Diabetes mellitus type 2, considered at the beginning as a metabolic disorder, converts
into a predominantly vascular disease, once its duration extends over several years
or/and when additional cardiovascular risk factors like arterial hypertension coexist.
Moreover, cardiovascular disease is the leading cause of death and complications in
patients with type 2 diabetes. Recently, it has been demonstrated in a large longitudinal
study that arterial stiffness is associated with higher risk of incident diabetes,
independent of traditional risk factors. Increase in arterial stiffness appeared to even
precede increase in fasting blood glucose. Moreover, we showed a reduced retinal
capillary density in patients with prediabetes compared to patients with normal glucose
metabolism (unpublished data). As a consequence, treatment of type 2 diabetes should
focus not only on metabolic control but also on improving vascular structure and
function, including endothelial function, the first stage of the atherosclerotic cascade.
In the last decade many studies have shown improved cardiovascular outcome in patients
with type 2 diabetes treated with recently developed antidiabetic medication. The
EMPA-REG Outcome trial evaluated the effect of a sodium-glucose cotransporter 2 inhibitor
(empagliflozin) and have shown improved cardiovascular outcomes and lower rate of death
from any cause in patients with type 2 diabetes who were at high risk for cardiovascular
events. Similarly, in the LEADER trial first occurrence of death from cardiovascular
causes, myocardial infarction, or stroke among patients with type 2 diabetes mellitus was
lower with a glucagon-like peptide 1 analogue (liraglutide) than with placebo.
Semaglutide is another glucagon-like peptide 1 analogue with an extended half-life of
approximately 1 week compared to liraglutide (efficacy and safety). Without any doubts,
the large-scale prospective trial (SUSTAIN-6) demonstrating improved cardiovascular
prognosis along with significant blood glucose reduction after treatment with semaglutide
are very impressive and convincing, and this study fulfilled the regulatory guidance to
establish cardiovascular safety of new therapies for type 2 diabetes. However this was
primarily a non-inferior trial, although it demonstrated superiority with respect to the
combined cardiovascular endpoint (p=0.02 for superiority). In the PIONEER-6 study
conducted in patients with type 2 diabetes at least above 50 years with cardiovascular or
chronic kidney disease or above 60 years and with cardiovascular risk factors, oral
semaglutide proved cardiovascular safety. Other benefits of semaglutide in patient
cohorts other than patients with type 2 diabetes has been described recently.
Several prospective studies reported a closer relation of organ damage with central
(aortic) as opposed to peripheral (brachial) systolic blood pressure (BP), and central
systolic BP was found to be independently associated with cardiovascular morbidity and
mortality. In accordance, central pulse pressure has been repeatedly found to
independently predict cardiovascular morbidity and mortality in various study cohorts.
Further-more, prospective data have now been published showing that the forward and
backward (reflected) wave amplitude predict independently cardiovascular complications.
New advanced technology allows us to assess vascular parameters also under ambulatory
conditions over 24 hours. Previously, we could demonstrate that the SGLT-2 inhibitors
empagliflozin and dapagliflozin as well as the DPP-4 inhibitor saxagliptin improved
parameters of vascular function and arterial stiffness and decreased central (aortic)
pulse and systolic pressures (i.e. afterload of the left ventricle). Our results provided
evidence for the concept that the better cardiovascular and renal outcomes observed with
empagliflozin in the EMPA-REG Outcome Study are related to improved vascular function.
So far, there are no clinical data or an in-depth analysis of the effects on vascular
function and stiffness after treatment with GLP-1 analogues, neither with liraglutide nor
with semaglutide. In mice, semaglutide reduced the development of atherosclerosis by
preventing the development of aortic plaques. Data supporting the concept that
semaglutide improves vascular structure and function, including endothelial function are
lacking, and our study aims at closing this knowledge gap by measuring various parameters
of vascular remodeling and function at the same time thereby allowing us to delineate a
complete profile of the vascular effects of semaglutide in the maco- and
microcirculation. Such an approach is now in particular of relevance, since the European
Medicines Agency (EMA) has already approved semaglutide s.c. (Ozempic) and semaglutide in
an oral formula (Rybelsus) within the EU.
Our hypothesis is that in face of its impressive anti-diabetic effect semaglutide exerts
beneficial effects on vascular structure and function, including endothelial function.
Since the arterial pulse wave along the arterial tree is reflected at each bifurcation
and thereby in particular at the ones of small arterioles, improvement in the vascular
structure and function in microcirculation will also have profound consequences for the
macrocirculation, as previously demonstrated, by lowering central pulse pressure and
central systolic pressure both considered as valid and reliably measurable vascular
parameters in the macrocirculation.
The main goal of the study is to demonstrate the effect of semaglutide on different
vascular parameters of the macro- and microcirculation. The primary objective is to
analyze the effect of semaglutide, compared to placebo on central (aortic) pulse
pressure. Flow mediated vasodilation (FMD), an indicator of the integrity of endothelial
function, is another parameter of the macrocirculation assessed in this study. Another
parameter of the macrocirculation, assessed both in resting condition and 24-hours
ambulatory conditions, in this study is pulse wave velocity (PWV), which is well known as
an independent risk factor for cardiovascular morbidity and mortality. To analyze
vascular remodeling processes in the microcirculation, we are measuring wall to lumen
ratio of small retinal arterioles non-invasively in-vivo that reflects vascular
remodeling of small arteries. Finally, only for a subgroup of up to 40 paitents
parameters of the renal circulation including total renal perfusion, separate cortical
and medullary renal perfusion and renal vascular resistance are measured using arterial
spin labeling magnetic resonance imaging (ASL-MRI).