DGAT1 overexpression in muscle by in vivo DNA electroporation increases intramyocellular lipid content

Berber D. Roorda, Matthijs K.C. Hesselink, Gert Schaart, Esther Moonen-Kornips, Pilar Martinez-Martinez, Mario Lösen, Marc H. De Baets, Ronald P. Mensink, and Patrick Schrauwen

Human Biology, Maastricht University, Maastricht NL-6200 MD

Corresponding Author: p.schrauwen{at}hb.unimaas.nl

In adipose tissue, the microsomal enzyme 1,2-Acyl CoA:diacylglyceroltransferase-1 (DGAT1) plays an important role in triglyceride storage. Because DGAT1 is expressed in skeletal muscle too, we aimed to directly test the effect of DGAT1 on muscular triglyceride storage by over-expressing DGAT1 using in vivo DNA-electroporation. A pcDNA3.1-DGAT1-construct in saline was injected in the left tibialis anterior (TA) muscle of rats, followed by the application of eight transcutaneous pulses, using the contralateral leg as sham-electroporated control. Electroporation of the DGAT1-construct led to significant over-expression of the DGAT1 protein. The functionality of DGAT1 over-expression is underscored by the pronounced, diet-responsive increase in intramyocellular lipid (IMCL) storage. In chow-fed rats, the DGAT1-positive myocytes showed significant higher IMCL content compared to the control leg, which was almost devoid of IMCL (1.99 ± 1.13% vs 0.017 ± 0.014% of total area fraction, p<0.05). High fat feeding increased IMCL levels in both DGAT1-positive and control myocytes, resulting in very high IMCL levels in DGAT1 overexpressing myocytes (4.96 ± 1.47 vs. 0.80 ± 0.14%, p<0.05). Our findings indicate that DGAT1 contributes to the storage of IMCL and that in vivo DNA-electroporation is a promising tool to examine functional consequences of altered gene expression in mature skeletal muscle.

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