Liver Fatty Acid Binding Protein Gene-Ablation Exacerbates Weight Gain in High-Fat Fed Female Mice

Loss of liver fatty acid binding protein (L‐FABP) decreases long chain fatty acid uptake and oxidation in primary hepatocytes and in vivo. On this basis, L‐FABP gene ablation would potentiate high‐fat diet‐induced weight gain and weight gain/energy intake. While this was indeed the case when L‐FABP null (?/?) mice on the C57BL/6NCr background were pair‐fed a high‐fat diet, whether this would also be observed under high‐fat diet fed ad libitum was not known. Therefore, this possibility was examined in female L‐FABP (?/?) mice on the same background. L‐FABP (?/?) mice consumed equal amounts of defined high‐fat or isocaloric control diets fed ad libitum. However, on the ad libitum‐fed high‐fat diet the L‐FABP (?/?) mice exhibited: (1) decreased hepatic long chain fatty acid (LCFA) β‐oxidation as indicated by lower serum β‐hydroxybutyrate level; (2) decreased hepatic protein levels of key enzymes mitochondrial (rate limiting carnitine palmitoyl acyltransferase A1, CPT1A; HMG‐CoA synthase) and peroxisomal (acyl CoA oxidase 1, ACOX1) LCFA β‐oxidation; (3) increased fat tissue mass (FTM) and FTM/energy intake to the greatest extent; and (4) exacerbated body weight gain, weight gain/energy intake, liver weight, and liver weight/body weight to the greatest extent. Taken together, these findings showed that L‐FABP gene‐ablation exacerbated diet‐induced weight gain and fat tissue mass gain in mice fed high‐fat diet ad libitum—consistent with the known biochemistry and cell biology of L‐FABP.     

Fatty Acid Binding Protein-1 (FABP1) and the Human FABP1 T94A Variant: Roles in the Endocannabinoid System and Dyslipidemias

The first discovered member of the mammalian FABP family, liver fatty acid binding protein (FABP1, L‐FABP), occurs at high cytosolic concentration in liver, intestine, and in the case of humans also in kidney. While the rat FABP1 is well studied, the extent these findings translate to human FABP1 is not clear—especially in view of recent studies showing that endocannabinoids and cannabinoids represent novel rat FABP1 ligands and FABP1 gene ablation impacts the hepatic endocannabinoid system, known to be involved in non‐alcoholic fatty liver (NAFLD) development. Although not detectable in brain, FABP1 ablation nevertheless also impacts brain endocannabinoids. Despite overall tertiary structure similarity, human FABP1 differs significantly from rat FABP1 in secondary structure, much larger ligand binding cavity, and affinities/specificities for some ligands. Moreover, while both mouse and human FABP1 mediate ligand induction of peroxisome proliferator activated receptor‐α (PPARα), they differ markedly in pattern of genes induced. This is critically important because a highly prevalent human single nucleotide polymorphism (SNP) (26–38 % minor allele frequency and 8.3 ± 1.9 % homozygous) results in a FABP1 T94A substitution that further accentuates these species differences. The human FABP1 T94A variant is associated with altered body mass index (BMI), clinical dyslipidemias (elevated plasma triglycerides and LDL cholesterol), atherothrombotic cerebral infarction, and non‐alcoholic fatty liver disease (NAFLD). Resolving human FABP1 and the T94A variant's impact on the endocannabinoid and cannabinoid system is an exciting challenge due to the importance of this system in hepatic lipid accumulation as well as behavior, pain, inflammation, and satiety.     

Common FABP4 Genetic Variants and Plasma Levels of Fatty Acid Binding Protein 4 in Older Adults

We examined common variants in the fatty acid binding protein 4 gene (FABP4) and plasma levels of FABP4 in adults aged 65 and older from the Cardiovascular Health Study. We genotyped rs16909187, rs1054135, rs16909192, rs10808846, rs7018409, rs2290201, and rs6992708 and measured circulating FABP4 levels among 3190 European Americans and 660 African Americans. Among European Americans, the minor alleles of six single nucleotide polymorphisms (SNP) were associated with lower FABP4 levels (all p ≤ 0.01). Among African Americans, the SNP with the lowest minor allele frequency was associated with lower FABP4 levels (p = 0.015). The C-A haplotype of rs16909192 and rs2290201 was associated with lower FABP4 levels in both European Americans (frequency = 16 %; p = 0.001) and African Americans (frequency = 8 %; p = 0.04). The haplotype combined a SNP in the first intron with one in the 3′untranslated region. However, the alleles associated with lower FABP4 levels were associated with higher fasting glucose in meta-analyses from the MAGIC consortium. These results demonstrate associations of common SNP and haplotypes in the FABP4 gene with lower plasma FABP4 but higher fasting glucose levels.     

