GLUT4 Content Research Articles

Enduring metabolic modulation in the cardiac tissue of elderly CD-1 mice two months post mitoxantrone treatment

Mitoxantrone (MTX) is a therapeutic agent used in the treatment of solid tumors and multiple sclerosis, recognized for its cardiotoxicity, with underlying molecular mechanisms not fully disclosed. The cardiotoxicity is influenced by risk factors, including age. Our study intended to assess the molecular effect of MTX on the cardiac muscle of old male CD-1 mice. Mice aged 19 months received a total cumulative dose of 4.5 mg/kg of MTX (MTX group) or saline solution (CTRL group). Two months post treatment, blood was collected, animals sacrificed, and the heart removed. MTX caused structural cardiac changes, which were accompanied by extracellular matrix remodeling, as indicated by the increased ratio between matrix metallopeptidase 2 and metalloproteinase inhibitor 2. At the metabolic level, decreased glycerol levels were found, together with a trend towards increased content of the electron transfer flavoprotein dehydrogenase. In contrast, lower glycolysis, given by the decreased content of glucose transporter GLUT4 and phosphofructokinase, seemed to occur. The findings suggest higher reliance on fatty acids oxidation, despite no major remodeling occurring at the mitochondrial level. Furthermore, the levels of glutamine and other amino acids (although to a lesser extent) were decreased, which aligns with decreased content of the E3 ubiquitin-protein ligase Atrogin-1, suggesting a decrease in proteolysis. As far as we know, this was the first study made in old mice with a clinically relevant dose of MTX, evaluating its long-term cardiac effects. Even two months after MTX exposure, changes in metabolic fingerprint occurred, highlighting enduring cardiac effects that may require clinical vigilance.

Walnut supplementation increases levels of UCP1 and CD36 in brown adipose tissue independently of diet type.

Dietary interventions that modulate the brown adipose tissue (BAT) thermogenic activity could represent a promising therapy for metabolic disorders. In order to examine if dietary walnuts intake regulates the expression of BAT thermogenic markers levels in healthy and metabolically challenged (fructose fed) animals, rats were initially divided into the control and fructose-fed groups. After nine weeks, these groups were subdivided into the one kept on the original regimens and the other supplemented with walnuts. High-fructose diet resulted in an increased relative BAT mass and no change in UCP1 content, while the walnut supplementation increased the amount of UCP1 in BAT, but did not affect 5-HT, NA, DHPG content and DHPG/NA ratio regardless of the diet. Moreover, the CD36 levels were increased following the walnut consumption, unlike FATP1, GLUT1, GLUT4, and glycogen content which remained unchanged. Additionally, the BAT levels of activated IR and Akt were not affected by walnut consumption, while ERK signaling was decreased. Overall, we found that walnut consumption increased UCP1 and CD36 content in the BAT of both control and metabolically challenged rats, suggesting that FFAs represent the BAT preferred substrate under the previously described circumstances. This further implies that incorporating walnuts into the everyday diet may help to alleviate some symptoms of the metabolic disorder.

Possible Markers for Distinguishing benign and Malignant Thyroid Tumors and Predicting Malignancy in Patients with Genetic Predisposition to Cancer.

We hypothesized that mutations in several genes disrupt oxidative metabolism, increasing the risk of developing tumors and their malignancy in patients with a family predisposition to cancer. The purpose of our study was to assess the characteristics of oxidative metabolism in patients with malignant and benign tumor with and without a family history of cancer and identify the marker predicting the likelihood of malignancy. We conducted a study on patients with thyroid pathology (thyrotoxicosis, benign tumor pathology of the thyroid gland, and thyroid cancer) who underwent treatment at LLC "Oncology Scientific Research Center" in Tbilisi, Georgia between 2020-2021. In patients' blood the thyroid hormones content, the oxidative metabolism parameters (activity of nonenzymatic antioxidant system (TAA), malondialdehyde (MDA) content), geometrical and rheological (deformability index (EDI), membrane proteins content) characteristics of erythrocytes were determined. in the patient's blood serum with benign tumor (47 patients) MDA exceeded (p<0.005) and TAA decreased (p<0.005) in comparison to the control level; in patients with thyroid cancer (35 patients), MDA also exceeded (p<0.005), while TAA increased (p<0.005) up to the control level. In patients with benign and malignant tumors, the size of erythrocytes increased compared to the control indicators (p<0.005); in patients with thyroid cancer and benign tumors with a family history of cancer (29 patients) EDI increased (p<0.005), content of GLUT1 in erythrocyte membranes decreased (p<0.005) compared to the control level. Alterations in redox metabolism play a crucial role in tumor formation; an imbalance between anti-/pro-oxidant systems may contribute to tumor formation and support its progression into a more malignant state. Thyroid cancer is characterized by a reduction in erythrocyte deformability, related to TSH levels. These alterations are less detectable in patients with benign thyroid tumors with a family history of cancer.

