Some Clinical Concerns of Non-Alcoholic Fatty Liver Disease Zeng Minde Mao Yimin Non-alcoholic fatty liver disease (NAFLD) is a genetic-environmental-metabolic stress-associated liver disease, which includes simple fatty liver (NAFL) and its progression to steatohepatitis (NASH) and cirrhosis.NAFLD can be a stand-alone disease, but is more often a hepatic pathological process of systemic disorders, and is often associated with the development of a metabolic syndrome (MS), a metabolic syndrome (MS). The 2004 World Symposium on Insulin Resistance (IR) included NAFLD among the major conditions that constitute the metabolic syndrome (MS), whose other components include visceral obesity, diabetes mellitus, hyperlipidemia, and hypertension. Currently, the prevalence of NAFLD ranges from 20% to 30% in developed countries in the West, and 12% to 24% in Asia-Pacific and North American countries. NAFLD is increasingly showing its clinical importance due to its high prevalence, low ageing trend, chronic progressive course, association with other chronic liver diseases, and impact on the occurrence of cardiovascular events. MAO Yimin, Department of Gastroenterology, Shanghai Renji Hospital, Shanghai, China I. Awareness of the etiology of NAFLD In 2002, the American Gastroenterological Association (AGA) suggested standardizing the nomenclature of fatty liver disease (FLD) according to the relationship between the etiology and the histological alterations, which include alcohol, IR, drugs, toxins, dyslipidaemia, weight loss, and idiopathic causes. Subsequently it became common to refer to the etiology of NAFLD associated with IR and genetic susceptibility as primary, and those caused by many environmental factors and inborn metabolic disorders as secondary. Some authors have accordingly proposed new etiologic classifications of steatohepatitis, including NASH, alcohol-associated steatohepatitis (AASH), virus-associated steatohepatitis (VASH), drug-associated steatohepatitis (DASH), and metabolism-associated steatohepatitis (MASH). Recent studies have shown that about 10% to 20% of NAFLD do not have IR, about 50% of NAFLD do not fully meet the diagnostic criteria for MS, and the cause of more than 20% of NAFLD is unknown.Angulo et al. found that 29% of 144 patients with pathologically confirmed NASH were neither obese nor diabetic and had normal lipids. A number of authors have emphasized that relevant risk factors should be actively explored in terms of genetic predisposition and environmental factors, which can be present in nonobese nondiabetic patients and precede IR, including metabolic dysregulation of adipose tissue distribution, postprandial hyperlipidemia, congenital/acquired mitochondrial insufficiency, budding status associated with small intestinal bacterial overgrowth and TNFα, iron overload, hypoxemia, non-IR-associated infections, and endocrine diseases, among others. Given the increasing prevalence of NAFLD in children and adolescents, attention should also be paid to underlying inborn metabolic disorders, such as lipid and fatty acid disorders, carbohydrate disorders, amino acid disorders, bile acid synthesis deficiency disorders, peroxisomal disorders, protein folding disorders (α1AT deficiency), disorders of RNA processing, and wilson’s disease, which can all present with FLD. ii. Pathogenesis and natural course of the disease The second strike theory proposed by Day et al. in 1998 is still the keynote to explain the pathogenesis of NAFLD. The first blow is caused by IR and fatty acid (FA) metabolism disorders causing fatty liver, Dounelly et al. study suggests that NAFLD intrahepatic FA accumulation to form triacylglycerol (TG) 60% from adipose tissue non-acylated FA, 25% from intrahepatic lipogenesis, 15% from diet; the second blow in the IR based on oxidative stress, mitochondrial insufficiency, cytokines and nutritional changes The second blow, based on IR, is induced by oxidative stress, mitochondrial insufficiency, cytokines, and nutritional changes that lead to the development of NASH and cirrhosis, in which the intrahepatic TG/FA ratio decreases with an increase in total polyunsaturated FA and free cholesterol. Phosphatidylcholine decreases, and