Fatty Acid Binding Domain Mediated Conjugation of Ultrafine Magnetic Nanoparticles with Albumin Protein

A novel bioconjugate of stearic acid capped maghemite nanoparticle (γ-Fe₂O₃) with bovine serum albumin (BSA) was developed by taking recourse to the fatty acid binding property of the protein. From FT-IR study, it was found that conjugation took place covalently between the amine group of protein molecule and carboxyl group of stearic acid capped maghemite nanoparticle. TEM study further signified the morphology of the proposed nanobioconjuagte. The binding constant of nanoparticle with protein molecule was evaluated from the optical property studies. Also, magnetic measurement (M–H) showed retaining of magnetic property by significant values of saturation magnetization and other hysteretic parameters.     

Serum Fatty Acid-Binding Protein 4 is Increased in Patients with Psoriasis

Psoriasis is associated with metabolic syndrome and cardiovascular disease. Fatty acid‐binding proteins (FABP) have been recognized as predictors of these systemic disorders. The aim of this study was to assess correlations between levels of serum heart and adipocyte fatty acid‐binding proteins (FABP3, FABP4) and disease severity, indicators of inflammation or metabolic disturbances, and topical treatment in psoriatic patients. Thirty‐seven patients with relapse of plaque‐type psoriasis and 16 healthy volunteers were recruited. Blood samples were collected before and after 14 days of therapy. Serum FABP concentrations were examined by enzyme‐linked immunosorbent assay for correlation with Psoriasis Area and Severity Index (PASI), body mass index (BMI), inflammatory or metabolic parameters, and treatment used. The median FABP4 serum levels were significantly increased (p = 0.038) in psoriatic patients, while FABP3 levels did not differ (p = 0.47) compared to the controls. No significant correlations were noted between the proteins and PASI, C‐reactive protein (CRP), BMI, or levels of glucose or lipids. FABP3 significantly correlated with white blood count (p = 0.03) and aspartate aminotransferase (p = 0.04). After topical treatment, there was no significant change in serum FABP3 [11.5 (4.9–30.3) vs. 12.9 (3.5–30.3) ng/ml] (p = 0.96), whereas FABP4 was decreased [27,286 (20,344–32,257) vs. 23,034 (18,320–29,874) pg/ml] (p = 0.12), losing its basal significance. FABP4 may be a marker of psoriasis, and FABP3 may be associated with inflammation or liver disorders in psoriatic patients. FABP do not appear to be useful for determining disease severity or the effectiveness of antipsoriatic treatment.     

High Dietary Fat Exacerbates Weight Gain and Obesity in Female Liver Fatty Acid Binding Protein Gene-Ablated Mice

Since liver fatty acid binding protein (L-FABP) facilitates uptake/oxidation of long-chain fatty acids in cultured transfected cells and primary hepatocytes, loss of L-FABP was expected to exacerbate weight gain and/or obesity in response to high dietary fat. Male and female wild-type (WT) and L-FABP gene-ablated mice, pair-fed a defined isocaloric control or high fat diet for 12 weeks, consumed equal amounts of food by weight and kcal. Male WT mice gained weight faster than their female WT counterparts regardless of diet. L-FABP gene ablation enhanced weight gain more in female than male mice—an effect exacerbated by high fat diet. Dual emission X-ray absorptiometry revealed high-fat fed male and female WT mice gained mostly fat tissue mass (FTM). L-FABP gene ablation increased FTM in female, but not male, mice—an effect also exacerbated by high fat diet. Concomitantly, L-FABP gene ablation decreased serum β-hydroxybutyrate in male and female mice fed the control diet and, even more so, on the high-fat diet. Thus, L-FABP gene ablation decreased fat oxidation and sensitized all mice to weight gain as whole body FTM and LTM—with the most gain observed in FTM of control vs high-fat fed female L-FABP null mice. Taken together, these results indicate loss of L-FABP exacerbates weight gain and/or obesity in response to high dietary fat.     

