APOE genotype dictates lipidomic signatures in primary human hepatocytes.

Apolipoprotein E (APOE) genetic variants are most notably known for their divergent impact on the risk of developing Alzheimer's disease. While APOE genotype has been consistently shown to modulate lipid metabolism in a variety of cellular contexts, the effect of APOE alleles on the lipidome in hepatocytes is unknown. In this study, we investigated the contribution of APOE alleles to lipidomic profiles of donor-derived primary human hepatocytes from 77 subjects. Lipidomic data obtained by liquid chromatography-mass spectrometry were analyzed across ε2/ε3, ε3/ε3, and ε3/ε4 genotypes to reveal how APOE modulates lipid relative levels over age and between groups. Hepatic APOE concentration, measured by ELISA, was assessed for correlation with lipid abundance in subjects grouped as per APOE genotype and sex. APOE genotype-specific differential lipidomic signatures associated with age for multiple lipid classes but did not differ between sexes. Compared to ε2/ε3, ε3/ε4 hepatocytes had higher abundance of acylcarnitines (AC) and acylphosphatidylglycerol (AcylPG) as a class, as well as higher medium and long-chain ACs, AcylPG, phosphatidylglycerol (PG), bis(monoacylglycerol)phosphate (BMP), monoacylglycerol (MG) and diacylglycerol (DG) species. The ε3/ε4 hepatocytes also exhibited a higher abundance of medium and long-chain ACs compared to the ε3/ε3 hepatocytes. Only in the ε3/ε4 hepatocytes, APOE concentration was lower and showed a negative correlation with BMP levels, specifically in females. APOE genotype dictates a differential lipidome in primary human hepatocytes. The lipids involved suggest mitochondrial dysfunction with accompanying alterations in neutral lipid storage, reflective of a general disturbance of free fatty acid metabolism in human hepatocytes with the ε4 allele.

Multi-omics analysis reveals hepatic lipid metabolism profiles and serum lipid biomarkers upon indoor relevant VOC exposure.

As a widespread indoor air pollutant, volatile organic compound (VOC) caused various adverse health effects, especial the damage to liver, which has become a growing public concern. However, the current toxic data are intrinsically restricted in the single or major VOC species. Limited knowledge is available regarding toxic effects, biomarkers and underlying mechanisms of real indoor VOC-caused liver damage. Herein, an indoor relevant VOC exposure model was established to evaluate the hepatic adverse outcomes. Machine learning and multi-omics approaches, including liver lipidomic, serum lipidomic and liver transcriptomic, were utilized to uncover the characteristics of liver damage, serum lipid biomarkers, and involved mechanism stimulated by VOC exposure. The result showed that indoor relevant VOC led to the abnormal hepatic lipid metabolism, mainly manifested as a decrease in triacylglycerol (TG) and its precursor substance diacylglycerol (DG), which could be contributed to the occurrence of hepatic adverse outcomes. In terms of serum lipid biomarkers, five lipid biomarkers in serum were uncovered using machine learning to reflect the hepatic lipid disorders induced by VOC. Multi-omics approaches revealed that the upregulated Dgkq disturbed the interconversion of DG and phosphatidic acid (PA), leading to a TG downregulation. The in-depth analysis revealed that VOC down-regulated FoxO transcription factor, contributing to the upregulation of Dgkq. Hence, this study can provide valuable insights into the understanding of liver damage caused by indoor relevant VOC exposure model VOC exposure, from the perspective of multi-omics analysis.

Dietary raffinose ameliorates hepatic lipid accumulation induced by cholic acid via modulation of enterohepatic bile acid circulation in rats.

