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Cullin RING E3 ligases (CRL) have emerged as key regulators of disease-modifying pathways and therapeutic targets. Cullin3 (Cul3)-containing CRL (CRL3) has been implicated in regulating hepatic insulin and oxidative stress signaling. However, CRL3 function in liver pathophysiology is poorly defined. Here, we report that hepatocyte Cul3 knockout results in rapid resolution of steatosis in obese mice. However, the remarkable resistance of hepatocyte Cul3 knockout mice to developing steatosis does not lead to overall metabolic improvement but causes systemic metabolic disturbances. Liver transcriptomics analysis identifies that CRL3 inactivation causes persistent activation of the nuclear factor erythroid 2-related factor 2 (NRF2) antioxidant defense pathway, which also reprograms the lipid transcriptional network to prevent TG storage. Furthermore, global metabolomics reveals that NRF2 activation induces numerous NAD + -consuming aldehyde dehydrogenases to increase the cellular NADH/NAD + ratio, a redox imbalance termed NADH reductive stress that inhibits the glycolysis-citrate-lipogenesis axis in Cul3 knockout livers. As a result, this NRF2-induced cellular lipid storage defect promotes hepatic ceramide accumulation, elevates circulating fatty acids, and worsens systemic insulin resistance in a vicious cycle. Hepatic lipid accumulation is restored, and liver injury and hyperglycemia are attenuated when NRF2 activation and NADH reductive stress are abolished in hepatocyte Cul3/Nrf2 double-knockout mice. The resistance to hepatic steatosis, hyperglycemia, and NADH reductive stress are observed in hepatocyte Keap1 knockout mice with NRF2 activation. In summary, our study defines a critical role of CRL3 in hepatic metabolic regulation and demonstrates that the CRL3 downstream NRF2 overactivation causes hepatic metabolic maladaptation to obesity and insulin resistance., Competing Interests: Competing interests statement:The authors declare no competing interest.

Fatty liver is a highly heterogenous condition driven by various pathogenic factors in addition to the severity of steatosis. Protein insufficiency has been causally linked to fatty liver with incompletely defined mechanisms. Here we report that fatty liver is a sulfur amino acid insufficient state that promotes metabolic inflexibility via limiting coenzyme A availability. We demonstrate that the nutrient-sensing transcriptional factor EB synergistically stimulates lysosome proteolysis and methionine adenosyltransferase to increase cysteine pool that drives the production of coenzyme A and glutathione, which support metabolic adaptation and antioxidant defense during increased lipid influx. Intriguingly, mice consuming an isocaloric protein-deficient Western diet exhibit selective hepatic cysteine, coenzyme A and glutathione deficiency and acylcarnitine accumulation, which are reversed by cystine supplementation without normalizing dietary protein intake. These findings support a pathogenic link of dysregulated sulfur amino acid metabolism to metabolic inflexibility that underlies both overnutrition and protein malnutrition-associated fatty liver development., (© 2022. The Author(s).)

The origins of nonalcoholic fatty liver disease (NAFLD) may lie in early intrauterine exposures. Here we examined the maternal response to chronic maternal high-fat (HF) diet and the impact of postweaning healthy diet on mechanisms for NAFLD development in juvenile nonhuman primate (NHP) offspring at 1 year of age. Pregnant females on HF diet were segregated as insulin resistant (IR; HF+IR) or insulin sensitive (IS; HF+IS) compared with control (CON)-fed mothers. HF+IR mothers have increased body mass, higher triglycerides, and increased placental cytokines. At weaning, offspring were placed on a CON or HF diet. Only offspring from HF+IR mothers had increased liver triglycerides and upregulated pathways for hepatic de novo lipid synthesis and inflammation that was irreversible upon switching to a healthy diet. These juvenile livers also showed a combination of classical and alternatively activated hepatic macrophages and natural killer T cells, in the absence of obesity or insulin resistance. Our findings suggest that maternal insulin resistance, including elevated triglycerides, insulin, and weight gain, initiates dysregulation of the juvenile hepatic immune system and development of de novo lipogenic pathways that persist in vitro and may be an irreversible "first hit" in the pathogenesis of NAFLD in NHP., (© 2014 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.)

