Interactions among the glucocorticoid receptor, lipoprotein lipase and adrenergic receptor genes and abdominal fat in the Québec Family Study

NR3C1 Glucocorticoid Receptor Gene Polymorphisms Are Associated with Membranous and IgA Nephropathies

Glomerular diseases (GNs) are responsible for approximately 20% of chronic kidney diseases. Glucocorticoid receptor gene (NR3C1) single nucleotide polymorphisms (SNPs) are implicated in differences in predisposition to autoimmunity and steroid sensitivity. The aim of this study was to evaluate the frequency of the NR3C1 SNPs—rs6198, rs41423247 and rs17209237—in 72 IgA nephropathy (IgAN) and 38 membranous nephropathy (MN) patients compared to 175 healthy controls and to correlate the effectiveness of treatment in IgAN and MN groups defined as a reduction of proteinuria <1 g/24 h after 12 months of treatment. Real-time polymerase chain reactions and SNP array-based typing were used. We found significant rs41423247 association with MN (p = 0.026); a significant association of rs17209237 with eGFR reduction after follow-up period in all patients with GNs (p = 0.021) and with the degree of proteinuria after 1 year of therapy in all patients with a glomerulopathy (p = 0.013) and IgAN (p = 0.021); and in the same groups treated with steroids (p = 0.021; p = 0.012). We also observed the association between rs41423247 and IgAN histopathologic findings (p = 0.012). In conclusion, our results indicate that NR3C1 polymorphisms may influence treatment susceptibility and clinical outcome in IgAN and MN.

The clinical significance of the glucocorticoid receptors: Genetics and epigenetics

The impacts of glucocorticoids (GCs) are mainly mediated by a nuclear receptor (GR) existing in almost every tissue. The GR regulates a wide range of physiological functions, including inflammation, cell metabolism, and differentiation playing a major role in cellular responses to GCs and stress. Therefore, the dysregulation or disruption of GR can cause deficiencies in the adaptation to stress and the preservation of homeostasis. The number of GR polymorphisms associated with different diseases has been mounting per year. Tackling these clinical complications obliges a comprehensive understanding of the molecular network action of GCs at the level of the GR structure and its signaling pathways. Beyond genetic variation in the GR gene, epigenetic changes can enhance our understanding of causal factors involved in the development of diseases and identifying biomarkers. In this review, we highlight the relationships of GC receptor gene polymorphisms and epigenetics with different diseases.

Role of NR3C1 and GAS5 genes polymorphisms in multiple sclerosis

Introduction: Multiple sclerosis (MS) as a progressive chronic disease of the central nervous system (CNS) is characterized by demyelination and axonal loss. Results of genetic studies and clinical trials have proved a key role for the immune system in the pathogenesis of MS. Glucocorticoids (GR) are regarded as potent therapeutic compounds for autoimmune and inflammatory diseases which act through their receptors encoded by Nuclear Receptor Subfamily 3 Group C Member 1 (NR3C1) gene. Meanwhile, the long non-coding RNA (lncRNA) growth arrest specific 5 (GAS5) interacts with GR through binding to the DNA-binding domain (DBD) region and reduces GR transcriptional activity.Methods: The purpose of our study was to evaluate the association between MS and polymorphisms within NR3C1 (rs6189/6190, rs56149945, rs41423247) and GAS5 (rs55829688) genes in 300 relapsing-remitting MS patients and 300 healthy subjects.Results: We demonstrated significant differences in distribution of genotype, allele and haplotype frequencies of rs6189, rs41423247 and rs55829688 between the study groups.Conclusion: Our data may suggest that rs6189, rs41423247 and rs55829688 are associated with the increased risk of MS development. Future studies are needed to verify our results in larger sample sizes and elaborate the underlying mechanisms for contribution of these variants in MS disease.

Stress and Obesity: Are There More Susceptible Individuals?

PURPOSE OF REVIEW

Stress has long been suspected to be interrelated to (abdominal) obesity. However, interindividual differences in this complex relationship exist. We suggest that the extent of glucocorticoid action partly explains these interindividual differences. We provide latest insights with respect to multiple types of stressors.

RECENT FINDINGS

Increased long-term cortisol levels, as measured in scalp hair, are strongly related to abdominal obesity and to specific mental disorders. However, not all obese patients have elevated cortisol levels. Possibly, the interindividual variation in glucocorticoid sensitivity, which is partly genetically determined, may lead to higher vulnerability to mental or physical stressors. Other evidence for the important role for increased glucocorticoid action is provided by recent studies investigating associations between body composition and local and systemic corticosteroids. Stress may play a major role in the development and maintenance of obesity in individuals who have an increased glucocorticoid exposure or sensitivity. These insights may lead to more effective and individualized obesity treatment strategies.

The role of glucocorticoid receptors in metabolic syndrome and psychiatric illness

Glucocorticoids (GCs) are involved in a large number of the physiological changes associated with metabolic syndrome and certain psychiatric illness. Although significance is often given to the concentration of GC, its biological action is determined by the activation of intracellular GC receptors (GR). Genetic polymorphisms of the GR and the large array of GR related cofactors can directly or indirectly affect the pathophysiology and evolution of these conditions. This review will discuss the effects of GR mutations on metabolic syndrome and psychotic depression.

Glucocorticoid receptor haplotype and metabolic syndrome: the Lifelines cohort study

OBJECTIVE

An excess of glucocorticoids (Cushing's syndrome) is associated with metabolic syndrome (MetS) features. Several single-nucleotide polymorphisms (SNPs) in the glucocorticoid receptor (GR) gene influence sensitivity to glucocorticoids and have been associated with aspects of MetS. However, results are inconsistent, perhaps due to the heterogeneity of the studied populations and limited samples. Furthermore, the possible association between functional GR SNPs and prevalence of MetS remains unexplored.

DESIGN

Cross-sectional population-based cohort study.

METHODS

MetS presence and carriage of functional GR SNPs (BclI, N363S, ER22/23EK, GR-9beta) were determined in 12 552 adult participants from Lifelines, a population-based cohort study in the Netherlands. GR SNPs were used to construct GR haplotypes.

RESULTS

Five haplotypes accounted for 99.9% of all GR haplotypes found. No main effects of functional GR haplotypes on MetS were found, but the association of GR haplotype 4 (containing N363S) with MetS was influenced by interaction with age, sex and education status (P < 0.05). Stratified analysis revealed that haplotype 4 increased MetS presence in younger men (at or below the median age of 47; odds ratio 1.77, P = 0.005) and in people of low education status (odds ratio 1.48, P = 0.039).

CONCLUSIONS

A glucocorticoid receptor haplotype that confers increased sensitivity to glucocorticoids appears to increase the risk of metabolic syndrome, but only among younger men and less educated individuals, suggesting gene-environment interactions.

Advances in the assessment of cortisol exposure and sensitivity

PURPOSE OF REVIEW

To review recent progress in the field of cortisol exposure and sensitivity, and its implications for research concerning obesity and related metabolic disturbances.

RECENT FINDINGS

In the past few years, scalp hair analysis had been successfully introduced as a marker for long-term cortisol exposure. With this relatively novel method, increased long-term cortisol levels have been linked to cardiovascular disease, metabolic syndrome, and stress-related measures. At the tissue level, the effect of cortisol is modulated by genetically determined glucocorticoid sensitivity. Polymorphisms in the glucocorticoid receptor gene that influence glucocorticoid sensitivity have been associated with differences in metabolic syndrome components.

