Global estrogen receptor-α knockout has differential effects on cortical and cancellous bone in aged male mice

Estrogen receptor-α knockout (ERKO) in female rodents results in bone loss associated with increased osteocyte sclerostin expression; whether this also occurs in males is unknown. Here, we examined the effects of ERKO on femoral cortical geometry, trabecular microarchitecture, and osteocyte sclerostin expression of the femur and lumbar vertebrae. At 14 months of age, male ERKO and wild-type (WT) littermates ( n = 6 per group) were sacrificed, and femora and vertebra were collected. Cortical geometry and trabecular microarchitecture were assessed via micro-computed tomography; osteocyte sclerostin expression was assessed via immunohistochemistry. ANCOVA with body weight was used to compare ERKO and WT for cortical geometry; t-tests were used for all other outcomes. Regardless of skeletal site, ERKO mice had greater trabecular bone volume and trabecular number and decreased trabecular separation compared with WT. In the femoral diaphysis, ERKO had lower total area, cortical area, and cortical thickness compared with WT. The percentage of sclerostin+ osteocytes was increased in ERKO animals in cortical bone but not in cancellous bone of the femur or the lumbar vertebrae. In conclusion, ERKO improved trabecular microarchitecture in aged male mice, but negatively altered femoral cortical geometry associated with a trend towards increased cortical sclerostin expression.

Soy protein improves tibial whole-bone and tissue-level biomechanical properties in ovariectomized and ovary-intact, low-fit female rats

BACKGROUND

Osteoporosis and related fractures, decreased physical activity, and metabolic dysfunction are serious health concerns for postmenopausal women. Soy protein might counter the negative effects of menopause on bone and metabolic health due to the additive or synergistic effects of its bioactive components.

OBJECTIVE

To evaluate the effects of ovariectomy (OVX) and a soy-protein diet (SOY) on bone outcomes in female, low-capacity running (LCR) rats selectively bred for low aerobic fitness as a model of menopause.

METHODS

At 27 weeks of age, LCR rats (N = 40) underwent OVX or sham (SHAM) surgery and were randomized to one of two isocaloric and isonitrogenous plant-protein-based dietary treatments: 1) soy-protein (SOY; soybean meal); or, 2) control (CON, corn-gluten meal), resulting in four treatment groups. During the 30-week dietary intervention, animals were provided ad libitum access to food and water; body weight and food intake were measured weekly. At completion of the 30-week intervention, body composition was measured using EchoMRI; animals were fasted overnight, euthanized, and blood and hindlimbs collected. Plasma markers of bone formation (osteocalcin, OC; N-terminal propeptide of type I procollagen, P1NP) and resorption (tartrate-resistant acid phosphatase, TRAP5b; C-terminal telopeptide of type I collagen, CTx) were measured using ELISA. Tibial trabecular microarchitecture and cortical geometry were evaluated using μCT; and torsional loading to failure was used to assess cortical biomechanical properties. Advanced glycation end-product (AGE) content of the femur was measured using a fluorimetric assay, and was expressed relative to collagen content measured by a colorimetric OH-proline assay. Two-factor ANOVA or ANOVCA was used to test for significant main and interactive effects of ovarian status (OV STAT: OVX vs. SHAM) and DIET (SOY vs. CON); final body weight was included as a covariate for body-weight-dependent cortical geometry and biomechanical properties.

RESULTS

OVX had significantly greater CTx than SHAM; SOY did not affect bone turnover markers. OVX adversely affected trabecular microarchitecture as evidenced by reduced BV/TV, trabecular thickness (Tb.Th), trabecular number (Tb.N), and connectivity density (Conn.D), and by increased trabecular separation (Tb.Sp) and structural model index (SMI). SOY increased BV/TV only in ovary-intact animals. There was no effect of OVX or SOY on tibial cortical geometry. In SHAM and OVX rats, SOY significantly improved whole-bone strength and stiffness; SOY also increased tissue-level stiffness and tended to increase tissue-level strength (p = 0.067). There was no effect of OVX or SOY on AGE content.

CONCLUSION

Soy protein improved cortical bone biomechanical properties in female low-fit rats, regardless of ovarian hormone status.

Soy Protein Isolate Suppresses Bone Resorption and Improves Trabecular Microarchitecture in Spontaneously Hyperphagic, Rapidly Growing Male OLETF Rats

BACKGROUND

Traditionally, milk proteins have been recommended for skeletal health; recently, soy proteins have emerged as popular alternatives. Excess adiposity appears detrimental to skeletal health, as obese adolescents have increased fracture rates compared with healthy controls. However, soy protein effects on skeletal health during excess adiposity remain unknown.

OBJECTIVE

The study objective was to examine the effects of isocaloric diets containing milk protein isolate (MPI), soy protein isolate (SPI), or a 50/50 combination (MIX) as the sole protein source on metabolic health indicators and bone outcomes in rapidly growing, hyperphagic, male Otsuka Long Evans Tokushima Fatty (OLETF) rats.

METHODS

OLETF rats, aged 4 wk, were randomly assigned to 3 treatment groups (MPI, SPI, or MIX, n = 20 per group) and provided with access to experimental diets ad libitum for 16 wk.

RESULTS

Body mass did not differ between the groups, but SPI had lower percentage body fat than MPI (P = 0.026). Insulin was lower in MPI than in MIX (P = 0.033) or SPI (P = 0.044), but fasting blood glucose was not different between the groups. SPI significantly reduced serum cholesterol compared with MPI (P = 0.001) and MIX (P = 0.002). N-terminal propeptide of type I collagen (P1NP) was higher in MIX than MPI (P = 0.05); C-terminal telopeptide of type 1 collagen (CTx) was higher in MPI than SPI (P < 0.001) and MIX (P < 0.001); the P1NP to CTx ratio was significantly higher in SPI and MIX than in MPI (P < 0.001). Trabecular separation was reduced in SPI compared with MPI (P = 0.030) and MIX (P = 0.008); trabecular number was increased in SPI compared with MIX (P = 0.038). No differences were seen in cortical geometry and biomechanical properties.

CONCLUSIONS

In the context of excess adiposity, soy- and milk-based proteins have comparable effects on cortical bone geometry and biomechanical properties, whereas soy-based proteins favorably affect the trabecular microarchitecture, and the combination of both proteins may offer additional benefits to bone remodeling in rapidly growing male OLETF rats.

Obesity and type 2 diabetes, not a diet high in fat, sucrose, and cholesterol, negatively impacts bone outcomes in the hyperphagic Otsuka Long Evans Tokushima Fatty rat

BACKGROUND

Obesity and type 2 diabetes (T2D) increase fracture risk; however, the association between obesity/T2D may be confounded by consumption of a diet high in fat, sucrose, and cholesterol (HFSC).

OBJECTIVE

The study objective was to determine the main and interactive effects of obesity/T2D and a HFSC diet on bone outcomes using hyperphagic Otuska Long Evans Tokushima Fatty (OLETF) rats and normophagic Long Evans Tokushima Otsuka (LETO) controls.

