Brain structural networks and connectomes: the brain–obesity interface and its impact on mental health

Abstract

PurposeObesity is a complex and multifactorial disease identified as a global epidemic. Convergent evidence indicates that obesity differentially influences patients with neuropsychiatric disorders providing a basis for hypothesizing that obesity alters brain structure and function associated with the brain’s propensity toward disturbances in mood and cognition. Herein, we characterize alterations in brain structures and networks among obese subjects (ie, body mass index [BMI] ≥30 kg/m2) when compared with non-obese controls.Patients and methodsWe obtained noninvasive diffusion tensor imaging and generalized q-sampling imaging scans of 20 obese subjects (BMI=37.9±5.2 SD) and 30 non-obese controls (BMI=22.6±3.4 SD). Graph theoretical analysis and network-based statistical analysis were performed to assess structural and functional differences between groups. We additionally assessed for correlations between diffusion indices, BMI, and anxiety and depressive symptom severity (ie, Hospital Anxiety and Depression Scale total score).ResultsThe diffusion indices of the posterior limb of the internal capsule, corona radiata, and superior longitudinal fasciculus were significantly lower among obese subjects when compared with controls. Moreover, obese subjects were more likely to report anxiety and depressive symptoms. There were fewer structural network connections observed in obese subjects compared with non-obese controls. Topological measures of clustering coefficient (C), local efficiency (Elocal), global efficiency (Eglobal), and transitivity were significantly lower among obese subjects. Similarly, three sub-networks were identified to have decreased structural connectivity among frontal–temporal regions in obese subjects compared with non-obese controls.ConclusionWe extend knowledge further by delineating structural interconnectivity alterations within and across brain regions that are adversely affected in individuals who are obese.

The Dynamics of Functional Brain Networks Associated With Depressive Symptoms in a Nonclinical Sample

“…In sum, participants with high depressive symptoms engaged more in a state characterized by an increased coupling of the precuneus with regions in the DM network (PL state 3), and less in a state where the precuneus shifts away from connections in this network (PL state 8). We proposed that this imbalance might result in maladaptive cognitive styles that ultimately contribute to sad mood and depressive symptoms, which aligns with other studies implicating abnormal FC of the precuneus in patients with depression (Sheline et al, 2009;Li et al, 2013;Chen et al, 2018).…”

A systematic review of diffusion tensor imaging studies in obesity

“…Twenty-one out of twenty-eight retrieved studies [23][24][25][26][27][28]32,33,46,[49][50][51][52][53][54][55][56][57][58][59] used samples of adults. Five studies [60][61][62][63][64] were performed on adolescents between 12 and 19 years, and two studies 65,66 were performed on children between 7 and 11 years.…”

“…Five studies [60][61][62][63][64] were performed on adolescents between 12 and 19 years, and two studies 65,66 were performed on children between 7 and 11 years. Twenty-six studies [23][24][25][26][27][28]32,33,46,50,[52][53][54][56][57][58][60][61][62][63][64][65][66][67][68][69] used a sample composed of both men and women, while two studies 59,70 were performed on women only. All selected studies used a crosssectional approach.…”

Depressive and anxiety symptoms and suicidality in adolescent and young adult females with moderate to severe obesity before and after weight loss surgery

“…While some have postulated that shared genetic risks 33 and the underlying chronic inflammatory state in obesity are a common link in noted psychiatric alterations, 34 others report that structural changes in the brain in severe obesity may be a potential contributor to mood and emotional changes. 35 Diffusion indices which measure structural connectivity in areas of the brain that control feeding behaviours have been shown to correlate negatively with BMI, depression and anxiety symptoms. 35 Whether changes in the hormonal milieu observed in states of severe obesity cause these structural changes is yet to be determined.…”

“…35 Diffusion indices which measure structural connectivity in areas of the brain that control feeding behaviours have been shown to correlate negatively with BMI, depression and anxiety symptoms. 35 Whether changes in the hormonal milieu observed in states of severe obesity cause these structural changes is yet to be determined. 23 Another study in 37 adolescents who underwent RYGB showed fewer symptoms of anxiety and depression 4 months after surgery.…”