Association studies of BMI and type 2 diabetes in the neuropeptide Y pathway: a possible role for NPY2R as a candidate gene for type 2 diabetes in men

Functionally Significant Variants in Genes Associated with Abdominal Obesity: A Review

The high prevalence of obesity and of its associated diseases is a major problem worldwide. Genetic predisposition and the influence of environmental factors contribute to the development of obesity. Changes in the structure and functional activity of genes encoding adipocytokines are involved in the predisposition to weight gain and obesity. In this review, variants in genes associated with adipocyte function are examined, as are variants in genes associated with metabolic aberrations and the accompanying disorders in visceral obesity.

The molecular phenotype of kisspeptin neurons in the medial amygdala of female mice

Reproduction is regulated through the hypothalamic-pituitary-gonadal (HPG) axis, largely via the action of kisspeptin neurons in the hypothalamus. Importantly, Kiss1 neurons have been identified in other brain regions, including the medial amygdala (MeA). Though the MeA is implicated in regulating aspects of both reproductive physiology and behavior, as well as non-reproductive processes, the functional roles of MeA Kiss1 neurons are largely unknown. Additionally, besides their stimulation by estrogen, little is known about how MeA Kiss1 neurons are regulated. Using a RiboTag mouse model in conjunction with RNA-seq, we examined the molecular profile of MeA Kiss1 neurons to identify transcripts that are co-expressed in MeA Kiss1 neurons of female mice and whether these transcripts are modulated by estradiol (E₂) treatment. RNA-seq identified >13,800 gene transcripts co-expressed in female MeA Kiss1 neurons, including genes for neuropeptides and receptors implicated in reproduction, metabolism, and other neuroendocrine functions. Of the >13,800 genes co-expressed in MeA Kiss1 neurons, only 45 genes demonstrated significantly different expression levels due to E₂ treatment. Gene transcripts such as Kiss1, Gal, and Oxtr increased in response to E₂ treatment, while fewer transcripts, such as Esr1 and Cyp26b1, were downregulated by E₂. Dual RNAscope and immunohistochemistry was performed to validate co-expression of MeA Kiss1 with Cck and Cartpt. These results are the first to establish a profile of genes actively expressed by MeA Kiss1 neurons, including a subset of genes regulated by E₂, which provides a useful foundation for future investigations into the regulation and function of MeA Kiss1 neurons.

Gene-diet interaction in response to defatted flaxseed flour supplementation on obesity-related traits in Chinese overweight and obese adults: A randomized controlled trial

Effects of dietary fiber on obesity-related traits in previous studies were inconsistent. The aim of the present study was to explore whether variants in genes related to satiety and appetite can modulate the effect of dietary fiber on obesity-related traits. Fifty-one overweight or obese adults were randomly allocated to two groups to consume control biscuits (n = 24) or biscuits containing defatted flaxseed flour (n = 27) at breakfast for 8 wk. Four single-nucleotide polymorphisms related to satiety and appetite were genotyped: rs11076023 on the FTO gene, rs16147 on the NPY gene, rs155971 on the PCSK1 gene, and rs6265 on the BDNF gene. A linear regression model was used to evaluate the gene-diet interaction between obesity-related traits. Compared with control biscuits, defatted flaxseed-flour biscuits significantly reduced body weight (P = 0.001) and body mass index (BMI) (P = 0.001) in A-allele carriers (AA + AT) of rs11076023 on the FTO gene but not in non-carriers (TT) (P for the interaction = 0.005 and 0.006) and decreased fasting serum glucose in participants with CC genotype (P = 0.019) but had less effect in T-allele carriers (TT + TC) (P = 0.021) of rs16147 on the NPY gene (P for the interaction = 0.002). Compared with the control biscuits, defatted flaxseed flour significantly reduced body weight (P < 0.001) in T-allele carriers (TT + TC) of rs155971 on the PCSK1 gene but not in non-carriers (CC) (P for the interaction = 0.041) and reduced body weight (P = 0.001) and BMI (P < 0.001) in A-allele carriers (AA + AG) of rs6265 on the BDNF gene but not non-carriers (GG) (P for the interaction = 0.017 and 0.018). Variants of genes related to satiety and appetite could modulate the effect of defatted flaxseed flour on obesity-related traits.

Hypothalamic CREB Regulates the Expression of Pomc-Processing Enzyme Pcsk2

Background: The hypothalamic proopiomelanocortin (Pomc) neurons act as first-order sensors of systemic energy stores, providing signals that regulate caloric intake and energy expenditure. In experimental obesity, dietary saturated fatty acids affect Pomc endopeptidases (PCs), resulting in the abnormal production of the neurotransmitters α-melanocyte-stimulating hormone (α-MSH) and β-endorphin, thus impacting energy balance. The cAMP response element-binding protein (CREB) is one of the transcription factors that control the expression of Pomc endopeptidases; however, it was previously unknown if dietary fats could affect CREB and consequently the expression of Pomc endopeptidases. Methods: Here, we used single-cell RNA sequencing analysis, PCR, immunoblot, ELISA and immunofluorescence histological assays to determine the impact of a high-fat diet (HFD) on the expression and function of hypothalamic CREB and its impact on the melanocortinergic system. Results: The results indicate that CREB is expressed in arcuate nucleus Pomc neurons and is activated as early as nine hours after the introduction of a high-fat diet. The inhibition of hypothalamic CREB using a short-hairpin RNA lentiviral vector resulted in increased diet-induced body-mass gain and reduced energy expenditure. This was accompanied by reduced expression of the Pomc endopeptidases, protein convertase 2, which are encoded by Pcsk2, and by the loss of the high-fat-diet-induced effect to inhibit the production of α-MSH. Conclusions: This study provides the first evidence for the involvement of CREB in the abnormal regulation of the hypothalamic Pomc endopeptidase system in experimental obesity.

Targeting appetite and satiety in diabetes and obesity, via G protein-coupled receptors

Type 2 diabetes and obesity have reached pandemic proportions throughout the world, so much so that the World Health Organisation coined the term "Globesity" to help encapsulate the magnitude of the problem. G protein-coupled receptors (GPCRs) are highly tractable drug targets due to their wide involvement in all aspects of physiology and pathophysiology, indeed, GPCRs are the targets of approximately 30% of the currently approved drugs. GPCRs are also broadly involved in key physiologies that underlie type 2 diabetes and obesity including feeding reward, appetite and satiety, regulation of blood glucose levels, energy homeostasis and adipose function. Despite this, only two GPCRs are the target of approved pharmaceuticals for treatment of type 2 diabetes and obesity. In this review we discuss the role of these, and select other candidate GPCRs, involved in various facets of type 2 diabetic or obese pathophysiology, how they might be targeted and the potential reasons why pharmaceuticals against these targets have not progressed to clinical use. Finally, we provide a perspective on the current development pipeline of anti-obesity drugs that target GPCRs.

