**7. Treatment of NAFLD/NASH**

**5. CYP7A1**

116 Cholesterol - Good, Bad and the Heart

Our previous study showed that dysregulated expression of enzymes involved in BA synthesis led to the accumulation of BA in the livers of SHRSP5/Dmcr rats fed an HFC diet [36]. We further investigate the role of CYP7A1 in the pathogenesis of hypertension-associated NASH, and evaluated its hepatic levels in hypertensive SHR and SHRSP5/Dmcr rats, and the normotensive WKY strain [28]. Constitutive CYP7A1 levels were markedly higher (over 300-fold) in the hypertensive strains compared with those in the normotensive WKY strain. Upregulation of CYP7A1 may result in an excessive accumulation of toxic BAs, such as hydrophobic BAs, which may lead to oxidative stress and liver damage. In addition, Kamisako et al. showed that the Nrf2 pathway may regulate the expression of genes associated with BA synthesis and fatty acid metabolism, including CYP7A1 [57]. Our study showed increased activation of Nrf2 signaling in the livers of hypertensive rats fed a control diet compared with the normotensive WKY, which might be the

The prevalence and severity of human NAFLD/NASH varies with gender and age [58]. Yatsuji et al. studied 193 Japanese patients with NASH (86 women and 107 men) and showed a predominance of the disease in women over 50 years old, yet a greater prevalence in men aged 30–40 years [59]. Williams et al. reported that NAFLD patients were more likely to be male, older, and hypertensive [60]. The incidence of NAFLD/NASH is higher in men than premenopausal women (less than 50 years of age), while this immediately increases in women after menopause. Therefore, sex hormones such as estradiol may influence gender differences in NASH. In our study, we regarded female SHRSP5/Dmcr rats aged 12–24 weeks to correspond to the menopausal age in women. We also found female rats were less susceptible to HFC diet-induced liver damage compared with males [61]. Hence, our rat model may be useful for studies into gender differences in HFC-induced NASH. In order to investigate the related mechanisms, mature female and male SHRSP5/Dmcr rats (10 weeks old) were fed either an HFC or control diet for 2, 8, and 14 weeks. The severity of hepatic fibrosis was markedly lower in the female rats compared with the males. Although HFC feeding significantly reduced serum estradiol levels in female rats at 2 weeks, these levels were still much higher in females compared with males during HFC feeding, suggesting that this female hormone may contribute to the gender difference in NASH. In addition, only minor gender differences were noted in the expression of CYP7A1, CYP8B1, CYP27A1, and CYP7B1, the enzymes involved in BA synthesis, as well as MRP3 and BSEP, the proteins associated with BA transport. On the other hand, the enzymes implicated in BA detoxification, UGT and SULT2A1, as well as the nuclear receptors, CAR and PXR, were significantly suppressed in the male rats fed the HFC diet, whereas expression of these proteins was only slightly changed in females following HFC feeding. Since estradiol, which markedly decreases in women after menopause, may stabilize CAR and PXR proteins [61, 62], these results suggested a stronger capacity of BA detoxification associated with higher estradiol levels may be responsible for the resistance to HFC-induced liver damage and hepatic fibrosis in female rats compared with males.

responsible for the overexpression of CYP7A1 in the hypertensive strains [28].

**6. Gender differences in NASH development**

NAFLD/NASH is related to poor lifestyle, including unhealthy diet habit and lack of exercise, which may, in turn, lead to excessive weight gain. Therefore, dietary intervention and exercise, targeted at weight loss, are the primary therapies for obesity-related NAFLD/NASH [63]. Vilar-Gomezet al. evaluated the effect of weight loss through lifestyle modifications on the improvement of NASH-related histologic features [64]. The study included 293 patients with NASH who followed a recommended lifestyle over 52 weeks to reduce body weight, including a low-fat, hypocaloric diet (750 kcal per day) and walking (200 min per week). Among these patients, 30% lost ≥5% of their weight at 52 weeks, 25% showed resolution of steatohepatitis, and 47% showed reduced nonalcoholic fatty liver disease activity score (NAS). This study also reported that the extent of weight loss was associated with histologic improvement. A higher proportion of patients with ≥5% weight loss had NASH resolution compared with those with ≤5% weight loss. Furthermore, 45% of patients with ≥10% weight loss showed regression of hepatic fibrosis.

