In sickle-cell disease, a single glutamic acid in beta-globin is replaced with valine. Because valine is hydrophobic, whereas glutamic acid is hydrophilic, this change makes the hemoglobin prone to abnormal aggregation.
Valine, like other branched-chain amino acids, is associated with insulin resistance: higher levels of valine are observed in the blood of diabetic mice, rats, and humans. In humans, a protein restricted diet lowers blood levels of valine and decreases fasting blood glucose levels.
* Amino acids which are essential amino acids which cannot be made by the human body and, therefore, must be obtained in the diet.
Tillery, Enger and Ross