Mitochondrial Adenosine Triphosphate Content Research Articles

Alterations of Myocardial Mitochondrial Morphology and Function in a Canine Model of Premature Ventricular Contractions-Induced Cardiomyopathy.

Changes in myocardial mitochondrial morphology and function in premature ventricular contractions (PVCs)-induced cardiomyopathy (PVCCM) remain poorly studied. Here, we investigated the effects of PVCs with different coupling intervals (CIs) on myocardial mitochondrial remodelling in a canine model of PVCCM. Twenty-one beagles underwent pacemaker implantation and were randomised into the sham (n = 7), short-coupled PVCs (SCP, n = 7), and long-coupled PVCs (LCP, n = 7) groups. Right ventricular (RV) apical bigeminy was produced for 12-week to induce PVCCM in the SCP (CI, 250 ms) and LCP (CI, 350 ms) groups. Echocardiography was performed at baseline and biweekly thereafter to evaluate cardiac function. Masson's trichrome staining measured ventricular interstitial fibrosis. The ultrastructural morphology of the myocardial mitochondria was analysed using transmission electron microscopy. Mitochondrial Ca2+ concentration, reactive oxygen species (ROS) levels, adenosine triphosphate (ATP) content, membrane potential, and electron transport chain (ETC) complex activity were measured to assess myocardial mitochondrial function. Twelve-week-PVCs led to left ventricular (LV) enlargement with systolic dysfunction, disrupted mitochondrial morphology, increased mitochondrial Ca2+ concentration and ROS levels, decreased mitochondrial ATP content and membrane potential, and impaired ETC complex activity in both the SCP and LCP groups (all p < 0.01 vs the sham group). Ventricular fibrosis was observed only in canines with LCP. Worse cardiac function and more pronounced abnormalities in mitochondrial morphology and function were observed in the LCP group than to the SCP group (all p < 0.05). We demonstrated myocardial mitochondrial abnormalities in dogs with PVCCM, characterised by abnormal mitochondrial morphology, mitochondrial Ca2+ overload, oxidative stress, and impaired mitochondrial energy metabolism. Compared to SCP, long-term LCP exposure resulted in more severe mitochondrial remodelling and cardiac dysfunction in dogs.

Oleuropein alleviates sepsis-induced acute lung injury via the AMPK/Nrf-2/HO-1 signaling

Objective: To explore the effect of oleuropein on sepsis-induced acute lung injury (ALI) in vitro and in vivo and investigate the underlying mechanism. Methods: In an lipopolysaccharide (LPS)-mediated cell model of sepsis-induced ALI and a cecal ligation and puncture-induced mouse model of septic ALI, CCK-8 assay and flow cytometry analysis were used to detect cell activity and apoptosis. ELISA and relevant assay kits were used to measure the levels of inflammatory cytokines and oxidative stress, respectively. Western blot was applied to determine the expression of apoptosis- and AMP-activated protein kinase (AMPK)/nuclear factor erythroid 2-related factor-2 (Nrf-2)/heme oxygenase-1 (HO-1) signaling-associated proteins. JC-1 staining, adenosine triphosphate (ATP) assay kit, and MitoSOX Red assays were performed to detect mitochondrial membrane potential, ATP content, and mitochondrial ROS formation, respectively. Moreover, lung injury was evaluated by measuring lung morphological alternations, lung wet-to-dry ratio, myeloperoxidase content, and total protein concentration. Results: Oleuropein reduced inflammatory reaction, oxidative damage, and apoptosis, and ameliorated mitochondrial dysfunction in LPS-exposed BEAS-2B cells and mice with septic ALI. Besides, oleuropein activated the AMPK/Nrf-2/HO-1 signaling pathway. However, these effects of oleuropein were abrogated by an AMPK inhibitor compound C. Conclusions: Oleuropein can protect against sepsis-induced ALI in vitro and in vivo by activating the AMPK/Nrf-2/HO-1 signaling, which might be a potential therapeutic agent for the treatment of sepsis-induced ALI.

