An insulin resistance associated neural correlate of impulsivity in type 2 diabetes mellitus

Genome-wide association studies (GWAS) and post-GWAS analyses of impulsivity: A systematic review

Impulsivity is related to a host of mental and behavioral problems. It is a complex construct with many different manifestations, most of which are heritable. The genetic compositions of these impulsivity manifestations, however, remain unclear. A number of genome-wide association studies (GWAS) and post-GWAS analyses have tried to address this issue. We conducted a systematic review of all GWAS and post-GWAS analyses of impulsivity published up to December 2023. Available data suggest that single nucleotide polymorphisms (SNPs) in more than a dozen of genes (e.g., CADM2, CTNNA2, GPM6B) are associated with different measures of impulsivity at genome-wide significant levels. Post-GWAS analyses further show that different measures of impulsivity are subject to different degrees of genetic influence, share few genetic variants, and have divergent genetic overlap with basic personality traits such as extroversion and neuroticism, cognitive ability, psychiatric disorders, substance use, and obesity. These findings shed light on controversies in the conceptualization and measurement of impulsivity, while providing new insights on the underlying mechanisms that yoke impulsivity to psychopathology.

An Evaluation of Difficulty in Emotion Regulation, Impulsivity, and Emotional Eating in Children and Adolescents Diagnosed with Type 1 Diabetes Mellitus

OBJECTIVE

The aim of this study was to investigate difficulties in emotion regulation, emotional eating, and impulsivity in children diagnosed with type 1 diabetes mellitus (T1DM).

MATERIALS AND METHODS

The study included 53 children who were diagnosed with T1DM, and a control group of 50 subjects. The Schedule for Affective Disorders and Schizophrenia for School-age Children-Present and Lifetime Version, Difficulties in Emotion Regulation Scale- Short Form (DERS-16), Emotional Eating Scale-Child and Adolescent Form (EES-C), and the Barratt Impulsivity Scale 11-Short Form (BIS-11) were administered to the participants.

RESULTS

In the T1DM group, the disease duration was a mean of 52.7 ± 40.62 months, and only 17% had good metabolic control. The rate of psychiatric disorder determined was significantly higher in the T1DM group (P = .001). No significant difference was determined between the 2 groups in respect of the DERS-16, EES-C, and BIS-11 total and subscale scores. However, in multivariate linear regression, the increase in BIS-11 total score was affected by increasing DERS impulse (β = 0.475), decreasing age (β = -0.209), and presence of T1DM (β = 0.211). An increase in the DERS-16 total score was associated with the presence of psychiatric disorder (β = -0.258) and an increase in BIS-11-A (the second scale assesses concentration problems) (β = 0.317) score. In the T1DM group, the glycated hemoglobin level was lower in the group with insulin treatment with the injection method (8.2 ± 2.1%) than in those with the pump method (9.1 ± 1.5%) (P = .069).

CONCLUSION

It is important that mental health professionals take an active role in all processes of the disease in order to protect the mental health of children with T1DM. Cite this article as: Yıldız Miniksar D, Öz B, Kılıç M, et al. An evaluation of difficulty in emotion regulation, impulsivity, and emotional eating in children and adolescents diagnosed with type 1 diabetes mellitus. Turk Arch Pediatr. 2024;59(1):78-86.

Household Food Insecurity and Cognition in Youth and Young Adults with Youth-Onset Diabetes

Objective

We evaluated the association of household food insecurity (FI) with cognition in youth and young adults with type 1 diabetes (T1D) or type 2 diabetes (T2D).

Design

In this cross-sectional study, age-adjusted scores for composite Fluid Cognition, and sub-domain scores for Receptive Language and Inhibitory Control and Attention, were modeled stratified by diabetes-type using linear regression, with FI in the past year as the predictor, controlling for covariates. Tests for processing speed, inhibitory control/attention, working memory, episodic memory, and cognitive flexibility were administered to measure composite Fluid Cognition score. The NIHT-CB Picture Vocabulary Test was used to assess Crystallized Cognition score and rapid identification of congruent versus noncongruent items were used to assess Inhibitory Control and Attention score.

