Immunometabolic dysregulation is associated with reduced cortical thickness of the anterior cingulate cortex

Association between physical activity and sedentary behavior and depression in US adults with cardiovascular disease: NHANES 2007-2016

BACKGROUND

Previous studies reported the effect of physical activity (PA) or sedentary behavior (SB) on increasing occurrence of depression in patients with cardiovascular disease, leading to a higher risk of adverse clinical outcomes. However, the association between the combination of PA and SB and depression in patients with cardiovascular disease remained unstudied.

METHODS

Patients with cardiovascular disease (aged ≥18 years) who participated in the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2016. Multivariable logistic regression was used to investigate the association between PA, SB, and depression.

RESULTS

Among the 2585 patients (mean age 64.43 years; 54.65 % male) in this study, the prevalence of depression was 16.40 %. After adjustment for age, gender, race, education level, marital status, poverty income ratio, employment status, smoking, alcohol use, BMI, hypertension, and number of cardiovascular diseases, depression was negatively associated with higher PA (adjusted OR = 0.567, 95 % CI 0.403, 0.799) and positively associated with higher SB (adjusted OR = 1.472, 95 % CI 1.089, 1.990), respectively. The risk of depression associated with higher PA and lower SB was significantly lower (adjusted OR = 0.464, 95 % CI 0.307, 0.702) compared to those with lower PA but higher SB.

LIMITATIONS

This was a cross-sectional study with limited ability to make causal inferences.

CONCLUSIONS

Our findings indicate that patients with higher PA and lower SB have a lower risk of depression than those with low PA levels and high SB levels. Moving more and sitting less is a potential preventive measure against depression in patients with cardiovascular disease.

Mapping pathways to neuronal atrophy in healthy, mid-aged adults: From chronic stress to systemic inflammation to neurodegeneration?

Growing evidence implicates systemic inflammation in the loss of structural brain integrity in natural ageing and disorder development. Chronic stress and glucocorticoid exposure can potentiate inflammatory processes and may also be linked to neuronal atrophy, particularly in the hippocampus and the human neocortex. To improve understanding of emerging maladaptive interactions between stress and inflammation, this study examined evidence for glucocorticoid- and inflammation-mediated neurodegeneration in healthy mid-aged adults. N = 169 healthy adults (mean age = 39.4, 64.5% female) were sampled from the general population in the context of the ReSource Project. Stress, inflammation and neuronal atrophy were quantified using physiological indices of chronic stress (hair cortisol (HCC) and cortisone (HEC) concentration), systemic inflammation (interleukin-6 (IL-6), high-sensitive C-reactive protein (hs-CRP)), the systemic inflammation index (SII), hippocampal volume (HCV) and cortical thickness (CT) in regions of interest. Structural equation models were used to examine evidence for pathways from stress and inflammation to neuronal atrophy. Model fit indices indicated good representation of stress, inflammation, and neurological data through the constructed models (CT model: robust RMSEA = 0.041, robust χ2 = 910.90; HCV model: robust RMSEA <0.001, robust χ2 = 40.95). Among inflammatory indices, only the SII was positively associated with hair cortisol as one indicator of chronic stress (β = 0.18, p < 0.05). Direct and indirect pathways from chronic stress and systemic inflammation to cortical thickness or hippocampal volume were non-significant. In exploratory analysis, the SII was inversely related to mean cortical thickness. Our results emphasize the importance of considering the multidimensionality of systemic inflammation and chronic stress, with various indicators that may represent different aspects of the systemic reaction. We conclude that inflammation and glucocorticoid-mediated neurodegeneration indicated by IL-6 and hs-CRP and HCC and HEC may only emerge during advanced ageing and disorder processes, still the SII could be a promising candidate for detecting associations between inflammation and neurodegeneration in younger and healthy samples. Future work should examine these pathways in prospective longitudinal designs, for which the present investigation serves as a baseline.

Irritable Bowel Syndrome Is Associated With Brain Health by Neuroimaging, Behavioral, Biochemical, and Genetic Analyses

BACKGROUND

Irritable bowel syndrome (IBS) interacts with psychopathology in a complex way; however, little is known about the underlying brain, biochemical, and genetic mechanisms.

METHODS

To clarify the phenotypic and genetic associations between IBS and brain health, we performed a comprehensive retrospective cohort study on a large population. Our study included 171,104 participants from the UK Biobank who underwent a thorough assessment of IBS, with the majority also providing neuroimaging, behavioral, biochemical, and genetic information. Multistage linked analyses were conducted, including phenome-wide association analysis, polygenic risk score calculation, and 2-sample Mendelian randomization analysis.

RESULTS

The phenome-wide association analysis showed that IBS was linked to brain health problems, including anxiety and depression, and poor cognitive performance. Significantly lower brain volumes associated with more severe IBS were found in key areas related to emotional regulation and higher-order cognition, including the medial orbitofrontal cortex/ventromedial prefrontal cortex, anterior insula, anterior and mid-cingulate cortices, dorsolateral prefrontal cortex, and hippocampus. Higher triglycerides, lower high-intensity lipoprotein, and lower platelets were also related (p < 1 × 10-10) to more severe IBS. Finally, Mendelian randomization analyses demonstrated potential causal relationships between IBS and brain health and indicated possible mediating effects of dyslipidemia and inflammation.

