Fasting, Not Calories, Drives the - PowerPoint Presentation

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Fasting, Not Calories, Drives the Metabolic and Molecular Response to a Calorie Restricted Diet

AbstractCalorie restriction (CR) promotes metabolic health, healthspan and longevity in diverse species including mice, and there is great interest in dissecting the physiological and molecular mechanisms that underlie the benefits of CR. Recently, it has been shown that fasting for a portion of each day has metabolic benefits in both mice and humans, and promotes mouse lifespan. These findings complicate the interpretation of rodent CR studies, which typically implement CR by feeding the animals only once per day. As CR-fed animals rapidly consume their food, such a regimen, collaterally imposes fasting. Here, we used a series of novel feeding paradigms to dissect the effects of calories and fasting on the organismal metabolism of both sexes of C57BL/6J and DBA/2J. We found that the imposition of fasting was required for a number of the metabolic and molecular effects of a CR diet, including improved insulin sensitivity. We further demonstrate that fasting alone recapitulates many of the physiological and molecular effects of a CR diet, and that fasting is required for the beneficial effects of a CR diet on frailty, cognition, and lifespan of C57BL/6J male mice. Our results shed new light on how when and how much we eat regulate metabolic health and longevity, and suggest that daily prolonged fasting, not reduced calorie intake, may be responsible for many of the physiological and molecular benefits of a CR diet.

Heidi H. Pak

1,2,3

, Spencer A. Haws

3,4,5

, Mikaela Koller

1,2

, Cara L. Green

1,2

, Nicole E. Richardson

1,2

,

Shany

E. Yang

1,2

, Sabrina Dumas

1,2

,

Lindsey

Bray

1,2

, John M. Denu

4,5

, and Dudley W.

Lamming

1,2

1

Department of Medicine, University of Wisconsin-Madison,

2

William

S. Middleton Memorial Veterans Hospital, Madison, WI, USA

3

Department

of Nutritional Sciences,

University of

Wiscons

-Madison

4

Biomolecular

Chemistry, University of Wisconsin-Madison, and

5

Wisconsin

Institute for Discovery, Madison, WI, USA

Background and Experiment DesignAnimals and Diet: Randomized 9-week old male and female C57BL/6J and DBA/2J mice were placed on AL diet, one of three CR regimens, or time restricted diet (Table 1).

Mouse Metabolic Phenotyping: Over the course of four months, mice weight and body composition, glucose homeostasis, and metabolic parameters (O­­2, CO2, energy expenditure, and food consumption) were measured.Tissue Collection: Tissues were collected either in the fasted or fed stateLight

Dark

Light/Dark

A

d libitum

Calorie Restriction

A period of fasting is necessary for CR to improve insulin sensitivityFigure 1: Fasting is required for insulin sensitivity as measured by insulin tolerance test. A)

Glucose tolerance test of C57BL/6J and DBA2J male and female mice after 8 weeks on diet (n = 10-12 mice per group) B) Insulin tolerance test of C57BL/6J and DBA2J male and female mice after 9 weeks on diet (n = 10-12 mice per group) Data are represented as means and each symbol represents significance with adjusted p-value of <0.05 using multiple comparison with one-way ANOVA and Tukey’s post hoc test: *, compared from AL values; @, compared from TR.cr values; #, compared from CR values.

Fasting, not calories, promotes fatty acid oxidationFigure 2. Fasting is required for the distinct fuel utilization curve in response to calorie restriction. A) Timed-course representation of recorded respiratory exchange ratios (RER). Values are means ± SE (n = 10-12 mice/group) B) Fatty acid (FA) and carbohydrate/protein (C/P) oxidation values measured from the last 24-hours post-feeding. Data are represented as means and each symbol represents significance with adjusted p-value of <0.05 using multiple comparison with one-way ANOVA and Tukey’s post hoc test: *, compared from AL values; @, compared from TR.cr values; #, compared from CR values.

Fasting alone is sufficient to recapitulate the effects of a CR dietFigure 3: Fasting, without calorie restriction, recapitulates calorie restriction effect in C57BL/6J male mice.A) Glucose tolerance test after 8 weeks on diet (1 g/kg of body weight). B) Insulin tolerance test after 9 weeks on diet (0.5 U/kg of body weight).

C) Timed-course representation of recorded respiratory exchange ratios (RER) and D) calculated fuel selection values measured from the last 24-hours post feeding. E) Heatmap representation of phenotypes measures. F) Overlap of phenotypes between different feeding regimen. Data are represented as means and each symbol represents significance with adjusted p-value of <0.05 using multiple comparison with one-way ANOVA and Tukey’s post hoc test: *, compared from AL values.

Fasting without CR is sufficient to produce similar transcriptomic signature in liver and white adipose tissueFigure 5: Fasting, without calorie restriction, produces similar transcriptomic signature in liver and white adipose tissue. A) Overlap in number of differentially expressed genes (DEGs) between CR and TR.al when compared to AL. Numbers in Venn diagram represents number of genes within each diet (large circle) and significant number of functionally enriched pathways (small circle).

B) Overlap in number of DEGs between CR and TR.al when CR is compared to TR.al. C-D) Significantly upregulated and downregulated genes of CR and TR.al group with identified pathways from network construction in liver and iWAT. Bar graph represents pathways identified with enrichment p-values of <0.05 computed with the hypergeometric test. Red – pathways expressed in the same direction between liver and iWAT, blue – pathways expressed in the opposite direction between liver and iWAT, green – pathways expressed only for TR.al, purple – pathways expressed in both direction