Apple Polyphenol Extract Alleviates High-Fat-Diet-Induced Hepatic Steatosis in Male C57BL/6 Mice by Targeting LKB1/AMPK Pathway

Dietary dicarbonyl compounds exacerbated immune dysfunction and hepatic oxidative stress under high-fat diets in vivo

High-fat diets (HFDs) predispose to obesity and liver dysfunctions, and α-dicarbonyl compounds (α-DCs) present in highly processed foods are also implicated in relevant pathological processes. However, the synergistic harmful effects of α-DCs co-administered with HFDs remain to be elucidated. In this study, 6-week-old C57BL/6 mice were fed with a HFD co-administered with 0.5% methylglyoxal (MGO)/glyoxal (GO) in water for 8 weeks, and multi-omics approaches were employed to investigate the underlying toxicity mechanisms. The results demonstrated that the MGO intervention with a HFD led to an increased body weight and blood glucose level, accompanied by the biological accumulation of α-DCs and carboxymethyl-lysine, as well as elevated serum levels of inflammatory markers including IL-1β, IL-6, and MIP-1α. Notably, hepatic lesions were observed in the MGO group under HFD conditions, concomitant with elevated levels of malondialdehyde. Transcriptomic analysis revealed enrichment of pathways and differentially expressed genes (DEGs) associated with inflammation and oxidative stress in the liver. Furthermore, α-DC intervention exacerbated gut microbial dysbiosis in the context of a HFD, and through Spearman correlation analysis, the dominant genera such as Fusobacterium and Bacteroides in the MGO group and Colidextribacter and Parabacteroides in the GO group were significantly correlated with a set of DEGs involved in inflammatory and oxidative stress pathways in the liver. This study provides novel insights into the healthy implications of dietary ultra-processed food products in the context of obesity-associated disorders.

Exploring the Potential of Ribes nigrum L., Aronia melanocarpa (Michx.) Elliott, and Sambucus nigra L. Fruit Polyphenol-Rich Composition and Metformin Synergy in Type 2 Diabetes Management

Type 2 diabetes, characterized by insulin resistance and impaired glucose homeostasis, is commonly managed through lifestyle interventions and medications such as metformin. Although metformin is generally well-tolerated, it may cause gastrointestinal adverse effects and, in rare cases, precipitate lactic acidosis, necessitating cautious use in individuals with renal dysfunction. Additionally, concerns regarding its impact on hepatic function have led to its discontinuation in cirrhotic patients. This study explores the potential synergistic benefits of a polyphenol-rich blend containing black currant, chokeberry, and black elderberry extracts alongside metformin in managing type 2 diabetes. In vitro results highlighted distinct effects of AMPK pathway modulation, showcasing reductions in cholesterol and triglyceride levels alongside a notable enhancement in glucose uptake. The blend, when combined with metformin, significantly reduced insulin levels and fasting glucose concentrations in an in vivo model. Furthermore, hepatic analyses unveiled a modulation in cellular pathways, suggesting a potential influence on lipid metabolism, attenuation of inflammatory pathways, a decrease in cellular stress response, and antioxidant defense mechanisms, collectively implying a potential reduction in liver fat accumulation. The findings suggest a potential complementary role of polyphenols in enhancing the efficacy of metformin, possibly allowing for reduced metformin dosage and mitigating its side effects. Further clinical studies are warranted to validate these findings and establish the safety and efficacy of this nutraceutical approach in managing type 2 diabetes.

Total flavonoids of Broussonetia papyrifera alleviate non-alcohol fatty liver disease via regulating Nrf2/AMPK/mTOR signaling pathways

BACKGROUNDS

Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent chronic liver diseases. The leaves of Broussonetia papyrifera contain a large number of flavonoids, which have a variety of biological functions.

METHODS

In vitro experiments, free fatty acids were used to stimulate HepG2 cells. NAFLD model was established in vivo in mice fed with high fat diet (HFD) or intraperitoneally injected with Tyloxapol (Ty). At the same time, Total flavonoids of Broussonetia papyrifera (TFBP) was used to interfere with HepG2 cells or mice.

RESULTS

The results showed that TFBP significantly decreased the lipid accumulation induced by oil acid (OA) with palmitic acid (PA) in HepG2 cells. TFBP decreased the total cholesterol (TC), the triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and increased high-density lipoprotein cholesterol (HDLC) in serum. TFBP could also effectively inhibit the generation of reactive oxygen species (ROS) and restrained the level of myeloperoxidase (MPO), and enhance the activity of superoxide dismutase (SOD) to alleviate the injury from oxidative stress in the liver. Additionally, TFBP activated nuclear factor erythroid-2-related factor 2 (Nrf2) pathway to increasing the phosphorylation of AMP-activated protein kinase (AMPK). Meanwhile, protein levels of mTORC signaling pathway were evidently restrained with the treatment of TFBP.

