Fructose and glucose combined with free fatty acids induce metabolic disorders in HepG2 cell: A new model to study the impacts of high-fructose/sucrose and high-fat diets in vitro

Role of glucose metabolism reprogramming in keratinocytes in the link between psoriasis and metabolic syndrome

The mechanism linking psoriasis to metabolic syndrome (MetS) remains poorly understood. Recent reports indicate upregulation of glycolysis-related proteins in psoriatic keratinocytes (KCs). However, the role of glucose metabolism reprogramming in psoriatic KCs, psoriasis, and psoriasis with MetS remains unclear. In this study, we confirmed glucose metabolism reprogramming in psoriatic KCs by examining glycolysis-related genes, proteins, and metabolites. We found that inhibiting glucose metabolism reprogramming in psoriasiform KCs led to improvements in psoriasiform features. Notably, we observed enhanced glucose metabolism reprogramming in KCs within psoriatic skin lesions of patients with MetS. In vitro, high-glucose and high-fat culture intensified glucose metabolism reprogramming in psoriasiform KCs partially via the AKT/mTOR pathway. These findings highlight a strong link between the glycolytic switch and KC function and suggest that glucose metabolism reprogramming in KCs contributes to heightened psoriatic inflammation in MetS.

Dietary regimens appear to possess significant effects on the development of combined antiretroviral therapy (cART)-associated metabolic syndrome

INTRODUCTION

This study investigated the interactions between a low protein high calorie (LPHC) diet and an integrase inhibitor-containing antiretroviral drug regimen (INI-CR)in light of evidence suggesting that the initiation of cART in patients with poor nutritional status is a predictor of mortality independent of immune status.

METHODS

Freshly weaned Sprague Dawley rats (120) were randomized into the standard, LPHC and normal protein high calorie (NPHC) diet groups (n = 40/group) initially for 15 weeks. Thereafter, experimental animals in each diet group were further randomized into four treatment sub-groups (n = 10/group) Control (normal saline), group 1(TDF+3TC+DTG and Tesamorelin), group 2 (TDF+3TC+DTG), and Positive control (AZT+3TC+ATV/r) with treatment and diets combined for 9 weeks. Weekly body weights, fasting blood glucose (FBG), oral glucose tolerance test (OGTT); lipid profiles, liver weights, hepatic triglycerides and adiposity were assessed at week 24.

RESULTS

At week 15, body weights increased between the diet group in phase 1(standard 146 ± 1.64 vs. 273.1 ± 1.56 g), (NPHC, 143.5 ± 2.40 vs. 390.2 ± 4.94 g) and (LPHC, 145.5 ± 2.28 g vs. 398.3 ± 4.89 g) (p< 0.0001). A similar increase was noted in the FBG and OGTT (p< 0.0001). In phase 2, there was an increase in FBG, OGTT, body weights, lipid profile, liver weights, hepatic triglycerides, adiposity and insulin levels in group 2 and positive control in both NPHC and LPHC diet groups (p<0.0001). Growth hormone levels were decreased in Tesamorelin-free group 2 and positive control in both NPHC and LPHC (p< 0.0001).

CONCLUSIONS

The obesogenic activities of the LPHC diet exceeded that of the NPHC diet and interacted with both integrase-containing and classical cART drug regimens to reproduce cART associated metabolic dysregulation. The effects were however reversed by co-administration with tesamorelin, a synthetic growth hormone releasing hormone analogue.

6-Methyl flavone inhibits Nogo-B expression and improves high fructose diet-induced liver injury in mice

Excessive fructose consumption increases hepatic de novo lipogenesis, resulting in cellular stress, inflammation and liver injury. Nogo-B is a resident protein of the endoplasmic reticulum that regulates its structure and function. Hepatic Nogo-B is a key protein in glycolipid metabolism, and inhibition of Nogo-B has protective effects against metabolic syndrome, thus small molecules that inhibit Nogo-B have therapeutic benefits for glycolipid metabolism disorders. In this study we tested 14 flavones/isoflavones in hepatocytes using dual luciferase reporter system based on the Nogo-B transcriptional response system, and found that 6-methyl flavone (6-MF) exerted the strongest inhibition on Nogo-B expression in hepatocytes with an IC50 value of 15.85 μM. Administration of 6-MF (50 mg· kg-1 ·d-1, i.g. for 3 weeks) significantly improved insulin resistance along with ameliorated liver injury and hypertriglyceridemia in high fructose diet-fed mice. In HepG2 cells cultured in a media containing an FA-fructose mixture, 6-MF (15 μM) significantly inhibited lipid synthesis, oxidative stress and inflammatory responses. Furthermore, we revealed that 6-MF inhibited Nogo-B/ChREBP-mediated fatty acid synthesis and reduced lipid accumulation in hepatocytes by restoring cellular autophagy and promoting fatty acid oxidation via the AMPKα-mTOR pathway. Thus, 6-MF may serve as a potential Nogo-B inhibitor to treat metabolic syndrome caused by glycolipid metabolism dysregulation.

Ferulic acid supplementation alleviates hyperuricemia in high-fructose/fat diet-fed rats via promoting uric acid excretion and mediating the gut microbiota

The prevalence of hyperuricemia (HUA) has been rising, and it is typically accompanied by renal injury and intestinal flora disorder, leading to a non-negligible health crisis. Ferulic acid (FA), as a familiar polyphenol, has been proven to exert anti-hyperuricemic properties via inhibiting uric acid (UA) synthesis; however, the detailed underlying mechanisms remain unclear. The aim of this study was to explore the regulatory effect of FA on UA excretion as a potential strategy for reducing UA levels, and the comorbidities of HUA. FA treatment downregulated the expression of urate absorption transporter genes and repressed the toll-like receptor 4 (TLR4)/nuclear factor kappa-B (NF-κB) pathway in UA-stimulated HK-2 cells. To examine these effects in vivo, FA or allopurinol (positive control) was given to rats with HUA induced by a high-fructose/fat diet (HFFD) for 20 weeks. FA markedly decreased the serum UA, blood urea nitrogen, and creatinine levels. The expression of urate absorption transporters was downregulated, whereas the expression of secretion transporters was upregulated in the kidneys and intestines of FA-treated HUA rats. Additionally, FA mitigated renal oxidative stress, and suppressed the activation of the TLR4/NF-κB pathway and the downstream inflammatory response-related markers in the kidneys. Moreover, FA remodeled the composition of the gut microbiota, characterized by an increase in beneficial bacteria (e.g., Lactobacillus and Ruminococcus) and a decrease in pathogenic bacteria (e.g., Bacteroides). In conclusion, our study validated FA as an effective nutrient to ameliorate HFFD-induced HUA, suggesting its potential to mitigate the HUA-associated renal impairment and intestinal microbiota disturbance.

