A Novel Mutation in LXRα Uncovers a Role for Cholesterol Sensing in Limiting Metabolic Dysfunction-Associated Steatohepatitis (MASH).

Liver x receptor alpha (LXRα, Nr1h3) functions as an important intracellular cholesterol sensor that regulates fat and cholesterol metabolism at the transcriptional level in response to the direct binding of cholesterol derivatives. We have generated mice with a mutation in LXRα that reduces activity in response to endogenous cholesterol derived LXR ligands while still allowing transcriptional activation by synthetic agonists. The mutant LXRα functions as a dominant negative that shuts down cholesterol sensing. When fed a high fat, high cholesterol diet LXRα mutant mice rapidly develop pathologies associated with Metabolic Dysfunction-Associated Steatohepatitis (MASH) including ballooning hepatocytes, liver inflammation, and fibrosis. Strikingly LXRα mutant mice have decreased liver triglycerides but increased liver cholesterol. Therefore, MASH-like phenotypes can arise in the absence of large increases in triglycerides. Reengaging LXR signaling by treatment with synthetic agonist reverses MASH suggesting that LXRα normally functions to impede the development of liver disease.

Cross-sectional characterization of renal function in cats with caudal stomatitis.

OBJECTIVES: The objective of the study was to compare renal functional biomarkers in cats and in caudal stomatitis (CS) and in age-matched control cats. METHODS: A cross-sectional, case-control study was conducted on 44 client-owned cats with CS that were prospectively enrolled and evaluated for a Comprehensive Oral Health Assessment and Treatment at one of four institutions. Renal function was assessed with measurement of serum creatinine, urea nitrogen, serum symmetric dimethylarginine, urinalysis, urine protein:creatinine ratio and urine protein electrophoresis. Affected gingiva was biopsied to confirm the diagnosis of stomatitis. Renal biochemical analyses from the experimental group were compared with those of 44 age-matched controls without CS enrolled prospectively or retrospectively after presenting to the primary institution for routine healthcare. Control cats were included if they were clinically stable, their chronic illnesses were well managed and minimal dental disease was present on examination. Renal biomarkers were compared between groups using a t-test or the Mann-Whitney U-test. Frequency of azotemia, proteinuria and the clinical diagnosis of renal disease were compared using Fisher's exact test. RESULTS: Relative to the control group, cats in the CS group had significantly lower serum creatinine (P <0.001) and albumin concentrations (P <0.001), urine specific gravity (P = 0.024) and hematocrit (P = 0.003), and higher serum phosphorus (P <0.001), potassium (P <0.001) and globulin concentrations (P <0.001), white blood cell count (P <0.001) and urine protein:creatinine ratio (P = 0.009). There were no significant differences in serum symmetric dimethylarginine or urea nitrogen concentrations. No clinically significant findings were noted on urine protein electrophoresis. There were no significant differences in the frequency of azotemia, proteinuria or renal disease categories between the two groups. CONCLUSIONS AND RELEVANCE: The present study does not demonstrate a significant difference in the frequency of kidney disease between cats with and without CS. Longitudinal evaluation is warranted to investigate the relationship between renal disease and CS.

Evaluation of renal values during treatment for heartworm disease in 27 client-owned dogs.

BACKGROUND: Canine heartworm disease (CHD) caused by Dirofilaria immitis remains a common preventable disease with increasing incidence in some parts of the USA. The treatment guidelines of the American Heartworm Society (AHS) currently recommend monthly macrocyclic lactone administration, 28 days of doxycycline given orally every 12 h and three injections of melarsomine dihydrochloride (1 injection on day 2 of treatment followed 30 days later by 2 injections 24 h apart). Minocycline has also been utilized when doxycycline is unavailable. The systemic effects of CHD, which particularly impact cardiac and renal function, have been described, with infected dogs often experiencing renal damage characterized by an increase in serum concentrations of renal biomarkers. Although the AHS treatment protocol for CHD has been shown to be safe and effective in most cases, the potential for complications remains. No study as of yet has evaluated changes in symmetric dimethylarginine (SDMA), a sensitive marker of renal function, during treatment for CHD. The purpose of the present study was to evaluate renal function in dogs by measuring serum creatinine and SDMA concentrations during the adulticide treatment period. METHODS: Serum creatinine and SDMA concentrations were measured in 27 client-owned dogs affected by CHD at the following time points: prior to starting doxycycline or minocycline therapy (baseline), during doxycycline or minocycline therapy (interim), at the time of the first dose of melarsomine (first dose), at the time of the second dose of melarsomine (second dose) and at the dog's follow-up visit after treatment, occurring between 1 and 6 months after completion of therapy (post-treatment). Concentrations of creatinine and SDMA were compared between time points using a mixed effects linear model. RESULTS: Mean SDMA concentrations following the second dose of melarsomine were significantly lower (-1.80 ug/dL, t-test, df = 99.067, t = -2.694, P-Value = 0.00829) than baseline concentrations. There were no other statistically significant differences in the concentration of either biomarker between the baseline and the other time points in CHD dogs undergoing treatment. CONCLUSIONS: The results suggest that the current AHS protocol may not have a substantial impact on renal function.

