Carbohydrates Overview

Carbohydrates

• Two classes of carbohydrates: simple and compound.
• Simple carbohydrates are known as monosaccharides because they contain a single sugar unit.
• Compound carbohydrates include disaccharides (two sugar units), oligosaccharides (3-10 sugar units), and polysaccharides (more than 10 units).
• Glucose is considered the most important monosaccharide for human nutritional needs.
• Fructose is also known as fruit sugar.
• Fructose is formed from the breakdown of sucrose and glucose.
• Galactose is a component of glycoprotein found in the brain and nerve tissues.
• Galactose is a component of milk sugar.
• Galactose is used as a chemical marker to distinguish between different blood types.
• Sucrose is also known as common table sugar.
• Sucrose is obtained from sugar canes and beets.
• Lactose is also known as milk sugar.
• Lactose is found in dairy products.
• Maltose is also known as malt sugar.
• Maltose is found in cereals and wheat.
• Glycogen is a polysaccharide similar in structure to amylopectin.
• Liver and muscle cells store glycogen in humans.
• Cellulose is a structural component of plant cell walls.
• Cellulose shares a structure similar to amylose.
• Cellulose is a polysaccharide that is not digestible by humans.
• Cellulose provides proper intestinal functioning due to its high concentration of plant fibers.

Glucose Metabolism

• Blood glucose levels are regulated by various metabolic processes.
• Hypoglycemia refers to low blood glucose levels.
• Hypoglycemia is caused by an imbalance between glucose utilization and production.
• Hypoglycemia promotes glycogenolysis (glycogen breakdown) and glycolysis (glucose catabolism).

Diabetes Mellitus

• Diabetes mellitus (DM) is a complication that develops rapidly (acute) over time (chronic).
• DM complications affect various organ systems and can dramatically impair quality of life.
• DM complications are less common and severe when blood sugar levels are well-controlled.
• Modifiable risk factors include lifestyle, smoking, obesity, high blood pressure, elevated cholesterol levels, and lack of regular exercise.
• Non-modifiable risk factors include genetics, age, and gender.

Classifications of Diabetes Mellitus

• Type 1 Diabetes Mellitus is caused by the pancreas failing to produce enough insulin.
• Type 1 Diabetes Mellitus is due to genetics.
• Type 2 Diabetes Mellitus is characterized by insulin resistance.
• Type 2 Diabetes Mellitus is strongly inherited and does not involve beta cell autoantibodies.
• Gestational Diabetes Mellitus is diagnosed during pregnancy.
• Other types of diabetes mellitus are associated with secondary conditions, such as genetic defects in beta cell functioning, changes during pregnancy, and endocrine dysfunctions.

Methods for Quantification of Blood Glucose

• RBS (Random Blood Sugar) - used for patients presenting with insulin shock or hyperglycemia.
• FBS (Fasting Blood Sugar)- requires patients to not eat or drink for at least 8-10 hours before the test.
• 2-Hour PPBS (2-Hour Post-Prandial Blood Sugar) - a standardized glucose load of 75g is given to patients and a glucose measurement is taken two hours after.
• OGTT (Oral Glucose Tolerance Test) - a standardized glucose load is given, and glucose measurements are taken at different intervals.
• IVGTT (Intravenous Glucose-Tolerance Test) - used for patients with gastrointestinal disorders.

Inborn Errors of Carbohydrate Metabolism

• Galactosemia is a deficiency in the enzymes galactokinase, galactose 1-phosphate uridyl transferase, or uridyl diphosphate glucose 4-epimerase.
• The most common deficiency in galactosemia is galactose 1-phosphate uridyl transferase leading to excessive galactose in the blood and excretion in urine.
• Infants with galactosemia develop diarrhea and vomiting within days of consuming milk or formula containing lactose.

Risk Factors for Diabetes Mellitus

• Family history of diabetes in a first-degree relative.
• Membership in a high-risk minority population: African, Hispanic, Native American, or Asian American.
• History of GDM or delivering babies >9 lbs.
• Hypertension (>140/90).
• Low HDL (<500mg/dL).
• Obesity.
• History of gestational diabetes.

Tests for Diabetes Mellitus

• Blood tests to measure fasting blood sugar (FBS), HbA1c, and random blood sugar (RBS).
• Microalbuminuria tests.
• Glucose challenge test using 50g glucose.
• 3-Hour GTT (Glucose Tolerance Test) using 100g glucose.

Fructosamine

• Fructosamine is also known as glycosylated albumin, glycated albumin, or plasma protein ketoamine.
• Fructosamine provides information about short-term (2-3 weeks) glucose control.