Lack of downstream insulin-mimetic effects of visfatin/eNAMPT on glucose and fatty acid metabolism in skeletal muscles.
OBJECTIVE
Recent studies regarding downstream effects of visfatin/eNAMPT in skeletal muscles have attracted much attention as the previous reports suggested this adipokine may exert insulin-mimetic effects. However, studies in vivo present conflicting data and are still controversial. In this present work, we sought to investigate whether visfatin/eNAMPT is able to reproduce insulin effects on glucose transport and lipid metabolism.


METHODS
We have used isolated skeletal muscles with different fibre type composition (Soleus and EDL) to examine glucose transport, GLUT-4 translocation, phosphorylation of insulin signalling pathway proteins, as well as the key parameters for fatty acid metabolism.


RESULTS
We found that, in vitro exposure to visfatin/eNAMPT increased skeletal muscle glucose transport but only in EDL (+20%) and not in Soleus muscle (+5%). Interestingly, classical insulin signalling pathways were not significantly involved in this process. Concomitantly, visfatin/eNAMPT exerted no significant effects on muscle's fatty acids (FA) metabolism as no change in either palmitate oxidation or esterification was observed. Importantly, combined insulin and visfatin effects were not found, suggesting non-additivity.


CONCLUSIONS
Our data suggest that visfatin/eNAMPT plays a rather limited role in regulating skeletal muscle glucose transport and FA metabolism.
Department of Physiology, Medical University of Bialystok, Poland.
E
E
Harasim
A
A
Chabowski
J
J
Górski
D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000187:drug effects* / Q000378:metabolism*; D054409:Nicotinamide Phosphoribosyltransferase / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects
D005227:Fatty Acids; D051275:Glucose Transporter Type 4; D007328:Insulin; D054409:Nicotinamide Phosphoribosyltransferase; D005947:Glucose