Absorption Of Long-chain Fatty Acids Research Articles

Reduction of specific enterocytes from loss of intestinal LGR4 improves lipid metabolism in mice

Whether intestinal Leucine-rich repeat containing G-protein-coupled receptor 4 (LGR4) impacts nutrition absorption and energy homeostasis remains unknown. Here, we report that deficiency of Lgr4 (Lgr4iKO) in intestinal epithelium decreased the proportion of enterocytes selective for long-chain fatty acid absorption, leading to reduction in lipid absorption and subsequent improvement in lipid and glucose metabolism. Single-cell RNA sequencing demonstrates the heterogeneity of absorptive enterocytes, with a decrease in enterocytes selective for long-chain fatty acid-absorption and an increase in enterocytes selective for carbohydrate absorption in Lgr4iKO mice. Activation of Notch signaling and concurrent inhibition of Wnt signaling are observed in the transgenes. Associated with these alterations is the substantial reduction in lipid absorption. Decrement in lipid absorption renders Lgr4iKO mice resistant to high fat diet-induced obesity relevant to wild type littermates. Our study thus suggests that targeting intestinal LGR4 is a potential strategy for the intervention of obesity and liver steatosis.

Molecular Drug Simulation and Experimental Validation of the CD36 Receptor Competitively Binding to Long-Chain Fatty Acids by 7-Ketocholesteryl-9-carboxynonanoate.

Long-chain fatty acids (LCFAs) are one of the main energy-supplying substances in the body. LCFAs with different lengths and saturations may have contrasting biological effects that exacerbate or alleviate progress against a variety of systemic disorders of lipid metabolism in organisms. Nonalcoholic fatty liver disease is characterized by chronic inflammation and steatosis, mainly caused by the ectopic accumulation of lipids in the liver, especially LCFAs. CD36 is a scavenger receptor that recognizes and mediates the transmembrane absorption of LCFAs and is expressed in a variety of cells throughout the body. In previous studies, our group found that 7-ketocholesteryl-9-carboxynonanoate (oxLig-1) has the biological effect of targeting CD36 to inhibit oxidized low-density lipoprotein lipotoxicity-induced lipid metabolism disorder; it has an ω-carboxyl physiologically active center and is structurally similar to LCFAs. However, the biological mechanism of oxLig-1 binding to CD36 and competing for binding to different types of LCFAs is still not clear. In this study, molecular docking and molecular dynamics simulation were utilized to simulate and analyze the binding activity between oxLig-1 and different types of LCFAs to CD36 and confirmed by the enzyme-linked immunosorbent assay (ELISA) method. Absorption, distribution, metabolism, excretion, and toxicity (ADMET) platform was applied to predict the drug-forming properties of oxLig-1, and HepG2 cells model of oleic acid and nonalcoholic fatty liver disease (NAFLD) model mice were validated to verify the biological protection of oxLig-1 on lipid lowering. The results showed that there was a co-binding site of LCFAs and oxLig-1 on CD36, and the binding driving forces were mainly hydrogen bonding and hydrophobic interactions. The binding abilities of polyunsaturated LCFAs, oxLig-1, monounsaturated LCFAs, and saturated LCFAs to CD36 showed a decreasing trend in this order. There was a similar decreasing trend in the stability of the molecular dynamics simulation. ELISA results similarly confirmed that the binding activity of oxLig-1 to CD36 was significantly higher than that of typical monounsaturated and saturated LCFAs. ADMET prediction results indicated that oxLig-1 had a good drug-forming property. HepG2 cells model of oleic acid and NAFLD model mice study results demonstrated the favorable lipid-lowering biological effects of oxLig-1. Therefore, oxLig-1 may have a protective effect by targeting CD36 to inhibit the excessive influx and deposition of lipotoxicity monounsaturated LCFAs and saturated LCFAs in hepatocytes.

