Longitudinal Changes in Measured Glomerular Filtration Rate, Renal Fibrosis and Biomarkers in a Rat Model of Type 2 Diabetic Nephropathy

Fucoidan Improves Early Stage Diabetic Nephropathy via the Gut Microbiota-Mitochondria Axis in High-Fat Diet-Induced Diabetic Mice

Diabetic nephropathy (DN) is a common microvascular complication of diabetes. Fucoidan, a polysaccharide containing fucose and sulfate group, ameliorates DN. However, the underlying mechanism has not been fully understood. This study aimed to explore the effects and mechanism of fucoidan on DN in high-fat diet-induced diabetic mice. A total of 90 C57BL/6J mice were randomly assigned to six groups (n = 15) as follows: normal control (NC), diabetes mellitus (DM), metformin (MTF), low-dose fucoidan (LFC), medium-dose fucoidan (MFC), and high-dose fucoidan (HFC). A technique based on fluorescein isothiocyanate (FITC-sinistin) elimination kinetics measured percutaneously was applied to determine the glomerular filtration rate (GFR). After 24 weeks, the mice were sacrificed and an early stage DN model was confirmed by GFR hyperfiltration, elevated urinary creatinine, normal urinary albumin, tubulointerstitial fibrosis, and glomerular hypertrophy. Fucoidan significantly improved the GFR hyperfiltration and renal fibrosis. An enriched SCFAs-producing bacteria and increased acetic concentration in cecum contents were found in fucoidan groups, as well as increased renal ATP levels and improved mitochondrial dysfunction. The renal inflammation and fibrosis were ameliorated through inhibiting the MAPKs pathway. In conclusion, fucoidan improved early stage DN targeting the microbiota-mitochondria axis by ameliorating mitochondrial oxidative stress and inhibiting the MAPKs pathway.

The current state of preclinical modeling of human diabetic cardiomyopathy using rodents

The prevalence of diabetic cardiomyopathy (DCM), a specific cardiovascular complication of diabetes mellitus, has recently increased. Its pathogenesis is not fully understood, and no consensus regarding therapeutic options has been reached. Experimental studies on rodents are expected to yield further data at the preclinical stage. The present paper describes and quantitatively compares the experimental protocols intended to mimic human DCM. Experimental articles (conducted between 1990 and 2022) were identified from online electronic databases according to the PRISMA Protocol. The Cochrane Q-test was used to estimate study heterogeneity; the quality of each individual study was assessed using SYRCLE's risk of bias tool for animal studies. Sensitivity analysis was performed according to the leave-one-out method. Publication bias across studies was assessed using Egger's weighted regression and Duval and Tweedie 'trim and fill' method. A wide spectrum of protocols - from 651 papers, was examined (type 1 or 2 diabetes mellitus, as well as obesity models). They were found to vary in their presentation of DCM according to a variety of hemodynamic, echocardiographic, histopathologic and metabolic parameters. Particular attention was paid to comorbid conditions, and cardiac performance featured as systolic, diastolic dysfunction, or refractory heart failure. The majority of models displayed diastolic dysfunction, as well as myocardial fibrosis and left ventricle hypertrophy, which mimics early stage DCM. Unlike in humans, animal DCM rarely progressed to the symptomatic heart failure with reduced ejection fraction (HFrEF). The ability of individual procedures to reflect refractory heart failure or biventricular dysfunction - in the end-stage DCM has remained unclear.

Rodent models to study type 1 and type 2 diabetes induced human diabetic nephropathy

INTRODUCTION

Diabetic nephropathy (DN), an outcome of prolonged diabetes, has affected millions of people worldwide and every year the incidence and prevalence increase substantially. The symptoms may start with mild manifestations of the disease such as increased albuminuria, serum creatinine levels, thickening of glomerular basement membrane, expansion of mesangial matrix to severe pathological symptoms such as glomerular lesions and tubulointerstitial fibrosis which may further proceed to cardiovascular dysfunction or end-stage renal disease.

PERSPECTIVE

Numerous therapeutic interventions are being explored for the management of DN, however, these interventions do not completely halt the progression of this disease and hence animal models are being explored to identify critical genetic and molecular parameters which could help in tackling the disease. Rodent models which mostly include mice and rats are commonly used experimental animals which provide a wide range of advantages in understanding the onset and progression of disease in humans and also their response to a wide range of interventions helps in the development of effective therapeutics. Rodent models of type 1 and type 2 diabetes induced DN have been developed utilizing different platforms and interventions during the last few decades some of which mimic various stages of diabetes ranging from early to later stages. However, a rodent model which replicates all the features of human DN is still lacking. This review tries to evaluate the rodent models that are currently available and understand their features and limitations which may help in further development of more robust models of human DN.