Setting

The SEARCH for Diabetes in Youth study, representative of 5 U.S. states.

Participants

Included 1574 youth and young adults with T1D or T2D, mean age of 21 years, mean diabetes duration of 11 years, 51% non-Hispanic white, and 47% had higher HbA1c levels (>9% HbA1c).

Results

Approximately 18% of the 1,240 participants with T1D and 31% of the 334 with T2D experienced FI. The food-insecure group with T1D had a lower composite Fluid Cognition score (β= -2.5, 95% confidence interval (CI)= -4.8, -0.1) and a lower Crystallized Cognition score (β= -3.4, CI= -5.6, -1.3) than food-secure peers. Findings were attenuated to non-significance after adjustment for demographics. Among T2D participants, no associations were observed. In participants with T1D effect modification by glycemic levels were found in the association between FI and composite Fluid Cognition score but adjustment for socioeconomic characteristics attenuated the interaction (p=0.0531).

Conclusions

Food-insecure youth and young adults with T1D or T2D did not have different cognition compared to those who were food-secure after adjustment for confounders. Longitudinal research is needed to further understand relations amongst these factors.

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

Type 2 diabetes and major depressive disorder (MDD) are the leading causes of disability worldwide and have a high comorbidity rate with fatal outcomes. Despite the long-established association between these conditions, the underlying molecular mechanisms remain unknown. Since the discovery of insulin receptors in the brain and the brain's reward system, evidence has accumulated indicating that insulin modulates dopaminergic (DA) signalling and reward behaviour. Here, we review the evidence from rodent and human studies, that insulin resistance directly alters central DA pathways, which may result in motivational deficits and depressive symptoms. Specifically, we first elaborate on the differential effects of insulin on DA signalling in the ventral tegmental area (VTA) - the primary DA source region in the midbrain - and the striatum as well as its effects on behaviour. We then focus on the alterations induced by insulin deficiency and resistance. Finally, we review the impact of insulin resistance in DA pathways in promoting depressive symptoms and anhedonia on a molecular and epidemiological level and discuss its relevance for stratified treatment strategies.

Differential impact of glycemic control and comorbid conditions on the neurophysiology underlying task switching in older adults with type 2 diabetes

Type 2 diabetes is known to negatively affect higher order cognition and the brain, but the underlying mechanisms are not fully understood. In particular, glycemic control and common comorbidities are both thought to contribute to alterations in cortical neurophysiology in type 2 diabetes, but their specific impact remains unknown. The current study probed the dynamics underlying cognitive control in older participants with type 2 diabetes, with and without additional comorbid conditions (i.e., cardiovascular disease, nephropathy, peripheral neuropathy, retinopathy), using a task switching paradigm and a dynamic functional brain mapping method based on magnetoencephalography (MEG). We hypothesized that neural dynamics would be differentially impacted by the level of glycemic control (i.e., diabetes itself) and the burden of additional comorbid conditions. Supporting this hypothesis, our findings indicated separable, but widespread alterations across frontal, parietal, temporal and cerebellum regions in neural task-switch costs in type 2 diabetes that were differentially attributable to glycemic control and the presence of comorbid conditions. These effects were spatially non-overlapping and the effects were not statistically related to one another. Further, several of the effects that were related to the presence of comorbidities were associated with behavioral performance, indicating progressive deficits in brain function with extended disease. These findings provide insight on the underlying neuropathology and may inform future treatment plans to curtail the neural impact of type 2 diabetes.

