High-fat diet induces mouse liver steatosis with a concomitant decline in energy metabolism: attenuation by eicosapentaenoic acid (EPA) or hydroxytyrosol (HT) supplementation and the additive effects upon EPA and HT co-administration

Reduced Liver Mitochondrial Energy Metabolism Impairs Food Intake Regulation Following Gastric Preloads and Fasting

The capacity of the liver to serve as a peripheral sensor in the regulation of food intake has been debated for over half a century. The anatomical position and physiological roles of the liver suggest it is a prime candidate to serve as an interoceptive sensor of peripheral tissue and systemic energy state. Importantly, maintenance of liver ATP levels and within-meal food intake inhibition is impaired in human subjects with obesity and obese pre-clinical models. We demonstrate that decreased hepatic mitochondrial energy metabolism in liver-specific, heterozygous PGC1a mice results in reduced mitochondrial response to changes in ΔGATP and tissue ATP following fasting. These impairments in liver energy state are associated with larger and longer meals during chow feeding, impaired dose-dependent food intake inhibition in response to mixed and individual nutrient oral pre-loads, and greater acute fasting-induced food intake. These data support previous work proposing liver-mediated food intake regulation through modulation of peripheral satiation signals.

Experimental colonization with H. hepaticus, S. aureus and R. pneumotropicus does not influence the metabolic response to high-fat diet or incretin-analogues in wildtype SOPF mice

OBJECTIVES

We here assessed whether typical pathogens of laboratory mice affect the development of diet-induced obesity and glucose intolerance, and whether colonization affects the efficacy of the GLP-1R agonist liraglutide and of the GLP-1/GIP co-agonist MAR709 to treat obesity and diabetes.

METHODS

Male C57BL/6J mice were experimentally infected with Helicobacter hepaticus, Rodentibacter pneumotropicus and Staphylococcus aureus and compared to a group of uninfected specific and opportunistic pathogen free (SOPF) mice. The development of diet-induced obesity and glucose intolerance was monitored over a period of 26 weeks. To study the influence of pathogens on drug treatment, mice were then subjected for 6 days daily treatment with either the GLP-1 receptor agonist liraglutide or the GLP-1/GIP co-agonist MAR709.

RESULTS

Colonized mice did not differ from SOPF controls regarding HFD-induced body weight gain, food intake, body composition, glycemic control, or responsiveness to treatment with liraglutide or the GLP-1/GIP co-agonist MAR709.

CONCLUSIONS

We conclude that the occurrence of H. hepaticus, R. pneumotropicus and S. aureus does neither affect the development of diet-induced obesity or type 2 diabetes, nor the efficacy of GLP-1-based drugs to decrease body weight and to improve glucose control in mice.

Relevant Aspects of Combined Protocols for Prevention of N(M)AFLD and Other Non-Communicable Diseases

Obesity is a global health issue characterized by the excessive fat accumulation, leading to an increased risk of chronic noncommunicable diseases (NCDs), including metabolic dysfunction-associated fatty liver disease (MAFLD), which can progress from simple steatosis to steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. Currently, there are no approved pharmacological protocols for prevention/treatment of MAFLD, and due the complexity lying beneath these mechanisms, monotherapies are unlikely to be efficacious. This review article analyzes the possibility that NCDs can be prevented or attenuated by the combination of bioactive substances, as they could promote higher response rates, maximum reaction results, additive or synergistic effects due to compounds having similar or different mechanisms of action and/or refraining possible side effects, related to the use of lower doses and exposures times than monotherapies. Accordingly, prevention of mouse MAFLD is observed with the combination of the omega-3 docosahexaenoic acid with the antioxidant hydroxytyrosol, whereas attenuation of mild cognitive impairment is attained by folic acid plus cobalamin in elderly patients. The existence of several drawbacks underlying published monotherapies or combined trials, opens space for adequate and stricter experimental and clinical tryouts to achieve meaningful outcomes with human applicability.

Gentiopicroside improves non-alcoholic steatohepatitis by activating PPARα and suppressing HIF1

Gentiopicroside (GPS) is a highly water-soluble small-molecule drug and the main bioactive secoiridoid glycoside of Gentiana scabra that has been shown to have hepatoprotective effects against non-alcoholic steatohepatitis (NASH), a form of non-alcoholic fatty liver disease (NAFLD) that can progress to cirrhosis and hepatocellular carcinoma. However, the effects of GPS on NASH and the underlying mechanisms remain obscure. Firstly, a high-fat, high-cholesterol (HFHC) diet and a high-sugar solution containing d-fructose and d-glucose were used to establish a non-alcoholic steatohepatitis (NASH) mice model. Secondly, we confirmed GPS supplementation improve metabolic abnormalities and reduce inflammation in NASH mice induced by HFHC and high-sugar solution. Then we used metabolomics to investigate the mechanisms of GPS in NASH mice. Metabolomics analysis showed GPS may work through the Peroxisome Proliferator-Activated Receptor (PPAR) signaling pathway and glycine, serine, and threonine metabolism. Functional metabolites restored by GPS included serine, glycine, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Western blot and qRT-PCR analysis confirmed GPS improve NASH by regulating PPARα and Hypoxia-Inducible Factor-1α (HIF-1α) signaling pathways. In vitro, studies further demonstrated EPA and DHA enhance fatty acid oxidation through the PPARα pathway, while serine and glycine inhibit oxidative stress through the HIF-1α pathway in palmitic acid-stimulated HepG2 cells. Our results suggest GPS's anti-inflammatory and anti-steatosis effects in NASH progression are related to the suppression of HIF-1α through the restoration of L-serine and glycine and the activation of PPARα through increased EPA and DHA.

Anti-Obesity Effects of GABA in C57BL/6J Mice with High-Fat Diet-Induced Obesity and 3T3-L1 Adipocytes

Obesity is the excessive accumulation of body fat resulting from impairment in energy balance mechanisms. In this study, we aimed to investigate the mechanism whereby GABA (γ-aminobutyric acid) prevents high-fat diet-induced obesity, and whether it induces lipolysis and browning in white adipose tissue (WAT), using high-fat diet (HFD)-fed obese mice and 3T3-L1 adipocytes. We demonstrated that GABA substantially inhibits the body mass gain of mice by suppressing adipogenesis and lipogenesis. Consistent with this result, histological analysis of WAT demonstrated that GABA decreases adipocyte size. Moreover, we show that GABA administration decreases fasting blood glucose and improves serum lipid profiles and hepatic lipogenesis in HFD-fed obese mice. Furthermore, Western blot and immunofluorescence analyses showed that GABA activates protein kinase A (PKA) signaling pathways that increase lipolysis and promote uncoupling protein 1 (UCP1)-mediated WAT browning. Overall, these results suggest that GABA exerts an anti-obesity effect via the regulation of lipid metabolism.

Protectin D1 inhibits TLR4 signaling pathway to alleviate non-alcoholic steatohepatitis via upregulating IRAK-M

Non-alcoholic steatohepatitis (NASH) is a prevalent metabolic disease, characterized by the hepatic steatosis, inflammation, and fibrosis, which is lack of effective treatment currently. Protectin D1 (PTD1), a lipid mediator from omega-3 fatty acid docosahexaenoic acid (DHA), has displayed wide pharmacological actions including anti-inflammation in a variety of diseases, but the role of PTD1 on NASH remains unclear. In this study, using the methionine and choline deficient (MCD) fed NASH model, we explored the effect and underlying mechanism of PTD1 on NASH in mice. Our results showed PTD1 improved MCD-induced steatosis, hepatocellular injury, inflammation and fibrosis. Furthermore, PTD1 inhibited MCD-induced activation of TLR4 downstream molecules (TAK1, p38 and p65) without affecting the levels of TLR4 and phosphorylated IRAK-1. Notably, the levels of IRAK-M protein and the binding between IRAK-M and TRAF6 in the liver were also increased by PTD1 in NASH mice. Moreover, IRAK-M knockout remarkedly reverted the beneficial effects of PTD1 on the NASH in mice. Thus, these results demonstrated that PTD1 could protect mice from NASH by inhibiting the activation of TLR4 downstream signaling pathway, which might be related to the upregulation of IRAK-M, indicating that PTD1 may provide a new treatment for NASH.

