Receptor and postreceptor defects contribute to the insulin resistance in noninsulin-dependent diabetes mellitus

A review: Mechanism and prospect of gastrodin in prevention and treatment of T2DM and COVID-19

Gastrodin is an extract from the dried tuber of the Chinese herb Gastrodia elata (Tian ma), with anti-inflammatory, antioxidant, and antiviral properties. Recent studies have shown that, compared to commonly used diabetes drugs, gastrodin has antidiabetic effects in multiple ways, with characteristics of low cost, high safety, less side effects, protection of β-cell function, relieving insulin resistance and alleviating multiple complications. In addition, it is confirmed that gastrodin can protect the function of lung and other organs, enhance antiviral activity via upregulating the type I interferon (IFN-I), and inhibit angiotensin II (AngII), a key factor in "cytokine storm" caused by COVID-19. Therefore, we reviewed the effect and mechanism of gastrodin on type 2 diabetes mellitus (T2DM), and speculated other potential mechanisms of gastrodin in alleviating insulin resistance from insulin signal pathway, inflammation, mitochondrial and endoplasmic reticulum and its potential in the prevention and treatment of COVID-19. We hope to provide new direction and treatment strategy for basic research and clinical work: gastrodin is considered as a drug for the prevention and treatment of diabetes and COVID-19.

Insulin signaling and its application

The discovery of insulin in 1921 introduced a new branch of research into insulin activity and insulin resistance. Many discoveries in this field have been applied to diagnosing and treating diseases related to insulin resistance. In this mini-review, the authors attempt to synthesize the updated discoveries to unravel the related mechanisms and inform the development of novel applications. Firstly, we depict the insulin signaling pathway to explain the physiology of insulin action starting at the receptor sites of insulin and downstream the signaling of the insulin signaling pathway. Based on this, the next part will analyze the mechanisms of insulin resistance with two major provenances: the defects caused by receptors and the defects due to extra-receptor causes, but in this study, we focus on post-receptor causes. Finally, we discuss the recent applications including the diseases related to insulin resistance (obesity, cardiovascular disease, Alzheimer's disease, and cancer) and the potential treatment of those based on insulin resistance mechanisms.

The role of pioglitazone in the fight against insulin resistance, atherosclerosis, cardiovascular disease, and non-alcoholic fatty liver disease

Modern strategies for the treatment of type 2 diabetes mellitus involve the use of pathogenetically based approaches aimed at achieving optimal glycemic control and its long-term retention. Timely and rational use of 9 classes of hypoglycemic drugs, including as part of combination therapy, makes it possible to achieve significant success in diabetes therapy. One of the fundamental principles in the treatment of type 2 diabetes mellitus is the effect on insulin resistance. For this purpose, two groups of drugs are used: biguanides and thiazolidinediones (glitazones). The action of glitazones is directly related to an increase in the sensitivity of insulin-dependent tissues to insulin and a pronounced decrease in hyperinsulinemia in patients with type 2 diabetes. Of particular interest are the pathways of insulin signal transduction, the mechanisms of insulin resistance, and the possibilities of pathogenetic therapy with thiazolidinediones. Pioglitazone is currently the only available member of the thiazolidinedione class in the world, allowing to expand the management of diabetes mellitus by reducing insulin resistance in muscle and adipose tissue and glucose production by the liver. Its use can have a number of pleiotropic effects, including on cardiovascular diseases and non-alcoholic fatty liver disease, which expands the priorities for choosing hypoglycemic therapy in patients with type 2 diabetes at various stages of therapy.

The Association Between Fasting Blood Sugar and Index of Nutritional Quality in Adult Women

Aim

It's unclear whether diet quality affects glycemic management. The index of nutritional quality (INQ) can examine diets both quantitatively and qualitatively (INQ). Hence, this study aimed to determine whether INQ and fasting blood sugar (FBS) are related among Iranian women.

Methods

This cross-sectional study was conducted on 360 adult Iranian women. Data were collected on the participants' general characteristics, medical history, anthropometric indices, physical activity, and dietary intake. For nutrient intake assessment, a valid food frequency questionnaire (FFQ) was used, and INQ was then calculated using the daily nutrient intake.

Results

After adjusting for age, FBS was significantly inverse associated with INQ for vitamins A (B = −0.193, p < 0.01), magnesium (B = −0.137, p < 0.01), phosphor (B = −0.175, p < 0.01), zinc (B = −0.113, p < 0.01), vitamin K (B = −0.197, p < 0.01), manganese (B = −0.111, p < 0.01) and selenium (B = −0.123, p < 0.01). The association between FBS and INQ for Se and Mn was disappeared after further adjustment for gender, body mass index (BMI), menopausal status, and total energy intake.

Conclusion

There was a significant inverse relationship between FBS and the INQ of vitamin A, manganese, phosphor, zinc, vitamin K, magnesium, and selenium. Prospective cohort studies should be conducted to establish a causal relationship between FBS and INQ.

Insulin facilitates corneal wound healing in the diabetic environment through the RTK-PI3K/Akt/mTOR axis in vitro

Diabetic patients can develop degenerative corneal changes, termed diabetic keratopathy, during the course of their disease. Topical insulin has been shown to reduce corneal wound area and restore sensitivity in diabetic rats, and both the insulin receptor (IR) and insulin-like growth factor 1 receptor (IGF-1R) stimulate cell signaling of the PI3K-Akt pathway. The purpose of this study was to assess a mechanism by which improved wound healing occurs by characterizing expression within the PI3K-Akt pathway in corneal epithelial and stromal cells. In vitro scratch tests were used to evaluate wound healing outcomes under variable glucose conditions in the presence or absence of insulin. Protein expression of intracellular kinases in the PI3K pathway, stromal cell markers, and GLUT-1 was evaluated by immunoblotting.TGF-β1 expression was evaluated by ELISA. Insulin promoted in vitro wound healing in all cell types. In human corneal epithelial cells, insulin did not induce PI3K-Akt signaling; however, in all other cell types evaluated, insulin increased expression of PI3K-Akt signaling proteins compared to vehicle control. Fibroblasts variably expressed α-SMA under all treatment conditions, with significant increases in α-SMA and TGF-β1 occurring in a dose-dependent manner with glucose concentration. These results indicate that insulin can promote corneal cellular migration and proliferation by inducing Akt signaling. Exogenous insulin therapy may serve as a novel target of therapeutic intervention for diabetic keratopathy.

Insulin Clearance in Obesity and Type 2 Diabetes

Plasma insulin clearance is an important determinant of plasma insulin concentration. In this review, we provide an overview of the factors that regulate insulin removal from plasma and discuss the interrelationships among plasma insulin clearance, excess adiposity, insulin sensitivity, and type 2 diabetes (T2D). We conclude with the perspective that the commonly observed lower insulin clearance rate in people with obesity, compared with lean people, is not a compensatory response to insulin resistance but occurs because insulin sensitivity and insulin clearance are mechanistically, directly linked. Furthermore, insulin clearance decreases postprandially because of the marked increase in insulin delivery to tissues that clear insulin. The commonly observed high postprandial insulin clearance in people with obesity and T2D likely results from the relatively low insulin secretion rate, not an impaired adaptation of tissues that clear insulin.

p300 or CBP is required for insulin-stimulated glucose uptake in skeletal muscle and adipocytes

While current thinking posits that insulin signaling to GLUT4 exocytic translocation and glucose uptake in skeletal muscle and adipocytes is controlled by phosphorylation-based signaling, many proteins in this pathway are acetylated on lysine residues. However, the importance of acetylation and lysine acetyltransferases to insulin-stimulated glucose uptake is incompletely defined. Here, we demonstrate that combined loss of the acetyltransferases E1A binding protein p300 (p300) and cAMP response element binding protein binding protein (CBP) in mouse skeletal muscle causes a complete loss of insulin-stimulated glucose uptake. Similarly, brief (i.e. 1 h) pharmacological inhibition of p300/CBP acetyltransferase activity recapitulates this phenotype in human and rodent myotubes, 3T3-L1 adipocytes, and mouse muscle. Mechanistically, these effects are due to p300/CBP-mediated regulation of GLUT4 exocytic translocation and occurs downstream of Akt signaling. Taken together, we highlight a fundamental role for acetylation and p300/CBP in the direct regulation of insulin-stimulated glucose transport in skeletal muscle and adipocytes.

