Activated polyamine catabolism leads to low cholesterol levels by enhancing bile acid synthesis

Metabolic support by macrophages sustains colonic epithelial homeostasis

The intestinal epithelium has a high turnover rate and constantly renews itself through proliferation of intestinal crypt cells, which depends on insufficiently characterized signals from the microenvironment. Here, we showed that colonic macrophages were located directly adjacent to epithelial crypt cells in mice, where they metabolically supported epithelial cell proliferation in an mTORC1-dependent manner. Specifically, deletion of tuberous sclerosis complex 2 (Tsc2) in macrophages activated mTORC1 signaling that protected against colitis-induced intestinal damage and induced the synthesis of the polyamines spermidine and spermine. Epithelial cells ingested these polyamines and rewired their cellular metabolism to optimize proliferation and defense. Notably, spermine directly stimulated proliferation of colon epithelial cells and colon organoids. Genetic interference with polyamine production in macrophages altered global polyamine levels in the colon and modified epithelial cell proliferation. Our results suggest that macrophages act as "commensals" that provide metabolic support to promote efficient self-renewal of the colon epithelium.

Polyamine-Linked Cholesterol Incorporation in Rift Valley Fever Virus Particles Promotes Infectivity

Viruses rely on an array of cellular metabolites to replicate and form progeny virions. One set of these molecules, polyamines, are small aliphatic molecules, which are abundant in most cells, that support virus infection; however, the precise roles of polyamines in virus infection remain incompletely understood. Recent work demonstrated that polyamine metabolism supports cellular cholesterol synthesis through translation of the key transcription factor SREBP2. Here, we show that the bunyavirus Rift Valley fever virus (RVFV) relies on both cholesterol and polyamines for virus infection. Depletion of cellular cholesterol or interruption of cholesterol trafficking negatively impacts RVFV infection. Cholesterol is incorporated into RVFV virions and mediates their infectivity in a polyamine-dependent manner; we find that the virus derived from polyamine-depleted cells lacks cholesterol within the virion membrane. Conversely, we find that virion-associated cholesterol is linked to the incorporation of spermidine within the virion. Our prior work demonstrated that polyamines facilitate pH-mediated fusion and genome release, which may be a consequence of cholesterol depletion within virions. Thus, our work highlights the metabolic connection between polyamines and cholesterol synthesis to impact bunyavirus infection. These data demonstrate the connectedness between cellular metabolic pathways and reveal potential avenues of therapeutic intervention.

Treatment-Interval Changes in Serum Levels of Albumin and Histidine Correlated with Treatment Interruption in Patients with Locally Advanced Head and Neck Squamous Cell Carcinoma Completing Chemoradiotherapy under Recommended Calorie and Protein Provision

We investigated risk factors for treatment interruption (TI) in patients with locally advanced head and neck squamous-cell carcinoma (LAHNSCC) following concurrent chemoradiotherapy (CCRT), under the provision of recommended calorie and protein intake; we also evaluated the associations between clinicopathological variables, calorie and protein supply, nutrition–inflammation biomarkers (NIBs), total body composition change (TBC), and a four-serum-amino-acid metabolite panel (histidine, leucine, ornithine, and phenylalanine) among these patients. Patients with LAHNSCC who completed the entire planned CCRT course and received at least 25 kcal/kg/day and 1 g of protein/kg/day during CCRT were prospectively recruited. Clinicopathological variables, anthropometric data, blood NIBs, CCRT-related factors, TBC data, and metabolite panels before and after treatment were collected; 44 patients with LAHNSCC were enrolled. Nine patients (20.4%) experienced TIs. Patients with TIs experienced greater reductions in hemoglobin, serum levels of albumin, uric acid, histidine, and appendicular skeletal mass, and suffered from more grade 3/4 toxicities than those with no TI. Neither increased daily calorie supply (≥30 kcal/kg/day) nor feeding tube placement was correlated with TI. Multivariate analysis showed that treatment-interval changes in serum albumin and histidine levels, but not treatment toxicity, were independently associated with TI. Thus, changes in serum levels of albumin and histidine over the treatment course could cause TI in patients with LAHNSCC following CCRT.

