CiteULike: omalbam's molecular

Crosstalk Between GlcNAcylation and Phosphorylation: Roles in Insulin Resistance and Glucose Toxicity.

Ronald J Copeland — 2008-07-09T23:14:44-00:00

American journal of physiology. Endocrinology and metabolism (29 April 2008)

O-linked-beta-N-acetylglucosamine (O-GlcNAc) is a dynamic post-translational modification that, analogous to phosphorylation, cycles on and off serine and/or threonine hydroxyl groups. Cycling of O-GlcNAc is regulated by the concerted actions of O-GlcNAc transferase and O-GlcNAcase. GlcNAcylation is a nutrient/stress sensitive modification that regulates proteins involved in a wide array of biological processes, including transcription, signaling, and metabolism. GlcNAcylation is involved in the etiology of glucose toxicity and chronic hyperglycemia induced insulin resistance, a major hallmark of Type II diabetes. Several reports demonstrate a strong positive correlation between GlcNAcylation and the development of insulin resistance. However, recent studies suggest that inhibiting GlcNAcylation does not prevent hyperglycemia-induced insulin resistance, suggesting that other mechanisms must also be involved. To date, proteomic analyses have identified more than 600 GlcNAcylated proteins in diverse functional classes. However, O-GlcNAc sites have been mapped on only a small percentage (<15%) of these proteins, most of which were isolated from brain or spinal cord tissue and not from other metabolically relevant tissues. Mapping the sites of GlcNAcylation is not only necessary to elucidate the complex crosstalk between GlcNAcylation and phosphorylation, but also is key to the design of site-specific mutational studies, and necessary for the generation of site-specific antibodies, both of which will help further decipher O-GlcNAc's functional roles. Recent technical advances in O-GlcNAc site mapping methods should now finally allow for a much needed increase in site-specific analyses to address the functional significance of O-GlcNAc in insulin resistance, glucose toxicity as well as other major biological processes. Key words: O-GlcNAc, diabetes, hexosamine biosynthetic pathway, insulin resistance, glucose toxicity.

Variations in the uncoupling protein-3 gene are associated with specific obesity phenotypes

Annet van Abeelen — 2008-04-21T19:09:45-00:00

Eur J Endocrinol, Vol. 158, No. 5. (1 May 2008), pp. 669-676.

ObjectiveUncoupling protein 3 (UCP-3) uncouples oxidative metabolism from ATP synthesis, resulting in the production of heat instead of energy storage. Single nucleotide polymorphisms (SNPs) in UCP-3 might result in a reduced function or expression of UCP-3 and therefore lead to an increased capacity to store energy as fat. DesignWe conducted a population-based, cross-sectional single-center study among 400 Dutch men between 40 and 80 years. MethodsSeven SNPs in the UCP-3 gene were genotyped by means of an allele-specific real-time TaqMan PCR. Linear regression analyses were performed to examine the independent effects of these SNPs on obesity phenotypes. ResultsWe found a significant association between homozygosity for the minor allele of rs647126, rs1685356, and rs2075577 and an increase in body mass index (BMI; P=0.033, P=0.016, and P=0.019 respectively). Heterozygosity for rs1685354 was associated with a significant decrease in visceral fat mass (P=0.030). ConclusionsOur results suggest that genetic variations in the UCP-3 gene are associated with an increase in BMI. A plausible mechanism by which these SNPs lead to an increase in BMI is that due to these SNPs, the UCP-3 activity might be decreased. As a result, uncoupling activity may also decrease, which will lead to an increase in body weight and BMI. 10.1530/EJE-07-0834

Evaluation of Gene Expression Profiles in Thyroid Nodule Biopsy Material to Diagnose Thyroid Cancer

Stephanie Durand — 2008-04-21T17:03:02-00:00

J Clin Endocrinol Metab, Vol. 93, No. 4. (1 April 2008), pp. 1195-1202.

