New perspectives in the regulation of hepatic glycolytic and lipogenic genes by insulin and glucose: a role for the transcription factor sterol regulatory element binding protein-1c

Elevated systemic total bile acids escalate susceptibility to alcohol-associated liver disease

Excessive alcohol consumption is a major global health problem. Individuals with alcoholic liver disease often exhibit elevated serum total bile acids (TBAs). Nevertheless, the extent to which high TBA contributes to alcohol-associated liver disease (AALD) remains elusive. To investigate this, wild-type mice were categorized into normal (nTBA) and high (hTBA) TBA groups. Both groups underwent chronic-binge ethanol feeding for 4 weeks, followed by additional weekly ethanol doses. Ethanol feeding worsened AALD in both male and female mice with elevated serum TBA, characterized by liver dysfunction and steatosis. Decreased hepatic expression of genes involved in mitochondrial β-oxidation and lipid transport in ethanol-fed hTBA mice suggests that altered fatty acid metabolism contributed to AALD. Our findings, which represent the first to link high serum TBA to increased AALD susceptibility, underscore the importance of proactive serum TBA screening as a valuable tool for identifying individuals at high risk of developing AALD.

Short-chain fatty acids in nonalcoholic fatty liver disease: New prospects for short-chain fatty acids as therapeutic targets

Nonalcoholic fatty liver disease (NAFLD) is a stress-induced liver injury related to heredity, environmental exposure and the gut microbiome metabolism. Short-chain fatty acids (SCFAs), the metabolites of gut microbiota (GM), participate in the regulation of hepatic steatosis and inflammation through the gut-liver axis, which play an important role in the alleviation of NAFLD. However, little progress has been made in systematically elucidating the mechanism of how SCFAs improve NAFLD, especially the epigenetic mechanisms and the potential therapeutic application as clinical treatment for NAFLD. Herein, we adopted PubMed and Medline to search relevant keywords such as 'SCFAs', 'NAFLD', 'gut microbiota', 'Epigenetic', 'diet', and 'prebiotic effect' to review the latest research on SCFAs in NAFLD up to November 2023. In this review, firstly, we specifically discussed the production and function of SCFAs, as well as their crosstalk coordination in the gut liver axis. Secondly, we provided an updated summary and intensive discussion of how SCFAs affect hepatic steatosis to alleviate NAFLD from the perspective of genetic and epigenetic. Thirdly, we paid attention to the pharmacological and physiological characteristics of SCFAs, and proposed a promising future direction to adopt SCFAs alone or in combination with prebiotics and related clinical drugs to prevent and treat NAFLD. Together, this review aimed to elucidate the function of SCFAs and provide new insights to the prospects of SCFAs as a therapeutic target for NAFLD.

In vitro Adipocyte Differentiation Inhibition and in vivo Effects on Lipid Metabolism in High-Fat Diet-Induced Obesity of Euphorbia humifusa

Euphorbia humifusa Willd (Euphorbiaceae) is a functional raw material with various pharmacological activities. This study aimed to validate the inhibitory effect of Euphorbia humifusa extract (EHE) on adipocyte differentiation in vitro and in a high-fat-diet (HFD)-induced mouse model to evaluate the E.a humifusa as a novel anti-obesity and lipid metabolism enhancer agent. EHE effects on obesity and lipid metabolism were assessed in HFD-induced obese mice after 4-week treatments. Results were compared among four treatment groups (n = 7/group): low fat diet (LFD), high fat diet (HFD), and HFD-induced obese mice treated with either 100 or 200 mg/kg/day EHE (EHE100 and EHE200, respectively). EHE (50 to 200 μg/ml) and quercetin (50 μg/ml) significantly reduced 3T3-L1 preadipocyte differentiation (p < 0.001), in a concentration-dependent manner. EHE affected lipid metabolism, as evidenced by changes in serum lipid components. The HFD-EHE100 and HFD-EHE200 groups exhibited significantly (p < 0.05) reduced triglycerides (TG, 97.50 ± 6.56 and 82.50 ± 13.20 mg/dL, respectively) and low-density lipoprotein-cholesterol (LDL-c: 40.25 ± 4.99 and 41.25 ± 6.36 mg/dL, respectively) compared to the HFD group (TG: 129.25 ± 19.81 mg/dL; LDL-c: 51.75 ± 11.59 mg/dL). Haematoxylin and Eosin (H&E) and Oil red O staining showed that EHE markedly reduced lipid accumulation and inhibited lipogenesis in the liver. Interestingly, EHE significantly (p < 0.01) reduced the expression of adipogenic transcription factors in liver tissue. Our results indicated that EHE has the potential to be a therapeutic agent for addressing obesity and lipid metabolism.

Periodontitis exacerbates atherosclerosis through Fusobacterium nucleatum-promoted hepatic glycolysis and lipogenesis

AIMS

Positive associations between periodontitis (PD) and atherosclerosis have been established, but the causality and mechanisms are not clear. We aimed to explore the causal roles of PD in atherosclerosis and dissect the underlying mechanisms.

METHODS AND RESULTS

A mouse model of PD was established by ligation of molars in combination with application of subgingival plaques collected from PD patients and then combined with atherosclerosis model induced by treating atheroprone mice with a high-cholesterol diet (HCD). PD significantly aggravated atherosclerosis in HCD-fed atheroprone mice, including increased en face plaque areas in whole aortas and lesion size at aortic roots. PD also increased circulating levels of triglycerides and cholesterol, hepatic levels of cholesterol, and hepatic expression of rate-limiting enzymes for lipogenesis. Using 16S ribosomal RNA (rRNA) gene sequencing, Fusobacterium nucleatum was identified as the most enriched PD-associated pathobiont that is present in both the oral cavity and livers. Co-culture experiments demonstrated that F. nucleatum directly stimulated lipid biosynthesis in primary mouse hepatocytes. Moreover, oral inoculation of F. nucleatum markedly elevated plasma levels of triglycerides and cholesterol and promoted atherogenesis in HCD-fed ApoE-/- mice. Results of RNA-seq and Seahorse assay indicated that F. nucleatum activated glycolysis, inhibition of which by 2-deoxyglucose in turn suppressed F. nucleatum-induced lipogenesis in hepatocytes. Finally, interrogation of the molecular mechanisms revealed that F. nucleatum-induced glycolysis and lipogenesis by activating PI3K/Akt/mTOR signalling pathway in hepatocytes.

CONCLUSIONS

PD exacerbates atherosclerosis and impairs lipid metabolism in mice, which may be mediated by F. nucleatum-promoted glycolysis and lipogenesis through PI3K/Akt/mTOR signalling in hepatocytes. Treatment of PD and specific targeting of F. nucleatum are promising strategies to improve therapeutic effectiveness of hyperlipidaemia and atherosclerosis.

Effects of Coix seed extract, Lactobacillus paracasei K56, and their combination on the glycolipid metabolism in obese mice

Coix seed extract (CSE) and probiotics have been reported to regulate glycolipid metabolism through different modes of action. We tested the effects of CSE, Lactobacillus paracasei K56, and their combination to determine whether they have synergistic effects on glycolipid metabolism of obese mice. We fed male C57BL/6J mice with high-fat diet for 8 weeks to establish an obesity model. The obesity mice were selected and divided into five groups: the model control group and four intervention groups. After 10 weeks of continuous gavage intervention, the mice in the intervention groups exhibited lower body weight (lower about 2.31-4.41 g, vs. HFD 42.25 g, p < 0.01), and epididymal (lower about 0.58-0.92 g, vs. HFD 2.50 g, p < 0.01) and perirenal fat content (lower about 0.24-0.42 g, vs. HFD 0.88 g, p < 0.05); decreased fasting blood glucose, total cholesterol, triglycerides, and VLDL; and increased HLDL, respiratory exchange ratio, energy expenditure, and amount of exercise performed. K56 + CSE-combined intervention groups were more effective in lowering blood glucose, IL-1β, and TNF-α levels than the CSE and K56 alone interventions. The content of fatty acid synthase and SREBP-1c protein in liver tissue was lower. The combination has synergistic effects on weight control, fat reduction, and blood glucose regulation by improving the chronic inflammatory state and reducing the content of lipid synthesis-related enzymes of obese mice, which can hinder chronic disease progression. PRACTICAL APPLICATION: Coix seed extract can be used in obese people to regulate abnormal glucose and lipid metabolism and delay the development of chronic diseases.

