Alpha-, Delta- and PP-cells: Are They the Architectural Cornerstones of Islet Structure and Co-ordination?
Open accessAbstract
Islet non-β-cells, the α- δ- and pancreatic polypeptide cells (PP-cells), are important components of islet architecture and intercellular communication. In α-cells, glucagon is found in electron-dense granules; granule exocytosis is calcium-dependent via P/Q-type Ca 2+ -channels, which may be clustered at designated cell membrane sites. Somatostatin-containing δ-cells are neuron-like, creating a network for intra-islet communication. Somatostatin 1-28 and 1-14 have a short bioactive half-life, suggesting inhibitory action via paracrine signaling. PP-cells are the most infrequent islet cell type. The embryologically separate ventral pancreas anlage contains PP-rich islets that are morphologically diffuse and α-cell deficient. Tissue samples taken from the head region are unlikely to be representative of the whole pancreas. PP has anorexic effects on gastro-intestinal function and alters insulin and glucagon secretion. Islet architecture is disrupted in rodent diabetic models, diabetic primates and human Type 1 and Type 2 diabetes, with an increased α-cell population and relocation of non-β-cells to central areas of the islet. In diabetes, the transdifferentiation of non-β-cells, with changes in hormone content, suggests plasticity of islet cells but cellular function may be compromised. Understanding how diabetes-related disordered islet structure influences intra-islet cellular communication could clarify how non-β-cells contribute to the control of islet function.
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When GLP-1 binds to GLP-1R on δ-cells, it activates these cells and promotes the secretion of somatostatin.
“When GLP-1 binds to GLP-1R on δ-cells, it activates these cells and promotes the secretion of somatostatin.243”
From Glucagon-like peptide-1 receptor: mechanisms and advances in therapy (2024) · cites this paper as [243]
The δ-Cells section states that pancreatic δ-cells secrete somatostatin. The Role of Glucagon section says activation of glucagon receptors on δ-cells stimulates somatostatin secretion, but our copy does not say that GLP-1 binds GLP-1R on δ-cells or activates them to produce this effect. Page numbers were not available in the indexed passages. (LLM, conf=0.84)
Experimental — accuracy not yet measuredT2D is attributed to both beta-cell dysfunction and alpha-cell dysfunction.
“T2D is not only attributed to beta-cell dysfunction but also alpha-cell dysfunction.141,142”
From A review of current trends with type 2 diabetes epidemiology, aetiology, pathogenesis, treatments and future perspectives (2021) · cites this paper as [141]
Islet alpha-cell populations increase in T1D, whereas in T2D patients alpha-cell numbers can be increased or unaltered.
“It is well established that islet alpha-cell populations increase in T1D, whereas in T2D, patients can have alpha-cell numbers increased or unaltered.141”
From A review of current trends with type 2 diabetes epidemiology, aetiology, pathogenesis, treatments and future perspectives (2021) · cites this paper as [141]
Islet alpha-cells are usually found in the periphery of the islets, but in diabetes many alpha-cells are found in the centre as well.
“Islet alpha-cells are usually found in the periphery of the islets, but in diabetes, many of the alpha-cells are found in the centre as well; in rodent models, this can be reversed by restoring normoglycaemia.141,152”
From A review of current trends with type 2 diabetes epidemiology, aetiology, pathogenesis, treatments and future perspectives (2021) · cites this paper as [141]
Changes in the islets of T2D patients have been postulated to induce altered signalling within the islets, which contributes to the phenotype of this disease.
“The changes in the islets of T2D patients have been postulated to induce altered signalling within the islets, which contributes to the phenotype of this disease.141”
From A review of current trends with type 2 diabetes epidemiology, aetiology, pathogenesis, treatments and future perspectives (2021) · cites this paper as [141]
In rodent models, migration of alpha-cells to the centre can be reversed by restoring normoglycaemia.
