Tumor necrosis factor-α-induced changes in insulin-producing β-cells

Microbiota and Glucidic Metabolism: A Link with Multiple Aspects and Perspectives

The global prevalence of overweight and obesity has dramatically increased in the last few decades, with a significant socioeconomic burden. In this narrative review, we include clinical studies aiming to provide the necessary knowledge on the role of the gut microbiota in the development of diabetic pathology and glucose-metabolism-related disorders. In particular, the role of a certain microbial composition of the fermentative type seems to emerge without a specific link to the development in certain subjects of obesity and the chronic inflammation of the adipose tissues, which underlies the pathological development of all the diseases related to glucose metabolism and metabolic syndrome. The gut microbiota plays an important role in glucose tolerance. Conclusion. New knowledge and new information is presented on the development of individualized therapies for patients affected by all the conditions related to reduced glucose tolerance and insulin resistance.

Potentials of curcumin against polycystic ovary syndrome: Pharmacological insights and therapeutic promises

Polycystic ovary syndrome (PCOS) is a common hormonal disorder among women (4%-20%) when the ovaries create abnormally high levels of androgens, the male sex hormones that are typically present in women in trace amounts. The primary characteristics of PCOS include oxidative stress, inflammation, hyperglycemia, hyperlipidemia, hyperandrogenism, and insulin resistance. Generally, metformin, spironolactone, eflornithine and oral contraceptives are used to treat PCOS, despite their several side effects. Therefore, finding a potential candidate for treating PCOS is necessary. Curcumin is a major active natural polyphenolic compound derived from turmeric (Curcuma longa). A substantial number of studies have shown that curcumin has anti-inflammatory, anti-oxidative stress, antibacterial, and anti-apoptotic activities. In addition, curcumin reduces hyperglycemia, hyperlipidemia, hyperandrogenism, and insulin resistance in various conditions, including PCOS. The review highlighted the therapeutic aspects of curcumin against the pathophysiology of PCOS. We also offer a hypothesis to improve the development of medicines based on curcumin against PCOS.

Adipose Tissue Secretion Pattern Influences β-Cell Wellness in the Transition from Obesity to Type 2 Diabetes

The dysregulation of the β-cell functional mass, which is a reduction in the number of β-cells and their ability to secure adequate insulin secretion, represents a key mechanistic factor leading to the onset of type 2 diabetes (T2D). Obesity is recognised as a leading cause of β-cell loss and dysfunction and a risk factor for T2D. The natural history of β-cell failure in obesity-induced T2D can be divided into three steps: (1) β-cell compensatory hyperplasia and insulin hypersecretion, (2) insulin secretory dysfunction, and (3) loss of β-cell mass. Adipose tissue (AT) secretes many hormones/cytokines (adipokines) and fatty acids that can directly influence β-cell function and viability. As this secretory pattern is altered in obese and diabetic patients, it is expected that the cross-talk between AT and pancreatic β-cells could drive the maintenance of the β-cell integrity under physiological conditions and contribute to the reduction in the β-cell functional mass in a dysmetabolic state. In the current review, we summarise the evidence of the ability of the AT secretome to influence each step of β-cell failure, and attempt to draw a timeline of the alterations in the adipokine secretion pattern in the transition from obesity to T2D that reflects the progressive deterioration of the β-cell functional mass.

Role of the Gut Microbiome in Beta Cell and Adipose Tissue Crosstalk: A Review

In the last decades, obesity has reached epidemic proportions worldwide. Obesity is a chronic disease associated with a wide range of comorbidities, including insulin resistance and type 2 diabetes mellitus (T2D), which results in significant burden of disease and major consequences on health care systems. Of note, intricate interactions, including different signaling pathways, are necessary for the establishment and progression of these two closely related conditions. Altered cell-to-cell communication among the different players implicated in this equation leads to the perpetuation of a vicious circle associated with an increased risk for the development of obesity-related complications, such as T2D, which in turn contributes to the development of cardiovascular disease. In this regard, the dialogue between the adipocyte and pancreatic beta cells has been extensively studied, although some connections are yet to be fully elucidated. In this review, we explore the potential pathological mechanisms linking adipocyte dysfunction and pancreatic beta cell impairment/insulin resistance. In addition, we evaluate the role of emerging actors, such as the gut microbiome, in this complex crosstalk.

