Type B insulin resistance syndrome

Newly emerging type B insulin resistance (TBIR) during treatment with eculizumab for AQP4-IgG-positive neuromyelitis optica spectrum disorder (NMOSD): fatal outcome

BACKGROUND

Aquaporin-4 immunoglobulin G (AQP4-IgG) antibody-positive neuromyelitis optica spectrum disorders (NMOSD) are frequently associated with other autoimmune disorders, including systemic lupus erythematosus (SLE). Eculizumab (ECU) is a highly effective long-term treatment for NMOSD. However, ECU is known to increase significantly the risk of infection with encapsulated bacteria and sepsis. Recently, increased insulin resistance (IR) in patients with NMOSD has been suggested. Type B IR (TBIR) is a rare autoimmune condition often accompanying or preceding SLE. TBIR has not yet been reported in NMOSD.

OBJECTIVE

To report an ECU-treated patient with AQP4-IgG-positive NMOSD who developed fatal septic complications after the emergence of TBIR.

METHODS

Description of the clinical course over a period of 8 years.

RESULTS

A female patient was diagnosed with NMOSD at the age of 16 years. A variety of disease-modifying drugs failed to achieve sufficient disease control, resulting in severe tetraparesis. Treatment with ECU was started 6 years after NMOSD diagnosis and stabilized the disease. The patient developed TBIR 8 months after initiation of ECU therapy. Following high-dose intravenous methylprednisolone therapy for a clinical relapse and three further courses of ECU, the patient was admitted with severe pneumonia caused by the encapsulated bacterium Klebsiella pneumoniae and hypoglycemia. Despite multimodal therapy, the patient died from sepsis-related multiorgan failure 18 months after initiation of ECU.

CONCLUSIONS

TBIR should be considered as differential diagnosis in patients with NMOSD presenting with disturbed glucose metabolism, irrespective of the presence of SLE. More real-world data are needed on the risk/benefit ratio of ECU treatment in patients who have co-existing autoimmune comorbidities that may compromise immune function. Strategies to mitigate the risk of serious infection in patients treated with ECU are discussed.

Systematic Review-Type B Insulin Resistance With Isolated Hypoglycemia and Suppressed Insulin

OBJECTIVE

Type B insulin resistance syndrome is a rare autoimmune disorder affecting glucose homeostasis, characterized by serum autoantibodies to the insulin receptor (AIRAbs). Patients typically present with severe insulin resistance. A mixed hyper- and hypoglycemia phenotype may also occur, as may isolated hypoglycemia. The classic biochemical pattern comprises elevated insulin levels despite hypoglycemia; however, a small proportion of cases demonstrate "isolated hypoglycemia with low insulin." The primary objectives of this systematic review were to identify the clinical characteristics and outcome of this subgroup.

DESIGN

Systematic review of cases with hypoglycemia with suppressed insulin. Exclusions: hyperglycemia, elevated insulin, AIRAbs not confirmed.

METHODS

PubMed, Medline, and Embase databases were searched up until February 2023 and complemented by manual citation search. The Joanna Briggs Institute critical appraisal checklist for case reports was used to assess bias.

RESULTS

A total of 5342 articles were identified after duplicate removal. Eleven, all case reports, met all inclusion criteria and were included. Cases belonging to this subgroup were more diverse in sex, age, and ethnicity when compared with type B insulin resistance as a whole. Of the 11 cases, 3 developed lymphoma. High-dose corticosteroid therapy appeared to be effective therapy for the hypoglycemia, with often rapid response.

CONCLUSIONS

Isolated hypoglycemia with low insulin forms a rare subgroup of type B insulin resistance. These patients lack the common characteristics of hyperinsulinemic hypoglycemia and hyperglycemia/insulin resistance. Furthermore, while coexisting autoimmune disease is commonly observed, there is potentially an association with aggressive lymphoma, the onset of which may be delayed.

Recurrent hypoglycemia induced by clopidogrel: A case report and mini review

This report describes a patient who developed recurrent hypoglycemia episodes after 23 days of antiplatelet therapy with clopidogrel for left subclavian artery stent implantation. The patient suffered from palpitation, profuse sweating and weakness on the 23rd day of clopidogrel treatment. The minimum plasma glucose was 2.2 mmol/L, and the hypoglycemia was associated with significantly elevated levels of insulin. A diagnosis of insulin autoimmune syndrome (IAS) was made with the presence of insulin autoantibody and a comprehensive differential diagnosis of other conditions related with hypoglycemia. Clopidogrel was stopped, and the patient was treated with acarbose and had frequent low-carbohydrate meals; his hypoglycemia did not occur within 10 days. To date, seven cases of IAS induced by clopidogrel have been reported. Most reported cases were male aged in their 70s, and the hypoglycemic attack appeared 1-4 weeks after exposure to clopidogrel, characterized by severe hyperinsulinemia hypoglycemia with high titers of insulin autoantibodies. Most IAS cases can resolve spontaneously when they stop using the trigger medicine. Severe cases had been treated with drugs that reduce pancreatic insulin secretion (such as somatostatin and diazoxide), immunosuppressants (glucocorticoids, azathioprine and rituximab) and even immunoadsorption to remove the insulin autoantibody from the body. Considering the hypoglycemic attack might increase the risk of cardiovascular events among patients taking clopidogrel, we recommend that doctors should be aware of IAS as a rare severe adverse effect of clopidogrel, and be vigilant for the symptoms related with hypoglycemia in clopidogrel users.

Changes in Cells Associated with Insulin Resistance

Insulin is a polypeptide hormone synthesized and secreted by pancreatic β-cells. It plays an important role as a metabolic hormone. Insulin influences the metabolism of glucose, regulating plasma glucose levels and stimulating glucose storage in organs such as the liver, muscles and adipose tissue. It is involved in fat metabolism, increasing the storage of triglycerides and decreasing lipolysis. Ketone body metabolism also depends on insulin action, as insulin reduces ketone body concentrations and influences protein metabolism. It increases nitrogen retention, facilitates the transport of amino acids into cells and increases the synthesis of proteins. Insulin also inhibits protein breakdown and is involved in cellular growth and proliferation. On the other hand, defects in the intracellular signaling pathways of insulin may cause several disturbances in human metabolism, resulting in several chronic diseases. Insulin resistance, also known as impaired insulin sensitivity, is due to the decreased reaction of insulin signaling for glucose levels, seen when glucose use in response to an adequate concentration of insulin is impaired. Insulin resistance may cause, for example, increased plasma insulin levels. That state, called hyperinsulinemia, impairs metabolic processes and is observed in patients with type 2 diabetes mellitus and obesity. Hyperinsulinemia may increase the risk of initiation, progression and metastasis of several cancers and may cause poor cancer outcomes. Insulin resistance is a health problem worldwide; therefore, mechanisms of insulin resistance, causes and types of insulin resistance and strategies against insulin resistance are described in this review. Attention is also paid to factors that are associated with the development of insulin resistance, the main and characteristic symptoms of particular syndromes, plus other aspects of severe insulin resistance. This review mainly focuses on the description and analysis of changes in cells due to insulin resistance.

