Altered biogenesis of microRNA-1 is associated with cardiac dysfunction in aging of spontaneously hypertensive rats.

Currently we face the issues of aging-associated pathologies, particularly those leading to heart failure. With that in mind, in current research we focus on aging and hypertension combination as a widely spread threating problem. In a row with functional and morphological characterization of these aging- and hypertension-associated cardiac changes, we evaluate biogenesis of microRNA-1 being one of major microRNAs in the heart. The aim of this study was to check the hypothesis if dysregulation of microRNA-1 biogenesis is associated with heart failure in aged and especially aged hypertensive rats. The experiments were carried out on male SHR and Wistar rats of age 6 months (young) and 18 months (old). The evaluation of hemodynamic parameters was performed in heart left ventricles of narcotized rats using the ultra-small 2F catheter. The development of fibrosis was determined using light and electron microscopy. Levels of mature and immature forms of microRNA-1 and mRNA encoding the proteins involved in its biogenesis were determined using reverse transcription and quantitative PCR. Aging of both Wistar and SHRs is accompanied with altered hemodynamic parameters compared with correspondent younger mates. SHRs, especially old ones, demonstrated significant heart fibrosis. In aged animals, the level of primary microRNA-1 in Wistar rats were 7 times higher (p < 0.05) and in SHR 17 times higher (p < 0.05) in comparison with young rats of the same strain. We also observed 22 times higher level of immature microRNA-1 in the heart of Wistar and 5.9 times higher level for aged hypertensive rats (p < 0.05) compared to young rats. At the same time, the level of mature microRNA-1 occurred 2.5 and 3.2 times lower in respective groups (p < 0.05). In the current study, we observe the significant dysregulation of microRNA-1 processing in the heart associated with aging and arterial hypertension.

Effects of intermittent hypoxia training on leukocyte pyruvate dehydrogenase kinase 1 (PDK-1) mRNA expression and blood insulin level in prediabetes patients.

PURPOSE: Intermittent hypoxia training/treatment (IHT) is an emerging therapeutic approach to alleviate chronic diseases, such as diabetes. The present study investigated the effects of IHT on blood leucocyte pyruvate dehydrogenase kinase 1 (PDK-1) mRNA expression and its relationship with the changes in blood insulin level. METHODS: Seven adult healthy volunteers and 11 prediabetic patients participated in this study. A 3-week course of IHT consisted of a 40-min session of 4 cycles of 5-min 12% O2 and 5-min room air breathing per day, 3 sessions per week for 3 weeks (i.e., total 9 sessions of IHT). Plasma insulin levels and leukocyte PDK-1 mRNA expression were determined at various time points either under fasting condition or following oral glucose tolerance test (OGTT). Correlation between the IHT-induced changes in PDK-1 mRNA and insulin or glucose levels in the same serological samples was analyzed. RESULTS: At pre-IHT baseline, PDK-1 mRNA expression was two times higher in prediabetes than control subjects. IHT resulted in significant augmentation in PDK-1 mRNA expression (> twofold) in prediabetes at the end of 3-week IHT and remained elevated 1 month after IHT, which was correlated with a significantly reduced insulin release and lower blood glucose after glucose loading with OGTT. CONCLUSION: IHT can trigger beneficial effects in normalizing blood insulin levels in prediabetic patients under oral glucose load, which were closely correlated with an enhanced mRNA expression of PDK-1 in leukocytes. Further clinical trials are warranted to validate the utility of IHT as a non-invasive complementary therapy against diabetes-associated pathologies.

Liver mitochondrial respiratory plasticity and oxygen uptake evoked by cobalt chloride in rats with low and high resistance to extreme hypobaric hypoxia.

High-altitude intolerance and consequently high-altitude sickness, is difficult to predict. Liver is an essential organ in glucose and lipid metabolism, and may play key role in the adaptation to high altitude. In response to extreme high altitude, mitochondrial respiration exhibits changes in substrate metabolism, mitochondrial electron transport chain activity, and respiratory coupling. We determined the cobalt chloride (CoCl2) effects on liver mitochondrial plasticity and oxygen uptake in rats with low resistance (LR) and high resistance (HR) to extreme hypobaric hypoxia. The polarographic method proposed by Chance and Williams was used as a simple and effective tool to trace mitochondrial functionality and oxygen consumption. HR rats had more efficient processes of NADH- and FAD-generated mitochondrial oxidation. CoCl2 promoted more efficient NADH-generated and diminished less efficient FAD-generated mitochondrial respiratory reactions in HR rats. CoCl2 diminished both aerobic and anaerobic processes in LR rats. Glutamate and pyruvate substrates of NADH-generated mitochondrial pathways were highly affected by CoCl2. Red blood cells acted as cobalt depots in HR and LR rats. We have unveiled several mechanisms leading to differentiated mitochondrial respiratory responses to hypobaric hypoxia in LR and HR rats. Our study strongly supports the existence of adaptive liver mitochondrial plasticity to extreme hypoxia.

