Elena Piccinin

Peroxisome proliferator-activated receptor α (PPARα) is a nuclear receptor that plays a central role in metabolic adaptation by regulating gene expression programs involved in lipid utilization and energy homeostasis. Although the hepatic functions of PPARα and its target genes are well characterized, less is known about its transcriptional activity in extrahepatic tissues. Pemafibrate (K-877), a selective PPARα modulator (SPPARMα), is a high-affinity PPARα ligand with improved potency and selectivity compared with conventional fibrates. Here, we investigated pemafibrate-induced tissue-specific transcriptional responses comparing wild type and whole-body PPARα-deficient littermate mice. Twelve-week-old male PPARα+/+ and PPARα-/- mice were treated daily with pemafibrate (0.1 mg/kg) or vehicle by oral gavage for 14 days. We performed genome-wide transcriptomic analyses in the liver, jejunum, kidney, soleus muscle, and BAT. Pemafibrate-induced transcriptional changes were entirely dependent on PPARα, as no differentially expressed genes were detected in PPARα-/- mice. The magnitude and nature of the response were tissue-specific, with the strongest transcriptional effects observed in the liver and jejunum, whereas the kidney, soleus muscle, and BAT showed limited responses. In the liver, pemafibrate primarily induced the expression of genes involved in fatty acid metabolism, mitochondrial function, and energy production. In the jejunum, pemafibrate activated lipid metabolic programs together with tissue-specific pathways related to cellular homeostasis. Collectively, our findings show that pemafibrate is a highly selective PPARα activator with a preferential transcriptional activity in the liver and intestine after oral administration. This study provides a resource for defining tissue-specific PPARα-responsive gene networks and expands our understanding of PPARα functions beyond the liver.

MicroRNAs (miRNAs) are small endogenous RNAs involved in gene expression modulation at post-transcriptional level, regulating several biological processes ranging from differentiation to proliferation and preservation of cell and tissue identity. Evidence describe the ability of miRNAs to move between organisms of distinct species, a phenomenon referred to as “trans-kingdom” exchange. Notably, plant miRNAs can be transferred to other species, including humans, and potentially target and modulate genes. Here, we investigated for the first time the trans-kingdom capability of apple-derived microRNAs (miRNAs) to influence human intestinal cells (HT-29 and HCT116) in vitro . Our data demonstrate that synthetic apple-derived miR-482a-3p and miR-858 can be internalized by human colonic cell lines and significantly reduce cell proliferation. Through an in silico analysis followed by gene expression and luciferase reporter assays, we show that apple-derived miR-482a-3p targets the human c-MYB gene in intestinal cell lines, thereby directly contributing to the regulation of the enterocyte cell cycle. This study supports the trans-kingdom hypothesis by providing evidence that plant-derived miRNAs can directly modulate enterocyte lifespan and metabolic activity.

Background & Aims: Metabolic dysfunction‐associated steatohepatitis (MASH) is a growing cause of chronic liver disease, characterized by fat accumulation, inflammation and fibrosis, which development depends on mitochondrial dysfunction and oxidative stress. Highly expressed in the liver during fasting, peroxisome proliferator‐activated receptor‐γ coactivator‐1α (PGC‐1α) regulates mitochondrial and oxidative metabolism. Given the relevant role of mitochondrial function in MASH, we investigated the relationship between PGC‐1α and steatohepatitis.Methods: We measured the hepatic expression of Pgc‐1α in both MASH patients and wild‐type mice fed a western diet (WD) inducing steatosis and fibrosis. We then generated a pure C57BL6/J strain loss of function mouse model in which Pgc‐1α is selectively deleted in the liver and we fed these mice with a WD supplemented with sugar water that accurately mimics human MASH.Results: We observed that the hepatic expression of Pgc‐1α is strongly reduced in MASH, in both humans and mice. Moreover, the hepatic ablation of Pgc‐1α promotes a considerable reduction of the hepatic mitochondrial respiratory capacity, setting up a bioenergetic harmful environment for liver diseases. Indeed, the lack of Pgc‐1α decreases mitochondrial function and increases inflammation, fibrosis and oxidative stress in the scenario of MASH. Intriguingly, this profibrotic phenotype is not linked with obesity, insulin resistance and lipid disbalance.Conclusions: In a MASH model the hepatic ablation of Pgc‐1α drives fibrosis independently from lipid and glucose metabolism. These results add a novel mechanistic piece to the puzzle of the specific and crucial role of mitochondrial function in MASH development.

