Osmolarity and glucose differentially regulate aldose reductase activity in cultured mouse podocytes

Neutrophil (dys)function due to altered immuno-metabolic axis in type 2 diabetes: implications in combating infections

Metabolic and inflammatory pathways are highly interdependent, and both systems are dysregulated in Type 2 diabetes (T2D). T2D is associated with pre-activated inflammatory signaling networks, aberrant cytokine production and increased acute phase reactants which leads to a pro-inflammatory 'feed forward loop'. Nutrient 'excess' conditions in T2D with hyperglycemia, elevated lipids and branched-chain amino acids significantly alter the functions of immune cells including neutrophils. Neutrophils are metabolically active cells and utilizes energy from glycolysis, stored glycogen and β-oxidation while depending on the pentose phosphate pathway for NADPH for performing effector functions such as chemotaxis, phagocytosis and forming extracellular traps. Metabolic changes in T2D result in constitutive activation and impeded acquisition of effector or regulatory activities of neutrophils and render T2D subjects for recurrent infections. Increased flux through the polyol and hexosamine pathways, elevated production of advanced glycation end products (AGEs), and activation of protein kinase C isoforms lead to (a) an enhancement in superoxide generation; (b) the stimulation of inflammatory pathways and subsequently to (c) abnormal host responses. Neutrophil dysfunction diminishes the effectiveness of wound healing, successful tissue regeneration and immune surveillance against offending pathogens. Hence, Metabolic reprogramming in neutrophils determines frequency, severity and duration of infections in T2D. The present review discusses the influence of the altered immuno-metabolic axis on neutrophil dysfunction along with challenges and therapeutic opportunities for clinical management of T2D-associated infections.

Plasma Insulin/Erythrocytic Aldose Reductase Ratio as a Predictor for Hepatocellular Carcinoma among Type II Diabetics and Hepatitis C Virus-infected Patients

BACKGROUND

Hepatocellular carcinoma (HCC) is a possible oncogenic progression during persistent hepatitis C-infection +/- type II diabetes mellitus (DM). We aim to investigate the plasma insulin, erythrocytic aldose reductase (AR) and sorbitol dehydrogenase (SDH) as possible predictive tools for HCC in hepatitis C-infected patients (HCV) +/- DM. Erythrocytes (RBCs) were adopted as a possible vehicle for pre-malignant variations being of short life span.    Methods: The study included 20 healthy control and 100 patients of 48-64 years old, divided into 5 equal groups as; type II DM, HCC, HCC with DM, DM- HCV infected and non-DM HCV infected. Plasma levels of AFP and insulin were measured.

RESULTS

It showed an elevated AR, significant reduction of SDH in RBCs and plasma of DM patients. These values were greatly elevated among HCV, HCC, diabetic HCV, and diabetic HCC patients. All DM patients showed elevated insulin levels than normoglycemic controls.

CONCLUSION

The study substantiated the use of RBCs as a vehicle for early diagnostic markers better than plasma. We recommend the use of insulin/ erythrocytic AR ratio as a new laboratory marker for predicting HCC among type II diabetics or non-treated HCV-infected patients with control insulin/ erythrocytic AR ratio by each laboratory.

Linearolactone Induces Necrotic-like Death in Giardia intestinalis Trophozoites: Prediction of a Likely Target

Linearolactone (LL) is a neo-clerodane type diterpene that has been shown to exert giardicidal effects; however, its mechanism of action is unknown. This work analyzes the cytotoxic effect of LL on Giardia intestinalis trophozoites and identifies proteins that could be targeted by this active natural product. Increasing concentrations of LL and albendazole (ABZ) were used as test and reference drugs, respectively. Cell cycle progression, determination of reactive oxygen species (ROS) and apoptosis/necrosis events were evaluated by flow cytometry (FCM). Ultrastructural alterations were analyzed by transmission electron microscopy (TEM). Ligand–protein docking analyses were carried out using the LL structure raised from a drug library and the crystal structure of an aldose reductase homologue (GdAldRed) from G. intestinalis. LL induced partial arrest at the S phase of trophozoite cell cycle without evidence of ROS production. LL induced pronecrotic death in addition to inducing ultrastructural alterations as changes in vacuole abundances, appearance of perinuclear and periplasmic spaces, and deposition of glycogen granules. On the other hand, the in silico study predicted that GdAldRed is a likely target of LL because it showed a favored change in Gibbs free energy for this complex.

Status and Trends of the Association Between Diabetic Nephropathy and Diabetic Retinopathy From 2000 to 2021: Bibliometric and Visual Analysis

Background: Diabetic nephropathy (DN) and diabetic retinopathy (DR) are microvascular complications of diabetes that share a similar pathogenesis and clinical relevance. The study aimed to visually analyze the research status and development trend of the relationship between DN and DR by means of bibliometrics and knowledge mapping.

Methods: Publications were collected from the Science Citation Index-Expanded of the Web of Science Core Collection between 2000 and 2021. CiteSpace, Alluvial Generator, and Microsoft Excel were used to analyze and present the data.

