Docosahexaenoic acid inhibits proteolytic processing of sterol regulatory element-binding protein-1c (SREBP-1c) via activation of AMP-activated kinase

Ketogenesis protects against MASLD-MASH progression through mechanisms that extend beyond overall fat oxidation rate

The progression of metabolic-dysfunction-associated steatotic liver disease (MASLD) to metabolic-dysfunction-associated steatohepatitis (MASH) involves complex alterations in both liver-autonomous and systemic metabolism that influence the liver's balance of fat accretion and disposal. Here, we quantify the relative contribution of hepatic oxidative pathways to liver injury in MASLD-MASH. Using NMR spectroscopy, UHPLC-MS, and GC-MS, we performed stable-isotope tracing and formal flux modeling to quantify hepatic oxidative fluxes in humans across the spectrum of MASLD-MASH, and in mouse models of impaired ketogenesis. We found in humans with MASH, that liver injury correlated positively with ketogenesis and total fat oxidation, but not with turnover of the tricarboxylic acid cycle. The use of loss-of-function mouse models demonstrated that disruption of mitochondrial HMG-CoA synthase (HMGCS2), the rate-limiting step of ketogenesis, impairs overall hepatic fat oxidation and induces a MASLD-MASH-like phenotype. Disruption of mitochondrial β-hydroxybutyrate dehydrogenase (BDH1), the terminal step of ketogenesis, also impaired fat oxidation, but surprisingly did not exacerbate steatotic liver injury. Taken together, these findings suggest that quantifiable variations in overall hepatic fat oxidation may not be a primary determinant of MASLD-to-MASH progression, but rather, that maintenance of hepatic ketogenesis could serve a protective role through additional mechanisms that extend beyond quantified overall rates of fat oxidation.

Regulatory effect of β-glucan secreted by Rhizobium pusense on triglyceride metabolism and their relationships with the modulation of intestinal microbiota in mice fed a high-fat diet

The present study investigated the regulatory effects of β-glucan secreted by Rhizobium pusense (RPG) on triglyceride metabolism and gut microbiota in mice fed a high-fat diet. The results indicated that supplementation with RPG significantly reduced body weight gain, blood glucose levels, and the tissue index of epididymal white adipose tissue (eWAT) and subcutaneous adipose tissue (SAT). Conversely, it increased the tissue index of brown adipose tissue (BAT). Furthermore, RPG supplementation effectively decreased the levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in the serum. Regarding its influence on the triglyceride (TG) mechanism, RPG decreased TG levels in both serum and liver, while elevating TG levels in feces. Moreover, it moderated the composition of gut microbiota in mice fed a high-fat diet, particularly altering functionally relevant intestinal microbial phylotypes, leading to enhanced levels of short-chain fatty acids (SCFAs) in feces. Additionally, RPG treatment regulated the mRNA and protein levels of genes responsible for TG metabolism in the AMPK pathway, indicating an impact on TG synthesis and excretion in the liver. Pearson's correlation network analysis demonstrated strong correlations between key microbial phylotypes responsive to RPG intervention and parameters associated with TG metabolic disorders. SCFA levels were also found to correlate with the mRNA expression levels of genes involved in TG metabolism. Finally, lipidomics analyses were performed to investigate the underlying mechanisms of RPG intervention (glycerophospholipid metabolic pathway) and to identify potential lipid biomarkers, such as TG (18:2/20:4/22:6), TG (18:1/20:4/22:6), TG (20:1/18:1/22:4), PC (17:0/20:4), TG (18:1/20:4/22:5), PC (22:4/22:6), PC (20:0/22:6), PC (20:0e/20:4), DG (18:3e/18:2), DG (10:0/18:2), DG (18:2/14:2), TG (10:0/18:2/20:4), TG (16:1/14:3/18:2) and TG (16:0/14:2/22:6). Overall, our results suggest that RPG could activate the hepatic AMPK signaling pathway by regulating gut microbiota and metabolites through gut-liver crosstalk to exert a lipid-lowering effect in mice fed a high-fat diet and improve obesity.

Caffeine: a potential mechanism for anti-obesity

Obesity refers to the excessive accumulation of fat caused by a long-term imbalance between energy intake (EI) and energy expenditure (EE). Over recent years, obesity has become a major public health challenge. Caffeine is a natural product that has been demonstrated to exert anti-obesity effects; however, the mechanisms responsible for the effect of caffeine on weight loss have yet to be fully elucidated. Most obesity-related deaths are due to cardiovascular disease. Recent research has demonstrated that caffeine can reduce the risk of death from cardiovascular disease; thus, it can be hypothesized that caffeine may represent a new therapeutic agent for weight loss. In this review, we synthesize data arising from clinical and animal studies over the last decade and discuss the potential mechanisms by which caffeine may induce weight loss, focusing particularly on increasing energy consumption, suppressing appetite, altering lipid metabolism, and influencing the gut microbiota. Finally, we summarize the major challenges associated with caffeine and anti-obesity research and highlight possible directions for future research and development.

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.

Probiotics Increase Intramuscular Fat and Improve the Composition of Fatty Acids in Sunit Sheep through the Adenosine 5'-Monophosphate-Activated Protein Kinase (AMPK) Signaling Pathway

This experiment aims to investigate the impact of probiotic feed on growth performance, carcass traits, plasma lipid biochemical parameters, intramuscular fat and triglyceride content, fatty acid composition, mRNA expression levels of genes related to lipid metabolism, and the activity of the enzyme in Sunit sheep. In this experiment, 12 of 96 randomly selected Sunit sheep were assigned to receive the basic diet or the basic diet supplemented with probiotics. The results showed that supplementation with probiotics significantly increased the loin eye area, and decreased plasma triglycerides and free fatty acids, increasing the content of intramuscular fat and triglycerides in the muscle and improving the composition of the fatty acids. The inclusion of probiotics in the diet reduced the expression of adenosine 5'-monophosphate-activated protein kinase alpha 2 (AMPKα2) mRNA and carnitine palmitoyltransferase 1B (CPT1B) mRNA, while increasing the expression of acetyl-CoA carboxylase alpha (ACCα) mRNA, sterol regulatory element-binding protein-1c (SREBP-1c) mRNA, fatty acid synthase mRNA, and stearoyl-CoA desaturase 1 mRNA. The results of this study indicate that supplementation with probiotics can regulate fat deposition and improves the composition of fatty acids in Sunit sheep through the signaling pathways AMPK-ACC-CPT1B and AMPK-SREBP-1c. This regulatory mechanism leads to an increase in intramuscular fat content, a restructuring of muscle composition of the fatty acids, and an enhancement of the nutritional value of meat. These findings contribute to a better understanding of the food science of animal resources and provide valuable references for the production of meat of higher nutritional value.

Honokiol acts as an AMPK complex agonist therapeutic in non-alcoholic fatty liver disease and metabolic syndrome

BACKGROUND

Non-alcoholic fatty liver (NAFLD) and its related metabolic syndrome have become major threats to human health, but there is still a need for effective and safe drugs to treat these conditions. Here we aimed to identify potential drug candidates for NAFLD and the underlying molecular mechanisms.

METHODS

A drug repositioning strategy was used to screen an FDA-approved drug library with approximately 3000 compounds in an in vitro hepatocyte model of lipid accumulation, with honokiol identified as an effective anti-NAFLD candidate. We systematically examined the therapeutic effect of honokiol in NAFLD and metabolic syndrome in multiple in vitro and in vivo models. Transcriptomic examination and biotin-streptavidin binding assays were used to explore the underlying molecular mechanisms, confirmed by rescue experiments.

