Mitochondrial dysfunction in type 2 diabetes:A neglected path to skeletal muscle atrophy

Over the course of several decades,robust research has firmly established the significance of mitochondrial pathology as a central contributor to the onset of skeletal muscle atrophy in individuals with diabetes.However,the specific intricacies governing this process remain elusive.Extensive evidence highlights that individuals with diabetes regularly confront the severe consequences of skeletal muscle degradation.Deciphering the sophisticated mechanisms at the core of this pathology requires a thorough and meticulous exploration into the nuanced factors intricately associated with mitochondrial dysfunction.

Changes of Reactive Oxygen Species and Related Enzymes in Mitochondria Respiratory Metabolism During the Ripening of Peach Fruit

The fruits of peach cultivar Yuhua 3 were used as materials to investigate the changes of active oxygen and related enzymes in mitochondria respiratory metabolism during ripening of peach fruit, involving their influence on the proceeding of peach fruit senescence. The results showed that the large decrease in firmness occurred between maturity II and IV. The decrease in firmness coincided with an increase in respiratory intensity. Obvious peaks of respiratory intensity lagging to the rapid change of fruit firmness could be shown during peach ripening. Reactive oxygen species （ROS） had a cumulative process and positively correlated with respiratory intensity. During peach ripening, the content of Ca^2＋ increased, the activities of succinic dehydrogenase （SDH）, cytochrome C oxidase （CCO）, H＋-ATPase, and Ca^2＋-ATPase decreased varying in different degree at the later step of ripening. These suggested a close relationship existed between ROS metabolism and mitochondrial respiration, namely, both ROS metabolism and mitochondrial respiration probably played important roles in ripening and senescing of peach fruit.

Succinylation modification:a potential therapeutic target in stroke

Stroke is a leading cause of mortality and disability worldwide.Ischemic cell death triggered by the compromised supply of blood oxygen and glucose is one of the major pathophysiology of strokeinduced brain injury.Impaired mitochondrial energy metabolism is observed minutes after stroke and is closely associated with the progression of neuropathology.Recently,a new type of posttranslational modification,known as lysine succinylation,has been recognized to play a significant role in mitochondrial energy metabolism after ischemia.However,the role of succinylation modification in cell metabolism after stroke and its regulation are not well understood.We aimed to review the effects of succinylation on energy metabolism,reactive oxygen species generation,and neuroinflammation,as well as Sirtuin 5 mediated desuccinylation after stroke.We also highlight the potential of targeting succinylation/desuccinylation as a promising strategy for the treatment of stroke.The succinylation level is dynamically regulated by the nonenzymatic or enzymatic transfer of a succinyl group to a protein on lysine residues and the removal of succinyl catalyzed by desuccinylases.Mounting evidence has suggested that succinylation can regulate the metabolic pathway through modulating the activity or stability of metabolic enzymes.Sirtuins,especially Sirtuin 5,are characterized for their desuccinylation activity and have been recognized as a critical regulator of metabolism through desuccinylating numerous metabolic enzymes.Imbalance between succinylation and desuccinylation has been implicated in the pathophysiology of stroke.Pharmacological agents that enhance the activity of Sirtuin 5 have been employed to promote desuccinylation and improve mitochondrial metabolism,and neuroprotective effects of these agents have been observed in experimental stroke studies.However,their therapeutic efficacy in stroke patients should be validated.

Oxidative stress and mitochondrial dysfunction of retinal ganglion cells injury exposures in long-term blue light

AIM:To investigate the phototoxic effect of long-term excessive narrow-band blue light in staurosporine-induced differentiated retinal ganglion cells-5(SSRGC-5).METHODS:SSRGC-5 cells were divided into two groups,blue light group(BL group)and control group.Cell viability was assessed by using CCK-8 assay.Metabolic profile analysis was performed by using Seahorse extracellular flux analyzer.Mitochondria ultrastructure were studied via transmission electron microscope(TEM).Mitochondria contents and oxidative stress was evaluated by flow cytometry.Western blotting was performed to monitor the changes in mitogen-activated protein kinases(MAPK)pathway and PI3 K/AKT pathway.RESULTS:Blue light caused morphological changes of SSRGC-5 cells.The cell viability was significantly decreased from 3 h in BL group.Intercellular ROS and mitochondrial superoxide levels were increased following blue light exposure.Metabolic profiling identified blue light induced SSRGC-5 cells to have severely compromised mitochondrial function.This was accompanied by impaired mitochondrial ultrastructure and remodeling,increased expression of the mitochondrial related proteins,and increased glycolysis as compensation.Moreover,the results showed that blue light induced higher expression of p-p38,p38,p-JNK,p-ERK,p-cJun,c-Jun,and p-AKT.CONCLUSION:These findings indicate that excessive narrow-band blue light induces oxidative stress and mitochondrial metabolic remodeling dysregulate in SSRGC-5 cells.Activated MAPK and AKT signaling pathways are involved in this process.

