Insulin resistance: Genetic associations with depression and cognition in population based cohorts

Association among obesity, insulin resistance, and depressive symptoms: a mediation analysis

BACKGROUND

The mechanistic role of insulin resistance(IR) between obesity and Depressive Symptoms has long been debated.

OBJECTIVE

This study aims to explore the relationship between BMI and Depressive Symptoms to investigate the mediating role of IR in this association.

METHODS

We rigorously selected data from the National Health and Nutrition Examination Survey (NHANES) from 2005 to 2018. Multivariate logistic regression analysis, Restricted cubic splines (RCS) and Subgroup analysis were employed to assess the correlation between obesity and Depressive Symptoms. Mediation analysis was conducted to examine the role of IR in the relationship between Overweight/obesity and Depressive Symptoms.

RESULTS

After strict exclusion, the final analysis included 12,744 participants. Multivariate logistic regression analysis indicated a significant association between obesity and Depressive Symptoms. Subgroup analysis revealed an interaction from lack of exercise and vigorous activity levels to the association between obesity and Depressive Symptoms in the physical activity group (P for interaction < 0.05); A significant interaction was found between BMI and smoking status (P for interaction < 0.05). BMI was found to have an S-shaped association with Depressive Symptoms, becoming positively correlated after reaching a turning point (BMI > 23.22 kg/m², p < 0.001). IR partially mediated the potential impact of overweight/obesity on Depressive Symptoms (IR: 54.13%, p = 0.018).

CONCLUSION

Our study confirms a significant association between obesity and Depressive Symptoms. IR partially mediates the association between overweight/obesity and Depressive Symptoms. Furthermore, appropriate physical exercise and smoking may reduce the risk of depressive symptoms.

Differential associations of somatic and cognitive-affective symptoms of depression with inflammation and insulin resistance: cross-sectional and longitudinal results from the Emotional Distress Sub-Study of the GRADE study

AIMS/HYPOTHESIS

Insulin resistance and inflammation are components of a biological framework that is hypothesised to be shared by type 2 diabetes and depression. However, depressive symptoms include a large heterogeneity of somatic and cognitive-affective symptoms, and this may obscure the associations within this biological framework. Cross-sectional and longitudinal data were used to disentangle the contributions of insulin resistance and inflammation to somatic and cognitive-affective symptoms of depression.

METHODS

This secondary analysis used data from the Emotional Distress Sub-Study of the GRADE trial. Insulin resistance and inflammation were assessed using the HOMA-IR estimation and high-sensitivity C-reactive protein (hsCRP) levels, respectively, at baseline and at the study visits at year 1 and year 3 (HOMA-IR) and every 6 months (hsCRP) for up to 3 years of follow-up. Depressive symptoms were assessed at baseline using the Patient Health Questionnaire (PHQ-8), and a total score as well as symptom cluster scores for cognitive-affective and somatic symptoms were calculated. For the cross-sectional analyses, linear regression analyses were performed, with inflammation and insulin resistance at baseline as dependent variables. For the longitudinal analyses, linear mixed-effect regression analyses were performed, with inflammation and insulin resistance at the various time points as dependent variables. In all analyses, depressive symptoms (total score and symptom cluster scores) were the independent variables, controlled for important demographic, anthropometric and metabolic confounders. For the analysis of insulin resistance (HOMA-IR), data from 1321 participants were analysed. For the analysis of inflammation (hsCRP), data from 1739 participants were analysed.

RESULTS

In cross-sectional analysis and after adjustment for potential confounders, a one-unit increase in PHQ-8 total score was significantly associated with a 0.8% increase in HOMA-IR (p=0.007), but not with hsCRP (0.6% increase, p=0.283). The somatic symptom score was associated with a 5.8% increase in HOMA-IR (p=0.004). Single-item analyses of depressive symptoms showed that fatigue (3.6% increase, p=0.002) and increased/decreased appetite (3.5% increase, p=0.009) were significantly associated with HOMA-IR cross-sectionally. The cognitive-affective symptom score was not significantly associated with HOMA-IR at baseline. In longitudinal analyses, a one-unit increase in PHQ-8 total score was significantly associated with a 0.8% increase in hsCRP over time (p=0.014), but not with HOMA-IR over time (0.1% decrease, p=0.564). Again, only the somatic symptom cluster was significantly associated with hsCRP over time (5.2% increase, p=0.017), while the cognitive-affective symptom score was not.

