Hepatic Free Fatty Acid Research Articles

Single and Mixed Strains of Probiotics Reduced Hepatic Fat Accumulation and Inflammation and Altered Gut Microbiome in a Nonalcoholic Steatohepatitis Rat Model.

As gut dysbiosis has been implicated in the pathogenesis of nonalcoholic steatohepatitis (NASH), probiotic supplementation might be a potential treatment for this condition. The aim of this study was to evaluate the effects of single- and mixed-strain probiotics on the severity of NASH induced by a high-fat, high-fructose (HFHF) diet and their mechanisms of action. Male Sprague-Dawley rats were divided into four groups (n = 7 per group): control group, NASH group, NASH + single-strain group, and NASH + mixed-strain group. In the single-strain and mixed-strain groups, rats received Lactobacillus plantarum B7 and Lactobacillus rhamnosus L34 + Lactobacillus paracasei B13 by oral gavage once daily, respectively. The duration of the study was 6 weeks. Liver tissue was used for histopathology, hepatic fat content was assessed by Oil Red O staining and hepatic free fatty acid (FFA), and hepatic TLR4 and CD14 expression were assessed by immunohistochemistry. Fresh feces was collected for gut microbiota analysis. Liver histology revealed a higher degree of fat accumulation, hepatocyte ballooning, and lobular inflammation in the NASH group, which improved in probiotics-treated groups. The amounts of hepatic fat droplets and hepatic FFA levels were more pronounced in the NASH group than in the control and treatment groups. Serum TNF- α levels were significantly higher in the NASH group than in control and probiotic groups. The expression of CD14 and TLR4 increased in the NASH group as compared with the control and probiotics-treated groups. Alpha diversity was reduced in the NASH group, but increased in both treatment groups. The relative abundance of Lactobacillus significantly decreased in the NASH group, but increased in both treatment groups. The relative abundance of Akkermansia significantly increased in the NASH group, but decreased in both treatment groups. In conclusion, both single-strain and mixed-strain probiotics could improve NASH histology by suppressing inflammatory responses in the liver, with this improvement potentially being associated with changes in the gut microbiota.

Impaired Fat Absorption from Intestinal Tract in High-Fat Diet Fed Male Mice Deficient in Proglucagon-Derived Peptides.

(1) Background: Proglucagon-derived peptides (PDGPs) including glucagon (Gcg), GLP-1, and GLP-2 regulate lipid metabolism in the liver, adipocytes, and intestine. However, the mechanism by which PGDPs participate in alterations in lipid metabolism induced by high-fat diet (HFD) feeding has not been elucidated. (2) Methods: Mice deficient in PGDP (GCGKO) and control mice were fed HFD for 7 days and analyzed, and differences in lipid metabolism in the liver, adipose tissue, and duodenum were investigated. (3) Results: GCGKO mice under HFD showed lower expression levels of the genes involved in free fatty acid (FFA) oxidation such as Hsl, Atgl, Cpt1a, Acox1 (p < 0.05), and Pparα (p = 0.05) mRNA in the liver than in control mice, and both FFA and triglycerides content in liver and adipose tissue weight were lower in the GCGKO mice. On the other hand, phosphorylation of hormone-sensitive lipase (HSL) in white adipose tissue did not differ between the two groups. GCGKO mice under HFD exhibited lower expression levels of Pparα and Cd36 mRNA in the duodenum as well as increased fecal cholesterol contents compared to HFD-controls. (4) Conclusions: GCGKO mice fed HFD exhibit a lesser increase in hepatic FFA and triglyceride contents and adipose tissue weight, despite reduced β-oxidation in the liver, than in control mice. Thus, the absence of PGDP prevents dietary-induced fatty liver development due to decreased lipid uptake in the intestinal tract.

Endoplasmic reticulum stress in a circumventricular organ-hypothalamic neuronal circuit alters hepatic glucose and lipid metabolism during obesity

