Role of beta-cell dysfunction, ectopic fat accumulation and insulin resistance in the pathogenesis of type 2 diabetes mellitus

Effects of gliclazide add on metformin on serum omentin-1 levels in patients with type 2 diabetes mellitus

BACKGROUND

Omentin is a newly identified adipokine that has beneficial influence against cardiovascular disorders. Hence, considering the impact of anti-diabetic drug on omentin levels may provide an adjuvant strategy to protect diabetic patients against valuable clinical hazards.

AIM OF THE STUDY

To investigate the influence of metformin alone or in combination with gliclazide on the level of serum omentin among patients with type 2 diabetes mellitus (T2DM).

PATIENTS AND METHODS

A total of 70 newly diagnosed patients with T2DM were enrolled in this randomized, double-blind prospective study, and divided into two equal groups based on treatment regimen in which Group 1 treated with metformin (1000 mg) and Group 2 treated with metformin (1000 mg) plus gliclazide (80 mg). Blood glucose levels, HbA1C, insulin levels, and serum omentin-1 were measured at baseline and after 12 weeks of treatment.

RESULT

Use of gliclazide as an add-on therapy to metformin in patients with T2DM result in better glycemic control evidenced by significant reductions in the levels of blood glucose levels and HbA1C and much more improvement in insulin sensitivity evidenced by significant decreased in insulin resistance index, whereas it has adverse impact on serum omentin-1 levels evidenced by significant decrement in omentin-1 level in comparison to their pretreatment levels among Group 2 patients.

CONCLUSIONS

Adding of gliclazide to metformin in treatment of patients with T2DM might extend the therapeutic action of metformin in regarding much better controlling of glycemic indices, but, at the same time, it might attenuate the cardioprotective effects of metformin by its adverse influence on serum omentin-1 levels.

Management of diabolical diabetes mellitus and periodontitis nexus: Are we doing enough?

Periodontitis is the commonest oral disease affecting population worldwide. This disease is notorious for the devastation of tooth supporting structures, ensuing in the loss of dentition. The etiology for this disease is bacterial biofilm, which accumulates on the teeth as dental plaque. In addition to the biofilm microorganisms, other factors such as environmental, systemic and genetic are also responsible in progression of periodontitis. Diabetes mellitus (DM) is metabolic disorder which has an impact on the global health. DM plays a crucial role in the pathogenesis of periodontitis. Periodontitis is declared as the “sixth” major complication of DM. Evidence based literature has depicted an enhanced incidence and severity of periodontitis in subjects with DM. A “two way” relationship has been purported between periodontitis and DM. Mutual management of both conditions is necessary. Periodontal therapy (PT) may assist to diminish the progression of DM and improve glycemic control. Various advanced technological facilities may be utilized for the purpose of patient education and disease management. The present paper clarifies the etio-pathogenesis of periodontitis, establishing it as a complication of DM and elaborating the various mechanisms involved in the pathogenesis. The role of PT in amelioration of DM and application of digital communication will be discussed. Overall, it is judicious to create an increased patient cognizance of the periodontitis-DM relationship. Conjunctive efforts must be undertaken by the medical and oral health care professionals for the management of periodontitis affected DM patients.

Anti-diabetes effect of chronic intermittent hypobaric hypoxia through improving liver insulin resistance in diabetic rats

AIM

Cumulating evidence demonstrated that chronic intermittent hypobaric hypoxia (CIHH) had beneficial effects on the body. The present study was to investigate the anti-diabetes effect of CIHH in type-2 diabetic rats for the first time.

MAIN METHODS

Sprague-Dawley rats were randomly divided into 4 groups: control group (CON), diabetes mellitus group (DM, induced by high-fat diet combined with low-dose streptozotocin), CIHH treatment group (CIHH, simulated 5000-m altitude, 6h per day for 28 days), and diabetes mellitus plus CIHH treatment group (DM+CIHH). Histopathology of liver, systolic arterial blood pressure (SAP), blood biochemicals, glucose and insulin tolerance were determined. The expression of proteins associated with insulin signaling pathway as well as hypoxia induced factors were assayed.

