Insulin Degradation Research Articles

Application of Integrated Optical Density in Evaluating Insulin Expression in the Endocrine Pancreas During Chronic Ethanol Exposure and β-Carotene Supplementation: A Novel Approach Utilizing Artificial Intelligence

Background: β-carotene is an essential antioxidant, providing protection against type 2 diabetes mellitus, cardiovascular illnesses, obesity, and metabolic syndrome. This study investigates the impact of β-carotene on biochemical parameters and pancreatic insulin expression in mice exposed to ethanol. Methods: Thirty-six C57BL/6 mice (Mus musculus) were divided into six groups: 1. C (control), 2. LA (3% alcohol dose), 3. MA (7% alcohol dose), 4. B (0.52 mg/kg body weight/day β-carotene), 5. LA+B (3% alcohol dose + 0.52 mg/kg body weight/day β-carotene), and 6. MA+B (7% alcohol dose plus 0.52 mg/kg body weight/day β-carotene). After 28 days, the animals were euthanized for serum and pancreatic tissue collection. Biochemical analysis and pancreatic insulin expression were performed. One-way ANOVA was used. Results: The B, LA+B, and MA+B groups improved insulin levels and decreased HOMA-β versus the C group, with the LA+B and MA+B groups also showing lower ADH and ALDH levels than their nonsupplemented counterparts (p < 0.05). The B, LA+B, and MA+B groups showed a greater β-cell mass area compared to the unsupplemented groups. Additionally, the LA+B and MA+B groups demonstrated significantly increased β-cell area and integrated optical density compared to the LA and MA groups, respectively (p < 0.001). Conclusions: In mice, β-cell loss led to increased glucose release due to decreased insulin levels. β-carotene appeared to mitigate ethanol’s impact on these cells, resulting in reduced insulin degradation when integrated optical density was used. These findings suggest that antioxidant supplementation may be beneficial in treating ethanol-induced type 2 diabetes in animal models.

In Vitro Investigation of Insulin Dynamics During 4 Hours of Simulated Cardiopulmonary Bypass.

Hyperglycemia is common in patients undergoing cardiovascular surgery with cardiopulmonary bypass. We hypothesize that intraoperative hyperglycemia may be, at least partially, attributable to insulin loss due to adhesion on artificial surfaces and/or degradation by hemolysis. Thus, our primary aim was to investigate the loss of insulin in 2 different isolated extracorporeal circulation circuits (ECCs), that is, a conventional ECC (cECC) with a roller pump, and a mini-ECC (MiECC) system with a centrifugal pump. The secondary aim was to assess and compare the relationship between changes in insulin concentration and the degree of hemolysis in our 2 ECC models. Six cECC and 6 MiECC systems were primed with red packed blood cells and thawed fresh-frozen plasma (1:1). Four additional experiments were performed in cECC using only thawed fresh-frozen plasma. Human insulin (Actrapid) was added, targeting a plasma insulin concentration of 400 mU/L. Insulin concentration and hemolysis index were measured at baseline and hourly thereafter. The end points were the change in insulin level after 4 hours compared to baseline and hemolysis index after 4 hours. The insulin concentration and hemolysis index were analyzed by means of a saturated linear mixed-effect regression model with a random offset for each experiment to account for the repeated measure design of the study, resulting in mean estimates and 95% confidence intervals (CIs) of the primary end points as well as of pairwise contrasts with respect to ECC type. Insulin concentration decreased by 63% (95% CI, 48%-77%) in the MiECC and 92% (95% CI, 77%-106%) in the cECC system that contained red blood cells. Insulin loss was significantly higher in the cECC system compared to the MiECC (P = .022). In the cECC with only plasma, insulin did not significantly decrease (-4%; 95% CI, -21% to 14%). Hemolysis index in MiECC increased from 68 (95% CI, 46-91) to 76 (95% CI, 54-98) after 4 hours, in cECC from 81 (95% CI, 59-103) to 121 (95% CI, 99-143). Hemolysis index and percent change of insulin showed an excellent relationship (r = -0.99, P < .01). Our data showed that insulin levels substantially decreased during 4 hours of simulated cardiopulmonary bypass only in the ECC that contained hemoglobin. The decrease was more pronounced in the cECC, which also exhibited a greater degree of hemolysis. Our results suggest that insulin degradation by hemolysis products may be a stronger contributor to insulin loss than adhesion of insulin molecules to circuit surfaces.