Sex differences in behavioral and metabolic effects of gene inactivation: The neuropeptide Y and Y receptors in the brain

Brain and gonadal hormones interplay controls metabolic and behavioral functions in a sex-related manner. However, most translational neuroscience research related to animal models of endocrine and psychiatric disorders are often carried out in male animals only. The Neuropeptide Y (NPY) system shows sex-dependent differences and is sensitive to gonadal steroids. Based on published data from our and other laboratories, in this review we will discuss the sex related differences of NPY action on energy balance, bone homeostasis and behavior in rodents with the genetic manipulation of genes encoding NPY and its Y1, Y2 and Y5 cognate receptors. Comparative analyses of the phenotype of transgenic and knockout NPY and Y receptor rodents unravels sex dependent differences in the functions of this neurotransmission system, potentially helping to develop therapeutics for a variety of sex-related disorders including metabolic syndrome, osteoporosis and ethanol addiction.

Cortical Transcriptomic Alterations in Association With Appetitive Neuropeptides and Body Mass Index in Posttraumatic Stress Disorder

BACKGROUND

The molecular pathology underlying posttraumatic stress disorder (PTSD) remains unclear mainly due to a lack of human PTSD postmortem brain tissue. The orexigenic neuropeptides ghrelin, neuropeptide Y, and hypocretin were recently implicated in modulating negative affect. Drawing from the largest functional genomics study of human PTSD postmortem tissue, we investigated whether there were molecular changes of these and other appetitive molecules. Further, we explored the interaction between PTSD and body mass index (BMI) on gene expression.

METHODS

We analyzed previously reported transcriptomic data from 4 prefrontal cortex regions from 52 individuals with PTSD and 46 matched neurotypical controls. We employed gene co-expression network analysis across the transcriptomes of these regions to uncover PTSD-specific networks containing orexigenic genes. We utilized Ingenuity Pathway Analysis software for pathway annotation. We identified differentially expressed genes (DEGs) among individuals with and without PTSD, stratified by sex and BMI.

RESULTS

Three PTSD-associated networks (P < .01) contained genes in signaling families of appetitive molecules: 2 in females and 1 in all subjects. We uncovered DEGs (P < .05) between PTSD and control subjects stratified by sex and BMI with especially robust changes in males with PTSD with elevated vs normal BMI. Further, we identified putative upstream regulators (P < .05) driving these changes, many of which were enriched for involvement in inflammation.

CONCLUSIONS

PTSD-associated cortical transcriptomic modules contain transcripts of appetitive genes, and BMI further interacts with PTSD to impact expression. DEGs and inferred upstream regulators of these modules could represent targets for future pharmacotherapies for obesity in PTSD.

Candidate genes for predicting the survival of patients with gastric cancer: a study based on The Cancer Genome Atlas (TCGA) database

Background

Gastric cancer (GC) is the second most frequent cause of cancer-related mortality in the world, and the five-year survival rate for GC remains very low universally. In recent years, it has become a consensus that genetic changes are associated with carcinogenesis of GC, and precision medicine based on genetic changes is one of the most popular treatments for GC patients. However, the association between some genes and GC-related protein signaling pathways is still not well understood. This study revealed that seven genes were closely related to the survival probability in GC patients.

Methods

We downloaded the gene expression data of GC patients from The Cancer Genome Atlas (TCGA) databases, and integrated bioinformatic analysis was performed, such as differential gene expression analysis, including Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) pathways analyses, as well as survival analysis. The r package “survival” was used to analyze the Kaplan-Meier survival analysis, which showed the associations between specific gene expressions and the outcomes of patients with GC to identify which genes could be potential prognostic biomarkers.

Results

This study revealed that seven genes: alcohol dehydrogenase 4 (ADH4), histamine receptor H3 (HRH3), neuropeptide Y2 receptor (NPY2R), apolipoprotein AI (APOA1), N-acetylgalactosaminyltransferase 14 (GALNT14), leucine-rich repeats and IQ motif containing 1 (LRRIQ1), and coiled-coil-domain-containing 57 (CCDC57). These seven genes were closely related to the survival probability of GC patients (P<0.05).

Conclusions

Our study found seven genes which could be considered as candidate prognostic biomarkers and therapeutic targets.

The gender-specific expression of neuropeptide Y and neuropeptide Y receptors in human atrial tissue during cardiopulmonary bypass surgery

Background

Cardiac sympathetic nervous system is usually activated in cardiopulmonary bypass (CPB) surgery, accompanied by excessive release of norepinephrine (NE). Neuropeptide Y (NPY) has been shown to regulate NE release in the terminal of sympathetic fiber, which is a target for regulating heart function. The expression of NPY and NPY receptor (NPYR) genes in the human atrial tissues during CPB in cardiac surgery was investigated in the present study.

Methods

A few discarded atrial tissues before and after CPB were collected in 22 patients with rheumatic cardiac valve diseases. The transcriptional levels of NPY and NPYRs were monitored by real-time quantitative polymerase chain reaction (RT-qPCR) method. Moreover, the correlation between the mRNA levels of NPY/NPYRs and the clinical data were investigated in detail.

Results

The mRNA levels of NPY Y1 and NPY Y5 genes were statistically attenuated in male patients after CPB. Conversely, the expression of NPY, NPY Y1 and NPY Y5 genes were enhanced in female patients. Correlation analysis suggested that there was a significant negative correlation between cardiac ejection fraction (EF) after CPB with the atrial transcriptional level of NPY in male patients.

Conclusions

These results suggested that the expression of NPY/NPYRs in human atrial tissue during CPB was gender specific and activated NPY signaling was only identified in female patients. The elevated expression level of NPY in male patients was correlated with lower cardiac EF after CPB.

Neurobiological characteristics underlying metabolic differences between males and females

The hypothalamus is the main integrating center for metabolic control. Our understanding of how hypothalamic circuits function to control appetite and energy expenditure has increased dramatically in recent years, due to the rapid rise in the incidence of obesity and the search for effective treatments. Increasing evidence indicates that these treatments will most likely differ between males and females. Indeed, sex differences in metabolism have been demonstrated at various levels, including in two of the most studied neuronal populations involved in metabolic control: the anorexigenic proopiomelanocortin neurons and the orexigenic neuropeptide Y/Agouti-related protein neurons. Here we review what is known to date regarding the sex differences in these two neuronal populations, as well as other neuronal populations involved in metabolic control and glial cells.

A Review of Single-Nucleotide Polymorphisms in Orexigenic Neuropeptides Targeting G Protein-Coupled Receptors

Many physiological pathways are involved in appetite, food intake, and the maintenance of energy homeostasis. In particular, neuropeptides within the central nervous system have been demonstrated to be critical signaling molecules for modulating appetite. Both anorexigenic (appetite-decreasing) and orexigenic (appetite-stimulating) neuropeptides have been described. The biological effects of these neuropeptides can be observed following central administration in animal models. This review focuses on single nucleotide polymorphisms (SNPs) in six orexigenic neuropeptides: agouti-related protein (AGRP), galanin, melanin concentrating hormone (MCH), neuropeptide Y (NPY), orexin A, and orexin B. Following a brief summary of the neuropeptides and their orexigenic activities, reports associating SNPs within the orexigenic neuropeptides to energy homeostasis, food intake, obesity, and BMI in humans are reviewed. Additionally, the NIH tool Variation Viewer was utilized to identify missense SNPs within the mature, biologically active neuropeptide sequences. For SNPs found through Variation Viewer, a concise discussion on relevant pharmacological structure-activity relationship studies for select SNPs is included. This review is meant to update reported orexigenic neuropeptide SNPs and demonstrate the potential utility of genomic sequence databases for finding SNPs that may result in altered receptor signaling for neuropeptide pathways associated with appetite.