A Comparison of Primary Human Hepatocytes and Hepatoma Cell Lines to Model the Effects of Fatty Acids, Fructose and Glucose on Liver Cell Lipid Accumulation

Non-alcoholic fatty liver disease (NAFLD) begins with lipid accumulation within hepatocytes, but the relative contributions of different macronutrients is still unclear. We investigated the impact of fatty acids, glucose and fructose on lipid accumulation in primary human hepatocytes (PHH) and three different cell lines: HepG2 (human hepatoblastoma−derived cell line), Huh7 (human hepatocellular carcinoma cell line) and McA-RH7777 (McA, rat hepatocellular carcinoma cell line). Cells were treated for 48 h with fatty acids (0 or 200 μM), glucose (5 mM or 11 mM) and fructose (0 mM, 2 mM or 8 mM). Lipid accumulation was measured via Nile Red staining. All cell types accumulated lipid in response to fatty acids (p < 0.001). PHH and McA, but not HepG2 or Huh7 cells, accumulated more lipid with 11 mM glucose plus fatty acids (p = 0.004, fatty acid × glucose interaction, for both), but only PHH increased lipid accumulation in response to fructose (p < 0.001). Considerable variation was observed between PHH cells from different individuals. Lipid accumulation in PHH was increased by insulin (p = 0.003) with inter-individual variability. Similarly, insulin increased lipid accumulation in both HepG2 and McA cells, with a bigger response in McA in the presence of fatty acids (p < 0.001 for fatty acid × insulin). McA were more insulin sensitive than either HepG2 or Huh7 cells in terms of AKT phosphorylation (p < 0.001 insulin × cell type interaction). Hence, glucose and fructose can contribute to the accumulation of lipid in PHH with considerable inter-individual variation, but hepatoma cell lines are not good models of PHH.

Hepatic glycerol shunt and glycerol-3-phosphate phosphatase control liver metabolism and glucodetoxification under hyperglycemia

OBJECTIVE

Glycerol-3-phosphate (Gro3P) phosphatase (G3PP) hydrolyzes Gro3P to glycerol that exits the cell, thereby operating a "glycerol shunt", a metabolic pathway that we identified recently in mammalian cells. We have investigated the role of G3PP and the glycerol shunt in the regulation of glucose metabolism and lipogenesis in mouse liver.

METHODS

We generated hepatocyte-specific G3PP-KO mice (LKO), by injecting AAV8-TBG-iCre to male G3PP^fl/fl mice. Controls received AAV8-TBG-eGFP. Both groups were fed chow diet for 10 weeks. Hyperglycemia (16-20 mM) was induced by glucose infusion for 55 h. Hepatocytes were isolated from normoglycemic mice for ex vivo studies and targeted metabolomics were measured in mice liver after glucose infusion.

RESULTS

LKO mice showed no change in body weight, food intake, fed and fasted glycemia but had increased fed plasma triglycerides. Hepatic glucose production from glycerol was increased in fasted LKO mice. LKO mouse hepatocytes displayed reduced glycerol production, elevated triglyceride and lactate production at high glucose concentration. Hyperglycemia in LKO mice led to increased liver weight and accumulation of triglycerides, glycogen and cholesterol together with elevated levels of Gro3P, dihydroxyacetone phosphate, acetyl-CoA and some Krebs cycle intermediates in liver. Hyperglycemic LKO mouse liver showed elevated expression of proinflammatory cytokines and M1-macrophage markers accompanied by increased plasma triglycerides, LDL/VLDL, urea and uric acid and myocardial triglycerides.

CONCLUSIONS

The glycerol shunt orchestrated by G3PP acts as a glucose excess detoxification pathway in hepatocytes by preventing metabolic disturbances that contribute to enhanced liver fat, glycogen storage, inflammation and lipid build-up in the heart. We propose G3PP as a novel therapeutic target for hepatic disorders linked to nutrient excess.

Dietary Ferulic Acid Ameliorates Metabolism Syndrome-Associated Hyperuricemia in Rats via Regulating Uric Acid Synthesis, Glycolipid Metabolism, and Hepatic Injury

Ferulic acid is a well-known phenolic acid compound and possesses multiple health-promoting and pharmacological effects. Metabolic syndrome (MetS) and hyperuricemia (HUA) have become health problems worldwide and are closely connected. The aim of this study was to explore the influence of ferulic acid on MetS-related HUA and its underlying mechanisms. Rats were administered high-fructose and high-fat diet (HFFD) with or without ferulic acid (0.05 and 0.1%) for 20 weeks. Intake of HFFD resulted in obesity, hyperglycemia, insulin resistance, and dyslipidemia, which were alleviated by ferulic acid consumption. Treatment of rats with ferulic acid diminished the levels of lipids and inflammatory cytokines and enhanced the activities of antioxidant enzymes in the liver caused by HFFD. Additionally, administration of ferulic acid blocked a HFFD-induced elevation in activities and mRNA expression of enzymes involving in uric acid (UA) synthesis. Molecular docking analysis denoted that ferulic acid bound to the active center of these enzymes, indicative of the potential interaction with each other. These two aspects might partially be responsible for the decrement in serum UA content after ferulic acid ingestion. In conclusion, ferulic acid supplementation ameliorated lipid and glucose metabolic abnormalities, hepatic damage, and UA formation in MetS rats. There was a dose correlation between lipid deposition and UA synthesis-related indicators. These findings implied that ferulic acid could be applied as a promising dietary remedy for the management of MetS-associated HUA.

