Pathophysiology of prediabetes and treatment implications for the prevention of type 2 diabetes mellitus

Exposure of cumulative atherogenic index of plasma and the development of prediabetes in middle-aged and elderly individuals: evidence from the CHARLS cohort study

BACKGROUND

The impact of dynamic changes in the degree of atherosclerosis on the development of prediabetes remains unclear. This study aims to investigate the association between cumulative atherogenic index of plasma (CumAIP) exposure during follow-up and the development of prediabetes in middle-aged and elderly individuals.

METHODS

A total of 2,939 prediabetic participants from the first wave of the China Health and Retirement Longitudinal Study (CHARLS) were included. The outcomes for these patients, including progression to diabetes and regression to normal fasting glucose (NFG), were determined using data from the third wave. CumAIP was calculated as the ratio of the average AIP values measured during the first and third waves to the total exposure duration. The association between CumAIP and the development of prediabetes was analyzed using multivariable Cox regression and restricted cubic spline (RCS) regression.

RESULTS

During a median follow-up period of 3 years, 15.21% of prediabetic patients progressed to diabetes, and 22.12% regressed to NFG. Among the groups categorized by CumAIP quartiles, the proportion of prediabetes progressing to diabetes gradually increased (Q1: 10.61%, Q2: 13.62%, Q3: 15.65%, Q4: 20.95%), while the proportion regressing to NFG gradually decreased (Q1: 23.54%, Q2: 23.71%, Q3: 22.18%, Q4: 19.05%). Multivariable-adjusted Cox regression showed a significant positive linear correlation between high CumAIP exposure and prediabetes progression, and a significant negative linear correlation with prediabetes regression. Furthermore, in a stratified analysis, it was found that compared to married individuals, those who were unmarried (including separated, divorced, widowed, or never married) had a relatively higher risk of CumAIP-related diabetes.

CONCLUSION

CumAIP is closely associated with the development of prediabetes. High CumAIP exposure not only increases the risk of prediabetes progression but also hinders its regression within a certain range. These findings suggest that monitoring and maintaining appropriate AIP levels may help prevent the deterioration of blood glucose levels.

Predicting Type 2 Diabetes Metabolic Phenotypes Using Continuous Glucose Monitoring and a Machine Learning Framework

Type 2 diabetes (T2D) and prediabetes are classically defined by the level of fasting glucose or surrogates such as hemoglobin HbA1c. This classification does not take into account the heterogeneity in the pathophysiology of glucose dysregulation, the identification of which could inform targeted approaches to diabetes treatment and prevention and/or predict clinical outcomes. We performed gold-standard metabolic tests in a cohort of individuals with early glucose dysregulation and quantified four distinct metabolic subphenotypes known to contribute to glucose dysregulation and T2D: muscle insulin resistance, β-cell dysfunction, impaired incretin action, and hepatic insulin resistance. We revealed substantial inter-individual heterogeneity, with 34% of individuals exhibiting dominance or co-dominance in muscle and/or liver IR, and 40% exhibiting dominance or co-dominance in β-cell and/or incretin deficiency. Further, with a frequently-sampled oral glucose tolerance test (OGTT), we developed a novel machine learning framework to predict metabolic subphenotypes using features from the dynamic patterns of the glucose time-series ("shape of the glucose curve"). The glucose time-series features identified insulin resistance, β-cell deficiency, and incretin defect with auROCs of 95%, 89%, and 88%, respectively. These figures are superior to currently-used estimates. The prediction of muscle insulin resistance and β-cell deficiency were validated using an independent cohort. We then tested the ability of glucose curves generated by a continuous glucose monitor (CGM) worn during at-home OGTTs to predict insulin resistance and β-cell deficiency, yielding auROC of 88% and 84%, respectively. We thus demonstrate that the prediabetic state is characterized by metabolic heterogeneity, which can be defined by the shape of the glucose curve during standardized OGTT, performed in a clinical research unit or at-home setting using CGM. The use of at-home CGM to identify muscle insulin resistance and β-cell deficiency constitutes a practical and scalable method by which to risk stratify individuals with early glucose dysregulation and inform targeted treatment to prevent T2D.

Investigating the Effects of Diet-Induced Prediabetes on Skeletal Muscle Strength in Male Sprague Dawley Rats

Type 2 diabetes mellitus, a condition preceded by prediabetes, is documented to compromise skeletal muscle health, consequently affecting skeletal muscle structure, strength, and glucose homeostasis. A disturbance in skeletal muscle functional capacity has been demonstrated to induce insulin resistance and hyperglycemia. However, the modifications in skeletal muscle function in the prediabetic state are not well elucidated. Hence, this study investigated the effects of diet-induced prediabetes on skeletal muscle strength in a prediabetic model. Male Sprague Dawley rats were randomly assigned to one of the two groups (n = 6 per group; six prediabetic (PD) and six non-pre-diabetic (NPD)). The PD group (n = 6) was induced with prediabetes for 20 weeks. The diet that was used to induce prediabetes consisted of fats (30% Kcal/g), proteins (15% Kcal/g), and carbohydrates (55% Kcal/g). In addition to the diet, the experimental animals (n = 6) were supplied with drinking water that was supplemented with 15% fructose. The control group (n = 6) was allowed access to normal rat chow, consisting of 35% carbohydrates, 30% protein, 15% fats, and 20% other components, as well as ordinary tap water. At the end of week 20, the experimental animals were diagnosed with prediabetes using the American Diabetes Association (ADA) prediabetes impaired fasting blood glucose criteria (5.6-6.9 mmol/L). Upon prediabetes diagnosis, the animals were subjected to a four-limb grip strength test to assess skeletal muscle strength at week 20. After the grip strength test was conducted, the animals were euthanized for blood and tissue collection to analyze glycated hemoglobin (HbA1c), plasma insulin, and insulin resistance using the homeostatic model of insulin resistance (HOMA-IR) index and malondialdehyde (MDA) concentration. Correlation analysis was performed to examine the associations of skeletal muscle strength with HOMA-IR, plasma glucose, HbA1c, and MDA concentration. The results demonstrated increased HbA1c, FBG, insulin, HOMA-IR, and MDA concentrations in the PD group compared to the NPD group. Grip strength was reduced in the PD group compared to the NPD group. Grip strength was negatively correlated with HbA1c, plasma glucose, HOMA-IR, and MDA concentration in the PD group. These observations suggest that diet-induced prediabetes compromises muscle function, which may contribute to increased levels of sedentary behavior during prediabetes progression, and this may contribute to the development of hyperglycemia in T2DM.

Prediabetes-Associated Changes in Skeletal Muscle Function and Their Possible Links with Diabetes: A Literature Review

The skeletal muscle plays a critical role in regulating systemic blood glucose homeostasis. Impaired skeletal muscle glucose homeostasis associated with type 2 diabetes mellitus (T2DM) has been observed to significantly affect the whole-body glucose homeostasis, thereby resulting in other diabetic complications. T2DM does not only affect skeletal muscle glucose homeostasis, but it also affects skeletal muscle structure and functional capacity. Given that T2DM is a global health burden, there is an urgent need to develop therapeutic medical therapies that will aid in the management of T2DM. Prediabetes (PreDM) is a prominent risk factor of T2DM that usually goes unnoticed in many individuals as it is an asymptomatic condition. Hence, research on PreDM is essential because establishing diabetic biomarkers during the prediabetic state would aid in preventing the development of T2DM, as PreDM is a reversible condition if it is detected in the early stages. The literature predominantly documents the changes in skeletal muscle during T2DM, but the changes in skeletal muscle during prediabetes are not well elucidated. In this review, we seek to review the existing literature on PreDM- and T2DM-associated changes in skeletal muscle function.

Efficacy and Safety of Pitavastatin in Patients with Impaired Glucose Tolerance: An Updated Review

This review provides an updated overview of the efficacy and safety of pitavastatin in patients with impaired glucose tolerance (IGT). IGT is a prediabetic state characterized by elevated blood glucose levels that do not meet the criteria for diabetes. The review explores the potential benefits of pitavastatin in reducing cardiovascular risk and improving lipid profiles in individuals with IGT. It also examines the glycemic effects of pitavastatin, including its impact on fasting blood glucose levels, insulin sensitivity, and beta-cell function. The review highlights the need for individualized treatment approaches, taking into account the patient's overall cardiovascular risk profile and glycemic control needs. While pitavastatin has shown modest improvements in glycemic control, it is not a substitute for lifestyle modifications or standard antidiabetic medications. Future directions for research include long-term follow-up studies, mechanistic investigations, and comparative analyses to further understand the glycemic effects of pitavastatin in IGT. Overall, this narrative review provides valuable insights for healthcare professionals involved in the management of individuals with IGT, emphasizing the importance of a comprehensive approach to reduce cardiovascular risk and optimize glycemic control.

Changes in insulin resistance, glucose effectiveness, and first and second phases of insulin secretion in women aged 45-60 years old in Taiwan

BACKGROUND

In women after menopause, the incidence of diabetes mellitus increases. Increased insulin resistance (IR), decreased glucose effectiveness (GE), and the first and second phases of insulin secretion (FPIS and SPIS), are the four most important factors that trigger glucose intolerance and diabetes (diabetogenic factor [DF]). In the cross-sectional study, we enrolled nondiabetic women between the ages of 45 and 60 years to observe the changes in DFs during the perimenopausal period and to elucidate the underlying mechanisms of diabetes in menopausal women.