Increased Amount of Polyunsaturated Fatty Acids in the Intestinal Contents of Patients with Morbid Obesity

IntroductionObesity is associated with disturbed gut microbiota homeostasis that translates into altered intestinal and blood metabolite profiles. The long-chain fatty acid (LCFA) may be absorbed in the intestine, but until now, their composition in intestinal contents of patients with obesity has not been studied. The aim of the present study was to verify whether obesity is related to any changes in fecal LCFA content and whether intestinal LCFA content may be associated with the health status of patients with obesity.MethodsThe fatty acid composition has been studied in stool samples obtained from 26 patients with morbid obesity and 25 lean subjects by gas chromatography–mass spectrometry. The dietary habits were assessed using the Food Frequency Questionnaire (FFQ-6).ResultsOur results show for the first time that lean subjects and patients with obesity differ in their stool LCFA profiles. The levels of most n-3 polyunsaturated fatty acids (PUFAs) and n-6 PUFAs were significantly higher in fecal samples from people with obesity than in those from lean controls.ConclusionsBased on the current knowledge, we have defined three hypotheses that may explain proving the cause-and-effect relationships observed differences in fecal LCFA profiles between patients with obesity and lean subjects. They may be related to alterations in fat digestion and/or LCFA absorption and diet. However, proving the cause-and-effect relationships requires further research.Graphical

Cathelicidin-WA Facilitated Intestinal Fatty Acid Absorption Through Enhancing PPAR-γ Dependent Barrier Function.

The molecular mechanisms underlying the cellular uptake of long-chain fatty acids and the regulation of this process have been debated in recent decades. Here, we established an intestinal barrier dysfunction model in mice and Caco2 cell line by Lipopolysaccharide (LPS), and evaluated the fatty acid uptake capacity of the intestine. We found that LPS stimulation restricted the absorption of long chain fatty acid (LCFA), while Cathelicidin-WA (CWA) pretreatment facilitated this physiological process. At the molecular level, our results demonstrated that the stimulatory effects of CWA on intestinal lipid absorption were dependent on cluster determinant 36 and fatty acid transport protein 4, but not fatty acid–binding protein. Further, an enhanced intestinal barrier was observed in vivo and in vitro when CWA alleviated the fatty acid absorption disorder induced by LPS stimulation. Mechanistically, peroxisome proliferator-activated receptor (PPAR-γ) signaling was considered as a key pathway for CWA to enhance LCFA absorption and barrier function. Treatment with a PPAR-γ inhibitor led to impaired intestinal barrier function and suppressed LCFA uptake. Moreover, once PPAR-γ signaling was blocked, CWA pretreatment could not maintain the stability of the intestinal epithelial cell barrier or LCFA uptake after LPS stimulation. Collectively, these findings suggested that PPAR-γ may serve as a target for specific therapies aimed at alleviating fatty acid uptake disorder, and CWA showed considerable potential as a new PPAR-γ agonist to strengthen intestinal barrier function against fatty acid malabsorption.

Mettl3 Deficiency Sustains Long-Chain Fatty Acid Absorption through Suppressing Traf6-Dependent Inflammation Response.

A better understanding of the molecular mechanism of intestinal fatty acid absorption could lead to novel approaches to treatment and prevention of fatty acid-related metabolic diseases. Although it is confirmed that absorption of long-chain fatty acids (LCFAs) decreases during the pathological processes, the genetic basis and molecular mechanisms remain largely unknown. N 6-methyladenosine (m6A) is the most prevalent internal modification on eukaryotic mRNA. Recently, m6A has been found to play important roles in inflammation and antiviral responses. In this study, we show that deficiency of Mettl3, the core methyltransferase of m6A, exerts antimalabsorption of LCFA activity in vitro through inhibiting the inflammation response mediated by LPS. To substantiate this finding further, we found the levels of triglycerides were also sustained in cells with depleted Mettl3, which were cultured in Transwell to polarize with villus formation to simulate the situation in vivo. Mechanistically, depletion of Mettl3 decreases the m6A level of Traf6 mRNA, thereby its transcripts are entrapped in the nucleus, followed by the decreased expression of Traf6, leading to the suppression of NF-κB and MAPK signaling pathway. Thus, the inflammation response was suppressed, resulting in the sustained absorption of LCFA. Moreover, we found that ectopic expression of Traf6 largely abolishes the sustained absorption LCFA in Mettl3 depletion cells. Collectively, silencing Mettl3 could sustain LCFA absorption through blocking the TRAF6-dependent inflammation response. Our work uncovers a critical function of m6A methylation and provides insight into critical roles of Mettl3 in LCFA absorption and inflammatory disease.

