Mechanism of action of natural products used in the treatment of diabetes mellitus

Diabetes mellitus(DM) is a metabolic disorder caused by insufficient or inefficient insulin secretary response and it is characterized by increased blood glucose levels(hyperglycemia).DM is a heterogonous group of syndromes.Glucose is the main energy source for the body,and in the case of DM,management of glucose becomes irregular.There are three key defects in the onset of hyperglycemia in DM,namely increased hepatic glucose production,diminished insulin secretion, and impaired insulin action.Conventional drugs treat diabetes by improving insulin sensitivity,increasing insulin production and/or decreasing the amount of glucose in blood.This article provides a comprehensive review of the mode of action of most popular hypoglycemic herbs,such as ginseng,bitter melon,fenugreek,banaba, Gymnema sylvestre and Coptis chinensis.The herbs act by increasing insulin secretion,enhancing glucose uptake by adipose and skeletal muscle tissues,inhibiting intestinal glucose absorption and inhibiting hepatic glucose production.Although evidence from animals and humans consistently supports the therapeutic effect of these phytomedicines,multicenter large-scale clinical trials have not been conducted to evaluate the safety and efficacy of these herbal medicines and their interaction with conventional drugs when administered simultaneously.     

Genistein reverses free fatty acid-induced insulin resistance in HepG2 hepatocytes through targeting JNK

This study investigated the effects and molecular mechanisms of genistein in improving insulin resistance induced by free fatty acids (FFAs) in HepG2 hepatocytes. A model of insulin resistance in HepG2 cells was established by adding palmitic acid (0.5 mmol/L) to the culture medium and the cells were treated by genistein. Glucose consumption of HepG2 cells was determined by glucose oxidase method. The levels of c-jun N-terminal kinase (JNK) phosphorylation, insulin receptor substrate-1 (IRS-1) Ser307 phosphorylation, JNK, IRS-1, phosphatidylinositol-3-kinase p85 (PI-3K p85) and glucose transporter 1 (GLUT1) proteins were detected by Western blotting. The results showed that after the treatment with palmitic acid for 24 h, the insulin-stimulated glucose transport in HepG2 cells was inhibited, and the glucose consumption was substantially reduced. Meanwhile, the expressions of IRS-1, PI-3K p85 protein and GLUT1 were obviously reduced, while the levels of JNK phosphorylation and IRS-1 Ser307 phosphorylation and the expression of JNK protein were significantly increased, as compared with cells of normal control. However, the aforementioned indices, which indicated the existence of insulin resistance, were reversed by genistein at 1-4 μmol/L in a dose-dependent manner. It was concluded that insulin resistance induced by FFAs in HepG2 hepatocytes could be improved by genistein. Genistein might reverse FFAs-induced insulin resistance in HepG2 cells by targeting JNK.     

Quantitative assessment of Parkinson''s disease deficits

OBJECTIVE To quantitatively analyze the tremor and rigidity due to Parkinson's disease.

METHODS 38 patients with Parkinson's disease (PD) ranging in age from 45 to 72 years and 211 normal subjects aged from 16 to 76 years were investigated. The frequency and range of tremor, the muscle tone of the upper limbs in elbow were detected by a computerized video motion detecting system and a new invented apparatus which can detects skeletal muscle tone.

RESULTS For the PD patients, the frequency of resting tremors was detected in 4 to 6 per second. For extensor and flexor in the PD patients, the value of muscle tone was higher than that of normal subjects and the value of muscle tone in flexor was higher than that of extensor. The rigidity increased gradually with repeat passive movement. The curves of rigidity were shown on computer screen or printed out. The data of rigidity were compared with the M-A Scale. A patient who was suspected to suffer from PD above by the equipments and found the muscle tone was higher than normal. In another PD patient the rigidity was obvious at one side and the muscle tone in "normal side" was also high. These equipments were used to record changes of rigidity and tremor in one more PD patient taking with different drugs in order to see the drug effect.

CONCLUSIONS Quantitative methods are useful to analyse the motion disorders due to PD.

     

Effect of ginsenopolypeptide on the 3H-TdR integration of human blood lymphocyte.

