Platelet mitochondrial function and endogenous coenzyme Q10 levels are reduced in patients after COVID-19.

BACKGROUND: After an acute treatment for coronavirus disease (COVID-19), some symptoms may persist for several weeks, for example: fatigue, headaches, muscle and joint pain, cough, loss of taste and smell, sleep and memory disturbances, depression. Many viruses manipulate mitochondrial function, but the exact mechanisms of SARS-CoV-2 virus effect remain unclear. We tested the hypothesis that SARS-CoV-2 virus may affect mitochondrial energy production and endogenous biosynthesis of coenzyme Q10 (CoQ10). METHODS: Ten patients after COVID-19 and 15 healthy individuals were included in the study. Platelets isolated from peripheral blood were used as an accessible source of mitochondria. High-resolution respirometry for the evaluation of platelets mitochondrial function, and HPLC method for CoQ10 determination were used. Oxidative stress was evaluated by TBARS concentration in plasma. RESULTS: Platelet mitochondrial respiratory chain function, oxidative phosphorylation and endogenous CoQ10 level were reduced in the patients after COVID-19. CONCLUSION: We assume that a reduced concentration of endogenous CoQ10 may partially block electron transfer in the respiratory chain resulting in a reduced adenosine triphosphate (ATP) production in the patients after COVID-19. Targeted mitochondrial therapy with CoQ10 supplementation and spa rehabilitation may improve mitochondrial health and accelerate the recovery of the patients after COVID-19. Platelet mitochondrial function and CoQ10 content may be useful mitochondrial health biomarkers after SARS-CoV-2 infection (Tab. 3, Fig. 3, Ref. 46).

Treatment with coenzyme Q10, omega-3-polyunsaturated fatty acids and their combination improved bioenergetics and levels of coenzyme Q9 and Q10 in skeletal muscle mitochondria in experimental model of arthritis.

Rheumatoid arthritis (RA) and its animal model adjuvant arthritis (AA) are inflammatory diseases characterized by chronic inflammation, systemic oxidative stress and disturbed mitochondrial bioenergetics of skeletal muscle. The present study aimed to evaluate the effects of coenzyme Q10 - CoQ10 (100 mg/kg b.w.), omega-3-polyunsaturated fatty acids - omega-3-PUFA (400 mg/kg b.w.) and their combined treatment in AA on impaired skeletal muscle mitochondrial bioenergetics, inflammation and changes in levels CoQ9 and CoQ10 in plasma. Markers of inflammation (C-reactive protein, monocyte-chemotactic protein-1), antioxidant capacity of plasma, respiratory chain parameters of skeletal muscle mitochondria and concentrations of CoQ9 and CoQ10 in plasma and in muscle tissue were estimated. Treatment of the arthritic rats with CoQ10, omega-3-PUFA alone and in combination partially reduced markers of inflammation and increased antioxidant capacity of plasma, significantly increased concentrations of coenzyme Q in mitochondria and improved mitochondrial function in the skeletal muscle. Combined treatment has similar effect on the mitochondrial function as monotherapies; however, it has affected inflammation and antioxidant status more intensively than monotherapies. Long-term supplementary administration of coenzyme Q10 and omega-3-PUFA and especially their combination is able to restore the impaired mitochondrial bioenergetics and antioxidant status in AA.

Is mitochondrial bioenergetics and coenzyme Q10 the target of a virus causing COVID-19?

