Lack of renoprotective effects of targeting the endothelin A receptor and (or) sodium glucose transporter 2 in a mouse model of Type 2 diabetic kidney disease

A new perspective on proteinuria and drug therapy for diabetic kidney disease

Diabetic kidney disease (DKD) is one of the leading causes of end-stage renal disease worldwide and significantly increases the risk of premature death due to cardiovascular diseases. Elevated urinary albumin levels are an important clinical feature of DKD. Effective control of albuminuria not only delays glomerular filtration rate decline but also markedly reduces cardiovascular disease risk and all-cause mortality. New drugs for treating DKD proteinuria, including sodium-glucose cotransporter two inhibitors, mineralocorticoid receptor antagonists, and endothelin receptor antagonists, have shown significant efficacy. Auxiliary treatment with proprietary Chinese medicine has also yielded promising results; however, it also faces a broader scope for development. The mechanisms by which these drugs treat albuminuria in patients with DKD should be described more thoroughly. The positive effects of combination therapy with two or more drugs in reducing albuminuria and protecting the kidneys warrant further investigation. Therefore, this review explores the pathophysiological mechanism of albuminuria in patients with DKD, the value of clinical diagnosis and prognosis, new progress and mechanisms of treatment, and multidrug therapy in patients who have type 2 diabetic kidney disease, providing a new perspective on the clinical diagnosis and treatment of DKD.

The sodium glucose co-transporter 2 inhibitor dapagliflozin ameliorates the fluid-retaining effect of the endothelin A receptor antagonist zibotentan

BACKGROUND

Endothelin A receptor antagonists (ETARA) slow chronic kidney disease (CKD) progression but their use is limited due to fluid retention and associated clinical risks. Sodium-glucose co-transporter 2 inhibitors (SGLT2i) cause osmotic diuresis and improve clinical outcomes in CKD and heart failure. We hypothesized that co-administration of the SGLT2i dapagliflozin with the ETARA zibotentan would mitigate the fluid retention risk using hematocrit (Hct) and bodyweight as proxies for fluid retention.

METHODS

Experiments were performed in 4% salt fed WKY rats. First, we determined the effect of zibotentan (30, 100 or 300 mg/kg/day) on Hct and bodyweight. Second, we assessed the effect of zibotentan (30 or 100 mg/kg/day) alone or in combination with dapagliflozin (3 mg/kg/day) on Hct and bodyweight.

RESULTS

Hct at Day 7 was lower in zibotentan versus vehicle groups [zibotentan 30 mg/kg/day, 43% (standard error 1); 100 mg/kg/day, 42% (1); and 300 mg/kg/day, 42% (1); vs vehicle, 46% (1); P < .05], while bodyweight was numerically higher in all zibotentan groups compared with vehicle. Combining zibotentan with dapagliflozin for 7 days prevented the change in Hct [zibotentan 100 mg/kg/day and dapagliflozin, 45% (1); vs vehicle 46% (1); P = .44] and prevented the zibotentan-driven increase in bodyweight (zibotentan 100 mg/kg/day + dapagliflozin 3 mg/kg/day = -3.65 g baseline corrected bodyweight change; P = .15).

CONCLUSIONS

Combining ETARA with SGLT2i prevents ETARA-induced fluid retention, supporting clinical studies to assess the efficacy and safety of combining zibotentan and dapagliflozin in individuals with CKD.

A systematic review on renal effects of SGLT2 inhibitors in rodent models of diabetic nephropathy

