Reduced anterior cingulate glutamate of comorbid skin-picking disorder in adults with obsessive-compulsive disorder

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Reduced anterior cingulate glutamate of comorbid skin-picking disorder in adults with obsessive-compulsive disorder Huirong Zheng , Wanqun Yang , Bin Zhang , Guanmin Hua , Shibin Wang , Fujun Jia , Guangquan Guo , Wenjing Wang , Dongming Quan PII: DOI: Reference:

S0165-0327(19)32989-1 https://doi.org/10.1016/j.jad.2020.01.059 JAD 11508

To appear in:

Journal of Affective Disorders

Received date: Revised date: Accepted date:

29 October 2019 8 January 2020 14 January 2020

Please cite this article as: Huirong Zheng , Wanqun Yang , Bin Zhang , Guanmin Hua , Shibin Wang , Fujun Jia , Guangquan Guo , Wenjing Wang , Dongming Quan , Reduced anterior cingulate glutamate of comorbid skin-picking disorder in adults with obsessive-compulsive disorder, Journal of Affective Disorders (2020), doi: https://doi.org/10.1016/j.jad.2020.01.059

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier B.V.

Highlights 

1H MRS glutamate in pACC is elevated in adult OCD with comorbid SPD



Results give some evidence that alterations of the glutamatergic system may play an important role in the pathophysiology of a subgroup of comorbid SPD in OCD.



The interaction we observed with skin picking symptoms in OCD may provide an additional explanation for some of the inconsistencies in the previous literature on ACC Glx

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This is the first single-voxel acquisition MRS study on pACC glutamate dysregulation related to SPD

Reduced anterior cingulate glutamate of comorbid skin-picking disorder in adults with obsessive-compulsive disorder Huirong Zheng, MD, PhD a 1*; Wanqun Yang, MD, PhDb 1, Bin Zhang, MD, PhDc d; Guanmin Hua, MDe; Shibin Wang, MD, PhDa ; Fujun Jia, MD, PhDa; Guangquan Guo, MDa; Wenjing Wang MD, PhDa; Dongming Quan, MDa a

Guangdong Mental Health Center, Guangdong Provincial People's Hospital,

Guangdong Academy of Medical Sciences, Affliated School of Medicine of South China University of Technology, Guangzhou, China b

Department of Radiology, Guangdong Provincial People's Hospital, Guangdong

Academy of Medical Sciences, Guangzhou, China c

Department of Psychiatry, Nanfang Hospital, Southern Medical University,

Guangzhou, China d

Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and

Brain-Inspired Intelligence, Guangzhou, China e

Guangzhou Yuexiu District Hospital of Traditional Chinese Medicine, Guangzhou, China

*

Corresponding authors. Huirong Zheng is to be contacted at Guangdong Mental

Health Center, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Affliated School of Medicine of South China University of Technology, No. 123 Huifu Xi Road, Guangzhou 510080, China E-mail address: [email protected] 1

These authors had equal contribution to this paper.

Word count: main body of text, 2857; abstract, 247

Abstract Background: Obsessive Compulsive Disorder (OCD) is characterized by hyperactivity in a network of forebrain structures, including the anterior cingulate cortex (ACC). Convergent evidence suggests that glutamatergic dysfunction may contribute to the disorder. Skin picking disorder (SPD) was listed as one of the obsessive-compulsive and related disorders, which is often comorbid with OCD and share overlapping phenomenology and pathophysiology. However, potential

confounding effects between the two diagnostic effects on neurotransmitter levels remain largely unexamined. Methods: We examined pregenual anterior cingulate cortex (pACC) glutamate and other neurochemicals in 62 subjects using a single-voxel acquisition 1H MRS at 3Tesla; of these, 47 subjects yielded usable measurements of both glutamate and glutamine and were included in the analysis (17 medicated with OCD alone, 13 medicated with comorbid OCD+SPD, 17 healthy control). Results: OCD with comorbid SPD showed significantly lower pACC glutamate than in patients without SPD (p=0.001) or control subjects (p=0.035). OCD without SPD subjects showed pACC glutamate levels indistinguishable from controls (p=0.501). In the OCD with SPD subjects, glutamate was correlated with Y-BOCS total score in female patients (n=9, r=0.69, p=0.041). Limitations: The main limitation of the study was the cross-sectional data. Our patients were on SSRI medication which may have modified the eff ect of SPD and OCD interaction on glutamate activity. Conclusion: Our results suggest that alterations of the glutamatergic system may play an important role in the pathophysiology of a subgroup of OCD and reduced pACC glutamate may be a biomarker of a distinct subset of OCD patients. Key words obsessive-compulsive disorder; skin-picking disorder; comorbidity; glutamate; MRS; cerebral metabolism changes

Introduction Obsessive-compulsive disorder (OCD) is a psychiatric disorder often characterized by incontrollable thoughts (obsessions) and the urge to engage in repetitive time-consuming behaviors (compulsions) that affects 2-2.5% of the population worldwide (Kessler, Berglund et al. 2005, Ruscio, Stein et al. 2010). Serotonergic antidepressants are the mainstay of the pharmacological treatment of OCD (Koran, Hanna et al. 2007, Soomro, Altman et al. 2008). Both pharmacological and psychotherapeutic treatments are of benefits to many patients; but more than a quarter prove refractory to current treatments, especially in comorbid body-focused repetitive

behaviors (Grant, Mancebo et al. 2015). Furthermore, remission is rare, and many „responders‟ continue to endure significant symptoms and suffering (Fireman, Koran et al. 2001, Koran, Hanna et al. 2007). New pathophysiological insights that may lead to novel treatments are urgently needed. The