Non-alcoholic fatty liver disease (NAFLD) is a leading cause of chronic hepatic disorders and is associated with metabolic conditions such type 2 diabetes. Accumulating evidence points to endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) in the subfornical organ (SFO), a circumventricular nucleus situated outside of the blood-brain-barrier, as a major contributor to NAFLD development during obesity. We recently reported that ER stress in SFO neurons that project to the hypothalamic paraventricular nucleus (PVN, SFO→PVN neurons) drives liver triglyceride accumulation during obesity. However, the mechanism by which ER stress in this neural network mediates obesity-related hepatic steatosis remains unknown. Elevations in hepatic gluconeogenesis, lipogenesis, and free fatty acid uptake are all associated with the development of fatty liver. Based on this, we hypothesized that ER stress in SFO→PVN neurons may contribute to NAFLD through alterations in hepatic glucose/lipid metabolism during obesity. To investigate this, we used an intersectional viral strategy to selectively inhibit ER stress in SFO→PVN neurons in C57Bl/6J male mice that were fed a high-fat diet (HFD, 60% kCal fat) for 7 wks (n=4-5/group) and then underwent selective PVN targeting of a retrogradely transported Cre-recombinase virus (CAV2-Cre-GFP; CAV2-GFP served as a control). Concurrently, a Cre inducible vector to overexpress the ER chaperone glucose-regulated peptide 78 (GRP78; AAV-FLEX-GRP78-mStrawberry) was targeted to the SFO. This approach results in the overexpression of GRP78 specifically in SFO→PVN neurons, which has been established as an effective means of reducing ER stress. Four weeks following selective inhibition of SFO→PVN neuronal ER stress, body weight (46±2 vs 43±1 g, CAV2-GFP vs CAV2-Cre, P=0.26), food intake, and adipose mass were not different between groups. However, diminishing UPR activation in this circumventricular-hypothalamic circuit resulted in a reduction in hepatomegaly (1.8±0.1 vs 1.5±0.1 g, CAV2-GFP vs CAV2-Cre, P=0.08), hepatic triglyceride levels (4.3±0.6 vs 2.3±0.4 mM, CAV2-GFP vs CAV2-Cre, p&lt;0.05), and plasma glucose (198±12 vs 168±8 mg/dL, CAV2-GFP vs CAV2-Cre, P=0.06). Interestingly, reducing ER stress in SFO→PVN neurons was also associated with a downregulation in hepatic mRNA levels of genes involved in hepatic gluconeogenesis (e.g. G6pase: 0.29±0.04; Pepck: 0.46±0.04 fold CAV2-GFP, both p&lt;0.05), de novo lipogenesis (e.g. SREBP1: 0.65±0.1 fold CAV2-GFP, P=0.05) and free fatty acid synthesis and uptake (e.g. Fasn: 0.57±0.11 fold CAV2-GFP, P=0.09 and FATP5: 0.42±0.03, fold CAV2-GFP, p&lt;0.05). Overactivation of the liver sympathetic nerves has recently been shown to contribute to obesity-related NAFLD, and inhibition of ER stress in SFO→PVN neurons resulted in a reduction in protein levels of hepatic tyrosine hydroxylase (TH), the rate limiting enzyme in catecholamine synthesis (0.58±0.03, fold CAV2-GFP, p&lt;0.05). Notably, hepatic TH levels were significantly correlated with liver glucose/lipid metabolism-related gene expression and triglyceride content (e.g. Pepck: R2=0.57; Fasn: R2=0.80; FATP5: R2=0.77; triglycerides: R2=0.70, all p&lt;0.05). Collectively, these results suggest that during obesity, ER stress in SFO→PVN neurons may drive liver sympathetic overactivity and subsequently disrupt hepatic glucose/lipid metabolism, thus contributing to NAFLD development. R01DK117007, R01HL141393, AHA932522. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Krüppel-like factor 10 protects against metabolic dysfunction-associated steatohepatitis by regulating HNF4α-mediated metabolic pathways

BackgroundKrüppel-like factor 10 (KLF10), a zinc finger transcription factor, plays a pivotal role in modulating TGF-β-mediated cellular processes such as growth, apoptosis, and differentiation. Recent studies have implicated KLF10 in regulating lipid metabolism and glucose homeostasis. This study aimed to elucidate the precise role of hepatic KLF10 in developing metabolic dysfunction-associated steatohepatitis (MASH) in diet-induced obese mice. MethodsWe investigated hepatic KLF10 expression under metabolic stress and the effects of overexpression or ablation of hepatic KLF10 on MASH development and lipidemia. We also determined whether hepatocyte nuclear factor 4α (HNF4α) mediated the metabolic effects of KLF10. ResultsHepatic KLF10 was downregulated in MASH patients and genetically or diet-induced obese mice. AAV8-mediated overexpression of KLF10 in hepatocytes prevented Western diet-induced hypercholesterolemia and steatohepatitis, whereas inactivation of hepatocyte KLF10 aggravated Western diet-induced steatohepatitis. Mechanistically, KLF10 reduced hepatic triglyceride and free fatty acid levels by inducing lipolysis and fatty acid oxidation and inhibiting lipogenesis, and reducing hepatic cholesterol levels by promoting bile acid synthesis. KLF10 highly induced HNF4α expression by directly binding to its promoter. The beneficial effect of KLF10 on MASH development was abolished in mice lacking hepatocyte HNF4α. In addition, the inactivation of KLF10 in hepatic stellate cells exacerbated Western diet-induced liver fibrosis by activating the TGF-β/SMAD2/3 pathway. ConclusionsOur data collectively suggest that the transcription factor KLF10 plays a hepatoprotective role in MASH development by inducing HNF4α. Targeting hepatic KLF10 may offer a promising strategy for treating MASH.

Four weeks SGLT2 inhibition improves beta cell function and glucose tolerance without affecting muscle free fatty acid or glucose uptake in subjects with type 2 diabetes.

