Manukyan Levon, Ubhayasekera Sarojini J K A, Bergquist Jonas, Sargsyan Ernest, Bergsten Peter
Department of Medical Cell Biology (L.M., E.S., P.B.), Uppsala University, SE-75123, Uppsala, Sweden; and Analytical Chemistry (S.J.K.A.U., J.B.), Department of Chemistry-Biomedical Center and Science for Life Laboratory, Uppsala University, SE-75123, Uppsala, Sweden.
Endocrinology. 2015 Mar;156(3):802-12. doi: 10.1210/en.2014-1467. Epub 2014 Dec 23.
Prolonged exposure to palmitate impairs β-cell function and mass. One of the proposed mechanisms is alteration in ceramide (Cer) generation. In the present study, exposure to palmitate induced the level of palmitoyl transferase and Cer synthases, enzymes of the Cer de novo and salvage pathways, and doubled total Cer levels, which was associated with decreased insulin secretion and augmented apoptosis in MIN6 cells and human islets. By inhibiting enzymes of the pathways pharmacologically with myriocin (ISP-1) or fumonisin B1 or by small interfering RNA (siRNA), we showed that Cer(14:0), Cer(16:0), Cer(20:1), and Cer(24:0) species, generated by the salvage pathway, are linked to the harmful effect of palmitate on β-cells. Oleate attenuates negative effects of palmitate on β-cells. When oleate was included during culture of MIN6 cells with palmitate, the palmitate-induced up-regulation of the enzymes of the de novo and salvage pathways was prevented resulting in normalized levels of all Cer species except Cer(20:1). Our data suggest that enhanced Cer generation in response to elevated palmitate levels involves both de novo and salvage pathways. However, the negative effects of palmitate on β-cells are attributed to generation of Cer species Cer(14:0), Cer(16:0), and Cer(24:0) via acylation of sphingosine.
长期暴露于棕榈酸会损害β细胞功能和数量。一种提出的机制是神经酰胺（Cer）生成的改变。在本研究中，暴露于棕榈酸会诱导棕榈酰转移酶和Cer合酶的水平升高，这两种酶分别参与Cer从头合成途径和补救途径，并且使总Cer水平增加了一倍，这与MIN6细胞和人胰岛中胰岛素分泌减少及细胞凋亡增加有关。通过用myriocin（ISP-1）或伏马菌素B1进行药理抑制这些途径的酶，或通过小干扰RNA（siRNA），我们发现由补救途径产生的Cer（14:0）、Cer（16:0）、Cer（20:1）和Cer（24:0）种类与棕榈酸对β细胞的有害作用有关。油酸可减轻棕榈酸对β细胞的负面影响。当在MIN6细胞与棕榈酸共同培养期间加入油酸时，棕榈酸诱导的从头合成途径和补救途径的酶上调被阻止，导致除Cer（20:1）外所有Cer种类的水平恢复正常。我们的数据表明，对升高的棕榈酸水平作出反应时，Cer生成的增加涉及从头合成途径和补救途径。然而，棕榈酸对β细胞的负面影响归因于通过鞘氨醇酰化产生的Cer种类Cer（14:0）、Cer（16:0）和Cer（24:0）。
