Effects of glycemic control on placental glucose transporters in women with hyperglycemia in pregnancy / 中华围产医学杂志

Objective:To investigate the expression of placental glucose transport protein (GLUT)1 and 4 in women with hyperglycemia in pregnancy.Methods:A total of 48 full-term singleton pregnant women who underwent elective cesarean section at Peking University First Hospital from January 2017 to December 2019 were included retrospectively, and were divided into pregestational diabetes mellitus (PGDM) group, gestational diabetes mellitus (GDM) group, and normal glucose tolerance (NGT) group (16 women in each). According to the blood glucose level after control during pregnancy, the PGDM and GDM groups were further divided into PGDM-, GDM-well controlled subgroups (both n=10), and PGDM-, GDM-uncontrolled subgroups (both n=6). The expression of GLUT1 and GLUT4 proteins, detected by Western blot, between different groups were compared and the correlation between GLUT1 and GLUT4 protein expression and the pre-pregnancy body mass index (BMI), pre-delivery weight,gestational weight gain (GWG), and neonatal birth weight were analyzed using two independent samples t-test, one-way analysis of variance, Kruskal-Wallis H-test, Chi-square test, and Pearson correlation analysis. Results:(1) The pre-pregnanct BMI and insulin treatment ratio in PGDM group were higher than those in GDM group and NGT group [27.0 kg/m 2 (22.1-29.9 kg/m 2) vs 22.9 kg/m 2 (20.5-25.7 kg/m 2) and 21.7 kg/m 2 (20.5-24.3 kg/m 2); 13/16 vs 1/16 and 0/16; all P<0.05]. In the PGDM group, fasting blood glucose at the second trimester and mean glycosylated hemoglobin during the second and the third trimester were higher than those in the GDM group [(6.1±1.2) vs (5.0±0.4) mmol/L; (5.9±0.5)% vs (5.2±0.3)%; both P<0.05]. (2) GLUT1 protein level was the highest in the PGDM group, followed by the GDM and NGT group (1.251±0.354 vs 1.004±0.368 vs 0.733±0.216, both P<0.05). And all the subgroups had higher protein level than NGT group [PGDM-good (1.270±0.417); PGDM-uncontrolled (1.218±0.245), GDM-well controlled (0.900±0.424); GDM-uncontrolled (1.177±0.158); LSD test,all P<0.05]. The variation of GLUT4 protein level was consistent with GLUT1. There was no significant difference in GLUT1 and GLUT4 expression between PGDM-uncontrolled and PGDM-well controlled subgroups, neither between GDM-uncontrolled and GDM-well controlled subgroups (all P>0.05). (3) GLUT1 and GLUT4 in the PGDM-well controlled subgroup, as well as GLUT1 in the GDM-uncontrolled subgroup, had a positive correlation with GWG ( r=0.635, 0.810, and 0.833, all P<0.05). Conclusions:The increased expression of placental GLUT1 and GLUT4 were associated with different types of gestational hyperglycemia and GWG. However, glucose control has little effect on placental GLUT expression.

Biochemical and Molecular Mechanisms of Glucose Uptake Stimulated by Physical Exercise in Insulin Resistance State: Role of Inflammation / Mecanismos Bioquímicos e Moleculares da Captação da Glicose Estimulada pelo Exercício Físico no Estado de Resistência à Insulina: Papel da Inflamação

Abstract Obesity associated with systemic inflammation induces insulin resistance (IR), with consequent chronic hyperglycemia. A series of reactions are involved in this process, including increased release of proinflammatory cytokines, and activation of c-Jun N-terminal kinase (JNK), nuclear factor-kappa B (NF-κB) and toll-like receptor 4 (TLR4) receptors. Among the therapeutic tools available nowadays, physical exercise (PE) has a known hypoglycemic effect explained by complex molecular mechanisms, including an increase in insulin receptor phosphorylation, in AMP-activated protein kinase (AMPK) activity, in the Ca2+/calmodulin-dependent protein kinase kinase (CaMKK) pathway, with subsequent activation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), Rac1, TBC1 domain family member 1 and 4 (TBC1D1 and TBC1D4), in addition to a variety of signaling molecules, such as GTPases, Rab and soluble N-ethylmaleimide-sensitive factor attached protein receptor (SNARE) proteins. These pathways promote greater translocation of GLUT4 and consequent glucose uptake by the skeletal muscle. Phosphoinositide-dependent kinase (PDK), atypical protein kinase C (aPKC) and some of its isoforms, such as PKC-iota/lambda also seem to play a fundamental role in the transport of glucose. In this sense, the association between autophagy and exercise has also demonstrated a relevant role in the uptake of muscle glucose. Insulin, in turn, uses a phosphoinositide 3-kinase (PI3K)-dependent mechanism, while exercise signal may be triggered by the release of calcium from the sarcoplasmic reticulum. The objective of this review is to describe the main molecular mechanisms of IR and the relationship between PE and glucose uptake.

