Peripheral insulin sensitivity predicting cognitive function in euthymic bipolar disorder patients

Neurocognitive correlates of metabolic dysregulation in individuals with mood disorders: a systematic review and meta-analysis

Individuals with mood disorders are predisposed to metabolic dysfunction, while those with metabolic dysregulation such as diabetes and obesity experience more severe depressive symptoms. Both metabolic dysfunction and mood disorders are independently associated with cognitive deficits. Therefore, given their close association, this study aimed to explore the association between metabolic dysfunction in individuals with mood disorders in relation to cognitive outcomes. A comprehensive search comprised of these three domains was carried out; a random-effects meta-analysis pooling mean cognitive outcomes was conducted (PROSPERO ID: CRD42022295765). Sixty-three studies were included in this review; 26 were synthesized in a quantitative meta-analysis. Comorbid metabolic dysregulation was associated with significantly lower global cognition among individuals with mood disorders. These trends were significant within each mood disorder subgroup, including major depressive disorder, bipolar disorder, and self-report depression/depressive symptoms. Type 2 diabetes was associated with the lowest cognitive performance in individuals with mood disorders, followed by peripheral insulin resistance, body mass index ⩾25 kg/m2, and metabolic syndrome. Significant reduction in scores was also observed among individual cognitive domains (in descending order) of working memory, attention, executive function, processing speed, verbal memory, and visual memory. These findings demonstrate the detrimental effects of comorbid metabolic dysfunction in individuals with mood disorders. Further research is required to understand the underlying mechanisms connecting mood disorders, metabolism, and cognition.

The relationship between peripheral insulin resistance and social cognitive deficits among euthymic patients with bipolar disorder

BACKGROUND

Despite extensive literature documenting emotion-related social-cognitive deficits in euthymic patients with bipolar disorder (BD), the factors contributing to these deficits have not been definitively established. To address this gap, the present study aimed to examine the association between peripheral insulin resistance (IR) and emotion-related social-cognitive abilities in BD patients and controls.

METHOD

Sixty-five BD patients and 38 non-psychiatric controls were recruited, and their social cognitive ability and IR were measured using the Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT) and the homeostasis model assessment of insulin resistance (HOMA-IR), respectively.

RESULTS

The study found that the BD patients scored significantly lower than the non-psychiatric controls in the task of emotional management. The BD patients had a higher mean HOMA-IR value as compared with the controls but this result was not statistically significant (p = 0.051). The interaction between BD diagnosis and HOMA-IR value was significant on the MSCEIT Facilitating emotions branch and Facilitation subscale (p = 0.024, p = 0.010), and post-hoc analyses revealed that the BD patients in the higher HOMA-IR group had significantly lower scores than BD patients in the lower HOMA-IR group and the non-psychiatric controls in the higher HOMA-IR group on both the MSCEIT Facilitating emotion branch and Facilitation subscale.

LIMITATIONS

Due to the cross-sectional nature of the study, causality could not be inferred. The study did not examine potential mediators or moderators between IR and social cognition.

CONCLUSIONS

The results suggested that BD patients with IR experience additional impairment in specific domains of social cognition.

Appetite-regulating hormones in bipolar disorder: A systematic review and meta-analysis

Impaired hormonal regulation of appetite may contribute to higher cardiovascular risk in bipolar disorder (BD). We performed a systematic review and meta-analysis of studies investigating peripheral blood levels of appetite-regulating hormones in BD and controls. A total of 32 studies were included. Leptin and insulin levels were significantly elevated in patients with BD during euthymia, but not in other mood states. Greater differences in the number of male participants between patients with BD and healthy controls were associated with higher effect size estimates for the levels of insulin. There were significant positive correlations of effect size estimates for the levels of adiponectin with the percentage of individuals with type I BD and duration of BD. Our findings point to the mechanisms underlying high rates of cardiometabolic comorbidities in BD. Moreover, they suggest that investigating hormonal regulation of appetite might help to understand differences in the neurobiology of BD types.

Mitochondrial DNA Copy Number Is Associated With Treatment Response and Cognitive Function in Euthymic Bipolar Patients Receiving Valproate

BACKGROUND

Bipolar disorder (BD) is associated with cognitive impairment and mitochondrial dysfunction. However, the associations among mitochondrial DNA copy number (MCN), treatment response, and cognitive function remain elusive in BD patients.

METHODS

Sixty euthymic BD patients receiving valproate (VPA) and 66 healthy controls from the community were recruited. The indices of metabolic syndrome (MetS) were measured. Quantitative polymerase chain reaction analysis of blood leukocytes was used to measure the MCN. Cognitive function was measured by calculating perseverative errors and completed categories on the Wisconsin Card Sorting Test (WCST). The VPA treatment response was measured using the Alda scale.

RESULTS

BD patients had significantly higher MCN, triglyceride, and C-reactive protein (CRP) levels, waist circumference, and worse performance on the WCST than the controls. Regression models showed that BD itself and the VPA concentration exerted significant effects on increased MCN levels. Moreover, the receiver operating characteristic curve analysis showed that an MCN of 2.05 distinguished VPA responders from nonresponders, with an area under the curve of 0.705 and a sensitivity and specificity of 0.529 and 0.816, respectively. An MCN level ≥2.05 was associated with 5.39 higher odds of being a VPA responder (P = .006). BD patients who were stratified into the high-MCN group had a higher VPA response rate, better WCST performance, lower CRP level, and less MetS.

CONCLUSIONS

The study suggests a link between the peripheral MCN and cognitive function in BD patients. As an inflammatory status, MetS might modulate this association.