An integrative genomics approach identifies activation of thioredoxin/thioredoxin reductase-1-mediated oxidative stress defense pathway and inhibition of angiogenesis in obese nondiabetic human subjects

Multi-omic integration reveals cell-type-specific regulatory networks of insulin resistance in distinct ancestry populations

Our knowledge of the cell-type-specific mechanisms of insulin resistance remains limited. To dissect the cell-type-specific molecular signatures of insulin resistance, we performed a multiscale gene network analysis of adipose and muscle tissues in African and European ancestry populations. In adipose tissues, a comparative analysis revealed ethnically conserved cell-type signatures and two adipocyte subtype-enriched modules with opposite insulin sensitivity responses. The modules enriched for adipose stem and progenitor cells as well as immune cells showed negative correlations with insulin sensitivity. In muscle tissues, the modules enriched for stem cells and fibro-adipogenic progenitors responded to insulin sensitivity oppositely. The adipocyte and muscle fiber-enriched modules shared cellular-respiration-related genes but had tissue-specific rearrangements of gene regulations in response to insulin sensitivity. Integration of the gene co-expression and causal networks further pinpointed key drivers of insulin resistance. Together, this study revealed the cell-type-specific transcriptomic networks and signaling maps underlying insulin resistance in major glucose-responsive tissues. A record of this paper's transparent peer review process is included in the supplemental information.

Obesity and aging: Molecular mechanisms and therapeutic approaches

The epidemic of obesity is a major challenge for health policymakers due to its far-reaching effects on population health and potentially overwhelming financial burden on healthcare systems. Obesity is associated with an increased risk of developing acute and chronic diseases, including hypertension, stroke, myocardial infarction, cardiovascular disease, diabetes, and cancer. Interestingly, the metabolic dysregulation associated with obesity is similar to that observed in normal aging, and substantial evidence suggests the potential of obesity to accelerate aging. Therefore, understanding the mechanism of fat tissue dysfunction in obesity could provide insights into the processes that contribute to the metabolic dysfunction associated with the aging process. Here, we review the molecular and cellular mechanisms underlying both obesity and aging, and how obesity and aging can predispose individuals to chronic health complications. The potential of lifestyle and pharmacological interventions to counter obesity and obesity-related pathologies, as well as aging, is also addressed.

Integrative Analysis of Glucometabolic Traits, Adipose Tissue DNA Methylation, and Gene Expression Identifies Epigenetic Regulatory Mechanisms of Insulin Resistance and Obesity in African Americans

Decline in insulin sensitivity due to dysfunction of adipose tissue (AT) is one of the earliest pathogenic events in type 2 diabetes. We hypothesize that differential DNA methylation (DNAm) controls insulin sensitivity and obesity by modulating transcript expression in AT. Integrating AT DNAm profiles with transcript profile data measured in a cohort of 230 African Americans (AAs) from the African American Genetics of Metabolism and Expression cohort, we performed cis-expression quantitative trait methylation (cis-eQTM) analysis to identify epigenetic regulatory loci for glucometabolic trait-associated transcripts. We identified significantly associated cytosine-guanine dinucleotide regions for 82 transcripts (false discovery rate [FDR]-P < 0.05). The strongest eQTM locus was observed for the proopiomelanocortin (POMC; ρ = -0.632, P = 4.70 × 10^-27) gene. Epigenome-wide association studies (EWAS) further identified 155, 46, and 168 cytosine-guanine dinucleotide regions associated (FDR-P < 0.05) with the Matsuda index, S_I, and BMI, respectively. Intersection of EWAS, transcript level to trait association, and eQTM results, followed by causal inference test identified significant eQTM loci for 23 genes that were also associated with Matsuda index, S_I, and/or BMI in EWAS. These associated genes include FERMT3, ITGAM, ITGAX, and POMC In summary, applying an integrative multiomics approach, our study provides evidence for DNAm-mediated regulation of gene expression at both previously identified and novel loci for many key AT transcripts influencing insulin resistance and obesity.

Selenium and Selenoproteins in Adipose Tissue Physiology and Obesity

Selenium (Se) homeostasis is tightly related to carbohydrate and lipid metabolism, but its possible roles in obesity development and in adipocyte metabolism are unclear. The objective of the present study is to review the current data on Se status in obesity and to discuss the interference between Se and selenoprotein metabolism in adipocyte physiology and obesity pathogenesis. The overview and meta-analysis of the studies on blood Se and selenoprotein P (SELENOP) levels, as well as glutathione peroxidase (GPX) activity in obese subjects, have yielded heterogenous and even conflicting results. Laboratory studies demonstrate that Se may modulate preadipocyte proliferation and adipogenic differentiation, and also interfere with insulin signaling, and regulate lipolysis. Knockout models have demonstrated that the selenoprotein machinery, including endoplasmic reticulum-resident selenoproteins together with GPXs and thioredoxin reductases (TXNRDs), are tightly related to adipocyte development and functioning. In conclusion, Se and selenoproteins appear to play an essential role in adipose tissue physiology, although human data are inconsistent. Taken together, these findings do not support the utility of Se supplementation to prevent or alleviate obesity in humans. Further human and laboratory studies are required to elucidate associations between Se metabolism and obesity.

Genetic analysis of hsCRP in American Indians: The Strong Heart Family Study

Background

Increased serum levels of C-reactive protein (CRP), an important component of the innate immune response, are associated with increased risk of cardiovascular disease (CVD). Multiple single nucleotide polymorphisms (SNP) have been identified which are associated with CRP levels, and Mendelian randomization studies have shown a positive association between SNPs increasing CRP expression and risk of colon cancer (but thus far not CVD). The effects of individual genetic variants often interact with the genetic background of a population and hence we sought to resolve the genetic determinants of serum CRP in a number of American Indian populations.

Methods

The Strong Heart Family Study (SHFS) has serum CRP measurements from 2428 tribal members, recruited as large families from three regions of the United States. Microsatellite markers and MetaboChip defined SNP genotypes were incorporated into variance components, decomposition-based linkage and association analyses.

Results

CRP levels exhibited significant heritability (h² = 0.33 ± 0.05, p<1.3 X 10⁻²⁰). A locus on chromosome (chr) 6, near marker D6S281 (approximately at 169.6 Mb, GRCh38/hg38) showed suggestive linkage (LOD = 1.9) to CRP levels. No individual SNPs were found associated with CRP levels after Bonferroni adjustment for multiple testing (threshold <7.77 x 10⁻⁷), however, we found nominal associations, many of which replicate previous findings at the CRP, HNF1A and 7 other loci. In addition, we report association of 46 SNPs located at 7 novel loci on chromosomes 2, 5, 6(2 loci), 9, 10 and 17, with an average of 15.3 Kb between SNPs and all with p-values less than 7.2 X 10⁻⁴.

