Effects of Low-Protein Diets Supplemented with Branched-Chain Amino Acid on Lipid Metabolism in White Adipose Tissue of Piglets

Different Fatty Acid Supplementation in Low-Protein Diets Regulate Nutrient Utilization and Lipid and Amino Acid Metabolism in Weaned Pigs Model

This study was conducted to evaluate the effects of a low-protein (LP) diet supplemented with sodium butyrate (SB), medium-chain fatty acids (MCFAs) and n-3 polyunsaturated fatty acids (PUFAs) on nutrient utilization and lipid and amino acid metabolism in weaned pigs. A total of 120 Duroc × Landrace × Yorkshire pigs (initial body weight: 7.93 ± 0.65 kg) were randomly assigned to five dietary treatments, including the control diet (CON), LP diet, LP + 0.2% SB diet (LP + SB), LP + 0.2% MCFA diet (LP + MCFA) and LP + 0.2% n-3 PUFA diet (LP + PUFA). The results show that the LP + MCFA diet increased (p < 0.05) the digestibility of dry matter and total P in pigs compared with the CON and LP diets. In the liver of the pigs, the metabolites involved in sugar metabolism and oxidative phosphorylation significantly changed with the LP diet compared with the CON diet. Compared with the LP diet, the altered metabolites in the liver of the pigs fed with the LP + SB diet were mainly associated with sugar metabolism and pyrimidine metabolism; the altered metabolites in the liver of pigs fed with the LP + MCFA and LP + PUFA diets were mainly associated with lipid metabolism and amino acid metabolism. In addition, the LP + PUFA diet increased (p < 0.05) the concentration of glutamate dehydrogenase in the liver of pigs compared with the LP diet. Furthermore, the LP + MCFA and LP + PUFA diets increased (p < 0.05) the mRNA abundance of sterol regulatory element-binding protein 1 and acetyl-CoA carboxylase in the liver compared with the CON diet. The LP + PUFA diet increased (p < 0.05) mRNA abundances of fatty acid synthase in the liver compared with the CON and LP diets. Collectively, the LP diet supplemented with MCFAs improved nutrient digestibility, and the LP diet supplemented with MCFAs and n-3 PUFAs promoted lipid and amino acid metabolisms.

Low-protein diets supplemented with isoleucine alleviate lipid deposition in broilers through activating 5' adenosine monophosphate-activated protein kinase and janus kinase 2/signal transducer and activator of transcription 3 signaling pathways

This study aimed to evaluate the effect of isoleucine (Ile) on growth performance, meat quality and lipid metabolism of broilers fed a low-protein diet (LPD). The 396 one-day-old male Cobb broilers were allocated to 4 treatment groups as follows: control diet (CON), LPD, LPD + 0.13% Ile (LPD-LI) and LPD + 0.26% Ile (LPD-HI), with nine replicates of 11 broilers each for 42 d. The Ile increased average daily gain, average daily feed intake, fiber density and the mRNA level of myosin heavy chain (MyHC)-I in breast muscle, and decreased feed to gain ratio, shear force, fiber diameter and the mRNA level of MyHC-IIb in breast muscle, which were impaired by the LPD. Compared to the LPD group, broilers in LPD-LI and LPD-HI groups had lower serum lipid levels, liver fat content, abdominal adipose percentage and mRNA levels of peroxisome proliferator-activated receptor-γ, CCAAT/enhancer binding protein-α, ki-67, topoisomerase II alpha (TOP2A) and thioredoxin-dependent peroxidase 2 in abdominal adipose and liver X receptors-α, sterol regulatory element binding protein 1 (SREBP1), acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) in liver, and higher mRNA levels of peroxisome proliferator activated receptor-α, carnitine palmitoyl-transferase 1 (CPT-1), and acyl-CoA oxidase 1 (ACOX1) in liver, which were equal to the CON levels. A LPD supplemented with Ile decreased enzyme activities of ACC and FAS in liver and glycerol-3-phosphate dehydrogenase and TOP2A in abdominal adipose, and increased enzyme activities of CPT-1 and ACOX1 in liver. Furthermore, Ile supplementation enhanced the mRNA level of leptin receptor and protein levels of phospho-5' adenosine monophosphate-activated protein kinase (AMPK), mechanistic target of rapamycin, ribosomal protein 70 S6 kinase, janus kinase 2 (JAK2), and signal transducer and activator of transcription 3 (STAT3), and decreased the protein level of SREBP1 in the liver of broilers in LPD group. In conclusion, dietary supplementation with Ile to 0.83% could improve growth performance and meat quality and alleviate lipid deposition of broilers fed a LPD through activating AMPK and JAK2/STAT3 signaling pathways.

