Threonine, but Not Lysine and Methionine, Reduces Fat Accumulation by Regulating Lipid Metabolism in Obese Mice

SHMT, SHMTML and PRPS1 synergize to regulate blood digestion and nutrient metabolism in Aedes aegypti mosquitoes

Mosquitoes rely on vertebrate blood for nutrients vital for ovarian development. The enzyme serine hydroxymethyltransferase (SHMT) is crucial for amino acid and one‑carbon metabolism, playing a significant role in blood digestion and nutrient use in mosquitoes, though its functional mechanism remains further investigation. Using CRISPR/Cas9 to knock out the SHMT gene, we observed impaired blood digestion, delayed ovarian development, and inability to fly in mosquitoes. Multi-omics analysis revealed that SHMT deletion affected genes and metabolites related to amino acid metabolism. Knocking down SHMT-responsive genes mitochondrial-like serine hydroxymethyltransferase (SHMTML) and ribose-phosphate pyrophosphokinase 1 (PRPS1) also hindered blood digestion and ovarian development, mirroring SHMT-deficient mosquitoes. The interaction between SHMT, SHMTML, and PRPS1 was confirmed through various experiments, including Co-IP, GST pull-down, immunofluorescence colocalization, BiFC, molecular docking, and functional studies. Further research reveals that missing any of these proteins in mosquitoes results in ammonia and reactive oxygen species buildup, leading to mitochondrial problems, midgut cell damage, and abnormal enzyme expression. This study highlights a new molecular mechanism of SHMT and emphasizes its crucial interaction with SHMTML and PRPS1 in blood digestion and nutrient metabolism in vector mosquitoes. These findings may offer a strategic foundation for the development of innovative mosquito control measures.

Soybean hull polysaccharides ameliorate lipid metabolic disorders and gut microbiota dysbiosis in high-fat diet-fed zebrafish

Soybean hull polysaccharide (ASP), a pectic polysaccharide with potential effects on regulating lipid metabolism through gut microbiota and their metabolites, was studied to explore its regulatory mechanisms. The study examined the alleviating effect of ASP on high-fat diet (HFD) zebrafish through histopathological examination and biochemical analysis. Additionally, the lipid-lowering mechanism was analyzed combined with metabolomics and the proliferation of gut microbiota. Results showed that ASP significantly ameliorated body weight and blood lipids and also reduced hepatic lipid accumulation and hepatic lipid peroxidation damage. Bioinformatics analyses showed that ASP administration (240 μg/day) generated significant gut microbiota structural changes in high-fat diet-fed zebrafish, in particular, reducing Proteobacteria and increasing Cetobacterium relative abundance levels. ASP upregulates propionic acid, linoleic acid, 6-hydroxyhexanoic acid, and l-threonine biosynthesis by mediating gut microbiota regulation of amino acid and lipid metabolic pathways. Utilizing a correlation network derived from Spearman's correlation coefficients, significant microbial phylotypes that react to ASP demonstrated a strong association with parameters linked to lipid metabolic disorders. Fecal metabolites (e.g. propionic acid) were positively correlated with gut microbiota (e.g. Cetobacterium) in the high-dose ASP group. Our results provide a theoretical basis for new ASP prebiotic formulations to target the gut microbiota and prevent lipid metabolic disorders.

New insights into the effects of dietary amino acid composition on meat quality in pigs: A review

Pork is an affordable protein source with higher nutrient density. In recent years, meat quality in pigs is getting increasing attention, which has a direct impact on the economic value of pork. Dietary amino acids play a key role in pig production, not only regulating pig growth and health, but also contributing significantly to meat quality. In this review, we discuss the effect of skeletal muscle composition on meat quality. Importantly, we summarize the levels of essential amino acids (EAAs), such as lysine, methionine, threonine, tryptophan and branched-chain amino acids (BCAAs), in diets for finishing pigs to improve meat quality. The beneficial effects of flavor amino acids on meat quality, including flavor production, muscle fiber-type composition and intramuscular fat deposition, are further systematically summarized. We also focus on the impact of dietary amino acid levels on environmental benefits, although research in this area is still limited. Considering that the previously established EAA requirements are based on the principle of maximizing growth rate and feed conversion, this review will provide new insights into the effects of dietary amino acids on aspects of meat quality and highlight the current gaps to promote future research.

Threonine modulates the STAT3-SCD1 pathway to reduce fatty acid metabolism in duck hepatocytes

Dietary threonine (Thr) is known to influence fat deposition in poultry, but the precise mechanisms behind its regulatory effects on hepatic lipid metabolism remain elusive. Prior research indicated that including supplemental Thr in the feed may influence STAT3 (Signal Transducer and Activator of Transcription 3) levels in the liver of meat ducks. Numerous studies have recorded the function of STAT3 in regulating fatty acid (FA) metabolism in mammals. The primary objective of this study was to investigate whether Thr influences FA metabolism and triglycerides (TG) deposition in duck liver by regulating STAT3 expression. Primary hepatocytes were isolated from duck embryos and treated for 36 h with different doses of Thr (0, 10, 25, 50, 200 μM) in vitro or with a constructed STAT3 overexpression plasmid to examine the content of FAs and TG. RNA-seq was used to detect changes in gene expression in hepatocytes following STAT3 overexpression. The results demonstrated that both the exogenous addition of Thr and the overexpression of STAT3 significantly suppressed the capacity of hepatocytes for FAs deposition (P < 0.05). The overexpression of STAT3 also inhibited TG accumulation under conditions in response to Thr deficiency (P < 0.01). Transcriptomic analyses indicated that the overexpression of STAT3 inhibits the activity of triglyceride metabolism and unsaturated fatty acid biosynthesis (P < 0.01). Finally, a dual-luciferase reporter test demonstrated that STAT3 may systematically target and inhibit SCD1 transcription (P < 0.01). The present study indicates that supplemental Thr (50 μM) inhibits hepatic FA deposition via the STAT3-SCD1 pathway. This work enhances our comprehension of the functional roles of Thr and STAT3 in modulating lipid metabolism within duck livers. Moreover, it provides a partial theoretical foundation for the nutritional prevention and pharmacological intervention of lipid metabolism disorders in poultry.

Metabolic signatures of metabolic dysfunction-associated steatotic liver disease in severely obese patients

BACKROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) can lead to liver fibrosis, cirrhosis, and hepatocellular carcinoma. Still, most patients with MASLD die from cardiovascular diseases indicating metabolic alterations related to both liver and cardiovascular pathology.

AIMS AND METHODS

The aim of this study was to assess biologic pathways behind MASLD progression from steatosis to metabolic dysfunction-associated steatohepatitis (MASH) using non-targeted liquid chromatography-mass spectrometry analysis in 106 severely obese individuals (78 women, mean age 47.7 7 ± 9.2 years, body mass index 41.8 ± 4.3 kg/m²) undergoing laparoscopic Roux-en-Y gastric bypass.

RESULTS

We identified several metabolites that are associated with MASLD progression. Most importantly, we observed a decrease of lysophosphatidylcholines LPC(18:2), LPC(18:3), and LPC(20:3) and increase of xanthine when comparing those with steatosis to those with MASH. We found that indole propionic acid and threonine were negatively correlated to fibrosis, but not with the metabolic disturbances associated with cardiovascular risk. Xanthine, ketoleucine, and tryptophan were positively correlated to lobular inflammation and ballooning but also with insulin resistance, and dyslipidemia, respectively. The results did not change when taking into account the most important genetic risk factors of MASLD.

CONCLUSIONS

Our findings suggest that there are several separate biological pathways, some of them independent of insulin resistance and dyslipidemia, associating with MASLD.

Study on serum metabolomics characteristics of obese patients with erectile dysfunction

Erectile dysfunction (ED) is a common male sexual health problem that can be associated with obesity. This study aimed to identify serum metabolic differences and pathways related to ED in obese men using non-targeted metabolomics techniques. We included 54 obese male patients with (n = 27) and without (n = 27) ED. We collected 5 mL of fasting elbow vein blood and analyzed serum metabolites using ultra-high-performance liquid chromatography-mass spectrometry. Multivariate statistical methods (principal component analysis and orthogonal partial least squares discriminant analysis) were used to identify differential metabolites between the groups. Finally, pathway analysis using the Kyoto encyclopedia of genes and genomes database identified 4 differential metabolic pathways in obese men with ED compared to obese men without ED. A total of 77 differential metabolites were identified in obese men with ED compared to the control group (obese men without ED) using a threshold of variable importance in the projection > 1 and P < .05. Pathway analysis revealed 4 main differences: glycine, serine and threonine metabolism, glycerophospholipid metabolism, aminoacyl-tRNA biosynthesis, and D-glutamine and D-glutamate metabolism. Specific metabolites associated with these pathways included betaine aldehyde, choline, L-threonine, phosphatidylcholine, L-serine, and D-glutamine. Our findings suggest abnormalities in fatty acid metabolism, phospholipid metabolism, and amino acid metabolism between obese men with and without ED. Metabolites such as betaine aldehyde, choline, L-threonine, phosphatidylcholine, L-serine, and D-glutamine may be potential biomarkers for distinguishing obese men with ED.