SUMMARY

Hair analysis provides exciting new opportunities to study the influence of long-term cortisol exposure on a wide range of health outcomes, in both observational and interventional studies. We propose that addition of genetically determined glucocorticoid sensitivity to these studies may bring about a more thorough understanding of the long-term effects of cortisol.

Glucocorticoid sensitivity in health and disease

Glucocorticoids regulate many physiological processes and have an essential role in the systemic response to stress. For example, gene transcription is modulated by the glucocorticoid-glucocorticoid receptor complex via several mechanisms. The ultimate biologic responses to glucocorticoids are determined by not only the concentration of glucocorticoids but also the differences between individuals in glucocorticoid sensitivity, which is influenced by multiple factors. Differences in sensitivity to glucocorticoids in healthy individuals are partly genetically determined by functional polymorphisms of the gene that encodes the glucocorticoid receptor. Hereditary syndromes have also been identified that are associated with increased and decreased sensitivity to glucocorticoids. As a result of their anti-inflammatory properties, glucocorticoids are widely used in the treatment of allergic, inflammatory and haematological disorders. The variety in clinical responses to treatment with glucocorticoids reflects the considerable variation in glucocorticoid sensitivity between individuals. In immune-mediated disorders, proinflammatory cytokines can induce localized resistance to glucocorticoids via several mechanisms. Individual differences in how tissues respond to glucocorticoids might also be involved in the predisposition for and pathogenesis of the metabolic syndrome and mood disorders. In this Review, we summarize the mechanisms that influence glucocorticoid sensitivity in health and disease and discuss possible strategies to modulate glucocorticoid responsiveness.

Analysis of factors that determine weight gain during smoking cessation therapy

Cigarette smokers are generally known to gain weight after quitting smoking, and such weight gain is thought to contribute to the worsening of glucose tolerance. While smoking cessation therapy such as nicotine replacement is useful to minimize post-cessation weight gain, substantial gain occurs even during the therapy. The purpose of the present study was to identify factors associated with weight gain during smoking cessation therapy. We evaluated 186 patients(132 males and 54 females)who visited our outpatient clinic for smoking cessation, and successfully achieved smoking abstinence. We performed gender-adjusted regression analysis for the rate of BMI increase from the beginning of cessation to 3 months after initiation. Furthermore, we performed multivariate analysis to investigate factors that determine the BMI increase after smoking cessation. The mean BMI significantly (p<0.0001) increased from 23.5 ± 3.6 kg/m(2) at the initial consultation to 23.9 ± 3.8 kg/m(2) at 3 months after the start of therapy. There was no significant difference in the extent of BMI increase between nicotine patch and varenicline therapy groups. Factors significantly correlated with the %BMI increase at 3 months after the start of therapy were triglyceride (p = 0.0006, βa = 0.260), high-density lipoprotein cholesterol (p = 0.0386, βa = -0.168), daily cigarette consumption (p = 0.0385, βa = 0.154), and the Fagerström Test for Nicotine Dependence (FTND) score (p = 0.0060, βa = 0.203). Stepwise multivariate analysis demonstrated that triglyceride and the FTND score were the factors determining the post-cessation BMI increase and that the FTND score was the strongest one. The present study demonstrated that smokers with a high FTND score are more likely to gain weight during smoking cessation therapy. Thus, smokers with a high nicotine dependency may require intervention against weight gain in the cessation clinic.

Genetic association of adrenergic receptor alpha 2A with obesity and type 2 diabetes

OBJECTIVE

The sympathetic nervous system (SNS) is linked to glucose, lipid, and protein metabolism. The α2A -adrenergic receptor (ADRA2A) is involved in the SNS and mediates inhibition of insulin secretion and lipolysis. The association of ADRA2A single-nucleotide polymorphisms (SNPs) with obesity and/or type 2 diabetes (T2D) was investigated.

DESIGN AND METHODS

Genotyping was performed in a case-control study of 1,177 Swedish individuals, including lean and obese subjects with normal glucose tolerance (NGT) and T2D patients. ADRA2A mRNA expression was measured in pancreatic islets isolated from T2D patients and nondiabetic subjects.

RESULTS

SNP rs553668 was associated with T2D in men (odds ratio [OR] = 1.47; 95% confidence interval [CI] = 1.08-2.01; P = 0.015) but this association was lost after adjusting for age and for body mass index (BMI). Associations were also detected when comparing obese NGT and lean NGT subjects (OR = 1.49; 95% CI = 1.07-2.07; P = 0.017), and in obese (OR = 1.62; 95% CI = 1.06-2.49; P = 0.026), but not in lean T2D. In women, multiple logistic regression regarding SNP rs521674 demonstrated an increased OR of 7.61 (95% CI = 1.70-34.17; P = 0.008) for T2D when including age as a covariant. Correcting for BMI removed the significant association. When age was included in the model, association also found when obese T2D patients were compared with lean NGT subjects (P = 0.041). ADRA2A mRNA expression in human pancreatic islets was detectable, but with no statistically significant difference between the diabetic and the control groups.

CONCLUSIONS

ADRA2A genetic polymorphisms are mainly associated with obesity and possibly with T2D in a Swedish population.

Associations between polymorphisms in the glucocorticoid-receptor gene and cardiovascular risk factors in a Chinese population

Background

Glucocorticoid is an important regulator of energy homeostasis. Glucocorticoid receptor (GR) gene polymorphisms that contribute to variability in glucocorticoid sensitivity have been identified. We explored the associations of single-nucleotide polymorphisms (SNPs) of the GR gene with traditional cardiovascular risk factors in the Chinese Han population.

Methods

We recruited 762 consecutive adults who underwent a regular physical examination at Beijing Xuanwu Hospital. Blood pressure, glucose, lipid levels (total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein [LDL] cholesterol and triglycerides), body mass index (BMI), and waist-to-hip ratio were measured. Fourteen tag SNPs and 5 functional SNPs were selected and genotyped using the high-throughput Sequenom genotyping platform. Differences between genotypes/alleles for each SNP were adjusted for sex and age and tested using a general linear model procedure. Various models of inheritance, including additive, dominant, and recessive, were tested.

Results

Among the 19 SNPs examined, 5 markers were associated with cardiovascular risk factors. The rs41423247 GG genotype and the rs7701443 AA genotype were associated with higher BMI and systolic blood pressure (P < 0.0004), and the rs17209251 GG genotype was associated with higher systolic blood pressure (P < 0.0004). Lower systolic blood pressure, total cholesterol, and LDL cholesterol were observed among rs10052957 A allele carriers (P < 0.0004), and lower plasma glucose and LDL-cholesterol concentrations were observed among rs2963156 TT carriers (P < 0.0004).

Conclusions

Polymorphism of the GR gene was associated with cardiovascular risk factors and may contribute to susceptibility to cardiovascular disease.

BclI glucocorticoid receptor polymorphism is associated with greater body fatness: the Hoorn and CODAM studies

CONTEXT

The BclI polymorphism in the glucocorticoid receptor (GR) gene is associated with enhanced glucocorticoid (GC) sensitivity.

OBJECTIVE

Our objective was to investigate the association of the BclI polymorphism with body fatness and insulin resistance.

DESIGN AND SETTING

We conducted an observational cohort study, combining data from 2 cohort studies enriched with individuals with impaired glucose metabolism and/or diabetes mellitus type 2 (DM2).

