Category: Metabolism of Lipids

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Starvation induced metabolic alterations

A 23 –year- old female was brought for consultation by her mother who was troubled by her daughter’s continuous fatigue, dizziness and loss of weight. The patient was 6 feet 2 inches tall and weighed 100 pounds. Further questioning revealed that the young woman had been virtually fasting for 4 months hoping to obtain a ‘skinny figure’ as a prelude to a career in modeling. Physical examination revealed dehydration and a fruity odor in her breath. Laboratory results revealed – Blood glucose 50 mg%. Which substance would most likely be detected in abnormally high concentration upon patient’s urine test? A)...

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Implications of suppressed TCA cycle in Diabetes Mellitus

A 22- year-old diabetic comes to the Accident and Emergency department. She gives a 2-day history of vomiting and abdominal pain. She is drowsy and her breathing is deep and rapid. There is distinctive smell from her breath. She has been diagnosed with Diabetic ketoacidosis. Diabetic ketoacidosis is a complication of uncontrolled diabetes mellitus. The TCA cycle in diabetes mellitus is suppressed and the excess Acetyl co A, resulting from fatty acid oxidation is channeled towards the pathway of ketogenesis. Which of the following intermediates of TCA cycle is depleted in Type 1 Diabetes mellitus to suppress TCA cycle? A)...

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Cholesterol transport and Tangier disease

Tangier disease is a disease of cholesterol transport. The first case was identified in a patient who lived on the island of Tangier and who had characteristic orange-colored tonsils, a very low HDL level, and an enlarged liver and spleen. Due to a mutation in the transport protein the cholesterol cannot properly exit the cell to bind to apo A (that forms HDL). This results in a very low HDL levels. Cholesterol obtained by HDL from cell membranes is converted to cholesterol esters. Which of the following enzymes catalyzes the esterification of cholesterol? A. HMG Co A reductase B. Lecithin:...

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Cholesterol content and membrane fluidity

Membrane fluidity is required for the proper movement of erythrocytes through capillaries of the spleen. Patients with spur cell anemia have increased cholesterol content (> 40%) in the membranes of their erythrocytes, resulting in decreased membrane fluidity. Thus, erythrocytes from these patients are destroyed in the spleen. Which of the following statements is incorrect concerning the significance of cholesterol? A. Elevated levels of cholesterol are associated with atherosclerosis. B. The serum total cholesterol content should be less than 200 mg/dl. C. Cholesterol is a major component of gall stones. D. Excess cholesterol is excreted from the liver in the bile...

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Elevated Acylcarnitine compounds and associated hypoglycemia- What is the defect?

Case details A 5- year-old boy suffered gastroenteritis for two days and was brought to emergency in the semiconscious state. Blood glucose at the time of admission was 45 mg/dl and his urine was negative for glucose and ketone bodies. Glucose was administered intravenously and his condition improved within 10 minutes. Subsequent laboratory investigations revealed elevated acylcarnitine residues. The child was diagnosed with an enzyme deficiency. The parents were instructed to feed the child more frequently. Which of the following enzymes might be deficient? A. Acyl Co A synthetase B. Carnitine Acyl transferase-1 C. Translocase D. Carnitine Acyl transferase-2 E....

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Diabetic ketoacidosis- Enzyme for ketones formation?

Case details A 54- year-old man with Type 1 diabetes is referred to an ophthalmologist for evaluation of developing cataract. Blood chemistry results are shown below- Fasting blood glucose   198 mg/dl Hemoglobin A                  15 gm/dl Hemoglobin A 1c             10% of total Hb Urine ketones                   Positive Urine glucose                    Positive Which of the following enzymes is most strongly associated with ketones formation in this patient? A) Pyruvate dehydrogenase complex B) Thioesterase C) Thiophorase D) Thiokinase E) Thiolase. The correct answer is- E- Thiolase. Out of the given options thiolase is the only enzyme involved in the ketogenesis. The process of ketogenesis starts from...

