Running exercise and food restriction affect bone chemical properties in young female rats.

PURPOSE: To investigate the effects of a combination of running and food restriction on the chemical properties of the bone in young female rats using Raman spectroscopy. Furthermore, we investigated whether the chemical property parameters correlated with the bone-breaking strength. METHODS: Female Sprague-Dawley rats (7 weeks old) were randomly divided into four groups: sedentary and ad libitum feeding (SED, n = 8), voluntary running exercise and ad libitum feeding (EX, n = 8), sedentary and 30% food-restricted (SED-FR, n = 8), and voluntary running exercise and 30% food-restricted (EXFR, n = 8). The experiment was conducted for a period of 12 weeks. Four parameters measured by Raman spectroscopy were used to evaluate the bone chemical quality. RESULTS: Exercise and restriction had significant interactions on the mineral to matrix ratio. The mineral- to-matrix ratio in the SED-FR group was significantly higher than that in the SED group and significantly lower in the EX-FR group than that in the SED-FR group. Running exercise had significant effects on increasing the crystallinity and carbonate-to-phosphate ratio. In the ad libitum intake condition, there were significant positive correlations between breaking energy and crystallinity (r = 0.593) and between breaking energy and carbonate-to-phosphate ratio (r = 0.854). CONCLUSION: Our findings show that running exercise and food restriction, alone or in combination, affect the chemical properties of bone. Furthermore, under ad libitum intake conditions, positive correlations were found between the breaking energy and crystallinity, or carbonate-to-phosphate ratio.

Soy protein intake increased bone mineral density under nonenergy-deficiency conditions but decreased it under energy-deficiency conditions in young female rats.

Many young individuals attempt to lose too much weight because of a false body image, which induces low bone mineral density (BMD) resulting from energy restriction. In addition, a decrease in estrogen has been observed along with the decrease in BMD. Estrogen is responsible for maintaining bone mass, and soybeans contain high levels of isoflavones, which have estrogen-like effects. Thus, we hypothesized that soy protein prevents low BMD caused by energy deficiency in young female rats. The purpose of this study was to examine the effect of soy protein intake on bone loss by energy deficiency in young female rats. Female Sprague-Dawley rats (6 weeks old) were randomly divided into the following 4 experimental groups: ad libitum feeding and casein diet (AL-Cas); ad libitum feeding and soy diet (AL-Soy); 40% energy restriction and casein diet (ER-Cas); and 40% energy restriction and soy diet (ER-Soy). The experimental period was 10.5 weeks. The AL-soy group had significantly higher BMD of the femur than the AL-Cas group (AL-Cas = 156 ± 5 mg/cm2, AL-Soy = 165 ± 7 mg/cm2; P < .05). Meanwhile, the ER-Soy group had significantly lower BMD of the tibia, femur, and lumbar spine than the ER-Cas group (ER-Cas = 147 ± 7 mg/cm2, ER-Soy = 133 ± 10 mg/cm2; P < .01). These results show that compared with ad libitum control groups, soy protein resulted in higher BMD under nonenergy deficiency, but under energy-deficiency conditions, it resulted in lower BMD.

Female Athlete Triad and Male Athlete Triad Syndrome Induced by Low Energy Availability: An Animal Model.

Energy availability (EA) is defined the difference in energy intake and exercise energy expenditure. Reduction of EA (i.e. Low energy availability, LEA) often causes abnormalities of reproduction system and drastic bone loss in some female athletes, the phenomenon is called as female athlete triad. More than ever before, it is considered a serious problem, the reason of these are (1) the syndrome occurred in female athletes but also male athletes, (2) LEA is leads to dysfunction of various organs other than reproductive system (Relative energy deficiency in sport, RED-S). On the other hand, we have focused on this syndrome and have proposed novel insights into the physiological effects of LEA on bone and solutions through nutritional treatment by recreating it in animal models. In this review, we will summarize the epidemiological and physiological perspectives of these diseases from historical background to recent findings, and introduce the usefulness of using animal models to explore mechanisms and treatments.

Low-carbohydrate, high-fat diet, and running exercise influence bone parameters in old mice.

We examined the effects and interactions of a low-carbohydrate, high-fat (LCHF) diet and voluntary running exercise on bone in older mice. Male 19-mo-old mice were divided into four groups by diet (control vs. LCHF) and exercise (sedentary vs. voluntary running). The control diet was 55% carbohydrate, 23% protein, and 22% fat, and the LCHF diet was 10% carbohydrate, 33% protein, and 57% fat as percentages of calories. The experiment ended when the mice reached 24 mo old. Statistical analysis was conducted using two-way analysis of variance with diet and exercise. The LCHF diet decreased bone mineral content (BMC), bone mineral density, bone volume fraction, and trabecular number. There was no significant interaction between diet and exercise on many bone parameters. However, there were significant diet and exercise interactions on lumbar BMC and tibial trabecular total tissue volume and average cortical thickness. The LCHF diet attenuated the benefit of running exercise on lumbar BMC and caused running to have a negative effect on tibial trabecular total tissue volume. Our study suggests that the LCHF diet impairs bone mass and some trabecular microstructure and reduces the benefit of exercise on lumbar BMC in old mice.NEW & NOTEWORTHY An LCHF diet is used in treatment and prevention of diseases or improving exercise performance. However, some studies have shown that an LCHF diet diminishes bone in young rodents. Our study demonstrates that an LCHF diet impairs bone mass and some trabecular microstructure in old mice, which are similar to the previous studies using young rodents. Moreover, our study shows that an LCHF diet reduces the benefit of exercise on lumbar BMC in old mice.

