Effects of ATRA on diabetic rats with renal ischemia-reperfusion injury

Alpha-cyperone mitigates renal ischemic injury via modulation of HDAC-2 expression in diabetes: Insights from molecular dynamics simulations and experimental evaluation

Chronic diabetes mellitus is reported to be associated with acute kidney injury. The enzyme histone deacetylase-2 (HDAC-2) was found to be upregulated in diabetes-related kidney damage. Alpha-cyperone (α-CYP) is one of the active ingredients of Cyperus rotundus that possesses antioxidant and anti-inflammatory effects. We evaluated the effect of α-CYP on improving oxidative stress and tissue inflammation following renal ischemia/reperfusion (I/R) injury in diabetic rats. The effect of α-CYP on HDAC-2 expression in renal homogenates and in the NRK-52 E cell line was evaluated following renal I/R injury and high glucose conditions, respectively. Molecular docking was used to investigate the binding of α-CYP with the HDAC-2 active site. Both renal function and oxidative stress were shown to be impaired in diabetic rats due to renal I/R injury. Significant improvements in kidney/body weight ratio, creatinine clearance, serum creatinine, blood urea nitrogen (BUN), and uric acid were observed in diabetic rats treated with α-CYP (50 mg/kg) two weeks prior to renal I/R injury. α-CYP treatment also improved histological alterations in renal tissue and lowered levels of malondialdehyde, myeloperoxidase, and hydroxyproline. Treatment with α-CYP suppressed the increased HDAC-2 expression in the renal tissue of diabetic rats and in the NRK-52 E cell line. The molecular docking reveals that α-CYP binds to HDAC-2 with good affinity, ascertained by molecular dynamics simulations and binding free energy analysis. Overall, our data suggest that α-CYP can effectively prevent renal injury in diabetic rats by regulating oxidative stress, tissue inflammation, fibrosis and inhibiting HDAC-2 activity.

Correlation between glycated hemoglobin A1c, urinary microalbumin, urinary creatinine, β2 microglobulin, retinol binding protein and diabetic retinopathy

BACKGROUND

Retinopathy is the most common microvascular disease of type 2 diabetes, and seriously threatens the life, health and quality of life of patients. It is worth noting that the development of diabetic retinopathy (DR) can be hidden, with few symptoms. Therefore, the preliminary screening of diabetic patients should identify DR as soon as possible, delay disease progression, and play a vital role in its diagnosis and treatment.

AIM

To investigate the correlation between glycated hemoglobin A1c (HbA1c), urinary microalbumin (U-mALB), urinary creatinine (U-CR), mALB/U-CR ratio, β2 microglobulin (β2MG), retinol binding protein (RBP) and DR.

METHODS

A total of 180 patients with type 2 diabetes mellitus attending the Second People’s Hospital of Hefei from January 2022 to August 2022 were retrospectively enrolled by ophthalmologists. Based on whether they had combined retinopathy and its degree, 68 patients with diabetes mellitus without retinopathy (NDR) were assigned to the NDR group, 54 patients with non-proliferative DR (NPDR) to the NPDR group, and 58 patients with proliferative DR to the PDR group. General data, and HbA1c, mALB, β2MG, RBP, mALB/U-CR and U-CR results were collected from the patients and compared among the groups. Pearson's correlation method was used to analyze the correlation between HbA1c, mALB, β2MG, RBP, mALB/U-CR and U-CR indices, and multiple linear regression was applied to identify the risk factors for DR. Receiver operator characteristic (ROC) curves were also drawn.

RESULTS

The differences in age, gender, systolic and diastolic blood pressure between the groups were not statistically significantly (P > 0.05), but the difference in disease duration was statistically significant (P < 0.05). The differences in fasting blood glucose, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, total cholesterol, and triglyceride between the groups were not statistically significant (P > 0.05). HbA1c in the PDR group was higher than that in the NPDR and NDR groups (P < 0.05). The levels of mALB, β2MG, RBP, mALB/U-CR and U-CR in the PDR group were higher than those in the NPDR and NDR groups (P < 0.05). Multiple linear regression analysis showed that disease duration, HbA1c, mALB, β2MG, RBP, mALB/U-CR and U-CR were risk factors for the development of DR. The ROC curve showed that the area under the curve (AUC) for the combination of indices (HbA1c + mALB + mALB/U-CR + U-CR + β2MG + RBP) was 0.958, with a sensitivity of 94.83% and specificity of 96.72%, which was higher than the AUC for single index prediction (P < 0.05).

CONCLUSION

HbA1c, mALB, mALB/U-CR, U-CR, β2MG and RBP can reflect the development of DR and are risk factors affecting PDR, and the combination of these six indices has predictive value for PDR.