Changes of Reactive Oxygen Species and Related Enzymes in Mitochondrial Respiration During Storage of Harvested Peach Fruits

Peach fruits [Prumus persica （L.） Batsch, cv. Yuhuasanhao] were used as materials to investigate the changes of reactive oxygen species （ROS） and related enzymes in mitochondria respiration during storage and then their influence on senescence of harvested Peach fruits was studied. The results showed that low temperature （5℃） strongly inhibited the reduction of firmness and the increase in respiration rate. During storage at ambient temperature （20℃）, ROS had a cumulative process while malondialdehye （MDA） content continued to increase in associated with enhanced membrane lipid peroxidation. Lipoxygenase （LOX） activity was strongly inhibited under the low temperature condition. The activities of succinic dehydrogenase （SDH）, cytochrome C oxidase （CCO）, and Ca^2＋-ATPase declined to a certain extent at ambient temperature, while they showed higher activities at low temperature, which may be related to lower membrane lipid peroxidation at low temperature. Higher Ca^2＋ content at ambient temperature may be responsible for impairment of mitochondrial function, thus, leading to fruit senescence. The results showed that under low temperature condition, the low accumulation of ROS and the low level of membrane lipid peroxidation could maintain the function of mitochondria that would help to delay the senescence of peach fruits. These suggested a close relationship existed between ROS metabolism and mitochondrial respiration. It can be inferred that the low temperature helps to delay senescence of peach fruits via suppression of ROS and related enzymes, maintain better homeostasis of Ca^2＋ in mitochondria and thus better mitochondrial functions.

Green Tea Polyphenols Attenuate High-Fat Diet-Induced Renal Oxidative Stress through SIRT3-Dependent Deacetylation

Fifty male Wistar rats were fed a standard chow diet or a high-fat （HF） diet, and different concentrations of green tea polyphenols （GTPs） （0.8, 1.6, and 3.2 g/L） were administered in the drinking water. We found that the malondialdehyde （MDA） level in the HF diet group was significantly higher than that in the control （CON） group （P〈0.05）. Decreased peroxisome proliferato r-activated receptor （PPAR）-α and sirtuin 3 （SlRT3） expression, and increased manganese superoxide dismutase （MnSOD） acetylation levels were also detected in the HF diet group （P〈0.05）. GTP treatment upregulated SlRT3 and PPARa expression, increased the ppora mRNA level, reduced the MnSOD acetylation level, and decreased MDA production in rats fed a HF diet （P〈0.05）. No significant differences in total renal MnSOD and PPAR-y coactivator-1α （PGCI-α） expression were detected. The reduced oxidative stress detected in kidney tissues after GTP treatment was partly due to the higher SIRT3 expression, which was likely mediated by PPARα.

Human intestinal acyl-CoA synthetase 5 is sensitive to the inhibitor triacsin C

AIM:To investigate whether human acyl-CoA synthetase 5(ACSL5) is sensitive to the ACSL inhibitor triacsin C.METHODS:The ACSL isoforms ACSL1 and ACSL5 from rat as well as human ACSL5 were cloned and recombinantly expressed as 6xHis-tagged enzymes.Ni 2+-affinity purified recombinant enzymes were assayed at pH 7.5 or pH 9.5 in the presence or absence of triacsin C.In addition,ACSL5 transfected CaCo2 cells and intestinal human mucosa were monitored.ACSL5 expression in cellular systems was verified using Western blot and immunofluorescence.The ACSL assay mix included TrisHCl(pH 7.4),ATP,CoA,EDTA,DTT,MgCl 2,[9,103 H] palmitic acid,and triton X-100.The 200 μL reaction was initiated with the addition of solubilized,purified recombinant proteins or cellular lysates.Reactions were terminated after 10,30 or 60 min of incubation with Doles medium.RESULTS:Expression of soluble recombinant ACSL proteins was found after incubation with isopropyl betaD-1-thiogalactopyranoside and after ultracentrifugation these were further purified to near homogeneity with Ni 2+-affinity chromatography.Triacsin C selectively and strongly inhibited recombinant human ACSL5 protein at pH 7.5 and pH 9.5,as well as recombinant rat ACSL1(sensitive control),but not recombinant rat ACSL5(insensitive control).The IC50 for human ACSL5 was about 10 μmol/L.The inhibitory triacsin C effect was similar for different incubation times(10,30 and 60 min) and was not modified by the N-or C-terminal location of the 6xHis-tag.In order to evaluate ACSL5 sensitivity to triacsin C in a cellular environment,stable human ACSL5 CaCo2 transfectants and mechanically dissected normal human intestinal mucosa with high physiological expression of ACSL5 were analyzed.In both models,ACSL5 peak activity was found at pH 7.5 and pH 9.5,corresponding to the properties of recombinant human ACSL5 protein.In the presence of triacsin C(25 μmol/L),total ACSL activity was dramatically diminished in human ACSL5 transfectants as well as in ACSL5-rich human intestinal mucosa.CONCLUSION:The data strongly indicate that human ACSL5 is sensitive to triacsin C and does not compensate for other triacsin C-sensitive ACSL isoforms.

Effect of Emodin on ATP Metabolism of Reno-Cortical Mitochondria

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Effects of dichloroacetate on the activation of the mitochondrial pathway in C6 cells in vitro

Mitochondria are increasingly recognized as important targets for tumor treatment because of their central roles in apoptotic pathways and cellular metabolism. Dichloroacetate （DCA）, a low molecular weight mitochondria-targeting agent, exhibits potential therapeutic effects for tumors. Based on the effects of DCA on tumor cellular metabolism, we carried out this study to investigate the anti-tumor activity of DCA in C6 glioma cells in vitro. The results showed that DCA was able to increase the activity of pyruvate dehydrogenase （PDH）, induce the production of reactive oxygen species （ROS） and reduce the mitochondrial membrane potential （MMP） in C6 ceils in vitro （P〈0.05 or 0.01）, indicating that the anti-tumor effects of DCA in C6 cells could be through the activation of the mitochondrial pathway. In conclusion, mitochondria could be a viable therapeutic target for the treatment of glioma.