Impact of insulin and insulin resistance on brain dopamine signalling and reward processing- an underexplored mechanism in the pathophysiology of depression?

Potassium and calcium channels in different nerve cells act as therapeutic targets in neurological disorders

The central nervous system, information integration center of the body, is mainly composed of neurons and glial cells. The neuron is one of the most basic and important structural and functional units of the central nervous system, with sensory stimulation and excitation conduction functions. Astrocytes and microglia belong to the glial cell family, which is the main source of cytokines and represents the main defense system of the central nervous system. Nerve cells undergo neurotransmission or gliotransmission, which regulates neuronal activity via the ion channels, receptors, or transporters expressed on nerve cell membranes. Ion channels, composed of large transmembrane proteins, play crucial roles in maintaining nerve cell homeostasis. These channels are also important for control of the membrane potential and in the secretion of neurotransmitters. A variety of cellular functions and life activities, including functional regulation of the central nervous system, the generation and conduction of nerve excitation, the occurrence of receptor potential, heart pulsation, smooth muscle peristalsis, skeletal muscle contraction, and hormone secretion, are closely related to ion channels associated with passive transmembrane transport. Two types of ion channels in the central nervous system, potassium channels and calcium channels, are closely related to various neurological disorders, including Alzheimer's disease, Parkinson's disease, and epilepsy. Accordingly, various drugs that can affect these ion channels have been explored deeply to provide new directions for the treatment of these neurological disorders. In this review, we focus on the functions of potassium and calcium ion channels in different nerve cells and their involvement in neurological disorders such as Parkinson's disease, Alzheimer's disease, depression, epilepsy, autism, and rare disorders. We also describe several clinical drugs that target potassium or calcium channels in nerve cells and could be used to treat these disorders. We concluded that there are few clinical drugs that can improve the pathology these diseases by acting on potassium or calcium ions. Although a few novel ion-channel-specific modulators have been discovered, meaningful therapies have largely not yet been realized. The lack of target-specific drugs, their requirement to cross the blood-brain barrier, and their exact underlying mechanisms all need further attention. This review aims to explain the urgent problems that need research progress and provide comprehensive information aiming to arouse the research community's interest in the development of ion channel-targeting drugs and the identification of new therapeutic targets for that can increase the cure rate of nervous system diseases and reduce the occurrence of adverse reactions in other systems.

Associations of insulin resistance estimated by glucose disposal rate with frailty progression

OBJECTIVES

To investigate the relationship between estimated glucose disposal rates (eGDR) and the progression of frailty, using longitudinal data.

METHODS

We analyzed four waves of data from the China Health and Retirement Longitudinal Study (CHARLS) from 2011 to 2018, involving 6,778 middle-aged and older adults. eGDR was calculated using a specific formula, categorizing participants into high and low eGDR groups based on the lowest quartile (8.5). Frailty status was assessed using the frailty index (FI). Linear mixed-effects models were employed to analyze the association between eGDR and frailty progression, as well as the impact of transitions in eGDR.

RESULTS

We found that the baseline FI was significantly higher in the low eGDR group compared to the high eGDR group. Furthermore, participants in the low eGDR group exhibited a faster progression of frailty, compared to those in the high eGDR group. Among non-frail participants at baseline, the association between low eGDR and accelerated frailty progression was even more pronounced. Further analysis revealed that, compared to participants who maintained a stable high eGDR, those who transitioned from high to low eGDR and those who consistently remained in the low eGDR group both experienced significantly accelerated frailty progression. On the contrary, participants who transitioned from low to high eGDR did not show a significant acceleration in frailty progression compared to those who consistently maintained a high eGDR.

CONCLUSION

Low eGDR is linked to accelerated frailty progression in middle-aged and older Chinese adults. Transitioning from low to high eGDR may mitigate this progression, highlighting the importance of eGDR in frailty management.

A short-term, high-caloric diet has prolonged effects on brain insulin action in men

Brain insulin responsiveness is linked to long-term weight gain and unhealthy body fat distribution. Here we show that short-term overeating with calorie-rich sweet and fatty foods triggers liver fat accumulation and disrupted brain insulin action that outlasted the time-frame of its consumption in healthy weight men. Hence, brain response to insulin can adapt to short-term changes in diet before weight gain and may facilitate the development of obesity and associated diseases.