METHODS

We randomly enrolled 4194 women who underwent health checkups. Using demographic and biochemical data, IR, FPIS, SPIS, and GE were calculated using previously published equations. The relationship between the DFs and age was evaluated using a simple correlation.

RESULTS

Body mass index, blood pressure, fasting plasma glucose, low-density lipoprotein cholesterol, triglyceride, and SPIS were higher, and GE was lower in older women (≥52 years old). A significant decrease in GE and increased SPIS were observed with age. However, no changes were observed in IR or FPIS.

CONCLUSION

The IR and FPIS did not change during perimenopause. Increased SPIS may compensate for the decrease in GE, which is probably one of the reasons for the higher incidence of diabetes in menopausal women.

Persistence or regression of prediabetes and coronary artery calcification among adults without diabetes

OBJECTIVE

The effect of changes in glycemic status on subclinical atherosclerosis is uncertain. We assessed the association of persistence, regression, or progression of prediabetes with coronary artery calcium score (CACS) as a measure of subclinical atherosclerosis.

DESIGN

A cross-sectional study, comprising 126 765 adults, and longitudinal sub-study, comprising 40 622 adults (with baseline and at least 1 follow-up computed tomography scan to assess changes in CACS), were undertaken.

METHODS

Changes in glycemic status over 1.5 years (interquartile range, 1.0-2.0) before the first CACS assessment were categorized according to 6 groups: persistent normoglycemia (reference), normoglycemia to prediabetes, normoglycemia to diabetes, prediabetes to normoglycemia, persistent prediabetes, and prediabetes to diabetes. Logistic regression was used to calculate the odds ratios (ORs) and 95% CIs for prevalent coronary artery calcification (CAC). Mixed models with random intercepts and random slopes were used to estimate 5-year CAC progression rates.

RESULTS

Mean (SD) age was 41.3 (7.0) years (74.7% male) (n = 126 765). Multivariable-adjusted OR for prevalent CAC was 1.13 (95% CI, 1.08-1.18) for persistent prediabetes, 1.05 (0.98-1.12) for regression to normoglycemia, and 1.46 (95% CI, 1.27-1.67) for progression from prediabetes to diabetes, compared with persistent normoglycemia. Coronary artery calcification progression increased significantly in all prediabetes groups. Multivariable-adjusted ratio of 5-year CAC progression rates was 1.19 (95% CI, 1.16-1.22) (persistent prediabetes), 1.11 (1.07-1.14) (regression to normoglycemia), and 1.63 (95% CI, 1.26-2.10) (progression from prediabetes to diabetes).

CONCLUSIONS

Unfavorable changes in glycemic status, including persistence of prediabetes or progression to diabetes from prediabetes, were associated with increased risk of CAC.

Prevalence and Characteristics of Prediabetes and Metabolic Syndrome in Seemingly Healthy Persons at a Health Check-Up Clinic

Purpose

This study investigated the prevalence and characteristics of prediabetes (PreDM) and metabolic syndrome (MetS) in seemingly healthy persons attending a health check-up clinic at a tertiary care hospital.

Patients and Methods

This was a cross-sectional study that enrolled 1213 subjects (339 male, 874 female) who underwent an annual health check-up at Siriraj Hospital, Bangkok, Thailand from 2009 to 2019. Factors that independently related to PreDM were analyzed using unconditional logistic regression analysis with adjustments for age, BMI, and gender.

Results

The prevalence of PreDM and MetS was 54.3% and 19.7% respectively. Participants with impaired fasting glucose (IFG) and glycated hemoglobin (HbA_1c) 38.8–46.4 mmol/mol had significantly higher waist circumference (WC) and blood pressure (BP) compared to those with IFG or HbA_1c 38.8–46.4 mmol/mol alone (P < 0.05). Among three PreDM subgroups, the average age was lowest in the HbA_1c 38.8–46.4 mmol/mol subgroup (P < 0.001). PreDM participants with MetS were older (p = 0.03), had higher WC, BP, fasting plasma glucose and serum triglyceride level (all P < 0.001) but had lower serum high-density lipoprotein (HDL) cholesterol level (P < 0.001). Multivariate analysis revealed high MetS score, obesity, and low serum HDL cholesterol level to be independently associated with PreDM with odds ratios of 9.02 (95% confidence interval [CI]: 4.03–20.18), 1.8 (95% CI: 1.07–3.04), and 1.42 (95% CI: 1.02–1.96), respectively.

Conclusion

The prevalence of PreDM and MetS was relatively high in seemingly healthy persons. Distinct PreDM subgroups with or without MetS exhibited diverse clinical and biochemical features suggesting dissimilar pathogenesis.

Epidemiology of prediabetes mellitus among hill tribe adults in Thailand

Background

Prediabetes is a major silent health problem that leads to the development of diabetes within a few years, particularly among those who have a low socioeconomic status. Hill tribe people are vulnerable to prediabetes due to their unique cultural cooking methods and their hard work on farms, as well as their low economic status and educational levels. This study aimed to estimate the prevalence of prediabetes among hill tribe people in Thailand and identify the related factors.

Methods

This cross-sectional study included participants who belong to one of the six main hill tribes: Akah, Lahu, Hmong, Yao, Karen, and Lisu. The study was conducted in 30 hill tribe villages in Chiang Rai Province, Thailand. A validated questionnaire was administered, and 5-mL blood specimens were collected. Data were collected between November 2019 and March 2020. Logistic regression was used to determine the associations between independent variables and prediabetes.

Results

A total of 1,406 participants were recruited for the study; 67.8% were women, 77.2% were between 40 and 59 years old, and 82.9% were married. The majority worked in the agricultural sector (57.2%), had an annual income ≤ 50,000 baht (67.5%), and had never attended school (69.3%). The prevalence of prediabetes was 11.2%. After controlling for age and sex, five factors were found to be associated with prediabetes. Members of the Akha and Lisu tribes had 2.03 (95% CI = 1.03–3.99) and 2.20 (95% CI = 1.10–4.42) times higher odds of having prediabetes than Karen tribe members, respectively. Those with hypertension (HT) had 1.47 (95% CI = 1.03–2.08) times higher odds of having prediabetes than those with normal blood pressure. Those with a normal total cholesterol level had 2.43 (95% CI = 1.65–3.58) times higher odds of having prediabetes than those with a high total cholesterol level. Those with a high triglyceride level had 1.64 (95% CI = 1.16–2.32) times higher odds of having prediabetes than those with a normal triglyceride level. Those with a high low-density lipoprotein cholesterol (LDL-C) level had 1.96 (95% CI = 1.30–2.96) times higher odds of having prediabetes than those with a normal LDL-C level.

Conclusion

Appropriate dietary guidelines and exercise should be promoted among hill tribe people between 30 and 59 years old to reduce the probability of developing prediabetes.

Cardiovascular profiling in the diabetic continuum: results from the population-based Gutenberg Health Study

Aims

To assess the prevalence of type 2 diabetes mellitus (T2DM) and prediabetes in the general population and to investigate the associated cardiovascular burden and clinical outcome.

Methods and Results

The study sample comprised 15,010 individuals aged 35–74 years of the population-based Gutenberg Health Study. Subjects were classified into euglycaemia, prediabetes and T2DM according to clinical and metabolic (HbA1c) information. The prevalence of prediabetes was 9.5% (n = 1415) and of T2DM 8.9% (n = 1316). Prediabetes and T2DM showed a significantly increased prevalence ratio (PR) for age, obesity, active smoking, dyslipidemia, and arterial hypertension compared to euglycaemia (for all, P < 0.0001). In a robust Poisson regression analysis, prediabetes was established as an independent predictor of clinically-prevalent cardiovascular disease (PR_prediabetes 1.20, 95% CI 1.07–1.35, P = 0.002) and represented as a risk factor for asymptomatic cardiovascular organ damage independent of traditional risk factors (PR 1.04, 95% CI 1.01–1.08, P = 0.025). Prediabetes was associated with a 1.5-fold increased 10-year risk for cardiovascular disease compared to euglycaemia. In Cox regression analysis, prediabetes (HR 2.10, 95% CI 1.76–2.51, P < 0.0001) and T2DM (HR 4.28, 95% CI 3.73–4.92, P < 0.0001) indicated for an increased risk of death. After adjustment for age, sex and traditional cardiovascular risk factors, only T2DM (HR 1.89, 95% CI 1.63–2.20, P < 0.0001) remained independently associated with increased all-cause mortality.

Conclusion

Besides T2DM, also prediabetes inherits a significant cardiovascular burden, which translates into poor clinical outcome and indicates the need for new concepts regarding the prevention of cardiometabolic disorders.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00392-021-01879-y.

Diet-induced prediabetes: effects of exercise treatment on risk factors for cardiovascular complications

BACKGROUND

An animal model of prediabetes that has been developed in our laboratory using a high fat high carbohydrate diet and lack of physical activity displays risk factors for cardiovascular complications. The effect of exercise against these risk factors in this animal model remains unknown. Therefore, we evaluated the effect of intermittent and regular exercise treatment on the risk factors for cardiovascular complications in this animal model of prediabetes.