glycolipotoxicity of FA via adaptive non-oxidative pathways promotes the development of MS. McCullough et al. reported that NASH occurs in 17% of NAFL in 5-10 years, with a 15%-25% incidence of cirrhosis in the latter within 10-15 years.Angulo et al. followed 257 cases of NAFLD for 3.5-11 years, of which 54 were re-liver biopsied, and found that 13% had remission of the lesions, 59% had stable lesions, and 28% showed progressive liver damage and Cirrhosis. In recent years, there have been more reports of long follow-up consecutive liver biopsies to observe the progression of NAFLD, and the results do not vary much, in 3-20 years about 20% of patients have improved lesions, 50% have stable lesions, and 30% have progressive lesions.The occurrence of MS in association with NAFLD is related to the duration of the disease and the extent of the lesions, and the presence of NAFLD in about 50% to 80% of NAFLD meets the diagnostic criteria of MS by WHO, and it is more common in patients with NASH. More common, Hsiao et al. observed the correlation between the severity of fatty liver (ultrasound) and MS risk factors in 16486 cases of NAFLD, and found that the incidence of MS was significantly higher in those with severe fatty liver than in those with mild fatty liver.EUsteat et al. regularly followed up 129 patients with NAFLD for 13.7 years, of which 71 were NASH and 4 cirrhosis, and as a result of 19 deaths, the The incidence of liver disease-related deaths was 2.8%, while the incidence of cardiovascular disease deaths was as high as 15.5% III. Association of NAFLD with other chronic liver diseases 1. NAFLD and Alcoholic Liver Disease (ALD) The two diseases are similar in their pathologic changes, and it is sometimes difficult to distinguish between them. Confirmation of history of alcohol consumption and the amount of alcohol consumed plays a key role in differentiating the two diseases. Prospective studies and meta-analyses in Italy have shown that 30 g/d of alcohol is the risk threshold for the development of ALD. Alcohol consumption for the diagnosis of ALD was >40 g/d for men and >20 g/d for women in China, >60 g/d for men and >40 g/d for women in the Asia-Pacific region, and >62.5 g/d for men and >60 g/d for women in the United States Agri-Food Guide (ADG). Alcohol consumption to exclude NAFLD is <140g/w for men and <70g/w for women in China and Asia-Pacific; <210g/w for men and <140g/w for women in Western countries.The history of alcohol consumption in ALD is generally more than 5 years, but it has been reported that alcoholic fatty liver disease can occur in about 2 weeks at 80~160 g/d. Excessive alcohol consumption, obesity, and excessive alcohol consumption with obesity increase the risk of FLD by 3.6, 11.6, and 17 times, respectively. Drinking ≥50 g/d increases obesity, while 125-250 g/w increases the prevalence of diabetes. Recently Bedogni et al. reported that in a group of patients with suspected liver disease who were excluded from HBV and HCV and followed for a mean of 8.5 years, each 20 g/d increase in alcohol intake was associated with a 17% increase in the incidence of fatty liver and a 10% increase in morbidity and mortality. 2. NAFLD and Chronic Hepatitis C (CHC) About 40% to 86% of patients with CHC have hepatocellular steatosis, which is roughly of two types, one is viral One is viral fatty liver, which is caused by the direct action of HCV gene type 3 viral proteins, especially core proteins (CHC-3); the other is metabolic fatty liver, which is mainly seen in those infected with HCV gene types I and IV viruses (CHC-1, CHC-4), and is caused by IR and MS-related factors.Bedossa et al. reported the results of a prospective study of 278 cases of CHC in combination with NAFLD, with 57% of those with CHC alone and 57% of those with CHC alone. CHC in 57%, CHC+fatty liver in 34%, and CHC+NASH in 9%.The expected factors for the occurrence of CHC with fatty liver/NASH were increased HOMA-IR and TG levels and decreased HDL-C levels in CHC-1 and CHC-4, and increased AST levels in CHC-3. Concurrent NAFLD may affect CHC lesions in the following four ways: (i) increased MS component and its incidence; (ii) increased fibrosis in 40% of CHC+NAFLD