ASIATIC ACID INFLUENCES GLUCOSE HOMEOSTASIS IN P. BERGHEI MURINE MALARIA INFECTED SPRAGUE-DAWLEY RATS

Background: Glucose homeostasis derangement is a common pathophysiology of malaria whose aetiology is still controversial. The Plasmodium parasite, immunological and inflammatory responses, as well as chemotherapeutics currently used cause hypoglycaemia in malaria. Anti-parasitic and anti-disease drugs are required to combat malaria while ameliorating the pathophysiology of the infection. Asiatic acid has anti-hyperglycaemic, antioxidant, pro-oxidant properties useful in glucose homeostasis but its influence in malaria is yet to be reported. Here we present findings on the influence of asiatic acid on glucose metabolism in vivo using P. berghei-infected Sprague Dawley rats. Materials and Methods: Acute as well as sub-chronic studies were carried out in vivo where physicochemical properties and glucose homeostasis were monitored after administration of asiatic acid (10mg/kg) in both non-infected and infected animals. Glucose metabolism associated biochemical changes in malaria were also investigated. Results: In acute studies, asiatic acid improved oral glucose response while in the sub-chronic state it maintained food and water intake and suppressed parasitaemia. Normoglycaemic control was maintained in infected animals through insulin suppression and increasing glucagon secretion, in both acute and chronic studies. Asiatic acid administration curtailed lactate concentration towards normal. Conclusion: Per oral post-infection asiatic acid administration preserved drinking and eating habits, inhibited sickness behaviour while suppressing parasitaemia. Reciprocal relationship between insulin and glucagon concentrations was maintained influencing glucose homeostasis positively and inhibition of hyperlactaemia in malaria

Asiatic acid influences glucose homeostasis in P. berghei murine malaria infected sprague-dawley rats

Background: Glucose homeostasis derangement is a common pathophysiology of malaria whose aetiology is still controversial. The Plasmodium parasite, immunological and inflammatory responses, as well as chemotherapeutics currently used cause hypoglycaemia in malaria. Anti-parasitic and anti-disease drugs are required to combat malaria while ameliorating the pathophysiology of the infection. Asiatic acid has anti-hyperglycaemic, antioxidant, pro-oxidant properties useful in glucose homeostasis but its influence in malaria is yet to be reported. Here we present findings on the influence of asiatic acid on glucose metabolism in vivo using P. berghei-infected Sprague Dawley rats.Materials and Methods: Acute as well as sub-chronic studies were carried out in vivo where physicochemical properties and glucose homeostasis were monitored after administration of asiatic acid (10mg/kg) in both non-infected and infected animals. Glucose metabolism associated biochemical changes in malaria were also investigated.Results: In acute studies, asiatic acid improved oral glucose response while in the sub-chronic state it maintained food and water intake and suppressed parasitaemia. Normoglycaemic control was maintained in infected animals through insulin suppression and increasing glucagon secretion, in both acute and chronic studies. Asiatic acid administration curtailed lactate concentration towards normal.Conclusion: Per oral post-infection asiatic acid administration preserved drinking and eating habits, inhibited sickness behaviour while suppressing parasitaemia. Reciprocal relationship between insulin and glucagon concentrations was maintained influencing glucose homeostasis positively and inhibition of hyperlactaemia in malaria.Keywords: Asiatic acid, malaria, Plasmodium berghei, glucose homeostasis, anti disease, anti-parasiti

Changes in Renal Function and Oxidative Status Associated with the Hypotensive Effects of Oleanolic Acid and Related Synthetic Derivatives in Experimental Animals.

