***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Falls warrant investigation as a risk factor for nursing home admission because falls are common and are associated with functional disability and because they may be preventable . METHODS We conducted a prospect i ve study of a probability sample of 1103 people over 71 years of age who were living in the community . Data on demographic and medical characteristics , use of health care , and cognitive , functional , psychological , and social functioning were obtained at base line and one year later during assessment s in the participants ' homes . The primary outcome studied was the number of days from the initial assessment to a first long-term admission to a skilled-nursing facility during three years of follow-up . Patients were assigned to four categories during follow-up : those who had no falls , those who had one fall without serious injury , those who had two or more falls without serious injury , and those who had at least one fall causing serious injury . RESULTS A total of 133 participants ( 12.1 percent ) had long-term admissions to nursing homes . In an unadjusted model , the risk of admission increased progressively , as compared with that for the patients with no falls , for those with a single noninjurious fall ( relative risk , 4.9 ; 95 percent confidence interval , 3.2 to 7.5 ) , those with multiple noninjurious falls ( relative risk , 8.5 ; 95 percent confidence interval , 3.4 to 21.2 ) , and those with at least one fall causing serious injury ( relative risk , 19.9 ; 95 percent confidence interval , 12.2 to 32.6 ) . Adjustment for other risk factors lowered these ratios to 3.1 ( 95 percent confidence interval , 1.9 to 4.9 ) for one noninjurious fall , 5.5 ( 95 percent confidence interval , 2.1 to 14.2 ) for two or more noninjurious falls , and 10.2 ( 95 percent confidence interval , 5.8 to 17.9 ) for at least one fall causing serious injury , but the association between falls and admission to a nursing home remained strong and significant . The population attributable risk of long-term admission to a nursing home for these three groups ( the proportion of admissions directly attributable to the three categories of falls ) was 13 percent , 3 percent , and 10 percent , respectively . CONCLUSIONS Among older people living in the community falls are a strong predictor of placement in a skilled-nursing facility ; interventions that prevent falls and their sequelae may therefore delay or reduce the frequency of nursing home admissions BACKGROUND We previously showed that human muscle protein synthesis ( MPS ) increased during infusion of amino acids ( AAs ) and peaked at ≈120 min before returning to baseline rates , despite elevated plasma AA concentrations . OBJECTIVE We tested whether a protein meal elicited a similar response and whether signaling responses that regulate messenger RNA translation matched MPS changes . DESIGN Eight postabsorptive healthy men ( ≈21 y of age ) were studied during 8.5 h of primed continuous infusion of [1,2-¹³C₂]leucine with intermittent quadriceps biopsies for determination of MPS and anabolic signaling . After 2.5 h , subjects consumed 48 g whey protein . RESULTS At 45 - 90 min after oral protein bolus , mean ( ± SEM ) myofibrillar protein synthesis increased from 0.03 ± 0.003 % to 0.10 ± 0.01%/h ; thereafter , myofibrillar protein synthesis returned to baseline rates even though plasma essential AA ( EAA ) concentrations remained elevated ( + 130 % at 120 min , + 80 % at 180 min ) . The activity of protein kinase B ( PKB ) and phosphorylation of eukaryotic initiation factor 4 G preceded the rise of MPS and increases in phosphorylation of ribosomal protein kinase S6 ( S6K1 ) , and 4E-binding protein 1 ( 4EBP1 ) was superimposable with MPS responses until 90 min . However , although MPS decreased thereafter , all signals , with the exception of PKB activity ( which mirrored insulin responses ) , remained elevated , which echoed the slowly declining plasma EAA profile . The phosphorylation of eukaryotic initiation factor 2α increased only at 180 min . Thus , discordance existed between MPS and the mammalian