PDIA4 and obesity due to melanocortin 4 receptor deficiency: In addition, upregulation of protein disulfide isomerase family A member 4 (PDIA4), an endoplasmic stress response protein, known for its role in modulating the immune response and insulin resistance in muscle cells (24), suggests an intricate molecular adaptation of monocytes from individuals with obesity that might be involved in developing comorbidities.