Obese pregnant women may transmit their metabolic phenotype to offspring, leading to a cycle of obesity and diabetes over generations. Early childhood obesity predicts nonalcoholic fatty liver disease (NAFLD), the most common chronic human liver disease. The fetus may be vulnerable to steatosis because immature fetal adipose depots are not available to buffer the excess transplacental lipid delivery in maternal obesity. In animal models, in utero high-fat diet exposure results in an increase in the accumulation of liver triglycerides in offspring and increased hepatic oxidative stress and apoptosis, perhaps priming the liver for later development of NAFLD. Innate immune dysfunction and necroinflammatory changes have been observed in postnatal offspring liver of animals born to high-fat-fed dams. Postweaning, livers of offspring exposed to maternal high-fat feeding in utero share pathophysiologic features with human NAFLD, including increased de novo lipogenesis and decreased free fatty acid oxidation. Human studies using magnetic resonance imaging have shown that maternal BMI predicts infant intrahepatocellular lipid storage, as seen in animal models. The generational transfer of NAFLD may occur via epigenetic changes in offspring liver. Transmission of microbiota from mother to infant may impact energy retention and immune function that contribute to a predisposition to NAFLD.

The incidence of pediatric nonalcoholic fatty liver disease has increased dramatically, and growing evidence indicates that the pathophysiology may be unique from the adult form, suggesting a role for early-life events. Recent radiologic techniques have now demonstrated that maternal obesity contributes to hepatic fat storage in newborn infants. In this review, we will explore how maternal obesity and a hyperlipidemic environment can initiate liver histopathogenesis in utero, including steatosis, mitochondrial dysfunction, oxidative stress, and inflammatory priming. Thus, early exposure to excess lipids may represent the "first hit" for the fetal liver, placing it on a trajectory toward future metabolic disease.

Objectives: To assess precision magnetic resonance imaging in the neonate and determine whether there is an early maternal influence on the pattern of neonatal fat deposition in the offspring of mothers with gestational diabetes mellitus (GDM) and obesity compared with the offspring of normal-weight women., Study Design: A total of 25 neonates born to normal weight mothers (n = 13) and to obese mothers with GDM (n = 12) underwent magnetic resonance imaging for the measurement of subcutaneous and intra-abdominal fat and magnetic resonance spectroscopy for the measurement of intrahepatocellular lipid (IHCL) fat at 1-3 weeks of age., Results: Infants born to obese/GDM mothers had a mean 68% increase in IHCL compared with infants born to normal-weight mothers. For all infants, IHCL correlated with maternal prepregnancy body mass index but not with subcutaneous adiposity., Conclusion: Deposition of liver fat in the neonate correlates highly with maternal body mass index. This finding may have implications for understanding the developmental origins of childhood nonalcoholic fatty liver disease., (Copyright © 2013 Mosby, Inc. All rights reserved.)

