BIOQUI - 04/08/2023

Understanding Cholesterol: Structure and Synthesis

Cholesterol Structure

• Cholesterol is often misunderstood; it has a complex structure consisting of multiple rings, reminiscent of cyclopentane.

• It is classified as an alcohol due to the presence of a single hydroxyl group, distinguishing it from lipids despite its association with them.

Biochemical Pathways

• The synthesis of cholesterol involves several metabolic pathways, primarily starting from acetyl-CoA.

• Acetyl-CoA is produced through various biochemical processes, including glycolysis which ends in pyruvate formation.

Synthesis Complexity

• The synthesis process requires three molecules of acetyl-CoA and involves multiple enzymatic steps.

• A key enzyme in this pathway is HMG-CoA reductase, crucial for converting HMG-CoA into mevalonate.

Cholesterol Management and Clinical Implications

Statins and Hypercholesterolemia

• HMG-CoA reductase inhibitors (statins), such as simvastatin and lovastatin, are commonly used to manage high cholesterol levels.

• Normal cholesterol levels are considered up to 200 mg/dL; however, treatment decisions should be based on individual clinical situations rather than just numerical values.

Risk Factors for Treatment

• Factors influencing treatment initiation include lifestyle (e.g., exercise), dietary habits, body mass index (BMI), and presence of conditions like diabetes or hypertension.

Functions and Risks Associated with Cholesterol

Biological Roles

• Cholesterol serves multiple functions: it's a precursor for bile acids, steroid hormones, and vitamin D.

• It plays a critical role in cell membrane structure and integrity.

Health Risks Linked to High Cholesterol

• Elevated cholesterol levels can lead to serious health issues such as atherosclerosis, cardiovascular diseases (angina pectoris), myocardial infarction, and cerebrovascular accidents.

Steroid Hormones Derived from Cholesterol

Hormonal Pathways

• Cholesterol is the precursor for various steroid hormones including progestogens, glucocorticoids (like cortisol), mineralocorticoids (like aldosterone), androgenic hormones (like testosterone), and estrogens.

Estrogen Production Sites

Hormonal Functions and Their Impact on Women's Health

Role of Hormones in Ovarian Development

• Hormones play a crucial role in ovarian development, follicle maturation, endometrial development, libido maintenance, and vaginal lubrication.

• Postmenopausal women often face issues like bone resorption and osteoporosis due to hormonal changes.

Progesterone's Cycle and Function

• Progesterone levels remain low throughout the menstrual cycle except during ovulation when they slightly increase; if fertilization occurs, progesterone rises further.

• The primary function of progesterone is to prepare the endometrium for embryo implantation and maintain it during pregnancy.

Testosterone Production and Its Effects

• Testosterone is produced in both adrenal glands and ovaries in women; it contributes to various physiological functions.

• In men, testosterone influences voice deepening, facial hair growth, libido maintenance, and secondary sexual characteristics; similar effects are noted in women regarding libido.

Importance of Vitamin D3

• Vitamin D3 (cholecalciferol) enhances calcium absorption in the intestines and reabsorption in kidneys, playing a vital role in bone health.

• During the COVID-19 pandemic, studies highlighted vitamin D's importance for immune response; many older adults had insufficient levels due to limited sun exposure.

Cholesterol's Role in Body Functions

• Cholesterol regulates membrane fluidity and rigidity; it is eliminated from the body as bile acids synthesized from cholesterol.

• Bile acids emulsify fats in the intestine to aid digestion; their synthesis from cholesterol underscores its significance beyond just being a fat component.

Implications of High Cholesterol Levels

• Hypercholesterolemia can lead to significant reabsorption of cholesterol at intestinal levels, complicating treatment efforts.

Tratamiento de la Hipercolesterolemia y Cirugía Endoscópica

Intervenciones Quirúrgicas en Hipercolesterolemia

• El tratamiento para la hipercolesterolemia incluye intervenciones quirúrgicas como las sextinas y cirugía, especialmente en casos de cálculos biliares.

• La cirugía endoscópica se ha vuelto común, siendo rápida y menos problemática en comparación con métodos tradicionales.