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Is plasma serine a marker for psychosis?
1130
BIOL PSYCHIATRY 1992;31:1130-1135
Is Plasma Serine a Marker for Psychosis? G. F. Carl, M.P. Brogan, and B.K. Young
There is some disagreement in the literature concerning the use of plasma serine concentrations as a biological marker for psychoses including schizophrenia. The groups studying this phenomenon have used different methodologies, including gas chromatography and classical amino acid analysis. In the present study, using high pressure liquid chromatography to analyze plasma amino acids from schizophrenics and controls, we found no difference in plasma serine concentrations. None of the plasma amino acid concentrations that were measured differed significantly between schizophrenics and: controls but the basic amino acids tended toward higher concentrations in schiz~,~hrenics.
Introduction In 1983, Waziri et al. reported that plasma serine concentrations were higher in psychotics than they were in nonpsychotics and that the serine concentrations increased as the psychosis score increased. They suggested that the plasma serine/cysteine ratio might be used as a marker for psychoses including schizophrenia, mania, and paranoid disorder. In a subsequent study, Waziri et al (1984) reported that plasma serine levels were higher in active psychotics than they were in the same psychotics after amelioration of symptoms but that, even in patients without active psychoses, the plasma serine levels were higher than they were in either nonpsychotic psychiatric patients or in nonpatient controls. In a later study, Waziri et al (1985) reported that psychotically depressed patients could be differentiated from non-psychotically depressed patients using plasma serine levels. The metabolism of serine was shown to be different in psychotic patients when compared with nonpsychotics (Wilcox et al 1985). The half-life of serine in the plasma of psychotic patients separated into two distinct populations: one for which the mean was longer than the mean half-life of serine in the plasma from nonpsychotics and one for which the mean was shorter (Wilcox et al 1985). In addition, plasma serine hydroxymethyltransferase activity was shown to be lower in the psychotic population (Wilcox et al 1985; Waziri et al 1985). On the other hand, Bminvels and Pepplinkhuizen (1984) studied a small population of episodic psychotic patients and found a subnormal plasma serine concentration accompanied by a psychedelic symptomology in response to a serine load. But, in a subsequent investigation in fibroblasts from these patients no abnormalities could be found in serine or folate metabolizing enzymes (Fekkes and Bruinvels 1986). Waziri and Mott (1986) found that treatment of their psychotics with neuroleptics caused a decrease in the plasma serine concentration but not to control levels, but the neuroleptics had no effect on the plasma serine hydroxymethyitransferase activity.
From the Departments of Neurology and Psychiatry, Medical College of Georgia and Medical Research Service (151), VA Medical Center, Augusta, GA. Address inquiries to: G. F. Carl, Medical Research (151), VA Medical Center, Augusta, GA 30910. Received Alail 20, 1990; revised February 10, 1992. © 1992 Society of Biological Psychiatry
0006-3223/92/$05.00
Plasma Serine in Schizophrenia
BIOLPSYCHIATRY 1992;31:1130-1135
1131
Support for the involvement of serine and glycine in psychoses was provided by Macciardi et al (1990) who, using discriminant analysis on plasma concentrations of five amino acids (glutamate, serine, glycine, isoleucine, and threonine), were able to predict the diagnostic group of 83% of 75 subjects (32 controls and 43 schizophrenics). Unlike Waziri's group (1985), Macciardi et al (1990) were unable to diagnose the psychosis on the basis of plasma serine concentrations alone, but the mean plasma serine concentration that they found in schizophrenics was significantly higher than the mean in controls. Waziri et al (1990) recently showed that concentrations of both serine and glycine were increased in the temporal lobes of schizophrenics when compared with controls and that the Kmof serine hydroxymethyltransferase for serine was higher in this brain region as well, lending further support to their hypothesis. No significant difference was observed in the frontal lobe for any of these variables between schizophrenics and controls. In contradiction to these studies, Perry and Hansen (1985) examined a relatively large group of schizophrenic patients for plasma and cerebrospinal fluid (CSF) serine concentrations but found no difference in serine concentrations in either plasma or CSF. They indicated that differences in methodology might account for the different results they obtained when compared with those of Waziri et al (1983, 1984). Indeed, Wazifi and Mort (1986) reported a study of the methodologies used to assay plasma serine levels. They