Terpenoid-Rich Extract of Dillenia indica L. Bark Displays Antidiabetic Action in Insulin-Resistant C2C12 Cells and STZ-Induced Diabetic Mice by Attenuation of Oxidative Stress

Insulin resistance (IR) plays a key role in the pathogenesis and clinical outcome of patients with multiple diseases and diabetes. In this study, we examined the antidiabetic effects of a terpenoid-rich extract from Dillenia indica L. bark (TRDI) in palmitic acid-induced insulin resistance (PA-IR) in C2C12 myotube and a streptozotocin (STZ)-induced diabetic mice model and explored the possible underlying mechanism. TRDI showed potential DPPH- and ABTS-radical scavenging effects with a half-maximal inhibitory concentration (IC₅₀) value of 9.76 ± 0.50 µg/mL and 17.47 ± 1.31 µg/mL, respectively. Furthermore, TRDI strongly mitigated α-glucosidase activity with an IC₅₀ value of 3.03 ± 1.01 µg/mL, which was 92-fold higher than the positive control, acarbose (IC₅₀ = 279.49 ± µg/mL). TRDI stimulated the insulin receptor substrarte-1 (INS-1), downregulated phosphoinositide-dependent kinase-1 (PDK1) and protein kinase B (Akt) in both normal and PA-IR C2C12 cells as well as in STZ-induced diabetic mice, enhanced glucose transporter 4 (GLUT4) translocation to the plasma membrane (PM), and increased glucose absorption. Furthermore, TRDI administration significantly reduced PA-induced reactive oxygen species (ROS) formation in C2C12 cells and increased the protein level of numerous antioxidant enzymes such as superoxide dismutase 1 (SOD1), catalase (CAT), glutathione peroxidase-1 (GPx-1) and thioredoxin reductase (TrxR) both in vitro and in vivo. Furthermore, TRDI facilitated nuclear factor erythroid 2 related factor 2 (Nrf2) nuclear translocation and increased HO-1 expression in PA-IR C2C12 cells and STZ-induced diabetic mice. However, for the inhibition of Nrf2, TRDI failed to resist the effects of IR. Thus, this study provides new evidence to support the use of TRDI for diabetes treatment.

Involvement of AMP-activated Protein Kinase α/Nuclear Factor (Erythroid-derived 2) Like 2-iniatived Signaling Pathway in Cytoprotective Effects of Wasabi 6-(Methylsulfinyl) Hexyl Isothiocyanate

6-(Methylsulfinyl) hexyl isothiocyanate (6-MSITC) is an active ingredient present in Wasabi, which is a popular pungent spice used in Japanese cuisine. Our previous studies suggested that the primary antioxidant activity of 6-MSITC may link to other biological activity. This study aimed to clarify how the antioxidant activity of 6-MSITC contributes to preventing overloaded lipid stress in hepatic cell model. HepG2 cells were treated with 6-MSITC at defined concentrations and times in normal medium or in combined fatty acids (CFA) medium, and the targeted proteins were detected by Western blotting. The kinetic data revealed that 6-MSITC activated AMP-activated protein kinase α (AMPKα) and nuclear factor (erythroid-derived 2) like 2 (Nrf2), and then enhanced the protein expression of Forkhead box protein O1 (FOXO1) and Sirtuin1 as well as that of the Nrf2 target proteins, NAD(P)H:quinone oxidoreductase 1 (NQO1) and heme oxygenase (HO-1). Furthermore, lipid metabolic stress was mimicked in HepG2 cells by overloading CFA. 6-MSITC significantly alleviated CFA-induced formation of thiobarbituric acid reactive substances and fat accumulation. Signaling analysis data revealed that 6-MSITC enhanced phosphorylation of AMPKα, upregulated the expression of Nrf2, NQO1, heme oxygenase 1, FOXO1, and Siruin1, and downregulated the expression of PPARα. Taken together, our results suggested that the AMPKα/Nrf2-mediated signaling pathways might be involved in the cytoprotective effects of Wasabi 6-MSITC against metabolic lipid stress.

Metabolism and Health Effects of Rare Sugars in a CACO-2/HepG2 Coculture Model

Non-alcoholic fatty liver disease (NAFLD) has become the most prevalent liver disease worldwide and is impacted by an unhealthy diet with excessive calories, although the role of sugars in NAFLD etiology remains largely unexplored. Rare sugars are natural sugars with alternative monomers and glycosidic bonds, which have attracted attention as sugar replacers due to developments in enzyme engineering and hence an increased availability. We studied the impact of (rare) sugars on energy production, liver cell physiology and gene expression in human intestinal colorectal adenocarcinoma (Caco-2) cells, hepatoma G2 (HepG2) liver cells and a coculture model with these cells. Fat accumulation was investigated in the presence of an oleic/palmitic acid mixture. Glucose, fructose and galactose, but not mannose, l-arabinose, xylose and ribose enhanced hepatic fat accumulation in a HepG2 monoculture. In the coculture model, there was a non-significant trend (p = 0.08) towards higher (20–55% increased) median fat accumulation with maltose, kojibiose and nigerose. In this coculture model, cellular energy production was increased by glucose, maltose, kojibiose and nigerose, but not by trehalose. Furthermore, glucose, fructose and l-arabinose affected gene expression in a sugar-specific way in coculture HepG2 cells. These findings indicate that sugars provide structure-specific effects on cellular energy production, hepatic fat accumulation and gene expression, suggesting a health potential for trehalose and l-arabinose, as well as a differential impact of sugars beyond the distinction of conventional and rare sugars.

Maca extracts regulate glucose and lipid metabolism in insulin-resistant HepG2 cells via the PI3K/AKT signalling pathway

This work focused on the separation of the active ingredients of maca (Lepidium meyenii Walpers) and evaluated the antioxidative capability of these components with effects on improving glucose and lipid metabolism in insulin-resistant HepG2 cells. DPPH free radical scavenging and reducing power assays were used to evaluate the antioxidant activity of maca extracts. An insulin-resistant HepG2 cell model induced by glucose, fructose, oleic acid, and palmitic acid was adopted to investigate the effects of maca extracts on regulating glucose and lipid metabolism in this study. LC-MS/MS was then used for determination of the maca n-butanol (NBT) subfraction. The results showed that maca ethanol extract and subfractions of this extract exhibited certain antioxidant capacity. Furthermore, the NBT subfraction reversed the disorders in glucose and lipid metabolism in insulin-resistant HepG2 cells and significantly increased the mRNA expression of phosphoinositide 3-kinases (PI3K) and AKT in insulin-resistant HepG2 cells in a dose-dependent manner. In addition, the LC-MS/MS results showed that the NBT subfraction contained many active ingredients. Overall, this study suggests that the NBT subfraction of the ethanol extract rich in glucosinolates modulates insulin resistance via PI3K/AKT activation in insulin-resistant HepG2 cells and might exert potentially beneficial effects in improving or treating glucose and lipid metabolic disorders.

