The Prolonged Activation of the p65 Subunit of the NF-Kappa-B Nuclear Factor Sustains the Persistent Effect of Advanced Glycation End Products on Inflammatory Sensitization in Macrophages.

Advanced glycation end products (AGEs) prime macrophages for lipopolysaccharide (LPS)-induced inflammation. We investigated the persistence of cellular AGE-sensitization to LPS, considering the nuclear content of p50 and p65 nuclear factor kappa B (NFKB) subunits and the expression of inflammatory genes. Macrophages treated with control (C) or AGE-albumin were rested for varying intervals in medium alone before being incubated with LPS. Comparisons were made using one-way ANOVA or Student t-test (n = 6). AGE-albumin primed macrophages for increased responsiveness to LPS, resulting in elevated levels of TNF, IL-6, and IL-1beta (1.5%, 9.4%, and 5.6%, respectively), compared to C-albumin. TNF, IL-6, and IL-1 beta secretion persisted for up to 24 h even after the removal of AGE-albumin (area under the curve greater by 1.6, 16, and 5.2 times, respectively). The expressions of Il6 and RelA were higher 8 h after albumin removal, and Il6 and Abca1 were higher 24 h after albumin removal. The nuclear content of p50 remained similar, but p65 showed a sustained increase (2.9 times) for up to 24 h in AGE-albumin-treated cells. The prolonged activation of the p65 subunit of NFKB contributes to the persistent effect of AGEs on macrophage inflammatory priming, which could be targeted for therapies to prevent complications based on the AGE-RAGE-NFKB axis.

Glucose Transport and Utilization in the Hippocampus: From Neurophysiology to Diabetes-Related Development of Dementia.

The association of diabetes with cognitive dysfunction has at least 60 years of history, which started with the observation that children with type 1 diabetes mellitus (T1D), who had recurrent episodes of hypoglycemia and consequently low glucose supply to the brain, showed a deficit of cognitive capacity. Later, the growing incidence of type 2 diabetes mellitus (T2D) and dementia in aged populations revealed their high association, in which a reduced neuronal glucose supply has also been considered as a key mechanism, despite hyperglycemia. Here, we discuss the role of glucose in neuronal functioning/preservation, and how peripheral blood glucose accesses the neuronal intracellular compartment, including the exquisite glucose flux across the blood-brain barrier (BBB) and the complex network of glucose transporters, in dementia-related areas such as the hippocampus. In addition, insulin resistance-induced abnormalities in the hippocampus of obese/T2D patients, such as inflammatory stress, oxidative stress, and mitochondrial stress, increased generation of advanced glycated end products and BBB dysfunction, as well as their association with dementia/Alzheimer's disease, are addressed. Finally, we discuss how these abnormalities are accompained by the reduction in the expression and translocation of the high capacity insulin-sensitive glucose transporter GLUT4 in hippocampal neurons, which leads to neurocytoglycopenia and eventually to cognitive dysfunction. This knowledge should further encourage investigations into the beneficial effects of promising therapeutic approaches which could improve central insulin sensitivity and GLUT4 expression, to fight diabetes-related cognitive dysfunctions.

Variants in HSD11B1 gene modulate susceptibility to diabetes kidney disease and to insulin resistance in type 1 diabetes.

