## 4 Discussion
No alteration in the levels of the enzymes after long-term administration of a very low-carbohydrate, low-protein diet in C57 BL/6] mice was observed. In turn, in a study by [PERSON] et al. [35], animals fed a diet consisting of 50% protein had high ALT and normal AST in comparison to those receiving an AIN-93M diet. These results were interpreted as hepatic lesions. [PERSON] et al. [36] observed an increase in ALT and AST to the same degree, in terms of enhancement of protein in diet. These authors concluded that protein (independently of other macronutrients) is a risk factor for liver injury. The main histological characteristic of nonalcoholic fatty liver disease (NAFLD) is the fat accumulation within hepatocytes in the form of TAG (a lesion originally termed \"steatosis\"). Thus, the minimum criterion for the histological diagnosis of this disease is more than 5% steatotic hepatocytes in a liver tissue section [37,38]. The steatosis extent is often evaluated semi-quantitatively, with the most reproducible method based on the division of the liver parenchyma into thirds. Then, the percentage involvement by steatotic hepatocytes is categorized as follows: 0-5%--none; 5-33%--mild steatosis; 33-66%--moderate steatosis; and more than 66%--severe steatosis [39,40]. Histological assays performed in the present study showed that, in the case of animals from the LCHP\({}_{\rm ch}\) group, the involvement by steatotic hepatocytes with their liver tissue was at a level that corresponds to mild steatosis (compared to no steatosis in AIN\({}_{\rm ch}\) group and mild steatosis in WD\({}_{\rm ch}\)). Many studies have shown that NAFLD can result from hepatitis infection, type II diabetes, a high-fat diet, lack of exercise or a combination of these factors [41]. Histologically, NAFLD may include steatosis alone. Additionally, it can comprise also changes associated with hepatocyte ballooning, nonalcoholic steatohepatitisitis, such as inflammation, necrosis and fibrosis. [PERSON] et al. [41] showed that a high-fat diet caused hepatic steatosis. Accumulation of lipids within the mice hepatocytes was induced by consumption of a 42% fat diet. Similar results were obtained by [PERSON] at al. [42]. Prolonged (80 wks HFD) feeding led to steatosis. Compared to a standard diet, a significant increase in lipid deposition in the livers of high-fat-diet-fed mice was observed [43]. In the study of [PERSON] et al. [44], 12-week HFD feeding induced macrovesicular liver steatosis, with a 6.5-fold elevation in the steatosis score in comparison to the control group. In our studies, it was observed that not only the WD\({}_{\rm ch}\) but also the LCHP\({}_{\rm ch}\) diet enriched with cholesterol also induced liver steatosis in rats. Moreover, the highest lipid concentration in the liverswas observed in rats fed the LCHP\({}_{\text{ch}}\) diet. [PERSON] et al. [45] showed that a high-protein diet has an antisteatotic and antiobeseogenic impact. Additionally, it prevents fatty liver in mice without inducing side effects. However, in this experiment, a diet containing \(\sim\)35% energy from protein, 5-10% energy from fat and 55-60% energy from carbohydrate was used. Serum VLDL-TGs enriched with SFAs are highly correlated with insulin resistance and adiposity. The LC diet decreased these VLDL particles and TG SFAs without affecting whole-body adiposity [46]. Added to this, liver fat accumulation creates self-reinforcing cycles that contribute to type 2 diabetes. Fatty liver leads to enhanced export of VLDL, which increases fat delivery to all tissues [47]. The dietary intake of fatty acids (FAs) affects the overall composition and distribution of FAs in the body. Adipose tissue is known as the body's largest energy storage organ in the form of TAG, being mobilized (through the lipolysis pathway) to deliver energy to other organs [48]. In our study, a significant increase in SFA as well as MUFA share was observed in WD\({}_{\text{ch}}\) and LCHP\({}_{\text{ch}}\), while PUFA was decreased as compared to the AIN\({}_{\text{ch}}\) group.