New insights into the regulation of bile acids synthesis during the early stages of liver regeneration: A human and experimental study.

BACKGROUND AND AIMS: Liver regeneration is essential for the preservation of homeostasis and survival. Bile acids (BAs)-mediated signaling is necessary for liver regeneration, but BAs levels need to be carefully controlled to avoid hepatotoxicity. We studied the early response of the BAs-fibroblast growth factor 19 (FGF19) axis in healthy individuals undergoing hepatectomy for living donor liver transplant. We also evaluated BAs synthesis in mice upon partial hepatectomy (PH) and acute inflammation, focusing on the regulation of cytochrome-7A1 (CYP7A1), a key enzyme in BAs synthesis from cholesterol. METHODS: Serum was obtained from twelve human liver donors. Mice underwent 2/3-PH or sham-operation. Acute inflammation was induced with bacterial lipopolysaccharide (LPS) in mice fed control or antoxidant-supplemented diets. BAs and 7α-hydroxy-4-cholesten-3-one (C4) levels were measured by HPLC-MS/MS; serum FGF19 by ELISA. Gene expression and protein levels were analyzed by RT-qPCR and western-blot. RESULTS: Serum BAs levels increased after PH. In patients with more pronounced hypercholanemia, FGF19 concentrations transiently rose, while C4 levels (a readout of CYP7A1 activity) dropped 2 h post-resection in all cases. Serum BAs and C4 followed the same pattern in mice 1 h after PH, but C4 levels also dropped in sham-operated and LPS-treated animals, without marked changes in CYP7A1 protein levels. LPS-induced serum C4 decline was attenuated in mice fed an antioxidant-supplemented diet. CONCLUSIONS: In human liver regeneration FGF19 upregulation may constitute a protective response from BAs excess during liver regeneration. Our findings suggest the existence of post-translational mechanisms regulating CYP7A1 activity, and therefore BAs synthesis, independent from CYP7A1/Cyp7a1 gene transcription.

Comprehensive analysis of epigenetic and epitranscriptomic genes’ expression in human NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a multifactorial condition with a complex etiology. Its incidence is increasing globally in parallel with the obesity epidemic, and it is now considered the most common liver disease in Western countries. The precise mechanisms underlying the development and progression of NAFLD are complex and still poorly understood. The dysregulation of epigenetic and epitranscriptomic mechanisms is increasingly recognized to play pathogenic roles in multiple conditions, including chronic liver diseases. Here, we have performed a comprehensive analysis of the expression of epigenetic and epitranscriptomic genes in a total of 903 liver tissue samples corresponding to patients with normal liver, obese patients, and patients with non-alcoholic fatty liver (NAFL) and non-alcoholic steatohepatitis (NASH), advancing stages in NAFLD progression. We integrated ten transcriptomic datasets in an unbiased manner, enabling their robust analysis and comparison. We describe the complete landscape of epigenetic and epitranscriptomic genes’ expression along the course of the disease. We identify signatures of genes significantly dysregulated in association with disease progression, particularly with liver fibrosis development. Most of these epigenetic and epitranscriptomic effectors have not been previously described in human NAFLD, and their altered expression may have pathogenic implications. We also performed a comprehensive analysis of the expression of enzymes involved in the metabolism of the substrates and cofactors of epigenetic and epitranscriptomic effectors. This study provides novel information on NAFLD pathogenesis and may also guide the identification of drug targets to treat this condition and its progression towards hepatocellular carcinoma. (AU)

Comprehensive analysis of epigenetic and epitranscriptomic genes' expression in human NAFLD.

Non-alcoholic fatty liver disease (NAFLD) is a multifactorial condition with a complex etiology. Its incidence is increasing globally in parallel with the obesity epidemic, and it is now considered the most common liver disease in Western countries. The precise mechanisms underlying the development and progression of NAFLD are complex and still poorly understood. The dysregulation of epigenetic and epitranscriptomic mechanisms is increasingly recognized to play pathogenic roles in multiple conditions, including chronic liver diseases. Here, we have performed a comprehensive analysis of the expression of epigenetic and epitranscriptomic genes in a total of 903 liver tissue samples corresponding to patients with normal liver, obese patients, and patients with non-alcoholic fatty liver (NAFL) and non-alcoholic steatohepatitis (NASH), advancing stages in NAFLD progression. We integrated ten transcriptomic datasets in an unbiased manner, enabling their robust analysis and comparison. We describe the complete landscape of epigenetic and epitranscriptomic genes' expression along the course of the disease. We identify signatures of genes significantly dysregulated in association with disease progression, particularly with liver fibrosis development. Most of these epigenetic and epitranscriptomic effectors have not been previously described in human NAFLD, and their altered expression may have pathogenic implications. We also performed a comprehensive analysis of the expression of enzymes involved in the metabolism of the substrates and cofactors of epigenetic and epitranscriptomic effectors. This study provides novel information on NAFLD pathogenesis and may also guide the identification of drug targets to treat this condition and its progression towards hepatocellular carcinoma.

