AKT1 polymorphisms are associated with risk for metabolic syndrome

Antidiabetic potency and molecular insights of natural products bearing indole moiety: A systematic bioinformatics investigation targeting AKT1

Diabetic mellitus (DM) is a chronic disorder, and type 2 DM (T2DM) is the most prevalent among all categories (nearly 90%) across the globe every year. With the availability of potential drugs, the prevalence rate has remained uncontrollable, while natural resources showed a promising potency, and exploring such potential candidates at the preclinical stage is essential. An extensive literature search selected 89 marine and plant-derived indole derivatives with anti-inflammatory, antioxidant, lipid-lowering, etc., activities. However, as we know, drugs have not been able to convert from 'lead' to 'mainstream' due to inadequate drug-ability profiles, as our systematic investigation proved and selected herdmanine_A (HERD_A) and penerpene_D (PENE_D) as the most potential antidiabetic candidates from the library of indole derivatives. Based on our previous network pharmacology study, we selected three new target enzymes: Acetyl-CoA carboxylase 2 (ACACB; PDB ID: 3JRX), cyclin-dependent kinase 4 (CDK4; PDB ID: 3G33), and alpha serine/threonine-protein kinase 1 (AKT1; PDB ID: 3O96) to assess the antidiabetic potency of selected indole derivatives through binding energy or docking score. To conduct molecular docking studies with these enzymes, we used the PyRx-AutoDock platform. Furthermore, molecular dynamic simulation at 100 ns, physicochemical analysis, pharmacokinetics, toxicity assessment, and drug-likeness evaluation suggested that HERD_A and penerpene PENE_D were the most potent inhibitors against AKT1 compared to koenimbine (most potential based on the recorded IC50 value) and murrayakonine_A (most potential based on the docking score). In summary, HERD_A and/or PENE_D have the potential to be used as alternative therapeutic agent for the treatment of diabetes after some pharmacological investigation.

Assessing 48 SNPs in Hypertensive Paediatric Patients and Young Adults with Review of Genetic Background of Essential Hypertension

Essential hypertension in paediatric patients and young adults is rising, mostly on account of obesity-related hypertension. Clinically, the difference between obese hypertensive and non-obese hypertensive individuals is evident; yet, the pathophysiology of essential and obesity-related hypertension is multifactorial, complex and not fully understood. The aim of our study was to obtain a comprehensive view of the clinical differences between obesity-related hypertension and hypertension in non-obese paediatric patients and young adults and to do genetic tests to possibly highlight some of the pathophysiological differences with a review of their genetic backgrounds. Four hundred and thirty-six hypertensive paediatric patients and young adults were included in the study, and a study of 48 single-nucleotide polymorphisms, using Kompetitive allele specific PCR, was conducted. The subjects were divided into 243 non-obese participants with hypertension and 193 obese participants with hypertension. The data for the clinical comparison of both groups were collected as well. The differences in some clinical and biochemical parameters were confirmed. Genetic tests showed a significant difference in one allele frequency between both groups in five SNPs: rs6232, rs6235, rs12145833, rs59744560 and rs9568856. In rs6235 and rs59744560, a direct effect of different allele states could be implied. Obesity-related hypertension at a young age differs from essential hypertension in those non-obese. The reported genetic differences could be important in understanding the complex pathophysiology of early-onset obesity-related hypertension and should be further evaluated.

Dynamic Regulation of Cysteine Oxidation and Phosphorylation in Myocardial Ischemia-Reperfusion Injury

Myocardial ischemia-reperfusion (I/R) injury significantly alters heart function following infarct and increases the risk of heart failure. Many studies have sought to preserve irreplaceable myocardium, termed cardioprotection, but few, if any, treatments have yielded a substantial reduction in clinical I/R injury. More research is needed to fully understand the molecular pathways that govern cardioprotection. Redox mechanisms, specifically cysteine oxidations, are acute and key regulators of molecular signaling cascades mediated by kinases. Here, we review the role of reactive oxygen species in modifying cysteine residues and how these modifications affect kinase function to impact cardioprotection. This exciting area of research may provide novel insight into mechanisms and likely lead to new treatments for I/R injury.