patients, with age and ALT level as independent predictors; (iii) low sustained response to viral therapy (SVR), which was significantly lower in CHC-1 than in CHC-3 (39% vs. 72%); and (iv) increased hepatocellular cancer (HCC) risk, hepatic steatosis was associated with postoperative recurrence of HCV-associated HCC, with recurrence rates of 19%, 76%, and 92% at 1, 3, and 5 years postoperatively in the hepatic steatosis group; and 12%, 52%, and 60%, respectively, in the non-hepatic steatosis group.3. NAFLD and chronic hepatitis B (CHB) Lin et al. observed 5,406 adults in Taiwan, China, who were HBV carriers ( HBVC) and ultrasonographically diagnosed fatty liver (SLF) on liver injury. The prevalence of HBVC was 25.1%, SLF was 33.4%, and the synergy index of HBVC+SLF on liver injury was 1.4, with male and overweight as independent influences. Several cities in China have reported a prevalence of CHB+NAFLD of about 15%-20%, which is age-related, with an ultrasound-pathologic diagnostic concordance rate of about 65%, and dyslipidemic changes in about half of the patients. Recently Bondini et al. reported the results of a prospective clinicopathologic study of 153 patients with CHB combined with NAFLD, 68% with CHB alone, 19% with CHB+NAFL, and 13% with CHB+NASH; the age of CHB vs. CHB+NAFLD was 42 vs. 55 years old; and the incidence of waist circumference, hypertension, and dyslipidemia was significantly higher in those with CHB+NAFLD than in those with CHB alone. The incidence of waist circumference, hypertension and dyslipidemia in CHB+NAFLD was significantly higher than that in CHB alone; about 40% of patients showed progressive fibrosis, and in addition to correlation with HBV-DNA levels, abdominal obesity was also an independent influence.4. NAFLD and drug-induced liver injury (DILI) The two diseases share common pathophysiological mechanisms, and are associated with mitochondrial insufficiency, oxidative stress, and elevated expression of CyP2E1. Both obesity and diabetes can be independent risk factors for DILI, which is a common cause of secondary NAFLD. Pharmacologic fatty liver is closer to ALD than diabetes-induced NAFLD, and phospholipid deposits are often found. Hepatic steatosis is often an early pathologic manifestation of DILI and is mixed with the hepatocellular injury, cholestatic, and mixed types of DILI, but the incidence of it becoming an independent lesion type of DILI is rare, usually <2%. Acute lesions are common in the small vesicular type of hepatic lipidosis type, while chronic lesions are common in the large vesicular type. Recently Farantino et al. reported a prospective study on the occurrence of acute DILI in patients with NAFLD, 174 cases of CHC vs. 74 cases of NAFLD, the incidence of acute DILI was 2.4%, which was 4 times higher than that of CH. Both central abdominal obesity and NAFLD were independent risk factors, and the drugs that cause acute DILI include antihypertensive drugs, antiplatelet coagulant drugs, antibiotics, nonsteroidal anti-inflammatory drugs, and proton pump inhibitors. In view of the fact that weight loss drugs, insulin sensitizers, lipid-lowering drugs, antihypertensive drugs, antigout drugs and other drugs commonly used in the treatment of NAFLD can induce DILI, clinical vigilance is needed. IV. NAFLD and the risk of cardiovascular disease (CVD) 1. Importance of carotid atherosclerosis in NAFLD Recently, it has been reported that the brachial artery-mediated vasodilatation (FMV) of the endothelial function test was significantly decreased in NAFLD compared with CHC, CHB and healthy controls after correcting for age, sex, BMI, IR, and other components of MS; and the FMV, which is a reliable indicator of early atherosclerosis, reflected a significant decrease in vascular wall stiffness, which is the most important factor in the development of atherosclerosis. sclerosis, the carotid intima-media (IMT), which reflects fatty infiltration of the vessel wall with fibrofatty or fibrocalcified lesions, was significantly thickened, and the authors emphasized that the strong correlation of NAFLD with early atherosclerosis outweighs its interrelationships with other phenotypes of MS.Perseghin et al. examined 21 newly