Title : Amelioration of the Ace/Ace2 imbalance and oxidative stress by chicory seed extract (CSE) in the kidney tissue of the stz-induced Diabetic ratsAmelioration of the Ace/Ace2 imbalance and oxidative stress by chicory seed extract (CSE) in the kidney tissue of the stz-induced diabetic rats
Abstract:
The kidney's local Renin-Angiotensin System (RAS) plays a role in diabetic nephropathy (DN). Damage to the kidneys follows the imbalances between reactive oxygen species (ROS) and antioxidant systems and between the pathologic and protective arms of the RAS axis. The pathologic arm follows angiotensin II (AngII) production by angiotensin-converting enzyme (ACE). The angiotensin-(1-7) [Ang-(1-7)] produced by the angiotensin-converting enzyme 2 (ACE2) opposes the damaging effects of the pathologic arm. In DN, the pathologic arm of the RAS system is activated while the opposite arm is suppressed. Thus, the ACE/ACE2 and AngII/Ang-(1-7) ratios are expected to rise.
We injected rats with streptozotocin (STZ, 55 mg/kg) to create late-stage diabetes (LT2D) with FBS above 300 mg/dl. To create early-stage diabetes (ET2D), with stable FBS between 140-220 mg/dl, some rats were further injected with niacinamide (NIA, 200 mg/kg, 15 min later). Daily intraperitoneal injections of CSE (125 mg/Kg) or metformin (100 mg/kg) started on day ten after diabetes induction and lasted 21 days; aspirin (120 mg/kg) was given orally by gavage. Citrate (20 mM, pH 4.5, 0.3 ml) was used as a vehicle.
There were nine study groups (n = 6): the Control consisted of Groups 1 (Control, non-diabetic) and Group 2 (CSE-Control); ET2D consisted of Group 3 (NIA/STZ or ET2D), Group 4 (CSE-NIA/STZ), and Groups 5 (Met-NIA/STZ); and LT2D consisted of Group 6 (STZ or LT2D), Group 7 (CSE-STZ), Group 8 (Met-STZ), and Group 9 (Asp-STZ).
The kidney tissues were used to measure, by real-time PCR, the expression levels of the mRNA for angiotensinogen (Agt), ACE, and ACE2. ELISA measured the concentrations (ng/mg total protein) of AngII and Ang-(1-7). Protein carbonyl content (PCC, nmol/mg total protein) revealed the extent of oxidative stress. Masson's trichrome staining of tissue sections and ImageJ software helped evaluate the extent of fibrous connective tissue formation.
The most significant observation after diabetes induction was an increased ACE/ACE2 ratio, PCC, and fibrosis in kidney tissues of the LT2D rats (STZ group) (p = 0.12, p = 0.0106, and p = 0.0051, respectively, STZ vs. Control). ACE/ACE2 was reversed, and the balance was restored only by CSE (p = 0.0051, CSE-STZ vs. STZ). AngII/Ang-(1-7) ratio did not change across all groups. Fibrosis and PCC increased in the kidney tissue of LT2D rats due to collagen fiber and free radical accumulation, respectively. CSE (p = 0.0008, STZ vs. CSE-STZ) and metformin (p = 0.0134, STZ vs. Met-STZ) significantly alleviated PCC or oxidative stress; aspirin did not change it.
CSE did not, but metformin (p = 0.0035, STZ vs. Met-STZ) and aspirin (p = 0.0213, STZ vs. Asp-STZ) decreased fibrosis significantly. According to the results, CSE acted beneficially via decreasing ROS and ACE/ACE2 ratio. The parallel yet less significant changes in all the measured parameters in ET2D rats (for example, PCC, p = 0.0174 and fibrosis, p = 0.0196; STZ vs. NIA/STZ) indicate that kidney damage starts early in the course of diabetes development in the prediabetic state, and prevention by better blood sugar control using dietary supplements may delay kidney damage.
Audience Takeaway:
- The ACE/ACE2 ratio tends to increase in the kidney tissue during the aggravation of diabetes.
- The AngII/Ang-(1-7) ratio does not contribute to the progression of DN.
- Chicory extract is capable of lowering the ACE/ACE2 ratio.
- The antioxidant properties of chicory phytochemicals play a role in reducing oxidative stress (PCC) in the kidney tissue.
- Metformin and aspirin perform better than chicory extract in attenuating collagen fiber accumulation (fibrosis) in diabetic kidney tissue.
