Microvascular insulin resistance associates with enhanced muscle glucose disposal in CD36 deficiency.
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ABSTRACT:
SUBMITTER: Shibao C
PROVIDER: S-EPMC10889024 | biostudies-literature | 2024 Feb
REPOSITORIES: biostudies-literature
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Microvascular insulin resistance associates with enhanced muscle glucose disposal in CD36 deficiency.
Shibao Cyndya C Peche Vivek S VS Williams Ian M IM Samovski Dmitri D Pietka Terri A TA Abumrad Naji N NN Gamazon Eric E Goldberg Ira J IJ Wasserman David D Abumrad Nada A NA
medRxiv : the preprint server for health sciences 20240218
Dysfunction of endothelial insulin delivery to muscle associates with insulin resistance. CD36, a fatty acid transporter and modulator of insulin signaling is abundant in endothelial cells, especially in capillaries. Humans with inherited 50% reduction in CD36 expression have endothelial dysfunction but whether it is associated with insulin resistance is unclear. Using hyperinsulinemic/euglycemic clamps in <i>Cd36</i><sup><i>-/-</i></sup> and wildtype mice, and in 50% CD36 deficient humans and m ...[more]
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Project description:Aims/hypothesisMicrovascular dysfunction contributes to insulin resistance. CD36, a fatty acid transporter and modulator of insulin signalling, is abundant in microvascular endothelial cells. Humans carrying the minor allele (G) of CD36 coding variant rs3211938 have 50% reduced CD36 expression and show endothelial dysfunction. We aimed to determine whether G allele carriers have microvascular resistance to insulin and, if so, how this affects glucose disposal.MethodsOur multi-disciplinary approach included hyperinsulinaemic-euglycaemic clamps in Cd36-/- and wild-type mice, and in individuals with 50% CD36 deficiency, together with control counterparts, in addition to primary human-derived microvascular endothelial cells with/without CD36 depletion.ResultsInsulin clamps showed that Cd36-/- mice have enhanced insulin-stimulated glucose disposal but reduced vascular compliance and capillary perfusion. Intravital microscopy of the gastrocnemius showed unaltered transcapillary insulin flux. CD36-deficient humans had better insulin-stimulated glucose disposal but insulin-unresponsive microvascular blood volume (MBV). Human microvascular cells depleted of CD36 showed impaired insulin activation of Akt, endothelial NO synthase and NO generation. Thus, in CD36 deficiency, microvascular insulin resistance paradoxically associated with enhanced insulin sensitivity of glucose disposal.Conclusions/interpretationCD36 deficiency was previously shown to reduce muscle/heart fatty acid uptake, whereas here we showed that it reduced vascular compliance and the ability of insulin to increase MBV for optimising glucose and oxygen delivery. The muscle and heart respond to these energy challenges by transcriptional remodelling priming the tissue for insulin-stimulated glycolytic flux. Reduced oxygen delivery activating hypoxia-induced factors, endothelial release of growth factors or small intracellular vesicles might mediate this adaptation. Targeting NO bioavailability in CD36 deficiency could benefit the microvasculature and muscle/heart metabolism.Trial registrationClinicaltrials.gov NCT03012386 DATA AVAILABILITY: The RNAseq data generated in this study have been deposited in the NCBI Gene Expression Omnibus ( www.ncbi.nlm.nih.gov/geo/ ) under accession code GSE235988 ( https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE235988 ).
| S-EPMC11832635 | biostudies-literature
Project description:IntroductionMetabolic flexibility is the ability of a system to switch between metabolic substrates. Human and murine skeletal muscle tissues and cells with decreased activity of the regulatory RNA-binding protein, human antigen R (HuR), have decreased capacity for fat oxidation, and thus decreased metabolic flexibility. In this study, we aimed to assess the preference for carbohydrates in mice lacking HuR in skeletal muscle.MethodsExperiments were performed on weight-matched control and HuR knockout mice of both sexes. Palmitate and pyruvate oxidation were performed in mouse muscle following the release of 14CO2. In vivo glucose and lipid uptake were assayed in mouse tissue following nonmetabolizable 3H-2-deoxyglucose or 14C-bromopalmitate injection. Transcriptomic analyses were performed in the skeletal muscle of all mice, followed by qPCR validation of select genes. Serum lactate and glucose levels were measured in mice via tail nick, and the muscle glycogen level was measured through colorimetric assay. Indirect calorimetry was used to measure respiratory exchange ratios.ResultsMale muscle-specific HuR knockout mice showed increased glucose uptake relative to controls, specifically in skeletal muscle, and have increased muscle glycogen content. These mice also displayed greater respiratory exchange ratios than controls. None of these differences were noted in females. Transcriptomics showed far more differences between male and female mice than between control and HuR knockout mice. However, differential gene expression between male and female mice was diminished by 50% following the removal of HuR. Male HuR knockout mouse skeletal muscle had increased glycolytic gene expression relative to controls but showed no difference relative to females of the same genotype. Both palmitate and pyruvate oxidation were decreased in the skeletal muscle of male HuR knockout mice relative to controls, and serum lactate levels were increased. No notable differences were seen in females between genotypes.DiscussionThe increase in the markers of glucose utilization with decreased HuR activity in male mice may indicate a switch toward glycolysis as compensation for decreased fat oxidation. These results continue to highlight a sex dependence on HuR as a driver of fat oxidation in mouse skeletal muscle while also indicating that muscle itself shows greater ambiguity between males and females following the removal of HuR.
