Triglyceride Secretion Research Articles

Nuclear receptors FXR and SHP regulate protein N-glycan modifications in the liver.

Nuclear receptors farnesoid X receptor (FXR) and small heterodimer partner (SHP) are key regulators of metabolism. Here, we report a previously unknown function for the hepatic FXR-SHP axis in controlling protein N-linked glycosylation. Transcriptome analysis in liver-specific Fxr-Shp double knockout (LDKO) livers revealed induction of genes encoding enzymes in the N-glycosylation pathway, including Mgat5, Fut8, St3gal6, and St6gal1 FXR activation suppressed Mgat5, while Shp deletion induced St3gal6 and St6gal1 Increased percentages of core-fucosylated and triantennary glycan moieties were seen in LDKO livers, and proteins with the "hyperglycoforms" preferentially localized to exosomes and lysosomes. This up-regulation of N-glycosylation machinery was specific to the Golgi apparatus and not the endoplasmic reticulum. The increased glycan complexity in the LDKO correlated well with dilated unstacked Golgi ribbons and alterations in the secretion of albumin, cholesterol, and triglycerides. Our findings demonstrate a role for the FXR-SHP axis in maintaining glycoprotein diversity in the liver.

Clodronate, an inhibitor of the vesicular nucleotide transporter, ameliorates steatohepatitis and acute liver injury

The vesicular nucleotide transporter (VNUT) is responsible for the vesicular storage and release of ATP from various ATP-secreting cells, and it plays an essential role in purinergic signaling. Although extracellular ATP and its degradation products are known to mediate various inflammatory responses via purinoceptors, whether vesicular ATP release affects steatohepatitis and acute liver injury is far less understood. In the present study, we investigated the effects of clodronate, a potent and selective VNUT inhibitor, on acute and chronic liver inflammation in mice. In a model of methionine/choline-deficient diet-induced non-alcoholic steatohepatitis (NASH), the administration of clodronate reduced hepatic inflammation, fibrosis, and triglyceride accumulation. Clodronate also protected mice against high-fat/high-cholesterol diet-induced steatohepatitis. Moreover, prophylactic administration of clodronate prevented d-galactosamine and lipopolysaccharide-induced acute liver injury by reducing inflammatory cytokines and hepatocellular apoptosis. In vitro, clodronate inhibited glucose-induced vesicular ATP release mediated by VNUT and reduced the intracellular level and secretion of triglycerides in isolated hepatocytes. These results suggest that VNUT-dependent vesicular ATP release plays a crucial role in the recruitment of immune cells, cytokine production, and the aggravation of steatosis in the liver. Pharmacological inhibition of VNUT may provide therapeutic benefits in liver inflammatory disorders, including NASH and acute toxin-induced injury.

Lipoprotein receptor SR-B1 deficiency enhances adipose tissue inflammation and reduces susceptibility to hepatic steatosis during diet-induced obesity in mice

Scavenger receptor class B type 1 (SR-B1) is a membrane lipoprotein receptor/lipid transporter involved in the pathogenesis of atherosclerosis, but its role in obesity and fatty liver development is unclear. Here, we determined the effects of SR-B1 deficiency on plasma metabolic and inflammatory parameters as well as fat deposition in adipose tissue and liver during obesity. To induce obesity, we performed high-fat diet (HFD) exposure for 12 weeks in male SR-B1 knock-out (SR-B1−/−, n = 14) and wild-type (WT, n = 12) mice. Compared to HFD-fed WT mice, plasma from HFD-fed SR-B1−/− animals exhibited increased total cholesterol, triglycerides (TG) and tumor necrosis factor-α (TNF-α) levels. In addition, hypertrophied adipocytes and macrophage-containing crown-like structures (CLS) were observed in adipose tissue from HFD-fed SR-B1 deficient mice. Remarkably, liver from obese SR-B1−/− mice showed attenuated TG content, dysregulation in hepatic peroxisome proliferator-activated receptors (PPARs) expression, increased hepatic TG secretion, and altered hepatic fatty acid (FA) composition. In conclusion, we show that SR-B1 deficiency alters the metabolic environment of obese mice through modulation of liver and adipose tissue lipid accumulation. Our findings provide the basis for further elucidation of SR-B1's role in obesity and fatty liver, two major public health issues that increase the risk of advanced chronic diseases and overall mortality.