RESULTS

Honokiol significantly inhibited metabolic syndrome and NAFLD progression as evidenced by improved hepatic steatosis, liver fibrosis, adipose inflammation, and insulin resistance. Mechanistically, the beneficial effects of honokiol were largely through AMPK activation. Rather than acting on the classical upstream regulators of AMPK, honokiol directly bound to the AMPKγ1 subunit to robustly activate AMPK signaling. Mutation of honokiol-binding sites of AMPKγ1 largely abolished the protective capacity of honokiol against NAFLD.

CONCLUSION

These findings clearly demonstrate the beneficial effects of honokiol in multiple models and reveal a previously unappreciated signaling mechanism of honokiol in NAFLD and metabolic syndrome. This study also provides new insights into metabolic disease treatment by targeting AMPKγ1 subunit-mediated signaling activation.

Coffee peel extracts ameliorate non-alcoholic fatty liver disease via a fibroblast growth factor 21-adiponectin signaling pathway

Coffee peel (CP) contains abundant phytochemicals which might prevent non-alcoholic fatty liver disease (NAFLD). The present study aimed to identify the main phytochemicals in CP extracts, and to investigate whether CP extracts could ameliorate NAFLD through a hepatic fibroblast growth factor (FGF) 21-adiponectin signaling pathway. Caffeine and seven monomers of flavonoids were identified from CP extracts by using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). After 8 weeks of intervention, the mice fed a high-fat and high-sugar diet showed the pathophysiological characteristics of NAFLD. Treatment with CP extracts significantly alleviated hepatic steatosis and insulin resistance and reduced the concentrations of serum alanine transaminase, FGF21, and triglyceride, and hepatic interleukin-6, interleukin-1β, and tumor necrosis factor-α, while increasing serum adiponectin concentrations. Meanwhile, CP extract supplementation significantly decreased the gene and protein expression levels of FGF21, while enhancing adiponectin expression levels. The present study demonstrated that CP extracts contained caffeine and seven monomers of flavonoids, and protected against NAFLD through regulating the FGF21-adiponectin signaling pathway.

Fatty acids composition and in vivo biochemical effects of Aleurites moluccana seed (Candlenut) in obese wistar rats

BACKGROUND

Candlenut (CN) has been used indiscriminately for weight loss. In vivo effects of CN in different doses are scarce.

OBJECTIVE

To evaluate the effects of CN ingestion in obese rats.

DESIGN

Thirty animals (obese and non-obese) received one of three different types of treatments: placebo, CN ingestion in a popular therapeutic regimen (8 days with oral administration of 0.2 mg/kg followed by 20 days with doses of 0.4 mg/kg), and ingestion of a doubled popular dose-called 2CN. Treatment was maintained for 28 days.

RESULTS

The fatty acid profile of CN indicated mainly linolelaidic and palmitoleic acids. Rats receiving CN and 2CN showed reduced plasmatic levels of glucose and lipoproteins (p < 0.05). A dose-dependent carcass fat reduction was observed (p < 0.05). Blood levels of aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT) reduced with CN and increased with 2CN doses (p < 0.05). Alanine aminotransferase (ALT) and the atherogenic index remained similar among all treatments (p > 0.05). Hepatic vacuolation decreased with CN, but the 2CN dose produced mononuclear leucocyte infiltrate.

CONCLUSIONS

Although CN presented beneficial effects on the metabolism of rats, it also caused increased risk of liver damage.

Influence of the nutritional status and oxidative stress in the desaturation and elongation of n-3 and n-6 polyunsaturated fatty acids: Impact on non-alcoholic fatty liver disease

Polyunsaturated fatty acids (PUFA) play essential roles in cell membrane structure and physiological processes including signal transduction, cellular metabolism and tissue homeostasis to combat diseases. PUFA are either consumed from food or synthesized by enzymatic desaturation, elongation and peroxisomal β-oxidation. The nutritionally essential precursors α-linolenic acid (C18:3n-3; ALA) and linoleic acid (C18:2n-6; LA) are subjected to desaturation by Δ6D/Δ5D desaturases and elongation by elongases 2/5, enzymes that are induced by insulin and repressed by PUFA. Maintaining an optimally low n-6/n-3 PUFA ratio is linked to prevention of the development of several diseases, including nonalcoholic fatty liver disease (NAFLD) that is characterized by depletion of PUFA promoting hepatic steatosis and inflammation. In this context, supplementation with n-3 PUFA revealed significant lowering of hepatic steatosis in obese patients, whereas prevention of fatty liver by high-fat diet in mice is observed in n-3 PUFA and hydroxytyrosol co-administration. The aim of this work is to review the role of nutritional status and nutrient availability on markers of PUFA biosynthesis. In addition, the impact of oxidative stress developed as a result of NAFLD, a redox imbalance that may alter the expression and activity of the enzymes involved, and diminished n-3 PUFA levels by free-radical dependent peroxidation processes will be discussed.

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.

Mitoprotective Effects of a Synergistic Nutraceutical Combination: Basis for a Prevention Strategy Against Alzheimer’s Disease

Evidence to date suggests the consumption of food rich in bioactive compounds, such as polyphenols, flavonoids, omega-3 fatty acids may potentially minimize age-related cognitive decline. For neurodegenerative diseases, such as Alzheimer’s disease (AD), which do not yet have definitive treatments, the focus has shifted toward using alternative approaches, including prevention strategies rather than disease reversal. In this aspect, certain nutraceuticals have become promising compounds due to their neuroprotective properties. Moreover, the multifaceted AD pathophysiology encourages the use of multiple bioactive components that may be synergistic in their protective roles when combined. The objective of the present study was to determine mechanisms of action underlying the inhibition of Aβ_1–42-induced toxicity by a previously determined, three-compound nutraceutical combination D₅L₅U₅ for AD. In vitro experiments were carried out in human neuroblastoma BE(2)-M17 cells for levels of ROS, ATP mitophagy, and mitobiogenesis. The component compounds luteolin (LUT), DHA, and urolithin A (UA) were independently protective of mitochondria; however, the D₅L₅U₅ preceded its single constituents in all assays used. Overall, it indicated that D₅L₅U₅ had potent inhibitory effects against Aβ_1–42-induced toxicity through protecting mitochondria. These mitoprotective activities included minimizing oxidative stress, increasing ATP and inducing mitophagy and mitobiogenesis. However, this synergistic nutraceutical combination warrants further investigations in other in vitro and in vivo AD models to confirm its potential to be used as a preventative therapy for AD.

DHA Suppresses Hepatic Lipid Accumulation via Cyclin D1 in Zebrafish

With the widespread use of high-fat diets (HFDs) in aquaculture, fatty livers are frequently observed in many fish species. The aim of this study was to investigate if docosahexaenoic acid (DHA) could be used to reduce the fatty liver in zebrafish generated by a 16% soybean oil-HFD over 2 weeks of feeding. The DHA was added to iso-lipidic HFD at 0.5, 1.0, and 2.0% of diet. Supplementation of DHA reduced growth and feed efficiency in a dose dependent manner being lowest in the HFDHA2.0 group. Hepatic triglyceride (TG) in zebrafish fed 0.5% DHA-supplemented HFD (HFDHA0.5) was significantly lower than in the HFD control. Transcriptional analyses of hepatic genes showed that lipid synthesis was reduced, while fatty acid β-oxidation was increased in the HFDHA0.5 group. Furthermore, the expression of Cyclin D1 in liver of zebrafish fed HFDHA0.5 was significantly reduced compared to that in fish fed HFD. In zebrafish liver cells, Cyclin D1 knockdown and blocking of Cyclin D1-CDK4 signal led to inhibited lipid biosynthesis and elevated lipid β-oxidation. Besides, DHA-supplemented diet resulted in a rich of Proteobacteria and Actinobacteriota in gut microbiota, which promoted lipid β-oxidation but did not alter the expression of Cyclin D1 in germ-free zebrafish model. In conclusion, DHA not only inhibits hepatic lipid synthesis and promotes lipid β-oxidation via Cyclin D1 inhibition, but also facilitates lipid β-oxidation via gut microbiota. This study reveals the lipid-lowering effects of DHA and highlights the importance of fatty acid composition when formulating fish HFD.