Enhancing bile tolerance of Lactobacilli is involved in the hypolipidemic effects of liraglutide

Liraglutide is an analog of human glucagon-like peptide-1 which play essential roles in regulation of glycolipid metabolism. To investigate role of lactic acid bacteria (LAB) in lipid-lowering effect of liraglutide, 40 mice were divided into normal food diet (NFD), high-fat food (HFD), 10.0 mg/kg/d simvastatin-treated HFD (SIM + HFD), 200 and 400 µg/kg/d liraglutide-treated HFD (LL + HFD and HL + HFD) groups for 5 weeks. We found that liraglutide could upregulate cholesterol 7α-hydroxylase (CYP7A1) and LDL-receptor (LDLR), whereas downregulate 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR). Besides, liraglutide enhance abundance of lactobacillaceae in gut of hyperlipidemic mice and increase bile tolerance ability of LAB by upregulating bile salt hydrolases, and the lysate of liraglutide-sensitive LAB could also directly downregulate HMGCR, the key enzyme in cholesterol synthesis, and inhibit hepatocyte steatosis. These findings might provide new theoretical guidance for clinical application of liraglutide and research and development of antiobesity, hypolipidemic, and cholesterol-lowering drugs or functional foods.

Exploratory Data Analysis of Cell and Mitochondrial High-Fat, High-Sugar Toxicity on Human HepG2 Cells

Non-alcoholic steatohepatitis (NASH), one of the deleterious stages of non-alcoholic fatty liver disease, remains a significant cause of liver-related morbidity and mortality worldwide. In the current work, we used an exploratory data analysis to investigate time-dependent cellular and mitochondrial effects of different supra-physiological fatty acids (FA) overload strategies, in the presence or absence of fructose (F), on human hepatoma-derived HepG2 cells. We measured intracellular neutral lipid content and reactive oxygen species (ROS) levels, mitochondrial respiration and morphology, and caspases activity and cell death. FA-treatments induced a time-dependent increase in neutral lipid content, which was paralleled by an increase in ROS. Fructose, by itself, did not increase intracellular lipid content nor aggravated the effects of palmitic acid (PA) or free fatty acids mixture (FFA), although it led to an up-expression of hepatic fructokinase. Instead, F decreased mitochondrial phospholipid content, as well as OXPHOS subunits levels. Increased lipid accumulation and ROS in FA-treatments preceded mitochondrial dysfunction, comprising altered mitochondrial membrane potential (ΔΨm) and morphology, and decreased oxygen consumption rates, especially with PA. Consequently, supra-physiological PA alone or combined with F prompted the activation of caspase pathways leading to a time-dependent decrease in cell viability. Exploratory data analysis methods support this conclusion by clearly identifying the effects of FA treatments. In fact, unsupervised learning algorithms created homogeneous and cohesive clusters, with a clear separation between PA and FFA treated samples to identify a minimal subset of critical mitochondrial markers in order to attain a feasible model to predict cell death in NAFLD or for high throughput screening of possible therapeutic agents, with particular focus in measuring mitochondrial function.

Palmitate and Fructose Interact to Induce Human Hepatocytes to Produce Pro-Fibrotic Transcriptional Responses in Hepatic Stellate Cells Exposed to Conditioned Media

BACKGROUND/AIMS

Excessive consumption of dietary fat and sugar is associated with an elevated risk of nonalcoholic fatty liver disease (NAFLD). Hepatocytes exposed to saturated fat or sugar exert effects on nearby hepatic stellate cells (HSCs); however, the mechanisms by which this occurs are poorly understood. We sought to determine whether paracrine effects of hepatocytes exposed to palmitate and fructose produced profibrotic transcriptional responses in HSCs.

METHODS

We performed expression profiling of mRNA and lncRNA from HSCs treated with conditioned media (CM) from human hepatocytes treated with palmitate (P), fructose (F), or both (PF).

RESULTS

In HSCs exposed to CM from palmitate-treated hepatocytes, we identified 374 mRNAs and 607 lncRNAs showing significant differential expression (log₂ foldchange ≥ |1|; FDR ≤0.05) compared to control cells. In HSCs exposed to CM from PF-treated hepatocytes, the number of differentially expressed genes was much higher (1198 mRNAs and 3348 lncRNAs); however, CM from fructose-treated hepatocytes elicited no significant changes in gene expression. Pathway analysis of differentially expressed genes showed enrichment for hepatic fibrosis and hepatic stellate cell activation in P- (FDR =1.30E-04) and PF-(FDR =9.24E-06)
groups. We observed 71 lncRNA/nearby mRNA pairs showing differential expression under PF conditions. There were 90 mRNAs and 264 lncRNAs strongly correlated between the PF group and differentially expressed transcripts from a comparison of activated and quiescent HSCs, suggesting that some of the transcriptomic changes occurring in response to PF overlap with HSC activation.

CONCLUSION

The results reported here have implications for dietary modifications in the prevention and treatment of NAFLD.

Ethyl acetate subfractions from ethanol extracts of fermented oats (Avena sativa L.) exert anti-cancer properties in vitro and in vivo through G2/M and S Phase arrest and apoptosis

Background: Cancer is a major public problem and poses a long-term impact on patients' life, work, and study. Oats are widely recognized as healthy food and fermented oats were rich in the higher contents of polyphenols. However, the role of fermented oats in cancer remains elusive.

Methods: The effect of ethyl acetate subfractions (EASs) from ethanol extracts of oats fermented by Rhizopus oryzae 3.2751 on cancer cells was verified by series experiments in vitro and in vivo. The cell viability, colony formation, cell cycle, apoptosis, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and western blot were determined in vitro. The toxicity of EASs and xenograft mouse model were performed in vivo.

Results: MTT assay indicated that EASs interference suppressed the proliferation of four human cancer cells in a dose-dependent manner without a significant impact on two normal cells. EASs (0.2, 0.4, and 0.8 μg/mL) resulted in the G2/M and S phase arrest, apoptosis, depolarization of MMP, and ROS generation in HepG2 cells by flow cytometry. p53, JNK, caspase-9, and caspase-3 were activated and the expression of Bax was promoted, while the expression of Bcl-2 was reduced in HepG2 cells exposed to EASs via western blot. Furthermore, the in vivo study using a xenograft mouse model demonstrated that EASs attenuated the tumor growth with low systemic toxicity.

