Altered Plasma Free Amino Acid Levels in Obese Traumatized Malayappa
Jeevanandam,
Lois Ramias,
and William
Man
R. Schiller
Obesity is a major nutritional disorder that produces many abnormal metabolic responses. The effect of injury-induced stresses acting synergistically with the state of excessive body fat is not well known. Plasma levels of circulating free amino acids reflect the net status of protein breakdown and utilization. Hypoaminoacidemia is a common finding in severe injury and its significance in obese subjects was investigated. We measured in 10 obese (body mass index [BMI] > 30) and 10 non-obese (BMI < 30) traumatized (Iniury Severity Score [MS] 17 to 50) patients, the plasma levels of free amino acids in the early “flow” phase of injury when subjects were receiving maintenance fluids without calories or nitrogen. Postabsorptive control samples were obtained from 10 obese and 10 non-obese volunteers. Obese controls showed an increase in valine, leucine, isoleucine, and glutamic acid levels, and a decrease in glycine. tryptophan, threonine. histidine, taurine, citrulline, and cystine levels compared with lean controls. Hypoaminoacidemia was equally seen in traumatized obese and non-obese patients, and it was mainly due to a 24% decrease in nonessential amino acids. Remarkably, essential amino acid levels were the same in all groups. Arginine and ornithine levels were significantly different in traumatized obese compared with non-obese patients. The hypoglycinemia seen in non-obese trauma patients was absent in obese patients. The changes in levels of sulphur-containing amino acids also suggest that monitoring of these levels should be included in the nutritional management of obese trauma patients. Copyright 0 1991 by W.B. Saunders Company
0
IS DEFINED as a condition with “an excess of body fat frequently resulting in a significant impairment of health.“’ It is a metabolic and nutritional disorder that constantly interferes with normal hormonal responses. Obesity by itself can lead to and exacerbate other systemic diseases. Aberrations in lipolytic mechanisms,’ glucose utilization,3 and diminished responsiveness to exogenous insulin3-’ have been well documented in obesity. Compared with lean subjects, obese subjects have elevated resting energy expenditure (REE), probably related to an increased lean body mass (LBM).6 Traumatized obese patients mobilize relatively more protein and less fat compared with non-obese subjects.‘However, normal obese subjects are more efficient in conserving body nitrogen during a fast and they lose nitrogen, as well as body weight, at a slower rate than the non-obese in their unstressed state.’ Little information is available on obesity regarding plasma amino acid levels, which reflect the net result of ingestion and production balanced by utilization rates and represent the sum of all factors influencing total amino acid flux. Hyperaminoacidemia appears to be a manifestation of the insulin-ineffectiveness characteristic of obesity.9 Hypoaminoacidemia” and insulin resistance” with increased mobilization of protein sources are hallmarks of the trauma response. Altered biological mechanisms in severely injured obese patients have not been carefully investigated previously. It is not clear how the disrupted metabolism in obese subjects (body mass index [BMI] > 30) may alter their ability to respond to the superimposed, injury-induced stress. The objectives of the present study were to compare the patterns of the individual free amino acid levels during the catabolic “flow” phase of multiple trauma in obese and non-obese adults and to investigate their significances in relation to the values seen in similar healthy, unstressed normal control groups. A better understanding of the apparent mechanisms of these metabolic changes may be helpful in tailoring the optimal composition of nutritional support in critically injured obese subjects.