The Role of Lipophagy in the Development and Treatment of Non-Alcoholic Fatty Liver Disease.

Non-alcoholic fatty liver disease (NAFLD) or metabolic (dysfunction) associated liver disease (MAFLD), is, with a global prevalence of 25%, the most common liver disorder worldwide. NAFLD comprises a spectrum of liver disorders ranging from simple steatosis to steatohepatitis, fibrosis, cirrhosis and eventually end-stage liver disease. The cause of NAFLD is multifactorial with genetic susceptibility and an unhealthy lifestyle playing a crucial role in its development. Disrupted hepatic lipid homeostasis resulting in hepatic triglyceride accumulation is an hallmark of NAFLD. This disruption is commonly described based on four pathways concerning 1) increased fatty acid influx, 2) increased de novo lipogenesis, 3) reduced triglyceride secretion, and 4) reduced fatty acid oxidation. More recently, lipophagy has also emerged as pathway affecting NAFLD development and progression. Lipophagy is a form of autophagy (i.e. controlled autolysosomal degradation and recycling of cellular components), that controls the breakdown of lipid droplets in the liver. Here we address the role of hepatic lipid homeostasis in NAFLD and specifically review the current literature on lipophagy, describing its underlying mechanism, its role in pathophysiology and its potential as a therapeutic target.

Lipopolysaccharide and lipoteichoic acid influence milk production ability via different early responses in bovine mammary epithelial cells

Lipopolysaccharide (LPS) and lipoteichoic acid (LTA) are cell wall components of Escherichia coli and Staphylococcus aureus, which cause clinical and subclinical mastitis, respectively. However, the reason of the difference in symptoms by pathogen type remains unclear. In this study, the influence of LPS and LTA on early response and milk production in lactating bovine mammary epithelial cells (BMECs) was comparatively investigated. The results showed that LPS decreased the secretion of β-casein, lactose, and triglycerides, whereas LTA decreased the secretion of lactose and triglycerides but increased lactoferrin production without any influence on β-casein secretion. In addition, the influence of milk lipid droplet size in BMECs and gene expression related to milk fat synthesis was different between LPS and LTA. LPS increased the gene expression of interleukin (IL)-1β, tumor necrosis factor-α, and IL-8 through the activation of the nuclear factor-κB (NF-κB), p38, and c-Jun N-terminal kinase pathways, whereas LTA increased IL-1β and CC chemokine ligand 5 expression through the activation of the NF-κB pathway. Moreover, these cytokines and chemokines differently affected the milk production ability of BMECs. These results suggested that the pathogen-specific symptoms may be related to the differences in the early response of BMECs to bacterial toxins.

PRAP1 is a novel lipid-binding protein that promotes lipid absorption by facilitating MTTP-mediated lipid transport

Microsomal triglyceride transfer protein (MTTP) is an endoplasmic reticulum resident protein that is essential for the assembly and secretion of triglyceride (TG)-rich, apoB-containing lipoproteins. Although the function and structure of mammalian MTTP have been extensively studied, how exactly MTTP transfers lipids to lipid acceptors and whether there are other biomolecules involved in MTTP-mediated lipid transport remain elusive. Here we identify a role in this process for the poorly characterized protein PRAP1. We report that PRAP1 and MTTP are partially colocalized in the endoplasmic reticulum. We observe that PRAP1 directly binds to TG and facilitates MTTP-mediated lipid transfer. A single amino acid mutation at position 85 (E85V) impairs PRAP1's ability to form a ternary complex with TG and MTTP, as well as impairs its ability to facilitate MTTP-mediated apoB-containing lipoprotein assembly and secretion, suggesting that the ternary complex formation is required for PRAP1 to facilitate MTTP-mediated lipid transport. PRAP1 is detectable in chylomicron/VLDL-rich plasma fractions, suggesting that MTTP recognizes PRAP1-bound TG as a cargo and transfers TG along with PRAP1 to lipid acceptors. Both PRAP1-deficient and E85V knock-in mutant mice fed a chow diet manifested an increase in the length of their small intestines, likely to compensate for challenges in absorbing lipid. Interestingly, both genetically modified mice gained significantly less body weight and fat mass when on high-fat diets compared with littermate controls and were prevented from hepatosteatosis. Together, this study provides evidence that PRAP1 plays an important role in MTTP-mediated lipid transport and lipid absorption.

