Leptin Receptor Gene Polymorphisms and the Risk of Non-Alcoholic Fatty Liver Disease and Coronary Atherosclerosis in the Chinese Han Population

Association between genetic polymorphisms of leptin receptor and preeclampsia in Chinese women

OBJECTIVE

Leptin signaling plays an important role in regulating metabolism and reproduction. In the present study, we investigated the relationship between polymorphisms of leptin receptor (LEPR) gene A223G and A668G and preeclampsia (PE) and evaluated influences of genotypes on clinical, metabolic, and oxidative stress indices in Chinese women.

METHODS

This is a case-control study including 322 patients with PE and 1295 healthy pregnant women. The two polymorphisms were genotyped by polymerase chain reaction-restriction fragments length polymorphism method. Clinical and biochemical parameters were analyzed.

RESULTS

The frequencies of the AA + AG genotypes (28.6% vs. 36.1%) and A allele (14.9% vs. 19.8%) of LEPR A223G polymorphism, and those of the AA + AG genotypes (17.7% vs. 24.6%) and A allele (9.0% vs. 12.9%) of LEPR A668G polymorphism were significantly lower in the PE group than those in the control group. The 223A and 668A alleles were protective factors against PE in the regression model, which included age and delivery body mass index as covariates (OR = 0.684, 95% CI: 0.506-0.926, p = .014; OR = 0.650, 95% CI: 0.456-0.927, p = .017, respectively). When the 668GG/223GG combined genotype served as the reference category, the 668A/223A combined allele had further enhanced the protective effect on PE (OR = 0.558, 95% CI: 0.374-0.833, p = .004). Patients possessing the LEPR 223A allele had higher total antioxidant capacity and lower oxidative stress index (p < .05), while those with the LEPR 668A allele had higher high-density lipoprotein cholesterol levels (p = .045) compared with those carrying the corresponding GG genotype.

CONCLUSIONS

The 223A and 668A alleles of LEPR polymorphisms are genetic protective factors for PE in Chinese women. The two alleles may exert a beneficial effect on oxidative stress and lipid metabolism in patients.

Identification of Key Target Genes and Pathway Analysis in Nonalcoholic Fatty Liver Disease Via Integrated Bioinformatics Analysis

Purpose

This study aimed at exploring the mechanisms underlying nonalcoholic fatty liver disease (NAFLD) and developing new diagnostic biomarkers for nonalcoholic steatohepatitis (NASH).

Methods

The microarray dataset GES83452 was downloaded from the NCBI-GEO database, and the differentially expressed RNAs (DERs) were screened between the NAFLD and non-NAFLD samples of the baseline and 1-year follow-up time point group based on the Limma package.

Results

A total of 561 DERs (268 downregulated and 293 upregulated) were screened in the baseline time point group, and 1163 DERs (522 downregulated and 641 upregulated) were screened in the 1-year follow-up time point group. A total of 74 lncRNA-miRNA pairs and 523 miRNA-mRNA pairs were obtained in order to construct a lncRNA-miRNA-mRNA regulatory network. Subsequently, functional enrichment analysis revealed 28 GO and 9 KEGG pathways in the ceRNA regulatory network. LEPR and CXCL10 are involved in the Cytokine-cytokine receptor interaction (P = 1.86E-02), and the FOXO1 is involved in both the insulin signaling pathway (P = 1.79E-02) and the pathways in cancer (P = 2.87E-02).

Conclusion

LEPR, CXCL10, and FOXO1 were the characteristic target genes for NAFLD.

