Spermidine ameliorates non-alcoholic fatty liver disease through regulating lipid metabolism via AMPK

Spermidine mitigates ferroptosis in free fatty acid-induced AML-12 cells through the ATF4/SLC7A11/GCLM/GPX4 pathway

Non-alcoholic fatty liver disease (NAFLD) is a prominent cause of chronic liver disease worldwide. Spermidine (SPD), a naturally occurring polyamine, has shown potential in alleviating the accumulation of hepatic lipids and reducing NAFLD symptoms in overweight mice. Nonetheless, the specific mechanisms through which SPD exerts its effects remain largely unknown. This study seeks to explore the protective effects of SPD on NAFLD and to clarify the underlying mechanisms. An in vitro model of NAFLD was established by inducing steatosis in AML-12 cells through the use of free fatty acids (FFAs). Our experimental results demonstrate that SPD significantly reduces NAFLD development induced by FFAs. This reduction is primarily achieved through the inhibition of cellular ferroptosis, as evidenced by decreased levels of Fe2+, malondialdehyde (MDA), and reactive oxygen species (ROS). Additionally, SPD was found to enhance cellular activity and ameliorate mitochondrial dysfunction and oxidative stress caused by FFA exposure. Further mechanistic studies have revealed that SPD upregulates the expression of solute transporter family 7a member 11 (SLC7A11), glutamate-cysteine ligase modifier subunit (GCLM), and glutathione peroxidase (GPX4). This upregulation is mediated by the activation of activating transcription factor 4 (ATF4). Knockdown experiments of ATF4 confirmed that its inhibition reverses the upregulation of SLC7A11, GCLM, and GPX4, thereby negating the protective effects of SPD. In conclusion, our findings suggest that SPD mitigates NAFLD by modulating the ATF4/SLC7A11/GCLM/GPX4 signaling pathway, resulting in the suppression of ferroptosis and the improvement of cellular health. These insights provide a novel molecular mechanism and identify potential therapeutic targets for the treatment of NAFLD.

Protective effects of spermidine levels against cardiovascular risk factors: An exploration of causality based on a bi-directional Mendelian randomization analysis

The study investigated the causal relationships between spermidine levels and CVD risk factors using a bi-directional MR approach. Employing genetic variants from extensive GWAS datasets as IVs, the study aimed to determine whether spermidine levels can influence CVD risk factors such as blood pressure, blood glucose, and lipid profiles, and vice versa. The findings suggest a protective role of elevated spermidine levels against hypertension, elevated blood glucose, and lipid profiles (LDL-C and HDL-C). Specifically, increased spermidine levels were significantly associated with lower risk of hypertension (IVW beta = -0.0013453913, p = 0.01597648) and suppression risk of elevated blood glucose (IVW beta = -0.08061330, p = 0.02450205). Additionally, there was a notable association with lipid modulation, showing a decrease in LDL-C (IVW beta = -0.01849161, p = 0.01086728) and an increase in HDL-C (IVW beta = 0.0044608332, P = 0.01760051). Conversely, the influence of CVD risk factors on spermidine levels was minimal, with the exception that elevated blood glucose levels resulted in reduced spermidine levels. (IVW beta = -0.06714391, P = 0.01096123). These results underline the potential of spermidine as a modifiable dietary target for the prevention and management of cardiovascular diseases. Further investigations are warranted to explore the underlying biological mechanisms and the applicability of these findings in broader and diverse populations.

Increased hepatic putrescine levels as a new potential factor related to the progression of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a chronic liver condition that often progresses to more advanced stages, such as metabolic dysfunction-associated steatohepatitis (MASH). MASH is characterized by inflammation and hepatocellular ballooning, in addition to hepatic steatosis. Despite the relatively high incidence of MASH in the population and its potential detrimental effects on human health, this liver disease is still not fully understood from a pathophysiological perspective. Deregulation of polyamine levels has been detected in various pathological conditions, including neurodegenerative diseases, inflammation, and cancer. However, the role of the polyamine pathway in chronic liver disorders such as MASLD has not been explored. In this study, we measured the expression of liver ornithine decarboxylase (ODC1), the rate-limiting enzyme responsible for the production of putrescine, and the hepatic levels of putrescine, in a preclinical model of MASH as well as in liver biopsies of patients with obesity undergoing bariatric surgery. Our findings reveal that expression of ODC1 and the levels of putrescine, but not spermidine nor spermine, are elevated in hepatic tissue of both diet-induced MASH mice and patients with biopsy-proven MASH compared with control mice and patients without MASH, respectively. Furthermore, we found that the levels of putrescine were positively associated with higher aspartate aminotransferase concentrations in serum and an increased SAF score (steatosis, activity, fibrosis). Additionally, in in vitro assays using human HepG2 cells, we demonstrate that elevated levels of putrescine exacerbate the cellular response to palmitic acid, leading to decreased cell viability and increased release of CK-18. Our results support an association between the expression of ODC1 and the progression of MASLD, which could have translational relevance in understanding the onset of this disease. © 2024 The Pathological Society of Great Britain and Ireland.

Probiotic yogurt regulates gut microbiota homeostasis and alleviates hepatic steatosis and liver injury induced by high-fat diet in golden hamsters

This study aimed to investigate the beneficial effects of probiotic yogurt on lipid metabolism and gut microbiota in metabolic-related fatty liver disease (MAFLD) golden hamsters fed on a high-fat diet (HFD). The results demonstrated that probiotic yogurt significantly reversed the adverse effects caused by HFD, such as body and liver weight gain, liver steatosis and damage, sterol deposition, and oxidative stress after 8 weeks of intervention. qRT-PCR analysis showed that golden hamsters fed HFD had upregulated genes related to adipogenesis, increased free fatty acid infiltration, and downregulated genes related to lipolysis and very low-density lipoprotein secretion. Probiotic yogurt supplements significantly inhibited HFD-induced changes in the expression of lipid metabolism-related genes. Furthermore, 16S rRNA gene sequencing of the intestinal content microbiota suggested that probiotic yogurt changed the diversity and composition of the gut microbiota in HFD-fed hamsters. Probiotic yogurt decreased the ratio of the phyla Firmicutes/Bacteroidetes, the relative abundance of the LPS-producing genus Desulfovibrio, and bacteria involved in lipid metabolism, whereas it increased the relative abundance of short-chain fatty acids producing bacteria in HFD-fed hamsters. Predictive functional analysis of the microbial community showed that probiotic yogurt-modified genes involved in LPS biosynthesis and lipid metabolism. In summary, these findings support the possibility that probiotic yogurt significantly improves HFD-induced metabolic disorders through modulating intestinal microflora and lipid metabolism and effectively regulating the occurrence and development of MAFLD. Therefore, probiotic yogurt supplementation may serve as an effective nutrition strategy for the treatment of patients with MAFLD clinically.

