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BackgroundChildren with obesity have hypertrophic cardiac remodeling. Hypertension is common in pediatric obesity, and may independently contribute to hypertrophy. We hypothesized that both the degree of obesity and ambulatory blood pressure (ABP) would independently associate with measures of hypertrophic cardiac remodeling in children.MethodsChildren, aged 8–17 years, prospectively underwent cardiovascular magnetic resonance (CMR) and ABP monitoring. Left ventricular (LV) mass indexed to height2.7 (LVMI), myocardial thickness and end-diastolic volume were quantified from a 3D LV model reconstructed from cine balanced steady state free precession images. Categories of remodeling were determined based on cutoff values for LVMI and mass/volume. Principal component analysis was used to define a “hypertrophy score” to study the continuous relationship between concentric hypertrophy and ABP.ResultsSeventy-two children were recruited, and 68 of those (37 healthy weight and 31 obese/overweight) completed both CMR and ABP monitoring. Obese/overweight children had increased LVMI (27 ± 4 vs 22 ± 3 g/m2.7, p < 0.001), myocardial thickness (5.6 ± 0.9 vs 4.9 ± 0.7 mm, p < 0.001), mass/volume (0.69 ± 0.1 vs 0.61 ± 0.06, p < 0.001), and hypertrophy score (1.1 ± 2.2 vs −0.96 ± 1.1, p < 0.001). Thirty-five percent of obese/overweight children had concentric hypertrophy. Ambulatory hypertension was observed in 26% of the obese/overweight children and none of the controls while masked hypertension was observed in 32% of the obese/overweight children and 16% of the controls. Univariate linear regression showed that BMI z-score, systolic BP (24 h, day and night), and systolic load correlated with LVMI, thickness, mass/volume and hypertrophy score, while 24 h and nighttime diastolic BP and load also correlated with thickness and mass/volume. Multivariate analysis showed body mass index z-score and systolic blood pressure were both independently associated with left ventricular mass index (β=0.54 [p < 0.001] and 0.22 [p = 0.03]), thickness (β=0.34 [p < 0.001] and 0.26 [p = 0.001]) and hypertrophy score (β=0.47 and 0.36, both p < 0.001).ConclusionsIn children, both the degree of obesity and ambulatory blood pressures are independently associated with measures of cardiac hypertrophic remodeling, however the correlations were generally stronger for the degree of obesity. This suggests that interventions targeted at weight loss or obesity-associated co-morbidities including hypertension may be effective in reversing or preventing cardiac remodeling in obese children.

SummaryThe E4 allele of Apolipoprotein E (APOE) is associated with both metabolic dysfunction and a heightened pro-inflammatory response – two findings that may be intrinsically linked through the concept of immunometabolism. Here, we combined bulk, single-cell, and spatial transcriptomics with cell-specific and spatially resolved metabolic analyses to systematically address the role of APOE across age, neuroinflammation, and AD pathology. RNAseq highlighted immunometabolic changes across the APOE4 glial transcriptome, specifically in subsets of metabolically distinct microglia enriched in the E4 brain during aging or following an inflammatory challenge. E4 microglia display increased Hif1α expression, a disrupted TCA cycle, and are inherently pro-glycolytic, while spatial transcriptomics and MALDI mass spectrometry imaging highlight an E4-specific response to amyloid that is characterized by widespread alterations in lipid metabolism. Taken together, our findings emphasize a central role for APOE in regulating microglial immunometabolism.