Displacement Micropump with Check Valves for Diabetes Care—The Challenge of Pumping Insulin at Negative Pressure

The displacement micropump with passive check valves is an attractive solution for precise insulin infusion in patients with type I diabetes. Unlike most insulin pumps that push insulin from a cartridge using a piston, a displacement micropump will first pull insulin from the reservoir before infusing it into the patient. This dual sequence introduces new challenges in terms of insulin stability, notably if the reservoir is not pressurized. After an introduction to displacement micropumps and a brief review of the insulin degradation mechanism, micropump design rules are discussed in light of microfluidic theory.

Elucidating the Degradation Pathways of Human Insulin in the Solid State

While there have been significant advances in the development of peptide oral dosage forms in recent years, highlighted by the clinical and commercial success of approved peptides such as Rybelsus®, there remain several barriers in the way of broad range applicability of this approach to peptide delivery. One such barrier includes the poor physical and chemical stability inherent to their structures, which persists in the solid state although degradation typically occurs at different rates and via different pathways in comparison to the solution state. Using insulin as a model peptide, this work sought to contribute to the development of analytical techniques for investigating common insulin degradation pathways. Chemically denatured, deamidated and aggregated samples were prepared and used to benchmark circular dichroism spectroscopy, reverse phase HPLC and size exclusion chromatography methods for the investigation of unfolding, chemical modifications and covalent aggregation of the insulin molecule respectively. Solid state degraded samples were prepared by heating insulin powder at 60 °C and 75% relative humidity for 1, 3, 5 and 7 d, and the degradation profiles of the samples were evaluated and compared with those observed in solution. While no unfolding was observed to occur, significant deamidation and covalent aggregation were detected. Reductive disulfide bond cleavage using dithiothreitol allowed for separation of the insulin A- and B-chains, offering a facile yet novel means of assessing the mechanisms of deamidation and covalent aggregation occurring in the solid state.

A comprehensive review of oral chitosan drug delivery systems: Applications for oral insulin delivery

Abstract Pharmaceutical scientists have long struggled to develop reliable and efficient systems of administering insulin orally due to multiple barriers, including stomach acidity, enzymatic degradation, and mucus barriers. However, various strategies were developed to avoid insulin degradation in the gastrointestinal tract (GIT) and promote membrane permeability and biological activity. Among these strategies, chitosan polymer-based carriers are widely researched due to their ability to protect insulin in the alimentary canal and deliver it effectively through the intestinal mucosa, improving its bioavailability. To improve chitosan properties, chemical and physical modifications have been developed, and recently, nanoparticles, microparticles, and beads of chitosan exhibited potential systems for oral insulin delivery (OID). This review facilitates an outline of the types of diabetes mellitus, insulin biosynthesis, and gastrointestinal barriers against oral insulin. Moreover, the limitations of subcutaneous insulin delivery and alternative routes of administration are also discussed. As an ideal and most convenient oral administration route, the challenges of safe insulin delivery through the GIT and strategies to elevate its bioavailability are highlighted. In addition, this review focuses on recent advancements in chitosan based carriers for OID and their potential future applications.

Ursodeoxycholic Acid-Decorated Zwitterionic Nanoparticles for Orally Liver-Targeted Close-Looped Insulin Delivery.

Oral insulin therapies targeting the liver and further simulating close-looped secretion face significant challenges due to multiple trans-epithelial barriers. Herein, ursodeoxycholic acid (UDCA)-decorated zwitterionic nanoparticles (NPs) (UC-CMs@ins) are designed to overcome these barriers, target the liver, and respond to glycemia, thereby achieving oral one-time-per-day therapy. UC-CMs@ins show excellent mucus permeability through the introduction of zwitterion (carboxy betaine, CB). Furthermore, UC-CMs@ins possess superior cellular internalization via proton-assisted amino acid transporter 1 (PAT1, CB-receptor) and apical sodium-dependent bile acid transporter (ASBT, UDCA-receptor) pathways. Moreover, UC-CMs@ins exhibit excellent endolysosomal escape ability and improve the basolateral release of insulin into the bloodstream via the ileal bile acid-binding protein and the heteromeric organic solute transporter (OSTα- OSTβ) routes compared with non-UDCA-decorated C-CMs@ins. Therefore, CB and UDCA jointly overcome mucus and intestinal barriers. Additionally, UC-CMs@ins prevent insulin degradation in the gastrointestinal tract for crosslinked structure, improve insulin accumulation in the liver for UDCA introduction, and effectively regulate glycemia for "closed-loop" glucose control. Surprisingly, oral ingestion of UC-CMs@ins shows a superior effect on glycemia (≈22h, normoglycemia) and improves postprandial glycemic levels in diabetic mice, illustrating the enormous potential of the prepared NPs as a platform for oral insulin administration in diabetes treatment.