CONCLUSION

Our experiments proved that TFBP has the therapeutic effect in NAFLD, and the activation of Nrf2 and AMPK signaling pathways should make sense.

Preventive Effects of Apple Polyphenol Extract on High-Fat-Diet-Induced Hepatic Steatosis Are Related to the Regulation of Hepatic Lipid Metabolism, Autophagy, and Gut Microbiota in Aged Mice

Our previous study confirmed that the ameliorated effects of an intervention with an apple polyphenol extract (APE) on hepatic steatosis induced by a high-fat diet (HFD) are dependent on SIRT1. Since SIRT1 expression decreases with age, it remains unclear whether APE intervention is effective against hepatic steatosis in aged mice. Thus, 12-month-old C57BL/6 male mice were fed with an HFD to establish an aging model of hepatic steatosis and treated with 500 mg/(kg·bw·d) APE for 12 weeks. Young mice (two months old) and baseline mice were used as controls to examine the effects of natural aging on hepatic steatosis. Compared with baseline mice, no obvious difference in hepatic histopathological assessment was observed for both young and aged mice on normal diets. Meanwhile, HFD induced much higher nonalcoholic fatty liver disease (NAFLD) activity scores in aged mice than in young mice. APE intervention ameliorated lipid and glucose metabolic disorders and liver injury in HFD-fed aged mice, improved hepatic steatosis, and reduced NAFLD activity scores. The upregulated expressions of SIRT1, HSL, ATG5, Ulk1, and Becn1 and downregulated expressions of HMGCR and FOXO1 suggested improved lipid metabolism and activated autophagy. APE intervention decreased the ratio of Firmicutes/Bacteroidetes and elevated the Akkermansia probiotics abundance. In summary, HFD showed a more significant effect on hepatic steatosis compared to the natural aging process in aged mice, and APE might be a promising dietary ingredient for alleviating hepatic steatosis.

Natural compounds against nonalcoholic fatty liver disease: A review on the involvement of the LKB1/AMPK signaling pathway

Although various therapeutic approaches are used to manage nonalcoholic fatty liver disease (NAFLD), the best approach to NAFLD management is unclear. NAFLD is a liver disorder associated with obesity, metabolic syndrome, and diabetes mellitus. NAFLD progression can lead to cirrhosis and end-stage liver disease. Hepatic kinase B1 (LKB1) is an upstream kinase of 5'-adenosine monophosphate-activated protein kinase (AMPK), a crucial regulator in hepatic lipid metabolism. Activation of LKB1/AMPK inhibits fatty acid synthesis, increases mitochondrial β-oxidation, decreases the expression of genes encoding lipogenic enzymes, improves nonalcoholic steatohepatitis, and suppresses NAFLD progression. One potential opening for new and safe chemicals that can tackle the NAFLD pathogenesis through the LKB1-AMPK pathway includes natural bioactive compounds. Accordingly, we summarized in vitro and in vivo studies regarding the effect of natural bioactive compounds such as a few members of the polyphenols, terpenoids, alkaloids, and some natural extracts on NAFLD through the LKB1/AMPK signaling pathway. This manuscript may shed light on the way to finding a new therapeutic agent for NAFLD management.

Lactoferrin Alleviates Ethanol-Induced Injury via Promoting Nrf2 Nuclear Translocation in BRL-3A Rat Liver Cells

Our previous animal studies found that the preventive effects of lactoferrin (Lf) on alcoholic liver injury (ALI) are associated with nuclear factor E2-related factor 2 (Nrf2). To further explore the causality, experiments were performed using rat normal liver BRL-3A cells. Lf treatment reduced ethanol-induced death and apoptosis; meanwhile, Lf treatment alleviated excessive LDH release. These findings confirmed the protection of Lf against ethanol-induced injury in BRL-3A cells. Mechanistically, Lf treatment reversed the reduction in nuclear Nrf2 induced by ethanol without affecting the cytoplasmic Nrf2 level, which led to antioxidant enzyme activity restoration. However, the blocking of Nrf2 nuclear translocation by ML385 eliminated the protective effects of Lf. In a conclusion, Lf protects BRL-3A cells from ethanol-induced injury via promoting Nrf2 nuclear translocation.

Apple Polyphenol Extract Ameliorates Atherosclerosis and Associated Cognitive Impairment through Alleviating Neuroinflammation by Weakening TLR4 Signaling and NLRP3 Inflammasome in High-Fat/Cholesterol Diet-Fed LDLR-/- Male Mice