KEY FINDINGS

Diabetic rats showed impaired glucose tolerance, dyslipidemia, hepatic steatosis and hepatic insulin resistance in addition to increased SAP. However, SAP, serum triglyceride and cholesterol were decreased, and hepatic steatosis and insulin resistance were improved in DM+CIHH rats. Furthermore, the protein expression of glucokinase (GCK), insulin receptor substrates (IRS-1 and IRS-2), and HIF1α were increased, while the expression of phosphoenolpyruvate carboxykinase (PEPCK), was markedly reduced in DM+CIHH rats.

SIGNIFICANCE

We conclude that CIHH treatment has anti-diabetes effects through ameliorating insulin resistance via hepatic HIF-insulin signaling pathway in type-2 diabetic rats.

Comparison of Experimental Diabetic Periodontitis Induced by Porphyromonas gingivalis in Mice

Periodontitis is one of the severe complications in diabetic patients and gingival epithelium plays an initial role on the onset and progression of this disease. However the potential mechanism is yet sufficiently understood. Meanwhile, the research on the correlational experimental animal models was also insufficient. Here, we established periodontitis with type 2 diabetes in db/db and Tallyho/JngJ (TH) mice and periodontitis with type 1 diabetes in streptozotocin induced diabetes C57BL/6J (STZ-C57) mice by oral infection of periodontal pathogen Porphyromonas gingivalis W50. We demonstrated that periodontal infected mice with high blood glucose levels showed dramatically more alveolar bone loss than their counterparts, in which infected db/db mice exhibited the most bone defects. No contrary impact could be observed between this periodontal infection and onset and severity of diabetes. The expressions of PTPN2 were inhibited whereas the expression of JAK1, STAT1, and STAT3 increased dramatically in gingival epithelia and the serum TNF-α also significantly increased in the mice with diabetic periodontitis. Our results indicated that the variations of inflammation-related protein expressions in gingival epithelia might lead to the phenotype differences in the mice with diabetic periodontitis.

TAB3 involves in hepatic insulin resistance through activation of MAPK pathway

Insulin resistance is often accompanied by chronic inflammatory responses. The mitogen-activated protein kinase (MAPK) pathway is rapidly activated in response to many inflammatory cytokines. But the functional role of MAPKs in palmitate-induced insulin resistance has yet to be clarified. In this study, we found that transforming growth factor β-activated kinase binding protein-3 (TAB3) was up-regulated in insulin resistance. Considering the relationship between transforming growth factor β-activated kinase (TAK1) and MAPK pathway, we assumed TAB3 involved in insulin resistance through activation of MAPK pathway. To certify this hypothesis, we knocked down TAB3 in palmitate treated HepG2 cells and detected subsequent biological responses. Importantly, TAB3 siRNA directly reversed insulin sensitivity by improving insulin signal transduction. Moreover, silencing of TAB3 could facilitate hepatic glucose uptake, reverse gluconeogenesis and improve ectopic fat accumulation. Meanwhile, we found that the positive effect of knocking down TAB3 was more significant when insulin resistance occurred. All these results indicate that TAB3 acts as a negative regulator in insulin resistance through activation of MAPK pathway.

The Subtle Balance between Lipolysis and Lipogenesis: A Critical Point in Metabolic Homeostasis

Excessive accumulation of lipids can lead to lipotoxicity, cell dysfunction and alteration in metabolic pathways, both in adipose tissue and peripheral organs, like liver, heart, pancreas and muscle. This is now a recognized risk factor for the development of metabolic disorders, such as obesity, diabetes, fatty liver disease (NAFLD), cardiovascular diseases (CVD) and hepatocellular carcinoma (HCC). The causes for lipotoxicity are not only a high fat diet but also excessive lipolysis, adipogenesis and adipose tissue insulin resistance. The aims of this review are to investigate the subtle balances that underlie lipolytic, lipogenic and oxidative pathways, to evaluate critical points and the complexities of these processes and to better understand which are the metabolic derangements resulting from their imbalance, such as type 2 diabetes and non alcoholic fatty liver disease.