METHODS

Following prediabetes induction, animals were randomly assigned to the following groups (n = 6): non-diabetic, prediabetic, intermittently exercising prediabetic and regularly exercising prediabetic. Exercise exposure was 7 weeks long. Body weight changes, caloric intake, blood glucose, total cholesterol, and triglyceride concentration was measured after 20 and 29 weeks while blood pressure was only measured after 29 weeks. Plasma endothelial nitric oxide synthase, malonaldehyde, glutathione peroxidase, tumour necrosis factor-alpha and C-reactive protein concentration from the heart were measured 2 weeks post-exercise termination (week 30).

RESULTS

We found increased body weight, caloric intake and mean arterial pressure in the prediabetic group by comparison to the non-prediabetic group. The same trend was observed in blood glucose and triglyceride concentrations. However, all of these parameters were reduced in the intermittently exercising prediabetic and regularly exercising prediabetic groups. This reduction was further accompanied by a decrease in the endothelial nitric oxide synthase, tumour necrosis factor-alpha and C-reactive protein concentration with improved oxidative stress biomarkers.

CONCLUSIONS

The progression of pre-diabetes to diabetes is slowed or possibly stopped by exercise (regular or intermittent). Additionally, biomarker profiles indicative of cardiovascular disease in pre-diabetics are improved by exercise.

The Mechanisms of the Development of Atherosclerosis in Prediabetes

Lifestyle changes, such as overeating and underexercising, can increase the risk of prediabetes. Diabetes is one of the leading causes of atherosclerosis, and recently it became clear that the pathophysiology of atherosclerosis progresses even before the onset of diabetic symptoms. In addition to changes in platelets and leukocytes in the hyperglycemic state and damage to vascular endothelial cells, extracellular vesicles and microRNAs were found to be involved in the progression of prediabetes atherosclerosis. This review discusses the cellular and molecular mechanisms of these processes, with an intention to enable a comprehensive understanding of the pathophysiology of prediabetes and atherosclerosis.

Expression and clinical significance of miR-1 and miR-133 in pre-diabetes

Pre-diabetes represents an intermediate state of altered glucose metabolism between normal glucose levels and type 2 diabetes mellitus (T2D), and is considered a significant risk factor for the development of T2D and related complications. Early detection of pre-diabetes may allow for the use of timely and effective treatment strategies to prevent its progression. Circulating microRNAs (miRNAs/miRs) that reflect changes in diabetes-related tissues, including the pancreas, liver, skeletal and heart muscle, and adipose tissue are promising biomarkers of disease progression. In our previous study, it was demonstrated that the cardiac and skeletal muscle specific miR-1 and miR-133 are upregulated in the blood of patients with T2D and cardiovascular disease. Since both miRNAs have been shown to be implicated in insulin resistance, an important feature of pre-diabetes, we hypothesised that their expression may be increased prior to clinical diagnosis of T2D, and may thus serve as biomarkers for pre-diabetes. The expression levels of circulating miRNAs were evaluated by reverse transcription-quantitative PCR in whole blood samples from 55 subjects, including 28 pre-diabetes individuals with impaired fasting glucose (FG) and impaired glucose tolerance, and 27 healthy controls. The individuals with pre-diabetes exhibited significantly higher expression levels of miR-1 and miR-133 compared with the controls (P<0.05). Target prediction search revealed that both miR-1 and miR-133 target several pathways involved in the pathophysiology of diabetes. Pearson's correlation analysis revealed that the two miRNAs were positively correlated with blood glucose parameters, including FG, 2-h oral glucose tolerance test and glycated haemoglobin A1c levels, as well as with insulin resistance (P<0.05). Multivariate logistic regression analysis revealed that the two miRNAs were significantly and directly associated with pre-diabetes, and this association remained significant after adjustment for several confounding variables (P<0.05). Moreover, linear regression analysis showed that the Homeostatic Model Assessment-Insulin Resistance was the only significant predictor to be significantly associated with both miRNAs (P<0.05). In discriminating pre-diabetes individuals from healthy controls, the area under the curves (AUCs) of the receiver operating characteristic curves (ROCs) were 0.813 and 0.810 for miR-1 and miR-133 respectively (P<0.05). Despite the relatively small number of participants, the present study showed for the first time that circulating levels of miR-1 and miR-133 were increased in individuals with pre-diabetes, and they were associated with important features of pre-diabetes. Thus, they may serve as clinical biomarkers for the early-stages of T2D.

Identification of metabolic markers predictive of prediabetes in a Korean population

Prediabetes (PD) is a high-risk state of developing type 2 diabetes, and cardiovascular and metabolic diseases. Metabolomics-based biomarker studies can provide advanced opportunities for prediction of PD over the conventional methods. Here, we aimed to identify metabolic markers and verify their abilities to predict PD, as compared to the performance of the traditional clinical risk factor (CRF) and previously reported metabolites in other population-based studies. Targeted metabolites quantification was performed in 1723 participants in the Korea Association REsource (KARE) cohort, from which 500 normal individuals were followed up for 6 years. We selected 12 significant metabolic markers, including five amino acids, four glycerophospholipids, two sphingolipids, and one acylcarnitine, at baseline, resulting in a predicted incidence of PD with an area under the curve (AUC) of 0.71 during follow-up. The performance of these metabolic markers compared to that of fasting glucose was significantly higher in obese patients (body mass index: BMI ≥ 25 kg/m², 0.79 vs. 0.58, P < 0.001). The combination with metabolic markers, CRF, and fasting glucose yielded the best prediction performance (AUC = 0.86). Our results revealed that metabolic markers were not only associated with the risk of PD, but also improved the prediction performance in combination with conventional approaches.

RIPK3-mediated inflammation is a conserved β cell response to ER stress

Islet inflammation is an important etiopathology of type 2 diabetes; however, the underlying mechanisms are not well defined. Using complementary experimental models, we discovered RIPK3-dependent IL1B induction in β cells as an instigator of islet inflammation. In cultured β cells, ER stress activated RIPK3, leading to NF-kB-mediated proinflammatory gene expression. In a zebrafish muscle insulin resistance model, overnutrition caused islet inflammation, β cell dysfunction, and loss in an ER stress-, ripk3-, and il1b-dependent manner. In mouse islets, high-fat diet triggered the IL1B expression in β cells before macrophage recruitment in vivo, and RIPK3 inhibition suppressed palmitate-induced β cell dysfunction and Il1b expression in vitro. Furthermore, in human islets grafted in hyperglycemic mice, a marked increase in ER stress, RIPK3, and NF-kB activation in β cells were accompanied with murine macrophage infiltration. Thus, RIPK3-mediated induction of proinflammatory mediators is a conserved, previously unrecognized β cell response to metabolic stress and a mediator of the ensuing islet inflammation.

Diet-induced rodent models of obesity-related metabolic disorders-A guide to a translational perspective

Diet is a critical element determining human health and diseases, and unbalanced food habits are major risk factors for the development of obesity and related metabolic disorders. Despite technological and pharmacological advances, as well as intensification of awareness campaigns, the prevalence of metabolic disorders worldwide is still increasing. Thus, novel therapeutic approaches with increased efficacy are urgently required, which often depends on cellular and molecular investigations using robust animal models. In the absence of perfect rodent models, those induced by excessive consumption of fat and sugars better replicate the key aspects that are the root causes of human metabolic diseases. However, the results obtained using these models cannot be directly compared, particularly because of the use of different dietary protocols, and animal species and strains, among other confounding factors. This review article revisits diet-induced models of obesity and related metabolic disorders, namely, metabolic syndrome, prediabetes, diabetes and nonalcoholic fatty liver disease. A critical analysis focused on the main pathophysiological features of rodent models, as opposed to the criteria defined for humans, is provided as a practical guide with a translational perspective for the establishment of animal models of obesity-related metabolic diseases.

Omega-3 fatty acids plus vitamin for women with gestational diabetes or prediabetes: a meta-analysis of randomized controlled studies

INTRODUCTION

Omega-3 fatty acids plus vitamin (e.g. vitamin D and E) may be beneficial to treat gestational diabetes mellitus (GDM), and we aimed to study the influence of omega-3 fatty acids plus vitamin versus placebo on the treatment efficacy of GDM.

METHODS

We searched the databases including PubMed, Embase, and the Cochrane Central Register of Controlled Trials, and randomized controlled trials (RCTs) assessing the influence of omega-3 fatty acids and vitamins combination supplementation versus placebo on metabolic status of GDM were included.

RESULTS

Five RCTs were included in the meta-analysis. Compared with control intervention for women with GDM or prediabetes, omega-3 fatty acids plus vitamin substantially reduced fasting plasma glucose (FPG, mean difference [MD] = -11.25; 95% confidence intervals [CI] = -13.73 to -8.77; p < .00001), insulin (MD=-6.16; 95% CI=-7.92 to -4.39; p < .00001), homeostasis model of assessment-insulin resistance (HOMA-IR, MD = 173.51; 95% CI = 164.72 to 182.30; p < .00001) and triglycerides (MD = 173.51; 95% CI = 164.72 to 182.30; p < .00001), as well as increased total antioxidant capacity (TAC, MD = 173.51; 95% CI = 164.72 to 182.30; p < .00001), but revealed no significant impact on total cholesterol (MD = 173.51; 95% CI = 164.72 to 182.30; p < .00001), low‑density lipoprotein cholesterol (LDL-C, MD = 173.51; 95% CI = 164.72 to 182.30; p < .00001), preterm delivery (OR = 173.51; 95% CI = 164.72 to 182.30; p < .00001) or macrosomia > 4000 g (OR = 173.51; 95% CI = 164.72 to 182.30; p < .00001).