Good Cop, Bad Cop: The Opposing Effects of Macrophage Activation State on Maintaining or Damaging Functional β-Cell Mass

Loss of functional β-cell mass is a hallmark of Type 1 and Type 2 Diabetes. Macrophages play an integral role in the maintenance or destruction of pancreatic β-cells. The effect of the macrophage β-cell interaction is dependent on the activation state of the macrophage. Macrophages can be activated across a spectrum, from pro-inflammatory to anti-inflammatory and tissue remodeling. The factors secreted by these differentially activated macrophages and their effect on β-cells define the effect on functional β-cell mass. In this review, the spectrum of macrophage activation is discussed, as are the positive and negative effects on β-cell survival, expansion, and function as well as the defined factors released from macrophages that impinge on functional β-cell mass.

Nanocurcumin alleviates insulin resistance and pancreatic deficits in polycystic ovary syndrome rats: Insights on PI3K/AkT/mTOR and TNF-α modulations

INTRODUCTION AND AIMS

Polycystic ovary syndrome (PCOS) is a widespread endocrine disorder affecting females. Mechanisms underlying PCOS complicated pathology remain largely unknown, making current treatment only symptomatic. Increasing reports suggest impaired PI3K/AKT/mTOR pathway and tumor necrosis factor-α (TNF-α) levels are involved in cellular proliferation and metabolism-related disorders. However, rare data explored their role in PCOS. Hence, this study investigated TNF-α and pancreatic PI3K/AKT/mTOR levels in PCOS animal model and evaluated their effects on developed pancreatic deficits. Secondly; we explored the impact of nanocurcumin as powerful anti-inflammatory supplement against these developed pancreatic pathologies.

METHODS

PCOS was induced in rats using letrozole. Nanocurcumin was formulated to increase solubility and bioavailability of curcumin. Transmission electron microscopy (TEM), zeta potential and Infra-red spectroscopy (FT-IR) were used for characterization. Nanocurcumin was orally ingested for 15 days.

FINDINGS

PCOS group exhibited significant disturbance in sex hormones, oxidative stress markers, and TNF-α levels as determined by immunoassay. Western blotting revealed significant reduction of PI3K/AKT/mTOR levels leading to impaired insulin sensitivity, decreased β cells function and mass as confirmed by HOMA assessments and immunohistochemistry. Nanocurcumin significantly improved oxidative markers, glucose indices and TNF-α levels. It reinstated PI3K/AKT/mTOR levels, alleviated insulin resistance, and retained islets integrity consequently restoring normal sex hormonal levels.

SIGNIFICANCE

To the best of our knowledge, the study is the first to report pancreatic role of PI3K/AKT/mTOR and TNF-α in PCOS and the first to demonstrate nanocurcumin promising potential against PCOS-related pancreatic molecular and histological pathologies that can indeed offer better control of the disease.

Tumor Necrosis Factor-Alpha: Role in Development of Insulin Resistance and Pathogenesis of Type 2 Diabetes Mellitus