Hydroxytyrosol attenuates ethanol-induced liver injury by ameliorating steatosis, oxidative stress and hepatic inflammation by interfering STAT3/iNOS pathway

Objective: Hydroxytyrosol (HT) is a polyphenol with a wide range of biological activities. Excessive drinking can lead to oxidative stress and inflammation in the liver, which usually develop into alcohol liver disease (ALD). At present, there is no specific drug to treat ALD. In this paper, the protection effect of HT on ALD and the underline mechanism were studied.Methods: HepG2 cells were exposed to ethanol in vitro and C57BL/6J mice were fed with a Lieber-DeCarli ethanol liquid diet in vivo.Results: triglyceride (TG) level in serum and the expression of fatty acid synthase (FASN) were reduced significantly by the treatment with HT The acetaldehyde dehydrogenase (ALDH) activity was increased, the serum level of malondialdehyde (MDA) was decreased, catalase (CAT) and glutathione (GSH) were increased, suggesting that HT may reduce its oxidative damage to the body by promoting alcohol metabolism. Furthermore, according to the mRNA levels of tnf-α, il-6 and il-1β, HT inhibited ethanol-induced inflammation significantly. The anti-inflammatory mechanism of HT may be related to suppress the STAT3/iNOS pathway.Dissussion: Our study showed that HT could ameliorate ethanol-induced hepatic steatosis, oxidative stress and inflammation and provide a new candidate for the prevention and treatment of ALD.

Bioactive dipeptides mitigate high-fat and high-fructose corn syrup diet-induced metabolic-associated fatty liver disease via upregulation of Nrf2/HO-1 expressions in C57BL/6J mice

Metabolic-associated fatty liver disease (MAFLD), formerly referred to as non-alcoholic fatty liver disease (NAFLD), is a common liver disease characterized by an abnormal buildup of fat in liver. This study aimed to investigate whether bioactive dipeptides mitigate high-fat and high-fructose corn syrup diet (HFFD)-induced MAFLD in C57BL/6J mice. Sixty male C57BL/6J mice were randomly divided into six groups. The naïve group (untreated) was fed a standard chow diet and other groups were fed with HFFD along with vehicle and bioactive dipeptides treatment throughout experiment period. The control group received vehicle, YF10 and YF50 groups received Tyr-Phe, 10 and 50 mg/kg/day, FY10 and FY50 groups received Phe-Tyr, 10 and 50 mg/kg/day. At the end of experiment, body weight was recorded, and glucose homeostasis was assessed. Mice were sacrificed and blood samples were collected to measure biochemical parameters. Further, liver, visceral fat pads, and other organs were acutely dissected, weighed, and processed. Histopathological and immunohistochemical changes were analyzed. Long-term HFFD feeding resulted in elevated body weight gain, liver weight, visceral adiposity, liver injury, fasting hyperglycemia, hyperinsulinemia, and hyperlipidemia. It also increased severe hepatic steatosis, chronic low-grade inflammation, oxidative stress, mitochondrial dysfunction, and lipid peroxidation. However, bioactive dipeptides dose-dependently alleviated these complications which are associated with MAFLD by modulating adipokines secretion and antioxidant defense system via upregulation of Nrf2/HO-1 expressions. This study highlights potential of bioactive dipeptides as a promising approach for prevention and/or treatment of MAFLD induced by HFFD, providing novel insights into alternative therapeutic strategies.

Targeted proteomic analysis reveals that crocodile oil from Crocodylus siamensis may enhance hepatic energy metabolism in rats

The liver is a key organ governing body energy metabolism. Dietary fats influence energy metabolism and mitochondrial functioning. Crocodile oil (CO) is rich in mono- and polyunsaturated fatty acids that contain natural anti-inflammatory and healing properties. Our study examined how CO affects the expressions of liver proteins involved in energy metabolism in rats. Twenty-one male Sprague Dawley rats were divided into three groups and underwent oral gavage with 3 ml/kg of sterile water (N group), CO (CO group), or palm oil (PO group) for 7 weeks. Body weight, energy intake, liver weight, liver indexes, blood lipid profiles, and liver-energy intermediates were measured. The liver proteome was analyzed using shotgun proteomics, and the functions and network interactions of several candidate proteins were predicted using the STITCH v.5.0 software. Body weights, energy intake, liver contents, and lipid profiles did not differ between the groups. However, hepatic oxaloacetate and malate levels were significantly higher in the CO group than in the PO group. Targeted proteomics reveals that 22 out of 1,790 unique proteins in the CO group were involved in energy-generating pathways, including the tricarboxylic acid cycle and oxidative phosphorylation (OXPHOS), and were correlated with the AMP-activated protein kinase signaling pathway. Cluster analysis of 59 differentially expressed proteins showed that OXPHOS-associated proteins were upregulated in the CO group and that three glycolytic metabolism-related proteins were downregulated in the CO group. CO may enhance hepatic energy metabolism by regulating the expressions of energy expenditure-related proteins.

Green Pea (Pisum sativum L.) Hull Polyphenol Extract Alleviates NAFLD through VB6/TLR4/NF-κB and PPAR Pathways

Green pea hull is a processing byproduct of green pea and rich in polyphenols. Nonalcoholic fatty liver disease (NAFLD) is a chronic metabolic disease characterized by accumulation of lipids in the liver for which there are no effective treatment strategies. Here, a mouse model of NAFLD induced by a DSS+high-fat diet (HFD) was established to investigate the effect of green pea hull polyphenol extract (EGPH). The results show that EGPH relief of NAFLD was a combined effect, including reducing hepatic fat accumulation, improving antioxidant activity and blood lipid metabolism, and maintaining glucose homeostasis. Increased intestinal permeability aggravated NAFLD. Combined metabolomics and transcriptomic analysis showed that vitamin B6 is the key target substance for EGPH to alleviate NAFLD, and it may be the intestinal flora metabolite. After EGPH intervention, the level of vitamin B6 in mice was significantly increased, and more than 60% in the blood enters the liver, which activated or inhibited PPAR and TLR4/NF-κB signaling pathways to relieve NAFLD. Our research could be a win-win for expanding the use of green pea hull and the search for NAFLD prophylactic drugs.

Dynamic Alterations to Hepatic MicroRNA-29a in Response to Long-Term High-Fat Diet and EtOH Feeding

MicroRNA-29a (miR-29a) is a well characterized fibro-inflammatory molecule and its aberrant expression is linked to a variety of pathological liver conditions. The long-term effects of a high-fat diet (HFD) in combination with different levels of EtOH consumption on miR-29a expression and liver pathobiology are unknown. Mice at 8 weeks of age were divided into five groups (calorie-matched diet plus water (CMD) as a control group, HFD plus water (HFD) as a liver disease group, HFD plus 2% EtOH (HFD + 2% E), HFD + 10% E, and HFD + 20% E as intervention groups) and fed for 4, 13, 26, or 39 weeks. At each time point, analyses were performed for liver weight/body weight (BW) ratio, AST/ALT ratio, as well as liver histology assessments, which included inflammation, estimated fat deposition, lipid area, and fibrosis. Hepatic miR-29a was measured and correlations with phenotypic traits were determined. Four-week feeding produced no differences between the groups on all collected phenotypic traits or miR-29a expression, while significant effects were observed after 13 weeks, with EtOH concentration-specific induction of miR-29a. A turning point for most of the collected traits was apparent at 26 weeks, and miR-29a was significantly down-regulated with increasing liver injury. Overall, miR-29a up-regulation was associated with a lower liver/BW ratio, fat deposition, inflammation, and fibrosis, suggesting a protective role of miR-29a against liver disease progression. A HFD plus increasing concentrations of EtOH produces progressive adverse effects on the liver, with no evidence of beneficial effects of low-dose EtOH consumption. Moreover, miR-29a up-regulation is associated with less severe liver injury.

New Perspectives on the Associations between Blood Fatty Acids, Growth Parameters, and Cognitive Development in Global Child Populations

Malnutrition is prevalent in low-middle-income countries (LMICs), but it is usually clinically diagnosed through abnormal anthropometric parameters characteristic of protein energy malnutrition (PEM). In doing so, other contributors or byproducts of malnutrition, notably essential fatty acid deficiency (EFAD), are overlooked. Previous research performed mainly in high-income countries (HICs) shows that deficiencies in essential fatty acids (EFAs) and their n-3 and n-6 polyunsaturated fatty acid (PUFA) byproducts (also known as highly unsaturated fatty acids or HUFAs) lead to both abnormal linear growth and impaired cognitive development. These adverse developmental outcomes remain an important public health issue in LMICs. To identify EFAD before severe malnutrition develops, clinicians should perform blood fatty acid panels to measure levels of fatty acids associated with EFAD, notably Mead acid and HUFAs. This review demonstrates the importance of measuring endogenous fatty acid levels for measuring fatty acid intake in various child populations in LMICs. Featured topics include a comparison of fatty acid levels between global child populations, the relationships between growth and cognition and PUFAs and the possible mechanisms driving these relationships, and the potential importance of EFAD and HUFA scores as biomarkers of overall health and normal development.