found differences in plasma serine levels between psychotics and controls using both gas chromatography (their standard method) and high pressure liquid chromatography (HPLC). However, no difference was found using the classical amino acid analyzer. They compared protein precipitation methods and found that when plasma was treated with trichloroacetic acid before analysis for amino acids, both gas chromatographic and HPLC analyses found differences in serine levels between psychotics and controls, but, when sulfosalicylic acid was used to precipitate protein, neither gas chromatography nor the classical amino acid analyzer showed any difference in plasma serine levels. They concluded that the sulfosalicylic acid precipitation of plasma protein was masking the difference in serine levels. However, Macciardi et al (1990) used sulfosalicylic acid precipitation followed by classical amino acid analysis and found a significant difference in mean plasma serine concentration between controls and schizophrenics, but they were apparently unaware of the methodological controversy. In an attempt to resolve this controversy, Waziri's group (Baruah et al 1991) used gas chromatography-mass spectrometry to measure plasma serine and glycine levels. Though this more rigorous methodology indicated that there was indeed overlap between schizophrenics and controls in plasma serine levels, there was still a significant difference between the mean plasma concentrations in these two groups. We report here the results of our study of plasma amino acid levels in hospitalized, chronic schizophrenics. We used methods that were different from those of Waziri's group (1983, 1984, 1985, 1986) and from those of Perry and Hansen (1985) and Macciardi et al (1990).
Methods
Subjects Thirteen well-nourished, male chronic schizophrenic patients from the V A psychiatric unit, aged 29-52, were matched with 13 nonpsychotic controls (hospital employees) for age, gender, and race (Table 1). Blood was collected in EDTA Vacutainer tubes by venipuncture at 7:00 am after an overnight fast~ Eight additional nonfasting schizophrenic
1132
BIOL PSYCHIATRY 1992;31:1130-1135
G.F. Carl et al
Table 1. Male Subjects Schizophrenics
n Mean age Age range Race Black White
Fasting
Nonfasting
Controls
13 38.6 29-52
8 37.8 34--43
13 37.7 28-54
6 2
4
4
9
9
patients aged 34-43 were studied to examine the effect of fasting. The diagnosis of schizophrenia was based on DSM-III-R criteria. Nine of the 13 fasting patients were taking antipsychotic medication at the time blood was taken and four were drug free. Six of the eight nonfasting patients were on medication.
Amino-Acid Determinations Plasma amino acids were determined by a modification of the method of Hill et al (1979). Linear standard curves were generated for each amino acid. Glycine and threonine were separated by our modification. A plasma sample was spiked with each amino acid separately and the peak area was compared with the pre-spike area to check quantitation. Bloods of the schizophrenics and controls were drawn at the same time and were centrifuged within 1 hr of drawing. The plasma was stored at - 2 0 ° for up to 2 years before analysis. Because of the protracted storage period, and because it is well known that plasma peptides have a certain instability, it must be acknowledged that there might be some slippage in the data. However, plasma from subjects and from controls was drawn at the same time, and any possible shift could be presumed to he shared by both. Conversion of glutamine to glutamate during storage prevented us from reporting the concentrations of these amino acids separately. Plasma (100 Ixl) plus 0.25 I~mol fluorophenylalanine (25 ttl, internal standard) (Aldrich, Milwaukee) were treated with methanol (2.0 ml), and the protein precipitate was pelleted by centrifugation (1000 x g, 10 rain). An aliquot of the supernatant (500 Ixl) was diluted 1:1 with 0.5 M potassium borate, pH 10.5, and loaded into a Gilson auto injector. One minute before injection, the sample was mixed with 250 ttl of derivatizing solution containing 2.5 mg o-phthaldehyde (Pierce Chemical Co., Chicago), 0.05 M potassium borate, pH 10.5 (added as 25 Ixl aqueous 0.5 M potassium borate), and 2.5 M mercaptoethanol in methanol. A 20-ttl aliquot was injected automatically onto a 5 ttm C18 column and eluted with a linear gradient over 25 rain from 100% solvent A (91% 35 mM sodium acetate, pH 6.5, 5% methanol, 4% tetrahydrofuran, by volume) to 100% solvent B (40% 35 mM sodium acetate, pH 6.5, 60% methanol, by volume) using a Waters gradient HPLC system (Model 720 Controller with one Model 6000A pump and one Model M-45 pump, a Model U6K injector and a Model 420 fluorescence detector with a 340 nm excitation filter, and a 425 nm emission filter). This method yields plasma amino acid concentrations comparable to those produced by the classical amino acid analyzer, albeit, in general, slightly lower (Furst et al 1990).