Young and undamaged recombinant albumin alleviates T2DM by improving hepatic glycolysis through EGFR and protecting islet β cells in mice

BACKGROUND

Albumin is the most abundant protein in serum and serves as a transporter of free fatty acids (FFA) in blood vessels. In type 2 diabetes mellitus (T2DM) patients, the reduced serum albumin level is a risk factor for T2DM development and progression, although this conclusion is controversial. Moreover, there is no study on the effects and mechanisms of albumin administration to relieve T2DM. We examined whether the administration of young and undamaged recombinant albumin can alleviate T2DM in mice.

METHODS

The serum albumin levels and metabolic phenotypes including fasting blood glucose, glucose tolerance tests, and glucose-stimulated insulin secretion were studied in db/db mice or diet-induced obesity mice treated with saline or young, undamaged, and ultrapure rMSA. Apoptosis assays were performed at tissue and cell levels to determine the function of rMSA on islet β cell protection. Metabolic flux and glucose uptake assays were employed to investigate metabolic changes in saline-treated or rMSA-treated mouse hepatocytes and compared their sensitivity to insulin treatments.

RESULTS

In this study, treatment of T2DM mice with young, undamaged, and ultrapure recombinant mouse serum albumin (rMSA) increased their serum albumin levels, which resulted in a reversal of the disease including reduced fasting blood glucose levels, improved glucose tolerance, increased glucose-stimulated insulin secretion, and alleviated islet atrophy. At the cellular level, rMSA improved glucose uptake and glycolysis in hepatocytes. Mechanistically, rMSA reduced the binding between CAV1 and EGFR to increase EGFR activation leading to PI3K-AKT activation. Furthermore, rMSA extracellularly reduced the rate of fatty acid uptake by islet β-cells, which relieved the accumulation of intracellular ceramide, endoplasmic reticulum stress, and apoptosis. This study provided the first clear demonstration that injections of rMSA can alleviate T2DM in mice.

CONCLUSION

Our study demonstrates that increasing serum albumin levels can promote glucose homeostasis and protect islet β cells, which alleviates T2DM.

Tilianin Protects against Nonalcoholic Fatty Liver Disease in Early Obesity Mice

Non-alcoholic fatty liver disease (NAFLD) has emerged as one of the most frequent types of liver disease in pediatric populations with obesity. Tilianin has multiple biological activities including anti-inflammatory and antioxidant. Here, we aim to explore the functions and possible mechanisms of tilianin on NAFLD in obese children. A high-fat high-carbohydrate (HFHC) diet was used to feed 21-d-old mice. Tilianin was administered at a dose of 10 or 20 mg/kg daily. HFHC-fed mice gained weight, increased liver index. The liver showed hepatocyte ballooning, inflammatory infiltration, and steatosis. Elevated levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transpeptidase (GGT), low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) and reduced the high-density lipoprotein cholesterol (HDL-C) level were found in HFHC-fed mice. Administration of tilianin significantly reduced these impairments. We further evaluated proteins related to lipid metabolism and observed that LXRα, SREBP-1c, FAS and ACC1 expression were blunted following tilianin administration. In addition, tilianin suppressed reactive oxygen species (ROS) overproduction and lipid peroxide 4-Hydroxynonenal expression, ascribed to its oxidative stress-modulating capacity. Tilianin also reversed the increase in F4/80 expression and proinflammatory cytokine levels. Of note, tilianin administration resulted in decreased protein levels of active caspase-1 and NOD-like receptor protein 3 (NLRP3) in HFHC-fed mice. Our study suggests that tilianin may ameliorate NAFLD in early obese mice by modulating lipids metabolism, oxidative stress, and inflammation, which may in part involve inhibiting NLRP3 inflammasome activation.

Cranberry Proanthocyanidins as a Therapeutic Strategy to Curb Metabolic Syndrome and Fatty Liver-Associated Disorders

While the prevalence of metabolic syndrome (MetS) is steadily increasing worldwide, no optimal pharmacotherapy is readily available to address its multifaceted risk factors and halt its complications. This growing challenge mandates the development of other future curative directions. The purpose of the present study is to investigate the efficacy of cranberry proanthocyanidins (PACs) in improving MetS pathological conditions and liver complications; C57BL/6J mice were fed either a standard chow or a high fat/high sucrose (HFHS) diet with and without PACs (200 mg/kg), delivered by daily gavage for 12 weeks. Our results show that PACs lowered HFHS-induced obesity, insulin resistance, and hyperlipidemia. In conjunction, PACs lessened circulatory markers of oxidative stress (OxS) and inflammation. Similarly, the anti-oxidative and anti-inflammatory capacities of PACs were noted in the liver in association with improved hepatic steatosis. Inhibition of lipogenesis and stimulation of beta-oxidation could account for PACs-mediated decline of fatty liver as evidenced not only by the expression of rate-limiting enzymes but also by the status of AMPKα (the key sensor of cellular energy) and the powerful transcription factors (PPARα, PGC1α, SREBP1c, ChREBP). Likewise, treatment with PACs resulted in the downregulation of critical enzymes of liver gluconeogenesis, a process contributing to increased rates of glucose production in type 2 diabetes. Our findings demonstrate that PACs prevented obesity and improved insulin resistance likely via suppression of OxS and inflammation while diminishing hyperlipidemia and fatty liver disease, as clear evidence for their strength of fighting the cluster of MetS abnormalities.

Kidney Proximal Tubule GLUT2-More than Meets the Eye

Tubulopathy plays a central role in the pathophysiology of diabetic kidney disease (DKD). Under diabetic conditions, the kidney proximal tubule cells (KPTCs) are exposed to an extensive amount of nutrients, most notably glucose; these nutrients deteriorate KPTCs function and promote the development and progression of DKD. Recently, the facilitative glucose transporter 2 (GLUT2) in KPTCs has emerged as a central regulator in the pathogenesis of DKD. This has been demonstrated by identifying its specific role in enhancing glucose reabsorption and glucotoxicity, and by deciphering its effect in regulating the expression of the sodium-glucose transporter 2 (SGLT2) in KPTCs. Moreover, reduction/deletion of KPTC-GLUT2 has been recently found to ameliorate DKD, raising the plausible idea of considering it as a therapeutic target against DKD. However, the underlying molecular mechanisms by which GLUT2 exerts its deleterious effects in KPTCs remain vague. Herein, we review the current findings on the proximal tubule GLUT2 biology and function under physiologic conditions, and its involvement in the pathophysiology of DKD. Furthermore, we shed new light on its cellular regulation during diabetic conditions.

The Farnesoid X Receptor as a Master Regulator of Hepatotoxicity

The nuclear receptor farnesoid X receptor (FXR, NR1H4) is a bile acid (BA) sensor that links the enterohepatic circuit that regulates BA metabolism and elimination to systemic lipid homeostasis. Furthermore, FXR represents a real guardian of the hepatic function, preserving, in a multifactorial fashion, the integrity and function of hepatocytes from chronic and acute insults. This review summarizes how FXR modulates the expression of pathway-specific as well as polyspecific transporters and enzymes, thereby acting at the interface of BA, lipid and drug metabolism, and influencing the onset and progression of hepatotoxicity of varying etiopathogeneses. Furthermore, this review article provides an overview of the advances and the clinical development of FXR agonists in the treatment of liver diseases.

Resting metabolic rate, abdominal fat pad and liver metabolic gene expression in female rats provided a snacking diet from weaning to adulthood

Our female rat model with continuous, ad libitum access to snacks and chow from weaning to adulthood closely mimics human feeding behavior from childhood onwards. It causes weight gain, enlarged abdominal fat pads, reduced insulin sensitivity and leptin resistance without an increase in total caloric intake. Our current study investigated if this change in energy partitioning is due to a decrease in resting metabolic rate (RMR). In addition, we determined if carbohydrate and lipid metabolism changes in abdominal fat pads and liver. RMR, using indirect calorimetry, was determined in control and snacking rats every two weeks from Days 28-29 to Days 76-77. RMR decreased with age in both groups, but there was no difference between snacking and control rats at any age. At termination, abdominal fat pads (parametrial, retroperitoneal and mesenteric) and liver samples were collected for determination of gene expression for 21 genes involved in carbohydrate and lipid metabolism using RT-qPCR. Analysis of gene expression data showed a striking difference between metabolic profiles of control and snacking rats in abdominal fat pads and liver, with a distinct segregation of genes for both lipid and carbohydrate metabolism that correlated with an increase in body weight and fat pad weights. Genes involved in lipogenesis were upregulated in abdominal fat pads, while genes involved in adipogenesis, and lipid recycling were upregulated in the liver. In conclusion, snacking in addition to chow from weaning in female rats causes a repartitioning of energy that is not due to depressed RMR in snacking rats. Rather, snacking from weaning causes a shift in gene expression resulting in energy partitioning toward enhanced abdominal fat pad lipogenesis, and adipogenesis and lipid recycling in liver.