Activated PKR inhibits pancreatic β-cell proliferation through sumoylation-dependent stabilization of P53

Double-stranded RNA-dependent protein kinase (PKR) is intimately involved in type 2 diabetes due to its role in insulin resistance in peripheral tissues and anti-proliferative effect on pancreatic β-cells. Activated PKR was found to inhibit β-cell proliferation, partially through accumulation of P53. However the molecular mechanisms underlying PKR-dependent upregulation of P53 remain unknown. The results of the present study showed that PKR can be specifically activated in PKR overexpressing β-cells by a low dosage of the previously synthesized compound 1H-benzimidazole1-ethanol,2,3-dihydro-2-imino-a-(phenoxymethyl)-3-(phenylmethyl)-,monohydrochloride (BEPP), and this led to upregulation of P53 through sumoylation-dependent stability. Activated PKR was found to interact with sumo-conjugating enzyme Ubc9, and P53 sumoylation relies on a PKR-Ubc9 protein-protein interaction. Additionally, a ceramide signal was needed for PKR activation to be triggered by glucolipotoxicity and TNFα stimulation, and stabilization of P53 required endogenous ceramide accumulation. Glucolipotoxicity and pro-inflammatory cytokines therefore promote the sumoylation-dependent stability of P53 via the ceramide/PKR/Ubc9 signalling pathway that is involved in pancreatic β-cell proliferation inhibition in the development of type 2 diabetes.

Nonalcoholic fatty liver disease and type 2 diabetes: common pathophysiologic mechanisms

Nonalcoholic fatty liver disease (NAFLD) is an independent risk factor for advanced liver disease, type 2 diabetes (T2DM), and cardiovascular diseases. The prevalence of NAFLD in the general population is around 30 %, but it is up to three times higher in those with T2DM. Among people with obesity and T2DM, the NAFLD epidemic also is worsening. Therefore, it is important to identify early metabolic alterations and to prevent these diseases and their progression. In this review, we analyze the pathophysiologic mechanisms leading to NAFLD, particularly, those common to T2DM, such as liver and muscle insulin resistance. However, it is mainly adipose tissue insulin resistance that results in increased hepatic de novo lipogenesis, inflammation, and lipotoxicity. Although genetics predispose to NAFLD, an unhealthy lifestyle, including high-fat/high-sugar diets and low physical activity, increases the risk. In addition, alterations in gut microbiota and environmental chemical agents, acting as endocrine disruptors, may play a role.

Advanced glycation end-products induce apoptosis in pancreatic islet endothelial cells via NF-κB-activated cyclooxygenase-2/prostaglandin E2 up-regulation

Microvascular complications eventually affect nearly all patients with diabetes. Advanced glycation end-products (AGEs) resulting from hyperglycemia are a complex and heterogeneous group of compounds that accumulate in the plasma and tissues in diabetic patients. They are responsible for both endothelial dysfunction and diabetic vasculopathy. The aim of this study was to investigate the cytotoxicity of AGEs on pancreatic islet microvascular endothelial cells. The mechanism underlying the apoptotic effect of AGEs in pancreatic islet endothelial cell line MS1 was explored. The results showed that AGEs significantly decreased MS1 cell viability and induced MS1 cell apoptosis in a dose-dependent manner. AGEs dose-dependently increased the expressions of cleaved caspase-3, and cleaved poly (ADP-ribose) polymerase in MS1 cells. Treatment of MS1 cells with AGEs also resulted in increased nuclear factor (NF)-κB-p65 phosphorylation and cyclooxygenase (COX)-2 expression. However, AGEs did not affect the expressions of endoplasmic reticulum (ER) stress-related molecules in MS1 cells. Pretreatment with NS398 (a COX-2 inhibitor) to inhibit prostaglandin E₂ (PGE₂) production reversed the induction of cleaved caspase-3, cleaved PARP, and MS1 cell viability. Moreover, AGEs significantly increased the receptor for AGEs (RAGE) protein expression in MS1 cells, which could be reversed by RAGE neutralizing antibody. RAGE Neutralizing antibody could also reverse the induction of cleaved caspase-3 and cleaved PARP and decreased cell viability induced by AGEs. These results implicate the involvement of NF-κB-activated COX-2/PGE₂ up-regulation in AGEs/RAGE-induced islet endothelial cell apoptosis and cytotoxicity. These findings may provide insight into the pathological processes within the pancreatic islet microvasculature induced by AGEs accumulation.