Current views on neuropeptide Y and diabetes-related atherosclerosis

Diabetes-induced atherosclerotic cardiovascular disease is the leading cause of death of diabetic patients. Neuronal regulation plays a critical role in glucose metabolism and cardiovascular function under physiological and pathological conditions, among which, neurotransmitter neuropeptide Y has been shown to be closely involved in these two processes. Elevated central neuropeptide Y level promotes food intake and reduces energy expenditure, thereby increasing adiposity. Neuropeptide Y is co-localized with noradrenaline in central and sympathetic nervous systems. As a major peripheral vascular contractive neurotransmitter, through interactions with its receptors, neuropeptide Y has been implicated in the pathology and progression of diabetes, by promoting the proliferation of endothelial cells and vascular fibrosis, which may contribute to diabetes-induced cardiovascular disease. Neuropeptide Y also participates in the pathogenesis of atherosclerosis, the major form of cardiovascular disease, via aggravating endothelial dysfunction, growth of vascular smooth muscle cells, formation of foam cells and platelets aggregation. This review highlights the causal role of neuropeptide Y and its receptor system in the development of diabetes mellitus and one of its complications: atherosclerotic cardiovascular disease. The information from this review provides both critical insights onto the mechanisms underlying the pathogenesis of atherosclerosis and evidence for the development of therapeutic strategies.

Association Study of Arcuate Nucleus Neuropeptide Y Neuron Receptor Gene Variation And Serum Npy Levels in Clozapine Treated Patients With Schizophrenia

Background

Antipsychotic-induced weight gain (AIWG) leads to metabolic consequences and comorbidity, social stigmatization and nonadherence in patients with schizophrenia. Neuropeptide Y (NPY) has an important role in appetite and body weight regulation. Associations between AIWG and serum NPY levels, and genetic polymorphisms (SNPs) associated with its serum levels have been little studied in these patients.

Subjects and methods

Associations between serum NPY concentration and other metabolic and inflammatory markers, and 215 SNPs in 21 genes (NPY gene, NPY receptor genes and genes encoding arcuate nucleus NPY neuron receptors) were studied in 180 patients with schizophrenia on clozapine treatment.

Results

The serum levels of NPY correlated with levels of resistin (r = 0.31, P < 0.001) and age (r = 0.22, P = 0.003). In the general linear univariate model the best-fitting model with explanatory factors age, serum resistin level, serum insulin level, BMI and gender explained 18.0% (P < 0.001) of the variance of serum NPY. Genetic risk score (GRSNPY) analysis found twelve significant (P < 0.05) serum NPY concentration related SNPs among α7 nicotinic acetylcholine receptor gene CHRNA7, insulin receptor gene INSR, leptin receptor gene LEPR, glucocorticoid receptor (GR) gene NR3C1, and NPY gene. However, after permutation test of gene score the predictive value of GRSNPY remained non-significant (P = 0.078).

Conclusions

Serum NPY level does not seem to be a feasible biomarker of AIWG. Serum NPY level alterations are not significantly associated with the candidate gene polymorphisms studied.

Association of Neuropeptide Y Gene rs16147 Polymorphism with Cardiovascular Risk Factors, Adipokines, and Metabolic Syndrome in Patients with Obesity

BACKGROUND AND AIMS

The NPY gene has 4 exons, and it is located at 7p15.1. The main genetic variant described in this gene is rs16147. The aim of this study was to investigate the relationship of NPY rs16147 with body weight, insulin resistance, serum adipokine levels, and risk of metabolic syndrome (MetS).

METHODS

A population of 1,005 obese patients was analyzed in a cross-sectional survey. Weight, fat mass, waist circumference, blood pressure, basal glucose, C-reactive protein, insulin, insulin resistance (homeostasis model assessment of insulin resistance [HOMA-IR]), lipid profile, and adipocytokine (leptin, adiponectin, and resistin) levels were measured. The genotype of the NPY gene polymorphism (rs16147) was studied.

RESULTS

Body mass index (1.0 ± 0.1; p < 0.05), weight (2.8 ± 0.4 kg; p < 0.05), fat mass (1.8 ± 0.3 kg; p < 0.05), waist circumference (1.9 ± 0.2 cm; p < 0.05), leptin level (15.4 ± 8.2 ng/mL; p < 0.05), insulin level (5.1 ± 1.3 mIU/L; p < 0.05), and HOMA-IR (1.4 ± 0.1 units; p < 0.05) were lower in A allele carriers than in non-A allele carriers in males. Males with an A allele had a lower percentage of MetS (54.8 vs. 69.1%; p < 0.05), central obesity (94.5 vs. 100%; p < 0.05), and hyperglycemia (24.7 vs. 33.8%; p < 0.05) than non-A allele carriers. Logistic regression analysis indicated that male non-A allele carriers had an increased risk of MetS (odds ratio [OR] = 1.26, 95% confidence interval [CI] = 1.17-1.83; p = 0.034), an increased risk of central obesity (OR = 1.08, 95% CI = 1.02-1.11; p = 0.044), and an increased risk of hyperglycemia (OR = 1.20, 95% CI = 1.09-1.79; p = 0.028) after adjusting for age.

CONCLUSIONS

In obese males, the rs164147 polymorphism of the NPY gene is associated with leptin, insulin level, HOMA-IR, and an increased risk of MetS and its related phenotypes, such as central obesity and hyperglycemia.

Neuropeptide Y is an angiogenic factor in cardiovascular regeneration

In diabetic cardiomyopathy, there is altered angiogenic signaling and increased oxidative stress. As a result, anti-angiogenic and pro-inflammatory pathways are activated. These disrupt cellular metabolism and cause fibrosis and apoptosis, leading to pathological remodeling. The autonomic nervous system and neurotransmitters play an important role in angiogenesis. Therapies that promote angiogenesis may be able to relieve the pathology in these disease states. Neuropeptide Y (NPY) is the most abundantly produced and expressed neuropeptide in the central and peripheral nervous systems in mammals and plays an important role in promoting angiogenesis and cardiomyocyte remodeling. It produces effects through G-protein-coupled Y receptors that are widely distributed and also present on the myocardium. Some of these receptors are also involved in diseased states of the heart. NPY has been implicated as a potent growth factor, causing cell proliferation in multiple systems while the NPY3-36 fragment is selective in stimulating angiogenesis and cardiomyocyte remodeling. Current research is focusing on developing a drug delivery mechanism for NPY to prolong therapy without having significant systemic consequences. This could be a promising innovation in the treatment of diabetic cardiomyopathy and ischemic heart disease.