Plasmatic Magnesium Deficiency in 101 Outpatients Living with Type 2 Diabetes Mellitus

(1) Background: Magnesium deficiency is usually associated with type 2 diabetes mellitus (T2DM). Individuals living with T2DM with hypomagnesemia show a more rapid disease progression and have an increased risk for diabetes complications. (2) Methods: This is a cross-sectional and descriptive study in the National Institute of Nutrition and Food Technology of Tunis in Tunisia, including all adult outpatients (≥18 years old) with a diagnosis of T2DM from 1 September 2018 to 31 August 2019. The aim of this study was to evaluate the prevalence of plasmatic magnesium deficiency in a Tunisian population of T2DM and to study the relationship between magnesium status and intake, glycemic control and long-term diabetes-related complications. (3) Results: Among the 101 T2DM outpatients, 13 (12.9%) presented with a plasmatic magnesium deficiency. The mean age was 56 ± 7.9 years with a female predominance (62%, n = 63). The mean of the plasmatic magnesium level was 0.79 ± 0.11 mmol/L (0.5–1.1), and the mean of 24 h urinary magnesium excretion was 87.8 ± 53.8 mg/24 h [4.8–486.2]. HbA1c was significantly higher in the plasmatic magnesium deficiency group than the normal magnesium status group (10% ± 1.3 vs. 8.3% ± 1.9; p = 0.04), with a significant difference in participants with a poor glycemic control (HbA1c > 7%) (100%, n = 13/13 vs. 53%, n = 47/88; p = 0.001). A weak negative relationship was also found between plasmatic magnesium and HbA1c (r = −0.2, p = 0.03). Peripheral artery disease was more commonly described in individuals with low plasmatic magnesium levels than in individuals with normal levels (39%, n = 5 vs. 0%, n = 0; p < 0.001). The mean plasmatic magnesium level in participants without diabetic nephropathy and also peripheral artery disease was significantly higher compared to individuals with each long-term diabetes-related complication (0.8 mmol/L ± 0.1 vs. 0.71 mmol/L ± 0.07; p = 0.006) and (0.8 mmol/L ± 0.1 vs. 0.6 mmol/L ± 0.08; p < 0.001), respectively. (4) Conclusions: Hypomagnesemia was identified in individuals with T2DM, causing poor glycemic control and contributing to the development and progression of diabetes-related microvascular and macrovascular complications.

Role of Pancreatic Stellate Cell-Derived Exosomes in Pancreatic Cancer-Related Diabetes: A Novel Hypothesis

Pancreatic ductal adenocarcinoma (PDAC) is a devastating condition characterised by vague symptomatology and delayed diagnosis. About 30% of PDAC patients report a history of new onset diabetes, usually diagnosed within 3 years prior to the diagnosis of cancer. Thus, new onset diabetes, which is also known as pancreatic cancer-related diabetes (PCRD), could be a harbinger of PDAC. Diabetes is driven by progressive β cell loss/dysfunction and insulin resistance, two key features that are also found in PCRD. Experimental studies suggest that PDAC cell-derived exosomes carry factors that are detrimental to β cell function and insulin sensitivity. However, the role of stromal cells, particularly pancreatic stellate cells (PSCs), in the pathogenesis of PCRD is not known. PSCs are present around the earliest neoplastic lesions and around islets. Given that PSCs interact closely with cancer cells to drive cancer progression, it is possible that exosomal cargo from both cancer cells and PSCs plays a role in modulating β cell function and peripheral insulin resistance. Identification of such mediators may help elucidate the mechanisms of PCRD and aid early detection of PDAC. This paper discusses the concept of a novel role of PSCs in the pathogenesis of PCRD.

Ethnopharmacological, Phytochemical, Pharmacological, and Toxicological Review on Senna auriculata (L.) Roxb.: A Special Insight to Antidiabetic Property

Avartaki (Senna auriculata (L.) Roxb. syn. Cassia auriculata L.; Family- Fabaceae ) is a traditional medicinal plant, widely used for the treatment of various ailments in Ayurveda and Siddha system of medicine in India. Almost all the parts of the plant, such as flowers, leaves, seeds, barks, and roots have been reported for their medicinal uses. Traditionally, it has been used in the treatment of diabetes, asthma, rheumatism, dysentery, skin disease, and metabolic disorders. The principle phytochemicals in Senna auriculata (L.) Roxb. are alkaloids, anthraquinone, flavone glycosides, sugar, saponins, phenols, terpenoids, flavonoids, tannins, steroids, palmitic acid, linoleic acid, benzoic acid 2-hydroxyl methyl ester, 1-methyl butyl ester, resorcinol, α-tocopherol-β-D-mannosidase, epicatechin, ferulic acid, quercetin-3-O-rutinoside, quercetin, proanthocyanidin B1. The extracts from its different parts and their isolated compounds possess a wide range of pharmacological activities such as antidiabetic, antioxidant, anti-inflammatory, antihyperlipidemic, hepatoprotective, nephroprotective, cardioprotective, anti-atherosclerotic, anticancer, antimutagenic, antimicrobial, antiulcer, antipyretic, anthelmintic, immunomodulatory, antifertility, anti-venom, and anti-melanogenesis. The toxicological findings from preclinical studies ensured the safety of the plant, but comprehensive clinical studies are required for the safety and efficacy of the plant in humans. The current review article aimed to provide up-to-date information about Senna auriculata (L.) Roxb. covering its ethnomedicinal, phytochemical, pharmacological, and toxicological aspects with special emphasis on its clinical implications in diabetes.

Type 2 diabetes - unmet need, unresolved pathogenesis, mTORC1-centric paradigm

The current paradigm of type 2 diabetes (T2D) is gluco-centric, being exclusively categorized by glycemic characteristics. The gluco-centric paradigm views hyperglycemia as the primary target, being driven by resistance to insulin combined with progressive beta cells failure, and considers glycemic control its ultimate treatment goal. Most importantly, the gluco-centric paradigm considers the non-glycemic diseases associated with T2D, e.g., obesity, dyslipidemia, hypertension, macrovascular disease, microvascular disease and fatty liver as 'risk factors' and/or 'outcomes' and/or 'comorbidities', rather than primary inherent disease aspects of T2D. That is in spite of their high prevalence (60-90%) and major role in profiling T2D morbidity and mortality. Moreover, the gluco-centric paradigm fails to realize that the non-glycemic diseases of T2D are driven by insulin and, except for glycemic control, response to insulin in T2D is essentially the rule rather than the exception. Failure of the gluco-centric paradigm to offer an exhaustive unifying view of the glycemic and non-glycemic diseases of T2D may have contributed to T2D being still an unmet need. An mTORC1-centric paradigm maintains that hyperactive mTORC1 drives the glycemic and non-glycemic disease aspects of T2D. Hyperactive mTORC1 is proposed to act as double-edged agent, namely, to interfere with glycemic control by disrupting the insulin receptor-Akt transduction pathway, while concomitantly driving the non-glycemic diseases of T2D. The mTORC1-centric paradigm may offer a novel perspective for T2D in terms of pathogenesis, clinical focus and treatment strategy.

Endoplasmic reticulum stress causes insulin resistance by inhibiting delivery of newly synthesized insulin receptors to the cell surface

Accumulation of unfolded proteins in the endoplasmic reticulum (ER) causes ER stress and activates a signaling network known as the unfolded protein response (UPR). Here we characterize how ER stress and the UPR inhibit insulin signaling. We find that ER stress inhibits insulin signaling by depleting the cell surface population of the insulin receptor. ER stress inhibits proteolytic maturation of insulin proreceptors by interfering with transport of newly synthesized insulin proreceptors from the ER to the plasma membrane. Activation of AKT, a major target of the insulin signaling pathway, by a cytosolic, membrane-bound chimera between the AP20187-inducible FV2E dimerization domain and the cytosolic protein tyrosine kinase domain of the insulin receptor was not affected by ER stress. Hence, signaling events in the UPR, such as activation of the JNK mitogen-activated protein (MAP) kinases or the pseudokinase TRB3 by the ER stress sensors IRE1α and PERK, do not contribute to inhibition of signal transduction in the insulin signaling pathway. Indeed, pharmacologic inhibition and genetic ablation of JNKs, as well as silencing of expression of TRB3, did not restore insulin sensitivity or rescue processing of newly synthesized insulin receptors in ER-stressed cells. [Media: see text].