PATIENTS AND METHODS

We examined 1228 participants (mean age 64.7 years, 45% women) from the Cohort Study on Diabetes and Atherosclerosis Maastricht (CODAM, n = 543) and the Hoorn Study (n = 685). Body mass index (BMI), waist and hip circumferences, and waist-to-hip ratio (WHR) were obtained; insulin resistance was estimated using the homeostasis model assessment for insulin resistance (HOMA2-IR).

RESULTS

We identified 519 noncarriers (CC), 540 heterozygous (CG) carriers, and 169 homozygous (GG) carriers of the G-allele of the BclI polymorphism. Homozygous carriers had a higher BMI (28.9 vs 27.9 kg/m(2)) and waist (99.6 vs 97.2 cm) and hip (105.5 vs 103.2 cm) circumference compared with noncarriers, also after adjustment for age, sex, cohort, glucose tolerance, and lifestyle risk factors: β = 0.94 kg/m(2) (95% confidence interval, 0.24-1.63), β = 2.84 cm (0.95;4.73) and β = 2.38 cm (0.88-3.87), respectively. Similar results were obtained when comparing homozygous carriers with heterozygous carriers: β = 1.03 kg/m(2) (0.34-1.72), β = 2.20 cm (0.31-4.08) and β = 1.99 cm (0.51-3.48), respectively. There were no differences in WHR. Ln-HOMA2-IR was higher in GG carriers compared with CG carriers; 0.29 vs 0.17 [β = 0.09 (0.01-0.17)], but this effect was attenuated after adjustment for BMI [β = 0.04 (-0.04 to 0.11)].

CONCLUSION

Homozygous carriers of the BclI polymorphism of the GR gene have significantly greater total body fatness, contributing to higher HOMA2-IR, compared with heterozygous carriers and noncarriers.

Primary generalized familial and sporadic glucocorticoid resistance (Chrousos syndrome) and hypersensitivity

Familial or sporadic primary generalized glucocorticoid resistance or Chrousos syndrome is a rare genetic condition characterized by generalized, partial, target-tissue insensitivity to glucocorticoids and a consequent hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis. Primary generalized glucocorticoid hypersensitivity (PGGH) represents the mirror image of the former, and is characterized by generalized, partial, target-tissue hypersensitivity to glucocorticoids, and compensatory hypoactivation of the HPA axis. The molecular basis of both conditions has been ascribed to mutations in the human glucocorticoid receptor (hGR) gene, which impair the molecular mechanisms of hGR action and alter tissue sensitivity to glucocorticoids. This review summarizes the pathophysiology, molecular mechanisms and clinical aspects of Chrousos syndrome and PGGH.

The Human Obesity Gene Map: The 2003 Update

This is the tenth update of the human obesity gene map, incorporating published results up to the end of October 2003 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. Transgenic and knockout murine models relevant to obesity are also incorporated (N = 55). As of October 2003, 41 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. QTLs reported from animal models currently number 183. There are 208 human QTLs for obesity phenotypes from genome-wide scans and candidate regions in targeted studies. A total of 35 genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 272 studies reporting positive associations with 90 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, more than 430 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.

The Human Obesity Gene Map: The 2004 Update

This paper presents the eleventh update of the human obesity gene map, which incorporates published results up to the end of October 2004. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTLs) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2004, 173 human obesity cases due to single-gene mutations in 10 different genes have been reported, and 49 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 166 genes which, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 221. The number of human obesity QTLs derived from genome scans continues to grow, and we have now 204 QTLs for obesity-related phenotypes from 50 genome-wide scans. A total of 38 genomic regions harbor QTLs replicated among two to four studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably with 358 findings of positive associations with 113 candidate genes. Among them, 18 genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, >600 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful publications and genomic and other relevant sites can be found at http://obesitygene.pbrc.edu.

Visceral adipose tissue: emerging role of gluco- and mineralocorticoid hormones in the setting of cardiometabolic alterations

Several clinical and experimental lines of evidence have highlighted the detrimental effects of visceral adipose tissue excess on cardiometabolic parameters. Besides, recent findings have shown the effects of gluco-and mineralocorticoid hormones on adipose tissue and have also underscored the interplay existing between such adrenal steroids and their respective receptors in the modulation of adipose tissue biology. While the fundamental role played by glucocorticoids on adipocyte differentiation and storage was already well known, the relevance of the mineralocorticoids in the physiology of the adipose organ is of recent acquisition. The local and systemic renin–angiotensin–aldosterone system (RAAS) acting on adipose tissue seems to contribute to the development of the cardiometabolic phenotype so that its modulation can have deep impact on human health. A better understanding of the pathophysiology of the adipose organ is of crucial importance in order to identify possible therapeutic approaches that can avoid the development of such cardiovascular and metabolic sequelae.

The skin-blanching assay

The skin-blanching assay is used for the determination and bioequivalence of dermatologic glucocorticoids (GCs). The exact mechanism of the production of blanching is not fully understood, but it is considered that local vasoconstriction of the skin microvasculature and the consequent blood-flow reduction cause this phenomenon. Several factors influence skin blanching, including drug concentration, duration of application, nature of vehicle, occlusion, posture and location. The intensity of vasoconstriction can be measured in several ways: visual or quantitative methods, such as reflectance spectroscopy, thermography, laser Doppler velocimetry and chromametry. In literature, contradicting results in the correlation of the skin-blanching assay with different tests to determine GC sensitivity have been reported, limiting its clinical usefulness.

Association of glucocorticoid receptor polymorphism A3669G with decreased risk of developing diabetes in patients with Cushing's syndrome

OBJECTIVE

Glucocorticoid receptor (GR) polymorphisms alter glucocorticoid (GC) sensitivity and have been associated with altered metabolic profiles. We evaluate the prevalence of the four GR (NR3C1) polymorphisms BclI, N363S, ER22/23EK, and A3669G in patients with Cushing's syndrome (CS) compared with healthy controls (HC) and we investigate their role in the development of metabolic abnormalities in patients with CS according to their hormonal profile.

PATIENTS AND METHODS

Sixty-one patients with CS and 71 sex- and age-matched HC were genotyped.

RESULTS

BclI variant was markedly higher in patients with CS compared with HC (62 vs 41%, P<0.05) while no significant differences were found among other polymorphisms. A very low frequency of N363S and the ER22/23EK was observed. In CS patients, despite the significantly increased levels of morning serum cortisol in BclI carriers compared with wild type no clinical or metabolic differences were found. In contrast, A3669G GR carriers showed a significantly reduced prevalence of type 2 diabetes mellitus compared with wild type (19 vs 68%, P=0.001) despite the higher levels of both serum morning (21.7±6 vs 27.3±8.6 μg/dl, P=0.009) and midnight cortisol (18.8±5.8 vs 24.0±8.0 μg/dl, P=0.01). The negative association between diabetes and A3669G GR polymorphism remained significant when data were adjusted for potential confounding factors.

CONCLUSIONS

The A3669G polymorphism of the GR gene plays a protective role in patients with CS, attenuating the effects of GC excess on glucose metabolism as shown by their reduced risk of diabetes.

