Klug Molly E, Crain Eden, Hayes Anna M R, Shanmugam Mugil V, de La Serre Claire B, Kanoski Scott E
Human and Evolutionary Biology Section, Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California, USA.
Department of Nutritional Sciences, University of Georgia, Athens, Georgia, USA.
Compr Physiol. 2025 Oct;15(5):e70044. doi: 10.1002/cph4.70044.
Obesity is associated with increased gut permeability, which contributes to a state of chronic low-grade inflammation. Obesity is also linked with altered neurocognitive functions, including impaired learning and memory. Whether these changes are secondary to neuroinflammation versus other comorbidities associated with obesity is unknown. Here, we modeled the chronic low-grade inflammation that accompanies diet-induced obesity, but in the absence of obesity or consumption of an obesogenic diet. Male rats were implanted with intraperitoneal osmotic minipumps, continuously dispensing either saline (control) or lipopolysaccharide (LPS), an endotoxin produced in the gut that triggers inflammation when in circulation. Immunohistochemistry results revealed that LPS exposure led to neuroinflammation, with an increased number of Ionized Calcium-Binding Molecule 1 (Iba1) cells in the amygdala and hippocampus in LPS rats. Given that these brain regions are associated with impulse control, anxiety-like behavior, and learning and memory, we tested whether chronic LPS treatment impacted these behaviors. Interestingly, LPS exposure did not affect hippocampal-dependent memory in the Morris water maze, novel location recognition, or novel object in context memory tests, suggesting that neuroinflammation in the absence of obesity does not induce memory impairments. Further, chronic LPS significantly decreased anxiety-like behavior in the open field test and food impulsivity in an operant-based procedure. LPS animals also had significantly lower corticosterone and melatonin levels compared to controls, which may contribute to these behavioral outcomes. These results suggest that the low-grade inflammation associated with obesity is not sufficient alone to drive obesity-associated memory impairments but does reduce anxiety and food-motivated impulsive responses.
肥胖与肠道通透性增加有关,这会导致慢性低度炎症状态。肥胖还与神经认知功能改变有关,包括学习和记忆受损。这些变化是继发于神经炎症还是与肥胖相关的其他合并症尚不清楚。在这里,我们模拟了饮食诱导肥胖伴随的慢性低度炎症,但不存在肥胖或食用致胖饮食的情况。雄性大鼠被植入腹腔渗透微型泵,持续注射生理盐水(对照组)或脂多糖(LPS),脂多糖是肠道产生的一种内毒素,在循环时会引发炎症。免疫组织化学结果显示,LPS暴露导致神经炎症,LPS处理的大鼠杏仁核和海马体中离子钙结合分子1(Iba1)细胞数量增加。鉴于这些脑区与冲动控制、焦虑样行为以及学习和记忆有关,我们测试了慢性LPS处理是否会影响这些行为。有趣的是,LPS暴露在莫里斯水迷宫、新位置识别或情境记忆测试中的新物体测试中并未影响海马体依赖的记忆,这表明在没有肥胖的情况下神经炎症不会诱导记忆障碍。此外,慢性LPS在旷场试验中显著降低了焦虑样行为,并在基于操作性的程序中降低了食物冲动性。与对照组相比,LPS处理的动物皮质酮和褪黑素水平也显著降低,这可能导致了这些行为结果。这些结果表明,与肥胖相关的低度炎症单独不足以导致与肥胖相关的记忆障碍,但确实会减少焦虑和食物动机性冲动反应。
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