IRS1 and obesity due to melanocortin 4 receptor deficiency: Studies have shown that LF upregulates insulin receptor (IR), insulin receptor substrate-1 (IRS-1), glucose transporter 4 (GLUT4), PI3K and AKT in liver protein expression (30), increases peroxisome proliferator-activated receptor γ and regulatory protein SIRT-1 expression (28), and is negatively correlated with chronic inflammation-induced metabolic disorders of insulin resistance, hyperglycemia, and obesity, and positively correlated with insulin sensitivity (48).