Diabetes is one of the most concerned metabolic diseases worldwide and threaten public health. In the present work, two polysaccharide-rich extracts from Apocynum venetum leaves were extracted using distilled water and alkaline solution (0.05 M NaOH), and fully characterized. Hypoglycemic and hypolipidemic effects of two polysaccharide-rich extracts on high-fat diet and streptozocin-induced type 2 diabetic mice were investigated. Treatment of alkaline extracted polysaccharide-rich products significantly decreased the levels of fasting blood glucose, serum insulin, glycated serum protein, as well as serum lipids profiles including total cholesterol, triacylglycerols, low-density lipoprotein cholesterol, and nonesterified fatty acid. Meanwhile, the reduced glycogen contents in liver were prominently improved, and the oxidative damage were markedly ameliorated by alkaline extracted polysaccharide products in diabetic mice. Furthermore, both polysaccharide-rich extracts could reverse the gut microbiota dysbiosis in diabetic mice by increasing the abundance of genera Odoribacter, Anaeroplasma, Parasutterella, and Muribaculum; while by decreasing the abundance of genera Enterococcus, Klebsiella, and Aerococcus. This study provides new sights for exploitation of Apocynum venetum extracts as a promising anti-diabetic nutraceutical for the treatment of type 2 diabetes and metabolic syndrome.

Salinity is an important but little-studied abiotic stressor affecting plant growth. Although several previous reports have examined salt-tolerant plant microbial communities, we still lack a comprehensive understanding about the functional characteristics and genomic information of this population.

Pectins are synthesized and methyl-esterified in the Golgi apparatus and then demethylesterified by pectin methylesterases (PMEs) located in the cell wall. The degree of methylesterification affects the functional properties of pectin, and thereby influences plant growth and development, as well as defense responses. However, little is known about the mechanisms that regulate pectin demethylesterification. Here, we show that in seed coat mucilage the absence of the MYB52 transcription factor is correlated with an increase in PME activity and a decrease in the degree of pectin methylesterification. Decreased methylesterification in myb52 mutant is also correlated with an increase in the calcium content of the seed mucilage. Chromatin immunoprecipitation analysis and molecular genetic studies suggest that MYB52 transcriptionally activates PECTIN METHYLESTERASE INHIBITOR 6 (PMEI6), PMEI14 and SUBTILISIN-LIKE SERINE PROTEASE 1.7 (SBT1.7) by binding to their promoters. PMEI6 and SBT1.7 have previously been shown to be involved in seed coat mucilage demethylesterification. Our characterization of two PMEI14 mutants suggests that PMEI14 has a role in seed coat mucilage demethylesterification, although its activity may be confined to the seed coat in contrast to PMEI6, which functions in the whole seed. Our demonstration that MYB52 negatively regulates pectin demethylesterification in seed coat mucilage and the identification of components of the molecular network involved provides new insight into the regulatory mechanism controlling pectin demethylesterification and increases our understanding of the transcriptional regulation network involved in seed coat mucilage formation.