Effects of Ketosis on Brain Function in Patients With T1DM

To test the hypothesis that a ketogenic diet increases hypoglycemia tolerance and improves brain function and cognitive performance during hypoglycemia, the researchers propose a randomized mechanistic study using insulin infusions and neuroimaging. The study will leverage an existing randomized controlled trial (RCT) in 32 young adults with T1D who will receive a ketogenic vs a standard carbohydrate diet for 12 weeks. Researchers will conduct a euglycemic-hypoglycemic insulin clamp using a continuous infusion of insulin, along with a glucose infusion that is adjusted to keep blood glucose levels normal (90 mg/dL), followed by a slow drop to hypoglycemia (50 mg/dL). Researchers will assess activation and connectivity of relevant brain areas by magnetic resonance imaging (MRI). Using continuous imaging during the gradual glycemic descent from 90 mg/dL to 50 mg/dL, the researchers will establish the glycemic threshold at which the hypothalamus becomes activated. Using a combination of MRI modalities, they will assess brain activation and connectivity changes during hypoglycemia versus euglycemia, both during rest and in relation to a cognitive task. Brain findings will be integrated with physiologic (blood levels of glucose, ketones, free fatty acids, counter-regulatory hormones) and behavioral (reaction time, cognitive task performance, hypoglycemia symptoms scale) parameters. In additional studies, researchers will give an oral ketone drink to raise blood ketone levels in participants in the standard carbohydrate diet arm. They will perform the same insulin infusion and MRI investigations to clarify the mechanistic role of ketones in mediating brain activation patterns. Comparison will be between nutritional vs no ketosis, exogenous vs no ketosis, and nutritional vs exogenous ketosis.

Inclusion criteria

• Males and females with T1D for at least 1 year
• Age 18 to 40 years
• Tanner stage ≥ IV
• BMI 18.5-35 kg/m2
• Stable glycemic control (HbA1c 6.5-9%)
• Use of a continuous glucose monitor (CGM)
• Use of an insulin pump
• Attendance of at least 1 diabetes care visit over the past 12 months (including virtual)

Exclusion criteria

• Ketoacidosis or severe hypoglycemia with seizure or coma in the past 6 months
• Dietary restrictions or intolerances that are incompatible with the planned food deliveries, e.g. celiac disease, gastroparesis, certain food allergies
• Following a weight-loss or otherwise restrictive diet
• Vigorous exercise >2 hours on >3 days a week
• History of an eating disorder or at risk for eating disorder, assessed by the Eating Disorders Diagnostic Scale (EDDS)
• Major medical illness or use of medications other than insulin and metformin that could interfere with metabolic or glycemic variables
• Significant psychiatric illness
• Smoking, use of recreational drugs, or excessive alcohol consumption
• Pregnancy or breastfeeding
• Anemia
• For participants who undergo MRI:

• Standard MRI exclusion criteria
• Irregular menses
• Use of psychotropic medication other than SSRIs or other mild antidepressant or anxiety medications (unless these medications are safe to be held for several days to allow for the acquisition of MRI data).