Differential expression and localization of neuropeptide Y peptide in pancreatic islet of diabetic and high fat fed rats

Neuropeptide Y (NPY) inhibits insulin secretion. Increased numbers of pancreatic islet cells expressing NPY have been observed in type 1 diabetic rats. To understand the functional significance of NPY expression in islet cells, we investigated the effects of high fat feeding and diabetic conditions on the expression and location of NPY expressing cells in normal and diabetic rats. Twenty rats were maintained on either normal chow (ND) or a high fat dietary regimen (HFD) for 4 weeks. In half of each group, type 1 or type 2 diabetes (groups T1DM and T2DM, respectively) was induced by injection of streptozotocin. At 8 weeks rats were euthanized and the pancreases were processed for immunofluorescence labeling (NPY/insulin, NPY/glucagon, NPY/somatostatin, and NPY/pancreatic polypeptide). Compared with the ND group, HFD rats had significantly fewer alpha cells, but beta cells were similar, while T1DM and T2DM rats showed significant increases in the proportions of alpha, delta, and PP cells. Robust increases in NPY-positive islet cells were found in the HFD, T1DM, and T2DM rats compared with ND controls. In ND rats, 99.7% of the NPY-positive cells were PP cells. However, high fat feeding and diabetes resulted in significant increases in NPY-positive delta cells, with concomitant decreases in NPY-positive PP cells. In summary, high-fat feeding and diabetes resulted in changes in the hormonal composition of pancreatic islet and increased number of NPY-expressing islet cells. Under diabetic conditions NPY expression switched from predominantly a characteristic of PP cells to predominantly that of delta cells. This may be a factor in reduced pancreatic hormone secretion during diabetes.

Adrenomedullin signaling pathway polymorphisms and adverse pregnancy outcomes

OBJECTIVE

Reduced maternal plasma levels of the peptide vasodilator adrenomedullin have been associated with adverse pregnancy outcomes. We measured the extent to which genetic polymorphisms in the adrenomedullin signaling pathway are associated with birth weight, glycemic regulation, and preeclampsia risk.

STUDY DESIGN

We genotyped 1,353 women in the Pregnancy, Infection, and Nutrition Postpartum Study for 37 ancestry-informative markers and for single-nucleotide polymorphisms in adrenomedullin (ADM), complement factor H variant (CFH), and calcitonin receptor-like receptor (CALCRL). We used linear and logistic regression to model the association between genotype and birth weight, glucose loading test (GLT) results, preeclampsia, and gestational diabetes (GDM). All models were adjusted for pregravid body mass index, maternal age, and probability of Yoruban ancestry. p values of < 0.05 were considered statistically significant.

RESULTS

Among Caucasian women, ADM rs57153895, a proxy for rs11042725, was associated with reduced birth weight z-score. Among African-American women, ADM rs57153895 was associated with increased birth weight z-score. Two CALCRL variants were associated with GDM risk. CFH rs1061170 was associated with higher GLT results and increased preeclampsia risk.

CONCLUSION

Consistent with studies of plasma adrenomedullin and adverse pregnancy outcomes, we found associations between variants in the adrenomedullin signaling pathway and birth weight, glycemic regulation, and preeclampsia.

GLP-1 responses are heritable and blunted in acquired obesity with high liver fat and insulin resistance

OBJECTIVE Impaired incretin response represents an early and uniform defect in type 2 diabetes, but the contributions of genes and the environment are poorly characterized. RESEARCH DESIGN AND METHODS We studied 35 monozygotic (MZ) and 75 dizygotic (DZ) twin pairs (discordant and concordant for obesity) to determine the heritability of glucagon-like peptide 1 (GLP-1) responses to an oral glucose tolerance test (OGTT) and the influence of acquired obesity to GLP-1, glucose-dependent insulinotropic peptide (GIP), and peptide YY (PYY) during OGTT or meal test. RESULTS The heritability of GLP-1 area under the curve was 67% (95% CI 45-80). Cotwins from weight-concordant MZ and DZ pairs and weight-discordant MZ pairs but concordant for liver fat content demonstrated similar glucose, insulin, and incretin profiles after the OGTT and meal tests. In contrast, higher insulin responses and blunted 60-min GLP-1 responses during the OGTT were observed in the heavier as compared with leaner MZ cotwins discordant for BMI, liver fat, and insulin sensitivity. Blunted GLP-1 response to OGTT was observed in heavier as compared with leaner DZ cotwins discordant for obesity and insulin sensitivity. CONCLUSIONS Whereas the GLP-1 response to the OGTT is heritable, an acquired unhealthy pattern of obesity characterized by liver fat accumulation and insulin resistance is closely related to impaired GLP-1 response in young adults.

Maternal genotype and gestational diabetes

OBJECTIVE

To determine whether genetic variants associated with glucose homeostasis are associated with gestational diabetes (GDM).

STUDY DESIGN

We genotyped 899 self-identified Caucasian women and 386 self-identified African-American women in the Pregnancy, Infection and Nutrition (PIN) Studies cohorts for 38 single-nucleotide polymorphisms (SNPs) associated with type II diabetes (T2DM) and/or glucose homeostasis in European populations.

RESULTS

GDM was diagnosed in 56 of 899 (6.2%) Caucasian and 24 of 386 (6.2%) African-American women. Among Caucasian women, GDM was associated with carriage of TCF7L2 rs7901695, MTNR1B rs10830963 and GCKR rs780094 alleles that are associated with T2DM and fasting glucose in nonpregnant populations. Among African-American participants, we found an increased risk among TSPAN8 rs7961581 C allele homozygotes and reduced risk among carriers of the JAZF1 rs864745 T allele.

CONCLUSION

We found several SNPs that are associated with GDM risk in the PIN cohorts. Maternal genotyping may identify women at risk for impaired gestational glucose tolerance.

Heredity and cardiometabolic risk: naturally occurring polymorphisms in the human neuropeptide Y(2) receptor promoter disrupt multiple transcriptional response motifs

OBJECTIVES

The neuropeptide Y(2) G-protein-coupled receptor (NPY2R) relays signals from PYY or neuropeptide Y toward satiety and control of body mass. Targeted ablation of the NPY2R locus in mice yields obesity, and studies of NPY2R promoter genetic variation in more than 10,000 human participants indicate its involvement in control of obesity and BMI. Here we searched for genetic variation across the human NPY2R locus and probed its functional effects, especially in the proximal promoter.

METHODS AND RESULTS

Twin pair studies indicated substantial heritability for multiple cardiometabolic traits, including BMI, SBP, DBP, and PYY, an endogenous agonist at NPY2R. Systematic polymorphism discovery by resequencing across NPY2R uncovered 21 genetic variants, 10 of which were common [minor allele frequency (MAF) >5%], creating one to two linkage disequilibrium blocks in multiple biogeographic ancestries. In vivo, NPY2R haplotypes were associated with both BMI (P = 3.75E-04) and PYY (P = 4.01E-06). Computational approaches revealed that proximal promoter variants G-1606A, C-599T, and A-224G disrupt predicted IRF1 (A>G), FOXI1 (T>C), and SNAI1 (A>G) response elements. In neuroendocrine cells transfected with NPY2R promoter/luciferase reporter plasmids, all three variants and their resulting haplotypes influenced transcription (G-1606A, P < 2.97E-06; C-599T, P < 1.17E-06; A-224G, P < 2.04E-06), and transcription was differentially augmented or impaired by coexpression of either the cognate full-length transcription factors or their specific siRNAs at each site. Endogenous expression of transcripts for NPY2R, IRF1, and SNAI1 was documented in neuroendocrine cells, and the NPY2R mRNA was differentially expressed in two neuroendocrine tissues (adrenal gland, brainstem) of a rodent model of hypertension and the metabolic syndrome, the spontaneously hypertensive rat.