Acute Effects of Moderate Aerobic Dance Exercise on Moods, Appetite, and Energy Intake in Young Adult Women.

Energy intake (EI) has been identified as a key factor of health controlled by exercise. Aerobic dance exercise (ADEX) is a popular exercise for fitness that one can enjoy. This present study aims to examine the influence of ADEX on moods, appetite, and EI. Thirty-one young female college students completed two 1-h experimental conditions: sedentary (SED) and ADEX followed by an ad libitum lunch. Visual analog scales and measurement of salivary α-amylase activity were used to assess appetite, fatigue, and stress at pre act, post act, and pre lunch, respectively. The rating of perceived exertion (RPE) of the SED or ADEX activities was measured using the Borg scale (range, 6-20). The participants completed the Profile of Mood States 2nd Edition-Adult Short at pre and post act only on the ADEX experimental day to assess the degree to which total mood disturbance (TMD), negative mood disturbance (NMD), and positive mood disturbance (PMD) have correlations with EI. In results, ADEX increased in RPE but did not affect TMD, NMD, PMD, hunger, fullness, appetite, and EI. Additionally, the ADEX-induced relative changes in EI were not determined to be significantly correlated with RPE in ADEX or the change in TMD, NMD, or PMD by ADEX. Our study suggests that ADEX does not affect mood, appetite, and EI. In addition, individual mood changes caused by ADEX do not correlate with EI in young adult women.

Jump Exercise and Food Restriction on Bone Parameters in Young Female Rats.

We examined the effect of jump exercise on bone parameters in young female rats under food restriction. Seven-week-old female rats were divided into four groups: a sedentary and ad libitum feeding group (n = 10), a jump exercise and ad libitum feeding group (n = 9), a sedentary and 30% food restriction group (n = 9), and a jump exercise and 30% food restriction group (n = 10). The jump groups jumped 20 times/day, 5 times/week. The experiment lasted for 13 weeks. There were no interactions of jump exercise and food restriction on bone. Jump exercise under food restriction conditions induced higher bone strength, bone mineral content, bone area, bone mineral density (BMD), and cortical bone volume in young female rats, similar to rats under ad libitum feeding conditions. Bone strength parameters were not significantly different between ad libitum intake and food restriction with jump exercise training; however, BMD, bone size, and bone mass in the food restriction groups did not reach the levels of those in the ad libitum conditions group with jump exercise training. Neither jump exercise nor food restriction had a significant effect on serum estradiol or IGF-1. Our study reveals jump exercise attenuates loss of biomechanical properties and some bone sites with food restriction in young female rats.

The Preventive Effect of Calcium Supplementation on Weak Bones Caused by the Interaction of Exercise and Food Restriction in Young Female Rats During the Period from Acquiring Bone Mass to Maintaining Bone Mass.

Increasing calcium (Ca) intake is important for female athletes with a risk of weak bone caused by inadequate food intake. The aim of the present study was to examine the preventive effect of Ca supplementation on low bone strength in young female athletes with inadequate food intake, using the rats as an experimental model. Seven-week-old female Sprague-Dawley rats were divided into four groups: the sedentary and ad libitum feeding group (SED), voluntary running exercise and ad libitum feeding group (EX), voluntary running exercise and 30% food restriction group (EX-FR), and a voluntary running exercise, 30% food-restricted and high-Ca diet group (EX-FR+Ca). To Ca supplementation, we used 1.2% Ca diet as "high-Ca diet" that contains two-fold Ca of normal Ca diet. The experiment lasted for 12 weeks. As a result, the energy availability, internal organ weight, bone strength, bone mineral density, and Ca absorption in the EX-FR group were significantly lower than those in the EX group. The bone strength and Ca absorption in the EX-FR+Ca group were significantly higher than those in the EX-FR group. However, the bone strength in the EX-FR+Ca group did not reach that in the EX group. These results suggested that Ca supplementation had a positive effect on bone strength, but the effect was not sufficient to prevent lower bone strength caused by food restriction in young female athletes.

The Impact of Different Amounts of Calcium Intake on Bone Mass and Arterial Calcification in Ovariectomized Rats.

