Introduction Islet dysfunction in type 2 diabetes is bi-hormonal involving both defective insulin secretion and augmented glucagon secretion ( Unger & Orci 1975 ), the latter resulting in chronic elevation of circulating glucagon levels ( Larsson
Linda Ahlkvist, Bilal Omar, Anders Valeur, Keld Fosgerau, and Bo Ahrén
D. PAULINE ALEXANDER, R. ASSAN, H. G. BRITTON, and D. A. NIXON
Whilst it is well known that the foetal pancreas of several species contains insulin there is little information available concerning the presence of glucagon in foetal life. In the work reported in this paper the concentration of glucagon or 'glucagon-like' material was estimated in the maternal and foetal plasma, pancreas, parts of the gastro-intestinal tract and amniotic and allantoic fluids of the sheep.
Pregnant ewes bearing foetuses aged 59–143 days (term 148 days) were anaesthetized by the spinal administration of procaine hydrochloride. The foetus was exposed by Caesarian section during which samples of the amniotic and allantoic fluids were removed. Catheters were inserted into a maternal dorsalis pedis artery and a tributary of an umbilical artery. Heparinized blood samples were removed simultaneously from the mother and foetus within 15 min of inducing spinal anaesthesia. The plasma was separated immediately by centrifugation at 4 °C. Tissue samples from the pancreas and
L van Bloemendaal, J S ten Kulve, S E la Fleur, R G Ijzerman, and M Diamant
), oxyntomodulin (OXM) and glucagon-like peptide 1 (GLP-1), have been identified as players in the regulation of feeding by relaying meal-related information on nutritional status to the brain. Based on more than three decades of experimental evidence from rodent
T. P. Mommsen and T. W. Moon
Salmon glucagon-like peptide (GLP), bovine glucagon (B-glucagon) and anglerfish glucagon (AF-glucagon), all activate glucose production in teleost hepatocytes through gluconeogenesis and glycogenolysis, but notable species differences exist in their respective effectiveness. In trout hepatocytes, gluconeogenesis appears to be the main target of hormone action. In eel cells, sampled in November, glycogenolysis was activated threefold, while gluconeogenesis was increased by 12% only. In March, glycogenolytic activation was 1·7-fold, while gluconeogenesis was increased by about 1·7-fold after exposure to B-glucagon. In brown bullhead cells, increases in glycogenolysis from seven- (GLP) to tenfold (B- and AF-glucagon) were noted, while activation of gluconeogenesis was slight. Fragments of two AF-glucagons (19–29) revealed only insignificant metabolic activity. Treatment of eel cells with B-glucagon led to large (up to 20-fold) increases in intracellular cyclic AMP (cAMP) concentrations, while exposure to GLP was accompanied by a modest (< twofold) increase in cAMP, although metabolic effectiveness (gluconeogenesis and glycogenolysis) was similar for the two treatments. Under identical conditions, brown bullhead cellular cAMP responded poorly. Levels of cAMP peaked within 15 min following hormone application. The results imply that no simple or direct relationship exists between the amount of intracellular cAMP and the metabolic action of the glucagon family of hormones. It can further be concluded that GLPs are important regulators of hepatic metabolism, influencing identical targets as glucagon, while the mechanisms of action seem to differ.
Journal of Endocrinology (1990) 126, 109–118
F Bertuzzi, C Berra, C Socci, A M Davalli, G Pozza, and A E Pontiroli
Hyperglucagonemia is commonly found in insulin-dependent as well as in non-insulin-dependent diabetes mellitus, and is likely to be caused by absolute or relative insulin deficiency. The aim of the present study was to evaluate whether a chronic glucagon exposure (1·0 μm for 4 h) modifies the insulin response to acute stimuli with glucagon (1·0 μm), arginine (10·0 mm) and glucose (16·7 mm), or the glucagon response to arginine and glucose, in human islets. Chronic exposure to glucagon did not affect the insulin response to glucose and arginine, but inhibited its response to glucagon (44·6 ± 9·3 vs 168·6 ± 52·3 pg/islet per 20 min, P<0·05); the latter effect was not observed when exposure to glucagon was discontinuous (2·0 μm glucagon alternated with control medium for 30 min periods). The chronic exposure to glucagon also reduced the glucagon response to arginine (−4·9 ± 5·7 vs 19·9 ± 7·9 pg/islet per 20 min, P<0·05) without affecting the inhibition of glucagon release exerted by glucose. These data indicate that chronic exposure to glucagon desensitizes pancreatic α and β cells in response to selected stimuli.
Journal of Endocrinology (1997) 152, 239–243
Shou-Si Lu, Yun-Li Yu, Hao-Jie Zhu, Xiao-Dong Liu, Li Liu, Yao-Wu Liu, Ping Wang, Lin Xie, and Guang-Ji Wang
play is an important role in the regulation of endocrine pancreatic secretion. The intestinal products of the proglucagon gene, glucagon-like peptide-1 (GLP-1), has been shown to contribute significantly to the overall insulin response to oral glucose
Antonella Amato, Sara Baldassano, Rosa Liotta, Rosa Serio, and Flavia Mulè
Introduction Glucagon-like peptide 1 (GLP1), produced by intestinal enteroendocrine L-cells in response to the ingestion of nutrients ( Schirra et al . 1996 ), is highly insulinotropic and an inhibitor of gastrointestinal motility, effects that
Sara Baldassano, Anna Lisa Bellanca, Rosa Serio, and Flavia Mulè
Introduction Glucagon-like peptide 2 (GLP2) is a 33-amino acid peptide, produced by the processing of the proglucagon gene within the mucosal L-cells of the intestine and specific neurons located in the brainstem. The actions of GLP2 are transduced
Li Wang, Yufeng Zhao, Baosong Gui, Rongguo Fu, Feng Ma, Jun Yu, Ping Qu, Lei Dong, and Chen Chen
insulin resistance, causing an increase in blood glucose level ( Weir & Bonner-Weir 2004 , Prentki & Nolan 2006 , Wajchenberg 2007 ). The islet α-cell also regulates blood glucose level by secreting glucagon, which activates gluconeogenesis to increase
Sara Baldassano, Antonella Amato, Francesco Cappello, Francesca Rappa, and Flavia Mulè
, including the proglucagon-derived peptides, glucagon-like peptide-1 (GLP1), and GLP2, and there is evidence for a link among GLP2, intestinal growth, and increased energy intake ( Xiao et al . 1999 , Shin et al . 2005 , Nelson et al . 2008 ). GLP2 is a