Context: Detection of thyroid cancer among benign nodules on fine-needle aspiration biopsies (FNAB), which presently relies on cytological examination, is expected to be improved by new diagnostic tests set up from genomic data. Objective: The aim of the study was to use a set of genes discriminating benign from malignant tumors, on the basis of their expression levels, to build tumor classifiers and evaluate their capacity to predict malignancy on FNAB. Design: We analyzed the level of expression of 200 potentially informative genes in 56 thyroid tissue samples (benign or malignant tumors and paired normal tissue) using nylon macroarrays. Gene expression data were subjected to a weighted voting algorithm to generate tumor classifiers. The performances of the classifiers were evaluated on a series of 26 sham FNAB, i.e. FNAB carried out on thyroid nodules after surgical resection. Results: A series of 19 genes with a similar expression in follicular adenomas and normal tissue and discriminating follicular adenomas+normal tissue from the following: 1) follicular thyroid carcinomas (FTCs), 2) papillary thyroid carcinomas (PTCs), or 3) both FTCs and PTCs. These were used to generate four classifiers, the FTCs, PTCs, common (FTC+PTCs), and global classifiers. In 23 of the 26 sham FNAB, the four classifiers yielded a diagnosis in agreement with the diagnosis of the pathologist used as reference; in the three other cases, the correct diagnosis was given by three of four classifiers. Conclusions: We developed a procedure of molecular diagnosis of benign vs. malignant tumors applicable to the material collected by FNAB. The molecular test complied with a preclinical validation stage; it must be now evaluated on ultrasound-guided FNAB in a large-scale prospective study. 10.1210/jc.2007-1571

Polymorphisms Associated with Cholesterol and Risk of Cardiovascular Events

Sekar Kathiresan — 2008-03-20T07:22:21-00:00

N Engl J Med, Vol. 358, No. 12. (20 March 2008), pp. 1240-1249.

Background Common single-nucleotide polymorphisms (SNPs) that are associated with blood low-density lipoprotein (LDL) or high-density lipoprotein (HDL) cholesterol modestly affect lipid levels. We tested the hypothesis that a combination of such SNPs contributes to the risk of cardiovascular disease. Methods We studied SNPs at nine loci in 5414 subjects from the cardiovascular cohort of the Malmo Diet and Cancer Study. We first validated the association between SNPs and either LDL or HDL cholesterol and subsequently created a genotype score on the basis of the number of unfavorable alleles. We used Cox proportional-hazards models to determine the time to the first cardiovascular event in relation to the genotype score. Results All nine SNPs showed replication of an association with levels of either LDL or HDL cholesterol. With increasing genotype scores, the level of LDL cholesterol increased from 152 mg to 171 mg per deciliter (3.9 to 4.4 mmol per liter), whereas HDL cholesterol decreased from 60 mg to 51 mg per deciliter (1.6 to 1.3 mmol per liter). During follow-up (median, 10.6 years), 238 subjects had a first cardiovascular event. The genotype score was associated with incident cardiovascular disease in models adjusted for covariates including baseline lipid levels (P<0.001). The use of the genotype score did not improve the clinical risk prediction, as assessed by the C statistic. However, there was a significant improvement in risk classification with the use of models that included the genotype score, as compared with those that did not include the genotype score. Conclusions A genotype score of nine validated SNPs that are associated with modulation in levels of LDL or HDL cholesterol was an independent risk factor for incident cardiovascular disease. The score did not improve risk discrimination but did modestly improve clinical risk reclassification for individual subjects beyond standard clinical factors. 10.1056/NEJMoa0706728

Genetic tests for common diseases: new insights, old concerns

David Melzer — 2008-03-14T20:01:07-00:00

BMJ, Vol. 336, No. 7644. (15 March 2008), pp. 590-593.

10.1136/bmj.39506.601053.BE

Genome-Wide Association Analysis Identifies Loci for Type 2 Diabetes and Triglyceride Levels.

Richa Saxena — 2007-05-07T08:53:58-00:00

Science (26 April 2007)

New strategies for prevention and treatment of type 2 diabetes (T2D) require improved insight into disease etiology. We analyzed 386,731 common single nucleotide polymorphisms (SNPs) in 1,464 patients with T2D and 1,467 matched controls, each characterized for measures of glucose metabolism, lipids, obesity, and blood pressure. With collaborators (FUSION and WTCCC/UKT2D) we identify and confirm three loci associated with T2D -- in a non-coding region near CDKN2A and CDKN2B, in an intron of IGF2BP2, and an intron of CDKAL1 -- and replicate associations near HHEX and in SLC30A8 found by a recent whole genome association study. We identify and confirm association of a SNP in an intron of glucokinase regulatory protein with serum triglycerides. The discovery of associated variants in unsuspected genes and outside coding regions illustrates the ability of genome-wide association studies to provide potentially important clues into the pathogenesis of common diseases.