diagnosed young non-diabetic individuals with NAFLD with 21 matched healthy individuals, by MRI Perseghin et al. measured intrahepatic fat content, epicardial fat content, and phosphocreatine (Pcr)/ATP ratio, a marker of myocardial energy metabolism, in 21 newly diagnosed young non-diabetic patients with NAFLD and 21 matched healthy individuals by MRI and MRS, and found that patients with NAFLD had an increased level of hepatic fat content accompanied by an increased level of epicardial fat content, and that Pcr/ATP ratios were significantly lower, and that the heart could develop abnormal LV energy metabolism early in life, in the absence of other morphologic and functional alterations.NAFLD Patients have an increased likelihood of 10-year predicted cardiovascular events and the risk of CVD precedes liver failure. In a cohort follow-up of NAFLD and comparison with controls, it was found that the lower survival of NAFLD patients than controls was mainly due to a higher CVD mortality rate.2. NAFLD as an Independent Risk Factor for CVD NAFLD influences the development of CVD independently of other traditional risk factors, and the possible pathophysiologic mechanisms include: (1) IR: hepatic IR aggravates systemic and cardiac IR; (2) Abnormalities in lipid profile and its distribution: the liver and the heart are the first organs for visceral fat mobilization, and liver fat content can serve as a source of fat ectopic to the heart, and there is a common lipotoxic mechanism; (3) Oxidative stress: the production of free radicals and oxLDL invites endothelial damage, affects the stability of the vascular wall plaques, and contributes to the rupture of vulnerable plaques; (4) A state of low-grade inflammation: the liver and the adipose tissues of NAFLD release inflammatory factors and other mediators, affecting the vascular wall, and the adipose tissue. Low-grade inflammatory state: NAFLD liver and adipose tissue can release inflammatory factors and other mediators, affecting the vascular wall and myocardial metabolism; ⑤ Other: such as postprandial hyperlipidemia, low lipocalin levels, etc. V. Serological markers related to NASH 1. Hepatocyte apoptosis and damage markers ① ck-18: it is a cytokeratin fragment produced by hemiacyl asparaginase (caspase), and the specificity of diagnosing NASH with a cutoff value of 380U/L is 94%, and the sensitivity is 91%; ② ALT, AST, GGT: the sensitivity of diagnosing NASH with elevated ALT is only 40%. Elevated AST has been observed to be valuable in CHC-3 and CHB patients. In patients with NASH, more attention is paid to the AST/ALT ratio (AAR), although both ALT and AST elevation may be released by injured hepatocytes, but AST elevation is also related to sinusoidal gap cell contouring disorder, AAR in NASH can be >0.8, but <2, which is different from ALD. GGT is a membrane-bound enzyme, and its level of persistent increase can reflect IR, which is related to the presence of hyper-TG anemia and diabetes mellitus. 2. Markers of oxidative stress ① Increased levels of oxLDL, thiobarbituric acid reactive substances (TBARS), and epoxide-reduced protein (TRX) can be seen in some NASH patients, but have not been widely verified; ② Malondialdehyde (MDA), superoxide dismutase (SOD), reduced glutathione (GSH), oxidized glutathione (GSSG), glutathione peroxidase GSH-PX, glutathione transferase, and glutathione transferases are also found in some NASH patients. PX, glutathione transferase (GST), and other levels of alteration, failed to observe consistent findings, and lacked clinical evaluation value. 3. Inflammatory markers ① Increased levels of TNFα/IL-6 and decreased levels of lipocalin; ② Increased levels of high-sensitivity CRP; ③ Increased levels of cc-superfactoring factor ligand-2 (ccl-2)/monocyte chemotactic protein-1 (MCP-1) ratio. These three tests help to distinguish NASH from NAFL. 4. Markers related to IR/MS: (1) Increased levels of IL-6, CRP, and GGT; (2) Increased levels of RBP-4 and Resistin; (3) Increased levels of Acylation Stimulating Protein (ASP) are related to IR and TG; (4) Homocysteinemia is related to IR and CVD risk factors; (5) Increased levels of ASP are related to TG; (6) Increased levels of CVD risk