Plasma Serine in Schizophrenia
nlOL PSYCHL~TRY 1992;31:1130-1135
1133
Table 2. Plasma Amino Acid Concentrations (t~mol/L) of Patients and Controls Schizophrenics Nonfasting ALA ARG ASN ASP GLU + GLN GLY HIS ISL LEU LYS MET ORN PIlE SER TAU THR TRP TYR VAL
367.7 62.1 50.9 4.5 626.4 171.9 72.5 82.0 113.3 139.3 17.0 112.0 51.1 101.8 67.8 179.3 70.5 63.5 285.5
_ 96.5 .4- 14.6 ± 18.6 ± 3.6 ± 172.3 ± 42.4 ± 10.0 _ 20.5 ± 20.0 ± 50.2 ± 10.6 ± 49.1 ± 8.1 ± 31.6 _ 17.2 _ 41.9 ± 20.6 ± 21.3 ± 58.5
Fasting 333.4 63.8 49.6 7.3 623.2 215.7 73.~: 79.0 119.6 144.1 13.4 87.1 54.3 109.1 81.6 178.9 91.2 60.9 252.2
_ _ ± ± + ± ± ± _ ± ± ± _ ± ± ± ± -+
71.0 17.5 17.4 7.6 158.1 39.1 11.5 13.7 14.7 22.3 5.7 38.6 4.1 29.8 26.4 34.1 12.3 9.9 17.6
Controls 370.8 52.9 47.3 4.3 598.9 193.1 63.0 90.0 126.3 120.4 12.6 105.8 52.7 107.5 61.4 177.2 76.5 55.7 276.4
__. 83.0 ± 16.1 ± 17.6 ± 3.0 ± 161.7 ± 39.9 ± 13.0 ± 16.5 ± 24.7 ± 33.5 ± 8.0 ± 25.0 ± 8.4 ± 27.9 ± 20.6 ± 33.7 ± 26.6 ± 15.8 _ 51.6
P 0.497 0.244 0.899 0.337 0.839 0.079 0.078 0.274 0.394 0.243 0.491 0.303 0.623 0.866 0.097 0.990 0.230 0.531 0.230
Concentrations are expressed as means __ SD. No significant differences were found atp < 0.05 using ~ one-way ANOVA.
Statistics Plasma amino acid concentrations from controls and fasting and nonfasting schizophrenics separately were comp~ued using a one-way analysis of variance at the 95% confidence level.
