Xiao Ke Qing (XKQ) granule has been clinically used to treat type 2 diabetes mellitus (T2DM) for 10 years in Chinese traditional medication. However, its mechanisms against hyperglycemia remain poorly understood. This study aims to investigate XKQ mechanisms on diabetes and diabetic liver disease by using the KKAy mice model. Our results indicate that XKQ can significantly reduce food and water intake. XKQ treatment also remarkably decreases both the fasting blood glucose and blood glucose in the oral glucose tolerance test. Additionally, XKQ can significantly decrease the serum alanine aminotransferase level and liver index and can alleviate the fat degeneration in liver tissues. Moreover, XKQ can ameliorate insulin resistance and upregulate the expression of IRS-1, PI3K (p85), p-Akt, and GLUT4 in the skeletal muscle of KKAy mice. XKQ is an effective drug for T2DM by ameliorating insulin resistance and regulating the PI3K/Akt signaling pathway in the skeletal muscle.
Animals ; Blood Glucose ; drug effects ; metabolism ; Diabetes Mellitus, Type 2 ; drug therapy ; metabolism ; Disease Models, Animal ; Drugs, Chinese Herbal ; pharmacology ; Female ; Glucose Tolerance Test ; Glucose Transporter Type 4 ; metabolism ; Hypoglycemic Agents ; pharmacology ; Insulin ; blood ; Insulin Resistance ; Liver ; drug effects ; pathology ; Mice ; Mice, Inbred C57BL ; Phosphatidylinositol 3-Kinases ; metabolism ; Proto-Oncogene Proteins c-akt ; metabolism ; Signal Transduction ; drug effects

PURPOSE: To characterize the relationship between serum estradiol levels and the expression of glucose transporter type 4 (Glut4) in the pubococcygeus and iliococcygeus muscles in female rats. METHODS: The muscles were excised from virgin rats during the metestrus and proestrus stages of the estrous cycle, and from sham and ovariectomized rats implanted with empty or estradiol benzoate–filled capsules. The expression of estrogen receptors (ERs) was inspected in the muscles at metestrus and proestrus. Relative Glut4 expression, glycogen content, and serum glucose levels were measured. Appropriate statistical tests were done to identify significant differences (P≤0.05). RESULTS: The pubococcygeus and iliococcygeus muscles expressed ERα and ERβ. Glut4 expression and glycogen content in the pubococcygeus muscle were higher at proestrus than at metestrus. No significant changes were observed in the iliococcygeus muscle. In ovariectomized rats, the administration of estradiol benzoate increased Glut4 expression and glycogen content in the pubococcygeus muscle alone. CONCLUSIONS: High serum estradiol levels increased Glut4 expression and glycogen content in the pubococcygeus muscle, but not in the iliococcygeus muscle.
Animals ; Benzoates ; Blood Glucose ; Capsules ; Estradiol* ; Estrous Cycle ; Female ; Glucose Transport Proteins, Facilitative* ; Glucose Transporter Type 4* ; Glucose* ; Glycogen ; Humans ; Metabolism ; Metestrus ; Muscles* ; Ovariectomy ; Pelvic Floor* ; Proestrus ; Rats* ; Receptors, Estrogen

