Isozyme Phenotypic Difference of Varicorhinus macrolepis Malic Enzyme

By using polyacrylamide gel electrophoresis and biochemical straining method, malic enzyme isozyme in 10 organs of male or female Varicorhinus macrolepis were analyzed. The results showed that malic enzyme exists in heart, gonads, eyes and gills tissues in both female and male V. macrolepis. There was only one ME-2 in heart and ME-1 in eye of female fish, while there were ME-1 and ME-2 in heart and ME-2 in eyes of male fish. Ovary contained ME-1 and ME-2, while spermary only contained ME-1. In kidney and spleen tissues, malic enzyme was found only in female fish, while in muscle, malic enzyme existed only in male fish. The phenotypic of malic enzyme had obvious differences no matter in the same organ of different sexes in V. macrolepis or different organs in the same sex. But there were no differences among different individuals of the same sex. The results will provide basic data for developmental genetics, breed improvement and directed breeding of V. macrolepis, and lay a foundation for its development and protection.

Mitochondrial malic enzyme 2 promotes breast cancer metastasis via stabilizing HIF-1α under hypoxia

Objective: α-ketoglutarate(α-KG) is the substrate to hydroxylate collagen and hypoxia-inducible factor-1α(HIF-1α), which are important for cancer metastasis. Previous studies have shown that the upregulation of collagen prolyl 4-hydroxylase in breast cancer cells stabilizes the expression of HIF-1α by depleting α-KG levels. We hypothesized that mitochondrial malic enzyme 2(ME2) might also affect HIF-1α expression via modulating α-KG levels in breast cancer cells.Methods: We evaluated ME2 protein expression in 100 breast cancer patients using immunohistochemistry and correlated with clinicopathological indicators. The effect of ME2 knockout on cancer metastasis was evaluated using an orthotopic breast cancer model. The effect of ME2 knockout or knockdown on the levels of α-KG and HIF-1α proteins in breast cancer cell lines was determined both in vitro and in vivo.Results: ME2 was found to be upregulated in the human breast cancerous tissues compared with the matched precancerous tissues(P<0.001). The elevated expression of ME2 was associated with a poor prognosis(P=0.019).ME2 upregulation was also related to lymph node metastasis(P=0.016), pathological staging(P=0.033), and vascular cancer embolus(P=0.014). Also, ME2 knockout significantly inhibited lung metastasis in vivo. In the tumors formed by ME2 knockout cells, the levels of α-KG were significantly increased and collagen hydroxylation level did not change significantly but HIF-1α protein expression was significantly decreased, compared to the control samples. In cell culture, cells with ME2 knockout or knockdown demonstrated significantly higher α-KG levels but significantly lower HIF-1α protein expression than control cells under hypoxia. Exogenous malate and α-KG exerted similar effect on HIF-1α in breast cancer cells to ME2 knockout or knockdown. Additionally,treatment with malate significantly decreased 4 T1 breast cancer lung metastasis. ME2 expression was associated with HIF-1α levels in human breast cancer samples(P=0.008).Conclusions: Our results provide evidence that upregulation of ME2 is associated with a poor prognosis of breast cancer patients and propose a mechanistic understanding of a link between ME2 and breast cancer metastasis.

Relationship between Muscular Malic Enzyme Activity and Meat Quality in Pigs

[ Objective] To investigate the relationship between muscular malic enzyme （ME） activity and meat quality in pigs. [ Method] Three pig breeds, Exi pigs, Changye x Exi hybrid pigs and Landrace xYorkshire pigs were selected. Then the ME activity and meat traits were detected, and the relationship between ME activity and meat quality were analyzed with SAS software. [ Result] The Exi pigs had the highest ME activity and intra- muscular fat （IMF） content （ P 〈 0.05）. The pH2 value, drip loss and muscle shear force of Landrace xYorkshire pigs were higher than that of Exi pigs significantly （P 〈 0.05）. [ Conclusion] The ME activity has a certain correlation with meat quality of pigs. The muscular ME activity has signifi- cantly positive correlation with IMF content and significantly negative correlation with drip loss and muscle shear force.