The New Kid on the Block: The Mechanisms of Action of Hyperleptinemia in Coronary Artery Disease and Atherosclerosis

Leptin is an adipocytokine that consists of 167 amino acids. It functions as a regulator of hunger and energy expenditure. Leptin loses its ability to carry out its physiological function at high serum levels, and many studies have associated this loss of function with the development of coronary artery disease (CAD). This literature review aims to outline the steps by which leptin leads to CAD and atherosclerosis. Two independent researchers extracted animal and human studies from PubMed and Google Scholar databases. We applied PubMed search builder options: pathology, pathophysiology, metabolism, and physiology to focus the search results. This study concluded that the mechanism by which leptin might lead to CAD via pressor and depressor effects on vascular tone, enhancing atherosclerotic plaques, and through numerous single nucleotide polymorphisms, the most common being that of the leptin receptor gene rs113701. 

Identifying potential biomarkers of nonalcoholic fatty liver disease via genome-wide analysis of copy number variation

BACKGROUND

The prevalence of Non-alcoholic fatty liver disease (NAFLD) is increasing and emerging as a global health burden. In addition to environmental factors, numerous studies have shown that genetic factors play an important role in the development of NAFLD. Copy number variation (CNV) as a genetic variation plays an important role in the evaluation of disease susceptibility and genetic differences. The aim of the present study was to assess the contribution of CNV to the evaluation of NAFLD in a Chinese population.

METHODS

Genome-wide analysis of CNV was performed using high-density comparative genomic hybridisation microarrays (ACGH). To validate the CNV regions, TaqMan real-time quantitative PCR (qPCR) was utilized.

RESULTS

A total of 441 CNVs were identified, including 381 autosomal CNVs and 60 sex chromosome CNVs. By merging overlapping CNVs, a genomic CNV map of NAFLD patients was constructed. A total of 338 autosomal CNVRs were identified, including 275 CNVRs with consistent trends (197 losses and 78 gains) and 63 CNVRs with inconsistent trends. The length of the 338 CNVRs ranged from 5.7 kb to 2.23 Mb, with an average size of 117.44 kb. These CNVRs spanned 39.70 Mb of the genome and accounted for ~ 1.32% of the genome sequence. Through Gene Ontology and genetic pathway analysis, we found evidence that CNVs involving nine genes may be associated with the pathogenesis of NAFLD progression. One of the genes (NLRP4 gene) was selected and verified by quantitative PCR (qPCR) method with large sample size. We found the copy number deletion of NLRP4 was related to the risk of NAFLD.

CONCLUSIONS

This study indicate the copy number variation is associated with NAFLD. The copy number deletion of NLRP4 was related to the risk of NAFLD. These results could prove valuable for predicting patients at risk of developing NAFLD.

Unraveling the Role of Leptin in Liver Function and Its Relationship with Liver Diseases

Since its discovery twenty-five years ago, the fat-derived hormone leptin has provided a revolutionary framework for studying the physiological role of adipose tissue as an endocrine organ. Leptin exerts pleiotropic effects on many metabolic pathways and is tightly connected with the liver, the major player in systemic metabolism. As a consequence, understanding the metabolic and hormonal interplay between the liver and adipose tissue could provide us with new therapeutic targets for some chronic liver diseases, an increasing problem worldwide. In this review, we assess relevant literature regarding the main metabolic effects of leptin on the liver, by direct regulation or through the central nervous system (CNS). We draw special attention to the contribution of leptin to the non-alcoholic fatty liver disease (NAFLD) pathogenesis and its progression to more advanced stages of the disease as non-alcoholic steatohepatitis (NASH). Likewise, we describe the contribution of leptin to the liver regeneration process after partial hepatectomy, the mainstay of treatment for certain hepatic malignant tumors.

Association of leptin and leptin receptor polymorphisms with coronary artery disease in a North Chinese Han population

INTRODUCTION:

Leptin (LEP) is a peptide hormone that acts via leptin receptor (LEPR) binding. Genetic evidence from different human populations has implicated LEP/LEPR in the pathogenesis of coronary artery disease (CAD), and suggests that certain LEP/LEPR gene polymorphisms may increase the risk of CAD. The aim of this study was to assess two single nucleotide polymorphisms (SNPs) in LEP genes (rs2167270 and rs7799039) and two in LEPR genes (rs6588147, rs1137100) for association with CAD.