Insulin Resistance: The Increased Risk of Cancers

Insulin resistance, also known as impaired insulin sensitivity, is the result of a decreased reaction of insulin signaling to blood glucose levels. This state is observed when muscle cells, adipose tissue, and liver cells, improperly respond to a particular concentration of insulin. Insulin resistance and related increased plasma insulin levels (hyperinsulinemia) may cause metabolic impairments, which are pathological states observed in obesity and type 2 diabetes mellitus. Observations of cancer patients confirm that hyperinsulinemia is a major factor influencing obesity, type 2 diabetes, and cancer. Obesity and diabetes have been reported as risks of the initiation, progression, and metastasis of several cancers. However, both of the aforementioned pathologies may independently and additionally increase the cancer risk. The state of metabolic disorders observed in cancer patients is associated with poor outcomes of cancer treatment. For example, patients suffering from metabolic disorders have higher cancer recurrence rates and their overall survival is reduced. In these associations between insulin resistance and cancer risk, an overview of the various pathogenic mechanisms that play a role in the development of cancer is discussed.

Immune-endocrine network in diabetes-tuberculosis nexus: does latent tuberculosis infection confer protection against meta-inflammation and insulin resistance?

Tuberculosis patients with diabetes, have higher sputum bacillary load, delayed sputum conversion, higher rates of drug resistance, higher lung cavitary involvement and extra-pulmonary TB infection, which is called as "Diabetes-Tuberculosis Nexus". However, recently we have shown a reciprocal relationship between latent tuberculosis infection and insulin resistance, which has not been reported before. In this review, we would first discuss about the immune-endocrine network, which operates during pre-diabetes and incipient diabetes and how it confers protection against LTBI. The ability of IR to augment anti-TB immunity and the immunomodulatory effect of LTBI to quench IR were discussed, under IR-LTB antagonism. The ability of diabetes to impair anti-TB immunity and ability of active TB to worsen glycemic control, were discussed under "Diabetes-Tuberculosis Synergy". The concept of "Fighter Genes" and how they confer protection against TB but susceptibility to IR was elaborated. Finally, we conclude with an evolutionary perspective about how IR and LTBI co-evolved in endemic zones, and have explained the molecular basis of "IR-LTB" Antagonism" and "DM-TB Synergy", from an evolutionary perspective.

Clinical Features and Outcome Analysis of Type B Insulin Resistance Syndrome: A Single-Center Study in China

CONTEXT

Type B insulin resistance syndrome (TBIRS) is a rare condition, for which effective treatment remains challenging.

OBJECTIVE

This work aimed to summarize the clinical characteristics of TBIRS and explore effective therapeutic strategies.

METHODS

The clinical manifestations, biochemical indices, and treatment of 8 patients (3 men and 5 women) with TBIRS from Peking Union Medical College Hospital were retrospectively analyzed and their clinical outcomes were evaluated.

RESULTS

The average age of the patients was 49.5 ± 16.5 years, and the duration of the disease ranged from 2 months to 1 year. Seven patients with hyperglycemia had normal/lower triglycerides (TGs) and lower insulin-like growth factor 1 (IGF-1) levels. One patient complained of intractable hypoglycemia. Five patients had accompanied systemic lupus erythematosus, 2 had mixed connective tissue disease, and 1 had undifferentiated connective tissue disease. Five patients had acanthosis nigricans and 3 women of child-bearing age had hyperandrogenism. All 8 patients were treated with glucocorticoids combined with immunosuppressants, among whom, 5 received high-dose glucocorticoid pulse therapy followed by conventional-dose glucocorticoid therapy, all of whom achieved partial remission within 2 to 4 weeks. Among the 3 patients receiving conventional glucocorticoid therapy, 2 achieved partial remission within 2 to 4 weeks. Six patients were tracked for 10 weeks to 4 years; 4 and 2 achieved complete and partial remission, respectively.

CONCLUSION

Decreased serum complement 3 and IGF-1 levels and normal/decreased TG levels act as striking biochemical features of TBIRS. High-dose glucocorticoid pulse therapy followed by conventional-dose long-term therapy combined with immunosuppressants achieves good clinical efficacy.

Atypical diabetes with spontaneous remission associated with systemic lupus erythematosus in an adolescent girl of African ancestry, a case report

BACKGROUND

New-onset diabetes in youth encompasses type 1 diabetes, type 2 diabetes, monogenic diabetes, and rarer subtypes like Type B insulin resistance syndrome and ketosis-prone atypical diabetes in African populations. Some cases defy classification, posing management challenges. Here, we present a case of a unique, reversible diabetes subtype.

CASE PRESENTATION

We describe an adolescent African girl recently diagnosed with systemic lupus erythematosus. At age 15, she presented with ketoacidosis, HbA1c of 108.7 mmol/mol (12.1%), and positive anti-insulin antibodies. Initially diagnosed with type 1 diabetes, insulin was prescribed. Due to the presence of obesity and signs of insulin resistance, we added metformin. Concurrently, she received treatment for lupus with hydroxychloroquine, mycophenolate mofetil, and prednisone. After discharge, she stopped insulin due to cultural beliefs. Five months later, her glycemia and HbA1c normalized (37 mmol/mol or 5.5%) without insulin, despite corticosteroid therapy and weight gain. Autoantibodies normalized, and lupus activity decreased. Genetic testing for monogenic diabetes was negative, and the type 1 genetic risk score was exceptionally low.

CONCLUSIONS

We present a complex, reversible diabetes subtype. Features suggest an autoimmune origin, possibly influenced by overlapping HLA risk haplotypes with lupus. Lupus treatment or immunomodulation may have impacted diabetes remission. Ancestry-tailored genetic risk scores are currently designed to improve diagnostic accuracy.

A rare case of autoimmune dysglycemia syndrome associated with systemic lupus erythematosus and dermatomyositis

Autoimmune dysglycemia syndrome (ADS) is a rare condition that presents as episodes of hypoglycemia as well as hyperglycemia and is classified as insulin autoimmune syndrome (IAS) and type B insulin resistance (TBIR). Autoimmunity plays a key role in the pathogenesis of this disorder, as evidenced by the presence of autoantibodies against endogenous insulin or the insulin receptor, and by its association with rheumatologic disorders. Treatment usually includes glycemic control and immunomodulatory agents. We report a case of a 31-year-old woman who was admitted for severe hypoglycemia. Further workup revealed underlying systemic lupus erythematosus (SLE) with renal involvement. During hospitalization, she continued to experience episodes of fasting hypoglycemia, as well as episodes of postprandial hyperglycemia. Hypoglycemia associated with a high serum insulin concentration and positive anti-insulin antibodies were consistent with IAS. Likewise, hyperglycemia and hypoglycemia in association with weight loss, acanthosis nigricans, polycystic ovarian syndrome, and normotriglyceridemia strongly suggested TBIR, although testing for antibodies against the insulin receptor was not available in Peru. Immunosuppressive therapy and metformin were indicated, resulting in remission of SLE and ADS. Years later, the patient exhibited features of dermatomyositis, such as Raynaud’s phenomenon, muscular weakness, heliotrope exanthema, and elevated muscle enzymes. Once again, the patient received immunosuppressive therapy. ADS is an infrequent cause of hypoglycemia, and the coexistence of its two pathophysiological mechanisms in a patient with SLE and subsequent development of dermatomyositis is even more rare. Our case is the first one reported describing this association.

