer clefts in other homologs. Moreover, the mutant Met122Ala showed much stronger substrate affinity and higher catalytic efficiency because less steric repulsion acted on the substrates. Taken together, these results showed that, in PE8, Arg79 and Met122 play important roles in substrate binding and the binding pocket shaping, respectively. Our study provides new insight into the catalytic mechanism of LPCE, which may facilitate the development of structure-based therapeutics and other biocatalytic applications.

Triglyceride metabolism in exercising muscle

Triglycerides are stored within lipid droplets in skeletal muscle and can be hydrolyzed to produce fatty acids for energy production through β-oxidation and oxidative phosphorylation. While there was some controversy regarding the quantitative importance of intramyocellular triglyceride (IMTG) as a metabolic substrate, recent advances in proton magnetic resonance spectroscopy and confocal microscopy support earlier tracer and biopsy studies demonstrating a substantial contribution of IMTG to energy production, particularly during moderate-intensity endurance exercise. This review provides an update on the understanding of IMTG utilization during exercise, with a focus on describing the key regulatory proteins that control IMTG breakdown and how these proteins respond to acute exercise and in the adaptation to exercise training. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.

Multi-omics Integrative Investigation of Fatty Acid Metabolism in Obese and Lean Subcutaneous Tissue

White adipose tissue (WAT) plays a central role in whole-body energy homeostasis through storage and release of fatty acids. A deeper understanding of the complex and highly integrated pathways regulating WAT fatty acid metabolism, and how they are altered with obesity, is necessary for diagnostic and therapeutic innovations in nutritional disorders. In this multi-omics study, we investigated the influence of obesity on fatty acid metabolism in human subcutaneous adipose tissue (SAT) using an approach that integrated transcriptomic, peptidomic, and fatty acid analyses. Notably, all analyses were conducted in the same adipose tissue sample from each participant, thus minimizing the chance of spurious results. In a sample of SAT from the periumbilical abdominal region of obese (n = 11, mean body mass index [BMI] = 35.0 ± 1.2 kg/m²) and lean subjects (n = 9, mean BMI = 22.1 ± 0.5 kg/m²), we found that obese SAT tended to have higher relative amounts of specific monounsaturated fatty acids and n-6 polyunsaturated fatty acids, and lower amounts of saturated fatty acids (p < 0.05). These changes were associated with differential regulation of lipogenic and lipolytic pathways in obese SAT. Fatty acid analysis showed changes in estimated fatty acid desaturase and elongase activities between lean and obese SAT (p < 0.05). Biomarkers of lipogenesis (e.g., fatty acid synthase protein) were differentially regulated between lean and obese SAT. These changes were noted in conjunction with increases in extracellular matrix remodeling proteins. Transcriptomic data revealed that the key regulators of lipolysis were reduced in obese SAT. This integrative multi-omics analysis collectively shows that obese SAT has a distinct fatty acid signature compared to lean SAT and the pathways underlying fatty acid metabolism are broadly regulated at the level of gene expression and protein abundance.

Insulin Receptor Signaling in POMC, but Not AgRP, Neurons Controls Adipose Tissue Insulin Action

Insulin is a key regulator of adipose tissue lipolysis, and impaired adipose tissue insulin action results in unrestrained lipolysis and lipotoxicity, which are hallmarks of the metabolic syndrome and diabetes. Insulin regulates adipose tissue metabolism through direct effects on adipocytes and through signaling in the central nervous system by dampening sympathetic outflow to the adipose tissue. Here we examined the role of insulin signaling in agouti-related protein (AgRP) and pro-opiomelanocortin (POMC) neurons in regulating hepatic and adipose tissue insulin action. Mice lacking the insulin receptor in AgRP neurons (AgRP IR KO) exhibited impaired hepatic insulin action because the ability of insulin to suppress hepatic glucose production (hGP) was reduced, but the ability of insulin to suppress lipolysis was unaltered. To the contrary, in POMC IR KO mice, insulin lowered hGP but failed to suppress adipose tissue lipolysis. High-fat diet equally worsened glucose tolerance in AgRP and POMC IR KO mice and their respective controls but increased hepatic triglyceride levels only in POMC IR KO mice, consistent with impaired lipolytic regulation resulting in fatty liver. These data suggest that although insulin signaling in AgRP neurons is important in regulating glucose metabolism, insulin signaling in POMC neurons controls adipose tissue lipolysis and prevents high-fat diet-induced hepatic steatosis.

Fat-Specific Sirt6 Ablation Sensitizes Mice to High-Fat Diet-Induced Obesity and Insulin Resistance by Inhibiting Lipolysis

Sirt6 is an NAD⁺-dependent deacetylase that is involved in the control of energy metabolism. However, the tissue-specific function of Sirt6 in the adipose tissue remains unknown. In this study, we showed that fat-specific Sirt6 knockout (FKO) sensitized mice to high-fat diet-induced obesity, which was attributed to adipocyte hypertrophy rather than adipocyte hyperplasia. The adipocyte hypertrophy in FKO mice likely resulted from compromised lipolytic activity as an outcome of decreased expression of adipose triglyceride lipase (ATGL), a key lipolytic enzyme. The suppression of ATGL in FKO mice was accounted for by the increased phosphorylation and acetylation of FoxO1, which compromises the transcriptional activity of this positive regulator of ATGL. Fat-specific Sirt6 KO also increased inflammation in the adipose tissue, which may have contributed to insulin resistance in high-fat diet-fed FKO mice. We also observed that in obese patients, the expression of Sirt6 expression is reduced, which is associated with a reduction of ATGL expression. Our results suggest Sirt6 as an attractive therapeutic target for treating obesity and obesity-related metabolic disorders.