COVID-19 ‒ a coronavirus disease, affected almost all countries in the world. It is a new virus disease, nobody has prior immunity to it, human population is prone to infections. In March 11 2020, WHO declared the pandemic status. The main symptoms include: fever, dry cough and fatigue. Virus proteins need mitochondrial energy for their own survival and replication. Upon viral infections, mitochondrial dynamics and metabolism can be modulated, which can influence the energy production in the host cells. Coenzyme Q10 is an integral component of mitochondrial respiratory chain and the key component of mitochondrial ATP production. The exact pathobiochemical mechanism of the disease is unknown. Modulated mitochondrial dynamics and metabolism with lower CoQ10 levels in viral infections leads us to the hypothesis that one of the main pathobiochemical effects of SARS-Cov-2 virus could be mitochondrial bioenergetics dysfunction with CoQ10 deficit leading to the reduction of its endogenous biosynthesis. The mechanism might be virus induced oxidative stress causing a mutation of one or more of the nine COQ genes, resulting in primary CoQ10 deficiency. New perspective for patients with COVID-19 may be supportive targeting therapy with coenzyme Q10 to increase the energy production, immunity and decrease oxidative stress (Fig. 1, Ref. 51). Keywords: COVID-19, virus, mitochondrial bioenergetics, coenzyme Q10, oxidative stress.

The importance of coenzyme Q10 and its ratio to cholesterol in the progress of chronic kidney diseases linked to non- -communicable diseases.

OBJECTIVES: The mortality of patients with chronic kidney diseases (CKD) increases with the decrease in glomerular filtration rate (eGFR). In the progress of CKD that is closely linked to non-communicable diseases (NCDs), the role of coenzyme Q10 (CoQ10) is not fully evaluated. We aimed to evaluate the importance of CoQ10, CoQ10/cholesterol ratio, and oxidative stress in the progress of CKD. PATIENTS AND METHODS: The control group was constituted of 19 healthy subjects who volunteered to enrol in the study, CKD group consisted of 58 patients with CKD, of whom 54 had CKD combined with hypertension, 22 had CKD combined with hypertension and diabetes type 2 , and 18 had CKD combined with hypertension and statin therapy. We observed age, BMI, creatinine, uric acid, eGFR, hemoglobin, CRP, glucose, lipids fraction, and liver enzymes. Coenzyme Q10-TOTAL (ubiquinol+ubiquinone) in platelets and plasma were determined using HPLC method with UV detection. Indexed of CoQ10/lipid fractions were evaluated. Oxidative stress was determined as thiobarbituric acid­reactive substances (TBARS). RESULTS: With increased stages of CKD, eGFR and CoQ10 as well as its ratio to lipids were significantly reduced while TBARS increased. CONCLUSION: We assume that lower endogenous CoQ10 level may be one of the reasons of kidney dysfunction. CoQ10/lipids ratio and increase in oxidative stress can predict the progression of CKD in patients with arterial hypertension, diabetes mellitus and dyslipidemia (Tab. 2, Fig. 4, Ref. 49).

Platelet mitochondrial bioenergetic analysis in patients with nephropathies and non-communicable diseases: a new method.

OBJECTIVES: To test the hypothesis if mitochondrial bioenergetic function analyzed in circulating platelets may represent peripheral signature of mitochondrial dysfunction in nephropathy associated to non-communicable human diseases such as cardiovascular diseases, diabetes and with statins treatment. METHODS: High-resolution respirometry was used for analysis of mitochondrial bioenergetics in human platelets isolated from peripheral blood. This method is less-invasively compared to skeletal muscle biopsy. Patients with nephropathies and in combination with non-communicable diseases were included in the study. RESULTS: This pilot study showed platelet mitochondrial bioenergy dysfunction in patients with nephropathies and non-communicable diseases. Positive effect of treatment with 10 mg atorvastatin on platelet mitochondrial respiratory chain Complex I-linked respiration and ATP production in patients with nephropathies, diabetes and 80 mg atorvastatin in patient with nephropathy and dialysis was found. Positive effect of 80 mg fluvastatin treatment, and negative effect of thrombocytopenia and renal transplantation on platelet mitochondrial bioenergy was determined. CONCLUSION: High-resolution respirometry allowed detection of small changes in platelet mitochondrial function. This method could be used as a sensitive bioenergetic test of mitochondrial function for diagnosis and monitoring the therapy in patients with nephropathy (Tab. 1, Fig. 3, Ref. 39).

Effects of complete water fasting and regeneration diet on kidney function, oxidative stress and antioxidants.