Pancreatic microexons regulate islet function and glucose homeostasis.

Pancreatic islets control glucose homeostasis by the balanced secretion of insulin and other hormones, and their abnormal function causes diabetes or hypoglycaemia. Here we uncover a conserved programme of alternative microexons included in mRNAs of islet cells, particularly in genes involved in vesicle transport and exocytosis. Islet microexons (IsletMICs) are regulated by the RNA binding protein SRRM3 and represent a subset of the larger neural programme that are particularly sensitive to SRRM3 levels. Both SRRM3 and IsletMICs are induced by elevated glucose levels, and depletion of SRRM3 in human and rat beta cell lines and mouse islets, or repression of particular IsletMICs using antisense oligonucleotides, leads to inappropriate insulin secretion. Consistently, mice harbouring mutations in Srrm3 display defects in islet cell identity and function, leading to hyperinsulinaemic hypoglycaemia. Importantly, human genetic variants that influence SRRM3 expression and IsletMIC inclusion in islets are associated with fasting glucose variation and type 2 diabetes risk. Taken together, our data identify a conserved microexon programme that regulates glucose homeostasis.

Oxygen in Metabolic Dysfunction and Its Therapeutic Relevance.

Significance: In recent years, a number of studies have shown altered oxygen partial pressure at a tissue level in metabolic disorders, and some researchers have considered oxygen to be a (macro) nutrient. Oxygen availability may be compromised in obesity and several other metabolism-related pathological conditions, including sleep apnea-hypopnea syndrome, the metabolic syndrome (which is a set of conditions), type 2 diabetes, cardiovascular disease, and cancer. Recent Advances: Strategies designed to reduce adiposity and its accompanying disorders have been mainly centered on nutritional interventions and physical activity programs. However, novel therapies are needed since these approaches have not been sufficient to counteract the worldwide increasing rates of metabolic disorders. In this regard, intermittent hypoxia training and hyperoxia could be potential treatments through oxygen-related adaptations. Moreover, living at a high altitude may have a protective effect against the development of abnormal metabolic conditions. In addition, oxygen delivery systems may be of therapeutic value for supplying the tissue-specific oxygen requirements. Critical Issues: Precise in vivo methods to measure oxygenation are vital to disentangle some of the controversies related to this research area. Further, it is evident that there is a growing need for novel in vitro models to study the potential pathways involved in metabolic dysfunction to find appropriate therapeutic targets. Future Directions: Based on the existing evidence, it is suggested that oxygen availability has a key role in obesity and its related comorbidities. Oxygen should be considered in relation to potential therapeutic strategies in the treatment and prevention of metabolic disorders. Antioxid. Redox Signal. 35, 642-687.

Cerium Oxide Nanoparticles Regulate Insulin Sensitivity and Oxidative Markers in 3T3-L1 Adipocytes and C2C12 Myotubes.

Insulin resistance is associated with oxidative stress, mitochondrial dysfunction, and a chronic low-grade inflammatory status. In this sense, cerium oxide nanoparticles (CeO2 NPs) are promising nanomaterials with antioxidant and anti-inflammatory properties. Thus, we aimed to evaluate the effect of CeO2 NPs in mouse 3T3-L1 adipocytes, RAW 264.7 macrophages, and C2C12 myotubes under control or proinflammatory conditions. Macrophages were treated with LPS, and both adipocytes and myotubes with conditioned medium (25% LPS-activated macrophages medium) to promote inflammation. CeO2 NPs showed a mean size of ≤25.3 nm (96.7%) and a zeta potential of 30.57 ± 0.58 mV, suitable for cell internalization. CeO2 NPs reduced extracellular reactive oxygen species (ROS) in adipocytes with inflammation while increased in myotubes with control medium. The CeO2 NPs increased mitochondrial content was observed in adipocytes under proinflammatory conditions. Furthermore, the expression of Adipoq and Il10 increased in adipocytes treated with CeO2 NPs. In myotubes, both Il1b and Adipoq were downregulated while Irs1 was upregulated. Overall, our results suggest that CeO2 NPs could potentially have an insulin-sensitizing effect specifically on adipose tissue and skeletal muscle. However, further research is needed to confirm these findings.