MATERIALS
BESITY
Metabolism, Vol40, No 4 (April), 1991: pp 385-390
AND METHODS
Subjects Twenty multiple trauma victims and 20 healthy normal subjects were included in the study. Clinical characteristics of these adult subjects are summarized in Table 1. The patients were studied during their clinical care in the Trauma Intensive Care Unit of the Level I Trauma Center at St. Joseph’s Hospital and Medical Center, Phoenix, AZ. The protocol was reviewed and approved by the Institutional Review Board. The risks and benefits were explained and discussed with each patient or legal guardian and written informed consent was obtained before initiating the study. There were 10 patients (five male, five female) with BMI greater than 30 in the obese range (171% rt 8% ideal body weight), and 10 patients (five male, five female) with BMI less than 30 in the non-obese range (108% * 4% ideal body weight). The patients were evaluated and resuscitated according to their individual needs as determined by the trauma team. At the time of study, none of the patients were septic or had multiple organ failure, diabetes, recent weight loss, or liver, renal, or malignant disease. No subjects had obvious signs of malnutrition before the incident. Injuries were scored according to the Injury Severity Score (ISS) based on the abbreviated injury score (AIS) of the three most serious injuries.” All had at least one major injury and multiple minor injuries, with ISS ranging from 10 to 50. All patients were studied within 48 to 60 hours of major injury, when they were receiving maintenance fluid (normal saline) and electrolytes, but without calories or nitrogen. Hypermetabolism in these patients was estimated by comparison of patient’s basal energy expenditure (BEE) as calculated from
From the Trauma Center, St. Joseph’s Hospital and Medical Center, Phoenix, AZ. Supported in part by a grant (82-9286) from the Arizona Disease Control Research Commission. Presented in part at the 73rd annual meeting of FASEB held at New Orleans, LA, March 19-25, 1989 and published as an abstract (FASEB Journal 3:A355, 1989). Address reprint requests to Malayappa Jeevanandam, PhD, Trauma Center, St. Joseph’s Hospital and Medical Center, 350 W Thomas Rd, Phoenix, AZ 85013. Copyright 0 1991 by U! B. Saunders Company 0026-0495l91i4004-0009$03.00l0 385
386
JEEVANANDAM,
RAMIAS, AND SCHILLER
Table 1. Clinical Data of Study Subjects
Control No. and sex Age
(vrl
Weight (kg)
(kg/m’)
Trauma
Obese
Non-obese
Obese
5M/5F
5M/5F
5Ml5F
5Ml5F
44 2 6
39 f 3
48 2 6
31 t 5
107 + 4
73 + 3
104 + 8
77 * 4
25 2 1 1.8 + 0.1 32 t 3
36 +
25 +
1
Non-obese
BSA (ml)
-
-
ISS
-
-
36 IT2 2.1 * 0.1 26 f 3
-
147 f 7
155 -t 7
141 + 12
120 + 7
BMI
REE/BEE (%) Plasma glucose (mg/dL) Plasma insulin (+lU/mL) Nitrogen excretion (g/d) Creatinine excretion (g/d)
1
98 * 3
85 ? 3
(85-l 17)
(75-101)
11.6 2 0.5
6.3 + 0.6
-
-
12.6 + 3.0
8.2 t 1.6
24.8 2 2.7
16.7 + 2.9
2.01 2 0.24
1.53 2 0.15
NOTE. Values are mean + SEM (range).
Harris-Benedict equations, with the REE measured by indirectcalorimetry, gas-exchange technique, using computer-assisted Horizon Metabolic Cart (Sensormedics, Anaheim, CA). In this catabolic flow phase of injury, when the patient’s condition was stable and resuscitation complete, a venous blood sample was drawn at 8:00 AM. Using a Foley catheter, 24-hour urine collection was made after blood sampling for the estimation of daily nitrogen and creatinine excretions. During this time none of the patients received nitrogen or calories. Twenty normal, healthy volunteers (10 male, 10 female) matched for age and sex participated in the study as controls. There were 10 (five male, five female) subjects in the obese range and 10 (five male, five female) in the non-obese range. They were active and not on any medication that might affect the energy and protein metabolism. None had a history of diabetes or other chronic disorders. The obese subjects were carefully evaluated for other chronic diseases and none were morbidly obese. The usual activities and dietary habits of these control subjects were not restricted. A morning postabsorptive fasting venous blood sample was collected.
and non-obese normals (NON). The obesity-related effects of trauma were analyzed between these four closely matched groups. Following conventional procedures, the amino acids were grouped as branched-chain amino acids (BCAA: valine, leucine, and isoleucine), essential amino acids (EAA: BCAA along with phenylalanine, tryptophan, methionine, threonine, and lysine), nonessential amino acids (NEAAZ alanine, glycine, serine, glutamine, proline, arginine, histidine, taurine, glutamine, tyrosine, ornithine, citrulline, asparagine, and cystine), and large neutral amino acids (LNAA: BCAA plus tyrosine and phenylalanine). The sum of eight EAA and 14 NEAA are given as total amino acids (TAA) in plasma.
Statistics All results and individual and total plasma amino acid levels for each group are reported as mean 2 SEM. Significances of differences between variables were calculated with nonpaired Student’s t testI using pooled mean square analysis, and the correlations were calculated by linear regression. A P value of .05 or less was considered statistically significant.
