Divide and Conquer: Isolating Negative Symptoms in Schizophrenia
20 March 2013. The debilitating negative symptoms of schizophrenia garner the spotlight in two new studies published online March 6 in JAMA Psychiatry. The first, led by Donald Goff of the Nathan S. Kline Institute for Psychiatric Research in Orangeburg, New York, finds that 16 weeks of taking folate and vitamin B12 supplements can selectively improve negative symptoms, but only among a subset of people with a particular genotypic variant related to folate absorption. The second report, a brain imaging study led by Aristotle Voineskos of the University of Toronto in Canada, finds that people with deficit syndrome, a subtype of schizophrenia characterized by profound negative symptoms, have distinct axon pathway structure that differentiates them from the non-deficit form of schizophrenia.
Focus on the negative
The findings offer hope for understanding the causes of and finding ways to treat negative symptoms, which include social withdrawal, apathy, and reduced emotional expression. Once considered less dire than the hallucinations and delusions of positive symptoms, negative symptoms are now recognized as key barriers to work and independent living. This has renewed interest for finding therapies that can deal with negative symptoms, which are not touched by antipsychotic medication.
“We are just desperate for novel therapies to test,” says William Carpenter of the University of Maryland in Baltimore, who was not involved in either study.
The studies also validate an approach that considers subsets of schizophrenia’s varied symptoms in isolation. Focusing on such subsets could identify subtypes of the disorder, and get cleaner answers to the causes and treatment of schizophrenia than studies that do not take into account this variability. “You really have to deconstruct schizophrenia into its component parts,” Carpenter told SRF.
Carpenter and colleagues originally suggested that negative symptoms were one of these components, and in 2001, Carpenter and colleague Brian Kirkpatrick took this further by proposing that people with high levels of negative symptoms constituted a subtype of schizophrenia, which they termed “deficit syndrome” (Kirkpatrick et al., 2001). People with the deficit subtype of schizophrenia also suffer from hallucinations and delusions, but their negative symptoms are more pronounced than those with non-deficit schizophrenia. Deficit syndrome is estimated to include 15-25 percent of cases of schizophrenia.
As the measurement of negative symptoms becomes more refined (see SRF related news story on a new clinical scale), tracking how negative symptoms interact with the other symptoms could also bring some clarity to drug trials. For example, social withdrawal due to paranoia is quite a different thing than social withdrawal due to a sincere lack of interest in other people. In the first case, the social withdrawal could be ameliorated with antipsychotic drugs, but not in the second case. “These are tangibly different pathologic phenomena,” Carpenter says.
Carpenter’s group has tried to differentiate between negative symptoms that are primary to schizophrenia and those that are secondary to other aspects of schizophrenia (Kirkpatrick et al., 2006). Keeping track of this is crucial to meaningful drug trials, which could conclude whether a drug improved negative symptoms in their own right, or if the improvements were just along for the ride.
Folate is a vitamin that humans need to get from their diet, and it has many brain-related functions, including neural tube formation, neurotransmitter synthesis, DNA replication, and DNA methylation, by which it influences gene expression. Epidemiology has linked famine, and presumably low folate levels in pregnant mothers, to increased risk for schizophrenia in their offspring (see SRF related news story). Adults with schizophrenia exhibit low folate levels in their blood, too, which worsens with negative symptom severity (Goff et al., 2004)—something that suggests adding back folate as a treatment strategy. Though grains have been fortified with folate in the United States since 1998, inefficiencies in how folate is absorbed and used in the body by a cadre of enzymes could leave someone effectively folate deficient. Consistent with this, Goff and colleagues previously found that folate could improve negative symptoms in people with schizophrenia, but only in those carrying a genotype affecting an enzyme involved in folate metabolism, called methylenetetrahydrofolate reductase (MTHFR) (Hill et al., 2011; see SRF related news story and accompanying Q&A with Roffman on folate metabolism and schizophrenia).
