Olfactory performance segregates effects of anhedonia and anxiety on social function in patients with schizophrenia

Spectrum-effect relationship combined with bioactivity evaluation to discover the main anxiolytic active components of Baihe Dihuang decoction

ETHNOPHARMACOLOGICAL RELEVANCE

Anxiety disorders leads to a decline in quality of life and increased risk of morbidity and mortality. The Baihe Dihuang decoction (BDD) is a classic Chinese medical formula that has been widely used to treat anxiety disorders for thousands of years in China. However, the pharmacodynamic material that is responsible for the antianxiety of BDD remains unclear.

AIM OF THE STUDY

To screen the main ingredients of anti-anxiety in BDD based on the establishment of spectrum-effect relationship and verified experiment.

METHODS

The UPLC-Q-TOF/MS technique was utilized to establish fingerprints of various fractions of BDD and identify the main compounds. The anti-anxiety effects of BDD were comprehensively evaluated through multiple assessments, including the open field test, elevated plus maze test, and neurotransmitters tests. Then, the spectrum-effect relationship was established through Pearson correlation analysis, gray correlation analysis, orthogonal partial least squares regression analysis. The spectrum-effect relationship results were confirmed through various measures on an anxiety condition cell model, induced by a corticosterone and lipopolysaccharide intervention. These measures included assessing neuronal cell viability, morphology, apoptosis, synaptic damage, and the expression of neurotransmitters and inflammatory factors.

RESULTS

In the UPLC-Q-TOF-MS fingerprint, 46 common peaks were identified. The pharmacological results indicated that different fractions of BDD have strong effects on improving anxiety-like behavior and regulating neurotransmitters. Among them, butanol fraction has the highest comprehensive evaluation score of anti-anxiety efficacy, which is main active fraction of BDD for anti-anxiety. The analysis of the spectrum-effect relationship revealed that the 46 peaks exhibited varying degrees of correlation with the anti-anxiety efficacy indicators of BDD. Among them, 14 components have a high correlation with the anti-anxiety efficacy indicators, which may be the potential anti-anxiety efficacy components of BDD. The in vitro activity verification of active components verified our prediction, regaloside A, B, C, D, H, acteoside, and isoacteoside improved neuronal cell viability, cell morphology, apoptosis, and synaptic damage. Additionally, regaloside A, B, C, D, H and acteoside regulated the neurotransmitter levels, while regaloside A, B, C, D, acteoside and isoacteoside inhibited the levels of inflammatory cytokines.

CONCLUSION

The butanol fraction was found to be the main active fraction of BDD, and 14 compounds were the major anxiolytic active components. The results of verifying the major active components were consistent with the predicted results of the spectrum-effect analysis. The developed spectrum-effect analysis in this study demonstrates high accuracy and reliability for screening active components in TCMs.

Unraveling the Link between Olfactory Deficits and Neuropsychiatric Disorders

Smell loss has caught public attention during the recent COVID-19 pandemic. Research on olfactory function in health and disease gains new momentum. Smell deficits have long been recognized as an early clinical sign associated with neuropsychiatric disorders. Here we review research on the associations between olfactory deficits and neuropathological conditions, focusing on recent progress in four areas: (1) human clinical studies of the correlations between smell deficits and neuropsychiatric disorders; (2) development of olfactory mucosa-derived tissue and cell models for studying the molecular pathologic mechanisms; (3) recent findings in brain imaging studies of structural and functional connectivity changes in olfactory pathways in neuropsychiatric disorders; and (4) application of preclinical animal models to validate and extend the findings from human subjects. Together, these studies have provided strong evidence of the link between the olfactory system and neuropsychiatric disorders, highlighting the relevance of deepening our understanding of the role of the olfactory system in pathophysiological processes. Following the lead of studies reviewed here, future research in this field may open the door to the early detection of neuropsychiatric disorders, personalized treatment approaches, and potential therapeutic interventions through nasal administration techniques, such as nasal brush or nasal spray.

