Renoprotective effects of empagliflozin in type 1 and type 2 models of diabetic nephropathy superimposed with hypertension

Recent Advances in Understanding Peripheral and Gut Immune Cell-Mediated Salt-Sensitive Hypertension and Nephropathy

Hypertension is the primary modifiable risk factor for cardiovascular, renal, and cerebrovascular diseases and is considered the main contributing factor to morbidity and mortality worldwide. Approximately 50% of hypertensive and 25% of normotensive people exhibit salt sensitivity of blood pressure, which is an independent risk factor for cardiovascular disease. Human and animal studies demonstrate that the immune system plays an important role in the etiology and pathogenesis of salt sensitivity of blood pressure, kidney damage, and vascular diseases. Antigen-presenting and adaptive immune cells are implicated in salt-sensitive hypertension and salt-induced renal and vascular injury. Elevated sodium activates antigen-presenting cells to release proinflammatory cytokines including IL (interleukin) 6, tumor necrosis factor-α, IL-1β, and accumulate isolevuglandin-protein adducts. In turn, these activate T cells release prohypertensive cytokines including IL-17A. Moreover, high-salt intake is associated with gut dysbiosis, leading to inflammation, oxidative stress, and blood pressure elevation but the mechanistic contribution to salt-sensitivity of blood pressure is not clearly understood. Here, we discuss recent advances in research investigating the cause, potential biomarkers, and therapeutic targets for salt-sensitive hypertension as they pertain to the gut microbiome, immunity, and inflammation.

Sex-dependent effects of Canagliflozin on kidney protection in mice with combined hypertension-type 1 diabetes

Canagliflozin (CANA) is a sodium-glucose cotransporter 2 (SGLT2) inhibitor with blood glucose lowering effects. CANA also promotes kidney protection in patients with cardiovascular diseases and type 2 diabetes (T2D), as well as in normoglycemic patients with hypertension or heart failure. Clinical studies, although conduct in both sexes, do not report sex-dependent differences in T2DM treated with CANA. However, the impact of CANA in type 1 diabetes, as well in sex-dependent outcomes in such cohort needs further understanding. To analyze the effects of CANA in mice with combined hypertension and type 1 diabetes, diabetes was induced by STZ injection (5 days, 50mg/kg/day) in both male and female 8 weeks old genetic hypertensive mice (Lin), whereas the control (Lin) received 0.1M sodium citrate injections. 8 weeks after STZ. Mice were fed either regular or CANA-infused diet for 4 weeks. 8 weeks after STZ, hyperglycemia was present in both male and female mice. CANA reversed BG increase mice fed regular diet. Male LinSTZ mice had elevated water intake, urine output, urinary albumin to creatinine ratio (ACR), kidney lesion score, and creatinine clearance compared to the Lin control group. Kidney injury was improved in male LinSTZ + CANA group in male mice. Water intake and urine output were not statistically significantly different in female LinSTZ compared to female LinSTZ+ CANA. Moreover, CANA did not improve kidney injury in female mice, showing no effect in creatinine clearance, lesion score and fibrosis when compared to LinSTZ fed regular diet. Here we show that Canagliflozin might exert different kidney protection effects in male compared to female mice with hypertension and type 1 diabetes. Sex-dimorphisms were previously found in the pathophysiology of diabetes induced by STZ. Therefore, we highlight the importance of in-depth investigation on sex-dependent effects of CANA, taking in consideration the unique characteristics of disease progression for each sex.

Canagliflozin and irbesartan ameliorate renal fibrosis via the TGF-β1/Smad signaling pathway in Dahl salt-sensitive rats

OBJECTIVES

This study assessed the antifibrotic effects of canagliflozin, with or without irbesartan, on renal injury in Dahl salt-sensitive (SS) rats fed a high-salt (HS) diet.

METHODS

After the preconditioning stage, Dahl SS rats (n = 47) were divided into five experimental groups as follows: low-salt (LS, n = 7), HS (n = 10), HS with canagliflozin (n = 10), HS with irbesartan (n = 10), and HS with canagliflozin and irbesartan (n = 10).

RESULTS

The HS diet increased systolic blood pressure (SBP), renal fibrosis, fibrotic protein expression, and transforming growth factor-β1 (TGF-β1)/Smad2/3 pathway protein expression compared with the findings in the LS group. Irbesartan reduced SBP and slowed the loss of renal function. Canagliflozin significantly reduced body weight and renal fibrosis and suppressed the TGF-β1/Smad2/3 pathway. The combined therapy exerted better renoprotective effects on all outcome parameters.

CONCLUSIONS

These results indicate that canagliflozin and irbesartan exert different effects on renal injury in SS hypertensive rats, and the combined regimen could have stronger effects than either monotherapy.

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.