The metabolite 2-hydroxyglutarate (2HG) can be produced as either a D(R)- or L(S)- enantiomer, each of which inhibits alpha-ketoglutarate (αKG)-dependent enzymes involved in diverse biologic processes. Oncogenic mutations in isocitrate dehydrogenase produce D-2HG, which causes a pathologic blockade in cell differentiation. On the other hand, oxygen limitation leads to accumulation of L-2HG, which can facilitate physiologic adaptation to hypoxic stress in both normal and malignant cells. Here we demonstrate that purified lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) catalyze stereospecific production of L-2HG via ‘promiscuous’ reduction of the alternative substrate αKG. Acidic pH enhances production of L-2HG by promoting a protonated form of αKG that binds to a key residue in the substrate-binding pocket of LDHA. Acid-enhanced production of L-2HG leads to stabilization of hypoxia-inducible factor 1 alpha (HIF-1α) in normoxia. These findings offer insights into mechanisms whereby microenvironmental factors influence production of metabolites that alter cell fate and function.

This study is aimed at determining the relationship of flavonoid structures to their chemical and intracellular antioxidant activities. The antioxidant activities of 60 flavonoids were investigated by three different antioxidant assays, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, oxygen radical absorption capacity (ORAC), and cellular antioxidant activity (CAA) assays. The result showed 6 flavonoids as good cellular antioxidants evaluated for the first time. The cellular antioxidant activities of compounds 7-methoxy-quercetin, 3-O-methylquercetin, 8-hydroxy-kaempferol, quercetin-3-O-α-arabinofuranose, kaempferol-7-O-glucopyranoside, and luteolin6-C-glucoside were linked with the upregulation of antioxidant enzyme activities (superoxide dismutase, catalase, and glutathione peroxidase). A structure-activity relationship suggested that 2,3-double bond, 4-keto groups, 3′,4′-catechol structure, and 3-hydroxyl in the flavonoid skeleton played important roles in the antioxidant behavior. Furthermore, the cell proliferative assay revealed a low cytotoxicity for 3-O-methylquercetin. The present results provide valuable information for the dietary application of flavonoids with different structures for high antioxidant.

A DXR gene, AvDXR (GenBank accession no. FJ459894), and a DXS gene, AvDXS (GenBank accession no. FJ455512), were isolated from the leaves of Amomum villosum, one of the most well-known and authentic herbs in South China. The 1,749-bp full-length cDNA of AvDXR encoded a peptide of 472 amino acids, and the 2,347-bp full-length cDNA of AvDXS encoded a peptide of 715 amino acids. The deduced amino acid sequences of the AvDXR and AvDXS proteins share high homology with DXRs and DXSs from other plant species, and AvDXS belongs to class 1 plant DXS. The characterization based on bioinformatic analysis indicated that the AvDXR and AvDXS encoded functional proteins as DXR and DXS, respectively. The functional color assay in Escherichia coli with pAC-BETA implied that AvDXR and AvDXS encoded functional proteins that manipulated the biosynthesis of isoprenoid precursors. Both AvDXR and AvDXS were expressed extensively in the leaves, stems, roots, pericarps and seeds of A. villosum. AvDXS expression was similar in all tissues investigated, whereas higher levels of AvDXR were observed in the fruits, the main part for the accumulation of volatile oil in this plant. AvDXR was transformed into tobacco to confirm its function further. Overexpression of AvDXR in transgenic T1 generation tobacco increased DXR activity, photosynthetic pigment content and volatile isoprenoid components, and the increase of photosynthetic pigment content was consistent with the AvDXR transcription level. This study demonstrated that AvDXR plays important role in isoprenoid biosynthesis and it is useful for metabolic engineering.

Background Although many treatments for ipsilateral proximal and shaft femoral fractures have been developed, controversy exists regarding their optimal management. The purpose of this retrospective study was to discuss the effectiveness of the bridge-link type combined fixation system (BCFS) and evaluate functional outcomes in treating patients with these complex fractures. Patients and methods We retrospectively reviewed 14 cases of ipsilateral proximal and shaft femoral fractures treated from January 2012 to December 2016. All cases were treated by BCFS combined with minimally invasive percutaneous plate osteosynthesis (MIPPO). Clinical and radiographic data were collected during regular post-operative follow-up visits. Functional outcomes were determined according to the Friedman and Wyman scoring system. Results The proximal femoral fractures were emergency diagnoses in 11 cases and delayed diagnoses in 3 cases. The delay time was 5–6 days, with an average of 5.3 days. The mean operation time was 179.6 min (range 135–231 min) with a blood loss volume that ranged from 430 to 535 ml (average 483.6 ml). Follow-up was conducted in 13 cases between 9 and 30 months post-operation, with an average follow-up time of 17.3 months. The proximal femoral fractures were united in 12 cases at the final follow-up. One case had nonunion 13 months after the operation, underwent valgus intertrochanteric osteotomy, and healed 6 months later. The femoral shaft fractures obtained rigid union at the latest follow-up in 12 cases. One case endured nonunion 12 months after the operation. After the revision surgery and iliac bone grafting, the fracture healed 6 months later. Eight of the cases had good functional results, 4 had fair results, and results were poor in 1 case at the final follow-up. Conclusions The treatment of ipsilateral proximal femoral and shaft fractures with BCFS in combination with MIPPO demonstrated a high likelihood of union for both fractures and good functional results.