Enterohepatic circulation of 12α-hydroxylated (12αOH) bile acid (BA) is enhanced depending on the energy intake in high-fat diet-fed rats. Such BA metabolism can be reproduced using a diet supplemented with cholic acid (CA), which also induces simple steatosis, without inflammation and fibrosis, accompanied by some other symptoms that are frequently observed in the condition of non-alcoholic fatty liver in rats. We investigated whether supplementation of the diet with raffinose (Raf) improves hepatic lipid accumulation induced by the CA-fed condition in rats. After acclimation to the AIN-93-based control diet, male Wistar rats were fed diets supplemented with a combination of Raf (30 g/kg diet) and/or CA (0·5 g/kg diet) for 4 weeks. Dietary Raf normalised hepatic TAG levels (two-way ANOVA P < 0·001 for CA, P = 0·02 for Raf and P = 0·004 for interaction) in the CA-supplemented diet-fed rats. Dietary Raf supplementation reduced hepatic 12αOH BA concentration (two-way ANOVA P < 0·001 for CA, P = 0·003 for Raf and P = 0·03 for interaction). The concentration of 12αOH BA was reduced in the aortic and portal plasma. Raf supplementation increased acetic acid concentration in the caecal contents (two-way ANOVA P = 0·001 as a main effect). Multiple regression analysis revealed that concentrations of aortic 12αOH BA and caecal acetic acid could serve as predictors of hepatic TAG concentration (R2 = 0·55, P < 0·001). However, Raf did not decrease the secondary 12αOH BA concentration in the caecal contents as well as the transaminase activity in the CA diet-fed rats. These results imply that dietary Raf normalises hepatic lipid accumulation via suppression of enterohepatic 12αOH BA circulation.

Serum Afamin a Novel Marker of Increased Hepatic Lipid Content.

Aim: Afamin is a liver-produced glycoprotein, a potential early marker of metabolic syndrome. Here we investigated regulation of afamin in a course of the metabolic disease development and in response to 3-month exercise intervention. Methods: We measured whole-body insulin sensitivity (euglycemic hyperinsulinemic clamp), glucose tolerance, abdominal adiposity, hepatic lipid content (magnetic resonance imaging/spectroscopy), habitual physical activity (accelerometers) and serum afamin (enzyme-linked immunosorbent assay) in 71 middle-aged men with obesity, prediabetes and newly diagnosed type 2 diabetes. Effects of 3-month exercise were investigated in 22 overweight-to-obese middle-aged individuals (16M/6F). Results: Prediabetes and type 2 diabetes, but not obesity, were associated with increased serum afamin (p<0.001). Afamin correlated positively with hepatic lipids, fatty liver index and liver damage markers; with parameters of adiposity (waist circumference, %body fat, adipocyte diameter) and insulin resistance (fasting insulin, C-peptide, HOMA-IR; p<0.001 all). Moreover, afamin negatively correlated with whole-body insulin sensitivity (M-value/Insulin, p<0.001). Hepatic lipids and fasting insulinemia were the most important predictors of serum afamin, explaining >63% of its variability. Exercise-related changes in afamin were paralleled by reciprocal changes in insulinemia, insulin resistance and visceral adiposity. No significant change in hepatic lipid content was observed. Conclusions: Subjects with prediabetes and type 2 diabetes had the highest serum afamin levels. Afamin was more tightly related to hepatic lipid accumulation, liver damage and insulin resistance than to obesity.

Effects of dietary fibres on gut microbial metabolites and liver lipid metabolism in growing pigs.

This study was conducted to investigate the effects of dietary supplementation with wheat bran fibre, inulin and their combination on growth performance, short-chain fatty acids (SCFAs) production in caecum and colon and liver lipid metabolism in growing pigs. A total of 48 Duroc × Landrace × Yorkshire cross-bred growing pigs (73 ± 2 days of age; 24.37 ± 2.86 kg) were allocated to four groups randomly, each group consisting of six pens with two pigs each. The pigs were fed a control diet (CON), a diet containing 2% wheat bran fibre (WB), a diet containing 2% inulin (IN), and a diet containing both of 1% wheat bran fibre and 1% inulin (MIX), respectively. The trial lasted for 28 days. The results showed that MIX fed pigs had a higher percentage of fat in the liver than those fed the CON (p < .05). IN, WB or MIX feeding decreased the concentrations of acetate and total SCFAs in colon compared with CON (p < .01). Feeding WB or IN also decreased the colonic butyrate concentrations compared with CON (p < .01). However, the serum level of valeric acid was elevated in the IN, WB and MIX group (p < .01). MIX fed pigs tended to have lower levels of propionate in serum than the WB fed pigs (p = .098). MIX feeding enhanced the mRNA expression of lipid synthesis-related genes in liver compared with CON (p < .05). Feeding IN decreased the expression of bile acids synthesis-related genes in liver and increased mRNA expression of SCFAs transporter SLC16A1 in colon compared with CON (p < .05). In this study, these data indicated that the combined supplementation of wheat bran fibre and inulin decreased the SCFAs concentrations in the colon, enhanced the genes FAS and HNF-4α mRNA expression in liver and induced liver lipid accumulation in growing pigs.