METHODS

At 8weeks of age, male OLETF and LETO rats were randomized to either a control (CON, 10 en% from fat as soybean oil) or HFSC (45 en% from fat as soybean oil/lard, 17 en% sucrose, and 1wt%) diet, resulting in four treatment groups. At 32weeks, total body bone mineral content (BMC) and density (BMD) and body composition were measured by dual-energy X-ray absorptiometry, followed by euthanasia and collection of blood and tibiae. Bone turnover markers and sclerostin were measured using ELISA. Trabecular microarchitecture of the proximal tibia and geometry of the tibia mid-diaphysis were measured using microcomputed tomography; whole-bone and tissue-level biomechanical properties were evaluated using torsional loading of the tibia. Two-factor ANOVA was used to determine main and interactive effects of diet (CON vs. HFSC) and obesity/T2D (OLETF vs. LETO) on bone outcomes.

RESULTS

Hyperphagic OLEFT rats had greater final body mass, body fat, and fasting glucose than normophagic LETO, with no effect of diet. Total body BMC and serum markers of bone formation were decreased, and bone resorption and sclerostin were increased in obese/T2D OLETF rats. Trabecular bone volume and microarchitecture were adversely affected by obesity/T2D, but not diet. Whole-bone and tissue-level biomechanical properties of the tibia were not affected by obesity/T2D; the HFSC diet improved biomechanical properties only in LETO rats.

CONCLUSIONS

Obesity/T2D, regardless of diet, negatively impacted the balance between bone formation and resorption and trabecular bone volume and microarchitecture in OLETF rats.

Exercise initiated after the onset of insulin resistance improves trabecular microarchitecture and cortical bone biomechanics of the tibia in hyperphagic Otsuka Long Evans Tokushima Fatty rats

The present study extends our previous findings that exercise, which prevents the onset of insulin resistance and type 2 diabetes (T2D), also prevents the detrimental effects of T2D on whole-bone and tissue-level strength. Our objective was to determine whether exercise improves bone's structural and material properties if insulin resistance is already present in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat. The OLETF rat is hyperphagic due to a loss-of-function mutation in cholecystokinin-1 receptor (CCK-1 receptor), which leads to progressive obesity, insulin resistance and T2D after the majority of skeletal growth is complete. Because exercise reduces body mass, which is a significant determinant of bone strength, we used a body-mass-matched caloric-restricted control to isolate body-mass-independent effects of exercise on bone. Eight-wk old, male OLETF rats were fed ad libitum until onset of hyperglycemia (20weeks of age), at which time they were randomly assigned to three groups: ad libitum fed, sedentary (O-SED); ad libitum fed, treadmill running (O-EX); or, sedentary, mild caloric restriction to match body mass of O-EX (O-CR). Long-Evans Tokushima Otsuka rats served as the normophagic, normoglycemic controls (L-SED). At 32weeks of age, O-SED rats had T2D as evidenced by hyperglycemia and a significant reduction in fasting insulin compared to OLETFs at 20weeks of age. O-SED rats also had reduced total body bone mineral content (BMC), increased C-terminal telopeptide of type I collagen (CTx)/tartrate resistant acid phosphatase isoform 5b (TRAP5b), decreased N-terminal propeptide of type I procollagen (P1NP), reduced percent cancellous bone volume (BV/TV), trabecular number (Tb.N) and increased trabecular separation (Tb.Sp) and structural model index (SMI) of the proximal tibia compared to L-SED. T2D also adversely affected biomechanical properties of the tibial diaphysis, and serum sclerostin was increased and β-catenin, runt-related transcription factor 2 (Runx2) and insulin-like growth factor-I (IGF-I) protein expression in bone were reduced in O-SED vs. L-SED. O-EX or O-CR had greater total body bone mineral density (BMD) and BMC, and BV/TV, Tb.N, Tb.Sp, and SMI compared to O-SED. O-EX had lower CTx and CR greater P1NP relative to O-SED. O-EX, not O-CR, had greater cortical thickness and area, and improved whole-bone and tissue-level biomechanical properties associated with a 4-fold increase in cortical bone β-catenin protein expression vs. O-SED. In summary, EX or CR initiated after the onset of insulin resistance preserved cancellous bone volume and structure, and EX elicited additional benefits in cortical bone.

Insulin-Stimulated Bone Blood Flow and Bone Biomechanical Properties Are Compromised in Obese, Type 2 Diabetic OLETF Rats

Type 2 diabetes (T2D) increases skeletal fragility and fracture risk; however, the underlying mechanisms remain to be identified. Impaired bone vascular function, in particular insulin‐stimulated vasodilation and blood flow is a potential, yet unexplored mechanism. The purpose of this study was to determine the effects of T2D on femoral biomechanical properties, trabecular microarchitecture, and insulin‐stimulated bone vasodilation by comparison of hyperphagic Otsuka Long‐Evans Tokushima Fatty (OLETF) rats with normoglycemic control OLETF rats. Four‐week old, male OLETF rats were randomized to two groups: type 2 diabetes (O‐T2D) or normoglycemic control (O‐CON). O‐T2D were allowed ad libitum access to a rodent chow diet and O‐CON underwent moderate caloric restriction (30% restriction relative to intake of O‐T2D) to maintain normal body weight (BW) and glycemia until 40 weeks of age. Hyperphagic O‐T2D rats had significantly greater BW, body fat, and blood glucose than O‐CON. Total cross‐sectional area (Tt.Ar), cortical area (Ct.Ar), Ct.Ar/Tt.Ar, and polar moment of inertia of the mid‐diaphyseal femur adjusted for BW were greater in O‐T2D rats versus O‐CON. Whole‐bone biomechanical properties of the femur assessed by torsional loading to failure did not differ between O‐T2D and O‐CON, but tissue‐level strength and stiffness adjusted for BW were reduced in O‐T2D relative to O‐CON. Micro–computed tomography (μCT) of the distal epiphysis showed that O‐T2D rats had reduced percent bone volume, trabecular number, and connectivity density, and greater trabecular spacing compared with O‐CON. Basal tibial blood flow assessed by microsphere infusion was similar in O‐T2D and O‐CON, but the blood flow response to insulin stimulation in both the proximal epiphysis and diaphyseal marrow was lesser in O‐T2D compared to O‐CON. In summary, impaired insulin‐stimulated bone blood flow is associated with deleterious changes in bone trabecular microarchitecture and cortical biomechanical properties in T2D, suggesting that vascular dysfunction might play a causal role in diabetic bone fragility. © 2017 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Exercise improves femoral whole-bone and tissue-level biomechanical properties in hyperphagic OLETF rats

