Rate Of Lipogenesis Research Articles

LXR Agonist T0901317's Hepatic Impact Overrules Its Atheroprotective Action in Macrophages, Driving Early Atherogenesis in Chow-Diet-Fed Male Apolipoprotein E Knockout Mice.

Preclinical studies regarding the potential of liver X receptor (LXR) agonists to inhibit macrophage foam cell formation and the development of atherosclerotic lesions are generally executed in mice fed with Western-type diets enriched in cholesterol and fat. Here, we investigated whether LXR agonism remains anti-atherogenic under dietary conditions with a low basal hepatic lipogenesis rate. Hereto, atherosclerosis-susceptible male apolipoprotein E knockout mice were fed a low-fat diet with or without 10 mg/kg/day LXR agonist T0901317 supplementation for 8 weeks. Importantly, T0901317 significantly stimulated atherosclerosis susceptibility, despite an associated increase in the macrophage gene expression levels of cholesterol efflux transporters ABCA1 and ABCG1. The pro-atherogenic effect of T0901317 coincided with exacerbated hypercholesterolemia, hypertriglyceridemia, and a significant rise in hepatic triglyceride stores and macrophage numbers. Furthermore, T0901317-treated mice exhibited elevated plasma MCP-1 levels and monocytosis. In conclusion, these findings highlight that the pro-atherogenic hepatic effects of LXR agonism are dominant over the anti-atherogenic effects in macrophages in determining the overall atherosclerosis outcome under low-fat diet feeding conditions. A low-fat diet experimental setting, as compared to the commonly used high-fat-diet-based preclinical setup, thus appears more sensitive in uncovering the potential relevance of the off-target liver effects of novel anti-atherogenic therapeutic approaches that target macrophage LXR.

Direct and systemic actions of growth hormone receptor (GHR)-signaling on hepatic glycolysis, de novo lipogenesis and insulin sensitivity, associated with steatosis

BackgroundEvidence is accumulating that growth hormone (GH) protects against the development of steatosis and progression of non-alcoholic fatty liver disease (NAFLD). GH may control steatosis indirectly by altering systemic insulin sensitivity and substrate delivery to the liver and/or by the direct actions of GH on hepatocyte function. ApproachTo better define the hepatocyte-specific role of GH receptor (GHR) signaling on regulating steatosis, we used a mouse model with adult-onset, hepatocyte-specific GHR knockdown (aHepGHRkd). To prevent the reduction in circulating insulin-like growth factor 1 (IGF1) and the subsequent increase in GH observed after aHepGHRkd, subsets of aHepGHRkd mice were treated with adeno-associated viral vectors (AAV) driving hepatocyte-specific expression of IGF1 or a constitutively active form of STAT5b (STAT5bCA). The impact of hepatocyte-specific modulation of GHR, IGF1 and STAT5b on carbohydrate and lipid metabolism was studied across multiple nutritional states and in the context of hyperinsulinemic:euglycemic clamps. ResultsChow-fed male aHepGHRkd mice developed steatosis associated with an increase in hepatic glucokinase (GCK) and ketohexokinase (KHK) expression and de novo lipogenesis (DNL) rate, in the post-absorptive state and in response to refeeding after an overnight fast. The aHepGHRkd-associated increase in hepatic KHK, but not GCK and steatosis, was dependent on hepatocyte expression of carbohydrate response element binding protein (ChREBP), in re-fed mice. Interestingly, under clamp conditions, aHepGHRkd also increased the rate of DNL and expression of GCK and KHK, but impaired insulin-mediated suppression of hepatic glucose production, without altering plasma NEFA levels. These effects were normalized with AAV-mediated hepatocyte expression of IGF1 or STAT5bCA. Comparison of the impact of AAV-mediated hepatocyte IGF1 versus STAT5bCA in aHepGHRkd mice across multiple nutritional states, indicated the restorative actions of IGF1 are indirect, by improving systemic insulin sensitivity, independent of changes in the liver transcriptome. In contrast, the actions of STAT5b are due to the combined effects of raising IGF1 and direct alterations in the hepatocyte gene program that may involve suppression of BCL6 and FOXO1 activity. However, the direct and IGF1-dependent actions of STAT5b cannot fully account for enhanced GCK activity and lipogenic gene expression observed after aHepGHRkd, suggesting other GHR-mediated signals are involved. ConclusionThese studies demonstrate hepatocyte GHR-signaling controls hepatic glycolysis, DNL, steatosis and hepatic insulin sensitivity indirectly (via IGF1) and directly (via STAT5b). The relative contribution of these indirect and direct actions of GH on hepatocytes is modified by insulin and nutrient availability. These results improve our understanding of the physiologic actions of GH on regulating adult metabolism to protect against NAFLD progression.