Intermittent hypoxia training in prediabetes patients: Beneficial effects on glucose homeostasis, hypoxia tolerance and gene expression.

The present study aimed at examining beneficial effects of intermittent hypoxia training (IHT) under prediabetic conditions. We investigate the effects of three-week IHT on blood glucose level, tolerance to acute hypoxia, and leukocyte mRNA expression of hypoxia inducible factor 1α (HIF-1α) and its target genes, i.e. insulin receptor, facilitated glucose transporter-solute carrier family-2, and potassium voltage-gated channel subfamily J. Seven healthy and 11 prediabetic men and women (44-70 years of age) were examined before, next day and one month after three-week IHT (3 sessions per week, each session consisting 4 cycles of 5-min 12% O2 and 5-min room air breathing). We found that IHT afforded beneficial effects on glucose homeostasis in patients with prediabetes reducing fasting glucose and during standard oral glucose tolerance test. The most pronounced positive effects were observed at one month after IHT termination. IHT also significantly increased the tolerance to acute hypoxia (i.e. SaO2 level at 20th min of breathing with 12% O2) and improved functional parameters of respiratory and cardiovascular systems. IHT stimulated HIF-1α mRNA expression in blood leukocytes in healthy and prediabetic subjects, but in prediabetes patients the maximum increase was lagged. The greatest changes in mRNA expression of HIF-1α target genes occurred a month after IHT and coincided with the largest decrease in blood glucose levels. The higher expression of HIF-1α was positively associated with higher tolerance to hypoxia and better glucose homeostasis. In conclusion, our results suggest that IHT may be useful for preventing the development of type 2 diabetes. Impact statement The present study investigated the beneficial effects of intermittent hypoxia training (IHT) in humans under prediabetic conditions. We found that three-week moderate IHT induced higher HIF-1α mRNA expressions as well as its target genes, which were positively correlated with higher tolerance to acute hypoxia and better glucose homeostasis in both middle-aged healthy and prediabetic subjects. This small clinical trial has provided new data suggesting a potential utility of IHT for management of prediabetes patients.

The role of nitric oxide in endotoxin-induced cardiodepression.

OBJECTIVE: To determine the participation of inducible nitric oxide synthase (iNOS) in cardiodepressive phenomena during late preconditioning caused by subtoxic doses of lipopolysaccharide (LPS). METHODS: Spontaneously beating hearts isolated from male Wistar rats (350 g to 400 g), intact or preconditioned with LPS (0.25 mg/kg given intraperitoneally 18 h before heart excision), were used to measure contractile performance during 30 min of ischemia and 40 min of reperfusion in the Langendorff mode. For selective iNOS blockade, hearts were perfused with phenylene-1,3-bis(ethane-2-isothiourea) (50 nmol/L). Expression of iNOS (determined using Western blotting) and NOS activities were determined in frozen myocardial tissues. RESULTS: Subtoxic doses of LPS caused iNOS induction in the heart and depression of contractile function, but improved heart postischemic recovery. In all groups of animals, expression of iNOS was higher in the right than left ventricles. Ischemia and postischemic reperfusion of intact heart intensified production of nitric oxide (NO), predominantly by iNOS. The preconditioning led to iNOS activation during ischemia in the left ventricle and iNOS depression in the right ventricle, owing to feedback caused by the initially higher iNOS expression and activity in the right ventricle. Postischemic reperfusion diminished NOS activities in preconditioned myocardial tissues. Blockade of iNOS significantly slowed preconditioned heart recovery and partially restored left ventricular developed pressure, but only after 20 min of reperfusion. CONCLUSIONS: iNOS-produced NO plays a role in the development of delayed cardioprotection and cardiodepressive effects (in part) after extravasal administration of a minimal dose of endotoxin.