Aster Proteins Facilitate Nonvesicular Plasma Membrane to ER Cholesterol Transport in Mammalian Cells.

The mechanisms underlying sterol transport in mammalian cells are poorly understood. In particular, how cholesterol internalized from HDL is made available to the cell for storage or modification is unknown. Here, we describe three ER-resident proteins (Aster-A, -B, -C) that bind cholesterol and facilitate its removal from the plasma membrane. The crystal structure of the central domain of Aster-A broadly resembles the sterol-binding fold of mammalian StARD proteins, but sequence differences in the Aster pocket result in a distinct mode of ligand binding. The Aster N-terminal GRAM domain binds phosphatidylserine and mediates Aster recruitment to plasma membrane-ER contact sites in response to cholesterol accumulation in the plasma membrane. Mice lacking Aster-B are deficient in adrenal cholesterol ester storage and steroidogenesis because of an inability to transport cholesterol from SR-BI to the ER. These findings identify a nonvesicular pathway for plasma membrane to ER sterol trafficking in mammals.

Interferon-mediated reprogramming of membrane cholesterol to evade bacterial toxins.

Plasma membranes of animal cells are enriched for cholesterol. Cholesterol-dependent cytolysins (CDCs) are pore-forming toxins secreted by bacteria that target membrane cholesterol for their effector function. Phagocytes are essential for clearance of CDC-producing bacteria; however, the mechanisms by which these cells evade the deleterious effects of CDCs are largely unknown. Here, we report that interferon (IFN) signals convey resistance to CDC-induced pores on macrophages and neutrophils. We traced IFN-mediated resistance to CDCs to the rapid modulation of a specific pool of cholesterol in the plasma membrane of macrophages without changes to total cholesterol levels. Resistance to CDC-induced pore formation requires the production of the oxysterol 25-hydroxycholesterol (25HC), inhibition of cholesterol synthesis and redistribution of cholesterol to an esterified cholesterol pool. Accordingly, blocking the ability of IFN to reprogram cholesterol metabolism abrogates cellular protection and renders mice more susceptible to CDC-induced tissue damage. These studies illuminate targeted regulation of membrane cholesterol content as a host defense strategy.

Hepatic GATA4 regulates cholesterol and triglyceride homeostasis in collaboration with LXRs.

GATA4 is a transcription factor known for its crucial role in the development of many tissues, including the liver; however, its role in adult liver metabolism is unknown. Here, using high-throughput sequencing technologies, we identified GATA4 as a transcriptional regulator of metabolism in the liver. GATA4 expression is elevated in response to refeeding, and its occupancy is increased at enhancers of genes linked to fatty acid and lipoprotein metabolism. Knocking out GATA4 in the adult liver (Gata4LKO) decreased transcriptional activity at GATA4 binding sites, especially during feeding. Gata4LKO mice have reduced plasma HDL cholesterol and increased liver triglyceride levels. The expression of a panel of GATA4 binding genes involved in hepatic cholesterol export and triglyceride hydrolysis was down-regulated in Gata4LKO mice. We further demonstrate that GATA4 collaborates with LXR nuclear receptors in the liver. GATA4 and LXRs share a number of binding sites, and GATA4 was required for the full transcriptional response to LXR activation. Collectively, these results show that hepatic GATA4 contributes to the transcriptional control of hepatic and systemic lipid homeostasis.

The risk of hospitalisation from RSV is not increased by co-infection in children under 24-months-of-age.

The recent pandemic prompted renewed interest in paediatric respiratory infections, including whether co-infections - particularly with RSV - have an adverse prognostic impact. We evaluated the charts of all children presenting with respiratory symptoms to our unit between October 2022 and April 2023, each of whom was subjected to a multiplex PCR assay to detect eight viral targets and one bacterial target and examine the relationships between mono- and co-infections and hospitalization outcomes. We observed that younger age and RSV infection were both associated with the need for hospitalisation and the duration of hospitalisation after adjusting for confounders. Co-infection was, however, not associated with these outcomes.   Conclusion: This real-world data add to a growing consensus that RSV increases the risk of hospitalisation, while other co-infections, except for co-infection with SARS-CoV-2, do not. Given the timeframe over which our study was conducted, only a few children had SARS-CoV-2 co-infection, so we could not confirm any significant effect from this interaction. What is Known: • RSV increases the risk of hospitalisation and the need tor ventilatory support, especially in very young children. What is New: • Younger age and RSV infection were both associated with the need for hospitalisation and the duration of hospitalisation after adjusting for confounders. • Co-infection was, however, not associated with these outcomes.