Conclusion

In agreement with evidence from other populations, these data show CRP serum levels are under considerable genetic influence; and include loci, such as near CRP and other genes, that replicate results from other ethnic groups. These findings also suggest possible novel loci on chr 6 and other chromosomes that warrant further investigation.

Genetic Regulation of Enoyl-CoA Hydratase Domain-Containing 3 in Adipose Tissue Determines Insulin Sensitivity in African Americans and Europeans

Insulin resistance (IR) is a harbinger of type 2 diabetes (T2D) and partly determined by genetic factors. However, genetically regulated mechanisms of IR remain poorly understood. Using gene expression, genotype, and insulin sensitivity data from the African American Genetics of Metabolism and Expression (AAGMEx) cohort, we performed transcript-wide correlation and expression quantitative trait loci (eQTL) analyses to identify IR-correlated cis-regulated transcripts (cis-eGenes) in adipose tissue. These IR-correlated cis-eGenes were tested in the European ancestry individuals in the Metabolic Syndrome in Men (METSIM) cohort for trans-ethnic replication. Comparison of Matsuda index-correlated transcripts in AAGMEx with the METSIM study identified significant correlation of 3,849 transcripts, with concordant direction of effect for 97.5% of the transcripts. cis-eQTL for 587 Matsuda index-correlated genes were identified in both cohorts. Enoyl-CoA hydratase domain-containing 3 (ECHDC3) was the top-ranked Matsuda index-correlated cis-eGene. Expression levels of ECHDC3 were positively correlated with Matsuda index, and regulated by cis-eQTL, rs34844369 being the top cis-eSNP in AAGMEx. Silencing of ECHDC3 in adipocytes significantly reduced insulin-stimulated glucose uptake and Akt Ser⁴⁷³ phosphorylation. RNA sequencing analysis identified 691 differentially expressed genes in ECHDC3-knockdown adipocytes, which were enriched in γ-linolenate biosynthesis, and known IR genes. Thus, our studies elucidated genetic regulatory mechanisms of IR and identified genes and pathways in adipose tissue that are mechanistically involved in IR.

Adipose Tissue Transferrin and Insulin Resistance

Context

Excessive body iron stores are a risk factor for decreased insulin sensitivity (SI) and diabetes. We hypothesized that transcriptional dysregulation of genes involved in iron metabolism in adipocytes causes insulin resistance.

Objective and Design

To define the genetic regulation of iron metabolism and its role in SI, we used gene expression, genotype, and SI data from an African American cohort (N = 256). Replication studies were performed in independent European ancestry cohorts. In vitro studies in human adipocytes were performed to define the role of a selected gene in causing insulin resistance.

Results

Among 62 transcripts representing iron homeostasis genes, expression of 30 in adipose tissue were correlated with SI. Transferrin (TF) and ferritin heavy polypeptide were most positively and negatively associated with SI, respectively. These observations were replicated in two independent European ancestry adipose data sets. The strongest cis-regulatory variant for TF expression (rs6785596; P = 7.84 × 10-18) was identified in adipose but not muscle or liver tissue. Variants significantly affected the normal relationship of serum ferritin to insulin resistance. Knockdown of TF in differentiated Simpson-Golabi-Behmel syndrome adipocytes by short hairpin RNA decreased intracellular iron, reduced maximal insulin-stimulated glucose uptake, and reduced Akt phosphorylation. Knockdown of TF caused differential expression of 465 genes, including genes involved in glucose transport, mitochondrial function, Wnt-pathway/ SI, chemokine activity, and obesity. Iron chelation recapitulated key changes in the expression profile induced by TF knockdown.

Conclusion

Genetic regulation of TF expression in adipose tissue plays a novel role in regulating SI.

Transcriptional Regulatory Mechanisms in Adipose and Muscle Tissue Associated with Composite Glucometabolic Phenotypes

OBJECTIVE

Tissue-specific gene expression is associated with individual metabolic measures. However, these measures may not reflect the true but latent underlying biological phenotype. This study reports gene expression associations with multidimensional glucometabolic characterizations of obesity, glucose homeostasis, and lipid traits.

METHODS

Factor analysis was computed by using orthogonal rotation to construct composite phenotypes (CPs) from 23 traits in 256 African Americans without diabetes. Genome-wide transcript expression data from adipose and muscle were tested for association with CPs, and expression quantitative trait loci (eQTLs) were identified by associations between cis-acting single-nucleotide polymorphisms (SNPs) and gene expression.

RESULTS

The factor analysis identified six CPs. CPs 1 through 6 individually explained 34%, 12%, 9%, 8%, 6%, and 5% of the variation in 23 glucometabolic traits studied. There were 3,994 and 929 CP-associated transcripts identified in adipose and muscle tissue, respectively; CP2 had the largest number of associated transcripts. Pathway analysis identified multiple canonical pathways from the CP-associated transcripts. In adipose and muscle, significant cis-eQTLs were identified for 558 and 164 CP-associated transcripts (q-value < 0.01), respectively.

CONCLUSIONS

Adipose and muscle transcripts comprehensively define pathways involved in regulating glucometabolic disorders. Cis-eQTLs for CP-associated genes may act as primary causal determinants of glucometabolic phenotypes by regulating transcription of key genes.

Obesity Associated Modulation of miRNA and Co-Regulated Target Transcripts in Human Adipose Tissue of Non-Diabetic Subjects

OBJECTIVE

Micro RNAs (miRNAs) are a class of non-coding regulatory RNAs. We performed a transcriptome-wide analysis of subcutaneous adipose tissue and in vitro studies to identify miRNAs and co-regulated target transcripts associated with insulin sensitivity (SI) and obesity in human.

METHODS

We selected 20 insulin-resistant (IR, SI=2.0±0.7) and 20 insulin-sensitive (IS, SI=7.2±2.3) subjects from a cohort of 117 metabolically characterized non-diabetic Caucasians for comparison.