OBJECTIVE: The aim of the study was to observe the influence of 11-days complete water fasting (WF) and regeneration diet (RD) on renal function, body weight, blood pressure and oxidative stress. BACKGROUND: Therapeutic WF is considered a healing method. METHODS: Ten volunteers drank only water for 11 days, followed by RD for the next 11 days. Data on body weight, blood pressure, kidney functions, antioxidants, lipid peroxidation, cholesterols, triacylglycerols and selected biochemical parameters were obtained. RESULTS: WF increased uric acid and creatinine and decreased glomerular filtration rate. After RD, the parameters were comparable to baseline values. Urea was not affected. Lipid peroxidation (TBARS) decreased and maintained stable after RD. Fasting decreased α-tocopherol and increased γ-tocopherol, no significant changes were found after RD. Coenzyme Q10 decreased after RD. HDL-cholesterol decreased in WF. Total- and LDL-cholesterol decreased after RD. Other biochemical parameters were within the range of reference values. CONCLUSIONS: The effect of the complete fasting on kidney function was manifested by hyperuricemia. Renal function was slightly decreased, however maintained within the reference values. After RD, it returned to baseline values. The positive effect of the complete water fasting was in the reduction of oxidative stress, body weight and blood pressure (Tab. 3, Ref. 25).

Participation of heart mitochondria in myocardial protection against ischemia/reperfusion injury: benefit effects of short-term adaptation processes.

Acute streptozotocin diabetes mellitus (DM) as well as remote ischemic preconditioning (RPC) has shown a favorable effect on the postischemic-reperfusion function of the myocardium. Cardioprotective mechanisms offered by these experimental models involve the mitochondria with the changes in functional properties of membrane as the end-effector. The aim was to find out whether separate effects of RPC and DM would stimulate the mechanisms of cardioprotection to a maximal level or whether RPC and DM conditions would cooperate in stimulation of cardioprotection. Experiments were performed on male Wistar rats divided into groups: control, DM, RPC and DM treated by RPC (RPC+DM). RPC protocol of 3 cycles of 5-min hind limb ischemia followed by 5-min reperfusion was used. Ischemic-reperfusion injury was induced by 30-min ischemia followed by 40-min reperfusion of the hearts in Langendorff mode. Mitochondria were isolated by differential centrifugation, infarct size assessed by staining with 1 % 2,3,5-triphenyltetrazolium chloride, mitochondrial membrane fluidity with a fluorescent probe DPH, CoQ(9) and CoQ(10) with HPLC. Results revealed that RPC as well as DM decreased the infarct size and preserved mitochondrial function by increasing the mitochondrial membrane fluidity. Both used models separately offered a sufficient protection against ischemic-reperfusion injury without an additive effect of their combination.

Remote ischemic preconditioning of the heart: protective responses in functional and biophysical properties of cardiac mitochondria.

UNLABELLED: Remote ischemic preconditioning (RIP)-induced protection of myocardial energetics was well documented on the level of tissue, but data concerning the involvement of mitochondria were missing. We aimed at the identification of changes in membrane properties and respiratory functions induced in rat heart mitochondria by RIP. Experiments were performed on 46 male Wistar rats divided into control and RIP-treated groups of 21 animals each. Blood flow in the occluded area was recorded by MRI angiography in four animals. RIP protocol comprised of three successive 5-min occlusions each followed by 5-min reperfusions of descending branches of the right hind limb femoral artery. The efficacy of RIP was evaluated as the extent of RIP-induced protection against damage to the functions of mitochondria isolated by differential centrifugation after 30-min global ischemia followed by 40-min reperfusion of the hearts in Langendorff mode. ASSESSMENTS: mitochondrial membrane fluidity with a fluorescent probe DPH, CoQ(9) and CoQ(10) with HPLC, mitochondrial respiration with the Oxygraph-2k (Oroboros). Results revealed that RIP was affecting the mitochondria. The immediate protection conferred by RIP involves beneficial and prognostically significant effects: a total elimination of ischemia/reperfusion-induced depression of mitochondrial membrane fluidity and a trend for better preservation of mitochondrial state 3 respiration.