Erucic Acid is Differentially Taken up and Metabolized in Rat Liver and Heart

Because X-linked adrenoleukodystrophy is treated using erucic acid (22:1n-9), we assessed its metabolism in rat liver and heart following infusion of [14-¹⁴C]22:1n-9 (170 Ci/kg) under steady-state-like conditions. In liver, 2.3-fold more tracer was taken up as compared to heart, accounted entirely by increased incorporation into the organic fraction (4.2-fold). The amount of tracer entering the aqueous fraction, which represents β-oxidation, was not different between groups; however a significantly elevated proportion of tracer was in the heart aqueous fraction. In both tissues, 76% of the radioactivity found in the organic fraction was esterified in neutral lipids, while only about 10% was found esterified into phospholipids. In liver, 56% of lipid radioactivity was found in cholesteryl esters, whereas in heart 64% was found in triacylglycerols. Because 22:1n-9 can be chain shortened, we assessed tracer metabolism using phenacyl fatty acid derivatives esterified from saponified esterified neutral lipid (triacylglycerol/cholesteryl ester) and phospholipid fractions. In heart esterified neutral lipids, 75% of tracer was recovered as 22:1n-9 and only 10% as oleic acid (18:1n-9), while in liver only 25% of the tracer was recovered as 22:1n-9, while 50% was found as stearic acid (18:0) and 10% as 18:1n-9. In liver and heart phospholipids, the tracer was distributed amongst the n-9 fatty acid family. Thus, 22:1n-9 under went tissue selective metabolism, with conversion to 18:0 the dominant pathway in the liver presumably for export in the neutral lipids, while in heart it was found primarily as 22:1n-9 in neutral lipids and used for β-oxidation.     

Streptozotocin-Induced Diabetes Partially Attenuates the Effects of a High-Fat Diet on Liver and Brain Fatty Acid Composition in Mice

The current study addresses the effects of a high-fat diet on liver and brain fatty acid compositions and the interaction of that diet with diabetes in a type 1 mouse model. Adult, male, normal and streptozotocin-induced diabetic C57BL/6 mice were fed standard (14 % kcal from fat) or high-fat (54 % kcal from fat, hydrogenated vegetable shortening and corn oil) diets for 8 weeks. Liver and whole brain total phospholipid fatty acid compositions were then determined by TLC/GC. In the liver of non-diabetic mice, the high-fat diet increased the percentages of 18:1n-9, 20:4n-6, and 22:5n-6 and decreased 18:2n-6 and 22:6n-3. Diabetes increased 16:0 in liver, and decreased 18:1n-7 and 20:4n-6. The effects of the high-fat diet on liver phospholipids in diabetic mice were similar to those in non-diabetic mice, or were of smaller magnitude. In the brain, the high-fat diet increased 18:0 and 20:4n-6 of non-diabetic, but not diabetic mice. Brain 22:5n-6 acid was increased by the high-fat diet in both non-diabetic and diabetic mice, but this increase was smaller in diabetic mice. Diabetes alone did not alter the percentage of any individual fatty acid in brain. This indicates that the effects of a high-fat diet on liver and brain phospholipid fatty acid compositions are partially attenuated by concomitant hyperglycemia with hypoinsulinemia.     

Genetic Background and Diet Impact Beef Fatty Acid Composition and Stearoyl-CoA Desaturase mRNA Expression

The intramuscular fat composition of ruminant meats influences the quality of the final product, which explains the increasing interest in assessing the fatty acid profile of meat from different production systems. In this study, it was hypothesized that there are breed- and diet-induced variations on lipid metabolism in the muscle, which may be, at least partially, modulated by the stearoyl-CoA desaturase (SCD) gene expression levels. Forty purebred young bulls from two phylogenetically distant autochthonous cattle breeds, Alentejana and Barrosã (n = 20 for each breed), were assigned to two different diets (low vs. high silage) and slaughtered at 18 months of age. Meat fatty acid composition, including the detailed conjugated linoleic acid (CLA) isomeric profile, was determined along with the SCD mRNA levels. Meat from Barrosã bulls fed the low silage diet was richer in monounsaturated fatty acids, CLA and trans fatty acids, when compared to that from Alentejana bulls. The meat content in polyunsaturated fatty acids was similar across experimental groups. Moderate positive correlations between the SCD mRNA levels and the products of this enzyme activity were found, although they were not reflected on the calculated desaturase indices. Overall, these findings highlight the importance of taking into account the genetic background while devising feeding strategies to manipulate beef fatty acid composition.     

