Obesity, Inflammation and the Brain

Brain inflammation produces a variety of emotional, behavior and cognitive symptoms.

I remember clearly a patient I cared for with central nervous system lupus erythrematosis (SLE). With SLE flairs she developed flagrant psychotic symptoms including hallucinations requiring inpatient psychiatric care.

Between flares she had no significant psychiatric symptoms.

Nicole Castanon and two colleagues from France have published a review of the role of obesity-associated inflammation and brain dysfunction.

Obesity is linked to a variety of blood markers of inflammation including proinflammatory cytokines, IL-6, interleuking and TNF. These inflammatory markers diminish with weight loss accomplished by either diet restriction or bariatric surgery.

The authors note evidence obesity is associated with the following:

• Depression (not all studies and not confirmed in animal models)
• Anxiety
• Memory and other cognitive impairment
• Increased age-related cognitive decline

So how could primarily a peripheral body condition impact the brain?

Figure from Castonon et al

The authors summarize potential mechanisms in a nice figure that I have reproduced here as it is open-access under the Creative Common Attribution License. See the citation below for the source of this figure.

Increased adipose (fat) tissue is known to promote local inflammation including recruitment of microphages and secretion of inflammatory chemicals. 

This peripheral adipose inflammation can transfer to the brain through the vagus nerve, hormones or other blood inflammtory chemicals and cellular pathways.

Brain evidence for this transfer has been noted via inflammation in the hippocampus, basal ganglia and prefrontal cortex.

Additional obesity-related brain inflammatory effect has been noted through dysruption of the hypothalamic/pituitary/adrenal (HPA) axis and changes in brain serotonin and dopamine metabolism.

A second potential pathway is described as working through changes in the gut in obesity. Obesity is linked to changes in gut bacteria composition, a change that results in increased gut permeability. This permeability change potentially promotes increased gut-blood absorption of endotoxins that can promote a systemic anti-inflammatory response. 

The authors note their review of this topic supports weight management approaches to limit the effect of obesity on the brain. Additionally, there may be some evidence to investigate anti-inflammatory diet and drug interventions for those with combined obesity and brain disorders. 

Readers with more interest in this topic can access the free full-text manuscript by clicking on the link below.

Photo of blue jay in the snow is from the author's files.

Figure of obesity-brain interaction is from Castanon, Lasselin and Capuron, citation below.

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Castanon N, Lasselin J, & Capuron L (2014). Neuropsychiatric comorbidity in obesity: role of inflammatory processes. Frontiers in endocrinology, 5 PMID: 24860551