Importance of the assessment of coenzyme Q10, alpha-tocopherol and oxidative stress for the diagnosis and therapy of infertility in men.

UNLABELLED: Male infertility is one of the most stressful factors of couples, being present in about 40% cases. It is usually caused by a low number of sperm (oligozoospermia) or poor sperm motility (asthenozoospermia). The sperm motility is used as an indicator of semen quality and male infertility. To the impairment of male reproduction health can contribute genetic, nutritional and environmental factors, smoking and drugs. It is well documented that excessive reactive oxygen species (ROS) production decreases sperm motility, impairs sperm function, damages the morphology of spermatozoa (1, 2). To the decreased sperm motility contribute also disturbances of sperm mitochondrial function and energy production, low levels of coenzyme Q10 and carnitine, as well as sperm mitochondrial deoxyribonucleic acid (DNA) defects. The origin of sperm dysfunction, however, is not well understood. BACKGROUND: Oxidative stress has been established as a major factor in the pathogenesis of male infertility. Low level of coenzyme Q10 contributes to the decreased sperm motility, which plays a vital role in sperm mitochondrial energy production and neutralization of reactive oxygen species (ROS).The aim of the present study was to find out, if an assessment of coenzyme Q10-TOTAL (CoQ10-TOTAL), α-tocopherol, γ-tocopherol and oxidative stress could contribute to the diagnosis of infertility in men. SUBJECTS AND METHODS: Two groups of infertile men, according to sperm motility (a+b and b+c) were included in the study. CoQ10-TOTAL, α-tocopherol, γ-tocopherol in plasma and seminal fluid, and parameter of oxidative stress (thiobarbituric acid reactive substances - TBARS) in plasma were determined. RESULTS: Higher sperm density and decreased sperm pathology were found in group a+b vs b+c (class a and b - fast and weak forward motility, class c - nonprogressive motility). Concentrations of CoQ10-TOTAL and α-tocopherol were significantly increased in seminal fluid of groups a+b vs b+c, opposite results were estimated in plasma. Concentrations of γ-tocopherol in plasma and seminal fluid of both groups were similar. Plasmatic TBARS concentrations were increased in both groups of infertile men. CONCLUSION: We suppose that incorporation of oxidative stress assessment, CoQ10-TOTAL and α-tocopherol concentrations in seminal fluid and plasma into routine andrology can play an important role for the diagnosis and targeted therapy of male infertility (Tab. 1, Ref. 16).

Ratio of lipid parameters to coenzyme Q10 could be used as biomarker of the development of early complications of obesity in children.

BACKGROUND: Chronic obesity is associated with reduced levels of antioxidants, increased free oxygen radicals, and oxidative stress. Child obesity may lead to the development of complications, such as changes in metabolism, metabolic syndrome, neurological, cardiological, respiratory, renal, gastrointestinal, endocrinological, and musculoskeletal conditions. The aim of the present study is to establish whether there is a correlation between basal CoQ10 plasma concentration and the ratio of lipid parameters to CoQ10 in obese children. METHODS: The study included 101 obese children and 20 non-obese children, aged 10-18 years. Antioxidants - CoQ10-OX, α-tocopherol, ß-carotene - in plasma were measured by HPLC method with UV detector, and plasma malondialdehyde spectrophotometrically. RESULTS: High correlation was found between plasma concentration of CoQ10 and the ratio of total Chol/CoQ10-OX as well as between CoQ10-OX and the ratio of HDL Chol/CoQ10 in plasma of obese children. The lowest correlation was between plasma concentration of CoQ10-OX and the ratio of LDL Chol/CoQ10 , as well as between CoQ10-OX and the ratio of TAG/CoQ10 in obese children. CONCLUSION: An increase of the ratios of lipid parameters to CoQ10 is associated with child obesity and could be used as biomarkers of early complications in the development of obesity in children (Tab. 3, Fig. 5, Ref. 22).

