Louis K. Dahl Memorial Lecture. Renal and cardiovascular mechanisms of hypertension in obesity

Prognostic impact of renal sinus fat accumulation in patients with chronic kidney disease

BACKGROUND

Obesity is associated with the development and progression of chronic kidney disease (CKD). In the general population, the amount of renal sinus fat was associated with hypertension and renal impairment. However, its impact upon those with CKD remains uncertain.

METHODS

We prospectively included CKD patients who underwent renal biopsy and simultaneously measured their renal sinus fat volume. The association between the percentage of renal sinus fat volume, which was adjusted by kidney volume, and renal outcomes was investigated.

RESULTS

A total of 56 patients (median 55 years old, 35 men) were included. Among baseline characteristics, age and visceral fat volume were positively correlated with the percentage of renal sinus fat volume (p < 0.05). The percentage of renal sinus fat volume was associated with hypertension (p < 0.01) and tended to be associated with max glomerular diameter (p = 0.078) and urine angiotensinogen creatinine ratio (p = 0.064) after adjustment with several clinical factors. The percentage of renal sinus fat volume was significantly associated with a future > 50% decline in estimated glomerular filtration rate (p < 0.05).

CONCLUSIONS

Among those with CKD who required renal biopsy, the amount of renal sinus fat was associated with poor renal outcomes accompanied by systemic hypertension.

Obesity, kidney dysfunction and hypertension: mechanistic links

Excessive adiposity raises blood pressure and accounts for 65-75% of primary hypertension, which is a major driver of cardiovascular and kidney diseases. In obesity, abnormal kidney function and associated increases in tubular sodium reabsorption initiate hypertension, which is often mild before the development of target organ injury. Factors that contribute to increased sodium reabsorption in obesity include kidney compression by visceral, perirenal and renal sinus fat; increased renal sympathetic nerve activity (RSNA); increased levels of anti-natriuretic hormones, such as angiotensin II and aldosterone; and adipokines, particularly leptin. The renal and neurohormonal pathways of obesity and hypertension are intertwined. For example, leptin increases RSNA by stimulating the central nervous system proopiomelanocortin-melanocortin 4 receptor pathway, and kidney compression and RSNA contribute to renin-angiotensin-aldosterone system activation. Glucocorticoids and/or oxidative stress may also contribute to mineralocorticoid receptor activation in obesity. Prolonged obesity and progressive renal injury often lead to the development of treatment-resistant hypertension. Patient management therefore often requires multiple antihypertensive drugs and concurrent treatment of dyslipidaemia, insulin resistance, diabetes and inflammation. If more effective strategies for the prevention and control of obesity are not developed, cardiorenal, metabolic and other obesity-associated diseases could overwhelm health-care systems in the future.

Time to acute kidney injury and its predictors among newly diagnosed Type 2 diabetic patients at government hospitals in Harari Region, East Ethiopia

BACKGROUND

Incidence of Acute Kidney Injury (AKI) among Type 2 diabetic patients is significantly increasing. But, earlier studies has focused on the admitted patients which may hide the true nature of the Acute Kidney Injury among Type 2 Diabetic (T2D) patients. So, this study was conducted to determine the time to Acute Kidney Injury and its predictors among Type 2 Diabetic patients in Harari Region, East Ethiopia.

METHODS

We conducted a retrospective cohort study among type 2 diabetic patients who had been receiving treatment at government hospitals of Harari region, Ethiopia from 2013 to 2017. We extracted data from patients' medical records. We estimated incidence rate and compared survival curves between different exposure groups using Kaplan-Meier and log-rank test. Weibull regression model was fitted to the data to identify the predictor variables. Variables with p-value <0.05 were considered statistically significant.

RESULTS

Overall, 14.5% (95%CI: 11.7-17.9) of the study population developed acute kidney injury, with median survival time of 57 months. The significant predictors were physical activity [Adjusted Time Ratio (ATR):95%CI; 0.6 (0.49-0.75)], congestive heart failure [ATR:95%CI; 0.84 (0.71-0.99)], chronic kidney disease [ATR:95%CI; 0.77(0.65-0.91)], hypertension [ATR:95%CI; 0.78(0.65-0.91)], obesity [ATR:95%CI; 0.84(0.74-0.96)], diabetic nephropathy [ATR:95%CI; 0.80(0.65-0.98)], diuretics & beta blockers [ATR:95%CI; 0.85(0.74-0.97)], and delay of follow-up [ATR:95%CI; 0.97(0.96-0.98)].

CONCLUSIONS

Incidence of acute kidney injury was high in our study area. Hence, identification and controlling of comorbidities along with regular monitoring of kidney function are needed to prevent or delay the risk of acute kidney injury in type 2 diabetic patients.

Is Aberrant Reno-Renal Reflex Control of Blood Pressure a Contributor to Chronic Intermittent Hypoxia-Induced Hypertension?

Renal sensory nerves are important in the regulation of body fluid and electrolyte homeostasis, and blood pressure. Activation of renal mechanoreceptor afferents triggers a negative feedback reno-renal reflex that leads to the inhibition of sympathetic nervous outflow. Conversely, activation of renal chemoreceptor afferents elicits reflex sympathoexcitation. Dysregulation of reno-renal reflexes by suppression of the inhibitory reflex and/or activation of the excitatory reflex impairs blood pressure control, predisposing to hypertension. Obstructive sleep apnoea syndrome (OSAS) is causally related to hypertension. Renal denervation in patients with OSAS or in experimental models of chronic intermittent hypoxia (CIH), a cardinal feature of OSAS due to recurrent apnoeas (pauses in breathing), results in a decrease in circulating norepinephrine levels and attenuation of hypertension. The mechanism of the beneficial effect of renal denervation on blood pressure control in models of CIH and OSAS is not fully understood, since renal denervation interrupts renal afferent signaling to the brain and sympathetic efferent signals to the kidneys. Herein, we consider the currently proposed mechanisms involved in the development of hypertension in CIH disease models with a focus on oxidative and inflammatory mediators in the kidneys and their potential influence on renal afferent control of blood pressure, with wider consideration of the evidence available from a variety of hypertension models. We draw focus to the potential contribution of aberrant renal afferent signaling in the development, maintenance and progression of high blood pressure, which may have relevance to CIH-induced hypertension.

Hypertension in Obesity: Novel Insights

BACKGROUND

The relationship between obesity and hypertension has been established in both adults and children. The combination of obesity, hypertension and other cardiovascular risk factors significantly increases the likelihood of adverse cardiovascular effects and raises concerns about aggressive treatment strategies.

OBJECTIVE

Despite the impressive elements which indicate an important role for excessive weight gain in increasing blood pressure, not all obese patients are hypertensive. A subgroup of obese people may not develop hypertension. Furthermore, masked hypertension occurs more common among obese patients, and body fat distribution has a major role in the development of hypertension.

METHOD

We conducted a research of the relevant literature regarding obesity-induced hypertension and possible treatment strategies.

RESULTS

Successful weight loss is correlated with blood pressure reduction and requires a multidisciplinary approach that includes personalized dietary interventions combined with regular exercise and cognitive behavioral therapy.

CONCLUSION

Pharmacological therapy may be considered as part of a comprehensive obesity management strategy. More research and new treatment therapies are required in this field.