Measurements Heparinized blood was centrifuged at 10,000 x g in a refrigerated centrifuge (Sontall RC-SB, DuPont Instruments, Wilmington, DE). An aliquot (1 mL) of plasma was deproteinized by 100 pL of 50% sulphosalicilic acid (SCA) containing the internal standard aminoethyl-E-cysteine (AEC), vortexed and centrifuged at 10,000 x g for 15 minutes. A known aliquot of the supernatant was diluted with an equal volume of lithiam citrate buffer (pH 2.2) and filtered through a 0.22~urn millipore filter. The filtrate was stored at -80°C freezer and analyzed in duplicate within 2 weeks. Individual amino acids were determined by the automated ion-exchange method using an amino acid analyzer (Model 7300, Beckman Instruments, Palo Alto, CA) as described previously.” This procedure was standardized using a calibrated mixture of pure amino acids. The coefficient of variation of multiple analyses was within 2%. The internal standard method eliminates the error due to loss in the analytical technique. Total nitrogen in the excreted urine was measured using a Chemiluminescence Digital Nitrogen Analyzer (Antek Instruments, Houston, TX). Urinary creatinine was determined with a microcentrifugal analyzer (Multistat-Plus III, Instrumentation Laboratory, Lexington, MA).
Calculations The patients were grouped as obese trauma (OT) and non-obese trauma (NOT), and the normal controls were obese normals (ON)
RESULTS The clinical data of the age-, sex-, and weight-matched adult trauma patients and control subjects are given in Table 1. All the patients were severely injured, mainly by motor vehicle accidents, and had at least one major and multiple minor injuries. The obese patients (BMI 36 f 2) had a mean ISS of 26 2 3 and the non-obese patients (BMI 25 + 1) had a mean ISS of 32 k 3. All subjects were hypermetabolic, since their measured REE was approximately 50% more than the BEE predicted by the age-, sex-, height-, and weight-based Harris-Benedict equations. The trauma patients were highly catabolic and hyperglycemic. The obese trauma patients mobilized more protein sources, as seen by their increased loss of nitrogen in the flow phase of injury. Plasma levels of individual EAA and NEAA in the injured trauma victims and uninjured controls are given in Tables 2 and 3, respectively. These data allow the comparison of the fasting amino acid levels due to the state of obesity in controls (ON v NON), due to acute trauma injury in controls (NON v NOT), due to trauma among obese subjects (ON v OT), and due to obesity among trauma
307
OBESE TRAUMA
Table 2. Plasma Essential Amino Acids Pattern in Normal and Trauma Patients PVaiues
Jeevanandam,
Lois Ramias,
and William
Man
R. Schiller
Obesity is a major nutritional disorder that produces many abnormal metabolic responses. The effect of injury-induced stresses acting synergistically with the state of excessive body fat is not well known. Plasma levels of circulating free amino acids reflect the net status of protein breakdown and utilization. Hypoaminoacidemia is a common finding in severe injury and its significance in obese subjects was investigated. We measured in 10 obese (body mass index [BMI] > 30) and 10 non-obese (BMI < 30) traumatized (Iniury Severity Score [MS] 17 to 50) patients, the plasma levels of free amino acids in the early “flow” phase of injury when subjects were receiving maintenance fluids without calories or nitrogen. Postabsorptive control samples were obtained from 10 obese and 10 non-obese volunteers. Obese controls showed an increase in valine, leucine, isoleucine, and glutamic acid levels, and a decrease in glycine. tryptophan, threonine. histidine, taurine, citrulline, and cystine levels compared with lean controls. Hypoaminoacidemia was equally seen in traumatized obese and non-obese patients, and it was mainly due to a 24% decrease in nonessential amino acids. Remarkably, essential amino acid levels were the same in all groups. Arginine and ornithine levels were significantly different in traumatized obese compared with non-obese patients. The hypoglycinemia seen in non-obese trauma patients was absent in obese patients. The changes in levels of sulphur-containing amino acids also suggest that monitoring of these levels should be included in the nutritional management of obese trauma patients. Copyright 0 1991 by W.B. Saunders Company
0
IS DEFINED as a condition with “an excess of body fat frequently resulting in a significant impairment of health.“’ It is a metabolic and nutritional disorder that constantly interferes with normal hormonal responses. Obesity by itself can lead to and exacerbate other systemic diseases. Aberrations in lipolytic mechanisms,’ glucose utilization,3 and diminished responsiveness to exogenous insulin3-’ have been well documented in obesity. Compared with lean subjects, obese subjects have elevated resting energy expenditure (REE), probably related to an increased lean body mass (LBM).6 Traumatized obese patients mobilize relatively more protein and less fat compared with non-obese subjects.‘However, normal obese subjects are more efficient in conserving body nitrogen during a fast and they lose nitrogen, as well as body weight, at a slower rate than the non-obese in their unstressed state.’ Little information is available on obesity regarding plasma amino acid levels, which reflect the net result of ingestion and production balanced by utilization rates and represent the sum of all factors influencing total amino acid flux. Hyperaminoacidemia appears to be a manifestation of the insulin-ineffectiveness characteristic of obesity.9 Hypoaminoacidemia” and insulin resistance” with increased mobilization of protein sources are hallmarks of the trauma response. Altered biological mechanisms in severely injured obese patients have not been carefully investigated previously. It is not clear how the disrupted metabolism in obese subjects (body mass index [BMI] > 30) may alter their ability to respond to the superimposed, injury-induced stress. The objectives of the present study were to compare the patterns of the individual free amino acid levels during the catabolic “flow” phase of multiple trauma in obese and non-obese adults and to investigate their significances in relation to the values seen in similar healthy, unstressed normal control groups. A better understanding of the apparent mechanisms of these metabolic changes may be helpful in tailoring the optimal composition of nutritional support in critically injured obese subjects.
