Expression and Purification of Delta Sleep-Inducing Peptide Fused with Protein Transduction Domain and Human Serum Albumin in Pichia pastoris.

BACKGROUND: Sleep is a natural part of every individual's life. Delta sleep-inducing peptide (DSIP) is a nonapeptide that could promote sleep through the induction of slow wave sleep. However, little is known about the pharmacological effect of DSIP on insomnia. OBJECTIVES: The main objective of this study was to analyze the pharmacological effect of DSIP on insomnia. METHODS: We designed a fusion protein containing N-terminal TAT-based transduction domain followed by human serum albumin and DSIP and designated this protein as PHD fusion protein. The PHD fusion protein were expressed in Pichia pastoris and purified. Mice were administered single subcutaneous injections three concentrations of PHD fusion protein (0.5, 1, 2 mg/kg), and the pharmacological activity of PHD fusion protein was studied using classic pentobarbitalinduced sleep test. RESULTS: We expressed the PHD fusion protein in P. pastoris; furthermore, the PHD fused protein was purified to near homogeneity by DEAE Sepharose FF, Phenyl Sepharose HP and Blue Sepharose 6 FF. Our result showed that the increase of pentobarbital-induced hypnotic effect characterized by reducing sleep latency and prolonged sleep duration was observed for increasing concentrations of PHD fusion protein (P<0.05); moreover, different dose of PHD fusion protein could induce the mice to re-sleep in a dose-dependent manner, whereas higher doses of PHD fusion protein (1.0, 2.0 mg/kg) significantly increased the rate of sleep re-onset compared with the vehicle group of mice (P<0.05). CONCLUSION: PHD fusion protein increased the hypnotic effects of pentobarbital by reducing sleep latency and prolonged sleep duration. The present study suggested PHD fusion protein could be a new drug candidate for insomnia.

Delta sleep-inducing peptide and glucocorticoid-induced leucine zipper: potential links between circadian mechanisms and obesity?

As the obesity pandemic has accelerated, investigators have begun to explore alternative mechanisms linking circadian biology and sleep to adipose tissue metabolism and obesity. This manuscript reviews recent findings in murine and human models demonstrating the oscillatory expression of the mRNAs encoding the core circadian regulatory proteins in adipose tissue. Comparative transcriptomic analyses of circadian oscillating genes have been used to identify the 'delta sleep-inducing peptide immunoreactor', also known as 'glucocorticoid-induced leucine zipper (GILZ)', as a potential link in this chain. The GILZ gene has been found to differentially regulate stromal stem cell adipogenic and osteogenic differentiation in a reciprocal manner. In adipose and other metabolically active tissues, the circadian oscillation of GILZ expression is subject to entrainment by external stimuli. Together, these observations suggest that GILZ is an attractive candidate for future studies evaluating the role of circadian mechanisms in adipose tissue physiology and pathology.