Gender and race influence metabolic benefits of fitness in children: a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Increasing obesity and poor cardiovascular fitness (CVF) contribute to higher rates of type 2 diabetes mellitus (T2DM) in children. While the relative contributions of fitness and body fat on development of insulin resistance (IR) in children and adolescents remains unresolved, gender- and race-specific differences likely exist in the degree to which CVF influences IR and risk for T2DM. Better understanding of how gender and race affect interactions between body fat, CVF, and metabolic health would be helpful in designing effective and targeted strategies to reduce obesity-associated disease risk. We evaluated whether metabolic benefits of fitness on reducing inflammation and insulin resistance (IR) are affected by gender and race.</p> <p>Methods</p> <p>This cross-sectional study included 203 healthy children (mean age 12.2 y, 50% male, 46% non-Hispanic white (NHW), 54% racially diverse (RD)). Fasting insulin, glucose, hsCRP, and adiponectin were measured; race was self-reported; cardiovascular fitness (CVF) was evaluated by the Progressive Aerobic Cardiovascular Endurance Run. Associations between inflammation and gender, race, and CVF were evaluated using analysis of covariance. Multivariate regression analysis identified independent predictors of IR.</p> <p>Results</p> <p>Fitness and inflammation were inversely related in both males and females (p < 0.01); this effect was marginally stronger in RD children (p = 0.06) and non-overweight males (p = 0.07). High BMI (p < 0.001), low fitness (p = 0.006), and (female) gender (p = 0.003) were independently associated with higher HOMA-IR. In males, BMI and fitness, but not race independently predicted HOMA-IR. In females, BMI and race, but not fitness independently predicted HOMA-IR.</p> <p>Conclusions</p> <p>In middle school children, the beneficial effects of fitness vary based on gender and race. High CVF has an enhanced anti-inflammatory effect in male and RD children. While BMI is the strongest predictor of IR in the study group as a whole, fitness is a significant predictor of IR only in males, and race is a significant predictor of IR only in females.</p

Mechanically-induced osteogenesis in the cortical bone of pre- to peripubertal stage and peri- to postpubertal stage mice

<p>Abstract</p> <p>Background</p> <p>Exercise during postnatal development plays a key role in determining adult bone mass and reducing the risk of fracture and osteoporosis later in life. However, the relationship between mechanically-induced osteogenesis and age is unclear. Elevated levels of estrogen during puberty may inhibit periosteal bone formation. Thus, magnitudes of mechanically-induced osteogenesis may be vary with pubertal state.</p> <p>Methods</p> <p>The present study uses a murine model to examine age-related changes in bone formation at the femoral midshaft with voluntary exercise. Pre- to peripubertal mice aged 3 weeks and peri- to postpubertal mice aged 7 weeks were randomly divided into sedentary and exercised groups and subjected to histomorphometric comparison after 4 weeks of treatment.</p> <p>Results</p> <p>Results of the experiment indicate that exercise significantly increased osteogenesis on the periosteal and endocortical surface of the mice in the older age group (<it>P </it>< 0.05). Exercise had no significant effect on bone formation of mice in the younger age group, although exercised mice exhibited more bone growth on average than controls. Endocortical apposition was the primary method of bone formation for all mice in the experiment; however exercised mice in the older age group were able to add more bone on the periosteal surface than age-matched controls and exercised mice in the younger age group (<it>P </it>< 0.05). Medullary area increased with age, but exercised mice in both age groups had smaller medullary cavities relative to overall bone area than controls.</p> <p>Conclusion</p> <p>These findings suggest that the amount and location of mechanically-induced osteogenesis differs by age during skeletal development. Late adolescence may be the optimal time to accrue bone mass and maximize bone strength.</p

A 12-Week Aerobic Exercise Program Reduces Hepatic Fat Accumulation and Insulin Resistance in Obese, Hispanic Adolescents

The rise in obesity-related morbidity in children and adolescents requires urgent prevention and treatment strategies. Currently, only limited data are available on the effects of exercise programs on insulin resistance, and visceral, hepatic, and intramyocellular fat accumulation. We hypothesized that a 12-week controlled aerobic exercise program without weight loss reduces visceral, hepatic, and intramyocellular fat content and decreases insulin resistance in sedentary Hispanic adolescents. Twenty-nine postpubertal (Tanner stage IV and V), Hispanic adolescents, 15 obese (7 boys, 8 girls; 15.6 +/- 0.4 years; 33.7 +/- 1.1 kg/m(2); 38.3 +/- 1.5% body fat) and 14 lean (10 boys, 4 girls; 15.1 +/- 0.3 years; 20.6 +/- 0.8 kg/m(2); 18.9 +/- 1.5% body fat), completed a 12-week aerobic exercise program (4 x 30 min/week at >= 70% of peak oxygen consumption (VO(2) peak)). Measurements of cardiovascular fitness, visceral, hepatic, and intramyocellular fat content (magnetic resonance imaging (MRI)/magnetic resonance spectroscopy (MRS)), and insulin resistance were obtained at baseline and postexercise. In both groups, fitness increased (obese: 13 +/- 2%, lean: 16 +/- 4%; both P <0.01). In obese participants, intramyocellular fat remained unchanged, whereas hepatic fat content decreased from 8.9 +/- 3.2 to 5.6 +/- 1.8%; P <0.05 and visceral fat content from 54.7 +/- 6.0 to 49.6 +/- 5.5 cm(2); P <0.05. Insulin resistance decreased indicated by decreased fasting insulin (21.8 +/- 2.7 to 18.2 +/- 2.4 mu U/ml; P <0.01) and homeostasis model assessment of insulin resistance (HOMA(IR)) (4.9 +/- 0.7 to 4.1 +/- 0.6; P <0.01). The decrease in visceral fat correlated with the decrease in fasting insulin (R(2) = 0.40; P <0.05). No significant changes were observed in any parameter in lean participants except a small increase in lean body mass (LBM). Thus, a controlled aerobic exercise program, without weight loss, reduced hepatic and visceral fat accumulation, and decreased insulin resistance in obese adolescents