Daishi Nonaka

Intracellular Renin Protects Cardiomyocytes from Ischemic Injury in Diabetic Heart

Background: Local Renin-Angiotensin-Aldosterone system (RAS) is important in cardiac pathophysiology. We investigated the expression and distribution of intracellular renin after ischemia, and the effects of renin on mitochondrial function in diabetic heart. Methods: In Goto-Kakizaki (DM) and Wistar (non-DM) rats, Langendorff-perfused hearts were subjected to ischemia by coronary artery ligation for 90 min. Infarct Size (IS) and expression of RAS components were examined. Mitochondrial membrane potential (ΔΨm), uncoupling protein-2 (UCP2), NAD/NADH ratio, and ATP were measured in renin-treated myocytes or isolated mitochondria. Results: After ischemia, LV function (LVDP; 76 ± 4 vs. 52 ± 4 mmHg, LVEDP; 18 ± 2 vs. 29 ± 4 mmHg, p<0.05, DM; n=9, non-DM; n=9, respectively) was prevented and IS (44.2 ± 2.1 vs. 53.7 ± 2.9 %, p<0.05) was significantly small in DM hearts. These cardioprotective effects were abolished when DM hearts were treated with direct renin inhibitor (LVDP; 77 ± 3 vs. 55 ± 4 mmHg, LVEDP; 16 ± 1 vs. 27 ± 3 mmHg, IS; 40.8 ± 2.9 vs. 52.1 ± 3.4 %, p<0.05, DM; n=5, DM plus DRI; n=5, respectively). Renin expression in the ischemic area was increased in DM hearts. Electron microscopy showed predominant renin localization within mitochondria. In permeabilized myocytes or isolated mitochondria, renin hyperpolarized ΔΨm, increased NAD/NADH ratio and preserved ATP content. Ischemiainduced UCP2 expression was reduced in DM. Conclusions: Intracellular renin, which mainly localizes within mitochondria, increased during ischemia and protected cardiomyocytes in diabetic hearts. This protective effect of renin is at least partially because of the reduction of UCP2 and the acceleration of electron transport chain, which resulted in the prevention of mitochondrial depolarization and ATP production.

Intracellular Renin Inhibits Mitochondrial Permeability Transition Pore via Activated Mitochondrial Extracellular Signal-Regulated Kinase (ERK) 1/2 during Ischemia in Diabetic Hearts

Although beneficial effects of non-secreting intracellular renin (ns-renin) against ischemia have been reported, the precise mechanism remains unclear. In this study, we investigated the roles of ns-renin and mitochondrial extracellular signal-related kinase (ERK) 1/2 on mitochondrial permeability transition pore (mPTP) opening during ischemia in diabetes mellitus (DM) hearts. When isolated hearts from Wistar rats (non-DM hearts) and Goto-Kakizaki rats (DM hearts) were subjected to ischemia for 70 min by left anterior descending coronary artery ligation, DM hearts exhibited higher left ventricular (LV) developed pressure and lower LV end-diastolic pressure than non-DM hearts, suggesting ischemic resistance. In addition, DM hearts showed increased intracellular renin (int-renin, including secreting and non-secreting renin) in the ischemic area, and a direct renin inhibitor (DRI; aliskiren) attenuated ischemic resistance in DM hearts. ERK1/2 was significantly phosphorylated after ischemia in both whole cell and mitochondrial fractions in DM hearts. In isolated mitochondria from DM hearts, rat recombinant renin (r-renin) significantly phosphorylated mitochondrial ERK1/2, and hyperpolarized mitochondrial membrane potential (ΔΨm) in a U0126 (an inhibitor of mitogen-activated protein kinases/ERK kinases)-sensitive manner. R-renin also attenuated atractyloside (Atr, an mPTP opener)-induced ΔΨm depolarization and Atr-induced mitochondrial swelling in an U0126-sensitive manner in isolated mitochondria from DM hearts. Furthermore, U0126 attenuated ischemic resistance in DM hearts, whereas it did not alter the hemodynamics in non-DM hearts. Our results suggest that the increased int-renin during ischemia may inhibit mPTP opening through activation of mitochondrial ERK1/2, which may be involved in ischemic resistance in DM hearts.

Recent changes in blood pressure levels, hypertension prevalence and treatment rates, and the rate of reaching target blood pressure in the elderly

Abstract Antihypertensive treatment has beneficial effects in the elderly. Surveying the situation of blood pressure in the elderly is quite important for planning strategies to manage elderly hypertensives. The aim of the present study was to investigate changes in blood pressure in the elderly over the past 15 years. As part of a physical check-up program between 2001 and 2015, 29,363 elderly participants (≥65 years of age) attended and were enrolled in the present study. The characteristics of the participants in each year were analyzed cross-sectionally and the results were compared over the 15 years. Changes in blood pressure, hypertension prevalence, and treatment rates, and the rate of reaching target blood pressure in the elderly were investigated. The prevalence of hypertension during the study period increased with increasing participant age. However, both the treatment rate and the rate of reaching target blood pressure in treated subjects improved. The blood pressure of treated hypertensive elderly subjects decreased from 146.1/83.0 to 130.6/75.4 mm Hg, and the reduction was most evident after revision of Japanese Society of Hypertension guidelines regarding target blood pressure in elderly hypertensives. Blood pressure in the entire cohort of elderly subjects decreased from 133.8/78.4 mm Hg in 2001 to 127.9/74.6 mm Hg in 2015. Blood pressure in elderly subjects had decreased over the 15-year study period primarily due to reductions in blood pressure in elderly hypertensive patients on medication. Guidelines for the treatment of hypertension have had a beneficial effect on the management of hypertension in the elderly.

