Type

Journal Article

Authors

P Newsholme
P R Flatt
N H McClenaghan
J P G Malthouse
C Hewage
M Corless
L Brennan

Subjects

Biochemistry

Topics
drug effects magnetic resonance spectroscopy glutamic acid models biological pharmacology gamma glutamylcyclotransferase glucose glutamine clone cells aspartic acid animals metabolism islets of langerhans carbon isotopes

13C NMR analysis reveals a link between L-glutamine metabolism, D-glucose metabolism and gamma-glutamyl cycle activity in a clonal pancreatic beta-cell line. (2003)

Abstract Pancreatic islet cells and clonal beta-cell lines can metabolise L-glutamine at high rates. The pathway of L-glutamine metabolism has traditionally been described as L-glutamine-->L-glutamate-->2-oxoglutarate-->oxidation in TCA cycle following conversion to pyruvate. Controversially, the metabolism of D-glucose to L-glutamate in beta cells is not widely accepted. However, L-glutamate has been proposed to be a stimulation-secretion coupling factor in glucose-induced insulin secretion. We aimed to investigate the metabolism of glutamine and glucose by using (13)C NMR analysis. BRIN-BD11 cells were incubated in the presence of 16.7 mmol/l [1-(13)C]glucose, 2 mmol/l [2-(13)C]L-glycine or 2 mmol/l [1,2-(13)C]glutamine in the presence or absence of other amino acids or inhibitors. After an incubation period the cellular metabolites were extracted using a PCA extract procedure. After neutralisation, the extracts were prepared for analysis using (13)C-NMR spectroscopy. Using (13)C NMR analysis we have shown that L-glutamine could be metabolised in BRIN-BD11 cells via reactions constituting part of the gamma-glutamyl cycle producing glutathione. Moderate or high activities of the enzymes required for these pathways of metabolism including glutaminase, gamma-glutamyltransferase and gamma-glutamylcysteine synthetase were observed. We additionally report significant D-glucose metabolism to L-glutamate. Addition of the aminotransferase inhibitor, aminooxyacetate, attenuated L-glutamate production from D-glucose. We propose that L-glutamine metabolism is important in the beta cell for generation of stimulus-secretion coupling factors, precursors of glutathione synthesis and for supplying carbon for oxidation in the TCA cycle. D-glucose, under appropriate conditions, can be converted to L-glutamate via an aminotransferase catalysed step.
Collections Ireland -> University College Dublin -> PubMed

Full list of authors on original publication

P Newsholme, P R Flatt, N H McClenaghan, J P G Malthouse, C Hewage, M Corless, L Brennan

Experts in our system

1
Philip Newsholme
University College Dublin
Total Publications: 51
 
2
J.Paul G. Malthouse
University College Dublin
Total Publications: 71
 
3
Lorraine Brennan
University College Dublin
Total Publications: 166