MG53's non-physiologic interaction with insulin receptor: lack of effect on insulin-stimulated Akt phosphorylation in muscle, heart and liver tissues.

Rationale: MG53's known function in facilitating tissue repair and anti-inflammation has broad applications to regenerative medicine. There is controversy regarding MG53's role in the development of type 2 diabetes mellitus. Objective: This study aims to address this controversy - whether MG53's myokine function contributes to inhibition of insulin signaling in muscle, heart, and liver tissues. Study design: We determined the binding affinity of the recombinant human MG53 (rhMG53) to the insulin receptor extracellular domain (IR-ECD) and found low affinity of interaction with Kd (>480 nM). Using cultured C2C12 myotubes and HepG2 cells, we found no effect of rhMG53 on insulin-stimulated Akt phosphorylation (p-Akt). We performed in vivo assay with C57BL/6J mice subjected to insulin stimulation (1 U/kg, intraperitoneal injection) and observed no effect of rhMG53 on insulin-stimulated p-Akt in muscle, heart and liver tissues. Conclusion: Overall, our data suggest that rhMG53 can bind to the IR-ECD, however has a low likelihood of a physiologic role, as the Kd for binding is ~10,000 higher than the physiologic level of MG53 present in the serum of rodents and humans (~10 pM). Our findings question the notion proposed by Xiao and colleagues - whether targeting circulating MG53 opens a new therapeutic avenue for type 2 diabetes mellitus and its complications.

Fetuin-B Interacts With Insulin Receptor-ß and Promotes Insulin Resistance in Retina Cells.

Purpose: The purpose of this study was to investigate the correlation between insulin and Fetuin-B (FETUB) and the influence of FETUB on insulin signaling pathway in diabetic retinopathy (DR). Methods: Enzyme-linked immunosorbent assay (ELISA) was used to analyze FETUB and insulin levels in the serum and aqueous fluid of patients with DR and healthy controls. Quantitative PCR (q-PCR), Western blotting, and ELISA were used to examine FETUB expression in ARPE-19, BV2, and Müller cells under insulin stimulation. Co-immunoprecipitation was used to investigate the interaction of FETUB with insulin receptor-ß (IRß). Insulin resistance (IR)-BV2 and IR-Müller cells were treated with FETUB recombinant protein or FETUB short hairpin RNA (shRNA) to explore the influence of FETUB on insulin signaling pathway in DR. LY294002 (a PI3K pathway inhibitor) was used to determine whether FETUB affects glucose metabolism via the PI3K/Akt pathway. Results: In aqueous fluid, FETUB concentrations were positively correlated with insulin levels. FETUB expression increased in Müller and BV2 cells under insulin regulation, and FETUB interacted with IRß in retinal cells and mice retina. The interaction between IRß and FETUB increased in BV2 and Müller cells under high-glucose than in controls. Insulin signaling pathway activation was suppressed in FETUB recombinant protein-treated BV2 and Müller cells but increased in FETUB shRNA-transfected cells. FETUB shRNA could not reverse LY294002-mediated inhibition of glucose transporter-4 expression. Conclusions: Retinal cells are the source of insulin-regulated FETUB. The FETUB interacts with IRß and affects insulin signaling pathway in BV2 and Müller cells. FETUB may aggravate IR in BV2 and Müller cells via the PI3K/Akt pathway.

WormCNN-Assisted Establishment and Analysis of Glycation Stress Models in C. elegans: Insights into Disease and Healthy Aging.

Glycation Stress (GS), induced by advanced glycation end-products (AGEs), significantly impacts aging processes. This study introduces a new model of GS of Caenorhabditis elegans by feeding them Escherichia coli OP50 cultured in a glucose-enriched medium, which better simulates human dietary glycation compared to previous single protein-glucose cross-linking methods. Utilizing WormCNN, a deep learning model, we assessed the health status and calculated the Healthy Aging Index (HAI) of worms with or without GS. Our results demonstrated accelerated aging in the GS group, evidenced by increased autofluorescence and altered gene expression of key aging regulators, daf-2 and daf-16. Additionally, we observed elevated pharyngeal pumping rates in AGEs-fed worms, suggesting an addictive response similar to human dietary patterns. This study highlights the profound effects of GS on worm aging and underscores the critical role of computer vision in accurately assessing health status and aiding in the establishment of disease models. The findings provide insights into glycation-induced aging and offer a comprehensive approach to studying the effects of dietary glycation on aging processes.

