Insulin Resistance and the IGF-I-Cortical Bone Relationship in Children Ages 9-13 Years

IGF-I is a pivotal hormone in pediatric musculoskeletal development. Although recent data suggest that the role of IGF-I in total body lean mass and total body bone mass accrual may be compromised in children with insulin resistance, cortical bone geometric outcomes have not been studied in this context. Therefore, we explored the influence of insulin resistance on the relationship between IGF-I and cortical bone in children. A secondary aim was to examine the influence of insulin resistance on the lean mass-dependent relationship between IGF-I and cortical bone. Children were otherwise healthy, early adolescent black and white boys and girls (ages 9 to 13 years) and were classified as having high (n = 147) or normal (n = 168) insulin resistance based on the homeostasis model assessment of insulin resistance (HOMA-IR). Cortical bone at the tibia diaphysis (66% site) and total body fat-free soft tissue mass (FFST) were measured by peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA), respectively. IGF-I, insulin, and glucose were measured in fasting sera and HOMA-IR was calculated. Children with high HOMA-IR had greater unadjusted IGF-I (p < 0.001). HOMA-IR was a negative predictor of cortical bone mineral content, cortical bone area (Ct.Ar), and polar strength strain index (pSSI; all p ≤ 0.01) after adjusting for race, sex, age, maturation, fat mass, and FFST. IGF-I was a positive predictor of most musculoskeletal endpoints (all p < 0.05) after adjusting for race, sex, age, and maturation. However, these relationships were moderated by HOMA-IR (pInteraction < 0.05). FFST positively correlated with most cortical bone outcomes (all p < 0.05). Path analyses demonstrated a positive relationship between IGF-I and Ct.Ar via FFST in the total cohort (βIndirect Effect = 0.321, p < 0.001). However, this relationship was moderated in the children with high (βIndirect Effect = 0.200, p < 0.001) versus normal (βIndirect Effect = 0.408, p < 0.001) HOMA-IR. These data implicate insulin resistance as a potential suppressor of IGF-I-dependent cortical bone development, though prospective studies are needed

Daytime Sleepiness Underlies the Link Between Adverse Parenting and Youth Psychopathology Among Adolescent Girls

Introduction: Adverse parenting is associated with sleep problems in adolescence, including sleep quality, inadequate sleep, and daytime sleepiness. Adolescents who experience sleep problems are at greater risk for developing internalizing and externalizing problems. However, research on the intervening role of sleep in the link between adverse parenting and youth psychopathology remains limited. The present study aimed to examine the indirect effects of adverse parenting on youth internalizing and externalizing psychopathology via sleep problems, and to examine the moderating role of gender in associations between parenting and sleep. Methods: Participants were 101 low-income youth aged 9–12 (52.5% female; 75.2% African-American) and their primary caregivers. Families were from a non-metropolitan region in the Southeastern United States. Data were collected at two time points (T1; Mage = 10.28, SD = 1.2; T2; Mage = 12.08, SD = 1.2). Adverse parenting was measured at T1, youth-reported sleep problems (inadequacy, disturbance) and daytime sleepiness were assessed at T2, and parent-reported internalizing and externalizing symptoms were measured at T2. Results: Daytime sleepiness served as an intervening variable in associations between adverse parenting and internalizing and externalizing problems, but sleep problems did not. This indirect association was moderated by gender, such that the association between adverse parenting and daytime sleepiness only emerged as significant for girls. Conclusions: These findings suggest that daytime-related sleep behaviors may serve as a mechanism through which harsh or neglectful parenting is related to internalizing and externalizing psychopathology in adolescence, particularly for adolescent girls