RESULTS

After global profiling, 3 miRNAs had marginally different expressions between IR and IS subjects. A total of 14 miRNAs were significantly correlated with %fat mass, body mass index (BMI), or SI. The qRT-PCR validated the correlation of miR-148a-3p with BMI (r=-0.70, P=2.73X10(-6)). MiRNA target filtering analysis identified DNA methyltransferase 1 (DNMT1) as one of the target genes of miR-148a-3p. DNMT1 expression in adipose tissue was positively correlated with BMI (r=0.47, p=8.42X10(-7)) and was inversely correlated with miR-148a-3p (r=-0.34). Differentiation of SGBS preadipocytes showed up-regulation of miR-148a-3p and down-regulation of DNMT1 in differentiated adipocytes. After transfecting miR-148a-3p mimics into HeLa-S3 cells, DNMT1 was down-regulated, while transfection of adipose stem cells with miR-148a-3p inhibitor up-regulated DNMT1.

CONCLUSIONS

Our results indicate that miR-148a-3pmediated regulation of DNMT1 expression may play a mechanistic role in obesity.

Genetic regulation of adipose tissue transcript expression is involved in modulating serum triglyceride and HDL-cholesterol

Dyslipidemia is a major contributor to the increased cardiovascular disease and mortality associated with obesity and type 2 diabetes. We hypothesized that variation in expression of adipose tissue transcripts is associated with serum lipid concentrations in African Americans (AAs), and common genetic variants regulate expression levels of these transcripts. Fasting serum lipid levels, genome-wide transcript expression profiles of subcutaneous adipose tissue, and genome-wide SNP genotypes were analyzed in a cohort of non-diabetic AAs (N=250). Serum triglyceride (TRIG) and high density lipoprotein-cholesterol (HDL-C) levels were associated (FDR<0.01) with expression level of 1021 and 1875 adipose tissue transcripts, respectively, but none associated with total cholesterol or LDL-C levels. Serum HDL-C-associated transcripts were enriched for salient biological pathways, including branched-chain amino acid degradation, and oxidative phosphorylation. Genes in immuno-inflammatory pathways were activated among individuals with higher serum TRIG levels. We identified significant cis-regulatory SNPs (cis-eSNPs) for 449 serum lipid-associated transcripts in adipose tissue. The cis-eSNPs of 12 genes were nominally associated (p<0.001) with serum lipid level in genome wide association studies in Global Lipids Genetics Consortium (GLGC) cohorts. Allelic effect direction of cis-eSNPs on expression of MARCH2, BEST1 and TMEM258 matched with effect direction of these SNP alleles on serum TRIG or HDL-C levels in GLGC cohorts. These data suggest that expressions of serum lipid-associated transcripts in adipose tissue are dependent on common cis-eSNPs in African Americans. Thus, genetically-mediated transcriptional regulation in adipose tissue may play a role in reducing HDL-C and increasing TRIG in serum.

Exploring genetic susceptibility to obesity through genome functional pathway analysis

OBJECTIVE

Obesity has been reaching epidemic levels in recent decades, with a growing body of research identifying predisposing genetic components. To explore the relationship of genetic factors contributing to obesity, an analytical computer-based gene-profiling approach utilizing an updated list of clinically relevant and known obesity-related genes was undertaken.

METHODS

An updated list of 494 genes reportedly associated with obesity was compiled, and the GeneAnalytics profiling software was utilized to interrogate genomic databases from GeneCards® to cross-reference obesity gene sets against tissues and cells, diseases, genetic pathways, gene ontology (GO)-biological processes and GO-molecular functions, phenotypes, and compounds.

RESULTS

Obesity-related fields identified by GeneAnalytics algorithms included 8 diseases, 46 pathways, 62 biological processes, 22 molecular functions, 148 phenotypes, and 286 compounds impacting adipogenesis, signal transduction by G-protein coupled receptors, and lipid metabolism involving insulin-related genes (IGF1, INS, IRS1). GO-biological processes identified feeding behavior, cholesterol metabolic process, and glucose and cholesterol homeostasis pathways, while GO-molecular processes pertained to receptor binding, affecting glucose homeostasis, body weight, and circulating insulin and triglyceride levels.

CONCLUSIONS

The gene-profiling model suggests that pathogenesis of obesity relates to the coordination of biological responses to glucose and intracellular lipids possibly through a disruption of biochemical cascades and cellular signaling arising from affected receptors.

Association of Nuclear Factor-Erythroid 2-Related Factor 2, Thioredoxin Interacting Protein, and Heme Oxygenase-1 Gene Polymorphisms with Diabetes and Obesity in Mexican Patients

The nuclear factor-erythroid 2- (NF-E2-) related factor 2 (Nrf2) is abated and its ability to reduce oxidative stress is impaired in type 2 diabetes and obesity. Thus, the aim of this study was to explore if polymorphisms in Nrf2 and target genes are associated with diabetes and obesity in Mexican mestizo subjects. The rs1800566 of NAD(P)H:quinone oxidoreductase 1 (NQO1) gene, rs7211 of thioredoxin interacting protein (TXNIP) gene, rs2071749 of heme oxygenase-1 (HMOX1) gene, and the rs6721961 and the rs2364723 from Nrf2 gene were genotyped in 627 diabetic subjects and 1020 controls. The results showed that the rs7211 polymorphism is a protective factor against obesity in nondiabetic subjects (CC + CT versus TT, OR = 0.40, P = 0.005) and in women (CC versus CT + TT, OR = 0.7, P = 0.016). TT carriers had lower high-density lipoprotein cholesterol levels and lower body mass index. The rs2071749 was positively associated with obesity (AA versus AG + GG, OR = 1.25, P = 0.026). Finally, the rs6721961 was negatively associated with diabetes in men (CC versus CA + AA, OR = 0.62, P = 0.003). AA carriers showed lower glucose concentrations. No association was found for rs1800566 and rs2364723 polymorphisms. In conclusion, the presence of Nrf2 and related genes polymorphisms are associated with diabetes and obesity in Mexican patients.