Insulin-inspired hippocampal neuron-targeting technology for protein drug delivery.

Hippocampal neurons can be the first to be impaired with neurodegenerative disorders, including Alzheimer's disease (AD). Most drug candidates for causal therapy of AD cannot either enter the brain or accumulate around hippocampal neurons. Here, we genetically engineered insulin-fusion proteins, called hippocampal neuron-targeting (Ht) proteins, for targeting protein drugs to hippocampal neurons because insulin tends to accumulate in the neuronal cell layers of the hippocampus. In vitro examinations clarified that insulin and Ht proteins were internalized into the cultured hippocampal neurons through insulin receptor-mediated macropinocytosis. Cysteines were key determinants of the delivery of Ht proteins to hippocampal neurons, and insulin B chain mutant was most potent in delivering cargo proteins. In vivo accumulation of Ht proteins to hippocampal neuronal layers occurred after intracerebroventricular administration. Thus, hippocampal neuron-targeting technology can provide great help for developing protein drugs against neurodegenerative disorders.

The Impact of Dibutyl Phthalate on Insulin Signaling in Human Skeletal Muscle Cells.

BACKGROUND: In China, the environmental concern of Dibutyl Phthalate (DBP) exposure significantly endangers human health by inducing insulin resistance (IR). Skeletal muscle tissue plays a critical role in this process. However, the precise molecular mechanisms through which DBP interferes with the insulin signaling pathway remain to be fully elucidated. This study aims to explore the molecular mechanisms by which DBP induces IR in skeletal muscle, focusing on the phosphatidylinositol 3-kinase (PI3K)-serine/threonine kinase (AKT)-glucose transporter 4 (GLUT4) signaling pathway. METHODS: To investigate the molecular mechanisms underlying DBP-induced IR, an experimental study was established on a human skeletal muscle cell line (HSkMC). Expression levels of mRNA and proteins associated with key signaling genes within the insulin receptor (INSR)-insulin receptor substrate (IRS)-PI3K-AKT-GLUT4 pathway were assessed using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot techniques. Additionally, this study explored the effects of DBP alone and in combination with a PI3K inhibitor (BKM120) or phosphatase and tensin homolog (PTEN) overexpression lentivirus on these signaling components. RESULTS: Results from this study demonstrated that DBP exposure significantly decreased mRNA levels of INSR, IRS1, PI3K, AKT2, and GLUT4 in HSkMC cells compared to untreated control cells. This reduction was exacerbated when DBP was combined with BKM120 or PTEN overexpression lentivirus, suggesting a synergistic effect. Furthermore, DBP treatment reduced the expression and phosphorylation of AKT2, indicating a disruption in the insulin signaling pathway. CONCLUSIONS: This study elucidates a molecular mechanism by which DBP induces IR in skeletal muscle cells, primarily through the deregulation of the PI3K-dependent insulin signaling pathway. These insights enhance comprehension of the pathophysiological changes associated with IR caused by environmental pollutants like DBP, potentially guiding future strategies for prevention and intervention.

Farrerol alleviates insulin resistance and hepatic steatosis of metabolic associated fatty liver disease by targeting PTPN1.