Studies of Association of Variants Near the HHEX, CDKN2A/B, and IGF2BP2 Genes With Type 2 Diabetes and Impaired Insulin Release in 10,705 Danish Subjects: Validation and Extension of Genome-Wide Association Studies

Niels Grarup — 2008-03-14T19:12:33-00:00

Diabetes, Vol. 56, No. 12. (1 December 2007), pp. 3105-3111.

OBJECTIVE In the present study, we aimed to validate the type 2 diabetes susceptibility alleles identified in six recent genome-wide association studies in the HHEX/KIF11/IDE (rs1111875), CDKN2A/B (rs10811661), and IGF2BP2 (rs4402960) loci, as well as the intergenic rs9300039 variant. Furthermore, we aimed to characterize quantitative metabolic risk phenotypes of the four variants. RESEARCH DESIGN AND METHODS The variants were genotyped in the population-based Inter99 cohort (n = 5,970), the ADDITION Study (n = 1,626), a population-based sample of young healthy subjects (n = 377), and in additional type 2 diabetic case (n = 2,111) and glucose-tolerant (n = 521) subjects. The case-control studies involved a total of 4,089 type 2 diabetic patients and 5,043 glucose-tolerant control subjects. RESULTS We validated association of variants near HHEX/KIF11/IDE, CDKN2A/B, and IGF2BP2 with type 2 diabetes. Interestingly, in middle-aged people, the rs1111875 C-allele of HHEX/KIF11/IDE strongly associated with lower acute insulin response during an oral glucose tolerance test (P = 6 x 107). In addition, decreased insulin release following intravenous tolbutamide injection was observed in young healthy subjects (P = 0.02). Also, a reduced insulin release was observed for the CDKN2A/B rs10811661 T-allele after both oral and intravenous glucose challenges (P = 0.001 and P = 0.009, respectively). CONCLUSIONS We validate that variants in the proximity of the HHEX/KIF11/IDE, CDKN2A/B, and IFG2BP2 loci associate with type 2 diabetes. Importantly, variations within the HHEX/KIF11/IDE and CDKN2A/B loci confer impaired glucose- and tolbutamide-induced insulin release in middle-aged and young healthy subjects, suggesting a role for these variants in the pathogenesis of pancreatic beta-cell dysfunction. 10.2337/db07-0856

Polymorphism Interaction Analysis (PIA): a method for investigating complex gene-gene interactions

Leah Mechanic — 2008-03-07T09:32:16-00:00

BMC Bioinformatics, Vol. 9, No. 1. (2008)

BACKGROUND:The risk of common diseases is likely determined by the complex interplay between environmental and genetic factors, including single nucleotide polymorphisms (SNPs). Traditional methods of data analysis are poorly suited for detecting complex interactions due to sparseness of data in high dimensions, which often occurs when data are available for a large number of SNPs for a relatively small number of samples. Validation of associations observed using multiple methods should be implemented to minimize likelihood of false-positive associations. Moreover, high-throughput genotyping methods allow investigators to genotype thousands of SNPs at one time. Investigating associations for each individual SNP or interactions between SNPs using traditional approaches is inefficient and prone to false positives. RESULTS:We developed the Polymorphism Interaction Analysis tool (PIA version 2.0) to include different approaches for ranking and scoring SNP combinations, to account for imbalances between case and control ratios, stratify on particular factors, and examine associations of user-defined pathways (based on SNP or gene) with case status. PIA v. 2.0 detected 2-SNP interactions as the highest ranking model 77% of the time, using simulated data sets of genetic models of interaction (minor allele frequency=0.2; heritability=0.01; N=1600) generated previously [Velez DR, White BC, Motsinger AA, Bush WS, Ritchie MD, Williams SM, Moore JH: A balanced accuracy function for epistasis modeling in imbalanced datasets using multifactor dimensionality reduction. Genet Epidemiol 2007, 31:306-315.]. Interacting SNPs were detected in both balanced (20 SNPs) and imbalanced data (case:control 1:2 and 1:4, 10 SNPs) in the context of non-interacting SNPs.CONCLUSIONS:PIA v. 2.0 is a useful tool for exploring gene*gene or gene*environment interactions and identifying a small number of putative associations which may be investigated further using other statistical methods and in replication study populations.

Insulin gene mutations as a cause of permanent neonatal diabetes.

J Støy — 2008-03-05T17:02:50-00:00

Proc Natl Acad Sci U S A, Vol. 104, No. 38. (18 September 2007), pp. 15040-15044.

