Intermittent Fasting Promotes White Adipose Browning and Decreases Obesity by Shaping the Gut Microbiota

Abstract

While activation of beige thermogenesis is a promising approach for treatment of obesity-associated diseases, there are currently no known pharmacological means of inducing beiging in humans. Intermittent fasting is an effective and natural strategy for weight control, but the mechanism for its efficacy is poorly understood. Here, we show that an every-other-day fasting (EODF) regimen selectively stimulates beige fat development within white adipose tissue and dramatically ameliorates obesity, insulin resistance, and hepatic steatosis. EODF treatment results in a shift in the gut microbiota composition leading to elevation of the fermentation products acetate and lactate and to the selective upregulation of monocarboxylate transporter 1 expression in beige cells. Microbiota-depleted mice are resistance to EODF-induced beiging, while transplantation of the microbiota from EODF-treated mice to microbiota-depleted mice activates beiging and improves metabolic homeostasis. These findings provide a new gut-microbiota-driven mechanism for activating adipose tissue browning and treating metabolic diseases.

Keywords: beige adipocytes; browning; every-other-day fasting (EODF); gut microbiota; intermittent fasting; metabolic syndrome; obesity; short-chain fatty acid.

Figure 1. EODF treatment increases energy expenditure through WAT beiging

(A) Cumulative food intake. n=14–16 mice/group. (B) Body weight. n=14–16 mice/group. (C) Normalized mass of body depots. n=7–8 mice/group. (D) Circadian rectal temperature on fed day. n=14–16 mice/group. (E–F) Daily total energy expenditure (E) and respiratory exchange ratio (F) during one cycle of EODF. On day 1 (“Fasted”), the EODF mice were fasted while the AL mice fed a chow diet. On day 2 (“Fed”), both groups had ad libitum access to chow. Data marked as “1 cycle” show the average value of the two days (“Fasted” plus “Fed”). n=4 mice/group. (G) Representative image for inguinal WAT of AL(left) and EODF (right) mouse. Scale bar: 5 mm. (H) Ucp1 mRNA expression in inguinal WAT in the fed state. n=7–8 mice/group. (I) Representative H&E (upper) and UCP1 (lower) staining of inguinal WAT sections. Scale bar: 50 μm. Data are presented as mean ± SEM. Different lowercase letters indicate different statistical significance by two-tailed unpaired t-test, a, p < 0.05; b, p < 0.01; c, p < 0.005; and d, p < 0.001 versus AL. See also Figure S1–S5.

Figure 2. EODF induces inguinal WAT beiging independent of β-AR and FGF21 signaling

(A) mRNA expression of thermogenic genes in inguinal WAT of mice under 30°C in the fed state. n= 10 mice/group. (B) Body weight of mice before and after EODF treatment at 30°C. n= 10 mice/group. (C) Fat mass of mice before and after EODF treatment at 30°C. n= 10 mice/group. (D) Representative H&E staining of inguinal WAT sections from EODF (at 30°C) mice (right) and AL mice (left). Scale bar: 100 μm. (E) Representative UCP1 immunohistochemical staining of inguinal WAT sections from EODF (at 30°C) mice (right) and AL mice (left). Scale bar: 100 μm. (F–G) Liver Fgf21 mRNA expression (F) and serum FGF21 levels (G) of Ppara wild-type (Ppara^+/+) and Pparα null (Ppara^−/−) mice with or without EODF treatment in the fed state. n = 5 mice/group. (H) mRNA expression of Ucp1 in inguinal WAT of Ppara^+/+ and Ppara^−/− mice with or without EODF treatment in the fed state. n = 5 mice/group. (I) Serum acetate and lactate levels of mice at 30°C. n= 10 mice/group. (J) mRNA expression of Mct1 in inguinal WAT of Ppara^+/+ and Ppara^−/− mice with or without EODF treatment in the fed state. n = 5 mice/group (K) Serum acetate and lactate levels of Ppara^+/+ and Ppara^−/− mice with or without EODF treatment. n = 5 mice/group. Data are presented as mean ± SEM. Different lowercase letters indicate statistical significance by two-tailed unpaired t-test, a, p < 0.05; c, p < 0.005; and d, p < 0.001. Black letters show the effects of EODF (EODF versus AL within the same strain), red letters the effects of Ppara knockout (Pparα^−/− versus Ppara^+/+ mice within the same treatment). SCFAs, short chain fatty acids.

Figure 3. Gut microbiota mediates EODF induced WAT beiging

(A) Length of small intestine of AL mice, EODF mice, mice transplanted with AL microbiota (AL/MT), and mice transplanted with EODF microbiota (EODF/MT). n=8 mice/group. (B) UniFrac distances of AL and EODF mice. n=7–8 mice/group. (C) Z-scores for genera between AL and EODF mice. n=7–8 mice/group. (D) Hierarchical clustering diagram comparing ceca of AL and EODF mice. n=7–8 mice/group. (E) Representative Phyla Operational Taxonomic Unit (OTU) abundance (%) of ceca of AL and EODF mice. n=7–8 mice/group. (F) Ucp1 mRNA expression in inguinal WAT in the fed state. n= 8 mice/group. Data are presented as mean ± SEM. Different lowercase letters indicate different statistical significance by two-tailed unpaired t-test (E) or one-way ANOVA with Bonferroni posttest (A, F), a, p < 0.05; b, p < 0.01; c, p < 0.005; and d, p < 0.001. Black letters versus AL, and green letters versus AL/MT. See also Figure S6.

