Previous research has suggested that curcumin potentially induces mitochondrial biogenesis in skeletal muscle via increasing cyclic AMP (cAMP) levels. However, the regulatory mechanisms for this phenomenon remain unknown. The purpose of the present study was to clarify the mechanism by which curcumin activates cAMP-related signalling pathways that upregulate mitochondrial biogenesis and respiration in skeletal muscle.

The effect of curcumin treatment (i.p., 100 mg/kg-BW/d for 28 d) on mitochondrial biogenesis was determined in rats. The effects of curcumin and exercise (swimming for 2 h/d for 3 d) on the cAMP signalling pathway were determined in the absence and presence of phosphodiesterase (PDE) or protein kinase A (PKA) inhibitors. Mitochondrial respiration, citrate synthase (CS) activity, cAMP content and protein expression of cAMP/PKA signalling molecules were analysed.

Curcumin administration increased cytochrome c oxidase subunit (COX-IV) protein expression, and CS and complex I activity, consistent with the induction of mitochondrial biogenesis by curcumin. Mitochondrial respiration was not altered by curcumin treatment. Curcumin and PDE inhibition tended to increase cAMP levels with or without exercise. In addition, exercise increased the phosphorylation of phosphodiesterase 4A (PDE4A), whereas curcumin treatment strongly inhibited PDE4A phosphorylation regardless of exercise. Furthermore, curcumin promoted AMP-activated protein kinase (AMPK) phosphorylation and PPAR gamma coactivator (PGC-1α) deacetylation. Inhibition of PKA abolished the phosphorylation of AMPK.

The present results suggest that curcumin increases cAMP levels via inhibition of PDE4A phosphorylation, which induces mitochondrial biogenesis through a cAMP/PKA/AMPK signalling pathway. Our data also suggest the possibility that curcumin utilises a regulatory mechanism for mitochondrial biogenesis that is distinct from the exercise-induced mechanism in skeletal muscle.

The present study aimed to evaluate the quality of Internet information on the Mediterranean diet and to determine the relationship between the quality of information and the website source.

Website sources were categorized as institutional, pharmaceutical, non-pharmaceutical commercial, charitable, support and alternative medicine. Content quality was evaluated using the DISCERN rating instrument, the Health On the Net Foundation's (HON) code principles, and Journal of the American Medical Association (JAMA) benchmarks. Readability was graded by the Flesch Reading Ease score and Flesch–Kincaid Grade Level score.

The phrase ‘Mediterranean diet’ was entered as a search term into the six most commonly used English-language search engines.

The first thirty websites forthcoming by each engine were examined.

Of the 180 websites identified, thirty-two met our inclusion criteria. Distribution of the website sources was: institutional, n 8 (25 %); non-pharmaceutical commercial, n 12 (38 %); and support, n 12 (38 %). As evaluated by the DISCERN, thirty-one of the thirty-two websites were rated as fair to very poor. Non-pharmaceutical commercial sites scored significantly lower than institutional and support sites (P = 0·002). The mean Flesch Reading Ease score and mean Flesch–Kincaid Grade Level were 55·9 (fairly difficult) and 7·2, respectively. The Flesch–Kincaid Grade Level score determines the difficulty of material by measuring the length of words and sentences and converting the results into a grade level ranging from 0 to 12 (US grade level).

Due to the poor quality of website information on the Mediterranean diet, patients or consumers who are interested in the Mediterranean diet should get advice from physicians or dietitians.