The adhesion GPCR GPR116/ADGRF5 has a dual function in pancreatic islets regulating somatostatin release and islet development

Glucose homeostasis is maintained by hormones secreted from different cell types of the pancreatic islets and controlled by manifold input including signals mediated through G protein-coupled receptors (GPCRs). RNA-seq analyses revealed expression of numerous GPCRs in mouse and human pancreatic islets, among them Gpr116/Adgrf5. GPR116 is an adhesion GPCR mainly found in lung and required for surfactant secretion. Here, we demonstrate that GPR116 is involved in the somatostatin release from pancreatic delta cells using a whole-body as well as a cell-specific knock-out mouse model. Interestingly, the whole-body GPR116 deficiency causes further changes such as decreased beta-cell mass, lower number of small islets, and reduced pancreatic insulin content. Glucose homeostasis in global GPR116-deficient mice is maintained by counter-acting mechanisms modulating insulin degradation. Our data highlight an important function of GPR116 in controlling glucose homeostasis.

Biochemical Toxicological Study of Insulin Overdose in Rats: A Forensic Perspective.

Due to nonspecific pathological changes and the rapid degradation of insulin in postmortem blood samples, the identification of the cause of death during insulin overdose has always been a difficulty in forensic medicine. At present, there is a lack of studies on the toxicological changes and related mechanisms of an insulin overdose, and the specific molecular markers of insulin overdose are still unclear. In this study, an animal model of insulin overdose was established, and 24 SD rats were randomly divided into a control group, insulin overdose group, and a recovery group (n = 8). We detected the biochemical changes and analyzed the toxicological mechanism of an insulin overdose. The results showed that after insulin overdose, the rats developed irregular convulsions, Eclampsia, Opisthotonos, and other symptoms. The levels of glucose, glycogen, and C-peptide in the body decreased significantly, while the levels of lactate, insulin, and glucagon increased significantly. The decrease in plasma K+ was accompanied by the increase in skeletal muscle K+. The PI3K-AKT signaling pathway was significantly activated in skeletal muscle, and the translocation of GLUT4/Na+-K+-ATPase to sarcolemma was significantly increased. Rare glycogenic hepatopathy occurred in the recovery group after insulin overdose. Our study showed that insulin overdose also plays a role in skeletal muscle cells, mainly through the PI3K-Akt signaling pathway. Therefore, the detection of signaling pathway proteins of the skeletal muscle cell membrane GLUT4 and Na+-K+-ATPase has a certain auxiliary diagnostic value for forensic insulin overdose identification. Glycogen detection in the liver and skeletal muscle is important for the diagnosis of insulin overdose, but it still needs to be differentiated from other causes of death. Skeletal muscle has great potential for insulin detection, and the ratio of insulin to the C-peptide (I:C) can determine whether an exogenous insulin overdose is present.

