Glycemic Index and Glycemic Load — MCQs
Which glycogen storage disease does not affect muscles?
Which type of carbohydrate is absorbed most efficiently from the gastrointestinal tract?
Which of the following is false regarding management of diabetes in pregnancy?
Which of the following is FALSE about insulin action?
A patient had dinner at 8 PM at night and does his blood sugar test at 7 AM in the morning. What is the major source of glucose at this time?
Which of the following represents a normal response to an OGTT?
Which drug reduces postprandial hyperglycemia in type 2 diabetes?
All of these cause hyperglycemia except:
Glycemic index is defined as:
Low glycemic index food is:
Glycemic Index and Glycemic Load Indian Medical PG Practice Questions and MCQs
Question 1: Which glycogen storage disease does not affect muscles?
- A. Type 4 (Andersen disease)
- B. Type 2 (Pompe disease)
- C. Type 1 (Von Gierke disease) (Correct Answer)
- D. Type 3 (Cori disease)
Explanation: ***Type 1 (Von Gierke disease)*** - This is caused by a deficiency in **glucose-6-phosphatase**, an enzyme found primarily in the **liver** and **kidneys** but **NOT in muscle tissue**. - Since muscles do not express glucose-6-phosphatase and rely on glycogen phosphorylase for energy mobilization, this disease **does not affect muscle function**. - Clinical features include severe **hypoglycemia**, **lactic acidosis**, **hepatomegaly**, and **growth retardation**, but patients have **normal muscle strength and function**. *Type 2 (Pompe disease)* - Also known as **acid maltase deficiency**, this disease severely affects **all muscle types** including cardiac, skeletal, and smooth muscles. - It is a **lysosomal storage disease** causing progressive **muscle weakness**, **cardiomyopathy**, and **respiratory failure**. - This is the most significant muscle-affecting GSD. *Type 3 (Cori disease)* - Caused by **debranching enzyme (amylo-1,6-glucosidase) deficiency**, affecting both **liver and muscles**. - Patients develop **hepatomegaly**, **hypoglycemia**, and progressive **myopathy** with muscle weakness. - Muscle involvement is common and clinically significant. *Type 4 (Andersen disease)* - Due to **branching enzyme deficiency**, primarily causing **liver cirrhosis** and **hepatosplenomegaly**. - While mainly hepatic, this disease **can involve muscles** causing hypotonia and muscle weakness in some patients. - The abnormal, unbranched glycogen ("amylopectin-like") accumulates in multiple tissues including muscle.
Question 2: Which type of carbohydrate is absorbed most efficiently from the gastrointestinal tract?
- A. Disaccharides
- B. Polysaccharides
- C. Monosaccharides (Correct Answer)
- D. 5-carbon sugars
Explanation: ***Monosaccharides*** - **Monosaccharides**, like glucose and fructose, are the simplest forms of carbohydrates and do not require further digestion. - They are directly absorbed into the bloodstream from the intestinal lumen via specific **transporters** on the enterocyte membrane. *Disaccharides* - **Disaccharides**, such as sucrose and lactose, must first be broken down into their constituent monosaccharides by **brush border enzymes** (e.g., lactase, sucrase) before absorption can occur. - This additional enzymatic step makes their absorption less efficient than that of monosaccharides. *Polysaccharides* - **Polysaccharides**, including starch and glycogen, are complex carbohydrates requiring extensive digestion by enzymes like **amylase** in the mouth and small intestine. - This multi-step breakdown into monosaccharides is the least efficient process and takes the longest time. *5-carbon sugars* - While 5-carbon sugars (**pentoses**) like ribose and deoxyribose are monosaccharides and can be absorbed, they are not a primary energy source in the diet and are not absorbed as efficiently or in as large quantities as the metabolically more significant 6-carbon monosaccharides (hexoses like glucose). - The question asks which *type* of carbohydrate is most efficiently absorbed, and **monosaccharides** as a general category (including 6-carbon sugars) are the most efficient.
Question 3: Which of the following is false regarding management of diabetes in pregnancy?