Integrated omics analysis revealed the Tinospora cordifolia intervention modulated multiple signaling pathways in hypertriglyceridemia patients-a pilot clinical trial

Purpose

Hypertriglyceridemia (HTG) is strongly associated with the various types of disease conditions and evolving as epidemics. Hence, it is important to identify molecules that lower the triglyceride and chylomicron levels. Tinospora cordifolia is an illustrious Ayurveda drug, has proved juvenile and immunomodulatory properties.

Methods

Twenty four (24) patients having >499 mg/dL TG and 130-230 mg/dL of cholesterol were randomized and given 100 mL/day (~3.0 g) water extract of T. cordifolia (TCE) for 14 days. Basal parameters were analyzed before and after TC intervention to analyzed primary outcomes. Further, unbiased metabolomics and proteomics profiling was explored to assess the efficacy of TCE in HTG patients.

Results

TCE intervention decreased the levels of triglycerides, and VLDL to 380.45 ± 17.44, and 31.85 ± 5.88, and increased the HDL levels to 47.50 ± 9.05 mg/dL significantly (p < 0.05). Metabolomics analysis identified the significant alteration in 69 metabolites and 72 proteins in plasma of HTG patients. TCE intervention reduced the level of isoprostanes, ROS, BCAA, and fatty acid derivatives, significantly. The annotation databases, Metboanalyst predicted Akt and Rap1 signaling, and ECM-receptor interaction is the most affected in HTG patients. TCE intervention normalized these events by increasing the peroxisome biogenesis and modulating Akt and Rap1 signaling pathway.

Conclusion

T. cordifolia intervention suppresses the baseline in HTG patients. Omics analysis showed that TCE intervention modulates the Akt and Rap signaling, and peroxisome biogenesis to control the cellular switches and signaling pathways. Hence, TCE can be used as a supplement or alternate of standard drugs being used in the management of HTG.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-022-00985-6.

Sex-related differences in urinary immune-related metabolic profiling of alopecia areata patients

INTRODUCTION

Alopecia areata is a well-known autoimmune disease affecting humans. Polyamines are closely associated with proliferation and inflammation, and steroid hormones are involved in immune responses. Additionally, bile acids play roles in immune homeostasis by activating various signaling pathways; however, the roles of these substances and their metabolites in alopecia areata remain unclear.

OBJECTIVES

In this study, we aimed to identify differences in metabolite levels in urine samples from patients with alopecia areata and healthy controls.

METHODS

To assess polyamine, androgen, and bile acid concentrations, we performed high-performance liquid chromatography-tandem mass spectrometry.

RESULTS

Our results showed that spermine and dehydroepiandrosterone levels differed significantly between male patients and controls, whereas ursodeoxycholic acid levels were significantly higher in female patients with alopecia areata than in controls.

CONCLUSION

Our findings suggested different urinary polyamine, androgen, and bile acid concentrations between alopecia areata patients and normal controls. Additionally, levels of endogenous substances varied according to sex, and this should be considered when developing appropriate treatments and diagnostic techniques. Our findings improve our understanding of polyamine, androgen, and bile acid profiles in patients with alopecia areata and highlight the need to consider sex-related differences.

Exogenous putrescine affects polyamine and arginine metabolism in rat liver following bile ductus ligation

Rat bile duct ligation (BDL) represents a useful method that mimics obstructive extrahepatic cholestasis, which is known to be a frequent disorder in humans. Polyamines (putrescine, spermidine, and spermine) are one of the key molecules regulating cell proliferation and differentiation. This work aimed to evaluate the potential beneficial properties of putrescine in rat BDL model by studying several biochemical parameters reflecting liver function and polyamine metabolism. Rats that were subjected to BDL were injected with putrescine (150 mg/kg) for 9 days, while in parallel another group with BDL remained untreated. Two control groups were included as well, sham-opened and putrescine-treated group. The following plasma parameters: ALT, AST, γ-GT, ALP, bilirubin, bile acids, as well as liver malondialdehyde and polyamine concentration and the activity of enzymes involved in polyamine metabolism were studied. After BDL, significant alterations in plasma biochemical parameters occurred, where a 9-day putrescine treatment significantly alleviated liver function deterioration. Putrescine also increased liver polyamines’ concentrations and polyamine and diamine oxidase activities in rats submitted to BDL. Our results demonstrated, for the first time, that putrescine plays an important role in preserving liver tissue function in rats with experimentally induced cholestasis.

