Increased Perinatal Remodelling of the Pancreas in Somatostatin-Deficient Mice: Potential Role of Transforming Growth Factor-Beta Signalling in Regulating Beta Cell Growth in Early Life

C. C. Richardson; K. To; V. L. Foot; A. C. Hauge-Evans; D. Carmignac; M. R. Christie

doi:10.1055/s-0034-1390427

Hormone and Metabolic Research, Table of Contents

Horm Metab Res 2015; 47(01): 56-63
DOI: 10.1055/s-0034-1390427

Endocrine Research

Increased Perinatal Remodelling of the Pancreas in Somatostatin-Deficient Mice: Potential Role of Transforming Growth Factor-Beta Signalling in Regulating Beta Cell Growth in Early Life

C. C. Richardson

¹Division of Diabetes and Nutritional Sciences, King’s College London, London, UK

,

K. To

¹Division of Diabetes and Nutritional Sciences, King’s College London, London, UK

,

V. L. Foot

¹Division of Diabetes and Nutritional Sciences, King’s College London, London, UK

,

A. C. Hauge-Evans

¹Division of Diabetes and Nutritional Sciences, King’s College London, London, UK

,

D. Carmignac

²Division of Molecular Neuroendocrinology, National Institute for Medical Research, The Ridgeway, Mill Hill, London, UK

,

M. R. Christie

¹Division of Diabetes and Nutritional Sciences, King’s College London, London, UK

› Author Affiliations

Abstract

Early postnatal life is a critical period for development of the endocrine pancreas, involving remodelling of islet cells and maturation of secretory responses. Factors that regulate these processes are undefined. Somatostatin-secreting delta-cells are abundant in the developing pancreas and, because somatostatin inhibits growth, the hormone may regulate islet expansion in early life. The aim of this study was to investigate effects of somatostatin-deficiency on proliferation, apoptosis and pancreas expansion in the first 3 weeks of life in mice. Pancreases from control or somatostatin-knockout mice were analysed for beta cell, alpha cell and pancreatic volumes by morphometry, proliferation by BrdU incorporation and apoptosis by TUNEL labelling. Signalling pathways associated with proliferation and apoptosis were studied by immunohistochemistry and Western blotting. Knockout mice grew normally in the first 3 weeks of life, but had high circulating insulin that normalised by day 21. Beta cell, alpha cell and pancreatic volumes were decreased in knockout mice, accompanied by reduced proliferation and increased apoptosis in the pancreas. Decreased growth was not due to impaired Akt signalling, as Akt phosphorylation and nuclear cyclin-D2 increased in the knockout pancreas. Levels of TGF-β1, a factor implicated in tissue remodelling, together with SMAD phosphorylation through which TGF-β mediates its effects, were increased in the knockout pancreas. Beta cell expansion was impaired in knockout mice, potentially compensating for increased insulin secretion from islets lacking inhibitory effects of somatostatin, and was associated with increased TGF-β1 levels. TGF-β1 may represent an important regulator of beta cell mass in early life.

Key words

pancreas development - insulin secretion - pancreatic islets - delta cells

Full Text

References

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