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Reprotoxic and Endocrine Substances
Published in Małgorzata Pośniak, Emerging Chemical Risks in the Work Environment, 2020
Katarzyna Miranowicz-Dzierżawska
The pancreas is an organ composed of two functionally different organs: exocrine pancreas, the largest digestive gland of the human body, and endocrine pancreas, the source of insulin, glucagon, somatostatin, and pancreatic polypeptide. While the exocrine pancreas plays the largest role in the digestive process (digestive enzymes), as it transforms food into substances which can be absorbed by the body, the endocrine pancreas influences every aspect of nutritional and intracellular changes. This function is applicable both to the amount of absorbed food and the storage of the products of the digestive process in the cells. The impairment of intrapancreatic secretion or abnormal response of target tissues to hormone activity leads to severe abnormalities in digestive homeostasis, including clinically relevant syndromes, collectively known as diabetes [Greenspan and Gardner 2004].
Signaling and Architectural Cues Necessary for 3D Diabetic Tissue Models
Published in Karen J.L. Burg, Didier Dréau, Timothy Burg, Engineering 3D Tissue Test Systems, 2017
Rosalyn D. Abbott, David L. Kaplan
In the pancreas (Figure 17.2), the acinar and ductal cells are responsible for exocrine functions, while the hormone-producing cells, β-, α-, δ-, and pp-cells, are responsible for the endocrine functions (Greggio et al. 2015). For diabetes models, the most relevant cell types are β- and α-cells, since the β-cells lower blood glucose levels by secreting insulin, while the α-cells increase blood glucose levels by secreting glucagon (Peyser et al. 2014). The β-cells and α-cells, together with somatostatin-producing δ-cells, pancreatic polypeptide producing pp-cells, and ghrelin producing cells, form the islets of Langerhans (Stendahl et al. 2009). Islets comprise 1%–2% of the total adult human pancreatic volume, with approximately one million islets scattered within the exocrine pancreas (Carroll 1992). Islets are extensively vascularized by fenestrated endothelial networks and innervated by sympathetic, parasympathetic, and sensory nerves (Carroll 1992; Brunicardi et al. 1996; Ahren 2000). The unique multicellular connections within the pancreas necessitate the synchronization of a multitude of signals to obtain the appropriate function of the β-cell under basal and glucose-stimulated conditions. Examples of known paracrine effects on the secretion of insulin by β-cells include the stimulatory effect of glucagon secreted by α-cells and the inhibitory effect of somatostatin by δ-cells.
Intelligent Scaffold–Mediated Enhancement of the Viability and Functionality of Transplanted Pancreatic Islets to Cure Diabetes Mellitus
Published in Gilson Khang, Handbook of Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine, 2017
Min Jun Kim, Hae Hyun Hwang, Dong Yun Lee
There are some trials that utilize a combination of natural and synthetic polymers as a scaffold to take advantage of the properties from both polymer types.142,143 For example, a three-dimensional PLGA scaffold entrapping ECM molecules including collagen type I gel, fibronectin, and collagen type IV was first developed.143 First of all, a PLGA scaffold that had a controlled pore structure was microfabricated by using a layer-by-layer technique with PLGA polymer solution. Then, human islets entrapped in ECM gel were embedded within the PLGA scaffold. The islets cultured in the ECM gel with the scaffold could display an ability to secrete insulin similar to that of fresh islets, meaning that the PLGA-ECM scaffold do not affect the viability and function of islets. Moreover, expression of pancreatic genes such as insulin, glucagon, somatostatin, pancreatic polypeptide (PP), PDX-1 (pancreatic and duodenal homeobox 1), glucokinase (GCK), sulfonylurea receptor-1 (SUR-1), and glucose transporter2 (GLUT-2) was significantly increased in the PLGA-ECM scaffold. Interestingly, islets cultured in ECM gel within a PLGA scaffold showed better results as compared to islets cultured in ECM gel without a PLGA scaffold. This result demonstrated that geometrically controlled and microfabricated PLGA scaffolds could provide more favorable microenvironments for islets.
Combined high-intensity interval training as an obesity-management strategy for adolescents
Published in European Journal of Sport Science, 2023
António Videira-Silva, Megan Hetherington-Rauth, Luís B. Sardinha, Helena Fonseca
On the other hand, the (accurate) perception of exercise efficacy on weight and fitness among HIIT participants, may explain the difference found in compliance between-groups (Taddeo, Egedy, & Frappier, 2008). Indeed, HIIT showed to be associated with better health-related outcomes compared to TT. In line with the study of Tjonna et al. (2009) and Racil et al. (2013), HIIT was the only group showing a significant decrease in BMI z-score (main outcome), both relative (BFM) and absolute body fat (TBFM) and central adiposity (WHtR and Trunk FM) at six months. These results may be explained by a synergic effect of increased energy expenditure in the HIIT group associated with higher levels of daily MVPA and Ex MVPA, and a significant decrease in energy intake. According to Thivel et al., daily total energy intake during the ad libitum meals may be reduced in about 6–11% after high-intensity exercise, compared to low-intensity or no-exercise conditions in adolescents with obesity (2012). High intensity PA may lead to a higher mobilization of anorexic peptides (e.g. PYY3-36), glucagon-like peptide 1, cholecystokinin and/or pancreatic polypeptide, that have been shown to be sensitive to exercise intensity (Martins, Morgan, & Truby, 2008; Ueda et al., 2009), consequently resulting in a lower energy intake.