Adipose Tissue-specific Knockout Mice Research Articles

Zinc finger protein ZNF638 regulates triglyceride metabolism via ANGPTL8 in an estrogen dependent manner

Background and aimTriglyceride (TG) levels are closely related to obesity, fatty liver and cardiovascular diseases, while the regulatory factors and mechanism for triglyceride homeostasis are still largely unknown. Zinc Finger Protein 638 (ZNF638) is a newly discovered member of zinc finger protein family for adipocyte function in vitro. The aim of the present work was to investigate the role of ZNF638 in regulating triglyceride metabolism in mice. MethodsWe generated ZNF638 adipose tissue specific knockout mice (ZNF638 FKO) by cross-breeding ZNF638 flox to Adiponectin-Cre mice and achieved adipose tissue ZNF638 overexpression via adenoviral mediated ZNF638 delivery in inguinal adipose tissue (iWAT) to examined the role and mechanisms of ZNF638 in fat biology and whole-body TG homeostasis. ResultsAlthough ZNF638 FKO mice showed similar body weights, body composition, glucose metabolism and serum parameters compared to wild-type mice under chow diet, serum TG levels in ZNF638 FKO mice were increased dramatically after refeeding compared to wild-type mice, accompanied with decreased endothelial lipoprotein lipase (LPL) activity and increased lipid absorption of the small intestine. Conversely, ZNF638 overexpression in iWAT reduced serum TG levels while enhanced LPL activity after refeeding in female C57BL/6J mice and obese ob/ob mice. Specifically, only female mice exhibited altered TG metabolism upon ZNF638 expression changes in fat. Mechanistically, RNA-sequencing analysis revealed that the TG regulator angiopoietin-like protein 8 (Angptl8) was highly expressed in iWAT of female ZNF638 FKO mice. Neutralizing circulating ANGPTL8 in female ZNF638 FKO mice abolished refeeding-induced TG elevation. Furthermore, we demonstrated that ZNF638 functions as a transcriptional repressor by recruiting HDAC1 for histone deacetylation and broad lipid metabolic gene suppression, including Angptl8 transcription inhibition. Moreover, we showed that the sexual dimorphism is possibly due to estrogen dependent regulation on ZNF638-ANGPTL8 axis. ConclusionWe revealed a role of ZNF638 in the regulation of triglyceride metabolism by affecting Angptl8 transcriptional level in adipose tissue with sexual dimorphism.

Adipocyte-specific CDK7 ablation leads to progressive loss of adipose tissue and metabolic dysfunction.

Adipose tissue regulates whole-body energy homeostasis. Both lipodystrophy and obesity, the extreme and opposite aspects of adipose tissue dysfunction, result in metabolic disorders: insulin resistance and hepatic steatosis. Cyclin-dependent kinases (CDKs) have been reported to be involved in adipose tissue development and functions. Using adipose tissue-specific knockout mice, here we demonstrate that the deletion of CDK7 in adipose tissue results in progressive lipodystrophy, insulin resistance, impaired adipokine secretion and downregulation of fat-specific genes, which are aggravated on high-fat diet and during ageing. Our studies suggest that CDK7 is a key regulatory component of adipose tissue maintenance and systemic energy homeostasis.

Adaptor protein APPL1 coordinates HDAC3 to modulate brown adipose tissue thermogenesis in mice

ObjectivesThe activation of brown adipose tissue (BAT) is considered as a promising therapeutic target for obesity. APPL1 (Adaptor protein containing the Pleckstrin homology domain, Phosphotyrosine binding domain and Leucine zipper motif) is an intracellular adaptor protein and its genetic variation is correlated with BMI and body fat distribution in diabetic patients. However, little is known about the roles of APPL1 in BAT thermogenesis. Materials/methodsIn this study, adipose tissue specific knockout (ASKO) mice were generated to evaluate APPL1's role in BAT thermogenesis in vivo, and possible signaling pathways were further explored in cultured brown adipocytes. ResultsAfter high fat diet challenge, APPL1 ASKO mice developed more severe obesity, glucose intolerance and insulin resistance compared with control mice. Metabolic cage study showed that APPL1 deficiency impaired energy expenditure and adaptive thermogenesis in ASKO mice. PET-CT analysis showed decreased standardized uptake value (SUV) in the inter-scapular region which indicated impaired BAT activity in ASKO mice. Further study showed deletion of APPL1 attenuated brown fat specific gene expression, such as UCP1 and PGC1α in both BAT and brown adipocytes. In cultured brown adipocytes, upon cAMP stimulation, APPL1 shuttled from cytosol to nuclei. Co-IP and ChIP study showed that APPL1 could directly interact with histone deacetylase 3 (HDAC3) to mediate chromatin remodeling and UCP1 gene expression. ConclusionsOur data demonstrated the essential role of APPL1 in regulating brown adipocytes thermogenesis via interaction with HDAC3, which may have potential therapeutic implications for treatment of obesity.

The E3 ligase synoviolin controls body weight and mitochondrial biogenesis through negative regulation of PGC-1β.

Obesity is a major global public health problem, and understanding its pathogenesis is critical for identifying a cure. In this study, a gene knockout strategy was used in post-neonatal mice to delete synoviolin (Syvn)1/Hrd1/Der3, an ER-resident E3 ubiquitin ligase with known roles in homeostasis maintenance. Syvn1 deficiency resulted in weight loss and lower accumulation of white adipose tissue in otherwise wild-type animals as well as in genetically obese (ob/ob and db/db) and adipose tissue-specific knockout mice as compared to control animals. SYVN1 interacted with and ubiquitinated the thermogenic coactivator peroxisome proliferator-activated receptor coactivator (PGC)-1β, and Syvn1 mutants showed upregulation of PGC-1β target genes and increase in mitochondrion number, respiration, and basal energy expenditure in adipose tissue relative to control animals. Moreover, the selective SYVN1 inhibitor LS-102 abolished the negative regulation of PGC-1β by SYVN1 and prevented weight gain in mice. Thus, SYVN1 is a novel post-translational regulator of PGC-1β and a potential therapeutic target in obesity treatment.