In vitro digestibility and angiotensin converting enzyme (ACE) inhibitory activity of solid-state fermented fava beans (Vicia faba L.)

Reducing the content of quickly absorbed carbohydrates and saturated fats in snack formulations while increasing the consumption of high-quality proteins are effective strategies to prevent obesity in childhood. Thus, the nutritional value, digestibility, and functionality of fava beans (Vicia faba L.) fermented with Pleurotus ostreatus were examined as potential ingredients for food design. Solid-state fermentation enhanced the protein content by 16% with a rise in essential (25%) and non-essential (15%) amino acids while decreasing total carbohydrate content and tannin levels. Moreover, fermentation modified the amino acid profile released during digestion, increasing amino acids such as valine, isoleucine, and threonine, which are vital for health and development in childhood. Furthermore, the bioaccessible fraction of the fermented bean showed a 60% of ACE inhibition and improved magnesium bioaccessibility. Consequently, fava beans fermented with Pleurotus ostreatus emerged as a new ingredient in the development of new protein-rich snacks tailored for children and adolescents.

Untargeted Metabolite Profiling Reveals Acute Toxicity of Pentosidine on Adipose Tissue of Rats

Background: Pentosidine is an advanced glycation end product that is commonly found in heat-processed foods. Pentosidine has been involved in the occurrence and development of some chronic diseases. It was reported that pentosidine exposure can impair the function of the liver and kidneys. Adipose tissue, as an active endocrine organ, plays an important role in maintaining the normal physiological function of cells. However, the metabolic mechanism that causes pentosidine to induce toxicity in adipose tissue remains unclear. Methods: In the study, thirty male Sprague-Dawley rats were divided into a normal diet group, low dose group, and high dose group. A non-targeted metabolomics approach was used to compare the metabolic profiles of adipose tissue between the pentosidine and normal diet groups. Furthermore, histopathological observation and body weight change analysis were performed to test the results of the metabolomics analysis. Results: A total of forty-two differential metabolites were identified. Pentosidine mainly disturbed twelve metabolic pathways, such as ascorbate and aldarate metabolism, glycine, serine, and threonine metabolism, sulfur metabolism, pyruvate metabolism, etc. Additionally, pyruvic acid was identified as a possible key upregulated metabolite involved in thirty-four metabolic pathways. α-Ketoglutaric acid was named as a probable key downregulated metabolite involved in nineteen metabolic pathways based on enrichment network analysis. In addition, histopathological analysis and body weight changes confirmed the results of the metabolomics analysis. Conclusions: These results provided a new perspective for the molecular mechanisms of adipose tissue toxicity induced by pentosidine.

Regulatory mechanisms of amino acids in ferroptosis

Ferroptosis, an iron-dependent non-apoptotic regulated cell death process, is associated with the pathogenesis of various diseases. Amino acids, which are indispensable substrates of vital activities, significantly regulate ferroptosis. Amino acid metabolism is involved in maintaining iron and lipid homeostasis and redox balance. The regulatory effects of amino acids on ferroptosis are complex. An amino acid may exert contrasting effects on ferroptosis depending on the context. This review systematically and comprehensively summarized the distinct roles of amino acids in regulating ferroptosis and highlighted the emerging opportunities to develop clinical therapeutic strategies targeting amino acid-mediated ferroptosis.

Leucine Supplementation Modulates Lipid Metabolism and Inflammation in Early Weaning Piglets

Early weaning can induce the programmed dysregulation of glycolipid metabolism and inflammation in adult animals. The primary objective of this study was to evaluate the efficacy of leucine supplementation administered promptly after early weaning in mitigating these adverse effects in piglets. At day 21, 24 piglets were randomly selected and divided into 3 groups: EW group where the piglets were weaned at day 21 and fed basal diet, EWL group where the piglets were weaned at day 21 and fed the basal diet with supplementation of 1% leucine, and C group where the piglets were fed basal diet and weaned at 28 days. Each group contained eight replicates, with one piglet per replicate. The results indicated that early weaning had an impact on gut health and could activate the inhibitor of the kappa B kinase gamma/inhibitor kappa B alpha/NF-kappa-B (IKKγ/IκBα/NF-κB) signaling pathway to ameliorate pro-inflammatory factor and apoptosis levels. Furthermore, early weaning reduced the activity of fatty acid β oxidation (FAβO) and affected genes linked with lipid metabolism. Supplementing with leucine can improve the effects of these factors. In summary, leucine may alleviate the influences of early weaning on the lipid metabolism and inflammation in piglets.

Aqueous extract of fermented Eucommia ulmoides leaves alleviates hyperlipidemia by maintaining gut homeostasis and modulating metabolism in high-fat diet fed rats

BACKGROUND

As a traditional Chinese medicinal herb, the lipid-lowing biological potential of Eucommia ulmoides leaves (EL) has been demonstrated. After fermentation, the EL have been made into various products with lipid-lowering effects and antioxidant activity. However, the anti-hyperlipidemic mechanism of fermented Eucommia ulmoides leaves (FEL) is unclear now.

PURPOSE

To evaluate the effects of FEL on hyperlipidemia and investigate the mechanism based on regulating gut homeostasis and host metabolism.

METHODS

Hyperlipidemia animal model in Wistar rats was established after 8 weeks high-fat diet (HFD) fed. The administered doses of aqueous extract of FEL (FELE) were 128, 256 and 512 mg/kg/d, respectively. Serum biochemical parameters detection, histopathological sections analysis, 16S rDNA sequencing of gut microbiota and untargeted fecal metabolomics analysis, were performed to determine the therapeutic effects and predict related pathways of FELE on hyperlipidemia. The changes of proteins and genes elated to lipid were detected by Immunofluorescence (IF) and quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

56 Components in FELE were identified by UPLC-MS, with organic acids, flavonoids and phenolic acids accounting for the majority. The intervention of FELE significantly reduced the body weight, lipid accumulation and the levels of total cholesterol (TC), triglycerides (TG), and low-density lipoprotein-cholesterol (LDL-C) in hyperlipidemia rats, while increased the level of High-density lipoprotein-cholesterol (HDL-C). Meanwhile, FELE improved the inflammatory makers and oxidative stress factors, which is tumor necrosis factor-α (TNF-α), monocyte chemotactic protein-1 (MCP-1), interleukin-6 (IL-6), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT). These results demonstrated that FETE can effectively reduce blood lipids and alleviate inflammation and oxidative damage caused by hyperlipidemia. Mechanistically, FELE restore the homeostasis of gut microbiota by reducing the Firmicutes/Bacteroidetes ratio and increasing the abundance of probiotics, especially Lactobacillus, Rombousia, Bacteroides, Roseburia, Clostridia_UCG-014_Unclassified, while modulated metabolism through amino acid, bile acid and lipid-related metabolism pathways. In addition, the Pearson correlation analysis found that the upregulated bilirubin, threonine, dopamine and downregulated lipocholic acid, d-sphingosine were key metabolites after FELE intervention. IF and qRT-PCR analysis showed that FELE upregulated the expression of fatty acid oxidation proteins and genes (PPARα, CPT1A), bile acid synthesis and excretion proteins and genes (LXRα, CYP7A1, FXR), and downregulated the expression of adipogenic gene (SREBP-1c) by regulating gut microbiota to improve metabolism and exert a lipid-lowering effect.

CONCLUSION

This work filled the lipid-lowering mechanism gap of FEL. FELE can improve HFD-induced hyperlipidemia by regulating the gut microbiota homeostasis and metabolism. Thus, FEL has the potential to develop into the novel raw material of lipid-lowering drugs.

Metabolic liability for weight gain in early adulthood

While weight gain is associated with a host of chronic illnesses, efforts in obesity have relied on single "snapshots" of body mass index (BMI) to guide genetic and molecular discovery. Here, we study >2,000 young adults with metabolomics and proteomics to identify a metabolic liability to weight gain in early adulthood. Using longitudinal regression and penalized regression, we identify a metabolic signature for weight liability, associated with a 2.6% (2.0%-3.2%, p = 7.5 × 10-19) gain in BMI over ≈20 years per SD higher score, after comprehensive adjustment. Identified molecules specified mechanisms of weight gain, including hunger and appetite regulation, energy expenditure, gut microbial metabolism, and host interaction with external exposure. Integration of longitudinal and concurrent measures in regression with Mendelian randomization highlights the complexity of metabolic regulation of weight gain, suggesting caution in interpretation of epidemiologic or genetic effect estimates traditionally used in metabolic research.

Metabolic effects of an essential amino acid supplement in adolescents with PCOS and obesity

OBJECTIVE

Polycystic ovary syndrome (PCOS) is characterized by hyperandrogenism, insulin resistance, and hepatic steatosis (HS). Because dietary essential amino acid (EAA) supplementation has been shown to decrease HS in various populations, this study's objective was to determine whether supplementation would decrease HS in PCOS.

