SUMMARY Impaired angiogenesis has been implicated in adipose tissue dysfunction and the development of obesity and associated metabolic disorders. Here, we report the unexpected finding that vascular endothelial growth factor B (VEGFB) gene transduction into mice inhibits obesity-associated inflammation and improves metabolic health without changes in body weight or ectopic lipid deposition. Mechanistically, the binding of VEGFB to VEGF receptor 1 (VEGFR1, also known as Flt1) activated the VEGF/VEGFR2 pathway and increased capillary density, tissue perfusion, and insulin supply, signaling, and function in adipose tissue. Furthermore, endothelial Flt1 gene deletion enhanced the effect of VEGFB, activating the thermogenic program in subcutaneous adipose tissue, which increased the basal metabolic rate, thus preventing diet-induced obesity and related metabolic complications. In obese and insulin-resistant mice, Vegfb gene transfer, together with endothelial Flt1 gene deletion, induced weight loss and mitigated the metabolic complications, demonstrating the therapeutic potential of the VEGFB/VEGFR1 pathway.

Background: Endothelial cells (ECs) display considerable functional heterogeneity depending on the vessel and tissue in which they are located. While these functional differences are presumably imprinted in the transcriptome, the pathways and networks which sustain EC heterogeneity have not been fully delineated. Methods: To investigate the transcriptomic basis of EC specificity, we analyzed single-cell RNA-sequencing (scRNA-seq) data from tissue-specific mouse ECs generated by the Tabula Muris consortium. We employed a number of bioinformatics tools to uncover markers and sources of EC heterogeneity from scRNA-seq data. Results: We found a strong correlation between tissue-specific EC transcriptomic measurements generated by either scRNA-seq or bulk RNA-seq, thus validating the approach. Using a graph-based clustering algorithm, we found that certain tissue-specific ECs cluster strongly by tissue (e.g. liver, brain) whereas others (i.e. adipose, heart) have considerable transcriptomic overlap with ECs from other tissues. We identified novel markers of tissue-specific ECs and signaling pathways that may be involved in maintaining their identity. Sex was a considerable source of heterogeneity in the endothelial transcriptome and we discovered Lars2 to be a gene that is highly enriched in ECs from male mice. In addition, we found that markers of heart and lung ECs in mice were conserved in human fetal heart and lung ECs. Finally, we identified potential angiocrine interactions between tissue-specific ECs and other cell types by analyzing ligand and receptor expression patterns. Conclusions: In summary, we use scRNA-seq data generated by the Tabula Muris consortium to uncover transcriptional networks that maintain tissue-specific EC identity and to identify novel angiocrine and functional relationships between tissue-specific ECs.

Protein hyperacetylation is associated with glucose intolerance and insulin resistance, suggesting that the enzymes regulating the acetylome play a role in this pathological process. Sirtuin 3 (SIRT3), the primary mitochondrial deacetylase, has been linked to energy homeostasis. Thus, it is hypothesized that the dysregulation of the mitochondrial acetylation state, via genetic deletion of SIRT3, will amplify the deleterious effects of a high-fat diet (HFD). Hyperinsulinemic-euglycemic clamp experiments show, for the first time, that mice lacking SIRT3 exhibit increased insulin resistance due to defects in skeletal muscle glucose uptake. Permeabilized muscle fibers from HFD-fed SIRT3 knockout (KO) mice showed that tricarboxylic acid cycle substrate–based respiration is decreased while fatty acid–based respiration is increased, reflecting a fuel switch from glucose to fatty acids. Consistent with reduced muscle glucose uptake, hexokinase II (HKII) binding to the mitochondria is decreased in muscle from HFD-fed SIRT3 KO mice, suggesting decreased HKII activity. These results show that the absence of SIRT3 in HFD-fed mice causes profound impairments in insulin-stimulated muscle glucose uptake, creating an increased reliance on fatty acids. Insulin action was not impaired in the lean SIRT3 KO mice. This suggests that SIRT3 protects against dietary insulin resistance by facilitating glucose disposal and mitochondrial function.

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Endothelial cells (ECs) are critical for several aspects of cardiovascular disease therapy, including vascular regeneration, personalized drug development, and tissue engineering. Human pluripotent stem cells (hPSCs) afford us with an unprecedented opportunity to produce virtually unlimited quantities of human ECs. In this review, we highlight key developments and outstanding challenges in our ability to derive ECs de novo from hPSCs. Furthermore, we consider strategies for recapitulating the vessel and tissue-specific functional heterogeneity of ECs in vitro. Finally, we discuss ongoing attempts to utilize hPSC-derived ECs and their progenitors for various therapeutic applications. Continued progress in generating hPSC-derived ECs will profoundly enhance our ability to discover novel drug targets, revascularize ischemic tissues, and engineer clinically relevant tissue constructs.