Sodium glucose co-transporter-2 (SGLT2) inhibition lowers glucose levels independently of insulin, leading to reduced insulin secretion and increased lipolysis, resulting in elevated circulating free fatty acids (FFAs). While SGLT2 inhibition improves tissue insulin sensitivity, the increase in circulating FFAs could reduce insulin sensitivity in skeletal muscle and the liver. We aimed to investigate the effects of SGLT2 inhibition on substrate utilization in skeletal muscle and the liver and to measure beta-cell function and glucose tolerance. Thirteen metformin-treated individuals with type 2 diabetes were randomized to once-daily empagliflozin 25 mg or placebo for 4 weeks in a crossover design. Skeletal muscle glucose and FFA uptake together with hepatic tissue FFA uptake were measured using [18F]FDG positron emission tomography/computed tomography (PET/CT) and [11C]palmitate PET/CT. Insulin secretion and action were estimated using the oral minimal model. Empagliflozin did not affect glucose (0.73 ± 0.30 vs. 1.16 ± 0.64, μmol/g/min p = 0.11) or FFA (0.60 ± 0.30 vs. 0.56 ± 0.3, μmol/g/min p = 0.54) uptake in skeletal muscle. FFA uptake in the liver (21.2 ± 10.1 vs. 19 ± 8.8, μmol/100 ml/min p = 0.32) was unaffected. Empagliflozin increased total beta-cell responsivity (20 ± 8 vs. 14 ± 9, 10-9min-1, p < 0.01) and glucose effectiveness (2.6 × 10-2 ± 0.3 × 10-2 vs. 2.4 × 10-2 ± 0.3 × 10-2, dL/kg/min, p = 0.02). Despite improved beta-cell function and glucose tolerance, empagliflozin does not appear to affect skeletal muscle FFA or glucose uptake.

6,7-Dimethoxycoumarin, Gardenoside and Rhein combination improves non-alcoholic fatty liver disease in rats

Ethnopharmacological relevanceThis study explores the potential therapeutic benefits of using a three-component DGR (composed of specific compounds) to target the NLRP3 inflammasome in the context of non-alcoholic fatty liver disease (NAFLD). Aim of the studyTo assess the impact of a three-component DGR on NAFLD, specifically examining its effects on liver lipid accumulation, inflammation, and the diversity of intestinal microbial communities. MethodsNAFLD was induced in 8-week-old Sprague Dawley rats by feeding them a high-fat emulsion diet every morning for 8 consecutive weeks. Oral administration of DGR or its constituent equivalents in the afternoon. The pharmacological effects of DGR were evaluated using H&E, ORO and ELISA methods to determine the changes in serum and liver tissue indexes of rat-models. Immunohistochemical staining and Western blot were used to assess the interaction between DGR, NLRP3 and IL-1β. ResultsThe induction of NAFLD resulted in elevated hepatic triglycerides (TG), total cholesterol (TC), and free fatty acids (FFA). However, these alterations were ameliorated upon administration of DGR. It is noteworthy that DGR exhibited superior efficacy in comparison to its constituent compounds, manifesting augmented antioxidant activity, diminished hepatic damage, and the attenuation of pro-inflammatory factors. Both DGR and its individual monomeric constituents exhibited the capacity to attenuate the activation of the NLRP3 inflammasome in the liver, leading to an amelioration of the pathological characteristics associated with NAFLD. An analysis of the intestinal flora unveiled an elevated abundance of p_Firmicutes (1.1-fold), p_Cyanobacteria (5.76-fold), and p_Verrucomicrobia (5.2-fold), accompanied by a heightened p_Firmicutes to p_Bacteroidetes ratio (5.49-fold). ConclusionsIn the non-alcoholic fatty liver disease (NAFLD) rat model, the concurrent administration of three-component DGR effectively regulated lipid deposition, suppressed liver inflammation, and restored balance in the intestinal flora, thereby improving NAFLD pathology. These findings propose a promising therapeutic strategy for NAFLD, centered on inhibiting the NLRP3 inflammasome through the use of the three-component DGR.

Targeted Delivery of Celastrol via Chondroitin Sulfate Derived Hybrid Micelles for Alleviating Symptoms in Nonalcoholic Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) is caused by an accumulation of excess fat in the liver leading to oxidative stress and liver cell injury, as well as overproduction of inflammatory cytokines. CD44 has been identified as a potential therapeutic target in the development of NAFLD to nonalcoholic steatohepatitis. Here, chondroitin sulfate (CS) is selected to construct a CD44-targeted delivery system for the treatment of NAFLD. Specifically, two CS-derived amphiphilic materials including CS conjugated with either 4-aminophenylboronic acid pinacol ester (CS-PBE) or phenformin (CS-PFM) were synthesized, respectively. The presence of PBE moieties on CS-PBE rendered the vehicle with enhanced loading capacity and scavenging potential against reactive oxygen species, while the presence of guanidine moieties on CS-PFM enhanced the internalization of vehicles in the differentiated hepatocytes. Next, celastrol (CLT) was encapsulated in the hybrid micelle to afford CS-Hybrid/CLT, which demonstrates sufficient stability, enhanced cellular uptake efficiencies in differentiated HepG2 cells, and therapeutic potential to alleviate lipid accumulation in differentiated HepG2 cells. In a high-fat-diet-induced NAFLD rat model, CS-Hybrid/CLT micelles demonstrated the capacity to dramatically decrease hepatic lipid accumulation and free fatty acid levels with greatly improved pathologic liver histology and downregulated hepatic inflammation levels. These results suggest that CS-based amphiphilic micelles may offer a promising strategy to effectively deliver therapeutic cargos to the liver for the treatment of NAFLD.

