How to assess it at the bedside and in a research protocol

Transcription

1 ESPEN Congress Nice 2010 Body composition How to assess it at the bedside and in a research protocol Andrea Rossi Mauro Zamboni

2 Body composition: How to assess it at bedside and in a research protocol Andrea Rossi Mauro Zamboni Department of Medicine Section of Geriatrics University of Verona 32th ESPEN Congress Nice, September 6th, 2010

3 OBJECTIVES: methods for quantifyng fat in vivo methods for quantifyng Adipose Tissue in vivo methods for muscle quality evaluation in vivo methods for quantifyng fat in organs

4 Relation between chemical fat (or lipid) and adipose tissue Shen W, Wang Z, Heymsfield SB, Obes Res 2003; 11; 1; 2003

5 The five levels of human body composition Triglycerides altro idrogeno carbonio ossigeno Livello I atomico altro proteine lipidi acqua Livello II molecolare adipocytes,collagen, vessels, water, etc ECS ECF massa cellulare Livello III cellulare altro sangue osso tessuto adiposo muscolo scheletr. Livello IV tissutale Livello V S. Heymsfield, 1994

6 Most widely used current methods for quantifyng fat in vivo UWW (underwater weighing) Bioimpedence Air-displacement plethysmography system DXA

7 Air-Displacement Plethysmography (BOD POD) Diaphragm Oscillates 6/min Works on the gas law - expansion of Boyles Law Air instead of water displacement used Determines volume by measuring changes in pressure Changes in pressure can be used to calculate volume and then density the SIRI equation is used: Body mass= fat mass + FFM Fat Mass = (4,95/body density-4,5) x body mass. where FM density = g/cm 3 ; FFM density = g/cm 3

8 Air-Displacement Plethysmography (BOD POD) Advantages and disadvantages Takes 5 minutes Can host subjects until 400 kilos Error Range of 2% similar to underwater weighting Reliability CV=1.7% lower than for hydrostic weighing No water exposure, but chamber is not portable and subject could become claustrophobic Expensive

9 Dual Energy X-ray Absorbiometry Detectors FAT MASS (1) Photons (1) Subject (3) (2) WATER PROTEINS GLYCOGEN MINERALS BONE MASS (3) Collimator (pinhole for pencil beam, slit for fan beam) LEAN SOFT TISSUE (2) X Ray source (provides a broad photon beam filtered producing two main energy peaks. The difference in attenuation between the two energy peaks is particular to each element)

10 Dual-energy X-ray Absorpiometry (DXA) X-ray source 40 KeV Filter Tissues A = R B 70 KeV were R is the ratio between the attenuation of the lower energy ray (A) and the higher energy ray (B). Elements with higher atomic weight (such as calcium) are highly attenuating and have an higher R.

11 Dual-energy X-ray Absorpiometry (DXA) R Na Mg P Cl S K Ca Fat Free Mass Bone Mineral H C N O Fat Mass Atomic weight

12 Three compartiments model, lean soft tissue (2), fat mass (1), bone mass (3) FAT (1) BODY WEIGHT WATER SOFT TISSUE LEAN MASS PROTEINS GLYCOGEN MINERALS BONE MASS (3) LEAN SOFT TISSUE (2) Adapted from Hoffman DJ et al. In press

13 TOTAL BODY Dual-energy X-ray Absorpiometry (DXA) Total body. Women 59 kg, BMI 22.6 Total body. Women kg 104, BMI 34 Brownbill RA and Ilich JZ, 2004

14 Advantages and disadvantages of DEXA Advantages x-ray exposure is minimal (< 1 mrem for 1 scan) subregion evaluation is allowed quick: total body scan Pencil beam DXA (20-25 min) Fan beam DXA (< min) used in large clinical trials not invasive Highly precise and reproducible technique (CV for fat mass 1-1.7% and for FFM %) Disadvantages costs (machine and technicians) not transportable lose accuracy with incresing body thickness, than lose precision and accuracy in thicker obese subjects radiation exposure (as a day of sunbathing) weight and dimensions limits

15 Brownbill RA, Ilich JZ; BMC medical Imaging; 2005 Weight and dimensions limits of different DXA models Manufacturer/ Densitometer Weight Limit kg (lb) Table Dimensions cm GE Lunar Prodigy idxa Advance (350) Kg GE Lunar Prodigy 136 (300) GE Lunar DPX-MD 136 (300) Hologic QDR series 136 (300) Hologic Discovery Series (350) Kg Norland XR (250) Norland XR (250)