Resumo A obesidade associada à inflamação sistêmica induz resistência à insulina (RI), com consequente hiperglicemia crônica. Este processo envolve o aumento na liberação de citocinas pró-inflamatórias, ativação da enzima c-Jun N-terminal cinase (JNK), do fator nuclear kappa-B (NF-κB) e dos receptores do tipo Toll 4 (TLR4). Dentre as ferramentas terapêuticas disponíveis, o exercício físico (EF) tem efeito hipoglicemiante conhecido, explicado por mecanismos moleculares complexos. Dentre eles, ocorre aumento na fosforilação do receptor da insulina, na atividade da proteína quinase ativada por AMP (AMPK), na via da proteína cinase cinase dependente de Ca+2/calmodulina (CaMKK), com posterior ativação do coativador-1α do receptor ativado por proliferador do peroxissoma (PGC-1α), proteínas Rac1, TBC1 membro das famílias de domínio 1 e 4 (TBC1D1 e TBC1D4), além de uma variedade de moléculas de sinalização, como as proteínas GTPases, Rab e proteína solúvel de fusão sensível a N-etil-maleimida (SNARE); estas vias promovem maior translocação de transportador de glicose do tipo 4 (GLUT4) e consequente captação de glicose pelo músculo esquelético. A cinase fosfatidilinositol-dependente (PDK), proteína quinase C atípica (aPKC) e algumas das suas isoformas, como a PKC-iota/lambda também parecem desempenhar papel fundamental no transporte de glicose. Nesse sentido, a associação entre autofagia e EF também tem demonstrado papel relevante na captação de glicose muscular. A insulina, por sua vez, utiliza um mecanismo dependente da fosfatidilinositol-3-quinase (PI3K), enquanto que o sinal do EF pode ter início mediante liberação de cálcio pelo retículo sarcoplasmático e concomitante ativação da AMPK. O objetivo desta revisão é descrever os principais mecanismos moleculares da RI e da relação entre o EF e a captação de glicose.

Avaliação do mecanismo epigenético por metilação do DNA e da expressão de GLUT4 em tecido muscular esquelético de ratos adultos, proles de ratas com doença periodontal / Evaluation of the epigenetic mechanism by DNA methylation and GLUT4 expression in skeletal muscle tissue of adult rats, prole of rats with periodontal disease

Atualmente, está bem estabelecido que o ambiente fetal está ligado à saúde materna, e estímulos ou agressões anormais durante a vida intra-uterina podem resultar em mudanças na fisiologia e metabolismo da prole, aumentando o risco de doenças na vida adulta. Tal fenômeno é conhecido como programação fetal. Alterações na metilação do DNA e expressão gênica são consideradas mecanismos moleculares responsáveis por esta programação. Estudos anteriores demonstraram que a doença periodontal (DP) materna promove resistência insulínica, aumento nas concentrações plasmáticas de citocinas, redução do conteúdo de GLUT4 e do seu índice de translocação para membrana plasmática em sua prole adulta. E citocinas, como por exemplo, o TNF-α, têm sido relacionadas com a redução da expressão de GLUT4 por meio da ativação do fator de transcrição nuclear κappa B (NF-κB). Além disso, esta citocina pode estimular algumas serinas quinases, incluindo IκB quinase (IKK), c-Jun amino-terminal kinase (JNK) e quinases reguladas por sinais extracelulares (ERKs) que estão envolvidas na resistência insulínica. Tais achados evidenciam a necessidade de realizar mais estudos para verificar os mecanismos envolvidos nestas alterações. Portanto, os objetivos do presente estudo foram avaliar em ratos adultos, proles de ratas com DP: 1) massa corpórea ao longo de 75 dias de idade; 2) glicemia e insulinemia; 3) expressão do RNAm da proteína transportadora de glicose GLUT4 e do IRS1 em muscular esquelético gastrocnêmio (MG); 4) o grau de metilação do DNA na região promotora do gene do GLUT4 em MG; 5) fosforilação das proteínas JNK, IKKα/ß, ERK 1/2, NF-κBp65 e NF-κBp50 e seus conteúdos totais em MG; 6) conteúdo total de TNF-α em MG. As ratas foram divididas em dois grupos: 1) com doença periodontal (DP), no qual esta doença foi induzida por meio de ligadura com fio de seda ao redor do 1º molar inferior; 2) ratas controle (CN). Após 7 dias da colocação da ligadura, as ratas de ambos os grupos foram colocadas para acasalamento, verificou-se diariamente, por esfregaço vaginal, o dia da copulação. As ratas prenhas foram separadas em caixas individuais. Quando os filhotes machos destas ratas completaram 75 dias, realizaram-se os experimentos: 1) glicemia e insulinemia; 2) expressão do RNAm do GLUT4 e do IRS1 em MG; 3) o grau de metilação do DNA na região promotora do gene do GLUT4 em MG; 4) fosforilação das proteínas JNK, IKKα/ß, ERK 1/2, NF-κBp65 e NF-κBp50 e seus conteúdos totais em MG; 5) conteúdo total de TNF-α em MG. Os resultados demonstraram que a doença periodontal materna promove na sua prole adulta baixo peso ao nascimento (BPN), resistência insulínica, aumento do conteúdo total de TNF-α em MG, aumento do grau de fosforilação de IKKα/ß, ERK 1/2, NF-κBp65 (grau de fosforilação e conteúdo) e NF-κBp50 em MG, diminuição na expressão gênica da proteína transportadora de glicose GLUT4 e aumento na expressão gênica do IRS1; porém não promove nessa prole alteração no grau de metilação do DNA na região promotora do gene do GLUT4, e no grau de fosforilação da proteína JNK em MG. Portanto, este estudo é de fundamental importância para o entendimento de alguns dos mecanismos envolvidos na relação entre a doença periodontal materna e resistência à insulina na prole adulta. Além disso, mostra que a saúde bucal materna ideal pode ajudar a prevenir doenças futuras na prole adulta(AU)