Liver mitochondrial respiratory function and coenzyme Q content in rats on a hypercholesterolemic diet treated with atorvastatin.

Statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, are effective drugs in the treatment of hypercholesterolemia, however, their undesirable actions are not fully known. We investigated the effects of atorvastatin on the oxidative phosphorylation and membrane fluidity in liver mitochondria, and also on the coenzyme Q (CoQ) content in the mitochondria, liver tissue, and plasma of rats on a standard (C) and hypercholesterolemic (HCh) diet. Atorvastatin was administered at either low (10 mg kg(-1)) or high dose (80 mg kg(-1)) for four weeks. The high dose of the drug decreased the concentrations of total cholesterol and triacylglycerols in the plasma and liver of rats on a HCh diet. Administration of atorvastatin was associated with decreased oxygen uptake (state 3), and oxidative phosphorylation rate in the mitochondria of both C and HCh rats. Further, the drug influenced mitochondrial membrane fluidity and dose-dependently reduced concentrations of oxidized and reduced forms of CoQ in the mitochondria. Our findings point to an association between in vivo administration of atorvastatin and impaired bioenergetics in the liver mitochondria of rats, regardless of diet, in conjunction with simultaneous depletion of oxidized and reduced CoQ forms from the mitochondria. This fact may play a significant role in the development of statin-induced hepatopathy.

Effects of atorvastatin on heart mitochondrial function and coenzyme Q content in the experiment.

We focused on determination of whether atorvastatin: 1) reduces CoQ content, 2) impairs mitochondrial function and 3) induces dose-dependent changes. Although the high dose of atorvastatin exerted a beneficial effect on the lipid peroxidation in plasma, coenzyme Q content was reduced and heart mitochondrial function was impaired. Physicians should be aware when prescribing statins mainly in higher doses to the patients with co-existing proved or supposed CoQ10 deficiency resulting from age-related decline, and metabolic or mitochondrial diseases (Ref. 3).

Complementary therapy in diabetic patients with chronic complications: a pilot study.

BACKGROUND: Oxidative stress and dysregulation of antioxidant function play a pivotal role in the diabetic complications. METHODS: Fifty-nine patients with diabetes were randomly assigned into three groups. 1) PL group (n = 19): Polarized light (PL) was applied to neuropathic ulcers of diabetic foot twice daily for ten minutes in pulse regimen during three months. 2) QALA group (n = 20): Antioxidants (60 mg hydrosoluble CoQ10, 100 mg alpha-lipoic acid (ALA) and 200 mg vitamin E) were used in two daily doses for three months. 3) QALAPL group (n = 20): Patients used antioxidants along with PL applications. To test for differences in means, paired Student's t-test (before and after three months) was used. RESULTS: Three months application of PL significantly increased plasma concentrations of coenzyme Q10, alpha-tocopherol, tau-tocopherol and beta-carotene, and decreased lactate dehydrogenase (LDH) activity. Supplementation with antioxidants decreased plasma lipid peroxides, increased concentration of CoQ10 and improved echocardiographic parameters. Simultaneous application of PL and antioxidants significantly stimulated plasma CoQ10 and alpha-tocopherol concentrations, decreased LDH activity and contributed to improvement in heart left ventricular function in diabetics. CONCLUSION: Thus the data show that supportive therapy with PL along with the antioxidants hydrosoluble CoQ10, alpha-lipoic acid and vitamin E is an effective way of controlling the complications of type 2 diabetes (Tab. 7, Fig. 2, Ref. 44).

Losartan improved respiratory function and coenzyme Q content in brain mitochondria of young spontaneously hypertensive rats.

