Mechanical forces in diabetic kidney disease: a trigger for impaired glucose metabolism

The pivotal role of glucose transporter 1 in diabetic kidney disease

Diabetes mellitus (DM) is a significant public health problem. Diabetic kidney disease (DKD) is the most common complication of DM, and its incidence has been increasing with the increasing prevalence of DM. Given the association between DKD and mortality in patients with DM, DKD is a significant burden on public health resources. Despite its significance in DM progression, the pathogenesis of DKD remains unclear. Aberrant glucose uptake by cells is an important pathophysiological mechanism underlying DKD renal injury. Glucose is transported across the bilayer cell membrane by a glucose transporter (GLUT) located on the cell membrane. Multiple GLUT proteins have been identified in the kidney, and GLUT1 is one of the most abundantly expressed isoforms. GLUT1 is a crucial regulator of intracellular glucose metabolism and plays a key pathological role in the phenotypic changes in DKD mesangial cells. In an attempt to understand the pathogenesis of DKD better, we here present a review of studies on the role of GLUT1 in the development and progression of DKD.

Tirzepatide alleviates oxidative stress and inflammation in diabetic nephropathy via IL-17 signaling pathway

Oxidative stress (OS) and inflammation play essential roles in the development of diabetic nephropathy (DN). Tirzepatide (TZP) has a protective effect in diabetes. However, its underlying mechanism in DN remains unclear. DN model mice were induced by intraperitoneal injection of streptozotocin (STZ; 60 mg/kg), followed by administration of different doses of TZP (3 and 10 nmol/kg) via intraperitoneal injection for 8 weeks. The effects of TZP on DN were evaluated by detecting DN-related biochemical indicators, kidney histopathology, apoptosis, OS, and inflammation levels. Additionally, to further reveal the potential mechanism, we investigated the role of TZP in modulating the IL-17 pathway. TZP reduced serum creatinine (sCR), blood urea nitrogen (BUN), and advanced glycosylation end products (AGEs) levels, while simultaneously promoting insulin secretion in diabetic mice. Additionally, TZP attenuated tubular and glomerular injury and reduced renal apoptosis levels. Further studies found that TZP increased the levels of SOD and CAT, and decreased MDA. Meanwhile, TZP also reduced the expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in both mouse serum and kidney homogenates. TZP effectively inhibited the IL-17 pathway, and subsequent intervention with an IL-17 pathway agonist (IL-17A) reversed the suppressive effects of TZP on OS and inflammation. TZP can improve DN by inhibiting OS and inflammation through the suppression of the IL-17 pathway.

Crocetin ameliorative effect on diabetic nephropathy in rats through a decrease in transforming growth factor-β and an increase in glyoxalase-I activity

BACKGROUND & AIMS

Glycation, oxidative stress, and inflammation due to the elevation of transforming growth factor-β1 (TGF-β1) participate in diabetic nephropathy (DN). Thus, we investigated for the first time the effect of crocetin (Crt) on the renal histopathological parameters, TGF-β1 and glycation, oxidative stress, as well as inflammatory markers in the DN rat model.

METHODS

Forty male Wistar rats were randomly divided into 4 equal groups: normal (N), N + Crt, DN, and DN + Crt. DN was induced in rats with a combination of nephrectomy and streptozotocin. Treated groups received 100 mg/kg of Crt via intraperitoneal injection monthly for 3 months. Different glycation (glycated albumin, glycated LDL, Methylglyoxal, and pentosidine), oxidative stress (advanced oxidation protein products, malondialdehyde, glutathione, and paraoxonase-I (PON-1)), and inflammatory markers (tumor necrosis factor-α, myeloperoxidase, and TGF-β1), blood glucose, insulin, lipid profile, creatinine in the serum, and proteinuria, as well as the glyoxalase-1 (GLO-1) activity, was determined.

RESULTS

Crt decreased renal biochemical (Cre and PU) and histopathological (glomerulosclerosis) renal dysfunction parameters, diverse glycation, oxidative stress, and inflammatory markers in the DN rats. Furthermore, the treatment corrected glycemia, insulin resistance, and dyslipidemia as well as induced the activities of GLO-1 and PON-1. Over and above, the treatment decreased TGF-β1 in their serum (p > 0.001).

CONCLUSIONS

Crocetin improved DN owing to an advantageous effect on metabolic profile. Further, the treatment with a reducing effect on TGF-β1, oxidative stress, glycation, and inflammation markers along with an increase in Glo-1 activity showed multiple protective effects on kidney tissue.

Antioxidant Effect of the Ethyl Acetate Extract of Potentilla indica on Kidney Mitochondria of Streptozotocin-Induced Diabetic Rats

Diabetes mellitus (DM) is a metabolic disorder characterized by persistent hyperglycemia. This state may lead to an increase in oxidative stress, which contributes to the development of diabetes complications, including diabetic kidney disease. Potentilla indica is a traditional medicinal herb in Asia, employed in the treatment of several diseases, including DM. In this study, we investigated the antioxidant effect of the ethyl acetate extract of Potentilla indica both in vitro and on kidneys of streptozotocin-induced diabetic male rats. Firstly, phytochemicals were identified via UPLC-MS/MS, and their in vitro antioxidant capabilities were evaluated. Subsequently, male Wistar rats were assigned into four groups: normoglycemic control, diabetic control, normoglycemic treated with the extract, and diabetic treated with the extract. At the end of the treatment, fasting blood glucose (FBG) levels, creatinine, blood urea nitrogen (BUN), and uric acid were estimated. Furthermore, the kidneys were removed and utilized for the determination of mitochondrial reactive oxygen species (ROS) production, mitochondrial respiratory chain complex activities, mitochondrial lipid peroxidation, glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT) activities. The in vitro findings showed that the major phytochemicals present in the extract were phenolic compounds, which exhibited a potent antioxidant activity. Moreover, the administration of the P. indica extract reduced creatinine and BUN levels, ROS production, and lipid peroxidation and improved mitochondrial respiratory chain complex activity and GSH-Px, SODk, and CAT activities when compared to the diabetic control group. In conclusion, our data suggest that the ethyl acetate extract of Potentilla indica possesses renoprotective effects by reducing oxidative stress on the kidneys of streptozotocin-induced diabetic male rats.

Eugenia sonderiana O. Berg leaves: Phytochemical characterization, evaluation of in vitro and in vivo antidiabetic effects, and structure-activity correlation

Several medicinal plants have drawn the attention of researchers by its phytochemical composition regarding their potential for treating chronic complications of diabetes mellitus. In this context, plants of the Myrtaceae family popularly used in Brazil for the treatment of diabetes mellitus, including Eugenia sonderiana, have shown beneficial effects due to the presence of phenolic compounds and saponins in their chemical constitution. Thus, the present work aimed to perform the phytochemical characterization of the hydroethanolic extract of E. sonderiana leaves using high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS), along with in vitro and in vivo studies of antidiabetic activity. The chemical characterization revealed the presence of phenolic compounds, flavonoids, neolignans, tannins, and saponins. In addition, the extract exhibited minimum inhibitory concentrations of alpha-amylase and alpha-glycosidase higher than the acarbose in the in vitro tests. Also, the in vivo tests revealed a slight increase in body mass in diabetic rats, as well as a significant decrease in water and feed consumption provided by the extract. Regarding serum biochemical parameters, the extract showed significant activity in decreasing the levels of glucose, hepatic enzymes, and triglycerides, in addition to maintaining HDL cholesterol levels within normal ranges, protecting the cell membranes against oxidative damage. Thus, the extract of E. sonderiana leaves was considered promising pharmaceutical ingredient in the production of a phytotherapy medication.

Physical properties of food or bile redirection do not contribute to the intestinal adaptations after Roux-en-Y Gastric Bypass in rats

Objective

Metabolic and morphological adaptations of the intestine have been suggested to play a role in the various therapeutic benefits of Roux-en-Y Gastric Bypass (RYGB) surgery. However, the precise underlying mechanisms remain unclear. In this study, the effects of physical properties of ingested food and redirection of biliopancreatic secretions on intestinal remodeling were investigated in RYGB operated rats.

Methods

RYGB employing two different Roux Limb (RL) lengths was performed on high fat diet induced obese rats. Post-operatively, rats were fed either Solid or isocaloric Liquid diets. Metabolic and morphological remodeling of intestine was compared across both diet forms (Solid and Liquid diets) and surgical models (Short RL and Long RL).