BACKGROUND AND AIM: 11ß-Hydroxysteroid dehydrogenase 1 has been implicated in insulin resistance (IR) in the setting of metabolic disorders, and single nucleotide polymorphisms (SNPs) in its encoding gene (HSD11B1) have been associated with type 2 diabetes and metabolic syndrome. In type 1 diabetes (T1D), IR has been related to the development of chronic complications. We investigated the association of HSD11B1 SNPs with microvascular complications and with IR in a Brazilian cohort of T1D individuals. MATERIALS AND METHODS: Five SNPs were genotyped in 466 T1D individuals (57% women; median of 37 years old, diabetes duration of 25 years and HbA1c of 8.4%). RESULTS: The minor allele T of rs11799643 was nominally associated with diabetic retinopathy (OR = 0.52; confidence interval [CI] 95% = 0.28-0.96; P = .036). The minor allele C of rs17389016 was nominally associated with overt diabetic kidney disease (DKD) (OR = 1.90; CI 95% = 1.07-3.37; P = .028). A follow-up study revealed that 29% of the individuals lost ≥5 mL min-1 × 1.73 m2 per year of the estimated glomerular filtration rate (eGFR). In these individuals (eGFR decliners), C allele of rs17389016 was more frequent than in non-decliners (OR = 2.10; CI 95% = 1.14-3.89; P = .018). Finally, minor allele T of rs846906 associated with higher prevalence of arterial hypertension, higher body mass index and waist circumference, thus conferring risk to a lower estimated glucose disposal rate, a surrogate marker of insulin sensitivity (OR = 1.23; CI 95% = 1.06-1.42; P = .004). CONCLUSION: SNPs in the HSD11B1 gene may confer susceptibility to DKD and to IR in T1D individuals.

Alcohol Use Disorder is Associated with Upregulation of MicroRNA-34a and MicroRNA-34c in Hippocampal Postmortem Tissue.

BACKGROUND: To investigate epigenetic mechanisms potentially involved in the cognitive decline associated with chronic alcohol intake, we evaluated the expressions of three micro-RNAs (miR-34a, -34b, and -34c) highly expressed in the hippocampus and involved in neuronal physiology and pathology. MiR-34a participates in functioning and survival of mature neurons; miR-34b is associated with Alzheimer-like disorders; and miR-34c is implicated in the memory impairment of Alzheimer disease in rodents and humans. METHODS: A total of 69 cases were selected from the Biobank for Aging Studies and categorized according to the absence (n = 50) or presence (n = 19) of alcohol use disorder (AUD). Cases presenting with neuropathological diagnoses of dementias were excluded. Total RNA was extracted from hippocampal paraffinized slices, complementary DNA was synthesized from miRs, and RT-qPCR was performed with TaqMan® assays. RESULTS: Higher expressions of miR-34a and miR-34c, but not of miR-34b, were found in the group with AUD in comparison with the group without AUD after adjustment for potential confounders (age, sex, body mass index, presence of hypertension, diabetes mellitus, smoking, and physical inactivity). CONCLUSIONS: Hippocampal upregulation of miR-34a and miR-34c may be involved in the cognitive decline associated with chronic alcohol consumption.

RAGE Mediates Cholesterol Efflux Impairment in Macrophages Caused by Human Advanced Glycated Albumin.

We addressed the involvement of the receptor for advanced glycation end products (RAGE) in the impairment of the cellular cholesterol efflux elicited by glycated albumin. Albumin was isolated from type 1 (DM1) and type 2 (DM2) diabetes mellitus (HbA1c > 9%) and non-DM subjects (C). Moreover, albumin was glycated in vitro (AGE-albumin). Macrophages from Ager null and wild-type (WT) mice, or THP-1 transfected with siRNA-AGER, were treated with C, DM1, DM2, non-glycated or AGE-albumin. The cholesterol efflux was reduced in WT cells exposed to DM1 or DM2 albumin as compared to C, and the intracellular lipid content was increased. These events were not observed in Ager null cells, in which the cholesterol efflux and lipid staining were, respectively, higher and lower when compared to WT cells. In WT, Ager, Nox4 and Nfkb1, mRNA increased and Scd1 and Abcg1 diminished after treatment with DM1 and DM2 albumin. In Ager null cells treated with DM-albumin, Nox4, Scd1 and Nfkb1 were reduced and Jak2 and Abcg1 increased. In AGER-silenced THP-1, NOX4 and SCD1 mRNA were reduced and JAK2 and ABCG1 were increased even after treatment with AGE or DM-albumin. RAGE mediates the deleterious effects of AGE-albumin in macrophage cholesterol efflux.