Conclusions: EASs exhibited anti-cancer activities in vitro and in vivo via cell cycle arrest and apoptosis. This finding suggests that polyphenol-enriched composition from fermented oats might become a promising candidate for impeding the development and progression of liver cancer.

Physicochemical Properties and Effects of Honeys on Key Biomarkers of Oxidative Stress and Cholesterol Homeostasis in HepG2 Cells

Manuka honey and newly developed honeys (arjuna, guggul, jiaogulan and olive) were examined for their physicochemical, biochemical properties and effects on oxidative stress and cholesterol homeostasis in fatty acid-induced HepG2 cells. The honeys exhibited standard moisture content (<20%), electrical conductivity (<0.8 mS/cm), acidic pH, and monosaccharides (>60%), except olive honey (<60% total monosaccharides). They all expressed non-Newtonian behavior and 05 typical regions of the FTIR spectra as those of natural ones. Guggul and arjuna, manuka honeys showed the highest phenolic contents, correlating with their significant antioxidant activities. Arjuna, guggul and manuka honeys demonstrated the agreement of total cholesterol reduction and the transcriptional levels of AMPK, SREBP2, HCMGR, LDLR, LXRα. Jiaogulan honey showed the least antioxidant content and activity, but it was the most cytotoxic. Both jiaogulan and olive honeys modulated the tested gene in the pattern that should lead to a lower TC content, but this reduction did not occur after 24 h. All 2% concentrations of tested honeys elicited a clearer effect on NQO1 gene expression. In conclusion, the new honeys complied with international norms for natural honeys and we provide partial evidence for the protective effects of manuka, arjuna and guggul honeys amongst the tested ones on key biomarkers of oxidative stress and cholesterol homeostasis, pending further studies to better understand their modes of action.

Liver Phosphoenolpyruvate Carboxykinase-1 Downregulation via siRNA-Functionalized Graphene Oxide Nanosheets Restores Glucose Homeostasis in a Type 2 Diabetes Mellitus In Vivo Model

Metabolic disorders have been increasing at an alarming rate, and one such example of metabolic disorder is type 2 diabetes mellitus (T2DM). Unregulated gluconeogenesis in T2DM results in increased hepatic glucose output that causes fasting and postprandial hyperglycaemia. Extensive proofs have shown that the downregulation of the key rate-limiting enzyme phosphoenolpyruvate carboxykinase-1 (PCK-1) of gluconeogenesis improved glucose homeostasis in vivo. In the present study, we have synthesized and characterized liver-specific stearic acid conjugated octaarginine (StA-R8) functionalized 4arm-2K-PEGamineylated graphene oxide nanosheets (GPR8) for the delivery of siRNA against PCK-1 in T2DM C57BL/6 mice. We found that a single intravenous administration of siRNA (3 mg/kg BW) conjugated to GPR8 (GPR8:PCK-1_{siRNA(3 mg/kg BW)} conjugate) in an optimized N/P ratio exploited as a therapeutic nanoformulation maintained glucose homeostasis for nearly 4 weeks in the T2DM mice. Efficient silencing of PCK-1 in T2DM liver tissue increased the phosphorylation of serine-256 of FOXO-1, thus showing a marked decrease in hepatic gluconeogenesis. Gluconeogenesis control and consequently glucose output from the liver furthermore partially enhanced liver and muscle insulin sensitivity results in the stimulation of the insulin/AKT-2 signaling pathway which indirectly restored glucose homeostasis in the treated T2DM group. Our therapeutic nanoformulation also improved glycogen storage in the liver and membrane translocation of GLUT4 in the muscle of the treated T2DM group. In conclusion, GPR8:PCK-1_{siRNA (3 mg/Kg BW)} restored glucose homeostasis by controlling the hepatic glucose production and improved peripheral insulin sensitivity as a consequence of reduced hyperglycemia. Thus, the current approach offered an alternative strategy for the therapeutics for T2DM.

Pelargonidin-3-O-glucoside Derived from Wild Raspberry Exerts Antihyperglycemic Effect by Inducing Autophagy and Modulating Gut Microbiota

Increasing evidence indicates that anthocyanins exert beneficial effects on type 2 diabetes (T2D), but the underlying mechanism remains unclear. Herein, the hyperglycemia-lowering effect of Pg3G derived from wild raspberry was investigated on high-glucose/high-fat (HG+HF)-induced hepatocytes and db/db diabetic mice. Our results indicated that Pg3G promoted glucose uptake in HG+HF-induced hepatocytes. Moreover, Pg3G induced autophagy, whereas autophagy inhibitors blocked the hypoglycemic effect of Pg3G. Transcriptional factor EB (TFEB) was found to be linked to Pg3G-induced autophagy. In vivo study showed that Pg3G treatment contributed to the improvement of glucose tolerance, insulin sensitivity, and induction of autophagy. Furthermore, Pg3G not only modified the gut microbiota composition, as indicated by an increased abundance of Prevotella, and elevated Bacteroidetes/Firmicutes ratio, but also strengthened the intestinal barrier integrity. This study unveils a novel mechanism that Pg3G attenuates hyperglycemia through inducing autophagy and modulating gut microbiota, which implicates a potential nutritional intervention strategy for T2D.

Atorvastatin prevents hearing impairment in the presence of hyperlipidemia

It is known that hyperlipidemia is a risk factor for sensorineural hearing loss. However, the biological mechanisms underlying hyperlipidemia and hearing impairment have not been completely elucidated in the cochlea. Based on our previous study of human subjects, elderly people taking drugs for hyperlipidemia showed better hearing than those not taking any medications. We hypothesized that drugs for hyperlipidemia, such as statins, may have the potential to prevent hearing impairment. The aim of this study was to investigate the correlation between hyperlipidemia and hearing impairment and the hearing preservation effect of atorvastatin using a hyperlipidemic mouse model with diet-induced obesity (DIO). Here, we demonstrate that DIO mice had a significant hearing impairment as well as increased levels of reactive oxygen species (ROS) and hair cell death due to reduced levels of pAKT and superoxide dismutase 2 (SOD2). However, these changes were significantly prevented by atorvastatin. Oxidative stress-induced intrinsic apoptosis was decreased by the high expression of Nrf2 and antioxidant genes, which improved mitochondrial function and ROS via activation of the PI3K-pAKT pathway by atorvastatin. Therefore, atorvastatin has the potential to prevent hearing impairment via redox balance in the presence of hyperlipidemia.