Antihyperlipidemic Activity of Gut-Restricted LXR Inverse Agonists.

Hyperlipidemia and increased circulating cholesterol levels are associated with increased cardiovascular disease risk. The liver X receptors (LXRs) are regulators of de novo lipogenesis and cholesterol transport and have been validated as potential therapeutic targets for the treatment of atherosclerosis. However, efforts to develop LXR agonists to reduce cardiovascular diseases have failed due to poor clinical outcomes-associated increased hepatic lipogenesis and elevated low-density lipoprotein (LDL) cholesterol (C). Here, we report that LXR inverse agonists are effective in lowering plasma LDL cholesterol and triglycerides in several models of hyperlipidemia, including the Ldlr null mouse model of atherosclerosis. Mechanistic studies demonstrate that LXR directly regulates the expression of Soat2 enzyme in the intestine, which is directly responsible for the re-uptake or excretion of circulating lipids. Oral administration of a gut-specific LXR inverse agonist leads to reduction of Soat2 expression in the intestine and effectively lowers circulating LDL cholesterol and triglyceride levels without modulating LXR target genes in the periphery. In summary, our studies highlight the therapeutic potential of the gut-restricted molecules to treat hyperlipidemia and atherosclerosis through the intestinal LXR-Soat2 axis.

Renal Osteodystrophy due to Secondary Hyperparathyroidism in a Cat.

A 6 yr old neutered male mixed-breed cat presented for renal transplantation (RTx) for chronic kidney disease. Severe periodontal disease was identified, and before initiation of immunosuppressive therapy, a comprehensive oral health assessment and treatment procedure was performed to reduce the burden of existing oral infection. Dental radiography revealed diffuse, severe bone demineralization across the mandible and maxilla, with thinning of the cortices. Nasal turbinates were easily visualized owing to the decreased opacity of maxillary bone. Generalized bone resorption left teeth to appear minimally attached. A Vitamin D panel revealed a severely elevated parathyroid hormone level. Full mouth extractions were performed. Seven days following this procedure, RTx was performed. Serum creatinine concentration was within normal limits by 48 hr after surgery and remained normal until discharge 12 days after RTx. At 3.5 mo after RTx, the cat was mildly azotemic, and the parathyroid hormone level was elevated but significantly decreased from the original measurement. Secondary hyperparathyroidism is a common abnormality in cats with chronic kidney disease. However, clinical manifestations of hyperparathyroidism are rare in this species. This is a novel presentation of a cat demonstrating bone loss in the oral cavity as a result of renal secondary hyperparathyroidism.

Liver X receptors and liver physiology.

The liver x receptors LXRα (NR1H3) and LXRß (NR1H2) are members of the nuclear hormone receptor superfamily of ligand dependent transcription factors that regulate transcription in response to the direct binding of cholesterol derivatives. Studies using genetic knockouts and synthetic ligands have defined the LXRs as important modulators of lipid homeostasis throughout the body. This review focuses on the control of cholesterol and fatty acid metabolism by LXRs in the liver and how modifying LXR activity can influence the pathology of liver diseases.

Long-term effectiveness of a hyaluronic acid soft tissue filler in patients with facial lipoatrophy, morphological asymmetry, or debilitating scars.

