Numerous studies have revealed lowered antioxidant and enhanced peroxidative status in diabetes mellitus [28]. In the current study, activities of SOD CAT were reduced significantly in the kidneys of diabetic rats. These observations emphasise the critical importance of maintaining the antioxidant potential of the pancreatic β-cells in order to ensure both their survival and insulin secretion capacity during times of increased oxidative stress. The decreased activities of SOD and CAT in kidneys during diabetes mellitus may be due to the production of reactive oxygen free-radical, which can itself reduce the activity of these enzymes.
Reduced glutathione (GSH) is a potent-free radical scavenger within the islet of β-cells and is an important factor acting against the progressive destruction of β-cells following partial pancreatectomy [29]. Depletion of GSH results in enhanced lipid peroxidation. This can cause increased GSH consumption and can be correlated to the increase in the level of oxidised glutathione (GSSG). Treatment with A. squamosa alone, along with reduced and reducing dose combinations of Glipizide results in the elevation of GSH levels in a better way than with Glipizide alone. This protects the cell membrane against oxidative damage by regulating the redox status of protein in the membrane [30]. SOD and CAT destroy peroxides and play a significant role in providing antioxidant defense in many organisms. CAT is involved in the elimination of H2O2. SOD acts to convert the dismutase superoxide radical to H2O2,;the functions of all three enzymes are interconnected and a lowering of their activity results in the accumulation of lipid peroxides and increased oxidative stress in diabetic rats. Treatment with A. squamosa in reduced and reducing dose combination of Glipizide increased the activity of these enzymes as compared to treatment with A. squamosa and Glipizide alone. Better activity was found in reduced dose 3.75 and 2.5 mg/kg Glipizide combination with A. squamosa compared to Glipizide alone.
The increase in the activities of plasma SGPT and SGOT indicated that diabetes mellitus may induce hepatic dysfunction. The enzymes associated directly with the conversion of amino acids to keto acids are SGPT and SGOT, the activities of both being increased in the diabetic condition. An increase in the activities of SGPT and SGOT are also reported in the liver of diabetic animals. Treatment with A. squamosa alone or in combination with the Glipizide normalised these enzyme activities. The reduced and reducing dose combinations of Glipizide showed results very similar to Glipizide alone. Similarly, increased activities of SGPT and SGOT in the diabetic liver were also reported [26]. The increased protein catabolism accompanying gluconeogenesis and urea formation that is seen in the diabetic state might be responsible for the elevation of these tissue transaminases. The rise in SGOT activity is due to hepatocellular damage and is usually accompanied by a rise in SGPT. This might be the reason for the elevated activities of these enzymes, which were brought back to near normal values by A. squamosa treatment alone and in combination with the Glipizide and A. squamosa, thus resulting in better control of blood sugar levels.
Emerging epidemiological data indicates that diabetes is a potential predisposing factor for neuropsychiatric deficits as stroke, cerebrovascular diseases, diabetic encephalopathy, depression and anxiety. Diabetic encephalopathy, characterised by impaired cognitive functions and neurochemical and structural abnormalities, involves direct neuronal damage caused by intracellular glucose. The direct glucose toxicity in the neurons is due especially to increased intracellular glucose oxidation, which leads to an increase in reactive species production [31]. Oxidative stress seems to play a central role in brain damage both in human and experimentally diabetic rats. Recently, it was reported that oxidative damage to rat synapses contributes to the cognitive deficit [32]. In the present study, STZ-treatment produced a significant increase in blood-glucose level. A. squamosa treatment along with Glipizide significantly prevented this rise in blood-glucose level and maintained the body weight of diabetic animals. This effect was observed due to the strong antioxidant and direct stimulatory action of A. squamosa treatment along with Glipizide on the pancreatic beta-cell that could contribute towards hypoglycemic activity.