We report 10 heterozygous mutations in the human insulin gene in 16 probands with neonatal diabetes. A combination of linkage and a candidate gene approach in a family with four diabetic members led to the identification of the initial INS gene mutation. The mutations are inherited in an autosomal dominant manner in this and two other small families whereas the mutations in the other 13 patients are de novo. Diabetes presented in probands at a median age of 9 weeks, usually with diabetic ketoacidosis or marked hyperglycemia, was not associated with beta cell autoantibodies, and was treated from diagnosis with insulin. The mutations are in critical regions of the preproinsulin molecule, and we predict that they prevent normal folding and progression of proinsulin in the insulin secretory pathway. The abnormally folded proinsulin molecule may induce the unfolded protein response and undergo degradation in the endoplasmic reticulum, leading to severe endoplasmic reticulum stress and potentially beta cell death by apoptosis. This process has been described in both the Akita and Munich mouse models that have dominant-acting missense mutations in the Ins2 gene, leading to loss of beta cell function and mass. One of the human mutations we report here is identical to that in the Akita mouse. The identification of insulin mutations as a cause of neonatal diabetes will facilitate the diagnosis and possibly, in time, treatment of this disorder.

ChREBP, but not LXRs, is required for the induction of glucose-regulated genes in mouse liver

2008-03-04T17:01:41-00:00

J. Clin Invest, Vol. 118, No. 3. (March 2008), pp. 956-964.

The transcription factor carbohydrate-responsive element–binding protein (ChREBP) has emerged as a central regulator of lipid synthesis in liver because it is required for glucose-induced expression of the glycolytic enzyme liver–pyruvate kinase (L-PK) and acts in synergy with SREBP to induce lipogenic genes such as acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS). Liver X receptors (LXRs) are also important regulators of the lipogenic pathway, and the recent finding that ChREBP is a direct target of LXRs and that glucose itself can bind and activate LXRs prompted us to study the role of LXRs in the induction of glucose-regulated genes in liver. Using an LXR agonist in wild-type mice, we found that LXR stimulation did not promote ChREBP phosphorylation or nuclear localization in the absence of an increased intrahepatic glucose flux. Furthermore, the induction of ChREBP, L-PK, and ACC by glucose or high-carbohydrate diet was similar in LXRα/β knockout compared with wild-type mice, suggesting that the activation of these genes by glucose occurs by an LXR-independent mechanism. We used fluorescence resonance energy transfer analysis to demonstrate that glucose failed to promote the interaction of LXRα/β with specific cofactors. Finally, siRNA silencing of ChREBP in LXRα/β knockout hepatocytes abrogated glucose-induced expression of L-PK and ACC, further demonstrating the central role of ChREBP in glucose signaling. Taken together, our results demonstrate that glucose is required for ChREBP functional activity and that LXRs are not necessary for the induction of glucose-regulated genes in liver.

Combined immunostaining with galectin-3, fibronectin-1, CITED-1, Hector Battifora mesothelial-1, cytokeratin-19, peroxisome proliferator-activated receptor-gamma, and sodium/iodide symporter antibodies for the differential diagnosis of non-medullary thyroid carcinoma

Ying Liu — 2008-02-26T16:58:44-00:00

Eur J Endocrinol, Vol. 158, No. 3. (1 March 2008), pp. 375-384.

ObjectivesThe microscopic distinction between benign and malignant thyroid lesions in clinical practice is still largely based on conventional histology. This study was performed to evaluate the diagnostic value of galectin-3 (Gal-3), Hector Battifora mesothelial-1 (HBME-1), cytokeratin (CK)-19, CBP P300-interacting transactivator with glutamic acid E- and aspartic acid D-rich C-terminal domain (CITED-1), fibronectin (FN)-1, peroxisome proliferator-activated receptor (PPAR)-gamma, and intracellular sodium/iodide symporter (iNIS) immunostaining in a large panel of thyroid neoplasms. Our study differed from earlier ones with regard to the identification of optimal semiquantitative cut-off levels using receiver operator curve (ROC) analysis and hierarchical cluster analysis. MethodsWe used tissue arrays containing 177 thyroid tissues: 100 benign tissues (including normal thyroid, Graves disease, multinodular goiter, and follicular adenoma (FA)) and 77 thyroid carcinomas (including papillary thyroid carcinoma (PTC), follicular thyroid carcinoma, and follicular variant of PTC (FVPTC)). Antibody staining was scored semiquantitatively based on the ROC analyses and with hierarchical cluster analysis. ResultsIn general, we found overexpression of FN-1, CITED-1, Gal-3, CK-19, HBME-1, and iNIS in malignant thyroid lesions. Gal-3, FN-1, and iNIS had the highest accuracy in the differential diagnosis of follicular lesions. A panel of Gal-3, FN-1, and iNIS, identified by hierarchical cluster analysis, had a 98% accuracy to differentiate between FA and malignant thyroid lesions. In addition, HBME-1 was found to be useful in the differentiation between FA and FVPTC (accuracy 88%). ConclusionWe conclude that identifying optimal antibody panels with cluster analysis increases the diagnostic value in the differential diagnosis of thyroid neoplasms, the combination of FN-1, Gal-3, and iNIS having the best accuracy (98%). 10.1530/EJE-07-0492