Long-Term Protein Restriction Modulates Lipid Metabolism in White Adipose Tissues and Alters Colonic Microbiota of Shaziling Pigs

Obesity is a matter of concern to the public. Abundant evidence has been accumulated that nutritional intervention is a promising strategy to address this health issue. The objective of this study is to investigate alterations in the lipid metabolism in white adipose tissues and the gut microbiota of Shaziling pigs challenged by long-term protein restriction. Results showed that compared with the control group, reducing the protein level by 20% (−20%) increased the mRNA abundance of FABP4 in white adipose tissues (p < 0.05). This occurred in conjunction with increases in PPARγ protein expression. Conversely, the protein expression of C/EBPα was reduced in the −20% group (p < 0.05). Moreover, the −20% group had increased/decreased phosphorylation of AMPKα/mTOR, respectively (p < 0.05). As for the colonic gut microbiota, a 20% reduction in the protein level led to increased Lachnospiraceae XPB1014 group abundance at the genus level (p < 0.01). Collectively, these results indicated that a 20% protein reduction could modulate lipid metabolism and alter the colonic microbiota of Shaziling pigs, an approach which might be translated into a treatment for obesity.

The Role of Gut Microbiota in the Skeletal Muscle Development and Fat Deposition in Pigs

Pork quality is a factor increasingly considered in consumer preferences for pork. The formation mechanisms determining meat quality are complicated, including endogenous and exogenous factors. Despite a lot of research on meat quality, unexpected variation in meat quality is still a major problem in the meat industry. Currently, gut microbiota and their metabolites have attracted increased attention in the animal breeding industry, and recent research demonstrated their significance in muscle fiber development and fat deposition. The purpose of this paper is to summarize the research on the effects of gut microbiota on pig muscle and fat deposition. The factors affecting gut microbiota composition will also be discussed, including host genetics, dietary composition, antibiotics, prebiotics, and probiotics. We provide an overall understanding of the relationship between gut microbiota and meat quality in pigs, and how manipulation of gut microbiota may contribute to increasing pork quality for human consumption.

Camellia (Camellia oleifera Abel.) Seed Oil Regulating of Metabolic Phenotype and Alleviates Dyslipidemia in High Fat-Fed Mice through Serum Branch-Chain Amino Acids

Camellia (Camellia oleifera Abel.) seed oil (CO) has been shown to effectively reduce the blood lipid level of its host due to its fatty acid content, but the specific molecular mechanism associated with the metabolic phenotype after digestion is not clear. Here, we further investigated the relationship between branched-chain amino acids (BCAA) and the metabolic phenotype that may exhibit the anti-dyslipidemia effect of CO on mice fed a high-fat diet for 30 day C57BL/6J male mice were allocated to three groups: the control group (Cont), the high-fat feed group (HFD), and a high-fat feed group with CO treatment (CO). A serum sample was collected to detect lipid biomarkers and BCAA concentration. Notably, Low-density lipoprotein (LDL), Total Cholesterol (TC), and Triglycerides (TG) showed a significant decrease, whereas High-density lipoprotein (HDL) increased in CO mice but not in the HFD group. The concentration of Isoleucine (Ile), leucine (Leu), and valine (Val) was similar between the Cont and CO groups compared with the HFD group, exhibiting an inhibition induced by CO in mice fed with a high-fat diet. A metabolic phenotype from serum examined by non-targeted metabolite analysis using UHPLC/MS showed most metabolites exhibited lipid and BCAA metabolism. The results indicated that CO treatment notably regulated the metabolism of arachidonic acid and steroid biosynthesis in response to HFD-induced dyslipidemia. In addition, the expression of PPARγ genes that correlated with the BCAA and serum lipid biomarkers were compared, and significant inhibition was noticed, which might lead to the potential exposure of the anti-dyslipidemia mechanism of CO in HFD-fed mice. In conclusion, the expression of PPARγ genes, serum lipid level, BCAA concentration, and the metabolic phenotype was significantly positive in correlation with a high-fat diet, whereas oral CO improved the biomarkers and metabolism of some specific serum metabolites in HFD-fed mice.

