Hepatic intralobular mapping of fructose metabolism in the rat liver

Abstract

Detailed mapping of glucose and lactate metabolism along the radius of the hepatic lobule was performed in situ in rat livers perfused with 1.5 mM lactate before and during the addition of 5 mM fructose. The majority of fructose uptake occurred in the periportal region ; 45 % of fructose taken up in the periportal half of the lobular volume being converted into glucose. Periportal lactate uptake was markedly decreased by addition of fructose. Basal perivenous lactate output, which was derived from glucose synthesized periportally, was increased in the presence of fructose. During fructose infusion there was a small decrease in cell pH periportally, but acidification of up to 0.5 pH units perivenously. The evidence suggests that in situ the apparent direct conversion of fructose into lactate represents, to a sub-

Liver zonation in children with non‐alcoholic fatty liver disease: Associations with dietary fructose and uric acid concentrations

“…This zonation of hepatic functions mainly affects glucose/energy metabolism, ammonia detoxification and xenobiotic metabolism . With regard to glucose/energy metabolism, hepatocytes located in the periportal zone specialize in functions such as beta oxidation that require high oxygen tension, whereas in contrast, perivenous hepatocytes specialize in functions such as lipogenesis, and glycolysis, that can occur at much lower oxygen concentrations …”

Bifunctional Homodimeric Triokinase/FMN Cyclase

“…Triokinase (EC 2.7.1.28) catalyzes the third and final step of the classical Hers pathway for fructose metabolism: the 1-OH group of the sugar is phosphorylated by fructokinase, the product fructose 1-phosphate is converted to dihydroxyacetone phosphate and D-glyceraldehyde by aldolase B, and finally D-glyceraldehyde (GA) 4 is phosphorylated to D-glyceraldehyde 3-phosphate by triokinase (1). In the so-called GA crossroads, triokinase phosphorylates GA, overriding competing enzymes (2).…”

“…In the so-called GA crossroads, triokinase phosphorylates GA, overriding competing enzymes (2). Despite the relevance of the Hers pathway in liver (1)(2)(3)(4)(5) and the much heralded concerns on the effects of the high consumption of fructose in human health (5)(6)(7)(8)(9)(10)(11)(12), mammalian triokinase, contrary to fructokinase and aldolase B (13,14), is still without an established molecular identity, and it is not yet firmly associated to a specific gene. However, there are a few reports suggesting that mammalian triokinase could be a product of DAK (15,16), a gene named by homology to yeast and bacterial genes coding for ATP-dependent dihydroxyacetone (DHA) kinases (17,18), some of which are known to be active as GA kinases too (18,19).…”

Efeitos Distintos Da Ingestão De Frutose E Glicose Sobre a Ressíntese De Glicogênio Muscular E Hepático Após Exercício Em Ratos Submetidos a Treinamento De Natação

“…Estudos demonstraram que a adição de pequenas quantidades de frutose em fígado perfundido de rato provocou imediata, mas temporária, diminuição das concentrações hepáticas de ATP e Pi. Fato esse que é atribuído à formação de frutose-1-fosfato pela frutoquinase, que fosforila rapidamente a frutose, utilizando uma molécula de ATP (30,32). Outro ponto importante é a influência da frutose-1-fosfato sobre as enzimas glicogênio sintase e glicogênio fosforilase, que respectivamente são as enzimas responsáveis pela síntese e degradação das moléculas de glicogênio (6).…”