Prenatal developmental changes in glucose transporters, intermediary metabolism and hormonal receptors related to the IGF/insulin-glucose axis in the heart and adipose tissue of bovines

Abstract

-Glucose transporter ontogenesis is likely to play a key role in glucose uptake by foetal tissues in order to satisfy their energy requirements. We thus investigated developmental changes in the bovine heart and perirenal adipose tissue in two glucose transporter isoforms, namely GLUT1 and GLUT4, the latter being responsible for the regulation of glucose uptake by insulin. Other key players of the glucose/insulin axis were also assessed. Plasma glucose concentration in the foetus was lower at 8 and 8.5 months of age than previously. In the heart, GLUT1 protein level markedly decreased between 3 and 4 months of age, whereas the number of insulin and IGF-I binding sites continually decreased, especially between 7 and 8 or 8.5 months of age. On the contrary, the GLUT4 level increased until 8 months of age and remained high until 2 weeks after birth. The activities of enzymes of glucose metabolism (namely phosphofructokinase [PFK] and lactate dehydrogenase [LDH]) increased throughout gestation and reached a plateau at 6 and 8.5 months of age for PFK and LDH, respectively. The activities of enzymes involved in fatty acid metabolism increased especially at birth. In perirenal adipose tissue, high mitochondrial activity was detected before birth which is a characteristic of brown adipose tissue. Furthermore, lipoprotein lipase activity and GLUT4 protein level markedly increased to reach a maximum at 6-7 and 8 months of age, and sharply decreased thereafter, whereas GLUT1 protein level increased between 6 and 7 months of age. In conclusion, considerable changes in the regulation of the insulin/glucose axis were observed from 6 months onwards of foetal development in both the heart and adipose tissue of cattle, which probably alters the potential of these tissues to use glucose or fat as energy sources.

Intramuscular fat content in meat-producing animals: development, genetic and nutritional control, and identification of putative markers

“…The genetic correlation of IMF content is on average positive with tenderness (r G 5 0.41) or negative with Warner-Bratzler shear force (r G 5 20.50) in cattle. As marbling score in these animals is genetically highly correlated with muscle lipid content (r G 5 0.91), selection based on the former may lead to a correlated improvement in tenderness (for review, see Hocquette et al, 2006). This relationship explains most of the efforts dedicated to the development of live scanning for IMF content as a selection tool in the United States and Australia (Reverter et al, Intramuscular fat content in meat-producing animals 2000; Hassen et al, 2001;Sapp et al, 2002).…”

Ontogenesis of muscle and adipose tissues and their interactions in ruminants and other species

“…Available data on genes and enzymes of the main lipogenic pathways in ruminants has been recently reviewed (Bernard et al, 2008). Similar precursors and lipogenic pathways are probably involved in TAG deposition Bonnet, Cassar-Malek, Chilliard and Picard in perirenal BAT of ovine (Vernon, 1986) and bovine Hocquette et al, 2006) foetuses.…”

“…To date, only HSL has been identified in bovine WAT through its mRNA abundance (Bonnet et al, 1998;Sumner and Mcnamara, 2007;Xu et al, 2008) and its activity (Sprinkle et al, 1998;Kazala et al, 2003). The thermogenic protein UCP1, together with enzymes involved in the citric acid cycle and the respiratory chain, are expressed in bovine foetal BAT, allowing FA oxidation and heat production (Casteilla et al, 1989;Smith et al, 2004;Hocquette et al, 2006).…”

Transient Congenital Hypothyroidism Alters Gene Expression of Glucose Transporters and Impairs Glucose Sensing Apparatus in Young and Aged Offspring Rats

“…Mooradian et al have reported that thyroid hormones have different effects on GLUTs expression during development and in adulthood [32]. Furthermore, thyroid hormones have species-specific and tissue-specific effects on GLUT1 and GLUT4 expression in insulin sensitive tissues [25, 32, 60]. During fetal life, GLUT1 is predominant in insulin sensitive tissues and transition of this dominancy to GLUT4 after birth is regulated by thyroid hormones [25, 26].…”