Association between triglyceride-glucose (TyG) index and the incidence of depression in US adults with diabetes or pre-diabetes

BACKGROUND

The relationship between the triglyceride glucose (TyG) index and the incidence of depression in populations with diabetes or pre-diabetes remains unclear. This study aims to investigate the association between the TyG index and depression incidence in diabetic/pre-diabetic populations.

METHOD

Data from the 2005-2018 National Health and Nutrition Examination Survey (NHANES) were analyzed. After adjustment for confounders, multivariate logistic regression models were fitted to investigate the association between TyG index and depression incidence. Restricted cubic splines (RCS), subgroup analysis, interaction analysis, and mediation analysis were also constructed.

RESULTS

A total of 8,970 participants with diabetes or pre-diabetes were enrolled. The linear positive association between TyG index and the incidence of depression was observed. Insulin resistance partly mediates this association in mediation analysis. There is a U-shape association between TyG index and the incidence of depression in diabetic/pre-diabetic populations whose ethnicity is Other Hispanic (p for nonlinearity =0.0237). Subgroup analysis evaluated the robustness of our findings and interaction analysis showed that this association can be modified by race/ethnicity.

CONCLUSION

There is a linear positive association between the TyG index and the incidence of depression in populations with diabetes or pre-diabetes.

Unlocking the Link Between Gut Microbiota and Psychopathological Insights in Anorexia Nervosa: A Systematic Review

OBJECTIVE

This systematic review explores the associations between qualitative/quantitative changes in gut microbiota and psychopathological symptoms or other clinical features in patients with eating disorders (EDs). Secondary outcomes include exploring gut microbiota changes in EDs and potential relationships with psychotropic drug use.

METHOD

A systematic search was conducted across biomedical databases from inception to June 2024 according to PRISMA guidelines. The risk of bias was assessed, and a narrative synthesis was performed due to the heterogeneity of the outcomes.

RESULTS

Only findings related to anorexia nervosa (AN) were identified. Ten studies, of which seven were longitudinal, two cross-sectional, and one interventional (N = 350 patients with AN, and 304 HCs), were included. Despite no clear links between diversity metrics and clinical symptoms being observed, specific taxa belonging to phylum Firmicutes, such as Clostridium, Roseburia, Lactobacillus, Faecalibacterium, and Bifidobacterium belonging to Actinobacteriota correlated with ED psychopathology, including anxiety and depressive symptoms.

CONCLUSIONS

Changes in microbiota were related to anxiety and depressive symptoms, as well as altered eating behaviours by modulating inflammation and insulin pathways through short-chain fatty acids (SCFAs), that also lead to neurotransmitter imbalances. Further studies are required to replicate these finding and to explore whether similar patterns are observed in other EDs.

The interface of depression and diabetes: treatment considerations

This state-of-the-art review explores the relationship between depression and diabetes, highlighting the two-way influences that make treatment challenging and worsen the outcomes of both conditions. Depression and diabetes often co-occur and share genetic, lifestyle, and psychosocial risk factors. Lifestyle elements such as diet, physical activity, and sleep patterns play a role on the development and management of both conditions, highlighting the need for integrated treatment strategies. The evidence suggests that traditional management strategies focusing on either condition in isolation fall short of addressing the intertwined nature of diabetes and depression. Instead, integrated care models encompassing psychological support and medical management are recommended to improve treatment efficacy and patient adherence. Such models require collaboration across multiple healthcare disciplines, including endocrinology, psychiatry, and primary care, to offer a holistic approach to patient care. This review also identifies significant patient-related barriers to effective management, such as stigma, psychological resistance, and health literacy, which need to be addressed through patient-centered education and support systems. Future directions for research include longitudinal studies in diverse populations to further elucidate causal relationships and the exploration of novel therapeutic targets, as well as the effectiveness of healthcare models aimed at preventing the onset of one condition in individuals diagnosed with the other.

