Mechanistic studies on the antidiabetic activity of a polysaccharide-rich extract of Radix Ophiopogonis.

To study the hypoglycemic mechanisms of a polysaccharide-rich extract of Radix Ophiopogonis, the influences of the extract on activity of NIT-1 insulinoma cells damaged by streptozotocin (STZ), activity of α-glucosidase, glucose absorption into intestinal brush border membrane vesicles, gluconeogenesis by H4IIE hepatoma cells and glucose uptake by 3T3-L1 adipocytes were investigated. The results show that the extract improved the activity of NIT-1 cells damaged by STZ, inhibited glucose absorption into intestinal brush border membrane vesicles and reduced the activity of α-glucosidase. However, gluconeogenesis in H4IIE cells and glucose uptake in 3T3-L1 adipocytes did not change significantly in the presence of the extract. These results suggest that the hypoglycemic mechanisms of the polysaccharide-rich extract of Radix Ophiopogonis are caused by protection in pancreatic islet cells and the inhibition of carbohydrate digestion and absorption. This is possibly the first report on the underlying mechanisms responsible for the antidiabetic effect of Radix Ophiopogonis.

Low-Magnitude High-Frequency Vibration Decreases Body Weight Gain and Increases Muscle Strength by Enhancing the p38 and AMPK Pathways in db/db Mice.

OBJECTIVE: To evaluate the effect LMHFV on body weight gain, NAFLD and muscle strength and explore effect in mitochondrial biogenesis, AMPKα and p38 pathways. METHODS: Vibration platform used in this study provides specific whole-body cyclic mechanical stimulation at low magnitude (0.3 g) and high frequency (50 Hz). Diabetic mice (8-9 mice per group) (C57BL/KsJ-m+/+Leprdb) were randomly divided into untreated group (no vibration) and two vibration groups. Lean mice (8 mice) were used as non-diabetic control for both groups. Two diabetic vibration groups received LMHFV every day for 20 min/day and 40 min/day separately. RESULTS: After 8 weeks of treatment, results showed that body weight, liver weight, fat pad weight, glucose level and insulin level were lower in vibration group when compared with the untreated group. The ratio of fat in liver was significantly decreased after vibration treatment. Muscle strength was significantly increased after vibration. Mitochondrial biogenesis-related gene expression was increased in soleus, gastrocnemius and liver. AMPKα mRNA expression level was increased in soleus and gastrocnemius after vibration treatment. p38 and AMPKα mRNA expression level and protein expression level in liver were enhanced with vibration treatment. Moreover, phosphorylation of p38 and AMPKα was enhanced in liver. CONCLUSION: LMHFV applied in our study decreases body weight gain and improves muscle strength and NAFLD in diabetic mice which were partly through improving mitochondrial biogenesis by enhancing p38 and AMPKα pathway.

The effects of phenytoin and its metabolite 5-(4-hydroxyphenyl)-5-phenylhydantoin on cellular glucose transport.

Glucose is the principal fuel for brain metabolism and its movement across the blood-brain barrier depends on Glut1. Impaired glucose transport to the brain may have deleterious consequences. For example, Glut1 deficiency syndrome (Glut1DS) is the result of heterozygous loss of function Glut1 mutation leading to energy failure of the brain and subsequently, epileptic encephalopathy. To preserve the integrity of the energy supply to the brain in patients with compromised glucose transport function, consumption of compounds with glucose transport inhibiting properties should be avoided. Phenytoin is a widely used anticonvulsant that affects carbohydrate metabolism. In this study, the hypothesis that phenytoin and its metabolite 5-(4-hydroxyphenyl)-5-phenylhydantoin (HPPH) affect cellular glucose transport was tested. With a focus on Glut1, the effects of phenytoin and HPPH on cellular glucose transport were studied. Glucose uptake assay measuring the zero-trans influx of radioactive-labeled glucose analogues showed that phenytoin and HPPH did not exert immediate effects on erythrocyte Glut1 activity or glucose transport in Hs68 control fibroblasts, Glut1DS primary fibroblasts isolated from two patients, or in rat primary astrocytes. Prolonged exposure to the two compounds could stimulate glucose transport by up to 30-60% over the control level (p <0.05) in Hs68 and Glut1DS fibroblasts as well as in rat astrocytes. The stimulation of glucose transport by HPPH was dose-dependent and accompanied by an up-regulation of GLUT1 mRNA expression (p <0.05). In conclusion, phenytoin and HPPH do not compromise cellular glucose transport. Prolonged exposure to these compounds can modify carbohydrate homeostasis by up-regulating glucose transport in both normal and Glut1DS conditions in vitro.

A Chinese 2-herb formula (NF3) promotes hindlimb ischemia-induced neovascularization and wound healing of diabetic rats.

Diabetic foot ulcer is closely associated with peripheral vascular disease. Enhancement of tissue oxidative stress, reduction of nitric oxide (NO) and angiogenic growth factors, and abnormal matrix metalloproteinase (MMP) activity are pathophysiological factors in post-ischemic neovascularization and diabetic wound healing. Our previous study demonstrated that the Chinese 2-herb formula, NF3, showed significant wound healing effects on diabetic foot ulcer rats. A novel rat diabetic foot ulcer with hindlimb ischemia model was established in order to strengthen our claims on the diabetic wound healing and post-ischemic neovascularization effects of NF3. Our results demonstrate that NF3 can significantly reduce the wound area of the diabetic foot ulcer rat with hindlimb ischemia by 21.6% (p<0.05) compared with the control group. In addition, flow cytometric analysis revealed that NF3 could boost circulating EPC levels for local wound vessel incorporation. Immunohistochemical analysis showed that NF3 could significantly augment blood vessel density, VEGF and eNOS expression, and attenuate tissue oxidative stress of ischemic muscles (p<0.001). NF3 significantly stimulated MMP activity involved in angiogenesis. Our study shows, for the first time, the beneficial effects of NF3 in wound healing and post-ischemic neovascularization in diabetes.

Saxifragifolin B from Androsace umbellata induced apoptosis on human hepatoma cells.

Bioassay-guided phytochemical study of Androsace umbellata led to the successful isolation of saxifragifolin B (SB) for the first time. The anti-tumor effect of SB was firstly reported that it was shown to have potent cytotoxicity on human hepatoma HepG2 cells with IC50 value of 11.9 microM at 24 h. Mechanistic studies were conducted, the accumulation of sub-G1 population and the externalization of phosphatidylserine suggested that SB exerted its cytotoxic effect by induction of programmed cell death, which was confirmed by activation of PARP and caspase-3. Furthermore, SB-induced apoptosis on HepG2 cells was mediated by activation of caspase-8 and -9, mitochondrial membrane potential (Deltapsim) collapse and the leakage of cytochrome c. In summary, this study provided evidence that SB isolated from A. umbellata could induce apoptosis on human hepatoma HepG2 cells and described the molecular mechanism. Our finding revealed the potential of SB as new chemotherapeutic agent for human hepatoma.