Identification of Rubisco anxiolytic-like peptides (rALPs) by comprehensive analysis of spinach green leaf protein digest

Natural Products From Plants Targeting Leptin Resistance for the Future Development of Anti-Obesity Agents

Obesity is a serious health threat, which has affected 16% of adults globally in 2022 and shows a trend toward youthfulness. Leptin, as a regulator of body weight, can suppress appetite and promote energy expenditure, making it potential in obesity treatment. Nevertheless, with the progress of relevant research, it is worth noting that monotherapy with leptin is not an effective strategy since most obese individuals are hyperleptinemic and resistant to leptin, where high levels of leptin fail to exert its weight-loss effects. Therefore, the potential to unlock the weight-loss properties of leptin using pharmacology to improve resistance has provided a new direction for this field. However, most synthetic medicines have retreated from the market due to their undesirable side effects, while natural products are increasingly sought after for drug development due to their minimal side effects. Indeed, natural products are ideal alternatives to oral synthetic agents since a growing body of research has demonstrated their desirable effects on improving leptin resistance through potential therapeutic targets like the JAK2/STAT3 signaling pathway, protein tyrosine phosphatase 1B, the exchange proteins directly activated by cAMP/Ras-related protein 1 signaling pathway, endoplasmic reticulum stress, pro-opiomelanocortin gene, and leptin levels. This review outlines natural products that can improve leptin resistance by inhibiting or activating these targets and evaluates their efficacy in experiments and human clinical trials, offering insights for the development of anti-obesity agents. However, more high-quality clinical research is necessary to validate these findings, as current clinical evidence is constrained by heterogeneity and small sample sizes.

Ovomemolins: Egg-derived peptides that improved cognitive decline after oral administration in mice

Eggs not only contain all the molecules necessary to nurture new life but are also rich in nutrients such as high-quality protein. For example, epidemiologic studies have shown that egg intake is positively correlated with cognitive function. Thus, we specifically examined the effect of ovalbumin, a major protein present in egg whites, on cognitive function. First, we found that an orally administered enzymatic digest of ovalbumin improves cognitive function in mice fed a high-fat diet. Then, we narrowed down candidate peptides based on the prediction of peptide production according to enzyme-substrate specificity and comprehensive peptide analysis of the digest. We found that three peptides, namely ILPEY, LYRGGLEP, and ILELP, improve cognitive function after oral administration. We also showed that ILPEY, LYRGGLEP, and ILELP were present in the digest and named them ovomemolins A (OMA), B, and C, respectively. Notably, ovomemolins are the first peptides derived from egg whites that have been shown to improve cognitive function. The cognitive improvement induced by OMA, the most abundant of the peptides in the digest, was inhibited by methyllycaconitine, an antagonist of α7nAChR, which is known to be related to memory. These results suggest that OMA improves cognitive function through the acetylcholine system. After OMA administration, brain-derived neurotrophic factor (BDNF) mRNA expression and the number of 5-bromo-2'-deoxyuridine-positive cells suggested that OMA increases hippocampal BDNF expression and neurogenesis.

Efficacy of a fish hydrolysate supplement on sleep quality: A randomized, double-blind, placebo-controlled, crossover clinical trial

BACKGROUND & AIMS

Sleep disturbances are widespread in modern societies and linked to a variety of diseases, creating an urgent need for the development of products that help combat sleep difficulties. One suitable nutritional supplement may be a fish hydrolysate composed of low molecular weight peptides.

METHODS

This two-arm, double-blind, randomized, placebo-controlled crossover study investigated the effect of a 4-week fish hydrolysate intervention on sleep in a healthy German population reporting poor sleep quality, assessed with the Pittsburgh Sleep Quality Index (PSQI). Further sleep parameters were measured using an online diary and a wrist wearable device. Additionally, questionnaires related to stress, anxiety, depression, and well-being were evaluated and salivary cortisol and product satisfaction were assessed.

RESULTS

The 4-week fish hydrolysate supplementation significantly improved subjective sleep quality measured with the PSQI-score (p = .002). Moreover, individuals reported improvements in sleep efficacy and a reduction in sleep disturbances and daytime sleepiness during fish hydrolysate intake (p = .013, p = .046, p = .004 respectively), but not during placebo phase (all p > .05). No significant intra-individual differences were found between fish hydrolysate and placebo supplementation (p > .05).

CONCLUSIONS

Although no significant intra-individual differences were found between fish hydrolysate and placebo supplementation, the significant improvement in subjective sleep quality from baseline to treatment phase suggests that fish hydrolysate is a safe nutritional supplement to support individuals with self-reported sleep problems.

CLINICAL TRIAL REGISTRATION

The study is registered at ClinicalTrials.gov with the Identifier NCT04983355.