The role of EEG and neuroimaging in the diagnosis of non-convulsive status epilepticus in Subacute Encephalopathy with Seizures in Alcoholics (SESA syndrome): a case report and overview of the literature.

Epileptic seizures are frequently associated with liver dysfunction and alcoholism. Subacute encephalopathy with seizures in chronic alcoholics (SESA) is an underrecognized condition with peculiar clinical, EEG and neuroradiological features.We report the case of a 58-year-old man with previous alcohol use disorder (AUD) and acute-on chronic liver failure on alcohol-related cirrhosis, referred for urgent Orthotopic Liver Transplantation evaluation. The patient presented with delirium, aphasia and progressive deterioration of consciousness leading to intensive care unit admission. EEG showed slow activity with superimposed lateralized periodic discharges (LPDs) over the left temporo-occipital regions and ictal discharges with focal motor phenomena, consistent with focal status epilepticus. Antiseizure treatment with lacosamide and levetiracetam was administered with progressive improvement of consciousness.Brain MRI disclosed T2/FLAIR areas of hyperintensity in the left pulvinar and T2/FLAIR hyperintensity with corresponding DWI hyperintensity in the left hippocampal cortex, suggestive of post/peri-ictal excitotoxic changes with anatomical correspondence to focal LPDs distribution. SWI demonstrated decreased prominence of cortical veins in the left temporo-occipital region consistent with increased venous blood oxygenation in compensatory hyperperfusion.In conclusion, SESA should be suspected in the differential diagnosis of patients with AUD presenting with focal neurological deficits, seizures and focal EEG abnormalities. In this context, EEG and brain MRI represent useful tools with both diagnostic and prognostic value.

Effect of patient-ventilator asynchrony on lung and diaphragmatic injury in experimental acute respiratory distress syndrome in a porcine model.

BACKGROUND: Patient-ventilator asynchrony during mechanical ventilation may exacerbate lung and diaphragm injury in spontaneously breathing subjects. We investigated whether subject-ventilator asynchrony increases lung or diaphragmatic injury in a porcine model of acute respiratory distress syndrome (ARDS). METHODS: ARDS was induced in adult female pigs by lung lavage and injurious ventilation before mechanical ventilation by pressure assist-control for 12 h. Mechanically ventilated pigs were randomised to breathe spontaneously with or without induced subject-ventilator asynchrony or neuromuscular block (n=7 per group). Subject-ventilator asynchrony was produced by ineffective, auto-, or double-triggering of spontaneous breaths. The primary outcome was mean alveolar septal thickness (where thickening of the alveolar wall indicates worse lung injury). Secondary outcomes included distribution of ventilation (electrical impedance tomography), lung morphometric analysis, inflammatory biomarkers (gene expression), lung wet-to-dry weight ratio, and diaphragmatic muscle fibre thickness. RESULTS: Subject-ventilator asynchrony (median [interquartile range] 28.8% [10.4] asynchronous breaths of total breaths; n=7) did not increase mean alveolar septal thickness compared with synchronous spontaneous breathing (asynchronous breaths 1.0% [1.6] of total breaths; n=7). There was no difference in mean alveolar septal thickness throughout upper and lower lung lobes between pigs randomised to subject-ventilator asynchrony vs synchronous spontaneous breathing (87.3-92.2 µm after subject-ventilator asynchrony, compared with 84.1-95.0 µm in synchronised spontaneous breathing;). There were also no differences between groups in wet-to-dry weight ratio, diaphragmatic muscle fibre thickness, atelectasis, lung aeration, or mRNA expression levels for inflammatory cytokines pivotal in ARDS pathogenesis. CONCLUSIONS: Subject-ventilator asynchrony during spontaneous breathing did not exacerbate lung injury and dysfunction in experimental porcine ARDS.

Multicentre, randomised, open-label, parallel-group, clinical phase II study to evaluate immunonutrition in improving efficacy of immunotherapy in patients with metastatic non-small cell lung cancer, undergoing systematic nutritional counseling.

