β-hydroxy-β-methyl butyrate, but not α-ketoisocaproate and excess leucine, stimulates skeletal muscle protein metabolism in growing pigs fed low-protein diets

Double-Edge Effects of Leucine on Cancer Cells

Leucine is an essential amino acid that cannot be produced endogenously in the human body and therefore needs to be obtained from dietary sources. Leucine plays a pivotal role in stimulating muscle protein synthesis, along with isoleucine and valine, as the group of branched-chain amino acids, making them one of the most popular dietary supplements for athletes and gym-goers. The individual effects of leucine, however, have not been fully clarified, as most of the studies so far have focused on the grouped effects of branched-chain amino acids. In recent years, leucine and its metabolites have been shown to stimulate muscle protein synthesis mainly via the mammalian target of the rapamycin complex 1 signaling pathway, thereby improving muscle atrophy in cancer cachexia. Interestingly, cancer research suggests that leucine may have either anti-cancer or pro-tumorigenic effects. In the current manuscript, we aim to review leucine's roles in muscle protein synthesis, tumor suppression, and tumor progression, specifically summarizing the molecular mechanisms of leucine's action. The role of leucine is controversial in hepatocellular carcinoma, whereas its pro-tumorigenic effects have been demonstrated in breast and pancreatic cancers. In summary, leucine being used as nutritional supplement for athletes needs more attention, as its pro-oncogenic effects may have been identified by recent studies. Anti-cancer or pro-tumorigenic effects of leucine in various cancers should be further investigated to achieve clear conclusions.

Effects of sex on fat deposition through gut microbiota and short-chain fatty acids in weaned pigs

Nitrogen pollution resulting from excessive feed consumption poses a significant challenge for modern swine production. Precision nutrition technology seems to be an effective way to solve this problem; therefore, understanding the law of pig body composition deposition is a prerequisite. This study investigated the sex effects on growth performance, body composition, nutrient deposition, gut microbiota, and short-chain fatty acids (SCFA) in weaned piglets. Eighty weaned pigs were randomly allocated to 2 treatments according to the sex of pigs. An individual pig was considered as a treatment replicate. Six body weights (BW 5, 7, 11, 15, 20, and 25 kg) were chosen as experimental points; for each point 10 piglets close to the average BW (5 males and 5 females) were slaughtered, and there was one growth phase between each 2 BW points. Results indicated that the males had higher average daily gain (ADG) and average daily feed intake (ADFI) compared to the females (P < 0.05) at growth phases 15 to 20 kg BW and 20 to 25 kg BW. Meanwhile, males at 20 kg BW had higher body fat content than females (P < 0.10). Males showed a higher body fat (P < 0.05) deposition rate at phase 15 to 20 kg BW (P < 0.05) than females. For pigs at 20 kg BW, the relative abundance of RuminococcaceaeUCG-005, Clostridium, Christensenellaceae_R-7_group, and Peptostreptococcaceae was significantly increased in males (P < 0.05) but that of Bifidobacterium was decreased (P < 0.05). At 25 kg BW, the relative abundance of Ruminococcaceae_NK4A214_group, Fibrobacter, RuminococcaceaeUCG-009, Ralstonia, Klebsiel, and Christensenellaceae_R-7_group in males was higher when compared with females (P < 0.05). In terms of SCFA, females exhibited higher concentrations of propionate compared to males (P < 0.05). The results of the current study indicated that sex influenced fat deposition through changes in the composition of gut microbiota and the content of SCFA, which has significant implications for the realization of precision nutrition in modern swine production.

ß-Hydroxy-ß-methylbutyrate: A feed supplement influencing performance, bone metabolism, intestinal morphology, and muscle quality of laying hens: a preliminary one-point study

Laying hens, selectively bred for high egg production, often suffer from bone fragility and fractures, impacting their welfare and causing economic losses. Additionally, gut health and muscle quality are crucial for overall health and productivity. This study aimed to evaluate the effects of ß-Hydroxy-ß-methylbutyrate (HMB) supplementation on performance, bone metabolism, intestinal morphology, and muscle quality in laying hens. Forty-eight Bovans Brown hens were divided into a control group and an HMB-supplemented group (0.02% HMB in diet). The study spanned from the 31st to the 60th wk of age. Assessments included bone mechanical testing, serum hormonal analysis, histological analysis of bone and intestine, and muscle quality analysis. The HMB supplementation led to decreased feed intake without affecting body weight or laying rate in laying hens. It caused an increase in both mean daily and total egg weight, indicating improved feed utilization, without influencing the feed intake to egg weight ratio. Enhanced bone formation markers and altered intestinal morphometric parameters were observed, along with improved trabecular bone structure. However, no changes in measured other bone quality indices, including geometric, densitometric, or mechanical properties were observed. Muscle analysis revealed no significant changes in overall meat quality, except for a decrease in cholesterol content and alterations in the fatty acid profile, notably a reduction in total n-3 polyunsaturated and total polyunsaturated fatty acids (PUFA). In conclusion, although not all effects of HMB supplementation were unequivocally beneficial, the positive changes in performance data and trabecular bone microarchitecture support further research into various doses and durations of supplementation. Such studies are necessary to fully understand and optimize the benefits of HMB for enhancing the health and productivity of laying hens.

