Long-term exposure of INS-1 rat insulinoma cells to linoleic acid and glucose in vitro affects cell viability and function through mitochondrial-mediated pathways

Abstract

Obesity with excessive levels of circulating free fatty acids (FFAs) is tightly linked to the incidence of type 2 diabetes. Insulin resistance of peripheral tissues and pancreatic β-cell dysfunction are two major pathological changes in diabetes and both are facilitated by excessive levels of FFAs and/or glucose. To gain insight into the mitochondrial-mediated mechanisms by which long-term exposure of INS-1 cells to excess FFAs causes β-cell dysfunction, the effects of the unsaturated FFA linoleic acid (C 18:2, n-6) on rat insulinoma INS-1 β cells was investigated. INS-1 cells were incubated with 0, 50, 250 or 500 μM linoleic acid/0.5% (w/v) BSA for 48 h under culture conditions of normal (11.1 mM) or high (25 mM) glucose in serum-free RPMI-1640 medium. Cell viability, apoptosis, glucose-stimulated insulin secretion, Bcl-2, and Bax gene expression levels, mitochondrial membrane potential and cytochrome c release were examined. Linoleic acid 500 μM significantly suppressed cell viability and induced apoptosis when administered in 11.1 and 25 mM glucose culture medium. Compared with control, linoleic acid 500 μM significantly increased Bax expression in 25 mM glucose culture medium but not in 11.1 mM glucose culture medium. Linoleic acid also dose-dependently reduced mitochondrial membrane potential (ΔΨm) and significantly promoted cytochrome c release from mitochondria in both 11.1 mM glucose and 25 mM glucose culture medium, further reducing glucose-stimulated insulin secretion, which is dependent on normal mitochondrial function. With the increase in glucose levels in culture medium, INS-1 β-cell insulin secretion function was deteriorated further. The results of this study indicate that chronic exposure to linoleic acid-induced β-cell dysfunction and apoptosis, which involved a mitochondrial-mediated signal pathway, and increased glucose levels enhanced linoleic acid-induced β-cell dysfunction.

Metformin‐induced autophagy and irisin improves INS‐1 cell function and survival in high‐glucose environment via AMPK/SIRT1/PGC‐1α signal pathway

“…In order to explore the effects of different high-glucose cultivation systems and cultivation time on INS-1 cells, we conducted the cultivation of INS-1 cells in high-glucose environment and found that INS-1 cell proliferation was declined with the increase of glucose concentration and the prolongation of culture time. Compared with the normal control group, INS-1 cell proliferation was declined significantly when cultured in the medium containing 33.3 mmol/L glucose for 24 hr, which is also consistent with previous studies (Tuo, Wang, Li, & Chen, 2011).…”

Geldanamycin Derivative Ameliorates High Fat Diet-Induced Renal Failure in Diabetes

“…We noted an imbalance in mitochondrial complex I and III in the renal mitochondria in db/db mice [38], [39]. In cultured cells, linoleic acid and other NEFA has been shown to cause loss of mitochondrial membrane potential, activation of caspase 3, 7, and 9, cytochrome c release and apoptosis, [Ca 2+ ] m efflux and peroxynitrite generation [25], [40]. We provided evidence that the last action of NEFA is mediated by hsp90β1 [26].…”

Forkhead box O1 mediates defects in palmitate-induced insulin granule exocytosis by downregulation of calcium/calmodulin-dependent serine protein kinase expression in INS-1 cells

“…Studies have indicated that abnormal regulation of the insulin synthesis pathway and lipotoxicity generated by diet or NEFA [28,29] could contribute to type 2 diabetes individually or in combination. However, the modulatory mechanisms are still incompletely understood.…”