Update on Glycosphingolipids Abundance in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most frequent type of primary liver cancer. Low numbers of HCC patients being suitable for liver resection or transplantation and multidrug resistance development during pharmacotherapy leads to high death rates for HCC patients. Understanding the molecular mechanisms of HCC etiology may contribute to the development of novel therapeutic strategies for prevention and treatment of HCC. UDP-glucose ceramide glycosyltransferase (UGCG), a key enzyme in glycosphingolipid metabolism, generates glucosylceramide (GlcCer), which is the precursor for all glycosphingolipids (GSLs). Since UGCG gene expression is altered in 0.8% of HCC tumors, GSLs may play a role in cellular processes in liver cancer cells. Here, we discuss the current literature about GSLs and their abundance in normal liver cells, Gaucher disease and HCC. Furthermore, we review the involvement of UGCG/GlcCer in multidrug resistance development, globosides as a potential prognostic marker for HCC, gangliosides as a potential liver cancer stem cell marker, and the role of sulfatides in tumor metastasis. Only a limited number of molecular mechanisms executed by GSLs in HCC are known, which we summarize here briefly. Overall, the role GSLs play in HCC progression and their ability to serve as biomarkers or prognostic indicators for HCC, requires further investigation

Differences in the Active Endometrial Microbiota across Body Weight and Cancer in Humans and Mice

Obesity is a risk factor for endometrial cancer. The aim of this study was to determine whether actively replicating microbiota in the endometrium differ between obese vs. lean and cancer vs. benign states. We performed 16S rRNA amplicon sequencing on endometrial tissues from lean and obese women with and without endometrial cancer, and lean and obese mice. Results displayed human endometrial microbiota clustered into three community types (R = 0.363, p = 0.001). Lactobacillus was dominant in community type 1 (C1) while community type 2 (C2) had high levels of Proteobacteria and more cancer samples when compared to C1 (p = 0.007) and C3 (p = 0.0002). A significant increase in the prevalence of the C2 community type was observed across body mass index and cancer (χ2 = 14.24, p = 0.0002). The relative abundance of Lactobacillus was lower in cancer samples (p = 0.0043), and an OTU with 100% similarity to Lactobacillus iners was enriched in control samples (p = 0.0029). Mouse endometrial microbiota also clustered into three community types (R = 0.419, p = 0.001) which were not influenced by obesity. In conclusion, obesity and cancer are associated with community type prevalence in the human endometrium, and Lactobacillus abundance is associated with normal uterine histologies in humans and mice

Knockout of glucose transporter GLUT6 has minimal effects on whole body metabolic physiology in mice

Glucose transporter 6 (GLUT6) is a member of the facilitative glucose transporter family. GLUT6 is upregulated in several cancers but is not widely expressed in normal tissues. Previous studies have shown that GLUT6 knockdown kills endometrial cancer cells that express elevated levels of the protein. However, whether GLUT6 represents a viable anticancer drug target is unclear because the role of GLUT6 in normal metabolic physiology is unknown. Herein we generated GLUT6 knockout mice to determine how loss of GLUT6 affected whole body glucose homeostasis and metabolic physiology. We found that the mouse GLUT6 (Slc2a6) gene expression pattern was similar to humans with mRNA found primarily in brain and spleen. CRISPR-Cas9-mediated deletion of Slc2a6 did not alter mouse development, growth, or whole body glucose metabolism in male or female mice fed either a chow diet or Western diet. GLUT6 deletion did not impact glucose tolerance or blood glucose and insulin levels in male or female mice fed either diet. However, compared with wild-type littermate controls, GLUT6 null female mice had a relatively minor decrease in fat accumulation when fed Western diet and had a lower respiratory exchange ratio when fed chow diet. Collectively, these data show that GLUT6 is not a major regulator of whole body metabolic physiology; therefore, GLUT6 inhibition may have minimal adverse effects if targeted for cancer therapy

