Actinidin-Enriched Kiwifruit Concentrate (Kwd+®) Improves Protein Utilization Efficiency and Modulates Body Composition and Muscle Function in a Protein Source-Dependent Manner
Aug 2026· International Journal of Molecular Sciences· Vol 27, pp. 7086· 0 citations· 65 references
Medicine
Abstract
Protein utilization efficiency is a key determinant of metabolic health, body composition, and muscle function, particularly under high-protein dietary conditions and when using plant-based protein sources with lower digestibility. However, the extent to which enhancing early gastric proteolysis translates into improved whole-body protein utilization remains unclear. The present in vivo study investigated whether supplementation with an actinidin-enriched kiwifruit concentrate (Kwd+®) modulates protein utilization efficiency and physiological outcomes under normoproteic and hyperproteic dietary conditions using casein or pea protein as dietary sources. Rats were fed normoproteic casein (NP), high-protein casein (CHP), or high-protein pea (PHP) diets with or without Kwd+® supplementation for 8 weeks. Gastric protein hydrolysis patterns were evaluated by SDS–PAGE, while metabolic outcomes were assessed through body composition, plasma amino acid profiling, skeletal muscle morphology, and contractile function. Kwd+® supplementation enhanced gastric proteolysis in a protein source-dependent manner. Despite the absence of significant changes in circulating amino acid concentrations after multiple comparison correction, Kwd+® improved markers of protein utilization efficiency depending on dietary protein source. In animals fed a high-protein pea diet, supplementation significantly reduced fat mass relative to accumulated protein intake, indicating improved nutrient partitioning. In contrast, in animals fed a high-protein casein diet, Kwd+® increased muscle mass relative to protein intake, suggesting enhanced anabolic efficiency. Under normoproteic conditions, Kwd+® supplementation was associated with an increased muscle fiber cross-sectional area and improved fatigue resistance without alterations in fiber type composition or contractile protein abundance. These findings demonstrate that modulation of early gastric proteolysis through actinidin produces protein source-dependent effects on protein utilization efficiency, nutrient partitioning, and muscle function. This work highlights a novel nutritional strategy to improve metabolic outcomes and muscle performance, particularly in the context of high-protein and plant-based diets.
Simple Summary Goose meat is a valuable source of dietary protein, but improving feed efficiency while maintaining desirable meat characteristics remains a challenge in commercial goose production. Conventional soybean lecithin has limited water dispersibility, which may constrain its nutritional effects. In a 64-day feeding trial, 600 female Jiangnan White geese were assigned to a basal diet, three diets containing 50, 100, or 200 mg/kg hydroxylated lecithin, or a diet containing 100 mg/kg conventional soybean lecithin. Growth performance, serum lipid-related and antioxidant indices, carcass traits, meat quality, flavour-associated components, fatty acid composition, and the expression of selected lipid metabolism-related genes in the liver, breast muscle, and leg muscle were evaluated. Hydroxylated lecithin supplementation was associated with higher final body weight and average daily gain, while the 100 and 200 mg/kg treatments reduced the feed conversion ratio relative to the basal diet. The treatments also altered selected serum indices, muscle shear force, flavour-associated components, and tissue-specific gene expression. The two lecithin sources produced partly distinct response profiles, but neither source showed a uniform advantage across all measured outcomes. These findings provide evidence for further evaluation of hydroxylated lecithin in goose diets, while the underlying mechanisms require direct functional investigation.
Simple Summary Lowering the dietary crude protein (CP) content by 1–4% in finishing pigs, when appropriately paired with restricting amino acids, enhances feed efficiency and decreases nitrogen excretion without negatively affecting performance. Adding 0.05–0.1% N-carbamylglutamate (NCG) to these low-protein diets addresses potential protein deficiencies by promoting arginine synthesis, fostering muscle growth, and improving nitrogen utilization. This study investigated the optimum level of two different crude protein densities (low and high) and dietary N-carbamylglutamate supplementation on finishing pigs’ performance, blood profile, gut health, and meat quality. Low-protein diets (13% CP) improved nitrogen retention, blood parameters (blood urea nitrogen, BUN), and carcass amino acids, while 0.1% NCG supplementation improved gut health, and meat quality in finishing pigs. Lowering protein levels is beneficial for improving nitrogen retention and blood parameters, and supplementing with 0.1% NCG can improve gut health and meat quality. In conclusion, a combination of a low-protein diet (13% CP) and 0.1% NCG supplementation is an effective strategy to improve carcass characteristics, blood parameters, gut health, and nitrogen utilization without detrimental effects on performance in finishing pigs.
Usman Kayode Kolawole, Kyejin Lee, Youngjong Han et al.· Animals· 0 citations
Feather keratin is an abundant but poorly utilized protein resource for animal nutrition due to its highly recalcitrant structure. Here, we investigated whether the food-grade probiotic Bacillus subtilis natto can directly hydrolyze intact chicken feathers and evaluated the resulting fermentation product as a safe and functional feed protein using multidimensional omics. B. subtilis natto efficiently degraded feathers in sterile tap water, accompanied by bacterial proliferation and increased extracellular proteolytic activity. Recombinant nattokinase was produced and purified to support mechanistic interpretation of keratinolysis. The hydrolysate comprised a soluble fraction enriched in free amino acids and short peptides, as well as an insoluble fraction containing keratin-derived nano/microparticles and bacterial cells. Bioinformatic annotation of hydrolysate peptides suggested potential roles in cell-cell junction organization, tight-junction regulation, and diverse transport and metabolic processes. In a 30-day mouse feeding trial, hydrolysate supplementation showed no adverse effects on growth, organ histology, or serum biochemical indices, while elevating IgA. Intestinal transcriptomic and proteomic profiling indicated enhanced mucosal immune programs and barrier-associated pathways. 16S rRNA sequencing further revealed a remodeled gut microbiota characterized by enrichment of multiple probiotic genera, accompanied by altered short-chain fatty acid profiles. Collectively, these data establish a simple probiotic fermentation strategy to valorize feather waste into a biosafe, omics-validated functional feed protein with potential benefits for gut homeostasis.