16 Most used current methods for quantifyng Adipose Tissue in vivo Computed Tomography Magnetic Resonance

17 Tissue organ level of body composition Adipose Subcutaneous tissue Visceral Organs Residual Skeletal Muscle Mineral Wang ZM,Pierson RN, Heymsfield SB Am J Clin Nutr 1992; 56; 19-28

18 Abdominal Magnetic Resonance Imaging (MRI) L4-5 visceral adipose tissue (VAT) Superficil and deep AT subcutaneous adipose tissue (SCAT) University of Verona

19 Magnetic Resonance Imaging (MRI) Appendicular protocol Abdominal rotocollo Appendicolar protocol Image 1 Image 46 Image 24 Heymsfield S, Ross R, Wang Z Handbook of Obesity; 2000

20 MRI Validation Studies Correlation (SEE, %) Reference Subject (N) IV Subcut. AT Visceral AT Total AT SM Seidell et al., 1990 Sobel et al., 1991 Ross et al., 1991 Engstrom et al., 1991 Human (7) Comparison with CT Midabdomen 0.79 (4.9) 0.79 (12.8) 0.99 (4.4) Human (11) Umbilicus 0.98 (8) 0.93 (20) Rat (21) Whole body 0.98 (12) 0.98 (13.6) 0.99 (8.7) Human (3) Comparison with Cadavers Thigh muscle CSA 0.99 NOTE: MRI, magnetic resonance imaging; SEE, standard error of estimate; IV, independent variable; AT, adipose tissue; SM, skeletal muscle; CT, computerized axial tomography; CSA, cross-sectional area. Heymsfield S, Ross R, Wang Z Handbook of Obesity; 2000

21 MRI Reliability Studies Coefficient of Variation (%) Reference Subject (N) T MRI Sequence Staten et al., 1989 Seidell et al., 1990 Garard et al., 1991 Ross et al., 1991 Ross et al., 1993 Sohlström et al., 1993 Ross et al., 1994 Abate et al., 1994 Ross et al., 1995a Anatomical Position Human 0.5 SE Midabdomen Subcut. AT Visceral AT Total AT LT Human 1.5 IR Umbilicus Human 1.5 SE 6 abdomen images Rat 1.5 SE Whole body Human 1.5 SE L4-L Whole body Human 0.02 SR Whole body Human 1.5 SE Proximal thigh CV s for MRI are about two to three time greater than those reported for studies using CT * Cadaver 0.35 SE Abdomen Human 1.5 SE L4-L5 1.0 NOTE: MRI, magnetic resonance imaging; T, strength of magnet in Teslas; AT, adipose tissue; LT, lean tissue; SE, spin-echo; IR, inverse recovery; SR, saturation recovery; L4-L5, lumbar vertebrae 4 5. * Reported as nonsubcutaneous adipose tissue. Heymsfield S, Ross R, Wang Z Handbook of Obesity; 2000

22 Magnetic Resonance Imaging (MRI) Advantages Does not use ionizing radiation High quality image and can accurately quantify both subcutaneous & visceral fat Relatively rapid (approx 30 min for whole body scan) Can be used for longitudinal studies Disadvantages Not available appropriate image analysis software Less precise for intermuscular fat quantification Some exclusions (e.g. pacemakers) Expensive Artifacts ( shading at the peripheries of images due to inhomogeneity in the magnetic field)

23 Ectopic fat deposition consequences Lipid overflow ectopic fat Muscle fat ( Intracellular lipid) Altered FFA metabolism Altered release of adipokines Epicardial fat Liver fat and altered function flcardiac function flinsulin sensitivity Dyslipidemia flβ-cell function Atherosclerosis NASH Pancreas fat and altered function FFA = free fatty acids NASH = nonalcoholic steatohepatitis Adapted from Després J-P, Lemieux I. Nature. 2006;444: Molavi B et al. Curr Opin Cardiol. 2006;21:

24 Most widely used current methods for muscle quality evaluation in vivo intermuscular fat (extramyocellular fat) CT MRI intramyocellular fat CT muscle attenuation MRS Magnetic resonance spectroscopy

25 Intermuscular Fat (CT) Less More Most Deposition of fat between skeletal muscle bundles and beneath the muscle fascia Gallagher D Am J Clin Nutr 2005

26 Quantification of Intermuscular Adipose Tissue in the Erector Spinae Muscle by MRI: Agreement With Histological Evaluation Rossi et al. Obesity 2010 Mar 18