AKT1 Polymorphism (rs10138227) and Risk of Colorectal Cancer in Moroccan Population: A Case Control Study

BACKGROUND

LMTK3 and AKT1 each have a role in carcinogenesis and tumor progression. The analysis of single nucleotide polymorphisms of AKT1 and LMTK3 could lead to more complete and accurate risk estimates for colorectal cancer.

AIM

We evaluated the association between single nucleotide polymorphisms (SNPs) of AKT1 and LMTK3 and the risk of colorectal cancer in a case-control study in Moroccan population.

METHODS

Genomic DNA from 70 colorectal cancer patients and 50 healthy control subjects was extracted from whole blood. Genotyping was performed by direct sequencing after polymerase chain reactions for the 7 SNPs (AKT1rs1130214G/T, AKT1rs10138227C/T, AKT1rs3730358C/T, AKT1rs1000559097G/A, AKT1rs2494737A/T, LMTK3rs8108419G/A, and LMTK3rs9989661A/G.). Study subjects provided detailed information during the collection. All P values come from bilateral tests.

RESULTS

In the logistic regression analysis, a significantly high risk of colorectal cancer was associated with TC/TT genotypes of rs10138227 with adjusted odds ratio [OR] equal to 2.82 and 95% confidence interval [CI] of 1.15 to 6.91.

CONCLUSION

Our results suggest that the SNP AKT1rs10138227 could affect susceptibility to CRC, probably by modulating the transcriptional activity of AKT1. However, larger independent studies are needed to validate our results.

AKT1 Regulates Endoplasmic Reticulum Stress and Mediates the Adaptive Response of Pancreatic β Cells

Isoforms of protein kinase B (also known as AKT) play important roles in mediating insulin and growth factor signals. Previous studies have suggested that the AKT2 isoform is critical for insulin-regulated glucose metabolism, while the role of the AKT1 isoform remains less clear. This study focuses on the effects of AKT1 on the adaptive response of pancreatic β cells. Using a mouse model with inducible β-cell-specific deletion of the Akt1 gene (βA1KO mice), we showed that AKT1 is involved in high-fat-diet (HFD)-induced growth and survival of β cells but is unnecessary for them to maintain a population in the absence of metabolic stress. When unchallenged, βA1KO mice presented the same metabolic profile and β-cell phenotype as the control mice with an intact Akt1 gene. When metabolic stress was induced by HFD, β cells in control mice with intact Akt1 proliferated as a compensatory mechanism for metabolic overload. Similar effects were not observed in βA1KO mice. We further demonstrated that AKT1 protein deficiency caused endoplasmic reticulum (ER) stress and potentiated β cells to undergo apoptosis. Our results revealed that AKT1 protein loss led to the induction of eukaryotic initiation factor 2 α subunit (eIF2α) signaling and ER stress markers under normal-chow-fed conditions, indicating chronic low-level ER stress. Together, these data established a role for AKT1 as a growth and survival factor for adaptive β-cell response and suggest that ER stress induction is responsible for this effect of AKT1.

Intersections and Clinical Translations of Diabetes Mellitus with Cancer Promotion, Progression and Prognosis

The association between cancer and dysglycemia has been well documented. It is underappreciated, however, that sustained dysglycemia could potentially be a catalyst toward a pro-cancer physiologic milieu and/or increase the burden of cancer. Hyperglycemia, hyperinsulinemia and energy metabolism at large impact a cascade of growth pathways, epi/genetic modifications, and mitochondrial changes that could feasibly link to tumor processes. Oxidative stress is a recurring motif in cell dysfunction: in diabetes, oxidative stress and reactive oxygen species (ROS) feature prominently in the damage and demise of pancreatic beta cells, as well as cell damage contributing to diabetes-related complications. Oxidative stress may be one intersection at which metabolic and oncogenic processes cross paths with deleterious results in the development of precancer, cancer, and cancer progression. This would augur for tight glucose control. Regrettably, some medical societies have recently relaxed hemoglobin A1c targets. A framework for the hyperglycemic state is presented that helps account and translate the full scope of effects of dysglycemia to ultimately improve clinical best practices.