BBT improves glucose homeostasis by ameliorating β-cell dysfunction in type 2 diabetic mice

Impaired glucose-stimulated insulin secretion (GSIS) and increasing β-cell death are two typical dysfunctions of pancreatic β-cells in individuals that are destined to develop type 2 diabetes, and improvement of β-cell function through GSIS enhancement and/or inhibition of β-cell death is a promising strategy for anti-diabetic therapy. In this study, we discovered that the small molecule, N-(2-benzoylphenyl)-5-bromo-2-thiophenecarboxamide (BBT), was effective in both potentiating GSIS and protecting β-cells from cytokine- or streptozotocin (STZ)-induced cell death. Results of further studies revealed that cAMP/PKA and long-lasting (L-type) voltage-dependent Ca(2) (+) channel/CaMK2 pathways were involved in the action of BBT against GSIS, and that the cAMP/PKA pathway was essential for the protective action of BBT on β-cells. An assay using the model of type 2 diabetic mice induced by high-fat diet combined with STZ (STZ/HFD) demonstrated that BBT administration efficiently restored β-cell functions as indicated by the increased plasma insulin level and decrease in the β-cell loss induced by STZ/HFD. Moreover, the results indicated that BBT treatment decreased fasting blood glucose and HbA1c and improved oral glucose tolerance further highlighting the potential of BBT in anti-hyperglycemia research.

Role of the ubiquitin-proteasome system and autophagy in regulation of insulin sensitivity in serum-starved 3T3-L1 adipocytes

The ubiquitin-proteasome system (UPS) and autophagy are two conserved intracellular proteolytic pathways, responsible for degradation of most cellular proteins in living cells. Currently, both the UPS and autophagy have been suggested to be associated with pathogenesis of insulin resistance and diabetes. However, underlying mechanism remains largely unknown. The purpose of the present study is to investigate the impact of the UPS and autophagy on insulin sensitivity in serum-starved 3T3-L1 adipocytes. Our results show that serum depletion resulted in activation of the UPS and autophagy, accompanied with increased insulin sensitivity. Inhibition of the UPS with bortezomib (BZM), a highly selective, reversible 26S proteasome inhibitor induced compensatory activation of autophagy but did not affect significantly insulin action. Genetic and pharmacological inhibition of autophagy dramatically mitigated serum starvation-elevated insulin sensitivity. In addition, autophagy inhibition compromised UPS function and led to endoplasmic reticulum (ER) stress and unfolded protein response (UPR). Inability of the UPS by BMZ exacerbated autophagy inhibition-induced ER stress and UPR. These results suggest that protein quality control maintained by the UPS and autophagy is required for preserving insulin sensitivity. Importantly, adaptive activation of autophagy plays a critical role in serum starvation-induced insulin sensitization in 3T3-L1 adipocytes.

Population distribution of the sagittal abdominal diameter (SAD) from a representative sample of US adults: comparison of SAD, waist circumference and body mass index for identifying dysglycemia

Background

The sagittal abdominal diameter (SAD) measured in supine position is an alternative adiposity indicator that estimates the quantity of dysfunctional adipose tissue in the visceral depot. However, supine SAD’s distribution and its association with health risk at the population level are unknown. Here we describe standardized measurements of SAD, provide the first, national estimates of the SAD distribution among US adults, and test associations of SAD and other adiposity indicators with prevalent dysglycemia.