CONCLUSION/INTERPRETATION

The results highlight the associations of depressive symptoms with markers of inflammation and insulin resistance, both cross-sectionally and longitudinally, in individuals with type 2 diabetes. In particular, somatic symptoms of depression appear to be the driver of these associations, even after controlling for concomitant conditions, with a potential role for fatigue and issues with appetite.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01794143.

Genetically predicted brain cortical structure mediates the causality between insulin resistance and cognitive impairment

Background

Insulin resistance is tightly related to cognition; however, the causal association between them remains a matter of debate. Our investigation aims to establish the causal relationship and direction between insulin resistance and cognition, while also quantifying the mediating role of brain cortical structure in this association.

Methods

The publicly available data sources for insulin resistance (fasting insulin, homeostasis model assessment beta-cell function and homeostasis model assessment insulin resistance, proinsulin), brain cortical structure, and cognitive phenotypes (visual memory, reaction time) were obtained from the MAGIC, ENIGMA, and UK Biobank datasets, respectively. We first conducted a bidirectional two-sample Mendelian randomization (MR) analysis to examine the susceptibility of insulin resistance on cognitive phenotypes. Additionally, we applied a two-step MR to assess the mediating role of cortical surficial area and thickness in the pathway from insulin resistance to cognitive impairment. The primary Inverse-variance weighted, accompanied by robust sensitivity analysis, was implemented to explore and verify our findings. The reverse MR analysis was also performed to evaluate the causal effect of cognition on insulin resistance and brain cortical structure.

Results

This study identified genetically determined elevated level of proinsulin increased reaction time (beta=0.03, 95% confidence interval [95%CI]=0.01 to 0.05, p=0.005), while decreasing the surface area of rostral middle frontal (beta=-49.28, 95%CI=-86.30 to -12.27, p=0.009). The surface area of the rostral middle frontal mediated 20.97% (95%CI=1.44% to 40.49%) of the total effect of proinsulin on reaction time. No evidence of heterogeneity, pleiotropy, or reverse causality was observed.

Conclusions

Briefly, our study noticed that elevated level of insulin resistance adversely affected cognition, with a partial mediation effect through alterations in brain cortical structure.

Efficacy and Safety of Antidiabetic Agents for Major Depressive Disorder and Bipolar Depression: A Meta-Analysis of Randomized, Double-Blind, Placebo-Controlled Trials

BACKGROUND

This meta-analysis aimed to determine the efficacy and safety of antidiabetic agents in the treatment of major depressive disorder and bipolar depression.

METHODS

Randomized controlled trials (RCTs) of antidiabetic agents in major depressive disorder or bipolar depression were searched in three electronic databases and three clinical trial registry websites from their inception up to October 2023. The differences in changes in the depression rating scale scores from baseline to endpoint or pre-defined sessions, response rate, remission rate, rate of side effects and dropout rate between antidiabetic agents and placebo were meta-analyzed.

RESULTS

Six RCTs involving 399 participants were included in the final meta-analysis, which did not find that antidiabetics outperformed the placebo in reducing depressive symptoms. The standardized mean difference (SMD) in the depression scores from baseline to endpoint was 0.25 (95% CI -0.1, 0.61). However, a subgroup analysis found a significant difference between antidiabetics and placebos in reducing depressive symptoms in Middle Eastern populations, with an SMD of 0.89 (95% CI 0.44, 1.34).

CONCLUSIONS

The current meta-analysis does not support the efficacy of antidiabetics being superior to the placebo in the treatment of unipolar and bipolar depression. However, a subgroup analysis indicates that patients from the Middle East may benefit from adding an antidiabetic medication to their ongoing medication(s) for their depression. Larger studies with good-quality study designs are warranted.

Association of metabolic syndrome and its components with the risk of depressive symptoms: A systematic review and meta-analysis of cohort studies

BACKGROUND

The purpose of this meta-analysis was to quantitatively analyze the association between metabolic syndrome (MetS) and the risk of depressive symptoms.

METHODS

Three electronic databases (PubMed, Embase, and PsycINFO) were searched for articles published through February 15, 2022. Cohort studies evaluating the association between MetS and depressive symptoms were selected for inclusion in this study. A random-effects model was used to evaluate the pooled estimates of MetS, including each of its components, associated with depressive symptoms.