Sympathetic Regulation of Slc2a4 Gene Expression: Participation of a Putative cAMP Responsive Element (CRE) Site in the Slc2a4 Promoter.

BACKGROUND/AIMS: Studies have indicated that sympathetic activity enhances GLUT4 expression (Slc2a4 gene) by activating beta-adrenergic receptors. This could be mediated by a direct enhancer effect of cyclic AMP-responsive element binding protein (CREB) and family members upon Slc2a4 gene. However, a cAMP responsive element (CRE) in Slc2a4 promoter has never been demonstrated. METHODS: Slc2a4 CRE-site was searched by in silico analysis. In skeletal muscles from rats displaying high sympathetic activity (SHR), Slc2a4 CRE-site was investigated by electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assay; and Slc2a4 expression was analyzed by RT-qPCR. Functional activity of the CRE-site was investigated by luciferase assay, 2 hours after 8-br-cAMP stimulation, in 3T3L1 adipocytes transientely transfected with native and mutated CRE-sites. RESULTS: In silico analysis indicated the -480/-473 segment as a putative CRE-site, with 62.5% of identity to CRE consensus sequence, and highly preserved in mouse, rat and human. CREB/CREM binding in this CRE-site was confirmed to occur in vitro (EMSA) and in vivo (ChIP assay). Enhancer activity of this segment in Slc2a4 transcription was confirmed in 3T3-L1 cells. Finally, in extensor digitorum longus muscle from SHR, 80% increase in Slc2a4 mRNA expression was observed to be accompanied by increased CREB/CREM binding into the CRE-site both in vitro and in vivo. CONCLUSION: This study demonstrates the presence of a functional CRE-site at -480/-473 sequence of the Slc2a4 gene. This CRE-site has an enhancing activity on Slc2a4 expression and participates in the Slc2a4 increased expression observed in glycolytic muscles of rats displaying high sympathetic activity.

Palmitate-induced Slc2a4/GLUT4 downregulation in L6 muscle cells: evidence of inflammatory and endoplasmic reticulum stress involvement.

BACKGROUND: Obesity is strongly associated to insulin resistance, inflammation, and elevated plasma free fatty acids, but the mechanisms behind this association are not fully comprehended. Evidences suggest that endoplasmic reticulum (ER) stress may play a role in this complex pathophysiology. The aim of the present study was to investigate the involvement of inflammation and ER stress in the modulation of glucose transporter GLUT4, encoded by Slc2a4 gene, in L6 skeletal muscle cells. METHODS: L6 cells were acutely (2 h) and chronically (6 and 12 h) exposed to palmitate, and the expression of several proteins involved in insulin resistance, ER stress and inflammation were analyzed. RESULTS: Chronic and acute palmitate exposure significantly reduced GLUT4 protein (~ 39%, P < 0.01) and its mRNA (18%, P < 0.01) expression. Only acute palmitate treatment increased GRP78 (28%, P < 0.05), PERK (98%, P < 0.01), eIF-2A (35%, P < 0.01), IRE1a (60%, P < 0.05) and TRAF2 (23%, P < 0.05) protein content, and PERK phosphorylation (106%, P < 0.001), but did not elicit eIF-2A, IKK phosphorylation or increased XBP1 nuclear content. Additionally, acute and chronic palmitate increased NFKB p65 nuclear content (~ 30%, P < 0.05) and NFKB binding activity to Slc2a4 gene promoter (~ 45%, P < 0.05). CONCLUSION: Different pathways are activated in acute and chronic palmitate induced-repression of Slc2a4/GLUT4 expression. This regulation involves activation of initial component of ER stress, such as the formation of a IRE1a-TRAF2-IKK complex, and converges to NFKB-induced repression of Slc2a4/GLUT4. These results link ER stress, inflammation and insulin resistance in L6 cells.

Dysregulation between TRIM63/FBXO32 expression and soleus muscle wasting in diabetic rats: potential role of miR-1-3p, -29a/b-3p, and -133a/b-3p.

