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Energy restriction is associated with lower bone mineral density of the tibia and femur in lean but not obese female rats.

ABSTRACT: Energy restriction decreases bone mineral density (BMD), and epidemiological studies suggest that the risk of weight loss-induced bone loss is greater in lean than in heavier individuals. Our goal in this study was to determine how bone density and geometry respond to energy restriction in mature obese rats compared with lean rats. At 6 mo of age, 36 diet-induced obese and lean female Sprague-Dawley rats were allocated to control (CTL; ad libitum; n = 18) and energy-restricted (EnR; 40% restriction; n = 18) diets. After 10 wk of dietary intervention, obese EnR rats lost more weight (-91 +/- 34 g) than lean EnR rats(-61 +/- 14 g) (P < 0.02), [corrected] whereas body weight did not change significantly in the 2 CTL groups (14 +/- 23 g). Only the lean EnR (and not obese EnR) rats showed lower BMD compared with CTL rats at the tibia, distal, and proximal femur and femoral neck, and trabecular bone volume (P < 0.05). Serum estradiol declined in lean EnR rats compared with baseline (P < 0.05) but not in the obese EnR rats. In addition, the final serum 25-hydroxyvitamin D (25OHD) concentration was higher (P < 0.05) in obese than in lean EnR rats. Serum parathyroid hormone decreased (P < 0.05) from baseline to final in lean and obese CTL, but not EnR rats. These data support the hypothesis that energy restriction in lean rats compared with obese rats is more detrimental to bone, and it is possible that the greater decline in estrogen and lower levels of 25OHD contribute to this effect.

SUBMITTER: Hawkins J

PROVIDER: S-EPMC2793120 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

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Energy restriction is associated with lower bone mineral density of the tibia and femur in lean but not obese female rats.

Hawkins Jaleah J Cifuentes Mariana M Pleshko Nancy L NL Ambia-Sobhan Hasina H Shapses Sue A SA

The Journal of nutrition 20091118 1

Energy restriction decreases bone mineral density (BMD), and epidemiological studies suggest that the risk of weight loss-induced bone loss is greater in lean than in heavier individuals. Our goal in this study was to determine how bone density and geometry respond to energy restriction in mature obese rats compared with lean rats. At 6 mo of age, 36 diet-induced obese and lean female Sprague-Dawley rats were allocated to control (CTL; ad libitum; n = 18) and energy-restricted (EnR; 40% restrict ...[more]

PMID: 19923391

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Project description:Childhood obesity is associated with biologic and behavioral characteristics that may impact bone mineral density (BMD) and structure. The objective was to determine the association between obesity and bone outcomes, independent of sexual and skeletal maturity, muscle area and strength, physical activity, calcium intake, biomarkers of inflammation, and vitamin D status. Tibia and radius peripheral quantitative CT scans were obtained in 91 obese (BMI>97th percentile) and 51 non-obese adolescents (BMI>5th and <85th percentiles). Results were converted to sex- and race-specific Z-scores relative to age. Cortical structure, muscle area and muscle strength (by dynamometry) Z-scores were further adjusted for bone length. Obese participants had greater height Z-scores (p<0.001), and advanced skeletal maturity (p<0.0001), compared with non-obese participants. Tibia cortical section modulus and calf muscle area Z-scores were greater in obese participants (1.07 and 1.63, respectively, both p<0.0001). Tibia and radius trabecular and cortical volumetric BMD did not differ significantly between groups. Calf muscle area and strength Z-scores, advanced skeletal maturity, and physical activity (by accelerometry) were positively associated with tibia cortical section modulus Z-scores (all p<0.01). Adjustment for muscle area Z-score attenuated differences in tibia section modulus Z-scores between obese and non-obese participants from 1.07 to 0.28. After multivariate adjustment for greater calf muscle area and strength Z-scores, advanced maturity, and less moderate to vigorous physical activity, tibia section modulus Z-scores were 0.32 (95% CI -0.18, 0.43, p=0.06) greater in obese, vs. non-obese participants. Radius cortical section modulus Z-scores were 0.45 greater (p=0.08) in obese vs. non-obese participants; this difference was attenuated to 0.14 with adjustment for advanced maturity. These findings suggest that greater tibia cortical section modulus in obese adolescents is attributable to advanced skeletal maturation and greater muscle area and strength, while less moderate to vigorous physical activities offset the positive effects of these covariates. The impact of obesity on cortical structure was greater at weight bearing sites.

Project description:Although caloric restriction (CR) could delay biologic aging in humans, it is unclear if this would occur at the cost of significant bone loss. We evaluated the effect of prolonged CR on bone metabolism and bone mineral density (BMD) in healthy younger adults. Two-hundred eighteen non-obese (body mass index [BMI] 25.1?±?1.7?kg/m(2) ), younger (age 37.9?±?7.2 years) adults were randomly assigned to 25% CR (CR group, n?=?143) or ad libitum (AL group, n?=?75) for 2 years. Main outcomes were BMD and markers of bone turnover. Other outcomes included body composition, bone-active hormones, nutrient intake, and physical activity. Body weight (-7.5?±?0.4 versus 0.1?±?0.5?kg), fat mass (-5.3?±?0.3 versus 0.4?±?0.4?kg), and fat-free mass (-2.2?±?0.2 versus -0.2?±?0.2?kg) decreased in the CR group compared with AL (all between group p < 0.001). Compared with AL, the CR group had greater changes in BMD at 24 months: lumbar spine (-0.013?±?0.003 versus 0.007?±?0.004?g/cm(2) ; p < 0.001), total hip (-0.017?±?0.002 versus 0.001?±?0.003?g/cm(2) ; p < 0.001), and femoral neck (-0.015?±?0.003 versus -0.005?±?0.004?g/cm(2) ; p?=?0.03). Changes in bone markers were greater at 12 months for C-telopeptide (0.098?±?0.012 versus 0.025?±?0.015??g/L; p < 0.001), tartrate-resistant acid phosphatase (0.4?±?0.1 versus 0.2?±?0.1?U/L; p?=?0.004), and bone-specific alkaline phosphatase (BSAP) (-1.4?±?0.4 versus -0.3?±?0.5?U/L; p?=?0.047) but not procollagen type 1 N-propeptide; at 24 months, only BSAP differed between groups (-1.5?±?0.4 versus 0.9?±?0.6?U/L; p?=?0.001). The CR group had larger increases in 25-hydroxyvitamin D, cortisol, and adiponectin and decreases in leptin and insulin compared with AL. However, parathyroid hormone and IGF-1 levels did not differ between groups. The CR group also had lower levels of physical activity. Multiple regression analyses revealed that body composition, hormones, nutrients, and physical activity changes explained ?31% of the variance in BMD and bone marker changes in the CR group. Therefore, bone loss at clinically important sites of osteoporotic fractures represents a potential limitation of prolonged CR for extending life span. Further long-term studies are needed to determine if CR-induced bone loss in healthy adults contributes to fracture risk and if bone loss can be prevented with exercise.

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Energy restriction is associated with lower bone mineral density of the tibia and femur in lean but not obese female rats.

Publications

Energy restriction is associated with lower bone mineral density of the tibia and femur in lean but not obese female rats.

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