Effects of long-term metformin administration associated with high-intensity interval training on physical performance, glycogen concentration, GLUT-4 content, and NMR-based metabolomics in healthy rats.

The aim was to investigate the long-term effects of metformin ingestion on high-intensity interval training on performance, glycogen concentration (GC), GLUT-4 content, and metabolomics outcomes in rats. Fifty male Wistar rats were randomly divided into baseline, metformin (500 mg daily), and control groups. Training consisted of 4 sets of 10 jumps with 30 s of passive recovery per day, 5 days/week for 8 weeks. The intensity equivalent was 50% of body mass (BM) in the first four weeks and 70% of BM in the last four weeks. The animals were submitted to a weekly jump test until exhaustion at 50% of BM. Serum and tissues were collected at baseline and after 4 and 8 weeks for biochemical and metabolomics analysis. The number of jumps increased in the Control group without a significant difference between groups at 4 and 8 weeks. GLUT4 was lower in the gastrocnemius muscle in the Metformin at the fourth week compared to Control (P=0.03) and compared to Metformin (P=0.02) and Control (P=0.01) at eight weeks. Hepatic and soleus GC were not altered by metformin. Gastrocnemius GC was lower after 8 weeks in the Metformin group compared to Control (P=0.01). Significantly lower levels of pyruvate and phenylalanine and higher levels of ethanol, formate, betaine, very low-density lipoprotein, low-density lipoprotein, and creatine were found in the Metformin compared to the Control. Although chronic administration of metformin decreased food intake and negatively influenced the synthesis of muscle glycogen, it did not significantly change physical performance compared to the Control.

Effects of Treadmill Running at Different Light Cycles in Mice with Metabolic Disorders.

Type 2 diabetes mellitus accounts for about 90% of cases of diabetes and is considered one of the most important problems of our time. Despite a significant number of studies on glucose metabolism, the molecular mechanisms of its regulation in health and disease remain insufficiently studied. That is why non-drug treatment of metabolic disorders is of great relevance, including physical activity. Metabolic changes under the influence of physical activity are very complex and are still difficult to understand. This study aims to deepen the understanding of the effect of physical exercise on metabolic changes in mice with diabetes mellitus. We studied the effect of forced treadmill running on body weight and metabolic parameters in mice with metabolic disorders. We developed a high-fat-diet-induced diabetic model of metabolic disorders. We exposed mice to forced treadmill running for 4 weeks. We determined glucose and insulin levels in the blood plasma biochemically and analyzed Glut-4 and citrate synthase in M. gastrocnemius muscle tissue using Western blotting. The research results show that daily treadmill running has different effects on different age groups of mice with metabolic disorders. In young-age animals, forced running has a more pronounced effect on body weight. At week 12, young obese mice had a 17% decrease in body weight. Body weight did not change in old mice. Moreover, at weeks 14 and 16, the decrease in body weight was more significant in the young mice (by 17%) compared to the old mice (by 6%) (p < 0.05). In older animals, it influences the rate of glucose uptake. At 60 min, the blood glucose in the exercised older mice decreased to 14.46 mmol/L, while the glucose concentration in the non-exercised group remained at 17 mmol/L. By 120 min, in mice subjected to exercise, the blood glucose approached the initial value (6.92 mmol/L) and amounted to 8.35 mmol/L. In the non-exercised group, this difference was 45%. The effects of physical activity depend on the time of day. The greater effect is observed when performing shift training or exercise during the time when animals are passive (light phase). In young mice, light phase training had a significant effect on increasing the content of Glut-4 in muscle tissue (84.3 ± 11.3%, p < 0.05 with control group-59.3 ± 7.8%). In aged mice, shift training caused an increase in the level of Glut-4 in muscle tissue (71.3 ± 4.1%, p < 0.05 with control group-56.4 ± 10,9%). In the group of aged mice, a lower CS level was noticed in all groups in comparison with young mice. It should also be noted that we observed that CS increased during exercise in the group of young mice, especially during light phase training. The CS content in the light phase subgroup (135.8 ± 7.0%) was higher than in the dark phase subgroup (113.3 ± 7.7%) (p = 0.0006). The CS decreased in aged chow-fed mice and increased in the high-fat-fed group. The CS content in the chow diet group (58.2 ± 5.0%) was 38% lower than in the HFD group (94.9 ± 8.8%).

Preventive Effect of Molecular Iodine in Pancreatic Disorders from Hypothyroid Rabbits.