Diabetes mellitus (DM) induces a variable degree of muscle sarcopenia, which may be related to protein degradation and to the expression of both E3 ubiquitin ligases and some specific microRNAs (miRNAs). The present study investigated the effect of diabetes and acute muscle contraction upon the TRIM63 and FBXO32 expression as well as the potential involvement of some miRNAs. Diabetes was induced by streptozotocin and studied after 30 days. Soleus muscles were harvested, stimulated to contract in vitro for twitch tension analysis (0.5 Hz), 30 min later for tetanic analysis (100 Hz), and 30 min later were frozen. TRIM63 and FBXO32 proteins were quantified by western blotting; Trim63 mRNA, Fbxo32 mRNA, miR-1-3p, miR-29a-3p, miR-29b-3p, miR-133a-3p, and miR-133b-3p were quantified by qPCR. Diabetes induced sarcopenia by decreasing (P < 0.05) muscle weight/tibia length index, maximum tetanic contraction and relaxation rates, and absolute twitch and tetanic forces (P < 0.05). Diabetes decreased (P < 0.05) the Trim63 and Fbxo32 mRNAs (30%) and respective proteins (60%), and increased (P < 0.01) the miR-29b-3p (2.5-fold). In muscle from diabetic rats, acute contractile stimulus increased TRIM63 protein, miR-1-3p, miR-29a-3p, and miR-133a/b-3p, but decreased miR-29b-3p (P < 0.05). Independent of the metabolic condition, after muscle contraction, both TRIM63 and FBXO32 proteins correlated significantly with miR-1-3p, miR-29a/b-3p, and miR-133a/b-3p. All diabetes-induced regulations were reversed by insulin treatment. Concluding, the results depict that muscle wasting in long-term insulinopenic condition may not be accompanied by increased proteolysis, pointing out the protein synthesis as an important modulator of muscle sarcopenia in DM.

Periapical lesions decrease Akt serine phosphorylation and plasma membrane GLUT4 content in rat skeletal muscle.

OBJECTIVES: Periapical lesion (PL) promotes insulin resistance; however, the mechanisms underlying this alteration are not fully understood. Therefore, in this study, we aimed to evaluate the Akt serine phosphorylation status and GLUT4 expression levels in the gastrocnemius muscle (GM) of rats with PL. MATERIALS AND METHODS: Male Wistar rats (n = 42) were distributed equally into control (CN) and PL groups. The pulpal tissue of the PL group rats was exposed to the oral environment for 30 days. Thereafter, glucose and insulin levels were assessed, followed by homeostasis model assessment of insulin resistance (HOMA-IR). The Akt serine phosphorylation and GLUT4 levels of microsomal (M) and plasma membrane (PM) fractions were evaluated by western blotting and analyzed statistically. RESULTS: Compared to CN group rats, PL group rats had lower insulin sensitivity (as observed by HOMA-IR), lower Akt serine phosphorylation status after insulin stimulus, and lower GLUT4 levels in the PM fraction. However, the M fraction in the PL group did not differ significantly from that of the CN group. CONCLUSIONS: PL decreases insulin sensitivity, Akt phosphorylation, and PM GLUT4 content. CLINICAL RELEVANCE: The present study indicates that preventing endodontic disease can thwart insulin resistance.

Aerobic exercise training enhances the in vivo cholesterol trafficking from macrophages to the liver independently of changes in the expression of genes involved in lipid flux in macrophages and aorta.

