Gluconeogenesis and P-enolpyruvate carboxykinase in liver and kidney of long-term fasted quails

The activity of cytoplasmic and mitochondrial phosphoenolpyruvate carboxykinase (PEPCK) in kidney and liver, and in vivo gluconeogenic activity, were determined during different phases of prolonged fasting in quails. The fasting-induced changes in the activity of kidney cytoplasmic PEPCK were positively correlated with the changes in gluconeogenesis. Both activities increased at the initial phase (I) of fasting to levels 65% to 100% higher than fed values, and decreased during the protein-sparing period (phase II), although remaining higher than in fed birds. At the catabolic final phase (III) both kidney cytoplasmic PEPCK activity and gluconeogenesis increased markedly, attaining levels 115% to 150% higher than fed values. The activity of liver cytoplasmic PEPCK, present in appreciable amounts in quails, did not change during phases I and II of fasting, but increased to levels 60% higher than fed values at the final phase (III). Plasma glucose levels at phase III did not differ significantly from those at phases I and II. In both kidney and liver the activity of the mitochondrial PEPCK was not significantly affected by fasting. The data suggest that the kidney cytoplasmic PEPCK is the main enzyme responsible for gluconeogenesis adjustments during food deprivation in quails, and that this function is complemented at the final phase by enzyme present in liver cytosol.

Effect of administration of clofibrate and clofenapate on kidney mitochondria of the rat

Abstract is not available.

Oxidation of succinate in heart, brain, and kidney mitochondria in hypobaria and hypoxia

Exposure of rats to hypobaric stress for periods of up to 36 h caused a consistent change in the succinate-NT reductase activity of the heart mitochondria whereas there was no significant change in the activities of either succinate dehydrogenase and succinate-NT reductase of the brain and the kidney. Mitochondrial succinate dehydrogenase of the heart, the brain and the kidney was activated 2- to 7-fold with the substrate and malonate. The activations obtained with oxalate, citrate and dinitrophenol were relatively lower in comparison to succinate and malonate. Benzohydroquinone and 2-nitrophenol had no stimulatory effect on the heart, the brain and the kidney mitochondria. THE ACTIVATIONS OBTAINED WITH THE VARIOUS EFFECTORS PARTIALLY (OR COMPLETELY IN THE CASE OF SUCCINATE) REVERSED ON WASHING THE MITOCHONDRIAL SAMPLES WITH THE SUCROSE HOMOGENIZING MEDIUM. The effect of ubiquinol, which also activated the enzyme, was only partially reversed after the second preincubation with succinate in the brain and the kidney whereas in the heart the activity was fully reversed. The increased activity of succinate dehydrogenase obtained with ATP and ADP was further enhanced by Mg2+ exclusively in the brain mitochondria, suggesting the possibility of Mg2+-AIP complex as the active species. Succinate-NT reductase of the heart, the brain and the kidney mitochondria showed a high activation with ubiquinone whereas its reduced form had no stimulatory effect.

A hexokinase effect in the inhibition of oxidative phosphorylation in heart muscle mitochondria by Adriamycin

The inhibitory action of the anticancer antibiotic, Adriamycin, on succinate-dependent oxidative phosphorylation in heart mitochondria was markedly potentiated by the presence of hexokinase in the reaction medium. This 'hexokinase effect' was not observed in the oxidation of NAD+-linked substrates, or when liver or kidney mitochondria were used in place of heart mitochondria. These results offer a biochemical explanation for the extreme cardiac toxicity of the drug.

Heat exposure and hypothyroid conditions decrease hydrogen peroxide generation in liver mitochondria

Exposure of rats to heat (39 +/- 1 degree C) decreased H2O2 generation in mitochondria of the liver, but not of the kidney or the heart. The effect was obtained with three substrates, succinate, glycerol 1-phosphate and choline, with a decrease to 50% in the first 2-3 days of exposure, and a further decrease on longer exposure. The dehydrogenase activity with only glycerol 1-phosphate decreased, which is indicative of the hypothyroid condition, whereas choline dehydrogenase activity remained unchanged and that of succinate dehydrogenase decreased on long exposure. The serum concentration of thyroxine decreased in heat-exposed rats. Thyroxine treatment of rats increased H2O2 generation. Hypothyroid conditions obtained by treatment with propylthiouracil or thyroidectomy caused a decrease in H2O2 generation and changes in dehydrogenase activities similar to those with heat exposure. Treatment of heat-exposed or thyroidectomized rats with thyroxine stimulated H2O2 generation by a mechanism apparently involving fresh protein synthesis. The results indicate that H2O2 generation in mitochondria of heat-exposed animals is determined by thyroid status.

