Comprehensive expression analysis of hormone-like substances in the subcutaneous adipose tissue of the common bottlenose dolphin Tursiops truncatus.

Marine mammals possess a specific subcutaneous fat layer called blubber that not only insulates and stores energy but also secretes bioactive substances. However, our understanding of its role as a secretory organ in cetaceans is incomplete. To exhaustively explore the hormone-like substances produced in dolphin subcutaneous adipose tissue, we performed seasonal blubber biopsies from captive female common bottlenose dolphins (Tursiops truncatus; N = 8, n = 32) and analyzed gene expression via transcriptomics. Analysis of 186 hormone-like substances revealed the expression of 58 substances involved in regulating energy metabolism, tissue growth/differentiation, vascular regulation, immunity, and ion/mineral homeostasis. Adiponectin was the most abundantly expressed gene, followed by angiopoietin protein like 4 and insulin-like growth factor 2. To investigate the endocrine/secretory responses of subcutaneous adipose tissue to the surrounding temperature, we subsequently compared the mean expression levels of the genes during the colder and warmer seasons. In the colder season, molecules associated with appetite suppression, vasodilation, and tissue proliferation were relatively highly expressed. In contrast, warmer seasons enhanced the expression of substances involved in tissue remodeling, immunity, metabolism, and vasoconstriction. These findings suggest that dolphin blubber may function as an active secretory organ involved in the regulation of metabolism, appetite, and tissue reorganization in response to changes in the surrounding environment, providing a basis for elucidating the function of hormone-like substances in group-specific evolved subcutaneous adipose tissue.

Characterization of glutamate decarboxylase mediating gamma-amino butyric acid increase in the early germination stage of soybean (Glycine max [L.] Merr).

Glutamate decarboxylase (GAD) is an enzyme that catalyzes the production of gamma-amino butyric acid (GABA) from glutamate through a decarboxylation reaction. A full-length cDNA encoding glutamate decarboxylase (GmGAD1) was isolated from germinating soybean seeds (Glycine max [L.] Merr.). The GmGAD1 gene had a 1512-bp open reading frame, which encodes 503 amino acids. According to its sequence similarity with other GAD genes, GmGAD1 was classified into GAD1 in the plant GAD family. Recombinant GmGAD1 protein expressed in E. coli catalyzed alpha-decarboxylation of glutamic acid. The levels of GABA were rapidly increased in soybean seeds during the early imbibition period (6 h) of germination or during the soaking treatment, whereas mRNA of GmGAD1 gene was not detected in these materials. The GmGAD1 protein was observed in seeds of various states such as developing, matured and soaking. These data suggest that the increased levels of GABA during the early stage of germination or soaking treatment were mediated by GmGAD1 protein synthesized in developing soybean seeds.