Lipidomic profiling of the hepatic esterified fatty acid composition in diet-induced nonalcoholic fatty liver disease in genetically diverse Collaborative Cross mice

A preclinical model of severe NASH-like liver injury by chronic administration of a high-fat and high-sucrose diet in mice

Non-alcoholic fatty liver disease (NAFLD) is a progressive liver disease, affecting 32% of adults globally. If left untreated, NAFLD may progress to more advanced forms of the disease, including non-alcoholic steatohepatitis (NASH), liver cirrhosis, and fibrosis. Early NAFLD detection is critical to prevent disease progression. Using an obesogenic high-fat and high-sucrose (HF/HS) diet, we characterized the progression of NAFLD in male and female Collaborative Cross CC042 mice at 20-, 40-, and 60-week intervals of chronic HF/HS diet feeding. The incidence and severity of liver steatosis, inflammation, and fibrosis increased in both sexes over time, with male mice progressing to a NASH-like disease state faster than female mice, as indicated by earlier and more pronounced changes in liver steatosis. Histopathological indication of macrovesicular steatosis and gene expression changes of key lipid metabolism genes were found to be elevated in both sexes after 20 weeks of HF/HS diet. Measurement of circulating markers of inflammation (CXCL10 and TNF-α), histopathological analysis of immune cell infiltrates, and gene expression changes in inflammation-related genes indicated significant liver inflammation after 40 and 60 weeks of HF/HS diet exposure in both sexes. Liver fibrosis, as assessed by Picosirius red and Masson's trichrome staining and changes in expression of key fibrosis related genes indicated significant changes after 40 and 60 weeks of HF/HS diet exposure. In conclusion, we present a preclinical animal model of dietary NAFLD progression, which recapitulates human pathophysiological and pathomorphological changes, that could be used to better understand the progression of NAFLD and support development of new therapeutics.

Selective transcriptomic dysregulation of metabolic pathways in liver and retina by short- and long-term dietary hyperglycemia

A high glycemic index (HGI) diet induces hyperglycemia, a risk factor for diseases affecting multiple organ systems. Here, we evaluated tissue-specific adaptations in the liver and retina after feeding HGI diet to mice for 1 or 12 month. In the liver, genes associated with inflammation and fatty acid metabolism were altered within 1 month of HGI diet, whereas 12-month HGI diet-fed group showed dysregulated expression of cytochrome P450 genes and overexpression of lipogenic factors including Srebf1 and Elovl5. In contrast, retinal transcriptome exhibited HGI-related notable alterations in energy metabolism genes only after 12 months. Liver fatty acid profiles in HGI group revealed higher levels of monounsaturated and lower levels of saturated and polyunsaturated fatty acids. Additionally, HGI diet increased blood low-density lipoprotein, and diet-aging interactions affected expression of mitochondrial oxidative phosphorylation genes in the liver and disease-associated genes in retina. Thus, our findings provide new insights into retinal and hepatic adaptive mechanisms to dietary hyperglycemia.

Bacteroides thetaiotaomicron ameliorates mouse hepatic steatosis through regulating gut microbial composition, gut-liver folate and unsaturated fatty acids metabolism

Gut microbiota plays an essential role in the progression of nonalcoholic fatty liver disease (NAFLD), making the gut-liver axis a potential therapeutic strategy. Bacteroides genus, the enriched gut symbionts, has shown promise in treating fatty liver. However, further investigation is needed to identify specific beneficial Bacteroides strains for metabolic disorders in NAFLD and elucidate their underlying mechanisms. In this study, we observed a positive correlation between the abundance of Bacteroides thetaiotaomicron (B. theta) and the alleviation of metabolic syndrome in the early and end stages of NAFLD. Administration of B. theta to HFD-fed mice for 12 weeks reduced body weight and fat accumulation, decreased hyperlipidemia and insulin resistance, and prevented hepatic steatohepatitis and liver injury. Notably, B. theta did not affect these indicators in low-fat diet (LFD)-fed mice and exhibited good safety. Mechanistically, B. theta regulated gut microbial composition, characterized by a decreased Firmicutes/Bacteroidetes ratio in HFD-Fed mice. It also increased gut-liver folate levels and hepatic metabolites, alleviating metabolic dysfunction. Additionally, treatment with B. theta increased the proportion of polyunsaturated fatty acid in the mouse liver, offering a widely reported benefit for NAFLD improvement. In conclusion, this study provides evidence that B. theta ameliorates NAFLD by regulating gut microbial composition, enhancing gut-liver folate and unsaturated fatty acid metabolism, highlighting the therapeutic role of B. theta as a potential probiotic for NAFLD.

Heterogeneity in the response to n-3 polyunsaturated fatty acids

PURPOSE OF REVIEW

A central goal in the study of long chain n-3 polyunsaturated fatty acids (PUFA) is to translate findings from the basic sciences to the population level to improve human health and prevent chronic diseases. A tenet of this vision is to think in terms of precision medicine and nutrition, that is, stratification of individuals into differing groups that will have different needs across the lifespan for n-3 PUFAs. Therefore, there is a critical need to identify the sources of heterogeneity in the human population in the dietary response to n-3 PUFA intervention.

RECENT FINDINGS

We briefly review key sources of heterogeneity in the response to intake of long chain n-3 PUFAs. These include background diet, host genome, composition of the gut microbiome, and sex. We also discuss the need to integrate data from newer rodent models (e.g. population-based approaches), multi -omics, and analyses of big data using machine learning and data-driven cluster analyses.

SUMMARY

Accounting for vast heterogeneity in the human population, particularly with the use of big data integrated with preclinical evidence, will drive the next generation of precision nutrition studies and randomized clinical trials with long-chain n-3 PUFAs.