Leptin's sexual dimorphism results from genotype by sex interactions mediated by testosterone

Distinct Plasma Immune Profile in ALS Implicates sTNFR-II in pAMPK/Leptin Homeostasis

Amyotrophic lateral sclerosis (ALS) is a clinically highly heterogeneous disease with a survival rate ranging from months to decades. Evidence suggests that a systemic deregulation of immune response may play a role and affect disease progression. Here, we measured 62 different immune/metabolic mediators in plasma of sporadic ALS (sALS) patients. We show that, at the protein level, the majority of immune mediators including a metabolic sensor, leptin, were significantly decreased in the plasma of sALS patients and in two animal models of the disease. Next, we found that a subset of patients with rapidly progressing ALS develop a distinct plasma assess immune–metabolic molecular signature characterized by a differential increase in soluble tumor necrosis factor receptor II (sTNF-RII) and chemokine (C-C motif) ligand 16 (CCL16) and further decrease in the levels of leptin, mostly dysregulated in male patients. Consistent with in vivo findings, exposure of human adipocytes to sALS plasma and/or sTNF-RII alone, induced a significant deregulation in leptin production/homeostasis and was associated with a robust increase in AMP-activated protein kinase (AMPK) phosphorylation. Conversely, treatment with an AMPK inhibitor restored leptin production in human adipocytes. Together, this study provides evidence of a distinct plasma immune profile in sALS which affects adipocyte function and leptin signaling. Furthermore, our results suggest that targeting the sTNF-RII/AMPK/leptin pathway in adipocytes may help restore assess immune–metabolic homeostasis in ALS.

Quantile-specific heritability of sibling leptin concentrations and its implications for gene-environment interactions

"Quantile-dependent expressivity" occurs when the effect size of a genetic variant depends upon whether the phenotype (e.g., leptin) is high or low relative to its distribution. Leptin concentrations are strongly related to adiposity, whose heritability is quantile dependent. Whether inheritance of leptin concentrations is quantile dependent, and whether this explains the greater heritability in women than men in accordance with their greater adiposity, and explains other gene-environment interactions, remains to be determined. Therefore, leptin and leptin receptor concentrations from 3068 siblings in 1133 sibships from the Framingham Heart Study Third Generation Cohort were analyzed. Free leptin index (FLI) was calculated as the ratio of leptin to soluble leptin receptor concentrations. Full-sib (β_FS) regression slopes were robustly estimated by quantile regression with nonparametric significance assigned from 1000 bootstrap samples. The analyses showed β_FS increased significantly with increasing percentiles of the offspring's age- and sex-adjusted leptin distribution (P_linear = 0.0001), which was accelerated at the higher concentrations (P_quadratic = 0.0003). β_FS at the 90th percentile (0.418 ± 0.066) was 4.7-fold greater than at the 10th percentile (0.089 ± 0.032, P_difference = 3.6 × 10^-6). Consistent with quantile-dependent expressivity, the β_FS was greater in female sibs, which was attributable to their higher leptin concentrations. Reported gene-environment interactions involving adiposity and LEP, LEPR, MnSOD, PPARγ, PPARγ2, and IRS-1 polymorphisms were consistent with quantile-dependent expressivity of leptin concentrations. β_FS for leptin receptor concentrations and free leptin index also increased significantly with increasing percentiles of their distributions (P_linear = 0.04 and P_linear = 8.5 × 10^-6, respectively). In conclusion, inherited genetic and shared environmental effects on leptin concentrations were quantile dependent, which likely explains male-female differences in heritability and some gene-environment interactions.

The Impact of Appetite-Regulating Neuropeptide Leptin on Alcohol Use, Alcohol Craving and Addictive Behavior: A Systematic Review of Preclinical and Clinical Data

AIMS

The appetite regulating hormone leptin, which is mainly secreted from adipose tissue, is an important regulator of food intake and modulator of reward-driven behavior. Leptin exerts its biological actions via binding to the leptin receptor, which is expressed in the hypothalamus, but also in the hippocampus, the amygdala and the substantia nigra. In the ventral tegmental area (VTA), leptin attenuates the firing rate of dopaminergic neurons that project to the Nucleus accumbens (NAc), which serves as relay to other brain areas of the "addiction network", such as the prefrontal cortex. This suggests that leptin plays a role in the processing of rewards in the context of substance use disorders such as alcohol use disorder, especially through attenuation of dopaminergic activity in the mesolimbic reward system. This supports the plausibility of leptin's potential effects in alcohol use disorder.

METHODS

We searched MEDLINE from 1990 to February 2020. All abstracts were screened for relevance and we only included publications reporting original data with a full text available in English language. Studies that did not report leptin-data, reviews or case reports/series were not included.

RESULTS

We identified a total of N=293 studies of whom a total of N=55 preclinical and clinical studies met the specified criteria. N=40 studies investigated the effects of alcohol on leptin plasma levels, N=9 studies investigated the effects of leptin on alcohol craving and N=6 studies investigated the effects of leptin on relapse and alcohol consumption.

