Associations of Haplotypes Upstream of IRS1 with Insulin Resistance, Type 2 Diabetes, Dyslipidemia, Preclinical Atherosclerosis, and Skeletal Muscle LOC646736 mRNA Levels.

The genomic region ~500 kb upstream of IRS1 has been implicated in insulin resistance, type 2 diabetes, adverse lipid profile, and cardiovascular risk. To gain further insight into this chromosomal region, we typed four SNPs in a cross-sectional cohort and subjects with type 2 diabetes recruited from the same geographic region. From 16 possible haplotypes, 6 haplotypes with frequencies >0.

Heme oxygenase-1 drives metaflammation and insulin resistance in mouse and man.

Obesity and diabetes affect more than half a billion individuals worldwide. Interestingly, the two conditions do not always coincide and the molecular determinants of "healthy" versus "unhealthy" obesity remain ill-defined. Chronic metabolic inflammation (metaflammation) is believed to be pivotal.

Potential role of upstream stimulatory factor 1 gene variant in familial combined hyperlipidemia and related disorders.

Objective: Genetic studies implicated upstream stimulatory factor 1 (USF1) in familial combined hyperlipidemia because the rs2073658 minor allele was associated with reduced risk of familial combined hyperlipidemia and related disorders. The molecular mechanisms whereby rs2073658 influences trait expression have remained elusive.

Methods And Results: Plasma lipids, rs2073658 genotypes (N=372), and hepatic transcript levels (N=96) of USF1 and genes involved in hepatic lipoprotein production were determined in obese subjects.

Cross-talk between interferon-γ and hedgehog signaling regulates adipogenesis.

Objective: T cells and level of the cytokine interferon-γ (IFN-γ) are increased in adipose tissue in obesity. Hedgehog (Hh) signaling has been shown to potently inhibit white adipocyte differentiation. In light of recent findings in neurons that IFN-γ and Hh signaling cross-talk, we examined their potential interaction in the context of adipogenesis.

Cholesteryl ester transfer protein and hepatic lipase gene polymorphisms: effects on hepatic mRNA levels, plasma lipids and carotid atherosclerosis.

Objective: HDL modifying effects of cholesteryl ester transfer protein (CETP) and hepatic lipase (LIPC) depend in part on each other. We studied associations of CETP-Taq1B and -514C>T-LIPC polymorphisms with hepatic mRNA levels, and their combined effects on plasma lipids and carotid atherosclerosis.

Methods: We genotyped the CETP-Taq1B and the -514C>T-LIPC polymorphisms in 67 obese women in whom hepatic CETP and LIPC transcript levels were determined as well as in 1549 participants of the Salzburg Atherosclerosis Prevention Program in Subjects at High Individual Risk (SAPHIR).

The mitochondrial T16189C polymorphism is associated with coronary artery disease in Middle European populations.

Background: The pivotal role of mitochondria in energy production and free radical generation suggests that the mitochondrial genome could have an important influence on the expression of multifactorial age related diseases. Substitution of T to C at nucleotide position 16189 in the hypervariable D-loop of the control region (CR) of mitochondrial DNA (mtDNA) has attracted research interest because of its suspected association with various multifactorial diseases. The aim of the present study was to compare the frequency of this polymorphism in the CR of mtDNA in patients with coronary artery disease (CAD, n = 482) and type 2 diabetes mellitus (T2DM, n = 505) from two study centers, with healthy individuals (n = 1481) of Middle European descent in Austria.

The human organic anion transporter genes OAT5 and OAT7 are transactivated by hepatocyte nuclear factor-1α (HNF-1α).

Organic anion transporters (OATs) are anion exchangers that transport small hydrophilic anions and diuretics, antibiotics, nonsteroidal anti-inflammatory drugs, antiviral nucleoside analogs, and antitumor drugs across membrane barriers of epithelia of diverse organs. Three OATs are present in human liver: OAT2, OAT5, and OAT7. Given that hepatocyte nuclear factor-1α (HNF-1α) has previously been shown to regulate the expression of several hepatocellular transporter genes, we investigated whether the liver-specific human OAT genes are also regulated by HNF-1α.

The T-381C SNP in BNP gene may be modestly associated with type 2 diabetes: an updated meta-analysis in 49 279 subjects.