Supplementation of omega-3 and dietary factors can influence the cholesterolemia and triglyceridemia in hyperlipidemic Schnauzer dogs: A preliminary report

Primary hyperlipidaemia in Schnauzer is characterized by increased plasma triglycerides (TG) and/or total cholesterol (TC) concentration and is associated with an increased risk of developing pancreatitis, insulin resistance and seizures. In humans, omega-3 fatty acids in addition to a low-fat diet can be used to reduce TG and TC. This study evaluated the therapeutic efficacy of omega-3 fatty acids associated to a diet management with two different fat content in Schnauzer with primary hyperlipidaemia. Eighteen dogs with primary hyperlipidaemia were divided into two groups: group 1, n = 10, 8 females, 2 males, age (mean ± standard deviation) of 7.13 ± 2.70 years and body weight (BW) (mean ± standard deviation) of 7.25 ± 1.22 kg were treated with fish oil (approximately 730 mg/day of omega-3) associated with a low-fat and low-calorie diet (approximately 24g of fat/1000 kcal) for 90 days (T90); and group 2, n = 8 dogs, 6 females, 2 males, with 7.0 ± 1.77 years old and average BW of 8.36 ± 1.51 kg, treated with fish oil (approximately 730 mg/day of omega-3) and maintenance diet with moderate amount of fat (approximately 33g of fat/1000 kcal) for 90 days. Plasma TG and TC concentrations and lipoprotein (LP) profile (VLDL, LDL, HDL) were evaluated before and after treatment. TG and TC serum concentrations, expressed in mg/dL (mean ± standard deviation), before and after treatment in group 1 were: TG = 391.30 ± 487.86 (T0) and 118.7 ± 135.21 (T90); TC = 308.2 ± 63.06 (T0) and 139 ± 36.91 (T90). As for group 2, TG = 391.63 ± 336.89 (T0) and 250.75 ± 211.56 (T90); TC = 257.25 ± 92.88 (T0) and 207.25 ± 63.79 (T90). A reduction (p<0.05) of TG and TC was observed in both groups. The distribution of TG and TC among LP was not different between the pre (T0) and post treatment (T90) periods. After 90 days of treatment, the administration of omega-3 fatty acids, associated with a low-fat or maintenance diet reduced triglyceridemia and cholesterolemia without altering LP profile. The current investigation shows that both therapies were effective in reducing plasma TC and TG concentrations without altering LP profile.

ω3PUFAs improve hepatic steatosis in postnatal overfed rats and HepG2 cells by inhibiting acetyl-CoA carboxylase

Postnatal overfeeding can lead to persistent increases in hepatic lipid synthesis and the risk of nonalcoholic fatty liver disease (NAFLD) in adulthood. The ω3 polyunsaturated fatty acids (ω3PUFAs) exhibit beneficial effects on NAFLD. Here, we employed a rat model and an in vitro HepG2 cell model to investigate whether fish oil (FO) affects hepatic lipid synthesis due to postnatal overfeeding. Male Sprague-Dawley were divided into litter sizes of three (small litters, SLs) or 10 (normal litters, NLs) on postnatal day 3 and were fed standard chow or FO diet beginning on postnatal week 3 to generate NL, SL, NL-FO, and SL-FO groups. The results indicated that the FO diet reduced the postnatal overfeeding-induced body weight gain and NAFLD characteristics (such as serum and liver triglyceride (TG) and hepatic steatosis). In addition, FO restored the expression of hepatic lipid metabolism-related genes (including SCD1, FASN, CPT1, LPL, ACC, and SREBP-1c) in SL-FO rats. Specifically, the activity and expression pattern of ACC were consistent with SREBP-1c. Furthermore, HepG2 cells were treated with oleic acid (OA), followed by eicosapentenoic acid (EPA), with or without SREBP-1c siRNA. The cellular lipid droplets, TG content, and the expression of ACC (by 75%) and SREBP-1c (by 45%) were increased by OA stimulation (p < .05), which was inhibited by EPA treatment. However, the effect of EPA treatment was abolished when SREBP-1c was silenced. In conclusion, ω3PUFAs-rich diet may be an effective way to reverse the developmental programming of hepatic lipid synthesis, at least partially, by inhibiting ACC through modulating SREBP-1c.

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.

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.

Astilbin lowers the effective caffeine dose for decreasing lipid accumulation via activating AMPK in high-fat diet-induced obese mice

BACKGROUND

Caffeine has an anti-obesity effect, although chronic excessive caffeine consumption also causes caffeinism, which is marked by increased anxiety or depression, amongst other symptoms. The present study aimed to investigate whether the addition of flavonoids such as astilbin can reduce the caffeine dose needed to inhibit obesity.

RESULTS

ICR mice (n = 80) were fed with normal diet, high-fat diet (HFD), HFD supplemented with astilbin, caffeine, or astilbin + caffeine for 12 weeks. When diets supplemented with astilbin, 0.3 g kg^-1 diet caffeine had the same effect as 0.6 g kg^-1 diet caffeine alone, and 0.6 g kg^-1 diet caffeine combined with astilbin most effectively inhibited HFD-induced obesity. Astilbin improved the anti-obesity effects of caffeine on lipid accumulation via the activation of AMP-activated protein kinase α (AMPKα). (i) Activated AMPKα decreased lipid biosynthesis by suppressing the activity or mRNA expression of 3-hydroxy-3-methylglutaryl-CoA reductase, sterol regulatory element binding protein 1c and its target gene fatty acid synthase. (ii) Activated AMPKα also up-regulated lipolysis by enhancing the expression of adipose triglyceride lipase and increasing the phosphorylation of hormone-sensitive lipase. (iii) Finally, activated AMPKα increased carnitine acyltransferase and acyl-CoA oxidase activities, which further promoted fatty acid β-oxidation.

CONCLUSION

The results obtained in the present study indicate that astilbin may decrease the effective dose of caffeine needed for an anti-obesity effect and also suggest that it suppresses fat accumulation via the activation of AMPK. © 2020 Society of Chemical Industry.

Targeting n-3 Polyunsaturated Fatty Acids in Non-Alcoholic Fatty Liver Disease

BACKGROUND

Non-Alcoholic Fatty Liver Disease (NAFLD) is characterized by abnormal hepatic accumulation of triacylglycerides in the absence of alcohol consumption, in association with Oxidative Stress (OS), a pro-inflammatory state and Insulin Resistance (IR), which are attenuated by n-3 long-chain polyunsaturated Fatty Acids (FAs) C20-C22 (LCPUFAs) supplementation. Main causes of NAFLD comprise high caloric intake and a sedentary lifestyle, with high intakes of saturated FAs.

METHODS

The review includes several searches considering the effects of n-3 LCPUFAs in NAFLD in vivo and in vitro models, using the PubMed database from the National Library of Medicine- National Institutes of Health.

RESULT

The LCPUFAs eicosapentaenoic acid (C20:5 n-3, EPA) and docosahexaenoic acid (C22:6 n- 3, DHA) have a positive effect in diminishing liver steatosis, OS, and the levels of aspartate aminotransferase, alanine aminotransferase and pro-inflammatory cytokines, with improvement of insulin sensitivity and adiponectin levels. The molecular pathways described for n-3 LCPUFAs in cellular and animal models and humans include peroxisome proliferator-activated receptor-α activation favouring FA oxidation, diminution of lipogenesis due to sterol responsive element binding protein-1c downregulation and inflammation resolution. Besides, nuclear factor erythroid-2-related factor-2 activation is elicited by n-3 LCPUFA-derived oxidation products producing direct and indirect antioxidant responses, with concomitant anti-fibrogenic action.