Mechanisms of sodium balance: total body sodium, surrogate variables, and renal sodium excretion

The classical concepts of human sodium balance include 1) a total pool of Na+ of ≈4,200 mmol (total body sodium, TBS) distributed primarily in the extracellular fluid (ECV) and bone, 2) intake variations of 0.03 to ≈6 mmol·kg body mass−1·day−1, 3) asymptotic transitions between steady states with a halftime (T½) of 21 h, 4) changes in TBS driven by sodium intake measuring ≈1.3 day [ΔTBS/Δ(Na+ intake/day)], 5) adjustment of Na+ excretion to match any diet thus providing metabolic steady state, and 6) regulation of TBS via controlled excretion (90–95% renal) mediated by surrogate variables. The present focus areas include 1) uneven, nonosmotic distribution of increments in TBS primarily in “skin,” 2) long-term instability of TBS during constant Na+ intake, and 3) physiological regulation of renal Na+ excretion primarily by neurohumoral mechanisms dependent on ECV rather than arterial pressure. Under physiological conditions 1) the nonosmotic distribution of Na+ seems conceptually important, but quantitatively ill defined; 2) long-term variations in TBS represent significant deviations from steady state, but the importance is undetermined; and 3) the neurohumoral mechanisms of sodium homeostasis competing with pressure natriuresis are essential for systematic analysis of short-term and long-term regulation of TBS. Sodium homeostasis and blood pressure regulation are intimately related. Real progress is slow and will accelerate only through recognition of the present level of ignorance. Nonosmotic distribution of sodium, pressure natriuresis, and volume-mediated regulation of renal sodium excretion are essential intertwined concepts in need of clear definitions, conscious models, and future attention.

Utility of Doppler sonography for renal artery stenosis screening in obese children with hypertension

Pediatric hypertension guidelines recommend Doppler renal ultrasonography as a screening study for the evaluation of possible renal artery stenosis (RAS) in normal-weight children ≥ 8 years of age who are suspected of having RAS and who will cooperate with the procedure. Obese children are excluded because of technical and vascular concerns. There are no data on RI in obese children. This is a retrospective review of children aged 1.5-18 who received Doppler imaging studies over a 10-year period. A total of 174 patients were studied. There was no significant difference between the RI values based on BMI. Of the 174 individuals in the study 22 obtained follow-up CT/MRA after abnormal Doppler ultrasounds. On advanced imaging 3 were confirmed to have RAS. Obesity does not seem to influence RI.RI alone should not be used as a screening tool for RAS. An approach toward diagnosis is suggested based on BMI, renin levels, and ultrasound.

Association of body mass index with mortality and postoperative survival in renal cell cancer patients, a meta-analysis

Obesity is one of the major risk factors of cancer. However, how body mass index (BMI) influences the prognosis of renal cell cancer (RCC) patient is unclear. In this work, we have performed a meta-analysis to elucidate the role of abnormal weight in RCC mortality and postoperative survival. Articles related to BMI and RCC mortality as well as postoperative survival has been identified by searching PUBMED and ENBASE. Totally, 19 articles have been selected for this meta-analysis, 5 articles for RCC mortality and 14 for postoperative survival. Compared to normal weight, the estimated relative risks of RCC mortality are 0.71 (95% CI: 0.34–1.49), 1.19 (95% CI: 1.05–1.35) and 1.71 (95% CI: 1.27–2.00) respectively for the underweight, overweight and obesity patients. The risk of RCC mortality increase 5% for each 1 kg/m² increment of BMI. However, the estimated hazard ratios of cancer specific postoperative survival are 2.62 (95% CI: 1.67–4.11), 0.72 (95% CI: 0.63–0.83) and 0.66 (95% CI: 0.49–0.89) respectively for underweight, overweight and obesity RCC patients. The risk of hazard ratio decrease 5% for each 1 kg/m² increment of BMI. In addition, the hazard ratios of postoperative overall survival show a similar tendency. These results indicate an opposite association of BMI with mortality and postoperative survival in renal cell cancer patients.

Insulin Resistance in Kidney Disease: Is There a Distinct Role Separate from That of Diabetes or Obesity?

Insulin resistance is a central component of the metabolic dysregulation observed in obesity, which puts one at risk for the development of type 2 diabetes and complications related to diabetes such as chronic kidney disease. Insulin resistance and compensatory hyperinsulinemia place one at risk for other risk factors such as dyslipidemia, hypertension, and proteinuria, e.g., development of kidney disease. Our traditional view of insulin actions focuses on insulin-sensitive tissues such as skeletal muscle, liver, adipose tissue, and the pancreas. However, insulin also has distinct actions in kidney tissue that regulate growth, hypertrophy, as well as microcirculatory and fibrotic pathways which, in turn, impact glomerular filtration, including that governed by tubuloglomerular feedback. However, it is often difficult to discern the distinct effects of excess circulating insulin and impaired insulin actions, as exist in the insulin resistance individual, from the associated effects of obesity or elevated systolic blood pressure on the development and progression of kidney disease over time. Therefore, we review the experimental and clinical evidence for the distinct impact of insulin resistance on kidney function and disease.

Obesity and hypertension

The imbalance between energy intake and expenditure is the main cause of excessive overweight and obesity. Technically, obesity is defined as the abnormal accumulation of ≥20% of body fat, over the individual's ideal body weight. The latter constitutes the maximal healthful value for an individual that is calculated based chiefly on the height, age, build and degree of muscular development. However, obesity is diagnosed by measuring the weight in relation to the height of an individual, thereby determining or calculating the body mass index. The National Institutes of Health have defined 30 kg/m² as the limit over which an individual is qualified as obese. Accordingly, the prevalence of obesity in on the increase in children and adults worldwide, despite World Health Organization warnings. The growth of obesity and the scale of associated health issues induce serious consequences for individuals and governmental health systems. Excessive overweight remains among the most neglected public health issues worldwide, while obesity is associated with increasing risks of disability, illness and death. Cardiovascular diseases, the leading cause of mortality worldwide, particularly hypertension and diabetes, are the main illnesses associated with obesity. Nevertheless, the mechanisms underlying obesity-associated hypertension or other associated metabolic diseases remains to be adequately investigated. In the present review, we addressed the association between obesity and cardiovascular disease, particularly the biological mechanisms linking obesity and hypertension.

New developments in the pathogenesis of obesity-induced hypertension

Obesity is a disorder that develops from the interaction between genotype and environment involving social, behavioral, cultural, and physiological factors. Obesity increases the risk for type 2 diabetes mellitus, hypertension, cardiovascular disease, cancer, musculoskeletal disorders, chronic kidney and pulmonary disease. Although obesity is clearly associated with an increased prevalence of hypertension, many obese individuals may not develop hypertension. Protecting factors may exist and it is important to understand why obesity is not always related to hypertension. The aim of this review is to highlight the knowledge gap for the association between obesity, hypertension, and potential genetic and racial differences or environmental factors that may protect obese patients against the development of hypertension and other co-morbidities. Specific mutations in the leptin and the melaninocortin receptor genes in animal models of obesity without hypertension, the actions of α-melanocyte stimulating hormone, and SNS activity in obesity-related hypertension may promote recognition of protective and promoting factors for hypertension in obesity. Furthermore, gene-environment interactions may have the potential to modify gene expression and epigenetic mechanisms could also contribute to the heritability of obesity-induced hypertension. Finally, differences in nutrition, gut microbiota, exposure to sun light and exercise may play an important role in the presence or absence of hypertension in obesity.

Comparative transcriptional profiling of renal cortex in rats with inherited stress-induced arterial hypertension and normotensive Wistar Albino Glaxo rats

Background

The renal function plays a leading role in long-term control of arterial pressure. The comparative analysis of renal cortex transcriptome in ISIAH rats with inherited stress-induced arterial hypertension and normotensive WAG rats was performed using RNA-Seq approach. The goal of the study was to identify the differentially expressed genes (DEGs) related to hypertension and to detect the pathways contributing to the differences in renal functions in ISIAH and WAG rats.

