Faculty Bibliography

BACKGROUND & AIM/UNASSIGNED:Metabolic dysfunction-associated steatotic liver disease (MASLD) is a growing health issue. Identifying factors that prevent hepatic lipid accumulation could inform new MASLD prevention or treatment strategies. We previously demonstrated that adipocyte microsomal triglyceride transfer protein (MTP) regulates intracellular lipolysis by inhibiting adipose triglyceride lipase activity. The aim of this study was to investigate the impact of adipose MTP deficiency on MASLD. METHODS/UNASSIGNED: RESULTS/UNASSIGNED: CONCLUSION/UNASSIGNED:These findings highlight the importance of regulated FA flux from adipose tissue to the liver and the liver's adaptive capacity to utilize adipose-derived FAs in maintaining hepatic health. Modulation of adipocyte FA release may represent a therapeutic strategy to reduce hepatic steatosis. IMPACT AND IMPLICATIONS/UNASSIGNED:This study provides significant insights into the role of adipose-specific microsomal triglyceride transfer protein in regulating hepatic lipid metabolism and its potential implications for treating metabolic dysfunction-associated steatotic liver disease. By demonstrating that microsomal triglyceride transfer protein deficiency in adipose tissue leads to increased fatty acid oxidation and reduced hepatic steatosis through enhanced PPARα activation, the research underscores the importance of adipose-liver crosstalk in maintaining liver health. These findings suggest that targeting adipocyte fatty acid release could be a promising therapeutic strategy to mitigate hepatic lipid accumulation and combat metabolic dysfunction-associated steatotic liver disease, offering a novel approach to addressing this growing health issue.

Excessive accumulation of lipids within cardiomyocytes can sometimes initiate cardiomyopathy, while in other situations excess lipids do not cause harm. To understand how pathologic and non-pathologic lipid accumulation differ, we isolated lipid droplets (LDs) from two genetically altered mouse lines and from wild-type (WT) mice after an overnight fast. The LDs from MHC-peroxisomal proliferator-activated receptor γ1(MHC-Pparg1) transgenic mice were threefold larger than those from either fasted WT or non-cardiomyopathy MHC-diacylglycerol acyl transferase 1 (MHC-Dgat1) transgenic mice. Proteomic analysis of the LD-associated membrane proteins (LDAMPs) showed that MHC-Pparg1 LDs had less perilipin (PLIN). Proteins associated with lipolysis and LD formation (CIDEs and MTP), lipid synthesis, and Pparg signaling pathways were increased in MHC-Pparg1 LDAMPs. Unlike in MHC-Pparg1, MHC-Dgat1 LDAMPs exhibited increased mitochondrial peroxidative proteins with reduced adipose triglyceride lipase (Pnpla2), and Pparg coactivator 1 alpha (Pgc1A). Cardiomyocytes from MHC-Pparg1 hearts had transmission electron microscopy (TEM) images of ongoing lipolysis and greater amounts of lipolytic proteins. In contrast, images from MHC-Dgat1 cardiomyocytes showed more lipophagy. Consistent with the proteomic study and EM images, cardiac immunofluorescence staining showed that PLIN5 protein, thought to block LD lipolysis, was markedly reduced with MHC-Pparg1 overexpression, while hormone-sensitive lipase was increased. The autophagosome marker protein LC3B was increased in MHC-Dgat1 but not in MHC-Pparg1 hearts. Potentially toxic lipids like diacylglycerols and ceramides were increased in hearts but not LDs from MHC-Pparg1 mice. Our data indicate that cardiomyocyte LDs vary in size, composition, and metabolism. Cardiotoxicity was associated with greater LD lipolysis, which we postulate leads to intracellular release of toxic lipids.