Mechanism of Notoginseng Radix et Rhizoma in regulating PI3K/Akt/mTORC1-mitochondrial energy metabolism to treat chronic renal failure in rats with blood stasis syndrome

This study observed the effects of Notoginseng Radix et Rhizoma on the phosphatidylinositol 3-kinase(PI3K)/protein kinase B(Akt)/mammalian target of rapamycin complex 1(mTORC1) signaling pathway and mitochondrial energy metabolism in the rat model of adriamycin-induced renal fibrosis with blood stasis syndrome to explore the mechanism of Notoginseng Radix et Rhizoma in protecting the kidney. Thirty male rats with adriamycin-induced renal fibrosis were randomized into model, low-, medium-, and high-dose Notoginseng Radix et Rhizoma, and positive control groups(n=6). Six clean SD male rats were selected into the normal group. The normal group and model group were administrated with normal saline, and other groups with corresponding drugs. After 8 weeks of treatment, the renal function, renal pathology, adenosine triphosphate(ATP) levels, Na~+-K~+-ATPase and Ca~(2+)-Mg~(2+)-ATPase activities, and the protein levels of ATP5B, mTORC1, 70 kDa ribosomal protein S6 kinase(P70S6K), P85, Akt, p-Akt, and SH2-containing inositol phosphatase(SHIP2) in the renal tissue were determined. Compared with the normal group, the model group showed elevated levels of blood urea nitrogen(BUN) and serum creatinine(SCr)(P&lt;0.01). Compared with the model group, Notoginseng Radix et Rhizoma and the positive control lowered the levels of BUN and SCr, which were significant in the medium-and high-dose Noto-ginseng Radix et Rhizoma groups and the positive control group(P&lt;0.05). Compared with the model group, Notoginseng Radix et Rhizoma and the positive control alleviated the pathological changes in the renal tissue, such as vacuolar and fibroid changes, glomerulus atrophy, cystic expansion of renal tubules, and massive infiltration of inflammatory cells. Compared with the normal group, the model group showed decreased mitochondrial ATP content and Na~+-K~+-ATPase and Ca~(2+)-Mg~(2+)-ATPase activities in the renal tissue(P&lt;0.05), and medium-and high-dose Notoginseng Radix et Rhizoma and positive control mitigated such decreases(P&lt;0.05). Compared with the model group, medium-and high-dose Notoginseng Radix et Rhizoma and the positive control up-regulated the protein levels of ATP5B and SHIP2 and down-regulated the protein levels of mTORC1, P70S6K, P85, Akt, and p-Akt(P&lt;0.05 or P&lt;0.01 or P&lt;0.001). Notoginseng Radix et Rhizoma may exert an anti-fibrosis effect by inhibiting the activation of the PI3K/Akt/mTORC1 pathway to restore mitochondrial energy metabolism, thus protecting the kidney.

Cloning and functional analysis prohibitins protein-coding gene EuPHB1 in Eucommia ulmoides Oliver

As multifunctional proteins, prohibitins(PHBs) participate in many cellular processes and play essential roles in organisms. In this study, using rapid amplification of cDNA end (RACE) technology, EuPHB1 was cloned from Eucommia ulmoides Oliver (E. ulmoides). A subcellular localization assay preliminarily located EuPHB1 in mitochondria. Then EuPHB1 was transformed into tobacco, and phenotype analyses showed that overexpression of EuPHB1 caused leaves to become chlorotic and shrivel. Furthermore, genes related to hormone and auxin signal transduction, auxin binding, and transport, such as ethylene-responsive transcription factor CRF4-like and ABC transporter B family member 11-like, were significantly inhibited in response to EuPHB1 overexpression. Its overexpression disturbs the original signal transduction pathway, thus causing the corresponding phenotypic changes in transgenic tobacco. Indeed, such overexpression caused fading of palisade tissue and an increase in the number of certain mesophyll cells. It also increased adenosine triphosphate (ATP) synthase activity, mitochondrial membrane potential, ATP content, and reactive oxygen species (ROS) levels in cells. Our results suggest that EuPHB1 expression promotes cellular energy metabolism by accelerating the oxidative phosphorylation of the mitochondrial respiratory chain. Elevated levels of EuPHB1 in the mitochondria, which helps supply the extra energy required to support rapid rates of cell division.

