Future detection and monitoring of diabetes may entail analysis of both β-cell function and volume: how markers of β-cell loss may assist

Hepatopancreatic metabolic disorders and their implications in the development of Alzheimer's disease and vascular dementia

Dementia has been faced with significant public health challenges and economic burdens that urges the need to develop safe and effective interventions. In recent years, an increasing number of studies have focused on the relationship between dementia and liver and pancreatic metabolic disorders that result in diseases such as diabetes, obesity, hypertension and dyslipidemia. Previous reports have shown that there is a plausible correlation between pathologies caused by hepatopancreatic dysfunctions and dementia. Glucose, insulin and IGF-1 metabolized in the liver and pancreas probably have an important influence on the pathophysiology of the most common dementias: Alzheimer's and vascular dementia. This current review highlights recent studies aimed at identifying convergent mechanisms, such as insulin resistance and other diseases, linked to altered hepatic and pancreatic metabolism, which are capable of causing brain changes that ultimately lead to dementia.

Serum microcystin-LR levels and risk of gestational diabetes mellitus: A Chinese nested case-control study

Background

Previous experimental studies have reported an association between microcystin-LR (MC-LR) and glucose homeostasis, but whether exposure to MC-LR is a risk factor for the pathogenesis of gestational diabetes mellitus (GDM) requires further epidemiological study. This study aims to explore the effects of MC-LR on GDM.

Methods

A prospective nested case-control study was performed in the Hunan Provincial Maternal and Child Health Hospital (HPMCHH) in South China. A total of 119 patients with GDM and 238 controls were enrolled in the study. The two independent samples t-test, or chi-square test was used to compare the difference between the GDM group and the non-GDM group. Binary logistic regression was used to obtain odds ratios (ORs) by controlling for confounders.

Results

The cumulative incidence of GDM in our sample was 13.7%. The detection rate of MC-LR in the GDM group were significantly higher than those in the control group (44.2% vs. 29.4%; p=0.007). Our results show that an elevated serum MC-LR level in the first trimester of pregnancy was related to an increased risk of GDM (OR: 1.924; 95% CI: 1.092-3.391; p<0.05). When stratified by age, educational level, parity, and passive smoking, significantly relationships were observed among those aged >30 years, lower income, higher education, none passive smoking, and more likely to be multiparous.

Conclusions

Our data reveals that serum MC-LR level in the first trimester is independently associated with GDM.

Progression from prediabetes to type 2 diabetes mellitus induced by overnutrition

Prediabetes has developed into a global pandemic, its prevalence increasing year by year. Although lifestyle changes are advocated as the basis for prediabetes treatment, some patients fail to choose or adhere to appropriate interventions. The basis for selecting an appropriate intervention is determining the stage and cause of the disease. In this review, we aimed to examine the various types and disease processes of prediabetes caused by overnutrition, the present review supporting the hypothesis that overnutrition-induced hyperinsulinemia precedes insulin resistance (IR) and independently causes β-cell dysfunction. Tissue insulin resistance is the main feature of prediabetes with the crosstalk between tissues promoting the formation of systemic insulin resistance. Finally, both β-cell dysfunction induced by hyperinsulinemia or IR and reduced β-cell mass can lead to abnormal insulin secretion and contribute to development of type 2 diabetes mellitus (T2DM). Hence, overnutrition can cause multiple prediabetes phenotypes resulting in development of T2DM through different trajectories. Future diagnosis and treatment should therefore more carefully consider the disease phenotype and stage of development in patients with prediabetes to reduce the incidence of T2DM.

Protective effect of fermented Diospyros lotus L. extracts against the high glucose-induced apoptosis of MIN6 cells

