Oxidative/nitrosative stress and protein damages in aqueous humor of hyperglycemic rabbits: effects of two oral antidiabetics, pioglitazone and repaglinide

Biochemical Changes in Anterior Chamber of the Eye in Diabetic Patients-A Review

This article aims to provide a comprehensive review of the biochemical changes observed in the anterior chamber of the eye in diabetic patients. The increased levels of inflammatory markers, alterations in antioxidant defense mechanisms, and elevated levels of advanced glycation end products (AGEs) in the aqueous humor (AH) are explored. Additionally, the impact of these biochemical changes on diabetic retinopathy progression, increased intraocular pressure, and cataract formation is discussed. Furthermore, the diagnostic and therapeutic implications of these findings are presented. This study explores potential biomarkers for detecting diabetic eye disease at an early stage and monitoring its progression. An investigation of the targeting of inflammatory and angiogenic pathways as a potential treatment approach and the role of antioxidant agents in managing these biochemical changes is performed.

The role of oxidative damage in cataract etiopathogenesis

Background

Cataract usually occurs due to age and diabetes, but the mechanisms of cataract formation have not yet been fully elucidated. In this study, the relationship between cataract and oxidative stress was evaluated by examining the aqueous humor reflecting lens metabolism.

Objective

In this study, the effect of oxidative stress on the etiopathogenesis of cataract was investigated through the total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI), and arylesterase (ARE) levels in aqueous humor samples of patients with cataract.

Design

A prospective cohort study.

Methods

This study was conducted on patients who were scheduled for cataract surgery between June 2020 and March 2021. The patients were divided into four groups according to their cataract density as grades 1, 2, 3, and 4. TOS, TAS, and ARE levels of aqueous humor samples were measured spectrophotometrically, and comparisons were made between groups.

Results

A total of 100 eyes of 100 patients were included in this study. TAS levels were found significantly higher in the grade 2 group compared with the grade 4 group (p = 0.006). In addition, a significant negative correlation was present between cataract grade and TAS level (r = -0.237; p = 0.018). There was no significant difference between diabetic and nondiabetic patients in terms of TAS, TOS, OSI, and ARE levels.

Conclusion

The aqueous humor of patients with a high degree of cataract is characterized by low antioxidant capacity. Decreased antioxidant capacity has a role in cataract formation and progression.

Evaluation of antioxidative enzymes levels and lipid peroxidation products levels in diabetic and non diabetic senile cataract patients

Background

The current study aimed to investigate the Superoxide dismutase, Glutathione Peroxidase activity, Advanced oxidation Protein products levels, Malondialdehyde levels, Baseline Conjugated Diene concentration, and 8-Isoprostaglandin F2α (8-IPG-F2α) quantification in diabetic and non-diabetic senile cataract patients to find out the pathomechanism of early onset of cataract in diabetic patients.

Methods

This case-control study was performed on 184 subjects undergoing cataract surgery. For 8-IPG-F2α quantification, 35 diabetics and non-diabetic lenses and the entire study included 22 patients with diabetic senile cataracts and non-diabetic senile cataracts of aqueous humor age ≥ 40 years. Ninety-two patients with diabetic senile cataract and non-diabetic senile cataract lenses aged ≥ 40 years were incorporated for all other studies. The student's t-test was used for statistical analysis.

Results

From the study population, the mean age was 63.82 ± 0.6, and 75% of them were female. Higher female prevalence in both groups was observed. The results revealed that the superoxide dismutase and glutathione peroxidase activity were significantly reduced in diabetic patients compared to non-diabetic patients (p < 0.001) in both lenses and aqueous humor. Malondialdehyde, conjugated diene, and 8-IPG-F2α levels significantly increased in diabetic patients when compared to non-diabetic (p < 0.01), and advanced oxidation protein products levels also significantly increased in diabetic patients when compared to non-diabetics in both lenses and aqueous humor (p < 0.001).

Conclusion

The current study revealed that oxidative stress and Lipid per-oxidation have an imperative role in the diabetic-related complication, specifically in the lens, may have a responsibility in the pathomechanism of early onset of cataracts coupled with diabetes mellitus.

Coordinated regulation of gene expression and microRNA changes in adipose tissue and circulating extracellular vesicles in response to pioglitazone treatment in humans with type 2 diabetes