Plant Protein-Derived Active Peptides: A Comprehensive Review

Active peptides are a class of physiologically active protein fragments, which can be prepared from different sources. In the past few decades, the production of peptides with various effects from different plant proteins continues to receive academic attention. With advances in extraction, purification, and characterization techniques, plant protein-derived active peptides continue to be discovered. They have been proven to have various functional activities such as antioxidant, antihypertensive, immunomodulatory, antimicrobial, anti-inflammatory, antidiabetic, antithrombotic, and so on. In this review, we searched Web of Science and China National Knowledge Infrastructure for relevant articles published in recent years. There are 184 articles included in this manuscript. The current status of plant protein-derived active peptides is systematically introduced, including their sources, preparation, purification and identification methods, physiological activities, and applications in the food industry. Special emphasis has been placed on the problems of active peptide exploration and the future trend. Based on these, it is expected to provide theoretical reference for the further exploitation of plant protein-derived active peptides, and promote the healthy and rapid development of active peptide industry.

Rice Endoplasmic Protein-Derived Peptides, Rice-Ghretropins A and B, Stimulate Ghrelin Release in MGN3-1 Cells and Increase Plasma Acylated Ghrelin and Food Intake in Mice

In this study, we demonstrated that novel rice-derived bioactive peptides promote the secretion of ghrelin, an endogenous orexigenic hormone secreted from the stomach. The enzymatic digest of rice endosperm protein with subtilisin, a microorganism-derived enzyme, stimulated acylated ghrelin secretion in the ghrelin-releasing cell line MGN3-1 and increased food intake after oral administration in mice. By performing a comprehensive analysis based on structure-activity relationships, we selected candidate peptides from over 30,000 peptides in the rice digest. Among them, we found that QAFEPIRSV and TNPWHSPRQGSF, corresponding to the amino acid sequence of the rice endoplasmic proteins glutelin A1 or A2(52-60) and B1 or B2(31-42), respectively, stimulated acylated ghrelin release in MGN3-1 cells. We named them rice-ghretropins A and B. Pyroglutamate formation of rice-ghretropin A, [pyr¹]-rice-ghretropin A, also promoted ghrelin secretion. Furthermore, oral administration of rice-ghretropins increased food intake, plasma ghrelin concentration, and small intestinal transit in mice. In addition, the subtilisin digest of the rice protein significantly increased food intake for 4 h in 9 month-old (control: 0.61 ± 0.049 g; digest: 0.83 ± 0.059 g) and 24 month-old mice (control: 0.52 ± 0.067 g; digest: 1.01 ± 0.064 g). In summary, we found that novel bioactive peptides, namely, rice-ghretropins, from the enzymatic digest of rice endosperm stimulated acylated ghrelin secretion and increased food intake. This is the first report of rice-derived exogenous bioactive peptides that increase acylated ghrelin secretion.

An orally active plant Rubisco-derived peptide increases neuronal leptin responsiveness

Nutrient excess, such as the intake of a high-fat diet, reduces hypothalamic responses to exogenously administered leptin and induces dietary obesity; however, orally active components that attenuate neural leptin dysregulation have yet to be identified. We herein demonstrated that YHIEPV, derived from the pepsin-pancreatin digestion of the green leaf protein Rubisco, increased the leptin-induced phosphorylation of STAT3 in ex vivo hypothalamic slice cultures. We also showed that YHIEPV mitigated palmitic acid-induced decreases in leptin responsiveness. Furthermore, orally administered YHIEPV promoted leptin-induced reductions in body weight and food intake in obese mice. In addition, dietary-induced body weight gain was significantly less in mice orally or centrally administered YHIEPV daily than in saline-control mice. Cellular leptin sensitivity and the levels of proinflammatory-related factors, such as IL1β and Socs-3, in the hypothalamus of obese mice were also restored by YHIEPV. YHIEPV blocked cellular leptin resistance induced by forskolin, which activates Epac-Rap1 signaling, and reduced the level of the GTP-bound active form of Rap1 in the brains of obese mice. Collectively, the present results demonstrated that the orally active peptide YHIEPV derived from a major green leaf protein increased neural leptin responsiveness and reduced body weight gain in mice with dietary obesity.

Appetite regulation by plant-derived bioactive peptides for promoting health

Appetite is closely regulated not only by gut hormonal and neuronal peptides but also by exogenous peptides derived from food proteins. Food proteins are now recognized to contain many thousands of bioactive compounds that provide additional health benefits beyond their nutritional effects. Bioactive peptides are beneficial to the life and/or to regulate physiological functions. Although animal protein products have been widely applied in the food industry, exploring the possibilities of developing functional foods based on plant protein-derived peptides is considered attractive for achieving sustainable development goals. In addition, peptides from plant proteins have the potential to treat numerous diseases or risk factors and may therefore facilitate a healthy life expectancy. In this review, we discuss the identified plant-based bioactive peptides and their appetite regulating effects. Plant-based bioactive peptides may provide new opportunities to discover novel approaches that can improve and prevent diseases in a sustainable environment.