CONCLUSIONS

The supplementation of omega-3 fatty acids in combination with vitamin D or E can improve glycemic control, alleviate oxidative stress, and reduce triglycerides, but had no effects on total cholesterol, preterm delivery or macrosomia > 4000 g in women with GDM or prediabetes.

A meta-analysis of the effects of resistance training on blood sugar and pregnancy outcomes

PROBLEM

There are different conclusions about the effects of resistance training on blood sugar levels and pregnancy outcomes in gestational diabetes mellitus (GDM) patients.

BACKGROUND

Resistance training is recommended as an easier and more practical method to exercise for women with GDM due to their growing belly. Although some researchers have explored this notion, there are no consistent conclusions about its effects.

AIM

To explore whether resistance training has an effect on blood sugar levels and pregnancy outcomes in patients with GDM in randomized controlled trials.

METHOD

Pubmed, Cochrane Library, CINAHL, Embase, Scopus, Web of Science, Clinical Trials, CKNI, Wanfang Database, VIP Database, and Chinese Biomedical Literature Database were systematically searched since their establishment to April 2019. Relevant meta-analyses, reviews, and eligible literature were also searched. The quality of the included literature was evaluated according to the Cochrane Assessment Manual 5.1.0. Meta-analysis was performed using Revman 5.3 software.

FINDINGS

A total of four studies (n = 242 patients) were included. Compared to the control group, there were statistical differences in fasting blood glucose level [MD=-0.37, 95%CI=(-0.65, -0.09), Z = 2.62, P = 0.009], average 2-h post-meal blood glucose level [MD=-0.96, 95%CI=(-1.80, -0.12), Z = 2.25, P = 0.02], insulin dosage [MD=-0.58, 95%CI=(-0.99, -0.17), Z = 2.75, P = 0.006], rate of insulin injection [RR=0.52, 95%CI=(0.31, 0.86), Z = 2.54, P = 0.01], and incidence of macrosomia [RR=0.15, 95%CI=(0.04,0.66), Z = 2.53, P = 0.01] in the intervention group consisting of GDM patients. There were no statistical differences in preterm delivery outcomes [RR=0.44, 95%CI=(0.09, 2.16), Z = 1.01, P = 0.31].

CONCLUSION

Resistance training can improve blood sugar levels, insulin usage, and some adverse pregnancy outcomes in patients with GDM and is therefore worthy of clinical promotion.

Role of Magnesium in Type 2 Diabetes Mellitus

Magnesium (in its ionized and biologically active form, Mg²⁺) is an essential trace element that participates in numerous physiologic processes. Abnormal Mg²⁺ homeostasis can lead to many metabolic disorders, including diabetes mellitus (DM) and its complications. Mg²⁺ participates in energy generation and is required for DNA and RNA synthesis, reproduction, and protein synthesis. Additionally, Mg²⁺ acts as a calcium antagonist and protects vascular endothelial cells from oxidative stress. Imbalances in Mg²⁺ status, more frequently hypomagnesemia, inhibit glucose transporter type 4 translocation, increase insulin resistance, affect lipid metabolism, induce oxidative stress, and impair the antioxidant system of endothelial cells, In these ways, hypomagnesemia contributes to the initiation and progression of DM and its macrovascular and microvascular complications. In this review, we summarize recent advances in knowledge of the mechanisms whereby Mg²⁺ regulates insulin secretion and sensitivity. In addition, we discuss the future prospects for research regarding the mechanisms whereby Mg²⁺ status impacts DM and its complications.

Dietary supplements for prediabetes: A protocol for a systematic review and meta-analysis

BACKGROUND

The number of prediabetic individuals is at a high level worldwide and they have an increased risk of developing diabetes, causing severe physical impairment and heavy financial burden. Recently, using various dietary supplements is increasingly common, and relevant trials of different diseases are increasing correspondingly. The effects of dietary supplements have been confirmed in some studies among prediabetic individuals. However, there remains no comprehensive systematic review to assess the efficacy and safety of dietary supplements intake in prediabetic individuals.

METHODS

We plan to search and retrieve applicable randomized controlled trials of dietary supplements for prediabetic individuals in the following databases before June 2020: PubMed, Web of Science, EMBASE, the Cochrane Library, the Cochrane Central Register of Controlled Trials(CENTRAL), Allied and Complementary Medicine Database(AMED), Chinese Biomedical Literature database, Wan Fang database, Chinese Scientific Journal database (VIP), Chinese National Knowledge Infrastructure database(CNKI), and the ClinicalTrials.gov website. Two reviewers will separately perform study selection, data extraction, methodological quality assessment and quality of evidence assessment. Data analysis and publication bias will be conducted by Review Manager 5.3.

RESULTS AND CONCLUSIONS

This evidence-based medicine systematic review will prove the efficacy and safety of multifarious dietary supplements for prediabetes.

ETHICS AND DISSEMINATION

As this systematic review is based merely on already published literature, no approval of the ethics committee is required. We will disseminate this systematic review to a peer-reviewed journal.

PROTOCOL REGISTRATION NUMBER

INPLASY202040057.

Circulating miR-103 family as potential biomarkers for type 2 diabetes through targeting CAV-1 and SFRP4

AIMS

MicroRNA-103 (miR-103) family plays important roles in regulating glucose homeostasis in type 2 diabetes mellitus (DM2). However, the underlying mechanisms remain poorly characterized. The objective of this study was to test the hypothesis that circulating miR-103a and miR-103b, which regulate CAV-1 and SFRP4, respectively, are novel biomarkers for diagnosis of DM2.

METHODS

We determined the predictive potential of circulating miR-103a and miR-103b in pre-DM subjects (pre-DM), noncomplicated diabetic subjects, and normal glucose-tolerance individuals (control) using bioinformatic analysis, qRT-PCR, luciferase assays, and ELISA assays.

RESULTS

We found that both miR-103a and miR-103b had high complementarity and conservation, modulated reporter gene expression through seed sequences in the 3'UTRs of CAV-1 and SFRP4 mRNA, and negatively regulated their mRNA and protein levels, respectively. We also found that increased miR-103a and decreased miR-103a in plasma were significantly and negatively correlated with reduced CAV-1 levels and elevated SFRP4 levels in pre-DM and DM2, respectively, and were significantly associated with glucose metabolism, HbA1c levels, and other DM2 risk factors for progression from a normal individual to one with pre-DM. Furthermore, we demonstrated that the reciprocal changes in circulating miR-103a and miR-103b not only provided high sensitivity and specificity to differentiate the pre-DM population but also acted as biomarkers for predicting DM2 with high diagnostic value.

CONCLUSIONS

These findings suggest that circulating miR-103a and miR-103b may serve as novel biomarkers for diagnosis of DM2, providing novel insight into the mechanisms underlying pre-DM.

The effect of omega-3 and vitamin D co-supplementation on glycemic control and lipid profiles in reproductive-aged women with pre-diabetes and hypovitaminosis D: a randomized controlled trial

BACKGROUND

Prediabetes can predispose the individual to type 2 diabetes in the long-term. The present study was conducted to determine the effectiveness of vitamin D and omega-3 co-supplementation on glycemic control and serum lipid profiles in women of reproductive age with prediabetes and hypovitaminosis D.

METHODS

The present factorial, triple-blind, clinical trial was conducted on 168 women of reproductive age with prediabetes and hypovitaminosis D. The participants were assigned to four groups based on block randomization method: the placebo group received omega-3 and vitamin D placebos; the omega-3 group took omega-3 supplements and vitamin D placebos; the vitamin D group received omega-3 placebos and vitamin D supplements and the co-supplementation group. The groups received every 2 weeks 50,000 IU pearls of vitamin D and twice-daily doses of 1000-mg omega-3 tablets or placebos for 8 weeks. Dietary intake, physical activity, anthropometric indices and blood biochemical tests were measured at the beginning and end of the study. Analysis was performed using two-way mixed ANOVA.

RESULTS

A significant reduction was observed in fasting glucose, insulin, homeostasis model assessment-beta cell function, weight and waist circumference in the co-supplementation group compared to the other three groups (P < 0.05). Moreover, high-density lipoprotein-cholesterol levels increased significantly in the co-supplementation group compared to the other three groups (P < 0.05). Despite the fact that homeostasis model assessment-insulin resistance, total cholesterol, triglyceride and low-density lipoprotein-cholesterol levels decreased after intervention in the co-supplementation group, there was no significant difference between the groups in these outcomes.

CONCLUSION

Vitamin D and omega-3 co-supplementation improved fasting serum glucose, insulin, high-density lipoprotein-cholesterol level, homeostasis model assessment-beta cell function, weight and waist circumference in women of reproductive age with prediabetes and hypovitaminosis D. This co-supplementation can therefore be recommended for glycemic control in these women.Trial registration Iranian Registry of Clinical Trials Code: IRCT20100130003226N17. Registered on 9 Feb. 2019.

