Extracellular vesicles released by hepatocytes from gastric infusion model of alcoholic liver disease contain a MicroRNA barcode that can be detected in blood.

Extracellular vesicles (EVs) released during cell stress, or demise, can contain a barcode of the cell origin, including specific microRNAs (miRNAs). Here, we tested the hypothesis that during early alcoholic steatohepatitis (ASH) development, hepatocytes (HCs) release EVs with an miRNA signature that can be measured in circulation. A time-course experiment showed that after 2 weeks of intragastric infusion, a time point that results in isolated steatosis, there was no increase of blood EVs. After 4 weeks of infusion, mice developed features of early ASH accompanied by a marked increase in the level of EVs in blood (P < 0.05), as well as in culture media of isolated HCs (P < 0.001) and hepatic macrophages (P < 0.001), with HCs being the predominant source of EVs. The transcriptome analysis of HC-EVs from ASH mice detected differentially expressed miRNAs, including nine significantly up-regulated and four significantly down-regulated miRNAs. Target prediction and pathway analyses of the up-regulated miRNAs identified 121 potential target genes involved in inflammatory and cancer pathways, such as nuclear factor kappa B, EGF, Wnt, and B-cell lymphoma 2. Three miRNAs, let7f, miR-29a, and miR-340, were increased in blood EVs from ASH mice (P < 0.05), but not in blood EVs from three other models of chronic liver injury, including bile duct ligation, nonalcoholic steatohepatitis, and obese mice, as well as EVs released from hepatocytes exposed to ethanol. Blood EV level (P < 0.01) and three miRNAs (P < 0.05) were significantly increased in patients with ambulatory mild ALD as compared to nonalcoholics. CONCLUSION: Damaged hepatocytes from ASH mice are a key EV source with a specific miRNA cargo, which are specific for ASH-related liver injury. These findings uncover EVs as a potentially novel diagnostic for ASH. (Hepatology 2017;65:475-490).

The role of dietary fat in obesity-induced insulin resistance.

Consumption of excess calories results in obesity and insulin resistance and has been intensively studied in mice and humans. The objective of this study was to determine the specific contribution of dietary fat rather than total caloric intake to the development of obesity-associated insulin resistance. We used an intragastric feeding method to overfeed excess calories from a low-fat diet (and an isocalorically matched high-fat diet) through a surgically implanted gastric feeding tube to generate obesity in wild-type mice followed by hyperinsulinemic-euglycemic clamp studies to assess the development of insulin resistance. We show that overfeeding a low-fat diet results in levels of obesity similar to high-fat diet feeding in mice. However, despite a similar body weight, obese high-fat diet-fed mice are more insulin resistant than mice fed an isocaloric low-fat diet. Therefore, increased proportion of calories from dietary fat further potentiates insulin resistance in the obese state. Furthermore, crossover diet studies revealed that reduction in dietary fat composition improves glucose tolerance in obesity. In the context of the current obesity and diabetes epidemic, it is particularly important to fully understand the role of dietary macronutrients in the potentiation and amelioration of disease.