In the new study, first author Joshua Roffman and colleagues explored folate’s effects in a larger sample, and considered variants within genes encoding multiple folate-related enzymes: folate hydrolase 1 (FOLH1), methionine synthase (MTR), catechol O-methyltransferase (COMT), and MTHFR. Using a randomized, double-blind, placebo-controlled design, the study tested the effects of daily intake of 2 mg of folic acid and 400 μg of vitamin B12, which enhances folate’s actions. Of the 140 people with schizophrenia enrolled in the trial, 94 were assigned to folate plus vitamin B12 and 46 to placebo; 121 completed the trial.
Sixteen weeks later, negative symptoms had not improved significantly in the folate group as a whole, but there was a significant finding when genotype was taken into account. Among those carrying two copies of the 484T allele in FOLH1, folate reduced negative symptoms compared to placebo by an average of 0.59 points per week on the Scale for the Assessment of Negative Symptoms (SANS). In contrast, no significant difference was found between folate and placebo among 484C allele carriers. For the MTHFR genotype highlighted in their previous study, the difference between folate and placebo missed statistical significance (p = 0.17). The improvements stemmed largely from reductions in alogia, a poverty of speech.
No changes to positive symptoms were detected, which argues that the negative symptom improvement here was not just a byproduct of reducing psychosis. This suggests that modulating the folate pathway may be an inroad to treating negative symptoms themselves—at least in those whose folate metabolism is somehow compromised, or whose diet lacks folate.
Delineating deficit syndrome
The second study addresses negative symptoms through the lens of deficit syndrome, a subtype of schizophrenia marked by profound and stable social withdrawal, apathy, and blunted emotion. Beyond the different symptom profile of deficit syndrome compared to the rest of “non-deficit” schizophrenia, neurodevelopmental, epidemiological, and brain imaging studies have also reported differences (Kirkpatrick et al., 2001).
First author Voineskos and colleagues looked for brain signatures of deficit syndrome with the latest brain imaging techniques, including measurements of cortical thickness and diffusion tensor imaging (DTI) of the axon-containing white matter tracts. The researchers scanned 77 people with schizophrenia, 18 of whom met the deficit criteria, and 79 healthy controls. In one analysis—a careful comparison of regions previously implicated in schizophrenia—18 deficit cases were individually matched with 18 non-deficit cases for medication history, age of onset, illness duration, and age. The deficit cases had disrupted white matter structures in three fiber tracts that connect brain regions involved in emotional and social function: the right inferior longitudinal fasciculus, the right arcuate fasciculus, and the left uncinate fasciculus.
This disruption emerged in the larger, unmatched sample, too, with the same tract abnormalities detected in the 18 deficit cases versus the 59 non-deficit cases and 79 healthy controls. Positive symptom scores did not differ between the deficit and non-deficit groups, which suggests that the tract irregularities were linked specifically to negative symptoms. In contrast, the researchers found a similar pattern of reduced cortical thickness in deficit and non-deficit cases relative to controls. This casts cortical thinning as a generic feature of schizophrenia (see SRF overview story on cortical thinning).
The differences found in the brains of people with deficit syndrome bolster the idea that deficit syndrome is a distinct subtype of schizophrenia, and suggest that future studies would do well to keep track of the symptom profiles of study participants. Not only might it help clarify results, but it may also eventually help target brain regions that are crucial for real-world function.—Michele Solis.