Although NAFLD/NASH is closely linked with obesity and diabetes, it may also occur in the absence of these diseases [65]. As described before, the hypertensive SHRSP5/Dmcr rat represents a good model of NAFLD/NASH without obesity and diabetes [20]. We used this model to investigate the efficacy of dietary intervention for improving HFC-induced NASH [66]. Rats were fed an HFC diet for 2 weeks (before the appearance of hepatic fibrosis) or 8 weeks (after the appearance of fibrosis), then subsequently fed a control diet for 6 or 12 weeks. We found that dietary intervention prior to the appearance of fibrosis markedly improved steatosis and suppressed the HFC-induced increase in serum AST, ALT, and TC. On the other hand, dietary intervention after the appearance of fibrosis was unable to suppress the increase in serum ALT and hepatic TC. Although the dietary intervention (in both cases) reset the increased expression of fibrosis-relative proteins, TGF-β1 and α-SMA, it only slightly reduced the fibrotic area compared with continuous HFC feeding. Taken together, dietary intervention was able to completely or partially improve steatosis, inflammation, and cholesterol accumulation in the livers of rats fed an HFC diet, although this was not enough to improve hepatic fibrosis.

In addition, several pharmacological agents use in the treatment of NASH, including vitamin E and pioglitazone, have been tested [67, 68]. Oxidative stress and insulin resistance are considered as key factors implicated in the progression of NASH, and are, therefore, attractive targets for the treatment of NASH [69]. Sanyal et al. tested the efficacy of vitamin E, a lipid-soluble antioxidant, and pioglitazone, an insulin sensitizer, in NASH patients without diabetes [69]. The 247 patients included in this study received 800 IU vitamin E (84 subjects), 30 mg pioglitazone (80 subjects), or placebo (83 subjects) daily for 96 weeks. Both vitamin E and pioglitazone were associated with improvements in hepatic steatosis and lobular inflammation, as well as a reduction of serum AST and ALT, compared with the placebo. However, neither drug had a significant effect on hepatic fibrosis. In conclusion, lifestyle intervention (controlled dietary intake as well as exercise) may be the first choice for NAFLD/NASH treatment and should be optimized, while pharmacological management can be used as an auxiliary method, and should be further tested in large studies with long-term outcomes.

**8. Conclusions**

**Author details**

, Hisao Naito2

and Tamie Nakajima<sup>1</sup>

1 College of Life and Health Sciences, Chubu University, Kasugai, Japan

\*Address all correspondence to: tnasu23@med.nagoya-u.ac.jp

The British Journal of Nutrition. 2011;**106**(1):6-14

nursing practice. Home Healthc Now. 2017;**35**(2):72-82

Journal of Nutrition. 2015;**114**(10):1667-1673

\*

2 Department of Public Health, Fujita Health University School of Medicine, Toyoake, Japan

[1] Lecerf JM, de Lorgeril M. Dietary cholesterol: From physiology to cardiovascular risk.

[2] Lajous M, Bijon A, Fagherazzi G, Balkau B, Boutron-Ruault MC, Clavel-Chapelon F. Egg and cholesterol intake and incident type 2 diabetes among French women. The British

[3] Rouen PA, Wallace BR. The 2015-2020 dietary guidelines: Overview and implications for