METHODS

A randomized, double-blind, crossover, placebo-controlled trial was conducted in 21 adolescents with PCOS (BMI 37.3 ± 6.5 kg/m2, age 15.6 ± 1.3 years). Liver fat, very low-density lipoprotein (VLDL) lipogenesis, and triacylglycerol (TG) metabolism were measured following each 28-day phase of placebo or EAA.

RESULTS

Compared to placebo, EAA was associated with no difference in body weight (p = 0.673). Two markers of liver health improved: HS was lower (-0.8% absolute, -7.5% relative reduction, p = 0.013), as was plasma aspartate aminotransferase (AST) (-8%, p = 0.004). Plasma TG (-9%, p = 0.015) and VLDL-TG (-21%, p = 0.031) were reduced as well. VLDL-TG palmitate derived from lipogenesis was not different between the phases, nor was insulin sensitivity (p > 0.400 for both). Surprisingly, during the EAA phase, participants reported consuming fewer carbohydrates (p = 0.038) and total sugars (p = 0.046).

CONCLUSIONS

Similar to studies in older adults, short-term EAA supplementation in adolescents resulted in significantly lower liver fat, AST, and plasma lipids and thus may prove to be an effective treatment in this population. Additional research is needed to elucidate the mechanisms for these effects.

Molecular mechanism and therapeutic significance of essential amino acids in metabolically associated fatty liver disease

Non-alcoholic fatty liver disease (NAFLD), also known as metabolically associated fatty liver disease (MAFLD), is a systemic metabolic disease characterized by lipid accumulation in the liver, lipid toxicity, insulin resistance, intestinal dysbiosis, and inflammation that can progress from simple steatosis to nonalcoholic steatohepatitis (NASH) and even cirrhosis or cancer. It is the most prevalent illness threatening world health. Currently, there are almost no approved drug interventions for MAFLD, mainly dietary changes and exercise to control weight and regulate metabolic disorders. Meanwhile, the metabolic pathway involved in amino acid metabolism also influences the onset and development of MAFLD in the body, and most amino acid metabolism takes place in the liver. Essential amino acids are those amino acids that must be supplemented from outside the diet and that cannot be synthesized in the body or cannot be synthesized at a rate sufficient to meet the body's needs, including leucine, isoleucine, valine (collectively known as branched-chain amino acids), tryptophan, phenylalanine (which are aromatic amino acids), histidine, methionine, threonine and lysine. The metabolic balance of the body is closely linked to these essential amino acids, and essential amino acids are closely linked to the pathophysiological process of MAFLD. In this paper, we will focus on the metabolism of essential amino acids in the body and further explore the therapeutic strategies for MAFLD based on the studies conducted in recent years.

Excessive Tryptophan and Phenylalanine Induced Pancreatic Injury and Glycometabolism Disorder in Grower-finisher Pigs

BACKGROUND

The increase in circulating insulin levels is associated with the onset of type 2 diabetes (T2D), and the levels of branched-chain amino acids and aromatic amino acids (AAAs) are altered in T2D, but whether AAAs play a role in insulin secretion and signaling remains unclear.

OBJECTIVES

This study aimed to investigate the effects of different AAAs on pancreatic function and on the use of insulin in finishing pigs.

METHODS

A total of 18 healthy finishing pigs (Large White) with average body weight of 100 ± 1.15 kg were randomly allocated to 3 dietary treatments: Con, a normal diet supplemented with 0.68% alanine; Phe, a normal diet supplemented with 1.26% phenylalanine; and Trp, a normal diet supplemented with 0.78% tryptophan. The 3 diets were isonitrogenous. There were 6 replicates in each group.

RESULTS

Herein, we investigated the effects of tryptophan and phenylalanine on pancreatic function and the use of insulin in finishing pigs and found that the addition of tryptophan and phenylalanine aggravated pancreatic fat deposition, increased the relative content of saturated fatty acids, especially palmitate (C16:0) and stearate (C18:0), and the resulting lipid toxicity disrupted pancreatic secretory function. We also found that tryptophan and phenylalanine inhibited the growth and secretion of β-cells, downregulated the gene expression of the PI3K/Akt pathway in the pancreas and liver, and reduced glucose utilization in the liver.

CONCLUSIONS

Using fattening pigs as a model, multiorgan combined analysis of the insulin-secreting organ pancreas and the main insulin-acting organ liver, excessive intake of tryptophan and phenylalanine will aggravate pancreatic damage leading to glucose metabolism disorders, providing new evidence for the occurrence and development of T2D.

Hedan tablet ameliorated non-alcoholic steatohepatitis by moderating NF-κB and lipid metabolism-related pathways via regulating hepatic metabolites

Non-alcoholic steatohepatitis (NASH) is a severe form of fatty liver disease. If not treated, it can lead to liver damage, cirrhosis and even liver cancer. However, advances in treatment have remained relatively slow, and there is thus an urgent need to develop appropriate treatments. Hedan tablet (HDP) is used to treat metabolic syndrome. However, scientific understanding of the therapeutic effect of HDP on NASH remains limited. We used HDP to treat a methionine/choline-deficient diet-induced model of NASH in rats to elucidate the therapeutic effects of HDP on liver injury. In addition, we used untargeted metabolomics to investigate the effects of HDP on metabolites in liver of NASH rats, and further validated its effects on inflammation and lipid metabolism following screening for potential target pathways. HDP had considerable therapeutic, anti-oxidant, and anti-inflammatory effects on NASH. HDP could also alter the hepatic metabolites changed by NASH. Moreover, HDP considerable moderated NF-κB and lipid metabolism-related pathways. The present study found that HDP had remarkable therapeutic effects in NASH rats. The therapeutic efficacy of HDP in NASH mainly associated with regulation of NF-κB and lipid metabolism-related pathways via arachidonic acid metabolism, glycine-serine-threonine metabolism, as well as steroid hormone biosynthesis.

Regulation of Sacha Inchi protein on fecal metabolism and intestinal microorganisms in mice

Introduction

With the increasing demand for protein utilization, exploring new protein resources has become a research hotspot. Sacha Inchi Protein (SIP) is a high-quality plant protein extracted from Sacha Inchi meal. This study aimed to investigate the impact of SIP on mouse metabolomics and gut microbiota diversity and explore the underlying pathways responsible for its health benefits.

Methods

In this study, the structural composition of SIP was investigated, and the effects of SIP on fecal metabolomics and intestinal microorganisms in mice were explored by LC-MS metabolomics technology analysis and 16S rRNA gene sequencing.

Results

The results showed that SIP was rich in amino acids, with the highest Manuscript Click here to view linked References content of arginine, which accounted for 22.98% of the total amino acid content; the potential fecal metabolites of mice in the SIP group involved lipid metabolism, sphingolipid metabolism, arginine biosynthesis, and amino acid metabolism; SIP altered the microbial composition of the cecum in mice, decreased the Firmicutes/Bacteroidetes value, and It decreased the abundance of the harmful intestinal bacteria Actinobacteriota and Desulfobacterota, and increased the abundance of the beneficial intestinal bacteria Faecalibaculum, Dubosiella.

Discussion

In conclusion, SIP is a high-quality plant protein with great potential for development in lipid-lowering, intestinal health, and mental illness, providing valuable clues for further research on its health-promoting mechanisms.

l-valine supplementation disturbs vital molecular pathways and induces apoptosis in mouse testes

The branched-chain amino acids (BCAAs: leucine, isoleucine and valine) are essential for animal growth and metabolic health. However, the effect of valine on male reproduction and its underlying molecular mechanism remain largely unknown. Here, we showed that l-valine supplementation (0.30% or 0.45%, water drinking for 3 weeks) did not change body and testis weights, but significantly altered morphology of sertoli cells and germ cells within seminiferous tubule, and enlarged the space between seminiferous tubules within mouse testis. l-valine treatment (0.45%) increased significantly the Caspase3/9 mRNA levels and CASPASE9 protein levels, therefore induced apoptosis of mouse testis. Moreover, gene expression levels related to autophagy (Atg5 and Lamb3), DNA 5 mC methylation (Dnmt1, Dnmt3a, Tet2 and Tet3), RNA m6A methylation (Mettl14, Alkbh5 and Fto), and m6A methylation binding proteins (Ythdf1/2/3 and Igf2bp1/2) were significantly reduced. Protein abundances of ALKBH5, FTO and YTHDF3 were also significantly reduced, but not for ATG5 and TET2. Testis transcriptome sequencing detected 537 differentially expressed genes (DEGs, 26 up-regulated and 511 down-regulated), involved in multiple important signaling pathways. RT-qPCR validated 8 of 9 DEGs (Cd36, Scd1, Insl3, Anxa5, Lcn2, Hsd17b3, Cyp11a1, Cyp17a1 and Agt) to be decreased significantly, consistent with RNA-seq results. Taken together, l-valine treatment could disturb multiple signaling pathways (autophagy and RNA methylation etc.), and induce apoptosis to destroy the tissue structure of mouse testis.