An often-overlooked comorbidity of type 2 diabetes (T2D) is increased fracture risk. Since traditional T2D therapies focus solely on glucose homeostasis, there is an increased need for effective treatment strategies that improve both metabolic and bone health. The current study evaluated if previously reported protective effects of exercise (EX) on cortical bone geometry and biomechanical properties are due to the prevention of obesity compared with obese Otsuka Long-Evans Tokushima Fatty (OLETF) rats or the unique skeletal effects of exercise. Four-week-old male OLETF rats were randomly assigned to 1 of 3 groups, each fed a standard rodent chow diet until 40 weeks of age: ad libitum-fed sedentary (O-SED), ad libitum-fed EX (O-EX), or a control group body-weight-matched to the O-EX group by caloric restriction (O-CR). Ad libitum-fed sedentary Long-Evans Tokushima Otsuka (L-SED) rats were used as a lean control. EX or CR prevented the excess body mass accumulation and elevated HbA1c observed in O-SED. Total-body bone mineral density was greater in O-EX than O-CR, but similar to L-SED and O-SED. O-EX and O-CR had lower osteocalcin and TRAP5b than O-SED and L-SED. EX or CR prevented the ∼3-fold increase in CTx in O-SED versus L-SED. EX increased femoral cortical mass accumulation and expansion at the mid-diaphysis compared with O-CR. EX or CR significantly increased tissue-level stiffness and strength compared with O-SED and L-SED, but O-EX had greater whole-bone stiffness than all other groups. In summary, EX has distinct advantages over CR for improving bone biomechanical properties in hyperphagic OLETF rats.

Serum sclerostin decreases following 12months of resistance- or jump-training in men with low bone mass

PURPOSE

We previously reported that 12months of resistance training (RT, 2×/wk, N=19) or jump training (JUMP, 3×/wk, N=19) increased whole body and lumbar spine BMD and increased serum bone formation markers relative to resorption in physically active (≥4h/wk) men (mean age: 44±2y; median: 44y) with osteopenia of the hip or spine. The purpose of this secondary analysis was to examine the effects of the RT or JUMP intervention on potential endocrine mediators of the exercise effects on bone, specifically IGF-I, PTH and sclerostin.

METHODS

Fasting blood samples were collected after a 24-h period of no exercise at baseline and after 12months of RT or JUMP. IGF-I, PTH and sclerostin were measured in serum by ELISA. The effects of RT or JUMP on IGF-I, PTH and sclerostin were evaluated using 2×2 repeated measures ANOVA (time, group). This study was conducted in accordance with the Declaration of Helsinki and was approved by the University of Missouri IRB.

RESULTS

Sclerostin concentrations in serum significantly decreased and IGF-I significantly increased after 12months of RT or JUMP; while PTH remained unchanged.

CONCLUSION

The beneficial effects of long-term, progressive-intensity RT or JUMP on BMD in moderately active men with low bone mass are associated with decreased sclerostin and increased IGF-I.

One bout of exercise alters free-living postprandial glycemia in type 2 diabetes

PURPOSE

Elevated postprandial glycemic (PPG) excursions are significant risk factors for cardiovascular disease in type 2 diabetes patients. In this study, we tested if and for how many meals a single bout of exercise would reduce PPG responses to subsequent meals in type 2 diabetes (T2D) patients using a continuous glucose monitor system (CGMS).

METHODS

We recruited nine sedentary (<30 min·wk(-1) of exercise) individuals with T2D (mean ± SD; body mass index = 36.0 ± 1.1 kg·m(-2), age = 60.3 ± 1.0 yr, HbA1c = 6.3% ± 0.2%). The subjects consumed a eucaloric diet (51% carbohydrate, 31% fat, and 18% protein) consisting of three meals, identical in composition, for a 2-d period while wearing a continuous glucose monitor system in two different conditions (exercise [EX], one 60-min bout at 60%-75% of heart rate reserve performed before breakfast), vs a sedentary [SED] condition). We quantified 24-h average glucose, PPG area under the curve (AUC; 4-h glucose AUC after meals), and PPG-2 h (2 h postprandial glucose).

RESULTS

EX significantly reduced average [glucose] during the first 24-h period (P = 0.03). EX caused a reduction in PPG-AUC (P = 0.02) for all of the meals during the 2 d (main effect between conditions). A comparison between the EX and the SED conditions at each meal revealed that EX reduced PPG-AUC after the second meal of day 1 (lunch) (P = 0.04). PPG-2 h was not significantly different between EX and SED.

CONCLUSIONS

Although a single EX bout does lower 24-h average [glucose], it only significantly lowered PPG-AUC at the second meal after the bout, suggesting that daily exercise may be needed to most effectively improve PPG at the advent of exercise training in T2D patients.

Effectiveness of resistance training or jumping-exercise to increase bone mineral density in men with low bone mass: A 12-month randomized, clinical trial

PURPOSE

To examine the effects of 12 mo of resistance training (RT, 2×/wk, N=19) or jump training (JUMP, 3×/wk, N=19) on bone mineral density (BMD) and bone turnover markers (BTM) in physically active (≥ 4h/wk) men (mean age: 44 ± 2 y; median: 44 y) with osteopenia of the hip or spine.

METHODS

Participants rated pain and fatigue following each RT or JUMP session. All participants received supplemental calcium (1200 mg/d) and vitamin D (10 μg/d). BMD was measured at 0, 6, and 12 mo using DXA scans of the whole body (WB), total hip (TH) and lumbar spine (LS). BTM and 25 OHD were measured by ELISA. The effects of RT or JUMP on BMD and BTM were evaluated using 3x2 repeated measures ANOVA (time, group). This study was conducted in accordance with the Declaration of Helsinki and was approved by the University of Missouri IRB.

RESULTS

At baseline, 36 of 38 participants were vitamin D sufficient (25OHD >50 nmol/L); at 12 mo, all participants were 25OHD sufficient. 25OHD did not differ between groups. WB and LS BMD significantly increased after 6 months of RT or JUMP and this increase was maintained at 12 mo; TH BMD increased only in RT. Osteocalcin increased significantly after 12 mo of RT or JUMP; CTx decreased significantly after 6 mo and returned to baseline concentrations at 12 mo in both RT and JUMP. Pain and fatigue ratings after RT or JUMP sessions were very low at 0, 6, and 12 mo.

CONCLUSION

RT or JUMP, which appeared safe and feasible, increased BMD of the whole body and lumbar spine, while RT also increased hip BMD, in moderately active, osteopenic men.

Obesity-related changes in bone structural and material properties in hyperphagic OLETF rats and protection by voluntary wheel running

PURPOSE

To examine how the development of obesity and the associated insulin resistance affect bone structural and material properties, and bone formation and resorption markers in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat model.

METHODS

This was a 36-week study of sedentary, hyperphagic, male OLETF rats (OLETF-SED), exercise-treated OLETF rats (OLETF-EX) and sedentary non-hyperphagic controls (LETO-SED) with data collection at 13, 20, and 40 weeks of age (n = 5-8 animals per group per timepoint).