target of rapamycin complex 1 ( mTORC1 ) and signaling ( ie , S6K1 and 4EBP1 phosphorylation ) . CONCLUSIONS We confirm our previous findings that MPS responses to AAs are transient , even with oral protein bolus . However , changes in MPS only reflect elevated mTORC1 signaling during the upswing in MPS Men have more muscle than women , but most studies evaluating sex differences in muscle protein metabolism have been unable to discern sexual dimorphism in basal muscle protein turnover rates in young and middle-aged adults . We hypothesized that the anabolic response to nutritional stimuli ( i.e. , amino acids and insulin ) would be greater in young/middle-aged men than women . We therefore measured the rates of muscle protein synthesis ( MPS ) in 16 healthy individuals [ 8 men and 8 women , matched for age ( mean + /- SE : 37.7 + /- 1.5 yr ) and body mass index ( 25.2 + /- 0.7 kg/m2 ) ] after an  overnight fast ( plasma insulin approximately 5 microU/ml and plasma phenylalanine approximately 60 microM ) and during a hyperinsulinemic-hyperaminoacidemic-euglycemic clamp ( plasma insulin approximately 28 microU/ml ; plasma phenylalanine approximately 110 microM ; plasma glucose approximately 5.4 mM ) . The rates of MPS were not different between men and women ( ANOVA main effect for sex ; P = 0.49 ) . During the clamp , the rate of MPS increased by approximately 50 % ( P = 0.003 ) with no difference in the increases from basal values between men and women ( + 0.019 + /- 0.004 vs. + 0.018 + /- 0.010%/h , respectively ; P = 0.93 ) . There were also no differences between men and women in the basal concentrations of muscle phosphorylated Akt(Ser473 ) , Akt(Thr308 ) , mTOR(Ser2448 ) , and p70s6k(Thr389 ) or in the hyperinsulinemia-hyperaminoacidemia-induced increases in phosphorylation of those signaling elements ( P > or = 0.25 ) . We conclude that there are no major differences in the rate of MPS and its intracellular control during basal conditions and during hyperinsulinemia-hyperaminoacidema between young and middle-aged adult men and women OBJECTIVE To investigate changes in body composition after 12 months of high-intensity progressive resistance training ( PRT ) in relation to changes in insulin resistance ( IR ) or glucose homeostasis in older adults with type 2 diabetes . RESEARCH DESIGN AND METHODS One-hundred three participants were r and omized to receive either PRT or sham exercise 3 days per week for 12 months . Homeostasis model assessment 2 of insulin resistance ( HOMA2-IR ) and glycosylated hemoglobin ( HbA1c ) were used as indices of IR and glucose homeostasis . Skeletal muscle mass ( SkMM ) and total fat mass were assessed using bioelectrical impedance . Visceral adipose tissue , mid-thigh cross-sectional area , and mid-thigh muscle attenuation were quantified using computed tomography . RESULTS Within the PRT group , changes in HOMA2-IR were associated with changes in SkMM ( r = −0.38 ; P = 0.04 ) and fat mass ( r = 0.42 ; P = 0.02 ) . Changes in visceral adipose tissue tended to be related to changes in HOMA2-IR ( r = 0.35 ; P = 0.07 ) . Changes in HbA1c were related to changes in mid-thigh muscle attenuation ( r = 0.52 ; P = 0.001 ) . None of these relationships were present in the sham group ( P > 0.05 ) . Using ANCOVA models , participants in the PRT group who had increased SkMM had decreased HOMA2-IR ( P = 0.05 ) and HbA1c ( P = 0.09 ) compared with those in the PRT group who lost SkMM . Increases in SkMM in the PRT group decreased HOMA2-IR ( P = 0.07 ) and HbA1c ( P < 0.05 ) compared with those who had increased SkMM in the sham group . CONCLUSIONS Improvements in metabolic health in older adults with type 2 diabetes were mediated through improvements in body composition only if they were achieved through high-intensity PRT To determine the in vivo effect of amino acids ( AAs ) alone or in combination with insulin on splanchnic and muscle protein dynamics , we infused stable isotope tracers of AAs in 36 healthy subjects and sample d from femoral artery and vein and hepatic vein . The subjects were r and omized into six groups and were studied at baseline and during infusions of saline ( group 1 ) , insulin ( 0.5 mU. kg(-1 ) . min(-1 ) ) ( group 2 ) , insulin plus replacement of AAs ( group 3 ) insulin plus high-dose AAs ( group 4 ) , or somatostatin and baseline replacement doses of insulin , glucagon and GH plus high dose of AAs ( group 5 ) or saline ( group 6 ) . Insulin reduced muscle release of AAs mainly by inhibition of protein breakdown . Insulin also enhanced AA-induced muscle protein synthesis ( PS ) and reduced leucine transamination . The main effect of AAs on muscle was the enhancement of PS .  