Drugs designed specifically to activate liver X receptors (LXRs) have beneficial effects on lowering cholesterol metabolism and inflammation but unfortunately lead to severe hepatic steatosis. The transcription factor CCAAT/enhancer binding protein beta (C/EBPβ) is an important regulator of liver gene expression but little is known about its involvement in LXR-based steatosis and cholesterol metabolism. The present study investigated the role of C/EBPβ expression in LXR agonist (T0901317)-mediated alteration of hepatic triglyceride (TG) and lipogenesis in mice. C/EBPβ deletion in mice prevented LXR agonist-mediated induction of lipogenic gene expression in liver in conjunction with significant reduction of liver TG accumulation. Surprisingly, C/EBPβ(-/-) mice showed a major increase in liver mitochondrial electron chain function compared to WT mice. Furthermore, LXR activation in C/EBPβ(-/-) mice increased the expression of liver ATP-binding cassette transporter ABCG1, a gene implicated in cholesterol efflux and reducing blood levels of total and LDL-cholesterol. Together, these findings establish a central role for C/EBPβ in the LXR-mediated steatosis and mitochondrial function, without impairing the influence of LXR activation on lowering LDL and increasing HDL-cholesterol. Inactivation of C/EBPβ might therefore be an important therapeutic strategy to prevent LXR activation-mediated adverse effects on liver TG metabolism without disrupting its beneficial effects on cholesterol metabolism., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Chronic hepatitis C virus (HCV) infection greatly increases the risk for type 2 diabetes and nonalcoholic steatohepatitis; however, the pathogenic mechanisms remain incompletely understood. Here we report gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) transcription and associated transcription factors are dramatically up-regulated in Huh.8 cells, which stably express an HCV subgenome replicon. HCV increased activation of cAMP response element-binding protein (CREB), CCAAT/enhancer-binding protein (C/EBPβ), forkhead box protein O1 (FOXO1), and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and involved activation of the cAMP response element in the PEPCK promoter. Infection with dominant-negative CREB or C/EBPβ-shRNA significantly reduced or normalized PEPCK expression, with no change in PGC-1α or FOXO1 levels. Notably, expression of HCV nonstructural component NS5A in Huh7 or primary hepatocytes stimulated PEPCK gene expression and glucose output in HepG2 cells, whereas a deletion in NS5A reduced PEPCK expression and lowered cellular lipids but was without effect on insulin resistance, as demonstrated by the inability of insulin to stimulate mobilization of a pool of insulin-responsive vesicles to the plasma membrane. HCV-replicating cells demonstrated increases in cellular lipids with insulin resistance at the level of the insulin receptor, increased insulin receptor substrate 1 (Ser-312), and decreased Akt (Ser-473) activation in response to insulin. C/EBPβ-RNAi normalized lipogenic genes sterol regulatory element-binding protein-1c, peroxisome proliferator-activated receptor γ, and liver X receptor α but was unable to reduce accumulation of triglycerides in Huh.8 cells or reverse the increase in ApoB expression, suggesting a role for increased lipid retention in steatotic hepatocytes. Collectively, these data reveal an important role of NS5A, C/EBPβ, and pCREB in promoting HCV-induced gluconeogenic gene expression and suggest that increased C/EBPβ and NS5A may be essential components leading to increased gluconeogenesis associated with HCV infection.

Acetylation has recently emerged as an important mechanism for controlling a broad array of proteins mediating cellular adaptation to metabolic fuels. Acetylation is governed, in part, by SIRTs (sirtuins), class III NAD(+)-dependent deacetylases that regulate lipid and glucose metabolism in liver during fasting and aging. However, the role of acetylation or SIRTs in pathogenic hepatic fuel metabolism under nutrient excess is unknown. In the present study, we isolated acetylated proteins from total liver proteome and observed 193 preferentially acetylated proteins in mice fed on an HFD (high-fat diet) compared with controls, including 11 proteins not previously identified in acetylation studies. Exposure to the HFD led to hyperacetylation of proteins involved in gluconeogenesis, mitochondrial oxidative metabolism, methionine metabolism, liver injury and the ER (endoplasmic reticulum) stress response. Livers of mice fed on the HFD had reduced SIRT3 activity, a 3-fold decrease in hepatic NAD(+) levels and increased mitochondrial protein oxidation. In contrast, neither SIRT1 nor histone acetyltransferase activities were altered, implicating SIRT3 as a dominant factor contributing to the observed phenotype. In Sirt3⁻(/)⁻ mice, exposure to the HFD further increased the acetylation status of liver proteins and reduced the activity of respiratory complexes III and IV. This is the first study to identify acetylation patterns in liver proteins of HFD-fed mice. Our results suggest that SIRT3 is an integral regulator of mitochondrial function and its depletion results in hyperacetylation of critical mitochondrial proteins that protect against hepatic lipotoxicity under conditions of nutrient excess.

Aging is associated with various metabolic disorders that may have their origin in the liver, including non-alcoholic fatty liver disease, obesity, type 2 diabetes mellitus, and atherosclerosis. Although well-characterized in models of caloric restriction, relatively little is known about the role of sirtuins and acetylation under conditions of caloric excess. Sirtuins are NAD (+)-dependent protein deacetylases that mediate adaptive responses to a variety of stresses, including calorie restriction and metabolic stress. Sirtuin 3 (SIRT3) is localized within the mitochondrial matrix, where it regulates acetylation levels of a diverse set of metabolic enzymes. When normal mice are fed a high fat diet they demonstrate reduced SIRT3 activity, impaired mitochondrial function, and hyperacetylation of a diverse set of proteins in their livers. Furthermore, SIRT3 knockout mice have signs of accelerated aging and cancer. Understanding SIRT3?s biochemical function and regulation in the liver under conditions of caloric excess may potentially increase our understanding of the normal aging process and diseases associated with aging, such as diabetes, fatty liver disease, or cancer.