Pathogenesis of Alcohol-Associated Fatty Liver: Lessons From Transgenic Mice

Alcohol-associated liver disease (ALD) is a major public health issue that significantly contributes to human morbidity and mortality, with no FDA-approved therapeutic intervention available. The health burden of ALD has worsened during the COVID-19 pandemic, which has been associated with a spike in alcohol abuse, and a subsequent increase in hospitalization rates for ALD. A key knowledge gap that underlies the lack of novel therapies for ALD is a need to better understand the pathogenic mechanisms that contribute to ALD initiation, particularly with respect to hepatic lipid accumulation and the development of fatty liver, which is the first step in the ALD spectrum. The goal of this review is to evaluate the existing literature to gain insight into the pathogenesis of alcohol-associated fatty liver, and to synthesize alcohol’s known effects on hepatic lipid metabolism. To achieve this goal, we specifically focus on studies from transgenic mouse models of ALD, allowing for a genetic dissection of alcohol’s effects, and integrate these findings with our current understanding of ALD pathogenesis. Existing studies using transgenic mouse models of ALD have revealed roles for specific genes involved in hepatic lipid metabolic pathways including fatty acid uptake, mitochondrial β-oxidation, de novo lipogenesis, triglyceride metabolism, and lipid droplet formation. In addition to reviewing this literature, we conclude by identifying current gaps in our understanding of how alcohol abuse impairs hepatic lipid metabolism and identify future directions to address these gaps. In summary, transgenic mice provide a powerful tool to understand alcohol’s effect on hepatic lipid metabolism and highlight that alcohol abuse has diverse effects that contribute to the development of alcohol-associated fatty liver disease.

Association of cord blood asprosin concentration with atherogenic lipid profile and anthropometric indices

BACKGROUND

Elevated lipids in umbilical cord blood affect fetal programming, leading to a higher risk of developing cardiovascular disease in later life. However, the causes of changes in the lipid profile of umbilical cord blood are not clear yet. This study aimed for the first time to determine the association of asprosin concentration with TAG, TC, HDL-C, LDL-C concentrations and TAG/HDL-C, TC/HDL-C, LDL-C/HDL-C and non-HDL-C/HDL-C ratio in umbilical cord blood as well as newborn anthropometric indices. This cross-sectional study was based on 450 mother- newborn pairs of a birth cohort study in Sabzevar, Iran. Multiple linear regression was used to estimate the association of lipid concentration and lipid ratios as well as birth weight (BW), birth length (BL), head circumference (HC) and chest circumference (CC) with asprosin in cord blood samples controlled for the relevant covariates.

RESULT

In fully adjusted models, each 1 ng/mL increase in asprosin was associated with 0.19 (95% CI 0.06, 0.31, P < 0.01), 0.19 (95% CI 0.10, 0.29, P < 0.01), 0.17 (95% CI 0.09, 0.25, P < 0.01), 0.17 (95% CI 0.09, 0.25, P < 0.01), 0.01 (95% CI 0.00, 0.013, P < 0.01), 0.01 (95% CI 0.01, 0.01, P < 0.01), 0.01 (95% CI 0.01, 0.01, P < 0.01) and 0.01 (95% CI 0.01, 0.01, P < 0.01) increase in TAG, TC, LDL-C, TAG/HDL-C, TC/HDL-C, LDL-C/HDL-C and non-HDL-C/HDL-C ratio respectively. Moreover, higher asprosin levels was positively associated with newborn BW, BL, HC and CC; however, these associations were not statistically significant.

CONCLUSION

Overall, our findings support the positive association between cord asprosin concentration and the development of atherogenic lipid profile in newborns. Further studies are needed to confirm the findings of this study in other populations.

D-Mannose Regulates Hepatocyte Lipid Metabolism via PI3K/Akt/mTOR Signaling Pathway and Ameliorates Hepatic Steatosis in Alcoholic Liver Disease

This study investigated the protective properties and mechanisms of D-mannose against hepatic steatosis in experimental alcoholic liver disease (ALD). Drinking-water supplementation of D-mannose significantly attenuated hepatic steatosis in a standard mouse ALD model established by chronic-binge ethanol feeding, especially hepatocyte lipid deposition. This function of D-mannose on lipid accumulation in hepatocytes was also confirmed using ethanol-treated primary mouse hepatocytes (PMHs) with a D-mannose supplement. Meanwhile, D-mannose regulated lipid metabolism by rescuing ethanol-mediated reduction of fatty acid oxidation genes (PPARα, ACOX1, CPT1) and elevation of lipogenic genes (SREBP1c, ACC1, FASN). PI3K/Akt/mTOR signaling pathway was involved in this effect of D-mannose on lipid metabolism since PI3K/Akt/mTOR pathway inhibitors or agonists could abolish this effect in PMHs. Overall, our findings suggest that D-mannose exhibits its anti-steatosis effect in ALD by regulating hepatocyte lipid metabolism via PI3K/Akt/mTOR signaling pathway.

Mitochondria, oxidative stress and nonalcoholic fatty liver disease: A complex relationship

According to the 'multiple-hit' hypothesis, several factors can act simultaneously in nonalcoholic fatty liver disease (NAFLD) progression. Increased nitro-oxidative (nitroso-oxidative) stress may be considered one of the main contributors involved in the development and risk of NAFLD progression to nonalcoholic steatohepatitis (NASH) characterized by inflammation and fibrosis. Moreover, it has been repeatedly postulated that mitochondrial abnormalities are closely related to the development and progression of liver steatosis and NAFLD pathogenesis. However, it is difficult to determine with certainty whether mitochondrial dysfunction or oxidative stress are primary events or a simple consequence of NAFLD development. On the one hand, increasing lipid accumulation in hepatocytes could cause a wide range of effects from mild to severe mitochondrial damage with a negative impact on cell fate. This can start the cascade of events, including an increase of cellular reactive nitrogen species (RNS) and reactive oxygen species (ROS) production that promotes disease progression from simple steatosis to more severe NAFLD stages. On the other hand, progressing mitochondrial bioenergetic catastrophe and oxidative stress manifestation could be considered accompanying events in the vast spectrum of abnormalities observed during the transition from NAFL to NASH and cirrhosis. This review updates our current understanding of NAFLD pathogenesis and clarifies whether mitochondrial dysfunction and ROS/RNS are culprits or bystanders of NAFLD progression.

Role of Lipogenesis Rewiring in Hepatocellular Carcinoma

Metabolic rewiring is one of the hallmarks of cancer. Altered de novo lipogenesis is one of the pivotal metabolic events deregulated in cancers. Sterol regulatory element-binding transcription factor 1 (SREBP1) controls the transcription of major enzymes involved in de novo lipogenesis, including ACLY, ACACA, FASN, and SCD. Studies have shown the increased de novo lipogenesis in human hepatocellular carcinoma (HCC) samples. Multiple mechanisms, such as activation of the AKT/mechanistic target of rapamycin (mTOR) pathway, lead to high SREBP1 induction and the coordinated enhanced expression of ACLY, ACACA, FASN, and SCD genes. Subsequent functional analyses have unraveled these enzymes' critical role(s) and the related de novo lipogenesis in hepatocarcinogenesis. Importantly, targeting these molecules might be a promising strategy for HCC treatment. This paper comprehensively summarizes de novo lipogenesis rewiring in HCC and how this pathway might be therapeutically targeted.

