Docosahexaenoic acid increases cellular adiponectin mRNA and secreted adiponectin protein, as well as PPARg mRNA, in 3T3-L1 adipocytes Richard T. Oster, Justine M. Tishinsky, Zongfei Yuan, and Lindsay E. Robinson Abstract: Adiponectin, a protein secreted from adipose tissue, has been shown to have anti-diabetic and anti-inflammatory effects, but its regulation is not completely understood. Long-chain n-3 fatty acids eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA) may be involved in adiponectin regulation as they are potential ligands for per- oxisome proliferator-activated receptor-g (PPARg), a key transcription factor for the adiponectin gene. To examine this, 3T3-L1 adipocytes were incubated with 125 mmolÁL –1 EPA, DHA, palmitic, or oleic acids complexed to albumin, or with albumin alone (control) for 24 h. Adipocytes were also incubated for 24 h with EPA and DHA plus bisphenol-A-diglycidyl ether (BADGE), a PPARg antagonist. Both EPA and DHA increased (p < 0.05) secreted adiponectin concentration com- pared with the control (44% and 102%, respectively), but did not affect cellular adiponectin protein content. Incubation with BADGE and DHA inhibited increases in secreted adiponectin protein, suggesting that DHA may act through a PPARg-dependent mechanism. However, BADGE had no effect on EPA-induced increases in secreted adiponectin protein. Only DHA enhanced (p < 0.05) PPARg and adiponectin mRNA expression compared wtih the control. Our results demon- strate that DHA increases cellular adiponectin mRNA and secreted adiponectin protein in 3T3-L1 adipocytes, possibly by a mechanism involving PPARg. Moreover, DHA increased adiponectin concentration to a greater extent (40% more, p < 0.05) compared with EPA, emphasizing the need to consider the independent actions of EPA and DHA in adipocytes. Key words: n-3 fatty acids, docosahexaenoic acid, eicosapentaenoic acid, 3T3-L1 adipocytes, adiponectin, peroxisome proliferator-activated receptor-g. Re ´sume ´: L’adiponectine est une prote ´ine se ´cre ´te ´e par le tissu adipeux reconnue pour ses proprie ´te ´s antidiabe ´toge `nes et anti-in- flammatoires, mais dont la re ´gulation n’est pas totalement e ´lucide ´e. L’acide eicosapentanoı ¨que (20:5n-3; EPA) et l’acide docasa- hexanoı ¨que (22:6n-3; DHA), des acides gras n-3 a ` longues chaı ˆnes pourraient e ˆtre implique ´s dans la re ´gulation de l’adiponectine, car ce sont des ligands potentiels des re ´cepteurs g au facteur active ´ de prolife ´ration des peroxysomes (PPARg), facteur cle ´ dans la transcription du ge `ne de l’adiponectine. Pour analyser cette the `se, on incube durant 24 h des adipocytes 3T3-L1 en pre ´sence de 125 mmolÁL –1 d’EPA, de DHA, d’acide palmitique ou ole ´ique combine ´a ` de l’albumine ou seulement en pre ´sence d’albumine (contro ˆle). On incube aussi durant 24 h les adipocytes en pre ´sence d’EPA et de DHA et d’e ´ther de diglycidyle du bisphe ´nol A (BADGE), un antagoniste du PPARg. Comparativement aux valeurs de contro ˆle, l’EPA et le DHA e ´le `vent de 44 % et 102 % res- pectivement la concentration d’adiponectine se ´cre ´te ´e (p < 0,05), mais n’ont pas d’effet sur le contenu cellulaire d’adiponectine. L’incubation avec le BADGE et le DHA inhibe l’augmentation de se ´cre ´tion d’adiponectine, sugge ´rant ainsi que le DHA agirait par l’entremise d’un me ´canisme de ´pendant du PPARg. Par contre, le BADGE n’affecte pas l’augmentation de la se ´cre ´tion d’adi- ponectine suscite ´ par l’EPA. Comparativement aux valeurs de contro ˆle, seul le DHA ame ´liore (p < 0,05) l’expression de l’ARNm de l’adiponectine et du PPARg. Nos observations de ´montrent que le DHA augmente la concentration cellulaire d’ARNm de l’adi- ponectine et la se ´cre ´tion d’adiponectine dans les adipocytes 3T3-L1 probablement par l’entremise d’un me ´canisme impliquant le PPARg. De plus, le DHA e ´le `ve davantage la concentration d’adiponectine (plus de 40 %, p < 0,05) comparativement a ` l’EPA, ce qui indique la ne ´cessite ´ d’analyser inde ´pendamment les actions de l’EPA et du DHA dans les adipocytes. Mots-cle ´s : acides gras n-3, acide docasahexanoı ¨que, acide eicosapentanoı ¨que, adipocytes 3T3-L1, adiponectine, re ´cepteurs g au facteur active ´ de prolife ´ration des peroxysomes. [Traduit par la Re ´daction] Received 10 August 2009. Accepted 18 September 2010. Published on the NRC Research Press Web site at apnm.nrc.ca on 27 November 2010. Abbreviations: BADGE, bisphenol-A-diglycidyl ether; BSA, bovine serum albumin; CVD, cardiovascular disease; EPA, eicosapentaenoic acid; DHA, docosahexaenoic acid; PPARg, peroxisome proliferator-activated receptor-g; PUFA, polyunsaturated fatty acids. R.T. Oster, J.M. Tishinsky, Z. Yuan, and L.E. Robinson. 1 Department of Human Health and Nutritional Sciences, Animal Science and Nutrition Building, University of Guelph, Guelph, ON N1G 2W1, Canada. 1 Corresponding author (e-mail: lrobinso@uoguelph.ca). 783 Appl. Physiol. Nutr. Metab. 35: 783–789 (2010) doi:10.1139/H10-076 Published by NRC Research Press Appl. Physiol. Nutr. Metab. Downloaded from www.nrcresearchpress.com by UNIV GUELPH on 01/24/14 For personal use only.