BACKGROUND/UNASSIGNED:Movement of circulating lipids into tissues and arteries requires transfer across the endothelial cell (EC) barrier. This process allows the heart to obtain fatty acids, its chief source of energy, and apoB-containing lipoproteins to cross the arterial endothelial barrier, leading to cholesterol accumulation in the subendothelial space. Multiple studies have established elevated postprandial TRLs (triglyceride-rich lipoproteins) as an independent risk factor for cardiovascular disease. We explored how chylomicrons affect ECs and transfer their fatty acids across the EC barrier. METHODS/UNASSIGNED:C]oleate, we studied the uptake and release of this labeled by ECs. RESULTS/UNASSIGNED:]C labeled chylomicron triglycerides exited ECs primarily in phospholipids. EVs from chylomicron-treated versus untreated ECs were larger, more abundant, and contained specific microRNAs. Treatment of macrophages and naive ECs with media from chylomicron-treated ECs increased expression of inflammatory genes. CONCLUSIONS/UNASSIGNED:EC chylomicron metabolism produces EVs that increase macrophage inflammation and create LDs. Media containing these EVs also increases EC inflammation, illustrating an autocrine inflammatory process. Fatty acids within chylomicron triglycerides are converted to phospholipids within EVs. Thus, EC uptake of chylomicrons constitutes an important pathway for vascular inflammation and tissue lipid acquisition.

AIMS/OBJECTIVE:Activation of the transcriptional factor Krüppel-like factor 5 (KLF5) is detrimental to chronic heart failure. We explored the involvement of KLF5 in myocardial ischemia/reperfusion injury. METHODS AND RESULTS/RESULTS:Yorkshire pigs underwent 75΄ of ischemia, followed by 3h or 24h of reperfusion. C57BL/6J mice underwent 30΄ of ischemia, followed by 10', 2h, 12h, 24h, or 4 weeks of reperfusion. Hearts and isolated cardiomyocytes were analyzed for gene expression. We assessed cardiac function, infarct size (IS), oxidative stress, and fibrosis in mice subjected to pharmacologic or genetic KLF5 inhibition, as well as pharmacologic inhibition of NADPH oxidases or Glucose Transporter (GLUT)1 and GLUT4. Bulk RNA sequencing, untargeted 1H-NMR metabolomics and LC-MS lipidomics were performed. Isolated primary murine cardiomyocytes were infected with recombinant adenovirus expressing KLF5. During reperfusion, cardiοmyocyte KLF5 expression was increased in porcine and murine hearts. Pharmacologic or cardiomyocyte-specific genetic inhibition of KLF5 reduced IS and improved cardiac function in mice. Importantly, acute KLF5 inhibition during early reperfusion suppressed fibrosis and preserved systolic cardiac function 4 weeks post-ischemia/reperfusion. This improvement was associated with lower NOX4 expression, less oxidative stress, and suppressed inflammation and cell apoptosis. Pharmacologic inhibition of NOX4 conferred the same benefit. Metabolomic analysis indicated that KLF5 inhibition lowered glucose-derived metabolites (UDP-Glucose and Lactate) at early reperfusion. Accordingly, cardiac GLUT1 and GLUT4 levels were increased with ischemia/reperfusion, which was reverted by KLF5 inhibition. Pharmacologic inhibition of both GLUT1/4 reduced IS. Finally, myocardial KLF5 overexpression increased GLUT1 mRNA levels and mouse mortality. CONCLUSIONS:Ischemia/reperfusion increases cardiomyocyte KLF5 expression in pigs and mice. This constitutes a central element of myocardial injury pathophysiology and is associated with stimulation of GLUT1 and GLUT4 expression, activation of NOX4, oxidative stress, inflammation and apoptosis. Acute KLF5 inhibition during reperfusion constitutes a novel therapeutic approach against myocardial ischemia/reperfusion injury.