CONCLUSION

The discussed effects of n-3 LCPUFA supplementation support its use in NAFLD, although having a limited value in NASH, a contention that may involve n-3 LCPUFA oxygenated derivatives. Clinical trials establishing optimal dosages, intervention times, type of patients and possible synergies with other natural products are needed in future studies.

The requirements for sterol regulatory element-binding protein (Srebp) and stimulatory protein 1 (Sp1)-binding elements in the transcriptional activation of two freshwater fish Channa striata and Danio rerio elovl5 elongase

Fish are a major source of beneficial n-3 LC-PUFA in human diet, and there is considerable interest to elucidate the mechanism and regulatory aspects of LC-PUFA biosynthesis in farmed species. Long-chain polyunsaturated fatty acid (LC-PUFA) biosynthesis involves the activities of two groups of enzymes, the fatty acyl desaturase (Fads) and elongase of very long-chain fatty acid (Elovl). The promoters of elovl5 elongase, which catalyses the rate-limiting reaction of elongating polyunsaturated fatty acid (PUFA), have been previously described and characterized from several marine and diadromous teleost species. We report here the cloning and characterization of elovl5 promoter from two freshwater fish species, the carnivorous snakehead fish (Channa striata) and zebrafish. Results show the presence of sterol-responsive elements (SRE) in the core regulatory region of both promoters, suggesting the importance of sterol regulatory element-binding protein (Srebp) in the regulation of elovl5 for both species. Mutagenesis luciferase and electrophoretic mobility shift assays further validate the role of SRE for basal transcriptional activation. In addition, several Sp1-binding sites located in close proximity with SRE were present in the snakehead promoter, with one having a potential synergy with SRE in the regulation of elovl5 expression. The core zebrafish elovl5 promoter fragment also directed in vivo expression in the yolk syncytial layer of developing zebrafish embryos.

Impact of the Co-Administration of N-3 Fatty Acids and Olive Oil Components in Preclinical Nonalcoholic Fatty Liver Disease Models: A Mechanistic View

Nonalcoholic fatty liver disease (NAFLD) is present in approximately 25% of the population worldwide. It is characterized by the accumulation of triacylglycerol in the liver, which can progress to steatohepatitis with different degrees of fibrosis, stages that lack approved pharmacological therapies and represent an indication for liver transplantation with consistently increasing frequency. In view that hepatic steatosis is a reversible condition, effective strategies preventing disease progression were addressed using combinations of natural products in the preclinical high-fat diet (HFD) protocol (60% of fat for 12 weeks). Among them, eicosapentaenoic acid (C20:5n-3, EPA) and docosahexaenoic acid (C22:5n-3, DHA), DHA and extra virgin olive oil (EVOO), or EPA plus hydroxytyrosol (HT) attained 66% to 83% diminution in HFD-induced steatosis, with the concomitant inhibition of the proinflammatory state associated with steatosis. These supplementations trigger different molecular mechanisms that modify antioxidant, antisteatotic, and anti-inflammatory responses, and in the case of DHA and HT co-administration, prevent NAFLD. It is concluded that future studies in NAFLD patients using combined supplementations such as DHA plus HT are warranted to prevent liver steatosis, thus avoiding its progression into more unmanageable stages of the disease.

Cyp1b1 directs Srebp-mediated cholesterol and retinoid synthesis in perinatal liver; Association with retinoic acid activity during fetal development

Background

Cytochrome P450 1b1 (Cyp1b1) deletion and dietary retinol deficiency during pregnancy (GVAD) affect perinatal liver functions regulated by Srebp. Cyp1b1 is not expressed in perinatal liver but appears in the E9.5 embryo, close to sites of retinoic acid (RA) signaling.

Hypothesis

Parallel effects of Cyp1b1 and retinol on postnatal Srebp derive from effects in the developing liver or systemic signaling.

Approach

Cluster postnatal increases in hepatic genes in relation to effects of GVAD or Cyp1b1 deletion. Sort expression changes in relation to genes regulated by Srebp1 and Srebp2.Test these treatments on embryos at E9.5, examining changes at the site of liver initiation. Use in situ hybridization to resolve effects on mRNA distributions of Aldh1a2 and Cyp26a1 (RA homeostasis); Hoxb1 and Pax6 (RA targets). Assess mice lacking Lrat and Rbp4 (DKO mice) that severely limits retinol supply to embryos.

Results

At birth, GVAD and Cyp1b1 deletion stimulate gene markers of hepatic stellate cell (HSC) activation but also suppress Hamp. These treatments then selectively prevent the postnatal onset of genes that synthesize cholesterol (Hmgcr, Sqle) and fatty acids (Fasn, Scd1), but also direct cholesterol transport (Ldlr, Pcsk9, Stard4) and retinoid synthesis (Aldh1a1, Rdh11). Extensive support by Cyp1b1 is implicated, but with distinct GVAD interventions for Srebp1 and Srebp2. At E9.5, Cyp1b1 is expressed in the septum transversum mesenchyme (STM) with β-carotene oxygenase (Bco1) that generates retinaldehyde. STM provides progenitors for the HSC and supports liver expansion. GVAD and Cyp1b1-/- do not affect RA-dependent Hoxb1 and Pax6. In DKO embryos, RA-dependent Cyp26a1 is lost but Hoxb1 is sustained with Cyp1b1 at multiple sites.

Conclusion

Cyp1b1-/- suppresses genes supported by Srebp. GVAD effects distinguish Srebp1 and Srebp2 mediation. Srebp regulation overlaps appreciably in cholesterol and retinoid homeostasis. Bco1/Cyp1b1 partnership in the STM may contribute to this later liver regulation.

Iron-induced derangement in hepatic Δ-5 and Δ-6 desaturation capacity and fatty acid profile leading to steatosis: Impact on extrahepatic tissues and prevention by antioxidant-rich extra virgin olive oil

The administration of iron induces liver oxidative stress and depletion of long-chain polyunsaturated fatty acids (LCPUFAs), n-6/n-3 LCPUFA ratio enhancement and fat accumulation, which may be prevented by antioxidant-rich extra virgin olive oil (AR-EVOO) supplementation. Male Wistar rats were subjected to a control diet (50 mg iron/kg diet) or iron-rich diet (IRD; 200 mg/kg diet) with alternate AR-EVOO for 21 days. Liver fatty acid (FA) analysis was performed by gas-liquid chromatography (GLC) after lipid extraction and fractionation, besides Δ-5 desaturase (Δ-5 D) and Δ6-D mRNA expression (qPCR) and activity (GLC) measurements. The IRD significantly (p < 0.05) increased hepatic total fat, triacylglycerols, free FA contents and serum transaminases levels, with diminution in those of n-6 and n-3 LCPUFAs, higher n-6/n-3 ratios, lower unsaturation index and Δ5-D and Δ6-D activities, whereas the mRNA expression of both desaturases was enhanced over control values, changes that were prevented by concomitant AR-EVOO supplementation. N-6 and n-3 LCPUFAs were also decreased by IRD in extrahepatic tissues and normalized by AR-EVOO. In conclusion, AR-EVOO supplementation prevents IRD-induced changes in parameters related to liver FA metabolism and steatosis, an effect that may have a significant impact in the treatment of iron-related pathologies or metabolic disorders such as non-alcoholic fatty liver disease.

