Quantifying dietary macronutrient sources of carbon for bone collagen biosynthesis using natural abundance stable carbon isotope analysis.

The diets of laboratory rats were isotopically and nutritionally manipulated using purified C3 and/or C4 macronutrients to investigate the routing of dietary carbon to bone collagen biosynthesis. Diets were formulated with purified proteins, carbohydrates and lipids of defined composition and natural abundance stable isotope ratios. Bulk protein and constituent amino acid delta(13)C values determined for whole diet and bone collagen provided the basis for assessing isotopic fractionation and estimating the degree of routing versus synthesis de novo of essential, non-essential and conditionally indispensable amino acids.

Effects of hydrolysis on the delta13C values of individual amino acids derived from polypeptides and proteins.

This study investigates the effects of hydrolysis on the delta13C values of individual amino acids (IAAs) derived from polypeptide standards, and modern and ancient bone collagen. All IAAs were derivatised to their trifluoroacetyl/isopropyl (TFA/IP) esters for delta13C determination using gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Firstly, authentic single poly amino acid standards (SPAAs; n = 5) were hydrolysed for 4, 10, 24 and 48 h.

Natural abundance stable carbon isotope evidence for the routing and de novo synthesis of bone FA and cholesterol.

This research reported in this paper investigated the relationship between diet and bone FA and cholesterol in rats raised on a variety of isotopically controlled diets comprising 20% C3 or C4 protein (casein) and C3 and/or C4 nonprotein or energy (sucrose, starch, and oil) macronutrients. Compound-specific stable carbon isotope analysis (delta13C) was performed on the FA (16:0, 18:0, 18:1, and 18:2) and cholesterol isolated from the diet (n = 4) and bone (n = 8) of these animals. The dietary signals reflected by the bone lipids were investigated using linear regression analysis.