Dietary Fuels and Malnutrition Causes

Dietary Fuels

• Carbohydrates come from glycogen in the liver and muscles.
• Salivary and pancreatic amylase digest carbohydrates.
• Intestinal brush borders break down sugars with enzymes like lactase.
• Fats include triglycerides and essential fatty acids.
• Pancreatic lipase and bile help absorb fats in the intestines.
• Fats are packaged in chylomicrons and flow through the lymphatic channels.
• Proteins' amino acids are substrates for gluconeogenesis.
• Pepsin and hydrochloric acid in the stomach digest proteins.
• Pancreatic proteases like trypsin digest proteins.

Malnutrition Causes

• Malnutrition can occur when one or more dietary components are inadequate for daily metabolic needs.
• It can occur in underdeveloped countries or areas with war and famine due to poor calorie intake.
• Common in states that have increased demands, such as pregnancy, infection, or trauma
• Altered diets such as chronic alcoholism, anorexia nervosa, or bulimia can lead to malnutrition.
• Drugs or absorption conditions can inhibit nutrient absorption, leading to malnutrition.
• Malnutrition is a condition caused by insufficient intake of essential nutrients, leading to various pathological states.

Severe Acute Malnutrition (SAM)

• SAM was previously called protein-calorie malnutrition and is common in countries, regions, or areas affected by war.
• Body proteins are compartmentalized in skeletal muscles and the liver.
• The body enters a catabolic state where it starts breaking down muscle and fat for energy
• Characterized by a depletion of skeletal muscle, causing weakness and affecting movement

Marasmus

• Marasmus is characterized by inadequate protein and calorie intake.
• Emaciation occurs, affecting somatic protein (skeletal muscle) the most.
• There is decreased muscle and fat because both are used for energy.
• Anemia and vitamin deficiencies can occur due to insufficient food intake.
• Marasmus patients experience decreased immunity and recurring infections.
• Muscle wasting and atrophy are key features.

Kwashiorkor

• Kwashiorkor means "disease of the deposed child."
• It is mainly protein deprivation, primarily affecting visceral protein stored in the liver.
• Skeletal muscle and fat are spared, and glucose from liver glycogen is the main energy source.
• The liver cannot synthesize key proteins like albumin and clotting factors.
• Upregulation of VLDL occurs, leading to fatty liver changes.
• Clinical features include hepatomegaly, fatty liver, low albumin (leading to edema), diarrhea, hypoplastic bone marrow, decreased immunity, and altered skin and hair.
• Swelling is characteristic due to low protein levels, with puffy eyes (peri-orbital edema), edema in hands, ankles, legs, and ascites.

Secondary Protein-Energy Malnutrition

• Secondary PEM can lead to decreased skeletal muscle fat and swelling from low protein
• It occurs with inadequate food intake due to age, illness, alcohol use, or medications.
• Common in patients living in poverty, homelessness, and older adults, also in patients with AIDS, chronic inflammation, or who are bedridden.
• It is also caused by malabsorption syndromes like celiac disease
• Results in increased infections and poor wound healing.

Cachexia

• Cachexia is emaciation due to secondary causes, commonly chronic inflammation or malignant states.
• It is a secondary form of inadequate protein-calorie malnutrition.
• Caused by cytokine production, particularly Tumor Necrosis Factor (TNF).
• Clinical presentation similar to marasmus like severe emaciation where muscle and fat are depleted
• It is often associated with serious conditions such as cancer, heart failure, chronic kidney disease, and AIDS
• Key Features:
  • Loss of skeletal muscle mass
    • Increased breakdown of muscle proteins (catabolism)
    • Driven by pro-inflammatory cytokines (like TNF-alpha, IL-6, and interleukin-1)
  • Fat loss
    • Fat breakdown is also abnormal
  • Increased metabolic rate
    • Metabolism speeds up

TNF Clinical Significance

• The boards will ask about a patient that has colon cancer or AIDS with involuntary weight loss and muscle wasting, what is the cytokine that is producing the systemic event?
• The answer is TNF alpha, it suppresses appetite and depletes lipids.

Cachexia vs Marasmus and Kwashiorkor

• Marasmus and Kwashiorkor are forms of malnutrition caused by insufficient nutrient intake, while cachexia is a wasting syndrome that is driven by underlying illness and inflammation.

Marasmus: ○ It occurs due to caloric and protein deficiency. ○ Primarily affects children and leads to severe weight loss, muscle wasting, and fat depletion. This is a starvation state caused by lack of food or inadequate food intake. Kwashiorkor: ○ It is caused by severe protein deficiency despite adequate caloric intake. ○ Common in areas with limited access to high-quality proteins, leading to edema (swelling), fatty liver, and muscle wasting. ○ Affected individuals often look swollen due to fluid retention, but they still have fat in their bodies, which is unlike the extreme fat loss seen in cachexia. Cachexia: ○ It’s driven by inflammation and disease rather than simple nutrient deficiency. ○ It involves muscle wasting and fat loss, often with an increase in metabolic rate, even in the presence of adequate or increased food intake. ○ Unlike marasmus and kwashiorkor, the body is actively breaking down its own muscle and fat due to the systemic effects of chronic illness or inflammation, regardless of how much food is consumed.