Pancreatic alterations such as inflammation and insulin resistance accompany hypothyroidism. Molecular iodine (I2) exerts antioxidant and differentiation actions in several tissues, and the pancreas is an iodine-uptake tissue. We analyzed the effect of two oral I2 doses on pancreatic disorders in a model of hypothyroidism for 30 days. Adult female rabbits were divided into the following groups: control, moderate oral dose of I2 (0.2 mg/kg, M-I2), high oral dose of I2 (2.0 mg/kg, H-I2), oral dose of methimazole (MMI; 10 mg/kg), MMI + M-I2,, and MMI + H-I2. Moderate or high I2 supplementation did not modify circulating metabolites or pancreatic morphology. The MMI group showed reductions of circulating thyroxine (T4) and triiodothyronine (T3), moderate glucose increments, and significant increases in cholesterol and low-density lipoproteins. Acinar fibrosis, high insulin content, lipoperoxidation, and overexpression of GLUT4 were observed in the pancreas of this group. M-I2 supplementation normalized the T4 and cholesterol, but T3 remained low. Pancreatic alterations were prevented, and nuclear factor erythroid-2-related factor-2 (Nrf2), antioxidant enzymes, and peroxisome proliferator-activated receptor gamma (PPARG) maintained their basal values. In MMI + H-I2, hypothyroidism was avoided, but pancreatic alterations and low PPARG expression remained. In conclusion, M-I2 supplementation reestablishes thyronine synthesis and diminishes pancreatic alterations, possibly related to Nrf2 and PPARG activation.

SAT386 Constitutive Overexpression Of Microrna-93 As A Cause Of Metabolic Dysfunction And Hyperandrogenism In Polycystic Ovary Syndrome (PCOS): Evidence From A Transgenic (Mir-93+) Murine Model

Abstract Disclosure: Y. Chen: None. H. Wu: None. B.A. Gower: None. R. Azziz: Advisory Board Member; Self; Arora Forge. Consulting Fee; Self; Fortress Biotech, Spruce Biosciences, Core Access Surgical Technologies, Rani Therapeutics. Grant Recipient; Self; Ferring Pharmaceuticals, Foundation for Research and Education Excellence. Stock Owner; Self; Martin Imaging. Background: PCOS appears to result from enhanced stimuli, either increased LH or insulin, and exaggerated responsiveness of ovarian theca cell androgen biosynthesis to these stimuli. However, the etiology of the enhanced stimuli remains unclear. We previously reported that a specific microRNA, miR-93, regulates GLUT4 content in adipocytes; and that in PCOS miR-93 overexpression in adipocytes results in suppressed GLUT4 expression and insulin-meditated glucose uptake in these cells, and is associated with whole-body insulin resistance (IR). These data suggest that constitutive miR-93 overexpression may underly the metabolic dysfunction and, possibly, the hyperandrogenism of PCOS. Objective: To test the hypothesis in a transgenic murine model that miR-93 overexpression results in the metabolic and hyperandrogenic features of PCOS. Materials and methods: We generated a novel miR-93 overexpressed (miR-93+) mouse model in collaboration with InGenious Targeting Laboratory (Ronkonkoma, NY). The mouse miR-93 sequence with the R26/CAG promoter was inserted immediately downstream of loxP flanked stop cassette in intron 1 of ROSA26 locus. miR-93 insertion was not expected to cause unwanted phenotypes resulting from modification of the Rosa26 locus. When mating miR-93+ transgenic mice to whole body Cre mice (The Jackson Lab) the stop code is removed, and miR-93 is overexpressed systemically. Results: In miR-93+ mice, miR-93 was overexpressed in adipose tissue (AT), muscle, liver, heart, kidneys, and ovaries. Phenotypically, miR-93+ mice had reduced GLUT4 expression in AT, and higher fasting serum insulin, higher fasting serum glucose, and higher testosterone levels. In PCOS women, increased CYP17A1 expression in theca cells is associated with excess androgen production. Consistent with this PCOS phenotype, Cyp17a1 expression in miR-93+ mice ovaries were also increased. In addition, the ovaries of miR-93+ mice had reduced expression of Cdkn1a, similar to that observed in granulosa cells from PCOS patients. miR-93+ mice gained more weight and epididymal AT than controls. miR-93+ mice also demonstrated a lesser response to insulin during an insulin tolerance test (ITT) and exhibited altered estrous cycles as compared to wild type. Conclusion: We successfully developed a miR-93 overexpressed (miR93+) murine model, which demonstrates IR, hyperandrogenemia, exaggerated ovarian Cyp17a1 expression, increased weight gain, and abnormal estrous (ovulatory) cyclicity, mimicking the PCOS phenotype. These results provide further evidence to support the role for constitutive overexpression of miR-93 in the metabolic and hyperandrogenic features of PCOS. These data also suggest a potential model to study the mechanisms mediating the effect of miR-93 overexpression on IR and on the PCOS phenotype in tissues and conditions not readily accessible in human subjects. Presentation Date: Saturday, June 17, 2023

