Alleviating effects and mechanisms of action of large-leaf yellow tea drinking on diabetes and diabetic nephropathy in mice

Our previous study found that large-leaf yellow tea(LYT)had interesting hypoglycemic activity in high-fat diet-induced obese mice and highly safety in healthy mice. To study the anti-diabetic potential of LYT, the present study further investigated the preventive effects and mechanisms of action of LYT administration on diabetes and diabetic nephropathy in high-fat diet plus streptozotocin-induced diabetic mice. Results showed that LYT infusions(1/100 and 1/50, m/V)as drinking fluid for 4 weeks reduced diabetic polydipsia and polyuria, enhanced glucose tolerance and insulin sensitivity, and lowered fasting blood glucose level. The underlying mechanisms involve downregulation of gluconeogenesis(lower protein levels of TXNIP and FBP and enzyme activity of FBP), upregulation of lipid catabolism(higher protein levels of CPT-1α and PPARα), downregulation of lipogenesis(lower protein level of SREBP-1), and modification of the structure and abundance of gut microbiota to modulate metabolic homeostasis. Moreover, LYT administration prevented diabetic nephropathy, possibly due to reduced glucose-caused osmotic diuresis and lowered levels of renal PKC-β2, NLRP3 as well as membrane PKC-α, AQP2 and glycosylated AQP2 proteins. Taken together, LYT exhibits the activities in alleviating diabetic symptoms, ameliorating glucose and lipid dysmetabolism and fatty liver, and preventing diabetic nephropathy in diabetic mice. These activities may be explored for the prevention and treatment of diabetes in humans.

Analysis on Antibacterial, Detumescent and Antioxidant Activity of Huoshan Large-leaf Yellow Tea

[Objectives] To provide experimental basis for the effective development and utilization of Huoshan large-leaf yellow tea resources and the screening of safe and effective active ingredients of large-leaf yellow tea. [Methods] The active substances of Huoshan large-leaf yellow tea were extracted by hot-water extraction, and the freeze-dried powder of Huoshan large-leaf yellow tea was obtained by freeze drying. The antibacterial activity of the extract was preliminarily confirmed using the Oxford cup method, and its antimicrobial spectrum was analyzed using 14 strains. A xylene-induced mouse auricle swelling test was carried out to detect the swelling inhibition rate of the extract and analyze its in-vitro detumescent activity. Then, the antioxidant activity of the extract was identified through a DPPH free radical scavenging capacity test and a ferric reducing antioxidant power assay. [Results] The extract had significant inhibitory effects on various bacteria. The extract could effectively inhibit the growth of Escherichia coli, Staphylococcus aureus, Enterococcus hirae, Acinetobacter baumannii, Klebsiella pneumonia, Pseudomonas aeruginosa, Bacillus subtilis , and other strains. The diameter of the inhibition zone increased with the increase of sample concentration. The extract had a significant inhibitory effect on auricle swelling induced by xylene in mice. When the concentration of the drug reached 1.0 mg/mL, its inhibition rate on mouse auricle swelling reached 55.2% ( P <0.01), slightly lower than the swelling inhibition rate of the aspirin group (66.52%, P <0.01). The results of the antioxidant test showed that large-leaf yellow tea extract also had strong activity. Within the concentration range of 0.1-1.0 mg/mL, its DPPH radical scavenging rate increased with the increase of sample concentration. Within the concentration range of 0.1-1.0 mg/mL, its DPPH radical scavenging rate increased with the increase of sample concentration. When the concentration reached 1.0 mg/mL, the scavenging rate reached 69.75%. The Fe 3+ -reduction capacity of the extract also increased with the increase of sample concentration within the concentration range of 0.1-2.5 mg/mL. When the concentration was 2.5 mg/mL, the reducing power of the extract reached 1.43±0.04. However, its DPPH free radical scavenging rate and reducing power were slightly lower than the capacity of V C at the same concentration. [Conclusions] The extract of Huoshan large-leaf yellow tea obtained by hot-water extraction had strong activity in many aspects, including inhibiting the growth of various microbes, subsiding swelling in vitro and resisting oxidation. These experimental results provide certain guiding significance for the basic research of Huoshan large-leaf yellow tea extract, as well as experimental data support for the subsequent development of functional foods and drugs of Huoshan large-leaf yellow tea.