CONCLUSIONS

For the first time, this study provides a comprehensive understanding of the relationship between IBS and brain health phenotypes, integrating perspectives from neuroimaging, behavioral performance, biochemical factors, and genetics, which is of great significance for clinical applications to potentially address brain health impairments in patients with IBS.

Causal relationships between blood lipids and major psychiatric disorders: Univariable and multivariable mendelian randomization analysis

BACKGROUND

Whether the positive associations of blood lipids with psychiatric disorders are causal is uncertain. We conducted this two-sample Mendelian randomization (MR) analysis to comprehensively investigate associations of blood lipids with psychiatric disorders.

METHODS

Univariable and multivariable models were established for MR analyses. Inverse variance-weighted (IVW) MR was employed as the main approach; weighted median and MR-Egger were used as sensitivity analysis methods. The possibility of violating MR assumptions was evaluated utilizing several sensitivity analyses, including heterogeneity statistics, horizontal pleiotropy statistics, single SNP analysis, leave-one-out analysis and MR-PRESSO analysis. As instrumental variables, we screened 362 independent single-nucleotide polymorphisms (SNP) related to blood lipids from a recent genome-wide association study involving 76,627 individuals of European ancestry, with a genome-wide significance level of p < 5 × 10- 8. Summary-level information for the six psychiatric disorders was extracted from Psychiatric Genomics Consortium and Alzheimer Disease Genetics Consortium.

RESULTS

We observed eight significant associations in univariable MR analysis, four of which were corroborated by multivariable MR (MVMR) analysis modified for the other three lipid traits: high-density lipoprotein cholesterol (HDL-C) level with the risk of PTSD (OR = 0.91, 95% CI = 0.85-0.97, p = 0.002) and AD (OR = 0.79, 95% CI = 0.71-0.88, p < 0.001) and triglycerides (TG) level with the risk of MDD (OR = 1.02, 95% CI = 1.003-1.03, p = 0.01) and panic disorder (OR = 0.83, 95% CI = 0.74-0.92, p < 0.001). In addition, four associations were not significant in MVMR analysis after adjustment for three lipid traits: total cholesterol (TC) level with the risk of PTSD, low-density lipoprotein cholesterol (LDL-C) level with the risk of MDD and AD and TG level with the risk of AD.

CONCLUSIONS

Our results show that blood lipids and psychiatric disorders may be related in a causal manner. This shows that abnormal blood lipid levels may act as reliable biomarker of psychiatric disorders and as suitable targets for their prevention and treatment.

The effects of cytomegalovirus on brain structure following sport-related concussion

The neurotrophic herpes virus cytomegalovirus is a known cause of neuropathology in utero and in immunocompromised populations. Cytomegalovirus is reactivated by stress and inflammation, possibly explaining the emerging evidence linking it to subtle brain changes in the context of more minor disturbances of immune function. Even mild forms of traumatic brain injury, including sport-related concussion, are major physiological stressors that produce neuroinflammation. In theory, concussion could predispose to the reactivation of cytomegalovirus and amplify the effects of physical injury on brain structure. However, to our knowledge this hypothesis remains untested. This study evaluated the effect of cytomegalovirus serostatus on white and grey matter structure in a prospective study of athletes with concussion and matched contact-sport controls. Athletes who sustained concussion (n = 88) completed MRI at 1, 8, 15 and 45 days post-injury; matched uninjured athletes (n = 73) completed similar visits. Cytomegalovirus serostatus was determined by measuring serum IgG antibodies (n = 30 concussed athletes and n = 21 controls were seropositive). Inverse probability of treatment weighting was used to adjust for confounding factors between athletes with and without cytomegalovirus. White matter microstructure was assessed using diffusion kurtosis imaging metrics in regions previously shown to be sensitive to concussion. T1-weighted images were used to quantify mean cortical thickness and total surface area. Concussion-related symptoms, psychological distress, and serum concentration of C-reactive protein at 1 day post-injury were included as exploratory outcomes. Planned contrasts compared the effects of cytomegalovirus seropositivity in athletes with concussion and controls, separately. There was a significant effect of cytomegalovirus on axial and radial kurtosis in athletes with concussion but not controls. Cytomegalovirus positive athletes with concussion showed greater axial (P = 0.007, d = 0.44) and radial (P = 0.010, d = 0.41) kurtosis than cytomegalovirus negative athletes with concussion. Similarly, there was a significant association of cytomegalovirus with cortical thickness in athletes with concussion but not controls. Cytomegalovirus positive athletes with concussion had reduced mean cortical thickness of the right hemisphere (P = 0.009, d = 0.42) compared with cytomegalovirus negative athletes with concussion and showed a similar trend for the left hemisphere (P = 0.036, d = 0.33). There was no significant effect of cytomegalovirus on kurtosis fractional anisotropy, surface area, symptoms and C-reactive protein. The results raise the possibility that cytomegalovirus infection contributes to structural brain abnormalities in the aftermath of concussion perhaps via an amplification of concussion-associated neuroinflammation. More work is needed to identify the biological pathways underlying this process and to clarify the clinical relevance of this putative viral effect.