Angiopoietin-like 3 (ANGPTL3) inhibits lipases that hydrolyze triglycerides (TGs) in TG-rich lipoproteins (TRLs). We evaluated TRL-TGs, TRL particle (apolipoprotein B), palmitate, and glucose kinetics during a mixed-meal test that included intravenous and oral tracer administrations in people with extremely rare compound heterozygous ANGTPL3 loss-of-function mutations (ANGPTL3^-/- group, n = 3) and matched control participants (n = 7). Multi-organ (liver, muscle, and adipose tissue) insulin sensitivity was evaluated with a two-step hyperinsulinemic-euglycemic clamp procedure and glucose and palmitate tracer infusions. We find that plasma TG and TRL particle concentrations are more than 10-fold lower in the ANGPTL3^-/- than in the control group due to both markedly reduced liver-derived TRL particle and TG secretion rates combined with increased plasma clearance of both liver- and gut-derived TRLs. Palmitate and glucose kinetics during the meal test are not different between the groups. We conclude that the biological function of ANGPTL3 reaches beyond inhibiting intravascular lipase activity.

AIMS/HYPOTHESIS/OBJECTIVE:Microvascular dysfunction contributes to insulin resistance. CD36, a fatty acid transporter and modulator of insulin signalling, is abundant in microvascular endothelial cells. Humans carrying the minor allele (G) of CD36 coding variant rs3211938 have 50% reduced CD36 expression and show endothelial dysfunction. We aimed to determine whether G allele carriers have microvascular resistance to insulin and, if so, how this affects glucose disposal. METHODS:and wild-type mice, and in individuals with 50% CD36 deficiency, together with control counterparts, in addition to primary human-derived microvascular endothelial cells with/without CD36 depletion. RESULTS:mice have enhanced insulin-stimulated glucose disposal but reduced vascular compliance and capillary perfusion. Intravital microscopy of the gastrocnemius showed unaltered transcapillary insulin flux. CD36-deficient humans had better insulin-stimulated glucose disposal but insulin-unresponsive microvascular blood volume (MBV). Human microvascular cells depleted of CD36 showed impaired insulin activation of Akt, endothelial NO synthase and NO generation. Thus, in CD36 deficiency, microvascular insulin resistance paradoxically associated with enhanced insulin sensitivity of glucose disposal. CONCLUSIONS/INTERPRETATION/CONCLUSIONS:CD36 deficiency was previously shown to reduce muscle/heart fatty acid uptake, whereas here we showed that it reduced vascular compliance and the ability of insulin to increase MBV for optimising glucose and oxygen delivery. The muscle and heart respond to these energy challenges by transcriptional remodelling priming the tissue for insulin-stimulated glycolytic flux. Reduced oxygen delivery activating hypoxia-induced factors, endothelial release of growth factors or small intracellular vesicles might mediate this adaptation. Targeting NO bioavailability in CD36 deficiency could benefit the microvasculature and muscle/heart metabolism. TRIAL REGISTRATION/BACKGROUND:Clinicaltrials.gov NCT03012386 DATA AVAILABILITY: The RNAseq data generated in this study have been deposited in the NCBI Gene Expression Omnibus ( www.ncbi.nlm.nih.gov/geo/ ) under accession code GSE235988 ( https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE235988 ).