Neuroeconomically dissociable forms of mental accounting are altered in a mouse model of diabetes

Those with diabetes mellitus are at high-risk of developing psychiatric disorders, especially mood disorders, yet the link between hyperglycemia and altered motivation has not been thoroughly explored. Here, we characterized value-based decision-making behavior of a streptozocin-induced diabetic mouse model on Restaurant Row, a naturalistic neuroeconomic foraging paradigm capable of behaviorally capturing multiple decision systems known to depend on dissociable neural circuits. Mice made self-paced choices on a daily limited time-budget, accepting or rejecting reward offers based on cost (delays cued by tone pitch) and subjective value (flavors), in a closed-economy system tested across months. We found streptozocin-treated mice disproportionately undervalued less-preferred flavors and inverted their meal-consumption patterns shifted toward a more costly strategy overprioritizing high-value rewards. These foraging behaviors were driven by impairments in multiple decision-making processes, including the ability to deliberate when engaged in conflict and cache the value of the passage of time as sunk costs. Surprisingly, diabetes-induced changes in motivation depended not only on the type of choice being made, but also on the salience of reward-scarcity in the environment. These findings suggest that complex relationships between metabolic dysfunction and dissociable valuation algorithms underlying unique cognitive heuristics and sensitivity to opportunity costs can disrupt distinct computational processes leading to comorbid psychiatric vulnerabilities.

Association Between Four Non-Insulin-Based Insulin Resistance Indices and the Risk of Post-Stroke Depression

Purpose

Research suggests that insulin resistance (IR) is associated with acute ischemic stroke (AIS) and depression. The use of insulin-based IR assessments is complicated. Therefore, we explored the relationship between four non-insulin-based IR indices and post-stroke depression (PSD).

Patients and Methods

A total of 638 consecutive AIS patients were enrolled in this prospective cohort study. Clinical data were collected to compute indices such as the triglyceride glucose (TyG) index, triglyceride glucose-body mass index (TyG-BMI), insulin resistance metabolic score (METS-IR), and triglyceride/high-density lipoprotein cholesterol ratio (TG/HDL-C). One month post-stroke, neuropsychological assessments were conducted using the 17-item Hamilton Depression Scale. Binary logistic regression analysis was performed to explore the relationship between the four non-insulin-based IR indices and PSD.

Results

Ultimately, 381 patients completed the 1-month follow-up, including 112 (29.4%) with PSD. The PSD group exhibited significantly higher levels of the four IR indices compared to the non-PSD group. Logistic regression analysis demonstrated that these indicators were independently associated with PSD occurrence, both before and after adjusting for potential confounders (all P < 0.001). Tertile analyses indicated that the highest tertile group had a greater risk of PSD occurrence than the lowest tertile group for four IR indicators, even after adjusting for potential confounders (all P < 0.05). Restricted cubic spline analysis revealed a linear dose-response relationship between the four IR indices and PSD. In the subgroup analysis, only the TyG index showed a significant interaction with diabetes (P for interaction = 0.014). The area under curve values for the TyG index, TyG-BMI, METS-IR, and TG/HDL-C were 0.700, 0.721, 0.711, and 0.690, respectively.

Conclusion

High TyG index, TyG-BMI, METS-IR, and TG/HDL-C at baseline were independent risk factors for PSD in AIS. Each of these indicators exhibits predictive value for PSD occurrence, aiding in the early identification of high-risk groups.

Association of TyG Index and TG/HDL-C Ratio with Trajectories of Depressive Symptoms: Evidence from China Health and Retirement Longitudinal Study

OBJECTIVES

To explore whether the triglyceride-glucose (TyG) index and the triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio are associated with the trajectories of depressive symptoms.

METHODS

In this longitudinal study, 4215 participants aged 45 years and older were recruited from the China Health and Retirement Longitudinal Study from 2011 to 2018. The trajectories of depressive symptoms, measured by the 10-item Center for Epidemiologic Studies Depression Scale (CESD-10), were identified using group-based trajectory modeling. Multinomial logistic models and restricted cubic spline analysis were used to investigate the relationships between the TyG index and the TG/HDL-C ratio and the trajectories of depressive symptoms. Stratified analyses were conducted based on sex, age, place of residence, and body mass index (BMI).

