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Muscle protein synthesis rate in men and women. Panels A and B show the mixed skeletal muscle protein fractional synthesis rate (FSR) during basal, post-absorptive conditions (fasted) and liquid mixed meal consumption (fed) in men and women ( A ) and the meal-induced change in the FSR in men and women ( B ). Graphs show the median (central horizontal line), 25 th and 75 th percentiles 

Muscle protein synthesis rate in men and women. Panels A and B show the mixed skeletal muscle protein fractional synthesis rate (FSR) during basal, post-absorptive conditions (fasted) and liquid mixed meal consumption (fed) in men and women ( A ) and the meal-induced change in the FSR in men and women ( B ). Graphs show the median (central horizontal line), 25 th and 75 th percentiles 

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Women have less muscle than men but lose it more slowly during aging. To discover potential underlying mechanism(s) for this we evaluated the muscle protein synthesis process in postabsorptive conditions and during feeding in twenty-nine 65-80 year old men (n = 13) and women (n = 16). We discovered that the basal concentration of phosphorylated eEF...

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... were then washed and resuspended in 1% SDS. Total RNA was quantified (in m g per g wt weight) spectrophotomet- rically at 260 nm and protein was quantified (in mg per g wt weight) at 595 nm using Bradford reagents at a 1:10 dilution to reduce SDS interference. Due to lack of sufficient muscle tissue, these analyses were carried out in only 9 of the 13 men and 7 of the 16 women. Leucine rate of appearance (Ra) in plasma was calculated by dividing the rate of [5,5,5– 2 H 3 ]leucine infusion by the steady state plasma KIC TTR during basal, postabsorptive conditions and feeding. Leucine Ra during basal conditions is an index of the rate of whole-body proteolysis; during feeding, leucine Ra represents the sum of the rate of leucine release into plasma from proteolysis plus the rate of transfer of absorbed leucine from the meal into the systemic circulation. The fractional synthesis rate (FSR) of mixed muscle protein was calculated from the rate of incorporation of [5,5,5- 2 H 3 ]leucine into muscle protein, using a standard precursor-product model as follows: FSR = D E p /E ic 6 1/ t 6 100; where D E p is the change between two consecutive biopsies in extent of labeling (TTR) of protein-bound leucine. E ic is the mean labeling over time of the precursor for protein synthesis and t is the time between biopsies. The free leucine labeling in muscle tissue fluid was chosen to represent the immediate precursor for MPS (i.e., aminoacyl- t RNA) [37]. Values for FSR are expressed as % ? h 2 1 . The absolute rate of muscle protein synthesis (g protein per hour) was calculated by multiplying the FSR by the total appendicular muscle protein mass, which was assumed to be 20% of total appendicular muscle mass. We have recently found that differences in the rates of muscle protein synthesis in different muscles are negligible[38]; thus, it is reasonable to extrapolate our data obtained in the vastus lateralis to all skeletal muscles in the body. The translation efficiency (mg protein produced per m g RNA per hour) was calculated by dividing the product of the muscle protein FSR (in % ? h 2 1 ) and the muscle protein concentration (in mg per g wet tissue) by the muscle total RNA concentration (in m g per g wet tissue) [23,24]. All data sets were tested for normality. Differences between men and women in subject characteristics and single time-point measurements (e.g., plasma sex hormone and CRP concentrations) were evaluated by using Student’s t-test for normally distributed data and the Mann-Whitney U test for data which were not normally distributed (i.e., plasma SHBG, testosterone, progesterone, 17ß- estradiol and CRP concentrations). Analysis of variance (ANOVA) was used to evaluate possible differences between men and women in plasma glucose, insulin, and leucine concentrations, muscle protein FSR, muscle intracellular signaling elements, and muscle mRNA expression during postabsorptive and fed conditions. If necessary, data were log transformed to achieve normally distributed data sets before analysis. A P value