Exploration of hypoglycemic effect of an extract from leaves of a plant from Tunisian pharmacopeia: Artemisia campestris (Asteraceae)

Background and objectives

A lot of research has been directed towards medicinal plants which are considered as a source of multiple phytotherapic substances endowed with hypoglycemic activities that could be used to treat diabetes and its complications. Our study was carried out in Wistar rats to investigate the hypoglycemic effect of n-Butanol Fraction from Artemisia campestris leaf Methanolic Extract (BFACME).

Methods

Two experimental models were used in rats: orally induced hyperglycemia (OGTT) and isolated perfused liver (IPRL).

Results

BFACME at 550 mg/kg BW dose significantly reduced fasting glucose level in normal rats as compared to controls. The decrease of glycaemia was 12.6% more significant than that obtained with the standard drug glibenclamide (10 mg/kg BW), an oral antidiabetic preparation belonging to sulfonylurea class. In OGTT model, BFACME at the highest doses of 550 and 400 mg/kg BW significantly reduced the postprandial hyperglycemic peak compared to controls. In the IPRL model, treatment with BFACME significantly decreased glucose concentrations after 30 min of perfusion with 30 mM glucose solely when insulin was present. The higher doses of BFACME lead to glucose concentration at basal level as early as 90 min, while the lowest dose does not restore this concentration even to t = 120min. The best initial glucose concentration retrieval was obtained with 0.7 mg BFACME/mL/g liver. At this dose, BFACME improves the decrease of glucose level caused by only insulin by about 18%.

Conclusion

The BFACME appears to exert a hypoglycemic activity by potentiating the insulin action.

Hepatic oxidative stress in pigmented P23H rhodopsin transgenic rats with progressive retinal degeneration

Retinitis pigmentosa (RP) comprises a group of inherited retinal degenerative conditions characterized by primary degeneration of the rod photoreceptors. Increased oxidative damage is observed in the retina, aqueous humor, and plasma of RP animal models and patients. The hepatic oxidative status may also be affected in RP due to oxidative damage influencing soluble macromolecules exiting the retina or to alterations in the melanopsin system resulting in chronic circadian desynchronization that negatively alters the oxidative stress defense system. P23H rats were crossed with pigmented Long Evans rats to produce offspring exhibiting the clinical conditions of RP. We measured hepatic malondialdehyde and 4-hydroxyalkenal concentrations as oxidative stress markers; nitrite level as a total nitrosative damage marker; total antioxidant capacity; and the activities of catalase, superoxide dismutase (SOD), and glutathione S-transferase. Retinal visual function was assessed based on optomotor and electroretinogram responses. P23H transgenic rats exhibited diminished visual acuity, contrast sensitivity, and electroretinographic responses according to the level of retinal degeneration. P23H rats at 30 days of age already demonstrated only 47% of the hepatic total antioxidant capacity of wild-type animals. Hepatic catalase and SOD activities were also reduced in P23H rats after 120 days, but we detected no difference in glutathione S-transferase activity. P23H rats had increased hepatic oxidative and nitrosative damage markers. GSH/GSSG ratio showed a significant diminution in P23H rats at P120 compared to WT. We conclude that the liver is under increased oxidative stress in P23H rats. Further studies are required, however, to clarify the contribution of systemic oxidative damage to the pathogenesis of RP.

Protective effects of phycocyanin on ischemia/reperfusion liver injuries

In this study, phycocyanin (Pc) extracted from Spirulina platensis was used to evaluate its antioxidants effects after ischemia/reperfusion injury (IRI) using the ex-vivo model of isolated perfused rat liver. The rats were divided into eight groups : Control group, where livers were directly perfused after their removal; Cold Ischemia group (CI), livers were treated in the same way as the control group, except that after their collection, they were stored for 12 h and 24 h in the Krebs Henseleit (KH) preservation solution at 4 °C and Treated group (PHY), livers were preserved in the same way as the preceding group except that the KH solution was enriched with phycocyanin at two different concentrations. Pc, a powerful antioxidant, significantly reduced ischemia/reperfusion injury in the liver. In fact, the addition of phycocyanin to the preservation solution significantly decreased the activity of liver transaminases (AST) and (ALT), alkaline phosphatase (ALP), the rate of lipid peroxidation (MDA) and the activity of certain antioxidant enzymes, essentially glutathione-S-transferase (GST) and glutathione peroxidase (GPx). On the other hand, Pc increases the level of thiol groups in hepatic tissues. In conclusion, the results show the Pc-enriched KH conservation solution is effective in preserving the hepatic graft and protecting it against IRI by acting as a potent antioxidant against the products of oxidative stress.

Effects of Nitrite Addition to IGL-1 Solution on Rat Liver Preservation

BACKGROUND The ability of nitrite to provide protection following ischemia/reperfusion (I/R) has been demonstrated, but its mechanism is still poorly understood. This study aimed to determine the optimal nitrite concentration to add into Institut Georges Lopez (IGL-1) storage solution and to assess its effect on antioxidant enzymes and autophagy. MATERIAL AND METHODS Livers from Sprague-Dawley rats were conserved in IGL-1 for 24 hours at 4°C or in IGL-1 enriched with nitrite at 50, 500 and 1,000 nM, respectively, before being perfused ex-vivo at 37 °C for 120 minutes. Sham livers were perfused ex vivo without cold preservation. RESULTS All biological and functional parameters of the preserved livers were significantly impaired as compared to shams. Interestingly, the supplementation of nitrite to IGL-1 protected the liver from I/R injury. Among the doses of nitrite evaluated, the 50 nM was proved efficient: it significantly reduced cytolysis, mitochondrial damage, and lipid peroxidation, and enhanced antioxidant enzyme activity (superoxide dismutase, catalase, and glutathione peroxidase activity) and hepatic function parameters (portal resistance, bile flow, and bromosulfophthalein clearance). In addition, increased levels of the autophagy parameters were observed when 50 nM of nitrite were added to IGL-1 solution, but this effect disappeared completely with higher concentrations of nitrite. CONCLUSIONS It seems that 50 nM of nitrite added to IGL-1 is the optimal concentration able to maintain cell integrity and hepatic function through autophagy induction and oxidative stress prevention.