Lipidized PrRP Analog Exhibits Strong Anti-Obesity and Antidiabetic Properties in Old WKY Rats with Obesity and Glucose Intolerance.

Prolactin-releasing peptide (PrRP) is an anorexigenic neuropeptide that has potential for the treatment of obesity and its complications. Recently, we designed a palmitoylated PrRP31 analog (palm11-PrRP31) that is more stable than the natural peptide and able to act centrally after peripheral administration. This analog acted as an anti-obesity and glucose-lowering agent, attenuating lipogenesis in rats and mice with high-fat (HF) diet-induced obesity. In Wistar Kyoto (WKY) rats fed a HF diet for 52 weeks, we explored glucose intolerance, but also prediabetes, liver steatosis and insulin resistance-related changes, as well as neuroinflammation in the brain. A potential beneficial effect of 6 weeks of treatment with palm11-PrRP31 and liraglutide as comparator was investigated. Liver lipid profiles, as well as urinary and plasma metabolomic profiles, were measured by lipidomics and metabolomics, respectively. Old obese WKY rats showed robust glucose intolerance that was attenuated by palm11-PrRP31, but not by liraglutide treatment. On the contrary, liraglutide had a beneficial effect on insulin resistance parameters. Despite obesity and prediabetes, WKY rats did not develop steatosis owing to HF diet feeding, even though liver lipogenesis was enhanced. Plasma triglycerides and cholesterol were not increased by HFD feeding, which points to unincreased lipid transport from the liver. The liver lipid profile was significantly altered by a HF diet that remained unaffected by palm11-PrRP31 or liraglutide treatment. The HF-diet-fed WKY rats revealed astrogliosis in the brain cortex and hippocampus, which was attenuated by treatment. In conclusion, this study suggested multiple beneficial anti-obesity-related effects of palm11-PrRP31 and liraglutide in both the periphery and brain.

Dietary Isoleucine and Valine: Effects on Lipid Metabolism and Ureagenesis in Pigs Fed with Protein Restricted Diets.

A mixture of valine (Val) and isoleucine (Ile) not only decreases the negative impact of very low protein (VLP) diets on the growth of pigs, but also influences the nitrogen (N) balance and lipid metabolism; however, the underlying pathways are not well understood. This study aimed to investigate the effect of dietary Val and Ile on lipogenesis, lipolysis, and ureagenesis under protein restriction. After one week of acclimation, forty three-week-old pigs were randomly assigned to following dietary treatments (n = 8/group) for 5 weeks: positive control (PC): normal protein diet; negative control (NC): VLP diet; HV: NC supplemented with Val; HI: NC supplemented with Ile; and HVI: NC supplemented with both Val and Ile. HVI partially improved the body weight and completely recovered the feed intake (FI) of pigs fed with NC. HVI increased thermal radiation and improved the glucose clearance. HVI had a lower blood triglyceride than PC and blood urea N than NC. NC and HV promoted lipogenesis by increasing the transcript of fatty acid synthase (FAS) in the liver and lipoprotein lipase (LPL) in adipose tissue but reducing hormone-sensitive lipase (HSL) in the liver. HVI reduced the increased rate of lipogenesis induced by the NC group through normalizing the mRNA abundance of hepatic FAS, sterol regulatory element binding transcription factor 1, and HSL and LPL in adipose tissue. NC, HV, HI, and HVI reduced the ureagenesis by decreasing the protein abundance of carbamoyl phosphate synthetase I, ornithine transcarboxylase, and arginosuccinate lyase in the liver. Overall, HVI improved the growth, FI, and glucose clearance, and decreased the rate of lipogenesis induced by VLP diets.