Protective Effect of α-Linolenic Acid on Non-Alcoholic Hepatic Steatosis and Interleukin-6 and -10 in Wistar Rats

Consumption of omega-3 (n-3) polyunsaturated fatty acids (PUFA) is related to improvement in the inflammatory response associated with decreases in metabolic disorders of obesity, such as low-grade inflammation and hepatic steatosis. Linseed (Linum usitatissimum) oil is a primary source of n-3 fatty acids (FAs) of plant origin, particularly α-linolenic acid, and provides an alternative for the ingestion of n-3 PUFA by persons allergic to, or wishing to avoid, animal sources. In our study, we evaluated the effect of the consumption of different lipidic sources on metabolic and inflammatory parameters in Wistar rats. We split 56 male rats into four groups that were fed for 60 days with the following diets: sesame oil, (SO, Sesamum indicum), linseed oil (LO), SO + LO (SLO), and a control group (CG) fed with animal fat. Our results reveal that the use of LO or SLO produced improvements in the hepatic tissue, such as lower values of aspartate aminotransferase, liver weight, and hepatic steatosis. LO and SLO reduced the weight of visceral fats, weight gain, and mediated the inflammation through a decrease in interleukin (IL)-6 and increase in IL-10. Though we did not detect any significant differences in the intestine histology and the purinergic system enzymes, the consumption of α-linolenic acid appears to contribute to the inflammatory and hepatic modulation of animals compared with a diet rich in saturated FAs and or unbalanced in n-6/n-3 PUFAs, inferring possible use in treatment of metabolic disorders associated with obesity and cardiovascular diseases.

Lipidomic biomarkers and mechanisms of lipotoxicity in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) represents the most common form of chronic liver disease worldwide (about 25% of the general population) and 3-5% of patients develop non-alcoholic steatohepatitis (NASH), characterized by hepatocytes damage, inflammation and fibrosis, which increase the risk of developing liver failure, cirrhosis and hepatocellular carcinoma. The pathogenesis of NAFLD, particularly the mechanisms whereby a minority of patients develop a more severe phenotype, is still incompletely understood. In this review we examine the available literature on initial mechanisms of hepatocellular damage and inflammation, deriving from toxic effects of excess lipids. Accumulating data indicate that the total amount of triglycerides stored in the liver cells is not the main determinant of lipotoxicity and that specific lipid classes act as damaging agents. These lipotoxic species affect the cell behavior via multiple mechanisms, including activation of death receptors, endoplasmic reticulum stress, modification of mitochondrial function and oxidative stress. The gut microbiota, which provides signals through the intestine to the liver, is also reported to play a key role in lipotoxicity. Finally, we summarize the most recent lipidomic strategies utilized to explore the liver lipidome and its modifications in the course of NALFD. These include measures of lipid profiles in blood plasma and erythrocyte membranes that can surrogate to some extent lipid investigation in the liver.

Docosahexaenoic acid and hydroxytyrosol co-administration fully prevents liver steatosis and related parameters in mice subjected to high-fat diet: A molecular approach

Attenuation of high-fat diet (HFD)-induced liver steatosis is accomplished by different nutritional interventions. Considering that the n-3 PUFA docosahexaenoic acid (DHA) modulates lipid metabolism and the antioxidant hydroxytyrosol (HT) diminishes oxidative stress underlying fatty liver, it is hypothesized that HFD-induced steatosis is suppressed by DHA and HT co-administration. Male C57BL/6J mice were fed a control diet (CD; 10% fat, 20% protein, 70% carbohydrates) or a HFD (60% fat, 20% protein, 20% carbohydrates) for 12 weeks, without and with supplementation of DHA (50 mg/kg/day), HT (5 mg/kg/day) or both. The combined DHA + HT protocol fully prevented liver steatosis and the concomitant pro-inflammatory state induced by HFD, with suppression of lipogenic and oxidative stress signaling, recovery of fatty acid oxidation capacity and enhancement in resolvin availability affording higher inflammation resolution capability. Abrogation of HFD-induced hepatic steatosis by DHA and HT co-administration represents a crucial therapeutic strategy eluding disease progression into stages lacking efficacious handling at present time.

Diosgenin ameliorates palmitic acid-induced lipid accumulation via AMPK/ACC/CPT-1A and SREBP-1c/FAS signaling pathways in LO2 cells

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and is characterized by excessive hepatic lipid accumulation. Many studies have suggested that lipid overload is the key initial factor that contributes to hepatic steatosis. Our previous study indicated that diosgenin (DSG) has a beneficial effect on energy metabolism, but the underlying mechanism remains unclear.

METHODS

Human normal hepatocytes (LO2 cells) were incubated with palmitic acid to establish the cell model of nonalcoholic fatty liver. The effects of DSG on lipid metabolism, glucose uptake and mitochondrial function were evaluated. Furthermore, the mechanism of DSG on oxidative stress, lipid consumption and lipid synthesis in LO2 cells was investigated.

RESULTS

The results indicated that palmitic acid induced obvious lipid accumulation in LO2 cells and that DSG treatment significantly reduced the intracellular lipid content. DSG treatment upregulated expression of lipolysis proteins, including phospho-AMP activated protein kinase (p-AMPK), phospho-acetyl-coA carboxylase (p-ACC) and carnitine acyl transferase 1A (CPT-1A), and inhibited expression of lipid synthesis-related proteins, including sterol regulatory element-binding protein 1c (SREBP-1c) and fatty acid synthase (FAS). Additionally, DSG-treated cells displayed a marked improvement in mitochondrial function, with less production of reactive oxygen species and a higher mitochondrial membrane potential compared with the model group.

CONCLUSION

This study suggests that DSG can reduce intracellular lipid accumulation in LO2 cells and that the underlying mechanism may be related to the improving oxidative stress, increasing fatty acid β-oxidation and decreasing lipid synthesis. The above changes might be mediated by the activation of the AMPK/ACC/CPT-1A pathway and inhibition of the SREBP-1c/FAS pathway.

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

High-fat-diet (HFD) feeding is associated with liver oxidative stress (OS), n-3 long-chain polyunsaturated fatty acid (n-3 LCPUFA) depletion, hepatic steatosis and mitochondrial dysfunction. Our hypothesis is that the HFD-induced liver injury can be attenuated by the combined supplementation of n-3 LCPUFA eicosapentaenoic acid (EPA) and the antioxidant hydroxytyrosol (HT). The C57BL/6J mice were administered an HFD (60% fat, 20% protein, 20% carbohydrates) or control diet (CD; 10% fat, 20% protein, 70% carbohydrates), with or without EPA (50 mg kg-1 day-1), HT (5 mg kg-1 day-1), or EPA + HT (50 and 5 mg kg-1 day-1, respectively) for 12 weeks. We measured the body and liver weights and dietary and energy intakes along with liver histology, FA composition, steatosis score and associated transcription factors, mitochondrial functions and metabolic factors related to energy sensing through the AMP-activated protein kinase (AMPK) and PPAR-γ coactivator-1α (PGC-1α) cascade. It was found that the HFD significantly induced liver steatosis, with a 66% depletion of n-3 LCPUFAs and a 100% increase in n-6/n-3 LCPUFA ratio as compared to the case of CD (p < 0.05). These changes were concomitant with (i) a 95% higher lipogenic and 70% lower FA oxidation signaling, (ii) a 40% diminution in mitochondrial respiratory capacity and (iii) a 56% lower ATP content. HFD-induced liver steatosis was also associated with (iv) a depressed mRNA expression of AMPK-PGC-1α signaling components, nuclear respiratory factor-2 (NRF-2) and β-ATP synthase. These HFD effects were significantly attenuated by the combined EPA + HT supplementation in an additive manner. These results suggested that EPA and HT co-administration partly prevented HFD-induced liver steatosis, thus strengthening the importance of combined interventions in hepatoprotection in non-alcoholic fatty liver disease.