Stress exposure alters brain mRNA expression of the genes involved in insulin signalling, an effect modified by a high fat/high fructose diet and cinnamon supplement

In occidental societies, high fat and high sugar diets often coincide with episodes of stress. The association is likely to modify brain energy control. Brain insulin signalling is rarely studied in stressed individuals consuming high fat diets. Furthermore the effects of cinnamon supplement are not known in these conditions. Therefore, we exposed rats, over a 12-week period, to a control (C) or a high fat/high fructose (HF/HFr) diet that induces peripheral insulin resistance. A cinnamon supplement (C+CN and HF/HFr +CN) was added or not. After diet exposure, one group of rats was exposed to a 30-min restraint followed by a 10-min open-field test, their combination featuring a moderate stressor, the other rats staying unstressed in their home cages. The insulin signalling in hippocampus and frontal cortex was studied through the mRNA expression of the following genes: insulin receptor (Ir), insulin receptor substrate (Irs1), glucose transporters (Glut1 and Glut3), glycogen synthase (Gys1) and their modulators, Akt1 and Pten. In C rats, stress enhanced the expression of Ir, Irs1, Glut1, Gys1 and Akt1 mRNA. In C+CN rats, stress induced an increase in Pten but a decrease in Gys1 mRNA expression. In HF/HFr rats, stress was associated with an increase in Pten mRNA expression. In HF/HFr+CN rats, stress increased Pten mRNA expression but also decreased Gys1 mRNA expression. This suggests that a single moderate stress favours energy refilling mechanisms, an effect blunted by a previous HF/HFr diet and cinnamon supplement.

Polymorphism rs1385129 Within Glut1 Gene SLC2A1 Is Linked to Poor CD4+ T Cell Recovery in Antiretroviral-Treated HIV+ Individuals

Untreated HIV infection is associated with progressive CD4+ T cell depletion, which is generally recovered with combination antiretroviral therapy (cART). However, a significant proportion of cART-treated individuals have poor CD4+ T cell reconstitution. We investigated associations between HIV disease progression and CD4+ T cell glucose transporter-1 (Glut1) expression. We also investigated the association between these variables and specific single nucleotide polymorphisms (SNPs) within the Glut1 regulatory gene AKT (rs1130214, rs2494732, rs1130233, and rs3730358) and in the Glut1-expressing gene SLC2A1 (rs1385129 and rs841853) and antisense RNA 1 region SLC2A1-AS1 (rs710218). High CD4+Glut1+ T cell percentage is associated with rapid CD4+ T cell decline in HIV-positive treatment-naïve individuals and poor T cell recovery in HIV-positive individuals on cART. Evidence suggests that poor CD4+ T cell recovery in treated HIV-positive individuals is linked to the homozygous genotype (GG) associated with SLC2A1 SNP rs1385129 when compared to those with a recessive allele (GA/AA) (odds ratio = 4.67; P = 0.04). Furthermore, poor response to therapy is less likely among Australian participants when compared against American participants (odds ratio: 0.12; P = 0.01) despite there being no difference in prevalence of a specific genotype for any of the SNPs analyzed between nationalities. Finally, CD4+Glut1+ T cell percentage is elevated among those with a homozygous dominant genotype for SNPs rs1385129 (GG) and rs710218 (AA) when compared to those with a recessive allele (GA/AA and AT/TT respectively) (P < 0.04). The heterozygous genotype associated with AKT SNP 1130214 (GT) had a higher CD4+Glut1+ T cell percentage when compared to the dominant homozygous genotype (GG) (P = 0.0068). The frequency of circulating CD4+Glut1+ T cells and the rs1385129 SLC2A1 SNP may predict the rate of HIV disease progression and CD4+ T cell recovery in untreated and treated infection, respectively.

Cannabis and a lower BMI in psychosis: What is the role of AKT1?

