Introduction
The Clinical Practice Guidelines (CPG) propose recommendations for the diagnosis,
treatment and follow-up of non-alcoholic fatty liver disease (NAFLD) patients and
are the product of a joint effort by the European Association for the Study of the
Liver (EASL), European Association for the Study of Diabetes (EASD) and European Association
for the Study of Obesity (EASO). They update a position statement based on the 2009
EASL Special Conference [1].
The data have been retrieved by an extensive PubMed search up to April 2015. The final
statements are graded according to the level of evidence and strength of recommendation,
which are adjustable to local regulations and/or team capacities (table 1) [2]. In
particular, screening for NAFLD in the population at risk should be in the context
of the available resources, considering the burden for the national healthcare systems
and the currently limited effective treatments. The document is intended both for
practical use and for advancing the research and knowledge of NAFLD in adults, with
specific reference to paediatric NAFLD, whenever necessary. The final purpose is to
improve patient care and awareness of the importance of NAFLD, and to assist stakeholders
in the decision-making process by providing evidence-based data, which also takes
into consideration the burden of clinical management for the healthcare system.
Definition
NAFLD is characterised by excessive hepatic fat accumulation, associated with insulin
resistance (IR), and defined by the presence of steatosis in >5% of hepatocytes according
to histological analysis or by the proton density fat fraction (PDFF, providing a
rough estimation of the volume fraction of fatty material in the liver) >5.6% assessed
by proton magnetic resonance spectroscopy (1H-MRS) or quantitative fat/water selective
magnetic resonance imaging (MRI). NAFLD includes two pathologically distinct conditions
with different prognoses: non-alcoholic fatty liver (NAFL) and non-alcoholic steatohepatitis
(NASH); the latter covers a wide spectrum of disease severity, including fibrosis,
cirrhosis and hepatocellular carcinoma (HCC) (table 2).
The diagnosis of NAFLD requires exclusion of both secondary causes and a daily alcohol
consumption ≥30 g for men and 20 g for women [1]. The relationship between alcohol
and liver injury depends on several cofactors (type of alcoholic beverage, drinking
patterns, duration of exposure, individual/genetic susceptibility), rendering simple
quantitative thresholds at least partly arbitrary. Specifically, patients consuming
moderate amounts of alcohol may be still predisposed to NAFLD if they have metabolic
risk factors. Of note, the overall impact of metabolic risk factors on the occurrence
of steatosis appears to be higher than that of alcohol in these patients [3]. The
definitive diagnosis of NASH requires a liver biopsy.
Recommendations
Patients with IR and/or metabolic risk factors (i.e., obesity or metabolic syndrome
(MetS)) should undergo diagnostic procedures for the diagnosis of NAFLD, which relies
on the demonstration of excessive liver fat (A1)
Individuals with steatosis should be screened for secondary causes of NAFLD, including
a careful assessment of alcohol intake. The interaction between moderate amounts of
alcohol and metabolic factors in fatty liver should always be considered (A1)
Other chronic liver diseases, that may coexist with NAFLD, should be identified as
this might result in more severe liver injury (B1)
Prevalence and Incidence
NAFLD is the most common liver disorder in Western countries, affecting 17-46% of
adults, with differences according to the diagnostic method, age, sex and ethnicity
[4]. It parallels the prevalence of MetS and its components, which also increases
the risk of more advanced disease, both in adults and in children. NAFLD is also present
in 7% of normal-weight (lean) persons [5], more frequently in females, at a younger
age and with normal liver enzymes. Their liver disease may nonetheless be progressive
[6].
NAFLD incidence has rarely been measured. It was 20-86/1,000 person-years based on
elevated liver enzymes and/or on ultrasound (US), and 34/1,000 per year by 1H-MRS
[7].
The need for NAFLD screening in the community has been questioned given the high direct
and indirect costs of testing, the low predictive value of non-invasive tests, the
risks of liver biopsy and the lack of effective treatments [8]. However, the progressive
form of NAFLD (i.e. NASH), particularly when associated with advanced fibrosis, should
be identified in patients at risk (age > 50 years, type 2 diabetes mellitus (T2DM)
or MetS), because of its prognostic implications. Validated cost-utility studies on
extensive screening programmes are eagerly awaited. Similarly, although familial clustering
occurs, family screening is not generally advisable, with the exception of cases with
defined inherited diseases (e.g. lysosomal acid lipase deficiency).
Recommendations
All individuals with steatosis should be screened for features of MetS, independent
of liver enzymes. All individuals with persistently abnormal liver enzymes should
be screened for NAFLD, because NAFLD is the main reason for unexpectedly elevated
liver enzymes (A1)
In subjects with features of MetS, screening for NAFLD by liver enzymes and/or ultrasound
should be part of routine work-up. In high risk individuals (age > 50 years, T2DM,
MetS) case finding of advanced disease (i.e. NASH with fibrosis) is advisable (A2)
Pathogenesis: Lifestyle and Genes
A high-calorie diet, excess (saturated) fats, refined carbohydrates, sugar-sweetened
beverages, a high fructose intake and a Western diet [9] have all been associated
with weight gain and obesity, and more recently with NAFLD. High fructose consumption
may increase the risk of NASH and advanced fibrosis, although the association may
be confounded by excess calorie intake or by unhealthy lifestyles and sedentary behaviour
[10], which are more common in NAFLD [11].