Results

The analysis revealed 716 genes differentially expressed in renal cortex of ISIAH and WAG rats, 42 of them were associated with arterial hypertension and regulation of blood pressure (BP). Several Gene Ontology (GO) terms significantly enriched with DEGs suggested the existence of the hormone dependent interstrain differences in renal cortex function. Multiple DEGs were associated with regulation of blood pressure and blood circulation, with the response to stress (including oxidative stress, hypoxia, and fluid shear stress) and its regulation. Several other processes which may contribute to hypertension development in ISIAH rats were: ion transport, regulation of calcium ion transport, homeostatic process, tissue remodeling, immune system process and regulation of immune response.

KEGG analysis marked out several pathways significantly enriched with DEGs related to immune system function, to steroid hormone biosynthesis, tryptophan, glutathione, nitrogen, and drug metabolism.

Conclusions

The results of the study provide a basis for identification of potential biomarkers of stress-sensitive hypertension and for further investigation of the mechanisms that affect renal cortex function and hypertension development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0306-9) contains supplementary material, which is available to authorized users.

Triple Burden of Obesity, Undernutrition, and Cardiovascular Disease Risk among Indian Tribes

BACKGROUND

Socio-cultural transitions among individuals from vulnerable groups introduce epidemiological transition, with a concomitant increase in the prevalence of undernutrition, obesity, and cardiovascular disease risks. An accepted conventional wisdom exists for Indian tribes that they are undernourished and away from lifestyle-related diseases. However, the extent of this triple burden affecting them is unknown. In this study, we assessed this triple burden among the 9 major tribes of India.

METHODS AND FINDINGS

During January 2011 to December 2013, we conducted a cross-sectional study among 1066 men and 1090 women constituting a total of 2156 adults belonging to the 9 major tribal groups: Santals, Oraons, and Koras (West Bengal); Santals, Bhumijs, and Bathudis (Odisha); and Dhodias, Kuknas, and Chaudharis (Gujarat) to estimate the prevalence of the triple burden (undernutrition, overweight or obesity, and hypertension). A high prevalence of undernutrition and hypertension was observed among the Koras (51.9%and 10.6%, respectively), Bathudis (51.3% and 12.1%, respectively), and Oraons (49.6% and 16.5%, respectively). However, the prevalence of overweight and hypertension among the Bhumijs (17.7% and 14.7%, respectively), Dhodias (23.8% and 12.9%, respectively), Kuknas (15.8% and 11.3%, respectively), and Santals of West Bengal (12.2% and 11.8%, respectively) and Odisha (15% and 9.6%, respectively) was most alarming. The prevalence of overweight or obesity among the women was 10.9% and 1.5%, respectively, with 14.0% hypertensive women. The prevalence of overweight and obesity among the men was 14.8% and 1.7%, respectively, with 9.2% hypertensive men. Undernutrition was highly prevalent among men and women. However, data from the past 30 years on systolic blood pressure (SBP) and body mass index (BMI) revealed that the studied tribes were at a higher risk than the general Indian population. In addition, a vast gender disparity with relation to the disease and risk prevalence was observed.

CONCLUSION

The alarming trend of an increasing prevalence of overweight/obesity, undernutrition, and hypertension is observed among indigenous populations of India, emphasizing the incorporation of a specific health management policy.

Increased incidence of diuretic use in critically ill obese patients

OBJECTIVE

Sodium retention occurs commonly in cardiac and liver disease, requiring the administration of diuretics to restore fluid balance. Whether obesity is associated with sodium retention has not been fully evaluated.

METHODS

In a large single-center cohort of critically ill patients, we evaluated whether admission body mass index was associated with the administration of either oral or intravenous diuretics during the intensive care unit (ICU) stay.

MAIN RESULTS

Of 7724 critically ill patients, 3946 (51.1%) were prescribed diuretics during the ICU stay. Overweight, class I obesity, and class II/III obesity were associated with a 1.35 (95% confidence interval [CI], 1.20-1.53; P < .001), 1.56 (95% CI, 1.35-1.80; P < .001), and 1.91 (95% CI, 1.61-2.26; P < .001) adjusted risk of receiving diuretics within the ICU, respectively. In adjusted analysis, a 5-kg/m(2) increment of body mass index was associated with a 1.19 (95% CI, 1.14-1.23; P < .001) increased adjusted risk of within-ICU diuretics. Among those patients receiving loop diuretics, obese patients received significantly larger daily diuretic doses.

CONCLUSION

Critically ill obese patients are more likely to receive diuretics during their stay in the ICU and to receive higher dosages of diuretics. Our data suggest that obesity is an independent risk factor for sodium retention.

Reduced carotid baroreceptor distensibility-induced baroreflex resetting contributes to impairment of sodium regulation in rats fed a high-fat diet

Decreased carotid arterial compliance has been reported in obese subjects and animals. Carotid baroreceptors are located at the bifurcation of the common carotid artery, and respond to distension of the arterial wall, suggesting that higher pressure is required to obtain the same distension in obese subjects and animals. A hyperosmotic NaCl solution induces circulatory volume expansion and arterial pressure (AP) increase, which reflexively augment renal excretion. Thus, we hypothesized that sodium regulation via the baroreflex might be impaired in response to chronic hyperosmotic NaCl infusion in rats fed a high-fat diet. To examine this hypothesis, we used rats fed a high-fat (Fat) or normal (NFD) diet, and measured mean AP, water and sodium balance, and renal function in response to chronic infusion of hyperosmotic NaCl solution via a venous catheter. Furthermore, we examined arterial baroreflex characteristics with static open-loop analysis and distensibility of the common carotid artery. Significant positive water and sodium balance was observed on the 1st day of 9% NaCl infusion; however, this disappeared by the 2nd day in Fat rats. Mean AP was significantly higher during 9% NaCl infusion in Fat rats compared with NFD rats. In the open-loop analysis of carotid sinus baroreflex, a rightward shift of the neural arc was observed in Fat rats compared with NFD rats. Furthermore, distensibility of the common carotid artery was significantly reduced in Fat rats. These results indicate that a reduced baroreceptor distensibility-induced rightward shift of the neural arc might contribute to impairment of sodium regulation in Fat rats.

Differential transcriptional activity of kidney genes in hypertensive ISIAH and normotensive WAG rats

Transcriptional activity of the kidney genes was compared in hypertensive ISIAH and normotensive WAG rats using the oligonucleotide microarray technique. Most of differentially expressed genes were downregulated in ISIAH kidney both in renal cortex and medulla. According to functional annotation the kidney function in ISIAH rats is based on altered expression of many genes working in stress-related mode. The alterations in gene expression are likely related to both pathophysiological and compensatory mechanisms. The further studies of genes differentially expressed in ISIAH and WAG kidney will help to reveal new hypertensive genes and mechanisms specific for stress-induced arterial hypertension.

Catheter-based radiorefrequency renal denervation lowers blood pressure in obese hypertensive dogs

BACKGROUND

Obesity-induced hypertension appears to be due, in part, to increased renal sympathetic activity. Catheter-based renal denervation (RD) has been reported to lower arterial blood pressure (BP) in humans with resistant hypertension, many of whom are obese. This study was performed to assess the impact of radiofrequency-induced RD on renal function, BP, renal norepinephrine (NE), and histology of nerves along the renal artery in obese, hypertensive dogs, an experimental model that closely mimics cardiorenal and metabolic changes in obese hypertensive humans.

METHODS

After control measurements of cardiovascular and renal function were obtained in obese dogs fed a high-fat diet, bilateral RD was performed using the St. Jude Medical EnligHTN RD system. After RD, BP was measured continuously for 8 weeks, and glomerular filtration rate (GFR) was measured biweekly for 6 weeks. At the end of the study, renal arteries were collected for histological analysis, and kidneys were obtained for NE measurement.

RESULTS

Eight weeks after RD, systolic BP fell from 157 ± 5 mm Hg pre-RD to 133 ± 3 mm Hg (P < 0.01), and mean arterial pressure decreased by 9 mm Hg compared with pre-RD (P < 0.01). There were no significant changes in GFR. Renal nerve injury was most prevalent 0.28-3.5mm from the renal artery lumen. RD caused injury in 46% of the renal nerves observed and reduced renal tissue NE by 42% (P < 0.01).