Sirt1 Mediates Vitamin D Deficiency-Driven Gluconeogenesis in the Liver via mTorc2/Akt Signaling

As an active form of vitamin D (VD), 1,25-dihydroxyvitamin D (1,25(OH)₂D₃) is involved in the development of many metabolic diseases, such as diabetes, autoimmune diseases, and tumours. While prospective epidemiological studies have consistently implicated VD deficiency in the regulation of glucose metabolism and insulin sensitivity, the specific mechanism remains unclear. Here, we generated 1α(OH)ase-null mice (targeted ablation of the 25-hydroxyvitamin D 1α hydroxylase enzyme) and found that these mice developed hepatic glucose overproduction, glucose intolerance, and hepatic insulin resistance accompanied by reduced Sirtuin 1 (Sirt1) expression. The chromatin immunoprecipitation (ChIP) and a luciferase reporter assay revealed that 1,25(OH)₂D₃-activated VD receptor (VDR) directly interacted with one VD response element (VDRE) in the Sirt1 promoter to upregulate Sirt1 transcription, triggering a cascade of serine/threonine kinase (AKT) phosphorylation at S473 and FOXO1 phosphorylation at S256. This phosphorylation cascade reduced the expression of gluconeogenic genes, eventually attenuating glucose overproduction in the liver. In addition, a signaling pathway was found to modulate gluconeogenesis involving VDR, Sirt1, Rictor (a component of mTOR complex 2 [mTorc2]), AKT, and FOXO1, and Sirt1 and FOXO1 were identified as key modulators of dysregulated gluconeogenesis due to VD deficiency.

SREBP-1c and lipogenesis in the liver: an update1

Sterol Regulatory Element Binding Protein-1c is a transcription factor that controls the synthesis of lipids from glucose in the liver, a process which is of utmost importance for the storage of energy. Discovered in the early nineties by B. Spiegelman and by M. Brown and J. Goldstein, it has generated more than 5000 studies in order to elucidate its mechanism of activation and its role in physiology and pathology. Synthetized as a precursor found in the membranes of the endoplasmic reticulum, it has to be exported to the Golgi and cleaved by a mechanism called regulated intramembrane proteolysis. We reviewed in 2002 its main characteristics, its activation process and its role in the regulation of hepatic glycolytic and lipogenic genes. We particularly emphasized that Sterol Regulatory Element Binding Protein-1c is the mediator of insulin effects on these genes. In the present review, we would like to update these informations and focus on the response to insulin and to another actor in Sterol Regulatory Element Binding Protein-1c activation, the endoplasmic reticulum stress.

Effect of starch-hydrocolloid complexes with heat-moisture treatment on in vivo digestibility

The purpose of this study was to investigate the effect of starch-hydrocolloid (gum arabic, xanthan gum, and guar gum) complexes with heat-moisture treatment (HMT) on in vivo digestibility. In vivo digestibility experiments revealed that the body weight, liver weight, and fat index of mice in the intervention group were significantly reduced compared with those in the high-fat group. Glucose tolerance improved, and blood lipid levels, liver and adipose tissue morphology returned to normal. The results of mRNA expression levels showed that the intervention of corn starch-hydrocolloid complexes after HMT down-regulated the expression level of genes related to fat synthesis compared with the high-fat group, which could decrease lipid deposition and stabilize blood lipid levels. Results revealed that starch-xanthan gum complex (1 : 40 ratio) with HMT could markedly reduce the digestibility of starch. Overall, this study provides new ideas for the application of low-glycemic-index and functional foods.

Loss of Acot12 contributes to NAFLD independent of lipolysis of adipose tissue

In this study, we hypothesized that deregulation in the maintenance of the pool of coenzyme A (CoA) may play a crucial role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Specific deletion of Acot12 (Acot12-/-), the major acyl-CoA thioesterase, induced the accumulation of acetyl-CoA and resulted in the stimulation of de novo lipogenesis (DNL) and cholesterol biosynthesis in the liver. KEGG pathway analysis suggested PPARα signaling as the most significantly enriched pathway in Acot12-/- livers. Surprisingly, the exposure of Acot12-/- hepatocytes to fenofibrate significantly increased the accumulation of acetyl-CoA and resulted in the stimulation of cholesterol biosynthesis and DNL. Interaction analysis, including proximity-dependent biotin identification (BioID) analysis, suggested that ACOT12 may directly interact with vacuolar protein sorting-associated protein 33A (VPS33A) and play a role in vesicle-mediated cholesterol trafficking and the process of lysosomal degradation of cholesterol in hepatocytes. In summary, in this study, we found that ACOT12 deficiency is responsible for the pathogenesis of NAFLD through the accumulation of acetyl-CoA and the stimulation of DNL and cholesterol via activation of PPARα and inhibition of cholesterol trafficking.

Molecular mechanisms of lipotoxicity-induced pancreatic β-cell dysfunction

Type 2 diabetes (T2D), a heterogeneous disorder derived from metabolic dysfunctions, leads to a glucose overflow in the circulation due to both defective insulin secretion and peripheral insulin resistance. One of the critical risk factor for T2D is obesity, which represents a global epidemic that has nearly tripled since 1975. Obesity is characterized by chronically elevated free fatty acid (FFA) levels, which cause deleterious effects on glucose homeostasis referred to as lipotoxicity. Here, we review the physiological FFA roles onto glucose-stimulated insulin secretion (GSIS) and the pathological ones affecting many steps of the mechanisms and modulation of GSIS. We also describe in vitro and in vivo experimental evidences addressing lipotoxicity in β-cells and the role of saturation and chain length of FFA on the potency of GSIS stimulation. The molecular mechanisms underpinning lipotoxic-β-cell dysfunction are also reviewed. Among them, endoplasmic reticulum stress, oxidative stress and mitochondrial dysfunction, inflammation, impaired autophagy and β-cell dedifferentiation. Finally therapeutic strategies for the β-cells dysfunctions such as the use of metformin, glucagon-like peptide 1, thiazolidinediones, anti-inflammatory drugs, chemical chaperones and weight are discussed.

The Effect of Inflammation and Insulin Resistance on Lipid and Lipoprotein Responsiveness to Dietary Intervention

Lipids and lipoproteins are major targets for cardiovascular disease (CVD) prevention. Findings from a limited number of clinical trials suggest diet-induced atherogenic lipoprotein lowering can be altered in the presence of chronic low-grade inflammation or insulin resistance. This review summarizes results from randomized controlled trials that have examined diet-induced changes in lipids/lipoproteins by inflammatory or insulin sensitivity status. In addition, mechanisms to explain these clinical observations are explored. Post hoc analyses of data from a limited number of randomized controlled trials suggest attenuation of diet-induced lipid/lipoprotein lowering in individuals with inflammation and/or insulin resistance. These findings are supported by experimental studies showing that inflammatory stimuli and hyperinsulinemia alter genes involved in endogenous cholesterol synthesis and cholesterol uptake, reduce cholesterol efflux, and increase fatty acid biosynthesis. Further a priori defined research is required to better characterize how chronic low-grade inflammation and insulin resistance modulate lipid and lipoprotein responsiveness to guide CVD risk reduction in individuals presenting with these phenotypes.

Metabolic Syndrome Pathophysiology and Predisposing Factors

Metabolic syndrome (MetS) is a cluster of cardiometabolic risk factors with high prevalence among adult populations and elevated costs for public health systems worldwide. Despite the lack of consensus regarding the syndrome definition and diagnosis criteria, it is characterized by the coexistence of risk factors such as abdominal obesity, atherogenic dyslipidemia, elevated blood pressure, a prothrombotic and pro-inflammatory state, insulin resistance (IR), and higher glucose levels, factors indubitably linked to an increased risk of developing chronic conditions, such as type 2 diabetes (T2D) and cardiovascular disease (CVD). The syndrome has a complex and multifaceted origin not fully understood; however, it has been strongly suggested that sedentarism and unbalanced dietary patterns might play a fundamental role in its development. The purpose of this review is to provide an overview from the syndrome epidemiology, costs, and main etiological traits from its relationship with unhealthy diet patterns and sedentary lifestyles.