Successful treatment with artificial pancreas for a patient who attempted suicide using a high-dose insulin s.c. injection

Background

Artificial pancreas is usually used to manage hyperglycemia. We controlled prolonged hypoglycemia induced by insulin overdose using artificial pancreas.

Case Presentation

A 56‐year‐old female patient with type 2 diabetes mellitus was admitted to the emergency department after overdosing on 1,800 units each of insulin aspart and insulin degludec. She had also ingested 2 weeks of anti‐anxiety medication. When the patient arrived at the hospital, her blood glucose level was 30 mg/dL and she was in a coma. Artificial pancreas (STG‐55; Nikkiso, Tokyo, Japan) was used to control blood glucose levels because we were unable to predict the duration or degree of hypoglycemia. Blood glucose levels were safely controlled without the development of hypo‐ or hyperglycemia. Finally, the patient was discharged without any complications on day 7.

Conclusion

The STG‐55 artificial pancreas was very useful and convenient for controlling blood glucose levels in our insulin overdose patient.

The Role of Diabetes Mellitus in Diseases of the Gallbladder and Biliary Tract

BACKGROUND

The increasing prevalence of diabetes mellitus worldwide continues to pose a heavy burden. Though its gastrointestinal impact is appropriately recognized, the lesser known associations may be overlooked.

OBJECTIVE

We aim to review the negative implications of diabetes on the gallbladder and the biliary tract.

METHODS

A MEDLINE® database search of literature was conducted with emphasis on the previous five years, combining keywords such as "diabetes," "gallbladder," and "biliary".

RESULTS

The association of diabetes to the formation of gallstones, gallbladder cancer, and cancer of the biliary tract are discussed along with diagnosis and treatment.

CONCLUSION

Though we uncover the role of diabetic neuropathy in gallbladder and biliary complications, the specific individual diabetic risk factors behind these developments is unclear. Also, in addition to diabetes control and surgical gallbladder management, the treatment approach also requires further focus.

The Effects of Oral Magnesium Supplementation on Glycemic Response among Type 2 Diabetes Patients

Background: Magnesium (Mg) supplementation may help control glycemic response among type 2 diabetes (T2D) patients. Objective: This study means to determine whether Mg supplementation improves glycemic control indicators in patients with T2D. Methods: After one week of the dietary stabilization phase, 42 T2D patients were stratified according to sex, age, fasting blood sugar (FBS) and Mg levels and then randomly allocated into two groups. The intervention group was on 250 mg/day of elemental Mg for three months while the control group did not receive any type of supplements throughout the intervention period. Results: The daily administration of 250 mg of elemental Mg indicated a significant improvement in HbA1C (8.32 to 7.96%, p < 0.001), insulin levels (IL) (15.56 to 12.18 μIU/mL, p < 0.001), C-peptide (2.28 to 1.90 ng/mL, p = 0.001), HOMA.IR (6.16 to 4.44, p < 0.001) and HOMA.β% (59.99 to 52.37, p = 0.036) of the intervention group when compared with the control group after three months of intervention. Conclusion: The results of this study revealed that oral Mg supplementation reduces insulin resistance and improves the glycemic control indicators among T2D patients. Trial registration: current controlled trials PHRC/HC/32/15. Registered 5 October 2015.

Mechanisms of Insulin Action and Insulin Resistance

The 1921 discovery of insulin was a Big Bang from which a vast and expanding universe of research into insulin action and resistance has issued. In the intervening century, some discoveries have matured, coalescing into solid and fertile ground for clinical application; others remain incompletely investigated and scientifically controversial. Here, we attempt to synthesize this work to guide further mechanistic investigation and to inform the development of novel therapies for type 2 diabetes (T2D). The rational development of such therapies necessitates detailed knowledge of one of the key pathophysiological processes involved in T2D: insulin resistance. Understanding insulin resistance, in turn, requires knowledge of normal insulin action. In this review, both the physiology of insulin action and the pathophysiology of insulin resistance are described, focusing on three key insulin target tissues: skeletal muscle, liver, and white adipose tissue. We aim to develop an integrated physiological perspective, placing the intricate signaling effectors that carry out the cell-autonomous response to insulin in the context of the tissue-specific functions that generate the coordinated organismal response. First, in section II, the effectors and effects of direct, cell-autonomous insulin action in muscle, liver, and white adipose tissue are reviewed, beginning at the insulin receptor and working downstream. Section III considers the critical and underappreciated role of tissue crosstalk in whole body insulin action, especially the essential interaction between adipose lipolysis and hepatic gluconeogenesis. The pathophysiology of insulin resistance is then described in section IV. Special attention is given to which signaling pathways and functions become insulin resistant in the setting of chronic overnutrition, and an alternative explanation for the phenomenon of ‟selective hepatic insulin resistanceˮ is presented. Sections V, VI, and VII critically examine the evidence for and against several putative mediators of insulin resistance. Section V reviews work linking the bioactive lipids diacylglycerol, ceramide, and acylcarnitine to insulin resistance; section VI considers the impact of nutrient stresses in the endoplasmic reticulum and mitochondria on insulin resistance; and section VII discusses non-cell autonomous factors proposed to induce insulin resistance, including inflammatory mediators, branched-chain amino acids, adipokines, and hepatokines. Finally, in section VIII, we propose an integrated model of insulin resistance that links these mediators to final common pathways of metabolite-driven gluconeogenesis and ectopic lipid accumulation.

Muscle and adipose tissue insulin resistance: malady without mechanism?

Insulin resistance is a major risk factor for numerous diseases, including type 2 diabetes and cardiovascular disease. These disorders have dramatically increased in incidence with modern life, suggesting that excess nutrients and obesity are major causes of "common" insulin resistance. Despite considerable effort, the mechanisms that contribute to common insulin resistance are not resolved. There is universal agreement that extracellular perturbations, such as nutrient excess, hyperinsulinemia, glucocorticoids, or inflammation, trigger intracellular stress in key metabolic target tissues, such as muscle and adipose tissue, and this impairs the ability of insulin to initiate its normal metabolic actions in these cells. Here, we present evidence that the impairment in insulin action is independent of proximal elements of the insulin signaling pathway and is likely specific to the glucoregulatory branch of insulin signaling. We propose that many intracellular stress pathways act in concert to increase mitochondrial reactive oxygen species to trigger insulin resistance. We speculate that this may be a physiological pathway to conserve glucose during specific states, such as fasting, and that, in the presence of chronic nutrient excess, this pathway ultimately leads to disease. This review highlights key points in this pathway that require further research effort.

Hematopoietic-Derived Galectin-3 Causes Cellular and Systemic Insulin Resistance

In obesity, macrophages and other immune cells accumulate in insulin target tissues, promoting a chronic inflammatory state and insulin resistance. Galectin-3 (Gal3), a lectin mainly secreted by macrophages, is elevated in both obese subjects and mice. Administration of Gal3 to mice causes insulin resistance and glucose intolerance, whereas inhibition of Gal3, through either genetic or pharmacologic loss of function, improved insulin sensitivity in obese mice. In vitro treatment with Gal3 directly enhanced macrophage chemotaxis, reduced insulin-stimulated glucose uptake in myocytes and 3T3-L1 adipocytes and impaired insulin-mediated suppression of glucose output in primary mouse hepatocytes. Importantly, we found that Gal3 can bind directly to the insulin receptor (IR) and inhibit downstream IR signaling. These observations elucidate a novel role for Gal3 in hepatocyte, adipocyte, and myocyte insulin resistance, suggesting that Gal3 can link inflammation to decreased insulin sensitivity. Inhibition of Gal3 could be a new approach to treat insulin resistance.