The Association Between the FTO Gene and Fat Mass in Humans Develops by the Postnatal Age of Two Weeks.

Abel López-Bermejo — 2008-02-18T16:12:09-00:00

J Clin Endocrinol Metab (5 February 2008)

Objective: Little is known about the genetic determinants of fat mass around birth. We hypothesized that the common rs9939609 single nucleotide polymorphism (SNP) in FTO is associated with fat mass and metabolic parameters in neonates. Design: Cross-sectional, hospital-based study. Patients: Two hundred and thirty-four full-term, healthy newborns [122 girls and 112 boys; gestational age (mean, range): 39.0 (37.0-42.0) w, birth weight: 3.2 (1.9-4.2) Kg]. Methods: Cord-blood insulin, IGF-I, IGFBP-1, adiponectin and visfatin, measured by specific immunoassays. Body composition, assessed by dual energy X-ray absorptiometry at approximately 13 d (range, 9-20 d). Genotyping of rs9939609 by retriction fragment length polymorphism analysis. Results: The rs9939609 SNP in FTO was not associated with birth weight; however it was associated with serum visfatin (p<0.001), with weight and ponderal index at age 2 weeks (p<0.05), and with total, truncal and abdominal fat (p<0.05 to p=0.01), so that AA homozygotes had 37% higher plasma visfatin concentration and 17%, 20% and 17% higher total, truncal and abdominal fat mass, respectively, than T-carrier neonates. Conclusion: Our findings support a role of the common rs9939609 SNP in FTO gene in the early stages of fat accretion in humans, and disclose novel associations between this SNP and both serum visfatin and abdominal fat mass in neonates.

The Role of Membrane Glycoprotein Plasma Cell Antigen 1/Ectonucleotide Pyrophosphatase Phosphodiesterase 1 in the Pathogenesis of Insulin Resistance and Related Abnormalities

Ira Goldfine — 2008-02-09T17:38:20-00:00

Endocr Rev, Vol. 29, No. 1. (1 February 2008), pp. 62-75.

Insulin resistance is a major feature of most patients with type 2 diabetes mellitus (T2D). A number of laboratories have observed that membrane glycoprotein plasma cell antigen 1 (PC-1) [ectonucleotide pyrophosphatase phosphodiesterase 1] is either overexpressed or overactive in muscle, adipose tissue, fibroblasts, and other tissues of insulin-resistant individuals, both nondiabetic and diabetic. Moreover, in cultured cells in vitro and in transgenic mice in vivo, PC-1 overexpression impairs insulin stimulation of insulin receptor (IR) activation and downstream signaling. PC-1 binds to the connecting domain of the IR alpha-subunit that is located in residues 485599. The connecting domain transmits insulin binding in the alpha-subunit to activation of tyrosine kinase activation in the -subunit. When PC-1 is overexpressed, it inhibits insulin-induced IR -subunit tyrosine kinase activity. In addition, a polymorphism of PC-1 (K121Q) in various ethnic populations is closely associated with insulin resistance, T2D, and cardio- and nephrovascular diseases. The product of this polymorphism has a 2- to 3-fold increased binding affinity for the IR and is more potent than the wild-type PC-1 protein (K121K) in inhibiting the IR. These data suggest therefore that PC-1 is a candidate protein that may play a role in human insulin resistance and T2D by its overexpression, its overactivity, or both. 10.1210/er.2007-0004

Clock genes are implicated in the human metabolic syndrome

P Gómez-Abellán — 2007-07-24T23:26:48-00:00

International Journal of Obesity, Vol. aop, No. current.

The CAG repeat polymorphism in the androgen receptor gene is associated with HDL-cholesterol but not with coronary atherosclerosis or myocardial infarction.