It is well established that the fetal environment is linked to maternal health, and abnormal stimuli or aggressions during intrauterine life can result in changes in the physiology and metabolism of offspring, increasing the risk of disease in adult life, this phenomenon is known as fetal programming. Changes in DNA methylation and gene expression are considered molecular mechanisms responsible for this programming. Previous studies have demonstrated that maternal periodontal disease (PD) promotes insulin resistance, increased plasma concentrations of cytokines, reduced GLUT4 content and its plasma membrane translocation index in its adult offspring. And cytokines, such as TNF-α, have been linked to reduced GLUT4 expression through the activation of nuclear transcription factor kappa B (NF-κB). In addition, this cytokine can stimulate some serine kinases including IκB kinase (IKK), c-Jun amino-terminal kinase (JNK) and extracellular signal­regulated kinases (ERKs) that are involved in insulin resistance. These findings evidenced the need for further studies to verify the mechanisms involved in these changes. Therefore, the objectives of the present study were to evaluate in adult rats, offspring of rats with PD: 1) birth weight and during the 75 days of age; 2) glycemia and insulinemia; 3) GLUT4 and IRS1 mRNA expression in skeletal muscle gastrocnemius (MG); 4) the degree of DNA methylation in the promoter region of the GLUT4 gene in MG; 5) phosphorylation of JNK, IKKα/ß, ERK 1/2, NF-κBp65 and NF-κBp50 proteins and their total contents in MG; 6) TNF-α content in MG. Female Wistar rats were distributed into a control group and an experimental periodontal disease group, in which the disease is induced by ligation with silk thread around the 1st molar. Seven days after ligature placement, animals from both groups mated and daily vaginal smears were taken to verify the presence of sperm. Pregnant rats were kept in individual cages. The body weights of the offspring were measured once weekly from birth until 75 days of age. When male offspring of these rats completed 75 days, the experiments were performed: 1) glycemia and insulinemia; 2) GLUT4 and IRS1 mRNA expression in skeletal muscle gastrocnemius (MG); 3) the degree of DNA methylation in the promoter region of the GLUT4 gene in MG; 4) phosphorylation of JNK, IKKα/ß, ERK 1/2, NF-κBp65 and NF-κBp50 proteins and their total contents in MG; 5) TNF-α content in MG. The results demonstrated that maternal periodontal disease promotes in its adult offspring low birth weight (LBW), insulin resistance, increased TNF-α content in MG, increased IKKα/ß, ERK 1/2, NF-κBp65 (phosphorylation status and content) and NF-κBp50 phosphorylation status in the MG, decrease in gene expression of GLUT4 and increase in IRS1 gene expression; but does not promote in this progeny change in the degree of DNA methylation in the promoter region of the GLUT4 gene, and JNK phosphorylation status in MG. Therefore, this study is of fundamental importance for the understanding of some of the mechanisms involved in the relationship between maternal periodontal disease and insulin resistance in adult offspring. In addition, it shows that ideal maternal oral health can help prevent future illnesses in adult offspring(AU)

Role of Rab proteins in glucose transporter 4 translocation:research advances / 中国药理学与毒理学杂志

Insulins maintain blood glucose homeostasis in the body by stimulating glucose uptake into muscle and adipose tissues through glucose transporter type 4 (GLUT4)translocation. Recent studies have showed that Rab proteins,as a key regulatory factor for the translocation of GLUT4 to the cell membrane,participate in the formation,translocation and fusion of GLUT4 vesicles. This paper describes several types Rab proteins and the Rab GTPase activating protein,protein kinase B substrate of 160 kU(AS160)in terms of regulatory mechanisms for GLUT4 translocation. Studies on the translocation mechanism by which GLUT4 is regulated by Rabs aim to explain the mechanism of insulin resistance in type 2 diabetes,and provide a new approach to diabetes.

Activation of AMPK and PPARγby emodin influences glucose uptake in 3 T3-L1 adipocytes / 中国药理学通报

Aim To investigate glucose uptake effects and mechanism of emodin in 3T3-L1 adipocytes. Methods LPS-induced differentiated 3 T3-L1 adipo-cytes were divided into control group and emodin ( 1 , 10, 50 μmol · L-1 ) groups. Then, 6-NBDG uptake and the expression of cell surface GLUT4 , PPARγ, AMPKα1/2 , p-AMPKα1/2 , IRS-1 , p-IRS-1 , Adi-ponectin, chREBP-α and chREBP-β were detected. The ability of 6-NBDG uptake in LPS-induced 3 T3-L1 adipocytes was also evaluated following interference with AMPK inhibitor and PPARγinhibitor, respective-ly. Meanwhile, STZ-induced diabetic rats were ran-domly divided into control group and emodin treatment group. The mRNA expression of Adiponectin and pro-tein expression of cell surface GLUT4 , AMPKα1/2 , p-AMPKα1/2 were measured. Results Compared with the control group, emodin improved the mRNA expres-sion of cell surface GLUT4, Adiponectin, chREBP-αand chREBP-β, and protein expression of cell surface GLUT4 , PPARγ, IRS-1 , p-IRS-1 , AMPKα1/2 and p-AMPKα1/2 in 3T3-L1 adipocytes(P<0. 05). Emodin enhanced 6-NBDG uptake and the uptake of emodin group was both decreased following interference with AMPK inhibitor and PPARγ inhibitor, respectively ( P<0. 05 ) . Emodin also increased the mRNA expression of Adiponectin and protein expression of cell surface GLUT4 , AMPKα1/2 and p-AMPKα1/2 in adipose tis-sue of T2 DM rats ( P <0. 05 ) . Conclusion Emodin can enhance glucose uptake in 3 T3-L1 adipocytes and the mechanism is probably associated with activating Adiponectin and IRS-1 , thereby activating AMPK and PPARγ.

