Measurement of squalene in human tissues and plasma: validation and application

Abstract

A method is described for accurate and reproducible measurement of squalene in plasma, feces, urine, bile, and tissue that depends on isolation by alumina column chromatography after mild saponification and on measurement by gas-liquid chromatography. Recoveries from all tissues exceeded 80% and from plasma 96%; losses were accurately corrected by appropriate additions of squalene as an overall recovery standard.Squalene measurements in more than 20 foodstuffs showed a 5000-fold variation, the richest source being olive oil (7 mg/g); however, the mean intake/person day in the United States appears to be in the range of 30 mg. Squalene concentrations in more than 25 hurnan tissues also varied widely; the highest levels were in skin (about 475 µg/g dry weight) and adipose tissue (about 275 µg /g), while only moderate amounts were found in sites of active cholesterol synthesis (liver, 75 µg/g; small intestine, 42 µg/g). There was a direct relationship between plasma levels of squalene and triglycerides but not with cholesteroi. Plasma squalene levels rose strikingly with increased dietary squalene and varied directly but not consistently with cholesterol synthesis rates. The large amounts excreted in skin surface lipids are presumed to reflect de novo synthesis in the skin, rather than transfer from plasma; only trivial amounts were excreted in feces and urine.

Keywords

• gas-liquid chromatography
• internal standards
• stability during storage
• diet squalene
• hyperglyceridemia