BACKGROUND: Nutritional support, including nutritional counseling and oral nutritional supplements (ONS), has been recommended as a first-line strategy in patients with non-small cell lung cancer (NSCLC). Evidence on the efficacy of immunonutrition during immunotherapy in these patients is positive, but still limited some secondary endpoints, such as treatment toxicity and tolerance. We hypothesize that early systematic provision of ONS with a high-protein-high calorie mixture containing immunonutrients (Impact®) in addition to nutritional counseling, compared to nutritional counseling alone, is beneficial to patients with NSCLC receiving immunotherapy with or without chemotherapy. We designed the present study to evaluate the efficacy of early systematic provision of ONS enriched with immunonutrients compared to nutritional counseling alone, in patients with NSCLC undergoing immunotherapy. Study endpoints were: treatment response (primary endpoint: progression-free survival), treatment tolerance and toxicity, body weight, body composition, protein-calorie intake, quality of life, fatigue, muscle strength and immunological profile. METHODS: This is a pragmatic, multicentre, randomized (1:1), parallel-group, open label, controlled, pilot clinical trial (N = 180). DISCUSSION: The improvement of efficacy of nutritional support in oncology still deserves many efforts. Immunonutrition represents a promising approach also in patients with NSCLC, but evidence on its efficacy on clinical outcomes during immunotherapy is still inconclusive. The present pilot study, which guarantees early high-quality nutritional care (assessment and treatment) to all patients in agreement with current guidelines and recommendations, could represent one of the first proofs of efficacy of early oral immunonutrition in patients with cancer undergoing immunotherapy. Further large randomized trials addressing the improvement of supportive care could be hypothesized, accordingly. TRIAL REGISTRATION: This study is registered on ClinicalTrials.gov Identifier: NCT05384873.

Randomized trial of sucrosomial iron supplementation in patients with chemotherapy-related anemia treated with ESA.

BACKGROUND: Iron supplementation improves the erythropoiesis-stimulating agents' (ESAs) response in chemotherapy-related anemia. The primary aim of our study is to assess the efficacy of sucrosomial iron, a new oral iron formulation, in cancer patients with chemotherapy-induced anemia treated with ESAs. The secondary objectives included the efficacy into two subgroups of patients (iron replete and functional iron deficiency) between the two study arms, safety and the effect on transfusion need. METHODS: In this randomized, multicentre, open-label, phase III clinical trial, 60 cancer patients were enrolled. Each patient was randomly assigned (1:1) to receive 12 weeks of oral sucrosomial iron at the dose of 30 mg daily in combination with ESAs or no supplementation to ESA treatment. The endpoint considered for efficacy was the proportion of patients achieving complete hematological response at 12 weeks (increase in Hb > 2 g/dL from baseline, without RBC transfusions in the previous 28 days or achieving Hb ≥ 12 g/dL). RESULTS: There was a statistically significant association between oral sucrosomial iron supplementation in combination with ESAs and the achievement of a complete hematological response. This response was achieved within 12 weeks by 31% of patients in the control group and by 52% of patients supplemented with oral sucrosomial iron. A trend of greater response in sucrosomial iron arm was found in both subgroups. No difference was observed about safety and transfusion need. CONCLUSIONS: Sucrosomial iron is well tolerated and its combination with ESAs improves the hematological response in cancer patients with chemotherapy-related anemia. TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION: This study has been reviewed by the Institutional Ethics Committee of the IRCCS Policlinico San Matteo Foundation, Pavia, Italy (28/04/2015; prot. N. 20,150,002,059), and by the Institutional Ethics Committee of the other Italian oncological centers involved in this study.

The value of EEG attenuation in the prediction of outcome in COVID-19 patients.

INTRODUCTION: During the COVID-19 pandemic, electroencephalography (EEG) proved to be a useful tool to demonstrate brain involvement. Many studies reported non-reactive generalized slowing as the most frequent pattern and epileptiform activity in a minority of patients. OBJECTIVE: To investigate the prevalence of diffuse unreactive background attenuation or suppression and its correlation with outcome in a cohort of COVID-19 patients. METHODS: The EEGs recorded during the first year of the COVID-19 pandemic were retrospectively evaluated to identify the main pattern and focus on the occurrence of a low-voltage background, either attenuated (10-20 µV) or suppressed (< 10 µV). We sought a correlation between in-hospital mortality and low-voltage EEG. In a subsample of patients, biomarkers of inflammation, hypoxemia and organ failure were collected. Brain imaging was also evaluated. RESULTS: Among 98 EEG performed in 50 consecutive patients, diffuse unreactive slowing was the most prevalent pattern (54%), followed by unreactive attenuation or suppression pattern (26%), being the latter significantly correlated with an unfavourable outcome (p = 0.0004). Survivors showed significantly lower interleukine-6 values compared to non-survivors. Patients with attenuated EEG and non-survivors also showed lower PaO2/FiO2 values. Neuroradiological findings were very heterogeneous with a prevalence of lesions suggestive of a microangiopathic substrate. CONCLUSIONS: EEG attenuation or suppression may be more frequent than previously reported and significantly associated with a poor outcome. SARS-CoV-2 infection may result in encephalopathy and reduced EEG voltage through mechanisms that are still unknown but deserve attention given its negative impact on prognosis.

