KCNQ1 p.D446E Variant as a Risk Allele for Arrhythmogenic Phenotypes: Electrophysiological Characterization Reveals a Complex Phenotype Affecting the Slow Delayed Rectifier Potassium Current (IKs) Voltage Dependence by Causing a Hyperpolarizing Shift and a Lack of Response to Protein Kinase A Activation.

Genetic testing is crucial in inherited arrhythmogenic channelopathies; however, the clinical interpretation of genetic variants remains challenging. Incomplete penetrance, oligogenic, polygenic or multifactorial forms of channelopathies further complicate variant interpretation. We identified the KCNQ1/p.D446E variant in 2/63 patients with long QT syndrome, 30-fold more frequent than in public databases. We thus characterized the biophysical phenotypes of wildtype and mutant IKs co-expressing these alleles with the ß-subunit minK in HEK293 cells. KCNQ1 p.446E homozygosity significantly shifted IKs voltage dependence to hyperpolarizing potentials in basal conditions (gain of function) but failed to shift voltage dependence to hyperpolarizing potentials (loss of function) in the presence of 8Br-cAMP, a protein kinase A activator. Basal IKs activation kinetics did not differ among genotypes, but in response to 8Br-cAMP, IKs 446 E/E (homozygous) activation kinetics were slower at the most positive potentials. Protein modeling predicted a slower transition of the 446E Kv7.1 tetrameric channel to the stabilized open state. In conclusion, biophysical and modelling evidence shows that the KCNQ1 p.D446E variant has complex functional consequences including both gain and loss of function, suggesting a contribution to the pathogenesis of arrhythmogenic phenotypes as a functional risk allele.

A metagenomic study identifies a Prevotella copri enriched microbial profile associated with non-alcoholic steatohepatitis in subjects with obesity.

BACKGROUND AND AIM: Non-alcoholic fatty liver disease (NAFLD) is the most common cause of liver disease. Increasing evidence indicates that the gut microbiota can play an important role in the pathophysiology of NAFLD. Recently, several studies have tested the predictive value of gut microbiome profiles in NAFLD progression; however, comparisons of microbial signatures in NAFLD or non-alcoholic steatohepatitis (NASH) have produced discrepant results, possibly due to ethnic and environmental factors. Thus, we aimed to characterize the gut metagenome composition of patients with fatty liver disease. METHODS: Gut microbiome of 45 well-characterized patients with obesity and biopsy-proven NAFLD was evaluated using shot-gun sequencing: 11 non-alcoholic fatty liver controls (non-NAFL), 11 with fatty liver, and 23 with NASH. RESULTS: Our study showed that Parabacteroides distasonis and Alistipes putredenis were enriched in fatty liver but not in NASH patients. Notably, in a hierarchical clustering analysis, microbial profiles were differentially distributed among groups, and membership to a Prevotella copri dominant cluster was associated with a greater risk of developing NASH. Functional analyses showed that although no differences in LPS biosynthesis pathways were observed, Prevotella-dominant subjects had higher circulating levels of LPS and a lower abundance of pathways encoding butyrate production. CONCLUSIONS: Our findings suggest that a Prevotella copri dominant bacterial community is associated with a greater risk for NAFLD disease progression, probably linked to higher intestinal permeability and lower capacity for butyrate production.

Genome-Wide Association Study Identifies a Functional SIDT2 Variant Associated With HDL-C (High-Density Lipoprotein Cholesterol) Levels and Premature Coronary Artery Disease.

