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Impact of obesity on the liver – Part 2

• Several data have accumulated suggesting that obesity may be associated with liver disease and disease progression.
• Accordingly, the worldwide epidemic of obesity is likely to become a relevant source of morbidity and mortality in the general population.

Liver Disease in Obese Subjects

• A bright liver at ultrasound and increased levels of hepatic enzymes are the hallmarks of the whole spectrum of NAFLD.
• They are common in obesity, and their prevalence increases progressively with increasing BMI.
• At liver biopsy, subjects with moderate or severe fatty change, lipogranulomas, focal necroses, or parenchymal inflammation are significantly more obese than patients without these changes.
• In the general population of the Dionysos study, fatty liver at ultrasonography was documented in 10–15% of normal individuals and in up to 76% of obese subjects not drinking alcohol in toxic amounts.
• Compared with controls, the risk for steatosis was 4.6-fold increased in obese persons and only 5.8-fold higher in persons who were obese and drank heavily.
• Large differences in the prevalence of steatosis exist in the general population.
• In a large, multiethnic, population-based sample where the distribution of hepatic triglyceride content was analyzed.
• It was done by the sensitive proton magnetic resonance spectroscopy.
• Almost one third of the population had hepatic steatosis, and most subjects with hepatic steatosis had normal levels of ALT (79%).

The frequency of hepatic steatosis varied significantly with:
• Ethnicity (45% in Hispanics, 33% in whites, 24% in blacks).
• Sex (42% in white men, 24% in white women).
• The higher prevalence of steatosis in Hispanics was due to the higher prevalence of obesity and insulin resistance.
• Finally, liver fat varies with the degree of obesity.
• In longitudinal studies even small changes in body weight (on average 1.3–2.5 kg) are associated with the ultrasonographic appearance/disappearance of steatosis.
• Compared with ultrasonography, the sensitivity of ALT for the diagnosis of primary NAFLD is much lower.
• Abdominal obesity was one of the most predictive factors of NAFLD.

Pathogenesis of Metabolic Liver Disease

• The role of adipose tissue, namely the central (or upper body) obesity phenotype associated with increased visceral fat, in the pathogenesis of NAFLD is primary.
• Liver fat accumulation is largely dependent on recirculating free fatty acids (FFAs) from the adipose tissue pool.
• The visceral adipose tissue has greater lipolytic potential than the more abundant sc adipose tissue.
• The release of FFA from visceral fat depots directly into the portal circulation is one of the mechanisms of hepatic injury.
• Studies based on proton magnetic resonance spectroscopy have shown that the amount of intrahepatocellular lipids increases by approximately 20% for any 1% increase in total or sc adipose tissue, but doubles for any 1% increase in intraabdominal adipose tissue.
• This explains why even modest changes in visceral fat may cause steatosis.
• Accumulation of triglycerides in the hepatocytes is the result of both increased inflow of FFA and de novo lipogenesis.
• By stable isotope techniques, it has been estimated that in the presence of steatosis 59% of the triglycerides present in the liver arise from re-circulation from adipose tissue, 26% from de novo lipogenesis from dietary carbohydrates—a value much higher than reported in normal subjects—and 15% from dietary lipids.
• In a few cases, steatosis leads to lipotoxicity.

This causes:
– Apoptosis.
– Necrosis.
– Generation of oxidative stress.
– Inflammation.
– The resulting chronic injury activates a fibrogenic response that eventually leads to end-stage liver disease.
– Increased FFA concentrations, in turn, may be responsible for insulin resistance in muscle tissue.
– Whereas in adipose tissue insulin resistance further prevents the insulin-mediated suppression of lipolysis.
– Adipose tissue is an endocrine organ, and over 100 factors secreted by adipose tissue have been identified as potentially responsible for liver lipotoxicity.
– Their secretion is increased with increased visceral fat mass, with the notable exception of adiponectin and chronic inflammation.
– Excess visceral body fat remains a nearly necessary condition.

Nonalcoholic Fatty Liver Disease Fatty Liver You Can Reverse It The Liver Cleansing Diet

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