RESULTS

A total of 11 cohort studies were selected including >2.65 million participants. There was a significant association between MetS and depressive symptoms risk, albeit with a high degree of heterogeneity (relative risk = 1.29, 95 % confidence interval: 1.12-1.48; I2 = 79.3 %). This association was consistently significant in Western countries, but it was not significant in Asian countries. When stratified by sex, age, and geographical region, MetS and its components exhibited varying degrees of association with depressive symptoms.

CONCLUSIONS

MetS is a risk factor for depressive symptoms. Further large-scale prospective cohort studies are required to confirm our findings.

Suicide-Related Single Nucleotide Polymorphisms, rs4918918 and rs10903034: Association with Dementia in Older Adults

Dementia has enormous implications for patients and the health care system. Genetic markers are promising for detecting the risk of cognitive impairment. We hypothesized that genetic variants associated with suicide risk might significantly increase the risk of cognitive decline because suicide in older adults is often a consequence of cognitive impairment. We investigated several single-nucleotide polymorphisms that were initially associated with suicide risk in dementia older adults and identified the APOE gene alleles. The study was performed with subjects over the age of 65: 112 patients with dementia and 146 healthy volunteers. The MMSE score was used to assess cognitive functions. Study participants were genotyped using real-time PCR (APOE: rs429358, rs7412; genes associated with suicide: rs9475195, rs7982251, rs2834789, rs358592, rs4918918, rs3781878, rs10903034, rs165774, rs16841143, rs11833579 rs10898553, rs7296262, rs3806263, and rs2462021). Genotype analysis revealed the significance of APOEε4, APOEε2, and rs4918918 (SORBS1) when comparing dementia and healthy control groups. The association of APOEε4, APOEε2, and rs10903034 (IFNLR1) with the overall MMSE score was indicated. The study found an association with dementia of rs4918918 (SORBS1) and rs10903034 (IFNLR1) previously associated with suicide and confirmed the association of APOEε4 and APOEε2 with dementia.

Bushen Jieyu Tiaochong Formula reduces apoptosis of granulosa cells via the PERK-ATF4-CHOP signaling pathway in a rat model of polycystic ovary syndrome with chronic stress

ETHNOPHARMACOLOGICAL RELEVANCE

Polycystic ovary syndrome (PCOS) is a common and complex endocrine disorder that is also an important cause of infertility. Adverse psychological stress can aggravate the occurrence and development of PCOS. Bushen Jieyu Tiaochong Formula (BJTF), a prescription of Traditional Chinese Medicine (TCM), has been used in the treatment of PCOS and shown to be effective in reducing negative emotion. However, the therapeutic mechanism has yet to be clearly elucidated. In the current study, we investigated the potential mechanism of action of BJTF.

AIM OF THE STUDY

To investigate the role of PERK-ATF4-CHOP signaling in the molecular mechanisms that mediate the effects of BJTF in a rat model of PCOS, with chronic stress induced by letrozole and a chronic unpredictable mild stress (CUMS) paradigm.

MATERIALS AND METHODS

In addition to the normal control group, the PCOS combined with CUMS model rats were randomly assigned to a model group, a Diane-35 (ethinylestradiol 35 μg/cyproterone acetate 2 mg)-treated positive control group, or one of three BJTF-treated groups receiving a low, medium, or high dose. Behavioral testing, including the sucrose preference test and open field test, was conducted, and hematoxylin and eosin (H&E) staining was used to observe changes in the pathological morphology of ovarian tissue. Free testosterone (FT), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) levels in serum were quantified by enzyme-linked immunosorbent assays (ELISA). The hippocampal levels of norepinephrine (NE), 5-hydroxytryptamine/serotonin (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) were measured using high-performance liquid chromatography-electrochemical detection (HPLC-ECD). Apoptotic granulosa cells were detected using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Furthermore, quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemistry were used to detect the expression of glucose-regulated protein 78 (GRP78) and CHOP in the ovarian tissues. The expression levels of GRP78, CHOP, PERK, and ATF4 in ovarian tissues were also measured by western blotting.

RESULTS

Treatment with either BJTF or Diane-35 ameliorated the abnormal cystic dilatation of follicles in the model rats and reduced the serum levels of FT and LH, and the LH/FSH ratio. BJTF treatment also attenuated chronic psychological stress-like behavior and regulated the expression and metabolism of cerebral monoamine neurotransmitters. The efficacy of BJTF was greater than that of Diane-35, with the optimal effects observed at the medium dose. BJTF also lowered the apoptotic index of ovarian granulosa cells and downregulated the expression of GRP78, CHOP, and ATF4. Although the expression level of PERK was not significantly altered by BJTF, the mean PERK expression level was the lowest in the medium-dose BJTF group.