DNA methylation of genes in adipose tissue

Body fat distribution plays an important role in determining metabolic health. Whereas central obesity is closely associated with the development of CVD and type 2 diabetes, lower body fat appears to be protective and is paradoxically associated with improved metabolic and cardiovascular profiles. Physiological studies have demonstrated that fatty acid handling differs between white adipose tissue depots, with lower body white adipose tissue acting as a more efficient site for long-term lipid storage. The regulatory mechanisms governing these regional differences in function remain to be elucidated. Although the local microenvironment is likely to be a contributing factor, recent findings point towards the tissues being intrinsically distinct at the level of the adipocyte precursor cells (pre-adipocytes). The multi-potent pre-adipocytes are capable of generating cells of the mesenchymal lineage, including adipocytes. Regional differences in the adipogenic and replicative potential of these cells, as well as metabolic and biochemical activity, have been reported. Intriguingly, the genetic and metabolic characteristics of these cells can be retained through multiple generations when the cells are cultured in vitro. The rapidly emerging field of epigenetics may hold the key for explaining regional differences in white adipose tissue gene expression and function. Epigenetics describes the regulation of gene expression that occurs independently of changes in DNA sequence, for instance, DNA methylation or histone protein modification. In this review, we will discuss the contribution of DNA methylation to the determination of cells of adipogenic fate as well as the role DNA methylation may play during adipocyte terminal differentiation.

Apolipoprotein A5 and lipoprotein lipase interact to modulate anthropometric measures in Hispanics of Caribbean origin

Apolipoprotein A5 (APOA5) and lipoprotein lipase (LPL) proteins interact functionally to regulate lipid metabolism, and single-nucleotide polymorphisms (SNPs) for each gene have also been associated independently with obesity risk. Evaluating gene combinations may be more effective than single SNP analyses in identifying genetic risk, but insufficient minor allele frequency (MAF) often limits evaluations of potential epistatic relationships. Populations with multiple ancestral admixtures may provide unique opportunities for evaluating genetic interactions. We examined relationships between LPL m107 (rs1800590) and APOA5 S19W (rs3135506) and lipid and anthropometric measures in Caribbean origin Hispanics (n = 1,019, aged 45-75 years) living in the Boston metropolitan area. Significant interaction terms between LPL m107 and APOA5 S19W were observed for BMI (P = 0.003) and waist circumference (P = 0.019). Higher BMI (P = 0.001), waist (P = 0.011) and hip (P = 0.026) circumference were observed in minor allele (G) carriers for LPL m107 who also carried the APOA5 S19W minor allele (G). Additionally, extreme obesity (BMI > or = 40 kg/m(2)) risk was higher (odds ratio = 4.02; 95% confidence interval: 1.81-8.91; global P = 0.008) for minor allele carriers for both SNPs (LPL TG+GG, APOA5 CG+GG) compared to major allele carriers for both SNPs. In summary, we identified significant interactions for APOA5 S19W and LPL m107 for obesity in Caribbean Hispanics. Population-specific MAFs increase the difficulties of replicating gene-gene interactions, but may support the hypothesis that combinations of frequencies in selected genes could heighten obesity susceptibility in a given population. Analyses of gene-gene interactions may improve understanding of genetically based obesity risk, and underscore the need for further study of groups with multiple ancestral admixtures.

The human glucocorticoid receptor: molecular basis of biologic function

The characterization of the subfamily of steroid hormone receptors has enhanced our understanding of how a set of hormonally derived lipophilic ligands controls cellular and molecular functions to influence development and help achieve homeostasis. The glucocorticoid receptor (GR), the first member of this subfamily, is a ubiquitously expressed intracellular protein, which functions as a ligand-dependent transcription factor that regulates the expression of glucocorticoid-responsive genes. The effector domains of the GR mediate transcriptional activation by recruiting coregulatory multi-subunit complexes that remodel chromatin, target initiation sites, and stabilize the RNA-polymerase II machinery for repeated rounds of transcription of target genes. This review summarizes the basic aspects of the structure and actions of the human (h) GR, and the molecular basis of its biologic functions.

Clinical features associated with glucocorticoid receptor polymorphisms. An overview

The glucocorticoid receptor (GR) is crucial for the effects of glucocorticoids (GCs). Several polymorphisms of the GR are associated with altered sensitivity to GCs. For the ER22/23EK polymorphism, a relative GC resistance has been demonstrated. In vivo, this was suggested by a smaller response to a dexamethasone suppression test (DST), whereas in vitro experiments showed a diminished transactivational activity. The associated features of ER22/23EK carriers consist of favorable metabolic and body compositional conditions. In elderly subjects this polymorphism was associated with longevity and decreased risk of dementia. Interestingly, recent studies also showed an increased risk of major depression. In contrast, the N363S polymorphism was reported to be associated with an enhanced sensitivity to GCs, as was demonstrated by a DST. This polymorphism has also been associated with increased body mass index (BMI) and LDL-cholesterol levels, as well as increased risk of cardiovascular disease. However, additional studies yielded conflicting results, showing no associations with being overweight. The BclI polymorphism is also associated with increased GC sensitivity. In addition, associations with increased abdominal fat mass, Crohn's disease and, remarkably, major depression have been reported. Another GR polymorphism, located in exon 9beta, is associated with increased expression and stabilization of the dominant negative splice variant GR-beta. Carriers of this polymorphism displayed a relative GC resistance in vitro as evidenced by diminished transrepressional activity, which is important for the immune system and inflammation. Associations have been found with increased inflammatory parameters, cardiovascular disease, and rheumatoid arthritis. In this article, studies concerning these clinically relevant GR variants are discussed.

Multiple genes influence BMI on chromosome 7q31-34: the NHLBI Family Heart Study

The National Heart, Lung, and Blood Institute Family Heart Study (FHS) genome-wide linkage scan identified a region of chromosome 7q31-34 with a lod score of 4.9 for BMI at D7S1804 (131.9 Mb). We report the results of linkage and association to BMI in this region for two independent FHS samples. The first sample includes 225 FHS pedigrees with evidence of linkage to 7q31-34, using 1,132 single-nucleotide polymorphisms (SNPs) and 7 microsatellites. The second represents a case-control sample (318 cases; BMI >25 and 325 controls; BMI <25) derived from unrelated FHS participants who were not part of the genome scan. The latter set was genotyped for 606 SNPs, including 37 SNPs with prior evidence for association in the linked families. Although variance components linkage analysis using only SNPs generated a peak lod score that coincided with the original linkage scan at 131.9 Mb, a conditional linkage analysis showed evidence of a second quantitative trait locus (QTL) near 143 cM influencing BMI. Three SNPs (rs161339, rs12673281, and rs1993068) located near the three genes pleiotrophin (PTN), diacylglycerol (DAG) kinase iota (DGK iota), and cholinergic receptor, muscarinic 2 (CHRM2) demonstrated significant association in both linked families (P = 0.0005, 0.002, and 0.03, respectively) and the case-control sample (P = 0.01, 0.0003, and 0.03, respectively), regardless of the genetic model tested. These findings suggest that several genes may be associated with BMI in the 7q31-34 region.

Glucocorticoid receptor gene variant is associated with increased body fatness in youngsters

OBJECTIVE

Sensitivity to glucocorticoids is known to be highly variable between individuals and is partly determined by polymorphisms in the glucocorticoid receptor (GR) gene. We investigated the relationship between four GR gene polymorphisms and body composition during puberty and at young adult age.

DESIGN

An observational study with repeated measurements.

PATIENTS

Two comparable young Dutch cohorts with a generational difference of about 20 years were investigated. The first cohort consisted of 284 subjects born between 1961 and 1965. Measurements were performed from 13 to 36 years of age. The second cohort consisted of 235 subjects born between 1981 and 1989. Measurements were performed from 8 to 14 years of age.