Licorice extract suppresses adipogenesis through regulation of mitotic clonal expansion and adenosine monophosphate-activated protein kinase in 3T3-L1 cells

Licorice, the root of Glycyrrhiza glabra, has been observed to possess an anti-obesity effect. Previous research has suggested that licorice acetone extract (LE) has an influence on mitotic clonal expansion (MCE) and adenosine monophosphate-activated protein kinase (AMPK), which play a key role in regulating adipogenesis. This study sought further insight into the molecular mechanism of LE's anti-obesity effect using 3T3-L1 adipocytes in vitro. LE inhibited 3T3-L1 adipogenesis, and the inhibitory effect of LE on adipogenesis was most significant in the early stage of adipogenic differentiation. LE inhibited the protein expression of cyclins and cyclin-dependent kinases in the MCE stage and arrested cells in the G1 phase of the cell cycle. Furthermore, it activated AMPK via phosphorylation. Moreover, the expression levels of lipid metabolism-related genes were regulated by LE. These findings suggest the anti-obesity effect of LE via MCE and AMPK regulation. PRACTICAL APPLICATIONS: Although the anti-obesity effects of licorice have been studied, the application of functional food-related anti-obesity effects of licorice has been less than that of other extracts. The present study increases the reliability of the anti-obesity effect of licorice by suggesting a new mechanism of action and expands the application of functional foods related to the anti-obesity effect of licorice. A new mechanistic insight will not only improve the scientific knowledge but will also help to predict the side effects of licorice's anti-obesity application.

Aging exacerbates high-fat diet-induced steatohepatitis through alteration in hepatic lipid metabolism in mice

BACKGROUND AND AIM

Aging is an independent risk factor for the progression of non-alcoholic steatohepatitis. Here, we investigated the role of age-related alterations in fatty acid metabolism in dietary steatohepatitis using lipidomics analysis.

METHODS

Male 8-week and 55-week-old C57BL/6 J mice were fed a high-fat diet (HFD) for 8 weeks. The quality and quantity of lipid molecular species in the liver were evaluated using the lipidomics approach.

RESULTS

Elder mice fed an HFD developed more severe steatohepatitis than young mice. Oxidative stress and inflammatory cytokines in the liver were exacerbated following HFD feeding in elder mice compared with young mice. In elder mice, de novo fatty acid synthesis was promoted, whereas β oxidation was blunted following HFD feeding, and lipid secretion from the liver was reduced. The expression of sirtuin 1 was not only reduced with age as expected but also significantly decreased due to intake of HFD. In the lipidomics analysis, the concentrations of diacylglycerol and TAG molecular species containing monounsaturated fatty acids were markedly increased following HFD feeding in elder mice compared with young mice. In contrast, the concentration of phosphatidylethanolamine and phosphatidylcholine molecular species containing polyunsaturated fatty acids were remarkably decreased following HFD feeding in elder mice compared with young mice, and the expression of fatty acid desaturase was blunted.

CONCLUSIONS

Aging-dependent alterations in lipid metabolism under excessive lipid supply most likely enhance hepatic lipotoxicity, thereby exacerbating metabolic steatohepatitis in elderly.

Diabetic‑induced alterations in hepatic glucose and lipid metabolism: The role of type 1 and type 2 diabetes mellitus (Review)

Diabetes mellitus (DM) is a growing health concern in society. Type 1 and type 2 DM are the two main types of diabetes; both types are chronic diseases that affect glucose metabolism in the body and the impaired regulation of glucose and lipid metabolism promotes the development and progression of DM. During the physiological metabolism process, the liver serves a unique role in glucose and lipid metabolism. The present article aimed to review the association between DM and glucose metabolism in the liver and discuss the changes of the following hepatic glucose fluxes: Gluconeogenesis, glucose/glucose 6-phosphate cycling, glycogenolysis, glycogenesis and the pentose phosphate pathway. Moreover, the incidence of fatty liver in DM was also investigated.

Bifidobacterium animalis subsp. lactis 420 for Metabolic Health: Review of the Research

The growing worldwide epidemic of obesity and associated metabolic health comorbidities has resulted in an urgent need for safe and efficient nutritional solutions. The research linking obesity with gut microbiota dysbiosis has led to a hypothesis that certain bacterial strains could serve as probiotics helping in weight management and metabolic health. In the search for such strains, the effect of Bifidobacterium animalis subsp. lactis 420 (B420) on gut microbiota and metabolic health, and the mechanisms of actions, has been investigated in a variety of in vitro, pre-clinical, and clinical studies. In this review, we aim to highlight the research on B420 related to obesity, metabolic health, and the microbiota. Current research supports the hypothesis that gut dysbiosis leads to an imbalance in the inflammatory processes and loss of epithelial integrity. Bacterial components, like endotoxins, that leak out of the gut can invoke low-grade, chronic, and systemic inflammation. This imbalanced state is often referred to as metabolic endotoxemia. Scientific evidence indicates that B420 can slow down many of these detrimental processes via multiple signaling pathways, as supported by mechanistic in vitro and in vivo studies. We discuss the connection of these mechanisms to clinical evidence on the effect of B420 in controlling weight gain in overweight and obese subjects. The research further indicates that B420 may improve the epithelial integrity by rebalancing a dysbiotic state induced by an obesogenic diet, for example by increasing the prevalence of lean phenotype microbes such as Akkermansia muciniphila. We further discuss, in the context of delivering the health benefits of B420: the safety and technological aspects of the strain including genomic characterization, antibiotic resistance profiling, stability in the product, and survival of the live probiotic in the intestine. In summary, we conclude that the clinical and preclinical studies on metabolic health suggest that B420 may be a potential candidate in combating obesity; however, further clinical studies are needed.

Alcohol effects on hepatic lipid metabolism

Alcoholic liver disease (ALD) is the most prevalent type of chronic liver disease with significant morbidity and mortality worldwide. ALD begins with simple hepatic steatosis and progresses to alcoholic steatohepatitis, fibrosis, and cirrhosis. The severity of hepatic steatosis is highly associated with the development of later stages of ALD. This review explores the disturbances of alcohol-induced hepatic lipid metabolism through altered hepatic lipid uptake, de novo lipid synthesis, fatty acid oxidation, hepatic lipid export, and lipid droplet formation and catabolism. In addition, we review emerging data on the contributions of genetics and bioactive lipid metabolism in alcohol-induced hepatic lipid accumulation.

Positioning Metabolism as a Central Player in the Diabetic Heart

In type 2 diabetes (T2D), the leading cause of death is cardiovascular complications. One mechanism contributing to cardiac pathogenesis is alterations in metabolism, with the diabetic heart exhibiting increased fatty acid oxidation and reduced glucose utilisation. The processes classically thought to underlie this metabolic shift include the Randle cycle and changes to gene expression. More recently, alternative mechanisms have been proposed, most notably, changes in post-translational modification of mitochondrial proteins in the heart. This increased understanding of how metabolism is altered in the diabetic heart has highlighted new therapeutic targets, with an aim to improve cardiac function in T2D. This review focuses on metabolism in the healthy heart and how this is modified in T2D, providing evidence for the mechanisms underlying this shift. There will be emphasis on the current treatments for the heart in diabetes, alongside efforts for metabocentric pharmacological therapies.

Fat and Sugar-A Dangerous Duet. A Comparative Review on Metabolic Remodeling in Rodent Models of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a common disease in Western society and ranges from steatosis to steatohepatitis to end-stage liver disease such as cirrhosis and hepatocellular carcinoma. The molecular mechanisms that are involved in the progression of steatosis to more severe liver damage in patients are not fully understood. A deeper investigation of NAFLD pathogenesis is possible due to the many different animal models developed recently. In this review, we present a comparative overview of the most common dietary NAFLD rodent models with respect to their metabolic phenotype and morphological manifestation. Moreover, we describe similarities and controversies concerning the effect of NAFLD-inducing diets on mitochondria as well as mitochondria-derived oxidative stress in the progression of NAFLD.

Vitamin E Ameliorates Lipid Metabolism in Mice with Nonalcoholic Fatty Liver Disease via Nrf2/CES1 Signaling Pathway

BACKGROUND

Vitamin E has been reported to have a beneficial effect on nonalcoholic fatty liver disease (NAFLD); however, the underlying mechanism of action has not yet been clearly defined.

AIM

We aimed to evaluate the effects and mechanisms of vitamin E on lipid and glucose homeostasis both in vivo and in vitro.

METHODS

An NAFLD model was established in C57BL/6 mice fed a 30% fructose solution for 8 weeks. Subsequently, NAFLD mice were given vitamin E (70 mg/kg) for 2 weeks. In addition, L02 cells were treated with 5 mM fructose and 100 nM vitamin E to explore the potential mechanisms of action.