M Hersberger — 2008-01-29T20:04:58-00:00

Clin Chem, Vol. 51, No. 7. (July 2005), pp. 1110-1115.

BACKGROUND: Age-adjusted morbidity and mortality rates from coronary heart disease (CHD) are higher in men than in women. Androgens are suspected to be responsible for the male disadvantage. The genomic effect of androgens is mediated by the androgen receptor (AR), which has a polymorphic CAG repeat in exon 1. The number of repeats is inversely related to the transcriptional activity of the AR on target genes. METHODS: We investigated the association of this CAG repeat polymorphism with CHD and myocardial infarction (MI) in 2 independent case-control studies involving 544 Caucasian men. RESULTS: The number of CAG repeats in the AR gene correlated significantly with HDL-cholesterol (HDL-C) in controls (r = 0.21; P = 0.015). This effect was independent of triglycerides, body mass index, alcohol intake, smoking, and age in a multiple regression model (R(2) = 50%). Despite decreased HDL-C, lower CAG repeat numbers were not associated with increased risk for CHD (odds ratio = 0.82; 95% confidence interval, 0.50-1.36; P = 0.44) or MI in carriers of AR genes with lower CAG repeat numbers (odds ratio = 0.72; 95% confidence interval, 0.37-1.39; P = 0.33). CONCLUSIONS: Shorter, more androgenic AR alleles with fewer CAG repeats are associated with lower HDL-C, but not with an increased risk for CHD or MI, which argues against a detrimental androgen effect on cardiovascular risk under physiologic conditions.

SHBG gene promoter polymorphisms in men are associated with serum sex hormone-binding globulin, androgen and androgen metabolite levels, and hip bone mineral density.

AL Eriksson — 2008-01-27T02:17:52-00:00

J Clin Endocrinol Metab, Vol. 91, No. 12. (December 2006), pp. 5029-5037.

CONTEXT: SHBG regulates free sex steroid levels, which in turn regulate skeletal homeostasis. Twin studies have demonstrated that genetic factors largely account for interindividual variation in SHBG levels. Glucuronidated androgen metabolites have been proposed as markers of androgenic activity. OBJECTIVE: Our objective was to investigate whether polymorphisms in the SHBG gene promoter [(TAAAA)(n) microsatellite and rs1799941 single-nucleotide polymorphism] are associated with serum levels of SHBG, sex steroids, or bone mineral density (BMD) in men. DESIGN AND STUDY SUBJECTS: We conducted a population-based study of two cohorts of Swedish men: elderly men (MrOS Sweden; n congruent with 3000; average age, 75.4 yr) and young adult men (GOOD study; n = 1068; average age, 18.9 yr). MAIN OUTCOME MEASURES: We measured serum levels of SHBG, testosterone, estradiol, dihydrotestosterone, 5alpha-androstane-3alpha,17beta-diol glucuronides, androsterone glucuronide, and BMD determined by dual-energy x-ray absorptiometry. RESULTS: In both cohorts, (TAAAA)(n) and rs1799941 genotypes were associated with serum levels of SHBG (P < 0.001), dihydrotestosterone (P < 0.05), and 5alpha-androstane-3alpha,17beta-diol glucuronides (P < 0.05). In the elderly men, they were also associated with testosterone and BMD at all hip bone sites. The genotype associated with high levels of SHBG was also associated with high BMD. Interestingly, male mice overexpressing human SHBG had increased cortical bone mineral content in the femur, suggesting that elevated SHBG levels may cause increased bone mass. CONCLUSIONS: Our findings demonstrate that polymorphisms in the SHBG promoter predict serum levels of SHBG, androgens, and glucuronidated androgen metabolites, and hip BMD in men.

Assessing the probability that a positive report is false: an approach for molecular epidemiology studies.

S Wacholder — 2007-03-10T13:50:49-00:00

J Natl Cancer Inst, Vol. 96, No. 6. (17 March 2004), pp. 434-442.

Too many reports of associations between genetic variants and common cancer sites and other complex diseases are false positives. A major reason for this unfortunate situation is the strategy of declaring statistical significance based on a P value alone, particularly, any P value below.05. The false positive report probability (FPRP), the probability of no true association between a genetic variant and disease given a statistically significant finding, depends not only on the observed P value but also on both the prior probability that the association between the genetic variant and the disease is real and the statistical power of the test. In this commentary, we show how to assess the FPRP and how to use it to decide whether a finding is deserving of attention or "noteworthy." We show how this approach can lead to improvements in the design, analysis, and interpretation of molecular epidemiology studies. Our proposal can help investigators, editors, and readers of research articles to protect themselves from overinterpreting statistically significant findings that are not likely to signify a true association. An FPRP-based criterion for deciding whether to call a finding noteworthy formalizes the process already used informally by investigators--that is, tempering enthusiasm for remarkable study findings with considerations of plausibility.

