Pathophysiology of resistant hypertension in chronic kidney disease

Contribution of selected vasoactive systems to blood pressure regulation in two models of chronic kidney disease

It is generally accepted that angiotensin II plays an important role in high blood pressure (BP) development in both 2-kidney-1-clip (2K1C) Goldblatt hypertension and in partial nephrectomy (NX) model of chronic kidney disease (CKD). The contribution of sympathetic nervous system and nitric oxide to BP control in these models is less clear. Partial nephrectomy or stenosis of the renal artery was performed in adult (10-week-old) male hypertensive heterozygous Ren-2 transgenic rats (TGR) and normotensive control Hannover Sprague Dawley (HanSD) rats and in Wistar rats. One and four weeks after the surgery, basal blood pressure (BP) and acute BP responses to the consecutive blockade of renin-angiotensin (RAS), sympathetic nervous (SNS), and nitric oxide (NO) systems were determined in conscious rats. Both surgical procedures increased plasma urea, a marker of renal damage; the effect being more pronounced following partial nephrectomy in hypertensive TGR than in normotensive HanSD rats with a substantially smaller effect in Wistar rats after renal artery stenosis. We demonstrated that the renin-angiotensin system does not play so fundamental role in blood pressure maintenance during hypertension development in either CKD model. By contrast, a more important role is exerted by the sympathetic nervous system, the activity of which is increased in hypertensive TGR-NX in the developmental phase of hypertension, while in HanSD-NX or Wistar-2K1C it is postponed to the established phase. The contribution of the vasoconstrictor systems (RAS and SNS) was increased following hypertension induction. The role of NO-dependent vasodilation was unchanged in 5/6 NX HanSD and in 2K1C Wistar rats, while it gradually decreased in 5/6 NX TGR rats.

Safety and efficacy of orally administered telmisartan for the treatment of systemic hypertension in cats: Results of a double-blind, placebo-controlled, randomized clinical trial

BACKGROUND

Information regarding the efficacy of telmisartan for feline systemic arterial hypertension is limited.

OBJECTIVES

To evaluate the safety and efficacy of PO administered telmisartan solution in hypertensive cats.

ANIMALS

Client-owned cats with indirect systolic arterial blood pressure (SBP) of 160-200 mm Hg, based on multiple measurements.

METHODS

This multicenter trial consisted a 28-day, prospective, randomized, double-blind, placebo-controlled, parallel group, efficacy phase and a 154-day extended-use telmisartan phase. Hypertensive cats were randomly assigned to receive 1.5 mg telmisartan/kg PO q12h for 14 days, followed by 2 mg telmisartan/kg PO q24h, or equivalent volume of placebo. Systolic blood pressure was measured on days 0, 14, and 28. Change in SBP compared to baseline was calculated for days 14 and 28. Telmisartan efficacy was defined as significant decrease in SBP at day 14 compared to placebo and a clinically relevant (>20 mm Hg) decrease in SBP at day 28.

RESULTS

Two-hundred twenty-one cats were included. On day 14, least squares mean (95% confidence interval) SBP decrease was significantly larger in telmisartan-treated (-23.3 mm Hg [-28.2 to -18.3]) versus placebo-treated (-7.5 mm Hg [-13.6 to -1.5]) cats (P = .0005). On day 28, telmisartan treatment resulted in a clinically relevant SBP decrease (-23.9 mm Hg [-27.8 to -20.0]), whereas placebo did not (-11.6 mm Hg [-17.4 to -5.9 mm Hg]). The decrease in SBP persisted over the 6-month trial in telmisartan-treated cats.

CONCLUSIONS AND CLINICAL IMPORTANCE

Telmisartan significantly decreased SBP to a clinically relevant extent and was well tolerated in hypertensive cats.

Evaluation of orally administered telmisartan for the reduction of indirect systolic arterial blood pressure in awake, clinically normal cats

OBJECTIVES

The aim of this study was to compare the effects of multiple once- or twice-daily oral dosage rates of the angiotensin II, type-1 receptor blocker, telmisartan (TEL), or placebo (PLA) on indirect systolic arterial blood pressure (SBP) in awake, clinically normal cats.