Polydatin Improves Sepsis-Associated Encephalopathy by Activating Sirt1 and Reducing p38 Phosphorylation.

Our previous study confirmed that polydatin (PD) can alleviate sepsis-induced multiorgan dysfunction (in the vascular endothelium, kidney, and small intestine) by activating Sirt1 and that PD protects against traumatic brain injury in rats via increased Sirt1 and inhibition of the p38-mediated mitogen-activated protein kinase (MAPK) pathway. We aim to investigate whether PD may also attenuate sepsis-associated encephalopathy (SAE). In this study, we constructed an SAE mouse model by cecal ligation and puncture (CLP) and measured Sirt1 protein activity, p38 phosphorylation, brain tissue pathological damage, pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), mitochondrial function (mitochondrial membrane potential, ATP content, and reactive oxygen species), neurological function, and animal survival time. Sirt1 selective inhibitor Ex527 and p38 inhibitor SB203580 were used to explore the possible mechanism of PD in SAE. We confirmed that PD inhibits neuroinflammation evidenced by reduced proinflammatory cytokines. In addition, PD protects mitochondria as demonstrated by restored mitochondrial membrane potential and adenosine triphosphate (ATP) content, and decreased reactive oxygen species (ROS) level. As we expected, p38 inhibition reduces neuroinflammation and mitochondrial damage. In contrast, Sirt1 inhibition aggravates cerebral cortex mitochondrial damage and neuroinflammation and promotes phosphorylation of p38. Mechanistically, PD treatment suppressed p38 phosphorylation and consequently reduced the neuroinflammatory response, and these effects were blocked by the Sirt selective inhibitor Ex527. This study, to the best of our knowledge, is the first to demonstrate that PD alleviates SAE, at least partially, by upregulating Sir1-mediated neuroinflammation inhibition and mitochondrial function protection.

Levosimendan in rats decreases acute kidney injury after cardiopulmonary resuscitation by improving mitochondrial dysfunction.

BackgroundAcute kidney injury (AKI), the most common complication after cardiac resuscitation, is highly prevalent and harmful. There is increasing evidence that levosimendan can improve cardiac output, increase renal blood flow, and prevent AKI. As a novel calcium sensitizer, levosimendan may exert its protective effect via mitochondria.MethodsRat models of asphyxia-induced cardiac arrest and cardiopulmonary resuscitation (CPR) were set up. Thirty healthy adult male SD rats were randomly divided into CPR group (CPR group, n=10), levosimendan-treated group (levo group, n=10), and sham-operated group (sham group, n=10). Twelve hours after CPR, serum renal function indicators were measured, the kidney injury and mitochondrial morphological changes were observed. Oxygen uptake of the mitochondria, mitochondrial adenosine triphosphate (ATP) and mitochondrial free Ca2+ concentration were measured. Oxidative stress-related indicator levels in rat kidney tissues were further detected to analyze the differences in apoptosis rates among these three groups. Mitochondrial optic atrophy 1 (Opa1), dynamin-related protein 1 (Drp1), and apoptosis-related proteins were detected using Western blotting.ResultsCompared with the sham group, the CPR group had a significant increase in renal tissue damage. PAS staining and HE stains confirmed that CPR led to renal histopathological damage and destruction of the mitochondrial structure. Levosimendan improved the histopathological and ultrastructural damages of kidneys. Further analysis revealed that mitochondrial ATP content, NADH dehydrogenase, succinate dehydrogenase/cytochrome C oxidase, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (CSH-Px) decreased. Free Ca2+ concentration and malondialdehyde (MDA) significantly increased (all P<0.05) in the kidney tissues of rats in the CPR group. However, mitochondrial ATP content, NADH dehydrogenase, succinate dehydrogenase/cytochrome C oxidase, SOD, CAT, and CSH-Px increased, whereas free Ca2+ concentration and MDA decreased (all P<0.05) in the levo group. The apoptosis rate increased in the CPR group. There were significantly increased levels of Drp1 protein levels, and significantly decreased Opa1 expression (all P<0.05). However, the levo group showed the opposite effects (all P<0.05).ConclusionsLevosimendan can alleviate AKI following CPR, which may be achieved by improving mitochondrial dysfunction and suppressing the mitochondrial apoptosis pathway.