CONCLUSIONS

In this review of preclinical and clinical data, we assess the role of leptin in alcohol use and the development and maintenance of an alcohol use disorder, alcohol craving and relapse. Integrating the existing preclinical and clinical data on leptin may reveal new and innovative targets for the treatment of substance use disorders in the future.

Dietary Melatonin Protects Against Behavioural, Metabolic, Oxidative, and Organ Morphological Changes in Mice that are Fed High-Fat, High- Sugar Diet

BACKGROUND

Metabolic syndrome is a complex pattern of disorders that occur jointly and is associated with an increased risk of cardiovascular and cerebrovascular disease. Therefore the need for more-efficient options of treatment has become imperative.

OBJECTIVE

This study examined the effect of dietary-melatonin in the management of behavioural, metabolic, antioxidant, and organ changes due to high-fat/high-sugar (HFHS) diet-induced metabolic syndrome in mice.

METHODS

Mice were randomly assigned into five groups of ten animals each. Groups were normal control [fed standard diet (SD)], HFHS control, and 3 groups of melatonin incorporated into HFHS at 2.5, 5, and 10 mg/kg of feed. Mice were fed for seven weeks, and body weight was assessed weekly. Open-field behaviours, radial-arm, and Y-maze spatial memory were scored at the end of the experimental period. Twenty-four hours after the last behavioural test, blood was taken for estimation of blood glucose levels after an overnight fast. Animals were then euthanised, and blood was taken for estimation of plasma insulin, leptin, and adiponectin levels, and serum lipid profile. The liver, kidneys, and brain were excised and processed for general histology, while homogenates of the liver and whole brain were used to assess oxidative stress parameters.

RESULTS

Results showed that dietary melatonin (compared to HFHS diet) was associated with a decrease in body weight, food intake, and novelty-induced behaviours; and an increase in spatial-working memory scores. A decrease in glucose, insulin, leptin, and malondialdehyde levels; and an increase in adiponectin levels and superoxide dismutase activity were also observed. Histomorphological/ histomorphometric examination revealed evidence of organ injury with HFHS diet, and varying degrees of amelioration with melatonin-supplemented diet.

CONCLUSION

In conclusion, dietary melatonin supplementation may have beneficial effects in the management of the metabolic syndrome.

Posttraumatic Stress Disorder, Overweight, and Obesity: A Systematic Review and Meta-analysis

Previous reports have suggested a high prevalence of overweight and obesity among individuals with posttraumatic stress disorder (PTSD). Few studies, however, systematically analyze the relationship between PTSD and body mass index (BMI). We conducted a systematic review and meta-analysis aimed at estimating the association between PTSD and BMI. Fifty-four articles were reviewed, 30 of which (with 191,948 individuals with PTSD and 418,690 trauma-exposed individuals or healthy controls) were eligible for inclusion in the meta-analysis. The pooled standard mean difference, based on a random-effects model, was 0.41 (95% confidence interval, 0.28-0.54; z = 6.26; p < .001). Statistical heterogeneity between the included studies was high (p < .001; I = 99%). Despite limitations, the findings of this systematic review and meta-analysis suggest an association between PTSD and BMI. Furthermore, longitudinal studies tentatively indicate that PTSD may lead to an increase in BMI and, as such, to the development of overweight/obesity, particularly in women. Further prospective studies and research elaborating the nature and etiology of the association are required.

Genetic susceptibility to dental caries differs between the sexes: a family-based study

Many of the factors affecting susceptibility to dental caries are likely influenced by genetics. In fact, genetics accounts for up to 65% of inter-individual variation in dental caries experience. Sex differences in dental caries experience have been widely reported, with females usually exhibiting a higher prevalence and severity of disease across all ages. The cause for this sex bias is currently uncertain, although it may be partly due to the differential effects of genetic factors between the sexes: gene-by-sex interactions. In this family based study (N = 2,663; 740 families; ages 1-93 years), we assessed dental caries via intra-oral examination and generated six indices of caries experience (DMFS, dfs, and indices of both pit-and-fissure surface caries and smooth surface caries in both primary and permanent dentitions). We used likelihood-based methods to model the variance in caries experience conditional on the expected genetic sharing among relatives in our sample. This modeling framework allowed us to test two lines of evidence for gene-by-sex interactions: (1) whether the magnitude of the cumulative effect of genes differs between the sexes, and (2) whether different genes are involved. We observed significant evidence of gene-by-sex interactions for caries experience in both the primary and permanent dentitions. In the primary dentition, the magnitude of the effect of genes was greater in males than females. In the permanent dentition, different genes may play important roles in each of the sexes. Overall, this study provides the first direct evidence that sex differences in dental caries experiences may be explained, in part, by gene-by-sex interactions.

Short duration of sleep is associated with hyperleptinemia in Taiwanese adults

BACKGROUND

Higher plasma levels of leptin have been associated with increased cardiometabolic risk. The aim of this study was to investigate the association between short duration of sleep and hyperleptinemia in Taiwanese adults.