The triterpene oleanolic acid (OA) is known to possess antihypertensive actions. In the present study we to compared the effects of the triterpene on mean arterial blood pressure (MAP) and kidney function following acute administration in normotensive animals with those of its related oleanane synthetic derivatives (brominated oleanolic acid, Br-OA and oleanolic acid methyl ester, Me-OA). We also used experimental models of hypertension to further explore the effects of sub-chronic oral OA treatment and evaluated influences on oxidative status.OA was extracted from dried flower buds of Syzygium aromaticum using a previously validated protocol in our laboratory. Me-OA and Br-OA were synthesized according to a method described. Rats were supplemented with lithium chloride (12 mmol L-1) prior to experimentation in order to raise plasma lithium to allow measurements of lithium clearance and fractional excretion (FELi) as indices of proximal tubular Na+ handling. Anaesthetized animals were continuously infused via the right jugular with 0.077M NaCl. MAP was measured via a cannula inserted in the carotid artery, and urine was collected through a cannula inserted in the bladder. After a 3.5 h equilibration, MAP, urine flow, electrolyte excretion rates were determined for 4 h of 1 h control, 1.5 h treatment and 1.5 h recovery periods. OA, Me-OA and Br-OA were added to the infusate during the treatment period. We evaluated sub-chronic effects on MAP and kidney function in normotensive Wistar rats and in two animal models of hypertension, spontaneously hypertensive rats (SHR) and Dahl salt-sensitive (DSS) rats, during 9-week administration of OA (p.o.). Tissue oxidative status was examined in these animals at the end of the study. Increasing evidence suggests that and renal function disturbances and oxidative stress play major roles in the pathogenesis of hypertension.Acute infusion OA and oleanane derivatives displayed qualitatively similar effects in decreasing MAP and increasing urinary Na+ outputs. The drugs increased the FENa and FELi without influencing GFR indicating that at least part of the overall natriuretic effect involved proximal tubular Na+ reabsorption. Sub-chronic OA administration (p.o.) also elicited hypotensive responses in Wistar, DSS and SHR rats. The MAP lowering effect was more marked in hypertensive animals and were positively correlated with increased urinary Na+ excretion. Compared with respective control rats, OA treatment reduced malondialdehyde (MDA, a marker of lipid peroxidation) and increased activities of antioxidant enzymes; superoxide dismutase and glutathione peroxidase in hepatic, cardiac and renal tissues.OA and oleanane derivatives have similar effects on MAP, kidney function and oxidative stress. The amelioration of oxidative stress and blood pressure lowering effects by OA are more marked in hypertensive animals and correlated with an increased urinary Na+ output.The results of this study are novel in that they show 1) a correlation between blood pressure reduction and increased urinary Na+ excretion by OA, 2) a more marked MAP reduction in hypertensive animals and 3) a drug-induced decrease in proximal tubule Na+ reabsorption. The results may also be clinically relevant because OA is effective via oral administration

Comparison of GFR (A) and MAP (B) of control (untreated) rats and animals administered OA, Me-OA and Br-OA (90 μg h^-1) during the 4 h experimental period.

<p>All drugs were administered for 1.5 h during the treatment period. Values are presented as means, and vertical bars indicate SEM (n = 6 in each group). * p < 0.001 by comparison with control animals at each corresponding time. # p < 0.05 by comparison with OA-treated animals.</p

Comparison of the effects of OA and derivatives infusion on urine flow and total amount of electrolytes excreted during 1.5 h treatment period.

<p>* p < 0.05 by comparison with control animals</p><p># p < 0.05 by comparison with OA-treated animals.</p><p>Values are presented as means ± SEM (n = 6 in each group).</p><p>Comparison of the effects of OA and derivatives infusion on urine flow and total amount of electrolytes excreted during 1.5 h treatment period.</p

Effects of the administration of various doses of OA (30, 60, 120 mg kg^-1) on MAP Wistar (A), SHR (B) and DSS (C) rats over a 9-week experimental period. Values are presented as means, and vertical bars indicate SEM (n = 6 in each group).

<p>* p < 0.05 by comparison with control animals at each corresponding time (shown only for 120 mg kg^-1 for image clarity).</p

Reaction scheme for the synthesis of OA derivatives as previously described [22].

<p>Reagents: (a) CH₂N₂, Et₂O, THF; (b) IBX, DMSO; (c) <i>m</i>CPBA, CH₂Cl₂; (d) Br₂, HBr, AcOH.</p

Effects of the administration of various doses of OA (30, 60, 120 mg kg^-1) on 24 h urine flow (A-C) and Na⁺ excretion (D-F) rates with control Wistar, SHR and DSS animals over a 9-week experimental period.

<p>Values are presented as means, and vertical bars indicate SEM (n = 6 in each group). * p < 0.05 by comparison with control animals at each corresponding time.</p

Comparison of (A) urinary Na⁺ excretion (B), FE_{Na proximal} tubule (C) FE_{Li proximal}, and FE_{Li distal} (D) of control rats and animals infused OA, Me-OA and Br-OA.

<p>Drugs were administered for 1.5 h during the treatment period. Values are presented as means, and vertical bars indicate SEM (n = 6 in each group). * p < 0.05 by comparison with control animals at each corresponding time. # p < 0.05 by comparison with OA-treated animals.</p

Comparison of the changes in MAP (A), urinary Na⁺ excretion (B); correlation between MAP and Na⁺ changes (C) in OA or derivative-administered animals during the 1.5 h treatment period.

<p>In panels A and B, group values are presented as means, and vertical bars indicate SEM (n = 6 in each group). In panel C, individual values of each animal are presented.</p