CONCLUSION

We conclude that common genetic variation in the proximal NPY2R promoter influences transcription factor binding so as to alter gene expression in neuroendocrine cells, and consequently cardiometabolic traits in humans. These results unveil a novel control point, whereby cis-acting genetic variation contributes to control of complex cardiometabolic traits, and point to new transcriptional strategies for intervention into neuropeptide actions and their cardiometabolic consequences.

Neuropeptide Y2 receptor (NPY2R) expression in saliva predicts feeding immaturity in the premature neonate

Background

The current practice in newborn medicine is to subjectively assess when a premature infant is ready to feed by mouth. When the assessment is inaccurate, the resulting feeding morbidities may be significant, resulting in long-term health consequences and millions of health care dollars annually. We hypothesized that the developmental maturation of hypothalamic regulation of feeding behavior is a predictor of successful oral feeding in the premature infant. To test this hypothesis, we analyzed the gene expression of neuropeptide Y2 receptor (NPY2R), a known hypothalamic regulator of feeding behavior, in neonatal saliva to determine its role as a biomarker in predicting oral feeding success in the neonate.

Methodology/Principal Findings

Salivary samples (n = 116), were prospectively collected from 63 preterm and 13 term neonates (post-conceptual age (PCA) 26 4/7 to 41 4/7 weeks) from five predefined feeding stages. Expression of NPY2R in neonatal saliva was determined by multiplex RT-qPCR amplification. Expression results were retrospectively correlated with feeding status at time of sample collection. Statistical analysis revealed that expression of NPY2R had a 95% positive predictive value for feeding immaturity. NPY2R expression statistically significantly decreased with advancing PCA (Wilcoxon test p value<0.01), and was associated with feeding status (chi square p value  =  0.013).

Conclusions/Significance

Developmental maturation of hypothalamic regulation of feeding behavior is an essential component of oral feeding success in the newborn. NPY2R expression in neonatal saliva is predictive of an immature feeding pattern. It is a clinically relevant biomarker that may be monitored in saliva to improve clinical care and reduce significant feeding-associated morbidities that affect the premature neonate.

Polymorphisms in the neuropeptide Y gene and the risk of obesity: findings from two prospective cohorts

CONTEXT

Neuropeptide Y (NPY) increases appetite and food intake in animals. Conflicting evidence has been found for the association between polymorphisms of the NPY gene and obesity in humans.

OBJECTIVE

The objective of the investigation was to study four single-nucleotide polymorphisms (SNPs) in the NPY gene [rs17149106 (G>T), rs16147 (C>T), rs16139 (T>C), rs5574 (C>T)] with body adiposity.

DESIGN

The study design included a candidate gene association study from two cohorts.

PARTICIPANTS

Two thousand seventy-one women from the Nurses' Health Study and 1268 men from the Health Professionals Follow-Up study participated in the study.

MAIN OUTCOME MEASURES

Weight and height were self-reported at baseline and updated every 2 yr to calculate body mass index (BMI).

RESULTS

Two SNPs (rs17149106 (G>T) and rs16139 (T>C)), with minor allele frequencies of 4%, were associated with elevated risks of obesity (BMI ≥ 30 kg/m(2)) in both cohorts. The pooled adjusted odds ratios [95% confidence interval (CI)] were 1.72 (95% CI 1.20-2.47) and 1.79 (95% CI 1.24-2.60), respectively. Haplotype analyses reflected the associations with the individual SNP. TTCC carriers, with the minor allele of both SNPs, had an increased risk of obesity (odds ratio 1.89; 95% CI 1.29-2.75) compared with those carrying the common haplotype GCTT. Carriers of the rs16139 C allele had greater BMI than noncarriers with a pooled mean difference of +0.58 kg/m(2) (95% CI 0.01-1.15) among women and men. Both rs17149106 and rs16139 were associated with weight gain since adolescence/early adulthood but were not associated with abdominal adiposity as measured by waist circumference and waist to hip ratio.

CONCLUSIONS

NPY gene variants were significantly associated with weight changes from young adulthood to middle age and with risk of obesity.

Polymorphisms in the NPY2R gene show significant associations with BMI that are additive to FTO, MC4R, and NPFFR2 gene effects

Neuropeptide Y (NPY) is an appetite hormone that acts centrally to control feeding behavior. The 5' and exon 2 regions of NPY2R, one of five NPY receptor genes, have been weakly and inconsistently implicated with obesity. With the ATG start site of the gene at the beginning of exon 2, single-nucleotide polymorphisms (SNPs) across intron 1 may show stronger associations with obesity than expected. Two 5' SNPs, three intron 1 SNPs, and one synonymous exon 2 SNP were genotyped on 2,985 white Utah subjects. Previously associated FTO, NPY, NPY1R, MC4R, PPARGC1A, OR7D4, and four NPFFR2 SNPs were also genotyped and related to BMI. One NPY2R 5' SNP (rs12649641, P = 0.008), an exon 2 SNP (rs2880415, P = 0.009), and an intron 1 SNP (rs17376826, P = 7 × 10(-6)) were each significantly associated with BMI. All three SNPs, plus FTO (rs9939609, P = 1.5 × 10(-6)) and two NPFFR2 SNPs (rs4129733, P = 3.7 × 10(-13) and rs11940196, 4.2 × 10(-10)) remained significant in a multiple regression additive model. Diplotypes using the estimated haplotypes of NPY2R, NPFFR2, and MC4R were significantly associated with BMI (P = 1.0 × 10(-10), 3.2 × 10(-8), and 1.1 × 10(-4), respectively). Haplotypes of NPY2R, NPFFR2, and MC4R, plus the FTO SNP, explained 9.6% of the BMI variance. SNP effect sizes per allele for the four genes ranged from 0.8 to 3.5 kg/m(2). We conclude that haplotypes containing the rs17376826 SNP in intron 1 of NPY2R have strong associations with BMI, some NPFFR2 haplotypes are strongly protective against or increase risk of obesity, and both NPY2R and NPFFR2 play important roles in obesity predisposition independent of FTO and MC4R.

Of mice and men: neuropeptide Y and its receptors are associated with atherosclerotic lesion burden and vulnerability

