INS and diabetes mellitus: In a multivariable regression model including characteristics that differed between the C-peptide quartiles, plasma C-peptide levels (as a continuous variable) were inversely associated with diabetes duration, use of insulin, plasma HDL cholesterol (all p < 0.0001) and eGFR (p = 0.003), and positively associated with plasma triglycerides, BMI, (both p < 0.0001), history of hypertension (p = 0.04) and use of sulphonylureas (p = 0.02) (data not shown).