Cannabis use has been associated with favorable outcomes on metabolic risk factors. The cause of this relation is still unknown. In this study we investigated whether this effect is mediated by the AKT1 gene, as activation of the related enzyme by cannabis may cause metabolic changes. Six Single Nucleotide Polymorphisms (SNPs) of the AKT1 gene (rs1130214, rs1130233, rs2494732, rs2498784, rs3730358, and rs3803300) of patients with psychotic disorders (n=623) were related to Body Mass Index (BMI), levels of glycosylated hemoglobin (HBA1c) and total metabolic risk. Next, mediation analysis was performed with BMI as outcome, cannabis as predictor, and AKT1 as mediator. Cannabis use was inversely related to BMI but not with levels of HBA1c and total metabolic risk. Moreover, out of 6 AKT1 SNPs, rs2494732 was associated with cannabis use, but AKT1 did not mediate the effect of cannabis on BMI. In conclusion, cannabis use is likely to be associated with a lower BMI in patients with a psychotic disorder. Moreover, AKT1 risk alleles may increase the incidence of cannabis use in patients with a psychotic disorder, but AKT1 does not appear to mediate the effect of cannabis on BMI.

Lack of association between genetic polymorphism of FTO, AKT1 and AKTIP in childhood overweight and obesity

OBJECTIVE

Obesity is a chronic disease caused by both environmental and genetic factors. Epidemiological studies have documented that increased energy intake and sedentary lifestyle, as well as a genetic contribution, are forces behind the obesity epidemic. Knowledge about the interaction between genetic and environmental components can facilitate the choice of the most effective and specific measures for the prevention of obesity. The aim of this study was to assess the association between the FTO, AKT1, and AKTIP genes and childhood obesity and insulin resistance.

METHODS

This was a case-control study in which SNPs in the FTO (rs99396096), AKT1, and AKTIP genes were genotyped in groups of controls and obese/overweight children. The study included 195 obese/overweight children and 153 control subjects.

RESULTS

As expected, the obese/overweight group subjects had higher body mass index, higher fasting glucose, HOMA-IR index, total cholesterol, low-density lipoprotein, and triglycerides. However, no significant differences were observed in genes polymorphisms genotype or allele frequencies.

CONCLUSION

The present results suggest that AKT1, FTO, and AKTIP polymorphisms were not associated with obesity/overweight in Brazilians children. Future studies on the genetics of obesity in Brazilian children and their environment interactions are needed.

Predicting diabetes mellitus genes via protein-protein interaction and protein subcellular localization information

BACKGROUND

Diabetes mellitus characterized by hyperglycemia as a result of insufficient production of or reduced sensitivity to insulin poses a growing threat to the health of people. It is a heterogeneous disorder with multiple etiologies consisting of type 1 diabetes, type 2 diabetes, gestational diabetes and so on. Diabetes-associated protein/gene prediction is a key step to understand the cellular mechanisms related to diabetes mellitus. Compared with experimental methods, computational predictions of candidate proteins/genes are cheaper and more effortless. Protein-protein interaction (PPI) data produced by the high-throughput technology have been used to prioritize candidate disease genes/proteins. However, the false interactions in the PPI data seriously hurt computational methods performance. In order to address that particular question, new methods are developed to identify candidate disease genes/proteins via integrating biological data from other sources.

RESULTS

In this study, a new framework called PDMG is proposed to predict candidate disease genes/proteins. First, the weighted networks are building in terms of the combination of the subcellular localization information and PPI data. To form the weighted networks, the importance of each compartment is evaluated based on the number of interacted proteins in this compartment. This is because the very different roles played by different compartments in cell activities. Besides, some compartments are more important than others. Based on the evaluated compartments, the interactions between proteins are scored and the weighted PPI networks are constructed. Second, the known disease genes are extracted from OMIM database as the seed genes to expand disease-specific networks based on the weighted networks. Third, the weighted values between a protein and its neighbors in the disease-related networks are added together and the sum is as the score of the protein. Last but not least, the proteins are ranked based on descending order of their scores. The candidate proteins in the top are considered to be associated with the diseases and are potential disease-related proteins. Various types of data, such as type 2 diabetes-associated genes, subcellular localizations and protein interactions, are used to test PDMG method.

