Chongye Fang

Caffeine is responsible for the bloodglucose-lowering effects of green tea and Puer tea extractsin BALB/c mice.

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.

Pu-Erh Tea Extract Induces the Degradation of FET Family Proteins Involved in the Pathogenesis of Amyotrophic Lateral Sclerosis

FET family proteins consist of fused in sarcoma/translocated in liposarcoma (FUS/TLS), Ewings sarcoma (EWS), and TATA-binding protein-associated factor 15 (TAF15). Mutations in the copper/zinc superoxide dismutase (SOD1), TAR DNA-binding protein 43 (TDP-43), and FET family proteins are associated with the development of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease. There is currently no cure for this disease and few effective treatments are available. Epidemiological studies indicate that the consumption of tea is associated with a reduced risk of developing neurodegenerative diseases. The results of this study revealed that components of a pu-erh tea extract (PTE) interacted with FET family proteins but not with TDP-43 or SOD1. PTE induced the degradation of FET family proteins but had no effects on TDP-43 or SOD1. The most frequently occurring ALS-linked FUS/TLS mutant protein, R521C FUS/TLS, was also degraded in the presence of PTE. Furthermore, ammonium chloride, a lysosome inhibitor, but not lactacystin, a proteasome inhibitor, reduced the degradation of FUS/TLS protein by PTE. PTE significantly reduced the incorporation of R521C FUS/TLS into stress granules under stress conditions. These findings suggest that PTE may have beneficial health effects, including preventing the onset of FET family protein-associated neurodegenerative diseases and delaying the progression of ALS by inhibiting the cytoplasmic aggregation of FET family proteins.

Pu-erh Tea Water Extract Mediates Cell Cycle Arrest and Apoptosis in MDA-MB-231 Human Breast Cancer Cells

Pu-erh tea is believed to have health benefits, the growth inhibition activity of Pu-erh tea on breast cancer cell has not been investigated. In this study, we examined the activity of Pu-erh tea water extract on apoptosis and cell cycle arrest in the human breast adenocarcinoma cell line MDA-MB-231 and clarified its underlying mechanism of action. We found that Pu-erh tea extract inhibited cell proliferation and induced apoptosis in a dose-dependent manner. We also found that Pu-erh tea extract inhibited tumor cell growth within 24 h via accumulation of cells in S phase. Further experiments showed that at 24 h, Pu-erh tea extract up-regulated the expressions of P-p53 (Ser15), p21 and P-JNK and down-regulated the expressions of PCNA, CyclinD1 and CyclinE at the protein level in MDA-MB-231 cells. In particular, the JNK-specific inhibitor SP600125 restored the induction of P-JNK, P-p53 (Ser15), p21, CyclinD1 and CyclinE by Pu-erh tea extract. Our results indicate that Pu-erh tea water extract inhibits cell proliferation of MDA-MB-231 cells through the induction of apoptosis and the stimulation of cell cycle arrest, which is mediated via activation of the JNK-related pathway.

Epigallocatechin Gallate Targets Notch to Attenuate the Inflammatory Response in the Immediate Early Stage in Human Macrophages

Inflammation plays important roles at different stages of diabetes mellitus, tumorigenesis, and cardiovascular diseases. (−)-Epigallocatechin gallate (EGCG) can attenuate inflammatory responses effectively. However, the immediate early mechanism of EGCG in inflammation remains unclear. Here, we showed that EGCG attenuated the inflammatory response in the immediate early stage of EGCG treatment by shutting off Notch signaling and that the effect did not involve the 67-kDa laminin receptor, the common receptor for EGCG. EGCG eliminated mature Notch from the cell membrane and the nuclear Notch intercellular domain, the active form of Notch, within 2 min by rapid degradation via the proteasome pathway. Transcription of the Notch target gene was downregulated simultaneously. Knockdown of Notch 1/2 expression by RNA interference impaired the downregulation of the inflammatory response elicited by EGCG. Further study showed that EGCG inhibited lipopolysaccharide-induced inflammation and turned off Notch signaling in human primary macrophages. Taken together, our results show that EGCG targets Notch to regulate the inflammatory response in the immediate early stage.

Caffeine Promotes Conversion of Palmitic Acid to Palmitoleic Acid by Inducing Expression of fat-5 in Caenorhabditis elegans and scd1 in Mice

The synthesis and metabolism of fatty acids in an organism is related to many biological processes and is involved in several diseases. The effects of caffeine on fatty acid synthesis and fat storage in Caenorhabditis elegans and mice were studied. After 6 h of food deprivation, adult C. elegans were treated with 0.1 mg/mL caffeine for 24 h. Quantitative reverse-transcription polymerase chain reaction showed that, among all the genes involved in fat accumulation, the mRNA expression of fat-5 in caffeine-treated C. elegans was significantly higher than that of controls, whereas fat-6 and fat-7 displayed no significant difference. Gas chromatography-mass spectrometry was used to verify the fatty acid composition of C. elegans. Results showed that the ratio of palmitoleic acid (16:1) to that of palmitic acid (16:0) was higher in the caffeine-treated group. Several mutant strains, including those involved in the insulin-like growth factor-1, dopamine, and serotonin pathways, and nuclear hormone receptors (nhrs), were used to assess their necessity to the effects of caffeine. We found that mdt-15 was essential for the effects of caffeine, which was independent of nhr-49 and nhr-80. Caffeine may increase fat-5 expression by acting on mdt-15. In high fat diet (HFD), but not in normal diet (ND) mice, caffeine induced expression of scd1 in both subcutaneous and epididymal white adipose tissue, which was consistent with the palmitoleic/palmitic ratio results by gas chromatograph analysis. In mature adipocytes, caffeine treatment induced both mRNA and protein expression of scd1 and pgc-1α. Overall, our results provided a possible mechanism on how caffeine modulates metabolism homeostasis in vivo.

Low Concentrations of Caffeine and Its Analogs Extend the Lifespan of Caenorhabditis elegans by Modulating IGF-1-Like Pathway

Caffeine has been reported to delay aging and protect aging-associated disorders in Caenorhabditis elegans. However, the effects of low concentration of caffeine and its analogs on lifespan are currently missing. Herein, we report that at much lower concentrations (as low as 10 μg/ml), caffeine extended the lifespan of C. elegans without affecting food intake and reproduction. The effect of caffeine was dependent on IGF-1-like pathway, although the insulin receptor homolog, daf-2 allele, e1371, was dispensable. Four caffeine analogs, 1-methylxanthine, 7-methylxanthine, 1,3-dimethylxanthine, and 1,7-dimethylxanthine, also extended lifespan, whereas 3-methylxanthine and 3,7-dimethylxanthine did not exhibit lifespan-extending activity.