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Role of ACAT in the esterification of cholesterol

See the image below and note the role of ACAT (Acyl Co A cholesterol acyl transferase) in the esterification of cholesterol. Cholesterol is stored in the cell in the form of cholesteryl esters. Esterification involves the coupling of cholesterol with a fatty acid, generally this fatty acid is a- A. Saturated fatty acid B. Monounsaturated fatty acid C. Polyunsaturated fatty acid D. Dienoic acid E. Any of the above. Figure-1- Uptake of LDL and fate of cholesterol The correct answer is- Monounsaturated fatty acid, Commonly Oleic acid is used for the esterification (figure-2) Oleic acid is a mono- unsaturated fatty...

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The role of Phytosterols in reducing the risk of heart disease

A 65-year-old man has been taking low-dose aspirin to reduce his risk of heart disease. He adds phytosterols to his daily regime for which of the following? A. To reduce circulating triglyceride levels B. To reduce circulating cholesterol levels C. To reduce endogenous cholesterol synthesis D. To decrease insulin secretion E. To reduce fatty acid biosynthesis The answer is B: To reduce circulating cholesterol levels. Phytosterols interfere with cholesterol absorption in the intestine (through blockage of cholesterol incorporation into the mixed micelles, which are necessary for intestinal epithelial cells to absorb dietary cholesterol), (figure-1), thereby leading to a reduction in...

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Milky plasma- Your diagnosis ??

A teenage boy presents with moderate to severe epigastric pain. Physical examination reveals extensive eruptive xanthomas and hepatosplenomegaly. A blood sample reveals milky plasma. Which of the following is the most likely lipoprotein to be elevated in this patient’s plasma? A. Chylomicrons B. Chylomicron remnants C. HDL D. IDL E. LDL The correct answer is A- Chylomicrons. Clinical features and history are suggestive of Type I Hyperlipidemia (Chylomicronemia) that occurs due to deficiency of Lipoprotein lipase . Familial lipoprotein lipase deficiency is an example of a primary disorder in which a deficiency of lipoprotein lipase in tissue leads to a...

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Significance of Lipoproteins

Case details A 50 -year-old male presents with weakness in his left leg. History reveals that he is a known hypertensive and a diabetic from the past 5 years, but is non- compliant to medication. Based on the clinical findings and imaging of the brain, he has been diagnosed with “Brain stroke”. His serum total cholesterol is abnormally elevated. Which of the following would also be expected to be abnormally high? A. Chylomicrons B. LDL C. HDL D. VLDL E. IDL The correct option is- B, LDL (Low density lipoprotein) Lipids absorbed from the diet and synthesized by the liver...

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Classification of lipoproteins as per density

Chylomicrons, intermediate- density- lipoproteins (IDLs), low- density- lipoproteins (LDLs), and very low-density lipoproteins (VLDLs) are all serum lipoproteins. What is the correct ordering of these particles from the lowest to the highest density? A.LDLs, IDLs, VLDLs and chylomicrons B. Chylomicrons, VLDLs, IDLs, LDLs C.VLDLs, IDLs, LDLs and Chylomicrons D.LDLs, VLDLs, IDLs, Chylomicrons E. Chylomicrons, IDLS, VLDLs and LDLs. The correct answer is B- Chylomicrons, VLDLs, IDLs, LDLs Based on density Lipoproteins can be classified as follows Since fat is less dense than water, the density of a lipoprotein decreases as the proportion of lipid to protein increases.  Lipoproteins with high lipid...

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Respiratory Distress syndrome- Case discussion

Case Details An infant is born prematurely at 28 weeks and has developed increasing difficulty in breathing. His skin starts to turn blue from lack of oxygen(cyanosis).He is diagnosed with Respiratory distress syndrome due to deficiency of lung surfactant . Which of the following is the phospholipid of primary importance in surfactant? A. Dipalmitoyl phosphatidyl choline B. Dipalmitoyl phosphatidyl ethanolamine C. Dipalmitoyl phosphoglyceride D. Dipalmitoyl phosphatidyl Inositol E. Dipalmitoyl phosphatidyl serine  Case discussion The correct answer is A- Dipalmitoyl phosphatidyl choline. Respiratory distress syndrome, also known as hyaline membrane disease, occurs almost exclusively in premature infants. Lung surfactant is a...