CONCLUSIONS

Catheter-based RD with the St. Jude Medical EnligHTN system lowers BP in obese dogs without significantly compromising renal function.

The magnitude of obesity and its relationship to blood pressure among the residents of enugu metropolis in South East Nigeria

Background:

Obesity in developing nations is no longer as uncommon as it was thought to be decades ago however paucity of data on the burden of obesity from urban communities was observed by previous workers.

Aim:

To determine the magnitude of obesity and its relationship to blood pressure among urban adult residents in Enugu metropolis.

Subjects and Methods:

A cross-sectional community survey of adults who were not known to have diabetes or hypertension by self-report was carried out. Four parts of the metropolis selected by simple random sampling were used and consenting individuals aged 18-70 years were consecutively recruited. Anthropometric measurements were done using standard procedures as specified in the World Health Organization STEPs instrument. Obesity was determined using widely acknowledged body mass index (BMI) ≥30 kg/m². Descriptive and inferential statistical analyses was performed using SPSS with P value set at <0.05.

Results:

A high prevalence of obesity of 21.2% (95% confidence interval [CI]: 18.3-24.1) was found among the participants with significant female gender preponderance. The burden increased with age with the middle age group highly involved. Attainment of age of 40 years and above had an increased odd of developing obesity (odds ratio = 1.8; 95% CI: 1.3-2.6). There was a relationship between blood pressure and BMI as shown by positive correlation, higher BMI among hypertensive subjects and high burden of elevated blood pressure among obese subjects (91/164; 55.5%).

Conclusion:

A high magnitude of obesity existed among this apparently healthy unaware adults resident in an urban Nigerian city and obesity is associated with elevation in blood pressure.

Systemic and renal oxidative stress in the pathogenesis of hypertension: modulation of long-term control of arterial blood pressure by resveratrol

Hypertension affects over 25% of the global population and is associated with grave and often fatal complications that affect many organ systems. Although great advancements have been made in the clinical assessment and treatment of hypertension, the cause of hypertension in over 90% of these patients is unknown, which hampers the development of targeted and more effective treatment. The etiology of hypertension involves multiple pathological processes and organ systems, however one unifying feature of all of these contributing factors is oxidative stress. Once the body's natural anti-oxidant defense mechanisms are overwhelmed, reactive oxygen species (ROS) begin to accumulate in the tissues. ROS play important roles in normal regulation of many physiological processes, however in excess they are detrimental and cause widespread cell and tissue damage as well as derangements in many physiological processes. Thus, control of oxidative stress has become an attractive target for pharmacotherapy to prevent and manage hypertension. Resveratrol (trans-3,5,4'-Trihydroxystilbene) is a naturally occurring polyphenol which has anti-oxidant effects in vivo. Many studies have shown anti-hypertensive effects of resveratrol in different pre-clinical models of hypertension, via a multitude of mechanisms that include its function as an anti-oxidant. However, results have been mixed and in some cases resveratrol has no effect on blood pressure. This may be due to the heavy emphasis on peripheral vasodilator effects of resveratrol and virtually no investigation of its potential renal effects. This is particularly troubling in the arena of hypertension, where it is well known and accepted that the kidney plays an essential role in the long term regulation of arterial pressure and a vital role in the initiation, development and maintenance of chronic hypertension. It is thus the focus of this review to discuss the potential of resveratrol as an anti-hypertensive treatment via amelioration of oxidative stress within the framework of the fundamental physiological principles of long term regulation of arterial blood pressure.

The associations of adipokines with selected markers of the renin-angiotensinogen-aldosterone system: the multi-ethnic study of atherosclerosis

Among obese individuals, increased sympathetic nervous system activity results in increased renin and aldosterone production, as well as renal tubular sodium reabsorption. This study determined the associations between adipokines and selected measures of the reninangiotensinogen-aldosterone system (RAAS). The sample was 1,970 men and women from the Multi-Ethnic Study of Atherosclerosis who were free of clinical cardiovascular disease at baseline and had blood assayed for adiponectin, leptin, plasma renin activity (PRA) and aldosterone. The mean age was 64.7 years and 50% were female. The mean (SD) PRA and aldosterone were 1.45 (0.56) ng/ml and 150.1 (130.5) pg/ml, respectively. After multivariable adjustment, a 1-SD increment of leptin was associated with a 0.55 ng/ml higher PRA and 8.4 pg/ml higher aldosterone (p < 0.01 for both). Although adiponectin was not significantly associated with PRA levels, the same increment in this adipokine was associated with lower aldosterone levels (−5.5 pg/ml, p = 0.01). Notably, the associations between aldosterone and both leptin and adiponectin were not materially changed with additional adjustment for PRA. Exclusion of those taking anti-hypertensive medications modestly attenuated the associations. The associations between leptin and both PRA and aldosterone were not different by gender but were significantly stronger among non-Hispanic Whites and Chinese Americans than African and Hispanic Americans (p < 0.01). The findings suggest that both adiponectin and leptin may relevant to blood pressure regulation via the RAAS, that the associations appear to be robust to anti-hypertension medication use and that the associations are likely different by ethnicity.

Body mass index and risk of renal cell cancer: a dose-response meta-analysis of published cohort studies

Obesity is accepted as one of the major risk factors for renal cell cancer (RCC). However, conflicting results persist for the pooled risks based on the results from case-control and cohort studies combined, and the exact shape of the dose-response relationship has not been clearly defined yet. To help elucidate the role of obesity, PubMed and Embase databases were searched for published cohort studies on associations between body mass index (BMI) and risk of RCC. Random-effects models and dose-response meta-analyses were used to pool study results. Subgroup analyses were conducted by the available characteristics of studies and participants. Cohort studies (21) with 15,144 cases and 9,080,052 participants were identified. Compared to normal weight, the pooled relative risks and the corresponding 95% confidence intervals of RCC were 1.28(1.24-1.33) for preobesity and 1.77(1.68-1.87) for obesity, respectively. A nonlinear dose-response relationship was also found for RCC risk with BMI (p = 0.000), and the risk increased by 4% for each 1 kg/m(2) increment in BMI. There was no significant between-study heterogeneity among studies (I(2) = 35.6% for preobesity and I(2) = 44.2% for obesity, respectively). Subgroup analysis showed a basically consistent result with the overall analysis. These results suggest that increased BMI are associated with increased risk of RCC both for men and women.

Obesity, hypertension, and chronic kidney disease

Obesity is a major risk factor for essential hypertension, diabetes, and other comorbid conditions that contribute to development of chronic kidney disease. Obesity raises blood pressure by increasing renal tubular sodium reabsorption, impairing pressure natriuresis, and causing volume expansion via activation of the sympathetic nervous system and renin–angiotensin–aldosterone system and by physical compression of the kidneys, especially when there is increased visceral adiposity. Other factors such as inflammation, oxidative stress, and lipotoxicity may also contribute to obesity-mediated hypertension and renal dysfunction. Initially, obesity causes renal vasodilation and glomerular hyperfiltration, which act as compensatory mechanisms to maintain sodium balance despite increased tubular reabsorption. However, these compensations, along with increased arterial pressure and metabolic abnormalities, may ultimately lead to glomerular injury and initiate a slowly developing vicious cycle that exacerbates hypertension and worsens renal injury. Body weight reduction, via caloric restriction and increased physical activity, is an important first step for management of obesity, hypertension, and chronic kidney disease. However, this strategy may not be effective in producing long-term weight loss or in preventing cardiorenal and metabolic consequences in many obese patients. The majority of obese patients require medical therapy for obesity-associated hypertension, metabolic disorders, and renal disease, and morbidly obese patients may require surgical interventions to produce sustained weight loss.

