Abstract
The global incidence of diabetes mellitus is on the rise, with brain damage being one of its associated complications. Portulacaria afra (P. afra), a medicinal plant native to South Africa, has been traditionally used in treating diseases such as diabetes, diarrhoea, fever, hypertension, and various skin and blood disorders. This study investigated the potential of P. afra aqueous leaf extract to protect against diabetes-induced brain damage. Thirty-two (32) male Sprague-Dawley rats aged between 56 and 70 days were randomly allocated into groups and administered the following treatment regimens for 28 days. Group 1- non-diabetic control (NDC) group: non-diabetic rats received plain drinking water and standard rat chow daily. Group 2 - diabetic negative control (DC) group: diabetic rats received plain drinking water and standard rat chow daily. Group 3 - metformin (DMET) group: diabetic rats received plain drinking water, standard rat chow and 500 mg/kg metformin daily. Group 4 - diabetic P. afra (DPA): diabetic rats received plain drinking water, standard rat chow and aqueous leaf extract of P. afra (100 mg/kg) daily. Diabetes was induced with a single intravenous tail vein injection of streptozotocin (STZ) at 55 mg/kg body weight while the control group was injected with citrate buffer. Body mass was measured twice weekly. At the end of the 28-day experimental period, the rats were fasted overnight and fasting blood glucose concentration was determined. Thereafter the rats were euthanised and the whole brain was excised. Respiratory chain enzyme activity and oxidative stress markers were determined by calorimetric methods. Neurotrophic factors, pro-inflammatory cytokines, apoptotic markers, and gliosis markers, were determined using enzyme-linked immunoassay (ELISA) kits. Hippocampal and cortical micro and macro morphometry were evaluated through cresyl violet staining and ImageJ analysis. The oral administration of P. afra aqueous extract significantly increased the superoxide dismutase (SOD), reduced glutathione (GSH), and concentrations of brain-derived neurotrophic factor (BDNF), myelin basic protein (MBP) and complex1 in the diabetic brain (p<0.05). P. afra also significantly reduced the elevated malondialdehyde (MDA), tumour necrosis factor-alpha (TNF-α), nuclear factor kappa B (NF-κB) and interleukin 6 (IL-6), caspase 3, AIF1, GFAP concentrations in the diabetic brain (p<0.05). The histological examination of the hippocampus and cortex supported the observed biochemical changes, showing increased cell counts, and improved cellular integrity in different hippocampal regions and the cortical layers of the diabetic brain. These findings suggest that the oral administration of crude aqueous P. afra
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leaf extract may possess potential health benefits against diabetes-related neurodegenerative damage, demonstrating significant biochemical and neuroprotective effects in the diabetic brain.