👤 Jeffrey E Gerst

Infiltration of adipocytes into the pancreatic parenchyma has been linked to impaired insulin secretion in individuals with increased genetic risk of T2D and prediabetic conditions. However, the study of this ectopic fat depot has been limited by the lack of suitable in vitro models. Here, we developed a novel 3D model of functionally mature human pancreatic adipose tissue organoids by aggregating human pancreatic adipose tissue-derived stromal vascular fraction (SVF) cells into organoids and differentiating them over 19 days. These organoids carry biological properties of the in situ pancreatic fat, presenting levels of adipogenic markers comparable to native pancreatic adipocytes and improved lipolytic and anti-lipolytic response compared to conventional 2D cultures. The organoids harbour a small population of immune cells, mimicking in vivo adipose environment. Furthermore, they express GIPR, allowing investigation of incretin effects in pancreatic fat. In accordance, GIP and the dual GLP1R/GIPR agonist tirzepatide stimulate lipolysis but had distinct effects on the expression of proinflammatory cytokines. This novel adipose organoid model is a valuable tool to study the metabolic impact of incretin signalling in pancreatic adipose tissue, revealing potential therapeutic targets of incretins beyond islets. The donor-specific metabolic memory of these organoids enables examination of the pancreatic fat-islet crosstalk in a donor-related metabolic context. Show less

Obesity, especially visceral fat accumulation, increases the risk of type 2 diabetes (T2D). The purpose of this study was to investigate the impact of T2D on the pancreatic fat depot. Pancreatic fat pads from 17 partial pancreatectomized patients (PPP) were collected, pancreatic preadipocytes isolated, and in vitro differentiated. Patients were grouped using HbA1c into normal glucose tolerant (NGT), prediabetic (PD), and T2D. Transcriptome profiles of preadipocytes and adipocytes were assessed by RNAseq. Insulin sensitivity was estimated by quantifying AKT phosphorylation on Western blots. Lipogenic capacity was assessed with oil red O staining, lipolytic activity via fatty acid release. Secreted factors were measured using ELISA. Comparative transcriptome analysis of preadipocytes and adipocytes indicates defective upregulation of genes governing adipogenesis ( Show less

Cdc48/p97 and the ubiquilin family of UBA-UBL proteins are known for their role in the retrotranslocation of damaged proteins from the endoplasmic reticulum. We demonstrate that Cdc48 and the ubiquilin-like proteins in yeast also play a role in the anterograde trafficking of proteins, in this case the vacuolar protease, Cps1. Show less

The human Batten disease gene CLN3 and yeast orthologue BTN1 encode proteins of unclear function. We show that the loss of BTN1 phenocopies that of BTN2, which encodes a retromer accessory protein involved in the retrieval of specific cargo from late endosomes (LEs) to the Golgi. However, Btn1 localizes to Golgi and regulates soluble N-ethyl-maleimide sensitive fusion protein attachment protein receptor (SNARE) function to control retrograde transport. Specifically, BTN1 overexpression and deletion have opposing effects on phosphorylation of the Sed5 target membrane SNARE, on Golgi SNARE assembly, and on Golgi integrity. Although Btn1 does not interact physically with SNAREs, it regulates Sed5 phosphorylation by modulating Yck3, a palmitoylated endosomal kinase. This may involve modification of the Yck3 lipid anchor, as substitution with a transmembrane domain suppresses the deletion of BTN1 and restores trafficking. Correspondingly, deletion of YCK3 mimics that of BTN1 or BTN2 with respect to LE-Golgi retrieval. Thus, Btn1 controls retrograde sorting by regulating SNARE phosphorylation and assembly, a process that may be adversely affected in Batten Disease patients. Show less

Although COPI function on the early secretory pathway in eukaryotes is well established, earlier studies also proposed a nonconventional role for this coat complex in endocytosis in mammalian cells. Here we present results that suggest an involvement for specific COPI subunits in the late steps of endosomal protein sorting in Saccharomyces cerevisiae. First, we found that carboxypeptidase Y (CPY) was partially missorted to the cell surface in certain mutants of the COPIB subcomplex (COPIb; Sec27, Sec28, and possibly Sec33), which indicates an impairment in endosomal transport. Second, integral membrane proteins destined for the vacuolar lumen (i.e., carboxypeptidase S [CPS1]; Fur4, Ste2, and Ste3) accumulated at an aberrant late endosomal compartment in these mutants. The observed phenotypes for COPIb mutants resemble those of class E vacuolar protein sorting (vps) mutants that are impaired in multivesicular body (MVB) protein sorting and biogenesis. Third, we observed physical interactions and colocalization between COPIb subunits and an MVB-associated protein, Vps27. Together, our findings suggest that certain COPI subunits could have a direct role in vacuolar protein sorting to the MVB compartment. Show less