Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving oxidoreductase
Reexamination Certificate
1998-02-27
2002-04-09
Badio, Barbara P. (Department: 1616)
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving oxidoreductase
Reexamination Certificate
active
06368816
ABSTRACT:
This application is a 371 of PCT/GB96/02134 filed Aug. 28, 1996.
This invention relates to the interconversion of inactive 11-keto steroids with their active 11&bgr;-hydroxy equivalents, to methods by which the conversion of the inactive to the active form may be controlled, and to useful therapeutic effects which may be obtained as a result of such control. More specifically, but not exclusively, the invention is concerned with interconversion between cortisone and cortisol in humans.
Glucocorticoids such as cortisol have a number of diverse effects on different body tissues. For example, the use of cortisol as an anti-inflammatory agent was described in our International Patent Application WO 90/04399, which was concerned with the problem that therapeutically administered cortisol tends to be converted in the body to inactive cortisone by 11&bgr;-hydroxysteroid dehydrogenase enzymes. Our earlier invention provided for the potentiation of cortisol by the administration of an inhibitor of the 11&bgr;-dehydrogenase activity of these enzymes.
Another major physiological effect of cortisol is its antagonism to insulin, and it is known for example that high concentrations of cortisol in the liver substantially reduce insulin sensitivity in that organ, thus tending to increase gluconeogenesis and consequently raising blood sugar levels [1]. This effect is particularly disadvantageous in patients suffering from impaired glucose tolerance or diabetes mellitus, in whom the action of cortisol can serve to exacerbate insulin resistance. Indeed, in Cushing's syndrome, which is caused by excessive circulating concentrations of cortisol, the antagonism of insulin can provoke diabetes mellitus in susceptible individuals [2].
As mentioned above, it is known that cortisol can be converted in the body to cortisone by the 11&bgr;-dehydrogenase activity of 11&bgr;-hydroxysteroid dehydrogenase enzymes. It is also known that the reverse reaction, converting inactive cortisone to active cortisol, is accomplished in certain organs by 11&bgr;-reductase activity of these enzymes. This activity is also known as corticosteroid 11&bgr;-reductase, cortisone 11&bgr;-reductase, or corticosteroid 11&bgr;-oxidoreductase.
It has only recently become apparent that there are at least two distinct isozymes of 11&bgr;-hydroxysteroid dehydrogenase (collectively abbreviated as 11&bgr;-HSD, which term is used, where appropriate, in this specification). Aldosterone target organs and placenta express a high affinity NAD
+
-dependent enzyme (11&bgr;-HSD2) [3]. This has been characterised in placenta and kidney [4,5] and cDNA clones have been isolated [6,9]. 11&bgr;-HSD2 catalyses 11&bgr;-dehydrogenase activity exclusively [4,7]. In contrast, the previously purified, liver derived isozyme (11&bgr;-HSD1) is a lower affinity, NADP
+
/NADPH-dependent enzyme [10,11]. Expression of 11&bgr;-HSD1 in a range of cell lines encodes either a bi-directional enzyme [11,12] or a predominant 11&bgr;-reductase [13,15] which, far from inactivating glucocorticoids, regenerates active 11&bgr;-hydroxysteroid from otherwise inert 11-keto steroid. 11&bgr;-reductase activity, best observed in intact cells, activates 11-keto steroid to alter target gene transcription and differentiated cell function [13,14]. 11&bgr;-HSD1 and 11&bgr;-HSD2 are the products of different genes and share only 20% amino acid homology [6,7].
As far as the applicants are aware no previous attempts have been made to modify the action of 11&bgr;-reductase. We have now found that it is possible to inhibit this activity in vivo, and in doing so we have created the possibility of a novel medicament for use in treating many of the deleterious effects of glucocorticoid excess. In one aspect, therefore, the invention provides the use of an inhibitor of 11&bgr;-reductase in the manufacture of a medicament for control of 11-keto steroid conversion to 11&bgr;-hydroxysteroid in vivo.
