Loss of Hepatic Mitochondrial Long-Chain Fatty Acid Oxidation Confers Resistance to Diet-Induced Obesity and Glucose Intolerance - PubMed (original) (raw)

Loss of Hepatic Mitochondrial Long-Chain Fatty Acid Oxidation Confers Resistance to Diet-Induced Obesity and Glucose Intolerance

Jieun Lee et al. Cell Rep. 2017.

Abstract

The liver has a large capacity for mitochondrial fatty acid β-oxidation, which is critical for systemic metabolic adaptations such as gluconeogenesis and ketogenesis. To understand the role of hepatic fatty acid oxidation in response to a chronic high-fat diet (HFD), we generated mice with a liver-specific deficiency of mitochondrial long-chain fatty acid β-oxidation (Cpt2L-/- mice). Paradoxically, Cpt2L-/- mice were resistant to HFD-induced obesity and glucose intolerance with an absence of liver damage, although they exhibited serum dyslipidemia, hepatic oxidative stress, and systemic carnitine deficiency. Feeding an HFD induced hepatokines in mice, with a loss of hepatic fatty acid oxidation that enhanced systemic energy expenditure and suppressed adiposity. Additionally, the suppression in hepatic gluconeogenesis was sufficient to improve HFD-induced glucose intolerance. These data show that inhibiting hepatic fatty acid oxidation results in a systemic hormetic response that protects mice from HFD-induced obesity and glucose intolerance.

Keywords: Fgf21; Gdf15; NAFLD; NASH; diabetes; fatty acid oxidation; gluconeogenesis; hormesis; ketogenesis; obesity; steatosis.

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Conflict of interest statement

Conflict of interest

The authors declare that they have no conflicts of interest with the contents of this article.

Figures

Figure 1. Liver-specific deficiency in fatty acid oxidation is protective against HFD-induced body weight gain and adiposity

(A) Body weight and femur lengths of male Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=12). (B) Body compositions of male Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks measured by EchoMRI (n=12). (C) Wet weights of iWAT and gWAT unilateral depots, liver (left lobe) and kidney for male Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=12). (D) H&E stained sections of iWAT from male Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks. Scale bar, 100 μm. (E) Adipocyte size distribution from H&E stained sections of iWAT from Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks. (F) Serum metabolites in male Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=6). (G) Serum lucose and insulin in male Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=6). (H) Serum leptin and adiponectin in male Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=6). (I) Blood acylcarnitines of male Cpt2lox/lox and Cpt2L−/− mice following a 16-week chronic high fat feeding (n=5–8). (J) Urine acylcarnitines of male Cpt2lox/lox and Cpt2L−/− mice following a 16-week chronic high fat feeding (n=6). Urine acylcarnitine values were normalized to creatinine values. Data are expressed as mean ± SEM. *p<0.05; **p<0.01; ***p<0.001.

Figure 2. Loss of hepatic fatty acid oxidation induces oxidative stress

(A) H&E stained sections of liver from male Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks. (B) Liver TAG content of male Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=6). (C) Measure of liver damage via serum ALT activity in male Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=6). (D) TBARS assay measuring lipid peroxidation in liver of male Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=6). (E) Total glutathione in livers of Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=7). (F) Western blot of Hsp27 in livers of Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks. (G) Gene expression of fatty acid synthesis genes in livers of Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=6). (H) Western blots of proteins in fatty acid synthesis in livers of Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks. All blots were normalized to Hsc70. (I) Total saponified fatty acid concentration in Liver and iWAT of Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=5–6). See also Table S2. (J) Enrichment of fatty acids by chain length in Liver and iWAT of Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=5–6). See also Table S2.

Figure 3. Loss of hepatic fatty acid oxidation induces hepatokines

(A) Western blot for mitochondrial complexes and Hsc70 in livers of Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks. (B) Gene expression of fatty acid metabolism and Pparα target genes in livers of Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=6). (C) Liver mRNA of igfbp1, gdf15, and fgf21 in Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=6). (D) Serum concentrations of Igfbp1, Gdf15 and Fgf21 in Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks (n=6). Data are expressed as mean ± SEM. *p<0.05; **p<0.01; ***p<0.001.

Figure 4. Metabolic alterations upon the loss of hepatic fatty acid oxidation

(E) 1H-NMR in liver of Cpt2lox/lox and Cpt2L−/− mice fed a high fat diet for 16 weeks (n=6). (F) 1H-NMR in serum of Cpt2lox/lox and Cpt2L−/− mice fed a high fat diet for 16 weeks (n=6). (G) 1H-NMR in kidney of Cpt2lox/lox and Cpt2L−/− mice fed a high fat diet for 16 weeks (n=6). (H) NMR analysis of 1-13C-lactate incorporation into glucose in 24hr fasted mice (n=3). (I) Isotopomer analysis of 1-13C-lactate incorporation into glucose in 24hr fasted mice (n=3). (J) Total bile acids in serum of Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 9wks (n=4–7). (K) Bile acid metabolic genes in ileum of Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 9wks (n=4). Data are expressed as mean ± SEM. *p<0.05; **p<0.01; ***p<0.001.

Figure 5. Loss of hepatic fatty acid oxidation improves glucose tolerance and insulin sensitivity

(A) Intraperitoneal glucose tolerance test (ipGTT) including area under the curve in male Cpt2lox/lox and Cpt2L−/− mice fed a chow diet (n=8–11). (B) Hyperinsulinemic-euglycemic clamp showing glucose infusion rate (GIR), endogenous glucose production (EGP) and insulin suppression of EGP (n=7–9). (C) Body weight of male Cpt2lox/lox and Cpt2L−/− mice fed a high fat diet for 4 wks (n=11–12). (D) ipGTT including area under the curve in male Cpt2lox/lox and Cpt2L−/− mice fed a high fat diet for 4 wks (n=11–12). (E) Serum insulin levels measured at baseline and glucose stimulated (15min) conditions in Cpt2lox/lox and Cpt2L−/− mice fed a high fat diet for 4 wks (n=6). (F) Intraperitoneal insulin tolerance test (ipITT) including area above curve in male Cpt2lox/lox and Cpt2L−/− mice fed a high fat diet for 5 wks (n=11–12). Data are expressed as mean ± SEM. *p<0.05; **p<0.01; ***p<0.001.

Figure 6. Loss of hepatic fatty acid oxidation increases energy expenditure in response to high fat feeding

(A) Energy expenditure under dark and light cycles of female Cpt2lox/lox and Cpt2L−/− mice after 4 wks on high fat diet (n=10–13). (B) Metabolic parameters of female Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 4wks (n=10–13). Data are expressed as mean ± SEM. *p<0.05; **p<0.01; ***p<0.001.

Figure 7. Loss of hepatic fatty acid oxidation at thermoneutrality normalizes body weight during high fat feeding

(A) Body weight of female Cpt2lox/lox and Cpt2L−/− mice fed a high fat diet at thermoneutrality (30°C) for 16 weeks (n=11–12). (B) Wet weights of iWAT and gWAT unilateral depots, liver (left lobe), kidney and heart of female Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks at 21°C (n=12–14) or 30°C (n=11–12). (C) Gene expression in livers of female Cpt2lox/lox and Cpt2L−/− mice fed a HFD for 16wks at 21°C or 30°C (n=6). Data are expressed as mean ± SEM. *p<0.05; **p<0.01; ***p<0.001.

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Loss of Hepatic Mitochondrial Long-Chain Fatty Acid Oxidation Confers Resistance to Diet-Induced Obesity and Glucose Intolerance - PubMed (original) (raw)