Genetic variants at the PDZ-interacting domain of the scavenger receptor class B type I interact with diet to influence the risk of metabolic syndrome in obese men and women

Interaction of Human OATP1B1 with PDZK1 Is Required for Its Trafficking to the Hepatocyte Plasma Membrane

Uptake of xenobiotics by hepatocytes is mediated by specific proteins, including organic anion transporting polypeptides (OATPs), residing on the basolateral (sinusoidal) plasma membrane. Many of the OATPs have PDZ consensus binding sites, determined by their C-terminal 4 amino acids, while others do not. Mouse and rat OATP1A1 are associated with PDZK1, which is necessary for their trafficking to the plasma membrane. humanOATP1B1 (hOATP1B1) is a major drug transporter in human liver. Although localized to the plasma membrane, it was thought to lack a PDZ consensus motif, suggesting that the trafficking paradigm for murine OATPs is not applicable to human liver. The aim of the present study was to determine whether hOATP1B1 is a ligand for hPDZK1. hOATP1B1 immunoprecipitates with hPDZK1 following co-expression in 293T cells as well as in normal human liver. Co-expression with each of the 4 PDZ domains revealed interaction with domain 1 only. A truncated version of hOATP1B1 that lacks its terminal 4 amino acid PDZ binding motif as well as hOATP1B3, which does not contain a PDZ binding consensus motif, failed to interact with hPDZK1. Immunofluorescence microscopy of hOATP1B1 in stably transfected HeLa cells that endogenously express hPDZK1 showed that it distributes predominantly along the plasma membrane whereas hOATP1B1 lacking its terminal 4 amino acids distributes primarily intracellularly with little plasma membrane localization. Similar to findings in rats and mice, human OATP1B1 is a ligand for PDZK1 and requires interaction with PDZK1 for optimal trafficking to the hepatocyte plasma membrane. SIGNIFICANCE: Previous studies suggested that OATP1B1, a major xenobiotic transporter in human liver, does not have a PDZ binding consensus motif and does not follow the paradigm for subcellular trafficking and function that was established for OATP1A1 in murine liver. We now demonstrated that OATP1B1 but not OATP1B3 has a PDZ binding consensus motif that mediates binding to PDZK1 and is required for its trafficking to the plasma membrane. Such interaction could be an important previously unrecognized modulator of transport function.

Relationship between heavy drinking, binge drinking, and metabolic syndrome in obese and non-obese Korean male adults

BACKGROUND/OBJECTIVES

Obesity and alcohol drinking are associated with metabolic syndrome. However, few studies show the relationship between alcohol drinking and metabolic syndrome according to varying degrees of obesity. This study aimed to determine the association between alcohol drinking and metabolic syndrome in obese and non-obese Korean male adults.

SUBJECTS/METHODS

This cross-sectional study included 5,867 males aged ≥ 20 years who were examined at the Soonchunhyang University health promotion center during June 2008–December 2010. The subjects were divided into non-obese (body mass index [BMI] < 25 kg/m²) and obese (BMI ≥ 25 kg/m²) groups and further divided according to weekly alcohol consumption into nondrinking (0 drinks/week), moderate drinking (≤ 14 drinks/week), and heavy drinking (> 14 drinks/week) groups. The subjects were also categorized into binge drinking and non-binge drinking groups. To obtain odds ratios (ORs) for metabolic syndrome, binary logistic regression analysis was performed.

RESULTS

The overall metabolic syndrome prevalence was 27.3% (12.8%, non-obese group; 50.4%, obese group). After adjusting for age, physical activity, and smoking, in the non-obese group, the OR for heavy drinking with binge drinking (reference: nondrinking) was 1.56 (95% confidence interval [CI] = 1.12–2.18), with a significant increase in metabolic syndrome prevalence. In the obese group, the OR for heavy drinking with binge drinking was 1.42 (95% CI = 1.07–1.88), showing a significant increase in metabolic syndrome prevalence (P < 0.05).

CONCLUSIONS

In both non-obese and obese Korean males, heavy drinking with binge drinking was associated with increased risk of metabolic syndrome. Thus, both non-obese and obese males should restrict their alcohol intake and not indulge in binge drinking.

