-
Frontiers in Endocrinology 2022Although important for digestion and metabolism in repose, the healthy endocrine pancreas also plays a key role in facilitating energy transduction around physical... (Review)
Review
Although important for digestion and metabolism in repose, the healthy endocrine pancreas also plays a key role in facilitating energy transduction around physical exercise. During exercise, decrements in pancreatic β-cell mediated insulin release opposed by increments in α-cell glucagon secretion stand chief among the hierarchy of glucose-counterregulatory responses to decreasing plasma glucose levels. As a control hub for several major glucose regulatory hormones, the endogenous pancreas is therefore essential in ensuring glucose homeostasis. Type 1 diabetes (T1D) is pathophysiological condition characterised by a destruction of pancreatic β-cells resulting in pronounced aberrations in glucose control. Yet perhaps less considered is the impact of T1D on all other pancreatic endocrine cell responses during exercise and whether they differ to those observed in healthy man. For physicians, understanding how the endocrine pancreas responds to exercise in people with and without T1D may serve as a useful model from which to identify whether there are clinically relevant adaptations that need consideration for glycaemic management. From a physiological perspective, delineating differences or indeed similarities in such responses may help inform appropriate exercise test interpretation and subsequent program prescription. With more complex advances in automated insulin delivery (AID) systems and emerging data on exercise algorithms, a timely update is warranted in our understanding of the endogenous endocrine pancreatic responses to physical exercise in people with and without T1D. By placing our focus here, we may be able to offer a nexus of better understanding between the clinical and engineering importance of AIDs requirements during physical exercise.
Topics: Blood Glucose; Diabetes Mellitus, Type 1; Exercise; Glucagon; Glucagon-Secreting Cells; Glucose; Humans; Insulin; Islets of Langerhans; Male
PubMed: 36147573
DOI: 10.3389/fendo.2022.981723 -
Peptides Dec 2022Chromogranin A (CgA) is a 439 amino acid protein secreted by neuroendocrine cells. Proteolytic processing of CgA results in the production of different bioactive... (Review)
Review
Chromogranin A (CgA) is a 439 amino acid protein secreted by neuroendocrine cells. Proteolytic processing of CgA results in the production of different bioactive peptides. These peptides have been associated with inflammatory bowel disease, diabetes, and cancer. One of the chromogranin A-derived peptides is ∼52 amino acid long Pancreastatin (PST: human (h)CgA, murine (m)CgA). PST is a glycogenolytic peptide that inhibits glucose-induced insulin secretion from pancreatic islet β-cells. In addition to this metabolic role, evidence is emerging that PST also has inflammatory properties. This review will discuss the immunomodulatory properties of PST and its possible mechanisms of action and regulation. Moreover, this review will discuss the potential translation to humans and how PST may be an interesting therapeutic target for treating inflammatory diseases.
Topics: Humans; Animals; Mice; Chromogranin A; Pancreatic Hormones; Chromogranins; Peptides; Amino Acids
PubMed: 36244579
DOI: 10.1016/j.peptides.2022.170893 -
Diabetes Apr 2020Secretion of glucagon from the pancreatic α-cells is conventionally seen as the first and most important defense against hypoglycemia. Recent findings, however, show... (Review)
Review
Secretion of glucagon from the pancreatic α-cells is conventionally seen as the first and most important defense against hypoglycemia. Recent findings, however, show that α-cell signals stimulate insulin secretion from the neighboring β-cell. This article focuses on these seemingly counterintuitive local actions of α-cells and describes how they impact islet biology and glucose metabolism. It is mostly based on studies published in the last decade on the physiology of α-cells in human islets and incorporates results from rodents where appropriate. As this and the accompanying articles show, the emerging picture of α-cell function is one of increased complexity that needs to be considered when developing new therapies aimed at promoting islet function in the context of diabetes.