BACKGROUND/OBJECTIVES: The anti-diabetic activity of pear through inhibition of α-glucosidase has been demonstrated. However, little has been reported about the effect of pear on insulin signaling pathway in obesity. The aims of this study are to establish pear pomace 50% ethanol extract (PPE)-induced improvement of insulin sensitivity and characterize its action mechanism in 3T3-L1 cells and high-fat diet (HFD)-fed C57BL/6 mice. MATERIALS/METHODS: Lipid accumulation, monocyte chemoattractant protein-1 (MCP-1) secretion and glucose uptake were measure in 3T3-L1 cells. Mice were fed HFD (60% kcal from fat) and orally ingested PPE once daily for 8 weeks and body weight, homeostasis model assessment of insulin resistance (HOMA-IR), and serum lipids were measured. The expression of proteins involved in insulin signaling pathway was evaluated by western blot assay in 3T3-L1 cells and adipose tissue of mice. RESULTS: In 3T3-L1 cells, without affecting cell viability and lipid accumulation, PPE inhibited MCP-1 secretion, improved glucose uptake, and increased protein expression of phosphorylated insulin receptor substrate 1 [p-IRS-1, (Tyr⁶³²)], p-Akt, and glucose transporter type 4 (GLUT4). Additionally, in HFD-fed mice, PPE reduced body weight, HOMA-IR, and serum lipids including triglyceride and LDL-cholesterol. Furthermore, in adipose tissue, PPE up-regulated GLUT4 expression and expression ratio of p-IRS-1 (Tyr⁶³²)/IRS, whereas, down-regulated p-IRS-1 (Ser³⁰⁷)/IRS. CONCLUSIONS: Our results collectively show that PPE improves glucose uptake in 3T3-L1 cells and insulin sensitivity in mice fed a HFD through stimulation of the insulin signaling pathway. Furthermore, PPE-induced improvement of insulin sensitivity was not accompanied with lipid accumulation.
3T3-L1 Cells ; Adipose Tissue ; Animals ; Blotting, Western ; Body Weight ; Cell Survival ; Chemokine CCL2 ; Diet, High-Fat ; Ethanol* ; Glucose ; Glucose Transport Proteins, Facilitative ; Glucose Transporter Type 4 ; Homeostasis ; Insulin Receptor Substrate Proteins ; Insulin Resistance* ; Insulin* ; Lipid Metabolism ; Mice ; Obesity ; Pyrus* ; Triglycerides

Recent evidence suggests that caveolin-1 (Cav-1), the major protein constituent of caveolae, plays a prominent role in neuronal nutritional availability with cellular fate regulation besides in several cellular processes such as cholesterol homeostasis, regulation of signal transduction, integrin signaling and cell growth. Here, we aimed to investigate the function of Cav-1 and glucose transporter 4 (GLUT4) upon glucose deprivation (GD) in PC12 cells. The results demonstrated firstly that both Cav-1 and GLUT4 were up-regulated by glucose withdrawal in PC12 cells by using Western blot and laser confocal technology. Also, we found that the cell death rate, mitochondrial membrane potential (MMP) and intracellular free Ca(2+) concentration ([Ca(2+)]i) were also respectively changed followed the GD stress tested by CCK8 and flow cytometry. After knocking down of Cav-1 in the cells by siRNA, the level of [Ca(2+)]i was increased, and MMP was reduced further in GD-treated PC12 cells. Knockdown of Cav-1 or methylated-β-Cyclodextrin (M-β-CD) treatment inhibited the expression of GLUT4 protein upon GD. Additionally, we found that GLUT4 could translocate from cytoplasm to cell membrane upon GD. These findings might suggest a neuroprotective role for Cav-1, through coordination of GLUT4 in GD.
Animals ; Calcium ; metabolism ; Caveolin 1 ; metabolism ; Gene Knockdown Techniques ; Glucose ; chemistry ; Glucose Transporter Type 4 ; metabolism ; Homeostasis ; PC12 Cells ; Protein Transport ; RNA, Small Interfering ; Rats ; Signal Transduction ; Up-Regulation ; beta-Cyclodextrins