Inverse Association Between Metabolic Syndrome and Altitude: A Cross-Sectional Study in an Adult Population of Ecuador.

Background: Metabolic syndrome (MetS) is characterized by the clustering of hyperglycemia, hypertension, hypertriglyceridemia, low high-density lipoprotein cholesterol levels and central adiposity. Altitude has been proposed as a protective factor to prevent the development of MetS and its components. Aim: To determine whether living at geographical elevation is associated with MetS and its individual components after adjustment for potential confounders in an Ecuadoran population. Methods: The study included 260 Ecuadoran university graduates over 20 years of age, from the coastal or the Andean Altiplano region. The altitude of residence was imputed with the postal code of each participant residence according to the data of the Ecuadoran Geophysical Institute of the National Polytechnic School. MetS was defined according to the harmonizing definition. Logistic regression models were fitted to assess the relationship between altitude level and the prevalence of MetS and its individual components. To test the internal validity, re-sampling techniques were used (1,000 bootstrap samples). Results: Living at high altitude was associated with less hypercholesterolemia (OR = 0.24; p < 0.001), hyperglycemia (OR = 0.25; p < 0.05) and MetS (OR = 0.24; p < 0.05), after adjusting for potential confounders. At high altitude the bootstrapped logistic regression models showed lower prevalence of hypercholesterolemia (OR = 0.30; p < 0.05), hyperglycemia (OR = 0.22; p < 0.001) and MetS (OR = 0.28; p < 0.05). The MetS score (0-5 points) showed a reduction in the number of MetS components at high altitude compared to sea level (B = -0.34; p = 0.002). A statistically significant lower self-reported energy intake was found in high altitude compared to sea level after adjustment for potential confounders (p < 0.001). Conclusion: In the present study concerning a small Ecuadoran population composed of highly educated adults living at the coast and the Andean Altiplano, living at high altitude (2,758-2,787 m) was associated with a lower prevalence of MetS, hypercholesterolemia and hyperglycemia, compared to the participants at sea level (4-6 m). In addition, an inverse association between altitude and self-reported energy intake was found after adjusting for covariates, suggesting a physiological role of appetite at high altitude even in acclimated subjects.

Inflammation stimulates hypoxia-inducible factor-1α regulatory activity in 3T3-L1 adipocytes with conditioned medium from lipopolysaccharide-activated RAW 264.7 macrophages.

Obesity is a multifactorial, chronic, inflammatory disease that involves different processes, such as adipose tissue hypoxia. The aim of the current study was to characterize the effects of conditioned medium (CM) from lipopolysaccharide (LPS)-activated macrophages on the regulation of hypoxia-inducible factor 1α (HIF-1α)-related genes in murine adipocytes. For the in vitro analyses, 3T3-L1 murine adipocytes (9 days postdifferentiation) were incubated either in CM (25% medium of RAW 264.7 murine macrophages with 24 hr 500 ng/ml LPS), LPS at 500 ng/ml, or hypoxia (Hx; 1% O2 , 94% N2 , 5% CO2 ) for 24 hr. For the in vivo experiments, mice were fed a high-fat diet. Both epididymal white adipose tissue (eWAT) and adipocytes in CM showed upregulation of Glut1, Mcp1, Il10, Tnf, and Il1b. The secretion of IL-6, TNF-α, and MCP-1 was also increased in CM-treated adipocytes. Moreover, increased levels of HIF-1α subunit and nuclear factor kappa B p65 were found after CM treatment, linking Hx, and inflammation. HIF-1α directly bound vascular endothelial growth factor A (Vegfa) and uncoupling protein 2 (Ucp2) genes, up- and downregulating its expression, respectively. Furthermore, the oxygen consumption rate was 30% lower in CM. The siRNA knockdown of mammalian target of rapamycin (Mtor) reversed the induction of HIF-1α found in CM. The macrophage infiltration simulated through CM seems to be a similar environment to an abnormally enlarged eWAT. We have evidenced that HIF-1α plays a regulatory role in the expression of Vegfa and Ucp2 in CM. Finally, the inhibition of the mTOR pathway prevented the HIF-1α activation induced by CM. The involvement of HIF-1α under proinflammatory conditions provides insight into the origins of Hx in obesity.