Dietary β-Hydroxy-β-Methylbutyrate Supplementation Affects Growth Performance, Digestion, TOR Pathway, and Muscle Quality in Kuruma Shrimp (Marsupenaeus japonicas) Fed a Low Protein Diet

An 8-week feeding trial was performed to evaluate the effects of dietary β-hydroxy-β-methylbutyrate (HMB) supplementation on growth performance and muscle quality of kuruma shrimp (Marsupenaeus japonicas) (initial weight: 2.00 ± 0.01 g) fed a low protein diet. The positive control diet (HP) with 490 g/kg protein and negative control diet (LP) with 440 g/kg protein were formulated. Based on the LP, 0.25, 0.5, 1, 2 and 4 g/kg β-hydroxy-β-methylbutyrate calcium were supplemented to design the other five diets named as HMB0.25, HMB0.5, HMB1, HMB2 and HMB4, respectively. Results showed that compared with the shrimp fed LP, the HP, HMB1 and HMB2 groups had significantly higher weight gain and specific growth rate, while significantly lower feed conversion ratio (p < 0.05). Meanwhile, intestinal trypsin activity was significantly elevated in the above three groups than that of the LP group. Higher dietary protein level and HMB inclusion upregulated the expressions of target of rapamycin, ribosomal protein S6 kinase, phosphatidylinositol 3-kinase, and serine/threonine-protein kinase in shrimp muscle, accompanied by the increases in most muscle free amino acids contents. Supplementation of 2 g/kg HMB in a low protein diet improved muscle hardness and water holding capacity of shrimp. Total collagen content in shrimp muscle increased with increasing dietary HMB inclusion. Additionally, dietary inclusion of 2 g/kg HMB significantly elevated myofiber density and sarcomere length, while reduced myofiber diameter. In conclusion, supplementation of 1-2 g/kg HMB in a low protein diet improved the growth performance and muscle quality of kuruma shrimp, which may be ascribed to the increased trypsin activity and activated TOR pathway, as well as elevated muscle collagen content and changed myofiber morphology caused by dietary HMB.

The effect of supplementation with β-hydroxy-β-methylbutyric acid (HMB) to pregnant sows on the mucosal structure, immunolocalization of intestinal barrier proteins, VIP and leptin in the large intestine in their offspring

The large intestine epithelium plays an important role in water absorption and participates in fluid, acid-base and electrolyte balance, and the removal of waste products. The large intestine is rich in microorganism-presented enzyme activity. Apart from energy supply, the colon also participates in the synthesis of trophic factors and the modulation of the immune system and the systemic inflammatory response. The current study investigated the effects of dietary HMB administration to pregnant sows on the postnatal development of the colon in their offspring, at weaning. From the 70th to the 90th day of gestation, sows received either a basal diet (n = 12) or the basal diet supplemented with HMB (n = 12) at a dose of 0.2 g/kg of body weight/day. Maternal HMB treatment increased serum IgG and glucose concentrations and decreased serum urea concentration in the piglets. Basal histomorphometric analysis of offspring large intestines showed that prenatal HMB treatment led to a reduction in the thickness of the mucosa, submucosa and both types of myenterons, as well as reduced crypt thickness. The immunoreaction performed to mark T0 lymphocytes and total T lymphocytes in the colon wall showed that prenatal HMB treatment decreased the number of both types of lymphocytes. Greater expression for cadherin was found in the colon of piglets delivered by the HMB-treated sows. The expression of both tight junction proteins (occludin and claudin-3), as well as that of leptin, was stronger in the HMB-treated group. Vasoactive intestinal peptide (VIP) expression was stronger in the submucosal plexuses in the HMB maternal treated piglets, while no changes were observed in the myenteric plexuses. The results obtained indicate that the administration of HMB to pregnant sows significantly influenced the expression of leptin, VIP and some proteins of the intestinal barrier in their offspring, with less influence on large intestine basal morphology.

