Niacin skin flush and membrane polyunsaturated fatty acids in schizophrenia from the acute state to partial remission: a dynamic relationship

Developing a risk assessment model for treatment-resistant schizophrenia: The role of niacin receptor GPR109A and prostaglandin receptors DP1, EP2, and EP4 in the niacin-induced flushing pathway

Schizophrenia patients show attenuated niacin flush responses compared to healthy controls (HC) attributed to abnormalities in the niacin-induced flushing pathway. Underlying immunological abnormalities may reduce the niacin receptor GPR109A's response and implicated in treatment-resistant schizophrenia (TRS). This pathway involves GPR109A and the downstream vasodilatory prostaglandins (PGs), PGD2 and PGE2, along with their receptors DP1, EP2, and EP4, contributing to vasodilation and neuroprotection. We hypothesized that the niacin receptor GPR109A, PGs, and their receptors play a significant role in the pathogenesis of TRS. We aimed to investigate GPR109A, DP1, PGD2, PGE2, EP2, and EP4 as potential biomarkers for identifying TRS and construct a risk assessment model for TRS. We recruited 58 TRS, 67 NTRS patients, and 115 HC. We observed significant differences in niacin flush responses and expression levels of GPR109A, PGE2, DP1, EP2, and EP4 between the schizophrenia and HC groups. TRS group exhibited lower expression levels of GPR109A, DP1, EP2, and EP4 than NTRS group. Receiver operating characteristic curve analysis combining the six markers for schizophrenia versus HC yielded an area under the curve (AUC) of 0.98, whereas an analysis combining the four markers for TRS versus NTRS yielded an AUC of 0.91. Niacin-induced flushing signaling cascade enrichment is linked to the intensity of the inflammatory response, with associated mediators and their receptor affinities potentially regulating pharmacological effects. These findings suggest that the niacin receptor GPR109A and PG receptors DP1, EP2, and EP4, which are involved in the niacin-induced flushing pathway, may serve as biomarkers for predicting TRS.

Blunted niacin skin flushing response in violent offenders with schizophrenia: A potential auxiliary diagnostic biomarker

Schizophrenia (SZ) is associated with an increased risk of violence, with clinical diagnosis primarily relies on symptomatology. The niacin skin flushing response (NSFR) is proposed as a potential biomarker for SZ, but its effectiveness in violent offenders with schizophrenia (VOSZ) remains unevaluated. This study investigates whether the diagnostic model differentiating general SZ patients (GSZ) from healthy controls (HCs) using NSFR can also distinguish VOSZ from HCs. SZ patients were continuously sampled based on the International Classification of Diseases, 10th Edition, and categorized into VOSZ (with a history of violent crimes), and GSZ (without such history). HCs had no psychiatric illnesses or violent crime history. A total of 315 VOSZ, 296 GSZ, and 281 HCs were recruited. Least absolute shrinkage and selection operator regression was used to select variables and construct diagnostic models based on NSFR. No significant differences in age, sex or BMI were observed among groups. Both VOSZ and GSZ exhibited similar blunted NSFR compared to HCs. The diagnostic model constructed by 14 NSFR variables distinguishing GSZ from HCs was successfully transferred to distinguish VOSZ from HCs, with areas under the curve of 0.796 (specificity = 81.6%, sensitivity = 64.2%) and 0.798 (specificity = 80.0%, sensitivity = 70.2%), respectively. Moreover, NSFR was unrelated to illness severity, violence, or antipsychotic dosage in VOSZ, suggesting it is a trait indicator of SZ. This study supports the NSFR as an objective diagnostic biomarker for distinguishing VOSZ from HCs, expanding its applicability, although it may not specifically identify violent offenders among SZ patients.

Patients with first-episode psychosis in northern Taiwan: neurocognitive performance and niacin response profile in comparison with schizophrenia patients of different familial loadings and relationship with clinical features

BACKGROUND

Examining patients with first-episode psychosis (FEP) provides opportunities to better understand the mechanism underlying these illnesses. By incorporating quantitative measures in FEP patients, we aimed to (1) determine the baseline distribution of clinical features; (2) examine the impairment magnitude of the quantitative measures by comparing with external controls and then the counterparts of schizophrenia patients of different familial loadings; and (3) evaluate whether these quantitative measures were associated with the baseline clinical features.

METHODS

Patients with FEP were recruited from one medical center, two regional psychiatric centers, and two private clinics in northern Taiwan with clinical features rated using the Positive and Negative Syndrome Scale (PANSS) and Personal and Social Performance (PSP) scale. Quantitative measurements included the Continuous Performance Test (CPT), Wisconsin Card Sorting Test (WCST), niacin response abnormality (NRA), and minor physical anomalies and craniofacial features (MPAs). To evaluate the relative performance of the quantitative measures in our FEP patients, four external comparison groups from previous studies were used, including three independent healthy controls for the CPT, WCST, and NRA, respectively, and one group of treatment-resistant schizophrenia patients for the MPAs. Additionally, patients from simplex families and patients from multiplex families were used to assess the magnitude of FEP patients' impairment on the CPT, WCST, and NRA.

RESULTS

Among the 80 patients with FEP recruited in this study (58% female, mean age = 25.6 years, mean duration of untreated psychosis = 132 days), the clinical severity was mild to moderate (mean PANSS score = 67.3; mean PSP score = 61.8). Patients exhibited both neurocognitive and niacin response impairments (mean Z-scores: -1.24 for NRA, - 1.06 for undegraded d', - 0.70 for degraded d', - 0.32 for categories achieved, and 0.44 for perseverative errors) but did not show MPAs indicative of treatment resistance. Among these quantitative measures, three of the four neurocognitive indices were correlated with the baseline clinical features, whereas NRA did not show such correlation.

CONCLUSIONS

This FEP study of Taiwanese patients revealed the presence of neurocognitive performance and niacin response and their different relationships with clinical features, rendering this sample useful for future follow-up and incorporation of multiomics investigation.

Attenuated niacin response is associated with a subtype of first-episode drug-naïve psychosis characterized as serious negative symptoms

Although the phenomenon of attenuated niacin response (ANR) has been widely replicated in some patients with first-episode psychosis (FEP), its relevance to the negative symptoms (NS) of psychosis remains unclear. Total of 240 patients with drug-naïve FEP and 101 healthy controls (HCs) were recruited, and 209 were followed up for 1 year. Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS), and niacin-induced responses were measured using laser Doppler flowmetry. We calculated the log-transform EC50 [concentration of methyl nicotinate required to elicit a half-maximal blood flow (MBF) response] and MBF values. Core-NS was generated by factor analysis of the PANSS-NS subscale and cluster analysis to produce subtypes. Significant differences were found in the log10 (EC50) values between the FEP and HC groups (p < 0.001), supporting the ANR in patients with FEP. A higher NS severity was found in the ANR subgroup than that in other patients. Factor analysis determined that a two-dimensional model included core NS and rigidity of thinking. The log10 (EC50) value was significantly associated with only the core NS. Cluster analysis revealed three subtypes-36.7% (cluster-1, n = 88), 16.7% (cluster-2, n = 40), and 46.7% (cluster-3, n = 112). Cluster-2 characterized by extensive NS appeared to have a more remarkable ANR and less symptomatic improvement than those with other clusters during follow-up. No significant changes were found in the niacin response trajectories between the baseline and follow-up. Our findings indicate a significant correlation between ANR and core NS in patients with FEP. ANR may be a potential biomarker for certain subtypes with NS-dominated characteristics and poor symptomatic remission.