factors; (7) Increased levels of CVD risk factors; (8) Increased levels of CVD risk factors; and (9) Increased levels of CVD risk factors. CVD risk factors; ⑤ low levels of dehydroepiandrosterone sulfide (DHEA) are associated with insulin sensitivity, oxygen stress, and fibrogenesis.5. Hepatic Fibrosis Marker Combinations ①BAAT: BMI, age ≥50 years, ALT ≥2ULN, TG ≥1.7mmol; ②Fibrotest: α2 macroglobulin, hepatic beadstreak, GGT, APOA1, bilirubin; ③ European liver fibrosis combination model: hyaluronic acid (HA), type III procollagen peptide, matrix metalloproteinase inhibitor-1; ④ HA scoring system: age, BMI, AAR, diabetes mellitus, HA; ⑤ Triple assessment model: lipocalin, IR, type IV collagen-TS; ⑥ NAFLD fibrosis scoring system: age, BMI, platelet count, albumin, AAR, hyperglycemia. VI. Imaging assessment 1. Degree of fatty liver Ultrasound, CT and conventional MRI are sensitive only when hepatocellular lipoatrophy is >33%, and H1-MRI can detect lesions with hepatic fat content >5% ww. Lindon et al. have recently proposed a system of ultrasound assessment for the diagnosis of fatty liver and believe that quantitative assessment of hepatic echogenicity, echogenicity penetration and septal visibility, as well as clarity of hepatic vascular structure can help to distinguish between mild, moderate, and severe fatty liver. Fibroscan examination of liver stiffness KeHeber et al. reported that the mean KPa value of liver stiffness was 6.9 for F0-F1 and 18.8 for F2-F4, and that a KPa value of 10 was used as the cutoff value for >F2, with a sensitivity of 88% and a specificity of 72%.Fukuzawa et al. reported that the KPa values of F1 and F2 were 6.9 and 18.8, respectively. Fukuzawa et al. also reported that the mean KPa values of F1 and F2 ranged from 6.8 to 8.4, and those of F3 and F4 ranged from 35.4 to 59.1, with a significant difference between F1-2 and F3-4.3. Visceral fat (VF) accumulation Usually, a VF area of 100 cm2 is used as a criterion for determining central obesity, but Chinese people are susceptible to VF accumulation even with a BMI of 18-25 kg/O, and the MS prevalence is similar to that of central obesity with a VF area of 80 cm2. The prevalence of MS in VF area up to 80 cm2 is similar to that of central obesity. 4. Thickening of IMT IMT ≥1.1L is a sign of early atherosclerosis, and the thickening of IMT is closely related to the degree of hepatic fibrosis. VII. Histological scoring system 1. Kleiner et al. NAFLD histological scoring system consists of 14 histological indicators, of which hepatocyte lipoatrophy (0-3 points), ballooning (0-2 points), intrafollicular inflammation (0-2 points), and fibrosis (0-4 points) have semiquantitative scoring, and the other 9 are indicated by “yes” or “no”. The other 9 items were indicated as “yes” or “no”. In order to assess short-term reversible liver injury especially the changes after clinical treatment, the other 3 quantitative indexes (0~8 points) without fibrosis indexes were used as the activity scoring system called NAS, NAS 0~2 points can exclude NASH, NAS 3~4 points are suspected NASH, and NAS>5 points diagnose NASH.2. NAFLD histological scoring system of Mendler et al. by Hepatocellular lipoatrophy (1~4 points), ballooning (0~3 points), intrafollicular inflammation and necrosis (0~3 points), Mallory vesicles (0~3 points), perisinusoidal fibrosis (0~3 points), and confluent zone fibrosis (0~6 points), which consisted of 6 indexes. The activity score (AS) consisted of 4 items totaling 0~12 points, including ballooning lesions, intrafollicular inflammation and necrosis, Mallory vesicles and perisinusoidal fibrosis. In addition, the severity of NAFLD was assessed according to the points of AS and the scoring of the degree of fibrosis in the confluent area (1~3 degrees). VIII. Comprehensive management of NAFLD 1. Basic principles ①Pre-treatment evaluation to establish the diagnosis of NAFLD, understand the degree of lesions and associated MS; ②Treatment of primary underlying diseases; ③Adherence to lifestyle intervention as the basic treatment; ④Avoidance of other hepatic damage factors, especially alcohol and drug damage; ⑤Those who are not effective after 3~6 months of basic treatment, with liver function abnormalities/MS, and those who have a NAS>5 in liver biopsy, can be treated with drug-assisted therapy. If the treatment is not effective after 3~6 months of basic treatment, those with abnormal liver function/MS, those with NAS >5 on liver biopsy, can be treated with drug-assisted therapy, and those with end-stage liver disease need to consider liver transplantation; 6. Treatment monitoring, assessing the efficacy and safety of the interventions and guiding the subsequent treatments, and dynamically observing not only the liver lesions, but also MS and other metabolic risk factors, tumorigenesis, and CVD events. 