Non-persistent endocrine disrupting chemicals (npEDCs) can affect multiple organs and systems in the body. Whether npEDCs can accumulate in the human brain is largely unknown. The major aim of this pilot study was to examine the presence of environmental phenols and parabens in two distinct brain regions: the hypothalamus and white-matter tissue. In addition, a potential association between these npEDCs concentrations and obesity was investigated. Post-mortem brain material was obtained from 24 individuals, made up of 12 obese and 12 normal-weight subjects (defined as body mass index (BMI) > 30 and BMI < 25 kg/m², respectively). Nine phenols and seven parabens were measured by isotope dilution TurboFlow-LC-MS/MS. In the hypothalamus, seven suspect npEDCs (bisphenol A, triclosan, triclocarban and methyl-, ethyl-, n-propyl-, and benzyl paraben) were detected, while five npEDCs (bisphenol A, benzophenone-3, triclocarban, methyl-, and n-propyl paraben) were found in the white-matter brain tissue. We observed higher levels of methylparaben (MeP) in the hypothalamic tissue of obese subjects as compared to controls (p = 0.008). Our findings indicate that some suspected npEDCs are able to cross the blood–brain barrier. Whether the presence of npEDCs can adversely affect brain function and to which extent the detected concentrations are physiologically relevant needs to be further investigated.

Beta klotho (KLB) is a fundamental component in fibroblast growth factor receptor (FGFR) signaling as it serves as an obligatory coreceptor for the endocrine hormones fibroblast growth factor 19 (FGF19) and fibroblast growth factor 21 (FGF21). Through the development of FGF19- and FGF21 mimetics, KLB has emerged as a promising drug target for treating various metabolic diseases, such as type 2 diabetes (T2D), non-alcoholic fatty liver disease (NAFLD), and cardiovascular disease. While rodent studies have significantly increased our understanding of KLB function, current clinical trials that test the safety and efficacy of KLB-targeting drugs raise many new scientific questions about human KLB biology. Although most KLB-targeting drugs can modulate disease activity in humans, individual patient responses differ substantially. In addition, species-specific differences in KLB tissue distribution may explain why the glucose-lowering effects that were observed in preclinical studies are not fully replicated in clinical trials. Besides, the long-term efficacy of KLB-targeting drugs might be limited by various pathophysiological conditions known to reduce the expression of KLB. Moreover, FGF19/FGF21 administration in humans is also associated with gastrointestinal side effects, which are currently unexplained. A better understanding of human KLB biology could help to improve the efficacy and safety of existing or novel KLB/FGFR-targeting drugs. In this review, we provide a comprehensive overview of the current understanding of KLB biology, including genetic variants and their phenotypic associations, transcriptional regulation, protein structure, tissue distribution, subcellular localization, and function. In addition, we will highlight recent developments regarding the safety and efficacy of KLB-targeting drugs in clinical trials. These insights may direct the development and testing of existing and future KLB-targeting drugs.

Background/Objectives: Nutraceuticals, including short-chain fatty acids (SCFAs) and antioxidants (AOXs), are nutrient-derived bioactive compounds considered as potential treatments for metabolic-associated steatotic liver disease (MASLD). However, in vitro studies of their effects are limited by inconsistent experimental conditions, including differences in cell lines, methods of steatosis induction, and culture media, and by reliance on qualitative rather than quantitative assessments. Here, we systematically evaluate the anti-steatotic potential of eight commonly used nutraceuticals—three SCFAs (butyrate, acetate, and propionate) and five AOXs (resveratrol, curcumin, berberine, chlorogenic acid, and vitamin E)—using a standardized in vitro approach. Methods: Following a systematic literature review to identify common experimental conditions, we developed an assay to validate steatosis induction and quantified the effects of the nutraceuticals. For our studies we used the HepG2 liver cancer cell line and the Fa2N-4 immortalized hepatocyte cell line. Steatosis was modeled by stimulating cells with free fatty acids and fructose for 48 h. Nutraceuticals were added either concurrently with steatotic stimulation, to assess preventive effects, or after 24 h to assess therapeutic effects. Anti-steatotic drugs (resmetirom, semaglutide, obeticholic acid, and a DGAT2 inhibitor) were included as positive controls. Intracellular triglyceride levels were measured to quantify steatosis. Results: A systematic review of 46 studies revealed large differences in culture conditions, steatosis induction, and nutraceutical assessment. In our experiments, most nutraceuticals did not reduce intracellular triglycerides, with the exception of vitamin E. Surprisingly, butyrate, berberine, and curcumin increased triglyceride accumulation. Resmetirom was the only drug that significantly decreased triglycerides, while obeticholic acid, semaglutide, and the DGAT2 inhibitor showed minimal or inconsistent effects. Fa2N-4 cells were generally more sensitive than HepG2 cells, showing larger absolute changes in triglyceride levels in response to both nutraceuticals and resmetirom. Conclusions: We established a standardized in vitro assay to evaluate the anti-steatotic potential of nutraceuticals. Using this system, we found that SCFAs and AOXs did not consistently reduce intracellular triglycerides, highlighting the need for quantitative assessments and careful validation when studying anti-steatotic interventions in vitro.