Time-Restricted Feeding Prevents Ablation of Diurnal Rhythms in Gastric Vagal Afferent Mechanosensitivity Observed in High-Fat Diet-Induced Obese Mice

Abstract

Mechanosensitive gastric vagal afferents (GVAs) are involved in the regulation of food intake. GVAs exhibit diurnal rhythmicity in their response to food-related stimuli, allowing time of day-specific satiety signaling. This diurnal rhythmicity is ablated in high-fat-diet (HFD)-induced obesity. Time-restricted feeding (TRF) has a strong influence on peripheral clocks. This study aimed to determine whether diurnal patterns in GVA mechanosensitivity are entrained by TRF. Eight-week-old male C57BL/6 mice (N = 256) were fed a standard laboratory diet (SLD) or HFD for 12 weeks. After 4 weeks of diet acclimatization, the mice were fed either ad libitum or only during the light phase [Zeitgeber time (ZT) 0-12] or dark phase (ZT12-24) for 8 weeks. A subgroup of mice from all conditions (n = 8/condition) were placed in metabolic cages. After 12 weeks, ex vivo GVA recordings were taken at 3 h intervals starting at ZT0. HFD mice gained more weight than SLD mice. TRF did not affect weight gain in the SLD mice, but decreased weight gain in the HFD mice regardless of the TRF period. In SLD mice, diurnal rhythms in food intake were inversely associated with diurnal rhythmicity of GVA mechanosensitivity. These diurnal rhythms were entrained by the timing of food intake. In HFD mice, diurnal rhythms in food intake and diurnal rhythmicity of GVA mechanosensitivity were dampened. Loss of diurnal rhythmicity in HFD mice was abrogated by TRF. In conclusion, diurnal rhythmicity in GVA responses to food-related stimuli can be entrained by food intake. TRF prevents the loss of diurnal rhythmicity that occurs in HFD-induced obesity.SIGNIFICANCE STATEMENT Diurnal control of food intake is vital for maintaining metabolic health. Diet-induced obesity is associated with strong diurnal changes in food intake. Vagal afferents are involved in regulation of feeding behavior, particularly meal size, and exhibit diurnal fluctuations in mechanosensitivity. These diurnal fluctuations in vagal afferent mechanosensitivity are lost in diet-induced obesity. This study provides evidence that time-restricted feeding entrains diurnal rhythmicity in vagal afferent mechanosensitivity in lean and high-fat-diet (HFD)-induced obese mice and, more importantly, prevents the loss of rhythmicity in HFD-induced obesity. These data have important implications for the development of strategies to treat obesity.

Keywords: circadian rhythmicity; obesity; stomach; time-restricted feeding; vagal afferents.

Figure 1.

Schematic of the 12-week feeding regime. The shaded areas indicate food availability. At 8 weeks of age, the mice were allocated into two groups with AL access to either an SLD (gray shaded area indicates food availability) or an HFD (black shaded area indicates food availability). After 4 weeks, the mice were further subdivided into three groups per diet. One group/diet had AL access to food (SLD-AL and HFD-AL). The second group/diet only had access to food during the LP from ZT0 to ZT12 (SLD-LP and HFD-LP). A third group/diet only had access to food during the DP from ZT12 to ZT24 (SLD-DP and HFD-DP). These feeding regimes continued for a further 8 weeks.

Figure 2.

Mouse body weight and gonadal fat pad mass. A, Weight gain (grams) in mice fed an SLD (open symbols) or HFD (closed symbols) for 4 weeks, for diet acclimatization and then split into three groups/diet (at dotted line) and fed either AL (circles; n = 48/diet group), just during the LP (ZT0–12; triangles; n = 40/diet group), or just during the DP (ZT12-ZT0; squares; n = 40/diet group). ***p < 0.001 versus all other groups, mixed-model ANOVA at weeks 5–12. ^###p < 0.001 versus HFD-AL mice, ^†††p < 0.001 versus HFD-LF. B, C, Final body weight (grams) (B) and gonadal fat pad mass (grams) (C) in SLD and HFD mice fed AL (n = 48/diet group), just during the LP (n = 48/diet group), or just during the DP (n = 48/diet group). ^ap < 0.05 versus all other groups; ^bp < 0.05 versus all HFD groups; ^cp < 0.05 versus all SLD groups; and ^dp < 0.05 versus HDF-AL group, two-way ANOVA, Tukey's post hoc test.