Angiopoietin-like protein 3, an emerging cardiometabolic therapy target with systemic and cell-autonomous functions.

Angiopoietin like protein 3 (ANGPTL3) is best known for its function as an inhibitor of lipoprotein and endothelial lipases. Due to the capacity of genetic or pharmacologic ANGPTL3 suppression to markedly reduce circulating lipoproteins, and the documented cardioprotection upon such suppression, ANGPTL3 has become an emerging therapy target for which both antibody and antisense oligonucleotide (ASO) therapeutics are being clinically tested. While the antibody is relatively selective for circulating ANGPTL3, the ASO also depletes the intra-hepatocellular protein, and there is emerging evidence for cell-autonomous functions of ANGPTL3 in the liver. These include regulation of hepatocyte glucose and fatty acid uptake, insulin sensitivity, LDL/VLDL remnant uptake, VLDL assembly/secretion, polyunsaturated fatty acid (PUFA) and PUFA-derived lipid mediator content, and gene expression. In this review we elaborate on (i) why ANGPTL3 is considered one of the most promising new cardiometabolic therapy targets, and (ii) the present evidences for its intra-hepatocellular or cell-autonomous functions.

Fructose Consumption During Pregnancy Influences Milk Lipid Composition and Offspring Lipid Profiles in Guinea Pigs.

Excess dietary fructose is a major public health concern (1-4). Evidence shows increased fructose intake can cause insulin resistance, hepatic de novo lipogenesis, hypertriglyceridemia, obesity and non-alcoholic fatty liver disease (NAFLD) (5-9). However, little is known about the effects of fructose during pregnancy and its influence on offspring development and predisposition to later-life disease. To determine whether moderately increased maternal fructose intake could have health consequences on offspring, we have investigated the effects of 10% w/v fructose water intake during preconception and pregnancy. Female Dunkin Hartley guinea pigs were fed a control diet (CD) or fructose diet (FD;10% kcal from fructose) ad-libitum 60 days prior to mating and throughout gestation. Offspring were culled at weaning, day 21 (d21). Compared to CD dams, FD dams had altered glucose metabolism and increased milk free fatty acid content. Matsuda-DeFronzo insulin sensitivity index (M-ISI) from OGTT plasma showed no significant difference in whole-body insulin sensitivity between FD and CD dams 60 days post-dietary intervention and during midgestation. Fetal exposure to increased maternal fructose resulted in offspring with significantly altered serum free fatty acids at days 0, 7, 14, and 21 [including pentadecanoic acid (15:0), dma16:0, margaric acid (17:0) palmitoleic acid, total omega-7 and total saturates], increased levels of uric acid and triglycerides were also observed at d21. We have demonstrated that increased fructose intake during pregnancy can cause significant changes in maternal metabolic function and milk composition, which alters offspring metabolism. Taken together, these changes in pregnancy outcomes and feto-maternal condition may underlie their offspring's predisposition to metabolic dysfunction during later-life.

Bio-synthesized sardine oil concentrate alters the composition of hepatic lipids in rats: A lipidomic approach.