Results

RYGB surgery in rats induced weight loss and improved glucose tolerance which was independent of physical properties of ingested food and biliopancreatic secretions. Intestinal glucose utilization after RYGB was not determined by either food form or biliopancreatic secretions. The GLUT-1 expression in RL was not influenced by physical properties of food. Furthermore, both physical properties of food and biliopancreatic secretions showed no effects on intestinal morphological adaptations after RYGB.

Conclusion

Results of this study demonstrate that physical properties of food and bile redirection are not major determinants of intestinal remodeling after RYGB in rats.

Decreased DANCR contributes to high glucose-induced extracellular matrix accumulation in human renal mesangial cell via regulating the TGF-β/Smad signaling

Glomerulosclerosis is one of the major histopathologic changes in diabetic kidney diseases (DKD), which is characterized by excessive deposition of extracellular matrix (ECM) in the glomerulus mainly produced by mesangial cells in response to transforming growth factor-β (TGF-β) stimuli under diabetic conditions. Despite TGF-β has been implicated as a major pathogenic factor in the development of diabetic glomerulosclerosis, clinical trials of monoclonal antibodies against TGF-β failed to demonstrate therapeutic benefits. Thus, developing alternative therapeutic strategies to effectively block the TGF-β/Smad signaling could be of paramount importance for DKD treatment. Emerging evidence indicates that dysregulation of certain lncRNAs can lead to aberrant activation of TGF-β/Smad signaling. Herein, we identified a novel lncRNA, named DANCR, which could efficiently function as a negative regulator of TGF-β/Smad signaling in mesangial cells. Ectopic expression of DANCR could specifically block the activation of TGF-β/Smad signaling induced by high-glucose or TGF-β in human renal mesangial cells (HRMCs). Mechanistically, DANCR functions to stabilize nemo-like kinase (NLK) mRNA through interaction with insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2), resulting in enhanced phosphorylating on the linker region of activated Smad2/3 in the nucleus. Taken together, our data have uncovered an lncRNA-based regulatory modality of the TGF-β/Smad signaling and identified DANCR as an endogenous blocker of TGF-β/Smad signaling in HRMCs, which may represent a potential therapeutic target against the diabetic glomerulosclerosis.

The Pillars for Renal Disease Treatment in Patients with Type 2 Diabetes

The diabetes epidemic and the increasing number of patients with diabetic chronic vascular complications poses a significant challenge to health care providers. Diabetic kidney disease is a serious diabetes-mediated chronic vascular complication and represents a significant burden for both patients and society in general. Diabetic kidney disease not only represents the major cause of end stage renal disease but is also paralleled by an increase in cardiovascular morbidity and mortality. Any interventions to delay the development and progression of diabetic kidney disease are important to reduce the associated cardiovascular burden. In this review we will discuss five therapeutic tools for the prevention and treatment of diabetic kidney disease: drugs inhibiting the renin-angiotensin-aldosterone system, statins, the more recently recognized sodium-glucose co-transporter-2 inhibitors, glucagon-like peptide 1 agonists, and a novel non-steroidal selective mineralocorticoid receptor antagonist.

Nutrient sensing, signaling transduction, and autophagy in podocyte injury: implications for kidney disease

Podocytes are terminally differentiated epithelial cells of the renal glomerular tuft and these highly specialized cells are essential for the integrity of the slit diaphragm. The biological function of podocytes is primarily based on a complex ramified structure that requires sufficient nutrients and a large supply of energy in support of their unique structure and function in the glomeruli. Of note, the dysregulation of nutrient signaling and energy metabolic pathways in podocytes has been associated with a range of kidney diseases i.e., diabetic nephropathy. Therefore, nutrient-related and energy metabolic signaling pathways are critical to maintaining podocyte homeostasis and the pathogenesis of podocyte injury. Recently, a growing body of evidence has indicated that nutrient starvation induces autophagy, which suggests crosstalk between nutritional signaling with the modulation of autophagy for podocytes to adapt to nutrient deprivation. In this review, the current knowledge and advancement in the understanding of nutrient sensing, signaling, and autophagy in the podocyte biology, injury, and pathogenesis of kidney diseases is summarized. Based on the existing findings, the implications and perspective to target these signaling pathways and autophagy in podocytes during the development of novel preventive and therapeutic strategies in patients with podocyte injury-associated kidney diseases are discussed.

Pathophysiology of mesangial expansion in diabetic nephropathy: mesangial structure, glomerular biomechanics, and biochemical signaling and regulation

Diabetic nephropathy, a kidney complication arising from diabetes, is the leading cause of death in diabetic patients. Unabated, the growing epidemic of diabetes is increasing instances of diabetic nephropathy. Although the main causes of diabetic nephropathy have been determined, the mechanisms of their combined effects on cellular and tissue function are not fully established. One of many damages of diabetic nephropathy is the development of fibrosis within the kidneys, termed mesangial expansion. Mesangial expansion is an important structural lesion that is characterized by the aberrant proliferation of mesangial cells and excess production of matrix proteins. Mesangial expansion is involved in the progression of kidney failure in diabetic nephropathy, yet its causes and mechanism of impact on kidney function are not well defined. Here, we review the literature on the causes of mesangial expansion and its impacts on cell and tissue function. We highlight the gaps that still remain and the potential areas where bioengineering studies can bring insight to mesangial expansion in diabetic nephropathy.

1,8 cineole protects type 2 diabetic rats against diabetic nephropathy via inducing the activity of glyoxalase-I and lowering the level of transforming growth factor-1β

Purpose

Diabetes leading to the production and circulation of glycation products along with the reduction of the activity of glyoxalase-I (GLO-I) contribute to diabetic nephropathy. Therefore, we studied the effect of 1,8 cineole (Cin) on the formation of diverse glycation products and the activity of GLO-I as well as renal histopathological alterations in the type-2 diabetic rat.

Methods

Type 2 diabetes was induced in rats with a combination of streptozotocin and nicotinamide (55 + 200 mg/kg). Two groups of rats, normal and diabetic, were treated intragastrically with Cin (200 mg/kg) once daily for 2 months. Fasting blood sugar, insulin resistance index, lipid profile, the activity of GLO-I, glycation products (Glycated albumin, Glycated LDL, Methylglyoxal, and advanced glycation end products), and oxidative stress (Advanced oxidation protein products, malondialdehyde, oxidized LDL, and reduced glutathione), inflammatory markers (Tumor necrosis factor-α and Transforming growth factor-1β), creatinine in the serum (Cre), and proteinuria (PU) in the urine of all rats was determined as well as renal histopathological alterations were investigated.

Results

Cin reduced biochemical (Cre and PU) and histopathological (glomerulosclerosis) indicators of renal dysfunction in the diabetic rat compared to untreated diabetic rats. Moreover, the treatment decreased different glycation, oxidative stress, and pro-inflammatory markers (p < 0.001). Further, Cin had an advantageous effect on glucose and lipid metabolism.

Conclusions

Cin ameliorated diabetic nephropathy via reduction of TGF-1β following to decrease the formation of different glycation products, oxidative stress, and inflammatory process with the induction of the activity of glyoxalase-I in type 2 diabetic rats.

Repurposing drugs for highly prevalent diseases: pentoxifylline, an old drug and a new opportunity for diabetic kidney disease

Diabetic kidney disease is one of the most frequent complications in patients with diabetes and constitutes a major cause of end-stage kidney disease. The prevalence of diabetic kidney disease continues to increase as a result of the growing epidemic of diabetes and obesity. Therefore, there is mounting urgency to design and optimize novel strategies and drugs that delay the progression of this pathology and contain this trend. The new approaches should go beyond the current therapy focussed on the control of traditional risk factors such as hyperglycaemia and hypertension. In this scenario, drug repurposing constitutes an economic and feasible approach based on the discovery of useful activities for old drugs. Pentoxifylline is a nonselective phosphodiesterase inhibitor currently indicated for peripheral artery disease. Clinical trials and meta-analyses have shown renoprotection secondary to anti-inflammatory and antifibrotic effects in diabetic patients treated with this old known drug, which makes pentoxifylline a candidate for repurposing in diabetic kidney disease.

