Genetic Contribution of Variants near SORT1 and APOE on LDL Cholesterol Independent of Obesity in Children

Protective Association of APOC1/rs4420638 with Risk of Obesity: A case-control Study in Portuguese Children

The association of the rs4420638 polymorphism, near the APOC1 gene, was examined with the risk of obesity among Portuguese children. A sample of 446 Portuguese individuals (231 boys and 215 girls) of European descent, aged 3.2 to 13.7 years old (mean age: 7.98 years), were selected to conduct a case-control study. Body mass index (BMI), BMI Z-scores, and waist circumference were calculated. Genotyping was performed by real time PCR using a pre-designed TaqMan probe. Logistic regression and the nonparametric Mann-Whitney test were used to test the associations. The association results revealed a significant protective effect from the minor G-allele of SNP rs4420638 against obesity, with an odds ratio (OR) of 0.619 (95% CI 0.421-0.913; p = 0.0155) in the additive model, and OR of 0.587 (95% CI 0.383-0.9; p = 0.0145) in the dominant model. Moreover, comparing genotype groups (AA vs. AG + GG), significantly lower values (p < 0.05) for the anthropometric traits weight, height, BMI, BMI Z-score and waist circumference, were observed in the carriers of allele G. The present study provides further evidence for the APOE/APOC1 candidate-region association with the risk of obesity. This was the first study to describe the protective association of the rs4420638 minor G-allele against obesity in childhood exclusively.

Sorting through the extensive and confusing roles of sortilin in metabolic disease

Sortilin is a post-Golgi trafficking receptor homologous to the yeast vacuolar protein sorting receptor 10 (VPS10). The VPS10 motif on sortilin is a 10-bladed β-propeller structure capable of binding more than 50 proteins, covering a wide range of biological functions including lipid and lipoprotein metabolism, neuronal growth and death, inflammation, and lysosomal degradation. Sortilin has a complex cellular trafficking itinerary, where it functions as a receptor in the trans-Golgi network, endosomes, secretory vesicles, multivesicular bodies, and at the cell surface. In addition, sortilin is associated with hypercholesterolemia, Alzheimer's disease, prion diseases, Parkinson's disease, and inflammation syndromes. The 1p13.3 locus containing SORT1, the gene encoding sortilin, carries the strongest association with LDL-C of all loci in human genome-wide association studies. However, the mechanism by which sortilin influences LDL-C is unclear. Here, we review the role sortilin plays in cardiovascular and metabolic diseases and describe in detail the large and often contradictory literature on the role of sortilin in the regulation of LDL-C levels.

Associations of genetic variants of lysophosphatidylcholine metabolic enzymes with levels of serum lipids

OBJECTIVE

Metabolic disturbance of lysophosphatidylcholine (LPC) is related with dyslipidemia. Therefore, eight single-nucleotide polymorphisms (SNPs) were selected from LPC metabolic enzymes to study their associations with obesity and serum levels of lipids.

METHODS

A total of 3305 children were recruited from four independent studies. Eight SNPs of LPC metabolic enzymes were selected and genotyped with the matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). The multivariable linear regression model was applied to detect the associations of eight SNPs with obesity-related phenotypes and levels of lipids in each study. Meta-analyses were used to combine the results of four studies.

RESULTS

Only SNP rs4420638 of APOC-1 gene was associated with serum lipids even after Bonferroni correction. The rs4420638 was positively associated with TC (β = 0.15, P = 8.59 × 10^-9) and low-density-lipoprotein-cholesterol (LDL-C, β = 0.16, P = 9.98 × 10^-14) individually.

CONCLUSION

The study firstly revealed the association between APOC-1/rs4420638 and levels of serum lipids in Chinese children, providing evidence for susceptible gene variants of dyslipidemia.

Expression of obesity- and type-2 diabetes-associated genes in omental adipose tissue of individuals with obesity

AIMS

Obesity and type 2 diabetes mellitus are two pathologies that share metabolic abnormalities in most of the cases; however, there are differences as well. Some studies have reported that approximately 30% of obese patients have normal glucose and lipid levels in blood despite an accumulation of abdominal adipose tissue. Here, we compare the gene expression in adipose tissue of several genes associated with obesity and/or diabetes between obese patients without T2D and obese patients with T2D.

METHODS

Omental adipose tissue was collected during the patients elective bariatric surgery. Gene expression was determined by real-time PCR. Phenotypic variables were correlated with gene expression and 2^^-ΔΔCt relative expression analysis between groups was performed.