Modifying nutritional substrates induces macrovesicular lipid droplet accumulation and metabolic alterations in a cellular model of hepatic steatosis

BACKGROUND AND AIMS

Nonalcoholic fatty liver disease (NAFLD) begins with steatosis, where a mixed macrovesicular pattern of large and small lipid droplets (LDs) develops. Since in vitro models recapitulating this are limited, the aims of this study were to develop mixed macrovesicular steatosis in immortalized hepatocytes and investigate effects on intracellular metabolism by altering nutritional substrates.

METHODS

Huh7 cells were cultured in 11 mM glucose and 2% human serum (HS) for 7 days before additional sugars and fatty acids (FAs), either with 200 µM FAs (low fat low sugar; LFLS), 5.5 mM fructose + 200 µM FAs (low fat high sugar; LFHS), or 5.5 mM fructose + 800 µM FAs (high fat high sugar; HFHS), were added for 7 days. FA metabolism, lipid droplet characteristics, and transcriptomic signatures were investigated.

RESULTS

Between the LFLS and LFHS conditions, there were few notable differences. In the HFHS condition, intracellular triacylglycerol (TAG) was increased and the LD pattern and distribution was similar to that found in primary steatotic hepatocytes. HFHS-treated cells had lower levels of de novo-derived FAs and secreted larger, TAG-rich lipoprotein particles. RNA sequencing and gene set enrichment analysis showed changes in several pathways including those involved in metabolism and cell cycle.

CONCLUSIONS

Repeated doses of HFHS treatment resulted in a cellular model of NAFLD with a mixed macrovesicular LD pattern and metabolic dysfunction. Since these nutrients have been implicated in the development of NAFLD in humans, the model provides a good physiological basis for studying NAFLD development or regression in vitro.

High Glucose Induces Lipid Accumulation via 25-Hydroxycholesterol DNA-CpG Methylation

This work investigates the relationship between high-glucose (HG) culture, CpG methylation of genes involved in cell signaling pathways, and the regulation of carbohydrate and lipid metabolism in hepatocytes. The results indicate that HG leads to an increase in nuclear 25-hydroxycholesterol (25HC), which specifically activates DNA methyltransferase-1 (DNMT1), and regulates gene expression involved in intracellular lipid metabolism. The results show significant increases in ^5mCpG levels in at least 2,225 genes involved in 57 signaling pathways. The hypermethylated genes directly involved in carbohydrate and lipid metabolism are of PI3K, cAMP, insulin, insulin secretion, diabetic, and NAFLD signaling pathways. The studies indicate a close relationship between the increase in nuclear 25HC levels and activation of DNMT1, which may regulate lipid metabolism via DNA CpG methylation. Our results indicate an epigenetic regulation of hepatic cell metabolism that has relevance to some common diseases such as non-alcoholic fatty liver disease and metabolic syndrome.

Dexmedetomidine alleviates insulin resistance in hepatocytes by reducing endoplasmic reticulum stress

PURPOSE

Dexmedetomidine (DEX) stabilizes intraoperative blood glucose levels and reduces insulin resistance (IR), a common perioperative complication. However, the molecular mechanisms underlying these effects remain unclear. Since endoplasmic reticulum stress (ERS) is a mechanism of IR, this study sought to examine whether DEX can effectively alleviate IR by reducing ERS.

METHODS

HepG2 and LO2 cells were treated with different concentrations of insulin. The glucose content assay and Cell Counting Kit-8 (CCK-8) were then employed to determine the optimal insulin concentration capable of inducing IR without affecting cell viability. Insulin-resistant hepatocytes were cultured with different concentrations of DEX for 24 h, and the glucose concentration in the supernatant was measured. ERS was assessed by qPCR and western blotting. The latter was also used to quantify the expression of phosphorylated protein kinase B (p-AKT), phosphoenolpyruvate carboxykinase (PEPCK), and glucose 6 phosphatase (G6Pase), which are key proteins involved in the action of insulin.

RESULTS

After 48-h of culturing with 10 μg/mL insulin, glucose consumption in hepatocytes was found to be reduced. IR hepatocytes cultured with 10, 100, or 1000 ng/ml DEX for 24 h showed a concentration-dependent increase in glucose consumption. Elevated mRNA and protein levels of ERS markers binding immunoglobulin protein (BIP) and ER protein 29 (ERp29), were reversed by DEX treatment. Moreover, reduced p-AKT and increased PEPCK and G6Pase protein levels in IR hepatocytes were also restored following DEX treatment.

CONCLUSION

DEX may alleviate IR in hepatocytes by reducing ERS serving to restore insulin action via the IRS-1/PI3K/AKT pathway.

Augmentation of Glucotoxicity, Oxidative Stress, Apoptosis and Mitochondrial Dysfunction in HepG2 Cells by Palmitic Acid

Hyperglycemia and hyperlipidemia are the hallmarks of diabetes and obesity. Experimental and epidemiological studies have suggested that dietary management and caloric restriction are beneficial in reducing the complications of diabesity. Studies have suggested that increased availability of energy metabolites like glucose and saturated fatty acids induces metabolic, oxidative, and mitochondrial stress, accompanied by inflammation that may lead to chronic complications in diabetes. In the present study, we used human hepatoma HepG2 cells to investigate the effects of high glucose (25 mM) and high palmitic acid (up to 0.3 mM) on metabolic-, inflammatory-, and redox-stress-associated alterations in these cells. Our results showed increased lipid, protein, and DNA damage, leading to caspase-dependent apoptosis and mitochondrial dysfunction. Glucolipotoxicity increased ROS production and redox stress appeared to alter mitochondrial membrane potential and bioenergetics. Our results also demonstrate the enhanced ability of cytochrome P450s-dependent drug metabolism and antioxidant adaptation in HepG2 cells treated with palmitic acid, which was further augmented with high glucose. Altered NF-kB/AMPK/mTOR-dependent cell signaling and inflammatory (IL6/TNF-α) responses were also observed. Our results suggest that the presence of high-energy metabolites enhances apoptosis while suppressing autophagy by inducing inflammatory and oxidative stress responses that may be responsible for alterations in cell signaling and metabolism.