Ethnic and gender susceptibility to metabolic risk

BACKGROUND

Aggregation of metabolic risk factors-i.e., elevated plasma triglyceride (TG), reduced high-density lipoprotein cholesterol (HDL-C), elevated blood pressure, and raised plasma glucose-convey increased risk for atherosclerotic cardiovascular disease and type 2 diabetes.

METHODS

This study was carried out to determine the association of waist girth, ethnicity, and gender with susceptibility for metabolic risk. Included were 1671 adult women (50.7% black) and 1339 men (46.5% black) enrolled in the Dallas Heart Study. Subjects were stratified into three categories by waist girth-low, intermediate, and high, corresponding to BMI ranges of <25 kg/m(2), 25-29.9 kg/m(2), and ≥30 kg/m(2).

RESULTS

Risk factor prevalence rose progressively through each waist-girth category. However, even among those with high waist-girth, prevalence of three or more risk factors was less than 50%. Several differences among the ethnic groups were noted; for example, Hispanic men had a higher prevalence of elevated TG compared to whites; black men, on the other hand, had a lower frequency of high TG. There were also fewer black men with low HDL-C than in the other groups. Black and Hispanic men had a higher prevalence of elevated glucose and updated homeostasis model assessment of insulin resistance (HOMA2-IR) than whites. More black men had elevated blood pressure than other groups. These differences were less pronounced among ethnic groups of women.

CONCLUSION

Although ethnic and gender differences in risk factor prevalence may exist, it is notable that the majority of subjects, even when obese, did not have elevated risk factors. This finding points to the need to focus largely on subjects with metabolic risk factors when implementing therapeutic interventions.

Is there a link between hyperuricemia, morning blood pressure surge, and non-dipping blood pressure pattern in metabolic syndrome patients?

Background:

Hypertensive patients usually have a blunted nocturnal decrease, or even increase, in blood pressure during sleep. There is also a tendency for increased occurrence of cardiovascular events between 6 and 12 am due to increased morning blood pressure surge (MBPS). Co-occurrence of metabolic syndrome (MetS) and hypertension is also a common problem. Hyperuricemia might trigger the development of hypertension, chronic renal failure, and insulin resistance. In this study, we aimed to determine whether there is a relationship between hyperuricemia, MetS, nocturnal blood pressure changes, and MBPS.

Method:

A total of 81 newly diagnosed hypertensive MetS patients were included in this study. Ambulatory blood pressure monitoring of patients was done and patients’ height, weight, and waist and hip circumferences were recorded. Fasting blood glucose (FBG), lipid profile, creatinine, potassium, uric acid, hematocrit levels were studied.

Results:

Non-dipper (ie, those whose blood pressure did not drop overnight) patients had higher waist–hip ratios (WHR) (P = 0.003), uric acid (P = 0.0001), FBG (P = 0.001), total and low-density lipoprotein cholesterol levels (P = 0.0001). Risk analysis revealed that hyperuricemia was a risk factor for non-dipping pattern (P < 0.0001, odds ratio = 8.1, 95% confidence interval = 1.9–33.7). Patients in the highest quadrant for uric acid levels had higher FBG (P = 0.001), low-density lipoprotein cholesterol (P = 0.017), WHR (P = 0.01), MBPS (P = 0.003), and night diastolic blood pressure compared with lowest quadrant patients (P = 0.013). Uric acid levels were also positively correlated with night ambulatory blood pressure (ABP) (r = 0.268, P =0.05), night diastolic blood pressure (r =0.3, P =0.05), and MBPS (r =0.3, P =0.05).

Conclusion:

Evaluation of hypertensive patients should also include an assessment of uric acid level and anthropometric measurements such as abdominal obesity. Hyperuricemia seems to be closely related to undesired blood pressure patterns and this may signal to the clinician that an appropriate therapeutic approach is required.

Higher leptin is associated with hypertension: the Multi-Ethnic Study of Atherosclerosis

Adipokines are secreted from adipose tissue, influence energy homeostasis and may contribute to the association between obesity and hypertension. Among 1897 participants enrolled in the Multi-Ethnic Study of Atherosclerosis, we examined associations between blood pressure and leptin, tumor necrosis factor-α (TNFα), resistin and total adiponectin. The mean age and body mass index (BMI) was 64.7 years and 28.1, respectively, and 50% were female. After adjustment for risk factors, a 1-s.d.-increment higher leptin level was significantly associated with higher systolic (5.0 mm Hg), diastolic (1.9), mean arterial (2.8) and pulse pressures (3.6), as well as a 34% higher odds for being hypertensive (P<0.01 for all). These associations were not materially different when the other adipokines, as well as BMI, waist circumference or waist-to-hip ratio, were additionally added to the model. Notably, the associations between leptin and hypertension were stronger in men, but were not different by race/ethnic group, BMI or smoking status. Adiponectin, resistin and TNFα were not independently associated with blood pressure or hypertension. Higher serum leptin, but not adiponectin, resistin or TNFα, is associated with higher levels of all measures of blood pressure, as well as a higher odds of hypertension, independent of risk factors, anthropometric measures and other selected adipokines.

Effects of body size and hypertension treatments on cardiovascular event rates: subanalysis of the ACCOMPLISH randomised controlled trial

BACKGROUND

In previous clinical trials in high-risk hypertensive patients, paradoxically higher cardiovascular event rates have been reported in patients of normal weight compared with obese individuals. As a prespecified analysis of the Avoiding Cardiovascular Events through Combination Therapy in Patients Living with Systolic Hypertension (ACCOMPLISH) trial, we aimed to investigate whether the type of hypertension treatment affects patients' cardiovascular outcomes according to their body size.

METHODS

On the basis of body-mass index (BMI), we divided the full ACCOMPLISH cohort into obese (BMI ≥30, n=5709), overweight (≥25 to <30, n=4157), or normal weight (<25, n=1616) categories. The ACCOMPLISH cohort had already been randomised to treatment with single-pill combinations of either benazepril and hydrochlorothiazide or benazepril and amlodipine. We compared event rates (adjusted for age, sex, diabetes, previous cardiovascular events, stroke, or chronic kidney disease) for the primary endpoint of cardiovascular death or non-fatal myocardial infarction or stroke. The analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00170950.

FINDINGS

In patients allocated benazepril and hydrochlorothiazide, the primary endpoint (per 1000 patient-years) was 30·7 in normal weight, 21·9 in overweight, and 18·2 in obese patients (overall p=0·0034). However, in those allocated benazepril and amlodipine, the primary endpoint did not differ between the three BMI groups (18·2, 16·9, and 16·5, respectively; overall p=0·9721). In obese individuals, primary event rates were similar with both benazepril and hydrochlorothiazide and benazepril and amlodipine, but rates were significantly lower with benazepril and amlodipine in overweight patients (hazard ratio 0·76, 95% CI 0·59-0·94; p=0·0369) and those of normal weight (0·57, 0·39-0·84; p=0·0037).

INTERPRETATION

Hypertension in normal weight and obese patients might be mediated by different mechanisms. Thiazide-based treatment gives less cardiovascular protection in normal weight than obese patients, but amlodipine-based therapy is equally effective across BMI subgroups and thus offers superior cardiovascular protection in non-obese hypertension.

FUNDING

Novartis Pharmaceuticals.

Association between body size and blood pressure in children from different ethnic origins

Objective

To assess associations between body size and blood pressure in children (5-6 years) from different ethnic origins.

Method

Five ethnic groups of the ABCD cohort were examined: Dutch (n=1 923), Turkish (n=99), Moroccan (n=187), Black-African (n=67) and Black-Caribbean (n=121). Data on body-mass-index (BMI), waist-to-height ratio (WHtR), fat-mass-index (FMI), and systolic blood pressure (SBP) and diastolic blood pressure (DBP), were collected. Linear regression analysis with restricted cubic splines was used to examine non-linear associations between body size and blood pressure, adjusted for age, sex, height and birth weight.