This paper reports the study of the effect of ginsenopolypeptide on 3H-TdR integration in normal human blood lymphocytes in vitro with micro-blood culture method of 3H-TdR integration. The results showed that the effect of ginsenopolypeptide on 3H-TdR integration in normal human peripheral blood lymphocytes which can be activated by phytoagglutinin was enhanced at low dosage and inhibited at high dosage, and its stimulating spike was 10(-6) micrograms/ml (P less than 0.01).

     

Construction of human insulin gene expression recombinant and its effect on blood glucose of diabetic rats

OBJECTIVE To study the effect of human insulin gene modified fibroblasts on blood glucose in diabetic rats.

METHODS An expression vector containing human insulin gene was constructed by recombinant DNA technique and introduced into fibroblast Ltk- cells by lipofectin-mediated DNA transfection. Following G418 screening, the survived cells were selected and enriched. Finally a cell line, PRI-12 was generated for the highest insulin production. Then, these cells were injected into streptozocin (STZ)-induced diabetic rats.

RESULTS Insulin DNA transfected Ltk- cells were able to express insulin at a high level in a long-term culture. Furthermore, these Ltk- transfectants could decrease blood glucose significantly (P < 0.01) and obviously increase the body weight (P < 0.01) when they were injected into STZ-induced diabetic rats.

CONCLUSIONS These results suggest that the cell lines transfected insulin gene could secrete insulin and execute effect on diabetic rats. The study provides support for the view that somatic cell gene therapy offers a potential approach to delivery insulin into diabetes mellitus.

     

Mechanism by which statins influence insulin signaling pathway

Recent studies have shown that statins can influence insulin resistance （IR） in animal models and inhumans.1.2 However, the mechanism by which statins influence the insulin signaling pathway （ISP） remains obscure. It has been proposed that the pleiotropic effects of statins might be involved in regulation of IR.The phosphatidylinositol 3-kinase （PI3K）-Akt/protein kinase B （PKB） pathway is the main ISE Insulin binding to insulin receptor initiates PI3K-Akt pathway by phosphorylates tyrosine residue of IR substrate proteins （IRSs） including IRS-1 and IRS-2. Activation of the PI3K leads to the accumulation of phosphatidylinositol 3,4,5-triphosphate （PIP3）. PIP3 activates serine/ threonine kinase （Akt）. Glucose transporter-4 （GLUT-4） translocates to plasma membrane from cytosol by serine phosphorylation of Akt and directly regulates glucose metabolism in liver, muscle and adipose tissue （Figure 1）. However, an overall mechanism by which statins influence ISP remained obscure.     

Chronic Hyperinsulinism Induced Down-regulation of Insulin Post-Recentor Signaling Transduction in Hep G2 Cells

Summary: To study the regulatory effect of acute and chronic insulin treatment on insulin post-re-ceptor signaling transduction pathway in a human hepatoma cell line (Hep G2), Hep G2 cells wereincubated in the presence or absence of insulin with different concentrations in serum free mediafor 16 h and then stimulated with 100 nmol/L insulin for 1 min. Protein levels of insulin receptorβ-subunit (IRβ), insulin receptor substrate-1 (IRS-1) and p85 subunit of phosphatidylinositol 3-kinase (PI 3-kinase) were determined in total cell lysates by Western-immunoblot. Phosphorylat-ed proteins IRβ, IRS-1 and interaction of PI 3-kinase with IRS-1 were determined by immunopre-cipitation. Results showed that 1-min insulin stimulation rapidly induced tyrosine phosphorylationof IRβ and IRS-l, which in turn, resulting in association of PI 3-kinase with IRS-1. 1-100 nmol/L chronic insulin treatment induced a dose-dependent decrease in the protein level of IRβ and aslight decrease in the protein level of IRS-1. There wass more marked reduction in the phospho-rylation of IRβ, IRS-1, reaching a nadir of 22 % (P＜0. 01) and 15 % (P＜0. 01) of control lev-els, respectively, after 16 h treatment with 100 nmol/L insulin. The association between IRS-1and PI 3-kinase was decreased by 66 % (P＜0. 01). There was no significant change in PI 3-ki-nase protein levels. These data suggest that chronic insulin treatment can induce alterations ofIRβ, IRS-1 and PI 3-kinase three early steps in insulin action, which contributes significantly toinsulin resistance, and may account for desensitization of insulin action.     