Molecular Changes in the Nasal Cavity after N, N-dimethyl-p-toluidine Exposure

N, N-dimethyl-p-toluidine (DMPT; Cas No. 99-97-8), an accelerant for methyl methacrylate monomers in medical devices, is a nasal cavity carcinogen according to a 2-yr cancer study of male and female F344/N rats, with the nasal tumors arising from the transitional cell epithelium. In this study, we exposed male F344/N rats for 5 days to DMPT (0, 1, 6, 20, 60, or 120 mg/kg [oral gavage]) to explore the early changes in the nasal cavity after short-term exposure. Lesions occurred in the nasal cavity including hyperplasia of transitional cell epithelium (60 and 120 mg/kg). Nasal tissue was rapidly removed and preserved for subsequent laser capture microdissection and isolation of the transitional cell epithelium (0 and 120 mg/kg) for transcriptomic studies. DMPT transitional cell epithelium gene transcript patterns were characteristic of an antioxidative damage response (e.g., Akr7a3, Maff, and Mgst3), cell proliferation, and decrease in signals for apoptosis. The transcripts of amino acid transporters were upregulated (e.g., Slc7a11). The DMPT nasal transcript expression pattern was similar to that found in the rat nasal cavity after formaldehyde exposure, with over 1,000 transcripts in common. Molecular changes in the nasal cavity after DMPT exposure suggest that oxidative damage is a mechanism of the DMPT toxic and/or carcinogenic effects.

Tissue-Specific and Genetic Regulation of Insulin Sensitivity-Associated Transcripts in African Americans

Integrative multiomics analyses of adipose and muscle tissue transcripts, S, and genotypes revealed novel genetic regulatory mechanisms of insulin resistance in African Americans.

Serum amyloid A impairs the antiinflammatory properties of HDL

HDL from healthy humans and lean mice inhibits palmitate-induced adipocyte inflammation; however, the effect of the inflammatory state on the functional properties of HDL on adipocytes is unknown. Here, we found that HDL from mice injected with AgNO3 fails to inhibit palmitate-induced inflammation and reduces cholesterol efflux from 3T3-L1 adipocytes. Moreover, HDL isolated from obese mice with moderate inflammation and humans with systemic lupus erythematosus had similar effects. Since serum amyloid A (SAA) concentrations in HDL increase with inflammation, we investigated whether elevated SAA is a causal factor in HDL dysfunction. HDL from AgNO3-injected mice lacking Saa1.1 and Saa2.1 exhibited a partial restoration of antiinflammatory and cholesterol efflux properties in adipocytes. Conversely, incorporation of SAA into HDL preparations reduced antiinflammatory properties but not to the same extent as HDL from AgNO3-injected mice. SAA-enriched HDL colocalized with cell surface-associated extracellular matrix (ECM) of adipocytes, suggesting impaired access to the plasma membrane. Enzymatic digestion of proteoglycans in the ECM restored the ability of SAA-containing HDL to inhibit palmitate-induced inflammation and cholesterol efflux. Collectively, these findings indicate that inflammation results in a loss of the antiinflammatory properties of HDL on adipocytes, which appears to partially result from the SAA component of HDL binding to cell-surface proteoglycans, thereby preventing access of HDL to the plasma membrane.

The nutrigenetic influence of the interaction between dietary vitamin E and TXN and COMT gene polymorphisms on waist circumference: a case control study

Background

Abdominal obesity (AO) is a common modifiable risk factor for certain non-communicable diseases associated with enhanced oxidative stress (OS). The objective of this work was to investigate whether the interaction between antioxidant vitamin intake and OS-related polymorphisms modulates gene-associated anthropometry in a Spanish population.

Methods

A total of 246 subjects with AO, and 492 age and gender matched non-AO subjects were included in the study. Anthropometric, biochemical, and OS parameters, and antioxidant dietary intake data were assessed using validated procedures. DNA from white blood cells was isolated and the genotype of seven polymorphisms from genes involved in OS (pro-oxidant and antioxidant) were analyzed using the SNPlex system. The effects of the c.-793T > C polymorphism on promoter activity and thus thioredoxin (TXN) activity were examined using reporter assays.

Results

The AO group had higher 8-Oxo-2′-deoxyguanosine levels and took in less vitamin A and vitamin E compared to the non-AO group. Logistic regression analysis revealed that the rs2301241 polymorphism in TXN and rs740603 in catechol-O-methyltransferase (COMT) were associated with waist circumference (WC) and AO. Moreover, these polymorphisms were more strongly associated with variations in WC in subjects with low vitamin E intakes. A promoter assay revealed that the T to C conversion at c.-793 (rs2301241) induced a more than two fold increase in reporter gene expression.

Conclusions

WC is associated both with dietary vitamin E intake and genetic variants of TXN and COMT suggesting that existence of a complex nutrigenetic pathway that involves regulation of AO.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0652-4) contains supplementary material, which is available to authorized users.

Potential role of recombinant adeno-associated virus human thioredoxin-PR39 in cell and vascular protection against hypoxia

The aim of the present study was to successfully construct a recombinant adeno-associated virus (rAAV) vector containing the human thioredoxin (hTRX)-PR39 chimeric gene (rAAV/hTRX-PR39), and verify that the vector was able to maintain a sustained, stable and efficient expression to achieve protein production in the cell. In the present study, a chicken embryo model was utilized to analyze the therapeutical effect of rAAV/hTRX-PR39 in cerebral ischemia diseases. ECV304 cells were transfected with rAAV/hTRX-PR39 and incubated under conditions of 20, 5 and 1% O₂. Subsequently, the expression levels of vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor (VEGFR)-1, VEGFR-2, fibroblast growth factor receptor (FGFR)-1 and syndecan-4 were detected by reverse transcription-quantitative polymerase chain reaction. Under hypoxic conditions, the mRNA expression levels of VEGF, VEGFR-1, VEGFR-2, FGFR-1 and syndecan-4 were found to increase in the PR39-transfected group when compared with the control group, while no statistically significant difference was observed between the PR39-transfected group and the control group under conditions of 20% O₂. In addition, hTRX-PR39 was shown to increase the density of the vasculature and the survival rate of the chick embryos. Under hypoxic conditions, it was hypothesized that rAAV/hTRX-PR39 was capable of promoting angiogenesis, which may subsequently protect the cells from impairment by hypoxia. In conclusion, rAAV/hTRX-PR39 was demonstrated to promote vascularization and cell survival in hypoxia; thus, rAAV/hTRX-PR39 may have potential for use in therapy targeting cerebral ischemia.

Redox implications in adipose tissue (dys)function--A new look at old acquaintances

Obesity is an energy balance disorder associated with dyslipidemia, insulin resistance and diabetes type 2, also summarized with the term metabolic syndrome or syndrome X. Increasing evidence points to “adipocyte dysfunction”, rather than fat mass accretion per se, as the key pathophysiological factor for metabolic complications in obesity. The dysfunctional fat tissue in obesity characterizes a failure to safely store metabolic substrates into existing hypertrophied adipocytes and/or into new preadipocytes recruited for differentiation. In this review we briefly summarize the potential of redox imbalance in fat tissue as an instigator of adipocyte dysfunction in obesity. We reveal the challenge of the adipose redox changes, insights in the regulation of healthy expansion of adipose tissue and its reduction, leading to glucose and lipids overflow.