Angiotensin-(1–7) improves glycemic control in animal models of cardiometabolic syndrome. The tissue-specific sites of action and blood pressure dependence of these metabolic effects, however, remain unclear. We hypothesized that angiotensin-(1–7) improves insulin sensitivity by enhancing peripheral glucose delivery. Adult male C57BL/6J mice were placed on standard chow or 60% high fat diet for 11 weeks. Angiotensin-(1–7) [400 ng/kg/min] or saline was infused subcutaneously during the last 3 weeks of diet, and hyperinsulinemic-euglycemic clamps were performed at the end of treatment. High-fat fed mice exhibited modest hypertension (systolic blood pressure: 137±3 high-fat versus 123±5 mmHg chow; p=0.001), which was not altered by angiotensin-(1–7) [141±4 mmHg; p=0.574]. Angiotensin-(1–7) did not alter body weight or fasting glucose and insulin in chow or high-fat fed mice. Angiotensin-(1–7) increased the steady-state glucose infusion rate needed to maintain euglycemia in high-fat fed mice (31±5 angiotensin-(1–7) versus 16±1 mg/kg/min vehicle; p=0.017) reflecting increased whole-body insulin sensitivity, with no effect in chow-fed mice. The improved insulin sensitivity in high-fat fed mice was due to an enhanced rate of glucose disappearance (34±5 angiotensin-(1–7) versus 20±2 mg/kg/min vehicle; p=0.049). Angiotensin-(1–7) enhanced glucose uptake specifically into skeletal muscle by increasing translocation of glucose transporter 4 to the sarcolemma. Our data suggest that angiotensin-(1–7) has direct insulin-sensitizing effects on skeletal muscle, independent of changes in blood pressure. These findings provide new insight into mechanisms by which angiotensin-(1–7) improves insulin action, and provide further support for targeting this peptide in cardiometabolic disease.

Rationale: Coronary artery disease (CAD) is the leading cause of death worldwide, but there are currently no methods to stimulate artery growth or regeneration in diseased hearts. Studying how arteries are built during development could illuminate strategies for re-building these vessels during ischemic heart disease. We previously found that Dach1 deletion in mouse embryos resulted in small coronary arteries. However, it was not known whether Dach1 gain-of-function would be sufficient to increase arterial vessels and whether this could benefit injury responses. Objective: We investigated how Dach1 overexpression in endothelial cells affected transcription and artery differentiation, and how it influenced recovery from myocardial infarction (MI). Methods and Results: Dach1 was genetically overexpressed in coronary endothelial cells (ECs) in either developing or adult hearts using ApjCreER. This increased the length and number of arterial end branches expanded arteries during development, in both the heart and retina, by inducing capillary ECs to differentiate and contribute to growing arteries. Single-cell RNA sequencing (scRNAseq) of ECs undergoing Dach1-induced arterial specification indicated that it potentiated normal artery differentiation, rather than functioning as a master regulator of artery cell fate. ScRNAseq also showed that normal arterial differentiation is accompanied by repression of lipid metabolism genes, which were also repressed by Dach1. In adults, Dach1 overexpression did not cause a statistically significant change artery structure prior to injury, but increased the number of perfused arteries in the injury zone post-MI. Conclusions: Our data demonstrate that increasing Dach1 is a novel method for driving artery specification and extending arterial branches, which could be explored as a means of mitigating the effects of CAD.

Aims Non-compaction cardiomyopathy is a devastating genetic disease caused by insufficient consolidation of ventricular wall muscle that can result in inadequate cardiac performance. Despite being the third most common cardiomyopathy, the mechanisms underlying the disease, including the cell types involved, are poorly understood. We have previously shown that endothelial cell-specific deletion of the chromatin remodeller gene Ino80 results in defective coronary vessel development that leads to ventricular non-compaction in embryonic mouse hearts. We aimed to identify candidate angiocrines expressed by endocardial and ECs inwildtype and LVNC conditions in Tie2Cre;Ino80fl/fl transgenic embryonic mouse hearts, and test the effect of these candidates on cardiomyocyte proliferation and maturation. Methods and results We used single-cell RNA-sequencing to characterize endothelial and endocardial defects in Ino80-deficient hearts. We observed a pathological endocardial cell population in the non-compacted hearts and identified multiple dysregulated angiocrine factors that dramatically affected cardiomyocyte behaviour. We identified Col15A1 as a coronary vessel-secreted angiocrine factor, downregulated by Ino80-deficiency, that functioned to promote cardiomyocyte proliferation. Furthermore, mutant endocardial and endothelial cells (ECs) up-regulated expression of secreted factors, such as Tgfbi, Igfbp3, Isg15, and Adm, which decreased cardiomyocyte proliferation and increased maturation. Conclusions These findings support a model where coronary ECs normally promote myocardial compaction through secreted factors, but that endocardial and ECs can secrete factors that contribute to non-compaction under pathological conditions.