Nucleus accumbens microstructure mediates the relationship between obesity and eating behavior in adults

Altered asymmetry of amygdala volume mediates food addiction and weight gain

Background

Food addiction and an impulsive personality can increase overeating, which can lead to weight gain. The amygdala and nucleus accumbens (NAcc) are critical for regulating obesogenic behaviour. However, whether the amygdala or the NAcc acts as the neural basis for the regulation of food addiction, impulsive personality, and body weight remains unclear.

Methods

We examined the differences in the volume of the amygdala and NAcc, especially the lateralization index (LI), between 33 obese participants and 39 age- and sex-matched healthy controls. The associations of the LI of each brain region with clinical variables and body mass index (BMI) were identified using network analysis. Finally, we explored the relationships among the LIs of brain regions, impulsive personality, food addiction, and BMI through a multiple chain mediation model.

Results

We observed a significant decrease in the LI of the amygdala in the obese group compared with the healthy group (F = 20.276, p < 0.001), which indicates that the right amygdala was larger than the left amygdala in the obese group. Network analysis revealed that the LI of the amygdala was very closely associated with nonplanning impulsivity, food addiction and BMI. The results of the mediation analysis indicated that increased nonplanning impulsiveness could lead to weight gain through increased food addiction (β = 0.069, SE = 0.043, 95% CI [0.014, 0.184]). Moreover, in this symptom chain, the LI of the amygdala can mediate the relationship between food addiction and BMI (β = 0.018, SE = 0.014, 95% CI [0.002, 0.061]).

Conclusion

Our observations indicate a substantial reduction in the LI of the amygdala among individuals with obesity, suggesting a structural predisposition. The findings reveal a potential neural mechanism that can help explain the interplay between impulsivity, food addiction, and obesity.

Relationships between abdominal adipose tissue and neuroinflammation with diffusion basis spectrum imaging in midlife obesity

OBJECTIVE

This study investigated how obesity, BMI ≥ 30 kg/m2, abdominal adiposity, and systemic inflammation relate to neuroinflammation using diffusion basis spectrum imaging.

METHODS

We analyzed data from 98 cognitively normal midlife participants (mean age: 49.4 [SD 6.2] years; 34 males [34.7%]; 56 with obesity [57.1%]). Participants underwent brain and abdominal magnetic resonance imaging (MRI), blood tests, and amyloid positron emission tomography (PET) imaging. Abdominal visceral and subcutaneous adipose tissue (VAT and SAT, respectively) was segmented, and Centiloids were calculated. Diffusion basis spectrum imaging parameter maps were created using an in-house script, and tract-based spatial statistics assessed white matter differences in high versus low BMI values, VAT, SAT, insulin resistance, systemic inflammation, and Centiloids, with age and sex as covariates.

RESULTS

Obesity, high VAT, and high SAT were linked to lower axial diffusivity, reduced fiber fraction, and increased restricted fraction in white matter. Obesity was additionally associated with higher hindered fraction and lower fractional anisotropy. Also, individuals with high C-reactive protein showed lower axial diffusivity. Higher restricted fraction correlated with continuous BMI and SAT particularly in male individuals, whereas VAT effects were similar in male and female individuals.

CONCLUSIONS

The findings suggest that, at midlife, obesity and abdominal fat are associated with reduced brain axonal density and increased inflammation, with visceral fat playing a significant role in both sexes.

White adipose tissue distribution and amount are associated with increased white matter connectivity

Obesity represents a significant public health concern and is linked to various comorbidities and cognitive impairments. Previous research indicates that elevated body mass index (BMI) is associated with structural changes in white matter (WM). However, a deeper characterization of body composition is required, especially considering the links between abdominal obesity and metabolic dysfunction. This study aims to enhance our understanding of the relationship between obesity and WM connectivity by directly assessing the amount and distribution of fat tissue. Whole-body magnetic resonance imaging (MRI) was employed to evaluate total adipose tissue (TAT), visceral adipose tissue (VAT), and subcutaneous adipose tissue (SAT), while MR liver spectroscopy measured liver fat content in 63 normal-weight, overweight, and obese males. WM connectivity was quantified using microstructure-informed tractography. Connectome-based predictive modeling was used to predict body composition metrics based on WM connectomes. Our analysis revealed a positive dependency between BMI, TAT, SAT, and WM connectivity in brain regions involved in reward processing and appetite regulation, such as the insula, nucleus accumbens, and orbitofrontal cortex. Increased connectivity was also observed in cognitive control and inhibition networks, including the middle frontal gyrus and anterior cingulate cortex. No significant associations were found between WM connectivity and VAT or liver fat. Our findings suggest that altered neural communication between these brain regions may affect cognitive processes, emotional regulation, and reward perception in individuals with obesity, potentially contributing to weight gain. While our study did not identify a link between WM connectivity and VAT or liver fat, further investigation of the role of various fat depots and metabolic factors in brain networks is required to advance obesity prevention and treatment approaches.