Insulin sensitivity is associated with the observed variation of de novo lipid synthesis and body composition in finishing pigs

Variations in body composition among pigs can be associated with insulin sensitivity given the insulin anabolic effect. The study objectives were to characterize this association and to compare de novo lipogenesis and the gene expression in the adipose tissue of pigs of the same genetic background. Thirty 30–95 kg of body weight (BW) pigs, catheterized in the jugular vein participated into an oral glucose tolerance test (OGTT; 1.75 g glucose/kg of BW) to calculate insulin-related indexes. The 8 fattest and the 8 leanest pigs were used to determine the relative mRNA abundance of studied genes. The rate of lipogenesis was assessed by incorporation of [U-13C]glucose into lipids. The QUICKI and Matsuda indexes negatively correlated with total body lipids (r = − 0.67 and r = − 0.59; P < 0.01) and de novo lipogenesis (r = − 0.58; P < 0.01). Fat pigs had a higher expression level of lipogenic enzymes (ACACA, ACLY; P < 0.05) than lean pigs. The reduced insulin sensitivity in fat pigs was associated with a higher expression level of glucose-6-phosphate dehydrogenase (G6PD) and a lower expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ). In conclusion, pigs with increased body lipids have lower insulin sensitivity which is associated with increased de novo lipogenesis.

A simple method for quantifying de novo lipogenesis rate and substrate selection in cell cultures by 13C NMR isotopomer analysis of the crude lipid fraction

De novo lipogenesis (DNL) is critical for cell growth and maintenance, and acetyl-CoA precursors can be derived from different substrates. We developed a 13 C NMR analysis of lipid extracts from cultured microglia cells administered with [U-13 C]glucose that informs overall lipogenic activity as well as the contribution of glucose to lipogenic acetyl-CoA. BV-2 microglial cell line cultured with glucose and glutamine was provided with [U-13 C]glucose and unlabeled glutamine for 24 h and studied in either the presence or absence of lipopolysaccharide (LPS). Cells were then extracted for lipids and the crude lipid fraction was analyzed by 13 C NMR. 13 C-isotopomer signals in the fatty acid ω - 1 and ω - 2 signals representing consecutive or non-consecutive enrichment of the fatty acid chain by [1,2-13 C2 ]acetyl-CoA were quantified and applied to a probabilistic model of acetyl-CoA precursor and fatty acid enrichment. Glucose contributed 72 ± 2% of lipogenic acetyl-CoA while DNL from all sources accounted for 16 ± 2% of lipid turnover. With LPS, there was a significant decrease in glucose contribution (59 ± 4%, p < 0.05) while DNL was unchanged (11 ± 3%). A simple 13 C NMR analysis of the crude lipid fractions of BV-2 cells administered with [U-13 C]glucose informs DNL activity and the contribution of glucose to the acetyl-CoA precursors. While DNL was preserved in the presence of LPS, there was redirection of lipogenic acetyl-CoA sources from glucose to other substrates. Thus, in the present article, we describe a novel and simple 13 C NMR analysis approach to disclose the overall lipogenic activity and substrate contribution to DNL, suitable for evaluating DNL rates in cell cultures.

Nutrient-related metabolite profiles explain differences in body composition and size in Nile tilapia (Oreochromis niloticus) from different lakes

This study investigated how metabolite analysis can explain differences in tissue composition and size in fish from different habitats. We, therefore, studied Nile tilapia (Oreochromis niloticus) from three Ethiopian lakes (Gilgel Gibe, Ziway, and Langano) using dried bloodspot (DBS) analysis of carnitine esters and free amino acids. A total of sixty (N = 60) Nile tilapia samples were collected comprising twenty (n = 20) fish from each lake. The proximate composition of the targeted tissues (muscle, skin, gill, gut, and liver) were analyzed. The DBS samples were analyzed for acylcarnitine and free amino acid profiles using quantitative electrospray tandem mass spectrometry. Metabolite ratios were calculated from relevant biochemical pathways that could identify relative changes in nutrient metabolism. The mean weight of Nile tilapia sampled from each lake showed weight variation among the lakes, fish from Lake Ziway were largest (178 g), followed by Gilgel Gibe reservoir (134 g) and Lake Langano (118 g). Fish from Gilgel Gibe showed significantly higher fat composition in all tissues (P < 0.05) except the liver in which no significant variation was observed. The source of fish affected the tissue fat composition. Marked differences were observed in Nile tilapia metabolic activity between the lakes. For instance, the lower body weight and condition of the fish in Lake Langano coincided with several metabolite ratios pointing to a low flow of glucogenic substrate to the citric acid cycle. The low propionyl to acetylcarnitine ratio (C3:C2) in Gilgel Gibe fish is indicating that more of the available acetyl CoA is not led into the citric acid cycle, but instead will be used for fat synthesis. The metabolic markers for lipogenesis and metabolic rate could explain the high-fat concentration in several parts of the body composition of fish from Gilgel Gibe. Our results show that nutrition-related blood metabolite ratios are useful to understand the underlying metabolic events leading to the habitat-dependent differences in the growth of Nile tilapia, and by extension, other species.