BackgroundThe microglial immune response is a significant contributor to Alzheimer’s disease (AD) pathophysiology and neurodegeneration. Aging microglia accumulate lipid droplets (LDs), have high levels of reactive oxygen species, secrete pro‐inflammatory cytokines, and are defective in phagocytosis. The E4 allele of Apolipoprotein E (APOE) is the strongest genetic risk factor for late‐onset AD, and is associated with heightened neuroinflammation and increased LD formation. We hypothesize E4 microglia have increased LD formation under basal conditions and a higher capacity to form LDs under stress, resulting in greater pro‐inflammatory cytokine production. We characterized LD development in microglia in the context of APOE genotype and analyzed LD surface proteins and lipid content from control and lipopolysaccharide (LPS) stimulated ApoE3 and ApoE4 mice.MethodPrimary microglia were isolated from mice expressing human ApoE3 and ApoE4. Microglia were exposed to 250uM oleic acid (OA), 10ug/mL LPS, OA+LPS, dead N2A cells, or dead N2As+LPS. ApoE3 and ApoE4 expressing mice were injected with saline (control) or LPS (5mg/kg) and perfused at 24h. Livers were extracted, the LD enriched supernatant fraction was collected after centrifugation, and proteomic and lipidomic analyses were performed.ResultPrimary microglia from ApoE4 mice accumulated more LDs at baseline, with exogenous OA, LPS stimulation, and N2As as a percentage of E3 control across multiple experiments (E3 v E4 p‐values: baseline, 0.0317; LPS, 0.0032; OA, 0.0277; N2A, 0.0192). Western blots on LD fractions confirm LD enrichment by surface protein, PLIN2, along with increased expression of PLIN2 (i.e. more LDs) in E4 LPS mice. Proteomics reveal LD fractions from E4 mice are enriched for proteins involved in innate immunity, while E3 LDs are enriched for proteins involved in lipid b‐oxidation.ConclusionE4 microglia accumulate more LDs compared to E3 microglia under all conditions tested. The proteomic profile of E4 liver LDs support the hypothesis that E4 expression increases inflammation under basal conditions, and upon stimulation, causes a more robust response. Increased LD formation is present in non‐aged, non‐diseased E4 cells, suggesting preclinical dysfunction associated with the highest risk APOE genotype. A better understanding of LD dynamics within these cells and their functional implications can provide targets to improve E4‐related outcomes.

BackgroundMetabolic dysfunction and neuroinflammation characterize Alzheimer’s disease (AD), but it is unclear if these two facets of the disease are linked. The E4 allele of Apolipoprotein E (APOE) is the strongest genetic risk factor for late‐onset AD and is associated with increased neuroinflammation. Recent data from our lab and others show that E4 is also associated with increased aerobic glycolysis. These two findings may be intrinsically linked through the concept of ‘immunometabolism’ ‐ an emerging paradigm that implicates increased glycolysis as a core requirement during pro‐inflammatory activation, whereas increased oxidative phosphorylation is required for anti‐inflammatory responses.MethodPrimary microglia were isolated from targeted replacement mice expressing human APOE isoforms and stimulated with pro‐inflammatory (lipopolysaccharide (LPS); IFNγ + TNFα) or anti‐inflammatory (IL‐10; IL‐4 + IL‐13) cytokines. Metabolic responses were measured using the Agilent Seahorse platform and targeted metabolomics. We also performed single‐cell RNA sequencing on brains from APOE targeted replacement mice at 3‐, 10‐, and 18 months of age +/‐ LPS.ResultSeahorse revealed increased glycolysis and decreased mitochondrial respiration in E4 microglia. Targeted metabolomics revealed increased lactate and succinate in E4 microglia, metabolites known to accumulate in pro‐inflammatory macrophages. Aged E4 brains were uniquely found to harbor a metabolically distinct subcluster of microglia that expressed a signature similar to the established ‘disease associated microglia’ phenotype, even in the absence of neuropathology. SCENIC regulon analysis linked this cluster to the transcription network of HIF1a, and increased expression of HIF1a was validated in E4 microglia. In LPS‐treated animals, two distinct microglia subclusters emerged in E4 brains that were defined by altered expression of genes relating to oxidative phosphorylation and mitochondrial function.ConclusionOur findings reveal that age and LPS treatment induce a distinct metabolic response in E4 microglia. The accumulation of lactate and succinate and increased glycolysis in E4 microglia indicate altered metabolic preference conducive to pro‐inflammatory activation, whereas the decreased mitochondrial respiration may preclude effective anti‐inflammatory responses. We propose that this altered metabolism skews E4 microglia towards a phenotype that favors chronic neuroinflammation and neurodegeneration. Thus, reprogramming metabolism in E4 microglia may provide a novel therapeutic avenue for the treatment of AD.