Combined docosahexaenoic acid and thyroid hormone supplementation as a protocol supporting energy supply to precondition and afford protection against metabolic stress situations

Liver preconditioning (PC) refers to the development of an enhanced tolerance to injuring stimuli. For example, the protection from ischemia-reperfusion (IR) in the liver that is obtained by previous maneuvers triggering beneficial molecular and functional changes. Recently, we have assessed the PC effects of thyroid hormone (T_3; single dose of 0.1 mg/kg) and n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFAs; daily doses of 450 mg/kg for 7 days) that abrogate IR injury to the liver. This feature is also achieved by a combined T₃ and the n-3 LCPUFA docosahexaenoic acid (DHA) using a reduced period of supplementation of the FA (daily doses of 300 mg/kg for 3 days) and half of the T₃ dosage (0.05 mg/kg). T₃ -dependent protective mechanisms include (i) the reactive oxygen species (ROS)-dependent activation of transcription factors nuclear factor-κB (NF-κB), AP-1, signal transducer and activator of transcription 3, and nuclear factor erythroid-2-related factor 2 (Nrf2) upregulating the expression of protective proteins. (ii) ROS-induced endoplasmic reticulum stress affording proper protein folding. (iii) The autophagy response to produce FAs for oxidation and ATP supply and amino acids for protein synthesis. (iv) Downregulation of inflammasome nucleotide-bonding oligomerization domain leucine-rich repeat containing family pyrin containing 3 and interleukin-1β expression to prevent inflammation. N-3 LCPUFAs induce antioxidant responses due to Nrf2 upregulation, with inflammation resolution being related to production of oxidation products and NF-κB downregulation. Energy supply to achieve liver PC is met by the combined DHA plus T₃ protocol through upregulation of AMPK coupled to peroxisome proliferator-activated receptor-γ coactivator 1α signaling. In conclusion, DHA plus T₃ coadministration favors hepatic bioenergetics and lipid homeostasis that is of crucial importance in acute and clinical conditions such as IR, which may be extended to long-term or chronic situations including steatosis in obesity and diabetes. © 2019 IUBMB Life, 71(9):1211-1220, 2019.

Spheroid-Induced Epithelial-Mesenchymal Transition Provokes Global Alterations of Breast Cancer Lipidome: A Multi-Layered Omics Analysis

Metabolic rewiring has been recognized as an important feature to the progression of cancer. However, the essential components and functions of lipid metabolic networks in breast cancer progression are not fully understood. In this study, we investigated the roles of altered lipid metabolism in the malignant phenotype of breast cancer. Using a spheroid-induced epithelial-mesenchymal transition (EMT) model, we conducted multi-layered lipidomic and transcriptomic analysis to comprehensively describe the rewiring of the breast cancer lipidome during the malignant transformation. A tremendous homeostatic disturbance of various complex lipid species including ceramide, sphingomyelin, ether-linked phosphatidylcholines, and ether-linked phosphatidylethanolamine was found in the mesenchymal state of cancer cells. Noticeably, polyunsaturated fatty acids composition in spheroid cells was significantly decreased, accordingly with the gene expression patterns observed in the transcriptomic analysis of associated regulators. For instance, the up-regulation of SCD, ACOX3, and FADS1 and the down-regulation of PTPLB, PECR, and ELOVL2 were found among other lipid metabolic regulators. Significantly, the ratio of C22:6n3 (docosahexaenoic acid, DHA) to C22:5n3 was dramatically reduced in spheroid cells analogously to the down-regulation of ELOVL2. Following mechanistic study confirmed the up-regulation of SCD and down-regulation of PTPLB, PECR, ELOVL2, and ELOVL3 in the spheroid cells. Furthermore, the depletion of ELOVL2 induced metastatic characteristics in breast cancer cells via the SREBPs axis. A subsequent large-scale analysis using 51 breast cancer cell lines demonstrated the reduced expression of ELOVL2 in basal-like phenotypes. Breast cancer patients with low ELOVL2 expression exhibited poor prognoses (HR = 0.76, CI = 0.67–0.86). Collectively, ELOVL2 expression is associated with the malignant phenotypes and appear to be a novel prognostic biomarker in breast cancer. In conclusion, the present study demonstrates that there is a global alteration of the lipid composition during EMT and suggests the down-regulation of ELOVL2 induces lipid metabolism reprogramming in breast cancer and contributes to their malignant phenotypes.

Docosahexaenoic acid-thyroid hormone combined protocol as a novel approach to metabolic stress disorders: Relation to mitochondrial adaptation via liver PGC-1α and sirtuin1 activation

Docosahexaenoic acid (DHA) and 3,3',5-triiodothyronine (T₃ ) combined protocol affords protection against liver injury via AMPK signaling supporting energy requirements. The aim of this work was to test the hypothesis that a DHA + T₃ accomplish mitochondrial adaptation through downstream upregulation of PPAR-γ coactivator 1α (PGC-1α). Male Sprague-Dawley rats were given daily oral doses of 300 mg DHA/kg or saline (controls) for three consecutive days, followed by 0.05 mg T₃ /kg (or hormone vehicle) ip at the fourth day, or single dose of 0.1 mg T₃ /kg alone. Liver mRNA levels were assayed by qPCR, NAD⁺ /NADH ratios, hepatic proteins, histone 3 acetylation and serum T₃ and β-hydroxybutyrate levels were determined by specific ELISA kits. Combined DHA + T₃ protocol led to increased liver AMPK, PGC-1α, NRF-2, COX-IV, and β-ATP synthase mRNAs, with concomitant higher protein levels of COX-IV and NRF-2, 369% enhancement in the NAD⁺ /NADH ratio, 47% decrease in histone 3 acetylation and 162% increase in serum levels of β-hydroxybutyrate over control values. These changes were reproduced by the higher dose of T₃ without major alterations by DHA or T₃ alone. In conclusion, liver mitochondrial adaptation by DHA + T₃ is associated with PGC-1α upregulation involving enhanced transcription of the coactivator, which may be contributed by PGC-1α deacetylation and phosphorylation by SIRT1 and AMPK activation, respectively. This contention is supported by NRF-2-dependent enhancement in COX-1 and β-ATP synthase induction with higher fatty acid oxidation resulting in a significant ketogenic response, which may represent a suitable strategy for hepatic steatosis with future clinical applications. © 2018 BioFactors, 45(2):271-278, 2019.

Dietary supplement of Smilax china L. ethanol extract alleviates the lipid accumulation by activating AMPK pathways in high-fat diet fed mice

Background

Obesity has become a public health concern worldwide because it is linked to numerous metabolic disorders, such as hyperlipidemia, hypertension and cardiovascular disease. Therefore, there is an urgent need to develop new therapeutic strategies that are efficacious and have minimal side effects in obesity treatment. This study examined the effect of dietary supplement of Smilax china L. ethanol extract (SCLE) on high-fat diet (HFD) induced obesity.

Methods

Fifty ICR mice were fed a normal diet, high-fat diet (HFD) or HFD supplemented with 0.25, 0.5% or 1% SCLE for 8 weeks. Body weight, intraperitioneal adipose tissue (IPAT) weight, serum biochemical parameters, and liver lipids were measured. Activity, mRNA and protein expressions of lipid metabolism-related enzymes were analyzed.