Roffman JL, Lamberti JS, Achtyes E, Macklin EA, Galendez GC, Raeke LH, Silverstein NJ, Smoller JW, Hill M, Goff DC. Randomized Multicenter Investigation of Folate Plus Vitamin B12 Supplementation in Schizophrenia. JAMA Psychiatry. 2013 Mar 6:1-9. Abstract
Voineskos AN, Foussias G, Lerch J, Felsky D, Remington G, Rajji TK, Lobaugh N, Pollock BG, Mulsant BH. Neuroimaging Evidence for the Deficit Subtype of Schizophrenia. JAMA Psychiatry. 2013 Mar 6:1-9. Abstract
Comments on Related News
Related News: MTHFR, COMT Genes Work Together to Bring Down Cortical Activation in SchizophreniaComment by: Jennifer Barnett
Submitted 19 December 2008
Posted 19 December 2008
The recent studies of Prata and colleagues and Roffman and colleagues shed considerable further light on the ongoing mysteries of the catechol-O-methyltransferase Val158Met polymorphism and its effects on the proposed “inverted-U” shape of cortical dopamine function. Both study teams should be congratulated on these high-quality studies using what are, for neuroimaging experiments, impressive numbers of both patients and controls.
Our understanding of the effects of the COMT Val/Met polymorphism in humans remains incomplete despite no shortage of elegant studies and intriguing results. In their landmark 2001 paper, Egan and colleagues reported that Val carriers showed poorer cognitive function, a higher risk for schizophrenia, and reduced prefrontal efficiency when compared with Met carriers. These associations, along with a multitude of other psychological and psychiatric phenotypes, have since been tested in labs across the world. Meta-analyses of the available data have concluded that there is little influence of the Val/Met polymorphism on risk for schizophrenia (Allen et al., 2008; Fan et al., 2005; Munafo et al., 2005) or cognitive function (Barnett et al., 2008). Perhaps because of the increased cost and difficulty of collecting imaging data compared with cognitive or disease status, rather fewer studies have been published testing the hypothesis that Val/Met affects prefrontal cortical efficiency, but those few (e.g., Ho et al., 2005) do appear consistent with the original report .
Prata et al. (2008) studied the effects of Val/Met on cortical activation during a verbal fluency task and report an interesting, if somewhat unintuitive result: that there are opposite effects of genotype on task performance and cortical activation in patients with schizophrenia, compared with those seen in healthy controls. In patients, Val alleles were associated with poorer task performance, while in controls, there was no significant difference between genotype groups. The trend, however, was for better task performance among Val-carrying controls, and the group x genotype interaction term was significant. These results were interestingly reflected in regional activation patterns, where in the right peri-Sylvian region Val alleles were associated with increased activation in patients, and decreased activation in controls. Further analyses suggested that these group x genotype interactions may partly reflect genetically driven differences in functional connectivity. Explanations for these opposite effects in patients and controls are consistent with an inverted-U shape of dopaminergic function where patients lie on the left-hand side of the U (suboptimal dopamine) and controls lie somewhat to the right of the center, such that increased cortical dopamine (as experienced by Met carriers) is slightly disadvantageous. Interestingly, we found the same pattern when comparing the effect of Val/Met genotype on N-back performance in patients and controls (Barnett et al., 2008); it is good to see these non-linear behavioral results supported by structural and functional imaging data.
The Val/Met polymorphism is certainly not the only determinant of COMT function, and we now know that other SNPs within the gene greatly affect the amount of COMT expressed (Nackley et al., 2006). Moreover, in affecting cortical dopamine and norepinephrine, COMT does not operate alone. Roffman and colleagues’ study (Roffman et al., 2008) very nicely demonstrates how much we have still to learn about potential gene-gene interaction (epistatic) effects. They studied brain activation during a working memory task and analyzed the combined effects of Val/Met and a functional polymorphism in MTHFR, a gene with plausible biological interactions with COMT. In this study, COMT genotype alone did not predict variation in activation in dorsolateral prefrontal cortex. There was a three-way interaction, however, between COMT and MTHFR genotypes and diagnostic group, such that MTHFR genotype appeared to modulate prefrontal activation most in Val/Val patients (who would be expected to have the lowest prefrontal dopamine), and among Met/Met controls (who would be expected to have the highest prefrontal dopamine, potentially putting them beyond the optimal level in the inverted-U model).