Exploring the biological mechanism of qi deficiency syndrome with chronic obstructive pulmonary disease (COPD) based on integrated pharmacology

To explore the potential biological mechanism of chronic obstructive pulmonary disease (COPD) qi deficiency syndrome, we used the integrated pharmacology network computing platform and carried out experimental verification. Using an integrated pharmacology strategy to analyze the potential biological targets of COPD qi deficiency syndrome. Based on the established qi deficiency syndrome rat model of COPD, the biological targets of lung and skeletal muscle were detected by electron microscopy, adenosine triphosphate (ATP) content assays, and western blotting. According to the integrated pharmacological results, it was found that the locations of cell components related to COPD qi deficiency syndrome were mainly mitochondria. Electron microscopy results using lung tissue showed that mitochondria in the lipopolysaccharide (LPS group) and pulmonary instillation of LPS combined with cigarette smoke (LPS+CS group) were swollen, deformed, and fragmented, with disappearing or broken crista. Results also showed that the total content of ATP in the lung and skeletal muscle of both groups was significantly lower than that in the control group at the 12 th week ( P < .05). At the 12 th week, the expression of dynamin-related protein 1 (DRP1) and mitofusin 1 (MFN1) protein was significantly difference than that of the control group ( P < .05). At the 10 th and 14 th weeks, changes in fission and fusion proteins in mitochondria of the lung and skeletal muscle were further detected. There was also a significant difference in the expression between the two groups compared to that in the control group at the 10 th week and 14 th week ( P < .05). These findings suggest that the changes in mitochondrial morphology and ATP content and the unbalanced expression of DRP1 and MFN1 might be the key mechanisms underlying qi deficiency syndrome in rats with COPD.

Metformin improves boar sperm quality via 5'-AMP-activated protein kinase-mediated energy metabolism in vitro.

Sperm are specialized cells that require adenosine triphosphate (ATP) to support their function. Maintaining sperm energy homeostasis in vitro is vitally important to improve the efficacy of boar sperm preservation. Metformin can activate 5′-AMP-activated protein kinase (AMPK) to improve metabolic flexibility and maintain energy homeostasis. Thus, the aim of the present study was to investigate whether metformin can improve boar sperm quality through AMPK mediation of energy metabolism. Sperm motility parameters, membrane integrity, acrosome integrity, mitochondrial membrane potential (ΔΨm), ATP content, glucose uptake, and lactate efflux were analyzed. Localization and expression levels of AMPK and phospho-Thr172-AMPK (p-AMPK) were also detected by immunofluorescence and western blotting. We found that metformin treatment significantly increased sperm motility parameters, ΔΨm, and ATP content during storage at 17 °C. Moreover, results showed that AMPK was localized at the acrosomal region, connecting piece, and midpiece of sperm and p-AMPK was distributed at the post-acrosomal region, connecting piece, and midpiece. When sperm were incubated with metformin for 4 h at 37 °C, sperm motility parameters, ΔΨm, ATP content, p-AMPK, glucose uptake, and lactate efflux all significantly increased, whereas the addition of Compound C treatment, an inhibitor of AMPK, counteracted these positive effects. Together, our results suggest that metformin promotes AMPK activation, which contributes to the maintenance of energy hemostasis and mitochondrial activity, thereby maintaining boar sperm functionality and improving the efficacy of semen preservation.

The intestine responds to heart failure by enhanced mitochondrial fusion through glucagon-like peptide-1 signalling.