Autism Spectrum Disorder: A Neuro-Immunometabolic Hypothesis of the Developmental Origins

Fetal neuroinflammation and prenatal stress (PS) may contribute to lifelong neurological disabilities. Astrocytes and microglia, among the brain's non-neuronal "glia" cell populations, play a pivotal role in neurodevelopment and predisposition to and initiation of disease throughout lifespan. One of the most common neurodevelopmental disorders manifesting between 1-4 years of age is the autism spectrum disorder (ASD). A pathological glial-neuronal interplay is thought to increase the risk for clinical manifestation of ASD in at-risk children, but the mechanisms remain poorly understood, and integrative, multi-scale models are needed. We propose a model that integrates the data across the scales of physiological organization, from genome to phenotype, and provides a foundation to explain the disparate findings on the genomic level. We hypothesize that via gene-environment interactions, fetal neuroinflammation and PS may reprogram glial immunometabolic phenotypes that impact neurodevelopment and neurobehavior. Drawing on genomic data from the recently published series of ovine and rodent glial transcriptome analyses with fetuses exposed to neuroinflammation or PS, we conducted an analysis on the Simons Foundation Autism Research Initiative (SFARI) Gene database. We confirmed 21 gene hits. Using unsupervised statistical network analysis, we then identified six clusters of probable protein-protein interactions mapping onto the immunometabolic and stress response networks and epigenetic memory. These findings support our hypothesis. We discuss the implications for ASD etiology, early detection, and novel therapeutic approaches. We conclude with delineation of the next steps to verify our model on the individual gene level in an assumption-free manner. The proposed model is of interest for the multidisciplinary community of stakeholders engaged in ASD research, the development of novel pharmacological and non-pharmacological treatments, early prevention, and detection as well as for policy makers.

Potential novel biomarkers in small intestine for obesity/obesity resistance revealed by multi-omics analysis

Background

Although obesity is caused by different factors, individual susceptibility to obesity differs among people under the same circumstances. The microbiota in the caecum or fresh faeces and metabolites in blood or urine contribute to obesity resistance; however, the microbiota or metabolites in the small intestine have not been extensively studied.

Methods

To investigate the relationship between the microbiota or metabolites in the small intestine and susceptibility to obesity, eighty-eight male C57BL/6 mice were fed a high-fat diet (HFD) for 8 weeks to establish two models of obesity and obesity resistance. For further study, six mice were chosen from among the obesity models, and twelve mice were randomly chosen from among the obesity resistance models. After fasting plasma glucose and behavioural testing, the mice were fed in single cages for another 4 weeks to observe their weight and food intake. All mice were sacrificed at 20 weeks of age. Serum ALT, AST, HDL, LDL, TG and TC levels were measured using an automatic biochemical analyser. The microbiota and metabolites in the small intestine contents were analysed using 16 S sequencing and an ultrahigh-performance liquid chromatographic system, respectively. Transcripts in the jejunum were evaluated using full-length transcriptome sequencing and verified by qPCR.

Results

The results showed that HFD induced depression and anxiety behaviours and higher fasting plasma glucose, ALT, AST, HDL, LDL, TG and TC levels in the obese mice; however, these levels were improved in obese resistance mice. The correlation analysis showed that the phosphatidylcholine, TG, and phosphatidylethanolamine levels were higher in obese mice and correlated positively with intestinal microflora (Desulfovibrio and Gemella) and the Cxcl10 gene. A higher abundance of Clostridium_sensu_stricto_1 in obesity-resistant mice correlated negatively with the metabolite contents (neuromedin N and enkephalin L) and Pck1 gene expression and correlated positively with certain metabolites (5-hydroxy-L-tryptophan, cinnamyl alcohol and 1 H-indole-3-acetamide) and genes expression (Gdf15, Igfbp6 and Spp1).

Conclusion

Clostridium_sensu_stricto_1, neuromedin N, enkephalin L, Pck1, 5-hydroxy-L-tryptophan, Cxcl10 and cinnamyl alcohol may be novel biomarkers in the small intestine for obesity/obesity resistance. These might be helpful for obesity prevention or for treating obese patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-022-01711-0.

C-Reactive protein and the kynurenic acid to quinolinic acid ratio are independently associated with white matter integrity in major depressive disorder