Despite considerable interest in gene-gene and gene-environment interactions among schizophrenia researchers, replications of such interactions have been relatively few and far between. While it is notoriously difficult to demonstrate biological interaction from statistical data alone, Roffman’s study provides us with hope that a really good hypothesis may still give us reason to try and do so.
Allen NC, Bagade S, McQueen MB, Ioannidis JP, Kavvoura FK, Khoury MJ, Tanzi RE, Bertram L. Systematic meta-analyses and field synopsis of genetic association studies in schizophrenia: the SzGene database. Nat Genet. 2008 Jul 1;40(7):827-34. Abstract
Barnett JH, Scoriels L, Munafò MR. Meta-analysis of the cognitive effects of the catechol-O-methyltransferase gene Val158/108Met polymorphism. Biol Psychiatry. 2008 Jul 15;64(2):137-44. Abstract
Fan JB, Zhang CS, Gu NF, Li XW, Sun WW, Wang HY, Feng GY, St Clair D, He L. Catechol-O-methyltransferase gene Val/Met functional polymorphism and risk of schizophrenia: a large-scale association study plus meta-analysis. Biol Psychiatry. 2005 Jan 15;57(2):139-44. Abstract
Ho BC, Wassink TH, O'Leary DS, Sheffield VC, Andreasen NC. Catechol-O-methyl transferase Val158Met gene polymorphism in schizophrenia: working memory, frontal lobe MRI morphology and frontal cerebral blood flow. Mol Psychiatry. 2005 Mar 1;10(3):229, 287-98. Abstract
Munafò MR, Bowes L, Clark TG, Flint J. Lack of association of the COMT (Val158/108 Met) gene and schizophrenia: a meta-analysis of case-control studies. Mol Psychiatry. 2005 Aug 1;10(8):765-70. Abstract
Nackley AG, Shabalina SA, Tchivileva IE, Satterfield K, Korchynskyi O, Makarov SS, Maixner W, Diatchenko L. Human catechol-O-methyltransferase haplotypes modulate protein expression by altering mRNA secondary structure. Science. 2006 Dec 22;314(5807):1930-3. Abstract
Prata DP, Mechelli A, Fu CH, Picchioni M, Kane F, Kalidindi S, McDonald C, Howes O, Kravariti E, Demjaha A, Toulopoulou T, Diforti M, Murray RM, Collier DA, McGuire PK. Opposite Effects of Catechol-O-Methyltransferase Val158Met on Cortical Function in Healthy Subjects and Patients with Schizophrenia. Biol Psychiatry. 2008 Dec 1; Abstract
Roffman JL, Gollub RL, Calhoun VD, Wassink TH, Weiss AP, Ho BC, White T, Clark VP, Fries J, Andreasen NC, Goff DC, Manoach DS. MTHFR 677C --> T genotype disrupts prefrontal function in schizophrenia through an interaction with COMT 158Val --> Met. Proc Natl Acad Sci U S A. 2008 Nov 11;105(45):17573-8. Abstract
View all comments by Jennifer Barnett
Related News: MTHFR, COMT Genes Work Together to Bring Down Cortical Activation in Schizophrenia
Comment by: S.H. Lin
Submitted 15 January 2009
Posted 19 January 2009
I recommend the Primary Papers
The “inverted-U” shape of cortical dopamine function with regard to the COMT Val158Met polymorphism is an interesting issue worthy of discussion. The COMT enzyme may modulate the balance of tonic and phasic dopamine function depending on the area-specific neurochemical environment (Bilder et al., 2004). There is thought to be a complex nonlinear relationship between dopamine availability and brain function (Williams et al., 2007).