of # 0.05 was considered statistically significant. Data in the text are presented as mean 6 SEM or median with 25 th and 75 th percentiles in brackets for skewed data sets; data in tables and figures are presented as indicated in the legends. Men and women were matched for age and BMI (Table 1). Total body FFM, total muscle mass and leg muscle volume were , 25% less in women than in men; however, the relative contribution of muscle mass to total body FFM was not different in men and women (Table 1). Plasma SHBG concentration was not different between men and women (Table 2). Plasma testosterone concentration was 10 times greater ( P , 0.001) in men than in women whereas plasma progesterone and 17ß-estradiol concentrations were not different between the sexes (Table 2). Plasma CRP concentration was not different between men and women (Table 2). Basal plasma glucose and insulin concentrations were not different between men and women (Table 3). Feeding increased plasma glucose concentration by , 25% ( P , 0.001) and plasma insulin concentration by , 200% ( P , 0.001) with no differences between the sexes (Table 3). Basal plasma leucine concentration was , 15% less in women than in men (Table 3), and feeding increased plasma leucine concentration by , 15% ( P , 0.001) in both sexes (Table 3). Rates of leucine Ra during basal, postabsorptive conditions (an index of whole-body protein breakdown) and total leucine Ra during feeding were not different in men (2.24 6 0.08 and 2.56 6 0.08 m mol kg 2 1 FFM ? min 2 1 , respectively) and women (2.20 6 0.09 and 2.62 6 0.09 m mol kg 2 1 FFM ? min 2 1 , respectively). The capacity for MPS (i.e., total RNA-to-protein ratio in muscle) tended to be greater (by , 20%; P = 0.18) in women than in men (5.8 6 0.6 vs. 4.7 6 0.5 m g RNA ? mg protein 2 1 , respectively). Mixed muscle protein FSR during basal, postabsorptive conditions was , 30% greater ( P = 0.02) in women than in men (Figure 1). Feeding had no effect on the FSR in women but increased ( P , 0.01) it in men to values similar to those in women (Figure 1). The absolute rate of muscle protein synthesis, adjusted for differences in total muscle mass between the sexes, was 116 [104, 143] mg of muscle protein per hour per kg of appendicular skeletal muscle mass in women and 90 [78, 115] mg of muscle protein per hour per kg of appendicular skeletal muscle mass in men (P = 0.02); it increased by 35 [13, 79] mg per hour per kg of appendicular skeletal muscle mass in response to the meal in men ( P , 0.01), but did not change significantly from basal values (by 11 [ 2 10, 41] mg of muscle protein per hour per kg of appendicular skeletal muscle mass) in women. The rate of MPS in relation to muscle RNA concentration, a measure of the translational efficiency in muscle, was not different between men and women during basal, postabsorptive conditions (0.012 6 0.003 vs. 0.013 6 0.002 mg protein ? m g RNA 2 1 ? h 2 1 ) and increased with feeding in men (to 0.019 6 0.006 mg protein ? m g RNA 2 1 ? h 2 1 ; P = 0.058 vs basal) but not in women (to 0.015 6 0.001 mg protein ? m g RNA 2 1 ? h 2 1 ). In the postabsorptive state, the extent of phosphorylation of Akt Thr308 , p70s6k Thr389 , eIF4E Ser209 and eIF4E-BP1 Thr37/46 in muscle was not different in men and women (Figure 2). The feeding-induced increases in the phosphorylation of Akt , p70s6k Thr389 (both P , 0.01) were also not different in the two sexes (Figure 2). In contrast, feeding increased (P , 0.01) the phosphorylation of eIF4E Ser209 and eIF4E-BP1 Thr37/46 in men but had no effect on their phosphorylation in women (Figure 2). Phosphor- ylated eEF2 Thr56 in muscle was , 40% less ( P , 0.05) in women than in men both during postabsorptive conditions and feeding (Figure 2); there was a tendency for a decrease in the phosphorylation of eEF2 Thr56 in both sexes with feeding (Figure 2) but this difference did not reach statistical significance ( P = 0.103). The mRNA concentrations of myostatin and myoD during postabsorptive conditions were not different in men and women (Figure 3). Feeding decreased the concentration of myostatin mRNA ( P , 0.05) and increased the concentration of myoD mRNA ( P , 0.05) to the same extent in the two sexes (Figure 3). In this study we uncovered marked sexual dimorphism between older men and women in a variety