Intracellular Counter-regulatory Mechanisms Following Low Blood Glucose

Diabetes mellitus type I (DMI) is characterized by lack of endogenous insulin and these patients are 100% dependent on insulin substitution to survive. Diabetes mellitus type II (DMII) is characterized by reduced insulin sensitivity and sometimes also reduced insulin production, thus patients with DMII might also be dependent on insulin substitution. Insulin is produced in- and secreted from the pancreas when blood glucose concentration rises during- and after a meal. Insulin increases cellular uptake of glucose leading to lower blood glucose concentration. Substitution with insulin is/can be necessary in DM, but at the same time it induces the risk of hypoglycemia. This makes treatment with insulin a balancing act between hyper- and hypoglycemia. A hypoglycemic episode is a dreaded consequence of insulin overdosing, and also a very frequent reason for hospital admission in patients with DM. Examples of hypoglycemic symptoms may be; shaking, a sense of hunger, sweating, irritability progressing to lack of relevant cerebral responses and eventually coma, convulsions and possibly death. People with diabetes lose the ability to sense of low blood glucose with time, because of a lack of appropriate counter-regulatory responses, hereby increasing the risk of severe hypoglycemia. Understanding normal physiologic counter regulatory mechanisms during hypoglycemia is of major importance to patients with DM and has the potential to change medical treatment in diabetes, to reduce the risk of hypoglycemia. Hypothesis: Hypoglycemia counteracts insulin signaling via hormone-dependent intracellular counter-regulatory mechanisms, involving phosphorylation of specific signaling proteins. Aim: To define counter-regulatory mechanisms in muscle- and fat tissue during hypoglycemia, and to investigate the effect of insulin on lipid metabolism in healthy- and type I diabetic subjects.

No insulin administered. Instead of insulin infusion, a small amount of saline is administered to keep the subject blinded. Three muscle biopsies and two fat biopsies will be obtained. A palmitic acid tracer will be given to estimate fatty acid metabolism. Forearm pletysmography will be performed twice.

Insulin (Insuman Rapid) is administered once as a bolus of 0,1 IU/kg. Three muscle biopsies and two fat biopsies will be obtained. A palmitic acid tracer will be given to estimate fatty acid metabolism Forearm pletysmography will be performed twice

Insulin (Insuman rapid) is administered once as a bolus injection of 0,1 IU/kg and glucose is given at the same time to avoid hypoglycemia in this arm. Three muscle biopsies and to fat biopsies is obtained. A palmitic acid tracer is given to estimate fatty acid metabolism Forearm pletysmography will be performed twice

Insulin and growth hormone signalling, expressed as CHANGE in phosphorylation of intracellular target proteins and mRNA expression of target genes in muscle- and fat-tissue.

Change in phosphorylation of target proteins and mRNA expression of target genes assessed with western blotting technique.

Biopsies obtained on each study day (arm). Muscle biopsies: time (t)= -30min, t= 30min and t= 75min. Fat biopsies: t= 30min and t= 75min

Biopsies obtained on each study day (arm). Muscle biopsies: time (t)= -30min, t= 30min and t= 75min. Fat biopsies: t= 30min and t= 75min

Assessment of glucose metabolism by forearm pletysmography and heated hand technique (duration of pletysmography = 30 min.)

Measured at t = -30min., t=0min, t=15min, t= 30min., t=45min., t=60min., t= 75min., t=90min. and t=105min. on each study day (arm)

A palmitic acid tracer will be given once per trial day to estimate fatty acid metabolism. Duration 1 hour.

BMI > 19 and < 26 Written Consent Exclusion Criteria: Epilepsy Cardiac arrythmia Ischemic heart disease Other medical illness

Voss TS, Vendelbo MH, Kampmann U, Hingst JR, Wojtaszewski JFP, Svart MV, Moller N, Jessen N. Acute Hypoglycemia in Healthy Humans Impairs Insulin-Stimulated Glucose Uptake and Glycogen Synthase in Skeletal Muscle: A Randomized Clinical Study. Diabetes. 2017 Sep;66(9):2483-2494. doi: 10.2337/db16-1559. Epub 2017 Jun 8.

Voss TS, Vendelbo MH, Kampmann U, Pedersen SB, Nielsen TS, Johannsen M, Svart MV, Jessen N, Moller N. Effects of insulin-induced hypoglycaemia on lipolysis rate, lipid oxidation and adipose tissue signalling in human volunteers: a randomised clinical study. Diabetologia. 2017 Jan;60(1):143-152. doi: 10.1007/s00125-016-4126-x. Epub 2016 Oct 12.