Relationship between tyrosine phosphorylation and protein expression of insulin receptor and insulin resistance in gestational diabetes mellitus

Summary： The relationship between tyrosine phosphorylation （TP） and protein expression of insulin receptor （InsR） and insulin resistance （IR） in patients with gestational diabetes mellitus （GDM） was investigated. The InsR expression and TP in skeleton muscle tissue were determined by Western blotting and immunoprecipitation in women with GDM （GDM group, n=22）, normal pregnant women （normal pregnancy group, n=22） and normal non-pregnant women （normal non-pregnant group, n=13）. Fasting plasma glucose （FPG） and fasting insulin （FINS） were measured by oxidase assay and immunoradioassay. The results showed that the levels of FPG （5.61±0.78 mmol/L）, FINS （15.42±5.13 mU/L） and Ho- meostasis model assessment-IR （HOMA-IR） （1.21±0.52） in GDM group were significantly higher than those in normal pregnancy group （4.43±0.46 mmol/L, 10.56±3.07 mU/L and 0.80±0.31 respectively） （P〈0.01）. The levels of FINS and HOMA-IR in normal pregnancy group were significantly higher than those in normal non-pregnant group （7.56±2.31 mU/L and 0.47±0.26 respectively） （P〈0.01）. There was no significant difference in the InsR expression level among the three groups （P〉0.05）. TP of InsR with insulin stimulation was significantly decreased in GDM group （0.20±0.05） as compared with normal pregnancy group （0.26±0.06） （P〈0.01）. TP of InsR with insulin stimulation in normal pregnancy group was lower than that in normal non-pregnant group （0.31±0.06） （P〈0.01）. TP of InsR with insulin stimu- lation was negatively related with HOMA-IR in GDM group （r=-0.525, P〈0.01）. There was no correlation between the protein expression of InsR and HOMA-IR in GDM group （r=-0.236, P〉0.05）. It was suggested that there is no significant correlation between the protein expression of InsR in skeletal muscle and IR in GDM, but changes in TP of InsR are associated with IR in GDM.     

Transplantation of encapsulated neonatal porcine islet-like cluster cells into diabetic rats.

OBJECTIVE To evaluate the function of alginate poly-L-ysine membrane in protecting porcine to rat islet xenografts.

METHODS Newborn porcine islet-like cluster cells (ICC) were obtained by digesting pancreas with type XI collagenase. After 2-3 days' incubation, encapsulated ICC were formed through instrument. In vitro, insulin release and insulin stimulating test was performed. In vivo, encapsulated ICC were transplanted into streptozotocin-induced diabetic rats.

RESULTS Unlike ICC only (insulin can be tested within 14 days) encapsulated ICC maintained insulin release at certain level for nearly 28 days. High insulin response to 16.7 mM glucose and 10 mM theophylline significantly differed from low insulin response to 5.6 mM or 16.7 mM glucose (P < 0.01). Extended survival of porcine ICC xenografts implanted in diabetic rats had been achieved by encapsulation. After transplantation, rats sustained normal glycemia for average 4 months. The capsules with ICC obtained from experimental group could be stained with neutral red. Insulin release of survival capsules with ICC in response to 16.7 mM glucose and 10 mM theophylline was 3 times more as compared to the insulin response to 5.6 mM glucose. Sections of encapsulated ICC (H&E) showed fairly good cell clusters and the membranes were generally free of fibrosis and host cell adherence.

CONCLUSIONS Artificial membrane can protect discordant islet xenografts from rejection.

     

Evaluation of glucose metabolic disorder: insulin resistance and insulin receptors in critically ill children.

OBJECTIVE To explore the pathogenesis of glucose metabolic disorder and insulin resistance in critically ill children under severe stress.

METHODS To test glucose, lactate, glucagon, insulin, c-peptide, cortisol levels in 50 critically ill children. While we measured 125I-insulin binding to erythrocytes of 13 critically ill children who had hyperglycemia and hyperinsulinemia. Glucose and lactate were measured biochemically. Insulin, c-peptide, cortisol and glucagon were determined by RIA. Erythrocytes insulin receptor was detected by insulin radioreceptor assay.