Spermidine activates adipose tissue thermogenesis through autophagy and fibroblast growth factor 21

Spermidine exerts protective roles in obesity, while the mechanism of spermidine in adipose tissue thermogenesis remains unclear. The present study first investigated the effect of spermidine on cold-stimulation and β3-adrenoceptor agonist-induced thermogenesis in lean and high-fat diet-induced obese mice. Next, the role of spermidine on glucose and lipid metabolism in different types of adipose tissue was determined. Here, we found that spermidine supplementation did not affect cold-stimulated thermogenesis in lean mice, while significantly promoting the activation of adipose tissue thermogenesis under cold stimulation and β3-adrenergic receptor agonist treatment in obese mice. Spermidine treatment markedly enhanced glucose and lipid metabolism in adipose tissues, and these results were associated with the activated autophagy pathway. Moreover, spermidine up-regulated fibroblast growth factor 21 (FGF21) signaling and its downstream pathway, including PI3K/AKT and AMPK pathways in vivo and in vitro. Knockdown of Fgf21 or inhibition of PI3K/AKT and AMPK pathways in brown adipocytes abolished the thermogenesis-promoting effect of spermidine, suggesting that the effect of spermidine on adipose tissue thermogenesis might be regulated by FGF21 signaling via the PI3K/AKT and AMPK pathways. The present study provides new insight into the mechanism of spermidine on obesity and its metabolic complications, thereby laying a theoretical basis for the clinical application of spermidine.

Mitochondrial Quality Control: Its Role in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease, is characterized by hepatic steatosis and metabolic dysfunction and is often associated with obesity and insulin resistance. Recent research indicates a rapid escalation in MASLD cases, with projections suggesting a doubling in the United States by 2030. This review focuses on the central role of mitochondria in the pathogenesis of MASLD and explores potential therapeutic interventions. Mitochondria are dynamic organelles that orchestrate hepatic energy production and metabolism and are critically involved in MASLD. Dysfunctional mitochondria contribute to lipid accumulation, inflammation, and liver fibrosis. Genetic associations further underscore the relationship between mitochondrial dynamics and MASLD susceptibility. Although U.S. Food and Drug Administration-approved treatments for MASLD remain elusive, ongoing clinical trials have highlighted promising strategies that target mitochondrial dysfunction, including vitamin E, metformin, and glucagon-like peptide-1 receptor agonists. In preclinical studies, novel therapeutics, including nicotinamide adenine dinucleotide+ precursors, urolithin A, spermidine, and mitoquinone, have shown beneficial effects, such as improving mitochondrial quality control, reducing oxidative stress, and ameliorating hepatic steatosis and inflammation. In conclusion, mitochondrial dysfunction is central to MASLD pathogenesis. The innovative mitochondria-targeted approaches discussed in this review offer a promising avenue for reducing the burden of MASLD and improving global quality of life.

Co-administration of curcumin and polyamines in high-fat diet induced obese rats: Assessment of changes in serum polyamine levels and some tissue parameters

Obesity is a non-communicable chronic disease that continues to increase around the world. Recently, it has been shown that curcumin positively affects lipid, energy metabolism, and body weight change. Moreover, polyamines are aliphatic polycations, which can be found in all mammalian cells and foods and have been shown to prevent obesity through many different mechanisms. However, whether the co-administration of curcumin and polyamines has synergistic effects has yet to be clarified. Our study aimed to examine the effects of curcumin and polyamines on obesity and to assess the changes in serum polyamine levels and tissue parameters. 28 Sprague-Dawley male rats were fed a high-fat diet for 10 weeks to develop obesity, and then they were randomly divided into 4 groups as the control group (CONT), curcumin group (CUR), polyamine group (POL), curcumin and polyamine group (CUR+POL) and supplements were administered for 6 weeks. As a result, the lowest feed consumption in rats was recorded in the CUR+POL group, and the group with the lowest weight after supplements was the POL group, then the CUR+POL, CONT, and CUR groups, respectively. N-acetyl putrescine and GABA levels increased significantly after obesity development. The total histopathological score in fat, liver, and kidney tissues increased significantly in the CONT group. In the CUR+POL group, damage to the tissues was in the direction of recovery compared to the other groups, and the expression of NF-κB was significantly low. These results suggest that combined curcumin and polyamines may have protective effects.

Harnessing metabolism of hepatic macrophages to aid liver regeneration

Liver regeneration is a dynamic and regulated process that involves inflammation, granulation, and tissue remodeling. Hepatic macrophages, abundantly distributed in the liver, are essential components that actively participate in each step to orchestrate liver regeneration. In the homeostatic liver, resident macrophages (Kupffer cells) acquire a tolerogenic phenotype and contribute to immunological tolerance. Following toxicity-induced damage or physical resection, Kupffer cells as well as monocyte-derived macrophages can be activated and promote an inflammatory process that supports the survival and activation of hepatic myofibroblasts and thus promotes scar tissue formation. Subsequently, these macrophages, in turn, exhibit the anti-inflammatory effects critical to extracellular matrix remodeling during the resolution stage. However, continuous damage-induced chronic inflammation generally leads to hepatic macrophage dysfunction, which exacerbates hepatocellular injury and triggers further liver fibrosis and even cirrhosis. Emerging macrophage-targeting strategies have shown efficacy in both preclinical and clinical studies. Increasing evidence indicates that metabolic rewiring provides substrates for epigenetic modification, which endows monocytes/macrophages with prolonged "innate immune memory". Therefore, it is reasonable to conceive novel therapeutic strategies for metabolically reprogramming macrophages and thus mediate a homeostatic or reparative process for hepatic inflammation management and liver regeneration.

Spermidine from arginine metabolism activates Nrf2 and inhibits kidney fibrosis

Kidney metabolism may be greatly altered in chronic kidney disease. Here we report that arginine metabolism is the most altered in unilateral ureteral obstruction (UUO)-induced fibrosis of the kidneys in metabolomic analysis. Spermidine is the most increased metabolite of arginine. In human glomerulonephritis, the amount of spermidine shown by immunostaining is associated with the amount of fibrosis. In human proximal tubule cells, spermidine induces nuclear factor erythroid 2-related factor 2 (Nrf2). Subsequently, fibrotic signals, such as transforming growth factor β1 secretion, collagen 1 mRNA, and oxidative stress, represented by a decrease in the mitochondrial membrane potential is suppressed by spermidine. UUO kidneys of Arg2 knockout mice show less spermidine and significantly exacerbated fibrosis compared with wild-type mice. Nrf2 activation is reduced in Arg2 knockout UUO kidneys. Spermidine treatment prevents significant fibrotic progression in Arg2 knockout mice. Spermidine is increased in kidney fibrosis, but further increases in spermidine may reduce fibrosis.

Gut microbiota and anti-aging: Focusing on spermidine

The human gut microbiota plays numerous roles in regulating host growth, the immune system, and metabolism. Age-related changes in the gut environment lead to chronic inflammation, metabolic dysfunction, and illness, which in turn affect aging and increase the risk of neurodegenerative disorders. Local immunity is also affected by changes in the gut environment. Polyamines are crucial for cell development, proliferation, and tissue regeneration. They regulate enzyme activity, bind to and stabilize DNA and RNA, have antioxidative properties, and are necessary for the control of translation. All living organisms contain the natural polyamine spermidine, which has anti-inflammatory and antioxidant properties. It can regulate protein expression, prolong life, and improve mitochondrial metabolic activity and respiration. Spermidine levels experience an age-related decrease, and the development of age-related diseases is correlated with decreased endogenous spermidine concentrations. As more than just a consequence, this review explores the connection between polyamine metabolism and aging and identifies advantageous bacteria for anti-aging and metabolites they produce. Further research is being conducted on probiotics and prebiotics that support the uptake and ingestion of spermidine from food extracts or stimulate the production of polyamines by gut microbiota. This provides a successful strategy to increase spermidine levels.