CONCLUSION

Using these rodent models can help to understand different aspects of human DN although further research is required to develop more robust models utilizing diverse genetic platforms which may, in turn, assist in developing effective interventions to target the disease at different levels.

Transcutaneous measurement of renal function in two rodent models of obstructive nephropathy

OBJECTIVE

Glomerular filtration rate (GFR) is a key indicator of renal function. In both clinical practice and pre-clinical research, serum levels of endogenous filtration markers, such as creatinine, are often used to estimate GFR. However, these markers often do not reflect minor changes in renal function. In this study, we therefore set out to evaluate the applicability of transcutaneous GFR (tGFR) measurements to monitor the changes in renal function, as compared to plasma creatinine (pCreatinine), in two models of obstructive nephropathy, namely unilateral ureteral obstruction (UUO) or bilateral ureteral obstruction followed by release (BUO-R) in male Wistar rats.

RESULTS

UUO animals showed a significant reduction in tGFR compared to baseline; whereas pCreatinine levels were not significantly changed. In BUO animals, tGFR drops 24 h post BUO and remains lower upon release of the obstruction until day 11. Concomitantly, pCreatinine levels were also increased 24 h after obstruction and 24 h post release, however after 4 days, pCreatinine returned to baseline levels. In conclusion, this study revealed that the tGFR method is superior at detecting minor changes in renal function as compared to pCreatinine measurements.

Transdermal Measurement of Glomerular Filtration Rate in Preclinical Research

The measurement of glomerular filtration rate (GFR) is essential to understanding renal physiology, including the monitoring of disease progression and treatment effectiveness. Transdermal measurement of glomerular filtration rate (tGFR) using a miniaturized fluorescence monitor in combination with a fluorescent exogenous GFR tracer has become a common technique to measure GFR in the preclinical setting, especially in rodent models. It allows for close to real-time measurement of GFR in conscious unrestrained animals and overcomes several limitations of other GFR measures. Its widespread use is reflected by published research articles and conference abstracts from different research fields, including in the assessment of new and existing kidney therapeutics, evaluation of nephrotoxicity, screening of novel chemical or medical agents, and fundamental understanding of kidney function.

Methods for Assessment of the Glomerular Filtration Rate in Laboratory Animals

BACKGROUND

The glomerular filtration rate (GFR), as the benchmark of renal function, has been widely used in clinical practice and basic medical research. Currently, most researchers still rely on endogenous markers, such as plasma creatinine, blood urea nitrogen, and cystatin C, to evaluate renal function in laboratory animals. While inexpensive and simple to use, methods based on endogenous markers are often inaccurate and susceptible to several internal physiological factors. Thus, it is necessary to establish a method to precisely assess the GFR, especially when detecting early changes in GFR during acute kidney injury, and hyperfiltration usually caused by pregnancy or diabetic nephropathy. In addition, laboratory animals have higher tolerance for invasive procedures than humans, allowing novel technologies to be applied on them for GFR monitoring. In recent years, significant progress has been made in developing new methods to assess GFR in animals. However, no publication has reviewed these techniques.

SUMMARY

This article summarized the majority of methods used to assess the GFR in animals in recent decades and discussed their working principles, workflows, advantages, and limitations, providing a wealth of reference and information for researchers interested in studying the kidney function in animals and developing techniques to monitor the GFR.

Effects of soluble guanylate cyclase stimulator on renal function in ZSF-1 model of diabetic nephropathy

BACKGROUND

Diabetic nephropathy is associated with endothelial dysfunction and oxidative stress, in which the nitric oxide-soluble guanylate cyclase-cyclic guanosine monophosphate (NO-sGC-cGMP) signaling pathway is impaired. We hypothesize that sGC stimulator Compound 1 can enhance NO signaling, reduce proteinuria in a diabetic nephropathy preclinical model with diminished NO bioavailability and increased oxidized sGC. Therefore, we evaluated the effect of sGC stimulator Compound 1 on the renal effect in obese ZSF1 (ZSF1 OB) rats.

MATERIALS AND METHODS

The sGC stimulator Compound 1, the standard of care agent Enalapril, and a combination of Compound 1 and Enalapril were administered chronically to obese ZSF1 rats for 6 months. Mean arterial pressure, heart rate, creatinine clearance for glomerular filtration rate (eGFR), urinary protein excretion to creatinine ratio (UPCR), and urinary albumin excretion ratio (UACR) were determined during the study. The histopathology of glomerular and interstitial lesions was assessed at the completion of the study.

RESULTS

While both Compound 1 and Enalapril significantly reduced blood pressure, the combination of Compound 1 and Enalapril normalized blood pressure levels. Compound 1 improved eGFR and reduced UPCR and UACR. A combination of Enalapril and Compound 1 resulted in a marked reduction in UPCR and UACR and improved GFR.