Results

Ethnic differences were found in associations of BMI with SBP and DBP (SBP: p=0.001 and DBP: p=0.01) and FMI with SBP (p=0.03). BMI and FMI had a relatively large positive association with SBP in Turkish children (BMI: β=2.46mmHg; 95%CI:1.20-3.72; FMI: β=2.41mmHg; 95%CI:1.09-3.73) compared to Dutch (BMI: β=1.31mmHg; 95%CI:0.71-1.92; FMI: β=0.84mmHg; 95%CI:0.23-1.45). Black-Caribbean and Moroccan children showed high blood pressure with low BMI and FMI. Moroccan children showed higher SBP with high BMI and FMI. WHtR was positively associated with SBP and DBP, similar in all ethnic groups. Generally, strongest associations with blood pressure were found for BMI in all ethnic groups.

Conclusion

Ethnic-specific associations between BMI, and FMI and blood pressure are present at young age, with Turkish children showing the highest increase in blood pressure with increasing body size. The higher blood pressure in the Black-Caribbean and Moroccan children with low BMI needs further research. WHtR or FMI do not seem to be associated more strongly to blood pressure than BMI in any ethnic group.

Salt sensitivity of blood pressure: developmental and sex-related effects

Epidemiologic studies have shown convincingly that drastically reducing salt intake in the community is accompanied by blood pressure reductions that are comparable to those achieved by antihypertensive medication. Moreover, many subjects with hypertension are salt sensitive. This implies that, in these subjects, blood pressure is more responsive to changes in salt intake than in subjects with normal blood pressure. The presence of conventional risk factors associated with the metabolic syndrome correlates with salt sensitivity. However, women appear to be more salt sensitive than men. Sparse data indicate that the salt sensitivity of blood pressure is greater in subjects with low birth weight. Experimental studies in rats have also shown that hypertensive offspring of dams maintained on low-protein diets throughout or in late pregnancy are more salt sensitive. This is accompanied by increased expression of the thick ascending limb Na-K-2Cl symporter (NKCC2). Perinatal interventions aimed at persistently lowering blood pressure in genetically hypertensive rats have consistently proven to be very effective and are often accompanied by a wave of natriuresis exclusively at 4 wk of age. In sum, in addition to conventional metabolic risk factors for cardiovascular disease, low birth weight and possibly its sequels such as catch-up growth should be viewed as modifiable risk factors for salt sensitivity of blood pressure. Female sex may also be a nonmodifiable risk factor for salt sensitivity. Experimental data indicate that NKCC2 may well be an important determinant of salt sensitivity in acquired (developmental) hypertension.

Effects of weight loss on renal function in overweight Japanese men

Obesity is known as an independent risk factor for renal injury. Sympathetic nerve activation may have an important role of the pathogenesis of obesity, and hypertension may underpin the development of cardiovascular events. In the present study, we evaluated the effects of weight loss (WL) on renal function, especially focusing on sympathetic nervous activity. In 154 overweight or obese Japanese men (89 normotensive and 65 untreated mild hypertensive subjects), body weight, body mass index (BMI), total body fat mass, blood pressure (BP), serum creatinine, blood urea nitrogen, creatinine clearance (CCr) (calculated with the Cockcroft-Gault equation) and plasma norepinephrine (NE) were measured before and after a 12-month period of WL with a mild caloric-restricted diet and exercise. A significant WL was defined as 10% or more WL compared with the entry period. In total, 97 (63.0%) subjects succeeded in significant (by 14.3%) WL at 12 months, and 57 subjects (37.0%) did not succeed in significant WL but they lost 7.7% weight. At entry, levels of plasma NE, serum creatinine and fat mass were significantly lower and CCr was greater in the group with a significant WL compared with those without WL. BMI, total body fat mass and plasma NE significantly decreased, and CCr increased with WL. At both baseline and at the 12-month period, fat mass and plasma NE negatively correlated with CCr and positively correlated with creatinine at each time point. Changes in fat mass and plasma NE over 12 months correlated with changes in creatinine, and only changes in fat mass negatively correlated with changes in CCr. Basal fat mass and plasma NE correlated positively with serum creatinine at 12 months and negatively with CCr at the same time point. In multiple regression analyses, basal plasma NE and fat mass were significant determinants of serum creatinine levels and CCr at 12 months. In conclusion, WL improved renal function (as evident from measures of creatinine and CCr) in overweight individuals. Basal plasma NE levels and total body fat mass could be predictors for improvement in renal function associated with WL. Suppression of sympathetic nervous activation associated with WL may have a role in the ameliorative effects on renal function.

PPARgamma-dependent regulation of adenylate cyclase 6 amplifies the stimulatory effect of cAMP on renin gene expression

The second messenger cAMP plays an important role in the regulation of renin gene expression. Nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) is known to stimulate renin gene transcription acting through PPARγ-binding sequences in renin promoter. We show now that activation of PPARγ by unsaturated fatty acids or thiazolidinediones drastically augments the cAMP-dependent increase of renin mRNA in the human renin-producing cell line Calu-6. The underlying mechanism involves potentiation of agonist-induced cAMP increase and up-regulation of adenylate cyclase 6 (AC6) gene expression. We identified a palindromic element with a 3-bp spacer (Pal3) in AC6 intron 1 (AC6Pal3). AC6Pal3 bound PPARγ and mediated trans-activation by PPARγ agonist. AC6 knockdown decreased basal renin mRNA level and attenuated the maximal PPARγ-dependent stimulation of the cAMP-induced renin gene expression. AC6Pal3 decoy oligonucleotide abrogated the PPARγ-dependent potentiation of cAMP-induced renin gene expression. Treatment of mice with PPARγ agonist increased AC6 mRNA kidney levels. Our data suggest that in addition to its direct effect on renin gene transcription, PPARγ "sensitizes" renin gene to cAMP via trans-activation of AC6 gene. AC6 has been identified as PPARγ target gene with a functional Pal3 sequence.

Mechanisms of obesity-induced hypertension

The relationship between obesity and hypertension is well established both in children and adults. The mechanisms through which obesity directly causes hypertension are still an area of research. Activation of the sympathetic nervous system has been considered to have an important function in the pathogenesis of obesity-related hypertension. The arterial-pressure control mechanism of diuresis and natriuresis, according to the principle of infinite feedback gain, seems to be shifted toward higher blood-pressure levels in obese individuals. During the early phases of obesity, primary sodium retention exists as a result of increase in renal tubular reabsorption. Extracellular-fluid volume is expanded and the kidney-fluid apparatus is resetted to a hypertensive level, consistent with a model of hypertension because of volume overload. Plasma renin activity, angiotensinogen, angiotensin II and aldosterone values display significant increase during obesity. Insulin resistance and inflammation may promote an altered profile of vascular function and consequently hypertension. Leptin and other neuropeptides are possible links between obesity and the development of hypertension. Obesity should be considered as a chronic medical condition, which is likely to require long-term treatment. Understanding of the mechanisms associated with obesity-related hypertension is essential for successful treatment strategies.

Roux-en-Y gastric bypass reverses renal glomerular but not tubular abnormalities in excessively obese diabetics

BACKGROUND

Obesity and type 2 diabetes are associated with renal dysfunction, which improves after Roux-en-Y gastric bypass (RYGB). During a 12-month follow-up period, we studied prospectively the changes in glomerular and tubular functions that occurred in excessively obese diabetic and non diabetic subjects after RYGB.

METHODS

The cohort included 35 patients, 54% of whom had type 2 diabetes. Glomerular filtration rate (GFR) was estimated using creatinine clearance. Tubular function was studied by measuring the ratio of urinary cystatin C to urinary creatinine (UCC ratio).

