Absence of Glucose Uptake by Liver Microsomes: An Explanation for the Complete Latency of Glucose Dehydrogenase

Romanelli, Angela; St-Denis, Jean-François; Vidal, Hubert; Tchu, Simone; Vandewerve, G.

doi:10.1006/bbrc.1994.1619

Cited by 24 publications

(12 citation statements)

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“…Glucose dehydrogenase is an NADP-requiring intraluminal microsomal enzyme whose activity is largely undetectable in intact microsomes (36). The results show that untreated microsomes were largely intact (no detectible glucose dehydrogenase activity over a 180-min incubation period) (Fig.…”

Section: Metabolites Of the 11 ␤-Hsd1 Enzyme Reaction Regulate Pentosementioning

confidence: 81%

“…Baseline studies examined the effect of substrate concentration (0 -2 M 11-DHC), cell number (0-5-6 ϫ 10 6 fat cells/ml) and time (0 -120 min) on corticosterone production to verify consistent linear rates of 11 ␤-HSD1 activity throughout the assay. The dehydrogenase reaction of 11 ␤-HSD1 (C 3 11-DHC) was measured in intact cells under identical assay conditions by the disappearance of (36,37).…”

Section: Methodsmentioning

confidence: 99%

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Evidence That the 11 β-Hydroxysteroid Dehydrogenase (11 β-HSD1) Is Regulated by Pentose Pathway Flux

McCormick

Wang

Mick

2006

Journal of Biological Chemistry

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11 ␤-hydroxysteroid dehydrogenase type 1 (11 ␤-HSD1) catalyzes the interconversion of biologically inactive 11 keto derivatives (cortisone, 11-dehydrocorticosterone) to active glucocorticoids (cortisol, corticosterone) in fat, liver, and other tissues. It is located in the intraluminal compartment of the endoplasmic reticulum. Inasmuch as an oxo-reductase requires NADPH, we reasoned that 11 ␤-HSD1 would be metabolically interconnected with the cytosolic pentose pathway because this pathway is the primary producer of reduced cellular pyridine nucleotides. To test this theory, 11 ␤-HSD1 activity and pentose pathway were simultaneously measured in isolated intact rodent adipocytes. Established inhibitors of NAPDH production via the pentose pathway (dehydroandrostenedione or norepinephrine) inhibited 11 ␤-HSD1 oxo-reductase while decreasing cellular NADPH content. Conversely these compounds slightly augmented the reverse, or dehydrogenase, reaction of 11 ␤-HSD1. Importantly, using isolated intact microsomes, the inhibitors did not directly alter the tandem microsomal 11 ␤-HSD1 and hexose-6-phosphate dehydrogenase enzyme unit. Metabolites of 11 ␤-HSD1 (corticosterone or 11-dehydrocorticosterone) inhibited or increased pentose flux, respectively, demonstrating metabolic interconnectivity. Using isolated intact liver or fat microsomes, glucose-6 phosphate stimulated 11 ␤-HSD1 oxo-reductase, and this effect was blocked by selective inhibitors of glucose-6-phosphate transport. In summary, we have demonstrated a metabolic interconnection between pentose pathway and 11 ␤-HSD1 oxo-reductase activities that is dependent on cytosolic NADPH production. These observations link cytosolic carbohydrate flux with paracrine glucocorticoid formation. The clinical relevance of these findings may be germane to the regulation of paracrine glucocorticoid formation in disturbed nutritional states such as obesity.The intracellular peri-receptor availability of glucocorticoids is not determined simply by their circulating concentrations and protein binding interactive kinetics. Ostensibly, the intracellular concentration of the active glucocorticoids (cortisol, corticosterone) is governed more so by 11 ␤-hydroxysteroid dehydrogenase type 1 (11 ␤-HSD1), 2 a bidirectional enzyme that facilitates the equilibrium between the aforesaid active steroids and their biologically inactive 11-keto derivatives (cortisone, 11-dehydrocorticosterone) (1-3). 11 ␤-HSD1 is ubiquitous (4), located in microsomes (5), and has a low substrate affinity (6) (K m in M) involving pyridine nucleotide cofactors, with NADP(H) having a greater affinity than NAD(H) (6, 7). Recently, 11 ␤-HSD1 has garnered attention as a potential participant in the pathoetiology of obesity, insulin resistance, and type II diabetes (2,3,8,9). Specifically, the dysregulation of 11 ␤-HSD1 in particular tissues may augment intracellular active glucocorticoid concentrations. In addition, it is certainly plausible that in human obesity, although normal circulating blood cortisol levels are foun...

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Section: Metabolites Of the 11 ␤-Hsd1 Enzyme Reaction Regulate Pentosementioning

confidence: 81%

Section: Methodsmentioning

confidence: 99%

Evidence That the 11 β-Hydroxysteroid Dehydrogenase (11 β-HSD1) Is Regulated by Pentose Pathway Flux

McCormick

Wang

Mick

2006

Journal of Biological Chemistry

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“…Some investigators believe that NADP cannot cross the ER-membrane and must be generated inside the ER lumen (5, 58), while others believe that NADP may enter the ER from the cytosol (38,51). A cytosolic source of NADP associated with chronic alcohol exposure is CYP2E1 (33).…”

Section: Discussionmentioning

confidence: 99%

Increased 11β-hydroxysteroid dehydrogenase type-1 and hexose-6-phosphate dehydrogenase in liver and adipose tissue of rat offspring exposed to alcohol in utero