Date plum persimmon (Diospyros lotus L.) is a fruit crop from the Ebenaceae family. Its microorganism-fermented extract (DPEML) was shown to exhibit a hypoglycemic effect in our previous work. Here, we investigated the effects of DPEML fermented by Microbacterium flavum YM18-098 and Lactobacillus plantarum B7 on the high glucose-induced apoptosis of MIN6 cells and explored its potential cell protective mechanisms. DPEML ameliorated the apoptosis of MIN6 cells cultured under high glucose conditions, thereby improving cell viability. DPEML upregulated the Bcl-2/Bax mRNA ratio to obstruct an intrinsic apoptotic pathway and concomitantly downregulated the expression of the apoptosis-linked proteins, AIF, and Cyt-C, in high glucose-induced MIN6 cells. Furthermore, DPEML promoted the insulin secretion of MIN6 cells grown under chronically high-glucose conditions by upregulating Ins mRNA expression. In summary, our study suggested that DPEML is a promising functional food for the development of therapeutics for the treatment of Type 2 diabetes mellitus. PRACTICAL APPLICATIONS: We investigated the effects of DPEML fermented by Microbacterium flavum YM18-098 and Lactobacillus plantarum B7 on the high glucose-induced apoptosis of MIN6 cells and explored its potential cell protective mechanisms. DPEML ameliorated the apoptosis of MIN6 cells cultured under high glucose conditions, thereby improving cell viability. DPEML upregulated the Bcl-2/Bax mRNA ratio to obstruct an intrinsic apoptotic pathway and concomitantly downregulated the expression of the apoptosis-linked proteins, AIF and Cyt-C, in high glucose-induced MIN6 cells. Furthermore, DPEML promoted the insulin secretion of MIN6 cells grown under chronically high-glucose conditions by upregulating Ins mRNA expression. We suggested that DPEML is a promising functional food for the development of therapeutics for the treatment of Type 2 diabetes mellitus.

Analysis of Patents Issued in China for Antihyperglycemic Therapies for Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is prevalent, with a dramatic increase in recent years. Moreover, its microvascular and macrovascular complications cause significant societal issues. The demand for new and effective antidiabetic therapies grows with each passing day and motivates organizations and individuals to pay more attention to such products. In this article, we focused on oral antihyperglycemic drugs patented in China and introduced them according to their antihyperglycemic mechanisms. By searching the website of State Intellectual Property Office of the People's Republic of China (http://www.sipo.gov.cn), 2,500 antihyperglycemic patents for T2DM were identified and analyzed. These consisted of 4 patents for derivatives of herbal extracts (0.2%), 162 patents for herbal extracts (6.5%), 61 compositions for traditional Chinese medicine (TCM) (2.4%), 2,263 patents for synthetic compounds (90.5%), and 10 (0.4%) patents of the combination of synthetic compounds and TCM. As the most common drugs for diabetes mellitus, synthetic compounds can also be classified into several categories according to their working mechanisms, such as insulin secretion promotor agents, insulin sensitizer agents, α-glucosidase inhibitors, and so forth. This article discussed the chemical structure, potential antihyperglycemic mechanism of these antihyperglycemic drugs in patents in China. Expert opinion: Insulin sensitivity and β-cell function could be improved by weight loss to prevent prediabetes into T2DM. However, 40-50% patients with impaired glucose tolerance (IGT) still progress to T2DM, even after successful long-term weight loss. Antihyperglycemic remedies provide a treatment option to improve insulin sensitivity and maintain β-cell function. Combination therapy is the best treatment for diabetes. Combination therapy can reduce the dosage of each single drug option, and avoid the side effects. Drugs with different mechanisms are complementary, and are better adapted to patients with changing conditions. Classical combination therapies include combinations such as sulfonylureas plus biguanides or glucosidase inhibitors, biguanide plus glucosidase inhibitors or insulin sensitizers, insulin treatment plus biguanides or glucosidase inhibitors. The general principle of combination therapy is that two drugs with different mechanisms are selected jointly, and the combination of three types of hypoglycemic drugs is not recommended. After reading a large amount of literature, we have rarely found a case of three oral hypoglycemic agents, which may mean that the combination of three oral hypoglycemic agents is unnecessary and has unpredictable risks. There is no objection to the idea of multi-drug therapy. But multiple drugs can only be used when it shows a significant benefit to the patients. Combined use of multiple antidiabetic drugs poses a risk to patients due to drug interactions and overtreatment.

Secretagogin is increased in plasma from type 2 diabetes patients and potentially reflects stress and islet dysfunction

Beta cell dysfunction accompanies and drives the progression of type 2 diabetes mellitus (T2D), but there are few clinical biomarkers available to assess islet cell stress in humans. Secretagogin, a protein enriched in pancreatic islets, demonstrates protective effects on beta cell function in animals. However, its potential as a circulating biomarker released from human beta cells and islets has not been studied. In this study primary human islets, beta cells and plasma samples were used to explore secretion and expression of secretagogin in relation to the T2D pathology. Secretagogin was abundantly and specifically expressed and secreted from human islets. Furthermore, T2D patients had an elevated plasma level of secretagogin compared with matched healthy controls, which was confirmed in plasma of diabetic mice transplanted with human islets. Additionally, the plasma secretagogin level of the human cohort had an inverse correlation to clinical assessments of beta cell function. To explore the mechanism of secretagogin release in vitro, human beta cells (EndoC-βH1) were exposed to elevated glucose or cellular stress-inducing agents. Secretagogin was not released in parallel with glucose stimulated insulin release, but was markedly elevated in response to endoplasmic reticulum stressors and cytokines. These findings indicate that secretagogin is a potential novel biomarker, reflecting stress and islet cell dysfunction in T2D patients.

