Dietary Intake of Tryptophan and Metformin Response

Inclusion criteria

• healthy adult male or non-pregnant female volunteers (age 20-40)
• able and willing to give consent

Exclusion criteria

• Age less than 20 or greater than 40
• Women who are pregnant, nursing, or at risk of becoming pregnant
• Body mass index (BMI) less than 20 or greater than 28
• Changes of more than 5 pounds in weight (increase or decrease) during the month prior to enrollment in the study
• Participation in more than 300 minutes of exercise per week during the month prior to enrollment in the study
• Known diabetes or pre-diabetes (based on prior diagnoses, use of medications to lower glucose; or fasting blood glucose > 100mg/dL at screening)
• Untreated hypertension (defined as systolic blood pressure > 140mmHg and diastolic blood pressure > 90mmHg)
• Current or past mood disorder, including major depression, anxiety, or bipolar disorder
• Conditions causing intestinal malabsorption, including celiac disease or a history of intestinal or gastric bypass surgery
• History of liver disease and/or aspartate aminotransferase (AST) or alanine aminotransferase (ALT) more than 3 times upper limit of normal (ULN)
• Estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m2 as calculated by the Modification of Diet in Renal Disease equation
• Currently taking or intending to take during the study duration any medication known to affect glycemic parameters, such as glucocorticoids, growth hormone, or fluoroquinolones
• Use of medications and herbal or vitamin supplements during the study
• Contraindications to safe use of metformin, including planned radiologic or angiographic study requiring contrast within one week of the study completion
• Objection to taking metformin
• Participation in any other interventional study during the study duration
• Use of nicotine-containing products, including inhaled, chewed, or patches during the study.
• Use of drugs of abuse.
• Restrictions that prevent adherence to standardized meals or unwillingness to adhere to a pre-specified meal plan, including abstinence from alcohol and limitation of caffeine intake to one drink daily.