Objective: Low HDL-C (high-density lipoprotein cholesterol) is the most frequent dyslipidemia in Mexicans, but few studies have examined the underlying genetic basis. Our purpose was to identify genetic variants associated with HDL-C levels and cardiovascular risk in the Mexican population. Approach and Results: A genome-wide association studies for HDL-C levels in 2335 Mexicans, identified four loci associated with genome-wide significance: CETP, ABCA1, LIPC, and SIDT2. The SIDT2 missense Val636Ile variant was associated with HDL-C levels and was replicated in 3 independent cohorts (P=5.9×10−18 in the conjoint analysis). The SIDT2/Val636Ile variant is more frequent in Native American and derived populations than in other ethnic groups. This variant was also associated with increased ApoA1 and glycerophospholipid serum levels, decreased LDL-C (low-density lipoprotein cholesterol) and ApoB levels, and a lower risk of premature CAD. Because SIDT2 was previously identified as a protein involved in sterol transport, we tested whether the SIDT2/Ile636 protein affected this function using an in vitro site-directed mutagenesis approach. The SIDT2/Ile636 protein showed increased uptake of the cholesterol analog dehydroergosterol, suggesting this variant affects function. Finally, liver transcriptome data from humans and the Hybrid Mouse Diversity Panel are consistent with the involvement of SIDT2 in lipid and lipoprotein metabolism. Conclusions: This is the first genome-wide association study for HDL-C levels seeking associations with coronary artery disease in the Mexican population. Our findings provide new insight into the genetic architecture of HDL-C and highlight SIDT2 as a new player in cholesterol and lipoprotein metabolism in humans.

The Role of the ATP-Binding Cassette A1 (ABCA1) in Human Disease.

Cholesterol homeostasis is essential in normal physiology of all cells. One of several proteins involved in cholesterol homeostasis is the ATP-binding cassette transporter A1 (ABCA1), a transmembrane protein widely expressed in many tissues. One of its main functions is the efflux of intracellular free cholesterol and phospholipids across the plasma membrane to combine with apolipoproteins, mainly apolipoprotein A-I (Apo A-I), forming nascent high-density lipoprotein-cholesterol (HDL-C) particles, the first step of reverse cholesterol transport (RCT). In addition, ABCA1 regulates cholesterol and phospholipid content in the plasma membrane affecting lipid rafts, microparticle (MP) formation and cell signaling. Thus, it is not surprising that impaired ABCA1 function and altered cholesterol homeostasis may affect many different organs and is involved in the pathophysiology of a broad array of diseases. This review describes evidence obtained from animal models, human studies and genetic variation explaining how ABCA1 is involved in dyslipidemia, coronary heart disease (CHD), type 2 diabetes (T2D), thrombosis, neurological disorders, age-related macular degeneration (AMD), glaucoma, viral infections and in cancer progression.

Endothelial Dysfunction, Inflammation and Coronary Artery Disease: Potential Biomarkers and Promising Therapeutical Approaches.

Coronary artery disease (CAD) and its complications are the leading cause of death worldwide. Inflammatory activation and dysfunction of the endothelium are key events in the development and pathophysiology of atherosclerosis and are associated with an elevated risk of cardiovascular events. There is great interest to further understand the pathophysiologic mechanisms underlying endothelial dysfunction and atherosclerosis progression, and to identify novel biomarkers and therapeutic strategies to prevent endothelial dysfunction, atherosclerosis and to reduce the risk of developing CAD and its complications. The use of liquid biopsies and new molecular biology techniques have allowed the identification of a growing list of molecular and cellular markers of endothelial dysfunction, which have provided insight on the molecular basis of atherosclerosis and are potential biomarkers and therapeutic targets for the prevention and or treatment of atherosclerosis and CAD. This review describes recent information on normal vascular endothelium function, as well as traditional and novel potential biomarkers of endothelial dysfunction and inflammation, and pharmacological and non-pharmacological therapeutic strategies aimed to protect the endothelium or reverse endothelial damage, as a preventive treatment for CAD and related complications.

Raet1e Polymorphisms Are Associated with Increased Risk of Developing Premature Coronary Artery Disease and with Some Cardiometabolic Parameters: The GEA Mexican Study.