Wheat Flour, Enriched with γ-Oryzanol, Phytosterol, and Ferulic Acid, Alleviates Lipid and Glucose Metabolism in High-Fat-Fructose-Fed Rats

(1) Background: Modern dietary patterns with a high intake of fat and fructose, as well as refined carbohydrates, closely relate to lipid/glucose metabolic disorders. The main objective of this study is to provide new thoughts in designing functional food with some lipid/glucose metabolism regulating effects for obese people. (2) Methods: The alleviating abilities of γ-oryzanol, phytosterol or ferulic acid-enriched wheat flour on lipid/glucose metabolic dysfunction were evaluated in male SD rats induced by a high-fat-fructose diet. The underlying mechanisms were clarified using western blot. (3) Results: In an in vitro cell model, γ-oryzanol, phytosterol and ferulic acid regulate lipid/glucose metabolism by increasing the phosphorylation of AMPK and Akt, and PI3K expression, as well as decreasing expressions of DGAT1 and SCD. The in vivo study shows that ferulic acid and γ-oryzanol-enriched flours are beneficial for managing body weight, improving glucose metabolism, hyperlipidemia and hepatic lipid accumulation. Phytosterol-enriched flour exerted remarkable effects in regulating hyperinsulinemia, insulin resistance and hyperuricemia. Western blot analysis of proteins from liver samples reveals that these enriched flours alleviated hepatic lipid accumulation and insulin resistance through their elevation in the phosphorylation of AMPK and Akt. (4) Conclusions: Our study indicates that these enriched flours can serve as a health-promoting functional food to regulate obesity-related lipid/glucose metabolic dysfunction in rats.

Challenging metabolic tissues with fructose: tissue-specific and sex-specific responses

Excessive consumption of free sugars (which typically includes a composite of glucose and fructose) is associated with an increased risk of developing chronic metabolic diseases including obesity, non-alcoholic fatty liver disease (NAFLD), type 2 diabetes and cardiovascular disease. Determining the utilisation, storage and fate of dietary sugars in metabolically relevant tissues is fundamental to understanding their contribution to metabolic disease risk. To date, the study of fructose metabolism has primarily focused on the liver, where it has been implicated in impaired insulin sensitivity, increased fat accumulation and dyslipidaemia. Yet we still have only a limited understanding of the mechanisms by which consumption of fructose, as part of a mixed meal, may alter hepatic fatty acid synthesis and partitioning. Moreover, surprisingly little is known about the metabolism of fructose within other organs, specifically subcutaneous adipose tissue, which is the largest metabolically active organ in the human body and is consistently exposed to nutrient fluxes. This review summarises what is known about fructose metabolism in the liver and adipose tissue and examines evidence for tissue-specific and sex-specific responses to fructose.

Artemisia sphaerocephala Krasch polysaccharide prevents hepatic steatosis in high fructose-fed mice associated with changes in the gut microbiota

High fructose (HF) diet-induced liver steatosis is associated with intestinal microbiota dysbiosis.

Differential capability of metabolic substrates to promote hepatocellular lipid accumulation

PURPOSE

Excessive storage of triacylglycerides (TAGs) in lipid droplets within hepatocytes is a hallmark of non-alcoholic fatty liver disease (NAFLD), one of the most widespread metabolic disorders in Western societies. For the purpose of exploring molecular pathways in NAFLD development and testing potential drug candidates, well-characterised experimental models of ectopic TAG storage in hepatocytes are needed.

METHODS

Using an optimised Oil Red O assay, immunoblotting and real-time qRT-PCR, we compared the capability of dietary monosaccharides and fatty acids to promote lipid accumulation in HepG2 human hepatoma cells.

RESULTS

Both high glucose and high fructose resulted in intracellular lipid accumulation after 48 h, and this was further augmented (up to twofold, as compared to basal levels) by co-treatment with the lipogenesis-stimulating hormone insulin and the pro-inflammatory cytokine tumour necrosis factor alpha (TNF-α), respectively. The fatty acids palmitic and oleic acid were even more effective than these carbohydrates, inducing significantly elevated TAG storage already after 24 h of treatment. Highest (about threefold) increases in lipid accumulation were observed upon treatment with oleic acid, alone as well as in combinations with palmitic acid or with high glucose and insulin. Increases in protein levels of a major lipid droplet coat protein, perilipin-2 (PLIN2), mirrored intracellular lipid accumulation following different treatment regimens.

CONCLUSIONS

Several treatment regimens of excessive fat and sugar supply promoted lipid accumulation in HepG2 cells, albeit with differences in the extent and rapidity of steatogenesis. PLIN2 is a candidate molecular marker of sustained lipid accumulation in HepG2 cells.

Multi-scale, whole-system models of liver metabolic adaptation to fat and sugar in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a serious public health issue associated with high fat, high sugar diets. However, the molecular mechanisms mediating NAFLD pathogenesis are only partially understood. Here we adopt an iterative multi-scale, systems biology approach coupled to in vitro experimentation to investigate the roles of sugar and fat metabolism in NAFLD pathogenesis. The use of fructose as a sweetening agent is controversial; to explore this, we developed a predictive model of human monosaccharide transport, signalling and metabolism. The resulting quantitative model comprising a kinetic model describing monosaccharide transport and insulin signalling integrated with a hepatocyte-specific genome-scale metabolic network (GSMN). Differential kinetics for the utilisation of glucose and fructose were predicted, but the resultant triacylglycerol production was predicted to be similar for monosaccharides; these predictions were verified by in vitro data. The role of physiological adaptation to lipid overload was explored through the comprehensive reconstruction of the peroxisome proliferator activated receptor alpha (PPARα) regulome integrated with a hepatocyte-specific GSMN. The resulting qualitative model reproduced metabolic responses to increased fatty acid levels and mimicked lipid loading in vitro. The model predicted that activation of PPARα by lipids produces a biphasic response, which initially exacerbates steatosis. Our data support the evidence that it is the quantity of sugar rather than the type that is critical in driving the steatotic response. Furthermore, we predict PPARα-mediated adaptations to hepatic lipid overload, shedding light on potential challenges for the use of PPARα agonists to treat NAFLD.