Effects of Type II Diabetes Mellitus on Tendon Homeostasis and Healing

Over 300,000 tendon repairs are performed annually in the United States to repair damage to tendons as a result of either acute trauma or chronic tendinopathy. Individuals with type II diabetes mellitus (T2DM) are four times more likely to experience tendinopathy, and up to five times more likely to experience a tendon tear or rupture than non-diabetics. As nearly 10% of the US population is diabetic, with an additional 33% pre-diabetic, this is a particularly problematic health care challenge. Tendon healing in general is challenging and often unsatisfactory due to the formation of mechanically inferior scar-tissue rather than regeneration of native tendon structure. In T2DM tendons, there is evidence of an amplified scar tissue response, which may be associated with the increased the risk of rupture or impaired restoration of range of motion. Despite the dramatic effect of T2DM on tendon function and outcomes following injury, there are few therapies available to promote improved healing in these patients. Several recent studies have enhanced our understanding of the pro-inflammatory environment of T2DM healing and have assessed potential treatment approaches to mitigate pathological progression in pre-clinical models of diabetic tendinopathy. This review discusses the current state of knowledge of diabetic tendon healing from molecular to mechanical disruptions and identifies promising approaches and critical knowledge gaps as the field moves toward identification of novel therapeutic strategies to maintain or restore tendon function in diabetic patients. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:13-22, 2020.

Development of non-invasive diabetes risk prediction models as decision support tools designed for application in the dental clinical environment

The objective was to develop a predictive model using medical-dental data from an integrated electronic health record (iEHR) to identify individuals with undiagnosed diabetes mellitus (DM) in dental settings. Retrospective data retrieved from Marshfield Clinic Health System's data-warehouse was pre-processed prior to conducting analysis. A subset was extracted from the preprocessed dataset for external evaluation (Nvalidation) of derived predictive models. Further, subsets of 30%-70%, 40%-60% and 50%-50% case-to-control ratios were created for training/testing. Feature selection was performed on all datasets. Four machine learning (ML) classifiers were evaluated: logistic regression (LR), multilayer perceptron (MLP), support vector machines (SVM) and random forests (RF). Model performance was evaluated on Nvalidation. We retrieved a total of 5319 cases and 36,224 controls. From the initial 116 medical and dental features, 107 were used after performing feature selection. RF applied to the 50%-50% case-control ratio outperformed other predictive models over Nvalidation achieving a total accuracy (94.14%), sensitivity (0.941), specificity (0.943), F-measure (0.941), Mathews-correlation-coefficient (0.885) and area under the receiver operating curve (0.972). Future directions include incorporation of this predictive model into iEHR as a clinical decision support tool to screen and detect patients at risk for DM triggering follow-ups and referrals for integrated care delivery between dentists and physicians.

Health risks and interventions in prediabetes: A review

Prediabetes is a condition which appears prior to the development of diabetes in which blood glucose is abnormally high but do not reach the diagnostic threshold of type 2 diabetes mellitus. It is characterized by a cluster of metabolic abnormalities viz. dysglycemia, dyslipidemia, hypertension, physical inactivity, obesity, insulin resistance, procoagulant state, endothelial dysfunction, oxidative stress and inflammation, placing prediabetic subjects to an increased risk for diabetes and its complications. Recent studies demonstrate that complications of diabetes i.e. microvascular and macrovascular complications may manifest in some prediabetic subjects. This article reviews prediabetes-related risk factors and health issues. In addition, this article also highlights the interventions to prevent the development of diabetes in prediabetic subjects.

Changes in the levels of 12/15-lipoxygenase, apoptosis-related proteins and inflammatory factors in the cortex of diabetic rats and the neuroprotection of baicalein

This study was designed to investigate the neuroprotective effects of baicalein and the effect of the cortical 12/15-lipoxygenase (12/15-LOX) pathway on diabetic cognitive dysfunction. Our results showed that spatial learning and memory ability, as well as cortex neurons, were significantly impaired after the onset of diabetes. The fasting blood glucose and random blood glucose levels in the model group were significantly higher than those in the normal group. The levels of TG and TC in the plasma of the model group were significantly increased, but there was no significant difference in the LDL level. The insulin content in the plasma of diabetic rats was significantly lower than that of the normal group. The levels of inflammatory factors and 12(S)-HETE were significantly increased in diabetic rats, as were the protein expression levels of cPLA2, 12/15-LOX, p38MAPK, phospho-p38MAPK, caspase-3, caspase-9 and Aβ_1-42; by contrast, protein expression of Bcl-2 was significantly decreased. Administration of baicalein was shown to improve the spatial learning and memory ability and significantly decrease the levels of inflammatory cytokines. However, baicalein did not significantly influence the levels of blood glucose, lipids or insulin in rats. Baicalein treatment significantly protected diabetes rats from neuron death; significantly attenuated the overexpression of cPLA2, 12/15-LOX, p38MAPK, phospho-p38MAPK, caspase-3, caspase-9 and Aβ_1-42; and upregulated the expression of Bcl-2. These findings suggest that baicalein improves the cognitive function of diabetic rats by directly acting in the brain rather than by regulating the levels of blood glucose, lipids or insulin. In addition, baicalein can protect rat cortical neurons from damage caused by diabetes via inhibiting the 12/15-LOX pathway and relieving inflammation and apoptosis of the central nervous system.

Therapeutic Options Targeting Oxidative Stress, Mitochondrial Dysfunction and Inflammation to Hinder the Progression of Vascular Complications of Diabetes

Type 2 diabetes mellitus is a leading cause of morbidity and mortality worldwide, given its serious associated complications. Despite constant efforts and intensive research, an effective, ubiquitous treatment still eludes the scientific community. As such, the identification of novel avenues of research is key to the potential discovery of this evasive "silver bullet." We focus on this review on the matter of diabetic injury to endothelial tissue and some of the pivotal underlying mechanisms, including hyperglycemia and hyperlipidemia evoked oxidative stress and inflammation. In this sense, we revisited the most promising therapeutic interventions (both non-pharmacological and antidiabetic drugs) targeting oxidative stress and inflammation to hinder progression of vascular complications of diabetes. This review article gives particular attention to the relevance of mitochondrial function, an often ignored and understudied organelle in the vascular endothelium. We highlight the importance of mitochondrial function and number homeostasis in diabetic conditions and discuss the work conducted to address the aforementioned issue by the use of various therapeutic strategies. We explore here the functional, biochemical and bioenergetic alterations provoked by hyperglycemia in the endothelium, from elevated oxidative stress to inflammation and cell death, as well as loss of tissue function. Furthermore, we synthetize the literature regarding the current and promising approaches into dealing with these alterations. We discuss how known agents and therapeutic behaviors (as, for example, metformin, dietary restriction or antioxidants) can restore normality to mitochondrial and endothelial function, preserving the tissue's function and averting the aforementioned complications.

ICP-DRC-MS analysis of serum essential and toxic element levels in postmenopausal prediabetic women in relation to glycemic control markers

PURPOSE

Assessment of the influence of prediabetes on serum trace element and electrolyte levels in postmenopausal women.

METHODS

A total of 80 prediabetic and 80 healthy postmenopausal women took part in the present study. Serum was analyzed for glucose, insulin, insulin resistance index (HOMA-IR), total cholesterol (TC), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyltransferase (GGT). Glycated haemoglobin (HbA1c) levels were also assessed. Serum levels of 28 elements were estimated using inductively-coupled plasma mass spectrometry with dynamic reaction cell technology (ICP-DRC-MS).

RESULTS

Prediabetic women were characterized by significantly higher HbA1c, glucose, insulin, HOMA-IR, ALT, and GGT values. Of trace elements, only serum zinc (Zn) levels were significantly lower in prediabetics by 10% (p=0.001) when compared to the controls. Serum Zn levels were characterized by a significant inverse correlation with HbA1c (r=- 0.205; p=0.009), insulin (r=- 0.246; p=0.002), and HOMA-IR (r=- 0.227; p=0.004). Multiple regression analysis demonstrated a significant inverse association between serum Zn (β=-0.169; p=0.031) and Sr (β=-0.192; p=0.012) and HOMA-IR values after adjustment for anthropometric and biochemical parameters (p for a model <0.001). Although serum Zn was significantly associated with HbA1c both in crude and adjusted models, no significant relationship was detected after adjustment for age and anthropometric parameters.

CONCLUSIONS

Prediabetic postmenopausal women are characterized by significantly lower levels of serum Zn concentration, whereas serum Zn and Sr levels were inversely associated with insulin resistance.

Chronic hyperglycemia mediated physiological alteration and metabolic distortion leads to organ dysfunction, infection, cancer progression and other pathophysiological consequences: An update on glucose toxicity

Chronic exposure of glucose rich environment creates several physiological and pathophysiological changes. There are several pathways by which hyperglycemia exacerbate its toxic effect on cells, tissues and organ systems. Hyperglycemia can induce oxidative stress, upsurge polyol pathway, activate protein kinase C (PKC), enhance hexosamine biosynthetic pathway (HBP), promote the formation of advanced glycation end-products (AGEs) and finally alters gene expressions. Prolonged hyperglycemic condition leads to severe diabetic condition by damaging the pancreatic β-cell and inducing insulin resistance. Numerous complications have been associated with diabetes, thus it has become a major health issue in the 21st century and has received serious attention. Dysregulation in the cardiovascular and reproductive systems along with nephropathy, retinopathy, neuropathy, diabetic foot ulcer may arise in the advanced stages of diabetes. High glucose level also encourages proliferation of cancer cells, development of osteoarthritis and potentiates a suitable environment for infections. This review culminates how elevated glucose level carries out its toxicity in cells, metabolic distortion along with organ dysfunction and elucidates the complications associated with chronic hyperglycemia.