Avaliação da fosforilação da AKT e do conteúdo da proteína transportadora de glicose GLUT4 em tecido muscular esquelético de ratos adultos, proles de ratas com doença periodontal / Evaluation of Akt phosphorylation and glucose transporter protein 4 (GLUT4) content in gastrocnemius skeletal muscle tissue of adult rats, offspring of rats with periodontal disease

A hipótese da programação fetal sugere que estímulos ou agressões durante a vida intrauterina podem resultar em alterações permanentes na fisiologia e metabolismo da descendência, aumentando o risco de doenças na vida adulta. Estudos demonstraram que tanto a doença periodontal (DP) como o aumento do tecido adiposo elevam a concentração plasmáticas de citocinas. E citocinas, como por exemplo, o TNF-, têm sido relacionadas com a redução da expressão de GLUT4 e resistência à insulina. Sabendo que o GLUT4 é importante para homeostase glicídica, o objetivo do presente estudo foi avaliar em ratos, proles de ratas com doença periodontal ao nascimento, a massa corpórea, e na vida adulta: 1) massa corpórea ao longo de 75 dias de idade; 2) o conteúdo da proteína transportadora de glicose GLUT4 e o seu índice de translocação em tecido muscular esquelético gastrocnêmio (MG); 3) o grau de fosforilação em serina da Akt em MG. As ratas foram distribuidas em dois grupos: a) com doença periodontal (DP), no qual esta doença foi induzida por meio de ligadura com fio de seda ao redor do 1º molar inferior de ambos os lados; b) ratas controle (CN). Após 7 dias da colocação da ligadura, as ratas de ambos os grupos foram colocadas para acasalamento, verificou-se diariamente, por esfregaço vaginal, o dia da copulação. As ratas prenhas foram separadas em caixas individuais. A massa corpórea da prole foi avaliada ao nascimento e durante os 75 dias de idade. Quando os filhotes machos destas ratas completaram 75 dias, realizou-se: 1) dosagem de glicemia e insulinemia; 2) avaliação da proteína transportadora de glicose GLUT4 e seu índice de translocação em MG; 3) avaliação do grau de fosforilação em serina da Akt em MG. Os resultados demonstraram que a doença periodontal materna promove em sua prole ao nascimento baixo peso e na vida adulta: 1) nenhuma alteração nas concentrações plasmáticas de glicose; 2) aumento nas concentrações plasmáticas de insulina; 3) redução na sensibilidade..

The fetal programming hypothesis suggests that intrauterine stimuli or aggression can induce metabolic and physiology changes in offspring, increasing the diseases risk in adulthood. Studies have demonstrated that periodontal disease (PD) and adipose tissue augmentation enhance the cytokines levels. Cytokines such as TNF-α have been associated with reduced GLUT4 expression and insulin resistance. Knowing that GLUT4 is important for glucose homeostasis, the aim of present study was to evaluate in adult rats, offspring of rats with periodontal disease: 1) birth weight and during the 75 days of age; 2) GLUT4 content and its translocation index in gastrocnemius skeletal muscle tissue (GM); 3) Akt serine phosphorylation status in MG. Female Wistar rats were distributed into a control group (CN, n = 4) and a experimental periodontal disease group (PD, n = 4), in which the disease is induced by ligation with silk thread around the 1st molar. Seven days after ligature placement, animals from both groups mated and daily vaginal smears were taken to verify the presence of sperm. Pregnant rats were kept in individual cages. The body weights of the offspring were measured once weekly from birth until 75 days of age. When male offspring of these rats completed 75 days, the experiments were performed: 1) assessment of plasma concentrations of glucose and insulin; 2) evaluation of the GLUT4 content and its translocation index in GM; 3) Akt serine phosphorylation status in GM. The results showed that maternal periodontal disease causes in their offspring low birth weight, and in adulthood: 1) no changes in glycemia; 2) increase in insulinemia; 3) insulin resistance; 4) decrease in GLUT4 content in the plasma membrane and its translocation index in GM; 5) reduction in the Akt serine phosphorylation status in GM. Therefore, we can conclude that maternal periodontal disease causes low birth weight and alterations in the final stage of insulin signaling in skeletal muscle of...