Effects of Dietary Protein Levels on Fecal Amino Acids Excretion and Apparent Digestibility, and Fecal and Ileal Microbial Amino Acids Composition in Weaned Piglets

Background and Aims: The purpose of this study was to determine the effects of low protein diets with the same Lys, Met + Cys, Thr, and Trp levels as in high protein diets on the fecal amino acid excretion and apparent digestibility, and ileal and fecal microbial amino acids composition in weaned piglets.

Methods: Fifty-four 21-day-old Duroc × Landrace × Yorkshire weaned piglets were randomly divided into three groups and fed with corn-soybean meal basal diets, in which the crude protein (CP) content was 20% (H-CP), 17% (M-CP), and 14% (L-CP), respectively. The experiment included a 7-day adaptation period and a 45-day trial period. Six piglets in each group were randomly slaughtered on days 10, 25, and 45 of the trial period, and the intestinal contents, intestinal mucosa, and feces were collected.

Results: The results showed that the interaction between feeding time and dietary CP levels was reflected in the apparent digestibility of dietary CP and amino acid (AA) (p < 0.01). With the increase of age, the apparent digestibility of CP and AA were increased (p < 0.01). With the increase of CP levels, the excretion of nitrogen (N) was decreased (p < 0.01), whereas the flow of microbial AA in the ileum and feces were increased (p < 0.01). The interaction between feeding time and dietary CP levels was also reflected in the composition of AA in the ileum and stool of piglets (p < 0.01). The proportion of His, Lyr, Met, Cys, and Ser was lower than the average, whereas the proportion of Phe, Leu, Pro, Ala, Glu, and Asp was higher than the average. With the increase of age, the AA content of microorganisms increased (p < 0.01).

Conclusion: All in all, this work revealed the changes of N, CP, and AA excretion and digestibility of feces and microorganisms of piglets under the combined action of different dietary protein levels and different feeding times, and also the changes of AA composition of intestinal microorganisms and AA composition of microorganisms.

Different Proportions of Branched-Chain Amino Acids Modulate Lipid Metabolism in a Finishing Pig Model

This study aimed to investigate the effect of the supplementation of branched-chain amino acids (BCAAs) at different ratios in protein restriction diets on lipid metabolism in a finishing pig model. The BCAA supplementation (leucine/isoleucine/valine = 2:1:1 and 2:1:2) ameliorated the poor growth performance and carcass characteristics, particularly high fat mass caused by a protein-restricted diet. Serum adiponectin increased while leptin decreased in BCAA diets in comparison to the 12% CP group. BCAA supplementation also increased the low-protein expression of AMPK and SIRT1 caused by protein restriction. The mRNA and protein levels of peroxisome proliferation-activated receptor-γ (PPARγ) and acetyl-CoA carboxylase (ACC) were highest in the protein-restricted group and lowered in the 2:1:1 or 2:1:2 group. In conclusion, BCAAs supplemented in an adequate ratio range of 2:1:1 to 2:1:2 (2:1:2 is recommended) in reduced protein diets could modulate lipid metabolism by accelerating the secretion of adipokines and fatty acid oxidation.

Branched-Chain Amino Acid Supplementation Does Not Preserve Lean Mass or Affect Metabolic Profile in Adults with Overweight or Obesity in a Randomized Controlled Weight Loss Intervention

BACKGROUND

Branched-chain amino acid (BCAA) supplementation has been shown to increase muscle mass or prevent muscle loss during weight loss.

OBJECTIVE

We aimed to investigate the effects of a BCAA-supplemented hypocaloric diet on lean mass preservation and insulin sensitivity.

METHODS

A total of 132 Chinese adults (63 men and 69 women aged 21-45 y, BMI 25-36 kg/m2) were block randomly assigned by gender and BMI into 3 hypocaloric diet (deficit of 500 kcal/d) groups: standard-protein (14%) with placebo (control, CT) or BCAA supplements at 0.1 g · kg-1 body weight · d-1 (BCAA) or high-protein (27%) with placebo (HP). The subjects underwent 16 wk of dietary intervention with provision of meals and supplements, followed by 8 wk of weight maintenance with provision of supplements only. One-way ANOVA analysis was conducted to analyze the primary (lean mass and insulin sensitivity) and secondary outcomes (anthropometric and metabolic parameters) among the 3 groups. Paired t-test was used to analyze the change in each group.