Pathogenesis of type 2 diabetes mellitus (T2DM) and development of insulin resistance are characterized by multi-stimuli factors notably glucolipotoxicity, generation of reactive oxygen species (ROS), epigenetic factors, activation of various transcriptional mediated pathways along with the augmented levels of various pro-inflammatory cytokines. Among the various pro-inflammatory cytokines, tumor necrosis factor-alpha (TNF-α) is one the most important pro-inflammatory mediator that is critically involved in the development of insulin resistance and pathogenesis of T2DM. TNF-α is mainly produced in adipocytes and/or peripheral tissues, and induces tissue-specific inflammation through the involvement of generation of ROS and activation of various transcriptional mediated pathways. The raised level of TNF-α induces insulin resistance in adipocytes and peripheral tissues by impairing the insulin signaling through serine phosphorylation that leads to the development of T2DM. Anti-TNF-α treatment strategies have been developed to reduce the incidence of insulin resistance and development of T2DM. In this article, we have briefly described how TNF-α plays crucial role to induce insulin resistance and pathogenesis of T2DM. To block the inflammatory responses by blocking TNF-α and TNF-α signaling may be an effective strategy for the treatment of insulin resistance and T2DM. J. Cell. Biochem. 119: 105-110, 2018. © 2017 Wiley Periodicals, Inc.

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.

The central role of calcium in the effects of cytokines on beta-cell function: implications for type 1 and type 2 diabetes

The appropriate regulation of intracellular calcium is a requirement for proper cell function and survival. This review focuses on the effects of proinflammatory cytokines on calcium regulation in the insulin-producing pancreatic beta-cell and how normal stimulus-secretion coupling, organelle function, and overall beta-cell viability are impacted. Proinflammatory cytokines are increasingly thought to contribute to beta-cell dysfunction not only in type 1 diabetes (T1D), but also in the progression of type 2 diabetes (T2D). Cytokine-induced disruptions in calcium handling result in reduced insulin release in response to glucose stimulation. Cytokines can alter intracellular calcium levels by depleting calcium from the endoplasmic reticulum (ER) and by increasing calcium influx from the extracellular space. Depleting ER calcium leads to protein misfolding and activation of the ER stress response. Disrupting intracellular calcium may also affect organelles, including the mitochondria and the nucleus. As a chronic condition, cytokine-induced calcium disruptions may lead to beta-cell death in T1D and T2D, although possible protective effects are also discussed. Calcium is thus central to both normal and pathological cell processes. Because the tight regulation of intracellular calcium is crucial to homeostasis, measuring the dynamics of calcium may serve as a good indicator of overall beta-cell function.

Tumor necrosis factor-α induces transcriptional activation of nuclear factor-κB in insulin-producing β-cells

We previously showed that tumor necrosis factor-α (TNF-α) induces the dysregulation of intracellular calcium [Ca(2+)](i) in β-cells by decreasing the levels of the cytoplasmic Ca(2+) binding protein calbindin-D(28k). The purpose of the present study was to test the hypothesis that TNF-α-induced dysregulation of [Ca(2+)](i) in insulin-producing β-cells causes proteolytic degradation of IκBα and consequently leads to the transcriptional activation of nuclear factor-κB (NF-κB). To test this hypothesis, rat insulinoma (RINr 1046-38) cells, which are an insulin-secreting transformed β-cell line that constitutively expresses calbindin-D(28k), were treated with increasing concentrations of TNF-α. Using the FunctionELISA procedure to measure degradation of the IκBα subunit as Phospho-IκBα, it was found that, while in the control RIN cell lysate there was no Phospho-IκBα present, in the RIN cells exposed to 2, 5, 10, 20 and 30 ng/ml TNF-α, 17.176±2.85, 17.292±4.35, 53.77±5.63, 30.58±4.89 and 12±3.27 ng/ml Phospho-IκBα/mg of total cell protein was observed, respectively (n=3, P<0.05). Upon treatment of RIN cells with 2, 5, 10, 20 and 30 ng/ml TNF-α, the relative increases in the NF-κB transcriptional activities based on the DNA binding activity of NF-κB determined using an ELISA-based kit were 6.86±0.76-, 8.42±1.27-,7.8±2.32-, 10.28±1.96- and 6.3±1.57-fold, respectively (n=3, P<0.05). The nuclear translocation of NF-κB measured by immunofluorescence showed that, while the ratio of fluorescence in nuclei to that in the cytoplasm of untreated RIN cells was 0.2078±0.0778 (n=11), in RIN cells treated with 10 ng/ ml TNF-α, the ratio was 0.6267±0.1186 (n=11), indicating a statistically significant increase (P<0.05) in the nuclear translocation of NF-κB. These observations suggest that, in insulin-producing β-cells, the TNF-α-induced degradation of IκBα leads to nuclear translocation and the transcriptional activation of NF-κB.