In an animal model, new evidence has been reported supporting the role of raet1e as an atherosclerosis-associated gene. Our objective was to establish if raet1e polymorphisms are associated with the risk of developing premature coronary artery disease (CAD) or with the presence of cardiometabolic parameters. After an informatic analysis, five polymorphisms were chosen and determined in 1158 patients with premature CAD and 1104 controls using 5' exonuclease TaqMan genotyping assays. Standardized questionnaires were applied to all participants to obtain family medical history, demographic information, history of nutritional habits, physical activity, alcohol consumption, and pharmacological treatment. The functional effect of the rs7756850 polymorphism was analyzed by luciferase assays. Under different models, adjusted by age, gender, body mass index, current smoking, and type 2 diabetes mellitus, the rs6925151 (OR = 1.250, p heterozygote = 0.026; OR = 1.268, p codominant1 = 0.034), rs9371533 (OR = 1.255, p heterozygote = 0.024), rs7756850 (OR = 1.274, p heterozygote = 0.016; OR = 1.294, p codominant1 = 0.031), and rs9383921 (OR = 1.232, p heterozygote = 0.037) polymorphisms were associated with increased risk of premature CAD. When compared to the rs7756850 G allele, the C allele showed a decreased luciferase activity. In premature CAD patients, associations with low levels of adiponectin, with a high presence of hypertension, and with high levels of gamma-glutamyltransferase and total cholesterol were observed. In healthy controls, associations with a decrease in LDL pattern B, aspartate aminotransaminase, and hypo-α-lipoproteinemia were detected. An association of the raet1e polymorphisms with an increased risk of developing premature CAD and with cardiometabolic parameters has been shown for the first time. In addition, the functional effect of the rs7756850 polymorphism was defined.

A combined linkage and association strategy identifies a variant near the GSTP1 gene associated with BMI in the Mexican population.

Obesity is a major public health concern in Mexico and worldwide. Although the estimated heritability is high, common variants identified by genome-wide association studies explain only a small proportion of this heritability. A combination of linkage and association strategies could be a more robust and powerful approach to identify other obesity-susceptibility variants. We thus sought to identify novel genetic variants associated with obesity-related traits in the Mexican population by combining these methods. We performed a genome-wide linkage scan for body mass index (BMI) and other obesity-related phenotypes in 16 Mexican families using the Sequential Oligogenic Linkage Analysis Routines Program. Associated single-nucleotide polymorphisms (SNPs) were tested for associations in an independent cohort. Two suggestive BMI-linkage peaks (logarithm of odds ⩾1.5) were observed at chromosomal regions 11q13 and 13q22. Only rs614080 in the 11q13 region was significantly associated with BMI and related traits in these families. This association was also significant in an independent cohort of Mexican adults. Moreover, this variant was significantly associated with GSTP1 gene expression levels in adipose tissue. In conclusion, the rs614080 SNP near the GSTP1 gene was significantly associated with BMI and GSTP1 expression levels in the Mexican population.

Receptor-interacting protein 2 (RIP2) gene polymorphisms are associated with increased risk of subclinical atherosclerosis and clinical and metabolic parameters. The Genetics of Atherosclerotic Disease (GEA) Mexican study.

The receptor-interacting protein 2 (Rip2) is a serine/threonine kinase involved in multiple nuclear factor-κB (NFκB) activation pathways and is a key regulator of cellular lipid metabolism and cardiovascular disease. The aim of the present study was to evaluate the role of RIP2 gene polymorphisms as susceptibility markers for subclinical atherosclerosis (SA). Using an informatics analysis, four RIP2 gene polymorphisms with predicted functional effects (rs2293808, rs43133, rs431264, and rs16900627) were selected. The polymorphisms were genotyped in 405 individuals with SA (calcium score>0 assessed by computed tomography) and 1099 controls (calcium score=0). Clinical, anthropometric, tomographic and biochemical traits were measured. The association between the RIP2 polymorphisms and SA was evaluated using logistic regression analyses. Pair wise linkage disequilibrium (LD, D') estimations between polymorphisms and haplotype reconstruction were performed with Haploview version 4:1. Under different models adjusted by age, gender, body mass index, hypertension, diabetes mellitus, smoking habit, total cholesterol, HDL-cholesterol, LDL-cholesterol and triglyceride levels, rs43133 (OR=1.43, 95% CI: 1.05-1.94, P=0.022), and rs16900627 (OR=1.59, 95% CI: 1.00-2.54, Pdom=0.048 and OR=1.60, 95% CI: 1.05-2.54, Padd=0.028) were associated with increased risk of developing SA. Moreover, rs2293808, and rs431264 were associated with clinical or metabolic parameters in SA individuals and in healthy controls. The four polymorphisms were in high linkage disequilibrium and the GAAG haplotype was associated with increased risk of developing SA (OR=1.47, P=0.027). This study shows for the first time, that RIP2 polymorphisms are associated with increased risk of SA and with some clinical and metabolic parameters.