Enriched functional milk fat ameliorates glucose intolerance and triacylglycerol accumulation in skeletal muscle of rats fed high-fat diets

PURPOSE

We examined the effect of a functional milk fat (FMF) on the glucose metabolism and its association with the intramuscular triacylglycerol (TAG) content in rats fed high-fat diets.

METHODS

Male Wistar rats were fed for 60 days with S7 (soybean oil 7%), S30 (soybean oil 30%), MF30 (soybean oil 3% + milk fat 27%), or FMF30 (soybean oil 3% + FMF 27%) diets. An oral glucose tolerance test was performed. The levels of key metabolites in gastrocnemius muscle and mRNA levels of genes involved in glucose and lipid metabolism in muscle, epididymal white adipose tissue (EWAT), and serum were assessed.

RESULTS

The S30 diet induced glucose intolerance and led to TAG, citrate, and glucose accumulation in muscle. Moreover, we observed a downregulation of uncoupling proteins (Ucp2 and Ucp3) and insulin receptor substrate-1 (Irs1) genes, lower carnitine palmitoyl transferase-1b (CPT-1b), and phosphofructokinase-1 (PFK1) activities in muscle and lower expression of adiponectin (Adipoq) in EWAT. The FMF30 diet ameliorated the glucose intolerance and normalized the glucose and TAG levels in muscle, preventing the accumulation of citrate and enhancing glucose utilization by the PFK1. The beneficial effects might also be related to the higher expression of Adipoq in EWAT, its receptor in muscle (Adipor1), and the expression of Ucp2, Ucp3, and Irs1 in muscle, restoring the alterations observed with the S30 diet.

CONCLUSIONS

FMF30 modulated key genes involved in glucose and lipid metabolism in skeletal muscle, improving the glucose utilization and preventing TAG, glucose, and citrate accumulation.

Eicosapentaenoic acid-enriched phospholipids alleviate glucose and lipid metabolism in spontaneously hypertensive rats with CD36 mutation: a precise nutrition strategy

Previous studies have found that eicosapentaenoic acid-enriched phospholipids (EPA-PLs) alleviated glucose and lipid metabolism, which was accompanied by an increase of cluster of differentiation 36 (CD36). However, the effects of EPA-PLs on glucose and lipid metabolism in the case of CD36 mutation are unclear. Thus, spontaneously hypertensive rats/NCrl (SHR) were used as a CD36 mutation model to determine the effects of dietary 2% EPA-PLs for 4 weeks on glucose and lipid metabolism. The results showed that the intervention of EPA-PLs significantly alleviated the abnormal increase of serum free fatty acid levels and glycerol levels in SHRs. Moreover, the administration of EPA-PLs decreased the triglyceride levels and cholesterol levels by 31.1% and 37.9%, respectively, in the liver. Dietary EPA-PLs had no effect on epididymal fat weight, but EPA-PLs inhibited adipocyte hypertrophy in SHRs. Further mechanistic research found that EPA-PL pretreatment significantly reduced triacylglycerol catabolism and increased fatty acid β-oxidation. Additionally, the administration of EPA-PLs decreased the area under the curve of the intraperitoneal glucose tolerance test and fasting serum insulin levels by activating the IRS/PI3K/AKT signaling pathway. Furthermore, EPA-PL pretreatment significantly increased the CD36 gene expression in the liver tissues, adipose tissues and muscle tissues even in the case of CD36 mutation. These results indicated that EPA-PLs alleviate glucose and lipid metabolism in the case of CD36 mutation, which provides a precise nutrition strategy for people with CD36 mutation.

FAM3A maintains metabolic homeostasis by interacting with F1-ATP synthase to regulate the activity and assembly of ATP synthase

Reduced mitochondrial ATP synthase (ATPS) capacity plays crucial roles in the pathogenesis of metabolic disorders. However, there is currently no effective strategy for synchronously stimulating the expressions of ATPS key subunits to restore its assembly. This study determined the roles of mitochondrial protein FAM3A in regulating the activity and assembly of ATPS in hepatocytes. FAM3A is localized in mitochondrial matrix, where it interacts with F1-ATPS to initially activate ATP synthesis and release, and released ATP further activates P2 receptor-Akt-CREB pathway to induce FOXD3 expression. FOXD3 synchronously stimulates the transcriptions of ATPS key subunits and assembly genes to increase its assembly and capacity, augmenting ATP synthesis and inhibiting ROS production. FAM3A, FOXD3 and ATPS expressions were reduced in livers of diabetic mice and NAFLD patients. FOXD3 expression, ATPS capacity and ATP content were reduced in various tissues of FAM3A-deficient mice with dysregulated glucose and lipid metabolism. Hepatic FOXD3 activation increased ATPS assembly to ameliorate dysregulated glucose and lipid metabolism in obese mice. Hepatic FOXD3 inhibition or knockout reduced ATPS capacity to aggravate HFD-induced hyperglycemia and steatosis. In conclusion, FAM3A is an active ATPS component, and regulates its activity and assembly by activating FOXD3. Activating FAM3A-FOXD3 axis represents a viable strategy for restoring ATPS assembly to treat metabolic disorders.

Effect of Structured Phenolic Lipids with EPA/DHA and Gallic Acid against Metabolic-Associated Fatty Liver Disease (MAFLD) in Mice

Obesity is the leading risk factor for developing metabolic (dysfunction)-associated fatty liver disease (MAFLD). The food industry has an essential role in searching for new strategies to improve primary food sources to revert some of the metabolic alterations induced by obesity. There is consistent evidence that long-chain polyunsaturated fatty acids (n-3 LCPUFA) belonging to the n-3 series, i.e., eicosapentaenoic (20:5n-3, EPA) and docosahexaenoic (22:6n-3, DHA) acids, could revert some alterations associated with obesity-induced metabolic diseases. A relevant tool is the synthesis of structured acylglycerols (sAG), which include EPA or DHA at the sn-2 position. On the other hand, it has been reported that a crucial role of antioxidants is the reversion of MAFLD. In this work, we studied the effects of new molecules incorporating gallic acid (GA) into EPA/DHA-rich structured lipids. Mice were fed with a high-fat diet (60%) for three months and were then divided into five groups for supplementation with sAG and sAG structured with gallic acid (structured phenolic acylglycerols, sPAG). sPAG synthesis was optimized using a 2²-screening factorial design based on the response surface methodology (RSM). Our results show that treatment of sPAG was effective in decreasing visceral fat, fasting glycemia, fasting insulin, suggesting that this new molecule has a potential use in the reversal of MAFLD-associated alterations.

ATP Secretion and Metabolism in Regulating Pancreatic Beta Cell Functions and Hepatic Glycolipid Metabolism

Diabetes (DM), especially type 2 diabetes (T2DM) has become one of the major diseases severely threatening public health worldwide. Islet beta cell dysfunctions and peripheral insulin resistance including liver and muscle metabolic disorder play decisive roles in the pathogenesis of T2DM. Particularly, increased hepatic gluconeogenesis due to insulin deficiency or resistance is the central event in the development of fasting hyperglycemia. To maintain or restore the functions of islet beta cells and suppress hepatic gluconeogenesis is crucial for delaying or even stopping the progression of T2DM and diabetic complications. As the key energy outcome of mitochondrial oxidative phosphorylation, adenosine triphosphate (ATP) plays vital roles in the process of almost all the biological activities including metabolic regulation. Cellular adenosine triphosphate participates intracellular energy transfer in all forms of life. Recently, it had also been revealed that ATP can be released by islet beta cells and hepatocytes, and the released ATP and its degraded products including ADP, AMP and adenosine act as important signaling molecules to regulate islet beta cell functions and hepatic glycolipid metabolism via the activation of P2 receptors (ATP receptors). In this review, the latest findings regarding the roles and mechanisms of intracellular and extracellular ATP in regulating islet functions and hepatic glycolipid metabolism would be briefly summarized and discussed.

Therapeutic Properties and Use of Extra Virgin Olive Oil in Clinical Nutrition: A Narrative Review and Literature Update

Extra virgin olive oil (EVOO) is a cornerstone of the Mediterranean diet (MedD). In this narrative review, we synthesize and illustrate the various characteristics and clinical applications of EVOO and its components—such as oleic acid, hydroxytyrosol, and oleuropein—in the field of clinical nutrition and dietetics. The evidence is split into diet therapy, oleic acid-based enteral nutrition formulations and oral supplementation formulations, oleic acid-based parenteral nutrition, and nutraceutical supplementation of minor components of EVOO. EVOO has diverse beneficial health properties, and current evidence supports the use of whole EVOO in diet therapy and the supplementation of its minor components to improve cardiovascular health, lipoprotein metabolism, and diabetes mellitus in clinical nutrition. Nevertheless, more intervention studies in humans are needed to chisel specific recommendations for its therapeutic use through different formulations in other specific diseases and clinical populations.