Increased production of free radicals and impairment of mitochondrial function are important factors in the pathogenesis of hypertension. This study examined the impact of hypertension on mitochondrial respiratory chain function, coenzyme Q(9) (CoQ(9)), coenzyme Q(10) (CoQ(10)), and alpha-tocopherol content in brain mitochondria, and the effect of blockade of angiotensin II type 1 receptors (AT1R) in the prehypertensive period on these parameters. In addition, blood pressure, heart and brain weight to body weight ratios, and the geometry of the basilar artery supplying the brain were evaluated. In the 9th week blood pressure and heart weight/body weight ratio were significantly increased and brain weight/body weight ratio was significantly decreased in spontaneously hypertensive rats (SHR) when compared to Wistar rats (WR). The cross-sectional area of the basilar artery was increased in SHR. Glutamate-supported respiration, the rate of ATP production, and concentrations of CoQ(9), CoQ(10), and alpha-tocopherol were decreased in SHR. The succinate-supported function and cytochrome oxidase activity were not changed. The treatment of SHR with losartan (20 mg/kg/day) from 4th to 9th week of age exerted preventive effect against hypertension, heart and arterial wall hypertrophy, and brain weight/body weight decline. After the therapy, the rate of ATP production and the concentration of CoQ increased in comparison to untreated SHR. The impairment of energy production and decreased level of lipid-soluble antioxidants in brain mitochondria as well as structural alterations in the basilar artery may contribute to increased vulnerability of brain tissue in hypertension. Long-term treatment with AT1R blockers may prevent brain dysfunction in hypertension.

Subcellular mechanisms of adaptation in the diabetic myocardium: Relevance to ischemic preconditioning in the nondiseased heart.

Although hyperglycemia is one factor that determines the outcome of myocardial ischemic insult, it is still not clear whether it is causally related to decreased ischemic tolerance in diabetic patients. In contrast to clinical and epidemiological studies demonstrating a higher risk of cardiovascular disorders in diabetic patients, experimental data are not unequivocal and suggest that, aside from higher myocardial vulnerability, diabetes mellitus may be associated with the triggering of adaptive processes leading to paradoxically lower susceptibility to ischemia. It has been proposed that this phenomenon shares some molecular pathways with short-term preconditioning and other forms of endogenous protection against ischemia/reperfusion injury in the nondiseased heart. The present article reviews some controversial findings of enhanced resistance to ischemia in the diabetic heart that stem from experimental studies in different models of myocardial ischemia/reperfusion injury. Specifically, it addresses the issue of potential mechanisms of increased resistance to ischemia in an experimental model of streptozotocin-induced diabetes, particularly with respect to the role of reactive oxygen species, hyperglycemia as one of the stress factors, and cell-signalling mechanisms mediated by 'prosurvival' cascades of protein kinases in relation to the mechanisms of classical ischemic preconditioning. Finally, mechanisms involved in the suppression of protection in the diabetic myocardium including the effect of concomitant pathology, such as hypercholesterolemia, are discussed.

Protection against ischemia-induced ventricular arrhythmias and myocardial dysfunction conferred by preconditioning in the rat heart: involvement of mitochondrial K(ATP) channels and reactive oxygen species.

Ischemic preconditioning (I-PC) induced by brief episodes of ischemia and reperfusion (I/R) protects the heart against sustained I/R. Although activation of mitochondrial K(ATP) channels (mitoK(ATP)) interacting with reactive oxygen species (ROS) has been proposed as a key event in this process, their role in the antiarrhythmic effect is not clear. This study was designed: 1) to investigate the involvement of mito K(ATP) opening in the effect of I-PC (1 cycle of I/R, 5 min each) on ventricular arrhythmias during test ischemia (TI, 30-min LAD coronary artery occlusion) in Langendorff-perfused rat hearts and subsequent postischemic contractile dysfunction, and 2) to characterize potential mechanisms of protection conferred by I-PC and pharmacological PC induced by mito K(ATP) opener diazoxide (DZX), with particular regards to the modulation of ROS generation. Lipid peroxidation (an indicator of increased ROS production) was determined by measurement of myocardial concentration of conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS) in non-ischemic controls, non-preconditioned and preconditioned hearts exposed to TI, I-PC alone, as well as after pretreatment with DZX, mito K(ATP) blocker 5-hydroxydecanoate (5-HD) and antioxidant N-acetylcysteine (NAC). Total number of ventricular premature beats (VPB) that occurred in the control hearts (518+/-71) was significantly (P<0.05) reduced by I-PC (195+/-40), NAC (290+/-56) and DZX (168+/-22). I-PC and NAC suppressed an increase in CD and TBARS caused by ischemia indicating lower production of ROS. On the other hand, I-PC and DZX themselves moderately enhanced ROS generation, prior to TI. Bracketing of I-PC with 5-HD suppressed both, ROS production during PC and its cardioprotective effect. In conclusion, potential mechanisms of protection conferred by mito K(ATP) opening in the rat heart might involve a temporal increase in ROS production in the preconditioning phase triggering changes in the pro/antioxidant balance in the myocardium and attenuating ROS production during subsequent prolonged ischemia.

