Fig 1.
Age-dependent hepatic steatosis occurs in HSLSKO and HSLAKO mice but not in HSLLKO mice.
5-hour-fasted 3-month-old and 8-month-old mice were used (n = 6). A. HSLSKO body weight; B. HSLSKO liver weight; C. HSLSKO liver TG content; D. HSLLKO body weight; E. HSLLKO liver weight; F. HSLLKO liver TG content; G. HSLAKO body weight; H. HSLAKO liver weight; I. HSLAKO liver TG content. HSLSKO, systemic HSL knockout mice; HSLLKO, liver HSL knockout mice; HSLAKO, adipose HSL knockout mice. *, p < 0.05; **, p<0.01; ***, p<0.001 for all figures.
Fig 2.
Histological confirmation of hepatic steatosis in HSLSKO and HSLAKO livers, but not in HSLLKO liver.
8-month-old mice were fasted for 5 hours. Representative H&E sections of liver are shown from mice of each genotype.
Fig 3.
Lipodystrophy and macrophage infiltration of white adipose tissue of HSLAKO mice.
A. masses of different fat depots at 3 months. B. masses of different fat depots at 8 months. Mice were fasted for 5 hours (n = 6). PG, perigonadal; PR, perirenal; Mes, mesenteric; Sub, subcutaneous fat. C. 3-month-old mice and D. 8-month-old mice adipose expression of transcripts related to TG metabolism. Fas, fatty acid synthase; Acc1, acetyl-CoA carboxylase 1; Cd36, cluster of differentiation 36, (a transporter for fatty acids); Fabp4, fatty acid binding protein 4; Ppar-γ, peroxisome proliferator-activated receptor gamma; Dgat1, diacylglycerol O-acyltransferase 1; Dgat2, diacylglycerol O-acyltransferase 2. Mice fasted for 5 hours were used (n = 6). E. Protein expression in adipose tissue. Western blots of the indicated proteins, 8-month-old mice adipose tissue. F. H&E staining of white adipose tissue, showing the high prevalence of crown-like structures (arrows), X100; Inset, enlarged image of a crown-like structure, > 200; G. markers of macrophage and of inflammation in adipose tissue (n = 6); H. distribution of adipocyte diameter. 8-month-old mice fasted for 5 hours were used.
Fig 4.
Plasma levels of energy-related metabolites and hormones in HSLAKO mice.
14-hour overnight fasted mice were used for the following measurements: A. Glucose level; B. FFA level and C. TG level. 5-hour fasted mice were used for the following: D. Adiponectin. E. Leptin and F. Insulin. n = 6.
Fig 5.
Insulin sensitivity and glucose tolerance in HSLAKO mice.
A. ITT for 3-month-old mice. B. Area under the curve (AUC) for ITT at 3 months. C. ITT for 8-month-old mice. D. AUC for ITT at 8 months. E, F and G. skeletal muscle TG content in HSLSKO, HSLAKO and HSLLKO mice, respectively. H, I. Glucose levels during the GTT in 3- and 8-month-old mice. J, K. Insulin levels during the GTT at 3 and 8 months, respectively.
Fig 6.
Low levels of ketogenesis, fatty acid oxidation and VLDL production in HSLAKO livers.
A. plasma 3-hydroxybutyrate (3-HB). B. transcripts related to β-oxidation in liver. C. β-oxidation in liver slices, measured as production of CO2 from FA substrates. 8-month-old mice were used (n = 6). D. plasma TG levels following injection of the LPL inhibitor, P407.
Fig 7.
Evaluation of lipolysis, inflammation and fibrosis in HSLAKO livers.
A. transcripts related to TG degradation (n = 6). B. Western blot of hepatic ATGL. C. hepatic TG hydrolase activity. D. plasma ALT levels (n = 6). E. inflammation-related transcripts (n = 6). F. fibrosis-related transcripts (n = 6). 8-month-old mice were studied. ATGL, adipose triglyceride lipase; ALT, alanine aminotransferase.
Fig 8.
Hepatic steatosis in HSL deficiency is driven by adipose HSL deficiency.
Comparison among the four mouse strains studied reveals the mechanism of hepatic steatosis in HSL deficiency: normal controls, systemic HSL-deficient mice (HSLSKO), adipose HSL-deficient mice (HSLAKO), liver HSL-deficient mice (HSLLKO). HSL deficiency in adipose tissue is sufficient to cause hepatic steatosis of a similar degree to systemic HSL deficiency. In contrast, HSL deficiency in liver has no detectable impact on hepatic fat content. WAT: white adipose tissue.