Prenatal diagnosis of methylmalonic aciduria by analysis of organic acids and total homocysteine in amniotic fluid

Background Methylmalonic aciduria （MMA） is the most frequent disease of organic aciduria in China. Various biochemical strategies are followed for the prenatal diagnosis of MMA. However, since fetuses affected by MMA have decreased excretion of methylmalonic acid, the difficulties of prenatal biochemical diagnosis are obvious. Gas chromatography mass spectrometry （GC/MS） and tandem mass spectrometry （ESl/MS/MS） have allowed us to identify the disease in affected fetuses. The aim of this study was to determine the value of analysis of organic acids and total homocysteine in amniotic fluid in prenatal diagnosis of MMA. Methods The clinical diagnoses and outcomes of nine probands with MMA and the prenatal diagnoses based on biochemical analysis of nine fetuses at risk for MMA were investigated. Amniotic fluid samples from pregnancies at risk for MMA and metabolically normal pregnancies were obtained at 16-24 weeks of gestation. Methylmalonic acid and methylcitric acid were measured by GC/MS, propionylcarnitine was analyzed by ESl/MS/MS, and total homocysteine was determined by fluorescence polarization immunoassay. Results In two pregnancies, high levels of methylmalonic acid, methylcitric acid, propionylcarnitine, and total homocysteine indicated combined MMA and homocysteinemia in the fetuses. One of the mothers continued pregnancy and received cobalamin supplement as prenatal treatment, and the other terminated her pregnancy. In one pregnancy, significantly elevated levels of methylmalonic acid, methylcitric acid, and propionylcarnitine, and normal level of total homocysteine was found indicating isolated MMA in the fetus; abortion was performed on this case. In the other six pregnancies, all the levels of the above mentioned metabolites were normal suggesting that the fetuses were not affected by MMA. The diagnoses were confirmed after delivery by testing urinary organic acids and plasma total homocysteine. Conclusions The metabolic abnormalities of MMA occur early in gestation. The level of total homocysteine in amniotic fluid may be an additional indicator of fetal combined MMA and homocysteinemia. Determination of total homocysteine level in amniotic fluid may become a convenient and reliable method for prenatal diagnosis of the disease.

Cellular senescence-driven transcriptional reprogramming of the MAFB/NOTCH3 axis activates the PI3K/AKT pathway and promotes osteosarcoma progression

Osteosarcoma is the most common primary malignancy of bones and primarily occurs in adolescents and young adults.However,a second smaller peak of osteosarcoma incidence was reported in the elderly aged more than 60.Elderly patients with osteosarcoma exhibit different characteristics compared to young patients,which usually results in a poor prognosis.The mechanism underlying osteosarcoma development in elderly patients is intriguing and of significant value in clinical applications.Senescent cells can accelerate tumor progression by metabolic reprogramming.Recent research has shown that methylmalonic acid(MMA)was significantly up-regulated in the serum of older individuals and played a central role in the development of aggressive characteristics.We found that the significant accumulation of MMA in elderly patients imparted proliferative potential to osteosarcoma cells.The expression of MAFB was excessively up-regulated in osteosarcoma specimens and was further enhanced in response to MMA accumulation as the patient aged.Specifically,we first confirmed a novel molecular mechanism between cellular senescence and cancer,in which the MMA-driven transcriptional reprogramming of the MAFB-NOTCH3 axis accelerated osteosarcoma progression via the activation of PI3K-AKT pathways.Moreover,the down-regulation of the MAFB-NOTCH3 axis increased the sensitivity and effect of AKT inhibitors in osteosarcoma through significant inhibition of AKT phosphorylation.In conclusion,we confirmed that MAFB is a novel age-dependent biomarker for osteosarcoma,and targeting the MAFB-NOTCH3 axis in combination with AKT inhibition can serve as a novel therapeutic strategy for elderly patients with osteosarcoma in experimental and clinical trials.