A rare case of autoimmune dysglycemia syndrome associated with systemic lupus erythematosus and dermatomyositis

Autoimmune dysglycemia syndrome (ADS) is a rare condition that presents as episodes of hypoglycemia as well as hyperglycemia and is classified as insulin autoimmune syndrome (IAS) and type B insulin resistance (TBIR). Autoimmunity plays a key role in the pathogenesis of this disorder, as evidenced by the presence of autoantibodies against endogenous insulin or the insulin receptor, and by its association with rheumatologic disorders. Treatment usually includes glycemic control and immunomodulatory agents. We report a case of a 31-year-old woman who was admitted for severe hypoglycemia. Further workup revealed underlying systemic lupus erythematosus (SLE) with renal involvement. During hospitalization, she continued to experience episodes of fasting hypoglycemia, as well as episodes of postprandial hyperglycemia. Hypoglycemia associated with a high serum insulin concentration and positive anti-insulin antibodies were consistent with IAS. Likewise, hyperglycemia and hypoglycemia in association with weight loss, acanthosis nigricans, polycystic ovarian syndrome, and normotriglyceridemia strongly suggested TBIR, although testing for antibodies against the insulin receptor was not available in Peru. Immunosuppressive therapy and metformin were indicated, resulting in remission of SLE and ADS. Years later, the patient exhibited features of dermatomyositis, such as Raynaud’s phenomenon, muscular weakness, heliotrope exanthema, and elevated muscle enzymes. Once again, the patient received immunosuppressive therapy. ADS is an infrequent cause of hypoglycemia, and the coexistence of its two pathophysiological mechanisms in a patient with SLE and subsequent development of dermatomyositis is even more rare. Our case is the first one reported describing this association.

Case report: Allogeneic stem cell transplantation for type B insulin resistance

Type B insulin resistance (TBIR) is a rare, often fulminant form of insulin resistance caused by autoantibodies against the insulin receptor. If left untreated, its mortality is high. Various immunosuppressive regimens have shown efficacy, but treatment effects are variable and time-delayed, and drug-induced complications may arise. We report a patient with TBIR arising as a complication of Wiskott-Aldrich syndrome. Stable remission of TBIR was achieved through allogeneic peripheral blood stem cell transplantation (PBSCT) over a follow-up period of more than 1.5 years. We thus demonstrate that PBSCT can be considered a treatment option in TBIR where conventional immunosuppressive therapy is ineffective or contraindicated.

Molecular Mechanisms for the Vicious Cycle between Insulin Resistance and the Inflammatory Response in Obesity

The comprehensive anabolic effects of insulin throughout the body, in addition to the control of glycemia, include ensuring lipid homeostasis and anti-inflammatory modulation, especially in adipose tissue (AT). The prevalence of obesity, defined as a body mass index (BMI) ≥ 30 kg/m², has been increasing worldwide on a pandemic scale with accompanying syndemic health problems, including glucose intolerance, insulin resistance (IR), and diabetes. Impaired tissue sensitivity to insulin or IR paradoxically leads to diseases with an inflammatory component despite hyperinsulinemia. Therefore, an excess of visceral AT in obesity initiates chronic low-grade inflammatory conditions that interfere with insulin signaling via insulin receptors (INSRs). Moreover, in response to IR, hyperglycemia itself stimulates a primarily defensive inflammatory response associated with the subsequent release of numerous inflammatory cytokines and a real threat of organ function deterioration. In this review, all components of this vicious cycle are characterized with particular emphasis on the interplay between insulin signaling and both the innate and adaptive immune responses related to obesity. Increased visceral AT accumulation in obesity should be considered the main environmental factor responsible for the disruption in the epigenetic regulatory mechanisms in the immune system, resulting in autoimmunity and inflammation.

Endogenous hyperinsulinemic hypoglycemia: case series and literature review

PURPOSE

Endogenous hyperinsulinemic hypoglycemia (EHH) is an uncommon disease characterized by inappropriately high plasma insulin levels despite low plasma glucose levels. Some rare etiologies can lead to EHH. Correct diagnosis is a prerequisite for treatment. Hence, although challenging, it is crucial for patients with EHH to identify the different causes.

METHODS

We describe a case series of three patients, all of whom had obvious hypoglycemic symptoms and extraordinary hyperinsulinemia. Their plasma glucose, insulin, and C-peptide levels were tested simultaneously when hypoglycemia occurred. Moreover, other biochemical indices and relevant antibody levels were measured and imaging examinations were conducted.

RESULTS

According to their medical history, physical examination, laboratory results, and imaging findings, the three patients were diagnosed with insulinoma, type B insulin resistance syndrome, and insulin autoimmune syndrome. After precise treatments, hypoglycemia was ultimately eliminated.

CONCLUSION

Although these diseases have similar symptoms and biochemical abnormalities, the treatment and prognosis are different. The case series presented here highlights the challenges in the differential diagnosis of EHH. An accurate diagnosis is necessary for hypoglycemia treatment.

Coexistence of Type B Insulin Resistance and Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) in Type 2 Diabetes Mellitus: Various Manifestations With the Same Pathophysiologic Base?

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a rarely reported disease. The association between diabetes mellitus (DM) and CIDP has been a matter of controversy. Here we presented a 59-year old male patient with uncontrolled type 2 DM presented with simultaneous type B insulin resistance (TBIRS) and CIDP. Both blood glucose and neurological manifestations responded well to corticosteroid therapies. Although the pathogenesis of CIDP remains to be elucidated, the role of antibodies in the pathogenesis of TBIRS and CIDP might be a promising platform for further studies to provide additional insights into the origin of these 2 rare complications.

The triglycerides-glucose index and the triglycerides to high-density lipoprotein cholesterol ratio are both effective predictors of in-hospital death in non-diabetic patients with AMI

Background

The triglycerides-glucose index (TyG) and the triglycerides to high-density lipoprotein cholesterol (TG/HDL-C) are simple indicators for assessing insulin resistance in epidemiological studies. We aimed to clarify the relationship between indicators of insulin resistance and prognosis in non-diabetic acute myocardial infarction (AMI) patients.

Methods

A total of 1,648 AMI patients without diabetes were enrolled from the Department of Cardiology, Zhongda Hospital, between 2012.03 and 2018.12. The medical history, laboratory and imaging data of patients were collected through the medical record system, and all-cause death events were recorded. Pearson analysis was used to study the correlation among different variables. Logistic regression analysis was used to analyze the predictive effect of TyG and TG/HDL-C in in-hospital death of AMI patients.

