Role of dietary therapies in the prevention and treatment of hypertension.

Blood pressure naturally rises with increasing age. The rate of change in blood pressure with age is regulated in part by genetic factors, but can also be altered through sustained dietary modification. Dietary approaches to modify blood pressure remain an important part of cardiovascular health promotion, which is especially important given the aging of the general population coupled with the increasing prevalence of obesity and metabolic disturbances. Specific modification of dietary components such as macronutrients and micronutrients could be helpful to lower blood pressure and alter the slope of blood pressure change whereas nutritional supplements are less likely to have a substantial beneficial effect. Population-wide generalizations regarding diet are impractical as individualized strategies are more likely to be successful in facilitating long-term benefits in improving blood-pressure control. Consequently, more effort needs to be focused on evaluating data from large-scale observational and interventional studies and interpreting their information in a clinically relevant manner, which is likely to be helpful for individual patients. Providing education on the relationship between diet and blood pressure from an early age is most likely to produce tangible benefits.

Low-dose paclitaxel ameliorates fibrosis in the remnant kidney model by down-regulating miR-192.

Transforming growth factor (TGF)-ß has been shown to play a central role in the development of tubulointerstitial fibrosis, which can be corrected via treatment with paclitaxel. The biology of microRNA (miR) can be modulated by paclitaxel. We hypothesized that paclitaxel may attenuate renal fibrosis in a rat model of remnant kidney disease by inhibiting TGF-ß induced-miRs. Rats in groups of 12 were subjected to 5/6 nephrectomy and received low-dose intraperitoneal injection of paclitaxel. Renal functions were assessed at 8 weeks. The TGF-ß signalling cascade and ECM proteins were evaluated by real-time polymerase chain reaction (TRT-PCR) and immunofluorescence microscopy. Animals with remnant kidneys developed hypertension, which was not relieved with paclitaxel treatment. However, paclitaxel treatment resulted in dampening the proteinuric response, reduction in serum BUN, creatinine levels and urine protein : creatinine ratio and normalization of creatinine clearance. These effects were accompanied by the inhibition of Smad2/3 activation, attenuation of renal fibrosis and normalization of integrin-linked kinase (ILK), COL(I)A1, COL(IV)A2 and α-SMA expression. Also, paclitaxel down-regulated the expression of miR-192, miR-217 and miR -377, while miR-15 was up-regulated in the remnant kidney. In vitro, in tubular epithelial cells (NRK-52E), paclitaxel also inhibited TGF-ß1-induced Smad2/3 activation and normalized ILK, COL(I)A1, COL(IV)A2 and α-SMA expression. Furthermore, ChIP analyses indicated that Taxol suppressed Smad3-mediated miR-192 transcriptional activity. Over-expression of miR-192 in NRK-52E mimicked the changes seen in the remnant kidney, while inclusion of miR-192 inhibitor in the culture medium blocked TGF-ß1-induced COL(I)A1 and COL(IV)A2 expression, while ILK and α-SMA were unaffected. These data suggest that low-dose paclitaxel ameliorates renal fibrosis via modulating miR-192 pathobiology and TGF-ß/Smad signalling.

The scleroderma kidney: progress in risk factors, therapy, and prevention.

Scleroderma renal crisis (SRC) is characterized by malignant hypertension, oliguric/anuric acute renal failure, and important mortality, with a 5-year survival rate of 65%. SRC occurs in 2% to 5% of patients with systemic sclerosis (SSc), particularly those with diffuse cutaneous SSc in the first years of disease evolution. Several retrospective studies have found high-dose corticosteroid therapy to be associated with increased risk of SRC, and anti-RNA-polymerase III antibodies have been detected in one third of patients with SRC. Treatment relies on the early control of blood pressure with increasing doses of angiotensin-converting enzyme inhibitors, eventually associated with calcium channel blockers together with dialysis if necessary. After 2 years on dialysis, eligible patients should be considered for renal transplantation. The strategy for prevention of SRC lacks consensus. However, corticosteroids and/or nephrotoxic drugs should be avoided in patients with diffuse cutaneous SSc.

Dietary nitrate attenuates oxidative stress, prevents cardiac and renal injuries, and reduces blood pressure in salt-induced hypertension.