of aspects of muscle protein metabolism. The differences we observed between older men and women, namely a , 30% greater basal rate of mixed MPS in women than in men and resistance of MPS to feeding a liquid mixed meal (providing a total of , 10 g of protein) in women, are consistent with a recent study in which comprehensive oligonu- cleotide microarrays were used to discover potential differences between men and women in the expression of genes involved in the regulation of muscle mass [39]; in this study it was found that women had a two-fold greater expression of two genes that encode proteins with inhibitory properties on growth factor pathways in muscle. On the other hand, the results from our study are in clear contrast to the results from previous workers who searched for potential sex differences in human muscle protein metabolism and found none [20–22]. However, those earlier studies were conducted in young adults (average age: 23–27 y) and we hypothesized that sex differences in human muscle protein turnover would only become apparent at life stages when muscle mass was changing (e.g., during adolescent growth or wasting during aging) and/or possibly during acute anabolic or catabolic challenges (e.g., with feeding or injury). To our knowledge the current work is the first to demonstrate in human beings sex differences in the rate of MPS and provides some insight concerning the control of MPS and the different rates of muscle loss with aging between men and women. The greater basal rate of mixed MPS in older women was probably mediated by a combination of a greater capacity for protein synthesis combined with a relatively more active translational process at the elongation stage of protein synthesis because first, there was the trend for a , 20% greater muscle RNA-to-protein ratio in women than in men, indicating a greater capacity for MPS [24] in them and secondly, muscle of older women had a 40% smaller degree of phosphorylation of eEF2 Thr56 , a molecule regulating elongation of nascent protein chains which is deactivated by phosphorylation [25]. We found no differences between sexes in the extent of phosphorylation for components of the PKB/mTOR/p70s6k signaling pathway, or the phosphorylation of elements involved in the regulation of translation initiation (eIF4E and eIF4e-BP1) at baseline (fasted). Furthermore, the expression in muscle of mRNA for myostatin and myoD, cell regulatory proteins affecting muscle size [26–29], was not different between the sexes, which makes it unlikely that they are involved in regulating the basal ...
Context 2
... nm and protein was quantified (in mg per g wt weight) at 595 nm using Bradford reagents at a 1:10 dilution to reduce SDS interference. Due to lack of sufficient muscle tissue, these analyses were carried out in only 9 of the 13 men and 7 of the 16 women. Leucine rate of appearance (Ra) in plasma was calculated by dividing the rate of [5,5,5– 2 H 3 ]leucine infusion by the steady state plasma KIC TTR during basal, postabsorptive conditions and feeding. Leucine Ra during basal conditions is an index of the rate of whole-body proteolysis; during feeding, leucine Ra represents the sum of the rate of leucine release into plasma from proteolysis plus the rate of transfer of absorbed leucine from the meal into the systemic circulation. The fractional synthesis rate (FSR) of mixed muscle protein was calculated from the rate of incorporation of [5,5,5- 2 H 3 ]leucine into muscle protein, using a standard precursor-product model as follows: FSR = D E p /E ic 6 1/ t 6 100; where D E p is the change between two consecutive biopsies in extent of labeling (TTR) of protein-bound leucine. E ic is the mean labeling over time of the precursor for protein synthesis and t is the time between biopsies. The free leucine labeling in muscle tissue fluid was chosen to represent the immediate precursor for MPS (i.e., aminoacyl- t RNA) [37]. Values for FSR are expressed as % ? h 2 1 . The absolute rate of muscle protein synthesis (g protein per hour) was calculated by multiplying the FSR by the total appendicular muscle protein mass, which was assumed to be 20% of total appendicular muscle mass. We have recently found that differences in the rates of muscle protein synthesis in different muscles are negligible[38]; thus, it is reasonable