METHODS

We examined the association between duration of sleep and hyperleptinemia in 254 men and women recruited from the physical examination center at a regional hospital in southern Taiwan. Hyperleptinemia was defined as a plasma leptin level of 8.13 ng/mL and above. Short sleep duration was defined as < 6.5 h/day. Multiple logistic regression analysis was used to assess the association between short duration of sleep and hyperleptinemia.

RESULTS

In females, short duration of sleep (< 6.5 h/day; OR = 2.15, 95% CI = 0.99-4.78), greater hip circumference (OR = 3.00, CI = 1.13-8.78), higher percent body fat (OR = 1.75, CI = 1.07-2.95), and higher white blood cell counts (OR = 1.67, CI = 1.26-2.28) were associated with an increased risk of hyperleptinemia. In males, greater body weight was significantly associated with an increased risk of hyperleptinemia (OR = 3.55, 95% CI = 1.46-10.23). There was also a trend of association (p = 0.096) between short duration of sleep and an increased risk of hyperleptinemia (OR = 4.98, 95% CI = 0.80-42.40).

CONCLUSIONS

In this study of healthy Taiwanese adults, short duration of sleep was significantly associated with hyperleptinemia in women, and the association was independent of adiposity.

Pathogenesis of the metabolic syndrome: insights from monogenic disorders

Identifying rare human metabolic disorders that result from a single-gene defect has not only enabled improved diagnostic and clinical management of such patients, but also has resulted in key biological insights into the pathophysiology of the increasingly prevalent metabolic syndrome. Insulin resistance and type 2 diabetes are linked to obesity and driven by excess caloric intake and reduced physical activity. However, key events in the causation of the metabolic syndrome are difficult to disentangle from compensatory effects and epiphenomena. This review provides an overview of three types of human monogenic disorders that result in (1) severe, non-syndromic obesity, (2) pancreatic beta cell forms of early-onset diabetes, and (3) severe insulin resistance. In these patients with single-gene defects causing their exaggerated metabolic disorder, the primary defect is known. The lessons they provide for current understanding of the molecular pathogenesis of the common metabolic syndrome are highlighted.

Significant genotype by diet (G × D) interaction effects on cardiometabolic responses to a pedigree-wide, dietary challenge in vervet monkeys (Chlorocebus aethiops sabaeus)

Nutrient composition of a diet (D) has been shown to interact with genetic predispositions (G) to affect various lipid phenotypes. Our aim in this study was to confirm G × D interaction and determine whether the interaction extends to other cardiometabolic risk factors such as glycemic measures and body weight. Subjects were vervet monkeys (Chlorocebus aethiops sabaeus; n = 309) from a multigenerational pedigreed colony initially fed with a plant-based diet, standard primate diet (18% calories from protein, 13% from fat, and 69% from carbohydrates), and subsequently challenged for 8 weeks with a diet modeled on the typical American diet (18% calories from protein, 35% from fat, and 47% from carbohydrates). Our results showed that although exposure to the challenge diet did not result in significant changes in weight, most lipid and glycemic biomarkers moved in an adverse direction (P < 0.01). Quantitative genetic analyses showed that cardiometabolic phenotypes were significantly heritable under both dietary conditions (P < 0.05), and there was significant evidence of G × D interaction for these phenotypes. We observed significant differences in the additive genetic variances for most lipid phenotypes (P < 10(-4) ), indicating that the magnitude of genetic effects varies by diet. Furthermore, genetic correlations between diets differed significantly from 1 with respect to insulin, body weight, and some lipid phenotypes (P < 0.01). This implied that distinct genetic effects are involved in the regulation of these phenotypes under the two dietary conditions. These G × D effects confirm and extend previous observations in baboons (Papio sp.) and suggest that mimicking the typical human nutritional environment can reveal genetic influences that might not be observed in animals consuming standard, plant-based diets.

Genetic variation within a metabolic motif in the chromogranin a promoter: pleiotropic influence on cardiometabolic risk traits in twins

BACKGROUND

The cardiometabolic syndrome comprised of multiple correlated traits, but its origin is incompletely understood. Chromogranin A (CHGA) is required for formation of the catecholamine secretory pathway in sympathochromaffin cells. In twin pair studies, we found that CHGA traits aggregated with body mass index (BMI), as well as its biochemical determinant leptin. METHODS Here we used the twin method to probe the role of heredity in generating such risk traits, and then investigated the role of risk-trait-associated CHGA promoter genetic variation in transfected chromaffin cells. Trait heritability (h(2)) and shared genetic determination among traits (pleiotropy, genetic covariance, ρ(G)) were estimated by variance components in twin pairs.

