A Novel Automated System Yields Reproducible Temporal Feeding Patterns in Laboratory Rodents

Abstract

Background The impact of temporal feeding patterns remains a major unanswered question in nutritional science. Progress has been hampered by the absence of a reliable method to impose temporal feeding in laboratory rodents, without the confounding influence of food-hoarding behavior. Objective The aim of this study was to develop and validate a reliable method for supplying crushed diets to laboratory rodents in consistent, relevant feeding patterns for prolonged periods. Methods We programmed our experimental feeding station to deliver a standard diet [StD; Atwater Fuel Energy (AFE) 13.9% fat] or high-fat diet (HFD; AFE 45% fat) during nocturnal grazing [providing 1/24th of the total daily food intake (tdF/I) of ad libitum–fed controls every 30 min] and meal-fed (3 × 1-h periods of ad libitum feeding) patterns in male rats (Sprague-Dawley: 4 wk old, 72–119 g) and mice [C57/Bl6J wild-type (WT): 6 mo old, 29–37 g], and ghrelin-null littermates (Ghr−/−; 27–34 g). Results Grazing yielded accurate, consistent feeding events in rats, with an approximately linear rise in nocturnal cumulative food intake [tdF/I (StD): 97.4 ± 1.5% accurate compared with manual measurement; R2 = 0.86; tdF/I (HFD): 99.0 ± 1.4% accurate; R2 = 0.86]. Meal-feeding produced 3 nocturnal meals of equal size and duration in StD-fed rats (tdF/I: 97.4 ± 0.9% accurate; R2 = 0.90), whereas the second meal size increased progressively in HFD-fed rats (44% higher on day 35 than on day 14; P < 0.01). Importantly, cumulative food intake in grazing and meal-fed rats was identical. Similar results were obtained in WT mice except that less restricted grazing induced hyperphagia (compared with meal-fed WT mice; P < 0.05 from day 1). This difference was abolished in Ghr−/− mice, with meal initiation delayed and meal duration enhanced. Neither pattern elevated corticosterone secretion in rats, but meal-feeding aligned ultradian pulses. Conclusions We have established a consistent, measurable, researcher-defined, stress-free method for imposing temporal feeding patterns in rats and mice. This approach will facilitate progress in understanding the physiologic impact of feeding patterns.

Mastication stimuli regulate the heartbeat rate through rhythmic regulation by the hypothalamic-autonomic system; molecular and telemetric studies in weaning-stage rats

“…This probe also enabled us to monitor animal movement (activity) by differentiating the time course of the radio wave strength. The major peaks of activity were observed at 20–23 h and 3–8 h in the one-day trace of day 8 ( Figure 3A ), which overlapped with the time distribution of the animals’ feeding behavior reported previously ( Ritskes and Strubbe, 2007 and Tilston et al, 2019 ). The higher activity observed in C group might be associated with the feeding behavior related to the chow diet, for example, the time spent handling and masticating the diet.…”

“…As the values were calculated from the data averaged every 5 min (5 values/5 min), the coincidence of parasympathetic activation and total autonomic activation may have occurred at a time scale close to 5 min. Accordingly, more frequent upregulation of HR by mastication and its downregulation by the cessation of mastication may have occurred in rats fed intermittently at approximately 20-min intervals ( Tilston et al, 2019 ). Accordingly, the significantly lower HR in the C group ( Figure 3D ) could be due to the overall dominance of the parasympathetic system.…”

Binding domain characterization of growth hormone secretagogue receptor

“…[ 15 , 16 , 17 ] Ghrelin plays an important role in modulating feeding patterns, insulin secretion, and glucose metabolism. [ 18 , 19 ] In contrast to ghrelin, a 28-amino acid octanoylated peptide, [ 15 ] adenosine is a purinergic nucleotide and it activates GHS-R1a through a binding domain distinct from that of ghrelin and MK-0677. [ 16 , 17 ] Even though they both activate GHS-R1a, when administering ghrelin and adenosine to rats, only ghrelin stimulates GH release.…”