Revisiting New Classes of Chalcones from Antidiabetic Perspectives

Elevated blood sugar levels and a plethora of other, more diverse diseases, including changes to protein, carbohydrate, and lipid metabolism, are the only hallmarks of diabetes mellitus. Recent research has shown that mice lacking PTP1B had better glucose tolerance, less diet-induced obesity, and insulin sensitivity in general. In the therapy of serious diabetic problems, natural chalcones have recently been discovered, which have superior selectivity and do not affect pharmacokinetics. This is in response to the present demand for improved PTP-1B inhibitors. No appropriate formulation has been developed for the inhibitors based on natural products chalcones as they have not been tested clinically for toxicological characteristics. The review article has extensively covered various unknown natural chalcone compounds, such as kuwanon J, kuwanon R, kuwanon V, isoliquiritigenin, xanthoangelol, xanthoangelol D, xanthoangelol E, xanthoangelolF, xanthoangelol K, 4-hydroxyderricin, 5,4’-dihydroxy-6,7- furanbavachalcone, licochalcone A, licochalcone B, licochalcone C, licochalcone D, licochalcone E, echinatin, laxichalcone, broussochalcone, macdentichalcone, (2E)1, 1-(5,7-dihydroxy-2,2-dimethyl-2H-benzopyran-8-yl)}3-phenyl-2-propen-1-one, often known as 2E(abyssinone-VI-4-O-methyl ether, 1-(5,7-dihydroxy-2,2,6-trimethyl-2H-benzopyran-8-yl)-3-(4-methoxyphenyl)- 2-propen-1-one) show great promise as a diabetic medication because it can inhibit insulin degradation by targeting the therapeutic target protein tyrosine phosphatase 1B (PTP-1B). These chalcone-based PTP-1B inhibitors derived from natural products are not currently used in clinical trials and have not attracted much interest from contemporary medicine due to a lack of clinical investigation into their toxicological profiles necessary to create an appropriate formulation. These chalcone-based PTP-1B inhibitors may soon unlock new opportunities in diabetotherapeutics.

Alzheimer's disease from a diabetic brain: Exploring the molecular process to determine the potential therapy target from marine sources

Background: The prevalence of Alzheimer’s Disease (AD) among Type 2 Diabetes Mellitus (T2D) patients has reached almost 30%. Despite the rapid development, treatments for patients with T2D have not succeeded in controlling the neurodegenerative processes that occur in these patients' brains, leading to AD pathology. Several studies have demonstrated that marine sources can inhibit several AD pathogenesis pathways in T2D patients. This review aimed to determine the effect of marine species-sourced compounds at the molecular level in inhibiting and preventing the pathogenesis of AD in T2D patients. Method: Combinations of several terms were used to search for peer-reviewed literature published in PubMed, Scopus, and Google Scholar. Result: Marine organisms-sourced compounds inhibited various target signalling pathways between T2D and AD, such as an inhibitor of β-site-amyloid precursor protein cleaving enzyme 1 (BACE1) also known as β-secretase, glycogen synthase kinase-3 beta (GSK3B), insulin degradation enzyme (IDE), the mammalian target of rapamycin (mTOR), nuclear factor kappa-light-chain-enhancer (NF-κb), and nuclear factor erythroid 2-related factor 2 (Nrf2). Conclusion: Marine sources can be considered as a potential therapy to prevent or slow AD progression in T2D patients.

The Insulin-Degrading Enzyme from Structure to Allosteric Modulation: New Perspectives for Drug Design.

The insulin-degrading enzyme (IDE) is a Zn2+ peptidase originally discovered as the main enzyme involved in the degradation of insulin and other amyloidogenic peptides, such as the β-amyloid (Aβ) peptide. Therefore, a role for the IDE in the cure of diabetes and Alzheimer's disease (AD) has been long envisaged. Anyway, its role in degrading amyloidogenic proteins remains not clearly defined and, more recently, novel non-proteolytic functions of the IDE have been proposed. From a structural point of view, the IDE presents an atypical clamshell structure, underscoring unique enigmatic enzymological properties. A better understanding of the structure-function relationship may contribute to solving some existing paradoxes of IDE biology and, in light of its multifunctional activity, might lead to novel therapeutic approaches.

Modulation of the Activity of the Insulin-Degrading Enzyme by Aβ Peptides.

The insulin-degrading enzyme (IDE) is an evolutionarily conserved protease implicated in the degradation of insulin and amyloidogenic peptides. Most of the biochemical and biophysical characterization of IDE's catalytic activity has been conducted using solutions containing a single substrate, i.e., insulin or Aβ(1-40). IDE's activity toward a particular substrate, however, is likely to be influenced by the presence of other substrates. Here, we show by a kinetic assay based on insulin's helical circular dichroic signal and MALDI TOF mass spectrometry that Aβ peptides modulate IDE's activity toward insulin in opposing ways. Aβ(1-40) enhances IDE-dependent degradation of insulin, whereas Aβ(pyroE3-42), the most pathogenic pyroglutamate-modified Aβ peptide in AD, inhibits IDE's activity. Intriguingly, Aβ(pyroE3-42) also inhibits IDE's ability to degrade Aβ(1-40). Together, our results implicate Aβ peptides in the abnormal catabolism of IDE's key substrates.

