Antilipolytic and antilipogenic effects of the CPT-1b inhibitor oxfenicine in the white adipose tissue of rats

Modulators for palmitoylation of proteins and small molecules

As an essential form of lipid modification for maintaining vital cellular functions, palmitoylation plays an important role in in the regulation of various physiological processes, serving as a promising therapeutic target for diseases like cancer and neurological disorders. Ongoing research has revealed that palmitoylation can be categorized into three distinct types: N-palmitoylation, O-palmitoylation and S-palmitoylation. Herein this paper provides an overview of the regulatory enzymes involved in palmitoylation, including palmitoyltransferases and depalmitoylases, and discusses the currently available broad-spectrum and selective inhibitors for these enzymes.

N-acetyloxfenicine strongly induces mitohormesis in mice as well as in insects

Mitohormesis defines the increase in fitness induced by adaptive responses to mild mitochondrial stress. Here, we show that N-acetyloxfenicine (NAO) exerted higher thermotolerance than an endogenous mitohormesis inducer, N-acetyltyrosine (NAT). This activity was not observed in armyworm larvae injected with oxfenicine, suggesting the importance of N-acetylation. NAO-induced hormetic effect was triggered by transient perturbation of mitochondria, which causes a small increase in ROS production and leads to retrograde responses including enhanced expression of antioxidant enzyme genes via activation of FoxO transcription factors. Furthermore, pretreatment with NAO significantly repressed stress-induced peroxidation of lipids in mice and growth of colorectal cancer HCT116 cells that had been transplanted into nude mice. Taken together, NAO is a potent mitohormesis inducer that is similar to NAT in terms of structure and functions.

PHDs/CPT1B/VDAC1 axis regulates long-chain fatty acid oxidation in cardiomyocytes

Cardiac metabolism is a high-oxygen-consuming process, showing a preference for long-chain fatty acid (LCFA) as the fuel source under physiological conditions. However, a metabolic switch (favoring glucose instead of LCFA) is commonly reported in ischemic or late-stage failing hearts. The mechanism regulating this metabolic switch remains poorly understood. Here, we report that loss of PHD2/3, the cellular oxygen sensors, blocks LCFA mitochondria uptake and β-oxidation in cardiomyocytes. In high-fat-fed mice, PHD2/3 deficiency improves glucose metabolism but exacerbates the cardiac defects. Mechanistically, we find that PHD2/3 bind to CPT1B, a key enzyme of mitochondrial LCFA uptake, promoting CPT1B-P295 hydroxylation. Further, we show that CPT1B-P295 hydroxylation is indispensable for its interaction with VDAC1 and LCFA β-oxidation. Finally, we demonstrate that a CPT1B-P295A mutant constitutively binds to VDAC1 and rescues LCFA metabolism in PHD2/3-deficient cardiomyocytes. Together, our data identify an oxygen-sensitive regulatory axis involved in cardiac metabolism.

The role and therapeutic implication of CPTs in fatty acid oxidation and cancers progression

Cancer cells must maintain metabolic homeostasis under a wide range of conditions and meet their own energy needs in order to survive and reproduce. In addition to glycolysis, cancer cells can also perform various metabolic strategies, such as fatty acid oxidation (FAO). It has been found that the proliferation, survival, drug resistance and metastasis of cancer cells depend on FAO. The carnitine palmitoyltransferase (CPT), including CPT1 and CPT2, located on the mitochondrial membrane, are important mediators of FAO. In recent years, many researchers have found that CPT has a close relationship with the metabolic development of tumor cells, not only provides energy for cancer cells development and metastasis by promoting FAO but also affects the occurrence and invasion through other signal pathways or cytokines or microRNA. This review summarized the role of CPTs in several kinds of tumors and the developed targeted inhibitors of CPTs, as well as the potential gene therapy and immunotherapy of CPTs, hoping to better explore the mechanism and role of CPTs in the future and providing useful ideas for clinical treatment.

N-acetyltyrosine-induced redox signaling in hormesis

A suite of adaptations allows insects to survive in hostile terrestrial environments for long periods of time. Temperature represents a key environmental factor for most ectothermic insects, and they rapidly acclimate to high and low temperatures. Vast amounts of data in this research field support the idea that an insect's ability to tolerate fluctuating temperatures can be regarded as a biphasic hormetic dose response. Observation indicates that their thermal hormetic response represents a conservative estimate of their intrinsic capacity for rapid adaptation to environmental changes in nature because they naturally experience diel or seasonal temperature fluctuations. It is therefore reasonable to suppose that the hormetic response in insects reflects a surplus physiological capacity to deal with temperature changes that they would experience naturally. Although it has been unknown how thermal acclimation is induced, a stress-dependent increase in N-acetyltyrosine (NAT) was recently found to occur in insect larvae who had endured high temperatures. NAT treatment was demonstrated to induce thermotolerance in several tested insect species. NAT was also identified in the serum of humans as well as mice, and its concentration in mice was shown to be increased by heat and restraint stress, with NAT pretreatment lowering the concentrations of corticosterone and peroxidized lipids in stressed mice. These recent findings may give us some hints about how long a hormetic response lasts. Here, I will discuss recent findings underlying hormetic responses induced by an intrinsic factor, NAT, and how the hormetic response may begin and end.

Dioxygen and Metabolism; Dangerous Liaisons in Cardiac Function and Disease

The heart must consume a significant amount of energy to sustain its contractile activity. Although the fuel demands are huge, the stock remains very low. Thus, in order to supply its daily needs, the heart must have amazing adaptive abilities, which are dependent on dioxygen availability. However, in myriad cardiovascular diseases, “fuel” depletion and hypoxia are common features, leading cardiomyocytes to favor low-dioxygen-consuming glycolysis rather than oxidation of fatty acids. This metabolic switch makes it challenging to distinguish causes from consequences in cardiac pathologies. Finally, despite the progress achieved in the past few decades, medical treatments have not improved substantially, either. In such a situation, it seems clear that much remains to be learned about cardiac diseases. Therefore, in this review, we will discuss how reconciling dioxygen availability and cardiac metabolic adaptations may contribute to develop full and innovative strategies from bench to bedside.

Examination of carnitine palmitoyltransferase 1 abundance in white adipose tissue: implications in obesity research

Carnitine palmitoyltransferase 1 (CPT1) is essential for the transport of long-chain fatty acids into the mitochondria for oxidation. Recently, it was reported that decreased CPT1b mRNA in adipose tissue was a contributing factor for obesity in rats. We therefore closely examined the expression level of Cpt1 in adipose tissue from mice, rats, and humans. Cpt1a is the predominate isoform in adipose tissue from all three species. Rat white adipose tissue has a moderate amount of Cpt1b mRNA, but it is very minor compared with Cpt1b expression in muscle. Total CPT1 activity in adipose tissue is also minor relative to other tissues. Both Cpt1a and Cpt1b mRNA were increased in gonadal fat but not inguinal fat by diet-induced obesity in mice. We also measured CPT1a and CPT1b expression in subcutaneous adipose tissue from human subjects with a wide range of body mass indexes (BMIs). Interestingly, CPT1a expression positively correlated with BMI (R = 0.46), but there was no correlation with CPT1b (R = 0.04). Our findings indicate that white adipose tissue fatty acid oxidation capacity is minor compared with that of metabolically active tissues. Furthermore, given the already low abundance of Cpt1b in white adipose tissue, it is unlikely that decreases in its expression can quantitatively decrease whole body energy expenditure enough to contribute to an obese phenotype.