to extrapolate our data obtained in the vastus lateralis to all skeletal muscles in the body. The translation efficiency (mg protein produced per m g RNA per hour) was calculated by dividing the product of the muscle protein FSR (in % ? h 2 1 ) and the muscle protein concentration (in mg per g wet tissue) by the muscle total RNA concentration (in m g per g wet tissue) [23,24]. All data sets were tested for normality. Differences between men and women in subject characteristics and single time-point measurements (e.g., plasma sex hormone and CRP concentrations) were evaluated by using Student’s t-test for normally distributed data and the Mann-Whitney U test for data which were not normally distributed (i.e., plasma SHBG, testosterone, progesterone, 17ß- estradiol and CRP concentrations). Analysis of variance (ANOVA) was used to evaluate possible differences between men and women in plasma glucose, insulin, and leucine concentrations, muscle protein FSR, muscle intracellular signaling elements, and muscle mRNA expression during postabsorptive and fed conditions. If necessary, data were log transformed to achieve normally distributed data sets before analysis. A P value of # 0.05 was considered statistically significant. Data in the text are presented as mean 6 SEM or median with 25 th and 75 th percentiles in brackets for skewed data sets; data in tables and figures are presented as indicated in the legends. Men and women were matched for age and BMI (Table 1). Total body FFM, total muscle mass and leg muscle volume were , 25% less in women than in men; however, the relative contribution of muscle mass to total body FFM was not different in men and women (Table 1). Plasma SHBG concentration was not different between men and women (Table 2). Plasma testosterone concentration was 10 times greater ( P , 0.001) in men than in women whereas plasma progesterone and 17ß-estradiol concentrations were not different between the sexes (Table 2). Plasma CRP concentration was not different between men and women (Table 2). Basal plasma glucose and insulin concentrations were not different between men and women (Table 3). Feeding increased plasma glucose concentration by , 25% ( P , 0.001) and plasma insulin concentration by , 200% ( P , 0.001) with no differences between the sexes (Table 3). Basal plasma leucine concentration was , 15% less in women than in men (Table 3), and feeding increased plasma leucine concentration by , 15% ( P , 0.001) in both sexes (Table 3). Rates of leucine Ra during basal, postabsorptive conditions (an index of whole-body protein breakdown) and total leucine Ra during feeding were not different in men (2.24 6 0.08 and 2.56 6 0.08 m mol kg 2 1 FFM ? min 2 1 , respectively) and women (2.20 6 0.09 and 2.62 6 0.09 m mol kg 2 1 FFM ? min 2 1 , respectively). The capacity for MPS (i.e., total RNA-to-protein ratio in muscle) tended to be greater (by , 20%; P = 0.18) in women than in men (5.8 6 0.6 vs. 4.7 6 0.5 m g RNA ? mg protein 2 1 , respectively). Mixed muscle protein FSR during basal, postabsorptive conditions was , 30% greater ( P = 0.02) in women than in men (Figure 1). Feeding had no effect on the FSR in women but increased ( P , 0.01) it in men to values similar to those in women (Figure 1). The absolute rate of muscle protein synthesis, adjusted for differences in total muscle mass between the sexes, was 116 [104, 143] mg of muscle protein per hour per kg of appendicular skeletal muscle mass in women and 90 [78, 115] mg of muscle protein per hour per kg of appendicular skeletal muscle mass in men (P = 0.02); it increased by 35 [13, 79] mg per hour per kg of appendicular skeletal muscle mass in response to the meal in men ( P , 0.01), but did not change significantly from basal values (by 11 [ 2 10, 41] mg of muscle protein per hour per kg of appendicular skeletal muscle mass) in women. The rate of MPS in relation to muscle RNA concentration, a measure of the translational efficiency in muscle, was not different between men and women during basal, postabsorptive conditions (0.012 6 0.003 vs. 0.013 6 0.002 mg protein ? m g RNA 2 1 ? h 2 1 ) and increased with feeding in men (to 0.019 6 0.006 mg protein ? m g RNA 2 1 ? h 2 1 ; P = 0.058 vs basal) but not in women (to 0.015 6 0.001 mg protein ? m g RNA 2 1 ? h 2 1 ). In the postabsorptive state, the extent