Atherosclerosis-associated hepatic secretion of VLDL but not PCSK9 is dependent on cargo receptor protein Surf4

Plasma LDL is produced from catabolism of VLDL and cleared from circulation mainly via the hepatic LDL receptor (LDLR). Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes LDLR degradation, increasing plasma LDL-C levels. Circulating PCSK9 is mainly secreted by the liver, whereas VLDL is exclusively secreted by hepatocytes. However, the mechanism regulating their secretion is not completely understood. Surfeit 4 (Surf4) is a cargo receptor localized in the ER membrane. It recruits cargos into coat protein complex II vesicles to facilitate their secretion. Here, we investigated the role of Surf4 in VLDL and PCSK9 secretion. We generated Surf4 liver-specific knockout mice and found that knockout of Surf4 did not affect PCSK9 secretion, whereas it significantly reduced plasma levels of cholesterol, triglyceride, and lipid-binding protein apolipoprotein B (apoB). In cultured human hepatocytes, Surf4 coimmunoprecipitated and colocalized with apolipoprotein B100, and Surf4 silencing reduced secretion of apolipoprotein B100. Furthermore, knockdown of Surf4 in LDLR knockout (Ldlr−/−) mice significantly reduced triglyceride secretion, plasma levels of apoB and non-HDL-C, and the development of atherosclerosis. However, Surf4 liver-specific knockout mice and Surf4 knockdown in Ldlr−/− mice displayed similar levels of liver lipids and plasma alanine aminotransferase activity as control mice, indicating that inhibition of Surf4 does not cause notable liver damage. Expression of stearoyl-CoA desaturase-1 was also reduced in the liver of these mice, suggesting a reduction in de novo lipogenesis. In summary, hepatic deficiency of Surf4 reduced VLDL secretion and the development of atherosclerosis but did not cause significant hepatic lipid accumulation or liver damage.

Generation and validation of a conditional knockout mouse model for the study of the Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz Syndrome (SLOS) is a developmental disorder (OMIM #270400) caused by autosomal recessive mutations in the Dhcr7 gene, which encodes the enzyme 3β-hydroxysterol-Δ7 reductase. SLOS patients present clinically with dysmorphology and neurological, behavioral, and cognitive defects, with characteristically elevated levels of 7-dehydrocholesterol (7-DHC) in all bodily tissues and fluids. Previous mouse models of SLOS have been hampered by postnatal lethality when Dhcr7 is knocked out globally, while a hypomorphic mouse model showed improvement in the biochemical phenotype with aging and did not manifest most other characteristic features of SLOS. We report the generation of a conditional knockout of Dhcr7 (Dhcr7flx/flx), validated by generating a mouse with a liver-specific deletion (Dhcr7L-KO). Phenotypic characterization of liver-specific knockout mice revealed no significant changes in viability, fertility, growth curves, liver architecture, hepatic triglyceride secretion, or parameters of systemic glucose homeostasis. Furthermore, qPCR and RNA-Seq analyses of livers revealed no perturbations in pathways responsible for cholesterol synthesis, either in male or in female Dhcr7L-KO mice, suggesting that hepatic disruption of postsqualene cholesterol synthesis leads to minimal impact on sterol metabolism in the liver. This validated conditional Dhcr7 knockout model may now allow us to systematically explore the pathophysiology of SLOS, by allowing for temporal, cell and tissue-specific loss of DHCR7.

Fixed-time and continuous assays of very-low-density lipoprotein secretion rate from rat liver: mean vs. instantaneous velocity.

Aim of the studyThe secretion rate of triglyceride from rat liver is assayed by the measurement of triglyceride accumulation in plasma when its clearance is inhibited. The aim of the study was to measure and compare the secretion rate of triglyceride from rat liver by two methods of fixed-time and continuous assays.Material and methodsA single dose of 200 mg of poloxamer-407 (P-407) was injected i.p. into starved male rats. The secretion rate of triglyceride was measured by fixed-time and continuous assays.ResultsThe time course for the changes of serum triglyceride following injection of P-407 showed three distinct phases: a lag period of about 30 minutes, a linear increase in serum triglyceride that lasted more than 4 hours, and a slight decline of triglyceride accumulation that lasted about 24 hours. The mean rate of triglyceride secretion was 234.1 ±9.6 mg/dl/h during the linear phase. The linear phase was divided into five time protocols of 240, 180, 120, 60, and 30 minutes and the secretion rate was measured at three points of time in each protocol. The mean rate of triglyceride secretion was 3.91 ±0.15, 3.83 ±0.16, 3.76 ±0.29, 3.57 ±0.43 and 3.13 ±0.34 mg/dl/min in these protocols respectively. In the kinetic assay, the change in the absorbance per three successive five minutes (ΔA/Δt) was measured and the secretion rate was calculated as 3.82 ±0.11 mg/dl/min.ConclusionsThe rate of triglyceride secretion can be measured by both fixed-time and kinetic assays and was about 3.82 ±0.11 mg/dl/min. The results of the two methods are more corresponded as the mean and instantaneous velocity respectively.