Glucagon-like peptide-1 (GLP-1) is a neuroendocrine hormone secreted by the intestine. Its receptor (GLP-1R) is expressed in various organs, including the heart. However, the dynamics and function of the GLP-1 signal in heart failure remains unclear. We investigated the impact of the cardio-intestinal association on hypertensive heart failure using miglitol, an α-glucosidase inhibitor known to stimulate intestinal GLP-1 production. Dahl salt-sensitive (DS) rats fed a high-salt diet were assigned to miglitol, exendin (9-39) (GLP-1R blocker) and untreated control groups and treated for 11 weeks. Control DS rats showed marked hypertension and cardiac dysfunction with left ventricular dilatation accompanied by elevated plasma GLP-1 levels and increased cardiac GLP-1R expression as compared with age-matched Dahl salt-resistant (DR) rats. Miglitol further increased plasma GLP-1 levels, suppressed adverse cardiac remodelling, and mitigated cardiac dysfunction. In cardiomyocytes from miglitol-treated DS hearts, mitochondrial size was significantly larger with denser cristae than in cardiomyocytes from control DS hearts. The change in mitochondrial morphology reflected enhanced mitochondrial fusion mediated by protein kinase A activation leading to phosphorylation of dynamin-related protein 1, expression of mitofusin-1 and OPA-1, and increased myocardial adenosine triphosphate (ATP) content. GLP-1R blockade with exendin (9-39) exacerbated cardiac dysfunction and led to fragmented mitochondria with disarrayed cristae in cardiomyocytes and reduction of myocardial ATP content. In cultured cardiomyocytes, GLP-1 increased expression of mitochondrial fusion-related proteins and ATP content. When GLP-1 and exendin (9-39) were administered together, their effects cancelled out. Increased intestinal GLP-1 secretion is an adaptive response to heart failure that is enhanced by miglitol. This could be an effective strategy for treating heart failure through regulation of mitochondrial dynamics.

Manipulation of cellular energy reveals the relationship between ultraweak luminescence and cellular energy during senescence of strawberry (Fragaria × ananassa) fruits

The goal of this study was to investigate the ultraweak luminescence (UWL) of strawberry fruits in relation to mitochondrial functions and energy production during strawberry senescence. Fully ripe strawberry fruits and mitochondria isolated from those fruits were treated with either adenosine triphosphate (ATP) or the respiratory chain uncoupler 2,4-dinitrophenol (DNP). The activities of H+-ATPase and Ca2+-ATPase, the content of ATP, the free radical O2− as well as the UWL intensity were measured. Our results showed that activities of H+-ATPase and Ca2+-ATPase as well as the ATP content gradually decreased during fruit senescence in all three groups. Compared with the control, DNP treatment exacerbated, while ATP treatment reduced the decrease of H+-ATPase and Ca2+-ATPase activity, the energy charge and UWL intensity. UWL intensity was positively correlated with mitochondrial function and ATP content. Our results strongly suggest that mitochondria are a major source of UWL of strawberry fruits, and that the cellular energy ATP plays important roles in senescence of strawberry fruits, and in UWL formation. Our study provides convincing evidence of the interrelationship between cellular energy and UWL, which helps researchers to better understand the process of senescence in strawberry fruits.

Effect of propofol on mitochondrial ATP content and ATPase activity in hippocampus of rats with cerebral ischemia-reperfusion injury.

