Serum insulin, proinsulin and proinsulin/insulin ratio in type 2 diabetic patients: as an index of beta-cell function or insulin resistance

Metformin restores prohormone processing enzymes and normalizes aberrations in secretion of proinsulin and insulin in palmitate-exposed human islets

AIM

To elucidate how proinsulin synthesis and insulin was affected by metformin under conditions of nutrient overstimulation.

MATERIALS AND METHODS

Isolated human pancreatic islets from seven donors were cultured at 5.5 mmol/L glucose and 0.5 mmol/L palmitate for 12, 24 or 72 h. Metformin (25 μmol/L) was introduced after initial 12 h with palmitate. Proinsulin and insulin were measured. Expression of prohormone convertase 1/3 (PC1/3) and carboxypeptidase E (CPE), was determined by western blot. Adolescents with obesity, treated with metformin and with normal glucose tolerance (n = 5), prediabetes (n = 14), or type 2 diabetes (T2DM; n = 7) were included. Fasting proinsulin, insulin, glucose, 2-h glucose and glycated haemoglobin were measured. Proinsulin/insulin ratio (PI/I) was calculated.

RESULTS

In human islets, palmitate treatment for 12 and 24 h increased proinsulin and insulin proportionally. After 72 h, proinsulin but not insulin continued to increase which was coupled with reduced expression of PC1/3 and CPE. Metformin normalized expression of PC1/3 and CPE, and proinsulin and insulin secretion. In adolescents with obesity, before treatment, fasting proinsulin and insulin concentrations were higher in subjects with T2DM than with normal glucose tolerance. PI/I was reduced after metformin treatment in subjects with T2DM as well as in subjects with prediabetes, coupled with reduced 2-h glucose and glycated haemoglobin.

CONCLUSIONS

Metformin normalized proinsulin and insulin secretion after prolonged nutrient-overstimulation, coupled with normalization of the converting enzymes, in isolated islets. In adolescents with obesity, metformin treatment was associated with improved PI/I, which was coupled with improved glycaemic control.

Investigation and Causes of Spontaneous (Non-Diabetic) Hypoglycaemia in Adults: Pitfalls to Avoid

Although adult spontaneous (non-diabetic) hypoglycaemia is rare, its recognition is important for the preventative or curative treatment of the underlying cause. Establishing Whipple's triad-low blood glucose, neuroglycopaenia and resolution of neuroglycopaenia on increasing blood glucose levels to normal or above-is essential to verify hypoglycaemia. Awareness that hypoglycaemia may occur in severely ill patients is important for its prevention. Further investigation in such cases is unnecessary unless another cause of hypoglycaemia is suspected. Patients are often asymptomatic and normoglycaemic at review. Their history of medication, self-medication, access to hypoglycaemic drugs, alcohol use and comorbidity may provide aetiological clues. The investigation involves obtaining blood samples during symptoms for laboratory glucose measurement or provoking fasting or postprandial hypoglycaemia as directed by symptoms. If confirmed, insulin, c-peptide, proinsulin and beta-hydroxybutyrate are analysed in hypoglycaemic samples. These will classify hypoglycaemia due to non-ketotic hyperinsulinaemia, non-ketotic hypoinsulinaemia and ketotic hypoinsulinaemia, and direct investigations to identify the underlying cause. There are, however, many pitfalls that may mislabel healthy individuals as "hypoglycaemic" or misdiagnose treatable or preventable causes of spontaneous hypoglycaemia. Clinical acumen and appropriate investigations will mostly identify hypoglycaemia and its cause.

