Niels Juel Christensen
I was born in Denmark in 1939. My grandfather was a pharmacist and another member of my family a well-known fine art painter. I did well in school and was admitted to a boarding school to obtain the general certificate of education. I wanted to become a medical doctor and studied medicine at the University of Århus. When I was a child and would come down with high fever, our general practitioner always came to our house and examined me carefully. This may have influenced my choice to study medicine. My wish to be a scientist studying physiology and medical problems in humans was probably influenced by my teachers at the University. As a medical student I also had an appointment at a dialysis unit, where patients with acute renal failure due to traffic accidents or preeclampsia would be dialyzed a few times to see, if the kidney would recover. My job was to assemble the dialysis machinery. A doctor from the Department of Physiology would come and supervise the dialysis of the patient.
After I had obtained my final examination from the University (cand. med.), I asked one of my teachers, professor Knud Lundbæk in 1964, if he would help me to obtain a doctoral thesis. Lundbæk was well known internationally for his studies of diabetic angiopathy. He wanted me to examine blood flow in the feet of diabetic patients. I build a plethysmograph and observed that the spontaneous variability in the resting blood flow was markedly reduced in some diabetic patients despite a normal blood flow. This was undoubtedly a sign of sympathetic denervation. A similar abnormality was later reported from a group in Great Britain, that beat-to-beat variation in heart rate was reduced in diabetes.
I became interested in studying catecholamines. We found that insulin increased norepinephrine in plasma and decreased plasma volume and albumin. We also showed that the kidney is insulin sensitive. Insulin or oral glucose increased temporarily albumin excretion in normal subjects, but oral glucose had no effect in juvenile diabetics. This has later been explained by others. Insulin contracts podocytes in the glomerulus. Permanent albuminuria develops after podocytes have died. Thus diabetic nephropathy may at least in part be due to insulin deficiency rather than hyperglycemia.
I also did clinical work and became a specialist in internal medicine and endocrinology. In 1977 I was offered a position as chief physician at the new Herlev University Hospital in Copenhagen. Professor Laurids Korsgaard Christensen was head of the endocrine department and well known for his studies of thyroid diseases. I worked in the Clinic but had also ample time to work in the laboratory. In 1988 I became head of the Department of Endocrinology, Internal medicine and Cardiology and from 1993 Professor of Endocrinology at the University of Copenhagen.
I had many excellent collaborators and we studied sympathetic activity during exercise, in tetraplegics and in the elderly and conducted experiments to counter act the effect of gravity on the circulation. My laboratory obtained samples from space in collaboration with ESA, NASA and Roscosmos and I also visited Star City in Russia. We found unexpectedly that sympathetic activity is increased in space despite the lack of gravitational stress. This finding has been confirmed and is most likely a compensatory reaction to vasorelaxation in space. The mechanism of the observed vasodilatation has not been explained.
We continued with our studies of catecholamines, but we also developed a method for measuring RNA (RT-PCR-HPLC). With this technique we discovered a long non-coding RNA molecule (designated lnc heg RNA, Gen Bank EU137727)), which was closely and inversely related to TSH receptor autoantibodies. Transfection studies showed that heg RNA increased TLR7 mRNA and decreased CD14 mRNA. Therefore CD14 may not be available for TLR4 for production of antibodies. A drug which can increase the level of lnc heg RNA in monocytes may perhaps limit the development of early autoimmune diabetes.
Several young doctors have worked in my laboratory to obtain their Ph.D. or thesis. I have been teaching medical students for more than 40 years and have also been awarded a prize as the best teacher of the year. Apart from science I am interested in history, the work of Albert Camus and enjoy spending time with my children and grandchildren.