Methods and Findings

In the 2011–2012 National Health and Nutrition Examination Survey, supine SAD was measured (“abdominal height”) between arms of a sliding-beam caliper at the level of the iliac crests. From 4817 non-pregnant adults (age ≥20; response rate 88%) we used sample weights to estimate SAD’s population distribution by sex and age groups. SAD’s population mean was 22.5 cm [95% confidence interval 22.2–22.8]; median was 21.9 cm [21.6–22.4]. The mean and median values of SAD were greater for men than women. For the subpopulation without diagnosed diabetes, we compared the abilities of SAD, waist circumference (WC), and body mass index (BMI, kg/m²) to identify prevalent dysglycemia (HbA1c ≥5.7%). For age-adjusted, logistic-regression models in which sex-specific quartiles of SAD were considered simultaneously with quartiles of either WC or BMI, only SAD quartiles 3 (p<0.05 vs quartile 1) and 4 (p<0.001 vs quartile 1) remained associated with increased dysglycemia. Based on continuous adiposity indicators, analyses of the area under the receiver operating characteristic curve (AUC) indicated that the dysglycemia model fit for SAD (age-adjusted) was 0.734 for men (greater than the AUC for WC, p<0.001) and 0.764 for women (greater than the AUC for WC or BMI, p<0.001).

Conclusions

Measured inexpensively by bedside caliper, SAD was associated with dysglycemia independently of WC or BMI. Standardized SAD measurements may enhance assessment of dysfunctional adiposity.

Hypoglycaemic role of wheatgrass and its effect on carbohydrate metabolic enzymes in type II diabetic rats

Diabetes mellitus (DM) is a leading cause of morbidity and mortality in the world. Insulin resistance and insulin insufficiency is the major factor for the prognosis of type II diabetes. Consistent high glucose level leads to multiple secondary complications in diabetic patients. Hence, hypoglycaemic drugs are of significance for reducing the risk of secondary complications in type II diabetes. Various hypoglycaemic drugs are already available in the market, but they are associated with several side effects. Therefore, traditional herbs have emerged as safer alternative for effective hypoglycaemic treatment. The juvenile grass of common wheat is known as wheatgrass (WG). It is commonly used as a health drink and has potent antioxidant efficacy. It has been used to cure DM in folk medicine. The current study was planned to test the hypoglycaemic effect and pathways regulated by WG on DM. We analysed the glucose and insulin levels in plasma, the activity of glucose oxidative enzymes, hexokinase and glucose 6 phosphate dehydrogenase, in serum and glycogen levels in liver of the male albino Wistar rats. Activity of glucose oxidative enzymes and the levels of insulin and liver glycogen were decreased in rats with diabetes, but they were reversed on treatment with WG. Hence, we conclude that WG can act as a potent anti-hyperglycaemic agent.

HCC development is associated to peripheral insulin resistance in a mouse model of NASH

NAFLD is the most common liver disease worldwide but it is the potential evolution to NASH and eventually to hepatocellular carcinoma (HCC), even in the absence of cirrhosis, that makes NAFLD of such clinical importance. Aim: we aimed to create a mouse model reproducing the pathological spectrum of NAFLD and to investigate the role of possible co-factors in promoting HCC. Methods: mice were treated with a choline-deficient L-amino-acid-defined-diet (CDAA) or its control (CSAA diet) and subjected to a low-dose i.p. injection of CCl₄ or vehicle. Insulin resistance was measured by the euglycemic-hyperinsulinemic clamp method. Steatosis, fibrosis and HCC were evaluated by histological and molecular analysis. Results: CDAA-treated mice showed peripheral insulin resistance at 1 month. At 1–3 months, extensive steatosis and fibrosis were observed in CDAA and CDAA+CCl₄ groups. At 6 months, equal increase in steatosis and fibrosis was observed between the two groups, together with the appearance of tumor. At 9 months of treatment, the 100% of CDAA+CCl₄ treated mice revealed tumor versus 40% of CDAA mice. Insulin-like Growth Factor-2 (IGF-2) and Osteopontin (SPP-1) were increased in CDAA mice versus CSAA. Furthermore, Immunostaining for p-AKT, p-c-Myc and Glypican-3 revealed increased positivity in the tumors. Conclusions: the CDAA model promotes the development of HCC from NAFLD-NASH in the presence of insulin resistance but in the absence of cirrhosis. Since this condition is increasingly recognized in humans, our study provides a model that may help understanding mechanisms of carcinogenesis in NAFLD.

