Effect of cholesterol on lipogenesis and VLDL–TG assembly and secretion in goose primary hepatocytes

Role of intestinal testosterone-degrading bacteria and 3/17β-HSD in the pathogenesis of testosterone deficiency-induced hyperlipidemia in males

Testosterone deficiency can cause abnormal lipid metabolism in men, leading to hyperlipidemia. We identified the testosterone-degrading bacterium Pseudomonas nitroreducens in the fecal samples of male patients with hyperlipidemia. Gastric administration of P. nitroreducens in mice led to testosterone deficiency and elevated blood lipid levels. Whole-genome sequencing of P. nitroreducens revealed the presence of 3/17β-hydroxysteroid dehydrogenase (3/17β-HSD), a gene responsible for testosterone degradation, which is also associated with hyperlipidemia. Microbiota analysis of fecal samples collected from 158 patients with hyperlipidemia and 151 controls revealed that the relative abundance of P. nitroreducens and 3/17β-HSD in the fecal samples of patients with hyperlipidemia was significantly higher than that in controls. These results suggest that P. nitroreducens and 3/17β-HSD may be related to the onset of testosterone deficiency-induced hyperlipidemia. Therefore, treatments targeted at eradicating testosterone-degrading bacteria are a potential future option for patients with testosterone-induced hyperlipidemia and should thus be studied further.

Perturbation of lipid metabolism in 3T3-L1 at different stages of preadipocyte differentiation and new insights into the association between changed metabolites and adipogenesis promoted by TBBPA or TBBPS

Tetrabromobisphenol A (TBBPA) and tetrabromobisphenol S (TBBPS) are widely distributed brominated flame retardants. While TBBPA has been demonstrated to stimulate adipogenesis, TBBPS is also under suspicion for potentially inducing comparable effects. In this study, we conducted a non-targeted metabolomics to examine the metabolic changes in 3T3-L1 cells exposed to an environmentally relevant dose of TBBPA or TBBPS. Our findings revealed that 0.1 µM of both TBBPA and TBBPS promoted the adipogenesis of 3T3-L1 preadipocytes. Multivariate analysis showed significant increases in glycerophospholipids, sphingolipids, and steroids relative levels in 3T3-L1 cells exposed to TBBPA or TBBPS at the final stage of preadipocyte differentiation. Metabolites set composed of glycerophospholipids was found to be highly effective predictors of adipogenesis in 3T3-L1 cells exposed to TBBPA or TBBPS (revealed from the receiver operating characteristic curve with an area under curve > 0.90). The results from metabolite set enrichment analysis suggested both TBBPA and TBBPS exposures significantly perturbed steroid biosynthesis in adipocytes. Moreover, TBBPS additionally disrupted the sphingolipid metabolism in the adipocytes. Our study presents new insights into the obesogenic effects of TBBPS and provides valuable information about the metabolites associated with adipogenesis induced by TBBPA or TBBPS.

Analysis of the Inhibitory Effect of hsa-miR-145-5p and hsa-miR-203a-5p on Imatinib-Resistant K562 Cells by GC/MS Metabolomics Method

Imatinib (IM) resistance is considered to be a significant challenge in the management of chronic myeloid leukemia (CML). Previous studies have reported that hsa-miR-145-5p and hsa-miR-203a-5p can overcome IM resistance and hsa-miR-203a-5p can alter glutathione metabolism in IM-resistant cells. The purpose of this study was to examine whether hsa-miR-145-5p or hsa-miR-203a-5p counters IM resistance by targeting the overall metabolic profile of IM-resistant K562 cells. The metablic profiling of cell lysates obtained from IM-sensitive, IM-resistant, and miR-transfected IM-resistant K562 cells was carried out using the GC-MS technique. Overall, 75 major metabolites were detected, of which 32 were present in all samples. The pathway analysis of MetaboAnalyst 5.0 revealed that the majorly enriched pathways included glucose metabolism, fatty acid biosynthesis, lipogenesis, and nucleotide metabolism. Eleven of identified metabolites, l-glutamine, l-glutamic acid, l-lactic acid, phosphoric acid, 9,12-octadecadienoic acid, 9-octadecenoic acid, myristic acid, palmitic acid, cholesterol, and β-alanine, appeared in enriched pathways. IM-resistant cells had comparatively higher concentrations of all of these metabolites. Notably, the introduction of hsa-miR-145-5p or hsa-miR-203a-5p into resistant cells resulted in a decrease in levels of these metabolites. The efficacy of miR-203a-5p was particularly remarkable in comparison with miR-145-5p, as evidenced by partial least-squares-discriminant analysis (PLS-DA), which showed a high level of similarity in metabolic profile between IM-sensitive K562 cells and IM-resistant cells transfected with hsa-miR-203a-5p. The results indicate that GC-MS-based metabolic profiling has the potential to distinguish between drug-resistant and -sensitive cells. This approach can also be used to routinely monitor therapeutic response in drug-resistant patients, thus, enabling personalized therapy.

