Angiotensin-converting enzyme insertion/deletion gene polymorphism in inflammatory bowel diseases

Role of Renin-Angiotensin-converting Enzyme Level and ACE Gene Polymorphism in Patients with Nonalcoholic Fatty Liver Disease

Introduction

In this study, we aimed to investigate the histological and clinical effect of angiotensin-converting enzyme (ACE) and ACE gene polymorphism in nonalcoholic fatty liver disease (NAFLD) and their roles in the progression of the disease.

Materials and methods

Liver function tests, body mass index, waist circumference, lipid parameters, fasting blood glucose (FBG), hemoglobin A1c (HbA1c), homeostasis model assessment-IR (HOMA-IR), ACE, and ACE gene polymorphism were evaluated in the NAFLD group and control group. The study group was evaluated by dividing the group into four subgroups by ACE gene polymorphism (D/D homozygous, I/I homozygous, D/I heterozygous, I/D heterozygous). Liver biopsies were evaluated according to Brunt Classification.

Results

A total of 31 patients who were diagnosed with NAFLD and 40 healthy individuals were included in the study. The ACE level was found to be 11.69 ± 1.99 in the NAFLD group and 11.52 ± 1.72 in the control group (p = 0.70). There was a negative correlation between ACE levels and HOMA-IR levels (p = 0.008, r= −0.512). Biochemical parameters were not different among ACE gene polimorphism subgroups, except FBG (between D/D, I/D and D/I, I/D; p = 0.02). When the ACE levels were compared in terms of grade and stage, no significant difference was found (for stage and grade p = 0.68). The ACE gene polymorphism subgroups did not differ by histopathologic findings; grade and stage (for grade p = 0.42, for stage p = 0.92).

Conclusion

In this study, we could not find a correlation of ACE and ACE gene polymorphism with metabolic risk factors and the disease severity in NAFLD.

How to cite this article

Tekatas DD, Bahcecioglu IH, Ispiroglu M, Sahin A, Ilhan N, Yalniz M, Demirel U. Role of Renin–Angiotensin-converting Enzyme Level and ACE Gene Polymorphism in Patients with Nonalcoholic Fatty Liver Disease. Euroasian J Hepato-Gastroenterol 2016;6(2):137-142.

Anti-Inflammatory Action of Angiotensin 1-7 in Experimental Colitis

Background

There is evidence to support a role for angiotensin (Ang) 1–7 in reducing the activity of inflammatory signaling molecules such as MAPK, PKC and SRC. Enhanced angiotensin converting enzyme 2 (ACE2) expression has been observed in patients with inflammatory bowel disease (IBD) suggesting a role in its pathogenesis, prompting this study.

Methods

The colonic expression/activity profile of ACE2, Ang 1–7, MAS1-receptor (MAS1-R), MAPK family and Akt were determined by western blot and immunofluorescence. The effect of either exogenous administration of Ang 1–7 or pharmacological inhibition of its function (by A779 treatment) was determined using the mouse dextran sulfate sodium model.

Results

Enhanced colonic expression of ACE2, Ang1-7 and MAS1-R was observed post-colitis induction. Daily Ang 1–7 treatment (0.01–0.06 mg/kg) resulted in significant amelioration of DSS-induced colitis. In contrast, daily administration of A779 significantly worsened features of colitis. Colitis-associated phosphorylation of p38, ERK1/2 and Akt was reduced by Ang 1–7 treatment.

Conclusion

Our results indicate important anti-inflammatory actions of Ang 1–7 in the pathogenesis of IBD, which may provide a future therapeutic strategy to control the disease progression.

Review article: the pathophysiological roles of the renin-angiotensin system in the gastrointestinal tract

BACKGROUND

The renin-angiotensin system (RAS) is a homeostatic pathway widely known to regulate cardiovascular and renal physiology; however, little is known about its influence in gastrointestinal tissues.

AIM

To elicit the anatomical distribution and physiological significance of the components of the RAS in the gastrointestinal tract.

METHODS

An extensive online literature review including Pubmed and Medline.