A recent study reported an association between the brain natriuretic peptide (BNP) promoter T-381C polymorphism (rs198389) and protection against type 2 diabetes (T2D). As replication in several studies is mandatory to confirm genetic results, we analyzed the T-381C polymorphism in seven independent case-control cohorts and in 291 T2D-enriched pedigrees totalling 39 557 subjects of European origin. A meta-analysis of the seven case-control studies (n = 39 040) showed a nominal protective effect [odds ratio (OR) = 0.

Transcriptional co-activator peroxisome proliferator-activated receptor (PPAR)gamma co-activator-1beta is involved in the regulation of glucose-stimulated insulin secretion in INS-1E cells.

Peroxisome proliferator-activated receptor-gamma co-activator-1 (PGC-1) alpha and -beta play pivotal roles in the regulation of intermediary metabolism. We have previously shown that PGC-1alpha-mediated upregulation of beta-cell sterol element binding protein (SREBP) gene expression impairs insulin secretion via increased transcription of uncoupling protein 2 (UCP2). PGC-1beta, in contrast to PGC-1alpha, directly binds to and acts as a co-activator of SREBPs and the forkhead transcription factor 2A (FOXA2) involved in pancreas development and function.

TCF7L2 is reproducibly associated with type 2 diabetes in various ethnic groups: a global meta-analysis.

TCF7L2 variants have been consistently associated with type 2 diabetes (T2D) in populations of different ethnic descent. Among them, the rs7903146 T allele is probably the best proxy to evaluate the effect of this gene on T2D risk in additional ethnic groups. In the present study, we investigated the association between the TCF7L2 rs7903146 polymorphism and T2D in Moroccans (406 normoglycemic individuals and 504 T2D subjects) and in white Austrians (1,075 normoglycemic individuals and 486 T2D subjects).

Associations of PPARGC1A haplotypes with plaque score but not with intima-media thickness of carotid arteries in middle-aged subjects.

Background And Purpose: Peroxisome proliferator activated receptor gamma coactivator 1alpha (PGC-1alpha, PPARGC1A) integrates the transcriptional program of mitochondrial biogenesis. Mitochondria are the main source of cellular reactive oxygen species implicated in atherogenesis. We therefore ascertained associations of PPARGC1A polymorphisms with asymptomatic carotid atherosclerosis.

Role of peroxisome proliferator-activated receptor-gamma coactivator-1alpha in the transcriptional regulation of the human uncoupling protein 2 gene in INS-1E cells.

A role of uncoupling protein 2 (UCP2) as negative modulator of insulin secretion has been suggested, but the transcriptional pathways regulating beta-cell UCP2 gene expression have been established in rodents only. We show here that the underlying sequence motifs are not conserved in the human gene and provide evidence for regulatory mechanisms involving the transcriptional cofactor peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1alpha). PGC-1alpha potentiates thyroid hormone (T(3))-mediated transcriptional activation of the human UCP2 gene in INS-1E cells.

[Pathophysiology and genetics of obesity].

Obesity has become the most prevalent nutritional disorder in post-industrialised societies and it is associated with the development of severe and costly complications such as type 2 diabetes mellitus and coronary heart disease or cancer. A large proportion of the risk of obesity is determined by the genetic susceptibility of an individual, but environmental factors conducive for the disorder play an important role in its phenotypic expression. Several candidate genes emerged from studies in animal models of obesity, but human pathophysiology is likely to be more complex.

Complex haplotypes of the PGC-1alpha gene are associated with carbohydrate metabolism and type 2 diabetes.

Peroxisome proliferator-activated receptor coactivator-1alpha (PGC-1alpha) is a transcriptional coactivator implicated in transcriptional programs of hepatic gluconeogenesis, oxidative phosphorylation, and insulin release by beta-cells. To study associations of the PGC-1alpha gene locus with carbohydrate metabolism and type 2 diabetes in humans, we identified several polymorphisms in the promoter region that were located in a haplotype block distinct from a second haplotype block containing part of intron 2 and extending beyond exon 13. Each block contained five common haplotypes.

