ABC | Volume 113, Nº5, November 2019

Original Article Muniz et al. Metabolic disorders in a modified dyslipidemia model Arq Bras Cardiol. 2019; 113(5):896-902 The increased liver weight in the HL/HCD group is related to the strong presence of fat vesicles in hepatocytes, as observed in the liver morphological evaluation (Figure 1). A previous study with mice on a high-fat and high-cholesterol diet, without cholic acid, for 16 weeks presented similar results regarding liver weight and hepatic tissue lipid accumulation. 11 In our study, the cholic acid probably accelerated the dyslipidemic effects of cholesterol in the HL/HCD group, given that we identified metabolic disorders in only 6 weeks, whereas the study by Jung et al. 11 reached the same effects in 16 weeks. The serum lipid impairment observed in animals fed HL/HCD is characteristic of dyslipidemia, and the marked increase in LDL-c may be related to the reduction in LDL-c receptor activity in hepatocytes. Previous studies revealed changes in TC and TG serum levels of rats and mice fed a high-fat and high-cholesterol diet. 10,12 However, the experimentation periods of the reported studies (9 and 12 weeks, respectively) were longer than that used in the present study. The serum lipid profile of the animals fed HLD did not differ from those fed STD. Studies with Wistar rats on 50% to 55% lard diets (67% to 75% of the diet energy) for four weeks showed similar results. 8,9 The harmful effect of very high intake of saturated fatty acids and its relation to dyslipidemia have been questioned. 1 Siri et al. 21 highlighted that the effects of saturated fat on serum lipid profile could be modulated by the content and/or availability of polyunsaturated fatty acids, so that saturated fat would only increase LDL-c if the polyunsaturated fat intake is below a threshold level (5% of the diet energy). 22 Our results confirmed that the excessive intake of saturated fatty acids explains only part of the changes in serum lipid profile. Other factors influence these changes, such as dietary cholesterol, obesity, insulin resistance, and hypertriglyceridemia. 23,24 High ALT and AST serum levels are characteristic of NAFLD and are associated with insulin resistance. In this study, increased ALT and AST serum levels were compatible with the hepatic damages observed in the animals fed HL/HCD. Other studies also found increased ALT and AST serum levels in mice fed a high-fat and high-cholesterol diet. 11,12 The morphological evaluation showed marked changes in the hepatic tissue of animals fed HL/HCD, such as fatty macrovesicles and inflammatory infiltrates, characterizing a moderate hepatic steatosis, 25 whichwas confirmed by the results of the hepatic enzymes (ALT and AST). Fat accumulation in the liver of these animals is related to high cholesterol consumption, as this overload in the cells alters the cholesterol homeostasis. 26 In addition, the accumulation of intermediate lipidmetabolites, such as diacylglycerol and acylcarnitines, is associated with inflammation and insulin resistance. 27,28 A previous study suggested that high dietary cholesterol is a critical factor for the progression of hepatic steatosis and inflammation in animal models. However, features of NAFLD are more evident when the supplemented cholesterol is associated with cholic acid in a high-fat diet, as observed in our study. The presence of inflammatory infiltrate in the hepatic tissue promotes cytokine and chemokine secretion, such as tumor necrosis factor α (TNF- α ) and interleukin 6 (IL-6), which induce insulin resistance. In this metabolic disorder, the increased lipolysis of TG stored in the adipose tissue raises fatty acid production. The fatty acids released in the circulation, in turn, inhibit the anti-lipolytic action of insulin and promote higher lipid absorption by the liver, leading to dyslipidemia and hepatic steatosis. 3,32,33 Hamsters on a 10-week hyperlipidemic diet containing cholesterol (0.2%) developed dyslipidemia and hepatic steatosis, with impaired TC, TG, LDL-c, ALT, and AST serum concentrations. 34 Liver histopathological analysis of Sprague-Dawley rats fed a high-cholesterol diet (1.5%) also revealed hepatic steatosis and inflammation. 35 One limitation of our study was the impossibility to use more accurate methods to evaluate liver fat macro- and microvesicles and foam cells, such as Oil Red and immunohistochemistry, respectively, which could allow us to analyze liver damages quantitatively. Moreover, we recommend further studies, including a treatment with lard and cholic acid, to investigate whether cholic acid can enhance the metabolic effects of lard cholesterol. Conclusion A high-fat diet with lard (20%) and cholesterol (1%) triggered dyslipidemia with severe liver damage in rats in a shorter experimental time than the previously reported models. The high-lard diet without supplementation of cholesterol led to body weight gain, but not to dyslipidemia. This model may be useful to investigate metabolic disorders in different experimental designs related to dyslipidemia and its comorbidities. Acknowledgments The authors thank the FAPEG (Fundação de Amparo à Pesquisa do Estado de Goiás, Brazil) for the research funding and scholarship, and Professor Maria Aderuza Horst, Ph.D., for assistance with animal procedures. Author contributions Conception and design of the research and Obtaining financing: Naves MMV; Acquisition of data: Muniz LB, Alves‑Santos AM, Camargo F, Martins DB, Celes MRN; Analysis and interpretation of the data, Statistical analysis and Writing of the manuscript: Muniz LB, Alves-Santos AM; Critical revision of the manuscript for intellectual content: Martins DB, Celes MRN, Naves MMV. Potential Conflict of Interest No potential conflict of interest relevant to this article was reported. Sources of Funding This study was funded by FAPEG. Study Association This article is part of the project of Post-Doctoral of Lidiane B. Muniz, conducted at Universidade Federal de Goiás. 900