Time-Restricted Feeding Restores Obesity-Induced Alteration in Adipose Tissue Immune Cell Phenotype

Abstract

Studies suggest that time-restricted feeding (TRF) may prevent obesity and its commodities. At present, little is known about how TRF impacts immune cells, and whether such an effect is linked to altered metabolic parameters under condition of a high-fat diet (HFD)-induced obesity. To address these issues, we conducted a study in which we determined whether TRF has therapeutic efficacy against weight gain, adiposity, as well as associated immune cell disturbance found in obese mice. Six-week-old male C57BL/6 mice were fed a low-fat diet (LFD) or HFD ad libitum for six weeks, after which time a subgroup of HFD mice was switched to the 10 h TRF paradigm (HFD-TRF) for additional eight weeks. We found that TRF intervention reduced HFD-induced weight gain. Even with comparable fat mass and mean adipocyte area, the HFD-TRF group had lower mRNA levels of proinflammatory cytokine Tnfα and chemokine Ccl8, along with reduced numbers of adipose tissue macrophages (ATM), CD11c⁺ ATM, and CD8⁺ T cell compared to the HFD group, while maintaining CD8⁺ to CD4⁺ ratio at levels similar to those in the LFD group. Furthermore, TRF intervention was effective in improving glucose tolerance and reducing HOMA-IR. Taken together, our findings suggest that TRF restores the obesity-induced alteration in immune cell composition, and this effect may in part contribute to health benefits (including insulin sensitivity) of practicing TRF.

Keywords: T cells; insulin resistance; macrophages; obesity; time-restricted feeding.

Figure 1

Therapeutic effects of time-restricted feeding (TRF) on body weight. (A) Schematic outline of the three feeding regimens used in this study. Six-weeks of C57BL/6J mice were fed low-fat diet (LFD) or high-fat diet (HFD) ad libitum for 6 weeks until 12 weeks of age. The HFD group were further divided two groups for the following regimens: continuous HFD ad libitum or HFD-TRF (10-h/daytime-restricted access to food during active period) for 8 weeks until 20 weeks of age. (B) Average body weight (±SEM, n = 7 mice). Significant differences among groups were determined by ANOVA followed by post hoc Tukey’s test. HFD, HFD-TRF (vs. LFD), * p < 0.05; HFD-TRF (vs. HFD), # p < 0.05.

Figure 2

Effects of time-restricted feeding (TRF) on adipose tissue. C57BL/6 mice were fed a low-fat diet or high-fat diet ad libitum (LFD and HFD, respectively) for 14 weeks. Time-restricted feeding was started after 6 weeks of ad libitum consumption of a high-fat diet. (A) Fat distribution: epididymal adipose tissue, inguinal subcutaneous adipose tissue, retroperitoneal adipose tissue; (B) average adipocyte size area; (C) representative H&E-stained histological sections of epididymal adipose tissue in the LFD, HFD, and HFD-TRF groups. Scale bar, 100 μm. Data are presented as mean ± SEM (n = 7). ^a,b,c Different superscripts indicate significant difference at least at p < 0.05 by ANOVA with Tukey’s post hoc test.

Figure 3

Effects of time-restricted feeding (TRF) on infiltration of adipose tissue macrophages (ATM). Epididymal adipose tissue was analyzed by flow cytometry after 14 weeks of different feeding regimens. LFD, low-fat diet ad libitum; HFD, high-fat diet ad libitum; HFD-TRF, 8 weeks of time-restricted feeding after 6 weeks of high-fat diet ad libitum. (A) Total ATM numbers; (B) frequency of CD11c⁺ ATM; (C) representative flow cytometry histograms of CD11c expression in ATM. Data are presented as mean ± SEM (n = 7). ^a,b,c Different superscripts indicate significant difference at least at p < 0.05 by ANOVA with Tukey’s post hoc test.

Figure 4

Effects of time-restricted feeding (TRF) on infiltration of T cells. Stromal vascular fraction of epididymal adipose tissue was analyzed by flow cytometry after 14 weeks of different feeding regimens. LFD, low-fat diet ad libitum; HFD, high-fat diet ad libitum; HFD-TRF, 8 weeks of time-restricted feeding after 6 weeks of high-fat diet ad libitum. (A) Total T, CD4 T, CD8 T cell numbers; (B) ratio of CD8 to CD4 T cells. Data are presented as mean ± SEM (n = 7). ^a,b,c Different superscripts indicate significant difference at least at p < 0.05 by ANOVA with Tukey’s post hoc test.

Figure 5

Effects of time-restricted feeding (TRF) on inflammatory mediator gene expressions in AT. Quantitative real-time RT-PCR analysis of selected proinflammatory macrophages (F4/80 and CD11c), cytokine (TNFα) and chemokines (Ccl2, Ccl8) in epididymal fat after 14 weeks of different feeding regimens. LFD, low-fat diet ad libitum; HFD, high-fat diet ad libitum; HFD-TRF, 8 weeks of time-restricted feeding after 6 weeks of high-fat diet ad libitum. Data are presented as mean ± SEM (n = 7). ^a,b,c Different superscripts indicate significant difference at least at p < 0.05 by ANOVA with Tukey’s post hoc test.

Figure 6

Effects of time-restricted feeding (TRF) on HOMA-IR and glucose tolerance. C57BL/6 mice were fed with a low-fat diet ad libitum (LFD), high-fat diet ad libitum (HFD), high-fat diet ad libitum followed by time-restricted feeding (HFD-TRF) for 12 weeks. (A) Fasting blood glucose; (B) fasting insulin; (C) insulin resistance index (HOMA-IR), measured as FBG (mmol/L) × FI (mU/L)/22.5. (D,E) Glucose and area of glucose under the curve (AUC) during glucose tolerance test upon i.p. injection of 1.2g glucose/kg body weight. Data are presented as mean ± SEM (n = 7). ^a,b,c Different superscripts indicate significant difference at least at p < 0.05 by ANOVA with Tukey’s post hoc test. HFD (vs. LFD), * p < 0.05; HFD-TRF (vs. HFD), ^# p < 0.05.