The Effects of Dapagliflozin on HDL Particles Subtypes and Reverse Cholesterol Transport in Type 2 Diabetic Patients

Sodium glucose co-transport-2 (SGLT-2) inhibitors (SGLT-2i), a new class of glucose-lowering agents, reduce tubular glucose reabsorption, thus lowering blood glucose without stimulating insulin release. SGLT-2i have been found to be effective in improving glucose control in type 2 diabetic patients at any disease stage, and also when added to insulin in type 1 diabetic patients. In addition to the glycosuric effect, SGLT-2i reduce body weight and blood pressure and determine an increase in HDL cholesterol levels. HDL mediate reverse cholesterol transport, by extracting cholesterol from peripheral tissues and cells and vehiculating it to the liver. This function, which is regulated that by enzyme cholesteryl esther transfer protein (CETP), is considered a fundamental mechanism of protection from accumulation of cholesterol in the vasculature and a physiologic barrier against atherosclerosis development and protection. The sophisticated method to precisely assess reverse cholesterol transport in vitro are available in our research lab. Although it has been reported that therapy with SGLT-2i raise HDL concentrations by about 4 mg/dL (0.1 mmol/L), the mechanisms remains unclear and it is important to assess whether or not this quantitative increase is coupled to functional improvement in reverse cholesterol transport. In fact, previous studies on HDL-raising therapies have clarified that not all HDL particles and functional and HDL cholesterol levels might not be representative of the reverse cholesterol transport processes. In addition to cholesterol transport, normal HDL particles also have anti-oxidant and anti-inflammatory properties, that are important to translate HDL cholesterol levels into cardiovascular protection. Several HDL subclasses have been identified, having different composition and anti-atherosclerotic properties.

Dapagliflozin (Bristol-Myers Squibb Company [BMS]-512148) is a highly potent, selective, and reversible inhibitor of sodium-glucose cotransporter 2 (SGLT2), the major transporter responsible for renal glucose reabsorption. Dapagliflozin lowers plasma glucose by inhibiting the renal reabsorption of glucose and by promoting its urinary excretion. A tablet formulation of dapagliflozin for oral administration has been approved in over 40 countries including the European Union (EU) and the United States (US) and is under review in numerous countries around the world. Dapagliflozin is approved by AIFA with determination number 909/2013 dated 16/10/2013, and marketing authorization number 042494070/E. In the Phase 2b and 3 program, dapagliflozin has been studied as monotherapy and in combination with metformin, pioglitazone, glimepiride, sitagliptin, and insulin. As of 15-Nov-2012 (date of most recent pooled analysis), a total of 9,412 subjects with T2DM were treated in 16 Phase 3, double-blind, controlled clinical studies conducted to evaluate the safety and efficacy of dapagliflozin; 5,952 subjects in these studies were treated with dapagliflozin for up to 80 weeks. The Phase 2b and 3 program established that dapagliflozin is effective in reducing HbA1c in a broad range of subjects regardless of disease progression/duration or concomitant use of antidiabetic therapies. Improvements in glycemic control were seen when dapagliflozin was given as monotherapy; as add-on combination therapy to sitagliptin or metformin, to sulfonylurea (glimepiride), to thiazolidinedione (pioglitazone), or to insulin (± oral antidiabetic drugs [OADs]); or as initial combination therapy with metformin.

HDL levels and function. Observational studies provide overwhelming evidence that a low high-density lipoprotein (HDL)-cholesterol level increases the risk of coronary events, both in healthy subjects and in patients with coronary heart disease. Based on in vitro experiments, several mechanistic explanations for the atheroprotective function of HDL have been suggested. The HDL functions currently most widely held to account for the antiatherogenic effect include participation in reverse cholesterol transport, protection against endothelial dysfunction, and inhibition of oxidative stress. Yet, several recent pharmacological and genetic studies have failed to demonstrate that increased plasma levels of HDL-C resulted in decreased cardiovascular disease risk, giving rise to a controversy regarding whether plasma levels of HDL-C reflect HDL function, or that HDL is even as protective as assumed. The evidence from preclinical and clinical studies shows that HDL can promote the regression of atherosclerosis when the levels of functional particles are increased from endogenous or exogenous sources. The data show that regression results from a combination of reduced plaque lipid and macrophage contents, as well as from a reduction in its inflammatory state. Although more research will be needed regarding basic mechanisms and to establish that these changes translate clinically to reduced cardiovascular disease events, that HDL can regress plaques suggests that the recent trial failures do not eliminate HDL from consideration as an atheroprotective agent but rather emphasizes the important distinction between HDL function and plasma levels of HDL-C. While HDL from healthy subjects can directly stimulate endothelial cell production of nitric oxide and anti-inflammatory, anti-apoptotic, and anti-thrombotic effects as well as endothelial repair processes, growing evidence suggests that the vascular effects of HDL can be highly heterogeneous and vasoprotective properties of HDL are altered in patients with coronary disease. In fact, HDL has been shown to undergo a loss of function in several pathophysiological states, as in the acute phase response, obesity and chronic inflammatory diseases. Some of these diseases were also shown to be associated with increased risk for cardiovascular disease. One such disease that is associated with HDL dysfunction and accelerated atherosclerosis is diabetes mellitus, a disease in which the HDL particle undergoes diverse structural modifications that result in significant changes in its function, such as glycation and oxidation.

In Phase 2b/3 clinical trials, Dapagliflozin has been shown to raise HDL cholesterol levels by about 4 mg/dl (1 mmol/l), which is generally considered a clinically-meaningful change. As this HDL cholesterol increase is carried out with concomitant improvement in glucotoxicity and body weight reduction, it is possible that treatment with Dapagliflozin also improves HDL function. This is important because clinical, epidemiological and experimental studies indicate that HDL function may be more important than HDL cholesterol levels in determining the protective cardiovascular effects of HDL particles. In addition, knowing the effects of Dapagliflozin on HDL function can help interpreting the increase in HDL cholesterol levels observed in Dapagliflozin-treated patients. Finally, discovery of extra-glycemic effects of Dapagliflozin will shed new light on the potential benefits of therapy with Dapagliflozin and SGLT2i in general. So far, no study evaluated the effects of Dapagliflozin (or other SGLT2i) on HDL function.We hypothesize that Dapagliflozin, in addition to raising HDL cholesterol levels, also increases HDL functionality, measured as reverse cholesterol transport and anti-oxidant capacity, in patients with T2DM.

This will be a randomized, placebo controlled, parallel group study in 36 type 2 diabetic patients to assess the effects of Dapagliflozin on HDL levels and function.

The general objective of the project is to detect a significant differences in the changes versus baseline of the patients' HDL cholesterol efflux capacity, HDL levels, HDL subclasses, HDL anti-oxidant activity, CETP activity, serum/plasma cytokines and adipokines (IL-6, IL-8, PAI-1, TNF-α, visfatin, resistin, adiponectin, leptin) in patients randomized to dapagliflozin compared to those randomized to placebo