Risk factors contributing to type 2 diabetes and recent advances in the treatment and prevention

Type 2 diabetes is a serious and common chronic disease resulting from a complex inheritance-environment interaction along with other risk factors such as obesity and sedentary lifestyle. Type 2 diabetes and its complications constitute a major worldwide public health problem, affecting almost all populations in both developed and developing countries with high rates of diabetes-related morbidity and mortality. The prevalence of type 2 diabetes has been increasing exponentially, and a high prevalence rate has been observed in developing countries and in populations undergoing "westernization" or modernization. Multiple risk factors of diabetes, delayed diagnosis until micro- and macro-vascular complications arise, life-threatening complications, failure of the current therapies, and financial costs for the treatment of this disease, make it necessary to develop new efficient therapy strategies and appropriate prevention measures for the control of type 2 diabetes. Herein, we summarize our current understanding about the epidemiology of type 2 diabetes, the roles of genes, lifestyle and other factors contributing to rapid increase in the incidence of type 2 diabetes. The core aims are to bring forward the new therapy strategies and cost-effective intervention trials of type 2 diabetes.

Effects of Chinese Fructus Mume formula and its separated prescription extract on insulin resistance in type 2 diabetic rats

The effect of Fructus Mume formula and its separated prescription extract on insulin resistance in type 2 diabetic rats was investigated. The rat model of type 2 diabetes was established by feeding on a high-fat diet for 8 weeks and by subsequently intravenous injection of small doses of streptozotocin. Rats in treatment groups, including the Fructus Mume formula treatment group (FM), the cold property herbs of Fructus Mume formula treatment group (CFM), the warm property herbs of Fructus Mume formula treatment group (WFM), were administrated with Fructus Mume formula and its separated prescription extract by gavage, while the rats in diabetic model group (DM) and metformin group (MET) were given by gavage with normal saline and metformin correspondingly. The body weight before and after treatment was measured, and the oral glucose tolerance test (OGTT) and the insulin release test (IRT) were performed. The homeostasis model assessment-insulin resistance index (HOMA-IR) was calculated. The protein and mRNA expression levels of Insr, β-arrestin-2, Irs-1 and Glut-4 in the liver, skeletal muscle and fat tissues were detected by using Western blotting and RT-PCR respectively. The results demonstrated that, as compared with DM group, OGTT, IRT (0 h, 1 h) levels and HOMR-IR in treatment groups were all reduced, meanwhile their protein and mRNA expression levels of Insr, Irs-1 and Glut-4 in the liver, skeletal muscle and fat tissues were obviously increased, and their protein and mRNA expression levels of β-arrestin-2 in the liver and skeletal muscle tissues were also markedly increased. It was suggested that the Fructus Mume formula and its separated prescription extracts could effectively improve insulin resistance in type 2 diabetic rats, which might be related to the up-regulated expression of Insr, Irs-1 and Glut-4 in the liver, skeletal muscle and fat tissues, and β-arrestin-2 in the liver and skeletal muscle tissues.

Potential Roles of Stevia rebaudiana Bertoni in Abrogating Insulin Resistance and Diabetes: A Review

Insulin resistance is a key factor in metabolic disorders like hyperglycemia and hyperinsulinemia, which are promoted by obesity and may later lead to Type II diabetes mellitus. In recent years, researchers have identified links between insulin resistance and many noncommunicable illnesses other than diabetes. Hence, studying insulin resistance is of particular importance in unravelling the pathways employed by such diseases. In this review, mechanisms involving free fatty acids, adipocytokines such as TNFα and PPARγ and serine kinases like JNK and IKKβ, asserted to be responsible in the development of insulin resistance, will be discussed. Suggested mechanisms for actions in normal and disrupted states were also visualised in several manually constructed diagrams to capture an overall view of the insulin-signalling pathway and its related components. The underlying constituents of medicinal significance found in the Stevia rebaudiana Bertoni plant (among other plants that potentiate antihyperglycemic activities) were explored in further depth. Understanding these factors and their mechanisms may be essential for comprehending the progression of insulin resistance towards the development of diabetes mellitus.