Momentary gustative-olfactory sensitivity and tonic heart rate variability are independently associated with motivational behavior

Deficits in motivational functioning including impairments in reward learning or reward sensitivity are common in psychiatric disorders characterized by anhedonia. Recently, anhedonic symptoms have been exacerbated by the pandemic caused by the Coronavirus disease 2019 (COVID-19) in the general population. The present study examined the putative associations between loss of smell (anosmia) and taste (ageusia) sensitivity, irrespective of COVID-19 infection, and anhedonia, measured by a signal-detection task probing the ability to modify behavior as a function of rewards (Probabilistic Reward Task; PRT). Tonic heart rate variability (HRV) was included in the model, due to its association with both smell and taste sensitivity as well as motivational functioning. The sample included 114 healthy individuals (81 females; mean age 22.2 years), who underwent a laboratory session in which dispositional traits, resting HRV and PRT performance were assessed, followed by a 4-days ecological momentary assessment to obtain daily measures of anosmia and ageusia. Lower levels of tonic HRV and lower momentary levels of smell and taste sensitivity were associated with impaired reward responsiveness and ability to shape future behavioral choices based on prior reinforcement experiences. Overall, the current results provide initial correlational evidence that could be fruitfully used to inform future experimental investigations aimed at elucidating the disruptive worldwide mental health consequences triggered by the pandemic.

Olfactory Dysfunction in Mental Illness

PURPOSE OF REVIEW

Olfactory dysfunction contributes to the psychopathology of mental illness. In this review, we describe the neurobiology of olfaction, and the most common olfactory alterations in several mental illnesses. We also highlight the role, hitherto underestimated, that the olfactory pathways play in the regulation of higher brain functions and its involvement in the pathophysiology of psychiatric disorders, as well as the effect of inflammation on neurogenesis as a possible mechanism involved in olfactory dysfunction in psychiatric conditions.

RECENT FINDINGS

The olfactory deficits present in anxiety, depression, schizophrenia or bipolar disorder consist of specific alterations of different components of the sense of smell, mainly the identification of odours, as well as the qualifications of their hedonic valence (pleasant or unpleasant). Epidemiological findings have shown that both environmental factors, such as air pollutants, and inflammatory disease of the upper respiratory tract, can contribute to an increased risk of mental illness, at least in part, due to peripheral inflammatory mechanisms of the olfactory system. In this review, we describe the neurobiology of olfaction, and the most common olfactory function alterations in several psychiatric conditions and its role as a useful symptom for the differential diagnosis. We also highlight the effect of inflammation on neurogenesis as a possible mechanism involved in olfactory dysfunction in these psychiatric conditions.

Olfactory impairment in psychiatric disorders: Does nasal inflammation impact disease psychophysiology?

Olfactory impairments contribute to the psychopathology of mental illnesses such as schizophrenia and depression. Recent neuroscience research has shed light on the previously underappreciated olfactory neural circuits involved in regulation of higher brain functions. Although environmental factors such as air pollutants and respiratory viral infections are known to contribute to the risk for psychiatric disorders, the role of nasal inflammation in neurobehavioral outcomes and disease pathophysiology remains poorly understood. Here, we will first provide an overview of published findings on the impact of nasal inflammation in the olfactory system. We will then summarize clinical studies on olfactory impairments in schizophrenia and depression, followed by preclinical evidence on the neurobehavioral outcomes produced by olfactory dysfunction. Lastly, we will discuss the potential impact of nasal inflammation on brain development and function, as well as how we can address the role of nasal inflammation in the pathophysiological mechanisms underlying psychiatric disorders. Considering the current outbreak of Coronavirus Disease 2019 (COVID-19), which often causes nasal inflammation and serious adverse effects for olfactory function that might result in long-lasting neuropsychiatric sequelae, this line of research is particularly critical to understanding of the potential significance of nasal inflammation in the pathophysiology of psychiatric disorders.

Olfactory dysfunction and face processing of social cognition in first-episode psychosis

Olfactory functional deficits have been reported in psychotic disorders. Olfactory dysfunction has a predictive value for prognosis and disease course. Thus, it is important to know which specific symptoms and cognitive changes are associated with olfactory dysfunction in early-stage psychosis. Deficits in social cognition are a difficult problem in psychosis. Here we conduct a detailed assessment of odor function and face processing and show that odor discrimination capacity is specifically associated with face processing function in patients with first episode psychosis. This finding indicates that the high-throughput olfactory assessment may aid a prediction of the difficult clinical dimension from early-stage psychosis.