BACKGROUND: Regular exercise prevents and regresses atherosclerosis by improving lipid metabolism and antioxidant defenses. Exercise ameliorates the reverse cholesterol transport (RCT), an antiatherogenic system that drives cholesterol from arterial macrophages to the liver for excretion into bile and feces. In this study we analyzed the role of aerobic exercise on the in vivo RCT and expression of genes and proteins involved in lipid flux and inflammation in peritoneal macrophages, aortic arch and liver from wild type mice. METHODS: Twelve-week-old male mice were divided into sedentary and trained groups. Exercise training was performed in a treadmill (15 m/min, 30 min/day, 5 days/week). Plasma lipids were determined by enzymatic methods and lipoprotein profile by fast protein liquid chromatography. After intraperitoneal injection of J774-macrophages the RCT was assessed by measuring the recovery of (3)H-cholesterol in plasma, feces and liver. The expression of liver receptors was determined by immunoblot, macrophages and aortic mRNAs by qRT-PCR. (14)C-cholesterol efflux mediated by apo A-I and HDL2 and the uptake of (3)H-cholesteryl oleoyl ether ((3)H-COE)-acetylated-LDL were determined in macrophages isolated from sedentary and trained animals 48 h after the last exercise session. RESULTS: Body weight, plasma lipids, lipoprotein profile, glucose and blood pressure were not modified by exercise training. A greater amount of (3)H-cholesterol was recovered in plasma (24 h and 48 h) and liver (48 h) from trained animals in comparison to sedentary. No difference was found in (3)H-cholesterol excreted in feces between trained and sedentary mice. The hepatic expression of scavenger receptor class B type I (SR-BI) and LDL receptor (B-E) was enhanced by exercise. We observed 2.8 and 1.7 fold rise, respectively, in LXR and Cyp7a mRNA in the liver of trained as compared to sedentary mice. Macrophage and aortic expression of genes involved in lipid efflux was not systematically changed by physical exercise. In agreement, (14)C-cholesterol efflux and uptake of (3)H-COE-acetylated-LDL by macrophages was similar between sedentary and trained animals. CONCLUSION: Aerobic exercise in vivo accelerates the traffic of cholesterol from macrophages to the liver contributing to prevention and regression of atherosclerosis, independently of changes in macrophage and aorta gene expression.

High glucose concentration stimulates NHE-1 activity in distal nephron cells: the role of the Mek/Erk1/2/p90RSK and p38MAPK signaling pathways.

AIMS: In models of diabetes, distal nephron cells contribute to glucose uptake and oxidation. How these cells contribute to the use of glucose for the regulation of H(+) extrusion remains unknown. We used Madin-Darby Canine Kidney (MDCK) cells to investigate the effect of acute or chronic high glucose concentration on the abundance and activity of the Na(+)/H(+) exchanger (NHE-1). METHODS: Using RT-PCR, we also evaluated the mRNA expression for sodium glucose co-transporters SGLT1 and SGLT2. Protein abundance was analyzed using immunoblotting, and intracellular pH (pHi) recovery was evaluated using microscopy in conjunction with the fluorescent probe BCECF/AM. The Na(+)-dependent pHi recovery rate was monitored with HOE-694 (50 µM) and/or S3226 (10 µM), specific NHE-1 and NHE-3 inhibitors. RESULTS: MDCK cells did not express the mRNA for SGLT1 or SGLT2 but did express the GLUT2, NHE-1 and NHE-3 proteins. Under control conditions, we observed a greater contribution of NHE-1 to pHi recovery relative to the other H(+) transporters. Acute high glucose treatment increased the HOE-694-sensitive pHi recovery rate and p-Erk1/2 and p90(RSK) abundance. These parameters were reduced by PD-98059, a Mek inhibitor (1 µM). Chronic high glucose treatment also increased the HOE-694-sensitive pHi recovery rate and p-p38MAPK abundance. Both parameters were reduced by SB-203580, a p38MAPK inhibitor (10 µM). CONCLUSION: These results suggested that extracellular high glucose stimulated NHE-1 acutely and chronically through Mek/Erk1/2/p90(RSK) and p38MAPK pathways, respectively.

Glucose transporter 1 expression accompanies hypoxia sensing in the cyclic canine corpus luteum.