BACKGROUND: Soft tissue fillers are typically used for rejuvenating an aging face; they are also employed in the treatment of certain pathologic conditions, including facial lipoatrophy, morphological asymmetry, and debilitating scars. AIMS: The aim of this clinical study was to evaluate the effectiveness and safety of Princess® Volume (PV) in patients with facial lipoatrophy (FLA), morphological asymmetry (MA), or debilitating scars (DS). PATIENTS/METHODS: This prospective, noncomparative, multicenter clinical study consisted of five visits spread across 36 weeks. Up to 60 adult patients suffering from moderate facial lipoatrophy, facial morphological asymmetry, or debilitating scars on the face were to be included. All patients were treated with an HA filler (PV). RESULTS: At Week 4, the treatment success rate in the SP was 98% (95% CI [90.4%, 100%]), as assessed by both the investigators and the patients. According to the independent reviewer, the success rate was 93% (95% CI [82.7%, 98.0%]). At Week 24, the effect was maintained in most patients, with success rates of 80% as evaluated by the investigator and 79% by the patient (95% CI [67.6%, 89.8%] and [65.6%, 88.4%], respectively). At Week 36, success rates dropped to 61% as assessed by the investigator and 59% by the patient (95% CI [46.8%, 73.5%] and [45.0%, 71.9%], respectively). CONCLUSIONS: The clinical study has proven that Princess® Volume is a safe and effective therapeutic solution for the correction of soft tissue defects in FLA and facial MA, but limited success rate to DS.

Inflammation Triggers Liver X Receptor-Dependent Lipogenesis.

Immune cell function can be modulated by changes in lipid metabolism. Our studies indicate that cholesterol and fatty acid synthesis increases in macrophages between 12 and 18 h after the activation of Toll-like receptors with proinflammatory stimuli and that the upregulation of lipogenesis may contribute to the resolution of inflammation. The inflammation-dependent increase in lipogenesis requires the induction of the liver X receptors, members of the nuclear receptor superfamily of transcription factors, by type I interferons in response to inflammatory signals. Instead of the well-established role for liver X receptors in stimulating cholesterol efflux, we demonstrate that liver X receptors are necessary for the proper resumption of cholesterol synthesis in response to inflammatory signals. Thus, liver X receptors function as bidirectional regulators of cholesterol homeostasis, driving efflux when cholesterol levels are high and facilitating synthesis in response to inflammatory signals. Liver X receptor activity is also required for the proper shutdown of a subset of type I interferon-stimulated genes as inflammation subsides, placing the receptors in a negative-feedback loop that may contribute to the resolution of the inflammatory response.

Structural analysis identifies an escape route from the adverse lipogenic effects of liver X receptor ligands.

Liver X receptors (LXRs) are attractive drug targets for cardiovascular disease treatment due to their role in regulating cholesterol homeostasis and immunity. The anti-atherogenic properties of LXRs have prompted development of synthetic ligands, but these cause major adverse effects-such as increased lipogenesis-which are challenging to dissect from their beneficial activities. Here we show that LXR compounds displaying diverse functional responses in animal models induce distinct receptor conformations. Combination of hydrogen/deuterium exchange mass spectrometry and multivariate analysis allowed identification of LXR regions differentially correlating with anti-atherogenic and lipogenic activities of ligands. We show that lipogenic compounds stabilize active states of LXRα and LXRß while the anti-atherogenic expression of the cholesterol transporter ABCA1 is associated with the ligand-induced stabilization of LXRα helix 3. Our data indicates that avoiding ligand interaction with the activation helix 12 while engaging helix 3 may provide directions for development of ligands with improved therapeutic profiles.

Exploring individual and social learning in jackdaws (Corvus monedula).

Information about novel environments or foods can be gathered via individual or social learning. Whereas individual learning is assumed to be more costly and less effective than social learning, it also yields more detailed information. Juveniles are often found to be more explorative than adults. Still under the protection of their parents, this allows them to sample their environment in preparation for later in life. We tested individual and social learning in jackdaws (Corvus monedula) of different age groups in a semi-natural group setting. Juvenile and adult jackdaws differed in their learning propensity. Juveniles spent more time at the test apparatus, were more explorative, and caused the apparatus to open. Almost all the openings at the apparatus matched the demonstrated method. As more observers became available, the juveniles could observe each other. Individuals preferentially watched successful conspecifics and those they could scrounge food from. Lower-ranking individuals tended to watch higher ranking ones; higher ranking individuals preferentially watched conspecifics of similar rank. The control group did not manipulate the apparatus. Due to the lack of this baseline, it was difficult to determine for certain whether the opening technique was acquired via individual or social learning. We conclude that if social learning played a role, the underlying mechanism was most likely local or stimulus enhancement. It is, however, more parsimonious to assume that juveniles were more explorative than adults, and that their opening technique was potentially easier to acquire than the one demonstrated to adults.

