The role of glucagon on type 2 diabetes at a glance

GLP-1 receptor agonist-induced diabetic ketoacidosis: A case report

RATIONALE

Glucagon-like peptide-1 is an endogenous incretin that plays an active role in weight loss and hypoglycemia. Dulaglutide is a long-acting glucagon-like peptide-1 receptor agonist (GLP-1RA), which has been approved for the treatment of patients with type 2 diabetes (T2D). GLP-1RAs can increase insulin secretion and inhibit glucagon release, thereby leading to a decrease in blood glucose levels within the body. Specifically, GLP-1RAs control postprandial blood glucose levels by inhibiting hepatic glucose production and delaying gastric emptying. However, attention should be given to gastrointestinal adverse reactions. There are currently a few cases of GLP-1RA causing diabetic ketoacidosis (DKA).

PATIENT CONCERNS

The following report details the case of a 50-year-old Chinese female who has been living with diabetes for 12 years. Initially diagnosed with T2D, she was subsequently identified as a patient with latent autoimmune diabetes in adults (LADA) following treatment. The patient presented severe nausea, vomiting, and fatigue 1 day after injecting dulaglutide 1 time and discontinuing insulin therapy. She was diagnosed with severe DKA in the emergency department.

DIAGNOSES

LADA and DKA.

INTERVENTIONS

Changed from dulaglutide to insulin therapy.

OUTCOMES

After discontinuing dulaglutide and switching to insulin for blood glucose reduction, the patient's DKA was corrected, and blood glucose levels returned to normal.

LESSONS

This case suggests that clinicians should be alert to patients with severe DKA in cases of severe gastrointestinal adverse reactions after the use of GLP-1RAs. In addition, in most countries, GLP-1RAs are administered to patients with T2D, but we should consider the use of GLP-1RAs in patients with type 1 diabetes and LADA.

Small molecules targeting selective PCK1 and PGC-1α lysine acetylation cause anti-diabetic action through increased lactate oxidation

Small molecules selectively inducing peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1α acetylation and inhibiting glucagon-dependent gluconeogenesis causing anti-diabetic effects have been identified. However, how these small molecules selectively suppress the conversion of gluconeogenic metabolites into glucose without interfering with lipogenesis is unknown. Here, we show that a small molecule SR18292 inhibits hepatic glucose production by increasing lactate and glucose oxidation. SR18292 increases phosphoenolpyruvate carboxykinase 1 (PCK1) acetylation, which reverses its gluconeogenic reaction and favors oxaloacetate (OAA) synthesis from phosphoenolpyruvate. PCK1 reverse catalytic reaction induced by SR18292 supplies OAA to tricarboxylic acid (TCA) cycle and is required for increasing glucose and lactate oxidation and suppressing gluconeogenesis. Acetylation mimetic mutant PCK1 K91Q favors anaplerotic reaction and mimics the metabolic effects of SR18292 in hepatocytes. Liver-specific expression of PCK1 K91Q mutant ameliorates hyperglycemia in obese mice. Thus, SR18292 blocks gluconeogenesis by enhancing gluconeogenic substrate oxidation through PCK1 lysine acetylation, supporting the anti-diabetic effects of these small molecules.

Insulin Dynamics and Pathophysiology in Youth-Onset Type 2 Diabetes

Youth-onset type 2 diabetes (T2D) is increasing around the globe. The mounting disease burden of youth-onset T2D portends substantial consequences for the health outcomes of young people and for health care systems. The pathophysiology of this condition is characterized by insulin resistance and initial insulin hypersecretion ± an inherent insulin secretory defect, with progressive loss of stimulated insulin secretion leading to pancreatic β-cell failure. Research studies focusing on youth-onset T2D have illuminated key differences for youth- vs adult-onset T2D, with youth having more profound insulin resistance and quicker progression to loss of sufficient insulin secretion to maintain euglycemia. There is a need for therapies that are targeted to improve both insulin resistance and, importantly, maintain sufficient insulin secretory function over the lifespan in youth-onset T2D.

Spatially resolved distribution of pancreatic hormones proteoforms by MALDI-imaging mass spectrometry

Zinc plays a crucial role both in the immune system and endocrine processes. Zinc restriction in the diet has been shown to lead to degeneration of the endocrine pancreas, resulting in hormonal imbalance within the β-cells. Proteostasismay vary depending on the stage of a pathophysiological process, which underscores the need for tools aimed at directly analyzing biological status. Among proteomics methods, MALDI-ToF-MS can serve as a rapid peptidomics tool for analyzing extracts or by histological imaging. Here we report the optimization of MALDI imaging mass spectrometry analysis of histological thin sections from mouse pancreas. This optimization enables the identification of the major islet peptide hormones as well as the major accumulated precursors and/or proteolytic products of peptide hormones. Cross-validation of the identified peptide hormones was performed by LC-ESI-MS from pancreatic islet extracts. Mice subjected to a zinc-restricted diet exhibited a relatively lower amount of peptide intermediates compared to the control group. These findings provide evidence for a complex modulation of proteostasis by micronutrients imbalance, a phenomenon directly accessed by MALDI-MSI.

Correlation between islet α cell function and peripheral neuropathy in patients with type 2 diabetes mellitus

BACKGROUND

This study explored the correlation between pancreatic islet α cell function, as reflected by the plasma glucagon levels, and Diabetic Peripheral Neuropathy (DPN) in patients with Type 2 Diabetes Mellitus (T2DM).

METHODS

A total of 358 patients with T2DM were retrospectively enrolled in this study and divided into the Non-DPN (NDPN) group (n = 220) and the DPN group (n = 138). All patients underwent an oral glucose tolerance test to detect levels of blood glucose, insulin and glucagon, and the Area Under the Curve (AUC) for Glucagon (AUCglu) was used to estimate the overall glucagon level. The Peripheral Nerve Conduction Velocity (PNCV), Amplitude (PNCA) and Latency (PNCL) were obtained with electromyography, and their Z scores were calculated.

RESULTS

There were significant differences regarding the age, disease duration, serum levels of alanine aminotransferase, aspartate aminotransferase, urea nitrogen, high-density lipoprotein, and 2h-C peptide between these two groups (p < 0.05). The NDPN group had higher glucagon levels at 30, 60 and 120 min and AUCglu (p < 0.05). The Z-scores of PNCV and PNCA showed an increasing trend (p < 0.05), while the Z-score of PNCL showed a decreasing trend (p < 0.05). The glucagon levels were positively correlated with PNCV and PNCA, but negatively correlated with PNCL, with Gluca30min having the strongest correlation (p < 0.05). Gluca30min was independently related to PNCV, PNCL, PNCA and DPN, respectively (p < 0.05). The function of pancreatic α islet cells, as reflected by the plasma glucagon level, is closely related to the occurrence of DPN in T2DM patients.

CONCLUSION

Gluca30min may be a potentially valuable independent predictor for the occurrence of DPN.

Underlying Mechanisms behind the Brain-Gut-Liver Axis and Metabolic-Associated Fatty Liver Disease (MAFLD): An Update

Metabolic-associated fatty liver disease (MAFLD) includes several metabolic dysfunctions caused by dysregulation in the brain-gut-liver axis and, consequently, increases cardiovascular risks and fatty liver dysfunction. In MAFLD, type 2 diabetes mellitus, obesity, and metabolic syndrome are frequently present; these conditions are related to liver lipogenesis and systemic inflammation. This study aimed to review the connection between the brain-gut-liver axis and MAFLD. The inflammatory process, cellular alterations in hepatocytes and stellate cells, hypercaloric diet, and sedentarism aggravate the prognosis of patients with MAFLD. Thus, to understand the modulation of the physiopathology of MAFLD, it is necessary to include the organokines involved in this process (adipokines, myokines, osteokines, and hepatokines) and their clinical relevance to project future perspectives of this condition and bring to light new possibilities in therapeutic approaches. Adipokines are responsible for the activation of distinct cellular signaling in different tissues, such as insulin and pro-inflammatory cytokines, which is important for balancing substances to avoid MAFLD and its progression. Myokines improve the quantity and quality of adipose tissues, contributing to avoiding the development of MAFLD. Finally, hepatokines are decisive in improving or not improving the progression of this disease through the regulation of pro-inflammatory and anti-inflammatory organokines.