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Adipose tissue (AT) buffers nutrient excess determining overall metabolic health.

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Redox insight in lipid storage and adipogenesis of AT is reviewed.

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Redox modulation of AT as therapeutic target in obesity/syndrome X is considered.

Urinary 8-iso-prostaglandin F2α as a marker of metabolic risks in the general Japanese population: The ROAD study

OBJECTIVE

To determine whether 8-iso-prostaglandin F2α (8-iso-PGF2α) is a reliable biomarker of the accumulation of metabolic risks [e.g., overweight, hypertension, impaired glucose tolerance (IGT), and dyslipidemia].

METHODS

This was a cross-sectional study of the baseline characteristics of a Japanese general population cohort study: Research on Osteoarthritis/Osteoporosis Against Disability (ROAD). Of 1,690 participants, 1,527 fulfilled all questionnaires and examinations. Free and conjugated urinary 8-iso-PGF2α levels and metabolic syndrome (MetS) components including blood pressure, HbA1c, total cholesterol, high-density lipoprotein cholesterol (HDL-C), and non-HDL-C were analyzed. The data were analyzed by ANCOVA, multiple regression analysis, and multinomial logistic analysis.

RESULTS

8-iso-PGF2α was significantly associated with HbA1c and significantly inversely associated with total cholesterol and non-HDL-C. Notably, IGT with an HbA1c cut-off of 5.5% was significantly associated with 8-iso-PGF2α level in participants aged ≤50 years. Multinomial logistic regression analysis revealed 8-iso-PGF2α level was significantly associated with a greater number of MetS risks present; this association was stronger in younger participants. In participants aged ≥71 years, 8-iso-PGF2α was significantly associated with a greater number of MetS risks with higher IGT cut-offs.

CONCLUSIONS

Urinary 8-iso-PGF2α can be a reliable marker of IGT and the accumulation of MetS risks, especially in younger people.

Integrative network analysis reveals different pathophysiological mechanisms of insulin resistance among Caucasians and African Americans

Background

African Americans (AA) have more pronounced insulin resistance and higher insulin secretion than European Americans (Caucasians or CA) when matched for age, gender, and body mass index (BMI). We hypothesize that physiological differences (including insulin sensitivity [S_I]) between CAs and AAs can be explained by co-regulated gene networks in tissues involved in glucose homeostasis.

Methods

We performed integrative gene network analyses of transcriptomic data in subcutaneous adipose tissue of 99 CA and 37 AA subjects metabolically characterized as non-diabetic, with a range of S_I and BMI values.

Results

Transcripts negatively correlated with S_I in only the CA or AA subjects were enriched for inflammatory response genes and integrin-signaling genes, respectively. A sub-network (module) with TYROBP as a hub enriched for genes involved in inflammatory response (corrected p = 1.7E-26) was negatively correlated with S_I (r = −0.426, p = 4.95E-04) in CA subjects. S_I was positively correlated with transcript modules enriched for mitochondrial metabolism in both groups. Several S_I-associated co-expressed modules were enriched for genes differentially expressed between groups. Two modules involved in immune response to viral infections and function of adherens junction, are significantly correlated with S_I only in CAs. Five modules involved in drug/intracellular transport and oxidoreductase activity, among other activities, are correlated with S_I only in AAs. Furthermore, we identified driver genes of these race-specific S_I-associated modules.

Conclusions

S_I-associated transcriptional networks that were deranged predominantly in one ethnic group may explain the distinctive physiological features of glucose homeostasis among AA subjects.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0078-0) contains supplementary material, which is available to authorized users.

Adipose tissue gene expression and metabolic health of obese adults

Obese subjects with a similar body mass index (BMI) exhibit substantial heterogeneity in gluco- and cardiometabolic heath phenotypes. However, defining genes that underlie the heterogeneity of metabolic features among obese individuals and determining metabolically healthy and unhealthy phenotypes remain challenging. We conducted unsupervised hierarchical clustering analysis of subcutaneous adipose tissue transcripts from 30 obese men and women ⩾40 years old. Despite similar BMIs in all subjects, we found two distinct subgroups, one metabolically healthy (group 1) and one metabolically unhealthy (group 2). Subjects in group 2 showed significantly higher total cholesterol (P=0.005), low-density lipoprotein cholesterol (P=0.006), 2-h insulin during oral glucose tolerance test (P=0.015) and lower insulin sensitivity (SI, P=0.029) compared with group 1. We identified significant upregulation of 141 genes (for example, MMP9 and SPP1) and downregulation of 17 genes (for example, NDRG4 and GINS3) in group 2 subjects. Intriguingly, these differentially expressed transcripts were enriched for genes involved in cardiovascular disease-related processes (P=2.81 × 10(-11)-3.74 × 10(-02)) and pathways involved in immune and inflammatory response (P=8.32 × 10(-5)-0.04). Two downregulated genes, NDRG4 and GINS3, have been located in a genomic interval associated with cardiac repolarization in published GWASs and zebra fish knockout models. Our study provides evidence that perturbations in the adipose tissue gene expression network are important in defining metabolic health in obese subjects.

The role of reactive oxygen species in obesity therapeutics

Obesity is a major risk factor for multiple severe health conditions, including cardiovascular diseases, diabetes and cancer. It is often related to an increased risk of morbidity and mortality and, as it can be accompanied by non-fatal health problems, quality of life is seriously reduced due to related conditions including hypertension, sleep apnea, osteoarthritis, respiratory problems and infertility. Evidence suggests that oxidative stress is related to obesity and its complications. In obese patients, there is an increase in levels of reactive oxygen species and nitrogen species and antioxidant defenses are undermined in comparison to normal-weight counterparts. In addition, these parameters inversely correlate with central adiposity. In this review, the authors discuss current concepts concerning the relationship between obesity and oxidative stress and mitochondrial impairment. Potential interventions to improve redox balance are also explored.