AIMS: Reduced bioavailability of endogenous nitric oxide (NO) is a central pathophysiological event in hypertension and other cardiovascular diseases. Recently, it was demonstrated that inorganic nitrate from dietary sources is converted in vivo to form nitrite, NO, and other bioactive nitrogen oxides. We tested the hypothesis that dietary inorganic nitrate supplementation may have therapeutic effects in a model of renal and cardiovascular disease. METHODS AND RESULTS: Sprague-Dawley rats subjected to unilateral nephrectomy and chronic high-salt diet from 3 weeks of age developed hypertension, cardiac hypertrophy and fibrosis, proteinuria, and histological as well as biochemical signs of renal damage and oxidative stress. Simultaneous nitrate treatment (0.1 or 1 mmol nitrate kg⁻¹ day⁻¹), with the lower dose resembling the nitrate content of a diet rich in vegetables, attenuated hypertension dose-dependently with no signs of tolerance. Nitrate treatment almost completely prevented proteinuria and histological signs of renal injury, and the cardiac hypertrophy and fibrosis were attenuated. Mechanistically, dietary nitrate restored the tissue levels of bioactive nitrogen oxides and reduced the levels of oxidative stress markers in plasma (malondialdehyde) and urine (Class VI F2-isoprostanes and 8-hydroxy-2-deoxyguanosine). In addition, the increased circulating and urinary levels of dimethylarginines (ADMA and SDMA) in the hypertensive rats were normalized by nitrate supplementation. CONCLUSION: Dietary inorganic nitrate is strongly protective in this model of renal and cardiovascular disease. Future studies will reveal if nitrate contributes to the well-known cardioprotective effects of a diet rich in vegetables.

Antihypertensive effect of a standardized aqueous extract of Cecropia glaziovii Sneth in rats: an in vivo approach to the hypotensive mechanism.

Cecropia glaziovii Sneth is a common tree at the Southeastern Brazilian coast. As many other species of the genus, it shares the reputed folk use to treat heart failure, cough, asthma and bronchitis. The plant has been cultivated under controlled conditions and the 2% aqueous extract (AE) prepared with the dried leaves was standardized by its chemical contents on catechins, flavonoids and procyanidins. The present paper reports the antihypertensive activity of AE and of n-butanol fraction (BuF), an enriched semi-purified butanolic fraction used to isolate the main chemical constituents. Oral administration of AE and BuF induced hypotension in normotensive rats. The effect of AE (0.5 g/kg/bi, p.o.) was time and dose-dependent peaking at 2-3 weeks after daily administration. BuF was faster but not more active than AE. Both extracts decreased the hypertension of spontaneous hypertensive rats, the hypertension induced in rats by L-NAME treatment and that induced by constriction of one renal artery. The antihypertensive effect was maintained for as long as 60 days of treatment and was reversible upon drug washout at the same rate of its establishment. Acute i.v. administration of BuF to anesthetized rats induced a fast short-lasting hypotension and inhibited the pressor responses to noradrenaline, angiotensin I and angiotensin II by 40%. These results were indirect indications that the hypotension induced by AE is not related to ACE inhibition, increased NO synthesis, or specific blockade of alpha1 and AT1 receptors. It can be suggested that BuF interferes with the calcium handling mechanisms in smooth muscle cells and neurons. Intravenous injection of five out of nine compounds isolated from BuF produced immediate but short-lasting hypotension that does not correlate with the onset of the hypotension after oral treatment. This finding suggests that they may not be the compounds directly responsible for the delayed and sustained hypotension after per os administration of AE. The many compounds isolated from AE are under evaluation to determine its pharmacokinetics, mechanisms of action and interactions necessary to yield the plant effect. Although its mechanism is still unknown, AE seems to be an effective and safe antihypertensive phytomedicine.

Preventive effects of Shichimotsu-koka-to on renal lesions in stroke-prone spontaneously hypertensive rats.