We have performed a systematic review of studies reporting on the renal effects of SGLT2 inhibitors in rodent models of diabetes. In 105 studies, SGLT2 inhibitors improved not only the glycemic control but also various aspects of renal function in most cases. These nephroprotective effects were similarly reported whether treatment with the SGLT2 inhibitor started concomitant with the onset of diabetes (within 1 week), early after onset (1-4 weeks) or after nephropathy had developed (>4 weeks after onset) with the latter probably having the greatest translational value. They were observed across various animal models of type 1 and type 2 diabetes/obesity (4 and 23 models, respectively), although studies in the type 2 diabetes model of db/db mice more often had negative data than in other models. Among possibly underlying pathophysiological mechanisms of nephroprotection, treatment with SGLT2 inhibitors had beneficial effects on lipid metabolism, blood pressure, glomerulosclerosis as well as renal tubular fibrosis, apoptosis, oxidative stress, and inflammation. These pathomechanisms highly influence atherosclerosis and renal health, which are two major factors that lead to an enhanced mortality in patients with diabetes and/or chronic kidney disease. Interestingly, renal SGLT2 inhibitor effects did not always correlate with those on glucose homeostasis, particularly in a limited number of direct comparative studies with other anti-diabetic treatments, indicating that nephroprotection may at least partly occur by mechanisms other than improving glycemic control. Our analyses did not provide evidence for different nephroprotective efficacy between SGLT2 inhibitors. Importantly, only four of 105 studies reported on female animals, and none provided direct comparative data between sexes. We conclude that more data on female animals and more direct comparative studies with other anti-diabetic compounds and combinations of treatments are needed.

Endothelin Receptor Antagonists in Kidney Disease

Endothelin (ET) is found to be increased in kidney disease secondary to hyperglycaemia, hypertension, acidosis, and the presence of insulin or proinflammatory cytokines. In this context, ET, via the endothelin receptor type A (ETA) activation, causes sustained vasoconstriction of the afferent arterioles that produces deleterious effects such as hyperfiltration, podocyte damage, proteinuria and, eventually, GFR decline. Therefore, endothelin receptor antagonists (ERAs) have been proposed as a therapeutic strategy to reduce proteinuria and slow the progression of kidney disease. Preclinical and clinical evidence has revealed that the administration of ERAs reduces kidney fibrosis, inflammation and proteinuria. Currently, the efficacy of many ERAs to treat kidney disease is being tested in randomized controlled trials; however, some of these, such as avosentan and atrasentan, were not commercialized due to the adverse events related to their use. Therefore, to take advantage of the protective properties of the ERAs, the use of ETA receptor-specific antagonists and/or combining them with sodium-glucose cotransporter 2 inhibitors (SGLT2i) has been proposed to prevent oedemas, the main ERAs-related deleterious effect. The use of a dual angiotensin-II type 1/endothelin receptor blocker (sparsentan) is also being evaluated to treat kidney disease. Here, we reviewed the main ERAs developed and the preclinical and clinical evidence of their kidney-protective effects. Additionally, we provided an overview of new strategies that have been proposed to integrate ERAs in kidney disease treatment.

Sodium glucose co-transporter 2 (SGLT2) inhibition via dapagliflozin improves diabetic kidney disease (DKD) over time associatied with increasing effect on the gut microbiota in db/db mice

BACKGROUND

The intestinal microbiota disorder gradually aggravates during the progression of diabetes. Dapagliflozin (DAPA) can improve diabetes and diabetic kidney disease(DKD). However, whether the gut microbiota plays a role in the protection of DAPA for DKD remains unclear.

METHODS

To investigate the effects of DAPA on DKD and gut microbiota composition during disease progression, in our study, we performed 16S rRNA gene sequencing on fecal samples from db/m mice (control group), db/db mice (DKD model group), and those treated with DAPA (treat group) at three timepoints of 14weeks\18weeks\22weeks.

RESULTS

We found that DAPA remarkably prevented weight loss and lowered fasting blood glucose in db/db mice during disease progression, eventually delaying the progression of DKD. Intriguingly, the study strongly suggested that there is gradually aggravated dysbacteriosis and increased bile acid during the development of DKD. More importantly, comparisons of relative abundance at the phylum level and partial least squares-discriminant analysis (PLS-DA) plots roughly reflected that the effect of DAPA on modulating the flora of db/db mice increased with time. Specifically, the relative abundance of the dominant Firmicutes and Bacteroidetes was not meaningfully changed among groups at 14 weeks as previous studies described. Interestingly, they were gradually altered in the treat group compared to the model group with a more protracted intervention of 18 weeks and 22 weeks. Furthermore, the decrease of Lactobacillus and the increase of norank_f:Muribaculaceae could account for the differences at the phylum level observed between the treat group and the model group at 18 weeks and 22 weeks.

CONCLUSION

We firstly found that the protective effect of DAPA on DKD may be related to the dynamic improvement of the gut microbiota over time, possibly associated with the impact of DAPA on the bile acid pool and its antioxidation effect.