Results Using methanol to extract plasma amino acids followed by derivatization with a fluorochrome and separation by HPLC [a completely different method for the analysis of plasma amino acids than used by Waziri et al (1983, 1984, 1985, 1986), Perry and Hansen (1985) or Macciardi et al (1990)], we found no difference in the plasma serine concentrations between schizophrenics and controls (Table 2). Though there were no significant differences in any plasma amino acid concentrations between either the patient and control groups or between the patient fasting and nonfasting groups, the basic amino acids, histidine, lysine, and arginine tended to be higher in the schizophrenics. Discussion Perry and Hansen (1985) were unable to show a difference in plasma serine concentrations between schizophrenics and controls using sulfosalicylic acid to precipitate the plasma proteins followed by classical al~no acid analysis on a mixed ion exchange resin with post-column derivatization with ninhydrin for quantitation. Waziri and Mott (1986) con-
1134
BIOL PSYCHIATRY 1992;31:1130-1135
G.F. Carl et al
firmed that they found no difference in plasma serine concentration between their psychotics and nonpsychotics using the method of Perry and Hansen nor could they find a difference in plasma serine concentrations between these populations if they use~ sulfosalicylic acid to precipitate the plasma proteins followed by analysis using gas chromatography (their standard method). They blamed their failure to see a difference in plasma serine levels on the use of sulfosalicylic acid to precipitate proteins. However, Macciardi et al (1990) later, but apparently independently, using the same method as Perry and Hansen (1985), did show a significant difference in plasma serine concentration between schizophrenics and controls. In the present study we used neither sulfosalicylic acid nor the trichloroacetic acid used routinely by Waziri's group. Instead, we used 20 volumes of methanol to precipitate the protein. Like Waziri's group, we derivatized the amino acids prior to separation, but, unlike the other groups, we separated the amino acid derivatives by HPLC using a reverse phase column. We detected and quantitated the amino acids using fluorescence. Using this totally different method, we found no difference in plasma serine levels between the hospitalized schizophrenic population and hospital workers matched for age, race and gender. Our data agree with that of Perry and Hansen (1985) that no difference in plasma serine concentration exists between schizophrenics and controls. We, like Perry and Hansen and Macciardi et al (1990), used only schizophrenics to make our comparisons, whereas Waziri et al (1983, 1984, 1985, 1986) used psychotic patients which in three out of four cases included schizophrenics (1983, 1984, 1986) and in one case (1983) separated schizophrenics out as a separate group showing high plasma serine concentrations. It is l~ssible that differences in the psychiatric populations or diagnostic procedures or possibly even drug treatments are causing the differences between the observations of Waziri and et al and Macciardi et al on one hand and Perry and Hansen and us on the other. The authors are grateful to Drs. Susan Haverstock and Richard Borison for the diagnoses and patient access, to Gale Ganter-Schultz for performing the amino acid analyses, and to Dr. Edward Orr for performing the statistical analyses.
References Baruah S, Waziri R, HegwoodTS, Mallis LM (1991) Plasma serine in schizophrenics and controls measured by gas chromatography-mass spectrometry. Psychiatry Res 37:261-270. Bminvels J, Pepplinkhuizen L (1984) Impaired glycine-serine conversion and increased plasma taurine levels in episodic psychotic patients with psychedelic symptoms. J Psychiatry Res 18:307-318. Fekkes D, Bminvels J (1986) Serine and folate metabolism in fibroblasts from episodic psychotic patients with psychedelic symptoms. Biol Psychiatry 21:951-959. Furst P, Pollack L, GraserTA, Godel H, Stehle P (1990) Appraisal of four pre-column derivatization methods for the high performance liquid chromatographic determination of free amino acids in biological materials. J Chromatog 499:557-569. Hill DW, Waiters FH, Wilson TD, Stuart JD (1979) High performance liquid chromatographic determination of amino acids in the picomole range. Analyt Chem 51:1338-1341. Macciardi F, Lucca A, Catalano M, Marino C, Zanardi R, Smeraldi E (1990) Amino acid patterns in schizophrenia: Some new findings. Psychiatry Res 32'63-70. Perry TL, Hansen S (1985) Interconversion of serine and glycine is normal in psychotic patients. Psychiatry Res 15:109-113.
Plasma Serine in Schizophrenia
BIOL PSYCHIATRY 1992;31:! 130-1135
1135
Waziri R, Mott J (1986) Drag effects on serine metabo!ism in psychiatric patients. Psychiatry Res 18:119-126. Waziri R, Wilson R, Sherman AD (1983) Plasma serhl~-to~cysteine ratio as a biological marker for psychosis. Br J Psychiatry 143:69-73. Waziri R, Wilcox J, Sherman AD, Mott J (1984) Sefine metabolism and psychosis. Psychiatry ICes 12:121-136. Waziri R, Mott J, Wilcox J (1985) D~4"-ferentiationof psychotic from nonpsychotic depression by a biological marker. J Affecgve Disord 9:175-180. Waziri R, Bamah S, Hegwood TS, Sherman AD (1990) Abnormal serine hydmxymethyltransferase activity in the temporal lobes of schizophrenics. Neurosci Lett 120:237--?A0. Wilcox J, Waziri R, Sherman A, Mort J (1985) Metabolism of an ingested serine load in psychotic and nonpsychotic subjects. Biol Psychiawy 20:41--49.