RESULTS

Body mass and fat (%) were significantly greater in OLETF-SED versus controls. OLETF-SED were insulin resistant at 13 and 20 weeks, with overt diabetes by 40 weeks. At 13weeks, OLETF-SED had lower total body BMC and BMD and serum P1NP compared with LETO-SED. Differences in total body BMC and BMD between OLETF-SED and LETO-SED persisted at 20 weeks, with reductions in total and cortical BMD of the tibia. OLETF-SED also had lesser femur diameter, cross-sectional area, polar moment of area, and torque at fracture than LETO-SED. By 40 weeks, OLETF-SED had elevated bone resorption and reduced intrinsic bone strength. OLETF-EX did not show the excessive weight gain, obesity, insulin resistance or diabetes observed in OLETF-SED. OLETF-EX had greater BMD than OLETF-SED, and structural and material properties of the femur were significantly increased in OLETF-EX relative to OLETF-SED and LETO-SED.

CONCLUSIONS

The negative skeletal effects of excessive adiposity and insulin resistance were evident early in the progressive obesity with lasting negative impacts on intrinsic and extrinsic bone strength. Exercise protected against obesity-associated skeletal changes with marked benefits on the biomechanical properties of bone.

The effects of improved metabolic risk factors on bone turnover markers after 12 weeks of simvastatin treatment with or without exercise

OBJECTIVE

Emerging evidence supports an association between metabolic risk factors and bone turnover. Statins and exercise independently improve metabolic risk factors; however whether improvements in metabolic risk factor affects bone turnover is unknown. The purpose of the present study was to: 1) evaluate the relationship between metabolic risk factors and bone turnover; and 2) determine if improvements in metabolic risk factors after 12 weeks of statin treatment, exercise or the combination affect bone turnover.

METHODS

Fifty participants with ≥2 metabolic syndrome defining characteristics were randomly assigned to one of three groups: statin (STAT: simvastatin, 40 mg/day), exercise (EX: brisk walking and/or slow jogging, 45 minutes/day, 5 days/week), or the combination (STAT+EX). Body composition and whole body bone mineral density were measured with dual energy X-ray absorptiometry. Serum markers of bone formation (bone specific alkaline phosphatase, BAP; osteocalcin, OC), resorption (C-terminal peptide of type I collagen, CTX) and metabolic risk factors were determined. Two-factor (time, group) repeated-measures ANCOVA was used to examine changes of metabolic risk factors and bone turnover. General linear models were used to determine the effect of pre-treatment metabolic risk factors on post-treatment bone turnover marker outcomes.

RESULTS

Participants with ≥4 metabolic syndrome defining characteristics had lower pre-treatment OC than those with 3 or fewer. OC was negatively correlated with glucose, and CTX was positively correlated with cholesterol. STAT or STAT+EX lowered total and LDL cholesterol. The OC to CTX ratio decreased in all groups with no other significant changes in bone turnover. Higher pre-treatment insulin or body fat predicted a greater CTX reduction and a greater BAP/CTX increase.

CONCLUSION

Metabolic risk factors were negatively associated with bone turnover markers. Short-term statin treatment with or without exercise lowered cholesterol and all treatments had a small effect on bone turnover.

Physical Activity-Associated Bone Loading During Adolescence and Young Adulthood Is Positively Associated With Adult Bone Mineral Density in Men

Physical activity during growth increases bone mass and strength; however, it remains unclear whether these benefits persist. The purpose of this study was to determine: (a) if bone loading during adolescence (13-18 years) or young adulthood (19-29 years) in men is associated with greater bone mineral density (BMD) in adulthood; (b) if current participation in high-impact activity (ground reaction force>4×body weight) and/or resistance training is associated with greater BMD; and, (c) if continuous participation in a high-impact activity from adolescence to adulthood is associated with greater BMD. Apparently healthy, physically active men aged 30 to 65 years (n=203) participated in this cross-sectional study. Exercise-associated bone loading was estimated based on ground reaction forces of historical physical activity. Current BMD was measured using dual-energy X-ray absorptiometry. Participants were grouped based on current participation in a high-impact activity (n=18), resistance training (n=57), both (n=14), or neither (n=114); groups were compared by two-way analysis of covariance. Bone loading during adolescence and young adulthood were significant, positive predictors of BMD of the whole body, total hip, and lumbar spine, adjusting for lean body mass and/or age in the regression models. Individuals who currently participate in a high-impact activity had greater lumbar spine BMD than nonparticipants. Men who continuously participated in a high-impact activity had greater hip and lumbar spine BMD than those who did not. In conclusion, physical activity-associated bone loading both during and after skeletal growth is positively associated with adult bone mass.

Iron and the endurance athlete

Iron is a trace mineral that is highly significant to endurance athletes. Iron is critical to optimal athletic performance because of its role in energy metabolism, oxygen transport, and acid-base balance. Endurance athletes are at increased risk for suboptimal iron status, with potential negative consequences on performance, because of the combination of increased iron needs and inadequate dietary intake. This review paper summarizes the role of iron in maximal and submaximal exercise and describes the effects of iron deficiency on exercise performance. Mechanisms that explain the increased risk of iron deficiency in endurance athletes, including exercise-associated inflammation and hepcidin release on iron sequestration, are described. Information on screening athletes for iron deficiency is presented, and suggestions to increase iron intake through diet modification or supplemental iron are provided.

Physical activity and bone health

Osteoporosis and related fractures cause significant morbidity and mortality worldwide and result in enormous costs to affected individuals and society. Lifestyle choices across the lifespan impact osteoporosis and fracture risk. Physical activity is a viable strategy for the prevention and treatment of low bone mass.

Weight-loss-associated changes in bone mineral density and bone turnover after partial weight regain with or without aerobic exercise in obese women

Background/Objectives

Moderate, long-term weight loss results in loss of bone mass in overweight or obese premenopausal women. However, whether these changes persist during weight maintenance or regain remains to be determined.

Subjects/Methods

Overweight or obese (BMI: 25.8–42.5 kg/m²) women (n=40) with at least two risk factors for the metabolic syndrome participated in this 12-mo study that examined the effects of prescribed weight loss and regain, with or without exercise, on bone turnover and on bone mineral density (BMD) in a subset of participants (n=24). During the first 6 mo, participants lost ~10% of their initial body weight via energy restriction and supervised aerobic exercise. Following weight loss, participants were randomly assigned to either an exercise or a no-exercise treatment for the regain (+50% of weight lost) phase. A one-way (time) repeated measures ANOVA tested the effects of weight loss on BMD and bone turnover, and a two-way RM ANOVA (time, exercise) was used to examine the effects of exercise during weight regain.

Results

Hip (p=0.007) and lumbar spine (p=0.05) BMD decreased with weight loss, and remained reduced after weight regain with or without exercise. Likewise, the weight-loss-associated increases in osteocalcin (p<0.001) and C-terminal peptide of type I collagen (p<0.001) persisted following weight regain, independent of exercise.

Conclusions

the results of the present study, which is the first to examine changes in bone mass and turnover during carefully controlled weight regain, suggest that weight-loss-induced perturbations in bone mass and turnover persist after partial weight regain, regardless of whether regular, weight-bearing aerobic exercise was continued.

Effects of current exercise and diet on late-life cognitive health of former college football players

OBJECTIVE

To determine the relative influence of current exercise and diet on the late-life cognitive health of former Division I collision-sport collegiate athletes (ie, football players) compared with noncollision-sport athletes and non-athletes.

