INS and metabolic syndrome: For instance, PQQ administration not only reduced glucose and increased insulin plasma concentration in streptozotocin (STZ)-treated animals that developed diabetes [75,76], but also positively modified the serum lipid profile by attenuating dyslipidemia, i.e., lowered levels of TAG, cholesterol, low-density lipoprotein cholesterol (LDL-C) and very-low-density lipoprotein cholesterol (VLDL-C).