Assessing olfactory, memory, social and circadian phenotypes associated with schizophrenia in a genetic model based on Rim

Schizophrenia shows high heritability and several of the genes associated with this disorder are involved in calcium (Ca2+) signalling and synaptic function. One of these is the Rab-3 interacting molecule-1 (RIM1), which has recently been associated with schizophrenia by Genome Wide Association Studies (GWAS). However, its contribution to the pathophysiology of this disorder remains unexplored. In this work, we use Drosophila mutants of the orthologue of RIM1, Rim, to model some aspects of the classical and non-classical symptoms of schizophrenia. Rim mutants showed several behavioural features relevant to schizophrenia including social distancing and altered olfactory processing. These defects were accompanied by reduced evoked Ca2+ influx and structural changes in the presynaptic terminals sent by the primary olfactory neurons to higher processing centres. In contrast, expression of Rim-RNAi in the mushroom bodies (MBs), the main memory centre in flies, spared learning and memory suggesting a differential role of Rim in different synapses. Circadian deficits have been reported in schizophrenia. We observed circadian locomotor activity deficits in Rim mutants, revealing a role of Rim in the pacemaker ventral lateral clock neurons (LNvs). These changes were accompanied by impaired day/night remodelling of dorsal terminal synapses from a subpopulation of LNvs and impaired day/night release of the circadian neuropeptide pigment dispersing factor (PDF) from these terminals. Lastly, treatment with the commonly used antipsychotic haloperidol rescued Rim locomotor deficits to wildtype. This work characterises the role of Rim in synaptic functions underlying behaviours disrupted in schizophrenia.

Reduced odor detection and hedonic changes in asymptomatic university students as SARS-CoV-2 emerged locally

Aerosol droplets have emerged as the primary mode of SARS-Cov-2 transmission and can be spread by infectious asymptomatic/pre-symptomatic persons rendering indicators of latent viral infection essential. Olfactory impairment is now a recognized symptom of COVID-19 and is rapidly becoming one of the most reliable indicators of the disease. We compared olfaction data from asymptomatic students, who were assessed as SARS-CoV-2 was unknowingly spreading locally, to students tested prior to the arrival of the virus. This study was naturalistic by design as testing occurred in the context of four research studies, all of which used the same inclusion/exclusion criteria and the same protocol to objectively assess odor detection, identification, and hedonics with physiological tests. Data from students (Cohort II; N=22) with probable SARS-CoV-2 exposure were compared to students tested just prior to local virus transmission (Cohort I; N=25), and a normative sample of students assessed over the previous four years (N=272). Students in Cohort II demonstrated significantly reduced odor detection sensitivity compared to students in Cohort I (t=2.60; P=.01; d=0.77; CI, 0.17, 1.36), with a distribution skewed towards reduced detection sensitivity (D=0.38; P=.005). Categorically, the exposed group was significantly more likely to have hyposmia (OR=7.74; CI, 3.1, 19.40), particularly the subgroup assessed in the final week before campus closure (OR=13.61; CI, 3.40, 35.66;). The exposed cohort also rated odors as less unpleasant (P<.001, CLES=0.77). A limitation of our study is that participants were not tested for COVID-19 as testing was unavailable in the area. Objective measures of olfaction may detect olfactory impairment in asymptomatic persons who are otherwise unaware of smell loss. The development of cost-effective, objective olfaction tests that could be self-administered regularly could aid in early detection of SARS-CoV-2 exposure, which is vital to combatting this pandemic.