Transdiagnostic Perspective of Impulsivity and Compulsivity in Obesity: From Cognitive Profile to Self-Reported Dimensions in Clinical Samples with and without Diabetes

Impulsive and compulsive behaviors have both been observed in individuals with obesity. The co-occurrence of obesity and type 2 diabetes (T2D) is more strongly associated with impulsivity, although there are no conclusive results yet. A multidimensional assessment of impulsivity and compulsivity was conducted in individuals with obesity in the absence or presence of T2D, compared with healthy, normal-weight individuals, with highly impulsive patients (gambling disorders), and with highly compulsive patients (anorexia nervosa). Decision making and novelty seeking were used to measure impulsivity, and cognitive flexibility and harm avoidance were used for compulsivity. For impulsivity, patients with obesity and T2D showed poorer decision-making ability compared with healthy individuals. For compulsivity, individuals with only obesity presented less cognitive flexibility and high harm avoidance; these dimensions were not associated with obesity with T2D. This study contributes to the knowledge of the mechanisms associated with diabetes and its association with impulsive–compulsive behaviors, confirming the hypothesis that patients with obesity and T2D would be characterized by higher levels of impulsivity.

The Association Between Diabetes Mellitus and Mild Behavioral Impairment Among Mild Cognitive Impairment: Findings from Singapore

BACKGROUND

Mild behavioral impairment (MBI) describes persistent behavioral changes in later life as an at-risk state for dementia. While cardiovascular risk factors (CVRFs) are linked to dementia, it is uncertain how CVRFs are associated with MBI.

OBJECTIVE

To determine the prevalence of MBI and its association with CVRFs among cognitively normal (CN) and mild cognitive impairment (MCI) individuals in Singapore.

METHODS

172 individuals (79 CN and 93 MCI) completed the MBI-checklist (MBI-C). The prevalence of MBI and MBI-C sub-domain characteristics among CN and MCI were examined. Regression models evaluated the relationships between MBI-C sub-domain scores with CVRFs.

RESULTS

The prevalence of MBI and mean MBI-C total score were significantly higher among MCI than CN (34.4%versus 20.3%, p = 0.022 and 7.01 versus 4.12, p = 0.04). The highest and lowest-rated sub-domains among CN and MCI were impulse dyscontrol and abnormal thoughts and perception respectively. Within the MCI cohort, a higher proportion of individuals with diabetes mellitus (DM) had MBI compared to individuals without DM (28.1%versus 10.4%, p = 0.025). The interaction of DM and MCI cohort resulted in significantly higher mean MBI-C total, decreased motivation, emotional dysregulation, impulse dyscontrol, and abnormal thoughts and perception sub-domain scores.

CONCLUSION

The prevalence of MBI is higher among a Singapore cohort compared to Caucasian cohorts. The associations of DM with both the presence and severity of MBI among MCI suggest that DM may be a risk factor for MBI. The optimization of DM may be a potential therapeutic approach to improve clinical outcomes among MCI with MBI.

GLP-1 and hunger modulate incentive motivation depending on insulin sensitivity in humans

OBJECTIVE

To regulate food intake, our brain constantly integrates external cues, such as the incentive value of a potential food reward, with internal state signals, such as hunger feelings. Incentive motivation refers to the processes that translate an expected reward into the effort spent to obtain the reward; the magnitude and probability of a reward involved in prompting motivated behaviour are encoded by the dopaminergic (DA) midbrain and its mesoaccumbens DA projections. This type of reward circuity is particularly sensitive to the metabolic state signalled by peripheral mediators, such as insulin or glucagon-like peptide 1 (GLP-1). While in rodents the modulatory effect of metabolic state signals on motivated behaviour is well documented, evidence of state-dependent modulation and the role of incentive motivation underlying overeating in humans is lacking.

METHODS

In a randomised, placebo-controlled, crossover design, 21 lean (body mass index [BMI] < 25 kg/m²) and 16 obese (BMI³ 30 kg/m²) volunteer participants received either liraglutide as a GLP-1 analogue or placebo on two separate testing days. Incentive motivation was measured using a behavioural task in which participants were required to exert physical effort using a handgrip to win different amounts of food and monetary rewards. Hunger levels were measured using visual analogue scales; insulin, glucose, and systemic insulin resistance as assessed by the homeostasis model assessment of insulin resistance (HOMA-IR) were quantified at baseline.