Interleukin 35 Polymorphisms Are Associated with Decreased Risk of Premature Coronary Artery Disease, Metabolic Parameters, and IL-35 Levels: The Genetics of Atherosclerotic Disease (GEA) Study.

Interleukin 35 (IL-35) is a heterodimeric cytokine involved in the development of atherosclerosis. The aim of the present study was to establish if the polymorphisms of IL-12A and EBI3 genes that encode the IL-35 subunits are associated with the development of premature coronary artery disease (CAD) in Mexican individuals. The IL-12A and EBI3 polymorphisms were determined in 1162 patients with premature CAD and 873 controls. Under different models, the EBI3 rs428253 (OR = 0.831, Padd = 0.036; OR = 0.614, Prec = 0.033; OR = 0.591, Pcod2 = 0.027) and IL-12A rs2243115 (OR = 0.674, Padd = 0.010; OR = 0.676, Pdom = 0.014; OR = 0.698, Phet = 0.027; OR = 0.694, Pcod1 = 0.024) polymorphisms were associated with decreased risk of developing premature CAD. Some polymorphisms were associated with clinical and metabolic parameters. Significant different levels of IL-35 were observed in EBI3 rs4740 and rs4905 genotypes only in the group of healthy controls. In summary, our study suggests that the EBI3 and IL-12A polymorphisms play an important role in decreasing the risk of developing premature CAD; it also demonstrates the relationship of the EBI3 rs4740 and rs4905 genotypes with IL-35 levels in healthy individuals.

Hepatic miR-33a/miR-144 and their target gene ABCA1 are associated with steatohepatitis in morbidly obese subjects.

BACKGROUND AND AIM: Abnormal cholesterol metabolism may contribute to the pathogenesis of non-alcoholic steatohepatitis (NASH) and fibrosis. miR-33 and miR-144 regulate adenosine triphosphate binding cassette transporter (ABCA1) and other target genes involved in cholesterol efflux, fatty acid oxidation and inflammation. We explored relationships between non-alcoholic fatty liver disease (NAFLD) and the hepatic expression of ABCA1/ABCG1, as well as other target genes regulated by miR-33 (carnitine O-octanoyltransferase, CROT and hydroxyacyl-CoA-dehydrogenase ß-subunit, HADHB) and miR-144 (toll-like receptor-2, TLR2). Moreover, we evaluated whether the expression of these genes is correlated with miR-33a/b and miR-144 expression in Mexican individuals with morbid obesity. METHODS: Eighty-four morbidly obese subjects undergoing bariatric surgery were included in this study. Liver biopsies were obtained to measure hepatic triglyceride and free cholesterol contents, as well as ABCA1, ABCG1, CROT, HADHB, TLR2, miR-33a/b and miR-144 expression. RESULTS: Hepatic free cholesterol content was significantly increased in NASH as compared to non-NASH subjects, while ABCA1 and ABCG1 protein levels significantly decreased with NASH and fibrosis progression. The relative expression of miR-33a and miR-144 correlated inversely with ABCA1 but not with ABCG1 protein levels. Moreover, both miRNAs increased significantly in NASH individuals. miR-33 target genes CROT and HADHB correlated inversely with miR-33a. However, the expression of these genes was not associated with NASH. CONCLUSIONS: miR-33a/144 and their target gene ABCA1 may contribute to the pathogenesis of NASH in morbidly obese subjects.

Role of adiponectin and free fatty acids on the association between abdominal visceral fat and insulin resistance.

