Department of Biomedical Sciences, University of Cagliari, Monserrato, CA, Italy.
Department of Biomedical Sciences, University of Cagliari, Monserrato, CA, Italy.
Tissue Cell. 2021 Feb;68:101471. doi: 10.1016/j.tice.2020.101471. Epub 2020 Nov 27.
The TLQP-21 peptide potentiates glucose-stimulated insulin secretion, hence we investigated its endogenous response to glucose.
Fasted mice received intraperitoneal glucose (3 g/kg), or saline (controls), and were sacrificed 30 and 120 min later (4 groups, n = 6/group). We investigated TLQP-21 in pancreas and plasma using immunohistochemistry, enzyme-linked immunosorbent assay (ELISA) and high performance liquid chromatography (HPLC), as well as TLQP-21 receptors (gC1q-R and C3a-R1) expression in pancreas by immunohistochemistry.
In pancreas, TLQP-immunoreactivity (TLQP-ir.) was shown in insulin-, glucagon- and somatostatin-containing cells. Upon glucose, TLQP-ir. decreased at 30 min (∼40 % vs. controls), while returning to basal values at 120 min. In all groups, C3a-R1 was localized in ∼50 % of TLQP labelled islet cells (mostly central), while gC1q-R was detected in ∼25 % of TLQP cells (mainly peripheral). HPLC fractions of control pancreas extracts, assessed by ELISA, confirmed the presence of a TLQP-21 compatible-form (∼2.5 kDa MW). In plasma, TLQP-ir. increased at 30 min (∼30 %), with highest concentrations at 120 min (both: p<0.05 vs. controls), while HPLC fractions showed an increase in the TLQP-21 compatible form.
Upon hyperglycaemia, TLQP-21 would be released from islets, to enhance insulin secretion but we cannot exclude an autocrine activity which may regulate insulin storage/secretion.
TLQP-21 肽增强葡萄糖刺激的胰岛素分泌，因此我们研究了其对葡萄糖的内源性反应。
禁食的小鼠接受腹腔内葡萄糖（3 g/kg）或生理盐水（对照），并在 30 和 120 分钟后处死（4 组，每组 n = 6）。我们使用免疫组织化学、酶联免疫吸附测定（ELISA）和高效液相色谱（HPLC）检测胰腺和血浆中的 TLQP-21，以及免疫组织化学检测胰腺中的 TLQP-21 受体（gC1q-R 和 C3a-R1）表达。
在胰腺中，TLQP-免疫反应性（TLQP-ir.）显示在胰岛素、胰高血糖素和生长抑素分泌细胞中。葡萄糖后，TLQP-ir. 在 30 分钟时降低（约 40%比对照），而在 120 分钟时恢复到基础值。在所有组中，C3a-R1 定位于约 50%的 TLQP 标记胰岛细胞（主要是中央），而 gC1q-R 则检测到约 25%的 TLQP 细胞（主要是外周）。ELISA 评估的对照胰腺提取物的 HPLC 馏分证实存在 TLQP-21 兼容形式（约 2.5 kDa MW）。在血浆中，TLQP-ir. 在 30 分钟时增加（约 30%），120 分钟时浓度最高（两者均 p<0.05 比对照），而 HPLC 馏分显示 TLQP-21 兼容形式增加。
在高血糖时，TLQP-21 可能从胰岛中释放出来，以增强胰岛素分泌，但我们不能排除其可能调节胰岛素储存/分泌的自分泌活性。