METHODS

Graduates (n = 400) of a Midwestern university (average age, 64.09 years; standard deviation, 13.32) completed a self-report survey to assess current demographics/physical characteristics, exercise, diet, cognitive difficulties, and physical and mental health.

RESULTS

Former football players reported more cognitive difficulties, as well as worse physical and mental health than controls. Among former football players, greater intake of total and saturated fat and cholesterol and lower overall diet quality were significantly correlated with cognitive difficulties; current dietary intake was not associated with cognitive health for the noncollision-sport athletes or nonathletes. Hierarchical regressions predicting cognitive difficulties indicated that income was positively associated with fewer cognitive difficulties and predicted 8% of the variance; status as a former football player predicted an additional 2% of the variance; and the interaction between being a football player and total dietary fat intake significantly predicted an additional 6% of the total variance (total model predicted 16% of variance). Greater intake of dietary fat was associated with increased cognitive difficulties, but only in the former football players, and not in the controls. Prior participation in football was associated with worse physical and mental health, while more frequent vigorous exercise was associated with higher physical and mental health ratings.

CONCLUSION

Former football players reported more late-life cognitive difficulties and worse physical and mental health than former noncollision-sport athletes and nonathletes. A novel finding of the present study is that current dietary fat was associated with more cognitive difficulties, but only in the former football players. These results suggest the need for educational interventions to encourage healthy dietary habits to promote the long-term cognitive health of collision-sport athletes.

Acute response of plasma markers of bone turnover to a single bout of resistance training or plyometrics

The time course of changes in plasma bone turnover markers following an acute bout of resistance training (RT) or plyometrics (PLY) has not been well characterized. This study is the first to compare the acute response of bone formation and resorption markers to a single bout of RT or PLY. Using a partially randomized, cross-over study design, 12 recreationally active men, aged 43 ± 5 yr, each completed four exercise trials: RT (Fed/Fasted) and PLY (Fed/Fasted). In addition to the RT and PLY trials, 5 of the original 12 participants also completed a fasted, no-exercise control trial to examine time-of-day variation. For each trial, blood was drawn immediately before exercise (PRE), immediately following exercise, and 15 min, 30 min, 1 h, 2 h, and 24 h following PRE for determination of plasma bone-specific alkaline phosphatase (BAP), osteocalcin (OC), tartrate-resistant acid phosphatase 5b (TRAP5b), COOH-terminal telopeptide of type I collagen (CTX), testosterone, parathyroid hormone, and cortisol. A one-factor repeated-measures ANOVA was performed for each trial to detect changes in bone markers during the 2 h following RT or PLY. TRAP5b transiently decreased during the 2 h following all exercise trials (main effect for time, P < 0.05), but returned to PRE concentrations 2 h postexercise. BAP, CTX, and OC remained unchanged, except for reductions in BAP and CTX following PLY-Fasted and PLY-Fed, respectively. During the control trial, BAP decreased, while TRAP5b, CTX, and OC remained unchanged. In general, plasma hormone concentrations decreased during the 2 h following PLY or RT, and cumulative decreases in TRAP5b during the 2 h following exercise were positively correlated with cumulative decreases in parathyroid hormone. The results of the present study suggest that the timing of the measurement of bone turnover markers relative to the last exercise bout is important for detection of exercise-associated changes in bone turnover markers, as the markers returned to preexercise values within 2 h of RT or PLY.

Bone formation is increased to a greater extent than bone resorption during a cycling stage race

This study examined the effects of participation in the Tour of Southland, a 6-day bicycle race, on serum markers of bone turnover in 5 elite male cyclists. During the race, energy intake matched expenditure. Osteocalcin was increased approximately 300% on days 1-5; and C-terminal telopeptide of type I collagen was elevated (43%) on day 3. Participation in a cycling stage race does not appear to have deleterious effects on bone turnover.

Weight loss-induced alterations in serum markers of bone turnover persist during weight maintenance in obese men and women

OBJECTIVE

Moderate weight loss alters bone turnover and reduces bone mineral density in overweight men and women. However, it is not known whether bone turnover is normalized during weight maintenance postweight loss. Thus, the objective of the present study was to examine changes in serum bone turnover markers during 9 months of weight maintenance following weight reduction on a very low-energy diet (VLED) in obese men and women.

METHODS

Thirty-seven men (n = 13) and women (n = 24) aged 50 +/- 9.8 years underwent 3 months of weight reduction on a VLED ( approximately 500 kcal/d) followed by 9 months on either a low-carbohydrate or low-fat weight maintenance diet ( approximately 1600 kcal/d). Concentrations of osteocalcin (OC) and C-terminal peptide of type I collagen (CTX) in serum were measured using enzyme-linked immunosorbent assay at baseline and at months 3, 6, and 12. Serum parathyroid (PTH) concentrations were measured using a chemiluminescent immunoassay at all 4 time points. Data were analyzed using a 3-factor-repeated measures analysis of variance.

RESULTS

Average weight loss was 19% +/- 3% and, during the 9-month weight maintenance period, average weight gain was approximately 3%, with no differences due to diet composition. Serum concentrations of OC and CTX significantly increased after weight reduction and remained elevated during weight maintenance. Serum PTH was reduced after weight loss. Percent changes in OC and CTX were correlated during weight maintenance (r = -0.437, p = 0.008), but not during weight loss. Percent changes in CTX and body weight were negatively correlated during weight loss (r = -0.474, p = 0.003) and maintenance (r = -0.455, p = 0.006).

CONCLUSIONS

Weight loss induced via a VLED may result in an imbalance between bone formation and resorption and accelerate remodeling. The deleterious effect of energy restriction on bone remodeling rate appears to persist during weight maintenance.

Bone formation is increased to a greater extent than bone resorption during a cycling stage race

This study examined the effects of participation in the Tour of Southland, a 6-day bicycle race, on serum markers of bone turnover in 5 elite male cyclists. During the race, energy intake matched expenditure. Osteocalcin was increased approximately 300% on days 1-5; and C-terminal telopeptide of type I collagen was elevated (43%) on day 3. Participation in a cycling stage race does not appear to have deleterious effects on bone turnover.

Bone loading during young adulthood predicts bone mineral density in physically active, middle-aged men

BACKGROUND

Physical activity during growth induces skeletal adaptations that increase bone strength; however, it remains unclear whether these benefits persist into middle age.

OBJECTIVE

We sought to determine if bone loading during adolescence (ages 13-18 years) or young adulthood (ages 19-29 years) in men is associated with greater bone mineral density (BMD) and reduced risk of low bone density in adulthood. We also sought to determine if participation in high-impact activities (ie, those that produce a ground reaction force [GRF] > 4 times the individual's body weight] during adolescence and/or young adulthood has a lasting positive effect on adult BMD.