Topics: Animals; Diabetes Mellitus; Glucagon; Glucagon-Secreting Cells; Humans; Insulin; Insulin Secretion; Paracrine Communication
PubMed: 31882565
DOI: 10.2337/dbi19-0002 -
Diabetes Dec 2023In type 1 diabetes, the reduced glucagon response to insulin-induced hypoglycemia has been used to argue that β-cell secretion of insulin is required for the full... (Review)
Review
In type 1 diabetes, the reduced glucagon response to insulin-induced hypoglycemia has been used to argue that β-cell secretion of insulin is required for the full glucagon counterregulatory response. For years, the concept has been that insulin from the β-cell core flows downstream to suppress glucagon secretion from the α-cells in the islet mantle. This core-mantle relationship has been supported by perfused pancreas studies that show marked increases in glucagon secretion when insulin was neutralized with antisera. Additional support comes from a growing number of studies focused on vascular anatomy and blood flow. However, in recent years this core-mantle view has generated less interest than the argument that optimal insulin secretion is due to paracrine release of glucagon from α-cells stimulating adjacent β-cells. This mechanism has been evaluated by knockout of β-cell receptors and impairment of α-cell function by inhibition of Gi designer receptors exclusively activated by designer drugs. Other studies that support this mechanism have been obtained by pharmacological blocking of glucagon-like peptide 1 receptor in humans. While glucagon has potent effects on β-cells, there are concerns with the suggested paracrine mechanism, since some of the supporting data are from isolated islets. The study of islets in static incubation or perifusion systems can be informative, but the normal paracrine relationships are disrupted by the isolation process. While this complicates interpretation of data, arguments supporting paracrine interactions between α-cells and β-cells have growing appeal. We discuss these conflicting views of the relationship between pancreatic α-cells and β-cells and seek to understand how communication depends on blood flow and/or paracrine mechanisms.
Topics: Humans; Glucagon; Glucagon-Secreting Cells; Insulin; Insulin-Secreting Cells; Insulin Secretion; Hypoglycemia; Islets of Langerhans; Glucose
PubMed: 37983524
DOI: 10.2337/db23-0292 -
Neuroscience Nov 2020Amylin is co-secreted with insulin by pancreatic β-cells in response to a meal and produced by neurons in discrete hypothalamic brain areas. Leptin is proportionally... (Review)
Review
Amylin is co-secreted with insulin by pancreatic β-cells in response to a meal and produced by neurons in discrete hypothalamic brain areas. Leptin is proportionally secreted by the adipose tissue. Both hormones control food intake and energy homeostasis post-weaning in rodents. While amylin's main site of action is located in the area postrema (AP) and leptin's is located in the mediobasal hypothalamus, both hormones can also influence the other's signaling pathway; amylin has been shown enhance hypothalamic leptin signaling, and amylin signaling in the AP may rely on functional leptin receptors to modulate its effects. These two hormones also play major roles during other life periods. During pregnancy, leptin levels rise as a result of an increase in fat depot resulting in gestational leptin-resistance to prepare the maternal body for the metabolic needs during fetal development. The role of amylin is far less studied during pregnancy and lactation, though amylin levels seem to be elevated during pregnancy relative to insulin. Whether amylin and leptin interact during pregnancy and lactation remains to be assessed. Lastly, during brain development, amylin and leptin are major regulators of cell birth during embryogenesis and act as neurotrophic factors in the neonatal period. This review will highlight the role of amylin and leptin, and their possible interaction, during these dynamic time periods of pregnancy, lactation, and early development.
Topics: Amyloid; Child Development; Female; Humans; Infant, Newborn; Islet Amyloid Polypeptide; Lactation; Leptin; Pregnancy; Receptors, Leptin
PubMed: 31846753
DOI: 10.1016/j.neuroscience.2019.11.034 -
Frontiers in Endocrinology 2022The primary cilium is a narrow organelle located at the surface of the cell in contact with the extracellular environment. Once underappreciated, now is thought to... (Review)
Review
The primary cilium is a narrow organelle located at the surface of the cell in contact with the extracellular environment. Once underappreciated, now is thought to efficiently sense external environmental cues and mediate cell-to-cell communication, because many receptors, ion channels, and signaling molecules are highly or differentially expressed in primary cilium. Rare genetic disorders that affect cilia integrity and function, such as Bardet-Biedl syndrome and Alström syndrome, have awoken interest in studying the biology of cilium. In this review, we discuss recent evidence suggesting emerging roles of primary cilium and cilia-mediated signaling pathways in the regulation of pancreatic β- and α-cell functions, and its implications in regulating glucose homeostasis.
