Background: Islamic Ramadan fasting is a holly religious ceremony that has many spiritual benefits. Additionally, it can be considered as the equivalent of calorie restriction that may affects physical health. The results of previous studies revealed that calorie restriction increases the lifespan in laboratory rodents via increases the expression of a histone deacetylase named SIRT1. Additionally, SIRT1 is known for its anti-inflammatory properties.

AIM: The aim of this study was to evaluate the effect of Ramadan fasting on the SIRT1 mRNA expression in healthy men.

Materials and Methods: Totally 43 volunteer men participated in this one-group before and after (self-controlled) study. Two ml blood samples were taken prior to fasting and at the end of the 30^th day of fasting. Routine biochemical factors and SIRT1 mRNA expression analysis were performed.

Results: Cholesterol and Low Density Lipoproteins increased however, High Density Lipoproteins level decreased after Ramadan fasting. The analysis of real-time PCR results revealed that SIRT1 mRNA expression in human peripheral blood mononuclear cells increased 4.63 fold in fasting state in comparison with non-fasting state.

Conclusion: Ramadan fasting have a significant effect on SIRT1 gene expression. Regards to immunosuppressive and anti-inflammatory properties of sirt1, further studies are needed to evaluate the effects of SIRT1 up regulation during Ramadan fasting on the autoimmune and inflammatory diseases.