**Core Concept**
When an individual fasts overnight, the body undergoes a series of physiological changes to adapt to the absence of food intake. One such adaptation involves the regulation of glucose metabolism, which is influenced by the activity and expression of glucose transporters (GLUTs) in different tissues.

**Why the Correct Answer is Right**
The correct answer is C. Adipocytes because the overnight fasting leads to a reduction in the levels of glucose transporter 4 (GLUT4) in adipocytes. GLUT4 is a key insulin-regulated glucose transporter that facilitates the uptake of glucose in adipose tissue and skeletal muscle. When insulin levels are low during fasting, the expression and translocation of GLUT4 to the plasma membrane are reduced, resulting in decreased glucose uptake in adipocytes. This adaptation helps to conserve glucose in the body by reducing glucose utilization in adipose tissue.

**Why Each Wrong Option is Incorrect**
**Option A:** Brain cells have a constant need for glucose to maintain their high metabolic rate, and their glucose uptake is not significantly affected by overnight fasting. The brain relies on glucose as its primary energy source, and its glucose transporters are not downregulated during fasting.

**Option B:** Red blood cells (RBCs) lack mitochondria and therefore do not require glucose for energy production. Instead, they rely on anaerobic glycolysis to generate energy from glucose. The glucose uptake in RBCs is not affected by insulin or fasting status.

**Option D:** Hepatocytes, the liver cells, are involved in glucose production and storage rather than uptake. During fasting, the liver increases glucose production through gluconeogenesis and glycogen breakdown, but the levels of glucose transporters in hepatocytes are not reduced.

**Clinical Pearl / High-Yield Fact**
During fasting, the body prioritizes glucose utilization in the brain and RBCs while reducing glucose uptake in adipose tissue to conserve glucose for essential functions.

**✓ Correct Answer: C. Adipocytes**