scholarly journals Insulin granule biogenesis and exocytosis

Author(s):  
Muhmmad Omar-Hmeadi ◽  
Olof Idevall-Hagren

Abstract Insulin is produced by pancreatic β-cells, and once released to the blood, the hormone stimulates glucose uptake and suppresses glucose production. Defects in both the availability and action of insulin lead to elevated plasma glucose levels and are major hallmarks of type-2 diabetes. Insulin is stored in secretory granules that form at the trans-Golgi network. The granules undergo extensive modifications en route to their release sites at the plasma membrane, including changes in both protein and lipid composition of the granule membrane and lumen. In parallel, the insulin molecules also undergo extensive modifications that render the hormone biologically active. In this review, we summarize current understanding of insulin secretory granule biogenesis, maturation, transport, docking, priming and eventual fusion with the plasma membrane. We discuss how different pools of granules form and how these pools contribute to insulin secretion under different conditions. We also highlight the role of the β-cell in the development of type-2 diabetes and discuss how dysregulation of one or several steps in the insulin granule life cycle may contribute to disease development or progression.

2019 ◽  
Vol 20 (15) ◽  
pp. 3699 ◽  
Author(s):  
Norikiyo Honzawa ◽  
Kei Fujimoto ◽  
Tadahiro Kitamura

To date, type 2 diabetes is considered to be a “bi-hormonal disorder” rather than an “insulin-centric disorder,” suggesting that glucagon is as important as insulin. Although glucagon increases hepatic glucose production and blood glucose levels, paradoxical glucagon hypersecretion is observed in diabetes. Recently, insulin resistance in pancreatic α cells has been proposed to be associated with glucagon dysregulation. Moreover, cell autonomous dysfunction of α cells is involved in the etiology of diabetes. In this review, we summarize the current knowledge about the physiological and pathological roles of glucagon.


2019 ◽  
Vol 218 (11) ◽  
pp. 3714-3729 ◽  
Author(s):  
Phuoc My Nguyen ◽  
Nikhil R. Gandasi ◽  
Beichen Xie ◽  
Sari Sugahara ◽  
Yingke Xu ◽  
...  

Insulin granule biogenesis involves transport to, and stable docking at, the plasma membrane before priming and fusion. Defects in this pathway result in impaired insulin secretion and are a hallmark of type 2 diabetes. We now show that the phosphatidylinositol 4-phosphate phosphatase Sac2 localizes to insulin granules in a substrate-dependent manner and that loss of Sac2 results in impaired insulin secretion. Sac2 operates upstream of granule docking, since loss of Sac2 prevented granule tethering to the plasma membrane and resulted in both reduced granule density and number of exocytic events. Sac2 levels correlated positively with the number of docked granules and exocytic events in clonal β cells and with insulin secretion in human pancreatic islets, and Sac2 expression was reduced in islets from type 2 diabetic subjects. Taken together, we identified a phosphoinositide switch on the surface on insulin granules that is required for stable granule docking at the plasma membrane and impaired in human type 2 diabetes.


PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0241939
Author(s):  
Ruiying Hu ◽  
Xiaodong Zhu ◽  
Mingyang Yuan ◽  
Kung-Hsien Ho ◽  
Irina Kaverina ◽  
...  

For sustainable function, each pancreatic islet β cell maintains thousands of insulin secretory granules (SGs) at all times. Glucose stimulation induces the secretion of a small portion of these SGs and simultaneously boosts SG biosynthesis to sustain this stock. The failure of these processes, often induced by sustained high-insulin output, results in type 2 diabetes. Intriguingly, young insulin SGs are more likely secreted during glucose-stimulated insulin secretion (GSIS) for unknown reasons, while older SGs tend to lose releasability and be degraded. Here, we examine the roles of microtubule (MT) and Gαo-signaling in regulating the preferential secretion of young versus old SGs. We show that both MT-destabilization and Gαo inactivation results in more SGs localization near plasma membrane (PM) despite higher levels of GSIS and reduced SG biosynthesis. Intriguingly, MT-destabilization or Gαo-inactivation results in higher secretion probabilities of older SGs, while combining both having additive effects on boosting GSIS. Lastly, Gαo inactivation does not detectably destabilize the β-cell MT network. These findings suggest that Gαo and MT can modulate the preferential release of younger insulin SGs via largely parallel pathways.