Fraxin Promotes the Activation of Nrf2/ARE Pathway via Increasing the Expression of Connexin43 to Ameliorate Diabetic Renal Fibrosis

Diabetic nephropathy (DN) is quickly becoming the largest cause of end-stage renal disease (ESRD) in diabetic patients, as well as a major source of morbidity and mortality. Our previous studies indicated that the activation of Nrf2/ARE pathway via Connexin43 (Cx43) considerably contribute to the prevention of oxidative stress in the procession of DN. Fraxin (Fr), the main active glycoside of Fraxinus rhynchophylla Hance, has been demonstrated to possess many potential pharmacological activities. Whereas, whether Fr could alleviate renal fibrosis through regulating Cx43 and consequently facilitating the activation of Nrf2/ARE pathway needs further investigation. The in vitro results showed that: 1) Fr increased the expression of antioxidant enzymes including SOD1 and HO-1 to inhibit high glucose (HG)-induced fibronectin (FN) and inflammatory cell adhesion molecule (ICAM-1) overexpression; 2) Fr exerted antioxidant effect through activating the Nrf2/ARE pathway; 3) Fr significantly up-regulated the expression of Cx43 in HG-induced glomerular mesangial cells (GMCs), while the knock down of Cx43 largely impaired the activation of Nrf2/ARE pathway induced by Fr; 4) Fr promoted the activation of Nrf2/ARE pathway via regulating the interaction between Cx43 and AKT. Moreover, in accordance with the results in vitro, elevated levels of Cx43, phosphorylated-AKT, Nrf2 and downstream antioxidant enzymes related to Nrf2 were observed in the kidneys of Fr-treated group compared with model group. Importantly, Fr significantly improved renal dysfunction pathological changes of renal fibrosis in diabetic db/db mice. Collectively, Fr could increase the Cx43-AKT-Nrf2/ARE pathway activation to postpone the diabetic renal fibrosis and the up-regulation of Cx43 is probably a novel mechanism in this process.

Renoprotective Role of Hypoxia-Inducible Factors and the Mechanism

BACKGROUND

The kidney requires abundant blood supply, and oxygen is transmitted by diffusion through blood vessels. Most physiological metabolism of the kidney depends on oxygen, so it is very sensitive to oxygen. An increasing pool of evidence suggests that hypoxia is involved in almost all acute and chronic kidney diseases (CKDs). Vascular damage, tubular injury, and fibrosis are the main pathologies associated during hypoxia. Hypoxia-inducible factors (HIFs) are the main mediators during hypoxia, but their functions remain controversial. This article reviewed recent studies and described its mechanisms on renoprotection.

SUMMARY

HIF is degraded rapidly during under normal oxygen. But under hypoxia, HIFs accumulate and many target genes are regulated by HIFs. Homeostasis during injury is maintained through these genes. Pretreatment of HIF can protect the kidney from acute hypoxia and can improve repair, but HIF's role in CKD and in renal tumor is still controversial. Due to its mechanism in kidney disease, many drugs toward HIFs are widely researched, even some of which have been used in clinical or in clinical research.

KEY MESSAGES

In this review, we described the known physiological mechanisms, target genes, and renal protective roles of HIFs, and we discussed several drugs that are researched due to such renal protective roles.

Human Glucose Transporters in Renal Glucose Homeostasis

The kidney plays an important role in glucose homeostasis by releasing glucose into the blood stream to prevent hypoglycemia. It is also responsible for the filtration and subsequent reabsorption or excretion of glucose. As glucose is hydrophilic and soluble in water, it is unable to pass through the lipid bilayer on its own; therefore, transport takes place using carrier proteins localized to the plasma membrane. Both sodium-independent glucose transporters (GLUT proteins) and sodium-dependent glucose transporters (SGLT proteins) are expressed in kidney tissue, and mutations of the genes coding for these glucose transporters lead to renal disorders and diseases, including renal cancers. In addition, several diseases may disturb the expression and/or function of renal glucose transporters. The aim of this review is to describe the role of the kidney in glucose homeostasis and the contribution of glucose transporters in renal physiology and renal diseases.

Nephroprotective Effect of the Virgin Olive Oil Polyphenol Hydroxytyrosol in Type 1-like Experimental Diabetes Mellitus: Relationships with Its Antioxidant Effect

The aim of this study was to determine whether hydroxytyrosol administration prevented kidney damage in an experimental model of type 1 diabetes mellitus in rats. Hydroxytyrosol was administered to streptozotocin-diabetic rats: 1 and 5 mg/kg/day p.o. for two months. After hydroxytyrosol administration, proteinuria was significantly reduced (67-73%), calculated creatinine clearance was significantly increased (26-38%), and the glomerular volume and glomerulosclerosis index were decreased (20-30%). Hydroxytyrosol reduced oxidative and nitrosative stress variables and thromboxane metabolite production. Statistical correlations were found between biochemical and kidney function variables. Oral administration of 1 and 5 mg/kg/day of hydroxytyrosol produced an antioxidant and nephroprotective effect in an experimental model of type 1-like diabetes mellitus. The nephroprotective effect was significantly associated with the systemic and renal antioxidant action of hydroxytyrosol, which also influenced eicosanoid production.

Narrative review on clinical considerations for patients with diabetes and COVID-19: More questions than answers

BACKGROUND-AIM

Diabetes, obesity and hypertension are common comorbidities associated with increased severity and mortality rates from Corona Virus Disease (COVID)-19.

METHODS

In this narrative review (using the PubMed database), we discuss epidemiological data and pathophysiological links between diabetes and COVID-19. The potential effects of glycaemic control and antidiabetic drugs on the prevalence and outcomes of COVID-19 are also reviewed, as well as the role of telemedicine and diabetes self-management in the post-COVID-19 era.

RESULTS

Diabetes has been linked to COVID-19 morbidity and mortality, although further research is needed to elucidate this association. In the meantime, physicians should be aware of the potential rise in the prevalence of diabetes (due to unhealthy lifestyle changes during the pandemic), its severity and complications and focus on achieving optimal diabetes prevention and management. Telemedicine and diabetes self-management may help towards this direction. Dipeptidyl-peptidase 4 (DPP4) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists and sodium-glucose transporter 2 (SGLT2) inhibitors may affect viral entry and infection, and thus COVID-19 outcomes, as shown in observational studies.

CONCLUSION

Diabetes has been associated with COVID-19 development and progression. Certain antidiabetic drugs may influence COVID-19 prevention and management. The results of ongoing randomized clinical trials will shed more light on this field.

Kidney disease in diabetes: From mechanisms to clinical presentation and treatment strategies

Metabolic and haemodynamic perturbations and their interaction drive the development of diabetic kidney disease (DKD) and its progression towards end stage renal disease (ESRD). Increased mitochondrial oxidative stress has been proposed as the central mechanism in the pathophysiology of DKD, but other mechanisms have been implicated. In parallel to increased oxidative stress, inflammation, cell apoptosis and tissue fibrosis drive the relentless progressive loss of kidney function affecting both the glomerular filtration barrier and the renal tubulointerstitium. Alteration of glomerular capillary autoregulation is at the basis of glomerular hypertension, an important pathogenetic mechanism for DKD. Clinical presentation of DKD can vary. Its classical presentation, often seen in patients with type 1 diabetes (T1DM), features hyperfiltration and albuminuria followed by progressive fall in renal function. Patients can often also present with atypical features characterised by progressive reduction in renal function without albuminuria, others in conjunction with non-diabetes related pathologies making the diagnosis, at times, challenging. Metabolic, lipid and blood pressure control with lifestyle interventions are crucial in reducing the progressive renal function decline seen in DKD. The prevention and management of DKD (and parallel cardiovascular disease) is a huge global challenge and therapies that target haemodynamic perturbations, such as inhibitors of the renin-angiotensin-aldosterone system (RAAS) and SGLT2 inhibitors, have been most successful.

Mitochondria in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of end stage renal disease (ESRD) in the USA. The pathogenesis of DKD is multifactorial and involves activation of multiple signaling pathways with merging outcomes including thickening of the basement membrane, podocyte loss, mesangial expansion, tubular atrophy, and interstitial inflammation and fibrosis. The glomerulo-tubular balance and tubule-glomerular feedback support an increased glomerular filtration and tubular reabsorption, with the latter relying heavily on ATP and increasing the energy demand. There is evidence that alterations in mitochondrial bioenergetics in kidney cells lead to these pathologic changes and contribute to the progression of DKD towards ESRD. This review will focus on the dialogue between alterations in bioenergetics in glomerular and tubular cells and its role in the development of DKD. Alterations in energy substrate selection, electron transport chain, ATP generation, oxidative stress, redox status, protein posttranslational modifications, mitochondrial dynamics, and quality control will be discussed. Understanding the role of bioenergetics in the progression of diabetic DKD may provide novel therapeutic approaches to delay its progression to ESRD.

