In silico and in vitro screening of marrubiin and marrubiin derivatives for antidiabetic activity on PTP1ß, C2C12 myocytes, chang liver hepatocytes and 3T3-L1 adipocytes
- Authors: Nicholas, Rudi Berto
- Date: 2013
- Subjects: Hypoglycemic agents , Diabetes -- Treatment -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10347 , http://hdl.handle.net/10948/d1020638
- Description: Diabetes mellitus (DM) is a life changing disease which affects a large portion of the population and the economy through high medical costs and loss of productivity. Marrubiin (MAR), a diterpenoid isolated from Leonotis leonurus, a plant indigenous to Southern Africa, is used by traditional healers to alleviate DM symptoms. This study aims to screen the inhibitory potential of MAR and MAR derivatives on PTP1β and glucose uptake properties of Chang liver, C2C12 and 3T3-L1 cells. Marrubiin and 19 of its derivatives were tested to determine the inhibition constants for PTP1β. A Ki of 21 μM and 0.047 μM was detected for oleanolic acid in silico and in vitro, respectively. All other diterpene derivatives did not display substantial levels of inhibition of PTP1β. Treatment of Chang liver cells with the various MAR derivatives (10 μM) did not significantly increase glucose uptake beyond metformin, a known antidiabetic drug. The various treatments showed a protective/proliferative effect on the C2C12 muscle cells with two MAR treatments (DC16 and DC18) significantly increasing glucose uptake as compared to metformin in C2C12 muscle cells. It was noted that DC17, DC18 and MAR significantly increased glucose uptake in 3T3-L1 adipocytes, relative to the control. Contrary to cytotoxicity studies with Chang liver and C2C12 muscle cells, adipocytes displayed no cytotoxicity to treatments while a significant increase in cell viability was seen for DC9 and DC15. To unravel the mechanism of action, Western blotting analysis was completed and an increased expression of PTP1β was observed for treatments with DC17 and DC6 was seen in adipocytes, while DC18 and metformin decreased expression significantly. This correlated with a significant decrease of Ser 612 phosphorylation of insulin receptor substrate (IRS1) for DC17. Real time qPCR of IRS1 and GLUT4 highlighted that DC17 and MAR were able to significantly increase expression of IRS1 and GLUT4, respectively. The results show that MAR and the selected derivatives (DC6, DC17, DC18) have been found to increase glucose uptake in peripheral tissue types with IRS1, GLUT4 and PTP1β being associated with the mechanism of action. However, a complete understanding of the mechanisms is yet to be established.
- Full Text:
- Date Issued: 2013
- Authors: Nicholas, Rudi Berto
- Date: 2013
- Subjects: Hypoglycemic agents , Diabetes -- Treatment -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10347 , http://hdl.handle.net/10948/d1020638
- Description: Diabetes mellitus (DM) is a life changing disease which affects a large portion of the population and the economy through high medical costs and loss of productivity. Marrubiin (MAR), a diterpenoid isolated from Leonotis leonurus, a plant indigenous to Southern Africa, is used by traditional healers to alleviate DM symptoms. This study aims to screen the inhibitory potential of MAR and MAR derivatives on PTP1β and glucose uptake properties of Chang liver, C2C12 and 3T3-L1 cells. Marrubiin and 19 of its derivatives were tested to determine the inhibition constants for PTP1β. A Ki of 21 μM and 0.047 μM was detected for oleanolic acid in silico and in vitro, respectively. All other diterpene derivatives did not display substantial levels of inhibition of PTP1β. Treatment of Chang liver cells with the various MAR derivatives (10 μM) did not significantly increase glucose uptake beyond metformin, a known antidiabetic drug. The various treatments showed a protective/proliferative effect on the C2C12 muscle cells with two MAR treatments (DC16 and DC18) significantly increasing glucose uptake as compared to metformin in C2C12 muscle cells. It was noted that DC17, DC18 and MAR significantly increased glucose uptake in 3T3-L1 adipocytes, relative to the control. Contrary to cytotoxicity studies with Chang liver and C2C12 muscle cells, adipocytes displayed no cytotoxicity to treatments while a significant increase in cell viability was seen for DC9 and DC15. To unravel the mechanism of action, Western blotting analysis was completed and an increased expression of PTP1β was observed for treatments with DC17 and DC6 was seen in adipocytes, while DC18 and metformin decreased expression significantly. This correlated with a significant decrease of Ser 612 phosphorylation of insulin receptor substrate (IRS1) for DC17. Real time qPCR of IRS1 and GLUT4 highlighted that DC17 and MAR were able to significantly increase expression of IRS1 and GLUT4, respectively. The results show that MAR and the selected derivatives (DC6, DC17, DC18) have been found to increase glucose uptake in peripheral tissue types with IRS1, GLUT4 and PTP1β being associated with the mechanism of action. However, a complete understanding of the mechanisms is yet to be established.
- Full Text:
- Date Issued: 2013
Factors influencing expatriates' ability to cross-culturally adjust
- Authors: Hesse, Anjuli
- Date: 2011
- Subjects: Aliens -- Psychological aspects , Adjustment (Psychology)
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9424 , http://hdl.handle.net/10948/1589 , Aliens -- Psychological aspects , Adjustment (Psychology)
- Description: Globalisation has led to an increasing growth of world trade which has directed business all over the world to become increasingly international and increased the number and power of multinational companies. These expatriates are confronted with societal norms different from their home cultures. This study investigated which factors influence cross-cultural adjustment the most and which factors are perceived by the expatriates to influence cross-cultural adjustment. Based on the literature review four different categories of factors influencing cross-cultural adjustment were identified (Individual, organisational, work-related and non-work related factors) A self-administered online questionnaire, based on existing questionnaires (Black’s (1988) cross-cultural adjustment questionnaire) and literature research, was developed in order to detect a relationship between factors and one of the three adjustment types (general, interaction and work) and to reveal the perceived importance of the factors. In this study all identified factors were perceived to be important for cross-cultural adjustment. However, language skills and spousal adjustment were perceived to be the most important factors and had indeed the strongest correlation towards cross-cultural adjustment. Based on the findings of this research project, recommendations for organisations and expatriates have been provided.
- Full Text:
- Date Issued: 2011
- Authors: Hesse, Anjuli
- Date: 2011
- Subjects: Aliens -- Psychological aspects , Adjustment (Psychology)
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9424 , http://hdl.handle.net/10948/1589 , Aliens -- Psychological aspects , Adjustment (Psychology)
- Description: Globalisation has led to an increasing growth of world trade which has directed business all over the world to become increasingly international and increased the number and power of multinational companies. These expatriates are confronted with societal norms different from their home cultures. This study investigated which factors influence cross-cultural adjustment the most and which factors are perceived by the expatriates to influence cross-cultural adjustment. Based on the literature review four different categories of factors influencing cross-cultural adjustment were identified (Individual, organisational, work-related and non-work related factors) A self-administered online questionnaire, based on existing questionnaires (Black’s (1988) cross-cultural adjustment questionnaire) and literature research, was developed in order to detect a relationship between factors and one of the three adjustment types (general, interaction and work) and to reveal the perceived importance of the factors. In this study all identified factors were perceived to be important for cross-cultural adjustment. However, language skills and spousal adjustment were perceived to be the most important factors and had indeed the strongest correlation towards cross-cultural adjustment. Based on the findings of this research project, recommendations for organisations and expatriates have been provided.
- Full Text:
- Date Issued: 2011
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