Diabetes ◽  
2018 ◽  
Vol 67 (Supplement 1) ◽  
pp. 772-P
Author(s):  
MARIKO HIGA ◽  
AYANA HASHIMOTO ◽  
MOE HAYASAKA ◽  
MAI HIJIKATA ◽  
AYAMI UEDA ◽  
...  

1970 ◽  
Vol 5 (1) ◽  
pp. 61-74 ◽  
Author(s):  
Alexandre de Souza E Silva ◽  
Maria Paula Gonçalves Mota

O trabalho tem como objetivo analisar os estudos que avaliaram os efeitos dos programas de treinamento aeróbio, força e combinado nos níveis de glicose sanguínea em indivíduos com diabetes do tipo 2. Foi utilizado o método de revisão sistemática, sendo utilizada a base de dados PubMed. As palavras chaves utilizadas para pesquisa foram training and diabetes. Foram identificados 484 artigos originais. Apenas 17 estudos respeitaram os critérios de inclusão. Os resultados evidenciam que os programas de treinamento aeróbio diminuíram os níveis de glicose. O programa de treinamento de força também foi favorável à diminuição dos níveis de glicose sanguínea. Já o programa de treinamento combinado não demonstrou efeitos favoráveis no controle da glicose sanguínea. Conclui-se que o programa de treinamento aeróbio e de força ajudam a controlar os níveis de glicose sanguínea em indivíduos com diabetes do tipo 2. Palavras-chave: diabetes mellitus, treinamento, glicose.ABSTRACTThe study aims to analyze the studies that evaluated the effects of aerobic, strength and combined programs training in blood glucose levels in people with type 2 diabetes. We used a systematic review method and is used to PubMed database. The key words used for searching were training and diabetes. We identified 484 original articles. Only 17 studies complied with the inclusion criteria. The results show that aerobic training programs decreased glucose levels. The strength training program was also favorable to decrease in blood glucose levels. But the combined training program has not shown favorable effects on blood glucose control. We conclude that the aerobic training and strength helps control blood glucose levels in individuals with type 2 diabetes. Keywords: diabetes mellitus, training, glucose.


2020 ◽  
Vol 18 ◽  
pp. 205873922098280
Author(s):  
Shuai Guo ◽  
Xujie Yu ◽  
Limei Wang ◽  
Jing Jing ◽  
Yuanyuan Sun ◽  
...  

Type 2 diabetes mellitus (T2DM) is a chronic, low-grade inflammation disease. T follicular helper (Tfh) cells and T cell immunoglobulin and mucin domain 3 (Tim-3) are implicated in many immune diseases. This study aims to explore whether Tim-3 expression on Tfh cells is associated with T2DM progression. White blood cells (WBCs) were harvested from 30 patients with T2DM and 20 healthy donors. The abundance of circulating Tfh cells (cTfh) and the frequency of Tim-3 were analyzed by flow cytometry. Levels of fasting plasma glucose (FPG), insulin, hemoglobin A1C (HbA1C), and fasting plasma C-peptide were measured. Body mass index (BMI) and diabetes duration were also recorded. Patients with T2DM had higher numbers of cTfh cells. In addition, cTfh cells showed a negative correlation with HbA1C and diabetes duration, a positive correlation with fasting plasma C-peptide. The frequency of Tim-3 on cTfh cells was higher among T2DM patients compared with healthy donors. The in vitro experiment showed that high glucose levels increased the abundance cTfh cells but had no effect on Tim-3 expression. Our results suggest that cTfh cells and associated Tim-3 frequency may contribute to the progression of T2DM, and high glucose levels may influence cTfh cells directly.


2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Musri Musman ◽  
Mauli Zakia ◽  
Ratu Fazlia Inda Rahmayani ◽  
Erlidawati Erlidawati ◽  
Safrida Safrida

Abstract Background Ethnobotany knowledge in a community has shaped local wisdom in utilizing plants to treat diseases, such as the use of Malaka (Phyllanthus emblica) flesh to treat type 2 diabetes. This study presented evidence that the phenolic extract of the Malaka flesh could reduce blood sugar levels in the diabetic induced rats. Methods The phenolic extract of the P. emblica was administrated to the glucose-induced rats of the Wistar strain Rattus norvegicus for 14 days of treatment where the Metformin was used as a positive control. The data generated were analyzed by the two-way ANOVA Software related to the blood glucose level and by SAS Software related to the histopathological studies at a significant 95% confidence. Results The phenolic extract with concentrations of 100 and 200 mg/kg body weight could reduce blood glucose levels in diabetic rats. The post hoc Dunnet test showed that the administration of the extract to the rats with a concentration of 100 mg/kg body weight demonstrated a very significant decrease in blood glucose levels and repaired damaged cells better than administering the extract at a concentration of 200 mg/kg weight body. Conclusion The evidence indicated that the phenolic extract of the Malaka flesh can be utilized as anti type 2 Diabetes mellitus without damaging other organs.


