Guava leaf tea has been used as a folk medicine for treating hyperglycemic conditions in Asia and Africa. The hypoglycemic efficacy of guava leaf has been documented by many scientists in these regions, but the hypogl...Guava leaf tea has been used as a folk medicine for treating hyperglycemic conditions in Asia and Africa. The hypoglycemic efficacy of guava leaf has been documented by many scientists in these regions, but the hypoglycemic mechanism is poorly understood. Guava leaves were extracted with methanol and the crude extract was partitioned against hexane, ethyl acetate, and butanol in sequence. The leftover in water is defined as the aqueous partition. A second smaller batch was extracted with hot water directly. Oral glucose tolerance test was carried out on healthy mice instead of diabetic mice that lack endogenous insulin. Glucose uptake was examined with 3T3-L1 adipocytes. Oxidative effect on PTP1B （protein tyrosine phosphatase 1b） was carried out with real-time PTP1B enzymatic assay. The aqueous partition of guava leaf extract possesses a potent inhibitory effect on PTP1B enzymatic activity and this PTP1B inhibition is through a slow oxidative but reversible inactivation on the enzyme. The reversible inactivation would suggest guava leaf extract may augment PTP1B inhibition alongside the endogenous H2O2 which itself is induced by insulin. In addition, our study confirmed the hypoglycemic efficacy being associated with guava leaf and found the most effective molecules reside in the aqueous partition which is also less cytotoxic to Chinese hamster ovary cells when compared to other less polar partitions. The guava leaf extract can modulate insulin activity through a redox regulation on PP1B enzymatic activity. It is speculated that a compound similar to gallocatechin in the aqueous partition can reduce an oxygen molecule to hydrogen peroxide which in turn oxidizes the catalytic residue Cys in PTP1B. Therefore, the guava leaf tea can serve as a functional hypoglycemic drink that is suitable for either healthy or diabetic subjects.展开更多
Objective： Recently, a high frequency of mutations in mitochondrial DNA （mtDNA） has been detected in ovarian cancer. To explore the alterations of proteins in mitochondria in ovarian cancer, a pair of human ovarian...Objective： Recently, a high frequency of mutations in mitochondrial DNA （mtDNA） has been detected in ovarian cancer. To explore the alterations of proteins in mitochondria in ovarian cancer, a pair of human ovarian carcinoma cell lines （SKOV3/SKOV3.ip1） with different metastatic potentials was examined. Methods： Cancer cells SKOV3.ipl were derived from the ascitic tumor cells of nude mice bearing a tumor of ovarian cancer cells SKOV3. SKOV3.ipl exhibited a higher degree of migration potential than its paired cell line SKOV3. The proteins in the mi- tochondria of these two cells were isolated and separated by 2-D gel electrophoresis. The differently expressed proteins were extracted and identified using matrix assisted laser desorption ionisation/time-of-flight/time-of-flight （MALDITOF/TOF）, and finally a selected protein candidate was further investigated by immunohistochemistry （IHC） method in nude mice bearing tumor tissues of these two cells. Results： A total of 35 spots with different expressions were identified between the two cells using 2D-polyacrylamide gel electrophoresis （PAGE） approach. Among them, 17 spots were detected only in either SKOV3 or SKOV3.ipl cells. Eighteen spots expressed different levels, with as much as a three-fold difference between the two cells. Twenty spots were analyzed using MALDI-TOF/TOF, and 11 of them were identified successfully; four were known to be located in mitochondria, including superoxide dismutase 2 （SOD2）, fumarate hydratase （FH）, mitochondrial ribosomal protein L38 （MRPL38）, and mRNA turnover 4 homolog （MRTO4）. An increased staining of SOD2 was observed in SKOV3.ipl over that of SKOV3 in IHC analysis. Conclusions： Our results indicate that the enhanced antioxidation and metabolic potentials of ovarian cancer cells might contribute to their aggressive and metastatic behaviors. The underlying mechanism warrants further study.展开更多
文摘Guava leaf tea has been used as a folk medicine for treating hyperglycemic conditions in Asia and Africa. The hypoglycemic efficacy of guava leaf has been documented by many scientists in these regions, but the hypoglycemic mechanism is poorly understood. Guava leaves were extracted with methanol and the crude extract was partitioned against hexane, ethyl acetate, and butanol in sequence. The leftover in water is defined as the aqueous partition. A second smaller batch was extracted with hot water directly. Oral glucose tolerance test was carried out on healthy mice instead of diabetic mice that lack endogenous insulin. Glucose uptake was examined with 3T3-L1 adipocytes. Oxidative effect on PTP1B （protein tyrosine phosphatase 1b） was carried out with real-time PTP1B enzymatic assay. The aqueous partition of guava leaf extract possesses a potent inhibitory effect on PTP1B enzymatic activity and this PTP1B inhibition is through a slow oxidative but reversible inactivation on the enzyme. The reversible inactivation would suggest guava leaf extract may augment PTP1B inhibition alongside the endogenous H2O2 which itself is induced by insulin. In addition, our study confirmed the hypoglycemic efficacy being associated with guava leaf and found the most effective molecules reside in the aqueous partition which is also less cytotoxic to Chinese hamster ovary cells when compared to other less polar partitions. The guava leaf extract can modulate insulin activity through a redox regulation on PP1B enzymatic activity. It is speculated that a compound similar to gallocatechin in the aqueous partition can reduce an oxygen molecule to hydrogen peroxide which in turn oxidizes the catalytic residue Cys in PTP1B. Therefore, the guava leaf tea can serve as a functional hypoglycemic drink that is suitable for either healthy or diabetic subjects.
文摘Objective： Recently, a high frequency of mutations in mitochondrial DNA （mtDNA） has been detected in ovarian cancer. To explore the alterations of proteins in mitochondria in ovarian cancer, a pair of human ovarian carcinoma cell lines （SKOV3/SKOV3.ip1） with different metastatic potentials was examined. Methods： Cancer cells SKOV3.ipl were derived from the ascitic tumor cells of nude mice bearing a tumor of ovarian cancer cells SKOV3. SKOV3.ipl exhibited a higher degree of migration potential than its paired cell line SKOV3. The proteins in the mi- tochondria of these two cells were isolated and separated by 2-D gel electrophoresis. The differently expressed proteins were extracted and identified using matrix assisted laser desorption ionisation/time-of-flight/time-of-flight （MALDITOF/TOF）, and finally a selected protein candidate was further investigated by immunohistochemistry （IHC） method in nude mice bearing tumor tissues of these two cells. Results： A total of 35 spots with different expressions were identified between the two cells using 2D-polyacrylamide gel electrophoresis （PAGE） approach. Among them, 17 spots were detected only in either SKOV3 or SKOV3.ipl cells. Eighteen spots expressed different levels, with as much as a three-fold difference between the two cells. Twenty spots were analyzed using MALDI-TOF/TOF, and 11 of them were identified successfully; four were known to be located in mitochondria, including superoxide dismutase 2 （SOD2）, fumarate hydratase （FH）, mitochondrial ribosomal protein L38 （MRPL38）, and mRNA turnover 4 homolog （MRTO4）. An increased staining of SOD2 was observed in SKOV3.ipl over that of SKOV3 in IHC analysis. Conclusions： Our results indicate that the enhanced antioxidation and metabolic potentials of ovarian cancer cells might contribute to their aggressive and metastatic behaviors. The underlying mechanism warrants further study.
