Prenatal growth restriction and postnatal growth restriction followed by accelerated growth independently program reduced bone growth and strength.

Low birth weight increases the risk of developing adult onset cardiovascular and metabolic diseases. Recently being born small has also been identified as a risk factor for adverse bone growth, development and adult fracture risk. Evidence also suggests that accelerated growth in offspring of normal birth weight, following periods of slowed growth, can also independently program adult diseases. The aim of this study was to determine the relative roles of prenatal and postnatal growth restriction on adult bone characteristics and strength. Bilateral uterine vessel ligation (Restricted) or sham surgery (Control) was performed on gestational day 18 in WKY rats to induce fetal growth restriction. Control, Reduced (reduced Control litter size to match Restricted) and Restricted pups were cross-fostered onto different Control (normal lactation) or Restricted (impaired lactation) mothers 1 day after birth. Femur length, dimensions, strength, mineral content and density were quantified using DXA and pQCT analysis. Markers of bone turnover were measured in offspring at 6 months. Restricted pups were born lighter than Controls with males, not females, remaining smaller than Control-on-Control at 6 months (P<0.05). Pups born of normal weight from a reduced litter suckling on a Restricted mother (Reduced-on-Restricted) grew slowly during lactation then quicker after weaning compared to Controls (P<0.05). Cortical bone mineral content, dimensions and strength were lower in Restricted-on-Restricted and Reduced-on-Restricted offspring compared to Controls with lower density in Reduced-on-Restricted females (P<0.05). The stress strain index of bone bending strength remained lower in the Restricted male offspring when body weight adjustments were made. Cross-fostering Restricted females, but not males, onto mothers with normal lactation (Restricted-on-Control) restored growth and bone parameters to Controls (P<0.05). Being born small, or postnatal growth restriction for normal birth weight offspring followed by accelerated growth, programs bone content and strength deficits. Deficits were corrected by improving postnatal nutrition for females born small, highlighting sex specific programming outcomes and impact of postnatal nutrition. These findings suggest a link between growth restriction and adult bone health with additional studies needed to further explore this link in humans.