Kynurenic acid (KynA) and quinolinic acid (QA) are neuroactive kynurenine pathway (KP) metabolites that have neuroprotective and neurotoxic properties, respectively. At least partly as a result of immune activation, the ratio of KynA to QA in the blood is reduced in major depressive disorder (MDD) and has been reported to be positively correlated with gray matter volume in depression. This study examined whether the inflammatory mediator, C-reactive protein (CRP) and the putative neuroprotective index, KynA/QA, were associated with white matter integrity in MDD, and secondly, whether any such associations were independent of each other or whether the effect of CRP was mediated by KynA/QA. One hundred and sixty-six participants in the Tulsa 1000 study with a DSM-V diagnosis of MDD completed diffusion tensor imaging and provided a serum sample for the quantification of CRP, KynA, and QA. Correlational tractography was performed using DSI Studio to map the specific white matter pathways that correlated with CRP and KynA/QA. CRP was negatively related to KynA/QA (standardized beta coefficient, SBC = -0.35 with standard error, Std.E = 0.13, p < 0.01) after controlling for nine possible confounders, i.e., age, sex, body mass index (BMI), medication status, lifetime alcohol use, severity of depression, severity of anxiety, length of illness, and smoking status. Higher concentrations of CRP were associated with decreased white matter integrity (fractional anisotropy, FA) of the bilateral cingulum and fornix after controlling for the nine potential confounders (SBC = -0.43, Std.E = 0.13, p = 0.002). Greater serum KynA/QA was associated with increased white matter integrity of the bilateral fornix, bilateral superior thalamic radiations, corpus callosum, and bilateral cingulum bundles after controlling for the same possible confounders (SBC = 0.26, Std.E = 0.09, p = 0.005). The relationship between CRP and FA was not mediated by KynA/QA. Exploratory analyses also showed that KynA/QA but not CRP was associated with self-reported positive affect, attentiveness, and fatigue measured with the PANASX (SBCs = 0.17-0.23). Taken together, these results are consistent with the hypothesis that within a subgroup of MDD patients, a higher level of systemic inflammation alters the balance of KP metabolism but also raise the possibility that CRP and neuroactive KP metabolites represent independent molecular mechanisms underlying white matter alterations in MDD.

Evidence of genetic overlap and causal relationships between blood-based biochemical traits and human cortical anatomy

Psychiatric disorders such as schizophrenia are commonly associated with structural brain alterations affecting the cortex. Recent genetic evidence suggests circulating metabolites and other biochemical traits play a causal role in many psychiatric disorders which could be mediated by changes in the cerebral cortex. Here, we leveraged publicly available genome-wide association study data to explore shared genetic architecture and evidence for causal relationships between a panel of 50 biochemical traits and measures of cortical thickness and surface area. Linkage disequilibrium score regression identified 191 genetically correlated biochemical-cortical trait pairings, with consistent representation of blood cell counts and other biomarkers such as C-reactive protein (CRP), haemoglobin and calcium. Spatially organised patterns of genetic correlation were additionally uncovered upon clustering of region-specific correlation profiles. Interestingly, by employing latent causal variable models, we found strong evidence suggesting CRP and vitamin D exert causal effects on region-specific cortical thickness, with univariable and multivariable Mendelian randomization further supporting a negative causal relationship between serum CRP levels and thickness of the lingual region. Our findings suggest a subset of biochemical traits exhibit shared genetic architecture and potentially causal relationships with cortical structure in functionally distinct regions, which may contribute to alteration of cortical structure in psychiatric disorders.

The association between clinical and biological characteristics of depression and structural brain alterations

BACKGROUND

Structural brain alterations are observed in major depressive disorder (MDD). However, MDD is a highly heterogeneous disorder and specific clinical or biological characteristics of depression might relate to specific structural brain alterations. Clinical symptom subtypes of depression, as well as immuno-metabolic dysregulation associated with subtypes of depression, have been associated with brain alterations. Therefore, we examined if specific clinical and biological characteristics of depression show different brain alterations compared to overall depression.

METHOD

Individuals with and without depressive and/or anxiety disorders from the Netherlands Study of Depression and Anxiety (NESDA) (328 participants from three timepoints leading to 541 observations) and the Mood Treatment with Antidepressants or Running (MOTAR) study (123 baseline participants) were included. Symptom profiles (atypical energy-related profile, melancholic profile and depression severity) and biological indices (inflammatory, metabolic syndrome, and immuno-metabolic indices) were created. The associations of the clinical and biological profiles with depression-related structural brain measures (anterior cingulate cortex [ACC], orbitofrontal cortex, insula, and nucleus accumbens) were examined dimensionally in both studies and meta-analysed.

RESULTS

Depression severity was negatively associated with rostral ACC thickness (B = -0.55, p_FDR = 0.03), and melancholic symptoms were negatively associated with caudal ACC thickness (B = -0.42, p_FDR = 0.03). The atypical energy-related symptom profile and immuno-metabolic indices did not show a consistent association with structural brain measures across studies.

CONCLUSION

Overall depression- and melancholic symptom severity showed a dose-response relationship with reduced ACC thickness. No associations between immuno-metabolic dysregulation and structural brain alterations were found, suggesting that although both are associated with depression, distinct mechanisms may be involved.

