High dietary fat induces NADPH oxidase-associated oxidative stress and inflammation in rat cerebral cortex

Epidemiological and experimental studies have suggested that high dietary intake of fats is associated with cognitive decline and a significantly increased risk of dementia. Since oxidative stress and inflammation have been speculated to be critical mechanisms underlying neurodegenerative diseases, we hypothesized that a high fat (HF) diet might induce cerebral oxidative stress or neural inflammation and subsequently contribute to the high risk of dementia. To test this hypothesis, male rats were placed on either a HF diet or a low fat (LF) diet starting at 1 month of age and lasting for 5 months. Intracellular reactive oxidative species (ROS) generation in the cerebral cortex was measured by the oxidant-sensitive dye 5-(6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (CM-H(2)DCFDA). Cortical tissue concentration of prostaglandin E(2) (PGE(2)) was determined using an enzymatic immunoassay. Expression of NADPH oxidase subunits, cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), nuclear transcription factor NF(kappa)-B (NF-kappaB) p65 subunit, Ikappa B(IkappaB), and phospho-Ikappa B(phospho-IkappaB) was evaluated by Western blot analysis. The HF diet significantly increased ROS generation and expression of gp91(phox), p22(phox), p47(phox), and p67(phox) NADPH oxidase subunits in cerebral cortex. Elevated PGE(2) levels and markedly increased COX-2 expression suggested a neural inflammatory response in response to excessive fat intake. These findings were further supported by significantly increased phospho-IkappaB and nuclear NF-kappaB expression that suggested a role of IkappaB phosphorylation in HF diet-induced NF-kappaB translocation. The present study revealed that HF diet induced neural oxidative stress, inflammation, and NF-kappaB activation in rat cerebral cortex, and provided novel evidence regarding the link between high dietary fat and increased risk of dementia.