In silico Study to Optimize the Dosage of Oleuropein with Metformin in Diabetes Management

Type 2 diabetes mellitus (T2DM) is a potentially fatal metabolic disorder worldwide, in this COVID-19 era. Long-term allopathic treatment has a variety of side effects, prompting the search for alternative therapies. Oleuropein, the primary bioactive ingredient of Olive Leaf Extract (OLE), has shown noteworthy actions to control T2DM. The present study provides a dynamic study of % improvement in GLUT4 concentration with different doses of metformin (150mg-500mg) in combination with 500mg using a dynamic in silico model developed in Cell Designer 4.4.2, a system biology tool. The results indicated that 300mg of metformin and 500mg of oleuropein is the optimum combination to treat diabetes, ensuring a 2% improvement in GLUT4 concentration and an effective reduction in the dose of the allopathic drug metformin when taken in combination with OLE for the improvement in T2DM. The optimal dose of metformin with oleuropein was obtained successfully using our proposed in silico dynamic model. The research could be used to create an in vivo model to examine the effectiveness of herbal medicine for T2DM.

Orange Peel Extract and Physical Exercise Synergistically Ameliorate Type 2 Diabetes Mellitus-Induced Dysmetabolism by Upregulating GLUT4 Concentration in Male Wistar Rats.

Diabetes mellitus (DM) is a chronic disease and one of the oldest known disorders. It is characterized by dysglycemia, dyslipidemia, insulin resistance (IR), and pancreatic cell dysfunction. Although different drugs, metformin (MET), glipizide, glimepiride, etc., have been introduced to treat type 2 DM (T2DM), these drugs are not without side effects. Scientists are now seeking natural treatments such as lifestyle modification and organic products known with limited side effects. Thirty-six male Wistar rats were randomized into six groups (n = 6 per group): control, DM untreated rats, DM+orange peel extract (OPE), DM+exercise (EX), DM+OPE +EX, and DM+MET. The administration was once daily through the oral route and lasted for 28 days. EX and OPE synergistically ameliorated the diabetic-induced increase in fasting blood sugar, homeostatic model assessment for insulin resistance (HOMA IR), total cholesterol (TC) and triglyceride (TG), TC/high-density lipoprotein (HDL), TG/HDL, triglyceride glucose (TyG) index, and hepatic lactate dehydrogenase, alanine transaminase, malondialdehyde, c-reactive protein, and tumour necrosis factor α when compared with the diabetic untreated group. Also, EX+OPE blunted DM-induced decrease in serum insulin, homeostasis model assessment of β-cell function (HOMA-B), homeostasis model assessment of insulin sensitivity (HOMA S), quantitative insulin-sensitivity check index (QUICK 1), HDL, total antioxidant capacity, superoxide dismutase, and hepatic glycogen. Furthermore, EX+OPE ameliorated the observed DM-induced decrease in glucose transporter type 4 (GLUT 4), expression. This study showed that OPE and EX synergistically ameliorate T2DM-induced dysglycaemia, dyslipidaemia, and down-regulation of GLUT4 expression.

AS160 expression, but not AS160 Serine-588, Threonine-642, and Serine-704 phosphorylation, is essential for elevated insulin-stimulated glucose uptake by skeletal muscle from female rats after acute exercise.

One exercise session can increase subsequent insulin-stimulated glucose uptake (ISGU) by skeletal muscle in both sexes. We recently found that muscle expression and phosphorylation of key sites of Akt substrate of 160 kDa (AS160; also called TBC1D4) are essential for the full-exercise effect on postexercise-ISGU (PEX-ISGU) in male rats. In striking contrast, AS160's role in increased PEX-ISGU has not been rigorously tested in females. Our rationale was to address this major knowledge gap. Wild-type (WT) and AS160-knockout (KO) rats were either sedentary or acutely exercised. Adeno-associated virus (AAV) vectors were engineered to express either WT-AS160 or AS160 mutated on key serine and threonine residues (Ser588, Thr642, and Ser704) to alanine to prevent their phosphorylation. AAV vectors were delivered to the muscle of AS160-KO rats to determine if WT-AS160 or phosphorylation-inactivated AS160 would influence PEX-ISGU. AS160-KO rats have lower skeletal muscle abundance of the GLUT4 glucose transporter protein. This GLUT4 deficit was rescued using AAV delivery of GLUT4 to determine if eliminating muscle GLUT4 deficiency would normalize PEX-ISGU. The novel results were as follows: (1) AS160 expression was required for greater PEX-ISGU; (2) rescuing muscle AS160 expression in AS160-KO rats restored elevated PEX-ISGU; (3) AS160's essential role for the postexercise increase in ISGU was not attributable to reduced muscle GLUT4 content; and (4) AS160 phosphorylation on Ser588, Thr642, and Ser704 was not essential for greater PEX-ISGU. In conclusion, these novel findings revealed that three phosphosites widely proposed to influence PEX-ISGU are not required for this important outcome in female rats.

