Biostimulant Properties of Protein Hydrolysates: Recent Advances and Future Challenges.

Over the past decade, plant biostimulants have been increasingly used in agriculture as environment-friendly tools that improve the sustainability and resilience of crop production systems under environmental stresses. Protein hydrolysates (PHs) are a main category of biostimulants produced by chemical or enzymatic hydrolysis of proteins from animal or plant sources. Mostly composed of amino acids and peptides, PHs have a beneficial effect on multiple physiological processes, including photosynthetic activity, nutrient assimilation and translocation, and also quality parameters. They also seem to have hormone-like activities. Moreover, PHs enhance tolerance to abiotic stresses, notably through the stimulation of protective processes such as cell antioxidant activity and osmotic adjustment. Knowledge on their mode of action, however, is still piecemeal. The aims of this review are as follows: (i) Giving a comprehensive overview of current findings about the hypothetical mechanisms of action of PHs; (ii) Emphasizing the knowledge gaps that deserve to be urgently addressed with a view to efficiently improve the benefits of biostimulants for different plant crops in the context of climate change.

Apparent jejunal amino acid digestibility, gut morphology, and the expression of intestinal amino acid transporters in pigs fed protein or free amino acids.

Dietary amino acids (AA) supplied as protein or in free form are not only digested and absorbed at different rates but can also induce differences in the intestinal physiology of pigs. We compared the apparent jejunal AA digestibility, intestinal morphology, and gene expression of AA transporters of pigs fed diets providing different forms of AA. Thirty growing pigs (33.7 ± 4.1 kg) were fed one of three experimental diets that provided AA either as protein from feather meal (INT), as free AA and small peptides obtained by extensive acid hydrolysis of feathers (HYD), or as a mix of individual purified AA with the same AA profile as HYD (FAA). Pigs were fed the same quantity of feed, energy, and AA. After 14 d, pigs were slaughtered 3 h after feeding a meal with indigestible markers. Digesta and tissue were collected from different sections of the small intestine. Jejunal digesta was used to measure apparent jejunal digestibility of AA. Samples of the duodenum, jejunum, and ileum were used to measure intestinal morphology and the gene expression of intestinal AA transporters. The measured apparent jejunal digestibility of AA of INT was lower compared to HYD and FAA (P < 0.05). The apparent jejunal digestibility of Cys, Gly, His, Met, and Pro was lower for FAA compared to HYD (P < 0.05). This may be due to the small peptides in HYD, which are absorbed faster than individual AA. The villi area in the ileum of HYD fed pigs was the highest (P < 0.05) among the treatments, which may be associated with the reabsorption of endogenous proteins, which occurs mostly in the ileum. In the duodenum, HYD and FAA had lower expression of PepT1 (P < 0.01) probably due to the rapid transit time of digesta compared to INT fed pigs. Pigs fed HYD expressed more ASCT2 (P = 0.02) and CAT-1 (P = 0.04) in the jejunum compared to the pigs fed the other diets. The expression of these transporters along the intestine depended on the relative abundance of readily absorbable dietary AA. Results showed that dietary AA form can have an influence on the morphology and on the expression of different AA transporters along the different sections of the small intestine.

The amino acids (AA) in the diet of pigs are usually supplied as a mix of proteins and free AA. Proteins need to be digested first before their constituent AA become available to the animal. Free AA, together with small peptides, are readily available without the need for digestion. Moreover, the different forms by which AA are supplied may also have an effect on intestinal physiology. In this experiment, pigs were fed different diets with the same AA profile but were provided either as protein, as free AA and small peptides originating from hydrolyzed protein, or as a mix of individual free AA. Results showed that feeding pigs free AA and/or small peptides resulted in higher apparent jejunal digestibility of AA compared to feeding proteins. Furthermore, the apparent jejunal digestibility of the AA of a hydrolyzed protein was higher than that of free AA. Providing diets with readily absorbable AA resulted in a higher surface area for absorption and an increase in the gene expression of AA transporters as opposed to proteins.

