| Background:At present,body composition,especially muscle mass,has been gradually used as an objective index for the diagnosis of malnutrition.The muscle is one of the most important functional components of the human body composition.Besides its functional roles in conjunction,supporting and protection,the muscle also plays very important roles in the vital physiological functions.And the consumpution,synthesis and repairment of the muscle are closely related with the prognosis of disease.It has recently been an important and emerging field in the measurement of body composition to accurately and rapidly investigate the muscle content in a cost-effective approach.There are more than a dozen tools that may use for measuring body compositions.However,so far there is not any well-rounded measurement method that can meet the above criteria among various analyses in the body composition.The Isotope Dilution is the reference method("gold standard")for the Total Body Water(TBWa);the Dual Energy X-ray Absorptiometry(DEXA)is the reference method for the Bone Mass(BM);Computerized Tomography(CT)and the Magnetic Resonance Imaging(MRI)are the reference method for the Fat Mass(FM).Among these three reference methods,the CT and MRI are the only two tools can approximately measure the muscle tissues by through measuring Fat Free Mass(FFM).The other two cannot directly measure the muscle tissues.Under such circumstances,the muscle tissues could only be calculated based upon the logical mathematical relationship between the relative content of water-fat-muscle(by using Archimedes,principle).However,because of the various between races and individuals,this calculation needs be adjusted by using constant that shall generate from a great number of sampling and measuring,and even doing like that,the accurate is still not guanranted in mathematically.Besides,all of these three methods are costly and with obvious defects in the clinical application:the Isotope Dilution needs an isotope tracer and it also involves very complex detecting processes;the CT and DEXA may bring about radiation damage;and the MRI is time-consuming,strenunous on computation.These shortcomings cause all of these references methods cannot be widely used as musle mass measurements clinically;and thus cause the measurement of muscle mass measurement still absence in the diagnosis of malnutrition and its monitoring.The Bioelectrical Impedance Analysis(BIA)is the application of Ohm's Law in physics.With human body' s static and dynamic resistance characteristics,the human body composition can be analyzed by the synthesis of the law of body composition,the Total Body Water,the density of the human body and relevant biological specifications including age,race and sex.Due to its simple design,non-invasive,fast and cheap in application,the BIA has been most widely adopted in clinic to measure the body composition.Nevertheless,the commencement of the BIA hugely relies on the Resistance Characteristics,the accuracy of its result is less precise and competitive as the above three "gold standards".How to improve the accuracy of the BIA in the measurement of body composition,and let it can be used as an accurately tool in various disease conditions,are becoming the very key and important agenda of the clinical nutrition research.Aim:Our study based on the utilization of the three“gold standards”in the measurement of respective body compositions,the approach will finally create a method with good accuracy and clinical accessibility to measure Chinese muscle compositions,in order to provide a methodological basis for the nutritional assessment under various disease conditions(such as Sarcopenia and Protein-Energy Malnutrition).Content:The research encompasses the following three parts:Research Part ?:To develop an algrothim that would substantially promote the accuracy of bioelectrical impedance analysis(BIA)on analyzing body composition of healthy Chinese population,We used Isotope Dilution,Magnetic Resonance Imaging(MRI)and Dual Energy X-ray Absorptiometry(DEXA)as reference methods for measuring Total Body Water(TBWa),Fat Mass(FM)and Bone Mass.We enrolled young healthy volunteers(aged 21-25 yr)from Peking Union Medical College(PUMC)and Tsinghua University.After volunteers passed conventional examination and signed consent inform sheets,he or she would officially be enrolled.All volunteers were examined by four body composition measurements:Isotope Dilution,MRI,DEXA and BIA.TBWa,FM and BM were measured by Isotope Dilution,MRI,and DEXA respectively.TBWa was measured with Isotope Dilution Measurement.Volunteers were given Double-Labeled Water(DLW,2H and 180)after a 72-hour-observation period.All subjects were administered DLW(60mg/kg)orally followed by 100 ml of distilled water.Urine was collected from subjects right before and five hours after the DLW administration.All urine samples were tested in the