METHODS

Eighty-six, apparently healthy, physically active men (aged 30-60 years) participated in this cross-sectional study. Bone loading during adolescence, young adulthood, and adulthood were calculated based on GRFs of the reported physical activities. Whole body, lumbar spine, total hip, and femoral neck BMD were assessed using dual-energy x-ray absorptiometry (DXA). Multiple linear regression was used to examine relationships between BMD and bone loading, including body weight and/or age as covariates; logistic regression was used to predict low bone density for age. Participants were grouped based on participation in high-impact activity (never [n = 42], adolescence only [n = 19], or both adolescence and young adulthood [n=23]), and BMDs were compared.

RESULTS

Bone loading during young adulthood, but not adolescence, was a significant positive predictor of adult BMD, with the full models explaining 33.4%, 31.7%, 44.6%, and 50.6% of the variance in whole body, lumbar spine, total hip, and femoral neck BMD, respectively. Ten participants (11.6%) had low bone density for age based on z scores of the hip or spine. Body weight and lean body mass, but not bone loading, were associated with reduced risk of low bone density for age. Individuals who participated in high-impact activity during both adolescence and young adulthood had greater BMD at all measured sites compared with those participated only during adolescence.

CONCLUSION

The results of the study support a lifelong exercise prescription for bone health to preserve the skeletal benefits of activity derived from activity during adolescence and young adulthood.

The effects of resistance training on metabolic health with weight regain

To determine whether resistance training effectively maintains improvements in cardiometabolic syndrome risk factors during weight regain, 9 individuals lost 4% to 6% of their body weight during an 8- to 12-week diet- and aerobic exercise-induced weight loss phase followed by a controlled weight regain phase (8-12 weeks), during which they regained approximately 50% of the lost weight while participating in a supervised resistance training program. Following weight loss (6.0%+/-0.3%), body mass index, body fat percentage, waist circumference, all abdominal adipose tissue depots, total cholesterol, low-density lipoprotein cholesterol, insulin, and homeostasis model assessment (HOMA) were significantly reduced, while quantitative insulin-sensitivity check index (QUICKI) and cardiorespiratory fitness (maximal oxygen consumption) significantly increased. During weight regain (48.3%+/-3.3% of lost weight), body fat percentage, waist circumference, and maximal oxygen consumption were maintained and muscular strength and lean body mass significantly increased. Abdominal adipose tissue depots, insulin, HOMA, and QUICKI did not significantly change after weight regain. Resistance training was effective in maintaining improvements in metabolic health during weight regain.

Exercise and the metabolic syndrome with weight regain

Weight loss improves metabolic syndrome (MetS) factors, but risk may return with weight regain. This study was designed to determine if exercise training can maintain improvements in MetS risk factors during weight regain. In a randomized control trial,102 overweight or obese (body mass index 25.0-39.9 kg/m(2)) men and women (age 21-52 yr), with characteristics of the MetS, lost 10% of body weight with supervised walking/jogging at 60% of maximal oxygen consumption (Vo(2 max)) (-400 kcal/session), 5 days/wk, and caloric restriction (-600 kcal/day) over a 4- to 6-mo period. After weight loss, 77 remaining subjects underwent programmed weight regain (+50% of lost weight) for 4-6 mo with random assignment to two groups: no exercise (NoEX) or continued supervised exercise (EX). Blood pressure, regional fat, glucose homeostasis, lipids, and inflammatory markers were assessed at baseline, post-weight loss, and post-weight regain. Groups were compared by two-way repeated-measures ANOVA on the 67 subjects. After weight loss (9.7 +/- 0.2% of body weight), significant (P < 0.05) improvements were observed in almost all parameters assessed. Following weight regain (54.4 +/- 1.6% of lost weight), the NoEX group exhibited deterioration in most metabolic markers, while the EX group maintained improvements in Vo(2 max), blood pressures, glucose homeostasis, high- and low-density lipoprotein cholesterol (HDL-C and LDL-C), oxidized LDL, and other markers of inflammation, but did not maintain improvements in triglyceride and cholesterol concentrations or abdominal fat. Results of this design of controlled human weight regain suggest that aerobic exercise can counter the detrimental effects of partial weight regain on many markers of disease risk.

Total body bone mineral content and density during weight loss and maintenance on a low- or recommended-dairy weight-maintenance diet in obese men and women

BACKGROUND

Diets high in either dairy or calcium during moderate weight reduction both prevent loss of bone mineral density (BMD) and suppress bone turnover. The purpose of this study was to determine whether recommended dairy and calcium intakes during weight maintenance favorably affect total body BMD (TBBMD) and bone mineral content (TBBMC) in obese adults.

METHODS

Obese men (n=49) and women (n=64), aged 40.8+/-0.6 years, underwent 12 weeks of moderate energy restriction (approximately 1200 kcal/day) followed by 24 weeks on either a low or recommended dairy weight maintenance diet. The TBBMC and TBBMD values were measured using dual energy X-ray absorptiometry at baseline, 12, 24 and 36 weeks. Concentrations of calcium, intact parathyroid hormone (iPTH), 25OH and 1,25 (OH)(2) vitamin D in plasma were also measured. Data were analyzed using a two-factor repeated measures analysis of variance.

RESULTS

After weight loss, women exhibited a small, but statistically significant, increase in TBBMC (1.17+/-0.57%), whereas TBBMD increased in the men (1.34+/-0.28%). The iPTH concentration decreased significantly in all subjects. Despite significantly greater intakes of calcium, vitamin D and protein compared with the recommended dairy diet, there were no treatment-related differences in outcome variables after 24 weeks of weight maintenance. The TBBMC remained unchanged in women during weight stabilization; both TBBMC and TBBMD decreased in men (-1.59+/-0.51% and -0.70+/-0.25%, respectively).

CONCLUSIONS

In summary, results of this study do not provide convincing evidence that moderate weight loss through energy restriction and mild exercise reduces TBBMC in obese men and women. Similarly, a weight-maintenance diet providing the recommended daily servings of dairy does not seem to affect changes in BMC after weight loss.

Serum markers of bone turnover are increased by modest weight loss with or without weight-bearing exercise in overweight premenopausal women

Weight loss improves metabolic fitness and reduces morbidity and mortality; however, weight reduction also reduces bone mineral density (BMD) and increases bone turnover. Weight-bearing aerobic exercise may preserve bone mass and maintain normal bone turnover during weight reduction. We investigated the impact of weight-bearing and nonweight-bearing exercise on serum markers of bone formation and breakdown during short-term, modest weight loss in overweight premenopausal women. Subjects (n = 36) were assigned to 1 of 3 weight-loss interventions designed to produce a 5% reduction in body weight over 6 weeks: (i) energy restriction only (n = 11; DIET); (ii) energy restriction plus nonweight-bearing exercise (n = 12, CYCLE); or (iii) energy restriction plus weight-bearing exercise (n = 13, RUN). Bone turnover markers were measured in serum collected at baseline and after weight loss. All groups achieved a ~5% reduction in body weight (DIET = 5.2%; CYCLE = 5.0%; RUN = 4.7%). Osteocalcin (OC) and C-terminal telopeptide of type I collagen (CTX) increased with weight loss in all 3 groups (p < 0.05), whereas bone alkaline phosphatase was unaltered by the weight-loss interventions. At baseline, OC and CTX were positively correlated (r = 0.36, p = 0.03), but the strength of this association was diminished (r = 0.30, p = 0.06) after weight loss. Modest weight loss, regardless of method, resulted in a significant increase in both OC and CTX. Low-impact, weight-bearing exercise had no effect on serum markers of bone formation or resorption in premenopausal women during weight loss. Future studies that examine the effects of high-impact, weight-bearing activity on bone turnover and BMD during weight loss are warranted.