Neuromodulatory peptides: Orally active anxiolytic-like and antidepressant-like peptides derived from dietary plant proteins

Mental disorders are a severe health problem, and the number of patients is growing worldwide. Increased anxiety and decreased motivation due to excessive mental stress further accelerated the severity of the problem. Enzymatic digestion of food proteins produces bioactive peptides with various physiological functions, some of which exhibit neuromodulatory effects with oral administration. Recently, studies reported that some peptides produced from plant proteins such as soybeans, leaves, and grains exhibit emotional regulatory functions such as strong anxiolytic-like and antidepressant-like effects comparable to pharmaceuticals. Conventionally, researchers investigated bioactive peptides by fractionation of protein hydrolysates and structure-activity relationship. As a novel methodology for analyzing bioactive peptides, the information obtained by peptidomics simultaneous analysis of the digested fractions of proteins using mass spectrometry has been effectively utilized. Some small-sized peptides such as dipeptides and tripeptides released food-derived proteins show emotional regulating effects. Moreover, some middle-sized peptides produced after intestinal digestion may exhibit the emotional regulating effect via the vagus nerve, and the importance of the gut-brain axis is also focused. As the central mechanism of emotional regulation, it has been found that these plant-derived peptides regulated monoamine neurotransmitter signaling and hippocampal neurogenesis.

Isolation and functionalities of bioactive peptides from fruits and vegetables: A reviews

Bioactive peptides have recently gained more research attention as potential therapies for the management of bodily disorders and metabolic syndromes of delicate health importance. On another note, there is a rising trend on a global scale for the consumption and adoption of fruit and vegetables for the fulfilment of dietary and health needs. Furthermore, fruits and vegetables are being more studied as base materials for the isolation of biologically functional components and accordingly, they have been investigated for their concomitant bioactive peptides. This review focuses on isolation and bio-functional properties of bioactive peptides from fruits and vegetables. This manuscript is potential in serving as a material collection for fundamental consultancy on peptides derived from fruits and vegetables, and further canvasses the necessitation for the use of these food materials as primal matter for such.

Plant-Derived Antioxidants Protect the Nervous System From Aging by Inhibiting Oxidative Stress

Alzheimer's disease (AD) has become a major disease contributing to human death and is thought to be closely related to the aging process. The rich antioxidant substances in plants have been shown to play a role in delaying aging, and in recent years, significant research has focused on also examining their potential role in AD onset and progression. Many plant-derived antioxidant research studies have provided insights for the future treatment and prevention of AD. This article reviews various types of plant-derived antioxidants with anti-aging effects on neurons. Also it distinguishes the different types of active substances that exhibit different degrees of protection for the nervous system and summarizes the mechanism thereof. Plant-derived antioxidants with neuroprotective functions can protect various components of the nervous system in a variety of ways and can have a positive impact on interventions to prevent and alleviate AD. Furthermore, when considering neuroprotective agents, glial cells also contribute to the defense of the nervous system and should not be ignored.

A milk-derived pentapeptide reduces blood pressure in advanced hypertension in a CCK system-dependent manner

Orally administered KFWGK exhibits potent and long-lasting antihypertensive effects in SHR with advanced hypertension, at which known hypotensive drugs are sometimes less effective. The minimum effective dose of KFWGK was 5 μg kg⁻¹.

Ser-Tyr and Asn-Ala, vasorelaxing dipeptides found by comprehensive screening, reduce blood pressure via different age-dependent mechanisms

To understand the changes in physiological responses due to aging, a number of bioactive probes based on different signal transduction pathways are necessary. In this study, we comprehensively and systematically investigated changes in blood vessel function with age using a 336-dipeptide library.

In the early stage of hypertension, the most potent vasorelaxant dipeptide was Ser-Tyr (SY) in the mesenteric artery isolated from spontaneously hypertensive rats (SHR). SY-induced vasorelaxation and anti-hypertensive effects were blocked by L-NAME, an inhibitor of nitric oxide synthase (NOS), suggesting that SY activates the NO system. On the other hand, the patterns of dipeptides with vasorelaxation activity in early and advanced stages of hypertension were different. In the advanced stage, the most potent vasorelaxing dipeptide was Asn-Ala (NA). Orally administered NA (1.5 mg/kg) reduced the blood pressure in the advanced stage, at which drugs were sometimes less effective, and the anti-hypertensive effects lasted for 6 hr. The NA-induced vasorelaxation and anti-hypertensive activity was blocked by lorglumide, an antagonist of the cholecystokinin CCK₁ receptor, suggesting that NA activated the CCK system.

Taken together, in the early and advanced stages of hypertension, SY and NA exhibited vasorelaxing and anti-hypertensive effects via the NO and CCK systems, respectively.