Concentration of tissue angiotensin II increases with severity of experimental pancreatitis

Diet-induced prediabetes: Effects on the activity of the renin-angiotensin-aldosterone system (RAAS) in selected organs

Derangements often observed with type 2 diabetes (T2D) are associated with disturbances in renin-angiotensin-aldosterone system (RAAS) activity. A positive correlation between local RAAS activity and the complications observed in T2D has been noted. However, the detrimental ramifications due to moderate hyperglycemia noted in prediabetes and the affected organ system and mechanistic pathways are not elucidated. Hence, this study investigated the effects of diet-induced prediabetes on RAAS in various organs.

MATERIALS AND METHODS

Male Sprague-Dawley rats were separated into two groups: non-pre-diabetic (NPD) through exposure to standard rat chow and diet-induced prediabetic (PD) group by exposure to a high-fat high carbohydrate diet for 32 weeks. RAAS activity in the skeletal muscle, adipose tissue, liver, pancreas and heart was determined through the analysis of RAAS components such as; renin, angiotensinogen, angiotensin-converting enzyme (ACE) and angiotensin II type 1 receptor (AT1R) via PCR as well as the quantification of angiotensin II and aldosterone concentration. Furthermore, NADPH oxidase, SOD and GPx1 concentrations were determined in the skeletal muscle, pancreas and heart in addition to the hepatic triglycerides.

RESULTS

The RAAS components were elevated in the PD group when compared to the NPD. This was further accompanied by increased NADPH oxidase and reduced SOD and GPx1 concentrations in the selected organs, in addition to the elevated hepatic triglycerides concentration in the PD by comparison to NPD.

CONCLUSION

Due to these observed changes, we suggest that local RAAS activity in the prediabetic state in selected organs elicits the derangements noted in T2D.

Angiotensin 1-7 ameliorates caerulein-induced inflammation in pancreatic acinar cells by downregulating Toll-like receptor 4/nuclear factor-κB expression

The present study aimed to investigate the effects of angiotensin (Ang) 1–7 on caerulein (CAE)-stimulated nuclear factor (NF)-κB, Toll-like receptor (TLR4) and cytokine expression using pancreatic acinar AR42J cells. AR42J cells were treated with 10 nmol/l CAE for various durations. In addition, cells were pretreated with various concentrations of Ang 1–7 or A779, a specific antagonist of Ang 1–7, and were stimulated with CAE for 12 h. Control cells were treated with vehicle (F-12K complete medium with 2% fetal bovine serum, 10 U/ml penicillin and 100 mg/ml streptomycin) alone. The mRNA and protein expression levels of TLR4, NF-κB, interleukin (IL)-6, IL-8, IL-10 and tumor necrosis factor-α (TNF-α) were determined by western blotting, immunofluorescence and reverse transcription-quantitative polymerase chain reaction. CAE treatment stimulated TLR4 and NF-κB expression within AR42J cells. Immunofluorescence indicated that TLR4 was expressed on the membranes and in the cytoplasm of AR42J cells, whereas NF-κB expression accumulated in the cytoplasm and nuclei. CAE-induced expression of TLR4 and NF-κB within AR42J cells was abrogated by 10⁻⁵ mmol/l Ang 1–7; however, TLR4 and NF-κB expression was enhanced with the addition of A779, particularly 10⁻⁵ mmol/l. In addition, treatment with 10⁻⁶ and 10⁻⁵ mmol/l Ang 1–7 significantly mitigated CAE-induced expression of IL-6, IL-8 and TNF-α, whereas it enhanced IL-10 expression. Conversely, A779 treatment enhanced the CAE-induced expression of IL-6, IL-8 and TNF-α, and reduced IL-10 expression in AR42J cells. In conclusion, these results suggested that Ang 1–7 may attenuate CAE-induced inflammation by downregulating TLR4, NF-κB and proinflammatory cytokine expression within AR42J cells. Therefore, Ang 1–7 may exert protective effects against the pathological progression of AP in a cell model of AP induced by CAE and may be considered in the development of treatments for this disease.