Predicting cell-type specific disease genes of diabetes with the biological network

Type 2 diabetes (T2D) is a chronic condition that can lead to significant harm, such as heart disease, kidney disease, nerve damage, and blindness. Although T2D-related genes have been identified through Genome-wide association studies (GWAS) and various computational methods, the biological mechanism of T2D at the cell type level remains unclear. Exploring cell type-specific genes related to T2D is essential to understand the cellular mechanisms underlying the disease. To address this issue, we introduce DiGCellNet (predicting Disease Genes with Cell type specificity based on biological Networks), a model that integrates graph convolutional network (GCN) and multi-task learning (MTL) to predict T2D-associated cell type-specific genes based on the biological network. Our work represents the first attempt to predict cell type-specific disease genes using GCN and MTL. We evaluate our approach by predicting genes specific to four cell types and demonstrate that the proposed DiGCellNet outperforms other models that combine node embeddings with traditional machine learning algorithms. Moreover, DiGCellNet successfully identifies CALM1 as a gene specific to beta cell type in T2D cases, and this association is confirmed using an independent dataset. The code is available at https://github.com/23AIBox/23AIBox-DiGCellNet.

An integrative view on glucagon function and putative role in the progression of pancreatic neuroendocrine tumours (pNETs) and hepatocellular carcinomas (HCC)

Cancer metabolism research area evolved greatly, however, is still unknown the impact of systemic metabolism control and diet on cancer. It makes sense that systemic regulators of metabolism can act directly on cancer cells and activate signalling, prompting metabolic remodelling needed to sustain cancer cell survival, tumour growth and disease progression. In the present review, we describe the main glucagon functions in the control of glycaemia and of metabolic pathways overall. Furthermore, an integrative view on how glucagon and related signalling pathways can contribute for pancreatic neuroendocrine tumours (pNETs) and hepatocellular carcinomas (HCC) progression, since pancreas and liver are the major organs exposed to higher levels of glucagon, pancreas as a producer and liver as a scavenger. The main objective is to bring to discussion some glucagon-dependent mechanisms by presenting an integrative view on microenvironmental and systemic aspects in pNETs and HCC biology.

Association of Glucagon to Insulin Ratio and Metabolic Syndrome in Patients with Type 2 Diabetes

There is a growing interest in the role of glucagon in type 2 diabetes mellitus (T2DM). Glucagon and insulin regulate glucose and lipid metabolism. Metabolic syndrome is an important risk factor for cardiovascular disease in patients with T2DM. We investigated the association between glucagon to insulin ratio and metabolic syndrome in patients with T2DM. This is a cross-sectional study involving 317 people with type 2 diabetes. Glucagon and insulin levels were measured in a fasted state and 30 min after ingesting a standard mixed meal. The Criteria of the International Diabetes Federation defined metabolic syndrome. Two hundred nineteen (69%) of the subjects had metabolic syndrome. The fasting glucagon to insulin ratio was significantly lower in patients with metabolic syndrome (14.0 ± 9.7 vs. 17.3 ± 10.3, p < 0.05). The fasting glucagon to insulin ratio was significantly lowered as the number of metabolic syndrome components increased. In hierarchical logistic regression analysis, the fasting glucagon to insulin ratio significantly contributed to metabolic syndrome even after adjusting for other covariates. The fasting glucagon to insulin ratio is inversely associated with metabolic syndrome in patients with type 2 diabetes. This suggests that glucagon-targeted therapeutics may reduce cardiovascular risk by improving metabolic syndrome.

An insulin-regulated arrestin domain protein controls hepatic glucagon action

Glucagon signaling is essential for maintaining normoglycemia in mammals. The arrestin fold superfamily of proteins controls the trafficking, turnover, and signaling of transmembrane receptors as well as other intracellular signaling functions. Further investigation is needed to understand the in vivo functions of the arrestin domain-containing 4 (ARRDC4) protein family member and whether it is involved in mammalian glucose metabolism. Here, we show that mice with a global deletion of the ARRDC4 protein have impaired glucagon responses and gluconeogenesis at a systemic and molecular level. Mice lacking ARRDC4 exhibited lower glucose levels after fasting and could not suppress gluconeogenesis at the refed state. We also show that ARRDC4 coimmunoprecipitates with the glucagon receptor, and ARRDC4 expression is suppressed by insulin. These results define ARRDC4 as a critical regulator of glucagon signaling and glucose homeostasis and reveal a novel intersection of insulin and glucagon pathways in the liver.

Glucoregulatory disruption in male mice offspring induced by maternal transfer of endocrine disrupting brominated flame retardants in DE-71

Introduction

Polybrominated diphenyl ethers (PBDEs) are commercially used flame retardants that bioaccumulate in human tissues, including breast milk. PBDEs produce endocrine and metabolic disruption in experimental animals and have been associated with diabetes and metabolic syndrome (MetS) in humans, however, their sex-specific diabetogenic effects are not completely understood. Our past works show glucolipid dysregulation resulting from perinatal exposure to the commercial penta-mixture of PBDEs, DE-71, in C57BL/6 female mice.

Methods

As a comparison, in the current study, the effects of DE-71 on glucose homeostasis in male offspring was examined. C57BL/6N dams were exposed to DE-71 at 0.1 mg/kg/d (L-DE-71), 0.4 mg/kg/d (H-DE-71), or received corn oil vehicle (VEH/CON) for a total of 10 wks, including gestation and lactation and their male offspring were examined in adulthood.

Results

Compared to VEH/CON, DE-71 exposure produced hypoglycemia after a 11 h fast (H-DE-71). An increased fast duration from 9 to 11 h resulted in lower blood glucose in both DE-71 exposure groups. In vivo glucose challenge showed marked glucose intolerance (H-DE-71) and incomplete clearance (L- and H-DE-71). Moreover, L-DE-71-exposed mice showed altered glucose responses to exogenous insulin, including incomplete glucose clearance and/or utilization. In addition, L-DE-71 produced elevated levels of plasma glucagon and the incretin, active glucagon-like peptide-1 (7-36) amide (GLP-1) but no changes were detected in insulin. These alterations, which represent criteria used clinically to diagnose diabetes in humans, were accompanied with reduced hepatic glutamate dehydrogenase enzymatic activity, elevated adrenal epinephrine and decreased thermogenic brown adipose tissue (BAT) mass, indicating involvement of several organ system targets of PBDEs. Liver levels of several endocannabinoid species were not altered.

Discussion

Our findings demonstrate that chronic, low-level exposure to PBDEs in dams can dysregulate glucose homeostasis and glucoregulatory hormones in their male offspring. Previous findings using female siblings show altered glucose homeostasis that aligned with a contrasting diabetogenic phenotype, while their mothers displayed more subtle glucoregulatory alterations, suggesting that developing organisms are more susceptible to DE-71. We summarize the results of the current work, generated in males, considering previous findings in females. Collectively, these findings offer a comprehensive account of differential effects of environmentally relevant PBDEs on glucose homeostasis and glucoregulatory endocrine dysregulation of developmentally exposed male and female mice.

AMPK inhibits liver gluconeogenesis: fact or fiction?

Is there a role for AMPK in the control of hepatic gluconeogenesis and could targeting AMPK in liver be a viable strategy for treating type 2 diabetes? These are frequently asked questions this review tries to answer. After describing properties of AMPK and different small-molecule AMPK activators, we briefly review the various mechanisms for controlling hepatic glucose production, mainly via gluconeogenesis. The different experimental and genetic models that have been used to draw conclusions about the role of AMPK in the control of liver gluconeogenesis are critically discussed. The effects of several anti-diabetic drugs, particularly metformin, on hepatic gluconeogenesis are also considered. We conclude that the main effect of AMPK activation pertinent to the control of hepatic gluconeogenesis is to antagonize glucagon signalling in the short-term and, in the long-term, to improve insulin sensitivity by reducing hepatic lipid content.