Open Repair for Juxtarenal Aortic Aneurysm: Short and Long-term Results.

BACKGROUND: The recent technological evolution has also allowed for the treatment of juxtarenal aortic aneurysm (JAA) with an endovascular technique, but short- and long-term results must be compared with the results of open treatment, which is the gold standard. In this study, we analyzed the short- and long-term results of open surgical treatment (open repair) in patients with JAA in our series. METHODS: From January 2006 to December 2016, 155 patients were treated for JAA with open repair; the data were analyzed retrospectively. The mean age was 71.17 years (standard deviation [SD] 7.1), and mean size of aneurysm was 6.15 cm (SD 1.1). The ASA classes 2, 3, and 4 were 20%, 74% and 6%, respectively. Follow-up included clinical visit and abdominal aorta Duplex scan after 1 and 6 months and annually. The mean follow-up interval was 48.6 (SD 32.4) months. RESULTS: The mean surgical time was 256 min (SD 69), the mean stay in the intensive care unit was 1.6 days (SD 1.2), and the mean total hospital stay was 10.2 days (SD 4.3). Aortic cross-clamping was usually suprarenal (110, 71%); in 39 (25%), the aortic clamping was between the renal arteries, and 6 patients (4%) required a supraceliac cross-clamping. The mean renal ischemia time due to aortic clamping was 17 min (SD 3.5). In 32 patients (21%), the left renal vein was sectioned for performing proximal aortic anastomosis and then reconstructed. Twelve patients (8%) required a renal revascularization, and in 49 patients (32%), an hypogastric bypass was performed. The 30-day mortality rate was 0.6%, and only 1 patient died in the postoperative due to intestinal infarction. The postoperative morbidities occurred in 15 cases (10%). Six patients had dehiscence of the laparotomy without the involvement of the muscle, 4 patients had an asymptomatic small increase of the troponin, and in 3 patients, there was an increase in creatinine >1.8 mg/dL. No dialysis was performed. Two patients had peripheral embolism in the lower limbs. Twenty-six patients (15%) died in the follow-up, but causes have never been related to aortic disease. CONCLUSIONS: Open repair of JAA is still safe, effective, and durable also in the long-term period and even in patients with multiple cardiovascular risk factors.

Serial magnetic resonance study in super refractory status epilepticus: progressive involvement of striatum and pallidus is a possible predictive marker of negative outcome.

Super refractory status epilepticus (SRSE) is a life-threatening condition in which seizures do not respond to third-line anticonvulsant drug therapy. SRSE is associated with high mortality. How often SRSE occurs, what are the risk factors leading to this condition, and what is the effect on clinical outcome of failure to control seizures are poorly defined. Several studies have evaluated magnetic resonance imaging (MRI) findings in status epilepticus (SE), confirming that SE may directly cause selective neuronal necrosis due to excitotoxic mechanisms, as described in clinical case reports and experimental models. The aim of our study is to illustrate, in a case of SRSE, MRI signal changes during time and to describe which cerebral structures are early involved in this difficult clinical condition. We investigated with serial MRI study a patient affected by childhood generalized epilepsy who developed SRSE of unknown etiology during adulthood. MRI scans showed brain signal changes according to progressive electro-clinical worsening, particularly an early involvement of striatum/pallidus. An extended literature exists about transient MRI changes in SE, but not enough about SRSE, because of the difficulties in executing serial MRI studies in patients with such risky condition. MRI findings in SRSE must be investigated with particular care in order to detect early changes in basal ganglia that could suggest severe prognosis.

Aortic Epithelioid Angiosarcoma after Endovascular Aneurysm Repair.

We report a case of epithelioid angiosarcoma of the abdominal aortic wall after endovascular treatment for abdominal aortic aneurysm (EVAR). A 60-year-old male, treated 7 years before with EVAR, presented with abdominal back pain, general fatigue, and fever. It was assumed to be a graft infection with periaortic tissue compatible with an inflammatory reaction. The endograft was therefore completely removed and a Dacron silver aorto-bisiliac graft was implanted. After a few days the patient worsened, the angio-computed tomography scan showed a progressive increase of the periaortic mass and numerous small nodules in the abdomen were also detected. The patient was again brought to surgery, an axillo-bifemoral bypass was performed, and the aorto-bisiliac graft was removed but the patient died after surgery. The histological examination showed an aortic epithelioid angiosarcoma with peritoneal metastasis.