Results: A total of 3,348 publications were retrieved and 3,285 were included in the analysis after deduplication. The publications demonstrated an annually increasing trend. The results of the collaborative network analysis showed that the United States, Steno Diabetes Center, and Tien Y. Wong were the most influential country, institution and author, in this field of research, respectively. The analysis of references and keywords showed that the pathogenesis of DN and DR and their relationship with cardiovascular disease are research hotspots. The clinical relevance and drug therapy for DN and DR will become frontiers of future research in this field.

Conclusion: This study is the first to visualize the correlation between DN and DR using a bibliometric approach. This study provides a reference of research trends for scholars.

The A allele of the rs759853 single nucleotide polymorphism in the AKR1B1 gene confers risk for diabetic kidney disease in patients with type 2 diabetes from a Brazilian population

OBJECTIVE

The AKR1B1 gene encodes an enzyme that catalyzes the reduction of glucose into sorbitol. Chronic hyperglycemia in patients with diabetes mellitus (DM) leads to increased AKR1B1 affinity for glucose and, consequently, sorbitol accumulation. Elevated sorbitol increases oxidative stress, which is one of the main pathways related to chronic complications of diabetes, including diabetic kidney disease (DKD). Accordingly, some studies have suggested the rs759853 polymorphism in the AKR1B1 gene is associated with DKD; however, findings are still contradictory. The aim was to investigate the association of the rs759853 polymorphism in the AKR1B1 gene and DKD.

METHODS

The sample comprised 695 patients with type 2 DM (T2DM) and DKD (cases) and 310 patients with T2DM of more than 10 years' duration, but no DKD (controls). The polymorphism was genotyped by real-time PCR.

RESULTS

Allelic and genotype frequencies of this polymorphism did not differ significantly between groups. However, the A/A genotype was associated with risk for DKD after adjustment for gender, triglycerides, BMI, presence of hypertension and diabetic retinopathy, and duration of DM, under both recessive (P = 0.048) and additive (P = 0.037) inheritance models.

CONCLUSION

Our data suggest an association between the AKR1B1 rs759853A/A genotype and risk for DKD in Brazilians T2DM patients.

Three dimensional modeling of biologically relevant fluid shear stress in human renal tubule cells mimics in vivo transcriptional profiles

The kidney proximal tubule is the primary site for solute reabsorption, secretion and where kidney diseases can originate, including drug-induced toxicity. Two-dimensional cell culture systems of the human proximal tubule cells (hPTCs) are often used to study these processes. However, these systems fail to model the interplay between filtrate flow, fluid shear stress (FSS), and functionality essential for understanding renal diseases and drug toxicity. The impact of FSS exposure on gene expression and effects of FSS at differing rates on gene expression in hPTCs has not been thoroughly investigated. Here, we performed RNA-sequencing of human RPTEC/TERT1 cells in a microfluidic chip-based 3D model to determine transcriptomic changes. We measured transcriptional changes following treatment of cells in this device at three different fluidic shear stress. We observed that FSS changes the expression of PTC-specific genes and impacted genes previously associated with renal diseases in genome-wide association studies (GWAS). At a physiological FSS level, we observed cell morphology, enhanced polarization, presence of cilia, and transport functions using albumin reabsorption via endocytosis and efflux transport. Here, we present a dynamic view of hPTCs response to FSS with increasing fluidic shear stress conditions and provide insight into hPTCs cellular function under biologically relevant conditions.

Extreme Glycemic Fluctuations Debilitate NRG1, ErbB Receptors and Olig1 Function: Association with Regeneration, Cognition and Mood Alterations During Diabetes

Neuronal regeneration is crucial for maintaining intact neural interactions for perpetuation of cognitive and emotional functioning. The NRG1-ErbB receptor signaling is a key pathway for regeneration in adult brain and also associated with learning and mood stabilization by modulating synaptic transmission. Extreme glycemic stress is known to affect NRG1-ErbB-mediated regeneration in brain; yet, it remains unclear how the ErbB receptor subtypes are differentially affected due to such metabolic variations. Here, we assessed the alterations in NRG1, ErbB receptor subtypes to study the regenerative potential, both in rodents as well as in neuronal and glial cell models of hyperglycemia and hypoglycemic insults during hyperglycemia. The pro-oxidant and anti-oxidant status leading to degenerative changes in brain regions were determined. The spatial memory and anxiogenic behaviour of experimental rodents were tested using 'T' maze and Elevated Plus Maze. Our data revealed that the extreme glycemic discrepancies during diabetes and recurrent hypoglycemia lead to altered expression of NRG1, ErbB receptor subtypes, Syntaxin1 and Olig1 that shows association with impaired regeneration, synaptic dysfunction, demyelination, cognitive deficits and anxiety.

