Mitochondrial bound hexokinase type I in normal and streptozotocin diabetic rat retina

Contribution of Müller Cells in the Diabetic Retinopathy Development: Focus on Oxidative Stress and Inflammation

Diabetic retinopathy is a neurovascular complication of diabetes and the main cause of vision loss in adults. Glial cells have a key role in maintenance of central nervous system homeostasis. In the retina, the predominant element is the Müller cell, a specialized cell with radial morphology that spans all retinal layers and influences the function of the entire retinal circuitry. Müller cells provide metabolic support, regulation of extracellular composition, synaptic activity control, structural organization of the blood–retina barrier, antioxidant activity, and trophic support, among other roles. Therefore, impairments of Müller actions lead to retinal malfunctions. Accordingly, increasing evidence indicates that Müller cells are affected in diabetic retinopathy and may contribute to the severity of the disease. Here, we will survey recently described alterations in Müller cell functions and cellular events that contribute to diabetic retinopathy, especially related to oxidative stress and inflammation. This review sheds light on Müller cells as potential therapeutic targets of this disease.

Therapeutic effect of Keap1-Nrf2-ARE pathway-related drugs on age-related eye diseases through anti-oxidative stress

Age-related eye diseases, including cataract, glaucoma, diabetic retinopathy (DR), and age-related macular degeneration (AMD), are the leading causes of vision loss in the world. Several studies have shown that the occurrence and development of these diseases have an important relationship with oxidative stress in the eye. The Keap1-Nrf2-ARE pathway is a classical pathway that resists oxidative stress and inflammation in the body. This pathway is also active in the development of age-related eye diseases. A variety of drugs have been shown to treat age-related eye diseases through the Keap1-Nrf2-ARE (Kelch-like ECH-Associating protein 1- nuclear factor erythroid 2 related factor 2-antioxidant response element) pathway. This review describes the role of oxidative stress in the development of age-related eye diseases, the function and regulation of the Keap1-Nrf2-ARE pathway, and the therapeutic effects of drugs associated with this pathway on age-related eye diseases.

Tribbles Homolog 3 Mediates the Development and Progression of Diabetic Retinopathy

The current understanding of the molecular pathogenesis of diabetic retinopathy does not provide a mechanistic link between early molecular changes and the subsequent progression of the disease. In this study, we found that human diabetic retinas overexpressed TRIB3 and investigated the role of TRIB3 in diabetic retinal pathobiology in mice. We discovered that TRIB3 controlled major molecular events in early diabetic retinas via HIF1α-mediated regulation of retinal glucose flux, reprogramming cellular metabolism, and governing of inflammatory gene expression. These early molecular events further defined the development of neurovascular deficit observed in mice with diabetic retinopathy. TRIB3 ablation in the streptozotocin-induced mouse model led to significant retinal ganglion cell survival and functional restoration accompanied by a dramatic reduction in pericyte loss and acellular capillary formation. Under hypoxic conditions, TRIB3 contributed to advanced proliferative stages by significant upregulation of GFAP and VEGF expression, thus controlling gliosis and aberrant vascularization in oxygen-induced retinopathy mouse retinas. Overall, our data reveal that TRIB3 is a master regulator of diabetic retinal pathophysiology that may accelerate the onset and progression of diabetic retinopathy to proliferative stages in humans and present TRIB3 as a potentially novel therapeutic target for diabetic retinopathy.

Effect of Caralluma tuberculata on regulation of carbohydrate metabolizing genes in alloxan-induced rats

ETHNOPHARMACOLOGICAL RELEVANCE

Caralluma tuberculata (C. tuberculata) has traditionally been used in Pakistan and other parts of the world as a folk treatment for diabetes mellitus. A few studies indicated its antihyperglycemic effect, however, the mystery remained unfolded as how did it modify the pathophysiological condition.

AIM OF STUDY

Hence, this study aimed to explore underlying mechanism(s) for its hypoglycemic activity at biochemical and molecular levels.

MATERIALS AND METHODS

Methanol extract (ME) of C. tuberculata as well as its hexane (HF) and aqueous (AF) fractions were explored for their effect on total glycogen in liver and skeletal muscle of alloxan-induced rats by spectroscopy. Moreover, the expression of genes related to hepatic carbohydrate metabolizing enzymes was quantified. At molecular level, mRNA expression of glucose transporter 2 (GLUT-2), glycogen synthase (GS), glucokinase (GK), hexokinase 1 (HK-1), pyruvate kinase (PK), glucose 6 phosphate dehydrogenase (G-6-PDH), pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6 phosphatase (G-6-Pase) was determined by using quantitative real time polymerase chain reaction (qRT-PCR) after administration of ME (350 mg), HF(3 mg), AF (10 mg) and metformin (500 mg). The doses were administered twice daily according to per kg of body weight.

RESULTS

A significant reduction in hepatic and skeletal muscle glycogen content was exhibited. The data of qRT-PCR revealed that gene's expression of GLUT-2 was significantly decreased after treatment with ME and HF, whilst it was unaltered by AF, however, a significant decrease was observed in genes corresponding to GS, GK and HK-1 after treatment with ME. Similarly, there was a significant decrease in expression of genes corresponding to GS, GK and HK-1 following treatment with HF. Surprisingly, post-treatment with AF didn't modify the gene's expression of GS and GK, whilst it caused a profound decrease in expression of HK-1 gene. Contrarily, the expression of gene related to PK was significantly up-regulated post-administration with ME, HF and AF. The expression levels of G-6-PDH, however, remained unaltered after treatment with the experimental extract and fractions of the plant. In addition, HF and AF did not cause any modification in PEPCK, whereas ME caused a significant down-regulation of the gene. Treatment with all the extract and fractions of the plant caused a substantial decrease in the gene's expression of PC, while there was a significant increase in the expression of gene related to G-6-Pase.

CONCLUSION

The three experimental extract and fractions caused a substantial decrease in glycogen content in liver and skeletal muscle tissues. The analysis by qRT-PCR showed that glucose transport via GLUT-2 was profoundly declined by ME and HF. The expression of genes related to various metabolic pathways involved in metabolism of carbohydrate in hepatocytes revealed explicitly that the ME, HF and AF decreased the phenomena of glycogenesis and gluconeogenesis. Contrarily, all the extract and fractions of the plant activated glycogenolysis and glycolysis but did not modify the pentose phosphate shunt pathway.