CONCLUSIONS

The results show that the proteins/genes functionally exerting a direct influence over diabetes are consistently placed at the head of the queue. PDMG expands and ranks 445 candidate proteins from the seed set including original 27 type 2 diabetes proteins. Out of the top 27 proteins, 14 proteins are the real type 2 diabetes proteins. The literature extracted from the PubMed database has proved that, out of 13 novel proteins, 8 proteins are associated with diabetes.

Association between Polymorphisms of the AKT1 Gene Promoter and Risk of the Alzheimer's Disease in a Chinese Han Population with Type 2 Diabetes

AIMS

Alzheimer's disease (AD) is a multifactor disease that has been reported to have a close association with type 2 diabetes (T2D) where the v-akt murine thymoma viral oncogene homolog 1 (AKT1) plays an important role in the protein synthesis pathways and cell apoptosis processes. Evidence has been shown that AKT1 protein may be related to AD risk among patients with T2D. The aim of this study was to analyze the potential association between single nucleotide polymorphisms of AKT1 promoter and the risk of AD among patients with T2D.

METHODS

The association between AKT1 polymorphisms and AD risk in patients with T2D was assessed among 574 consecutive unrelated subjects including 112 AD patients with T2D, 231 patients with AD, and 231 healthy controls in a case-control study. The cognitive function of all subjects was assessed using MMSE. Six single nucleotide polymorphisms with minor allele frequency >0.2 (rs2498786, rs74090038, rs2494750, rs2494751, rs5811155, and rs2494752) in AKT1 promoter were analyzed by polymerase chain reaction (PCR), and the concentration of AKT1 protein in serum was tested using enzyme-linked immunosorbent assay (ELISA).

RESULTS

Overall, there was statistically significant difference in AKT1 rs2498786 polymorphism. The CC frequency of AKT1 rs2498786 polymorphism in AD with T2D group and AD control group was significantly higher than that in healthy control group (PAD+T2D vs. health < 0.0001, PAD vs. health < 0.0001). However, the difference was not found between AD with T2D group and AD control group. Compared with healthy control group, the plasma levels of AKT1 protein in AD with T2D group (PAD+T2D vs. health < 0.0001) and AD control group (PAD vs. health = 0.0003) decreased significantly. Among genotypes of AKT1 rs2498786 polymorphism, the AKT1 protein level in GG genotype was significantly higher than that in GC genotype (PGG vs. GC < 0.0001) and CC genotype (PGG vs. CC < 0.0001).

CONCLUSION

The study suggests that AKT1 rs2498786 polymorphism in insulin signaling pathway may be associated with AD risk and different genotypes may affects levels of protein expression. However, the polymorphism is not shown to be exclusive in AD patients with T2D.

ZBTB42 mutation defines a novel lethal congenital contracture syndrome (LCCS6)

Lethal congenital contracture syndrome (LCCS) is a lethal autosomal recessive form of arthrogryposis multiplex congenita (AMC). LCCS is genetically heterogeneous with mutations in five genes identified to date, all with a role in the innervation or contractile apparatus of skeletal muscles. In a consanguineous Saudi family with multiple stillbirths presenting with LCCS, we excluded linkage to all known LCCS loci and combined autozygome analysis and whole-exome sequencing to identify a novel homozygous variant in ZBTB42, which had been shown to be enriched in skeletal muscles, especially at the neuromuscular junction. Knockdown experiments of zbtb42 in zebrafish consistently resulted in grossly abnormal skeletal muscle development and myofibrillar disorganization at the microscopic level. This severe muscular phenotype is successfully rescued with overexpression of the human wild-type ZBTB42 gene, but not with the mutant form of ZBTB42 that models the human missense change. Our data assign a novel muscular developmental phenotype to ZBTB42 in vertebrates and establish a new LCCS6 type caused by ZBTB42 mutation.