뽕잎 추출물 기원 Flavonoid Rich Fraction의 항비만효과

Background: This study investigated the anti-obesity effect of the flavonoid rich fraction (FRF) and its constituent, rutin obtained from the leaf of Morus alba L., on the lipid accumulation mechanism in 3T3-L1 adipocyte and C57BL/6 mouse models.BRMethods and Results: In Oil Red O staining, FRF (1,000 ㎍/㎖) treatments showed inhibition rate of 35.39% in lipid accumulation compared to that in the control. AdipoRedTM assay indicated that the triglyceride content in 3T3-L1 adipocytes treated with FRF (1,000 ㎍/㎖) was reduced to 23.22%, and free glycerol content was increased to 106.04% that of the control. FRF and its major constituent, rutin affected mRNA gene expression. Rutin contributed to the inhibition of Sterol regulatory element binding protein-1c (SREBP-1c) gene expression, and inhibited the transcription factors SREBP-1c, peroxisome proliferator-activated receptor gamma (PPAR-γ), CCAAT/enhancer binding protein α (C/EBPα), fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC). In addition, the effect of FRF administration on obesity development in C57BL/6 mice fed high-fat diet (HFD) was investigated. FRF suppressed weight gain, and reduced liver triglyceride and leptin secretion. FRF exerted potential anti-inflammatory effects by improving insulin resistance and adiponectin levels, and could thus be used to help counteract obesity. The mRNA expressions of PPAR-γ, FAS, ACC, and CPT-1 were determined in liver tissue. Quantitative real-time PCR analysis was also performed to evaluate the expression of IL-1β, IL-6, and TNF-α in epididymal adipose tissue. Compared to the control group, mice fed the HFD showed the up-regulation in PPAR-γ, FAS, IL-6, and TNF-α genes, and down-regulation in CPT1 gene expression. FRF treatement markedly reduced the expression of PPAR-γ, FAS, IL-6, and TNF-α compared to those in HFD control, whereas increased the expression level of CPT1.BRConclusions: These results suggest that the FRF and its major active constituent, rutin, can be used as effective anti-obesity agents.

Vesicular ATP release from hepatocytes plays a role in the progression of nonalcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is becoming a growing public health problem along with the increase of metabolic syndrome worldwide. Extracellular nucleotides are known to serve as a danger signal by initiating purinergic signaling in many inflammatory disorders, although the role of purinergic signaling in the progression of NASH remains to be clarified. Vesicular nucleotide transporter (VNUT) is a key molecule responsible for vesicular ATP release to initiate purinergic signaling. Here, we studied the role of VNUT in the progression of nonalcoholic steatohepatitis. VNUT was expressed in mouse hepatocytes and associated, at least in part, with apolipoprotein B (apoB)-containing vesicles. High glucose stimulation evoked release of appreciable amount of ATP from hepatocytes, which disappeared in hepatocytes of Vnut knockout (Vnut−/−) mice. Glucose treatment also stimulated triglyceride secretion from hepatocytes, which was inhibited by PPADS and MRS211, antagonists of P2Y receptors, and clodronate, a VNUT inhibitor, and was significantly reduced in Vnut−/− mice. In vivo, postprandial secretion of triglyceride from hepatocytes was observed, while the serum triglyceride level was significantly reduced in Vnut−/− mice. On a high-fat diet, the liver of wild type mice exhibited severe inflammation, fibrosis, and macrophage infiltration, which is similar to NASH in humans, while this NASH pathology was not observed in Vnut−/− mice. These results suggest that VNUT-mediated vesicular ATP release regulates triglyceride secretion and involves in chronic inflammation in hepatocytes. Since blockade of vesicular ATP release protects against progression of steatohepatitis, VNUT may be a pharmacological target for NASH.