| S-EPMC11880248 | biostudies-literature
Project description:Identifying the mechanisms by which insulin regulates glucose metabolism in skeletal muscle is critical to understanding the etiology of insulin resistance and type 2 diabetes. Our knowledge of these mechanisms is limited by the difficulty of obtaining in vivo intracellular data. To quantitatively distinguish significant transport and metabolic mechanisms from limited experimental data, we developed a physiologically based, multiscale mathematical model of cellular metabolic dynamics in skeletal muscle. The model describes mass transport and metabolic processes including distinctive processes of the cytosol and mitochondria. The model simulated skeletal muscle metabolic responses to insulin corresponding to human hyperinsulinemic-euglycemic clamp studies. Insulin-mediated rate of glucose disposal was the primary model input. For model validation, simulations were compared with experimental data: intracellular metabolite concentrations and patterns of glucose disposal. Model variations were simulated to investigate three alternative mechanisms to explain insulin enhancements: Model 1 (M.1), simple mass action; M.2, insulin-mediated activation of key metabolic enzymes (i.e., hexokinase, glycogen synthase, pyruvate dehydrogenase); or M.3, parallel activation by a phenomenological insulin-mediated intracellular signal that modifies reaction rate coefficients. These simulations indicated that models M.1 and M.2 were not sufficient to explain the experimentally measured metabolic responses. However, by application of mechanism M.3, the model predicts metabolite concentration changes and glucose partitioning patterns consistent with experimental data. The reaction rate fluxes quantified by this detailed model of insulin/glucose metabolism provide information that can be used to evaluate the development of type 2 diabetes.
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Project description:ObjectiveTo quantify glucose-mediated glucose disposal with and without basal insulin replacement and insulin-mediated glucose disposal in subjects with impaired fasting glucose (IFG).Research design and methodsWe used the hyperglycemic/pancreatic clamp and stepped euglycemic clamp techniques to quantify glucose disposal and suppression of endogenous glucose production (EGP) in those with normal glucose tolerance (NGT; n = 14) and those with IFG (n = 14).ResultsTotal body glucose-mediated glucose uptake, measured with the hyperglycemic/pancreatic clamp, was not significantly affected by the basal plasma insulin levels in subjects with IFG and those with NGT. Compared with subjects with NGT, those with IFG had significantly lower glucose-mediated glucose uptake (by 15%) during the hyperglycemic clamp performed with and without basal insulin replacement. In contrast, insulin-mediated glucose disposal was comparable in both groups. The suppression of EGP by hyperglycemia was similar in both groups. However, the suppression of EGP by insulin was attenuated in those with IFG compared with those with NGT.ConclusionsThe results of the present study have demonstrated that (i) glucose-mediated glucose disposal is impaired in those with IFG; (ii) insulin-mediated glucose uptake in IFG is normal; and (iii) insulin action to suppress EGP is impaired.
