Figure 6. A model of microbial regulation of glucose metabolism in host colonocytes.

Microbes increase blood glucose levels and increase PDH levels and activity to facilitate oxidative metabolism of glucose in the mitochondria. In contrast, GF mice are hypoglycemic, and their colonocytes respond by increased expression of GLUTs. Although this leads to increased glucose uptake, Glu-6-P and pyruvate levels are diminished because of their conversion to lactate, which is increased in GF colonocytes. This increase in glycolysis can be attributed to decreased PDH expression/activity and decreased oxidative metabolism in the mitochondria. Not only are PDH levels decreased, but also enzymatic activity is inhibited via phosphorylation of the E1a regulatory subunit due to increased expression of PDK2 in GF colonocytes.