Lee N, Kelly P, Trilok-Kumar G, Chisenga M, Kweka B, Faurholt-Jepsen D, Krogh-Madsen R, AM Shaw J, M. Paglinawan-Modoc D, Solon J, Frahm Olsen M, Stefanovski D, Cox S, Nitsch D, Keogh R, Filteau S. Long-term health after Severe Acute Malnutrition in children and adults- the role of the Pancreas (SAMPA): Protocol

Background: Prenatal growth retardation may increase the risk of later chronic non-communicable diseases (NCDs), including diabetes; however, long-term effects of wasting malnutrition in childhood or adulthood are less studied. Pancreatic exocrine and endocrine functions, both critical for nutrition and NCD aetiology, may not fully recover following malnutrition. However, the evidence and mechanistic information is piecemeal. We hypothesise that wasting malnutrition at any age has long-term detrimental effects on endocrine and exocrine pancreatic structure and function. Methods: The SAMPA international research programme will assess pancreatic structure and function in 3700 participants from ongoing observational nutrition cohorts, two adolescent and four adult, in Zambia, Tanzania, Philippines, and India. Pancreas size, structure, and calcification will be assessed by ultrasound and computed tomography (CT) scan; exocrine function by faecal elastase and serum lipase; and endocrine function by haemoglobin A1c (HbA1c) and blood glucose, insulin and C-peptide concentrations during an oral glucose tolerance test (OGTT). In-depth hormonal analyses of incretins, glucagon, proinsulin and trypsinogen during OGTT and intravenous glucose tolerance tests will be done in subsets of adult participants. Pancreatic size and function outcomes will be compared between people with and without prior wasting malnutrition. Analyses will investigate effect modification by sex, current age, time since malnutrition, current body mass index and dietary patterns. Mathematical modelling of OGTT data will be used to estimate the relative contribution to glucose dysregulation of decreased insulin production, changes in insulin clearance and increased insulin resistance. Proinsulin/insulin ratio will be analysed in archived samples from the Tanzanian cohort using a nested case-control design to investigate whether abnormal values precede diabetes. Conclusions: SAMPA, a large-scale multi-centre research programme using data from people with or without prior wasting malnutrition to assess several aspects of pancreatic phenotype, will provide coherent evidence for future policies and programmes for malnutrition and diabetes.

Fasting Proinsulin Independently Predicts Incident Type 2 Diabetes in the General Population

Fasting proinsulin levels may serve as a marker of β-cell dysfunction and predict type 2 diabetes (T2D) development. Kidneys have been found to be a major site for the degradation of proinsulin. We aimed to evaluate the predictive value of proinsulin for the risk of incident T2D added to a base model of clinical predictors and examined potential effect modification by variables related to kidney function. Proinsulin was measured in plasma with U-PLEX platform using ELISA immunoassay. We included 5001 participants without T2D at baseline and during a median follow up of 7.2 years; 271 participants developed T2D. Higher levels of proinsulin were associated with increased risk of T2D independent of glucose, insulin, C-peptide, and other clinical factors (hazard ratio (HR): 1.28; per 1 SD increase 95% confidence interval (CI): 1.08–1.52). Harrell’s C-index for the Framingham offspring risk score was improved with the addition of proinsulin (p = 0.019). Furthermore, we found effect modification by hypertension (p = 0.019), eGFR (p = 0.020) and urinary albumin excretion (p = 0.034), consistent with an association only present in participants with hypertension or kidney dysfunction. Higher fasting proinsulin level is an independent predictor of incident T2D in the general population, particularly in participants with hypertension or kidney dysfunction.

Endoplasmic Reticulum (ER) Stress and Its Role in Pancreatic β-Cell Dysfunction and Senescence in Type 2 Diabetes

An increased life span and accompanying nutritional affluency have led to a rapid increase in diseases associated with aging, such as obesity and type 2 diabetes, imposing a tremendous economic and health burden on society. Pancreatic β-cells are crucial for controlling glucose homeostasis by properly producing and secreting the glucose-lowering hormone insulin, and the dysfunction of β-cells determines the outcomes for both type 1 and type 2 diabetes. As the native structure of insulin is formed within the endoplasmic reticulum (ER), ER homeostasis should be appropriately maintained to allow for the proper metabolic homeostasis and functioning of β-cells. Recent studies have found that cellular senescence is critically linked with cellular stresses, including ER stress, oxidative stress, and mitochondrial stress. These studies implied that β-cell senescence is caused by ER stress and other cellular stresses and contributes to β-cells’ dysfunction and the impairment of glucose homeostasis. This review documents and discusses the current understanding of cellular senescence, β-cell function, ER stress, its associated signaling mechanism (unfolded protein response), and the effect of ER stress on β-cell senescence and dysfunction.

