Human pregnancy is frequently accompanied by nausea and vomiting that may become severe and life-threatening, as in hyperemesis gravidarum (HG), the cause of which is unknown. Growth Differentiation Factor-15 (GDF15), a hormone known to act on the hindbrain to cause emesis, is highly expressed in the placenta and its levels in maternal blood rise rapidly in pregnancy. Variants in the maternal GDF15 gene are associated with HG. Here we report that fetal production of GDF15, and maternal sensitivity to it, both contribute substantially to the risk of HG. We found that the great majority of GDF15 in maternal circulation is derived from the feto-placental unit and that higher GDF15 levels in maternal blood are associated with vomiting and are further elevated in patients with HG. Conversely, we found that lower levels of GDF15 in the non-pregnant state predispose women to HG. A rare C211G variant in GDF15 which strongly predisposes mothers to HG, particularly when the fetus is wild-type, was found to markedly impair cellular secretion of GDF15 and associate with low circulating levels of GDF15 in the non-pregnant state. Consistent with this, two common GDF15 haplotypes which predispose to HG were associated with lower circulating levels outside pregnancy. The administration of a long-acting form of GDF15 to wild-type mice markedly reduced subsequent responses to an acute dose, establishing that desensitisation is a feature of this system. GDF15 levels are known to be highly and chronically elevated in patients with beta thalassemia. In women with this disorder, reports of symptoms of nausea or vomiting in pregnancy were strikingly diminished. Our findings support a causal role for fetal derived GDF15 in the nausea and vomiting of human pregnancy, with maternal sensitivity, at least partly determined by pre-pregnancy exposure to GDF15, being a major influence on its severity. They also suggest mechanism-based approaches to the treatment and prevention of HG.

GDF15, a hormone acting on the brainstem, has been implicated in the nausea and vomiting of pregnancy, including its most severe form, hyperemesis gravidarum (HG), but a full mechanistic understanding is lacking1-4. Here we report that fetal production of GDF15 and maternal sensitivity to it both contribute substantially to the risk of HG. We confirmed that higher GDF15 levels in maternal blood are associated with vomiting in pregnancy and HG. Using mass spectrometry to detect a naturally labelled GDF15 variant, we demonstrate that the vast majority of GDF15 in the maternal plasma is derived from the feto-placental unit. By studying carriers of rare and common genetic variants, we found that low levels of GDF15 in the non-pregnant state increase the risk of developing HG. Conversely, women with β-thalassaemia, a condition in which GDF15 levels are chronically high5, report very low levels of nausea and vomiting of pregnancy. In mice, the acute food intake response to a bolus of GDF15 is influenced bi-directionally by prior levels of circulating GDF15 in a manner suggesting that this system is susceptible to desensitization. Our findings support a putative causal role for fetally derived GDF15 in the nausea and vomiting of human pregnancy, with maternal sensitivity, at least partly determined by prepregnancy exposure to the hormone, being a major influence on its severity. They also suggest mechanism-based approaches to the treatment and prevention of HG.

Genetic variants in proteins can interfere with measurement of their circulating concentrations. Given the growing biomedical importance of GDF-15, we wished to establish whether a common histidine to aspartate variant present in position 6 of the mature GDF-15 protein (H202D variant) interfered with its measurement by two commonly used immunoassays. We first examined the detectability of recombinant monomers, homodimers and heterodimers of GDF-15 by assays and/or reagents used in two widely used immunoassays (Roche Elecsys GDF-15 and the R&D antibody combinations used in their Quantikine and DuoSet ELISAs). The Roche assay detected the H and D containing peptides similarly but the assays based on the R&D reagents consistently underreported concentrations of the D-containing variant peptide. Measurements of plasma concentrations of GDF-15 in genotyped human participants showed that the R&D reagents reported values in heterozygotes were ~25% lower, and in homozygotes, 50% lower than the Roche assay. We finally studied the activation of the GDF-15 receptor, GFRAL-Ret, in a cell based assay and found that the activities of the HH and DD containing GDF-15 peptide were indistinguishable. These results have implications for the interpretation of genetic epidemiological studies which have used the R&D reagents to measure GDF-15, and for the emerging clinical use of GDF-15 as a diagnostic and prognostic biomarker. We provide correction equations, which may be of utility for the analysis of data generated with the R&D reagents where the genotype of the participants is known.

Background Pulmonary arterial hypertension (PAH) covers a range of life-limiting conditions characterized by increased mean pulmonary arterial pressures leading to right heart failure and eventually death, if left untreated. In approximately 25% of cases of idiopathic PAH genetic analysis reveals a mutation in one of several genes, the most common being bone morphogenetic type II receptor (BMPR2). There is substantial evidence implicating inflammation in the pathogenesis of PAH. We questioned whether potential inflammatory drivers were different in BMPR2-mutation positive PAH and in PAH without any mutations. Methods Patients with confirmed mutations in BMPR2 (BMPR2mut, n=54) and patients without any driving mutations (n=56) were recruited from the national UK- PAH cohort. Levels of IL-6, IL-8, IL-10, TNF-α, VEGF-A and G-CSF were measured in plasma samples from these and healthy controls (n=56). Results Both BMPR2­-mutation positive and PAH patients without mutations had high levels of IL-6, IL-8, TNF-α and VEGF-A compared to controls. Only PAH patients without mutations had higher levels of IL-10 while only BMPR2­-mutation carrying patients had higher levels of G-CSF compared to controls. VEGF-A levels were substantially higher in PAH without mutation compared to the BMPR2mut group. Only IL-6 was a significant discriminator for mortality in the BMPR2mut cohort (cumulative survival for patients with an IL-6 level of ≥1.6 pg/ml at 3 years is 65% compared to 96% for patients with an IL-6 level of <1.6 pg/ml, P=0.0013, figure 1A). IL-6 appears to outperform NT-proBNP in this respect (cumulative survival for patients with an NT-proBNP level of >130 ng/ml at 3 years was 76% compared to 84% for patients with an NT-proBNP level of ≤130 ng/ml, P=0.37, figure 1B). The converse was true in PAH without mutation (cumulative survival for patients with an IL-6 level of >1.3 pg/ml at 3 years is 81% compared to 92% for patients with an IL-6 level of ≤1.3 pg/ml, P=0.048, figure 1C). Cumulative survival for patients with a NT-proBNP level of >239 ng/ml at 3 years was 80% compared to 96% for patients with NT-proBNP level of <239 pg/ml, (P=0.01, figure 1D). Conclusions BMPR2-mutation positive patients have a different inflammatory profile compared to PAH patients without mutations. The selection of biomarkers of inflammation to predict clinical outcomes may therefore differ between these groups.

Classical Galactosaemia (CG) (OMIM #230400) is a rare inborn error of galactose metabolism caused by deficiency of the enzyme galactose-1-phosphate uridylyltransferase (GALT). Long-term complications persist in treated patients despite dietary galactose restriction with significant variations in outcomes suggesting epigenetic glycosylation influences. Primary Ovarian Insufficiency (POI) is a very significant complication affecting females with follicular depletion noted in early life. We studied specific glycan synthesis, leptin system and inflammatory gene expression in white blood cells as potential biomarkers of infertility in 54 adults with CG adults (27 females and 27 males) (age range 17–51 yr) on a galactose-restricted diet in a multi-site Irish and Dutch study. Gene expression profiles were tested for correlation with a serum Ultra-high Performance Liquid Chromatography (UPLC)-Immunoglobulin (IgG)-N-glycan galactose incorporation assay and endocrine measurements.