Figure 3.

Food intake in mice fed an SLD or HFD AL (n = 8/diet group) just during the LP (n = 8/diet group) or just during the DP (n = 8/diet group). A, The 24 h food intake in grams consumed (Ai) and energy intake in kilojoules (Aii). ^ap < 0.01 versus SLD-AL; ^bp < 0.01 versus HFD-AL; ^cp < 0.01 versus SLD-DP; ^dp < 0.01 versus all other groups; and ^dp < 0.01 versus all HFD groups, two-way ANOVA, Tukey's post hoc test. B, Meal size in grams consumed (Bi), energy intake in kilojoules (Bii), and meal number (Biii). The gray shaded and unshaded regions represent the dark and LP measurements, respectively. ^ap < 0.05 versus LP-SLD-AL; ^bp < 0.05 versus LP-SLD-LP; ^cp < 0.05 versus DP-SLD-DP; ^dp < 0.05 versus LP-HFD-LP, and ^ep < 0.05 versus LP-HFD-AL, two-way ANOVA, Tukey's post hoc test.

Figure 4.

Diurnal variation in GVA mechanosensitivity is still present after 4 weeks of HFD feeding. A, Response of gastric tension receptors to a 3 g stretch in mice fed AL either an SLD (n = 20; n ≥ 5/time point; ○) or an HFD (n = 20; n ≥ 5/time point; ●) for 4 weeks. There is no significant difference in the diurnal variation of gastric tension receptor responses to a 3 g stretch between SLD- and HFD-fed mice. B, Response of gastric mucosal receptors to mucosal stroking with a 50 mg von Frey hair in mice fed AL either an SLD (○) or HFD (●) for 4 weeks. p > 0.05, two-way ANOVA.

Figure 5.

Diurnal variation in GVA tension receptor mechanosensitivity in mice fed either an SLD (A; n = 128; n ≥ 5/time points/diet regime) or an HFD (B; n = 128; n ≥ 5/time points/diet regime) for 12 weeks. A, Diurnal variation in tension receptor responses to a 3 g stretch observed in mice fed an SLD AL (■) was maintained when feeding was restricted to the DP (ZT12–24; ●), but reversed when feeding was limited to the LP (ZT0–12; ○). B, Diurnal variation in gastric tension receptor responses to a 3 g stretch observed in SLD-mice was lost in mice fed an HFD AL (■). Diurnal variation in gastric tension receptor mechanosensitivity was maintained in HFD mice when food availability was restricted to the DP (ZT12–24; ●). In addition, although reversed, diurnal variation in tension receptor mechanosensitivity was also maintained in HFD mice when food availability was restricted to the LP (ZT0–12; ○). *p < 0.05 versus responses at an equivalent time point in mice fed AL (■), two-way ANOVA, Tukey's post hoc test. #p < 0.05 versus responses at an equivalent time point in mice fed just during the 12 h dark period (●), two-way ANOVA, Tukey's post hoc test.

Figure 6.

Diurnal variation in GVA mucosal receptor mechanosensitivity in mice fed either an SLD (A; n = 128; n ≥ 5/time points/diet regime) or an HFD (B; n = 128; n ≥ 5/time points/diet regime) for 12 weeks. A, Diurnal variation in mucosal receptor responses to mucosal stroking with a 50 mg von Frey hair observed in mice fed an SLD AL (■) was maintained when feeding was restricted to the DP (ZT12–24; ●), but reversed when feeding was limited to the LP (ZT0–12; ○). B, Diurnal variation in gastric mucosal receptor responses to mucosal stroking with a 50 mg von Frey hair observed in SLD-mice was lost in mice fed an HFD AL (■). Diurnal variation in gastric mucosal receptor mechanosensitivity was maintained in HFD mice when food availability was restricted to the DP (ZT12–24; ●). In addition, although reversed, diurnal variation in mucosal receptor mechanosensitivity was also maintained in HFD mice when food availability was restricted to the LP (ZT0–12; ○). *p < 0.05 versus responses at an equivalent time point in mice fed AL (■), two-way ANOVA, Tukey's post hoc test. #p < 0.05 versus responses at an equivalent time point in mice fed just during the 12 h dark period (●), two-way ANOVA, Tukey's post hoc test.