Grain-sized moxibustion at Zusanli (ST36) promotes hepatic autophagy in rats with hyperlipidemia by regulating the ULK1 and TFEB expression through the AMPK/mTOR signaling pathway

Objective

Grain-sized moxibustion is an effective treatment for hyperlipidemia, but how it regulates dyslipidemia and liver lipid deposits still needs to be fully understood. This study explored the molecular biological mechanism of grain-sized moxibustion to regulate hepatic autophagy in hyperlipidemic rats by affecting ULK1 and TFEB through the AMPK/mTOR signaling pathway.

Methods

Thirty male Sprague-Dawley (SD) rats were fed a high-fat diet for eight weeks to induce hyperlipidemia. Hyperlipidemic rats were divided into the HFD group, HFD + Statin group, HFD + CC + Moxi group, and grain-sized moxibustion intervention group (HFD + Moxi group). The control (Blank) group consisted of normal rats without any intervention. Grain-sized moxibustion and drug interventions were initiated eight weeks after high-fat diet induction and continued for ten weeks. Serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), and high-density lipoprotein (HDL), as well as hepatic triglyceride (TG), were measured after treatment. Hepatic steatosis and the expression of LC3I, LC3II, p62, p-AMPK, AMPK, p-mTOR, mTOR, ULK1, p-ULK1, and TFEB in the liver were analyzed.

Results

Compared with the HFD group, grain-sized moxibustion improved hyperlipidemia and hepatocyte steatosis, increased the LC3, p-AMPK, p-ULK1, and nuclear TFEB expression in the liver, but decreased the p62 and p-mTOR expression.

Conclusion

Grain-sized moxibustion at ST36 acupoints could regulate the blood lipid level of SD rats with hyperlipidemia, increase the expression level of ULK1 and TFEB by activating the AMPK/mTOR signaling pathway in liver tissues, and initiate the transcription of autophagy genes such as LC3.

AMP-activated protein kinase: An energy sensor and survival mechanism in the reinstatement of metabolic homeostasis

Cells are programmed to favorably respond towards the nutrient availability by adapting their metabolism to meet energy demands. AMP-activated protein kinase (AMPK) is a highly conserved serine/threonine energy-sensing kinase. It gets activated upon a decrease in the cellular energy status as reflected by an increased AMP/ATP ratio, ADP, and also during the conditions of glucose starvation without change in the adenine nucelotide ratio. AMPK functions as a centralized regulator of metabolism, acting at cellular and physiological levels to circumvent the metabolic stress by restoring energy balance. This review intricately highlights the integrated signaling pathways by which AMPK gets activated allosterically or by multiple non-canonical upstream kinases. AMPK activates the ATP generating processes (e.g., fatty acid oxidation) and inhibits the ATP consuming processes that are non-critical for survival (e.g., cell proliferation, protein and triglyceride synthesis). An integrated signaling network with AMPK as the central effector regulates all the aspects of enhanced stress resistance, qualified cellular housekeeping, and energy metabolic homeostasis. Importantly, the AMPK mediated amelioration of cellular stress and inflammatory responses are mediated by stimulation of transcription factors such as Nrf2, SIRT1, FoxO and inhibition of NF-κB serving as main downstream effectors. Moreover, many lines of evidence have demonstrated that AMPK controls autophagy through mTOR and ULK1 signaling to fine-tune the metabolic pathways in response to different cellular signals. This review also highlights the critical involvement of AMPK in promoting mitochondrial health, and homeostasis, including mitophagy. Loss of AMPK or ULK1 activity leads to aberrant accumulation of autophagy-related proteins and defective mitophagy thus, connecting cellular energy sensing to autophagy and mitophagy.

Restoring polyamine levels by supplementation of spermidine modulates hepatic immune landscape in murine model of NASH

AIMS

To determine if changes in polyamines metabolism occur during non-alcoholic steatohepatitis (NASH) in human patients and mice, as well as to assess systemic and liver-specific effects of spermidine administration into mice suffering from advanced NASH.

MATERIALS AND METHODS

Human fecal samples were collected from 50 healthy and 50 NASH patients. For the preclinical studies C57Bl6/N male mice fed GAN or NIH-31 diet for 6 months were ordered from Taconic and liver biopsy was performed. Based on severity of liver fibrosis, body composition and body weight, the mice from both dietary groups were randomized into another two groups: half receiving 3 mM spermidine in drinking water, half normal water for subsequent 12 weeks. Body weight was measured weekly and glucose tolerance and body composition were assessed at the end. Blood and organs were collected during necropsy, and intrahepatic immune cells were isolated for flow cytometry analysis.

RESULTS

Metabolomic analysis of human and murine feces confirmed that levels of polyamines decreased along NASH progression. Administration of exogenous spermidine to the mice from both dietary groups did not affect body weight, body composition or adiposity. Moreover, incidence of macroscopic hepatic lesions was higher in NASH mice receiving spermidine. On the other hand, spermidine normalized numbers of Kupffer cells in the livers of mice suffering from NASH, although these beneficial effects did not translate into improved liver steatosis or fibrosis severity.

CONCLUSION

Levels of polyamines decrease during NASH in mice and human patients but spermidine administration does not improve advanced NASH.

Spermidine suppresses the activation of hepatic stellate cells to cure liver fibrosis through autophagy activator MAP1S

BACKGROUND AND AIMS

Liver diseases present a wide range of fibrosis, from fatty liver with no inflammation to steatohepatitis with varying degrees of fibrosis, to established cirrhosis leading to HCC. In a multivariate analysis, serum levels of spermidine were chosen as the top metabolite from 237 metabolites and its levels were drastically reduced along with progression to advanced steatohepatitis. Our previous studies that showed spermidine supplementation helps mice prevent liver fibrosis through MAP1S have prompted us to explore the possibility that spermidine can alleviate or cure already developed liver fibrosis.

METHODS

We collected tissue samples from patients with liver fibrosis to measure the levels of MAP1S. We treated wild-type and MAP1S knockout mice with CCl₄ -induced liver fibrosis with spermidine and isolated HSCs in culture to test the effects of spermidine on HSC activation and liver fibrosis.

RESULTS

Patients with increasing degrees of liver fibrosis had reduced levels of MAP1S. Supplementing spermidine in mice that had already developed liver fibrosis after 1 month of CCl₄ induction for an additional 3 months resulted in significant reductions in levels of ECM proteins and a remarkable improvement in liver fibrosis through MAP1S. Spermidine also suppressed HSC activation by reducing ECM proteins at both the mRNA and protein levels, and increasing the number of lipid droplets in stellate cells.

CONCLUSIONS

Spermidine supplementation is a potentially clinically meaningful approach to treating and curing liver fibrosis, preventing cirrhosis and HCC in patients.

Metabolomic analysis shows dysregulation in amino acid and NAD+ metabolism in palmitate treated hepatocytes and plasma of non-alcoholic fatty liver disease spectrum

There is an alarming increase in incidence of fatty liver disease worldwide. The fatty liver disease spectrum disease ranges from simple steatosis (NAFL) to steatohepatitis (NASH) which culminates in cirrhosis and cancer. Altered metabolism is a hallmark feature associated with fatty liver disease and palmitic acid is the most abundant saturated fatty acid, therefore, the aim of this study was to compare metabolic profiles altered in hepatocytes treated with palmitic acid and also the differentially expressed plasma metabolites in spectrum of nonalcoholic fatty liver. The metabolites were analyzed by liquid chromatography-mass spectrometry (LC-MS) platform. Hepatocyte cell lines PH5CH8 and HepG2 cells when treated with 400 μM dose of palmitic acid showed typical features of steatosis. Metabolomic analysis of lipid treated hepatocyte cell lines showed differential changes in phenylalanine and tyrosine pathways, fatty acid metabolism and bile acids. The key metabolites tryptophan, kynurenine and carnitine differed significantly between subjects with NAFL, NASH and those with cirrhosis. As the tryptophan-kynurenine axis is also involved in denovo synthesis of NAD+, we found significant alterations in the NAD+ related metabolites in both palmitic acid treated and also fatty liver disease with cirrhosis. The study underscores the importance of amino acid and NAD+supplementation as promising strategies in fatty liver disorder.