High cholesterol intake remodels cholesterol turnover and energy homeostasis in Nile tilapia (Oreochromis niloticus)

The roles of dietary cholesterol in fish physiology are currently contradictory. The issue reflects the limited studies on the metabolic consequences of cholesterol intake in fish. The present study investigated the metabolic responses to high cholesterol intake in Nile tilapia (Oreochromis niloticus), which were fed with four cholesterol-contained diets (0.8, 1.6, 2.4 and 3.2%) and a control diet for eight weeks. All fish-fed cholesterol diets showed increased body weight, but accumulated cholesterol (the peak level was in the 1.6% cholesterol group). Then, we selected 1.6% cholesterol and control diets for further analysis. The high cholesterol diet impaired liver function and reduced mitochondria number in fish. Furthermore, high cholesterol intake triggered protective adaptation via (1) inhibiting endogenous cholesterol synthesis, (2) elevating the expression of genes related to cholesterol esterification and efflux, and (3) promoting chenodeoxycholic acid synthesis and efflux. Accordingly, high cholesterol intake reshaped the fish gut microbiome by increasing the abundance of Lactobacillus spp. and Mycobacterium spp., both of which are involved in cholesterol and/or bile acids catabolism. Moreover, high cholesterol intake inhibited lipid catabolic activities through mitochondrial β-oxidation, and lysosome-mediated lipophagy, and depressed insulin signaling sensitivity. Protein catabolism was elevated as a compulsory response to maintain energy homeostasis. Therefore, although high cholesterol intake promoted growth, it led to metabolic disorders in fish. For the first time, this study provides evidence for the systemic metabolic response to high cholesterol intake in fish. This knowledge contributes to an understanding of the metabolic syndromes caused by high cholesterol intake or deposition in fish.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-022-00158-7.

Lipid droplet dynamics in healthy and pyometra-affected canine endometrium

BACKGROUND

Accumulation of lipid droplets (LDs) was recently observed in pyometra-affected uteri. As data about their nature and function are missing we intended to compare the localization, quality and quantity of LDs in canine healthy and pyometra-affected tissues and in an in vitro model.

METHODS AND RESULTS

We characterized LDs in healthy and pyometra uterine tissue samples as well as in canine endometrial epithelial cells (CEECs) in vitro by means of histochemistry, immunohistochemistry, transmission electron microscopy, western blot, and RT-qPCR. Oil Red O (ORO) staining and quantification as well as p-phenylenediamine staining showed a higher number of LDs in epithelial cells of pyometra samples. Immunohistochemistry revealed that the amount of LDs coated by perilipin2 (PLIN2) protein was also higher in pyometra samples. Transmission electron microscopy showed an increase of LD size in surface and glandular epithelial cells of pyometra samples. In cell culture experiments with CEECs, supplementation with oleic acid alone or in combination with cholesterol lead to an increased LD accumulation. The expression of PLIN2 at protein and mRNA level was also higher upon oleic acid supplementation. Most LDs were double positive for ORO and PLIN2. However, ORO positive LDs lacking PLIN2 coating or LDs positive for PLIN2 but containing a lipid class not detectable by ORO staining were identified.

CONCLUSIONS

We found differences in the healthy and pyometra-affected endometrium with respect to LDs size. Moreover, several kinds of LDs seem to be present in the canine endometrium. In vitro studies with CEECs could show their responsiveness to external lipids. Since epithelial cells reacted only to oleic acid stimulation, we assume that the cyclic lipid accumulation in the canine endometrium is based mainly on triglycerides and might serve as energy provision for the developing early embryo. Further studies are necessary to verify the complex role of lipids in the healthy and pyometra-affected canine endometrium.

