A novel hypothesis linking low-grade ketonaemia to cardio-renal benefits with sodium-glucose cotransporter-2 inhibitors

Empagliflozin increases plasma levels of citrulline, histidine, and α-aminobutyric acid in patients with type 2 diabetes: effects of a sodium-glucose co-transporter 2 inhibitor on the plasma amino acid profile

BACKGROUND

To investigate effects of empagliflozin on plasma amino acids in people with type 2 diabetes.

RESEARCH DESIGN AND METHODS

In a randomized, active-controlled, open-label trial, 58 patients with type 2 diabetes were randomized to 10 mg/day empagliflozin (n = 29) or standard treatment without empagliflozin (control group, n = 29) and treated for 12 weeks. We obtained blood samples at baseline and 12 weeks and assessed the plasma amino acid profile by liquid chromatography-mass spectrometry liquid chromatography. We also calculated the Fischer ratio (the ratio of branched-chain to aromatic amino acids).

RESULTS

In the empagliflozin group but not in the control group, plasma levels of citrulline, histidine, and α-aminobutyric acid (AABA), the Fischer ratio, and serum high-molecular weight (HMW) adiponectin increased significantly (p = 0.0099, 0.0277, 0.0318, 0.0135, and 0.0304, respectively) and plasma plasminogen activator inhibitor-1 (PAI-1) decreased significantly (p = 0.0014). In the empagliflozin group, the change in plasma citrulline was positively correlated with the changes in HMW adiponectin (r = 0.488, p = 0.0084) and the Fischer ratio (r = 0.393, p = 0.0353) but negatively correlated with the change in ferritin (r= -0.533,p = 0.0051); the change in plasma histidine was negatively correlated with the change in PAI-1 (r= -0.398, p = 0.0397) and urinary albumin creatinine ratio (r= -0.478, p = 0.0088).

CONCLUSION

Empagliflozin significantly increases plasma citrulline, histidine, and AABA in people with type 2 diabetes.

CLINICAL TRIAL REGISTRATION

www.umin.ac.jp identifier is UMIN000025418.

Narrative review investigating the nephroprotective mechanisms of sodium glucose cotransporter type 2 inhibitors in diabetic and nondiabetic patients with chronic kidney disease

Background and aims

Outcome trials using sodium glucose cotransporter type 2 inhibitors have consistently shown their potential to preserve kidney function in diabetic and nondiabetic patients. Several mechanisms have been introduced which may explain the nephroprotective effect of sodium glucose cotransporter type 2 inhibitors beyond lowering blood glucose. This current narrative review has the objective to describe main underlying mechanisms causing a nephroprotective effect and to show similarities as well as differences between proposed mechanisms which can be observed in patients with diabetic and nondiabetic chronic kidney disease.

Methods

We performed a narrative review of the literature on Pubmed and Embase. The research string comprised various combinations of items including "chronic kidney disease", "sodium glucose cotransporter 2 inhibitor" and "mechanisms". We searched for original research and review articles published until march, 2022. The databases were searched independently and the agreements by two authors were jointly obtained.

Results

Sodium glucose cotransporter type 2 inhibitors show systemic, hemodynamic, and metabolic effects. Systemic effects include reduction of blood pressure without compensatory activation of the sympathetic nervous system. Hemodynamic effects include restoration of tubuloglomerular feedback which may improve pathologic hyperfiltration observed in most cases with chronic kidney disease. Current literature indicates that SGLT2i may not improve cortical oxygenation and may reduce medullar oxygenation.

Conclusion

Sodium glucose cotransporter type 2 inhibitors cause nephroprotective effects by several mechanisms. However, several mediators which are involved in the underlying pathophysiology may be different between diabetic and nondiabetic patients.

Serum uric acid lowering and effects of sodium-glucose cotransporter-2 inhibitors on gout: A meta-analysis and meta-regression of randomized controlled trials

AIMS

To pool the effects of sodium-glucose cotransporter-2 (SGLT2) inhibitors on gout and to investigate the association of these effects with baseline serum uric acid (SUA), SUA lowering, and underlying conditions, such as type 2 diabetes mellitus (T2DM)/heart failure (HF).

METHODS

PubMed, Embase, Web of Science, Cochrane Library and clinical trial registry websites were searched for randomized controlled trials (RCTs) or post hoc analyses (≥1-year duration; PROSPERO:CRD42023418525). The primary outcome was a composite of gouty arthritis/gout flares and commencement of anti-gout drugs (SUA-lowering drugs/colchicine). Hazard ratios (HRs) with 95% confidence interval (CI) were pooled using a generic inverse-variance method with a random-effects model. Mixed-effects model univariate meta-regression analysis was performed.

RESULTS

Five RCTs involving 29 776 patients (T2DM, n = 23 780) and 1052 gout-related events were identified. Compared to placebo, SGLT2 inhibitor use was significantly associated with reduced risk of composite gout outcomes (HR 0.55, 95% CI 0.45-0.67; I2  = 61%, P < 0.001). Treatment benefits did not differ between trials being conducted exclusively in baseline HF versus those conducted in patients with T2DM (P-interaction = 0.37), but were greater with dapagliflozin 10 mg and canagliflozin 100/300 mg (P < 0.01 for subgroup differences). Sensitivity analysis excluding trials that evaluated the effects of empagliflozin 10/25 mg (HR 0.68, 95% CI 0.57-0.81; I2  = 0%) accentuated the benefits of SGLT2 inhibitors with no between-trial heterogeneity (HR 0.46, 95% CI 0.39-0.55; I2  = 0%). Univariate meta-regression found no impact of baseline SUA, SUA lowering on follow-up, diuretic use, or other variables on their anti-gout effects.