RESULTS Glucose, lactate, insulin, c-peptide, glucagon, cortisol, insulin/glucose, insulin/glucagon ratio in patients were higher than those in normal controls (P < 0.05). As compared with normal controls, the maximum 125I-insulin bound and insulin receptor number per cell were significantly lower (P < 0.01). But there was no difference of mean value in receptor affinity (P > 0.05).

CONCLUSIONS Hyperglycemia is common in critically ill children during stress, which may be attributed to hormones disturbance and tissure insulin resistance. Insulin receptor defect due to comprehensive factors was one of the important causes for insulin resistance. The blood glucose level can be used as an predicting index in ICU.

     

筋脉通胶囊血清有效成分可预防大鼠高血糖浓度引起的施万细胞凋亡

Objective: To evaluate the effect of serum containing Jinmaitong Capsule (筋脉通胶囊, JMT) on apoptosis of Schwann cells (SCs) that are cultured in high glucose at the cellular and molecular levels. Methods: SCs were cultured in Dulbecco''s modi?ed Eagle''s medium (control group), high glucose (50 mmol/L) medium supplemented with 20% rat serum (HG group), and 50 mmol/L glucose medium supplemented with serum containing JMT (JMT group). SC apoptosis was detected using a terminal deoxynucleotidyl transferase dUTP nick end labeling kit. The expression of Bcl-2 and the caspase-3 p20 subunit in SCs were detected by real-time fluorogenic quantitative polymerase chain reaction and confocal laser scanning microscopy, respectively. Results: No apoptosis was detected in SCs that were cultured in the control group. The percentage of apoptosis of SCs cultured in the HG group was much higher than that in the control group. The apoptosis of SCs in the JMT group was lower than that in the HG group. Fluorescence intensity of Bcl-2 and the expression of Bcl-2 mRNA in SCs that were cultured in the HG group were much lower than those in the control group and much higher than those in the JMT group (P<0.01). The fluorescence intensity of caspase-3 p20 and the expression of caspase-3 p20 mRNA in SCs that were cultured in the HG group were much higher than those in the control group (P<0.01), and they were remarkably lower in the JMT group (P<0.01). Conclusions: JMT effectively prevents SC apoptosis that is induced by high glucose. This effect may be because of increased expression of Bcl-2 mRNA and protein and decreased expression of caspase-3 p20 mRNA and protein.     

Effect of Huanglian Jiedu Decoction (黄连解毒汤) on glucose transporter 4 expression in adipose and skeletal muscle tissues of insulin resistant rats

Objective： To investigate the effects of Huanglian Jiedu Decoction （黄连解毒汤, HLJDD） on glucose transporter 4 （GLUT4） protein expressions in insulin-resistant murine target tissues. Methods： The experimental male Wistar rats were established into insulin resistant models by injecting streptozotocin （STZ 30 mg/kg） via caudal vein and feeding them with high fat high caloric diet, and randomly divided into the model group, the aspirin group and the HLJDD group. Besides, a normal group was set up for control. Changes of body weight （BW）, levels of serum fasting blood glucose （FBG）, serum fasting insulin （FINS） and oral glucose tolerance test （OGTT） were routinely determined. The expression of GLUT4 protein in adipose and skeletal muscle tissues before and after insulin stimulation was determined with Western blot. Results： In the HLJDD group after treatment, BW and FBG got decreased, OGTT improved, and the expression and translocation of GLUT4 protein elevated obviously, either before or after insulin stimulation, as compared with those in the model group, showing significant differences respectively. Conclusion： The mechanism of improving insulin resistance by HLJDD is probably associated with its effect in elevating GLUT4 protein expression and translocation in adipose and skeletal muscle tissues of insulin resistant rats.     

Exercise therapy of non-insulin dependent diabetes mellitus a report of 10 year studies. The efficacy of exercise therapy.

The effect of a physical training course of 1-2 month duration using cycloergometer with the intensity of VO2 max 60%, 30 min per day was observed in non-insulin dependent diabetes mellitus (NIDDM) patients. The results showed a decrease of plasma glucose and insulin levels, sigma PG and sigma IRI and an improvement of blood lipid constitution. These were accompanied by a decreased erythrocyte insulin receptor binding rate and a reduction of receptor binding sites of both high and low affinity receptors.

