PORNTITA WIBOONTHANASARN, MD21 NOVEMBER 2012

Pediatric nonalcoholic fatty liver disease

Outline

Definition Epidemiology Etiopathogenesis Risk factors Clinical features Diagnosis Treatment Prognosis

NAFLD/ NASH

Nonalcoholic fatty liver disease (NAFLD) is a multifactorial condition, ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) with or without fibrosis

Etiopathogenesis of primary NAFLD in children is unknown

The most common causes of chronic liver disease worldwide 20–30% of adults and 3–10% of children in Western countries

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Definitions of the spectrum of NAFLD

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Epidemiology

widely distributed worldwide variable in prevalence (3–10% in all individuals from

South and North America, Europe, Asia and Australia)

70–80% in obese male-to-female ratio of 2:1 more prevalent in adolescents BUT can occur in very

young children WHO : next 10–20 yrs, many low-income and

middle-income countries will experience the ‘double burden’ of the disease—undernutrition and obesity coexisting in the same population.

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Etiology

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Pathogenesis

The ‘two-hit’ theoryI. intrahepatic lipid accumulation (hepatic steatosis)II. inflammatory progression to nonalcoholic steatohepatitis

(NASH)In the first ‘hit’

I. hepatic metabolism of fructose promotes de novo lipogenesis and intrahepatic lipid, inhibition of mitochondrial β-oxidation of long-chain fatty acids, triglyceride formation and steatosis, hepatic and skeletal muscle insulin resistance, and hyperglycemia.

In the second ‘hit’ owing to the molecular instability of its five-membered

furanose ring, fructose promotes protein fructosylation and formation of reactive oxygen species (ROS), which require quenching by hepatic antioxidants.

Many patients with NASH also have micronutrient deficiencies and do not have enough antioxidant capacity to prevent synthesis of ROS, resulting in necroinflammation.

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Pathogenesis

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Pathogenesis

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Risk factors

obesity/visceral adiposity sedentary lifestyle insulin resistance predisposing genetic background : race ⁄

ethnicity age and gender

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Genetic factor

Role of PNPLA3 in lipid processing is not known, but this protein may also affect other ectopic lipid depots, as visceral adipose tissue is related to intrahepatic lipid accumulation

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Clinical features

most children have asymptomatic or signs of liver disease, despite histological damage.

Few of them complain of fatigue and/or vague RUQ discomfort

accidental finding by USG performed for other clinical indications or by a routine laboratory assessment showing hypertransaminasemia

PE : hepatomegaly is often , acanthosis nigricans, a sign related to hyperinsulinemia (50% of cases of pediatric NASH)

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Clinical features

20–80% of children with NAFLD can present with hypertriglyceridemia and/or hypercholesterolemia

several metabolic impairments (increased baseline waist circumference, hypertension and insulin resistance)

increase the risk of developing type 2DM , metabolic syndrome and cardiovascular disease

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Clinical features

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Investigation

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Diagnostic tool

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Liver biopsy

the gold standard for assessing NAFLD distinguish between NASH and hepatic

steatosis, determine the severity of liver damage and the presence and extent of fibrosis, rule out other diagnoses such as autoimmune hepatitis and Wilson disease

minimum criterion for the diagnosis of NAFLD in both adults and children is the presence of steatosis in >5% of hepatocytes

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Liver histology

nonalcoholic steatohepatitis

simple steatosis (fatty liver)

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NOVEL NONINVASIVE LABORATORYASSESSMENT OF NAFLD STAGES AND GRADES

Serum Markers of Hepatic Inflammation Markers of Oxidative Stresshepatic lipid peroxidation

Markers of ApoptosisCaspase-cleaved CK18 fragments

Markers of Hepatic FibrosisThe pediatric NAFLD fibrosis indexThe European liver fibrosis (ELF) panel

OTHER BIOCHEMICAL PREDICTORS

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Imaging method

Ultrasonography Unenhanced computed tomography MRI Fibroscan Magnetic resonance elastography (MRE)