RESULTS

Five distinct trajectories of depressive symptoms characterized by stable low, stable moderate, decreasing, increasing, and stable high were identified during a follow-up of 7 years. The associations of the TyG index and the TG/HDL-C ratio with trajectories of depressive symptoms are not entirely consistent. After adjusting for covariates, a higher TyG index at baseline was associated with lower odds of being on the decreasing trajectory of depressive symptoms (ORad = 0.61, 95% CI: 0.40-0.92) compared to the stable low trajectory, and restricted cubic spline analysis revealed a negative linear relationship between the TyG index and the likelihood of a decreasing trajectory of depressive symptoms. However, the relationship between the TG/HDL-C ratio and the decreasing trajectory of depressive symptoms was no longer statistically significant when all confounders were controlled (ORad = 0.72, 95% CI: 0.50-1.04). Additionally, this negative association between the TyG index and decreasing trajectory of depressive symptoms was observed among 45-64-year-old individuals, female participants, those living in rural areas, and those with a normal BMI.

LIMITATIONS

This study was conducted in a middle-aged and elderly population in China, and extrapolation to other regions and populations requires further confirmation.

CONCLUSIONS

Compared to the TG/HDL-C ratio, the TyG index may be a better predictor for trajectories of depressive symptoms in middle-aged and older adults. Considering that the pathology of depression progresses long term, our findings may have utility for identifying available and reliable markers for the development of depression.

Association between triglyceride glucose-body mass index and depression among US adults: A cross-sectional study

OBJECTIVES

The triglyceride glucose-body mass index (TyG-BMI) is a well-established surrogate marker for insulin resistance. While an association between insulin resistance and depression has been identified, that between TyG-BMI and depression remains unclear. Therefore, we used data from the National Health and Nutrition Examination Survey (NHANES) database to investigate this.

STUDY DESIGN

This cross-sectional study included 9673 adults (aged ≥20 years) from the NHANES in the United States from 2011 to 2020.

METHODS

Depressive symptoms were assessed using a nine-item version of the Patient Health Questionnaire. The covariates included age, sex, race/ethnicity, marital status, educational level, poverty-income ratio, smoking status, alcohol intake, diabetes status, cardiovascular disease, hypertension, physical activity, high-density lipoprotein, low-density lipoprotein, and total cholesterol. Multivariate logistic regression models, subgroup analyses, and threshold saturation effect analyses were conducted.

RESULTS

After adjusting for age, sex, race/ethnicity, marital status, education level, poverty-income ratio, smoking status, drinking status, diabetes status, cardiovascular disease, hypertension, physical activity, total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol, the threshold saturation effect showed a TyG-BMI inflection point of 174.4. Below the inflection point, a 10-unit increase in TyG-BMI was associated with a 12 % lower prevalence of depression. Above the inflection point, each 10-unit increase in TyG-BMI was associated with a 4 % increase in prevalence of depression.

CONCLUSIONS

TyG-BMI had a U-shaped relationship with prevalence of depression. There was a significant link between higher TyG-BMI levels and increased prevalence of depression. When the TyG-BMI value was below 174.4, any further increase in TyG-BMI was associated with a significantly lower prevalence of depression.

Anhedonia is associated with a specific depression profile and poor antidepressant response

BACKGROUND

Anhedonic features within major depressive disorder (MDD) have been associated with worse course and outcome and may predict nonresponse to treatment. However, a detailed clinical profile of anhedonia in MDD is still lacking.

MATERIALS AND METHODS

One thousand two hundred ninety-four patients with MDD were selected from the cross-sectional European multicenter Group for the Study of Resistant Depression study. Anhedonia was assessed through the Montgomery-Åsberg Depression Rating Scale anhedonia item "inability to feel." Clinical and demographic features were then analyzed.