Methionine deficiency does not increase polyamine turnover through depletion of hepatic S-adenosylmethionine in juvenile Atlantic salmon

During the last few decades, plant protein ingredients such as soya proteins have replaced fishmeal in the diets of aquacultured species. This may affect the requirement and metabolism of methionine as soya contains less methionine compared with fishmeal. To assess whether methionine limitation affects decarboxylated S-adenosylmethionine availability and polyamine status, in the present study, juvenile Atlantic salmon were fed a methionine-deficient plant protein-based diet or the same diet supplemented with dl-methionine for 8 weeks. The test diets were compared with a fishmeal-based control diet to assess their effects on the growth performance of fish. Methionine limitation reduced growth and protein accretion, but when fish were fed the dl-methionine-supplemented diet their growth and protein accretion equalled those of fish fed the fishmeal-based control diet. Methionine limitation reduced free methionine concentrations in the plasma and muscle, while those in the liver were not affected. S-adenosylmethionine (SAM) concentrations were higher in the liver of fish fed the methionine-deficient diet, while S-adenosylhomocysteine concentrations were not affected. Putrescine concentrations were higher and spermine concentrations were lower in the liver of fish fed the methionine-deficient diet, while the gene expression of SAM decarboxylase (SAMdc) and the rate-limiting enzyme of polyamine synthesis ornithine decarboxylase (ODC) was not affected. Polyamine turnover, as assessed by spermine/spermidine acetyltransferase (SSAT) abundance, activity and gene expression, was not affected by treatment. However, the gene expression of the cytokine TNF-α increased in fish fed the methionine-deficient diet, indicative of stressful conditions in the liver. Even though taurine concentrations in the liver were not affected by treatment, methionine and taurine concentrations in muscle decreased due to methionine deficiency. Concomitantly, liver phospholipid and cholesterol concentrations were reduced, while NEFA concentrations were elevated. In conclusion, methionine deficiency did not increase polyamine turnover through depletion of hepatic SAM, as assessed by SSAT activity and abundance.

Dietary arginine affects energy metabolism through polyamine turnover in juvenile Atlantic salmon (Salmo salar)

In the present study, quadruplicate groups of juvenile Atlantic salmon (Salmo salar) were fed plant protein-based diets with increasing arginine inclusions (range 28·8-37·4 g/kg DM) to investigate whether arginine supplementation affects growth and lipid accumulation through an elevated polyamine turnover. Dietary lysine was held at a constant concentration, just below the requirement. All other amino acids were balanced and equal in the diets. Arginine supplementation increased protein and fat accretion, without affecting the hepatosomatic or visceralsomatic indices. Dietary arginine correlated with putrescine in the liver (R 0·78, P= 0·01) and with ornithine in the muscle, liver and plasma (P= 0·0002, 0·003 and 0·0002, respectively). The mRNA of ornithine decarboxylase, the enzyme producing putrescine, was up-regulated in the white adipose tissue of fish fed the high-arginine inclusion compared with those fed the low-arginine diet. Concomitantly, spermidine/spermine-(N1)-acetyltransferase, the rate-limiting enzyme for polyamine turnover that consumes acetyl-CoA, showed an increased activity in the liver of fish fed the arginine-supplemented diets. In addition, lower acetyl-CoA concentrations were observed in the liver of fish fed the high-arginine diet, while ATP, which is used in the process of synthesising spermidine and spermine, did not show a similar trend. Gene expression of the rate-limiting enzyme for β-oxidation of long-chain fatty acids, carnitine palmitoyl transferase-1, was up-regulated in the liver of fish fed the high-arginine diet. Taken together, the data support that increased dietary arginine activates polyamine turnover and β-oxidation in the liver of juvenile Atlantic salmon and may act to improve the metabolic status of the fish.

High levels of dietary phytosterols affect lipid metabolism and increase liver and plasma TAG in Atlantic salmon (Salmo salarL.)