Although studies have supported the beneficial effects of the ingredients of apple polyphenol extract (APE), a polyphenol mixture being extracted from whole fresh apples, on neurodegenerative diseases, the role of APE in atherosclerosis-related cognitive impairment remains unclear. To clarify the role of APE in regulating cognitive dysfunction in mice with atherosclerosis and the underlying mechanisms, high-fat/cholesterol diet-fed male LDLR-/- mice were gavaged with 125 or 500 mg/(kg·bw·d) APE solution or sterile double-distilled water for consecutive 8 weeks, and age-matched C57BL/6 male mice were employed as normal control. APE intervention increased the serum concentration of high-density apolipoprotein cholesterol, improved atherosclerosis, and ameliorated cognitive function of mice by inhibiting the phosphorylation of tau protein, supporting with significantly reduced platform latency and obviously increased swimming distance in the target quadrant according to the Morris water maze test. APE intervention alleviated neuroinflammation by attenuating the activation of microglia and astrocytes and inhibiting TLR4 signaling with reduced protein expression of NF-κB, MyD88, TRIF, and IKKβ. Meanwhile, APE intervention inactivated NLRP3 inflammasome with downregulated protein expression of caspase-1, IL-18, and IL-1β. Additionally, APE intervention improved the damaged brain barrier structure by upregulating the protein expression of ZO-1 and occludin. Therefore, our research supplemented new data, supporting the potential of APE as an effective dietary bioactive ingredient to improve atherosclerosis and associated cognitive impairment.

Effect of (poly)phenol-rich 'Daux Belan' apple supplementation on diet-induced obesity and glucose intolerance in C57BL/6NCrl mice

Obesity is a state of metabolic dysfunction that can lead to dyslipidemia and impaired glucose homeostasis. Apple polyphenols have been shown to ameliorate dyslipidemia/metabolic dysfunction in humans. The influence of apple (poly)phenols on energy metabolism in high-fat (HF) diet-induced obese mice remains controversial. This study examined the effect of dietary supplementation of (poly)phenol-rich 'Daux Belan' apple (DB; 6.2 mg gallic acid equivalence (GAE)/mouse/day; 0.15% (poly)phenol) in the form of freeze-dried powder on glucose and lipid metabolism in male HF-fed C57BL/6NCrl mice, in comparison to low-(poly)phenol-containing 'Zestar' apple (Z; 0.4 mg GAE/mouse/day). Obesity, glucose intolerance, hypertriglyceridemia, and hepatic lipid vacuolation were induced by HF feeding while circulating cholesterol levels remained unchanged. DB apple supplementation did not protect against HF-induced body weight gain, hyperglycemia, hepatic triglyceride level elevation, and hepatic lipid vacuolation at the tested dosage. Future studies should be conducted with increased DB dosage and employ apple (poly)phenols supplemented in the form of extracts or sugar-free powder.

Phloroglucinol possesses anti-inflammatory activities by regulating AMPK/Nrf2/HO-1 signaling pathway in LPS-stimulated RAW264.7 murine macrophages

BACKGROUND

Inflammation is closely related to the pathogenesis of chronic illnesses. Secondary metabolites of marine seaweeds are recognized as reliable sources of bioactive compounds due to their health benefits besides their nutritional value. The objective of this study was to determine the potential anti-inflammatory effect of phloroglucinol (Phl) in RAW264.7 murine macrophages after lipopolysaccharides (LPS) stimulation.

METHODS

MTT, nitric oxide (NO), and DCFH-DA assays were conducted to determine cell viability, NO production, and reactive oxygen species (ROS) generation respectively. Pro-inflammatory cytokines and prostaglandin E2 (PGE2) levels were measured using ELISA assay kits. Protein expression levels were determined by western blot analysis.

RESULTS

Phl treatment showed a promising anti-inflammatory effect by reducing NO production, secretion of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), PGE2 production, protein expression levels of inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2), and ROS generation in LPS-stimulated RAW264.7 murine macrophages. Phl treatment upregulated heme oxygenase-1 (HO-1) expression by inducing nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and activating AMPK. However, Zinc protoporphyrin (ZnPP), an inhibitor of HO-1, partially reversed these effects, including NO production, pro-inflammatory cytokine secretion, iNOS, COX-2 and HO-1 expression, and ROS generation.

CONCLUSION

Phl has potential anti-inflammatory activities by regulating AMPK/Nrf2/HO-1 pathway in LPS-stimulated RAW264.7 murine macrophages.

Beyond energy provider: multifunction of lipid droplets in embryonic development

Since the discovery, lipid droplets (LDs) have been recognized to be sites of cellular energy reserves, providing energy when necessary to sustain cellular life activities. Many studies have reported large numbers of LDs in eggs and early embryos from insects to mammals. The questions of how LDs are formed, what role they play, and what their significance is for embryonic development have been attracting the attention of researchers. Studies in recent years have revealed that in addition to providing energy for embryonic development, LDs in eggs and embryos also function to resist lipotoxicity, resist oxidative stress, inhibit bacterial infection, and provide lipid and membrane components for embryonic development. Removal of LDs from fertilized eggs or early embryos artificially leads to embryonic developmental arrest and defects. This paper reviews recent studies to explain the role and effect mechanisms of LDs in the embryonic development of several species and the genes involved in the regulation. The review contributes to understanding the embryonic development mechanism and provides new insight for the diagnosis and treatment of diseases related to embryonic developmental abnormalities.