BIOL PSYCHIATRY 1992;31:1130-1135
Is Plasma Serine a Marker for Psychosis? G. F. Carl, M.P. Brogan, and B.K. Young
There is some disagreement in the literature concerning the use of plasma serine concentrations as a biological marker for psychoses including schizophrenia. The groups studying this phenomenon have used different methodologies, including gas chromatography and classical amino acid analysis. In the present study, using high pressure liquid chromatography to analyze plasma amino acids from schizophrenics and controls, we found no difference in plasma serine concentrations. None of the plasma amino acid concentrations that were measured differed significantly between schizophrenics and: controls but the basic amino acids tended toward higher concentrations in schiz~,~hrenics.
Introduction In 1983, Waziri et al. reported that plasma serine concentrations were higher in psychotics than they were in nonpsychotics and that the serine concentrations increased as the psychosis score increased. They suggested that the plasma serine/cysteine ratio might be used as a marker for psychoses including schizophrenia, mania, and paranoid disorder. In a subsequent study, Waziri et al (1984) reported that plasma serine levels were higher in active psychotics than they were in the same psychotics after amelioration of symptoms but that, even in patients without active psychoses, the plasma serine levels were higher than they were in either nonpsychotic psychiatric patients or in nonpatient controls. In a later study, Waziri et al (1985) reported that psychotically depressed patients could be differentiated from non-psychotically depressed patients using plasma serine levels. The metabolism of serine was shown to be different in psychotic patients when compared with nonpsychotics (Wilcox et al 1985). The half-life of serine in the plasma of psychotic patients separated into two distinct populations: one for which the mean was longer than the mean half-life of serine in the plasma from nonpsychotics and one for which the mean was shorter (Wilcox et al 1985). In addition, plasma serine hydroxymethyltransferase activity was shown to be lower in the psychotic population (Wilcox et al 1985; Waziri et al 1985). On the other hand, Bminvels and Pepplinkhuizen (1984) studied a small population of episodic psychotic patients and found a subnormal plasma serine concentration accompanied by a psychedelic symptomology in response to a serine load. But, in a subsequent investigation in fibroblasts from these patients no abnormalities could be found in serine or folate metabolizing enzymes (Fekkes and Bruinvels 1986). Waziri and Mott (1986) found that treatment of their psychotics with neuroleptics caused a decrease in the plasma serine concentration but not to control levels, but the neuroleptics had no effect on the plasma serine hydroxymethyitransferase activity.