GW9662 ameliorates nonalcoholic steatohepatitis by inhibiting the PPARγ/CD36 pathway and altering the gut microbiota

Background & aimsPeroxisome proliferator-activated receptors (PPARs) are currently among the most focused-on therapeutic targets for non-alcoholic steatohepatitis (NASH), although no clinical transformation has been achieved to date. In this study, we aimed to evaluate the effects of GW9662 on choline-deficient, L-amino acid-defined high-fat diet (CDAA-HFD)-induced NASH mice and reveal the mechanism underlying this effect. MethodsGW9662 (1 mg/kg) was administered in CDAA-HFD mouse model of NASH. The effect of GW9662 on hepatic lipid metabolism was investigated using liver RNA-seq and HepG2 cells induced by oleic acid and palmitic acid. In addition, 16S rRNA gene sequencing was performed to analyze the effects of GW9662 on the composition and function of the fecal microbiota. ResultsGW9662 improved the CDAA-HFD caused elevation in the levels of ALT, AST, hepatic free fatty acids and triglycerides. The liver pathological analysis indicated that GW9662 alleviated the hepatic steatosis and fibrosis. The NAFLD activity score and RNA-Seq revealed that GW9662 mainly regulated the fatty acids transport and lipid synthesis by inhibiting PPARγ, CD36, FABP1, FASN, and SCD1, and through the up-regulation of PPARα. Moreover, GW9662 reduced the epididymal fat weight. GW9662 reversed the gut microbiota disorder by increasing the abundance of the beneficial bacteria Dubosiella and Lactobacillus and decreasing the abundance of harmful bacteria Lachnospiraceae_NK4A136_group, Helicobacteraceae, Desulfovibriaceae, and Rickenaceae. ConclusionsGW9662 ameliorated lipid metabolism by inhibiting the PPARγ/CD36 pathway and altering the composition of the gut microbiota in NASH mice. Therefore, the PPARγ antagonist GW9662 deserves more attention as a potential therapeutic agent for NASH.

OR15-05 Maternal Obesogenic Diet Exposure Leads To Transgenerational Worsening Of Offspring NAFLD In Male Mice

Abstract Disclosure: H. Hinrichs: None. S.J. Ballentine: None. M.D. Thompson: None. Background: The Developmental Origins of Health and Disease (DOHaD) hypothesis states that development of chronic disease is impacted by early life or in utero exposures. Recent studies have found that exposure to maternal obesity/obesogenic diet increases the susceptibility of offspring to non-alcoholic fatty liver disease (NAFLD). We have shown that maternal obesogenic diet exposure (MODE) in mice leads to worse NAFLD progression to fibrosis in first generation offspring with associated changes in the microbiome. Evidence indicates that some developmentally programmed phenotypes are passed transgenerationally or to the third generation of offspring. The goal of the current study was to evaluate if MODE-induced programming of worse NAFLD progression is passed transgenerationally. Methods: F0 Female mice were fed chow (CON) or high fat-fructose-cholesterol (HFFC) diet for 6 weeks and bred with lean males. F1 and F2 females were fed chow diet and mated with chow-fed males to yield an F3 generation where only the F0 female was fed HFFC diet. F3 male offspring were weaned to HFFC diet for 7 weeks to induce progressive NAFLD. Liver was collected for histopathologic analysis. NAFLD activity scoring (NAS) was performed by a pathologist blinded to group. Results: F3 HFFC offspring had decreased liver weight and liver weight/body weight ratio compared to F3 CON offspring. F3 HFFC offspring had increased hepatic free fatty acids, but no difference in hepatic triglycerides and cholesterol. Mac-2 and CD45 staining was increased in F3 HFFC offspring. Sirius red staining for collagen was also increased in F3 HFFC offspring. NAS scoring confirmed histologic finding showing an increased frequency of higher inflammation and total NAS scores in F3 HFFC offspring. Fibrosis scores were also higher in F3 HFFC offspring. Conclusions: MODE leads to transgenerational transmission of worse NAFLD progression in male offspring. This suggests a role for an epigenetic mechanism involved in developmental programming of NAFLD. Future studies will focus on the mechanisms of this transgenerational event. Presentation: Friday, June 16, 2023

Novel approach using [18F]FTHA-PET and de novo synthesized VLDL for assessment of FFA metabolism in a rat model of diet induced NAFLD