ObjectiveStudy on the influence of the cerebral Ischemia-reperfusion Injury (IRI) on mitochondrial adenosine triphosphate (ATP) content and ATPase activity in hippocampus of rats, as well as the protective effect of propofol on IRI in rats.MethodsA total of 40 male SD rats were randomly divided into 5 groups: sham operation group (Group A), ischemia reperfusion control group (Group B) and ischemic reperfusion with propofol pretreatment group (C group). Group C was further divided into three sub groups according to the different doses of propofol: Group C1 (50 mg/kg), Group C2 (100 mg/kg) and Group C3 (150 mg/kg). The rats from Groups B and C were applied for the IRI model preparation by blockage of the blood flow in arteria carotis communis. For the Groups A, arteria carotis communis were separated without blockage of the blood flow. Before preparation of IRI model for rats in Group C, different doses of propofol were intraperitoneally injected into the rats. For rats in Groups A and B, only saline solution with same volume was intraperitoneally injected at the same time. The ultra-structures of mitochondria in hippocampus of rats were observed under transmission electron microscope, and the mitochondrial degeneration rate was counted. The contents of ATP were determined by HPLC and the ATPase activity was characterized by ATPase activity assay kit.Results(1) Mitochondria in the hippocampus from Groups B and C showed different degrees of ultrastructural damage and more significant mitochondrial degeneration than those from Group A. The degree of damage and the rate of degeneration were in the order of B > C1 > C2 > C3 and the difference was statistically significant (P < 0.01). (2) The contents of ATP and the ATPase activity in hippocampus from Groups B and C were significantly lower than those of Group A, while these indices from Group C were significantly higher than those in the B group, and the sequence was C3 > C2 > C1, indicating that the ATP content and ATPase activity were significantly correlated with the dose of propofol, and the difference was statistically significant (P < 0.05).ConclusionIn summary, the contents of ATP and ATPase activity in hippocampus of rats can be decreased by cerebral IRI. The structure and function of the impaired mitochondria in IRI rats could be significantly improved by propofol, and the improvement effect is related to the dose of propofol.

Selective blockade of mGlu5 metabotropic glutamate receptors is protective against hepatic mitochondrial dysfunction in 6‐OHDA lesioned Parkinsonian rats

Non-motor symptoms including those involving the splanchnic district are present in Parkinson's disease (PD). The authors previously reported that PD-like rats, bearing a lesion of the nigrostriatal pathway induced by the injection of 6-hydroxydopamine (6-OHDA), have impaired hepatic mitochondrial function. Glutamate intervenes at multiple levels in PD and liver pathophysiologies. The metabotropic glutamate receptor 5 (mGluR5) is abundantly expressed in brain and liver and may represent a pharmacological target for PD therapy. This study investigated whether and how chronic treatment with 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a well-characterized mGluR5 antagonist, may influence hepatic function with regard to neuronal cell loss in PD-like rats. Chronic treatment with MPEP was started immediately (Early) or 4 weeks after (Delayed) intrastriatal injection of 6-OHDA and lasted 4 weeks. Early MPEP treatment significantly prevented the decrease in adenosine triphosphate (ATP) production/content and counteracted increased reactive oxygen species (ROS) formation in isolated hepatic mitochondria of PD-like animals. Early MPEP administration also reduced the toxin-induced neurodegenerative process; improved survival of nigral dopaminergic neurons correlated with enhanced mitochondrial ATP content and production. ATP content/production, in turn, negatively correlated with ROS formation suggesting that the MPEP-dependent improvement in hepatic function positively influenced neuronal cell survival. Delayed MPEP treatment had no effect on hepatic mitochondrial function and neuronal cell loss. Antagonizing mGluR5 may synergistically act against neuronal cell loss and PD-related hepatic mitochondrial alterations and may represent an interesting alternative to non-dopaminergic therapeutic strategies for the treatment of PD.

Incorporation of β-sitosterol into mitochondrial membrane enhances mitochondrial function by promoting inner mitochondrial membrane fluidity

Recent findings suggest that mitochondrial membrane fluidity could influence mitochondrial energy metabolism. β-sitosterol (BS) is a common plant sterol that is prevalent in plant oils, nuts, cereals and plant food products. Its chemical structure is very similar to that of cholesterol. As a cholesterol analog, BS is highly lipid soluble and largely resides in the membranes of cells or organelles where it may have an influence on the membrane fluidity. The present study reports that, with the cholesterol chelator 2-hydroxypropyl-β-cyclodextrin (HPβCD) as its carrier, BS is able to increase the fluidity of the inner mitochondrial membrane (IMM) without affecting the fluidity of the outer mitochondrial membrane (OMM), and consequently to increase the mitochondrial membrane potential (∆Ψm) and mitochondrial ATP content. It has been previously proposed that a therapeutical boost in adenosine triphosphate (ATP) levels in mitochondria may be beneficial for neurodegenerative diseases such as Alzheimer's disease (AD). Given that dietary administration of plant sterols could increase brain BS concentrations, these results may provide a better understanding of the beneficial effects of plant sterol-enriched nutrients on neurodegenerative diseases such as AD.

