Relationship between transforming growth factor beta1 and progression of hypertensive renal disease

Elevated Plasma Transforming Growth Factor β1 Levels Predict the Development of Hypertension in Normotensives: The 14-Year Follow-Up Study

BACKGROUND

Transforming growth factor β1 (TGF-β1) is a multifunctional cytokine. There is growing evidence that TGF-β1 is involved in the pathogenesis of hypertension and the development of target organ damage in hypertensives. Although several studies have shown that TGF-β1 induced vascular hypertrophy and remodelling in various vascular diseases, there are no longitudinal data on hypertension in the epidemiological studies. The present study tested the hypothesis whether elevated TGF-β1 levels can predict the development of hypertension.

METHODS

In 2002-2004, 528 subjects received health examinations in Uku town, southwestern Japan. We examined blood pressure (BP), body mass index, and blood test. Data on fasting plasma TGF-β1 were obtained from 528 individuals. Of these, 149 normotensives (BP <140/90 mm Hg without antihypertensive medications) at baseline were followed-up for 14 years.

RESULTS

The receiver-operating characteristic curve was used and the calculated cutoff value was 8.9 ng/ml. Of 149 normotensives at baseline, 59 subjects developed hypertension. Plasma TGF-β1 levels were significantly associated with the development of hypertension after adjustment for confounding factors. To further examine the association between them, we performed logistic regression analysis. We divided the baseline plasma TGF-β1 levels into 2 groups using a cutoff value. The significant high odds ratio [3.582 (95% confidence interval, 1.025-12.525)] for the development of hypertension was found in the highest group of TGF-β1 level vs. the lowest group after adjustment for confounders.

CONCLUSIONS

This is the first report demonstrating the causal relationship between them. Elevated plasma TGF-β1 levels predicted the development of hypertension in normotensives in a population of community-dwelling Japanese.

Genetic deficiency of Smad3 protects the kidneys from atrophy and interstitial fibrosis in 2K1C hypertension

Although the two-kidney, one-clip (2K1C) model is widely used as a model of human renovascular hypertension, mechanisms leading to the development of fibrosis and atrophy in the cuffed kidney and compensatory hyperplasia in the contralateral kidney have not been defined. Based on the well-established role of the transforming growth factor (TGF)-β signaling pathway in renal fibrosis, we tested the hypothesis that abrogation of TGF-β/Smad3 signaling would prevent fibrosis in the cuffed kidney. Renal artery stenosis (RAS) was established in mice with a targeted disruption of exon 2 of the Smad3 gene (Smad3 KO) and wild-type (WT) controls by placement of a polytetrafluoroethylene cuff on the right renal artery. Serial pulse-wave Doppler ultrasound assessments verified that blood flow through the cuffed renal artery was decreased to a similar extent in Smad3 KO and WT mice. Two weeks after surgery, systolic blood pressure and plasma renin activity were significantly elevated in both the Smad3 KO and WT mice. The cuffed kidney of WT mice developed renal atrophy (50% reduction in weight after 6 wk, P < 0.0001), which was associated with the development of interstitial fibrosis, tubular atrophy, and interstitial inflammation. Remarkably, despite a similar reduction of renal blood flow, the cuffed kidney of the Smad3 KO mice showed minimal atrophy (9% reduction in weight, P = not significant), with no significant histopathological alterations (interstitial fibrosis, tubular atrophy, and interstitial inflammation). We conclude that abrogation of TGF-β/Smad3 signaling confers protection against the development of fibrosis and atrophy in RAS.

Evaluation of Transforming Growth Factor Beta-1 Gene 869T/C Polymorphism with Hypertension: A Meta-Analysis

Association between transforming growth factor beta-1 gene (TGFB1) 869T/C polymorphism and hypertension has been widely evaluated, yet with conflicting results. As meta-analysis is a reliable way to resolve discrepancies; I aimed to evaluate this association. Data were available from 9 study populations involving 6151 subjects. Overall, comparison of allele 869C with 869T generated a significant 30% increased hypertension risk (95% confidence interval [95% CI]: 1.11–1.51; P = 0.001), which was strengthened for homozygous comparison (869CC versus 869TT) with odds ratio (OR) doubled to 1.62 (95% CI: 1.23–2.14; P = 0.001). Stratified analysis by study design demonstrated stronger associations in population-based studies than in hospital-based studies with OR, except in the dominant model, being increased by 7.94–18.61%. Likewise, ethnicity-based analysis exhibited a contradictory association between Asians and Whites. Conclusively, these findings support the notion that TGFB1 gene 869T/C polymorphism may influence the risk of hypertension, especially in Asian populations.

