Rhythmic neuronal activities of the rat nucleus of the solitary tract are impaired by short-term high fat diet - implications for daily control of satiety by the brainstem

Abstract

ABSTRACTTemporal partitioning of daily food intake is crucial for survival and involves the integration of internal circadian states and external influences such as the light-dark cycle and the composition of diet. These intrinsic and extrinsic factors are interdependent with misalignment of circadian rhythms promoting body weight gain, while consumption of a calorie dense diet elevates the risk of obesity and blunts circadian rhythms. Since cardiovascular disease, metabolic disorders, and cancer are comorbid with obesity, understanding the relationships between brain activity and diet is of pivotal importance. Recently, we defined for the first time the circadian properties of the dorsal vagal complex of the brainstem, a structure implicated in the control of food intake and autonomic tone, but if and how 24 h rhythms in this area are influenced by diet remains unresolved. Here we focused on a key structure of this complex, the nucleus of the solitary tract, and using a range of approaches, we interrogated how its neuronal and cellular rhythms are affected by high-fat diet. We report that short term consumption of this diet increases food intake during the day and blunts daily rhythms in gene expression and neuronal discharge in the nucleus of the solitary tract. These alterations in this structure occur without prominent body weight gain, suggesting that high-fat diet acts initially to reduce activity in the nucleus of the solitary tract, thereby disinhibiting mechanisms that suppress daytime feeding.GRAPHICAL ABSTRACT