Effects of ursolic acid on glucose metabolism, the polyol pathway and dyslipidemia in non-obese type 2 diabetic mice.

Ursolic acid (UA) is a pentacyclic triterpenoid compound that naturally occurs in fruits, leaves and flowers of medicinal herbs. This study investigated the dose-response efficacy of UA (0.01 and 0.05%) on glucose metabolism, the polyol pathway and dyslipidemia in streptozotocin/nicotinamide-induced diabetic mice. Supplement with both UA doses reduced fasting blood glucose and plasma triglyceride levels in non-obese type 2 diabetic mice. High-dose UA significantly lowered plasma free fatty acid, total cholesterol and VLDL-cholesterol levels compared with the diabetic control mice, while LDL-cholesterol levels were reduced with both doses. UA supplement effectively decreased hepatic glucose-6-phosphatase activity and increased glucokinase activity, the glucokinase/glucose-6-phosphatase ratio, GLUT2 mRNA levels and glycogen content compared with the diabetic control mice. UA supplement attenuated hyperglycemia-induced renal hypertrophy and histological changes. Renal aldose reductase activity was higher, whereas sorbitol dehydrogenase activity was lower in the diabetic control group than in the non-diabetic group. However, UA supplement reversed the biochemical changes in polyol pathway to normal values. These results demonstrated that low-dose UA had preventive potency for diabetic renal complications, which could be mediated by changes in hepatic glucose metabolism and the renal polyol pathway. High-dose UA was more effective anti-dyslipidemia therapy in non-obese type 2 diabetic mice.

Conservation of glycolytic oscillations in Saccharomyces cerevisiae and human pancreatic b-cells: a study of metabolic robustness

The present study compares two computer models of the first part of glucose catabolism in different organisms in search of evolutionarily conserved characteristics of the glycolysis cycle and proposes the main parameters that define the stable steady-state or oscillatory behavior of the glycolytic system. It is suggested that in both human pancreatic b-cells and Saccharomyces cerevisiae there are oscillations that, despite differences in wave form and period of oscillation, share the same robustness strategy: the oscillation is not controlled by only one but by at least two parameters that will have more or less control over the pathway flux depending on the initial state of the system as well as on extra-cellular conditions. This observation leads to two important interpretations: the first is that in both S. cerevisiae and human b-cells, despite differences in enzyme kinetics and mechanism of feedback control, evolution seems to have kept an oscillatory behavior coupled to the glucose concentration outside the cytoplasm, and the second is that the development of drugs to regulate metabolic dysfunctions in more complex systems may require further study, not only determining which enzyme is controlling the flux of the system but also under which conditions and how its control is maintained by the enzyme or transferred to other enzymes in the pathway as the drug starts acting.

Bordetella pertussis extract induces increase in the activities of glycolytic enzymes in mouse liver.

The hypoglycemic effect of Bordetella pertussis (Challenge strain No.18323) purified cell extract (protein with traces of carbohydrates, 2 mg%) administered (0.1 mg/100 g body wt. i.v.) into mice on the activities of the key regulatory enzymes, viz. glucokinase, phosphofructokinase, pyruvate kinase, glyceraldehyde phosphodehydrogenase, glucose-6-phosphate dehydrogenase (G-6-PD) and lactate dehydrogenase, of glycolytic pathway in liver has been studied at varying intervals after injection. The maximum hypoglycaemic effect was observed at the end of 12 hr, while activities of all the enzymes studied showed significant enhancement after 18 hr, thus suggesting increased glucose utilization towards the formation of pyruvate. Actinomycin D is found to inhibit stimulation of G-6-PD activity in B. pertussis treated animals, thereby indicating the role of B. pertussis in synthesis of this enzyme.