Analysis of the circular RNA transcriptome in endometrial cancer

Circular RNAs (circRNAs) are a naturally occurring family of non-coding RNA that may regulate gene expression in mammals. circRNAs are more stable than messenger RNAs due to their resistance to RNA exonuclease. A growing body of evidence has shown that the expression of circRNAs is regulated during development in a tissuespecific manner. CircRNAs have been implicated in a number of cancers; however, their role in endometrial cancer (EC) is completely unknown. Here, we report the circular transcriptome specific for EC as determined by RNA sequencing. We found that the overall abundance of circRNAs is lower in EC than in normal endometrium. Further, there are numerous 'hotspot' genes from which circRNAs are transcribed that may account for alterations in circRNA expression between the normal and malignant endometrium. Most importantly, we have also identified circRNAs that are differentially expressed between malignant and normal endometrial tissue. The functional significance of these circRNAs in cancer remains to be determined, but they may serve as potential biomarkers for the diagnosis of EC or monitoring of EC progression

UGCG influences glutamine metabolism of breast cancer cells

UDP-glucose ceramide glucosyltransferase (UGCG) is the key enzyme in glycosphingolipid (GSL) metabolism by being the only enzyme that generates glucosylceramide (GlcCer) de novo. Increased UGCG synthesis is associated with pro-cancerous processes such as increased proliferation and multidrug resistance in several cancer types. We investigated the influence of UGCG overexpression on glutamine metabolism in breast cancer cells. We observed adapted glucose and glutamine uptake in a limited energy supply environment following UGCG overexpression. Glutamine is used for reinforced oxidative stress response shown by increased mRNA expression of glutamine metabolizing proteins such as glutathione-disulfide reductase (GSR) resulting in increased reduced glutathione (GSH) level. Augmented glutamine uptake is also used for fueling the tricarboxylic acid (TCA) cycle to maintain the proliferative advantage of UGCG overexpressing cells. Our data reveal a link between GSL and glutamine metabolism in breast cancer cells, which is to our knowledge a novel correlation in the field of sphingolipid research

UGCG overexpression leads to increased glycolysis and increased oxidative phosphorylation of breast cancer cells

The only enzyme in the glycosphingolipid (GSL) metabolic pathway, which produces glucosylceramide (GlcCer) de novo is UDP-glucose ceramide glucosyltransferase (UGCG). UGCG is linked to pro-cancerous processes such as multidrug resistance development and increased proliferation in several cancer types. Previously, we showed an UGCG-dependent glutamine metabolism adaption to nutrient-poor environment of breast cancer cells. This adaption includes reinforced oxidative stress response and fueling the tricarboxylic acid (TCA) cycle by increased glutamine oxidation. In the current study, we investigated glycolytic and oxidative metabolic phenotypes following UGCG overexpression (OE). UGCG overexpressing MCF-7 cells underwent a metabolic shift from quiescent/aerobic to energetic metabolism by increasing both glycolysis and oxidative glucose metabolism. The energetic metabolic phenotype was not associated with increased mitochondrial mass, however, markers of mitochondrial turnover were increased. UGCG OE altered sphingolipid composition of the endoplasmic reticulum (ER)/mitochondria fractions that may contribute to increased mitochondrial turnover and increased cell metabolism. Our data indicate that GSL are closely connected to cell energy metabolism and this finding might contribute to development of novel therapeutic strategies for cancer treatment

Eosinophil function in adipose tissue is regulated by Kruppel-like factor 3 (KLF3)

The conversion of white adipocytes to thermogenic beige adipocytes represents a potential mechanism to treat obesity and related metabolic disorders. However, the mechanisms involved in converting white to beige adipose tissue remain incompletely understood. Here we show profound beiging in a genetic mouse model lacking the transcriptional repressor Krüppel-like factor 3 (KLF3). Bone marrow transplants from these animals confer the beige phenotype on wild type recipients. Analysis of the cellular and molecular changes reveal an accumulation of eosinophils in adipose tissue. We examine the transcriptomic profile of adipose-resident eosinophils and posit that KLF3 regulates adipose tissue function via transcriptional control of secreted molecules linked to beiging. Furthermore, we provide evidence that eosinophils may directly act on adipocytes to drive beiging and highlight the critical role of these little-understood immune cells in thermogenesis