Clinical efficacies, underlying mechanisms and molecular targets of Chinese medicines for diabetic nephropathy treatment and management

Diabetic nephropathy (DN) has been recognized as a severe complication of diabetes mellitus and a dominant pathogeny of end-stage kidney disease, which causes serious health problems and great financial burden to human society worldwide. Conventional strategies, such as renin-angiotensin-aldosterone system blockade, blood glucose level control, and bodyweight reduction, may not achieve satisfactory outcomes in many clinical practices for DN management. Notably, due to the multi-target function, Chinese medicine possesses promising clinical benefits as primary or alternative therapies for DN treatment. Increasing studies have emphasized identifying bioactive compounds and molecular mechanisms of reno-protective effects of Chinese medicines. Signaling pathways involved in glucose/lipid metabolism regulation, antioxidation, anti-inflammation, anti-fibrosis, and podocyte protection have been identified as crucial mechanisms of action. Herein, we summarize the clinical efficacies of Chinese medicines and their bioactive components in treating and managing DN after reviewing the results demonstrated in clinical trials, systematic reviews, and meta-analyses, with a thorough discussion on the relative underlying mechanisms and molecular targets reported in animal and cellular experiments. We aim to provide comprehensive insights into the protective effects of Chinese medicines against DN.

Dioscorea zingiberensis ameliorates diabetic nephropathy by inhibiting NLRP3 inflammasome and curbing the expression of p66Shc in high-fat diet/streptozotocin-induced diabetic mice

OBJECTIVES

Diabetic nephropathy (DN) is a severe diabetic complication. Dioscorea zingiberensis (DZ) possesses excellent pharmacological properties with lower toxicity. The purpose of this study was to investigate the efficacy and mechanism of DZ in DN.

METHODS

DN was established by the high-fat diet combining intraperitoneal injection of streptozotocin in mice. The DZ (125 and 250 mg/kg/day) were intragastrical administered for 8 consecutive weeks. After treatment, blood, urine and kidney tissue were collected for biological detection, renal morphology, fibrosis and molecular mechanism research, respectively.

KEY FINDINGS

This study has shown that DZ significantly ameliorated kidney hypertrophy, renal structural damage and abnormal function of the kidney indicators (creatinine, urinary protein and blood urea nitrogen). Further molecular mechanism data suggested that the NLRP3/Cleaved-caspase-1 signal pathway was remarkably activated in DN, and DZ treatment reversed these changes, which indicated that it effectively attenuated inflammatory response caused by hyperglycaemia. In addition, DN inhibits hyperglycaemia-induced activation of oxidative stress by suppressing the expression of p66Shc proteins.

CONCLUSIONS

DZ could efficiently suppress oxidative stress and inflammatory responses to postpone the development of DN, and its mechanism might be related to inhibition of NLRP3 and p66Shc activities. Thus, DZ could be developed into a new therapeutic agent for DN.

The Na/K-ATPase Signaling and SGLT2 Inhibitor-Mediated Cardiorenal Protection: A Crossed Road?

In different large-scale clinic outcome trials, sodium (Na⁺)/glucose co-transporter 2 (SGLT2) inhibitors showed profound cardiac- and renal-protective effects, making them revolutionary treatments for heart failure and kidney disease. Different theories are proposed according to the emerging protective effects other than the original purpose of glucose-lowering in diabetic patients. As the ATP-dependent primary ion transporter providing the Na⁺ gradient to drive other Na⁺-dependent transporters, the possible role of the sodium–potassium adenosine triphosphatase (Na/K-ATPase) as the primary ion transporter and its signaling function is not explored.

Simulations of increased glomerular capillary wall strain in the 5/6-nephrectomized rat

Objective

Chronic glomerular hypertension is associated with glomerular injury and sclerosis; however, the mechanism by which increases in pressure damage glomerular podocytes remains unclear. We tested the hypothesis that increases in glomerular pressure may deleteriously affect podocyte structural integrity by increasing the strain of the glomerular capillary walls, and that glomerular capillary wall strain may play a significant role in the perpetuation of glomerular injury in disease states that are associated with glomerular hypertension.

Methods

We developed an anatomically accurate mathematical model of a compliant, filtering rat glomerulus to quantify the strain of the glomerular capillary walls in a remnant glomerulus of the 5/6‐nephrectomized rat model of chronic kidney disease. In terms of estimating the mechanical stresses and strains in the glomerular capillaries, this mathematical model is a substantial improvement over previous models which do not consider pressure‐induced alterations in glomerular capillary diameters in distributing plasma and erythrocytes throughout the network.

Results

Using previously reported data from experiments measuring the change of glomerular volume as a function of perfusion pressure, we estimated the Young's modulus of the glomerular capillary walls in both control and 5/6‐nephrectomized conditions. We found that in 5/6‐nephrectomized conditions, the Young's modulus increased to 8.6 MPa from 7.8 MPa in control conditions, but the compliance of the capillaries increased in 5/6‐nephrectomized conditions due to a 23.3% increase in the baseline glomerular capillary diameters. We found that glomerular capillary wall strain was increased approximately threefold in 5/6‐nephrectomized conditions over control, which may deleteriously affect both mesangial cells and podocytes. The magnitudes of strain in model simulations of 5/6‐nephrectomized conditions were consistent with magnitudes of strain that elicit podocyte hypertrophy and actin cytoskeleton reorganization in vitro.

Conclusions

Our findings indicate that glomerular capillary wall strain may deleteriously affect podocytes directly, as well as act in concert with other mechanical changes and environmental factors inherent to the in vivo setting to potentiate glomerular injury in severe renoprival conditions.

Preventive Effect of Eucalyptol on the Formation of Aorta Lesions in the Diabetic-Atherosclerotic Rat

Background:

Glycation, inflammation, and oxidative stress are the cardinal motivators of diabetes vascular complications. Here, we studied the effect of eucalyptol (EUC) on the formation of atheromatous lesions, glycation, oxidative stress, and inflammatory markers as well as insulin resistance, lipid profile, and activity of glyoxalase-1 (GLO-I) in the atherosclerotic rat model.

Methods:

Diabetic-atherosclerosis induced in rats with a combination of streptozotocin and atherogenic diet. Two groups of rats, normal and diabetic-atherosclerotic, were treated intragastrically with EUC (200 mg/kg) once daily for 3 months. Fasting blood sugar (FBS), insulin, insulin resistance index, lipid profile, the activity of GLO-I, low-density lipoprotein (LDL) glycation and oxidation markers, inflammatory markers, creatinine in the serum, and proteinuria in the urine of all rats were determined.

Results:

EUC inhibited the formation of any atheromatous lesions in atherosclerotic rats. Further, EUC displayed the lowering effect on glycemia, insulin resistance, LDL glycation, and oxidation products, and tumor necrosis factor (TNF)-α as well as it exhibited the improving effect on lipid profile, the activity of GLO-I, and renal function in the diabetic rat (P < 0.001).

Conclusions:

EUC prevented the formation of the atheromatous lesions and improved renal function in the atherosclerotic rat model due to a reduction of glycation, oxidative stress, and inflammatory mediators.

Roles of Sodium-Glucose Cotransporter 2 of Mesangial Cells in Diabetic Kidney Disease

We have been studying the presence of sodium-glucose cotransporter 2 (SGLT2) in mesangial cells and pericytes since 1992. Recent large placebo-controlled studies of SGLT2 inhibitors in patients with type 2 diabetes mellitus have reported desirable effects of the inhibitors on the diabetic kidney and the diabetic heart. Most studies have indicated that these effects of SGLT2 inhibitors could be mediated by the tubuloglomerular feedback system. However, a recent study about urine sodium excretion in the presence of an SGLT2 inhibitor did not show any increases in urine sodium excretion. A very small dose of an SGLT2 inhibitor did not inhibit SGLT2 at the S1 segment of proximal tubules. Moreover, SGLT2 inhibition protects against progression in chronic kidney disease with and without type 2 diabetes. In these circumstances, the tubuloglomerular feedback hypothesis involves several theoretical concerns that must be clarified. The presence of SGLT2 in mesangial cells seems to be very important for diabetic nephropathy. We now propose a novel mechanism by which the desirable effects of SGLT2 inhibitors on diabetic nephropathy are derived from the direct effect on SGLT2 expressed in mesangial cells.