Leafamine®, a Free Amino Acid-Rich Biostimulant, Promotes Growth Performance of Deficit-Irrigated Lettuce.

Water deficit causes substantial yield losses that climate change is going to make even more problematic. Sustainable agricultural practices are increasingly developed to improve plant tolerance to abiotic stresses. One innovative solution amongst others is the integration of plant biostimulants in agriculture. In this work, we investigate for the first time the effects of the biostimulant -Leafamine®-a protein hydrolysate on greenhouse lettuce (Lactuca sativa L.) grown under well-watered and water-deficit conditions. We examined the physiological and metabolomic water deficit responses of lettuce treated with Leafamine® (0.585 g/pot) or not. Root application of Leafamine® increased the shoot fresh biomass of both well-watered (+40%) and deficit-irrigated (+20%) lettuce plants because the projected leaf area increased. Our results also indicate that Leafamine® application could adjust the nitrogen metabolism by enhancing the total nitrogen content, amino acid (proline) contents and the total protein level in lettuce leaves, irrespective of the water condition. Osmolytes such as soluble sugars and polyols, also increased in Leafamine®-treated lettuce. Our findings suggest that the protective effect of Leafamine is a widespread change in plant metabolism and could involve ABA, putrescine and raffinose.

The effects of the oral supplementation of L-Cystine associated with reduced L-Glutathione-GSH on human skin pigmentation: a randomized, double-blinded, benchmark- and placebo-controlled clinical trial.

BACKGROUND: Glutathione has become a potential skin-lightening ingredient after the discovery of its anti-melanogenic properties. Various mechanisms of action have been considered to explain this property, one of them being the skewing of the melanin synthesis pathway toward the production of lighter pheomelanin instead of darker eumelanin, consequently producing a lightening effect. AIMS: To evaluate the skin lightening and anti-dark spot effects of oral supplementation with L-Cystine associated with L-Glutathione as compared to placebo and benchmark. METHODS: Effects of this L-Cystine-L-Glutathione oral combination were investigated in a 12-week randomized, double-blind, parallel-group, benchmark- and placebo-controlled trial involving 124 Asian female subjects. Women were randomly allocated into 4 equal groups (500 mg L-Cystine and 250 mg L-Glutathione, 250 mg reduced L-Glutathione, 500 mg L-Cystine, or a placebo, daily). Skin color was measured at baseline, after 6 and 12 weeks by spectrophotometry. Size and color of facial dark spots were determined from digital photographs. RESULTS: A significant skin lightening was observed after 12 weeks of oral supplementation with L-Cystine associated with L-Glutathione. This combination also induced a significant reduction in the size of facial dark spots after 6 and 12 weeks. It is noteworthy that the observed effects were not only significantly better than those obtained with placebo, but also with L-Cystine alone or L-Glutathione alone. CONCLUSION: The daily oral administration of 500 mg L-Cystine and 250 mg L-Glutathione during 12 weeks was a safe treatment to effectively lighten the skin and reduce the size of facial dark spots of Asian women.

Novel dietary strategies can improve the outcome of weight loss programmes in obese client-owned cats.

A randomised, single-blinded, positively controlled, field trial for weight loss in obese client-owned cats was undertaken to look at novel diets and dietary strategies that could improve owner compliance and, therefore, success of feline weight loss programmes. Three dietary strategies were evaluated: strategy A used a novel dry high fibre ration; strategy B used ready-prepared portions of dry and moist food; strategy C used an existing commercial dry high fibre ration fed with a measuring cup. Cats were assessed at weeks 4, 12 and 20, and adjustments to the energy allocation made if required. Mean weight loss at 20 weeks (A: 11.0+/-1.3%, B: 10.9+/-1.2%, C: 11.9+/-1.7%) and mean energy allocation (A: 31.0, B: 28.5 and C: 32.2 kcal/kg of target body weight/day) were similar amongst strategies. However, owners' subjective hunger score was significantly (P<0.001) higher with strategy C than with strategies A and B. Further, owner satisfaction was lowest with strategy C, and more owners also regarded food allowance as insufficient with this strategy. Novel diets and feeding strategies may improve outcome in feline weight loss programmes.

