Comparative evaluation for phytochemical composition and regulation of blood glucose, hepatic oxidative stress and insulin resistance in mice and HepG2 models of four typical Chinese dark teas

Abstract

BACKGROUND: Dark tea, comprising one of the six major teas, has many biological activities, which originate from their active substrates, such as polyphenols, polysaccharides, and so on. The hypoglycemic effect is one of its most prominent activities, although less is known about their evaluation and potential role in the hypoglycemic mechanism.RESULTS: In the present study, we separately analyzed the phytochemical composition, glycosidase inhibition and free radical scavenging activities, and hypoglycemic activity in type 2 diabetes mellitus mice, as well as the alleviation of insulin resistance in HepG2 cells of four dark tea aqueous extracts. The results showed that the phytochemical composition of dark tea aqueous extracts was significantly different, and they all had good glycosidase inhibition and free radical scavenging activities, in vivo hypoglycemic activity and alleviation of insulin resistance, and could also activate the phosphatidylinositol 3-kinase-Aktperixisome proliferation-activated receptor cascade signaling pathway to regulate glucose and lipid metabolism, change the key enzyme activities related to glucose metabolism and antioxidant activity, and reduce oxidative stress and inflammatory factor levels. Among them, Liubao brick tea (LBT) and Pu-erh tea (PET) possessed better glycosidase inhibitory activity, in vivo hypoglycemic activity and improved insulin resistance activity, whereas Qingzhuan brick tea and Fuzhuan brick tea had better free radical scavenging activity, which may be explained by their distinct phytochemical compositions, such as tea proteins, polysaccharides, polyphenols, catechins, and tea pigments and some elements.CONCLUSION: Dark tea is a highly attractive candidate for developing antidiabetic food, LBT and PET may be good natural sources of agricultural products with anti-diabetic effects.

Comparative Metagenomics Reveals Microbial Communities and Their Associated Functions in Two Types of Fuzhuan Brick Tea

“…Chlorophyll catabolites are an indispensable part of phytochemicals and human nutrition, as Karg et al (2021) reported that a phylloxanthobilin (a yellow chlorophyll catabolite) possesses antioxidative and anti-inflammatory activities. Citrobacter and unclassified Enterobacteriaceae abundances were also positively correlated with fructose and mannose metabolism, which may be related to the reduction of hyperglycemia by drinking FBT ( p < 0.05) ( Zhu et al, 2021 ); Comamonas abundances were also closely associated with the functions of homologous recombination, pyrimidine metabolism, and quorum sensing. In contrast, Enterobacter abundances were more associated with the metabolism pathways of glycerophospholipid metabolism ( Figure 4C ), which may participate in inhibiting fat accumulation and avoiding fatty liver produced ( Wu et al, 2016 ).…”

Valorization of Polysaccharides From Benincasa hispida: Physicochemical, Moisturizing, and Antioxidant Skincare Properties

“…Also, all cells have defense functions to resist peroxidative damage and protect cells from ROS damage, these members include SOD, CAT, GSH-Px (Shen et al, 2016). SOD can catalyze the disproportionation of superoxide anion into oxygen and hydrogen peroxide, CAT can decompose hydrogen peroxide into water and oxygen, and GSH-Px can convert toxic peroxide into non-toxic peroxide by redox glutathione (Zhu et al, 2021a). In this study, the activities of related antioxidant enzymes including SOD, CAT, and GSH-Px in H 2 O 2 -induced HDF-1 cells or galactose-evoked aging mice were significantly decreased, and the MDA level was greatly increased.…”

Advances in the Utilization of Tea Polysaccharides: Preparation, Physicochemical Properties, and Health Benefits

“…Oxidative stress has been reported to be associated with many diseases, such as cancer, Alzheimer’s disease, nephritis, arteriosclerosis, and diabetes, due to the overproduction of oxygen free radicals [ 4 ]. The liver is a vital detoxification organ in the human body and plays a key role in the metabolism of various endogenous and exogenous harmful substances [ 3 ].…”

“…Tea not only creates a lot of wealth but also generates tea culture and tea ceremony [ 1 ]. As a result, tea has become one of the most popular beverages in the world after water [ 2 , 3 , 4 ].…”

“…Tea’s biological and pharmacological activities are mainly attributed to the diversity of its chemical components. The chemical features of tea mainly include tea polyphenols (TPPs), tea polysaccharides (TPSs), tea proteins, catechins, theanine, and inorganic elements [ 4 ]. Tea polyphenols have long received attention for their excellent antioxidant properties for which accumulating evidence has been presented [ 7 ].…”