Arachidonic acid induces acetyl-CoA carboxylase 1 expression via activation of CREB1

Moderate levels of dietary arachidonic acid reduced lipid accumulation and tended to inhibit cell cycle progression in the liver of Japanese seabass Lateolabrax japonicus

To investigate the physiological roles of dietary arachidonic acid (ARA) in fish, a feeding trial with Japanese seabass was conducted, followed by a hepatic transcriptome assay. Six experimental diets differing basically in ARA level (0.05%, 0.22%, 0.37%, 0.60%, 1.38% and 2.32% of dry matter) were used in the feeding trial. Liver samples from fish fed diets with 0.05% and 0.37% ARA were subjected to transcriptomic assay, generating a total of 139 differently expressed unigenes, which were primarily enriched in lipid metabolism and cell cycle-related signaling pathways. Then, qRT-PCR validation on lipid metabolism and cell cycle-related genes as well as corresponding enzyme-linked immunosorbent assay of selected proteins were conducted with liver samples from all six groups. Moderated ARA levels reduced lipogenesis and stimulated β-oxidation concurrently, but high ARA levels seemed to affect lipid metabolism in complicated ways. Both gene expression and protein concentration of cell cycle-related proteins were decreased by moderate levels of dietary ARA. The lipid content and fatty acid composition in fish confirmed the transcription and protein concentration results related to lipid metabolism. In conclusion, moderate levels of dietary ARA (0.37% and 0.60%) reduced lipid accumulation and tended to inhibit cell cycle progression in the liver of Japanese seabass.

High-salt intake negatively regulates fat deposition in mouse

High-salt (HS) intake contributes to hypertension and cardiopathy, but the effect of HS on fat deposition is controversial. Feed intake, fat mass, the percentage of abdominal fat, heat production, rate of oxygen consumption and the respiratory exchange ratio of mice on a HS diet were significantly decreased (P < 0.01 or 0.05) compared with mice on a normal-salt (NS) diet. An in vitro experiment with differentiating pre-adipocytes showed reduced fat deposition in the presence of high concentrations of NaCl (>0.05 M). Abdominal fat mRNA profiles and protein measurements showed that 5 known genes involved in lipolysis were up-regulated significantly and 9 genes related to lipogenesis were down-regulated in HS mice. Abundant genes and some proteins (ATP2a1, AGT, and ANGPTL4) related to calcium ion metabolism or the renin-angiotensin system (RAS) were differentially expressed between HS and NS mice. Of special interest, CREB1 phosphorylation (S133 and S142), a key factor involved in calcium signaling and other pathways, was up-regulated in HS mice. By IPA analysis, a network mediated by calcium was established providing the molecular mechanisms underlying the negative effect of HS on fat deposition.

Arachidonic acid has a dominant effect to regulate lipogenic genes in 3T3-L1 adipocytes compared to omega-3 fatty acids

BACKGROUND

The effects of long-chain n-3 and n-6 polyunsaturated fatty acids (PUFA) on the regulation of adipocytes metabolism are well known. These fatty acids are generally consumed together in our diets; however, the metabolic regulation of adipocytes in the presence of these fatty acids when given together is not known.

OBJECTIVE

To investigate the effects of n-3 PUFA and arachidonic acid (AA), an n-6 PUFA, on the regulation of adipogenic and lipogenic genes in mature 3T3-L1 adipocytes.

METHODS

3T3-L1 adipocytes were incubated in the presence or absence of 100 µM of eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA; docosapentaenoic acid, DPA and AA, either alone or AA+n-3 PUFA; control cells received bovine serum albumin alone. The mRNA expression of adipogenic and lipogenic genes was measured. The fatty acid composition of adipocytes was analyzed using gas chromatography.

RESULTS

Individual n-3 PUFA or AA had no effect on the mRNA expression of peroxisome-proliferator-activated receptor-γ; however, AA+EPA and AA+DPA significantly increased (P<0.05) the expression compared to control cells (38 and 42%, respectively). AA and AA+EPA increased the mRNA expression of acetyl-CoA carboxylase 1 (P<0.05). AA treatment decreased the mRNA expression of stearoyl-CoA desaturase (SCD1) (P<0.01), while n-3 PUFA, except EPA, had no effect compared to control cells. AA+DHA and AA+DPA inhibited SCD1 gene expression (P<0.05) suggesting a dominant effect of AA. Fatty acids analysis of adipocytes revealed a higher accretion of AA compared to n-3 PUFA.

CONCLUSIONS

Our findings reveal that AA has a dominant effect on the regulation of lipogenic genes in adipocytes.