Determination of optimal blood pressure for patients with IgA nephropathy based on renal histology

Peripheral arterial stiffness is correlated with intrarenal arteriolosclerosis according to biopsies from patients with kidney disease

AIM

To investigate the possible associations between intrarenal arteriolosclerosis as determine by renal biopsy and endothelial function as well as arterial stiffness measured by peripheral arterial tonometry (EndoPAT).

METHODS

This was a cross-sectional study. Patients who underwent both renal biopsy and EndoPAT were recruited, and intrarenal arteriolosclerosis was graded according to the pathological slice. Endothelial function and arterial stiffness were both measured by EndoPAT and were expressed by the reactive hyperemia index (RHI) and augmentation index (AIx), respectively. AIx@75, representing the AIx standardized to a heart rate of 75 bpm was also determined.

RESULTS

In total, 113 patients were assessed, the mean age was 51 ± 13, and 68.1% were men. The natural logarithm RHI (LnRHI), AIx and AIx@75 were significantly different among different grades of intrarenal arteriolosclerosis (P = .030, P < .001, P < .001, respectively). In the multivariable adjusted model, for every SD increase in the AIx and AIx@75, the odds of having more severe arteriolosclerosis were 2.506 times (95% confidence interval [CI] 1.464-4.288, P = .001] and 3.191 times (95% CI 1.780-5.719, P < .001) higher, respectively, and the association between the LnRHI and intrarenal arteriolosclerosis was nullified (P = .059). The positive values of the AIx and AIx@75 for the diagnosis of severe intrarenal arteriolosclerosis were 0.80 (95% CI 0.73-0.88, P < .001) and 0.78 (95% CI 0.70-0.87, P < .001), respectively.

CONCLUSION

Subjects with more severe intrarenal arteriolosclerosis have greater peripheral vascular stiffness; AIx and AIx@75 reflected peripheral vascular stiffness could be used to identify patients with severe intrarenal arteriolosclerosis.

Pre-hypertension as a significant predictor of chronic kidney disease in a general population: the Ohasama Study

BACKGROUND

Hypertension is associated with an increased risk of development of chronic kidney disease (CKD). However, it is unclear whether pre-hypertension is related to the incidence of CKD.

METHODS

The incidence of CKD defined as positive proteinuria or estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m(2) was examined in 2150 inhabitants without pre-existing CKD from the general Japanese population. The association of blood pressure and CKD incidence was examined using a Cox regression model adjusted for age, sex, habitual smoking and drinking, obesity, history of cardiovascular disease, diabetes mellitus or hypercholesterolemia, eGFR at baseline, number of follow-up examinations and year of baseline examination. Participants were categorized according to the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure.

RESULTS

Participants were categorized into normotension (n = 586, 27.3 % ), pre-hypertension (n = 815, 37.9 % ), Stage 1 hypertension (n = 386, 18.0 % ) and Stage 2 hypertension (n = 363, 16.9 % ). During a mean follow-up of 6.5 years (14 023 person-years), 461 incidences of CKD were recorded. Compared to normotension, adjusted hazard ratios of CKD were significantly higher for pre-hypertension (1.49, P < 0.003), Stage 1 (1.83, P < 0.001) and Stage 2 (2.55, P < 0.001) hypertension. The population-attributable fraction of pre-hypertension (12.1 % ) was considered to be compatible to that of Stage 1 (8.6 % ) and Stage 2 (14.9 % ) hypertension.

CONCLUSION

This was the first study to demonstrate that pre-hypertension was significantly associated with an increased risk of CKD and was one of the considerable causes of CKD in the general population.

Prehypertension: is it relevant for nephrologists?

Blood pressure (BP) in the prehypertensive range is associated with an increased risk for cardiovascular (CV) disease. Patients with co-morbidities are at greater risk for chronic kidney disease (CKD) development in the presence of prehypertension. Lifestyle changes can alter the natural history of prehypertension; however, long-term adherence is rare and thus, their impact on outcomes is limited. Pharmacological therapy in patients with prehypertension and demonstrable target organ damage with blockers of the renin-angiotensin system has demonstrated benefits on markers of CKD outcomes such as microalbuminuria. There are no data, however, on 'hard end points' such as doubling of creatinine or need for renal replacement therapy. In patients with diabetes, monitoring changes in albuminuria, along with assessment of BP in the prehypertensive range, is important to optimize early management and impact the attenuation of CKD progression. Data from natural history studies in patients with type 1 diabetes indicate that increases within the microalbuminuria range antedate increases in BP within the prehypertensive range. Even within the microalbuminuria range, however, systolic BP increases above 125 mm Hg are predictive of nephropathy. Thus, nephrologists need to ensure that their colleagues appreciate the importance of not only early BP intervention but also of monitoring albuminuria changes in order to have maximal impact on CKD prevention.