Metabolic associated fatty liver disease (MAFLD) is the most common chronic liver disease worldwide, characterized by excess lipid deposition. Insulin resistance (IR) serves as a fundamental pathogenic factor in MAFLD. However, currently, there are no approved specific agents for its treatment. Farrerol, a novel compound with antioxidant and anti-inflammatory effects, has garnered significant attention in recent years due to its hepatoprotective properties. Despite this, the precise underlying mechanisms of action remain unclear. In this study, a network pharmacology approach predicted protein tyrosine phosphatase non-receptor type 1 (PTPN1) as a potential target for farrerol's action in the liver. Subsequently, the administration of farrerol improved insulin sensitivity and glucose tolerance in MAFLD mice. Furthermore, farrerol alleviated lipid accumulation by binding to PTPN1 and reducing the dephosphorylation of the insulin receptor (INSR) in HepG2 cells and MAFLD mice. Thus, the phosphoinositide 3-kinase/serine/threonine-protein kinases (PI3K/AKT) signalling pathway was active, leading to downstream protein reduction. Overall, the study demonstrates that farrerol alleviates insulin resistance and hepatic steatosis of MAFLD by targeting PTPN1.

Chronic stress induces insulin resistance and enhances cognitive impairment in AD.

BACKGROUND: Chronic stress can induce the cognitive impairment, and even promote the occurrence and development of Alzheimer's disease (AD). Evidence has suggested that chronic stress impacts on glucose metabolism, and both of these have been implicated in AD. Here we focused on the effect of insulin resistance in glucose metabolism, and further evaluated the changes in cognition and pathology. METHODS: Male 9-month-old wild-type and APP/PS1 mice were randomly divided into 4 groups. Mice in the chronic unpredictable mild stress (CUMS) groups were exposed for 4 weeks. Homeostatic Model Assessment (HOMA) was utilized to evaluate insulin sensitivity. A total of eighty-four genes related to the insulin signaling pathway were examined for rapid screening. Additionally, the phosphorylated protein expressions of insulin receptors (IR), IR substrate 1 (IRS1), c-Jun N-terminal kinase (JNK), and amyloid were detected in the hippocampus. Cognitive function was assessed through ethological methods. Cognitive function was assessed using both the Morris water maze (MWM) and the Passive avoidance test (PAT). RESULTS: Four weeks of CUMS exposure significantly increased the HOMA value, indicating reduced insulin sensitivity. The gene expressions of Insr and Lipe were downregulated. Additionally, the analysis revealed a significant interaction between the genotype (wild-type vs. APP/PS1) and CUMS treatment on the phosphorylated protein expressions of insulin receptor substrate 1 (IRS1). Specifically, CUMS exposure increased the inhibitory phosphorylation site (IRS1-pSer636) and decreased the excitatory phosphorylation site (IRS1-pTyr465) in the post-insulin receptor signaling pathway within the hippocampus of both wild-type and APP/PS1 mice. Moreover, CUMS exposure induced and exacerbated cognitive impairments in both wild-type and APP/PS1 mice, as assessed by the Morris water maze (MWM) and Passive avoidance test (PAT). However, there was no significant effect of CUMS on senile plaque deposition or levels of Aß42 and Aß40 in wild-type mice. CONCLUSIONS: Chronic stress significantly affects hippocampal cognitive function through insulin resistance and exacerbates AD pathology. This study reveals the complex relationship between chronic stress, insulin resistance, and AD, providing new insights for developing interventions targeting chronic stress and insulin resistance.

Metabolic and hormonal profiling in polycystic ovarian syndrome: insights into INSR gene variations.