BACKGROUND: Experimental studies have shown that high free fatty acid (FFA) and low adiponectin (ADIPO) levels are involved in the mechanisms by which adiposity promotes insulin resistance (IR). However, no previous clinical studies have simultaneously analysed the relative contribution of FFA and ADIPO levels on the relation of abdominal visceral fat (AVF) with insulin resistance. OBJECTIVE: To analyse the contribution of low ADIPO (adiponectin < =p25th: 8.67 µg/mL in women and 5.30 µg/mL in men), and high FFAs (FFAs > =p75th: 0.745 mEq/L in women and 0.60 mEq/L in men) to the association of high AVF (AVF > =p75th: 127 cm2 in women; 152.7 cm2 in men) with insulin resistance (HOMA-IR > =75th: 3.58 in women and 3.12 in men), in non-diabetic subjects. MATERIAL AND METHODS: A cross-sectional analysis was performed including 1217 control participants of the Genetics of Atherosclerotic Disease study (GEA). Clinical, tomographic and biochemical parameters were measured in all participants. Logistic regression models were used to assess the association of high AVF with IR stratifying according to gender, and to normal or low ADIPO and normal or high FFA serum levels. RESULTS: In comparison to referent group, in men low ADIPO unlike high FFA increased the risk of IR. Females with normal AVF and low ADIPO, or high AVF and normal ADIPO had aprox 3 folds risk of IR (OR [IC95%]: 3.7 [2.1-6.6], p < 0.001, and 3.4 [2.0-5.7], p < 0.001; respectively). The risk increased to 7.6 [4.2-13.8], p < 0.001 when high AVF and low ADIPO were present. Irrespective of AVF, the effect of low ADIPO on IR was higher than that seen for high FFA. Besides, our results suggest an additive effect of high AVF, high FFA and low ADIPO on the IR prevalence. CONCLUSIONS: The present study provides novel and important information about the combined effect of high AVF and low ADIPO on the risk of IR. Furthermore, our data suggest that the effect of low adiponectin levels on the high AVF-IR association is stronger than that observed for high FFA, suggesting that adiponectin could be used as biomarker to identify subjects at high risk for T2DM and CAD.

Hepatic lipase (LIPC) C-514T gene polymorphism is associated with cardiometabolic parameters and cardiovascular risk factors but not with fatty liver in Mexican population.

The aim of the present study was to evaluate the role of the C-514T (rs1800588) gene polymorphism of the hepatic lipase (LIPC) as susceptibility marker for fatty liver in the Mexican population. The polymorphism was genotyped by 5' exonuclease TaqMan assays in a group of 1468 subjects (980 with and 488 without fatty liver) belonging to the Genetics of Atherosclerotic Disease (GEA) Mexican Study. Anthropometric and biochemical measurements were performed on all individuals. The polymorphism was not associated with fatty liver, however, under dominant model, the TT genotype was associated with increased levels of triglycerides (P=0.0002), apolipoprotein A1 (P=0.015), triglycerides/HDL-cholesterol index (P=0.046) and increased frequency of type 2 diabetes mellitus (P=0.045). On the other hand, the same genotype was associated with the presence of small LDLs (P=0.003). The risk analysis showed that under a dominant model, the LIPC C-514T polymorphism was associated with increased risk of type 2 diabetes (OR=1.42, P=0.029), hypertriglyceridemia (OR=1.36, P=0.006), and coronary artery calcification (CAC)≥1 (OR=1.44, P=0.015) and decreased risk of hypoalphalipoproteinemia (OR=0.78, P=0.036). The results suggest that the LIPC C-154T polymorphism is associated with cardiometabolic parameters and cardiovascular risk factors but not with fatty liver in Mexican population. The association detected with CAC indicates that this polymorphism could be a marker for subclinical atherosclerosis.

SFRP5 hepatic expression is associated with non-alcoholic liver disease in morbidly obese women.

BACKGROUND AND AIMS: Secreted frizzled-related protein 5 (SFRP5) was recently described as a new adipokine protective for hepatic steatosis and other obesity-related complications in the mouse model. To date, SFRP5 expression in non-alcoholic fatty liver disease (NAFLD) has not been fully assessed in humans. We measured circulating SFRP5 levels and its expression in liver and adipose tissue, and evaluated its association with NAFLD in morbidly obese women. MATERIAL AND METHODS: Fifty-four morbidly obese women undergoing bariatric surgery were included in the study. Liver biopsies were used for histology and hepatic triglyceride content quantification. Circulating SFRP5 levels were measured through enzyme-linked immunoabsorbent assay, and SFRP5 expression was performed in hepatic and adipose tissue (subcutaneous and visceral). RESULTS: Although circulating SFRP5 levels showed a tendency to decrease with NAFLD progression, no significant differences were observed among non-alcoholic steatosis, steatohepatitis, and control subjects. Hepatic SFRP5 expression showed a negative correlation with hepatic triglyceride content (r = -0.349, P = 0.016 for mRNA and r = -0.291, P = 0.040 for SRFP5 protein) and ALT serum levels (r = -0.437, P = 0.001 for SRFP5 protein). In addition, hepatic SFRP5 protein levels were significantly lower in NASH than in control subjects (P = 0.006). CONCLUSION: This is the first study reporting an association of hepatic SFRP5 expression with NAFLD in humans.

