Pyridinoline (PYD) and deoxypyridinoline (DPD) are cross-linking aminoacids of collagen that are located mainly in bone and cartilage. When bone matrix is resorbed these cross-links are quantitatively excreted in the urine and therefore represent specific markers. We have measured the urinary excretion rate of PYD and DPD in 46 severely malnourished boys to assess their skeletal turnover and to relate this to their subsequent rate of growth. The children were aged 13 months (SD 6), and height-for-age was -3.6 (1.6) Z-score, and weight-for-height was -2.4 (0.8) Z-score. PYD excretion when malnourished and after "recovery" was 11.2 (4.6) nmol h-1m-2 and 32.2 (10.8) nmol h-1m-2 and DPD excretion was 2.6 (1.3) nmol h-1m-2 and 7.5 (3.0) nmol h-1m-2, respectively. The ratio of the two cross-links did not change with recovery. These data show that cartilage and bone turnover is much lower in the malnourished than in the recovered child. There was no difference in the degree of depression of turnover between the children with marasmus, marasmic-kwashiorkor, or kwashiorkor. The rate of height gain during recovery was significantly related to cross-link excretion, age, and weight-for-height on admission. These three factors accounted for 44% of the variance in the height velocity of the children. PYD and DPD excretion rate could be used to assess therapeutic interventions designed to alleviate stunting.
PIP: The Tropical Metabolism Research Unit at the University of the West Indies in Jamaica made anthropometric measurements of 46 13-month-old male infants to assess changes in bone resorption during malnutrition by measuring the urinary excretion rate of pyridinoline (PYD) and deoxypyridinoline (DPD) and to determine whether bone turnover is associated with recovery. Unit staff used standard methods to treat the malnourished boys, including an energy dense diet (cow's milk formulated from Perlargon and corn or coconut oil). Before treatment, their height-for-age stood at -3.6 Z-score and their weight-for-height was -2.4 Z-score. The rate of excretion of PYD and DPD in malnourished children was only about 33% of that after they recovered (11.2 nmol per hour per sq. meter vs. 32.2 nmol per hour per sq. meter and 2.6 nmol vs. 7.5 nmol per hour per sq. meter, respectively; p .001). Therefore, cartilage and bone turnover was considerably lower in the children when they were malnourished than when they recovered. Recovery did not alter the ratio of these 2 cross-link amino acids, however, suggesting that changes in endochondral growth relative to bone remodelling did not occur. The extent of depression in bone turnover was basically the same between children with marasmus, marasmic-kwashiorkor, or kwashiorkor. The rate of height gain of the children during recovery from malnutrition was significantly associated with age (p .001), PYD excretion at admission (p = .003), and weight-for-height at admission (p = .01), all 3 of which explained 44% of the variance in the rate of height gain of the children. Since this study demonstrated that PYD and DPD are associated with longitudinal growth in children recovering from malnutrition, more research on the effect of dietary manipulation on longitudinal growth should be done, which should define requirements for longitudinal growth and identify needed steps to prevent stunting.