RESULTS

The 3 groups demonstrated similar significant reductions in body weight (7.97%), fat mass (13.8%), and waist circumference (7.27%) after 16 wk of energy deficit. Lean mass loss in BCAA (4.39%) tended to be lower than in CT (5.39%) and higher compared with HP (3.67%) (P = 0.06). Calf muscle volume increased 3.4% in BCAA and intramyocellular lipids (IMCLs) decreased in BCAA (17%) and HP (18%) (P < 0.05) over 16 wk. During the 8 wk weight maintenance period, lean mass gain in BCAA (1.03%) tended to be lower compared with CT (1.58%) and higher than in HP (-0.002%) (P = 0.04). Lean mass gain differed significantly between CT and HP (P = 0.03). Insulin sensitivity and metabolic profiles did not differ among the groups throughout the study period.

CONCLUSIONS

BCAA supplementation does not preserve lean mass or affect insulin sensitivity in overweight and obese adults during weight loss. A higher protein diet may be more advantageous for lean mass preservation.

Dietary supplementation with betaine or glycine improves the carcass trait, meat quality and lipid metabolism of finishing mini-pigs

The objective of the study is to evaluate and compare the effects of betaine or glycine on carcass trait, meat quality and lipid metabolism of finishing Huan Jiang mini-pigs. Betaine called trimethylglycine is a methyl derivative of glycine, but few researches were conducted to compare the impact of dietary betaine and glycine on pigs. One hundred and forty-four Huan Jiang mini-pigs (body weight = 10.55 ± 0.15 kg; 70 d) were randomly divided to 3 treatment groups (basal diet, glycine or betaine). Results indicated that dietary betaine increased the average daily gain (ADG) and final weight (P < 0.05). Dietary glycine or betaine markedly reduced average backfat thickness (P < 0.05) and heightened lean percentage (P < 0.01) compared to the control group. Moreover, in comparison with the control group, betaine significantly improved the redness (a∗) and tenderness (shear force) of the longissimus dorsi (LD) muscle (P < 0.05), whereas glycine only raised the value of a∗ of the LD muscle (P < 0.05). These results showed that diet supplemented with 0.25% betaine and equimolar amounts of glycine could regulate cascass trait and meat quality of finishing Huan Jiang mini-pigs, and the effect of betaine was superior to that of glycine.

The role of protein restriction and interaction with antibiotics in the regulation of compensatory growth in pigs: growth performance, serum hormone concentrations, and messenger RNA levels in component tissues of the endocrine growth axis

The present study investigated the effects of protein restriction and antibiotics on the hypothalamus-pituitary-liver growth axis during the compensatory growth of growing and finishing pigs. Growth performance, serum hormones, and messenger RNA (mRNA) levels of hormones and their receptors in growth axis tissues were recorded for analyses. A total of 64 piglets (large white × Landrace × Duroc cross) with an initial weight of 10.07 ± 0.14 kg were randomly divided into 4 treatment groups of 16 piglets per group. The dietary treatments consisted of 2 protein levels (14% and 20%) and 2 antibiotic levels (no antibiotics and 20 mg/kg colistin sulfate with 50 mg/kg kitasamycin) in a 2 × 2 factorial arrangement. The study was performed over 30 d for the first stage (S1, restriction phase) and 74 d for the second stage (S2, realimentation phase). The 4 treatment diets were maintained throughout the duration in the restriction phase. The 4 groups were fed the same diet in the realimentation phase. The trial period totaled 104 d. Protein restriction decreased BW, average daily food intake, and ADG in weaning pigs (P < 0.01) and induced compensatory growth after feeding a normal diet during the growth of finishing pigs. Average daily gain increased during the last phase of compensatory growth (P < 0.01). Protein restriction increased serum GH and leptin (LEP) and the mRNA levels of liver IGF-1 receptor (IGF-1-R; P < 0.01) but decreased serum IGF-1 (P < 0.01) and the mRNA levels of liver GH receptor (GH-R; P < 0.01) and IGF-1 (P < 0.05) in weaning piglets. Serum GH was increased, but serum IGF-1 was decreased during the realimentation phase (P < 0.05). Antibiotics increased the mRNA levels of GHRH (P < 0.05) and decreased somatostatin (P < 0.01) in the hypothalamus of weaning pigs. Protein restriction and antibiotics had no interactions across the entire trial. In conclusion, the slowing of growth caused by early protein restriction may be compensated for in the later stages of pig raising, and the mechanism of compensation is related to the regulation of GH, IGF-1, GH-R, and IGF-1-R.