anterior

cingulate

cortex

(ACC)

is

a

key

component

of

the

cortical-striatal-thalamic-cortical (CSTC) brain circuitry, and its dysfunction thought to be a pathophysiological feature of OCD (Saxena and Rauch 2000). There is broad consensus that the disorder is associated with relative hypermetabolism within a network of structures in the forebrain and basal ganglia (Burguiere, Monteiro et al. 2015). Functional imaging studies have described abnormalities in the ACC, the caudate nucleus, the anterior thalamus and the orbitofrontal cortex that are often found to correlate with symptom severity; and to resolve with treatment(Maia, Cooney et al. 2008, Menzies, Chamberlain et al. 2008). Magnetic resonance spectroscopy (MRS) provides a noninvasive method to characterize the molecular biochemistry that may contribute to the neurochemical state of OCD. Several studies have reported such as reduced NAA levels in mPFC/ACC (Jang, Kwon et al. 2006, Yücel, Wood et al. 2008, Gnanavel, Sharan et al. 2014) and increased Cho levels in the thalamus (Mohamed, Smith et al. 2007), albeit with some inconsistency (Fan, Tan et al. 2010). More recently, convergent evidence suggests that abnormalities in the excitatory amino acid neurotransmitter glutamate may contribute to OCD, and that glutamate modulators may be of therapeutic utility (Bhattacharyya, Khanna et al. 2009, Pittenger, Bloch et al. 2011, Aida, Yoshida et al. 2015, Pittenger, Bloch et al. 2015). Several Glutamate-related genes have showed tentative associations with OCD (Samuels, Wang et al. 2011, Ortiz, Gasso et al. 2015). The possible contribution of abnormalities in glutamate homeostasis to OCD is therefore an increasingly active area of research. Several studies have reported some efficacy of glutamate-modulating medications in refractory OCD subjects (Pittenger 2015, Emamzadehfard, Kamaloo et al. 2016, Hage, Banaschewski et al. 2016, Paydary, Akamaloo et al. 2016). MRS measurements in specific brain regions support the hypothesis of glutamate abnormalities in OCD, but the results of these studies have not been consistent.(Yücel, Wood et al. 2008, Brennan, Tkachenko et al. 2015, Simpson, Kegeles et al. 2015).

Most MRS studies of OCD have been unable to quantify glutamate separately from glutamine. Instead, the reports focused on a composite measure, Glx, that includes both glutamate and glutamine rather than glutamate or glutamine levels (Simpson, Shungu et al. 2012, Gnanavel, Sharan et al. 2014). In the ACC, published results have been mixed. An early study reported a reduction in ACC Glx in pediatric OCD patients (Rosenberg, Mirza et al. 2004). A similar abnormality was reported in female adults with OCD in one study (Yücel, Wood et al. 2008); However, subsequent studies in adults have been more ambiguous, reporting no between-group difference in ACC Glx in some cases (Starck, Ljungberg et al. 2008, Bedard and Chantal 2011, Brennan, Tkachenko et al. 2015). Recently, another study in adults indicated elevated Glx in adult OCD (O'Neill, Lai et al. 2016). Currently, the results from MRS investigations on the ACC of OCD patients have heterogenic findings of either elevated, normal, or reduced glutamatergic compounds. It is necessary to perform more detailed investigations to understand the heterogeneity of glutamatergic dysfunction in OCD. One added complication of the existing MRS discordance is the potential for interaction with comorbid conditions. Skin-picking disorder (SPD) also known as neurotic excoriation is described as recurrent picking of skin leading to skin lesions and significant distress or functional impairment. SPD was recently listed as one of the obsessive-compulsive and related disorders since skin picking symptoms are frequently present in patients with OCD and share overlapping phenomenology, pathophysiology, and possible genetic underpinnings (Bienvenu, Wang et al. 2009, Grant, Odlaug et al. 2010, Oliveirra, Fitzpatrick et al. 2019). Elevated rates of skin picking have also been reported in OCD patients and their first-degree relatives (Cullen, Samuels et al. 2001). Based on earlier studies, approximately 16.3%-45.2% of OCD cases were accompanied by SPD (Calikusu, Yucel et al. 2003, Lovato, Ferrao et al. 2012). Although neuroimaging studies of SPD are sparse to date, a functional magnetic resonance imaging (fMRI) study has reported functionally lower activation of ACC in patients with SPD (Odlaug, Hampshire et al. 2016), which is dissimilar from the previous report of remarkable hyperactivity at rest in adults with OCD (Maia, Cooney et al. 2008). Interactive effects of OCD and SPD on MRS study on ACC are likely. It

has become increasingly clear that such comorbid symptomatology must be taken into account in analyzing MRS data. Therefore, we aim to clarify some of the ambiguities in MRS studies of OCD by using a 3-Tesla system with an echo time of 35ms to isolate the glutamate signal more clearly from the contributions of glutamine and macromolecules, in OCD patients with and without comorbid SPD.