A glucose-insulin-glucagon coupled model of the isoglycemic intravenous glucose infusion experiment

Type 2 diabetes (T2D) is a pathophysiology that is characterized by insulin resistance, beta- and alpha-cell dysfunction. Mathematical models of various glucose challenge experiments have been developed to quantify the contribution of insulin and beta-cell dysfunction to the pathophysiology of T2D. There is a need for effective extended models that also capture the impact of alpha-cell dysregulation on T2D. In this paper a delay differential equation-based model is developed to describe the coupled glucose-insulin-glucagon dynamics in the isoglycemic intravenous glucose infusion (IIGI) experiment. As the glucose profile in IIGI is tailored to match that of a corresponding oral glucose tolerance test (OGTT), it provides a perfect method for studying hormone responses that are in the normal physiological domain and without the confounding effect of incretins and other gut mediated factors. The model was fit to IIGI data from individuals with and without T2D. Parameters related to glucagon action, suppression, and secretion as well as measures of insulin sensitivity, and glucose stimulated response were determined simultaneously. Significant impairment in glucose dependent glucagon suppression was observed in patients with T2D (duration of T2D: 8 (6-36) months) relative to weight matched control subjects (CS) without diabetes (k1 (mM)-1: 0.16 ± 0.015 (T2D, n = 7); 0.26 ± 0.047 (CS, n = 7)). Insulin action was significantly lower in patients with T2D (a1 (10 pM min)-1: 0.000084 ± 0.0000075 (T2D); 0.00052 ± 0.00015 (CS)) and the Hill coefficient in the equation for glucose dependent insulin response was found to be significantly different in T2D patients relative to CS (h: 1.4 ± 0.15; 1.9 ± 0.14). Trends in parameters with respect to fasting plasma glucose, HbA1c and 2-h glucose values are also presented. Significantly, a negative linear relationship is observed between the glucagon suppression parameter, k1, and the three markers for diabetes and is thus indicative of the role of glucagon in exacerbating the pathophysiology of diabetes (Spearman Rank Correlation: (n = 12; (-0.79, 0.002), (-0.73,.007), (-0.86,.0003)) respectively).

d-Amino Acids and Classical Neurotransmitters in Healthy and Type 2 Diabetes-Affected Human Pancreatic Islets of Langerhans

The pancreatic islets of Langerhans are clusters of cells that function as endocrine units synthesizing and releasing insulin and a range of additional peptide hormones. The structural and chemical characteristics of islets change during type 2 diabetes development. Although a range of metabolites including neurotransmitters has been reported in rodent islets, the involvement of these cell-to-cell signaling molecules within human pancreatic islets in the pathophysiology of type 2 diabetes is not well known, despite studies suggesting that these molecules impact intra- and inter-islet signaling pathways. We characterize the enigmatic cell-to-cell signaling molecules, d-serine (d-Ser) and d-aspartate (d-Asp), along with multiple classical neurotransmitters and related molecules, in healthy versus type 2 diabetes-affected human islets using capillary electrophoresis separations. Significantly reduced d-Ser percentage and gamma-aminobutyric acid (GABA) levels were found in type 2 diabetes-affected islets compared to healthy islets. In addition, the negative correlations of many of the signaling molecules, such as d-Ser percentage (r = −0.35), d-Asp (r = −0.32), serotonin (r = −0.42), and GABA (r = −0.39) levels, with hemoglobin A1c (HbA1c) levels and thus with the progression of type 2 diabetes further demonstrate the disruption in intra- or inter-islet signaling pathways and suggest that these cell-to-cell signaling molecules may be potential therapeutic targets.

Therapeutic RNA-silencing oligonucleotides in metabolic diseases

Recent years have seen unprecedented activity in the development of RNA-silencing oligonucleotide therapeutics for metabolic diseases. Improved oligonucleotide design and optimization of synthetic nucleic acid chemistry, in combination with the development of highly selective and efficient conjugate delivery technology platforms, have established and validated oligonucleotides as a new class of drugs. To date, there are five marketed oligonucleotide therapies, with many more in clinical studies, for both rare and common liver-driven metabolic diseases. Here, we provide an overview of recent developments in the field of oligonucleotide therapeutics in metabolism, review past and current clinical trials, and discuss ongoing challenges and possible future developments.

Intercellular Communication in the Islet of Langerhans in Health and Disease

Blood glucose homeostasis requires proper function of pancreatic islets, which secrete insulin, glucagon, and somatostatin from the β-, α-, and δ-cells, respectively. Each islet cell type is equipped with intrinsic mechanisms for glucose sensing and secretory actions, but these intrinsic mechanisms alone cannot explain the observed secretory profiles from intact islets. Regulation of secretion involves interconnected mechanisms among and between islet cell types. Islet cells lose their normal functional signatures and secretory behaviors upon dispersal as compared to intact islets and in vivo. In dispersed islet cells, the glucose response of insulin secretion is attenuated from that seen from whole islets, coordinated oscillations in membrane potential and intracellular Ca2+ activity, as well as the two-phase insulin secretion profile, are missing, and glucagon secretion displays higher basal secretion profile and a reverse glucose-dependent response from that of intact islets. These observations highlight the critical roles of intercellular communication within the pancreatic islet, and how these communication pathways are crucial for proper hormonal and nonhormonal secretion and glucose homeostasis. Further, misregulated secretions of islet secretory products that arise from defective intercellular islet communication are implicated in diabetes. Intercellular communication within the islet environment comprises multiple mechanisms, including electrical synapses from gap junctional coupling, paracrine interactions among neighboring cells, and direct cell-to-cell contacts in the form of juxtacrine signaling. In this article, we describe the various mechanisms that contribute to proper islet function for each islet cell type and how intercellular islet communications are coordinated among the same and different islet cell types. © 2021 American Physiological Society. Compr Physiol 11:2191-2225, 2021.

Increased alpha and beta cell mass during mouse pregnancy is not dependent on transdifferentiation

Maternal pancreatic beta-cell mass (BCM) increases during pregnancy to compensate for relative insulin resistance. If BCM expansion is suboptimal, gestational diabetes mellitus can develop. Alpha-cell mass (ACM) also changes during pregnancy, but there is a lack of information about α-cell plasticity in pregnancy and whether α- to β-cell transdifferentiation can occur. To investigate this, we used a mouse model of gestational glucose intolerance induced by feeding low-protein (LP) diet from conception until weaning and compared pregnant female offspring to control diet-fed animals. Control and LP pancreata were collected for immunohistochemical analysis and serum glucagon levels were measured. In order to lineage trace α- to β-cell conversion, we utilized transgenic mice expressing yellow fluorescent protein behind the proglucagon gene promoter (Gcg-Cre/YFP) and collected pancreata for histology at various gestational timepoints. Alpha-cell proliferation increased significantly at gestational day (GD) 9.5 in control pregnancies resulting in an increased ACM at GD18.5, and this was significantly reduced in LP animals. Despite these changes, serum glucagon was higher in LP mice at GD18.5. Pregnant Gcg-Cre/YFP mice showed no increase in the abundance of insulin+YFP+glucagon- cells (phenotypic β-cells). A second population of insulin+YFP+glucagon+ cells was identified which also did not alter during pregnancy. However, there was an altered anatomical distribution within islets with fewer insulin+YFP+glucagon- cells but more insulin+YFP+glucagon+ cells being present in the islet mantle at GD18.5. These findings demonstrate that dynamic changes in ACM occur during normal pregnancy and were altered in glucose-intolerant pregnancies.

Fasting Glucagon Level in Type 2 Diabetes and Impaired Glucose Tolerance and Its Association With Diabetes-Associated Clinical Parameters: A Study From Karachi, Pakistan

Aim and objective

The study aims to analyze fasting glucagon in patients with type 2 diabetes and impaired glucose tolerance and correlate it with anthropometric and biochemical parameters in a large proportion of Pakistani people with diabetes. 

Methodology

The participants of the study were categorized into three groups based on oral glucose tolerance test, as per American Diabetes Association guidelines. Group A consisted of normal glucose tolerance subjects (n=30), Group B consisted of subjects with impaired glucose tolerance (n=30), and Group C had full-blown subjects with type 2 diabetes (n=30). Biochemical parameters, such as fasting glucagon, fasting plasma and 2-hour glucose, glycated hemoglobin, and lipid profile, and anthropometric parameters, such as body mass index (BMI), waist and hip circumference, waist-to-hip ratio, and systolic and diastolic blood pressure, were measured.

Results

The mean values of fasting glucagon level in Group A, Group B, and Group C were 39.24±4.5, 44.5±8.25, and 49.02±9.15 pg/ml, respectively. Statistically significant difference was not found in fasting glucagon level among these groups (p-value 0.614). Fasting glucagon was positively and independently correlated with 2-hour plasma glucose, systolic blood pressure, diastolic blood pressure, BMI, hip and waist circumference, and hip-to-waist ratio in Group C. In Group B, fasting glucagon was positively correlated with 2-hour plasma glucose, BMI, and hip circumference, while it was not correlated with fasting plasma glucose in both groups. In Group A, fasting glucagon found positively correlated with systolic blood pressure and hip circumference.

Conclusion

Our observation suggests that fasting plasma glucose is not concomitant with glucagon levels; however, glucagon suppression, after glucose intake, was dysregulated in type 2 diabetes and impaired glucose tolerance. Moreover, glucagon is associated with central obesity in type 2 diabetic patients.

