Proof of Concept Creatine Supplementation for Homocystinuria Study

Homocystinuria is a rare but potentially serious inherited condition due to cystathionine beta-synthase (CBS) deficiency which causes accumulation of homocysteine and its precursor methionine.

Our hypothesis is that high doses of orally supplemented creatine will lead to a reduction of endogenous production of homocysteine. Our hypothesis is based on the tight association of the metabolic pathways for creatine synthesis and the synthesis of S-adenosylhomocysteine (SAH) which is the immediate precursor of homocysteine. Suppression of endogenous creatine synthesis through provision of exogenous creatine will lead to reduced production of SAH and thus homocysteine.

Our objectives are:

• To test endogenous methionine turn over using stable isotope technique in response to creatine supplementation in healthy young adult men
• To test changes in blood levels of homocysteine, S-adenosylmethionine (SAM), SAH and methionine as well as creatine metabolites dependent on creatine supplementation

To test the endogenous methionine turn over in response to creatine supplementation we will use stable isotope techniques utilizing labelled carbon (13C), as 1-13C-Methionine. The tracer will be given along with protein shakes composed of specific amounts of protein (1g/kg/d) and its metabolic fate can be tracked by measuring 13C labelled carbon dioxide (CO2) in breath samples and 13C species in urine with mass spectrometer. Stable isotopes have been used previously and are currently being used for metabolic studies in healthy children and adults, including pregnancy. Our Lab has special experience with this technique and has used it for the study of other inborn errors of metabolism. For the measurement of plasma levels of homocysteine, methionine, SAM, SAH, creatine and its intermediates we will use mass spectrometry, employing well established methods in our lab.

We will perform a baseline study (without previous creatine supplementation and a treatment study (with previous creatine supplementation) in two separate study days. Participants will take a diet providing 1 gram of protein /kg/day for 7 days prior to the respective study. For the treatment, study participants will additionally take 20 grams of creatine per day for 7 days. On the study days probands will take hourly experimental meals containing the tracer methionine and breath samples and urine samples will be collected to determine 13C species coming from the ingested methionine. We will collect blood during the 6th hour of the study to determine methionine and creatine related metabolites.

Inclusion criteria

• Cis-male
• Men who are classified as normal body weight and BMI (18.5-25kg/m2)
• Free of any concurrent illness (cold, flu, vomiting etc.)
• Not be claustrophobic (we will place a clear hood, which can easily be removed, over your head for approximately 20 min to measure your energy expenditure)
• Not be enrolled in any other research studies (as this may affect our study results)

Exclusion criteria

• Men not in good health or have a metabolic, neurological, genetic, or immune disorder, including diabetes, hypoglycemia, hypertension and current or past history of kidney disease
• Men who have food allergies/sensitivities/intolerances to egg, corn, diary etc.
• Men who have current or recent past history of ingesting creatine supplements
• Men who are smokers
• Men who are following a non-traditional dietary pattern (e.g. Keto diet, Atkins diet, paleo diet, intermittent fasting, strict vegan, calorie restricted diet etc.)