Pioglitazone, a PPARγ agonist, is used to treat type 2 diabetes (T2D). PPARγ is highly expressed in adipose tissue (AT), however the effects of pioglitazone to improve insulin sensitivity are also evident in other tissues and PPARγ agonism has been shown to alter cancer derived extracellular vesicle (EV)-miRNAs. We hypothesized that pioglitazone modifies the cargo of circulating AT-derived EVs to alter interorgan crosstalk in people with diabetes. We tested our hypothesis in a 3-month trial in which 24 subjects with T2D were randomized to treatment with either pioglitazone 45 mg/day or placebo (NCT00656864). Levels of 42 adipocyte-derived EV-miRNAs were measured in plasma EVs using low density TaqMan arrays. Levels of differentially expressed EV-miRNAs and their most relevant target genes were also measure in adipose tissue from the same participants, using individual TaqMan assays. Levels of 5 miRNAs (i.e., miR-7-5p, miR-20a-5p, miR-92a-3p, miR-195-5p, and miR-374b-5p) were significantly downregulated in EVs in response to pioglitazone treatment relative to placebo. The opposite occurred for miR-195-5p in subcutaneous AT. Changes in miRNA expression in EVs and AT correlated with changes in suppression of lipolysis and improved insulin sensitivity, among others. DICER was downregulated and exosomal miRNA sorting-related genes YBX1 and hnRNPA2B1 displayed a downregulation trend in AT. Furthermore, analysis of EV-miRNA targeted genes identified a network of transcripts that changed in a coordinated manner in AT. Collectively, our results suggest that some beneficial pharmacologic effects of pioglitazone are mediated by adipose-specific miRNA regulation and exosomal/EV trafficking.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier NCT00656864.

[Changes of two-pore K+ channel TASK-1 in diabetic myocardial injury in rats]

OBJECTIVE

To investigate the changes of the two- pore K+ channel TASK-1 in diabetic rats with myocardial injury.

METHODS

Thirty-six SD rats were divided into normal group (N), diabetes at 4 weeks (DM 4W) group, and diabetes at 8 weeks (DM 8W) group. The cardiac functions of the rats were determined using cardiac ultrasonography, and the body weight and heart weight of the rats at different time points were measured to calculate the heart/body weight ratio (HW/BW). Myocardial fibrosis in the rats was assessed using Masson's staining. The protein expression of TASK-1 in the myocardium was detected using Western blotting. Whole- cell patch clamp technique was used to record the action potential duration (APD) and twopore domain potassium channel TASK- 1 current in acutely isolated rat ventricular myocytes. meanwhile, The inhibition of TASK-1 current was observed by the TASK-1 specific inhibitor ML-365.

RESULTS

Compared with the normal group, the diabetic rats showed significantly increased HW/BW (P < 0.05), end- diastole left ventricular diameter (LVIDd), end- systolic left ventricular diameter (LVIDs), and TASK-1 protein expression, with obviously decreased left ventricular diameter shortening rate (FS) and ejection fraction (EF) (P < 0.01). Masson staining showed that in diabetic rats, the collagen fibers were thickened, interwoven into a network with uneven arrangement and increased deposition. Compared with DM 4W group, the rats in DM 8W group exhibited progressive increases in LVIDd, LVIDs, HW/BW, and TASK-1 expression (P < 0.01 or 0.05); FS and EF were further decreased (P < 0.01). Masson staining showed worsened morphological changes of the myocardium with increased deposition. Compared with that in the normal group, the current of TASK- 1 in diabetic rats at 8 weeks was significantly reduced (P < 0.01) and the duration of action potential was extended (P < 0.05). The TASK-1 current was successfully inhibited by ML-365.

CONCLUSIONS

Diabetes can induce myocardial fibrosis and aggravate myocardial injury possibly in relation to changes in the protein expression and current of the two-port potassium channel TASK-1.

Aqueous Humour and Serum Levels of Nitric Oxide, Malondialdehyde and Total Antioxidant Status in Patients with Type 2 Diabetes with Proliferative Diabetic Retinopathy and Nondiabetic Senile Cataracts

OBJECTIVES

Diabetic retinopathy is associated with enhanced oxidative stress and/or reduction of antioxidant status. Several studies have examined the oxidative agents, such as nitric oxide (NO) and malondialdehyde (MDA), in the body fluids of patients with diabetes. However, total antioxidant status (TAS) in the aqueous humour of patients with diabetes has not been determined to date. To address this issue, we analyzed the aqueous humour and serum levels of NO, MDA and TAS in patients with type 2 diabetes and nondiabetic senile cataracts.

METHODS

This prospective study included 35 patients with type 2 diabetes and 35 age- and sex-matched healthy subjects in whom cataract surgery was indicated. Aqueous humour and serum MDA, NO and TAS levels were determined by spectrophotometric methods, respectively.

RESULTS

The analysis of MDA levels in the serum and aqueous humour revealed no significant differences in any of the groups (p>0.05). At the level of aqueous humour, patients with type 2 diabetes had significantly increased NO levels, compared to the controls (p=0.003). The control group also presented significantly higher TAS levels than the subgroup with type 2 diabetes in serum (p=0.001). However, there were no significant differences in the TAS levels of aqueous humour and serum NO levels in the groups (p>0.05).

CONCLUSIONS

Our results seem to demonstrate that the development of diabetic retinopathy is associated with high levels of aqueous humour NO and reduced serum antioxidant defenses. Therefore, inhibition of reactive oxygen species production and substitution of serum antioxidant status may be a therapeutic target for eye diseases associated with oxidative stress.