METHODS

Utilizing an incomplete crossover design and following a 14 day acclimation period, 28 healthy laboratory cats were randomized to undergo treatment with three of the following 14 day treatment protocols, each separated by a 1 week washout period: oral PLA q24h, oral TEL at a dosage of 1, 1.5, 2 or 3 mg/kg q24h, or oral TEL at a dosage of 1 or 1.5 mg/kg q12h. Using the Doppler ultrasound method, indirect SBP was measured daily during each treatment period, and daily during the first 5 days of each washout period, approximately 3 h after administration of the morning treatment.

RESULTS

Each treatment protocol was administered to a total of 12 cats. A statistically significant effect of treatment period was identified for the entire study; therefore, only data from the first treatment period (four cats per treatment group) were used for further analysis. Compared with PLA, during the first treatment period, SBP values were significantly lower in cats treated with TEL at all tested dosages by the second week of treatment. SBP remained significantly lower than in PLA-treated animals for 2 days following administration of the last dose in all TEL treatment groups. No clinical signs of hypotension were noted in any group.

CONCLUSIONS AND RELEVANCE

These results suggest that treatment with TEL at a total daily dose of 1-3 mg/kg - administered as a single dose, or split into two equal doses administered 12 h apart - results in a significant, relatively long-lasting reduction of SBP in clinically normal cats. TEL appears to be well tolerated by normal cats at the dosages tested.

Relationship between the exposure to cumulative cardiovascular health behaviors and factors and chronic kidney disease-The Kailuan study

It is unclear whether ideal cardiovascular health (CVH) behaviors and factors, particularly cumulative exposure to ideal CVH (cumCVH), is associated with chronic kidney disease (CKD). The aim of the study was to examine the effect of cumCVH on CKD using the data from the Kailuan study. The study included the 27,970 (21,199 males) of the Kailuan community (China). The participants were 19 to 98 years of age. They were followed in 2008-2009, 2010-2011, and 2012-2013 by the same medical staff that did the initial physical examinations in 2006-2007. Participants were censored on the visit reporting CKD. A CVH score was created based on the seven AHA health metrics. The cumCVH score was CVH1×timev1-v2+CVH2×timev2-v3+CVH3×timev3-v4. In the fully adjusted model, compared with the lowest quintile of cumCVH, individuals in the highest quintile had a 75% lower risk of CKD (95% confidence interval (CI): 66-82%). Every additional year lived with a 1-unit increase in ideal CVH was associated with an 11% (95% CI: 9-13%) reduction in the incidence of CKD. Furthermore, when we excluded each of the six metrics from the cumCVH score in turn, the association was unaffected after the exclusion of individual risk factors. Ideal CVH is associated with a reduced incidence of CKD. Measurements of cumCVH are more likely to reflect the lifetime risk of CKD and possibly of other health outcomes.

Hypertension in CKD Pregnancy: a Question of Cause and Effect (Cause or Effect? This Is the Question)

Chronic kidney disease (CKD) is increasingly encountered in pregnancy, and hypertension is frequently concomitant. In pregnancy, the prevalence of CKD is estimated to be about 3%, while the prevalence of chronic hypertension is about 5-8%. The prevalence of hypertension and CKD in pregnancy is unknown. Both are independently related to adverse pregnancy outcomes, and the clinical picture merges with pregnancy-induced hypertension and preeclampsia. Precise risk quantification is not available, but risks linked to CKD stage, hypertension, and proteinuria are probably multiplicative, each at least doubling the rates of preterm and early preterm delivery, small for gestational age babies, and related outcomes. Differential diagnosis (based upon utero-placental flows, fetal growth, and supported by serum biomarkers) is important for clinical management. In the absence of guidelines for hypertension in CKD pregnancies, the ideal blood pressure goal has not been established; we support a tailored approach, depending on compliance, baseline control, and CKD stages, with strict blood pressure monitoring. The choice of antihypertensive drugs and the use of diuretics and of erythropoiesis-stimulating agents (ESAs) are still open questions which only future studies may clarify.

Secondary Hypertension: Differential Diagnosis and Basic Principles of Treatment

Secondary hypertension occurs in 5-10% of cases in the patient population with primary hypertension. The most common forms of secondary hypertension are as follows: parenchymal renal disease (renoparenchymal hypertension), renal artery stenosis (renovascular hypertension), adrenal gland adenoma (primary hyperaldosteronism), a tumour of the adrenal gland marrow (pheochromocytoma) and adenoma of adrenal and pituitary glands (Cushing’s syndrome). In patients with a typical clinical picture of secondary hypertension, the appropriate diagnostic tests should be conducted based on the suspected form of secondary hypertension. Determining a diagnosis of secondary hypertension is gradual. First, the appropriate screening tests are performed. If the screening test is positive, then additional tests to confirm the forms of secondary hypertension are conducted. Once a diagnosis of the appropriate form of secondary hypertension is confirmed, tests to distinguish causes and laterality tests to determine the precise localisation of the pathological process are applied to evaluate the response to therapy. Analysing the results of endocrine diagnostic tests provides an accurate diagnosis and selection of optimal therapeutic procedures.