Shichimotsu-koka-to (SKT) has been prescribed to treat patients with essential and renal hypertension. We investigated the effects of SKT on renal lesions in stroke-prone spontaneously hypertensive rats (SHRSPs). SHRSPs were given an extract of SKT by mixing it with drinking water, from 8 through 29 weeks of age, so that the average intake of SKT extract was about 1.5 g/kg/d. At 29 weeks of age, the kidneys of SHRSPs exhibited proliferative arteritis characterized by the proliferation of smooth muscle cells in the interlobular arteries, dilation and degeneration of renal tubules, infiltration of inflammatory cells and hemorrhage, with partial swelling or necrotizing of glomeruli. In particular, arteritis and periarteritis were noted. The treatment of SHRSPs with SKT ameliorated this morphological damage in the kidney and significantly decreased urea nitrogen in the serum. Treatment with SKT also strongly decreased the xanthine oxidase (XOD) activity and significantly increased the superoxide dismutase (SOD) activity in the kidney of SHRSPs; consequently, these values became close to those in normotensive Wistar Kyoto rats (WKYs). These results indicate that treatment with SKT ameliorated the histopathological damage and change in activity of enzymes related to free radicals in the kidney of SHRSPs, which may be important mechanisms for SKT for protecting SHRSPs from renal dysfunction.

Dietary alteration of dihomogamma-linolenic acid/arachidonic acid ratio in a rat 5/6-renal-ablation model. The Nutrition & Kidney Disease Research Group.

Interest in the modulation of renal diseases by polyunsaturated fatty acids (PUFA) led this group to examine the effects of borage oil (BO) and corn oil (CO) in the rat 5/6-renal-ablation model. BO is a rich source of gamma-linolenic acid (GLA; 18:3n-6), which is elongated to dihomogamma-linolenic acid (DGLA; 20:3n-6). CO is a rich source of linoleic acid (LA; 18:2n-6), a GLA and arachidonic acid (AA; 20:4n-6) precursor. The purpose of this study was to assess whether an increased DGLA:AA ratio as provided by BO would confer benefits beyond those provided by LA present in corn oil. Forty rats were used for the experiment. Seven rats were used for presurgery measurements. The remaining animals were subjected to 5/6 nephrectomy. Surviving rats (N = 30) were fed regular laboratory diet (RLD) for 7 days, at which time seven rats were used to obtain 1-wk postnephrectomy data. The remainder were then allocated to receive either RLD (N = 8), 15% BO (N = 8), or 15% CO (N = 7) diets for 20 wk. Body weight, renal phospholipid levels, renal function (proteinuria and GFR), glomerular histology, glomerular macrophage infiltration, urinary prostaglandin levels (thromboxane B2 (TxB2), 6-keto-PGF1 alpha), plasma lipid levels, and blood pressure were measured. Diets were well tolerated by all groups with a similar age-related gain in weight throughout the study. Efficacy of the PUFA diets was confirmed by alteration in renal tissue phospholipids; LA decreased in the RLD and BO groups, but not in the CO group. AA was higher in the BO and CO rats, but only the BO group showed a rise in GLA and DGLA incorporation. Proteinuria increased progressively in the RLD group but remained at 1-wk postsurgery levels in the BO and CO groups. Decline in GFR and mesangial expansion were significantly lessened by BO supplementation only. Both PUFA diets limited glomerulosclerosis and macrophage infiltration, but direct comparisons between BO and CO groups revealed significantly less glomerulosclerosis and macrophage infiltration in the BO group. Both BO and CO attenuated the rise in the TxB2 excretion rate and restored the 6-keto-PGF1 alpha:TxB2 ratio to the 1-wk postsurgery level. Plasma lipid levels rose in all groups, but the rise in cholesterol level was less in the BO and CO rats, CO being the most efficacious in this regard. BP increased progressively in RLD rats, but not in the BO and CO groups, BO providing a markedly greater hypotensive effect. In summary, both CO and BO supplemented PUFA diets limited glomerular injury in the renal-ablated rats. However, BO supplementation was more effective than CO supplementation at preserving GFR, limiting mesangial expansion and glomerulosclerosis, and reducing glomerular macrophage infiltration.

Long-term comparison between captopril and nifedipine in the progression of renal insufficiency.