Endogenous protective mechanisms in remodeling of rat heart mitochondrial membranes in the acute phase of streptozotocin-induced diabetes.

The aim of present study was to investigate functional and physical alterations in membranes of heart mitochondria that are associated with remodeling of these organelles in acute phase of streptozotocin-induced diabetes and to elucidate the role of these changes in adaptation of the heart to acute streptozotocin-induced diabetes (evaluated 8 days after single dose streptozotocin application to male Wistar rats). Action of free radicals on the respiratory chain of diabetic-heart mitochondria was manifested by 17 % increase (p<0.05) in oxidized form of the coenzyme Q(10) and resulted in a decrease of states S3 and S4 respiration, the respiratory control index, rate of phosphorylation (all p<0.01) and the mitochondrial transmembrane potential (p<0.05), but the ADP/O ratio decreased only moderately (p>0.05). On the contrary, membrane fluidity and the total mitochondrial Mg2+-ATPase activity increased (both p<0.05). In diabetic heart mitochondria, linear regression analysis revealed a reciprocal relationship between the increase in membrane fluidity and decrease in trans-membrane potential (p<0.05, r = 0.67). Changes in membrane fluidity, transmembrane potential, Mg2+-ATPase activity and the almost preserved ADP/O ratio appear as the manifestation of endogenous protective mechanisms participating in the functional remodeling of mitochondria which contributes to adaptation of the heart to diabetes.

The effect of antioxidant treatment and NOS inhibition on the incidence of ischemia-induced arrhythmias in the diabetic rat heart.

Contrary to clinical trials, experimental studies revealed that diabetes mellitus (DM) may initiate, besides increased myocardial vulnerability to ischemia-reperfusion injury (I/R) and pro/antioxidant dysbalance, development of adaptation leading to an enhanced tolerance to I/R. The aims were to characterize 1) susceptibility to ischemia-induced ventricular arrhythmias in the diabetic rat heart 2) its response to antioxidant N-acetylcysteine (NAC) and a NOS inhibitor L-NAME, and 3) the effect of DM on endogenous antioxidant systems. Seven days after streptozotocin injection (65 mg/kg, i.p.), Langendorff-perfused control (C) and DM hearts were subjected to 30-min occlusion of the LAD coronary artery with or without prior 15-min treatment with L-NAME (100 microM) or NAC (4 mM). Total number of ventricular premature beats (VPB), as well the total duration of ventricular tachycardia (VT) were reduced in the DM group (from 533+/-58 and 37.9+/-10.2 s to 224.3+/-52.6 and 19+/-13.5 s; P<0.05). In contrast to the antiarrhythmic effects of L-NAME and NAC in controls group (VPB 290+/-56 and 74+/-36, respectively; P<0.01 vs. control hearts), application of both drugs in the diabetics did not modify arrhythmogenesis (L-NAME: VPB 345+/-136, VT 25+/-13 s; NAC: VPB 207+/-50, VT 12+/-3.9 s; P>0.05 vs non-treated diabetic hearts). Diabetic state was associated with significantly elevated levels of CoQ10 and CoQ9 (19.6+/-0.8 and 217.3+/-9.5 vs. 17.4+/- 0.5 and 185.0+/-5.0 nmol/g, respectively, in controls; P<0.05), as well as alpha-tocopherol (38.6+/-0.7 vs. 31.5+/-2.1 nmol/g in controls; P<0.01) in the myocardial tissue. It is concluded that early period of DM is associated with enhanced resistance to ischemia-induced arrhythmias. Diabetes mellitus might induce adaptive processes in the myocardium leading to lower susceptibility to antioxidant and L-NAME treatment.