LC-MS/MS analysis of visceral and subcutaneous adipose tissue proteomes in young goats with focus on innate immunity and inflammation related proteins

The endocrine role of adipose tissue and its involvement in several physiological and pathological processes are well recognized. Studies on human, mouse and rat adipose tissues have made clear that subcutaneous and visceral deposits play different roles, which is also reflected by different protein and gene expression patterns. In ruminants, fat tissues play important biological roles not only for animal health, but also for quality and gain in meat and milk production. Yet very few studies have explored the ruminant adipose tissue proteomes. The aim of our study was to compare subcutaneous and visceral adipose tissues of goat, focusing on proteins involved in immune and inflammatory response. A 2-D LC-MS/MS approach followed by cluster analysis shows a clear distinction between subcutaneous and visceral fat tissue proteomes, and qualitative RT-PCR based analysis of 30 potential adipokines further confirmed the individual expression patterns of 26 of these, including 7 whose mRNA expression was observed for the first time in adipose tissues. This study provides a first description of adipose tissue proteomes in goat, and presents observations on novel proteins related to metabolic and inflammatory pathways. The mass spectrometry data have been deposited to the ProteomeXchange Consortium with the data set identifier PXD000564.

BIOLOGICAL SIGNIFICANCE

The proteomic analysis of different subcutaneous and visceral adipose tissue deposits showed tissue specific differences in protein expressions of well known as well as novel adipokines. This highlights the importance of sampling site when studying adipose tissue's metabolic roles. The protein expression characteristics of adipose tissues was evaluated by quantitative RT-PCR, and confirmed that adipose tissues play a central role in controlling inflammation, detoxification and coagulation pathways, as well as regulation of body fat mobilization in dairy animals. These findings are of particular interest in farm animals where health and production traits are important for animal welfare and for economic gains.

Expression quantitative trait analyses to identify causal genetic variants for type 2 diabetes susceptibility

Type 2 diabetes (T2D) is a common metabolic disorder which is caused by multiple genetic perturbations affecting different biological pathways. Identifying genetic factors modulating the susceptibility of this complex heterogeneous metabolic phenotype in different ethnic and racial groups remains challenging. Despite recent success, the functional role of the T2D susceptibility variants implicated by genome-wide association studies (GWAS) remains largely unknown. Genetic dissection of transcript abundance or expression quantitative trait (eQTL) analysis unravels the genomic architecture of regulatory variants. Availability of eQTL information from tissues relevant for glucose homeostasis in humans opens a new avenue to prioritize GWAS-implicated variants that may be involved in triggering a causal chain of events leading to T2D. In this article, we review the progress made in the field of eQTL research and knowledge gained from those studies in understanding transcription regulatory mechanisms in human subjects. We highlight several novel approaches that can integrate eQTL analysis with multiple layers of biological information to identify ethnic-specific causal variants and gene-environment interactions relevant to T2D pathogenesis. Finally, we discuss how the eQTL analysis mediated search for “missing heritability” may lead us to novel biological and molecular mechanisms involved in susceptibility to T2D.

Genetics of oxidative stress in obesity

Obesity is a multifactorial disease characterized by the excessive accumulation of fat in adipose tissue and peripheral organs. Its derived metabolic complications are mediated by the associated oxidative stress, inflammation and hypoxia. Oxidative stress is due to the excessive production of reactive oxygen species or diminished antioxidant defenses. Genetic variants, such as single nucleotide polymorphisms in antioxidant defense system genes, could alter the efficacy of these enzymes and, ultimately, the risk of obesity; thus, studies investigating the role of genetic variations in genes related to oxidative stress could be useful for better understanding the etiology of obesity and its metabolic complications. The lack of existing literature reviews in this field encouraged us to gather the findings from studies focusing on the impact of single nucleotide polymorphisms in antioxidant enzymes, oxidative stress-producing systems and transcription factor genes concerning their association with obesity risk and its phenotypes. In the future, the characterization of these single nucleotide polymorphisms (SNPs) in obese patients could contribute to the development of controlled antioxidant therapies potentially beneficial for the treatment of obesity-derived metabolic complications.

(+)-Usnic Acid-induced Myocardial Toxicity in Rats

(+)-Usnic acid (UA) has been known to be a strong uncoupler, and mitochondrial and endoplasmic reticulum (ER)–related stresses are suggested to be involved in the mechanism of hepatotoxicity. However, it has not been clarified whether UA causes toxicity in other mitochondria-rich organs such as the heart. We elucidated whether UA induces cardiotoxicity and its mechanism. UA was orally administered to rats for 14 days, and laboratory and histopathological examinations were performed in conjunction with toxicogenomic analysis. As a result, there was no alteration in blood chemistry, whereas cytoplasmic rarefaction of myocardium was observed microscopically. This finding corresponded to the swollen mitochondria observed ultrastructurally. Immunohistochemically, expression of prohibitin, indicating mitochondrial imbalance, increased in the sarcoplasmic area. Toxicogenomic analysis highlighted the upregulation of gene groups consisting of oxidative stress, ER stress, and amino acid limitation. Interestingly, the number of upregulated genes was larger in the amino acid limitation-related gene group than that in other groups, implying that amino acid limitation might be one of the sources of oxidative stress, not only mitochondria and ER-originated stresses. In conclusion, the heart was manifested to be one of the target organs of UA. Mitochondrial imbalance with complex stresses may be involved in the toxic mechanism.

Reduced blood nrf-2 mRNA in local overweight boys at risk of metabolic complications: a study in San Luis City, San Luis, Argentina

BACKGROUND

Childhood overweight (OW) is a matter of public health concern because of its long-term impact on adulthood health. NF-E2-related factor 2 (Nrf-2) regulates the antioxidant/lipogenic response to a sustained positive energy balance that prevails during weight gain. Here we aimed at studying a possible link between OW and Nrf-2-dependent antioxidant/lipogenic response in a local population of boys at risk of metabolic complications.

METHODS

We measured clinical and biochemical parameters related to lipid metabolism, oxidative stress, and metabolic syndrome in a population of OW boys [body mass index (BMI) percentile ≥85(th) and <95(th), n=22] and normal weight boys (NW; BMI percentile<85(th), n=27) from San Luis City, San Luis, Argentina.

RESULTS

Compared to NW, OW boys had lower insulin sensitivity, an altered plasma lipid profile, and increased markers of oxidative stress and inflammatory fatty acids. OW boys also had a higher atherogenic index and peripheral insulin resistance than NW boys. We also found that glutathione peroxidase activity and the reduced glutathione to oxidized glutathione ratio were lower in OW boys than NW boys, suggesting that OW boys may have an altered antioxidant response to oxidative stress. Finally, Nrf-2 expression negatively correlated with metabolic syndrome parameters in OW boys.