| S-EPMC6286408 | biostudies-literature
Project description:BackgroundEstimated glucose disposal rate (eGDR), a simple and noninvasive measure of insulin resistance, has been proven to be an independent risk factor for first-time stroke and all-cause mortality. In this study, we aimed to investigate the associations between eGDR and the stroke outcome in patients with first-time acute ischemic stroke (AIS).MethodsWe included first-time AIS patients with available data on eGDR in the China National Stroke Registry III (CNSR-III), and divided the subjects into lower eGDR group (eGDR ≤ 6 mg/kg/min) and higher eGDR group (eGDR > 6 mg/kg/min). The primary outcome was excellent functional outcome (modified Rankin Scale score 0-1) at 3 months. Secondary outcomes included stroke recurrence and favorable functional outcome (modified Rankin Scale score 0-2) at 3 months, and functional outcome and combined vascular event at one year. Univariate and multivariate analyses were performed to evaluate the association between eGDR and outcomes.ResultsA total of 6,271 patients with AIS were included in this study. The median values of eGDR in lower and higher eGDR group were 5.0 mg/kg/min (interquartile range, 4.2-5.6) and 7.6 mg/kg/min (interquartile range, 6.8-9.6), respectively. Patients with higher eGDR were significantly associated with higher incidence of excellent functional outcome (adjusted odds ratio, 1.24; 95% confidence interval, 1.06-1.45; P < 0.01) at 3 months and favorable (adjusted odds ratio, 1.55; 95% confidence interval, 1.24-1.93; P < 0.01) and excellent (adjusted odds ratio, 1.28; 95% confidence interval, 1.08-1.51; P < 0.01) functional outcome at one year. However, there was no significant difference in stroke recurrence between these two groups at 3 months (adjusted odds ratio, 0.81; 95% confidence interval, 0.61-1.06; P = 0.12) and one year (adjusted odds ratio, 0.91; 95% confidence interval, 0.73-1.14; P = 0.41).ConclusioneGDR is a predictor of functional outcome in patients with AIS, independent of traditional cardiovascular predictors.
| S-EPMC10464388 | biostudies-literature
Project description:The skeletal muscle is the largest organ in the body, by mass. It is also the regulator of glucose homeostasis, responsible for 80% of postprandial glucose uptake from the circulation. Skeletal muscle is essential for metabolism, both for its role in glucose uptake and its importance in exercise and metabolic disease. In this article, we give an overview of the importance of skeletal muscle in metabolism, describing its role in glucose uptake and the diseases that are associated with skeletal muscle metabolic dysregulation. We focus on the role of skeletal muscle in peripheral insulin resistance and the potential for skeletal muscle-targeted therapeutics to combat insulin resistance and diabetes, as well as other metabolic diseases like aging and obesity. In particular, we outline the possibilities and pitfalls of the quest for exercise mimetics, which are intended to target the molecular mechanisms underlying the beneficial effects of exercise on metabolic disease. We also provide a description of the molecular mechanisms that regulate skeletal muscle glucose uptake, including a focus on the SNARE proteins, which are essential regulators of glucose transport into the skeletal muscle. © 2020 American Physiological Society. Compr Physiol 10:785-809, 2020.
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Project description:Glucagon receptor (GCGR) agonists cause hyperglycemia but also weight loss. However, GCG-like peptide 1 receptor (GLP1R)/GCGR mixed agonists do not exhibit the diabetogenic effects often attributed to GCGR activity. Thus, we sought to investigate the effect of glucagon agonism on insulin action and glucose homeostasis. Acute GCGR agonism induced immediate hyperglycemia, followed by improved glucose tolerance and enhanced glucose-stimulated insulin secretion. Moreover, acute GCGR agonism improved insulin tolerance in a dose-dependent manner in both lean and obese mice. Improved insulin tolerance was independent of GLP1R, FGF21, and hepatic glycogenolysis. Moreover, we observed increased glucose infusion rate, disposal, uptake, and suppressed endogenous glucose production during euglycemic clamps. Mice treated with insulin and GCGR agonist had enhanced phosphorylation of hepatic AKT at Ser473; this effect was reproduced in isolated mouse primary hepatocytes and resulted in increased AKT kinase activity. These data reveal that GCGR agonism enhances glucose tolerance, in part, by augmenting insulin action, with implications for the use of GCGR agonism in therapeutic strategies for diabetes.