CONCLUSION

The sGC stimulator Compound 1 as a monotherapy slowed renal disease progression, and a combination of the sGC stimulator with Enalapril provided greater renal protection in a rodent model of diabetic nephropathy.

The Correlation between Microalbuminuria and Thyroid Nodules in Type 2 Diabetic Mellitus

OBJECTIVE

To investigate the correlation between thyroid nodules and microalbuminuria in type 2 diabetic mellitus.

METHODS

A total of 270 patients with type 2 diabetes at Tongzhou Branch of Dongzhimen Hospital were enrolled in this retrospective study. Data were collected from the inpatient electronic files between January 2018 and January 2020. The laboratory indexes of the two groups (thyroid nodule group with 172 cases and control group including 98 cases without thyroid nodules) were statistically analyzed by binomial logistic regression analysis and Spearman correlation analysis.

RESULTS

The proportion of microalbuminuria (MAU) in the thyroid nodule group was larger than that in the control group. Age, serum TT4, and FT4 in the thyroid nodule group were significantly higher compared with the control group. The binary logistic regression analysis indicated that age, sex, FT4, and MAU were the risk factors for thyroid nodule in T2DM patients. Spearman correlation analysis showed that the thyroid nodule was significantly positively correlated with MAU, age, FT4, and TT4.

CONCLUSIONS

MAU might be an independent risk factor for thyroid nodule in type 2 diabetic mellitus.

Multitarget molecule, PTUPB, to treat diabetic nephropathy in rats

BACKGROUND AND PURPOSE

Diabetic nephropathy is a common complications related to high morbidity and mortality in type 2 diabetes. We investigated the action of the dual modulator, PTUPB, a soluble epoxide hydrolase and cyclooxygenase-2 inhibitor against diabetic nephropathy.

EXPERIMENTAL APPROACH

Sixteen-week-old type 2 diabetic and proteinuric obese ZSF1 rats were treated with vehicle, PTUPB or enalapril for 8 weeks. Measurements were made of epoxyeicosatrienoic acids, thromboxane B2 (TBX2 ) and prostaglandin E2 (PGE2 ) in the kidney of these and lean ZSF1 rats along with their blood pressure.

KEY RESULT

Obese ZSF1 rats were diabetic with fivefold higher fasting blood glucose levels and markedly higher HbA1c levels compared with lean ZSF1 rats. PTUPB nor enalapril reduced fasting blood glucose or HbA1c but alleviated the development of diabetic nephropathy. In PTUPB-treated obese ZSF1 rats, glomerular nephrin expression was preserved. Enalapril also alleviated diabetic nephropathy. Diabetic renal injury in obese ZSF1 rats was accompanied by renal inflammation with six to sevenfold higher urinary MCP-1 (CCR2) level and renal infiltration of CD-68 positive cells. PTUPB and enalapril significantly reduced urinary MCP-1 levels and renal mRNA expression of cytokines. Both PTUPB and enalapril lowered blood pressure. PTUPB but not enalapril decreased hyperlipidaemia and liver injury in obese ZSF1 rats.

CONCLUSION AND IMPLICATIONS

Overall, the dual modulator PTUPB does not treat hyperglycaemia but can effectively alleviate hypertension, diabetic nephropathy, hyperlipidaemia and liver injury in type 2 diabetic rats. Our data further demonstrate that the renal actions of PTUPB are comparable with a current standard diabetic nephropathy treatment.

Urinary miRNA Biomarkers of Drug-Induced Kidney Injury and Their Site Specificity Within the Nephron

Drug-induced kidney injury (DIKI) is a major concern in both drug development and clinical practice. There is an unmet need for biomarkers of glomerular damage and more distal renal injury in the loop of Henle and the collecting duct (CD). A cross-laboratory program to identify and characterize urinary microRNA (miRNA) patterns reflecting tissue- or pathology-specific DIKI was conducted. The overall goal was to propose miRNA biomarker candidates for DIKI that could supplement information provided by protein kidney biomarkers in urine. Rats were treated with nephrotoxicants causing injury to distinct nephron segments: the glomerulus, proximal tubule, thick ascending limb (TAL) of the loop of Henle and CD. Meta-analysis identified miR-192-5p as a potential proximal tubule-specific urinary miRNA candidate. This result was supported by data obtained in laser capture microdissection nephron segments showing that miR-192-5p expression was enriched in the proximal tubule. Discriminative miRNAs including miR-221-3p and -222-3p were increased in urine from rats treated with TAL versus proximal tubule toxicants in accordance with their expression localization in the kidney. Urinary miR-210-3p increased up to 40-fold upon treatment with TAL toxicants and was also enriched in laser capture microdissection samples containing TAL and/or CD versus proximal tubule. miR-23a-3p was enriched in the glomerulus and was increased in urine from rats treated with doxorubicin, a glomerular toxicant, but not with toxicants affecting other nephron segments. Taken together these results suggest that urinary miRNA panels sourced from specific nephron regions may be useful to discriminate the pathology of toxicant-induced lesions in the kidney, thereby contributing to DIKI biomarker development needs for industry, clinical, and regulatory use.