SLC15A2 genomic variation is associated with the extraordinary response of sorafenib treatment: whole-genome analysis in patients with hepatocellular carcinoma

Reliable biomarkers are required to predict the response to sorafenib. We investigated genomic variations associated with responsiveness to sorafenib for patients with unresectable hepatocellular carcinoma (HCC). Blood samples from 2 extreme, 2 strong and 3 poor responders to sorafenib were subjected to whole-genome analysis. Then, we validated candidate genomic variations with another 174 HCC patients, and performed in vitro functional analysis and in silico analyses. Genomic data of >96 gigabases/sample was generated at average of ~34X sequencing depth. In total, 1813 genomic variations were matched to sorafenib responses in clinical data; 708 were located within regions for sorafenib-target genes or drug absorption, distribution, metabolism, and excretion (ADME)-related genes. From them, 36 variants were within the coding regions and 6 identified as non-synonymous single-nucleotide variants from 4 ADME-related genes (ABCB1, FMO3, MUSK, and SLC15A2). Validation genotyping confirmed sequencing results and revealed patients genotype for rs2257212 in SLC15A2 showed longer progression-free survival (HR = 2.18). In vitro study displayed different response to sorafenib depending on the genotype of SLC15A2. Structural prediction analysis revealed changes of the phosphorylation levels in protein, potentially affecting sorafenib-associated enzymatic activity. Our finding using extreme responder seems to generate robust biomarker to predict the response of sorafenib treatment for HCC.

New candidate loci identified by array-CGH in a cohort of 100 children presenting with syndromic obesity

Syndromic obesity is defined by the association of obesity with one or more feature(s) including developmental delay, dysmorphic traits, and/or congenital malformations. Over 25 syndromic forms of obesity have been identified. However, most cases remain of unknown etiology. The aim of this study was to identify new candidate loci associated with syndromic obesity to find new candidate genes and to better understand molecular mechanisms involved in this pathology. We performed oligonucleotide microarray-based comparative genomic hybridization in a cohort of 100 children presenting with syndromic obesity of unknown etiology, after exhaustive clinical, biological, and molecular studies. Chromosomal copy number variations were detected in 42% of the children in our cohort, with 23% of patients with potentially pathogenic copy number variants. Our results support that chromosomal rearrangements are frequently associated with syndromic obesity with a variety of contributory genes having relevance to either obesity or developmental delay. A list of inherited or apparently de novo duplications and deletions including their enclosed genes and not previously linked to syndromic obesity was established. Proteins encoded by several of these genes are involved in lipid metabolism (ACOXL, MSMO1, MVD, and PDZK1) linked with nervous system function (BDH1 and LINGO2), neutral lipid storage (PLIN2), energy homeostasis and metabolic processes (CDH13, CNTNAP2, CPPED1, NDUFA4, PTGS2, and SOCS6).

Olive oil polyphenols enhance the expression of cholesterol efflux related genes in vivo in humans. A randomized controlled trial

Both oleic acid and polyphenols have been shown to increase high-density lipoprotein (HDL) cholesterol and to protect HDL from oxidation, a phenomenon associated with a low cholesterol efflux from cells. Our goal was to determine whether polyphenols from olive oil could exert an in vivo nutrigenomic effect on genes related to cholesterol efflux in humans. In a randomized, controlled, cross-over trial, 13 pre/hypertensive patients were assigned 30 ml of two similar olive oils with high (961 mg/kg) and moderate (289 mg/kg) polyphenol content. We found an increase in ATP binding cassette transporter-A1, scavenger receptor class B type 1, peroxisome proliferator-activated receptor (PPAR)BP, PPARα, PPARγ, PPARδ and CD36 gene expression in white blood cells at postprandial after high polyphenol olive oil when compared with moderate polyphenol olive oil intervention (P<.017), with COX-1 reaching borderline significance (P=.024). Linear regression analyses showed that changes in gene expression were related to a decrease in oxidized low-density lipoproteins and with an increase in oxygen radical absorbance capacity and olive oil polyphenols (P<.05). Our results indicate a significant role of olive oil polyphenols in the up-regulation of genes involved in the cholesterol efflux from cells to HDL in vivo in humans. These results are in agreement with previous ones concerning the fact that benefits associated with polyphenol-rich olive oil consumption on cardiovascular risk could be mediated through an in vivo nutrigenomic effect in humans.

All-cause and cardiovascular mortality risk estimation using different definitions of metabolic syndrome in Lithuanian urban population

OBJECTIVE

The objective of the study was to assess mortality risk in the subjects with diagnosed metabolic syndrome (MS) using National Cholesterol Educational Program (NCEP-ATPIII), American Heart Association and National Heart Lung and Blood Institute (AHA/NHLBI) International Diabetes Federation (IDF) and Joint Interim Societies (JIS) definitions.

METHODS

Two random samples aged 35-64 years were examined in 1992-2002 in the framework within the Multinational Monitoring of Trends and Determinants in Cardiovascular Disease (MONICA) study (N=2455). The follow-up was carried out in terms of the end points reached from the baseline health examinations until December 31, 2009.