The Relationship between the Transforming Growth Factor β1 T29C Gene Polymorphism and Left Ventricular Geometry and Function in Hypertensive Subjects

The distribution of the T29C TGFβ1 gene polymorphism was analyzed in 198 hypertensives with left ventricular hypertrophy (LVH) and in 235 hypertensives without LVH. Circulating TGFβ1 levels, procollagen type III levels, microalbuminuria, and left ventricular geometry and function were evaluated in all the hypertensives with LVH subgrouped according to T29C TGFβ1 gene polymorphism. Circulating TGFβ1 was evaluated by ELISA technique, procollagen type III by a specific radioimmunoassay, microalbuminuria by radioimmunoassay, and left ventricular geometry and function by echocardiography. All groups were comparable for gender, age, and sex. Regarding T29C TGFβ1 gene polymorphism, prevalence of TC or CC genotypes was significantly (P < .05) higher in hypertensives with LVH than hypertensives without LVH TC and CC LVH hypertensives were characterized by a higher prevalence of subjects with microalbuminuria (P < .05 TC and CC versus TT), by increased levels of TGFβ1, procollagen type III, urinary albumin excretion, LVM, LVM/h_2.7, and lower values of left ventricular ejection fraction (P < .05 TC and CC versus TT). Our data suggest that T29C TGFβ1 gene polymorphism was associated with clinical characteristics adequate to recognize a subset of LVH hypertensives with a higher severity of hypertension.

Transforming growth factor beta1 T29C gene polymorphism and hypertension: relationship with cardiovascular and renal damage

Distribution of T29C TGFbeta1 gene polymorphism was analysed in 260 hypertensive and 134 normotensive subjects. Circulating TGFbeta1 and procollagen type III levels, microalbuminuria, left ventricular geometry and function were evaluated in all the hypertensives subgrouped according to T29C TGFbeta1 gene polymorphism. Circulating TGFbeta1 by ELISA technique, procollagen type III by a specific radioimmunoassay, microalbuminuria by radioimmunoassay, left ventricular geometry and function by echocardiography were determined. All groups were comparable for gender, age and sex. Regarding T29C TGFbeta1 gene polymorphism, prevalence of TC or CC genotypes was significantly (p<0.05) higher in hypertensives than normotensives. TC and CC hypertensives were characterized by a higher prevalence of subjects with microalbuminuria (p<0.001 TC vs TT; p<0.05 CC vs TT), left ventricular hypertrophy (p<0.01 TC and CC vs TT), and by increased levels of procollagen type III (p<0.05 TC and CC vs TT). TC hypertensives were also characterized by a significant increase (p<0.05) of LVM and LVM/h(2.7 )and of urinary albumin excretion (p<0.05) values than those detectable in TT hypertensives. Our data suggest that T29C TGFbeta1 gene polymorphism was associated to clinical characteristics suitable to recognize hypertensives with a higher severity of hypertension.

Lack of association between TGF-beta-1 genotypes and microalbuminuria in essential hypertensive men

BACKGROUND

Polymorphisms within the gene for transforming growth factor (TGF)-beta-1, a pro-fibrogenic cytokine pathophysiologically involved in hypertension and hypertensive target damage, might modulate the biological activity of the encoded protein. Through that mechanism, they might contribute to microalbuminuria, a marker of subclinical renal damage and a correlate of systemic inflammation and endothelial dysfunction in hypertension, a possibility never before tested. For this reason, we assessed the association of four TGF-beta-1 polymorphic variants (C-509T, Leu(10)-->Pro, Arg(25)-->Pro, Thr(263)-->Ile) with albuminuria in uncomplicated essential hypertensive men, using (circulating active + acid-activatable latent) TGF-beta-1 levels as an indirect index of their in vivo biological activity. Because of the close pathophysiological link of TGF-beta-1 with the renin-angiotensin system, we also tested the behaviour of the angiotensin converting enzyme (ACE) deletion/insertion (D/I) polymorphism.

METHODS

Albuminuria (three overnight collections), office and 24-h BP, left ventricular mass index (LVMI), BMI, renal function, glucose, lipids, plasma TGF-beta-1 (n = 162, ELISA) were measured in 222 genetically unrelated, never-treated, uncomplicated Caucasian hypertensive men. ACE D/I polymorphisms were analysed by the polymerase chain reaction technique or a 5' nuclease assay with further restriction analysis when required.

RESULTS

Urine albumin levels or microalbuminuria (albuminuria > or =15 microg/min) did not differ by TGF-beta-1 genotypes, but both parameters were more frequent in ACE D/D homozygotes. Plasma TGF-beta-1 was similar across genetic backgrounds and was unrelated to albuminuria. Cardiovascular, renal, metabolic parameters were homogeneously distributed across genotypes.

CONCLUSIONS

In contrast to its link with the ACE D/I genotype, microalbuminuria was independent of TGF-beta-1 polymorphism in this group of never-treated, uncomplicated essential hypertensive men.

Transforming growth factor beta1 and additional renoprotective effect of combination ACE inhibitor and angiotensin II receptor blocker in hypertensive subjects with minor renal abnormalities: a 24-week randomized controlled trial

OBJECTIVE

To verify the benefit of renin-angiotensin system blockade in hypertension, the effects of 24 weeks' losartan and ramipril treatment, both alone and in combination, on urinary albumin excretion (UAE) and circulating transforming growth factor beta1 (TGF beta1) have been evaluated in hypertensive subjects with minor renal abnormalities.