Perspectives in liver redox imbalance: Toxicological and pharmacological aspects underlying iron overloading, nonalcoholic fatty liver disease, and thyroid hormone action

Oxidative stress is an imbalance between oxidants and antioxidants in favor of the oxidants, leading to a disruption of redox signaling and control, and/or molecular damage altering cellular functions. This redox imbalance may trigger different responses depending on the antioxidant potential of a given cell, the level of reactive oxygen/nitrogen species (ROS/RNS) attained and the time of exposure, with protective effects being induced at low ROS/RNS levels in acute or short-term conditions, and harmful effects after high ROS/RNS exposure in prolonged situations. Relevant conditions underlying liver redox imbalance include iron overload associated with ROS production via Fenton chemistry and the magnitude of the iron labile pool achieved, with low iron exposure inducing protective effects related to nuclear factor-κB, signal transducer and activation of transcription 3, and nuclear factor erythroid-related factor 2 (Nrf2) activation and upregulation of ferritin, hepcidin, acute-phase response and antioxidant components, whereas high iron exposure causes drastic oxidation of biomolecules, mitochondrial dysfunction, and cell death due to necrosis, apoptosis and/or ferroptosis. Redox imbalance in nonalcoholic fatty liver disease (NAFLD) is related to polyunsaturated fatty acid depletion, lipogenic factor sterol regulatory element-binding protein-1c upregulation, fatty acid oxidation-dependent peroxisome proliferator-activated receptor-α downregulation, low antioxidant factor Nrf2 and insulin resistance, a phenomenon that is exacerbated in nonalcoholic steatohepatitis triggering an inflammatory response. Thyroid hormone (T₃ ) administration determines liver preconditioning against ischemia-reperfusion injury due to the redox activation of several transcription factors, AMP-activated protein kinase, unfolded protein response and autophagy. High grade liver redox imbalance occurring in severe iron overload is adequately handled by iron chelation, however, that underlying NAFLD/NASH is currently under study in several Phase II and Phase III trials.

Dichloroacetate reactivates pyruvate-supported peroxide removal by liver mitochondria and prevents NAFLD aggravation in NAD(P)+ transhydrogenase-null mice consuming a high-fat diet

The mechanisms by which a high-fat diet (HFD) promotes non-alcoholic fatty liver disease (NAFLD) appear to involve liver mitochondrial dysfunction and redox imbalance. The functional loss of the enzyme NAD(P)+ transhydrogenase, a main source of mitochondrial NADPH, results in impaired mitochondrial peroxide removal, pyruvate dehydrogenase inhibition by phosphorylation, and progression of NAFLD in HFD-fed mice. The present study aimed to investigate whether pharmacological reactivation of pyruvate dehydrogenase by dichloroacetate attenuates the mitochondrial redox dysfunction and the development of NAFLD in NAD(P)+ transhydrogenase-null (Nnt-/-) mice fed an HFD (60% of total calories from fat). For this purpose, Nnt-/- mice and their congenic controls (Nnt+/+) were fed chow or an HFD for 20 weeks and received sodium dichloroacetate or NaCl in the final 12 weeks via drinking water. The results showed that HFD reduced the ability of isolated liver mitochondria from Nnt-/- mice to remove peroxide, which was prevented by the dichloroacetate treatment. HFD-fed mice of both Nnt genotypes exhibited increased body and liver mass, as well as a higher content of hepatic triglycerides, but dichloroacetate treatment attenuated these abnormalities only in Nnt-/- mice. Notably, dichloroacetate treatment decreased liver pyruvate dehydrogenase phosphorylation levels and prevented the aggravation of NAFLD in HFD-fed Nnt-/- mice. Conversely, dichloroacetate treatment elicited moderate hepatocyte ballooning in chow-fed mice, suggesting potentially toxic effects. We conclude that the protection against HFD-induced NAFLD by dichloroacetate is associated with its role in reactivating pyruvate dehydrogenase and reestablishing the pyruvate-supported liver mitochondrial capacity to handle peroxide in Nnt-/- mice.

Salvianolic acid B inhibits the progression of liver fibrosis in rats via modulation of the Hedgehog signaling pathway

Salvianolic acid B (Sal B) has previously reported anti-hepatic fibrosis effects, though it is not clear if it can inhibit hepatic fibrosis by regulating the hedgehog (Hh) signaling pathway. The aim of the present study was to explore the roles and mechanism of Sal B in preventing and treating liver fibrosis in rats. The study also aimed to determine the role of the Hh signaling pathway in this process. A rat model of liver fibrosis was induced through the subcutaneous injection of 50% carbon tetrachloride, followed by treatment with Sal B. After gavage, blood was collected to detect serum markers of liver injury. The degree of liver fibrosis and tissue damage was assessed using histopathological analysis. Western blotting and reverse transcription-quantitative PCR were used to detect the expression levels of TGF-β1 and Hh signaling pathway-related genes, including Sonic hedgehog (Shh) protein, membrane protein receptor protein patched homolog 1 (Ptch1), membrane protein receptor Smoothened (Smo) and transcription factor glioma-associated oncogene homolog 1 (Gli1). Serum alanine aminotransferase, aspartate aminotransferase and total bilirubin levels were decreased, whilst levels of albumin were increased in rats with liver fibrosis that were treated with Sal B (P<0.05). Additionally, significant increases in TGF-β1, Shh, Ptch1, Smo, Gli1 and α-smooth muscle actin expression levels were observed in the liver tissues of rats with hepatic fibrosis (P<0.05). However, Sal B treatment significantly reduced the expression levels of these proteins (P<0.05). In conclusion, the results of the present study suggested that the Hh signaling pathway may be activated during the process of rat liver fibrosis. Thus, Sal B may exert its anti-hepatic fibrosis effects, at least in part, by inhibiting the activation of the Hh signaling pathway.

A dipeptidyl peptidase IV inhibitory peptide relieves palmitic acid-induced endoplasmic reticulum stress in HepG2 cells independent of inhibiting dipeptidyl peptidase IV activity

The peptide VLATSGPG (VLA) is known to inhibit dipeptidyl peptidase IV (DPP-IV), although its mechanism in relieving endoplasmic reticulum (ER) stress is unclear. In this study, we found that treating HepG2 cells with 1.0 mM VLA reduced DPP-IV activity by 73.7 ± 4.8% without changing the DPP-IV mRNA expression level. In addition, 1.0 and 0.5 mM VLA alleviated palmitic acid (PA)-induced cell death and intracellular calcium imbalances. The levels of apoptosis-related proteins (caspase-3, caspase-9, and CHOP) were reduced by VLA treatment, which was presumed to be related to ER stress. Further studies confirmed that VLA alleviated PA-induced morphological damage to the ER and reduced the levels of the ER stress marker proteins (BIP, p-PERK, and p-IRE1α). VLA alleviated PA-induced ER stress in HepG2 cells independent of DPP-IV enzymatic activity inhibition. These findings have implications for developing novel treatment approaches for liver diseases caused by ER stress.

Beneficial effects of dietary supplementation with olive oil, oleic acid, or hydroxytyrosol in metabolic syndrome: Systematic review and meta-analysis

BACKGROUND AND AIMS

Olive oil and components might have a beneficial effect on Metabolic Syndrome (MetS). The aim of this review and meta-analysis was to assess whether those effects are related to hydroxytyrosol or oleic acid contents, or the combination of them as olive oil, and how powerful is this effect.

METHODS

A systematic literature search was performed in MEDLINE via Pubmed, Web of Science (WOS) core collection, and Virtual Health Library (VHL) via LILACS and IBECS (Spain). MeSH terms used were "obesity", "body weight", "body mass index", "adipose tissue", "lipid metabolism", "LDL", "HDL", "VLDL", "insulin resistance", "glucose", "insulin", "hypertension", "arterial pressure", "olive oil", "oleic acid", and other (non-MeSH) terms: "total antioxidant capacity", "total antioxidant status", "hydroxytyrosol" (PROSPERO ID: CRD42021247614). Results of the included studies were meta-analyzed with the RevMan 5.3 program, assuming a random effects model.