New insights from continuous glucose monitoring into the route to diabetes

AIM

Type 2 diabetes mellitus (T2DM) is preceded by a period of impaired glucoregulation. We investigated if continuous glucose monitoring system (CGMS) (1) could improve our capacity to predict the development of T2DM in subjects at risk. (2) Find out if impaired fasting glucose/impaired glucose tolerance differentiation through CGMS would also elucidate differences in clinical phenotypes.

MATERIAL AND METHODS

Observational study of 209 hypertensive patients, aged 18 to 85 years who wore at entry a CGMS. Two CGMS metrics, percent of time under the 100 mg/dL glycaemic threshold (TU100) (impaired fasting glucose surrogate phenotype) and area above the 140 mg/dL glycemic threshold (AO140) (impaired glucose tolerance surrogate phenotype) were measured. The median follow-up was 32 months (6-72 mo), and there were 17 new cases of T2DM.

RESULTS

In a multivariate Cox proportional hazard survival analysis including the conventional prediabetes-defining criteria and the 2 CGMS-derived variables, only TU100 and HbA_1c were significant and independent variables in predicting T2DM development. An increase in 0.1 in TU100 resulted in a 0.69 (95% CI, 0.54-0.88; P < .01) odds ratio of developing T2DM. With cut-off points of 0.5 for TU100 and 5.7% for HbA_1c , the test "TU < 0.5 and HbA_1c  > 5.7%" had a sensitivity of 0.81 (SD, 0.10), a specificity of 0.83 (SD, 0.03), and a likelihood ratio of 4.82 (SD, 1.03) for T2DM development.

CONCLUSIONS

Continuous glucose monitoring system allows for a better T2DM risk-development categorization than fasting glucose and HbA_1c in a high-risk population. Continuous glucose monitoring system-derived phenotyping reveals clinical differences, not disclosed by conventional fasting plasma glucose/HbA_1c categorization. These differences may correlate with distinct pathophysiological mechanisms.

The Relationship Between Health-Related Quality of Life and Anabolic Hormone Levels in Middle-Aged and Elderly Men With Prediabetes: A Cross-Sectional Study

The aim of this study was to compare health-related quality of life (HRQoL) between men with prediabetes (PD) and a control group as well as to investigate the relationship between HRQoL and anabolic hormones. The analysis was carried out in 176 middle-aged (40–59 years) and elderly (60 80 years) men with PD, and 184 control peers. PD was defined according the American Diabetes Association and HRQoL was assessed by the SF-36 questionnaire. Total testosterone (TT), calculated free testosterone, dehydroepiandrosterone sulfate (DHEAS), and insulin-like growth factor 1 (IGF-1) were measured. Analysis of the standardized physical and mental component summary scores (SF-36_p and SF-36_m) revealed that patients with PD had lower SF-36_p and SF-36_m than control group (p < .02 and p < .001). Middle-aged men with PD had lower SF-36_p and SF-36_m than control peers, whereas elderly men with PD had lower only SF-36_p. In men with PD negative correlations between glycated hemoglobin (HbA1c) and SF-35_m score (r = −0.3768; p = .02) and between HbA1c and SF-36_p score (r = −0.3453; p = .01) were reported. In middle-aged prediabetic men, SF-36_p was associated with high free testosterone and low HbA1c while SF-36_m with high TT and high DHEAS. In elderly patients with PD, SF-36_p was associated with high TT, high IGF-1, and low HbA1c, while SF-36_m correlated with high free testosterone and high DHEAS. In conclusion, PD in men is associated with decreased HRQoL in comparison with healthy men, and generally better quality of life is associated with higher testosterone, higher free testosterone, higher DHEAS, and lower HbA1c.

Metabolic activation-driven mitochondrial hyperpolarization predicts insulin secretion in human pancreatic beta-cells

Mitochondrial metabolism plays a central role in insulin secretion in pancreatic beta-cells. Generation of protonmotive force and ATP synthesis from glucose-originated pyruvate are critical steps in the canonical pathway of glucose-stimulated insulin secretion. Mitochondrial metabolism is intertwined with pathways that are thought to amplify insulin secretion with mechanisms distinct from the canonical pathway, and the relative importance of these two pathways is controversial. Here I show that glucose-induced mitochondrial membrane potential (MMP) hyperpolarization is necessary for, and predicts, the rate of insulin secretion in primary cultured human beta-cells. When glucose concentration is elevated, increased metabolism results in a substantial MMP hyperpolarization, as well as in increased rates of ATP synthesis and turnover marked by faster cell respiration. Using modular kinetic analysis I explored what properties of cellular energy metabolism enable a large glucose-induced change in MMP in human beta-cells. I found that an ATP-dependent pathway activates glucose or substrate oxidation, acting as a positive feedback in energy metabolism. This activation mechanism is essential for concomitant fast respiration and high MMP, and for a high magnitude glucose-induced MMP hyperpolarization and therefore for insulin secretion.

Effect of Changing Work Stressors and Coping Resources on the Risk of Type 2 Diabetes: The OHSPIW Cohort Study

OBJECTIVE

Little is known about the relationship between changing psychosocial work conditions and type 2 diabetes. We determined whether changing work stressors and coping resources affect the risk of type 2 diabetes.

RESEARCH DESIGN AND METHODS

In this prospective cohort (2003-2014) of 3,740 workers without diabetes (OHSPIW [Occupational Health Study of Petroleum Industry Workers]), participants completed an evaluation of work-related stress and coping resources and type 2 diabetes diagnosis at baseline and 12 years follow-up (two waves). The changes in work stressors and coping resources were measured with the Occupation Stress Inventory-Revised and the Instrument for Stress-Related Job Analysis (Version 6.0). Type 2 diabetes was diagnosed on the basis of an oral glucose tolerance test supplemented by physician report.

RESULTS

Increased task stressors (relative risk [RR] 1.57 [95% CI 1.03-2.63]) and decreased coping resources (RR 1.68 [95% CI 1.02-2.83]) were associated with risk of type 2 diabetes. The main risk factors were increased role overload, increased role insufficiency, increased physical environment stressors, decreased self-care, and decreased rational coping. Increased coping resources also had a buffering effect on increased task stressors and type 2 diabetes.

CONCLUSIONS

Changes in work stressors and coping resources have an influence on the risk for type 2 diabetes, highlighting the importance of preventive measures against adverse psychosocial work conditions and reduced coping resources for diabetes prevention in the workplace.

Magnesium upregulates insulin receptor and glucose transporter-4 in streptozotocin-nicotinamide-induced type-2 diabetic rats

Objective. We investigated the effects of magnesium supplementation on glucose tolerance, insulin sensitivity, oxidative stress as well as the concentration of insulin receptor and glucose transporter-4 in streptozotocin-nicotinamide induced type-2 diabetic (T2D) rats. Methods. Rats were divided into four groups designated as: 1) control (CTR); 2) diabetic untreated (DU); 3) diabetic treated with 1 mg of Mg/kg diet (Mg1-D); and 4) diabetic treated with 2 mg of Mg/kg diet (Mg2-D). T2D was induced with a single intraperitoneal (i.p.) injection of freshly prepared streptozotocin (55 mg/kg) aft er an initial i.p. injection of nicotinamide (120 mg/kg). Glucose tolerance, insulin sensitivity, lipid profile, malondialdehyde (MAD) and glutathione content, insulin receptors (INSR) and glucose transporter-4 (GLUT4), fasting insulin and glucose levels were measured, and insulin resistance index was calculated using the homeostatic model assessment of insulin resistance (HOMA-IR). Results. Magnesium supplementation improved glucose tolerance and lowered blood glucose levels almost to the normal range. We also recorded a noticeable increase in insulin sensitivity in Mg-D groups when compared with DU rats. Lipid perturbations associated T2D were significantly attenuated by magnesium supplementation. Fasting glucose level was comparable to control values in the Mg-D groups while the HOMA-IR index was significantly lower compared with the DU rats. Magnesium reduced MDA but increased glutathione concentrations compared with DU group. Moreover, INSR and GLUT4 levels were elevated following magnesium supplementation in T2D rats. Conclusion. These findings demonstrate that magnesium may mediate effective metabolic control by stimulating the antioxidant defense, and increased levels of INSR and GLUT4 in diabetic rats.

Shared Genetic Control of Brain Activity During Sleep and Insulin Secretion: A Laboratory-Based Family Study

Over the past 20 years, a large body of experimental and epidemiologic evidence has linked sleep duration and quality to glucose homeostasis, although the mechanistic pathways remain unclear. The aim of the current study was to determine whether genetic variation influencing both sleep and glucose regulation could underlie their functional relationship. We hypothesized that the genetic regulation of electroencephalographic (EEG) activity during non-rapid eye movement sleep, a highly heritable trait with fingerprint reproducibility, is correlated with the genetic control of metabolic traits including insulin sensitivity and β-cell function. We tested our hypotheses through univariate and bivariate heritability analyses in a three-generation pedigree with in-depth phenotyping of both sleep EEG and metabolic traits in 48 family members. Our analyses accounted for age, sex, adiposity, and the use of psychoactive medications. In univariate analyses, we found significant heritability for measures of fasting insulin sensitivity and β-cell function, for time spent in slow-wave sleep, and for EEG spectral power in the delta, theta, and sigma ranges. Bivariate heritability analyses provided the first evidence for a shared genetic control of brain activity during deep sleep and fasting insulin secretion rate.

