Glutamine and Insulin Sensitivity in Type I Diabetes

Insulin is crucial to help the body metabolize ('burn') sugar (glucose). Even though juvenile (type 1) diabetes (T1D) is primarily due to the lack of insulin, patients with T1D tend to become less sensitive to insulin, particularly during adolescence. The overall objective of this project is to gain further insight into the possible benefits of supplementation with glutamine (GLN), a natural dietary amino acid, enhancing insulin sensitivity in adolescents with T1D. To elucidate the impact of glutamine, the investigators will use a method called the 'euglycemic, hyperinsulinemic clamp': it consists of giving an IV drip of insulin, while the drop in blood sugar is prevented by giving variable, precisely measured amounts of glucose by vein: the amount of glucose required to prevent a drop in blood sugar reflects the body's sensitivity to insulin. The investigators will also give an IV drip of glucose and arginine (a building block of protein) 'tagged' with non-radioactive isotopes to better understand how glutamine may work. This procedure will be performed in 2 groups of 10 adolescents in the morning either after a strenuous exercise performed the previous afternoon (group 1; n=10), or after a sedentary day (group 2; n=10). Each subject will be studied twice, once after taking oral GLN, once after placebo, in separate clinical research center (CRC) admissions a few weeks apart, in random order. Should the investigators hypothesis prove to be true, it would warrant long term studies to determine whether sustained dietary GLN supplementation can decrease insulin requirements and ultimately improve diabetes control in teenagers with T1DM, If successful, this approach could potentially have a significant positive impact in terms of adolescent health.

Type I Diabetes, Insulin Resistance, Glutamine, Amino Acids, Glucagon like peptide 1, Glutathione, Citrulline, Arginine, Nitric Oxide

Participants will keep a diary of food intake and activity as well as wear an accelerometer (to measure overall movement) for 2-3 days prior to the admission. Subject will come to the Clinical Research Center for approximately 24 hours. They will receive a drink containing Glutamine (0.25 g/kg/dose). Afterwards they will have an afternoon exercise session consisting of 15-min bouts of exercise, interspersed with 5-min rest periods in between for a total of 75min. Blood glucose will be checked during rest intervals. They will be served a controlled dinner. Before bedtime another dose of the same drink will be given. Overnight blood glucose will be monitored closely. In the morning, another dose of the same drink will be given. Subjects will have two isotope infusions (non-radioactive) running concomitantly and a hyperinsulinemic-euglycemic clamp will be performed. Afterwards lunch will be served and subject discharged home.

Participants will keep a diary of food intake and activity as well as wear an accelerometer (to measure overall movement) for 2-3 days prior to the admission. Subject will come to the Clinical Research Center for approximately 24 hours. They will receive a PLACEBO drink. Afterwards they will have an afternoon exercise session consisting of 15-min bouts of exercise, interspersed with 5-min rest periods in between for a total of 75min. Blood glucose will be checked during rest intervals. They will be served a controlled dinner. Before bedtime another dose of the same drink will be given. Overnight blood glucose will be monitored closely. In the morning, another dose of the same drink will be given. Subjects will have two isotope infusions (non-radioactive) running concomitantly and a hyperinsulinemic-euglycemic clamp will be performed. Afterwards lunch will be served and subject discharged home.

Insulin sensitivity as measured by hyperinsulinemic-euglycemic clamp. Insulin sensitivity was calculated by dividing the average glucose infusion rate (mL glucose infusion/kg body weight/min) by the average insulin concentration (uU/mL).

Inclusion Criteria: Type I diabetes diagnosed for > 12 months. Minimal weight of 40 kg Tanner stage IV or beyond All insulin programs, including intermediate/short acting insulins, Lantus/Detemir and short acting insulin or insulin pump therapy. HbA1C between 7.5 and 10% BMI between 10th to 85th percentile Patients on stable thyroid replacement therapy will be allowed to participate. Exclusion Criteria: Celiac disease (any patient with history of positive serology or consuming a gluten-free diet) Cystic Fibrosis Chronic steroid therapy Chronic medications that may interfere with glucose metabolism or liver function History of mental retardation Presence of diabetic complications Positive pregnancy test Presence of significant anemia (Hb<11 g/dL) Presence of intercurrent infection

Mauras N, Xing D, Fox LA, Englert K, Darmaun D. Effects of glutamine on glycemic control during and after exercise in adolescents with type 1 diabetes: a pilot study. Diabetes Care. 2010 Sep;33(9):1951-3. doi: 10.2337/dc10-0275. Epub 2010 Jun 28.

Torres-Santiago L, Mauras N, Hossain J, Weltman AL, Darmaun D. Does oral glutamine improve insulin sensitivity in adolescents with type 1 diabetes? Nutrition. 2017 Feb;34:1-6. doi: 10.1016/j.nut.2016.09.003. Epub 2016 Sep 20.