Integrated analysis of metabolomic and transcriptomic profiling reveals the effect of Atractylodes oil on Spleen Yang Deficiency Syndrome in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Spleen Yang Deficiency Syndrome (SYDS), which is a syndrome commonly treated with Traditional Chinese Medicine (TCM), manifests as overall metabolic dysfunction caused mainly by digestive system disorders. Atractylodes lancea (Thunb.) DC. (AL) is a widely used traditional herb with the efficacy of eliminate dampness and strengthen the spleen, Atractylodes oil (AO) is a medicinal component of AL and can be used to treat various gastrointestinal disorders. However, its effects on SYDS and underlying mechanisms have not been clarified to date.

AIM OF THE STUDY

The present study aimed to investigate the efficacy of AO in the improvement of the symptoms of SYDS in rat and the underlying mechanism by integrating transcriptomics, and metabolomics.

MATERIALS AND METHODS

The SYDS rats induced by reserpine were treated with AO. The protective effect of AO on SYDS rats was evaluated by serum biochemical detection, histopathological analyses. Enzyme-linked immunosorbent assay (ELISA), colorimetric assay and immunofluorescence (IF) were performed to determine the levels of relevant indicators of mitochondrial function and energy metabolism in the liver. Liver metabolites and transcript levels were assessed by non-targeted metabolomics and transcriptomics to analyze potential molecular mechanisms and targets. The expression of the corresponding proteins was verified using Western blotting.

RESULTS

AO not only regulated the digestion, absorption function and oxidative stress status of SYDS rats, but also improved mitochondrial function and alleviated energy metabolism disorders in SYDS rats. Metabolomic and transcriptomic analyses demonstrated that AO regulation is mainly exerted in amino acid metabolism, unsaturated fatty acid metabolism, TCA cycle as well as PPAR and AMPK signaling pathways. In addition, The AMPK signaling pathway was verified and AO promoted AMPK phosphorylation and the expression of SIRT1, PGC-1α, and PPARα in SYDS rats.

CONCLUSIONS

The therapeutic effect of AO on SYDS is potentially attributable to activation of the AMPK/SIRT1/PGC-1α signaling pathway, which enhances transport and regulation of energy metabolism.

Heat-moisture treatment enhances the ordered degree of starch structure in whole chestnut flour and alters its gut microbiota modulation in mice fed with high-fat diet

Currently, chestnuts attract more attention among consumers due to its rich nutritional functions, but systematic evaluation on the effect of thermal processing on its nutritional value is still limited. In this work, based on results of microstructural properties that heat-moisture treatment (HMT) could enhance the total ordered degree of starch structure in whole chestnut flour (CN) and promote the formation of anti-enzymatic component, in vitro experiment was then conducted and confirmed that HMT could significantly reduce the predicted glycemic index (pGI) of CN from 75.6 to 64.3 and improve its dietary fiber content from 7.06 to 13.42 g/100 g (p < 0.05). Further dietary intervention studies with CN and heat-moisture treated CN (HMT-CN) supplementation on the high-fat diet (HFD) consuming mice were discussed in terms of gut microbiota and its metabolites changes. The results showed that both CN and HMT-CN significantly resisted the weight gain induced by HFD, while HMT-CN had better serum lipid regulation effect. However, they had different effects on the gut metabolism pathways, among which CN inhibited the production of stearamine by promoting the proliferation of Dubosiella, while HMT-CN contributed to the growth of Lachnoclostridium, Desulfovibrio, and Faecalibaculum which stimulated the formation of associated metabolites including jwh-018-d11, valylproline, tetranor-12(S)-HETE, and PA (3:0/18:0). Overall, these discoveries could provide basic data for the effective utilization of CN in food industry processing.

Abrupt Photoperiod Changes Differentially Modulate Hepatic Antioxidant Response in Healthy and Obese Rats: Effects of Grape Seed Proanthocyanidin Extract (GSPE)

Disruptions of the light/dark cycle and unhealthy diets can promote misalignment of biological rhythms and metabolic alterations, ultimately leading to an oxidative stress condition. Grape seed proanthocyanidin extract (GSPE), which possesses antioxidant properties, has demonstrated its beneficial effects in metabolic-associated diseases and its potential role in modulating circadian disruptions. Therefore, this study aimed to assess the impact of GSPE administration on the liver oxidant system of healthy and diet-induced obese rats undergoing a sudden photoperiod shift. To this end, forty-eight photoperiod-sensitive Fischer 344/IcoCrl rats were fed either a standard (STD) or a cafeteria diet (CAF) for 6 weeks. A week before euthanizing, rats were abruptly transferred from a standard photoperiod of 12 h of light/day (L12) to either a short (6 h light/day, L6) or a long photoperiod (18 h light/day, L18) while receiving a daily oral dose of vehicle (VH) or GSPE (25 mg/kg). Alterations in body weight gain, serum and liver biochemical parameters, antioxidant gene and protein expression, and antioxidant metabolites were observed. Interestingly, GSPE partially ameliorated these effects by reducing the oxidative stress status in L6 through an increase in GPx1 expression and in hepatic antioxidant metabolites and in L18 by increasing the NRF2/KEAP1/ARE pathway, thereby showing potential in the treatment of circadian-related disorders by increasing the hepatic antioxidant response in a photoperiod-dependent manner.

Leucine Supplementation Ameliorates Early-Life Programming of Obesity in Rats

The advanced cessation of lactation elevates the risk of programmed obesity and obesity-related metabolic disorders in adulthood. This study used multiomic analysis to investigate the mechanism behind this phenomenon and the effects of leucine supplementation on ameliorating programmed obesity development. Wistar/SD rat offspring were subjected to early weaning (EW) at day 17 (EWWIS and EWSD groups) or normal weaning at day 21 (CWIS and CSD groups). Half of the rats from the EWSD group were selected to create a new group with 2-month leucine supplementation at day 150. The results showed that EW impaired lipid metabolic gene expression and increased insulin, neuropeptide Y, and feed intake, inducing obesity in adulthood. Six lipid metabolism-related genes (Acot1, Acot2, Acot4, Scd, Abcg8, and Cyp8b1) were influenced by EW during the entire experimental period. Additionally, adult early-weaned rats exhibited cholesterol and fatty acid β-oxidation disorders, liver taurine reduction, cholestasis, and insulin and leptin resistance. Leucine supplementation partly alleviated these metabolic disorders and increased liver L-carnitine, retarding programmed obesity development. This study provides new insights into the mechanism of programmed obesity development and the potential benefits of leucine supplementation, which may offer suggestions for life planning and programmed obesity prevention.

ARTICLE HIGHLIGHTS

Early-weaned adult rats showed excess lipid accumulation and metabolic defects. Early weaning disrupts lipid metabolism and secretion of neuropeptide Y and insulin. The altered lipid metabolic gene expression in this study is vital in programming. Leucine mitigates metabolic disorders and hampers programmed obesity development.

Multi-omics approach to socioeconomic disparity in metabolic syndrome reveals roles of diet and microbiome

The epidemy of metabolic syndrome (MetS) is typically preceded by adoption of a "risky" lifestyle (e.g., dietary habit) among populations. Evidence shows that those with low socioeconomic status (SES) are at an increased risk for MetS. To investigate this, we recruited 123 obese subjects (body mass index [BMI] ≥ 30) from Chicago. Multi-omic data were collected to interrogate fecal microbiota, systemic markers of inflammation and immune activation, plasma metabolites, and plasma glycans. Intestinal permeability was measured using the sugar permeability testing. Our results suggest a heterogenous metabolic dysregulation among obese populations who are at risk of MetS. Systemic inflammation, linked to poor diet, intestinal microbiome dysbiosis, and gut barrier dysfunction may explain the development of MetS in these individuals. Our analysis revealed 37 key features associated with increased numbers of MetS features. These features were used to construct a composite metabolic-inflammatory (MI) score that was able to predict progression of MetS among at-risk individuals. The MI score was correlated with several markers of poor diet quality as well as lower levels of gut microbial diversity and abnormalities in several species of bacteria. This study reveals novel targets to reduce the burden of MetS and suggests access to healthy food options as a practical intervention.

Insoluble Dietary Fiber from Okara Combined with Intermittent Fasting Treatment Synergistically Confers Antiobesity Effects by Regulating Gut Microbiota and Its Metabolites

Insoluble dietary fiber (IDF) was recently revealed to have an antiobesity impact. However, the impact and potential mechanism of high-purity IDF derived from okara (HPSIDF) on obesity caused by a high-fat diet (HFD) remain unclear. Except for dietary supplementation, intermittent fasting (IF) has attracted extensive interest as a new dietary strategy against obesity. Thus, we hypothesize that HPSIDF combined with IF treatment may be more effective in preventing obesity. In this study, HPSIDF combined with IF treatment synergistically alleviated HFD-induced dyslipidemia, impaired glucose homeostasis, systemic inflammation, and fat accumulation. Furthermore, gut microbiota dysbiosis and lowered short-chain fatty acid synthesis were recovered by HPSIDF combined with IF treatment. Meanwhile, metabolomic analysis of feces revealed that HPSIDF combined with IF treatment obviously reversed the alterations of metabolic pathways and differential metabolites induced by HFD, which were linked to the modulations of the gut microbiota. Collectively, our findings indicated that HPSIDF combined with IF treatment has great potential to substantially enhance antiobesity efficacy by modulating the gut microbiota and its metabolites.