Egg consumption may improve factors associated with glycemic control and insulin sensitivity in adults with pre- and type II diabetes

Daily consumption of one large egg for 12 weeks improves fasting blood glucose, ATP-binding cassette protein family A1, and apolipoprotein A1 in overweight or obese individuals with pre- and type II diabetes.

Prevalence of prediabetes and modifiable factors in an ethnic group of Mexico: the Comcáac Project

OBJECTIVE

To determine the prevalence of and modifiable factors associated with prediabetes in the Comcáac Indians.

DESIGN

Cross-sectional study where prediabetes was defined using fasting plasma glucose, 2 h plasma glucose and glycated Hb (HbA1c). Physical, anthropometric and biochemical measurements, medical record, socio-economic, dietary and physical activity information were collected. The modifiable factors associated with prediabetes were assessed using multiple logistic regression. Settings Comcáac Indian communities of Punta Chueca and El Desemboque, Sonora, Mexico.

SUBJECTS

Adults (n 227) aged 20 years or older.

RESULTS

The sex- and age-adjusted prevalence (95 % CI) of prediabetes was 47·1 (40·8, 53·5) % in the overall population; age-adjusted prevalence was 47·3 (35·6, 59·0) % in men and 46·7 (39·1, 54·3) % in women. The modifiable factors associated with a risk of prediabetes (OR; 95 % CI) were light-intensity physical activity (per 1 h/week increase: 1·04; 1·01, 1·07) and insulin resistance (homeostasis model assessment of insulin resistance score >6·1 v. <4·1: 4·62; 1·37, 15·51). Increased consumption of a traditional dietary pattern based on fish and seafood, low-fat cereals, fruits and vegetables was a protective factor (0·49; 0·31, 0·79). All variables were modelled together and adjusted for age and sex.

CONCLUSIONS

The high prediabetes prevalence found in the Comcáac community is alarming because it represents a large number of people who are at risk for type 2 diabetes. The identification of modifiable factors associated with prediabetes that are specific to this population may be useful for designing effective strategies to prevent prediabetes.

Effect of Linagliptin Versus Metformin on Glycemic Variability in Patients with Impaired Glucose Tolerance

BACKGROUND

Impaired glucose tolerance (IGT) and glycemic variability may be associated with increased risk of micro- and macrovascular complications. The aim of this study was to assess the effect of linagliptin versus metformin on glycemic variability in patients with IGT.

MATERIAL AND METHODS

A randomized, double-blind clinical trial with parallel groups was carried out in 16 adult patients with IGT, overweight or obesity. All patients signed an informed consent. The therapies were randomly assigned: (a) metformin 500 mg bid (n = 8) or (b) linagliptin 5 mg a.m. and placebo p.m. (n = 8), both for 90 days. At the beginning of the trial and 3 months later, fasting glucose, glycated hemoglobin A1c, oral glucose tolerance test (OGTT), and glycemic variability [area under the curve (AUC) of glucose, mean amplitude of glycemic excursion (MAGE), standard deviation (SD) of glucose, coefficient of variation (CV) of glucose, and mean blood glucose (MBG)] were measured. Mann-Whitney U, Wilcoxon, and Fisher exact tests were used for statistical analyses.

RESULTS

Both groups were similar in basal characteristics. After linagliptin administration, a significant decrease in glucose levels at 120 min of OGTT (9.0 ± 0.9 vs. 6.9 ± 2.2 mmol/L, P = 0.012) was observed. Glycemic variability showed a similar behavior and there were no significant differences in the AUC, MAGE, SD of glucose, CV of glucose, and MBG between groups.

CONCLUSION

Linagliptin administration resulted in better glycemic control according to the decrease of glucose levels by the OGTT at 120 min in patients with IGT. Meanwhile, glycemic variability was not modified in any of the study groups.

Insulin-Stimulated Bone Blood Flow and Bone Biomechanical Properties Are Compromised in Obese, Type 2 Diabetic OLETF Rats

Type 2 diabetes (T2D) increases skeletal fragility and fracture risk; however, the underlying mechanisms remain to be identified. Impaired bone vascular function, in particular insulin‐stimulated vasodilation and blood flow is a potential, yet unexplored mechanism. The purpose of this study was to determine the effects of T2D on femoral biomechanical properties, trabecular microarchitecture, and insulin‐stimulated bone vasodilation by comparison of hyperphagic Otsuka Long‐Evans Tokushima Fatty (OLETF) rats with normoglycemic control OLETF rats. Four‐week old, male OLETF rats were randomized to two groups: type 2 diabetes (O‐T2D) or normoglycemic control (O‐CON). O‐T2D were allowed ad libitum access to a rodent chow diet and O‐CON underwent moderate caloric restriction (30% restriction relative to intake of O‐T2D) to maintain normal body weight (BW) and glycemia until 40 weeks of age. Hyperphagic O‐T2D rats had significantly greater BW, body fat, and blood glucose than O‐CON. Total cross‐sectional area (Tt.Ar), cortical area (Ct.Ar), Ct.Ar/Tt.Ar, and polar moment of inertia of the mid‐diaphyseal femur adjusted for BW were greater in O‐T2D rats versus O‐CON. Whole‐bone biomechanical properties of the femur assessed by torsional loading to failure did not differ between O‐T2D and O‐CON, but tissue‐level strength and stiffness adjusted for BW were reduced in O‐T2D relative to O‐CON. Micro–computed tomography (μCT) of the distal epiphysis showed that O‐T2D rats had reduced percent bone volume, trabecular number, and connectivity density, and greater trabecular spacing compared with O‐CON. Basal tibial blood flow assessed by microsphere infusion was similar in O‐T2D and O‐CON, but the blood flow response to insulin stimulation in both the proximal epiphysis and diaphyseal marrow was lesser in O‐T2D compared to O‐CON. In summary, impaired insulin‐stimulated bone blood flow is associated with deleterious changes in bone trabecular microarchitecture and cortical biomechanical properties in T2D, suggesting that vascular dysfunction might play a causal role in diabetic bone fragility. © 2017 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Proteomic approach to detect changes in hippocampal protein levels in an animal model of type 2 diabetes

In our previous study, we demonstrated that type 2 diabetes affects blood-brain barrier integrity and ultrastructural morphology in Zucker diabetic fatty (ZDF) rats at 40 weeks of age. In the present study, we investigated the possible candidates for diabetes-related proteins in the hippocampus of ZDF rats and their control littermates (Zucker lean control, ZLC), by using two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF). Approximately 2756 protein spots were detected by 2D-DIGE, and an increase or decrease of more than 1.4-fold was observed for 13 proteins in the hippocampal homogenates of ZDF rats relative to those of ZLC rats. Among these proteins, we found four proteins whose levels were significantly lower in the hippocampi of ZDF rats than in those of ZLC rats: glial fibrillary acidic protein (GFAP), apolipoprotein A-I preprotein (apoAI-P), myelin basic protein (MBP), and rCG39881, isoform CRA_a. Among these proteins, apoAI-P protein levels were decreased most prominently in ZDF rats than in ZLC rats, based on Western blot analysis. In addition, immunohistochemical and Western blot studies demonstrated that MBP, not GFAP, immunoreactivity and protein levels were significantly decreased in the hippocampus of ZDF rats compared to ZLC rats. In addition, ultrastructural analysis showed that ZDF rats showed myelin degeneration and disarrangement in the hippocampal tissue. These results suggest that chronic type 2 diabetes affects hippocampal function via reduction of MBP and apoAI-P levels as well as disarrangement of myelin.

CMD-05, a novel promising clinical anti-diabetic drug candidate, in vivo and vitro studies

Dipeptidyl peptidase IV (DPP-IV) inhibitor has been expected to be a new class of anti-diabetic agent. The present study was designed to characterize the pharmacological profiles of CMD-05, a novel DPP-IV inhibitor discovered in our laboratory, in vitro and in vivo. The IC₅₀ of CMD-05 on DPP-IV inhibitory activity was approximately 12 nM while vildagliptin was 3.5 nM in vitro. In diabetes rat model established by high fat diet/low dose streptozotocin, CMD-05 inhibited DPP-IV activity, significantly improved glucose tolerance, increased GLP-1 and insulin levels in plasma. Long-term administration of CMD-05 decreased HbA1c and TG levels and improved the islet function without significantly effect on body weight. Furthermore, CMD-05 reduced INS-1 cell apoptosis and increased GLP-1 secretion in NCI-H716. After oral administration, CMD-05 reached peak concentration at 30 min with half-life of 288 minutes and the inhibitory rate of DPP-IV greater than 50% lasted for 15 h. In fasted normal rats, CMD-05 didn't cause significant hypoglycemia. CMD-05 had a lower cytotoxicity than vildagliptin in vitro and its maximum tolerance dose in mice is beyond 2000 mg/kg. These results indicated that CMD-05 has similar activity with vildagliptin in vivo and has a much longer half-life and lower cytotoxicity than vildagliptin.

Effect of Chinese Herbal Medicine Jinlida Granule in Treatment of Patients with Impaired Glucose Tolerance

BACKGROUND

Diabetes mellitus (DM) remains a major health problem worldwide. Several clinical trials have shown the superiority of the Traditional Chinese Medicine in delaying or reversing the development and progression of DM. This study aimed to evaluate the efficacy of Jinlida (JLD) granule, a Chinese herbal recipe, in the treatment of impaired glucose tolerance (IGT) and its effect on the prevention of DM.