Materials and Methods Subjects This study was carried out under guidelines established by the Guangdong Provincial People‟s Hospital Institutional Review Board. Written informed consent was obtained from all subjects after study procedures were fully explained. A total of 62 subjects were scanned; of these, 47 subjects yielded usable measurements of both glutamate and glutamine and were included in the analysis (17 with OCD alone, 13 with comorbid OCD+SPD, 17 age-and-gender matched healthy control). Women and men based on DSM-5 criteria were recruited by media advertisements and referrals. A board-certified psychiatrist with expertise in SPD and body-focused repetitive behaviors conducted a structured clinical interview with each participant to confirm the diagnosis. Clinical symptomatology was rated using the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), Hamilton Depressive Rating Scale (HAMD), Hamilton Anxiety Scale (HAMA) and the Yale-Brown Obsessive Compulsive Scale modified for Neurotic Excoriation (NE-YBOCS). Subjects were between 18 and 45 years of age. All patients were on a stable SSRI medication regimen (for 8 weeks or more). To be enrolled in the study, subjects with OCD alone had to have a Y-BOCS score＞16. Subjects with comorbid OCD+SPD had to meet full DSM-5 criteria for both disorders and have both Y-BOCS＞16 and NE-YBOCS＞16. Subjects with other concurrent Axis I diagnoses, including depression, bipolar disorder, psychotic disorders, substance abuse, or comorbid medical conditions affecting brain function (i.e., history of seizure disorder, pregnancy, etc.) were excluded. Participants were recruited from December 2016 through November 2018 at the Guangdong Provincial People‟s Hospital. Demographic information and clinical data are given in Table 1.

MRS Data Acquisition and Quantitation Protocol All participants underwent whole-brain MRI and localized MRS using a 3-Tesla (3T) Philips Ingenia （ Digital Network Architecture MRI ） system equipped with a 16-channel head coil. Structural MRI was acquired with an axia loblique (genu-splenium parallel) magnetization-prepared rapid gradient-echo (MPRAGE) pulse-sequence. This MPRAGE and “coronal” and “sagittal” resliced copies were used to prescribe MRS. A neuroradiologist reviewed MRIs to exclude subjects with clinical abnormalities. Single-voxel water-suppressed stimulated echo acquisition mode (STEAM) MRS (TR/TE=2000/35 ms, 128 Number of excitation ) was acquired from ACC site. A voxel measuring 3×2.5×3cm was placed midline in the pregenual anterior cingulate cortex (pACC, BA32), as in Fig. 1A. Voxel size was selected to maximize the ACC volume being sampled and thus maximize signal to noise ratio, without including a large volume of surrounding structures. Each MRS voxel was shimmed locally with pencil beam shimming. MR spectra were fit with LCModel yielding levels of glutamate (Glu), glutamine (Gln),

and

the

other

proton

neurometabolites

N-acetyl-aspartate+

N-acetyl-aspartyl-glutamate(tNAA),creatine+phosphocreatine(Cr), choline-containing compounds (Cho) and myo-inositol (mI); all referenced to unsuppressed water (Fig. 1B) and expressed in Institutional Units (IU). Spectra were analyzed with LC model using a basis set derived from scans of metabolite solutions using the same acquisition sequence. The basis set included aspartate, creatine, Glu, Gln, mI, choline, phosphorylcholine, phosphocreatine, glycerophosphorylcholine, N-acetylaspartate, and phosphocreatine. Values for each of the individual neurometabolite signals were rejected if the Cramer-Rao Lower Bound of the spectral fit exceeded 20%, except Gln (rejected if the Cramer-Rao Lower Bound of the spectral fit exceeded 50%). Spectra with obvious artifact or poor quality (linewidth＞0.1 ppm, signal-to-noise＜4) were aslo rejected. Statistical Methods

All statistical analyses were performed using IBM SPSS Statistics 21 (CITE). Data analyses were conducted on six dependent measures: Glu, Gln, mI, Cho, Cr, and tNAA. The data were first screened for distributional properties, outliers, and missing values. No variables were rejected by this process. The data are expressed as mean± SD. The primary tests between group analyses (OCD, OCD+SPD, and controls) were conducted through ANOVA or Chi-square tests. Results were considered statistically significant different when P<0.05. Post-hoc tests were done using the Bonferroni correction. The secondary analyses between groups (OCD, OCD+SPD) or within group (male, female) were conducted through independent T-test or Mann-Whitney U test. In an exploratory analysis, measured glutamate and other metabolites were correlated with clinical ratings using Spearman correlation.

Results Demographic and clinical characteristics of all OCD patients and controls Table 1 presents the demographic and clinical characteristics of all three groups (age range 18-42 years; median age 27 years; 25 females). The three groups did not differ significantly in age, education, or male-female ratio. There were no significant differences between the two patient groups on total YBOCS score and presence of obsessive or compulsive symptoms. However, OCD with SPD subjects showed greater anxiety symptom (HAMA scores) than OCD subjects without SPD（t(28)=-3.59, p =0.001, table 1). Also OCD with SPD group showed significant HAMA difference in female patients comparable to OCD without SPD subjects (t(14)=-2.79, p=0.02, table 1). No other two group comparisons were significant. ACC glutamate and glutamine in OCD patients and those with comorbid SPD compared to controls. In a three-group analysis (N = 47), ANOVA revealed a significant difference in glutamate levels between OCD, OCD with SPD, and controlled subjects (F (2, 44) = 7.858, p =0 .001, see table 2). In post hoc test, a significant difference was found between OCD and OCD with SPD. OCD with SPD subjects had significantly lower glutamate levels than OCD group (p=0.001, Bonferroni). Compared with the controlled group, the OCD with SPD group also showed lower glutamate levels