RESULTS

The stronger correlations in the obese without T2D or reference group was between ICAM1 and HbA1c; HP and TC and LDL while in the obese with diabetes or case group the correlation occurred between CSF1 and BMI. A correlation between HP and TC was found in the case group as well. The expression of VEGFA, CCND2, IL1R1 and PTEN was downregulated in the obese with T2D group.

CONCLUSIONS

This study identified genes whose expression is different between obese subjects with and without diabetes. Those genes are related to inflammation, cholesterol transport, adipocyte differentiation/expansion and browning.

Association of Apolipoprotein E gene polymorphism with the risk of T2DM and obesity among Egyptian subjects

BACKGROUND

Numerous reports investigated the involvement of apolipoprotein E (APOE) polymorphisms with elevated risk of type 2 diabetes mellitus (T2DM) and obesity. The principal objective of this study is to assess the contribution of APOE polymorphisms (rs429358 and rs7412) with the risk of T2DM and obesity.

SUBJECTS AND METHODS

This work was designed involving 400 participants [100 healthy controls, 100 T2DM patients, 100 obese patients, and 100 T2DM + obese patients]. Genomic deoxyribonucleic acid (DNA) of the APOE polymorphisms was characterized using the PCR-RFLP assay.

RESULTS

The common predominant genotype of the study population is the APOE Ɛ3/Ɛ3 [T2DM patients (46%), obese patients (52%), T2DM + obese patients (37%), and healthy controls (58%)]. The frequencies of the APOE Ɛ4/Ɛ4 genotype and the APOE*Ɛ4 allele were significantly elevated among T2DM patients (p-value < 0.05). Additionally, the frequencies of the APOE Ɛ2/Ɛ2 genotype and the APOE*Ɛ2 allele were significantly increased among obese patients (p-value < 0.05). Moreover, the frequencies of the APOE Ɛ2/Ɛ2 genotype, APOE*Ɛ2 allele, APOE Ɛ4/Ɛ4 genotype, and APOE*Ɛ4 allele were statistically significant among T2DM + obese patients (p-value < 0.05).

CONCLUSIONS

APOE*Ɛ2 and APOE*Ɛ4 alleles were considered as independent risk factor among T2DM + obese patients. Furthermore, the APOE*Ɛ2 allele was correlated with elevated risk of obesity, while the APOE*Ɛ4 allele was correlated with elevated risk of T2DM.

Metabolic syndrome in a sample of Egyptian adolescent girls and its association with apolipoprotein E

AIM

Obesity and its metabolic complications are increasing in childhood and extend to adulthood. The aims of this study were to assess the prevalence of metabolic syndrome (MS) in a sample of Egyptian adolescent girls and investigate its association with apolipoprotein E.

METHODS

A cross-sectional study design was used, including 200 Egyptian adolescent girls aged between 12 and 18 years. They were subjected to blood pressure (BP) measurement, anthropometric measurements (weight, height and waist circumference (WC)), laboratory investigations (fasting glucose and lipid profile) and molecular analysis (Apo E).

RESULTS

Overweight/obese girls were suffering significantly, more than normal-weight girls, from hypertension (66.7 vs. 40.8%), diabetes diagnosed by elevated fasting blood glucose (46.7 vs. 31.2%) and low high-density lipoprotein (HDL) (64 vs. 59.2%). Girls with MS had significantly higher values of body mass index Z-score, WC, BP, cholesterol and triglycerides and significantly lower HDL. Allele E3 (59.1 vs. 55.1%) was more frequent among girls with MS, while allele E4 (41 vs. 36.4) was more frequent among girls without MS. MS was the most prominent among girls with the E3/E4 genotype (35.7%), who had the highest frequency of elevated cholesterol, triglycerides, low-density lipoprotein and blood glucose, while girls with the E2/E4 genotype, which was rare among both groups, had the highest frequency of elevated BP (68.8%) and low HDL (71.4%).

CONCLUSION

MS was significantly more prominent among overweight/obese adolescent girls with the E3/E4 genotype, who had the highest frequency of disturbed lipid profile and blood glucose.

Association between APOE polymorphisms and lipid profile in Mexican Amerindian population

BACKGROUND

Apolipoprotein E (ApoE) is a glycoprotein that plays an important role in lipid homeostasis at both cerebral and systemic levels. Moreover, the differential distribution of APOE gene alleles among different populations, means that ApoE isoforms could have different effects on lipids metabolism. The present study aims to evaluate the relationship between APOE gene alleles and the lipid profile in a Mexican Amerindian (MA) population.