Inhibition of hepatic lipogenesis enhances liver tumorigenesis by increasing antioxidant defence and promoting cell survival

The metabolic pathway of de novo lipogenesis is frequently upregulated in human liver tumours, and its upregulation is associated with poor prognosis. Blocking lipogenesis in cultured liver cancer cells is sufficient to decrease cell viability; however, it is not known whether blocking lipogenesis in vivo can prevent liver tumorigenesis. Herein, we inhibit hepatic lipogenesis in mice by liver-specific knockout of acetyl-CoA carboxylase (ACC) genes and treat the mice with the hepatocellular carcinogen diethylnitrosamine (DEN). Unexpectedly, mice lacking hepatic lipogenesis have a twofold increase in tumour incidence and multiplicity compared to controls. Metabolomics analysis of ACC-deficient liver identifies a marked increase in antioxidants including NADPH and reduced glutathione. Importantly, supplementing primary wild-type hepatocytes with glutathione precursors improves cell survival following DEN treatment to a level indistinguishable from ACC-deficient primary hepatocytes. This study shows that lipogenesis is dispensable for liver tumorigenesis in mice treated with DEN, and identifies an important role for ACC enzymes in redox regulation and cell survival

Mitochondrial uncoupler SHC517 reverses obesity in mice without affecting food intake.

AimsMitochondrial uncouplers decrease caloric efficiency and have potential therapeutic benefits for the treatment of obesity and related metabolic disorders. Herein we investigate the metabolic and physiologic effects of a recently identified small molecule mitochondrial uncoupler named SHC517 in a mouse model of diet-induced obesity.MethodsSHC517 was administered as an admixture in food. The effect of SHC517 on in vivo energy expenditure and respiratory quotient was determined by indirect calorimetry. A dose-finding obesity prevention study was performed by starting SHC517 treatment concomitant with high fat diet for a period of 12 days. An obesity reversal study was performed by feeding mice western diet for 4 weeks prior to SHC517 treatment for 7 weeks. Biochemical assays were used to determine changes in glucose, insulin, triglycerides, and cholesterol. SHC517 concentrations were determined by mass spectrometry.ResultsSHC517 increased lipid oxidation without affecting body temperature. SHC517 prevented diet-induced obesity when administered at 0.05% and 0.1% w/w in high fat diet and reversed established obesity when tested at the 0.05% dose. In the obesity reversal model, SHC517 restored adiposity to levels similar to chow-fed control mice without affecting food intake or lean body mass. SHC517 improved glucose tolerance and fasting glucose levels when administered in both the obesity prevention and obesity reversal modes.ConclusionsSHC517 is a mitochondrial uncoupler with potent anti-obesity and insulin sensitizing effects in mice. SHC517 reversed obesity without altering food intake or compromising lean mass, effects that are highly sought-after in anti-obesity therapeutics

Mitochondrial uncoupler BAM15 reverses diet-induced obesity and insulin resistance in mice

Obesity is a health problem affecting more than 40% of US adults and 13% of the global population. Anti-obesity treatments including diet, exercise, surgery and pharmacotherapies have so far failed to reverse obesity incidence. Herein, we target obesity with a pharmacotherapeutic approach that decreases caloric efficiency by mitochondrial uncoupling. We show that a recently identified mitochondrial uncoupler BAM15 is orally bioavailable, increases nutrient oxidation, and decreases body fat mass without altering food intake, lean body mass, body temperature, or biochemical and haematological markers of toxicity. BAM15 decreases hepatic fat, decreases inflammatory lipids, and has strong antioxidant effects. Hyperinsulinemic-euglycemic clamp studies show that BAM15 improves insulin sensitivity in multiple tissue types. Collectively, these data demonstrate that pharmacologic mitochondrial uncoupling with BAM15 has powerful anti-obesity and insulin sensitizing effects without compromising lean mass or affecting food intake