In the past, numerous studies revealed that supplementation with
carnitine has multiple effects on performance characteristics and gene expression in livestock and model animals. The molecular mechanisms underlying these observations are still largely unknown. Increasing evidence suggests that
microRNAs (
miRNAs), a class of
small non-coding RNA molecules, play an important role in post-transcriptional regulation of gene expression and thereby influencing several physiological and
pathological processes. Based on these findings, the aim of the present study was to investigate the influence of
carnitine supplementation on the
miRNA expression profile in skeletal muscle of obese Zucker rats using
miRNA microarray analysis.
RESULTS: Obese Zucker rats supplemented with
carnitine had higher concentrations of total
carnitine in plasma and muscle than obese control rats (P < 0.05).
miRNA expression profiling in skeletal muscle revealed a subset of 152
miRNAs out of the total number of
miRNAs analysed (259) were identified to be differentially regulated (adjusted P-value < 0.05) by
carnitine supplementation. Compared to the obese control group, 111
miRNAs were up-regulated and 41 down-regulated by
carnitine supplementation (adjusted P-value < 0.05). 14 of these
miRNAs showed a log2 ratio ≥ 0.5 and 7
miRNAs showed a log2 ratio ≤ -0.5 (adjusted P-value < 0.05). After confirmation by qRT-PCR, 11
miRNAs were found to be up-regulated and 6
miRNAs were down-regulated by
carnitine supplementation (P < 0.05). Furthermore, a total of 1,446 target genes within the validated
miRNAs were revealed using combined three bioinformatic algorithms. Analysis of Gene Ontology (GO) categories and KEGG pathways of the predicted targets revealed that
carnitine supplementation regulates
miRNAs that target a large set of genes involved in
protein-localization and -transport, regulation of transcription and
RNA metabolic processes, as well as genes involved in several signal transduction pathways, like
ubiquitin-mediated proteolysis and longterm depression, are targeted by the
miRNAs regulated by
carnitine supplementation.
CONCLUSION: The present study shows for the first time that supplementation of
carnitine affects a large set of
miRNAs in skeletal muscle of obese Zucker rats suggesting a novel mechanism through which
carnitine exerts its multiple effects on gene expression, which were observed during the past.