RESULTS

Cox regressions demonstrated that MS defined by IDF and JIS definitions remained the only significant determinants for all-cause mortality (RR=1.48 and RR=1.41; p<0.05) and cardiovascular disease (CVD) mortality in men (RR=1.81 and RR=1.66; p<0.05). In men (without previous CVD) the NCEP-ATPIII definition had increased mortality risk from CVD (RR=1.98; p=0.012), than in men with identified MS by the IDF and the new JIS definition. In women the MS was not associated with risk of mortality from CVD.

CONCLUSION

The MS definitions according to the IDF and JIS criteria appear to be a slightly better predictor of all-cause mortality and mortality from CVD; MS according to the NCEP-ATPIII criteria appears to be a better predictor of mortality from CVD in men.

Association between ESR1 rs1884051 polymorphism and dietary total energy and plant protein intake on obesity in Korean men

ESR1 has been listed in the Human Obesity Gene Map as candidate gene associated with obesity. Thus, in this study, we investigated the effect of the ESR1 rs1884051 polymorphism on obesity-related variables, together with their modulations by dietary intake in Korean men. The obesity-related variables and dietary intake of 3,039 Korean men aged 40-59 years from KoGES database were analyzed. Body weight (P = 0.007), BMI (P = 0.003), waist-hip ratio (= 0.011), fat body mass (P = 0.010), and body fat percentage (P = 0.040) were significantly lower in subjects with the minor T allele of ESR1 rs1884051 than in subjects carrying the C allele. Moreover, the rs1884051 T allele was associated with a decreased risk of obesity prevalence (P = 0.040). Among the subjects whose total energy intake was below the median, carrier of the minor T allele of ESR1 rs1884051 had a lower BMI (P = 0.003) when compared with subjects carrying the C allele. In addition, among subjects whose plant protein intake was above the median, carrier of the minor T allele of ESR1 rs1884051 had a lower BMI (P = 0.044) compared with subjects carrying the C allele. Our findings demonstrate that there is a significant association between the ESR1 rs1884051 variant and obesity-related variables and this association can be potentially modified by dietary energy and plant protein intake.

PDZ adaptors: their regulation of epithelial transporters and involvement in human diseases

Homeostasis in the body is at least partially maintained by mechanisms that control membrane permeability, and thereby serve to control the uptake of essential substances (e.g., nutrients) and the efflux of unwanted substances (e.g., xenobiotics and metabolites) in epithelial cells. Various transporters play fundamental roles in such bidirectional transport, but little is known about how they are organized on plasma membranes. Protein-protein interactions may play a key role: several transporters in epithelial cells interact with the so-called adaptor proteins, which are membrane anchored and interact with both transporters and other membranous proteins. Although most of the evidences for transporter-adaptor interaction has been obtained in vitro, recent studies suggest that adaptor-mediated transporter regulation does occur in vivo and could be relevant to human diseases. Thus, protein-protein interaction is not only associated with the formation of macromolecular complexes but is also involved in various cellular events, and may provide transporters with additional functionality by forming transporter networks on plasma membranes. Interactions between xenobiotic transporters and PSD95/Dlg/ZO1 (PDZ) adaptors were previously reviewed by Kato and Tsuji (2006. Eur J Pharm Sci 27:487-500); the present review focuses on the latest findings about PDZ adaptors as regulators of transporter networks and their potential role in human diseases.