Simvastatin decreased coenzyme Q in the left ventricle and skeletal muscle but not in the brain and liver in L-NAME-induced hypertension.

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (statins) have been proven to reduce effectively cholesterol level and morbidity and mortality in patients with coronary heart disease and/or dyslipoproteinemia. Statins inhibit synthesis of mevalonate, a precursor of both cholesterol and coenzyme Q (CoQ). Inhibited biosynthesis of CoQ may be involved in some undesirable actions of statins. We investigated the effect of simvastatin on tissue CoQ concentrations in the rat model of NO-deficient hypertension induced by chronic L-NAME administration. Male Wistar rats were treated daily for 6 weeks with L-NAME (40 mg/kg) or with simvastatin (10 mg/kg), another group received simultaneously L-NAME and simvastatin in the same doses. Coenzyme Q(9) and Q(10) concentrations were analyzed by high performance liquid chromatography. L-NAME and simvastatin alone had no effect on CoQ concentrations. However, simultaneous application of L-NAME and simvastatin significantly decreased concentrations of both CoQ homologues in the left ventricle and slightly decreased CoQ(9) concentration in the skeletal muscle. No effect was observed on CoQ level in the liver and brain. We conclude that the administration of simvastatin under the condition of NO-deficiency reduced the level of CoQ in the heart and skeletal muscle what may participate in adverse effect of statins under certain clinical conditions.

Functional remodeling of heart mitochondria in acute diabetes: interrelationships between damage, endogenous protection and adaptation.

Rats with streptozotocin-diabetes develop mechanisms of endogenous protection (MEP) that participate actively in functional remodeling of cardiac sarcolemma. Remodeling of sarcolemma is a sign of damage but it also protects the cells of the diabetic heart (DH) against additional energy disbalance due to excessive Ca(2+) entry. Since yet, cardiac mitochondria (MIT) were investigated predominantly from the aspect of damage only. Aims of the present study were: i) to distinguish between acute diabetes-induced changes in function of rat heart MIT which clearly belong to damage from those that reflect the MEP and participate in functional remodeling of the MIT; ii) elucidate the significance of MEP-induced changes in heart MIT for cardiac energetics. Acute diabetes (8 days) was induced in adult male Wistar rats by streptozotocin (STZ, 65 mg.kg(-1) i.p., single dose). On the day 8 after STZ administration, the diabetic animals exhibited 300-330 % increase in blood glucose, triacylglycerols and cholesterol as well as 89.6 % increase in glycohemoglobin (all p < 0.01). The blood level of insulin dropped by 53 % (p < 0.02). State 3 and state 4 oxygen consumptions of DH MIT were decreased against the controls, leading to drop of the respiratory control index (17.9 and 7.3 %) and oxidative phosphorylation rate (OPR, 27.5 and 24.6 %; all p < 0.003-0.02). These effects of damage yielding in strained energy balance of the acute DH were partially alleviated by MEP. The latter involved temporary preservation of the ADP : O ratio, with participation of elevated MIT Mg(2+)-ATPase activity as well as increased formation of MIT substrate and energy transition pores (both p < 0.05). Hence, the energy disbalance of the acute DH was finally manifested in 13 % loss in its AMP content only (p < 0.05). Results indicate that MIT in STZ-DH are functionally remodeled. Defective O2 consumption by MIT renders molecular changes suggestive of a mild hypoxic state but an increase in Mg(2+)-ATPase activity and facilitated energy delivery from MIT to the cytoplasm indicate the presence of MEP acting in the MIT and alleviating the effect of decreased oxidative energy production in the acute DH.