Recommendations
Unhealthy lifestyles play a role in the development and progression of NAFLD. The
assessment of dietary and physical activity habits is part of a comprehensive NAFLD
screening (A1)
Several genetic modifiers of NAFLD have been identified [12], but a minority has been
robustly validated (supplementary table 1; available at
http://content.karger.com/ProdukteDB/produkte.asp?doi=443344
). The best-characterised genetic association is with PNPLA3, initially identified
from genome-wide association studies and confirmed in multiple cohorts and ethnicities
as a modifier of NAFLD severity across the entire histological spectrum [13,14]. Recently,
the TM6SF2 gene has been reported as another disease modifier [15,16] and may have
clinical utility assisting risk stratification for liver-related vs. cardiovascular
morbidity.
The PNPLA3 rs738409 variant also confers susceptibility and affects the histological
pattern of NAFLD and fibrosis in obese children and adolescents [17]. A NASH risk score
based on four polymorphisms has been validated in obese children with increased liver
enzymes [18].
Recommendations
Carriers of the PNPLA3 I148M and the TM6SF2 E167K variants have a higher liver fat
content and increased risk of NASH. NAFLD due to these variants is not systematically
associated with features of insulin resistance. Genotyping may be considered in selected
patients and clinical studies but is not recommended routinely (B2)
Liver Biopsy
Liver biopsy is essential for the diagnosis of NASH and is the only procedure that
reliably differentiates NAFL from NASH, despite limitations due to sampling variability
[19].
NAFL encompasses: a) steatosis alone, b) steatosis with lobular or portal inflammation,
without ballooning, and c) steatosis with ballooning but without inflammation [20].
The diagnosis of NASH requires the joint presence of steatosis, ballooning and lobular
inflammation [20,21,22]. Other histological features can be seen in NASH, but are
not necessary for the diagnosis: portal inflammation, polymorphonuclear infiltrates,
Mallory-Denk bodies, apoptotic bodies, clear vacuolated nuclei, microvacuolar steatosis
and megamitochondria. Perisinusoidal fibrosis is also frequent, but not part of the
diagnostic criteria; the term ‘borderline’ NASH is confusing, unnecessary and should
be abandoned. The prospectively designed FLIP algorithm increases observer agreement
and precisely defines the grading of ballooning [22]. ‘Burned-out NASH’ describes
regression of advanced disease (steatosis, inflammation or ballooning) in patients
exposed to metabolic risk factors.
The NAFLD Activity Score (NAS) scoring system should not be used for the diagnosis
of NASH but rather for the evaluation of disease severity, once the diagnosis has
been established by the overall pathological assessment. Although NAS is correlated
with aminotransferase and homeostasis model assessment of insulin resistance (HOMA-IR)
[23], they have a low prognostic value [24]. The steatosis, activity and fibrosis
(SAF) score [22] is an alternative with good reproducibility and provides a more accurate
and comprehensive description. Fibrosis staging relies on the Kleiner classification
[21] (used in a simplified pattern in SAF) [22].
In children, NASH displays many of the features observed in adults, even though the
distribution of lesions may be different. Portal inflammation is a frequent feature,
but can also be seen in adults with more severe disease [25]. Hepatocellular ballooning
and Mallory-Denk bodies are only sporadically observed in paediatric NASH, and portal-based
chronic inflammation is predominant [21]. Based on the distinctive histological pattern,
a specific histological score (Paediatric NAFLD Histological Score - PNHS) has been
validated for a better classification of children with/without NASH [26].
Non-Invasive Assessment
Non-invasive markers should aim to: i) in primary care settings, identify the risk
of NAFLD among individuals with increased metabolic risk; ii) in secondary and tertiary
care settings, identify those with worse prognosis, e.g. severe NASH; iii) monitor
disease progression; iv) predict response to therapeutic interventions. Achieving
these objectives could reduce the need for liver biopsy.
Steatosis
Rationale: Steatosis should be documented whenever NAFLD is suspected as the primary
disease or as a coexisting condition. It also predicts future diabetes mellitus, cardiovascular
events and arterial hypertension. In clinical practice, quantification of fat content
is not of interest, except as a surrogate of treatment efficacy, and is therefore
not generally recommended.
In individual patients, especially in tertiary care centres, steatosis should be identified
by imaging, preferably US, because it is more widely available and cheaper than the
gold standard, MRI (supplementary table 2; available at
http://content.karger.com/ProdukteDB/produkte.asp?doi=443344
). The best-validated steatosis scores are the fatty liver index (FLI), the SteatoTest®
and the NAFLD liver fat score; they have all been externally validated in the general
population or in grade 3 obese persons and variably predict metabolic, hepatic and
cardiovascular outcomes/mortality. These scores are associated with IR and reliably
predict the presence, not the severity, of steatosis [30]. Another imaging technique,
the controlled attenuation parameter (CAP) can diagnose steatosis, but has a limited
ability to discriminate histological grades and has never been compared with 1H-MRS-measured
steatosis. Also, the data from studies comparing CAP with US are inconclusive. Thus
more data are needed to define the role of CAP.