RESULTS

Vitamin E reversed the impaired glucose tolerance of fructose-treated mice. Histopathological examination showed that liver steatosis was significantly relieved in vitamin E-treated mice. These effects may be attributed to the upregulation of nuclear factor erythroid-2-related factor 2 (Nrf2), carboxylesterase 1 (CES1), and downregulated proteins involved in lipid synthesis by vitamin E treatment. In vivo, vitamin E also significantly reduced lipid accumulation in fructose-treated L02 cells, and the Nrf2 inhibitor ML385 reversed the protective effects of vitamin E.

CONCLUSION

These data indicated that the therapeutic effects of vitamin E on lipid and glucose homeostasis may be associated with activation of the Nrf2/CES1 signaling pathway.

The unfolded protein response and hepatic lipid metabolism in non alcoholic fatty liver disease

Nonalcoholic fatty liver disease is a major public health burden. Although many features of nonalcoholic fatty liver disease pathogenesis are known, the specific mechanisms and susceptibilities that determine an individual's risk of developing nonalcoholic steatohepatitis versus isolated steatosis are not well delineated. The predominant and defining histologic and imaging characteristic of nonalcoholic fatty liver disease is the accumulation of lipids. Dysregulation of lipid homeostasis in hepatocytes leads to transient generation or accumulation of toxic lipids that result in endoplasmic reticulum (ER) stress with inflammation, hepatocellular damage, and apoptosis. ER stress activates the unfolded protein response (UPR) which is classically viewed as an adaptive pathway to maintain protein folding homeostasis. Recent studies have uncovered the contribution of the UPR sensors in the regulation of hepatic steatosis and in the cellular response to lipotoxic stress. Interestingly, the UPR sensors can be directly activated by toxic lipids, independently of the accumulation of misfolded proteins, termed lipotoxic and proteotoxic stress, respectively. The dual function of the UPR sensors in protein and lipid homeostasis suggests that these two types of stress are interconnected likely due to the central role of the ER in protein folding and trafficking and lipid biosynthesis and trafficking, such that perturbations in either impact the function of the ER and activate the UPR sensors in an effort to restore homeostasis. The precise molecular similarities and differences between proteotoxic and lipotoxic ER stress are beginning to be understood. Herein, we provide an overview of the mechanisms involved in the activation and cross-talk between the UPR sensors, hepatic lipid metabolism, and lipotoxic stress, and discuss the possible therapeutic potential of targeting the UPR in nonalcoholic fatty liver disease.

Novel anti-obesity effect of scutellarein and potential underlying mechanism of actions

AIMS

Scutellarein (Sc), a natural compound and an active ingredient of Erigeron breviscapus (vant.), shows anti-inflammatory and antioxidant properties and has the potential for obesity treatment. However, no previous in vivo study has been conducted to assess the role of Sc in obesity. This study investigated the effects of Sc on obesity and associated hyperlipidemia and fatty liver and explores the underlying mechanisms of action in a mouse model.

METHODS

The study was conducted using a well-established mouse model of obesity induced by high-fat diet (HFD) feeding. Anti-obesity effects were assessed using body weight, abdominal circumference, white adipose tissue, adiposity index, and fatty liver index. Lipid lowering and liver protective effects were examined by blood sample analysis. Lipid dystopia deposition was confirmed by liver pathological sections. The signaling pathways of lipid metabolism and cytokine/inflammatory mediator were evaluated using Real-Time PCR and Western blot.

RESULTS

Central obesity, dyslipidemia, inflammation, and hepatic steatosis were developed in mice fed with HFD. Administration of Sc at a dose of 50 mg/kg for 16 weeks effectively attenuated all obesity indicators tested. Further studies revealed the antagonistic effect of Sc on hyperlipidemia was a result of the repression of the lipid synthesis pathway, de novo pathway, HMGCR, promoting fatty acid oxidation (PPARα, CPT-1a) and increased cholesterol output (PPARγ-LXRα-ABCA1). The anti-inflammatory effect was attributed to blocking the expression of inflammatory genes, including TNF-α, IL-6, NF-κB.

CONCLUSIONS

These results suggest that Sc possesses important novel anti-obesity effects accompanying lipid lowering and anti-inflammation-based liver protective effects. These favorable effects are causally associated with the suppression of gene expression of inflammatory cytokines and fine regulation of genes responsible for energy metabolism. Our results advance the understanding of the pharmacological actions of Sc, and provides a role for Sc in effective management of obesity.

Role of Myeloid-Epithelial-Reproductive Tyrosine Kinase and Macrophage Polarization in the Progression of Atherosclerotic Lesions Associated With Nonalcoholic Fatty Liver Disease

Recent lines of evidence highlight the involvement of myeloid-epithelial-reproductive tyrosine kinase (MerTK) in metabolic disease associated with liver damage. MerTK is mainly expressed in anti-inflammatory M2 macrophages where it mediates transcriptional changes including suppression of proinflammatory cytokines and enhancement of inflammatory repressors. MerTK is regulated by metabolic pathways through nuclear sensors including LXRs, PPARs, and RXRs, in response to apoptotic bodies or to other sources of cholesterol. Nonalcoholic fatty liver disease (NAFLD) is one of the most serious public health problems worldwide. It is a clinicopathological syndrome closely related to obesity, insulin resistance, and oxidative stress. It includes a spectrum of conditions ranging from simple steatosis, characterized by hepatic fat accumulation with or without inflammation, to nonalcoholic steatohepatitis (NASH), defined by hepatic fat deposition with hepatocellular damage, inflammation, and accumulating fibrosis. Several studies support an association between NAFLD and the incidence of cardiovascular diseases including atherosclerosis, a major cause of death worldwide. This pathological condition consists in a chronic and progressive inflammatory process in the intimal layer of large- and medium-sized arteries. The complications of advanced atherosclerosis include chronic or acute ischemic damage in the tissue perfused by the affected artery, leading to cellular death. By identifying specific targets influencing lipid metabolism and cardiovascular-related diseases, the present review highlights the role of MerTK in NAFLD-associated atherosclerotic lesions as a potential innovative therapeutic target. Therapeutic advantages might derive from the use of compounds selective for nuclear receptors targeting PPARs rather than LXRs regulating macrophage lipid metabolism and macrophage mediated inflammation, by favoring the expression of MerTK, which mediates an immunoregulatory action with a reduction in inflammation and in atherosclerosis.

Comparison of the Effects of Long-chain Monounsaturated Fatty Acid Positional Isomers on Lipid Metabolism in 3T3-L1 Cells

Long chain monounsaturated fatty acids (LC-MUFAs) have shown beneficial health effects in previous studies. They occur as mixtures of positional isomers (PIs) in food. The functionalities of LC-MUFA PIs have not been studied extensively. Common LC-MUFA PIs, namely cis-octadecenoic acid (c-18:1), cis-eicosenoic acid (c-20:1), and cis-docosenoic acid (c-22:1), were screened based on their effects on lipid accumulation. We selected nine fatty acids (FAs) to assess their effects on cellular lipid metabolism using 3T3-L1 preadipocytes. Lipid accumulation was found to be higher in cells treated with LC-MUFAs than in the non-treated cells. When comparing the influence of chain length of LC-MUFAs, TG levels tended to be higher in cells treated with c-22:1 group than that of the c18:1 and c-20:1 groups. Among the c-22:1 group, c9-22:1 treatment showed higher lipid accumulation, and was accompanied with elevated expression of transcription factors related to adipogenesis and lipogenesis, such as PPARγ and C/EBPα, and SREBP-1, respectively. In contrast, the effects of c-20:1 FAs were less pronounced than those of c-18:1 and c-22:1. Levels of accumulated lipid in cells treated with c15-20:1 were the same as in non-treated control. PPARγ, C/EBPα, and SREBP-1 were expressed at lower levels with c15-20:1 FA. Furthermore, mRNA levels of SCD-1 and FAS were lowered more by c15- and c11-20:1 than by other MUFAs. These results revealed that differences in the effects of LC-MUFAs on lipid metabolism depend on their chain lengths and on the position of the double bond.

