Study Title:

DHA Boosts Adiponectin Levels

Study Abstract

Adiponectin, made exclusively by adipocytes is a 30 kDa secretory protein assembled post translationally into low molecular weight, middle molecular weight and high molecular weight homo oligomers. PPARgamma ligands thiozolidinediones (TZD) which are widely used in the treatment of type II diabetes, increase adiponectin levels. PPARgamma also has several putative ligands which include fatty acid derivatives. Overnight treatment of rat adipocytes with pioglitazone, docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA) triggered a 2-fold increase in the synthesis and secretion of HMW adiponectin and this increase was blocked by the addition of PPARgamma inhibitor GW9662. Inhibition of glycosylation using 2-2' dipyridyl decreased the synthesis of high molecular weight adiponectin by pioglitazone, EPA and DHA but there was increased secretion of trimeric adiponectin resulting from increased translation. Although pioglitazone, DHA and EPA increased adiponectin synthesis by over 60% there was no increase in total protein synthesis, and there was no corresponding change in adiponectin mRNA expression, indicating the up-regulation of translation. We examined the possibility of transacting factors in the cytoplasmic extracts from adipocytes treated with pioglitazone or DHA. In vitro translation of adiponectin mRNA was inhibited by S-100 fraction, of control adipocytes, and increased by S-100 extracts from adipocytes treated with pioglitazone or DHA. Consistent with this observation both pioglitazone and DHA treatments increased the association of adiponectin mRNA with the heavier polysome fractions. Together, these data suggest that pioglitazone and the fish oils DHA or EPA are PPARgamma agonists in adipocytes with regards to adiponectin expression, and the predominant mode of adiponectin stimulation is via an increase in translation. Key words: adiponectin, PPAR gamma agonists, adipocyte, Translational regulation.

Study Information

Banga A, Unal R, Tripathi P, Pokrovskaya I, Owens RJ, Kern PA, Ranganathan G.
Adiponectin translation is increased by the PPAR{gamma} agonists pioglitazone and {omega}-3 fatty acids.
Am J Physiol Endocrinol Metab.
2008 December
University of Arkansas for Medical Science.

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