CONCLUSIONS

Administration of BJTF has the therapeutic potential to promote the homeostasis of the reproductive endocrine environment and to restore follicular development and ovulation, possibly through the inhibition of the PERK-ATF4-CHOP signaling pathway, leading to downregulation of GRP78 expression to further delay ovarian granule cell apoptosis mediated by endoplasmic reticulum stress (ERS). Moreover, BJTF could improve behavioral performance by regulating cerebral monoamine neurotransmitters in this rat model. These findings provide a new perspective for treating PCOS related to psychological stress using TCM.

Transcriptome-wide association study for postpartum depression implicates altered B-cell activation and insulin resistance

Postpartum depression (PPD) affects 1 in 7 women and has negative mental health consequences for both mother and child. However, the precise biological mechanisms behind the disorder are unknown. Therefore, we performed the largest transcriptome-wide association study (TWAS) for PPD (482 cases, 859 controls) to date using RNA-sequencing in whole blood and deconvoluted cell types. No transcriptional changes were observed in whole blood. B-cells showed a majority of transcriptome-wide significant results (891 transcripts representing 789 genes) with pathway analyses implicating altered B-cell activation and insulin resistance. Integration of other data types revealed cell type-specific DNA methylation loci and disease-associated eQTLs (deQTLs), but not hormones/neuropeptides (estradiol, progesterone, oxytocin, BDNF), serve as regulators for part of the transcriptional differences between cases and controls. Further, deQTLs were enriched for several brain region-specific eQTLs, but no overlap with MDD risk loci was observed. Altogether, our results constitute a convergence of evidence for pathways most affected in PPD with data across different biological mechanisms.

Genetic association between major depressive disorder and type 2 diabetes mellitus: Shared pathways and protein networks

BACKGROUND

Major depressive disorder (MDD) and type 2 diabetes mellitus (T2DM) are common public health disorders that often co-occur. This study aims to determine whether gene expression profiles from individuals with MDD or T2DM overlap and if there are any functional interconnectivity between identified genes using protein-protein interaction (PPI).

METHODS

The DNA microarray datasets were extracted from the Gene Expression Omnibus. Gene expression dataset GSE98793 from a case-control study of MDD (64 healthy control subjects, 128 patients) and dataset GSE15653 from a case-control study of T2DM (nine controls, nine individuals with T2DM) were used for this secondary and post-hoc analysis. GO enrichment analyses and Reactome pathway enrichment analysis were performed for functional enrichment analyses with the shared genes. PPI networks, PPI clusters and hub genes were performed to detect the potential relationships among differentially expressed genes (DEG) -encoding proteins in both MDD and T2DM.

RESULTS

A total of 3640 DEGs were identified in the MDD group when compared to the control group, whereas 3700 DEGs were identified in the T2DM group when compared to the control groups, among which 244 DEGs were overlap genes. The identified DEGs were enriched for Interleukin-4 and Interleukin-13 signaling, neutrophil degranulation, as well as other select species of the innate immune system. The biological processes of neurofibrillary tangle assembly regulation, tau-protein kinase activity regulation, amyloid-beta clearance regulation, amyloid-beta formation regulation and neuron apoptotic processes were also identified. Molecular function analysis indicated that identified genes were mainly enriched for amyloid-beta binding. 925 out of 1006 protein-protein interactions and six sub-networks were identified reflecting the disparate biological domains of overlapping genes. Ten hub genes further highlight the putative importance of tau-protein kinase activity, inflammatory response and neuron apoptotic regulatory processes across MDD and T2DM.

CONCLUSIONS

Our results indicate that an overlapping genetic architecture subserves MDD and T2DM. Genes relevant to the innate immune system, tau protein formation, and cellular aging were identified. Results indicate that the common, often comorbid, conditions of MDD and T2DM have a pathoetiologic nexus.