BACKGROUND: Polycystic Ovary Syndrome (PCOS) is a hormonal disorder characterized by irregular periods, excess androgen levels, and polycystic ovaries, affecting many women of reproductive age. METHODS AND RESULTS: This study employed statistical and molecular analyses to compare hormone and metabolic markers between PCOS patients and controls. Sanger sequencing identified two INSR gene variants linked to high insulin and pre-diabetic conditions. Statistically, no significant age differences were detected (p = 0.492) between the overall PCOS patient pool and controls. However, a substantial variation in Vitamin D levels was observed within PCOS patients compared to controls (p = 0.0006), suggesting an association with PCOS. Correlations between Vitamin D and insulin, as well as HbA1c levels (R2 = 0.141 and 0.143, respectively), suggest Vitamin D's potential impact on glycemic control. Significant differences were found in HbA1c (p < 0.0001), insulin (p < 0.0001), and LDL (p = 0.0004) levels between PCOS patients and controls, highlighting marked disparities in these metabolic markers. LH levels also showed a significant contrast (p < 0.0001), while progesterone levels displayed a notable difference (p = 0.007) between the two groups. Correlation analyses within PCOS patients demonstrated associations among LDL, HbA1c, and insulin, with no such correlations observed in control cases. Additionally, Sanger sequencing identified two INSR gene variants, c.3614C > T (p.Pro1205Leu) and c.3355C > T (p.Arg1119Trp), associated with high insulin, LH, and pre-diabetic conditions. These amino acid changes may trigger metabolic imbalances and hormonal irregularities, potentially contributing to the development of PCOS. CONCLUSIONS: The findings highlight the multifaceted nature of PCOS, revealing significant metabolic, hormonal, and genetic differences compared to controls. These insights may inform tailored interventions and management strategies for the complex associations characteristic of PCOS.

Nitric oxide in modulating oxidative stress mediated skeletal muscle insulin resistance.

Insulin resistance (IR) being the major cause behind different metabolic disorders, has attracted a lot of attention. Epidemiological data shows marked rise in the cases over a period of time. Nitric oxide (NO), produced from nitric oxide synthases (NOS), is involved in a variety of biological functions, alteration in which causes various disorders like hypertension, atherosclerosis, and angiogenesis-associated disorders. IR has been found to be a contributing factor, which is associated with abnormal NO signalling. Skeletal muscle is essential for metabolism, both for its role in glucose uptake and its importance in metabolic disease. In this article, we give an overview of the significance of NO in oxidative stress (OS) mediated IR, describing its role in different conditions that are associated with skeletal muscle IR. NO is found to be involved in the activation of insulin receptor downstream pathway, which suggests absence of NO could lead to reduced glucose uptake, and may ultimately result in IR.

Agonist Discovery for Membrane Proteins on Live Cells by Using DNA-encoded Libraries.

Identifying biologically active ligands for membrane proteins is an important task in chemical biology. We report an approach to directly identify small molecule agonists against membrane proteins by selecting DNA-encoded libraries (DELs) on live cells. This method connects extracellular ligand binding with intracellular biochemical transformation, thereby biasing the selection toward agonist identification. We have demonstrated the methodology with three membrane proteins: epidermal growth factor receptor (EGFR), thrombopoietin receptor (TPOR), and insulin receptor (INSR). A ∼30 million and a 1.033 billion-compound DEL were selected against these targets, and novel agonists with subnanomolar affinity and low micromolar cellular activities have been discovered. The INSR agonists activated the receptor by possibly binding to an allosteric site, exhibited clear synergistic effects with insulin, and activated the downstream signaling pathways. Notably, the agonists did not activate the insulin-like growth factor 1 receptor (IGF-1R), a highly homologous receptor whose activation may lead to tumor progression. Collectively, this work has developed an approach toward "functional" DEL selections on the cell surface and may provide a widely applicable method for agonist discovery for membrane proteins.

Theaflavins mitigate diabetic symptoms in GK rats by modulating the INSR/PI3K-Akt/GSK-3 pathway and intestinal microbiota.

Dietary management and interventions are crucial in the clinical management of diabetes. Numerous active dietary components in black tea have demonstrated positive effects on blood glucose levels and metabolic functions. However, limited research has explored the potential of theaflavins (TF), polyphenols in black tea, for diabetes management. In this study, high-purity TF was administered to Goto-Kakizaki (GK) diabetic model rats for four weeks to investigate its impact on diabetic pathology and analyze the underlying mechanisms through liver transcriptomics, hepatocyte metabolomics, and gut microbiome analysis. The findings indicated that continuous administration of TF (100 mg/kg) significantly suppressed blood glucose levels, reduced insulin resistance, and decreased the expression of oxidative stress indicators and inflammatory factors in GK rats. Further analysis revealed that TF might alleviate insulin resistance by improving hepatic glycogen conversion and reducing hepatic lipid deposition through modulation of key pathways, such as peroxisome proliferator-activated receptors and PI3K/AKT/GSK-3 pathways within the liver, thereby ameliorating diabetic symptoms. Additionally, TF intake facilitated the restoration of the intestinal microbial community structure by reducing the abundance of harmful bacteria and increasing the abundance of beneficial bacteria. It also reduced endotoxin lipopolysaccharide production, thereby lowering the chances of insulin resistance development and enhancing its efficacy in regulating blood glucose levels. These findings offer a novel perspective on the potential of black tea and its active constituents to prevent and treat diabetes and other metabolic disorders, providing valuable references for identifying and applying active dietary components from tea.