As mentioned above, one of the major physiological effects of cortisol is insulin antagonism in the liver, and in a specific aspect the invention therefore provides the use of an inhibitor of 11&bgr;-reductase in the manufacture of a medicament for inhibiting hepatic gluconeogenesis [1]. Cortisol promotes hepatic gluconeogenesis by several mechanisms, including antagonism of the effects of insulin on glucose transport, and interactions with insulin and glucose in the regulation of several enzymes which control glycolysis and gluconeogenesis. These include glucokinase, 6-phosphofructokinase, pyruvate kinase, phosphoenolpyruvate carboxykinase (PEPCK), and glucose-6-phosphatase. Inhibiting production of cortisol from cortisone in the liver therefore enhances hepatic glucose uptake and inhibits hepatic glucose production by several mechanisms [16]. Moreover, the influence of inhibiting 11&bgr;-reductase activity in the liver of patients with insulin resistance or glucose intolerance may be greater than in healthy subjects because in insulin resistance or deficiency the influence of cortisol on PEPCK has been shown to be greater [17]; obese patients secrete more cortisol [18]; insulin resistant patients are more sensitive to glucocorticoids [19]; and insulin down-regulates 11&bgr;-HSD1 expression [15,20] so that 11&bgr;-reductase activity may be enhanced in conditions of insulin resistance or deficiency.
Our studies have also shown that 11&bgr;-HSD1 is expressed in rat adipose tissue and in adipocyte cell lines in culture, where it converts 11-dehydrocorticosterone to corticosterone (the rat equivalents of human cortisone and cortisol, respectively). This suggests that similar 11&bgr;-reductase activity will be observed in human adipose tissue, with the result that inhibition of the enzyme will result in alleviation of the effects of insulin resistance in adipose tissue in humans. This would lead to greater tissue utilisation of glucose and fatty acids, thus reducing circulating levels. The invention therefore provides, in a further aspect, the use of an inhibitor of 11&bgr;-reductase in the manufacture of a medicament for increasing insulin sensitivity in adipose tissue.
The results of our studies have encouraged us to believe that inhibition of intracellular cortisol production will also lead to increased insulin sensitivity in other tissues which are acted upon by insulin, for instance skeletal muscle [21]. Inhibiting the 11&bgr;-reductase therefore promises to reverse the effects of insulin resistance in muscle tissue, and to promote the up-take of essential molecules such as glucose and free fatty acids into muscle cells with consequent improved muscle metabolism and reduction of circulating levels of glucose and fatty acids. In a further aspect, the invention therefore provides the use of an inhibitor of 11&bgr;-reductase in the manufacture of a medicament for increasing insulin sensitivity in skeletal muscle tissue.
It is also known that glucocorticoid excess potentiates the action of certain neurotoxins, which leads to neuronal dysfunction and loss. We have studied the interconversion between 11-dehydrocorticosterone and corticosterone in rat hippocampal cultures, and have found (surprisingly in view of the damaging effects of glucocorticoids) that 11&bgr;-reductase activity dominates over 11&bgr;-dehydrogenase activity in intact hippocampal cells [22]. The reason for this activity is unknown, but this result indicates that glucocorticoid excess may be controlled in hippocampal cells (and by extension in the nervous system in general) by use of an 11&bgr;-reductase inhibitor, and the invention therefore provides in an alternative aspect the use of an inhibitor of 11&bgr;-reductase in the manufacture of a medicament for the prevention or reduction of neuronal dysfunction and loss due to glucocorticoid potentiated neurotoxicity. It is also possible that glucocorticoids are involved in the cognitive
Edwards Christopher Richard Watkin
Seckl Jonathan Robert
Walker Brian Robert
Badio Barbara P.
Frommer & Lawrence & Haug LLP
Kowalski Thomas J.
The University of Edinburgh
LandOfFree
Regulation of intracellular glucocorticoid concentrations does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Regulation of intracellular glucocorticoid concentrations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Regulation of intracellular glucocorticoid concentrations will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2831907