Adiponectin plays a central role as an antidiabetic and antiatherogenic adipokine. AdipoR1 and AdipoR2 serve as receptors for adiponectin in vitro, and their reduction in obesity seems to be correlated with reduced adiponectin sensitivity. Here we show that adenovirus-mediated expression of AdipoR1 and R2 in the liver of Lepr(-/-) mice increased AMP-activated protein kinase (AMPK) activation and peroxisome proliferator-activated receptor (PPAR)-alpha signaling pathways, respectively. Activation of AMPK reduced gluconeogenesis, whereas expression of the receptors in both cases increased fatty acid oxidation and lead to an amelioration of diabetes. Alternatively, targeted disruption of AdipoR1 resulted in the abrogation of adiponectin-induced AMPK activation, whereas that of AdipoR2 resulted in decreased activity of PPAR-alpha signaling pathways. Simultaneous disruption of both AdipoR1 and R2 abolished adiponectin binding and actions, resulting in increased tissue triglyceride content, inflammation and oxidative stress, and thus leading to insulin resistance and marked glucose intolerance. Therefore, AdipoR1 and R2 serve as the predominant receptors for adiponectin in vivo and play important roles in the regulation of glucose and lipid metabolism, inflammation and oxidative stress in vivo.
β-fructofuranosidase (FFase) of Aspergillus niger ATCC 20611 can transfer fructosyl residues from one sucrose to another for the synthesis of glucose and fructooligosaccharides composed of 1-kestose (GF 2 ), nystose (GF 3 ), and β-fructofuranosylnystose (GF 4 ). The FFase gene, under the control of the sporamin gene promoter from sweet potato, was introduced into tobacco plants. Sporamin promoter activity is induced by sugar and exhibits preferential expression in stem and root tissues. Thin-layer and high performance liquid chromatographic analyses showed that soluble extracts from the transgenic plants contained considerable amounts of fructooligosaccharides such as GF 2 and GF 3 . The conversion of sucrose into fructooligosaccharides did not affect plant growth or development. Our results indicate that the transgenic plants could be utilized as bioreactors, and this opens up the possibility for efficient production of fructooligosaccharides in sucroseproducing plants such as sugar beet and sugarcane.
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