Impact of Serotonin Transporter Absence on Brain Insulin Receptor Expression, Plasma Metabolome Changes, and ADHD-like Behavior in Mice fed a Western Diet.

The impaired function of the serotonin transporter (SERT) in humans has been linked to a higher risk of obesity and type 2 diabetes, especially as people age. Consuming a "Western diet" (WD), which is high in saturated fats, cholesterol, and sugars, can induce metabolic syndrome. Previous research indicated that mice carrying a targeted inactivation of the Sert gene (knockout, KO) and fed a WD display significant metabolic disturbances and behaviors reminiscent of ADHD. These abnormalities might be mediated via a dysfunction in insulin receptor (IR) signaling, which is also associated with adult ADHD. However, the impact of Sert deficiency on IR signaling and systemic metabolic changes has not been thoroughly explored. In this study, we conducted a detailed analysis of locomotor behavior in wild-type (WT) and KO mice fed a WD or control diet. We investigated changes in the blood metabolome and examined, via PCR, the expression of insulin receptor A and B isoforms and key regulators of their function in the brain. Twelve-month-old KO mice and their WT littermates were fed a WD for three weeks. Nuclear magnetic resonance spectroscopy analysis of plasma samples showed that KO mice on a WD had higher levels of lipids and lipoproteins and lower levels of glucose, lactate, alanine, valine, and isoleucine compared to other groups. SERT-KO mice on the control diet exhibited increased brain levels of both IR A and B isoforms, accompanied by a modest increase in the negative regulator ENPP. The KO mice also displayed anxiety-like behavior and reduced exploratory activity in an open field test. However, when the KO animals were fed a WD, the aberrant expression levels of IR isoforms in the KO mice and locomotor behavior were ameliorated indicating a complex interaction between genetic and dietary factors that might contribute to ADHD-like symptoms. Overall, our findings suggest that the lack of Sert leads to a unique metabolic phenotype in aged mice, characterized by dysregulated IR-related pathways. These changes are exacerbated by WD in the blood metabolome and are associated with behavioral abnormalities.

Insulin enhances acid-sensing ion channel currents in rat primary sensory neurons.

Insulin has been shown to modulate neuronal processes through insulin receptors. The ion channels located on neurons may be important targets for insulin/insulin receptor signaling. Both insulin receptors and acid-sensing ion channels (ASICs) are expressed in dorsal root ganglia (DRG) neurons. However, it is still unclear whether there is an interaction between them. Therefore, the purpose of this investigation was to determine the effects of insulin on the functional activity of ASICs. A 5 min application of insulin rapidly enhanced acid-evoked ASIC currents in rat DRG neurons in a concentration-dependent manner. Insulin shifted the concentration-response plot for ASIC currents upward, with an increase of 46.2 ± 7.6% in the maximal current response. The insulin-induced increase in ASIC currents was eliminated by the insulin receptor antagonist GSK1838705, the tyrosine kinase inhibitor lavendustin A, and the phosphatidylinositol-3 kinase antagonist wortmannin. Moreover, insulin increased the number of acid-triggered action potentials by activating insulin receptors. Finally, local administration of insulin exacerbated the spontaneous nociceptive behaviors induced by intraplantar acid injection and the mechanical hyperalgesia induced by intramuscular acid injections through peripheral insulin receptors. These results suggested that insulin/insulin receptor signaling enhanced the functional activity of ASICs via tyrosine kinase and phosphatidylinositol-3 kinase pathways. Our findings revealed that ASICs were targets in primary sensory neurons for insulin receptor signaling, which may underlie insulin modulation of pain.