In pregnancy, maternal HDL is specifically enriched in, and carries the highest proportion of, DHA in plasma

Arachidonic acid (AA) and docosahexaenoic acid (DHA) are important for neurological development. The aim was to determine the distribution and relative enrichment of AA and DHA among lipoprotein fractions prior to pregnancy, throughout gestation and in the post-partum period. Our hypothesis was that in pregnancy, in contrast to the non-pregnant state, AA and DHA are carried in highest concentration in the very low density lipoprotein (VLDL) fraction secondary to increased gestational liver triglyceride secretion. Two independent prospective, observational cohort studies carried out in Glasgow were combined; one early in pregnancy and one later in pregnancy with post-partum follow up. Across the pregnancy timeline plasma lipoproteins were isolated using sequential ultracentrifugation and lipoprotein fatty acids were extracted and analysed by gas chromatography. High density lipoprotein (HDL) had the highest concentration of AA and DHA compared to other lipoproteins. HDL became progressively enriched in the proportion of triglycerides at 16 weeks of gestation, which peaked at 35 weeks and returned to baseline at 13 weeks postpartum. HDL DHA per HDL-cholesterol and HDL DHA per apoA-I became progressively enriched at 16 weeks of gestation, peaked at 25 weeks and returned to baseline at 13 weeks postpartum, whereas HDL AA (per HDL-C or HDL-apoA-I) did not differ. DHA is carried primarily in HDL rather than VLDL. HDL has anti-oxidant properties that might afford DHA protection against oxidation.

Hepatic Carbohydrate Response Element Binding Protein Activation Limits Nonalcoholic Fatty Liver Disease Development in a Mouse Model for Glycogen Storage Disease Type 1a.

Background and AimsGlycogen storage disease (GSD) type 1a is an inborn error of metabolism caused by defective glucose‐6‐phosphatase catalytic subunit (G6PC) activity. Patients with GSD 1a exhibit severe hepatomegaly due to glycogen and triglyceride (TG) accumulation in the liver. We have shown that the activity of carbohydrate response element binding protein (ChREBP), a key regulator of glycolysis and de novo lipogenesis, is increased in GSD 1a. In the current study, we assessed the contribution of ChREBP to nonalcoholic fatty liver disease (NAFLD) development in a mouse model for hepatic GSD 1a.Approach and ResultsLiver‐specific G6pc–knockout (L‐G6pc −/−) mice were treated with adeno‐associated viruses (AAVs) 2 or 8 directed against short hairpin ChREBP to normalize hepatic ChREBP activity to levels observed in wild‐type mice receiving AAV8–scrambled short hairpin RNA (shSCR). Hepatic ChREBP knockdown markedly increased liver weight and hepatocyte size in L‐G6pc −/− mice. This was associated with hepatic accumulation of G6P, glycogen, and lipids, whereas the expression of glycolytic and lipogenic genes was reduced. Enzyme activities, flux measurements, hepatic metabolite analysis and very low density lipoprotein (VLDL)‐TG secretion assays revealed that hepatic ChREBP knockdown reduced downstream glycolysis and de novo lipogenesis but also strongly suppressed hepatic VLDL lipidation, hence promoting the storage of “old fat.” Interestingly, enhanced VLDL‐TG secretion in shSCR‐treated L‐G6pc −/− mice associated with a ChREBP‐dependent induction of the VLDL lipidation proteins microsomal TG transfer protein and transmembrane 6 superfamily member 2 (TM6SF2), the latter being confirmed by ChIP‐qPCR.ConclusionsAttenuation of hepatic ChREBP induction in GSD 1a liver aggravates hepatomegaly because of further accumulation of glycogen and lipids as a result of reduced glycolysis and suppressed VLDL‐TG secretion. TM6SF2, critical for VLDL formation, was identified as a ChREBP target in mouse liver. Altogether, our data show that enhanced ChREBP activity limits NAFLD development in GSD 1a by balancing hepatic TG production and secretion.

Spontaneous liver disease in wild-type C57BL/6JOlaHsd mice fed semisynthetic diet.