Reduced estrogen secretion and low calcium (Ca) intake are risk factors for bone loss and arterial calcification in female rodents. To evaluate the effects of Ca intake at different amounts on bone mass changes and arterial calcification, 8-wk-old female Wistar rats were randomly placed in ovariectomized (OVX) control and OVX with vitamin D3 plus nicotine (VDN) treatment groups. The OVX with VDN rats were then divided into six groups to receive different amounts of Ca in their diets: 0.01%, 0.1%, 0.3%, 0.6%, 1.2%, or 2.4% Ca. After 8 wk of administration, low Ca intake groups with 0.01% and 0.1% Ca diets had significantly reduced bone mineral density (BMD) and bone mechanical properties as compared with those of the other groups, whereas high Ca intake groups with 1.2% and 2.4% Ca diets showed no differences as compared with the 0.6% Ca intake group. For both the 0.01% and 2.4% Ca intake groups, Ca levels in their thoracic arteries were significantly higher as compared with those of the 0.6% Ca diet group, and that was highly correlated with serum PTH levels. An increase in relative BMP-2 mRNA expression in the arterial tissues of the 0.01% and 2.4% Ca diet groups was also observed. These results suggested that extremely low Ca intake during periods of estrogen deficiency may be a possible risk for the complications of reduced BMD and arterial calcification and that extremely high Ca intake may promote arterial calcification with no changes in BMD.

The Interaction of Voluntary Running Exercise and Food Restriction Induces Low Bone Strength and Low Bone Mineral Density in Young Female Rats.

There is a concern that the combination of exercise with food intake reduction has a risk of reducing bone strength and bone mass in young female athletes. We examined the influence of the interaction of voluntary running exercise and food restriction on bone in young female rats. Seven-week-old female Sprague-Dawley rats were divided into four groups: the sedentary and ad libitum feeding group (SED), voluntary running exercise and ad libitum feeding group (EX), sedentary and 30 % food restriction group (SED-FR), and voluntary running exercise and 30 % food restriction group (EX-FR). The experiment lasted 12 weeks. Statistical analysis was carried out by two-way analysis of variance with exercise and restriction as the between-subjects factors. As a result, there were significant interactions of running and restriction on energy availability, breaking force, breaking energy, and bone mineral density (BMD). Breaking force and energy in the EX group were significantly higher than in the SED group; breaking force and energy were significantly lower in the EX-FR group than in the EX group, and breaking force in the EX-FR group was significantly lower than that in the SED-FR group. BMD in the EX-FR group was significantly lower than in the EX and SED-FR groups. These results suggest that food restriction induced low bone strength in young female rats engaging in voluntary running exercise. Also, through the interaction of exercise and food restriction, voluntary running exercise combined food restriction, unlike ad libitum feeding conditions, induced low bone strength, and low BMD in young female rats.

Food restriction causes low bone strength and microarchitectural deterioration in exercised growing male rats.

The pathogenesis of bone disorders in young male athletes has not been well understood. We hypothesized that bone fragility is caused by low energy availability, due to insufficient food intake and excessive exercise energy expenditure in young male athletes. To examine this hypothesis, we investigated the influence of food restriction on bone strength and bone morphology in exercised growing male rats, using three-point bending test, dual-energy X-ray absormetry, and micro-computed tomography. Four-week-old male Sprague-Dawley rats were divided randomly into the following groups: the control (Con) group, exercise (Ex) group, food restriction (R) group, and food restriction plus exercise (REx) group after a 1-wk acclimatization period. Thirty-percent food restriction in the R and REx groups was carried out in comparison with that in the Con group. Voluntary running exercise was performed in the Ex and REx groups. The experimental period lasted 13 wk. At the endpoint of this experiment, the bone strength of the femurs and tibial BMD in the REx group were significantly lower than those in the Con group. Moreover, trabecular bone volume and cortical bone volume in the REx group were also significantly lower than those in the Con group. These findings indicate that food restriction causes low bone strength and microarchitectural deterioration in exercised growing male rats.

Influence of food restriction combined with voluntary running on bone morphology and strength in male rats.

Athletes, in particular endurance athletes and dancers, are chronically exposed to a state of low energy availability due to insufficient dietary energy intake and massive exercise energy expenditure. Low energy availability sometimes causes bone fragility, thereby increasing the risk of bone disorders. Although the decrease in energy availability shows no sexual dimorphism, epidemiological studies have reported that bone disorders are less frequent in male athletes than in female athletes. We hypothesized that bone tissue was not affected by low energy availability in males. The purpose of this study was to examine the influence of food restriction combined with voluntary running training on bone morphology and strength in adult male rats. Fourteen-week-old male Sprague-Dawley rats were divided randomly into four groups: control (C) group, food restriction (R) group, exercise (Ex) group, and food restriction plus exercise (REx) group. For the R and REx groups, 30 % food restriction was carried out in comparison with the C group. Bone strength, bone mineral density (BMD), bone architecture, and bone turnover rate were measured after a 13-week experimental period. Bone strength was not significantly lower in the REx group compared with the C group. BMD and trabecular bone volume showed no difference among groups. These findings indicate that bone morphology and strength were little affected by food restriction combined with exercise training in adult male rats.