Background: Metabolic dysfunction-associated steatotic liver disease (MASLD) represents the hepatic manifestation of increased adiposopathy, whose pathogenetic features have been proposed as tumourigenic triggers for colorectal cancer (CRC). We aim to identify specific metabolic signatures involved in CRC development that may be used as non-invasive biomarkers, paving the way for specific and personalized strategies of CRC prevention and early detection. Methods: We retrospectively assessed CRC onset during a time frame of 8 years in a cohort of 1145 out-patients individuals who had previously been evaluated for Metabolic Syndrome. Results: 28 patients developed CRC. No association between CRC development and visceral and general obesity was detected, while baseline fasting plasma glucose (FPG) and non-invasive liver fibrosis scores were significantly higher in patients with CRC, compared to those who did not develop cancer. Liver steatosis and MASLD were more frequently diagnosed in patients who developed CRC compared to no cancer developers. Canonical correlations among metabolic biomarkers were not present in CRC developers, differently from no cancer group. In ROC analysis, FPG and non-invasive scores also showed good sensitivity and specificity in predicting colon cancer. We then calculated ORs for metabolic biomarkers, finding that higher FPG and non-invasive scores were associated with an increased risk of developing CRC. Conclusion: MASLD and increased FPG may play a role in the clinical background of CRC, bringing to light the fascinating possibility of a reversed gut–liver axis communication in the pathogenesis of CRC. Thus, the use of non-invasive scores of fatty liver may be helpful to predict the risk of CRC and serve as novel prognostic factors for prevention and therapeutic strategies.

Aims/hypothesis: Roux-en-Y gastric bypass surgery (RYGB) frequently results in remission of type 2 diabetes as well as exaggerated secretion of glucagon-like peptide-1 (GLP-1). Here, we assessed RYGB-induced transcriptomic alterations in the small intestine and investigated how they were related to the regulation of GLP-1 production and secretion in vitro and in vivo. Methods: Human jejunal samples taken perisurgically and 1 year post RYGB (n=13) were analysed by RNA-seq. Guided by bioinformatics analysis we targeted four genes involved in cholesterol biosynthesis, which we confirmed to be expressed in human L cells, for potential involvement in GLP-1 regulation using siRNAs in GLUTag and STC-1 cells. Gene expression analyses, GLP-1 secretion measurements, intracellular calcium imaging and RNA-seq were performed in vitro. OGTTs were performed in C57BL/6j and iScd1^−/− mice and immunohistochemistry and gene expression analyses were performed ex vivo. Results: Gene Ontology (GO) analysis identified cholesterol biosynthesis as being most affected by RYGB. Silencing or chemical inhibition of stearoyl-CoA desaturase 1 (SCD1), a key enzyme in the synthesis of monounsaturated fatty acids, was found to reduce Gcg expression and secretion of GLP-1 by GLUTag and STC-1 cells. Scd1 knockdown also reduced intracellular Ca²⁺ signalling and membrane depolarisation. Furthermore, Scd1 mRNA expression was found to be regulated by NEFAs but not glucose. RNA-seq of SCD1 inhibitor-treated GLUTag cells identified altered expression of genes implicated in ATP generation and glycolysis. Finally, gene expression and immunohistochemical analysis of the jejunum of the intestine-specific Scd1 knockout mouse model, iScd1^−/−, revealed a twofold higher L cell density and a twofold increase in Gcg mRNA expression. Conclusions/interpretation: RYGB caused robust alterations in the jejunal transcriptome, with genes involved in cholesterol biosynthesis being most affected. Our data highlight SCD as an RYGB-regulated L cell constituent that regulates the production and secretion of GLP-1. Graphical

Nonalcoholic fatty liver disease (NAFLD) is defined by a set of hepatic conditions ranging from steatosis to steatohepatitis (NASH), characterized by inflammation and fibrosis, eventually predisposing to hepatocellular carcinoma (HCC). Together with fatty acids (FAs) originated from adipose lipolysis and hepatic lipogenesis, intestinal‐derived FAs are major contributors of steatosis. However, the role of mono‐unsaturated FAs (MUFAs) in NAFLD development is still debated. We previously established the intestinal capacity to produce MUFAs, but its consequences in hepatic functions are still unknown. Here, we aimed to determine the role of the intestinal MUFA‐synthetizing enzyme stearoyl‐CoA desaturase 1 (SCD1) in NAFLD. We used intestinal‐specific Scd1‐KO (iScd1 ^−/−) mice and studied hepatic dysfunction in different models of steatosis, NASH, and HCC. Intestinal‐specific Scd1 deletion decreased hepatic MUFA proportion. Compared with controls, iScd1 ^−/− mice displayed increased hepatic triglyceride accumulation and derangement in cholesterol homeostasis when fed a MUFA‐deprived diet. Then, on Western diet feeding, iScd1 ^−/− mice triggered inflammation and fibrosis compared with their wild‐type littermates. Finally, intestinal‐Scd1 deletion predisposed mice to liver cancer. Conclusions: Collectively, these results highlight the major importance of intestinal MUFA metabolism in maintaining hepatic functions and show that gut‐derived MUFAs are protective from NASH and HCC.