不同性质的脂肪酸对脂肪变性L02肝细胞凋亡和葡萄糖调节蛋白78表达的影响

目的探讨不同性质脂肪酸对脂肪变性L02肝细胞凋亡和葡萄糖调节蛋白78(GRP78)表达的影响。方法用油酸(不饱和脂肪酸)和软脂酸(饱和脂肪酸)分别诱导建立L02细胞脂肪变性模型;油红O染色观察细胞内脂滴的变化;甘油三酯(TG)试剂盒检测细胞内TG含量;流式细胞术Annexin-V/PI双染检测细胞凋亡率;AO/EB染色法观察细胞凋亡形态;Westernblot和RT-PCR法分别检测GRP78蛋白和mRNA的表达。结果不同性质的脂肪酸均可导致L02细胞发生以甘油三酯升高为特点的脂肪变性。流式细胞术及AO/EB染色形态观察显示,两种类型的脂肪酸均可引起不同程度的肝细胞凋亡,软脂酸组在48和72h的细胞凋亡率显著高于对照组、DMSO组以及油酸组,同时伴有GRP78蛋白及mRNA表达的明显增加。结论油酸不能影响GRP78的表达,饱和脂肪酸可能通过上调葡萄糖调节蛋白78的表达诱导脂肪变性肝细胞的凋亡。     

激活素A及激活素结合蛋白在急性酒精性肝损伤小鼠肝组织中的表达

目的探讨激活素A(Activin A)及激活素结合蛋白(Follistatin,FS)在急性酒精性肝损伤小鼠肝组织中的表达。方法通过1次/12 h给予小鼠5 g/Kg酒精连续灌胃3次,复制急性酒精性肝损伤小鼠模型,采用实时定量RT-PCR检测小鼠肝组织Activin A及FS mRNA表达水平,免疫组织化学染色观察小鼠肝组织Activin A及FS蛋白的表达水平。结果急性酒精性肝损伤小鼠肝组织Activin A mRNA和蛋白表达水平均显著高于对照组(P<0.01);FS mRNA和蛋白表达水平与对照组比较,差异均无统计学意义(P>0.05)。结论急性酒精性肝损伤小鼠肝组织Activin A-FS表达失衡,以Activin A升高为主,提示Activin A-FS系统失衡可能与酒精性肝损伤有关。     

Seasonal Variations in the Fatty Acid Composition of Phospholipid and Triacylglycerol in Gonad and Liver of Mastacembelus simack

The seasonal effects on the fatty acid composition of triacylglycerol (TG) and phospholipid (PL) in the gonad and liver of Mastacembelus simack were determined using the gas chromatographic method. The most abundant fatty acids in the investigated seasons and tissues were palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1n‐9), palmitoleic acid (C16:1n‐7), arachidonic acid (C20:4n‐6), eicosapentaenoic acid (C20:5n‐3), and docosahexaenoic acid (C22:6n‐3). The distribution proportions of ∑SFA (saturated fatty acids), ∑MUFA (monounsaturated fatty acids) and ∑PUFA (polyunsaturated fatty acids) were found to be different among PL and TG fractions in all seasons. The total lipid content of gonad and liver were 1.32 (November)–4.90 % (September) and 1.32 (September)–3.94 % (January), respectively. It was shown that the total lipid and fatty acid compositions in the gonad and liver of fish were significantly influenced by seasons.     