Hypoglycemic Mechanism of Total Saponins of Momordica Charantia in Type 2 Diabetes Mellitus Rats / 天津医药

Objective To observe the hypoglycemic mechanism of total saponins of Momordica charantia (MC) in type 2 diabetes mellitus (DM) rats. Methods Among the selected 60 male Specific Pathogen Free (SPF)rats, 8 were random- ly chosen as control group, while others were fed with high fat and high glucose diet following streptozotocin injection from caudal vein 8 weeks after to construct type 2 DM models. After the DM models were successfully built, rats were then ran- domized into five groups: DM control group (n=8), the metformin group (n=8) and three groups of total saponins of MC with different dosage (n=8 in each group). The total saponins of MC groups include DM rats administrated with total saponins of MC 100, 200, 400 mg/(kg·d) for 8 weeks, the metformin group include DM rats administrated with metformin 50 mg/(kg·d) for 8 weeks. At the end of the experiment, the fasting blood glucose and insulin were examed. At the same time, a part of pan- creas islet, liver and skeletal muscle were preserved. The pancreas islet structure, the hepatic glycogen and Glucose trans- porter 4 (GLUT4) expression were observed by electron microscope, glycogen dyeing and immunoblot respectively. Results After 8 weeks treatment, compared to type 2 DM control group, fasting blood glucose and insulin values in MC groups were reduced more obviously. However, skeletal muscle GLUT4 expression level, insulin granules and hepatic glycogen increased obviously in MC groups. Conclusion Total saponins of MC has hypoglycemic effect. It’s mechanisms maybe include pro- moting the hepatic glycogen synthesis, inhibiting the hepatic glycogen decomposition and promoting insulin sensitivity by in- creasing peripheral tissue’s GLUT4 expression.

GLU4-may increase insulin sensitivity in type 2 diabetic rats / 中国医师杂志

Objective To investigate effect of berberine on fasting glucose , fasting serum insulin, islet morphology, and ex-pression of glucose transporter 4 (GLU-4) of islet in type 2 diabetes mellitus (T2DM) rats.The present study aimed to evaluate the ually, especially for high-dose group ( P <0.01).⑷Compared with normal group , INS of diabetic control group was significantly de-creased ( P <0.05), INS of low-dose, middle-dose, and high-dose groups were all increased gradually , especially for high-dose group ( P <0.01 ) .Conclusions Berberine has the effects of antidiabetes via ameliorate insulin sensitivity , and promotes GLUT-4 protein expression .

Expression of Akt and GLUT-4 in adipose tissue of women with gestational diabetes mellitus and pregnant women with excessive weight gain / 解放军医学杂志

 Objective To investigate the influence of glucose transporter 4 (GLUT-4) and protein kinase B (Akt) on gestational diabetes mellitus (GDM) by determining their expressions in adipose tissues from women with GDM, excessive weight gain pregnant women, and normal pregnant women. Methods Adipose tissues were obtained by biopsy during cesarean section from 15 pregnant women with normal glucose tolerance while their body mass index (BMI) increased in about 4kg/m (NG 2group), and 15 pregnant women with normal glucose tolerance with BMI increased by 8kg/m (NGT2 group), and 15 cases of GDM (GDM group). Adipose tissue were divided into two sections and incubated in the culture medium with or without insulin (1 X 10 mol/L) for 30 minutes. Fasting blood glucose (FBG) and fasting insulin (FINS) levels were determined with glucose oxidase and radioimmunoassay. Homeostatic model assessment of insulin resistance (HOMA-IR), and homeostatic model assessment of insulin secretions index (HOMA-IS) were calculated from the data. Phosphorylation of Akt (P-Akt) and GLUT-4 levels of cultured adipose tissue were examined by Western blotting. Results The FBG levels were similar in 3 groups. FINS, HOMA-IR and HOMA-IS were significantly different among the 3 groups (P0.05) in basal state. Compared with the basal state, however, the phosphorylation of Akt increased significantly in NGT1 group (P0.05) after insulin stimulation. The expression of GLUT-4 was significantly lower in GDM group and NGT2 group than in NGT1 group (P<0.05) in basal state. The expression of GLUT-4 increased much more in NGT1 group than in NGT2 group or GDM group (P<0.05) after insulin stimulation. Conclusion The excessive weight gain and normal glucose tolerance pregnant women almost share a similar expression with GDM women in the insulin signaling and glucose transporter proteins, Akt and GLUT-4, and their abnormal expression and function might play an important role in insulin resistance and GDM morbidity.

Avaliação da fosforilação da Akt e do conteúdo da proteína transportadora de glicose GLUT4 em músculo esquelético de ratos adultos com lesão periapical / Evaluation of phosphorylation of akt and content of glucose transporter protein glut4 in skeletal muscle of rats with periapical lesion

Atualmente, há certo consenso dentro da área odontológica relacionado ao fato de que inflamações crônicas nos dentes, podem eventualmente ocasionar desordens sistêmicas. A Lesão Periapical (LP) é caracterizada como uma inflamação oral e está associada ao aumento da quantidade de citocinas pró-inflamatórias, tais como, IL-6 e TNF-α, que possivelmente induzem resistência insulínica. A resistência à insulina pode ser definida como o estado no qual existe uma menor captação tecidual de glicose em resposta ao estímulo insulínico; no entanto, os mecanismos que causam resistência à insulina não são totalmente compreendidos. Estudos anteriores do nosso laboratório demonstraram que ratos adultos com LP apresentam alterações na etapa inicial da via do sinal insulínico e menor sensibilidade à insulina. Baseado nisto, mais estudos são necessários para verificar se estas alterações também estão presentes na continuidade da cascata insulínica e na expressão da proteína transportadora de glicose 4 (GLUT4). Os objetivos do presente estudo foram avaliar em ratos com LP: 1) glicemia e insulinemia (n=10); 2) sensibilidade à insulina por meio do índice de HOMA-IR (n=10); 3) grau de fosforilação em serina/treonina da Akt em tecido muscular esquelético gastrocnêmio (GM) (n=6); 4) conteúdo de GLUT4 e seu índice de translocação para membrana plasmática em GM (n=5). Para tanto, foram utilizados 32 ratos Wistar (2 meses de idade) distribuídos em dois grupos: a) ratos do grupo controle, sem a LP; b) ratos com LP induzida em molares superiores direito empregando-se broca em aço carbono dotada de esfera na extremidade com 0,1 mm. A partir dos resultados pôde-se observar que os ratos com LP apresentaram: 1) nenhuma diferença na glicemia e insulinemia; 2) redução na sensibilidade à insulina, avaliado pelo índice de HOMA-IR; 3) diminuição no grau de fosforilação em serina da Akt após estímulo insulínico em GM, mas nenhuma diferença no grau de fosforilação da Akt em treonina; 4) redução do...