Serum Vitamin D and Its Upregulated Protein, Thioredoxin Interacting Protein, Are Associated With Beta-Cell Dysfunction in Adult Patients With Type 1 and Type 2 Diabetes

OBJECTIVES

Diabetes mellitus is characterized by either complete deficiency of insulin secretion, as in type 1 diabetes, or decompensation of the pancreatic beta cells in type 2 diabetes. Both vitamin D (vitD) and thioredoxin interacting protein (TXNIP) have been shown to be involved in beta-cell dysfunction. Therefore, this study was designed to examine vitD and TXNIP serum levels in patients with diabetes and to correlate these levels with beta-cell function markers in both types of diabetes.

METHODS

The routine biochemical parameters and the serum levels of vitD and TXNIP were measured in 20 patients with type 1 diabetes and 20 patients with type 2 diabetes. The levels were then compared to those of 15 healthy control volunteers. Insulin, C-peptide and proinsulin (PI), vitD and TXNIP were measured by ELISA. Beta-cell dysfunction was assessed by homeostatic model assessment (HOMA-beta), proinsulin-to-C-peptide (PI/C) and proinsulin-to-insulin (PI/I) ratios. Correlations among various parameters were studied.

RESULTS

Patients with type 1 diabetes had significantly lower HOMA-beta, vitD and TXNIP levels; however, they had higher PI/C levels than the control group. Meanwhile, patients with type 2 diabetes had significantly higher C-peptide, proinsulin, PI/C, HOMA-insulin resistance (HOMA-IR) and lower HOMA-beta and vitD levels, with no significant difference in TXNIP levels as compared to the control group. In addition, vitD was significantly correlated positively with HOMA-beta and TXNIP and negatively with PI, PI/C, PI/I and HOMA-IR. TXNIP correlated positively with HOMA-beta and negatively with PI/C.

CONCLUSIONS

Our data showed that vitD and TXNIP were associated with different beta-cell dysfunction markers, indicating their potential abilities to predict the beta-cell status in people with diabetes.

Microcystin-LR induces dysfunction of insulin secretion in rat insulinoma (INS-1) cells: Implications for diabetes mellitus

Microcystins (MCs) are the most frequent cyanobacterial toxins observed in freshwater systems. Accumulating evidence suggests that MCs pose a serious threat to public health. However, the contributions of the exposure of MCs to the occurrence of human diseases remain largely unknown. This study provides the evidence of the effects of MC-LR on pancreatic β-cell function through the exposure of rat insulinoma (INS-1) cells to 0, 10, 20, or 40μM MC-LR for 72h and explores the underlying molecular mechanisms. Our results demonstrate that exposure to MC-LR for 72h suppresses cell viability, disturbs glucose-stimulated insulin secretion (GSIS), and decreases the expression of insulin protein. Moreover, MC-LR disrupts the cell cycle distribution and increases cell apoptosis at 20 or 40μM for 72h, respectively, indicating that the β-cell mass would be decreased by MC-LR exposure. A transcriptomic analysis revealed several key genes (e.g., Pdx-1, Neurod1, and Abcc8) involved in insulin secretion are significantly differentially expressed in INS-1 cells in response to MC-LR exposure. In addition, several signal transduction pathways associated with diabetes (e.g., type 1 and 2 diabetes) were also identified compared with the control cells. We recommend that MC be considered as a new environmental factor that promotes diabetes development. The identified key genes or pathways may potentially contribute to the future therapies in the environmental contaminants induced β-cell damage.

Transcription factor Ets-1 links glucotoxicity to pancreatic beta cell dysfunction through inhibiting PDX-1 expression in rodent models

AIMS/HYPOTHESIS

'Glucotoxicity' is a term used to convey the negative effect of hyperglycaemia on beta cell function; however, the underlying molecular mechanisms that impair insulin secretion and gene expression are poorly defined. Our objective was to define the role of transcription factor v-ets avian erythroblastosis virus E26 oncogene homologue 1 (Ets-1) in beta cell glucotoxicity.