The HIF1A rs2057482 polymorphism is associated with risk of developing premature coronary artery disease and with some metabolic and cardiovascular risk factors. The Genetics of Atherosclerotic Disease (GEA) Mexican Study.

The aim of the present study was to establish the role of HIF1A gene polymorphisms in the risk of developing premature coronary artery disease (CAD) in a well-characterized clinical cohort. Three polymorphisms in HIF1A (rs11549465, rs11549467, rs2057482) gene were genotyped in 949 patients with premature CAD, and 676 healthy controls (with negative calcium score by computed tomography). Under a dominant model adjusted for age, visceral to subcutaneous adipose tissue (VAT/SAT) ratio, hypertension, type 2 diabetes mellitus (T2DM), HDL-C levels, hypercholesterolemia and hypertriglyceridemia, the rs2057482 T allele was associated with decreased risk of premature CAD when compared to healthy controls (OR = 0.616, P(dom) = 0.020). The effect of the studied polymorphisms on various metabolic parameters and cardiovascular risk factors was explored. In this analysis, the rs2057482 T allele was associated with decreased risk of obesity, central obesity, hypertension, hypercholesterolemia, hypertriglyceridemia and increased risk of T2DM. Under a dominant model adjusted by age, the HIF1A rs2057482 T polymorphism was associated with high VAT/SAT ratio (P = 0.009) and HDL-C levels (P = 0.04) in healthy controls. The results suggest that HIF1A rs2057482 polymorphism is involved in the risk of developing CAD and is associated with some metabolic parameters and cardiovascular risk factors.

PNPLA3 I148M polymorphism is associated with elevated alanine transaminase levels in Mexican Indigenous and Mestizo populations.

The patatin like phospholipase domain-containing (PNPLA3) I148M variant is the strongest genetic factor associated with elevated alanine transaminase (ALT) levels in different populations, particularly in Hispanics who have the highest 148M risk allele frequency reported to date. It has been suggested that Indigenous ancestry is associated with higher ALT levels in Mexicans. The aim of the present study was to assess the frequency of the PNPLA3 148M risk allele in Mexican indigenous and Mestizo individuals, and to examine its association with serum ALT levels. The study included a total of 1624 Mexican individuals: 919 Indigenous subjects from five different native groups and 705 Mexican Mestizo individuals (141 cases with ALT levels ≥ 40 U/L and 564 controls with ALT <40 U/L). The I148M polymorphism was genotyped by TaqMan assays. The frequency of elevated ALT levels in Indigenous populations was 18.7%, and varied according to obesity status: 14.4% in normal weight, 19.9% in overweight and 24.5% in obese individuals. The Mexican indigenous populations showed the highest reported frequency of the PNPLA3 148M risk allele (mean 0.73). The M148M genotype was significantly associated with elevated ALT levels in indigenous individuals (OR = 3.15, 95 % CI 1.91-5.20; P = 7.1 × 10(-6)) and this association was confirmed in Mexican Mestizos (OR = 2.24, 95% CI 1.50-3.33; P = 8.1 × 10(-5)). This is the first study reporting the association between M148M genotype and elevated ALT levels in Indigenous Mexican populations. The 148M allele risk may be considered an important risk factor for liver damage in Mexican indigenous and Mestizo populations.

Analysis of association of MEF2C, SOST and JAG1 genes with bone mineral density in Mexican-Mestizo postmenopausal women.

