Four novel sleep-promoting peptides screened and identified from bovine casein hydrolysates using a patch-clamp model in vitro and Caenorhabditis elegans in vivo.

Bovine casein hydrolysates (CHs) have demonstrated sleep-promoting activities. However, only few peptides were identified from CHs with sleep-promoting effects. In this work, an in vitro model based on the electrophysiology of brain neurons was established for the evaluation of sleep-promoting effects. Based on this model, four novel peptides were systematically separated from CH. Compared with the control group, the action potential (AP) inhibitory rate of four peptides increased by 38.63%, 340.93%, 233.28%, and 900%, respectively, and the membrane potential (MP) change rate of four peptides increased by 319.78%, 503.09%, 381.22%, and 547.10%, respectively. These results suggested that four peptides have sleep-promoting activities. Furthermore, Caenorhabditis elegans (C. elegans) sleep behavior results indicated that all the four peptides could significantly increase the total sleep duration, the motionless sleep duration of C. elegans, implying that these four peptides can significantly improve sleep. The LC-MS/MS results showed that the primary structures of these novel peptides were HQGLPQEVLNENLLR (αs1-CN, f8-22), YKVPQLEIVPNSAEER (αs1-CN, f104-119), HPIKHQGLPQEVLNENLLR (αs1-CN, f4-22), and VPQLEIVPNSAEER (αs1-CN, f106-119). Overall, this study revealed that the four novel sleep-promoting peptides identified were strong candidates as potential functional ingredients in the development of sleep-promoting products.

Capsaicin Ameliorates the Redox Imbalance and Glucose Metabolism Disorder in an Insulin-Resistance Model via Circadian Clock-Related Mechanisms.

Circadian rhythms are closely associated with metabolic homeostasis. Metabolic disorders can be alleviated by many bioactive components through controlling of clock gene expressions. Capsaicin has been demonstrated with many beneficial effects including anti-obesity and anti-insulin resistance activities, yet whether the rhythmic expression of circadian clock genes are involved in the regulation of redox imbalance and glucose metabolism disorder by capsaicin remains unclear. In this work, the insulin resistance was induced in HepG2 cells by treatment of glucosamine. Glucose uptake levels, reactive oxygen species, H2O2 production, and mitochondrial membrane potential (MMP) were measured with/without capsaicin cotreatment. The mRNA and protein expressions of core circadian clock genes were evaluated by RT-qPCR and western blot analysis. Our study revealed that circadian misalignment could be ameliorated by capsaicin. The glucosamine-induced cellular redox imbalance and glucose metabolism disorder were ameliorated by capsaicin in a Bmal1-dependent manner.