Recommendations
US is the preferred first-line diagnostic procedure for imaging of NAFLD, as it provides
additional diagnostic information (A1)
Whenever imaging tools are not available or feasible (e.g., large epidemiological
studies), serum biomarkers and scores are an acceptable alternative for the diagnosis
of steatosis (B2)
A quantitative estimation of liver fat can only be obtained by 1H-MRS. This technique
is of value in clinical trials and experimental studies, but is expensive and not
recommended in the clinical setting (A1)
Steatohepatitis, NASH
Rationale: The diagnosis of NASH provides important prognostic information and indicates
an increased risk of fibrosis progression, cirrhosis and possibly hepatic comorbidities
(HCC). It may also prompt a closer follow-up and possibly a greater need for more
intensive therapy.
Clinical, biochemical or imaging measures cannot distinguish NASH from steatosis [31,32].
Cytokeratin-18 fragments (CK-18), which are generated during cell death (M65 fragments)
or apoptosis (M30 fragments), have modest accuracy for the diagnosis of NASH (66%
sensitivity, 82% specificity) [33,34]. CK-18 changes parallel histological improvement
but do not perform better than alanine transaminase (ALT) in identifying histological
responders [35]. To date, non-invasive tests are not validated for the diagnosis of
NASH.
Recommendations
NASH has to be diagnosed by a liver biopsy showing steatosis, hepatocyte ballooning
and lobular inflammation (A1)
Fibrosis
Rationale: Fibrosis is the most important prognostic factor in NAFLD and is correlated
with liver-related outcomes and mortality [24]. The presence of advanced fibrosis
identifies patients in need of in-depth hepatological investigation, including, on
a case-by-case basis, confirmatory biopsy and intensive therapies. Monitoring of fibrosis
progression is also necessary at variable time intervals.
Many serum markers have shown acceptable diagnostic accuracy as defined by an area
under the receiver operating characteristic curve (AUROC) >0.8 (supplementary table
3; available at
http://content.karger.com/ProdukteDB/produkte.asp?doi=443344
) [32]. NAFLD fibrosis score (NFS) and fibrosis 4 calculator (FIB-4) have been externally
validated in ethnically different NAFLD populations, with consistent results. NFS,
FIB-4, Enhanced Liver Fibrosis (ELF) and FibroTest® predict overall mortality, cardiovascular
mortality and liver-related mortality. NFS predicts incident diabetes, and changes
in NFS are associated with mortality. The tests perform best at distinguishing advanced
(≥F3) vs. non-advanced fibrosis but not significant (≥F2) or any (≥F1) fibrosis vs.
no fibrosis [36]. Importantly, the negative predictive values (NPVs) for excluding
advanced fibrosis are higher than the corresponding positive predictive values (PPVs)
[36,37]; therefore, non-invasive tests may be confidently used for first-line risk
stratification to exclude severe disease. However, predictive values depend on prevalence
rates and most of these studies have been conducted in tertiary centres where the
pre-test probability of advanced fibrosis is higher than in the community.
Among imaging techniques, transient elastography performs better for cirrhosis (F4)
than for advanced fibrosis (F3). Elastography has a higher rate of false-positive
than false-negative results and higher NPV than PPV [38], hence the ability to diagnose
bridging fibrosis or cirrhosis is insufficient for clinical decision-making. The main
shortcoming of transient elastography is unreliable results in the presence of high
BMI and/or thoracic fold thickness. In a large, unselected, European series, up to
20% of examinations had unreliable results [39], mainly in obese NAFLD [38]. The XL
probe should be used in these patients to reduce the failure rate, which remains high
(35%) [40].
There is no consensus on thresholds or strategies for use in clinical practice when
trying to avoid liver biopsy [32]. Some data suggest that the combination of elastography
and serum markers performs better than either method alone [41]. Importantly, longitudinal
data correlating changes in histological severity and in non-invasive measurements
are urgently needed.
Recommendations
Biomarkers and scores of fibrosis, as well as transient elastography, are acceptable
non-invasive procedures for the identification of cases at low risk of advanced fibrosis/cirrhosis
(A2). The combination of biomarkers/scores and transient elastography might confer
additional diagnostic accuracy and might save a number of diagnostic liver biopsies
(B2)
Monitoring of fibrosis progression in clinical practice may rely on a combination
of biomarkers/scores and transient elastography, although this strategy requires validation
(C2)
The identification of advanced fibrosis or cirrhosis by serum biomarkers/scores and/or
elastography is less accurate and needs to be confirmed by liver biopsy, according
to the clinical context (B2)
In selected patients at high risk of liver disease progression, monitoring should
include a repeat liver biopsy after at least 5-year follow-up (C2)
Non-Invasive Testing in Paediatric NAFLD
The position paper by the European Society for Paediatric Gastroenterology Hepatology
and Nutrition (ESPGHAN) Hepatology Committee has recently delineated diagnostic criteria
for paediatric NAFLD [42]. In obese children, NAFLD should always be suspected; elevated
aminotransferase levels and liver hyperechogenicity deserve further evaluation and
the exclusion of other causes of liver disease. Due to the poor sensitivity of these
tests in overweight/obese children, non-invasive markers and imaging techniques are
the first diagnostic step [43].
