Peripheral Selective Oxadiazolylphenyl Alanine Derivatives as Tryptophan Hydroxylase 1 Inhibitors for Obesity and Fatty Liver Disease

Synthesis and biological evaluation of xanthine derivatives with phenacyl group as tryptophan hydroxylase 1 (TPH1) inhibitors for obesity and fatty liver disease

Tryptophan hydroxylase 1 (TPH1) has emerged as a target for the treatment of metabolic diseases including obesity and fatty liver disease. A series of xanthine derivatives were synthesized and evaluated for their TPH1 inhibition. Among the synthesized compounds, compound 40 showed good in vitro activity and liver microsomal stability. Docking studies revealed that compound 40 showed better binding to TPH1 via key intermolecular interactions involving the xanthine scaffold, imidazo-thiazolyl ring, and hydroxyl-containing phenacyl moiety. In addition, compound 40 effectively suppressed the adipocyte differentiation of 3 T3-L1 cells.

Serotonin in the regulation of systemic energy metabolism

Serotonin is a well‐known neurotransmitter that is synthesized from the amino acid, tryptophan. To date, more than 14 different serotonin receptors have been discovered; they exist universally in our body and enable diverse biological functions in different organs. Central serotonin regulates mood and behavior, and impacts the systemic energy balance by decreasing appetite. A number of drugs that modulate central serotonin function (e.g., fenfluramine, sibutramine and lorcaserin) were approved and used as anti‐obesity drugs, but then later withdrawn due to adverse cardiovascular and carcinogenic effects. Over the past decade, the role of peripheral serotonin in regulating systemic energy metabolism has been extensively explored using tissue‐specific knockout animal models. By inhibiting the action of serotonin in liver and adipose tissues, hepatic steatosis was improved and lipid accumulation was mitigated, respectively. Recent findings show that modulation of the serotonergic system is a promising therapeutic target for metabolic diseases. This review summarizes the role of serotonin in regulating energy metabolism in different organs, and discusses the potential of serotonin modulation for treating metabolic diseases.

Identification of New Non-BBB Permeable Tryptophan Hydroxylase Inhibitors for Treating Obesity and Fatty Liver Disease

Serotonin (5-hydroxytryptophan) is a hormone that regulates emotions in the central nervous system. However, serotonin in the peripheral system is associated with obesity and fatty liver disease. Because serotonin cannot cross the blood-brain barrier (BBB), we focused on identifying new tryptophan hydroxylase type I (TPH1) inhibitors that act only in peripheral tissues for treating obesity and fatty liver disease without affecting the central nervous system. Structural optimization inspired by para-chlorophenylalanine (pCPA) resulted in the identification of a series of oxyphenylalanine and heterocyclic phenylalanine derivatives as TPH1 inhibitors. Among these compounds, compound 18i with an IC₅₀ value of 37 nM was the most active in vitro. Additionally, compound 18i showed good liver microsomal stability and did not significantly inhibit CYP and Herg. Furthermore, this TPH1 inhibitor was able to actively interact with the peripheral system without penetrating the BBB. Compound 18i and its prodrug reduced body weight gain in mammals and decreased in vivo fat accumulation.

Interaction between the HIF-1α gene rs1957757 polymorphism and CpG island methylation in the promoter region is associated with the risk of anti-tuberculosis drug-induced liver injury in humans: A case-control study

WHAT IS KNOWN AND OBJECTIVE

HIF-1α gene polymorphisms, including rs11549465, rs11549467, rs1957757 and rs10873142, cause liver cell damage or pulmonary disease. The aim of this study was to analyse the association between the polymorphisms of the loci of the HIF-1α gene and its CpG island methylation in the promoter region with the risk of anti-tuberculosis drug-induced liver injury (ADLI).

METHODS

286 patients with tuberculosis (TB) and ADLI (case group) and 286 patients with TB but without liver injury (control group) were matched one-to-one, among the 1728 TB patients recruited from July 2019 to July 2020. Genotyping of the four loci of the HIF-1α gene was confirmed using PCR-RFLP technology. Methylation of the HIF-1α gene was measured using the MSP method. The comparison of risk factors, HIF-1α genotype and methylation status between the case group and the control group was all achieved through univariate and multivariate conditional logistic regression.

RESULTS AND DISCUSSION

Univariate analysis showed that the frequency of rs1957757 mutation genotype and CpG island methylation was significantly higher in the case group than in the control group (P<0.001, all). In contrast, there was no statistical difference in the frequency of mutated genotypes at the other three loci between the two groups (p = 0.21, p = 0.12 and p = 0.55, respectively). Further, multivariate analysis showed that CpG islands were methylated, the mutation genotype of the rs1957757 locus was independently associated with the high risk of ADLI, and the adjusted OR (95%CI) reached 1.92 (1.32-2.63) and 2.01 (1.32-2.83), respectively. Furthermore, taking the rs1957757 locus wild genotype and CpG islands without methylation as the reference group, the mutation genotype and CpG island methylation increased the risk of ADLI, and the probability of ADLI could reach 4.73 times that of the reference group.

WHAT IS NEW AND CONCLUSION

This is the first demonstration of the association of HIF-1α gene polymorphism and CpG island methylation with ADLI risk stratification. The interaction between CpG islands methylated in the promoter region of the HIF-1α gene and its rs1957757 locus mutant genotype was associated with a higher risk of ADLI.