Identifying possible biomarkers of lower urinary tract symptoms using metabolomics and partial least square regression

INTRODUCTION

The objective of this study was to explore potential novel biomarkers for moderate to severe lower urinary tract symptoms (LUTS) using a metabolomics-based approach, and statistical methods with significant different features than previous reported.

MATERIALS AND METHODS

The patients and the controls were selected to participate in the study according to inclusion/exclusion criteria (n = 82). We recorded the following variables: International prostatic symptom score (IPSS), prostate volume, comorbidities, PSA, height, weight, triglycerides, glycemia, HDL cholesterol, and blood pressure. The study of 41 plasma metabolites was done using the nuclear magnetic resonance spectroscopy technique. First, the correlations between the metabolites and the IPSS were done using Pearson. Second, significant biomarkers of LUTS from metabolites were further analysed using a multiple linear regression model. Finally, we validated the findings using partial least square regression (PLS).

RESULTS

Small to moderate correlations were found between IPSS and methionine (-0.301), threonine (-0.320), lactic acid (0.294), pyruvic acid (0.207) and 2-aminobutyric-acid (0.229). The multiple linear regression model revealed that only threonine (p = 0.022) was significantly associated with IPSS, whereas methionine (p = 0.103), lactic acid (p = 0.093), pyruvic acid (p = 0.847) and 2-aminobutyric-acid (p = 0.244) lost their significance. However, all metabolites lost their significance in the PLS model.

CONCLUSION

When using the robust PLS-regression method, none of the metabolites in our analysis had a significant association with lower urinary tract symptoms. This highlights the importance of using appropriate statistical methods when exploring new biomarkers in urology.

Resistant starches from dietary pulses modulate the gut metabolome in association with microbiome in a humanized murine model of ageing

Emerging evidence suggests that plant-based fiber-rich diets improve ageing-associated health by fostering a healthier gut microbiome and microbial metabolites. However, such effects and mechanisms of resistant starches from dietary pulses remain underexplored. Herein, we examine the prebiotic effects of dietary pulses-derived resistant starch (RS) on gut metabolome in older (60-week old) mice carrying a human microbiome. Gut metabolome and its association with microbiome are examined after 20-weeks feeding of a western-style diet (control; CTL) fortified (5% w/w) with RS from pinto beans (PTB), black-eyed-peas (BEP), lentils (LEN), chickpeas (CKP), or inulin (INU; reference control). NMR spectroscopy-based untargeted metabolomic analysis yield differential abundance linking phenotypic differences in specific metabolites among different RS groups. LEN and CKP increase butyrate, while INU promotes propionate. Conversely, bile acids and cholesterol are reduced in prebiotic groups along with suppressed choline-to-trimethylamine conversion by LEN and CKP, whereas amino acid metabolism is positively altered. Multi-omics microbiome-metabolome interactions reveal an association of beneficial metabolites with the Lactobacilli group, Bacteroides, Dubosiella, Parasutterella, and Parabacteroides, while harmful metabolites correlate with Butyricimonas, Faecalibaculum, Colidextribacter, Enterococcus, Akkermansia, Odoribacter, and Bilophila. These findings demonstrate the functional effects of pulses-derived RS on gut microbial metabolism and their beneficial physiologic responses in an aged host.

Collagen Peptide Exerts an Anti-Obesity Effect by Influencing the Firmicutes/Bacteroidetes Ratio in the Gut

Alterations in the intestinal microbial flora are known to cause various diseases, and many people routinely consume probiotics or prebiotics to balance intestinal microorganisms and the growth of beneficial bacteria. In this study, we selected a peptide from fish (tilapia) skin that induces significant changes in the intestinal microflora of mice and reduces the Firmicutes/Bacteroidetes ratio, which is linked to obesity. We attempted to verify the anti-obesity effect of selected fish collagen peptides in a high-fat-diet-based obese mouse model. As anticipated, the collagen peptide co-administered with a high-fat diet significantly inhibited the increase in the Firmicutes/Bacteroidetes ratio. It increased specific bacterial taxa, including Clostridium_sensu_stricto_1, Faecalibaculum, Bacteroides, and Streptococcus, known for their anti-obesity effects. Consequently, alterations in the gut microbiota resulted in the activation of metabolic pathways, such as polysaccharide degradation and essential amino acid synthesis, which are associated with obesity inhibition. In addition, collagen peptide also effectively reduced all obesity signs caused by a high-fat diet, such as abdominal fat accumulation, high blood glucose levels, and weight gain. Ingestion of collagen peptides derived from fish skin induced significant changes in the intestinal microflora and is a potential auxiliary therapeutic agent to suppress the onset of obesity.

Nutrient sensors and their crosstalk

The macronutrients glucose, lipids, and amino acids are the major components that maintain life. The ability of cells to sense and respond to fluctuations in these nutrients is a crucial feature for survival. Nutrient-sensing pathways are thus developed to govern cellular energy and metabolic homeostasis and regulate diverse biological processes. Accordingly, perturbations in these sensing pathways are associated with a wide variety of pathologies, especially metabolic diseases. Molecular sensors are the core within these sensing pathways and have a certain degree of specificity and affinity to sense the intracellular fluctuation of each nutrient either by directly binding to that nutrient or indirectly binding to its surrogate molecules. Once the changes in nutrient levels are detected, sensors trigger signaling cascades to fine-tune cellular processes for energy and metabolic homeostasis, for example, by controlling uptake, de novo synthesis or catabolism of that nutrient. In this review, we summarize the major discoveries on nutrient-sensing pathways and explain how those sensors associated with each pathway respond to intracellular nutrient availability and how these mechanisms control metabolic processes. Later, we further discuss the crosstalk between these sensing pathways for each nutrient, which are intertwined to regulate overall intracellular nutrient/metabolic homeostasis.

Lysine Deprivation Suppresses Adipogenesis in 3T3-L1 Cells: A Transcriptome Analysis

Growing evidence proves that amino acid restriction can reverse obesity by reducing adipose tissue mass. Amino acids are not only the building blocks of proteins but also serve as signaling molecules in multiple biological pathways. The study of adipocytes' response to amino acid level changes is crucial. It has been reported that a low concentration of lysine suppresses lipid accumulation and transcription of several adipogenic genes in 3T3-L1 preadipocytes. However, the detailed lysine-deprivation-induced cellular transcriptomic changes and the altered pathways have yet to be fully studied. Here, using 3T3-L1 cells, we performed RNA sequencing on undifferentiated and differentiated cells, and differentiated cells under a lysine-free environment, and the data were subjected to KEGG enrichment. We found that the differentiation process of 3T3-L1 cells to adipocytes required the large-scale upregulation of metabolic pathways, mainly on the mitochondrial TCA cycle, oxidative phosphorylation, and downregulation of the lysosomal pathway. Single amino acid lysine depletion suppressed differentiation dose dependently. It disrupted the metabolism of cellular amino acids, which could be partially reflected in the changes in amino acid levels in the culture medium. It inhibited the mitochondria respiratory chain and upregulated the lysosomal pathway, which are essential for adipocyte differentiation. We also noticed that cellular interleukin 6 (IL6) expression and medium IL6 level were dramatically increased, which was one of the targets for suppressing adipogenesis induced by lysine depletion. Moreover, we showed that the depletion of some essential amino acids such as methionine and cystine could induce similar phenomena. This suggests that individual amino acid deprivation may share some common pathways. This descriptive study dissects the pathways for adipogenesis and how the cellular transcriptome was altered under lysine depletion.

Short-Term Decreasing and Increasing Dietary BCAA Have Similar, but Not Identical Effects on Lipid and Glucose Metabolism in Lean Mice

Branched-chain amino acids (BCAA) showed multiple functions in glycolipid metabolism and protein synthesis. However, the impacts on the metabolic health of low or high dietary BCAA remain controversial due to the various experimental conditions. Gradient levels of BCAA were supplemented in lean mice for four weeks: 0BCAA (without BCAA), 1/2BCAA (half BCAA), 1BCAA (regular BCAA), and 2BCAA (double BCAA). The results showed that the diet without BCAA caused energy metabolic disorders, immune defects, weight loss, hyperinsulinemia, and hyperleptinemia. 1/2BCAA and 2BCAA diets reduced body fat percentage, but 1/2 BCAA also decreased muscle mass. 1/2BCAA and 2BCAA groups improved lipid and glucose metabolism by affecting metabolic genes. Meanwhile, significant differences between low and high dietary BCAA were observed. The results of this study provide evidence and reference for the controversy about dietary BCAA levels, which indicates that the main difference between low and high BCAA dietary levels may present in the longer term.