A small-molecule inhibitor of hypoxia-inducible factor prolyl hydroxylase improves obesity, nephropathy and cardiomyopathy in obese ZSF1 rats

Prolyl hydroxylase (PH) enzymes control the degradation of hypoxia-inducible factor (HIF), a transcription factor known to regulate erythropoiesis, angiogenesis, glucose metabolism, cell proliferation, and apoptosis. HIF-PH inhibitors (HIF-PHIs) correct anemia in patients with renal disease and in animal models of anemia and kidney disease. However, the effects of HIF-PHIs on comorbidities associated with kidney disease remain largely unknown. We evaluated the effects of the HIF-PHI FG-2216 in obese ZSF1 (Ob-ZSF1) rats, an established model of kidney failure with metabolic syndrome. Following unilateral nephrectomy (Nx) at 8 weeks of age, rats were treated with 40 mg/kg FG-2216 or vehicle by oral gavage three times per week for up to 18 weeks. FG-2216 corrected blood hemoglobin levels and improved kidney function and histopathology in Nx-Ob-ZSF1 rats by increasing the glomerular filtration rate, decreasing proteinuria, and reducing peritubular fibrosis, tubular damage, glomerulosclerosis and mesangial expansion. FG-2216 increased renal glucose excretion and decreased body weight, fat pad weight, and serum cholesterol in Nx-Ob-ZSF1 rats. Additionally, FG-2216 corrected hypertension, improved diastolic and systolic heart function, and reduced cardiac hypertrophy and fibrosis. In conclusion, the HIF-PHI FG-2216 improved renal and cardiovascular outcomes, and reduced obesity in a rat model of kidney disease with metabolic syndrome. Thus, in addition to correcting anemia, HIF-PHIs may provide renal and cardiac protection to patients suffering from kidney disease with metabolic syndrome.

A systematic review and meta-analysis of cell-based interventions in experimental diabetic kidney disease

Regenerative, cell‐based therapy is a promising treatment option for diabetic kidney disease (DKD), which has no cure. To prepare for clinical translation, this systematic review and meta‐analysis summarized the effect of cell‐based interventions in DKD animal models and treatment‐related factors modifying outcomes. Electronic databases were searched for original investigations applying cell‐based therapy in diabetic animals with kidney endpoints (January 1998‐May 2019). Weighted or standardized mean differences were estimated for kidney outcomes and pooled using random‐effects models. Subgroup analyses tested treatment‐related factor effects for outcomes (creatinine, urea, urine protein, fibrosis, and inflammation). In 40 studies (992 diabetic rodents), therapy included mesenchymal stem/stromal cells (MSC; 61%), umbilical cord/amniotic fluid cells (UC/AF; 15%), non‐MSC (15%), and cell‐derived products (13%). Tissue sources included bone marrow (BM; 65%), UC/AF (15%), adipose (9%), and others (11%). Cell‐based therapy significantly improved kidney function while reducing injury markers (proteinuria, histology, fibrosis, inflammation, apoptosis, epithelial‐mesenchymal‐transition, oxidative stress). Preconditioning, xenotransplantation, and disease‐source approaches were effective. MSC and UC/AF cells had greater effect on kidney function while cell products improved fibrosis. BM and UC/AF tissue sources more effectively improved kidney function and proteinuria vs adipose or other tissues. Cell dose, frequency, and administration route also imparted different benefits. In conclusion, cell‐based interventions in diabetic animals improved kidney function and reduced injury with treatment‐related factors modifying these effects. These findings may aid in development of optimal repair strategies through selective use of cells/products, tissue sources, and dose administrations to allow for successful adaptation of this novel therapeutic in human DKD.

Protective effects of quercetin and crocin in the kidneys and liver of obese Sprague-Dawley rats with Type 2 diabetes: Effects of quercetin and crocin on T2DM rats