Currently, there is some consensus in the dental area related to the fact that chronic inflammation in teeth may eventually lead to systemic disorders. Periapical lesion (PL) is characterized as an oral inflammation and it is associated to the increase of proinflammatory citokines, such as IL-6 and TNF-alpha, that can possibly induce insulin resistance. Insulin resistance can be defined as the state in which there is a glucose uptake decrease by tissue in response to insulin stimulation, however, the mechanisms that cause insulin resistance are not totally understood. Former studies from our laboratory demonstrated that adult rats with periapical lesion showed changes in the initial stage of insulin signaling and lower insulin sensitivity. Based on that, more studies are needed in order to verify whether these changes are also present in the continuity of the insulin signaling cascade and glucose transporter protein 4 (GLUT4) expression. The aims of this study were to evaluate in rats with PL: 1) plasma glucose and insulin levels (n=10); 2) insulin sensitivity by the HOMA-IR index (n=10); 3) serine/ threonine phosphorylation status of Akt in skeletal muscle gastrocnemius (GM) (n=6); 4) content of GLUT4 protein and its translocation index for plasma membrane in GM (n=5). Therefore, 32 Wistar rats (2 months old) were used and divided into two groups: a) control rats without PL b) rats with PL induced in right upper molars by using a carbon steel drill fitted with ball 0.1 mm. From the results it was observed that rats with PL showed: 1) no difference in blood glucose and insulin; 2) decrease in insulin sensitivity assessed by HOMA-IR index; 3) decrease in the serine phosphorylation status of Akt in GM after insulin stimulation, but no difference in the phosphorylation status of Akt in threonine; 4) decrease in the GLUT4 content in the plasma membrane, but no change in the microsome. From these results we conclude that the PL promoted insulin resistance...

Aerobic exercise training induces metabolic benefits in rats with metabolic syndrome independent of dietary changes

OBJECTIVES: We evaluated the effects of aerobic exercise training without dietary changes on cardiovascular and metabolic variables and on the expression of glucose transporter Type 4 in rats with metabolic syndrome. METHODS: Twenty male spontaneously hypertensive rats received monosodium glutamate during the neonatal period. The animals were allocated to the following groups: MS (sedentary metabolic syndrome), MS-T (trained on a treadmill for 1 hour/day, 5 days/week for 10 weeks), H (sedentary spontaneously hypertensive rats) and H-T (trained spontaneously hypertensive rats). The Lee index, blood pressure (tail-cuff system), insulin sensitivity (insulin tolerance test) and functional capacity were evaluated before and after 10 weeks of training. Glucose transporter Type 4 expression was analyzed using Western blotting. The data were compared using analysis of variance (ANOVA) (p<0.05). RESULTS: At baseline, the MS rats exhibited lower insulin sensitivity and increased Lee index compared with the H rats. Training decreased the body weight and Lee index of the MS rats (MS-T vs. MS), but not of the H rats (H-T vs. H). There were no differences in food intake between the groups. At the end of the experiments, the systolic blood pressure was lower in the two trained groups than in their sedentary controls. Whole-body insulin sensitivity increased in the trained groups. Glucose transporter Type 4 content increased in the heart, white adipose tissue and gastrocnemius muscle of the trained groups relative to their respective untrained groups. CONCLUSION: In conclusion, the present study shows that an isolated aerobic exercise training intervention is an efficient means of improving several components of metabolic syndrome, that is, training reduces obesity and hypertension and increases insulin sensitivity. .

Thyroid-stimulating hormone inhibits glucose transporter4 translocation through an extra-thyroidal pathway in 3T3-L1 adipocytes / 中华老年医学杂志

Objective To test thyroid-stimulating hormone (TSH) suppress GLUT4 expression and translocation by stimulating TNF-α secretion in 3T3-L1 adipocytes via a cAMP-PKA pathway.Methods 3T3-L1 preadipocytes were induced to differentiate into adipocytes.The adipocytes were treated with bovine TSH,Forskolin,H89 and Rapamycin,respectively.The concentration of TNF-α in the cell culture medium was measured by ELISA.The level of GLUT4 mRNA in adipocytes was assessed by real time polymerase chain reaction.Protein levels of GLUT4 in total cell lysates and plasma membrane lysates were quantified by Western blotting.Results Incubating 3T3-L1 adipocytes with TSH markedly increased the concentration of TNF-α in medium in a time-and dosedependent manner (P ＜ 0.05); meanwhile,the levels of GLUT4 mRNA and total and plasma membrane GLUT4 protein were decreased in a dose-dependent manner (P＜0.05 or ＜0.01).H89 and rapamycin could block the above effects respectively (326.7±43.2 vs.341.9±12.0,P＞0.05).However,there was no statistical difference in the TNF-α levels between stimulation with 1 μmmol/L forskolin versus 0.04 μmmol/L bovine TSH (481.9± 28.4 vs.522.7± 36.2,P＞0.05).Conclusions TSH can down-regulate GLUT4 expression and translocation in 3T3-L1 adipocytes by stimulating TNF-α secretion through a cAMP-PKA pathway.

