In:
Arteriosclerosis, Thrombosis, and Vascular Biology, Ovid Technologies (Wolters Kluwer Health), Vol. 41, No. Suppl_1 ( 2021-09)
Abstract:
Introduction: Apolipoprotein (apo) A-I, the main apolipoprotein constituent of high-density lipoproteins, increases glucose-stimulated insulin secretion (GSIS) and is internalised by β-cells. Cholesterol accumulation in β-cells causes oxidative stress, reduces islet mass and decreases GSIS. ApoA-I increases GSIS in β-cells with high cholesterol levels, but it is not known if this is dependent on apoA-I internalisation. Hypothesis: Internalised apoA-I increases GSIS in β-cells with high cholesterol levels by lowering oxidative stress. Methods: Cholesterol-loaded Ins-1E insulinoma cells were incubated with unlabelled and/or Alexa Fluor488-labelled apoA-I. Alexa488-labelled apoA-I internalisation was quantified by flow cytometry and its intracellular location was determined by confocal microscopy and western blotting. ApoA-I binding partners on the Ins-1E surface were identified by mass spectroscopy. Generation of reactive oxygen species (ROS) in mitochondria was measured using MitoSOX. Results: ApoA-I was internalised by 43.4±3.6% of the Ins-1E cells (apoA-I + cells) in a dose-, time-, temperature- and cholesterol-dependent manner. ApoA-I internalisation was comparable under basal (2.8 mM) and high (25 mM) glucose conditions and mediated by an F 1 -ATPase β-subunit on the Ins-1E cell surface. Cell surface F 1 -ATPase β-subunit and cholesterol levels in apoA-I + Ins-1E cells were 1.7±0.3- and 1.3±0.1-fold higher, respectively, than in Ins-1E cells without internalised apoA-I (apoA-I - cells). Differentially expressed genes in the apoA-I + and apoA-I - Ins-1E cells were related to protein synthesis, the ER stress-related unfolded protein response, insulin secretion and mitochondrial function. Internalised apoA-I localised to mitochondria, lowered the cholesterol-mediated increase in ROS levels, and improved insulin secretion in cholesterol-loaded Ins-1E cells. The ATPase inhibitory factor 1, IF 1 , inhibited apoA-I internalisation and attenuated the apoA-I-mediated decrease of ROS levels in Ins-1E cells and isolated mouse islets. Conclusions: These results establish that internalised apoA-I restores insulin secretion in β-cells with high cholesterol levels by improving mitochondrial redox balance.
Type of Medium:
Online Resource
ISSN:
1079-5642
,
1524-4636
DOI:
10.1161/atvb.41.suppl_1.122
Language:
English
Publisher:
Ovid Technologies (Wolters Kluwer Health)
Publication Date:
2021
detail.hit.zdb_id:
1494427-3
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