Quercetin and crocin are the main active constituents of Eucommia and Gardenia species, respectively. This study was conducted to explore the effects of quercetin and crocin on fat reduction and renal fibrosis and the relationship of these compounds with autophagy. First, a model of high-fat diet- and streptozotocin-induced type 2 diabetes was established and then subjected model animals to 8 weeks of metformin, quercetin and crocin gavage. Then, a high glucose-induced rat mesangial cells (RMCs) model was established, and these cells were cocultured with quercetin and crocin. The results showed that quercetin and crocin can decrease fasting blood glucose levels, reduce fat accumulation in the liver, alleviate renal fibrosis, and reduce blood lipid levels. Quercetin and crocin increased autophagy-related protein (LC3, Atg5, Beclin-1 and p-AMPK) levels in the liver and decreased autophagy-related protein (LC3, Atg5, Beclin-1 and p-AMPK) levels in the kidneys. Moreover, quercetin and crocin inhibited the excessive proliferation of RMCs induced by high-glucose (HG) conditions, decreased autophagy-related protein (LC3, Atg5, Beclin-1 and p-AMPK) levels, and decreased TGF-β1 expression. Importantly, cotreatment with quercetin and crocin had a more significant effect than treatment with either compound alone. These results suggest that combined administration of quercetin and crocin can more significantly reduce blood glucose/lipid levels and improve renal fibrosis than administration of either compound alone and that AMPK-dependent autophagy might be involved in this process. Eucommia ulmoides Oliv. and Gardenia could be developed as drugs for Type 2 diabetes treatment.

Triantennary GalNAc Molecular Imaging Probes for Monitoring Hepatocyte Function in a Rat Model of Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a progressive form of nonalcoholic fatty liver disease that can lead to irreversible liver cirrhosis and cancer. Early diagnosis of NASH is vital to detect disease before it becomes life-threatening, yet noninvasively differentiating NASH from simple steatosis is challenging. Herein, bifunctional probes have been developed that target the hepatocyte-specific asialoglycoprotein receptor (ASGPR), the expression of which decreases during NASH progression. The results show that the probes allow longitudinal, noninvasive monitoring of ASGPR levels by positron emission tomography in the newly developed rat model of NASH. The probes open new possibilities for research into early diagnosis of NASH and development of drugs to slow or reverse its progression.

The Novel Phosphate and Bile Acid Sequestrant Polymer SAR442357 Delays Disease Progression in a Rat Model of Diabetic Nephropathy

As a gut-restricted, nonabsorbed therapy, polymeric bile acid sequestrants (BAS) play an important role in managing hyperlipidemia and hyperglycemia. Similarly, nonabsorbable sequestrants of dietary phosphate have been used for the management of hyperphosphatemia in end-stage renal disease. To evaluate the potential utility of such polymer sequestrants to treat type 2 diabetes (T2D) and its associated renal and cardiovascular complications, we synthesized a novel polymeric sequestrant, SAR442357, possessing optimized bile acid (BA) and phosphate sequestration characteristics. Long-term treatment of T2D obese ^cZucker fatty/Spontaneously hypertensive heart failure F1 hybrid (ZSF1) with SAR442357 resulted in enhanced sequestration of BAs and phosphate in the gut, improved glycemic control, lowering of serum cholesterol, and attenuation of diabetic kidney disease (DKD) progression. In comparison, colesevelam, a BAS with poor phosphate binding properties, did not prevent DKD progression, whereas losartan, an angiotensin II receptor blocker that is widely used to treat DKD, showed no effect on hyperglycemia. Analysis of hepatic gene expression levels of the animals treated with SAR442357 revealed upregulation of genes responsible for the biosynthesis of cholesterol and BAs, providing clear evidence of target engagement and mode of action of the new sequestrant. Additional hepatic gene expression pathway changes were indicative of an interruption of the enterohepatic BA cycle. Histopathological analysis of ZSF1 rat kidneys treated with SAR442357 further supported its nephroprotective properties. Collectively, these findings reveal the pharmacological benefit of simultaneous sequestration of BAs and phosphate in treating T2D and its associated comorbidities and cardiovascular complications. SIGNIFICANCE STATEMENT: A new nonabsorbed polymeric sequestrant with optimum phosphate and bile salt sequestration properties was developed as a treatment option for DKD. The new polymeric sequestrant offered combined pharmacological benefits including glucose regulation, lipid lowering, and attenuation of DKD progression in a single therapeutic agent.

Treatment With Treprostinil and Metformin Normalizes Hyperglycemia and Improves Cardiac Function in Pulmonary Hypertension Associated With Heart Failure With Preserved Ejection Fraction

