Effects of Poly-Gamma-glutamic Acid on Inflammatory and Metabolic Biomarkers in Sleep-Restricted Rats

To evaluate the effects of poly-gamma-glutamic acid (γ-PGA) administration on inflammatory and metabolic biomarkers in sleep-restricted rats, we conducted an experimental study with 30 Wistar male rats aged 10 weeks. These animals were evenly and randomly assigned to each of three groups including a normal control (NC) group, a sleep-restricted control (SRC) group, and a sleep-restricted experimental (SRE) group. During the 1-week period of experiments, saline for the NC group, caffeine (20 mg/kg) for the SRC group, and caffeine (20 mg/kg) and γ-PGA (25 mg/kg) for the SRE group were administered orally using a sonde attached to a syringe. At the end of the experiments, the rats were killed and their serum samples were collected to analyze levels of high-sensitivity C-reactive protein (hs-CRP), as an inflammatory biomarker, and biomarkers of glucose and lipid metabolism including lipoprotein cholesterol fractions, adiponectin, and leptin. The SRE group showed significantly lower hs-CRP levels than the SRC group (p = 0.03), whereas the SRC group tended to have higher levels of total cholesterol than the NC group and the SRE group. In the SRE group, no correlation of serum hs-CRP levels with weight and adiponectin and leptin levels was observed, although a reduction in weight was observed during the experimental period. No significant differences in other biomarkers were observed between groups. Based on these results, we suggest that γ-PGA administration may relieve pro-inflammation directly, not mediated by weight change or metabolic alteration, in sleep-restricted rats.