Bilobalide Protects Mitochondrial Function in Ovariectomized Rats by Up-regulation of mRNA and Protein Expression of Cytochrome c Oxidase Subunit I

Bilobalide (BB), a sesquiterpene trilactone from Ginkgo biloba has been proposed to have protective effects on mitochondrial function. Using ovariectomized rats to mimic the post-menopausal pathophysiological changes in women, this study demonstrated that BB treatment could prevent estrogen withdrawal-induced decrease in mitochondrial adenosine triphosphate content, cytochrome c oxidase subunit I (COXI) mRNA and protein levels and COX activity in hippocampal tissues as effectively as estradiol benzoate. But neither ovariectomy nor BB treatment affected citrate synthase activity. These results suggested that BB was able to regulate COX activity via up-regulation of the gene and protein expression of its mitochondrial DNA-coded subunits, and modulation of COX activity by BB might contribute to its protective effects on mitochondrial function. Given that ovariectomy induces decrease in estrogen levels similar to that of menopause, BB may be useful in developing therapy for neurodegenerative diseases such as Alzheimer's disease in post-menopausal females.

Increased vulnerability of brain to estrogen withdrawal-induced mitochondrial dysfunction with aging

In the present study, to determine whether aging could increase the vulnerability of the brain to estrogen withdrawal-induced mitochondrial dysfunction, we measured the cytochrome c oxidase (COX) activity and mitochondrial adenosine triphosphate (ATP) content in hippocampi of 2 groups of ovariectomized (OVX) Wistar rats aged 2 months (young) and 9 months (middle-aged), respectively. In addition, effects of genistein and estradiol benzoate (EB) were tested also. We observed only a transient alteration of COX activity and mitochondrial ATP content in hippocampi of young OVX rats but a prolonged lowering of COX activity and mitochondrial ATP content in hippocampi of middle-aged OVX rats. This suggested that with aging compensatory mechanisms of mitochondrial function were attenuated, thus exacerbated estrogen withdrawal-induced mitochondrial dysfunction in hippocampi. Significantly, EB/genistein treatment reversed this estrogen withdrawal-induced mitochondrial dysfunction in both young and middle-aged rats suggesting that genistein may be used as a substitute for estradiol to prevent age-related disease such as Alzheimer's disease in post-menopausal females.

Oral Administration of Amino Acidic Supplements Improves Protein and Energy Profiles in Skeletal Muscle of Aged Rats: Elongation of Functional Performance and Acceleration of Mitochondrial Recovery in Adenosine Triphosphate After Exhaustive Exertion

Sarcopenia is an inevitable age-related degenerative process chiefly characterized by decreased synthesis of muscle proteins and impaired mitochondrial function, leading to progressive loss of muscle mass. Here, we sought to probe whether long-term administration of oral amino acids (AAs) can increase protein and adenosine triphosphate (ATP) content in the gastrocnemius muscle of aged rats, enhancing functional performance. To this end, 6- and 24-month-old male Fisher 344 rats were divided into 3 groups: group A (6-month-old rats) and group B (24-month-old rats) were used as adult and senescent control group, respectively, while group C (24-month-old rats) was used as senescent treated group and underwent 1-month oral treatment with a mixture of mainly essential AAs. Untreated senescent animals exhibited a 30% reduction in total and fractional protein content, as well as a 50% reduction in ATP content and production, compared with adult control rats (p <0.001). Long-term supplementation with mixed AAs significantly improved protein and high-energy phosphate content, as well as the rate of mitochondrial ATP production, conforming their values to those of adult control animals (p <0.001). The improved availability of protein and high-energy substrates in the gastrocnemius muscle of treated aged rats paralleled a significant enhancement in functional performance assessed by swim test, with dramatic elongation of maximal exertion times compared with untreated senescent rats (p <0.001). In line with these findings, we observed that, after 6 hours of rest following exhaustive swimming, the recovery in mitochondrial ATP content was approximately 70% in adult control rats, approximately 60% in senescent control rats, and normalized in treated rats as compared with animals of the same age unexposed to maximal exertion (p <0.001). In conclusion, nutritional supplementation with oral AAs improved protein and energy profiles in the gastrocnemius of treated rats, enhancing functional performance and accelerating high-energy phosphate recovery after exhaustive exertion.