Non-alcoholic fatty liver disease (NAFLD) and its connection with insulin resistance, dyslipidemia, atherosclerosis and coronary heart disease

Non-alcoholic fatty liver disease is marked by hepatic fat accumulation not due to alcohol abuse. Several studies have demonstrated that NAFLD is associated with insulin resistance leading to a resistance in the antilipolytic effect of insulin in the adipose tissue with an increase of free fatty acids (FFAs). The increase of FFAs induces mitochondrial dysfunction and development of lipotoxicity. Moreover, in subjects with NAFLD, ectopic fat also accumulates as cardiac and pancreatic fat. In this review we analyzed the mechanisms that relate NAFLD with metabolic syndrome and dyslipidemia and its association with the development and progression of cardiovascular disease.

Oxidative stress and protein carbonylation in adipose tissue - implications for insulin resistance and diabetes mellitus

While historically considered simply as a depot for excess energy, white adipose tissue is a dynamically active endocrine organ capable of responding to a variety of efferent stimuli resulting in the synthesis and secretion of peptides, proteins and metabolites that serve as signal transducers to the peripheral and central circulation. Such regulation controls a variety of physiological processes including energy expenditure, food intake, reproductive capacity and responsiveness to insulin. Indeed, the accumulation of inflammatory cells in white adipose tissue is considered to be causative in the development of insulin resistance and eventually type 2 diabetes mellitus. A large body of evidence suggests that oxidative stress in adipose tissue not only correlates with insulin resistance but is also causative in its development. Moreover, using the available plasma oxidative stress biomarkers, many clinical studies have shown the presence of systemic oxidative stress in obese insulin resistant subjects, and its decrease after the successful treatment of obesity. In this review we emphasize the role of protein carbonylation in dysfunctional obese white adipose tissue and its metabolic implications. We focus on glutathione S-transferase A4 as the key enzyme for trans-4-hydroxy-2-nonenal and trans-4-oxo-2-nonenal removal from the cell, thus preventing protein carbonylation. This article is part of a Special Issue entitled: Posttranslational Protein modifications in biology and Medicine.

Adequate prescribing of medication does not necessarily translate into good control of diabetes mellitus

BACKGROUND

Patients with diabetes mellitus in Lithuania have access to almost all the latest blood glucose-lowering drugs available in the rest of the world. This study evaluated the effects of prescribing of treatment (oral medications, insulin, or both) in Lithuanian patients with type 1 or 2 diabetes and poor blood glucose control.

METHODS

The relevant information was obtained from specialized questionnaires completed by 26 consulting endocrinologists in Lithuania between October 1, 2008 and December 31, 2008. The study cohort comprised 865 randomly selected patients with diabetes mellitus and a glycosylated (HbA1c) level ≥7%. In total, there were 95 patients with type 1 diabetes and 770 with type 2 diabetes.

RESULTS

Linear regression for patients with type 1 diabetes revealed a weak trend towards higher doses of insulin reflecting lower HbA1c values. The mean dose of insulin in patients with type 1 diabetes before an endocrinology consultation was 57.1 ± 15.7 U/day (0.8 ± 0.2 U/kg), which increased significantly to 63.3 ± 16.5 U/day (0.9 ± 0.2 U/kg) after an endocrinology consultation (P < 0.05). Treatment prescribed for patients with type 2 diabetes depended on the duration of disease. Earlier treatment recommended for 68% of patients with type 2 diabetes was subsequently changed by the endocrinologist. Linear regression showed that the insulin dose prescribed before a specialist consultation as well as that recommended by an endocrinologist was significantly correlated with body mass index.

CONCLUSION

Appropriate prescribing of blood glucose-lowering drugs does not always translate into good metabolic control of diabetes mellitus. The mean HbA1c was 8.5% ± 1.3% in patients with type 2 diabetes treated with oral drugs alone versus 9.0% ± 1.3% in those treated with insulin alone.

