The beneficial effects of Polygonatum sibiricum Red. superfine powder on metabolic hypertensive rats via gut-derived LPS/TLR4 pathway inhibition.

BACKGROUND

Metabolic hypertension (MH) is characterized by elevated blood pressure accompanied by metabolic abnormalities, with the gut-derived lipopolysaccharide/toll like receptor 4 (LPS/TLR4) pathway an important triggering mechanism. The conventional Chinese plant Polygonatum sibiricum Red. is traditionally used as a medicinal and edible food source. Currently, several studies have examined its anti-obesity and anti-diabetic actions, with potential roles for MH treatment; however, specific P. sibiricum Red. roles in MH and associated mechanisms remain unclear.

OBJECTIVES

Our purpose was to identify the effects and mechanisms of P. sibiricum Red. superfine powder (PSP) in a MH rat model triggered by high sugar and high fat compounds in an excessive alcohol diet (ACHSFDs).

METHODS

A MH rat model was induced by ACHSFDs, and PSP was administered daily at 0.5 and 1.0 g/kg doses, respectively. Firstly, the effects of PSP on MH were assessed using blood pressure, serum lipid, and lipid deposition assays in the liver. Changes in intestinal flora were detected by high-throughput 16S rRNA sequencing, while metabolite short-chain fatty acids (SCFAs) and LPS levels were quantified by gas chromatography (GC) and enzyme-linked immunosorbent assay (ELISA), respectively. Hematoxylin & eosin (H&E) staining and transmission electron microscopy (TEM) were performed to evaluate histopathological changes in the rat colon. d-lactic acid (d-LA) levels and tight junction proteins (TJPs) expression were also measured to assess intestinal barrier function. Also, aortic endothelial microstructures, serum endothelin 1 (ET-1), and nitric oxide (NO) levels were investigated to determine vascular endothelial function. Finally, the TLR4/MyD88 signaling pathway in the aorta and gut was evaluated by western blotting, immunohistochemistry (IHC), and quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

Blood pressure and blood lipid metabolism disorders induced by ACHSFDs in MH rats were improved by PSP administration. Intestinal flora analyses revealed decreased SCFAs and LPS levels following PSP administration, which was accompanied by increased Streptococcus species levels and decreased Desulfobacter and Desulfovibrio species levels. PSP increased SCFAs levels, and the expression of SCFAs receptors GPCR41 and GPCR43 in the colon. Meanwhile, the expression of tight junction proteins (TJPs) such as Claudin-1, occludin were upregulated in the ileum and colon, while TLR4 and MyD88 were downregulated, thereby strengthening intestinal barrier integrity and reducing serum LPS levels. Additionally, PSP treatment improved vascular endothelial function by inhibiting the TLR4/MyD88 pathway in vessels, improving vascular endothelial cell shedding, and regulating the NO and ET-1 balance.

CONCLUSIONS

We demonstrated the beneficial effects and potential mechanisms of PSP in our MH rat model. Based on gut microbiota structure modulation and intestinal barrier improvements, PSP inhibited LPS-induced vascular TLR4/MyD88 signaling activation to improve vascular endothelial function, which in turn reduced blood pressure. Our study provides valuable insights on PSP therapy for MH.