(p=0.035, Bonferroni). There was no significant difference between OCD patients with or without SPD in ACC glutamine (F (2, 44) = 0.834, p= 0.441), or in glutamate +glutamine (F(2, 44) = 1.799, p = 0.177). Other metabolites in OCD patients and those with comorbid SPD compared to controls. In an ANOVA analysis, we examined other major metabolites measured in ACC by MRS: Cho, mI, Cr and tNAA (see Table 2). A nominally significant difference was found between OCD patients, with comorbid SPD patients and controlled subjects in ACC tNAA (F(2, 44)=3.773, p = 0.031). However, there was no significant difference between OCD patients with or without SPD in ACC tNAA (p=0.062). There were also no significant difference between OCD patients, with comorbid SPD patients and controlled subjects in ACC Cho, mI, and Cr. In OCD without SPD subjects, female patients had significantly lower Cr levels than OCD male subjects (Mann-Whitney U test =9.0, p=0.01). Associations between glutamate and glutamine levels and clinical measures in OCD patients and those with comorbid SPD To further investigate the relationship between ACC glutamate and clinical measures in both OCD groups, we performed a series of correlation analyses. In all OCD and comorbid SPD patients, ACC glutamate was negatively correlated with clinical measures of anxiety severity (n=30, r=-0.55, p=0.002). In the OCD without SPD group, no significant association was found between glutamate and Y-BOCS total score, YBOCS obsessions, YBOCS compulsions, HAMA, or HAMD scores. In the OCD with comorbid SPD group, glutamate was correlated with Y-BOCS total score in female patients (n=9, r=0.69, p=0.041). There were no other correlations in the OCD with SPD group between glutamate level and any of the other clinical measures.

Discussion Glutamatergic homeostasis and glutamate dysregulation contribute to OCD has garnered increasing attention in recent years (Ting and Feng 2008, Gnanavel, Sharan et al. 2014). We used 1H MRS to measure glutamate, glutamine, and other neurochemicals in the ACC, a brain region that exhibits abnormal metabolism

(Pittenger, Bloch et al. 2011, Simpson, Shungu et al. 2012) in patients with OCD. We found reduced pACC glutamate only in OCD patients with comorbid SPD. Correlation analysis suggested that glutamate levels were negatively correlated with anxiety, which is the predictor of pACC glutamate. A prior study has suggested that subclinical anxiety was closely related to brain metabolite ratios of OCD. It should be considered in assessing brain metabolite concentrations and may be central to the comprehension of OCD (Bedard and Chantal 2011). In addition, a correlation with Y-BOCS was found in the female OCD with SPD patients that consistent with a gender-specific association described in an earlier study examining ACC Glx in patients with OCD (Yücel, Wood et al. 2008). Gender-related differences in obsessive-compulsive symptoms and comorbid skin picking symptoms may be a gender-related reflection of the expression of the OCD phenotype (Torresan, Ramos-Cerqueira et al. 2009, Lovato, Ferrao et al. 2012).

Previous MRS investigations of ACC Glx in OCD have produced inconsistent results (Starck, Ljungberg et al. 2008, Bedard and Chantal 2011, O'Neill, Lai et al. 2016). There are several explanations that might be contributing to these discrepancies. Previously published studies of OCD have reported Glx rather than isolating glutamate (Ortiz, Ortiz et al. 2015, O'Neill, Lai et al. 2016); the fact that we find a statistically significant effect of diagnostic group on glutamate but not significant effect on combined glutamate+glutamine suggests that isolated glutamate may provide greater sensitivity to identify the underlying neurochemical abnormalities. Also conflicting results are possibly influenced by demographics (pediatric vs adult); pediatric OCD patients may differ from adults with respect to their ACC Glx (Rosenberg, Mirza et al. 2004). Finally, it may be necessary to account for comorbid conditions in such analyses in order to identify the maximum sensitivity between subgroups in glutamate.

Our failure to find abnormal Glu in pACC in OCD without SPD is consistent with some of these studies (Starck, Ljungberg et al. 2008, Bedard and Chantal 2011). There

are several possible explanations for the finding of glutamate differences only in patients with comorbid SPD. It is possible that SPD leads to reduced ACC glutamate in this ACC voxel and thus balances an OCD-related elevation in ACC glutamate. Although there is no MRS study of SPD to date, some studies have reported that supplementation of glutamate-modulating medications can improve skin picking symptoms (Deepmala, Slattery et al. 2015, Grant, Chamberlain et al. 2016, Sani, Gualtieri et al. 2019). It is also possible that SPD has no effect on ACC glutamate, but that SPD and OCD interact pathophysiologically in a way that reduces glutamate. It is unclear how such an interaction might occur. Exploration of these two possibilities will require replication of this investigation with the inclusion of an additional group with SPD but without OCD. Finally, it may be that OCD patients with SPD represent a distinct subgroup of OCD that is uniquely associated with low ACC glutamate, in some patients. The interaction we observed with skin picking symptoms in OCD patients may provide an additional explanation for some of the inconsistencies in the previous literature on ACC Glx.

This study has several limitations that should be considered. First, this was a cross sectional study, so causal interpretations are inherently limited. Future prospective research is now warranted to elucidate the associations observed in this study. Second, our participants received continuing medications, which might alter brain metabolism (Lissemore, Sookman et al. 2018). However, the effect of this confounding was minimized by ensuring a stable SSRI medication for at least 8 weeks before inclusion. Another limitation is the relatively small sample that also limits the generalizability of the findings. Future studies with larger samples will need to include a SPD alone group would enable eff ects of SPD and OCD interaction to be more clearly separated from those relating to glutamate change. Finally, this study didn‟t perform tissue segmentation (gray-matter, white-matte and CSF content) of the pACC voxels. It might be better to calculate tissue composition in future longitudinal study to separately clarify the difference in gray and white matter between groups.

In summary, our data provide support for the presence of glutamate abnormalities in the pACC of a subgroup of comorbid SPD in OCD. These results require replication and extension. In particular, clarification of the relationship between the effects of OCD and of SPD on ACC glutamate will be an interesting area for future research. The dysregulation of glutamate serves as a potential target for the OCD pharmacotherapy and the detailed mechanisms underlying the glutamate alterations within CSTC circuits merit further investigations from both neuroimaging and genetic studies.

