Carotid Body Dysfunction in Diet-Induced Insulin Resistance Is Associated with Alterations in Its Morphology

The carotid body (CB) is organized in clusters of lobules containing type I cells and type II cells, in a ratio of approximately 4:1. The CB undergoes structural and functional changes during perinatal development, in response to a variety of environmental stimuli and in pathological conditions. Knowing that the CB acts as a metabolic sensor involved in the control of peripheral insulin sensitivity and that its overactivation contributes to the genesis of metabolic disturbances, herein we tested if diet-induced insulin resistance is associated with morphological alterations in the proportion of type I and type II cells in the CB. Diet induced insulin resistant model (HFHSu) was obtained by submitting Wistar rats to 14 weeks of 60% lipid-rich diet and 35% of sucrose in drinking water. The HFHSu group was compared with an aged-matched control group. Glucose tolerance and insulin sensitivity were measured in conscious animals before diet administration and 14 weeks after the diet protocol. The expression of tyrosine hydroxylase (TH) and nestin were assessed by immunohistochemistry to identify type I and type II cells, respectively. TH expression was also quantified by Western blot. As expected, 14 weeks of HFHSu diet induced a decrease in insulin sensitivity as well as in glucose tolerance. HFHsu diet increased the number of TH-positive type I cells by 192% and decreased nestin-postive type 2 cells by 74%. This increase in type II cells observed by immunohistochemistry correlates with an increase by 107% in TH expression quantified by Western blot. These results suggest that changes in CB morphology are associated with metabolic disturbances invoked by administration of a hypercaloric diet.