Dietary raffinose ameliorates hepatic lipid accumulation induced by cholic acid via modulation of enterohepatic bile acid circulation in rats

Butyrate attenuates cold-induced hypertension via gut microbiota and activation of brown adipose tissue

OBJECTIVE

Chronic exposure to cold temperature is known to elevate blood pressure, leading to a condition known as cold-induced hypertension (CIH). Our previous research suggested correlations between alterations in gut microbiota, decrease in butyrate level, and the onset and progression of CIH. However, the role of butyrate in CIH and the underlying mechanisms need further investigation.

METHODS

We exposed Specific Pathogen Free (SPF) rats to continuous cold temperature (4 ± 1 °C) for 6 weeks to establish a CIH rat model. Rats were divided into different groups by dose and duration, and the rats under cold were administered with butyrate (0.5 or 1 g/kg/day) daily. We assessed hypertension-associated phenotypes, pathological morphological changes, and endocrine-related phenotypes of brown adipose tissue (BAT). The effects of butyrate on gut microbiota and intestinal content metabolism were evaluated by 16s RNA sequencing and non-targeted metabolomics, respectively.

RESULTS

The systolic blood pressure (SBP) of rats exposed to cold after supplemented with butyrate were significantly lower than that of the Cold group. Butyrate may increase the species, abundance, and diversity of gut microbiota in rats. Specifically, butyrate intervention enriched beneficial bacterial genera, such as Lactobacillaceae, and decreased the levels of harmful bacteria genera, such as Actinobacteriota and Erysipeiotrichaceae. Cold exposure significantly increased BAT cells and the number of mitochondria. After butyrate supplementation, the levels of peroxisome proliferator-activated receptor gamma coactivator 1a and fibroblast growth factor 21 in BAT were significantly elevated (P < 0.05), and the volume and number of lipid droplets increased. The levels of ANG II and high-density lipoprotein were elevated in the Cold group but decreased after butyrate supplementation.

CONCLUSION

Butyrate may attenuate blood pressure in CIH by promoting the growth of beneficial bacteria and the secretion of beneficial derived factors produced by BAT, thus alleviating the elevation of blood pressure induced by cold. This study demonstrates the anti-hypertensive effects of butyrate and its potential therapeutic mechanisms, offering novel insights to the prevention and treatment of CIH in populations living or working in cold environments.

Targeting antioxidant factor Nrf2 by raffinose ameliorates lipid dysmetabolism-induced pyroptosis, inflammation and fibrosis in NAFLD

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a persistent liver condition that affects both human health and animal productive efficiency on a global scale. A number of naturally occurring compounds activate nuclear factor erythroid 2-related factor 2 (Nrf2) as a transcription factor with important protective effects against many liver diseases, including NAFLD. Raffinose (Ra), an oligosaccharide extracted from several plants, exhibits diverse biological functions. However, the uncertainty lies in determining whether the activation of Nrf2 by Ra can provide a preventive effect on liver lipotoxicity.

PURPOSE

The aim of this study was to shed light on the molecular pathways by which Ra possesses its protective benefits against NAFLD.

METHODS

Experimental protocols were established using WT and Nrf2-null (Nrf2-/-) mice. Liver samples from each group were collected for Western blot, RT-qPCR, H & E, Sirius red and Oil red O staining. Additionally, serums were processed for ELISA. ALM12 cells were gathered for Western blot and immunofluorescence. Moreover, to elucidate the molecular mechanism of Ra, molecular docking was performed.

RESULTS

Our results indicated that Ra remarkably alleviated liver lipotoxic in vivo and in vitro. Ra treatment effectively corrected hepatic steatosis, the release of AST, ALT, TG, and TC, as well as the depletion of HDL and LDL. Meanwhile, Ra efficiently prevented inflammation by inhibiting the TLR4-MyD88-NF-κB pathway and pyroptosis. Additionally, these findings implied that Ra reduced the production of fibrosis-related proteins, which enhanced collagen deposition. Molecular docking revealed that Ra possessed the ability to bind specific regions of Nrf2, resulting in the enhancement of Nrf2 activation and nuclear translocation. Ra treatment restored serum redox factors and antioxidant enzymes to normal levels; however, these alterations were clearly reversed in Nrf2-/- mice.