Глюкозні транспортери сімейства GLUT у патогенезі проліферативної діабетичної ретинопатії пацієнтів із цукровим діабетом 2-го типу

The supply of glucose to neurons of the brain and retina is carried out by a specific, facilitated transport with the participation of sodium-independent glucose transporters of the GLUT family. Studying the mechanisms of glucose transport with pharmacological or genetic inhibition of transporters is considered as a promising way to reduce glucose-toxic damage to the retina to prevent diabetic retinopathy. We studied the content of GLUT1, GLUT3, GLUT4 and Hypoxia inducible factor 1 alpha (HIF-1α) in the plasma of patients with different stages of proliferative diabetic retinopathy (PDR), duration of type 2 diabetes (T2D) was up to 20 and over 20 years, and control group. Research on the level of transporters in the blood plasma was carried out by the method of immuno-enzymatic analysis using Elabscience kits (USA). No significant difference in the GLUT1 and GLUT4 blood plasma content was found between patients with PDR and control individuals, and the GLUT3 content was 2-fold higher. Also, the content of HIF-1α was 25% higher. No significant fluctuations in the content of transporters GLUT1, GLUT3, GLUT4, HIF-1α were found depending on the duration of T2DM, the degree of deepening of PDR and the level of hyperglycemia. Correlation analysis revealed a significant two-way correlation of the GLUT3 index with blood glucose level (r = 0.581), HbA1C (r = 0.553), GLUT1 (r = 0.440) and GLUT4 (r = 0.372). The conservatism of GLUT1 transporter content in the studied groups gives a reason to consider protein expression as genetically determined for the basic maintenance of homeostasis. The GLUT3 content increase in patients with PDR, which does not depend on the retinal damage degree, duration of T2D and glucose concentration, defines this mechanism of transport as the main pathogenetic link of glucose toxicity in neurons against the background of chronic hyperglycemia. Insulin-dependent transporter GLUT4 is probably not involved in the occurrence of PDR under of T2D.

Thermoneutral housing increases the obesogenic phenotype of mice, while some effects of exercise are reduced

Introduction: Mice are extensively used to investigate the molecular foundations of obesity and the beneficial effect of exercise training (ET). Mice are most often housed at ambient temperature, ~22°C, which is below their thermoneutral environment (~30°C). Mild cold stress at ambient temperature accelerates mouse metabolic rate and may confound translation of results to humans. Aiming to determine the metabolic adaptations of ET in an obesogenic environment, we hypothesized that thermoneutral housing would increase adiposity during high-fat feeding. Moreover, thermoneutral housing would blunt the effects of ET by relieving the added cold stress. Methods: After temperature acclimatization (3 weeks, 22°C vs. 30°C), C57BL/6J mice (n=68, ♀, Age: 11 weeks) were dual-housed for 8 weeks receiving a chow diet or a 60%E high-fat diet (HFD). HFD mice were then separated into two additional groups with access to voluntary wheel running for another 8 weeks. Metabolic parameters were measured using magnetic resonance imaging, indirect calorimetry, glucose tolerance tests, and maximal running capacity on treadmill. Brown and white adipose tissues and gastrocnemius muscle mRNA and protein content were analyzed using qPCR and immunoblotting analyses, respectively. Results: In chow-fed mice, thermoneutral housing decreased metabolic rate (VO2), fasting plasma glucose, and thermogenic genes in adipose tissue depots, without changes in skeletal muscle mitochondrial protein content compared to 22°C. In HFD mice, thermoneutral housing increased fat mass, induced glucose intolerance, and fasting plasma insulin levels compared to 22°C housing. This was despite decreased food intake and metabolic rate compared to HFD mice housed at 22°C. ET mice improved the exercise capacity and glucose tolerance independent of housing temperature. Interestingly, while ET at 30°C prevented further fat gain during the intervention, ET at 22°C decreased fat mass. Moreover, only ET at 22°C increased the metabolic rate during the active phase. Gene expression responded similarly to ET independent of housing temperature in adipose tissue depots. ET induced GLUT4, peroxiredoxin 2 and pyruvate dehydrogenase protein content to a lesser extent in muscle at 30°C housing. Conclusion: Adaptations to diet-induced obesity and ET in mice critically depend upon housing temperature. Our findings underscore housing temperature as a key consideration in research related the beneficial effect of exercise in an obesogenic environment. Disclosure of funding: SHR is supported by the Lundbeck Foundation and Independent Research Fund Denmark. LS and EAR are supported by the Novo Nordisk Foundation and Independent Research Fund Denmark. IK is supported by the Novo Nordisk Foundation. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Biomedical aspects of beta-glucan on glucose metabolism and its role on primary gene PIK3R1

