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Variations in arachidonic and docosahexaenoic acid content in the hepatic tissue of streptozotocin treated rats fed with different n6/n3 ratios

Introduction: Arachidonic (ARA) and docosahexaenoic (DHA) acids regulates important processes such as neurotransmission, cell survival and neuroinflammation. The regulation of bioconversion of PUFA from their precursors involves the activity of desaturase enzymes, elongases and transcription factors1. In insulin dependent diabetes mellitus (IDDM) PUFA bioconversion is significantly altered. Most investigators found in IDDM a decrease in 20:4n6 and/or increase in its precursors (18:2n6 and 20:3n6), and an unusual increase in 22:6n32. The aim of our study was to evaluate the influence of different n6/n3 ratios on hepatic content of ARA and DHA and on desaturase gene expression. Material and Methods: The rats were divided into 5 groups: CON (n6:n3, 7:1) CON-STZ (n6:n3, 7:1 and STZ injection), N3 (n6:n3, 0, 05 and STZ injection), N6 (n6:n3, 60:1 and STZ injection) and DHA (DHA 12% and STZ injection), The rats were made diabetic using intraperitoneal injection of streptozotocin (55 mg/kg body weight). The analysis of fatty acid composition was performed using a Shimadzu GC-MS QP2010 Ultra Gas Chromatograph Mass Spectrometer equipped with capillary column BPX70. The RT-qPCR was performed using a One-Step SYBR PrimeScript RT-PCR Kit II, on a Stratagene MxPro3005 thermocycler. For statistical data analysis, Statistica 2012 was used. Data were compared by analysis of variance and Tukey post hoc test. Results: ARA content was significantly decreased in N3 and DHA groups compared to the CON group. Moreover, ARA precursor, 20:3n6, was significantly increased in all STZ treated groups. In contrast, DHA content was increased in all groups compared to the CON with the exception of the N6 group. RT-qPCR analyses showed downregulation of ∆5 and ∆9 desaturase while ∆6 desaturase was downregulated in the N3 and DHA groups compared to the CON group. Discussion and Conclusions: Decreased expression of ∆5-desaturase in STZ treated rats is evident in increased concentrations of ARA precursor, 20:3n6. Nevertheless, ARA content is decreased only in rats groups fed low n6:n3 ratio diets because high n6:n3 ratio compensates decreased ∆5-desaturase expression. DHA metabolism is more complex and DHA content is maintained or increased even in groups with high n6:n3 ratio.

DHA, EPA, Diabetes, n6/n3 ratio

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