Variations in Tissue-Specific Expression of Adipose Differentiation-Related Protein Gene in Two Native Yunnan Chicken Breeds

ABSTRACT Adipose differentiation-related protein (ADFP) is a fatty acid-binding protein that can promote the absorption of long-chain fatty acids. However, few results have been published regarding its role in Yunnan Native chicken breeds. The aim of this study was to determine ADFP gene tissue-specific expression in Piao chickens (PC) and Wuliangshan black-bone chickens (WBC) by RT-qPCR. The ontogenetic expression levels of the ADFP gene were significantly different during growth and development phases in the subcutaneous fat, liver, and pectoralis muscle of PC, and in the subcutaneous fat, liver, and pectoralis muscle of WBC (p 0.05). The results suggest ADFPdifferential expression in the liver and pectoral muscles of PC and WBC during the growth and development phases (p<0.05). The observed expression patterns indicate that the ADFP gene plays an important role in lipid metabolism of PC and WBC, and that these patterns are expressed differently in the tissues of different chicken genotypes.

Molecular mechanisms of long-chain fatty acids absorption

The article presents about the role of several lipid-binding proteins expressed by the small intestine brush border membrane in the main steps of intestinal absorption of long-chain fatty acids and about changes in lipid profile caused by failed absorbtion. The system literature search is performed on Scopus databases, Web of Science, MedLine.

LCFA Uptake and FAT/CD36: molecular cloning, tissue expression and mRNA expression responses to dietary oil sources in grass carp (Ctenopharyngodon idellus)

ABSTRACTThe fatty acid translocase (FAT/CD36) plays an important role in trans-membrane uptake of long-chain fatty acids (LCFA) and has been identified and described in many organisms, while little is known about this gene in freshwater fish, and especially in the grass carp (Ctenopharyngodon idellus). In this study, the uptake of LCFA in hepatocytes of C. idellus was firstly determined and then FAT/CD36 gene was cloned; then the gene was sequenced and mRNA levels from different tissues and the effect of dietary oils on its expression were determined. Present data showed that trans-membrane absorption of LCFA was related to the type and concentration of fatty acids (FAs) and it could be inhibited by specific membrane uptake inhibitors. The FAT/CD36 isolated from grass carp contained 1422 bp and the open reading frame was predicted to have 1403 bp (GenBank access number: KU361231.1). FAT/CD36 was highly expressed in the brain and its lowest expression was in the gills. FAT/CD36 expression in white muscle was up-regulated when fish were fed with groundnut oil, whereas it was down-regulated in fish fed fish and linseed oils, respectively. These results indicated n-3 PUFA might inhibit the FAT/CD36 mRNA expression and therefore the oxidation of FAs.Abbreviations: Docosahexaenoic acid: DHA; Fatty acid: FA; Fatty acid translocase: FAT/CD36; Fish oil: FO; eicosapentaenoic acid: EPA; Groundnut oil: GO; Linseed oil: LO; Peroxisome proliferator-activated nuclear receptor: PPARs; Polyunsaturated fatty acid: PUFA; Unsaturated long-chain fatty acids: LCFA; Olive oil: OO

Cx47 fine-tunes the handling of serum lipids but is dispensable for lymphatic vascular function.

Mutations in the gap junction protein connexin47 (Cx47) are associated with lymphedema. However, the role of Cx47 in lymphatic pathophysiology is unknown. We demonstrate that Cx47 is expressed in lymphatic endothelial cells by whole-mount immunostaining and qPCR. To determine if Cx47 plays a role in lymphatic vessel function we analysed Cx47-/- mice. Cx47-deficiency did not affect lymphatic contractility (contractile amplitude or frequency) or lymphatic morphology (vessel diameter or number of valves). Interstitial fluid drainage or dendritic cell migration through lymphatic vessels was also not affected by Cx47-deficiency. Cx47 is dispensable for long-chain fatty acid absorption from the gut but rather promotes serum lipid handling as prolonged elevated triglyceride levels were observed in Cx47-deficient mice after oral lipid tolerance tests. When crossed with Apolipoprotein E-deficient (Apoe-/-) mice, LDL-cholesterol was decreased in young Cx47-/-Apoe-/- adults as compared to Apoe-/- mice, which was inverted later in life. Finally, advanced atherosclerotic plaques in thoracic-abdominal aortas of 15 months-old mice tended to be larger in Cx47-/-Apoe-/- mice. These plaques contained fewer macrophages but similar amounts of T lymphocytes, collagen and lipids than plaques of Apoe-/- mice. In conclusion, Cx47 is expressed in lymphatic endothelium and seems modestly implicated in multiple aspects of lymphatic pathophysiology.