Stable Isotope Laboratory of Institute of Geology and Geophysics,Chinese Academy of Sciences.Stable isotope ratio mass spectrometer(Finnigan MAT 252,Thermo Fisher Scientific Inc.,U.S.)was used for 2H and 180 testing.TBWa was measured with Magnetic Resonance Imaging(MRI)using 3.0 T MRI instrument(Discovery MR750w 3.0T,GE Co.Ltd,United States),following the procedure developed by International Atomic Energy Agency.Bone Mass was measured by Dual Energy X-ray Absorptiometry(DEXA)with Lunar apparatus(Prodigy,GE Co Ltd,USA).BIA was performed by measuring resistance and reactance at 5 Hz,50 Hz,100 Hz,250 Hz and 500 Hz frequencies with a multiple frequency BIA instrument(BCA-2A,Tsinghua Tong Fang Co.Ltd,China)equipped with eight electrodes.The octopolar resistance and reactance measurements were collected between the right wrist and the right ankle while the participants were supine.The impedance index(stature2/resistance;in cm2/?)was calculated for each person.All statistical and modeling processes were performed with R-language.Thirty healthy volunteers were recruited;and the raito of male and female was 1:1(15 male and 15 female).The average age of volunteers was 23.6±1.4 yrs and the BMI was 21.4± 1.3 kg/m2.TBWa of all subjects were firstly estimated with Isotope Dilution method based on 2H and 180 measurement.The prediction results from 2H measurement are very similar with that from 180 measurement.Next,the BIA was used to estimate TBWa and the results were compared with those from 2H isotope dilution test.The TBWa result from BIA was significantly higher,with a Pearson correlation of 0.962 between the two sets of results.The linear regression plot was exhibited.Results from BIA were comparable with that got from 2H isotope dilution test and the regression equation was Y = 0.879X +1.955,in which X represented the BIA result and Y represents result from 2H Isotope Dilution test,with R2 equaled to 0.9249 and 95Y%CI of ?(0.782,0.976).MRI and BIA were used to measure FM of all subjects and their results were compared.The result from BIA was significantly lower,with a Pearson correlation coefficient of 0.866.The regression equation is:Y=1.057X+0.846,in which X represents the BIA result and Y represents MRI results,with R2 equaled to 0.749 and 95%CI of ?(0.820,1.293).Bone mass(BM)of the subjects was estimated with both DEXA and BIA.Compared with DEXA,the BM result of BIA was significantly higher,with a Pearson correlation coefficient 0.952.The linear regression equation was:Y=0.671X + 0.374,in which X represented the BIA result and Y represented DEXA results,with R2 equaled to 0.785 and 95%CI of ?(0.535,0.807).In short,this part of our study established BIA adjustment equations that based on internationally recognized body composition gold standards.The results were reliable and repeatable.It provided a solidate base that to use BIA as an accurate,fast and covinent tool in clinical conditions to measure TBWa,FM,FFM and BM.Research Part II:In order to further verify the accuracy and repeatability of the BIA,adults who aged 25-35 yrs have their body compositions measured.The research result of Part I had confirmed that the correlation between the BIA and other standard methods was good.The DXA might measure a human' s muscle classification by section.With its convenience and repeatability,the DXA had been verified and applied by multiple international clinical research insititutions.Therefore,we adopted the DXA as the standard method to verify how the BIA could measure the muscle of young adults in this part of research.Participants met the following criteria had been recruited for the study:(1)Young adults aged between 25 to 34;(2)BMI 18.5-26.9 kg/m2;(3)Physical examination results were normal;(4)Male,or non-pregnancy and non-breastfeeding female(Non-breastfeeding period means more than 18 months after delivery);(5)Voluntarily enrolled and formal consent was obtained from each participant.We enrolled 209 volunteers in this part of research.The average age of volunteers was 27.61 ±2.98 yrs and BMI was 22.22±2.89 kg/m2.There were 104 males,averagely aged 27.27±2.79 yrs and BMI was 23.22±2.75 kg/m2.There were 105 female whose average age was 27.94±3.13 yrs and the BMI was 21.27±2.89 kg/m2.Laboratory tests were all in normal range.DXA measured FM was 16.00±5.99kg,BIA measured FM was 15.32±5.60 kg.Using DXA as reference,correlation r=0.935(P<0.001),linear equation was:y=0.9995x + 0.691(R2 =0.874,P<0.001).DXA measured lean body mass(LBM)was 76.73±8.87kg and the BIA measured LBM was 45.85±8.81kg.Using DXA as reference,correlation r =0.966,linear equation y =0.959 x ±1.046(R 2 = 0.934).Results of Torso LBM measurements were:DXA =20.85±3.93 kg,BIA = 20.43±3.97 kg,correlation r=0.931,linear equation:y =0.921 x+2.035(R2 = 0.867,p<0.001).Compared with Part I,we found there was no significant difference on the results of the BIA measurement on LBM of the total and