OBJECTIVE

Pulmonary hypertension (PH) due to left heart disease (group 2), especially in the setting of heart failure with preserved ejection fraction (HFpEF), is the most common cause of PH worldwide; however, at present, there is no proven effective therapy available for its treatment. PH-HFpEF is associated with insulin resistance and features of metabolic syndrome. The stable prostacyclin analog, treprostinil, is an effective and widely used Food and Drug Administration-approved drug for the treatment of pulmonary arterial hypertension. While the effect of treprostinil on metabolic syndrome is unknown, a recent study suggests that the prostacyclin analog beraprost can improve glucose intolerance and insulin sensitivity. We sought to evaluate the effectiveness of treprostinil in the treatment of metabolic syndrome-associated PH-HFpEF. Approach and Results: Treprostinil treatment was given to mice with mild metabolic syndrome-associated PH-HFpEF induced by high-fat diet and to SU5416/obese ZSF1 rats, a model created by the treatment of rats with a more profound metabolic syndrome due to double leptin receptor defect (obese ZSF1) with a vascular endothelial growth factor receptor blocker SU5416. In high-fat diet-exposed mice, chronic treatment with treprostinil reduced hyperglycemia and pulmonary hypertension. In SU5416/Obese ZSF1 rats, treprostinil improved hyperglycemia with similar efficacy to that of metformin (a first-line drug for type 2 diabetes mellitus); the glucose-lowering effect of treprostinil was further potentiated by the combined treatment with metformin. Early treatment with treprostinil in SU5416/Obese ZSF1 rats lowered pulmonary pressures, and a late treatment with treprostinil together with metformin improved pulmonary artery acceleration time to ejection time ratio and tricuspid annular plane systolic excursion with AMPK (AMP-activated protein kinase) activation in skeletal muscle and the right ventricle.

CONCLUSIONS

Our data suggest a potential use of treprostinil as an early treatment for mild metabolic syndrome-associated PH-HFpEF and that combined treatment with treprostinil and metformin may improve hyperglycemia and cardiac function in a more severe disease.

Both male and female obese ZSF1 rats develop cardiac dysfunction in obesity-induced heart failure with preserved ejection fraction

Heart failure with a preserved ejection fraction (HFpEF) is associated with multiple comorbidities, such as old age, hypertension, type 2 diabetes and obesity and is more prevalent in females. Although the male obese ZSF1 rat has been proposed as a suitable model to study the development of diastolic dysfunction and early HFpEF, studies in female animals have not been performed yet. Therefore, we aimed to characterize the cardiac phenotype in female obese ZSF1 rats and their lean counterparts. Additionally, we aimed to investigate whether differences exist in disease progression in obese male and female ZSF1 rats. Therefore, male and female ZSF1 rats, lean as well as obese (N = 6-9/subgroup), were used. Every two weeks, from 12 to 26 weeks of age, systolic blood pressure and echocardiographic measurements were performed, and venous blood was sampled. Female obese ZSF1 rats, as compared to female lean ZSF1 rats, developed diastolic dysfunction with cardiac hypertrophy and fibrosis in the presence of severe dyslipidemia, increased plasma growth differentiation factor 15 and mild hypertension, and preservation of systolic function. Although obese female ZSF1 rats did not develop hyperglycemia, their diastolic dysfunction was as severe as in the obese males. Taken together, the results from the present study suggest that the female obese ZSF1 rat is a relevant animal model for HFpEF with multiple comorbidities, suitable for investigating novel therapeutic interventions.

Intraglomerular Monocyte/Macrophage Infiltration and Macrophage-Myofibroblast Transition during Diabetic Nephropathy Is Regulated by the A2B Adenosine Receptor

Diabetic nephropathy (DN) is considered the main cause of kidney disease in which myofibroblasts lead to renal fibrosis. Macrophages were recently identified as the major source of myofibroblasts in a process known as macrophage–myofibroblast transition (MMT). Adenosine levels increase during DN and in vivo administration of MRS1754, an antagonist of the A_2B adenosine receptor (A_2BAR), attenuated glomerular fibrosis (glomerulosclerosis). We aimed to investigate the association between A_2BAR and MMT in glomerulosclerosis during DN. Kidneys/glomeruli of non-diabetic, diabetic, and MRS1754-treated diabetic (DM+MRS1754) rats were processed for histopathologic, transcriptomic, flow cytometry, and cellular in vitro analyses. Macrophages were used for in vitro cell migration/transmigration assays and MMT studies. In vivo MRS1754 treatment attenuated the clinical and histopathological signs of glomerulosclerosis in DN rats. Transcriptomic analysis demonstrated a decrease in chemokine-chemoattractants/cell-adhesion genes of monocytes/macrophages in DM+MRS1754 glomeruli. The number of intraglomerular infiltrated macrophages and MMT cells increased in diabetic rats. This was reverted by MRS1754 treatment. In vitro cell migration/transmigration decreased in macrophages treated with MRS1754. Human macrophages cultured with adenosine and/or TGF-β induced MMT, a process which was reduced by MRS1754. We concluded that pharmacologic blockade of A_2BAR attenuated some clinical signs of renal dysfunction and glomerulosclerosis, and decreased intraglomerular macrophage infiltration and MMT in DN rats.

