The preventive effect of total saponins from Panax japonicus on inflammation and insulin resistance in adipose tissue of mice induced by a high-fat diet

Total saponins from Panax japonicus alleviate insulin resistance via exosomal miR204/Elovl6-mediated adipocyte-macrophage crosstalk

BACKGROUND

Insulin resistance (IR) is a key factor in the development of type 2 diabetes, and M2-like macrophages are important in maintaining normal glucose homeostasis. Our previous research has demonstrated that the total saponins from Panax japonicus (TSPJ) reduce IR in adipocytes and promote the M2 polarization of macrophages, but the molecular mechanism is unclear.

PURPOSE

In the study, we aimed to elucidate whether TSPJ mitigate IR by enhancing the intercellular communication between adipocytes and macrophages and describe how the exosomes from bone marrow-derived macrophages (BMDMs) modulate the insulin sensitivity of adipocytes via miR204.

METHODS

We used both in vitro and in vivo models to study the effects of TSPJ on IR, with a particular emphasis on the exosomes from M2-type BMDMs. Furthermore, we investigated the mechanisms by which exosomal miR204 and its downstream target Elovl6 influence IR in an obese mouse model, as well as in adipocytes with double inhibition of miR204 and Elovl6.

RESULTS

In the animal model, TSPJ significantly increased miR204 expression in BMDMs-derived exosomes and decreased the level of Elovl6 in adipocytes. However, when the C75BL/6 mice had miR204 ablation, TSPJ became less capable of enhancing insulin sensitivity, and the expressions of Irs1, Insr, and Slc2a4 in the adipose tissue decreased. In the cell model where the macrophages carried miR204 ablation and the adipocytes had Elovl6 knockdown, the expressions of IR-related genes increased in the adipocytes.

CONCLUSIONS

TSPJ mitigated IR through adipocyte-BMDM crosstalk mediated by exosomes via the miR204/Elovl6 pathway.

Total saponins from Panax japonicus reduced lipid deposition and inflammation in hepatocyte via PHD2 and hepatic macrophage-derived exosomal miR-463-5p

ETHNOPHARMACOLOGICAL RELEVANCE

Panax japonicus (T. Nees) C.A. Mey. (PJ) is a traditional Chinese herbal medicine revered as the "King of Herbs" in Tujia and Hmong medical practices. Clinically, it is primarily used to treat weakness and fatigue, wound bleeding, arthritis, hyperlipidemia, and fatty liver. It is rich in saponins, and the total saponins from PJ (TSPJ), possess immunomodulatory, antioxidant, and lipid-lowering effects. These properties hold significant potential in managing liver-related metabolic diseases such as non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH).

AIM OF STUDY

Evaluate the therapeutic effects of TSPJ on lipid metabolism disorders in a NASH model and explore the possible underlying mechanisms.

MATERIALS AND METHODS

To model NASH, C57BL/6J mice were fed a high-fat diet (HFD) and RAW264.7 cells were stimulated with lipopolysaccharide (LPS) and palmitic acid (PA). The animal and cell models were also treated with TSPJ, and the changes in inflammation and lipid metabolism were measured. Additional models were created by transfecting lentiviral vectors to cause miR-463-5p knockdown in the C57BL/6J mouse and the RAW264.7 cells.

RESULTS

In the HFD-induced mice, TSPJ reduced the body weight and liver weight, lowered the serum levels of TG, T-CHO, ALT, and AST, and reduced the hepatic lipid droplet formation and vacuolization. In the RAW264.7 cells, TSPJ upregulated the M2 markers and downregulated the M1 markers. TSPJ also significantly increased the expression of miR-463-5p in the exosomes derived from the RAW264.7 cells or the primary mouse hepatic macrophages, and miR-463-5p suppressed the expression of PHD2 in hepatocytes to improve lipid metabolism. However, when the exosome secretion inhibitor GW4869 was applied, TSPJ became less effective in alleviating the lipid deposition and inflammation in hepatocytes.

