Abstract
The synthesis and metabolism of fatty acids in an organism is related to many biological processes and is involved in several diseases. The effects of caffeine on fatty acid synthesis and fat storage in Caenorhabditis elegans and mice were studied. After 6 h of food deprivation, adult C. elegans were treated with 0.1 mg/mL caffeine for 24 h. Quantitative reverse-transcription polymerase chain reaction showed that, among all the genes involved in fat accumulation, the mRNA expression of fat-5 in caffeine-treated C. elegans was significantly higher than that of controls, whereas fat-6 and fat-7 displayed no significant difference. Gas chromatography-mass spectrometry was used to verify the fatty acid composition of C. elegans. Results showed that the ratio of palmitoleic acid (16:1) to that of palmitic acid (16:0) was higher in the caffeine-treated group. Several mutant strains, including those involved in the insulin-like growth factor-1, dopamine, and serotonin pathways, and nuclear hormone receptors (nhrs), were used to assess their necessity to the effects of caffeine. We found that mdt-15 was essential for the effects of caffeine, which was independent of nhr-49 and nhr-80. Caffeine may increase fat-5 expression by acting on mdt-15. In high fat diet (HFD), but not in normal diet (ND) mice, caffeine induced expression of scd1 in both subcutaneous and epididymal white adipose tissue, which was consistent with the palmitoleic/palmitic ratio results by gas chromatograph analysis. In mature adipocytes, caffeine treatment induced both mRNA and protein expression of scd1 and pgc-1α. Overall, our results provided a possible mechanism on how caffeine modulates metabolism homeostasis in vivo.
Highlights
Caffeine is a psychoactive substance used worldwide
We found that caffeine promoted fat storage under fasting conditions by increasing expression of fat-5, which was independent of nuclear hormone receptor (NHR)-49 and NHR-80, but the presence of mdt-15 was necessary
We found that 0.1 mg/mL caffeine increased fat-5 expression by 2.5-fold, whereas 0.1 mg/mL caffeine did not affect the expression of fat-6 or fat-7 significantly (Figure 1B)
Summary
Caffeine is a psychoactive substance used worldwide. Caffeine is present in tea, coffee, chocolate, and soda beverages (Temple, 2009). Due to the correlation between adenosine receptors and the dopamine system, caffeine exerts various physiological, behavioral, and psychological effects (Kudlacek et al, 2003). Habitual intake of caffeine or coffee has been reported to correlate closely with the metabolism of glucose and fat, as reviewed by Heckman et al (2010). Caffeine has been shown to reduce body weight in animals (Zheng et al, 2004) and, in some studies, reduce weight gain in humans (Lopez-Garcia et al, 2006). We aimed to discover the effects of caffeine upon fatty acid synthesis and fat accumulation, and validated these effects in a model organism employed to investigate energy metabolism: Caenorhabditis elegans
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