A 24-year-old woman is admitted to the hospital with a diagnosis of acute appendicitis. She started having right lower quadrant abdominal pain approximately 30 hours earlier but did not go to the hospital because she thought the pain would subside on its own. The patient had no food, only sips of water, during that time. Blood pressure is 115/72 mm Hg and pulse is 106/min. Mucous membranes are dry and there is tenderness in the right lower quadrant of the abdomen. Laboratory evaluation shows mild leukocytosis, normal serum electrolytes, borderline low serum glucose levels, and moderate ketones in the urine. Based on the evaluation, it is suspected that this patient is utilizing ketone bodies as a significant reserve of energy. Which of the following tissues cannot use this energy source?

Question

A 24-year-old woman is admitted to the hospital with a diagnosis of acute appendicitis.  She started having right lower quadrant abdominal pain approximately 30 hours earlier but did not go to the hospital because she thought the pain would subside on its own.  The patient had no food, only sips of water, during that time.  Blood pressure is 115/72 mm Hg and pulse is 106/min.  Mucous membranes are dry and there is tenderness in the right lower quadrant of the abdomen.  Laboratory evaluation shows mild leukocytosis, normal serum electrolytes, borderline low serum glucose levels, and moderate ketones in the urine.  Based on the evaluation, it is suspected that this patient is utilizing ketone bodies as a significant reserve of energy.  Which of the following tissues cannot use this energy source?

Quizplus · Accepted Answer

11ec160b_36ca_2005_9249_53a7032bcf78_MD0001_00 After about 12-18 hours of fasting, the body's glycogen stores are depleted and gluconeogenesis is required to maintain blood glucose levels. As fasting continues, the body limits its reliance on gluconeogenesis in an effort to conserve protein and resorts instead to ketone body synthesis. Ketone bodies are generated in the liver from fatty acids and yield energy when converted to acetyl CoA in the mitochondria of target cells. The brain, kidneys, cardiac muscle, and skeletal muscle (Choices A, C, D & E) can all utilize ketones for energy. In the initial stages of fasting, the heart and skeletal muscle consume primarily ketone bodies to preserve glucose for the brain, but in prolonged starvation, even the brain will utilize ketone bodies for the majority of its energy needs. However, erythrocytes cannot use ketone bodies for energy because they lack mitochondria. The liver is also unable to utilize ketone bodies for energy because it lacks the enzyme succinyl CoA-acetoacetate CoA transferase (thiophorase), which is required to convert acetoacetate to acetoacetyl CoA. Educational objective: When glycogen stores are depleted during fasting, ketone bodies are produced in the liver and can be used as an energy source in the mitochondria of peripheral tissues. The brain preferentially uses glucose, but will utilize ketones for most of its energy needs during prolonged starvation. Erythrocytes lack mitochondria and are unable to use ketones.

A 24-Year-Old Woman Is Admitted to the Hospital with a Diagnosis