Quantifying cholesterol synthesis in vivo using (2)H(2)O: enabling back-to-back studies in the same subject

Area of Science:

• Metabolic Research
• Biochemistry
• tracer kinetics

Background:

• Deuterium oxide ((2)H(2)O) offers advantages for quantifying cholesterol synthesis, including homogeneous precursor labeling and long-term studies.
• Challenges with (2)H(2)O use include tracer half-life limitations for repeated measurements and assumptions about hydrogen incorporation (n) during synthesis.

Purpose of the Study:

• To assess the feasibility of a step-based approach for repeated cholesterol synthesis studies in the same subject.
• To determine if the number of hydrogens incorporated (n) during de novo cholesterol synthesis is influenced by nutritional status in vivo.

Main Methods:

• African-Green monkeys received multiple oral doses of (2)H(2)O, separated by one week, to assess reproducibility of cholesterol synthesis measurements.
• Mice on high-carbohydrate (HC) and carbohydrate-free (CF) diets were used to evaluate the impact of nutritional status on hydrogen incorporation (n).

Main Results:

• Comparable changes in plasma water and total plasma cholesterol labeling were observed in monkeys receiving repeated (2)H(2)O doses.
• Cholesterol synthesis rates showed better reproducibility when measured repeatedly in the same nonhuman primate compared to group comparisons.
• The number of incorporated hydrogens (n) was found to be approximately 25 in mice on an HC diet and 27 on a CF diet, indicating relative constancy.

Conclusions:

• It is feasible to acutely repeat cholesterol synthesis studies using (2)H(2)O, overcoming previous limitations.
• The number of hydrogens incorporated (n) during de novo cholesterol synthesis is relatively constant and not significantly affected by short-term dietary changes.