Cell-Specific Effects of Insulin in a Murine Model of Restenosis Under Insulin-Sensitive and Insulin-Resistant Conditions.

Restenosis following percutaneous revascularization is a major challenge in patients with insulin resistance and diabetes. Currently, the vascular effects of insulin are not fully understood. In vitro, insulin's effects on endothelial cells (ECs) are beneficial, whereas on vascular smooth muscle cells (SMCs), they are mitogenic. We previously demonstrated a suppressive effect of insulin on neointimal growth under insulin-sensitive conditions that was abolished in insulin-resistant conditions. Here, we aimed to determine the cell-specific effects of insulin on neointimal growth in a model of restenosis under insulin-sensitive and insulin-resistant conditions. Vascular cell-specific insulin receptor (IR)-deficient mice were fed a low-fat diet (LFD) or a high-fat, high-sucrose diet (HFSD) and implanted with an insulin pellet or vehicle prior to femoral artery wire injury. In insulin-sensitive conditions, insulin decreased neointimal growth only in controls. However, under insulin-resistant conditions, insulin had no effect in either control, EC-specific or SMC-specific IR-deficient mice. These data demonstrate that EC and SMC IRs are required for the anti-restenotic effect of insulin in insulin-sensitive conditions and that, in insulin resistance, insulin has no adverse effect on vascular SMCs in vivo.

A homeostatic gut-to-brain insulin antagonist restrains neuronally stimulated fat loss.

In C. elegans mechanisms by which peripheral organs relay internal state information to the nervous system remain unknown, although strong evidence suggests that such signals do exist. Here we report the discovery of a peptide of the ancestral insulin superfamily called INS-7 that functions as an enteroendocrine peptide and is secreted from specialized cells of the intestine. INS-7 secretion is stimulated by food withdrawal, increases during fasting and acts as a bona fide gut-to-brain peptide that attenuates the release of a neuropeptide that drives fat loss in the periphery. Thus, INS-7 functions as a homeostatic signal from the intestine that gates the neuronal drive to stimulate fat loss during food shortage. Mechanistically, INS-7 functions as an antagonist at the canonical DAF-2 receptor and functions via FOXO and AMPK signaling in ASI neurons. Phylogenetic analysis suggests that INS-7 bears greater resemblance to members of the broad insulin/relaxin superfamily than to conventional mammalian insulin and IGF peptides. The discovery of an endogenous insulin antagonist secreted by specialized intestinal cells with enteroendocrine functions suggests unexpected and important properties of the intestine and its role in directing neuronal functions.

Effects of heat stress on the feeding preference of yellow-feathered broilers and its possible mechanism.

Heat stress is the most critical factor affecting animal feeding in summer. This experiment was conducted to investigate the effects of heat stress on the feeding preference of yellow-feathered broilers and its possible mechanism. As a result, the preference of yellow-feathered broilers for Tenebrio molitor was significantly decreased, and the fear response and serum corticosterone of broilers were significantly increased when the ambient temperatures are 35 °C (P < 0.05). In the central nervous system, consistent with the change in feeding preference, decreased dopamine in the nucleus accumbens (NAc) and increased mRNA levels of MAO-B in the ventral tegmental area (VTA) and NAc were found in yellow-feathered broilers (P < 0.05). In addition, we found significantly increased mRNA levels of corticotropin-releasing hormone receptor 1, corticotropin-releasing hormone receptor 2 and glucocorticoid receptor in the VTA and NAc of female broilers (P < 0.05). However, no similar change was found in male broilers. On the other hand, the serum levels of insulin and glucagon-like peptide-1 were increased only in male broilers (P < 0.05). Accordingly, the mRNA levels of insulin receptor and glucagon-like peptide-1 receptor in the VTA and the phosphorylation of mTOR and PI3K were increased only in male broilers (P < 0.05). In summary, the preference of yellow-feathered broilers for Tenebrio molitor feed decreased under heat stress conditions, and hedonic feeding behavior was significantly inhibited. However, the mechanism by which heat stress affects hedonic feeding behavior may contain gender differences. The insulin signaling pathway may participate in the regulation of heat stress on the male broiler reward system, while stress hormone-related receptors in the midbrain may play an important role in the effect of heat stress on the reward system of female broilers.