Restoration of sterol-regulatory-element-binding protein-1c gene expression in HepG2 cells by peroxisome-proliferator-activated receptor-gamma co-activator-1alpha.

The expression of SREBP-1 (sterol-regulatory-element-binding protein-1) isoforms differs between tissues and cultured cell lines in that SREBP-1a is the major isoform in established cell lines, whereas SREBP-1c predominates in liver and most other human tissues. SREBP-1c is transcriptionally less active than SREBP-1a, but is a main mediator of hepatic insulin action and is selectively up-regulated by LXR (liver X receptor) agonists. LXR-mediated transactivation is co-activated by PGC-1alpha (peroxisome-proliferator-activated receptor-gamma co-activator-1alpha), which displays deficient expression in skeletal-muscle-derived cell lines.

Peroxisome proliferator-activated receptor-gamma coactivator-1 gene locus: associations with hypertension in middle-aged men.

Peroxisome proliferator-activated receptor-gamma coactivator-1 (PPARGC1/PGC-1) is a transcriptional coactivator of nuclear hormone receptors implicated in blood pressure regulation. We therefore ascertained whether the PPARGC1 gene locus is associated with hypertension. We studied associations of 3 polymorphisms in PPARGC1 transcripts with hypertension in 683 middle-aged men and 530 middle-aged women of a cross-sectional Austrian population.

Potentiation of liver X receptor transcriptional activity by peroxisome-proliferator-activated receptor gamma co-activator 1 alpha.

Peroxisome-proliferator-activated receptor (PPAR) gamma co-activator 1 alpha (PGC-1 alpha/PPARGC1) plays an important role in energy metabolism by co-ordinating transcriptional programmes of mitochondrial biogenesis, adaptive thermogenesis and fatty acid beta-oxidation. PGC-1 alpha has also been identified to play a role in the intermediary metabolism by co-activating key transcription factors of hepatic gluconeogenesis and glucose uptake in muscles. In the present study, we show that PGC-1 alpha serves as a co-activator for the liver X receptor (LXR) alpha, known to contribute to the regulation of cellular cholesterol homoeostasis.

A functional polymorphism in the promoter of UCP2 enhances obesity risk but reduces type 2 diabetes risk in obese middle-aged humans.

Obesity is frequently associated with type 2 diabetes. We previously observed an association of a functional G/A polymorphism in the uncoupling protein 2 (UCP2) promoter with obesity. The wild-type G allele was associated with reduced adipose tissue mRNA expression in vivo, reduced transcriptional activity in vitro, and increased risk of obesity.

Sterol regulatory element binding proteins: relationship of adipose tissue gene expression with obesity in humans.

Sterol regulatory element binding proteins (SREBPs) are transcription factors that are involved in adipogenesis and regulate the expression of genes controlling cholesterol and fatty acid biosynthesis. Animal experiments indicate that SREBP-1a, -1c, and -2 have distinct functions despite overlapping specificities for target genes. To study the possible relationships of SREBPs with obesity, we determined their expression levels in intra- and extraperitoneal adipose tissue samples of obese, post-obese and never-obese humans.

Peroxisome proliferator-activated receptor-gamma coactivator-1 gene locus: associations with obesity indices in middle-aged women.

Peroxisome proliferator-activated receptor-gamma coactivator-1 (PPARGC1) is a transcriptional coactivator that has been implicated in the regulation of genes involved in energy metabolism. We studied associations of two polymorphisms identified in PPARGC1 transcripts with obesity indices in 591 middle-aged men and 467 middle-aged women of a cross-sectional Austrian population. Because neither polymorphic site was likely to be a functional site, we analyzed sex-specific associations of two loci haplotype combinations with obesity indices.

Peroxisome proliferator-activated receptor (PPAR) gamma coactivator-1 recruitment regulates PPAR subtype specificity.

The peroxisome proliferator-activated receptors (PPAR) alpha and gamma play key roles in the transcriptional control of contrasting metabolic pathways such as adipogenesis and fatty acid beta-oxidation. Both ligand-activated nuclear receptors bind to common target gene response elements and interact with distinct domains of the transcriptional coactivator PGC-1 to attain their full transcriptional potency. Thus, PPAR subtype specificity may be determined by ligand availability and transcription factor or coactivator expression levels.