Both preventive and curative therapies have created a considerable demand for n-3 PUFAs (polyunsaturated fatty acids) from fish oil, such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, for human use. Bio-synthesized sardine oil (bioSO) concentrate containing an acylglycerols mixture with 50% n-3 PUFAs was obtained by Candida cylindracea lipase hydrolysis and subsequently used for in vivo tests in animals. Wistar rats received, by gavage, a dose of 0.2 g/kg/day of bioSO or unmodified sardine oil (unSO) or saline solution (control) for three consecutive days and the liver tissue was evaluated by a selective and sensitive lipidomic approach based on ultra-performance liquid chromatography-quadruple time-of-flight mass spectrometry (UPLC-QTOF-MSE) and gas chromatography (GC). In addition, antioxidant parameters, response of oxidative stress marker and estimated fatty acid desaturase indexes were determined. The use of bioSO led to an increase in Cer d18:1/16:0, PE-Cer d14:2/18:0 and highly unsaturated phosphatylcholines (PC 38:4, PC 40:6 and PC 42:8) in the hepatic tissue membranes. There was also an increase in DHA incorporation in animals that received bioSO in comparison with the control animals. No differences in superoxide dismutase and catalase activity levels were observed between the groups, and malondialdehyde levels and delta 5-desaturase activity were higher in animals supplemented with bioSO. These results indicate that bioSO increase the hepatic incorporation of DHA, especially those esterified as PCs, and are probably absorbed and transported more effectively than the unSO. Enzymatically hydrolyzed compounds containing antioxidants may be a viable alternative for obtaining n-3 PUFA-enriched functional lipids.

African walnuts attenuate ectopic fat accumulation and associated peroxidation and oxidative stress in monosodium glutamate-obese Wistar rats.

AIMS: African walnuts were previously shown to modulate hepatic lipid bio-accumulation in obesity. Herein, we investigated the impact of the nuts on fat accumulation in adipose and ectopic regions, and associated oxidatiive stress status in obese rats. MATERIALS AND METHODS: Whole ethanol extract (WE) of the nuts, and its liquid-liquid fractions-ethyl acetate (ET) and residue (RES) were separately administered to obese rats for 6 weeks. The normal (NC) and obese (OC) controls received normal saline and the standard control (SC), orlistat (5.14 mg/kg b.w.), during the same period. Thereafter, the animals were euthanized and the adipose, brain, kidneys and heart tissues were studied. RESULTS: The change in body weight to naso-anal length which increased by 63.52 % in OC compared to NC (p < 0.05), decreased by 57.88, 85.80 and 70.20 % in WE, ET and RES-treated groups, respectively, relative to the OC (p < 0.05). Also, adipose tissue weights were lowered upon treatment with the extracts and fractions versus OC (p < 0.05). Total lipids, phospholipids, triacylglycerol and cholesterol concentrations in the studied tissues which were higher in OC (p < 0.05) were lowered (p < 0.05) and compared favorably with SC. Further, malondialdehyde levels in the tissues were lowered upon treatment, compared to the OC (p < 0.05). Glutathione level and activities of glutathione peroxidase, superoxide dismutase and glutathione-S-transferase which were decreased (p < 0.05) in OC, were restored upon treatment with the extracts, relative to the obese control (p < 0.05). SIGNIFICANCE: African walnuts assuaged lipogenesis, oxidative stress and peroxidation in extra-hepatic tissues of obese rats, hence, may attenuate ectopic fat accumulation and its associated pathogenesis.

African Walnuts (Tetracarpidium conophorum) Modulate Hepatic Lipid Accumulation in Obesity via Reciprocal Actions on HMG-CoA Reductase and Paraoxonase.

