Mechanosensitive gastric vagal afferents (GVAs) are part of a coordinated set of mechanisms involved in the regulation of food intake. GVAs exhibit circadian variation in their response to mechanical stimuli allowing time of day specific satiety signalling1. This circadian variation is ablated by 12wks ad libitum access to a high fat diet (HFD). It is unclear whether the circadian pattern is entrainable to restricted food access.
We fed 8wk male C57BL/6 mice a standard diet (SLD; 18%kJ from fat) or a HFD (60%kJ from fat) ad libitum for 4wks, then each dietary group was divided so that half had access to food only during the light phase (LP:07:00-19:00) or dark phase (DP:19:00-07:00) for 8wks. From each group 8 mice were housed in metabolic cages to collect feeding data over the 12wks. Mice were sacrificed at 3hr intervals from 07:00 and recordings from GVA tension and mucosal receptors were taken2.
After 12wks both HFD groups weighed more than the SLD groups with no difference between LP and DP mice on the same diet. SLD-DP mice consumed more daily food through increased meal number (vs SLD and HFD LP mice) and meal size (vs HFD-DP). 24hr energy consumption was no different between SLD-DP, HFD-DP and HFD-LP mice. In SLD and HFD-DP mice, at 01:00 compared to 13:00 the response of tension receptors to 3g tension were reduced by 73% and 69% respectively. Mucosal receptor response to stroking (50mg) was reduced by 66% and 64% respectively. LP fed mice showed reversed circadian rhythms with 78%(SLD) and 59%(HFD) reductions in the tension response to tension and 65%(SLD) and 70%(HFD) reductions mucosal stroking at 13:00 compared to 01:00.
Circadian rhythms in GVA satiety signals can be entrained to a period of food access to largely maintain caloric intake. This entrainment is unaffected by HFD feeding.