Results

Over 0.5% SCLE had reduced cholesterol biosynthesis by the activation of AMP-activated protein kinase (AMPK), which subsequently suppressed the mRNA expression of both sterol regulatory element binding protein-2 and 3-hydroxy-3-methyl-glutaryl-CoA reductase. Thus, the plasma and liver cholesterol concentrations in the HFD-fed mice were decreased. AMPK activation caused by SCLE also significantly upregulated lipolysis by enhancing adipose triglyceride lipase and hormone-sensitive lipase activities. This accelerated triglyceride hydrolysis and fatty acid release. Finally, SCLE increased carnitine palmitoyltransferase 1 and acyl-CoA oxidase activities, which further promoted fatty acid β-oxidation.

Conclusion

SCLE could lead to a decrease in body weight gain and fat mass by inhibiting the lipid synthesis and promoting lipolysis and β-oxidation in HFD fed mice. The underlying mechanism is probably associated with regulating AMPK pathway.

Collaborative effects of chlorogenic acid and caffeine on lipid metabolismviathe AMPKα-LXRα/SREBP-1c pathway in high-fat diet-induced obese mice

The combination of CGA and caffeine exhibits anti-obesity effects and regulates lipid metabolismviathe AMPKα-LXRα/SREBP-1c signaling pathway in mice with high-fat diet-induced obesity.

Molecular mechanisms related to the hepatoprotective effects of antioxidant-rich extra virgin olive oil supplementation in rats subjected to short-term iron administration

Enhanced iron levels in liver are associated with oxidative stress development and damage with increased fat accumulation. The aim of this work was to assess the hypothesis that antioxidant-rich extra virgin olive oil (AR-EVOO) counteracts iron-rich diet (IRD)-induced oxidative stress hindering hepatic steatosis. Male Wistar rats were fed and IRD (200 mg iron/kg diet) versus a control diet (CD; 50 mg iron/kg diet) with alternate AR-EVOO supplementation (100 mg/day) for 21 days. IRD induced liver steatosis and oxidative stress (higher levels of protein oxidation and lipid peroxidation with glutathione depletion), mitochondrial dysfunction (decreased citrate synthase and complex I and II activities) and loss of polyunsaturated fatty acids (PUFAs), with a drastic enhancement in the sterol regulatory element-binding protein-1c (SREBP-1c)/peroxisome proliferator-activated receptor-α (PPAR-α) ratio upregulating the expression of lipogenic enzymes (acetyl-CoA carboxylase, fatty acid (FA) synthase and stearoyl desaturase 2) and downregulating those involved in FA oxidation (carnitine palmitoyl transferase and acyl-CoA oxidase) over values in the CD group. IRD also upregulated nuclear factor erythroid 2-related factor 2 (Nrf2) and its target genes. AR-EVOO supplementation alone did not modify the studied parameters, however, IRD combined with AR-EVOO administration returned IRD-induced changes to baseline levels of the CD group. It is concluded that IRD-induced non-alcoholic fatty liver disease (NAFLD) is prevented by AR-EVOO supplementation, which might be related to the protective effects of its components such as hydroxytyrosol, oleic acid, tocopherols and/or PUFAs, thus representing a suitable anti-steatotic strategy to avoid progression into more severe stages of the disease, underlying NAFLD associated with iron overloading pathologies or obesity.

Differential effects of EPA, DPA and DHA on cardio-metabolic risk factors in high-fat diet fed mice

The aim of the present study was to assess and compare the effects of eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) supplementation on lipid metabolism in 4 month-old male C57BL/6J mice fed a high-fat diet. The high-fat fed mice showed evidence of fatty liver, obesity and insulin resistance after being on the high-fat diet for 6 weeks compared with the control low-fat diet fed mice. Supplementation of the high-fat diet with either EPA, DPA or DHA prevented the fatty liver, prevented high serum cholesterol and serum glucose and prevented high liver cholesterol levels. DPA (but not EPA or DHA) was associated with a significantly improved homeostasis model assessment of insulin resistance (HOMA-IR) compared with the high-fat fed mice. Supplementation with DPA and DHA both prevented the decreased serum adiponectin levels, compared with EPA and the high-fat diet. In addition, supplementation with DPA and DHA both prevented the increased serum alanine aminotransferase (ALT) levels compared with EPA and the high-fat group, which can be attributed to down-regulation of TLR-4/NF-κB signaling pathway and decreasing lipogenesis in the liver. Therefore, DPA and DHA seem to exert similar effects in cardio-metabolic protection against the high-fat diet and these effects seem to be different to those of EPA.

Protectin DX Ameliorates Hepatic Steatosis by Suppression of Endoplasmic Reticulum Stress via AMPK-Induced ORP150 Expression

Docosahexaenoic acid (DHA) and its bioactive compounds may have suppressive effects on inflammation, endoplasmic reticulum (ER) stress, and insulin resistance. Protectin DX (PDX), a double lipoxygenase product from DHA has shown a suppressive effect on inflammation and insulin resistance. However, the effects of PDX on ER stress and hepatic steatosis have not been elucidated yet. Herein we report that PDX could stimulate the AMP-activated protein kinase (AMPK) phosphorylation, thereby upregulating oxygen-regulated protein 150 (ORP150) expression in a dose-dependent manner. Treatment of HepG2 cells with PDX attenuated the palmitate-induced triglyceride accumulation through regulation of the sterol regulatory element-binding protein 1 (SREBP1)-mediated pathway. To deal with the pharmacological significance in the protective effects of PDX on hepatic steatosis, we performed in vivo experiments. In a mouse model, the PDX administration would alleviate the high-fat diet-induced hepatic steatosis and trigger the hepatic AMPK phosphorylation and ORP150 expression. PDX improved palmitate-induced and HFD-induced impairment of hepatic lipid metabolism and steatosis through suppression of ER stress via an AMPK-ORP150-dependent pathway.

fat-1 mice prevent high-fat plus high-sugar diet-induced non-alcoholic fatty liver disease

High-fat and high-sugar (HFS) diets have been suggested to play a causal role in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). This study aimed to investigate whether fat-1 transgenic mice with a higher tissue content of n-3 polyunsaturated fatty acids (PUFAs) could prevent HFS diet-induced NAFLD, compared with wild-type mice. The fat-1 and wild-type littermates had free access to a 15% fructose solution plus high-fat diet, a 15% glucose solution plus high-fat diet, or a 15% sucrose solution plus high-fat diet, respectively. Caloric intake, weight gain, biochemical parameters, histology, and gene and protein expression levels were measured after 8 weeks of intervention. Liquid intake in glucose- or sucrose-fed mice was about 2-fold compared with that in fructose-fed mice. The wild-type mice given glucose showed the highest total caloric intake and weight gain compared to the other groups. The serum concentrations of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and alanine transaminase (ALT) were significantly lowered in fat-1 groups compared with their paired wild-type groups. Histological analysis showed that the wild-type groups fed the HFS diets developed hepatic lipid accumulation and steatosis, compared with the fat-1 groups. The gene and protein expression levels involved in fatty acid synthesis and the toll-like receptor (TLR)-4 signaling pathway were significantly inhibited in the fat-1 groups compared with the wild-type groups. The endogenously synthesized n-3 PUFAs of the three fat-1 groups, which inhibit fatty acid synthesis and the TLR-4 signaling pathway, prevent HFS diet-induced NAFLD.