Reduction of obesity and hepatic adiposity in high-fat diet-induced rats by besunyen slimming tea

Objective

Obesity is a significant risk factor for metabolic syndrome, type 2 diabetes mellitus, hypertension, nonalcoholic fatty liver disease, and cardiovascular disorders. As a well-known Chinese tea product, Besunyen Slimming Tea (BST) is believed to effectively reduce body weight (BW) and lipid profile. In this study, we aimed to elucidate the mechanisms and effects of BST on treating obesity and hepatic steatosis using a rat model fed with a high-fat diet (HFD).

Methods

Sprague-Dawley rats were subjected to random separation into three categories: Animals were fed (1) a normal diet food (ND); (2) HFD, and (3) HFD + BST (n = 12/category). After successfully establishing the obesity model at week 8, the HFD + BST received BST (0.6 g/0.6 kg) orally, and the ND and HFD received the same amount (2 ml) of distilled water orally.

Results

HFD + BST reduced waist circumference (7.84%, P = 0.015), food intake (14.66%, P = 0.011), final BW (12.73%, P = 0.010), BW gain (964.16%, P < 0.001), and body mass index (8.97%, P = 0.044) compared with the HFD. BST supplementation also decreased hyperlipidemia, inflammation, and insulin resistance in rats with HFD. Furthermore, BST suppressed hepatic lipidosis by decreasing de novo lipogenesis and increasing fatty acid oxidation.

Conclusions

The results of this study offer evidence supporting the potential health benefits of BST in the management of metabolic disorders and obesity.

6-Gingerol Ameliorates Hepatic Steatosis, Inflammation and Oxidative Stress in High-Fat Diet-Fed Mice through Activating LKB1/AMPK Signaling

6-Gingerol, one of the major pharmacologically active ingredients extracted from ginger, has been reported experimentally to exert hepatic protection in non-alcoholic fatty liver disease (NAFLD). However, the molecular mechanism remains largely elusive. RNA sequencing indicated the significant involvement of the AMPK signaling pathway in 6-gingerol-induced alleviation of NAFLD in vivo. Given the significance of the LKB1/AMPK pathway in metabolic homeostasis, this study aims to investigate its role in 6-gingerol-induced mitigation on NAFLD. Our study showed that 6-gingerol ameliorated hepatic steatosis, inflammation and oxidative stress in vivo and in vitro. Further experiment validation suggested that 6-gingerol activated an LKB1/AMPK pathway cascade in vivo and in vitro. Co-immunoprecipitation analysis demonstrated that the 6-gingerol-elicited activation of an LKB1/AMPK pathway cascade was related to the enhanced stability of the LKB1/STRAD/MO25 complex. Furthermore, radicicol, an LKB1 destabilizer, inhibited the activating effect of 6-gingerol on an LKB1/AMPK pathway cascade via destabilizing LKB1/STRAD/MO25 complex stability in vitro, thus reversing the 6-gingerol-elicited ameliorative effect. In addition, molecular docking analysis further predicated the binding pockets of LKB1 necessary for binding with 6-gingerol. In conclusion, our results indicate that 6-gingerol plays an important role in regulating the stability of the LKB1/STRAD/MO25 complex and the activation of LKB1, which might weigh heavily in the 6-gingerol alleviation of NAFLD.

Dietary Polyphenols Alleviate Autoimmune Liver Disease by Mediating the Intestinal Microenvironment: Challenges and Hopes

Autoimmune liver disease is a chronic liver disease caused by an overactive immune response in the liver that imposes a significant health and economic cost on society. Due to the side effects of existing medicinal medications, there is a trend toward seeking natural bioactive compounds as dietary supplements. Currently, dietary polyphenols have been proven to have the ability to mediate gut-liver immunity and control autoimmune liver disease through modulating the intestinal microenvironment. Based on the preceding, this Review covers the many forms of autoimmune liver illnesses, their pathophysiology, and the modulatory effects of polyphenols on immune disorders. Finally, we focus on how polyphenols interact with the intestinal milieu to improve autoimmune liver disease. In conclusion, we suggest that dietary polyphenols have the potential as gut-targeted modulators for the prevention and treatment of autoimmune liver disease and highlight new perspectives and critical issues for future pharmacological applications.