Recommendations
In children, predictors of fibrosis, including elastometry, acoustic radiation force
impulse (ARFI) imaging and serum biomarkers might help reduce the number of biopsies
(B2)
Common Metabolic Disorders Related to NAFLD
NAFLD is tightly associated with IR not only in the liver but also in muscle and adipose
tissues [44], and also with MetS, defined as the cluster of any three of the following
five features associated with IR: impaired fasting glucose (IFG) or T2DM, hypertriglyceridaemia,
low high-density lipoprotein(HDL)-cholesterol (gender-adjusted), increased waist circumference
(ethnicity adjusted) and high blood pressure [45]. As all components of MetS correlate
with liver fat content, independently of BMI, the presence of MetS in any given patient
should lead to an evaluation of the risk of NAFLD, and vice versa the presence of
NAFLD should lead to an assessment of all components of MetS.
Hepatic triacylglycerol accumulation is accompanied by abnormal hepatic energy metabolism
[46] and impaired insulin-mediated suppression of hepatic glucose and very low-density
lipoprotein production [47], leading to hyperglycaemia, hypertriglyceridaemia and
hyperinsulinaemia. In non-diabetic persons, the product of fasting glucose (in mmol/l)
and insulin (in mU/ml), divided by 22.5 (HOMA-IR) can serve as surrogate for IR [48],
and is therefore an acceptable alternative to more expensive and time-consuming dynamic
testing. Liver disease progression has been associated with persistence or worsening
of metabolic abnormalities, including HOMA-IR [49,50]. However, the validity of HOMA-IR
depends on the ability of insulin secretion to adapt to IR, questioning its suitability
in overt diabetes. Moreover, the assays for insulin measurements vary widely, and
there is no agreement on a threshold defining IR using HOMA-IR.
Recommendations
HOMA-IR provides a surrogate estimate of IR in persons without diabetes and can therefore
be recommended provided proper reference values have been established (A1)
HOMA-IR is of limited use for NAFLD diagnosis in patients with metabolic risk factors.
It could confirm altered insulin sensitivity, thereby favouring a diagnosis of IR-associated
NAFLD, in cases of diagnostic uncertainty (e.g. US-defined steatosis with normal body
weight) (B2)
During follow-up, HOMA-IR might help identify patients at risk of NASH or fibrosis
progression in selected cases. Improvement of HOMA-IR during weight loss may indicate
metabolic improvement that could be beneficial for NAFLD (C2)
Obesity
BMI and waist circumference, a measure of visceral adiposity, are positively related
to the presence of NAFLD [51] and predict advanced disease, particularly in the elderly
[52]. A large proportion of patients with cryptogenic cirrhosis have a high prevalence
of metabolic risk factors [53], suggesting that in the majority of cases of cryptogenic
cirrhosis are ‘burned-out’ NASH. Common comorbidities of obesity, such as T2DM, and
sleep apnoea [54], polycystic ovary syndrome and other endocrine disorders (hypogonadism),
further drive NAFLD prevalence and severity.
Importantly, patients with BMI <30 kg/m2 (or even <25 kg/m2) but with visceral fat
accumulation or dysfunctional adipose tissue can exhibit NAFLD with/without abnormal
liver enzymes [44,55]. The currently used concept of ‘metabolically healthy’ obese
individuals should be considered with caution, given that they may exhibit gene expression
similar to those of metabolically altered obese patients, and may have altered liver
tests and adverse health outcomes when longitudinally examined [56,57].
Recommendations
Obesity is the major phenotype and risk condition for NAFLD, driven by IR, which also
increases the risk of advanced disease (A1)
Most lean persons with NAFLD display IR and altered body fat distribution even though
they have less severe metabolic disturbance than overweight NAFLD. Follow-up is nonetheless
required because of possible disease progression (B2)
Diabetes mellitus
T2DM patients are insulin resistant, often obese, dyslipidaemic, display increased
liver enzymes [58] and tend to accumulate hepatic fat independently of BMI [59,60].
The prevalence of NAFLD is also higher in persons at risk of T2DM, defined as a glycosylated
haemoglobin A1c (HbA1c) of 5.7-6.4% (38.8-46.4 mmol/mol), IFG (fasting glucose: 100-125
mg/dl (5.55-6.94 mmol/l)) and/or impaired glucose tolerance (IGT; glucose: 140-199
mg/dl (7.77-11.04 mmol/l) at 2 h of the standardised 75 g oral glucose tolerance test
(OGTT)). Diabetes risk and T2DM closely associate with the severity of NAFLD, progression
to NASH, advanced fibrosis and the development of HCC [4,61], independently of liver
enzymes [6]. Conversely, US-defined NAFLD is associated with a 2- to 5-fold risk of
developing T2DM after adjustment for several lifestyle and metabolic confounders [62].