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Project description:ObjectiveFatty acid (FA) metabolism is tightly regulated across several tissues and impacts insulin sensitivity. CD36 facilitates cellular FA uptake, and CD36 genetic variants associate with lipid abnormalities and susceptibility to metabolic syndrome. The objective of this study was to gain insight regarding the in vivo metabolic influence of muscle and adipose tissue CD36. For this, we determined the relationships between CD36 alternative transcripts, which can reflect tissue-specific CD36 regulation, and measures of FA metabolism and insulin resistance.Research design and methodsThe relative abundance of alternative CD36 transcripts in adipose tissue and skeletal muscle from 53 nondiabetic obese subjects was measured and related to insulin sensitivity and FA metabolism assessed by hyperinsulinemic-euglycemic clamps and isotopic tracers for glucose and FA.ResultsTranscript 1C, one of two major transcripts in adipose tissue, that is restricted to adipocytes predicted systemic and tissue (adipose, liver, and muscle) insulin sensitivity, suggesting adipocyte CD36 protects against insulin resistance. Transcripts 1B and 1A, the major transcripts in skeletal muscle, correlated with FA disposal rate and triglyceride clearance, supporting importance of muscle CD36 in clearance of circulating FA. Additionally, the common CD36 single nucleotide polymorphism rs1761667 selectively influenced CD36 transcripts and exacerbated insulin resistance of glucose disposal by muscle.ConclusionsAlternative CD36 transcripts differentially influence tissue CD36 and consequently FA homeostasis and insulin sensitivity. Adipocyte CD36 appears to be metabolically protective, and its selective upregulation might have therapeutic potential in insulin resistance.
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Project description:Hypothalamic proopiomelanocortin (POMC) is essential for the physiological regulation of energy balance; however, its role in glucose homeostasis remains less clear. We show that hypothalamic arcuate nucleus (Arc)POMC-deficient mice, which develop severe obesity and insulin resistance, unexpectedly exhibit improved glucose tolerance and remain protected from hyperglycemia. To explain these paradoxical phenotypes, we hypothesized that an insulin-independent pathway is responsible for the enhanced glucose tolerance. Indeed, the mutant mice demonstrated increased glucose effectiveness and exaggerated glycosuria relative to wild-type littermate controls at comparable blood glucose concentrations. Central administration of the melanocortin receptor agonist melanotan II in mutant mice reversed alterations in glucose tolerance and glycosuria, whereas, conversely, administration of the antagonist Agouti-related peptide (Agrp) to wild-type mice enhanced glucose tolerance. The glycosuria of ArcPOMC-deficient mice was due to decreased levels of renal GLUT 2 (rGLUT2) but not sodium-glucose cotransporter 2 and was associated with reduced renal catecholamine content. Epinephrine treatment abolished the genotype differences in glucose tolerance and rGLUT2 levels, suggesting that reduced renal sympathetic nervous system (SNS) activity is the underlying mechanism for the observed glycosuria and improved glucose tolerance in ArcPOMC-deficient mice. Therefore, the ArcPOMC-SNS-rGLUT2 axis is potentially an insulin-independent therapeutic target to control diabetes.
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Project description:Lafora disease is a fatal, progressive myoclonus epilepsy caused in ~90% of cases by mutations in the EPM2A or EPM2B genes. Characteristic of the disease is the formation of Lafora bodies, insoluble deposits containing abnormal glycogen-like material in many tissues, including neurons, muscle, heart and liver. Because glycogen is important for glucose homeostasis, the aberrant glycogen metabolism in Lafora disease might disturb whole-body glucose handling. Indeed, Vernia et al. [Vernia, S., Heredia, M., Criado, O., Rodriguez de Cordoba, S., Garcia-Roves, P.M., Cansell, C., Denis, R., Luquet, S., Foufelle, F., Ferre, P. et al. (2011) Laforin, a dual-specificity phosphatase involved in Lafora disease, regulates insulin response and whole-body energy balance in mice. Hum. Mol. Genet., 20, 2571-2584] reported that Epm2a-/- mice had enhanced glucose disposal and insulin sensitivity, leading them to suggest that laforin, the Epm2a gene product, is involved in insulin signaling. We analyzed 3-month- and 6-7-month-old Epm2a-/- mice and observed no differences in glucose tolerance tests (GTTs) or insulin tolerance tests (ITTs) compared with wild-type mice of matched genetic background. At 3 months, Epm2b-/- mice also showed no differences in GTTs and ITTs. In the 6-7-month-old Epm2a-/- mice, there was no evidence for increased insulin stimulation of the phosphorylation of Akt, GSK-3 or S6 in skeletal muscle, liver and heart. From metabolic analyses, these animals were normal with regard to food intake, oxygen consumption, energy expenditure and respiratory exchange ratio. By dual-energy X-ray absorptiometry scan, body composition was unaltered at 3 or 6-7 months of age. Echocardiography showed no defects of cardiac function in Epm2a-/- or Epm2b-/- mice. We conclude that laforin and malin have no effect on whole-body glucose metabolism and insulin sensitivity, and that laforin is not involved in insulin signaling.
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