Associations between maternal pre-pregnancy BMI and infant striatal mean diffusivity

BACKGROUND

It is well-established that parental obesity is a strong risk factor for offspring obesity. Further, a converging body of evidence now suggests that maternal weight profiles may affect the developing offspring's brain in a manner that confers future obesity risk. Here, we investigated how pre-pregnancy maternal weight status influences the reward-related striatal areas of the offspring's brain during in utero development.

METHODS

We used diffusion tensor imaging to quantify the microstructure of the striatal brain regions of interest in neonates (N = 116 [66 males, 50 females], mean gestational weeks at birth [39.88], SD = 1.14; at scan [43.56], SD = 1.05). Linear regression was used to test the associations between maternal pre-pregnancy body mass index (BMI) and infant striatal mean diffusivity.

RESULTS

High maternal pre-pregnancy BMI was associated with higher mean MD values in the infant's left caudate nucleus. Results remained unchanged after the adjustment for covariates.

CONCLUSIONS

In utero exposure to maternal adiposity might have a growth-impairing impact on the mean diffusivity of the infant's left caudate nucleus. Considering the involvement of the caudate nucleus in regulating eating behavior and food-related reward processing later in life, this finding calls for further investigations to define the prognostic relevance of early-life caudate nucleus development and weight trajectories of the offspring.

The role of functional and structural properties of the nucleus accumbens subregions in eating behavior regulation of bulimia nervosa

OBJECTIVE

Although studies have demonstrated the involvement of the nucleus accumbens (NAc) in the neurobiology of eating disorders, its alterations in bulimia nervosa (BN) remain largely unknown. This study investigated the structural and functional properties of NAc in patients with BN.

METHOD

Based on the resting-state functional MRI and high-resolution anatomical T1-weighted imaging data acquired from 43 right-handed BN patients and 40 sex-, age- and education-matched right-handed healthy controls (HCs), the group differences in gray matter volume (GMV) and fractional amplitude of low-frequency fluctuation (fALFF) in slow-4 and -5 bands and functional connectivity (FC) of NAc subregions (core and shell) were compared. The relationships between MRI and clinical data were explored in the BN group.

RESULTS

Compared with HCs, BN patients showed preserved GMV, decreased fALFF in slow-5 band of the left NAc core and shell, decreased FC between left NAc core and right caudate, and increased FC between all NAc subregions and frontal regions, between all NAc subregions (except the right NAc core) and the supramarginal gyrus (SMG), and between right NAc shell and left middle temporal gyrus. FC between the NAc and SMG was correlated with emotional eating behaviors.

DISCUSSION

Our study revealed preserved GMV, local neuronal activity reduction and functional network reorganization of the NAc in BN. The functional network reorganization of the NAc mainly occurred in the frontal cortex and was correlated with emotional eating behavior. These findings may provide novel insights into the BN using NAc as an entry point.

PUBLIC SIGNIFICANCE

Although studies have demonstrated the involvement of the nucleus accumbens (NAc) in the neurobiology of eating disorders, its alterations in bulimia nervosa (BN) remain largely unknown. We used a multimodal MRI technique to systematically investigate structural and functional alterations in NAc subregions of BN patients and explored the associations between such alterations and maladaptive eating behaviors, hoping to provide novel insights into BN.