Topics: Cilia; Glucagon-Secreting Cells; Insulysin; Pancreatic Hormones; Signal Transduction
PubMed: 35832432
DOI: 10.3389/fendo.2022.922825 -
The Journal of Clinical Endocrinology... Jun 2022The bitter substance quinine modulates the release of a number of gut and gluco-regulatory hormones and upper gut motility. As the density of bitter receptors may be... (Randomized Controlled Trial)
Randomized Controlled Trial
CONTEXT
The bitter substance quinine modulates the release of a number of gut and gluco-regulatory hormones and upper gut motility. As the density of bitter receptors may be higher in the duodenum than the stomach, direct delivery to the duodenum may be more potent in stimulating these functions. The gastrointestinal responses to bitter compounds may also be modified by sex.
BACKGROUND
We have characterized the effects of intragastric (IG) versus intraduodenal (ID) administration of quinine hydrochloride (QHCl) on gut and pancreatic hormones and antropyloroduodenal pressures in healthy men and women.
METHODS
14 men (26 ± 2 years, BMI: 22.2 ± 0.5 kg/m2) and 14 women (28 ± 2 years, BMI: 22.5 ± 0.5 kg/m2) received 600 mg QHCl on 2 separate occasions, IG or ID as a 10-mL bolus, in randomized, double-blind fashion. Plasma ghrelin, cholecystokinin, peptide YY, glucagon-like peptide-1 (GLP-1), insulin, glucagon, and glucose concentrations and antropyloroduodenal pressures were measured at baseline and for 120 minutes following QHCl.
RESULTS
Suppression of ghrelin (P = 0.006), stimulation of cholecystokinin (P = 0.030), peptide YY (P = 0.017), GLP-1 (P = 0.034), insulin (P = 0.024), glucagon (P = 0.030), and pyloric pressures (P = 0.050), and lowering of glucose (P = 0.001) were greater after ID-QHCl than IG-QHCl. Insulin stimulation (P = 0.021) and glucose reduction (P = 0.001) were greater in females than males, while no sex-associated effects were found for cholecystokinin, peptide YY, GLP-1, glucagon, or pyloric pressures.
CONCLUSION
ID quinine has greater effects on plasma gut and pancreatic hormones and pyloric pressures than IG quinine in healthy subjects, consistent with the concept that stimulation of small intestinal bitter receptors is critical to these responses. Both insulin stimulation and glucose lowering were sex-dependent.
Topics: Cholecystokinin; Double-Blind Method; Energy Intake; Female; Gastrointestinal Motility; Ghrelin; Glucagon; Glucagon-Like Peptide 1; Glucose; Humans; Insulin; Male; Pancreatic Hormones; Peptide YY; Quinine
PubMed: 35325161
DOI: 10.1210/clinem/dgac182 -
Nutrients Oct 2023Diabetes mellitus represents a group of physiological dysfunctions characterized by hyperglycaemia resulting directly from insulin resistance (in the case of type 2...
Diabetes mellitus represents a group of physiological dysfunctions characterized by hyperglycaemia resulting directly from insulin resistance (in the case of type 2 diabetes mellitus-T2DM), inadequate insulin secretion/production, or excessive glucagon secretion (in type 1 diabetes mellitus-T1DM) [...].