Eliciting the Student Perspective on Point-of-Care Diagnostic Testing in Association with a Primary Care Rotation.

The majority of North American veterinary students enter general practice upon graduation. Tertiary teaching hospitals provide extensive case exposure; however, primary case responsibility and decision making are often provided by clinical faculty members. Primary care services at veterinary teaching hospitals are a central component of student preparation for general practice. Primary care cases allow students to function as the primary clinician, making real-time clinical decisions. To better emulate a private practice veterinary hospital, point-of-care diagnostics (hematology, blood chemistry, and blood coagulation) were introduced into two primary care services in North American veterinary colleges. One objective of the study was to determine the influence of point-of-care testing on students' diagnostic selections and attitudes toward point-of-care diagnostics. An additional objective was to determine student perception of the impact of the primary care service on the development of clinical decision making and their technical skills. During the study period, 166 students voluntarily completed a pre-rotation survey, and 81 completed a post-rotation survey. Questions elicited student opinions regarding the value and application of point-of-care diagnostics in a general practice setting and whether a primary care service impacted the students' overall comfort level with case management. Point-of-care diagnostics were recognized as significant assets, with 98% of students agreeing that point-of-care diagnostics improved patient care and outcome. Results supported that primary care services provide valuable experiences for students as primary case clinicians, with 93% of respondents agreeing or strongly agreeing that the rotation improved their diagnostic ability and confidence.

AAVMC Internship Program Guidelines 2018.

Veterinary internships are common 1-year post-graduate clinical training programs that are offered both at veterinary colleges and in private practice settings. To promote the quality of these training programs, the American Association of Veterinary Medical Colleges (AAVMC) charged a working group to develop these internship guidelines, which were approved by the AAVMC in 2018 and have also been endorsed by the American Association of Veterinary Clinicians. These guidelines are intended to be applicable to all internships, in both academic and private practice settings, and they place particular emphasis on three aspects of internship training programs: competency-based education, intern well-being, and program outcome.

Treatment of facial lipoatrophy, morphological asymmetry, or debilitating scars with the hyaluronic acid dermal filler Princess® FILLER.

PURPOSE: The aim of this study was to evaluate the effectiveness and safety of hyaluronic acid (HA) dermal filler when used in the face for medical reconstructive purposes. PATIENTS AND METHODS: Adult patients with moderately severe facial lipoatrophy (FLA), morphological asymmetry (MA) of the face, or debilitating scars (DS) on the face were included in a prospective, noncomparative, multicenter, postmarket clinical follow-up study. All patients were treated with an HA filler (Princess® FILLER), which was injected intradermally on study Day 1, with optional touch-up 2 weeks later. The effectiveness of the treatment was evaluated at Weeks 4 and 24, using a six-grade scale ranging from "excellent" to "worsening". The assessments were conducted by both the investigator and the patient and, at Week 4, by the independent photography reviewer as well. Adverse events were collected at each visit. RESULTS: Fifty-three patients were included in the study (FLA 23, MA 17, and DS 13), and 46 patients completed a 6-month follow-up (FLA 20, MA 15, and DS 11). At Week 4 (primary endpoint), the overall treatment success rate was 100% (FLA), 100% (MA), and 94% (DS), based on assessments made by the investigator, patients, and the independent reviewer, respectively. In most patients (~95%), the effect was sustained over 6 months. Treatment-related adverse events were reported in five patients (9%) and included injection site hematoma, injection site pain, and headache. CONCLUSION: Dermal filling with HA gel is a viable treatment option for the correction of various deformities of the face resulting from FLA, MA, or DS.

Deficiency of Dab2 (Disabled Homolog 2) in Myeloid Cells Exacerbates Inflammation in Liver and Atherosclerotic Plaques in LDLR (Low-Density Lipoprotein Receptor)-Null Mice-Brief Report.