RESULTS

The presence of anhedonia related to a distinct demographical (living alone) and clinical profile (thyroid diseases, diabetes, suicide risk, high number of previous depressive episodes, more severe MDD, and more frequent inpatient status). Furthermore, anhedonia was associated with nonresponse to treatment and treatment resistance, even after adjusting for confounding variables.

CONCLUSIONS

Our findings support the role of anhedonia as a modulating feature of MDD, being associated with a more severe depression profile. Moreover, anhedonic features are independent predictors of poor treatment response.

Role of Peripheral and Central Insulin Resistance in Neuropsychiatric Disorders

Insulin acts on different organs, including the brain, which helps it regulate energy metabolism. Insulin signaling plays an important role in the function of different cell types. In this review, we have summarized the key roles of insulin and insulin receptors in healthy brains and in different brain disorders. Insulin signaling, as well as insulin resistance (IR), is a major contributor in the regulation of mood, behavior, and cognition. Recent evidence showed that both peripheral and central insulin resistance play a role in the pathophysiology, clinical presentation, and management of neuropsychiatric disorders like Cognitive Impairment/Dementia, Depression, and Schizophrenia. Many human studies point out Insulin Resistance/Metabolic Syndrome can increase the risk of dementia especially Alzheimer's dementia (AD). IR has been shown to play a role in AD development but also in its progression. This review article discusses the pathophysiological pathways and mechanisms of insulin resistance in major neuropsychiatric disorders. The extent of insulin resistance can be quantified using IR biomarkers like insulin levels, HOMA-IR index, and Triglyceride glucose-body mass index (TyG-BMI) levels. IR has been shown to precede neurodegeneration. Human trials showed current treatment with certain antidiabetic drugs, as well as life style management, like weight loss and exercise for IR, have shown promise in the management of cognitive/neuropsychiatric disorders. This may pave the pathway to the development of new therapeutic approaches to these challenging disorders of dementia and psychiatric diseases. Recent clinical trials are showing some encouraging evidence for these pharmacological and nonpharmacological approaches for IR in psychiatric and cognitive disorders, even though more research is needed to apply this evidence into clinical practice. Early identification and management of IR may help as a strategy to potentially alter neuropsychiatric disorders onset as well as its progression.

Insulin resistance, clinical presentation and resistance to selective serotonin and noradrenaline reuptake inhibitors in major depressive disorder

BACKGROUND

The understanding of mechanisms underlying non-response to antidepressants is limited. The latest data highlights the role of insulin resistance (IR) in major depressive disorder (MDD) pathophysiology, presentation, and treatment efficacy. This work aimed to assess IR in MDD and explore the relationships between IR, MDD presentation and non-response to selective serotonin and noradrenaline reuptake inhibitors (SNRI).

METHODS

67 MDD individuals: 36 responsive (MDD T[+]), 31 non-responsive (MDD T[-]) to SNRI and 30 healthy controls were recruited. The treatment response criteria were: Clinical Global Impression Scale-Improvement score of 1 or 2 after ≥ 8 weeks of treatment. Participants were assessed by physician and self-report tools measuring depression, anhedonia, anxiety, bipolarity, sleep quality. Blood samples were collected to assess fasting glucose and insulin levels and calculate HOMA-IR (homeostasis model assessment of insulin resistance).

RESULTS

MDD T[-] vs. MDD T[+] had significantly higher body mass index, insulin levels, and HOMA-IR. MDD T[-] presented higher levels of depressed mood, appetite/weight changes, loss of interest, energy, overall depressive symptoms, and sleep impairment; some evaluations suggested higher anhedonia and anxiety in MDD T[-] vs. MDD T[+]. Insulin and IR were weakly but significantly correlated with the severity of psychomotor symptoms, energy level, thoughts of death/suicide, self-criticism, appetite/weight, depressed mood symptoms, sleep problems. IR was weakly but significantly correlated with anhedonia.

CONCLUSION

IR appears to be linked to depressive symptoms characteristic of the "metabolic" MDD subtype, such as psychomotor changes, energy level, anhedonia, sleep problems, appetite/weight changes, state and trait anxiety, sleep quality, and non-response to SNRI.