Nammi¹,

Dembele²,

Nyomba³

2007

American Journal of Physiology-Regulatory, Integrative and Comp

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Nammi S, Dembele K, Nyomba BL. Increased 11␤-hydroxysteroid dehydrogenase type-1 and hexose-6-phosphate dehydrogenase in liver and adipose tissue of rat offspring exposed to alcohol in utero. Am J Physiol Regul Integr Comp Physiol 292: R1101-R1109, 2007. First published November 22, 2006 doi:10.1152/ajpregu.00255.2006.-Rat offspring prenatally exposed to alcohol display features of metabolic syndrome characterized by a low birth weight, catch-up growth, dyslipidemia, and insulin-resistant diabetes with increased gluconeogenesis, during adult life. Gluconeogenesis is partly regulated by cyclic AMP-and glucocorticoid-dependent mechanisms. Glucocorticoid action at the receptor level depends on its circulating concentrations and is amplified at the prereceptor level by 11␤-hydroxysteroid dehydrogenase type 1 (11␤-HSD1), which regenerates active glucocorticoids from inactive forms. To determine whether 11␤-HSD1 is dysregulated in this rat model, we examined the expression and enzyme activity of 11␤-HSD1 and its regulator enzyme hexose-6-phosphate dehydrogenase (H6PD) in the liver of postnatal day 7 (neonatal) and 3-mo-old (adult) rat offspring prenatally exposed to alcohol. Measurements of 11␤-HSD1 and H6PD were also performed in the omental fat of adult rat offspring. In both neonatal and adult rats, prenatal alcohol exposure resulted in increased tissue corticosterone concentrations, increased expression, and oxoreductase activity of 11␤-HSD1, and a parallel increase of H6PD expression. The data suggest that due to both transcriptional and posttranscriptional dysregulations, rats exposed to alcohol early in life have increased 11␤-HSD1 activity, which may explain insulin-resistant diabetes in these animals later in life. prenatal exposure; programming SEVERAL PRENATAL ADVERSE FACTORS have been implicated in the pathogenesis of chronic diseases in adulthood. The importance of these factors was first recognized by epidemiological studies describing associations between intrauterine growth restriction (IUGR) and insulin resistance, type 2 diabetes, and cardiovascular diseases later in life (6). Since the offspring exposed to such prenatal factors were small at birth, these abnormalities are considered to be a consequence of IUGR. In animal models of IUGR employing malnutrition (44), placental ischemia (53), glucocorticoid exposure (8), or diabetes (62) during pregnancy, the offspring develop insulin resistance, glucose intolerance, and obesity with aging.

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“…Therefore, we determined the effects of E 2 on H6PD in intact microsomes. The integrity of the microsomal membrane was inferred from the latency of glucose dehydrogenase activity (Bublitz & Steavenson 1988b, Romanelli et al 1994, which was found to be O93% in all the preparations assayed. The reaction was started by the addition of microsomes, as described in the Materials and Methods section.…”

Section: (Two Sample T-test)mentioning

confidence: 99%

17β-Estradiol inhibits 11β-hydroxysteroid dehydrogenase type 1 activity in rodent adipocytes

Tagawa

Yuda

Kubota

et al. 2009

Journal of Endocrinology

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17b-Estradiol (E 2 ) serves as an anti-obesity steroid; however, the mechanism underlying this effect has not been fully clarified. The effect of E 2 on adipocytes opposes that of glucocorticoids, which potentiate adipogenesis and anabolic lipid metabolism. The key to the intracellular activation of glucocorticoid in adipocytes is 11b-hydroxysteroid dehydrogenase type 1 (11b-HSD1), which catalyses the production of active glucocorticoids (cortisol in humans and corticosterone in rodents) from inactive 11-keto steroids (cortisone in humans and 11-dehydrocorticosterone in rodents). Using differentiated 3T3-L1 adipocytes, we showed that E 2 inhibited 11b-HSD1 activity. Estrogen receptor (ER) antagonists, ICI-182 780 and tamoxifen, failed to reverse this inhibition. A significant inhibitory effect of E 2 on 11b-HSD1 activity was observed within 5-10 min. Furthermore, acetylation or a-epimerization of 17-hydroxy group of E 2 attenuated the inhibitory effect on 11b-HSD1. These results indicate that the inhibition of 11b-HSD1 by E 2 depends on neither an ER-dependent route, transcriptional pathway nor nonspecific fashion. Hexose-6-phosphate dehydrogenase, which provides the cofactor NADPH for full activation of 11b-HSD1, was unaffected by E 2 . A kinetic study revealed that E 2 acted as a non-competitive inhibitor of 11b-HSD1. The inhibitory effect of E 2 on 11b-HSD1 was reproduced in adipocytes isolated from rat mesenteric fat depots. This is the first demonstration that E 2 inhibits 11b-HSD1, thereby providing a novel insight into the anti-obesity mechanism of estrogen.

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Absence of Glucose Uptake by Liver Microsomes: An Explanation for the Complete Latency of Glucose Dehydrogenase

Cited by 24 publications

References 0 publications

Evidence That the 11 β-Hydroxysteroid Dehydrogenase (11 β-HSD1) Is Regulated by Pentose Pathway Flux

Evidence That the 11 β-Hydroxysteroid Dehydrogenase (11 β-HSD1) Is Regulated by Pentose Pathway Flux

Increased 11β-hydroxysteroid dehydrogenase type-1 and hexose-6-phosphate dehydrogenase in liver and adipose tissue of rat offspring exposed to alcohol in utero

17β-Estradiol inhibits 11β-hydroxysteroid dehydrogenase type 1 activity in rodent adipocytes

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