CONCLUSIONS

TSPJ significantly upregulated the expression of miR-463-5p in the exosomes of hepatic macrophages to thus downregulate PHD2 expression in hepatocytes and improve hepatic lipid metabolism.

Total saponins from Panax japonicus mediate the paracrine interaction between adipocytes and macrophages to promote lipolysis in the adipose tissue during aging via the NLRP3 inflammasome/GDF3/ATGL axis

Adipocytic lipolysis is strongly related to the increase of visceral fat, decrease of exercise capacity, and various other metabolic syndromes during aging. It is significantly influenced by the paracrine relationship between adipocytes and the adipose tissue macrophages (ATMs), and the cytokines secreted by ATMs have endocrine effects on adjacent tissues. We previously reported that the total saponins from Panax japonicus (TSPJs) can enhance lipid metabolism. In this work, we for the first time proved that TSPJs promoted adipocytic lipolysis by preventing NLRP3 activation in ATMs to inhibit the expression of GDF3. The decrease of GDF3 by TSPJs restored the expression of the adipose triglyceride lipase (ATGL) and phosphorylated hormone-sensitive lipase (p-HSL), both of which are known to decrease with aging. Thus, the NLRP3 inflammasome/GDF3/ATGL axis may be a worthy target in developing future clinical solutions for aging-related obesity.

Total saponins from Panax japonicus regulated the intestinal microbiota to alleviate lipid metabolism disorders in aging mice

Total saponins from Panax japonicus (TSPJ) have many beneficial physiological activities, particularly in alleviating the damages of aging and abnormal lipid metabolism. This work used mice models to investigate if TSPJ reduced obesity and regulated metabolic functions via the intestinal microbiota, the disturbance of which has been shown to cause aging-related diseases. The results showed that TSPJ significantly reduced the weight and blood lipid level of aging mice. Further analyses showed that TSPJ significantly inhibited adipogenesis, changed the composition of the intestinal flora, and protected the integrity of the intestinal barrier. It was inferred from the accumulated experimental data that TSPJ helped to combat obesity in aging mice by regulating the intestinal microbiota and promoting microbial metabolism.

Total saponins from Panax japonicus reduce inflammation in adipocytes through the miR155/SOCS1/NFκB signaling pathway

BACKGROUND

The rising incidence of metabolic diseases due to chronic inflammation in the adipose tissue has been attributed to factors such as high fat diet (HFD). Previous studies have demonstrated that the total saponins from Panax japonicus (TSPJ) can reduce HFD-induced adipocyte inflammation, but the underlying mechanism remains unclear. In this work, we explored the molecular mechanism by which TSPJ reduces inflammation response in adipocytes.

METHODS

We first established C57BL/6 mouse and 3T3-L1 adipocyte models. Lentiviruses packaged with the plasmids were injected into mice through the tail vein or into adipocytes to generate the in vivo and in vitro models with miR155 knockdown and overexpression. The mice were fed with HFD to trigger inflammation and administered TSPJ (25 mg/kg∙d and 75 mg/kg∙d) by gavage. The adipocytes were treated with palmitic acid (PA) to trigger inflammation response, then treated with TSPJ (25 μg/ml and 50 μg/ml). Finally, the expression of miR155, inflammatory factors, SOCS1, and NFκB pathway-related proteins was explored.

RESULTS

TSPJ significantly inhibited the expression of inflammation-related genes and the miR155 expression in adipocytes both in vitro and in vivo. The dual luciferase reporter gene assay revealed that miR155 mediated the downregulation of SOCS1. TSPJ significantly inhibited and upregulated the phosphorylation of the NFκB protein and the SOCS1 proteins, respectively.

CONCLUSION

TSPJ inhibits miR155 to upregulate the SOCS1 expression, which subsequently inhibits the NFκB signaling pathway, thereby mitigating the inflammatory response in the adipocytes of HFD mice.