Oral Presentation ANZOS-OSSANZ-AOCO Joint Annual Scientific Meeting 2017

Shifting light cycles abrogates circadian rhythmicity of gastric vagal afferent satiety signalling. (#28)

Stephen J Kentish 1 , Stewart Christie 1 , Hui Li 1 , George Hatzinikolas 1 , Gary Wittert 1 2 , Amanda Page 1 2
  1. University of Adelaide, Adelaide, SA, Australia
  2. Nutrition and Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA

Gastric vagal afferents (GVAs) play an important role in the regulation of food intake [1]. GVAs exhibit circadian rhythmicity in response to mechanical stimuli allowing time of day specific satiety signalling [2]. Disruption of the circadian clock is associated with increased risk of obesity [3]. We aimed to investigate the effect of disrupting the light cycle on GVA satiety signalling in health and high fat diet (HFD)-induced obesity.

C57BL/6 male mice (8wks old) were fed a standard mouse chow (SLD; 14% energy from fat) or HFD (60% energy from fat) ad libitum for 12 weeks. After 4 weeks on the respective diets they were placed into 2 groups/diet:  1) maintained in a normal light cycle environment (NL-mice; lights on 0600 to 1800); and 2) exposed to a rotating light cycle (RL-mice; 3 days lights on 0600 to 1800; 4 days lights on 1800 to 0600) for 8wks. In vitro GVA recordings [4] were taken at 3 hour intervals starting at 1800.  

The HFD-mice gained significantly more weight than SLD-mice and the HFD/RL mice gained significantly more weight than the HFD/NL mice (SLD/NL-mice: 8.19±0.2g; SLD/RL-mice: 9.01±0.2g; HFD/NL-mice: 20.63.±0.6g; HFD/RL-mice: 22.49±0.6g). SLD/NL-mice exhibited circadian oscillations in GVA mechanosensitivity with peaks at 1200 and troughs at 0000hr. Consistent with these results, food intake was greater during the dark phase (2.59±0.1g) compared to the light phase (0.53±0.1g: P<0.001) in SLD/NL-mice. Circadian rhythmicity in GVA mechanosensitivity and food intake was lost in SLD-RL, HFD-RL and HFD-NL-mice.  

In conclusion, rotating the light cycle and/or HFD feeding abrogates circadian rhythmicity of GVA satiety signalling and alters feeding behaviour.

Supported by NH&MRC (APP1046289)

  1. Kentish SJ & Page AJ J Physiol 2015; 593: 775-86
  2. Kentish SJ et al J Neurosci 2013; 33: 19238-42
  3. Turek FW et al Science 2005; 308:1043-5
  4. Page AJ et al J Neurophysiol 2002; 87: 2095-103