Severe COVID-19: insulin- and leptin-resistance in the immune system?!
The brain and immune system have top priority in our survival mechanisms. They should have consistent access to sufficient glucose for energy and as a building block for signaling- and structural molecules. Consequently, these organs are not dependent on insulin for glucose uptake, and therefore employ the insulin-independent GLUT1 for glucose transport. This you may find in textbooks. The question is then: why do some consider Alzheimer as type 3 diabetes and is intranasal insulin investigated as treatment option. Why does the knock-out of the insulin receptor in T-cells affect specific T-cell functions. And why do people with genetic leptin deficiency have low T-cell numbers, low sensitivity to T-cell activation, and low pro-inflammatory cytokine production? Insulin and leptin are emerging as key-players in the link between nutrition and the immune system. Insulin- and leptin-resistance are usually caused by an unhealthy lifestyle. Via their roles in meta-flammation, they are strongly associated with long-term risks of ‘typically Western diseases’, such as diabetes type 2, cardiovascular disease, some cancer types and neurodegenerative diseases. COVID-19 reminds us that insulin- and leptin-resistance are also major risks factors of a poor outcome following acute infection.
Frits A.J. Muskiet graduated in Biochemistry, obtained his PhD (catecholamine (metabolite) producing tumors) and specialised in Clinical Chemistry, all in the Groningen University and the University Medical Center Groningen (UMCG).Until his retirement he held a permanent position as Clinical Chemist in the UMCG with activities in patient care, teaching and research. He was appointed Professor of Pathophysiology and Clinical Chemical Analysis in the School of Pharmacy of the Faculty of Mathematics and Physics, and Associate Professor in the Faculty of Medical Sciences. He is still active in research and teaching and has a broad research interest with e.g. activities in nutrition, lifestyle in medicine, atherosclerosis, hemoglobinopathies and thalassemias, obstetrics and perinatology, psychiatry, evolutionary medicine and evidence based laboratory medicine. He has been an advisor of 34 PhD candidates and is (co)author of 288 PubMed registered publications.