A high-protein, high-fiber diet designed for weight loss improves satiety in dogs.

BACKGROUND: Weight-loss programs for dogs are often hampered by increased begging and scavenging behavior that ensues when food intake is restricted. HYPOTHESIS: A diet formulated to contain a high content of both protein and fiber is more satiating than diets that contain only high fiber or high protein. ANIMALS: Six entire female adult dogs (2 Shetland Sheepdogs, 2 Brittany Spaniels, 2 Labrador Retrievers) participated in the satiety studies; 105 adult female dogs of various breeds and ages were used for the palatability studies. METHODS: Three diets (high protein [103 g/1,000 kcal] high fiber [60 g/1,000 kcal] [HPHF]; high protein [104 g/1,000 kcal] moderate fiber [35 g/1,000 kcal] [HP]; moderate protein [86 g/1,000 kcal] high fiber [87 g/1,000 kcal] [HF]) were tested. Voluntary food intake was measured in 5 sequential crossover studies, and palatability was assessed with food preference tests. RESULTS: Protein digestibility was significantly lower for HF (mean +/- SD; 77.7% +/- 2.52%) than for both HPHF (81.1% +/- 0.96%) and HP (81.1% +/- 1.65%) (P < .001). Short-term food intake (food ingested when offered for 15 minutes every hour for 4 hours) was lower for HPHF than for both HP and HF (P = .038). Medium-term intake (food ingested when offered 3 hours after first meal) was lower for both HPHF (27 +/- 22.2 kcal/kg(0.73)) and HF (41 +/- 6.8 kcal/kg(0.73)) than for HP (57 +/- 18.8 kcal/kg(0.73)) (P = .041). Voluntary food intake 3 hours after feeding a restricted meal (25% daily maintenance energy requirements) was significantly lower on the HPHF diet than on either the HP (-51%, P = .0051) or HF (-47%, P = .014) diets. However, there was no significant difference between the energy intake on the HP and HF diets (7%, P = .37). The HPHF and HP diets had equivalent palatability, and both were more palatable than the HF diet (P < .001). CONCLUSIONS AND CLINICAL IMPORTANCE: The HPHF diet had a satiating effect as evidenced by reduced voluntary intake compared with HP and HF diets, and has the potential to lead to greater compliance in weight-loss programs.

Effects of dietary fat and energy on body weight and composition after gonadectomy in cats.

OBJECTIVE: To evaluate the effect of dietary fat and energy density on body weight gain, body composition, and total energy expenditure (TEE) in neutered and sexually intact cats. ANIMALS: 12 male and 12 female cats PROCEDURE: Male cats were castrated (castrated male [CM]) or underwent no surgical procedure (sexually intact male [IM]). Female cats underwent ovariectomy (spayed female [SF]) or laparotomy and ligation of both uterine tubes without ovary removal (sexually intact female [IF]). Cats were fed either the low-fat (LF) or high-fat (HF) diet for 26 weeks, with the final allocation consisting of 8 groups: IF-LF IF-HE SF-LF, SF-HF IM-LF, IM-HF, CM-LF, and CM-HF. Mean food intake for each group was recorded daily, and body weight was monitored weekly throughout the study. Body composition and TEE were measured before surgery in week 0 and at the end of the study (week 26) by isotope dilution (double-labelled water). RESULTS: N eutered cats gained significantly more body fat and body weight (53.80+/-5.79%) than sexually intact cats (27.11+/-5.79%) during the study. Body weight gain of neutered cats fed the HF diet was greater than those fed the LF diet. Following correction for body composition, TEE was similar in all groups and no pattern towards increased food intake was evident. CONCLUSIONS AND CLINICAL RELEVANCE: Weight gain in neutered cats was decreased by feeding an LF, low energy-dense diet. To prevent weight gain in cats after neutering, a suitable LF diet should be fed in carefully controlled meals rather than ad libitum.