Maternal obesity is thought to increase the offspring's risk of juvenile obesity and metabolic diseases; however, the mechanism(s) whereby excess maternal nutrition affects fetal development remain poorly understood. Here, we investigated in nonhuman primates the effect of chronic high-fat diet (HFD) on the development of fetal metabolic systems. We found that fetal offspring from both lean and obese mothers chronically consuming a HFD had a 3-fold increase in liver triglycerides (TGs). In addition, fetal offspring from HFD-fed mothers (O-HFD) showed increased evidence of hepatic oxidative stress early in the third trimester, consistent with the development of nonalcoholic fatty liver disease (NAFLD). O-HFD animals also exhibited elevated hepatic expression of gluconeogenic enzymes and transcription factors. Furthermore, fetal glycerol levels were 2-fold higher in O-HFD animals than in control fetal offspring and correlated with maternal levels. The increased fetal hepatic TG levels persisted at P180, concurrent with a 2-fold increase in percent body fat. Importantly, reversing the maternal HFD to a low-fat diet during a subsequent pregnancy improved fetal hepatic TG levels and partially normalized gluconeogenic enzyme expression, without changing maternal body weight. These results suggest that a developing fetus is highly vulnerable to excess lipids, independent of maternal diabetes and/or obesity, and that exposure to this may increase the risk of pediatric NAFLD.

CCAAT/enhancer-binding protein beta (C/EBPbeta) plays a key role in initiation of adipogenesis in adipose tissue and gluconeogenesis in liver; however, the role of C/EBPbeta in hepatic lipogenesis remains undefined. Here we show that C/EBPbeta inactivation in Lepr(db/db) mice attenuates obesity, fatty liver, and diabetes. In addition to impaired adipogenesis, livers from C/EBPbeta(-/-) x Lepr(db/db) mice had dramatically decreased triglyceride content and reduced lipogenic enzyme activity. C/EBPbeta deletion in Lepr(db/db) mice down-regulated peroxisome proliferator-activated receptor gamma2 (PPARgamma2) and stearoyl-CoA desaturase-1 and up-regulated PPARalpha independent of SREBP1c. Conversely, C/EBPbeta overexpression in wild-type mice increased PPARgamma2 and stearoyl-CoA desaturase-1 mRNA and hepatic triglyceride content. In FAO cells, overexpression of the liver inhibiting form of C/EBPbeta or C/EBPbeta RNA interference attenuated palmitate-induced triglyceride accumulation and reduced PPARgamma2 and triglyceride levels in the liver in vivo. Leptin and the anti-diabetic drug metformin acutely down-regulated C/EBPbeta expression in hepatocytes, whereas fatty acids up-regulate C/EBPbeta expression. These data provide novel evidence linking C/EBPbeta expression to lipogenesis and energy balance with important implications for the treatment of obesity and fatty liver disease.

Unlabelled: Nonalcoholic steatohepatitis (NASH) is characterized by steatosis, inflammation, and oxidative stress. To investigate whether the transcription factor CCAAT/Enhancer binding protein (C/EBPbeta) is involved in the development of NASH, C57BL/6J wild-type (WT) or C/EBPbeta knockout (C/EBPbeta-/-) mice were fed either a methionine and choline deficient (MCD) diet or standard chow. These WT mice fed a MCD diet for 4 weeks showed a 2- to 3-fold increase in liver C/EBPbeta messenger RNA and protein, along with increased expression of lipogenic genes peroxisome proliferators-activated receptor gamma and Fas. WT mice also showed increased levels of the endoplasmic reticulum stress pathway proteins phosphorylated eukaryotic translation initiation factor alpha, phosphorylated pancreatic endoplasmic reticulum kinase, and C/EBP homologous protein, along with inflammatory markers phosphorylated nuclear factor kappaB and phosphorylated C-jun N-terminal kinase compared to chow-fed controls. Cytochrome P450 2E1 protein and acetyl coA oxidase messenger RNA involved in hepatic lipid peroxidation were also markedly increased in WT MCD diet-fed group. In contrast, C/EBPbeta-/- mice fed a MCD diet showed a 60% reduction in hepatic triglyceride accumulation and decreased liver injury as evidenced by reduced serum alanine aminotransferase and aspartate aminotransferase levels, and by H&E staining. Immunoblots and real-time qPCR data revealed a significant reduction in expression of stress related proteins and lipogenic genes in MCD diet-fed C/EBPbeta-/- mice. Furthermore, circulating TNFalpha and expression of acute phase response proteins CRP and SAP were significantly lower in C/EBPbeta-/- mice compared to WT mice. Conversely, C/EBPbeta over-expression in livers of WT mice increased steatosis, nuclear factor-kappaB, and endoplasmic reticulum stress, similar to MCD diet-fed mice., Conclusion: Taken together, these data suggest a previously unappreciated molecular link between C/EBPbeta, hepatic steatosis and inflammation and suggest that increased C/EBPbeta expression may be an important factor underlying events leading to NASH.