Vitamin A and Diabetes

Recently, research data have shown that vitamin A (VA, retinol) as a micronutrient participates in the regulation of glucose and lipid metabolism. Since diabetes is a metabolic disease, it is imperative to reveal the relationship of VA and diabetes. This review was aimed to summarize the current understanding of VA and its metabolites in diabetes. Since April of 2020, the authors have searched the PubMed using key words and retrieved articles that focused on diabetes and VA or its metabolites. Based on the published data, it appears that the development of type 1 diabetes leads to reduction of blood VA level in human and animals, and increase of hepatic VA store in experimental animals. On the other hand, the mutual impacts of type 2 diabetes and VA intake and blood VA level on each other appear to be uncertain. Retinoic acid, the active metabolite of VA, has been studied extensively for the treatment of diabetic complications. The current data appear to indicate that the development of diabetes is associated with changes of VA metabolism. More carefully designed clinical and laboratory experiments are needed to reveal the impacts of diabetes on VA metabolism and the role of VA in the development and treatment of diabetes.

PARK7 Protects Against Chronic Kidney Injury and Renal Fibrosis by Inducing SOD2 to Reduce Oxidative Stress

Renal fibrosis is the final common pathway to chronic kidney diseases regardless of etiology. Parkinson disease protein 7 (PARK7) is a multifunctional protein involved in various cellular processes, but its pathophysiological role in kidneys remain largely unknown. Here, we have determined the role of PARK7 in renal fibrosis and have further elucidated the underlying mechanisms by using the in vivo mouse model of unilateral ureteric obstruction (UUO) and the in vitro model of transforming growth factor-b (TGFB1) treatment of cultured kidney proximal tubular cells. PARK7 decreased markedly in atrophic kidney tubules in UUO mice, and Park7 deficiency aggravated UUO-induced renal fibrosis, tubular cell apoptosis, ROS production and inflammation. In vitro, TGFB1 treatment induced fibrotic changes in renal tubular cells, which was accompanied by alterations of PARK7. Park7 knockdown exacerbated TGFB1-induced fibrotic changes, cell apoptosis and ROS production, whereas Park7 overexpression or treatment with ND-13 (a PARK7-derived peptide) attenuated these TGFB1-induced changes. Mechanistically, PARK7 translocated into the nucleus of renal tubular cells following TGFB1 treatment or UUO, where it induced the expression of SOD2, an antioxidant enzyme. Taken together, these results indicate that PARK7 protects against chronic kidney injury and renal fibrosis by inducing SOD2 to reduce oxidative stress in tubular cells.

Mechanism of circadian regulation of the NRF2/ARE pathway in renal ischemia-reperfusion

The nuclear erythroid 2-related factor 2 (NRF2)/antioxidant response element (ARE) pathway has been shown to provide strong protection against oxidative stress injury induced by renal ischemia-reperfusion (IR). However, the endogenous regulatory mechanism of the NRF2/ARE pathway in renal IR injury is incompletely understood. A rat model of renal IR was established by occlusion of the bilateral renal pedicle for 45 min, followed by reperfusion for 24 h. Renal injury was assessed by light microscopy and levels of serum creatinine, blood urea nitrogen and neutrophil gelatinase-associated lipocalin was measured using enzyme-linked immunosorbent assay. Renal oxidative stress was also evaluated by measuring superoxide dismutase and malondialdehyde in renal tissues. Protein expression levels of brain and muscle ARNT-like 1 (BMAL1), nuclear factor erythroid 2-related factor 2 (NRF2), NAD(P)H dehydrogenase [quinone] 1 (NQO1), glutamate-cysteine ligase modifier (GCLM) and heme oxygenase 1 (HO1) in the kidney were determined by western blotting and immunohistochemistry. Reverse transcription-quantitative PCR was used to evaluate rhythmic transcription of the core clock genes (CLOCK and BMAL1) and the NRF2 gene. The nature of the binding of BMAL1 to the promoter regions in the NRF2 gene was assessed by chromatin immunoprecipitation assays in rat kidneys. BMAL1 was found to bind to the promoter of the NRF2 gene through an E-BOX element associated with strongly rhythmic activation of NRF2 in both the normal kidney and those exposed to IR. The ARE-regulated anti-oxidative stress protein was affected by the circadian rhythm of the NRF2 gene. As the NRF2 level was at a circadian nadir, the expression of the proteins NQO1, GCLM and HO1 was weakened, resulting in more serious renal oxidative stress injury and pathological and functional impairment induced by IR. It can be concluded that the circadian rhythm of the NRF2/ARE pathway controlled by the circadian clock is essential for regulating antioxidant stress in renal IR injury, which might prompt new therapeutic strategies associated with the diurnal variability of human kidney disease, including renal transplantation.