     

Effect of Kaiyu Qingwei Granule (开郁清胃颗粒) on Insulin Receptor in Liver and Skeletal Muscular Cell Membrane in Diabetes Mellitus Rats

Objective: To investigate the effect of Kaiyu Qingwei granule (KYQWG, on the insulin binding capacity of liver and skeletal muscular cell membrane and serum insulin-like growth factor-1 (IGF-1) in streptozotocin-induced diabetic rats. Methods: Rats in four experimental groups were investigated: the control group, the model group, the KYQWG group and the Metformin group. The insulin binding rate (IBR) of liver and skeletal muscular cell membrane was detected by receptor-ligand ra-diometric method and changes of serum levels of glucose, insulin and IGF-1 were observed before and after 4 weeks of medication. Results: The KYQWG group had a lower blood glucose level and ffiR of liver and muscular cell membrane, as compared with those in the model group (P<0. 01 or P<0.05), and a higher level of IGF-1 than that in the model group(P<0.01), but had no obvious changes in the serum level of insulin. Conclusion: KYQWG may increase the serum level of IGF-1 in diabetic rats, thus to decrease the insulin resistance a     

Antihyperglycemic and antihyperlipidemic action of cinnamaldehyde in C57blks/j Db/db mice

OBJECTIVE:To investigate the effects of cinnamaldehyde(CA),an active and major compound in cinnamon,on glucose metabolism and insulin resistance in C57BLKS/J db/db mice.METHODS:Sixteen male C57BLKS db/db mice were randomly divided into control and CA treatment groups.CA was given(20 mg.kg-1.day-1,p.o.) for 4 weeks.Pure water was given to control and db/+ mice.Subsequently,the levels of fasting blood glucose(FBG),fasting serum insulin,triglyeride,cholesterol,low-density lipoprotein-cholesterol(LDL-C),high-density lipoprotein-cholesterol(HDL-C),and free fatty acids(FFA),as well as the mRNA content of adiponectin and tumor necrosis factor(TNF)-α in adipose tissue,glucose transporter type 4(GLUT-4) in skeletal muscle,and protein expressions of Akt,phospho-Akt(Thr308),AMPKα,phospho-AMPKα(Thr172) in skeletal muscle were measured.RESULTS:1) CA decreased serum levels of FBG and insulin as well as body weight in db/db mice;2) CA increased serum HDL-C levels;3) CA significantly decreased the mRNA expression of TNF-α in adipose tissue and upregulated mRNA expression of GLUT-4 in skeletal muscle;4) protein expression of p-Akt was increased in CA-treated mice,but Akt,AMPKα and p-AMPKα showed no change.CONCLUSION:CA has antihyperglycemic and antihyperlipidemic actions in db/db mice and could be useful in the treatment of type-2 diabetes.     

Sequence of fat partitioning and its relationship with whole body insulin resistance

Background Currently it is unclear whether lipid accumulation occurs in a particular sequence and its relationship with whole body insulin resistance （IR）. This study aimed to answer this question.Methods Male Sprague-Dawley （SD） rats were fed on a normal or a high-fat diet for 20 weeks. Serum triglycerides （TG）, serum free fatty acids （FFA）, fasting plasma glucose （FPG）, and liver and skeletal muscle TG were measured. The glucose infusion rate （GIR） and mRNA levels of acetyl-CoA carboxylase （ACC） and carnitine palmitoyltransferase-1 （CPT-1） in the liver and skeletal muscle were determined at different stages.Results Compared with rats fed on the normal diet, serum FFA was not significantly increased in rats fed on the high-fat diet until 20 weeks. In contrast, liver TG was significantly increased by the high-fat diet by four weeks （20-fold; P ＜0.01）,and remained elevated until the end of the study. However, skeletal muscle TG was not significantly increased by the high-fat diet until 20 weeks （10.6-fold; P＜0.01）, and neither was the FPG. The GIR was significantly reduced （1.6-fold; P ＜0.01） by the high-fat diet after 8 weeks. The mRNA levels of ACC gradually increased over time and CPT-1 decreased over time, in both the liver and skeletal muscle in rats fed the high-fat diet.Conclusions Lipid accumulation in the liver occurs earlier than lipid accumulation in the skeletal muscle. Fatty liver may be one of the early markers of whole body IR. Changes in the gene expression levels of ACC and CPT-1 may have important roles in the process of IR development.     

