Sapium ellipticum(Hochst) Pax ethanol leaf extract modulates glucokinase and glucose-6-phosphatase activities in streptozotocin induced diabetic rats

Objective:To examine the effects of Sapium ellipticum(SE) leaf extract on the hepatic activities of glucokinase and glucose-6-phosphatase in streptozotocin-induced diabetic Wistar rats.Methods:STZ-induced diabetic Wistar rats(four groups,n = 8) were used in this study.SE was assessed at two different doses,400 and 800 mg/kg BW,in comparison with metformin(METF)(12 mg/kg BW) as a reference antidiabetic drug.All treatments were done orally(p.o),twice daily at 8 h interval for a period of 21 days.Glucokinase and glucose-6-phosphatase activities were respectively determined using standard protocols.Hepatic and muscle glycogen contents were estimated as well.Results:STZ caused significant decrease in glucose-6-phosphatase activity and concomitant increase in glucokinase activity.SE extract especially at 400 mg dosage significantly reversed the alterations by increasing glucokinase activity by 40.31% and inhibiting glucose-6-phosphatase activity by 37.29% compared to diabetic control animals.However,the effects were significantly lower than that of METF which enhanced glucokinase activity by94.76% and simultaneously inhibited glucose-6-phosphatase activity by 49.15%.The extract also improved hepatic glycogen level by 32.37 and 27.06% at 400 and 800 mg dosage respectively.HPLC-MS analysis of some SE fractions in dynamic MRM mode(using the optimized compound-specific parameters) revealed among other active compounds,the presence of amentoflavone,which has been associated with antidiabetic function.Conclusions:The ability of SE extract to concurrently inhibit glucose-6-phosphatase and activate glucokinase in this study suggests that it may be a treatment option for type 2 diabetes patients,and the presence of amentoflavone in the plant extract may account for its anti-diabetic potential.

HEXOKINASE, GLUCOSE-6-PHOSPHATASE DEHYDROGENASE AND ALEOSE REDUCTASE IN HUMAN FETAL LENSES

The lens HK, G6PD, AR activity and its relationship with fetal age was determined.There is a positive correlation between the age of fetus and the activity(IU/mg pro.) of HK and G6PD(r=0.8069, 0.8204, P<0.01) and a negetive correlation between the age of fetus and activity of AR(r=-0.810 1,0.05>P>0.01).

Molecular Cloning of a Cytosolic G6PDH Gene from Populus Suaveolens and Its Expression to Improve the Cold Resistance of Tobacco Plants

Glucose-6-phosphate dehydrogenase (G6PDH,EC 1.1.1.49) is the first and main regulated enzyme of oxidative pentose phosphate pathway (OPPP),catalyzing the conversion of glucose-6-phosphate to 6-phospho-gluconolactone and playing important roles in the growth and development of plants. It is preciously reported that the enhancement of freezing resistance of Populus suaveolenscuttings is clear related to the distinct increase in cytosolic G6PDH activity. Here,a 1697 bp cDNA fragment (PsG6PDH) is amplified by RT-PCR from cold-induced total RNA of the freezing-tolerant P. suaveolens. A sequence analysis showed that PsG6PDH coding region had 1 530 bp and encoded 510 predicted amino acid residues. Genomic Southern analysis revealed that the isoform is encoded by a few copies of the gene in the poplar genome. The cloned gene PsG6PDHis cloned into binary vector pBI121 and used to transform tobacco. PCR and Southern blotting results verified integration of this gene into the genome of tobacco. Moreover,cold treatment experiments and membrane defense enzymeactivity analysis confirmed that overexpression of the PsG6PDHgene could enhance the tolerance to cold or frigid stresses in transgenic plants.

Characterization of glucose-6-phosphate dehydrogenase deficiency and identification of a novel haplotype 487G>A/IVS5-612(G>C) in the Achang population of southwestern China

The prevalence of glucose-6-phosphate dehydrogenase (G6PD) deficiency and its gene mutations were studied in the Achang population from Lianghe County in Southwestern China. We found that 7.31% (19 of 260) males and 4.35% (10 of 230) females had G6PD deficiency. The molecular analysis of G6PD gene exons 2―13 was performed by a PCR-DHPLC-Sequencing or PCR-Sequencing. Sixteen inde-pendent subjects with G6PD Mahidol (487G>A) and the new polymorphism IVS5-612 (G>C), which combined into a novel haplotype, were identified accounting for 84.2% (16/19). And 100% Achang G6PD Mahidol were linked to the IVS5-612 C. The percentage of G6PD Mahidol in the Achang group is close to that in the Myanmar population (91.3% 73/80), which implies that there are some gene flows between Achang and Myanmar populations. Interestingly, G6PD Canton (1376G>T) and G6PD Kaiping (1388G>A), which were the most common G6PD variants from other ethnic groups in China, were not found in this Achang group, suggesting that there are different G6PD mutation profiles in the Achang group and other ethnic groups in China. Our findings appear to be the first documented report on the G6PD genetics of the AChang people, which will provide important clues to the Achang ethnic group origin and will help prevention and treatment of malaria in this area.