A polymorphism of HMGA1 is associated with increased risk of metabolic syndrome and related components

The metabolic syndrome (MetS) is a common disorder, where systemic insulin-resistance is associated with increased risk for type 2 diabetes (T2D) and cardiovascular disease. Identifying genetic traits influencing risk and progression of MetS is important. We and others previously reported a functional HMGA1 gene variant, rs146052672, predisposing to T2D. Here we investigated the association of rs146052672 variant with MetS and related components. In a case-control study from Italy and Turkey, increased risk of MetS was seen among carriers of the HMGA1 variant. In the larger Italian cohort, this variant positively correlated with BMI, hyperglycemia and insulin-resistance, and negatively correlated with serum HDL-cholesterol. Association between rs146052672 variant and MetS occurred independently of T2D, indicating that HMGA1 gene defects play a pathogenetic role in MetS and other insulin-resistance-related conditions. Overall, our results indicate that the rs146052672 variant represents an early predictive marker of MetS, as well as a predictive tool for therapy.

Alterations in osteopontin modify muscle size in females in both humans and mice

PURPOSE

An osteopontin (OPN; SPP1) gene promoter polymorphism modifies disease severity in Duchenne muscular dystrophy, and we hypothesized that it might also modify muscle phenotypes in healthy volunteers.

METHODS

Gene association studies were carried out for OPN (rs28357094) in the FAMuSS cohort (n = 752; mean ± SD age = 23.7 ± 5.7 yr). The phenotypes studied included muscle size (MRI), strength, and response to supervised resistance training. We also studied 147 young adults that had carried out a bout of eccentric elbow exercise (age = 24.0 ± 5.2 yr). Phenotypes analyzed included strength, soreness, and serum muscle enzymes.

RESULTS

In the FAMuSS cohort, the G allele was associated with 17% increase in baseline upper arm muscle volume only in women (F = 26.32; P = 5.32 × 10), explaining 5% of population variance. In the eccentric damage cohort, weak associations of the G allele were seen in women with both baseline myoglobin and elevated creatine kinase. The sexually dimorphic effects of OPN on muscle were also seen in OPN-null mice. Five of seven muscle groups examined showed smaller size in OPN-null female mice, whereas two were smaller in male mice. The query of OPN gene transcription after experimental muscle damage in mice showed rapid induction within 12 h (100-fold increase from baseline), followed by sustained high-level expression through 16 d of regeneration before falling to back to baseline.

CONCLUSION

OPN is a sexually dimorphic modifier of muscle size in normal humans and mice and responds to muscle damage. The OPN gene is known to be estrogen responsive, and this may explain the female-specific genotype effects in adult volunteers.

Highlights from the functional single nucleotide polymorphisms associated with human muscle size and strength or FAMuSS study

The purpose of the Functional Single Nucleotide Polymorphisms Associated with Human Muscle Size and Strength study or FAMuSS was to identify genetic factors that dictated the response of health-related fitness phenotypes to resistance exercise training (RT). The phenotypes examined were baseline muscle strength and muscle, fat, and bone volume and their response to RT. FAMuSS participants were 1300 young (24 years), healthy men (42%) and women (58%) that were primarily of European-American descent. They were genotyped for ~500 polymorphisms and completed the Paffenbarger Physical Activity Questionnaire to assess energy expenditure and time spent in light, moderate, and vigorous intensity habitual physical activity and sitting. Subjects then performed a 12-week progressive, unilateral RT program of the nondominant arm with the dominant arm used as a comparison. Before and after RT, muscle strength was measured with the maximum voluntary contraction and one repetition maximum, while MRI measured muscle, fat, and bone volume. We will discuss the history of how FAMuSS originated, provide a brief overview of the FAMuSS methods, and summarize our major findings regarding genotype associations with muscle strength and size, body composition, cardiometabolic biomarkers, and physical activity.