The worldwide prevalence of Non-alcoholic Fatty Liver Disease (NAFLD) raises concerns about associated risk factors, such as obesity and type 2 Diabetes Mellitus, for leading causes of disability and death. Besides Magnetic Resonance Imaging (MRI) and Spectroscopy (MRS), functional imaging with Positron Emission Tomography (PET) could contribute to a deeper understanding of the pathophysiology of NAFLD. Here we describe a novel approach using the PET tracer [18F]FTHA, which is an analog of long-chain free fatty acids (FFA) and is taken up by tissues to enter mitochondria or to be incorporated into complex lipids for further export as very-low-density lipoprotein (VLDL). Male Sprague Dawley rats, after 6 weeks on a high-fat diet (HFD), were used as a model of diet induced NAFLD, while a standard diet (SD) served as a control group. Liver fat was estimated by MR spectroscopy at a 9.4T system for phenotyping. To measure hepatic FFA uptake, rats underwent 60min dynamic [18F]FTHA-PET scans after unrestricted access to food (HFD: n=6; SD: n=6) or overnight (≤16h) fasting (HFD: n=6; SD: n=5). FFA removal was assessed from incorporated 18F-residual in de novo synthesized VLDL out of plasma. MRS of the liver confirmed the presence of NAFLD (>5.6% fat). Under non-fasting conditions, hepatic [18F]FTHA uptake was significantly increased in NAFLD: SUVmean (p=0.03) within [0; 60] min interval, SUVmean (p=0.01) and SUVmax (p=0.03) within [30; 60] min interval. SUVs for hepatic uptake under fasting conditions were not significantly different between the groups. Analysis of FFA removal demonstrated elevated values of 18F-residue in the VLDL plasma fraction of the healthy group compared to the NAFLD (p=0.0569). Our novel approach for assessing FFA metabolism using [18F]FTHA demonstrated differences in the hepatic FFA uptake and FFA incorporation into VLDL between healthy and NAFLD rats. [18F]FTHA-PET could be used to study metabolic disturbances involved in the progression of NAFLD.

Effects of Individual Circulating FFAs on Plasma and Hepatic FFA Epoxides, Diols, and Epoxide-Diol Ratios as Indices of Soluble Epoxide Hydrolase Activity.

Oxylipins, oxidation products of unsaturated free fatty acids (FFAs), are involved in various cellular signaling systems. Among these oxylipins, FFA epoxides are associated with beneficial effects in metabolic and cardiovascular health. FFA epoxides are metabolized to diols, which are usually biologically less active, by soluble epoxide hydrolase (sEH). Plasma epoxide-diol ratios have been used as indirect measures of sEH activity. This study was designed to examine the effects of acute elevation of individual plasma FFAs on a variety of oxylipins, particularly epoxides, diols, and their ratios. We tested if FFA epoxide-diol ratios are altered by circulating FFA levels (i.e., substrate availability) independent of sEH activity. Wistar rats received a constant intravenous infusion of olive (70% oleic acid (OA)), safflower seed (72% linoleic acid (LA)), and fish oils (rich in ω-3 FFAs) as emulsions to selectively raise OA, LA, and ω-3 FFAs (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)), respectively. As expected, olive, safflower seed, and fish oil infusions selectively raised plasma OA (57%), LA (87%), EPA (70%), and DHA (54%), respectively (p < 0.05 for all). Raising plasma FFAs exerted substrate effects to increase hepatic and plasma epoxide and diol levels. These increases in epoxides and diols occurred to similar extents, resulting in no significant changes in epoxide-diol ratios. These data suggest that epoxide-diol ratios, often used as indices of sEH activity, are not affected by substrate availability or altered plasma FFA levels and that epoxide-diol ratios may be used to compare sEH activity between conditions of different circulating FFA levels.

1571-P: Plasma FGF5 Concentration Correlates Better with Hepatic Steatosis, Blood Glucose, and Specific Plasma Free Fatty Acids than with Other Tissue Fat Accumulation

A few studies reported an association between fibroblast growth factor-5 (FGF5) and NAFLD. We aimed to elucidate the physiologic implication of FGF5 in NAFLD and obesity. A total of 180 subjects [(24 healthy controls and 156 patients with biopsy-proven NAFLD and/or hepatic fat content (HFC) 5% or more on MRI-PDFF] were included to assess association between HFC and various metabolic factors including body fat and plasma levels of glucose, insulin, FGF5, FGF21, oxyntomodulin, incretins, and some free fatty acids (FFAs). Additionally, we analysed a subgroup of obese patients who would undergo laparoscopic sleeve gastrectomy (LSG) (n=50) to see correlation between changes in metabolic variables related to body weight (BW) and HFC before and 6 months after surgery. Plasma FGF5 correlated better with blood glucose and HFC than with total body fat, HOMR-IR, and visceral fat. In relation to plasma FFAs, both FGF5 and HFC together showed a positive correlation with plasma FFAs such as palmitic acid, linolenic acid, and arachidonic acid, but had an inverse correlation with nervonic acid, docosanoic acid, tetracosanoic acid, and hexacosanoic acid. FGF5 level showed an independent association with blood glucose and MRI-PDFF after adjusting for multiple factors. After LSG, BW decreased by an average of 24.6%, while HFC decreased from 19.5% ± 9.1% to 5.7 ± 2.9%, p &amp;lt;0.01). Plasma FGF5 also decreased after LSG (1625.0 ± 656.8 pg/ml vs. 966.8 ± 339.9 pg/ml, p &amp;lt;0.01). The amount of plasma FGF5 change showed a significant correlation with changes in HFC and blood glucose. In conclusion, our results showed that plasma FGF5 level correlated well with HFC, blood glucose, and specific plasma FFAs and also decreased with the improvement of hepatic steatosis after bariatric surgery. Further researches on the causal relationship between FGF5, glucose and lipid metabolism, and NAFLD are needed. Disclosure D.Lee: None. I.Park: None. Funding National Research Foundation of Korea (2021R1A5A2030333, 2019R1I1A2A02062305)

Ability of high fat diet to induce liver pathology correlates with the level of linoleic acid and Vitamin E in the diet.

