BackgroundWe previously described increased levels of growth and differentiation factor 15 (GDF-15) in skeletal muscle and serum of patients with mitochondrial diseases. Here we evaluated GDF-15 as a biomarker for mitochondrial diseases affecting children and compared it to fibroblast-growth factor 21 (FGF-21). To investigate the mechanism of GDF-15 induction in these pathologies we measured its expression and secretion in response to mitochondrial dysfunction.MethodsWe analysed 59 serum samples from 48 children with mitochondrial disease, 19 samples from children with other neuromuscular diseases and 33 samples from aged-matched healthy children. GDF-15 and FGF-21 circulating levels were determined by ELISA.ResultsOur results showed that in children with mitochondrial diseases GDF-15 levels were on average increased by 11-fold (mean 4046pg/ml, 1492 SEM) relative to healthy (350, 21) and myopathic (350, 32) controls. The area under the curve for the receiver-operating-characteristic curve for GDF-15 was 0.82 indicating that it has a good discriminatory power. The overall sensitivity and specificity of GDF-15 for a cut-off value of 550pg/mL was 67.8% (54.4%-79.4%) and 92.3% (81.5%-97.9%), respectively. We found that elevated levels of GDF-15 and or FGF-21 correctly identified a larger proportion of patients than elevated levels of GDF-15 or FGF-21 alone. GDF-15, as well as FGF-21, mRNA expression and protein secretion, were significantly induced after treatment of myotubes with oligomycin and that levels of expression of both factors significantly correlated.ConclusionsOur data indicate that GDF-15 is a valuable serum quantitative biomarker for the diagnosis of mitochondrial diseases in children and that measurement of both GDF-15 and FGF-21 improves the disease detection ability of either factor separately. Finally, we demonstrate for the first time that GDF-15 is produced by skeletal muscle cells in response to mitochondrial dysfunction and that its levels correlate in vitro with FGF-21 levels.

BackgroundMutations in the gene encoding thymidine kinase 2 (TK2) result in the myopathic form of mitochondrial DNA depletion syndrome which is a mitochondrial encephalomyopathy presenting in children. In order to unveil some of the mechanisms involved in this pathology and to identify potential biomarkers and therapeutic targets we have investigated the gene expression profile of human skeletal muscle deficient for TK2 using cDNA microarrays.ResultsWe have analysed the whole transcriptome of skeletal muscle from patients with TK2 mutations and compared it to normal muscle and to muscle from patients with other mitochondrial myopathies. We have identified a set of over 700 genes which are differentially expressed in TK2 deficient muscle. Bioinformatics analysis reveals important changes in muscle metabolism, in particular, in glucose and glycogen utilisation, and activation of the starvation response which affects aminoacid and lipid metabolism. We have identified those transcriptional regulators which are likely to be responsible for the observed changes in gene expression.ConclusionOur data point towards the tumor suppressor p53 as the regulator at the centre of a network of genes which are responsible for a coordinated response to TK2 mutations which involves inflammation, activation of muscle cell death by apoptosis and induction of growth and differentiation factor 15 (GDF-15) in muscle and serum. We propose that GDF-15 may represent a potential novel biomarker for mitochondrial dysfunction although further studies are required.

Background A population-based study to describe the impact of SARS-CoV-2 infection on pregnancy outcomes. Methods Prospective, population-based study including pregnant women consecutively attended at first/second trimester or at delivery at three hospitals in Barcelona, Spain. SARS-CoV-2 antibodies (IgG and IgM/IgA) were measured in all participants and nasopharyngeal RT-PCR was performed at delivery. The primary outcome was a composite of pregnancy complications in SARS-CoV-2 positive versus negative women: miscarriage, preeclampsia, preterm delivery, perinatal death, small-for-gestational age, neonatal admission. Secondary outcomes were components of the primary outcome plus abnormal fetal growth, malformation, intrapartum fetal distress. Outcomes were also compared between positive symptomatic and positive asymptomatic SARS-CoV-2 women. Results Of 2,225 pregnant women, 317 (14.2%) were positive for SARS-CoV-2 antibodies (n=314, 99.1%) and/or RT-PCR (n=36, 11.4%). Among positive women, 217 (68.5%) were asymptomatic, 93 (29.3%) had mild COVID-19 and 7 (2.2%) pneumonia, of which 3 required intensive care unit admission. In women with and without SARS-CoV-2 infection, the primary outcome occurred in 43 (13.6%) and 268 (14%), respectively [risk difference -0.4%, (95% CI: -4.1% to 4.1)]. As compared with non-infected women, women with symptomatic COVID-19 had increased rates of preterm delivery (7.2% vs. 16.9%, p=0.003) and intrapartum fetal distress (9.1% vs. 19.2%, p=0.004), while asymptomatic women had similar rates to non-infected cases. Among 143 fetuses from infected mothers, none had anti-SARS-CoV-2 IgM/IgA in cord blood. Conclusions The overall rate of pregnancy complications in women with SARS-CoV-2 infection was similar to non-infected women. However, symptomatic COVID-19 was associated with modest increases in preterm delivery and intrapartum fetal distress.