Aldose Reductase: A Novel Therapeutic Target for Inflammatory Pathologies.
Ramana KV, Srivastava SK.
Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas -77555, USA.
Aldose reductase (AR), that catalyzes the rate limiting step of the polyol pathway of glucose metabolism, besides reducing glucose to sorbitol, reduces a number of lipid peroxidation -derived aldehydes and their glutathione conjugates. Recent studies suggest that apart from its involvement in diabetic complications, AR's catalytic activity plays a key role in a number of inflammatory diseases such as atherosclerosis, sepsis, asthma, uveitis, and colon cancer. Furthermore, AR is overexpressed in human cancers such as liver, colon, breast, cervical and ovarian. Since AR inhibitors have already undergone up to phase-iii clinical trials for diabetic complications, they could be safe anti-inflammatory drugs. Therefore the future use of AR inhibitors in down-regulating major inflammatory pathologies such as cancer and cardiovascular diseases could relieve some of the major health concerns of worldwide.
PMID: 19778627 [PubMed - as supplied by publisher
SABC 2009
67. Targeting Aldose Reductase: A Novel Strategy in Treating Endocrine Resistance Using Combination Therapy
Treating estrogen receptor-positive breast cancer tumors with a combination of fidarestat (an inhibitor of aldose reductase enzyme) and letrozole (an aromatase inhibitor) could delay or stop tumor resistance to endocrine therapy, according to data presented at the CTRC-AACR San Antonio Breast Cancer Symposium.
"Single agents are less effective," said Rajeshwar Rao Tekmal, Ph.D., professor of obstetrics and gynecology at the University of Texas Health Science Center at San Antonio. "Many tumors develop resistance, so this combination approach could prolong that window when endocrine therapy is effective."
About two-thirds of breast cancer tumors initially are hormone sensitive or estrogen receptor-positive and respond well to endocrine therapy. However, close to half of those tumors develop resistance to endocrine therapy, said Tekmal.
In this preclinical study, researchers treated estrogen receptor-positive tumors already resistant to letrozole with letrozole and fidarestat. As an inhibitor of aldose reductase enzyme, fidarestat blocks the metabolism of glucose in cancer cells. Together, the combination effectively re-sensitized the cells to letrozole, allowing for effective endocrine therapy and more cell death.
Researchers believe increased glucose metabolism (polyol accumulation) contributes to oxidative stress, which, in turn, could alter intracellular signalling by affecting the regulation of protein kinases that are known to be involved in therapy resistance. Blocking the path of glucose metabolism may help to restore sensitivity to endocrine therapies or it may stop or delay the development resistance endocrine therapies in first place.
While this is a preclinical study, Tekmal believes it could lead to future drug treatments that will make endocrine therapy more effective for longer periods of time.
"This is a very promising study showing that combination treatments seem to work on resistance and re-sensitizing tumors that are resistant to endocrine therapies," he said.
Listen to a recording of the teleconference:
Download* the mp3 of the teleconference (13.2 MB, 58 minutes and 04 seconds)
Vitamin C: an aldose reductase inhibitor that normalizes erythrocyte sorbitol in insulin-dependent diabetes mellitus
J. J. Cunningham, P. L. Mearkle and R. G. Brown
Department of Nutrition, University of Massachusetts, Amherst 01003-1420.
OBJECTIVE: Diabetic hyperglycemia promotes sorbitol production from glucose via aldose reductase. Since the intracellular accumulation of sorbitol, or its sequelae, are postulated to contribute to the progression of chronic diabetic complications, aldose reductase inhibitors (ARI) offer therapeutic promise. Others have shown that vitamin C at pharmacologic doses decreases erythrocyte (RBC) sorbitol. We examined whether smaller, physiologic doses of vitamin C were also effective in individuals with insulin-dependent diabetes mellitus (IDDM) and whether vitamin C was an ARI in vitro. METHODS: Vitamin C supplements (100 or 600 mg) were taken daily for 58 days by young adults with IDDM and nondiabetic adults in an otherwise free-living design. Diabetic control was monitored by fasting plasma glucose, glycosylated hemoglobin, and glycosuria and was moderate to poor throughout the study. RBC sorbitol was measured at baseline and again at 30 and 58 days. Three-day dietary records and 24-hour urine collections were performed for each sampling day. RESULTS: RBC sorbitol levels were significantly elevated in IDDMs, on average doubled, despite their more than adequate dietary intakes of vitamin C and normal plasma concentrations. Vitamin C supplementation at either dose normalized the RBC sorbitol in IDDMs within 30 days. This correction of sorbitol accumulation was independent of changes in diabetic control. Furthermore, our in vitro studies show that ascorbic acid inhibited aldose reductase activity. CONCLUSIONS: Vitamin C supplementation is effective in reducing sorbitol accumulation in the erythrocytes of diabetics. Given its tissue distribution and low toxicity, we suggest a superiority for vitamin C over pharmaceutic ARIs.
Linear Mode