Diabetes-Modifying Antirheumatic Drugs: The Roles of DMARDs as Glucose-Lowering Agents

Systemic inflammation represents a shared pathophysiological mechanism which underlies the frequent clinical associations among chronic inflammatory rheumatic diseases (CIRDs), insulin resistance, type 2 diabetes (T2D), and chronic diabetes complications, including cardiovascular disease. Therefore, targeted anti-inflammatory therapies are attractive and highly desirable interventions to concomitantly reduce rheumatic disease activity and to improve glucose control in patients with CIRDs and comorbid T2D. Therapeutic approaches targeting inflammation may also play a role in the prevention of prediabetes and diabetes in patients with CIRDs, particularly in those with traditional risk factors and/or on high-dose corticosteroid therapy. Recently, several studies have shown that different disease-modifying antirheumatic drugs (DMARDs) used for the treatment of CIRDs exert antihyperglycemic properties by virtue of their anti-inflammatory, insulin-sensitizing, and/or insulinotropic effects. In this view, DMARDs are promising drug candidates that may potentially reduce rheumatic disease activity, ameliorate glucose control, and at the same time, prevent the development of diabetes-associated cardiovascular complications and metabolic dysfunctions. In light of their substantial antidiabetic actions, some DMARDs (such as hydroxychloroquine and anakinra) could be alternatively termed “diabetes-modifying antirheumatic drugs”, since they may be repurposed for co-treatment of rheumatic diseases and comorbid T2D. However, there is a need for future randomized controlled trials to confirm the beneficial metabolic and cardiovascular effects as well as the safety profile of distinct DMARDs in the long term. This narrative review aims to discuss the current knowledge about the mechanisms behind the antihyperglycemic properties exerted by a variety of DMARDs (including synthetic and biologic DMARDs) and the potential use of these agents as antidiabetic medications in clinical settings.

The Impact of Different Insulin-Related Measures on the Risk of Prediabetes Among the Chinese Han Population

INTRODUCTION

Diabetes mellitus (DM) has a serious impact on people's lives in the world. Interventions that affect risk factors for prediabetes can prevent and reduce diabetes occurrence. Proinsulin (PI), true insulin (TI), and proinsulin to insulin ratio (PI/TI) are risk factors for diabetes. The roles of these indicators in prediabetes are unclear. This study aimed to evaluate the impact of PI, TI, PI/TI, 2-h proinsulin (2hPI), 2-h true insulin (2hTI), and 2hPI/2hTI on the risk of prediabetes among the Chinese Han population.

METHODS

This cross-sectional study recruited 1688 subjects including 718 prediabetes cases and 970 non-prediabetes controls from Hainan Affiliated Hospital of Hainan Medical University. The cases involved 292 men and 426 women. The controls involved 324 men and 646 women. The mean age was 53.62 ± 12.43 years in the prediabetes group and 44.24 ± 12.87 years in the non-prediabetes group.

RESULTS

Our results showed that PI, TI, PI/TI, 2hPI, 2hTI, and 2hPI/2hTI were significantly correlated with prediabetes (all p < 0.05). Logistic regression analysis revealed that PI (OR 1.022, 95% CI 1.014-1.031, p = 0.00011), TI (OR 1.005, 95% CI 1.003-1.007, p = 0.00012), PI/TI (OR 1.517, 95% CI 1.080-2.131, p = 0.016), and 2hTI (OR 1.000, 95% CI 1.000-1.001, p = 0.002) were significantly associated with an increased risk of prediabetes. Receiver operating characteristic curve (ROC) analysis indicated that the area under the ROC curve (AUC) of the combination (PI + TI + PI/TI + 2hPI + 2hTI + 2hPI/2hTI) in diagnosing prediabetes was 0.627, which was larger than the diagnostic value of HOMA-IR (AUC 0.614) and HOMA-β (AUC 0.387).