CONCLUSIONS

Our data suggest that OW boys have a reduced antioxidant and lipogenic response to a positive energy balance, resulting in oxidative stress, insulin resistance, and risk of developing metabolic complications. Our data also provide a rationale for nutritional interventions aimed at restoring Nrf-2 expression to reduce the risk of metabolic complications in OW boys.

Leucine-rich repeat kinase 2 (LRRK2)-deficient rats exhibit renal tubule injury and perturbations in metabolic and immunological homeostasis

Genetic evidence links mutations in the LRRK2 gene with an increased risk of Parkinson's disease, for which no neuroprotective or neurorestorative therapies currently exist. While the role of LRRK2 in normal cellular function has yet to be fully described, evidence suggests involvement with immune and kidney functions. A comparative study of LRRK2-deficient and wild type rats investigated the influence that this gene has on the phenotype of these rats. Significant weight gain in the LRRK2 null rats was observed and was accompanied by significant increases in insulin and insulin-like growth factors. Additionally, LRRK2-deficient rats displayed kidney morphological and histopathological alterations in the renal tubule epithelial cells of all animals assessed. These perturbations in renal morphology were accompanied by significant decreases of lipocalin-2, in both the urine and plasma of knockout animals. Significant alterations in the cellular composition of the spleen between LRRK2 knockout and wild type animals were identified by immunophenotyping and were associated with subtle differences in response to dual infection with rat-adapted influenza virus (RAIV) and Streptococcus pneumoniae. Ontological pathway analysis of LRRK2 across metabolic and kidney processes and pathological categories suggested that the thioredoxin network may play a role in perturbing these organ systems. The phenotype of the LRRK2 null rat is suggestive of a complex biology influencing metabolism, immune function and kidney homeostasis. These data need to be extended to better understand the role of the kinase domain or other biological functions of the gene to better inform the development of pharmacological inhibitors.

Phospholipid biosynthesis genes and susceptibility to obesity: analysis of expression and polymorphisms

Recent studies have identified links between phospholipid composition and altered cellular functions in animal models of obesity, but the involvement of phospholipid biosynthesis genes in human obesity are not well understood. We analyzed the transcript of four phospholipid biosynthesis genes in adipose and muscle from 170 subjects. We examined publicly available genome-wide association data from the GIANT and MAGIC cohorts to investigate the association of SNPs in these genes with obesity and glucose homeostasis traits, respectively. Trait-associated SNPs were genotyped to evaluate their roles in regulating expression in adipose. In adipose tissue, expression of PEMT, PCYT1A, and PTDSS2 were positively correlated and PCYT2 was negatively correlated with percent fat mass and body mass index (BMI). Among the polymorphisms in these genes, SNP rs4646404 in PEMT showed the strongest association (p = 3.07E-06) with waist-to-hip ratio (WHR) adjusted for BMI. The WHR-associated intronic SNP rs4646343 in the PEMT gene showed the strongest association with its expression in adipose. Allele "C" of this SNP was associated with higher WHR (p = 2.47E-05) and with higher expression (p = 4.10E-04). Our study shows that the expression of PEMT gene is high in obese insulin-resistant subjects. Intronic cis-regulatory polymorphisms may increase the genetic risk of obesity by modulating PEMT expression.

Allelic expression imbalance screening of genes in chromosome 1q21-24 region to identify functional variants for Type 2 diabetes susceptibility

Type 2 diabetes (T2D)-associated SNPs are more likely to be expression quantitative trait loci (eQTLs). The allelic expression imbalance (AEI) analysis is the measure of relative expression between two allelic transcripts and is the most sensitive measurement to detect cis-regulatory effects. We performed AEI screening to detect cis-regulators for genes expressed in transformed lymphocytes of 190 Caucasian (CA) and African American (AA) subjects to identify functional variants for T2D susceptibility in the chromosome 1q21-24 region of linkage. Among transcribed SNPs studied in 115 genes, significant AEI (P < 0.001) occurred in 28 and 30 genes in CA and AA subjects, respectively. Analysis of the effect of selected AEI-SNPs (≥10% mean AEI) on total gene expression further established the cis-eQTLs in thioesterase superfamily member-4 (THEM4) (rs13320, P = 0.027), and IGSF8 (rs1131891, P = 0.02). Examination of published genome-wide association data identified significant associations (P < 0.01) of three AEI-SNPs with T2D in the DIAGRAM-v3 dataset. Six AEI single nucleotide polymorphisms, including rs13320 (P = 1.35E-04) in THEM4, were associated with glucose homeostasis traits in the MAGIC dataset. Evaluation of AEI-SNPs for association with glucose homeostasis traits in 611 nondiabetic subjects showed lower AIRG (P = 0.005) in those with TT/TC genotype for rs13320. THEM4 expression in adipose was higher (P = 0.005) in subjects carrying the T allele; in vitro analysis with luciferase construct confirmed the higher expression of the T allele. Resequencing of THEM4 exons in 192 CA subjects revealed four coding nonsynonymous variants, but did not explain transmission of T2D in 718 subjects from 67 Caucasian pedigrees. Our study indicates the role of a cis-regulatory SNP in THEM4 that may influence T2D predisposition by modulating glucose homeostasis.

An ACACB variant implicated in diabetic nephropathy associates with body mass index and gene expression in obese subjects

Acetyl coenzyme A carboxylase B gene (ACACB) single nucleotide polymorphism (SNP) rs2268388 is reproducibly associated with type 2 diabetes (T2DM)-associated nephropathy (DN). ACACB knock-out mice are also protected from obesity. This study assessed relationships between rs2268388, body mass index (BMI) and gene expression in multiple populations, with and without T2DM. Among subjects without T2DM, rs2268388 DN risk allele (T) associated with higher BMI in Pima Indian children (n = 2021; p-additive = 0.029) and African Americans (AAs) (n = 177; p-additive = 0.05), with a trend in European Americans (EAs) (n = 512; p-additive = 0.09), but not Germans (n = 858; p-additive = 0.765). Association with BMI was seen in a meta-analysis including all non-T2DM subjects (n = 3568; p-additive = 0.02). Among subjects with T2DM, rs2268388 was not associated with BMI in Japanese (n = 2912) or EAs (n = 1149); however, the T allele associated with higher BMI in the subset with BMI≥30 kg/m(2) (n = 568 EAs; p-additive = 0.049, n = 196 Japanese; p-additive = 0.049). Association with BMI was strengthened in a T2DM meta-analysis that included an additional 756 AAs (p-additive = 0.080) and 48 Hong Kong Chinese (p-additive = 0.81) with BMI≥30 kg/m(2) (n = 1575; p-additive = 0.0033). The effect of rs2268388 on gene expression revealed that the T risk allele associated with higher ACACB messenger levels in adipose tissue (41 EAs and 20 AAs with BMI>30 kg/m(2); p-additive = 0.018) and ACACB protein levels in the liver tissue (mixed model p-additive = 0.03, in 25 EA bariatric surgery patients with BMI>30 kg/m(2) for 75 exams). The T allele also associated with higher hepatic triglyceride levels. These data support a role for ACACB in obesity and potential roles for altered lipid metabolism in susceptibility to DN.