The interplay between nonalcoholic fatty liver disease and atherosclerotic cardiovascular disease

Therapeutic approaches that lower circulating low-density lipoprotein (LDL)-cholesterol significantly reduced the burden of cardiovascular disease over the last decades. However, the persistent rise in the obesity epidemic is beginning to reverse this decline. Alongside obesity, the incidence of nonalcoholic fatty liver disease (NAFLD) has substantially increased in the last three decades. Currently, approximately one third of world population is affected by NAFLD. Notably, the presence of NAFLD and particularly its more severe form, nonalcoholic steatohepatitis (NASH), serves as an independent risk factor for atherosclerotic cardiovascular disease (ASCVD), thus, raising interest in the relationship between these two diseases. Importantly, ASCVD is the major cause of death in patients with NASH independent of traditional risk factors. Nevertheless, the pathophysiology linking NAFLD/NASH with ASCVD remains poorly understood. While dyslipidemia is a common risk factor underlying both diseases, therapies that lower circulating LDL-cholesterol are largely ineffective against NASH. While there are no approved pharmacological therapies for NASH, some of the most advanced drug candidates exacerbate atherogenic dyslipidemia, raising concerns regarding their adverse cardiovascular consequences. In this review, we address current gaps in our understanding of the mechanisms linking NAFLD/NASH and ASCVD, explore strategies to simultaneously model these diseases, evaluate emerging biomarkers that may be useful to diagnose the presence of both diseases, and discuss investigational approaches and ongoing clinical trials that potentially target both diseases.

Using Untargeted LC-MS Metabolomics to Identify the Association of Biomarkers in Cattle Feces with Marbling Standard Longissimus Lumborum

Background: To improve the grade of beef marbling has great economic value in the cattle industry since marbling has the traits of high quality and comprehensive nutrition. And because of the marbling’s importance and complexity, it is indispensable to explore marbled beef at multiple levels. This experiment studied the relationship between fecal metabolites and marbling characters, and further screened biomarkers. Results: We performed fecal metabolomics analysis on 30 individuals selected from 100 crossbreed cattle (Luxi Yellow cattle ♀ × Japanese Wagyu cattle ♂), 15 with an extremely high-grade marbling beef and 15 with an extremely low-grade marbling beef. A total of 9959 and 8389 m/z features were detected in positive ionization and negative ionization mode by liquid chromatography-mass spectrometry (LC-MS). Unfortunately, the sample separation in the PCA is not obvious, and the predictive ability of the orthogonal partial least squares discrimination analysis (OPLS-DA) model is not good. However, we got six differential metabolites filtered by VIP > 1 and p < 0.05. After that, we used weighted correlation network analysis (WGCNA) and found out a module in each positive and negative mode most related to the trait of marbling beef, and then identified three metabolites in positive mode. By further annotation of the Kyoto encyclopedia of genes and genomes (KEGG), it was found that these metabolites involved a variety of metabolic ways, including sphingomyelin metabolism, linoleic acid metabolism, glycerophospholipid metabolism, and so on. Finally, receiver operating characteristic (ROC) analysis was used to evaluate the predictability of metabolites, and the result showed that SM(d18:0/16:1(9Z)) (AUC = 0.72), PC(15:0/18:2(9Z,12Z)) (AUC = 0.72), ADP (AUC = 0.71), PC(16:0/16:0) (AUC = 0.73), and 3-O-Sulfogalactosylceramide (d18:1/18:0) (AUC = 0.69) have an accuracy diagnosis. Conclusions: In conclusion, this study supports new opinions for the successive evaluation of marbling beef through metabolites. Furthermore, six non-invasive fecal metabolites that can evaluate beef marbling grade were found, including SM(d18:0/16:1(9Z)), PC(15:0/18:2(9Z,12Z)), ADP, PC(16:0/16:0), and 3-O-Sulfogalactosylceramide.

The untapped potential of spermidine alkaloids: Sources, structures, bioactivities and syntheses

Spermidine alkaloids are a kind of natural products possessing an aliphatic triamine structure with three or four methylene groups between two N-atoms. Spermidine alkaloids exist in plants, microorganisms, and marine organisms, which usually form amide structures with cinnamic acid or fatty acid derivatives. Their unique structures showed a wide range of biological activities such as neuroprotective, anti-aging, anti-cancer, antioxidant, anti-inflammatory, and antimicrobial. In order to better understand the research status of spermidine alkaloids and promote their applications in human health, this paper systematically reviewed the biological sources, structures, pharmacological actions, and synthetic processes of spermidine alkaloids over the past two decades. This will help to open up new pharmacological investigation fields and better drug design based on these spermidine alkaloids.

Elevation of Serum Spermidine in Obese Patients: Results from a Cross-Sectional and Follow-Up Study

Background: Spermidine, a natural polyamine, appears to be a promising intervention for the treatment of obesity in animal studies, but epidemiological studies on the association between spermidine and obesity are inadequate. Methods: In the cross-sectional study, a total of 4230 eligible Chinese rural participants aged ≥ 35 years at baseline were recruited, of whom 1738 completed the two-year follow-up. Serum spermidines were measured using high-performance liquid chromatography with a fluorescence detector. Obesity and change in BMI were used as outcomes. Multivariable logistic regression analysis was applied to obtain the odds ratios (ORs) and 95% confidence intervals (CIs). Results: Participants who were obese had higher serum spermidine concentrations than those who were of normal weight (median (IQR), 27.2 ng/mL (14.8−53.4 ng/mL) vs. 23.8 ng/mL (12.8−46.6 ng/mL), p = 0.002). Compared with participants in the first quartile, those in the third quartile (OR 1.327, 95% CI 1.050 to 1.678) and the fourth quartile (OR 1.417, 95% CI 1.121 to 1.791) had a significantly increased risk of prevalent obesity after adjustment for confounding factors. In the follow-up study, participants in the third quartile (OR 0.712, 95% CI 0.535 to 0.946) and the fourth quartile (OR 0.493, 95% CI 0.370 to 0.657) had significantly lower risks of an increase in BMI after adjustment for confounding factors, with the lowest quartile as the reference. Meanwhile, we found a nonlinear relationship between spermidine and BMI in the follow-up study (p < 0.001). Conclusions: Serum spermidine was positively associated with increased odds of obesity in the cross-sectional study but reduced odds of an increase in BMI in the follow-up study among Chinese adults. Future studies are warranted to determine the exact mechanism underlying the association between spermidine and obesity and the scope for interventions.

