Measurement of rates of cholesterol and fatty acid synthesis in vivo using tritiated water

Every organ in the body is capable of synthesizing cholesterol de novo but at rates that vary with a constellation of factors. A significant proportion of the hydrogen atoms present in cholesterol that is synthesized in the body are derived from water. Thus, although water ordinarily makes up the bulk of body mass, the acute enrichment of the body water pool with a sufficiently large amount of tritiated water over a short interval of time (usually 1 h) yields measurable rates of incorporation of the labeled water into newly generated cholesterol and also fatty acids. Such data can provide a quantitative measure of how specific genetic, dietary, and pharmacological manipulations impact not just the rate of cholesterol synthesis in particular organs but also rates of whole-body cholesterol production and turnover.