RESULTS

76 articles (67 different trials) were identified. Hydroxytyrosol had no effect on MetS [combined standardized mean differences (SMD) = 0.01 (CI 95%: [-0.23, 0.25], I² = 83%; p = 0.920)]. Oleic acid had no significant beneficial effect on MetS [SMD = 0.03 (CI 95%: [-0.01, 0.07], I² = 0%); p = 0.150], but it improved lipid profile [SMD = 0.06 (CI 95%: [-0.00, 0.12], I² = 0%); p = 0. 050]. Olive oil had no effect on MetS [SMD = -0.01 (CI 95%: [-0.05, 0.03]), I² = 55%; p = 0.550)]. The supplementation with hydroxytyrosol, oleic acid or olive oil showed a beneficial effect on antioxidant capacity related to components of MetS [SMD = 0.31 (CI 95%: [-0.34, 0.95], I² = 81%)]; p = 0.35).

CONCLUSION

Most articles compared olive oil and oleic acid with other strategies specially designed for MetS management. Our findings suggest that olive oil or oleic acid consumption are as good as the other strategies to manage MetS.

Mitochondria Matter: Systemic Aspects of Nonalcoholic Fatty Liver Disease (NAFLD) and Diagnostic Assessment of Liver Function by Stable Isotope Dynamic Breath Tests

The liver plays a key role in systemic metabolic processes, which include detoxification, synthesis, storage, and export of carbohydrates, lipids, and proteins. The raising trends of obesity and metabolic disorders worldwide is often associated with the nonalcoholic fatty liver disease (NAFLD), which has become the most frequent type of chronic liver disorder with risk of progression to cirrhosis and hepatocellular carcinoma. Liver mitochondria play a key role in degrading the pathways of carbohydrates, proteins, lipids, and xenobiotics, and to provide energy for the body cells. The morphological and functional integrity of mitochondria guarantee the proper functioning of β-oxidation of free fatty acids and of the tricarboxylic acid cycle. Evaluation of the liver in clinical medicine needs to be accurate in NAFLD patients and includes history, physical exam, imaging, and laboratory assays. Evaluation of mitochondrial function in chronic liver disease and NAFLD is now possible by novel diagnostic tools. "Dynamic" liver function tests include the breath test (BT) based on the use of substrates marked with the non-radioactive, naturally occurring stable isotope 13C. Hepatocellular metabolization of the substrate will generate 13CO2, which is excreted in breath and measured by mass spectrometry or infrared spectroscopy. Breath levels of 13CO2 are biomarkers of specific metabolic processes occurring in the hepatocyte cytosol, microsomes, and mitochondria. 13C-BTs explore distinct chronic liver diseases including simple liver steatosis, non-alcoholic steatohepatitis, liver fibrosis, cirrhosis, hepatocellular carcinoma, drug, and alcohol effects. In NAFLD, 13C-BT use substrates such as α-ketoisocaproic acid, methionine, and octanoic acid to assess mitochondrial oxidation capacity which can be impaired at an early stage of disease. 13C-BTs represent an indirect, cost-effective, and easy method to evaluate dynamic liver function. Further applications are expected in clinical medicine. In this review, we discuss the involvement of liver mitochondria in the progression of NAFLD, together with the role of 13C-BT in assessing mitochondrial function and its potential use in the prevention and management of NAFLD.

Lactobacillus acidophilus and vitamin C attenuate ethanol-induced intestinal and liver injury in mice

Ethanol exposure frequently induces intestinal and liver injury, dysbiosis of the gut microbiota and vitamin C (VC) deficiency. Gut microbiota-targeted therapy is emerging as an important adjuvant method for protecting the body against ethanol-induced injury, particularly probiotics containing Lactobacillus acidophilus (LA). However, the feasibility and efficiency of using synbiotics containing LA and VC against ethanol-induced injury remained largely undetermined. To examine the advantages of LA+VC, their effect was evaluated in an ethanol-fed mouse model. The results suggested that LA+VC restored gut microbiota homeostasis and reinstated the immune balance of colonic T-regulatory cells (CD4⁺CD45⁺forkhead box p3⁺). In addition, intestinal barrier disorders were improved via upregulating tight junction proteins (claudin-2, zona occludens-1 and occludin) and mucus secretion, which prevented the translocation of lipopolysaccharide into circulatory systems and subsequently reduced the expression of Toll-like receptor 4 in liver tissues. In this context, LA+VC treatment reduced the inflammatory response in the liver, which was likely responsible for the improved liver function in ethanol-challenged mice. Collectively, these results indicated that LA+VC treatment significantly protected the intestine and liver from ethanol damage by enhancing intestinal barrier function and reducing systemic inflammation. The present study paved the way for further exploration of synbiotics based on Lactobacillus species and VC.

The metabolic dysfunction of white adipose tissue induced in mice by a high-fat diet is abrogated by co-administration of docosahexaenoic acid and hydroxytyrosol

BACKGROUND

Nutritional interventions are promising tools for the prevention of obesity. The n-3 long-chain polyunsaturated fatty acid (n-3 LCPUFA) docosahexaenoic acid (DHA) modulates immune and metabolic responses while the antioxidant hydroxytyrosol (HT) prevents oxidative stress (OS) in white adipose tissue (WAT).

OBJECTIVE

The DHA plus HT combined protocol prevents WAT alterations induced by a high-fat diet in mice. Main related mechanisms.

METHODS

Male C57BL/6J mice were fed a control diet (CD; 10% fat, 20% protein, and 70% carbohydrates) or a high fat diet (HFD) (60% fat, 20% protein, and 20% carbohydrates) for 12 weeks, without and with supplementation of DHA (50 mg kg-1 day-1), HT (5 mg kg-1 day-1) or both. Measurements of WAT metabolism include morphological parameters, DHA content in phospholipids (gas chromatography), lipogenesis, OS and inflammation markers, mitochondrial activity and gene expression of transcription factors SREBP-1c, PPAR-γ, NF-κB (p65) and Nrf2 (quantitative polymerase chain reaction and enzyme-linked immunosorbent assay).

RESULTS

The combined DHA and HT intervention attenuated obesity development, suppressing the HFD-induced inflammatory and lipogenic signals, increasing antioxidant defenses, and maintaining the phospholipid LCPUFA n-3 content and mitochondrial function in WAT. At the systemic level, the combined intervention also improved the regulation of glucose and adipokine homeostasis.

CONCLUSION

The combined DHA and HT protocol appears to be an important nutritional strategy for the treatment of metabolic diseases, with abrogation of obesity-driven metabolic inflammation and recovery of a small-healthy adipocyte phenotype.

Functional milk fat enriched in conjugated linoleic acid prevented liver lipid accumulation induced by a high-fat diet in male rats

The aim was to investigate the potential effect of functional milk fat (FMF), naturally enriched in conjugated linoleic acid, on the prevention of liver lipid accumulation and some biochemical mechanisms involved in the liver triacylglycerol (TAG) regulation in high-fat (HF) fed rats. Male Wistar rats were fed (60 days) with S7 (soybean oil, 7%) or HF diets: S30 (soybean oil, 30%), MF30 (soybean oil, 3% + milk fat -MF-, 27%) or FMF30 (soybean oil, 3% + FMF, 27%). Nutritional parameters, hepatic fatty acid (FA) composition, liver and serum TAG levels, hepatic TAG secretion rate (TAG-SR), lipoprotein lipase (LPL) activity in adipose tissue and muscle, activities and/or mRNA levels of lipogenic and β-oxidative enzymes, and mRNA levels of transcription factors and FA transport proteins were assessed. The hepatic lipid accumulation induced by the S30 diet was associated with increased mRNA levels of FA transporters; and it was prevented by FMF through an increase in the hepatic TAG-SR, carnitine palmitoyltransferase-1a activity and peroxisome proliferator-activated receptor alpha mRNA levels, as well as by a reduction of the mRNA levels of FA transporters. The hypotriacylglyceridaemia observed in S30 was related with an increased LPL activity in adipose tissue and it was reverted by FMF through the increased hepatic TAG-SR. In brief, FMF prevented the liver lipid accumulation induced by HF diets by increasing the hepatic TAG-SR and β-oxidation, and reducing the hepatic FA uptake. The increased hepatic TAG-SR induced by FMF could be responsible for the attenuation of serum TAG alterations.