Fish Oil Supplementation Alleviates the Altered Lipid Homeostasis in Blood, Liver, and Adipose Tissues in High-Fat Diet-Fed Rats

This study investigated the effects of dietary supplementation of fish oil on the signals of lipid metabolism involved in hepatic cholesterol and triglyceride influx and excretion in high-fat diet (HFD)-fed rats. Fish oil (FO) repressed body (HFD, 533 ± 18.2 g; HFD+FO, 488 ± 28.0 g, p < 0.05) and liver weights (HFD, 5.7 ± 0.6 g/100 g of body weight; HFD+FO, 4.8 ± 0.4 g/100 g of body weight, p < 0.05) in HFD-fed rats. Fish oil could also improve HFD-induced imbalance of lipid metabolism in blood, liver, and adipose tissues including the significant decreases in plasma and liver total cholesterol (TC) (plasma-HFD, 113 ± 33.6 mg/dL; HFD+FO, 50.0 ± 5.95 mg/dL, p < 0.05; liver-HFD, 102 ± 13.0 mg/g liver; [corrected] HFD+FO, 86.6 ± 7.81 mg/g liver, [corrected] p < 0.05), blood, liver, and adipose triglyceride (TG) (blood-HFD, 52.5 ± 20.4 mg/dL; HFD+FO, 29.8 ± 4.30 mg/dL, p < 0.05; liver-HFD, 56.2 ± 10.0 mg/g liver; [corrected] HFD+FO, 30.3 ± 5.28 mg/g liver, [corrected] p < 0.05; adipose-HFD, 614 ± 73.2 mg/g liver, [corrected] HFD+FO, 409 ± 334 mg/g of adipose tissue, [corrected] p < 0.05), and low density (HFD, 79.8 ± 40.9 mg/dL; HFD+FO, 16.6 ± 5.47 mg/dL, p < 0.05) and very-low-density (HFD, 49.7 ± 33.3 mg/dL; HFD+FO, 10.4 ± 3.45 mg/dL, p < 0.05) lipoprotein and the significant increases in fecal TC (HFD, 12.2 ± 0.67 mg/g feces; [corrected] HFD+FO, 16.3 ± 2.04 mg/g feces, [corrected] < 0.05) and TG (HFD, 2.09 ± 0.10 mg/g feces; [corrected] HFD+FO, 2.38 ± 0.22 mg/g feces, [corrected] p < 0.05) and lipoprotein lipase activity of adipose tissues (HFD, 16.6 ± 3.64 μM p-nitrophenol; HFD+FO, 24.5 ± 4.19 μM p-nitrophenol, p < 0.05). Moreover, fish oil significantly activated the protein expressions of hepatic lipid metabolism regulators (AMPKα and PPARα) and significantly regulated the lipid-transport-related signaling molecules (ApoE, MTTP, ApoB, Angptl4, ApoCIII, ACOX1, and SREBPF1) in blood or liver of HFD-fed rats. These results suggest that fish oil supplementation improves HFD-induced imbalance of lipid homeostasis in blood, liver, and adipose tissues in rats.

Omega-3 fatty acids in obesity and metabolic syndrome: a mechanistic update

Strategies to reduce obesity have become public health priorities as the prevalence of obesity has risen in the United States and around the world. While the anti-inflammatory and hypotriglyceridemic properties of long-chain omega-3 polyunsaturated fatty acids (n-3 PUFAs) are well known, their antiobesity effects and efficacy against metabolic syndrome, especially in humans, are still under debate. In animal models, evidence consistently suggests a role for n-3 PUFAs in reducing fat mass, particularly in the retroperitoneal and epididymal regions. In humans, however, published research suggests that though n-3 PUFAs may not aid weight loss, they may attenuate further weight gain and could be useful in the diet or as a supplement to help maintain weight loss. Proposed mechanisms by which n-3 PUFAs may work to improve body composition and counteract obesity-related metabolic changes include modulating lipid metabolism; regulating adipokines, such as adiponectin and leptin; alleviating adipose tissue inflammation; promoting adipogenesis and altering epigenetic mechanisms.

Maresin 1 attenuates NAFLD by suppression of endoplasmic reticulum stress via AMPK-SERCA2b pathway

Maresin 1 (MAR1), which is derived from docosahexaenoic acid biosynthesized by macrophages, has been reported to improve insulin resistance. Recently, it has been documented that MAR1 could ameliorate inflammation and insulin resistance in obese mice. These findings led us to investigate the effects of MAR1 on hepatic lipid metabolism. We found that MAR1 could stimulate AMP-activated protein kinase (AMPK), thereby augmenting sarcoendoplasmic reticulum Ca²⁺-ATPase 2b (SERCA2b) expression. This stimulation suppressed lipid accumulation by attenuating the endoplasmic reticulum (ER) stress in hepatocytes under hyperlipidemic conditions. Attenuation was mitigated by knockdown of AMPK or thapsigargin, a SERCA2b inhibitor. We also demonstrated that MAR1 administration resulted in increased hepatic AMPK phosphorylation and Serca2b mRNA expression, whereas hepatic ER stress was reduced in high-fat diet (HFD)-fed mice. Moreover, MAR1 treatment suppressed hepatic lipid synthesis, thereby attenuating hepatic steatosis in HFD-fed mice. In conclusion, our results suggest that MAR1 ameliorates hepatic steatosis via AMPK/SERCA2b-mediated suppression of ER stress. Therefore, MAR1 may be an effective therapeutic strategy for treating non-alcoholic fatty liver disease (NAFLD) via regulation of ER stress-induced hepatic lipogenesis.

Benefits of Fish Oil Consumption over Other Sources of Lipids on Metabolic Parameters in Obese Rats

This study evaluated the effect of the consumption of different levels and sources of lipids on metabolic parameters of Wistar rats. Animals were fed with high-fat diet (HFD) containing 20% of lard for 12 weeks to cause metabolic obesity. Subsequently, the animals were divided into six groups and were fed diets with lipid concentrations of 5% or 20% of lard (LD), soybean oil (SO) or fish oil (FO), for 4 weeks. Data were submitted to analysis of variance (two-way) followed by Tukey post hoc test (p < 0.05). The groups that consumed FO showed less weight gain and lower serum levels of triacylglycerol (TAG), total cholesterol and fractions, aspartate aminotransferase (AST) activity, atherogenic index, less amount of fat in the carcass, decreased Lee index and lower total leukocyte counting (p < 0.05). These same parameters were higher in LD treatment (p < 0.05). In the concentration of 20%, carcass fat content, blood glucose levels, as well as alanine aminotransferase (ALT) and gamma glutamyl transferase (GGT) decreased in FO groups (p < 0.05). The SO group had intermediate results regarding the other two treatments (FO and LD). We concluded that fish oil intake was able to modulate positively the metabolic changes resulting from HFD.

n-3 Polyunsaturated Fatty Acids and Metabolic Syndrome Risk: A Meta-Analysis

The associations between n-3 polyunsaturated fatty acids (PUFAs) and metabolic syndrome (MetS) risk have demonstrated inconsistent results. The present study aimed to investigate whether higher circulating n-3 PUFAs and dietary n-3 PUFAs intake have a protective effect on MetS risk. A systematic literature search in the PubMed, Scopus, and Chinese National Knowledge Infrastructure (CNKI) databases was conducted up to March 2017. Odd ratios (ORs) from case-control and cross-sectional studies were combined using a random-effects model for the highest versus lowest category. The differences of n-3 PUFAs between healthy subjects and patients with MetS were calculated as weighted mean difference (WMD) by using a random-effects model. Seven case-control and 20 cross-sectional studies were included. A higher plasma/serum n-3 PUFAs was associated with a lower MetS risk (Pooled OR = 0.63, 95% CI: 0.49, 0.81). The plasma/serum n-3 PUFAs in controls was significantly higher than cases (WMD: 0.24; 95% CI: 0.04, 0.43), especially docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). However, no significant association was found between dietary intake of n-3 PUFAs or fish and MetS risk. The present study provides substantial evidence of a higher circulating n-3 PUFAs associated with a lower MetS risk. The circulating n-3 PUFAs can be regarded as biomarkers indicating MetS risk, especially DPA and DHA.