Our study (Liao et al., 2008) examined the relationships of three COMT SNPs—rs737865 in intro 1, rs4680 in exon 4 (Val158Met), and downstream rs165599—to schizophrenia and its related deficits in neurocognitive function in families of patients with schizophrenia in Taiwan. The study results indicated that the Val allele was associated with better performance on the WCST (i.e., greater Categories Achieved and Conceptual Level Response and fewer Perseverative Errors) or CPT (i.e., greater d'), which might be explained by an “inverted U” shaped relationship between dopamine levels and prefrontal cortex function (Cools and Robbins 2004; Mattay et al., 2003). This model reveals that an optimal functioning occurs within a narrow range of dopamine level, and both excessive and insufficient dopamine levels impair working memory performance. Our results indicate that the genetic variants in COMT might be involved in modulation of neurocognitive functions, hence conferring increased risk to schizophrenia.
Bilder, R.M., Volavka, J., Lachman, H.M. & Grace, A.A. (2004) The catechol-O-methyltransferase polymorphism: relations to the tonic-phasic dopamine hypothesis and neuropsychiatric pheno-types. Neuropsychopharmacology 29, 1943–1961. Abstract
Cools, R. and Robbins, T.W. (2004) Chemistry of the adaptive mind. Philos Transact A Math Phys Eng Sci 362, 2871–2888. Abstract
Liao S.Y., Lin S.H., Liu C.M., Hsieh M.H., Hwang T.J., Liu S.K., Guo S.C., Hwu, H.G., Chen W.J. (2008): Genetic variants in COMT and neurocognitive impairment in families of patients with schizophrenia. Genes, Brain and Behavior. Abstract
Mattay, V.S., Goldberg, T.E., Fera, F., Hariri, A.R., Tessitore, A., Egan, M.F., Kolachana, B., Callicott, J.H. and Weinberger, D.R. (2003) Catechol O-methyltransferase val158-met genotype and individual variation in the brain response to amphetamine. Proc Natl Acad Sci USA 100, 6186–6191. Abstract
Williams, H.J., Owen, M.J. and O‘Donovan, M.C. (2007) Is COMT a susceptibility gene for schizophrenia? Schizophr Bull 33, 635–641. Abstract
View all comments by S.H. Lin
Related News: Interpret With Care: Cortical Thinning in Schizophrenia
Comment by: Cynthia Shannon Weickert, SRF Advisor
Submitted 4 January 2012
Posted 4 January 2012
Thanks for your thought-provoking review of structural MRI changes in schizophrenia. I had a couple of quick comments.
You make the statement that, "Though cortical thickness itself is below the resolution of typical MRI, image analysis algorithms can now infer thickness across the entire cortical sheet as it winds its way throughout the brain." I thought sMRI gathers information for about 2 mm cubed or so. So maybe the point to make is that cortex thickness is not below the resolution, but the putative change in thickness is below the resolution. It would be interesting to know if the putative change in cortical thickness in schizophrenia could be better viewed with 3T or 7T scanners.
Also, I wonder how to interpret decreases in volume over five years that seem to be as much as 5 percent in some areas. How long could this continue to be progressive at this rate, and what would be the final cortical volume expected in the final decade of life? For example, if the DLPFC BA46 is about 3,500 microns thick, then a 5 percent loss/five years over 20 years would leave you with about 2,850 microns, and that would be about a 20 percent decrease in thickness. While postmortem studies may be limited, as Karoly points out, certainly we know that the frontal cortex is still "plump enough" to define cyto-architecturally, and to examine at the histological level. We also consider that there is about a 10 percent loss in cortical thickness in people with schizophrenia. Certainly, the cortex does not degenerate completely as would be expected with relentless progression of loss and accumulated deterioration of cortical grey matter over time.
Thus, this is an interesting issue, but many questions remain. Is there a lot of case-to-case variability that underlies these averages such that some cases lose more cortical volume and some do not lose any at all? Could it be that, while there is cortical volume loss, there are some patients in whom this loss slows or even reverses naturally over the course of the disease? What is the physical substrate of such cortical volume loss in people with schizophrenia? Can we prevent cortical volume loss over time, and would this be beneficial to patient outcomes?
View all comments by Cynthia Shannon Weickert