Does obesity-associated insulin resistance affect brain structure and function of adolescents differentially by sex?

Cognitive function 10 years after adolescent bariatric surgery

BACKGROUND

Adolescent bariatric surgery produces substantial weight loss and reduction of medical co-morbidities. Research in adult samples shows improved cognitive function postoperatively, although much less is known about the potential cognitive benefits of bariatric surgery in adolescents-especially at extended follow-up.

OBJECTIVE

Examine cognitive function 10 years after adolescent bariatric surgery.

SETTING

University hospital.

METHODS

A total of 99 young adults who underwent bariatric surgery as adolescents completed a computerized cognitive test battery as part of a larger 10-year postoperative assessment. All had been long-term participants in the Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) study.

RESULTS

Cognitive dysfunction was prevalent on tests of attention and executive function (e.g., Continuous Performance Test - Reaction Time 30%; Maze Errors - Overrun 30%), and 53.5% met research criteria for mild cognitive impairment (MCI). Modified Poisson regression with robust error variance revealed participants with preoperative hypertension and those completing Roux-en-Y gastric bypass were more likely to meet criteria for MCI at 10-year follow-up.

CONCLUSIONS

The current findings indicate that cognitive deficits are common 10 years after bariatric surgery. Additional studies are needed to clarify possible cohort effects, determine whether these cognitive deficits persist to even later follow-up (e.g., 20 yr after surgery), and identify underlying mechanisms and mitigation strategies.

Fetal cortical development and neurosonographic findings in obese pregnant women: a case control study from a tertiary hospital

PURPOSE

To investigate the effect of obesity on fetal cortical development.

METHODS

This prospective cross-sectional study was conducted with 91 pregnant women. Fetal neurosonography scans were performed in the third trimester, and according to body mass index (BMI) values, the patients were evaluated in two groups: obese (BMI ≥ 30 kg/m2) and normal weight (BMI < 30 kg/m2). During neurosonography, fetal insular depth and Sylvian fissures, parieo-occipital and cingulate fissure depth, frontal lobe length, and the sizes of the corpus callosum and cavum septum pellucidum were measured using a transvaginal approach. Fetal cortical development and Sylvian fissure operculization were graded.

RESULTS

The number of patients with grade 2 fetal cortical development was significantly higher among the pregnant women in the obese group compared to the normal weight group (n = 17, 41.5% and n = 8, 16.0%, respectively; p = 0.007). In the obese group, the number of pregnant women with grade 4 or below fetal Sylvian fissure operculization was significantly higher (n = 13, 31.7%), and the number of those with grade 9 or above operculization was significantly lower (n = 1, 2.5%) (p = 0.003). The fetal insular depth, frontal lobe anterior-posterior diameter, cingulate fissure depth, and corpus callosum thickness were lower in the obese group, albeit with no significant difference. Parieto-occipital depth significantly decreased in the obese group [6.8 (6) mm)] compared to the control group [10.5 (7.2) mm)] (p = 0.008). The fetal Sylvian fissure ratio and the cavum septum pellucidum ratio were found to be similar between the groups.

CONCLUSION

The data obtained from this study showed that obesity caused fetal cortical changes in pregnant women.

Appetite hormone dysregulation and executive dysfunction among adolescents with bipolar disorder and disruptive mood dysregulation disorder

Appetite hormone dysregulation may play a role in the pathomechanisms of bipolar disorder and chronic irritability. However, its association with executive dysfunction in adolescents with bipolar disorder and those with disruptive mood dysregulation disorder (DMDD) remains unclear. We included 20 adolescents with bipolar disorder, 20 adolescents with DMDD, and 47 healthy controls. Fasting serum levels of appetite hormones, including leptin, ghrelin, insulin, and adiponectin were examined. All participants completed the Wisconsin Card Sorting Test. Generalized linear models with adjustments for age, sex, body mass index, and clinical symptoms revealed that patients with DMDD had elevated fasting log-transformed insulin levels (p = .023) compared to the control group. Adolescents with DMDD performed worse in terms of the number of tries required to complete tasks associated with the first category (p = .035), and adolescents with bipolar disorder performed worse in terms of the number of categories completed (p = .035). A positive correlation was observed between log-transformed insulin levels and the number of tries required for the first category (β = 1.847, p = .032). Adolescents with DMDD, but not those with bipolar disorder, were more likely to exhibit appetite hormone dysregulation compared to healthy controls. Increased insulin levels were also related to executive dysfunction in these patients. Prospective studies should elucidate the temporal association between appetite hormone dysregulation, executive dysfunction, and emotional dysregulation.