Alternatively activated macrophages in types 1 and 2 diabetes

Macrophages are innate immune cells derived from monocytes, which, in turn, arise from myeloid precursor cells in the bone marrow. Macrophages have many important roles in the innate and adaptive immune response, as well as in tissue homeostasis. Two major populations have been defined: The classically activated macrophages that respond to intracellular pathogens by secreting proinflammatory cytokines and reactive oxygen species and alternatively activated macrophages which are induced during Th2 responses displaying anti-inflammatory activities. Both macrophage populations are central players in diabetes, the first one triggering inflammatory responses which initiates insulitis and pancreatic β cell death during type 1 diabetes, whereas the second population decreases hyperglycemia, insulitis, and inflammation in the pancreas, thereby negatively regulate type 1 diabetes. Obesity is an important factor in the development of type 2 diabetes; classically activated macrophages are a dominant cell population involved in the establishment of the inflammatory profile, insulin resistance, and activation of inflammatory signals during the development and progression of this disease. In contrast, alternatively activated macrophages regulate the release of proinflammatory cytokines, attenuating adipose tissue inflammation. Here, we review the advantages and disadvantages of these two macrophage populations with regard to their roles in types 1 and 2 diabetes.

Ultrastructural morphometric analysis of insulin secretory granules in human type 2 diabetes

We performed an ultrastructural morphometric analysis of insulin secretory granules in pancreatic beta cells from control and type 2 diabetic multiorgan donors. The volume density of insulin granules significantly (p < 0.05) reduced in beta cells from type 2 diabetic patients with respect to non-diabetic subjects, and this reduction was mainly attributable to a decrease in mature granules. On the contrary, no significant difference was observed in the volume density of docked granules between controls and type 2 diabetic patients. In addition, there was a significant positive correlation between the density volume of total insulin granules and stimulated insulin secretion in non-diabetic islets. In conclusion, we detected significant changes in the intracellular distribution of insulin secretory granules within the beta cell that might be related with the alterations in insulin secretion observed in type 2 diabetes patients.

The fat controller: adipocyte development

Obesity is a condition characterized by excess adipose tissue that results from positive energy balance and is the most common metabolic disorder in the industrialized world. The obesity epidemic shows no sign of slowing, and it is increasingly a global problem. Serious clinical problems associated with obesity include an increased risk for type 2 diabetes, atherosclerosis, and cancer. Hence, understanding the origin and development of adipocytes and adipose tissue will be critical to the analysis and treatment of metabolic diseases. Historically, albeit incorrectly, adipocytes were thought to be inert cells whose singular function was lipid storage. It is now known that adipocytes have other critical functions; the most important include sensitivity to insulin and the ability to produce and secrete adipocyte-specific endocrine hormones that regulate energy homeostasis in other tissues. Today, adipocytes are recognized as critical regulators of whole-body metabolism and known to be involved in the pathogenesis of a variety of metabolic diseases. All cells come from other cells and many cells arise from precursor cells. Adipocytes are not created from other adipocytes, but they arise from precursor cells. In the last two decades, scientists have discovered the function of many proteins that influence the ability of precursor cells to become adipocytes. If the expansion of the adipose tissue is the problem, it seems logical that adipocyte development inhibitors could be a viable anti-obesity therapeutic. However, factors that block adipocyte development and limit adipocyte expansion also impair metabolic health. This notion may be counterintuitive, but several lines of evidence support the idea that blocking adipocyte development is unhealthy. For this reason it is clear that we need a better understanding of adipocyte development.

miRNAs and diabetes mellitus

Diabetes is a chronic disease that manifests when insulin production by the pancreas is insufficient or when the body cannot effectively utilize the secreted insulin. The onset of diabetes often goes undetected until the later stages where subsequent glucose accumulation in the system (hyperglycemia) is observed. Over time, it leads to serious multi-organ damage, especially to the nerves and blood vessels. The WHO reports that approximately 346 million people worldwide are diagnosed with diabetes. With no cure available, long-term medical care for diabetes has become a global economic challenge globally. Hence, there is a need to explore novel early biomarkers and therapeutics for diabetes. One such potential molecule is the miRNAs. miRNAs are endogenous, noncoding RNAs that predominantly inhibit gene expression. Compelling evidence showed that altered miRNA expressions are linked to pathological conditions, including diabetes manifestation. This review focuses on the implications of miRNAs in diabetes and their related complications.