FFAR2 and type 2 diabetes mellitus: The correlation between the relative expression levels of the FFAR2 gene in the elderly group and the younger group, between the type 2 diabetes mellitus group and the non–type 2 diabetes mellitus group, between the high fasting blood glucose group and the normal fasting blood glucose group, and between the low HDL-C and high HDL-C groups were statistically analyzed and compared.