BACKGROUND:Persistent chylomicronemia is a genetic recessive disorder that is classically caused by familial chylomicronemia syndrome (FCS), but it also has multifactorial causes. The disorder is associated with the risk of recurrent acute pancreatitis. Plozasiran is a small interfering RNA that reduces hepatic production of apolipoprotein C-III and circulating triglycerides. METHODS:In a phase 3 trial, we randomly assigned 75 patients with persistent chylomicronemia (with or without a genetic diagnosis) to receive subcutaneous plozasiran (25 mg or 50 mg) or placebo every 3 months for 12 months. The primary end point was the median percent change from baseline in the fasting triglyceride level at 10 months. Key secondary end points were the percent change in the fasting triglyceride level from baseline to the mean of values at 10 months and 12 months, changes in the fasting apolipoprotein C-III level from baseline to 10 months and 12 months, and the incidence of acute pancreatitis. RESULTS:At baseline, the median triglyceride level was 2044 mg per deciliter. At 10 months, the median change from baseline in the fasting triglyceride level (the primary end point) was -80% in the 25-mg plozasiran group, -78% in the 50-mg plozasiran group, and -17% in the placebo group (P<0.001). The key secondary end points showed better results in the plozasiran groups than in the placebo group, including the incidence of acute pancreatitis (odds ratio, 0.17; 95% confidence interval, 0.03 to 0.94; P = 0.03). The risk of adverse events was similar across groups; the most common adverse events were abdominal pain, nasopharyngitis, headache, and nausea. Severe and serious adverse events were less common with plozasiran than with placebo. Hyperglycemia with plozasiran occurred in some patients with prediabetes or diabetes at baseline. CONCLUSIONS:Patients with persistent chylomicronemia who received plozasiran had significantly lower triglyceride levels and a lower incidence of pancreatitis than those who received placebo. (Funded by Arrowhead Pharmaceuticals; PALISADE ClinicalTrials.gov number, NCT05089084.).

BACKGROUND:Lipoprotein(a) [Lp(a)] is a driver of residual cardiovascular risk. Proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) decrease Lp(a) with significant heterogeneity in response. We investigated contributors to the heterogeneous response. METHODS:CHOlesterol Reduction and Residual Risk in Diabetes (CHORD) was a prospective study examining lipid lowering in participants with a low-density lipoprotein cholesterol (LDL-C) >100 mg/dL with and without diabetes (DM) on lipid lowering therapy (LLT) for 30-days with evolocumab 140 mg every 14 days combined with either atorvastatin 80 mg or ezetimibe 10 mg daily. Lp(a) level was measured by immunoturbidometry, and the apolipoprotein (a) [apo(a)] isoform size was measured by denaturing agarose gel electrophoresis and western blotting. We examined the change in Lp(a) levels from baseline to 30 days. RESULTS:Among 150 participants (mean age 50 years, 58% female, 50% non-White, 17% Hispanic, 50% DM), median (interquartile range) Lp(a) was 27.5 (8-75) mg/dL at baseline and 23 (3-68) mg/dL at 30 days, leading to a 10% (0-36) median reduction (P < 0.001). Among 73 (49%) participants with Lp(a) ≥30 mg/dL at baseline, there was a 15% (3-25) median reduction in Lp(a) (P < 0.001). While baseline Lp(a) level was not correlated with change in Lp(a) (r = 0.04, P = 0.59), apo(a) size directly correlated with Lp(a) reduction (P < 0.001). After adjustment for age, sex, race/ethnicity, DM, and type of LLT, apo(a) size remained positively associated with a reduction in Lp(a) (Beta 0.95, 95% confidence interval, 0.93-0.97, P < 0.001). CONCLUSION/CONCLUSIONS:Our data demonstrate variation in Lp(a) reduction with potent LLT. Change in Lp(a) was strongly associated with apo(a) isoform size.

Immune checkpoint inhibitor (ICI) therapies can increase the risk of cardiovascular events in survivors of cancer by worsening atherosclerosis. Here we map the expression of immune checkpoints (ICs) within human carotid and coronary atherosclerotic plaques, revealing a network of immune cell interactions that ICI treatments can unintentionally target in arteries. We identify a population of mature, regulatory CCR7⁺FSCN1⁺ dendritic cells, similar to those described in tumors, as a hub of IC-mediated signaling within plaques. Additionally, we show that type 2 diabetes and lipid-lowering therapies alter immune cell interactions through PD-1, CTLA4, LAG3 and other IC targets in clinical development, impacting plaque inflammation. This comprehensive map of the IC interactome in healthy and cardiometabolic disease states provides a framework for understanding the potential adverse and beneficial impacts of approved and investigational ICIs on atherosclerosis, setting the stage for designing ICI strategies that minimize cardiovascular disease risk in cancer survivors.