Dataset Information

Hepatocyte-specific IKK-? activation enhances VLDL-triglyceride production in APOE*3-Leiden mice.

ABSTRACT: Low-grade inflammation in different tissues, including activation of the nuclear factor ?B pathway in liver, is involved in metabolic disorders such as type 2 diabetes and cardiovascular diseases (CVDs). In this study, we investigated the relation between chronic hepatocyte-specific overexpression of IkB kinase (IKK)-? and hypertriglyceridemia, an important risk factor for CVD, by evaluating whether activation of IKK-? only in the hepatocyte affects VLDL-triglyceride (TG) metabolism directly. Transgenic overexpression of constitutively active human IKK-? specifically in hepatocytes of hyperlipidemic APOE*3-Leiden mice clearly induced hypertriglyceridemia. Mechanistic in vivo studies revealed that the hypertriglyceridemia was caused by increased hepatic VLDL-TG production rather than a change in plasma VLDL-TG clearance. Studies in primary hepatocytes showed that IKK-? overexpression also enhances TG secretion in vitro, indicating a direct relation between IKK-? activation and TG production within the hepatocyte. Hepatic lipid analysis and hepatic gene expression analysis of pathways involved in lipid metabolism suggested that hepatocyte-specific IKK-? overexpression increases VLDL production not by increased steatosis or decreased FA oxidation, but most likely by carbohydrate-responsive element binding protein-mediated upregulation of Fas expression. These findings implicate that specific activation of inflammatory pathways exclusively within hepatocytes induces hypertriglyceridemia. Furthermore, we identify the hepatocytic IKK-? pathway as a possible target to treat hypertriglyceridemia.

SUBMITTER: van Diepen JA

PROVIDER: S-EPMC3073472 | biostudies-other | 2011 May

REPOSITORIES: biostudies-other

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Hepatocyte-specific IKK-β activation enhances VLDL-triglyceride production in APOE*3-Leiden mice.

van Diepen Janna A JA Wong Man C MC Guigas Bruno B Bos Jasper J Stienstra Rinke R Hodson Leanne L Shoelson Steven E SE Berbée Jimmy F P JF Rensen Patrick C N PC Romijn Johannes A JA Havekes Louis M LM Voshol Peter J PJ

Journal of lipid research 20110228 5

Low-grade inflammation in different tissues, including activation of the nuclear factor κB pathway in liver, is involved in metabolic disorders such as type 2 diabetes and cardiovascular diseases (CVDs). In this study, we investigated the relation between chronic hepatocyte-specific overexpression of IkB kinase (IKK)-β and hypertriglyceridemia, an important risk factor for CVD, by evaluating whether activation of IKK-β only in the hepatocyte affects VLDL-triglyceride (TG) metabolism directly. Tr ...[more]

PMID: 21357939

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Project description:To assess basal and insulin-mediated VLDL-triglyceride (TG) kinetics and the relationship between VLDL-TG secretion and hepatic insulin resistance assessed by endogenous glucose production (EGP) in obese and lean men.A total of 12 normoglycemic, obese (waist-to-hip ratio >0.9, BMI >30 kg/m(2)) and 12 lean (BMI 20-25 kg/m(2)) age-matched men were included. Ex vivo-labeled [1-(14)C]VLDL-TGs and [3-(3)H]glucose were infused postabsorptively and during a hyperinsulinemic-euglycemic clamp to determine VLDL-TG kinetics and EGP. Body composition was determined by dual X-ray absorptiometry and computed tomography scanning. Energy expenditure and substrate oxidation rates were measured by indirect calorimetry.Basal VLDL-TG secretion rates were increased in obese compared with lean men (1.25 ± 0.34 vs. 0.86 ± 0.34 ?mol/kg fat-free mass [FFM]/min; P = 0.011), whereas there was no difference in clearance rates (150 ± 56 vs. 162 ± 77 mL/min; P = NS), resulting in greater VLDL-TG concentrations (0.74 ± 0.40 vs. 0.38 ± 0.20 mmol/L; P = 0.011). The absolute insulin-mediated suppression of VLDL-TG secretion was similar in the groups. However, the percentage reduction (-36 ± 18 vs. -54 ± 10%; P = 0.008) and achieved VLDL-TG secretion rates (0.76 ± 0.20 vs. 0.41 ± 0.19 ?mol/kg FFM/min; P < 0.001) were impaired in obese men. Furthermore, clearance rates decreased significantly in obese men, but there was no significant change in lean men (-17 ± 18 vs. 7 ± 20%; P = 0.007), resulting in less percentage reduction of VLDL-TG concentrations in obese men (-22 ± 20 vs. -56 ± 11%; P < 0.001). Insulin-suppressed EGP was similar (0.4 [0.0-0.8] vs. 0.1 [0.0-1.2] mg/kg FFM/min (median [range]); P = NS), and the percentage reduction was equivalent (-80% [57-98] vs. -98% [49-100], P = NS). Insulin-mediated glucose disposal was significantly reduced in obese men.Basal VLDL-TG secretion rates are increased in normoglycemic but insulin-resistant, obese men, resulting in hypertriglyceridemia. Insulin-mediated suppression of EGP is preserved in obese men, whereas suppression of VLDL-TG secretion is less pronounced in obese men. Compared with EGP, the inability to achieve suppression of VLDL-TG secretions to a level similar to control subjects during hyperinsulinemia seems to be an early manifestation in male obesity.

Dataset Information

Hepatocyte-specific IKK-? activation enhances VLDL-triglyceride production in APOE*3-Leiden mice.

Publications

Hepatocyte-specific IKK-β activation enhances VLDL-triglyceride production in APOE*3-Leiden mice.

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