Associations between BMI and brain structures involved in food intake regulation in first-episode schizophrenia spectrum disorders and healthy controls

Structural brain differences have been described in first-episode schizophrenia spectrum disorders (FES), and often overlap with those evident in the metabolic syndrome (MetS). We examined the associations between body mass index (BMI) and brain structures involved in food intake regulation in minimally treated FES patients (n = 117) compared to healthy controls (n = 117). The effects of FES diagnosis, BMI and their interactions on our selected prefrontal cortical thickness and subcortical gray matter volume regions of interest (ROIs) were investigated with hierarchical multivariate regressions, followed by post-hoc regressions for the individual ROIs. In a secondary analysis, we examined the relationships of other MetS risk factors and psychopathology with the brain ROIs. Both illness and BMI significantly predicted the grouped prefrontal cortical thickness ROIs, whereas only BMI predicted the grouped subcortical volume ROIs. For the individual ROIs, schizophrenia diagnosis predicted thinner left and right frontal pole and right lateral OFC thickness, and increased BMI predicted thinner left and right caudal ACC thickness. There were no significant main or interaction effects for diagnosis and BMI on any of the individual subcortical volume ROIs. Secondary analyses suggest associations between several brain ROIs and individual MetS risk factors, but not with psychopathology. Our findings indicate differential, independent effects for FES diagnosis and BMI on brain structures. Limited evidence suggests that the BMI effects are more prominent in FES. Exploratory analyses suggest associations between other MetS risk factors and some brain ROIs.

The effect of triglycerides in the associations between physical activity, sedentary behavior and depression: An interaction and mediation analysis

BACKGROUND

Previous studies reported that there were associations between physical activity (PA), sedentary behavior (SB), triglycerides (TG) and depression. However, it is unclear whether there is an interaction and/or mediation effect of TG in the associations between PA, SB and depression. This study was to explore the effects of TG in the associations between PA, SB and depression, respectively.

METHODS

Our study included 7,728 adults (aged ≥20 years) participating in the 2009-2018 National Health and Nutrition Examination Survey (NHANES), which was a nationally representative survey. With higher TG as a mediator, a four-way decomposition method was used to decompose the total effects of insufficient PA and prolonged SB on depression, respectively.

RESULTS

There were statistically significant associations between moderate-to-vigorous recreational activity (MVRA), SB, TG and depression (all P < 0.05), respectively. With higher TG as a mediator, there were interaction and mediation effects in the association between SB and depression, and the excess relative risk (95% CI) of reference interaction effect (INT_ref) and the total mediation effect were 0.15(0.01,0.29) and 0.03(0.00,0.06), respectively. While insufficient MVRA attributed a proportion of 80.42% for the controlled direct effect (CDE) and 6.28% for total mediation effect. In addition, similar findings were observed in those with hypertension, overweight/obesity, dyslipidemia, and metabolic syndromes.

LIMITATION

This was a cross-sectional study, and the ability to make causal inference was limited.

CONCLUSION

The controlled direct effect of MVRA, the mediation of TG, and the interaction between SB and TG played the vital roles in increasing the risk of depression.

The Neurocircuitry of Posttraumatic Stress Disorder and Major Depression: Insights Into Overlapping and Distinct Circuit Dysfunction-A Tribute to Ron Duman

The neurocircuitry that contributes to the pathophysiology of posttraumatic stress disorder and major depressive disorder, psychiatric conditions that exhibit a high degree of comorbidity, likely involves both overlapping and unique structural and functional changes within multiple limbic brain regions. In this review, we discuss neurobiological alterations that are associated with posttraumatic stress disorder and major depressive disorder and highlight both similarities and differences that may exist between these disorders to argue for the existence of a shared neurobiology. We highlight the key contributions based on preclinical studies, emerging from the late Professor Ronald Duman's research, that have shaped our understanding of the neurocircuitry that contributes to both the etiopathology and treatment of major depressive disorder and posttraumatic stress disorder.

Fifteen years of NESDA Neuroimaging: An overview of results related to clinical profile and bio-social risk factors of major depressive disorder and common anxiety disorders

The longitudinal Netherlands Study of Depression and Anxiety (NESDA) Neuroimaging study was set up in 2003 to investigate whether neuroanatomical and functional abnormalities during tasks of primary emotional processing, executive planning and memory formation, and intrinsic brain connectivity are i) shared by individuals with major depressive disorder (MDD) and common anxiety disorders; and ii) characterized by symptomatology-specific abnormalities. Furthermore, questions related to individual variations in vulnerability for onset, comorbidity, and longitudinal course could be investigated. Between 2005 and 2007, 233 individuals fulfilling a diagnosis of MDD, panic disorder, social anxiety disorder and/or generalized anxiety disorder and 68 healthy controls aging between 18 and 57 were invited from the NESDA main sample (n = 2981). An emotional faces processing task, an emotional word-encoding task, and an executive planning task were administered during 3T BOLD-fMRI acquisitions. In addition, resting state BOLD-fMRI was acquired and T1-weighted structural imaging was performed. All participants were invited to participate in the two-year and nine-year follow-up MRI measurement. Fifteen years of NESDA Neuroimaging demonstrated common morphological and neurocognitive abnormalities across individuals with depression and anxiety disorders. It however provided limited support for the idea of more extensive abnormalities in patients suffering from both depression and anxiety, despite their worse prognosis. Risk factors including childhood maltreatment and specific risk genes had an emotion processing modulating effect, apparently stronger than effects of diagnostic labels. Furthermore, brain imaging data, especially during emotion processing seemed valuable for predicting the long-term course of affective disorders, outperforming prediction based on clinical information alone.

Elevated lipids are associated with reduced regional brain structure in youth with bipolar disorder

OBJECTIVE

Abnormal blood lipid levels are common in bipolar disorder (BD) and correlate with mood symptoms and neurocognition. However, studies have not examined the lipid-brain structure association in BD or youth.