Previous studies proposed that the synergistic effect of fibroblast growth factor-21 (FGF-21) and insulin may be due to the improvement of insulin sensitivity by FGF-21. However, there is no experimental evidence to support this. This study was designed to elucidate the mechanism of synergistic effect of FGF-21 and insulin in the regulation of glucose metabolism. The synergistic effect of FGF-21 and insulin on regulating glucose metabolism was demonstrated by investigating the glucose absorption rate by insulin resistance HepG2 cell model and the blood glucose chances in type 2 diabetic db/db mice after treatments with different concentrations of FGF-21 or/and insulin; The synergistic metabolism was revealed through detecting GLUT1 and GLUT4 transcription levels in the liver by real-time PCR method. The experimental results showed that FGF-21 and insulin have a synergistic effect on the regulation of glucose metabolism. The results of real-time PCR showed that the effective dose of FGF-21 could up-regulate the transcription level of GLUT1 in a dose-dependent manner, but had no effect on the transcription level of GLUT4. Insulin (4 u) alone could up-regulate the transcription level of GLUT4, yet had no effect on that of GLUT1. Ineffective dose 0.1 mg kg(-1) FGF-21 alone could not change the transcription level of GLUT1 or GLUT4. However, when the ineffective dose 0.1 mg x kg(-1) FGF-21 was used in combination with insulin (4 u) significantly increased the transcription levels of both GLUT1 and GLUT4, the transcription level of GLUT1 was similar to that treated with 5 time concentration of FGF-21 alone; the transcription level of GLUT4 is higher than that treated with insulin (4 u) alone. In summary, in the presence of FGF-21, insulin increases the sensitivity of FGF-21 through enhancing GLUT1 transcription. Vice versa, FGF-21 increases the sensitivity of insulin by stimulating GLUT4 transcription in the presence of insulin. FGF-21 and insulin exert a synergistic effect on glucose metabolism through mutual sensitization.
Animals ; Blood Glucose ; Diabetes Mellitus, Experimental ; metabolism ; Drug Synergism ; Fibroblast Growth Factors ; pharmacology ; Glucose ; metabolism ; Glucose Transporter Type 1 ; metabolism ; Glucose Transporter Type 4 ; metabolism ; Hep G2 Cells ; Humans ; Insulin ; pharmacology ; Insulin Resistance ; Liver ; metabolism ; Mice

OBJECTIVETo explore the effects of arecoline on hepatic insulin resistance in type 2 diabetes rats and to elucidate its possible mechanism.

METHODSForty five Wistar rats were fed with high fructose diet for 12 weeks to induce type 2 diabetic rat model. rats were randomly divided into 5 groups (n = 8): control group, model group and model group were treated with different dose (0, 0.5, 1, 5 mg/kg) of arecoline. After 4 weeks, the fasting blood glucose, blood lipid and insulin level measured , mRNA expression of liver constitutive androstane receptor (CAR), pregnane X receptor (PXR), glucose-6-phosphatase (G6Pase), phosphoenolpyruvate carboxykinase (PEPCK), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) were detected by reverse transcription polymerase chain reaction (RT-PCR), the protein expression of p-AKT and glucose transporter4 (GLUT4) were detected by Western blot.

RESULTS1.5 mg/kg arecoline could significantly decrease the level of fasting blood glucose, blood lipid, blood insulin level and liver G6Pase, PEPCK, IL-6, TNF-alpha mRNA level in type 2 diabetes rats. 1.5 mg/kg arecoline also could significantly increase CAR, PXR mRNA level and p-AKT and GLUT4 protein expression.

CONCLUSIONArecoline improved hepatic insulin resistance in type 2 diabetes rats by increasing the mRNA levels of CAR and PXR leading to the creased glucose metabolism and inflammation related genes expression.

Animals ; Arecoline ; pharmacology ; Diabetes Mellitus, Experimental ; metabolism ; Diabetes Mellitus, Type 2 ; metabolism ; Glucose Transporter Type 4 ; metabolism ; Glucose-6-Phosphatase ; metabolism ; Insulin Resistance ; Interleukin-6 ; metabolism ; Intracellular Signaling Peptides and Proteins ; metabolism ; Liver ; drug effects ; metabolism ; Male ; Phosphoenolpyruvate Carboxykinase (GTP) ; metabolism ; Proto-Oncogene Proteins c-akt ; metabolism ; Rats ; Rats, Wistar ; Receptors, Cytoplasmic and Nuclear ; metabolism ; Receptors, Steroid ; metabolism ; Tumor Necrosis Factor-alpha ; metabolism

BACKGROUNDSuppression of myostatin (MSTN) has been associated with skeletal muscle atrophy and insulin resistance (IR). However, few studies link MSTN suppression by ladder-climbing training (LCT) and IR. Therefore, we intended to identify the correlation with IR between LCT and to analyze the signaling pathways through which MSTN suppression by LCT regulates IR.