A nano-delivery system based on preventing degradation and promoting absorption to improve the oral bioavailability of insulin

Oral insulin delivery can improve patient compliance and simulate the portal-peripheral insulin concentration gradient produced by endogenous insulin, so oral insulin delivery has a broad prospect. However, some characteristics of the gastrointestinal tract, lead to low oral bioavailability. Therefore, a “ternary mutual-assist” nano-delivery system based on poly(lactide-co-glycolide) (PLGA) as the backbone combined with ionic liquids (IL) and vitamin B12-chitosan (VB12-CS) was constructed in this study, the protein protection performance of IL improves the room temperature stability of the loaded insulin during nanocarrier preparation, transportation and storage to a certain extent, and the protein protection function of IL combined with the slow degradation property of PLGA and the pH-responsive function of VB12-CS to prevent the degradation of insulin in the gastrointestinal tract. In addition, the mucosal adhesion function of VB12-CS, VB12 receptor- and clathrin-mediated transcellular transport involving VB12-CS and IL, and paracellular transport mediated by IL and CS can be combined to improve the intestinal epithelial transport efficiency of insulin, thus, the nanocarrier has stronger preventing degradation and promoting absorption effects. Pharmacodynamic studies showed that after oral administration of VB12-CS-PLGA@IL@INS NPs to diabetic mice, the blood glucose level decreased to about 13 mmol/L, below the critical point of 16.7 mmol/L, and the blood glucose reached a normal level, which was 0.4 times of the blood glucose value before administration, its relative pharmacological bioavailability was 31.8 %, higher than the general nanocarriers (10–20 %) and more beneficial to the clinical transformation of oral insulin.

Microfabrication and Characterization of Chemically Actuated Implantable PLGA Reservoir-based Device for Controlled Drug Delivery

This paper proposes the fabrication and characterization of the drug delivery device (DDD) that is capable of delivering the drug to the target site using bio-degradable polymer. The insulin used as a model drug in this study was loaded into the microreservoir (5 mm * 5 mm * 0.5 mm) which was fabricated using Poly-Lactic-Co-Glycolic acid (PLGA) polymer. The permeation of the drug solution and the release rates were controlled by varying the thickness of the biodegradable membrane. The fabricated DDD was designed to deliver about 20 µL of the drug. Implantable formulations of insulin were generated using biodegradable polymer PLGA, which were further tested by loading different quantities of the drug. The activity of the implant was tested using in-vitro release by taking Phosphate-buffered saline (PBS), as well as in-vivo pharmacokinetic studies in Wistar rats. Insulin-loaded implants were inserted under the skin layer by minor surgery. The blood samples were collected at different time intervals, which were further analyzed by High-performance liquid chromatography (HPLC). The obtained results confirmed the presence of insulin in the blood by showing a retention time (RT) of 2.8 min at λ max of 280 nm. The results have shown that the insulin was found in the blood after 4 h of implant insertion and remained up to 48 h. This study clearly suggests that the fabricated device can be used for the successful delivery of insulin in the blood. The use of this DDD bypasses the degradation of insulin in the stomach and thus can be used as an effective drug carrier system for the delivery of insulin.

Nose-to-brain delivery of insulin nanoparticles for diabetes management: A review

Hyperglycemia and the onset of insulin resistance or deficiency, or both, are the hallmarks of the group of diseases known as diabetes. Ultimately, insulin subcutaneous injection is the most effective treatment for diabetic patients. However, most patients must self-administer insulin at least twice daily for the rest of their lives, as this form of administration is frequently uncomfortable and inconvenient. Infections, insulin precipitation, lipoatrophy, or lipohypertrophy are commonly observed at the injection site. To date, nasal, pulmonary, and oral methods of insulin administration have been explored. Although insulin stimulation is the ideal method for diabetic patients, there are several obstacles to overcome, such as rapid insulin degradation in the stomach and limited oral bioavailability. Various strategies have been approved to improve these parameters, including the use of enzyme inhibitors, mucoadhesive polymeric agents, absorption-enhancing agents, and chemical modifications. Insulin-loaded nanocarriers can bypass numerous physiological limitations. The current review discusses the approach of nanotechnology in nose-to-brain delivery of nanoparticles for diabetes management.