- A. In active labor, if RBS <70 mg/dL, D5 is started at 100-150 ml/hr till the RBS is >70 mg/dL
- B. In a patient being planned for induction of labor, night dose of intermediate insulin is given as planned, and the morning dose is withheld
- C. Elective C-section has no role in reducing incidence of brachial plexus injury (Correct Answer)
- D. Capillary blood glucose monitoring levels are kept at fasting- 95 mg/dL; 1 hr postprandial- 140 mg/dL; 2 hrs postprandial- 120 mg/dL
Explanation: ***Elective C-section has no role in reducing incidence of brachial plexus injury*** - This statement is **false** because **elective C-section** can significantly reduce the incidence of **brachial plexus injury** (BPI), especially in cases of suspected fetal macrosomia. - While not universally recommended for all diabetic pregnancies, an elective C-section is considered when the estimated **fetal weight** is substantial or when there's a history of **shoulder dystocia** to prevent birth trauma. *In active labor, if RBS <70 mg/dL, D5 is started at 100-150 ml/hr till the RBS is >70 mg/dL* - This is a **correct** management strategy for **hypoglycemia in labor**. Maintaining stable blood glucose levels (above 70 mg/dL) is crucial to prevent adverse outcomes for both mother and fetus. - The administration of **D5 (dextrose 5% in water)** intravenous solution at a specific rate helps to quickly raise and maintain blood glucose levels. *In a patient being planned for induction of labor, night dose of intermediate insulin is given as planned, and the morning dose is withheld* - This is a common and generally **correct** practice for insulin management before **induction of labor**. The night dose of intermediate insulin helps maintain basal glucose levels overnight. - Withholding the morning dose prevents **hypoglycemia** during labor when food intake is restricted, and insulin sensitivity may increase. Glucose is then typically supplemented through IV fluids as needed. *Capillary blood glucose monitoring levels are kept at fasting- 95 mg/dL; 1 hr postprandial- 140 mg/dL; 2 hrs postprandial- 120 mg/dL* - These are the generally accepted and **correct** target blood glucose levels for **diabetes in pregnancy** (both pre-existing and gestational diabetes). - Achieving these targets is essential to minimize the risk of **fetal macrosomia**, **neonatal hypoglycemia**, and other adverse perinatal outcomes.
Question 4: Which of the following is FALSE about insulin action?
- A. Insulin promotes glycolysis
- B. Insulin promotes ketogenesis (Correct Answer)
- C. Insulin promotes glycogen synthesis
- D. Insulin promotes lipogenesis
Explanation: ***Insulin promotes ketogenesis*** - Insulin is an **anabolic hormone** that works to prevent excessive **fat breakdown** and the formation of **ketone bodies**. - High insulin levels actively **inhibit** enzymes involved in ketogenesis, such as **carnitine palmitoyltransferase-1 (CPT1)**, thereby reducing the transport of fatty acids into mitochondria for oxidation. *Insulin promotes glycolysis* - Insulin stimulates **glycolysis**, particularly in the liver and muscle, by increasing the activity of key enzymes like **glucokinase** and **phosphofructokinase-1**. - This promotes the breakdown of glucose for **energy production** and provides substrates for fat synthesis. *Insulin promotes glycogen synthesis* - Insulin is a primary regulator of **glycogen synthesis** in the liver and muscles. - It activates **glycogen synthase** and inhibits glycogen phosphorylase, thereby shunting glucose towards storage as **glycogen**. *Insulin promotes lipogenesis* - Insulin promotes **lipogenesis** (fat synthesis) in adipose tissue and liver. - It increases glucose uptake into adipocytes and stimulates enzymes like **acetyl-CoA carboxylase** and **fatty acid synthase**, converting excess carbohydrates into fatty acids and subsequently **triglycerides**.
Question 5: A patient had dinner at 8 PM at night and does his blood sugar test at 7 AM in the morning. What is the major source of glucose at this time?