METHODSThe rats were randomly assigned to two types of diet: normal pellet diet (NPD, n = 8) and high-fat diet (HFD, n = 16). After 8 weeks, the HFD rats were randomly re-assigned to two groups (n = 8 for each group): HFD sedentary (HFD-S) and high-fat diet ladder-climbing training (HFD-LCT). HFD-LCT rats were assigned to LCT for 8 weeks. Western blotting, immunohistochemistry and enzyme assays were used to measure expression levels and activities of MSTN, GLUT4, PI3K, Akt and Akt-activated targets (mTOR, FoxO1 and GSK-3β).

RESULTSThe LCT significantly improved IR and whole-body insulin sensitivity in HDF-fed rats. MSTN protein levels decreased in matching serum (42%, P = 0.007) and muscle samples (25%, P = 0.035) and its receptor mRNA expression also decreased (16%, P = 0.041) from obese rats after LCT. But the mRNA expression of insulin receptor had no obvious changes in LCT group compared with NPD and HFD-S groups (P = 0.074). The ladder-climbing training significantly enhanced PI3K activity (1.7-fold, P = 0.024) and Akt phosphorylation (83.3%, P = 0.022) in HFD-fed rats, significantly increased GLUT4 protein expression (84.5%, P = 0.036), enhanced phosphorylation of mTOR (4.8-fold, P < 0.001) and inhibited phosphorylation of FoxO1 (57.7%, P = 0.020), but did not affect the phosphorylation of GSK-3β.

CONCLUSIONSThe LCT significantly reduced IR in diet-induced obese rats. MSTN may play an important role in regulating IR and fat accumulation by LCT via PI3K/Akt/mTOR and PI3K/Akt/FoxO1 signaling pathway in HFD-fed rats.

Animals ; Blotting, Western ; Diet, High-Fat ; adverse effects ; Glucose Tolerance Test ; Glucose Transporter Type 4 ; metabolism ; Immunohistochemistry ; Insulin Resistance ; physiology ; Male ; Myostatin ; metabolism ; Obesity ; etiology ; metabolism ; Phosphatidylinositol 3-Kinases ; metabolism ; Proto-Oncogene Proteins c-akt ; metabolism ; Quadriceps Muscle ; metabolism ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo study the effect of chronic intermittent hypoxia-induced inflammatory cytokines and reoxygenation on glucose transporter 4 (GLUT-4) expression in rat skeletal muscles.

METHODSTwenty-four male Sprague-Dawley rats were randomly assigned to blank control group, chronic intermittent hypoxia (CIH) group, and reoxygenation group. At the end of the experiment, fasting blood glucose (FBG), fasting blood insulin (FINS) and serum inflammatory cytokine levels were measured with glucose oxidase-peroxidase, insulin radioimmunoassay and ELISA, respectively. Homeostasis model assessment (IRI) was used to evaluate insulin resistance in the rats, and GLUT-4 protein expression in the skeletal muscles was measured with Western blotting.

RESULTSCompared with the blank control group, CIH resulted in significantly increased fasting blood glucose, blood insulin levels and insulin resistance index (IRI) (P<0.05); fasting blood glucose was significantly elevated in reoxygenation group (P<0.05). Inflammatory cytokines levels (IL-6 and TNF-α) were significantly higher in CIH group than in the blank control and reoxygenation groups (P<0.05), and were higher in reoxygenation group than in the blank control group. GLUT-4 expression in the skeletal muscles was significantly reduced after CIH (P<0.05) but increased after subsequent reoxygenation (P<0.05).

CONCLUSIONCIH can cause increased release of inflammatory cytokines to lower GLUT-4 protein expression in the skeletal muscles, which contributes to insulin resistance in adult rats.