Olfactory dysfunction in frontotemporal dementia and psychiatric disorders: A systematic review

Frontotemporal dementia (FTD) is a progressive neurodegenerative disease. Diagnosis of FTD, especially the behavioural variant, is challenging because of symptomatic overlap with psychiatric disorders (depression, schizophrenia, bipolar disorder). Olfactory dysfunction is common in both FTD and psychiatric disorders, and often appears years before symptom onset. This systematic review analysed 74 studies on olfactory function in FTD, depression, schizophrenia and bipolar disorder to identify differences in olfactory dysfunction profiles, focusing on the most common smell measures: odour identification and discrimination. Results revealed that FTD patients were severely impaired in odour identification but not discrimination; in contrast, patients diagnosed with schizophrenia showed impairments in both measures, while those diagnosed with depression showed no olfactory impairments. Findings in bipolar disorder were mixed. Therefore, testing odour identification and discrimination differentiates FTD from depression and schizophrenia, but not from bipolar disorder. Given the high prevalence of odour identification impairments in FTD, and that smell dysfunction predicts neurodegeneration in other diseases, olfactory testing seems a promising avenue towards improving diagnosis between FTD and psychiatric disorders.

Sex differences in hedonic judgement of odors in schizophrenia cases and healthy controls

The neurocircuitries subserving affective and olfactory processes overlap, are sexually dimorphic, and show disruptions in schizophrenia, suggesting their intersection may be a window on the core process producing psychosis. This study investigated diagnostic and sex differences in hedonic judgments of odors and smell identification in 26 schizophrenia cases and 27 healthy controls. Associations between olfaction measures and psychiatric symptoms were also examined. Cases and controls had similar identification accuracy of unpleasant odors, but cases were significantly less accurate in naming pleasant odors. In cases, greater negative symptom severity was related to abnormal hedonic judgments; specifically, higher pleasantness ratings for unpleasant odors and higher unpleasantness ratings for pleasant odors. Greater positive symptom severity was associated with lower pleasantness ratings for neutral odors. Regarding sex differences, male cases and female controls rated pleasant odors as significantly more unpleasant than male controls. Correlations between depression severity and pleasantness ratings of neutral odors were in opposite directions in male and female cases. These results suggest that a normal sexual dimorphism in the circuitry for hedonic odor judgments may interact with schizophrenia pathology, supporting the utility of olfactory hedonics as a sex-specific biomarker of this pathology.

Normal sexual dimorphism in theory of mind circuitry is reversed in Schizophrenia

The ability to mentalize, or theory of mind (ToM), is sexually dimorphic in humans and impaired in schizophrenia. This sex-stratified study probed cognitive (indexed by intelligence) and affective (indexed by olfactory tasks) contributions to ToM performance in 37 individuals with schizophrenia and 31 healthy controls. The schizophrenia group showed impairments in mental state identification and inferring intentions compared to controls. Higher intelligence was correlated with mental state identification and inferring intentions in healthy females, whereas better smell identification was associated with mental state identification in healthy males. Conversely, higher intelligence was associated with mental state identification and inferring intentions in schizophrenia males, while better smell identification was correlated with mental state identification in schizophrenia females. These findings suggest that for ToM circuitry, the cognitive influences in healthy females and affective influences in healthy males are reversed in schizophrenia and may be displaced to lower circuitries by disease pathology. Symptom associations with emotion and cognition are also dimorphic, plausibly due to similar pathology superimposed on normal sex-specific circuitries. Males appear to rely on limbic processing for ToM, and disruption to this circuitry may contribute to development of negative symptoms. These findings highlight the importance of utilizing sex-stratified designs in schizophrenia research.

Olfactory Functioning in First-Episode Psychosis

BACKGROUND

Though olfactory deficits are well-documented in schizophrenia, fewer studies have examined olfactory performance profiles across the psychosis spectrum. The current study examined odor identification, discrimination, and detection threshold performance in first-episode psychosis (FEP) patients diagnosed with schizophrenia, schizoaffective disorder, bipolar disorder with psychotic features, major depression with psychotic features, and other psychotic conditions.

METHOD

FEP patients (n = 97) and healthy adults (n = 98) completed birhinal assessments of odor identification, discrimination, and detection threshold sensitivity for lyral and citralva. Participants also completed measures of anticipatory pleasure, anhedonia, and empathy. Differences in olfactory performances were assessed between FEP patients and controls and within FEP subgroups. Sex-stratified post hoc analyses were employed for a complete analysis of sex differences. Relationships between self-report measures and olfactory scores were also examined.