Validation of non-invasive transcutaneous measurement for glomerular filtration rate in lean and obese C57BL/6J mice

AIM

The measurement of glomerular filtration rate (GFR) in experimental rodents is pivotal to understanding the progression of kidney disease and benefits of treatment strategies. A non-invasive clearance device has been developed, which measures transcutaneous decay of injected FITC-sinistrin in conscious rodents. The technique was validated against the well-established plasma clearance method in the same mice, but on consecutive days, using only models of uninephrectomy and polycystic kidney disease. We aimed to validate this widely used technique in the same lean or obese mice, at the same time.

METHODS

Five-week-old male C57BL/6J mice were randomised to a high fat diet (n = 12) or normal diet (n = 11) for 10 weeks. Transcutaneous and plasma clearance of FITC-sinistrin were measured simultaneously in each mouse.

RESULTS

In lean mice, there was a positive correlation between transcutaneous and plasma derived GFR (P < .01, R² = .704), although there was an approximate 40% underestimation by the transcutaneous method (P < .0001). In obese mice, no correlation was observed between transcutaneous and plasma derived GFR, nor elimination half-life which removes any effect of the conversion factor and injected dose. The limits of agreement in a Bland-Altman plot were narrower when we used new conversion factors derived from mice in the current study and, in lean mice, a generic conversion factor which assumes 20% extracellular volume.

CONCLUSION

The non-invasive clearance device may be useful for serial GFR measurements in lean and healthy mice, provided validation studies have been carried out, but its utility in obesity requires further study.

Diet-Induced Rodent Models of Diabetic Peripheral Neuropathy, Retinopathy and Nephropathy

Unhealthy dietary habits are major modifiable risk factors for the development of type 2 diabetes mellitus, a metabolic disease with increasing prevalence and serious consequences. Microvascular complications of diabetes, namely diabetic peripheral neuropathy (DPN), retinopathy (DR), and nephropathy (DN), are associated with high morbidity rates and a heavy social and economic burden. Currently, available therapeutic options to counter the evolution of diabetic microvascular complications are clearly insufficient, which strongly recommends further research. Animal models are essential tools to dissect the molecular mechanisms underlying disease progression, to unravel new therapeutic targets, as well as to evaluate the efficacy of new drugs and/or novel therapeutic approaches. However, choosing the best animal model is challenging due to the large number of factors that need to be considered. This is particularly relevant for models induced by dietary modifications, which vary markedly in terms of macronutrient composition. In this article, we revisit the rodent models of diet-induced DPN, DR, and DN, critically comparing the main features of these microvascular complications in humans and the criteria for their diagnosis with the parameters that have been used in preclinical research using rodent models, considering the possible need for factors which can accelerate or aggravate these conditions.

Renal olfactory receptor 1393 contributes to the progression of type 2 diabetes in a diet-induced obesity model

Olfactory receptors are G protein-coupled receptors that serve to detect odorants in the nose. Additionally, these receptors are expressed in other tissues, where they have functions outside the canonical smell response. Olfactory receptor 1393 (Olfr1393) was recently identified as a novel regulator of Na⁺-glucose cotransporter 1 (Sglt1) localization in the renal proximal tubule. Glucose reabsorption in the proximal tubule (via Sglt1 and Sglt2) has emerged as an important contributor to the development of diabetes. Inhibition of Sglt2 is accepted as a viable therapeutic treatment option for patients with type 2 diabetes and has been shown to delay development of diabetic kidney disease. We hypothesized that Olfr1393 may contribute to the progression of type 2 diabetes, particularly the development of hyperfiltration, which has been linked to increased Na⁺ reabsorption in the proximal tubule via the Sglts. To test this hypothesis, Olfr1393 wild-type (WT) and knockout (KO) mice were challenged with a high-fat diet to induce early-stage type 2 diabetes. After 16 wk on the high-fat diet, fasting blood glucose values were increased and glucose tolerance was impaired in the male WT mice. Both of these effects were significantly blunted in the male KO mice. In addition, male and female WT mice developed diabetes-induced hyperfiltration, which was attenuated in the Olfr1393 KO mice and corresponded with a reduction in luminal expression of Sglt2. Collectively, these data indicate that renal Olfr1393 can contribute to the progression of type 2 diabetes, likely as a regulator of Na⁺-glucose cotransport in the proximal tubule.