The standardised 75 g OGTT should therefore be performed in persons with increased
diabetes risk [63,64].
Insulin treatment increases body fat, but it does not appear to promote or worsen
NAFLD in diabetes [65,66]. While acute insulin infusion dose-dependently increases
liver fat content in T2DM [67], chronic insulin treatment improves adipose tissue
IR and therefore reduces NEFA flux and hepatic fat content.
Recommendations
In persons with NAFLD, screening for diabetes is mandatory, by fasting or random blood
glucose or HbA1c (A1) and, if available, by the standardised 75 g OGTT in high-risk
groups (B1).
In patients with T2DM, the presence of NAFLD should be looked for irrespective of
liver enzyme levels, since T2DM patients are at high risk of disease progression (A2).
Diagnostic Algorithm and Follow-Up
The incidental discovery of steatosis should lead to comprehensive evaluation of family
and personal history of NAFLD-associated diseases and the exclusion of secondary causes
of steatosis. Metabolic work-up has to include a careful assessment of all components
of MetS [63]. Similarly, the presence of obesity/T2DM or the incidental finding of
raised liver enzymes in patients with metabolic risk factors should prompt non-invasive
screening to predict steatosis, NASH and fibrosis (table 3).
Surrogate markers of fibrosis (NFS, FIB-4, ELF or FibroTest) should be calculated
for every NAFLD patient, in order to rule out significant fibrosis (≥F2). If significant
fibrosis cannot be ruled out, patients should be referred to a Liver Clinic for transient
elastography; if significant fibrosis is confirmed, the final diagnosis should be
made by liver biopsy (fig. 1). All cases with diabetes or diabetes risk should be
referred to a Diabetes Clinic for optimal management. Those at increased diabetes
risk should be included in a structured lifestyle modification programme. Obesity
should prompt the inclusion of the patient in a structured weight loss programme and/or
referral to an obesity specialist. Finally, all cases should receive comprehensive
cardiovascular disease (CVD) work-up.
The optimal follow-up of patients with NAFLD is as yet undetermined. Risk of progression
of both the hepatic disease and the underlying metabolic conditions as well as the
cost and workload for healthcare providers need to be considered. Monitoring should
include routine biochemistry, assessment of comorbidities and non-invasive monitoring
of fibrosis. NAFL patients without worsening of metabolic risk factors should be monitored
at 2- to 3-year intervals. Patients with NASH and/or fibrosis, should be monitored
annually, those with NASH cirrhosis at 6-month intervals. If indicated on a case-by-case
basis, liver biopsy could be repeated after 5 years.
Natural History and Complications
Disease Progression
In general, NAFLD is a slowly progressive disease, both in adults and in children,
but fibrosis rapidly progresses in 20% of cases [68]. The rate of progression corresponds
to 1 fibrosis stage every 14 years in NAFL and every 7 years in NASH, and is doubled
by arterial hypertension [68]. NASH is associated with an increased standardised mortality
ratio compared with the general population [69], and liver disease is the third most
common cause of death after CVD and cancer. US-diagnosed NAFLD is not associated with
increased mortality [70], presumably because progression to NASH and fibrosis is rare
for steatosis alone [49,50].
Recommendations
NASH patients with fibrosis associated with hypertension should receive closer monitoring
because of a higher risk of disease progression (B1)
Paediatric NAFLD is of concern because of the potential for severe liver-related complications
later in life [8]. NASH-related cirrhosis has been reported as early as 8 years of
age [71].
CVD
The prevalence and incidence of CVD is higher in NAFLD than in matched controls and
driven by the association between NAFLD and MetS components ([72,73] (supplementary
table 4; available at
http://content.karger.com/ProdukteDB/produkte.asp?doi=443344
). CVD is a more common cause of death than liver disease in NAFLD [73]. In most studies,
biochemical markers of atherosclerosis (low HDL-cholesterol, high triacylglycerol)
or inflammation (high-sensitive C-reactive protein), and increased levels of procoagulant/prothrombotic
factors are more common in NAFLD than in persons without steatosis [73]. Pre-atherogenic
lesions such as increased carotid intima-media thickness; coronary artery, abdominal
aortic and aortic valve calcifications; endothelial dysfunction and functional unresponsiveness
of the artery wall are more prevalent in NAFLD and are, in some studies, correlated
with histological severity. Other defects such as echocardiographic and ECG abnormalities
and altered cardiac energy metabolism have also been demonstrated [74]. They are largely
independent of traditional risk factors, duration of diabetes, glycaemic control,
drug treatment and MetS components. In the general population, US-detected steatosis
and its surrogate markers (e.g., FLI) are associated with a higher risk of CVD mortality
in the long term [75], and the risk increases further in NASH and in advanced fibrosis
[73].
The overall consensus is that CVD should be identified in NAFLD regardless of the
presence of traditional risk factors. Conversely, NAFLD screening should be performed
in persons at high CVD risk. An association between serum γ-glutamyltransferase (GGT)
and CVD incidence has been prospectively established, although it is insufficient
for devising follow-up protocols. Notably, CVD and metabolic risk factors are also
reported in adolescents and children with NAFLD [76].