Yijiao Wen, Jianjun Du, Xuanting Wang et al.· International Journal of Bio...· 0 citations
The objective of this study was to evaluate the effects of low‐protein dietary supplementation with NCG on productivity, egg quality and possible regulatory mechanisms in laying Hens. A total of 150 Beijing Type 2 laying hens at 300 days of age were randomly assigned to five groups: a control group, a low-protein diet group (LP), and three low‐protein diet groups supplemented with 0.06%, 0.12%, or 0.18% NCG. Daily feed intake, Egg number and egg weight were recorded daily on a replicate basis to calculate the egg production rate, average feed intake (ADFI), feed conversion ratio (FCR) and evaluate egg quality. Blood samples were collected from the jugular vein, and the serum was obtained to determine various biochemical parameters using an automatic biochemical analyzer. The protein secretory region of the magnum part of the oviduct was collected and immediately frozen in liquid nitrogen for RNA sequencing analysis. The RNA‐seq results were subsequently validated by real-time quantitative PCR (RT‐qPCR) using Pearson’s correlation analysis. Supplementation with 0.06% and 0.18% NCG in low‐protein diets significantly increased egg weight compared with the LP group (P < 0.05). Albumen height and Haugh unit were significantly increased in the 0.06% NCG group compared with the other groups (P < 0.05). The 0.12% NCG supplementation significantly increased serum BUN content (P < 0.05), whereas the 0.18% NCG supplementation significantly decreased serum phosphorus content (P < 0.05). Serum ALB and NO concentrations were significantly increased in the 0.06% and 0.18% NCG groups compared with the LP group (P < 0.05). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted to identify differentially expressed genes and enriched signaling pathways. The results demonstrated that the genes suppressor of cytokine signaling 3 (SOCS3), integrin subunit alpha 8 (ITGA8), platelet‐derived growth factor receptor alpha (PDGFRA), angiotensin‐converting enzyme (ACE), A disintegrin and metalloproteinase with thrombospondin motifs 1 (ADAMTS‐1), and apolipoprotein L domain containing 1 (APOLD1), which are associated with the PI3K/AKT/mTOR signaling pathway, were regulated by NCG supplementation under low‐protein dietary conditions. In conclusion, supplementation with 0.06% NCG in a low-protein diet improved egg weight and egg quality by regulating protein synthesis and secretion in the magnum part of the hen’s oviduct.
Unknown authors· Frontiers in Cell and Develo...· 0 citations
Fermented liquid feeding (FLF) has been proposed as a nutritional intervention with the potential to influence pork quality, yet its effects on intramuscular fat deposition and muscle lipid composition remain unclear. In this study, pigs were fed a basal dry feed, liquid feed, or FLF regimen for 173 days, and porcine muscle samples were subsequently evaluated for carcass traits, meat quality, lipid composition, and molecular changes associated with lipid deposition. Compared with CON, FLF reduced average backfat thickness, while intramuscular fat and triglyceride contents in the longissimus thoracis muscle were greater than those in CON and LF (p < 0.05). Fatty-acid profiling showed that FLF increased several major fatty acids, including palmitic acid. Metabolomic analysis identified contrast-specific changes in phosphatidylserine and phosphatidylethanolamine species. Proteomic analysis, together with Western blotting and RT-qPCR, showed higher abundances of PPARγ, FASN, and downstream lipogenic transcripts in the FLF group. These findings demonstrate that FLF modulates lipid deposition and lipid composition in porcine muscle and provide mechanistic insight into the nutritional regulation of pork quality formation.
L. Wang, Hefeng Luo, Zhongyang Guo et al.· Foods· 0 citations
Simple Summary Guanidinoacetic acid is the immediate precursor of creatine and plays an important role in regulating cellular energy metabolism. This study analyzed the results of 12 research studies published between 2016 and 2026 to evaluate the effects of dietary supplementation with guanidinoacetic acid in lambs. The results showed that guanidinoacetic acid improved feed intake, weight gain, and feed utilization efficiency in lambs. Furthermore, guanidinoacetic acid enhances antioxidant capacity in lambs by increasing the concentration of endogenous antioxidant defense enzymes and reducing levels of compounds associated with cellular damage. Guanidinoacetic acid promotes feed digestibility and improves the production of volatile fatty acids in the rumen. In meat, guanidinoacetic acid reduces fluid loss and increases protein content. Taken together, these findings indicate that guanidinoacetic acid is a promising additive for improving productivity, health, and meat quality in lambs.
J. F. Orzuna-Orzuna, J. E. Godina-Rodríguez, G. Mendoza-Martínez et al.· Biology· 0 citations
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