MEASUREMENTS

Associations between height, weight, BMI, fat mass (FM) and fat-free mass and four well-known functional polymorphisms were investigated. Results In boys in the younger cohort, the G-allele of the BclI polymorphism (haplotype 2) was associated with a higher body weight, weight-SDS, BMI, BMI-SDS and FM. These associations were not observed in the older cohort. Irrespective of genotype, the younger cohort showed a significantly higher total FM, body weight and BMI compared with the older cohort.

CONCLUSIONS

Because the associations between the G-allele of the BclI polymorphism in the GR gene and body FM in boys were only found in a healthy young population, but not in a comparable, generally leaner cohort from an older generation, it is suggested that carriers of this polymorphism are likely to be more vulnerable to fat accumulation in today's obesity promoting environment, than noncarriers.

Performance of a neuro-fuzzy model in predicting weight changes of chronic schizophrenic patients exposed to antipsychotics

Artificial intelligence has become a possible solution to resolve the problem of loss of information when complexity of a disease increases. Obesity phenotypes are observable clinical features of drug-naive schizophrenic patients. In addition, atypical antipsychotic medications may cause these unwanted effects. Here we examined the performance of neuro-fuzzy modeling (NFM) in predicting weight changes in chronic schizophrenic patients exposed to antipsychotics. Two hundred and twenty inpatients meeting DSMIV diagnosis of schizophrenia, treated with antipsychotics, either typical or atypical, for more than 2 years, were recruited. All subjects were assessed in the same study period between mid-November 2003 and mid-April 2004. The baseline and first visit's physical data including weight, height and circumference were used in this study. Clinical information (Clinical Global Impression and Life Style Survey) and genotype data of five single nucleotide polymorphisms were also included as predictors. The subjects were randomly assigned into the first group (105 subjects) and second group (115 subjects), and NFM was performed by using the FuzzyTECH 5.54 software package, with a network-type structure constructed in the rule block. A complete learned model trained from merged data of the first and second groups demonstrates that, at a prediction error of 5, 93% subjects with weight gain were identified. Our study suggests that NFM is a feasible prediction tool for obesity in schizophrenic patients exposed to antipsychotics, with further improvements required.

Leptin-adiposity relationship changes, plus behavioral and parental factors, are involved in the development of body weight in a Dutch children cohort

BACKGROUND

The development of body weight is determined by different factors, namely genetic, behavioral, parental and physiological.

OBJECTIVE

To investigate whether genetic, behavioral, parental and physiological factors are involved and the extent of involvement in the development of body weight at ages 12 and 13 y in a Dutch children cohort.

METHODS

In a Dutch cohort of 94 children at ages 12 and 13 y, we determined anthropometric measurements, body composition, leptin concentrations, TFEQ scores, physical activity, as well as 3 polymorphisms, and in the parents we determined anthropometric measurements and TFEQ scores.

RESULTS

11% of the children in the cohort were classified as overweight. The genotype frequency distributions of the PPARy2, GRL and CNTF genes at ages 12 and 13 y were not significantly different for the overweight children compared to the lean children. Overweight children showed higher dietary restraint and disinhibition scores. Overweight children's parents had a higher BMI, dietary restraint and disinhibition scores, compared to lean children's parents. A peak in leptin concentrations between 7 and 13 y was shown at 12 y. In lean boys, the decrease in leptin concentrations between 12 and 13 y was related to an increase in fat free mass. At the age of 12 y predominantly the physiological factors were predictors for body weight, and at the age of 13 y both the physiological and behavioral factors were predictors for body weight.

CONCLUSION

We conclude from this longitudinal study, that leptin appeared to play an important role in the development of body weight during puberty, in addition to behavioral and parental factors.

Glucocorticoids and cardiovascular disease

Chronic excessive activation of glucocorticoid receptors induces obesity, insulin resistance, glucose intolerance, dyslipidaemia and hypertension. Subtle abnormalities of the hypothalamic-pituitary-adrenal axis and/or of tissue sensitivity to glucocorticoids are also associated with these cardiovascular risk factors in patients with the metabolic syndrome. Furthermore, glucocorticoids have direct effects on the heart and blood vessels, mediated by both glucocorticoid and mineralocorticoid receptors and modified by local metabolism of glucocorticoids by the 11beta-hydroxysteroid dehydrogenase enzymes. These effects influence vascular function, atherogenesis and vascular remodelling following intra-vascular injury or ischaemia. This article reviews the systemic and cardiovascular effects of glucocorticoids, and the evidence that glucocorticoids not only promote the incidence and progression of atherogenesis but also modify the recovery from occlusive vascular events and intravascular injury. The conclusion is that manipulation of glucocorticoid action within metabolic and cardiovascular tissues may provide novel therapeutic avenues to combat cardiovascular disease.

Association analyses of adrenergic receptor polymorphisms with obesity and metabolic alterations

Genes involved in the regulation of catecholamine function may be important in obesity because of the role catecholamines play in energy expenditure and lipolysis. To determine if common single nucleotide polymorphisms (SNPs) in beta(1)-adrenergic receptor (ADRB1), beta(2)-adrenergic receptor (ADRB2), beta(3)-adrenergic receptor (ADRB3), and alpha(2)-adrenergic receptor (ADRA2A) genes associate with obesity and metabolic alterations, we recruited 74 healthy African American and 161 white men and women (age, 18-49 years) to participate in this case-control genetic association study. Genotypes were determined by polymerase chain reaction and restriction fragment length polymorphism. Associations between genotype and body mass index (BMI), percentage of body fat (by measuring skinfold thickness in 7 different sites), fasting (12-hour) plasma glucose, insulin, potassium concentrations, glycated hemoglobin, and insulin resistance (homeostasis model assessment [HOMA(IR)] score) were performed. Among whites, the ADRB1 Arg389-->Gly variant associated with insulin concentrations and HOMA(IR): mean +/- SD values for insulin and HOMA(IR) in Arg389 homozygotes and carriers of the Gly were 10 +/- 7.0 and 12 +/- 9.4 micro IU/mL (P = .02) and 2.1 +/- 1.7 and 2.6 +/- 2.2 (P = .057), respectively. Systolic blood pressure was higher in whites for carriers of the ADBR1 Ser49 compared to Gly49 homozygotes (124 +/- 12.6 vs 119 +/- 11.3 mm Hg, respectively; P = .02). Subsequent analysis revealed that these associations were attributable to a higher BMI among obese participants. The ADRA2A G1780A SNP associated with BMI and percentage of body fat in African Americans (P = .05). Interactions were detected between ADRA2A C-1291G and ADRB2 Gln27-->Glu variants for obesity in African Americans and between ADRA2A C-1291G SNP and ADBR1 haplotype for obesity in whites. We conclude that common SNPs in adrenergic receptor genes may be important susceptibility loci for obesity and related alterations. Because of the limited size of our populations, our results should be interpreted with caution and should be replicated in larger populations.

Genetics of the metabolic syndrome

The concept of a metabolic syndrome (MetS), a cluster of pre-clinical metabolic alterations commonly associated with obesity, is the object of much debate. Genetic studies have the potential to contribute to some of the key questions, including the true nature of the cluster of pre-clinical features and whether it is associated with human genetic variation. This review summarizes the evidence for the presence of familial aggregation for the individual components of MetS and their heritability levels. It also provides an overview of the studies that have dealt with candidate genes for MetS. Potential leads from genome-wide linkage scans are also discussed. The assumption is made that obesity, ectopic fat deposition and abnormal adipose tissue metabolism are responsible for alterations in lipid metabolism, which in turn generates the commonly observed pre-clinical shifts in glucose tolerance, lipids and lipoprotein profile, blood pressure, inflammatory markers, endothelial function, and a prothrombotic state. Progress in the understanding of the genetic basis of MetS should occur as soon as a consensus is reached on the true nature of MetS, its components and diagnostic criteria.