RESULTS

Baseline renal parameters, anthropometric characteristics, and changes in body mass index after the surgical procedures were similar between the 2 cohorts. At 12 months after RYGB, creatinine clearance decreased 15% in diabetics (P = .02) and 21% in nondiabetics (P = .03). A change in GFR was seen earlier in the nondiabetics (-29% after 6 months; P = .003). The UCC ratio was increased at both 6- and 12-month follow-ups (P = .03 and .003, respectively) only in the diabetic group.

CONCLUSION

GFR was improved at 12 months after RYGB, with nondiabetics showing a greater propensity score. Tubular function remained unchanged in the nondiabetic subjects, but worsening occurred in the diabetic subjects. These results underscore the importance of reversal of excessive obesity before the onset of frank diabetes.

Effect of the HMG-CoA reductase inhibitor rosuvastatin on early chronic kidney injury in obese zucker rats fed with an atherogenic diet

The obese Zucker rat (OZR) spontaneously develops hyperlipidemia, insulin resistance, and microalbuminuria. In this study, the initial metabolic, functional, and glomerular pathology in young OZR fed with an atherogenic diet resembles the characteristics of metabolic syndrome. Hyperlipidemia and other metabolic derangement cause early glomerular damage in OZR by 10 weeks of age, before overt diabetes is developed. Consequently, the effects of potential interventions should also be evaluated at the young age. In OZR fed with an atherogenic high-fat diet, low (5 mg/kg) and high (20 mg/kg) dosages of rosuvastatin started at 5 weeks and maintained for 10 weeks induced a significant improvement in metabolic abnormalities, blood pressure, and renal function, including microalbuminuria. The low dose of rosuvastatin significantly decreased mesangial expansion, and the high dose exerted a marked protective effect on the development of both glomerular hypertrophy and mesangial expansion. The statin also attenuated the inflammatory expression in the kidney cortex.

Diet-induced obesity causes cerebral vessel remodeling and increases the damage caused by ischemic stroke

Hypertension, elevated fasting blood glucose and plasma insulin develop in rats fed a high fat (HF) diet. Our goal was to assess the effects of obesity, beginning in childhood, on the adult cardiovascular system. We hypothesized that rats fed a HF diet would have larger ischemic cerebral infarcts and middle cerebral artery (MCA) remodeling. Three-week-old male Sprague Dawley rats were fed a HF (obese) or control diet for 10 weeks. Cerebral ischemia was induced by MCA occlusion (MCAO). MCA structure was assessed by pressure myography and cerebral vessel matrix metalloproteinase (MMP) activity and expression and collagen levels were measured in vessels from rats that did not undergo MCAO. The cerebral infarct was greater in the obese rats than the control (46.0+/-2.1 vs 28.0+/-7.5% of the hemisphere infarcted, obese vs control p<0.05). The MCAs from obese rats had smaller lumens (232+/-7.2 vs 254+/-7.8 microm obese vs control p<0.05) and thicker walls (19.6+/-0.8 vs 17.8+/-0.9 microm obese vs control p<0.05) and were less compliant than MCAs from control rats. MMP-2 activity and collagen I expression were increased in vessels from obese rats and MMP-13 expression was reduced. These results suggest that obesity, beginning in childhood, causes inward vessel remodeling with a concomitant increase in vessel stiffness due to increased collagen deposition. These changes in MCA structure may be responsible for the increase in the ischemic damage after MCAO.

Relationship of anthropometric indicators with blood pressure levels and the risk of hypertension in Nigerian adults

BACKGROUND AND PURPOSE

Studies on cardiovascular risks in relation to anthropometric factors are limited in Sub-Sahara Africa. The aims of this study were to examine the relationship between anthropometric parameters and blood pressure; and to evaluate body mass index (BMI) across the range of underweight and obesity as a primary risk factor of hypertension in adult Nigerians.

MATERIAL AND METHODS

2097 adults aged between 20 and 100 years consented and participated in this door-to-door survey. All participants underwent blood pressure and anthropometric measurements using standard procedures. The population study was separated in normotensive and hypertensive males and females and the possible risk for hypertension were categorized into different classes of value based on BMI definition.

RESULTS

The relative risks (odds ratio [OR] and 95% confidence interval [CI]) of developing hypertension among the obese compared with the underweight, normal weight, and overweight persons were (OR 5.75; CI 5.67-5.83), (OR 1.73; CI 1.65-1.81), and (OR 1.54; CI 1.46-1.62) for all the participants, respectively. Among obese (BMI >/= 30.0 Kg/m(2)) males, the OR for hypertension was three times (OR 2.78; CI 2.76-2.80) that of normal weight (BMI >/= 18.5-24.9 Kg/m(2)) males. Females with obesity had a risk of hypertension three times (OR 3.34; CI 3.33-3.35) that of normal weight females.

CONCLUSION

Our results indicated that the there was a significant positive correlation of obesity indicator with blood pressure. In Nigeria, we found a strong gradient between higher BMI and increased risk of hypertension among all ages. Approaches to reduce the risk of hypertension may include prevention of overweight and obesity.

Endothelin: 20 years from discovery to therapy

Since its identification as an endothelial cell-derived vasoconstrictor peptide in 1988, endothelin-1, the predominant member of the endothelin peptide family, has received considerable interest in basic medical science and in clinical medicine, which is reflected by more than 20 000 scientific publications on endothelin research in the past 20 years. The story of endothelin is unique as the gene sequences of endothelin receptors and the first receptor antagonists became available within only 4 years of the identification of the peptide sequence. The first clinical study in patients with congestive heart failure was published only 3 years thereafter. Yet, despite convincing experimental evidence of a pathogenetic role for endothelin in development, cell function, and disease, many initial clinical studies on endothelin antagonism were negative. In many of these studies, study designs or patient selection were inadequate. Today, for diseases such as pulmonary hypertension, endothelin antagonist treatment has become reality in clinical medicine, and ongoing clinical studies are evaluating additional indications, such as renal disease and cancer. Twenty years after the discovery of endothelin, its inhibitors have finally arrived in the clinical arena and are now providing us with new options to treat disease and prolong the lives of patients. Possible future indications include resistant arterial hypertension, proteinuric renal disease, cancer, and connective tissue diseases.

Can sibutramine alter systemic blood pressure in obese patients? Systematic review and meta-analysis

CONTEXT

Systemic arterial hypertension is part of the metabolic syndrome resulting from obesity.

OBJECTIVE

To evaluate the effect of sibutramine on overweight and obese patients' blood pressure through a systematic review.

METHODS

All the studies included needed to be randomized controlled trials. The methodological quality of the selected trials was assessed using the criteria described in the Cochrane Handbook. The participants were overweight and obese patients; the intervention was sibutramine compared with placebo. The primary outcome measurement was systolic and diastolic blood pressure and the secondary measurement was blood pressure. Studies were identified by searching the following sources: Literatura Latino-Americana e do Caribe em Ciências da Saúde (Lilacs), Medline, Cochrane reviews, manual searches, personal communication and contact with the pharmaceutical industry. There were no language, date or other restrictions. Data collection and extraction was performed by two reviewers, who independently obtained the full articles of all eligible papers.

RESULTS

Three meta-analyses were produced: 1) systolic blood pressure outcome (eight studies) did not show statistical significance between sibutramine and placebo: weighted mean difference (WMD) 1.57, confidence interval (CI) -0.03 to 3.18; 2) diastolic blood pressure outcome (ten studies) did not show statistical significance between sibutramine and placebo: WMD 1.13, CI -0.49 to 2.76; 3) blood pressure outcome (two studies) also did not show statistical significance between the groups: relative risk (RR) 0.69, CI 0.07 to 7.01.

CONCLUSIONS

The meta-analyses presented in this systematic review show that sibutramine does not have a statistically significant effect on blood pressure, compared with placebo.