Bicalutamide Elicits Renal Damage by Causing Mitochondrial Dysfunction via ROS Damage and Upregulation of HIF-1

Combined androgen blockade using bicalutamide (Bic) is a therapeutic choice for treating prostate cancer (PCa). However, even at regular clinical dosages, Bic frequently shows adverse effects associated with cardiovascular and renal damage. Previously, we found that Bic selectively damaged mesangial cells compared to tubular cells and in an in vivo rat model, we also found renal damage caused by Bic. In the present study, a rat mesangial cell model was used to further the investigation. Results indicated that Bic enhanced lactate dehydrogenase release, reactive oxygen species (ROS) production, lysosome population and kidney injury molecule-1 and decreased N-cadherin. Bic elicited mitochondrial swelling and reduced the mitochondrial potential, resulting in severe suppression of the oxygen consumption rate (OCR), maximum respiration and ATP production. The hypoxia-inducible factor (HIF)-1α transcriptional activity and messenger RNA were significantly upregulated in dose-dependent manners. The HIF-1α protein reached a peak value at 24 h then rapidly decayed. BCL2/adenovirus E1B 19-kDa protein-interacting protein 3 and cleaved caspase-3 were dose-dependently upregulated by Bic (60 μM) and that eventually led to cell apoptosis. It is suggested that Bic induces renal damage via ROS and modulates HIF-1α pathway and clinically, some protective agents like antioxidants are recommended for co-treatment.

Diabetic Nephropathy: An Overview

Diabetic nephropathy (DN) is one of the most feared diabetic chronic microvascular complications and the major cause of end-stage renal disease (ESRD). The classical presentation of DN is characterized by hyperfiltration and albuminuria in the early phases which is then followed by a progressive renal function decline. The presentation of diabetic kidney disease (DKD) can vary especially in patients with T2DM where concomitant presence of other glomerular/tubular pathologies and severe peripheral vascular disease can become important confounders. All-cause mortality in individuals with DKD is approximately 30 times higher than that in diabetic patients without nephropathy and a great majority of patients with DKD will die from cardiovascular disease before they reach ESRD. The management of metabolic and hemodynamic perturbations for the prevention and for the delay of progression of DKD is very important. DKD is a global challenge and a significant social and economic burden; research should aim at developing new ideas to tackle this devastating condition.

Lessons from the Trials for the Desirable Effects of Sodium Glucose Co-Transporter 2 Inhibitors on Diabetic Cardiovascular Events and Renal Dysfunction

Recent large placebo-controlled trials of sodium glucose co-transporter 2 (SGLT2) inhibitors revealed desirable effects on heart failure (HF) and renal dysfunction; however, the mechanisms underlying these effects are unknown. The characteristic changes in the early stage of diabetic cardiomyopathy (DCM) are myocardial and interstitial fibrosis, resulting in diastolic and subsequent systolic dysfunction, which leads to clinical HF. Pericytes are considered to play crucial roles in myocardial and interstitial fibrosis. In both DCM and diabetic retinopathy (DR), microaneurysm formation and a decrease in capillaries occur, triggered by pericyte loss. Furthermore, tubulointerstitial fibrosis develops in early diabetic nephropathy (DN), in which pericytes and mesangial cells are thought to play important roles. Previous reports indicate that pericytes and mesangial cells play key roles in the pathogenesis of DCM, DR and DN. SGLT2 is reported to be functionally expressed in pericytes and mesangial cells, and excessive glucose and Na+ entry through SGLT2 causes cellular dysfunction in a diabetic state. Since SGLT2 inhibitors can attenuate the high glucose-induced dysfunction of pericytes and mesangial cells, the desirable effects of SGLT2 inhibitors on HF and renal dysfunction might be explained by their direct actions on these cells in the heart and kidney microvasculature.

Amelioration of diabetic nephropathy by SGLT2 inhibitors independent of its glucose-lowering effect: A possible role of SGLT2 in mesangial cells

Several clinical studies have shown the beneficial effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors on diabetic nephropathy. The underlying mechanisms are not fully understood. We found that administration of canagliflozin at a low dose (0.01 mg/kg/day) did not affect either blood glucose levels or glycosuria, but it improved albuminuria and mesangial expansion in db/db mice to a similar extent as at a high dose (3.0 mg/kg/day) that lowered blood glucose levels. This indicated the existence of a tubular SGLT2-independent reno-protective mechanism. Here we focused on the potential role of SGLT2 in mesangial cells (MCs). Western blot analysis revealed the expression of SGLT2 in cultured mouse MCs. Exposure of MCs to high glucose levels for 72 h significantly increased the expression of SGLT2. Canagliflozin or ipragliflozin (both 100 nM) treatment inhibited glucose consumption in the medium under high-glucose conditions but not under normal-glucose conditions. Furthermore, canagliflozin inhibited high-glucose-induced activation of the protein kinase C (PKC)-NAD(P)H oxidase pathway and increases in reactive oxygen species (ROS) production. Thus, the inhibition of mesangial SGLT2 may cause an inhibition of PKC activation and ROS overproduction in diabetic nephropathy, and this may at least in part account for the reno-protective effect of SGLT2 inhibitors.

Impact of Pre-existing Comorbidities on Long-term Outcomes in Kidney Transplant Recipients

BACKGROUND

Outcomes of patients with end-stage renal disease are mainly affected by their comorbidities. Detailed data evaluating the impact of pre-transplant comorbidities on long-term outcome after kidney transplantation are largely missing.

METHODS

In a long-term retrospective analysis, we investigated 839 deceased donor kidney transplant recipients (KTRs) who received transplants between 1999 and 2014. The prevalence and impact of the most relevant comorbidities were studied in detail.

RESULTS

At the time of transplantation, 25% of KTRs had coronary artery disease (CAD), 16% had diabetes mellitus (DM), 11% had peripheral arterial disease (PAD), 8% had chronic heart failure (CHF), and 7% had cerebrovascular disease (CVD). KTRs with pre-existing CAD, DM, PAD, and CHF showed a significantly inferior patient survival. Multivariate analysis adjusting for all relevant factors and comorbidities confirmed CAD as most hazardous independent risk factor for premature death (hazard ratio [HR] 1.70; P = .002). A multivariate analysis revealed CHF and PAD as independent risk factors for death censored graft loss (HR 2.20; P = .003 and HR 1.80; P = .013). Diabetes was independently and significantly associated with T-cell- (HR 1.46; P = .020) and antibody-mediated rejections (HR 2.27; P = .030).

CONCLUSIONS

Detailed quantification of the impact of pre-transplant comorbidities may facilitate the evaluation of transplant candidates, guide post-transplant follow-up, and may help to further refine prediction algorithms and allocation systems.

Glucose dilates renal afferent arterioles via glucose transporter-1

Glomerular hyperfiltration occurs during the early stage of diabetes. An acute glucose infusion increases glomerular filtration rate. The involvement of tubuloglomerular feedback response and direct effect of glucose on the afferent arterioles (Af-Arts) have been suggested. However, the signaling pathways to trigger Af-Art dilatation have not been fully identified. Therefore, in the present study we tested our hypothesis that an increase in glucose concentration enhances endothelial nitric oxide synthesis activity and dilates the Af-Arts via glucose transporter-1 (GLUT1) using isolated mouse Af-Arts with perfusion. We isolated and microperfused the Af-Arts from nondiabetic C57BL/6 mice. The Af-Arts were preconstricted with norepinephrine (1 µM). When we switched the d-glucose concentration from low (5 mM) to high (30 mM) in the perfusate, the preconstricted Af-Arts significantly dilated by 37.8 ± 7.1%, but L-glucose did not trigger the dilation. GLUT1 mRNA was identified in microdisserted Af-Arts measured by RT-PCR. Changes in nitric oxide (NO) production in Af-Art were also measured using fluorescent probe when ambient glucose concentration was increased. When the d-glucose concentration was switched from 5 to 30 mM, NO generation in Af-Art was significantly increased by 19.2 ± 6.2% (84.7 ± 4.1 to 101.0 ± 9.3 U/min). l-Glucose had no effect on the NO generation. The GLUT1-selective antagonist 4-[({[4-(1,1-Dimethylethyl)phenyl]sulfonyl}amino)methyl]- N-3-pyridinylbenzamide and the nitric oxide synthase inhibitor N^G-nitro-l-arginine methyl ester blocked the high glucose-induced NO generation and vasodilation. In conclusion, we demonstrated that an increase in glucose concentration dilates the Af-Art by stimulation of the endothelium-derived NO production mediated by GLUT1.

