SUMMARY Brain-derived neurotrophic factor (BDNF) plays a key role in energy balance. In population studies, single nucleotide polymorphisms (SNPs) of the BDNF locus have been linked with obesity, but the mechanism by which these variants cause weight gain is unknown. Here, we examined human hypothalamic BDNF expression in association with 44 BDNF SNPs. We discovered that the minor C allele of rs12291063 is associated with lower human ventromedial hypothalamic BDNF expression (p<0.001) and greater adiposity in both adult and pediatric cohorts (p’s<0.05). We further demonstrated that the major T allele for rs12291063 possesses a binding capacity for the transcriptional regulator, heterogeneous nuclear ribonucleoprotein D0B, knockdown of which disrupts transactivation by the T allele. Binding and transactivation functions are both disrupted by substituting C for T. These findings provide a rationale for BDNF augmentation as a targeted treatment for obesity in individuals who have the rs12291063 CC genotype.

BackgroundIn rodents, hypothalamic brain-derived neurotrophic factor (BDNF) expression appears to be regulated by melanocortin-4 receptor (MC4R) activity. The impact of MC4R genetic variation on circulating BDNF in humans is unknown.ObjectiveTo compare BDNF concentrations of subjects with loss-of-function (LOF) and gain-of-function (GOF) MC4R variants to those of controls with common sequence MC4R.MethodsCirculating BDNF was measured in two cohorts with known MC4R sequence: 148 subjects of Pima Indian heritage ([mean±SD]: age 15.7±6.5y, BMI-Z 1.63±1.03), and 69 subjects of Hispanic heritage (10.8±3.6y, BMI-Z 1.57±1.07). MC4R variants were characterized in vitro by cell surface expression, receptor binding, and cAMP response after agonist administration. BDNF single nucleotide polymorphisms (SNPs) rs12291186, rs6265, and rs7124442 were also genotyped.ResultsIn the Pima cohort, no significant differences in serum BDNF was observed for 43 LOF-subjects versus 65 LOF-matched controls [age-, sex-, and BMI-matched] (P=0.29), or 20 GOF-subjects versus 20 GOF-matched controls (P=0.40). Serum BDNF was significantly associated with genotype for BDNF rs12291186 (P=0.006) and rs6265 (P=0.009), but not rs7124442 (P=0.99); BDNF SNPs did not interact with MC4R status to predict serum BDNF. In the Hispanic cohort, plasma BDNF was not significantly different among 21 LOF-subjects, 20 GOF-subjects, and 28 controls (P=0.79); plasma BDNF was not predicted by BDNF genotype or BDNF-x-MC4R genotype interaction.ConclusionsCirculating BDNF concentrations were not significantly associated with MC4R functional status, suggesting that peripheral BDNF does not directly reflect hypothalamic BDNF secretion and/or that MC4R signaling is not a significant regulator of the bulk of BDNF expression in humans.

Background/Objectives:The forkhead factor Foxa3 is involved in the early transcriptional events controlling adipocyte differentiation and plays a critical function in fat depot expansion in response to high-fat diet regimens and during aging in mice. No studies to date have assessed the potential associations of genetic variants in FOXA3 with human metabolic outcomes.Subjects/Methods:In this study, we sequenced FOXA3 in 392 children, adolescents and young adults selected from several cohorts of subjects recruited at the National Institute of Child Health and Human Development of the National Institutes of Health based on the availability of dual-energy X-ray absorptiometry data, magnetic resonance imaging scans and DNA samples. We assessed the association between variants present in these subjects and metabolic traits and performed in vitro functional analysis of two novel FOXA3 missense mutations identified.Results:Our analysis identified 14 novel variants and showed that the common single-nucleotide polymorphism (SNP) rs28666870 is significantly associated with greater body mass index, lean body mass and appendicular lean mass (P values 0.009, 0.010 and 0.013 respectively). In vitro functional studies showed increased adipogenic function for the FOXA3 missense mutations c.185C>T (p.Ser62Leu) and c.731C>T (p.Ala244Val) compared with FOXA3-WT.Conclusions:Our study identified novel FOXA3 variants and mutations, assessed the adipogenic capacity of two novel missense alterations in vitro and demonstrated for the first time the associations between FOXA3 SNP rs28666870 with metabolic phenotypes in humans.