Parasympathetic response to acute stress is attenuated in young Zucker obese rats

We compared arterial blood pressure (BP) and heart rate (HR) control in 9- to 11-week old obese Zucker rats (n=10; weight=452+/-45 g, average+/-SD) to age-matched, lean Zucker animals (n=13; weight=280+/-46 g). BP was measured by indwelling catheter. Baseline pressure was 113.1+/-7.0 mm Hg in the lean vs. 111.7+/-5.6 in the obese rats (NS). Baseline HR was 413+/-43 in the lean vs. 422+/-22 bpm in the obese animals (NS). Rats were classically conditioned by following a 15-second tone (CS+) with a 0.5-second tail shock. There were no between-group differences in the BP response to CS+. Conversely, heart rate (HR) decreased significantly (p<0.05) more during the last 10 s of the tone in the lean group (-46.0+/-21.5 bpm) vs. the obese (-17.8+/-21.7 bpm). This bradycardia was blocked by atropine. Finally, the change in HR divided by the change in arterial BP (DeltaHR/DeltaBP) following an intravenous bolus of phenylephrine (PE; 5 microg/kg) and following sodium nitroprusside (NP; 5 microg/kg) was determined. The DeltaHR/DeltaBP following PE was smaller in the obese (n=6; -1.36+/-0.60) vs. lean (n=5; -2.80+/-0.92); there was no difference in the response following NP. These data indicate that the BP response to a behavioral challenge did not differ in the obese rat vs. the lean animal, but that the obese subjects had an attenuated parasympathetic response to the stress, probably secondary to alterations in baroreflex function.

Multiple mechanisms involved in obesity-induced hypertension

Obesity and hypertension are two major cardiovascular risk factors gaining epidemic proportions in our modern world. The interplay between hypertension, obesity and their major detrimental outcome, cardiovascular disease, is multifaceted and can be represented as the three corners of a triangle. Obesity and hypertension both lead to cardiovascular complications. In addition, obesity per se can promote hypertension. In turn, cardiovascular diseases can also predispose to obesity and hypertension. Low levels of physical activity due to a weakened heart promote weight gain. Endothelial, vascular and renal dysfunctions, all consequences of high blood pressure, further worsen hypertension. The loop of mutually amplifying detrimental effects is thus closed: a 'vicious triangle' is established. The association between obesity and hypertension was recognised and described almost a century ago, but the mechanisms that underlie this connection are still not fully understood. Vasoconstriction and sodium retention seem to be the cornerstones of the obesity-hypertension puzzle. However, pathways possibly leading to vasoconstriction and sodium retention are numerous. Evidence has been gathered that hyperleptinaemia, hyperinsulinaemia and elevated free fatty acids may induce sympathetic activation and vasoconstriction. The latter is further potentiated by insulin resistance and endothelial dysfunction. Positive sodium balance and ensuing volume expansion may be due to increased renal tubular sodium reabsorption induced by sympathetic stimulation, insulin or by a hyperactive renin-angiotensin system. All enumerated factors act together toward a state of permanently elevated blood pressure.

The effects of high-fat diet on the renal structure and morphometric parametric of kidneys in rats

To characterize the kidney in a high-fat-induced obesity model, we examined the renal structure of adult Sprague-Dawley rats fed a control diet or a high-fat diet for 3 months. Ten adult female Sprague-Dawley rats were fed a diet consisting highly of fat (30%) for a period of 3 months. Ten control rats were maintained with standard rat chow. All animals were weighed every 10 days for 3 months. At the end of the experiment, the naso-anal length of the anaesthetized rats was measured to calculate body mass index, and subsequently whole kidneys of intracardially formalin-perfused animals were removed. Quantitative features of the kidney were analysed with the Cavalieri and physical dissector methods applied to serial paraffin sections. Kidney samples were also examined histologically. The body mass indices of the control and treatment groups were 4.528 +/- 0.242 and 5.876 +/- 0.318 kg m(-2), respectively. The difference between the body mass indices of the two groups was statistically significant (P < 0.01, Mann-Whitney U-test), suggesting that the animals fed with a high-fat diet may be overweight. Stereological examination of the kidneys revealed differences in kidney weight, total kidney volume, volume of cortex, medulla, glomeruli, proximal and distal tubules, and numerical density of glomeruli and glomerular height in the treatment group compared with the control group. Light microscopic investigation showed a dilatation in blood vessels and Bowman's space, mononuclear cell infiltration, degeneration in nephrons, including glomerulosclerosis and tubular defects, and an increase in the connective tissue in the kidneys in the treatment group. We concluded that a fatty diet is responsible for the rats' obesity and may lead to renal deformities as a result of histopathological changes such as dilatation, tubular defects, inflammation and connective tissue enlargement of the kidney.

Effect of drastic weight loss after bariatric surgery on renal parameters in extremely obese patients: long-term follow-up

Obesity is a health problem that is reaching epidemic proportions. Extreme obesity (body mass index [BMI] > or =40 kg/m2) is a type of obesity that usually does not respond to medical treatment, with surgery being the current treatment of choice. Extreme obesity is associated with cardiovascular disease, type 2 diabetes, dyslipidemia, and hypertension. Recently, obesity has been related with high rate of renal lesions, but renal function and renal parameters in extreme obesity scarcely are documented. The objective of this study was to evaluate the effect of weight loss after bariatric surgery (BS) on BP, renal parameters, and renal function in 61 extremely obese (EO) patients after 24 mo of follow-up. A total of 61 EO adults (37 women) were studied prospectively before and 24 mo after surgery. Control subjects were 24 healthy, normal-weight adults (15 women). Anthropometric, BP, and renal parameters were determined. Presurgery weight, BMI, GFR, 24-h proteinuria, and 24-h albuminuria were higher in the EO patients than in control subjects (P < 0.001). All parameters improved at 12 mo after BS. However, during the second year of follow-up, only 24-h albuminuria (P = 0.006) and BMI (P = 0.014) continued to improve. At 24 mo after BS, obesity-related renal alterations considerably improved. This improvement was observed mainly in the first year after surgery, when the majority of weight loss occurred. However, 24-h albuminuria still improves during the second year of follow-up. It is possible that this decrease in 24-h albuminuria is not GFR related but rather is attributable to the persistence of the decrease in BMI and to the improvement of other weight-related metabolic factors.

Renal cell cancer and body size at different ages: an Italian multicenter case-control study

An increased risk of renal cell cancer (RCC) has been reported in overweight persons. The authors aimed to clarify which anthropometric measures are associated with risk of RCC and whether risk may vary according to selected variables. Between 1992 and 2004, they carried out an Italian multicenter case-control study including 767 (494 men, 273 women) incident cases of RCC and 1,534 hospital controls, frequency-matched to cases. To estimate odds ratios and 95% confidence intervals, they used conditional logistic regression matched on study center, sex, and age and adjusted for period of interview, years of education, smoking habits, and family history of kidney cancer. Using body-size measurements taken 1 year prior to diagnosis/interview, the authors found an odds ratio of 1.3 (95% confidence interval (CI): 1.0, 1.7) among obese persons (body mass index (BMI; weight (kg)/height (m)(2)) > or =30) versus normal-weight persons (BMI <25) and an odds ratio of 1.5 (95% CI: 1.1, 2.0) among persons in the highest tertile of waist-to-hip ratio. Direct associations emerged for BMI > or =30 (vs. <25) at ages 30 years (odds ratio = 1.5, 95% CI: 1.0, 2.3) and 50 years (odds ratio = 1.5, 95% CI: 1.1, 2.0). The direct association with waist-to-hip ratio was stronger among women than among men. RCC risks among overweight and obese persons were apparently higher in never smokers, persons with the clear-cell histologic type, and persons with a Fuhrman nuclear grade of G3-G4.