MATERIALS
BESITY
Metabolism, Vol40, No 4 (April), 1991: pp 385-390
AND METHODS
Subjects Twenty multiple trauma victims and 20 healthy normal subjects were included in the study. Clinical characteristics of these adult subjects are summarized in Table 1. The patients were studied during their clinical care in the Trauma Intensive Care Unit of the Level I Trauma Center at St. Joseph’s Hospital and Medical Center, Phoenix, AZ. The protocol was reviewed and approved by the Institutional Review Board. The risks and benefits were explained and discussed with each patient or legal guardian and written informed consent was obtained before initiating the study. There were 10 patients (five male, five female) with BMI greater than 30 in the obese range (171% rt 8% ideal body weight), and 10 patients (five male, five female) with BMI less than 30 in the non-obese range (108% * 4% ideal body weight). The patients were evaluated and resuscitated according to their individual needs as determined by the trauma team. At the time of study, none of the patients were septic or had multiple organ failure, diabetes, recent weight loss, or liver, renal, or malignant disease. No subjects had obvious signs of malnutrition before the incident. Injuries were scored according to the Injury Severity Score (ISS) based on the abbreviated injury score (AIS) of the three most serious injuries.” All had at least one major injury and multiple minor injuries, with ISS ranging from 10 to 50. All patients were studied within 48 to 60 hours of major injury, when they were receiving maintenance fluid (normal saline) and electrolytes, but without calories or nitrogen. Hypermetabolism in these patients was estimated by comparison of patient’s basal energy expenditure (BEE) as calculated from
From the Trauma Center, St. Joseph’s Hospital and Medical Center, Phoenix, AZ. Supported in part by a grant (82-9286) from the Arizona Disease Control Research Commission. Presented in part at the 73rd annual meeting of FASEB held at New Orleans, LA, March 19-25, 1989 and published as an abstract (FASEB Journal 3:A355, 1989). Address reprint requests to Malayappa Jeevanandam, PhD, Trauma Center, St. Joseph’s Hospital and Medical Center, 350 W Thomas Rd, Phoenix, AZ 85013. Copyright 0 1991 by U! B. Saunders Company 0026-0495l91i4004-0009$03.00l0 385
386
JEEVANANDAM,
RAMIAS, AND SCHILLER
Table 1. Clinical Data of Study Subjects
Control No. and sex Age
(vrl
Weight (kg)
(kg/m’)
Trauma
Obese
Non-obese
Obese
5M/5F
5M/5F
5Ml5F
5Ml5F
44 2 6
39 f 3
48 2 6
31 t 5
107 + 4
73 + 3
104 + 8
77 * 4
25 2 1 1.8 + 0.1 32 t 3
36 +
25 +
1
Non-obese
BSA (ml)
-
-
ISS
-
-
36 IT2 2.1 * 0.1 26 f 3
-
147 f 7
155 -t 7
141 + 12
120 + 7
BMI
REE/BEE (%) Plasma glucose (mg/dL) Plasma insulin (+lU/mL) Nitrogen excretion (g/d) Creatinine excretion (g/d)
1
98 * 3
85 ? 3
(85-l 17)
(75-101)
11.6 2 0.5
6.3 + 0.6
-
-
12.6 + 3.0
8.2 t 1.6
24.8 2 2.7
16.7 + 2.9
2.01 2 0.24
1.53 2 0.15
NOTE. Values are mean + SEM (range).