Spermidine Ameliorates Nonalcoholic Steatohepatitis through Thyroid Hormone-Responsive Protein Signaling and the Gut Microbiota-Mediated Metabolism of Bile Acids

Spermidine, a natural polyamine and physiological autophagy inducer, is involved in various physiological processes. However, the impact and mechanism of spermidine on nonalcoholic steatohepatitis (NASH) remains unclarified. We found that daily spermidine intake was significantly lower in volunteers with liver dysfunction than the healthy controls, and the serum and fecal spermidine levels were negatively correlated with the NASH phenotypes. Spermidine supplementation significantly attenuated hepatic lipid accumulation, insulin resistance, hepatic inflammation, and fibrosis in NASH mice induced by a western diet. The ameliorating effect of spermidine on lipid accumulation might be partly regulated by thyroid hormone-responsive protein (THRSP) signaling and autophagy. Moreover, spermidine altered the profile of hepatic bile acids (BAs) and microbial composition and function. Furthermore, spermidine reversed the progression of hepatic steatosis, inflammation, and fibrosis in mice with preexisting NASH. Therefore, spermidine ameliorates NASH partly through the THRSP signaling and the gut microbiota-mediated metabolism of BAs, suggesting that spermidine might be a viable therapy for NASH.

Role of Polyamines and Hypusine in β Cells and Diabetes Pathogenesis

The polyamines-putrescine, spermidine, and spermine-are polycationic, low molecular weight amines with cellular functions primarily related to mRNA translation and cell proliferation. Polyamines partly exert their effects via the hypusine pathway, wherein the polyamine spermidine provides the aminobutyl moiety to allow posttranslational modification of the translation factor eIF5A with the rare amino acid hypusine (hydroxy putrescine lysine). The "hypusinated" eIF5A (eIF5Ahyp) is considered to be the active form of the translation factor necessary for the translation of mRNAs associated with stress and inflammation. Recently, it has been demonstrated that activity of the polyamines-hypusine circuit in insulin-producing islet β cells contributes to diabetes pathogenesis under conditions of inflammation. Elevated levels of polyamines are reported in both exocrine and endocrine cells of the pancreas, which may contribute to endoplasmic reticulum stress, oxidative stress, inflammatory response, and autophagy. In this review, we have summarized the existing research on polyamine-hypusine metabolism in the context of β-cell function and diabetes pathogenesis.

Circulating metabolite profile in young adulthood identifies long-term diabetes susceptibility: the Coronary Artery Risk Development in Young Adults (CARDIA) study

AIMS/HYPOTHESIS

The aim of this work was to define metabolic correlates and pathways of diabetes pathogenesis in young adults during a subclinical latent phase of diabetes development.

METHODS

We studied 2083 young adults of Black and White ethnicity in the prospective observational cohort Coronary Artery Risk Development in Young Adults (CARDIA) study (mean ± SD age 32.1 ± 3.6 years; 43.9% women; 42.7% Black; mean ± SD BMI 25.6 ± 4.9 kg/m2) and 1797 Framingham Heart Study (FHS) participants (mean ± SD age 54.7 ± 9.7 years; 52.1% women; mean ± SD BMI 27.4 ± 4.8 kg/m2), examining the association of comprehensive metabolite profiles with endophenotypes of diabetes susceptibility (adipose and muscle tissue phenotypes and systemic inflammation). Statistical learning techniques and Cox regression were used to identify metabolite signatures of incident diabetes over a median of nearly two decades of follow-up across both cohorts.

RESULTS

We identified known and novel metabolites associated with endophenotypes that delineate the complex pathophysiological architecture of diabetes, spanning mechanisms of muscle insulin resistance, inflammatory lipid signalling and beta cell metabolism (e.g. bioactive lipids, amino acids and microbe- and diet-derived metabolites). Integrating endophenotypes of diabetes susceptibility with the metabolome generated two multi-parametric metabolite scores, one of which (a proinflammatory adiposity score) was associated with incident diabetes across the life course in participants from both the CARDIA study (young adults; HR in a fully adjusted model 2.10 [95% CI 1.72, 2.55], p<0.0001) and FHS (middle-aged and older adults; HR 1.33 [95% CI 1.14, 1.56], p=0.0004). A metabolite score based on the outcome of diabetes was strongly related to diabetes in CARDIA study participants (fully adjusted HR 3.41 [95% CI 2.85, 4.07], p<0.0001) but not in the older FHS population (HR 1.15 [95% CI 0.99, 1.33], p=0.07).

CONCLUSIONS/INTERPRETATION

Selected metabolic abnormalities in young adulthood identify individuals with heightened diabetes risk independent of race, sex and traditional diabetes risk factors. These signatures replicate across the life course.

What we know about protein gut metabolites: Implications and insights for human health and diseases

Gut microbiota is a complex ecosystem of symbiotic bacteria that contribute to human metabolism and supply intestinal metabolites, whose production is mainly influenced by the diet. Dietary patterns characterized by a high intake of protein promotes the growth of proteolytic bacteria's, which produce metabolites from undigested protein fermentation. Microbioal protein metabolites can regulate immune, metabolic and neuronal responses in different target organs. Metabolic pathways of these compounds and their mechanisms of action on different pathologies can lead to the discovery of new diagnostic techniques, drugs and the potential use as functional ingredients in food. This review discusses the potential mechanisms by which amino acid catabolism is involved in microbial protein metabolites. In addition, results from several studies on the association of products from the intestinal metabolism of indigestible proteins and the state of health or disease of the host are revised.

Angiocrine polyamine production regulates adiposity

Reciprocal interactions between endothelial cells (ECs) and adipocytes are fundamental to maintain white adipose tissue (WAT) homeostasis, as illustrated by the activation of angiogenesis upon WAT expansion, a process that is impaired in obesity. However, the molecular mechanisms underlying the crosstalk between ECs and adipocytes remain poorly understood. Here, we show that local production of polyamines in ECs stimulates adipocyte lipolysis and regulates WAT homeostasis in mice. We promote enhanced cell-autonomous angiogenesis by deleting Pten in the murine endothelium. Endothelial Pten loss leads to a WAT-selective phenotype, characterized by reduced body weight and adiposity in pathophysiological conditions. This phenotype stems from enhanced fatty acid β-oxidation in ECs concomitant with a paracrine lipolytic action on adipocytes, accounting for reduced adiposity. Combined analysis of murine models, isolated ECs and human specimens reveals that WAT lipolysis is mediated by mTORC1-dependent production of polyamines by ECs. Our results indicate that angiocrine metabolic signals are important for WAT homeostasis and organismal metabolism.

Gut microbiota and related metabolites in the pathogenesis of nonalcoholic steatohepatitis and its resolution after bariatric surgery

Nonalcoholic fatty liver disease (NAFLD) is increasing in parallel with the rising prevalence of obesity, leading to major health and socioeconomic consequences. To date, the most effective therapeutic approach for NAFLD is weight loss. Accordingly, bariatric surgery (BS), which produces marked reductions in body weight, is associated with significant histopathological improvements in advanced stages of NAFLD, such as nonalcoholic steatohepatitis (NASH) and liver fibrosis. BS is also associated with substantial taxonomical and functional alterations in gut microbiota, which are believed to play a significant role in metabolic improvement after BS. Interestingly, gut microbiota and related metabolites may be implicated in the pathogenesis of NAFLD through diverse mechanisms, including specific microbiome signatures, short chain fatty acid production or the modulation of one-carbon metabolism. Moreover, emerging evidence highlights the potential association between gut microbiota changes after BS and NASH resolution. In this review, we summarize the current knowledge on the relationship between NAFLD severity and gut microbiota, as well as the role of the gut microbiome and related metabolites in NAFLD improvement after BS.

Synergistic effects of ISL1 and KDM6B on non-alcoholic fatty liver disease through the regulation of SNAI1

Background

The increasing incidence of non-alcoholic fatty liver disease (NAFLD) has been reported worldwide, which urges understanding of its pathogenesis and development of more effective therapeutical methods for this chronic disease. In this study, we aimed to investigate the effects of a LIM homeodomain transcription factor, islet1 (ISL1) on NAFLD.