Triptolide Attenuates Renal Tubular Epithelial-mesenchymal Transition Via the MiR-188-5p-mediated PI3K/AKT Pathway in Diabetic Kidney Disease

Triptolide possesses the trait of renal protection. Epithelial-mesenchymal transition (EMT) is closely linked to the pathogenesis of diabetic kidney disease (DKD). MicroRNAs have recently emerged as critical regulators of DKD. However, it is poorly understood whether triptolide alleviates renal EMT by regulating microRNAs in DKD. In this study, we found that triptolide decreased albuminuria, improved the renal structure and reduced renal EMT in rats with DKD. Furthermore, activation of the PI3K/AKT signaling pathway was increased in diabetic rats, which was partly reversed by triptolide. Triptolide also alleviated glucose-induced EMT in HK-2 cells in vitro. PI3K/AKT signaling pathway activation was reduced after triptolide treatment. Moreover, triptolide decreased the increase in miR-188-5p expression stimulated by high glucose levels in HK-2 cells. miR-188-5p inhibited PTEN expression by directly interacting with the PTEN 3'-untranslated region. Additionally, downregulation of miR-188-5p, which imitates the effects of triptolide, attenuated the activation of the PI3K/AKT pathway and HG-induced EMT, whereas miR-188-5p overexpression reversed the effects of triptolide on the PI3K/AKT pathway and EMT. In conclusion, we demonstrated that triptolide ameliorates renal EMT via the PI3K/AKT signaling pathway through the interaction between miR-188-5p and PTEN, indicating that miR-188-5p may be a therapeutic target of triptolide in DKD.

Losartan improves renal function and pathology in obese ZSF-1 rats

BACKGROUND

Losartan, a blocker of the angiotensin II type I receptor, is an important part of the standard of care for diabetic nephropathy (DN). The obese ZSF-1 rats display many aspects of the clinical features of human Type II DN. The current study was designed to examine the treatment effects of losartan on obese ZSF-1 rats and to evaluate the impact of the onset of dosing on efficacy.

METHODS

The rats (7-10 weeks) underwent a right uninephrectomy (Unx) or sham surgery. Losartan (3, 10, 30 mg/kg) was dosed 3 or 9 weeks post-Unx and continued for 12 weeks.

RESULTS

Treatment with losartan reduced urinary protein excretion and blood lipids (triglyceride and cholesterol) dose-dependently in both studies. The glomerular filtration rate (GFR) was significantly lower in obese ZSF-1 rats compared with those in lean rats, and losartan was efficacious against this endpoint, in particular with the earlier onset of treatment. Losartan also decreased tubulointerstitial fibrosis, and similar to GFR, earlier treatment conferred beneficial actions even at the lowest dose of 3 mg/kg. Several urinary biomarkers were elevated in the obese ZSF-1 rats, but the levels of sTNFR1, TIMP-1, L-FABP and KIM-1 were the only markers decreased by losartan.

CONCLUSIONS

Losartan was renoprotective in the ZSF-1 rats with DN, improving both the pathological and functional parameters of the disease. Importantly, the data also highlight the importance of treatment at earlier stages of the disease for protecting against decline in the GFR and the development of fibrosis.

Discovery and development of next generation sGC stimulators with diverse multidimensional pharmacology and broad therapeutic potential

Nitric oxide (NO)-sensitive soluble guanylyl cyclase (sGC), an enzyme that catalyzes the conversion of guanosine-5'-triphosphate (GTP) to cyclic guanosine-3',5'-monophophate (cGMP), transduces many of the physiological effects of the gasotransmitter NO. Upon binding of NO to the prosthetic heme group of sGC, a conformational change occurs, resulting in enzymatic activation and increased production of cGMP. cGMP modulates several downstream cellular and physiological responses, including but not limited to vasodilation. Impairment of this signaling system and altered NO-cGMP homeostasis have been implicated in cardiovascular, pulmonary, renal, gastrointestinal, central nervous system, and hepatic pathologies. sGC stimulators, small molecule drugs that synergistically increase sGC enzyme activity with NO, have shown great potential to treat a variety of diseases via modulation of NO-sGC-cGMP signaling. Here, we give an overview of novel, orally available sGC stimulators that Ironwood Pharmaceuticals is developing. We outline the non-clinical and clinical studies, highlighting pharmacological and pharmacokinetic (PK) profiles, including pharmacodynamic (PD) effects, and efficacy in a variety of disease models.

High resolution molecular and histological analysis of renal disease progression in ZSF1 fa/faCP rats, a model of type 2 diabetic nephropathy

ZSF1 rats exhibit spontaneous nephropathy secondary to obesity, hypertension, and diabetes, and have gained interest as a model system with potentially high translational value to progressive human disease. To thoroughly characterize this model, and to better understand how closely it recapitulates human disease, we performed a high resolution longitudinal analysis of renal disease progression in ZSF1 rats spanning from early disease to end stage renal disease. Analyses included metabolic endpoints, renal histology and ultrastructure, evaluation of a urinary biomarker of fibrosis, and transcriptome analysis of glomerular-enriched tissue over the course of disease. Our findings support the translational value of the ZSF1 rat model, and are provided here to assist researchers in the determination of the model’s suitability for testing a particular mechanism of interest, the design of therapeutic intervention studies, and the identification of new targets and biomarkers for type 2 diabetic nephropathy.