[PP.30.09] DOSE SALT INTAKE PREDICT THE NEW ONSET OF CHRONIC KIDNEY DISEASE?

Objective: Dietary salt, which is one of the most important modifiable factors in our life style, is associated not only with blood pressure but also with several cardiovascular diseases in a blood pressure–independent manner. We investigated if salt intake predicts new onset of chronic kidney disease (CKD) in the general population. Design and method: Consecutive 8,161 participants (male = 5,168, 55.8 ± 11.3 year-old) with normal estimated glomerular filtration rate (eGFR;> = 60 ml/min/1.73 m2) in our physical health check-up program were enrolled in this study. After baseline examination, participants were followed up (median 1,098 day) with the endpoint being the development of CKD (eGFR<60 ml/min/1.73 m2). Individual salt intake was estimated using spot urine by a previously reported method and GFR was estimated using the Japanese Society of Nephrology formula. Results: Salt intake was 8.9 ± 2.0 g/day in male and 8.6 ± 1.9 g/day in female subjects. eGFR was 80.1 ± 12.7 ml/min/1.73 m2 at baseline, and during the follow-up period, CKD developed in 706 subjects (29.9 per 1000 person-year), with the incidence being more frequent in male than female subjects (31.1 vs. 27.8 per 1000 person-year). Non-adjusted hazard ratio (HR) (95% confidence interval [CI]) of salt intake for the new CKD was 1.071 (1.034–1.109). Multivariate Cox-hazard analysis adjusted for body mass index, systolic blood pressure, heart rate, uric acid, fasting plasma glucose, low-density lipoprotein cholesterol, triglyceride, hemoglobin, smoking status and eGFR at baseline demonstrated that salt intake was a significant predictor of new onset CKD (HR = 1.077, 95%CI = 1.037–1.119). Univariate and adjusted multivariate liner regression analyses indicated the significant correlation between salt intake at baseline and yearly changes in eGFR (r = -0.081, p < 0.001 and r = -0.069, p < 0.001, respectively). Similar results were obtained in a sub-analysis performed in subjects with normal blood pressure (n = 5,863). Conclusions: Dietary salt intake is significantly associated with the development of CKD and decrease in eGFR in the general population, even in normotensive subjects. These results suggest that salt restriction is beneficial for the prevention of the impairment of kidney function and the development of CKD.

Suppression of Dynamin-Related Protein 1 by Eicosapentaenoic Acid Ameliorates Palmitate-Induced Lipotoxicity in Differenciated H9C2 Myocytes

Objective: Although previous clinical investigations have reported many preferable effects of eicosapentaenoic acid (EPA; n-3 polyunsaturated fatty acid) against cardiovascular disease, the precise mechanisms are not fully clarified. Since aberrant mitochondrial dynamics plays key roles for the pathogenesis of cardiovascular disease, we investigated the relationship between EPA-mediated cardiac protection and mitochondrial dynamics.Methods and Results: When differentiated H9c2 myocytes were exposed to palmitate (PAL; 400 μM, saturated fatty acid) for 24 hours, the PAL-treated myocytes exhibited depolarized mitochondrial membrane potential (ΔΨm: measured with JC10 ratio; 2.1±0.4 vs. 4.5±0.3 of control, P<0.01) and activated caspase3/7 (measured with luminescent assay; 4.1±0.7 fold increase from control, P<0.01), suggesting the PAL-induced lipotoxicity. The PAL-treated myocytes also showed dynamin-related protein 1 (Drp1) up-regulation and fragmented mitochondria (75.3±5.0 % of cells vs. 9.2±3.2 % of control, P<0.01), indicating aberrant mitochondrial dynamics by PAL. When the PAL-treated myocytes were co-incubated with EPA (50 μM), the caspase3/7 activation by PAL (1.5±0.3 fold increase vs. PAL, P<0.01) was attenuated and the ΔΨm depolarization by PAL was restored (2.9±0.2 vs. PAL, P<0.01). EPA also suppressed the PAL-induced Drp1 expression and mitochondrial fragmentation (37.6±6.4% vs. PAL, P<0.01). In addition, EPA alone reduced the Drp1 expression and exhibited elongated mitochondria.Conclusion: We conclude that EPA ameliorates the PAL-induced lipotoxicity by the regulation of mitochondrial dynamics through Drp1.