Impact of SGLT2 Inhibitors on Heart Failure: From Pathophysiology to Clinical Effects

Sympatholytic Mechanisms for the Beneficial Cardiovascular Effects of SGLT2 Inhibitors: A Research Hypothesis for Dapagliflozin's Effects in the Adrenal Gland

Heart failure (HF) remains the leading cause of morbidity and death in the western world, and new therapeutic modalities are urgently needed to improve the lifespan and quality of life of HF patients. The sodium-glucose co-transporter-2 (SGLT2) inhibitors, originally developed and mainly indicated for diabetes mellitus treatment, have been increasingly shown to ameliorate heart disease, and specifically HF, in humans, regardless of diabetes co-existence. Indeed, dapagliflozin has been reported to reduce cardiovascular mortality and hospitalizations in patients with HF and reduced ejection fraction (HFrEF). This SGLT2 inhibitor demonstrates these benefits also in non-diabetic subjects, indicating that dapagliflozin's efficacy in HF is independent of blood glucose control. Evidence for the effectiveness of various SGLT2 inhibitors in providing cardiovascular benefits irrespective of their effects on blood glucose regulation have spurred the use of these agents in HFrEF treatment and resulted in FDA approvals for cardiovascular indications. The obvious question arising from all these studies is, of course, which molecular/pharmacological mechanisms underlie these cardiovascular benefits of the drugs in diabetics and non-diabetics alike. The fact that SGLT2 is not significantly expressed in cardiac myocytes (SGLT1 appears to be the dominant isoform) adds even greater perplexity to this answer. A variety of mechanisms have been proposed over the past few years and tested in cell and animal models and prominent among those is the potential for sympatholysis, i.e., reduction in sympathetic nervous system activity. The latter is known to be high in HF patients, contributing significantly to the morbidity and mortality of the disease. The present minireview first summarizes the current evidence in the literature supporting the notion that SGLT2 inhibitors, such as dapagliflozin and empagliflozin, exert sympatholysis, and also outlines the main putative underlying mechanisms for these sympatholytic effects. Then, we propose a novel hypothesis, centered on the adrenal medulla, for the sympatholytic effects specifically of dapagliflozin. Adrenal medulla is responsible for the production and secretion of almost the entire amount of circulating epinephrine and of a significant percentage of circulating norepinephrine in the human body. If proven true experimentally, this hypothesis, along with other emerging experimental evidence for sympatholytic effects in neurons, will shed new light on the pharmacological effects that mediate the cardiovascular benefits of SGLT2 inhibitor drugs, independently of their blood glucose-lowering effects.

Association between Markers of Fibrosis and Heart Failure Incidence in Patients with Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) and chronic heart failure (HF) have close association, and several biomarkers have been studied to better understand this association and improve prediction of HF in T2DM. Furthermore, in recent clinical trials, sodium glucose cotransporter 2 inhibitors (SGLT2i), glucose-lowering drugs, improved HF outcomes. The objective of the present study was to evaluate association between circulating biomarkers of fibrosis and incidence of HF with preserved ejection fraction (HFpEF) in patients with T2DM receiving sodium glucose cotransporter 2 inhibitors (SGLT2i). Materials and Methods. At baseline, transthoracic echocardiography and laboratory assessment of N-terminal fragment of the brain natriuretic peptide (Nt-proBNP), soluble suppression of tumorigenesis-2 (sST2), galectin-3 (Gal-3), C-terminal propeptide of procollagen type I (PICP), N-terminal propeptide of procollagen type III (PIIINP), matrix metalloproteinase-9 (MMP-9), and tissue inhibitor of matrix proteinase-1 (TIMP-1) were done. After 3 years of follow-up, information about HF events (hospitalization for HF, established HF in outpatient department by a cardiologist) was obtained. Results. Seventy-two patients were included in the study. The mean age was 57 (49.7; 63.2) years; 44% were female. Most patients had T2DM for more than 4 years. All patients were overweight or had obesity, and 93% patients had arterial hypertension (AH). After 3 years of follow-up, HFpEF was established in 21% patients. Patients were divided into two groups according to the presence of HFpEF, and baseline characteristics were compared. Patients with HF were older and had longer diabetes and AH duration and higher Nt-proBNP, Gal-3, PIIINP, and PICP levels at baseline than patients without HF (all p < 0.05). Gal - 3 > 10 ng/ml (OR = 2.25; 95% CI, 1.88-5.66; p = 0.01) and NT - pro - BNP > 80 pg/ml (OR = 2.64; 95% CI, 1.56-4.44; p = 0.001) were associated with increased risk of HF incidence. Age > 60 years, diabetes duration > 10 years, and presence of abdominal obesity were independent predictors of HFpEF as well. Conclusions. T2DM patients treated with SLGT2i, who developed HFpEF after 3 years of follow-up, had higher PICP, PIIINP, Gal-3, and NT-proBNP serum concentrations at baseline, and Gal-3 level was an independent predictor of HFpEF.