Effects of glucocorticoids on lipid metabolism and AMPK in broiler chickens' liver

Adenosine monophosphate-activated protein kinase (AMPK) plays a pivotal role in the regulation of carbohydrate, lipid, and protein metabolism in animals. In this study, we examined whether any cross talk exists between glucocorticoids and AMPK in the regulation of the liver bile acid biosynthesis pathway. Dexamethasone treatment decreased the growth performance of broiler chickens. The liver mRNA levels of fatty acid transport protein (FATP-1), farnesoid X receptor (FXR), AMPK alpha 1 subunit (AMPKα1), and glucocorticoid receptor were significantly upregulated in DEX-treated broilers; the gene expression of liver cholesterol 7 alpha-hydroxylase (CYP7A1) was significantly downregulated. The protein level of liver CYP7A1 was significantly decreased by DEX treatment at both 24 and 72 h, while the protein level of p-AMPK/ t-AMPK stayed unchanged. In the in vitro cultured hepatocytes, compound C pretreatment blocked the increase in CYP7A1 protein level by DEX and significantly suppressed FATP-1, SREBP-1c, FXR, and CYP7A1 gene expression stimulated by DEX. Compound C treatment significantly reduces the protein level of p-AMPK, and the combination of compound C and DEX significantly reduces the protein level of t-AMPK. Thus, glucocorticoids affected liver AMPK and the bile acid synthesis signal pathway, and AMPK might be involved in the glucocorticoid effect of liver bile acid synthesis.

Effects of β-hydroxybutyricacid on the synthesis and assembly of very low-density lipoprotein in bovine hepatocytes in vitro

β-Hydroxybutyricacid (BHBA) is an important metabolite that involved in the development of ketosis and fatty liver in dairy cows. Dairy cows with fatty liver displayed high blood concentration of BHBA and very low-density lipoprotein (VLDL) assembly. The effects of BHBA on VLDL synthesis and assembly in hepatocytes of cows were unclear. In this study, bovine hepatocytes were cultured and treated with different concentrations of BHBA. We found that BHBA treatment upregulated the mRNA and protein levels of apolipoprotein B100 (ApoB 100), apolipoprotein E (ApoE) and microsomal triglyceride transfer protein (MTTP) and showed in a firstly increased and then decreased trend. Meanwhile, the mRNA and protein levels of LDLR showed in a reverse trend. Consequently, VLDL content was significantly increased in medium-dose BHBA treatment group, while decreased in high-dose group. These results indicate that the effects of BHBA on the VLDL synthesis showed in a dose-dependent manner that low levels of BHBA increase VLDL synthesis and high levels of BHBA decrease VLDL synthesis.

Effect of testosterone deficiency on cholesterol metabolism in pigs fed a high-fat and high-cholesterol diet

Background

Testosterone deficiency is associated with increased serum cholesterol levels. However, how testosterone deficiency precisely affects cholesterol metabolism remains unclear. Therefore, in the current study, we examined the effect of testosterone deficiency on cholesterol metabolism and liver gene expression in pigs fed a high-fat and high-cholesterol (HFC) diet.

Methods

Sexually mature male miniature pigs (6–7 months old) were randomly divided into 3 groups as follows: intact male pigs fed an HFC diet (IM + HFC), castrated male pigs fed an HFC diet (CM + HFC), and castrated pigs with testosterone replacement fed an HFC diet (CM + HFC + T). Serum testosterone levels and lipid profiles were measured, and gene expression levels associated with hepatic cholesterol metabolism were determined. Furthermore, total hepatic cholesterol contents and the activities of enzymes mediating hepatic cholesterol metabolism were measured.

Results

Serum testosterone levels were significantly decreased in CM + HFC pigs, and testosterone replacement attenuated castration-induced testosterone deficiency. Castration significantly increased the serum levels of total cholesterol, low-density lipoprotein cholesterol and triglycerides, as well as hepatic lipid contents in pigs fed an HFC diet. Compared with IM + HFC and CM + HFC + T pigs, low-density lipoprotein receptor (LDLR) mRNA expression and protein levels were significantly decreased in the livers of CM + HFC pigs. In contrast, we found that compared with IM + HFC pigs, hepatic proprotein convertase subtilisin/kexin type 9 (PCSK9) mRNA and serum PCSK9 protein levels were significantly increased in CM + HFC pigs. Moreover, testosterone treatment reversed the increase in PCSK9 expression in CM + HFC pigs. However, neither castration nor testosterone replacement affected the expression of the other hepatic genes that were tested.

Conclusions

This study demonstrated that castration-induced testosterone deficiency caused severe hypercholesterolemia in pigs fed an HFC diet; furthermore, these effects could be reversed by testosterone replacement therapy. Altered hepatic PCSK9 and LDLR expression, resulting in reduced LDL-cholesterol clearance, may contribute to the increased serum cholesterol levels induced by testosterone deficiency and an HFC diet. These results deepen our understanding of the underlying molecular mechanisms that mediate the effects of testosterone deficiency on cholesterol metabolism.