MIND-NL diet adherence moderates the relation of low-grade systemic inflammation with neuroinflammation and cognitive functioning: an exploratory cross-sectional study in older adults

BackgroundObservational studies have linked high adherence to the "Mediterranean-Dietary Approaches to Stop Hypertension Intervention for Neurodegenerative Delay" (MIND) diet to improved cognitive functions in older adults. The underlying peripheral and central mechanisms of this association remain poorly understood, although multiple nutrients in the MIND diet are known for their anti-inflammatory effects. Therefore, we explored the cross-sectional relation between MIND diet adherence (Dutch version), systemic inflammation, neuroinflammation, and cognitive functioning in older adults. In addition, we examined the role of intestinal barrier permeability in MIND diet associations with (neuro)inflammation. MethodsWe included 88 older adults (60-75 year) at risk of cognitive decline. MIND-NL diet adherence was assessed using a food frequency questionnaire. Systemic inflammation (C-reactive protein levels, white blood cell-counts and neutrophil-to-lymphocyte ratio) and intestinal barrier permeability (lipopolysaccharide-binding protein, zonulin, and lipopolysaccharide) markers were measured in blood. Neuroinflammation-associated metabolites (myo-inositol, choline and creatine) were measured in the dorsolateral prefrontal cortex with proton magnetic resonance spectroscopy (1H-MRS). Cognitive functioning was assessed with a neuropsychological test battery. ResultsLinear models showed that both MIND diet adherence and systemic inflammation did not predict neuroinflammation or cognition independently. However, MIND diet adherence significantly moderated the relation between systemic inflammation and neuroinflammation ({beta}=-0.11, p=0.04) as well as between systemic inflammation and cognition ({beta}=0.044, p=0.02). Specifically, in individuals with lower MIND diet adherence (identified as scores [≤]7), systemic inflammation was positively related to neuroinflammation, and negatively to cognition. Similarly, MIND diet adherence significantly moderated the relation between intestinal barrier permeability and neuroinflammation ({beta}=-0.17, p=0.05). Finally, within participants with lower MIND adherence (median split at [≤]8.75), systemic inflammation mediated the relation between the intestinal barrier permeability and neuroinflammation ({beta}=0.427 [0.072; 0.891], p=0.04). ConclusionOur findings suggest that higher MIND diet adherence might protect against the detrimental effect of systemic inflammation on neuroinflammation and cognitive functioning. Moreover, we demonstrated that greater adherence to the MIND diet may specifically protect against the systemic inflammation-mediated relationship between intestinal barrier permeability and neuroinflammation. These findings should be confirmed in randomised controlled trials.