Study on insulin resistance and genetic polymorphisms in essential hypertension patients of two different kinds of TCM constitution

Objective:To investigate the relationship of insulin resistance and the polymorphisms of insulin receptor-related genes in essential hypertension patients of two different kinds of TCM constitution.Methods:Oral glucose tolerance test (OGTT) and insulin release test (InRT) were conducted in 217 essential hypertensive patients of either sluggish meticulous (SM) constitution (139 cases) or prosperous impetuous (PI) constitution (78 cases),and the polymorphism of three genes, including insulin-like growth factor-1 receptor (IGF-1R),insulin receptor substrate-1 (IRS-1) and 2 (IRS-2) genes were detected.Results:(1) OGTT,InRT and insulin resistance index (Homa-IR) were higher and insulin sensitive index (ISI) was lower in the patients of SM constitution than those in patients of PI constitution.(2) Significant difference of ISI and Homa-IR was shown in patients of both constitutions with genotype G of the 3 genes.Conclusion:Decrease of insulin sensitivity and increase of insulin resistance are more obvious in hypertensive patients with genotype G of the 3 genes of SM constitution than in those of PI constitution.Therefore,the difference in constitution might be one of the genetic characteristics for insulin resistance in hypertensive patients.     

Th17 cells influence intestinal muscle contraction during <Emphasis Type="Italic">Trichinella spiralis</Emphasis> infection

Trichinella spiralis infection in rodents is a well-known model of intestinal inflammation associated with hypermotility. The aim of the study was to use this experimental model to elucidate if Thl 7 cells are involved in the development of gastrointestinal hypermotility. Colonic smooth muscle contractility was investigated in response to acetylcholine. The levels of IL-17, IL-23 and TGF-β1 in colon were measured by Western blotting. Flow cytometric detection of intracellular IFN-7/IL-4/ IL- 17 cytokine production was used to analyze the proportions of CD4＋ T cells subsets in colon. Our results showed that colonic muscle contractility was increased 2 weeks post infection （PI） and stayed high 12 weeks PI when no discernible inflammation was present in the gut. The proportion of Th17 cells and the expression of IL-17 were up-regulated in colon 2 weeks PI and returned to normal 8 weeks PI. The content of IL-17 was correlated with the colonic smooth muscle hypercontracility 2 weeks PI. Meanwhile, TGF-β1 was increased 2 weeks PI, while IL-23 was normal. Our results suggest that Th17 cells affect the colonic muscle contractility in mice infected with Trichinella spiralis at intestine stage but not at muscle stage and the effect of Th17 cells on muscle contractility might be induced by TGF-β1. Other cytokines might be involved in the hypercontracility of colonic smooth muscle at muscle stage.     

AMP-activated protein kinase acts as a negative regulator of high glucose-induced RANKL expression in human periodontal ligament cells

Background  It is well known that the function of periodontal ligament cells may be affected by high glucose levels. This study investigated the direct effect of high glucose on the expression of receptor activator of nuclear factor-kappa B ligand (RANKL) in human PDL (hPDL) cells. In addition, we examined whether this effect was mediated via AMPK activation.

Methods  We examined the expression of osteoprotegerin in hPDL cells cultured at different concentrations of glucose using real-time polymerase chain reaction (PCR), and Western blotting analysis. AMPK phosphorylation in hPDL cells was studied using immunoprecipitate kinase assay and Western blotting. The effect of AMPK activation on RANKL expression in hPDL cells was investigated by real-time PCR and Western blotting.

Results  High glucose levels caused an increase in RANKL mRNA and protein expression in hPDL cells. Moreover, the amount of p-AMPK and AMPK activity was lower in hPDL cells exposed to high glucose levels than in cells exposed to normal glucose levels. Suppression of AMPK by Compound C augmented RANKL expression, and AMPK activation by metformin significantly decreased RANKL expression in hPDL cells. Additionally, metformin down-regulated RANKL expression in hPDL cells exposed to high glucose via AMPK activation.

Conclusion  High glucose-induced up-regulation of RANKL could be due to decreased AMPK activity, and AMPK activation may be involved in regulating of RANKL expression in hPDL cells.