Glucagon-like peptide 1 agonist and effects on reward behaviour: A systematic review

INTRODUCTION

The roles of metabolic signals, including Glucagon-like peptide 1 (GLP-1), have been implicated in multiple domains outside metabolic regulation. There is a growing interest in repurposing Glucagon-like peptide 1 receptor agonists (GLP-1RAs) as therapeutics for motivation and reward-related behavioural disturbances. Herein, we aim to systematically review the extant evidence on the potential effects of GLP-1RAs on the reward system.

METHODS

The study followed PRISMA guidelines using databases such as OVID, PubMed, Scopus, and Google Scholar. The search focused on "Reward Behavior" and "Glucagon Like Peptide 1 Receptor Agonists" and was restricted to human studies. Quality assessment achieved by the NIH's Quality Assessment of Controlled Intervention Studies RESULTS: GLP-1RAs consistently reduced energy intake and influenced reward-related behaviour. These agents have been associated with decreased neurocortical activation in response to higher rewards and food cues, particularly high-calorie foods, and lowered caloric intake and hunger levels.

DISCUSSION

GLP-1RAs show promise in addressing reward dysfunction linked to food stimuli, obesity, and T2DM. They normalize insulin resistance, and might also modulate dopaminergic signalling and reduce anhedonia. Their effects on glycemic variability and cravings suggest potential applications in addiction disorders.

Type 2 diabetes mellitus is associated with manic morbidity in elderly patients with mood disorders

The association between mood disorders, especially bipolar disorder (BD), and metabolic disorders, is long known. However, to which extent metabolic disorders affect the course of mood disorders in late life is still open to inquiring. To assess the impact of type 2 diabetes mellitus (T2DM) on late-life mood disorders a retrospective chart review was performed. Elderly depressive patients (≥ 65 years) diagnosed with Major Depressive Disorder (N = 57) or BD (N = 43) and followed up for at least 18 months were included and subdivided according to the presence of T2DM comorbidity. Vascular encephalopathy (39.1% vs. 15.6%, P  = 0.021) and neurocognitive disorders (21.7% vs. 5.2%, P  = 0.028), were more frequently reported in patients with T2DM than in those without. Patients with T2DM showed a greater percentage of follow-up time in manic episodes (r = -0.23, P  = 0.020) and a higher rate of manic episode(s) during follow-up (21.7% vs. 5.2%, P  = 0.028) than those without. When restricting longitudinal analyses to patients with bipolar spectrum disorders, results were confirmed. In line with the well-known connection between BD and metabolic disorders, our data support an association between T2DM and unfavorable course of illness in the elderly with BD.

Insulin Resistance, Temperament and Personality Traits Are Associated with Anhedonia in a Transdiagnostic Sample

Anhedonia constitutes a core symptom of major depressive disorder (MDD) mediating the ultimate goal of MDD treatment: functional remission. Anhedonia is also present in other clinical populations, including patients with chronic pain. Recent data links anhedonia to insulin resistance (IR). Some researchers have underlined a different dimension of anhedonia as a temperament/personality trait. The objective of this post-hoc analysis was to explore the links between anhedonia (main outcome) and (1) IR, (2) temperamental, personality, and schizotypy traits (exposures). The study population included patients with MDD, fibromyalgia, and healthy controls. Participants were split into groups: (1) insulin resistant (IR[+] n = 69, HOMA-IR ≥ 2.1) and (2) insulin sensitive (IR[-] n = 69, HOMA-IR < 2.1). Anhedonia was significantly higher in the IR[+] group than the IR[-] group. IR was a predictor of higher anhedonia levels. IR[+] vs. IR[-] participants showed higher levels of anxiety and lower levels of hyperthymic affective temperaments, as well as conscientiousness and emotional stability personality traits. Depressive, irritable, and anxious temperaments, cognitive disorganization, and introvertive anhedonia positively predicted anhedonia, while hyperthymic temperament, conscientiousness, extraversion, and emotional stability traits negatively predicted anhedonia. IR partially mediated the relationship between depressive temperament and anhedonia. In sum, IR, affective temperaments, and personality traits are predictors of anhedonia.

