Endocrine Glands
Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard in Toxicologic Pathology, 2018
Rats and mice have similar pancreatic anatomy (Tsuchitani et al. 2016) and islet morphology (Table 19.2). Rodent pancreatic islets have a zonal distribution of cell types. Beta-cells are the predominant cell type and are located centrally within the islet, whereas α-, δ-, and PP-cells are present in lower numbers and are located at the periphery. Delta-cells associate intimately with α- and β-cells in the peripheral area of the islets. PP-cells are variable in number, and δ-cells can increase in number and become more centrally located during development of diabetes mellitus in susceptible strains/models (Adeghate and Ponery 2002). Rabbits are similar to rodents in regards to pancreatic islet morphology. Morphologically, the canine pancreas consists of three regions: left or splenic lobe, the right or duodenal lobe, and the intervening body (Tsuchitani et al. 2016). By using immunohistochemistry for insulin, as a marker for β-cells, and quantification using computer-assisted morphometry, Govendir et al. (1999) have shown that β-cell volume across the three areas of the pancreas differed with a significantly higher β-cell volume in the body and left lobes, 0.98 ± 0.05 and 0.97 ± 0.08 mm3, respectively, when compared with the right lobe (0.67 ± 0.06 mm3). This group also showed the potential pitfalls in determining β-cell volume. Their results depended on the orientation of sectioning of the pancreas (Wieczorek et al. 1998; Govendir et al. 1999).
The patient with acute endocrine problems
Ian Peate, Helen Dutton in Acute Nursing Care, 2014
The endocrine component of the pancreas consists of the islets of Langerhans, which contain hormone-secreting cells. Alpha cells secrete glucagon; beta cells, insulin; delta cells, somatostatin and gamma cells, pancreatic polypeptides. It is the alpha, beta and delta cells that have the primary role in blood glucose homeostasis. The plasma glucose level is the most important determinant of the rate of insulin release from the beta cells or glucagon from the alpha cells. High levels of glucose trigger insulin secretion and low plasma glucose leads to glucagon secretion which in turn promotes glycogenolysis by the liver. Thus insulin may be considered an anabolic hormone whereas glucagon is catabolic in nature. Insulin and glucagon have an inhibitory effect on each other and both can be inhibited by somatostatin: thus there is complex interplay between the three hormones. Figure 11.5 gives a summary of the control of blood glucose by pancreatic enzymes and the liver.
Medicinal Plants Research
Vikas Kumar, Addepalli Veeranjaneyulu in Herbs for Diabetes and Neurological Disease Management, 2018
Diabetes mellitus type 2 (NIDDM) which is multilevel and complex disease represent the majority of all the diabetes cases worldwide70 and is a result of serious compromise in genetics (mutation in the glucokinase gene) leading to predisposition to impaired insulin secretion and insulin resistance, and unhealthy lifestyle factors, such as: lack of exercise and proper sleep, over eating, drinking, constant stress, and others.71,72 Pancreatic abnormalities in islet secretory cells in NIDDM are noted in beta, alpha, and delta cells of the islets. Defects involving insulin secretion include relative decrease in insulin response, amino acid hypersensitivity of insulin, glucose insensitivity, amyloid polypeptide (IAPP) deposition in pancreatic islets.73,74 NIDDM could be also characterized by elevated lipid oxidation and inflammation, and hyperglycemia cause a significant damage of cellular membrane due to extensive production of ROS. NIDDM is closely associated with mutations in the insulin receptor gene responsible for insulin resistance.75 Stress, increased sugar consumption, chromium and copper deficiency, lacking of fibers and abundance of carbohydrates, lack of exercise and bad dietary habits, increased alcohol intake and smoking, and some environmental factors as well, are definitely contributing to onset and development of NIDDM.
Evidence for the existence and potential roles of intra-islet glucagon-like peptide-1
Published in Islets, 2021
Scott A. Campbell, Janyne Johnson, Peter E. Light
Glucose is an essential regulator of islet hormone secretion. Both beta and delta cells rely on glucose-stimulated secretion pathways, where hyperglycemia favors the release of insulin and somatostatin from the islet. In beta and delta cells, glucose entry and metabolism results in the closure of KATP channels, membrane depolarization, elevated intracellular calcium, and hormone secretion. This pathway in delta cells is more dependent on calcium-induced Ca2+ release, whereas beta cells depend on the activation of voltage-gated Ca2+ channels.60 The sodium-glucose transporter SGLT2 is expressed in 33–58% of human delta cells, and its current contributes to insulin-induced somatostatin secretion.108 In the presence of SGLT2 inhibitors like dapagliflozin, insulin-stimulated somatostatin secretion is modestly suppressed.108,109 As previously stated, the actions of GLP-1 in alpha cells are also glucose-dependent. In hyperglycemia, GLP-1R activation inhibits alpha cell hormone release, while receptor activation in hypoglycemia potentiates hormone secretion.100
Amyloid nomenclature 2022: update, novel proteins, and recommendations by the International Society of Amyloidosis (ISA) Nomenclature Committee
Published in Amyloid, 2022
Joel N. Buxbaum, Angela Dispenzieri, David S. Eisenberg, Marcus Fändrich, Giampaolo Merlini, Maria J. M. Saraiva, Yoshiki Sekijima, Per Westermark
Somatostatin is synthesised as a 116 aa residue polypeptide from which a 24 aa signal peptide is removed. The resulting 92 aa propeptide is further processed to yield somatostatins 14 or 28, constituting the C-terminus of the precursor (prosomatostatin) [12]. Somatostatin is expressed in the D (or delta) cells of the islets of Langerhans but also in cells in the gastrointestinal canal and in the brain. Two recent papers have described somatostatin as an amyloid fibril protein in somatostatinomas. One of the reports describes 4 patients. It was not possible to determine the exact form of somatostatin in the deposits [13]. The other paper describes the analysis of amyloid in an endocrine papillary tumour of the duodenum where the fibrillary protein was derived from the somatostatin precursor [14]. The exact portion of the precursor comprising the amyloid fibrils was not determined. The name will be amyloid protein ASom.
Pancreatic atrophy and exocrine insufficiency associate with the presence of diabetes in chronic pancreatitis patients, but additional mediators are operative
Published in Scandinavian Journal of Gastroenterology, 2021
Søren Schou Olesen, Rasmus Hagn-Meincke, Asbjørn Mohr Drewes, Emilie Steinkohl, Jens Brøndum Frøkjaer
We confirmed that pancreatic atrophy (indicated by reduced pancreatic volume) was independently associated with the presence of PPDM. This is in keeping with past studies and reflects the conventional view of PPDM as a result of beta cell loss and insulin deficiency [25]. However, in addition to insulin, a number of other peptide hormones are secreted from the pancreatic islet cells including glucagon (alpha cells) and pancreatic polypeptide (delta cells).These hormones are important for the maintenance of glucose homeostasis and regulate muscle and liver insulin sensitivity. Hence, islet cell destruction resulting from CP does not only lead to insulin deficiency, but also a lack of counter regulatory hormones, which results in a ‘brittle diabetes’ that can be difficult to treat and are associated with high risk of hypoglycemic episodes and hyperglycemic crisis [1,4].
Related Knowledge Centers
- Gastrointestinal Tract
- Ghrelin
- Granule
- Somatostatin
- Electron Microscope
- Stomach
- Insulin
- Cell
- Pancreatic Islets
- Urocortin III