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GLP-1 preserves β cell function via improvement on islet insulin signaling in high fat diet feeding mice

BACKGROUND

Numerous studies have shown that Glucagon like peptide-1 (GLP-1) treatment can protect β cell function, but the exact mechanism remains unclear. We hypothesized that GLP-1 may protect β cell function via its action on insulin signaling pathway.

METHODS

Mice were fed with high fat diet (HFD, 20 weeks) in the presence or absence of GLP-1 receptor agonist (exenatide) treatment. The islet structure was demonstrated by HE staining. Immunofluorescence antibodies targeting insulin and glucagon were used to illustrate α and β cell distribution. The insulin and glucagon abundance was measured by ELISA using pancreatic homogenates. The molecules involved in insulin signaling pathway (IRc, IRS1, IRS2, mTOR) in islet were examined with immunohistochemistry and immunoblotting. The effect of IRS1 silencing on mTOR and apoptosis were examined on NIT cells(β cell line)with immunoblotting and flow cytometry.

RESULTS

HE and immunofluorescence staining demonstrated that the normal structure of islet was deformed in HFD mice but preserved by exenatide. Insulin and glucagon contents were increased in islet and blood stream of HFD mice (HFD vs. Control, p<0.05) but resumed by exenatide. Meanwhile the expressions of IRc, IRS-1, mTOR from insulin signaling pathway and β cell apoptosis in the pancreas were significantly reduced (p<0.05) by HFD but reversed by exenatide.

CONCLUSION

Exenatide improved insulin signaling pathway that was suppressed by HFD in mice islet. Our results reveal a novel mechanism of the protective effects of GLP-1 on β cell function.

What Is an L-Cell and How Do We Study the Secretory Mechanisms of the L-Cell?

Synthetic glucagon-like peptide-1 (GLP-1) analogues are effective anti-obesity and anti-diabetes drugs. The beneficial actions of GLP-1 go far beyond insulin secretion and appetite, and include cardiovascular benefits and possibly also beneficial effects in neurodegenerative diseases. Considerable reserves of GLP-1 are stored in intestinal endocrine cells that potentially might be mobilized by pharmacological means to improve the body's metabolic state. In recognition of this, the interest in understanding basic L-cell physiology and the mechanisms controlling GLP-1 secretion, has increased considerably. With a view to home in on what an L-cell is, we here present an overview of available data on L-cell development, L-cell peptide expression profiles, peptide production and secretory patterns of L-cells from different parts of the gut. We conclude that L-cells differ markedly depending on their anatomical location, and that the traditional definition of L-cells as a homogeneous population of cells that only produce GLP-1, GLP-2, glicentin and oxyntomodulin is no longer tenable. We suggest to sub-classify L-cells based on their differential peptide contents as well as their differential expression of nutrient sensors, which ultimately determine the secretory responses to different stimuli. A second purpose of this review is to describe and discuss the most frequently used experimental models for functional L-cell studies, highlighting their benefits and limitations. We conclude that no experimental model is perfect and that a comprehensive understanding must be built on results from a combination of models.

Repositioning the Alpha Cell in Postprandial Metabolism

Glucose homeostasis is maintained in large part due to the actions of the pancreatic islet hormones insulin and glucagon, secreted from β- and α-cells, respectively. The historical narrative positions these hormones in opposition, with insulin primarily responsible for glucose-lowering and glucagon-driving elevations in glucose. Recent progress in this area has revealed a more complex relationship between insulin and glucagon, highlighted by data demonstrating that α-cell input is essential for β-cell function and glucose homeostasis. Moreover, the common perception that glucagon levels decrease following a nutrient challenge is largely shaped by the inhibitory effects of glucose administration alone on the α-cell. Largely overlooked is that a mixed nutrient challenge, which is more representative of typical human feeding, actually stimulates glucagon secretion. Thus, postprandial metabolism is associated with elevations, not decreases, in α-cell activity. This review discusses the recent advances in our understanding of how α-cells regulate metabolism, with a particular focus on the postprandial state. We highlight α- to β-cell communication, a term that describes how α-cell input into β-cells is a critical axis that regulates insulin secretion and glucose homeostasis. Finally, we discuss the open questions that have the potential to advance this field and continue to evolve our understanding of the role that α-cells play in postprandial metabolism.

Direct Effects of D-Chiro-Inositol on Insulin Signaling and Glucagon Secretion of Pancreatic Alpha Cells

The insulin resistance state of pancreatic α-cells seems to be related to glucagon hypersecretion in type 2 diabetes. Treatment that can improve the insulin sensitivity of α-cells could control glucagon levels in patients with diabetes mellitus. The aim of this study was to investigate the preventive role of D-chiro-inositol (DCI), which has insulin receptor-sensitizer effects on insulin signaling pathways and glucagon secretion in pancreatic α-TC1 clone 6 cells. Cells were chronically treated with palmitate to induce insulin resistance in the presence/absence of DCI. DCI treatment improved the insulin signaling pathway and restored insulin-mediated glucagon suppression in α-TC1-6 cells exposed to palmitate. These results indicate that DCI treatment prevents the insulin resistance of α-TC1-6 cells chronically exposed to palmitate. Our data provide evidence that DCI could be useful to improve the insulin sensitivity of pancreatic α-cells in diabetes treatment.

Aberration of the modulatory functions of intronic microRNA hsa-miR-933 on its host gene ATF2 results in type II diabetes mellitus and neurodegenerative disease development

BACKGROUND

MicroRNAs are ~ 22-nucleotide-long biological modifiers that act as the post-transcriptional modulator of gene expression. Some of them are identified to be embedded within the introns of protein-coding genes, these miRNAs are called the intronic miRNAs. Previous findings state that these intronic miRNAs are co-expressed with their host genes. This co-expression is necessary to maintain the robustness of the biological system. Till to date, only a few experiments are performed discretely to elucidate the functional relationship between few co-expressed intronic miRNAs and their associated host genes.

RESULTS

In this study, we have interpreted the underlying modulatory mechanisms of intronic miRNA hsa-miR-933 on its target host gene ATF2 and found that aberration can lead to several disease conditions. A protein-protein interaction network-based approach was adopted, and functional enrichment analysis was performed to elucidate the significantly over-represented biological functions and pathways of the common targets. Our approach delineated that hsa-miR-933 might control the hyperglycemic condition and hyperinsulinism by regulating ATF2 target genes MAP4K4, PRKCE, PEA15, BDNF, PRKACB, and GNAS which can otherwise lead to the development of type II diabetes mellitus. Moreover, we showed that hsa-miR-933 can regulate a target of ATF2, brain-derived neurotrophic factor (BDNF), to modulate the optimal expression of ATF2 in neuron cells to render neuroprotection for the inhibition of neurodegenerative diseases.

CONCLUSIONS

Our in silico model provides interesting resources for experimentations in a model organism or cell line for further validation. These findings may extend the common perception of gene expression analysis with new regulatory functionality.

LC-Q-TOF-MS Characterization of Polyphenols from White Bayberry Fruit and Its Antidiabetic Effect in KK-Ay Mice

The present study is to investigate the polyphenolic composition and in vivo antidiabetic effect of white-fleshed Chinese bayberry cultivar "Shui Jing". By liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS), 38 polyphenols were identified in the Shui Jing fruit extract (SJE), where proanthocyanidins (PAs), including epigallocatechin gallate (EGCG), as well as flavonols, including myricitrin and quercetrin, were the predominant ingredients. After a 5-week experiment, the SJE (200 mg/kg bodyweight) significantly reduced fasting blood glucose, elevated glucose tolerance, and insulin sensitivity in diabetic KK-A^y mice. It markedly attenuated bodyweight gain and decreased glycolipid metabolism-related markers including insulin, leptin, glucagon, triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c) and alanine aminotransferase (ALT) levels in mice. Liver weight and hepatic lipid accumulation were also significantly reduced by the SJE. Gene expressions of insulin 1 (INS1) and glycogen synthase kinase 3 β (GSK3b) were markedly inhibited while the hepatic phosphorylation of AMPKα was significantly increased in the liver of SJE-treated mice, indicating that the SJE may exert an antidiabetic effect through an AMPK-dependent pathway. In conclusion, white bayberry rich in PAs and flavonols may have great potential in the regulation of diabetes mellitus.

Dynamic Change of β to α Ratio in Islets of Chinese People With Prediabetes and Type 2 Diabetes Mellitus

OBJECTIVES

The present study aimed to investigate the dynamic change of α cells and β cells, and their ratios in prediabetes and type 2 diabetes in the Chinese population.