Altered expression of IRS2 and GRB2 in demyelination of peripheral neurons: Implications in diabetic neuropathy

Demyelination of the peripheral nerves and dysfunction of Schwann cells (SCs) are the chronic complications involved in the development of peripheral neuropathy among diabetic patients. Insulin signaling plays an important role in restoring the myelin proteins in diabetic peripheral neuropathy (DPN). Since insulin levels are altered in diabetes, it becomes of great interest to appreciate the role and regulation of docking and adaptor protein, how these proteins respond to variations in the levels of insulin as experienced in juvenile diabetes. Tyrosine phosphorylation of receptor protein kinases provides a docking site for the activation of adaptor proteins which are the key regulators of insulin signaling pathway. In this report, we studied the long term effect of insulin as a neurotrophic factor and identified the isoform of receptor substrate involved in the propagation of insulin signal in SCs. We also studied the ability of insulin to regulate the expression of different receptor substrates like insulin receptor substrate-1 (IRS1), insulin receptor substrate-2 (IRS2) and growth factor receptor-bound protein-2 (GRB2) that propagate the insulin signaling and also their variation in hyperglycemic SCs and sciatic nerve of the diabetic rats. Results confirmed that IRS2 is the key receptor substrate involved in insulin signal transduction. But, a radical increase in the phosphorylation of IRS2 at serine 731 prevents the recruitment of GRB2 adaptor protein which may fail further to connect the Ras and other pathways required to the cell for its survival and to maintain integrity. These findings prove that SCs and sciatic nerve express IRS proteins that are altered by diabetes and thereby insulin signaling downstream is impaired and that contribute to the pathogenesis of DPN.

Relationship between circulating levels of pancreatic proteolytic enzymes and pancreatic hormones

BACKGROUND

While the close morphological relationship between the exocrine and endocrine pancreas is well established, their functional interaction remains poorly understood. The aim of this study was to investigate the associations between circulating levels of pancreatic proteolytic enzymes and insulin, as well as other pancreatic hormones.

METHODS

Fasting venous blood samples were collected and analyzed for trypsin, chymotrypsin, insulin, glucagon, somatostatin, and pancreatic polypeptide. Linear regression analysis was used in unadjusted and two adjusted (accounting for prediabetes/diabetes, body mass index, smoking, and other covariates) statistical models.

RESULTS

A total of 93 individuals with a history of acute pancreatitis were included in this cross-sectional study. Chymotrypsin was significantly associated with insulin in the two adjusted models (p = 0.005; p = 0.003) and just missed statistical significance in the unadjusted model (p = 0.066). Chymotrypsin was significantly associated with glucagon in both unadjusted (p = 0.025) and adjusted models (p = 0.014; p = 0.015); as well as with somatostatin - in both unadjusted (p = 0.001) and adjusted models (p = 0.001; p = 0.002). Trypsin was not significantly associated with insulin in any of the models but was significantly associated with glucagon in both unadjusted (p < 0.001) and adjusted models (p < 0.001), and pancreatic polypeptide in both unadjusted (p < 0.001) and adjusted (p < 0.001) models.

CONCLUSION

The state of hyperinsulinemia is characterized by a dysfunction of the exocrine pancreas. In particular, chymotrypsin is increased in the state of hyperinsulinemia and trypsin is significantly associated with glucagon and pancreatic polypeptide.

MARCH1 regulates insulin sensitivity by controlling cell surface insulin receptor levels

Insulin resistance is a key driver of type 2 diabetes (T2D) and is characterized by defective insulin receptor (INSR) signalling. Although surface INSR downregulation is a well-established contributor to insulin resistance, the underlying molecular mechanisms remain obscure. Here we show that the E3 ubiquitin ligase MARCH1 impairs cellular insulin action by degrading cell surface INSR. Using a large-scale RNA interference screen, we identify MARCH1 as a negative regulator of INSR signalling. March1 loss-of-function enhances, and March1 overexpression impairs, hepatic insulin sensitivity in mice. MARCH1 ubiquitinates INSR to decrease cell surface INSR levels, but unlike other INSR ubiquitin ligases, MARCH1 acts in the basal state rather than after insulin stimulation. Thus, MARCH1 may help set the basal gain of insulin signalling. MARCH1 expression is increased in white adipose tissue of obese humans, suggesting that MARCH1 contributes to the pathophysiology of T2D and could be a new therapeutic target.

Oxidative Stress Parameters and Erythrocyte Membrane Adenosine Triphosphatase Activities in Streptozotocin-induced Diabetic Rats Administered Aqueous Preparation of Kalanchoe Pinnata Leaves

Background:

Diabetes mellitus is a chronic metabolic disease that according to the World Health Organization affects more than 382 million people. The rise in diabetes mellitus coupled with the lack of an effective treatment has led many to investigate medicinal plants to identify a viable alternative.

Objective:

To evaluate red blood cell (RBC) membrane adenosine triphosphatase (ATPase) activities and antioxidant levels in streptozotocin-induced diabetic rats administered aqueous preparation of Kalanchoe pinnata leaves.

Materials and Methods:

Diabetes mellitus was induced in rats by a single administration of streptozotocin (60 mg/kg). Diabetic rats were then treated with aqueous K. pinnata preparation (three mature leaves ~ 9.96 g/70 kg body weight or about 0.14 g/kg body weight/day) for 30 days. Serum glucose, RBC membrane ATPase activities, and antioxidant levels were determined.

Results:

We noted weight loss and reduced food consumption in the treated diabetic group. Serum glucose levels were reduced in the treated diabetic group compared to the other groups. Superoxide dismutase activity and glutathione levels were not significantly elevated in the treated group compared to the diabetic group. However, serum catalase activity was significantly (P < 0.05) increased in the treated diabetic group compared to the other groups. Serum thiobarbituric acid reactive substances were not significantly altered among the groups. There was a significant (P < 0.05) increase in Mg²⁺ ATPase activity and a nonsignificant increase in Na⁺/K⁺ ATPase activity in the RBC membrane of the treated diabetic group compared to the diabetic group.

Conclusion:

The consumption of aqueous preparation of K. pinnata may accrue benefits in the management of diabetes by lowering oxidative stress often associated with the disease and improving the availability of cellular magnesium through an increase in the magnesium ATPase pump in the RBC membrane for increased cellular metabolism of glucose through the glycolytic pathway.

SUMMARY

We noted weight loss and reduced food consumption in the diabetic rats treated with K. pinnata preparation

Serum glucose levels were reduced in diabetic rats treated with K. pinnata preparation

Serum catalase activity was significantly (P < 0.05) increased in diabetic rats treated with K. pinnata preparation

We also noted a significant (P < 0.05) increase in Mg²⁺ ATPase activity in the RBC membranes of diabetic rats treated with K. pinnata preparation

Overall, the consumption of aqueous preparation of K. pinnata lowered oxidative stress often associated with diabetes and improved availability of cellular magnesium through an increase in magnesium ATPase pump in the RBC membrane.

Quasi-Steady-State Analysis based on Structural Modules and Timed Petri Net Predict System's Dynamics: The Life Cycle of the Insulin Receptor

The insulin-dependent activation and recycling of the insulin receptor play an essential role in the regulation of the energy metabolism, leading to a special interest for pharmaceutical applications. Thus, the recycling of the insulin receptor has been intensively investigated, experimentally as well as theoretically. We developed a time-resolved, discrete model to describe stochastic dynamics and study the approximation of non-linear dynamics in the context of timed Petri nets. Additionally, using a graph-theoretical approach, we analyzed the structure of the regulatory system and demonstrated the close interrelation of structural network properties with the kinetic behavior. The transition invariants decomposed the model into overlapping subnetworks of various sizes, which represent basic functional modules. Moreover, we computed the quasi-steady states of these subnetworks and demonstrated that they are fundamental to understand the dynamic behavior of the system. The Petri net approach confirms the experimental results of insulin-stimulated degradation of the insulin receptor, which represents a common feature of insulin-resistant, hyperinsulinaemic states.

The forgotten role of glucose effectiveness in the regulation of glucose tolerance

Glucose effectiveness (SG) is the ability of glucose per se to stimulate its own uptake and to suppress its own production under basal/constant insulin concentrations. In an individual, glucose tolerance is a function of insulin secretion, insulin action and SG. Under conditions of declining insulin secretion and action (e.g. type 2 diabetes), the degree of SG assumes increasing significance in determining the level of glucose tolerance both in fasted and postprandial states. Although the importance of SG has been recognized for years, mechanisms that contribute to SG are poorly understood. Research data on modulation of SG and its impact in glucose intolerance is limited. In this review, we will focus on the role of SG in the regulation of glucose tolerance, its evaluation, and potential advantages of therapies that can enhance glucose-induced stimulation of glucose uptake and suppression of its own production in conditions of impaired insulin secretion and action.