The sirtuin class of histone deacetylases: regulation and roles in lipid metabolism.

After the completion of the human genome sequence and that from many other organisms, last decade has witnessed a spectacular gain of knowledge on gene functions. These studies provided new insights on the roles of genes in physiology and disease. Nonetheless, the availability of genetically modified models and of "omics" technologies such as next generation sequencing unveiled clear evidences on epigenetic regulation of many cellular functions. At this regard, sirtuins, belonging to class III histone deacetylase family, have emerged as regulators of metabolism as well as other cellular processes and seem ideally suited as targets of future therapeutical interventions. This review deals on general aspects of the biology of sirtuins and focuses on their relevance in lipid metabolism in different tissues, pointing to their exploitation as potential pharmacological targets of compounds that could be used as new therapeutic alternatives in several disorders ranging from type 2 diabetes and obesity to age-related cardiovascular and neurodegenerative diseases.

Energizing Genetics and Epi-genetics: Role in the Regulation of Mitochondrial Function.

Energy metabolism and mitochondrial function hold a core position in cellular homeostasis. Oxidative metabolism is regulated at multiple levels, ranging from gene transcription to allosteric modulation. To accomplish the fine tuning of these multiple regulatory circuits, the nuclear and mitochondrial compartments are tightly and reciprocally controlled. The fact that nuclear encoded factors, PPARγ coactivator 1α and mitochondrial transcription factor A, play pivotal roles in the regulation of oxidative metabolism and mitochondrial biogenesis is paradigmatic of this crosstalk. Here we provide an updated survey of the genetic and epigenetic mechanisms involved in the control of energy metabolism and mitochondrial function. Chromatin dynamics highly depends on post-translational modifications occurring at specific amino acids in histone proteins and other factors associated to nuclear DNA. In addition to the well characterized enzymes responsible for histone methylation/demethylation and acetylation/deacetylation, other factors have gone on the "metabolic stage". This is the case of the new class of α-ketoglutarate-regulated demethylases (Jumonji C domain containing demethylases) and of the NAD+-dependent deacetylases, also known as sirtuins. Moreover, unexpected features of the machineries involved in mitochondrial DNA (mtDNA) replication and transcription, mitochondrial RNA processing and maturation have recently emerged. Mutations or defects of any component of these machineries profoundly affect mitochondrial activity and oxidative metabolism. Finally, recent evidences support the importance of mtDNA packaging in replication and transcription. These observations, along with the discovery that non-classical CpG islands present in mtDNA undergo methylation, indicate that epigenetics also plays a role in the regulation of the mitochondrial genome function.

Conversion to Brivaracetam Monotherapy in Clinical Practice: A Retrospective Study.

INTRODUCTION: The study aimed to evaluate the effectiveness and safety of brivaracetam (BRV) as conversion monotherapy in adults with focal epilepsy treated in the context of real-world clinical practice. METHODS: This was a retrospective, observational, non-interventional study in adults with focal epilepsy who converted to BRV monotherapy following the withdrawal of background antiseizure medications (ASMs). Primary effectiveness outcome was the retention rate of BRV as single ASM at 6 and 12 months. Secondary outcomes included the 6- and 12-month rates of seizure freedom. Safety and tolerability outcomes included the frequency and type of adverse events (AEs) and the occurrence of treatment discontinuation due to AEs. RESULTS: A total of 44 participants with a median age of 63.5 (interquartile range 44-73.5) years were included; 17 subjects were seizure free at baseline, and 9 of them switched from levetiracetam because of lack of tolerability. The retention rate of BRV monotherapy was 88.6% (39/44) at 6 months and 83.9% (26/31) at 12 months. The rates of seizure freedom were 72.7% (32/44) in subjects with 6-month follow-up and 58.1% (18/31) in subjects with 12-month follow-up. The median maintenance dosage of BRV monotherapy was 150 (100-200) mg/day at 6 months and 125 (100-200) mg/day in subjects with 12-month follow-up. Adverse events were recorded in 6/44 (13.6%) participants and led to BRV discontinuation in 2/44 (4.5%) cases. The reported AEs were somnolence (n = 3), fatigue (n = 2), and irritability (n = 1); no serious AEs were experienced. In 21/44 (47.7%) participants, BRV monotherapy resulted from the direct switch from levetiracetam. The rates of treatment retention and seizure freedom at 6 and 12 months were higher among people who switched from levetiracetam to BRV monotherapy. CONCLUSION: Brivaracetam may be a valuable treatment of focal seizures in people who converted to monotherapy in a real-life setting.