Figure 4. Microbiota metabolites underlie the mechanism of EODF-induced beiging

(A) Orthogonal projection to latent structure-discriminant analysis (OPLS-DA) scores (left) and correlation coefficient-coded loadings plots for the models (right) from NMR spectra of cecal content aqueous extracts from mice after long-term EODF treatment. n= 7–8 mice/group. (B) OPLS-DA scores (left) and correlation coefficient-coded loadings plots for the models (right) from NMR spectra of cecal content aqueous extracts from mice after short-term EODF treatment. n= 10 mice/group. (C–D) Cecum and serum acetate (C) and lactate (D) levels from mice after long-term and short-term EODF treatment. n= 7–10 mice/group. (E, F) mRNA expression of Mct1 in inguinal WAT (E) and BAT (F) from mice after long-term EODF treatment in the fed state. n= 7–8 mice/group. (G) mRNA expression of Mct1 in inguinal WAT from mice after short-term EODF treatment in the fed state. n= 10 mice/group. Data are presented as mean ± SEM. Different lowercase letters indicate statistical significance by two-tailed unpaired t-test, a, p < 0.05; b, p < 0.01; and d, p < 0.001 versus AL. See also Figure S7.

Figure 5. EODF ameliorates metabolic dysfunction in DIO mice

(A) Representative AL and EODF mouse. Scale bar: 5 mm. (B) Cumulative food intake. (C) Body weight. (D) mRNA expression of thermogenic genes in inguinal WAT in the fed state. (E) Glucose tolerance test. (F) Liver function. Upper left, representative image of livers from AL mouse (left) and EODF mouse (right). Scale bar: 5 mm. Middle left, liver triglycerides. Lower left, serum ALT. Right, representative H&E staining of liver sections from AL (upper) and EODF(lower) mice. Scale bar: 100 μm. (G) Fat depot mass. (H) mRNA expression of thermogenic genes in interscapular BAT in the fed state. Data are presented as mean ± SEM. n=6 mice/group. Different lowercase letters indicate different statistical significance by two-tailed unpaired t-test, a, p < 0.05; b, p < 0.01; c, p < 0.005; and d, p < 0.001 versus AL.

Figure 6. Gut microbiota mediates the effects of EODF on metabolic syndrome in DIO mice

(A) Body weight. Before EODF or microbiota transplantation (MT) treatment, all mice were given access to control vehicle (CV) water or water supplemented with an antibiotics cocktail (AB) for 4 weeks. n=6–8 mice/group. (B) Fat mass. n=6–8 mice/group. (C) Serum ALT. n=6–8 mice/group. (D) Liver triglycerides. n=6–8 mice/group. (E) Representative H & E staining of liver sections. Scale bar: 100 μm. (F–G) Glucose tolerance test in CV-treated (F) or AB-treated (G) mice. n=6 mice/group. (H) Glucose tolerance test in MT mice receiving microbiota from AL (AL/MT) or EODF donors (EODF/MT). n= 8 mice/group. Data are presented as mean ± SEM. Different lowercase letters indicate statistical significance by two-tailed unpaired t-test, a, p < 0.05; b, p < 0.01; c, p < 0.005; and d, p < 0.001. Black letters show the effects of EODF or EODF/TM (EODF versus AL, or EODF/MT versus AL/MT with access to the same water).

Figure 7. Gut microbiota mediates the effects of EODF on inguinal WAT beiging in DIO mice

(A, B) mRNA expression of thermogenic genes in inguinal WAT in the fed state. All mice were given access to control vehicle (CV) water or water supplemented with an antibiotics cocktail (AB) for 4 weeks, and then treated with AL or EODF (A) or microbiota transplantation (MT, B). n=6–8 mice/group. (C) Representative H & E staining of inguinal WAT from mice transplanted with EODF microbiota (EODF/MT, right) and AL microbiota (AL/MT, left). Scale bar: 100 μm. (D) Representative UCP1 immunohistochemical staining of inguinal WAT sections from EODF/MT (right) and AL/MT (left) mice. Scale bar: 100 μm. (E, F) Daily total energy expenditure (E) and respiratory exchange ratio (F) of AL/MT and EODF/MT mice. n=6 mice/group. (G, H) Serum acetate (G) and lactate (H) of DIO mice after EODF or MT treatment. Before EODF or MT treatment, all mice were given access to CV or AB water for 4 weeks. n=6–8 mice/group. Data are presented as mean ± SEM. Different lowercase letters indicate statistical significance by two-way ANOVA with Sidak multiple comparisons (A) or two-tailed unpaired t-test (B, E–H), a, p < 0.05; c, p < 0.005; and d, p < 0.001. Black letters show the effects of EODF or EODF/MT (EODF versus AL, or EODF/MT versus AL/MT drunk with the same water), red letters the effects of microbiota depletion (AB versus CV within the same feeding regimen).