- A. Liver Glycogen (Correct Answer)
- B. Muscle Glycogen
- C. Gluconeogenesis
- D. Dietary Carbohydrate
- E. Ketone bodies
Explanation: ***Liver Glycogen*** - After an overnight fast (approximately 11 hours in this scenario), the primary mechanism for maintaining blood glucose levels is the breakdown of **liver glycogen** stores. - The liver is crucial for glucose homeostasis as it can release glucose directly into the bloodstream, a function muscle glycogen cannot perform. *Muscle Glycogen* - **Muscle glycogen** serves as an energy reserve primarily for the muscle itself and cannot be directly released into the bloodstream to maintain blood glucose levels. - It is utilized for physical activity and local energy demands within muscle cells. *Gluconeogenesis* - **Gluconeogenesis**, the synthesis of glucose from non-carbohydrate precursors, becomes increasingly important for glucose production after prolonged fasting (typically *after* liver glycogen stores are depleted). - While it contributes during an overnight fast, **liver glycogenolysis** is the dominant source initially. *Dietary Carbohydrate* - **Dietary carbohydrates** from the previous dinner (8 PM) would have been absorbed and utilized or stored as glycogen much earlier than 7 AM the next morning. - By 7 AM, the direct impact of the previous night's meal on circulating glucose is negligible, having been processed hours before. *Ketone Bodies* - **Ketone bodies** are alternative fuel sources produced during prolonged fasting or starvation, but they are **not glucose**. - While they can be used by tissues (brain, heart, muscle) for energy during extended fasting, they do not contribute to blood glucose levels and are metabolically distinct from glucose.
Question 6: Which of the following represents a normal response to an OGTT?
- A. Graph A
- B. Graph B
- C. Graph D (Correct Answer)
- D. Graph C
Explanation: ***Graph D*** - Graph D shows a **fasting glucose level** below 100 mg/dL, a peak below the renal threshold around 1 hour, and a return to baseline or below within 2-2.5 hours. This pattern is characteristic of normal glucose regulation. - A healthy individual can efficiently clear the glucose load from circulation, preventing sustained hyperglycemia. *Graph A* - Graph A shows significantly **elevated fasting glucose levels** (above 200 mg/dL) and a sustained, very high blood glucose response, peaking above 350 mg/dL and remaining well above the renal threshold. - This pattern is indicative of **diabetes mellitus**, where insulin production or sensitivity is severely impaired. *Graph B* - Graph B displays a high fasting glucose level (above 125 mg/dL) and a blood glucose curve that peaks very high (above 250 mg/dL), staying significantly above the renal threshold even at 2.5 hours. - This profile is suggestive of **impaired glucose tolerance** or **diabetes mellitus**, as the body struggles to effectively lower blood glucose after the glucose load. *Graph C* - Graph C shows a normal fasting glucose level but an **extremely rapid and high peak** much earlier than usual, followed by a precipitous drop below normal fasting levels after 1.5 hours, indicating **reactive hypoglycemia**. - This rapid rise and fall, with a nadir below fasting levels, is not a normal response and may be seen in conditions like **dumping syndrome** or early-stage diabetes with a delayed insulin response.
Question 7: Which drug reduces postprandial hyperglycemia in type 2 diabetes?
- A. Pioglitazone
- B. Acarbose (Correct Answer)
- C. Glyburide
- D. Metformin
Explanation: ***Acarbose*** - **Acarbose** is an **alpha-glucosidase inhibitor** that works by delaying the digestion and absorption of carbohydrates in the gut. - This delay in carbohydrate absorption directly reduces the postprandial (after-meal) rise in blood glucose levels. *Pioglitazone* - **Pioglitazone** is a **thiazolidinedione** that improves insulin sensitivity primarily in muscle and adipose tissue. - While it lowers overall blood glucose, its main effect is not specifically on postprandial hyperglycemia. *Glyburide* - **Glyburide** is a **sulfonylurea** that stimulates the pancreas to release more insulin. - It lowers blood glucose by increasing insulin secretion, which impacts both fasting and postprandial levels, but its primary action isn't specific to rapid postprandial peaks. *Metformin* - **Metformin** is a **biguanide** that primarily reduces hepatic glucose production and improves insulin sensitivity in peripheral tissues. - While it lowers both fasting and postprandial glucose, its main mechanism is not directly targeting the immediate digestion of carbohydrates after a meal.