Neuropeptide Y (NPY), a sympathetic and platelet-derived vascular mitogen and angiogenic factor, has been implicated in atherosclerosis in animal and human genetic studies. Here we evaluate its association with human and murine atherosclerosis, and assess the role of platelet-derived NPY in lesion vulnerability. NPY immunoreactivity (NPY-ir) was measured in the platelet-poor and platelet-rich (PRP) plasmas, and NPY receptors (mitogenic Y1R and angiogenic Y2 and Y5Rs), CD26/DPPIV (a protease forming Y2/Y5-selective agonist), CD31-positive vascularity, and lesion morphology assessed by histo- and immunocyto-chemistry-in patients with peripheral artery disease (PAD) and healthy volunteers, and in lard-fed ApoE-/- mice. NPY and NPY-R immunostaining was greater in lesions from PAD patients compared to normal vessels of healthy volunteers (p < 0.001), and localized to smooth muscle cells, macrophages, and adventitial/neovascular endothelial cells. CD26/DPPIV staining co-localized with CD31-positive endothelial cells only in atherosclerotic lesions. NPY-ir in PRP (but not plasma) and vascular immunostaining was higher (p < 0.05 and 0.001, respectively) in men (not women) with PAD compared to healthy subjects. A similar gender specificity was observed in mice. PRP NPY-ir levels correlated with lesion area (p = 0.03), necrotic core area, and the necrotic core-to-lesion area ratio (p < 0.01) in male, but not female, mice. Also males with neovascularized lesions had higher PRP NPY-ir levels than those lacking lesion microvessels (p < 0.05). NPY and its Rs are up-regulated in human and murine atherosclerotic lesions suggesting pathogenic role. DPPIV expression by microvascular endothelium in atherosclerotic tissue may shift NPY's affinity toward angiogenic Y2/Y5Rs, and thus enhance angiogenesis and lesion vulnerability. Remarkably, plaque neovascularization was associated with increased NPY-ir in PRP in males but not females, suggesting that platelet NPY may be a novel mediator/marker of lesion vulnerability particularly in males, for reasons that remain to be determined. Both animal and human data suggest that NPY is an important contributor to, and platelet NPY-ir a marker of, atherosclerotic lesion burden and vulnerability but only in males, perhaps due to androgen-dependent up-regulation of NPY, previously shown in rats.

Variation in the 5'-flanking region of the neuropeptide Y2 receptor gene and metabolic parameters

A previous report describes that neuropeptide Y (NPY)/NPY2 receptor (NPY2R) is involved in stress-induced visceral obesity. This is a report clarifying the effect on metabolic parameters of single nucleotide polymorphisms in the 5'-flanking region of NPY2R gene. Study participants are 317 people (98 men and 219 women, 40-79 years old) undergoing health checkups. The single nucleotide polymorphism typing of rs6857715 and rs6857530 located on the 5'-flanking region of the NPY2R gene was performed using allele-specific polymerase chain reaction method. Serum high-density lipoprotein cholesterol (HDL-C) level was significantly lower in men possessing rs6857715 TT genotype compared with CC and in men possessing rs6857530 GG genotype compared with AA. No significant difference was observed between each genotype and other metabolic parameters including body mass index, waist circumference, systolic and diastolic blood pressure, serum low-density lipoprotein cholesterol, triglyceride, and fasting plasma glucose. The variation in the 5'-flanking region of the NPY2R gene was associated with serum HDL-C level in men and was a predictor for serum HDL-C level independent of sex and serum triglyceride level.

Obesity and diabetes genetic variants associated with gestational weight gain

OBJECTIVE

We sought to determine whether genetic variants associated with diabetes and obesity predict gestational weight gain.

STUDY DESIGN

A total of 960 participants in the Pregnancy, Infection, and Nutrition cohorts were genotyped for 27 single-nucleotide polymorphisms (SNPs) associated with diabetes and obesity.

RESULTS

Among Caucasian and African American women (n = 960), KCNQ1 risk allele carriage was directly associated with weight gain (P < .01). In Bayesian hierarchical models among Caucasian women (n = 628), we found posterior odds ratios >3 for inclusion of TCF2 and THADA SNPs in our models. Among African American women (n = 332), we found associations between risk allele carriage and weight gain for the THADA and INSIG2 SNPs. In Bayesian variable selection models, we found an interaction between the TSPAN8 risk allele and pregravid obesity, with lower weight gain among obese risk allele carriers.

CONCLUSION

We found evidence that diabetes and obesity risk alleles interact with maternal pregravid body mass index to predict gestational weight gain.

Candidate molecular pathway genes related to appetite regulatory neural network, adipocyte homeostasis and obesity: results from the CARDIA Study

Appetite regulatory neural network and adipocyte homeostasis molecular pathways are critical to long-term weight maintenance. Associations between obesity-related phenotypes and four genes in these pathways - leptin (LEP), leptin receptor (LEPR), neuropeptide Y2 receptor (NPY2R) and peptide YY (PYY) were examined in CARDIA Study participants (aged 18-30 at recruitment in 1985-6). Weight, BMI and waist circumference were measured at baseline and at years 2, 5, 7, 10, 15, and 20. Genotyping was conducted using tag SNPs characterising common genetic variations in these genes. Generalized estimating equation (GEE) models estimated associations between SNPs and repeated anthropometric measurements, controlling for sex and age. False discovery rate was used to adjust for multiple testing. In African-Americans, SNPs across the LEP gene demonstrated significant overall associations with all obesity-related phenotypes. The associations between LEP rs17151919 with weight tended to strengthen with time - the difference in weight associated with each additional minor allele increased from 2.6 kg at baseline to 4.8 kg at year 20 (SNP*time interaction p = 0.0193). NPY2R gene SNPs were associated with waist circumference among African-American men (p = 0.0462). In Caucasians, LEP SNPs also tended to be associated with weight (p = 0.0471), and PYY rs11684664 was associated with obesity-related phenotypes in women only (p = 0.010-0.026). Several LEP, and NPY2R and PYY SNPs were associated with obesity-related phenotypes in young adults, particularly among African-Americans.

Recent progress in the genetics of common obesity

The genetic contribution to interindividual variation in common obesity has been estimated at 40-70%. Yet, despite a relatively high heritability, the search for obesity susceptibility genes has been an arduous task. This paper reviews recent progress made in the obesity genetics field with an emphasis on established obesity susceptibility loci identified through candidate gene as well as genome-wide studies. For the last 15 years, candidate gene and genome-wide linkage studies have been the two main genetic epidemiological approaches to identify genetic loci for common traits, yet progress has been slow and success limited. Only recently have candidate gene studies started to succeed; by means of large-scale studies and meta-analyses at least five variants in four candidate genes have been found to be robustly associated with obesity-related traits. Genome-wide linkage studies, however, have so far not been able to pinpoint genetic loci for common obesity. The genome-wide association approach, which has become available in recent years, has dramatically changed the pace of gene discoveries for common disease, including obesity. Three waves of large-scale high-density genome-wide association studies have already discovered at least 15 previously unanticipated genetic loci incontrovertibly associated with body mass index and extreme obesity risk. Although the combined contribution of these loci to the variation in obesity risk at the population level is small and their predictive value is typically low, these recently discovered loci are set to improve fundamentally our insights into the pathophysiology of obesity.

Neuropeptide Y gene polymorphisms are not associated with obesity in a South Indian population

BACKGROUND/OBJECTIVES

Neuropeptide Y (NPY) gene has been shown to have a critical role in the regulation of satiety, reproduction, central endocrine and cardiovascular systems. Among the primary functions associated with NPY are its acute effects on feeding behavior and energy expenditure. The aim of this study is to evaluate the relationship between obesity and NPY gene polymorphisms in a South Indian Population.

SUBJECTS/METHODS

Three polymorphisms in NPY gene (Leu7Pro, Ser50Ser and A7735G) were analyzed in 263 individuals of an endogamous Kota population. On the basis of body mass index (BMI), they were divided into two groups. Associations were tested using logistic regression and haplotype analyses and linkage disequilibrium (LD).