A genetic variant in proximity to the gene LYPLAL1 is associated with lower hunger feelings and increased weight loss following Roux-en-Y gastric bypass surgery

OBJECTIVE

Bariatric surgery is the most efficient treatment of severe obesity. We investigated to what extent BMI- or waist-hip ratio (WHR)-related genetic variants are associated with excess BMI loss (EBMIL) two years after Roux-en-Y gastric bypass (RYGB) surgery, and elucidated the affected biological pathways.

METHODS

Two-hundred fifty-one obese patients (age: 43 ± 10.7, preoperative BMI: 45.1 ± 6.1 kg/m(2), 186 women) underwent RYGB surgery and were followed up after two years with regard to BMI. Patients were genotyped for 32 single-nucleotide polymorphisms (SNPs) that were investigated with regard to their impact on response to RYGB and preoperatively measured Three Factor Eating Questionnaire (TFEQ) scores.

RESULTS

Homozygous T carriers of the SNP rs4846567 in proximity to the Lysophospholipase-like 1 (LYPLAL1) gene showed a 7% higher EBMIL compared to wild-type and heterozygous carriers (p = 0.031). TT-allele carriers showed furthermore lower scores for Hunger (74%, p < 0.001), lower Disinhibition (53%, p < 0.001), and higher Cognitive restraint (21%, p = 0.017) than GG/GT carriers in the TFEQ. Patients within the lowest quartile of Hunger scores had a 32% greater EBMIL compared to patients in the highest quartile (p < 0.001).

CONCLUSION

The LYPLAL1 genotype is associated with differences in eating behavior and loss of extensive body weight following RYGB surgery. Genotyping and the use of eating behavior-related questionnaires may help to estimate the RYGB-associated therapy success.

Phosphoprotein network analysis of white adipose tissues unveils deregulated pathways in response to high-fat diet

Despite efforts in the last decade, signaling aberrations associated with obesity remain poorly understood. To dissect molecular mechanisms that define this complex metabolic disorder, we carried out global phosphoproteomic analysis of white adipose tissue (WAT) from mice fed on low-fat diet (LFD) and high-fat diet (HFD). We quantified phosphorylation levels on 7696 peptides, and found significant differential phosphorylation levels in 282 phosphosites from 191 proteins, including various insulin-responsive proteins and metabolic enzymes involved in lipid homeostasis in response to high-fat feeding. Kinase-substrate prediction and integrated network analysis of the altered phosphoproteins revealed underlying signaling modulations during HFD-induced obesity, and suggested deregulation of lipogenic and lipolytic pathways. Mutation of the differentially-regulated novel phosphosite on cytoplasmic acetyl-coA forming enzyme ACSS2 (S263A) upon HFD-induced obesity led to accumulation of serum triglycerides and reduced insulin-responsive AKT phosphorylation as compared to wild type ACSS2, thus highlighting its role in obesity. Altogether, our study presents a comprehensive map of adipose tissue phosphoproteome in obesity and reveals many previously unknown candidate phosphorylation sites for future functional investigation.

Effect of Bariatric Weight Loss on the Adipose Lipolytic Transcriptome in Obese Humans

Background. Dysregulated lipolysis has been implicated in mechanisms of cardiometabolic disease and inflammation in obesity. Purpose. We sought to examine the effect of bariatric weight loss on adipose tissue lipolytic gene expression and their relationship to systemic metabolic parameters in obese subjects. Methods/Results. We biopsied subcutaneous adipose tissue in 19 obese individuals (BMI 42 ± 5 kg/m², 79% female) at baseline and after a mean period of 8 ± 5 months (range 3–15 months) following bariatric surgery. We performed adipose tissue mRNA expression of proteins involved in triglyceride hydrolysis and correlated their weight loss induced alterations with systemic parameters associated with cardiovascular disease risk. mRNA transcripts of adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL), and lipid droplet proteins comparative gene identification 58 (CGI-58) and perilipin increased significantly after weight loss (p < 0.05 for all). ATGL expression correlated inversely with plasma triglyceride (TG), hemoglobin A1C (HbA1C), and glucose, and HSL expression correlated negatively with glucose, while CGI-58 was inversely associated with HbA1C. Conclusion. We observed increased expression of adipose tissue lipolytic genes following bariatric weight loss which correlated inversely with systemic markers of lipid and glucose metabolism. Functional alterations in lipolysis in human adipose tissue may play a role in shaping cardiometabolic phenotypes in human obesity.

Insights from Genome-Wide Association Analyses of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is caused by hepatic steatosis, which can progress to nonalcoholic steatohepatitis, fibrosis/cirrhosis, and hepatocellular carcinoma in the absence of excessive alcohol consumption. Nonalcoholic fatty liver disease will become the number one cause of liver disease worldwide by 2020. Nonalcoholic fatty liver disease is correlated albeit imperfectly with obesity and other metabolic diseases such as diabetes, hyperlipidemia, and cardiovascular disease, but exactly how having one of these diseases contributes to the development of other metabolic diseases is only now being elucidated. Development of NAFLD and related metabolic diseases is genetically influenced in the population, and recent genome-wide association studies (GWASs) have discovered genetic variants that associate with these diseases. These GWAS-associated variants cannot only help us to identify individuals at high risk of developing NAFLD, but also to better understand its pathophysiology so that we can develop more effective treatments for this disease and related metabolic diseases in the future.