Changes in fluid composition and expression of ion channels in rat cervix during different phases of the estrus cycle

We investigated changes in the composition of cervical fluid at different phases of the female rat reproductive cycle. Fluid was collected from the cervix of rats by direct cervical flushing and analyzed for changes in Na⁺ and Cl^- content and osmolarity. Following sacrifice, the cervix was harvested and expressions of mRNA and protein for ENaCs, CFTR and AQPs were measured using qPCR and immunohistochemistry, respectively. Cervical fluid Na⁺ and Cl^- content was high during estrus, but osmolarity was high during metestrus and diestrus. Expressions of CFTR, AQP-1 and AQP-2 in the cervix were high during estrus, but low during diestrus. Expression of ENaC (α, β, γ), AQP-5 and AQP-7 was high during metestrus and diestrus and low during estrus. Changes in expression of ion channels in the cervix could explain changes in cervical fluid composition during the estrus cycle phases that could affect female fertility.

Angiotensin II Modulates Podocyte Glucose Transport

Podocytes play a central role in the maintenance of the glomerular filtration barrier and are cellular targets of angiotensin II (AngII). Non-hemodynamic pathways of AngII signaling regulate cellular function and mediate podocyte abnormalities that are associated with various glomerulopathies, including diabetic kidney disease. In this study we investigated the capacity of AngII to modulate glucose uptake in mouse podocytes expressing the human AT1 receptor (AT1R+) after 5 days of exposure to normal (NG, 5.6 mmol/L) or to high (HG, 30 mmol/L) glucose. Short (30 min) as well as long-term (24 h) incubations with AngII markedly enhanced glucose transport in both NG and HG cells. In podocytes cultured under NG conditions, AngII inhibited insulin-stimulated glucose uptake. Regardless of the presence or absence of AngII, no effect of insulin on glucose uptake was observed in HG cells. Stimulation of glucose transport by AngII was mediated by protein kinase C and by phosphoinositide 3-kinase. Glucose dependent surface expression of the glucose transporters GLUT1, GLUT2, and GLUT4 was modulated by AngII in a time and glucose concentration dependent manner. Furthermore, despite its inhibitory effect on insulin's action, AngII elevated the number of podocyte insulin receptors in both NG and HG cultured cells. These findings demonstrate that AngII modulates podocyte basal, as well as insulin-dependent glucose uptake by regulating glucose transporters and insulin signaling.

Investigation of synergistic mechanism and identification of interaction site of aldose reductase with the combination of gigantol and syringic acid for prevention of diabetic cataract

BACKGROUND

Gigantol and syringic acid (SA) have been shown to synergistically prevent formation of diabetic cataract (DC). However, the exact mechanism of this effect is unknown. Here, we investigate the effect of these compounds on the activity of aldose reductase (AR) and cataract formation.

METHODS

We examined the synergistic anti-cataract efficacy of gigantol and SA in the high glucose- and streptozotocin -induced DC rat model; synergism was evaluated using Jin's formula. We investigated possible mechanisms of action by measuring AR expression and activity and levels of sorbitol using enzyme kinetics, Western blot, and RT-PCR. Finally, we examined binding interaction between AR and both compounds using a combination of site-directed mutagenesis, recombinant expression of wild-type and mutant proteins, and enzyme kinetics.

RESULTS

Combination treatment of gigantol and SA synergistically protected both HLECs(human lens epithelial cells) grown in vitro and DC formation in STZ-induced rats in vivo. Synergism was attributed to inhibition of AR activity, downregulation of AR expression via impaired transcription, and decreased sorbitol levels. Enzyme kinetics studies showed that the activity of an AR Asn160Ala mutant protein was significantly decreased compared to wild-type AR, confirming that Asn160 is a key residue for interaction between AR and both compounds.

CONCLUSION

Combined administration of gigantol and SA synergize to enhance anti-cataract efficacy. The synergistic effect is mainly attributed to disruption of the polyol pathway and inhibition of AR activity.

Is rs759853 polymorphism in promoter of aldose reductase gene a risk factor for diabetic nephropathy? A meta-analysis

Background

So far, a number of case-control or cohort studies have been carried out to investigate the relationship between rs759853 polymorphism in the promoter of aldose reductase (AR) gene and the risk of diabetic nephropathy (DN). However, the results have generated considerable controversy. We performed this study to clarify the linkage between this gene mutation and the risk of DN.

Methods

A comprehensive literature search of electronic databases and a well-organized meta-analysis were conducted.

Results

Twelve comparisons and 4,735 individuals from nine published case-control or cohort studies were included finally. From none to large heterogeneity was observed, therefore, both fixed and random models were used. Significant differences were found between AR rs759853 polymorphism and susceptibility of DN from both type 1 and type 2 diabetes in all genetic models (allele contrast, OR = 1.37, CI (1.18, 1.59), P < 0.0001; additive model, OR = 1.78, CI (1.25, 2.53), P = 0.01; recessive model OR = 1.33 CI (1.08, 1.63), P = 0.008; dominant model, OR = 1.52, CI (1.26, 1.84), P < 0.0001; codominance model OR = 1.30 (1.15, 1.47), P < 0.0001). In stratified meta-analyses for type 2 diabetes by ethnicity, the significant relationship was found in allele contrast and dominant model in Caucasians, and in allele contrast and codominance model in Asians. However, data do not support the linkage between this gene mutation and the progression of DN. There was no significant publication bias.

Conclusions

The evidence currently available shows that the AR rs759853 polymorphism may correlate with the susceptibility of DN. However, data do not support the association between this DNA variation and the progression of DN.