METHODS:

We enrolled 271 North Chinese Han CAD patients, and 113 healthy age- and sex-matched controls. Genomic DNA was extracted from whole blood, and the four SNPs were assessed using a MassArray system.

RESULTS:

The G allele frequency at rs2167270 was significantly higher among CAD cases than among controls. The AG genotype at rs7799039 was associated with a significantly decreased risk of CAD unlike the AA genotype used as the reference. The A allele was significantly associated with the CAD patient group. Interestingly, statistically significant differences in genotype and allele frequency at LEP rs2167270 and rs7799039 existed among females but not among males.

CONCLUSIONS:

The current study detected a significant association between genetic variations at LEP rs7799039 and rs2167270 and the risk of CAD in a north Chinese population, and revealed that LEP rs2167270 and rs7799039 gene polymorphisms might act as predisposing factors for CAD.

New Insights into Adipokines as Potential Biomarkers for Type-2 Diabetes Mellitus

A large number of studies have been focused on investigating serum biomarkers associated with risk or diagnosis of type-2 diabetes mellitus. In the last decade, promising studies have shown that circulating levels of adipokines could be used as a relevant biomarker for diabetes mellitus progression as well as therapeutic future targets. Here, we discuss the possible use of recently described adipokines, including apelin, omentin-1, resistin, FGF-21, neuregulin-4 and visfatin, as early biomarkers for diabetes. In addition, we also include recent findings of other well known adipokines such as leptin and adiponectin. In conclusion, further studies are needed to clarify the pathophysiological significance and clinical value of these biological factors as potential biomarkers in type-2 diabetes and related dysfunctions.

Associations of leptin and leptin receptor genetic variants with coronary artery disease: a meta-analysis

Background: Some pilot studies already tried to investigate potential associations of leptin (LEP) and LEP receptor (LEPR) variants with coronary artery disease (CAD). However, the results of these studies were not consistent. Thus, we performed the present meta-analysis to explore associations between LEP/LEPR variants and CAD in a larger pooled population.

Methods: Systematic literature research of PubMed, Web of Science, Embase and CNKI was performed to identify eligible case–control studies on associations between LEP/LEPR variants and CAD. The initial search was conducted in September 2018 and the latest update was performed in December 2018. Q test and I² statistic were employed to assess between-study heterogeneities. If probability value(P-value) of Q test was less than 0.1 or I² was greater than 50%, random-effect models (REMs) would be used to pool the data. Otherwise, fixed-effect models (FEMs) would be applied for synthetic analyses.

Results: A total of ten studies published between 2006 and 2018 were eligible for analyses (1989 cases and 2601 controls). Pooled analyses suggested that LEP rs7799039 variant was significantly associated with CAD under over-dominant model (P=0.0007, odds ratio (OR) = 1.36, 95% confidence interval (CI): 1.14–1.63, I² = 41%, FEM) in overall population, and this significant finding was further confirmed in East Asians in subsequent subgroup analyses. However, no positive findings were observed for LEPR rs1137100 and rs1137101 variants in overall and subgroup analyses.

Conclusions: Our meta-analysis suggested that LEP rs7799039 variant might affect individual susceptibility to CAD.

Correlation Between Adiponectin Gene rs1501299 Polymorphism and Nonalcoholic Fatty Liver Disease Susceptibility: A Systematic Review and Meta-Analysis

Background

Metabolic related nonalcoholic fatty liver disease (NAFLD) is one of the most prevalent chronic liver diseases around the world. A single nucleotide polymorphism (SNP) rs1501299 (+276G>T) in the adiponectin gene has been recently revealed to be responsible for susceptibility to NAFLD. This meta-analysis intended to assess the association risk of NAFLD and rs1501299 polymorphism.