Diabetic nephropathy: Is there a role for oxidative stress?

Oxidative stress has been implicated in the pathophysiology of diabetic nephropathy. Studies in experimental animal models of diabetes strongly implicate oxidant species as a major determinant in the pathophysiology of diabetic kidney disease. The translation, in the clinical setting, of these concepts have been quite disappointing, and new theories have challenged the concepts that oxidative stress per se plays a role in the pathophysiology of diabetic kidney disease. The concept of mitochondrial hormesis has been introduced to explain this apparent disconnect. Hormesis is intended as any cellular process that exhibits a biphasic response to exposure to increasing amounts of a substance or condition: specifically, in diabetic kidney disease, oxidant species may represent, at determined concentration, an essential and potentially protective factor. It could be postulated that excessive production or inhibition of oxidant species formation might result in an adverse phenotype. This review discusses the evidence underlying these two apparent contradicting concepts, with the aim to propose and speculate on potential mechanisms underlying the role of oxidant species in the pathophysiology of diabetic nephropathy and possibly open future more efficient therapies to be tested in the clinical settings.

SGLT-2 inhibitors: Their pleiotropic properties

Type 2 diabetes mellitus has become a global pandemic. Nowadays, it is estimated that approximately 415 million people all over the world have diabetes. The sodium glucose co-transporters 2 inhibitors are a new class of glucose-lowering agents, which act through a novel mechanism by producing a decline in glucose re-absorption in the kidney, thereby increasing glycosuria and decreasing serum glucose levels. Data suggest that apart from lowering HbA1c, they produce a small but significant weight loss and a small decrease in blood pressure. Also, they possess nephro-protective potential. These drugs are demonstrated to restore intra-glomerular pressure by increasing angiotensin (1-7), which exerts vasodilatory and anti-inflammatory effects. Their profile on cardiovascular events is still under investigation. In this review, the pleiotropic potential of this novel class of glucose-lowering levels will be discussed. Further research is warranted to determine their safety in the long term.

Distribution of glucose transporters in renal diseases

Kidneys play an important role in glucose homeostasis. Renal gluconeogenesis prevents hypoglycemia by releasing glucose into the blood stream. Glucose homeostasis is also due, in part, to reabsorption and excretion of hexose in the kidney.Lipid bilayer of plasma membrane is impermeable for glucose, which is hydrophilic and soluble in water. Therefore, transport of glucose across the plasma membrane depends on carrier proteins expressed in the plasma membrane. In humans, there are three families of glucose transporters: GLUT proteins, sodium-dependent glucose transporters (SGLTs) and SWEET. In kidney, only GLUTs and SGLTs protein are expressed. Mutations within genes that code these proteins lead to different renal disorders and diseases. However, diseases, not only renal, such as diabetes, may damage expression and function of renal glucose transporters.

Probucol ameliorates renal injury in diabetic nephropathy by inhibiting the expression of the redox enzyme p66Shc

AIMS

Probucol is an anti-hyperlipidemic agent and a potent antioxidant drug that can delay progression of diabetic nephropathy (DN) and reverses renal oxidative stress in diabetic animal models; however, the mechanisms underlying these effects remain unclear. p66Shc is a newly recognized mediator of mitochondrial ROS production in renal cells under high-glucose (HG) ambience. We previously showed that p66Shc can serve as a biomarker for renal oxidative injury in DN patients and that p66Shc up-regulation is correlated with renal damage in vivo and in vitro. Here, we determined whether probucol ameliorates renal injury in DN by inhibiting p66Shc expression.

RESULTS

We found that the expression of SIRT1, Ac-H3 and p66Shc in kidneys of DN patients was altered. Also, probucol reduced the levels of serum creatinine, urine protein and LDL-c and attenuated renal oxidative injury and fibrosis in STZ induced diabetic mice. In addition, probucol reversed p-AMPK, SIRT1, Ac-H3 and p66Shc expression. Correlation analyses showed that p66Shc expression was correlated with p-AMPK and Sirt1 expression and severity of renal injury. In vitro pretreatment of HK-2 cells with p-AMPK and SIRT1 siRNA negated the beneficial effects of probucol. Furthermore, we noted that probucol activates p-AMPK and Sirt1 and inhibits p66shc mRNA transcription by facilitating the binding of Sirt1 to the p66Shc promoter and modulation of Ac-H3 expression in HK-2 cells under HG ambience.

INNOVATION AND CONCLUSION

Our results suggest for the first time that probucol ameliorates renal damage in DN by epigenetically suppressing p66Shc expression via the AMPK-SIRT1-AcH3 pathway.

Sodium glucose cotransporter 2 in mesangial cells and retinal pericytes and its implications for diabetic nephropathy and retinopathy

Retinopathy and nephropathy are life-threatening diabetic complications that decrease patient quality of life. Although the mechanisms underlying these conditions have been extensively studied, they remain unknown. Recent reports have demonstrated the presence of sodium glucose cotransporter 2 (SGLT2) in retinal pericytes and mesangial cells. Hyperglycemia results in functional and morphological changes in these cells, but these effects are attenuated by phlorizin, a nonselective SGLT inhibitor. Based on these findings, we hypothesized that SGLT2 plays a pivotal role in the development of diabetic nephropathy and retinopathy and that SGLT2 inhibitors may directly protect against these complications.

Synergistic Interaction of Hypertension and Diabetes in Promoting Kidney Injury and the Role of Endoplasmic Reticulum Stress

Diabetes mellitus and hypertension are major risk factors for chronic kidney injury, together accounting for >70% of end-stage renal disease. In this study, we assessed interactions of hypertension and diabetes mellitus in causing kidney dysfunction and injury and the role of endoplasmic reticulum (ER) stress. Hypertension was induced by aorta constriction (AC) between the renal arteries in 6-month-old male Goto-Kakizaki (GK) type 2 diabetic and control Wistar rats. Fasting plasma glucose averaged 162±11 and 87±2 mg/dL in GK and Wistar rats, respectively. AC produced hypertension in the right kidney (above AC) and near normal blood pressure in the left kidney (below AC), with both kidneys exposed to the same levels of glucose, circulating hormones, and neural influences. After 8 weeks of AC, blood pressure above the AC (and in the right kidney) increased from 109±1 to 152±5 mm Hg in GK rats and from 106±4 to 141±5 mm Hg in Wistar rats. The diabetic-hypertensive right kidneys in GK-AC rats had much greater increases in albumin excretion and histological injury compared with left kidneys (diabetes mellitus only) of GK rats or right kidneys (hypertension only) of Wistar-AC rats. Marked increases in ER stress and oxidative stress indicators were observed in diabetic-hypertensive kidneys of GK-AC rats. Inhibition of ER stress with tauroursodeoxycholic acid for 6 weeks reduced blood pressure (135±4 versus 151±4 mm Hg), albumin excretion, ER and oxidative stress, and glomerular injury, while increasing glomerular filtration rate in hypertensive-diabetic kidneys. These results suggest that diabetes mellitus and hypertension interact synergistically to promote kidney dysfunction and injury via ER stress.