Fatty acid desaturases in human adipose tissue: relationships between gene expression, desaturation indexes and insulin resistance

P Sjögren — 2008-01-24T20:57:17-00:00

Diabetologia, Vol. 51, No. 2. (1 February 2008), pp. 328-335.

Abstract Aims/hypothesis Fatty acid desaturases introduce double bonds into growing fatty acid chains. The key desaturases in humans are Δ5-desaturase (D5D), Δ6-desaturase (D6D) and stearoyl-CoA desaturase (SCD). Animal and human data implicate hepatic desaturase activities in insulin resistance, obesity and dyslipidaemia. However, the role of desaturase activity in adipose tissue is uncertain. We therefore evaluated relationships between adipose mRNA expression, estimated desaturase activities (fatty acid ratios) in adipose tissue and insulin resistance. Methods Subcutaneous adipose tissue mRNA expression of D5D (also known as FADS1), D6D (also known as FADS2) and SCD was determined in 75 individuals representative of the study population of 294 healthy 63-year-old men. Desaturation indexes (product/substrate fatty acid ratios) were generated from adipose tissue fatty acid composition in all individuals. Insulin resistance was defined as the upper quartile of the updated homeostasis model assessment (HOMA-2) index. Results The relevant desaturation indexes (16:1/16:0, 18:1/18:0, 20:4/20:3 and 18:3/18:2) reflected expression of SCD, but not of D5D or D6D in adipose tissue. Insulin-resistant individuals had a higher adipose tissue 18:1/18:0, but not 16:1/16:0 ratio than insulin-sensitive individuals. Individuals with a high adipose tissue 18:1/18:0 ratio were 4.4-fold (95% CI 1.8–11.8) more likely to be insulin resistant [threefold (95% CI 1.1–8.6) after adjustment for waist circumference and plasma triacylglycerol]. In a multiple regression model predicting HOMA-2, the independent effect of the 18:1/18:0 ratio was borderline (p = 0.086). Conclusions/interpretation Adipose tissue desaturation indexes of SCD reflect the expression of the gene encoding the enzyme in this tissue. Elevated SCD activity within adipose tissue is closely coupled to the development of insulin resistance.

Molecular characteristics in papillary thyroid cancers (PTCs) with no 131I uptake

Mian — 2007-12-14T09:35:41-00:00

Clinical Endocrinology, Vol. 68, No. 1. (January 2008), pp. 108-116.

Three Novel Mutations of the PHEX Gene in Three Chinese Families with X-linked Dominant Hypophosphatemic Rickets

Weibo Xia — 2008-01-12T17:56:36-00:00

Calcified Tissue International, Vol. 81, No. 6. (25 December 2007), pp. 415-420.

Abstract X-linked dominant hypophosphatemia (XLH, OMIM307800), the most prevalent form of inherited rickets in humans, is a dominant disorder of phosphate homeostasis characterized by growth retardation, rachitic and osteomalacic bone disease, hypophosphatemia, and renal phosphate wasting. The gene responsible for XLH was identified by positional cloning and designated PHEX (formerly PEX) to depict a phosphate-regulating gene homologous with endopeptidases on the X chromosome. Recently, extensive mutation analysis of the PHEX gene has revealed a wide variety of gene defects in XLH. The ethnic distribution of the mutations is very widespread but only a few mutations in Chinese have been reported. To analyze the molecular basis in three unrelated Chinese families with XLH, we determined the nucleotide sequence of the PHEX gene and fibroblast growth factor 23 (FGF23) gene of affected members. The serum FGF23 concentrations of these patients with XLH were also measured. Three different novel mutations were observed in these three families: one deletion mutation c.264delG causing p.W88 X; one missense mutation c.1673C>G causing p.P558A; one nonsense mutation c.1809G>A causing p.W603 X. Serum concentration of FGF23 in XLH patients of these three families was significantly higher than normal. The results suggest that PHEX gene mutations were responsible for XLH in these patients and these mutations may contribute to a higher serum FGF23 level.