CONCLUSION

This study reveals novel information on Ra's protective benefits against liver injury caused by abnormal lipid metabolism; these effects are mostly mediated by Nrf2 activation, suggesting a potential new medicine or treatment strategy for NAFLD.

Integrated transcriptome and metabolome analysis reveals a possible mechanism for the regulation of lipid metabolism via vitamin A in rice field eel (Monopterus albus)

To understand the effects of vitamin A on lipid deposition in rice field eels, integrated liver transcriptome and metabolome were conducted and the changes in the genes and metabolites were assessed. Three groups of rice field eel were fed with 0, 200, and 16,000 IU/kg vitamin A supplementations in their diets for 70 days. The total lipid content in the whole body of the rice field eels was significantly increased with the vitamin A supplementations (p < 0.05). Comparative transcriptome analysis revealed 14 pathways and 46 differentially expressed genes involved in lipid metabolism. Sphingolipid metabolism, glycerolipid metabolism, primary bile acid biosynthesis and steroid hormone biosynthesis were significantly enriched pathways. In these pathways, three differential genes phospholipid phosphatase 1a (PLPP1a), phospholipid phosphatase 2b (PLPP2b), cytochrome P450 21a2 (CYP21a2) were consistent with the change trend of lipid content, and the other three differential genes aldo-keto reductase family 1 member D1 (AKR1D1), uridine diphosphate glucuronic acid transferase 1a1 (UGT1a1), cytochrome P450 1a (CYP1a) were opposite. Metabolomic analysis revealed that primary bile acid biosynthesis, sphingolipid metabolism, steroid hormone biosynthesis and biosynthesis of unsaturated fatty acids were all critical for rice field eel metabolic changes in response to vitamin A. Six important differential metabolites (eicosapentaenoic acid, sphinganine, 11-beta-hydroxyprogesterone, hydroxyeicosatetraenoic acid, cholic acid, and glycochenodeoxycholate) were identified and have provided new insights into how vitamin A regulates lipid deposition. Integrated transcriptome and metabolome analyses revealed that primary bile acid biosynthesis was the only remarkably enriched pathway in both the transcriptome and metabolome while that sphingosine was the main metabolite. Based on the above results, we have concluded that vitamin A promotes lipid deposition in the rice field eel through the primary bile acid synthesis pathway, and lipid deposits are widely stored in cell membranes, mainly in the form of sphingosine. These results will provide reference data to help improve our understanding of how vitamin A regulates lipid metabolism.

Metabolic alterations of the gut-liver axis induced by cholic acid contribute to hepatic steatosis in rats

12α-Hydroxylated (12αOH) bile acids (BAs) selectively increase with high-fat diet intake. Dietary supplementation with cholic acid (CA) in rats is a possible strategy to reveal the causal link between 12αOH BAs and hepatic steatosis. The present study aimed to investigate the metabolic mechanism underlying the effect of 12αOH BAs on hepatic steatosis. Male WKAH rats were fed either a control (Ct) or CA-supplemented diet (0.5 g/kg). After the 12-week intervention, the CA diet elevated the 12αOH BA levels in the gut-liver axis. CA-fed rats showed greater hepatic lipid accumulation than in the Ct group, regardless of the dietary energy balance. Untargeted metabolomics suggested marked differences in the fecal metabolome of rats subjected to the CA diet compared with that of Ct, characterized by the depletion of fatty acids and enrichment of amino acids and amines. Moreover, the liver metabolome differed in the CA diet group, characterized by an alteration in redox-related pathways. The CA diet elevated nicotinamide adenine dinucleotide consumption owing to the activation of poly(ADP-ribose) polymerase 1, resulting in impaired peroxisome proliferator-activated receptor α signaling in the liver. The CA diet increased sedoheptulose 7-phosphate, and enhanced glucose-6-phosphate dehydrogenase activity, suggesting promotion of the pentose phosphate pathway that generates reducing equivalents. Integrated analysis of the gut-liver metabolomic data revealed the role of deoxycholic acid and its liver counterpart in mediating these metabolic alterations. These observations suggest that alterations in metabolites induced by 12αOH BAs in the gut-liver axis contribute to the enhancement of liver lipid accumulation.