Pathogenesis of selective insulin resistance in isolated hepatocytes

The development of insulin resistance (IR) in the liver is a key pathophysiologic event in the development of type 2 diabetes. Although insulin loses its ability to suppress glucose production, it largely retains its capacity to drive lipogenesis. This selective IR results in the characteristic hyperglycemia and dyslipidemia of type 2 diabetes. The delineation of two branched pathways of insulin receptor (InsR) signaling to glucose versus triglyceride production, one through FoxO and the other through SREBP-1c, provides a mechanism to account for this pathophysiological abnormality. We tested the complementary hypothesis that selective IR arises due to different intrinsic sensitivities of glucose production versus de novo lipogenesis to insulin as a result of cell-autonomous down-regulation of InsR number in response to chronic hyperinsulinemia. We demonstrate in mouse primary hepatocytes that chronic hyperinsulinemia abrogates insulin's inhibition of glucose production, but not its stimulation of de novo lipogenesis. Using a competitive inhibitor of InsR, we show that there is a 4-fold difference between levels of InsR inhibition required to cause resistance of glucose production versus lipogenesis to the actions of insulin. Our data support a parsimonious model in which differential InsR activation underlies the selective IR of glucose production relative to lipogenesis, but both processes require signaling through Akt1/2.

Surrogate measures of insulin sensitivity vs the hyperinsulinaemic-euglycaemic clamp: a meta-analysis

AIMS/HYPOTHESIS

We aimed to identify which surrogate index of insulin sensitivity has the strongest correlation with the reference measurement, the hyperinsulinaemic-euglycaemic clamp (HEC), to determine which surrogate measure should be recommended for use in large-scale studies.

METHODS

A literature search (1979-2012) was conducted to retrieve all articles reporting bivariate correlations between the HEC and surrogate measures of insulin sensitivity (in fasting samples or during the OGTT). We performed a random effects meta-analysis for each surrogate measure to integrate the correlation coefficients of the different studies.

RESULTS

The OGTT-based surrogate measures with the strongest pooled correlations (r) to the HEC were the Stumvoll metabolic clearance rate (Stumvoll MCR; r = 0.70 [95% CI 0.61, 0.77], n = 5), oral glucose insulin sensitivity (OGIS; r = 0.70 [0.57, 0.80], n = 6), the Matsuda index (r = 0.67 [0.61, 0.73], n = 19), the Stumvoll insulin sensitivity index (Stumvoll ISI; r = 0.67 [0.60, 0.72], n = 8) and the Gutt index (r = 0.65 [0.60, 0.69], n = 6). The fasting surrogate indices that correlated most strongly with the HEC and had narrow 95% CIs were the revised QUICKI (r = 0.68 [0.58, 0.77], n = 7), the QUICKI (r = 0.61 [0.55, 0.65], n = 35), the log HOMA-IR (r = -0.60 [-0.66, -0.53], n = 22) and the computer generated HOMA of insulin sensitivity (HOMA-%S; r = 0.57 [0.46, 0.67], n = 5).

CONCLUSIONS/INTERPRETATION

The revised QUICKI fasting surrogate measure appears to be as good as the OGTT-based Stumvoll MCR, OGIS, Matsuda, Stumvoll ISI and Gutt indices for estimating insulin sensitivity. It can therefore be recommended as the most appropriate index for use in large-scale clinical studies.

Synthesis and structure-activity relationship of non-phosphorus-based fructose-1,6-bisphosphatase inhibitors: 2,5-Diphenyl-1,3,4-oxadiazoles

With the aim of discovering a novel class of non-phosphorus-based fructose-1,6-bisphosphatase (FBPase) inhibitors, a series of 2,5-diphenyl-1,3,4-oxadiazoles were synthesized based on the hit compound (1) resulting from a high-throughput screening (HTS). Structure-activity relationship (SAR) studies led to the identification of several compounds with comparable inhibitory activities to AMP, the natural allosteric inhibitor of FBPase. Notably, compound 22 and 27b, bearing a terminal carboxyl or 1H-tetrazole, demonstrated remarkable inhibition to gluconeogenesis (GNG). In addition, both inhibition and binding mode to the enzyme were investigated by enzymatic kinetics and in silico experiments for representative compounds 16 and 22.

Serum ionized magnesium in diabetic older persons

OBJECTIVE

Several alterations of magnesium metabolism have been associated with type 2 diabetes pathophysiology, a condition particularly frequent in older persons. We aimed to evaluate serum total (Mg-tot) and serum ionized magnesium (Mg-ion) in older persons with type 2 diabetes in order to explore clinically applicable methods for the detection of magnesium deficit.

MATERIAL/METHODS

Mg-tot and Mg-ion were measured in 105 fasting subjects with type 2 diabetes (mean age: 71.1±0.8 years; M/F: 45/60) and in 100 age-matched non-diabetic control persons (mean age: 72.2±0.8 years; M/F: 42/58).

RESULTS

Mg-ion concentrations were significantly lower in diabetic persons compared with controls (0.49±0.05 mmol/L vs. 0.55±0.05 mmol/L; p<0.001). Mg-tot was also slightly but significantly lower in diabetic patients (0.82±0.007 mmol/L vs. 0.84±0.006 mmol/L; p<0.05). There was an almost complete overlap in the values of Mg-tot in older diabetic patients and controls; conversely, 44.8% of diabetic patients had Mg-ion values below 0.47 mmol/L, while none of the controls did. After adjustment for age, sex, BMI, and triglycerides, Mg-tot was significantly associated with FBG in all the participants (p<0.05) and Mg-ion was significantly associated with FBG in all the participants (p<0.01) and with HbA1c in diabetic participants (p<0.001).

CONCLUSIONS

Alterations of magnesium serum concentrations are common in type 2 diabetic older adults; Mg-ion evaluation may help to identify subclinical magnesium depletion (i.e. in patients with normal Mg-tot); the close independent associations of Mg-tot and Mg-ion with FBG and with HbA1c reinforce the possible link between magnesium homeostasis and altered glucose metabolism.

Improved glucose metabolism in vitro and in vivo by an allosteric monoclonal antibody that increases insulin receptor binding affinity

Previously we reported studies of XMetA, an agonist antibody to the insulin receptor (INSR). We have now utilized phage display to identify XMetS, a novel monoclonal antibody to the INSR. Biophysical studies demonstrated that XMetS bound to the human and mouse INSR with picomolar affinity. Unlike monoclonal antibody XMetA, XMetS alone had little or no agonist effect on the INSR. However, XMetS was a strong positive allosteric modulator of the INSR that increased the binding affinity for insulin nearly 20-fold. XMetS potentiated insulin-stimulated INSR signaling ∼15-fold or greater including; autophosphorylation of the INSR, phosphorylation of Akt, a major enzyme in the metabolic pathway, and phosphorylation of Erk, a major enzyme in the growth pathway. The enhanced signaling effects of XMetS were more pronounced with Akt than with Erk. In cultured cells, XMetS also enhanced insulin-stimulated glucose transport. In contrast to its effects on the INSR, XMetS did not potentiate IGF-1 activation of the IGF-1 receptor. We studied the effect of XMetS treatment in two mouse models of insulin resistance and diabetes. The first was the diet induced obesity mouse, a hyperinsulinemic, insulin resistant animal, and the second was the multi-low dose streptozotocin/high-fat diet mouse, an insulinopenic, insulin resistant animal. In both models, XMetS normalized fasting blood glucose levels and glucose tolerance. In concert with its ability to potentiate insulin action at the INSR, XMetS reduced insulin and C-peptide levels in both mouse models. XMetS improved the response to exogenous insulin without causing hypoglycemia. These data indicate that an allosteric monoclonal antibody can be generated that markedly enhances the binding affinity of insulin to the INSR. These data also suggest that an INSR monoclonal antibody with these characteristics may have the potential to both improve glucose metabolism in insulinopenic type 2 diabetes mellitus and correct compensatory hyperinsulinism in insulin resistant conditions.