From the Departments of Neurology and Psychiatry, Medical College of Georgia and Medical Research Service (151), VA Medical Center, Augusta, GA. Address inquiries to: G. F. Carl, Medical Research (151), VA Medical Center, Augusta, GA 30910. Received Alail 20, 1990; revised February 10, 1992. © 1992 Society of Biological Psychiatry
0006-3223/92/$05.00
Plasma Serine in Schizophrenia
BIOLPSYCHIATRY 1992;31:1130-1135
1131
Support for the involvement of serine and glycine in psychoses was provided by Macciardi et al (1990) who, using discriminant analysis on plasma concentrations of five amino acids (glutamate, serine, glycine, isoleucine, and threonine), were able to predict the diagnostic group of 83% of 75 subjects (32 controls and 43 schizophrenics). Unlike Waziri's group (1985), Macciardi et al (1990) were unable to diagnose the psychosis on the basis of plasma serine concentrations alone, but the mean plasma serine concentration that they found in schizophrenics was significantly higher than the mean in controls. Waziri et al (1990) recently showed that concentrations of both serine and glycine were increased in the temporal lobes of schizophrenics when compared with controls and that the Kmof serine hydroxymethyltransferase for serine was higher in this brain region as well, lending further support to their hypothesis. No significant difference was observed in the frontal lobe for any of these variables between schizophrenics and controls. In contradiction to these studies, Perry and Hansen (1985) examined a relatively large group of schizophrenic patients for plasma and cerebrospinal fluid (CSF) serine concentrations but found no difference in serine concentrations in either plasma or CSF. They indicated that differences in methodology might account for the different results they obtained when compared with those of Waziri et al (1983, 1984). Indeed, Wazifi and Mort (1986) reported a study of the methodologies used to assay plasma serine levels. They found differences in plasma serine levels between psychotics and controls using both gas chromatography (their standard method) and high pressure liquid chromatography (HPLC). However, no difference was found using the classical amino acid analyzer. They compared protein precipitation methods and found that when plasma was treated with trichloroacetic acid before analysis for amino acids, both gas chromatographic and HPLC analyses found differences in serine levels between psychotics and controls, but, when sulfosalicylic acid was used to precipitate protein, neither gas chromatography nor the classical amino acid analyzer showed any difference in plasma serine levels. They concluded that the sulfosalicylic acid precipitation of plasma protein was masking the difference in serine levels. However, Macciardi et al (1990) used sulfosalicylic acid precipitation followed by classical amino acid analysis and found a significant difference in mean plasma serine concentration between controls and schizophrenics, but they were apparently unaware of the methodological controversy. In an attempt to resolve this controversy, Waziri's group (Baruah et al 1991) used gas chromatography-mass spectrometry to measure plasma serine and glycine levels. Though this more rigorous methodology indicated that there was indeed overlap between schizophrenics and controls in plasma serine levels, there was still a significant difference between the mean plasma concentrations in these two groups. We report here the results of our study of plasma amino acid levels in hospitalized, chronic schizophrenics. We used methods that were different from those of Waziri's group (1983, 1984, 1985, 1986) and from those of Perry and Hansen (1985) and Macciardi et al (1990).
Methods
Subjects Thirteen well-nourished, male chronic schizophrenic patients from the V A psychiatric unit, aged 29-52, were matched with 13 nonpsychotic controls (hospital employees) for age, gender, and race (Table 1). Blood was collected in EDTA Vacutainer tubes by venipuncture at 7:00 am after an overnight fast~ Eight additional nonfasting schizophrenic
1132
BIOL PSYCHIATRY 1992;31:1130-1135
G.F. Carl et al
Table 1. Male Subjects Schizophrenics
n Mean age Age range Race Black White
Fasting
Nonfasting
Controls
13 38.6 29-52
8 37.8 34--43
13 37.7 28-54
6 2
4
4
9
9
patients aged 34-43 were studied to examine the effect of fasting. The diagnosis of schizophrenia was based on DSM-III-R criteria. Nine of the 13 fasting patients were taking antipsychotic medication at the time blood was taken and four were drug free. Six of the eight nonfasting patients were on medication.