Funding/support This work was supported by the Science and Technology Planning Project from Guangdong Province (2014A020212587), the Science and Technology Special Foundation of Guangdong Provincial People's Hospital (2017), the Natural Science Foundation of Guangdong Province (2018A030313989), and the Science and Technology Program of Guangzhou (201804010331).

Contributors HZ, WY, and BZ designed the study and performed MRS data collection. GH and SW undertook the clinical statistical analyses. FJ, GG, WW and DQ played an important role in the acquisition of clinical data. HZ drafted the manuscript and completed a first version of the article. All authors contributed to manuscript revision, read, and approved the submitted version.

Disclosure/ Conflict of interest All authors report no biomedical financial interests or potential conflicts of interest.

Acknowledgements We extend our sincere thanks to the all subjects who participated in this study. We thank Zhiwei Shen, MD, PhD for optimizing on magnetic resonance data acquisition

and analysis. Great thanks to Rani Angeli T.B. and James Sundquist, PhD, for providing invaluable help in modifying the manuscript.

References Aida, T., J. Yoshida, M. Nomura, A. Tanimura, Y. Iino, M. Soma, N. Bai, Y. Ito, W. Cui, H. Aizawa, M. Yanagisawa, T. Nagai, N. Takata, K. F. Tanaka, R. Takayanagi, M. Kano, M. Gotz, H. Hirase and K. Tanaka (2015). "Astroglial glutamate transporter deficiency increases synaptic excitability and leads to pathological repetitive behaviors in mice." Neuropsychopharmacology 40(7): 1569-1579. Bedard, M. J. and S. Chantal (2011). "Brain magnetic resonance spectroscopy in obsessive-compulsive disorder: the importance of considering subclinical symptoms of anxiety and depression." Psychiatry Res 192(1): 45-54. Bhattacharyya, S., S. Khanna, K. Chakrabarty, A. Mahadevan, R. Christopher and S. Shankar (2009). "Anti-brain autoantibodies and altered excitatory neurotransmitters in obsessive– compulsive disorder." Neuropsychopharmacology 34(12): 2489-2496. Bienvenu, O. J., Y. Wang, Y. Y. Shugart, J. M. Welch, M. A. Grados, A. J. Fyer, S. L. Rauch, J. T. McCracken, S. A. Rasmussen, D. L. Murphy, B. Cullen, D. Valle, R. Hoehn-Saric, B. D. Greenberg, A. Pinto, J. A. Knowles, J. Piacentini, D. L. Pauls, K. Y. Liang, V. L. Willour, M. Riddle, J. F. Samuels, G. Feng and G. Nestadt (2009). "Sapap3 and pathological grooming in humans: Results from the OCD collaborative genetics study." Am J Med Genet B Neuropsychiatr Genet 150B(5): 710-720. Brennan, B. P., O. Tkachenko, Z. J. Schwab, R. J. Juelich, E. M. Ryan, A. J. Athey, H. G. Pope, M. A. Jenike, J. T. Baker, W. D. Killgore, J. I. Hudson, J. E. Jensen and S. L. Rauch (2015). "An Examination of Rostral Anterior Cingulate Cortex Function and Neurochemistry in Obsessive-Compulsive Disorder." Neuropsychopharmacology 40(8): 1866-1876. Burguiere, E., P. Monteiro, L. Mallet, G. Feng and A. M. Graybiel (2015). "Striatal circuits, habits, and implications for obsessive-compulsive disorder." Curr Opin Neurobiol 30: 59-65. Calikusu, C., B. Yucel, A. Polat and C. Baykal (2003). "The relation of psychogenic excoriation with psychiatric disorders: a comparative study." Compr Psychiatry 44(3): 256-261. Cullen, B. A., J. F. Samuels, O. J. Bienvenu, M. Grados, R. Hoehn-Saric, J. Hahn, K. Y. Liang, D. Wellen, M. Dees, M. A. Riddle and G. Nestadt (2001). "The relationship of pathologic skin picking to obsessive-compulsive disorder." J Nerv Ment Dis 189(3): 193-195. Deepmala, J. Slattery, N. Kumar, L. Delhey, M. Berk, O. Dean, C. Spielholz and R. Frye (2015). "Clinical trials of N-acetylcysteine in psychiatry and neurology: A systematic review." Neurosci Biobehav Rev 55: 294-321.