METHODS

Pancreata from 27 nondiabetic (ND), 8 prediabetic (PreD), and 19 type 2 diabetic (T2D) organ donors were subjected to immunofluorescence staining with insulin and glucagon.

RESULTS

The β to α ratio in islets (β/α) in PreD was significantly higher than that in ND, resulting from an increase of β cells and a decrease of α cells per islet, but that in T2D was significantly lower than that in ND, resulting from a decrease of β cells and an increase of α cells per islet. The β-cell percentage and β/α ratio positively correlated and α-cell percentage negatively correlated with HbA1c (glycated hemoglobin) in ND and PreD, but these correlations disappeared when T2D subjects were included.

CONCLUSIONS

The islet β to α ratio increased in PreD individuals because of a relative α-cell loss and β-cell compensation and decreased after T2D onset because of both β-cell loss and α-cell reexpansion.

Combined effect of interventions with pure or enriched mixtures of (poly)phenols and anti-diabetic medication in type 2 diabetes management: a meta-analysis of randomized controlled human trials

PURPOSE

(Poly)phenols have been reported to confer protective effects against type 2 diabetes but the precise association remains elusive. This meta-analysis aimed to assess the effects of (poly)phenol intake on well-established biomarkers in people with type 2 diabetes or at risk of developing diabetes.

METHODS

A systematic search was conducted using the following selection criteria: (1) human randomized controlled trials involving individuals with prediabetes and type 2 diabetes; (2) one or more of the following biomarkers: glucose, glycated haemoglobin (HbA1c), insulin, pro-insulin, homeostatic model assessment of insulin resistance (HOMA-IR), islet amyloid polypeptide (IAPP)/amylin, pro-IAPP/pro-amylin, glucagon, C-peptide; (3) chronic intervention with pure or enriched mixtures of (poly)phenols. From 488 references, 88 were assessed for eligibility; data were extracted from 27 studies and 20 were used for meta-analysis. The groups included in the meta-analysis were: (poly)phenol mixtures, isoflavones, flavanols, anthocyanins and resveratrol.

RESULTS

Estimated intervention/control mean differences evidenced that, overall, the consumption of (poly)phenols contributed to reduced fasting glucose levels (- 3.32 mg/dL; 95% CI - 5.86, - 0.77; P = 0.011). Hb1Ac was only slightly reduced (- 0.24%; 95% CI - 0.43, - 0.044; P = 0.016) whereas the levels of insulin and HOMA-IR were not altered. Subgroup comparative analyses indicated a stronger effect on blood glucose in individuals with diabetes (- 5.86 mg/dL, 95% CI - 11.34, - 0.39; P = 0.036) and this effect was even stronger in individuals taking anti-diabetic medication (- 10.17 mg/dL, 95% CI - 16.59, - 3.75; P = 0.002).

CONCLUSIONS

Our results support that the consumption of (poly)phenols may contribute to lower glucose levels in individuals with type 2 diabetes or at risk of diabetes and that these compounds may also act in combination with anti-diabetic drugs.

Mathematical model of diabetes and lipid metabolism linked to diet, leptin sensitivity, insulin sensitivity and VLDLTG clearance predicts paths to health and type II diabetes

An original model of diabetes linked to carbohydrate and lipid intake is presented and applied to predict the effects on biomarkers of various diets. The variables (biomarkers) are concentrations of fasting plasma glucose, insulin, leptin, glucagon, non-esterified fatty acids (NEFA) and very low density lipoprotein triglyceride (VLDLTG), as well as muscle lipids, hepatic lipids, pancreatic lipids, fat mass and mass of β-cells. The model predicts isocaloric high carbohydrate low fat (HCLF) diet and low carbohydrate high fat (LCHF) diet trajectories to health which vary in fat mass by at most a few kilograms at steady state. The LCHF trajectories to health are faster than isocaloric HCLF trajectories with respect to fat mass loss, although these trajectories may be slower initially if parameters are adjusting from HCLF values. On LC diets, leptin sensitivity and VLDLTG clearance are thought to increase. Increasing leptin sensitivity and VLDLTG clearance is predicted to lower lipids including fat mass and VLDLTG. The model predicts that changes in VLDLTG due to a change in diet happen rapidly, approaching steady state values after a few weeks, reflecting leptin sensitivity and VLDLTG clearance which are much harder to measure. The model predicts that if only insulin sensitivity increases on a LC diet, steady state fat mass would increase slightly. If leptin and insulin sensitivities increase concurrently, the combined effect could be a decrease in fat mass, consistent with the fact that increasing insulin sensitivity is often associated with fat mass loss in trials. The model predicts trajectories to fat type II diabetes with hypertriglyceridemia due to high carbohydrate moderate fat diets, on which insulin rises before falling, as ectopic fat deposits increase; made fatter and more diabetic by higher lipid consumption. It predicts trajectories to non-diabetic states with raised fat mass, VLDLTG and muscle, hepatic and pancreatic lipids due to moderate carbohydrate high fat diets. The model predicts paths to lean type II diabetes, on a diet of moderate energy but low β-cell replication rate or high death rate.

Postprandial Lipemia Modulates Pancreatic Alpha-Cell Function in the Prediction of Type 2 Diabetes Development: The CORDIOPREV Study

Diabetes (T2DM) is a major global health issue, and developing new approaches to its prevention is of paramount importance. We hypothesized that abnormalities in lipid metabolism are involved in alpha-cell deregulation. We therefore studied the metabolic factors underlying alpha-cell dysfunction in T2DM progression after a dietary intervention (Mediterranean and low-fat). Additionally, we evaluated whether postprandial glucagon levels may be considered as a predictive factor of T2DM in cardiovascular patients. Non-T2DM participants from the CORDIOPREV study were categorized by tertiles of the area under the curve (AUC) for triacylglycerols and also by tertiles of AUC for glucagon. Our results showed that patients with higher triacylglycerols levels presented elevated postprandial glucagon (P = 0.009). Moreover, we observed higher risk of T2DM (hazard ratio: 2.65; 95% confidence interval: 1.56-4.53) in subjects with elevated glucagon. In conclusion, high postprandial lipemia may induce alpha-cell dysfunction in cardiovascular patients. Our results also showed that postprandial glucagon levels could be used to predict T2DM development.

NAFLD as a continuum: from obesity to metabolic syndrome and diabetes

BACKGROUND

The prevalence of non-alcoholic fatty liver disease (NAFLD) has been increasing rapidly. It is nowadays recognized as the most frequent liver disease, affecting a quarter of global population and regularly coexisting with metabolic disorders such as type 2 diabetes, hypertension, obesity, and cardiovascular disease. In a more simplistic view, NAFLD could be defined as an increase in liver fat content, in the absence of secondary cause of steatosis. In fact, the clinical onset of the disease is a much more complex process, closely related to insulin resistance, limited expandability and dysfunctionality of adipose tissue. A fatty liver is a main driver for a new recognized liver-pancreatic α-cell axis and increased glucagon, contributing to diabetes pathophysiology.

MAIN TEXT

This review will focus on the clinical and pathophysiological connections between NAFLD, insulin resistance and type 2 diabetes. We reviewed non-invasive methods and several scoring systems for estimative of steatosis and fibrosis, proposing a multistep process for NAFLD evaluation. We will also discuss treatment options with a more comprehensive view, focusing on the current available therapies for obesity and/or type 2 diabetes that impact each stage of NAFLD.

CONCLUSION

The proper understanding of NAFLD spectrum-as a continuum from obesity to metabolic syndrome and diabetes-may contribute to the early identification and for establishment of targeted treatment.

Reducing Glucokinase Activity to Enhance Insulin Secretion: A Counterintuitive Theory to Preserve Cellular Function and Glucose Homeostasis

Pancreatic beta-cells are the only cells in the body that can synthesize and secrete insulin. Through the process of glucose-stimulated insulin secretion, beta-cells release insulin into circulation, stimulating GLUT4-dependent glucose uptake into peripheral tissue. Insulin is normally secreted in pulses that promote signaling at the liver. Long before type 2 diabetes is diagnosed, beta-cells become oversensitive to glucose, causing impaired pulsatility and overstimulation in fasting levels of glucose. The resulting hypersecretion of insulin can cause poor insulin signaling and clearance at the liver, leading to hyperinsulinemia and insulin resistance. Continued overactivity can eventually lead to beta-cell exhaustion and failure at which point type 2 diabetes begins. To prevent or reverse the negative effects of overstimulation, beta-cell activity can be reduced. Clinical studies have revealed the potential of beta-cell rest to reverse new cases of diabetes, but treatments lack durable benefits. In this perspective, we propose an intervention that reduces overactive glucokinase activity in the beta-cell. Glucokinase is known as the glucose sensor of the beta-cell due to its high control over insulin secretion. Therefore, glycolytic overactivity may be responsible for hyperinsulinemia early in the disease and can be reduced to restore normal stimulus-secretion coupling. We have previously reported that reducing glucokinase activity in prediabetic mouse islets can restore pulsatility and enhance insulin secretion. Building on this counterintuitive finding, we review the importance of pulsatile insulin secretion and highlight how normalizing glucose sensing in the beta cell during prediabetic hyperinsulinemia may restore pulsatility and improve glucose homeostasis.