METHODS

This study examined low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C), triglycerides, and total cholesterol (TC) levels in relation to brain structure utilizing T1-weighted images, among participants ages 13-20 with BD (n = 55) and healthy controls (HC; n = 47). General linear models investigated group differences in the association of lipids with anterior cingulate cortex (ACC), hippocampus, and inferior parietal lobe structure, controlling for age, sex, body mass index, and intracranial volume. For significant associations, post hoc within-group analyses were undertaken. Exploratory vertex-wise analyses further investigated group differences in the lipid-brain structure association.

RESULTS

There were significant group differences in the association of LDL-C (β = -0.29 p = 0.001), and TC (β = -0.21 p = 0.016), with hippocampal volume, and triglycerides with ACC volume (β = -0.25 p = 0.01) and area (β = -0.26 p = 0.004). Elevated lipids were associated with smaller brain structure to a significantly greater extent in BD vs HC. Post hoc analyses revealed that elevated LDL-C (β = -0.27 p = 0.007) and reduced HDL-C (β = 0.24 p = 0.01) were associated with smaller hippocampal volume in the BD group. Exclusion of BD second-generation antipsychotic users did not alter these results. Vertex-wise analyses further showed that elevated lipids were associated with smaller brain structure to a significantly greater extent in BD vs HC, across the cortex.

CONCLUSION

Elevated lipids are associated with smaller brain structure in BD. Research evaluating lipid-brain structure associations prospectively and whether lipid optimization has salutary effects on brain structure is necessary.

Variation of HbA1c affects cognition and white matter microstructure in healthy, young adults

The metabolic serum marker HbA1c has been associated with both impaired cognitive performance and altered white matter integrity in patients suffering from diabetes mellitus. However, it remains unclear if higher levels of HbA1c might also affect brain structure and function in healthy subjects. With the present study we therefore aimed to investigate the relationship between HbA1c levels and cognitive performance as well as white matter microstructure in healthy, young adults. To address this question, associations between HbA1c and cognitive measures (NIH Cognition Toolbox) as well as DTI-derived imaging measures of white matter microstructure were investigated in a publicly available sample of healthy, young adults as part of the Humane Connectome Project (n = 1206, mean age = 28.8 years, 45.5% male). We found that HbA1c levels (range 4.1-6.3%) were significantly inversely correlated with measures of cognitive performance. Higher HbA1c levels were associated with significant and widespread reductions in fractional anisotropy (FA) controlling for age, sex, body mass index, ethnicity, and education. FA reductions were furthermore found to covary with measures of cognitive performance. The same pattern of results could be observed in analyses restricted to participants with HBA1c levels below 5.7%. The present study demonstrates that low-grade HbA1c variation below diagnostic threshold for diabetes is related to both cognitive performance and white matter integrity in healthy, young adults. These findings highlight the detrimental impact of metabolic risk factors on brain physiology and underscore the importance of intensified preventive measures independent of the currently applied diagnostic HbA1c cutoff scores.

Associations between depression, lifestyle and brain structure: A longitudinal MRI study

BACKGROUND

Depression has been associated with decreased regional grey matter volume, which might partly be explained by an unhealthier lifestyle in depressed individuals which has been ignored by most earlier studies. Also, the longitudinal nature of depression, lifestyle and brain structure associations is largely unknown. This study investigates the relationship of depression and lifestyle with brain structure cross-sectionally and longitudinally over up to 9 years.

METHODS

We used longitudinal structural MRI data of persons with depression and/or anxiety disorders and controls (N_{unique participants} = 347, N_observations = 609). Cortical thickness of medial orbitofrontal cortex (mOFC), rostral anterior cingulate cortex (rACC) and hippocampal volume were derived using FreeSurfer. Using Generalized Estimating Equations, we investigated associations of depression and lifestyle (Body mass index (BMI), smoking, alcohol consumption, physical activity and sleep duration) with brain structure and change in brain structure over 2 (n = 179) and 9 years (n = 82).

RESULTS

Depression status (B = -.053, p = .002) and severity (B = -.002, p = .002) were negatively associated with rACC thickness. mOFC thickness was negatively associated with BMI (B = -.004, p < .001) and positively with moderate alcohol consumption (B = .030, p = .009). All associations were independent of each other. No associations were observed between (change in) depression, disease burden or lifestyle factors with brain change over time.

CONCLUSIONS

Depressive symptoms and diagnosis were independently associated with thinner rACC, BMI with thinner mOFC, and moderate alcohol consumption with thicker mOFC. No longitudinal associations were observed, suggesting that regional grey matter alterations are a long-term consequence or vulnerability indicator for depression but not dynamically or progressively related to depression course trajectory.

Inflammation and depressive phenotypes: evidence from medical records from over 12 000 patients and brain morphology

BACKGROUND

Preclinical and human studies suggest an association between chronic inflammation and the development of depressive behaviors. This is proposed to occur through downstream effects of inflammatory cytokines on neuroplasticity, neurogenesis and neurotransmitter function, although the neural correlates remain poorly understood in humans.