Improved insulin sensitivity after treatment with PPARγ and PPARα ligands is mediated by genetically modulated transcripts

OBJECTIVES

We aimed to define the effects of peroxisomal proliferator-activated receptor γ (PPARγ) and PPARα agonist mono and combination therapy on adipose tissue and skeletal muscle gene expression in relation to insulin sensitivity. We further investigated the role of genetic polymorphisms in PPAR ligand-modulated genes in transcriptional regulation and glucose homeostasis.

MATERIALS AND METHODS

Genome-wide transcript profiles of subcutaneous adipose and skeletal muscle and metabolic phenotypes were assessed before and after 10 weeks of pioglitazone and fenofibrate mono or combination therapy in 26 patients with impaired glucose tolerance. To establish the functional role of single nucleotide polymorphisms (SNPs) in genes modulated by pioglitazone alone or in combination with fenofibrate, we examined genome-wide association data of continuous glycemic phenotypes from the Meta-Analyses of Glucose and Insulin-Related Traits Consortium study and adipose eQTL data from the Multi Tissue Human Expression Resource study.

RESULTS

PPARγ, alone or in combination with PPARα agonists, mediated upregulation of genes involved in the TCA cycle, branched-chain amino acid (BCAA) metabolism, fatty acid metabolism, PPAR signaling, AMPK and cAMP signaling, and insulin signaling pathways, and downregulation of genes in antigen processing and presentation, and immune and inflammatory response in adipose tissue. Remarkably few changes were found in muscle. Strong enrichment of genes involved in propanoate metabolism, fatty acid elongation in the mitochondria, and acetyl-CoA metabolic process were observed only in adipose tissue of the combined pioglitazone and fenofibrate treatment group. After examining Meta-Analyses of Glucose and Insulin-Related Traits Consortium data, SNPs in 22 genes modulated by PPAR ligands were associated with fasting plasma glucose and the expression of 28 transcripts modulated by PPAR ligands was under control of local genetic regulators (cis-eQTLs) in adipose tissue of Multi Tissue Human Expression Resource study twins.

CONCLUSION

We found differences in transcriptional mechanisms that may describe the insulin-sensitizing effects of PPARγ agonist monotherapy or in combination with a PPARα agonist. The regulatory and glucose homeostasis trait-associated SNPs in PPAR agonist-modulated genes are important candidates for future studies that may explain the interindividual variability in response to thiazolidinedione and fenofibrate treatment.

Effect of endoplasmic reticulum stress on inflammation and adiponectin regulation in human adipocytes

The endoplasmic reticulum (ER) of adipocytes plays a major role in the assembly and secretion of adipokines. The levels of serum adiponectin, secreted by adipocytes, are decreased in insulin resistance, diabetes, and obesity. The role of ER stress in downregulating adiponectin levels has been demonstrated in mouse models of obesity. Studies examining human adipose tissue have indicated that there is an increase in the ER stress transcript HSPA5 with increased body mass index (BMI). However, it is not established whether ER stress results in changes in adiponectin levels or multimerization in human adipocytes. We examined whether the induction of ER stress using tunicamycin, thapsigargin, or palmitate alters the messenger RNA (mRNA) and protein expression of adiponectin and the mRNA expression of chaperones ERP44 and ERO1 in adult-derived human adipocyte stem (ADHAS) cells. ER stress was measured using key indicators of ER stress-HSPA5, ERN1, CHOP, and GADD34, as well as changes in eIF2α phosphorylation. Because ER stress is suggested to be the proximal cause of inflammation in adipocytes, we further examined the change in inflammatory status by quantitating the change in Iκβ-α protein following the induction of ER stress. Our studies indicate that: (1) ER stress markers were increased to a higher degree using tunicamycin or thapsigargin compared to palmitate; (2) ER stress significantly decreased adiponectin mRNA in response to tunicamycin and thapsigargin, but palmitate did not decrease adiponectin mRNA levels. In all three instances, the induction of ER stress was accompanied by a decrease in adiponectin protein as well as adiponectin multimerization. All three inducers of ER stress increased tumor necrosis factor-α (TNF-α) mRNA and decreased Iκβ-α protein in adipocytes. The data suggest that ER stress modifies adiponectin secretion and induces inflammation in ADHAS cells.

Single nucleotide polymorphisms in JAZF1 and BCL11A gene are nominally associated with type 2 diabetes in African-American families from the GENNID study

Prior type 2 diabetes (T2D) genome-wide association studies (GWASs) have generated a list of well-replicated susceptibility loci in populations of European and Asian ancestry. To validate the trans-ethnic contribution of the single-nucleotide polymorphisms (SNPs) involved in these GWASs, we performed a family-based association analysis of 32 selected GWAS SNPs in a cohort of 1496 African-American (AA) subjects from the Genetics of NIDDM (GENNID) study. Functional roles of these SNPs were evaluated by screening cis-eQTLs in transformed lymphoblast cell lines available for a sub-group of Genetics of NIDDM (GENNID) families from Arkansas. Only three of the 32 GWAS-derived SNPs showed nominally significant association with T2D in our AA cohort. Among the replicated SNPs rs864745 in JAZF1 and rs10490072 in BCL11A gene (P=0.006 and 0.03, respectively, after adjustment for body mass index) were within the 1-lod drop support interval of T2D linkage peaks reported in these families. Genotyping of 19 tag SNPs in these two loci revealed no further common SNPs or haplotypes that may be a stronger predictor of T2D susceptibility than the index SNPs. Six T2D GWAS SNPs (rs6698181, rs9472138, rs730497, rs10811661, rs11037909 and rs1153188) were associated with nearby transcript expression in transformed lymphoblast cell lines of GENNID AA subjects. Thus, our study indicates a nominal role for JAZF1 and BCL11A variants in T2D susceptibility in AAs and suggested little overlap in known susceptibility to T2D between European- and African-derived populations when considering GWAS SNPs alone.