The AMPK pathway in fatty liver disease

Lipid metabolism disorders are the primary causes for the occurrence and progression of various liver diseases, including non-alcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (AFLD) caused by a high-fat diet and ethanol. AMPK signaling pathway plays an important role in ameliorating lipid metabolism disorders. Progressive research has clarified that AMPK signal axes are involved in the prevention and reduction of liver injury. Upregulation of AMK can alleviate FLD in mice induced by alcohol or insulin resistance, type 2 diabetes, and obesity, and most natural AMPK agonists can regulate lipid metabolism, inflammation, and oxidative stress in hepatocytes, consequently regulating FLD in mice. In NAFLD and AFLD, increasing the activity of AMPK can inhibit the synthesis of fatty acids and cholesterol by down-regulating the expression of adipogenesis gene (FAS, SREBP-1c, ACC and HMGCR); Simultaneously, by increasing the expression of fatty acid oxidation and lipid decomposition genes (CPT1, PGC1, and HSL, ATGL) involved in fatty acid oxidation and lipid decomposition, the body’s natural lipid balance can be maintained. At present, some AMPK activators are thought to be beneficial during therapeutic treatment. Therefore, activation of AMPK signaling pathway is a potential therapeutic target for disorders of the liver. We summarized the most recent research on the role of the AMPK pathway in FLD in this review. Simultaneously, we performed a detailed description of each signaling axis of the AMPK pathway, as well as a discussion of its mechanism of action and therapeutic significance.

The Ameliorating Effects of Apple Polyphenol Extract on High-Fat-Diet-Induced Hepatic Steatosis Are SIRT1-Dependent: Evidence from Hepatic-Specific SIRT1 Heterozygous Mutant C57BL/6 Mice

Apple polyphenol extract (APE) has been reported to possess protective effects against hepatic steatosis. To explore whether APE-induced alleviation of hepatic steatosis is SIRT1-dependent, the present study was carried out using wild-type and hepatic SIRT1 heterozygous mutant (Sirt1^+/-) C57BL/6 mice. On consideration of the sex disparity related to hepatic steatosis morbidity, both male and female mice were included in the study. Six to eight week old mice were fed a high-fat diet (HFD) and randomly assigned to one of the following groups: (1) wild-type mice (wt+HFD), (2) Sirt1^+/- mice (Sirt1^+/-+HFD), and (3) Sirt1^+/- mice with 500 mg/(kg·bw·d) APE intragastric administration (Sirt1^+/-+HAP). HFD-induced weight gain and triglyceride accumulation was more prominent in Sirt1^+/- mice in comparison to wild-type mice. Following APE treatment, these effects were significantly reduced along with the alleviation of hepatic steatosis via upregulated expression of SIRT1 at the protein and mRNA levels in both male and female mice. However, APE differentially regulated the genes related to lipid metabolism (Lkb1, Ampk, Hsl, Srebp-1c, Abcg1, and Cd36) in a sex-specific manner. Moreover, APE treatment altered gut microbiota composition, with an increased relative abundance of Akkermansia and a decreased Firmicutes/Bacterodetes ratio. Thus, our study provided new evidence supporting our hypothesis that APE-induced alleviation of hepatic steatosis is SIRT1-dependent.

Preventive Effect of Apple Polyphenol Extract on High-Fat Diet-Induced Hepatic Steatosis in Mice through Alleviating Endoplasmic Reticulum Stress

In this work, the protective effect of apple polyphenol extract (APE) on hepatic steatosis was investigated. Thirty-two C57BL/6J mice were assigned randomly to control group, hepatic steatosis group, lovastatin group, and APE group. After 8 weeks of intervention, APE supplementation markedly decreased the body weight gain, liver weight, liver index, epididymal adipose weight, epididymal adipose index, serum, and hepatic lipid levels. Hematoxylin and eosin staining revealed that APE supplementation alleviated histopathological changes of hepatic steatosis. Western blot revealed that APE downregulated the protein levels of GRP78, IRE1α, p-IRE1α, XBP1, PERK, p-PERK, p-eIF2α, ATF6, PPAR-γ, SREBP-1c, FAS, and ACC1. In conclusion, this study found that APE inhibited IRE1α-XBP1, PERK-eIF2α, and ATF6 signaling pathways to alleviate endoplasmic reticulum stress, thereby improving HFD-induced hepatic steatosis.

Apple polyphenol extract modulates bile acid metabolism and gut microbiota by regulating the circadian rhythms in daytime-restricted high fat diet feeding C57BL/6 male mice

The homeostasis of circadian clock linked to bile acid (BA) metabolism and gut microbiota has profound benefits in maintaining the health status of the host. The aim of this study was to investigate the prevention and regulation of apple polyphenol extract (APE) on BA metabolism and gut microbiota by means of modulation of circadian rhythms in mice. Eighty male C57BL/6 mice were randomized into four groups: 24-hour ad libitum standard chow group (AC), ad libitum HFD group (AF), restricted 12 h daytime HFD feeding group (DF), and daytime HFD feeding with APE treatment group (DP). Five weeks later, the mice were sacrificed at 6 h intervals over a 24 h period. The results showed that APE decreased body weight and induced daily rhythms of Cry1 and Rorα in the suprachiasmatic nucleus (SCN) and Clock, Cry1 and Cry2 in the ileum in daytime HFD mice. APE significantly increased the expression of hepatic FXR at ZT0 and BSEP at ZT12 and inhibited the expression of ileac FXR at ZT12, reduced levels of fecal TBAs, secondary BAs, and unconjugated BAs at ZT0. Meanwhile, APE regulated the diversity and composition of the gut microbiota, and increased the abundance of probiotics. Therefore, our work revealed that APE as a clock-regulating natural compound could modulate BA metabolism and gut microbiota and protect against circadian disruption in a clock-dependent manner.