RESULTS

There was no evidence of deviation from Hardy-Weinberg equilibrium. Logistic regression analysis did not reveal significant association with obesity and NPY single-nucleotide polymorphisms (SNPs) in the present study. All three SNPs were in weak LD with low r (2) values. Haplotype analysis also did not yield significant association between NPY gene and obesity (global P=0.756).

CONCLUSIONS

Our study did not validate the association between previously implicated SNPs in NPY gene and obesity in an Indian population. Population-specific validation of putative associations has far reaching implications for the future personal genomics medicine applications.

Genome-wide association of anthropometric traits in African- and African-derived populations

Genome-wide association (GWA) studies have identified common variants that are associated with a variety of traits and diseases, but most studies have been performed in European-derived populations. Here, we describe the first genome-wide analyses of imputed genotype and copy number variants (CNVs) for anthropometric measures in African-derived populations: 1188 Nigerians from Igbo-Ora and Ibadan, Nigeria, and 743 African-Americans from Maywood, IL. To improve the reach of our study, we used imputation to estimate genotypes at approximately 2.1 million single-nucleotide polymorphisms (SNPs) and also tested CNVs for association. No SNPs or common CNVs reached a genome-wide significance level for association with height or body mass index (BMI), and the best signals from a meta-analysis of the two cohorts did not replicate in approximately 3700 African-Americans and Jamaicans. However, several loci previously confirmed in European populations showed evidence of replication in our GWA panel of African-derived populations, including variants near IHH and DLEU7 for height and MC4R for BMI. Analysis of global burden of rare CNVs suggested that lean individuals possess greater total burden of CNVs, but this finding was not supported in an independent European population. Our results suggest that there are not multiple loci with strong effects on anthropometric traits in African-derived populations and that sample sizes comparable to those needed in European GWA studies will be required to identify replicable associations. Meta-analysis of this data set with additional studies in African-ancestry populations will be helpful to improve power to detect novel associations.

Molecular variation in neuropeptide Y and bone mineral density among men of African ancestry

Neuropeptide Y (NPY) is a physiological candidate gene for the regulation of body weight and has more recently been implicated in regulating bone mass. The current study sought to test if inherited variation in NPY might influence BMD in a population of African-ancestry men who have high bone mineral density (BMD). We genotyped 17 tagging single-nucleotide polymorphisms (SNPs) across the NPY gene region in 1,113 randomly selected men of African ancestry aged >or=40 years and tested for association with anthropometric characteristics and proximal femur BMD. The homozygous rare genotype of four SNPs was associated with a 0.92-1.59% decrease in stature (corrected P < 0.05). No SNP was associated with body mass index or body weight. Two SNPs in a 5-kb linkage disequilibrium block encompassing exons 3 and 4 were associated with proximal femur BMD, adjusted for age, body weight, and height (corrected P < 0.05). These results suggest that genetic variation at the NPY locus may contribute to bone density, independently of body weight.

Genetic variation in the hypothalamic pathways and its role on obesity

Over recent decades, the prevalence of obesity has increased dramatically worldwide. Although this epidemic is mainly attributable to modern (western) lifestyle, multiple twin and adoption studies indicate the significant role of genes in the individual's predisposition to becoming obese. As the hypothalamus plays a central role in controlling body weight, its regulatory circuits may represent a crucial system in the pathogenesis of the disorder. Genetic variations in genes in the hypothalamic pathways may therefore contribute to the susceptibility for obesity in humans and animals. We summarize current knowledge on the physiological role of the hypothalamus in body-weight regulation and review genetic studies on the hypothalamic candidate genes in relation to obesity. Together, data from functional and genetic studies as well as the new, common, obesity loci identified in genome-wide association scans support an important role for the hypothalamic genes in predisposing to obesity. However, findings are still inconclusive for many candidate genes. To improve our understanding of the genetic architecture of common obesity, we suggest that specific obesity phenotypes should be considered and different analytical approaches used. Such studies should consider multiple genes from the same physiological pathways, together with environmental risk factors.

Long-term effects of laparoscopic sleeve gastrectomy, gastric bypass, and adjustable gastric banding on type 2 diabetes

BACKGROUND

This study aimed to compare the efficacy of laparoscopic sleeve gastrectomy (SG) with that of laparoscopic gastric bypass (GBP) and laparoscopic adjustable gastric banding (AGB) for glucose homeostasis in morbidly obese subjects with type 2 diabetes mellitus (T2DM) at a 3-year follow-up assessment and to elucidate the role of weight loss in the T2DM resolution after SG.

METHODS

For this study, 60 morbidly obese T2DM patients (44 females and 16 males) who underwent AGB (24 patients), GBP (16 patients), or SG (20 patients) between 1996 and 2008 were retrospectively analyzed. Age, sex, body mass index (BMI), estimated weight loss (EWL), fasting glycemia, HbA1c, euglycemic hyperinsulinemic clamp, discontinuation of diabetes treatment, and time until interruption of therapy were evaluated.

RESULTS

In the study, 54 patients received oral hypoglycemic agents for at least 12 months before surgery, and 6 patients received insulin. The mean follow-up period was 36 months. The resolution rate was 60.8% for the AGB patients, 81.2% for the GBP patients, and 80.9% for the SG patients. The postoperative time until interruption of therapy was 12.6 months for the AGB patients, 3.2 months for the GBP patients, and 3.3 months for the SG patients. The hyperinsulinemic euglycemic clamp test was performed 12 months after surgery for the cured patients. Insulin resistance was restored to normal values in all the patients. The greatest improvement from preoperative values occurred in the SG group. For the not-cured GBP and SG patients, an improvement of 120 mg/dl in fasting plasma glucose was observed 3 months after the surgery, suggesting an enhancement in insulin sensitivity, which determines better medical control. The resolution rate remained constant at the 36-month follow-up evaluation in both the GBP and SG groups.

CONCLUSIONS

All three bariatric procedures are effective in treating diabetes, with a 3-year follow-up evaluation showing an effect that lasts. The AGB procedure was the least effective. The antidiabetic effect was similarly precocious after GBP and SG compared with AGB. This difference may indicate that a hormonal mechanism may be involved, independent of weight loss.

Using genome-wide pathway analysis to unravel the etiology of complex diseases

Several genome-wide association studies (GWAS) have been published on various complex diseases. Although, new loci are found to be associated with these diseases, still only very little of the genetic risk for these diseases can be explained. As GWAS are still underpowered to find small main effects, and gene-gene interactions are likely to play a role, the data might currently not be analyzed to its full potential. In this study, we evaluated alternative methods to study GWAS data. Instead of focusing on the single nucleotide polymorphisms (SNPs) with the highest statistical significance, we took advantage of prior biological information and tried to detect overrepresented pathways in the GWAS data. We evaluated whether pathway classification analysis can help prioritize the biological pathways most likely to be involved in the disease etiology. In this study, we present the various benefits and limitations of pathway-classification tools in analyzing GWAS data. We show multiple differences in outcome between pathway tools analyzing the same dataset. Furthermore, analyzing randomly selected SNPs always results in significantly overrepresented pathways, large pathways have a higher chance of becoming statistically significant and the bioinformatics tools used in this study are biased toward detecting well-defined pathways. As an example, we analyzed data from two GWAS on type 2 diabetes (T2D): the Diabetes Genetics Initiative (DGI) and the Wellcome Trust Case Control Consortium (WTCCC). Occasionally the results from the DGI and the WTCCC GWAS showed concordance in overrepresented pathways, but discordance in the corresponding genes. Thus, incorporating gene networks and pathway classification tools into the analysis can point toward significantly overrepresented molecular pathways, which cannot be picked up using traditional single-locus analyses. However, the limitations discussed in this study, need to be addressed before these methods can be widely used.

