Insulin core is hydrophobic but its periphery has hydrophillic regions

The core is made of cholesterol and triacygylcerols. It is hydrophobic.

The pKa, or acid dissociation constant, of an amino acid is strongly tied to the properties of the surrounding solvent. The hydrophobic core of a protein is a distinctly different environment than the water exposed surface of the protein and the pKa in the core is different than the normal, solvent exposed pKa. This is related to the dielectric constant, or the ease at which charge is "felt" over a distance, which is much lower in the hydrophobic core of the protein. In addition, the now fixed locations of other possibly charged amino acids nearby will also impact the pKa of the residue.

Cholesterol has many hydrophobic side chains and a single hydrophilic side chain. Because it contains both hydrophilic and hydrophobic groups, it is amphipathic.
yes cholesterol Hydrophobic , choestol not soluble in water

hydrophobic