Mouse models are frequently used to study mechanisms of human diseases. Recently, we observed a spontaneous bimodal variation in liver weight in C57BL/6JOlaHsd mice fed a semisynthetic diet. We now characterized the spontaneous variation in liver weight and its relationship with parameters of hepatic lipid and bile acid (BA) metabolism. In male C57BL/6JOlaHsd mice fed AIN-93G from birth to postnatal day (PN)70, we measured plasma BA, lipids, Very low-density lipoprotein (VLDL)-triglyceride (TG) secretion, and hepatic mRNA expression patterns. Mice were sacrificed at PN21, PN42, PN63 and PN70. Liver weight distribution was bimodal at PN70. Mice could be subdivided into two nonoverlapping groups based on liver weight: 0.6 SD 0.1 g (approximately one-third of mice, small liver; SL), and 1.0 SD 0.1 g (normal liver; NL; p<0.05). Liver histology showed a higher steatosis grade, inflammation score, more mitotic figures and more fibrosis in the SL versus the NL group. Plasma BA concentration was 14-fold higher in SL (p<0.001). VLDL-TG secretion rate was lower in SL mice, both absolutely (-66%, p<0.001) and upon correction for liver weight (-44%, p<0.001). Mice that would later have the SL-phenotype showed lower food efficiency ratios during PN21-28, suggesting the cause of the SL phenotype is present at weaning (PN21). Our data show that approximately one-third of C57BL/6JOlaHsd mice fed semisynthetic diet develop spontaneous liver disease with aberrant histology and parameters of hepatic lipid, bile acid and lipoprotein metabolism. Study designs involving this mouse strain on semisynthetic diets need to take the SL phenotype into account. Plasma lipids may serve as markers for the identification of the SL phenotype.

Fabrication of chitosan nanoparticles with phosphatidylcholine for improved sustain release, basolateral secretion, and transport of lutein in Caco-2 cells

Biopolymers-based nanoparticles delivery emerged alternatively to improve nutraceuticals and drug bioavailability. The intestinal physiology suggested a prerequisite of lipid moiety for carotenoid absorption. This study aimed to fabricate chitosan-based nanoparticles with phosphatidylcholine (PC) to enhance lutein bioavailability. Lutein encapsulated chitosan nanoparticles with PC (LCNPC) or without PC (LCN) were assessed for bioaccessibility, sustain release, cellular uptake/internalization, and basolateral secretion of lutein in Caco-2 cells. Standard lutein mixed micelles (LMM), and micelles derived through in vitro digestion of green leafy vegetables (GMM) treated as controls. The LCNPC showed reduced particle size, higher colloidal stability, homogeneous dispersion, and suitable for oral administration compared to LCN. The cellular uptake of lutein (20 h) in LCNPC was higher than LCN, LMM, and GMM, respectively. Interestingly, lutein uptake was maximum at 8 h in LMM and gradually decreased against sustain-release response in LCNPC and LCN, whereas considerably low lutein uptake from GMM at all time points. Further, LCNPC significantly increased basolateral secretion of triglyceride (TG) and positively correlated enhanced lutein uptake/internalization process than LCN and micelles. Also, LCNPC demonstrated the upregulation of endocytosis, paracellular, scavenger receptor class B type 1 (SRB-1), and peroxisome proliferator-activated receptor gamma (PPARγ) mediated lutein transport mechanism. These results suggested that fabrication of biopolymer-based nanoparticles with PC could provide greater insight to improve lutein bioavailability at enterocyte levels, to avoid age-related macular degeneration and other chronic diseases.

1921-P: Nonalcoholic Steatohepatitis in Mice with Hepatocyte-Specific Deletion of Mitochondrial Fission Factor

