Higher Steroid Production in the Right Adrenal Gland Compared to the Left One in db/db Mice, a Model of Type 2 Diabetic Obesity

Vertebrates exhibit a left–right asymmetry from the central structures to the peripheral paired endocrine organs. However, the asymmetries in paired endocrine glands and the pathological consequences of such asymmetries remain largely unknown. The adrenal gland constitutes a pair of peripheral end organs in the neuroendocrine system, responsible for producing steroid hormones under stimuli. In the present study, the lateralized asymmetry of left and right adrenal glands in leptin receptor-deficit db/db mice was investigated. First, a morphological and histological examination showed that adrenal mass and adrenal cortex volume in db/db mice were significantly higher than in non-diabetic control mice. Then, adrenal transcriptomic and serum metabolomic analyses were performed. Adrenal steroid profiling showed that the levels of corticosterone and aldosterone in the right adrenal gland of db/db mice were two times higher than in the left one. The expression of multiple genes related to adrenal regeneration and innervation in db/db mice was reduced in contrast to the increased steroid hormone secretion. Furthermore, an examination of morphogens in asymmetric adrenal development revealed a significant differential expression of Shh and its receptor gene Ptch1. In conclusion, the present study has provided evidence that a superior steroidogenesis exists in the right adrenal gland of db/db mice and suggested that Shh signaling may play an important role in asymmetric adrenal responses in type 2 diabetes and its complications.