To explore triheptanoin (C7 oil) compatibility with the ketogenic diet by evaluating EEG, and seizure rate, glycemia and ketosis in proven G1D patients receiving a ketogenic diet.

This is a single site, open label proof of principle exploratory trial to investigate the compatibility of C7 oil with the ketogenic diet in subjects diagnosed with G1D. The ketogenic diet will have been previously described by the patient's treating physician independently of this study and for clinical reasons. The ketogenic diet supplies over 50% of calories from fat, subjects, who are already tolerating over this much fat as part of their previously prescribed ketogenic diet, will replace 45% of their daily caloric intake with the triheptanoin for 24 hours, during a 48 hour inpatient stay. Subjects will have a continuous EEG to monitor for any potential C7 related changes in seizure before, during, and after triheptanoin oil ingestion.

Inclusion Criteria:

• Diagnosis of glucose transporter type 1 deficiency (G1D), confirmed by clinical genotyping at a CLIA-certified laboratory.
• Stable on ketogenic diet at 2.5:1 to 4:1 ratio (i.e., no changes in ratio will have taken place for 2 months). The initiation of a ketogenic diet is previous to - and thus is not part of this study.
• Males and females 30 months to 35 years and 11 months old inclusive.

Exclusion Criteria:

• Subjects with evidence of independent, unrelated metabolic and/or genetic disease.
• Subjects with a chronic gastrointestinal disorder, such as irritable bowel syndrome, crohn's disease, or colitis that could increase the subject's risk of developing diarrhea or stomach pain.
• Subjects with a BMI (body mass index) greater than or equal to 30.
• Subjects currently not on ketogenic diet.
• Women who are pregnant or breast feeding may not participate. Women who plan to become pregnant during the course of the study, or who are unwilling to use birth control to prevent pregnancy (including abstinence) may not participate. Females age 10 and over will be asked to provide a urine sample for a pregnancy test via dipstick. Subjects will be asked to agree to abstinence or another form of birth control for the duration of the study.
• Allergy/sensitivity to C7
• Previous use of triheptanoin less than 1 month prior to study initiation.
• Treatment with medium chain triglycerides in the last 24 hours.
• Subjects exhibiting signs of dementia, or diagnosed with any degenerative brain disorder (such as Alzheimer's disease) that would confound assessment of cognitive changes, in the opinion of the investigator.
• Active drug or alcohol use or dependence that, in the opinion of the investigator, would interfere with adherence to study requirements.
• Inability or unwillingness of subject or legal guardian/representative to give written informed consent, or assent for children age 10-17,
• Addition of a new antiseizure drug in the previous 3 months.

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