Prevalence of cardiometabolic risk factors and metabolic syndrome in obese Kuwaiti adolescents

BACKGROUND

Childhood and adolescent obesity is associated with insulin resistance, abnormal glucose metabolism, hypertension, dyslipidemia, inflammation, liver disease, and compromised vascular function. The purpose of this pilot study was to determine the prevalence of cardiometabolic risk factor abnormalities and metabolic syndrome (MetS) in a sample of obese Kuwaiti adolescents, as prevalence data might be helpful in improving engagement with obesity treatment in future.

METHODS

Eighty obese Kuwaiti adolescents (40 males) with a mean (standard deviation) age of 12.3 years (1.1 years) participated in the present study. All participants had a detailed clinical examination and anthropometry, blood pressure taken, and assessment of fasting levels of C-reactive protein, intracellular adhesion molecule, interleukin-6, fasting blood glucose, insulin, liver function tests (alanine aminotransferase, aspartate aminotransferase, gamma glutamyltransferase), lipid profile (cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides), insulin resistance by homeostasis model assessment, and adiponectin. MetS was assessed using two recognized criteria modified for use in younger individuals.

RESULTS

The cardiometabolic risk factors with highest prevalence of abnormal values included aspartate aminotransferase (88.7% of the sample) and insulin resistance by homeostasis model assessment (67.5%), intracellular adhesion molecule (66.5%), fasting insulin (43.5%), C-reactive protein (42.5%), low-density lipoprotein cholesterol (35.0%), total cholesterol (33.5%), and systolic blood pressure (30.0%). Of all participants, 96.3% (77/80) had at least one impaired cardiometabolic risk factor as well as obesity. Prevalence of MetS was 21.3% according to the International Diabetes Federation definition and 30% using the Third Adult Treatment Panel definition.

CONCLUSION

The present study suggests that obese Kuwaiti adolescents have multiple cardiometabolic risk factor abnormalities. Future studies are needed to test the benefits of intervention in this high-risk group. They also suggest that prevention of obesity in children and adults should be a major public health goal in Kuwait.

The persistent need for insulin sensitizers and other disease-modifying anti-diabetic drugs

Despite significant advances in diabetes care since the introductions of insulin and metformin, disease burden continues to grow. Large gaps in standard of care remain, and no robustly disease-modifying pharmacotherapy exists. Substantial research has been directed towards beta cell preservation and regeneration with no translational success, while little drug discovery or development is aimed at the other major cause of diabetes, namely, insulin resistance. Given the absence of convincing evidence that human beta cells can be regenerated, the diabetes community must broaden its focus to include new therapeutic strategies to limit, and reverse, insulin resistance.

The role of resistance and aerobic exercise training on insulin sensitivity measures in STZ-induced Type 1 diabetic rodents

Individuals with Type 1 Diabetes Mellitus (T1DM) can develop insulin resistance. Regular exercise may improve insulin resistance partially through increased expression of skeletal muscle GLUT4 content.

OBJECTIVE

To examine if different exercise training modalities can alter glucose tolerance through changes in skeletal muscle GLUT4 content in T1DM rats.

METHODS

Fifty rats were divided into 5 groups; control, diabetic control, diabetic resistance exercised, and diabetic high and low intensity treadmill exercised. Diabetes was induced using multiple low dose Streptozotocin (20 mg/kg/day) injections and blood glucose concentrations were maintained moderately hyperglycemic through subcutaneous insulin pellets. Resistance trained rats climbed a ladder with incremental loads, while treadmill trained rats ran on a treadmill at 27 or 15 m/min, respectively, all for 6 weeks.

RESULTS

At weeks 3 and 6, area under the curve measurements following an intravenous glucose tolerance test (AUC-IVGTT) in all diabetic groups were higher than control rats (p<0.05). At 6 weeks, all exercise groups had significantly lower AUC-IVGTT values than diabetic control animals (p<0.05). Treadmill trained rats had the lowest insulin dose requirement of the T1DM rats and the greatest reduction in insulin dosage was evident in high intensity treadmill exercise. Concomitant with improvements in glucose handling improvements, tissue-specific elevations in GLUT4 content were demonstrated in both red and white portions of vastus lateralis and gastrocnemius muscles, suggesting that glucose handling capacity was altered in the skeletal muscle of exercised T1DM rats.

CONCLUSIONS

These results suggest that, while all exercise modalities can improve glucose tolerance, each mode leads to differential improvements in insulin requirements and protein content alterations.

Intentional insulin overdose associated with minimal hypoglycemic symptoms in a non-diabetic patient

ABSTRACT

Non-accidental suicidal insulin overdose is a rare presentation among non-diabetic patients. It seems to be more common among working medical professionals.

OBJECTIVES

To present the case of a young patient, who despite injecting a large dose of rapid-acting insulin presented with only mild symptoms, and to familiarize the medical professionals involved in managing this condition with the recognition, pathophysiology and appropriate therapeutic interventions.

MATERIALS AND METHODS

We report the case of a previously healthy non-diabetic young medical professional who presented with a rapid-acting insulin overdose. On initial assessment the patient was alert and oriented, and glucose measurement was 1.4 mmol/L. The oral glucose gel and intramuscular glucagon failed to raise the glucose. Hypokalaemia, hypomagnesaemia, hypophosphataemia, lactic acidosis and ECG changes completed the presentation.

OUTCOMES

The treatment consisted of dextrose infusion and appropriate electrolytes replacement. An uneventful recovery was made, so 36 hours later the patient was discharged with psychiatric follow-up.

CONCLUSIONS

Insulin overdose should be considered as a differential diagnosis in hypoglycaemic patients when blood glucose fails to correct as expected. Improper management carries a significant risk of hypoglycaemic encephalopathy, which can cause lifelong cerebral changes.

Liver sinusoidal endothelial cells link hyperinsulinemia to hepatic insulin resistance

Insulin signaling in vascular endothelial cells (ECs) is critical to maintain endothelial function but also to mediate insulin action on peripheral glucose disposal. However, gene knockout studies have reached disparate conclusions. Thus, insulin receptor inactivation in ECs does not impair insulin action, whereas inactivation of Irs2 does. Previously, we have shown that endothelial ablation of the three Foxo genes protects mice from atherosclerosis. Interestingly, here we show that mice lacking FoxO isoforms in ECs develop hepatic insulin resistance through excessive generation of nitric oxide (NO) that impairs insulin action in hepatocytes via tyrosine nitration of insulin receptors. Coculture experiments demonstrate that NO produced in liver sinusoidal ECs impairs insulin's ability to suppress glucose production in hepatocytes. The effects of liver sinusoidal ECs can be mimicked by NO donors and can be reversed by NO inhibitors in vivo and ex vivo. The findings are consistent with a model in which excessive, rather than reduced, insulin signaling in ECs predisposes to systemic insulin resistance, prompting a reevaluation of current approaches to insulin sensitization.

Impaired Akt phosphorylation in insulin-resistant human muscle is accompanied by selective and heterogeneous downstream defects

AIMS/HYPOTHESIS

Muscle insulin resistance, one of the earliest defects associated with type 2 diabetes, involves changes in the phosphoinositide 3-kinase/Akt network. The relative contribution of obesity vs insulin resistance to perturbations in this pathway is poorly understood.

METHODS

We used phosphospecific antibodies against targets in the Akt signalling network to study insulin action in muscle from lean, overweight/obese and type 2 diabetic individuals before and during a hyperinsulinaemic-euglycaemic clamp.

RESULTS

Insulin-stimulated Akt phosphorylation at Thr309 and Ser474 was highly correlated with whole-body insulin sensitivity. In contrast, impaired phosphorylation of Akt substrate of 160 kDa (AS160; also known as TBC1D4) was associated with adiposity, but not insulin sensitivity. Neither insulin sensitivity nor obesity was associated with defective insulin-dependent phosphorylation of forkhead box O (FOXO) transcription factor. In view of the resultant basal hyperinsulinaemia, we predicted that this selective response within the Akt pathway might lead to hyperactivation of those processes that were spared. Indeed, the expression of genes targeted by FOXO was downregulated in insulin-resistant individuals.