Dietary Methionine Restriction Promotes Fat Browning and Attenuates Hepatic Lipid Accumulation in High-Choline-Fed Mice Associated with the Improvement of Thyroid Function

This study aims to explore the influences of a methionine-restricted diet (MRD) on fat browning and hepatic lipid accumulation in mice fed with a high-choline diet (HCD) and their possible mechanisms. ICR mice were randomly divided into three groups and fed with a normal diet (0.86% methionine + 0.20% choline, ND), HCD (0.86% methionine + 1.20% choline), or MRD (0.17% methionine + 1.20% choline) for 90 consecutive days. We found that MRD reduced body weight and fat mass; increased heat production and ambulatory locomotor activity; reduced hepatic and plasma lipid levels, hepatic fatty infiltration area, and adipocyte volume in white and brown adipose tissue; promoted fat browning, especially upregulated gene and protein expression levels of uncoupling protein 1 (UCP1); and promoted fat catabolism and inhibited fat anabolism in the liver and adipose tissue. Moreover, MRD increased antioxidant defenses and reduced inflammatory cytokine levels in the thyroid, blood, and liver. Furthermore, MRD improved thyroid morphological structure, promoted the synthesis and secretion of thyroid hormones, and enhanced the actions of thyroid hormones on its receptor organs (liver and adipose tissue). These findings suggested that MRD promoted fat browning and attenuated hepatic lipid accumulation in HCD mice associated with the improvement of thyroid function.

Proteomic and phosphoproteomic analysis reveal threonine deficiency increases hepatic lipid deposition in Pekin ducks via reducing STAT phosphorylation

Dietary threonine (Thr) deficiency enhances triglyceride (TG) deposition in the liver of Pekin ducks, which injures hepatic function and impairs growth performance. However, the underlying molecular mechanisms remain unclear. In the present study, we investigated the effects of dietary Thr deficiency on the expressions of proteins and phosphoproteins in liver of Pekin ducks, to identify the underlying molecular changes. A total of 300 one-day-old ducklings were divided into 3 groups with 10 replicates of 10 birds. All ducks were fed corn-wheat-peanut meal diets containing 0.46%, 0.71%, and 0.96% Thr, respectively, from 1 to 21 days of age. Growth performance, serum parameters, hepatic TG content, and expression of genes involved in lipid metabolism of Pekin ducks were determined. A Thr deficiency group (Thr-D, 0.46% Thr) and a Thr sufficiency group (Thr-S, 0.71% Thr) were selected for subsequent proteomic and phosphoproteomic analysis. The results showed that Thr-D reduced the growth performance (P < 0.001), and increased the plasma concentrations of cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and hepatic TG (P < 0.05). Thr-D increased gene expression related to fatty acid and TG synthesis (P < 0.05). A total of 176 proteins and 259 phosphosites (containing 198 phosphoproteins) were observed to be differentially expressed as a result of Thr-D. The upregulated proteins were enriched in the pathway related to amino acid metabolism, peroxisome. The downregulated proteins were enriched in linolenic and arachidonic acid metabolism, and the Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway. The upregulated phosphoproteins were enriched in the pathways related to fatty acid biosynthesis, fructose and mannose metabolism, and glycolysis/gluconeogenesis. Thr-D reduced the phosphorylation of STAT1 at S729 and STAT3 at S728, and expression of STAT5B. In contrast, Thr-D increased non-receptor tyrosine-protein kinase (TYK2) expression and STAT1 phosphorylation at S649. Taken together, dietary Thr-D increased hepatic TG accumulation by upregulating the expression of genes and proteins, and phosphoproteins related to fatty acid and triglyceride synthesis. Furthermore, these processes might be regulated by the JAK-STAT signaling pathway, especially the phosphorylation of STAT1 and STAT3.

L-threonine promotes healthspan by expediting ferritin-dependent ferroptosis inhibition in C. elegans

The pathways that impact longevity in the wake of dietary restriction (DR) remain still ill-defined. Most studies have focused on nutrient limitation and perturbations of energy metabolism. We showed that the L-threonine was elevated in Caenorhabditis elegans under DR, and that L-threonine supplementation increased its healthspan. Using metabolic and transcriptomic profiling in worms that were fed with RNAi to induce loss of key candidate mediators. L-threonine supplementation and loss-of-threonine dehydrogenaseincreased the healthspan by attenuating ferroptosis in a ferritin-dependent manner. Transcriptomic analysis showed that FTN-1 encoding ferritin was elevated, implying FTN-1 is an essential mediator of longevity promotion. Organismal ferritin levels were positively correlated with chronological aging and L-threonine supplementation protected against age-associated ferroptosis through the DAF-16 and HSF-1 pathways. Our investigation uncovered the role of a distinct and universal metabolite, L-threonine, in DR-mediated improvement in organismal healthspan, suggesting it could be an effective intervention for preventing senescence progression and age-induced ferroptosis.

Threonine supplementation prevents the development of fat deposition in mice fed a high-fat diet

Obesity is the main factor involved in the onset of many diseases. Threonine supplementation has been demonstrated to reduce fat mass and serum triglycerides in already obese mice. However, it is unclear whether threonine could inhibit the development of obesity in mice without previous high-fat diet induction. In the present study, mice were fed a chow diet (CD) or a high-fat diet (HFD), supplemented or not with threonine (3.0% in drinking water) for 15 weeks. Results showed that mice subjected to chronic threonine supplementation showed decreased body weight, epididymal white adipose tissue weight, serum low-density lipoprotein cholesterol, and total cholesterol in comparison with HFD-fed mice. In the epididymal adipose tissue, gene expressions of sterol regulatory element-binding protein 1c and fatty acid synthase were up-regulated, while hormone sensitive lipase, adiponectin and fibroblast growth factor 21 were down-regulated. In the liver tissue, gene expressions of sirtuin1, adenosine monophosphate-activated protein kinase and peroxisome proliferator activated receptor γ co-activator 1α were up-regulated by threonine supplementation in HFD-fed mice. These results suggest that long-term threonine supplementation inhibited fat mass and improved lipid metabolism, making it a potential agent to prevent the development of diet-induced obesity.

L-Serine Supplementation Blunts Fasting-Induced Weight Regain by Increasing Brown Fat Thermogenesis

Weight regain after fasting, often exceeding the pre-fasting weight, is a common phenomenon and big problem for the treatment of obesity. Thus, novel interventions maintaining reduced body weight are critically important to prevent metabolic disease. Here we investigate the metabolic effects of dietary L-serine supplementation, known to modulate various organ functions. C57BL/6N-Rj male mice were supplemented with or without 1% L-serine in their drinking water and fed with a chow or high-fat diet. Mice were fed either ad libitum or subjected to repeated overnight fasting. Body weight, body composition, glucose tolerance and energy metabolism were assessed. This was combined with a detailed analysis of the liver and adipose tissues, including the use of primary brown adipocytes to study mitochondrial respiration and protein expression. We find that L-serine supplementation has little impact on systemic metabolism in ad libitum-fed mice. Conversely, L-serine supplementation blunted fasting-induced body weight regain, especially in diet-induced obese mice. This reduction in body weight regain is likely due to the increased energy expenditure, based on elevated brown adipose tissue activity. Thus, L-serine supplementation during and after weight-loss could reduce weight regain and thereby help tackle one of the major problems of current obesity therapies.

Effects of exercise on NAFLD using non-targeted metabolomics in adipose tissue, plasma, urine, and stool

The mechanisms by which exercise benefits patients with non-alcoholic fatty liver disease (NAFLD), the most common liver disease worldwide, remain poorly understood. A non-targeted liquid chromatography-mass spectrometry (LC–MS)-based metabolomics analysis was used to identify metabolic changes associated with NAFLD in humans upon exercise intervention (without diet change) across four different sample types—adipose tissue (AT), plasma, urine, and stool. Altogether, 46 subjects with NAFLD participated in this randomized controlled intervention study. The intervention group (n = 21) performed high-intensity interval training (HIIT) for 12 weeks while the control group (n = 25) kept their sedentary lifestyle. The participants' clinical parameters and metabolic profiles were compared between baseline and endpoint. HIIT significantly decreased fasting plasma glucose concentration (p = 0.027) and waist circumference (p = 0.028); and increased maximum oxygen consumption rate and maximum achieved workload (p < 0.001). HIIT resulted in sample-type-specific metabolite changes, including accumulation of amino acids and their derivatives in AT and plasma, while decreasing in urine and stool. Moreover, many of the metabolite level changes especially in the AT were correlated with the clinical parameters monitored during the intervention. In addition, certain lipids increased in plasma and decreased in the stool. Glyco-conjugated bile acids decreased in AT and urine. The 12-week HIIT exercise intervention has beneficial ameliorating effects in NAFLD subjects on a whole-body level, even without dietary changes and weight loss. The metabolomics analysis applied to the four different sample matrices provided an overall view on several metabolic pathways that had tissue-type specific changes after HIIT intervention in subjects with NAFLD. The results highlight especially the role of AT in responding to the HIIT challenge, and suggest that altered amino acid metabolism in AT might play a critical role in e.g. improving fasting plasma glucose concentration.