Harris-Benedict equations, with the REE measured by indirectcalorimetry, gas-exchange technique, using computer-assisted Horizon Metabolic Cart (Sensormedics, Anaheim, CA). In this catabolic flow phase of injury, when the patient’s condition was stable and resuscitation complete, a venous blood sample was drawn at 8:00 AM. Using a Foley catheter, 24-hour urine collection was made after blood sampling for the estimation of daily nitrogen and creatinine excretions. During this time none of the patients received nitrogen or calories. Twenty normal, healthy volunteers (10 male, 10 female) matched for age and sex participated in the study as controls. There were 10 (five male, five female) subjects in the obese range and 10 (five male, five female) in the non-obese range. They were active and not on any medication that might affect the energy and protein metabolism. None had a history of diabetes or other chronic disorders. The obese subjects were carefully evaluated for other chronic diseases and none were morbidly obese. The usual activities and dietary habits of these control subjects were not restricted. A morning postabsorptive fasting venous blood sample was collected.
and non-obese normals (NON). The obesity-related effects of trauma were analyzed between these four closely matched groups. Following conventional procedures, the amino acids were grouped as branched-chain amino acids (BCAA: valine, leucine, and isoleucine), essential amino acids (EAA: BCAA along with phenylalanine, tryptophan, methionine, threonine, and lysine), nonessential amino acids (NEAAZ alanine, glycine, serine, glutamine, proline, arginine, histidine, taurine, glutamine, tyrosine, ornithine, citrulline, asparagine, and cystine), and large neutral amino acids (LNAA: BCAA plus tyrosine and phenylalanine). The sum of eight EAA and 14 NEAA are given as total amino acids (TAA) in plasma.
Statistics All results and individual and total plasma amino acid levels for each group are reported as mean 2 SEM. Significances of differences between variables were calculated with nonpaired Student’s t testI using pooled mean square analysis, and the correlations were calculated by linear regression. A P value of .05 or less was considered statistically significant.
Measurements Heparinized blood was centrifuged at 10,000 x g in a refrigerated centrifuge (Sontall RC-SB, DuPont Instruments, Wilmington, DE). An aliquot (1 mL) of plasma was deproteinized by 100 pL of 50% sulphosalicilic acid (SCA) containing the internal standard aminoethyl-E-cysteine (AEC), vortexed and centrifuged at 10,000 x g for 15 minutes. A known aliquot of the supernatant was diluted with an equal volume of lithiam citrate buffer (pH 2.2) and filtered through a 0.22~urn millipore filter. The filtrate was stored at -80°C freezer and analyzed in duplicate within 2 weeks. Individual amino acids were determined by the automated ion-exchange method using an amino acid analyzer (Model 7300, Beckman Instruments, Palo Alto, CA) as described previously.” This procedure was standardized using a calibrated mixture of pure amino acids. The coefficient of variation of multiple analyses was within 2%. The internal standard method eliminates the error due to loss in the analytical technique. Total nitrogen in the excreted urine was measured using a Chemiluminescence Digital Nitrogen Analyzer (Antek Instruments, Houston, TX). Urinary creatinine was determined with a microcentrifugal analyzer (Multistat-Plus III, Instrumentation Laboratory, Lexington, MA).
Calculations The patients were grouped as obese trauma (OT) and non-obese trauma (NOT), and the normal controls were obese normals (ON)
RESULTS The clinical data of the age-, sex-, and weight-matched adult trauma patients and control subjects are given in Table 1. All the patients were severely injured, mainly by motor vehicle accidents, and had at least one major and multiple minor injuries. The obese patients (BMI 36 f 2) had a mean ISS of 26 2 3 and the non-obese patients (BMI 25 + 1) had a mean ISS of 32 k 3. All subjects were hypermetabolic, since their measured REE was approximately 50% more than the BEE predicted by the age-, sex-, height-, and weight-based Harris-Benedict equations. The trauma patients were highly catabolic and hyperglycemic. The obese trauma patients mobilized more protein sources, as seen by their increased loss of nitrogen in the flow phase of injury. Plasma levels of individual EAA and NEAA in the injured trauma victims and uninjured controls are given in Tables 2 and 3, respectively. These data allow the comparison of the fasting amino acid levels due to the state of obesity in controls (ON v NON), due to acute trauma injury in controls (NON v NOT), due to trauma among obese subjects (ON v OT), and due to obesity among trauma
307
OBESE TRAUMA
Table 2. Plasma Essential Amino Acids Pattern in Normal and Trauma Patients PVaiues