The canine corpus luteum (CL) functions as a source of progesterone (P4) and 17ß-oestradiol (E2); however, the transport of energy substrates to maintain its high hormonal output has not yet been characterised. This study involved the localisation and temporal distribution of the facilitative glucose transporter 1 and the quantification of the corresponding protein (GLUT1) and gene (SLC2A1) expression. Some GLUT1/SLC2A1 regulatory proteins, such as hypoxia-inducible factor 1α (HIF1A) and fibroblast growth factor 2 (FGF2); mRNAs, such as HIF1A, FGF2 and vascular endothelial growth factor A (VEGFA); and VEGFA receptors 1 and 2 (FLT1 and KDR) were also analysed from days 10 to 70 after ovulation. Additionally, plasma P4 and E2 levels were assessed via chemiluminescence. Moreover, the canine KDR sequence has been cloned, thereby enabling subsequent semi-quantitative PCR analysis. Our results demonstrate time-dependent variations in the expression profile of SLC2A1 during dioestrus, which were accompanied by highly correlated changes (0.84

Sodium-glucose transporter 2 inhibitors in type 2 diabetes mellitus: navigating between Scylla and Charybdis.

Despite the extensive pharmacopeia for type 2 diabetes mellitus treatment, long-term glycemic control is far from being optimal, and morbimortality has increased. This demonstrates the importance of developing drugs with new mechanisms of actions, such as sodium-glucose transporter (SGLT) inhibitors (Charybdis). Since the beginning of 2000, numerous SGLT2-inhibitors have been developed and have started to be tested (Scylla) by the pharmaceutical companies that are engaged in this race. Although reductions in hemoglobin A1c have been shown in clinical trials, several issues related to the use of SGLT2 inhibitors deserve further investigation, rendering some aspects of their true safety still uncertain.

Atorvastatin administered before myocardial infarction in rats improves contractility irrespective of metabolic changes.

Statins have a beneficial effect after myocardial infarction, but the relationship between glucose transporters and their use before the event has not yet been studied. We assessed the effects of atorvastatin treatment pre- and post-myocardial infarction on cardiovascular function and glucose transporter 4 (GLUT4) in the heart. Wistar-Kyoto rats were treated with 20 mg/kg atorvastatin or vehicle for 14 days before coronary artery occlusion surgery (myocardial infarction) or sham surgery. Echocardiographic evaluations were carried out 48 h after myocardial infarction (protocol A) and after 7 days (protocol B), when atorvastatin was also administered. Plasma inflammatory markers and GLUT4 in the heart were also evaluated. Animals were divided into the following groups: sham-operated and vehicle (C), myocardial infarction and vehicle (I), sham-operated and atorvastatin (CAt) and myocardial infarction and atorvastatin (IAt). After 48 h, myocardial infarction induced higher left ventricular fractional shortening in IAt versus I (~ 60%, P = 0.036), and the ejection fraction was lower (protocol A ~ 37%; protocol B ~ 30%). Myocardial infarction was associated with a rise in plasma membrane GLUT4 after 48 h (~ 40%, P < 0.001), and a reduction in GLUT4 after 7 days (I 25%; IAt 49%, P < 0.001). Atorvastatin treatment for 48 h after the infarction did not change GLUT4 expression, and after 7 days it had an additional negative effect on GLUT4 content (~ 39%, P = 0.030). In conclusion, atorvastatin treatment pre- and post-myocardial infarction improved myocardial contractility after 48 h, but not after 7 days, and was not associated with an increase in GLUT4 expression.

Postmortem Brains from Subjects with Diabetes Mellitus Display Reduced GLUT4 Expression and Soma Area in Hippocampal Neurons: Potential Involvement of Inflammation.