Detection of the Bcl I polymorphism of the glucocorticoid receptor gene by single-tube allele-specific polymerase chain reaction

The Bcl I polymorphism of the glucocorticoid receptor gene, recently identified as an intronic C to G change 646 nucleotides downstream of exon 2, has been associated with increased sensitivity to glucocorticoids and its potential relevance in metabolic disturbances and in various disorders has been extensively investigated. In the present study, we designed a single-tube allele-specific polymerase chain reaction for genotyping this polymorphism in peripheral blood DNA samples. When the Bcl I polymorphism was detected with this novel method in a cohort of 247 healthy subjects, the observed genotype distribution matched the Hardy-Weinberg equilibrium (100 subjects homozygous for the wild-type, 124 heterozygous and 23 homozygous for the mutant allele). In 50 randomly selected subjects the Bcl I polymorphism was also determined using a traditional restriction fragment length polymorphism technique and DNA sequencing, and the results showed 100% coincidence with those obtained by our novel method. The method proved to be more rapid and less labour-intensive compared to currently used techniques, and it avoided the use of extensive instrumentals. We assume that this novel method may have a broad utility in clinical and molecular epidemiological studies aimed to elucidate the impact of the Bcl I polymorphism of the glucocorticoid receptor gene either on metabolic disturbances, or various disorders, including cancer treatment and hormone substitution therapies.

The human obesity gene map: the 2005 update

This paper presents the 12th update of the human obesity gene map, which incorporates published results up to the end of October 2005. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTL) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2005, 176 human obesity cases due to single-gene mutations in 11 different genes have been reported, 50 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 244 genes that, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 408. The number of human obesity QTLs derived from genome scans continues to grow, and we now have 253 QTLs for obesity-related phenotypes from 61 genome-wide scans. A total of 52 genomic regions harbor QTLs supported by two or more studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably, with 426 findings of positive associations with 127 candidate genes. A promising observation is that 22 genes are each supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. The electronic version of the map with links to useful publications and relevant sites can be found at http://obesitygene.pbrc.edu.

Influence of lipoprotein lipase gene Ser447Stop and β1-adrenergic receptor gene Arg389Gly polymorphisms and their interaction on obesity from childhood to adulthood: the Bogalusa Heart Study

OBJECTIVE

To investigate the influence of lipoprotein lipase (LPL) Ser447Stop and beta1-adrenergic receptor (ADRB1) Arg389Gly gene polymorphisms, individually and in combination, on obesity from childhood to adulthood.

DESIGN AND SUBJECTS

A community-based cohort of 1331 subjects (30% black and 70% white subjects) was followed over an average period of 23 years from childhood (age range: 4-17 years) to adulthood (age range:18-44 years).

MEASUREMENT

Body mass index (BMI, kg/m2) and LPL Ser447Stop and the ADRB1 Arg389Gly genotypes.

RESULTS

The frequency of the ADRB1 Gly389 allele was 0.25 in white subjects vs 0.39 in black subjects (P < 0.001); 0.08 vs 0.05 (P = 0.280) for the LPL Stop447 allele. There was no association between the LPL Stop447 allele and BMI among white and black subjects either in childhood and adulthood levels or annual change from childhood to adulthood. The ADRB1 Gly389 allele was associated with lower BMI only in black adults (P = 0.017). Further, the interaction effect of the LPL Stop447 allele and ADRB1 Gly389 allele on adult BMI or its annual change was significant in white subjects and in the total sample (P = 0.03-0.006). Childhood values tended to show a similar trend. Having both ADRB1 Gly389 allele and LPL Stop447 allele was associated with 71% (95% confidence interval: 26-89%) less odds for developing obesity from childhood to adulthood after adjusting for age, race, sex, and childhood BMI.

CONCLUSION

While Gly389 allele of the ADRB1 gene lowers obesity in black subjects, this allele in conjunction with Stop447 allele of the LPL gene lowers obesity in adults and attenuates the development of obesity from childhood to adulthood. These findings underscore the importance of gene-gene interaction in the assessment of genetic influences on complex traits such as obesity.

Multiple association analysis via simulated annealing (MASSA)

SUMMARY

Genome-wide association studies are now technically feasible and likely to become a fundamental tool in unraveling the ultimate genetic basis of complex traits. However, new statistical and computational methods need to be developed to extract the maximum information in a realistic computing time. Here we propose a new method for multiple association analysis via simulated annealing that allows for epistasis and any number of markers. It consists of finding the model with lowest Bayesian information criterion using simulated annealing. The data are described by means of a mixed model and new alternative models are proposed using a set of rules, e.g. new sites can be added (or deleted), or new epistatic interactions can be included between existing genetic factors. The method is illustrated with simulated and real data.

AVAILABILITY

An executable version of the program (MASSA) running under the Linux OS is freely available, together with documentation, at http://www.icrea.es/pag.asp?id=Miguel.Perez.

A testing framework for identifying susceptibility genes in the presence of epistasis

An efficient testing strategy called the "focused interaction testing framework" (FITF) was developed to identify susceptibility genes involved in epistatic interactions for case-control studies of candidate genes. In the FITF approach, likelihood-ratio tests are performed in stages that increase in the order of interaction considered. Joint tests of main effects and interactions are performed conditional on significant lower-order effects. A reduction in the number of tests performed is achieved by prescreening gene combinations with a goodness-of-fit chi2 statistic that depends on association among candidate genes in the pooled case-control group. Multiple testing is accounted for by controlling false-discovery rates. Simulation analysis demonstrated that the FITF approach is more powerful than marginal tests of candidate genes. FITF also outperformed multifactor dimensionality reduction when interactions involved additive, dominant, or recessive genes. In an application to asthma case-control data from the Children's Health Study, FITF identified a significant multilocus effect between the nicotinamide adenine dinucleotide (phosphate) reduced:quinone oxidoreductase gene (NQO1), myeloperoxidase gene (MPO), and catalase gene (CAT) (unadjusted P = .00026), three genes that are involved in the oxidative stress pathway. In an independent data set consisting primarily of African American and Asian American children, these three genes also showed a significant association with asthma status (P = .0008).

Corticosteroid receptor genetic polymorphisms and stress responsivity

A fundamental question in the neuroendocrinology of stress-related psychopathology is why some individuals flourish and others perish under similar adverse conditions. In this contribution we focus on the variants of mineralocorticorticoid (MR) and glucocorticoid receptors (GR) that operate in balance and coordinate behavioral, autonomic, and neuroendocrine response patterns involved in homeostasis and health. In the GR-gene, three single nucleotide polymorphism (SNPs) have been associated with changes in metabolic profile and cardiovascular parameters: the ER22/23EK with a favorable and the N363S and the Bcl1 with a more adverse profile. Importantly, the N363S and the Bcl1 are found to increase cortisol responses to a psychosocial stressor. As a result, the whole body will suffer from overexposure with possible adverse effects on metabolism, cardiovascular control, immune function, and behavior. Also in the MR gene, variants are being identified that are associated with dysregulated autonomic, behavioral, and neuroendocrine responses. The data suggest that these MR and GR variants contribute to individual differences in resilience and vulnerability to stressors, and that these receptors therefore are potential drug targets for recovery of homeostasis and health.