Material/Methods

We conducted a literature search on PubMed, Embase, and Cochrane Library databases. All involved studies were selected based on our search criteria. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to quantify the strength of the association. Subgroup analysis considered the effects of ethnicity, subject scope, and source of control. Publication bias was assessed by Begg’s tests.

Results

Eight qualified case-control studies with 1639 patients and 1426 controls demonstrated a significant correlation between rs1501299 polymorphism in adiponectin and NAFLD under the dominant model (OR=1.18, 95% CI=1.02–1.36), allelic contrast (OR=1.21, 95% CI=1.09–1.36), homozygote comparison (OR=1.63, 95% CI=1.26–2.01) and the recessive allele model (OR=1.58, 95% CI=1.23–2.02) with evident heterogeneity. No association was observed between the risk of NAFLD and the genotypic variants in heterozygote comparison (OR=1.11, 95% CI=0.95–1.29) without heterogeneity. Subgroup analysis suggested that the sample size could be the potential source of heterogeneity. Source of control was not the reason for between-study heterogeneity and further sensitivity analysis and publication bias revealed good consistency and symmetry in the pooling studies.

Conclusions

Results from our current meta-analysis gave insight into the correlation between rs1501299 polymorphism and the risk of NAFLD, indicating the variant of rs1501299 might be related to increased NAFLD susceptibility.

Association of TM6SF2 rs58542926 gene polymorphism with the risk of non-alcoholic fatty liver disease and colorectal adenoma in Chinese Han population

Background

Genetic factors affect the risk of non-alcoholic fatty liver disease (NAFLD) and colorectal adenoma (CRA) importantly. Transmembrane protein 6 superfamily member 2 (TM6SF2) rs58542926 is a significant genetic susceptibility site for NAFLD. The relationships of TM6SF2 rs58542926 with the risk of NAFLD and CRA in Chinese Han population were unclear. The aim of this study was to investigate the association of TM6SF2 rs58542926 with the risk of NAFLD and CRA, and the effect of CRA on TM6SF2 rs58542926 carried NAFLD patients.

Results

A total of 839 Chinese Han population were included in this retrospective study. TM6SF2 rs58542926 polymorphism was genotyped in B-type ultrasonography proven NAFLD patients with or without CRA, CRA patients and healthy controls, using polymerase chain reaction. Serum lipid profiles were determined using biochemical methods. Statistical analyses were performed using SPSS statistical software, version 16.0 for mac. There was a significant difference in the distribution of genotype and allele of TM6SF2 rs58542926 in NAFLD and NAFLD&CRA patients compared to controls. The CT + TT genotypes were tightly associated with the risk of NAFLD and NAFLD&CRA. TM6SF2 rs58542926 T allele promotes the abnormal regulation of lipids metabolism and liver injury in NAFLD patients and NAFLD&CRA patients. CRA aggravates the clinical performance of NAFLD in T allele carriers.

Conclusions

We demonstrated the significant association between TM6SF2 rs58542926 polymorphism and the risk of NAFLD and NAFLD&CRA in a Chinese Han population. The TM6SF2 rs58542926 T allele promotes the abnormal regulation of lipid profiles and liver injury in NAFLD patients, NAFLD&CRA patients, and overall subjects.

Association of Hepatic Steatosis With Subclinical Atherosclerosis: Systematic Review and Meta-Analysis