Replacing dietary fishmeal (FM) and fish oil (FO) with plant ingredients in Atlantic salmon (Salmo salarL.) diets decreases dietary cholesterol and introduces phytosterols. The aim of the present study was to assess the effect of dietary sterol composition on cholesterol metabolism in Atlantic salmon. For this purpose, two dietary trials were performed, in which Atlantic salmon were fed either 100 % FM and FO (FM-FO) diet or one of the three diets with either high (80 %) or medium (40 %) plant protein (PP) and a high (70 %) or medium (35 %) vegetable oil (VO) blend (trial 1); or 70 % PP with either 100 % FO or 80 % of the FO replaced with olive, rapeseed or soyabean oil (trial 2). Replacing ≥ 70 % of FM with PP and ≥ 70 % of FO with either a VO blend or rapeseed oil increased plasma and liver TAG concentrations. These diets contained high levels of phytosterols and low levels of cholesterol. Fish fed low-cholesterol diets, but with less phytosterols, exhibited an increased expression of genes encoding proteins involved in cholesterol uptake and synthesis. The expression of these genes was, however, partially inhibited in rapeseed oil-fed fish possibly due to the high dietary and tissue phytosterol:cholesterol ratio. Atlantic salmon tissue and plasma cholesterol concentrations were maintained stable independent of the dietary sterol content.

Genetically obese mice do not show increased gut permeability or faecal bile acid hydrophobicity

Gut barrier dysfunction may lead to metabolic endotoxaemia and low-grade inflammation. Recent publications have demonstrated gut barrier dysfunction in obesity induced by a diet high in fat, and a pathogenetic role for luminal bile acids has been proposed. We aimed to investigate whether genetically obese mice develop increased gut permeability and alterations in luminal bile acids on a diet with a regular fat content. We used seven obese male ob/ob mice of C57BL/6J background and ten male wild-type (WT) mice of the same strain. Faeces were collected for bile acid analysis. Intestinal permeability was measured in an Ussing chamber upon euthanasia, using 4 kDa fluorescein isothiocyanate dextran, as per mille (‰, 1/1000) of translocated dextran. We analysed the liver expression of lipopolysaccharide-binding protein (LBP), as well as serum LBP (ELISA). Intestinal permeability was not affected by genetic obesity (jejunum: 0·234 (sem 0·04) ‰ for obese v. 0·225 (sem 0·03) ‰ for WT, P= 0·93; colon: 0·222 (sem 0·06) ‰ for obese v. 0·184 (sem 0·03) ‰ for WT, P= 0·86), nor was liver LBP expression (relative expression: 0·55 (sem 0·08) for obese v. 0·55 (sem 0·13) for WT, P= 0·70). Serum LBP was 2·5-fold higher in obese than in WT mice (P= 0·001). Obese mice had increased daily excretion of total bile acids, but their faecal bile acid hydrophobicity was unchanged. In conclusion, genetic obesity did not impair gut barrier function in mice on a regular chow diet, nor was faecal bile acid hydrophobicity affected.

Altered glucose-stimulated insulin secretion in a mouse line with activated polyamine catabolism

Ubiquitous activation of polyamine catabolism has been demonstrated to have protective effects in mice on fat accumulation and insulin sensitivity/glucose tolerance in, both, normal conditions and after a high fat diet. We have analyzed the endocrine pancreas functionality in four months-old male mice overexpressing the rate limiting enzyme in the polyamine catabolism, spermidine/spermine N¹-acetyltransferase (SSAT). The pancreatic SSAT activity was 37-fold elevated in the transgenic mice, which reduced the total pancreatic and islet pools of spermidine (71%) and spermine (69%), and increased putrescine and N¹-acetyl spermidine. Reduction in the islet ATP levels (65%) was accompanied with increased transcription of 5'-AMP-activated protein kinase (AMPK) (1.5-fold) and Foxa2 (2.7-fold), and reduced HNF4α (67%) and HNF1α (92%), insulin 1 (47%), insulin 2 (50%), and Glut2 (57%). Moreover, the SSAT transgenic mice also presented increased beta cell area, decreased insulin production, and altered glucose-stimulated insulin secretion. It has been hypothesized that the acute activation of the polyamine catabolism produces a futile cycle that greatly decreases the energy reserves of the cell. The lower energy status would activate the energy expenditure regulator, AMPK, which would consequently repress the PI3K/Akt pathway, and activate the transcription factor Foxa2.

