Increased Metabolic Stress in Zucker Diabetic Fatty Rat Kidney and Pancreas

Abstract

Background/Aims: Obesity and diabetes (hereafter termed diabesity) are among the most challenging global health problems. Since the main pathophysiological complications in diabesity are hyperglycemia, hyperlipidemia, insulin resistance, cardiomyopathy, nephropathy, and urinary infections, the kidney and pancreas are the potential target organs affected in the above conditions. However, the precise molecular mechanisms of disease progression and complications are still unclear. The Zucker homozygous (FA/FA) diabetic fatty (ZDF) rat is a genetic model for obesity and type 2 diabetes. Our previous studies, using cardiac muscles have demonstrated metabolic and oxidative stress in ZDF rats. In the present study, our aim was to investigate oxidative stress associated metabolic complications in ZDF rat kidney and pancreas. Methods: Here we have measured oxidative stress, glutathione (GSH)-dependent metabolism and mitochondrial respiratory functions in the kidney and pancreas of ZDF and Zucker lean (ZL, +/FA) control rats. Results: Our results showed an increase in reactive oxygen species, NO production, lipid and protein peroxidation in ZDF rat kidney and pancreas accompanied by alterations in GSH-dependent metabolism and mitochondrial function. Western blot analysis has also confirmed increased expression of oxidative stress marker proteins in ZDF rats. Conclusion: We have demonstrated that ZDF rats develop metabolic complications associated with oxidative stress and mitochondrial dysfunction. Thus, these results might have implications in understanding the etiology and pathology of diabesity.

Increased Oxidative Stress and Mitochondrial Dysfunction in Zucker Diabetic Rat Liver and Brain

“…Isolated liver and brain tissues were homogenized (10% w/v) in isotonic 100mM potassium phosphate buffer (pH7.4) containing 1mM EDTA and 0.1mM phenylmethylsulfonylfluoride (PMSF, a protease inhibitor). The homogenate was centrifuged at 1000xg for 10 min and the supernatant was used for further purification of mitochondrial and microsomal fractions as previously described [13,14]. Protein concentration in tissue homogenate and the isolated sub-cellular fractions was measured using BioRad reagent.…”

“…Production of ROS in ZDF and ZL rat tissues was measured using the DCFDA fluorescence method as previously described [13,14]. Both, plasma membrane bound apocynin-sensitive NADPH oxidase (NOX)-dependent as well as mitochondrial-dependent ROS production were measured.…”

“…Protein peroxidation as a marker of increased oxidative stress was measured in ZDF and ZL rat tissue fractions by DNPH conjugation method as previously described [13,14,15]. NADPH-dependent membrane lipid peroxidation was measured as malonedialdehyde formed using the standard thiobarbituric acid method [13,14,15].…”

“…NADPH-dependent membrane lipid peroxidation was measured as malonedialdehyde formed using the standard thiobarbituric acid method [13,14,15]. Catalase activity was measured by the method of Beers and Sizer [16] in which the disappearance of peroxide was followed spectrophotometrically at 240 nm.…”

“…Studies have also suggested that prolonged exposure to insulin suppresses mitochondrial biogenesis and function and this may lead to impairment of insulin sensitivity [11,12]. Our recent studies [13,14] using cardiomyocytes from the left ventricle and cellular fractions from the kidney and pancreas of ZDF rats have shown increased oxidative stress and mitochondrial dysfunction. We, therefore, have extended our study to other metabolic tissues, such as liver and brain, to elucidate the mechanisms of metabolic and oxidative stress in ZDF rats.…”