The amount of fat mass is known to affect the plasma levels of certain biomarkers, which should be taken into account when analysing physiological data. This is particularly relevant for fat soluble substances which are preferentially sequestered into fat tissue because of their chemical nature. Carotenoids for example can be stored in adipocytes which may have implications for the antioxidant status in obese individuals. Plasma ascorbate is inversely associated with obesity which may suggest that the antioxidant is removed from circulation to be stored in fat tissue, despite being water soluble. Seasonal plasma vitamin D has also been shown to be affected by the fat levels of the individual. As well as nutrients and vitamins, other clinically useful biomarkers appear to be affected by the level of fat tissue present. These include products of metabolism, which can include markers for oxidative stress and glycation.
Advanced glycation end products (AGE) are clinically useful biomarkers that are formed from the nonenzymatic glycation of proteins, lipids and nucleic acids. The formation of AGE is increased under hyperglycaemic conditions such as with diabetic subjects. In addition, AGE products can be ingested in foods, which in combination with endogenously formed AGE creates a pool of AGE. High levels of AGE are associated with increased mortality and increased risk of cardiovascular disease. In a cross-sectional study1 dual energy x-ray absorptiometry was performed on 592 subjects (age 26 to 93 years) and concomitantly serum levels of the AGE product carboxymethyl-lysine (CML) was analysed. Total fat mass, appendicular fat mass and truncal fat mass were inversely associated with serum CML, but lean body mass was not. These results suggest that AGE products are sequestered in fat or that adipose interferes with AGE metabolism in some way.
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