Results

1. In AMI group, the TyG index was significantly increased in death groups compared to no-death groups (P = 0.025). TG/HDL-C was not significantly increased in the death group of AMI patients (P = 0.588). The patients were respectively divided into Q1-Q4 groups and T1-T4 groups according to the quartiles of TyG and TG/HDL-C. The trends of in-hospital mortality in the Q4 group of TyG and T4 group of TG/HDL-C were higher than in other groups, although these differences were not significant. 2. Pearson correlation analysis showed that TyG was positively correlated with lipid-related markers, including ApoB (r = 0.248, P < 0.001), total cholesterol (TC) (r = 0.270, P < 0.001), low-density lipoprotein cholesterol (LDL-C) (r = 0.238, P < 0.001). Spearman analysis showed that TG/HDL-C was also positively associated with TC (r = 0.107, P < 0.001), ApoB (r = 0.180, P < 0.001) and LDL-C (r = 0.164, P < 0.001). 3. Logistic regression analysis showed that TyG (OR = 3.106, 95% CI [2.122-4.547], P < 0.001) and TG/HDL-C (OR = 1.167, 95% CI [1.062-1.282], P = 0.001) were both important factors to predict the in-hospital death of AMI patients without diabetes.

Conclusions

TyG index and TG/HDL-C, as emerged simple markers of insulin resistance, were both important predictors of in-hospital death in AMI patients without diabetes.

Late Systemic Lupus Erythematosus-Associated Insulin Resistance Syndrome: A Rare Cause of De Novo Diabetes Mellitus

The association of type B insulin resistance syndrome (TBIRS) due to autoimmune diseases such as systemic lupus erythematosus (SLE) is uncommon. This is partly due to the lack of established criteria for the diagnosis of this resistance. However, some clinical aspects may suggest that the diagnosis does not necessarily have to be positive insulin receptor antibodies as such patients could respond to immunosuppressive treatment. Methods. We describe a case and have performed a literature review on PubMed/MEDLINE, EMBASE, and Google Scholar bibliographic databases to identify all case reports. All available studies from January 1975 through December 2020 were included. Data collected were tabulated, and outcomes were analyzed cumulatively. Results. Thirty-one cases of TBIRS associated with SLE have been described. These patients presented with catabolic symptoms and hyperglycemia in most cases, with an average time from the onset of symptoms of four months. In addition to that clinical characteristics related to SLE were variable, along with certain common characteristics such as acanthosis in 60% of patients. Almost all the patients had antibodies against insulin receptors. The insulin doses required by the patients ranged from 450 to 25,000 U daily. Remission was achieved in 80% of the patients with a two-year follow-up. Most patients associated with late-onset SLE, like our patient, achieved metabolic control after immunosuppressive treatment. Conclusion. High insulin resistance in patients with de novo diabetes mellitus (DM) without obesity should be considered as a possible clinical manifestation of an autoimmune disease such as SLE, with a good metabolic response to the immunosuppressive management established.

Practical Clinical Applications of Islet Autoantibody Testing in Type 1 Diabetes

BACKGROUND

The distinction between type 1 diabetes (T1D) and type 2 diabetes (T2D) is extremely important for the choice of therapy, body weight and dietary management, screening for coexistent autoimmune diseases and comorbidities, anticipated prognosis, and risk assessment in relatives. Not uncommonly, the presentation of the patient may not allow an unambiguous discrimination between T1D and T2D. To help resolve this challenge, the detection of islet autoantibodies can support the diagnosis of T1D.

CONTENT

The presence of islet autoantibodies in a person with diabetes indicates an autoimmune etiology therefore establishing the diagnosis of T1D. Presently 5 islet autoantibodies are available for routine clinical use: islet cell cytoplasmic autoantibodies (ICA), insulin autoantibodies (IAA), glutamic acid decarboxylase autoantibodies (GADA), insulinoma associated-2 autoantibodies (IA-2A), and zinc transporter-8 autoantibodies (ZnT8A). There are caveats to the selection of which islet autoantibodies should be measured. Islet autoantibodies can also predict the development of T1D. Therefore, once safe and effective therapies are available to prevent T1D, islet autoantibody testing is expected to become a routine part of medical practice. A very rare cause of autoimmune diabetes is the type B insulin resistance syndrome resulting from antagonistic autoantibodies to the insulin receptor. Rarely hypoglycemia can result from agonistic insulin receptor autoantibodies, or high-titer IAA causing the autoimmune insulin syndrome (i.e., Hirata disease).

SUMMARY

In summary, autoimmune causes of dysglycemia are increasing in clinical importance requiring the scrutiny of laboratorians. The determination of islet autoantibodies can greatly aid in the diagnosis and the prediction of T1D.

Development of a novel diagnostic assay for insulin receptor autoantibodies based on a patient with autoimmune hypoglycaemia

Differential diagnosis of hypoglycaemia can at times be challenging for patients who appear to be well. Here we identify the case of a 66-year-old Chinese man presenting with recurrent episodes of fasting hypoglycaemia and confusion without any other manifestations. He had no personal or family history of diabetes, nor was he on any hypoglycaemic drugs. The fasting insulin levels were elevated while the C-peptide and pro-insulin levels were slightly low or normal. Antibodies against insulin were negative and levels of insulin-like growth factors were normal. A series of imaging diagnosis excluded the presence of insulinoma or ectopic insulin-secreting neuroendocrine tumor. Ultimately, insulin receptor autoantibodies (IRAb) were detected by both immunoprecipitation assay and enzyme-linked immunosorbent assay (ELISA) developed in house. In a cell study, the immunoglobulins isolated from this patient exerted insulin-like effects on stimulation of post-insulin receptor signaling and glucose uptake as well as inhibited ¹²⁵I-insulin binding with insulin receptors. Collectively, this patient was diagnosed with IRAb-induced autoimmune hypoglycaemia. Although this patient had no obvious immune disorders, several autoantibodies were identified in his plasma samples, suggesting the patient might have mild aberrant autoimmunity and therefore generated IRAb. IRAb-related disease is uncommon and possibly underdiagnosed or missed due to the lack of simple detection methods for IRAb. Our in-house user-friendly ELISA kit provides a valuable tool for diagnosis of this disease.

Meroterpenoids From Ganoderma lucidum Mushrooms and Their Biological Roles in Insulin Resistance and Triple-Negative Breast Cancer

Ganoderma fungi as popular raw materials of numerous functional foods have been extensively investigated. In this study, five pairs of meroterpenoid enantiomers beyond well-known triterpenoids and polysaccharides, dayaolingzhiols I−M (1–5), were characterized from Ganoderma lucidum. Their structures were identified using spectroscopic and computational methods. Structurally, compound 1 features a novel dioxabicyclo[2.2.2]octan-3-one motif in the side chain. Ethnoknowledge-derived biological evaluation found that (+)-5 could activate Akt and AMPK phosphorylation in insulin-stimulated C2C12 cells, and (+)-5 could activate glucose uptake dose dependently in C2C12 cells. Furthermore, we found that (+)-1 (+)-4, and (–)-4 could significantly inhibit cell migration of the MDA-MB-231 cell line, of which (+)-4 showed significant inhibitory effects against cell migration of the MDA-MB-231 cell line in a dose-dependent manner. These findings revealed the meroterpenoidal composition of G. lucidum and its roles in the prevention of chronic diseases such as diabetes mellitus and triple-negative breast cancer.