Animals ; Blood Glucose ; Glucose Transporter Type 4 ; metabolism ; Hypoxia ; Insulin ; blood ; Insulin Resistance ; Interleukin-6 ; Male ; Muscle, Skeletal ; metabolism ; Rats ; Rats, Sprague-Dawley ; Tumor Necrosis Factor-alpha ; blood

Modified Si-Miao-San (mSMS) is composed of Rhizoma Coptidis, Cortex Phellodendri, Rhizoma Coptidis Semen Coicis and Atractylodes Rhizome. The prescription is used for the management of diabetes and insulin resistance in the clinic. This study aims to investigate its regulation of glucose disposal in adipocytes. Differentiated 3T3-L1 adipocytes were stimulated with conditioned medium derived from activated macrophages to induce insulin resistance and observed the effects of Mac-CM on insulin-mediated glucose uptake along the insulin receptor substrate-1/PI3K/Akt signaling pathway. Moreover, its regulation of AMPK phosphorylation was also investigated. mSMS enhanced AMPK phosphorylation and promoted basal glucose uptake in adipocytes; mSMS inhibited NF-κB activation by reducing P65 phosphorylation and improved insulin-stimulated IRS-1 tyrosine and Akt phosphorylation, leading to the restoration of insulin-mediated glucose uptake when cells were exposed to inflammatory stimulation. These beneficial effects were diminished in the presence of the AMPK inhibitor compound C. mSMS positively regulated AMPK activity, and this action contributed to improving insulin PI3K signaling by the beneficial regulation of IRS-1 function through inhibition of inflammation in adipocytes.
3T3-L1 Cells ; Adenosine Monophosphate ; metabolism ; Adenylate Kinase ; metabolism ; Adipocytes ; drug effects ; metabolism ; Animals ; Atractylodes ; Coix ; Coptis ; Diabetes Mellitus ; drug therapy ; metabolism ; Drugs, Chinese Herbal ; pharmacology ; therapeutic use ; Glucose ; metabolism ; Glucose Transporter Type 4 ; metabolism ; Inflammation ; metabolism ; prevention & control ; Insulin ; metabolism ; Insulin Receptor Substrate Proteins ; metabolism ; Insulin Resistance ; Mice ; NF-kappa B ; metabolism ; Phellodendron ; Phosphatidylinositol 3-Kinases ; metabolism ; Phosphorylation ; Phytotherapy ; Proto-Oncogene Proteins c-akt ; metabolism ; Signal Transduction

The present study was undertaken to evaluate the influence of the methanolic fruit extract of Momordica cymbalaria (MFMC) on PPARγ (Peroxisome Proliferator Activated Receptor gamma) and GLUT-4 (Glucose transporter-4) with respect to glucose transport. Various concentrations of MFMC ranging from 62.5 to 500 μg·mL(-1) were evaluated for glucose uptake activity in vitro using L6 myotubes, rosiglitazone was used as a reference standard. The MFMC showed significant and dose-dependent increase in glucose uptake at the tested concentrations, further, the glucose uptake activity of MFMC (500 μg·mL(-1)) was comparable with rosigilitazone. Furthermore, MFMC has shown up-regulation of GLUT-4 and PPARγ gene expressions in L6 myotubes. In addition, the MFMC when incubated along with cycloheximide (CHX), which is a protein synthesis inhibitor, has shown complete blockade of glucose uptake. This indicates that new protein synthesis is required for increased GLUT-4 translocation. In conclusion, these findings suggest that MFMC is enhancing the glucose uptake significantly and dose dependently through the enhanced expression of PPARγ and GLUT-4 in vitro.
Biological Transport ; Dose-Response Relationship, Drug ; Fruit ; Gene Expression ; drug effects ; Glucose ; metabolism ; Glucose Transporter Type 4 ; metabolism ; Hypoglycemic Agents ; pharmacology ; In Vitro Techniques ; Insulin ; metabolism ; Momordica ; Muscle Fibers, Skeletal ; drug effects ; PPAR gamma ; metabolism ; Plant Extracts ; pharmacology ; Protein Biosynthesis ; Protein Synthesis Inhibitors ; pharmacology ; Rosiglitazone ; Thiazolidinediones ; pharmacology ; Up-Regulation