Effect of 17-β-estradiol on the expression of glucose transporter 4 in rat primary culture skeletal muscle cells with insulin resistance induced by palmitinic acid / 中华老年医学杂志

Objective To investigate the effect of 17-β-estradiol (17-β-E2) on the expression of glucose transporter 4 (GLUT4) in rat primary culture skeletal muscle cells with insulin resistance (IR) induced by palmitinic acid (PA).Methods Rat skeletal muscle was primarily cultivated.The cells were identified by the technology of immunofluorescence.Cells were inclubated with 0.6 mmol/L palmitinic acid for 24 h to induce IR.The concentration of glucose in the medium was measured.The mRNA and protein expressions of protein kinase B (PKB/Akt) and GLUT4 were measured by real time polymerase chain reaction (PCR) and Western blot respectively.Results Compared the control with PA treated rats,the concentration of glucose in the medium was increased [(3.86±0.64)mmol/L vs.(5.43±0.55) mmol/L,q＝4.13,P＜0.05],uptake of glucose stimulated by insulin was decreased (P＜0.01),the expressions of GLUT4 and phosphorylation PKB/Akt were reduced in the PA group (all P＜0.05).In the 17-β-E2 (100 nmol/L) versus control,the concentration of glucose in the medium was higher [(3.86±0.64) vs.(3.77±0.35)mmol/L,q＝ 4.76,P＜0.05],uptake of glucose stimulated by insulin was increased (P＜0.01) and the expressions of GLUT4 and p-Akt were also increased (all P＜0.05).17-β-E2 (10 nmol/L and 100 nmol/L) reversed the decrease of basal and insulin-stimulated uptake of glucose induced by PA,reversed the decrease of GLUT4 and p-Akt expression induced by PA compared with the PA group (all P＜ 0.05).Conclusions 17-β-E2 inhibits insulin resistance induced by PA in rat primary culture skeletal muscle cells,the mechanism may be correlated with the up-regulation of expression of phospho-Akt and GLUT 4 induced by 17-β-E2.

Chronic ethanol feeding impairs AMPK and MEF2 expression and is associated with GLUT4 decrease in rat myocardium

Chronic and heavy alcohol consumption is one of the causes of heart diseases. However, the effects of ethanol on insulin sensitivity in myocardium has been unclear. To investigate the effects of ethanol on the expression of AMP-activated protein kinase (AMPK), myocyte enhancer factor 2 (MEF2) and glucose transporter 4 (GLUT4), all of which are involved in the regulation of insulin sensitivity, in the myocardium, we performed three parts of experiments in vivo and in vitro. I: Rats were injected with 5-amino-4-imidazolecarboxamide ribonucleotide (AICAR, 0.8 mg.kg(-1)) for 2 h. II: Rats received different dose (0.5, 2.5 or 5 g.kg(-1).d(-1)) of ethanol for 22-week. III: Primary neonatal rat cardiomyocytes were isolated and treated with or without 100 mM ethanol or 1 mM AICAR for 4 h. The cardiac protein and mRNA expression of AMPKalpha subunits, MEF2 and GLUT4 were observed by western-blotting and RT-PCR, respectively. Serum TNFalpha levels were assessed by ELISA. The results showed chronic ethanol exposure induced insulin resistance. Ethanol decreased the mRNA levels of AMPKalpha1 and alpha2, the protein levels of total- and phospho-AMPKalpha in cardiomyocytes. Similarly, ethanol showed inhibitory effects on both the mRNA and protein levels of MEF2A and 2D, and GLUT4 in a dose-response-like fashion. Correlation analysis implied an association between phospho-AMPKalpha and MEF2A or MEF2D, and between the levels of MEF2 protein and GLUT4 transcription. In addition, ethanol elevated serum TNFalpha level. Taken together, chronic ethanol exposure decreases the expression of AMPKalpha and MEF2, and is associated with GLUT4 decline in rat myocardium.