Dietary Arginine Supplementation during Gestation and Lactation Increases Milk Yield and Mammary Lipogenesis in Rats.

Arginine, an essential amino acid during the reproductive period, has been shown to enhance lactation performances in livestock. Whether it could help mothers with breastfeeding difficulties is not known. This study aimed to determine whether dietary arginine supplementation would enhance milk production in rat dams nursing large 12-pup litters and, if so, what mechanisms are involved. In 3 series of experiments, differing in dam killing timing, 59 primiparous, pregnant Sprague-Dawley rats (mean±SD weight: 254±24.7g) were randomly assigned to receive either 1) an AIN-93G diet supplemented with l-arginine at 2.0% (ARG diet), through lactation and gestation (AGL group); 2) a control AIN-93G diet including at 3.5% an isonitrogenous mix of amino acids that are not essential for lactation (MA diet), during gestation and lactation (MA group); or 3) the MA diet during gestation and the ARG diet during lactation (AL group). Milk flow was measured using deuterated water enrichment between days 11 and 18. Plasma hormones and mammary expression of genes involved in lactation were measured using ELISA and qRT-PCR, respectively, at lactation days 12, 18, or 21 in the 3 experiments. Data were analyzed by ANOVA. Dam food intake, pup weight gain, milk flow normalized to dam weight, and milk fat concentration were 17%, 9%, 20%, and 20% greater in the AGL group than in the MA group, respectively (P<0.05). Genes involved in lipogenesis and lipid regulation were overexpressed ≤2.76-fold in the mammary gland of AGL dams compared with MA dams (P<0.05) and plasma leptin concentration was 39% higher (P=0.008). Milk flow and composition and mammary gene expression of the AL group did not differ from those of the MA group, whereas milk fat concentration and flow were 26% and 37% lower than in the AGL group, respectively. Arginine supplementation during gestation and lactation enhances milk flow and mammary lipogenesis in rats nursing large litters.

The Long-Term Effects of High-Fat and High-Protein Diets on the Metabolic and Endocrine Activity of Adipocytes in Rats.

Simple SummaryThe increasing prevalence of worldwide obesity and growing awareness of its negative consequences are forcing scientists to take a new view of nutrition and search for new diets. Therefore, to find some new relationships between diet and metabolism, we analyzed the effects of the long-term (60 and 120 days) use of a high-protein diet (HPD) and of a high-fat diet (HFD) on the metabolic and endocrine functions of fat tissue and on biochemical indices in rat blood in the present study. This research helped us to understand the roles of diet in the metabolic and endocrine functioning of adipocytes. Our study indicated that an HFD has a negative effect on fat tissue function, whereas the HPD showed positive results, such as increased insulin sensitivity and improved glucose and lipid metabolism in isolated adipocytes in vitro.The increasing prevalence of overweight and obesity and the rising awareness of their negative consequences are forcing researchers to take a new view of nutrition and its consequences for the metabolism of whole organisms as well as the metabolism of their individual systems and cells. Despite studies on nutrition having been carried out for a few decades, not many of them have focused on the impacts of these diets on changes in the metabolism and endocrine functions of isolated adipocytes. Therefore, we decided to investigate the effects of the long-term use (60 and 120 days) of a high-fat diet (HFD) and of a high-protein diet (HPD) on basic metabolic processes in fat cells—lipogenesis, lipolysis, and glucose uptake—and endocrine function, which was determined according to the secretion of adipokines into the incubation medium. Our results proved that the HPD diet improved insulin sensitivity, increased the intracellular uptake of glucose (p < 0.01) and its incorporation into lipids (p < 0.01) and modulated the endocrine function of these cells (decreasing leptin secretion; p < 0.01). The levels of biochemical parameters in the serum blood also changed in the HPD-fed rats. The effects of the HFD were inverse, as expected. We observed a decrease in adiponectin secretion and a diminished rate of lipogenesis (p < 0.01). Simultaneously, the secretion of leptin and resistin (p < 0.01) from isolated adipocytes increased. In conclusion, we noted that the long-term use of HPD and HFD diets modulates the metabolism and endocrine functions of isolated rat adipocytes. We summarize that an HFD had a negative effect on fat tissue functioning, whereas an HPD had positive results, such as increased insulin sensitivity and an improved metabolism of glucose and lipids in fat tissue. Moreover, we noticed that negative metabolic changes are reflected more rapidly in isolated cells than in the metabolism of the whole organism.