Approach to Diagnosing a Pediatric Patient With Severe Insulin Resistance in Low- or Middle-income Countries

Diabetes mellitus (DM) in children is most often caused by impaired insulin secretion (type 1 DM). In some children, the underlying mechanism for DM is increased insulin resistance, which can have different underlying causes. While the majority of these children require insulin dosages less than 2.0 U/kg/day to achieve normoglycemia, higher insulin requirements indicate severe insulin resistance. Considering the therapeutic challenges in patients with severe insulin resistance, early diagnosis of the underlying cause is essential in order to consider targeted therapies and to prevent diabetic complications. Although rare, several disorders can attribute to severe insulin resistance in pediatric patients. Most of these disorders are diagnosed through advanced diagnostic tests, which are not commonly available in low- or middle-income countries. Based on a case of DM with severe insulin resistance in a Surinamese adolescent who was later confirmed to have autosomal recessive congenital generalized lipodystrophy, type 1 (Berardinelli-Seip syndrome), we provide a systematic approach to the differential diagnosis and work-up. We show that a thorough review of medical history and physical examination generally provide sufficient information to diagnose a child with insulin-resistant DM correctly, and, therefore, our approach is especially applicable to low- or middle-income countries.

Effect of a multitarget therapy with prednisolone, mycophenolate mofetil, and tacrolimus in a patient with type B insulin resistance syndrome complicated by lupus nephritis

Type B insulin resistance syndrome (TBIR) is a rare autoimmune disease characterised by autoantibodies targeting insulin receptors. TBIR is often complicated by systemic lupus erythematosus (SLE). We describe the case of a 59-year-old Japanese man with TBIR complicated with lupus nephritis (LN), who presented with nephrotic syndrome and severe hypoglycaemia. Treatment with prednisolone (PSL), mycophenolate mofetil (MMF), and tacrolimus (TAC) resulted in improved SLE activity and glucose intolerance with the reduction of anti-insulin receptor autoantibodies. To the best of our knowledge, this is the first reported case of TBIR complicated with LN that was successfully treated using multitarget therapy with PSL, MMF, and TAC.

Severe insulin resistance syndromes

Severe insulin resistance syndromes are a heterogeneous group of rare disorders characterized by profound insulin resistance, substantial metabolic abnormalities, and a variety of clinical manifestations and complications. The etiology of these syndromes may be hereditary or acquired, due to defects in insulin potency and action, cellular responsiveness to insulin, and/or aberrations in adipose tissue function or development. Over the past decades, advances in medical technology, particularly in genomic technologies and genetic analyses, have provided insights into the underlying pathophysiological pathways and facilitated the more precise identification of several of these conditions. However, the exact cellular and molecular mechanisms of insulin resistance have not yet been fully elucidated for all syndromes. Moreover, in clinical practice, many of the syndromes are often misdiagnosed or underdiagnosed. The majority of these disorders associate with an increased risk of severe complications and mortality; thus, early identification and personalized clinical management are of the essence. This Review aims to categorize severe insulin resistance syndromes by disease process, including insulin receptor defects, signaling defects, and lipodystrophies. We also highlight several complex syndromes and emphasize the need to identify patients, investigate underlying disease mechanisms, and develop specific treatment regimens.

Rare case of type B insulin resistance in association with systemic lupus erythematosus: illustrating diagnostic and management challenges

A 42 year-old Caribbean woman with, known type 2 diabetes, was admitted with worsening fatigue, arthritis and rashes. She was diagnosed with multisystem systemic lupus erythematosus and was initially treated with systemic steroids. During this admission, she had persistently elevated capillary glucose levels with insulin requirements over 8 U/kg/day that still did not control her blood glucose levels. Due to her profound hyperglycaemia, serum samples of fasting insulin, C-peptide, paired with blood glucose were analysed, which confirmed significant hyperinsulinaemia. Further analysis confirmed the presence of insulin receptor antibodies consistent with type B insulin resistance.She was started on intravenous cyclophosphamide (Euro-Lupus regimen) along with continuous glucose monitoring system. After completing her six cycles of cyclophosphamide, she no longer required insulin treatment. The goal of therapy for our patient with confirmed type B insulin resistance was to manage hyperglycaemia with high doses of insulin until autoantibodies were eliminated with immunosuppressive therapy.

A new look at brittle diabetes

"Brittle diabetes" was first used to describe a life "disrupted by episodes of hypoglycemia or hyperglycemia." Early descriptions focused on small case reports of mostly young women with psycho-social instability, recurrent diabetic ketoacidosis, poor patient compliance or maladaptation. We redefine "brittle diabetes" as occurring in four specific life stages each with distinct characteristics and associated conditions resulting in severely erratic glycemic control and poor outcomes. Once identified however these factors can often be reversed or significantly mitigated. The first group includes younger patients with associated psychiatric diseases such as bulimia and depression which require specific therapy and are treatable. A second group includes individuals who have another underlying medical condition resulting in disruption of insulin sensitivity or glucose utilization which must be sought. A third group, the largest we believe, has "geriatric type 1 diabetes" and develops severe glycemic instability due to frailty, chronic renal failure, dementia, vision loss, loss of counterregulation and other diseases of aging which lead to unintentional omission of insulin, insulin dosing errors and increasing insulin sensitivity. The fourth group, now seen around the world, suffers lack of insulin access and associated food insecurity. All four of these groups are described.

Searching for the Culprit: When Diabetic Ketoacidosis Presents With Insulin Autoantibodies

Objective

The main objective was to describe and review a unique case that presented with diabetic ketoacidosis, positive insulin autoantibodies (IAAbs, which are found in Hirata disease and are usually present with hypoglycemia), and laboratory findings characteristic of type B insulin resistance syndrome (TBIRS) and systemic lupus erythematosus. Confirmation of TBIRS was obtained in Germany as immunoassay for insulin receptor antibodies (IRAbs) is not available in the United States.

Methods

A literature review on TBIRS and cases that present with IAAbs and IRAbs simultaneously was conducted.

Results

We found 6 cases presenting with hypoglycemia, both antibodies, and treatment attempts with various management approaches that were different from the proposed National Institutes of Health (NIH) protocol for TBIRS. Our case is distinct because of the demographic background, presentation with diabetic ketoacidosis, comparatively lower insulin requirement, and no significant hypoglycemic episodes in the third phase.

Conclusion

We propose that access to IRAb immunoassays may be important for diagnosing milder cases of TBIRS, while IAAbs may provide prognostic and therapeutic insights. Despite completely different presentation from other TBIRS patients reviewed, we observed that the proposed NIH protocol consisting of dexamethasone, rituximab, and cyclophosphamide was successfully employed in our patient. Thus, we propose that our case and the findings regarding antibody testing and the NIH treatment regimen may assist clinicians with earlier recognition and effective management of milder cases of TBIRS.