Effects of Endurance Exercise and High-Fat Diet on Insulin Resistance and Ceramide Contents of Skeletal Muscle in Sprague-Dawley Rats / 당뇨병

BACKGROUND: We evaluated the effects of endurance exercise and a high-fat diet on insulin resistance and ceramide contents of skeletal muscle in Sprague-Dawley rats. METHODS: We randomly divided 32 rats into four groups: control (CON, n = 8), high fat diet (HF, n = 8), exercise (Ex, 24 m/min for 2 hours, 5 days/wk, n = 8), HF/Ex (n = 8). After 4-week treatments, plasma lipid profiles, glucose and insulin concentrations were measured. The triglycerides (TG), ceramide, and glucose transporter 4 (GLUT-4) contents were measured in the skeletal muscle. The rate of glucose transport was determined under submaximal insulin concentration during the muscle incubation. RESULTS: Free fatty acid levels were significantly higher in CON and HF than Ex (P = 0.032). Plasma glucose levels in HF were significantly higher than the two Ex groups (P = 0.002), and insulin levels were significantly higher in HF than in other three groups (P = 0.021). Muscular TG concentrations were significantly higher in HF than CON and Ex and also in HF/Ex than Ex, respectively (P = 0.005). Hepatic TG concentrations were significantly higher in HF than other three groups but Ex was significantly lower than HF/Ex (P = 0.000). Muscular ceramide content in HF was significantly greater than that in either Ex or HF/Ex (P = 0.031). GLUT-4 levels in CON and HF were significantly lower than those in Ex and HF/Ex (P = 0.009, P = 0.003). The glucose transport rate in submaximal insulin concentration was lower in CON than in either Ex or HF/Ex (P = 0.043), but not different from HF. CONCLUSION: This study suggests that high fat diet for 4 weeks selectively impairs insulin resistance, but not glucose transport rate, GLUT-4 and ceramide content in skeletal muscle per se. However, endurance exercise markedly affects the content of ceramide and insulin resistance in muscle.

Aging impairs insulin-stimulated glucose uptake in rat skeletal muscle via suppressing AMPKalpha

Insufficient intracellular fat oxidation is an important contributor to aging-related insulin resistance, while the precise mechanism underlying is unclear. AMP-activated protein kinase (AMPK) is an important regulator of intracellular fat oxidation and was evidenced to play a key role in high-glucose and high-fat induced glucose intolerance. In the present study, we investigated whether altered AMPK expression or activity was also involved in aging-related insulin resistance. Insulin sensitivity of rats' skeletal muscles was evaluated using in-vitro glucose uptake assay. Activity of alpha subunit of AMPK (AMPKalpha) was evaluated by measuring the phosphorylation of both AMPKalpha (P-AMPKalpha) and acetyl-CoA carboxylase (P-ACC), while expression of AMPKalpha was assessed by determining the mRNA levels of AMPKalpha1 and AMPKalpha2, and protein contents of AMPKalpha. Compared with 4-month old rats, 24-month old rats exhibited obviously impaired insulin sensitivity. At the same time, AMPKalpha activity significantly decreased, while AMPKalpha expression did not alter during aging. Glucose transporter 4 expression also decreased in old rats. Compared with 24-month old rats, administration of the specific activator of AMPK, 5-aminoimidazole-4-carboxamide riboside (AICAR), significantly elevated AMPKalpha activity and GluT4 expression. Also, aging-related insulin resistance was significantly ameliorated by AICAR treatment. In conclusion, aging-related insulin resistance is associated with impaired AMPKalpha activity and could be ameliorated by AICAR, thus indicating a possible role of AMPK in aging-induced insulin resistance.

Exercise type and muscle fiber specific induction of caveolin-1 expression for insulin sensitivity of skeletal muscle

It is well known that exercise can have beneficial effects on insulin resistance by activation of glucose transporter. Following up our previous report that caveolin-1 plays an important role in glucose uptake in L6 skeletal muscle cells, we examined whether exercise alters the expression of caveolin-1, and whether exercise-caused changes are muscle fiber and exercise type specific. Fifity week-old Sprague Dawley (SD) rats were trained to climb a ladder and treadmill for 8 weeks and their soleus muscles (SOL) and extensor digitorum longus muscles (EDL) were removed after the last bout of exercise and compared with those from non-exercised animals. We found that the expression of insulin related proteins and caveolins did not change in SOL muscles after exercise. However, in EDL muscles, the expression of insulin receptor beta (IRbeta) and glucose transporter-4 (GLUT-4) as well as phosphorylation of AKT and AMPK increased with resistance exercise but not with aerobic exercise. Also, caveolin-1 and caveolin-3 increased along with insulin related proteins only in EDL muscles by resistance exercise. These results suggest that upregulation of caveolin-1 in the skeletal muscle is fiber specific and exercise type specific, implicating the requirement of the specific mode of exercise to improve insulin sensitivity.

Implication of phosphorylation of the myosin II regulatory light chain in insulin-stimulated GLUT4 translocation in 3T3-F442A adipocytes

In adipocytes, insulin stimulates glucose transport primarily by promoting the translocation of GLUT4 to the plasma membrane. Requirements for Ca2+/ calmodulin during insulin-stimulated GLUT4 translocation have been demonstrated; however, the mechanism of action of Ca2+ in this process is unknown. Recently, myosin II, whose function in non-muscle cells is primarily regulated by phosphorylation of its regulatory light chain by the Ca2+/calmodulin-dependent myosin light chain kinase (MLCK), was implicated in insulin-stimulated GLUT4 translocation. The present studies in 3T3- F442A adipocytes demonstrate the novel finding that insulin significantly increases phosphorylation of the myosin II RLC in a Ca2+-dependent manner. In addition, ML-7, a selective inhibitor of MLCK, as well as inhibitors of myosin II, such as blebbistatin and 2,3-butanedione monoxime, block insulin- stimulated GLUT4 translocation and subsequent glucose transport. Our studies suggest that MLCK may be a regulatory target of Ca2+/calmodulin and may play an important role in insulin-stimulated glucose transport in adipocytes.