Cullin RING E3 ligases (CRL) have emerged as key regulators of disease-modifying pathways and therapeutic targets. Cullin3 (Cul3)-containing CRL (CRL3) has been implicated in regulating hepatic insulin and oxidative stress signaling. However, CRL3 function in liver pathophysiology is poorly defined. Here, we report that hepatocyte Cul3 knockout results in rapid resolution of steatosis in obese mice. However, the remarkable resistance of hepatocyte Cul3 knockout mice to developing steatosis does not lead to overall metabolic improvement but causes systemic metabolic disturbances. Liver transcriptomics analysis identifies that CRL3 inactivation causes persistent activation of the nuclear factor erythroid 2-related factor 2 (NRF2) antioxidant defense pathway, which also reprograms the lipid transcriptional network to prevent TG storage. Furthermore, global metabolomics reveals that NRF2 activation induces numerous NAD+-consuming aldehyde dehydrogenases to increase the cellular NADH/NAD+ ratio, a redox imbalance termed NADH reductive stress that inhibits the glycolysis-citrate-lipogenesis axis in Cul3 knockout livers. As a result, this NRF2-induced cellular lipid storage defect promotes hepatic ceramide accumulation, elevates circulating fatty acids, and worsens systemic insulin resistance in a vicious cycle. Hepatic lipid accumulation is restored, and liver injury and hyperglycemia are attenuated when NRF2 activation and NADH reductive stress are abolished in hepatocyte Cul3/Nrf2 double-knockout mice. The resistance to hepatic steatosis, hyperglycemia, and NADH reductive stress are observed in hepatocyte Keap1 knockout mice with NRF2 activation. In summary, our study defines a critical role of CRL3 in hepatic metabolic regulation and demonstrates that the CRL3 downstream NRF2 overactivation causes hepatic metabolic maladaptation to obesity and insulin resistance. [ABSTRACT FROM AUTHOR]

Pediatric NAFLD has distinct and variable pathology, yet causation remains unclear. We have shown that maternal Western-style diet (mWSD) compared with maternal chow diet (CD) consumption in nonhuman primates produces hepatic injury and steatosis in fetal offspring. Here, we define the role of mWSD and postweaning Western-style diet (pwWSD) exposures on molecular mechanisms linked to NAFLD development in a cohort of 3-year-old juvenile nonhuman primates offspring exposed to maternal CD or mWSD followed by CD or Western-style diet after weaning. We used histologic, transcriptomic, and metabolomic analyses to identify hepatic pathways regulating NAFLD. Offspring exposed to mWSD showed increased hepatic periportal collagen deposition but unchanged hepatic triglyceride levels and body weight. mWSD was associated with a downregulation of gene expression pathways underlying HNF4a activity and protein, and downregulation of antioxidant signaling, mitochondrial biogenesis, and PPAR signaling pathways. In offspring exposed to both mWSD and pwWSD, liver RNA profiles showed upregulation of pathways promoting fibrosis and endoplasmic reticulum stress and increased BiP protein expression with pwWSD. pwWSD increased acylcarnitines and decreased anti-inflammatory fatty acids, which was more pronounced when coupled with mWSD exposure. Further, mWSD shifted liver metabolites towards decreased purine catabolism in favor of synthesis, suggesting a mitochondrial DNA repair response. Our findings demonstrate that 3-year-old offspring exposed to mWSD but weaned to a CD have periportal collagen deposition, with transcriptional and metabolic pathways underlying hepatic oxidative stress, compromised mitochondrial lipid sensing, and decreased antioxidant response. Exposure to pwWSD worsens these phenotypes, triggers endoplasmic reticulum stress, and increases fibrosis. Overall, mWSD exposure is associated with altered expression of candidate genes and metabolites related to NAFLD that persist in juvenile offspring preceding clinical presentation of NAFLD. [ABSTRACT FROM AUTHOR]