Participation in road cycling vs running is associated with lower bone mineral density in men

The effects of regular non-weight-bearing (NWB) exercise on bone health are largely unknown. The objective of the study was to determine the effects of participation in NWB sports on bone health in adult male recreational athletes. Male cyclists (NWB; n = 27) and runners (weight-bearing [WB]; n = 16) aged 20 to 59 years were recruited from the community. Whole-body and regional bone mineral content and bone mineral density (BMD), and body composition were assessed using dual x-ray absorptiometry. Bone formation and resorption markers, and hormones were measured in serum. Bone-loading history was estimated from a sports participation history questionnaire. Nutrient intake and current physical activity were estimated from 7-day written logs. The NWB athletes had significantly lower BMD of the whole body and spine than the WB athletes, despite having similar age, weight, body mass index, body composition, hormonal status, current activity level, and nutrient intakes. Sixty-three percent of NWB athletes had osteopenia of the spine or hip, compared with 19% of WB athletes. Cyclists were 7 times more likely to have osteopenia of the spine than runners, controlling for age, body weight, and bone-loading history. There were no group differences in serum markers of bone turnover. Based on the results of this study, current bone loading is an important determinant of whole-body and lumbar spine BMD. Therefore, bone-loading activity should be sustained during adulthood to maintain bone mass.

Exercise and diet induced weight loss improves measures of oxidative stress and insulin sensitivity in adults with characteristics of the metabolic syndrome

Obesity and insulin resistance (IR) increase the risk for coronary heart disease; however, much of this risk is not attributable to traditional risk factors. We sought to determine whether weight loss associated with supervised aerobic exercise beneficially alters biomarkers of oxidative stress and whether these alterations are associated with improvements in measures of insulin resistance. Twenty-five sedentary and overweight to obese [body mass index (BMI) = 33.0 +/- 0.8 kg/m(2)] individuals, with characteristics of the metabolic syndrome, participated in a 4- to 7-mo weight loss program that consisted of energy restriction (reduced by approximately 500 kcal/day) and supervised aerobic exercise (5 days/wk, 45 min/day at 60% Vo(2 max); approximately 375 kcal/day). IR and insulin sensitivity were assessed by the calculation of the homeostasis model assessment (HOMA) and quantitative insulin sensitivity check index (QUICKI), respectively. Oxidative stress was assessed by oxidized LDL (oxLDL), myeloperoxidase (MPO), and low- and high- density lipoprotein (LDL and HDL) lipid hydroperoxide concentrations in serum. Indexes for antioxidative status included apolipoprotein A1 (apoA1) concentrations and paraoxonase-1 (PON1) activity and protein concentrations. Exercise- and diet-induced weight loss ( approximately 10%) significantly (P < 0.05) increased insulin sensitivity and reduced IR, oxLDL, and LDL lipid hydroperoxides but did not alter HDL lipid hydroperoxides or MPO concentrations. Lifestyle modification impacted systemic antioxidative status by increasing apoA1 concentrations and reducing serum PON1 protein and activity. Changes in oxidative stress were not associated with alterations in HOMA or QUICKI. Diet- and exercise-induced weight loss ( approximately 10%) improves measures of insulin sensitivity and beneficially alters biomarkers of oxidative status.

Weight-bearing, aerobic exercise increases markers of bone formation during short-term weight loss in overweight and obese men and women

We investigated the impact of weight-bearing, aerobic exercise- and diet-induced weight loss on markers of bone turnover during a larger study of changes in metabolic fitness during short-term weight reduction using a repeated-measures, within-subject experimental design. Subjects (N = 19) underwent 6 weeks of energy restriction (reduced by approximately 3140 kJ/d) and aerobic exercise ( approximately 1675 kJ/d, walking or jogging at 60% maximum oxygen consumption) to induce a 5% reduction in body weight. Bone turnover markers and hormones were measured in serum collected at baseline and after 6 weeks of weight loss. Despite a 5% reduction in body weight at week 6, markers of bone formation, osteocalcin, and bone alkaline phosphatase, were significantly increased, and resorption markers, C-terminal cross-links of type I collagen and soluble receptor activator of nuclear factor kappaB ligand, were unchanged after 6 weeks of energy restriction and exercise. The concentration of leptin was significantly reduced after weight loss, but insulin-like growth factor I (IGF-I) and cortisol levels were unaffected. In conclusion, weight-bearing, aerobic exercise training may favorably affect the balance between bone resorption and formation during weight loss.

Iron supplementation maintains ventilatory threshold and improves energetic efficiency in iron-deficient nonanemic athletes

OBJECTIVE

To determine the effect of iron supplementation on iron status and endurance capacity.

DESIGN

Randomized, double-blind iron supplementation.

SETTING

University of Missouri-Columbia and surrounding community.

SUBJECTS

Twenty iron-deficient (serum ferritin, sFer<16 microg/l; serum transferrin receptor, sTfR>8.0 mg/l; or sTfR/log sFer index >4.5), nonanemic (hemoglobin, Hb>120 g/l, women; >130 g/l, men) men and women (18-41 years) were recruited via fliers and newspaper advertisements; 20 of 31 eligible subjects participated.

INTERVENTIONS

A 30 mg measure of elemental iron as ferrous sulfate or placebo daily for 6 weeks.

RESULTS

Dietary iron intake and physical activity did not differ between groups before or after supplementation. Iron supplementation significantly increased sFer compared to placebo (P=0.01), but did not affect Hb or hematocrit. Iron supplementation prevented the decline in ventilatory threshold (VT) observed in the placebo group from pre- to post-supplementation (P=0.01); this effect was greater in individuals with lower sFer before intervention (P<0.05). Changes in sFer from pre- to post-treatment were positively correlated with changes in VT (P=0.03), independent of supplementation. The iron group significantly increased gross energetic efficiency during the submaximal test (P=0.04). Changes in sFer were negatively correlated with changes in average respiratory exchange ratio during the submaximal test (P<0.05).

CONCLUSIONS

Iron supplementation significantly improves iron status and endurance capacity in iron-deficient, nonanemic trained male and female subjects.