Trial registration ClinicalTrials.gov (NCT03995056).

Impacts of essential amino acids on energy balance

BACKGROUND

Obesity develops due to an imbalance in energy homeostasis, wherein energy intake exceeds energy expenditure. Accumulating evidence shows that manipulations of dietary protein and their component amino acids affect the energy balance, resulting in changes in fat mass and body weight. Amino acids are not only the building blocks of proteins but also serve as signals regulating multiple biological pathways.

SCOPE OF REVIEW

We present the currently available evidence regarding the effects of dietary alterations of a single essential amino acid (EAA) on energy balance and relevant signaling mechanisms at both central and peripheral levels. We summarize the association between EAAs and obesity in humans and the clinical use of modifying the dietary EAA composition for therapeutic intervention in obesity. Finally, similar mechanisms underlying diets varying in protein levels and diets altered of a single EAA are described. The current review would expand our understanding of the contribution of protein and amino acids to energy balance control, thus helping discover novel therapeutic approaches for obesity and related diseases.

MAJOR CONCLUSIONS

Changes in circulating EAA levels, particularly increased branched-chain amino acids (BCAAs), have been reported in obese human and animal models. Alterations in dietary EAA intake result in improvements in fat and weight loss in rodents, and each has its distinct mechanism. For example, leucine deprivation increases energy expenditure, reduces food intake and fat mass, primarily through regulation of the general control nonderepressible 2 (GCN2) and mammalian target of rapamycin (mTOR) signaling. Methionine restriction by 80% decreases fat mass and body weight while developing hyperphagia, primarily through fibroblast growth factor 21 (FGF-21) signaling. Some effects of diets with different protein levels on energy homeostasis are mediated by similar mechanisms. However, reports on the effects and underlying mechanisms of dietary EAA imbalances on human body weight are few, and more investigations are needed in future.

Green light exposure aggravates high-fat diet feeding-induced hepatic steatosis and pancreatic dysfunction in male mice

The increased incidence of metabolic syndrome (MetS) has been demonstrated to be closely associated with external environments, such as unhealthy ambient light exposure. Of note, spectral distribution of the light functions as a critical determinant of light's pathophysiological effects. However, the effects of the lighting spectrum on metabolic homeostasis and the specific target organs remain elusive. To address this concern, we in this study high-fat diet (HFD)-fed obese mice with different spectra of the light, and divided them into white light (WL)-treated group, green light (GL)-treated group and blue light (BL)-treated group. We found that compared with BL- or WL-treated obese mice, animals exposed to GL showed worsened metabolic status, including increased body weight gain, impaired glucose tolerance/insulin sensitivity, increased levels of serum lipids, and decreased levels of serum insulin. At the organ level, GL exposure particularly exacerbated hepatic lipid accumulation and enlarged the islet volume. Taking advantages of metabolomics and transcriptomics analyses, we screened out taurocholic acid (TCA) and adenosine (AD) as two promising metabolites mediating the deleterious effects of GL on the liver and islets, respectively. In detail, GL aggravates HFD-induced lipid synthesis and gluconeogenesis in the liver via the reduction of TCA, while triggering inflammation and cellular dysfunction in islets via the induction of AD. Collectively, our findings confirmed that GL and the HFD have a synergistic effect in the induction of metabolic disorders. DATA AVAILABILITY: All data supported the paper are present in the paper and/or the Supplementary Materials. The original datasets are also available from the corresponding author upon request.

Dietary whey and egg proteins interact with inulin fiber to modulate energy balance and gut microbiota in obese rats

Diets supplemented with protein and fiber are well known to reduce food intake and weight gain; however, less is known about the combined effects of protein and prebiotic fiber on energy balance and gut microbiota composition. We compared effects of diets containing high egg or whey protein with cellulose or prebiotic (inulin) fiber on energy balance, gut microbiota, hormones, and metabolites. Male obese rats (n=8/group) were allocated to four diets: Egg albumen+Cellulose (EC), Egg albumen+Inulin (EI), Whey protein+Cellulose (WC), and Whey protein+Inulin (WI). Results revealed that diet-induced hypophagia was transient with EC and prolonged with EI and WI, compared to WC. Importantly, CCK-1 receptor antagonist (Devazepide) attenuated the hypophagic effects of EC, EI, and WI. Further, EC, EI and WI decreased respiratory quotient, energy expenditure, weight and adiposity gains, and improved glycemia, relative to WC. Propranolol (β₁-β₂-receptor blocker) attenuated diet-induced changes in energy expenditure. Transcript abundance of thermogenic markers in brown adipose tissue, plasma hormones, and metabolites especially acyl-carnitines and glycerophospholipids, were differentially altered by diets. Diet explained 25% of compositional differences in cecal microbiomes, but diets with same fiber type did not differ. Microbiota differing between groups also strongly correlated with gut hormones and metabolites. Species most strongly correlated to a marker for butyrate production were in highest abundance in inulin diets. Together, these findings indicate that inulin enriched diets containing egg or whey protein improved energy balance, decreased adiposity, and modulated gut microbiota and metabolites, with CCK signaling partly mediating the satiety effects of diets.

Leucine, but not isoleucine or valine, affects serum lipid profiles and browning of WAT in mice

Branched chain amino acids (BCAA), especially leucine (Leu), have been reported to decrease fat deposition. However, opposite effects of BCAA on lipid metabolism have been observed. To determine the role of BCAA in lipid metabolism, an amino acid-defined diet was formulated and C57BL/6J mice were assigned into the following groups: amino acid-defined control diet and control diet supplemented with Leu, isoleucine, or valine. Nitrogen was balanced by proportionally mixed amino acids except BCAA. Results showed that dietary Leu supplementation significantly increased the levels of serum triglycerides, total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol and urea nitrogen. Metabolomics showed that biosynthesis of unsaturated fatty acids was altered by Leu supplementation. Leu treatment up-regulated the expression of genes related to fat synthesis and down-regulated the expression of genes related to fatty acid synthesis. Furthermore, the genes and proteins of selective markers involved in browning of white adipose tissue (WAT) were up-regulated by dietary supplementation with Leu. This study indicated that dietary supplementation with Leu, but not isoleucine or valine, significantly affected lipid metabolism by regulating lipid metabolism-related genes and serum fatty acid concentration, providing a new tool in the management of obesity and metabolic disorders.

Physiological Functions of Threonine in Animals: Beyond Nutrition Metabolism

Threonine (Thr), an essential amino acid for animals and the limiting amino acid in swine and poultry diets, which plays a vital role in the modulation of nutritional metabolism, macromolecular biosynthesis, and gut homeostasis. Current evidence supports that the supplementation of Thr leads to benefits in terms of energy metabolism. Threonine is not only an important component of gastrointestinal mucin, but also acts as a nutritional modulator that influences the intestinal immune system via complex signaling networks, particularly mitogen-activated protein kinase (MAPK) and the target of the rapamycin (TOR) signal pathway. Threonine is also recognized as an indispensable nutrient for cell growth and proliferation. Hence, optimization of Thr requirement may exert a favorable impact on the factors linked to health and diseases in animals. This review focuses on the latest reports of Thr in metabolic pathways and nutritional regulation, as well as the relationship between Thr and relevant physiological functions.

Gut Microbiome and Metabolome Profiles Associated with High-Fat Diet in Mice

Obesity can be caused by microbes producing metabolites; it is thus important to determine the correlation between gut microbes and metabolites. This study aimed to identify gut microbiota-metabolomic signatures that change with a high-fat diet and understand the underlying mechanisms. To investigate the profiles of the gut microbiota and metabolites that changed after a 60% fat diet for 8 weeks, 16S rRNA gene amplicon sequencing and gas chromatography-mass spectrometry (GC-MS)-based metabolomic analyses were performed. Mice belonging to the HFD group showed a significant decrease in the relative abundance of Bacteroidetes but an increase in the relative abundance of Firmicutes compared to the control group. The relative abundance of Firmicutes, such as Lactococcus, Blautia, Lachnoclostridium, Oscillibacter, Ruminiclostridium, Harryflintia, Lactobacillus, Oscillospira, and Erysipelatoclostridium, was significantly higher in the HFD group than in the control group. The increased relative abundance of Firmicutes in the HFD group was positively correlated with fecal ribose, hypoxanthine, fructose, glycolic acid, ornithine, serum inositol, tyrosine, and glycine. Metabolic pathways affected by a high fat diet on serum were involved in aminoacyl-tRNA biosynthesis, glycine, serine and threonine metabolism, cysteine and methionine metabolism, glyoxylate and dicarboxylate metabolism, and phenylalanine, tyrosine, and trypto-phan biosynthesis. This study provides insight into the dysbiosis of gut microbiota and metabolites altered by HFD and may help to understand the mechanisms underlying obesity mediated by gut microbiota.