Triglyceride-glucose index as a potential predictor of major adverse cardiovascular and cerebrovascular events in patients with coronary heart disease complicated with depression

Background

Triglyceride-glucose (TyG) index is a surrogate marker of insulin resistance and metabolic abnormalities, which is closely related to the prognosis of a variety of diseases. Patients with both CHD and depression have a higher risk of major adverse cardiovascular and cerebrovascular events (MACCE) and worse outcome. TyG index may be able to predict the adverse prognosis of this special population.

Methods

The retrospective cohort study involved 596 patients with both CHD and depression between June 2013 and December 2023. The primary outcome endpoint was the occurrence of MACCE, including all-cause death, stroke, MI and emergent coronary revascularization. The receiver operating characteristic (ROC) curve, Cox regression analysis, Kaplan-Meier survival analysis, and restricted cubic spline (RCS) analysis were used to assess the correlation between TyG index and MACCE risk of in patients with CHD complicated with depression.

Results

With a median follow-up of 31 (15-62) months, MACCE occurred in 281(47.15%) patients. The area under the ROC curve of TyG index predicting the risk of MACCE was 0.765(0.726-0.804) (P<0.01). Patients in the high TyG index group(69.73%) had a significantly higher risk of developing MACCE than those in the low TyG index group(23.63%) (P<0.01). The multifactorial RCS model showed a nonlinear correlation (nonlinear P<0.01, overall P<0.01), with a critical value of 8.80 for the TyG index to predict the occurrence of MACCE. The TyG index was able to further improve the predictive accuracy of MACCE.

Conclusions

TyG index is a potential predictor of the risk of MACCE in patients with CHD complicated with depression.

Association between the triglyceride glucose index and depression: a meta-analysis

Background

Obesity and diabetes have been associated with depressive symptoms. The aim of this systematic review and meta-analysis was to evaluate the association between the triglyceride glucose index (TyG index) a novel indicator of insulin resistance (IR) and depression in the adult population.

Methods

Relevant observational studies were acquired through comprehensive searches of the Medline, Web of Science, Embase, Wanfang, and China National Knowledge Internet databases. To account for heterogeneity, a random-effects model was employed to combine the findings. Additionally, multiple subgroup analyses were conducted to assess the impact of various study characteristics on the outcome.

Results

The meta-analysis comprised eight datasets from six cross-sectional studies, encompassing a total of 28,973 adults. The pooled findings suggested that subjects with a high TyG index, compared to those with a low TyG index, were associated with a higher prevalence of depression (odds ratio [OR]: 1.41, 95% confidence interval (CI): 1.28-1.56, p<0.001; I2 = 19%). Sensitivity analyses, by omitting one dataset at a time, showed consistent results (OR: 1.39-1.45, p<0.05). Further subgroup analyses showed consistent results in participants aged <50 years old and in those aged ≥50 years old, in men and in women, in studies with different cutoff values for the TyG index, and in studies with different methods for the diagnosis of depression (for each subgroup difference, p>0.05).

Conclusion

A high TyG index may be associated with a higher prevalence of depression in the adult population.

Insights from animal models on insulin signalling disturbances and related diseases in neurological and mental conditions

There has been a growing awareness of the need for scientific research to focus on somatic and mental comorbidities in recent years due to the emerging evidence showing their substantial overlap at numerous levels. In this special issue, initiated by members of the EU-funded PRIME consortium ("Prevention and Remediation of Insulin Multimorbidity in Europe; www.prime-study.eu), the focus is on the comorbidities of metabolic disturbances, especially related to insulin signalling dysregulation and mental and neurological disorders. Thus, while obesity, type 2 diabetes, and metabolic syndrome are commonly known to be insulin-related disorders, the last decades have shown that neurodegenerative disorders, such as Alzheimer's disease, as well as neurodevelopment disorders, such as obsessive-compulsive disorder (OCD), autism spectrum disorders (ASDs) and attention deficit / hyperactivity disorder (ADHD) also fall into this category. The special issue draws together a series of basic and clinical review articles that describe the current knowledge and future perspectives regarding insulin comorbidities across a multidisciplinary group of experts.

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.