Serum Markers of Inflammation and Endothelial Function are Elevated by Hormonal Contraceptive Use but not by Exercise-Associated Menstrual Disorders in Physically Active Young Women

The purpose of the study was to determine the effects of exercise-associated menstrual disorders and hormonal contraceptives (HC) on systemic inflammatory markers and endothelial function in female athletes. Thirty-nine active women (≥5 h of aerobic exercise per wk), aged 18-33 y, participated in this cross-sectional study comparing women with menstrual disorders (MD, n = 10; 0-9 cycles·y(-1)), eumenorrheic women (E, n = 13; 10-13 cycles·y(-1)), and HC users (HC, n = 16; 12 cycles·y(-1)). Fasting serum samples were collected during the early follicular phase (d2-5) for the menstruating women. Tumor necrosis factor-α (TNFα), interleukin-6 (IL-6), C-reactive protein (CRP), soluble vascular adhesion molecule-1 (sVCAM-1), total cholesterol (TC), high- and low density lipoprotein-cholesterol (HDL-C, LDL-C), triglycerides (TG), reproductive hormones, and cortisol were measured in serum. Estradiol, progesterone, and cortisol were not statistically different between MD and E groups; cortisol was significantly greater in the HC versus E group (p = 0.002). TC (p = 0.005), LDL-C (p = 0.03), and CRP (p = 0.05) were increased in the HC versus MD and E groups. TNF-α was significantly higher in the HC (p=0.001) compared with the E group. There were no significant group differences in the concentrations of sVCAM-1 or IL-6. TNF-α and cortisol were positively correlated (r=0.31, p = 0. 058), as were sVCAM-1 and estradiol (r = 0.41, p = 0.010). In conclusion, HC use, but not exercise- associated menstrual disorders, is associated with increased TNFα and LDL-C. Key PointsSerum lipids and markers of inflammation were not altered by exercise-associated oligomenorrhea or amenorrhea.Hormonal contraceptive users had elevated total and LDL cholesterol compared with regularly menstruating non-HC users.C-reactive protein and tumor necrosis factor-α, but not soluble vascular adhesion molecule-1, were increased in hormonal contraceptive users.The long-term effect of these changes on cardiovascular disease is unknown.

Psychosocial correlates of disordered eating in female collegiate athletes: validation of the ATHLETE questionnaire

Female athletes may be at greater risk for disordered eating than their nonathletic peers, but the psychological antecedents of this dysfunctional behavior in athletes have yet to be elucidated. The objective of this study was to develop an athletics-oriented measure of psychological predictors of disordered eating and to test its initial reliability and validity. Female athletes from 3 National Collegiate Athletics Association (NCAA) Division I universities completed the ATHLETE, a written questionnaire designed to assess psychosocial factors associated with disordered eating in athletes. Five distinct and internally consistent factors (Drive for Thinness and Performance, Social Pressure on Eating, Performance Perfectionism, Social Pressure on Body Shape, and Team Trust) were positively associated with and predictive of disordered eating behaviors in female athletes. The ATHLETE is a reliable and valid measure of psychological predictors of disordered eating in athletics and will be useful in studying the etiology of disordered eating in female athletes.

Nutrient intakes of men and women collegiate athletes with disordered eating

The objective of this study was to assess the macro- and micronutrient intakes of men and women collegiate athletes with disordered eating behaviors and to compare the nutrient intakes of athletes with restrictive- versus binge-eating behaviors. National Collegiate Athletic Association (NCAA) Division I University athletes (n = 232) were administered an anonymous, written questionnaire to compare nutrient intakes, desired weight change, and weight control behaviors in athletes with restrictive- (R) and binge- (B) eating behaviors to those in asymptomatic (A) athletes. T-tests, χ(2) statistic, and ANOVA were used to test for differences among disordered eating groups within genders (p < 0.05). Data are means ± standard error of the mean. Among men athletes, those with disordered eating consumed a smaller percentage of energy from carbohydrate compared to controls (R = 49.7 ± 1.5; B = 48.7 ± 2.3; A = 53.4 ± 0.7%). Among female athletes, those with disordered eating wanted to lose a greater percentage of their current body weight than did asymptomatic athletes (B = -6.1 ± 1.4; R = -6.7 ± 1.1; A = -3.7 ± 0.4%). Women who were classified with binge eating consumed significantly more alcohol than did controls (B = 6.8 ± 1.3; A = 3.9 ± 0.4 g alcohol per day). Athletes with disordered eating were more likely to report restricting their intake of carbohydrate and fat and using supplements to control their weight than asymptomatic athletes. Disordered eating was not associated with greater frequencies of inadequate micronutrient intake in either gender. Athletes with disordered eating may be at significantly greater risk for nutritional inadequacies than athletes who are asymptomatic due to macronutrient restriction and greater alcohol consumption. Key PointsAthletes with disordered eating were more likely to report restricting their intake of carbohydrate and fat and using supplements to control their weight than asymptomatic athletesAmong female athletes, those with disordered eating wanted to lose a greater percentage of their current body weight than did asymptomatic athletesDisordered eating was not associated with greater frequencies of inadequate micronutrient intake in either genderAthletes with disordered eating may be at significantly greater risk for nutritional inadequacies than athletes who are asymptomatic due to macronutrient restriction and greater alcohol consumption.

Nutrient Intakes and Dietary Behaviors of Male and Female Collegiate Athletes

The purpose of this study was to assess the dietary intakes and behaviors of male and female collegiate athletes. Athletes (n = 345) at a NCAA Division I university completed an anonymous questionnaire. T-tests, χ2 statistic and ANOVA were used to assess gender and sport differences. Multiple linear regression was used to assess gender differences in nutrient intakes, controlling for energy intake and to examine the relationships between desired weight change, dietary behaviors, and nutrient intakes. Only 15% and 26% of athletes had adequate intakes of carbohydrate and protein, respectively, based on recommendations for athletes. Males were more likely to exceed the Dietary Guidelines for fat, saturated fat, cholesterol, and sodium than females. Sixty-two percent of female athletes wanted to lose at least 5 lbs compared to 23% of males. The desire to lose weight was associated with decreased energy and macronutrient consumption, but not with inadequate micronutrient intakes.

Tissue iron deficiency without anemia impairs adaptation in endurance capacity after aerobic training in previously untrained women

BACKGROUND

We previously showed that iron supplementation significantly improves iron status and maximal work capacity in previously untrained, marginally iron-deficient women with a baseline serum transferrin receptor concentration > 8.0 mg/L. However, the effect of transferrin receptor status on adaptation in endurance capacity after aerobic training in these subjects has not been fully explored.

OBJECTIVE

Our objective was to examine the effect of baseline serum transferrin receptor status on adaptations in endurance capacity.

DESIGN

Forty-one untrained, iron-depleted, nonanemic women were randomly assigned to receive either 100 mg FeSO(4) or a placebo for 6 wk in a double-blind trial. All subjects trained on cycle ergometers 5 d/wk for the last 4 wk of the study. Endurance capacity was assessed at baseline and after treatment by using a 15-km time trial conducted on a cycle ergometer.

RESULTS

Significant treatment effects were observed for time to complete the 15-km time trial, work rate, and percentage of maximal oxygen uptake in subjects with a baseline serum transferrin receptor concentration > 8.0 mg/L. No significant treatment effects were observed in subjects with a normal baseline transferrin receptor concentration.

CONCLUSIONS

Our findings suggest that, in the presence of overt tissue iron deficiency, iron deficiency without anemia impairs adaptation in endurance capacity after aerobic training in previously untrained women. This impairment can be corrected with iron supplementation.