METHODS

This study included 1997 MA individuals of different ethnicities distributed throughout different states of Mexico. All individuals underwent anthropometric measurements as well as laboratory tests including fasting glucose (FG), total cholesterol (TC), triglycerides, low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C). TaqMan^® probe genotyping assays were used to genotype APOE. The Kruskal-Wallis test was performed to determine the correlation between APOE gene alleles and genotypes and the biochemical variables measured.

RESULTS

Among the biochemical variables analyzed, only the HDL-C and LDL-C levels showed statistical differences (p-value < .05) between individuals carrying different APOE alleles. For HDL-C, individuals carrying the E2 allele had higher HDL-C levels, followed by individuals carrying the E3 allele and carriers of the E4 allele presented the lowest levels of HDL-C (E2 > E3 > E4). This relationship was inversed for LDL-C levels (E2 < E3 < E4). Nevertheless, the difference of HDL-C levels between APOE-E3 and APOE-E4 carriers remained only in obese individuals.

CONCLUSIONS

Our results suggest that APOE gene genotypes play an important role in the differential modulation of lipid profiles in the MA population with obesity.

Transcription Factor Co-expression Networks of Adipose RNA-Seq Data Reveal Regulatory Mechanisms of Obesity

BACKGROUND

Transcription Factors (TFs) control actuation of genes in the genome and are key mediators of complex processes such as obesity. Master Regulators (MRs) are the genes at the top of a regulation hierarchy which regulate other genes.

OBJECTIVE

To elucidate clusters of highly co-expressed TFs (modules), involved pathways, highly inter-connected TFs (hub-TFs) and MRs leading to obesity and leanness, using porcine model for human obesity.

METHODS

We identified 817 expressed TFs in RNA-Sequencing dataset representing extreme degrees of obesity (DO; lean, obese). We built a single Weighted Transcription Factor Co-expression Network (WTFCN) and TF sub-networks (based on the DO). Hub-TFs and MRs (using iRegulon) were identi-fied in biologically relevant WTFCNs modules.

RESULTS

Single WTFCN detected the Red module significantly associated with DO (P < 0.03). This module was enriched for regulation processes in the immune system, e.g.: Immune system process (Padj = 2.50E-06) and metabolic lifestyle disorders, e.g. Circadian rhythm - mammal pathway (Padj = 2.33E-11). Detected MR, hub-TF SPI1 was involved in obesity, immunity and osteoporosis. Within the obese sub-network, the Red module suggested possible associations with immunity, e.g. TGF-beta signaling pathway (Padj = 1.73E-02) and osteoporosis, e.g. Osteoclast differentiation (Padj = 1.94E-02). Within the lean sub-network, the Magenta module displayed associations with type 2 diabetes, obesity and os-teoporosis e.g. Notch signaling pathway (Padj = 2.40E-03), osteoporosis e.g. hub-TF VDR (a prime candidate gene for osteoporosis).

CONCLUSION

Our results provide insights into the regulatory network of TFs and biologically relevant hub TFs in obesity.

Lipid regulatory genes polymorphism in children with and without obesity and cardiometabolic risk factors: The CASPIAN-III study

Background:

Genetically, predisposed children are considered as at-risk individuals for cardiovascular disease. In this study, we aimed to compare the frequency of four-lipid regulatory polymorphism in obese and normal-weight children with and without cardiometabolic risk factors.

Materials and Methods:

In this nested case–control study, 600 samples of four groups of participants consisted of those with normal weight with and without cardiometabolic risk factors and obese with and without cardiometabolic risk factors. Allelic and genotypic frequencies of GCKR (rs780094), GCKR (rs1260333), MLXIPL (rs3812316), and FADS (rs174547) polymorphisms were compared in the four studied groups.

Results:

Data of 528 samples were complete and included in this study. The mean (standard deviation) age of participants was 15.01 (2.21) years. Frequency of tt allele (minor allele) of GCKR (rs1260333) polymorphism was significantly lower in normal weight metabolically healthy participants than metabolically unhealthy normal weight (MUHNW) and obese children with and without cardiometabolic risk factor (P = 0.01). Frequency of ga allele of GCKR (rs780094) polymorphism was significantly higher in normal weight children with cardiometabolic risk factor than in their obese counterparts with cardiometabolic risk factor (P = 0.04). Frequency of cg and gg alleles (minor type) of MLXIPL (rs3812316) polymorphism in normal weight metabolically healthy participants was significantly higher than MUHNW (P = 0.04) and metabolically healthy obese children (P = 0.04).

