Sequence variants of the POMC gene and their associations with body composition in children

Co-occurrence of a maternally inherited DNMT3A duplication and a paternally inherited pathogenic variant in EZH2 in a child with growth retardation and severe short stature: atypical Weaver syndrome or evidence of a DNMT3A dosage effect?

Overgrowth syndromes are a clinically heterogeneous group of disorders characterized by localized or generalized tissue overgrowth and varying degrees of developmental and intellectual disability. An expanding list of genes associated with overgrowth syndromes include the histone methyltransferase genes EZH2 and NSD1, which cause Weaver and Sotos syndrome, respectively, and the DNA methyltransferase (DNMT3A) gene that results in Tatton-Brown–Rahman syndrome (TBRS). Here, we describe a 5-year-old female with a paternally inherited pathogenic mutation in EZH2 (c.2050C>T, p.Arg684Cys) and a maternally inherited 505-kb duplication of uncertain significance at 2p23.3 (encompassing five genes, including DNMT3A) who presented with intrauterine growth restriction, slow postnatal growth, short stature, hypotonia, developmental delay, and neuroblastoma diagnosed at the age of 8 mo. Her father had tall stature, dysmorphic facial features, and intellectual disability consistent with Weaver syndrome, whereas her mother had short stature, cognitive delays, and chronic nonprogressive leukocytosis. It has been previously shown that EZH2 directly controls DNA methylation through physical association with DNMTs, including DNMT3A, with concomitant H3K27 methylation and CpG promoter methylation leading to repression of EZH2 target genes. Interestingly, NSD1 is involved in H3K36 methylation, a mark associated with transcriptional activation, and exhibits exquisite dosage sensitivity leading to overgrowth when deleted and severe undergrowth when duplicated in vivo. Although there is currently no evidence of dosage effects for DNMT3A, the co-occurrence of a duplication involving this gene and a pathogenic alteration in EZH2 in a patient with severe undergrowth is suggestive of a similar paradigm and further study is warranted.

Association of IL-6 and CRP gene polymorphisms with obesity and metabolic disorders in children and adolescents

Activation of adipose tissue inflammation is associated with obesity caused by lipid accumulation in adipocytes. Through this activation, proinflammatory cytokines, such as Interleukin-6 (IL-6) and C-reactive protein (CRP) seem to influence metabolic disorders. The present study evaluated whether polymorphisms in the CRP (rs1205) and IL-6 (rs1800795, rs2069845) genes are associated with the development of metabolic disorders in children and adolescents. A cross-sectional study was performed, consisting of 470 students from the municipality of Santa Cruz do Sul, Brazil, aged 7-17 years. Body mass index (BMI) was classified according to overweight and obesity. Genotyping was performed by real-time Polymerase Chain Reaction (PCR). Anthropometric characteristics, biochemical markers, immunological markers and blood pressure were assessed. Descriptive statistics, chi-square and logistic regression were used for the analyses. No association was detected between the rs1800795 polymorphism and the assessed variables. Individuals with the risk genotype in the rs1205 gene were associated with the risk of developing hypercholesterolemia (OR 2.79; CI 1.40, 5.57; p = 0.003). Carriers of the risk genotype in the rs2069845 gene are associated with the risk of developing obesity (OR 3.07; CI 1.08, 8.72; p = 0.03). The polymorphism rs2069845 was associated with obesity and rs1205 was associated with the risk of developing hypercholesterolemia in Brazilian schoolchildren.

The IL-6 Gene G-174C Polymorphism Related to Health Indices in Greek Primary School Children

Interleukin-6 (IL-6) is a pleiotropic cytokine expressed in many tissues. A polymorphism in the IL-6 gene, associated with differences in IL-6 transcription rate, has been recently described. Subjects with the -174GG genotype are prone to lipid abnormalities. We investigated the effect of the G-174C IL-6 polymorphism on health indices and lipid values of 184 Greek primary school children. The genotype distribution of the polymorphism was 37.5% for GG and 52.2% and 10.3% for GC and CC, respectively. No differences were observed between genotype distribution and gender (p = 0.37). Boys homozygous for the G allele showed higher triglyceride levels than boys carrying the C allele (86 +/- 28 vs. 74 +/- 20 mg/dL, p = 0.02) and lower mid-upper arm muscle circumference (17.46 +/- 1.86 vs. 18.91 +/- 2.53 cm, p = 0.013). In addition, girls homozygous for the G allele had higher values for suprailiac skinfolds compared with those bearing the C allele (21.28 +/- 12.56 vs. 17.09 +/- 13.36 mm, p = 0.06). These findings were confirmed by multiple linear regression analysis, after controlling for age, sex, BMI, energy and total fat intake, and weekly physical activity. From the results of the present study, we concluded that individuals homozygous for G allele on the IL-6 gene have higher values in some parameters associated with obesity.