Paeoniflorin ameliorates AGEs-induced mesangial cell injury through inhibiting RAGE/mTOR/autophagy pathway

Glomerular mesangial cell plays a vital role in diabetic nephropathy (DN). Recent research has demonstrated that autophagy involved in the development of DN. Paeoniflorin (PF), a monoterpene glucoside, has been proved to attenuate advanced glycation end products (AGEs)-induced mesangial cell injury. However, the regulatory mechanism of PF on autophagy in mesangial cell remains unclear. The aim of this study was to explore the effect of PF on autophagy in AGEs-induced mesangial cell dysfunction. In this study, the leakage of the lactic dehydrogenase (LDH) into the extracellular medium was measured by LDH kit. Transmission electron microscopy (TEM) and mRFP-GFP-microtubule-associated protein light chain 3 (LC3) transfection were performed to observe the formation of autophagy in AGEs-induced mesangial cell. The RAGE/mTOR/autophagy pathway was analyzed by western blotting and small-interfering RNA transfection. Our results showed that the expression of LC3II, p62 were changed in a time-dependent manner in AGEs-stimulated mesangial cell. While PF could decrease the expression of LC3II/LC3I and reduce the number of autophagosomes. Knockdown of Atg5 promoted the protective effect of PF on AGEs-induced HBZY-1 injury. Furthermore, we found PF inhibited autophagy at least partly through inhibiting RAGE and upregulating the level of p-mTOR to against AGEs-induced mesangial cell dysfunction. Thus, PF could be a potential agent for the treatment of DN.

2017 update on the relationship between diabetes and colorectal cancer: epidemiology, potential molecular mechanisms and therapeutic implications

Worldwide deaths from diabetes mellitus (DM) and colorectal cancer increased by 90% and 57%, respectively, over the past 20 years. The risk of colorectal cancer was estimated to be 27% higher in patients with type 2 DM than in non-diabetic controls. However, there are potential confounders, information from lower income countries is scarce, across the globe there is no correlation between DM prevalence and colorectal cancer incidence and the association has evolved over time, suggesting the impact of additional environmental factors. The clinical relevance of these associations depends on understanding the mechanism involved. Although evidence is limited, insulin use has been associated with increased and metformin with decreased incidence of colorectal cancer. In addition, colorectal cancer shares some cellular and molecular pathways with diabetes target organ damage, exemplified by diabetic kidney disease. These include epithelial cell injury, activation of inflammation and Wnt/β-catenin pathways and iron homeostasis defects, among others. Indeed, some drugs have undergone clinical trials for both cancer and diabetic kidney disease. Genome-wide association studies have identified diabetes-associated genes (e.g. TCF7L2) that may also contribute to colorectal cancer. We review the epidemiological evidence, potential pathophysiological mechanisms and therapeutic implications of the association between DM and colorectal cancer. Further studies should clarify the worldwide association between DM and colorectal cancer, strengthen the biological plausibility of a cause-and-effect relationship through characterization of the molecular pathways involved, search for specific molecular signatures of colorectal cancer under diabetic conditions, and eventually explore DM-specific strategies to prevent or treat colorectal cancer.

Diabetic Nephropathy: Perspective on Novel Molecular Mechanisms

Diabetes mellitus (DM) is the major cause of end-stage renal disease (ESRD) globally, and novel treatments are urgently needed. Current therapeutic approaches for diabetic nephropathy (DN) are focussing on blood pressure control with inhibitors of the renin-angiotensin-aldosterone system, on glycaemic and lipid control, and life-style changes. In this review, we highlight new molecular insights aiding our understanding of the initiation and progression of DN, including glomerular insulin resistance, dysregulation of cellular substrate utilisation, podocyte-endothelial communication, and inhibition of tubular sodium coupled glucose reabsorption. We believe that these mechanisms offer new therapeutic targets that can be exploited to develop important renoprotective treatments for DN over the next decade.

Shikonin regulates C-MYC and GLUT1 expression through the MST1-YAP1-TEAD1 axis

The general mechanism underlying the tumor suppressor activity of the Hippo signaling pathway remains unclear. In this study, we explore the molecular mechanisms connecting the Hippo signaling pathway with glucose metabolism. We have found that two key regulators of glycolysis, C-MYC and GLUT1, are targets of the Hippo signaling pathway in human leukemia cells. Our results revealed that activation of MST1 by the natural compound shikonin inhibited the expression of GLUT1 and C-MYC. Furthermore, RNAi experiments confirmed the regulation of GLUT1 and C-MYC expression via the MST1-YAP1-TEAD1 axis. Surprisingly, YAP1 was found to positively regulate C-MYC mRNA levels in complex with TEAD1, while it negatively regulates C-MYC levels in cooperation with MST1. Hence, YAP1 serves as a rheostat for C-MYC, which is regulated by MST1. In addition, depletion of MST1 stimulates lactate production, whereas the specific depletion of TEAD1 has an opposite effect. The inhibition of lactate production and cellular proliferation induced by shikonin also depends on the Hippo pathway activity. Finally, a bioinformatic analysis revealed conserved TEAD-binding motifs in the C-MYC and GLUT1 promoters providing another molecular data supporting our observations. In summary, regulation of glucose metabolism could serve as a new tumor suppressor mechanism orchestrated by the Hippo signaling pathway.

Relationship between red cell distribution width and early renal injury in patients with gestational diabetes mellitus

Previous studies found that red cell distribution width was related to adverse cardiovascular events. However, few studies reported the relationship between red cell distribution width and early-stage renal injury in pregnant women with gestational diabetes mellitus. Using a cross-sectional design, 334 pregnant women with gestational diabetes mellitus were enrolled according to the criterion of inclusion and exclusion. Demographic and clinical examination data were collected. Depended on the urine albumin, study population were divided into case group (n = 118) and control group (n = 216). Compared with control group, the case group tend to be higher red cell distribution width level (13.6 ± 0.9 vs.12.5 ± 0.6, p < 0.001). The red cell distribution width was positively associated with albuminuria creatinine ratio (r = 0.567, p < 0.001). Multiple logistic regressions showed that red cell distribution width was still associated with early-stage renal injury after adjusting for many other potential cofounders. Compared with the first quartile, the risk ratio of the second, the third and the fourth quartile were 1.38 (95%CI: 1.06-1.80), 1.57 (95%CI: 1.21-2.97), 2.71 (95%CI: 2.08-3.54), respectively. Besides, systolic blood pressure, estimated glomerular filtration rate, uric acid and blood urea nitrogen were also significantly associated with renal injury in gestational diabetes mellitus patients. The elevated red cell distribution width level might be a predictor of early-stage renal injury in pregnant women with gestational diabetes mellitus. As an easy and routine examination index, red cell distribution width may provide better clinical guidance when combined with other important indices.

Sodium Glucose Cotransporter 2 (SGLT2) Plays as a Physiological Glucose Sensor and Regulates Cellular Contractility in Rat Mesangial Cells

PURPOSE

Mesangial cells play an important role in regulating glomerular filtration by altering their cellular tone. We report the presence of a sodium glucose cotransporter (SGLT) in rat mesangial cells. This study in rat mesangial cells aimed to evaluate the expression and role of SGLT2.

METHODS

The SGLT2 expression in rat mesangial cells was assessed by Western blotting and reverse transcription-polymerase chain reaction (RT-PCR). Changes in the mesangial cell surface area at different glucose concentrations and the effects of extracellular Na+ and Ca2+ and of SGLT and Na+/Ca2+ exchanger (NCX) inhibitors on cellular size were determined. The cellular sizes and the contractile response were examined during a 6-day incubation with high glucose with or without phlorizin, an SGLT inhibitor.

RESULTS

Western blotting revealed an SGLT2 band, and RT-PCR analysis of SGLT2 revealed the predicted 422-bp band in both rat mesangial and renal proximal tubular epithelial cells. The cell surface area changed according to the extracellular glucose concentration. The glucose-induced contraction was abolished by the absence of either extracellular Na+ or Ca2+ and by SGLT and NCX inhibitors. Under the high glucose condition, the cell size decreased for 2 days and increased afterwards; these cells did not contract in response to angiotensin II, and the SGLT inhibitor restored the abolished contraction.

CONCLUSIONS

These data suggest that SGLT2 is expressed in rat mesangial cells, acts as a normal physiological glucose sensor and regulates cellular contractility in rat mesangial cells.