Apple Polyphenols Extracts Ameliorate High Carbohydrate Diet-Induced Body Weight Gain by Regulating the Gut Microbiota and Appetite

To investigate the potential contribution of appetite regulation and modulation of gut microbiota to the ameliorated effects of apple polyphenols extracts (APE) on high carbohydrate diet (HCD)-induced body weight (BW) gain, we conducted this study. One hundred C57BL/6 male mice were randomly divided into seven groups and fed with the following diets for 12 weeks: chow diet (CON), HCD (HCD), high fructose and sucrose diet (HSCD), and HCD and HSCD with 125 or 500 mg/kg·day APE gavage. Compared to the CON group, the BW of mice in the HCD and HSCD groups increased significantly. HSCD induced a more significant weight gain in the white adipose tissue (WAT) and liver than HCD, accompanied by severe impairment of glucose tolerance and a larger diameter of adipocytes. On the other hand, by decreasing food intake, APE significantly reduced BW via mechanisms, including decreased weights of the WAT and liver, amelioration of glucose tolerance, and amplification of WAT browning by upregulating the mRNA levels of Ucp-1 and Cidea. Moreover, APE promoted transcription and secretion of GLP-1, with the increased expression of gut anorexigenic hormone peptides Ffar 2/3 in the colon and anorectic neuropeptide gene expression of Pomc, Cart, and Mc4r in the hypothalamus, causing increased satiety. Additionally, APE significantly increased Verrucomicrobia colonization and the relative abundance of Akkermansia. APE potentially ameliorates high simple carbohydrate diet-induced body weight gain by mechanisms related to gut microbiota regulation and appetite inhibition.

Protective effects of apple polyphenols on bone loss in mice with high fat diet-induced obesity

Obesity-induced inflammation can lead to an imbalance in bone formation and resorption. Our previous studies have demonstrated that apple polyphenols (AP) can reduce body weight and inflammation. But its effect...

Dietary Intake of Hydrolyzable Tannins and Condensed Tannins to Regulate Lipid Metabolism

Lipid metabolism disorder is a multifactor issue, which contributes to several serious health consequences, such as obesity, hyperlipidemia, atherosclerosis diabetes, non-alcoholic fatty liver etc. Tannins, applied as natural derived plant, are commonly used in the study of lipid metabolism disease with excellent safety and effectiveness, while producing less toxic and side effects. Meanwhile, recognition of the significance of dietary tannins in lipid metabolism disease prevention has increased. As suggested by existing evidence, dietary tannins can reduce lipid accumulation, block adipocyte differentiation, enhance antioxidant capacity, increase the content of short-chain fatty acids, and lower blood lipid levels, thus alleviating lipid metabolism disorder. This study is purposed to sum up and analyze plenty of documents on tannins, so as to provide the information required to assess the lipid metabolism of tannins.

Lactoferrin Alleviates Acute Alcoholic Liver Injury by Improving Redox-Stress Response Capacity in Female C57BL/6J Mice

Lactoferrin (Lf) can attenuate alcoholic liver injury (ALI) in male mice; however, the effects of Lf on acute ALI in female mice are still unknown. Female C57BL/6J mice were randomly divided into four groups and fed with different diets for 4 weeks: an AIN-93G diet for control (CON) and ethanol (EtOH) groups; an AIN-93G diet with 0.4 and 4% casein replaced by Lf for low-dose Lf (LLf) and high-dose Lf (HLf) groups. Acute ALI was induced by intragastric administration of ethanol (4.8 g/kgbw) every 12 h continuously for three times. HLf had obvious alleviating effects on acute ALI. Lf pretreatment did not affect hepatic alcohol metabolism key enzymes. Meanwhile, the ethanol-induced hepatic reactive oxygen species level increase was not ameliorated by Lf. Metabolomics and bioinformatics analysis results suggested an important role of redox-stress response capacity (RRC). Western blots showed HLf-promoted AKT and AMP-activated protein kinase activations and upregulated Nrf2 and LC3-II expressions, which was associated with RRC improvement. In summary, HLf could prevent acute ALI in female mice, and RRC likely played an important role.

Daily Dose of Bovine Lactoferrin Prevents Ethanol-Induced Liver Injury and Death in Male Mice by Regulating Hepatic Alcohol Metabolism and Modulating Gut Microbiota

SCOPE

Lactoferrin (Lf) possess a protective potential to liver, but whether it can prevent alcoholic liver injury (ALI) remains unclear.

