Fat-Specific Protein 27 Regulation of Vascular Function in Human Obesity

Endothelial-Specific Expression of CIDEC Improves High-Fat Diet-Induced Vascular and Metabolic Dysfunction

Cell death-inducing DNA fragmentation factor-α-like effector C (CIDEC), originally identified to be a lipid droplet-associated protein in adipocytes, positively associates with insulin sensitivity. Recently, we discovered that it is expressed abundantly in human endothelial cells and regulates vascular function. The current study was designed to characterize the physiological effects and molecular actions of endothelial CIDEC in the control of vascular phenotype and whole-body glucose homeostasis. To achieve this, we generated a humanized mouse model expressing endothelial-specific human CIDEC (E-CIDECtg). E-CIDECtg mice exhibited protection against high-fat diet-induced glucose intolerance, insulin resistance, and dyslipidemia. Moreover, these mice displayed improved insulin signaling and endothelial nitric oxide synthase activation, enhanced endothelium-dependent vascular relaxation, and improved vascularization of adipose tissue, skeletal muscle, and heart. Mechanistically, we identified a novel interplay of CIDEC-vascular endothelial growth factor A (VEGFA)-vascular endothelial growth factor receptor 2 (VEGFR2) that reduced VEGFA and VEGFR2 degradation, thereby increasing VEGFR2 activation. Overall, our results demonstrate a protective role of endothelial CIDEC against obesity-induced metabolic and vascular dysfunction, in part, by modulation of VEGF signaling. These data suggest that CIDEC may be investigated as a potential future therapeutic target for mitigating obesity-related cardiometabolic disease.

Human CIDEC transgene improves lipid metabolism and protects against high-fat diet-induced glucose intolerance in mice

Cell death–inducing DNA fragmentation factor-like effector C (CIDEC) expression in adipose tissue positively correlates with insulin sensitivity in obese humans. Further, E186X, a single-nucleotide CIDEC variant is associated with lipodystrophy, hypertriglyceridemia, and insulin resistance. To establish the unknown mechanistic link between CIDEC and maintenance of systemic glucose homeostasis, we generated transgenic mouse models expressing CIDEC (Ad-CIDECtg) and CIDEC E186X variant (Ad-CIDECmut) transgene specifically in the adipose tissue. We found that Ad-CIDECtg but not Ad-CIDECmut mice were protected against high-fat diet-induced glucose intolerance. Furthermore, we revealed the role of CIDEC in lipid metabolism using transcriptomics and lipidomics. Serum triglycerides, cholesterol, and low-density lipoproteins were lower in high-fat diet-fed Ad-CIDECtg mice compared to their littermate controls. Mechanistically, we demonstrated that CIDEC regulates the enzymatic activity of adipose triglyceride lipase via interacting with its activator, CGI-58, to reduce free fatty acid release and lipotoxicity. In addition, we confirmed that CIDEC is indeed a vital regulator of lipolysis in adipose tissue of obese humans, and treatment with recombinant CIDEC decreased triglyceride breakdown in visceral human adipose tissue. Our study unravels a central pathway whereby adipocyte-specific CIDEC plays a pivotal role in regulating adipose lipid metabolism and whole-body glucose homeostasis. In summary, our findings identify human CIDEC as a potential ‘drug’ or a ‘druggable’ target to reverse obesity-induced lipotoxicity and glucose intolerance.

Lipid Droplet-Associated Proteins in Cardiomyopathy

BACKGROUND

The heart requires a high rate of fatty-acid oxidation (FAO) to meet its energy needs. Neutral lipids are the main source of energy for the heart and are stored in lipid droplets (LDs), which are cytosolic organelles that primarily serve to store neutral lipids and regulate cellular lipid metabolism. LD-associated proteins (LDAPs) are proteins either located on the surface of the LDs or reside in the cytosol and contribute to lipid metabolism. Therefore, abnormal cardiac lipid accumulation or FAO can alter the redox state of the heart, resulting in cardiomyopathy, a group of diseases that negatively affect the myocardial function, thereby leading to heart failure and even cardiac death.

SUMMARY

LDs, along with LDAPs, are pivotal for modulating heart lipid homeostasis. The proper cardiac development and the maintenance of its normal function depend largely on lipid homeostasis regulated by LDs and LDAPs. Overexpression or deletion of specific LDAPs can trigger myocardial dysfunction and may contribute to the development of cardiomyopathy. Extensive connections and interactions may also exist between LDAPs. Key Message: In this review, the various mechanisms involved in LDAP-mediated regulation of lipid metabolism, the association between cardiac development and lipid metabolism, as well as the role of LDAPs in cardiomyopathy progression are discussed.

A Novel Proangiogenic Function of Fsp27 in Endothelium: You Only Live Thrice?

See Article Karki et al.