Increased uptake of fat, such as through the ingestion of high fat diet (HFD), can lead to fatty liver diseases and metabolic syndrome. It is not clear whether certain fatty acids may be more pathogenic than others to the liver. Linoleic acid (LA) is the most abundant polyunsaturated fatty acid in the Western diet and its excessive consumption can lead to increased lipid peroxidation. We hypothesized that a high level of LA in HFD will contribute significantly to the hepatic steatosis and injury, whereas vitamin E (VIT-E) may reverse the effects from LA by inhibiting lipid peroxidation. To test this hypothesis, we fed mice with the following diets for 20 weeks: a standard low-fat diet (CHOW), HFD with a low level of LA (LOW-LA, 1% of energy from LA), HFD with a high level of LA (HI-LA, 8% of energy from LA), or HI-LA diet with VIT-E supplement (HI-LA + VIT-E). We found that the HI-LA diet resulted in more body weight gain, larger adipocyte area, and higher serum levels of triglycerides (TG) and free fatty acids (FFA) relative to the CHOW and LOW-LA diets. In mice fed with the HI-LA diet, severer hepatic steatosis was seen with higher levels of hepatic TG and FFA. Expression of genes related to lipid metabolism was altered in the liver by HI-LA diet, including fibroblast growth factor 21 (Fgf21), cluster of differentiation 36 (Cd36), stearoyl-CoA desaturase 1 (Scd1), and acyl-CoA oxidase 1 (Acox1). Liver injury, inflammation and fibrotic response were all enhanced in mice fed with the HI-LA diet when compared with the LOW-LA diet. Notably, addition of VIT-E supplement, which restores the proper VIT-E/PUFA ratio, significantly reduced the detrimental effects of the high level of LA. Taken together, our results suggest that a high level of LA and a low ratio of VIT-E/PUFA in HFD can contribute significantly to metabolic abnormalities and hepatic injury.

Hepatic effect of subacute Fe2 O3 nanoparticles exposure in Sprague-Dawley rats by LC-MS/MS based lipidomics.

Fe2 O3 nanoparticles (Fe2 O3 NPs) are one of the components of food additives numbered E172 and have been widely used as food pigments to color sweets. Although a large number of studies have reported that Fe2 O3 NPs could induce hepatotoxicity, the pathogenesis is still unclear, especially the subacute effects on the metabolic network after oral exposure. Therefore, it is necessary to define a highly sensitive strategy to investigate the potential effects of Fe2 O3 NPs and the mechanism. In this study, an animal experiment showed that Fe2 O3 NPs had no obvious toxic effects on body weight, histopathology and oxide stress. In order to further investigate the potential effects of Fe2 O3 NPs in vivo, a more sensitive LC-MS/MS-based lipidomic study was performed. The results of multivariate statistical analysis and western blot analysis showed that Fe2 O3 NP exposure significantly affects the hepatic glycerophospholipid metabolism, decreasing triacylglycerol, diglyceride, lysophosphatidylethanolamine and free fatty acids, and increasing phosphatidylcholine, lysophosphatidylinositol and coenzyme Q9. These data provide further insight into the hepatic subacute effects of Fe2 O3 NPs obtained by conventional toxicology methods.

Exercise increases myocardial free fatty acid oxidation in subjects with metabolic dysfunction-associated fatty liver disease

Background and aimsMetabolic dysfunction-associated fatty liver disease (MAFLD) is associated with dyslipidemia and may promote cardiac lipotoxicity. Myocardial free fatty acids (FFA) oxidation (MOFFA) is normal in pre-diabetes, but reduced in heart failure. We hypothesized that during exercise MOFFA, very low-density lipoprotein triglycerides (VLDL-TG) secretion, hepatic FFA utilization, and lactate production differ among obese subjects with and without MAFLD. MethodsNine obese subjects with MAFLD and 8 matched subjects without MAFLD (Control) without a history of heart failure and cardiovascular disease were compared before and after 90-min exercise at 50% Peak oxygen consumption. Basal and exercise induced cardiac and hepatic FFA oxidation, uptake and re-esterification and VLDL-TG secretion were measured using [11C]palmitate positron-emission tomography and [1–14C]VLDL-TG. ResultsIn the heart, increased MOFFA was observed after exercise in MAFLD, whereas MOFFA decreased in Control (basal vs exercise, MAFLD: 4.1 (0.8) vs 4.8 (0.8) μmol·100 ml−1 min−1; Control: 4.9 (1.8) vs 4.0 (1.1); μmol·100 ml−1 min−1, mean (SD), p < 0.048). Hepatic FFA fluxes were significantly lower in MAFLD than Control and increased ≈ two-fold in both groups. VLDL-TG secretion was 50% greater in MAFLD at rest and similarly suppressed during exercise. Plasma lactate increased significantly less in MAFLD than Control during exercise. ConclusionsUsing robust tracer-techniques we found that obese subjects with MAFLD do not downregulate MOFFA during exercise compared to Control, possibly due to diminished lactate supply. Hepatic FFA fluxes are significantly lower in MAFLD than Control, but increase similarly with exercise. VLDL-TG export remains greater in MAFLD compared to Control. Basal and post-exercise myocardial and hepatic FFA, VLDL-TG and lactate metabolism is abnormal in subjects with MAFLD compared to Control.

