Pathogenesis of Hepatic Steatosis: Insights into Potential Treatment Options

Comprehensive Summary: Pathogenesis of Hepatic Steatosis – Insights into Potential Treatment Options

Lecturer: Prof. Anil Arora, Sir Ganga Ram Hospital

Format: CME/Conference Lecture

1. Main Clinical Topics Discussed

• Definition, epidemiology, and spectrum of hepatic steatosis / metabolic-associated fatty liver disease (MAFLD/MASLD)
• Molecular and cellular pathogenesis of non-alcoholic fatty liver disease (NAFLD)/metabolic dysfunction-associated steatohepatitis (MASH)
• Role of insulin signaling and insulin resistance in hepatic fat accumulation
• Adipose tissue pathophysiology and its systemic consequences
• Evolving theoretical frameworks explaining disease progression
• Emerging and current therapeutic targets

2. Key Learning Points, Guidelines, and Recommendations

Definition & Disease Spectrum

• Hepatic steatosis is defined as ectopic fat accumulation in >5% of hepatocytes; below this threshold is considered physiological
• Disease spectrum ranges from:

- Simple steatosis (ultrasonographic fatty liver) →

- Steatohepatitis (MASH/MELD) →

- Fibrosis →

- Cirrhosis →

- Hepatocellular carcinoma (HCC)

• NAFLD/MAFLD represents the hepatic manifestation of metabolic syndrome

Pathogenesis – Theoretical Evolution

• Two-hit hypothesis (Day & James, 1998):

- First hit: hepatic fat accumulation

- Second hit: triggers inflammation leading to NASH/cirrhosis

• Parallel pathway model (Herbert & Alexander, 2012):

- Simple steatosis and fibrosis can develop independently without obligate progression through inflammation

- Genetic factors may drive direct steatosis-to-cirrhosis progression

• Multiple-hit/multi-parallel hypothesis (current preferred model):

- Combines prior theories; multiple simultaneous insults drive disease heterogeneity and varied clinical phenotypes

Drivers of Disease Phenotypes

• Drivers of steatosis: Diabesity, high-caloric intake, insulin resistance, genetic susceptibility (e.g., PNPLA3 variants implied)
• Drivers of steatohepatitis (MASH): Cellular stress, metabolic dysregulation, reactive oxygen species (ROS)
• Drivers of fibrosis: Hepatic stellate cells, Kupffer cells, chemokines, genetic factors

3. Specific Clinical Data, Statistics, and Study Results Cited

• Community prevalence of NAFLD in India: 5–28% (data from Dr. A.A. and Dr. A.S.P. Singh)
• Prevalence is increasing across all age groups, including children and women
• NAFLD prevalence exceeds that of hepatitis B and hepatitis C combined in the Indian population
• Liver glycogen storage capacity: ~500 g in the liver; muscle glycogen stores measured in kilograms
• Without fat as an energy reserve, survival on glucose stores alone would be limited to 6–18 hours
• Semaglutide (GLP-1 receptor agonist) cited as the highest-selling pharmaceutical drug globally at time of lecture

4. Pathophysiological Mechanisms – Key Points

Insulin Signaling Pathway

• Normal insulin action: receptor binding → β-subunit dimerization → phosphorylation of IRS-1/IRS-2 → PI3K/AKT activation → stimulation of lipogenic genes via SREBP-1c → inhibition of gluconeogenesis
• Normal insulin effects: promotes de novo lipogenesis (DNL), inhibits fatty acid oxidation, inhibits gluconeogenesis, promotes glycolysis, inhibits apoptosis via BCL-2, facilitates GLUT4 translocation

Insulin Resistance State

• Leads to hyperinsulinemia → paradoxical acceleration of DNL
• Loss of inhibition of gluconeogenesis → hyperglycaemia
• Fatty acid oxidation disinhibited → increased circulating free fatty acids (FFAs)

De Novo Lipogenesis (DNL)

• Excess dietary glucose → pyruvate