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Reduced nucleus accumbens and caudate nucleus activation to a pleasant taste is associated with obesity in older adults.

ABSTRACT: Although obesity is recognized as a global health epidemic, insufficient research has been directed to understanding the rising prevalence of obesity in the fastest growing segment of the population, older adults. Late-life obesity has been linked to declines in physical health and cognitive function, with implications not only for the individual, but also for society. We investigated the hypothesis that altered brain responses to food reward is associated with obesity, using fMRI of response to pleasant and aversive taste stimuli in young and older adults performing a hedonic evaluation task. Correlations between higher levels of abdominal fat/body mass index and reduced fMRI activation to sucrose in dopamine-related brain regions (caudate, nucleus accumbens) were large in older adults. Significant associations between a hypofunctioning reward response and obesity suggest the hypothesis that decreased dopamine functioning may be a plausible mechanism for weight gain in older adults.

SUBMITTER: Green E

PROVIDER: S-EPMC3086067 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature

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Reduced nucleus accumbens and caudate nucleus activation to a pleasant taste is associated with obesity in older adults.

Green Erin E Jacobson Aaron A Haase Lori L Murphy Claire C

Brain research 20110324

Although obesity is recognized as a global health epidemic, insufficient research has been directed to understanding the rising prevalence of obesity in the fastest growing segment of the population, older adults. Late-life obesity has been linked to declines in physical health and cognitive function, with implications not only for the individual, but also for society. We investigated the hypothesis that altered brain responses to food reward is associated with obesity, using fMRI of response to ...[more]

PMID: 21362414

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Project description:Neuronal networks are regulated by three-dimensional spatial and structural properties. Despite robust evidence of functional implications in the modulation of cognition, little is known about the three-dimensional internal organization of cholinergic networks in the forebrain. Cholinergic networks in the forebrain primarily occur in subcortical nuclei, specifically the septum, nucleus basalis, globus pallidus, nucleus accumbens, and the caudate-putamen. Therefore, the present investigation analyzed the three-dimensional spatial organization of 14,000 cholinergic neurons that expressed choline acetyltransferase (ChAT) in these subcortical nuclei of the mouse forebrain. Point process theory and graph signal processing techniques identified three topological principles of organization. First, cholinergic interneuronal distance is not uniform across brain regions. Specifically, in the septum, globus pallidus, nucleus accumbens, and the caudate-putamen, the cholinergic neurons were clustered compared with a uniform random distribution. In contrast, in the nucleus basalis, the cholinergic neurons had a spatial distribution of greater regularity than a uniform random distribution. Second, a quarter of the caudate-putamen is composed of axonal bundles, yet the spatial distribution of cholinergic neurons remained clustered when axonal bundles were accounted for. However, comparison with an inhomogeneous Poisson distribution showed that the nucleus basalis and caudate-putamen findings could be explained by density gradients in those structures. Third, the number of cholinergic neurons varies as a function of the volume of a specific brain region but cell body volume is constant across regions. The results of the present investigation provide topographic descriptions of cholinergic somata distribution and axonal conduits, and demonstrate spatial differences in cognitive control networks. The study provides a comprehensive digital database of the total population of ChAT-positive neurons in the reported structures, with the x,y,z coordinates of each neuron at micrometer resolution. This information is important for future digital cellular atlases and computational models of the forebrain cholinergic system enabling models based on actual spatial geometry.

Project description:Previous research demonstrates that Slc6a15, a neutral amino acid transporter, is associated with depression susceptibility. However, no study examined Slc6a15 in the ventral striatum [nucleus accumbens (NAc)] in depression. Given our previous characterization of Slc6a15 as a striatal dopamine receptor 2 (D2)-neuron-enriched gene, we examined the role of Slc6a15 in NAc D2-neurons in mediating susceptibility to stress in male mice. First, we showed that Slc6a15 mRNA was reduced in NAc of mice susceptible to chronic social defeat stress (CSDS), a paradigm that produces behavioral and molecular adaptations that resemble clinical depression. Consistent with our preclinical data, we observed Slc6a15 mRNA reduction in NAc of individuals with major depressive disorder (MDD). The Slc6a15 reduction in NAc occurred selectively in D2-neurons. Next, we used Cre-inducible viruses combined with D2-Cre mice to reduce or overexpress Slc6a15 in NAc D2-neurons. Slc6a15 reduction in D2-neurons caused enhanced susceptibility to a subthreshold social defeat stress (SSDS) as observed by reduced social interaction, while a reduction in social interaction following CSDS was not observed when Slc6a15 expression in D2-neurons was restored. Finally, since both D2-medium spiny neurons (MSNs) and D2-expressing choline acetyltransferase (ChAT) interneurons express Slc6a15, we examined Slc6a15 protein in these interneurons after CSDS. Slc6a15 protein was unaltered in ChAT interneurons. Consistent with this, reducing Slc5a15 selectively in NAc D2-MSNs, using A2A-Cre mice that express Cre selectively in D2-MSNs, caused enhanced susceptibility to SSDS. Collectively, our data demonstrate that reduced Slc6a15 in NAc occurs in MDD individuals and that Slc6a15 reduction in NAc D2-neurons underlies stress susceptibility.SIGNIFICANCE STATEMENT Our study demonstrates a role for reduced Slc6a15, a neutral amino acid transporter, in nucleus accumbens (NAc) in depression and stress susceptibility. The reduction of Slc6a15 occurs selectively in the NAc D2-neurons. Genetic reduction of Slc6a15 induces susceptibility to a subthreshold stress, while genetic overexpression in D2-neurons prevents social avoidance after chronic social defeat stress.

Dataset Information

Reduced nucleus accumbens and caudate nucleus activation to a pleasant taste is associated with obesity in older adults.

Publications

Reduced nucleus accumbens and caudate nucleus activation to a pleasant taste is associated with obesity in older adults.

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