segmental body parts on population aged between 25 and 35.And the deviation,correlation to DXA measurement,the BIA results on body compositions were also similar and without significantly difference.In summary,the results of this part demonstrated that BIA measurements were consistent with DXA.Using DXA as gold standard,the deviations of BIA results were acceptable.Meanwhile,the results of this part found that although accuracy of BIA on measuring LBM was irrelavent with age,for guarant the roubtness of BIA using in the clinical condition,we also established adjustment equations according to the DXA data.As a result,this would be the first time to use standard BIA establish the normal reference range of healthy young people in China.Research Part III:Sarcopenia was defined as the progressive loss of skeletal muscle mass and strength in normal aging process,especially in the elder population.There were enromous evidences indicated that the sacropenia leaded to disability and kinds of chronic complications caused much more attention from the gerontologists.Although the gerontologists and nutritionists deemed that sarcopenia was very common which leaded the huge financial an individual cost,but there was no widely accepted consensus in current,including the diagnostic criteria,the International Classification of Diseases(ICD)code or therapy guidelines.Limited by racial differences,the sarcopenia incidence was reported obviously different which ranged from 7%to 24%.The working groups for sarcopenia had been set in Asia and Europe,while the elder sarcopenia consensus reports had been published in recent years.However,in different areas and different races,the cut-off points would be represented greatly variability.This part was based on the Part ? and ?,to investigate the muscle mass and function status of domestic elders.And the results would compare with the Asia and Europe evidences,to expect to provide data basis for setting sarcopenia diagnostic criteria of Chinese elders in future.Method:The volunteers would be recruited in two Beijing large communities.The inclusion criteria were:1)age was over 65 yrs;2)regular diet and living;3)no alcohol abuse,picky eater or other bad living habits;4)signed the informed consent form.In total of 400 cases,the male and female were separated a half.The average age was 71.98 ± 5.34 yrs,the average height was 160.9±8.2 cm,the average weight was 64.73±10.48 kg,and the average BMI was 24.93 ±3.13 kg/m2.There were 98 cases(24.5%)had no known diseases,281 cases(70.3%)were combined 1-3 kinds of disease that were mainly diabetes,hypertension and other chronic diseases,21 cases(5.2%)had over 3 kinds of diseases.All volunteers had completed physical measurement,and the average upper arm circumference was 27.67 ± 3.54 cm(17.6-38.5 cm),mean 95%CI(27.32,28.01);average triceps skinfold thickness was 21.68±7.86 mm(4.0-45.0 mm),mean 95%CI(20.91,22.46);average calf circumference was 35.44±3.65 cm(20.0-44.0 cm),mean 95%CI(34.23,34.90).Based on the BIA body composition measures,the FFM mean was 43.56±7.63kg,male:48.98±6.13 kg and female:38.13±4.46 kg.Skeletal muscle content mean was 23.55 ± 4.54 kg,males:26.80±3.63 kg and female:20.29 ± 2.61 kg.According to the body surface area,the skeletal muscle mass index(SMI)was counted,male:9.16 ± 0.55 kg/m2 and female:7.08 ± 0.52 kg/m2.Quality of life scores and skeletal muscle mass was not correlated(R2=0.0018,p=0.189).Summary:Reference to international standards,Chinese elder normal muscle mass range recommendations male:10.26-8.06 kg/m2 and female:8.12-6.04 kg/m2.There was no better correlation between BMI and muscle mass in elder with malnutrition,suggesting that BMI was not a good indicator for nutrition assessment in elder.Conclusion:This study was the first time to propose and establish a unified correcting equation of domestic BIA body composition measurement based on the 3 gold standards of body composition measurement.It would provide a proposal that benefits to solve the accuracy controversy of BIA application in the clinical nutrition evaluation that had been existed for a long time.Based on the unified correcting equation,it was the first time to apply clinical standard DXA method and corrected BIA method to measure body composition in 209 healthy adults in China,and to establish the normal range of skeletal muscle index based on different gender.Finally,400 elder in Beijing community were measured grip strength,walking speed,and muscle mass by using Asian and European standard sarcopenia diagnostic method.It was also the first time to establish the muscle mass of community elder and normal reference range by using corrected BIA method,and to set up the safe upper and lower limits of mucle mass based on different gender.This filled the gap in China,and inially establish the Chinese elderly sarcopenia diagnostic standard. |
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