An Overview of Novel Dietary Supplements and Food Ingredients in Patients with Metabolic Syndrome and Non-Alcoholic Fatty Liver Disease

Metabolic syndrome (MetS) is characterized by interconnected factors related to metabolic disturbances, and is directly related to the occurrence of some diseases such as cardiovascular diseases and type 2 diabetes. MetS is described as one or both of insulin resistance and visceral adiposity, considered the initial causes of abnormalities that include hyperglycemia, elevated blood pressure, dyslipidemia, elevated inflammatory markers, and prothrombotic state, as well as polycystic ovarian syndrome in women. Other than in MetS, visceral adiposity and the pro-inflammatory state are also key in the development of non-alcoholic fatty liver disease (NAFLD), which is the most prevalent chronic liver disease in modern society. Both MetS and NAFLD are related to diet and lifestyle, and their treatment may be influenced by dietary pattern changes and the use of certain dietary supplements. This study aimed to review the role of food ingredients and supplements in the management of MetS and NAFLD specifically in human clinical trials. Moreover, bioactive compounds and polyunsaturated fatty acids (PUFAs) may be used as strategies for preventing the onset of and treatment of metabolic disorders, such as MetS and NAFLD, improving the inflammatory state and other comorbidities, such as obesity, dyslipidemias, and cardiovascular diseases (CVD).

Systemic and vascular inflammation in an in-vitro model of central obesity

Metabolic disorders due to over-nutrition are a major global health problem, often associated with obesity and related morbidities. Obesity is peculiar to humans, as it is associated with lifestyle and diet, and so difficult to reproduce in animal models. Here we describe a model of human central adiposity based on a 3-tissue system consisting of a series of interconnected fluidic modules. Given the causal link between obesity and systemic inflammation, we focused primarily on pro-inflammatory markers, examining the similarities and differences between the 3-tissue model and evidence from human studies in the literature. When challenged with high levels of adiposity, the in-vitro system manifests cardiovascular stress through expression of E-selectin and von Willebrand factor as well as systemic inflammation (expressing IL-6 and MCP-1) as observed in humans. Interestingly, most of the responses are dependent on the synergic interaction between adiposity and the presence of multiple tissue types. The set-up has the potential to reduce animal experiments in obesity research and may help unravel specific cellular mechanisms which underlie tissue response to nutritional overload.

Obesity-induced vascular dysfunction and arterial stiffening requires endothelial cell arginase 1

AIMS

Elevation of arginase activity has been linked to vascular dysfunction in diabetes and hypertension by a mechanism involving decreased nitric oxide (NO) bioavailability due to L-arginine depletion. Excessive arginase activity also can drive L-arginine metabolism towards the production of ornithine, polyamines, and proline, promoting proliferation of vascular smooth muscle cells and collagen formation, leading to perivascular fibrosis. We hypothesized that there is a specific involvement of arginase 1 expression within the vascular endothelial cells in this pathology.

METHODS AND RESULTS

To test this proposition, we used models of type 2 diabetes and metabolic syndrome. Studies were performed using wild type (WT), endothelial-specific arginase 1 knockout (EC-A1-/-) and littermate controls(A1con) mice fed high fat-high sucrose (HFHS) or normal diet (ND) for 6 months and isolated vessels exposed to palmitate-high glucose (PA/HG) media. Some WT mice or isolated vessels were treated with an arginase inhibitor, ABH [2-(S)-amino-6-boronohexanoic acid. In WT mice, the HFHS diet promoted increases in body weight, fasting blood glucose, and post-prandial insulin levels along with arterial stiffening and fibrosis, elevated blood pressure, decreased plasma levels of L-arginine, and elevated L-ornithine. The HFHS diet or PA/HG treatment also induced increases in vascular arginase activity along with oxidative stress, reduced vascular NO levels, and impaired endothelial-dependent vasorelaxation. All of these effects except obesity and hypercholesterolemia were prevented or significantly reduced by endothelial-specific deletion of arginase 1 or ABH treatment.

CONCLUSION

Vascular dysfunctions in diet-induced obesity are prevented by deletion of arginase 1 in vascular endothelial cells or arginase inhibition. These findings indicate that upregulation of arginase 1 expression/activity in vascular endothelial cells has an integral role in diet-induced cardiovascular dysfunction and metabolic syndrome.

Isofraxidin, a coumarin component improves high-fat diet induced hepatic lipid homeostasis disorder and macrophage inflammation in mice

Isofraxidin (IF) is a coumarin compound produced in the functional foodsSiberian ginsengandApium graveolens.

Linking mitochondrial dysfunction, metabolic syndrome and stress signaling in Neurodegeneration

Mounting evidence suggests a link between metabolic syndrome (MetS) such as diabetes, obesity, non-alcoholic fatty liver disease in the progression of Alzheimer's disease (AD), Parkinson's disease (PD) and other neurodegenerative diseases (NDDs). For instance, accumulated Aβ oligomer is enhancing neuronal Ca²⁺ release and neural NO where increased NO level in the brain through post translational modification is modulating the level of insulin production. It has been further confirmed that irrespective of origin; brain insulin resistance triggers a cascade of the neurodegeneration phenomenon which can be aggravated by free reactive oxygen species burden, ER stress, metabolic dysfunction, neuorinflammation, reduced cell survival and altered lipid metabolism. Moreover, several studies confirmed that MetS and diabetic sharing common mechanisms in the progression of AD and NDDs where mitochondrial dynamics playing a critical role. Any mutation in mitochondrial DNA, exposure of environmental toxin, high-calorie intake, homeostasis imbalance, glucolipotoxicity is causative factors for mitochondrial dysfunction. These cumulative pleiotropic burdens in mitochondria leads to insulin resistance, increased ROS production; enhanced stress-related enzymes that is directly linked MetS and diabetes in neurodegeneration. Since, the linkup mechanism between mitochondrial dysfunction and disease phenomenon of both MetS and NDDs is quite intriguing, therefore, it is pertinent for the researchers to identify and implement the therapeutic interventions for targeting MetS and NDDs. Herein, we elucidated the pertinent role of MetS induced mitochondrial dysfunction in neurons and their consequences in NDDs. Further, therapeutic potential of well-known biomolecules and chaperones to target altered mitochondria has been comprehensively documented. This article is part of a Special Issue entitled: Oxidative Stress and Mitochondrial Quality in Diabetes/Obesity and Critical Illness Spectrum of Diseases - edited by P. Hemachandra Reddy.