Methods

Male C57BL/6J mice were fed with a diet high in fat content to produce NAFLD models. These models were then treated with overexpressed ISL1 (oe-ISL1), oe-Lysine-specific demethylase 6B (KDM6B), oe-SNAI1, or short hairpin RNA against SNAI1. We assessed triglyceride and cholesterol contents in the plasma and liver tissues and determined the expressions of ISL1, KDM6B and SNAI1 in liver tissues. Moreover, the in vitro model of lipid accumulation was constructed using fatty acids to explore the in vitro effect of ISL1/KDM6B/SNAI1 in NAFLD.

Results

The results showed that the expressions of ISL1, KDM6B, and SNAI1 where decreased, but contents of triglyceride and cholesterol increased in mice exposed to high-fat diet. ISL1 inhibited lipogenesis and promoted lipolysis and exhibited a synergizing effect with KDM6B to upregulate the expression of SNAI1. Moreover, both KDM6B and SNAI1 could inhibit lipogenesis and induce lipolysis. Importantly, the therapeutic effects of ISL1 on in vitro model of lipid accumulations was also confirmed through the modulation of KDM6B and SNAI1.

Conclusions

Taken together, these findings highlighted that ISL1 effectively ameliorated NAFLD by inducing the expressions of KDM6B and SNAI1, which might be a promising drug for the treatment of NAFLD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-021-00428-7.

Nicotinamide Riboside-Conditioned Microbiota Deflects High-Fat Diet-Induced Weight Gain in Mice

With obesity and type 2 diabetes (T2D) at epidemic levels, we need to understand the complex nature of these diseases to design better therapeutics. The underlying causes of both obesity and T2D are complex, but both are thought to develop, in part, based on contributions from the gut microbiota.

New Insights into the Roles and Mechanisms of Spermidine in Aging and Age-Related Diseases

High incidences of morbidity and mortality associated with age-related diseases among the elderly population are a socio-economic challenge. Aging is an irreversible and inevitable process that is a risk factor for pathological progression of diverse age-related diseases. Spermidine, a natural polyamine, plays a critical role in molecular and cellular interactions involved in various physiological and functional processes. Spermidine has been shown to modulate aging, suppress the occurrence and severity of age-related diseases, and prolong lifespan. However, the precise mechanisms through which spermidine exerts its anti-aging effects have not been established. In this review, we elucidate on the mechanisms and roles underlying the beneficial effects of spermidine in aging from a molecular and cellular perspective. Moreover, we provide new insights into the promising potential diagnostic and therapeutic applications of spermidine in aging and age-related diseases.

Bifidobacterium animalis subsp. lactis lkm512 Attenuates Obesity-Associated Inflammation and Insulin Resistance Through the Modification of Gut Microbiota in High-Fat Diet-Induced Obese Mice

SCOPE

The impacts of longevity-promoting probiotic Bifidobacterium animalis subsp. lactis LKM512 (LKM512) on metabolic disease remain unclear. Here, the authors aim to explore the potential of LKM512 on the host physiological function and gut microbiota in high-fat diet-induced obese mice.

METHODS AND RESULTS

LKM512 are orally administrated for 12 weeks, and the effects of LKM 512 on systemic inflammation and insulin resistance, as well as gut microbiota, are investigated in high-fat (HF) diet-induced obese mice. LKM512 supplementation ameliorates hepatic lipid accumulation, attenuates hepatic and adipose tissue inflammation, and improves intestinal barrier function. These results are associated with improved insulin sensitivity and metabolic endotoxemia. Furthermore, the colonization of LKM512 induces an increase in polyamine metabolism and production, together with significant alternations in the composition and function of gut microbiota in obese mice, which are correlated with these improved metabolic phenotypes in the host.

CONCLUSION

The probiotic strain LKM512 may become a promising strategy to improve obesity and related metabolic disorders.

Oral Spermidine Targets Brown Fat and Skeletal Muscle to Mitigate Diet-Induced Obesity and Metabolic Disorders

INTRODUCTION

Obesity causes many life-threatening diseases. It is important to develop effective approaches for obesity treatment. Oral supplementation with spermidine retards age-related processes, but its influences on obesity and various metabolic tissues remain largely unknow. This study aims to investigate the effects of oral spermidine on brown adipose tissue (BAT) and skeletal muscle as well as its roles in counteracting obesity and metabolic disorders.

METHODS AND RESULTS

Spermidine is orally administrated into high-fat diet (HFD)-fed mice. The weight gain, insulin resistance, and hepatic steatosis are attenuated by oral spermidine in HFD-fed mice, accompanied by an alleviation of white adipose tissue inflammation. Oral spermidine promotes BAT activation and metabolic adaptation of skeletal muscle in HFD-fed mice, evidenced by UCP-1 induction and CREB activation in both tissues. Notably, oral spermidine upregulates tyrosine hydroxylase in hypothalamus of HFD-fed mice; spermidine treatment increases tyrosine hydroxylase expression and norepinephrine production in neurocytes, which leads to CREB activation and UCP-1 induction in brown adipocytes and myotubes. Spermidine also directly promotes UCP-1 and PGC-1α expression in brown adipocytes and myotubes.

CONCLUSION

Spermidine serves as an oral supplement to attenuate obesity and metabolic disorders through hypothalamus-dependent or -independent BAT activation and skeletal muscle adaptation.

Integration of transcriptomics and metabolomics confirmed hepatoprotective effects of steamed shoot extracts of ginseng (Panax ginseng C.A. Meyer) on toxicity caused by overdosed acetaminophen

The study aimed, by integrating transcriptomics and metabolomics, to reveal novel biomarkers caused by overdosed acetaminophen (APAP) and liver protection substances procured by pre-administration of ginseng shoots extract (GSE). Totally 4918 genes and 127 metabolites were identified as differentially expressed genes and differential metabolites, respectively. According to KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment, such pathways as primary bile acid biosynthesis, bile secretion, retinol metabolism, histidine and several other amino-related metabolism were significantly altered by GSE and disturbed by subsequent overdosed APAP at the transcriptomic as well as metabolomic levels. Fifteen key biomarker metabolites related to these pathways were up-regulated in APAP-treated vs GSE-pretreated liver tissues, and were reported exerting anti-oxidant, anti-inflammatory, anti-apoptotic and/or immunomodulate functions, three of which even possessed direct hepatoprotection effects. Twenty five vital unigenes modulating these metabolites were further verified by correlation analysis and expression levels of fifteen of them were examined by qRT-PCR. Our findings indicate that GSE may be an effective dietary supplement for preventing the liver damage caused by the overdosed APAP.

The metabolic role of spermidine in obesity: Evidence from cells to community

Spermidine is a natural polyamine existing in all living cells known to play an important role in cellular functions. Recently, several studies have reported the effect of alterations in the spermidine pool on metabolic pathways. It has been shown that activation of spermidine/spermine N-1-acetyl-transferase (SSAT), the rate-limiting enzyme in polyamine catabolism, improved glucose and lipid metabolism. In addition, spermidine supplementation has been shown to protect against diet-induced obesity in animal models. However, some clinical studies demonstrated that polyamine levels are increased in childhood obesity and metabolic syndrome patients with type 2 diabetes (T2DM), while polyamine-rich food is associated with a lower incidence of cardiovascular disease (CVD). Therefore, this review aims to summarize and discuss the evidence from in vitro, in vivo and clinical studies on the possible roles of spermidine on metabolic pathways under physiological and obese conditions. All consistent and inconsistent findings are discussed and further studies aiming to fill any gaps in the knowledge are proposed.

