Salience network connectivity is reduced by a meal and influenced by genetic background and hypothalamic gliosis.

BACKGROUND/OBJECTIVES: The salience network (SN) comprises brain regions that evaluate cues in the external environment in light of internal signals. We examined the SN response to meal intake and potential genetic and acquired influences on SN function. SUBJECTS/METHODS: Monozygotic (MZ; 40 pairs) and dizygotic (15 pairs) twins had body composition and plasma metabolic profile evaluated (glucose, insulin, leptin, ghrelin, and GLP-1). Twins underwent resting-state functional magnetic resonance imaging (fMRI) scans before and after a standardized meal. The strength of SN connectivity was analyzed pre- and post-meal and the percentage change elicited by a meal was calculated. A multi-echo T2 MRI scan measured T2 relaxation time, a radiologic index of gliosis, in the mediobasal hypothalamus (MBH) and control regions. Statistical approaches included intraclass correlations (ICC) to investigate genetic influences and within-pair analyses to exclude genetic confounders. RESULTS: SN connectivity was reduced by a meal ingestion (ß = -0.20; P < 0.001). Inherited influences on both pre- and post-meal connectivity were present (ICC MZ twins 26%, P < 0.05 and 47%, P < 0.001, respectively), but not percentage change in response to the meal. SN connectivity in response to a meal did not differ between participants with obesity and of normal weight (χ2(1) = 0.93; P = 0.33). However, when participants were classified as having high or low signs of MBH gliosis, the high MBH gliosis group failed to reduce the connectivity in response to a meal (z = -1.32; P = 0.19). Excluding genetic confounders, the percentage change in SN connectivity by a meal correlated to body fat percentage (r = 0.24; P < 0.01). CONCLUSIONS: SN connectivity was reduced by a meal, indicating potential participation of the SN in control of feeding. The strength of SN connectivity is inherited, but the degree to which SN connectivity is reduced by eating appears to be influenced by adiposity and the presence of hypothalamic gliosis.

Initial evidence for hypothalamic gliosis in children with obesity by quantitative T2 MRI and implications for blood oxygen-level dependent response to glucose ingestion.

OBJECTIVE: In adults, hypothalamic gliosis has been documented using quantitative T2 neuroimaging, whereas functional magnetic resonance imaging (fMRI) has shown a defective hypothalamic response to nutrients. No studies have yet evaluated these hypothalamic abnormalities in children with obesity. METHODS: Children with obesity and lean controls underwent quantitative MRI measuring T2 relaxation time, along with continuous hypothalamic fMRI acquisition to evaluate early response to glucose ingestion. RESULTS: Children with obesity (N = 11) had longer T2 relaxation times, consistent with gliosis, in the mediobasal hypothalamus (MBH) compared to controls (N = 9; P = 0.004). Moreover, there was a highly significant group*region interaction (P = 0.002), demonstrating that signs of gliosis were specific to MBH and not to reference regions. Longer T2 relaxation times correlated with measures of higher adiposity, including visceral fat percentage (P = 0.01). Mean glucose-induced hypothalamic blood oxygen-level dependent signal change did not differ between groups (P = 0.11). However, mean left MBH T2 relaxation time negatively correlated with glucose-induced hypothalamic signal change (P < 0.05). CONCLUSION: Imaging signs of hypothalamic gliosis were present in children with obesity and positively associated with more severe adiposity. Children with the strongest evidence for gliosis showed the least activation after glucose ingestion. These initial findings suggest that the hypothalamus is both structurally and functionally affected in childhood obesity.

An everyday activity as a treatment for depression: the benefits of expressive writing for people diagnosed with major depressive disorder.

BACKGROUND: The benefits of expressive writing have been well documented among several populations, but particularly among those who report feelings of dysphoria. It is not known, however, if those diagnosed with Major Depressive Disorder (MDD) would also benefit from expressive writing. METHODS: Forty people diagnosed with current MDD by the Structured Clinical Interview for DSM-IV participated in the study. On day 1 of testing, participants completed a series of questionnaires and cognitive tasks. Participants were then randomly assigned to either an expressive writing condition in which they wrote for 20 min over three consecutive days about their deepest thoughts and feelings surrounding an emotional event (n=20), or to a control condition (n=20) in which they wrote about non-emotional daily events each day. On day 5 of testing, participants completed another series of questionnaires and cognitive measures. These measures were repeated again 4 weeks later. RESULTS: People diagnosed with MDD in the expressive writing condition showed significant decreases in depression scores (Beck Depression Inventory and Patient Health Questionnaire-9 scores) immediately after the experimental manipulation (Day 5). These benefits persisted at the 4-week follow-up. LIMITATIONS: Self-selected sample. CONCLUSIONS: This is the first study to demonstrate the efficacy of expressive writing among people formally diagnosed with current MDD. These data suggest that expressive writing may be a useful supplement to existing interventions for depression.