Comparison of protective effects of hesperetin and pectolinarigenin on high-fat diet-induced hyperlipidemia and hepatic steatosis in Golden Syrian hamsters.

A comparative study was conducted to determine whether hesperetin and pectolinarigenin could lower total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL), and high-density lipoprotein cholesterol (HDL) in a high-fat diet (HFD)-induced high lipid model in Golden Syrian hamsters. 48 Golden Syrian hamsters (8 weeks old) were fed with a HFD for 15 days. HFD induced significant increases in plasma TC, TG, LDL, and HDL. Then, these high lipid hamsters were divided into four groups and were administered with 0.5% sodium carboxymethyl cellulose (CMC-Na), hesperetin (100 mg/kg/day), pectolinarigenin (100 mg/kg/day) or atorvastatin (1.0 mg/kg/day), for 7 weeks. It was found that pectolinarigenin treatment resulted in significant reductions in body weight, adiposity index, serum levels of TC, TG and hepatic TC, TG and free fatty acid compared to those in control hamsters with hyperlipidemia (P<0.05). However, hesperetin treatment only caused reductions in plasma TC and hepatic TG levels. Besides, the hamsters treated with pectolinarigenin showed a relatively normal hepatic architecture compared to the hepatic steatosis shown in the control group. Moreover, the expressions of fatty-acid synthase (Fasn) and solute carrier family 27 member 1 (Slc27a1) involved in lipid biosynthesis, were suppressed in the pectolinarigenin-treated groups, and the expression of carnitine palmitoyltransferase 1A (Cpt1a) involved in fatty acid oxidation was increased in the pectolinarigenin-treated group. Taken together, these results suggest pectolinarigenin exerts stronger protective effects against hyperlipidemia and hepatic steatosis than hesperetin, which may involve the inhibition of lipid uptake and biosynthesis.

The effects of intermittent hypoxia on hepatic expression of fatty acid translocase CD36 in lean and diet-induced obese mice

BackgroundBoth obstructive sleep apnea (OSA) and non-alcoholic fatty liver disease (NAFLD) are prevalent within obese individuals. We aimed to investigate the effects of intermittent hypoxia (IH), a clinical feature of OSA, on hepatic expression of fatty acid translocase (CD36) in relation to liver injury in lean and diet-induced obese mice. MethodsFour-week-old male C57BL/6J mice were randomized to standard diet (SD) or high fat (HF) diet groups. At 13-week-old, all mice were exposed to either air or IH (IH30; thirty hypoxic episodes per hour) for four weeks. We assessed liver injury through lipid profile, oxidative and inflammatory stress, histological scoring and hepatic CD36 expression. ResultsIn lean mice, IH elevated serum and hepatic triglyceride and free fatty acid (FFA) levels, in line with upregulation of hepatic CD36 expression and myeloperoxidase (MPO)-positive cells in support of inflammatory infiltrates along with increase in serum malondialdehyde (MDA), C-X-C motif chemokine ligand 1(CXCL-1) and monocyte chemoattractant protein-1 (MCP-1). In diet-induced obese mice, an increase in hepatic alanine transaminase (ALT) activity, serum and hepatic levels of lipid parameters and inflammatory markers, serum MDA level, hepatic expressions of CD36 and α-smooth muscle actin (α-SMA), and MPO-positive cells was observed. IH potentiated hepatic ALT activity, serum CXCL-1 and hepatic interleukin-6 (IL-6), in line with inflammatory infiltrates, but paradoxically, reduced hepatic FFA level and hepatic CD36 expression, compared to obese mice without IH exposure. However, IH further augmented diet-induced liver steatosis and fibrosis as shown by histological scores. ConclusionThis study contributes to support that IH featuring OSA may lead to liver injury via differential regulation of hepatic CD36 expression in lean and diet-induced obese mice.

Differences in lipid metabolism in acquired versus preexisting glucose intolerance during gestation: role of free fatty acids and sphingosine-1-phosphate