Sfrp5 interacts with Slurp1 to regulate the accumulation of triglycerides in hepatocyte steatosis model

Secreted frizzled-related protein 5 (Sfrp5), an anti-inflammatory adipocytokine secreted by adipocytes, plays an important role in energy metabolism. Studies have shown that Sfrp5 plays a salutary role in the regulation of lipid metabolism, but its specific mechanism needs further study. In this study, we showed a lower level of Sfrp5 in subjects with diet-induced obesity than in normal-diet C57BL/6J mice. To further investigate Sfrp5-associated proteins in HepG2 cells, the immunoprecipitation assay and silver staining assay were performed. By mass spectrometry analysis, secreted lymphocyte antigen-6/urokinase-type plasminogen activator receptor-related peptide (Slurp-1) was found to interact with Sfrp5. Further verification was obtained through the positive and reverse immunoprecipitation assay. In this study, we found that the sole over-expression of Slurp1 promoted the expression of Sfrp5 in palmitate-induced HepG2 cells. In addition, our experimental evidence shows that the role of Slurp1 in decreasing TG level was greatly reduced in the case of suppression of expression of Sfrp5 in palmitate-induced model cells. Our study further found that Slurp1 regulates the synthesis pathway of triglyceride by interacting with Sfrp5 to alleviate triglyceride accumulation in palmitate-induced model cells. In summary, we are the first to discover the interaction between Sfrp5 and Slurp1, and we found that Slurp1 may regulate the accumulation of TG through Sfrp5.

Eicosapentaenoic Acid Improves Hepatic Metabolism and Reduces Inflammation Independent of Obesity in High-Fat-Fed Mice and in HepG2 Cells

The prevalence of nonalcoholic fatty liver disease (NAFLD) is increasing worldwide, concurrent with increased obesity. Thus, there is urgent need for research that can lead to effective NAFLD prevention/treatment strategies. Omega-3 polyunsaturated fatty acids (n-3 PUFAs), including eicosapentaenoic acid (EPA), improve inflammation- and dyslipidemia-related metabolic disorders; however, mechanisms mediating the benefits of n-3 PUFAs in NAFLD treatment are less understood. We previously reported that EPA reversed obesity-induced hepatic steatosis in high-fat (HF)-fed B6 mice. Utilizing a combination of biochemical analyses of liver tissues from HF and HF-EPA-fed mice and a series of in vitro studies in tumor necrosis factor-alpha (TNF-α)-stimulated HepG2 cells, we dissect the mechanistic effects of EPA in reducing hepatic steatosis, including the role of EPA-targeted microRNAs (miRNA). With EPA, hepatic lipid metabolism was improved in HF-EPA mice, as indicated by decreased protein and messenger RNA (mRNA) levels of fatty acid synthase (FASN) and acetyl-CoA carboxylase (Acaca) gene, and increased mRNA levels for the peroxisome proliferator activated receptor-α (Pparα), and carnitine palmitoyltransferase (Cpt) 1a and 2 genes in the HF-EPA mice. Additionally, inflammation was reduced, as shown by decreased tumor necrosis factor-alpha (Tnfα) gene expression. Accordingly, EPA also significantly reduced FASN and ACACA mRNAs in human HepG2 cells. Glycolysis, estimated by extracellular acidification rate, was significantly reduced in HepG2 cells treated with EPA vs. vehicle. Furthermore, we identified several miRNAs that are regulated by EPA in mouse liver, including miR-19b-3p, miR-21a-5p, and others, which target lipid metabolism and inflammatory pathways. In conclusion, our findings provide novel mechanistic evidence for beneficial effects of EPA in NAFLD, through the identification of specific genes and miRNAs, which may be further exploited as future NAFLD therapies.

Economical lipid production from Trichosporon oleaginosus via dissolved oxygen adjustment and crude glycerol addition

The effect of dissolved oxygen concentration on lipid accumulation in Trichosporon oleaginosus has been investigated. The experiment was performed in 15 L fermenters. The dissolved oxygen concentration varied by adjusting the agitation and aeration. High dissolved oxygen level at 50%-60% enhanced cell growth. Maintaining low dissolved oxygen concentration at 20%-30% during lipogenesis phase led to high final lipid content (51%) in Trichosporon oleaginosus. The consumptions of energy and cost of the process were evaluated. The energy consumption in the dissolved oxygen level optimized process was 41% less than that with dissolved oxygen level at 50%-60%. In addition, the cost was also reduced around one time in the dissolved oxygen level optimized process compared to the one with dissolved oxygen level at 50%-60%. The study provided a feasible way of enhancing lipid accumulation in Trichosporon oleaginosus and reducing the consumption of energy and cost of lipid production from Trichosporon oleaginosus.

Homeostasis of Glucose and Lipid in Non-Alcoholic Fatty Liver Disease

Industrialized society-caused dysregular human behaviors and activities such as overworking, excessive dietary intake, and sleep deprivation lead to perturbations in the metabolism and the development of metabolic syndrome. Non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease worldwide, affects around 30% and 25% of people in Western and Asian countries, respectively, which leads to numerous medical costs annually. Insulin resistance is the major hallmark of NAFLD and is crucial in the pathogenesis and for the progression from NAFLD to non-alcoholic steatohepatitis (NASH). Excessive dietary intake of saturated fats and carbohydrate-enriched foods contributes to both insulin resistance and NAFLD. Once NAFLD is established, insulin resistance can promote the progression to the more severe state of liver endangerment like NASH. Here, we review current and potential studies for understanding the complexity between insulin-regulated glycolytic and lipogenic homeostasis and the underlying causes of NAFLD. We discuss how disruption of the insulin signal is associated with various metabolic disorders of glucoses and lipids that constitute both the metabolic syndrome and NAFLD.

MicroRNAs as a Novel Tool in the Diagnosis of Liver Lipid Dysregulation and Fatty Liver Disease

In recent years, metabolic disorder, especially fatty liver disease, has been considered a major challenge to global health. The attention of researchers focused on expanding knowledge of the regulation mechanism behind these diseases and towards the new diagnostics tools and treatments. The pathophysiology of the fatty liver disease is undoubtedly complex. Abnormal hepatic lipid accumulation is a major symptom of most metabolic diseases. Therefore, the identification of novel regulation factors of lipid metabolism is important and meaningful. As a new diagnostic tool, the function of microRNAs during fatty liver disease has recently come into notice in biological research. Accumulating evidence supports the influence of miRNAs in lipid metabolism. In this review, we discuss the potential role of miRNAs in liver lipid metabolism and the pathogenesis of fatty liver disease.

Taurine improves low-level inorganic arsenic-induced insulin resistance by activating PPARγ-mTORC2 signalling and inhibiting hepatic autophagy

Inorganic arsenic (iAs) is reportedly associated with the increased incidence of type 2 diabetes in the population. Here, we found that iAs exposure significantly decreased the expression of glycolytic genes and glycogen content and increased gluconeogenesis gene levels in C57/BL6J mice. The expression of peroxisome proliferator-activated receptor γ (PPARγ), and mechanistic target of rapamycin complex 2 (mTORC2) were decreased in the livers of iAs-treated mice. Furthermore, in iAs-treated HepG2 cells, we found that PPARγ agonist rosiglitazone (RGS) increased the expression of mTORC2, inhibited autophagy, and improved glucose metabolism. mTORC2 agonist palmitic acid inhibited autophagy and improved glucose metabolism as well as the autophagosome formation inhibitor 3-methyladenine. Taurine, a natural compound, reversed impaired glucose metabolism and decreased expression of PPARγ and mTORC2 induced by iAs in mice liver and HepG2 cells. These data indicated that taurine administration could ameliorate iAs-induced insulin resistance through activating PPARγ-mTORC2 signalling and subsequently inhibiting hepatic autophagy.

Epigenetic-Transcriptional Regulation of Fatty Acid Metabolism and Its Alterations in Leukaemia

In recent years fatty acid metabolism has gained greater attention in haematologic cancers such as acute myeloid leukaemia. The oxidation of fatty acids provides fuel in the form of ATP and NADH, while fatty acid synthesis provides building blocks for cellular structures. Here, we will discuss how leukaemic cells differ from healthy cells in their increased reliance on fatty acid metabolism. In order to understand how these changes are achieved, we describe the main pathways regulating fatty acid metabolism at the transcriptional level and highlight the limited knowledge about related epigenetic mechanisms. We explore these mechanisms in the context of leukaemia and consider the relevance of the bone marrow microenvironment in disease management. Finally, we discuss efforts to interfere with fatty acid metabolism as a therapeutic strategy along with the use of metabolic parameters as biomarkers.

