The monounsaturated fatty acid oleate is the major physiological toxic free fatty acid for human beta cells

Abstract

Free fatty acids (FFAs) can cause glucose intolerance and diabetes. Lipotoxicity to the pancreatic beta cells is considered to be a major underlying cause for this phenomenon. The aim of this study was to analyse the toxicity profile of FFAs in the human EndoC-βH1 beta-cell line and to compare the results with isolated rat and human islets with special reference to the physiologically most prevalent FFAs palmitic acid (PA) and oleic acid (OA). Toxicity after a 2-day incubation with the different FFAs was analysed by the caspase-3 assay and confirmed by the propidium iodide and annexin V staining tests. The long-chain saturated PA (C16:0) and the monounsaturated OA (C18:1) were both toxic to human EndoC-βH1 beta cells and pseudoislets, as well as to rat islets, and, as confirmed in a pilot experiment, also to human islets. Furthermore, OA provided no protection against the toxicity of PA. Likewise, elaidic acid (EA, the trans isomer of OA; trans-OA) was significantly toxic, in contrast to the non-metabolisable analogues methylated PA (MePA) and methylated OA (MeOA). Fatty acids with a chain length < C16 were not toxic in EndoC-βH1 beta cells. Caspase-3 was also activated by linoleic acid (LA)(C18:2) but not by γ-linolenic acid (γ-LNA)(C18:3). Overall, only long-chain FFAs with chain lengths > C14, which generate hydrogen peroxide in the peroxisomal beta-oxidation, were toxic. This conclusion is also supported by the toxicity of the branched-chain FFA pristanic acid, which is exclusively metabolised in the peroxisomal beta-oxidation. The lack of a protective effect of the monounsaturated fatty acid OA has important consequences for a beta-cell protective lipid composition of a diet. A cardioprotective diet with a high OA content does not fulfil this requirement.

Toxicity of fatty acid profiles of popular edible oils in human EndoC-βH1 beta-cells

“…Medium-chain FFAs shorter than C16 are not toxic to EndoC-βH1 beta-cells 7 . In the present study, we demonstrate that a high content of medium-chain FFAs (C8-C14) in compositions with long-chain FFAs mirroring the FFA profile of coconut or palm kernel oil were able to reduce toxicity of these compositions.…”

“…Human EndoC-βH1 beta-cells (ENDOCELLS SARL, Paris, France) were cultured 6 and regularly tested for mycoplasma. Rat pancreatic islets were isolated as described 7 . Fig.…”

Fatty Acid-Stimulated Insulin Secretion vs. Lipotoxicity

“…Another type of experiment is based on a constant FA/albumin and a prolonged (48 h) treatment of the model β-cell lines together with toxicity analyses, based on increased H 2 O 2 generation and/or selected markers of apoptosis. The toxicity profile of FAs was analyzed using rat as well as human cell lines, and isolated rat and human islets [ 49 , 113 , 123 , 124 ]. The choice of cell line is also important, as the very differentiated human β-cell line EndoC-βH1 mimics the in vivo situation, unlike RINm5F and INS1 cells, where unsaturated FAs are poorly metabolized and thus the oleate can antagonize palmitate toxicicty [ 123 ].…”

Na dobre i na złe – czyli rola oddziaływania trzustki, śródbłonka i tkanki tłuszczowej w regulacji funkcjonowania komórek β i rozwoju cukrzycy typu 2 związanej z otyłością

“…The FA mixture that corresponded to the plasma profile of obese individuals with metabolic syndrome was enriched with saturated FAs (16:0, 18:0) and ω6 polyunsaturated FAs (PUFAs), including linoleic acid (LA; 18:2n6), γ-linolenic acid (LNA; 20:3n-6), and AA and had toxic effects on MIN6 cell viability, insulin secretion, and mitochondrial function [55]. Moreover, LA and LNA adversely affected cellular membrane fluidity and integrity in rat RINm5F cells and the human EndoC-βH1 β-cell line [56,57]. PUFAs are the major constituents of membrane phospholipids [58].…”