Emamzadehfard, S., A. Kamaloo, K. Paydary, A. Ahmadipour, A. Zeinoddini, A. Ghaleiha, P. Mohammadinejad, A. Zeinoddini and S. Akhondzadeh (2016). "Riluzole in Augmentation of Fluvoxamine for Moderate to Severe Obsessive Compulsive Disorder: Randomized, Double‐ blind, Placebo‐ Controlled Study." Psychiatry and Clinical Neurosciences. Fan, Q., L. Tan, C. You, J. Wang, C. A. Ross, X. Wang, T. Zhang, J. Li, K. Chen and Z. Xiao (2010). "Increased N-Acetylaspartate/creatine ratio in the medial prefrontal cortex among unmedicated obsessive-compulsive disorder patients." Psychiatry Clin Neurosci 64(5): 483-490. Fireman, B., L. M. Koran, J. L. Leventhal and A. Jacobson (2001). "The prevalence of clinically recognized obsessive-compulsive disorder in a large health maintenance organization." American Journal of Psychiatry 158(11): 1904-1910. Gnanavel, S., P. Sharan, S. Khandelwal, U. Sharma and N. R. Jagannathan (2014). "Neurochemicals measured by (1)H-MR spectroscopy: putative vulnerability biomarkers for obsessive compulsive disorder." MAGMA 27(5): 407-417. Grant, J. E., S. R. Chamberlain, S. A. Redden, E. W. Leppink, B. L. Odlaug and S. W. Kim (2016). "N-Acetylcysteine in the Treatment of Excoriation Disorder: A Randomized Clinical Trial." JAMA Psychiatry 73(5): 490-496. Grant, J. E., M. C. Mancebo, M. E. Mooney, J. L. Eisen and S. A. Rasmussen (2015). "Longitudinal course of body-focused repetitive behaviors in obsessive-compulsive disorder." Ann Clin Psychiatry 27(3): 185-191. Grant, J. E., B. L. Odlaug and S. W. Kim (2010). "A clinical comparison of pathologic skin picking and obsessive-compulsive disorder." Compr Psychiatry 51(4): 347-352. Hage, A., T. Banaschewski, J. K. Buitelaar, R. M. Dijkhuizen, B. Franke, D. J. Lythgoe, K. Mechler, S. C. Williams, R. W. Dittmann and T. Consortium (2016). "Glutamatergic medication in the treatment of obsessive compulsive disorder (OCD) and autism spectrum disorder (ASD) - study protocol for a randomised controlled trial." Trials 17(1): 141. Jang, J. H., J. S. Kwon, D. P. Jang, W. J. Moon, J. M. Lee, T. H. Ha, E. C. Chung, I. Y. Kim and S. I. Kim (2006). "A proton MRSI study of brain N-acetylaspartate level after 12 weeks of citalopram treatment in drug-naive patients with obsessive-compulsive disorder." Am J Psychiatry 163(7): 1202-1207. Kessler, R. C., P. Berglund, O. Demler, R. Jin, K. R. Merikangas and E. E. Walters (2005). "Lifetime prevalence and age-of-onset distributions of DSM-IV disorders in the National Comorbidity Survey Replication." Arch Gen Psychiatry 62(6): 593-602. Koran, L. M., G. L. Hanna, E. Hollander, G. Nestadt and H. B. Simpson (2007). "Practice guideline for the treatment of patients with obsessive-compulsive disorder." The American journal of psychiatry 164(7): 1. Lissemore, J. I., D. Sookman, P. Gravel, A. Berney, A. Barsoum, M. Diksic, T. E. Nordahl, G. Pinard, I. Sibon, J. Cottraux, M. Leyton and C. Benkelfat (2018). "Brain serotonin synthesis

capacity in obsessive-compulsive disorder: effects of cognitive behavioral therapy and sertraline." Transl Psychiatry 8(1): 82. Lovato, L., Y. A. Ferrao, D. J. Stein, R. G. Shavitt, L. F. Fontenelle, A. Vivan, E. C. Miguel and A. V. Cordioli (2012). "Skin picking and trichotillomania in adults with obsessive-compulsive disorder." Compr Psychiatry 53(5): 562-568. Maia, T. V., R. E. Cooney and B. S. Peterson (2008). "The neural bases of obsessive–compulsive disorder in children and adults." Development and psychopathology 20(04): 1251-1283. Menzies, L., S. R. Chamberlain, A. R. Laird, S. M. Thelen, B. J. Sahakian and E. T. Bullmore (2008). "Integrating evidence from neuroimaging and neuropsychological studies of obsessive-compulsive disorder: the orbitofronto-striatal model revisited." Neuroscience & Biobehavioral Reviews 32(3): 525-549. Mohamed, M. A., M. A. Smith, M. W. Schlund, G. Nestadt, P. B. Barker and R. Hoehn-Saric (2007). "Proton magnetic resonance spectroscopy in obsessive-compulsive disorder: a pilot investigation comparing treatment responders and non-responders." Psychiatry Res 156(2): 175-179. O'Neill, J., T. M. Lai, C. Sheen, G. C. Salgari, R. Ly, C. Armstrong, S. Chang, J. G. Levitt, N. Salamon, J. R. Alger and J. D. Feusner (2016). "Cingulate and thalamic metabolites in obsessive-compulsive disorder." Psychiatry Res Neuroimaging 254: 34-40. Odlaug, B. L., A. Hampshire, S. R. Chamberlain and J. E. Grant (2016). "Abnormal brain activation in excoriation (skin-picking) disorder: evidence from an executive planning fMRI study." Br J Psychiatry 208(2): 168-174. Oliveirra, E. C. B., C. L. Fitzpatrick, H. S. Kim, D. C. R. Gulassa, R. S. Amaral, N. M. Cristiana, A. Y. Hayashiuchi, D. S. McGrath and H. Tavares (2019). "Obsessive-compulsive or addiction? Categorical diagnostic analysis of excoriation disorder compared to obsessive-compulsive disorder and gambling disorder." Psychiatry Res 281: 112518. Ortiz, A. E., P. Gasso, S. Mas, C. Falcon, N. Bargallo, A. Lafuente and L. Lazaro (2015). "Association between genetic variants of serotonergic and glutamatergic pathways and the concentration of neurometabolites of the anterior cingulate cortex in paediatric patients with obsessive-compulsive disorder." World J Biol Psychiatry: 1-11. Ortiz, A. E., A. G. Ortiz, C. Falcon, A. Morer, M. T. Plana, N. Bargallo and L. Lazaro (2015). "1H-MRS of the anterior cingulate cortex in childhood and adolescent obsessive-compulsive disorder: a case-control study." Eur Neuropsychopharmacol 25(1): 60-68. Paydary, K., A. Akamaloo, A. Ahmadipour, F. Pishgar, S. Emamzadehfard and S. Akhondzadeh (2016). "N-acetylcysteine augmentation therapy for moderate-to-severe obsessive-compulsive disorder: randomized, double-blind, placebo-controlled trial." J Clin Pharm Ther 41(2): 214-219. Pittenger, C. (2015). "Glutamatergic agents for OCD and related disorders." Curr Treat Options Psychiatry 2(3): 271-283.