Recommendations
Cardiovascular complications frequently dictate the outcome of NAFLD and screening
of the cardiovascular system is mandatory in all persons A1
HCC
Large-scale epidemiological studies have repeatedly associated obesity and T2DM with
the risk of HCC, and the occurrence of HCC has also been reported in NAFLD/cryptogenic
cirrhosis. The cumulative incidence of NAFLD-associated HCC (>10-fold higher in T2DM
and obesity) varies according to study population (population-based, natural history
vs. clinic-based cohorts with/without fibrosis or cirrhosis) from 7.6% at 5 years
in persons with advanced fibrosis or cirrhosis to only 0.25% in a larger series, followed
for 5.6 years [77].
At diagnosis, patients with NAFLD-associated HCC are older than those with non-NAFLD
HCC, have more extrahepatic comorbidities, but a lower prevalence of cirrhosis (only
two-thirds of cases) (supplementary table 5; available at
http://content.karger.com/ProdukteDB/produkte.asp?doi=443344
). NAFLD-related HCC may, however, be diagnosed at more advanced stages, due to less
systematic surveillance, and receive less treatment. Conflicting data are reported
on survival. At present, NAFLD is the second leading indication for HCC-related transplantation
in the USA [78].
The large number of NAFLD cases at risk of HCC makes systematic surveillance largely
impracticable. PNPLA3 rs738409: C>G gene polymorphism has been associated with an
increased HCC risk and might provide patient-risk stratification for tailored HCC
surveillance in NAFLD, but it is not yet considered cost-effective (supplementary
table 1; available at
http://content.karger.com/ProdukteDB/produkte.asp?doi=443344
).
Recommendations
Although NAFLD is a risk factor for HCC, which may also develop in the pre-cirrhotic
stage, and the risk is further increased by the presence of the PNPLA3 rs738409 C>G
polymorphism, no recommendation can be currently made on the timing of surveillance
and its cost-effectiveness (B1)
Other Extrahepatic Disorders
Chronic kidney disease (CKD) can be found in 20-50% of NAFLD patients, particularly
in biopsy-proven NASH [79]. US-defined NAFLD carries a 1.5- to 2-fold adjusted risk
of incident CKD in type 1 diabetes mellitus [80].
NAFLD is also associated with colorectal cancer [81], metabolic bone disease (vitamin
D deficiency, osteoporosis) [62,82] and rare metabolic diseases (lipodystrophies,
glycogen storage diseases).
Treatment
Rationale: Successful treatment of NASH should improve outcomes, i.e. decrease NASH-related
mortality, reduce progression to cirrhosis or HCC. The resolution of the histological
lesions defining NASH is now accepted as a surrogate endpoint, particularly in clinical
trials. Only a few properly designed randomised controlled trials (RCTs) are available,
with improvement/regression of hepatic necroinflammation and/or fibrosis as primary
outcomes [83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105]
(table 4).
Diet and Lifestyle Changes
Rationale: Epidemiological evidence suggests a tight relationship between unhealthy
lifestyle and NAFLD [106], which makes lifestyle correction mandatory in all patients
(table 5). Of note, daily alcohol consumption up to 30 g (men) or 20 g (women) is
insufficient to induce alcoholic steatosis and might even be protective against NAFLD,
NASH and fibrosis as compared with total abstinence.
Relatively small amounts of weight loss reduce liver fat and improve hepatic IR [119].
In a pilot RCT of cognitive-behaviour therapy, lifestyle intervention resulted in
more weight loss, more frequent resolution of NASH and a borderline higher (p = 0.05)
reduction in the NAS score [93]. In a post hoc analysis, a weight loss ≥7% was associated
with histological improvement. In an uncontrolled, 12-month study with 261 paired
biopsies, a modest lifestyle-induced weight loss was associated with NASH regression
(25% of total cases) without worsening of fibrosis [120].
Pragmatic approaches combining dietary restriction and a progressive increase in aerobic
exercise/resistance training [121] are preferable and should be individually tailored.
No data are available on their long-term effects on the natural history of NAFLD.
Recommendations
Structured programmes aimed at lifestyle changes towards healthy diet and habitual
physical activity are advisable in NAFLD C2
Patients without NASH or fibrosis should only receive counselling for healthy diet
and physical activity and no pharmacotherapy for their liver condition B2
In overweight/obese NAFLD, a 7-10% weight loss is the target of most lifestyle interventions,
and results in improvement of liver enzymes and histology B1
Dietary recommendations should consider energy restriction and exclusion of NAFLD-promoting
components (processed food, and foods and beverages high in added fructose). The macronutrient
composition should be adjusted according to the Mediterranean diet B1
Both aerobic exercise and resistance training effectively reduce liver fat. The choice
of training should be tailored based on patients' preferences to be maintained in
the long-term B2
Drug Treatment
Rationale: Drug therapy should be indicated for progressive NASH (bridging fibrosis
and cirrhosis) but also for early-stage NASH with increased risk of fibrosis progression
(age > 50 years; diabetes, MetS, increased ALT [122]) or active NASH with high necroinflammatory
activity [123]. No drug has currently been tested in phase III trials and is approved
for NASH by regulatory agencies. Therefore, no specific therapy can be firmly recommended
and any drug treatment would be off-label (for reviews see [124,125,126], table 4).