Pathophysiology of Type 2 Diabetes in Children and Adolescents

BACKGROUND

The prevalence of type 2 diabetes (DM) in children is disturbingly increasing in parallel with the increasing childhood obesity. Better knowledge regarding the pathophysiology of type 2 DM in children is paramount to devise an effective management plan.

OBJECTIVE

Discuss the pathophysiology of type 2 DM in children and adolescents.

METHODS AND RESULTS

This is a comprehensive review of the literature on this topic. Type 2 DM in childhood is viewed as a continuum of insulin resistance (IR) which is determined by an underlying genetic predisposition, intrauterine environment, excessive food consumption, continued rapid weight gain, and poor lifestyle. Besides IR, this is compounded by multiple metabolic defects including β-cell dysfunction and inadequate insulin secretion, α-cell dysfunction, hyperglucagonemia and increased hepatic glucose production, lipotoxicity, inflammation, deficiencies in incretin production and action, and increased renal glucose reabsorption. The confluence of genetic and environmental factors underscores the complexity in disease progression.

CONCLUSION

A consistent single risk factor for type 2 DM is obesity and related IR and therefore it is essential to curtail the progression of obesity. It is important to investigate the role of stringent dietary and nutritional approaches, medications that enhance β-cell function and insulin sensitivity.

The Liver-α-Cell Axis and Type 2 Diabetes

Both type 2 diabetes (T2D) and nonalcoholic fatty liver disease (NAFLD) strongly associate with increasing body mass index, and together these metabolic diseases affect millions of individuals. In patients with T2D, increased secretion of glucagon (hyperglucagonemia) contributes to diabetic hyperglycemia as proven by the significant lowering of fasting plasma glucose levels following glucagon receptor antagonist administration. Emerging data now indicate that the elevated plasma concentrations of glucagon may also be associated with hepatic steatosis and not necessarily with the presence or absence of T2D. Thus, fatty liver disease, most often secondary to overeating, may result in impaired amino acid turnover, leading to increased plasma concentrations of certain glucagonotropic amino acids (e.g., alanine). This, in turn, causes increased glucagon secretion that may help to restore amino acid turnover and ureagenesis, but it may eventually also lead to increased hepatic glucose production, a hallmark of T2D. Early experimental findings support the hypothesis that hepatic steatosis impairs glucagon's actions on amino acid turnover and ureagenesis. Hepatic steatosis also impairs hepatic insulin sensitivity and clearance that, together with hyperglycemia and hyperaminoacidemia, lead to peripheral hyperinsulinemia; systemic hyperinsulinemia may itself contribute to worsen peripheral insulin resistance. Additionally, obesity is accompanied by an impaired incretin effect, causing meal-related glucose intolerance. Lipid-induced impairment of hepatic sensitivity, not only to insulin but potentially also to glucagon, resulting in both hyperinsulinemia and hyperglucagonemia, may therefore contribute to the development of T2D at least in a subset of individuals with NAFLD.

Association of glucagon-to-insulin ratio and nonalcoholic fatty liver disease in patients with type 2 diabetes mellitus

OBJECTIVE

The aim of this study is to investigate the association between glucagon-to-insulin ratio and the presence of nonalcoholic fatty liver disease on ultrasonography in participants with type 2 diabetes mellitus.

RESEARCH DESIGN AND METHODS

This cross-sectional study was performed with data obtained from 172 participants with type 2 diabetes mellitus admitted to a University hospital of Korea. Participants were assessed for serum fasting and postprandial serum glucagon-to-insulin ratio and divided into tertiles. Nonalcoholic fatty liver disease was defined as ultrasonographically detected fatty liver.

RESULTS

Prevalence of nonalcoholic fatty liver disease was significantly decreased across tertile of fasting and postprandial glucagon-to-insulin ratio ( p = 0.009 for trend, p = 0.001 for trend, respectively). Lower glucagon-to-insulin ratio was significantly associated with the presence of nonalcoholic fatty liver disease even after adjustment for potential confounding variables [fasting glucagon-to-insulin ratio: odds ratio (95% confidence interval), 2.68 (1.08-6.86)], postprandial glucagon-to-insulin ratio: [2.72 (1.03-7.35)]. The participants in the lowest tertile of fasting glucagon-to-insulin ratio had higher body mass index, visceral fat thickness, subcutaneous fat thickness, homeostasis model assessment-insulin resistance and shorter duration of diabetes mellitus.

CONCLUSION

This study suggests that lower glucagon relative insulin may be independently associated with nonalcoholic fatty liver disease in participants with type 2 diabetes.

Short Chain Fatty Acids, pancreatic dysfunction and type 2 diabetes

The microbiota living in gut influence the immune response, metabolism, mood and behavior. The diet plays a pivotal role in maintaining healthy gut microbiota composition and its fermentation leads to production of Short Chain Fatty Acids (SCFAs) mainly acetate, propionate and butyrate. During pancreatic dysfunction, insulin mediated suppression of glucagon is impaired leading to uncontrolled glucose production by liver and state of hyperglycemia. Insulin and glucagon balance is as important as insulin sensitivity which is reduced during Type 2 Diabetes (T2D). Glucagon like peptide-1 (GLP1) produced by Intestinal epithelial cells regulates insulin and glucagon secretion directly via GLP1 receptor on pancreatic cells or via nervous system. But half-life period of GLP1 is very short i.e. about 2 min, after which it is cleaved and inactivated. SCFAs are well documented to induce GLP1 but its direct effect on pancreatic dysfunction has not been reported. This review opens a new avenue to study the role of SCFAs as treatment to pancreatic dysfunction and T2D.

Molecular signaling mechanisms of renal gluconeogenesis in nondiabetic and diabetic conditions

The kidneys are as involved as the liver in gluconeogenesis which can significantly contribute to hyperglycemia in the diabetic condition. Substantial evidence has demonstrated the overexpression of rate-limiting gluconeogenic enzymes, especially phosphoenolpyruvate carboxykinase and glucose 6 phosphatase, and the accelerated glucose release both in the isolated proximal tubular cells and in the kidneys of diabetic animal models and diabetic patients. The aim of this review is to provide an insight into the mechanisms that accelerate renal gluconeogenesis in the diabetic conditions and the therapeutic approaches that could affect this process in the kidney. Increase in gluconeogenic substrates, reduced insulin concentration or insulin resistance, downregulation of insulin receptors and insulin signaling, oxidative stress, and inappropriate activation of the renin-angiotensin system are likely to participate in enhancing renal gluconeogenesis in the diabetic milieu. Several studies have suggested that controlling glucose metabolism at the renal level favors effective overall glycemic control in both type 1 and type 2 diabetes. Therefore, renal gluconeogenesis may be a promising target for effective glycemic control as a therapeutic strategy in diabetes.

Protective Effect of Ipragliflozin on Pancreatic Islet Cells in Obese Type 2 Diabetic db/db Mice

Ipragliflozin is a selective sodium glucose cotransporter 2 (SGLT2) inhibitor that increases urinary glucose excretion and subsequently improves hyperglycemia in patients with type 2 diabetes mellitus (T2DM). To assess the beneficial effect of ipragliflozin on the mass and function of pancreatic β-cells under diabetic conditions, obese T2DM db/db mice were treated with ipragliflozin for 5 weeks. Glucose and lipid metabolism parameters, pathological changes in pancreatic islet cells and insulin content were evaluated. Pathological examination of pancreatic islet cells comprised measuring the ratios of insulin- and glucagon-positive cells and levels of oxidative stress markers. Hemoglobin A1c, plasma glucose, non-esterified fatty acid and triglyceride levels in ipragliflozin-treated groups were reduced compared to the diabetic control (DM-control) group. Histopathological examination of pancreatic islet cells revealed strong insulin staining and reduced glucagon staining in the ipragliflozin 10 mg/kg-treated group compared with the DM-control group. The ratio of α- to β-cell mass was lower in the ipragliflozin 10 mg/kg-treated group than the DM-control group and was similar to that of the non-diabetic control group. The density of immunostaining for 4-hydroxy-2-nonenal, an oxidative stress marker, in pancreatic islets was significantly lower in the ipragliflozin 10 mg/kg-treated group than the DM-control group. Pancreatic insulin content tended to be higher in the ipragliflozin-treated groups than the DM-control group. Our findings demonstrate the benefit of ipragliflozin treatment in improving glucolipotoxicity and reducing oxidative stress in pancreatic islet cells. Treatment with ipragliflozin may protect against the progressive loss of islet β-cells in patients with T2DM.