Low Oxygen Consumption is Related to a Hypomethylation and an Increased Secretion of IL-6 in Obese Subjects with Sleep Apnea-Hypopnea Syndrome.

BACKGROUND: Deoxyribonucleic acid (DNA) methylation is an epigenetic modification involved in gene expression regulation, usually via gene silencing, which contributes to the risks of many multifactorial diseases. The aim of the present study was to analyze the influence of resting oxygen consumption on global and gene DNA methylation as well as protein secretion of inflammatory markers in blood cells from obese subjects with sleep apnea-hypopnea syndrome (SAHS). METHODS: A total of 44 obese participants with SAHS were categorized in 2 groups according to their resting oxygen consumption. DNA methylation levels were evaluated using a methylation-sensitive high resolution melting approach. RESULTS: The analyzed interleukin 6 (IL6) gene cytosine phosphate guanine (CpG) islands showed a hypomethylation, while serum IL-6 was higher in the low compared to the high oxygen consumption group (p < 0.05). Moreover, an age-related loss of DNA methylation of tumor necrosis factor (B = -0.82, 95% CI -1.33 to -0.30) and long interspersed nucleotide element 1 (B = -0.46; 95% CI -0.87 to -0.04) gene CpGs were found. Finally, studied CpG methylation levels of serpin peptidase inhibitor, clade E member 1 (r = 0.43; p = 0.01), and IL6 (r = 0.41; p = 0.02) were positively associated with fat-free mass. CONCLUSIONS: These findings suggest a potential role of oxygen in the regulation of inflammatory genes. Oxygen consumption measurement at rest could be proposed as a clinical biomarker of metabolic health.

Living at a Geographically Higher Elevation Is Associated with Lower Risk of Metabolic Syndrome: Prospective Analysis of the SUN Cohort.

Living in a geographically higher altitude affects oxygen availability. The possible connection between environmental factors and the development of metabolic syndrome (MetS) feature is not fully understood, being the available epidemiological evidence still very limited. The aim of the present study was to evaluate the longitudinal association between altitude and incidence of MetS and each of its components in a prospective Spanish cohort, The Seguimiento Universidad de Navarra (SUN) project. Our study included 6860 highly educated subjects (university graduates) free from any MetS criteria at baseline. The altitude of residence was imputed with the postal code of each individual subject residence according to the data of the Spanish National Cartographic Institute and participants were categorized into tertiles. MetS was defined according to the harmonized definition. Cox proportional hazards models were used to assess the association between the altitude of residence and the risk of MetS during follow-up. After a median follow-up period of 10 years, 462 incident cases of MetS were identified. When adjusting for potential confounders, subjects in the highest category of altitude (>456 m) exhibited a significantly lower risk of developing MetS compared to those in the lowest tertile (<122 m) of altitude of residence [Model 2: Hazard ratio = 0.75 (95% Confidence interval: 0.58-0.97); p for trend = 0.029]. Living at geographically higher altitude was associated with a lower risk of developing MetS in the SUN project. Our findings suggest that geographical elevation may be an important factor linked to metabolic diseases.

Effects of Hyperoxia on Oxygen-Related Inflammation with a Focus on Obesity.

Several studies have shown a pathological oxygenation (hypoxia/hyperoxia) on the adipose tissue in obese subjects. Additionally, the excess of body weight is often accompanied by a state of chronic low-degree inflammation. The inflammation phenomenon is a complex biological response mounted by tissues to combat injurious stimuli in order to maintain cell homeostasis. Furthermore, it is believed that the abnormal oxygen partial pressure occurring in adipose tissue is involved in triggering inflammatory processes. In this context, oxygen is used in modern medicine as a treatment for several diseases with inflammatory components. Thus, hyperbaric oxygenation has demonstrated beneficial effects, apart from improving local tissue oxygenation, on promoting angiogenesis, wound healing, providing neuroprotection, facilitating glucose uptake, appetite, and others. Nevertheless, an excessive hyperoxia exposure can lead to deleterious effects such as oxidative stress, pulmonary edema, and maybe inflammation. Interestingly, some of these favorable outcomes occur under high and low oxygen concentrations. Hereby, we review a potential therapeutic approach to the management of obesity as well as the oxygen-related inflammation accompanying expanded adipose tissue, based on elevated oxygen concentrations. To conclude, we highlight at the end of this review some areas that need further clarification.