Signaling pathways in brain involved in predisposition and pathogenesis of stress-related disease: genetic and kinetic factors affecting the MR/GR balance

Optimal regulation of the stress response is a prerequisite for adaptation, homeostasis, and health. There are two modes of operation in the stress response. First, an immediate response mode mediated by corticotrophin-releasing hormone-1 (CRH-1) receptors that organizes the behavioral, sympathetic, and hypothalamic-pituitary-adrenal (HPA) response to a stressor. Second, a slower mode, which facilitates behavioral adaptation, promotes recovery, and reestablishes homeostasis. Corticosteroid hormones are implicated in both stress system modes. On the one hand, cortisol and corticosterone determine the threshold or sensitivity of the fast responding mode, whereas the very same hormones in high concentrations facilitate termination of the stress response. In the brain, these actions exerted by the corticosteroid hormones are mediated by two distinct nuclear receptor types, that is, mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs). Whereas MRs maintain neuronal homeostasis and limit the disturbance by stress, GRs help to recover after the challenge and to store the experience for coping with future encounters. Imbalance in MR/GR-mediated actions compromises homeostatic processes in these neurons, which is thought to underlie maladaptive behavior and HPA dysregulation that may lead to aberrant metabolism, impaired immune function, and altered cardiovascular control. The balance in MR/GR-mediated actions depends on bioavailability of corticosteroids, access to the receptors, the stoichiometry of co-regulators, and other proteins as well as genetic factors, among which single nucleotide polymorphisms (SNPs) of the GRs are extensively documented. Stress can bias the receptor signaling pathways, changing "good" corticosteroid actions into "bad" ones.

Identification of common polymorphisms in the promoter of the UGT1A9 gene: evidence that UGT1A9 protein and activity levels are strongly genetically controlled in the liver

OBJECTIVES

Polymorphisms in UDP-glucuronosyltransferases (UGTs) can influence detoxifying capacities and have considerable therapeutic implications in addition to influence various (patho)physiological processes. UGT1A9 plays a central role in the metabolism of various classes of therapeutic drugs in addition to carcinogens and steroids. The great interindividual variability of UGT1A9-mediated glucuronidation remains poorly explained, while evidence for its genetic origin exists.

METHODS

The proximal UGT1A9 promoter was screened for polymorphisms by sequencing and, the contribution of single nucleotide polymorphisms (SNPs) to the variability of UGT1A9 protein levels and activity was evaluated.

RESULTS

We confirmed the presence of the -109 to -98 T10 polymorphism and found ten novel SNPs that generated a diversity of haplotypes in two independent populations. In a panel of 48 human liver microsomes, the UGT1A9 expression varied by 17-fold and was significantly correlated with SNPs -275, -331/-440, -665 and -2152. The base insertion T10 reported to increase reporter gene expression in HepG2 cells [] was not linked to -275 and -2152 SNPs and was not associated with changes in UGT1A9 protein levels. Compared to wild-type individuals, there were statistically significant higher glucuronidating activities in livers with the -275 and -2152 using mycophenolic acid and propofol as UGT1A9 substrates, indicating an extensive glucuronidator phenotype associated with these variants.

CONCLUSIONS

This is the first study to demonstrate that naturally occurring sequence variations in the UGT1A9 promoter are informative in predicting the levels of protein and glucuronidating activity, providing a potential mechanism for interindividual variation in UGT1A9-mediated metabolism.

Characterization of a promoter polymorphism in the glucocorticoid receptor gene and its relationship to three other polymorphisms

OBJECTIVE

Sensitivity to glucocorticoids within the normal population is highly variable and partly determined by polymorphisms in the glucocorticoid receptor (GR) gene (NR3C1). We investigated the exact sequence alteration of a TthIIII polymorphism in the GR gene, whether it is associated with glucocorticoid sensitivity, and its relationship to 3 polymorphisms of the GR gene (N363S, BclI, ER22/23EK).

DESIGN

Two dexamethasone (DEX) suppression tests were performed with 1 and 0.25 mg DEX, respectively.

PATIENTS

We genotyped a random subgroup of 209 participants of the Rotterdam Study, a population-based study in the elderly.

MEASUREMENTS

Anthropometric parameters, cortisol, insulin and glucose levels, and lipid concentrations were measured.

RESULTS

We identified the TthIIII polymorphism as a C to T mutation, 3807 bp upstream from the mRNA start site. We found 39.7% CC-carriers, 44.5% CT-carriers, and 15.8 % TT-carriers. No differences were found between TthIIII genotypes in sensitivity to DEX, baseline cortisol, insulin, glucose or cholesterol levels, or in anthropometric variables. However, all ER22/23EK-carriers also carried the TthIIII T-allele, and carriers of both these polymorphisms had a significantly smaller cortisol suppression after 1 mg DEX, lower fasting insulin levels, and lower total and low-density lipoprotein (LDL) cholesterol levels than TthIIII T carriers without the ER22/23EK variant and noncarriers. No interaction was found between the TthIIII variant and N363S or BclI polymorphisms.

CONCLUSIONS

The TthIIII polymorphism is not functional by itself. However, the ER22/23EK polymorphism is without exception linked to the TthIIII T polymorphism and this haplotype is associated with a relative resistance to glucocorticoids, and a healthy metabolic profile.

Pharmacogenetics of antipsychotic-induced weight gain

RATIONALE

Antipsychotic medications have been associated with considerable weight gain. The degree of inter-individual variability and known genetic contributions to obesity suggest a combination of genetic and environmental factors. In the absence of established mechanisms and valid predictors for this relevant adverse effect, pharmacogenetic studies may provide the basis for the development of individualized treatment and preventive interventions.

OBJECTIVE

The aim of the present review is to analyze the theoretical and empirical knowledge base for the selection of the most promising target genes that may contribute to antipsychotic-induced weight gain.

METHODS

Examination of the preclinical and clinical literature that can inform the rational choice of target genes that may play a role in the development of adverse changes in body composition associated with antipsychotic treatment.

RESULTS

Theoretically, candidate gene selection can be guided by knowledge about molecular pathways associated with obesity, receptors modulated by antipsychotic drugs, and enzymes implicated in their metabolism and bioavailability. While most available data relate to the general mechanisms of obesity and few studies have directly examined the genetic contributions to antipsychotic-induced weight gain, several genes warrant further investigation. These include the 5-HT(2C), pro-opiomelanocortin, leptin, ghrelin, tumor necrosis factor alpha, adiponectin, dopamine D(2) receptor, histamine-H(1) receptor, and alpha(1), beta(2) and beta(3) adrenergic receptor genes.

CONCLUSIONS

Pharmacogenetic studies can provide powerful tools for the pre-treatment identification of individuals at high risk for antipsychotic-induced weight gain, to uncover biological mechanisms that may even generalize to non-drug-induced weight gain, and to isolate novel targets for treatments of weight gain and obesity. To enhance power, future studies should pay close attention to population selection and avoidance/control of confounds, particularly past treatment exposure.

Polymorphisms in Genes Involved in the Corticosteroid Response and the Outcome of Childhood Acute Lymphoblastic Leukemia

BACKGROUND

Considerable variability in sensitivity to corticosteroids (CS) has been observed among individuals with regard to both the natural and synthetic compounds. The role of genetic polymorphisms in modulating CS function, and hence in disease susceptibility, has been extensively analyzed. Their impact on therapeutic response still remains to be explored. The role of cytochrome P450 (CYP) 3A4 in corticosteroid metabolism, and that of the glucocorticoid receptor (NR3C1) in regulation of responsive genes, renders CYP3A4 and NR3C1 polymorphisms as potential candidates for pharmacogenetic analysis.

