title: Caffeine is responsible for the bloodglucose-lowering effects of green tea and Puer tea extractsin BALB/c mice.
abstract: The present study was designed to determine the effects of Puer tea and green tea on blood glucose level. Male BALB/c mice were administered green tea extract (GTE) or Puer tea extract (PTE), either intragastrically or in their drinking water. The major components of these teas are epigallocatechin gallate (EGCG) and caffeine, respectively. Blood glucose measurement results showed that mice fed intragastrically or mice that drank GTE, PTE or caffeine showed significantly lower blood glucose levels compared to the control group. However, EGCG exhibited no influence on the blood glucose levels. When caffeine was eliminated from the GTE and PTE, the effect on the blood glucose levels was abolished, but the effect was recovered when caffeine was re-introduced into the extracts. Evaluation of hematological and biochemical indices at the time of the greatest caffeine-induced decrease in blood glucose levels showed that the effect of caffeine was specific. Microarray analyses were performed in 3T3-L1 preadipocytes and mature adipocytes treated with 0.1 mg · mL(-1) caffeine to identify factors that might be involved in the mechanisms underlying these effects. The results showed that few genes were changed after caffeine treatment in adipocytes, and of them only phospholipid transfer protein (PLTP) may be ralated to blood glucose. In conclusion, this study indicates that caffeine may be the key constituent of tea that decreases blood glucose levels, and it may be used to treat type 2 diabetes.
authors.affiliation: Ministry of Education Key Laboratory of Puer Tea Science at Yunnan Agricultural University, Kunming 650201 China; Yunnan Research Center for Advanced Tea Processing, Kunming 650201 China; Department of Pu-erh Tea and Medical Science, Hyogo College of Medicine, 1-1Mukogawa, Nishinomiya, Hyogo 663-8501, Japan.
authors.forename: Chong-Ye
authors.initials: CY
authors.lastname: Fang
authors.affiliation: Ministry of Education Key Laboratory of Puer Tea Science at Yunnan Agricultural University, Kunming 650201 China; Yunnan Research Center for Advanced Tea Processing, Kunming 650201 China.
authors.forename: Xuan-Jun
authors.initials: XJ
authors.lastname: Wang
authors.affiliation: Ministry of Education Key Laboratory of Puer Tea Science at Yunnan Agricultural University, Kunming 650201 China; Yunnan Research Center for Advanced Tea Processing, Kunming 650201 China.
authors.forename: Ye-Wei
authors.initials: YW
authors.lastname: Huang
authors.affiliation: Yunnan University, Kunming 650091, China. Electronic address: haosm@sina.com.
authors.forename: Shu-Mei
authors.initials: SM
authors.lastname: Hao
authors.affiliation: Ministry of Education Key Laboratory of Puer Tea Science at Yunnan Agricultural University, Kunming 650201 China; Yunnan Research Center for Advanced Tea Processing, Kunming 650201 China. Electronic address: shengj@ynau.edu.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Sheng
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D002110:Caffeine / Q000494:pharmacology*; D028241:Camellia sinensis / Q000737:chemistry*; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D049294:Phospholipid Transfer Proteins / Q000378:metabolism; D010936:Plant Extracts / Q000494:pharmacology*; D013662:Tea
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents; D049294:Phospholipid Transfer Proteins; D010936:Plant Extracts; D013662:Tea; C510091:phospholipid transfer protein, mouse; D002110:Caffeine
keywords: Blood glucose; Caffeine; EGCG; Normal mice; Puer tea extract (PTE); Type 2 diabetes