Admixture mapping of obesity-related traits in African Americans: the Atherosclerosis Risk in Communities (ARIC) Study

Obesity is an important cause of morbidity and mortality worldwide. In the United States, the prevalence of obesity is higher in African Americans than whites, even after adjustment for socioeconomic status (SES). This leads to the hypothesis that differences in genetic background may contribute to racial/ethnic differences in obesity-related traits. We tested this hypothesis by conducting a genome-wide admixture mapping scan using 1,350 ancestry-informative single-nucleotide polymorphisms (SNPs) in 3,531 self-identified blacks from the Atherosclerosis Risk in Communities (ARIC) study. We used these markers to estimate the overall proportions of European ancestry (PEAs) for each individual and then scanned for the association between PEA and obesity-related traits (both continuous and dichotomous) at each locus. The median (interquartile range) PEA was 0.151 (0.115). PEA was inversely correlated with continuous BMI, weight, and subscapular skinfold thickness, even after adjusting for socioeconomic factors. In contrast, PEA was positively correlated with BMI-adjusted waist circumference. Using admixture mapping on dichotomized traits, we identified a locus on 2p23.3 to be suggestively associated with BMI (locus-specific lod = 4.11) and weight (locus-specific lod = 4.07). After adjusting for global PEA, each additional copy of a European ancestral allele at the 2p23.3 peak was associated with a BMI decrease of approximately 0.92 kg/m(2) (P = 2.9 x 10(-5)). Further mapping in this region on chromosome 2 may be able to uncover causative variants underlying obesity, which may offer insights into the control of energy homeostasis.

The perceived onset of dieting and loss of control eating behaviors in overweight children

OBJECTIVE

The current study investigated the self-reported temporal relationships of dieting, binge eating, and overweight in childhood.

METHOD

One hundred five non-treatment-seeking overweight children ages 6-13 years were interviewed with the children's Eating Disorder Examination (ChEDE) and queried regarding dieting, loss of control (LOC) eating, and overweight history. Questionnaires of depressive symptoms, trait anxiety, and parent-reported problems were completed.

RESULTS

Sixty percent of the children reported having attempted at least one diet. These children had higher ChEDE scores (global, p < .001), greater body mass index (BMI) and body fat mass (p < or = .001), and a trend towards an earlier reported age of overweight onset (p = .06) compared with children who had never dieted. The 29.5% of children who reported LOC eating had significantly higher ChEDE scores (global, p < .001), ineffectiveness, negative self-esteem, and externalizing scores (all ps < .05) compared with those who had never experienced LOC eating. Most children reported becoming overweight before either dieting (79.4%) or experiencing LOC eating (63.6%). Among the 25.7% reporting both dieting and LOC eating, two thirds reported LOC eating before dieting. Participants who reported dieting before overweight had higher negative mood scores (p < .01). Children reporting dieting before LOC eating had higher ChEDE Weight Concern (p < .01) and global (p < .05) scores.

DISCUSSION

For overweight, non-treatment-seeking children, both dieting and LOC eating are common. Dieting precedes the development of LOC eating only one third of the time, but is associated with greater disordered eating cognitions. The relationship between childhood-onset dieting and LOC eating in overweight children requires further investigation to determine the causal pathways for the subsequent development of eating disorders.

Co-occurrence of two partially inactivating polymorphisms of MC3R is associated with pediatric-onset obesity

Both human linkage studies and MC3R knockout mouse models suggest that the MC3R may play an important role in energy homeostasis. Here we show that among 355 overweight and nonoverweight children, 8.2% were double homozygous for a pair of missense MC3R sequence variants (Thr6Lys and Val81Ile). Such children were significantly heavier (BMI and BMI SD score: P < 0.0001), had more body fat (body fat mass and percentage fat mass: P < 0.001), and had greater plasma leptin (P < 0.0001) and insulin concentrations (P < 0.001) and greater insulin resistance (P < 0.008) than wild-type or heterozygous children. Both sequence variants were more common in African-American than Caucasian children. In vitro expression studies found the double mutant MC3R was partially inactive, with significantly fewer receptor binding sites, decreased signal transduction, and less protein expression. We conclude that diminished MC3R expression in this double MC3R variant may be a predisposing factor for excessive body weight gain in children.

Pharmacogenetics of antipsychotic-induced weight gain

RATIONALE

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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