Elevated Expression of Glycerol-3-Phosphate Phosphatase as a Biomarker of Poor Prognosis and Aggressive Prostate Cancer.

Simple SummaryA number of diseases, including cancers, can be diagnosed with “biomarkers”, such as specific proteins, hormones, or mutations in some genes. These molecules reflect abnormal processes in the affected organs, and are useful for diagnosis and disease treatment options. The need exists to have reliable markers for various types of cancers such as prostate cancer (PC). Many cancers show high utilization of glucose for their growth; we recently identified an enzyme, glycerol 3-phosphate phosphatase (G3PP), that can modulate glucose utilization by cells. Our work revealed a high expression of G3PP in prostate cancer cells in patients with aggressive tumors. With further validation, G3PP expression in prostate cancer tumors may become a useful prognostic biomarker and aid in the management of patients with PC.The limitations of the biomarker prostate-specific antigen (PSA) necessitate the pursuit of biomarkers capable of better identifying high-risk prostate cancer (PC) patients in order to improve their therapeutic management and outcomes. Aggressive prostate tumors characteristically exhibit high rates of glycolysis and lipogenesis. Glycerol 3-phosphate phosphatase (G3PP), also known as phosphoglycolate phosphatase (PGP), is a recently identified mammalian enzyme, shown to play a role in the regulation of glucose metabolism, lipogenesis, lipolysis, and cellular nutrient-excess detoxification. We hypothesized that G3PP may relieve metabolic stress in cancer cells and assessed the association of its expression with PC patient prognosis. Using immunohistochemical staining, we assessed the epithelial expression of G3PP in two different radical prostatectomy (RP) cohorts with a total of 1797 patients, for whom information on biochemical recurrence (BCR), metastasis, and mortality was available. The association between biomarker expression, biochemical recurrence (BCR), bone metastasis, and prostate cancer-specific survival was established using log-rank and multivariable Cox regression analyses. High expression of G3PP in PC epithelial cells is associated with an increased risk of BCR, bone metastasis, and PC-specific mortality. Multivariate analysis revealed high G3PP expression in tumors as an independent predictor of BCR and bone metastasis development. High G3PP expression in tumors from patients eligible for prostatectomies is a new and independent prognostic biomarker of poor prognosis and aggressive PC for recurrence, bone metastasis, and mortality.

Dry heated whole sorghum flour (BRS 305) with high tannin and resistant starch improves glucose metabolism, modulates adiposity, and reduces liver steatosis and lipogenesis in Wistar rats fed with a high-fat high-fructose diet

This study aimed to evaluate the effect of dry heated whole sorghum flour (BRS 305 hybrid) on insulin resistance, glucose tolerance, adiposity, steatosis, and liver lipogenesis in rats fed with a high-fat high-fructose diet (HFHF). Male Wistar rats (n = 10/group), 45–50 days old, were fed with AIN93-M diet, HFHF (31% saturated fat and 20% fructose) and HFHF + sorghum flour (replacing 50% of dietary fiber, 100% starch, 19.8% protein and 22.5% lipids in the experimental diet), for 10 weeks. The sorghum flour restored the effect of the HFHF diet, decreasing triglycerides, uric acid, alanine aminotransferase (ALT), liver steatosis, and lipogenesis. Further, sorghum improved insulin sensitivity and glucose tolerance and increasing the concentration of PPARα protein in the liver. Thus, the BRS 305 whole sorghum flour with high tannin and resistant starch showed potential as a functional food, since it improves glucose metabolism, modulates adiposity, and reduces liver steatosis and lipogenesis in Wistar rats fed with a high-fat high-fructose diet.