Hormonal imbalance in patients with chronic renal failure in the pre-dialysis and dialysis periods (part1)

The review describes the problem of studying progressive changes of hormones concentrations (parathyroid hormone, insulin, somatotropin, prolactin) in patients with chronic renal failure on the pre-dialysis and dialysis stages. The pathogenetic relationships between kidney function deterioration and hormone concentrations as well as changes of their biological effects were evaluated. Parathyroid hormone is considered as an uraemic toxin, since its concentration in the blood begins to increase when the glomerular filtration rate decreases below 50 ml/min. All stages of chronic kidney disease are accompanied by disorders of calcium-phosphorus metabolism. Prolonged excess of parathyroid hormone leads to bone loss and to the progression to secondary hyperparathyroidism that is a frequent complication in patients with the later stages of chronic renal failure and, especially, in those on dialysis treatment. The elevation of insulin level in chronic renal failure is the consequence of progressive decrease in glomerular filtration rate and insulin excretion by proximal tubules. So, it results in insulin half-life prolongation. Long-term dialysis therapy eliminates factors that reduce the degradation of insulin by extrarenal tissues, which results in an improvement of their insulin sensitivity. Experimental and clinical studies have shown that an excess of somatotropin can adversely affect the kidneys that leads to glomerular hyperfiltration and the progression to glomerulosclerosis. The risk of possible side effects on kidneys should be taken into account when prescribing recombinant human insulin-like growth factor. The prolactin concentration is usually increased in chronic kidney disease due to reduced clearance and increased secretion. Hyperprolactinemia manifests as galactorrhea and hypogonadism. Dialysis therapy can’t normalize the increased concentration of prolactin. Modern options for pathogenetic treatment of endocrine disorders in patients with chronic renal failure are outlined in this article. It was found that kidneys play an important role in regulating hormones concentrations in the blood. Endocrine disorders are one of the most important components of the uraemic syndrome, which requires further clinical studies, aimed on the searching of better treatment strategies and prevention of hormonal imbalance on the pre-dialysis and dialysis stages of chronic kidney disease.

Insulin modulates the free energy landscape of insulin degrading enzyme as it transitions between closed and open states.

Insulin Degrading Enzyme (IDE) is an enzyme that has been linked to type-2 diabetes mellitus as it degrades molecules responsible for controlling blood glucose level including insulin, amylin, and glucagon. It is also responsible for degrading amyloid beta, the main component of the amyloid plaques found in the brains of people with Alzheimer's disease. IDE transitions between open and closed conformations in the process of degrading insulin, however the exact mechanism of these conformational changes is not fully understood. We ran two sets of molecular dynamics simulations following the string method with swarms of trajectories and bias exchange umbrella sampling protocols in order to produce a physical pathway for IDE transitioning between closed and open states and to investigate the effect of insulin on this conformational change. We observed a free energy barrier between the closed and open conformations of the insulin-free system that could be attributed to the breakage of the ASP426-LYS571, ASP82-LYS243 and GLU428-LYS899 salt bridges that connect the D2 and D3 domains of IDE. The insulin-bound system had a considerable change in the shape of the free energy landscape where the transition energy barrier was lowered. Additionally, insulin stabilized the open state conformation of IDE by lowering its free energy. We observed the formation of three salt bridges in the insulin-bound system that were not present in the insulin-free system. Dynamical Network and Principal Component Analyses of our trajectories provided intuition as to how the different clusters of atoms within IDE interact with each other and with insulin, and how these interactions contribute to the overall conformational change. In particular, the first domain of IDE (shown experimentally to be important in insulin degradation) was divided into two dynamical subdomains.

Sleeve Gastrectomy-Induced Weight Loss Increases Insulin Clearance in Obese Mice.

Sleeve gastrectomy (SG) successfully recovers metabolic homeostasis in obese humans and rodents while also resulting in the normalization of insulin sensitivity and insulinemia. Reduced insulin levels have been attributed to lower insulin secretion and increased insulin clearance in individuals submitted to SG. Insulin degradation mainly occurs in the liver in a process controlled, at least in part, by the insulin-degrading enzyme (IDE). However, research has yet to explore whether liver IDE expression or activity is altered after SG surgery. In this study, C57BL/6 mice were fed a chow (CTL) or high-fat diet (HFD) for 10 weeks. Afterward, the HFD mice were randomly assigned to two groups: sham-surgical (HFD-SHAM) and SG-surgical (HFD-SG). Here, we confirmed that SG improves glucose-insulin homeostasis in obese mice. Additionally, SG reduced insulinemia by reducing insulin secretion, assessed by the analysis of plasmatic C-peptide content, and increasing insulin clearance, which was evaluated through the calculation of the plasmatic C-peptide:insulin ratio. Although no changes in hepatic IDE activity were observed, IDE expression was higher in the liver of HFD-SG compared with HFD-SHAM mice. These results indicate that SG may be helpful to counteract obesity-induced hyperinsulinemia by increasing insulin clearance, likely through enhanced liver IDE expression.