The clinical impact of maternal weight on offspring health: lights and shadows in breast milk metabolome

INTRODUCTION

Pre-pregnancy overweight and obesity, depending on maternal nutrition and metabolic state, can influence fetal, neonatal and long-term offspring health, regarding cardio-metabolic, respiratory, immunological and cognitive outcomes. Thus, maternal weight can act, through mechanisms that are not full understood, on the physiology and metabolism of some fetal organs and tissues, to adapt themselves to the intrauterine environment and nutritional reserves. These effects could occur by modulating gene expression, neonatal microbiome, and through breastfeeding.

AREAS COVERED

In this paper, we investigated the potential effects of metabolites found altered in breast milk (BM) of overweight/obese mothers, through an extensive review of metabolomics studies, and the potential short- and long-term clinical effects in the offspring, especially regarding overweight, glucose homeostasis, insulin resistance, oxidative stress, infections, immune processes, and neurodevelopment.

EXPERT OPINION

Metabolomics seems the ideal tool to investigate BM variation depending on maternal or fetal/neonatal factors. In particular, BM metabolome alterations according to maternal conditions were recently pointed out in cases of gestational diabetes, preeclampsia, intrauterine growth restriction and maternal overweight/obesity. In our opinion, even if BM is the food of choice in neonatal nutrition, the deepest comprehension of its composition in overweight/obese mothers could allow targeted supplementation, to improve offspring health and metabolic homeostasis.

Spermidine at supraphysiological doses induces oxidative stress and granulosa cell apoptosis in mouse ovaries

Given that spermidine is associated with aging-related diseases and it is a potential target for delaying aging, functional studies on supraphysiological levels of spermidine are required. Our previous studies showed that the granulosa layer arranged irregular and the follicular oocytes were shrunk in female mice injected intraperitoneally with spermidine at 150 mg/kg (Body weight) after 24 h. It indicated that supraphysiological levels of spermidine induced ovarian damage in female mice. The objective of this study was to investigate the effect of acute administration of supraphysiological spermidine on the ovary and granulosa cells in mice. The results showed that treatment with spermidine at 150 mg/kg (intraperitoneal) significantly increased the levels of both H₂O₂ and malondialdehyde and reduced total antioxidant capacity and the activities of catalase and superoxide dismutase in mouse ovaries. The contents of putrescine and spermine increased significantly in the ovaries of mice treated with spermidine. Treatment with spermidine at 150 mg/kg increased the apoptotic rate and reactive oxygen species levels of granulosa cells in mouse ovaries. Furthermore, the protein expression of P53, CASPASE 8 (Cleaved/Pro), CASPASE 9 (Cleaved/Pro) and CASPASE 3 (Cleaved/Pro) in granulosa cells of mice treated with spermidine were significantly upregulated, while BCL2 expression was significantly downregulated. In summary, our study demonstrates for the first time that spermidine at supraphysiological doses causes ovarian oxidative stress and induces granulosa cell apoptosis via the P53 and/or BCL2-CASPASEs pathway.

Spermidine promotes melanin production through an MITF signalling pathway

Melanin plays an important role in determining skin colour. Apoptosis of melanocytes and defect in melanin production cause vitiligo. Various studies have been conducted to treat the disease, but its treatment is still difficult. Therefore, this study aimed to investigate the effect of spermidine, which is known as an inhibitor of ageing-related oxidized proteins, on melanogenesis. Even though spermidine above 50 μM had no effect on antioxidant activity and DOPA oxidation, it displayed tyrosinase activity. However, spermidine at 2000 μM was cytotoxic in B16F1 cells using MTT assay. Spermidine above 125 μM decreased the amount of intracellular hydrogen peroxide in a concentration-dependent manner in DCFH-DA analysis. It was also found that spermidine above 2000 μM increased melanin synthesis in living cells. However, spermidine above 1000 μM increased melanin synthesis in a concentration-dependent manner in H₂ O₂ -treated B16F1 cells. Furthermore, spermidine enhanced the expression of tyrosine hydroxylase via MITF transcription factor involved in melanogenesis in H₂ O₂ -treated B16F1 cells. Therefore, these results suggest that spermidine could be applied as a potential stimulator of melanin synthesis for the prevention of hair greying.

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.

Voluntary activity reverses spermidine-induced myocardial fibrosis and lipid accumulation in the obese male mouse

Obesity due to high calorie intake induces cardiac hypertrophy and dysfunction, thus contributing to cardiovascular morbidity and mortality. Recent studies in aging suggest that oral supplementation with the natural polyamine spermidine has a cardioprotective effect. Here, the hypothesis was tested that spermidine or voluntary activity alone or in combination protect the heart from adverse effects induced by obesity. Therefore, C57Bl/6 mice (n = 8–10 per group) were subjected to control or high fat diet (HFD) and were left untreated, or either received spermidine via drinking water or were voluntarily active or both. After 30 weeks, the mice were killed and the left ventricle of the hearts was processed for light and electron microscopy. Design-based stereology was used to estimate parameters of hypertrophy, fibrosis, and lipid accumulation. HFD induced cardiac hypertrophy as demonstrated by higher volumes of the left ventricle, cardiomyocytes, interstitium, myofibrils and cardiomyocyte mitochondria. These changes were not influenced by spermidine or voluntary activity. HFD also induced myocardial fibrosis and accumulation of lipid droplets within cardiomyocytes. These HFD effects were enhanced in spermidine treated animals but not in voluntarily active mice. This was even the case in voluntarily active mice that received spermidine. In conclusion, the data confirm the induction of left ventricular hypertrophy by high-fat diet and suggest that—under high fat diet—spermidine enhances cardiomyocyte lipid accumulation and interstitial fibrosis which is counteracted by voluntary activity.

Chemical activation of SAT1 corrects diet-induced metabolic syndrome

The pharmacological targeting of polyamine metabolism is currently under the spotlight for its potential in the prevention and treatment of several age-associated disorders. Here, we report the finding that triethylenetetramine dihydrochloride (TETA), a copper-chelator agent that can be safely administered to patients for the long-term treatment of Wilson disease, exerts therapeutic benefits in animals challenged with hypercaloric dietary regimens. TETA reduced obesity induced by high-fat diet, excessive sucrose intake, or leptin deficiency, as it reduced glucose intolerance and hepatosteatosis, but induced autophagy. Mechanistically, these effects did not involve the depletion of copper from plasma or internal organs. Rather, the TETA effects relied on the activation of an energy-consuming polyamine catabolism, secondary to the stabilization of spermidine/spermine N¹-acetyltransferase-1 (SAT1) by TETA, resulting in enhanced enzymatic activity of SAT. All the positive effects of TETA on high-fat diet-induced metabolic syndrome were lost in SAT1-deficient mice. Altogether, these results suggest novel health-promoting effects of TETA that might be taken advantage of for the prevention or treatment of obesity.

Effect of a lifestyle intervention program with energy-restricted Mediterranean diet and exercise on the serum polyamine metabolome in individuals at high cardiovascular disease risk: a randomized clinical trial

BACKGROUND

Many food items included in the Mediterranean diet (MedDiet) are rich in polyamines, small aliphatic amines with potential cardioprotective effects. The consumption of a MedDiet could increase polyamine concentrations. Based on experimental models, polyamine concentrations may be also influenced by physical activity (PA).