of phosphorylation of Akt Thr308 , p70s6k Thr389 , eIF4E Ser209 and eIF4E-BP1 Thr37/46 in muscle was not different in men and women (Figure 2). The feeding-induced increases in the phosphorylation of Akt , p70s6k Thr389 (both P , 0.01) were also not different in the two sexes (Figure 2). In contrast, feeding increased (P , 0.01) the phosphorylation of eIF4E Ser209 and eIF4E-BP1 Thr37/46 in men but had no effect on their phosphorylation in women (Figure 2). Phosphor- ylated eEF2 Thr56 in muscle was , 40% less ( P , 0.05) in women than in men both during postabsorptive conditions and feeding (Figure 2); there was a tendency for a decrease in the phosphorylation of eEF2 Thr56 in both sexes with feeding (Figure 2) but this difference did not reach statistical significance ( P = 0.103). The mRNA concentrations of myostatin and myoD during postabsorptive conditions were not different in men and women (Figure 3). Feeding decreased the concentration of myostatin mRNA ( P , 0.05) and increased the concentration of myoD mRNA ( P , 0.05) to the same extent in the two sexes (Figure 3). In this study we uncovered marked sexual dimorphism between older men and women in a variety of aspects of muscle protein metabolism. The differences we observed between older men and women, namely a , 30% greater basal rate of mixed MPS in women than in men and resistance of MPS to feeding a liquid mixed meal (providing a total of , 10 g of protein) in women, are consistent with a recent study in which comprehensive oligonu- cleotide microarrays were used to discover potential differences between men and women in the expression of genes involved in the regulation of muscle mass [39]; in this study it was found that women had a two-fold greater expression of two genes that encode proteins with inhibitory properties on growth factor pathways in muscle. On the other hand, the results from our study are in clear contrast to the results from previous workers who searched for potential sex differences in human muscle protein metabolism and found none [20–22]. However, those earlier studies were conducted in young adults (average age: 23–27 y) and we hypothesized that sex differences in human muscle protein turnover would only become apparent at life stages when muscle mass was changing (e.g., during adolescent growth or wasting during aging) and/or possibly during acute anabolic or catabolic challenges (e.g., with feeding or injury). To our knowledge the current work is the first to demonstrate in human beings sex differences in the rate of MPS and provides some insight concerning the control of MPS and the different rates of muscle loss with aging between men and women. The greater basal rate of mixed MPS in older women was probably mediated by a combination of a greater capacity for protein synthesis combined with a relatively more active translational process at the elongation stage of protein synthesis because first, there was the trend for a , 20% greater muscle RNA-to-protein ratio in women than in men, indicating a greater capacity for MPS [24] in them and secondly, muscle of older women had a 40% smaller degree of phosphorylation of eEF2 Thr56 , a molecule regulating elongation of nascent protein chains which is deactivated by phosphorylation [25]. We found no differences between sexes in the extent of phosphorylation for components of the PKB/mTOR/p70s6k signaling pathway, or the phosphorylation of elements involved in the regulation of translation initiation (eIF4E and eIF4e-BP1) at baseline (fasted). Furthermore, the expression in muscle of mRNA for myostatin and myoD, cell regulatory proteins affecting muscle size [26–29], was not different between the sexes, which makes it unlikely that they are involved in regulating the basal rate of MPS, although, we cannot from our data rule out differences in the muscle myostatin and myoD protein concentration (and ...

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... Studies have shown that higher estrogen levels are associated with lower AT stiffness, possibly reducing the risk of AT injury (Chidi-Ogbolu and Baar, 2018). The risk of AT injury is lower in premenopausal women than men and is similar in postmenopausal women when the estrogen level is equivalent to that in men (Maffulli et al., 1999;Smith et al., 2008;Huttunen et al., 2014). ...