Hepatic retinaldehyde deficiency is involved in diabetes deterioration by enhancing PCK1-and G6PC-mediated gluconeogenesis

Type 2 diabetes(T2D) is often accompanied with an induction of retinaldehyde dehydrogenase 1(RALDH1 or ALDH1A1) expression and a consequent decrease in hepatic retinaldehyde(Rald)levels. However, the role of hepatic Rald deficiency in T2D progression remains unclear. In this study, we demonstrated that reversing T2D-mediated hepatic Rald deficiency by Rald or citral treatments, or liverspecific Raldh1 silencing substantially lowered fasting glycemia levels, inhibited hepatic glucogenesis,and downregulated phosphoenolpyruvate carboxykinase 1(PCK1) and glucose-6-phosphatase(G6PC)expression in diabetic db/db mice. Fasting glycemia and Pck1/G6pc mRNA expression levels were strongly negatively correlated with hepatic Rald levels, indicating the involvement of hepatic Rald depletion in T2D deterioration. A similar result that liver-specific Raldh1 silencing improved glucose metabolism was also observed in high-fat diet-fed mice. In primary human hepatocytes and oleic acidtreated HepG2 cells, Rald or Rald + RALDH1 silencing resulted in decreased glucose production and downregulated PCK1/G6PC mRNA and protein expression. Mechanistically, Rald downregulated direct repeat 1-mediated PCK1 and G6PC expression by antagonizing retinoid X receptor a, as confirmed by luciferase reporter assays and molecular docking. These results highlight the link between hepatic Rald deficiency, glucose dyshomeostasis, and the progression of T2D, whilst also suggesting RALDH1 as a potential therapeutic target for T2D.

Diagnosis of hepatic glycogenosis in poorly controlled type 1 diabetes mellitus

Hepatic glycogenosis(HG) in type 1 diabetes is a underrecognized complication. Mauriac firstly described the syndrome characterized by hepatomegaly with altered liver enzymes, growth impairment, delay puberty and Cushingoid features, during childhood. HG in adulthood is characterized by the liver disorder(with circulating aminotransferase increase) in the presence of poor glycemic control(elevation of glycated hemoglobin, Hb A1 c levels). The advances in the comprehension of the metabolic pathways driving to the hepatic glycogen deposition point out the role of glucose transporters and insulin mediated activations of glucokinase and glycogen synthase, with inhibition of glucose-6-phosphatase. The differential diagnosis of HG consists in the exclusion of causes of liver damage(infectious, metabolic, obstructive and autoimmune disease). The imaging study(ultrasonography and/or radiological examinations) gives information about the liver alterations(hepatomegaly), but the diagnosis needs to be confirmed by the liver biopsy. The main treatment of HG is the amelioration of glycemic control that is usu-ally accompanied by the reversal of the liver disorder. In selected cases, more aggressive treatment options(transplantation) have been successfully reported.

Sapium ellipticum (Hochst) Pax ethanol leaf extract modulates glucokinase and glucose-6–phosphatase activities in streptozotocin induced diabetic rats

Objective: To examine the effects of Sapium ellipticum (S. ellipticum) extract on hepatic activities of glucokinase and glucose-6-phosphatase in streptozotocin (STZ)-induced diabetic Wistar rats.Methods: STZ-induced diabetic Wistar rats (four groups, n = 8) were used in this study. S.ellipticum was assessed at two different doses, 400 and 800 mg/kg BW, in comparison with metformin (12 mg/kg BW) as a standard antidiabetic drug. All treatments were done orally (p.o),twice daily at 8 h interval for a period of 21 days. Glucose-6-phosphatase and glucokinase activities were respectively determined. Hepatic and muscle glycogen contents were estimated as well.Results: STZ caused significant decrease in glucose-6-phosphatase activity and concomitant increase in glucokinase activity. S. ellipticum especially at 400 mg/kg significantly restored glucokinase activity by 40.31% and glucose-6-phosphatase activity by 37.29%. These effects were though significantly lower than that of metformin which enhanced glucokinase activity by 94.76% and simultaneously inhibited glucose-6-phosphatase activity by 49.15%. S.ellipticum also improved hepatic glycogen level by 32.37% and 27.06% at 400 and 800 mg/kg,respectively. HPLC-MS analysis of active S. ellipticum fractions in dynamic MRM mode (using the optimized compound-specific parameters) revealed among other active compounds, the presence of amentoflavone, which has been associated with anti-diabetic function.Conclusions: The ability of S. ellipticum extract to concurrently inhibit glucose-6-phosphatase and activate glucokinase in this study suggests that it may be a treatment option for type 2 diabetes patients and the presence of amentoflavone in the plant extract may account for its anti-diabetic potential.

Recent development and gene therapy for glycogen storage disease type Ia

Glycogen storage disease type Ia(GSD-Ia)is an autosomal recessive metabolic disorder caused by a deficiency in glucose-6-phosphatase-α(G6Pase-αor G6PC)that is expressed primarily in the liver,kidney,and intestine.G6Pase-αcatalyzes the hydrolysis of glucose-6-phosphate(G6P)to glucose and phosphate in the terminal step of gluconeogenesis and glycogenolysis,and is a key enzyme for endogenous glucose production.The active site of G6Pase-αis inside the endoplasmic reticulum(ER)lumen.For catalysis,the substrate G6P must be translocated from the cytoplasm into the ER lumen by a G6P transporter(G6PT).The functional coupling of G6Pase-αand G6PT maintains interprandial glucose homeostasis.Dietary therapies for GSD-Ia are available,but cannot prevent the long-term complication of hepatocellular adenoma that may undergo malignant transformation to hepatocellular carcinoma.Animal models of GSD-Ia are now available and are being exploited to both delineate the disease more precisely and develop new treatment approaches,including gene therapy.