The role of liver metabolism in compensatory-growth piglets induced by protein restriction and subsequent protein realimentation

The aim of this work was to study the role of hepatic metabolism of compensatory growth in piglets induced by protein restriction and subsequent protein realimentation. Thirty-six weaned piglets were randomly distributed in a control group and a treatment group. The control group piglets were fed with a normal protein level diet (18.83% CP) for the entire experimental period (day 1-28). The treatment group piglets were fed with a protein-restriction diet (13.05% CP) for day 1 to day 14, and the diet was restored to normal protein level diet for day 15 to day 28. RNA-seq is used to analyze samples of liver metabolism on day 14 and day 28, respectively. Hepatic RNA-sequencing analysis revealed that some KEGG signaling pathways involved in glycolipid metabolism (eg, "AMPK signaling pathway," "insulin signaling pathway," and "glycolysis or gluconeogenesis") were significantly enriched on day 14 and day 28. On day 14, protein restriction promoted hepatic lipogenesis by increasing the genes expression level of ACACA, FASN, GAPM, and SREBP1C, decreasing protein phosphorylation levels of AMPKɑ and ACC in AMPK signaling pathway. In contrast, on day 28, protein realimentation promoted hepatic gluconeogenesis by increasing the concentration of G6Pase and PEPCK, decreasing protein phosphorylation levels of IRS1, Akt, and FoXO1 in insulin signaling pathway. In addition, protein realimentation activated the GH-IGF1 axis between the liver and skeletal muscle. Overall, these findings revealed the importance of liver metabolism in achieving compensatory growth.

Effects of Dietary Crude Protein Levels on Fecal Crude Protein, Amino Acids Flow Amount, Fecal and Ileal Microbial Amino Acids Composition and Amino Acid Digestibility in Growing Pigs

Simple Summary

The purpose of this experiment was to evaluate a low protein corn-soybean meal-based diet with the same Lys, Met + Cys, Thr and Trp level as a high protein diet on fecal crude protein (CP), amino acid (AA) flow amount, AA digestibility and fecal and ileal microbial AA composition in growing pigs. Eighteen pigs with an initial body weight of (30 ± 1.35) kg were randomly divided into three groups, with six replicates in each group, and fed a corn-soybean meal-based diets with 12%, 15% and 18% CP levels, respectively. Our aim was to explain whether the addition of four crystalline essential AAs (EAA) to a low diet affected the digestibility of protein-bound NEAA (non-essential amino acid) and EAA and the composition of microbial AA in ileum and feces.

Abstract

The purpose of this experiment was to evaluate the effects of low protein corn-soybean meal-based diets on fecal CP, amino acid (AA) flow amount, AA digestibility and fecal and ileal microbial AA composition in growing pigs. Eighteen pigs (initial body weight = 30 ± 1.35) were randomly divided into three groups and fed with basal diets with CP levels of 12%, 15% and 18%, respectively. The Lys, Met + Cys, Thr and Trp level in the 12% CP and 15% CP groups is the same as 18% CP group by the addition of four crystalline Lys, Met + Cys, Thr and Trp to the diet. The results showed that with the decrease of dietary CP level from 18% to 12%, the fecal total nitrogen (N), CP and total AA (TAA) flow amount decreased linearly (p < 0.05). Dry matter (DM) digestibility, CP digestibility, TAA digestibility, essential amino acid (EAA) digestibility and non-essential amino acid (NEAA) digestibility increased linearly with the decrease of dietary CP concentration from 18% to 12%. Compared with 18% CP group, the flow amount of Asp, Ser, Glu, Gly, Tyr, Val, Leu and Phe in feces of pigs in the 15% CP group and 12% CP group decreased significantly, while the flow amount of Arg in the 15% CP group was lower than that in the 18% CP group and 12% CP group. The fecal microbial N and AA of the 15% CP group were higher than those of the 18% CP and 12% CP groups. Fecal TAA flow amount decreased linearly with the decrease of the dietary CP levels from 18% to 12%. Fecal TAA and NEAA flow amount also decreased linearly with the decrease of dietary CP level from 18% to 12%. Except for Glu, Gly, Met, Tyr, Thr and Phe, there were significant differences among the three groups in the composition of 17 kinds of AAs in fecal microorganisms. Among the 17 AA compositions of ileal microorganisms, except Tyr and Lys, the other AAs were significantly different among the three groups (p < 0.05)

Branched-chain amino acids, especially of leucine and valine, mediate the protein restricted response in a piglet model