Amino-Acid Determinations Plasma amino acids were determined by a modification of the method of Hill et al (1979). Linear standard curves were generated for each amino acid. Glycine and threonine were separated by our modification. A plasma sample was spiked with each amino acid separately and the peak area was compared with the pre-spike area to check quantitation. Bloods of the schizophrenics and controls were drawn at the same time and were centrifuged within 1 hr of drawing. The plasma was stored at - 2 0 ° for up to 2 years before analysis. Because of the protracted storage period, and because it is well known that plasma peptides have a certain instability, it must be acknowledged that there might be some slippage in the data. However, plasma from subjects and from controls was drawn at the same time, and any possible shift could be presumed to he shared by both. Conversion of glutamine to glutamate during storage prevented us from reporting the concentrations of these amino acids separately. Plasma (100 Ixl) plus 0.25 I~mol fluorophenylalanine (25 ttl, internal standard) (Aldrich, Milwaukee) were treated with methanol (2.0 ml), and the protein precipitate was pelleted by centrifugation (1000 x g, 10 rain). An aliquot of the supernatant (500 Ixl) was diluted 1:1 with 0.5 M potassium borate, pH 10.5, and loaded into a Gilson auto injector. One minute before injection, the sample was mixed with 250 ttl of derivatizing solution containing 2.5 mg o-phthaldehyde (Pierce Chemical Co., Chicago), 0.05 M potassium borate, pH 10.5 (added as 25 Ixl aqueous 0.5 M potassium borate), and 2.5 M mercaptoethanol in methanol. A 20-ttl aliquot was injected automatically onto a 5 ttm C18 column and eluted with a linear gradient over 25 rain from 100% solvent A (91% 35 mM sodium acetate, pH 6.5, 5% methanol, 4% tetrahydrofuran, by volume) to 100% solvent B (40% 35 mM sodium acetate, pH 6.5, 60% methanol, by volume) using a Waters gradient HPLC system (Model 720 Controller with one Model 6000A pump and one Model M-45 pump, a Model U6K injector and a Model 420 fluorescence detector with a 340 nm excitation filter, and a 425 nm emission filter). This method yields plasma amino acid concentrations comparable to those produced by the classical amino acid analyzer, albeit, in general, slightly lower (Furst et al 1990).
Plasma Serine in Schizophrenia
nlOL PSYCHL~TRY 1992;31:1130-1135
1133
Table 2. Plasma Amino Acid Concentrations (t~mol/L) of Patients and Controls Schizophrenics Nonfasting ALA ARG ASN ASP GLU + GLN GLY HIS ISL LEU LYS MET ORN PIlE SER TAU THR TRP TYR VAL
367.7 62.1 50.9 4.5 626.4 171.9 72.5 82.0 113.3 139.3 17.0 112.0 51.1 101.8 67.8 179.3 70.5 63.5 285.5
_ 96.5 .4- 14.6 ± 18.6 ± 3.6 ± 172.3 ± 42.4 ± 10.0 _ 20.5 ± 20.0 ± 50.2 ± 10.6 ± 49.1 ± 8.1 ± 31.6 _ 17.2 _ 41.9 ± 20.6 ± 21.3 ± 58.5
Fasting 333.4 63.8 49.6 7.3 623.2 215.7 73.~: 79.0 119.6 144.1 13.4 87.1 54.3 109.1 81.6 178.9 91.2 60.9 252.2
_ _ ± ± + ± ± ± _ ± ± ± _ ± ± ± ± -+
71.0 17.5 17.4 7.6 158.1 39.1 11.5 13.7 14.7 22.3 5.7 38.6 4.1 29.8 26.4 34.1 12.3 9.9 17.6
Controls 370.8 52.9 47.3 4.3 598.9 193.1 63.0 90.0 126.3 120.4 12.6 105.8 52.7 107.5 61.4 177.2 76.5 55.7 276.4
__. 83.0 ± 16.1 ± 17.6 ± 3.0 ± 161.7 ± 39.9 ± 13.0 ± 16.5 ± 24.7 ± 33.5 ± 8.0 ± 25.0 ± 8.4 ± 27.9 ± 20.6 ± 33.7 ± 26.6 ± 15.8 _ 51.6
P 0.497 0.244 0.899 0.337 0.839 0.079 0.078 0.274 0.394 0.243 0.491 0.303 0.623 0.866 0.097 0.990 0.230 0.531 0.230
Concentrations are expressed as means __ SD. No significant differences were found atp < 0.05 using ~ one-way ANOVA.
Statistics Plasma amino acid concentrations from controls and fasting and nonfasting schizophrenics separately were comp~ued using a one-way analysis of variance at the 95% confidence level.