Insulin had no effect on protein dynamics or leucine transamination in splanchnic bed . However , AAs reduced protein breakdown and increased synthesis in splanchnic bed in a dose-dependent manner . AAs also enhanced leucine transamination in both splanchnic and muscle beds . Thus insulin 's anabolic effect was mostly on muscle , whereas AAs acted on muscle as well as on splanchnic bed . Insulin achieved anabolic effect in muscle by inhibition of protein breakdown , enhancing AA-induced PS , and reducing leucine transamination . AAs largely determined protein anabolism in splanchnic bed by stimulating PS and decreasing protein breakdown OBJECTIVE Skeletal muscle protein metabolism is resistant to the anabolic action of insulin in healthy , nondiabetic older adults . This defect is associated with impaired insulin-induced vasodilation and mTORC1 signaling . We hypothesized that , in older subjects , pharmacological restoration of insulin-induced capillary recruitment would improve the response of muscle protein synthesis and anabolism to insulin . RESEARCH DESIGN AND METHODS Twelve healthy , nondiabetic older subjects ( 71 ± 2 years ) were r and omized to two groups . Subjects were studied at baseline and during local infusion in one leg of insulin alone ( Control ) or insulin plus sodium nitroprusside ( SNP ) at variable rate to double leg blood flow . We measured leg blood flow by dye dilution ; muscle microvascular perfusion with contrast enhanced ultrasound ; Akt/mTORC1 signaling by Western blotting ; and muscle protein synthesis , amino acid , and glucose kinetics using stable isotope method ologies . RESULTS There were no baseline differences between groups . Blood flow , muscle perfusion , phenylalanine delivery to the leg , and intracellular availability of phenylalanine increased significantly ( P < 0.05 ) in SNP only . Akt phosphorylation increased in both groups but increased more in SNP ( P < 0.05 ) . Muscle protein synthesis and net balance ( nmol · min−1 · 100 ml · leg−1 ) increased significantly ( P < 0.05 ) in SNP ( synthesis , 43 ± 6 to 129 ± 25 ; net balance , −16 ± 3 to 26 ± 12 ) but not in Control ( synthesis , 41 ± 10 to 53 ± 8 ; net balance , −17 ± 3 to −2 ± 3 ) . CONCLUSIONS Pharmacological enhancement of muscle perfusion and amino acid availability during hyperinsulinemia improves the muscle protein anabolic  effect of insulin in older adults Objective To determine if long-term ( 7 days ) infusion of insulin can ameliorate altered protein kinetics in skeletal muscle of severely burned patients and to investigate the hypothesis that changes in protein kinetics during insulin infusion are associated with an increased rate of transmembrane amino acid transport from plasma into the intracellular free amino acid pool . Summary Background Data In critically ill patients , vigorous nutritional support alone may often fail to entirely curtail muscle catabolism ; insulin stimulates muscle protein synthesis in normal volunteers . Methods Nine patients with severe burns were studied once during enteral feeding alone ( control period ) , and once after 7 days of high-dose insulin . The order of treatment with insulin was r and omized . Data were derived from a model based on a primed-continuous infusion of L-[15N]phenylalanine , sampling of blood from the femoral artery and vein , and biopsies of 
    Output:
    
Conclusions /interpretationThis study demonstrates the complex role of insulin in regulating skeletal muscle metabolism .
Insulin appears to have a permissive role in MPS in the presence of elevated AAs , and plays a clear role in reducing MPB independent of AA availability