Branched-chain amino acids (BCAAs) are reduced in various protein restricted models, while the detailed role of BCAAs in protein restricted response is still obscure. Thus, the current study mainly investigated the amino acid metabolism in protein restricted piglets and the effects of BCAA balance in a low-protein diet on growth performance, amino acid metabolism, intestinal structure, and gut microbiota with focus on which BCAAs contributed to the protein restricted response. The results showed that protein restriction increased serum Ser, Thr, Ala, Lys, and Trp but reduced His, Cys, Val, and Ile levels. Intestinal amino acid transporters mainly mediated the mechanism of amino acid uptake. The BCAA balance refreshed the serum BCAA pool, which further improved growth performance in protein restricted piglets. Leu, Val, and Ile balances increased serum BCAA concentrations, respectively, and Leu and Val but not Ile enhanced the feed intake and weight gain in protein restricted piglets. In addition, protein restriction impaired the villus structure and increased the number of goblet cells in the ileum. Also, gut microbiota (Spirochaetales, Gammaproteobacteria, Lactobacillales at the order level) were altered in protein restricted pigs, while the BCAA balance markedly improved Gammaproteobacteria, Lactobacillales, and Aeromonadales proliferation, which might mediate growth promotion and amino acid metabolism. In conclusion, protein restriction markedly affected the host amino acid metabolism (i.e., Ser, Thr, Lys, His, BCAAs). The BCAA balance (especially for supplementation with Leu and Val) improved the amino acid metabolism, growth performance, and gut microbiota communities.

Dietary supplementation of Morus nigra L. leaves decrease fat mass partially through elevating leptin-stimulated lipolysis in pig model

ETHNOPHARMACOLOGICAL RELEVANCE

Mulberry leaves are the dry leaves of Morus nigra L. trees, which are widely cultivated in central and southern China. Mulberry has a long history of medicinal use, such as anti-stress, lowering blood glucose and anti-obesity.

AIM OF THE STUDY

Explore the effects of mulberry leaves on fat deposition as well as the underlying mechanisms.

MATERIALS AND METHODS

Total of 48 fattening pigs weighing about 70 kg were randomly allotted to normal diet or die supplemented with 5% (w/w) mulberry leave powder. Changes of fat mass, indicated by backfat thickness was measured with Piggyback tester, blood triglyceride and cholesterol were tested using commercial biochemical kits, serum hormones were estimated by ELISA, and leptin-related signaling activity were assessed using western-blot.

RESULTS

Supplementation with Mulberry leaf feed (MF) significantly reduced serum triglyceride and free cholesterol concentrations and increased the ratio of high-density lipoprotein cholesterol (HDL-c) to low-density lipoprotein cholesterol (LDL-c), while serum glucose and free fatty acids remained unchanged. Dietary MF resulted in a significant reduction in the size of adipocytes and backfat thickness (P < 0.05). Accordingly, hormone-sensitive lipase (HSL) in backfat was significantly up-regulated and fatty acid synthase (FAS) was down-regulated by MF supplementation (both P < 0.05). Furthermore, MF supplementation significantly elevated circulating leptin and adiponectin without influencing serum insulin and glucocorticoid. Moreover, significantly higher leptin receptor (Leptin-R) and phosphorylated signal transducer and activator of transcription 3 (p-STAT3) were detected in MF-supplemented pigs, suggesting an enhanced leptin signaling induced by MF in the subcutaneous fat.

CONCLUSIONS

Mulberry leaves have obvious anti-obesity effects, providing a theoretical basis for the development of mulberry leaves as a drug against obesity.

Excessive BCAA regulates fat metabolism partially through the modification of m6A RNA methylation in weanling piglets

Background

Fat percentage and distribution in pigs are associated with their productive efficiency and meat quality. Dietary branched-chain amino acids (BCAA) regulate fat metabolism in weanling piglets with unknown mechanism. It is reported that N6-methyl-adenosine (m⁶A) is involved in fat metabolism in mice. The current study was designed to investigate the relationship between dietary branched-chain amino acids and fat metabolism through N6-methyl-adenosine (m⁶A) in weanling piglets.

Methods

A total of 18 healthy crossbred weaned piglets (Duroc × Landrace × Large White, 10.45 ± 0.41 kg) were divided into 3 treatments and were fed the low BCAA dose diet (L-BCAA), the normal dose BCAA diet (N-BCAA), or the high dose BCAA (H-BCAA) diet for 3 weeks.