Clinical and Laboratory Aspects of Insulin Autoantibody-Mediated Glycaemic Dysregulation and Hyperinsulinaemic Hypoglycaemia: Insulin Autoimmune Syndrome and Exogenous Insulin Antibody Syndrome

Autoimmune glycaemic dysregulation and hyperinsulinaemic hypoglycaemia mediated by insulin autoantibodies is an increasingly recognised but controversial phenomenon described in both exogenous insulin naïve (insulin autoimmune syndrome) and exposed (exogenous insulin antibody syndrome) individuals. There has been a significant proliferation of case reports, clinical studies and reviews in the medical literature in recent years which have collectively highlighted the discrepancy between experts in the field with regard to the nomenclature, definition, proposed pathophysiology, as well as the clinical and biochemical diagnostic criteria associated with the condition. The essential characteristics of the condition are glycaemic dysregulation manifesting as episodes of hyperglycaemia and unpredictable hyperinsulinaemic hypoglycaemia associated with high titres of endogenous antibodies to insulin. Although the hypoglycaemia is often life-threatening and initiation of targeted therapies critical, the diagnosis is often delayed and attributable to various factors including: the fact that existence of the condition is not universally accepted; the need to exclude surreptitious causes of hypoglycaemia; the diverse and often complex nature of the glycaemic dysregulation; and the challenge of diagnostic confirmation. Once confirmed, the available therapeutic options are expansive and the reported responses to these therapies have been variable. This review will focus on our evolving understanding, and the associated diagnostic challenges - both clinical and laboratory - of this complex condition.

A Lean Lady With Acanthosis Nigricans and Uncontrolled Diabetes Mellitus

A 47-year-old Asian Indian woman presented with uncontrolled hyperglycaemia and osmotic symptoms despite multiple oral antidiabetic medications and insulin. She had a history of recurrent oral ulcers, profound weight loss, and intermittent fever for one and a half years before the presentation. She had severe acanthosis nigricans, although her body mass index (BMI) was 14.6 kg/m².

Her blood glucose remained uncontrolled despite very large dosages of intravenous insulin (more than 12,000 units daily). Evaluation for possible underlying collagen vascular diseases and malignancies were negative. Her serum insulin levels were high. She tested negative for anti-insulin antibodies but positive for anti-insulin-receptor antibodies. She improved with a pulse dose of intravenous methylprednisolone but relapsed within one month. A second pulse dose was given following which a complete remission of diabetes and regression of acanthosis was observed.

Type B insulin resistance, a rare cause of severe insulin resistance, may respond favourably to immunosuppressive therapy with high-dose methylprednisolone.

Successful remission of type B insulin resistance syndrome without rituximab in an elderly male

SUMMARY

Type B insulin resistance syndrome (TBIR) is a rare autoimmune disease caused by antibodies against the insulin receptor. It should be considered in patients with dysglycaemia and severe insulin resistance when other more common causes have been ruled out. We report a case of a 72-year-old male with a 4-year history of type 2 diabetes who presented with hypercatabolism, vitiligo, acanthosis nigricans, and hyperglycaemia resistant to massive doses of insulin (up to 1000 U/day). Detection of anti-insulin receptor antibodies confirmed TBIR. The patient received six pulses of methylprednisolone and daily treatment with cyclophosphamide for 6 months. Response to treatment was evident after the fourth pulse of methylprednisolone, as indicated by weight gain, decreased glycosylated haemoglobin and decreased requirement of exogenous insulin that was later discontinued due to episodes of hypoglycaemia. Remission was eventually achieved and the patient is currently asymptomatic, does not require insulin therapy, has normal glycaemia and is awaiting initiation of maintenance therapy with azathioprine. Thus, TBIR remitted without the use of rituximab. This case highlights the importance of diagnosis and treatment in a timely fashion, as well as the significance of clinical features, available laboratory findings and medication. Large controlled studies are required to standardise a therapeutic protocol, particularly in resource-constrained settings where access to rituximab is limited.

LEARNING POINTS

Type B insulin resistance syndrome is a rare autoimmune disorder that should be considered in patients with dysglycaemia, severe insulin resistance and a concomitant autoimmune disease. Serological confirmation of antibodies against the insulin receptor is not necessary in all cases due to the high associated mortality without timely treatment. Although there is no standardised immunosuppressive treatment, a protocol containing rituximab, cyclophosphamide and steroids has shown a significant reduction in previously reported mortality rates. The present case, reports successful remission in an atypical patient using cyclophosphamide and methylprednisolone, which is an effective therapy in countries in which rituximab is not covered by health insurance. When there is improvement in the hypercatabolic phase, the insulin dose should be reduced and/or discontinued to prevent hypoglycaemia; a mild postprandial hyperglycaemic state should be acceptable.

Type B insulin resistance syndrome: a systematic review

A literature review on the clinical, laboratory, and treatment features of type B insulin resistance syndrome (TBIRS). Data from PubMed, the Virtual Health Library and Cochrane database were selected and analyzed using the REDCap application and R statistical program. From 182 papers, 65 were selected, which assessed 119 clinical cases, 76.5% in females and 42.9% in African-Americans, with an average age of 44 years. A common feature of TBIRS is co-occurrence of autoimmune diseases, such as systemic lupus erythematosus (most frequently reported). Hyperglycemia of difficult control was the mostly reported condition. Tests for anti-insulin receptor antibodies were positive in 44.2% of the cases. Disease management comprised fractional diet, insulin therapy (maximum dose given was 57 600 IU/day), plasmapheresis and immunosuppression with several classes of drugs, mainly glucocorticoids. Remission occurred in 69.7% of cases, in 30.3% of these spontaneously. The mortality rate was 15.38%. There was an inverse relationship between anti-insulin antibodies and remission (p = 0.033); and a positive correlation between combined immunosuppressive therapy and remission (p = 0.002). Relapse occurred in 7.6% of the cases. This rare syndrome has difficult-to-control diabetes, even with high doses of insulin, and it is usually associated with autoimmune diseases. Therapeutic advances using immunomodulatory therapy have led to significant improvements in the rate of remission.

Diagnosis of Flier's syndrome in a patient with nondiabetic hypoglycemia: a case report and critical appraisal of the literature

PURPOSE

Autoimmune hypoglycemia includes rare syndromes characterized by the presence of either anti-insulin antibodies (IAA) (Hirata's disease) or anti-insulin receptor (anti-ISR) antibodies (Flier's syndrome). Diagnosis is usually based on identification of the specific antibodies, in presence of the Whipple triad. However, most of these cases are classified as idiopathic diseases due to the difficulty to define the pathogenic culprit.

METHODS

Basic research methodologies, including Western Blot and ELISA tests, have been used in this study.