2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Stijn Crutzen ◽  
Tessa van den Born-Bondt ◽  
Petra Denig ◽  
Katja Taxis

Abstract Background Hypoglycaemia is a common and potentially avoidable adverse event in people with type 2 diabetes (T2D). It can reduce quality of life, increase healthcare costs, and reduce treatment success. We investigated self-management issues associated with hypoglycaemia and self-identified causes of hypoglycaemia in these patients. Methods In this mixed methods study qualitative semi-structured interviews were performed, which informed a subsequent quantitative survey in T2D patients. All interviews were audio recorded, transcribed verbatim and coded independently by two coders using directed content analysis, guided by the Theoretical Domains Framework. Descriptive statistics were used to quantify the self-management issues and causes of hypoglycaemia collected in the survey for the respondents that had experienced at least one hypoglycaemic event in the past. Results Sixteen participants were interviewed, aged 59–84 years. Participants perceived difficulties in managing deviations from routine, and they sometimes lacked procedural knowledge to adjust medication, nutrition or physical activity to manage their glucose levels. Grief and loss of support due to the loss of a partner interfered with self-management and lead to hypoglycaemic events. Work ethic lead some participant to overexerting themselves, which in turn lead to hypoglycaemic events. The participants had difficulties preventing hypoglycaemic events, because they did not know the cause, suffered from impaired hypoglycaemia awareness and/or did not want to regularly measure their blood glucose. When they did recognise a cause, they identified issues with nutrition, physical activity, stress or medication. In total, 40% of respondents reported regular stress as an issue, 24% reported that they regularly overestimated their physical abilities, and 22% indicated they did not always know how to adjust their medication. Around 16% of patients could not always remember whether they took their medication, and 42% always took their medication at regular times. Among the 83 respondents with at least one hypoglycaemic event, common causes for hypoglycaemia mentioned were related to physical activity (67%), low food intake (52%), deviations from routine (35%) and emotional burden (28%). Accidental overuse of medication was reported by 10%. Conclusion People with T2D experience various issues with self-managing their glucose levels. This study underlines the importance of daily routine and being able to adjust medication in relation to more physical activity or less food intake as well as the ability to reduce and manage stress to prevent hypoglycaemic events.


2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Marcio Krakauer ◽  
Jose Fernando Botero ◽  
Fernando J. Lavalle-González ◽  
Adrian Proietti ◽  
Douglas Eugenio Barbieri

Abstract Background Continuous glucose monitoring systems are increasingly being adopted as an alternative to self-monitoring of blood glucose (SMBG) by persons with diabetes mellitus receiving insulin therapy. Main body The FreeStyle Libre flash glucose monitoring system (Abbott Diabetes Care, Witney, United Kingdom) consists of a factory-calibrated sensor worn on the back of the arm which measures glucose levels in the interstitial fluid every minute and stores the reading automatically every 15 min. Swiping the reader device over the sensor retrieves stored data and displays current interstitial glucose levels, a glucose trend arrow, and a graph of glucose readings over the preceding 8 h. In patients with type 2 diabetes (T2D) receiving insulin therapy, pivotal efficacy data were provided by the 6-month REPLACE randomized controlled trial (RCT) and 6-month extension study. Compared to SMBG, the flash system significantly reduced the time spent in hypoglycemia and frequency of hypoglycemic events, although no significant change was observed in glycosylated hemoglobin (HbA1c) levels. Subsequent RCTs and real-world chart review studies have since shown that flash glucose monitoring significantly reduces HbA1c from baseline. Real-world studies in both type 1 diabetes or T2D populations also showed that flash glucose monitoring improved glycemic control. Higher (versus lower) scanning frequency was associated with significantly greater reductions in HbA1c and significant improvements in other measures such as time spent in hypoglycemia, time spent in hyperglycemia, and time in range. Additional benefits associated with flash glucose monitoring versus SMBG include reductions in acute diabetes events, all-cause hospitalizations and hospitalized ketoacidosis episodes; improved well-being and decreased disease burden; and greater treatment satisfaction. Conclusion T2D patients who use flash glucose monitoring might expect to achieve significant improvement in HbA1c and glycemic parameters and several associated benefits.


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