To verify the hypothesis that angiotensin-converting enzyme (ACE) inhibitors possess a unique renoprotective effect in progressive chronic renal disease, we decided to compare the effects of an ACE inhibitor and a calcium antagonist on both hypertension and the progression of non-diabetic renal insufficiency in a long-term study. A four-year, multicenter, prospective, randomized trial was conducted on 142 hypertensive patients (pts) with established chronic renal failure from six Italian nephrology departments. They were on standard antihypertensive therapy with a low-protein diet and underwent twice-monthly surveillance for a one year pre-randomization period. After that year, 121 pts were randomly allocated to captopril or slow-release nifedipine therapies for a three-year study period. The progression of renal insufficiency was monitored every two months. Blood pressure control was significantly better after randomization than during the year of standard antihypertensive therapy. The progression rate before randomization (BR) was definitely higher before than after randomization (AR): Creatinine clearance (CCr) change BR = -0.46 +/- 0.45 ml/min/month, creatinine clearance change AR = -0.23 +/- 0.43 ml/min/month (P less than 0.01). After randomization, the mean blood pressure values were virtually the same throughout the three year period of the study in the two groups treated by captopril (group I), or nifedipine (group II).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of increased dietary calcium on the development of reduced renal mass saline hypertension in rats.

A diet fortified with calcium carbonate has been reported to reduce blood pressure in low-renin and salt-sensitive hypertensive patients. We have therefore examined the effect of increased dietary calcium on the development of reduced renal mass-saline hypertension in rats, a classical, low-renin, volume, and sodium-dependent model of hypertension. Rats with 70-75% reduction in renal mass were divided into experimental and control groups. The experimental rats were fed a sodium-free diet supplemented with calcium carbonate (2.0% calcium) and drank 1% saline for 5 weeks. Control rats consumed the salt-free diet and drank 1% saline for the same period. In control rats, as previously observed, blood pressure progressive increased from a control value of 120.0 +/- 1.2 to 174.2 +/- 1.2 mm Hg by the fifth week. In contrast, in the calcium-supplemented rats the development of hypertension was significantly attenuated; the blood pressure only increased from 117.0 +/- 1.2 to 134.0 +/- 3.8 mm Hg by the fifth week. This was associated with a 30% decrease in saline intake by the fifth week, with proportionate decreases in urine volume and sodium excretion but not potassium excretion. Urinary magnesium excretion increased. No such changes were seen in control rats. At the end of the treatment period, plasma levels of sodium, potassium, calcium, creatinine, BUN, and protein were not different, but plasma chloride and magnesium were lower in experimental rats; vascular smooth muscle cell membrane potentials were also not different. These data show that dietary calcium carbonate can attenuate the development of reduced renal mass-saline hypertension in the rat, possibly in part by altering sodium and water intake.

Serum lipoproteins in patients with mild renal disease treated with the diuretic muzolimine.

Patients with renal functional impairment are prone to develop hypertension and hyperlipidemia, and both abnormalities tend to occur already at an early stage of kidney disease. In 18 patients with mild renal disease (glomerular filtration rate 65 +/- 5 ml/min) and hypertension (mean blood pressure 126 +/- 4 mm Hg), the effect of six weeks of treatment with the loop-diuretic muzolimine on serum lipoproteins was assessed. Compared to placebo values, the diuretic significantly increased serum low-density lipoprotein cholesterol (LDL-C) and apoprotein B (+ 18 and 11%, respectively, P less than 0.005) in 13 men or postmenopausal women, but not in 5 premenopausal women. Serum high-density lipoprotein cholesterol (HDL-C), and total triglycerides or lipoprotein triglyceride fractions were not consistently changed in both subgroups. Thus, the ratio LDL-C/HDL-C was increased from 3.2 +/- 0.3 to 3.9 +/- 0.3 (P less than 0.05) in the men or postmenopausal women, while no such tendency occurred in the premenopausal women (4.1 +/- 0.6 to 3.7 +/- 0.6). Changes in serum LDL-C were not associated with hemoconcentration or alterations in carbohydrate metabolism and were not related to variations in serum potassium or blood pressure. Increased serum levels of the atherogenic LDL-C fraction during diuretic treatment in men or postmenopausal women with renal disease may represent a potentially undesirable effect, particularly since such patients may tend to have hyperlipidemia in the untreated state.