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... In terms of sex, despite no statistical differences, women tended to exhibit numerically higher rates of MPS than older men. Differences in acute (i.e. over a few hours) MPS were previously reported between older men and women [15], with it being proposed that a greater basal (i.e. postabsorptive) MPS which operates over a majority of the diurnal cycle may explain slower age-related muscle loss in women than in men. ...
... These male-specific observations may not translate well to aging females, partially due to divergent body composition and hormone concentrations between the sexes that may impact postabsorptive or postprandial MPS (8)(9)(10)(11)(12)(13). Fortunately, however, there have been various efforts in recent years to define agingrelated sex differences in postabsorptive and postprandial mixed (14)(15)(16)(17)(18) and fraction-specific (i.e., myofibrillar) (19) muscle protein turnover. The evidence, however, remains controversial with contrasting observations regarding sex differences in MPS with advancing age (14)(15)(16)(17). ...
... The evidence, however, remains controversial with contrasting observations regarding sex differences in MPS with advancing age (14)(15)(16)(17). For example, it has been shown that females, regardless of age, have higher basal mixed MPS rates than males (16), whereas other findings suggest that sex differences are only apparent with age and postmenopause (18,20). Nevertheless, postmenopausal females typically have less muscle mass, are more susceptible to disuse-induced muscle wasting (21), and suffer from sarcopenia and musculoskeletal injuries at a greater rate in comparison to aging males (22,23). ...
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Background Age-associated loss of muscle mass and strength is an important predictor of disability in older persons. Although several mechanisms contribute to the decline in muscle mass and function seen with aging, the process is thought to be accelerated by an inadequate protein intake. However, the optimal amount and source of protein and the role of dietary protein intake over the life course remain uncertain. Objectives In a sample of community-dwelling adults in Western Norway, the current study examined both cross-sectional and longitudinal associations over 20 y of dietary protein intake with appendicular skeletal muscle mass (ASMM) and muscle strength measured by handgrip strength (HGS) in older age. Methods Dietary intake was assessed using food frequency questionnaires (FFQs) in middle age (46–49 y) and older age (67–70 y) within the community-based Hordaland Health Study. Results Adjusted, multivariate linear regression analyses revealed a negative cross-sectional association between the substitution of total protein (TP) and animal protein (AP), with fat and carbohydrates, on ASMM in women but not in men. No longitudinal associations were found between substitution of dietary protein intake and ASMM in either sex in adjusted models. Similarly, no cross-sectional or longitudinal associations were evident between substitution of dietary protein intake and HGS in either sex in adjusted models. Conclusion The findings in the current study highlight the need to clarify the role of dietary protein intake in the maintenance of muscle mass and muscle strength in healthy older adults.
... The data in Table 2 show that BMI, total muscle mass, muscle mass of body segments, visceral fat area, and WHR were significantly higher in males aged 20-60 years than in females (p < 0.0001), and BF% and total fat mass were significantly higher in females than in males (p < 0.0001). BMI, BF%, and total fat mass increased significantly (p < 0.05) in males aged [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49], and ≥ 50 years compared to 20-29 years. BMI and total fat mass peaked at 40-49 years (BMI = 25.75 kg/m 2 , total fat mass = 17.70 kg), with a slightly decreasing trend thereafter, whereas both BMI and BF% gradually increased with age in females. ...
... These findings agree with the results of the present study, and all of them indicate relatively stable muscle mass in both genders in young and middle age. With ageing, gender differences in muscle synthesis and catabolism begin to emerge between males and females, with older females having greater rates of muscle protein synthesis than males and less catabolism than males compared to matched older males (females: ~ 0.25%/year, males: ~ 0.40%/year) [37,38]. However, it is noteworthy that the total muscle mass and left and right upper and lower extremity muscle content of women in this study were significantly greater in the 30-39-, 40-49-, and ≥ 50-year groups than in the 20-29year group, which contradicts the results of previous studies. ...