Vildagliptin/pioglitazone combination improved the overall glycemic control in type I diabetic rats

Type I diabetes (TID) is generally assumed to be caused by an immune associated, if not directly immune-mediated, destruction of pancreatic β-cells. In patients with long-term diabetes, the pancreas lacks insulin-producing cells and the residual β-cells are unable to regenerate. Patients with TID are subjected to a lifelong insulin therapy which shows risks of hypoglycemia, suboptimal control and ketosis. In this study, we investigated the potential role of vildagliptin (Vilda) alone or in combination with pioglitazone (Pio), as treatment regimens for TID using streptozotocin (STZ)-induced TID model in rats. Daily oral administration of Vilda (5 mg/kg) alone or in combination with Pio (20 mg/kg) for 7 weeks significantly reduced blood glucose levels and HbA1c. It increased serum insulin levels and decreased serum glucagon. It also showed a strong antioxidant activity. Immunohistochemical analysis showed a marked improvement in β-cells in treated groups when compared with the diabetic group, which appeared in the normal cellular and architecture restoration of β-cells in the islets of Langerhans. Vilda alone or in combination with Pio has the ability to improve the overall glycemic control in type I diabetic rats and may be considered a hopeful and effective remedy for TID.

Elevated hepatic expression of H19 long noncoding RNA contributes to diabetic hyperglycemia

Excessive hepatic glucose production (HGP) contributes significantly to the hyperglycemia of type 2 diabetes; however, the molecular mechanism underlying this dysregulation remains poorly understood. Here, we show that fasting temporally increases the expression of H19 long noncoding RNA (lncRNA) in nondiabetic mouse liver, whereas its level is chronically elevated in diet-induced diabetic mice, consistent with the previously reported chronic hepatic H19 increase in diabetic patients. Importantly, liver-specific H19 overexpression promotes HGP, hyperglycemia, and insulin resistance, while H19 depletion enhances insulin-dependent suppression of HGP. Using genome-wide methylation and transcriptome analyses, we demonstrate that H19 knockdown in hepatic cells alters promoter methylation and expression of Hnf4a, a master gluconeogenic transcription factor, and that this regulation is recapitulated in vivo. Our findings offer a mechanistic explanation of lncRNA H19's role in the pathogenesis of diabetic hyperglycemia and suggest that targeting hepatic H19 may hold the potential of new treatment for this disease.

Association of Oxytocin with Glucose Intolerance and Inflammation Biomarkers in Metabolic Syndrome Patients with and without Prediabetes

OBJECTIVES

The aim of this study was to explore the differences in OXT levels in metabolic syndrome (MetS) subjects, newly diagnosed type 2 diabetes mellitus (T2D), and prediabetes subjects vs. MetS subjects without glucose intolerance (non-diabetic MetS). It was also intended to determine the relationship between plasma OXT levels and inflammatory markers in those subjects.

METHODS

Along with 45 lean and normoglycemic controls, a total of 190 MetS subjects (61 men, 129 women) were enrolled. Colorimetric enzymatic assays of the following components were performed: plasma OXT, high-sensitivity C-reactive protein (hs-CRP), macrophage chemoattractant protein 1 (MCP-1), plasminogen activator inhibitor 1 (PAI-1), matrix metalloproteinase 9 (MMP-9), resistin, adiponectin, leptin, macrophage migration inhibitory factor (MIF), tumor necrosis factor α (TNF-α), thrompospondin 1 (TSP-1), interleukin 10 (IL-10), interleukin 6 (IL-6), and glucagon.

RESULTS

hsCRP, PAI-1, resistin, leptin-to-adiponection-ratio (LAR), TNF-α, TSP-1, and MIF were significantly higher in both MetS groups (prediabetic and T2DM) than in MetS-only subjects. Leptin and MMP-9 were significantly higher in the MetS-T2DM group (but not in MetS-prediabetics) vs. MetS-only subjects. Conversely adiponectin, OXT, MCP-1, and IL-10 were significantly lower in both MetS groups (prediabetic and T2DM) than in MetS-only subjects. There was no marked discrepancy in either glucagon or IL-6 levels among the three MetS groups. In the entire MetS study population, OXT correlated substantially and proportionally with MCP-1, IL-10, and IL-6; it correlated negatively with HbA1c, fasting plasma glucose (FPG), PAI-1, MMP-9, TNF-α, TSP-1, resistin, adiponectin, leptin, LAR, and MIF. No association could be observed between OXT and glucagon.

CONCLUSIONS

OXT may be a substantial surrogate predictive/prognostic tool and putative pharmacotherapeutic target in metabolic anomalies and related disorders.

Heterogeneity in effects of genetically determined adiposity on insulin resistance and type 2 diabetes: The atherosclerosis risk in communities study

BACKGROUND

A recent genome-wide association study has identified 12 genetic variants robustly associated with body fat percentage (BF%) with diverse cardiometabolic consequences. We developed three genetic risk scores (GRSs) according to the associations of the 12 individual variants with type 2 diabetes (T2D) and test the GRSs' associations with insulin resistance and T2D in the Atherosclerosis Risk in Communities Study.

METHODS

In 6895 European-American participants, we calculated GRS-I as the number of BF%-increasing alleles from variants associated with increased risk of T2D, GRS-D from variants associated with decreased risk of T2D, and GRS-ALL from all 12 variants. Linear and logistic regression models were used to evaluate associations of the GRSs with insulin resistance and risk of T2D, respectively, adjusted for age, sex, smoking, and drinking, and additionally for body mass index (BMI).

RESULTS

GRS-D was significantly associated with decreased levels of fasting insulin (P = 0.014) and homeostasis assessment of insulin resistance (P = 0.023). While GRS-I was not associated with insulin resistance measures, it was with T2D (P = 0.002). Further adjustment for BMI did not substantially change the above associations. GRS-ALL was inversely associated with insulin resistance after controlling for covariates including BMI; GRS-ALL was not associated with T2D.

CONCLUSION

Genetically determined BF% has differential effects on cardiometabolic risk, which may partly explain the heterogeneity in obesity-induced cardiometabolic risk and have implications for developing new strategies mitigating obesity-induced cardiometabolic consequences.

A long-term mechanistic computational model of physiological factors driving the onset of type 2 diabetes in an individual

A computational model of the physiological mechanisms driving an individual's health towards onset of type 2 diabetes (T2D) is described, calibrated and validated using data from the Diabetes Prevention Program (DPP). The objective of this model is to quantify the factors that can be used for prevention of T2D. The model is energy and mass balanced and continuously simulates trajectories of variables including body weight components, fasting plasma glucose, insulin, and glycosylated hemoglobin among others on the time-scale of years. Modeled mechanisms include dynamic representations of intracellular insulin resistance, pancreatic beta-cell insulin production, oxidation of macronutrients, ketogenesis, effects of inflammation and reactive oxygen species, and conversion between stored and activated metabolic species, with body-weight connected to mass and energy balance. The model was calibrated to 331 placebo and 315 lifestyle-intervention DPP subjects, and one year forecasts of all individuals were generated. Predicted population mean errors were less than or of the same magnitude as clinical measurement error; mean forecast errors for weight and HbA1c were ~5%, supporting predictive capabilities of the model. Validation of lifestyle-intervention prediction is demonstrated by synthetically imposing diet and physical activity changes on DPP placebo subjects. Using subject level parameters, comparisons were made between exogenous and endogenous characteristics of subjects who progressed toward T2D (HbA1c > 6.5) over the course of the DPP study to those who did not. The comparison revealed significant differences in diets and pancreatic sensitivity to hyperglycemia but not in propensity to develop insulin resistance. A computational experiment was performed to explore relative contributions of exogenous versus endogenous factors between these groups. Translational uses to applications in public health and personalized healthcare are discussed.

