Neuroscience Division, Cognitive Neuroscience Department, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
Department of Embryology and Genetics, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico.
PLoS One. 2024 Jun 14;19(6):e0303934. doi: 10.1371/journal.pone.0303934. eCollection 2024.
The nerve growth factor (NGF) participates in cell survival and glucose-stimulated insulin secretion (GSIS) processes in rat adult beta cells. GSIS is a complex process in which metabolic events and ionic channel activity are finely coupled. GLUT2 and glucokinase (GK) play central roles in GSIS by regulating the rate of the glycolytic pathway. The biphasic release of insulin upon glucose stimulation characterizes mature adult beta cells. On the other hand, beta cells obtained from neonatal, suckling, and weaning rats are considered immature because they secrete low levels of insulin and do not increase insulin secretion in response to high glucose. The weaning of rats (at postnatal day 20 in laboratory conditions) involves a dietary transition from maternal milk to standard chow. It is characterized by increased basal plasma glucose levels and insulin levels, which we consider physiological insulin resistance. On the other hand, we have observed that incubating rat beta cells with NGF increases GSIS by increasing calcium currents in neonatal cells. In this work, we studied the effects of NGF on the regulation of cellular distribution and activity of GLUT2 and GK to explore its potential role in the maturation of GSIS in beta cells from P20 rats. Pancreatic islet cells from both adult and P20 rats were isolated and incubated with 5.6 mM or 15.6 mM glucose with and without NGF for 4 hours. Specific immunofluorescence assays were conducted following the incubation period to detect insulin and GLUT2. Additionally, we measured glucose uptake, glucokinase activity, and insulin secretion assays at 5.6 mM or 15.6 mM glucose concentrations. We observed an age-dependent variation in the distribution of GLUT2 in pancreatic beta cells and found that glucose plays a regulatory role in GLUT2 distribution independently of age. Moreover, NGF increases GLUT2 abundance, glucose uptake, and GSIS in P20 beta cells and GK activity in adult beta cells. Our results suggest that besides increasing calcium currents, NGF regulates metabolic components of the GSIS, thereby contributing to the maturation process of pancreatic beta cells.
神经生长因子（NGF）参与成年大鼠胰岛β细胞的细胞存活和葡萄糖刺激的胰岛素分泌（GSIS）过程。GSIS 是一个复杂的过程，其中代谢事件和离子通道活性被精细地耦联。GLUT2 和葡萄糖激酶（GK）通过调节糖酵解途径的速率在 GSIS 中发挥核心作用。葡萄糖刺激后的胰岛素双相释放是成熟的成年β细胞的特征。另一方面，从新生、哺乳和断奶大鼠获得的β细胞被认为是不成熟的，因为它们分泌低水平的胰岛素，并且不会响应高葡萄糖增加胰岛素分泌。大鼠的断奶（在实验室条件下为出生后第 20 天）涉及从母体乳汁到标准饲料的饮食转变。其特征是基础血浆葡萄糖和胰岛素水平增加，我们认为这是生理性胰岛素抵抗。另一方面，我们观察到，用 NGF 孵育新生大鼠β细胞会增加钙电流，从而增加 GSIS。在这项工作中，我们研究了 NGF 对 GLUT2 和 GK 的细胞分布和活性调节的影响，以探索其在 P20 大鼠胰岛β细胞 GSIS 成熟中的潜在作用。从成年和 P20 大鼠中分离胰岛细胞，并在有或没有 NGF 的情况下在 5.6mM 或 15.6mM 葡萄糖中孵育 4 小时。孵育后进行特定的免疫荧光测定以检测胰岛素和 GLUT2。此外，我们还在 5.6mM 或 15.6mM 葡萄糖浓度下测量葡萄糖摄取、葡萄糖激酶活性和胰岛素分泌测定。我们观察到胰岛β细胞中 GLUT2 分布存在年龄依赖性变化，发现葡萄糖独立于年龄调节 GLUT2 分布。此外，NGF 增加了 P20 胰岛β细胞中的 GLUT2 丰度、葡萄糖摄取和 GSIS，以及成年胰岛β细胞中的 GK 活性。我们的结果表明，除了增加钙电流外，NGF 还调节 GSIS 的代谢成分，从而有助于胰腺β细胞的成熟过程。
