Normal pregnancy is associated with a rise in insulin secretion, which begins at placental implantation and increases progressively in parallel with placental growth. Following placenta delivery there is a sharp postpartum decline in insulin secretion. Gestational diabetes (GDM),the development of diabetes for the first time during pregnancy, is associated with pancreatic beta-cell dysfunction. Rodent models have been used to elucidate the biological alterations in beta-cells during normal pregnancy. However, these findings have not been investigated in human pregnancy and little is understood about the mechanisms that contribute to beta-cell dysfunction in women with GDM.

From mouse models, it is proposed that lactogenic hormones (prolactin [PRL] and human placental lactogen [hPL]) secreted by the placenta drive beta-cell expansion in normal pregnancy. Lactogenic hormones activate the beta-cell membrane prolactin receptor (PRLR) to increase downstream serotonin production. Serotonin may either increase or decrease beta-cell proliferation, in a receptor-dependent manner: rodent models have shown that activation of the5-hydroxytryptophan receptor 2B (5-HT2B)increases beta-cell proliferation,whilst5-hydroxytryptophan receptor 1d (5-HT1D)receptor activation decreases proliferation. At midgestation,Htr2bmRNA levels are increased in mice, which normalise at the end of gestation, whilstHtr1dexpression is increased at the end of gestation. It is proposed that it is this switch in serotonin receptor expression that contributes to the change in beta-cell mass during and following pregnancy. Preliminary data from our existing nPOD project illustrates that PRLRand5-HT1D receptor expression is increased in3rdtrimesterhuman beta cells in women with normal pregnancy but not in GDM. However, we have further found thatthe5-HT2Breceptor is not detected in normal human pregnancy or GDM at any stage during in gestation. Hence, much is still to be understood regarding pancreatic pathogenic mechanisms in GDM whilst, even in normal pregnancy, mouse models may not fully clarify pregnancy-associated changes in pancreatic biology.

In this study extension, we propose to study the proteomic profile of human islets from women with normal pregnancy and GDM. Towards this, we will isolate human pancreatic islets using laser capture microdissection (LCM) and perform proteomic analysis of the isolated tissue by quantitative liquid chromatography-tandem mass spectrometry (LC-MS/MS) to evaluate differences in islet protein expression and uncover pathways that are altered during normal and GDM pregnancy. This will improve our understanding of the changes in beta-cell biology in normal pregnancy, as well as GDM, and potentially provide valuable insights on whether they may be harnessed as beta-cell regenerative therapies for patients with diabetes.