ACE and AT1 receptor gene polymorphisms and renal scarring in urinary bladder dysfunction

Vesicoureteral reflux and bladder dysfunction

The relationship between vesicoureteral reflux and bladder dysfunction is inseparable and has long been emphasized. However, the primary concern of all physicians treating patients with vesicoureteral reflux is the prevention of renal scarring and eventual deterioration of renal function.

Bladder dysfunction, urinary tract infection and vesicoureteral reflux are the three important factors which are closely related to each other and contribute to the formation of renal scar. Especially, there is ongoing discussion regarding the role of bladder dysfunction in the prognosis of both medically and surgically treated vesicoureteral reflux. The effect of bladder dysfunction on VUR is mostly via inadequate sphincter relaxation during infancy which is closer to immature bladder dyscoordination rather than true dysfunction. But after toilet training, functional obstruction caused by voluntary sphincter constriction during voiding is responsible through elevation in bladder pressure, thus distorting the architecture of bladder and ureterovesical junction. Reports suggest that voiding phase abnormalities in lower urinary tract dysfunction contributes to lower spontaneous resolution rate of VUR. However, filling phase abnormalities such as involuntary detrusor contraction can also cause VUR even in the absence of dysfunctional voiding. With regards to the effect of bladder dysfunction on treatment, meta-analysis reveals that the cure rate of VUR following endoscopic treatment is less in children with bladder bowel dysfunction but there is no difference for open surgery.

The pathophysiology of bladder dysfunction associated with UTI can be explained by the ‘milk-back’ of contaminated urine back into the bladder and significant residual urine resulting from functional outlet obstruction. In addition, involuntary detrusor contraction can decrease perfusion of the bladder mucosa thus decreasing mucosal immunity and creating a condition prone to UTI. In terms of renal scarring, dysfunctional voiding seems to be more closely related to renal damage in association with VUR than overactive bladder. However, studies show that UTI can induce renal scarring even without VUR present and urodynamic abnormalities are quite often detected in these cases. Whether reflux of sterile urine in bladder dysfunction can cause significant renal scarring, especially when intrarenal reflux is present remains controversial. Another issue that warrants further research is the direct relationship between bladder dysfunction and renal scarring, since some reports suggest that these two conditions share a common genotype.

Recently some studies have suggest VUR as a causal factor of bladder dysfunction, supported by the fact that bladder dysfunction resolves after injection therapy of VUR. Further study with more objective evaluation of bladder dysfunction may be needed.

Association between ACE polymorphism and risk of IgA nephropathy: a meta-analysis

BACKGROUND

and objective: The effect of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism on risk or progression of immunoglobulin A nephropathy (IgAN) is still debated.Therefore, a meta-analysis was performed to evaluate the association of ACE gene polymorphism with IgAN in different ethnic groups.

METHOD

A predefined search strategy was performed to collect data from electronic databases.

RESULTS

Twenty articles were identified for the analysis of the relationship between ACE polymorphism and IgAN risk, including 11 in Asians and nine in Caucasians. There was a markedly positive association between the D allele or DD genotype and IgAN risk in Asians (OR = 1.27, p = 0.006; OR = 1.83, p < 0.0001). However, a link between D allele or DD genotype and IgAN risk was not found in Caucasians (OR = 1.04, p = 0.46; OR = 1.13, p = 0.12). Ten investigations were included for analysis of the association of ACE polymorphism with IgAN progression, including six in Asians and four in Caucasians. These data did not support a link between the ACE D allele or DD genotype and IgAN progression in Asians and Caucasians (Asians: D: OR = 1.03, p = 0.80; DD: OR = 1.43, p = 0.16; Caucasians: D: OR = 1.29, p = 0.22; DD: OR = 1.31, p = 0.17).

CONCLUSIONS

The D allele or DD genotype is associated with IgAN risk in Asian, but not in Caucasian populations; there was no significant association between the D allele or DD gene and IgAN progression for Asians and Caucasians.

ACE gene insertion/deletion polymorphism and renal scarring in children with urinary tract infections

Urinary tract infection is a common bacterial disease that presents during childhood and may lead to renal scarring. Several studies have shown a strong association between the angiotensin converting enzyme (ACE) deletion polymorphism and renal scarring in children with vesicoureteric reflux (VUR). The purpose of this study was to investigate the possible correlation between the ACE deletion polymorphism and renal scarring in 186 children with urinary tract infection (UTI), of whom 90 were renal scar positive and 96 were renal scar negative. The control group consisted of 129 children with no UTI. Renal scars were diagnosed by means of (99m)Tc-dimercapto-succinic acid scans, and ACE genotypes were determined as II, ID, and DD by PCR analyses. The ACE genotype distribution was 10% II, 67% ID, and 23% DD in the renal scar-positive group, 18% IotaIota, 42% ID, and 40% DD in the renal scar-negative group, and 22% II, 47% ID, and 31% DD in the control group. No correlation was found between the DD genotype and renal scar formation in children with UTI. The same results were obtained following strafication of the patients by VUR and age of the first urinary tract infection. In conclusion, the results of this study suggest that the DD genotype is not an independent risk factor for renal scarring in children with UTI.