Childhood obesity is linked to putative neuroinflammation in brain white matter, hypothalamus, and striatum

Neuroinflammation is both a consequence and driver of overfeeding and weight gain in rodent obesity models. Advances in magnetic resonance imaging (MRI) enable investigations of brain microstructure that suggests neuroinflammation in human obesity. To assess the convergent validity across MRI techniques and extend previous findings, we used diffusion basis spectrum imaging (DBSI) to characterize obesity-associated alterations in brain microstructure in 601 children (age 9-11 years) from the Adolescent Brain Cognitive DevelopmentSM Study. Compared with children with normal-weight, greater DBSI restricted fraction (RF), reflecting neuroinflammation-related cellularity, was seen in widespread white matter in children with overweight and obesity. Greater DBSI-RF in hypothalamus, caudate nucleus, putamen, and, in particular, nucleus accumbens, correlated with higher baseline body mass index and related anthropometrics. Comparable findings were seen in the striatum with a previously reported restriction spectrum imaging (RSI) model. Gain in waist circumference over 1 and 2 years related, at nominal significance, to greater baseline RSI-assessed restricted diffusion in nucleus accumbens and caudate nucleus, and DBSI-RF in hypothalamus, respectively. Here we demonstrate that childhood obesity is associated with microstructural alterations in white matter, hypothalamus, and striatum. Our results also support the reproducibility, across MRI methods, of findings of obesity-related putative neuroinflammation in children.

Diffusion basis spectrum imaging as an adjunct to conventional MRI leads to earlier diagnosis of high-grade glioma tumor progression versus treatment effect

Background

Following chemoradiotherapy for high-grade glioma (HGG), it is often challenging to distinguish treatment changes from true tumor progression using conventional MRI. The diffusion basis spectrum imaging (DBSI) hindered fraction is associated with tissue edema or necrosis, which are common treatment-related changes. We hypothesized that DBSI hindered fraction may augment conventional imaging for earlier diagnosis of progression versus treatment effect.

Methods

Adult patients were prospectively recruited if they had a known histologic diagnosis of HGG and completed standard-of-care chemoradiotherapy. DBSI and conventional MRI data were acquired longitudinally beginning 4 weeks post-radiation. Conventional MRI and DBSI metrics were compared with respect to their ability to diagnose progression versus treatment effect.

Results

Twelve HGG patients were enrolled between August 2019 and February 2020, and 9 were ultimately analyzed (5 progression, 4 treatment effect). Within new or enlarging contrast-enhancing regions, DBSI hindered fraction was significantly higher in the treatment effect group compared to progression group (P = .0004). Compared to serial conventional MRI alone, inclusion of DBSI would have led to earlier diagnosis of either progression or treatment effect in 6 (66.7%) patients by a median of 7.7 (interquartile range = 0-20.1) weeks.

Conclusions

In the first longitudinal prospective study of DBSI in adult HGG patients, we found that in new or enlarging contrast-enhancing regions following therapy, DBSI hindered fraction is elevated in cases of treatment effect compared to those with progression. Hindered fraction map may be a valuable adjunct to conventional MRI to distinguish tumor progression from treatment effect.

Longitudinal Evidence of a Vicious Cycle Between Nucleus Accumbens Microstructure and Childhood Weight Gain

PURPOSE

Pediatric obesity is a growing public health concern. Previous work has observed diet to impact nucleus accumbens (NAcc) inflammation in rodents, measured by the reactive proliferation of glial cells. Recent work in humans has demonstrated a relationship between NAcc cell density-a proxy for neuroinflammation-and weight gain in youth; however, the directionality of this relationship in the developing brain and association with diet remains unknown.

METHODS

Waist circumference (WC) and NAcc cell density were collected in a large cohort of children (n > 2,000) participating in the Adolescent Brain Cognitive Development (ABCD) Study (release 3.0) at baseline (9-10 y) and at a Year 2 follow-up (11-12 y). Latent change score modeling (LCSM) was used to disentangle contributions of baseline measures to two-year changes in WC percentile and NAcc cellularity. In addition, the role of NAcc cellularity in mediating the relationship between diet and WC percentile was assessed using dietary intake data collected at Year 2.

RESULTS

LCSM indicates that baseline WC percentile influences change in NAcc cellularity and that baseline NAcc cell density influences change in WC percentile. NAcc cellularity was significantly associated with WC percentile at Year 2 and mediated the relationship between dietary fat consumption and WC percentile.

CONCLUSIONS

These results implicate a vicious cycle whereby NAcc cell density biases longitudinal changes in WC percentile and vice versa. Moreover, NAcc cell density may mediate the relationship between diet and weight gain in youth. These findings suggest that diet-induced inflammation of reward circuitry may lead to behavioral changes that further contribute to weight gain.