Membrane Deformability and Membrane Tension of Single Isolated Mitochondria

Mitochondria dynamics is crucial to many biological processes such as mitochondria fusion and fission, which is highly correlated to the mechanics of single mitochondria. However, the mechanobiological coupling of mitochondria has been poorly understood. Here membrane deformability and membrane tension of individual mitochondria isolated from MtDsRed labeled human embryonic T-Rex-293 kidney cells were measured using a micropipette aspiration assay. The results demonstrated that membrane deformation of isolated mitochondria exhibited an elastic transition phase followed by an equilibrium phase, and mitochondrial membrane tension was proportional to the area compressibility. It was also indicated that mitochondrial membrane deformability was significantly affected by physical chemical factors such as osmotic pressure or pH value, and was further correlated to mitochondrial functionality in different respiratory states and Ca2+ regulation. These findings provide a new insight into understanding the mechanical regulation of mitochondrial physiology.

IHG-1 must be localised to mitochondria to decrease Smad7 expression and amplify TGF-β1-induced fibrotic responses

TGF-ß1 is a prototypic profibrotic cytokine and major driver of fibrosis in the kidney and other organs. Induced in high glucose-1 (IHG-1) is a mitochondrial protein which we have recently reported to be associated with renal disease. IHG-1 amplifies responses to TGF-ß1 and regulates mitochondrial biogenesis by stabilising the transcriptional co-activator peroxisome proliferator-activated receptor gamma coactivator-1-alpha. Here we report that the mitochondrial localization of IHG-1 is pivotal in amplification of TGF-ß1 signaling. We demonstrate that IHG-1 expression is associated with repression of the endogenous TGF-ß1 inhibitor Smad7. Intriguingly, expression of a non-mitochondrial deletion mutant of IHG-1 (?mts-IHG-1) repressed TGF-ß1 fibrotic signaling in renal epithelial cells. In cells expressing ?mts-IHG-1 fibrotic responses including CCN2/connective tissue growth factor, fibronectin and jagged-1 expression were reduced following stimulation with TGF-ß1. ?mts-IHG-1 modulation of TGF-ß1 signaling was associated with increased Smad7 protein expression. ?mts-IHG-1 modulated TGF-ß1 activity by increasing Smad7 protein expression as it failed to inhibit TGF-ß1 transcriptional responses when endogenous Smad7 expression was knocked down. These data indicate that mitochondria modulate TGF-ß1 signal transduction and that IHG-1 is a key player in this modulation.

Renal ischemia in rats: Mitochondria function and laser autofluorescence

Ischemia-reperfusion injury is the major cause of organ dysfunction or even nonfunction following transplantation. It can attenuate the long-term survival of transplanted organs. To evaluate the severity of renal ischemia injury determined by histology, we applied laser(442 nm and 532 nm) induced fluorescence (LIF), mitochondria respiration, and membrane swelling to evaluate 28 Wistar rats that underwent left kidney warm ischemia for 20, 40, 60, or 80 minutes. LIF performed before ischemia (control) was repeated at 20, 40, 60, and 80 minutes thereafter. We harvested left kidney tissue samples immediately after LIF determination for histology and mitochondrial analyses: state 3 and 4 respiration, respiration control rate (RCR), and membrane swelling. The association of optic spectroscopy with histological damage showed: LIF, 442 nm (r(2) = 0.39, P < .001) and 532 nm, (r(2) = 0.18, P = .003); reflecting laser/fluorescence-induced, 442 nm (r(2) = 0.20, P = .002) and 532 nm (r(2) = 0.004, P = .67). The associations between mitochondria function and tissue damage were: state 3 respiration (r(2) = 0.43, P = .0004), state 4 respiration (r(2) = 0.03, P = 0.38), RCR (r(2) = 0.28, P = .007), and membrane swelling (r(2) = 0.02, P = .43). The intensity of fluorescence emitted by tissue excited by laser, especially at a wave length of 442 nm, was determined in real time. Mitochondrial state 3 respiration and respiratory control ratio also exhibited good correlations with the grade of ischemic tissue damage.

Lovastatin protects mithochondrial and renal function in kidney ischemia-reperfusion in rats

PURPOSE: To investigate the effect of lovastatin on renal ischemia followed by reperfusion. METHODS: Thirty one Wistar rats submitted to left renal ischemia for 60 minutes followed by contralateral nephrectomy were divided into two groups: A (n = 17, control, no treatment), and B (n = 14, lovastatin 15 mg/kg/day p.o. ten days before ischemia). The animals were sacrificed at the end of ischemia, after 24 hours and at seven days after reperfusion. Survival, serum urea and creatinine levels and renal mitochondrial function were evaluated. RESULTS: Mortality was 29.4% in group A and 0.7% in group B. Urea and creatinine levels were increased in both groups, but the values were significantly lower in group B. Mitochondrial function showed decoupling in 83.4% of group A, as opposed to 38.4/% of group B. CONCLUSIONS: The result shows a protective action of renal function by lovastatin administered before ischemia/reperfusion. Since most of the mitochondrial fraction presented membranes with the ability to maintain ATP production in group B, stabilization of the mitochondrial membrane should be considered as part of the protective action of lovastatin on renal function in ischemia/reperfusion.

