Expression during rat fetal development of GLUT12 – a member of the class III hexose transporter family

Abstract

Glucose is an essential molecule for most mammalian cells, and is particularly important during fetal development, when cells are rapidly dividing and differentiating. In rats, GLUT1 is present at high levels in most fetal tissues, with levels decreasing after birth. We used immunohistochemistry to localise GLUT12 protein, a recently identified member of the sugar transporter family, and GLUT1 during rat fetal development. GLUT12 staining was observed in heart muscle from gestational days 15 to 21. GLUT12 staining in skeletal muscle increased from gestational days 17 to 21, and GLUT12 was also detected in brown adipose tissue. The expression of GLUT12 in insulin-responsive tissues supports a potential role for GLUT12 in the provision of glucose to these tissues before the appearance of GLUT4. GLUT12 protein was also expressed in fetal chondrocytes from gestational day 15 onward, in kidney distal tubules and collecting ducts from day 19, and in lung bronchioles from day 19. The specific pattern of expression observed in the rat fetus suggests that GLUT12 may be important in hexose delivery to developing tissues.

Sweet talk: insights into the nature and importance of glucose transport in lung epithelium

“…Immunohistochemical staining of the rat fetus from gestational day 13 to 21 shows weak GLUT12 expression in the epithelial cell membrane of bronchioles at gestational day 19, which increases in intensity by day 21. Consistent with mRNA expression studies, GLUT1 protein was also observed in the airways at gestational day 19, decreasing in intensity at day 21 [57]. GLUT1 protein has also been detected in the alveolar epithelium of the fetal rat, although to date, GLUT1 protein has not been identified in either the airways or distal lung of the adult rat [59].…”

Expression of the gene encoding the high-K m glucose transporter 2 by the early postimplantation mouse embryo is essential for neural tube defects associated with diabetic embryopathy

“…Of the 14 SLC2 gene family members, expression of Glut1, Glut2, Glut3, Glut8 and Glut12 (also known as Slc2a1, Slc2a2, Slc2a3, Slc2a8 and Slc2a12) is detected in preimplantation mouse embryos [13][14][15][16][17][18]. GLUT12 protein is not detected in early postimplantation embryos, but it is detected later, during fetal development [17,19]. Only expression of Glut1, Glut2 and Glut3 has been detected during the stage of postimplantation development that is susceptible to diabetic embryopathy (day 7.5) [12,13,[20][21][22][23].…”

The facilitative glucose transporter GLUT12: what do we know and what would we like to know?

“…GLUT12 cDNA has also been cloned from mouse and cow, presenting respectively 83 and 87 % homology with the human isoform [24,49], and expression of GLUT12 has been reported in rat [18], horse [38] and dog [41].…”

“…Its mRNA is abundant in skeletal muscle, heart and prostate, and it is present at low levels in brain and kidney [30]. In rat, expression of GLUT12 protein has been described during foetal development in skeletal muscle, brown adipose tissue, heart, foetal chondrocytes, lung, kidney [18], mammary gland during pregnancy [19] and kidney distal tubes and collecting ducts [15]. In cow, its mRNA expression is abundant in spleen and skeletal muscle, less expressed in kidney, testis and mammary gland, and even lower expressed in liver, lung and intestine [24].…”

“…According to these data, authors propose that GLUT12´s physiological role during rat foetal development could be related to the uptake of different hexoses, other than glucose, and the glucose delivery to insulin sensitive tissue before GLUT4 appearance [18]. In extracts of human placenta from the first trimester and at term, a spatio-temporal difference in GLUT12 protein expression was described.…”