Oxidative stress and gene expression of antioxidant enzymes in the streptozotocin-induced diabetic rats under hyperbaric oxygen exposure

Abstract

Diabetes mellitus (DM) causes not only hyperglycemia but oxidative stress, resulting mainly enhanced production of mitochondrial reactive oxygen species (ROS). Hyperbaric oxygen (HBO) treatments are applied various diseases including diabetic patients with unhealing foot ulcers, however, and also increases the formation of ROS. Recently, it has been reported that oxidative stress worsens many pathological conditions including DM and obesity suggesting possible changes in regulation of genes associated with the oxidative stress, however, effects of HBO which could induce ROS on the gene expressions of oxidative stress parameters in DM animals are unknown. The purpose of this study is to investigate the effect of HBO exposure on the gene expression of three important antioxidant enzymes, cytosolic superoxide dismutase (Cu-Zn SOD), cytosolic glutathione peroxidase (GPx-1), and catalase (CAT) in DM rats, respectively. We used streptozotocin-induced DM model rats and examined both mRNA expressions and the activities of these antioxidant enzymes in the liver, skeletal muscle, and pancreas. The mRNA expressions of Cu-Zn SOD and CAT decreased significantly (p < 0.001), and GPx increased significantly (p < 0.001) in all the studied organs of DM rats under HBO exposure compared to those from DM-induced rats not exposed to HBO. Similarly, activities of these three enzymes changed in accordance with the mRNA levels. These results suggested that DM induction and HBO exposure might synergistically affect antioxidant enzymes, resulting increase of oxidative stress state. Thus, HBO exposure seems to be an excellent model system for investigating oxidative stress.

Keywords: Diabetes mellitus; catalase; glutathione peroxidase; hyperbaric oxygen; oxidative stress; superoxide dismutase.

Figure 1

Plasma glucose and insulin concentrations in non-diabetic groups and diabetic groups. Values are expressed as mean ± SEM (n = 6). ^a p < 0.05; ^b p < 0.01 compared with control value.

Figure 2

Comparison of lipid peroxidation levels (TBARS) in the erythrocyte, liver, skeletal muscle, and pancreas among non-diabetic rats in the non-HBO (control), non-diabetic rats in the HBO (HBO), diabetic rats in the non-HBO (DM), and diabetic rats in the HBO (DM + HBO) groups. TBARS values are indicated as nmol/g hemoglobin in erythrocytes and as nmol/mg protein in the various organs. Values are expressed as mean ± SEM (n = 6). ^a Represents significance at p < 0.05 and ^aa represents significance at p < 0.005 compared with the control groups. ^b Represents significance at p < 0.05 and ^bb represents significance at p < 0.005 compared with the DM groups.

Figure 3

Comparison of the antioxidant enzyme activities (Cu-Zn SOD, GPx, and CAT) in the erythrocyte among non-diabetic rats in the non-HBO (control), non-diabetic rats in the HBO (HBO), diabetic rats in the non-HBO (DM), and diabetic rats in the HBO (DM + HBO) groups. These antioxidant enzymes values are given as U/g hemoglobin in erythrocytes. Values are expressed as mean ± SEM (n = 6). ^a Represents significance at p < 0.05 and ^aa represents significance at p < 0.005 compared with the control groups. ^b Represents significance at p < 0.05 and ^bb represents significance at p < 0.005 compared with the DM groups.

Figure 4

Comparison of the antioxidant enzyme activities and mRNA expressions (Cu-Zn SOD, GPx, and CAT) in the liver (a), skeletal muscle (b), and pancreas (c) among non-diabetic rats in the non-HBO (control), nondiabetic rats in the HBO (HBO), diabetic rats in the non-HBO (DM), and diabetic rats in the HBO (DM + HBO) groups. These antioxidant enzymes values are given as U/mg protein in the various organs, mRNA expressions values are presented as the ratios of the densities of these antioxidants mRNAs and β-actin genes of all organs in all groups measured by Image J software. Values are expressed as mean ± SEM (n = 6). ^a Represents significance at p < 0.05 and ^aa represents significance at p < 0.005 compared with the control groups. b Represents significance at p < 0.05 and ^bb represents significance at p < 0.005 compared with the DM groups.

Figure 4

Comparison of the antioxidant enzyme activities and mRNA expressions (Cu-Zn SOD, GPx, and CAT) in the liver (a), skeletal muscle (b), and pancreas (c) among non-diabetic rats in the non-HBO (control), nondiabetic rats in the HBO (HBO), diabetic rats in the non-HBO (DM), and diabetic rats in the HBO (DM + HBO) groups. These antioxidant enzymes values are given as U/mg protein in the various organs, mRNA expressions values are presented as the ratios of the densities of these antioxidants mRNAs and β-actin genes of all organs in all groups measured by Image J software. Values are expressed as mean ± SEM (n = 6). ^a Represents significance at p < 0.05 and ^aa represents significance at p < 0.005 compared with the control groups. b Represents significance at p < 0.05 and ^bb represents significance at p < 0.005 compared with the DM groups.

Figure 4

Comparison of the antioxidant enzyme activities and mRNA expressions (Cu-Zn SOD, GPx, and CAT) in the liver (a), skeletal muscle (b), and pancreas (c) among non-diabetic rats in the non-HBO (control), nondiabetic rats in the HBO (HBO), diabetic rats in the non-HBO (DM), and diabetic rats in the HBO (DM + HBO) groups. These antioxidant enzymes values are given as U/mg protein in the various organs, mRNA expressions values are presented as the ratios of the densities of these antioxidants mRNAs and β-actin genes of all organs in all groups measured by Image J software. Values are expressed as mean ± SEM (n = 6). ^a Represents significance at p < 0.05 and ^aa represents significance at p < 0.005 compared with the control groups. b Represents significance at p < 0.05 and ^bb represents significance at p < 0.005 compared with the DM groups.