Preventive Effect of Salicylate and Pyridoxamine on Diabetic Nephropathy

Objective. Diabetic nephropathy is a life-threatening complication in patients with long-standing diabetes. Hemodynamic, inflammatory, and metabolic factors are considered as developmental factors for diabetic nephropathy. In this study, we evaluated whether pharmacological interventions with salicylate, compared to pyridoxamine, could prevent diabetic nephropathy in mice. Methods. Male mice overexpressing inducible nitric oxide synthase in pancreatic β-cells were employed as a diabetic model. Salicylate (3 g/kg diet) or pyridoxamine (1 g/L drinking water; ~200 mg/kg/day) was given for 16 weeks to assess the development of diabetic nephropathy. Treatment with long-acting insulin (Levemir 2 units/kg twice a day) was used as a control. Results. Although higher blood glucose levels were not significantly affected by pyridoxamine, early to late stage indices of nephropathy were attenuated, including kidney enlargement, albuminuria, and increased serum creatinine, glomerulosclerosis, and inflammatory and profibrotic gene expressions. Salicylate showed beneficial effects on diabetic nephropathy similar to those of pyridoxamine, which include lowering blood glucose levels and inhibiting macrophage infiltration into the kidneys. Attenuation of macrophage infiltration into the kidneys and upregulation of antiglycating enzyme glyoxalase 1 gene expression were found only in the salicylate treatment group. Conclusions. Treatment with salicylate and pyridoxamine could prevent the development of diabetic nephropathy in mice and, therefore, would be a potentially useful therapeutic strategy against kidney problems in patients with diabetes.

Diabetic nephropathy: What does the future hold?

The consensus management of diabetic nephropathy (DN) in 2015 involves good control of glycaemia, dyslipidaemia and blood pressure (BP). Blockade of the renin-angiotensin-aldosterone system using angiotensin-converting enzyme inhibitors, angiotensin-2 receptor blockers or mineralocorticoid inhibitors are key therapeutic approaches, shown to be beneficial once overt nephropathy is manifest, as either, or both, of albuminuria and loss of glomerular filtration rate. Some significant additional clinical benefits in slowing the progression of DN was reported from the Remission clinic experience, where simultaneous intensive control of BP, tight glycaemic control, weight loss, exercise and smoking cessation were prioritised in the management of DN. This has not proved possible to translate to more conventional clinical settings. This review briefly looks over the history and limitations of current therapy from landmark papers and expert reviews, and following an extensive PubMed search identifies the most promising clinical biomarkers (both established and proposed). Many challenges need to be addressed urgently as in order to obtain novel therapies in the clinic; we also need to examine what we mean by remission, stability and progression of DN in the modern era.

Cyclic mechanical stretch promotes energy metabolism in osteoblast-like cells through an mTOR signaling-associated mechanism

Energy metabolism is essential for maintaining function and substance metabolism in osteoblasts. However, the role of cyclic stretch in regulating osteoblastic energy metabolism and the underlying mechanisms remain poorly understood. In this study, we found that cyclic stretch (10% elongation at 0.1 Hz) significantly enhanced glucose consumption, lactate levels (determined using a glucose/lactate assay kit), intracellular adenosine triphosphate (ATP) levels (quantified using rLuciferase/Luciferin reagent) and the mRNA expression of energy metabolism-related enzymes [mitochondrial ATP synthase, L-lactate dehydrogenase A (LDHA) and enolase 1; measured by RT-qPCR], and increased the phosphorylation levels of Akt, mammalian target of rapamycin (mTOR) and p70s6k (measured by western blot analysis) in human osteoblast‑like MG‑63 cells. Furthermore, the inhibition of Akt or mTOR with an antagonist (wortmannin or rapamycin) suppressed the stretch-induced increase in glucose consumption, lactate levels, intracellular ATP levels and the expression of mitochondrial ATP synthase and LDHA, indicating the significance of the Akt/mTOR/p70s6k pathway in regulating osteoblastic energy metabolism in response to mechanical stretch. Thus, we concluded that cyclic stretch regulates energy metabolism in MG‑63 cells partially through the Akt/mTOR/p70s6k signaling pathway. The present findings provide novel insight into osteoblastic mechanobiology from the perspective of energy metabolism.

Beat it early: putative renoprotective haemodynamic effects of oral hypoglycaemic agents

Diabetic kidney disease represents a considerable burden; around one-third of patients with type 2 diabetes develop chronic kidney disease. In health, the kidneys play an important role in the regulation of glucose homeostasis via glucose utilization, gluconeogenesis and glucose reabsorption. In patients with diabetes, renal glucose homeostasis is significantly altered with an increase in both gluconeogenesis and renal tubular reabsorption of glucose. Environmental factors, both metabolic (hyperglycaemia, obesity and dyslipidaemia) and haemodynamic, together with a genetic susceptibility, lead to the activation of pro-oxidative, pro-inflammatory and pro-fibrotic pathways resulting in kidney damage. Hyperfiltration and its haemodynamic-driven insult to the kidney glomeruli is an important player in proteinuria and progression of kidney disease towards end-stage renal failure. Control of glycaemia and blood pressure are the mainstays to prevent kidney damage and slow its progression. There is emerging evidence that some hypoglycaemic agents may have renoprotective effects which are independent of their glucose-lowering effects. Sodium-glucose co-transporter-2 (SGLT-2) inhibitors may exert a renoprotective effect by a number of mechanisms including restoring the tubuloglomerular feedback mechanism and lowering glomerular hyperfiltration, reducing inflammatory and fibrotic markers induced by hyperglycaemia thus limiting renal damage. Simultaneous use of an SGLT-2 inhibitor and blockade of the renin-angiotensin-aldosterone system may be a strategy to slow progression of diabetic nephropathy more than either drug alone. The use of dipeptidyl peptidase-4 inhibitors and glucagon-like peptide 1 receptor agonists may exert a renoprotective effect by reducing inflammation, fibrosis and blood pressure. Given the burden of diabetic kidney disease, any additional renoprotective benefit with hypoglycaemic therapy is to be welcomed. Large randomized controlled trials are currently underway investigating if these new anti-diabetic agents can provide renoprotection in diabetes.

Diabetes mellitus, a complex and heterogeneous disease, and the role of insulin resistance as a determinant of diabetic kidney disease

Diabetes mellitus (DM) is increasingly recognized as a heterogeneous condition. The individualization of care and treatment necessitates an understanding of the individual patient's pathophysiology of DM that underpins their DM classification and clinical presentation. Classical type-2 diabetes mellitus is due to a combination of insulin resistance and an insulin secretory defect. Type-1 diabetes is characterized by a near-absolute deficiency of insulin secretion. More recently, advances in genetics and a better appreciation of the atypical features of DM has resulted in more categories of diabetes. In the context of kidney disease, patients with DM and microalbuminuria are more insulin resistant, and insulin resistance may be a pathway that results in accelerated progression of diabetic kidney disease. This review summarizes the updated classification of DM, including more rarer categories and their associated renal manifestations that need to be considered in patients who present with atypical features. The benefits and limitations of the tests utilized to make a diagnosis of DM are discussed. We also review the putative pathways and mechanisms by which insulin resistance drives the progression of diabetic kidney disease.

The effects of transdermal insulin treatment of streptozotocin-induced diabetic rats on kidney function and renal expression of glucose transporters

The tight glycemic control required to attenuate chronic complications in type 1 diabetes mellitus requires multiple daily injections of bolus insulin which cause hyperinsulinemic edema and hypertension due to Na(+) retention. Reports indicate that pectin insulin (PI)-containing dermal patches sustain controlled insulin release into the bloodstream of streptozotocin (STZ)-induced diabetic rats. This study investigated whether PI dermal patches can improve the impaired renal function in diabetes. PI patches were prepared by dissolving pectin/insulin in deionized water and solidified with CaCl(2). Short-term (five weeks) effects of thrice daily treatments with PI patches on renal function and urinary glucose outputs were assessed in diabetic animals. Blood and kidney samples were collected after five weeks for measurements of selected biochemical parameters. Blood was also collected for insulin measurement 6 h following treatments. The low plasma insulin concentrations exhibited by STZ-induced diabetic rats were elevated by the application of insulin-containing dermal patches to levels comparable with control non-diabetic rats. Untreated STZ-induced diabetic rats exhibited elevated urinary glucose, K(+) outputs and depressed urinary Na(+) outputs throughout the 5-week period. Treatment with PI dermal patches increased urinary Na(+) output and reduced urine flow, urinary glucose and K(+) excretion rates in weeks 4 and 5. PI dermal patches increased GFR of diabetic rats with concomitant reduction of plasma creatinine concentrations. Transdermal insulin treatment also decreased the renal expressions of GLUT1 and SGLT1 of STZ-induced diabetic rats. We conclude that PI dermal patches deliver physiologically relevant amounts of insulin that can improve kidney function in diabetes.