Renal sympathetic denervation in therapy resistant hypertension - pathophysiological aspects and predictors for treatment success

Many forms of human hypertension are associated with an increased systemic sympathetic activity. Especially the renal sympathetic nervous system has been found to play a prominent role in this context. Therefore, catheter-interventional renal sympathetic denervation (RDN) has been established as a treatment for patients suffering from therapy resistant hypertension in the past decade. The initial enthusiasm for this treatment was markedly dampened by the results of the Symplicity-HTN-3 trial, although the transferability of the results into clinical practice to date appears to be questionable. In contrast to the extensive use of RDN in treating hypertensive patients within or without clinical trial settings over the past years, its effects on the complex pathophysiological mechanisms underlying therapy resistant hypertension are only partly understood and are part of ongoing research. Effects of RDN have been described on many levels in human trials: From altered systemic sympathetic activity across cardiac and metabolic alterations down to changes in renal function. Most of these changes could sustainably change long-term morbidity and mortality of the treated patients, even if blood pressure remains unchanged. Furthermore, a number of promising predictors for a successful treatment with RDN have been identified recently and further trials are ongoing. This will certainly help to improve the preselection of potential candidates for RDN and thereby optimize treatment outcomes. This review summarizes important pathophysiologic effects of renal denervation and illustrates the currently known predictors for therapy success.

Sodium in feline nutrition

High sodium levels in cat food have been controversial for a long time. Nonetheless, high sodium levels are used to enhance water intake and urine volume, with the main objective of reducing the risk of urolithiasis. This article is a review of current evidence of the putative risks and benefits of high dietary sodium levels. Its secondary aim is to report a possible safe upper limit (SUL) for sodium intake. The first part of the manuscript is dedicated to sodium physiology, with a focus on the mechanisms of sodium homeostasis. In this respect, there is only few information regarding possible interactions with other minerals. Next, the authors address how sodium intake affects sodium balance; knowledge of these effects is critical to establish recommendations for sodium feed content. The authors then review the consequences of changes in sodium intake on feline health, including urolithiasis, blood pressure changes, cardiovascular alterations and kidney disease. According to recent, long-term studies, there is no evidence of any deleterious effect of dietary sodium levels as high as 740 mg/MJ metabolizable energy, which can therefore be considered the SUL based on current knowledge.

Comparative Pathology of Aging Great Apes: Bonobos, Chimpanzees, Gorillas, and Orangutans

The great apes (chimpanzees, bonobos, gorillas, and orangutans) are our closest relatives. Despite the many similarities, there are significant differences in aging among apes, including the human ape. Common to all are dental attrition, periodontitis, tooth loss, osteopenia, and arthritis, although gout is uniquely human and spondyloarthropathy is more prevalent in apes than humans. Humans are more prone to frailty, sarcopenia, osteoporosis, longevity past reproductive senescence, loss of brain volume, and Alzheimer dementia. Cerebral vascular disease occurs in both humans and apes. Cardiovascular disease mortality increases in aging humans and apes, but coronary atherosclerosis is the most significant type in humans. In captive apes, idiopathic myocardial fibrosis and cardiomyopathy predominate, with arteriosclerosis of intramural coronary arteries. Similar cardiac lesions are occasionally seen in wild apes. Vascular changes in heart and kidneys and aortic dissections in gorillas and bonobos suggest that hypertension may be involved in pathogenesis. Chronic kidney disease is common in elderly humans and some aging apes and is linked with cardiovascular disease in orangutans. Neoplasms common to aging humans and apes include uterine leiomyomas in chimpanzees, but other tumors of elderly humans, such as breast, prostate, lung, and colorectal cancers, are uncommon in apes. Among the apes, chimpanzees have been best studied in laboratory settings, and more comparative research is needed into the pathology of geriatric zoo-housed and wild apes. Increasing longevity of humans and apes makes understanding aging processes and diseases imperative for optimizing quality of life in all the ape species.