• Diabetes mellitus is caused by a reduction in the susceptibility of insulin receptors. • Beta-glucan is considered useful in reducing glucose levels. • Therapeutic properties of beta glucan are useful for immune modulation. • Action of beta-glucan are characterised by its molecular and structural efficacy. • Insulin resistance could be exacerbated by variations in class 1a PI3-kinases. Diabetes mellitus, one of the major metabolic threats to human health has elevated drastically all along the twenty-first century. Insulin that is released by beta-cells of the pancreas is the primary hormone linked to diabetes, and it directs the flow of glucose into muscle and blood. The insulin receptor helps in binding up glycogen synchronized hormone that is insulin which has two extracellular α and two transmembrane β subunits. The intracellular subunit or domain known as the tyrosine kinase domain activates once the insulin gets bound to the extracellular subunit followed by the activation of the insulin receptor substrate family (IRSI-4) which stimulates the PI3K/Akt pathway that is a key signaling system that controls apoptosis, cell proliferation, and a variety of other cell activities. The regulatory governmental subunit PIK3R1 heterodimer binds with the tyrosin-phosphorylated form via SH2 domains, allowing PIK3R1 to be recruited to the specified receptor, promoting PI3K activity. β- glucan plays a significant role in regulating the PI3K/Akt biochemical pathway via IRS1, PI3K-p85, and phosphorylated Akt, which increases insulin sensitivity and reduces the associated risks. Additionally, administration of these polysaccharides boosts GLUT4 concentrations in the pancreas and depresses glycogen synthase kinase-3 β levels across most cells, indicating that β-glucan serves as an anti-diabetic drug by activating the PI3K/Akt/GSK-3/GLUT-4 signal transduction pathways. Hence, the purpose of this review is to shed light on the activity and mechanism of the PIK3R1 gene on naturally produced β-glucan in the etiology of diabetes.

Skeletal Muscle Glycogen Concentrations And Glut4 Concentrations 72 H Following Eccentric Exercise

Muscle glycogen concentrations are significantly reduced 24-72 h after eccentric exercise that produces indices of skeletal muscle damage. It is suggested that the muscle damage produced by eccentric exercise contributes to the decrease in skeletal muscle glycogen concentrations after eccentric exercise. Decreased skeletal muscle glycogen concentrations are associated with lower GLUT4 protein concentrations 48 h after eccentric exercise. PURPOSE: To determine muscle glycogen concentrations and GLUT4 concentrations 72 h after eccentric exercise. METHODS: A total of 12 individuals performed concentric knee extensions (CON) with one leg, while the contralateral leg performed eccentric knee extensions (ECC). Subjects then cycled for 1 h at 65% of VO2peak. Muscle biopsies were obtained from the vastus lateralis of CON and ECC legs 72 h after exercise. Muscle biopsies were analyzed for muscle glycogen concentrations. Muscle damage was assessed by electron microscopy. Muscle soreness ratings were determined using a 10 point scale. Muscle biopsies were pooled and analyzed for total GLUT4 protein concentrations. RESULTS: Compared to the CON leg, muscle glycogen concentrations in the ECC leg were 25% lower 72 h after exercise (120.7 ± 8.28 vs. 157.3 ± 7.7 μmol.g wet wt-1, p < 0.05). Muscle damage such as myofibrillar disruptions and necrotic fibers were apparent in the ECC leg 72 h after exercise. Indices of muscle damage were not apparent in the CON leg. Ratings of muscle soreness in the ECC leg were higher than for the CON leg (4.43 ± 0.57 vs. 1.36 ± 0.50, p < 0.05). Total pooled GLUT4 protein concentrations were similar 72 h after exercise. CONCLUSIONS: Muscle glycogen concentrations were reduced and muscle damage was produced in the ECC leg 72 h after exercise. Pooled muscle GLUT4 protein concentrations were not altered 72 h after exercise.

Improving skeletal muscle insulin sensitivity via beta2 -agonist administration: a promising strategy to counteract metabolic disease and muscle loss.