RESULTS

We describe a 21-year-old young woman (PT), non-obese and non-diabetic, with a positive history of autoimmune diseases, admitted to the hospital for recurrent episodes of severe symptomatic hypoglycemia. Counterregulatory response to hypoglycemia was normal as well as the fasting test, so excluding both hormone deficiencies and insulinoma. Since an autoimmune hypoglycemic syndrome was suspected, the hyperactivation of the insulin pathway was experimentally evaluated. At this purpose, human hepatocarcinoma (HepG2) cells were incubated with serum obtained from the patient (PT) and from control individuals. Interestingly, a significant increase of phosphorylation of insulin receptor, Akt, and ERK1/2 was observed in the HepG2 cells incubated with PT serum compared with the controls. ELISA tests revealed significantly increased levels of anti-ISR antibodies in PT serum, while IAA were similar both in PT and in control sera, supporting diagnosis of Flier's syndrome.

CONCLUSIONS

This study emphasizes the importance to identify new strategies for the differential diagnosis of hypoglycemia, not always possible with the routinely used diagnostic tests.

Clinical Features of Type B Insulin Resistance in Japanese Patients: Case Report and Survey-Based Case Series Study

Type B insulin resistance (TBIR) is an extremely rare disease characterized by marked hyperglycemia and insulin resistance and often coexists with autoimmune diseases. The characteristics, symptoms, blood glucose patterns, comorbidities, and treatments of TBIR all vary and are not defined. In this study, we described a case of TBIR that developed 6 months after DPP-4 inhibitor administration and immediately after the patient caught a cold. Treatment using prednisolone and insulin-like growth factor-1 was effective. We also conducted an observational survey-based case series study in a Japanese cohort comprising 21 cases. The average age of onset of TBIR was 62.3 ± 14.8 (17-84) years, and 61.9% of subjects were male. The majority of patients (90.4%) were 50 years old and over. During the study period, there was a high percentage (85.7%) of episodes of hypoglycemia, which was the trigger for diagnosis in more than 50% of cases. Glycemic patterns included 7 cases of hyperglycemia (33.3%), 10 cases of hypoglycemia (47.6%), and 4 cases of both hyperglycemia and hypoglycemia (19.1%). In the hypoglycemic group, 90.0% of patients were male. Furthermore, 71.4% of cases were antinuclear antibody positive, and 81.0% of cases were complicated with autoimmune disease. Systemic lupus erythematosus (38.1%) and Sjögren's syndrome (23.8%) were relatively common as coexisting autoimmune diseases. Treatment was based on prednisolone use, which was used in 88.9% of patients. On the other hand, the effect of IGF-1 was limited. Overall, the prognosis of TBIR was good.

Insulin Autoimmune Syndrome After Exposure to Clopidogrel: A Case Report

BACKGROUND

Insulin autoimmune syndrome (IAS) is a rare cause of hypoglycemia that is characterized by hyperinsulinemia, hypoglycemia, and a high autoantibody titer. About 50% of patients with IAS have taken a medication containing sulfhydryl (-SH) groups. We present a case of IAS that developed after taking clopidogrel, a drug with an active metabolite that contains an SH-group.

CASE REPORT

IAS was suspected in a 63-year-old Chinese man because of high concentrations of insulin and C-peptide during hypoglycemic episodes, and positivity for anti-insulin autoantibody (IAA). During his first episode of hypoglycemia, no trigger medication was identified and prednisone therapy was effective. However, imaging examination revealed a colonic carcinoma and the patient was discharged to undergo surgery. He had no episodes of hypoglycemia for 10 weeks after discontinuation of the prednisone, but then hypoglycemia recurred. A review of his medication revealed that he had taken a 10-day course of clopidogrel just before the recurrence. Therefore, a specialized multidisciplinary team consisting of endocrinologists, dieticians, and clinical pharmacists took charge of his management. Prednisone therapy was restarted and tapered off over 16 weeks. The patient also consumed small, frequent, low-carbohydrate meals and was instructed to avoid trigger medications. No further episodes of hypoglycemia were detected. His insulin and C-peptide concentrations and his anti-IAA index normalized during the follow-up period.

CONCLUSION

SH-group-containing drugs might induce or exacerbate hypoglycemia in patients with a history of IAS. Furthermore, patients with IAS can benefit from multidisciplinary team management. We suggest herein an evaluation process for patients suspected of IAS.

Insulin Autoimmune Syndrome in a 25-Year-Old, Previously Healthy Kuwaiti Man

Insulin autoimmune syndrome (IAS) is a disease characterized by hyperinsulinaemic hypoglycaemia associated with autoantibodies against endogenous insulin. We have described a case of a 25-year-old, previously healthy Kuwaiti man who was admitted to the Mubarak Al-Kabeer hospital with a history of recurrent hypoglycaemia. The patient revealed that he had taken several different injectable anabolic steroids and growth hormone with oral amino acids and other tablets (fat burners) for bodybuilding in the last two months. He denied knowingly using insulin or insulin analogues. The patient had elevated fasting insulin level (>301 uIU/mL) and elevated insulin autoantibodies (>100.0 IU/mL). After appropriate work-up, he was diagnosed with IAS. After treatment with prednisolone (1 mg/kg/day), the patient had complete recovery. In patients with repeated hypoglycaemia, IAS should be considered in the differential diagnosis. Glucocorticoid therapy can be effective for the treatment of hypoglycaemia in patients with IAS.

Combined Immunosuppressive Therapy Induces Remission in Patients With Severe Type B Insulin Resistance: A Prospective Cohort Study

OBJECTIVE

Type B insulin resistance due to autoantibodies against the insulin receptor is characterized by diabetes refractory to massive doses of insulin, severe hypercatabolism, hyperandrogenism, and a high mortality rate. We analyzed the efficacy of combined immunosuppressive therapy in the management of this extreme form of diabetes.

RESEARCH DESIGN AND METHODS

We performed a prospective cohort study including patients with confirmed insulin receptor autoantibodies, monitored for median 72 months (25th, 75th interquartile range 25, 88), and treated with rituximab, high-dose pulsed steroids, and cyclophosphamide until remission, followed by maintenance therapy with azathioprine. Remission was defined as the amelioration of the hyperglycemia and discontinuation of insulin and/or normalization of hyperandrogenemia.

RESULTS

All data are given as median (25th, 75th interquartile range). Twenty-two patients aged 42 (25, 57) years, 86.4% women, fulfilled inclusion criteria. At baseline, fasting glucose was 307 (203, 398) mg/dL, HbA_1c was 11.8% (9.7, 13.6), total testosterone (women) was 126 (57, 571) ng/dL (normal 8-60), and daily insulin requirement was 1,775 (863, 2,700) units. After 5 (4, 6.3) months, 86.4% (19 of 22) of patients achieved remission, documented by discontinuation of insulin in all patients, normal fasting glucose of 80 (76, 92) mg/dL, HbA_1c of 5.5% (5.2, 6), and testosterone (women) of 28 (20, 47) ng/dL. During follow-up of 72 (25, 88) months, 13.6% (3 of 22) of patients developed disease recurrence, occurring 24 (22, 36) months after initial remission, which responded to repeated therapy. None of the patients died.