Targeting metabolic disorders by natural products

The most prevalent metabolic disorders are diabetes mellitus, obesity, dyslipidemia, osteoporosis and metabolic syndrome, which are developed when normal metabolic processes are disturbed. The most common pathophysiologies of the above disorders are oxidative stress, Nrf2 pathways, epigenetic, and change in miRNA expression. There is a challenge in the prevention and treatment of metabolic disorders due to severe adverse effects of some synthetic drugs, their high cost, lack of safety and poverty in some conditions, and insufficient accessibility for the general population in the world. With increasing interest in shifting from synthetic drugs to phytotherapy as an alternative treatment, there is still a gap in scientific evidences of plant-derived therapeutic benefits. One reason may be slow rate of translation of animal studies' findings into human clinical trials. Since metabolic disorders are multifactorial, it seems that poly-herbal medications, or drug-herbal combination are needed for their treatment. However, further researches to determine the most effective plant-derived metabolites, and their cellular mechanism in order to set priorities for well-designed animal and clinical trials, and also more studies with strong scientific evidences such as systematic review and meta-analysis of controlled studies are needed.

Multimarker screening of oxidative stress in aging

Aging is a complex process of organism decline in physiological functions. There is no clear theory explaining this phenomenon, but the most accepted one is the oxidative stress theory of aging. Biomarkers of oxidative stress, substances, which are formed during oxidative damage of phospholipids, proteins, and nucleic acids, are present in body fluids of diseased people as well as the healthy ones (in a physiological concentration). 8-iso prostaglandin F_2α is the most prominent biomarker of phospholipid oxidative damage, o-tyrosine, 3-chlorotyrosine, and 3-nitrotyrosine are biomarkers of protein oxidative damage, and 8-hydroxy-2^′-deoxyguanosine and 8-hydroxyguanosine are biomarkers of oxidative damage of nucleic acids. It is thought that the concentration of biomarkers increases as the age of people increases. However, the concentration of biomarkers in body fluids is very low and, therefore, it is necessary to use a sensitive analytical method. A combination of HPLC and MS was chosen to determine biomarker concentration in three groups of healthy people of a different age (twenty, forty, and sixty years) in order to find a difference among the groups.

Comparative effects of pioglitazone and metformin on oxidative stress markers in newly diagnosed type 2 diabetes patients: a randomized clinical trial

AIMS

Recent studies have suggested that pioglitazone exerts anti-oxidant properties which may countervail oxidative stress (OS). We aimed to elucidate the effects of pioglitazone on OS modulation and to compare its effects with metformin.

METHODS

Data from the randomized clinical trial (registration no.NCT01521624) were used. Newly diagnosed type 2 diabetes patients were assigned to pioglitazone 30mg daily (n=30), metformin 1000mg daily (n=50), or no medication (n=49). Recommendations for exercise and dietary modifications were provided for three groups. Serum concentrations of advanced oxidation protein products(AOPP), advanced glycation end products(AGE), ferritin reducing ability of plasma(FRAP), and enzymatic activities of paraoxonase(PON), lecithin-cholesterol asyltransferase(LCAT), and lipoprotein lipase(LPL) were measured at baseline and after three months.

RESULTS

In comparison with no medication, pioglitazone proved to be superior in OS amelioration (p<0.05 in all analyses). Compared with metformin, both medications were equally effective in decrement of AOPP and AGE, along with increment of PON (p=0.688, 0.140, and 0.273, respectively). FRAP concentrations increased significantly with metformin (p=0.012). On the other hand, pioglitazone yielded better efficacy in restoration of LCAT and LPL enzymatic activities (p=0.037, and <0.001, respectively).

CONCLUSIONS

Similar to metformin, three months treatment with Pioglitazone is beneficial in terms of OS alleviation and anti-oxidant capacity restoration.

Plasma plasminogen activator inhibitor-1 is associated with end-stage proliferative diabetic retinopathy in the Northern Chinese Han population

Objective. To identify predictors of end-stage proliferative diabetic retinopathy (PDR) in a cohort of individuals with type 2 diabetes mellitus (T2DM) from the Northern Chinese Han population. Methods. We investigated characteristics of 153 consecutive diabetic patients with end-stage PDR (62 males, 91 females), 123 consecutive PDR patients without end-stage PDR (48 males, 75 females), and 151 normal subjects (63 males, 88 females). Only one eye of each patient or healthy subject was included in this study. Univariate logistic regression models and multivariate logistic regression models were constructed to evaluate the predictors of end-stage PDR. Results. In univariate analysis, systolic blood pressure, diastolic blood pressure, duration of diabetes, family history of T2DM, and plasminogen activator inhibitor-1 (PAI-1) were significently associated with end-stage PDR. After multivariate analysis, family history of T2DM, plasma PAI-1 levels, smoking, and duration of diabetes were four positive predictors associated with end-stage PDR. Conclusions. Higher plasma levels of PAI-1 were associated with end-stage PDR in the Northern Chinese Han population with T2DM.