Dynamics of a glucose–insulin model

Diabetes mellitus is a noncommunicable disease, which is a serious threat to human health around the world. In this paper, we propose a simple glucose–insulin model with Michaelis–Menten function as insulin degradation rate to mimic the pathogenic mechanism of diabetes. By theoretical analysis, a unique positive equilibrium of model exists and it is globally asymptotically stable. The four strategies are designed for diabetes patients based on the sensitivity of parameters, including insulin injection and medicine treatments. Numerical simulations are given to support the theoretical results.

An autopsy case of fatal insulin preparation overdose

Insulin preparations, a group of drugs used to treat diabetes, are of great forensic interest because they are difficult to detect in blood while they are sometimes intentionally administered in large doses for suicide or murder. In this study, we validated a quantification method for insulin glargine and insulin lispro using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the blood sample from a case of suicidal overdose with insulin. Case: A woman in her 30s had a history of mental illness and diabetes. A day before her death, she informed her partner that she had self-administered large doses of insulin preparations and prescription drugs. Bovine insulin was used as the internal standard (IS). The blood sample (250 μL) was added to the diluent and IS solution, followed by 250 μL each of hexane and N,N-dimethylformamide, and the mixture was centrifuged (10000 g × 10 min). The supernatant was collected and 900 μL of 5% ammonium solution was added. The extract was analyzed using Nexera 30A, LCMS8060 (Shimadzu), L-column3 ODS C18 metal-free column (150 × 2.1 mm, 3 μm), ionization method: electrospray ionization+, multiple reaction monitoring conditions: insulin glargine [M + 6H]6+ 1011.5 > 1179.4, insulin lispro[M + 6H]6+ 968.9 > 217.0, bovine insulin (IS) [M + 6H]6+ 956.3 > 1120.9. The autopsy revealed no evidence of fatal injuries. Coronary artery stenosis was observed as a finding of endogenous disease, but there were no significant histopathological changes in the myocardium. Biochemical tests revealed the following: blood glucose level, 6 mg/dL; glucose in the vitreous region, 6 mg/dL; glycated hemoglobin (HbA1c), 11.2%; blood insulin level estimated using the chemiluminescent enzyme immunoassay method, 1.03 μU/mL (6.27 pmol/mL); and C-peptide concentration, 0.6 ng/mL (16.8 pmol/L). A drug screening test and simple quantification using LC-MS/MS detected many prescription drugs, but none of them were at intoxicating concentrations. The insulin analysis showed insulin glargine concentrations of 429 μU/mL in femoral blood and 1362 μU/mL in cardiac blood, and insulin lispro was detected in femoral and cardiac blood below the lower limit of quantification (<50 μU/mL). The cardiac/peripheral blood ratio, a measure of postmortem redistribution, was 3.2. Although the therapeutic ranges of insulin glargine and insulin lispro have not been defined, the femoral and cardiac blood concentrations of insulin lispro in this case was lower than the serum concentration (155 μU/mL) listed in the package insert. However, while the femoral and cardiac blood insulin glargine concentrations were considerably higher than the serum concentration (15 μU/mL) listed in the package insert. Considering that insulin is easily degraded in whole blood due to hemolysis, it is possible that insulin concentrations were even higher at the time of administration and death than those observed in autopsy specimens on the third postmortem day. However, since insulin lispro is a fast-acting analog of insulin (1–3 hours), it may have contributed to hypoglycemia but was not the direct cause of death, and hypoglycemia due to insulin glargine overdose was the most likely cause of death in this case. We quantified insulin lispro and insulin glargine in a case of suicide to determine insulin glargine's involvement in causing death. In future, it is necessary to examine postmortem degradation and redistribution of insulin and consider the appropriate concentration in postmortem samples of insulin poisoning.