DNA polymorphisms at the BCL11A, HBS1L-MYB, and beta-globin loci associate with fetal hemoglobin levels and pain crises in sickle cell disease

Sickle cell disease (SCD) is a debilitating monogenic blood disorder with a highly variable phenotype characterized by severe pain crises, acute clinical events, and early mortality. Interindividual variation in fetal hemoglobin (HbF) expression is a known and potentially heritable modifier of SCD severity. High HbF levels are correlated with reduced morbidity and mortality. Common single nucleotide polymorphisms (SNPs) at the BCL11A and HBS1L-MYB loci have been implicated previously in HbF level variation in nonanemic European populations. We recently demonstrated an association between a BCL11A SNP and HbF levels in one SCD cohort [Uda M, et al. (2008) Proc Natl Acad Sci USA 105:1620-1625]. Here, we genotyped additional BCL11A SNPs, HBS1L-MYB SNPs, and an SNP upstream of (G)gamma-globin (HBG2; the XmnI polymorphism), in two independent SCD cohorts: the African American Cooperative Study of Sickle Cell Disease (CSSCD) and an SCD cohort from Brazil. We studied the effect of these SNPs on HbF levels and on a measure of SCD-related morbidity (pain crisis rate). We strongly replicated the association between these SNPs and HbF level variation (in the CSSCD, P values range from 0.04 to 2 x 10(-42)). Together, common SNPs at the BCL11A, HBS1L-MYB, and beta-globin (HBB) loci account for >20% of the variation in HbF levels in SCD patients. We also have shown that HbF-associated SNPs associate with pain crisis rate in SCD patients. These results provide a clear example of inherited common sequence variants modifying the severity of a monogenic disease.

Progress in the genetics of common obesity: size matters

PURPOSE OF REVIEW

Over the past two decades serious efforts has been invested in the search for genes that predispose to common obesity, but progress has been slow and success limited. Genome-wide association, however, has revived optimism. Here we review recent advances in the field of obesity genetics and discuss the most important findings of candidate gene, genome-wide linkage studies and genome-wide association studies. We conclude by speculating about the way forward in the near future.

RECENT FINDINGS

Although large-scale candidate gene studies have placed MC4R more firmly on the human obesity map, the major breakthrough in obesity genetics was the discovery of FTO through genome-wide association. Variants located in the first intron of FTO were unequivocally associated with a 1.67-fold increased risk for obesity and a 0.40-0.66 kg/m2 increase in body mass index.

SUMMARY

Genome-wide association promises to enhance greatly our understanding of the genetic basis of common obesity, although candidate gene studies will remain a valuable approach because they allow more detailed analyses of biologically relevant candidates. A key factor contributing to continued success lies in large-scale data integration through international collaboration, which will provide the sample sizes required to identify genetic association with conclusive evidence.

Abnormal postprandial PYY response in insulin sensitive nondiabetic subjects with a strong family history of type 2 diabetes

OBJECTIVE

Gut-derived hormone peptide YY (PYY) is low in subjects with obesity and type 2 diabetes (T2D). However, it is unknown whether this is a primary defect or a consequence of metabolic disturbances. In this study, we aimed to assess whether low fasting and postprandial PYY secretion is an early defect, potentially promoting the development of obesity and T2D, and whether it is modified by macronutrient content.

DESIGN

Prospective cross-sectional cohort study.

SUBJECTS

Nine individuals with a strong family history of T2D (REL) and seven age and adiposity matched individuals with no family history of T2D (CON).

INTERVENTIONS

Metabolic studies including hyperinsulinemic-euglycemic clamp, dual X-ray absorptiometry and two meal tests containing 1000 kcal with an either high fat (76%) or high carbohydrate (76%) content.

MAIN OUTCOME MEASURES

Fasting and postprandial PYY levels were measured and analyzed for potential correlations with markers for adiposity and insulin resistance.

RESULTS

Insulin sensitivity was not different between REL and CON. Fasting glucose, insulin, triglycerides and PYY were also not different between groups. However, the postprandial incremental area under curve (AUC) of PYY was significantly lower in REL after the high carbohydrate (HCHO) meal (+27.3 vs +60.6% increase from baseline, P=0.038). The AUC of insulin during HCHO meal correlated negatively with both AUC and fasting level of PYY (r=-0.58 and -0.60, respectively, P<0.05).

CONCLUSIONS

A blunted postprandial PYY secretion is observed in a very early stage in the development of T2D in genetically susceptible individuals. This defect precedes the presence of insulin resistance and adiposity, and could therefore predispose to the development of T2D.

A survey of allelic imbalance in F1 mice

There are widespread, genetically determined differences in gene expression. However, methods that compare transcript levels between individuals are subject to trans-acting effects and environmental differences. By looking at allele-specific expression in the F1 progeny of inbred mice, we can directly test for allelic imbalance (AI), which must be due to cis-acting variants in the parental strains. We tested over one hundred genes for AI between C57Bl/6J and A/J alleles in F1 mice, including a validation set of 23 genes enriched for cis-acting variants and a second set of 92 genes whose orthologs were previously examined for AI in humans. We assayed an average of two transcribed SNPs per gene in liver, spleen, and brain from three male and three female F1 mice. In the set of 92 genes, we observed 33 genes (36%) with significant AI including genes with AI that was specific to certain tissues or transcripts. We also observed extensive tissue-specific AI, with 11 out of 92 genes (12%) having differences in AI between tissues. Interestingly, several genes with alternate transcripts have transcript-specific AI. Finally, we observed that the presence of AI in human genes was correlated to the presence of AI in the mouse orthologs (one-tailed P = 0.003), suggesting that certain genes may be more tolerant of cis-acting variation across species.

Common genetic variation in eight genes of the GH/IGF1 axis does not contribute to adult height variation

Stature (adult height) is one of the most heritable human traits, yet few genes, if any, have been convincingly associated with adult height variation in the general population. Here, we selected 150 tag SNPs from eight candidate genes in the growth hormone (GH)/insulin-like growth factor-1 (IGF1) axis (GHR, GHRH, GHRHR, IGF1, IGFALS, IGFBP3, JAK2, STAT5B), and genotyped them in approximately 2,200 individuals ascertained for short or tall stature. Nominally significant tag SNPs were then tested in three additional replication cohorts, including a family-based panel to rule out spurious associations owing to population stratification. Across the four height cohorts (N = 6,075 individuals), we did not observe any consistent associations between stature and common variants (> or =5% minor allele frequency) in these eight genes, including a common deletion of the growth hormone receptor gene exon 3. Tests of epistatic interactions between these genes did not yield any results beyond those expected by chance. Although we have not tested all genes in the GH/IGF1 axis, our results indicate that common variation in these GH/IGF1 axis genes is not a major determinant of stature, and suggest that if common variation contributes to adult height variation in the general population, the variants are in other, possibly unanticipated genes.