Homeostasis and the importance for a balance between AKT/mTOR activity and intracellular signaling

The AKT family of serine threonine kinases is of critical importance with regard to growth factor signaling, cell proliferation, survival and oncogenesis. Engagement of signaling receptors induces the lipid kinase, phosphatidylinositol 3-kinase (PI3K), which enables the activation of AKT. Responsive to the PI3K/AKT pathway is the mammalian target of rapamycin (mTOR), a major effector that is specifically implicated in the regulation of cell growth as a result of nutrient availability and cellular bioenergetics. These kinases mediate the activity of a multitude of intracellular signaling molecules and intersect with multiple pathways that regulate cellular processes. Elucidating the role of AKT/mTOR in metabolism and in hallmark signaling pathways that are aberrantly affected in cancer has provided a solid foundation of discoveries. From this, new research directions are emerging with regard to the role of AKT/mTOR in diabetes and T cell-mediated immunity. As a result, a new perspective is developing in how AKT/mTOR functions within intracellular signaling pathways to maintain cellular homeostasis. An appreciation is emerging that altered equilibrium of AKT/mTOR pathways contributes to disease and malignancy. Such new insights may lead to novel intervention strategies that may be useful to reprogram or reset the balance of intracellular signaling.

Characterization of the ZBTB42 gene in humans and mice

A 12 kb haplotype upstream of the key signaling protein gene, AKT1, has been associated with insulin resistance and metabolic syndrome (Devaney et al. 2010). The region contains the first exon and promoter sequences of AKT1, but also includes the complete transcript unit for a highly conserved yet uncharacterized zinc finger-containing protein (ZBTB42). One of the component SNPs of the 12 kb haplotype metabolic syndrome haplotype changes a conserved amino acid in the predicted ZBTB42 protein, increasing the potential significance of the ZBTB42 transcript unit for contributing to disease risk. Using RT-PCR of human and mouse cells, we verified that the two exon ZBTB42 was expressed and correctly spliced in human skeletal muscle, and murine C2C12 cells. Production of peptide antibodies showed the expected protein in human (47 kD) and mouse (49 kD) immunoblots, and murine tissue distribution showed strongest expression in muscle and ovary. Immunostaining showed nuclear localization of the ZBTB42 protein in human muscle. Confocal imaging analyses of murine muscle showed ZBTB42 distributed in the nucleoplasm, with particular enrichment in nuclei underlying the neuromuscular junctions. The genetic association data of metabolic syndrome, coupled with the molecular characterization of the ZBTB42 transcript unit and encoded protein presented here, suggests that ZBTB42 may be involved in metabolic syndrome phenotypes.

Functional characterization of a haplotype in the AKT1 gene associated with glucose homeostasis and metabolic syndrome

A small 12-kb haplotype upstream of the AKT1 gene has been found to be associated with insulin resistance phenotypes. We sought to define the functional consequences of the three component polymorphic loci (rs1130214, rs10141867, rs33925946) on AKT1 and the upstream ZBTB42 gene. 5' RACE analysis of AKT1 transcripts in human skeletal muscle biopsies showed the predominant promoter to be 2.5 kb upstream of exon 2, and distinct from those promoters previously reported in rat. We then studied the effect of each of the three haplotype polymorphisms in transcriptional reporter assays in muscle, bone, and fat cell culture models, and found that each modulated enhancer and repressor activity are in a cell-specific and differentiation-specific manner. Our results in promoter assays are consistent with the human phenotype data; we found an anabolic effect on muscle and bone with increased mRNA expression of AKT1, and catabolic effect on fat with decreased expression. To test the hypothesis that rs10141867 affects transcription levels of the novel zinc finger protein ZBTB42 in vivo, we developed the allele-specific expression assay using Taqman technology to test for allelic differences within heterozygotes. The allele containing the derived polymorphism (haplotype H2) showed a 1.75-fold increase in expression in human skeletal muscle. Our data show a particularly complex effect of the component polymorphisms of a single haplotype on cells and tissues, suggesting that the coordination of different tissue-specific effects may have driven selection for the H2 haplotype. In light of the recent abundance of SNP association studies, our approach can serve as a method for exploring the biological function of polymorphisms that show significant genotype/phenotype associations.