BackgroundThe prevalence of gestational diabetes mellitus (GDM) is increasing worldwide. There is increasing evidence that GDM is a heterogeneous disease with different subtypes. An important question in this context is whether impaired glucose tolerance (IGT), which is a typical feature of the disease, may already be present before pregnancy and manifestation of the disease. The latter type resembles in its clinical manifestation prediabetes that has not yet manifested as type 2 diabetes (T2DM). Altered lipid metabolism plays a crucial role in the disorder's pathophysiology. The aim was to investigate the role of lipids which are relevant in diabetes-like phenotypes in these both models with different time of initial onset of IGT.MethodsTwo rodent models reflecting different characteristics of human GDM were used to characterize changes in lipid metabolism occurring during gestation. Since the New Zealand obese (NZO)-mice already exhibit IGT before and during gestation, they served as a subtype model for GDM with preexisting IGT (preIGT) and were compared with C57BL/6 N mice with transient IGT acquired during gestation (aqIGT). While the latter model does not develop manifest diabetes even under metabolic stress conditions, the NZO mouse is prone to severe disease progression later in life. Metabolically healthy Naval Medical Research Institute (NMRI) mice served as controls.ResultsIn contrast to the aqIGT model, preIGT mice showed hyperlipidemia during gestation with elevated free fatty acids (FFA), triglycerides (TG), and increased atherogenic index. Interestingly, sphingomyelin (SM) concentrations in the liver decreased during gestation concomitantly with an increase in the sphingosine-1-phosphate (S1P) concentration in plasma. Further, preIGT mice showed impaired hepatic weight adjustment and alterations in hepatic FFA metabolism during gestation. This was accompanied by decreased expression of peroxisome proliferator-activated receptor alpha (PPARα) and lack of translocation of fatty acid translocase (FAT/CD36) to the hepatocellular plasma membrane.ConclusionThe preIGT model showed impaired lipid metabolism both in plasma and liver, as well as features of insulin resistance consistent with increased S1P concentrations, and in these characteristics, the preIGT model differs from the common GDM subtype with aqIGT. Thus, concomitantly elevated plasma FFA and S1P concentrations, in addition to general shifts in sphingolipid fractions, could be an interesting signal that the metabolic disorder existed before gestation and that future pregnancies require more intensive monitoring to avoid complications.Graphical This graphical abstract was created with BioRender.com.

Whole Eggs Improve High-Fat Diet-Induced Disorders of the Hepatic Lipid Profile and Gut Microbiota in Mice

The relationship between egg consumption and disturbances of hepatic lipid metabolism remains controversial. Recent studies indicate that egg consumption showed favorable effects on dyslipidemia, while underlying mechanisms remain largely undefined. In this study, the high-fat diet was fed to C57BL/6J mice to induce lipid metabolism disorders, aiming to disclose the effects of the whole eggs (WEs) and yolk-free egg substitute (YFES) on the hepatic lipid profile and gut microbiota. The daily WE/YFES dose for mice was 7.55 mg/g of mouse weight. The results showed that WE inhibited body weight gain and significantly decreased hepatic triglyceride (TG) by 49.6% while showing insignificant effects on the total cholesterol in the liver. Both WE and YFES alleviated hepatic oxidative stress by decreasing hepatic levels of malondialdehyde. Lipidomic analysis revealed that diacylglycerol, lysophosphatidylcholines, ceramide, and free fatty acids were the major lipid species upregulated by WE. Moreover, WE showed beneficial effects on gut microbiota by increasing the abundance of Bacteroidota while decreasing Proteobacteria levels. The correlation analysis showed that Lactobacillales and Bacteroides displayed a significant negative correlation with hepatic TG and free fatty acids (18:4), while positively correlated with phosphatidylethanolamine biomarkers. These results evidenced that WE was more effective than YFES in improving hepatic lipid profiles and regulating the gut microbiota, resulting in increased levels of probiotics and inhibited TG accumulation and oxidative stress through the gut–liver axis. Therefore, it could be concluded that the consumption of WE instead of YFES would be helpful in relieving hepatic dyslipidemia in the short term.

In Vivo Two-Photon Imaging Analysis of Dynamic Degradation of Hepatic Lipid Droplets in MS-275-Treated Mouse Liver.

The accumulation of hepatic lipid droplets (LDs) is a hallmark of non-alcoholic fatty liver disease (NAFLD). Appropriate degradation of hepatic LDs and oxidation of complete free fatty acids (FFAs) are important for preventing the development of NAFLD. Histone deacetylase (HDAC) is involved in the impaired lipid metabolism seen in high-fat diet (HFD)-induced obese mice. Here, we evaluated the effect of MS-275, an inhibitor of HDAC1/3, on the degradation of hepatic LDs and FFA oxidation in HFD-induced NAFLD mice. To assess the dynamic degradation of hepatic LDs and FFA oxidation in fatty livers of MS-275-treated HFD C57BL/6J mice, an intravital two-photon imaging system was used and biochemical analysis was performed. The MS-275 improved hepatic metabolic alterations in HFD-induced fatty liver by increasing the dynamic degradation of hepatic LDs and the interaction between LDs and lysozyme in the fatty liver. Numerous peri-droplet mitochondria, lipolysis, and lipophagy were observed in the MS-275-treated mouse fatty liver. Biochemical analysis revealed that the lipolysis and autophagy pathways were activated in MS-275 treated mouse liver. In addition, MS-275 reduced the de novo lipogenesis, but increased the mitochondrial oxidation and the expression levels of oxidation-related genes, such as PPARa, MCAD, CPT1b, and FGF21. Taken together, these results suggest that MS-275 stimulates the degradation of hepatic LDs and mitochondrial free fatty acid oxidation, thus protecting against HFD-induced NAFLD.