1087 - Rapid LPS Transport During Long-Chain Fatty Acid Absorption in Rat Small Intestine

1087 - Rapid LPS Transport During Long-Chain Fatty Acid Absorption in Rat Small Intestine

The Lymphatic System: A New Focus on its Role in Metabolism and Metabolic Disorders

Lymphatic vessels not only play a physiological role in maintenance of homeostasis and the immune response together with blood vessels, but also participate in the development of pathological states such as inflammation and cancer metastasis [1]. In addition, mesenteric lymphatic vessels have a specific function, including absorption of long-chain fatty acids from the small intestine. Several recent studies have shown that the lymph circulation plays an important role in not only lipid metabolism [2] but also carbohydrate metabolism [3], and that morphological and functional impairment of the lymphatic system may be related to the pathophysiology of metabolic syndrome [4] and type 2 diabetes mellitus

From fatty-acid sensing to chylomicron synthesis: Role of intestinal lipid-binding proteins

Today, it is well established that the development of obesity and associated diseases results, in part, from excessive lipid intake associated with a qualitative imbalance. Among the organs involved in lipid homeostasis, the small intestine is the least studied even though it determines lipid bioavailability and largely contributes to the regulation of postprandial hyperlipemia (triacylglycerols (TG) and free fatty acids (FFA)). Several Lipid-Binding Proteins (LBP) are expressed in the small intestine. Their supposed intestinal functions were initially based on what was reported in other tissues, and took no account of the physiological specificity of the small intestine. Progressively, the identification of regulating factors of intestinal LBP and the description of the phenotype of their deletion have provided new insights into cellular and molecular mechanisms involved in fat absorption. This review will discuss the physiological contribution of each LBP in the main steps of intestinal absorption of long-chain fatty acids (LCFA): uptake, trafficking and reassembly into chylomicrons (CM). Moreover, current data indicate that the small intestine is able to adapt its lipid absorption capacity to the fat content of the diet, especially through the coordinated induction of LBP. This adaptation requires the existence of a mechanism of intestinal lipid sensing. Emerging data suggest that the membrane LBP CD36 may operate as a lipid receptor that triggers an intracellular signal leading to the modulation of the expression of LBP involved in CM formation. This event could be the starting point for the optimized synthesis of large CM, which are efficiently degraded in blood. Better understanding of this intestinal lipid sensing might provide new approaches to decrease the prevalence of postprandial hypertriglyceridemia, which is associated with cardiovascular diseases, insulin resistance and obesity.

Targeting of Acyl-CoA synthetase 5 decreases jejunal fatty acid activation with no effect on dietary long-chain fatty acid absorption

BackgroundThe absorption of dietary long chain fatty acids (LCFA) largely occurs in the jejunum. LCFA are activated via conjugation with Coenzyme A (CoA), a reaction catalyzed by Acyl-CoA synthetases (ACS). Acyl-CoA sythesis is critical for dietary LCFA absorption; yet, the jejunal ACS enzymes that catalyze the reaction are largely unknown.FindingsHigh throughput mRNA sequencing of the mouse jejunum revealed that the expression of acyl-CoA synthetase 5 (Acsl5) and fatty-acid transport protein 4 (Fatp4) largely exceeded all other annotated ACS genes that activate LCFA. Interestingly, Acsl5 knockout (KO) mice displayed a decrease of 60% in jejunal total long chain acyl-CoA synthesis rate. Nevertheless, and despite of this decrease, dietary LCFA absorption and body-weight gain in response to high fat diet remained unaffected.ConclusionAcsl5 is a major activator of dietary LCFA, yet in Acsl5 KO mice residual ACS activity is sufficient for maintaining a normal LCFA absorption. Our findings provide further evidence for a robust small intestine LCFA absorption capacity.