Pelargonidin ameliorates CCl4-induced liver fibrosis by suppressing the ROS-NLRP3-IL-1β axis via activating the Nrf2 pathway

Liver fibrosis is a histological change that often occurs due to hepatic stellate cell (HSC) activation and excessive formation of an extracellular matrix in the liver. Pelargonidin (PEL) is a natural anthocyanidin existing in blueberries, berries, strawberries, and red radishes and has been demonstrated to possess health beneficial effects. Herein, we investigated the effect of PEL on liver fibrosis induced by CCl4 and hepatic stellate cells induced by transforming growth factor-β (TGF-β). We found that PEL administration prevented liver injury and liver fibrosis induced by CCl4 in a dose-dependent manner. Further data revealed that PEL increased liver nuclear factor E2-related factor 2 (Nrf2) and reduced liver oxidative stress and the expression levels of NLRP3, caspase-1 and IL-1β. In TGF-β-challenged HSCs (LX-2 cells), PEL effectively inhibited the LX-2 cell activation. In addition, the anti-fibrosis effects of PEL in LX-2 cells were abolished by Nrf2 knockdown. In summary, our study demonstrated that PEL ameliorated CCl4-induced liver fibrosis and HSC activation induced by TGF-β. The possible molecular mechanisms of PEL in liver fibrosis may be attributed to its suppression of ROS-NLRP3-IL-1β signaling by Nrf2 activation.

Nonalcoholic Fatty Liver Disease (NAFLD). Mitochondria as Players and Targets of Therapies?

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and represents the hepatic expression of several metabolic abnormalities of high epidemiologic relevance. Fat accumulation in the hepatocytes results in cellular fragility and risk of progression toward necroinflammation, i.e., nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Several pathways contribute to fat accumulation and damage in the liver and can also involve the mitochondria, whose functional integrity is essential to maintain liver bioenergetics. In NAFLD/NASH, both structural and functional mitochondrial abnormalities occur and can involve mitochondrial electron transport chain, decreased mitochondrial β-oxidation of free fatty acids, excessive generation of reactive oxygen species, and lipid peroxidation. NASH is a major target of therapy, but there is no established single or combined treatment so far. Notably, translational and clinical studies point to mitochondria as future therapeutic targets in NAFLD since the prevention of mitochondrial damage could improve liver bioenergetics.

Omega-3 fatty acid-rich fish oil supplementation prevents rosiglitazone-induced osteopenia in aging C57BL/6 mice and in vitro studies

Rosiglitazone is an effective insulin-sensitizer, however associated with bone loss mainly due to increased bone resorption and bone marrow adiposity. We investigated the effect of the co-administration of fish oil rich in omega-3 fatty acids (FAs) on rosiglitazone-induced bone loss in C57BL/6 mice and the mechanisms underlying potential preventive effect. Mice fed the iso-caloric diet supplemented with fish oil exhibited significantly higher levels of bone density in different regions compared to the other groups. In the same cohort of mice, reduced activity of COX-2, enhanced activity of alkaline phosphatase, lower levels of cathepsin k, PPAR-γ, and pro-inflammatory cytokines, and a higher level of anti-inflammatory cytokines were observed. Moreover, fish oil restored rosiglitazone-induced down-regulation of osteoblast differentiation and up-regulation of adipocyte differentiation in C3H10T1/2 cells and inhibited the up-regulation of osteoclast differentiation of RANKL-treated RAW264.7 cells. We finally tested our hypothesis on human Mesenchymal Stromal Cells differentiated to osteocytes and adipocytes confirming the beneficial effect of docosahexaenoic acid (DHA) omega-3 FA during treatment with rosiglitazone, through the down-regulation of adipogenic genes, such as adipsin and FABP4 along the PPARγ/FABP4 axis, and reducing the capability of osteocytes to switch toward adipogenesis. Fish oil may prevent rosiglitazone-induced bone loss by inhibiting inflammation, osteoclastogenesis, and adipogenesis and by enhancing osteogenesis in the bone microenvironment.

Soluble Fiber Inulin Consumption Limits Alterations of the Gut Microbiota and Hepatic Fatty Acid Metabolism Caused by High-Fat Diet

Diet shapes the gut microbiota which impacts hepatic lipid metabolism. Modifications in liver fat content are associated with metabolic disorders. We investigated the extent of dietary fat and fiber-induced alterations in the composition of gut microbiota and hepatic fatty acids (FAs). Mice were fed a purified low-fat diet (LFD) or high-fat diet (HFD) containing non-soluble fiber cellulose or soluble fiber inulin. HFD induced hepatic decreases in the amounts of C14:0, C16:1n-7, C18:1n-7 and increases in the amounts of C17:0, C20:0, C16:1n-9, C22:5n-3, C20:2n-6, C20:3n-6, and C22:4n-6. When incorporated in a LFD, inulin poorly affected the profile of FAs. However, when incorporated in a HFD, it (i) specifically led to an increase in the amounts of hepatic C18:0, C22:0, total polyunsaturated FAs (PUFAs), total n-6 PUFAs, C18:3n-3, and C18:2n-6, (ii) exacerbated the HFD-induced increase in the amount of C17:0, and (iii) prevented the HFD-induced increases in C16:1n-9 and C20:3n-6. Importantly, the expression/activity of some elongases and desaturases, as well as the gut microbiota composition, were impacted by the dietary fat and fiber content. To conclude, inulin modulated gut microbiota and hepatic fatty acid composition, and further investigations will determine whether a causal relationship exists between these two parameters.

Effects of Long-Term DHA Supplementation and Physical Exercise on Non-Alcoholic Fatty Liver Development in Obese Aged Female Mice

Obesity and aging are associated to non-alcoholic fatty liver disease (NAFLD) development. Here, we investigate whether long-term feeding with a docosahexaenoic acid (DHA)-enriched diet and aerobic exercise, alone or in combination, are effective in ameliorating NAFLD in aged obese mice. Two-month-old female C57BL/6J mice received control or high fat diet (HFD) for 4 months. Then, the diet-induced obese (DIO) mice were distributed into four groups: DIO, DIO + DHA (15% dietary lipids replaced by a DHA-rich concentrate), DIO + EX (treadmill running), and DIO + DHA + EX up to 18 months. The DHA-rich diet reduced liver steatosis in DIO mice, decreasing lipogenic genes (Dgat2, Scd1, Srebp1c), and upregulated lipid catabolism genes (Hsl/Acox) expression. A similar pattern was observed in the DIO + EX group. The combination of DHA + exercise potentiated an increase in Cpt1a and Ppara genes, and AMPK activation, key regulators of fatty acid oxidation. Exercise, alone or in combination with DHA, significantly reversed the induction of proinflammatory genes (Mcp1, Il6, Tnfα, Tlr4) in DIO mice. DHA supplementation was effective in preventing the alterations induced by the HFD in endoplasmic reticulum stress-related genes (Ern1/Xbp1) and autophagy markers (LC3II/I ratio, p62, Atg7). In summary, long-term DHA supplementation and/or exercise could be helpful to delay NAFLD progression during aging in obesity.

Protocols for Mitochondria as the Target of Pharmacological Therapy in the Context of Nonalcoholic Fatty Liver Disease (NAFLD)

Nonalcoholic fatty liver disease (NAFLD) is one of the most frequent metabolic chronic liver diseases in developed countries and puts the populations at risk of progression to liver necro-inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma. Mitochondrial dysfunction is involved in the onset of NAFLD and contributes to the progression from NAFLD to nonalcoholic steatohepatitis (NASH). Thus, liver mitochondria could become the target for treatments for improving liver function in NAFLD patients. This chapter describes the most important steps used for potential therapeutic interventions in NAFLD patients, discusses current options gathered from both experimental and clinical evidence, and presents some novel options for potentially improving mitochondrial function in NAFLD.

Dietary-Induced Low-Grade Inflammation in the Liver

The literature describes a close correlation between metabolic disorders and abnormal immune responses, like low-grade inflammation (LGI), which may be one mechanistic link between obesity and various comorbidities, including non-alcoholic fatty liver disease (NAFLD). In our study, we investigated the influence of dietary composition on obesity-derived LGI in the liver. We used a dietary induced obesity mouse model of C57BL/6J mice fed with high fat diet (HFD, 60% fat, 20% protein, 20% carbohydrates) and two different controls. One was rich in carbohydrates (10% fat, 20% protein, 70% carbohydrates), further referred to as the control diet (CD), and the other one is referred to as the standard diet (SD), with a more balanced macronutrient content (9% fat, 33% protein, 58% carbohydrates). Our results showed a significant increased NAFLD activity score in HFD compared to both controls, but livers of the CD group also differed in their macroscopic appearance from healthy livers. Hepatic fat content showed significantly elevated cholesterol concentrations in the CD group. Histologic analysis of the cellular immune response in the liver showed no difference between HFD and CD and expression analysis of immunologic mediators like interleukin (IL)-1β, IL-6, IL-10 and tumor necrosis factor alpha also point towards a pro-inflammatory response to CD, comparable to LGI in HFD. Therefore, when studying diet-induced obesity with a focus on inflammatory processes, we encourage researchers to carefully select controls and not use a control diet disproportionally rich in carbohydrates.