CONCLUSIONS

Our study showed that PI, TI, PI/TI, and 2hTI could significantly enhance the risk of prediabetes in the Chinese Han population, which suggested that PI, TI, PI/TI, and 2hTI might be available risk factors for prediabetes.

Quantifying the progression of non-alcoholic fatty liver disease in human biomimetic liver microphysiology systems with fluorescent protein biosensors

Metabolic syndrome is a complex disease that involves multiple organ systems including a critical role for the liver. Non-alcoholic fatty liver disease (NAFLD) is a key component of the metabolic syndrome and fatty liver is linked to a range of metabolic dysfunctions that occur in approximately 25% of the population. A panel of experts recently agreed that the acronym, NAFLD, did not properly characterize this heterogeneous disease given the associated metabolic abnormalities such as type 2 diabetes mellitus (T2D), obesity, and hypertension. Therefore, metabolic dysfunction-associated fatty liver disease (MAFLD) has been proposed as the new term to cover the heterogeneity identified in the NAFLD patient population. Although many rodent models of NAFLD/NASH have been developed, they do not recapitulate the full disease spectrum in patients. Therefore, a platform has evolved initially focused on human biomimetic liver microphysiology systems that integrates fluorescent protein biosensors along with other key metrics, the microphysiology systems database, and quantitative systems pharmacology. Quantitative systems pharmacology is being applied to investigate the mechanisms of NAFLD/MAFLD progression to select molecular targets for fluorescent protein biosensors, to integrate computational and experimental methods to predict drugs for repurposing, and to facilitate novel drug development. Fluorescent protein biosensors are critical components of the platform since they enable monitoring of the pathophysiology of disease progression by defining and quantifying the temporal and spatial dynamics of protein functions in the biosensor cells, and serve as minimally invasive biomarkers of the physiological state of the microphysiology system experimental disease models. Here, we summarize the progress in developing human microphysiology system disease models of NAFLD/MAFLD from several laboratories, developing fluorescent protein biosensors to monitor and to measure NAFLD/MAFLD disease progression and implementation of quantitative systems pharmacology with the goal of repurposing drugs and guiding the creation of novel therapeutics.

Basal insulin ameliorates post-breakfast hyperglycemia via suppression of post-breakfast proinsulin/C-peptide ratio and fasting serum free fatty acid levels in patients with type 2 diabetes

Background

In general, basal insulin targets fasting plasma glucose (FPG) levels, and prandial insulin targets postprandial glucose (PPG) levels. However, the effects of basal insulin on PPG levels are controversial. We investigated the effect of basal insulin on postprandial hyperglycemia using a test meal at breakfast as well as compared differences between degludec and glargine.

Methods

A total of 20 participants with type 2 diabetes were randomly assigned to degludec (n = 10) or glargine (n = 10). We initiated basal-bolus insulin therapy and titrated only basal insulin until FPG was < 6.1 mmol/L. We evaluated changes in post-breakfast glucose levels and changes in clinical parameters such as serum C-peptide (CPR), proinsulin (PI), and free fatty acids (FFA) levels between the pre- and post-titration periods. Differences between degludec and glargine in the post-titration period were also evaluated.

Results

Post-breakfast glucose levels significantly decreased by 46.1% in the post-titration period compared with the pre-titration period (n = 20, p < 0.001). These decreases correlated positively with decreases in the post-breakfast PI/CPR ratio (r = 0.692, p < 0.001) and in fasting FFA levels (r = 0.720, p < 0.001). There were no significant differences in post-breakfast glucose levels between degludec and glargine. However, the hypoglycemic rate with degludec was significantly lower than with glargine.

Conclusion

Our results suggest that basal insulin with either degludec or glargine decreases the incidence of post-breakfast hyperglycemia accompanied by decreasing the post-breakfast PI/CPR ratio and fasting FFA levels in patients with type 2 diabetes.