Safety and tolerability are essential prerequisites for drug treatment, because of
NASH-associated comorbidities and polypharmacy, a potential source of drug-drug interactions.
Insulin Sensitisers
There is scarce evidence for a histological efficacy of metformin in NASH [84,90,92].
The effect of metformin on liver fat is weak, because of its inability to restore
serum adiponectin levels in the short-term [127]. Some preclinical data support an
anti-tumorigenic activity of metformin on liver cancer [128], while the demonstration
of reduced rates of HCC in humans is limited to retrospective studies [129] and insufficient
for evidence-based recommendations.
Thiazolidinediones are peroxisome proliferator-activated receptor gamma (PPARγ) agonists
with insulin-sensitising effects. The PIVENS trial compared low dose pioglitazone
vs. vitamin E vs. placebo for 2 years in patients without overt diabetes. Pioglitazone
improved all histological features (except for fibrosis) and achieved resolution of
NASH more often than placebo [95]. The histological benefit occurred together with
ALT improvement and partial correction of IR. Similar results were reported in two
smaller and shorter RCTs [85,89]. Prolonged therapy with rosiglitazone, up to 2 years,
did not result in further histological improvement [88,94], although this was not
formally tested with pioglitazone. Side effects of glitazones are of concern: weight
gain, bone fractures in women, and rarely congestive heart failure. Despite the safety
and tolerability profile, pioglitazone can be used for selected patients with NASH,
particularly in T2DM where the drug has a registered use.
Incretin mimetics, acting on the glucose-insulin interplay have shown favourable results
in pre-marketing studies on liver enzymes [130]. A small pilot trial of daily injections
of liraglutide met the histological outcome of NASH remission without worsening of
fibrosis [105].
Antioxidants, Cytoprotective and Lipid-Lowering Agents
In the PIVENS trial, vitamin E (800 IU/day) improved steatosis, inflammation and ballooning
and induced resolution of NASH in 36% of patients (21% in the placebo arm) [95]. Reduced
ALT correlated with histological improvement, and histological non-responders did
not reduce ALT [131]. In the paediatric TONIC trial [98], vitamin E failed to reduce
aminotransferases, steatosis and inflammation but improved ballooning and doubled
the rate of NASH clearance vs. placebo. These results contrast with previous trials,
which were mostly negative in both adults and children. Concerns about long-term safety
of vitamin E exist, mainly an increase in overall mortality [132], in haemorrhagic
stroke [133] and prostate cancer in males older than 50 [134]. Vitamin E may be used
in non-cirrhotic non-diabetic NASH patients but further studies are needed before
firm recommendations can be made.
Ursodeoxycholic acid (UDCA) has been investigated in several RCTs, at different doses
and for up to 2 years, but only showed some biochemical but no histological improvements
[83,87,96].
A synthetic farnesoid X receptor agonist, obeticholic acid, improved IR in T2DM [135].
In the phase IIb FLINT trial, a 72-week treatment with obeticholic acid in non-cirrhotic
NASH patients improved all NASH lesions while improving fibrosis [99]. Main issues
with safety and tolerability were increased low-density lipoprotein(LDL)-cholesterol
and pruritus.
Preliminary data from small or uncontrolled studies suggested that n-3 polyunsaturated
fatty acids (PUFAs) might reduce liver fat [136], but two trials testing PUFAs on
histological outcomes were negative [102,104]. Available data on pentoxifylline and
orlistat are limited or inconclusive [86,91,97]. Also, data on lipid-lowering drugs
are poor; recent trials with ezetimibe were negative [101,103], whereas statins have
not been adequately tested. Their use in NAFLD is safe, with no increased risk of
hepatotoxicity, and may even significantly reduce aminotransferases [137].
Promising novel agents with anti-inflammatory, antifibrotic or insulin sensitising
properties (dual PPARα/δ agonists, dual chemokine receptor(CCR)2/CCR5 antagonists
and fatty acid/bile acid conjugates) and antifibrotic agents (anti-lysyl oxidase-like
(anti-LOXL2) monoclonal antibodies) are also being tested in late phase RCTs in NASH.
Recommendations
Pharmacotherapy should be reserved for patients with NASH, particularly for those
with significant fibrosis (stage F2 and higher). Patients with less severe disease,
but at high risk of disease progression (i.e., with diabetes, MetS, persistently increased
ALT, high necroinflammation) could also be candidates to prevent disease progression
B1
While no firm recommendations can be made, pioglitazone (most efficacy data, but off-label
outside T2DM) or vitamin E (better safety and tolerability in the short term) or their
combination could be used for NASH B2
The optimal duration of therapy is unknown; in patients with increased ALT at baseline,
treatment should be stopped if there is no reduction in aminotransferases after 6
months of therapy; in patients with normal ALT at baseline, no recommendations can
be made C2
Statins may be confidently used to reduce LDL-cholesterol and prevent cardiovascular
risk, with no benefits or harm on liver disease. Similarly n-3 polyunsaturated fatty
acids reduce both plasma and liver lipids, but there are no data to support their
use specifically for NASH (B1)
Iron Depletion
Hepatic iron accumulation is associated with IR, and iron depletion improves IR [138].