RESULTS

In this report, we demonstrate that incentive motivation increases with hunger in lean humans (F_(1,42) = 5.31, p = 0.026, β = 0.19) independently of incentive type (food and non-food reward). This effect of hunger is not evident in obese humans (F_(1,62) = 1.93, p = 0.17, β = -0.12). Motivational drive related to hunger is affected by peripheral insulin sensitivity (two-way interaction, F_{(1, 35)} = 6.23, p = 0.017, β = -0.281). In humans with higher insulin sensitivity, hunger increases motivation, while poorer insulin sensitivity dampens the motivational effect of hunger. The GLP-1 analogue application blunts the interaction effect of hunger on motivation depending on insulin sensitivity (three-way interaction, F_{(1, 127)} = 5.11, p = 0.026); no difference in motivated behaviour could be found between humans with normal or impaired insulin sensitivity under GLP-1 administration.

CONCLUSION

We report a differential effect of hunger on motivation depending on insulin sensitivity. We further revealed the modulatory role of GLP-1 in adaptive, motivated behaviour in humans and its interaction with peripheral insulin sensitivity and hunger. Our results suggest that GLP-1 might restore dysregulated processes of midbrain DA function and hence motivational behaviour in insulin-resistant humans.

Individual differences in impulsivity and need for cognition as potential risk or resilience factors of diabetes self-management and glycemic control

Objective

Impulsivity is marked by insufficient reflection and forethought, whereas Need for Cognition (NFC) also referred to as cognitive motivation or intellectual engagement is marked by elaborated thinking. The aim of this study was to investigate the potential role of these personality traits as resilience or risk factors, respectively, in diabetes self-management and glycaemic control. Further, it was examined whether diabetes-specific self-efficacy could serve as a mediator of these relationships.

Design/Measures

Data of 77 participants with type 2 diabetes was ascertained, using self-report instruments for NFC, impulsivity, diabetes-specific self-efficacy, and diabetes self-management. Glycemic control was assessed by the biomarker HbA_1c.

Results

While NFC was strongly positively associated with diabetes self-management and glycemic control, impulsivity showed a reverse pattern. Results of simple and serial mediation models showed that the effects on diabetes self-management and HbA1c of both, impulsivity and NFC, were mediated by self-efficacy.

Conclusion

The moderate to high standardized coefficients suggests that NFC might be an important protective factor and impulsivity a possible risk factor for effective diabetes self-management and glycemic control. These traits could be applied for an easy-to-use questionnaire-based patient screening, enabling trait-tailored treatments and programs which in turn may lower economic and health costs associated with poor diabetes-care.

Modulation of midbrain neurocircuitry by intranasal insulin

Insulin modulates dopamine neuron activity in midbrain and affects processes underlying food intake behaviour, including impulsivity and reward processing. Here, we used intranasal administration and task-free functional MRI in humans to assess time- and dose-dependent effects of insulin on functional connectivity of the dopaminergic midbrain - and how these effects varied depending on systemic insulin sensitivity as measured by HOMA-IR. Specifically, we used a repeated-measures design with factors dose (placebo, 40 IU, 100 IU, 160 IU), time (7 time points during a 90 min post-intervention interval), and group (low vs. high HOMA-IR). A factorial analysis identified a three-way interaction (with whole-brain significance) with regard to functional connectivity between midbrain and the ventromedial prefrontal cortex. This interaction demonstrates that systemic insulin sensitivity modulates the temporal course and dose-dependent effects of intranasal insulin on midbrain functional connectivity. It suggests that altered insulin sensitivity may impact on dopaminergic projections of the midbrain and might underlie the dysregulation of reward-related and motivational behaviour in obesity and diabetes. Perhaps most importantly, the time courses of midbrain functional connectivity we present may provide useful guidance for the design of future human studies that utilize intranasal insulin administration.