Improving skeletal muscle insulin sensitivity via beta2 -agonist administration: a promising strategy to counteract metabolic disease and muscle loss.

Muscle hypertrophic effect of inhaled beta2 -agonist is associated with augmented insulin-stimulated whole-body glucose disposal in young men.

Rodent studies highlight enhancement of glucose tolerance and insulin sensitivity as potential clinically relevant effects of chronic beta2‐agonist treatment. However, the doses administered to rodents are not comparable with the therapeutic doses used for humans. Thus, we investigated the physiological effects of prolonged beta2‐agonist treatment at inhaled doses resembling those used in respiratory diseases on insulin‐stimulated whole‐body glucose disposal and putative mechanisms in skeletal muscle and adipose tissue of healthy men. Utilizing a randomized placebo‐controlled parallel‐group design, we assigned 21 healthy men to 4 weeks daily inhalation of terbutaline (TER; 4 mg × day−1, n = 13) or placebo (PLA, n = 8). Before and after treatments, we assessed subjects’ whole‐body insulin‐stimulated glucose disposal and body composition, and collected vastus lateralis muscle and abdominal adipose tissue biopsies. Glucose infusion rate increased by 27% (95% CI: 80 to 238 mg × min−1, P = 0.001) in TER, whereas no significant changes occurred in PLA (95% CI: −37 to 195 mg × min−1, P = 0.154). GLUT4 content in muscle or adipose tissue did not change, nor did hexokinase II content or markers of mitochondrial volume in muscle. Change in lean mass was associated with change in glucose infusion rate in TER (r = 0.59, P = 0.03). Beta2‐agonist treatment in close‐to‐therapeutic doses may augment whole‐body insulin‐stimulated glucose disposal in healthy young men and part of the change is likely to be explained by muscle hypertrophy. These findings highlight the therapeutic potential of beta2‐agonists for improving insulin sensitivity.Key points While studies in rodents have highlighted beta2‐agonists as a means to augment insulin sensitivity, these studies utilized beta2‐agonists at doses inapplicable to humans.Herein we show that a 4‐week treatment period with daily therapeutic inhalation of beta2‐agonist increases insulin‐stimulated whole‐body glucose disposal in young healthy lean men.This effect was associated with an increase of lean mass but not with changes in GLUT4 and hexokinase II or basal glycogen content in skeletal muscle nor GLUT4 content in abdominal adipose tissue.These findings suggest that the enhanced insulin‐stimulated whole‐body glucose disposal induced by a period of beta2‐agonist treatment in humans, at least in part, is attributed to muscle hypertrophy.Our observations extend findings in rodents and highlight the therapeutic potential of beta2‐agonists to enhance the capacity for glucose disposal and whole‐body insulin sensitivity, providing important knowledge with potential application in insulin resistance.

Neuregulin 4 Downregulation Induces Insulin Resistance in 3T3-L1 Adipocytes through Inflammation and Autophagic Degradation of GLUT4 Vesicles

The adipokine Neuregulin 4 (Nrg4) protects against obesity-induced insulin resistance. Here, we analyze how the downregulation of Nrg4 influences insulin action and the underlying mechanisms in adipocytes. Validated shRNA lentiviral vectors were used to generate scramble (Scr) and Nrg4 knockdown (KD) 3T3-L1 adipocytes. Adipogenesis was unaffected in Nrg4 KD adipocytes, but there was a complete impairment of the insulin-induced 2-deoxyglucose uptake, which was likely the result of reduced insulin receptor and Glut4 protein. Downregulation of Nrg4 enhanced the expression of proinflammatory cytokines. Anti-inflammatory agents recovered the insulin receptor, but not Glut4, content. Proteins enriched in Glut4 storage vesicles such as the insulin-responsive aminopeptidase (IRAP) and Syntaxin-6 as well as TBC1D4, a protein involved in the intracellular retention of Glut4 vesicles, also decreased by Nrg4 KD. Insulin failed to reduce autophagy in Nrg4 KD adipocytes, observed by a minor effect on mTOR phosphorylation, at the time that proteins involved in autophagy such as LC3-II, Rab11, and Clathrin were markedly upregulated. The lysosomal activity inhibitor bafilomycin A1 restored Glut4, IRAP, Syntaxin-6, and TBC1D4 content to those found in control adipocytes. Our study reveals that Nrg4 preserves the insulin responsiveness by preventing inflammation and, in turn, benefits the insulin regulation of autophagy.

