Govt. Exams
Entrance Exams
Thyroid hormones upregulate LDL receptors and also inhibit HMG-CoA reductase. In hypothyroidism, all these effects are reversed, leading to increased cholesterol levels through multiple mechanisms.
Lp(a) levels are primarily determined by genetic factors (LPA gene polymorphisms) and are elevated in chronic kidney disease due to reduced catabolism. Lp(a) is an independent cardiovascular risk factor.
CPT-I is allosterically inhibited by malonyl-CoA, a key regulatory point linking fatty acid synthesis (high during fed state) with fatty acid oxidation (low during fed state).
Tangier disease results from mutations in ABCA1 gene, which encodes an ATP-binding cassette transporter essential for HDL biogenesis. This leads to severe HDL deficiency and cholesterol accumulation in tissues.
Small, dense LDL particles (Pattern B) are more atherogenic because they penetrate arterial walls more easily, are more susceptible to oxidation, and have reduced hepatic clearance compared to large, buoyant LDL particles.
Xanthomas (lipid deposits in skin and tendons) and corneal arcus (lipid deposition in cornea) are hallmark signs of severe hypercholesterolemia, typically with very high LDL cholesterol levels.
Eicosanoid synthesis begins with phospholipase A2-mediated release of arachidonic acid (C20 polyunsaturated fatty acid) from membrane phospholipids, which then serves as substrate for COX and LOX pathways.
ApoA-I is the major apolipoprotein of HDL, essential for LCAT activation and cholesterol esterification, promoting reverse cholesterol transport and HDL maturation.
Palmitate (C16) undergoes 7 cycles of beta-oxidation producing 8 acetyl-CoA molecules, 7 FADH2, and 7 NADH. Total ATP yield is approximately 129 ATP (accounting for initial activation cost).
Lipoprotein lipase deficiency causes Type I hyperlipoproteinemia with severe accumulation of chylomicrons and triglycerides (>1000 mg/dL), risk of acute pancreatitis.