Glycine metabolism in animals and humans: implications for nutrition and health

Glycine is a major amino acid in mammals and other animals. It is synthesized from serine, threonine, choline, and hydroxyproline via inter-organ metabolism involving primarily the liver and kidneys. Under normal feeding conditions, glycine is not adequately synthesized in birds or in other animals, particularly in a diseased state. Glycine degradation occurs through three pathways: the glycine cleavage system (GCS), serine hydroxymethyltransferase, and conversion to glyoxylate by peroxisomal D-amino acid oxidase. Among these pathways, GCS is the major enzyme to initiate glycine degradation to form ammonia and CO2 in animals. In addition, glycine is utilized for the biosynthesis of glutathione, heme, creatine, nucleic acids, and uric acid. Furthermore, glycine is a significant component of bile acids secreted into the lumen of the small intestine that is necessary for the digestion of dietary fat and the absorption of long-chain fatty acids. Glycine plays an important role in metabolic regulation, anti-oxidative reactions, and neurological function. Thus, this nutrient has been used to: (1) prevent tissue injury; (2) enhance anti-oxidative capacity; (3) promote protein synthesis and wound healing; (4) improve immunity; and (5) treat metabolic disorders in obesity, diabetes, cardiovascular disease, ischemia-reperfusion injuries, cancers, and various inflammatory diseases. These multiple beneficial effects of glycine, coupled with its insufficient de novo synthesis, support the notion that it is a conditionally essential and also a functional amino acid for mammals (including pigs and humans).

CCK1-Receptor Stimulation Protects Against Gut Mediator-Induced Lung Damage During Endotoxemia

Background/Aims: Cholecystokinin 1-receptor (CCK1-R) activation by long chain fatty acid (LCFA) absorption stimulates vago-vagal reflex pathways in the brain stem. The present study determines whether this reflex also activates the cholinergic anti-inflammatory pathway, a pathway known to modulate cytokine release during endotoxemia. Methods:Mesenteric lymph was obtained from wild type (WT) and CCK1-R knockout (CCK1-R^-/-) mice intraperitoneally challenged with Lipopolysaccharid (LPS) (endotoxemic lymph, EL) and intestinally infused with vehicle or LCFA-enriched solution. The lymph was analyzed for TNFα, IL-6 and IL-10 concentration and administered to healthy recipient mice via jugular infusion. Alveolar wall thickness, myeloperoxidase (MPO) and TUNEL positive cells were determined in lung tissue of recipient mice. Results: LCFA infusion in WT mice reduced TNFα concentration in EL by 49% compared to vehicle infusion, but had no effect in CCK1-R^-/- mice. EL significantly increased the alveolar wall thickness, the number of MPO-positive and TUNEL-positive cells compared to control lymph administration. LCFA infusion in WT, but not in CCK1R^-/- mice, significantly reduced these pathological effects of EL. Conclusion: During endotoxemia enteral LCFA absorption reduces TNFα release into mesenteric lymph and attenuates histomorphologic parameters of lung dysfunction. Failure to elicit this effect in CCK1R^-/- mice demonstrates that anti-inflammatory properties of LCFAs are mediated through CCK1-Rs.

Reduced absorption of long-chain fatty acids during methotrexate-induced gastrointestinal mucositis in the rat

Patients with chemotherapy-induced gastrointestinal mucositis suffer from weight loss and possibly malabsorption. Since long-chain fatty acids serve important functions in the body, we aimed to determine the intestinal capacity of fat absorption in rats with and without methotrexate-induced mucositis. Four days after intravenous injection with methotrexate (60mg/kg) or saline, rats received saturated ([U-(13)C]palmitic acid) and unsaturated ([U-(13)C]linoleic acid) fatty acids dissolved in oil, either as a single bolus by oral gavage or by continuous intraduodenal infusion. We determined plasma and liver label concentrations at specific time points. We confirmed methotrexate-induced mucositis by villus atrophy using microscopy. Methotrexate treatment severely reduced the appearance of [U-(13)C]palmitic- and [U-(13)C]linoleic acid in plasma and liver, compared to controls, either when administered as a bolus or continuously (all at least-63%, P<0.05). Liver [U-(13)C]palmitic acid appearance was higher than [U-(13)C]linoleic acid appearance, either when administered as a bolus (2.8-fold, P<0.01) or continuously (5.7-fold, P<0.01). The intestinal capacity to absorb long-chain fatty acids is severely reduced in rats with methotrexate-induced mucositis. Continuous administration does not overcome this impairment. The liver takes up and/or retains mainly saturated fatty acids during mucositis.