AIM

The aim of the study was to analyze the role of these polymorphisms in the outcome of a disease treated with CS drugs.

METHODS

Towards this aim we analyzed the CYP3A4-290A/G substitution and three NR3C1 polymorphisms (200G/A, 1220A/G and BclI RFLP) in 222 children with acute lymphoblastic leukemia (ALL) whose treatment protocols, among other components, contained corticosteroid drugs.

RESULTS

The analysis of survival probabilities in relation to the indicated genotypes showed only an association between homozygosity for allele G of the NR3C1 BclI RFLP polymorphism and overall survival (univariate and multivariate hazard ratio [HR] 2.7, 95% confidence interval [CI] 1.0, 7.6 and 5.2, 95% CI 1.4, 18.9, respectively). The association reflects a correlation with disease progression and prognosis, and may vary depending on risk of relapse.

CONCLUSION

A reduction in survival probability in children with ALL was associated with homozygosity for G allele of the NR3C1BclI RFLP polymorphism, particularly in certain patient subgroups. Further analysis is required to replicate this finding and to understand the mechanism underlying the observed association.

Identification of the BclI polymorphism in the glucocorticoid receptor gene: association with sensitivity to glucocorticoids in vivo and body mass index

OBJECTIVE

Sensitivity to glucocorticoids differs between individuals, partially due to genetic variation in the glucocorticoid receptor (GR) gene. We studied the sequence alteration of a previously described intronic BclI polymorphism of the GR gene, and investigated whether there was an association with sensitivity to glucocorticoids and anthropometric parameters in a group of healthy elderly individuals.

DESIGN AND MEASUREMENTS

In study group 1, two overnight dexamethasone suppression tests (DSTs) were performed: with 1 mg dexamethasone, and 2.5 years later with 0.25 mg dexamethasone. Anthropometric parameters were measured in a larger population (study group 2), as well as in a third study group, in which we also measured body composition by dual-energy X-ray absorbtiometry (DEXA) scans.

SUBJECTS

Groups 1 and 2, respectively, 191 and 1963 male and female participants of the Rotterdam study, a population-based study in Dutch elderly. Study group 3: 370 elderly males (mean age 77.8 +/- 0.2 years) from Zoetermeer, the Netherlands.

RESULTS

We identified the BclI restriction site polymorphism as a C/G substitution in intron 2, 646 nucleotides downstream from exon 2. After both 1 mg and 0.25 mg DST, heterozygous (CG) and homozygous G-allele carriers (GG) had lower cortisol levels than CC-carriers (P = 0.01 and P = 0.02, respectively). In study group 2, we found a lower body mass index (BMI; P = 0.006) and waist-hip ratio (WHR; P = 0.02) in G-allele carriers. In study group 3, again we found a lower BMI (P = 0.05) in G-allele carriers. No differences were found in fat mass. However, lean mass tended to be lower in G-allele carriers (P = 0.07).

CONCLUSIONS

We characterized a BclI-RFLP (restriction fragment length polymorphism) of the GR gene as a C/G polymorphism in intron 2 of which the G-allele was associated with hypersensitivity to glucocorticoids. This resulted in a lower BMI in older individuals in general, while our study in elderly males suggests that the lower BMI is probably due to a greater loss of lean mass during the ageing process.

Obesity--is it a genetic disorder?

Obesity is one of the most pressing problems in the industrialized world. Twin, adoption and family studies have shown that genetic factors play a significant role in the pathogenesis of obesity. Rare mutations in humans and model organisms have provided insights into the pathways involved in body weight regulation. Studies of candidate genes indicate that some of the genes involved in pathways regulating energy expenditure and food intake may play a role in the predisposition to obesity. Amongst these genes, sequence variations in the adrenergic receptors, uncoupling proteins, peroxisome proliferator-activated receptor, and the leptin receptor genes are of particular relevance. Results that have been replicated in at least three genome-wide scans suggest that key genes are located on chromosomes 2p, 3q, 5p, 6p, 7q, 10p, 11q, 17p and 20q. We conclude that the currently available evidence suggests four levels of genetic determination of obesity: genetic obesity, strong genetic predisposition, slight genetic predisposition, and genetically resistant. This growing body of research may help in the development of anti-obesity agents and perhaps genetic tests to predict the risk for obesity.

Association studies of genetic polymorphisms in central obesity: a critical review

During the past decade, mutations affecting liability to central obesity have been discovered at a phenomenal rate, and despite few consistently replicated findings, a number of intriguing results have emerged in the literature. Association studies have been proposed to identify the genetic determinants of complex traits such as central obesity. The advantages of the association method include its relative robustness to genetic heterogeneity and the ability to detect much smaller effect sizes than is detectable using feasible sample sizes in linkage studies. However, the current literature linking central obesity to genetic variants is teeming with reports of associations that either cannot be replicated or for which corroboration by linkage has been impossible to find. Explanations for this lack of reproducibility are well rehearsed, and typically include poor study design, incorrect assumptions about the underlying genetic architecture, and simple overinterpretation of data. These limitations create concern about the validity of association studies and cause problems in establishing robust criteria for undertaking association studies. In this article, the current status of the literature of association studies for genetic dissection of central obesity is critically reviewed.

Interactions among the beta2- and beta3- adrenergic receptor genes and total body fat and abdominal fat level in the HERITAGE Family Study

OBJECTIVE AND SUBJECTS

Interactions between markers in the beta2- and beta3-adrenergic receptor (ADR) genes and total body fat and computerized tomography-measured abdominal fat phenotypes were studied in the HERITAGE Family Study cohort of Black (n=205; 81 males and 124 females) and White (n=415; 198 males and 217 females) subjects before and after an endurance training program.

RESULTS

In Black subjects, beta2- and beta3-ADR gene variants showed evidence of interactions on changes in total body fat mass and abdominal fat area (P<0.005 and =0.010, respectively). Black subjects who were carriers of both beta2-ADR Arg16 and beta3-ADR Arg64 alleles had a greater decrease in total fat mass as well as abdominal total and subcutaneous, but not visceral fat areas in response to endurance training than subjects with other genotype combinations (P from 0.011 to 0.047). After correction for multiple tests, the findings remained essentially unchanged for total body fat mass and abdominal fat area, but became nonsignificant for subcutaneous fat area. The changes in abdominal fat correlated positively with the changes in fat mass (P<0.0001). The interactions between beta2 and beta3-ADR gene markers accounted for a maximum of 3% of the variances in the response of total fat mass and abdominal fat area to endurance training in Black subjects but it was not significant in White subjects.

CONCLUSION

Interactions between sequence variants in the beta2-beta3-ADR gene contributed to the changes in fat mass and abdominal adiposity in response to endurance training in Black subjects.

The human obesity gene map: the 2002 update

This is the ninth update of the human obesity gene map, incorporating published results through October 2002 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and various animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. For the first time, transgenic and knockout murine models exhibiting obesity as a phenotype are incorporated (N = 38). As of October 2002, 33 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and the causal genes or strong candidates have been identified for 23 of these syndromes. QTLs reported from animal models currently number 168; there are 68 human QTLs for obesity phenotypes from genome-wide scans. Additionally, significant linkage peaks with candidate genes have been identified in targeted studies. Seven genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 222 studies reporting positive associations with 71 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. More than 300 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.