Dietary Glycemic Index, Brain Function and Food Intake in Patients With Type 1 Diabetes Mellitus

High and low GI liquid test meals are matched for macronutrient composition (60% carbohydrate, 15% protein, 25% fat), micronutrient profiles, physical properties, palatability and sweetness. Meals will provide 25% of individual daily energy requirements as estimated by the Harris Benedict equation. A high glycemic index of \~90 is achieved by using corn syrup as a carbohydrate source.

High and low GI liquid test meals are matched for macronutrient composition (60% carbohydrate, 15% protein, 25% fat), micronutrient profiles, physical properties, palatability and sweetness. Meals will provide 25% of individual daily energy requirements as estimated by the Harris Benedict equation. A low glycemic index of \~40 is achieved by using uncooked corn starch as a carbohydrate source.

Insulin will be given intravenously for 5 hours. During the entire clamp protocol, glucose levels will be measured every 5 minutes. A basal insulin infusion will be started at 80% of the patients insulin pump basal rate, and will be adjusted between 0.1 and 2.5 mU/kg•min, depending upon the patient's plasma glucose level in relation to the target range target of 90-100 mg/dl.

A primed-variable infusion of insulin will be administered at the rate established to achieve euglycemia after a low glycemic index meal. This is expected to result in moderate hyperglycemia as the high GI meal is associated with higher insulin requirements. For patient safety, glucose levels will be measured every 30 minutes. If glucose levels are \> 400 mg/dl or \< 60 mg/dl, insulin infusion will be adjusted to maintain glucose levels target of 60-400 mg/dl.