Conclusion:

The findings of our study indicated that the minor allele of GCKR (rs1260333) single nucleotide polymorphisms (SNPs) could have pathogenic effect for obesity and cardiometabolic risk factors. Ga allele of GCKR (rs780094) SNPs had a protective effect on obesity. Minor alleles of MLXIPL (rs3812316) could have a protective effect for obesity and cardiometabolic risk factors.

Weighted gene co-expression network analysis of expression data of monozygotic twins identifies specific modules and hub genes related to BMI

Background

The therapeutic management of obesity is challenging, hence further elucidating the underlying mechanisms of obesity development and identifying new diagnostic biomarkers and therapeutic targets are urgent and necessary. Here, we performed differential gene expression analysis and weighted gene co-expression network analysis (WGCNA) to identify significant genes and specific modules related to BMI based on gene expression profile data of 7 discordant monozygotic twins.

Results

In the differential gene expression analysis, it appeared that 32 differentially expressed genes (DEGs) were with a trend of up-regulation in twins with higher BMI when compared to their siblings. Categories of positive regulation of nitric-oxide synthase biosynthetic process, positive regulation of NF-kappa B import into nucleus, and peroxidase activity were significantly enriched within GO database and NF-kappa B signaling pathway within KEGG database. DEGs of NAMPT, TLR9, PTGS2, HBD, and PCSK1N might be associated with obesity. In the WGCNA, among the total 20 distinct co-expression modules identified, coral1 module (68 genes) had the strongest positive correlation with BMI (r = 0.56, P = 0.04) and disease status (r = 0.56, P = 0.04). Categories of positive regulation of phospholipase activity, high-density lipoprotein particle clearance, chylomicron remnant clearance, reverse cholesterol transport, intermediate-density lipoprotein particle, chylomicron, low-density lipoprotein particle, very-low-density lipoprotein particle, voltage-gated potassium channel complex, cholesterol transporter activity, and neuropeptide hormone activity were significantly enriched within GO database for this module. And alcoholism and cell adhesion molecules pathways were significantly enriched within KEGG database. Several hub genes, such as GAL, ASB9, NPPB, TBX2, IL17C, APOE, ABCG4, and APOC2 were also identified. The module eigengene of saddlebrown module (212 genes) was also significantly correlated with BMI (r = 0.56, P = 0.04), and hub genes of KCNN1 and AQP10 were differentially expressed.

Conclusion

We identified significant genes and specific modules potentially related to BMI based on the gene expression profile data of monozygotic twins. The findings may help further elucidate the underlying mechanisms of obesity development and provide novel insights to research potential gene biomarkers and signaling pathways for obesity treatment. Further analysis and validation of the findings reported here are important and necessary when more sample size is acquired.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4257-6) contains supplementary material, which is available to authorized users.

Apolipoprotein E4, Gender, Body Mass Index, Inflammation, Insulin Resistance, and Air Pollution Interactions: Recipe for Alzheimer's Disease Development in Mexico City Young Females

Given the epidemiological trends of increasing Alzheimer's disease (AD) and growing evidence that exposure and lifestyle factors contribute to AD risk and pathogenesis, attention should be paid to variables such as air pollution, in order to reduce rates of cognitive decline and dementia. Exposure to fine particulate matter (PM2.5) and ozone (O3) above the US EPA standards is associated with AD risk. Mexico City children experienced pre- and postnatal high exposures to PM2.5, O3, combustion-derived iron-rich nanoparticles, metals, polycyclic aromatic hydrocarbons, and endotoxins. Exposures are associated with early brain gene imbalance in oxidative stress, inflammation, innate and adaptive immune responses, along with epigenetic changes, accumulation of misfolded proteins, cognitive deficits, and brain structural and metabolic changes. The Apolipoprotein E (APOE) 4 allele, the most prevalent genetic risk for AD, plays a key role in the response to air pollution in young girls. APOE 4 heterozygous females with >75% to <94% BMI percentiles are at the highest risk of severe cognitive deficits (1.5-2 SD from average IQ). This review focused on the relationships between gender, BMI, systemic and neural inflammation, insulin resistance, hyperleptinemia, dyslipidemia, vascular risk factors, and central nervous system involvement in APOE4 urbanites exposed to PM2.5 and magnetite combustion-derived iron-rich nanoparticles that can reach the brain. APOE4 young female heterozygous carriers constitute a high-risk group for a fatal disease: AD. Multidisciplinary intervention strategies could be critical for prevention or amelioration of cognitive deficits and long-term AD progression in young individuals at high risk.