RESULTS

CHGA, BMI, and leptin each displayed substantial h(2), and the traits also aggregated with several features of the metabolic syndrome (e.g., insulin resistance, blood pressure (BP), hypertension, catecholamines, and C-reactive protein (CRP)). Twin studies demonstrated genetic covariance (pleiotropy, ρ(G)) for CHGA, BMI, and leptin with other metabolic traits (insulin resistance, BP, and CRP). We therefore investigated the CHGA locus for mechanisms of codetermination with such metabolic traits. A common functional variant in the human CHGA promoter (G-462A, rs9658634, minor allele frequency ~21%) was associated with leptin and CRP secretion, as well as BMI, especially in women; marker-on-trait effects on BMI were replicated across twin populations on two continents. In CHGA promoter/luciferase reporter plasmids transfected into chromaffin cells, G-462A alleles differed markedly in reporter expression. The G-462A variant disrupted predicted transcriptional control by a PPARγ/RXRα motif and costimulation by PPARγ/RXRα and their cognate ligands, differentially activated the two alleles. During chromatin immunoprecipitation, endogenous PPARγ bound the motif.

CONCLUSIONS

Multiple features of the metabolic syndrome are thus under joint (pleiotropic) genetic determination, with CHGA as one such contributory locus: a common polymorphism in the promoter (G-462A) of CHGA predicts such heritable metabolic traits as BMI and leptin. CHGA promoter variant G-462A was not only associated with such metabolic traits but also disrupted a PPARγ/RXRα motif and responded differentially to characteristic trans-activators of that motif. The results suggest novel links between the catecholaminergic system and risk for the metabolic syndrome as well as systemic hypertension.

Nutrition and the aging male

Numerous studies have now found that good nutrition coupled with exercise are key factors to aging successfully. In addition, it is now clear that men who drink 2 shots of alcohol (red wine or other) do better. Women are limited to only 1 drink a day. This article examines some key nutritional factors involved in successful aging and highlights different needs between men and women.

Sex-specific genetic architecture of human fatness in Chinese: the SAPPHIRe Study

To dissect the genetic architecture of sexual dimorphism in obesity-related traits, we evaluated the sex-genotype interaction, sex-specific heritability and genome-wide linkages for seven measurements related to obesity. A total of 1,365 non-diabetic Chinese subjects from the family study of the Stanford Asia-Pacific Program of Hypertension and Insulin Resistance were used to search for quantitative trait loci (QTLs) responsible for the obesity-related traits. Pleiotropy and co-incidence effects from the QTLs were also examined using the bivariate linkage approach. We found that sex-specific differences in heritability and the genotype-sex interaction effects were substantially significant for most of these traits. Several QTLs with strong linkage evidence were identified after incorporating genotype by sex (G × S) interactions into the linkage mapping, including one QTL for hip circumference [maximum LOD score (MLS) = 4.22, empirical p = 0.000033] and two QTLs: for BMI on chromosome 12q with MLS 3.37 (empirical p = 0.0043) and 3.10 (empirical p = 0.0054). Sex-specific analyses demonstrated that these linkage signals all resulted from females rather than males. Most of these QTLs for obesity-related traits replicated the findings in other ethnic groups. Bivariate linkage analyses showed several obesity traits were influenced by a common set of QTLs. All regions with linkage signals were observed in one gender, but not in the whole sample, suggesting the genetic architecture of obesity-related traits does differ by gender. These findings are useful for further identification of the liability genes for these phenotypes through candidate genes or genome-wide association analysis.

Leptinemia and its association with stroke and coronary heart disease in the Jackson Heart Study

BACKGROUND

To examine the association of increased plasma leptin concentration with prevalent stroke and coronary heart disease (CHD) and to examine the genetic contributions of leptin to this association in the Jackson Heart Study cohort.

METHODS

A cohort of 5170 participants aged 21-84 years who underwent Exam I during 2000-2004 was analysed. Odds ratios (OR) of prevalent stroke and CHD were calculated using a logistic regression model adjusted for age, smoking, hypertension and waist circumference (WC). Variance component analysis was used to partition the phenotypic variance of leptin into the polygenic and environmental components.

RESULTS

The prevalence of stroke and CHD was 4.04% and 5.85% in women, and 4.88% and 8.92% in men, respectively. Body mass index (BMI) and WC were highly correlated with leptin both in men and women. In multivariate analysis stratified by sex, leptin was significantly associated with stroke (OR = 1.97, 95% CI = 1.21-3.21) in women after adjustment for age, smoking, systolic blood pressure, BMI and WC (P = 0.0079). No significant association was observed in men. Heritability of sex-, age-adjusted log-transformed leptin for this cohort was 38.0% and 37.8% after further adjustment for WC and hypertension, respectively. In addition, a sibship effect was also found to be significant and explained 12.2% of the total variance of leptin (P = 0.007).

CONCLUSION

There is a significant association of leptin with stroke in women, which is partly influenced by the genetic factor. The findings suggest that leptinemia is an independent risk factor for stroke in African American women.

States of serum leptin and insulin in children with epilepsy: risk predictors of weight gain

BACKGROUND AND OBJECTIVES

Weight gain is an adverse metabolic effect in some children with epilepsy. The studies done to detect the effect of antiepileptic drugs and weight homeostatic hormones, insulin and leptin, were limited and controversial.