"The metabolic syndrome... is dead": these reports are an exaggeration

The debates continue over the validity of the metabolic syndrome concept. The continuous increment of the obesity pandemic is almost worldwide paralleled by rising rates of metabolic syndrome prevalence. Then, it seems obvious that these debates drove the need for further investigations as well as a deeper cooperation between relevant national and international organizations regarding the issue. Instead, part of the scientific community elected to totally "dismiss" the concept of the metabolic syndrome. Meanwhile, the best available evidence from three consecutive large meta-analyses has systematically shown that people with metabolic syndrome are at increased risk of cardiovascular events. The most recent and largest of them included near one million patients (total n = 951,083). The investigators concluded that the metabolic syndrome is associated with a 2-fold increase in cardiovascular outcomes and a 1.5-fold increase in all-cause mortality rates. One of the ways to hit the metabolic syndrome is an utterly simplistic view on this concept as a predictive tool only. Of course, the presence of the metabolic syndrome possesses a definite predictive value, but first of all it is a widely accepted concept regarding a biological condition based on the complex and interrelated pathophysiological mechanisms starting from excess central adiposity and insulin resistance. Therefore, it is completely unfair to compare it with statistically constructed predictive tools, including stronger prognostic variables even unrelated to each other from the biological point of view. For example, in the criteria for metabolic syndrome (in contrast to Framingham score) age and cholesterol--presumably low density lipoprotein-cholesterol (LDL-C)--levels are not included, as well as a variety of strong predictors used in other risk-stratification scores: previous myocardial infarction, heart failure, smoking, family history, etc. However, the metabolic syndrome identifies additional important residual vascular risk mainly associated with insulin resistance and atherogenic dyslipidemia (low high density lipoprotein-cholesterol (HDL-C), high triglycerides, small, dense LDL-C). Therefore, the metabolic syndrome could be a useful additional contributor in estimation of global cardiovascular risk beyond age, high LDL-C or other standard risk factors. The components of the metabolic syndrome have partially overlapping mechanisms of pathogenic actions mediated through common metabolic pathways. Therefore their total combined effect could be less than the summed of the individual effects. The concept that the metabolic syndrome is a consequence of obesity and insulin resistance, provides a useful "life-style changes" approach for prevention and treatment: caloric restriction, weight-loss and increased physical activity. The next step could theoretically be pharmacological interventions such as metformin, acarbose, fibrates, weight-loss drugs (currently only orlistat is practically available) and perhaps glucagon-like peptide-1 agonists. A third step should probably be kept for bariatric surgery.

Fatty acid interactions with genetic polymorphisms for cardiovascular disease

PURPOSE OF REVIEW

The number of studies investigating interactions between genes and nutrients for cardiovascular disease continues to grow, and holds tremendous potential for reducing disease risk at the level of the individual genotype. However, understanding the limitations and challenges of interaction studies, whether of observational or interventional design, is essential for critical evaluation of these studies.

RECENT FINDINGS

Nutrient-gene interactions for cardiovascular disease both parallel and extend nutrition studies, encompassing both traditional and novel cardiovascular risk factors. Fatty acid quality, lipid metabolism, inflammation, postprandial metabolism, fatty liver and macronutrient-gene interactions for obesity and metabolic syndrome represent a subset of the major areas of recent focus. With few exceptions, however, studies of gene-nutrient interactions are limited to a single population.

SUMMARY

Gene-nutrient research will continue to expand as genome-wide association studies uncover new sources of genetic variability associated with cardiovascular risk. However, in addition to investigation of newly discovered variants, continuing efforts must focus on the confirmation of previously reported genetic associations and interactions in additional populations.

Novel variants at KCTD10, MVK, and MMAB genes interact with dietary carbohydrates to modulate HDL-cholesterol concentrations in the Genetics of Lipid Lowering Drugs and Diet Network Study

BACKGROUND

Several genome-wide association studies have identified novel loci (KCTD10, MVK, and MMAB) that are associated with HDL-cholesterol concentrations. Of the environmental factors that determine HDL cholesterol, high-carbohydrate diets have been shown to be associated with low concentrations.

OBJECTIVE

The objective was to evaluate the associations of 8 single nucleotide polymorphisms (SNPs) located within the KCTD10, MVK, and MMAB loci with lipids and their potential interactions with dietary carbohydrates.

DESIGN

KCTD10, MVK, and MMAB SNPs were genotyped in 920 subjects (441 men and 479 women) who participated in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) Study. Biochemical measurements were made by using standard procedures. Dietary intakes were estimated by using a validated questionnaire.

RESULTS

For the SNPs KCTD10_i5642G-->C and MVK_S52NG-->A, homozygotes for the major alleles (G) had lower HDL-cholesterol concentrations than did carriers of the minor alleles (P = 0.005 and P = 0.019, respectively). For the SNP 12inter_108466061A-->G, homozygotes for the minor allele (G) had higher total cholesterol and LDL-cholesterol concentrations than did AG subjects (P = 0.030 and P = 0.034, respectively). Conversely, homozygotes for the major allele (G) at MMAB_3U3527G-->C had higher LDL-cholesterol concentrations than did carriers of the minor allele (P = 0.034). Significant gene-diet interactions for HDL cholesterol were found (P < 0.001-0.038), in which GG subjects at SNPs KCTD10_i5642G-->C and MMAB_3U3527G-->C and C allele carriers at SNP KCTD10_V206VT-->C had lower concentrations only if they consumed diets with a high carbohydrate content (P < 0.001-0.011).

CONCLUSION

These findings suggest that the KCTD10 (V206VT-->C and i5642G-->C) and MMAB_3U3527G-->C variants may contribute to the variation in HDL-cholesterol concentrations, particularly in subjects with high carbohydrate intakes.