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Background Obesity is the most serious global epidemic and body composition is the main indicator to evaluate obesity. This study aimed to investigate the changing trends of body composition by age and gender in Beijing adults aged 20–60 years and explore the distribution of obesity rates in different age groups of both sexes under different evaluation criteria. Methods A total of 24,948 adults aged 20–60 years in Beijing, including 10,225 males and 14,192 females, were included, divided into four age groups (20–29, 30–39, 40–49, and ≥ 50 years) with each decade of age as an age group. Body composition indicators (BMI, fat mass, BF%, muscle mass, visceral fat area, and WHR) were measured in all subjects. Results BMI and total fat mass peaked in males aged 40–49 years (BMI = 25.75 kg/m², total fat mass = 17.70 kg). Female BMI, fat mass and BF% all increased significantly with age (p < 0.01). Total muscle peaked in males aged 30–39 years and decreased significantly thereafter (p < 0.0001). Visceral fat area and WHR increased significantly with age in both sexes (p < 0.0001). Age was significantly positively correlated with BMI, BF%, fat mass, WHR, and visceral fat area in both sexes (p < 0.0001), and age was negatively correlated with muscle mass in males (standard β = − 0.14, p < 0.0001) while positive in female (standard β = 0.05, p < 0.0001). Under the BMI criterion, the obesity rate peaked at 27.33% in males at the age of 20–29 years. Under the BF% criterion, the obesity rate peaked at 17.41% in males at the age of 30–39 years, and increased in females with age. The central obesity rate of both sexes increased with age under the criteria of WHR and visceral fat area. Conclusion The results of this study reveal that age- and sex-related patterns of body composition and obesity change among Beijing adults aged 20–60 years may differ across age groups and that such patterns of change should be considered when developing public health strategies.
... Moreover, whereas similar basal rates of MPS have been observed between obese and lean individuals [18], studies have reported a reduced postprandial response of MPS to protein ingestion in overweight/obese individuals vs. age-matched lean controls [19,20]. In addition, clinical studies have demonstrated an impaired muscle anabolic response to protein feeding and exercise training in postmenopausal women compared with older men and healthy young adults [21][22][23][24][25]. Hence, these data provide compelling rationale for developing targeted dietary interventions aimed at mitigating muscle loss during diet-induced energy restriction specifically in postmenopausal women. ...
Article
Background: Diet-induced weight loss is associated with a decline in lean body mass, as mediated by an impaired response of muscle protein synthesis (MPS). The dose-response of MPS to ingested protein, with or without resistance exercise, is well characterised during energy balance but limited data exist under conditions of energy restriction in clinical populations. Objective: To determine the dose-response of MPS to ingested whey protein following short-term diet-induced energy restriction in overweight, postmenopausal, women at rest and post-exercise. Design: Forty middle-aged (58.6±0.4 years), overweight (BMI: 28.6±0.4), postmenopausal women were randomised to one of four groups: Three groups underwent 5 days of energy restriction (∼800 kcal/d). On day 6, participants performed a unilateral leg resistance exercise bout before ingesting either a bolus of 15g (ERW15, n=10), 35g (ERW35, n=10) or 60g (ERW60, n=10) of whey protein. The fourth group (n=10) ingested a 35g whey protein bolus after 5 days of an energy balanced diet (EBW35, n=10). Myofibrillar fractional synthetic rate (FSR) was calculated under basal, fed (FED) and post-exercise (FED-EX) conditions by combining an L-[ring-13C6]phenylalanine tracer infusion with the collection of bilateral muscle biopsies. Results: Myofibrillar-FSR was greater in ERW35 (0.043±0.003%/h, P=0.013) and ERW60 (0.042±0.003%/h, P=0.026) than ERW15 (0.032±0.003%/h), with no differences between ERW35 and ERW60 (P=1.000). Myofibrillar-FSR was greater in FED (0.044±0.003%/h, P<0.001) and FED-EX (0.048±0.003%/h, P<0.001) than BASAL (0.027±0.003%/h), but no differences were detected between FED and FED-EX (P=0.732) conditions. No differences in myofibrillar FSR were observed between EBW35 (0.042±0.003%/h) and ERW35 (0.043±0.003%/h, P=0.744). Conclusion: A 35 g dose of whey protein, ingested with or without resistance exercise, is sufficient to stimulate a maximal acute response of MPS following short-term energy restriction in overweight, postmenopausal women, and thus may provide a per serving protein recommendation to mitigate muscle loss during a weight loss program. Trail registration: clinicaltrials.gov (NCT03326284). Trial registry: Clinicaltrials.gov (ID: NCT03326284).