CONCLUSIONS/INTERPRETATION

These results highlight non-linearity in Akt signalling and suggest that: (1) the pathway from Akt to glucose transport is complex; and (2) pathways, particularly FOXO, that are not insulin-resistant, are likely to be hyperactivated in response to hyperinsulinaemia. This facet of Akt signalling may contribute to multiple features of the metabolic syndrome.

High dietary magnesium intake is associated with low insulin resistance in the Newfoundland population

Background

Magnesium plays a role in glucose and insulin homeostasis and evidence suggests that magnesium intake is associated with insulin resistance (IR). However, data is inconsistent and most studies have not adequately controlled for critical confounding factors.

Objective

The study investigated the association between magnesium intake and IR in normal-weight (NW), overweight (OW) and obese (OB) along with pre- and post- menopausal women.

Design

A total of 2295 subjects (590 men and 1705 women) were recruited from the CODING study. Dietary magnesium intake was computed from the Willett Food Frequency Questionnaire (FFQ). Adiposity (NW, OW and OB) was classified by body fat percentage (%BF) measured by Dual-energy X-ray absorptiometry according to the Bray criteria. Multiple regression analyses were used to test adiposity-specific associations of dietary magnesium intake on insulin resistance adjusting for caloric intake, physical activity, medication use and menopausal status.

Results

Subjects with the highest intakes of dietary magnesium had the lowest levels of circulating insulin, HOMA-IR, and HOMA-ß and subjects with the lowest intake of dietary magnesium had the highest levels of these measures, suggesting a dose effect. Multiple regression analysis revealed a strong inverse association between dietary magnesium with IR. In addition, adiposity and menopausal status were found to be critical factors revealing that the association between dietary magnesium and IR was stronger in OW and OB along with Pre-menopausal women.

Conclusion

The results of this study indicate that higher dietary magnesium intake is strongly associated with the attenuation of insulin resistance and is more beneficial for overweight and obese individuals in the general population and pre-menopausal women. Moreover, the inverse correlation between insulin resistance and dietary magnesium intake is stronger when adjusting for %BF than BMI.

Diversity of Insulin Resistance in Monkeys with Normal Glucose Tolerance

Insulin resistance has been proposed as a critical factor in the development of Type II diabetes, hypertension, dyslipidemia, and coronary artery disease. However, even in normal healthy individuals, a wide range of in vivo insulin action has been found. In the present study we sought to examine this heterogeneity in insulin action in both normal and spontaneously obese nonhuman primates. Maximal insulin responsiveness as measured by a hyperinsulinemic euglycemic clamp, fasting plasma glucose, and insulin levels, beta-cell insulin response to glucose, glucose tolerance, and adiposity were measured in 22 male rhesus monkeys. Results showed that lean animals (body fat < or = 22%) had higher insulin-stimulated glucose uptake (M rate: 14.42+/-1.8 mg/kg FFM/min) compared to obese (8.08+/-0.8). The obese monkeys, with 23-49% body fat, had a wide range of M values (5.32-14.29 mg/kg FFM/min) which showed no relationship to degree of adiposity. In all monkeys, M values had a strong inverse correlation with fasting plasma insulin levels (r=-0.76; p<0.001), but not with fasting glucose or glucose disappearance rate. We conclude that neither degree of obesity above a critical threshold nor range of glucose tolerance is related to insulin resistance; however, in individuals with normal glucose tolerance an early reliable indicator of defective insulin action appears to be fasting insulin concentration. Longitudinal determination of basal insulin levels obtained under standardized conditions so as to minimize extraneous variability is likely to strengthen the ability to predict insulin resistance and possible later development of overt Type II diabetes.

Magnesium and vascular changes in hypertension

Many factors have been implicated in the pathogenesis of hypertension, including changes in intracellular concentrations of calcium, sodium, potassium, and magnesium. There is a significant inverse correlation between serum magnesium and incidence of cardiovascular diseases. Magnesium is a mineral with important functions in the body such as antiarrhythmic effect, actions in vascular tone, contractility, glucose metabolism, and insulin homeostasis. In addition, lower concentrations of magnesium are associated with oxidative stress, proinflammatory state, endothelial dysfunction, platelet aggregation, insulin resistance, and hyperglycemia. The conflicting results of studies evaluating the effects of magnesium supplements on blood pressure and other cardiovascular outcomes indicate that the action of magnesium in the vascular system is present but not yet established. Therefore, this mineral supplementation is not indicated as part of antihypertensive treatment, and further studies are needed to better clarify the role of magnesium in the prevention and treatment of cardiovascular diseases.

Accelerated atherosclerosis in Apoe-/- mice heterozygous for the insulin receptor and the insulin receptor substrate-1

OBJECTIVE

Prediabetic states are associated with accelerated atherosclerosis, but the availability of mouse models to study connections between these diseases has been limited. The aim of this study was to test the selective role of impaired insulin receptor/insulin receptor substrate-1 signaling on atherogenesis.

METHODS AND RESULTS

To address the effects of impaired insulin signaling associated with hyperinsulinemia on atherosclerosis in the absence of obesity and hyperglycemia, we generated insulin receptor (Insr)/insulin receptor substrate-1 (Insr1) double heterozygous apolipoprotein (Apoe)-knockout mice (Insr(+/-)Irs1(+/-)Apoe(-/-)) mice. Insr(+/-)Irs1(+/-)Apoe(-/-) mice fed a Western diet for 15 weeks showed elevated levels of fasting insulin compared to Insr(+/+)Irs1(+/+)Apoe(-/-) mice. There were no significant differences in glucose, triglyceride, HDL, VLDL, cholesterol levels or free fatty acid in the plasma of Insr(+/-)Irs1(+/-)Apoe(-/-) and Insr(+/+)Irs1(+/+)Apoe(-/-) mice. Atherosclerotic lesions were increased in male (brachiocephalic artery) and female (aortic tree) Insr(+/-)Irs1(+/-)Apoe(-/-) compared to Insr(+/+)Irs1(+/+)Apoe(-/-) mice. Bone marrow transfer experiments demonstrated that nonhematopoietic cells have to be Insr(+/-)Irs1(+/-) to accelerate atherosclerosis. Impaired insulin signaling resulted in decreased levels of vascular phospho-eNOS, attenuated endothelium-dependent vasorelaxation and elevated VCAM-1 expression in aortas of Insr(+/-)Irs1(+/-)Apoe(-/-) mice. In addition, phospho-ERK and vascular smooth muscle cell proliferation were significantly elevated in aortas of Insr(+/-)Irs1(+/-)Apoe(-/-) mice.

CONCLUSIONS

These results demonstrate that defective insulin signaling is involved in accelerated atherosclerosis in Insr(+/-)Irs1(+/-)Apoe(-/-) mice by promoting vascular dysfunction and inflammation.

The association of serum C-reactive protein, uric acid and magnesium with insulin resistance in Chinese postmenopausal women with prediabetes or early untreated diabetes

OBJECTIVES

This study aimed to evaluate the association of serum inflammatory markers (C-reactive protein (CRP) and uric acid (UA)), magnesium and other CVD risk factors with insulin resistance (IR) among Chinese postmenopausal women with prediabetes. STUDY DESIGN AND MAIN OUTCOMES MEASURES: This is a cross-sectional analysis of baseline data among 180 postmenopausal women with prediabetes or early untreated diabetes. Major anthropometric and biochemical measures included body mass index (BMI), waist to hip ratio (WHR), fasting and postload glucose and insulin, serum CRP, UA, lipids profile, and magnesium. IR was estimated using fasting glucose and insulin by homeostasis model assessment (HOMA).

RESULTS

Multivariate linear regression analyses indicated that Lg CRP, WHR, serum triglycerides (TGs) and magnesium were the major predictors of HOMA-IR. A multivariate logistic analyses showed that a CRP level above 3.0 mg/l was significantly associated with a 2.8-fold risk of having higher HOMA-IR (>2.52). BMI plays a key role in mediating the relationship of CRP and IR. Elevated serum TG (>1.71 mmol/l), WHR (>0.88), UA (>357 mmol/l) and lower serum magnesium (<0.78 mg/l) were associated with 5.26 (95%CI: 2.52-10.98, P<0.05), 3.02 (95%CI: 1.64-5.55, P<0.05), 1.97 (95%CI: 1.02-3.83, P=0.05) and 0.51 (95%CI: 0.28-0.81) folds risk of higher HOMA-IR, respectively in the unadjusted model. Serum magnesium, but not UA was an independent risk factor of HOMA-IR.