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Differential diagnosis

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Treatment

no guidelines for the management of NAFLD, both in adults and in childrenLifestyle changes : improves aminotransferases and

liver histology in children with NAFLD and should be the first line of treatmentDietary modificationPhysical activity

Pharmacological : aimed to improving insulin sensitivity and reducing oxidative stress

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Dietary modification

No information exists on recommending any particular type of diet or exercise

Recommendations for overweight pediatric NAFLD patients should include consultation with a registered dietitian to assess quality of diet and measurement of caloric intake, adoption of American Heart Association dietary strategies, and regular aerobic exercise

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Dietary modification

Circulation journal of the American Heart Association 2005

Dietary modification

A pragmatic approach may be to recommendreduced caloric and balanced diet, 20% fats, 50%–55%

carbohydrates, 15%–30% proteins consumption of low-glycemic index foods and

polyunsaturated fats from fish and flax seed oils reduced fructose intake Dietary polyunsatured fatty acid of the N-6 and N-3

families is a well-established down-regulator of lipogenesis.

docosahexaenoic acid supplementation in children with NAFLD improves liver steatosis and insulin sensitivity

Insulin sensitizing agent

MetforminFirst line for type 2 DMIncrease activity of 5’AMP-activated protein kinaseDecrease hepatic glucose production & hepatic insulin

resistance ThiazolidinedioneSelective agonist for peroxisome proliferator activated

nuclear receptor-γDecrease hepatic FFA (decrease lipolysis & increase β

oxidation) , redistribute fat content from liver to peripheral adipose tissue, promote insulin sensitivity

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Antioxidant

Vit E its function as a free radical scavenger or ability to inhibit

cytokines such as transforming growth factor (TGF-β)Caution : High-dose vitamin E therapy has been

associated with increased mortality

Gastroenterol Clin N Am 40 , 2011, page 541–559

Conclusion Neither vitamin E nor metformin was superior to placebo in attaining the primary outcome of sustained reduction in ALT level in patients with pediatric NAFLD.

Conclusion: metformin did not appear more effective than lifestyle intervention in ameliorating levels of aminotransferases , steatosis and liver histology in children with NAFLD.

Summary in treatment

Recommendations Intensive lifestyle modification improves

aminotransferases and liver histology in children with NAFLD and thus should be the first line of treatment.

Metformin at 500 mg twice daily offers no benefit to children with NAFLD and thus should not be prescribed. The effect of metformin administered at a higher dose is not known.

Vitamin E 800 IU/day (RRR α-tocopherol) offers histological benefits to children with biopsyproven NASH or borderline NASH but confirmatory studies are needed before its use can be recommended in clinical practice

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Prognosis

The prognosis of pediatric NAFLD with advanced fibrosis or cirrhosis : unknown owing to the limited numbers of studies with long-term follow-up.

any stage of NAFLD often develop cirrhosis in adulthood

No clinical or laboratory data reliably predicted the course of liver disease

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Prognosis

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Reference

Pediatric nonalcoholic fatty liver disease: a multidisciplinary approach NATURE REVIEWS GASTROENTEROLOGY & HEPATOLOGY , VOLUME 9, MARCH 2012 , page 152-161

Diagnosis of Nonalcoholic Fatty Liver Disease in Children and AdolescentsPosition Paper of the ESPGHAN Hepatology Committee , JPGN Volume 54, Number 5, May 2012

SLEISENGER AND FORDTRAN’S GASTROINTESTINAL AND LIVER DISEASE: PATHOPHYSIOLOGY ninth edition chapter 85

Nonalcoholic Fatty Liver Disease: Pathology and PathogenesisThe Annual Review of Pathology: Mechanisms of Disease 2010

The Diagnosis and Management of Non-Alcoholic Fatty Liver Disease: Practice Guideline by the AASLD, ACG and AGA, HEPATOLOGY, June 2012

Nonalcoholic Fatty Liver Disease: Pharmacologic and Surgical Options , Gastroenterol Clin N Am 40 (2011) page 541–559