... However, limited evidence suggests the anabolic response to the same protein/AA ingestion or infusion is not different between young [29] and middle-aged [30] adult females and males. In contrast, older females have been shown to exhibit a lower postprandial anabolic response to ingestion of the same protein as older males [31]. ...
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Background: The Dietary Guidelines for Americans (DGA) recommends consuming a variety of "Protein Foods" based on "ounce-equivalent" (oz-eq) portions. No study has assessed the same oz-eq portions of animal- vs. plant-based protein foods on essential amino acid (EAA) bioavailability for protein anabolism in young and older adults. Objectives: We assessed the effects of consuming two oz-eq portions of pork, eggs, black beans, and almonds on postprandial EAA bioavailability in young and older adults. Methods: We conducted two investigator-blinded, randomized crossover trials in young (n = 30; mean age ± SD: 26.0 ± 4.9 y) and older adults (n = 25; mean age ± SD: 64.2 ± 6.6 y). Participants completed four testing sessions where they consumed a standardized meal with two oz-eq of either unprocessed lean pork, whole eggs, black beans, or sliced almonds. Blood samples were taken at baseline and 30, 60, 120, 180, 240, and 300 min postprandially. Plasma EAA bioavailability was based on postprandial integrated positive areas under the curve. Results: Participant age did not affect EAA bioavailability among the four protein foods tested. Two oz-eq portions of pork (7.36 g EAA) and eggs (5.38 g EAA) resulted in greater EAA bioavailability than black beans (3.02 g EAA) and almonds (1.85 g EAA) in young and older adults, separately or combined (p < 0.0001 for all). Pork resulted in greater EAA bioavailability than eggs in young adults (p < 0.0001), older adults (p = 0.0007), and combined (p < 0.0001). There were no differences in EAA bioavailability between black beans and almonds. Conclusions: The same "oz-eq" portions of animal- and plant-based protein foods do not provide equivalent EAA content and postprandial bioavailability for protein anabolism in young and older adults.
... Although studies of sex differences in protein metabolism are still rare, emerging evidence suggests that protein metabolism is another area of physiology influenced by sex. For instance, a sex-dimorphic response to mixed meal ingestion has been observed, with a more pronounced anabolic response in males versus females (66,102). Amino acids are generally lower in the plasma of females versus males, with the exception of citrulline, cysteine, aspartate, glycine, serine, and taurine (89). ...
Article
Biological sex is a fundamental source of phenotypic variability across species. Males and females have different nutritional needs and exhibit differences in nutrient digestion and utilization, leading to different health outcomes throughout life. With personalized nutrition gaining popularity in scientific research and clinical practice, it is important to understand the fundamentals of sex differences in nutrition research. Here, we review key studies that investigate sex dimorphism in nutrition research: sex differences in nutrient intake and metabolism, sex-dimorphic response in nutrient-restricted conditions, and sex differences in diet and gut microbiome interactions. Within each area above, factors from sex chromosomes, sex hormones, and sex-specific loci are highlighted. 227 Annu. Rev. Nutr. 2022.42:227-250. Downloaded from www.annualreviews.org Access provided by Shanghai Jiao Tong University on 11/30/22. For personal use only.