MATERIALS AND METHODS

We evaluated the serum leptin and insulin as predictors of weight gain in children receiving long-term treatment with valproate (VPA), carbamazepine (CBZ), lamotrigine (LTG). This study included 90 patients (treated: 70; untreated: 20). Serum lipid profile, insulin and leptin were measured.

RESULTS

BMI, serum leptin and insulin were significantly elevated in VPA compared with controls, untreated patients and those treated with CBZ, LTG and combined therapy with LTG. Girls on VPA had higher BMI and leptin levels than boys. With VPA, serum insulin was correlated with BMI (r=0.625, p<0.01), leptin (r=0.823, p<0.001), treatment duration (r=0.775, p<0.01) and VPA dose (r=0.975, p<0.0001). Serum leptin was correlated with age (r=0.980, p<0.0001), BMI (r=0.704, p<0.01), serum insulin (r=0.823, p<0.001), LDL-c (r=0.630, p<0.01), HDL-c (r=-0.880, p<0.001), treatment duration (r=0.770, p<0.01) and VPA dose (r=0.970, p<0.001). BMI is correlated with serum insulin, leptin, LDL-c (r=0.835, p<0.001) and HDL-c (r=-0.955, p<0.0001).

CONCLUSION

Hyperinsulinemia and hyperleptinemia are common with VPA and marked among epileptic children who gained weight suggesting states of insulin and leptin resistances. These alterations were not demonstrated with CBZ or LTG. The relationship between VPA, leptin and weight seems to be gender specific. Serum leptin may serve as a sensitive parameter for weight gain and reduction with intervention programs during follow-up of girls with epilepsy.

Leptin is associated with blood pressure and hypertension in women from the National Heart, Lung, and Blood Institute Family Heart Study

Leptin is a key neuroendocrine hormone regulating food intake, metabolism, and fat accumulation, and it may also affect blood pressure and contribute to hypertension through sympathetic activation in the vasculature or at the renal level. Although previous studies have shown that the distribution of leptin is significantly different between males and females, as is the risk of hypertension between males and females, results regarding the role of leptin in the gender-specific regulation of blood pressure are controversial. Thus, we performed family-based association analyses in the National Heart, Lung, and Blood Institute Family Heart Study to test the hypothesis that LEPTIN gene variants and the plasma leptin level influence variability in blood pressure and the risk of hypertension differently by gender. We identified significant associations between LEPTIN single nucleotide polymorphisms with blood pressure and hypertension, but in postmenopausal women only. We also identified significant associations between plasma leptin levels and both blood pressure and hypertension in women. The current study supports a role for LEPTIN and plasma leptin levels in blood pressure regulation in women. It also provides insight into the gender differences in hypertension, as well as the differential distribution and activity of leptin in men and women.

Posttraumatic stress disorder and obesity: evidence for a risk association

BACKGROUND

There is evidence from cross-sectional studies that posttraumatic stress disorder (PTSD) may be associated with obesity. The aim of this study was to examine prospective longitudinal associations between PTSD and obesity in a community sample.

METHODS

A prospective, longitudinal, epidemiologic study with a representative community sample of adolescents and young adults (N=3021, aged 14-24 years at baseline) was conducted in Munich, Germany. Participants were assessed four times between 1995 and 2005 with the Munich-Composite International Diagnostic Interview. Associations between obesity (BMI > or =30) and DSM-IV PTSD were evaluated in 2007, using cross-sectional and prospective data during young adulthood.

RESULTS

The cumulative lifetime incidence of obesity in the sample at 10-year follow-up during young adulthood was 4.3% (women, 4.6%; men, 4.0%). Among women but not among men, obesity was associated with a lifetime history of PTSD (OR=3.8; 95% CI=1.4, 10.7) in the cross-sectional analyses. Prospective longitudinal analyses from 4-year follow-up to 10-year follow-up confirmed that obesity was predicted by antecedent subthreshold and full PTSD (OR=3.0; 95% CI=1.3, 7.0) among women but not among men. There were no associations between other mental disorders and obesity in the prospective analyses.

CONCLUSIONS

The findings indicate a possible causal pathway for the onset of obesity in females with PTSD symptoms. These findings need replication with regard to the pathophysiologic and behavioral mechanisms underlying this relationship.

Sex-specific genetic effects influence variation in body composition

AIMS/HYPOTHESIS

Despite well-known sex differences in body composition it is not known whether sex-specific genetic or environmental effects contribute to these differences.

METHODS

We assessed body composition in 2,506 individuals, from a young Dutch genetic isolate participating in the Erasmus Rucphen Family study, by dual-energy X-ray absorptiometry and anthropometry. We used variance decomposition procedures to partition variation of body composition into genetic and environmental components common to both sexes and to men and women separately and calculated the correlation between genetic components in men and women.

RESULTS

After accounting for age, sex and inbreeding, heritability ranged from 0.39 for fat mass index to 0.84 for height. We found sex-specific genetic effects for fat percentage (fat%), lean mass, lean mass index (LMI) and fat distribution, but not for BMI and height. Genetic correlations between sexes were significantly different from 1 for fat%, lean mass, LMI, android fat, android:gynoid fat ratio and WHR, indicating that there are sex-specific genes contributing to variation of these traits. Genetic variance was significantly higher in women for the waist, hip and thigh circumference and WHR, implying that genes account for more variance of fat distribution in women than in men. Environmental variance was significantly higher in men for the android:gynoid fat ratio.

