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Leucine modulates synthetic and degradative pathways in muscle, possibly providing metabolic benefits for both athletes and diseased populations. Leucine has become popular among athletes for improving performance and body composition, however little is known about the metabolic effects of the commonly consumed leucine-derived metabolite β-hydroxy-β-methyl butyrate (HMB). Our work measured the effects of HMB on metabolic protein expression, mitochondrial content and metabolism, as well as lipid content in skeletal muscle cells. Specifically, cultured C2C12 myotubes were treated with either a control or HMB ranging from 6.25 to 25 μM for 24 h and mRNA and/or protein expression, oxygen consumption, glucose uptake, and lipid content were measured. Contrary to leucine’s stimulatory effect on metabolism, HMB-treated cells exhibited significantly reduced regulators of lipid oxidation including peroxisome proliferator-activated receptor alpha (PPARα) and PPARβ/δ, as well as downstream target carnitine palmitoyl transferase, without alterations in glucose or palmitate oxidation. Furthermore, HMB significantly inhibited activation of the master regulator of energetics, AMP-activated protein kinase. As a result, HMB-treated cells also displayed reduced total mitochondrial content compared with true control or cells equivocally treated with leucine. Additionally, HMB treatment amplified markers of lipid biosynthesis (PPARγ and fatty acid synthase) as well as consistently promoted elevated total lipid content versus control cells. Collectively, our results demonstrate that HMB did not improve mitochondrial metabolism or content, and may promote elevated cellular lipid content possibly through heightened PPARγ expression. These observations suggest that HMB may be most beneficial for populations interested in stimulating anabolic cellular processes.

Hepatocellular carcinoma (HCC), the main pathological type of liver cancer, is linked to risk factors such as viral hepatitis, alcohol intake and non‐alcoholic fatty liver disease (NAFLD). Recent advances have greatly improved our understanding that NAFLD is playing a major risk factor for HCC. Peroxisome proliferator‐activated receptors (PPARs) are a class of transcription factors divided into three subtypes: PPARα (PPARA), PPARδ/β (PPARD) and PPARγ (PPARG). As important nuclear receptors, PPARs are involved in many physiological processes, and PPARs can improve NAFLD by regulating lipid metabolism, accelerating fatty acid oxidation and inhibiting inflammation. In recent years, some studies have shown that PPARs can participate in the occurrence and development of HCC by regulating metabolic pathways. In addition, PPAR modulators have been reported to inhibit the proliferation and metastasis of HCC cells and can enhance the curative effect of conventional treatments. This article reviews the role of PPARs in the occurrence and development of HCC, as well as its value in the diagnosis, treatment and prognosis of HCC, in order to provide directions for future research.

Inflammatory bowel disease (IBD) is one of the intractable diseases. Nutritional components associated with IBD have been identified, and it is known that excessive methionine intake exacerbates inflammation, and that tryptophan metabolism is involved in inflammation. Analysis of the gut microbiota has also progressed, where Lactobacillus regulate immune cells in the intestine and suppress inflammation. However, whether the methionine and tryptophan metabolic pathways affect the growth of intestinal Lactobacillus is unknown. Here we show how transient methionine, tryptophan, and niacin deficiency affects the host and gut microbiota in mouse models of colitis (induced by dextran sodium sulfate) fed a methionine‐deficient diet (1K), tryptophan and niacin‐deficient diet (2K), or methionine, tryptophan, and niacin‐deficient diet (3K). These diets induced body weight decrease and 16S rRNA analysis of mouse feces revealed the alterations in the gut microbiota, leading to a dramatic increase in the proportion of Lactobacillus in mice. Intestinal RNA sequencing data confirmed that the expression of several serine proteases and fat‐metabolizing enzymes were elevated in mice fed with methionine, tryptophan, and niacin (MTN) deficient diet. In addition, one‐carbon metabolism and peroxisome proliferator‐activated receptor (PPAR) pathway activation were also induced with MTN deficiency. Furthermore, changes in the expression of various immune‐related cytokines were observed. These results indicate that methionine, tryptophan, and niacin metabolisms are important for the composition of intestinal bacteria and host immunity. Taken together, MTN deficiencies may serve as a Great Reset of gut microbiota and host gene expression to return to good health. Methionine, tryptophan, and niacin (MTN) deficiency decreases Bacteroidales and recovery from MTN deficiency increases Lactobacillales. Gut microbiota was analyzed by 16S rRNA analysis.