RESULTS

There is evidence for RAS involvement in gastrointestinal physiology and pathophysiology, with all the components required for autonomous regulation identified throughout the gastrointestinal tract. The RAS is implicated in the regulation of glucose, amino acid, fluid and electrolyte absorption and secretion, motility, inflammation, blood flow and possibly malignant disease within the gastrointestinal tract. Animal studies investigating the effects of RAS blockade in a range of conditions including inflammatory bowel disease, functional gut disorders, gastrointestinal malignancy and even intestinal ischaemia have been encouraging to date. Given the ready availability of drugs that modify the RAS and their excellent safety profile, an opportunity exists for investigation of their possible therapeutic role in a variety of human gastrointestinal diseases.

CONCLUSIONS

The gastrointestinal renin-angiotensin system appears to be intricately involved in a number of physiological processes, and provides a possible target for novel investigative and therapeutic approaches.

Use of enterally delivered angiotensin II type Ia receptor antagonists to reduce the severity of colitis

BACKGROUND

Renin-angiotensin system blockade reduces inflammation in several organ systems. Having found a fourfold increase in angiotensin II type Ia receptor expression in a dextran sodium sulfate colitis model, we targeted blockade with angiotensin II type Ia receptor antagonists to prevent colitis development. Because hypotension is a major complication of angiotensin II type Ia receptor antagonists use, we hypothesized that use of angiotensin II type Ia receptor antagonists compounds which lack cell membrane permeability, and thus enteric absorption, would allow for direct enteral delivery at far higher concentrations than would be tolerated systemically, yet retain efficacy.

METHODS

Based on the structure of the angiotensin II type Ia receptor antagonist losartan, deschloro-losartan was synthesized, which has extremely poor cell membrane permeability. Angiotensin II type Ia receptor antagonist efficacy was evaluated by determining the ability to block NF-κB activation in vitro. Dextran sodium sulfate colitis was induced in mice and angiotensin II type Ia receptor antagonist efficacy delivered transanally was assessed.

RESULTS

In vitro, deschloro-losartan demonstrated near equal angiotensin II type Ia receptor blockade compared to losartan as well as another angiotensin II type Ia receptor antagonist, candesartan. In the dextran sodium sulfate model, each compound significantly improved clinical and histologic scores and epithelial cell apoptosis. Abundance of TNF-α, IL-1β, and IL6 mRNA were significantly decreased with each compound. In vitro and in vivo intestinal drug absorption, as well as measures of blood pressure and mucosal and colonic blood flow, showed significantly lower uptake of deschloro-losartan compared to losartan and candesartan.

CONCLUSIONS

This study demonstrated efficacy of high-dose angiotensin II type Ia receptor antagonists in this colitis model. We postulate that a specially designed angiotensin II type Ia receptor antagonist with poor oral absorption may have great potential as a new therapeutic agent for inflammatory bowel disease in the future.

The renin-angiotensin system and the gastrointestinal mucosa

The gastrointestinal (GI) tract is fundamental for the intake of fluid and electrolytes and accommodates a large proportion of bodily hemodynamics and host defence systems. Despite that the renin-angiotensin system (RAS) is a prominent regulatory system for fluid and electrolyte homeostasis its impact on GI physiology is only little explored. Recent data indicate that RAS is well expressed and active in the GI tract although exact physiological roles are to be settled. There are several reports showing influences by RAS and its key mediator angiotensin II (AngII) on intestinal epithelial fluid and electrolyte transport and data are accumulating, suggesting involvement in GI mucosal inflammation and carcinogenesis. Of particular interest is the increasing amount of experimental support for the involvement of AngII formation and actions via the AngII subtype 1 (AT1) receptor in the pathogenesis and treatment of inflammatory bowel disease. The picture of RAS in the GI tract is, however, far from complete. Because RAS is an important application area for reno-cardiovascular diseases, a number of pharmacological agents as well as research technologies already exist and can in the future be used for GI research. A marked expansion of knowledge concerning the role of RAS in GI physiology and pathophysiology is to be expected.