T cell cholesterol transport is a metabolic checkpoint that links intestinal immune responses to dietary lipid absorption.

The intrinsic pathways that control membrane organization in immune cells and the impact of such pathways on cellular function are not well defined. Here we report that the non-vesicular cholesterol transporter Aster-A links plasma membrane (PM) cholesterol availability in T cells to immune signaling and systemic metabolism. Aster-A is recruited to the PM during T-cell receptor (TCR) activation, where it facilitates the removal of newly generated "accessible" membrane cholesterol. Loss of Aster-A leads to excess PM cholesterol accumulation, resulting in enhanced TCR nano-clustering and signaling, and Th17 cytokine production. Finally, we show that the mucosal Th17 response is restrained by PM cholesterol remodeling. Ablation of Aster-A in T cells leads to enhanced IL-22 production, reduced intestinal fatty acid absorption, and resistance to diet-induced obesity. These findings delineate a multi-tiered regulatory scheme linking immune cell lipid flux to nutrient absorption and systemic physiology.

Cholesterol binding to VCAM-1 promotes vascular inflammation.

Hypercholesterolemia has long been implicated in endothelial cell (EC) dysfunction, but the mechanisms by which excess cholesterol causes vascular pathology are incompletely understood. Here we used a cholesterol-mimetic probe to map cholesterol-protein interactions in primary human ECs and discovered that cholesterol binds to and stabilizes the adhesion molecule VCAM-1. We show that accessible plasma membrane (PM) cholesterol in ECs is acutely responsive to inflammatory stimuli and that the nonvesicular cholesterol transporter Aster-A regulates VCAM-1 stability in activated ECs by controlling the size of this pool. Deletion of Aster-A in ECs increases VCAM-1 protein, promotes immune cell recruitment to vessels, and impairs pulmonary immune homeostasis. Conversely, depleting cholesterol from the endothelium in vivo dampens VCAM-1 induction in response to inflammatory stimuli. These findings identify cholesterol binding to VCAM-1 as a key step during EC activation and provide a biochemical explanation for the ability of excess membrane cholesterol to promote immune cell recruitment to the endothelium.

Damaging mutations in liver X receptor-α are hepatotoxic and implicate cholesterol sensing in liver health.

Liver X receptor-α (LXRα) regulates cellular cholesterol abundance and potently activates hepatic lipogenesis. Here we show that at least 1 in 450 people in the UK Biobank carry functionally impaired mutations in LXRα, which is associated with biochemical evidence of hepatic dysfunction. On a western diet, male and female mice homozygous for a dominant negative mutation in LXRα have elevated liver cholesterol, diffuse cholesterol crystal accumulation and develop severe hepatitis and fibrosis, despite reduced liver triglyceride and no steatosis. This phenotype does not occur on low-cholesterol diets and can be prevented by hepatocyte-specific overexpression of LXRα. LXRα knockout mice exhibit a milder phenotype with regional variation in cholesterol crystal deposition and inflammation inversely correlating with steatosis. In summary, LXRα is necessary for the maintenance of hepatocyte health, likely due to regulation of cellular cholesterol content. The inverse association between steatosis and both inflammation and cholesterol crystallization may represent a protective action of hepatic lipogenesis in the context of excess hepatic cholesterol.

Linking epigenetics to lipid metabolism: focus on histone deacetylases.

A number of recent studies revealed that epigenetic modifications play a central role in the regulation of lipid and of other metabolic pathways such as cholesterol homeostasis, bile acid synthesis, glucose and energy metabolism. Epigenetics refers to aspects of genome functions regulated in a DNA sequence-independent fashion. Chromatin structure is controlled by epigenetic mechanisms through DNA methylation and histone modifications. The main modifications are histone acetylation and deacetylation on specific lysine residues operated by two different classes of enzymes: Histone acetyltransferases (HATs) and histone deacetylases (HDACs), respectively. The interaction between these enzymes and histones can activate or repress gene transcription: Histone acetylation opens and activates chromatin, while deacetylation of histones and DNA methylation compact chromatin making it transcriptionally silent. The new evidences on the importance of HDACs in the regulation of lipid and other metabolic pathways will open new perspectives in the comprehension of the pathophysiology of metabolic disorders.