Suppressive Effects of Clerodendrum volubile P Beauv. [Labiatae] Methanolic Extract and Its Fractions on Type 2 Diabetes and Its Complications

Type 2 diabetes is the most prominent of all diabetes types, contributing to global morbidity and mortality. Availability and cost of treatment with little or no side effect especially in developing countries, remains a huge burden. This has led to the search of affordable alternative therapies especially from medicinal plants. In this study, the antidiabetic effect of the methanolic extract, dichloromethane (DCM), butanol (BuOH) and aqueous fractions of Clerodendrum volubile leaves were investigated in type 2 diabetic rats for their effect on glucose homeostasis, serum insulin level and hepatic biomarkers, lipid profile, pancreatic redox balance and Ca2+ levels, and β-cell distribution and function. The DCM was further fractionated to isolate the active compounds, biochanin and 5,7,4'-trimethoxykaempferol. They were investigated for their toxicity and ADMET properties, α-glucosidase and angiotensin I converting enzyme (ACE) inhibitory activities in silico. There were significant (p < 0.05) decrease in blood glucose, cholesterol, LDL-C, vLDL-C, triglyceride, AST and ALT levels in all treated groups, with DCM fraction showing the best activity. All treated rats showed significantly (p < 0.05) improved anti-oxidative activities. Treatment with the DCM fraction led to significant (p < 0.05) increased serum insulin and pancreatic Ca2+ levels, as well as improved β-cell distribution and function. DCM fraction also showed improved glucose tolerance. DCM fraction dose-dependently inhibited ACE activity. The toxicity class of the isolated compounds was predicted to be 5. They were also predicted to be potent inhibitors of cytochrome P (CYPs) 1A2, 2D6 and 3A4. They docked well with α-glucosidase and ACE. These results indicate the therapeutic potential of the plant against type 2 diabetes, with the DCM fraction being the most potent which may be attributed to the isolated flavones. It further suggests antihypertensive potentials of the DCM fraction. However, inhibition of CYPs by the flavones may suggest caution in usage with other prescribed drugs metabolized by these enzymes.

The Role of Glucagon in the Pathophysiology and Treatment of Type 2 Diabetes

Type 2 diabetes is a disease involving both inadequate insulin levels and increased glucagon levels. While glucagon and insulin work together to achieve optimal plasma glucose concentrations in healthy individuals, the usual regulatory balance between these 2 critical pancreatic hormones is awry in patients with diabetes. Although clinical discussion often focuses on the role of insulin, glucagon is equally important in understanding type 2 diabetes. Furthermore, an awareness of the role of glucagon is essential to appreciate differences in the mechanisms of action of various classes of glucose-lowering therapies. Newer drug classes such as dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 receptor agonists improve glycemic control, in part, by affecting glucagon levels. This review provides an overview of the effect of glucose-lowering therapies on glucagon on the basis of an extensive PubMed literature search to identify clinical studies of glucose-lowering therapies in type 2 diabetes that included assessment of glucagon. Clinical practice currently benefits from available therapies that impact the glucagon regulatory pathway. As clinicians look to the future, improved treatment strategies are likely to emerge that will either use currently available therapies whose mechanisms of action complement each other or take advantage of new therapies based on an improved understanding of glucagon pathophysiology.

A severe but reversible reduction in insulin sensitivity is observed in patients with insulinoma

BACKGROUND

Hypoglycemic manifestations are highly variable in patients with an insulinoma and largely independent of tumour size and severity of insulin hypersecretion.

OBJECTIVES

We investigated the clinical, biological and tumoral characteristics of insulinomas in a large monocentric series of patients and we evaluated their insulin sensitivity before and after successful pancreatic surgery.

PATIENTS AND METHODS

This was a retrospective analysis of 40 patients treated for an insulinoma between 1982 and 2012 in our academic hospital. Insulin sensitivity and beta cell function were evaluated by a HOMA test outside hypoglycaemic episodes in a large subset of these patients.

RESULTS

The mean age at onset of symptoms was 48.8±20.1 years and the mean age at diagnosis was 50.7±19.9 years. Neuroglycopenic symptoms were observed in 90% of patients. The most effective preoperative imaging technique to localize the tumour was endoscopic ultrasound. Insulin sensitivity was greatly reduced in patients with insulinoma (38.9%±22.3%), while beta cells function was increased (359.0±171.5%), but to a variable extent (range: 110.6-678.6%). After complete resection of the tumour and remission of hypoglycemic episodes, insulin sensitivity increased in all evaluated subjects (72.8±36.7%) and normalized in the majority.

CONCLUSION

Although neuroglycopenic symptoms are present in most patients, diagnosis of insulinoma is often delayed. Endoscopic ultrasound remains the most sensitive preoperative technique to localize the tumour. We also show that in response to chronic hyperinsulinemia, patients with insulinoma develop protective mechanisms responsible for a marked insulin resistance, which is reversible after complete resection of the tumour.

The effects of dipeptidyl peptidase-4 inhibitors on bone fracture among patients with type 2 diabetes mellitus: A network meta-analysis of randomized controlled trials

Aim

The association between dipeptidyl peptidase-4 inhibitors (DPP-4is), a class of anti-diabetes, and bone fracture in patients with type 2 diabetes mellitus (T2DM) is unknown. This meta-analysis aimed to systematically evaluate the effects of DPP-4is on bone fracture in T2DM patients.

Methods

We searched the Cochrane Library, Embase, Medline and ClinicalTrials.gov from inception through April 28th, 2016 to identify randomized controlled trials (RCTs) that compared DPP-4is with placebo or other anti-diabetes in T2DM patients. RCTs lasting more than 12 weeks and having data on bone fracture were included. We conducted random-effects meta-analysis to estimate odds ratios (ORs) and their 95% confidence intervals (CIs), and network meta-analysis (NMA) to supplement direct comparisons. Predictive interval plot and node-splitting method were used to evaluate the heterogeneity and inconsistency for NMA, while the funnel plot was applied to explore publication bias. Besides, study quality was assessed according to Cochrane risk of bias tool.

Results

We identified 75 RCTs with a total of 70,207 patients and 11 treatments: interventions included 5 DPP-4is (alogliptin, linagliptin, saxagliptin, sitagliptin, vildagliptin), while controls included placebo and 5 other anti-diabetes (sulfonylureas, glucagon-like peptide-1 receptor agonists, metformin, thiazolidinediones, sodium-glucose co-transporter 2 inhibitors). In the NMA, the risk of fracture for alogliptin tended to decrease when versus placebo (OR, 0.51; 95% CI, 0.29 to 0.88). Besides, aloglitpin had a lower risk compared with linagliptin (OR, 0.45; 95% CI, 0.20 to 0.99) and saxagliption (OR, 0.46; 95%CI, 0.25 to 0.84); the risk was higher with saxagliptin when versus sitagliptin (OR, 1.90; 95% CI, 1.04 to 3.47) and sulfonylureas (OR, 1.98; 95% CI, 1.06 to 3.71). In the direct pairwise meta-analysis, alogliptin was associated with a non-significant tendency to reduction of bone fracture compared with placebo (OR, 0.54; 95% CI, 0.29 to 1.01). Ranking probability analysis indicated alogliptin decreased the risk of bone fracture most with a probability of 76.3%.

Conclusion

Alogliptin may be associated with a lower risk of bone fracture compared with placebo, linagliptin, or saxagliptin, while other anti-diabetes did not seem to have an association with the risk of bone fracture.

Glucagon and glucagon-like peptide-1 as novel anti-inflammatory and immunomodulatory compounds

Glucagon and glucagon-like peptide-1 (GLP-1) are polypeptide hormones that are produced by pancreatic α-cells and the intestine, respectively, whose main function is to control glucose homeostasis. The glucagon and GLP-1 levels are imbalanced in diabetes. Furthermore, type 1 diabetic patients and animals present with a diminished inflammatory response, which is related to some morbidities of diabetes, such as a higher incidence of infectious diseases, including sepsis. The focus of this review is to briefly summarize the state of the art concerning the effects of glucagon and GLP-1 on the inflammatory response. Here, we propose that glucagon and GLP-1 have anti-inflammatory properties, making them possible prototypes for the design and synthesis of new compounds to treat inflammatory diseases. In addition, glucagon, GLP-1 or their analogues or new derivatives may not only be important for managing inflammatory diseases but may also have the therapeutic potential to prevent, cure or ameliorate diabetes in patients by counteracting the deleterious effects of pro-inflammatory cytokines on the function and viability of pancreatic β-cells. In addition, GLP-1, its analogues or drugs that inhibit GLP-1 metabolism may have a doubly beneficial effect in diabetic patients by inhibiting the inflammatory response and reducing glycaemia.