High potassium intake inhibits neointima formation in the rat carotid artery balloon injury model

Evaluation of the Effects of Aging on the Aorta Stiffness in Relation with Mineral and Trace Element Levels: an Optimized Method via Custom-Built Stretcher Device

Aortic stiffness represents the major cause of aging and tightly associated with hypertension, atherosclerosis, cardiovascular diseases, and increased mortality. Mechanical characteristics of the aorta play a vital role in the blood flow, circulation, systolic pressure, and aortic stiffness; however, the correlation of trace element and mineral levels with aortic stiffness has not been studied before. Balance in the trace elements and minerals is vital for the biological functions; however, natural aging may alter this balance. Thus, after measuring aortic stiffness of aged and young rat aortas by a custom-built stretcher device, trace element and mineral levels were evaluated via ICP-MS. Also, biomarkers of aging including blood pressure, arterial pressure glucose, insulin levels, and histochemical parameters were investigated as well. Aortic stiffness, blood glucose, plasma insulin, systolic, diastolic, and mean arterial pressure significantly increased by aging in the aorta of aged rats compared with the young ones. Also, Fe, Al, Co, Ni, Zn, Sr, Na, Mg, and K levels increased in the aged aorta samples compared with the young aorta samples of rats. Increased levels of the indicated elements may be correlated with the development and progression of aortic stiffness and vascular complications. Thus, possible mechanisms correlating aortic stiffness with the imbalance in the trace element and mineral levels should be further investigated.

Abdominal aortic calcification score predicts the occurrence of coronary artery disease in middle-aged peritoneal dialysis patients

AIM

Abdominal aortic calcification (AAC) score in dialysis patients was associated with coronary artery disease (CAD) in cross-sectional study, but the use of AAC score in the CAD prediction was not clear. We aimed to use AAC score in the estimation of CAD occurrence in middle-aged peritoneal dialysis (PD) patients.

METHODS

Middle-aged (45-65 years old) PD patients were recruited and followed up until CAD occurrence, patient mortality, or PD failure. We quantified AAC score by lateral lumbar radiography, and used receiver operation curve (ROC) analysis to find the cut-off value for CAD prediction.

RESULTS

There were 187 patients recruited for study with a mean follow-up of 1027 ± 427 days. AAC score in patients with CAD during follow-up period (9.7 ± 7.6, n = 41) was higher than in patients without CAD occurrence (5.5 ± 6.1, n = 146) (P < 0.001). Multivariate hazard ratio of AAC score for CAD was 1.07 (P = 0.044). ROC showed that AAC score of 5.5 had a sensitivity of 0.667 and a specificity of 0.581 in the prediction of CAD occurrence. Patients with AAC score above 5.5 had significantly higher cumulative incidence of CAD than patients with AAC score below 5.5 (Log-rank test, P = 0.003). Age (P = 0.002), diabetes (P = 0.002), hypertension (P = 0.032), longer dialysis vintage (P < 0.001) and lower serum potassium (P = 0.012) were parameters significantly associated with higher AAC score.

CONCLUSION

AAC score can predict CAD occurrence in PD patients. Age, diabetes, hypertension, dialysis vintage and serum potassium level are factors associated with higher AAC score.

Postulating the major environmental condition resulting in the expression of essential hypertension and its associated cardiovascular diseases: Dietary imprudence in daily selection of foods in respect of their potassium and sodium content resulting in oxidative stress-induced dysfunction of the vascular endothelium, vascular smooth muscle, and perivascular tissues

We hypothesize that the major environmental determinant of the expression of essential hypertension in America and other Westernized countries is dietary imprudence in respect of the consumption of daily combinations of foods containing suboptimal amounts of potassium and blood pressure-lowering phytochemicals, and supraphysiological amounts of sodium. We offer as premise that Americans on average consume suboptimal amounts of potassium and blood pressure-lowering phytochemicals, and physiologically excessive amounts of sodium, and that such dietary imprudence leads to essential hypertension through oxidative stress-induced vascular endothelial and smooth muscle dysfunction. Such dysfunctions restrict nitric oxide bioavailability, impairing endothelial cell-mediated relaxation of the underlying vascular smooth muscle, initiating and maintaining inappropriately increased peripheral and renal vascular resistance. The biochemical steps from oxidative stress to vascular endothelial dysfunction and its pernicious cardiovascular consequences are well established and generally accepted. The unique aspect of our hypothesis resides in the contention that Americans' habitual consumption of foods resulting in suboptimal dietary intake of potassium and supraphysiological intake of sodium result in oxidative stress, the degree of which, we suggest, will correlate with the degree of deviation of potassium and sodium intake from optimal. Because suboptimal intakes of potassium reflect suboptimal intakes of fruits and vegetables, associated contributors to oxidative stress include suboptimal intakes of magnesium, nitrate, polyphenols, carotenoids, and other phytochemical antioxidants for which fruits and vegetables contain abundant amounts. Currently Americans consume potassium-to-sodium in molar ratios of less than or close to 1.0 and the Institute of Medicine (IOM) recommends a molar ratio of 1.2. Ancestral diets to which we are physiologically adapted range from molar ratios of 5.0 to 10.0 or higher. Accordingly, we suggest that the average American is usually afflicted with oxidative stress-induced vascular endothelial dysfunction, and therefore the standards for normal blood pressure and pre-hypertension often reflect a degree of clinically significant hypertension. In this article, we provide support for those contentions, and indicate the findings that the hypothesis predicts.