In NAFLD, high ferritin levels are common, in the presence of variable transferrin
saturation, independent of gene polymorphisms of familial hemochromatosis. In these
patients, a phlebotomy programme to reduce iron stores to near iron deficiency improved
the NAS score, without worsening fibrosis [100], but more data are needed.
Paediatric NAFLD
In children, diet and exercise training reduce steatosis, but do not affect ballooning,
inflammation and fibrosis [139]. Although several drug-based therapies, such as vitamin
E and metformin, and dietary supplementation, including probiotics and docosahexaenoic
acid, have shown beneficial effects on ballooning, steatosis and inflammation, fibrotic
lesions are refractory to treatment [140] and the long-term outcome of paediatric
NASH remains poor [141].
Recommendations
Diet and physical activity improve steatosis and hepatic inflammation in paediatric
NAFLD, but no beneficial effects on fibrosis have ever been demonstrated. No safe
drug treatment has proven effective on fibrosis in paediatric NAFLD B1
Bariatric (Metabolic) Surgery
In patients unresponsive to lifestyle changes and pharmacotherapy, bariatric surgery
is an option for reducing weight and metabolic complications, with stable results
in the long term [142]. Surrogate markers indicate that bariatric surgery is effective
on NAFLD-associated liver injury, and there is also initial evidence for improved
necroinflammation and fibrosis [143]. A recent cohort study with 1-year follow-up
confirmed that bariatric surgery-associated weight loss cleared NASH in 85% of patients
and improved fibrosis in 34% [144], although the possible benefits should be balanced
against peri-/post-operative complications. No solid data on the comparative effects
of different bariatric procedures on liver fat are available.
Recommendations
By improving obesity and diabetes, bariatric (metabolic) surgery reduces liver fat
and is likely to reduce NASH progression; prospective data have shown an improvement
in all histological lesions of NASH, including fibrosis B1
Liver Transplantation
NAFLD-associated cirrhosis is among the top three indications for liver transplantation.
The 3- and 5-year survival is not different in NAFLD vs. no-NAFLD; NAFLD carries a
higher risk of death from cardiovascular complications and sepsis, whereas the risk
of graft failure is lower [145,146]. The overall mortality is associated with BMI
and diabetes, with 50% of cases with BMI > 35 kg/m2 dying within 1 year of transplantation
[147]. Transplant failure (10% and 45% at 10 and 20 years, respectively [148]) in
obese patients is rarely associated with recurrent NASH cirrhosis (≈2%) [146].
Recommendations
Liver transplantation is an accepted procedure in NASH patients with end-stage liver
disease, with comparable overall survival to other indications, despite a higher cardiovascular
mortality. NASH patients with liver failure and/or HCC are candidates for liver transplantation
A1
Disclosure Statement
Giulio Marchesini declares he does not have anything to disclose regarding funding
or conflict of interest with respect to this manuscript.
Christopher P. Day declares he has been a consultant/advisor for Abbott Laboratories
and Genfit and completed sponsored lectures for Abbott Laboratories.
Jean-François Dufour declares he has been a consultant/advisor for Intercept and Genfit.
Ali Canbay declares he does not have anything to disclose regarding funding or conflict
of interest with respect to this manuscript.
Valerio Nobili declares he does not have anything to disclose regarding funding or
conflict of interest with respect to this manuscript.
Vlad Ratziu declares he has been a consultant/advisor for Genfit. In addition he has
been on the advisory board for Gilead, Genfit, Roche and Galmed Pharmaceuticals.
Herbert Tilg declares he does not have anything to disclose regarding funding or conflict
of interest with respect to this manuscript.
Michael Roden has received research support and been involved in clinical trials for
Boehringer Ingelheim, Novartis Pharma and Sanofi-Aventis Germany. He has been a consultant/advisor
for GI Dynamics, Sanofi-Aventis Germany and Merck & Co. Inc. He has completed sponsored
lectures for Eli Lilly and Novo Nordisk.
Amalia Gastaldelli has received research support from Amylin-BMS-AstraZeneca and has
been a consultant/advisor for Roche, Eli-Lilly and Sanofi Aventis.
Hannele Yki-Järvinen declares she does not have anything to disclose regarding funding
or conflict of interest with respect to this manuscript.
Fritz Schick declares he does not have anything to disclose regarding funding or conflict
of interest with respect to this manuscript.
Roberto Vettor declares that he has been a consultant/advisor as well as received
grants/research support from Sanofi. In addition he has completed sponsored lectures
for Novo Nordisk, Sanofi and AstraZeneca.
Gema Frühbeck declares that she is on the Novo Nordisk Obesity Scientific Communication
Global Advisory Board.
Lisbeth Mathus-Vliegen declares she does not have anything to disclose regarding funding
or conflict of interest with respect to this manuscript.