BACKGROUND: Osteoporosis, a disease characterized by low bone mineral density (BMD), is an important health problem in Mexico. BMD is a highly heritable trait, with heritability estimates of 50-85%. Several candidate genes have been evaluated to identify those involved in BMD variation and the etiology of osteoporosis. This study investigated the possible association of single-nucleotide polymorphisms (SNPs) in the MEF2C, SOST and JAG1genes with bone mineral density (BMD) variation in postmenopausal Mexican-Mestizo women. METHODS: Four hundred unrelated postmenopausal women were included in the study. Risk factors were recorded and BMD was measured in total hip, femoral neck and lumbar spine using dual-energy X-ray absorptiometry. In an initial stage, a total of twenty-five SNPs within or near SOST gene and seven SNPs in the JAG1 gene were genotyped using a GoldenGate assay. In a second stage, three MEF2C gene SNPs were also genotyped and SOST and JAG1 gene variants were validated. Real time PCR and TaqMan probes were used for genotyping. RESULTS: Linear regression analyses adjusted by age, body mass index and ancestry estimates, showed that five SNPs in the SOST gene were significantly associated with BMD in total hip and femoral neck but not lumbar spine. The lowest p value was 0.0012, well below the multiple-test significance threshold (p=0.009), with mean effect size of -0.027 SD per risk allele. We did not find significant associations between BMD and MEF2C/JAG1 gene variants [rs1366594 "A" allele: ß=0.001 (95% CI -0.016; 0.017), P=0.938; rs2273061 "G" allele: ß=0.007 (95% CI -0.007; 0.023), p=0.409]. CONCLUSIONS: SOST polymorphisms may contribute to total hip and femoral neck BMD variation in Mexican postmenopausal women. Together, these and prior findings suggest that this gene may contribute to BMD variation across populations of diverse ancestry.

Selection scan in Native Americans of Mexico identifies FADS2 rs174616: Evidence of gene-diet interactions affecting lipid levels and Delta-6-desaturase activity.

Searching for positive selection signals across genomes has identified functional genetic variants responding to environmental change. In Native Americans of Mexico, we used the fixation index (Fst) and population branch statistic (PBS) to identify SNPs suggesting positive selection. The 103 most differentiated SNPs were tested for associations with metabolic traits, the most significant association was FADS2/rs174616 with body mass index (BMI). This variant lies within a linkage disequilibrium (LD) block independent of previously reported FADS selection signals and has not been clearly associated with metabolic phenotypes. We tested this variant in two independent cohorts with cardiometabolic data. In the Genetics of Atherosclerotic Disease (GEA) cohort, the derived allele (T) was associated with increased BMI, lower LDL-C levels and a decreased risk of subclinical atherosclerosis in women. Significant gene-diet interactions affected lipid, apolipoprotein and adiponectin levels with differences according to sex, involving mainly total and complex dietary carbohydrate%. In the Genotype-related Effects of PUFA trial, the derived allele was associated with lower Δ-6 desaturase activity and erythrocyte membrane dihomo-gamma-linolenic acid (DGLA) levels, and with increased Δ-5 desaturase activity and eicosapentaenoic acid levels. This variant interacted with dietary carbohydrate% affecting Δ-6 desaturase activity. Notably, the relationship of DGLA and other erythrocyte membrane LC-PUFA indices with HOMA-IR differed according to rs174616 genotype, which has implications regarding how these indices should be interpreted. In conclusion, this observational study identified rs174616 as a signal suggesting selection in an independent linkage disequilibrium block, was associated with cardiometabolic and erythrocyte measurements of LC-PUFA in two independent Mexican cohorts and showed significant gene-diet interactions.

A functional ABCA1 gene variant is associated with low HDL-cholesterol levels and shows evidence of positive selection in Native Americans.