Hepatic insulin resistance is a hallmark feature of nonalcoholic fatty liver disease and type-2 diabetes and significantly contributes to systemic insulin resistance. Abnormal activation of nutrient and stress-sensing kinases leads to serine/threonine phosphorylation of insulin receptor substrate (IRS) and subsequent IRS proteasome degradation, which is a key underlying cause of hepatic insulin resistance. Recently, members of the cullin-RING E3 ligases (CRLs) have emerged as mediators of IRS protein turnover, but the pathophysiological roles and therapeutic implications of this cellular signaling regulation is largely unknown. CRLs are activated upon cullin neddylation, a process of covalent conjugation of a ubiquitin-like protein called Nedd8 to a cullin scaffold. Here, we report that pharmacological inhibition of cullin neddylation by MLN4924 (Pevonedistat) rapidly decreases hepatic glucose production and attenuates hyperglycemia in mice. Mechanistically, neddylation inhibition delays CRL-mediated IRS protein turnover to prolong insulin action in hepatocytes. In vitro knockdown of either cullin 1 or cullin 3, but not other cullin members, attenuates insulin-induced IRS protein degradation and enhances cellular insulin signaling activation. In contrast, in vivo knockdown of liver cullin 3, but not cullin 1, stabilizes hepatic IRS and decreases blood glucose, which recapitulates the effect of MLN4924 treatment. In summary, these findings suggest that pharmacological inhibition of cullin neddylation represents a therapeutic approach for improving hepatic insulin signaling and lowering blood glucose. [ABSTRACT FROM AUTHOR]

Nonalcoholic fatty liver disease (NAFLD) is a global epidemic in obese children and adults, and the onset might have fetal origins. A growing body of evidence supports the role of developmental programming, whereby the maternal environment affects fetal and infant development, altering the risk profile for disease later in life. Human and nonhuman primate studies of maternal obesity demonstrate that risk factors for pediatric obesity and NAFLD begin in utero. The pathologic mechanisms for NAFLD are multifactorial but have centered on altered mitochondrial function/dysfunction that might precede insulin resistance. Compared with the adult liver, the fetal liver has fewer mitochondria, low activity of the fatty acid metabolic enzyme carnitine palmitoyl-CoA transferase-1, and little or no gluconeogenesis. Exposure to excess maternal fuels during fetal life uniquely alters hepatic fatty acid oxidation, tricarboxylic acid cycle activity, de novo lipogenesis, and mitochondrial health. These events promote increased oxidative stress and excess triglyceride storage, and, together with altered immune function and epigenetic changes, they prime the fetal liver for NAFLD and might drive the risk for nonalcoholic steatohepatitis in the next generation. [ABSTRACT FROM AUTHOR]

Spaceflight affects numerous organ systems in the body, leading to metabolic dysfunction that may have long-term consequences. Microgravity-induced alterations in liver metabolism, particularly with respect to lipids, remain largely unexplored. Here we utilize a novel systems biology approach, combining metabolomics and transcriptomics with advanced Raman microscopy, to investigate altered hepatic lipid metabolism in mice following short duration spaceflight. Mice flown aboard Space Transportation System -135, the last Shuttle mission, lose weight but redistribute lipids, particularly to the liver. Intriguingly, spaceflight mice lose retinol from lipid droplets. Both mRNA and metabolite changes suggest the retinol loss is linked to activation of PPARα-mediated pathways and potentially to hepatic stellate cell activation, both of which may be coincident with increased bile acids and early signs of liver injury. Although the 13-day flight duration is too short for frank fibrosis to develop, the retinol loss plus changes in markers of extracellular matrix remodeling raise the concern that longer duration exposure to the space environment may result in progressive liver damage, increasing the risk for nonalcoholic fatty liver disease. [ABSTRACT FROM AUTHOR]

