Supplementary Material for: Glucagon-Like Peptide-1-, but not Growth and Differentiation Factor 15-, Receptor Activation Increases the Number of Interleukin-6-Expressing Cells in the External Lateral Parabrachial Nucleus

Interleukin (IL)-6 in the hypothalamus and hindbrain is an important downstream mediator of suppression of body weight and food intake by glucagon-like peptide-1 (GLP-1) receptor stimulation. CNS GLP-1 is produced almost exclusively in prepro-glucagon neurons in the nucleus of the solitary tract. These neurons innervate energy balance-regulating areas, such as the external lateral parabrachial nucleus (PBNel); essential for induction of anorexia. Using a validated novel IL-6-reporter mouse strain, we investigated the interactions in PBNel between GLP-1, IL-6, and calcitonin gene-related peptide (CGRP, a well-known mediator of anorexia). We show that PBNel GLP-1R-containing cells highly (to about 80%) overlap with IL-6-containing cells on both protein and mRNA level. Intraperitoneal administration of a GLP-1 analogue exendin-4 to mice increased the proportion of IL-6-containing cells in PBNel 3-fold, while there was no effect in the rest of the lateral parabrachial nucleus. In contrast, injections of an anorexigenic peptide growth and differentiation factor 15 (GDF15) markedly increased the proportion of CGRP-containing cells, while IL-6-containing cells were not affected. In summary, GLP-1R are found on IL-6-producing cells in PBNel, and GLP-1R stimulation leads to an increase in the proportion of cells with IL-6-reporter fluorescence, supporting IL-6 mediation of GLP-1 effects on energy balance.

下丘脑与后脑内的白细胞介素-6（Interleukin-6, IL-6）是胰高血糖素样肽-1（glucagon-like peptide-1, GLP-1）受体激动介导体重与摄食抑制的重要下游介导因子。中枢神经系统（Central Nervous System, CNS）来源的GLP-1几乎仅由孤束核内的胰高血糖素原神经元产生，这类神经元可投射至能量平衡调控脑区，如外侧臂旁核外区（external lateral parabrachial nucleus, PBNel），该脑区对于厌食效应的诱导至关重要。本研究采用经过验证的新型IL-6报告基因小鼠品系，探究了外侧臂旁核外区内GLP-1、IL-6与降钙素基因相关肽（calcitonin gene-related peptide, CGRP，一种公认的厌食介导因子）之间的相互作用。研究结果显示，表达GLP-1受体的外侧臂旁核外区细胞，在蛋白与mRNA水平上与表达IL-6的细胞高度重合，重合度约达80%。向小鼠腹腔注射GLP-1类似物艾塞那肽（exendin-4）后，外侧臂旁核外区内表达IL-6的细胞比例升高了3倍，而外侧臂旁核其余区域则无此变化。与之相反，注射厌食肽生长分化因子15（growth and differentiation factor 15, GDF15）可显著升高表达CGRP的细胞比例，但对表达IL-6的细胞无明显影响。综上，外侧臂旁核外区产IL-6的细胞上表达GLP-1受体，且GLP-1受体激动可使表达IL-6报告基因荧光的细胞比例升高，这支持IL-6介导了GLP-1对能量平衡的调控效应。