Polystyrene Nanoplastics Induce Lipid Metabolism Disorder by Activating the PERK-ATF4 Signaling Pathway in Mice

Gestational exposure to micro- and nanoplastics leads to poor pregnancy outcomes by impairing placental trophoblast syncytialization

The omnipresent micro- and nanoplastics (MNPs), emerging environmental contaminants, have caused a widespread concern because of their potential threats to public health. Increasing evidence has indicated that MNPs were deeply involved in poor pregnancy outcomes, but the detailed mechanism remains obscure. In this research, we firstly identified that maternal exposure to MNPs during gestation increased both the number and rate of embryo resorption, while reducing embryonic weight, placental diameter and placental weight. This was accompanied by disrupted progesterone and estradiol synthesis in MNPs-treated mouse placentas. In addition, our data suggested that MNPs exposure disturbed placental development, as evidenced by the reduction of the total area of placenta, area of spongiotrophoblast layer and area of labyrinth layer. Subsequently, in vivo and in vitro experiments further indicated that MNPs compromised syncytialization process and decreased the expression of syncytialization markers in mouse placentas and human placental trophoblasts. Further investigation indicated that PERK/eIF2α/ATF4 signaling was activated in MNPs-treated mouse placentas and human placental trophoblasts. More importantly,inhibition of PERK partially restored syncytialization insufficiency caused by MNPs administration. On the whole, our results suggested that gestational exposure to MNPs disturbed placental trophoblasts syncytialization possibly through activating PERK/eIF2α/ATF4 pathway, resulting in aberrant placentation and poor pregnancy outcomes.

Unraveling the Metabolic Pathways Between Metabolic-Associated Fatty Liver Disease (MAFLD) and Sarcopenia

Metabolic-Associated Fatty Liver Disease (MAFLD) is a public health concern that is constantly expanding, with a fast-growing prevalence, and it affects about a quarter of the world's population. This condition is a significant risk factor for cardiovascular, hepatic, and oncologic diseases, such as hypertension, hepatoma, and atherosclerosis. Sarcopenia was long considered to be an aging-related syndrome, but today, it is acknowledged to be secondarily related to chronic diseases such as metabolic syndrome, cardiovascular conditions, and liver diseases, among other comorbidities associated with insulin resistance and chronic inflammation, besides inactivity and poor nutrition. The physiopathology involving MAFLD and sarcopenia has still not been solved. Inflammation, oxidative stress, mitochondrial dysfunction, and insulin resistance seem to be some of the keys to this relationship since this hormone target is mainly the skeletal muscle. This review aimed to comprehensively discuss the main metabolic and physiological pathways involved in these conditions. MAFLD and sarcopenia are interconnected by a complex network of pathophysiological mechanisms, such as insulin resistance, skeletal muscle tissue production capacity, chronic inflammatory state, oxidative stress, and mitochondrial dysfunction, which are the main contributors to this relationship. In addition, in a clinical analysis, patients with sarcopenia and MAFLD manifest more severe hepatitis fibrosis when compared to patients with only MAFLD. These patients, with both disorders, also present clinical improvement in their MAFLD when treated for sarcopenia, reinforcing the association between them. Lifestyle changes accompanied by non-pharmacological interventions, such as dietary therapy and increased physical activity, undoubtedly improve this scenario.

Polystyrene microplastics induce hepatic lipid metabolism and energy disorder by upregulating the NR4A1-AMPK signaling pathway

Microplastics (MPs) are widespread throughout global ecosystems, and their impact on living organisms has garnered increasing attention in recent years. Research has demonstrated that exposure to different sizes (0.08-100 μm) polystyrene microplastics (PS-MPs) can disrupt hepatic lipid and energy metabolism while promoting oxidative stress. Despite these findings, the precise molecular mechanisms underlying PS-MP-induced toxicity are not fully understood. NR4A1 is known to regulate apoptosis and lipid metabolism, but few studies have explored its role in modulating hepatic lipid metabolism following PS-MP exposure. In this study, animal experiments showed that PS-MPs reduced triglyceride levels and significantly increased reactive oxygen species (ROS) in liver tissue. Transcriptional profiles of mouse liver tissues were processed and analyzed using Ingenuity Pathway Analysis (IPA) software and Gene Set Enrichment Analysis (GSEA) to identify relevant pathways and molecular signatures. The results revealed a significant upregulation in NR4A1 gene expression after exposure to PS-MPs. PS-MP accumulation in the liver activated NR4A1 and the AMPK-autophagy pathway, reducing lipid biosynthesis. In vitro study, NR4A1 knockdown in hepatocytes exposed to PS-MPs reduced the expression of AMPK and lipid metabolism-related proteins. In summary, this study indicated that PS-MPs disrupt lipid metabolism in the liver by affecting the NR4A1, leading to liver damage. Prolonged exposure to these microplastics could raise concerns about long-term liver health and the regulation of overall metabolic functions.

Metabolic-Associated Fatty Liver Disease: The Influence of Oxidative Stress, Inflammation, Mitochondrial Dysfunctions, and the Role of Polyphenols

Metabolic-Associated Fatty Liver Disease (MAFLD) is a clinical-pathological scenario that occurs due to the accumulation of triglycerides in hepatocytes which is considered a significant cause of liver conditions and contributes to an increased risk of death worldwide. Even though the possible causes of MAFLD can involve the interaction of genetics, hormones, and nutrition, lifestyle (diet and sedentary lifestyle) is the most influential factor in developing this condition. Polyphenols comprise many natural chemical compounds that can be helpful in managing metabolic diseases. Therefore, the aim of this review was to investigate the impact of oxidative stress, inflammation, mitochondrial dysfunction, and the role of polyphenols in managing MAFLD. Some polyphenols can reverse part of the liver damage related to inflammation, oxidative stress, or mitochondrial dysfunction, and among them are anthocyanin, baicalin, catechin, curcumin, chlorogenic acid, didymin, epigallocatechin-3-gallate, luteolin, mangiferin, puerarin, punicalagin, resveratrol, and silymarin. These compounds have actions in reducing plasma liver enzymes, body mass index, waist circumference, adipose visceral indices, lipids, glycated hemoglobin, insulin resistance, and the HOMA index. They also reduce nuclear factor-KB (NF-KB), interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α), blood pressure, liver fat content, steatosis index, and fibrosis. On the other hand, they can improve HDL-c, adiponectin levels, and fibrogenesis markers. These results show that polyphenols are promising in the prevention and treatment of MAFLD.