METHODS

Sixty-five IGT patients were randomized to receive one bag of JLD granules three times daily (JLD group, n = 34) or no drug intervention (control group, n = 31) for 12 weeks. Oral glucose tolerance test, glycated hemoglobin A1c (HbA1c), body mass index, blood lipids levels, fasting insulin, and insulin resistance calculated using homeostatic model assessment (HOMA-IR) of all the patients were observed and compared before and after the treatment.

RESULTS

Sixty-one participants completed the trial (32 in JLD group and 29 in the control group). There were statistically significant decreases in HbA1c (P < 0.001), 2-h plasma glucose (P < 0.001), and HOMA-IR (P = 0.029) in JLD group compared with the control group after 12 weeks of treatment. After 12 weeks of treatment, two (6.9%) patients returned to normal blood glucose, and five (17.2%) patients turned into DM in control group, while in the JLD group, 14 (43.8%) returned to normal blood glucose and 2 (6.2%) turned into DM. There was a significant difference in the number of subjects who had normal glucose at the end of the study between two groups (P = 0.001).

CONCLUSIONS

JLD granule effectively improved glucose control, increased the conversion of IGT to normal glucose, and improved the insulin resistance in patients with IGT. This Chinese herbal medicine may have a clinical value for IGT.

Glucose time series complexity as a predictor of type 2 diabetes

BACKGROUND

Complexity analysis of glucose profile may provide valuable information about the gluco-regulatory system. We hypothesized that a complexity metric (detrended fluctuation analysis, DFA) may have a prognostic value for the development of type 2 diabetes in patients at risk.

METHODS

A total of 206 patients with any of the following risk factors (1) essential hypertension, (2) obesity or (3) a first-degree relative with a diagnosis of diabetes were included in a survival analysis study for a diagnosis of new onset type 2 diabetes. At inclusion, a glucometry by means of a Continuous Glucose Monitoring System was performed, and DFA was calculated for a 24-h glucose time series. Patients were then followed up every 6 months, controlling for the development of diabetes.

RESULTS

In a median follow-up of 18 months, there were 18 new cases of diabetes (58.5 cases/1000 patient-years). DFA was a significant predictor for the development of diabetes, with ten events in the highest quartile versus one in the lowest (log-rank test chi2 = 9, df = 1, p = 0.003), even after adjusting for other relevant clinical and biochemical variables. In a Cox model, the risk of diabetes development increased 2.8 times for every 0.1 DFA units. In a multivariate analysis, only fasting glucose, HbA_1c and DFA emerged as significant factors.

CONCLUSIONS

Detrended fluctuation analysis significantly performed as a harbinger of type 2 diabetes development in a high-risk population. Complexity analysis may help in targeting patients who could be candidates for intensified treatment. Copyright © 2016 The Authors. Diabetes/Metabolism Research and Reviews Published by John Wiley & Sons Ltd.

Impact of dietary fat composition on prediabetes: a 12-year follow-up study

Objective

Dietary fatty acid composition likely affects prediabetic conditions such as isolated impaired fasting glucose (IFG) or impaired glucose tolerance (IGT); however, this risk has not been evaluated in a large population nor has it been followed prospectively.

Design

Diet, physical activity, anthropometric, socio-economic and blood glucose data from the Atherosclerosis Risk in Communities (ARIC) study were obtained from BioLINCC. Cox proportional hazards regression models were used to evaluate associations of dietary SFA, MUFA, PUFA,n-3 fatty acid (FA) andn-6 FA intakes with incidence of one (isolated IFG) or two (IFG with IGT) prediabetic conditions at the end of 12-year follow-up.

Setting

Study volunteers were from counties in North Carolina, Mississippi, Minnesota and Maryland, USA.

Subjects

Data from 5288 volunteers who participated in the ARIC study were used for all analyses reported herein.

Results

The study population was 62% male and 84 % white, mean age 53·5 (sd5·7) years and mean BMI 26·2 (sd4·6) kg/m2. A moderately high intake of dietary MUFA (10–15 % of total daily energy) was associated with a 10 % reduced risk of isolated IFG incidence, while a high intake ofn-3 FA (>0·15 % of total daily energy) was associated with a 10 % increase in risk. Curiously, moderately high intake ofn-6 PUFA (4–5 % of total daily energy) was associated with a 12 % reduction in IFG and IGT incidence.

Conclusions

MUFA,n-3 andn-6 FA contribute differently to the development of isolated IFGv. IFG with IGT; and their mechanism may be more complex than originally proposed.

The role of patient education in the prevention and management of type 2 diabetes: an overview

The management of type 2 diabetes mellitus includes ability and empowerment of the patient to change lifestyle, maintain an adequate diet and physical activity, manage the disease, and follow a specific program of periodic medical checks and education sessions. In addition, the patient should be able to correctly identify and adequately solve problems related to the disease and actively collaborate with the healthcare system. To obtain these goals, therapeutic patient education (TPE) is now considered a crucial element not only in the treatment but also in the prevention of type 2 diabetes. Several trials showed that TPE is able to improve clinical, lifestyle, and psycho-social outcomes. Nevertheless, studies have not clarified the ideal characteristics of a comprehensive patient education program in clinical practice. Other work is needed to answer open questions regarding the type of PTE (individual or group education), themes, frequency and number of education sessions, contact time between educator and patient, background of educators, use of new technologies, and barriers to self-management. The present review discusses these points on the basis of the most recent data of the literature.

Mechanisms by which cocoa flavanols improve metabolic syndrome and related disorders

Dietary administration of cocoa flavanols may be an effective complementary strategy for alleviation or prevention of metabolic syndrome, particularly glucose intolerance. The complex flavanol composition of cocoa provides the ability to interact with a variety of molecules, thus allowing numerous opportunities to ameliorate metabolic diseases. These interactions likely occur primarily in the gastrointestinal tract, where native cocoa flavanol concentration is high. Flavanols may antagonize digestive enzymes and glucose transporters, causing a reduction in glucose excursion, which helps patients with metabolic disorders maintain glucose homeostasis. Unabsorbed flavanols, and ones that undergo enterohepatic recycling, will proceed to the colon where they can exert prebiotic effects on the gut microbiota. Interactions with the gut microbiota may improve gut barrier function, resulting in attenuated endotoxin absorption. Cocoa may also positively influence insulin signaling, possibly by relieving insulin-signaling pathways from oxidative stress and inflammation and/or via a heightened incretin response. The purpose of this review is to explore the mechanisms that underlie these outcomes, critically review the current body of literature related to those mechanisms, explore the implications of these mechanisms for therapeutic utility, and identify emerging or needed areas of research that could advance our understanding of the mechanisms of action and therapeutic potential of cocoa flavanols.

Hypomagnesemia in Type 2 Diabetes: A Vicious Circle?

Over the past decades, hypomagnesemia (serum Mg(2+) <0.7 mmol/L) has been strongly associated with type 2 diabetes mellitus (T2DM). Patients with hypomagnesemia show a more rapid disease progression and have an increased risk for diabetes complications. Clinical studies demonstrate that T2DM patients with hypomagnesemia have reduced pancreatic β-cell activity and are more insulin resistant. Moreover, dietary Mg(2+) supplementation for patients with T2DM improves glucose metabolism and insulin sensitivity. Intracellular Mg(2+) regulates glucokinase, KATP channels, and L-type Ca(2+) channels in pancreatic β-cells, preceding insulin secretion. Moreover, insulin receptor autophosphorylation is dependent on intracellular Mg(2+) concentrations, making Mg(2+) a direct factor in the development of insulin resistance. Conversely, insulin is an important regulator of Mg(2+) homeostasis. In the kidney, insulin activates the renal Mg(2+) channel transient receptor potential melastatin type 6 that determines the final urinary Mg(2+) excretion. Consequently, patients with T2DM and hypomagnesemia enter a vicious circle in which hypomagnesemia causes insulin resistance and insulin resistance reduces serum Mg(2+) concentrations. This Perspective provides a systematic overview of the molecular mechanisms underlying the effects of Mg(2+) on insulin secretion and insulin signaling. In addition to providing a review of current knowledge, we provide novel directions for future research and identify previously neglected contributors to hypomagnesemia in T2DM.

Delay in the Detrended Fluctuation Analysis Crossover Point as a Risk Factor for Type 2 Diabetes Mellitus

Detrended Fluctuation Analysis (DFA) measures the complexity of a glucose time series obtained by means of a Continuous Glucose Monitoring System (CGMS) and has proven to be a sensitive marker of glucoregulatory dysfunction. Furthermore, some authors have observed a crossover point in the DFA, signalling a change of dynamics, arguably dependent on the beta-insular function. We investigate whether the characteristics of this crossover point have any influence on the risk of developing type 2 diabetes mellitus (T2DM). To this end we recruited 206 patients at increased risk of T2DM (because of obesity, essential hypertension, or a first-degree relative with T2DM). A CGMS time series was obtained, from which the DFA and the crossover point were calculated. Patients were then followed up every 6 months for a mean of 17.5 months, controlling for the appearance of T2DM diagnostic criteria. The time to crossover point was a significant predictor risk of developing T2DM, even after adjusting for other variables. The angle of the crossover was not predictive by itself but became significantly protective when the model also considered the crossover point. In summary, both a delay and a blunting of the crossover point predict the development of T2DM.