The activation of hepatic and muscle polyamine catabolism improves glucose homeostasis

The mitochondrial biogenesis and energy expenditure regulator, PGC-1α, has been previously reported to be induced in the white adipose tissue (WAT) and liver of mice overexpressing spermidine/spermine N (1)-acetyltransferase (SSAT). The activation of PGC-1α in these mouse lines leads to increased number of mitochondria, improved glucose homeostasis, reduced WAT mass and elevated basal metabolic rate. The constant activation of polyamine catabolism produces a futile cycle that greatly reduces the ATP pools and induces 5'-AMP-activated protein kinase (AMPK), which in turn activates PGC-1α in WAT. In this study, we have investigated the effects of activated polyamine catabolism on the glucose and energy metabolisms when targeted to specific tissues. For that we used a mouse line overexpressing SSAT under the endogenous SSAT promoter, an inducible SSAT overexpressing mouse model using the metallothionein I promoter (MT-SSAT), and a mouse model with WAT-specific SSAT overexpression (aP2-SSAT). The results demonstrated that WAT-specific SSAT overexpression was sufficient to increase the number of mitochondria, reduce WAT mass and protect the mice from high-fat diet-induced obesity. However, the improvement in the glucose homeostasis is achieved only when polyamine catabolism is enhanced at the same time in the liver and skeletal muscle. Our results suggest that the tissue-specific targeting of activated polyamine catabolism may reveal new possibilities for the development of drugs boosting mitochondrial metabolism and eventually for treatment of obesity and type 2 diabetes.

Lipopolysaccharide-induced anti-inflammatory acute phase response is enhanced in spermidine/spermine N1-acetyltransferase (SSAT) overexpressing mice

Bacterial lipopolysaccharide (LPS) is an effective activator of the components of innate immunity. It has been shown that polyamines and their metabolic enzymes affect the LPS-induced immune response by modulating both pro- and anti-inflammatory actions. On the other hand, LPS causes changes in cellular polyamine metabolism. In this study, the LPS-induced inflammatory response in spermidine/spermine N(1)-acetyltransferase overexpressing transgenic mice (SSAT mice) was analyzed. In liver and kidneys, LPS enhanced the activity of the polyamine biosynthetic enzyme ornithine decarboxylase and increased the intracellular putrescine content in both SSAT overexpressing and wild-type mice. In survival studies, the enhanced polyamine catabolism and concomitantly altered cellular polyamine pools in SSAT mice did not affect the LPS-induced mortality of these animals. However, in the acute phase of LPS-induced inflammatory response, the serum levels of proinflammatory cytokines interleukin-1β and interferon-γ were significantly reduced and, on the contrary, anti-inflammatory cytokine interleukin-10 was significantly increased in the sera of SSAT mice compared with the wild-type animals. In addition, hepatic acute-phase proteins C-reactive protein, haptoglobin and α(1)-acid glycoprotein were expressed in higher amounts in SSAT mice than in the wild-type animals. In summary, the study suggests that SSAT overexpression obtained in SSAT mice enhances the anti-inflammatory actions in the acute phase of LPS-induced immune response.

Transgenic rodents with altered SSAT expression as models of pancreatitis and altered glucose and lipid metabolism

Depletion of pancreatic acinar cell polyamines in response to activation of polyamine catabolism is associated with the development of acute pancreatitis in experimental rodent models. The disease is characterized by general hallmarks seen also in human pancreatitis, such as accumulation of intraperitoneal ascites, acinar cell necrosis, and pancreatic as well as remote organ edema and inflammation. Thus, these animals make useful models for the human disease. Determination of these hallmarks can be used to assess the severity of the disease and to evaluate the efficacy of any therapy applied. The metabolic changes seen in genetically modified mice with either accelerated or inactivated polyamine catabolism have revealed that polyamine catabolism is involved in the regulation of glucose and lipid metabolism. The simplest method to determine the metabolic phenotype of the animal is to assess the concentrations of blood metabolites. Fasting blood glucose level is an indicator of overall glucose homeostasis, whereas fasting insulin level is a useful marker of insulin sensitivity. A more detailed analysis of glucose homeostasis and insulin sensitivity can be obtained by intraperitoneal glucose and insulin tolerance tests. Blood lipid levels mainly reflect triglyceride, free fatty acid, and cholesterol metabolism. Altered blood glucose and/or lipid levels are associated with several diseases, e.g., diabetes, Cushing's syndrome, hyperthyroidism, atherosclerosis, pancreatitis, and dysfunction of the liver and kidneys.