Pittenger, C., M. H. Bloch, S. Wasylink, E. Billingslea, R. Simpson, E. Jakubovski, B. Kelmendi, G. Sanacora and V. Coric (2015). "Riluzole augmentation in treatment-refractory obsessive-compulsive disorder: a pilot randomized placebo-controlled trial." J Clin Psychiatry 76(8): 1075-1084. Pittenger, C., M. H. Bloch and K. Williams (2011). "Glutamate abnormalities in obsessive compulsive disorder: neurobiology, pathophysiology, and treatment." Pharmacol Ther 132(3): 314-332. Rosenberg, D. R., Y. Mirza, A. Russell, J. Tang, J. M. Smith, S. P. Banerjee, R. Bhandari, M. Rose, J. Ivey and C. Boyd (2004). "Reduced anterior cingulate glutamatergic concentrations in childhood OCD and major depression versus healthy controls." Journal of the American Academy of Child & Adolescent Psychiatry 43(9): 1146-1153. Ruscio, A. M., D. J. Stein, W. T. Chiu and R. C. Kessler (2010). "The epidemiology of obsessive-compulsive disorder in the National Comorbidity Survey Replication." Mol Psychiatry 15(1): 53-63. Samuels, J., Y. Wang, M. A. Riddle, B. D. Greenberg, A. J. Fyer, J. T. McCracken, S. L. Rauch, D. L. Murphy, M. A. Grados and J. A. Knowles (2011). "Comprehensive family‐ based association study of the glutamate transporter gene SLC1A1 in obsessive‐ compulsive disorder." American Journal of Medical Genetics Part B: Neuropsychiatric Genetics 156(4): 472-477. Sani, G., I. Gualtieri, M. Paolini, L. Bonanni, E. Spinazzola, M. Maggiora, V. Pinzone, R. Brugnoli, G. Angeletti, P. Girardi, C. Rapinesi and G. D. Kotzalidis (2019). "Drug Treatment Of Trichotillomania (Hair-Pulling Disorder), Excoriation (Skin-Picking) Disorder, And Nail-Biting (Onychophagia)." Curr Neuropharmacol. Saxena, S. and S. L. Rauch (2000). "Functional neuroimaging and the neuroanatomy of obsessive-compulsive disorder." Psychiatric Clinics of North America 23(3): 563-586. Simpson, H. B., L. S. Kegeles, L. Hunter, X. Mao, P. Van Meter, X. Xu, M. B. Kimeldorf, S. L. Pearlstein, M. Slifstein and D. C. Shungu (2015). "Assessment of glutamate in striatal subregions in obsessive-compulsive disorder with proton magnetic resonance spectroscopy." Psychiatry Res 232(1): 65-70. Simpson, H. B., D. C. Shungu, J. Bender, X. Mao, X. Xu, M. Slifstein and L. S. Kegeles (2012). "Investigation of cortical glutamate–glutamine and γ-aminobutyric acid in obsessive– compulsive disorder by proton magnetic resonance spectroscopy." Neuropsychopharmacology 37(12): 2684-2692. Soomro, G. M., D. Altman, S. Rajagopal and M. Oakley-Browne (2008). "Selective serotonin re-uptake inhibitors (SSRIs) versus placebo for obsessive compulsive disorder (OCD)." Cochrane Database Syst Rev 1(1). Starck, G., M. Ljungberg, M. Nilsson, L. Jonsson, S. Lundberg, T. Ivarsson, S. Ribbelin, S. Ekholm, A. Carlsson, E. Forssell-Aronsson and M. L. Carlsson (2008). "A 1H magnetic

resonance spectroscopy study in adults with obsessive compulsive disorder: relationship between metabolite concentrations and symptom severity." J Neural Transm (Vienna) 115(7): 1051-1062. Ting, J. T. and G. Feng (2008). "Glutamatergic synaptic dysfunction and obsessive-compulsive disorder." Current chemical genomics 2: 62. Torresan, R. C., A. T. Ramos-Cerqueira, M. A. de Mathis, J. B. Diniz, Y. A. Ferrao, E. C. Miguel and A. R. Torres (2009). "Sex differences in the phenotypic expression of obsessive-compulsive disorder: an exploratory study from Brazil." Compr Psychiatry 50(1): 63-69. Yücel, M., S. J. Wood, R. M. Wellard, B. J. Harrison, A. Fornito, J. Pujol, D. Velakoulis and C. Pantelis (2008). "Anterior cingulate glutamate–glutamine levels predict symptom severity in women with obsessive–compulsive disorder." Australian and New Zealand Journal of Psychiatry 42(6): 467-477.

Figure 1.

A. Example midline pregenual anterior cingulate cortex voxel

placement, illustrated here. B. Glutamate, glutamine, and other metabolites were collected from the anterior cingulate cortex. MRS spectra (sample data shown in black) were fitted (shown in red) to derive concentrations. Abbreviations: Glu, glutamate;

Gln,

N-acetyl-aspartyl-glutamate;

glutamine; Cr,

creatine

tNAA, plus

choline-containing compounds; mI, myo-inositol.

