Perilipin2 down-regulation in β cells impairs insulin secretion under nutritional stress and damages mitochondria

Abstract

Perilipin 2 (PLIN2) is the lipid droplet (LD) protein in beta cells that increases under nutritional stress. Down-regulation of PLIN2 is often sufficient to reduce LD accumulation. To determine whether PLIN2 positively or negatively affects beta cell function under nutritional stress, PLIN2 was down-regulated in mouse beta cells, INS1 cells, and human islet cells. Beta cell specific deletion of PLIN2 in mice on a high fat diet reduced glucose-stimulated insulin secretion (GSIS) in vivo and in vitro. Down-regulation of PLIN2 in INS1 cells blunted GSIS after 24 h incubation with 0.2 mM palmitic acids. Down-regulation of PLIN2 in human pseudoislets cultured at 5.6 mM glucose impaired both phases of GSIS, indicating that PLIN2 is critical for GSIS. Down-regulation of PLIN2 decreased specific OXPHOS proteins in all three models and reduced oxygen consumption rates in INS1 cells and mouse islets. Moreover, we found that PLIN2 deficient INS1 cells increased the distribution of a fluorescent oleic acid analog to mitochondria and showed signs of mitochondrial stress as indicated by susceptibility to fragmentation and alterations of acyl-carnitines and glucose metabolites. Collectively, PLIN2 in beta cells have an important role in preserving insulin secretion, beta cell metabolism and mitochondrial function under nutritional stress.

Lipid droplets protect human β cells from lipotoxic-induced stress and cell identity changes

“…These results are not consistent with the current published work in rodents (24,37). However, they do partly agree with preprint findings in INS-1 cells (41). It is now unclear if this reflects species differences or the methodological approach.…”

“…It is now unclear if this reflects species differences or the methodological approach. Although this recent work had only limited molecular detail in how compromising LD formation negatively impacted β cell function, their physiological results showed that mitochondrial health and activity was negatively impacted in both rodent β cells and human islets (41). Notably, our RNA data also suggests that the integrity of PLIN2KD mitochondria are compromised ( Supp Fig.…”

Utilization of commercial collagens for preparing well-differentiated human beta cells for confocal microscopy

“…Lastly, we tested whether the morphology of two organelles (i.e., mitochondria and LDs) changes in human beta cells on C5533 in response to stimuli known to alter their morphology in a wide range of cells; FCCP is known to cause fragmentation of mitochondria, and nutritional load increases LDs ( 31 , 36 ). Both FCCP and high glucose + OA shortened the mitochondrial length and decreased the form factor in beta cells, providing evidence that both conditions fragment mitochondria in human beta cells in culture and support the utility of the protocol to obtain morphometric data ( Figures 5A–C , Supplementary Figures 3C–F ).…”

“…Briefly, images were converted to binary images of mitochondrial particles and automated morphometry of mitochondrial particles was performed to obtain mitochondrial length and form factor (perimeter 2 /(4π × area)) ( 29 , 30 ). The size and number of LDs were measured as published ( 31 ). The area of beta cells (INS + ) was also obtained by ImageJ/Fiji.…”