Question 8: All of these cause hyperglycemia except:
- A. Catecholamines
- B. Insulin (Correct Answer)
- C. Cortisol
- D. GH
Explanation: ***Insulin*** - Insulin's primary function is to **lower blood glucose levels** by facilitating glucose uptake into cells and promoting glycogen synthesis. - It counters the effects of hormones that elevate blood sugar, directly leading to a **decrease in hyperglycemia**. *Catecholamines* - **Catecholamines** (e.g., epinephrine, norepinephrine) increase blood glucose by promoting **glycogenolysis** and **gluconeogenesis**. - They also **inhibit insulin secretion**, further contributing to elevated blood sugar. *Cortisol* - **Cortisol** is a **glucocorticoid** that raises blood glucose by increasing **gluconeogenesis** and reducing peripheral **glucose utilization**. - It can also decrease insulin sensitivity, leading to **hyperglycemia**. *GH* - **Growth hormone (GH)** can induce **insulin resistance** in peripheral tissues, which leads to reduced glucose uptake. - It also promotes **gluconeogenesis**, both contributing to elevated blood glucose levels.
Question 9: Glycemic index is defined as:
- A. Glucose control in last 3 months
- B. Measure of the change in the blood glucose following ingestion of proteins
- C. Measure of the change in the blood glucose following ingestion of fats
- D. Measure of the change in blood glucose following the ingestion of carbohydrates. (Correct Answer)
Explanation: ***Measure of the change in blood glucose following the ingestion of carbohydrates.*** - The **glycemic index (GI)** specifically quantifies how much a particular **carbohydrate-containing food** raises blood glucose levels compared to a reference food (pure glucose or white bread). - This value reflects the rate at which **carbohydrates** are digested and absorbed into the bloodstream. *Glucose control in last 3 months* - This description refers to **HbA1c (glycated hemoglobin)**, which provides an average blood glucose level over the preceding 2-3 months. - HbA1c is a clinical measure of long-term glycemic control, not a property of individual foods. *Measure of the change in the blood glucose following ingestion of proteins* - While proteins can affect blood glucose, their impact is generally much smaller and slower compared to carbohydrates, and it's not what the **glycemic index** measures. - The primary role of protein in glucose metabolism is through **gluconeogenesis** or an insulin response, which is distinct from the immediate post-prandial glucose spike from carbohydrates. *Measure of the change in the blood glucose following ingestion of fats.* - Fats have a minimal direct impact on blood glucose levels; they are primarily digested into fatty acids and glycerol. - Although fats can slow down gastric emptying and carbohydrate absorption, they do not directly cause a significant rise in blood glucose and are not considered in the definition of the **glycemic index**.
Question 10: Low glycemic index food is:
- A. Easily digestible
- B. Increase glycogen deposits
- C. Has slower absorption (Correct Answer)
- D. Increases plasma glucose
Explanation: ***Has slower absorption*** - **Low glycemic index (GI)** foods are digested and absorbed more slowly, leading to a gradual rise in blood glucose and insulin levels. - This characteristic is beneficial for managing **blood sugar** and providing sustained energy. *Easily digestible* - **Easily digestible** foods often have a **high glycemic index** because their carbohydrates are rapidly broken down and absorbed. - Low GI foods, by contrast, contain more complex carbohydrates and fiber, making them slower to digest. *Increase glycogen deposits* - While all carbohydrates are eventually converted to **glucose** and can contribute to **glycogen synthesis**, low GI foods do not uniquely or preferentially increase glycogen deposits compared to high GI foods. - Glycogen synthesis is primarily influenced by insulin levels and the total amount of carbohydrates consumed, irrespective of GI. *Increases plasma glucose* - All carbohydrate-containing foods will eventually increase **plasma glucose**, but low GI foods cause a **slower and smaller rise** in blood glucose compared to high GI foods. - They prevent the sharp spikes in blood sugar that are associated with high GI foods.
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