Prehypertension increases the risk for renal arteriosclerosis in autopsies: the Hisayama Study

Information regarding the association between prehypertension BP level and renal arteriosclerosis is limited. In 652 consecutive population-based autopsy samples without hypertension treatment before death, the relationship between the severity of renal arteriosclerosis and BP levels classified according to the criteria of the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure was examined. The age- and gender-adjusted frequencies of renal arteriosclerosis linearly increased with elevating BP levels; both hypertensive and prehypertensive subjects had significantly higher frequencies of renal arteriosclerosis than subjects with normal BP (normal 11.9%; prehypertension 28.5%; stage 1 hypertension 32.9%; stage 2 hypertension 58.2%; all P < 0.01 versus normal). In a logistic regression model, prehypertension was significantly associated with renal arteriosclerosis after adjustment for other cardiovascular risk factors (prehypertension multivariate-adjusted odds ratio [mOR] 5.99 [95% confidence interval (CI) 2.20 to 15.97]; stage 1 hypertension mOR 6.99 [95% CI 2.61 to 18.72]; stage 2 hypertension mOR 22.21 [95% CI 8.35 to 59.08]). This significant association was observed for all renal arterial sizes. The similar association was also observed for arteriolar hyalinosis. When the subjects were divided into those with and those without target organ damage, the impact of prehypertension on renal arteriosclerosis was similar for both groups (subjects without target organ damage mOR 5.04 [95% CI 1.36 to 18.62]; subjects with target organ damage mOR 6.42 [95% CI 1.29 to 32.04]). These findings suggest that both hypertension and prehypertension are associated significantly with the severity of renal arteriosclerosis, regardless of the presence or absence of target organ damage.

Impact of Hypertension and Hypertension-Related Vascular Lesions in IgA Nephropathy

It remains poorly understood whether vascular pathology plays an important role in the progression of renal parenchymal disease in humans. Moreover, in the case of hypertensive patients with mild proteinuria, nephrologists tend to make a diagnosis of benign nephrosclerosis without renal biopsy. Among 172 patients who were treated at our hospital for biopsy-proven IgA nephropathy, we performed quantitative histopathological analysis in 38 patients with mild proteinuria of less than 0.5 g/day. We related these histopathological parameters with clinical data at biopsy and also with follow-up data. The percentage of glomeruli showing global sclerosis exceeded 10% of total glomeruli in 15 of the patients (39.5%) and exceeded 20% in 9 (23.7%). Arteriosclerosis and tubulointerstitial changes significantly correlated with glomerular sclerosis, but mesangial cell proliferation did not. Among the 38 patients, the 12 with hypertension showed more severe glomerular sclerosis, tubulointerstitial changes and arteriosclerosis compared with the 26 without hypertension, but the mesangial cell proliferation was identical between the two groups. Stepwise multiple regression analysis revealed that hypertension and urinary protein excretion (UPE) were independent risk factors for arteriosclerosis. The follow-up data of a mean period of 27.6 months showed that 9 of the 38 patients (23.7%) had an increase in UPE. Hypertension, arteriosclerosis, age, and UPE at biopsy were selected as the important risk factors for an increase in UPE in the follow-up. Our results provide not only clinical but histopathological evidence that hypertension affects the prognosis of mild proteinuric nephropathy through vascular lesions.

Role of genetic polymorphism in the SA gene on the blood pressure and prognosis of renal function in patients with immunoglobulin A nephropathy

The SA gene has been shown to be much more highly expressed in the kidneys of spontaneously hypertensive rats than in the corresponding wild-type strain. Genetic polymorphism of this gene has been shown to play a role in human hypertension, although the details of this association remain controversial. We investigated the possible associations between SA gene polymorphism and both hypertension and the prognosis of renal function in patients with immunoglobulin A nephropathy (IgAN). Genomic DNA was isolated from the peripheral blood of 367 individuals, including 274 patients with histologically proven IgAN and 100 controls without any history of renal disease. The SA genotype was determined by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) with Pst I. The frequencies of genotypes and alleles were not different between the patients with IgAN and those without renal disease. In the group without renal disease, the SA gene polymorphism was not associated with hypertension. However, in the patients with IgAN the A1 allele frequency was significantly higher in the hypertensives than in the normotensives. The renal survival of the patients with the A2 allele tended to be better than that of those without the A2 allele. The findings thus suggest that SA gene polymorphism may be associated with the renal prognosis of IgAN through its effect on blood pressure. Further, they suggest that the sensitivity to this gene polymorphism increases in patients with renal injury.