Effect of Empagliflozin on Macrovascular and Microvascular Circulation and on Endothelium Function

Diabetes mellitus, considered as a metabolic disorder, mutates into a predominantly vascular disease, once its duration extends over several years and/or when additional cardiovascular risk factors coexists, in particular arterial hypertension. In accordance, patients with type 2 diabetes die because of microvascular and macrovascular complications, and only rarely because of hypoglycaemic or hyperglycaemic shock syndromes. As a consequence, treatment of type 2 diabetes should focus not only on metabolic control but also on improving the global vascular risk. Analyses that have compared the importance of the various cardiovascular risk factors concluded that reductions of blood pressure and lipid levels are significantly more important than reduction of hyperglycemia. Of course, a multidisciplinary approach is desirable and the STENO-2 study has clearly indicated that in mid-term microvascular complications and in long-term macrovascular complications can be prevented in type 2 diabetes.

Vascular changes occurring in the course of type 2 diabetes, arterial hypertension and elevated global cardiovascular risk can now reliably assessed non-invasively, and already at the very early stage of vascular remodeling processes. For example, the guidelines of the European Society of Hypertension recommend several vascular parameters to be assessed already at the diagnosis of the disease in order to analyze early organ damage of the arteries. The measurement of pulse wave velocity, pulse wave analysis, central (aortic) systolic pressure and pulse pressure are tools to detect early vascular changes in the large arteries related to a faster wave reflection in the arterial tree. Wall to lumen ratio of retinal arteries, retinal capillary flow and flow mediated vasodilation are tools to detect changes in the microvascular circulation. These parameters are only infrequently measured in studies with type 2 diabetes, mainly due to lack of awareness that the vascular changes are the key prognostic factor in type-2 diabetes that ultimately determine the fate of the patient.

Empagliflozin is a novel selective SLGT-2 inhibitor that has been shown to improve glycaemic control after 2, 12, and 24 weeks as well as after 1 and 2 years. Empagliflozin produced dose dependent increases in glucosuria and clinically meaningful changes of glycemic parameters in type 2 diabetes in addition to weight loss. Most striking, empagliflozin was also found to lower systolic blood pressure by 5 mmHg. This reduction in blood pressure might be related to weight loss or/and concomitant loss of total body sodium content. However, the precise mechanism of the blood pressure reduction needs to be elucidated. Loss of sodium would lead to a less reactive contraction of the small arteries in response to increased sympathetic activity, angiotensin II and catecholamines.

Moreover, the endothelium dependent vasodilation after reactive hyperemia is a new non-invasive tool to detect changes on the organ perfusion level. To further assess flow-mediated/Endothelium dependent vasodilation we can assess the EndoPAT Risk Score.

These parameters are only infrequently measured in studies with type 2 diabetes, mainly due to the lack of expertise required to assess these vascular parameters and lack of awareness that vascular changes are the key prognostic factor in type 2 diabetes (and not glycosylated hemoglobin).

In summary, empagliflozin exert beneficial effects on a variety of cardiovascular risk factors, such as hyperglycaemia, hypertension and obesity. These changes should lead (so the hypothesis) to improved vascular and endothelial function in the micro- and macrocirculation.

However, the latter is nothing more than hypothesis and requires clear proof by clinical studies in patients with type 2 diabetes.