Effects of lobeglitazone on insulin resistance and hepatic steatosis in high-fat diet-fed mice

Lobeglitazone (Lobe) is a novel thiazolidinedione antidiabetic drug that reduces insulin resistance by activating peroxisome proliferator-activated receptor-gamma (PPARγ). However, the exact mechanisms of antidiabetic effects of Lobe have not been established in an animal model. The aim of this study was to evaluate the hypoglycemic effects of Lobe and investigate possible factors involved in Lobe-enhanced hepatic steatosis in high-fat diet (HFD)-fed mice. Mice were fed an HFD for 15 weeks. Lobe was administrated orally during the last 9 weeks. Lobe treatment significantly reduced insulin resistance and increased expression of hepatic glucose transporter 4 (GLUT4) and PPARs in HFD-fed mice. However, increased body weight and hepatic steatosis were not reduced by Lobe in these mice. Metabolomics fingerprinting showed that several lipogenesis-related hepatic and serum metabolites in HFD-fed mice had positive or negative correlations with Lobe administration. In particular, increased leptin levels during HFD were further increased by Lobe. HFD-induced signaling transducer and activator of transcription 3 (STAT3) phosphorylation in the hypothalamus was increased by Lobe. In addition, immunohistochemical analysis showed more proopiomelanocortin (POMC)-positive neurons in the hypothalamus of HFD-fed mice (with or without Lobe) compared with normal diet-fed mice. Despite improving leptin signaling in the hypothalamus and enhancing insulin sensitivity in HFD-fed mice, Lobe increased body weight and steatosis. Further research is necessary regarding other factors affecting Lobe-enhanced hepatic steatosis and hyperphagia.

Glucose-lowering effects and mechanisms of the bile acid-sequestering resin sevelamer

AIMS

Sevelamer, a non-absorbable amine-based resin used for treatment of hyperphosphataemia, has been demonstrated to have a marked bile acid-binding potential alongside beneficial effects on lipid and glucose metabolism. The aim of this study was to investigate the glucose-lowering effect and mechanism(s) of sevelamer in patients with type 2 diabetes.

MATERIALS AND METHODS

In this double-blinded randomized controlled trial, we randomized 30 patients with type 2 diabetes to sevelamer (n = 20) or placebo (n = 10). Participants were subjected to standardized 4-hour liquid meal tests at baseline and after 7 days of treatment. The main outcome measure was plasma glucagon-like peptide-1 excursions as measured by area under the curve. In addition, blood was sampled for measurements of glucose, lipids, glucose-dependent insulinotropic polypeptide, C-peptide, glucagon, fibroblast growth factor-19, cholecystokinin and bile acids. Assessments of gastric emptying, resting energy expenditure and gut microbiota composition were performed.

RESULTS

Sevelamer elicited a significant placebo-corrected reduction in plasma glucose with concomitant reduced fibroblast growth factor-19 concentrations, increased de novo synthesis of bile acids, a shift towards a more hydrophilic bile acid pool and increased lipogenesis. No glucagon-like peptide-1-mediated effects on insulin, glucagon or gastric emptying were evident, which points to a limited contribution of this incretin hormone to the glucose-lowering effect of sevelamer. Furthermore, no sevelamer-mediated effects on gut microbiota composition or resting energy expenditure were observed.

CONCLUSIONS

Sevelamer reduced plasma glucose concentrations in patients with type 2 diabetes by mechanisms that seemed to involve decreased intestinal and hepatic bile acid-mediated farnesoid X receptor activation.

BHLHE40, a third transcription factor required for insulin induction of SREBP-1c mRNA in rodent liver

In obesity, elevated insulin causes fatty liver by activating the gene encoding SREBP-1c, a transcription factor that enhances fatty acid synthesis. Two transcription factors, LXRα and C/EBPβ, are necessary but not sufficient for insulin induction of hepatic SREBP-1c mRNA. Here, we show that a third transcription factor, BHLHE40, is required. Immunoprecipitation revealed that BHLHE40 binds to C/EBPβ and LXRα in livers of rats that had fasted and then refed. Hepatic BHLHE40 mRNA rises rapidly when fasted rats are refed and when rat hepatocytes are incubated with insulin. Preventing this rise by gene knockout in mice or siRNAs in hepatocytes reduces the insulin-induced rise in SREBP-1c mRNA. Although BHLHE40 is necessary for insulin induction of SREBP-1c, it is not sufficient as demonstrated by failure of lentiviral BHLHE40 overexpression to increase hepatocyte SREBP-1c mRNA in the absence of insulin. Thus, an additional event is required for insulin to increase SREBP-1c mRNA.

LXRɑ participates in the mTOR/S6K1/SREBP-1c signaling pathway during sodium palmitate-induced lipogenesis in HepG2 cells

Background

The aim of this study was to investigate how the signaling pathway downstream of mTOR/S6K1 contributes to the regulation of SREBP-1c expression during lipogenesis in HepG2 cells.

Methods

The model of steatosis was established using human hepatocytes HepG2 and inducting them with sodium palmitate. mTOR, S6K1 and LXRα were inhibited by rapamycin, PF-4708671 and siRNA-LXRα, respectively. After a variety of different treatment, the levels of intracellular triglycerides, the accumulation of lipid droplets and the expression levels of related genes were detected.

Results

Rapamycin, PF-4708671 and siRNA-LXRα treatment could decrease the accumulation of triglycerides and lipid droplets induced by sodium palmitate in HepG2 cells, and the inhibitory effect could be enhanced by the combination of them. Sodium palmitate stimulated the expression of genes encoding mTOR, S6K1, LXRα, SREBP-1c and SREBP-1c target enzymes (FAS and ACC1) in HepG2 cells. Moreover, these genes were sensitive to rapamycin. PF-4708671 also decreased the expression of these genes, except for the mTOR gene, and the extent of reduction could be enhanced by combination with rapamycin. Knockdown of LXRα decreased the expression of SREBP-1c, FAS and ACC1, but it had no effect on the expression of mTOR or S6K1. Furthermore, rapamycin and PF-4708671 enhanced the inhibitory effect of siRNA-LXRα.

Conclusions

mTOR/S6K1 regulates the SREBP-1c signaling pathway through LXRα in sodium palmitate-induced HepG2 cells, suggesting LXRα might be a potential therapeutic target for NAFLD.

Long noncoding RNA Gomafu upregulates Foxo1 expression to promote hepatic insulin resistance by sponging miR-139-5p

Long non-coding RNA Gomafu is involved in diabetes-related diseases. However, its role in insulin resistance (IR) remains unclear. Our objective is to explore the role of Gomafu in hepatic IR and glucose intolerance. Gomafu expression was determined in livers of ob/ob mice and high-fat diet (HFD) mice. The binding activity of NF-κB on the Gomafu promoter was measured by chromatin immunoprecipitation and quantitative real-time PCR assays. Increased Gomafu expression was observed in the livers of obese mice. Besides, the binding of NF-κB on the Gomafu promoter was also observed in hepatocytes from ob/ob mice. Further study showed that knockdown of NF-κB p65 alleviated the increase in hepatic Gomafu expression in vivo and in vitro. Knockdown of hepatic Gomafu inhibited hepatic glucose production (HGP) and improved insulin sensitivity in obese mice, whereas, overexpression of hepatic Gomafu resulted in an increase in random and fasting blood glucose levels in lean mice. In addition, we demonstrated that Gomafu functioned as miR-139 sponge and led to the de-repression of its target gene Foxo1, which played an important role in gluconeogenesis and HGP in hepatocytes. Finally, silenced Foxo1 expression abolished the effect of Gomafu overexpression on gluconeogenesis and glucose production in hepatocytes. Taken together, our data suggested that the increase in Gomafu expression contributed to hepatic IR in obese mice.

FOXO family in regulating cancer and metabolism

FOXO proteins are a sub-group of a superfamily of forkhead box (FOX)-containing transcription factors (TFs). FOXOs play an important role in regulating a plethora of biological activities ranging from development, cell signaling, and tumorigenesis to cell metabolism. Here we mainly focus on reviewing the role of FOXOs in regulating tumor and metabolism. Moreover, how crosstalk among various pathways influences the function of FOXOs will be reviewed. Further, the paradoxical role for FOXOs in controlling the fate of cancer and especially resistance/sensitivity of cancer to the class of drugs that target PI3K/AKT will also be reviewed. Finally, how FOXOs regulate crosstalk between common cancer pathways and cell metabolism pathways, and how these crosstalks affect the fate of the cancer will be discussed.