Environmental RNA (eRNA) is gaining ground as an environmental monitoring tool. Whereas eDNA is mainly utilized for species detection, eRNA may provide additional classes of inference. The comparatively more rapid signal decay rates of eRNA provide narrower temporal windows for species presence, while detection of environmental messenger RNAs (e‐mRNAs) could provide evidence of genomic responses to environmental stressors. We explored e‐mRNA as an environmental tracer for stress imposed on animal populations by investigating the decay dynamics of e‐mRNA gene detections from target organism presence to recent presence. We tested seven select e‐mRNAs of known molecular targets of perfluorooctanesulfonic acid (PFOS) toxicity in tanks containing zebrafish (Danio rerio) exposed to an environmentally relevant concentration of PFOS. eRNA samples were collected just prior to fish removal following a 21‐day exposure and continued over nine timepoints across 3 days. The quantity and quality of total eRNA declined over time for both treatments, but were still detectable at 72 h post fish removal. The PFOS exposure failed to elicit observable shifts in e‐mRNA target concentrations compared to control tanks, perhaps because the selected gene targets are primarily responsive to PFOS in liver and kidney, which may not contribute strong eRNA signatures. Detection rates for all e‐mRNAs dropped significantly beyond 3 h post fish removal, with most being undetectable by 72 h. The signal lifespan of e‐mRNAs in this study implies that the detection of such traces will be a strong indicator of target organism presence (or recent presence), and that given the right combination of stressor concentrations, impacted tissues or organs, and gene targets, contaminant impacts on organism health should be detectable in environmental samples. Future studies targeting toxicologically effective stressor doses for well‐established gene targets will be an important advancement in establishing the utility of e‐mRNA as a noninvasive environmental stressor monitoring tool. We evaluated e‐mRNAs of known molecular targets of perfluorooctanesulfonic acid (PFOS) toxicity in zebrafish in a controlled laboratory experiment. The detection patterns of e‐mRNAs in our study imply that diminishing detection of these traces over time is a strong indicator of target organism presence (or very recent presence), providing a narrower timeframe of detection than eDNA provides. Our study also suggests that contaminant impacts on organism health should be detectable in water samples, given the right combination of stressor concentrations, impacted tissues or organs, and gene targets.

Background Peroxisome proliferator‐activated receptor agonists such as fibrates restore oxidative metabolism in cytotoxic T‐lymphocytes, thereby enhancing response to immune checkpoint inhibitors (ICI) in preclinical models. However, there is no evidence in humans on the clinical impact of fibrates as an adjunct to ICI. Methods In this cohort study of Veterans with non‐small cell lung cancer (NSCLC) receiving ICI, fibrate exposure was defined as a prescription filled within 90 days of an ICI infusion. Overall survival (OS), measured from the start of ICI, was compared between exposed and unexposed Veterans. Cox multivariable analysis (MVA) was used to identify factors associated with OS. A sensitivity analysis of Veterans with stage IV NSCLC who received docetaxel without ICI was similarly performed. Results The ICI cohort included 3593 Veterans, of whom 301 (8.5%) coincidentally received a fibrate. Veterans receiving fibrates were more likely to be older, white, male, and married, and to have greater comorbidity burden, but less likely to receive chemotherapy. Coincidental fibrates were associated with improved OS both on MVA (HR 0.86, 95%CI 0.75–0.99) and in a matched subset (HR 0.75, 95%CI 0.63–0.90). In contrast, among the cohort of 968 Veterans treated with chemotherapy, fibrates did not have a significant impact on OS by MVA (HR 0.99, 95%CI 0.79–1.25) or in a matched subset (HR 1.02, 95%CI CI 0.75–1.39). Conclusions Concomitant fibrates are associated with improved OS among NSCLC patients receiving ICI but not among those receiving chemotherapy. This hypothesis‐generating observation supports a potential role for fibrates as an adjunct to immunotherapy. Fibrates concomitant to immune checkpoint inhibitors are associated with improved survival in patients with non‐small cell lung cancer.

Background Aging is associated with fat atrophy and fibrosis with loss of adipocyte differentiation from preadipocytes. New approaches to this loss involve agents that can renew the proliferative and differentiative capacities of preadipocytes with the aim of creating new healthy adipose tissue that secrete adipokines that positively impact on skin health. Material & Methods We investigated the effect of Magnolol (ML), a naturally derived compound, on human primary pre‐adipocyte viability and proliferation as well as adipogenic gene expression and increase in lipid production. Cell proliferation was assessed using fluorescent signaling, and adipocyte differentiation was monitored by following morphological and microscopic changes. RNA purification and real‐time PCR were undertaken to examine gene expression changes, and Oil red O staining was used to confirm adipose cell transformation. Adipokine expression, in particular adiponectin quantification, was also undertaken. Results Magnolol, at a relatively low concentration, demonstrated clear adipogenic activity: with a significant increase in preadipocyte proliferation after 48 h and a significant accumulation of adipocytes as demonstrated by oil red staining. Increased gene expression of PLN1 and FABP4 and a significant increase in adiponectin protein expression was demonstrated. Conclusion Magnolol stimulates preadipocyte proliferation and conversion to adipokine‐producing adipocytes. This has the potential for a positive skin health and volumizing effect if used in a topical formulation.

