Research ArticleEvaluating the effects of refined carbohydrate and fat diets with acute ethanol consumption using a mouse model of alcoholic liver injury
Introduction
Alcoholism is a multifactorial and complex disorder responsible for 5.9% of deaths worldwide [1] (World Health Organization. Management of Substance Abuse Team, 2014). Excessive consumption of ethanol (Et-OH) induces alcoholic liver disease (ALD), a condition comprising a spectrum of clinical signs and morphological changes, ranging from fatty liver (steatosis) to more severe forms of chronic liver injury, such as hepatocellular carcinoma [2], [3]. Secondary cofactors, such as nutritional and hepatotoxic comorbid conditions, can also contribute to liver disease development [4]. Moreover, the increased prevalence of obesity and metabolic syndrome in the population may act as a risk factor to a burgeoning number of individuals with ALD manifestations [5], [6].
So far, most studies on the ALD mechanisms have used animal models of hepatocyte lipid accumulation associated with chronic Et-OH exposure [7], [8], [9]. These models are characterized by exacerbated liver inflammation and fibrosis associated with long-term ethanol exposure [10], [11]. However, acute exposure to Et-OH metabolites has also already been shown to cause liver inflammation [14], [15], but its effects on metabolic changes and lipid homeostasis have only been hypothesized to contribute to hepatic pathogenesis. The inflammatory responses associated with ALD are characterized by the increase of inflammatory cells in the liver, such as neutrophils and macrophages, and by the production of inflammatory mediators, i.e., cytokines (IL-6, TNF-α, IL-1β), known to contribute to the progression of liver injury [12]. Liver injury can initially manifest as simple steatosis, which then progresses to steatohepatitis, which may lead to severe liver diseases, such as cirrhosis and hepatocellular carcinoma [13].
It is well established that a high-fat diet enhances the liver injury caused by chronic Et-OH ingestion [16], [17], [18], and most experimental models, so far, have investigated the role of high-fat diets for long periods of time: from 6 to 24 weeks [19], [20]. However, carbohydrates can also be potentially involved in the liver damage induction since lipogenesis occurs in the liver, where dietary carbohydrates control the expression of key enzymes in the glycolytic and lipogenic pathways [16], [21]. Despite extensive research on ALD, the role of nutrition in its pathogenesis and the initial mechanisms underlying the disease progression remain unclear. Furthermore, the progression of inflammatory response induced by excessive consumption of rich diets in refined carbohydrate and/or fat combining with acute Et-OH consumption is poorly known.
Here, we explore the effects of short-term exposure to diets high in refined carbohydrates or high in refined carbohydrates and fat, plus acute Et-OH consumption, in ALD progression. In the current study, we used a mild-acute ALD mouse model fed with these diets for 4 weeks prior to acute Et-OH exposure and evaluated for bodyweight gain, adiposity and liver injury. Alcohol consumption and the current eating habits can provide an increased incidence of liver disease. However, it appears that interactions between diet and alcohol are dependent on the length of exposure and the quality of diet. Therefore, it is critical to understand the influence of diet in ALD development.
Section snippets
Mice
Wild-type C57BL/6 (6 to 8 weeks old) mice were obtained from the Animal Care facilities of the Universidade Federal de Minas Gerais (UFMG, Brazil). The animals were housed collectively in conventional cage or individually in metabolic cages. The Animal Ethics Committee of UFMG ethically approved the experiments (protocol number: 119/2012).
Diet and ethanol protocol
Mice were fed, for a period of 28 days, with one of the following diets: control (AIN93), a high- sugar and -butter (HSB) hypercaloric diet or a diet high in
Effects of acute Et-OH consumption associated with HSB and HC diets on BW and adiposity
The HSB diet increased BW gain, independently of Et-OH consumption (Fig. 1A), whereas the HC diet did not alter BW, also independently of Et-OH consumption (Fig. 1B). Data published elsewhere were consistent with the latter result [22].
High-fat diets are frequently associated with weight gain [29] and adiposity increase [22]. However, most studies are performed by feeding animals with high-fat diet for periods ranging from 6 to 24 weeks [19], [20]. Mice fed with HSB and HC diets for a short
Discussion
Here, we have investigated the effect of acute Et-OH consumption in liver histopathology, as well as metabolic changes and inflammatory profile, using a mouse model of ALD fed for a short period with two different hypercaloric diets: one high in refined carbohydrates and fats and another high in refined carbohydrates. Although both diets induced early stages of steatosis, their combination with acute Et-OH consumption accelerated the steatotic process. Moreover, combining fat, refined
Conclusion
This is the first in vivo study showing that the association of refined carbohydrates, fat and acute Et-OH consumption, even at short exposures, results in inflammatory liver damage, with signs of initial steatosis. Understanding this initial liver inflammatory and injury mechanisms may help to further our current knowledge on the processes leading to ALD progression and provide useful insights for future research concerning the treatment of this condition.
Declaration of interest
This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (PNPD/CAPES; 23038.005051/2012-48) and the Fundação de Amparo e Pesquisa de Minas Gerais (FAPEMIG; APQ-02,285-14). CNPq, CAPES and FAPEMIG had no role in the design, analysis or writing of this article. This manuscript was reviewed by a professional science editor and by a native English-speaking copyeditor to improve readability.
Acknowledgments
The authors thank Ilma Marçal (ICB/UFMG) for technical support.
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- 1
Instituto Nacional de Infectologia Evandro Chagas (INI), Fundação Oswaldo Cruz, Rio de Janeiro, Rio de Janeiro.
- 2
These authors contributed equally to this work.