Topics: Humans; Diabetes Mellitus, Type 2; Insulin; Glucagon; Blood Glucose; Diabetes Mellitus, Type 1
PubMed: 37836562
DOI: 10.3390/nu15194279 -
Pancreatology : Official Journal of the... Aug 2021/Objectives: The pathogenesis of hyperglycemia during acute pancreatitis (AP) remains unknown due to inaccessibility of human tissues and lack of animal models. We aimed...
BACKGROUND
/Objectives: The pathogenesis of hyperglycemia during acute pancreatitis (AP) remains unknown due to inaccessibility of human tissues and lack of animal models. We aimed to develop an animal model to study the mechanisms of hyperglycemia and impaired glucose tolerance in AP.
METHODS
We injected ferrets with intraperitoneal cerulein (50 μg/kg, 9 hourly injections) or saline. Blood samples were collected for glucose (0, 4, 8, 12, 24h); TNF-α, IL-6 (6h); amylase, lipase, insulin, glucagon, pancreatic polypeptide (PP), glucagon-like peptide-1 (GLP-1), and gastric inhibitory polypeptide (GIP) (24h). Animals underwent oral glucose tolerance test (OGTT), mixed meal tolerance test (MMTT) at 24h or 3 months, followed by harvesting pancreas for histopathology and immunostaining.
RESULTS
Cerulein-injected ferrets exhibited mild pancreatic edema, neutrophil infiltration, and elevations in serum amylase, lipase, TNF-α, IL-6, consistent with AP. Plasma glucose was significantly higher in ferrets with AP at all time points. Plasma glucagon, GLP-1 and PP were significantly higher in cerulein-injected animals, while plasma insulin was significantly lower compared to controls. OGTT and MMTT showed abnormal glycemic responses with higher area under the curve. The hypoglycemic response to insulin injection was completely lost, suggestive of insulin resistance. OGTT showed low plasma insulin; MMTT confirmed low insulin and GIP; abnormal OGTT and MMTT responses returned to normal 3 months after cerulein injection.
CONCLUSIONS
Acute cerulein injection causes mild acute pancreatitis in ferrets and hyperglycemia related to transient islet cell dysfunction and insulin resistance. The ferret cerulein model may contribute to the understanding of hyperglycemia in acute pancreatitis.
Topics: Acute Disease; Amylases; Animals; Blood Glucose; Ceruletide; Ferrets; Gastric Inhibitory Polypeptide; Glucagon; Glucagon-Like Peptide 1; Humans; Hyperglycemia; Insulin; Insulin Resistance; Interleukin-6; Lipase; Pancreatitis; Tumor Necrosis Factor-alpha
PubMed: 33994067
DOI: 10.1016/j.pan.2021.04.008 -
Nutrients Sep 2023Glucagon was initially regarded as a hyperglycemic substance; however, recent research has revealed its broader role in metabolism, encompassing effects on glucose,... (Review)
Review
Glucagon was initially regarded as a hyperglycemic substance; however, recent research has revealed its broader role in metabolism, encompassing effects on glucose, amino acids (AAs), and lipid metabolism. Notably, the interplay of glucagon with nutrient intake, particularly of AAs, and non-nutrient components is central to its secretion. Fasting and postprandial hyperglucagonemia have long been linked to the development and progression of type 2 diabetes (T2DM). However, recent studies have brought to light the positive impact of glucagon agonists on lipid metabolism and energy homeostasis. This review explores the multifaceted actions of glucagon, focusing on its regulation, signaling pathways, and effects on glucose, AAs, and lipid metabolism. The interplay between glucagon and other hormones, including insulin and incretins, is examined to provide a mechanistic understanding of its functions. Notably, the liver-α-cell axis, which involves glucagon and amino acids, emerges as a critical aspect of metabolic regulation. The dysregulation of glucagon secretion and its impact on conditions such as T2DM are discussed. The review highlights the potential therapeutic applications of targeting the glucagon pathway in the treatment of metabolic disorders.
Topics: Humans; Glucagon; Diabetes Mellitus, Type 2; Insulin; Amino Acids; Glucose
PubMed: 37764697
DOI: 10.3390/nu15183913