Cannabidiol attenuates diet-induced metabolic endotoxemia, neuroinflammation, and anxiety-like behaviors in male aged rats

Obesity and aging synergistically reinforce neuroinflammation and disruption of homeostatic mechanisms, triggering pathological behaviors such as increased anxiety. Cannabidiol (CBD) has been reported to exert anxiolytic, anti-inflammatory, and neuroprotective effects, supporting the hypothesis that it may attenuate the detrimental consequences of obesity, even in aged animals. To test this hypothesis, 18-month-old male Wistar rats were divided into four experimental groups: control + vehicle (CT + vehicle), CT + CBD, cafeteria diet + vehicle (CAF + vehicle) and CAF + CBD. The animals were fed their diets for 8 weeks. Oral treatment with CBD (15 mg/kg/day) or vehicle began in the 9th week and continued until the end of the experiment, concurrently with the ongoing diet. We found that the CAF increased anxiety-like behaviors in the open field and elevated plus maze tests, while CBD mitigated these behaviors in the open field. Obesogenic diet also increased circulating levels of lipopolysaccharide, which were reduced by CBD. In the prefrontal cortex, CAF increased levels of interleukin 6 (IL-6), which were decreased by CBD. Additionally, CBD reduced the expression of tumor necrosis factor-α (TNF-α) and toll-like receptor 4 (TLR4). CAF feeding also caused a reduction in the main endocannabinoids, 2-arachidonoylglycerol (2-AG) and anandamide (AEA). In the prefrontal cortex, CAF increased transcripts of cannabinoid receptor 1 (CB1) and reduced those of cannabinoid receptor 2 (CB2) and serotonin receptor 5-hydroxytryptamine receptor 1A (HTR1A). Moreover, levels of triggering receptor expressed on myeloid cells 2 (TREM2) were reduced by the diet. These findings support the notion that obesity, through its metabolic and inflammatory consequences, exacerbates neuroinflammation and contributes to the dysregulation of the endocannabinoid system in aged animals. Notably, CBD demonstrated the ability to attenuate inflammatory markers and improve anxiety-like behavior, suggesting its potential as a therapeutic strategy to counteract obesity-induced neurobiological alterations in aging.