Low calcium reperfusion of ischemic myocardium

The mechanisms underlying protection of ischemic myocardium by reperfusion with solutions containing reduced concentrations of calcium (Ca) were studied in isolated vascularly perfused rabbit interventricular septa at 37°C. After 45 min of total ischemia adenosine triphosphate (ATP), and phosphocreatine (PC) contents fell to 6.8 ± 0.82, and 12.4 ± 2.0 μ m/g dry tissue (d t) (± s.e.m.). After 5 min of reperfusion with 0.75 m m Ca these values had recovered significantly to 10.3 ± 1.0, and 33.3 ± 3.6, (μ m/g d t), while reperfusion with 2.5 m m Ca produced 5.9 ± 1.0 and 22.0 ± 2.6 (μ m/g d t). The significantly greater recovery of ATP and PC after 0.75 m m Ca reperfusion persisted after an additional 25 min of reperfusion with 2.5 m m Ca when compared to septa reperfused for the entire 30 min with 2.5 m m Ca. When mechanical work was reduced by cessation of stimulation during the first 5 min of reperfusion, ATP, PC and total creatine (TC) recovery were significantly improved in muscles exposed to 2.5 m m Ca but showed no additional improvement in muscles reperfused with 0.75 m m Ca. A further reduction to 100 μ m Ca reperfusion in quiescent muscles did significantly improve ATP, PC and TC recovery. Quiescence achieved with 16.0 m m K impaired ATP, PC and TC recovery. This effect was reversed by 100 μ m Ca reperfusion. Measurements of mitochondrial oxygen consumption, respiratory control and ADP O showed results parallel to the ATP, PC and TC determinations. Both mechanical work and Ca itself influence mitochondrial respiration, ATP, PC and TC content after ischemia. As previously demonstrated for mechanical function, metabolic recovery can be improved by interventions limited to the first 5 min of reperfusion.

Protection of mitochondrial function during ischemia by potassium cardioplegia: correlation with ischemic contracture.

The effect of potassium cardioplegia on mitochondrial function was evaluated in the ischemic isolated rat heart. Mitochondrial function as well as adenosine triphosphate (ATP) levels were determined at the initiation of ischemic contracture, at the completion of ischemic contracture, and 20 minutes following contracture completion. Group I received no cardioplegia prior to ischemia, while Group II received potassium cardioplegia prior to the onset of ischemia. The respiratory control index (RCI), which is the primary measure of the intactness of mitochondrial function, was calculated with both a NAD (nicotinamide adenine dinucleotide)-linked substrate and a FAD (flavin adenine dinucleotide)-linked substrate. Potassium cardioplegia significantly delayed ischemic contracture initiation and completion. Although the RCI and ATP levels decreased significantly at successive levels of contracture, there was no difference in the RCI or ATP content between Group I and Group II at contracture initiation or completion. Unlike previous investigations that have used a time-base to examine mitochondrial function and acute cardiac ischemic injury, we correlated mitochondrial function with the measurable physiologic event ischemic contracture. The data indicated that potassium cardioplegia preserved ATP content and mitochondrial function, and that contracture initiation and completion correlate well with specific ATP levels and mitochondrial respiratory control. The relationship between mitochondrial function and ATP content indicates that the beneficial effect of potassium cardioplegia on mitochondrial function may be secondary to the preservation of high-energy phosphate levels which provide energy for mitochondrial maintenance.