Diabetes mellitus (DM) is an important risk factor for dementia, which is a common neurodegenerative disorder. DM is known to activate inflammation, oxidative stress, and advanced glycation end products (AGEs) generation, all capable of inducing neuronal dysfunctions, thus participating in the neurodegeneration progress. In that process, disturbed neuronal glucose supply plays a key role, which in hippocampal neurons is controlled by the insulin-sensitive glucose transporter type 4 (GLUT4). We investigated the expression of GLUT4, nuclear factor NF-kappa B subunit p65 [NFKB (p65)], carboxymethyllysine and synapsin1 (immunohistochemistry), and soma area in human postmortem hippocampal samples from control, obese, and obese+DM subjects (41 subjects). Moreover, in human SH-SY5Y neurons, tumor necrosis factor (TNF) and glycated albumin (GA) effects were investigated in GLUT4, synapsin-1 (SYN1), tyrosine hydroxylase (TH), synaptophysin (SYP) proteins, and respective genes; NFKB binding activity in the SLC2A4 promoter; effects of increased histone acetylation grade by histone deacetylase 3 (HDAC3) inhibition. Hippocampal neurons (CA4 area) of obese+DM subjects displayed reduced GLUT4 expression and neuronal soma area, associated with increased expression of NFKB (p65). Challenges with TNF and GA decreased the SLC2A4/GLUT4 expression in SH-SY5Y neurons. TNF decreased SYN1, TH, and SYP mRNAs and respective proteins, and increased NFKB binding activity in the SLC2A4 promoter. Inhibition of HDAC3 increased the SLC2A4 expression and the total neuronal content of CRE-binding proteins (CREB/ICER), and also counterbalanced the repressor effect of TNF upon these parameters. This study revealed reduced postmortem human hippocampal GLUT4 content and neuronal soma area accompanied by increased proinflammatory activity in the brains of DM subjects. In isolated human neurons, inflammatory activation by TNF reduced not only the SLC2A4/GLUT4 expression but also the expression of some genes related to neuronal function (SYN1, TH, SYP). These effects may be related to epigenetic regulations (H3Kac and H4Kac status) since they can be counterbalanced by inhibiting HDAC3. These results uncover the improvement in GLUT4 expression and/or the inhibition of HDAC3 as promising therapeutic targets to fight DM-related neurodegeneration.

Carbohydrate- and lipid-enriched meals acutely disrupt glycemic homeostasis by inducing transient insulin resistance in rats.

Chronic intake of high-carbohydrate or high-lipid diets is a well-known insulin resistance inducer. This study investigates the immediate effect (1-6 h) of a carbohydrate- or lipid-enriched meal on insulin sensitivity. Fasted rats were refed with standard, carbohydrate-enriched (C), or lipid-enriched (L) meal. Plasma insulin, glucose, and non-esterified fatty acids (NEFA) were measured at 1, 2, 4, and 6 h of refeeding. The glucose-insulin index showed that either carbohydrates or lipids decreased insulin sensitivity at 2 h of refeeding. At this time point, insulin tolerance tests (ITTs) and glucose tolerance tests (GTTs) detected insulin resistance in C rats, while GTT confirmed it in L rats. Reduced glycogen and phosphorylated AKT and GSK3 content revealed hepatic insulin resistance in C rats. Reduced glucose uptake in skeletal muscle subjected to the fatty acid concentration that mimics the high NEFA level of L rats suggests insulin resistance in these animals is mainly in muscle. In conclusion, carbohydrate- or lipid-enriched meals acutely disrupt glycemic homeostasis, inducing a transient insulin resistance, which seems to involve liver and skeletal muscle, respectively. Thus, the insulin resistance observed when those types of diets are chronically consumed may be an evolution of repeated episodes of this transient insulin resistance.

Aerobic Exercise Training Reduces Atherogenesis Induced by Low-Sodium Diet in LDL Receptor Knockout Mice.