In nonhuman primates, we previously demonstrated that a maternal high-fat diet (MHFD) induces fetal nonalcoholic fatty liver disease (NAFLD) and alters the fetal metabolome. These changes are accompanied by altered acetylation of histone H3 (H3K14ac). However, the mechanism behind this alteration in acetylation remains unknown. As SIRT1 is both a lysine deacetylase and a crucial sensor of cellular metabolism, we hypothesized that SIRT1 may be involved in fetal epigenomic alterations. Here we show that in utero exposure to a MHFD, but not maternal obesity per se, increases fetal H3K14ac with concomitant decreased SIRT1 expression and diminished in vitro protein and histone deacetylase activity. MHFD increased H3K14ac and DBC1-SIRT1 complex formation in fetal livers, both of which were abrogated with diet reversal despite persistent maternal obesity. Moreover, MHFD was associated with altered expression of known downstream effectors deregulated in NAFLD and modulated by SIRT1 (e.g., PPARA, PPARG, SREBF1, CYP7A1, FASN, and SCD). Finally, ex vivo purified SIRT1 retains deacetylase activity on an H3K14ac peptide substrate with preferential activity toward acetylated histone H3; mutagenesis of the catalytic domain of SIRT1 (H363Y) abrogates H3K14ac deacetylation. Our data implicate SIRT1 as a likely molecular mediator of the fetal epigenome and metabolome under MHFD conditious. [ABSTRACT FROM AUTHOR]

Our group recently demonstrated that maternal high-fat diet (HFD) consumption is associated with non-alcoholic fatty liver disease, increased apoptosis, and changes in gluconeogenic gene expression and chromatin structure in fetal nonhuman primate (NHP) liver. However, little is known about the long-term effects that a HFD has on hepatic nervous system development in offspring, a system that plays an important role in regulating hepatic metabolism. Utilizing immunohistochemistry and Real-Time PCR, we quantified sympathetic nerve fiber density, apoptosis, inflammation, and other autonomic components in the livers of fetal and one-year old Japanese macaques chronically exposed to a HFD. We found that HFD exposure in-utero and throughout the postnatal period (HFD/HFD), when compared to animals receiving a CTR diet for the same developmental period (CTR/CTR), is associated with a 1.7 fold decrease in periportal sympathetic innervation, a 5 fold decrease in parenchymal sympathetic innervation, and a 2.5 fold increase in hepatic apoptosis in the livers of one-year old male animals. Additionally, we observed an increase in hepatic inflammation and a decrease in a key component of the cholinergic anti-inflammatory pathway in one-year old HFD/HFD offspring. Taken together, these findings reinforce the impact that continuous exposure to a HFD has in the development of long-term hepatic pathologies in offspring and highlights a potential neuroanatomical basis for hepatic metabolic dysfunction. [ABSTRACT FROM AUTHOR]

CCAAT/enhancer-binding protein β (C/EBPβ) plays a key role in initiation of adipogenesis in adipose tissue and gluconeogenesis in liver; however, the role of C/EBPβ in hepatic lipogenesis remains undefined. Here we show that C/EBPβ inactivation in Lepdb/db mice attenuates obesity, fatty liver, and diabetes. In addition to impaired adipogenesis, livers from C/EBPβ-/- x Leprdb/db mice had dramatically decreased triglyceride content and reduced lipogenic enzyme activity. C/EBPβ deletion in Leprdb/db mice down-regulated peroxisome proliferator-activated receptor γ2 (PPARγ2) and stearoyl-CoA desaturase-1 and up-regulated PPARα independent of SREBP1c. Conversely, C/EBPβ overexpression in wild-type mice increased PPARγ2 and stearoyl-CoA desaturase-1 mRNA and hepatic triglyceride content. In FAO cells, overexpression of the liver inhibiting form of C/EBPβ or C/EBPβ RNA interference attenuated palmitate-induced triglyceride accumulation and reduced PPARγ2 and triglyceride levels in the liver in vivo. Leptin and the anti-diabetic drug metformin acutely down-regulated C/EBPβ expression in hepatocytes, whereas fatty acids up-regulate C/EBPβ expression. These data provide novel evidence linking C/EBPβ expression to lipogenesis and energy balance with important implications for the treatment of obesity and fatty liver disease. [ABSTRACT FROM AUTHOR]