The role of MTHFDL in mediating intracellular lipogenesis in oleaginous Mortierella alpina.

The oleaginous fungus Mortierella alpina can synthesize a variety of polyunsaturated fatty acids, which are used extensively in industry for the production of arachidonic acid (AA). NADPH is the limiting factor and critical reducing agent in lipid biosynthesis. In the folate cycle, methylenetetrahydrofolate dehydrogenase (MTHFDL) catalyzes the conversion of methylene tetrahydrofolate into 10-formyl-tetrahydrofolate with the reduction of NADP+ to NADPH. MTHFDL RNAi was used to investigate the role of the folate cycle in lipogenesis. Gene knockdown decreased the transcript levels of MTHFDL by about 50 % and attenuated cell fatty acid synthesis. The observation of decreased NADPH levels and downregulated NADPH-producing genes in response to MTHFDL RNAi indicates a novel aspect of the NADPH regulatory mechanism. Thus, our study demonstrates that MTHFDL plays key role in the mediation of NADPH in lipogenesis in M. alpina.

Dietary docosahexaenoic acid plays an opposed role in ferroptotic and non-ferroptotic acute kidney injury.

Ferroptosis due to polyunsaturated fatty acid (PUFA) peroxidation has been implicated in the pathogenesis of acute kidney injury (AKI), suggesting the risk of dietary intake of PUFA for people susceptible to AKI. Clinically, however, in addition to ferroptosis, other mechanisms also contribute to different types of AKI such as inflammation associated necroptosis and pyroptosis. Therefore, the role of PUFA, especially ω3 PUFA which is a common food supplement, in various AKIs deserves further evaluation. In this study, rhabdomyolysis- and folic acid-induced AKI (Rha-AKI and FA-AKI) were established in mice fed with different fatty acids Histology of kidney, blood urea nitrogen and creatinine, lipid peroxidation, and inflammatory factors were examined. Results showed that these two types of AKIs had diametrically different pathogenesis indicated by that ferrostatin-1 (Fer-1), a lipid antioxidant, can attenuate FA-AKI rather than Rha-AKI. Further, dietary DHA (provided by fish oil) reduced tubular injury and renal lesion by inhibiting peroxidation and inflammation in mice with Rha-AKI while increasing cell death, tissue damage, peroxidation and inflammation in mice with FA-AKI. In human renal tubular epithelial cell line HK-2, MTT assay and DHE staining showed that both myoglobin and ferroptosis inducers can cause cell death and oxidative stress. Ferroptosis inducer-induced cell death was promoted by DHA, while such result was not observed in myoglobin-induced cell death when adding DHA. This study illustrates that the mechanisms of AKI might be either ferroptosis dependent or -independent and the deterioration effect of dietary DHA depends on whether ferroptosis is involved.