Role of Vitamin D Receptor (BsmI-VDR) and Insulin Receptor (NsiI-A/G) Gene Polymorphisms in Colorectal Adenoma Susceptibility.

Vitamin D deficiency and type 2 diabetes mellitus are risk factors for colorectal cancer, suggesting a role for vitamin D receptor (VDR) and insulin receptor (INSR) gene polymorphisms. We investigated the prevalence of the VDR-BsmI (rs1544410) and NsiI A/G-INSR (rs2059806) polymorphisms and their associations with colorectal adenoma (CRA) in a Romanian population. A case-control study was conducted with 110 participants (67 with CRA and 43 controls) who underwent colonoscopy. Polymerase chain reaction-restriction fragment length polymorphism analysis was used to determine the genotype and allele frequencies of the two polymorphisms. Regarding rs1544410 and CRA patients, genotype distribution was 35% B/B, 47% B/b, and 19% b/b. In the controls, the distribution was 21% B/B, 45% B/b, and 34% b/b. For rs2059806, 12% of CRA patients had A/A, 30% A/G, and 58% G/G, while 8% of the controls had A/A, 40% A/G, and 52% G/G. The recessive model showed an odds ratio of 2.84 (95% CI: 1.04-7.72, p = 0.033) for the b/b genotype. CRA patients with b/b or G/G genotypes were diagnosed at a younger age. The b allele of the rs1544410 was a risk factor for CRA. Patients with the b/b and G/G genotypes were diagnosed earlier.

Insulin and the blood-brain barrier.

The blood-brain barrier (BBB) predominantly regulates insulin transport into and levels within the brain. The BBB is also an important site of insulin binding and mediator of insulin receptor (INSR) signaling. The insulin transporter is separate from the INSR, highlighting the important, unique role of each protein in this structure. After a brief introduction on the structure of insulin and the INSR, we discuss the importance of insulin interactions at the BBB, the properties of the insulin transporter and the role of the BBB insulin transporter in various physiological conditions. We go on to further describe insulin BBB signaling and the impact not only within brain endothelial cells but also the cascade into other cell types within the brain. We close with future considerations to advance our knowledge about the importance of insulin at the BBB.

Insulin receptor at the blood-brain barrier: Transport and signaling.

The blood-brain barrier (BBB) is a unique system of the brain microvasculature that limits the exchange between the blood and the brain. Brain microvascular endothelial cells form the BBB as part of the neurovascular unit and express insulin receptors. The insulin receptor at the BBB has been studied in two different functional aspects. These functions include (1) the supplying of blood insulin to the brain and (2) the modulation of BBB function via insulin signaling. The first function involves drug delivery to the brain, while the second function is related to the association between central nervous system diseases and type 2 diabetes through insulin resistance. This chapter summarizes recent progress in research on the function of insulin receptors at the BBB.

MαCD-based plasma membrane outer leaflet lipid exchange in mammalian cells to study insulin receptor activity.

Signaling receptors on the plasma membrane, such as insulin receptor, can have their activity modulated to some extent by their surrounding lipids. Studying the contribution of membrane lipid properties such as presence of ordered lipid domains or bilayer thickness on the activity of receptors has been a challenging objective in living cells. Using methyl-alpha cyclodextrin-mediated lipid exchange, we are able to alter the lipids of the outer leaflet plasma membrane of mammalian cells to investigate the effect of the properties of the exchanged lipid upon receptor function in live cells. In this article, we describe the technique of lipid exchange in detail and how it can be applied to better understand lipid-mediated regulation of insulin receptor activity in cells.