Metabolic syndrome in childhood predicts adult metabolic syndrome and type 2 diabetes mellitus 25 to 30 years later

OBJECTIVE

To prospectively assess the association of the metabolic syndrome in childhood with adult metabolic syndrome and type 2 diabetes mellitus (T2DM) 25 to 30 years later.

STUDY DESIGN

Data from the National Heart Lung and Blood Institute Lipid Research Clinics (LRC) Princeton Prevalence Study (1973-1976) and the Princeton Follow-up Study (PFS, 2000-2004) were used. Body mass index (BMI = kg/m(2)) was used as the obesity measure in childhood because waist circumference was not measured at the LRC. The adult T2DM status of participants and their parents was obtained by participant report or fasting blood glucose >/=126 mg/dL. A logistic analysis for clustered samples was used to predict adult metabolic syndrome and T2DM, taking into account sibling correlations in the cohort. Pediatric metabolic syndrome, age at PFS, sex, race, change in BMI percentile, parental history of diabetes, and the interaction of pediatric metabolic syndrome and parental diabetes were explanatory variables.

RESULTS

Ages ranged from 5 to 19 years in the LRC and from 30 to 48 years in the PFS. Pediatric metabolic syndrome, parental diabetes, age at follow-up, and change in age-specific BMI percentile were significant predictors of metabolic syndrome in adulthood, and pediatric metabolic syndrome, age at follow-up, black race, and parental diabetes were significant predictors of T2DM.

CONCLUSIONS

Evaluating 5- to 19-year-old children for metabolic syndrome and family history of diabetes could identify children at increased risk of adult metabolic syndrome and T2DM, allowing prospective primary prevention of these outcomes.

Insulin resistance and impaired beta cell function in rheumatoid arthritis

OBJECTIVE

To identify factors that regulate glucose metabolism in rheumatoid arthritis (RA).

METHODS

We evaluated the homeostatic model assessment of insulin resistance (HOMA-IR) and beta cell function (HOMA-B) in 94 RA patients. We investigated the relationship between characteristics known to affect glucose metabolism in the general population (age, abdominal obesity [waist circumference], hypertension, antihypertensive therapy) as well as characteristics of RA (disease activity, glucocorticoid therapy) and insulin resistance and beta cell function.

RESULTS

Patients with high-grade inflammation (high-sensitivity C-reactive protein value >1.92 mg/liter) (n = 81) were more insulin resistant than patients with low-grade inflammation (n = 13), whereas beta cell function was similar in both groups. Insulin resistance and beta cell function were similar in both groups after adjustment for waist circumference. All recorded characteristics except for age were associated with HOMA-IR or/and HOMA-B in univariate analyses. In mixed regression models, abdominal obesity and patient's assessment of disease activity (by visual analog scale) were predictors of insulin resistance. The Disease Activity Score assessed using 28-joint counts for swelling and tenderness, tender joint count, and patient's assessment of disease activity were associated with reduced beta cell function, and the cumulative dose of glucocorticoids was associated with enhanced beta cell function. The cumulative glucocorticoid dose in all study patients was a mean of only 536 mg (95% confidence interval 239-1,173). In patients with high-grade inflammation, age was further associated with impaired beta cell function, whereas use of angiotensin-converting enzyme inhibitors or angiotensin II type 1 receptor blockers was associated with enhanced beta cell function.

CONCLUSION

The modifiable factors of abdominal obesity, antihypertensive therapy, disease activity, and use of glucocorticoids appear to affect glucose metabolism in RA.