Nonalcoholic fatty liver disease (NAFLD) is becoming common in the United States and throughout the world and can progress to cirrhosis, hepatocellular carcinoma, and death. There is a strong association between coronary artery disease and NAFLD due to common risk factors, such as metabolic syndrome, obesity, and diabetes mellitus. Subclinical atherosclerosis, defined as coronary artery calcification in asymptomatic patients, has been shown to have a higher incidence in patients with NAFLD. We performed a meta‐analysis to examine the association of NAFLD with subclinical atherosclerosis measured by coronary artery calcium (CAC) scoring. Data were extracted from 12 studies selected using a predefined search strategy. NAFLD was diagnosed by abdominal ultrasound or computed tomography scans. The rate of coronary artery calcification was analyzed using random effects models, and publication bias was assessed using Egger's regression test. A total of 42,410 subjects were assessed, including 16,883 patients with NAFLD. Mean CAC score was significantly higher in subjects with NAFLD compared to those without NAFLD (odds ratio with random effects model, 1.64; 95% confidence inteval, 1.42‐1.89). This association remained significant through subgroup analyses for studies with >1,000 subjects and a higher CAC score cutoff of >100. Higher aspartate aminotransferase levels were also associated with increased subclinical atherosclerosis (mean difference 1.77; 95% confidence interval, 1.19‐2.34). Conclusion: There is an increased prevalence of subclinical atherosclerosis in patients with NAFLD, where subclinical atherosclerosis is defined using a “real world” clinical biomarker, namely the CAC score. Prospective studies are needed to establish a causative link between NAFLD and coronary artery disease. (Hepatology Communications 2018; 00:000‐000)

Leptin, cardiovascular diseases and type 2 diabetes mellitus

Leptin, an adipokine that is implicated in the control of food intake via appetite suppression, may also stimulate oxidative stress, inflammation, thrombosis, arterial stiffness, angiogenesis and atherogenesis. These leptin-induced effects may predispose to the development of cardiovascular diseases. In the present review we discuss the evidence linking leptin levels with the presence, severity and/or prognosis of both coronary artery disease and non-cardiac vascular diseases such as stroke, carotid artery disease, peripheral artery disease (PAD) and abdominal aortic aneurysms (AAA) as well as with chronic kidney disease (CKD) and type 2 diabetes mellitus (T2DM). Leptin levels have been positively associated with the presence, severity, extent and lesion complexity of coronary atherosclerosis as well as with the presence, severity and poor clinical outcomes of both ischemic and hemorrhagic strokes. But conflicting results also exist. Furthermore, leptin was reported to independently predict common carotid intima-media thickness and carotid plaque instability. A link between hyperleptinemia and PAD has been reported, whereas limited data were available on the potential association between leptin and AAA. Elevated leptin concentrations have also been related to CKD incidence and progression as well as with insulin resistance, T2DM, micro- and macrovascular diabetic complications. Statins and antidiabetic drugs (including sitagliptin, metformin, pioglitazone, liraglutide and empagliflozin) may affect leptin levels. Further research is needed to establish the potential use (if any) of leptin as a therapeutic target in these diseases.

Association of Adipokines with Development and Progression of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease affecting 30% of the general population and 40% to 70% of obese individuals. Adipose tissue plays a crucial role in its pathogenesis, as it produces and secretes pro- and anti-inflammatory cytokines called adipokines. Adiponectin and leptin have well-determined actions in terms of NAFLD pathophysiology. Adiponectin deficiency is associated with a pro-inflammatory condition, as it is observed in obesity and other metabolic disorders. On the other hand, increased leptin levels, above the normal levels, act as a pro-inflammatory stimulus. Regarding other adipokines (resistin, visfatin, chemerin, retinol-binding protein 4, irisin), data about their contribution to NAFLD pathogenesis and progression are inconclusive. In addition, pharmacological agents like thiazolidinediones (pioglitazone and rosiglitazone), that are used in the management of NAFLD exert favourable effects on adipokine levels, which in turn may contribute to the improvement of liver function. This review summarizes the current knowledge and developments in the association between adipokines and NAFLD and discusses possible therapeutic implications targeting the modulation of adipokine levels as a potential tool for the treatment of NAFLD.

A meta-analysis of associations of LEPR Q223R and K109R polymorphisms with Type 2 diabetes risk

Background

Leptin receptor (LEPR) plays a pivotal role in the control of body weight, energy metabolism, and insulin sensitivity. Various genetic association studies were performed to evaluate associations of LEPR genetic variants with type 2 diabetes (T2D) susceptibility.