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Respiratory distress syndrome- A case report

An infant is born prematurely at 28 weeks and has developed increasing difficulty in breathing. His skin starts to turn blue from lack of oxygen(cyanosis).He is diagnosed with Respiratory distress syndrome due to deficiency of lung surfactant . Which of the following is the phospholipid of primary importance in surfactant? A. Dipalmitoyl phosphatidyl choline B. Dipalmitoyl phosphatidyl ethanolamine C. Dipalmitoyl phosphoglyceride D. Dipalmitoyl phosphatidyl Inositol E. Dipalmitoyl phosphatidyl serine Figure- Chest radiograph of an infant with respiratory distress syndrome of the newborn. For case discussion follow the link http://usmle.biochemistryformedics.com/respiratory-distress-syndrome-case-discussion/ Please help Biochemistry for Medics by “CLICKING ON THE ADVERTISEMENTS” every...

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Familial hypercholesterolemia- Case discussion

Case Details In familial hypercholesterolemia, cholesterol is deposited in various tissues because of the high concentration of LDL cholesterol in the plasma. Of particular concern is the oxidation of the excess blood LDL to form oxidized LDL (oxLDL). The oxLDL is taken up by immune-system cells called macrophages, which become engorged to form foam cells. Which statement best describes the formation of foam cells? A. LDL receptors on peripheral cells are upregulated B. LDL receptors for modified LDL (Ox LDL) are not down regulated C. LDL enters by pinocytosis to form foam cells D. There is increased de no synthesis...

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Familial hypercholesterolemia- A case report

Case Details In familial hypercholesterolemia, cholesterol is deposited in various tissues because of the high concentration of LDL cholesterol in the plasma. Of particular concern is the oxidation of the excess blood LDL to form oxidized LDL (oxLDL). The oxLDL is taken up by immune-system cells called macrophages, which become engorged to form foam cells. Which statement best describes the formation of foam cells? A. LDL receptors on peripheral cells are upregulated B. LDL receptors for modified LDL (Ox LDL) are not down regulated C. LDL enters by pinocytosis to form foam cells D. There is increased de no synthesis...

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Answer- Case study-Jamaican Sickness- A 35-year-old man in New York City, originally from Jamaica, purchased an illegally imported fruit from a street vendor….

QUESTION OF THE DAY A 35-year-old man in New York City, originally from Jamaica, purchased an illegally imported fruit from a street vendor and, within 4 hours of eating the fruit, began vomiting severely. When brought to the emergency department the man was severely dehydrated and exhibited several seizures. The toxic effects of the fruit were interfering with which of the following? A. Fatty acid release from the adipocytes B. Fatty acid entry into the liver cell C. Fatty acid activation D.Fatty acid oxidation E. Oxidative phosphorylation Answer- D- Fatty acid oxidation. The patient is suffering from Jamaican vomiting sickness....

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Case study- Jamaican Sickness-A 35-year-old man in New York City, originally from Jamaica

METABOLISM OF LIPIDS QUESTION OF THE DAY A 35-year-old man in New York City, originally from Jamaica, purchased an illegally imported fruit from a street vendor and, within 4 hour of eating the fruit, began vomiting severely. When brought to the emergency department the man was severely dehydrated and exhibited several seizures. Figure- Jamaican fruit (Ackee fruit) The toxic effects of the fruit were interfering with which of the following? A. Fatty acid release from the adipocytes B. Fatty acid entry into the liver cell C. Fatty acid activation D.Fatty acid oxidation E. Oxidative phosphorylation For answer, Follow the link...

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