Endocrine Abstracts

We investigated effects of ethanolic Persea americana Mill. (‘Avocado’) leaf extracts (PAE) on blood glucose and kidney function in rats. Extracts of the plant have been employed to treat hypertension and diabetes mellitus. Oral glucose tolerance tests (OGTT) were conducted in fasted non-diabetic and STZ-diabetic rats following a glucose load (0.86 g/kg, p.o.), followed by various PAE doses (60, 120 and 240 mg/kg). Rats treated with deionised water or standard hypoglycaemic drugs (insulin, metformin and glibenclamide) acted as untreated and treated positive controls, respectively. Blood glucose was monitored at 15-min intervals for the first hour, and hourly thereafter for 3 h. Blood was also collected for insulin or glucose measurements. Acute renal effects of PAE were investigated in anesthetized rats challenged with 0.077 M NaCl after a 3.5-h equilibration for 4 h of 1 h control, 1.5 h treatment and 1.5 h recovery periods. PAE was added to the infusate during the treatment period. Chronic effects of PAE on kidney function and hepatic glycogen synthesis were measure in rats after daily PAE treatment. Cytotoxicity of PAE was assessed by dye-reduction colorimetric (MTT) assay on proximal and distal tubule cell lines exposed for 24 h, 48 h and 72 h. OGGT responses to PAE indicated dose dependent hypoglycaemic in STZ-diabetic rats. PAE treatment did not affect plasma insulin in both groups. Chronic PAE significantly increased hepatic glycogen concentrations in non-diabetic and diabetic rats. Acute PAE infusion decreased urine flow, Na⁺ and K⁺ excretion rates both non-diabetic and diabetic rats whilst chronic treatment reduced plasma creatinine concentration and increased GFR in diabetic rats only. PAE induced minimal toxicity in proximal cell lines, but slight cytotoxicity in distal tubules cell lines. The findings of the study suggest that hypoglycaemic effects PAE are in part via increased hepatic glycogen synthesis, thereby lending support to the ethnomedical use of the extract in diabetes mellitus.