It has been suggested that the higher susceptibility of Hispanics to metabolic disease is related to their Native American heritage. A frequent cholesterol transporter ABCA1 (ATP-binding cassette transporter A1) gene variant (R230C, rs9282541) apparently exclusive to Native American individuals was associated with low high-density lipoprotein cholesterol (HDL-C) levels, obesity and type 2 diabetes in Mexican Mestizos. We performed a more extensive analysis of this variant in 4405 Native Americans and 863 individuals from other ethnic groups to investigate genetic evidence of positive selection, to assess its functional effect in vitro and to explore associations with HDL-C levels and other metabolic traits. The C230 allele was found in 29 of 36 Native American groups, but not in European, Asian or African individuals. C230 was observed on a single haplotype, and C230-bearing chromosomes showed longer relative haplotype extension compared with other haplotypes in the Americas. Additionally, single-nucleotide polymorphism data from the Human Genome Diversity Panel Native American populations were enriched in significant integrated haplotype score values in the region upstream of the ABCA1 gene. Cells expressing the C230 allele showed a 27% cholesterol efflux reduction (P< 0.001), confirming this variant has a functional effect in vitro. Moreover, the C230 allele was associated with lower HDL-C levels (P = 1.77 x 10(-11)) and with higher body mass index (P = 0.0001) in the combined analysis of Native American populations. This is the first report of a common functional variant exclusive to Native American and descent populations, which is a major determinant of HDL-C levels and may have contributed to the adaptive evolution of Native American populations.

Carbohydrate intake modulates the effect of the ABCA1-R230C variant on HDL cholesterol concentrations in premenopausal women.

The R230C variant of the ATP-binding cassette transporter A1 (ABCA1) gene has been consistently associated with decreased HDL-cholesterol (HDL-C) concentrations in several studies in the Mexican mestizo population. However, information on how diet composition modifies the effect of the ABCA1-R230C variant on HDL-C concentrations is very scarce. The aim of the present study was to analyze whether the effect of ABCA1-R230C on HDL-C concentrations is modulated by dietary factors in a nationwide population sample of 3591 adults from the National Health and Nutrition Survey conducted by the State's Employees' Social Security and Social Services Institute. All participants answered a validated questionnaire to assess health status and weekly food consumption. Fasting blood samples were drawn for biochemical analysis and DNA extraction, and the ABCA1-R230C variant was genotyped using TaqMan assays. Statistical analyses consisted of simple linear and multiple regression modeling adjusting for age, BMI, smoking, and alcohol consumption. The overall C risk allele frequency was 9.3% and the variant was significantly associated with low HDL-C concentrations in both sexes. A significant negative correlation between carbohydrate consumption and HDL-C concentrations was observed in women bearing the R230C variant (P = 0.021) and a significant gene-diet interaction was found only in premenopausal women (P = 0.037). In conclusion, the effect of the ABCA1-R230C gene variant on HDL-C concentrations is modulated by carbohydrate intake in premenopausal women. This finding may help design optimized dietary interventions according to sex and ABCA1-R230C genotype.

Association of Gut Microbiota with Atherogenic Dyslipidemia, and Its Impact on Serum Lipid Levels after Bariatric Surgery.

Gut microbiota has been suggested to modulate circulating lipids. However, the relationship between the gut microbiota and atherogenic dyslipidemia (AD), defined as the presence of both low HDL-C and hypertriglyceridemia, is not fully understood. Moreover, because obesity is among the main causes of secondary AD, it is important to analyze the effect of gut microbiota composition on lipid profiles after a weight loss intervention. We compared the microbial diversity and taxonomic composition in patients with AD (n = 41) and controls (n = 38) and sought correlations of genera abundance with serum lipid levels in 20 patients after weight loss induced by Roux-en-Y gastric bypass (RYGB) surgery. Gut microbiota composition was profiled using next-generation sequencing of 16S rRNA. Gut microbiota diversity was significantly lower in atherogenic dyslipidemia. Moreover, relative abundance of two genera with LDA score >3.5 (Megasphaera and LPS-producing Escherichia-Shigella), was significantly higher in AD subjects, while the abundance of four short chain fatty acids (SCFA) producing-genera (Christensenellaceae R-7, Ruminococcaceae UCG-014; Akkermansia and [Eubacterium] eligens group) was significantly higher in controls. Notably, [Eubacterium] eligens group abundance was also significantly associated with higher HDL-C levels in RYGB patients one year after surgery. Although dietary polyunsaturated fatty acid/saturated fatty acid (PUFA/SFA) ratio and PUFA intake were higher in controls than in AD subjects, of the four genera differentiated in cases and controls, only Akkermansia abundance showed a positive and significant correlation with PUFA/SFA ratio. Our results suggest that SCFA-producing bacteria promote a healthy lipid homeostasis, while the presence of LPS-producing bacteria such Escherichia-Shigella may contribute to the development of atherogenic dyslipidemia.