METHODS AND RESULTS

Four groups of male C57BL/6J mice are fed with different diets, namely, AIN-93G diet for control (CON) and ethanol (EtOH) groups, and AIN-93G diet with 0.4% and 4% casein replaced by Lf for low-dose Lf (LLf) and high-dose Lf (HLf) groups, respectively. ALI is induced by giving 20% ethanol ad libitum combined with four "binges". Lf can remarkably decrease EtOH-induced mortality. Lf promotes aldehyde dehydrogenase-2 (ALDH2) expression and suppressing cytochrome P450 2E1 (CYP2E1) overexpression, resulting in the reduced hepatic superoxide and inflammation levels, which ultimately leads to the hepatic injury alleviation. However, HLf increases acetyl-CoA carboxylase and fatty acid synthase protein levels, which suggests that excessive intake may weaken the beneficial effects of Lf. Moreover, LLf increases the relative abundances of Akkermansia and Lactobacillus. Additionally, the study shows that Lf likely exerts action in its digestive product forms rather than intact Lf molecular in normal condition.

CONCLUSION

LLf can ameliorate ALI, which is associated with the regulation of hepatic alcohol metabolism and the modulation of gut microbiota. However, excessive Lf intake may result in a diminished benefit.

Apple Polyphenol Extract Improves High-Fat Diet-Induced Hepatic Steatosis by Regulating Bile Acid Synthesis and Gut Microbiota in C57BL/6 Male Mice

Our previous study showed that apple polyphenol extract (APE) ameliorated high-fat diet-induced hepatic steatosis in C57BL/6 mice by targeting the LKB1/AMPK pathway; to investigate whether other mechanisms are involved in APE induction of improved hepatic steatosis, especially the roles of bile acid (BA) metabolism and gut microbiota, we conducted this study. Thirty-three C57BL/6 male mice were fed with high-fat diet for 12 weeks and concomitantly treated with sterilized water (CON) or 125 or 500 mg/(kg·bw·day) APE (low-dose APE, LAP; high-dose APE, HAP) by intragastric administration. APE treatment decreased total fecal BA contents, especially fecal primary BA levels, mainly including cholic acid, chenodeoxycholic acid, and muricholic acid. An upregulated hepatic Farnesoid X receptor (FXR) protein level and downregulated protein levels of cholesterol 7α-hydroxylase (CYP7A1) and cholesterol 7α-hydroxylase (CYP27A1) were observed after APE treatment, which resulted in the suppressed BA synthesis. Meanwhile, APE had no significant effects on mucosal injury and FXR expression in the jejunum. APE regulated the diversity of gut microbiota and microbiota composition, characterized by significantly increased relative abundance of Akkermansia and decreased relative abundance of Lactobacillus. Furthermore, APE might affect the reverse cholesterol transport in the ileum, evidenced by the changed mRNA levels of NPC1-like intracellular cholesterol transporter 1 (Npc1l1), liver X receptor (Lxr), ATP binding cassette subfamily A member 1 (Abca1), and ATP binding cassette subfamily G member 1 (Abcg1). However, APE did not affect the dihydroxylation and taurine metabolism of BA. The correlation analysis deduced no obvious interactions between BA and gut microbiota. In summary, APE, especially a high dose of APE, could alleviate hepatic steatosis, and the mechanisms were associated with inhibiting BA synthesis and modulating gut microbiota.

Genome-wide DNA methylation profiling of high-fat emulsion-induced hyperlipidemia mice intervened by a polysaccharide from Cyclocarya paliurus (Batal) Iljinskaja

Genome-wide DNA methylation was used to study the lipid-lowering effect of Cyclocarya paliurus (Batal) Iljinskaja polysaccharide (CPP). The objective of this study was to investigate the hypolipidemic effects and the potential underlying mechanisms of action of CPP-2 in high-fat emulsion (HFE)-induced mice. The results showed that CPP-2 reduced the level of genome-wide DNA methylation in the liver of HFE-induced mice, which had a lipid-lowering effect by regulating the AMP-activated protein kinase (AMPK) signaling-, fatty acid metabolism-, fatty acid biosynthesis- and adipocytokine signaling pathways. A series of lipid metabolism genes were screened out by conjoint analysis of the Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Hereafter, fatty acid synthase (FAS) and peroxisome proliferators-activated receptor α (PPARα) as target genes were selected to validate the accuracy of the results. The findings demonstrated that CPP-2 might be effective in lowering the lipid content, thereby protecting against HFE-induced hyperlipidemia.

Gut Microbiota and Its Metabolite Deoxycholic Acid Contribute to Sucralose Consumption-Induced Nonalcoholic Fatty Liver Disease

As important signal metabolites within enterohepatic circulation, bile acids (BAs) play a pivotal role during the occurrence and development of diet-induced nonalcoholic fatty liver disease (NAFLD). Here, we evaluated the functional effects of BAs and gut microbiota contributing to sucralose consumption-induced NAFLD of mice. The results showed that sucralose consumption significantly upregulated the abundance of intestinal genera Bacteroides and Clostridium, which produced deoxycholic acid (DCA) accumulating in multiple biological matrixes including feces, serum, and liver of mice. Subsequently, elevated hepatic DCA, one of the endogenous antagonists of the farnesol X receptor (Fxr), inhibited hepatic gene expression including a small heterodimer partner (Shp) and Fxr leading to sucralose-induced NAFLD in mice. Dietary supplements with fructo-oligosaccharide or metformin markedly restored genera Bacteroides and Clostridium abundance and the DCA level of sucralose-consuming mice, which eventually ameliorated NAFLD. These findings highlighted the effects of gut microbiota and its metabolite DCA on sucralose-induced NAFLD of mice.