BACKGROUND: Obesity is characterized by increased body fat and involves an imbalance between the synthesis and degradation of lipids. OBJECTIVE: The study aimed to investigate the effect of African walnuts (Tetracarpidium conophorum) on lipids storage and the regulatory enzymes of hepatic lipid metabolism in obese rats. METHODS: Nuts were extracted in ethanol (WE) and further separated to obtain the ethyl-acetate fraction (ET) and the residue (RES). These were administered orally to 3 groups of monosodium glutamate- obese rats (n = 6), respectively, for 6 weeks. Other groups in the study were: normal (NC), obese control (OC) and standard control (SC) which received orlistat. Hepatic total lipids, total phospholipids, triacylglycerol (TG), total cholesterol (TCHOL), 3-hydroxyl-3-methylglutaryl-CoA (HMG-CoA) reductase and paraoxonase were studied. RESULTS: Total lipids, TG and TCHOL which increased in OC compared to NC group, decreased. HMG-CoA reductase activity decreased in the 3 study groups relative to OC. Paraoxonase activity which decreased in OC was up-regulated, while the magnitude of hepatic cholesterol decreased from 94.32 % in OC to 52.19, 65.43 and 47.04 % with WE, ET and RES, respectively. Flavonoids, alkaloids, glycosides, tannins and saponins were detected in the nut. GC-MS analysis revealed 16, 18 and 10 volatile components in WE, ET and RES, respectively. Unsaturated fatty acids (linolenic acids: 33.33, 47.95 and 50.93 %, and α-linolenic acids: 25, 19.66 and 26.63 %) in WE, ET and RES, respectively, are the most abundant, and likely to be responsible for the observed activity. CONCLUSION: African walnuts can prevent hepatic lipid accumulation through reciprocal actions on HMG-CoA reductase and paraoxonase in obesity.

Daily cycle in hepatic lipid metabolism in obese mice, Neotomodon alstoni: Sex differences.

Disruption of circadian rhythms influences the pathogenesis of obesity, particularly with the basic regulation of food intake and metabolism. A link between metabolism and the circadian clock is the peroxisome proliferator-activated receptors (PPARs). The Neotomodon alstoni mouse, known as the "Mexican volcano mouse," may develop obesity if fed a normo-caloric diet. This manuscript documents the changes in part of the hepatic lipid homeostasis in both sexes of lean and obese N. alstoni mice, comparing the daily changes in the BMAL1 clock protein, in regulators of lipid metabolism (PGC-1α, PPARα-γ, SREBP-1c, and CPT-1α) and in free fatty acid (FFA) and hepatic triacylglyceride (TAG) metabolites in light-dark cycles. Hepatic tissue and blood were collected at 5, 10, 15, 19, and 24 h. Samples were analyzed by western blotting to determine the relative presence of protein. The results indicate that obesity affects daily changes in lipid metabolism and the BMAL1 profile in females considerably more than in males. These results suggest that the impact of obesity on lipid metabolism has important differences according to sex.

The relationship between aquaglyceroporin expression and development of fatty liver in diet-induced obesity and ob/ob mice.

Aquaporin (AQP) 7 and AQP9 are subcategorised as aquaglyceroporins which transport glycerin in addition to water. These AQPs may play a role in the homeostasis of energy metabolism. We examined the effect of AQP7, AQP9, and lipid metabolism-related gene expression in obese mice. In diet-induced obese (DIO) mice, excess lipid accumulated in the liver, which was hyperleptinemic and hyperinsulinemic. Hepatic AQP9 gene expression was significantly increased in both DIO and ob/ob mice compared to controls. The mRNA expression levels of fatty acid and triglyceride synthesis-related genes and fatty acid ß oxidation-related genes in the liver were also higher in both mouse models, suggesting that triglyceride synthesis in this organ is promoted as a result of glycerol release from adipocytes. Adipose AQP7 and AQP9 gene expressions were increased in DIO mice, but there was no difference in ob/ob mice compared to wild-type mice. In summary, adipose AQP7 and AQP9 gene expressions are increased by diet-induced obesity, indicating that this is one of the mechanisms by which lipid accumulates in response to a high fat diet, not the genetic mutation of ob/ob mice. Hepatic AQP9 gene expression was increased in both obesity model mice. AQP7 and AQP9 therefore have the potential of defining molecules for the characterisation of obesity or fatty liver and may be a target molecules for the treatment of those disease.

Effect of curcumin on hepatic heme oxygenase 1 expression in high fat diet fed rats: is there a triangular relationship?