METHODS

In Study 1, structural magnetic resonance imaging and serum inflammatory cytokine data were analyzed from 53 psychiatrically healthy female participants. Correlational analyses were conducted between interleukin-6 (IL-6) and volume in a priori regions implicated in the pathophysiology of major depressive disorder (MDD). In Study 2, medical data [including serum inflammatory acute phase reactants (C-reactive protein)] were analyzed for 12 589 participants. Participants were classified as having (n = 2541) v. not having (n = 10 048) probable lifetime MDD using phenotypes derived using machine-learning approaches. Non-parametric analyses compared inflammation between groups, whereas regression analyses probed whether inflammation predicted probable MDD classification while accounting for other variables.

RESULTS

In Study 1, significant negative correlations emerged between IL-6 and hippocampal, caudate, putamen and amygdalar volume. In Study 2, the MDD group showed a higher probability of elevated inflammation than the non-MDD group. Moreover, elevated inflammation was a significant predictor of probable MDD classification.

CONCLUSIONS

Findings indicate that inflammation is cross-sectionally related to reduced volume in brain regions implicated in MDD phenotypes among a sample of psychiatrically healthy women, and is associated with the presence of probable MDD in a large clinical dataset. Future investigations may identify specific inflammatory markers predicting first MDD onset.

Large-scale evidence for an association between low-grade peripheral inflammation and brain structural alterations in major depression in the BiDirect study

BACKGROUND

Preliminary research suggests that major depressive disorder (MDD) is associated with structural alterations in the brain; as well as with low-grade peripheral inflammation. However, even though a link between inflammatory processes and altered brain structural integrity has been purported by experimental research, well-powered studies to confirm this hypothesis in patients with MDD have been lacking. We aimed to investigate the potential association between structural brain alterations and low-grade inflammation as interrelated biological correlates of MDD.

METHODS

In this cross-sectional study, 514 patients with MDD and 359 healthy controls underwent structural MRI. We used voxel-based morphometry to study local differences in grey matter volume. We also assessed serum levels of high-sensitivity C-reactive protein (hsCRP) in each participant.

RESULTS

Compared with healthy controls (age [mean ± standard deviation] 52.57 ± 7.94 yr; 50% male), patients with MDD (49.14 ± 7.28 yr, 39% male) exhibited significantly increased hsCRP levels (Z = −5.562, p < 0.001) and significantly decreased grey matter volume in the prefrontal cortex and the insula. Prefrontal grey matter volume reductions were significantly associated with higher hsCRP levels in patients with MDD (x = 50, y = 50, z = 8; t1,501 = 5.15; k = 92; pFWE < 0.001). In the MDD sample, the significant negative association between hsCRP and grey matter appeared independent of age, sex, body mass index, current smoking status, antidepressant load, hospitalization and medical comorbidities.

LIMITATIONS

This study had a cross-sectional design.

CONCLUSION

The present study highlights the role of reduced grey matter volume and low-grade peripheral inflammation as interrelated biological correlates of MDD. The reported inverse association between peripheral low-grade inflammation and brain structural integrity in patients with MDD translates current knowledge from experimental studies to the bedside.

Interplay between pro-inflammatory cytokines, childhood trauma, and executive function in depressed adolescents

BACKGROUND

Pro-inflammatory cytokines have been linked to depression, early childhood trauma, and impairment in executive function in adults. Whether these links are present during adolescence, a time when vulnerability to depression is heightened, a point more proximal to childhood trauma, and a critical period of brain development, is not well understood.

METHOD

Serum levels of interleukin (IL)-6, IL-1β, and tumor necrosis factor alpha (TNF-α) were measured in 70 adolescents aged 12-17, including 40 with a DSM-IV depressive disorder (DEP), a sub-set (n = 22) of whom reported a history of childhood trauma (DEP-T), and 30 healthy controls (HCs). Participants completed performance-based (Parametric Go/No-Go Task) and observer-rated (Behavior Rating Inventory of Executive Function) measures of executive function. Procedures were conducted at a subspecialty clinic (Dec 2015-June 2017).

RESULTS

IL-6 was elevated in DEP and DEP-T adolescents compared to controls (p = .014) and TNF-α was elevated in DEP participants only (p = .040) compared to controls, whereas no group differences were found in IL-1β (p = .829). Additionally, DEP-T participants demonstrated relative deficits in performance-based (p = .044) and observer-rated inhibitory control (p = .049) compared to controls. Across the whole sample, TNF-α was associated with performance-based (r = -0.25, p = .039) and observer-rated (r = 0.32, p = .009) inhibitory control deficits. In subgroup analyses, TNF-α was associated with increased observer-rated inhibitory deficits in DEP, and at the trend level, with reduced inhibitory control performance in DEP-T.

CONCLUSIONS

The current results suggest that inflammation may be a marker of disease processes in adolescent depression. Though longitudinal studies are needed, depressed adolescents with childhood trauma exposure appear to constitute a uniquely vulnerable group in terms of objective risk for executive dysfunction. Immune dysregulation may partly contribute to this risk.