Dysbiosis of intestinal microbiota in early life aggravates high-fat diet induced dysmetabolism in adult mice

BACKGROUND

Accumulating evidence have shown that the intestinal microbiota plays an important role in prevention of host obesity and metabolism disorders. Recent studies also demonstrate that early life is the key time for the colonization of intestinal microbes in host. However, there are few studies focusing on possible association between intestinal microbiota in the early life and metabolism in adulthood. Therefore the present study was conducted to examine whether the short term antibiotic and/or probiotic exposure in early life could affect intestinal microbes and their possible long term effects on host metabolism.

RESULTS

A high-fat diet resulted in glucose and lipid metabolism disorders with higher levels of visceral fat rate, insulin-resistance indices, and leptin. Exposure to ceftriaxone in early life aggravated the negative influences of a high-fat diet on mouse physiology. Orally fed TMC3115 protected mice, especially those who had received treatment throughout the whole study, from damage due to a high-fat diet, such as increases in levels of fasting blood glucose and serum levels of insulin, leptin, and IR indices. Exposure to ceftriaxone during the first 2 weeks of life was linked to dysbiosis of the fecal microbiota with a significant decrease in the species richness and diversity. However, the influence of orally fed ceftriaxone on the fecal microbiota was limited to 12 weeks after the termination of treatment. Of note, at week 12 there were still some differences in the composition of intestinal microbiota between mice provided with high fat diet and antibiotic exposure and those only fed a high fat diet.

CONCLUSIONS

These results indicated that exposure to antibiotics, such as ceftriaxone, in early life may aggravate the negative influences of a high-fat diet on the physiology of the host animal. These results also suggest that the crosstalk between the host and their intestinal microbiota in early life may be more important than that in adulthood, even though the same intestinal microbes are present in adulthood.

Identification of the Potential Role of the Rumen Microbiome in Milk Protein and Fat Synthesis in Dairy Cows Using Metagenomic Sequencing

Simple Summary

The rumen is the main digestive and absorption organ of dairy cows. It contains abundant microorganisms and can effectively use human-indigestible plant mass. Therefore, we used metagenomics to explore the role of rumen microbes in the regulation of milk protein and fat in dairy cows. This study showed that Prevotella species and Neocallimastix californiae in the rumen of cows are related to the synthesis of milk components due to their important functions in carbohydrate, amino acid, pyruvate, insulin, and lipid metabolism and transportation metabolic pathways.

Abstract

The rumen contains abundant microorganisms that aid in the digestion of lignocellulosic feed and are associated with host phenotype traits. Cows with extremely high milk protein and fat percentages (HPF; n = 3) and low milk protein and fat percentages (LPF; n = 3) were selected from 4000 lactating Holstein cows under the same nutritional and management conditions. We found that the total concentration of volatile fatty acids, acetate, butyrate, and propionate in the rumen fluid was significantly higher in the HPF group than in the LPF group. Moreover, we identified 38 most abundant species displaying differential richness between the two groups, in which Prevotella accounted for 68.8% of the species, with the highest abundance in the HPF group. Functional annotation based on the Kyoto Encyclopedia of Gene and Genome (KEGG), evolutionary genealogy of genes: Non-supervised Orthologous Groups (eggNOG), and Carbohydrate-Active enzymes (CAZy) databases showed that the significantly more abundant species in the HPF group are enriched in carbohydrate, amino acid, pyruvate, insulin, and lipid metabolism and transportation. Furthermore, Spearman’s rank correlation analysis revealed that specific microbial taxa (mainly the Prevotella species and Neocallimastix californiae) are positively correlated with total volatile fatty acids (VFA). Collectively, we found that the HPF group was enriched with several Prevotella species related to the total VFA, acetate, and amino acid synthesis. Thereby, these fulfilled the host’s needs for energy, fat, and rumen microbial protein, which can be used for increased biosynthesis of milk fat and milk protein. Our findings provide novel information for elucidation of the regulatory mechanism of the rumen in the formation of milk composition.

Serum metabolic signature of binge-like palatable food consumption in female rats by nuclear magnetic resonance spectroscopy

Maladaptive eating behavior is a growing public health problem and compulsively eating excessive food in a short time, or binge eating, is a key symptom of many eating disorders. In order to investigate the binge-like eating behavior in female rats, induced by intermittent food restrictions/refeeding and frustration stress, we analyzed for the first time the metabolic profile obtained from serum of rats, through nuclear magnetic resonance (NMR) spectroscopy. In this experimental protocol, rats were exposed to chow food restricting/refeeding and frustration stress manipulation. This stress procedure consists of 15 min exposure to the odor and sight of a familiar chocolate paste, without access to it, just before offering the palatable food. In this model, a "binge-eating episode" was considered the significantly higher palatable food consumption within 2 h in restricted and stressed rats (R + S) than in the other three experimental groups: rats with no food restriction and no stress (NR + NS), only stressed rats (NR + S) or only restricted rats (R + NS). Serum samples from these four different rat groups were collected. The statistical analysis of the ¹ H NMR spectral profiles of the four sets of samples pointed to O- and N-acetyl glycoproteins as the main biomarkers for the discrimination of restriction effects. Other metabolites, such as threonine, glycine, glutamine, acetate, pyruvate and lactate, showed trends that may be useful to understand metabolic pathways involved in eating disorders. This study suggested that NMR-based metabolomics is a suitable approach to detect biomarkers related to binge-eating behavior.

Dietary supplementation with aromatic amino acids decreased triglycerides and alleviated hepatic steatosis by stimulating bile acid synthesis in mice

Emerging evidence shows that amino acids can modulate lipid metabolism. Aromatic amino acids (AAAs) serve as important precursors of several neurotransmitters and metabolic regulators that play a vital role in regulating nutrient metabolism. But whether AAAs have a lipid-lowering function remains unknown. Here mice were fed amino acid-defined diets containing AAAs at 1.82% and 3.64% for 3 weeks. We demonstrated that double AAA intake significantly decreased the serum and hepatic triglycerides and serum low-density lipoprotein cholesterol, but increased the high-density lipoprotein cholesterol as well as insulin tolerance. Combined metabolomic and transcriptomic analysis showed that the hepatic acidic pathway of bile acid synthesis was responsible for the improvement in lipid metabolism by AAA treatment. This study suggests that AAAs have the potential to ameliorate steatosis and provides a new alternative to improve lipid metabolism.

Valine Supplementation Does Not Reduce Lipid Accumulation and Improve Insulin Sensitivity in Mice Fed High-Fat Diet

Branched-chain amino acids (BCAAs), particularly leucine, were reported to decrease obesity and relevant metabolic syndrome. However, whether valine has a similar effect has rarely been investigated. In the present study, mice were assigned into four treatments (n = 10): chow diet supplemented with water (CW) or valine (CV) and high-fat diet supplemented with water (HW) or valine (HV). Valine (3%, w/v) was supplied in the drinking water. The results showed that valine treatment markedly increased serum triglyceride and insulin levels of chow diet-fed mice. The body weight, serum triglyceride level, white adipose tissue weight, and glucose and insulin intolerance were significantly elevated by valine supplementation in high-fat diet-fed mice. Metabolomics and transcriptomics showed that several genes related to fat oxidation were downregulated, and arachidonic acid and linoleic acid metabolism were altered in the HV group compared to the HW group. In conclusion, valine supplementation did not suppress lipid deposition and metabolic disorders in mice, which provides a new understanding for BCAAs in the modulation of lipid metabolism.

Spermidine ameliorates high-fat diet-induced hepatic steatosis and adipose tissue inflammation in preexisting obese mice

AIMS

The therapeutic effects of spermidine on preexisting obese mice have been not fully elucidated. In this study, we assessed the anti-obesity impact of spermidine on high-fat diet (HFD)-induced obese mice.

MAIN METHODS

C57BL/6J mice were fed a HFD for 16 weeks to induce obesity, and then treated with or without spermidine via drinking water for additional 8 weeks. The contributions of spermidine in regulating obesity phenotypes and metabolic syndrome were further evaluated.

KEY FINDINGS

Spermidine administration lowered fat mass and plasma lipid profile in HFD-induced obese mice without affecting body weight. In addition, spermidine attenuated hepatic steatosis by regulating lipid metabolism and enhancing antioxidant capacity. Moreover, spermidine reduced adipose tissue inflammation by decreasing inflammatory cytokine and chemokines expression, and these results might contributed to the enhanced thermogenic gene expression in brown adipose tissue. Furthermore, spermidine treatment enhanced gut barrier function by up-regulating tight junction- and mucin-related gene expression.

SIGNIFICANCE

Spermidine-mediated protective impacts involve the regulation of lipid metabolism, inflammation response, gut barrier function and thermogenesis. These findings demonstrate that spermidine has potentials in treating obesity.