Evolution of Molecular Targets in Melanoma Treatment

Melanoma is the deadliest type of skin cancers, accounting for more than 80% of skin cancer mortality. Although melanoma was known very early in the history of medicine, treatment for this disease had remained largely the same until very recently. Previous treatment options, including removal surgery and systemic chemotherapy, offered little benefit in extending the survival of melanoma patients. However, the last decade has seen breakthroughs in melanoma treatment, which all emerged following new insight into the oncogenic signaling of melanoma. This paper reviewed the evolution of drug targets for melanoma treatment based on the emergence of novel findings in the molecular signaling of melanoma. One of the findings that are most influential in melanoma treatment is that more than 50% of melanoma tumors contain BRAF mutations. This is fundamental for the development of BRAF inhibitors, which is the first group of drugs that significantly improves the overall survival of melanoma patients compared to the traditional chemotherapeutic dacarbazine. More recently, findings of the role of immune checkpoint molecules such as CTLA-4 and PD1/PD-L1 in melanoma biology have led to the development of a new therapeutic category: immune checkpoint inhibitors, which, for the first time in the history of cancer treatment, produced a durable response in a subset of melanoma patients. However, as this paper discussed next, there is still an unmet need for melanoma treatment. A significant population of patients did not respond to either BRAF inhibitors or immune checkpoint inhibitors. Of those patients who gained an initial response from those therapies, a remarkable percentage would develop drug resistance even when MEK inhibitors were added to the treatment. Finally, this paper discusses some possible targets for melanoma treatment.

Acute exercise in mice transiently remodels the hepatic lipidome in an intensity-dependent manner

Background

The content of triacylglycerol (TAG) in the liver is known to rapidly increase after a single bout of exercise followed by recovery to sedentary levels. The response of other hepatic lipids, and acyl chain composition of lipid classes, would provide a deeper understanding of the response of hepatic lipid metabolism to acute exercise.

Methods

Female mice performed a single bout of continuous exercise (CE), high-intensity interval exercise (HIIE), or no exercise (CON). The total content of various lipids in the liver, and fatty acids within lipid classes, were measured in tissues collected 3 h after exercise (Day 1) and the day following exercise (Day 2).

Results

The total concentration of TAG rose on Day 1 after exercise (P < 0.05), with a greater elevation in HIIE than CE (P < 0.05), followed by a decline toward CON levels on Day 2. The total concentration of other measured lipid classes was not significantly altered by exercise. However, n-6 polyunsaturated fatty acid relative abundance in diacylglycerol (DAG) was increased by HIIE (P < 0.05). In CON liver, TAG content was positively correlated with DAG and phosphatidylethanolamine (P < 0.05), while these statistical associations were disrupted in exercised mice on Day 1.

Conclusions

The response of lipid metabolism to exercise involves the coordination of metabolism between various tissues, and the lipid metabolism response to acute exercise places a metabolic burden upon the liver. The present findings describe how the liver copes with this metabolic challenge. The flexibility of the TAG pool size in the liver, and other remodeling of the hepatic lipidome, may be fundamental components of the physiological response to intense exercise.

Nicotinamide and ascorbic acid nanoparticles against the hepatic insult induced in rats by high fat high fructose diet: A comparative study

AIMS

Non-alcoholic fatty liver disease (NAFLD) caused by consumption of high levels of fat and sugars (HFHS) in diet is considered one of the most dangerous medical complications among children and adolescents. Nicotinamide is among the promising candidates in ameliorating HFHS diet-induced NAFLD, but its use is limited by the possibility of prompting hepatotoxicity in high doses. Ascorbic acid is another promising candidate, however its use as a hepatoprotective agent is limited by its chemical instability. Therefore, the aim of the study was to overcome their delivery limitations and enhance their hepatoprotective activity by loading into nanoparticles.

KEY FINDINGS

In the present study, upon incorporating nicotinamide or ascorbic acid in chitosan nanoparticles, they ameliorated the insulin-resistant status induced in rats by a high-fat-high-fructose (HFHF) diet. Both formulae decreased serum level of ALT and AST, as well as liver tissue total cholesterol, triglycerides and 8-hydroxy-2-deoxyguanosine (8-OHdG) levels. They also decreased oxidative and nitrosative stresses along with a significant increase in the hepatocellular energy. The biochemical findings were further confirmed by histopathological examination. Finally from the obtained data it could be concluded that chitosan nicotinamide nanoparticles at a dose level (10 mg/kg, p.o.) demonstrated beneficial pharmacological effect with safer toxicity profile than chitosan ascorbic acid nanoparticles.

SIGNIFICANCE

Nicotinamide chitosan nanoparticles could be recommended as daily supplement in the recovery from NAFLD.

Protective Effects of Eicosapentaenoic Acid Plus Hydroxytyrosol Supplementation Against White Adipose Tissue Abnormalities in Mice Fed a High-Fat Diet

Objective: Obesity induced by high-fat diet (HFD) elicits white adipose tissue dysfunction. In this study, we have hypothesized that the metabolic modulator eicosapentaenoic acid (EPA) combined with the antioxidant hydroxytyrosol (HT) attenuates HFD-induced white adipose tissue (WAT) alterations. Methods: C57BL/6J mice were administered with a HFD (60% fat, 20% protein, 20% carbohydrates) or control diet (CD; 10% fat, 20% protein, 70% carbohydrates), with or without EPA (50 mg/kg/day), HT (5 mg/kg/day), or both for 12 weeks. Determinations in WAT include morphological parameters, EPA and docosahexaenoic acid content in phospholipids (gas chromatography), lipogenesis, oxidative stress (OS) and inflammation markers, and gene expression and activities of transcription factors, such as sterol regulatory element-binding protein-1c (SREBP-1c), peroxisome proliferator-activated receptor-gamma (PPAR-γ), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) (p65 subunit) and nuclear factor erythroid 2-related factor 2 (Nrf2) (quantitative polymerase chain reaction and enzyme linked immunosorbent assay). Results: HFD led to WAT hypertrophy in relation to PPAR-γ downregulation. WAT metabolic dysfunction was characterized by upregulation of lipogenic SREBP-1c system, mitochondrial energy metabolism depression, loss of the antioxidant Nrf2 signaling with OS enhancement, n-3 long-chain polyunsaturated fatty acids depletion and activation of the pro-inflammatory NF-κB system. EPA and HT co-supplementation diminished HFD-dependent effects additively, reaching values close or similar to controls. Conclusion: Data presented strengthen the importance of combined protocols such as EPA plus HT to attenuate metabolic-inflammatory states triggered by obesity.

Fermented mulberry (Morus alba) leaves suppress high fat diet-induced hepatic steatosis through amelioration of the inflammatory response and autophagy pathway

BACKGROUND

A novel extract of mulberry leaves fermented with Cordyceps militaris (EMfC) is reported to exert anti-obesity activity, although their molecular mechanism during hepatic steatosis has not verified.

METHODS

To investigate the role of inflammation and autophagy during the anti-hepatic steatosis effects of EMfC, we measured alterations in the key parameters for inflammatory response and autophagy pathway in liver tissues of the high fat diet (HFD) treated C57BL/6N mice after exposure to EMfC for 12 weeks.

RESULTS

Significant anti-hepatic steatosis effects, including decreased number of lipid droplets and expression of Klf2 mRNA, were detected in the liver of the HFD + EMfC treated group. The levels of mast cell infiltration, expression of two inflammatory mediators (iNOS and COX-2), and the MAPK signaling pathway were remarkably decreased in the liver of HFD + EMfC treated group as compared to the HFD + Vehicle treated group. Furthermore, a similar inhibitory effect was measured for the expression levels of pro-inflammatory cytokines, including IL-1β, IL-6, TNF-α and NF-κB. The expression level of members in the AKT/mTOR signaling pathway (a central regulator in autophagy) was recovered after treatment with EMfC, and autophagy-related proteins (Beclin and LC3-II) were remarkably decreased in the HFD + EMfC treated group compared to the HFD + Vehicle treated group. Moreover, the HFD + EMfC treated group showed decreased transcript levels of autophagy-regulated genes including Atg4b, Atg5, Atg7 and Atg12.

CONCLUSIONS

Taken together, findings of the present study provide novel evidences that the anti-hepatic steatosis of EMfC is tightly linked to the regulation of the inflammatory response and autophagy pathway in the liver tissue of HFD-induced obesity mice.

