Ketogenic Diet Increases Serum and White Adipose Tissue SIRT1 Expression in Mice

Abstract

Overnutrition and its sequelae have become a global concern due to the increasing incidence of obesity and insulin resistance. A ketogenic diet (KD) is widely used as a dietary treatment for metabolic disorders. Sirtuin1 (SIRT1), a metabolic sensor which regulates fat homeostasis, is modulated by dietary interventions. However, the influence of nutritional ketosis on SIRT1 is still debated. We examined the effect of KD on adipose tissue, liver, and serum levels of SIRT1 in mice. Adult C57BL/6J male mice were randomly assigned to two isocaloric dietary groups and fed with either high-fat KD or normal chow (NC) for 4 weeks. Serum SIRT1, beta-hydroxybutyrate (βHB), glucose, and triglyceride levels, as well as SIRT1 expression in visceral (VAT), subcutaneous (SAT), and brown (BAT) adipose tissues, and in the liver, were measured. KD-fed mice showed an increase in serum βHB in parallel with serum SIRT1 (r = 0.732, p = 0.0156), and increased SIRT1 protein expression in SAT and VAT. SIRT1 levels remained unchanged in BAT and in the liver, which developed steatosis. Normal glycemia and triglycerides were observed. Under a KD, serum and white fat phenotypes show higher SIRT1, suggesting that one of the molecular mechanisms underlying a KD's potential benefits on metabolic health involves a synergistic interaction with SIRT1.

Keywords: SIRT1; adipose tissue; epigenetic regulators; ketogenic diet; ketone bodies; obesity.

Figure 1

Ketogenic diet effects on body weight and food intake. (A) Representative photographs of mice under normal chow (NC) and ketogenic diet (KD) at the end of dietary treatment. (B) Body weight analysis during dietary treatment showing weight gain (g) of mice under NC (n = 8) and KD (n = 10). Data are expressed as mean ± SEM. (C) Scatter dot plot showing average daily food intake (g) of mice under NC and KD. Data are expressed as mean ± SEM. **** p < 0.001. (D) Scatter dot plot showing average daily caloric intake (kcal) of mice under NC and KD. Data are expressed as mean ± SEM. ** p < 0.01. (E) Dot plot showing βHB concentration (mM) in serum from mice under NC (n = 6) and KD (n = 10) at the end of dietary treatment. Data are expressed as mean ± SEM. *** p < 0.005.

Figure 2

Ketogenic diet effects on fat mass. Analysis of fat coefficient (g fat/g body × 100) of: (A) perigonadal VAT, (B) SAT, and (C) interscapular BAT of mice under normal chow (NC, n = 6) and ketogenic diet (KD, n = 10) at the end of dietary treatment. Data are expressed as mean ± SEM.

Figure 3

(A) Dot plot showing SIRT1 concentration (ng/mL) in serum from mice under NC (n = 5) and KD (n = 8) at the end of dietary treatment. Data are expressed as mean ± SEM. * p < 0.05. (B) Pearson correlation analysis between serum βHB and SIRT1 levels in mice under KD (n = 10). r = 0.732, p = 0.0156.

Figure 4

Ketogenic diet effect on adipose tissue levels of SIRT1. Western Blotting analysis of SIRT1 expression on visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and interscapular brown adipose tissue (BAT) extracts from mice under normal chow (NC, n = 6) and ketogenic diet (KD, n = 10) at the end of dietary treatment. Densitometric analyses show protein expression levels expressed as arbitrary units ± SEM. * p  <  0.05.

Figure 5

KD treatment effect on liver. (A) Analysis of liver coefficient (g liver/g body × 100) of mice under normal chow (NC, n = 6) and ketogenic diet (KD, n = 10) at the end of dietary treatment. Data are expressed as mean ± SEM. **** p < 0.001. (B) Representative images of liver morphology by Hematoxylin and Eosin staining on sections obtained from mice under NC and KD at the end of dietary treatment. Magnification 10×. Scale bar = 50 micron. (C) Ketogenic diet effect on liver levels of SIRT1. Western Blotting analysis of SIRT1 expression on liver extracts from mice under normal chow (NC, n = 6) and ketogenic diet (KD, n = 10) at the end of dietary treatment. Densitometric analyses show protein expression levels expressed as arbitrary units ± SEM.

Figure 6

Ketogenic diet effect on blood levels of glucose and triglycerides. (A) Bar plot showing serum fasting glucose concentration (mg/dL) from mice under NC (n = 8) and KD (n = 10) at the end of dietary treatment. (B) Bar plot showing triglycerides (TG) serum concentration (mg/dL) from mice under NC (n = 8) and KD (n = 10) at the end of dietary treatment. Data are expressed as mean ± SEM.

Figure 7

Schematic illustration of experimental design of the study.