High fat diet (HFD) is associated with oxidative stress induced fatty liver. Curcumin, an extract of Curcuma longa, has been shown to possess potent antioxidant and hypolipidemic properties. In this study, we investigated the effect of curcumin treatment on hepatic heme oxygenase-1 (HO-1) expression along with pro-oxidant-antioxidant status and lipid accumulation in rats fed an HFD. Male Sprague-Dawley rats were distributed among 4 groups: Group 1, which was fed the control diet (10% of total calories from fat); Group 2, which was fed the HFD (60% of total calories from fat); and groups 3 and 4, which received the HFD supplemented with curcumin and the control diet supplemented with curcumin (1 g/kg diet; w/w), respectively, for 16 weeks. HFD caused increases in hepatic lipid levels, production of reactive oxygen species, and lipid peroxidation. Further, HO-1 expression was significantly decreased. Histopathological examination showed hepatic fat accumulation and slight fibrotic changes. Curcumin treatment reduced hepatic lipids and oxidative stress parameters, and HO-1 expression was significantly increased. These findings suggest that increased HO-1 expression, along with suppressed oxidative stress as well as reduced hepatic fat accumulation and fibrotic changes, contribute to the beneficial effects of curcumin in attenuating the pathogenesis of fatty liver induced metabolic diseases.

In vivo relaxation behavior of liver compounds at 7 Tesla, measured by single-voxel proton MR spectroscopy.

PURPOSE: To assess the proton T1 and T2 relaxation of in vivo hepatic water, choline and lipid resonances with possible J-coupling behavior of lipids in healthy volunteers at 7 Tesla (T). MATERIALS AND METHODS: Relaxation measurements were conducted on corn oil phantoms and on the hepatic tissue of 11 healthy volunteers at 7 T using a surface coil and a STEAM sequence. T1 's were determined by monoexponential fitting, and T2 's by both monoexponential and enhanced-exponential fitting (empirically designed to consider J-coupling of lipid resonances). RESULTS: In vivo T1 's at 7 T were estimated as follows: water (4.70 ppm), 1362 ± 83 ms; methyl- (0.90 ppm), 1026 ± 162 ms; methylene- (1.30 ppm), 514 ± 25 ms; α-olefinic- (2.02 ppm), 488 ± 220 ms; α-carboxyl- (2.24 ppm), 476 ± 89 ms; diacyl- (2.77 ppm), 479 ± 260 ms group of lipid chains; and choline compounds (3.22 ppm), 1084 ± 52 ms. The T2 's calculated with enhanced fitting were as follows: water, 15 ± 2 ms; methyl-, 34 ± 10 ms; methylene-, 41 ± 8 ms; α-olefinic-, 44 ± 19 ms; α-carboxyl-, 39 ± 15 ms; diacyl-, 44 ± 5 ms group of lipid chains; and choline compounds, 32 ± 9 ms. CONCLUSION: An accurate knowledge of in vivo relaxation and J-coupling behavior will significantly improve the quantification of an extended number of resolved liver metabolites at 7 T.

Longitudinal evaluation of hepatic lipid deposition and composition in ob/ob and ob/+ control mice.

Obesity is associated with insulin resistance (IR) and hepatosteatosis. Understanding the link between IR and hepatosteatosis could be relevant to chronic clinical outcomes. The objective of this study was to quantitatively assess lipid deposition (fractional lipid mass, fLM) and composition (fraction of polyunsaturated lipids, fPUL and mean chain length, MCL) in livers of ob/ob mice, a genetic model of obesity and mild diabetes, and ob/+ heterozygous control animals in a noninvasive manner using (1) H-MRS at 9.4T. For accurate quantification, intensity values were corrected for differences in T2 values while T1 effects were considered minimal due to the long TR values used. Values of fLM, fPUL and MCL were derived from T2 -corrected signal intensities of lipids and water resonance. Hepatic lipid signals were compared with fasted plasma insulin, glucose and lipid levels. Statistically significant correlations between fPUL and fasting plasma insulin/glucose levels were found in adolescent ob/ob mice. A similar correlation was found between fLM and fasting plasma insulin levels; however, the correlation between fLM and fasting plasma glucose levels was less obvious in adolescent ob/ob mice. These correlations were lost in adult ob/ob mice. The study showed that in adolescent ob/ob mice, there was an obvious link between lipid deposition/composition in the liver and plasma insulin/glucose levels. This correlation was lost in adult animals, probably due to the limited lipid storage capacity of the liver.