Prenatal programming of the small intestine in piglets: the effect of supplementation with 3-hydroxy-3-methylbutyric acid (HMB) in pregnant sows on the structure of jejunum of their offspring

When discussing the scale of the occurrence of diseases of the digestive system in farm animals, particularly pigs in the weaning period, it may be beneficial to study physiological and nutritional factors that could potentially affect the growth, development, and modelling of the structure and function of the digestive tract. Taking into account the reports on the beneficial effects of ß-hydroxy-ß-methylbutyrate (HMB) administration in the prenatal period on the development of various systems it was assumed that the HMB supplementation to pregnant sows can influence intestinal development in the offspring during weaning. Thus, the present experiment was conducted to evaluate the effect of HMB treatment of pregnant sows on jejunum development in offspring at weaning. From 70th day until the 90th day of gestation, sows received either a basal diet (n = 12) or the same diet supplemented with HMB (n = 12) at the dose of 0.2 g/kg of body weight/day. HMB given during prenatal time reduced the thickness of the longitudinal muscle; the apoptotic cell index in epithelium also significantly decreased after the HMB supplementation. Vasoactive intestinal (poly)peptide (VIP) expression in submucosal ganglia significantly increases in prenatally HMB treated piglets. The same strong reaction was observed with the expression of occludin, claudin-3, E-cadherin, and leptin in the jejunal epithelium. The obtained results indicate that the administration of HMB to pregnant sows significantly influenced the expression of VIP, leptin and some proteins of the intestinal barrier of their offspring less influencing the basal morphology.

Alterations of the Muscular Fatty Acid Composition and Serum Metabolome in Bama Xiang Mini-Pigs Exposed to Dietary Beta-Hydroxy Beta-Methyl Butyrate

Simple Summary

Pork is the most consumed meat source for humans, and the utilization of nutritional approaches to produce pork with an appropriate content of intramuscular fat (IMF) and a balanced ratio of different kinds of fatty acid is an important objective pursuit of swine production. We speculated that dietary supplementation of beta-hydroxy beta-methyl butyrate (HMB) may provide benefits in lipid metabolism of skeletal muscle. In this study, we try to investigate the effects of dietary HMB supplementation on muscular lipid metabolism in Bama Xiang mini-pigs. We found that HMB supplementation could decrease the IMF content and increase n3 polyunsaturated fatty acids as well as regulate the related metabolites (N-Methyl-l-glutamate and nummularine A) in the serum of Bama Xiang mini-pigs, thus improving their meat quality.

Abstract

This study aimed to investigate the effects of dietary beta-hydroxy beta-methyl butyrate (HMB) supplementation on muscular lipid metabolism in Bama Xiang mini-pigs. Thirty-two piglets (8.58 ± 0.40 kg, barrow) were selected and fed a basal diet supplemented either with 0 (control), 0.13%, 0.64%, or 1.28% HMB for 60 days. Throughout the experiments, they had free access to clean drinking water and diets. Data of this study were analyzed by one-way ANOVA using the SAS 8.2 software package, followed by a Tukey’s studentized range test to explore treatment effects. The results showed that compared to the control, 0.13% HMB decreased the intramuscular fat (IMF) content and increased polyunsaturated fatty acids (PUFAs) in Longissimus thoracis muscle (LTM), and increased the n3 PUFAs in soleus muscles (SM, p < 0.05). Moreover, HMB supplementation led to alterations in the mRNA expression of genes related to lipid metabolism. Serum metabolome profiling showed that in both LTM and SM of Bama Xiang mini-pigs, N-Methyl-l-glutamate was positively correlated with SFA and nummularine A was negatively correlated with C18:3n3 PUFA (p < 0.05). Therefore, N-Methyl-l-glutamate and nummularine A might be potential biomarkers of the HMB-supplemented group. These results suggested that dietary HMB supplementation could decrease the IMF content and increase n3 PUFAs as well as regulate the related metabolites (N-Methyl-l-glutamate and nummularine A) in the serum of pigs.

Leucine Supplementation: A Novel Strategy for Modulating Lipid Metabolism and Energy Homeostasis

Lipid metabolism is an important and complex biochemical process involved in the storage of energy and maintenance of normal biological functions. Leucine, a branched amino acid, has anti-obesity effects on glucose tolerance, lipid metabolism, and insulin sensitivity. Leucine also modulates mitochondrial dysfunction, representing a new strategy to target aging, neurodegenerative disease, obesity, diabetes, and cardiovascular disease. Although various studies have been carried out, much uncertainty still exists and further studies are required to fully elucidate the relationship between leucine and lipid metabolism. This review offers an up-to-date report on leucine, as key roles in both lipid metabolism and energy homeostasis in vivo and in vitro by acceleration of fatty acid oxidation, lipolysis, activation of the adenosine 5'-monophosphate-activated protein kinase (AMPK)-silent information regulator of transcription 1 (SIRT1)-proliferator-activated receptor γ coactivator-1α (PGC-1α) pathway, synthesis, and/or secretion of adipokines and stability of the gut microbiota.

Dietary β-hydroxy-β-methylbutyrate improves intestinal function in weaned piglets after lipopolysaccharide challenge

OBJECTIVES

The aim of this study was to explore the effects of β-hydroxy-β-methylbutyrate (HMB) on intestinal function of lipopolysaccharide (LPS)-challenged piglets.