Pre-diabetes is associated with altered functional connectivity density in cortical regions of the default-mode network

Insulin resistance and glucose dysregulation are associated with patterns of regional brain hypometabolism characteristic of Alzheimer's disease (AD). As predicted by evidence linking brain glucose metabolism to brain functional connectivity, type 2 diabetes is accompanied by altered functional connectivity density (FCD) in regions highly vulnerable to AD, but whether these alterations start at earlier stages such as pre-diabetes remain to be elucidated. Here, in addition to assessing whether pre-diabetes leads to a functional reorganization of densely connected cortical areas (hubs), we will assess whether such reorganization is conditioned by sex and/or insulin resistance, and contributes to improved cognition. One hundred and forty-four cognitively unimpaired middle-aged and older adults (55-78 years, 79 females), 73 with normoglycemia and 71 with pre-diabetes, underwent resting-state fMRI scanning. We first computed FCD mapping on cortical surfaces to determine the number of short- and long-range functional connections of every vertex in the cortex, and next used hubs showing aberrant FCD as seeds for the resting-state functional connectivity (rs-FC) calculation. ANCOVAs and linear multiple regression analyses adjusted by demographic and cardiometabolic confounders using frequentist and Bayesian approaches were applied. Analyses revealed higher long-range FCD in the right precuneus of pre-diabetic females and lower short-range FCD in the left medial orbitofrontal cortex (mOFC) of pre-diabetic individuals with higher insulin resistance. Although the mOFC also showed altered rs-FC patterns with other regions of the default mode network in pre-diabetic individuals, it was FCD of the precuneus and mOFC, and not the magnitude of their rs-FC, that was associated with better planning abilities and Mini-Mental State Examination (MMSE) scores. Results suggest that being female and/or having high insulin resistance exacerbate pre-diabetes-induced alterations in the FCD of hubs of the default-mode network that are particularly vulnerable to AD pathology. These changes in brain network organization appear to be compensatory for pre-diabetic females, likely assisting them to maintain cognitive functioning at early stages of glucose dysregulation.

Brain insulin resistance as a mechanistic mediator links peripheral metabolic disorders with declining cognition

BACKGROUND AND AIMS

Studies continue to investigate the underlying mechanism of the association between the increased risk of different types of cognitive decline and metabolic dysregulation. Brain insulin resistance (BIR) has been suggested to explain this association. The vital role of insulin in the body has been examined intensively and extensively; however, its role in the brain requires further investigation. Herein, we confined our focus to summarize the role of brain insulin signaling and the negative effect of dysmetabolism on insulin functioning in the brain.

METHODS

Published scientific manuscripts between 1998 and 2020 that discussed the effect of selected metabolic disorder conditions such as obesity, type 2 diabetes mellitus (T2DM), and high-fat diet (HFD) on brain functions were reviewed. The main keywords used were insulin resistance, brain insulin resistance, obesity, T2DM, and cognition.

RESULTS

Various metabolic disorders were linked to the increased risk of BIR, and was suggested to increase the probability of cognition impairment occurrence. Several proposed mechanisms explain this association among which insulin resistance and hyperinsulinemia were primary factors attributed to an increased risk of BIR among various metabolic disorders.

CONCLUSIONS

Understanding the trajectory of the association between metabolic disorders and alternation in cognition status could expand our vision of those overlapping conditions and pave the road to both treatment and preventative strategies for cognitive disorders.