METHODS

Primary islets and Min6 cells were exposed to high glucose and Ets-1 expression was measured. Recombinant adenovirus and transgenic mice were used to upregulate Ets-1 expression in beta cells in vitro and in vivo, and insulin secretion was assessed. The binding activity of H3/H4 histone on the Ets-1 promoter, and that of forkhead box (FOX)A2, FOXO1 and Ets-1 on the Pdx-1 promoter was measured by chromatin immunoprecipitation and quantitative real-time PCR assay.

RESULTS

High glucose induced upregulation of Ets-1 expression and hyperacetylation of histone H3 and H4 at the Ets-1 gene promoter in beta cells. Ets-1 overexpression dramatically suppressed insulin secretion and biosynthesis both in vivo and in vitro. Besides, Ets-1 overexpression increased the activity of FOXO1 but decreased that of FOXA2 binding to the pancreatic and duodenal homeobox 1 (PDX-1) homology region 2 (PH2), resulting in inhibition of Pdx-1 promoter activity and downregulation of PDX-1 expression and activity. In addition, high glucose promoted the interaction of Ets-1 and FOXO1, and the activity of Ets-1 binding to the Pdx-1 promoter. Importantly, PDX-1 overexpression reversed the defect in pancreatic beta cells induced by Ets-1 excess, while knockdown of Ets-1 prevented hyperglycaemia-induced dysfunction of pancreatic beta cells.

CONCLUSIONS/INTERPRETATION

Our observations suggest that Ets-1 links glucotoxicity to pancreatic beta cell dysfunction through inhibiting PDX-1 expression in type 2 diabetes.

β-cell failure in type 2 diabetes: postulated mechanisms and prospects for prevention and treatment

OBJECTIVE

This article examines the foundation of β-cell failure in type 2 diabetes (T2D) and suggests areas for future research on the underlying mechanisms that may lead to improved prevention and treatment.

RESEARCH DESIGN AND METHODS

A group of experts participated in a conference on 14-16 October 2013 cosponsored by the Endocrine Society and the American Diabetes Association. A writing group prepared this summary and recommendations.

RESULTS

The writing group based this article on conference presentations, discussion, and debate. Topics covered include genetic predisposition, foundations of β-cell failure, natural history of β-cell failure, and impact of therapeutic interventions.

CONCLUSIONS

β-Cell failure is central to the development and progression of T2D. It antedates and predicts diabetes onset and progression, is in part genetically determined, and often can be identified with accuracy even though current tests are cumbersome and not well standardized. Multiple pathways underlie decreased β-cell function and mass, some of which may be shared and may also be a consequence of processes that initially caused dysfunction. Goals for future research include to 1) impact the natural history of β-cell failure; 2) identify and characterize genetic loci for T2D; 3) target β-cell signaling, metabolic, and genetic pathways to improve function/mass; 4) develop alternative sources of β-cells for cell-based therapy; 5) focus on metabolic environment to provide indirect benefit to β-cells; 6) improve understanding of the physiology of responses to bypass surgery; and 7) identify circulating factors and neuronal circuits underlying the axis of communication between the brain and β-cells.

β-cell failure in type 2 diabetes: postulated mechanisms and prospects for prevention and treatment

OBJECTIVE

This article examines the foundation of β-cell failure in type 2 diabetes (T2D) and suggests areas for future research on the underlying mechanisms that may lead to improved prevention and treatment.

RESEARCH DESIGN AND METHODS

A group of experts participated in a conference on 14-16 October 2013 cosponsored by the Endocrine Society and the American Diabetes Association. A writing group prepared this summary and recommendations.

RESULTS

The writing group based this article on conference presentations, discussion, and debate. Topics covered include genetic predisposition, foundations of β-cell failure, natural history of β-cell failure, and impact of therapeutic interventions.

CONCLUSIONS

β-Cell failure is central to the development and progression of T2D. It antedates and predicts diabetes onset and progression, is in part genetically determined, and often can be identified with accuracy even though current tests are cumbersome and not well standardized. Multiple pathways underlie decreased β-cell function and mass, some of which may be shared and may also be a consequence of processes that initially caused dysfunction. Goals for future research include to (1) impact the natural history of β-cell failure; (2) identify and characterize genetic loci for T2D; (3) target β-cell signaling, metabolic, and genetic pathways to improve function/mass; (4) develop alternative sources of β-cells for cell-based therapy; (5) focus on metabolic environment to provide indirect benefit to β-cells; (6) improve understanding of the physiology of responses to bypass surgery; and (7) identify circulating factors and neuronal circuits underlying the axis of communication between the brain and β-cells.