DESIGN AND METHODS

Fifty-one patients with stage 1 and 2 essential hypertension and with UAE > or = 20 mg/24 h but with maintained renal function have been included. After a 4-week run-in with placebo administration, a randomized double-blind, three-arm double-dummy trial was used. All the hypertensives (HT) were allocated randomly to three treatment arms (17 patients for each group) and they were single-matched for age, gender, body mass index (BMI), systolic and diastolic blood pressure. Active treatment consisted of losartan (50 mg/day), ramipril (5 mg/day) and combined (losartan 50 mg/day plus ramipril 5 mg/day) for 24 weeks. Hydrochlorothiazide 12.5 mg/day was added in HT patients with uncontrolled blood pressure (> or = 140/90 mmHg) during the active treatment period. In all patients UAE, by immunonephelometric assay; circulating TGF beta1 by a solid-phase specific sandwich enzyme-linked immunosorbent assay (ELISA); and blood urea nitrogen (BUN), creatinine and creatinine clearance and potassium, by routine laboratory methods, were determined after placebo treatment and 24 weeks follow-up.

RESULTS

The three treatment groups were comparable for gender, age, BMI, blood pressure, UAE and renal function measurements. During the active treatment period it was necessary to add hydrochlorothiazide in five patients--two each of the losartan and ramipril groups and one of the combined group. At the end of treatment, significant (P < 0.05) reductions in systolic, diastolic and mean blood pressure, UAE and TGF beta1 levels were observed in all the groups. No change in renal function measurements were observed. The absolute and percentage reduction in UAE and TGF beta1 were significantly higher in the combined group than in the losartan or ramipril groups. No significant changes in absolute and percentage reduction of systolic, diastolic and mean blood pressure were found. All treatment regimens were well tolerated with few and transient side-effects.

CONCLUSION

These data indicate an additional renoprotective effect of dual blockade of the renin-angiotensin system (RAS) in hypertensive patients with minor renal abnormalities. In addition, the contemporaneus and marked decrease in TGF beta1 and UAE levels in hypertensives treated with combined therapy might indicate the presence of a subset of subjects who may benefit from complete RAS blockade.

Left ventricular filling abnormalities and obesity-associated hypertension: relationship with overproduction of circulating transforming growth factor β1

This study has been designed to evaluate the relationship among transforming growth factor beta1 (TGFbeta1) and some measurements of diastolic function in a population of hypertensive subjects with normal left ventricular ejection fraction. We studied 67 hypertensive outpatients who according to their BMI levels were subdivided into three groups: lean (L), overweight (OW) and obese (OB) hypertensives (HT). Circulating TGFbeta1 and M- and B-mode echocardiography was determined. All hypertensives were further subgrouped, according to European Society of Cardiology Guidelines, into two subsets of patients with normal diastolic function or with diastolic dysfunction. Prevalence of left ventricular hypertrophy (LVH) was determined in all the groups. TGFbeta1, left ventricular mass (LVM), LVM/h(2.7), E-wave deceleration time and isovolumic relaxation time (IVRT) were significantly (P < 0.005) higher and E/A velocity ratio was significantly (P < 0.05) lower in OW-HT and OB-HT than in L-HT. Prevalence of LVH was significantly higher (P < 0.03) in group OB-HT than in L-HT. TGFbeta1 (P < 0.004), LVM/h(2.7) (P < 0.001) and prevalence of LVH were (P < 0.01) significantly higher in hypertensives with diastolic dysfunction than hypertensives with normal diastolic function. TGFbeta1 levels were positively correlated with BMI (r = 0.60; P < 0.0001), LVM/h(2.7) (r = 0.28; P < 0.03), IVRT (r = 0.30; P < 0.02) and negatively with E/A ratio (r = -0.38; P < 0.002) in all HT. Multiple regression analysis indicated that TGFbeta1, BMI and IVRT were independently related to E/A ratio explaining 71% of its variability (r = 0.84; P < 0.0001). This relationship was independent of LVH, age and HR suggesting that TGFbeta1 overproduction may be considered a pathophysiological mechanism in the development of left ventricular filling abnormalities in obesity-associated hypertension.

Obesity and cardiovascular risk: the new public health problem of worldwide proportions

Obesity could be considered a new global health epidemic above all others, especially when it is characterized by central fat distribution. This is illustrated by dramatic provisional data, indicating a continuous increase in the trend of overweight and obese individuals in several countries, including the USA and countries in Europe. Several epidemiological, pathophysiological and clinical studies clearly indicate that two of the major independent risk factors for cardiovascular disease or events are being overweight, and obesity. Accordingly, weight loss and prevention of weight gain has to be considered one of the most important strategies to reduce the incidence of cardiovascular disease.