CONCLUSION

We found that SGLT2 inhibitors significantly reduced the risk of gout in individuals with T2DM/HF. Lack of an association with SUA-lowering effects suggests that metabolic and anti-inflammatory effects of SGLT2 inhibitors may predominantly mediate their anti-gout benefits.

Increase in hematocrit with SGLT-2 inhibitors - Hemoconcentration from diuresis or increased erythropoiesis after amelioration of hypoxia?

BACKGROUND AND AIMS

The SGLT2-inhibitors significantly reduce heart failure hospitalization and progression to end-stage kidney disease. An increase in hemoglobin/hematocrit is seen with SGLT2i-inhibitor treatment. This increase has been attributed to hemoconcentration resulting from a diuretic effect. In this review, we present evidence suggesting that the hematocrit increase is not due to hemoconcentration, but to an increase in erythropoiesis due to amelioration of hypoxia and more efficient erythropoietin production with SGLT2-inhibitor treatment.

METHODS

We performed a detailed review of the literature in PubMed for articles describing various mechanisms linking hematocrit increase with SGLT2-inhibitor use to their cardio-renal benefits.

RESULTS

The best predictor of cardio-renal benefits with SGLT2-inhibitors is an increase in hematocrit and hemoglobin. If this hemoconcentration is a results of diuresis, this would be associated with volume contraction and a deterioration in renal function, as seen with long-term diuretic use. This is the opposite of what is seen with the use of SGLT2-inhibitors, which are associated with long-term preservation of renal function. There is now growing evidence that the increase in hematocrit can be attributed to an increase in erythropoiesis due to amelioration of renal hypoxia and more efficient erythropoietin production with SGLT2-inhibitor treatment. Increased erythropoiesis leads to an increase in RBC count which improves myocardial/renal tissue oxygenation and function.

CONCLUSION

The increase in hematocrit with SGLT2i treatment is not due to hemoconcentration, but to an increase in erythropoiesis due to amelioration of hypoxia and more efficient erythropoietin production with SGLT2i treatment.

Characteristics and molecular mechanisms through which SGLT2 inhibitors improve metabolic diseases: A mechanism review

Metabolic diseases, such as diabetes, gout and hyperlipidemia are global health challenges. Among them, diabetes has been extensively investigated. Type 2 diabetes mellitus (T2DM), which is characterized by hyperglycemia, is a complex metabolic disease that is associated with various metabolic disorders. The newly developed oral hypoglycemic agent, sodium-glucose cotransporter 2 (SGLT2) inhibitor, has been associated with glucose-lowering effects and it affects metabolism in various ways. However, the potential mechanisms of SGLT2 inhibitors in metabolic diseases have not fully reviewed. Many of the effects beyond glycemic control must be considered off-target effects. Therefore, we reviewed the effects of SGLT2 inhibition on metabolic diseases such as obesity, hypertension, hyperlipidemia, hyperuricemia, fatty liver disease, insulin resistance, osteoporosis and fractures. Moreover, we elucidated their molecular mechanisms to provide a theoretical basis for metabolic disease treatment.

Hyperinsulinemia impairs the metabolic switch to ketone body utilization in proximal renal tubular epithelial cells under energy crisis via the inhibition of the SIRT3/SMCT1 pathway

OBJECTIVE

To investigate the effects and mechanism of hyperinsulinemia on the metabolic switch to β-hydroxybutyrate (BHB) absorption and utilization under a starvation or hypoxic environment in proximal tubular epithelial cells.

METHODS

A high-fat diet-induced hyperinsulinemia model in ZDF rats was used to test the expression of key enzymes/proteins of ketone body metabolism in the kidney. Notably, 12-week-old renal tubule SMCT1 specific knockout mice (SMCT1 flox/floxCre+) and control mice (SMCT1 flox/floxCre-) were used to confirm the roles of SMCT1 in kidney protection under starvation. The changes of key enzymes/proteins of energy metabolism, mitochondrial function, and albumin endocytosis in HK2 cells under low glucose/hypoxic environments with or without 50 ng/mL insulin were studied. Silent information regulation 2 homolog 3 (SIRT3) was overexpressed to evaluate the effect of hyperinsulinemia on the metabolic switch to BHB absorption and utilization through the SIRT3/SMCT1 pathway in HK2 cells.

RESULTS

In ZDF rats, the expression of HMGCS2 increased, the SMCT1 expression decreased, while SCOT remained unchanged. In renal tubule SMCT1 gene-specific knockout mice, starvation for 48 h induced an increase in the levels of urine retinol-binding protein, N-acetyl-β-glucosaminidase, and transferrin, which reflected tubular damages. In HK2 cells under an environment of starvation and hypoxia, the levels of key enzymes related to fatty acid oxidation and ketone body metabolism were increased, whereas glucose glycolysis did not change. The addition of 2 mmol/l BHB improved ATP production, mitochondrial biosynthesis, and endocytic albumin function, while cell apoptosis was reduced in HK2 cells. The addition of 50 ng/ml insulin resulted in the decreased expression of SMCT1 along with an impaired mitochondrial function, decreased ATP production, and increased apoptosis. The overexpression of SIRT3 or SMCT1 reversed these alterations induced by a high level of insulin both in low-glucose and hypoxic environments.

CONCLUSIONS

The increased absorption and utilization of BHB is part of the metabolic flexibility of renal tubular epithelial cells under starvation and hypoxic environments, which exhibits a protective effect on renal tubular epithelial cells by improving the mitochondrial function and cell survival. Moreover, hyperinsulinemia inhibits the absorption of BHB through the inhibition of the SIRT3/SMCT1 pathway.