Carbon, nitrogen, and sulfur elemental and isotopic variations in mouse hair and bone collagen during short-term graded calorie restriction.

This study characterized the effect of calorie restriction (CR) on elemental content and stable isotope ratio measurements of bone "collagen" and hair keratin. Adult mice on graded CR (10-40%; 84 days) showed decreased hair N, C, and S values (significantly for N) with increasing CR, alongside a significant increase in bone "collagen" N values and a decrease in "collagen" C values. We propose this was likely due to the intensified mobilization of endogenous proteins, as well as lipids in newly synthesized "collagen". Elemental analysis of bone "collagen" revealed decreased carbon, nitrogen, and sulfur % content with increasing CR which is attributed to a change in the bone "collagen" structure with extent of CR. This complexity challenges the use of elemental indicators in the assessment of collagen quality in archaeological studies where nutritional stress may be a factor.