CONCLUSIONS/INTERPRETATION

Sex-specific genetic effects underlie sexual dimorphism in several body composition traits. The findings are relevant for studies on the relationship of body composition with common diseases like cardiovascular disease and type 2 diabetes and for genetic association studies.

The vascular risk associations with migraine: relation to migraine susceptibility and progression

Migraine is a common disorder in which changes in cortical excitability, neuroinflammation and dysfunction of the vascular wall contribute to its pathophysiology. Repeated attacks of migraine over prolonged periods result in inflammatory arteriopathy of the cranial vessels. Several studies indicate that migraine is associated with special pattern of inflammatory markers and some adverse vascular risk factors including: increased levels of CRP, ILs, TNF-alpha and adhesion molecules which are markers of systemic inflammation, oxidative stress and thrombosis, increased body weight, high blood pressure, hypercholesterolemia, impaired insulin sensitivity, high homocysteine levels, stroke and coronary heart disease. Such comorbidities are not explained by bias but indicate possible shared underlying pathogenic mechanisms. Recent studies have shown involvement of cranial as well as peripheral vascular dysfunction with migraine indicating that migraine may be a local manifestation of a systemic disease rather than a primary brain phenomenon. The associated inflammatory process of migraine together with the associated adverse medical comorbidities exposes patients to endothelial vascular wall injury which further increases migraine susceptibility and progression as well as increases the risk for atherogenesis. The knowledge that migraine is a risk for vascular diseases raises important clinical implications, recommendations and future perspectives in migraine treatment and prevention.

Longitudinal changes in obesity and body mass index among adult survivors of childhood acute lymphoblastic leukemia: a report from the Childhood Cancer Survivor Study

PURPOSE

We examined the rate of increase in the body mass index (BMI; kg/m(2)) after final height attainment in survivors of acute lymphoblastic leukemia (ALL) and a noncancer comparison group.

METHODS

Childhood Cancer Survivor Study (CCSS) is a retrospectively ascertained cohort study that prospectively tracks the health status of adults who were diagnosed with childhood cancer between 1970 and 1986 and a comparison group of siblings. Changes in BMI from baseline enrollment to time of completion of follow-up (mean interval, 7.8 years) were calculated for 1,451 ALL survivors (mean age, 32.3 years at follow-up) and 2,167 siblings of childhood cancer survivors (mean age, 35.9 years).

RESULTS

The mean BMI of the CCSS sibling comparison group increased with age (women, 0.25 units/yr, 95% CI, 0.22 to 0.28 units; men, 0.23 units/yr, 95% CI, 0.20 to 0.25 units). Compared with CCSS siblings, ALL survivors who were treated with cranial radiation therapy (CRT) had a significantly greater increase in BMI (women, 0.41 units/yr, 95% CI, 0.37 to 0.45 units; men, 0.29 units/yr; 95% CI, 0.26 to 0.32 units). The rate of BMI increase was not significantly increased for ALL survivors who were treated with chemotherapy alone. Younger age at CRT exposure significantly modified risk.

CONCLUSION

CRT used in the treatment of childhood ALL is associated with a greater rate of increasing BMI, particularly among women treated with CRT during the first decade of life. Health care professionals should be aware of this risk and interventions to reduce or manage weight gain are essential in this high-risk population.

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.

Genotype x adiposity interaction linkage analyses reveal a locus on chromosome 1 for lipoprotein-associated phospholipase A2, a marker of inflammation and oxidative stress

Because obesity leads to a state of chronic, low-grade inflammation and oxidative stress, we hypothesized that the contribution of genes to variation in a biomarker of these two processes may be influenced by the degree of adiposity. We tested this hypothesis using samples from the San Antonio Family Heart Study that were assayed for activity of lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), a marker of inflammation and oxidative stress. Using an approach to model discrete genotypexenvironment (GxE) interaction, we assigned individuals to one of two discrete diagnostic states (or "adiposity environments"): nonobese or obese, according to criteria suggested by the World Health Organization. We found a genomewide maximum LOD of 3.39 at 153 cM on chromosome 1 for Lp-PLA(2). Significant GxE interaction for Lp-PLA(2) at the genomewide maximum (P=1.16 x 10(-4)) was also found. Microarray gene-expression data were analyzed within the 1-LOD interval of the linkage signal on chromosome 1. We found two transcripts--namely, for Fc gamma receptor IIA and heat-shock protein (70 kDa)--that were significantly associated with Lp-PLA(2) (P<.001 for both) and showed evidence of cis-regulation with nominal LOD scores of 2.75 and 13.82, respectively. It would seem that there is a significant genetic response to the adiposity environment in this marker of inflammation and oxidative stress. Additionally, we conclude that GxE interaction analyses can improve our ability to identify and localize quantitative-trait loci.