Zielona herbata a otyłość – wpływ katechin na metabolizm energetyczny

Streszczenie Otyłość jest chorobą metaboliczną, która obecnie zyskała rangę epidemii, stanowiąc jeden z najważniejszych problemów zdrowotnych, społecznych i ekonomicznych na świecie. Nieleczonej otyłości towarzyszy pogorszenie jakości życia oraz występowanie chorób towarzyszących, takich jak cukrzyca czy schorzenia układu sercowo-naczyniowego. W związku z tym poszukuje się nowych metod mających zastosowanie zarówno w profilaktyce otyłości, jak i w obniżaniu nadmiernej masy ciała. Zawarte w zielonej herbacie związki katechinowe, szczególnie galusan epigallokatechiny (EGCG), są jednymi z najintensywniej badanych substancji biologicznie czynnych. Przypisuje się im właściwości przeciwutleniające, przeciwzapalne, przeciwnowotworowe, a także wspomagające regulację masy ciała oraz zawartości tkanki tłuszczowej w organizmie. Liczne badania z udziałem ludzi wykazują, że regularne picie zielonej herbaty jest związane z mniejszą masą ciała, niższym BMI oraz z mniejszym obwodem pasa. Wyniki doświadczeń in vitro oraz na zwierzętach potwierdzają korzystny wpływ katechin na metabolizm energetyczny. Związki te obniżają wchłanianie lipidów i węglowodanów w przewodzie pokarmowym. Wpływają również na metabolizm tych związków, obniżając intensywność lipogenezy i adipogenezy, jednocześnie pobudzając lipolizę i utlenianie kwasów tłuszczowych, a także zwiększając wydatek energetyczny. Udowodniono, że katechiny mają wpływ na wychwyt glukozy przez komórki docelowe pobierające ten cukier poprzez insulinozależny transporter – GLUT4. W artykule omówiono literaturę przedmiotu oraz usystematyzowano zagadnienia związane z rolą katechin obecnych w zielonej herbacie w profilaktyce i wspomaganiu leczenia otyłości.

Liposomal Nanoparticle-Mediated miR-27b Influences Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells via Peroxisome Proliferator-Activated Receptor Gamma in a Microgravity Environment

This study was aimed at analyzing the effects of liposomal nanoparticle-based miR-27b on PPARγ and osteogenic differentiation of bone marrow mesenchymal stem cells under microgravity. The rat bone marrow mesenchymal stem cells were set as the research object, and the gyroscope was employed for simulation of microgravity. The cells were randomized into four groups, including the experimental group A (simulated microgravity+liposomal nanoparticle-mediated miR-27b transfection group), as well as the control groups: group B (simulated microgravity+negative control group), group C (simulated microgravity+transfection reagent group) and group D (normal gravity+liposomal nanoparticle-mediatedmiR-27b transfection group). After a two-week osteogenic induction in vitro, staining was performed to assess the lipogenesis rate of the samples. In addition, ALP activity and PPARγ mRNA level was detected. The number of alizarin staining-positive osteogenic nodules and ALP activity (0.21±0.44 King unit) in group A was significantly diminished compared to those in group B, C, and D. Moreover, its lipogenesis rate (9.31±1.02%) and PPARγ mRNA level (1.86±0.39) were significantly higher than those in group B, C, and D (P &lt; 0.05). The number of alizarin staining-positive osteogenic nodules and ALP activity (0.96±0.18 King unit) in group D were significantly reduced in comparison with those in groups B and C, while the lipogenesis rate (4.86±0.77%) and PPARγ mRNA level (0.93±0.34) were significantly higher than those in group B and C (P &lt; 0.05) without difference between group B and group C (P &gt; 0.05). Under a microgravity condition, liposomal nanoparticle-mediated miR-27b can impede the differentiation of BMSCs into osteoblasts via regulating PPARγ signal transduction.

Hrd1-mediated ACLY ubiquitination alleviate NAFLD in db/db mice

BackgroundThe functions of Acly in regulating nonalcoholic fatty liver disease (NAFLD) have been identified; however, the dynamic control of Acly expression under the pathological state of metabolic disorders has not been fully elucidated. Previous studies reported an ubiquitin-proteasome–mediated degradation of Acly, but the mechanism is still largely unknown. MethodsCo-IP–based mass spectrum (MS/MS) assays were performed in HepG2 and Hepa1-6 hepatocytes and mouse liver tissue. The protein-protein interaction and ubiquitin modification of Hrd1 on Acly were confirmed by co-IP based immuno-blotting. Acetyl-CoA levels and lipogenesis rates were determined. The roles of Hrd1 on NAFLD and insulin resistance were tested by adenovirus-mediated overexpression in db/db mice or in separated primary hepatocytes. ResultsHrd1, a subunit of the endoplasmic reticulum-associated degradation (ERAD) complex, interacted with and ubiquitinated Acly, thereby reducing its protein level. Hrd1 suppressed the acetyl-CoA level and inhibited lipogenesis through an Acly-dependent pathway. The expression of hepatic Hrd1 was negatively associated with NAFLD, whereas overexpression of Hrd1 ameliorated hepatic steatosis and enhanced insulin sensitivity, both in db/db mice and in separated mouse primary hepatocytes. ConclusionsOur results suggest that Acly, a master enzyme that regulates lipogenesis, is degraded by Hrd1 through ubiquitin modification. The activation of Hrd1 in hepatocytes might therefore represent a strategic approach for NAFLD therapy.