Sirtuins-Mediated System-Level Regulation of Mammalian Tissues at the Interface between Metabolism and Cell Cycle: A Systematic Review

Sirtuins are a family of highly conserved NAD+-dependent proteins and this dependency links Sirtuins directly to metabolism. Sirtuins' activity has been shown to extend the lifespan of several organisms and mainly through the post-translational modification of their many target proteins, with deacetylation being the most common modification. The seven mammalian Sirtuins, SIRT1 through SIRT7, have been implicated in regulating physiological responses to metabolism and stress by acting as nutrient sensors, linking environmental and nutrient signals to mammalian metabolic homeostasis. Furthermore, mammalian Sirtuins have been implicated in playing major roles in mammalian pathophysiological conditions such as inflammation, obesity and cancer. Mammalian Sirtuins are expressed heterogeneously among different organs and tissues, and the same holds true for their substrates. Thus, the function of mammalian Sirtuins together with their substrates is expected to vary among tissues. Any therapy depending on Sirtuins could therefore have different local as well as systemic effects. Here, an introduction to processes relevant for the actions of Sirtuins, such as metabolism and cell cycle, will be followed by reasoning on the system-level function of Sirtuins and their substrates in different mammalian tissues. Their involvement in the healthy metabolism and metabolic disorders will be reviewed and critically discussed.

Apple polyphenol extract alleviates lipid accumulation in free-fatty-acid-exposed HepG2 cells via activating autophagy mediated by SIRT1/AMPK signaling

Defective degradation of intracellular lipids induced by autophagy is causally linked to the development of non-alcoholic fatty liver disease (NAFLD). Natural agents that can restore autophagy could therefore have the potentials for clinical applications for this public health issue. Herein, we investigated the effects of apple polyphenol extract (APE) on fatty acid-induced lipids depositions in HepG2 cells. APE treatment alleviated palmitic acid and oleic acid-induced intracellular lipid accumulation, concomitant with the increased autophagy, restored lysosomal acidification, inhibited lipid synthesis and slight promotion of fatty acid oxidation. Mechanistically, APE up-regulated the expression of SIRT1, activated LKB1/AMPK pathway and inhibited mTOR signaling. Over-expressed or knock-down SIRT1 positively regulated AMPK and ATG7 expressions. SIRT1 and ATG7 knock-down impaired APE induction of improved lipid accumulation, increased intracellular TG content. Thus, APE induction of autophagy to ameliorate fatty acid-induced lipid deposition is SIRT1 dependent, APE conserved preventive potentials for clinical hepatosteatosis.

Sodium butyrate promotes milk fat synthesis in bovine mammary epithelial cells via GPR41 and its downstream signalling pathways

OBJECTIVE

Short-chain fatty acids were reported to be the precursors of milk fat and can stimulate the de novo synthesis of fatty acids in bovine mammary epithelial cells (bMECs). However, the mechanism has not been elucidated. The purpose of this study was to investigate the effects of sodium butyrate (NaB) on milk fat synthesis in bMECs and explore its potential mechanism.

METHODS

Bovine mammary epithelial cells (bMECs) were isolated for subsequent experimental uses. BODIPY staining and triglyceride kit were used to detect the milk fat synthesis in bMECs. Western blotting and RT-PCR assays were performed to detect the expression of related genes in bMECs. Immunoprecipitation was used to detect the acetylation of SREBP1 in bMECs.

RESULTS

The results showed that NaB significantly promoted milk fat synthesis, promoted the activity of mechanistic target of rapamycin (mTOR) and S6 kinase (S6K), inhibited the activity of AMP-activated protein kinase (AMPK), and promoted the gene expression of G protein-coupled receptor 41 (GPR41). Knockdown of GPR41 and sterol regulatory element binding protein 1 (SREBP1) and overexpression of sirtuin1 (SIRT1), mTOR inhibitor (rapamycin), and AMPK activator (AICIR) eliminated these effects. These results indicated that NaB increased the nuclear translocation of SREBP1 via the GPR41/AMPK/mTOR/S6K signalling pathway, promoted the acetylation of mature SREBP1a via GPR41/AMPK/SIRT1, and then promoted milk fat synthesis.

CONCLUSION

Taken together, these results demonstrated that NaB increased nuclear translocation and acetylation of SREBP1 to promote milk fat synthesis by activating GPR41 and its downstream signalling pathways.