Early-Life Adversity, but Not Suicide, Is Associated With Less Prefrontal Cortex Gray Matter in Adulthood

BACKGROUND

Suicide and major depression are prevalent in individuals reporting early-life adversity. Prefrontal cortex volume is reduced by stress acutely and progressively, and changes in neuron and glia density are reported in depressed suicide decedents. We previously found reduced neurotrophic factor brain-derived neurotrophic factor in suicide decedents and with early-life adversity, and we sought to determine whether cortex thickness or neuron or glia density in the dorsolateral prefrontal and anterior cingulate cortex are associated with early-life adversity or suicide.

METHODS

A total of 52 brains, constituting 13 quadruplets of nonpsychiatric controls and major depressive disorder suicide decedents with and without early-life adversity, were matched for age, sex, race, and postmortem interval. Brains were collected at autopsy and frozen, and dorsolateral prefrontal cortex and anterior cingulate cortex were later dissected, postfixed, and sectioned. Sections were immunostained for neuron-specific nuclear protein (NeuN) to label neurons and counterstained with thionin to stain glial cell nuclei. Cortex thickness, neuron and glial density, and neuron volume were measured by stereology.

RESULTS

Cortical thickness was 6% less with early-life adversity in dorsolateral prefrontal cortex and 12% less in anterior cingulate cortex (P < .05), but not in depressed suicide decedents in either region. Neuron density was not different in early-life adversity or with suicide, but glial density was 17% greater with early-life adversity in dorsolateral prefrontal cortex and 15% greater in anterior cingulate cortex, but not in suicides. Neuron volume was not different with early-life adversity or suicide.

CONCLUSIONS

Reported early-life adversity, but not the stress associated with suicide, is associated with thinner prefrontal cortex and greater glia density in adulthood. Early-life adversity may alter normal neurodevelopment and contribute to suicide risk.

The Impact of Stress and Major Depressive Disorder on Hippocampal and Medial Prefrontal Cortex Morphology

Volumetric reductions in the hippocampus and medial prefrontal cortex (mPFC) are among the most well-documented neural abnormalities in major depressive disorder (MDD). Hippocampal and mPFC structural reductions have been specifically tied to MDD illness progression markers, including greater number of major depressive episodes (MDEs), longer illness duration, and nonremission/treatment resistance. Chronic stress plays a critical role in the development of hippocampal and mPFC deficits, with some studies suggesting that these deficits occur irrespective of MDE occurrence. However, preclinical and human research also points to other stress-mediated neurotoxic processes, including enhanced inflammation and neurotransmitter disturbances, which may require the presence of an MDE and contribute to further brain structural decline as the illness advances. Specifically, hypothalamic-pituitary-adrenal axis dysfunction, enhanced inflammation and oxidative stress, and neurotransmitter abnormalities (e.g., serotonin, glutamate, gamma-aminobutyric acid) likely interact to facilitate illness progression in MDD. Congruent with stress sensitization models of MDD, with each consecutive MDE it may take lower levels of stress to trigger these neurotoxic pathways, leading to more pronounced brain volumetric reductions. Given that stress and MDD have overlapping and distinct influences on neurobiological pathways implicated in hippocampal and mPFC structural decline, further work is needed to clarify which precise mechanisms ultimately contribute to MDD development and maintenance.

Serum Markers of Inflammation Mediate the Positive Association Between Neuroticism and Depression

Background: The personality trait neuroticism has been implicated in a poor response to stress, may relate to increased concentrations of cytokines and the development of depression. Inflammatory mechanisms may also be associated with the onset, severity and symptoms of depression. Both are related to poor antidepressant treatment outcome. Therefore, mediators of inflammation may bridge the relationship between neuroticism and depression. Methods: To disentangle these interrelationships, the associations between neuroticism (according to NEO-PIR-N), depressive symptoms (BDI-II scores) and serum levels of hsCRP, TNF-α, IFN-γ, IL-2, IL-4, IL-5, IL-10, IL-12, IL-13, GM-CSF were investigated in a group of 212 participants, consisting of 37 depressed and 175 non-depressed subjects. A mediation model was used to investigate whether the impact of neuroticism on depressive symptoms may be mediated by cytokines. Results: Regression analyses revealed that IFN-γ, IL-5, and IL-12-levels, but none of the anti-inflammatory cytokines, were associated with the overall neuroticism score and several of the cytokines were related to the different facets of neuroticism. TNF-α, IFN-γ, IL-5, IL-12, and IL-13 were further related to the severity of depressive symptoms, as well as the somatic-affective and the cognitive dimensions of depression. Pro-inflammatory IFN-γ, IL-5 and IL-12 were identified as mediators of the positive prediction of depression severity by the degree of neuroticism. Conclusions: The current findings demonstrate that conditions related to long-term stress, such as depression and high neuroticism, are related to an up-regulation of inflammatory agents. Neuroticism may increase stress perception and, thus, increase the production of pro-inflammatory messenger molecules which are involved in the development of depression. This evidence may contribute to future anti-inflammatory interventions, particularly in subjects with high neuroticism who are at risk for developing depression. Furthermore, depressed patients with high neuroticism and cytokine levels may require early escalations in the intensity of treatment, along with additional therapeutic elements to increase the rate of treatment success.