Peroxisome proliferator‐activated receptor gamma (PPARγ), a member of the nuclear receptor superfamily, is activated by several compounds, including the thiazolidinediones. In addition to being a therapeutic target for obesity, hypolipidaemia and diabetes, perturbation of PPARγ signalling is now believed to be a strategy for treatment of several cancers, including breast. Although differential expression of PPARγ is observed in tumours compared to normal tissues and PPARγ agonists have been shown to inhibit tumour cell growth and survival, the interdependence of these observations is unclear. This study demonstrated that the potent, irreversible and selective PPARγ antagonist GW9662 prevented activation of PPARγ and inhibited growth of human mammary tumour cell lines. Controversially, GW9662 prevented rosiglitazone‐mediated PPARγ activation, but enhanced rather than reversed rosiglitazone‐induced growth inhibition. As such, these data support the existence of PPARγ‐independent pathways and question the central belief that PPARγ ligands mediate their anticancer effects via activation of PPARγ. British Journal of Pharmacology (2004) 143, 933–937. doi:10.1038/sj.bjp.0705973

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that function as ligand-activated transcription factors. They exist in three isoforms: PPARα, PPARβ/δ, and PPARγ. For all PPARs, lipids are endogenous ligands, linking them directly to metabolism. PPARs form heterodimers with retinoic X receptors, and upon ligand binding, they modulate the gene expression of downstream target genes, depending on the presence of co-repressors or co-activators. This results in a complex, cell type-specific regulation of proliferation, differentiation, and cell survival. PPARs are linked to metabolic disorders and are interesting pharmaceutical targets. PPARα and PPARγ agonists are already in clinical use for the treatment of hyperlipidemia and type 2 diabetes, respectively. More recently, PPARβ/δ activation came into focus as an interesting novel approach for the treatment of metabolic syndrome and associated cardiovascular diseases; however, this has been limited due to the highly controversial function of PPARβ/δ in cancer. This Special Issue of Cells brings together the most recent advances in understanding the various aspects of the action of PPARs, and it provides new insights into our understanding of PPARs, implying also the latest therapeutic perspectives for the utility of PPAR modulation in different disease settings.

Since the clear demonstration of lysophosphatidic acid (LPA)’s pathological roles in cancer in the mid-1990s, more than 1000 papers relating LPA to various types of cancer were published. Through these studies, LPA was established as a target for cancer. Although LPA-related inhibitors entered clinical trials for fibrosis, the concept of targeting LPA is yet to be moved to clinical cancer treatment. The major challenges that we are facing in moving LPA application from bench to bedside include the intrinsic and complicated metabolic, functional, and signaling properties of LPA, as well as technical issues, which are discussed in this review. Potential strategies and perspectives to improve the translational progress are suggested. Despite these challenges, we are optimistic that LPA blockage, particularly in combination with other agents, is on the horizon to be incorporated into clinical applications.

Polydatin (PD), a stilbenoid resveratrol-derivative in Vitaceae , Liliaceae , and Leguminosae , exhibits pharmacological protection in metabolic disorders. This study investigated Polydatin, as a potential pan-PPAR agonist for treating non-alcoholic fatty liver disease (NAFLD). High-throughput-virtual-screening (HTVS) was performed to identify potential pan-PPAR agonists, followed by in vitro testing of Polydatin in HepG2 steatosis model. Effects on lipid metabolism and oxidative stress, PPAR signaling gene expression analysis, and GC-MS profiling were compared with the hepatoprotectant Silymarin. Pan-PPAR targeted HTVS of PhytoHub natural products database, followed by molecular docking/dynamics simulations, revealed lead-candidate, Polydatin, which was tested in steatotic cells for gene and protein deregulations by qRT-PCR and western blot, followed by GC-MS analysis of biochemical metabolites. HTVS revealed 53 potential pan-PPAR agonists. Molecular docking and dynamics simulations suggested that PD, a stable ligand for PPARs (α,β/δ,γ), exhibited strong binding. Polydatin treatment decreased ALT, triglycerides, and oxidative stress, wherein ROS and malondialdehyde levels decreased by 60.94% and 28%, respectively. PD upregulated PPARs, AMPK, GLUT2, and CPT1α, while downregulating lipogenic enzymes (ACC1, FASN, SCD1). GC-MS analysis revealed Polydatin mediated impact on saturated FFAs-palmitic acid, stearic acid, and unsaturated fatty acid product of SCD1, oleic acid. HTVS identified PD as a promising pan-PPAR agonist, which favorably ameliorated changes in lipid, glucose, and overall energy metabolism in steatotic NAFLD, by modulating PPAR(α,β/δ,γ) expressions and associated downstream lipogenic and lipid-utilization mechanisms, supporting anti-steatotic efficacy of Polydatin.