Gut Microbial Fatty Acid Metabolites Reduce Triacylglycerol Levels in Hepatocytes

Hydroxy and oxo fatty acids were recently found to be produced as intermediates during gut microbial fatty acid metabolism. Lactobacillus plantarum produces these fatty acids from unsaturated fatty acids such as linoleic acid. In this study, we investigated the effects of these gut microbial fatty acid metabolites on the lipogenesis in liver cells. We screened their effect on sterol regulatory element binding protein‐1c (SREBP‐1c) expression in HepG2 cells treated with a synthetic liver X receptor α (LXRα) agonist (T0901317). The results showed that 10‐hydroxy‐12(Z)‐octadecenoic acid (18:1) (HYA), 10‐hydroxy‐6(Z),12(Z)‐octadecadienoic acid (18:2) (γHYA), 10‐oxo‐12(Z)‐18:1 (KetoA), and 10‐oxo‐6(Z),12(Z)‐18:2 (γKetoA) significantly decreased SREBP‐1c mRNA expression induced by T0901317. These fatty acids also downregulated the mRNA expression of lipogenic genes by suppressing LXRα activity and inhibiting SREBP‐1 maturation. Oral administration of KetoA, which effectively reduced triacylglycerol accumulation and acetyl‐CoA carboxylase 2 (ACC2) expression in HepG2 cells, for 2 weeks significantly decreased Srebp‐1c, Scd‐1, and Acc2 expression in the liver of mice fed a high‐sucrose diet. Our findings suggest that the hypolipidemic effect of the fatty acid metabolites produced by L. plantarum can be exploited in the treatment of cardiovascular diseases or dyslipidemia.     

EPA,DHA, and Lipoic Acid Differentially Modulate the n-3 Fatty Acid Biosynthetic Pathway in Atlantic Salmon Hepatocytes

The aim of the present study was to investigate how EPA, DHA, and lipoic acid (LA) influence the different metabolic steps in the n‐3 fatty acid (FA) biosynthetic pathway in hepatocytes from Atlantic salmon fed four dietary levels (0, 0.5, 1.0 and 2.0%) of EPA, DHA or a 1:1 mixture of these FA. The hepatocytes were incubated with [1‐¹⁴C] 18:3n‐3 in the presence or absence of LA (0.2 mM). Increased endogenous levels of EPA and/or DHA and LA exposure both led to similar responses in cells with reduced desaturation and elongation of [1‐¹⁴C] 18:3n‐3 to 18:4n‐3, 20:4n‐3, and EPA, in agreement with reduced expression of the Δ6 desaturase gene involved in the first step of conversion. DHA production, on the other hand, was maintained even in groups with high endogenous levels of DHA, possibly due to a more complex regulation of this last step in the n‐3 metabolic pathway. Inhibition of the Δ6 desaturase pathway led to increased direct elongation to 20:3n‐3 by both DHA and LA. Possibly the route by 20:3n‐3 and then Δ8 desaturation to 20:4n‐3, bypassing the first Δ6 desaturase step, can partly explain the maintained or even increased levels of DHA production. LA increased DHA production in the phospholipid fraction of hepatocytes isolated from fish fed 0 and 0.5% EPA and/or DHA, indicating that LA has the potential to further increase the production of this health‐beneficial FA in fish fed diets with low levels of EPA and/or DHA.     

Fatty Acid de Novo Synthesis in Adult Intrauterine Growth-Restricted Offspring,and Adult Male Response to a High Fat Diet

Intrauterine growth restriction (IUGR) with rapid catch‐up growth leads to adult obesity and insulin resistance. We have previously shown that IUGR male rats demonstrated increased de novo fatty acid synthesis in the subcutaneous (SC) fat, but not the visceral fat, during the nursing period prior to the onset of obesity. Young IUGR females do not exhibit the same increase. We further hypothesized that in male IUGR offspring, de novo synthesis is a programmed intrinsic effect that persists to adulthood and does not suppress in response to a high fat diet. We measured fatty acid de novo synthesis in IUGR adult males (6 months) using deuterium‐enriched drinking water as a stable isotope tracer, then further studied the response after consumption of an isocaloric high fat diet. Baseline de novo synthesis in adult females was also studied at age 9 months. Males demonstrated increased baseline de novo synthesis in both SC fat and visceral fat. Correspondingly, SC and visceral fat protein expression of lipogenic enzymes acetyl‐coA carboxylase‐α (ACCα) and fatty acid synthase were upregulated. After the isocaloric high fat diet, de novo synthesis was suppressed such that no differences remained between the two groups, although, IUGR SC fat demonstrated persistently increased lipogenic protein expression. In contrast, de novo synthesis among adult females is not impacted in IUGR. In conclusion, enhancement of male IUGR SC fat de novo synthesis appears to be an early consequence of metabolic programming, whereas enhancement in visceral fat appears to be a later consequence.     

