OBJECTIVE: To investigate the effect of signals mediated by activated CD28 in promoting survival of multiple myeloma (MM) cells and metabolic fitness and its possible mechanism. METHODS: The expression of CD28 on 4 MM cell lines (XG2, XG1, RPMI 8226 and U266) was determined by flow cytometry. Two cell lines with the highest or lowest CD28 expression were selected. The proliferation, cell cycle, migration and apoptosis of MM cells in vitro were determined in medium containing high glucose concentration or CD28 agonist monoclonal antibody with different bioassays. shRNA interference assay was used to knock down the expression of CD28 on U266 cells. Then, the effect of activated CD28 on glucose uptake rate and drug resistance in MM cells were analyzed using fluorescent glucose analogues (2-NBDG). The expression of Glut1/4, HkII and Fasn was determined with real time quantitative PCR. RESULTS: Flow cytometry analysis showed that all the four tested MM cell lines expressed CD28 and U266 cells had the highest positive rate. The results of in vitro experiment showed that CD28 activation could significantly up-regulate the expression of Glut4 and HkII, promote MM cell metabolic remodeling, enhance 2-NBDG/glucose uptake, increase energy metabolism, thereby elevating cell proliferation and migration abilities, leading to an increase in the number of cells in S- and G₂-phases. Meanwhile, activated CD28 subsequently up-regulated resistance of MM cells to bortezomib or dexamethasone. CONCLUSION MM cells express high levels of CD28 abnormally, and activation of CD28 can promote up-regulation of glucose uptake in MM cells, thereby promoting cell proliferation and enhancing drug resistance.
Humans ; Multiple Myeloma/pathology* ; CD28 Antigens/metabolism* ; Cell Proliferation ; Cell Line, Tumor ; Apoptosis ; Glucose/metabolism* ; Glucose Transporter Type 4/metabolism* ; Glucose Transporter Type 1

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

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

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

The hippocampus not only plays a role in appetite and energy balance, but also is particularly important in learning and memory. Figuring out the relationships of hippocampal glucose transporter 4 (GLUT4) with hippocampal glucose metabolism and hippocampus-dependent cognitive function is very important to clearly understand the pathophysiological basis of nutritional obesity and diabetes-related diseases, and treat obesity and cognitive dysfunction. Therefore, this study reviewed recent researches conducted on hippocampal GLUT4, hippocampal glucose metabolism, and hippocampus-dependent cognitive function. In this review, we mainly discussed: (1) The structure of GLUT4 and the distribution and function of GLUT4 in the hippocampus; (2) The translocation of GLUT4 in the hippocampus; (3) The relationships of the PI3K-Akt-GLUT4 signaling pathway with the high fat diet-induced changes of cognitive function and the glucose metabolism in the hippocampus; (4) The associations of the PI3K-Akt-GLUT4 signaling pathway with the diabetes-related cognitive dysfunction in the hippocampus; (5) The potential mechanisms of cognitive dysfunction induced by glucose metabolic disorder.
Cognition ; Diet, High-Fat ; Glucose ; Glucose Transporter Type 4 ; Hippocampus ; Signal Transduction

The advantages of monounsaturated fatty acids (MUFAs) on insulin resistance and type 2 diabetes mellitus (T2DM) have been well established. However, the molecular mechanisms of the anti-diabetic action of MUFAs remain unclear. This study examined the anti-hyperglycemic effect and explored the molecular mechanisms involved in the actions of fish oil- rich in MUFAs that had been acquired from hybrid catfish (Pangasius larnaudii×Pangasianodon hypophthalmus) among experimental type 2 diabetic rats. Diabetic rats that were fed with fish oil (500 and 1,000 mg/kg BW) for 12 weeks significantly reduced the fasting plasma glucose levels without increasing the plasma insulin levels. The diminishing levels of plasma lipids and the muscle triglyceride accumulation as well as the plasma leptin levels were identified in T2DM rats, which had been administrated with fish oil. Notably, the plasma adiponectin levels increased among these rats. The fish oil supplementation also improved glucose tolerance, insulin sensitivity and pancreatic histological changes. Moreover, the supplementation of fish oil improved insulin signaling (p-Akt(Ser473) and p-PKC-ζ/λ(Thr410/403)), p-AMPK(Thr172) and membrane GLUT4 protein expressions, whereas the protein expressions of pro-inflammatory cytokines (TNF-α and nuclear NF-κB) as well as p-PKC-θ(Thr538) were down regulated in the skeletal muscle. These data indicate that the effects of fish oil-rich in MUFAs in these T2DM rats were partly due to the attenuation of insulin resistance and an improvement in the adipokine imbalance. The mechanisms of the anti-hyperglycemic effect are involved in the improvement of insulin signaling, AMPK activation, GLUT4 translocation and suppression of pro-inflammatory cytokine protein expressions.
Adipokines ; Adiponectin ; AMP-Activated Protein Kinases ; Animals ; Blood Glucose ; Catfishes ; Cytokines ; Diabetes Mellitus, Type 2 ; Fasting ; Fatty Acids, Monounsaturated ; Fish Oils ; Glucose ; Glucose Transporter Type 4 ; Insulin ; Insulin Resistance ; Leptin ; Membranes ; Muscle, Skeletal ; Plasma ; Rats* ; 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

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

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