Interaction of Diet with the Metabolic Flux Signatures of the Unfolded Protein Response

Abstract Objectives Endoplasmic reticulum (ER) stress is involved in the progression of several diseases, including diet and obesity-related conditions such as nonalcoholic fatty liver disease. Our goal was to understand the role of diet on the unfolded protein response (UPR), an important pathway in ER stress response, in efforts to elucidate the role of the UPR in the progression to non-alcoholic fatty liver disease. Methods We used stable isotope labeling with tandem mass spectrometric analysis to characterize proteome-wide synthesis rates and de novo lipogenesis rates in vivo in mouse liver to generate metabolic flux signatures of the unfolded protein response. We initiated the unfolded protein response through treatment with tunicamycin. Diets rich in either unsaturated, oleic, acids, or saturated, palmitic, acids were given to mice for five weeks to determine the effect of dietary fatty acids on this induced ER stress response. Results With induction of the unfolded protein response, we observed reduced protein synthesis across most ontologies, but increased synthesis of ER proteins and chaperones. We also found reduced de novo lipogenesis after 48 and 72 hours of induced ER stress. Reduction in food intake and significant weight loss also occurred after 48 and 72 hours. Electron microscopy revealed striking morphological differences in the ER and accumulation of lipid droplets with ER stress. Diets high in unsaturated fatty acids had a lesser impact on the progression of the unfolded protein response. Conclusions These data begin to characterize how the unfolded protein response progresses over time, and the metabolic changes that occur with ER stress. Diets rich in saturated or unsaturated fatty acids had different effects on the metabolic signatures of the UPR, suggesting the type dietary fatty acid is important in properly handling ER stress. Funding Sources NIH.

Hepatic Mitochondrial Oxidative Metabolism and Lipogenesis Synergistically Adapt to Mediate Healthy Embryonic-to-Neonatal Transition in Chicken

During the normal embryonic-to-neonatal development, the chicken liver is subjected to intense lipid burden from high rates of yolk-lipid oxidation and also from the accumulation of the yolk-derived and newly synthesized lipids from carbohydrates. High rates of hepatic lipid oxidation and lipogenesis are also central features of non-alcoholic fatty liver disease (NAFLD) in both rodents and humans, but is associated with impaired insulin signaling, dysfunctional mitochondrial energetics and oxidative stress. However, these adverse effects are not apparent in the liver of embryonic and neonatal chicken, despite lipid burden. Utilizing comprehensive metabolic profiling, we identify that steady induction of hepatic mitochondrial tricarboxylic acid (TCA) cycle and lipogenesis are central features of embryonic-to-neonatal transition. More importantly, the induction of TCA cycle and lipogenesis occurred together with the downregulation of hepatic β-oxidation and ketogenesis in the neonatal chicken. This synergistic remodeling of hepatic metabolic networks blunted inflammatory onset, prevented accumulation of lipotoxic intermediates (ceramides and diacylglycerols) and reduced reactive oxygen species production during embryonic-to-neonatal development. This dynamic remodeling of hepatic mitochondrial oxidative flux and lipogenesis aids in the healthy embryonic-to-neonatal transition in chicken. This natural physiological system could help identify mechanisms regulating mitochondrial function and lipogenesis, with potential implications towards treatment of NAFLD.