CONCLUSION

The present study in prediabetic or early untreated diabetic Chinese postmenopausal women indicated that IR is significantly associated with increased inflammation (CRP and UA), serum TG, WHR and lower serum magnesium.

Prediction of recovery time from hypoglycemia in patients with insulin overdose

Insulin overdose results in prolonged hypoglycemia. We hypothesized that if a huge amount of insulin is subcutaneously injected, the duration of hypoglycemia depends on the dose of insulin rather than the type of insulin. We conducted a literature review of insulin overdose and 33 cases were included in this study. We assessed the correlation between recovery time from hypoglycemia and insulin dose. As a result, there was a significant correlation between recovery time from hypoglycemia and insulin dose (r=0.88, p<0.0001) and this correlation was expressed as y=0.045x; where y is time (h) and x is insulin dose (U), corresponding to that if 1000 U insulin is injected, hypoglycemia will persist for ~45 h. This equation may be useful to predict the duration of glucose supplementation for treatment of insulin overdose.

Metabolic surgery for the treatment of type 2 diabetes in patients with BMI <35 kg/m2: an integrative review of early studies

Type 2 diabetes mellitus (T2DM) resolution in morbidly obese patients following metabolic surgery suggests the efficacy of T2DM surgery in non-morbidly obese patients (body mass index [BMI] <35 kg/m(2)). This literature review examined research articles in English over the last 30 years (1979-2009) that addressed surgical resolution of T2DM in patients with a mean BMI <35. Weighted and simple means (95% CI) were calculated to analyze study outcomes. Sixteen studies met inclusion criteria; 343 patients underwent one of eight procedures with 6-216 months follow-up. Patients lost a clinically meaningful, not excessive, amount of weight (from BMI 29.4 to 24.2; -5.1), moving from the overweight into the normal weight category. There were 85.3% patients who were off T2DM medications with fasting plasma glucose approaching normal (105.2 mg/dL, -93.3), and normal glycated hemoglobin, 6% (-2.7). In subgroup comparison, BMI reduction and T2DM resolution were greatest following malabsorptive/restrictive procedures, and in the preoperatively mildly obese (30.0-35.0) vs overweight (25.0-25.9) BMI ranges. Complications were few with low operative mortality (0.29%). Novel and/or known mechanisms of T2DM resolution may be engaged by surgery at a BMI threshold <or=30. The majority of low-BMI patients experienced resolution of laboratory and clinical manifestations of T2DM without inappropriate weight loss.

Intracellular magnesium of obese and type 2 diabetes mellitus children

INTRODUCTION

Magnesium is a critical cofactor in numerous enzymatic reactions. Diabetic patients and obese subjects are often reported to have intracellular magnesium ([Mg(2+)](i)) deficiency. We studied the change of [Mg(2+)](i) in obese children and children with type 2 diabetes mellitus (DM2) after educational intervention or treatment.

METHODS

A total of 25 subjects were included: 13 with simple obesity (10 male, 3 female; mean age 16±8 years, intervention period 1.0±0.6 years), 12 with DM2 (8 male, 4 female; mean age 15±3 years, medication period 1.1±0.7 years), and 16 controls (8 male, 8 female; mean age 17±7 years). By using a fluorescent probe, mag-fura-2, we examined the basal and insulin-stimulated [Mg(2+)](i) of platelets in the blood. Plasma leptin, ghrelin, adiponectin, and resistin levels were determined with the use of enzyme-linked immunosorbent assay (ELISA).

RESULTS

Mean basal [Mg(2+)](i) was lower in the obesity (160±65 μmol/L) and DM2 groups (140±30 μmol/L) compared with the control group (330±28 μmol/L). The elevated [Mg(2+)](i) after insulin stimulation was also lower in these two groups (420±140 μmol/L, and 330±70 μmol/L, respectively) compared with the control group (690±270 μmol/L). In the DM2 group, the basal [Mg(2+)](i) was significantly increased after treatment, while in the obesity group, stimulated [Mg(2+)](i) was increased after intervention.

CONCLUSION

Platelet [Mg(2+)](i) increased after intervention in children with obesity or DM2.

Novel liver-specific TORC2 siRNA corrects hyperglycemia in rodent models of type 2 diabetes

The transcription factor TORC2 [transducer of regulated cAMP-responsive element-binding protein (CREB) activity 2] is a major regulator of hepatic gluconeogenesis and is increased in hyperglycemic rodent models. Because chronic hyperglycemia and increased hepatic glucose production, via increased gluconeogenesis, is a key feature of type 2 diabetes, an effective in vivo method to efficiently knock down TORC2 could provide a potential therapy for treating hyperglycemia and type 2 diabetes. To assess this, primary mouse hepatocytes, high-fat diet (HFD)-fed mice, and Zucker diabetic fatty (ZDF) rats were treated with a siRNA against TORC2 (siTORC2), which was delivered via a novel lipid nanoparticle system, or control siRNA (siCON). Compared with siCON, administration of siTORC2 resulted in highly efficient, sustained (1-3 wk) knockdown of TORC2 and its gluconeogenic target genes phosphoenolpyruvate carboxykinase and glucose-6-phophatase in primary mouse hepatocytes and in the livers of HFD-fed mice. In mice, this knockdown was specific to the liver and did not occur in kidney, skeletal muscle, or adipose tissue. In HFD-fed mice, siTORC2 reduced in vivo gluconeogenic capacity, fasting hepatic glucose production, and hyperglycemia, and led to improved hepatic and skeletal muscle insulin sensitivity. siTORC2 treatment also improved systemic hyperglycemia in ZDF rats. In conclusion, these results demonstrate the importance of TORC2 in modulating HGP in vivo and highlight a novel, liver-specific siRNA approach for the potential treatment of hyperglycemia and type 2 diabetes.

Sex steroids deficiency impairs glucose transporter 4 expression and its translocation through defective Akt phosphorylation in target tissues of adult male rat

There is a substantial body of evidence suggesting that altered level of sex steroids in male is associated with insulin resistance and type 2 diabetes mellitus. However, the mechanism of this effect is not apparent. Our recent study indicated that testosterone deprivation decreases insulin receptor expression and glucose oxidation in insulin target tissues. The present study was designed to assess the impact of deficiency of testosterone and estradiol on Akt phosphorylation, glucose transporter expression, and glucose uptake in skeletal muscle, adipose tissue, and liver of adult male rat. Adult male albino rats of Wistar strain were orchidectomized and supplemented with testosterone (100 microg/100 g body weight per day), estradiol (5 microg/100 g body weight per day), and their combination (100 microg testosterone plus 5 microg estradiol per 100 g body weight per day) for 15 days from the 11th day postorchidectomy. On the day after the last treatment, animals were perfused; and blood was collected for the assay of plasma glucose, serum insulin, testosterone, and estradiol. Gastrocnemius muscle, adipose tissue, and liver were dissected out and used for the assay of various parameters such as Akt phosphorylation, glucose transporter (GLUT) 2 and 4 expression, glucose uptake, and glycogenic and glycogenolytic enzymes activity. Castration elevated the blood glucose level, which was accompanied by inhibitory effect on serum insulin, Akt phosphorylation, GLUT4 expression and its plasma membrane population, glucose uptake, glycogen and glycogen synthase activity, and stimulatory effect on GLUT2 expression and glycogen phosphorylase activity in tissues studied. After testosterone and its combination with estradiol supplementation to castrated rats, a normal pattern of all these parameters was restored. Estradiol administration to castrated rats increased the Akt phosphorylation without altering other parameters studied. It is concluded from the present study that sex steroids deficiency-induced defective glucose uptake in skeletal muscle and adipose tissue is mediated through defective Akt phosphorylation and GLUT4 expression in plasma membrane.

Insulin sensitivity and responsiveness in vitro and in vivo

Insulin resistance is evident in several clinical conditions such as obesity, diabetes type II, hypercortisolism. The mechanisms behind this resistance at the level of the target cell can be evaluated with measurements of insulin sensitivity with techniques both in vitro and in vivo. In this review various techniques used to evaluate insulin action are discussed and also some clinical conditions associated with insulin resistance.