Localization of the Wilson’s disease protein product to mitochondria

Wilson’s disease (WND) is an inherited disorder of copper homeostasis characterized by abnormal accumulation of copper in several tissues, particularly in the liver, brain, and kidney. The disease-associated gene encodes a copper-transporting P-type ATPase, the WND protein, the subcellular location of which could be regulated by copper. We demonstrate that the WND protein is present in cells in two forms, the 160-kDa and the 140-kDa products. The 160-kDa product was earlier shown to be targeted to trans-Golgi network. The 140-kDa product identified herein is located in mitochondria as evidenced by the immunofluorescent staining of HepG2 cells with specific mitochondria markers and polyclonal antibody directed against the C terminus of the WND molecule. The mitochondrial location for the 140-kDa WND product was confirmed by membrane fractionation and by analysis of purified human mitochondria. The antibody raised against a repetitive sequence in the N-terminal portion of the WND molecule detects an additional 16-kDa protein, suggesting that the 140-kDa product was formed after proteolytic cleavage of the full-length WND protein at the N terminus. Thus, the WND protein is a P-type ATPase with an unusual subcellular localization. The mitochondria targeting of the WND protein suggests its important role for copper-dependent processes taking place in this organelle.

Fa'afaletui : a framework for the promotion of kidney health in an Australian Samoan community

Purpose Samoan communities in Australia exhibit a disproportionate rate of kidney disease compared with other Australians. This article describes a research project that used a culturally sensitive framework, Fa’afaletui, to help reduce the barriers of language and culture and increase our understanding of the factors contributing to kidney disease, in one Samoan community in Australia. Design Semistructured group interviews were undertaken with Samoan community families and groups. The interviews were analyzed according to key concepts embedded in the Fa’afaletui framework. Findings Four factors associated with health risks in this Samoan community emerged—diet and exercise; issues related to the collective (incorporating the village, church, and family); tapu or cultural protocols; and the importance of language. Conclusions The findings suggest that future kidney health promotion initiatives within this Samoan community will be more effective if they are sensitive to Samoan cultural norms, language, and context.

Adherence to fish oil intervention in patients with chronic kidney disease

Objective: With growing recognition of the role of inflammation in the development of chronic and acute disease, fish oil is increasingly used as a therapeutic agent, but the nature of the intervention may pose barriers to adherence in clinical populations. Our objective was to investigate the feasibility of using a fish oil supplement in hemodialysis patients. ---------- Design: This was a nonrandomized intervention study.---------- Setting: Eligible patients were recruited at the Hemodialysis Unit of Wesley Hospital, Brisbane, Queensland, Australia. Patients The sample included 28 maintenance hemodialysis patients out of 43 eligible patients in the unit. Exclusion criteria included patients regularly taking a fish oil supplement at baseline, receiving hemodialysis for less than 3 months, or being unable to give informed consent.---------- Intervention: Eicosapentaenoic acid (EPA) was administered at 2000 mg/day (4 capsules) for 12 weeks. Adherence was measured at baseline and weekly throughout the study according to changes in plasma EPA, and was further measured subjectively by self-report.---------- Results: Twenty patients (74%) adhered to the prescription based on changes in plasma EPA, whereas an additional two patients self-reported good adherence. There was a positive relationship between fish oil intake and change in plasma EPA. Most patients did not report problems with taking the fish oil. Using the baseline data, it was not possible to characterize adherent patients.---------- Conclusions: Despite potential barriers, including the need to take a large number of prescribed medications already, 74% of hemodialysis patients adhered to the intervention. This study demonstrated the feasibility of using fish oil in a clinical population.

Compliance, peritoneal dialysis and chronic kidney disease : lessons from the literature

Poor patient compliance with peritoneal dialysis (PD) has significant adverse effects on morbidity and mortality rates in individuals with chronic kidney disease (CKD). It also adds to the resource burdens of healthcare services and providers. This paper explores the notion of PD compliance in patients with CKD with reference to the relevant published literature. The analysis of the literature reveals that ‘PD compliance’ is a complex and challenging construct for both patients and health professionals. There is no universal definition of compliance that is widely adopted in practice and research, and therefore a lack of consensus on how to determine ‘compliant’ patient outcomes. There are also multiple and interconnected determinants of PD compliance that are context-bound, which healthcare professionals must be aware of, and which makes producing consensus of measuring PD compliance difficult. The complexity of the interventions required to produce even a modest improvement in PD compliance, which are described in this paper, are significant. Compliance with PD and other treatments for CKD is a multidimensional, context-bound concept, that to date has tended to efface the role and needs of the renal patient. We conclude the paper with the implications for contemporary practice.