Incidence of post-pyelonephritic renal scarring: a meta-analysis of the dimercapto-succinic acid literature

PURPOSE

We investigated ethnic differences in the risk of post-pyelonephritic renal scarring in infants and children for possible genetic determinants.

MATERIALS AND METHODS

We searched all peer reviewed articles published from 1980 through 2006 in the PubMed(R), MEDLINE(R) (Ovid), Cochrane Central Register of Controlled Trials and EMBASE(R) databases for the keywords, "renal scarring and pyelonephritis," "renal fibrosis" and "kidney scarring." References were included only when they specified acute pyelonephritis defined by a fever, positive urine culture and areas of photopenia in the renal cortex on 99mtechnetium dimercapto-succinic acid renal scans, repeat dimercapto-succinic acid scans obtained at least 3 months after acute pyelonephritis to assess for renal cortical scar formation and absence of recurrent urinary tract infection during followup. When possible data were analyzed according to patients and renal units.

RESULTS

Among 23 references the overall rates of renal scarring in terms of patients and renal units were 41.6% and 37.0%, respectively. In terms of patients the incidence of renal scarring following acute pyelonephritis varied by region, from 26.5% (Australia) to 49.0% (Asia). In terms of renal units the incidence of acquired renal cortical scarring varied by region, from 16.7% (Middle East) to 58.4% (Asia). When combined by vesicoureteral reflux status children and renal units with refluxing ureters exhibited an increased risk of renal scarring (odds ratios 2.8 and 3.7, respectively).

CONCLUSIONS

Although scarring was different across some regions, only scarring in Asian studies comparing patients displayed a statistically significant difference. A regional effect explained the heterogeneity observed in the overall estimate for patients and partly for renal units. The greatest risk of renal scarring may be imparted by the presence of vesicoureteral reflux.

Angiotensin II type 1 receptor polymorphisms and susceptibility to hypertension: a HuGE review

The angiotensin II type 1 receptor (AGTR1) plays an integral role in blood pressure control, and is implicated in the pathogenesis of hypertension. Polymorphisms within this gene have been extensively studied in association with hypertension; however, findings are conflicting. To clarify these data, we conducted a systematic review of association studies of AGTR1 polymorphisms and hypertension, and performed a meta-analysis of the rs5186 variant. Results show that the currently available literature is too heterogeneous to draw meaningful conclusions. The definition of hypertension and gender composition of individual studies helps to explain this heterogeneity. Although the structure and splicing pattern of AGTR1 would suggest a likely effect of polymorphisms within the promoter region on gene function, few studies have been conducted thus far. In conclusion, there is insufficient evidence that polymorphisms in the AGTR1 gene are risk factors for hypertension. However, most studies are inadequately powered, and larger well-designed studies of haplotypes are warranted.

Polymorphisms of the angiotensin converting enzyme and angiotensin II type 1 receptor genes and renal scarring in non-uropathic children with recurrent urinary tract infection

AIM

The aim of this study was to investigate whether the angiotensin converting enzyme (ACE) and angiotensin II type 1 receptor (A1166C) gene polymorphisms were associated with the renal scar formation secondary to recurrent urinary tract infection in children without uropathy.

METHODS

The polymorphisms were investigated by polymerase chain reaction in 97 children (81 females, 16 males; age, 2.5-13 years) with recurrent urinary tract infection and 100 healthy controls as a single centre study. Children with vesicoureteral reflux, bladder dysfunction and other uropathies were excluded. The dimercaptosuccinic acid (DMSA) scan performed at least 3 months after a proven urinary tract infection and the result of the last DMSA was taken into consideration.

RESULTS

Renal scarring was found in 30 patients (30.9%) using DMSA scan. The number of urinary tract infection attacks was significantly higher in patients with renal scarring compared with children without scarring (P<0.05). The follow-up period and male/female ratio of patients with or without renal scarring was similar (P>0.05). Age at the first urinary tract infection was lower in the group with scarring. The ACE insertion/deletion genotype distribution and D allele frequency were similar between patients and controls (P>0.05), and in patients with renal scarring and those without renal scarring. Also, the angiotensin II type 1 receptor gene polymorphism was not associated with renal parenchymal damage (P>0.05).

CONCLUSION

The results indicated that the ACE insertion/deletion and angiotensin II type 1 receptor gene polymorphisms were not independent risk factors for renal scar formation in recurrent urinary tract infection of paediatric patients without uropathy.