“Islet alpha-cells are usually found in the periphery of the islets, but in diabetes, many of the alpha-cells are found in the centre as well; in rodent models, this can be reversed by restoring normoglycaemia.141,152”
From A review of current trends with type 2 diabetes epidemiology, aetiology, pathogenesis, treatments and future perspectives (2021) · cites this paper as [141]
Both T1D and T2D induce major changes in the structure of animal and human pancreatic islets.
“Both T1D and T2D induce major changes in the structure of animal and human pancreatic islets.141”
From A review of current trends with type 2 diabetes epidemiology, aetiology, pathogenesis, treatments and future perspectives (2021) · cites this paper as [141]
In healthy individuals, beta-cells are situated centrally and peripherally and are the most abundant cell type (~70%).
“In healthy individuals, beta-cells are situated centrally and peripherally and are the most abundant cell type (~70%). Non-beta cells are found in the periphery of the islets and constitute ~30% of the cell population (20% alpha-cell and 10% other cell types).”
From A review of current trends with type 2 diabetes epidemiology, aetiology, pathogenesis, treatments and future perspectives (2021) · cites this paper as [141]
The altered islet architecture in T2D produces different intra-islet paracrine signalling which impairs metabolic homeostasis.
“The altered architecture in T2D produces different intra-islet paracrine signalling which impairs metabolic homeostasis.”
From A review of current trends with type 2 diabetes epidemiology, aetiology, pathogenesis, treatments and future perspectives (2021) · cites this paper as [141]
Islet architecture is altered in T2D with diminished beta-cells, more alpha-cells, more delta-cells, migration of alpha- and delta-cells into the centre, extracellular amyloid plaque deposits, intracellular IAPP oligomers in beta-cells, and enlarged alpha-cells.
“Islet architecture is altered in T2D with a greatly diminished population of beta-cells, more alpha-cells, more delta-cells, migration of alpha- and delta-cells into the centre, extracellular amyloid plaque deposits, intracellular IAPP oligomers in beta-cells, and enlarged alpha-cells.”
From A review of current trends with type 2 diabetes epidemiology, aetiology, pathogenesis, treatments and future perspectives (2021) · cites this paper as [141]
Dysfunctional regulation of the pancreatic islet by the nervous system contributes to the clinical phenotype of T2D.
“Dysfunctional regulation of the pancreatic islet by the nervous system contributes to the clinical phenotype of T2D, but whether or not this occurs before or after T2D diagnosis remains elusive, although it is reasonable to assume that it does, influencing the altered islet architecture observed in T2D.141,163”
From A review of current trends with type 2 diabetes epidemiology, aetiology, pathogenesis, treatments and future perspectives (2021) · cites this paper as [141]
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References 139 · Cited by 206
- Authors
- Brereton, M. F., Vergari, E., Zhang, Q., & Clark, A.
- Affiliations
- University of Oxford (GB)
- Venue
- Journal of Histochemistry & Cytochemistry
- Publisher
- SAGE Publications
- Published
- 2015-07-27
- Volume
- 63
- Issue
- 8
- Pages
- 575-591
- ISSN
- 0022-1554 (ISSN-L)
- 1551-5044
- PMC
- PMC4530398
- OpenAlex
- W1589179363
- Cited by
- 206
- References
- 139
- Citations by year
- 2026: 12 · 2025: 15 · 2024: 26 · 2023: 18 · 2022: 20 · 2021: 32 · 2020: 19 · 2019: 24 · 2018: 17 · 2017: 11 · 2016: 9 · 2015: 2
- FWCI
- 2.49
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Journal of Histochemistry & Cytochemistry (publishedVersion)
- Europe PMC (PubMed Central) (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- Funders
- Wellcome Trust
- Home Office
- Topics
- Health Sciences › Medicine › Surgery › Pancreatic function and diabetes
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Diabetes and associated disorders
- Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Diabetes Treatment and Management
- Keywords
- alpha cells, delta cells, pancreatic polypeptide cells, glucagon, somatostatin, P/Q-type calcium channels, granule exocytosis, paracrine signaling, islet architecture, diabetes mellitus
- MeSH terms
- Animals, Humans, Islets of Langerhans, Microscopy, Electron
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