Methods

A comprehensive search was conducted to identify all eligible case-control studies for examining the associations of LEPR single nucleotide polymorphisms (SNPs) Q223R (rs1137101) and K109R (rs1137100) with T2D risk. Odds ratios (OR) and corresponding 95% confidence intervals (CIs) were used to measure the magnitudes of association.

Results

For Q223R, 13 studies (11 articles) consisting of a total of 4030 cases and 2844 controls, and for K109R 7 studies (7 articles) consisting of 3319 cases and 2465 controls were available. Under an allele model, Q223R was not significantly associated with T2D risk (OR = 1.09, 95% CI: 0.80–1.48, P-value = 0.5989), which was consistent with results obtained under four genotypic models (ranges: ORs 1.08–1.20, 95% CIs: 0.58–2.02 to 0.64–2.26; P-values, 0.3650–0.8177, which all exceeded multiplicity-adjusted α = 0.05/5 = 0.01). In addition, no significant association was found between K109R and T2D risk based on either an allele model (OR = 0.93, 95% CI: 0.85–1.03, P-value = 0.1868) or four genotypic models (ranges: ORs 0.81–0.99, 95% CIs: 0.67–0.86 to 0.97–1.26, P-values, 0.0207–0.8804 which all exceeded multiplicity-adjusted α of 0.01). The magnitudes of association for these two SNPs were not dramatically changed in subgroup analyses by ethnicity or sensitivity analyses. Funnel plot inspections as well as Begg and Mazumdar adjusted rank correlation test and Egger linear regression test did not reveal significant publication biases in main and subgroup analyses. Bioinformatics analysis predicted that both missense SNPs were functionally neutral and benign.

Conclusions

The present meta-analysis did not detect significant genetic associations between LEPR Q223R and K109R polymorphisms and T2D risk.

Adipokines and Non-Alcoholic Fatty Liver Disease: Multiple Interactions

Accumulating evidence links obesity with low-grade inflammation which may originate from adipose tissue that secretes a plethora of pro- and anti-inflammatory cytokines termed adipokines. Adiponectin and leptin have evolved as crucial signals in many obesity-related pathologies including non-alcoholic fatty liver disease (NAFLD). Whereas adiponectin deficiency might be critically involved in the pro-inflammatory state associated with obesity and related disorders, overproduction of leptin, a rather pro-inflammatory mediator, is considered of equal relevance. An imbalanced adipokine profile in obesity consecutively contributes to metabolic inflammation in NAFLD, which is associated with a substantial risk for developing hepatocellular carcinoma (HCC) also in the non-cirrhotic stage of disease. Both adiponectin and leptin have been related to liver tumorigenesis especially in preclinical models. This review covers recent advances in our understanding of some adipokines in NAFLD and associated HCC.

Pathogenesis of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common and important chronic liver disease in the world. As the prevalence of obesity increases in adults and children, the incidence of NAFLD has increased rapidly, reaching 17% to 33%. NAFLD is clinically divided into two forms: simple fatty liver (SFL) and non-alcoholic steatohepatitis (NASH), with NASH accounting for 1/3-1/2 of all NAFLD cases. The probability of developing cirrhosis is 0.6%-3.0% in patients with SFL for 10-20 years, and as high as 15%-25% in patients with NASH for 10-15 years. Approximately 1% of cirrhosis cases develop hepatocellular carcinoma each year. The pathogenesis of NAFLD is still not completely clear. It is generally believed that age, sex, obesity, insulin resistance, cytokines, gene polymorphism, and intestinal microflora are involved in the pathogenesis of NAFLD. An in-depth understanding of the pathogenesis of NAFLD can provide a basis for treatment of this disease. In recent years, cytokines or genes have been reported as targets for NAFLD treatment with appreciated effects. Since there is currently no specific treatment for NAFLD, targeted therapy may have a profound impact on the prognosis of the disease.