Real-world use patterns of angiotensin receptor-neprilysin inhibitor (sacubitril/valsartan) among patients with heart failure within a large integrated health system.

BACKGROUND: Sacubitril/valsartan is a first-in-class angiotensin receptor-neprilysin inhibitor (ARNI) that is now preferred in guidelines over angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) for patients with heart failure with reduced ejection fraction (HFrEF). However, it has not been broadly adopted in clinical practice. OBJECTIVE: To characterize ARNI use within a large diverse real-world population and assess for any racial disparities. METHODS: We conducted a cross-sectional study within Kaiser Permanente Southern California. Adult patients with HFrEF who received ARNIs, ACEIs, or ARBs between January 1, 2014, and November 30, 2020, were identified. The prevalence of ARNI use among the cohort and patient characteristics by ARNIs vs ACEIs/ARBs use were described. Multivariable regression was performed to estimate odds ratios and 95% CIs of receiving ARNI by race and ethnicity. RESULTS: Among 12,250 patients with HFrEF receiving ACEIs, ARBs, or ARNIs, 556 (4.54%) patients received ARNIs. ARNI use among this cohort increased from 0.02% in 2015 to 7.48% in 2020. Patients receiving ARNIs were younger (aged 62 vs 69 years) and had a lower median ejection fraction (27% vs 32%) compared with patients receiving ACEIs/ARBs. They also had higher use of mineralocorticoid antagonists (24.1% vs 19.8%) and automatic implantable cardioverterdefibrillators (17.4% vs 13.3%). There were no significant differences in rate of ARNI use by race and ethnicity. CONCLUSIONS: Within a large diverse integrated health system in Southern California, the rate of ARNI use has risen over time. Patients given ARNIs were younger with fewer comorbidities, while having worse ejection fraction. Racial minorities were no less likely to receive ARNIs compared with White patients. DISCLOSURES: Dr Huang had stock ownership in Gilead and Pfizer. Dr Liang received support for article processing and medical writing.

Gut microbiome changes in Nonalcoholic fatty liver disease & alcoholic liver disease.

Nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) are some of the most common liver diseases worldwide. The human gut microbiome is dynamic and shifts in bacterial composition have been implicated in many diseases. Studies have shown that there is a shift in bacterial overgrowth favoring pro-inflammatory mediators in patients with advanced disease progression such as cirrhosis. Further investigation demonstrated that the transplantation of gut microbiota from advanced liver disease patients can reproduce severe liver inflammation and injury in mice. Various techniques in manipulating the gut microbiota have been attempted including fecal transplantation and probiotics. This review focuses on the changes in the gut microbiota as well as emerging lines of microbiome work with respect to NAFLD and ALD.

Sphingosine-1-phosphate signaling and the gut-liver axis in liver diseases.

The liver is the central organ involved in lipid metabolism and the gastrointestinal (GI) tract is responsible for nutrient absorption and partitioning. Obesity, dyslipidemia and metabolic disorders are of increasing public health concern worldwide, and novel therapeutics that target both the liver and the GI tract (gut-liver axis) are much needed. In addition to aiding fat digestion, bile acids act as important signaling molecules that regulate lipid, glucose and energy metabolism via activating nuclear receptor, G protein-coupled receptors (GPCRs), Takeda G protein receptor 5 (TGR5) and sphingosine-1-phosphate receptor 2 (S1PR2). Sphingosine-1-phosphate (S1P) is synthesized by two sphingosine kinase isoforms and is a potent signaling molecule that plays a critical role in various diseases such as fatty liver, inflammatory bowel disease (IBD) and colorectal cancer. In this review, we will focus on recent findings related to the role of S1P-mediated signaling pathways in the gut-liver axis.

The role of sphingosine kinase 2 in alcoholic liver disease.

Alcoholic liver disease (ALD) is one of the most common liver diseases worldwide. However, the exact mechanisms underlying ALD remain unclear. Previous studies reported that sphingosine kinase 2 (SphK2) plays an essential role in regulating hepatic lipid metabolism. In the current study, we demonstrate that compared to wild-type (WT) mice, SphK2 deficient (SphK2-/-) mice exhibited a greater degree of liver injury and hepatic lipid accumulation after feeding with an alcohol diet for 60 days. This is accompanied by a down-regulation of steroid 7-alpha-hydroxylase (Cyp7b1) and an up-regulation of pro-inflammatory mediators (Tnfα, F4/80, Il-1ß). In vitro experiments showed that alcohol induced SphK2 expression in mouse primary hepatocytes and cultured mouse macrophages. Furthermore, alcohol feeding induced a more severe intestinal barrier dysfunction in SphK2-/- mice than WT mice. Deficiency of SphK2 impaired the growth of intestinal organoids. Finally, SphK2 expression levels were down-regulated in the livers of human patients with alcoholic cirrhosis and hepatocellular carcinoma compared to healthy controls. In summary, these findings suggest that SphK2 is a crucial regulator of hepatic lipid metabolism and that modulating the SphK2-mediated signaling pathway may represent a novel therapeutic strategy for the treatment of ALD and other metabolic liver diseases.

Sphingosine Kinases/Sphingosine 1-Phosphate Signaling in Hepatic Lipid Metabolism.

The ever-increasing prevalence of metabolic diseases such as dyslipidemia and diabetes in the western world continues to be of great public health concern. Biologically active sphingolipids, such as sphingosine 1-phosphate (S1P) and ceramide, are important regulators of lipid metabolism. S1P not only directly functions as an active intracellular mediator, but also activates multiple signaling pathways via five transmembrane G-protein coupled receptors (GPCRs), S1PR1-5. S1P is exclusively formed by sphingosine kinases (SphKs). Two isoforms of SphKs, SphK1 and SphK2, have been identified. Recent identification of the conjugated bile acid-induced activation of S1PR2 as a key regulator of SphK2 opened new directions for both the sphingolipid and bile acid research fields. The role of SphKs/S1P-mediated signaling pathways in health and various human diseases has been extensively reviewed elsewhere. This review focuses on recent findings related to SphKs/S1P-medaited signaling pathways in regulating hepatic lipid metabolism.

Characterization of Nrf1b, a novel isoform of the nuclear factor-erythroid-2 related transcription factor-1 that activates antioxidant response element-regulated genes.

Nuclear factor E2-related factor 1 (Nrf1) is a basic leucine zipper transcription factor that plays an important role in the activation of cytoprotective genes through the antioxidant response elements. The previously characterized long isoform of Nrf1 (Nrf1a) is targeted to the endoplasmic reticulum and accumulates in the nucleus in response to activating signals. Here we characterized a novel Nrf1 protein isoform (Nrf1b) generated through an alternative promoter and first exon that lacks the ER targeting domain of Nrf1a. The 5'-flanking region of Nrf1b directed high levels of luciferase reporter expression in cells. RT-PCR and Western blotting showed Nrf1b is widely expressed in various cell lines and mouse tissues. Immunoblot analysis of subcellular fractions and imaging of green fluorescence protein (GFP)-tagged Nrf1b demonstrate Nrf1b is constitutively localized to the nucleus. Nrf1b can activate GAL4-dependent transcription when fused to the heterologous GAL4 DNA-binding domain. Gel-shift and coimmunoprecipitation experiments demonstrate that Nrf1b forms a complex with MafG, and expression of Nrf1b activates the expression of antioxidant response element containing reporters and genes in cells. These results suggest Nrf1b is targeted to the nucleus where it activates ARE-driven genes and may play a role in modulating antioxidant response elements.