Results

Our results show that compared with the N-BCAA group, the L-BCAA group had higher concentration of serum leptin (P < 0.05), while the H-BCAA group had lower concentration of serum adiponectin (P < 0.05). Fatty acid synthesis in pigs from the H-BCAA group was lower than those from the N-BCAA group with the down-regulation of lipogenic genes (ACACA, FASN, PPAR-r, SREBP-1c in ventral and dorsal fat, SREBP-1c in liver) and up-regulation of lipolysis genes (HSL, ATGL, CPT-1A, FABP4 in ventral fat, HSL in liver) (P < 0.05). Similarly, fatty acid synthesis in pigs from the L-BCAA group was also lower than those from the N-BCAA group with the decrease of lipogenic genes (ACACA in ventral, ACACA and FASN in dorsal fat, ACACA, FASN, SREBP-1c in liver) and the increase of lipolysis genes (ATGL, CPT-1A CD36, FABP4 in ventral fat and HSL, ATGL, CPT-1A in dorsal fat, CPT-1A) (P < 0.05). Feeding H-BCAA diet significantly reduced total m⁶A levels in ventral and dorsal fat and liver tissues (P < 0.05). The decrease of total m⁶A is associated with down-regulation of METTL3, METTL14 and FTO in dorsal fat and METTL3 and FTO in liver (P < 0.05). Decreased m⁶A modification of ACACA and FASN in ventral and dorsal adipose tissues was observed in pig fed with excessive BCAA.

Conclusion

These results suggest that insufficient or excessive BCAA decreased the fat deposition by increasing lipolysis and deceasing lipogenesis in adipose and liver tissues. Dietary excessive BCAA might regulate the process of lipid metabolism partly through the m⁶A RNA methylation.

Propionate alleviates high-fat diet-induced lipid dysmetabolism by modulating gut microbiota in mice

AIMS

The aims were to examine whether oral sodium propionate supplementation regulate lipid metabolism through modulating gut microbiota.

METHODS AND RESULTS

ICR male mice (26·98 ± 0·30 g) were randomly assigned to three groups (n = 10) and fed control diet (Con), high-fat diet (HFD) and HFD plus propionate (Pro) respectively. In this study, we found that HFD increased the weight of final body, inguinal white adipose tissues (iWAT), epididymal white adipose tissue (eWAT) and perirenal white adipose tissue (pWAT), as well as the adipocyte mean area of iWAT and eWAT in mice (P < 0·05), whereas sodium propionate treatment reduced the weight of iWAT and pWAT as well as adipocyte mean area of iWAT in mice fed a HFD (P < 0·05). Moreover, in the iWAT, the mRNA expression of lipogenesis genes, including peroxisome proliferator activated receptor γ, acetyl-CoA carboxylase and carnitine palmitoyl transferase-1β, was upregulated by HFD challenge (P < 0·05), and the elevation of these genes was nearly reversed to the level of control diet-fed mice by sodium propionate treatment. Meanwhile, sodium propionate treatment increased the hormone-sensitive lipase mRNA expression in the iWAT of HFD-fed mice (P < 0·05). High-throughput pyrosequencing of the 16S rRNA demonstrated that sodium propionate treatment significantly recovered the gut microbiota dysbiosis in HFD-fed mice, including the richness and diversity of microbiota and the ratio of Firmicutes to Bacteroidetes. Furthermore, the HFD-induced reductions in colonic levels of butyrate and valerate were reversed by sodium propionate treatment, which also normalized the serum LPS level seen in HFD-fed mice to the levels of the control diet-fed mice.

CONCLUSIONS

Collectively, these results indicated that sodium propionate treatment could improve lipid metabolism in HFD-fed mice, and the potential mechanisms might be via regulating gut microbiota.

SIGNIFICANCE AND IMPACT OF THE STUDY

We demonstrated for the first time that oral sodium propionate significantly improved HFD-induced dysbiosis of gut microbiota, indicating that the mitigative effect of propionate for HFD-induced lipid dysmetabolism might be mediated by gut microbiota in mice.

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.

β-Hydroxy-β-methylbutyrate modulates lipid metabolism in adipose tissues of growing pigs

BACKGROUND

The effects and roles of the leucine (Leu) metabolite β-hydroxy-β-methylbutyrate (HMB) in lipid metabolism in adipose tissues of pigs are still unknown.