Results Using methanol to extract plasma amino acids followed by derivatization with a fluorochrome and separation by HPLC [a completely different method for the analysis of plasma amino acids than used by Waziri et al (1983, 1984, 1985, 1986), Perry and Hansen (1985) or Macciardi et al (1990)], we found no difference in the plasma serine concentrations between schizophrenics and controls (Table 2). Though there were no significant differences in any plasma amino acid concentrations between either the patient and control groups or between the patient fasting and nonfasting groups, the basic amino acids, histidine, lysine, and arginine tended to be higher in the schizophrenics. Discussion Perry and Hansen (1985) were unable to show a difference in plasma serine concentrations between schizophrenics and controls using sulfosalicylic acid to precipitate the plasma proteins followed by classical al~no acid analysis on a mixed ion exchange resin with post-column derivatization with ninhydrin for quantitation. Waziri and Mott (1986) con-
1134
BIOL PSYCHIATRY 1992;31:1130-1135
G.F. Carl et al
firmed that they found no difference in plasma serine concentration between their psychotics and nonpsychotics using the method of Perry and Hansen nor could they find a difference in plasma serine concentrations between these populations if they use~ sulfosalicylic acid to precipitate the plasma proteins followed by analysis using gas chromatography (their standard method). They blamed their failure to see a difference in plasma serine levels on the use of sulfosalicylic acid to precipitate proteins. However, Macciardi et al (1990) later, but apparently independently, using the same method as Perry and Hansen (1985), did show a significant difference in plasma serine concentration between schizophrenics and controls. In the present study we used neither sulfosalicylic acid nor the trichloroacetic acid used routinely by Waziri's group. Instead, we used 20 volumes of methanol to precipitate the protein. Like Waziri's group, we derivatized the amino acids prior to separation, but, unlike the other groups, we separated the amino acid derivatives by HPLC using a reverse phase column. We detected and quantitated the amino acids using fluorescence. Using this totally different method, we found no difference in plasma serine levels between the hospitalized schizophrenic population and hospital workers matched for age, race and gender. Our data agree with that of Perry and Hansen (1985) that no difference in plasma serine concentration exists between schizophrenics and controls. We, like Perry and Hansen and Macciardi et al (1990), used only schizophrenics to make our comparisons, whereas Waziri et al (1983, 1984, 1985, 1986) used psychotic patients which in three out of four cases included schizophrenics (1983, 1984, 1986) and in one case (1983) separated schizophrenics out as a separate group showing high plasma serine concentrations. It is l~ssible that differences in the psychiatric populations or diagnostic procedures or possibly even drug treatments are causing the differences between the observations of Waziri and et al and Macciardi et al on one hand and Perry and Hansen and us on the other. The authors are grateful to Drs. Susan Haverstock and Richard Borison for the diagnoses and patient access, to Gale Ganter-Schultz for performing the amino acid analyses, and to Dr. Edward Orr for performing the statistical analyses.
References Baruah S, Waziri R, HegwoodTS, Mallis LM (1991) Plasma serine in schizophrenics and controls measured by gas chromatography-mass spectrometry. Psychiatry Res 37:261-270. Bminvels J, Pepplinkhuizen L (1984) Impaired glycine-serine conversion and increased plasma taurine levels in episodic psychotic patients with psychedelic symptoms. J Psychiatry Res 18:307-318. Fekkes D, Bminvels J (1986) Serine and folate metabolism in fibroblasts from episodic psychotic patients with psychedelic symptoms. Biol Psychiatry 21:951-959. Furst P, Pollack L, GraserTA, Godel H, Stehle P (1990) Appraisal of four pre-column derivatization methods for the high performance liquid chromatographic determination of free amino acids in biological materials. J Chromatog 499:557-569. Hill DW, Waiters FH, Wilson TD, Stuart JD (1979) High performance liquid chromatographic determination of amino acids in the picomole range. Analyt Chem 51:1338-1341. Macciardi F, Lucca A, Catalano M, Marino C, Zanardi R, Smeraldi E (1990) Amino acid patterns in schizophrenia: Some new findings. Psychiatry Res 32'63-70. Perry TL, Hansen S (1985) Interconversion of serine and glycine is normal in psychotic patients. Psychiatry Res 15:109-113.
Plasma Serine in Schizophrenia
BIOL PSYCHIATRY 1992;31:! 130-1135
1135
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