OBJECTIVE: Inflammatory macrophages promote the development of atherosclerosis. We have identified the adaptor protein Dab2 (disabled homolog 2) as a regulator of phenotypic polarization in macrophages. The absence of Dab2 in myeloid cells promotes an inflammatory phenotype, but the impact of myeloid Dab2 deficiency on atherosclerosis has not been shown. APPROACH AND RESULTS: To determine the role of myeloid Dab2 in atherosclerosis, Ldlr-/- mice were reconstituted with either Dab2-positive or Dab2-deficient bone marrow and fed a western diet. Consistent with our previous finding that Dab2 inhibits NFκB (nuclear factor κ-light-chain-enhancer of activated B cells) signaling in macrophages, Ldlr-/- mice reconstituted with Dab2-deficient bone marrow had increased systemic inflammation as evidenced by increased serum IL-6 (interleukin-6) levels and increased inflammatory cytokine expression levels in liver. Serum lipid levels were significantly lower in Ldlr-/- mice reconstituted with Dab2-deficient bone marrow, and further examination of livers from these mice revealed drastically increased inflammatory tissue damage and massive infiltration of immune cells. Surprisingly, the atherosclerotic lesion burden in Ldlr-/- mice reconstituted with Dab2-deficient bone marrow was decreased compared with Ldlr-/- mice reconstituted with wild-type bone marrow. Further analysis of aortic root sections revealed increased macrophage content and evidence of increased apoptosis in lesions from Ldlr-/- mice reconstituted with Dab2-deficient bone marrow but no difference in collagen or α-smooth muscle actin content. CONCLUSIONS: Dab2 deficiency in myeloid cells promotes inflammation in livers and atherosclerotic plaques in a mouse model of atherosclerosis. Nevertheless, decreased serum lipids as a result of massive inflammatory liver damage may preclude an appreciable increase in atherosclerotic lesion burden in mice reconstituted with Dab2-deficient bone marrow.

The Transcription Factor STAT6 Mediates Direct Repression of Inflammatory Enhancers and Limits Activation of Alternatively Polarized Macrophages.

The molecular basis of signal-dependent transcriptional activation has been extensively studied in macrophage polarization, but our understanding remains limited regarding the molecular determinants of repression. Here we show that IL-4-activated STAT6 transcription factor is required for the direct transcriptional repression of a large number of genes during in vitro and in vivo alternative macrophage polarization. Repression results in decreased lineage-determining transcription factor, p300, and RNA polymerase II binding followed by reduced enhancer RNA expression, H3K27 acetylation, and chromatin accessibility. The repressor function of STAT6 is HDAC3 dependent on a subset of IL-4-repressed genes. In addition, STAT6-repressed enhancers show extensive overlap with the NF-κB p65 cistrome and exhibit decreased responsiveness to lipopolysaccharide after IL-4 stimulus on a subset of genes. As a consequence, macrophages exhibit diminished inflammasome activation, decreased IL-1ß production, and pyroptosis. Thus, the IL-4-STAT6 signaling pathway establishes an alternative polarization-specific epigenenomic signature resulting in dampened macrophage responsiveness to inflammatory stimuli.

Complications of Uveitis: The Northern California Epidemiology of Uveitis Study.

PURPOSE: To describe the uveitis complications in a large, community-based cohort. METHODS: Retrospective, community-based, cross-sectional cohort study analyzing complications and associations with complications. RESULTS: A total of 844 cases of uveitis were found; 342 were new-onset, and 462 were prior-onset. In total, 29.5% of patients were affected by one or more complications associated with age, gender, course, and anatomic location of uveitis. Visual loss was experienced by 19.1% of patients and was associated with age, course of disease, and anatomic location of uveitis. Of the patients who developed glaucoma or elevated intraocular pressure over 30 mmHg, 3.9% (n = 33) were related solely to uveitis; 5.2% (n = 44) had an unclear or combined mechanism; and 1.8% (n = 15) were related solely to steroid response. Cystoid macular edema was associated with course of disease and anatomic location of uveitis. CONCLUSIONS: Complications affect a significant portion of uveitis patients, and are often associated with demographic and clinical factors.

Liver X receptors link lipid metabolism and inflammation.

The response of immune cells to pathogens is often associated with changes in the flux through basic metabolic pathways. Indeed, in many cases changes in metabolism appear to be necessary for a robust immune response. The Liver X receptors (LXRs) are members of the nuclear hormone receptor superfamily that regulate gene networks controlling cholesterol and lipid metabolism. In immune cells, particularly in macrophages, LXRs also inhibit proinflammatory gene expression. This Review will highlight recent studies that connect LXR-dependent control of lipid metabolism to regulation of the immune response.