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					Project Title: Isolation and characterisation of naturally occurring bioactive
compounds with insulin-releasing or glucose-lowering properties for the treatment of
diabetes.

Supervisors:

Dr Yasser Abdel-Wahab and Prof Peter R Flatt

Contact Details:

E-mail:y.abdel-wahab@ulster.ac.uk; Tel: (0)2870324354

Level:

PhD

Background to the project:

Diabetes mellitus affects 3-5% of the population and imposes increasing costs on the health
budget both directly through treatment and indirectly through complications. Current
antidiabetic therapy relies upon insulin replacement in type 1 and on either sulphonylureas or
biguanides for type 2 diabetes. The latter type is increasing in incidence rapidly in developed
nations causing great concern to the WHO. While drug treatment regimes can ameliorate
diabetes to some degree, they cannot reinstate normal blood glucose homeostasis or prevent
long-term complications such as neuropathy, retinopathy and cardiovascular disease. There is
thus a pressing need to improve diabetes therapy into the next millennium and central to this
is expansion of our drug arsenal to more precisely target effector proteins involved in insulin
secretion and action. Studies in our laboratory have revealed that amphibian skin secretions
are rich source of biologically-active peptides, many of which are structural and functional
analogues of endogenous vertebrate peptide hormones. In addition, a major line of our
research has concerned the screening and evaluation of plant materials with antidiabetic
properties and the pharmaceutical industry is interested in this area for drug discovery since
within these plants lies a hidden wealth of potentially useful natural products for diabetes
control. This research has already identified more than 40 plants from Europe, India or China
with proven ability to stimulate insulin secretion, enhance insulin action or decrease diabetic
hyperglycaemia. This PhD proposal will focus primarily on active compounds derived from
amphibian skin secretion/plant extracts such as Hoplobatrachus rugulosus, Xenopus amieti,
Lithobathes chricahuensis / T. indica and T. cordifolia. Active compounds will be subjected to
extensive in vitro and in vivo assays to fully characterise mechanism of action of these
compounds.


Methods to be used:
The proposed research will provide training in a wide range of techniques including: RP-
HPLC; ESI and MALDI-TOF mass spectrometry; tissue culture; measurement of insulin
secretion, cellular glucose uptake, signalling molecules (intracellular Ca2+ and other second
messenger pathways); peptide iodination, cell morphology; ELISA; RIA; acute and long term
studies in animal of obesity-diabetes. Established collaborations are in place for full structural
characterization and synthesis of isolated agents. This research will generate novel IP, high
quality publications and potential exploitation through pharmaceutical development.

Objectives of the research:

The major objective of the proposed research is to uncover novel antidiabetic agents from
natural sources, including amphibian skin secretions and plants used traditionally for
treatment of diabetes. Mechanisms of action will be delineated together with effectiveness in
countering diabetes in animal models. Previously validated in vitro systems will be exploited
for rapid and large scale screening for insulin-releasing and insulin-like activity. This will
involve bioassay-led chemical fractionation of an established panel of effective antidiabetic
plant materials and an existing library of amphibian skin peptides, leading to isolation and
full structural determination of novel chemical entities for potential treatment of diabetes.

Skills required of applicant:

The applicant should ideally have good practical laboratory, computer and skills and show
enthusiasm and commitment to work diligently on all aspects the research project to
completion under the leadership of his/her supervisors. A background in biomedical sciences,
pharmacology, nutrition or a related subject would be desirable.

References

Ojo OO, Abdel-Wahab YHA, Flatt PR, Mechkarska M and Conlon JM. (2011). Tigerinin-
1R: a potent, non-toxic insulin-releasing peptide isolated from the skinof the Asian frog,
Hoplobatrachus rugulosus. Diabetes, Obesity and Metabolism. 13(12):1114-1122.

Hannan JM, Ali L, Khaleque J, Akhter M, Flatt PR, Abdel-Wahab YH. (2011).
Antihyperglycaemic activity of Asparagus racemosus roots is partly mediated by inhibition of
carbohydrate digestion and absorption, and enhancement of cellular insulin action. Br J Nutr.
8:1-8.

Kasabri V, Flatt PR, Abdel-Wahab YHA (2010) Terminalia bellirica stimulates the secretion
and action of insulin and inhibits starch digestion and protein glycation in vitro. Br J Nutr.
103(2):212-7.

Yasser H.A. Abdel-Wahab, Steven Patterson, Peter R. Flatt, J. Michael Conlon (2010)
Brevinin-2-related peptide and its [D4K] analog stimulate insulin release in vitro and improve
glucose tolerance in mice fed a high fat diet. Hormone and Metabolic Research, 42(9):652-6.

Abdel-Wahab YHA, Power GJ, Ng MT, Flatt PR and Conlon JM (2008a). Insulin-releasing
properties of the frog skin peptide pseudin-2 and its [Lys18]-substituted analogue. Biol Chem
389:143–148.
Abdel-Wahab Y, Power GJ., Flatt PR, Woodhams DC, Rollins-Smith LA and Conlon JM
(2008b). A peptide of the phylloseptin family from the skin of the frog Hylomantis lemur
(Phyllomedusinae) with potent in vitro and in vivo insulin-releasing activity. Peptides, 29
(12):2136-2143.

				
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