Diabetes alters neuroeconomically dissociable forms of mental accounting

Those with diabetes mellitus are at high-risk of developing psychiatric disorders, yet the link between hyperglycemia and alterations in motivated behavior has not been explored in detail. We characterized value-based decision-making behavior of a streptozocin-induced diabetic mouse model on a naturalistic neuroeconomic foraging paradigm called Restaurant Row. Mice made self-paced choices while on a limited time-budget accepting or rejecting reward offers as a function of cost (delays cued by tone-pitch) and subjective value (flavors), tested daily in a closed-economy system across months. We found streptozocin-treated mice disproportionately undervalued less-preferred flavors and inverted their meal-consumption patterns shifted toward a more costly strategy that overprioritized high-value rewards. We discovered these foraging behaviors were driven by impairments in multiple decision-making systems, including the ability to deliberate when engaged in conflict and cache the value of the passage of time in the form of sunk costs. Surprisingly, diabetes-induced changes in behavior depended not only on the type of choice being made but also the salience of reward-scarcity in the environment. These findings suggest complex relationships between glycemic regulation and dissociable valuation algorithms underlying unique cognitive heuristics and sensitivity to opportunity costs can disrupt fundamentally distinct computational processes and could give rise to psychiatric vulnerabilities.

Consolidating evidence on the role of insulin resistance in major depressive disorder

PURPOSE OF REVIEW

The circular interactions between type 2 diabetes (TMD2) and major depressive disorder (MDD) are well documented but the understanding of their mechanisms has only recently gained more clarity. Latest research indicates, that the association between TMD2 and MDD is largely mediated by insulin resistance (IR).

RECENT FINDINGS

A metabolic subtype of MDD can be distinguished from other MDD subpopulations, that is characterized by predominantly atypical clinical presentation, IR and different responsiveness to antidepressant interventions. IR is a predictor of nonresponse to some antidepressants. The IR seems to be a state-marker of clinical or subclinical depression and the relationship between IR and MDD varies between sexes and ethnicities. Insulin has a direct impact on the monoaminergic systems known to underlie MDD symptoms: serotoninergic and dopaminergic, which are dysregulated in IR subjects. Several trials assessed the efficacy of insulin-sensitizing drugs in MDD with mixed results for metformin and more consistent evidence for pioglitazone and lifestyle intervention/physical activity.

SUMMARY

Recently published data suggest a significant role of IR in the clinical presentation, pathophysiology and treatment response in MDD. Further research of IR in MDD and integration of existing data into clinical practice are needed.

The association between insulin resistance and depressive symptoms - A national representative cross-sectional study

OBJECTIVE

Increasing evidence suggests a positive association between insulin resistance (IR) and depression. However, whether sex-or body mass index-specific differences exist remains controversial, and only few studies have analyzed specific symptom domains. Thus, the present study aimed to analyze the association between IR and depressive symptom domains and to clarify the effects of sex and body mass index.

METHODS

The study sample comprised 4007 participants, aged 19-79, from the Korea National Health and Nutrition Examination Study 2020. Participants completed health interviews and examinations, providing data on circulating insulin and glucose levels, the Patient Health Questionnaire-9 (PHQ-9), and related covariates. IR was calculated using the homeostasis model assessment of insulin resistance. Associations between IR and PHQ-9 were analyzed using negative binomial regression with adjustments for the complex survey design.

RESULTS

The association between log-transformed IR and PHQ-9 total scores was statistically significant (incidence rate ratio [IRR] = 1.17, 95% confidence interval [CI] = 1.07-1.29, p = 0.001). Only body mass index specific differences were statistically significant, as the association was only significant in those without obesity (IRR = 1.21, 95% CI = 1.06-1.38, p = 0.005). IR was associated with cognitive/affective (IRR = 1.23, 95% CI = 1.08-1.41, p = 0.002) and somatic (IRR = 1.14, 95% CI = 1.04-1.25, p = 0.005) depressive symptom domains. Sensitivity analyses revealed similar results.

CONCLUSIONS

IR was positively associated with cognitive/affective and somatic depressive symptoms in non-obese individuals.