Rapid alternative absorption of dietary long-chain fatty acids with upregulation of intestinal glycosylated CD36 in liver cirrhosis

Dietary long-chain fatty acid (LCFA) intake is an important risk factor for hepatic inflammation and hepatocarcinogenesis. An alternate route of dietary LCFA absorption has been suggested in patients with liver cirrhosis (LC). We aimed to determine this alternate route and to identify its mechanism. Twenty healthy control subjects and 47 patients with LC-n = 23 with portal hypertension [PH(+)LC] and 24 without portal hypertension [PH(-)LC)]-were enrolled. [¹³C]Palmitate (an LCFA) and octanoate (a medium-chain fatty acid [MCFA]) were administered by using gastrointestinal endoscopy. Breath ¹³CO₂ was measured to quantify metabolized fatty acids. We also examined intestinal specimens of patients in these groups. A more rapid increase in metabolized palmitate, which showed a pattern similar to that of octanoate metabolism, was observed in patients with LC than in healthy control subjects. The increase in the PH(-)LC group was higher than that in the PH(+)LC group. However, the concentration of metabolized palmitate increased with treatment of the PH(+)LC group with a portal-systemic shunt. Morphologic changes such as expanded lymph and blood vessels were present, and glycosylated CD36 increased in the jejunum of the PH(+)LC group. This group had high serum concentrations of glucagon-like peptide-2. These data suggest that dietary LCFAs, similar to MCFAs, are absorbed via blood vessels in patients with LC. Rapid absorption of LCFAs by an alternative method occurred in patients with LC. This altered LCFA processing is likely related to upregulation of intestinal glycosylated CD36 and could contribute to pathogenesis in patients with LC.

Intestinal absorption of long-chain fatty acids: evidences and uncertainties on the role of lipid binding proteins

Intestinal absorption of long-chain fatty acids: evidences and uncertainties on the role of lipid binding proteins

Reduced absorption of saturated fatty acids and resistance to diet-induced obesity and diabetes by ezetimibe-treated andNpc1l1−/−mice

The impact of NPC1L1 and ezetimibe on cholesterol absorption are well documented. However, their potential consequences relative to absorption and metabolism of other nutrients have been only minimally investigated. Thus studies were undertaken to investigate the possible effects of this protein and drug on fat absorption, weight gain, and glucose metabolism by using Npc1l1(-/-) and ezetimibe-treated mice fed control and high-fat, high-sucrose diets. Results show that lack of NPC1L1 or treatment with ezetimibe reduces weight gain when animals are fed a diabetogenic diet. This resistance to diet-induced obesity results, at least in part, from significantly reduced absorption of dietary saturated fatty acids, particularly stearate and palmitate, since food intake did not differ between groups. Expression analysis showed less fatty acid transport protein 4 (FATP4) in intestinal scrapings of Npc1l1(-/-) and ezetimibe-treated mice, suggesting an important role for FATP4 in intestinal absorption of long-chain fatty acids. Concomitant with resistance to weight gain, lack of NPC1L1 or treatment with ezetimibe also conferred protection against diet-induced hyperglycemia and insulin resistance. These unexpected beneficial results may be clinically important, given the focus on NPC1L1 as a target for the treatment of hypercholesterolemia.

Absorption intestinale des acides gras : faits et incertitudes

Over the two last decades, isolation and characterization of proteins involved in transport and metabolic fate of long-chain fatty acids have provided new insights on the molecular basis of fat absorption. This systematic cloning period has been followed by the functional genomics time which led to surprises. Indeed, disruption of several genes, thought to be crucial for long-chain fatty acid absorption, did not lead to clear phenotypes. This observation raises the question about the real physiological role of several lipid-binding proteins and enzymes found in the enterocyte. This mini-review assesses the present knowledge concerning the main steps of intestinal fat absorption: the cellular uptake and trafficking of long-chain fatty acids and the lipoprotein synthesis.