Biological, Psychological, and Social Determinants of Depression: A Review of Recent Literature

Depression is one of the leading causes of disability, and, if left unmanaged, it can increase the risk for suicide. The evidence base on the determinants of depression is fragmented, which makes the interpretation of the results across studies difficult. The objective of this study is to conduct a thorough synthesis of the literature assessing the biological, psychological, and social determinants of depression in order to piece together the puzzle of the key factors that are related to this condition. Titles and abstracts published between 2017 and 2020 were identified in PubMed, as well as Medline, Scopus, and PsycInfo. Key words relating to biological, social, and psychological determinants as well as depression were applied to the databases, and the screening and data charting of the documents took place. We included 470 documents in this literature review. The findings showed that there are a plethora of risk and protective factors (relating to biological, psychological, and social determinants) that are related to depression; these determinants are interlinked and influence depression outcomes through a web of causation. In this paper, we describe and present the vast, fragmented, and complex literature related to this topic. This review may be used to guide practice, public health efforts, policy, and research related to mental health and, specifically, depression.

The relationship between health-related quality of life and melancholic depressive symptoms is modified by brain insulin receptor gene network

To investigate whether expression-based polygenic risk scores for the insulin receptor gene network (ePRS-IRs) modifiy the association between type of depressive symptoms and health-related quality of life (HRQoL). This cross-sectional study includes 1558 individuals from the Helsinki Birth Cohort Study. Between 2001 and 2004, the Short Form-36 questionnaire was employed to assess mental and physical components of HRQoL and Beck Depression Inventory (BDI) to assess depressive symptoms. Depressive symptoms were categorized into minimal (BDI < 10), non-melancholic and melancholic types of depression. The ePRS-IRs were calculated for the hippocampal (hePRS-IR) and the mesocorticolimbic (mePRS-IR) regions of the brain. General linear regression models adjusted for age, sex, population stratification, lifestyle factors and body mass index were applied to analyze the data. Both types of depressive symptoms were associated with lower HRQoL (p < 0.0001). HePRS-IR modified the association between the types of depression and mental HRQoL (p for interaction = 0.005). Melancholic type of depressive symptoms was associated with higher mental HRQoL compared to the non-melancholic symptoms among individuals with low hePRS-IR (adjusted mean 4.1, 95% CI 0.7-7.4, p = 0.018). However, no such difference was evident in moderate or high hePRS-IR groups as higher hePRS-IR was associated with lower mental HRQoL (B = - 3.4, 95% CI - 5.6 to - 1.2) in individuals with melancholic type of depressive symptoms. No direct associations were detected between the ePRS-IRs and type of depressive symptoms or HRQoL. Variations in the glucose-insulin metabolism can lower HRQoL in individuals with melancholic depressive symptoms.

Incretin hormones, insulin, glucagon and advanced glycation end products in relation to cognitive function in older people with and without diabetes, a population-based study

AIM

The aim of this observational study was to investigate relationships between physiological levels of glucometabolic biomarkers and cognitive test results in a population-based setting.

METHODS

Cross-sectional data were obtained from the Swedish population-based Malmö Diet and Cancer Study Re-examination 2007-2012 comprising 3001 older people (mean age 72 years). Through oral glucose tolerance testing (OGTT), fasting and post-load levels of serum insulin, plasma glucagon, serum glucose-dependent insulinotropic peptide (GIP) and plasma glucagon-like peptide-1 (GLP-1) were measured. Insulin resistance and insulin sensitivity levels were calculated. In 454 participants, advanced glycation end products (AGEs) were estimated through skin autofluorescence. Associations between biomarkers and two cognitive tests, the Mini-Mental State Examination (MMSE) and A Quick Test of Cognitive Speed (AQT) respectively, were explored in multiple regression analyses.

RESULTS

Positive associations following adjustments for known prognostic factors were found between MMSE scores and insulin sensitivity (B = 0.822, P = 0.004), 2-h plasma glucagon (B = 0.596, P = 0.026), 2-h serum GIP (B = 0.581, P = 0.040) and 2-h plasma GLP-1 (B = 0.585, P = 0.038), whereas negative associations were found between MMSE scores and insulin resistance (B = -0.734, P = 0.006), fasting plasma GLP-1 (B = -0.544, P = 0.033) and AGEs (B = -1.459, P = 0.030) were found.

CONCLUSIONS

Higher levels of insulin sensitivity, GIP and GLP-1 were associated with better cognitive outcomes, but AGEs were associated with worse outcomes, supporting evidence from preclinical studies. Glucagon was linked to better outcomes, which could possibly reflect neuroprotective properties similar to the related biomarker GLP-1 which has similar intracellular properties. Longitudinal and interventional studies are needed to further evaluate neuromodulating effects of these biomarkers. Abstract presented at the European Association for the Study of Diabetes (EASD) 2019, Barcelona, Spain.