27 Rossi et al. Obesity 2010 Mar 18 Correlation between IMAT evaluated with MRI and % Histological fat infiltration N=17 M=12, F=5 R=.679, p<0.003

28 CT scan CT can differentiate tissues based on their attenuation characteristics, which depend on their density. X-ray attenuation is quantified as Hounsfield Units (HU) Air Adipose LDL-T Muscle Bone Tissue Muscle density - average value of muscle = lean, fat, collagen, blood vessels lower density means more fat Myosteatosis muscle density and/or intramuscular fat

29 LDLT women, 69 year, BMI 49, W 121 cm, diabetes Muscle density (Hounsfield unit) - average value of muscle = lean, fat, collagen, blood vessels lower density means more fat Myosteatosis muscle density and/or intramuscular fat University of Verona

30 1- Water suppressed PRESS boxes 2-Measurement of methylene (CH 2) and methyl grups (CH3) 3- IMCL and EMCL expressed either relative to peak area external oil phantom or to internal peak of non-water suppressed signal IMCL and EMCL: shift in frequency IMCL peak 1.4 EMCL peak 1.6 Larson-Meyer Eet al, 2006

31 Depletion and replenishment of intramyocellular lipids IMCL ppm ppm ppm

32 Muscle-associated Triglyceride Measured by CT and Magnetic Resonance Spectroscopy H-MRS CT IMCL vs EMCL yes no CV soleus CH 2 within subjects IMCL 7.25% EMCL 18.8% 1.9% CV tibial CH 2 within subjects IMCL 10.26% EMCL 28.5% 4.0% Technical problems high low

33 Most widely used current methods for quantifyng fat in organs Liver ectopic fat deposition Pancreas ectopic fat deposition Epicardic fat evaluation

34 LIVER, PANCREAS AND PSOAS MUSCLE FAT DEPOSITION EVALUATION with in and out of phase CHEMICAL-SHIFT technique University of Verona

35 Abdomen MRI in and out of phase images. ROI s for liver lipid content measurement BMI = 24 BMI = 31 In phase 10% Out of phase 70% University of Verona

36 Abdomen MRI in and out of phase images. ROI s for pancreas lipid content measurement BMI = 24 BMI = 31 In phase 10% Out of phase 60% University of Verona

37 Quantification of Pancreas Lipid content by Chemical- Shift technique MRI and by Histological Evaluation R2=.560, p<0.05 Lee SE et al Ann Surg 2010; 251:932-7

38 MR imaging spectrum of a fatty human liver Cassidy F H et al. Radiographics 2009;29:

39 Magnetic Resonance Spectroscopy Advantages MR spectroscopy accounts for the multiple spectral components of fatty acids Is the most direct method of fat quantification. Disadvantages In vivo abdominopelvic MR spectroscopy requires a skilled operator to correctly perform the examination, process the data, and interpret the results. Data analyses is complex, is prone to bias; and may not permit accurate, reproducible quantification of all fat signal components. Standard MR spectroscopic pulse sequences have relatively long minimum echo times may lead to quantification errors. Shimming the MR spectroscopy voxel tends to be time consuming and may lengthen overall examination time considerably.

40 Macroscopic appearance of epicardial fat Iacobellis G et al. (2005) Epicardial adipose tissue: anatomic, biomolecular and clinical relationships with the heart Nat Clin Pract Cardiovasc Med 2: doi: /ncpcardio0319

41 Rabkin SW. Obesity Reviews : and Iacobellis et al. Obesity Research : EPICARDIAL FAT: Echocardiography and Magnetic Resonance

42 Most widely used current methods for anthropometry BMI Waist Circumference Waist to hip ratio

43 Relationship Between BMI and Percent Body Fat in Men and Women Body Fat (%) Women 50 Men Body Mass Index (kg/m 2 ) Adapted from: Gallagher et al. Am J Clin Nutr 2000;72:694.

44 Waist Circumference and cardiovascular risk Han et al, 1995 Normal Moderate Risk men (cm) women (cm) < 94 < High Risk > 102 > 88

45 WHR cardiovascular risk Women Men At risk >0,8 >1

46 In clinical practice and for clinical studies in wide population Not Fat Mass, Not Adipose Tissue, Not Lipid fat infiltration, but Surrogates that are still good methods to predict total body adiposity, body fat distribution and cardiovascular risk

47 Merci pour votre attention