Effect of resistance training on osteopenic rat bones in neonatal streptozotocin-induced diabetes: Analysis of GLUT4 content and biochemical, biomechanical, densitometric, and microstructural evaluation

AimsTo investigate the effect of resistance training-RT on glycemia, expression of the glucose transporter-GLUT4, bone mineral density-BMD, and microstructural and biomechanical properties of osteopenic rat bones in neonatal streptozotocin-induced diabetes. Main methodsSixty-four 5-day-old male rats were divided into two groups: control and diabetic rats injected with vehicle or streptozotocin, respectively. After 55 days, densitometric analysis-DA of the tibia was performed. These groups were subdivided into four subgroups: non-osteopenic control-CN, osteopenic control-OC, non-osteopenic diabetic-DM, and osteopenic diabetic-OD. The OC and OD groups were suspended by their tails for 21 days to promote osteopenia in the hindlimb; subsequently, a second DA was performed. The rats were subdivided into eight subgroups: sedentary control-SC, sedentary osteopenic control-SOC, exercised control-EC, exercised osteopenic control-EOC, sedentary diabetic-SD, sedentary osteopenic diabetic-SOD, exercised diabetic-ED, and exercised osteopenic diabetic-EOD. For RT, the rats climbed a ladder with weights secured to their tails for 12 weeks. After RT, a third DA was performed, and blood samples, muscles, and tibias were assessed to measure glycemia, insulinemia, GLUT4 content, bone maximum strength, fracture energy, extrinsic stiffness, BMD, cancellous bone area, trabecular number, and trabecular width. Key findingsAfter RT, glycemia, GLUT4 content, BMD, and bone microstructural and biomechanical properties were improved in diabetic rats (osteopenic and non-osteopenic). However, RT had no effect on these parameters in the EC and SC groups. SignificanceThese results suggest that RT improves GLUT4 content, BMD, and microstructural and biomechanical properties of bone in osteopenic and non-osteopenic diabetic rats and is effective in controlling glycemia.

Acute melatonin administration improves exercise tolerance and the metabolic recovery after exhaustive effort

The present study investigated the effects of acute melatonin administration on the biomarkers of energy substrates, GLUT4, and FAT/CD36 of skeletal muscle and its performance in rats subjected to exhaustive swimming exercise at an intensity corresponding to the maximal aerobic capacity (tlim). The incremental test was performed to individually determine the exercise intensity prescription and 48 h after, the animals received melatonin (10 mg·kg−1) or vehicles 30 min prior to tlim. Afterwards, the animals were euthanized 1 or 3 h after the exhaustion for blood and muscles storage. The experiment 1 found that melatonin increased the content of glycogen and GLUT4 in skeletal muscles of the animals that were euthanized 1 (p < 0.05; 22.33% and 41.87%) and 3 h (p < 0.05; 37.62% and 57.87%) after the last procedures. In experiment 2, melatonin enhanced the tlim (p = 0.01; 49.42%), the glycogen content (p < 0.05; 40.03%), GLUT4 and FAT/CD36 in exercised skeletal muscles (F = 26.83 and F = 25.28, p < 0.01). In summary, melatonin increased energy substrate availability prior to exercise, improved the exercise tolerance, and accelerated the recovery of muscle energy substrates after the tlim, possibly through GLUT4 and FAT/CD36.

Deuterium-depleted water stimulates GLUT4 translocation in the presence of insulin, which leads to decreased blood glucose concentration

Deuterium (D) is a stable isotope of hydrogen (H) with a mass number of 2. It is present in natural waters in the form of HDO, at a concentration of 16.8 mmol/L, equivalent to 150 ppm. In a phase II clinical study, deuterium depletion reduced fasting glucose concentration and insulin resistance. In this study, we tested the effect of subnormal D-concentration on glucose metabolism in a streptozotocin (STZ)-induced diabetic rat model. Animals were randomly distributed into nine groups to test the effect of D2O (in a range of 25–150 ppm) on glucose metabolism in diabetic animals with or without insulin treatment. Serum glucose, fructose amine-, HbA1c, insulin and urine glucose levels were monitored, respectively. After the 8-week treatment, membrane-associated GLUT4 fractions from the soleus muscle were estimated by Western blot technique. Our results indicate that, in the presence of insulin, deuterium depletion markedly reduced serum levels of glucose, -fructose amine, and –HbA1c, in a dose-dependent manner. The optimal concentration of deuterium was between 125 and 140 ppm. After a 4-week period of deuterium depletion, the highest membrane-associated GLUT4 content was detected at 125 ppm. These data suggest that deuterium depletion dose-dependently enhances the effect of insulin on GLUT4 translocation and potentiates glucose uptake in diabetic rats, which explains the lower serum glucose, -fructose amine, and –HbA1c concentrations. Based on our experimental data, deuterium-depleted water could be used to treat patients with metabolic syndrome (MS) by increasing insulin sensitivity. These experiments indicate that naturally occurring deuterium has an impact on metabolic regulations.