RESULTS

Individuals with psychosis had poorer scores across all olfactory measures when compared to the control group. Within the psychosis cohort, patients with schizophrenia-associated psychosis had poorer odor identification, discrimination, and citralva detection threshold scores relative to controls. In schizophrenia patients, greater olfactory disturbance was associated with increased negative symptomatology, greater self-reported anhedonia, and lower self-reported anticipatory pleasure. Patients with mood-associated psychosis performed comparable to controls though men and women in this cohort showed differential olfactory profiles.

CONCLUSIONS

These findings indicate that olfactory deficits extend beyond measures of odor identification in FEP with greater deficits observed in schizophrenia-related subgroups of psychosis. Studies examining whether greater olfactory dysfunction confers greater risk for developing schizophrenia relative to other forms of psychosis are warranted.

Does the Social Functioning Scale reflect real-life social functioning? An experience sampling study in patients with a non-affective psychotic disorder and healthy control individuals

BACKGROUND

The ecological validity of retrospective measures of social functioning is currently unknown in patients with schizophrenia. In the present study, patients with a diagnosis of non-affective psychosis were compared with controls on two measures of social functioning: the Social Functioning Scale (SFS) and daily-life measures collected with the Experience Sampling Methodology (ESM). The associations between both measures were examined in each group of participants to test for the ecological validity of the SFS.

METHODS

A total of 126 participants with a non-affective psychotic disorder and 109 controls completed the SFS and a 6-day momentary ESM protocol assessing various aspects of social functioning. Multiple linear and multilevel regression analyses were performed to test for group differences in social functioning level and examine associations between the two assessment techniques.

RESULTS

Lower social functioning was observed in patients compared with controls on retrospective and momentary measures. The SFS interpersonal domain (social engagement/withdrawal and interpersonal behaviour dimensions) was associated with the percentage of time spent alone and negative appraisal of social interactions. The SFS activity domain (pro-social and recreational activities dimensions) was negatively associated with time spent in leisure activities.

CONCLUSIONS

The SFS showed some degree of ecological validity at assessing broad aspects of social functioning. Low scores on the SFS social engagement/withdrawal and interpersonal behaviour dimensions captured social isolation and social avoidance in daily life, but not lack of interest in socializing. Ecological validity of the SFS activity domain was low. ESM offers a rich alternative to classical assessment techniques of social functioning.

Anxiety does not contribute to social withdrawal in the subchronic phencyclidine rat model of schizophrenia

Social withdrawal should not be considered a direct measure of the negative symptoms of schizophrenia as it may result not only from asociality (primary negative symptom) but also from other altered processes such as anxiety. To understand the contribution of these two factors to social deficit, we investigated whether the social withdrawal observed in the subchronic phencyclidine (PCP) rat model of schizophrenia could be attributed to increased anxiety. Compared to saline controls, PCP-treated rats (5 mg/kg, twice daily for 7 days, followed by a washout period) spent significantly less time in social interaction, but did not show anxiety-like behaviors in different relevant behavioral paradigms. In addition, their social deficit was not affected by a behavioral procedure known to reduce anxiety-like behavior (repeated exposure to the same partner) nor by systemic administration of the classical anxiolytic diazepam. In contrast, PCP-induced social withdrawal was reversed by the cannabinoid agonist CP55,940, a drug with known anxiogenic properties. Furthermore, when using the social approach task, PCP-treated animals performed similarly to control animals treated with diazepam, but not to those treated with the anxiogenic compound pentylenetetrazole. Taken together, our results indicate that PCP-induced social withdrawal cannot be attributed to increased anxiety. These data are discussed in the context of primary versus secondary negative symptoms and the deficit syndrome of schizophrenia.

Deficits in the identification of pleasant odors predict the transition of an at-risk mental state to psychosis

OBJECTIVE

Existing knowledge of the relationship between olfactory identification (OI) ability and clinical risk of psychosis is inconsistent. To address this inconsistency, the aim of the present study was to identify the relationship between OI ability, with regard to the hedonic attributes of odors, and the risk of transition to psychosis in individuals with an ARMS.