Optimization of the extract from flower of Citrus aurantium L. var. amara Engl. and its inhibition of lipid accumulation

Flower of Citrus aurantium L. var. amara Engl. (CAVA) has been confirmed to have promising anti-obesity effects. However, the regulation of alkaloid extracts from flower of CAVA (Al) on lipid metabolism remain unknown. In this study, Al was optimized by ultrasound-assisted extraction using response surface methodology. The optimal conditions were ultrasonic time 72 min, ethanol concentration 78% and liquid/solid ratio 30 ml/g with the maximum alkaloid yield 5.66%. LC-MS assay indicated that the alkaloid compounds were enriched in Al after optimization. Nine alkaloid compounds were identified in Al by LC-MS assay and stachydrine, caffeine and cathine appeared as the major alkaloid compounds. Bioactivity assay showed that Al treatment significantly increased superoxide dismutase (SOD) activity, and reduced malonaldehyde (MDA) and reactive oxygen species (ROS) levels. Al administration also reversed oleic acid-induced hepatic steatosis in Hep G2 cells by inhibiting the expression of lipogenesis-signaling genes including fatty acid synthase (FAS), peroxisome proliferator-activated receptor subtype γ (PPARγ), uncoupling protein 2 (UCP2), and retinol binding protein (RBP4). However, OA-induced reduction of lipolysis-related gene carnitine palmitoyl transferase 1A (CPT1A) in Hep G2 cells was not improved by Al supplementation. Moreover, the increased SOD activity and decreased MDA and ROS contents were also observed in Caenorhabditis elegans by Al addition. Al intervention exhibited the ability to inhibit lipid accumulation in C. elegans by suppressing expression of lipid metabolism-related genes. These results suggested that the alkaloid extracts from the flower of CAVA showed great potential to regulate lipid metabolism. PRACTICAL APPLICATIONS: The extraction of alkaloid extracts from the flower of CAVA was optimized with a maximum yield of 5.66%. The regulatory effects and mechanisms of Al on lipid metabolism of Hep G2 cells and Caenorhabditis elegans were also investigated. More clinical studies are required to evaluate the potential of using alkaloids from the flower of CAVA as therapeutic agents against lipid metabolic disorders.

Acidic Activated Charcoal Prevents Obesity and Insulin Resistance in High-Fat Diet-Fed Mice

Obesity is becoming a major public health problem worldwide. Making charcoal from wood (“Sumi-yaki”) has been a traditional activity in the southern part of Nagano Prefecture for centuries, with activated charcoal having reported detoxifying effects. However, it is unclear whether activated charcoal also possesses anti-obesity properties. Additionally, since activated charcoal is usually alkaline and might be affected by gastric juice, we evaluated the effect of acidic activated charcoal on high-fat diet (HFD)-induced obesity. This study demonstrated that co-treatment of acidic activated charcoal with a HFD significantly improved obesity and insulin resistance in mice in a dose-dependent manner. Metabolomic analysis of cecal contents revealed that neutral lipids, cholesterol, and bile acids were excreted at markedly higher levels in feces with charcoal treatment. Moreover, the hepatic expressions of genes encoding cholesterol 7 alpha-hydroxylase and hydroxymethylglutaryl-CoA reductase/synthase 1 were up-regulated by activated charcoal, likely reflecting the enhanced excretions from the intestine and the enterohepatic circulation of cholesterol and bile acids. No damage or abnormalities were detected in the gastrointestinal tract, liver, pancreas, and lung. In conclusion, acidic activated charcoal may be able to attenuate HFD-induced weight gain and insulin resistance without serious adverse effects. These findings indicate a novel function of charcoal to prevent obesity, metabolic syndrome, and related diseases.