Association of SHBG gene polymorphism with menarche.

N Xita — 2008-01-11T17:11:45-00:00

Mol Hum Reprod, Vol. 11, No. 6. (June 2005), pp. 459-462.

The age of menarche may be subject to hereditary influences but the specific determinants are unknown. Our aim was to investigate the possible association of a functional (TAAAA)n polymorphism in the promoter of the sex hormone-binding globulin (SHBG) gene with the timing of menarche. This polymorphism has been associated with polycystic ovary syndrome (PCOS) and is considered to contribute to SHBG levels. We studied 130 healthy normal-weight adolescent females from a closed community in North-Western Greece. Information on menarche was obtained through interviews. The BMI was recorded. Genomic DNA was isolated from peripheral blood leukocytes for genotyping the TAAAA repeat region. We subdivided our subjects into two groups based on median age of menarche: those with menarche <13 years and those with menarche > or =13 years. Genotype analysis revealed six (TAAAA)n alleles containing 5-10 TAAAA repeats. The distribution of alleles was different in the two groups. Girls with late menarche had more frequently longer TAAAA alleles (>8 repeats), while girls with early menarche had shorter alleles at a greater frequency (P=0.048). The major contribution to early menarche was by the 6 TAAAA repeat allele. Furthermore, carriers of the longer allele genotypes had later menarche (13.24+/-1.15 years) than those with shorter allele genotypes (12.67+/-1.15, P=0.018). These findings provide evidence for a genetic contribution of SHBG gene to the age of menarche.

Sex hormone-binding globulin is synthesized in target cells

SM Kahn — 2008-01-11T16:35:12-00:00

J Endocrinol, Vol. 175, No. 1. (1 October 2002), pp. 113-120.

Sex hormone-binding globulin (SHBG) is a multifunctional protein that acts in humans to regulate the response to steroids at several junctures. It was originally described as a hepatically secreted protein that is the major binding protein for sex steroids in plasma, thereby regulating the availability of free steroids to hormone-responsive tissues. SHBG also functions as part of a novel steroid-signaling system that is independent of the classical intracellular steroid receptors. Unlike the intracellular steroid receptors that are ligand-activated transcription factors, SHBG mediates androgen and estrogen signaling at the cell membrane by way of cAMP. We have reviewed the current state of knowledge on the SHBG gene and the role of SHBG in steroid signaling (we shall not address its function as a plasma-binding protein). 10.1677/joe.0.1750113

11beta-HSD Type 1 Expression in Human Adipose Tissue: Impact of Gender, Obesity, and Fat Localization

Soren Paulsen — 2008-01-08T22:18:43-00:00

Obesity, Vol. 15, No. 8. (1 August 2007), pp. 1954-1960.

Objective: Pre-receptor amplification of glucocorticoids is, in part, determined by the isoenzymes 11beta-hydroxysteroid dehydrogenase (11beta-HSD) type 1 and type 2, interconverting inert cortisone and active cortisol. Increased tissue activity of cortisol may play a part in features of the metabolic syndrome. Our objective was to compare 11beta-HSD1 gene expression in different fat depots (visceral, subcutaneous abdominal, and subcutaneous gluteal) in lean and obese men and women. Research Methods and Procedures: A cross-sectional study design was used for healthy patients undergoing minor abdominal surgery (lean men, 10), minor gynecological surgery (lean woman, 10), or gastric banding operations (obese men, 10; and obese women, 10). Gene expressions of 11beta-HSD1 in adipose tissue samples were determined by real-time reverse transcriptase polymerase chain reaction (RT-PCR). Results: Lean women had lower 11beta-HSD1 gene expression in subcutaneous adipose tissue compared with men (62% lower, p < 0.01), whereas no significant difference was found between obese men and women. 11beta-HSD1 mRNA in human adipose tissue was higher in obese subjects compared with lean subjects in both women and men and in both subcutaneous and visceral adipose tissue. No difference in mRNA expression of 11beta-HSD1 between visceral and subcutaneous adipose tissue or between subcutaneous adipose tissue from different depots was found. Conclusions: 11beta-HSD1 in adipose tissue is increased in obesity in both women and men, and may contribute to the associated metabolic syndrome. As 11beta-HSD1 expression in lean women was found to be significantly lower than in lean males, the up-regulation associated with obesity may be relatively more devastating in women than in men, and may help explain the higher relative risk of cardiovascular disease in women suffering from the metabolic syndrome.