NRF-2 and nonalcoholic fatty liver disease

Currently, chronic liver diseases have conditioned morbidity and mortality, many of these with a metabolic, toxicologic, immunologic, viral, or other etiology. Thus, a transcription factor that has been of huge importance for biomedical research is NRF-2. The latter is considered a principal component of the antioxidant mechanism, and it has been acknowledged that it impairs the function of NRF-2 in many liver diseases and that it forms an essential part of the pathologic changes that occur in the liver to contain inflammation and damage. Within the investigations and experiments carried out, there are isolated drugs, many of them related to plants and natural extracts that possess antioxidant properties through the NRF-2 signaling pathway, or even involving the stimulation of the transcription target proteins of NRF-2. Notwithstanding all of these experimental findings, to date there is not sufficient clinical evidence to justify the use of NRF-2 in medical practice.

Apple pomace and rosemary extract ameliorates hepatic steatosis in fructose-fed rats: Association with enhancing fatty acid oxidation and suppressing inflammation

Apple pomace and rosemary (AR) have been reported to contain rich bioactive molecules, which have numerous metabolic effects. Our preliminary work revealed that AR ameliorated fructose-induced insulin resistance in rats by modulating sarcolemmal CD36 and glucose transporter-4. The present study aimed to further examine how AR improves metabolic disorders by investigating the effect of AR on hepatic steatosis induced by fructose overconsumption. The results demonstrated that AR (100 mg/kg daily by gavage for 5 weeks) attenuated chronic liquid fructose consumption-induced increases in liver triglyceride content in rats. Mechanistically, reverse transcription-quantitative PCR and western blot analysis results indicated that AR reversed fructose-induced suppression of hepatic peroxisome proliferator-activated receptor α, carnitine palmitoyl-transferase 1α, sirtuin 1 and peroxisome proliferator-activated receptor-γ coactivator 1α, which were associated with the fatty acid oxidative (FAO) pathway. In addition, AR treatment decreased the expression levels of the pro-inflammatory proteins NF-κB and tumor necrosis factor-α. However, AR had no effect on the genes related to lipogenesis and the very low-density lipoprotein-export pathway in rat liver. Thus, the present results suggested that AR treatment diminished long-term fructose overconsumption-induced fatty liver, which was associated with enhanced FAO and suppressed inflammation.

N-3 PUFAs inhibited hepatic ER stress induced by feeding of a high-saturated fat diet accompanied by the expression LOX-1

Excessive consumption of saturated fat leads to non-alcoholic fatty liver disease (NAFLD), which is attenuated by supplementation of n-3 polyunsaturated fatty acids (PUFAs). Endoplasmic reticulum (ER) stress is crucial in the development of NAFLD, but how high-saturated fat diet (HFD) causes ER stress and NAFLD remains unclear. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is involved in hepatic ER stress. We aimed to explore the roles of LOX-1 in HFD-induced ER stress. Male Sprague-Dawley rats were fed an HFD without or with supplementation of fish oil for 16 weeks. The effects of n-3 PUFAs on hepatic ER stress degrees and the expression levels of LOX-1 were examined. Then human L02 hepatoma cells were treated with palmitate or palmitate and DHA to determine the ER stress and LOX-1 expression levels in vitro. After that the expression of LOX-1 in L02 cells was either knocked-down or overexpressed to analyze the roles of LOX-1 in palmitate-induced ER stress. The feeding of HFD induced NAFLD development and ER stress in the liver, and LOX-1 expressing level, which were all reversed by fish oil supplementation. In vitro, DHA treatment reduced the expression of LOX-1, and palmitate-induced ER stress. SiRNA-mediated knock-down of LOX-1 inhibited palmitate-induced ER stress, whereas overexpression of LOX-1 dramatically induced ER stress in L02 cells.LOX-1 is critical for HFD-induced ER stress, and inhibition of its expression under the treatment of n-3 PUFAs could ameliorate HFD-induced NAFLD.

The Echinodermata PPAR: Functional characterization and exploitation by the model lipid homeostasis regulator tributyltin

The wide ecological relevance of lipid homeostasis modulators in the environment has been increasingly acknowledged. Tributyltin (TBT), for instance, was shown to cause lipid modulation, not only in mammals, but also in fish, molluscs, arthropods and rotifers. In vertebrates, TBT is known to interact with a nuclear receptor heterodimer module, formed by the retinoid X receptor (RXR) and the peroxisome proliferator-activated receptor (PPAR). These modulate the expression of genes involved in lipid homeostasis. In the present work, we isolated for the first time the complete coding region of the Echinodermata (Paracentrotus lividus) gene orthologues of PPAR and RXR and evaluated the ability of a model lipid homeostasis modulator, TBT, to interfere with the lipid metabolism in this species. Our results demonstrate that TBT alters the gonadal fatty acid composition and gene expression patterns: yielding sex-specific responses in fatty acid levels, including the decrease of eicosapentaenoic acid (C20:5 n-3, EPA) in males, and increase of arachidonic acid (20:4n-6, ARA) in females, and upregulation of long-chain acyl-CoA synthetase (acsl), ppar and rxr. Furthermore, an in vitro test using COS-1 cells as host and chimeric receptors with the ligand binding domain (LBD) of P. lividus PPAR and RXR shows that organotins (TBT and TPT (Triphenyltin)) suppressed activity of the heterodimer PPAR/RXR in a concentration-dependent manner. Together, these results suggest that TBT acts as a lipid homeostasis modulator at environmentally relevant concentrations in Echinodermata and highlight a possible conserved mode of action via the PPAR/RXR heterodimer.

Sacha inchi oil alleviates gut microbiota dysbiosis and improves hepatic lipid dysmetabolism in high-fat diet-fed rats

Dietary ω-3 polyunsaturated fatty acids (PUFAs) are beneficial for humans against the development of hyperlipidaemia, but the underlying mechanisms are still poorly understood. Here, we demonstrated that oral consumption of sacha inchi oil, which is rich in α-linolenic acid, alleviated dyslipidemia, hepatic steatosis and inflammatory infiltration in high-fat diet (HFD)-fed rats. Sacha inchi oil administration reversed gut microbiota dysbiosis and altered the gut microbiota metabolome and in particular prevented bile acid dysmetabolism caused by a HFD. Sacha inchi oil intake ameliorated hepatic lipid dysmetabolism in HFD-fed rats, via potentiating the biosynthesis and reuptake of bile acids, reducing the de novo lipogenesis, promoting fatty acid beta-oxidation, and alleviating the dysregulation of glycerolipid, glycerophospholipid, and sphingolipid metabolisms. The results showed that dietary sacha inchi oil can alleviate gut microbiota dysbiosis and reduce lipid dysmetabolism in HFD rats, and provide novel insights into the molecular mechanisms by which plant-derived ω-3 PUFAs prevent the development of hyperlipidaemia.

Cytoprotective effects of a proprietary red maple leaf extract and its major polyphenol, ginnalin A, against hydrogen peroxide and methylglyoxal induced oxidative stress in human keratinocytes

Phytochemicals from functional foods are common ingredients in dietary supplements and cosmetic products for anti-skin aging effects due to their antioxidant activities. A proprietary red maple (Acer rubrum) leaf extract (Maplifa™) and its major phenolic compound, ginnalin A (GA), have been reported to show antioxidant, anti-melanogenesis, and anti-glycation effects but their protective effects against oxidative stress in human skin cells remain unknown. Herein, we investigated the cytoprotective effects of Maplifa™ and GA against hydrogen peroxide (H2O2) and methylglyoxal (MGO)-induced oxidative stress in human keratinocytes (HaCaT cells). H2O2 and MGO (both at 400 μM) induced toxicity in HaCaT cells and reduced their viability to 59.2 and 61.6%, respectively. Treatment of Maplifa™ (50 μg mL-1) and GA (50 μM) increased the viability of H2O2- and MGO-treated cells by 22.0 and 15.5%, respectively. Maplifa™ and GA also showed cytoprotective effects by reducing H2O2-induced apoptosis in HaCaT cells by 8.0 and 7.2%, respectively. The anti-apoptotic effect of Maplifa™ was further supported by the decreased levels of apoptosis associated enzymes including caspases-3/7 and -8 in HaCaT cells by 49.5 and 19.0%, respectively. In addition, Maplifa™ (50 μg mL-1) and GA (50 μM) reduced H2O2- and MGO-induced reactive oxygen species (ROS) by 84.1 and 56.8%, respectively. Furthermore, flow cytometry analysis showed that Maplifa™ and GA reduced MGO-induced total cellular ROS production while increasing mitochondria-derived ROS production in HaCaT cells. The cytoprotective effects of Maplifa™ and GA in human keratinocytes support their potential utilization for cosmetic and/or dermatological applications.