The role of ACE2 in the renin-angiotensin-system: Etiology and therapy of COVID-19 from a pharmaceutical perspective.

Angiotensin-2 converting enzyme (ACE2), a key element of the renin-angiotensin-system (RAS), is not only the direct target of infection by the human SARS-Cov-2 virus but is at the same the root for the complex pathogenetic events of COVID-19. From a pharmaceutical perspective, several established classes of medicines are involved in different phases of the disease. From their known mechanisms of action, a comprehensive understanding of COVID-19 will be hopefully soon delineated. A set of proven medicines is available to cope at least with some of the pathologies involved. To arrive back to normal life, vaccinations and broad consideration of hygienic measures are to be complemented by effective medicines to treat airborne viral infections. Therapeutic schemes based on a comprehensive understanding of the disease will include drug combinations made up from both established drugs as well as novel drugs presently under development.

The "sugar dilemma".

Type 2 diabetes mellitus is characterized by insulin resistance and elevated blood glucose levels. Treatment protocols generally include dietary restriction of sugar, as well as drugs aiming at a reduction of blood glucose, mainly by activating the insulin system or supplementing insulin. This established approach does not take into account the outstanding physiological role of glucose as a key molecule in metabolism. Glucose is crucial to meet the high energy demand of the brain, which depends on it as an exclusive nutrient. Insulin independent glucose transporters GLUT1 import glucose into the brain. Reduction of blood glucose, as in current treatment concepts, may lead to energy deficiency in the brain and consecutively to worsening of - possibly already impaired - neurocognitive function. Reduced cell membrane fluidity of the vascular endothelium of the bloodbrain-barrier (BBB) - due to malnutrition and/or aging - is considered a major factor in pathogenesis of the cerebral metabolic syndrome, which is a key step in neurodegeneration. Under this aspect we suggest a novel approach to prophylaxis and treatment focusing on a sufficient supply of glucose to the brain.