Associations of leptin gene polymorphisms with production traits in pigs

The associations of leptin (LEP) gene polymorphisms C798T, T2411C, T3266G and T3469C with production traits were investigated in a F2 pig population produced by divergent crosses. The statistical model included genotype, sex, batch and genotype by sex interaction as fixed effects and sire as random effect. Polymorphism C798T was associated with variation in total teat number (p < 0.02) and left teat number (p < 0.03), and polymorphism T3469C was associated with weight at 21 days (p < 0.03), 42 days (p < 0.05), 63 days (p < 0.02) and 77 days of age (p < 0.04) as well as feed intake (p < 0.01), average daily gain (p < 0.01), feed conversion (p < 0.01), bacon depth (p < 0.03) and slaughter weight (p < 0.03). Phenotypic associations were also performed by combining T3469C and C798T genotypes. Interaction between C798T genotypes and sex was observed for some traits. LEP genotypes had significant influence on performance traits, and can be considered as potential genetic markers for selection. However, these results have to be validated in commercial herds.

Genetic and environmental influences on bone mineral density in pre- and post-menopausal women

Genetic factors influencing acquisition of peak bone mass account for a substantial proportion of the variation in bone mineral density (BMD), although the extent to which genes also contribute to variation in bone loss is debatable. Few prospective studies of related individuals have been carried out to address this issue. To gain insights into the nature of the genetic factors contributing to variation in BMD, we studied 570 women from large Amish families. We evaluated and compared the genetic contributions to BMD in pre- and post-menopausal women, with the rationale that genetic variation in pre-menopausal women is due primarily to genetic determinants of peak bone mass, while genetic variation in post-menopausal women is due to the combined genetic effects of peak bone mass and bone loss. Bone mineral density was measured at one point in time at the hip and spine by dual energy X-ray absorptiometry (DXA). We used variance decomposition procedures to partition variation in BMD into genetic and environmental effects common to both groups and to pre- and post-menopausal women separately. Total variation in BMD was higher in post- compared to pre-menopausal women. Genes accounted for 58-88% of the total variation in BMD in pre-menopausal women compared to 37-54% of the total variation in post-menopausal women. In absolute terms, however, the genetic variance was approximately similar between the two groups because the environmental variance was 3 1/2- to 4-fold larger in the post-menopausal group. The genetic correlation in total hip BMD was 0.81 between pre- and post-menopausal women and differed significantly from one, consistent with the presence of at least some non-overlapping genetic effects in the two groups for BMD at this site. Overall, these analyses suggest that many, but not all, of the genetic factors influencing variation in BMD are common to both pre- and post-menopausal women.

Genetics of leptin and obesity: a HuGE review

Leptin is an important regulator of the mass of adipose tissue and of body weight; it operates by inhibiting food intake and stimulating energy expenditure. Some polymorphic genes involved in the regulation of leptin-the leptin gene (LEP A19G), the leptin receptor gene (LEPR Q223R, K109R, and K656N), and the peroxisome proliferator-activated receptor-gamma gene (PPARG P12A and C161T)--have been investigated as possible factors associated with obesity. Allelic frequencies of these polymorphisms show ethnic variation. The authors performed a meta-analysis of the available data on the association between these polymorphisms and obesity based on case-control studies. Odds ratios and 95% confidence intervals for obesity associated with leptin polymorphisms were calculated by using both fixed- and random-effects models. Results suggest no evidence of association between the genes under study and obesity. The lack of association could be due to the complex pathogenesis of obesity, which involves a number of genetic and environmental factors. Large studies including testing of multiple genes in both obese and lean subjects, with epidemiologic data on dietary habits in different ethnic groups, are necessary to better understand the role of leptin in regulating weight in human populations.

Assessment of sex-specific genetic and environmental effects on bone mineral density

Although it is widely accepted that genes contribute significantly to the variation in bone mineral density (BMD), the nature of the genetic contribution is poorly defined. There are large gender differences in BMD, although whether sex-specific genetic effects influencing variation in BMD contribute to these differences is not known. To address this issue, we studied 929 subjects from large families participating in the Amish Family Osteoporosis Study. Bone mineral density was measured at the hip and spine by dual energy X-ray absorptiometry (DXA). We used variance decomposition procedures to partition variation in BMD into genetic and environmental effects common to both sexes and to men and women separately. After accounting for covariate effects, the heritability of BMD ranged from 0.63 to 0.72 in men and 0.80 to 0.87 in women. The residual environmental variance in BMD at the spine, but not hip, was significantly higher in men than in women (P < 0.05), reflecting a greater variance in BMD due to unexplained non-genetic factors in men. In contrast, there were no significant differences between men and women in the magnitude of the genetic variance in BMD, nor did the genetic correlation in BMD between men and women differ significantly from one. Overall, these analyses do not provide evidence for sex-specific genetic effects, suggesting that many of the genes influencing variation in BMD should be detectable in both men and women.

