Effect of Empagliflozin on Podocyte Specific Proteins in African American Veterans With NDKD

Chronic kidney disease (CKD) is a complex medical condition imposing deleterious effects on multiple organ systems. Prevention of increased cardiovascular mortality and progression to end-stage kidney disease (ESKD) are two major unmet medical needs in patients with CKD, with or without diabetes mellitus especially in those with albuminuria [1].

In patients with Non-Diabetic Kidney Disease (NDKD), the cornerstone of management includes blood pressure control, maintenance of normal body weight, dietary adherence, and avoidance of nephrotoxic drugs [2,3].

The management of diabetic kidney disease (DKD) has undergone extensive changes with the advent of several foundational classes of guideline based medical therapies (GDMT) for DKD. These include SGLT2i, GLP1-RAs, and Finerenone, along with Renin-Angiotensin System-inhibitors (RASi). While the benefits of the SGLT2i such as Empagliflozin for cardio-kidney outcomes in NDKD are well recognized from the landmark EMPA-KIDNEY trial [12], there is less understood in terms of mechanisms of benefit, especially in high-risk phenotypes for progression to kidney failure, such as APOL1 +ve gene mutation.

African Americans suffer from CKD at significantly higher rates and account for more than 35% of all patients receiving dialysis in the United States [1]. While T2D is the number one cause of CKD overall, and Black adults are twice as likely to develop T2D compared to White adults [1], recently identified genetic variants in the APOL1 gene may explain a significant proportion of the rising burden of albuminuric NDKD in African Americans (4). APOL1 risk variants G1 and G2 are trypanolytic factors that protect against trypanosomiasis but have been shown to be associated with significantly higher risk for development of NDKD (4). Though NDKD is quite prevalent in African-American patients, the precise mechanism of APOL1 risk variants involved in the pathogenesis and progression of NDKD in this patient population is unknown and requires further investigation [5,6], given the disproportionate burden of CKD and kidney failure in this population.

Abnormalities in podocyte biology play a central role in the pathogenesis of CKD. In CKD podocyte injury is a key component in the pathophysiology of the progressive kidney disease, which is also accompanied by systemic inflammation [6-8]. The degree of podocyte injury is currently best assessed by kidney biopsy, which is an invasive procedure and not performed in the vast majority of patients with CKD. Often times proteinuria accompanies the clinical picture. However non albuminuric CKD is a growing clinical entity. The patterns, and extent of podocyte injury in non-albuminuric CKD is less well understood([7,8] and their management is often challenging.

Several recent T2DM clinical trials have shown that SGLT2 inhibitors (SGLT2i) improve endothelial dysfunction. We and others [10,11] have shown decreased podocyte-specific urine protein injury markers production with SGLT2i in DKD [9-11]. Additionally, the literature suggests close cross-talk between the glomerular vascular endothelium and the podocyte [10]. The effect of SGLT2i on markers of podocyte injury, as well as markers of endothelial injury/inflammation deserve further elucidation. This maybe relevant in non albuminuric NDKD in lower eGFR stages (stages 3 and 4), albuminuric NDKD in stage 2, or more preserved eGFR states, in a population that may inherently be at high risk for progressive CKD and its subsequent rapid deterioration in kidney disease, such as APOL1 nephropathy.

In this pilot project, we plan to establish the degree to which podocyte inflammation or dysfunction in albuminuric or non-albuminuric NDKD, is modified by empagliflozin, an SGLT2i. Podocyte inflammation with increased excretion of podocyte-specific proteins such as Wilm's Tumor-1 has been noted in T2DM and other nephropathies [11,13-16]. We have studied and quantified the same biomarkers in diabetic nephropathy[11] and have also demonstrated amelioration and reduction of the same in DKD. However similar studies are lacking in NDKD, particularly in non albuminuric NDKD patients with low eGFR.

In this study, we focus on albuminuric or non-albuminuric NDKD where we would like to stratify two groups for inclusion: 1. Preserved eGFR such as 60 - 89 where we would like to see a concomitant UACR of at least 30 mg/g or 2. Less preserved eGFR between 20 - 59 with or without discernable albuminuria/UACR (see Inclusion criteria section of this protocol). This represents a wide range of baseline KDIGO risk using the KDIGO CKD heat map. The traditional method for assessing podocyte damage is by measuring urinary protein excretion. However other biomarkers may be more effective.

We and others have demonstrated that urinary exosomes are a defined entity in urine and estimation of podocyte specific proteins in urine exosomes may help identify and quantify podocyte inflammation [17-18].

Exosomes, are a class of extracellular vesicles, that are secreted from various tissues into the circulation or urine and they carry protein, nucleic acid and lipid cargoes and facilitate cell-to-cell communication. Exosomes have been proposed as potential biomarkers of specific physiological and pathological conditions. For example, exosomes have been implicated in the initiation and progression of diabetes mellitus and its complications [11,13]. However, the isolation of specific classes of exosomes in urine from CKD subjects to enable monitoring disease severity and level of inflammation has yet to be developed . Studying podocyte inflammation may also help to identify cross talk between podocyte , the glomerular endothelium, and systemic inflammation. [16-18] Moreover APOL1 mutation presence has been associated with progressive renal injury and even podocyte specific injury [19-24]. APOL1 mutation has been associated with systemic inflammation and podocytopathy, particularly in African Americans [24-26] Building on these preliminary data and literature review, the overall objective of this randomized, double-blinded, interventional, proof-of concept study is to understand the effect of empagliflozin 10 mg on markers of podocyte injury and systemic inflammation in patients with albuminuric or non-albuminuric NDKD. We plan to use singular 10mg dose (considered low dose) which has shown clinical efficacy in similar trials [12]. Please note our podocyte specific trial in diabetic CKD patients also used low dose SGLT2i, Canagliflozin 100mg [11] It will also explore the relationship between changes in markers of podocyte injury with the use of empagliflozin, in the backdrop of expression of APOL1 gene in individual patients. This will help elucidate mechanistic insights into the effects of SGLT2i on podocyte injury markers and markers of systemic inflammation in individuals with albuminuric or non-albuminuric NDKD, and further understand the effects in the backdrop of varying degrees of APOL1 expression.