Mild Exercise Does Not Prevent Atherosclerosis in APOE*3-Leiden.CETP Mice or Improve Lipoprotein Profile of Men with Obesity

DHCR24 inhibitor SH42 increases desmosterol without preventing atherosclerosis development in mice

The liver X receptor (LXR) is considered a therapeutic target for atherosclerosis treatment, but synthetic LXR agonists generally also cause hepatic steatosis and hypertriglyceridemia. Desmosterol, a final intermediate in cholesterol biosynthesis, has been identified as a selective LXR ligand that suppresses inflammation without inducing lipogenesis. Δ24-Dehydrocholesterol reductase (DHCR24) converts desmosterol into cholesterol, and we previously showed that the DHCR24 inhibitor SH42 increases desmosterol to activate LXR and attenuate experimental peritonitis and metabolic dysfunction-associated steatotic liver disease. Here, we aimed to evaluate the effect of SH42 on atherosclerosis development in APOE∗3-Leiden.CETP mice and low-density lipoproteins (LDL) receptor knockout mice, models for lipid- and inflammation-driven atherosclerosis, respectively. In both models, SH42 increased desmosterol without affecting plasma lipids. While reducing liver lipids in APOE∗3-Leiden.CETP mice, and regulating populations of circulating monocytes in LDL receptor knockout mice, SH42 did not attenuate atherosclerosis in either model.

Rev1 deficiency induces replication stress to cause metabolic dysfunction differently in males and females

DNA damage responses compete for cellular resources with metabolic pathways, but little is known about the metabolic consequences of impaired DNA replication, a process called replication stress. Here we characterized the metabolic consequences of DNA replication stress at endogenous DNA lesions by using mice with a disruption of Rev1, a translesion DNA polymerase specialized in the mutagenic replication of damaged DNA. Male and female Rev1 knockout (KO) mice were compared with wild-type (WT) mice and followed over time to study the natural course of body weight gain and glucose tolerance. Follow-up measurements were performed in female mice for in-depth metabolic characterization. Body weight and fat mass were only increased in female KO mice versus WT mice, whereas glucose intolerance and a reduction in lean mass were observed in both sexes. Female KO mice showed reduced locomotor activity while male KO mice showed increased activity as compared with their WT littermates. Further characterization of female mice revealed that lipid handling was unaffected by Rev1 deletion. An increased respiratory exchange ratio, combined with elevated plasma lactate levels and increased hepatic gluconeogenesis indicated problems with aerobic oxidation and increased reliance on anaerobic glycolysis. Supplementation with the NAD⁺ precursor nicotinamide riboside to stimulate aerobic respiration failed to restore the metabolic phenotype. In conclusion, replication stress at endogenous DNA lesions induces a complex metabolic phenotype, most likely initiated by muscular metabolic dysfunction and increased dependence on anaerobic glycolysis. Nicotinamide riboside supplementation after the onset of the metabolic impairment did not rescue this phenotype.NEW & NOTEWORTHY An increasing number of DNA lesions interferes with cellular replication leading to metabolic inflexibility. We utilized Rev1 knockout mice as a model for replication stress, and show a sex-dependent metabolic phenotype, with a pronounced reduction of lean mass and glucose tolerance. These data indicate that in obesity, we may end up in an infinite loop where metabolic disturbance promotes the formation of DNA lesions, which in turn interferes with cellular replication causing further metabolic disturbances.