Comparative analysis of plasma leptin levels in both genders of patients with essential hypertension and healthy subjects

While pathogenesis of hypertension is not clearly deciphered yet, increase in body weight, most of the time, is associated with hypertension. There are reports indicating that leptin, product of the Ob gene mainly synthesized in adipocytes, may have role(s) in hypertension, but contribution of the gender is rather contradictive. In the present study, plasma leptin levels in patients of both genders with hypertension and normotensive controls were measured and the relationship between plasma leptin levels and BMI were evaluated in both sexes. Total of 62 patients (31 M/31 F) diagnosed with essential hypertension who were not under any antihypertensive medication were admitted into the study. The control group was composed of 56 (25 M/31 F) age-, BMI- and sex-matched healthy normotensive volunteers. Plasma leptin levels were determined by a commercial ELISA kit. Plasma leptin and leptin/BMI levels (Mean +/- SEM) of women (n:62) were significantly higher than men (n:56) (20.10 +/- 1.47 ng/ml versus 4.72 +/- 0.50 ng/ml; p < 0.0001). Plasma leptin and leptin/BMI levels of patients of both genders with hypertension were significantly higher than in normotensive subjects (p < 0.05). Leptin and leptin/BMI levels in obese hypertensives were higher than obese normotensives (p < 0.05). Obese hypertensive women had higher leptin and leptin/BMI levels than obese normotensive women (p < 0.05). In conclusion, these results support the hypothesis that a possible link exists between leptin and hypertension. Further studies are needed to clarify how increased levels of leptin affects the pathophysiology of hypertension.

Genetics of leptin expression in baboons

OBJECTIVE

Leptin gene expression is higher in females than in males, and is regulated by many factors including energy intake and insulin, but little is known about the inheritance of leptin gene expression. We have investigated leptin (LEP) gene express-ion, to determine whether it is heritable, and whether the difference in LEP expression between males and females has a genetic component.

STUDY POPULATION

A total of 319 baboons (Papio hamadryas) (220 females, 99 males) from a captive, pedigreed colony.

MEASUREMENTS AND METHODS

We cloned a baboon LEP cDNA, and quantified LEP mRNA expression in baboon omental adipose tissue using a ribonuclease protection assay. In addition, we assayed circulating leptin levels, adipocyte cell volume, and weight. We used maximum likelihood-based variance decomposition methods to determine the genetic architecture of LEP levels, including testing for genotype-by-sex interaction.

RESULTS

Omental LEP mRNA expression was significantly and positively correlated with weight and adipocyte cell volume in baboons. Both mRNA and plasma levels of leptin were higher in females than in males, and both measures were heritable. The results of our genetic analysis show that there was a genotype-by-sex interaction in the levels of plasma leptin, but not in omental LEP mRNA.

CONCLUSIONS

As in humans, baboon leptin mRNA and protein levels are expressed at a higher level in females than in males. We detected evidence that the plasma levels were affected by genes that are differentially expressed in males and females, while the omental mRNA levels were not. This finding suggests that the genes that differentially regulate plasma leptin levels between males and females may exert their effects on post-transcriptional processes.

A quantitative trait locus on chromosome 22 for serum leptin levels adjusted for serum testosterone

OBJECTIVE

Studies have reported the existence of marked sexual dimorphism in serum leptin levels in humans with women having approximately two to three times the levels of men. We have shown that this sexual dimorphism has a strong genetic component arising from a genotype by sex interaction, but adjusting leptin levels for testosterone eliminates this interaction. Because interactions such as genotype x sex can confound the detection of quantitative trait loci (QTLs), we wanted to determine if there are QTLs associated with the expression of leptin adjusted for testosterone.

RESEARCH METHODS AND PROCEDURES

We performed a genome-wide scan using multipoint linkage analysis and implemented a general pedigree-based variance-component approach to identify genes with measurable effects on variation in leptin levels independent of testosterone in 318 Mexican Americans from the San Antonio Family Heart Study.

RESULTS

We detected significant evidence of linkage (log of the odds ratio = 3.44) for a QTL on chromosome 22.

DISCUSSION

Given these results, we hypothesize that a QTL on chromosome 22 may influence the level of leptin adjusted for testosterone.

A major predisposition locus for severe obesity, at 4p15-p14

Although the predisposition to morbid obesity is heritable, the identities of the disease-causing genes are largely unknown. Therefore, we have conducted a genomewide search with 628 markers, using multigenerational Utah pedigrees to identify genes involved in predisposition to obesity. In the genomewide search, we identified a highly significant linkage to high body-mass index in female patients, at D4S2632, with a multipoint heterogeneity LOD (HLOD) score of 6.1 and a nonparametric linkage (NPL) score of 5.3. To further delineate the linkage, we increased both the marker density around D4S2632 and the size of our pedigree data set. As a result, the linkage evidence increased to a multipoint HLOD score of 9.2 (at D4S3350) and an NPL score of 11.3. Evidence from almost half of the families in this analysis support this linkage, and therefore the gene in this region might account for a significant percentage of the genetic predisposition to severe obesity in females. However, further studies are necessary to clarify the effect that this gene has in males and in the general population.