This study investigated the efficacy of aerobic exercise training (AET) in the prevention of dyslipidemia, insulin resistance (IR), and atherogenesis induced by severe low-sodium (LS) diet. LDL receptor knockout (LDLR KO) mice were fed a low-sodium (LS) (0.15% NaCl) or normal-sodium (NS; 1.27% NaCl) diet, submitted to AET in a treadmill, 5 times/week, 60 min/day, 15 m/min, for 90 days, or kept sedentary. Blood pressure (BP), plasma total cholesterol (TC) and triglyceride (TG) concentrations, lipoprotein profile, and insulin sensitivity were evaluated at the end of the AET protocol. Lipid infiltration, angiotensin II type 1 receptor (AT1), receptor for advanced glycation end products (RAGE), carboxymethyllysine (CML), and 4-hydroxynonenal (4-HNE) contents as well as gene expression were determined in the brachiocephalic trunk. BP and TC and gene expression were similar among groups. Compared to the NS diet, the LS diet increased vascular lipid infiltration, CML, RAGE, 4-HNE, plasma TG, LDL-cholesterol, and VLDL-TG. Conversely, the LS diet reduced vascular AT1 receptor, insulin sensitivity, HDL-cholesterol, and HDL-TG. AET prevented arterial lipid infiltration; increases in CML, RAGE, and 4-HNE contents; and reduced AT1 levels and improved LS-induced peripheral IR. The current study showed that AET counteracted the deleterious effects of chronic LS diet in an atherogenesis-prone model by ameliorating peripheral IR, lipid infiltration, CML, RAGE, 4-HNE, and AT1 receptor in the intima-media of the brachiocephalic trunk. These events occurred independently of the amelioration of plasma-lipid profile, which was negatively affected by the severe dietary-sodium restriction.

Glucose-induced regulation of NHEs activity and SGLTs expression involves the PKA signaling pathway.

The effect of glucose on the intracellular pH (pH(i)) recovery rate (dpH(i)/dt) and Na(+)-glucose transporter (SGLT) localization was investigated in HEK-293 cells, a cell line that expresses endogenous NHE1, NHE3, SGLT1, and SGLT2 proteins. The activity of the Na(+)/H(+) exchangers (NHEs) was evaluated by using fluorescence microscopy. The total and membrane protein expression levels were analyzed by immunoblotting. In cells cultivated in 5 mM glucose, the pH(i) recovery rate was 0.169 ± 0.020 (n = 6). This value did not change in response to the acute presence of glucose at 2 or 10 mM, but decreased with 25 mM glucose, an effect that was not observed with 25 mM mannitol. Conversely, the chronic effect of high glucose (25 mM) increased the pH(i) recovery rate (~40%, P < 0.05), without changes in the total levels of NHE1, NHE3, or SGLT1 expression, but increasing the total cellular (~50%, P < 0.05) and the plasma membrane (~100%, P < 0.01) content of SGLT2. Treatment with H-89 (10(-6) M) prevented the stimulatory effect of chronic glucose treatment on the pH(i) recovery rate and SGLT2 expression in the plasma membrane. Our results indicate that the effect of chronic treatment with a high glucose concentration is associated with increased NHEs activity and plasma membrane expression of SGLT2 in a protein kinase A-dependent way. The present results reveal mechanisms of glucotoxicity and may contribute to understanding the diabetes-induced damage of this renal epithelial cell.

AGEs-Induced and Endoplasmic Reticulum Stress/Inflammation-Mediated Regulation of GLUT4 Expression and Atherogenesis in Diabetes Mellitus.

In recent decades, complex and exquisite pathways involved in the endoplasmic reticulum (ER) and inflammatory stress responses have been demonstrated to participate in the development and progression of numerous diseases, among them diabetes mellitus (DM). In those pathways, several players participate in both, reflecting a complicated interplay between ER and inflammatory stress. In DM, ER and inflammatory stress are involved in both the pathogenesis of the loss of glycemic control and the development of degenerative complications. Furthermore, hyperglycemia increases the generation of advanced glycation end products (AGEs), which in turn refeed ER and inflammatory stress, contributing to worsening glycemic homeostasis and to accelerating the development of DM complications. In this review, we present the current knowledge regarding AGEs-induced and ER/inflammation-mediated regulation of the expression of GLUT4 (solute carrier family 2, facilitated glucose transporter member 4), as a marker of glycemic homeostasis and of cardiovascular disease (CVD) development/progression, as a leading cause of morbidity and mortality in DM.