N-acetyl-aspartate+ phosphocreatine;

Cho,

Figure 2.

Glutamate and glutamine in patients between OCD and OCD+SPD.

A.

ACC glutamate differed across diagnostic groups (F (2, 44) = 7.86, p =0 .001). This difference derived from lower glutamate in OCD+SPD patients (p=0.001, Bonferroni); glutamate in OCD alone patients was indistinguishable from that in controls; ** p = 0.001. B. There was no significant between-group difference in ACC glutamine.

Figure 3. Clinical correlations with ACC glutamate. A. ACC glutamate was negatively correlated with Hamilton Anxiety Scale（HAMA）in OCD and OCD+SPD patients. B. In the OCD without SPD group, no significant association was found between glutamate and Y-BOCS total score. C. ACC glutamate was not correlated significantly with OCD symptom intensity, as measured by the Y-BOCS total score, across all OCD+SPD patients. However, when only female patients were considered, there was a positive correlation between Y-BOCS and ACC glutamate.

Table 1

Demographic and clinical characteristics

Measure

Control

OCD

OCD+SPD

n=17

n=17

n=13

Gender, male/female

8/9

10/7

4/9

0.31

Age, years

28.1±5.8

26.9±7.4

24.5±5.1

0.31

a

Male

27.4±4.7

28.9±6.7

25.6±2.6

0.58

a

Female

28.7±6.9

24.1±3.0

24.1±6.0

0.30

a

Education, years

16.1±2.4

14.5±2.7

14.0±2.2

0.07

a

Male

16.4±3.2

14.6±2.3

13.0±3.2

0.16

a

Female

15.8±1.6

14.3±3.6

14.4±1.7

0.35

a

Onset age, years

18.3±5.1

19.5±4.4

0.49b

Male

20.2±5.9*

22.8±1.0

0.42 b

Female

15.6±1.6

18.1±4.7

0.19 b

Y-BOCS

25.4±4.1

25.5±4.9

0.99 b

Male

25.9±4.1

23.8±7.1

0.49 b

Female

24.6±4.0

26.2±3.8

0.41 b

Y-BOCS obsessions

12.9±3.5

12.9±2.63

0.99 b

Male

12.6±3.8

12.0±4.1

0.79 b

Female

13.3±3.1

13.3±1.9

0.97 b

Y-BOCS Compulsions

12.4±4.9

12.5±2.6

0.92 b

Male

13.2±5.8

11.8±3.1

0.65 b

Female

11.3±2.9

12.9±2.4

0.25 b

NE-YBOCS

27.2±4.4

Male

25.5±6.0

Female

27.9±3.6

Significance

HAMD

9.4±3.0

10.1±3.8

0.58 b

Male

9.2±2.9

6.3±1.5**

0.08 b

Female

9.4±3.4

11.7±3.1

0.17 b

HAMA

11.1±2.9

15.2±3.2

0.001 b

Male

11.3±2.5

13.5±1.7

0.14 b

Female

10.9±3.6

15.9±3.5

0.02 b

Data are mean±standard deviation or n/n; a. 1-way ANOVA, main effect of diagnostic group; b. Independent-samples t-test; * Independent-samples t-test: p＜0.05 for male vs. female within OCD group; ** Independent-samples t-test: P＜0.01 for male vs. female within OCD+SPD group.

Table 2.

Metabolites in anterior cingulate cortex in healthy subjects and

patients between OCD and OCD+SPD. Measure

Control

OCD

OCD+SPD

F

P

Glu

10.58±2.38

12.10±3.90

7.53±2.92 a b

7.86

0.001

Male

11.43±1.62

12.07±4.85

7.03±2.87

Female

9.83±2.77

12.13±2.28

7.76±3.09

Gln

6.32±3.04

6.94±4.43

8.24±4.67

0.84

0.44

Male

6.41±2.45

8.20±4.99

9.54±6.02

Female

6.24±3.65

5.15±2.96

7.67±4.24

mI

1.78±1.60

2.22±1.53

3.32±2.91

2.12

0.13

Male

1.52±1.46

2.38±1.60

2.48±1.60

Female

2.02±1.64

2.00±1.51

3.70±3.43

Cr

8.07±1.07

8.10±1.15

7.41±2.25

0.94

0.40

Male

8.53±1.33

8.69±1.17**

8.16±1.13

Female

7.66±0.58

7.27±0.37

7.08±2.60

Cho

1.90±0.24

2.09±0.37

1.96±0.42

1.31

0.28

Male

1.99±0.23

2.23±0.31

1.92±0.28

Female

1.82±0.23

1.88±0.37

1.98±0.48

tNAA

8.18±1.01

8.14±1.52

6.58±2.66

3.77

0.03

Male

8.47±1.16

8.69±1.70

7.49±1.94

Female

7.92±0.71

7.35±0.81

6.17±2.94

Glu+Gln

16.90±2.64

19.04±4.86

15.78±6.11

1.97

0.15

Male

17.84±3.20

20.27±5.21

14.67±3.71

Female

16.07±1.83

17.28±4.02

16.27±7.07

Data are mean±standard deviation; a. Control subjects differ from OCD+SPD patients, p=0.035 (Bonferroni correction); b. OCD patients differ from OCD+SPD patients, p=0.001(Bonferroni correction);

**.

Male

patients

differ

from

female

patients,

p=0.01(Mann-WhitneyUtest);Glu,glutamate;Gln,glutamine;mI,myo-inositol;Cho,choline-compou nds;tNAA,N-acetyl-aspartate+N-acetyl-aspartyl-glutamate;Cr, creatine+phosphocreatine.