Dietary potassium regulates vascular calcification and arterial stiffness

Vascular calcification is a risk factor that predicts adverse cardiovascular complications of several diseases including atherosclerosis. Reduced dietary potassium intake has been linked to cardiovascular diseases such as hypertension and incidental stroke, although the underlying molecular mechanisms remain largely unknown. Using the ApoE-deficient mouse model, we demonstrated for the first time to our knowledge that reduced dietary potassium (0.3%) promoted atherosclerotic vascular calcification and increased aortic stiffness, compared with normal (0.7%) potassium-fed mice. In contrast, increased dietary potassium (2.1%) attenuated vascular calcification and aortic stiffness. Mechanistically, reduction in the potassium concentration to the lower limit of the physiological range increased intracellular calcium, which activated a cAMP response element-binding protein (CREB) signal that subsequently enhanced autophagy and promoted vascular smooth muscle cell (VSMC) calcification. Inhibition of calcium signals and knockdown of either CREB or ATG7, an autophagy regulator, attenuated VSMC calcification induced by low potassium. Consistently, elevated autophagy and CREB signaling were demonstrated in the calcified arteries from low potassium diet-fed mice as well as aortic arteries exposed to low potassium ex vivo. These studies established a potentially novel causative role of dietary potassium intake in regulating atherosclerotic vascular calcification and stiffness, and uncovered mechanisms that offer opportunities to develop therapeutic strategies to control vascular disease.

Hydration status affects osteopontin expression in the rat kidney

Osteopontin (OPN) is a secretory protein that plays an important role in urinary stone formation. Hydration status is associated with the development of urolithiasis. This study was conducted to examine the effects of dehydration and hydration on OPN expression in the rat kidney. Animals were divided into three groups, control, dehydrated, and hydrated. Kidney tissues were processed for light and electron microscope immunocytochemistry, in situ hybridization, and immunoblot analysis. Dehydration induced a significant increase in OPN protein expression, whereas increased fluid intake induced a decrease in protein expression. Under control conditions, OPN protein and mRNA expression were only detected in the descending thin limb (DTL). Dehydration induced increased expression in the DTL and the development of detectable expression in the thick ascending limb (TAL). In contrast, OPN expression levels declined to less than the controls in the DTL after hydration, while no expression of either protein or mRNA was detectable in the TAL. Immunoelectron microscopy demonstrated that hydration status altered tubular ultrastructure and intracellular OPN expression in the Golgi apparatus and secretory cytoplasmic vesicles. These data confirm that changes in oral fluid intake can regulate renal tubular epithelial cell OPN expression.

Primary aldosteronism (PA) and endothelial progenitor cell (EPC) bioavailability

OBJECTIVE

Patients with primary aldosteronism (PA) experience more cardiovascular events than patients with essential hypertension matched for risk factor profile. Endothelial progenitor cells (EPC) represent a bone marrow-derived cell population implicated in vascular healing whose number correlates to the cardiovascular risk factor profile. Aldosterone has been reported to decrease EPC proliferation in rats.

DESIGN AND PATIENTS

We assessed (i) the growth characteristics of EPC from six PA patients and six matched normotensive controls; (ii) the growth characteristics of EPC treated with increasing doses of aldosterone.

MEASUREMENTS

Senescence and cell-cycle analysis of EPC from PA patients and normotensive controls and of aldosterone-treated EPC from healthy volunteers.

RESULTS

No difference was found in the senescence rate between EPC from PA patients (72.4% senescent cells) and controls (70.7%, P > 0.05). No difference was also found in the cell-cycle distribution determined by FACS (controls: 75.2% cells in G0/G1 phase; PA: 73.5%, P > 0.05). Incubation of EPC with aldosterone did not modify their senescence rate (controls: 72.4% senescent cells; aldosterone 10 nmol/l: 70.9%; aldosterone 100 nmol/l 71.6%, P > 0.05 for all comparisons) and cell-cycle distribution (controls: 73.3% cells in G0/G1 phase; aldosterone 10 nmol/l: 74.9%; aldosterone 100 nmol/l: 75.4%, P > 0.05 for all comparisons). No expression of the mineralocorticoid receptor (MR) transcript was found in EPC by RT-PCR analysis.

CONCLUSIONS

High aldosterone levels, both in PA patients and in vitro, exert no direct or indirect effect on EPC growth characteristics.

Dietary minerals and modification of cardiovascular risk factors

High serum cholesterol, hypertension and obesity are major risk factors for cardiovascular diseases, and together with insulin resistance form a deadly disorder referred to as the metabolic syndrome. All the aspects of this syndrome are strongly related to dietary and lifestyle factors; therefore, it would be reasonable to look for dietary approaches to their modification. Mineral nutrients, such as calcium, potassium and magnesium, lower blood pressure, and especially calcium has beneficial effects also on serum lipids. Recent evidence suggests that increased intake of calcium may help in weight control as well. This review summarizes previous literature on the effects and use of dietary minerals on serum lipids, blood pressure and obesity, with specific focus on the effects of calcium. Calcium and magnesium as divalent cations can form insoluble soaps with fatty acids in the intestine and thus prevent the absorption of part of the dietary fat. Decreased absorption of saturated fat leads to reduction in serum cholesterol level via decreased production of VLDL and increased intake of LDL in the liver. Dietary calcium may also bind bile acids, which increases the conversion of cholesterol to bile acids in the liver. Furthermore, calcium appears to enhance the cholesterol-lowering effect of plant sterols. Thus, dietary combination of the mineral nutrients and plant sterols provides a promising novel approach to the modification of cardiovascular risk factors.