METHODS

A group of 81 individuals meeting the ARMS criteria according to the Comprehensive Assessment of At Risk Mental State were at baseline administered with the University of Pennsylvania Smell Identification Test. The hedonic attributes of odorants were normatively established. Participants were followed up for transition to psychosis for a mean period of 36.1months (SD:27.5months).

RESULTS

The presence of deficits in the identification of pleasant odors was found to be a risk factor for conversion from an ARMS to schizophrenia. The hazard ratio for each point in deficit scores in the Cox regression model was 1.455 (95% CI: 1.211-1.747), p<0.0001. Significant deficits in the identification of pleasant odors were associated with a risk for conversion at both early and late time points from baseline.

CONCLUSIONS

The findings imply that the impaired identification of pleasant odorants may be a risk factor for the transition of an ARMS into a psychotic disorder, and highlights the need for further research of OI in "at-risk" cohorts, taking into account the hedonic attributes of odors.

Olfactory identification in patients with schizophrenia - the influence of β-endorphin and calcitonin gene-related peptide concentrations

BACKGROUND

The relationship between the olfactory system and emotional processing is an area of growing interest in schizophrenia research. Both the orbitofrontal cortex and amygdala are involved in the processing of olfactory information, and olfactory deficits may be also influenced by endogenous opioids and calcitonin gene-related peptide (CGRP), which is probably involved in dopaminergic transmission. However, the relationship between endorphins and dopaminergic transmission has not been fully explored.

METHODS

Odor identification performance and valence interaction was evaluated among 50 schizophrenic patients and 50 controls. Schizophrenia symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). All study participants were subjected to the University of Pennsylvania Smell Identification Test (UPSIT), blood β-endorphin (BE) and CGRP measurement.

RESULTS

Insignificantly higher BE concentrations were observed in the patient group, while significantly higher UPSIT scores were seen in controls (mean UPSIT 32.48 vs 26.82). The patients demonstrated significantly more identification errors for pleasant (P=0.000) and neutral (P=0.055) odors than for unpleasant odors. Patients with higher BE concentrations made more identification errors concerning pleasant (R_s=-0.292; P=0.04) and neutral odors (R_s=-0.331; P=0.019). Although the concentration of CGRP was significantly higher in the patient sample (P<0.001), no relationship was observed between concentration and UPSIT performance. A strong negative correlation was observed between PANSS N score and UPSIT total score (R_s=-0.646; P=0.000), between PANSS N score and identification by valence for pleasant and neutral odors (UPSIT n/16: R_s=-0.450, P=0.001; UPSIT n/15: R_s=-0.586, P=0.000), and a weak negative correlation between PANSS N score and identification of unpleasant odors (UPSIT n/9: R_s=-0.325, P=0.021).

CONCLUSIONS

Schizophrenic patients present a unique pattern of smell identification characterized by aberrant hedonic ratings for pleasant odors but not unpleasant ones. Individuals with predominant negative symptoms and higher BE concentrations are most able to identify negative odors.

Molecular signatures associated with cognitive deficits in schizophrenia: a study of biopsied olfactory neural epithelium

Cognitive impairment is a key feature of schizophrenia (SZ) and determines functional outcome. Nonetheless, molecular signatures in neuronal tissues that associate with deficits are not well understood. We conducted nasal biopsy to obtain olfactory epithelium from patients with SZ and control subjects. The neural layers from the biopsied epithelium were enriched by laser-captured microdissection. We then performed an unbiased microarray expression study and implemented a systematic neuropsychological assessment on the same participants. The differentially regulated genes in SZ were further filtered based on correlation with neuropsychological traits. This strategy identified the SMAD 5 gene, and real-time quantitative PCR analysis also supports downregulation of the SMAD pathway in SZ. The SMAD pathway has been important in multiple tissues, including the role for neurodevelopment and bone formation. Here the involvement of the pathway in adult brain function is suggested. This exploratory study establishes a strategy to better identify neuronal molecular signatures that are potentially associated with mental illness and cognitive deficits. We propose that the SMAD pathway may be a novel target in addressing cognitive deficit of SZ in future studies.