Yuan Yuan1

**References**

In our previous study, we established a novel model of fibrotic steatohepatitis by feeding hypertensive SHRSP5/Dmcr rats an HFC diet. Histological features resembling human NASH were observed in the rats, suggesting that this model is useful for studying hypertension-associated NASH. We compared NASH development among hypertensive strains (SHRSP5/Dmcr and SHR) and the normotensive WKY strain, and showed that hypertension accelerates progression of HFC-induced NASH by elevating BA synthesis (CYP7A1), inducing increased activation of inflammatory signaling (MAPK and NF-κB), and suppressing signaling associated with antioxidant defense (Nrf2/Keap1). To elucidate the role of cholesterol in NASH development, we investigated the kinetics of cholesterol in this model, and found that the HFC diet induced dysregulation of BA synthesis and suppression of BA detoxification, therefore resulting in cytotoxic BA accumulation in hepatocytes, which further induced oxidative stress, followed by activation of signaling involved in hepatic inflammation and fibrosis (**Figure 1**). Sex differences in fibrogenesis were also observed in this model and were associated with a different sensitivity to BA toxicity. More sustained expression of nuclear receptors, CAR and PXR, and the enzymes involved in BA detoxification, UGT and SULT, contributed to the stronger resistance to HFC-induced liver damage in female rats compared with males. In conclusion, our studies demonstrate that dietary cholesterol may play a crucial role in the progression of NASH-associated hypertension and provide a basis for NAFLD/NASH treatment involving restriction of cholesterol intake.

The Role of Cholesterol in the Pathogenesis of Hypertension-Associated Nonalcoholic…

http://dx.doi.org/10.5772/intechopen.76199

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**Figure 1.** Possible mechanism underlying pathogenesis of HFC diet-induced fibrotic steatohepatitis in hypertensive SHRSP5/Dmcr rats [25, 35, 47]. In response to cholesterol accumulation in the liver triggered by HFC feeding, de novo cholesterol synthesis and its uptake were suppressed, indicated by a reduction in HMGCR, as well as LDLR and LPR1. The HFC diet induced dysregulated BA synthesis (upregulated CYP7A1 and CYP7B1, as well as downregulated CYP8B1 and CYP27A1) and export (downregulated BSEP and MRP2, as well as upregulated MRP3), and led to BA accumulation in hepatocytes. In addition, the HFC diet suppressed BA detoxification by decreasing the expression of nuclear receptors (PXR and CAR), and further downregulating SULT2A1 and UGT1A1, BA detoxification enzymes. Furthermore, cytotoxic BA accumulation in hepatocytes-induced oxidative stress, which activated inflammatory signaling (TNF-α, TGF-β/NF-κB, MAPK) and resulted in hepatitis. Hepatic inflammation-induced upregulation of fibrosis-related genes (α-SMA, PDGF-β, Col1a1) and led to hepatic fibrosis. Additionally, hypertension enhanced the deterioration of HFC-induced fibrotic steatohepatitis by upregulating CYP7A1, further leading to BA accumulation in hepatocytes and increased oxidative stress. On the other hand, hypertension induced the suppression of anti-oxidative signaling (Nrf-2/Keap1) following HFC feeding. Therefore, elevated oxidative stress and suppressed anti-oxidative capacity triggered a more severe inflammatory response in the hypertensive rats fed an HFC diet, as indicated by increased activation of inflammatory signaling (TNF-α, TGF-β/NF-κB, MAPK). BA, bile acid; HMGCR, 3-hydroxy 3-methyl-glutaryl-coenzyme A reductase; LDLR, low density lipoprotein receptor; LRP1, LDLR-related protein 1; CYP7A1, cholesterol 7α-hydroxylase; CYP8B1, sterol 12α-hydroxylase; CYP27A1, sterol 27-hydroxylase; CYP7B1, oxysterol 7α-hydroxylase; BSEP, bile salt export pump; MRP2, multidrug resistance-associated protein 2; MRP3, multidrug resistance-associated protein 3; FXR, farnesoid X receptor; PXR, pregnane X receptor; CAR, constitutive adrostane receptor; SULT2A1, sulfotransferase 2A1; UGT1A1, UDP-glucoronosyltransferase 1A1; TNF-α, tumor necrosis factor-α; TGF-β, transforming growth factor; NF-κB, nuclear factor kappa B; MAPK, mitogen-activated protein kinase; α-SMA, α-smooth muscle actin; PDGF-B, plateletderived growth factor subunit B; Col1a1, alpha 1 type 1 collagen; Nrf-2, nuclear factor erythroid 2-related factor 2; Keap1, Kelch-like ECH-associated protein 1.