碳水化合物反应元件结合蛋白对L02细胞糖脂代谢的影响

目的探讨碳水化合物反应元件结合蛋白(Carbohydrate response element binding protein,ChREBP)在高糖诱导肝细胞脂变中的作用。方法分别以18和25 mmol/L葡萄糖培养L02细胞,以11 mmol/L葡萄糖培养L02细胞作为对照,甘油三酯(TG)含量测定及油红O染色观察细胞脂变程度;免疫荧光观察细胞ChREBP的核转位情况;RT-PCR检测细胞肝型丙酮酸激酶(Liver pyruvate kinase,LPK)基因mRNA的表达水平,Western blot分析细胞脂肪酸合成酶(Fatty acid synthase,FAS)蛋白的表达水平。结果与对照组比较,高糖可使L02细胞内甘油三酯和脂滴含量增加,刺激ChREBP核转位,上调LPK基因mRNA和FAS蛋白的表达水平。结论葡萄糖可能通过其代谢产物经ChREBP-LPK-FAS途径诱导肝细胞脂肪变性。     

The Role of Vitamin D and Vitamin D Binding Protein in Chronic Liver Diseases

Vitamin D (calciferol) is a fat-soluble vitamin that has a significant role in phospho-calcium metabolism, maintaining normal calcium levels and bone health development. The most important compounds of vitamin D are cholecalciferol (vitamin D3, or VD3) and ergocalciferol (vitamin D2, or VD2). Besides its major role in maintaining an adequate level of calcium and phosphate concentrations, vitamin D is involved in cell growth and differentiation and immune function. Recently, the association between vitamin D deficiency and the progression of fibrosis in chronic liver disease (CLD) was confirmed, given the hepatic activation process and high prevalence of vitamin D deficiency in these diseases. There are reports of vitamin D deficiency in CLD regardless of the etiology (chronic viral hepatitis, alcoholic cirrhosis, non-alcoholic fatty liver disease, primary biliary cirrhosis, or autoimmune hepatitis). Vitamin D binding protein (VDBP) is synthesized by the liver and has the role of binding and transporting vitamin D and its metabolites to the target organs. VDBP also plays an important role in inflammatory response secondary to tissue damage, being involved in the degradation of actin. As intense research during the last decades revealed the possible role of vitamin D in liver diseases, a deeper understanding of the vitamin D, vitamin D receptors (VDRs), and VDBP involvement in liver inflammation and fibrogenesis could represent the basis for the development of new strategies for diagnosis, prognosis, and treatment of liver diseases. This narrative review presents an overview of the evidence of the role of vitamin D and VDBP in CLD, both at the experimental and clinical levels.     

Effects of Overexpression of Neurosecretory Protein GL-Precursor Gene on Glucose Homeostasis and Insulin Sensitivity in Mice

A high-fat diet (HFD) quickly induces obesity with insulin resistance and hyperglycemia. We previously reported that a novel hypothalamic small protein, named neurosecretory protein GL (NPGL), stimulates feeding and fat accumulation in mice. However, the effects of NPGL on insulin sensitivity and glucose homeostasis remain unknown. Hence, we subjected NPGL-precursor gene (Npgl)-overexpressing mice to the oral glucose tolerance test (OGTT) and intraperitoneal insulin tolerance test (IPITT) under normal chow (NC) and HFD conditions. Npgl overexpression promoted body mass gain and tended to increase food intake of NC-fed mice, whereas it had little effect on HFD-fed mice. The OGTT showed elevated blood glucose and insulin levels in Npgl-overexpressing NC-fed mice 15 min after glucose administration. Both the OGTT and IPITT demonstrated that Npgl overexpression decreased blood glucose levels in HFD-fed mice 60 min after glucose and insulin treatments. Notably, Npgl overexpression increased adipose tissue masses only in NC-fed mice, and it decreased blood glucose and insulin levels in HFD-fed mice at the experimental end point. It also increased the mRNA expression of galanin, one of the feeding and metabolic regulatory neuropeptides, in the hypothalamus of HFD-fed mice. Therefore, NPGL may alleviate HFD-induced hyperglycemia and insulin resistance in mice.