SOCS2 modulates adipose tissue inflammation and expansion in mice

IntroductionObesity is usually triggered by a nutrient overload that favors adipocyte hypertrophy and increases the number of pro-inflammatory cells and mediators into adipose tissue. These mediators may be regulated by suppressors of cytokine signaling (SOCS), such as SOCS2, which is involved in the regulation of the inflammatory response of many diseases, but its role in obesity is not yet known. We aimed to investigate the role of SOCS2 in metabolic and inflammatory dysfunction induced by a high-refined carbohydrate-containing diet (HC). Material and methodsMale C57BL/6 wild type (WT) and SOCS2 deficient (SOCS2−/−) mice were fed chow or an HC diet for 8 weeks. ResultsIn general, SOCS2 deficient mice, independent of the diet, showed higher adipose tissue mass compared with their WT counterparts that were associated with decreased lipogenesis rate in adipose tissue, lipolysis in adipocyte culture and energy expenditure. An anti-inflammatory profile was observed in adipose tissue of SOCS2−/− by reduced secretion of cytokines, such as TNF and IL-6, and increased M2-like macrophages and regulatory T cells compared with WT mice. Also, SOCS2 deficiency reduced the differentiation/expansion of pro-inflammatory cells in the spleen but increased Th2 and Treg cells compared with their WT counterparts. ConclusionThe SOCS2 protein is an important modulator of obesity that regulates the metabolic pathways related to adipocyte size. Additionally, SOCS2 is an inflammatory regulator that appears to be essential for controlling the release of cytokines and the differentiation/recruitment of cells into adipose tissue during the development of obesity.

Melatonin Supplementation Decreases Hypertrophic Obesity and Inflammation Induced by High-Fat Diet in Mice.

Obesity results from critical periods of positive energy balance characterized by caloric intake greater than energy expenditure. This disbalance promotes adipose tissue dysfunction which is related to other comorbidities. Melatonin is a low-cost therapeutic agent and studies indicate that its use may improve obesity-related disorders. To evaluate if the melatonin is efficient in delaying or even blocking the damages caused by excessive ingestion of a high-fat diet (HFD) in mice, as well as improving the inflammatory profile triggered by obesity herein, male C57BL/6 mice of 8 weeks were induced to obesity by a HFD and treated for 10 weeks with melatonin. The results demonstrate that melatonin supplementation attenuated serum triglyceride levels and total and LDL cholesterol and prevented body mass gain through a decreased lipogenesis rate and increased lipolytic capacity in white adipocytes, with a concomitant increment in oxygen consumption and Pgc1a and Prdm16 expression. Altogether, these effects prevented adipocyte hypertrophy caused by HFD and reflected in decreased adiposity. Finally, melatonin supplementation reduced the crown-like-structure (CLS) formation, characteristic of the inflammatory process by macrophage infiltration into white adipose tissue of obese subjects, as well as decreased the gene expression of inflammation-related factors, such as leptin and MCP1. Thus, the melatonin can be considered a potential therapeutic agent to attenuate the metabolic and inflammatory disorders triggered by obesity.

Novel Strategies to Treat Hepatic Steatosis and Steatohepatitis.

Concordant with soaring obesity rates, nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease in the world. The obesity epidemic demands interventions to reverse obesity-associated hepatic steatosis, NAFLD, and nonalcoholic steatohepatitis, and several new pharmacologic approaches have been developed within the past several years. Steatosis develops when energy delivery to the liver, modulated by rates of hepatic lipogenesis, exceeds the capacity of the liver to utilize or export this energy. Therefore, pharmacologic approaches to reverse hepatic steatosis have focused largely, though not exclusively, on (1) reducing substrate availability to the liver, (2) reducing hepatic lipid synthesis, and (3) increasing hepatic mitochondrial fat oxidation (Figure 1). This Perspective will discuss these three classes of emerging pharmacologic therapies against hepatic steatosis, with the ultimate intent to ameliorate NAFLD and/or nonalcoholic steatohepatitis, and the advantages and pitfalls afforded by each strategy to treat these epidemics of obesity-associated liver disease.

Quinoline-Glycomimetic Conjugates Reducing Lipogenesis and Lipid Accumulation in Hepatocytes.

Nonalcoholic fatty liver disease (NAFLD), which is characterized by excess accumulation of triglyceride in hepatocytes, is the major cause of chronic liver disease worldwide and no approved drug is available. The mechanistic target of rapamycin (mTOR) complexes has been implicated in promoting lipogenesis and fat accumulation in the liver, and thus, serve as attractive drug targets. The generation of non- or low cytotoxic mTOR inhibitors is required because existing cytotoxic mTOR inhibitors are not useful for NAFLD therapy. New compounds based on the privileged adenosine triphosphate (ATP) site binder quinoline scaffold conjugated to glucose and galactosamine derivatives, which have significantly low cytotoxicity, but strong mTORC1 inhibitory activity at low micromolar concentrations, have been synthesized. These compounds also effectively inhibit the rate of lipogenesis and lipid accumulation in cultured hepatocytes. This is the first report of glycomimetic-quinoline derivatives that reduce lipid load in hepatocytes.