Reduced absolute rate of myo-inositol biosynthesis of cultured bovine retinal capillary pericytes in high glucose

Circulating Metabolites and Lipids Are Associated to Diabetic Retinopathy in Individuals With Type 1 Diabetes

Omics-based methods may provide new markers associated to diabetic retinopathy (DR). We investigated a wide omics panel of metabolites and lipids related to DR in type 1 diabetes. Metabolomic analyses were performed using two-dimensional gas chromatography with time-of-flight mass spectrometry and lipidomic analyses using an ultra-high-performance liquid chromatography quadruple time-of-flight mass spectrometry method in 648 individuals with type 1 diabetes. Subjects were subdivided into no DR, mild nonproliferative DR (NPDR), moderate NPDR, proliferative DR, and proliferative DR with fibrosis. End points were any progression of DR, onset of DR, and progression from mild to severe DR tracked from standard ambulatory care and investigated using Cox models. The cohort consisted of 648 participants aged a mean of 54.4 ± 12.8 years, 55.5% were men, and follow-up was 5.1-5.5 years. Cross-sectionally, 2,4-dihydroxybutyric acid (DHBA), 3,4-DHBA, ribonic acid, ribitol, and the triglycerides 50:1 and 50:2 significantly correlated (P < 0.042) to DR stage. Longitudinally, higher 3,4-DHBA was a risk marker for progression of DR (n = 133) after adjustment (P = 0.033). We demonstrated multiple metabolites being positively correlated to a higher grade of DR in type 1 diabetes and several triglycerides being negatively correlated. Furthermore, higher 3,4-DHBA was an independent risk marker for progression of DR; however, confirmation is required.

The role of inositol and the principles of labelling, extraction, and analysis of inositides in mammalian cells

Inositides have an important impact on diverse areas of cellular regulation. However, since this area has grown exponentially from the mid 1980s onwards, many workers find themselves relatively new to the field. In this chapter, we establish a broad foundation for the rest of the book by covering some important principles of inositide methodologies. The focus is especially directed to those methods or aspects of methodology not covered in detail in other chapters. This includes the often neglected influence of the inositide precursor, inositol, and important background information relating to the labelling and extraction of inositides from cells and tissues. This introductory section also gives a "birds eye" view of important methods and protocols found within this volume and hopefully acts as a touchstone to assess which of the methodologies described within this book is most appropriate for your particular study(ies) of inositides.

Current and future pharmacological intervention for diabetic retinopathy

Diabetic retinopathy (DR) is a potentially visually devastating complication of chronic hyperglycaemia. Prospective, randomised clinical trials have delineated the standard prevention protocols, including intensive glycaemic, blood pressure, and lipid control, and laser photocoagulation treatment for neovascularisation and clinically significant macular oedema. However, despite these interventions, vision loss from DR still occurs at an alarming rate. Researchers have directed their efforts towards better understanding the specific biological and chemical changes occurring in DR to develop more targeted pharmacological prevention and treatment strategies. This review of diabetic retinopathy will primarily detail the therapies in development at present, including aldose reductase inhibitors, advanced glycosylation end product inhibitors, antioxidants, supplemental oxygen, growth factor modulators including vascular endothelial growth factor inhibitors and protein kinase C inhibitors, extracellular matrix modifiers including corticosteroids, and vitreous modulators. The experimental therapies alter several different pathways that lead to DR. Future research will further delineate these pathways, and therapy is likely to involve arresting several different promoters of DR.

Pharmacotherapy for diabetic retinopathy

PURPOSE OF REVIEW

Diabetic retinopathy (DR) is a potentially visually devastating complication of chronic hyperglycemia and other associated systemic abnormalities. Numerous large, prospective, randomized clinical trials have delineated the current standard prevention and treatment protocols including intensive glycemic and blood pressure control and laser photocoagulation for neovascularization and clinically significant macular edema. However, despite standard intervention, vision loss from DR still occurs at an alarming rate. Thus, more recently, researchers have directed their efforts towards better understanding the microscopic changes occurring in DR to develop more effective pharmacologic prevention and treatment strategies.

RECENT FINDINGS

Phase II and III clinical studies involving antivascular endothelial growth factor (VEGF) and protein kinase C (PKC) inhibitors for the management of diabetic macular edema are underway. Researchers recently found elevated pigment endothelium-derived factor (PEDF) associated with active neovascularization, a finding that counteracts prior claims of endogenous anti-angiogenic properties. Other clinical trials are underway to evaluate the efficacy of octreotide, celecoxib, and candesartan on DR. Small clinical studies have suggested beneficial treatment effects for triamcinolone acetonide, interferon alpha-2a, and supplemental oxygen; however, other studies involving losartan, vitamins C and E, and atorvastatin failed to show any benefit.

SUMMARY

Over the past decade, numerous animal models have led to a more thorough understanding of the early microvascular alterations and later neovascularization and edema observed in DR. These discoveries and subsequent human clinical studies involving direct and indirect growth factor modulation, extracellular matrix alteration, vitreolysis, and alternative DR pathways including dyslipidemia, hypoxia, and sorbitol are reviewed in this manuscript.

cDNA cloning and gene expression analysis of human myo-inositol 1-phosphate synthase

myo-Inositol 1-phosphate synthase (EC 5.5.1.4) (IPS) is a key enzyme in myo-inositol biosynthesis pathway. This study describes the molecular cloning of the full length human myo-inositol 1-phosphate synthase (hIPS) cDNA, tissue distribution of its mRNA and characterizes its gene expression in cultured HepG2 cells. Human testis, ovary, heart, placenta, and pancreas express relatively high level of hIPS mRNA, while blood leukocyte, thymus, skeletal muscle, and colon express low or marginal amount of the mRNA. In the presence of glucose, hIPS mRNA level increases 2- to 4-fold in HepG2 cells. hIPS mRNA is also up-regulated 2- to 3-fold by 2.5 microM lovastain. This up-regulation is prevented by mevalonic acid, farnesol, and geranylgeraniol, suggesting a G-protein mediated signal transduction mechanism in the regulation of hIPS gene expression. hIPS mRNA expression is 50% suppressed by 10mM lithium ion in these cells. Neither 5mM myo-inositol nor the three hormones: estrogen, thyroid hormone, and insulin altered hIPS mRNA expression in these cells.

Diabetic retinopathy and diabetic macular edema: pathophysiology, screening, and novel therapies

Diabetic retinopathy (DR) and diabetic macular edema (DME) are leading causes of blindness in the working-age population of most developed countries. The increasing number of individuals with diabetes worldwide suggests that DR and DME will continue to be major contributors to vision loss and associated functional impairment for years to come. Early detection of retinopathy in individuals with diabetes is critical in preventing visual loss, but current methods of screening fail to identify a sizable number of high-risk patients. The control of diabetes-associated metabolic abnormalities (i.e., hyperglycemia, hyperlipidemia, and hypertension) is also important in preserving visual function because these conditions have been identified as risk factors for both the development and progression of DR/DME. The currently available interventions for DR/DME, laser photocoagulation and vitrectomy, only target advanced stages of disease. Several biochemical mechanisms, including protein kinase C-beta activation, increased vascular endothelial growth factor production, oxidative stress, and accumulation of intracellular sorbitol and advanced glycosylation end products, may contribute to the vascular disruptions that characterize DR/DME. The inhibition of these pathways holds the promise of intervention for DR at earlier non-sight-threatening stages. To implement new therapies effectively, more individuals will need to be screened for DR/DME at earlier stages-a process requiring both improved technology and interdisciplinary cooperation among physicians caring for patients with diabetes.