Mitochondria are highly dynamic organelles continuously undergoing fission and fusion, referred as mitochondrial dynamics (MtD), to adapt to nutritional demand. Evidence suggested that impaired MtD leads to metabolic abnormalities such as nonalcoholic steatohepatitis (NASH)-like phenotypes, which are characterized by hepatic steatosis, inflammation and fibrosis. However, how MtD is involved in the development of NASH is poorly understood. In this study, we found mitochondrial fission factor (Mff), a critical mediator of mitochondrial fission, is upregulated in the liver from mice fed high-fat diet (HFD). To explore the role of Mff in the development of NASH, we generated liver-specific deletion of Mff (MffLiKO) mice. Histological analysis revealed that mitochondria are enlarged in the liver from MffLiKO mice fed normal chow diet (NCD), which is followed by hepatocyte apoptosis, slightly increased infiltration of inflammatory macrophages, and fibrosis. However, no lipid accumulation was observed in the liver from MffLiKO mice fed NCD. That is, only the impairment of Mff-regulated mitochondrial fission did not develop NASH-like phenotypes. On the other hand, the liver of MffLiKO mice fed HFD developed NASH-like phenotype with severer steatosis. Expression of mRNAs related to endoplasmic reticulum (ER) stress was markedly upregulated in the liver from MffLiKO mice. In addition, expression of genes related to hepatic triglyceride secretion was downregulated, with reduced hepatic triglyceride secretion in MffLiKO mice in vivo and in primary cultures of Mff-deficient hepatocytes in vitro. Interestingly, thapsigargin-induced ER stress suppressed triglyceride secretion in primary cultured hepatocytes in vitro. This study demonstrates that MffLiKO develop NASH-like-phenotypes in response to HFD and suggests that impaired MtD induces ER stress and thus reduces hepatic triglyceride secretion, which may play a role in the pathogenesis of NASH. Disclosure Y. Takeichi: None. T. Miyazawa: None. S. Sakamoto: None. R. Sakamoto: None. M. Nomura: None. Y. Ogawa: Research Support; Self; Mitsubishi Tanabe Pharma Corporation. Speaker’s Bureau; Self; Daiichi Sankyo, Mitsubishi Tanabe Pharma Corporation.

1083-P: Bromocriptine-QR (BQR) Reduces Hypertriglyceridemia (HTG) in Hypertensive Type 2 Diabetes (T2D) Subjects

Chronically elevated sympathetic nervous system (SNS) activity increases hepatic triglyceride (TG) synthesis and secretion and adipose free fatty acid mobilization leading to further hepatic TG synthesis and HTG. HTG often occurs in the presence of hypertension and this can be a biomarker of chronically elevated SNS activity. BQR, a dopamine agonist, is the only sympatholytic antidiabetes agent approved for T2D. Preclinical studies have repeatedly demonstrated that circadian-timed bromocriptine therapy ameliorates HTG. This study evaluated if circadian-timed BQR (1.6-4.8 mg/day) reduces HTG in a population of hypertensive HTG T2D subjects. Hypertensive HTG T2D subjects from the Cycloset Safety Trial (HbA1c ≥ 7.0) treated at baseline with diet +/- any one or two antidiabetes agents of sulfonylurea, metformin, thiazolidinedione or insulin (N = 378) and randomized to BQR or placebo for 24 weeks were analyzed for between group difference in change from baseline fasting plasma TG level. After 24 weeks of therapy, BQR significantly reduced fasting TG levels by between 34 to 219 mg/dl (13 to 36%) and HbA1c from -0.4 to -1.2 as the baseline fasting TG level rose from ≥ 150 to ≥ 400 mg/dl (Figure). These TG effects were even more pronounced in such subjects with elevated resting heart rate. Circadian-timed BQR reduces hypertriglyceridemia in T2D and this effect increases with increasing fasting TG level. Disclosure B. Chamarthi: Employee; Self; VeroScience LLC. M. Ezrokhi: Employee; Self; VeroScience LLC. A.H. Cincotta: Employee; Self; VeroScience LLC.

Meeting Sugar Intake Recommendation Is Protective Against Health Parameters Associated With Chronic Disease in College Students

Abstract Objectives Metabolic Syndrome (MetS) is an accumulation of health factors that increase an individual's chance of chronic diseases and disabling conditions, such as type II diabetes, heart attack, and stroke. Multiple studies have shown a positive association between sugar consumption and aggravation of parameters related to MetS. We analyzed the effects of meeting the acceptable macronutrient range (AMDR) for sugar consumption on MetS parameters among college students. We hypothesized that meeting this recommendation would be associated with positive outcomes for MetS parameters. Methods Plasma lipids, glucose, and waist circumference (WC) were measured in 167 Weber State Students (ages 18–65). A two-day diet record was collected and analyzed using diet and wellness plus. Participants were separated into two groups, based on whether or not they met the AMDR of consuming less than 25% of total calories from sugar. Mean comparisons between low sugar (LS) and high sugar (HS) consumers were performed using independent samples t-test. Results 63% of participants met the sugar AMDR recommendation. LS group participants presented lower WC (75.8 ± 10.5 vs. 75.5 ± 11.5 cm, P = 0.03) and plasma triglycerides (TG) (76.0 ± 47.6 vs. 121.6 ± 99.9 mg/dL, P = 0.001) compared to their HS counterparts. In addition, we observed a positive trend in the high-density lipoprotein cholesterol (HDL-C) (52.7 ± 16.9 vs 47.59 ± 17.14, P = 0.06) levels of the HS group, compared to the LS group. Conclusions We observed that the percentage of total calories consumed from sugar is an important modulator of circulating triglycerides and central adiposity. This is in accordance with previous studies, which show that excess fructose consumption exerts adipogenic effects, and can trigger de novo lipogenesis in the liver, resulting in increased triglyceride production and secretion. Funding Sources Weber State University Office of Undergraduate Research.