OBJECTIVES

We aimed to evaluate whether an intervention based on an energy-restricted MedDiet (er-MedDiet) and PA promotion, in comparison with an energy-unrestricted MedDiet and traditional health care, influences the serum pattern of polyamines and related metabolites in subjects at high risk of cardiovascular disease (CVD).

METHODS

This was a substudy from the PREDIMED-Plus trial, an ongoing randomized clinical trial including 6874 participants allocated either to an intensive weight-loss lifestyle intervention based on er-MedDiet, PA promotion, and behavioral support (er-MedDiet + PA group), or to an energy-unrestricted MedDiet and traditional health care group (MedDiet group). A total of 75 patients (n = 38, er-MedDiet + PA group; n = 37, MedDiet group) were included in this study. Serum concentrations of arginine, ornithine, polyamines, and acetyl polyamines at baseline and 26 wk of intervention were measured by an ultra-high-performance LC-tandem MS platform.

RESULTS

At week 26, study groups had similar adherence to the MedDiet but patients randomly assigned to the er-MedDiet + PA group showed significantly lower mean energy intake (-340.3 kcal/d; 95% CI: -567.3, -113.4 kcal/d; P = 0.004), higher mean PA (1290.6; 95% CI: 39.9, 2541.3 metabolic equivalent tasks · min/d; P = 0.043), and higher mean decrease in BMI (in kg/m2) (-1.3; 95% CI: -1.8, -0.6; P < 0.001) than the MedDiet group. However, no significant differences in serum polyamines or related metabolites were found between study groups after 26 wk of intervention and no significant between-group differences were found in glycated hemoglobin, HDL-cholesterol, or triglyceride concentrations.

CONCLUSIONS

In individuals at high CVD risk, an er-MedDiet with increased PA did not result in significant changes of serum concentrations of polyamines or related metabolites in comparison with an energy-unrestricted MedDiet and no increase in PA. This trial was registered at isrctn.com as ISRCTN89898870.

The Vascular Consequences of Metabolic Syndrome: Rodent Models, Endothelial Dysfunction, and Current Therapies

Metabolic syndrome is characterized by visceral obesity, dyslipidemia, hyperglycemia and hypertension, and affects over one billion people. Independently, the components of metabolic syndrome each have the potential to affect the endothelium to cause vascular dysfunction and disrupt vascular homeostasis. Rodent models of metabolic syndrome have significantly advanced our understanding of this multifactorial condition. In this mini-review we compare the currently available rodent models of metabolic syndrome and consider their limitations. We also discuss the numerous mechanisms by which metabolic abnormalities cause endothelial dysfunction and highlight some common pathophysiologies including reduced nitric oxide production, increased reactive oxygen species and increased production of vasoconstrictors. Additionally, we explore some of the current therapeutics for the comorbidities of metabolic syndrome and consider how these benefit the vasculature.

Spermidine Confers Liver Protection by Enhancing NRF2 Signaling Through a MAP1S-Mediated Noncanonical Mechanism

Spermidine (SPD), a naturally occurring polyamine, has been recognized as a caloric restriction mimetic that confers health benefits, presumably by inducing autophagy. Recent studies have reported that oral administration of SPD protects against liver fibrosis and hepatocarcinogenesis through activation of microtubule associated protein 1S (MAP1S)-mediated autophagy. Nuclear factor (erythroid-derived 2)-like 2 (NRF2) is a transcription factor that mediates cellular protection by maintaining the cell's redox, metabolic, and proteostatic balance. In this study, we demonstrate that SPD is a noncanonical NRF2 inducer, and that MAP1S is a component of this noncanonical pathway of NRF2 activation. Mechanistically, MAP1S induces NRF2 signaling through two parallel mechanisms, both resulting in NRF2 stabilization: (1) MAP1S competes with Kelch-like ECH-associated protein 1 (KEAP1) for NRF2 binding through an ETGE motif, and (2) MAP1S accelerates p62-dependent degradation of KEAP1 by the autophagy pathway. We further demonstrate that SPD confers liver protection by enhancing NRF2 signaling. The importance of both NRF2 and p62-dependent autophagy in SPD-mediated liver protection was confirmed using a carbon tetrachloride-induced liver fibrosis model in wild-type, Nrf2-/- , p62-/- and Nrf2-/- ;p62-/- mice, as the protective effect of SPD was significantly reduced in NRF2 or p62 single knockout mice, and completely abolished in the double knockout mice. Conclusion: Our results demonstrate the pivotal role of NRF2 in mediating the health benefit of SPD, particularly in the context of liver pathologies.

Dietary and Gut Microbiota Polyamines in Obesity- and Age-Related Diseases

The polyamines putrescine, spermidine, and spermine are widely distributed polycationic compounds essential for cellular functions. Intracellular polyamine pools are tightly regulated by a complex regulatory mechanism involving de novo biosynthesis, catabolism, and transport across the plasma membrane. In mammals, both the production of polyamines and their uptake from the extracellular space are controlled by a set of proteins named antizymes and antizyme inhibitors. Dysregulation of polyamine levels has been implicated in a variety of human pathologies, especially cancer. Additionally, decreases in the intracellular and circulating polyamine levels during aging have been reported. The differences in the polyamine content existing among tissues are mainly due to the endogenous polyamine metabolism. In addition, a part of the tissue polyamines has its origin in the diet or their production by the intestinal microbiome. Emerging evidence has suggested that exogenous polyamines (either orally administrated or synthetized by the gut microbiota) are able to induce longevity in mice, and that spermidine supplementation exerts cardioprotective effects in animal models. Furthermore, the administration of either spermidine or spermine has been shown to be effective for improving glucose homeostasis and insulin sensitivity and reducing adiposity and hepatic fat accumulation in diet-induced obesity mouse models. The exogenous addition of agmatine, a cationic molecule produced through arginine decarboxylation by bacteria and plants, also exerts significant effects on glucose metabolism in obese models, as well as cardioprotective effects. In this review, we will discuss some aspects of polyamine metabolism and transport, how diet can affect circulating and local polyamine levels, and how the modulation of either polyamine intake or polyamine production by gut microbiota can be used for potential therapeutic purposes.

Type 2 Diabetes Is Associated with a Different Pattern of Serum Polyamines: A Case⁻Control Study from the PREDIMED-Plus Trial

Objective: Polyamines are naturally occurring cationic molecules present in all living cells. Dysregulation of circulating polyamines has been reported in several conditions, but little is known about the levels of serum polyamines in chronic metabolic disorders such as type 2 diabetes (T2D). Therefore, the aim of this study was to evaluate the polyamine-related metabolome in a cohort of metabolic syndrome individuals with and without T2D. Design and methods: This was a nested case–control study within the PREDIMED-Plus trial that included 44 patients with T2D and 70 patients without T2D. We measured serum levels of arginine, ornithine, polyamines, and acetyl polyamines with an ultra-high performance liquid chromatography tandem mass spectrometry platform. Results: Our results showed that serum putrescine, directly generated from ornithine by the catalytic action of the biosynthetic enzyme ornithine decarboxylase, was significantly elevated in patients with T2D compared to those without T2D, and that it significantly correlated with the levels of glycosylated hemoglobin (HbA1c). Correlation analysis revealed a significantly positive association between fasting insulin levels and spermine. Multiple logistic regression analysis (adjusted for age, gender and body weight index) revealed that serum putrescine and spermine levels were associated with a higher risk of T2D. Conclusions: Our study suggests that polyamine metabolism is dysregulated in T2D, and that serum levels of putrescine and spermine are associated with glycemic control and circulating insulin levels, respectively.