OBJECTIVES

This study was conducted to investigate the effects of excess Leu versus HMB on growth, carcass traits, and lipid metabolism in adipose tissues of growing pigs.

METHODS AND RESULTS

Compared to control, the Leu/HMB group significantly increased/reduced weight of total fat mass, respectively, with a concurrent increase of serum adiponectin concentration (P < 0.05). Moreover, dietary HMB supplementation regulated the expression of genes involved in adipose tissue function, accompanied by increases/decreases in the phosphorylation of AMPKα/mTOR in perirenal adipose tissue, respectively (P < 0.05). Serum IL-15 concentration and the mRNA abundance of IL-15, PGC-1α, and NRF-1 were also increased in the HMB group (P < 0.05).

CONCLUSIONS

HMB supplementation can regulate adipose tissue function including fatty acid oxidation, lipolysis, and adipokine secretion. These effects may be partly mediated by AMPKα-mTOR pathway and associated with mitochondrial biogenesis, the AMPK-PGC-1α axis, and myokines secreted by muscle tissues.

Dietary Supplementation with Pioglitazone Hydrochloride and Chromium Methionine Improves Growth Performance, Meat Quality, and Antioxidant Ability in Finishing Pigs

This work was designed to investigate the synergistic effects of pioglitazone hydrochloride (PGZ) and chromium methionine (CrMet) on meat quality, muscle fatty acid profile, and antioxidant ability of pigs. Pigs in four groups were fed a basic diet or basic diet supplemented with 15 mg/kg of PGZ, 200 μg/kg of CrMet, or 15 mg/kg of PGZ + 200 μg/kg of CrMet. In comparison to the control group, the average daily feed intake, feed/gain ratio, and serum high-density lipoprotein level decreased in the PGZ + CrMet group. Dietary PGZ + CrMet supplementation increased carcass dressing percentage, intramuscular fat, and marbling score. The percentages of C18:1ω-9c, C18:2ω-6c, C18:3ω-3, and polyunsaturated fatty acid (PUFA) in the longissimus thoracis muscle were increased in the PGZ + CrMet group. Greater superoxide dismutase and glutathione peroxidase activities were observed in the PGZ + CrMet group compared to the control group. Collectively, these findings suggested that feed with PGZ and CrMet improved the growth performance and meat quality, especially for PUFA proportions and antioxidant ability.

Repletion of branched chain amino acids reverses mTORC1 signaling but not improved metabolism during dietary protein dilution

Objective

Dietary protein dilution (PD) has been associated with metabolic advantages such as improved glucose homeostasis and increased energy expenditure. This phenotype involves liver-induced release of FGF21 in response to amino acid insufficiency; however, it has remained unclear whether dietary dilution of specific amino acids (AAs) is also required. Circulating branched chain amino acids (BCAAs) are sensitive to protein intake, elevated in the serum of obese humans and mice and thought to promote insulin resistance. We tested whether replenishment of dietary BCAAs to an AA-diluted (AAD) diet is sufficient to reverse the glucoregulatory benefits of dietary PD.

Methods

We conducted AA profiling of serum from healthy humans and lean and high fat-fed or New Zealand obese (NZO) mice following dietary PD. We fed wildtype and NZO mice one of three amino acid defined diets: control, total AAD, or the same diet with complete levels of BCAAs (AAD + BCAA). We quantified serum AAs and characterized mice in terms of metabolic efficiency, body composition, glucose homeostasis, serum FGF21, and tissue markers of the integrated stress response (ISR) and mTORC1 signaling.

Results

Serum BCAAs, while elevated in serum from hyperphagic NZO, were consistently reduced by dietary PD in humans and murine models. Repletion of dietary BCAAs modestly attenuated insulin sensitivity and metabolic efficiency in wildtype mice but did not restore hyperglycemia in NZO mice. While hepatic markers of the ISR such as P-eIF2α and FGF21 were unabated by dietary BCAA repletion, hepatic and peripheral mTORC1 signaling were fully or partially restored, independent of changes in circulating glucose or insulin.

Conclusions

Repletion of BCAAs in dietary PD is sufficient to oppose changes in somatic mTORC1 signaling but does not reverse the hepatic ISR nor induce insulin resistance in type 2 diabetes during dietary PD.

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Dietary PD reduces serum BCAAs in humans and mice.

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Repletion of dietary BCAAs reverses somatic mTORC1 but not hepatic ISR signaling.

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Glucose control during dietary PD is unperturbed by BCAA repletion in diabetic mice.