HDL Receptor SR-B1 Deficiency Increased Inflammatory Dyslipidemia and Adipocyte Hypertrophy and Attenuated the Hepatic Steatosis in Murine Diet-Induced Obesity

Abstract Objectives We tested whether the scavenger receptor, class B type 1 (SR-B1), a physiologically relevant HDL receptor, modulates the metabolic and inflammatory phenotype of obese mice, accompanied by changes in adipocyte and hepatocyte lipid deposits. Methods Male SR-B1 knock-out (KO) mice and wild-type (WT) littermates were fed for 12 weeks with a high-fat diet (HFD, n = 12 per group) to induce obesity. Animals were euthanized after overnight food deprivation. Blood was obtained and adipose tissue and liver were removed. Plasma or frozen tissues were used for biochemical analyses or assessed by light microscopy and immunohistochemistry. Comparisons between WT and KO mice fed with HFD were performed and differences were considered statistically significant when P &amp;lt; 0.05. Results Compared to obese WT, obese HFD-fed SR-B1 KO mice showed increased plasma total cholesterol (p &amp;lt; 0.0001) and triglycerides (TG) (p &amp;lt; 0.01) as well as tumor necrosis factor-α (TNF-α) (p &amp;lt; 0.0001) levels. Also, these animals exhibited white fat with larger adipocytes (p &amp;lt; 0.0001) and increased macrophage-based crown-like structure formation (p &amp;lt; 0.01), compared to HFD-fed WT mice, revealing a more inflammatory adipose tissue. These changes in adipose tissue were associated with reduced hepatic steatosis: reduced hepatocyte lipid droplet area (p &amp;lt; 0.0001) and decreased liver TG content (p &amp;lt; 0.0001). In addition, obese SR-B1-deficient mice showed reduced hepatic peroxisome proliferator-activated receptor-γ (PPAR-γ) expression, more efficient hepatic fatty acid β-oxidation and increased very-low-density lipoprotein (VLDL)-TG secretion compared to obese HFD-fed WT mice Furthermore, liver fatty acid (FA) composition in obese SR-B1-deficient mice revealed a reduction in monounsaturated (MUFA) (p &amp;lt; 0.01), but an increase in polyunsaturated (PUFA) (p &amp;lt; 0.05), fatty acid content, compared to obese WT mice. Conclusions Our findings demonstrate that SR-B1 expression modulates high fat feeding-associated inflammatory dyslipidemia, adipocyte hypertrophy, and hepatic steatosis; key processes underlying the pathogenesis of highly prevalent chronic diseases, such as obesity and non-alcoholic fatty liver disease (NAFLD). Funding Sources FONDECYT 1,150,399, FONDECYT 1,180,525.

MTORC1-IRE1α pathway activation contributes to palmitate-elicited triglyceride secretion and cell death in hepatocytes.

Lipotoxicity induced by saturated fatty acids (SFA) plays a pivotal role in the pathogenesis of a variety of obesity-related metabolic disorders; however, the exact mechanism(s) underlying lipotoxicity development remains elusive. The liver plays a central role in regulating intrahepatic and circulatory lipid homeostasis. In the current study, we identified that mammalian target of rapamycin complex 1 (mTORC1) activation plays an important role in regulating the detrimental effects of SFA palmitate in hepatocytes, in specific cell death, and TG overproduction. Furthermore, our data confirmed that palmitate-induced mTORC1 activation is attributable to its stimulatory effect on IRE1α, one of three canonical pathways activated during ER stress. Importantly, IRE1α inhibition prevented palmitate-triggered cell death and TG overproduction, suggesting mTORC1-IRE1α pathway is mechanistically implicated in palmitate lipotoxicity. The data obtained in the current investigation support future study to explore the therapeutic potential of targeting the mTORC1-IRE1α pathway as a novel clinical strategy for the treatment of metabolic disorders involving lipotoxicity.