2. Lifestyle interventions Includes behavioral modification, dietary adjustments, and exercises. It has been reported that prospective study of children with NAFLD simple dietary control and exercise for 1 year, IR and NAFL are significantly improved. European observation of Mediterranean lifestyle with rational energy intake and dietary structure, control of alcohol consumption, smoking cessation, and adherence to exercise as the main features, can lead to a decrease of more than 50% in all-cause and individual-cause mortality of 70-90 year olds who have been following the long-term, which is related to the improvement of endothelial function and inflammation indexes, and the reduction of the incidence of MS and the incidence of CVD events. The NIH and other organizations in the United States recommend that a diet with 20% protein, ≥50% carbohydrates, ≤30% lipids, and 60 min/d of aerobic activity, at least 5 days per week, is reasonable. Basic treatment should not be abrogated, and it has been reported that with dietary control alone and no exercise, fatty liver can be reduced but fibrosis can be aggravated.3. Pharmacological treatment Currently, relevant drugs used in the treatment of NAFLD include insulin sensitizers, weight-loss drugs, lipid regulating drugs, blood pressure-lowering drugs, antioxidants, cytoprotectants, anti-inflammatory cytokines, and intestinal microecological modifiers, and other classes of drugs. Prospective multicenter trials are underway in the United States and Japan, among others, to observe the efficacy of insulin sensitizers with vitamin E in NAFLD. Given that insulin sensitizers, diet pills, lipid regulators and antihypertensive drugs have been observed to have adverse effects that potentially induce damage to mitochondrial function, it is important to actively develop mitochondrial protective agents. Whether the current hepatoprotective drugs can have the effect of improving mitochondrial structure and function also needs to be further explored. The use of statins has caused a reemergence of the efficacy of lipid regulation, anti-inflammatory, antioxidant, immunomodulation and improvement of endothelial function, etc. It has been demonstrated that the use of statins can reduce cardiovascular events, stroke and total mortality by 22%, 16% and 22%, respectively, which positively affects the overall improvement of prognosis in NAFLD. Preliminary clinical studies have shown that angiotensin II receptor antagonists (ARBs) ameliorate necroinflammation, hepatic fibrosis, and iron deposition in NASH liver histology; improve serum oxidative stress markers. Hepatic fibrosis markers, TNFα and ALT levels, ARB is also likely to be a direction for future expanded applications and research. Conclusion Since Ludwig et al. first named NASH in 1980 and suggested that it is associated with obesity and MS, the spectrum of diseases associated with NAFLD has been expanding, and the prognosis for it has been changed from benign, possibly benign, and probably non-benign in a continuous change of opinion, Poynard et al. pointed out that it is time to take NAFLD seriously! In the face of the challenge of NAFLD to the health of all mankind, multidisciplinary efforts should be made to strengthen collaborative research and further develop practical and effective interventions. A good doctor-patient relationship should be established in clinical diagnosis and treatment, and compliance with long-term follow-up should be improved in order to prolong patients’ lives and improve their quality of life in the process of prevention and treatment.