METHODS

Forty weaned piglets were used in a 2 × 2 factorial design. The major factors were challenge (saline or LPS) and diet (basal diet or 0.6% HMB-Ca diet). After 15 d of treatment with LPS or HMB, blood and intestine samples were obtained.

RESULTS

The results showed that in LPS-injected pigs, HMB supplementation significantly increased jejunal villus height and ileal villus height-to-crypt depth ratio and decreased ileal crypt depth (P < 0.05). HMB also improved intestinal function indicated by elevated activities of intestinal mucosal disaccharidase and tricarboxylic acid cycle key enzymes. Furthermore, HMB significantly downregulated mRNA expression of Sirt1 in jejunum and mRNA expression of AMPKα1 and Sirt1 in ileum (P < 0.05), with a concurrent decrease of AMPKα phosphorylation in jejunum and ileum. Microbiota analysis indicated that HMB supplementation significantly increased α-diversity and affected relative abundances of Romboutsia and Sarcina at the genus level, accompanied by increased concentrations of all short-chain fatty acids except propionate in the terminate ileum of LPS-injected piglets.

CONCLUSION

Dietary HMB supplementation could improve intestinal integrity, function, microbiota communities, and short-chain fatty acid concentrations in LPS-challenged piglets, suggesting its potential usage as a feed additive in weaned piglets to alleviate intestinal dysfunction triggered by immune stress.

Beta-hydroxy beta-methyl butyrate decreases muscle protein degradation via increased Akt/FoxO3a signaling and mitochondrial biogenesis in weanling piglets after lipopolysaccharide challenge

The aim of this study was to investigate the effects of dietary β-hydroxy-β-methylbutyrate (HMB) on lipopolysaccharide (LPS)-induced muscle atrophy and to investigate the mechanisms involved. Sixty pigs (21 ± 2 days old, 5.86 ± 0.18 kg body weight) were used in a 2 × 3 factorial design and the main factors included diet (0, 0.60%, or 1.20% HMB) and immunological challenge (LPS or saline). After 15 d of treatment with LPS and/or HMB, growth performance, blood parameters, and muscle protein degradation rate were measured. The results showed that in LPS-injected pigs, 0.60% HMB supplementation increased the average daily gain and average daily feed intake and decreased the feed : gain ratio (P < 0.05), with a concurrent increase of lean percentage. Moreover, 0.60% HMB supplementation decreased the serum concentrations of blood urea nitrogen, IL-1β, and TNF-α and the rate of protein degradation as well as cell apoptosis in selected muscles (P < 0.05). In addition, dietary HMB supplementation (0.60%) regulated the expression of genes involved in mitochondrial biogenesis and increased the phosphorylation of Akt and Forkhead Box O3a (FoxO3a) in selected muscles, accompanied by decreased protein expression of muscle RING finger 1 and muscle atrophy F-box. These results indicate that HMB may exert protective effects against LPS-induced muscle atrophy by normalizing the Akt/FoxO3a axis that regulates ubiquitin proteolysis and by improving mitochondrial biogenesis.

α-Ketoisocaproate and β-hydroxy-β-methyl butyrate regulate fatty acid composition and lipid metabolism in skeletal muscle of growing pigs

OBJECTIVES

This study aims to investigate the effects and roles of excess leucine (Leu) versus its metabolites α-ketoisocaproate (KIC) and β-hydroxy-β-methyl butyrate (HMB) on fatty acid composition and lipid metabolism in skeletal muscle of growing pigs.

METHODS AND RESULTS

Thirty-two pigs with a similar initial weight (9.55 ± 0.19 kg) were fed one of the four diets (basal diet, L-Leu, KIC-Ca and HMB-Ca) for 45 days. Results indicated that dietary treatments did not affect the intramuscular fat (IMF) content (p > 0.05), but differently influenced the fatty acid composition of longissimus dorsi muscle (LM) and soleus muscle (SM). In particular, the proportion of N3 PUFA specifically in LM was significantly decreased in the Leu group and increased in both KIC and HMB group relative to the basal diet group (p < 0.05). Furthermore, pigs fed KIC-supplemented diets exhibited decreased expression of FATP-1, ACC, ATGL, C/EBPα, PPARγ and SREBP-1c in LM and increased expression of FATP-1, FAT/CD36, ATGL and M-CPT-1 in SM relative to the basal diet control (p < 0.05).

CONCLUSIONS

These findings indicated that doubling dietary Leu content decreased the percentage of N3 PUFA mainly in glycolytic skeletal muscle, whereas KIC and HMB improved muscular fatty acid composition and altered lipid metabolism in skeletal muscle of growing pigs. The mechanism of action of KIC might be related to the TFs, and the mechanism of action of HMB might be associated with the AMPK-mTOR signalling pathway.