CONCLUSIONS

Combined immunosuppressive therapy has changed the natural history of this disease, from 54% mortality to a curable form of diabetes and, as such, should be recommended in patients with type B insulin resistance.

Insulin autoimmune syndrome: from diagnosis to clinical management

Autoimmune forms of hypoglycemia are a rare cause of low blood sugar levels among Caucasians, and often go misdiagnosed, exposing patients to lengthy series of pointless, potentially harmful and expensive tests. There are two types of autoimmune hypoglycemia. One is insulin autoimmune syndrome (IAS), which is characterized by hyperinsulinemic hypoglycemia, elevated insulin autoantibody (IAA) titers, no prior exposure to exogenous insulin, and no of pathological abnormalities of the pancreatic islets. This condition is also known as "Hirata's disease". The other is type B insulin resistance syndrome (TBIRS), a rare autoimmune disorder resulting in a broad array of abnormalities in glucose homeostasis-from hypoglycemia to extremely insulin-resistant hyperglycemia-caused by the presence of insulin receptor autoantibodies (IRAbs). This review focuses on these two syndromes, describing their epidemiology, possible genetic background, clinical presentation, pathophysiology, diagnosis and treatment.

Interpretation of Unexpectedly High Levels of Endocrine Tumor Markers

OBJECTIVE

Endocrine tumor markers (ETMs) are important and indispensable tools in the diagnosis and follow-up of endocrine tumors. Unexpectedly high level of ETM (UHLETM) is often encountered in clinical practice. The objectives of this article are to discuss the approach to UHLETMs and describe the most common UHLETMs.

METHODS

Literature review and personal experience with UHLETMs.

RESULTS

A UHLETM is defined as an ETM level much higher than what an endocrinologist would expect based on the patient's clinical information, other biochemical test results, and imaging findings. Most UHLETMs are false positive, in that they do not indicate the existence or growth of an endocrine tumor. The key issue, however, is how to convincingly prove that a UHLETM is false positive. The most important question to help resolve UHLETMs is whether the UHLETMs are due to false or true results. Some UHLETMs are due to interpretation errors, laboratory errors, or spurious test results, while the true levels of the ETMs are normal or unchanged from previous results. Other UHLETMs are due to nontumor conditions or medications, and the true levels of the ETMs are indeed very high. When it is not straightforward to assess whether certain UHLETMs are due to false or true results, they may be due to novel conditions.

CONCLUSION

UHLETMs provide endocrinologists great opportunities to learn the basic biology and measurement of ETMs. Unresolved UHLETMs are exciting clinical research opportunities which may lead to discovery of new diseases and new mechanisms of measurement interference.

ABBREVIATIONS

5-HIAAA = 5-hydroxyindoleacetic acid; 5-HTP = 5-hydroxytryptophan; CGA = chromogranin A; ETM = endocrine tumor marker; MTC = medullary thyroid carcinoma; UHLETM = unexpectedly high level of endocrine tumor marker.

The effect of non-TNF-targeted biologics and small molecules on insulin resistance in inflammatory arthritis

Inflammatory arthritides are chronic diseases characterised by an increase in cardiovascular risk, largely attributable to the synergy between high-grade systemic inflammation and an elevated prevalence of traditional cardiovascular risk factors. Amongst the latter, insulin resistance and type 2 diabetes (T2D) play a key position. Previous studies demonstrated a potential insulin-sensitizing effect of anti-TNF biologic medications. For converse, less is known about the role of newer biologics or small molecules. For this reason, we performed a systematic review of the literature in order to identify the available data on the effect on insulin resistance of non-TNF targeting biologics and small molecules approved for the treatment of inflammatory arthritides. The search strategy initially retrieved 486 records of which only 10 articles were selected for inclusion in the final review. According to the available evidence, some of the newest molecules, in particular tocilizumab and abatacept, may have a role in improving insulin sensitivity; for converse, anakinra-mediated effect on glucose metabolism may exploit different facets of T2D pathophysiology, such as the preservation of beta-cell function. However, the data available on this issue are largely inconsistent and future, adequately designed studies are still needed to clarify the differential impact of novel therapeutics on individual pathophysiological features of T2D and other emerging cardiovascular risk factors.

Unique pharmacology of a novel allosteric agonist/sensitizer insulin receptor monoclonal antibody

Objective

Insulin resistance is a key feature of Type 2 Diabetes (T2D), and improving insulin sensitivity is important for disease management. Allosteric modulation of the insulin receptor (IR) with monoclonal antibodies (mAbs) can enhance insulin sensitivity and restore glycemic control in animal models of T2D.

Methods

A novel human mAb, IRAB-A, was identified by phage screening using competition binding and surface plasmon resonance assays with the IR extracellular domain. Cell based assays demonstrated agonist and sensitizer effects of IRAB-A on IR and Akt phosphorylation, as well as glucose uptake. Lean and diet-induced obese mice were used to characterize single-dose in vivo pharmacological effects of IRAB-A; multiple-dose IRAB-A effects were tested in obese mice.

Results

In vitro studies indicate that IRAB-A exhibits sensitizer and agonist properties distinct from insulin on the IR and is translated to downstream signaling and function; IRAB-A bound specifically and allosterically to the IR and stabilized insulin binding. A single dose of IRAB-A given to lean mice rapidly reduced fed blood glucose for approximately 2 weeks, with concomitant reduced insulin levels suggesting improved insulin sensitivity. Phosphorylated IR (pIR) from skeletal muscle and liver were increased by IRAB-A; however, phosphorylated Akt (pAkt) levels were only elevated in skeletal muscle and not liver vs. control; immunochemistry analysis (IHC) confirmed the long-lived persistence of IRAB-A in skeletal muscle and liver. Studies in diet-induced obese (DIO) mice with IRAB-A reduced fed blood glucose and insulinemia yet impaired glucose tolerance and led to protracted insulinemia during a meal challenge.

Conclusion

Collectively, the data suggest IRAB-A acts allosterically on the insulin receptor acting non-competitively with insulin to both activate the receptor and enhance insulin signaling. While IRAB-A produced a decrease in blood glucose in lean mice, the data in DIO mice indicated an exacerbation of insulin resistance; these data were unexpected and suggested the interplay of complex unknown pharmacology. Taken together, this work suggests that IRAB-A may be an important tool to explore insulin receptor signaling and pharmacology.

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A novel anti-insulin receptor monoclonal antibody (IRAB-A) was identified that has both agonist and sensitizing activities.

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IRAB-A increases the receptor's affinity for insulin by binding to an allosteric site and does not compete with insulin.

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Mice injected once with IRAB-A show improved glycemia and reduced insulinemia, indicative of enhanced insulin sensitivity.

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In diet induced obese mice, the insulin sensitizing effect of IRAB-A appears to depend on the degree of insulin resistance.

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Chronic treatment of obese mice showed mixed effects on glucose homeostasis under normal fed or meal challenged conditions.