Gut microbiota plays a key role in obesity and non-alcoholic fatty liver disease (NAFLD), so synbiotics could be a therapeutic alternative. We aim to evaluate a nutritional intervention together with the administration of the bacteria Akkermansia muciniphila and the antioxidant quercetin in an in vivo model of early obesity and NAFLD. 21-day-old rats were fed with control or high-fat diet for six weeks. Then, all animals received control diet supplemented with/without quercetin and/or A. muciniphila for three weeks. Gut microbiota, NAFLD-related parameters, circulating bile acids (BAs) and liver gene expression were analyzed. The colonization with A. muciniphila was associated with less body fat, while synbiotic treatment caused a steatosis remission, linked to hepatic lipogenesis modulation. The synbiotic promoted higher abundance of Cyanobacteria and Oscillospira, and lower levels of Actinobacteria, Lactococcus, Lactobacillus and Roseburia. Moreover, it favored elevated unconjugated hydrophilic BAs plasma levels and enhanced hepatic expression of BA synthesis and transport genes. A. muciniphila correlated with circulating BAs and liver lipid and BA metabolism genes, suggesting a role of this bacterium in BA signaling. Beneficial effects of A. muciniphila and quercetin combination are driven by gut microbiota modulation, the shift in BAs and the gut-liver bile flow enhancement.

Acetaminophen overdose is one of the leading causes of acute liver failure and liver transplantation in the Western world. Magnesium is essential in several cellular processess. The Cyclin M family is involved in magnesium transport across cell membranes. Herein, we identify that among all magnesium transporters, only Cyclin M4 expression is upregulated in the liver of patients with acetaminophen overdose, with disturbances in magnesium serum levels. In the liver, acetaminophen interferes with the mitochondrial magnesium reservoir via Cyclin M4, affecting ATP production and reactive oxygen species generation, further boosting endoplasmic reticulum stress. Importantly, Cyclin M4 mutant T495I, which impairs magnesium flux, shows no effect. Finally, an accumulation of Cyclin M4 in endoplasmic reticulum is shown under hepatoxicity. Based on our studies in mice, silencing hepatic Cyclin M4 within the window of 6 to 24 h following acetaminophen overdose ingestion may represent a therapeutic target for acetaminophen overdose induced liver injury.

Retinoblastoma (Rb1) has been described as an essential player in white adipocyte differentiation in mice. No studies have been reported thus far in human adipose tissue or human adipocytes. We aimed to investigate the possible role and regulation of RB1 in adipose tissue in obesity using human samples and animal and cell models. Adipose RB1 (mRNA, protein, and activity) was negatively associated with BMI and insulin resistance (HOMA-IR) while positively associated with the expression of adipogenic genes (PPARγ and IRS1) in both visceral and subcutaneous human adipose tissue. BMI increase was the main contributor to adipose RB1 downregulation. In rats, adipose Rb1 gene expression and activity decreased in parallel to dietary-induced weight gain and returned to baseline with weight loss. RB1 gene and protein expression and activity increased significantly during human adipocyte differentiation. In fully differentiated adipocytes, transient knockdown of Rb1 led to loss of the adipogenic phenotype. In conclusion, Rb1 seems to play a permissive role for human adipose tissue function, being downregulated in obesity and increased during differentiation of human adipocytes. Rb1 knockdown findings further implicate Rb1 as necessary for maintenance of adipogenic characteristics in fully differentiated adipocytes.