Heterozygous PAX6 mutations may lead to hyper-proinsulinaemia and glucose intolerance: A case-control study in families with congenital aniridia

AIM

PAX6 is a transcription factor involved in embryonic development of many organs, including the eyes and the pancreas. Mutations of PAX6 gene is the main cause of a rare disease, congenital aniridia (CA). This case-control study aims to investigate the effects of PAX6 mutations on glucose metabolism and insulin secretion in families with CA.

METHODS

In all, 21 families with CA were screened by Sanger sequencing. Patients with PAX6 mutations and CA (cases) and age-matched healthy family members (controls) were enrolled. Oral glucose tolerance test (OGTT) was performed to detect diabetes or impaired glucose tolerance (IGT). Insulin and proinsulin secretion were evaluated.

RESULTS

Among 21 CA families, heterozygous PAX6 mutations were detected in five families. Among cases (n = 10) from the five families, two were diagnosed with newly identified diabetes and another two were diagnosed with IGT. Among controls (n = 12), two had IGT. The levels of haemoglobin A1c were 36 ± 4 mmol/mol (5.57 ± 0.46%) and 32 ± 5 mmol/L (5.21 ± 0.54%) in the cases and the controls, respectively (p = 0.049). More importantly, levels of proinsulin in the cases were significantly higher than that of the controls, despite similar levels of total insulin. The areas under the curve of proinsulin in the cases (6425 ± 4390) were significantly higher than that of the controls (3709 ± 1769) (p = 0.032).

CONCLUSION

PAX6 may participate in the production of proinsulin to insulin and heterozygous PAX6 mutations may be associated with glucose metabolism in CA patients.

Subgroup analysis of proinsulin and insulin levels reveals novel correlations to metabolic indicators of type 2 diabetes

Proinsulin, insulin and proinsulin/insulin (P/I) ratio have been reported to be correlated with fasting plasma glucose (FPG) and Hemoglobin A1c (HbA1c) in whole population study therefore sensitive predictors of T2D progression. However, by analyzing data collected from 2018-2019 from a cohort of 1579 East Asian individuals from Hainan Province of China, we find that the associations of proinsulin, insulin and P/I ratio with diabetic indicators have distinct, sometimes opposite regression patterns in normal, prediabetic and diabetic subgroups. The strength of the associations are generally weak in normal and prediabetic groups, and only moderate in diabetic group between postprandial proinsulin and HbA1c, between postprandial insulin and FPG or HbA1c, and between postprandial P/I ratio and FPG or HbA1c. Receiver operating characteristic (ROC) curve analysis shows these parameters are weaker than age in predicting diabetes development, with P/I ratio being the weakest. Proinsulin and insulin levels are tightly associated with insulin sensitivity across all subgroups, as measured by Matsuda index. Together, our results suggest that proinsulin, insulin or P/I ratio are weak predictors of diabetes development in the whole population, urging the need for stratifying strategies and novel perspectives in evaluating and predicting hyperglycemia progression.

Impaired Glucose-Stimulated Proinsulin Secretion Is an Early Marker of β-Cell Impairment Before Prediabetes Stage

CONTEXT

Evidence indicates that there is substantial impairment/loss of β-cell function/mass even before prediabetes. Elevated plasma proinsulin is a sign of β-cell dysfunction in patients with diabetes/prediabetes. However, the dynamic changes of glucose stimulated proinsulin secretion (GSPS) among nondiabetic individuals remain obscure.

OBJECTIVE

To examine GSPS and glucose-stimulated insulin secretion (GSIS) among individuals with normal glucose tolerance (NGT) and impaired glucose tolerance (IGT) and to evaluate whether impaired GSPS is an early biomarker of β-cell impairment in individuals with NGT who have subthreshold postprandial plasma glucose (PPG).

DESIGN AND PARTICIPANTS

We evaluated GSPS and GSIS in 116 Chinese adults without diabetes (mean age ± SD, 33.31 ± 9.10 years; mean BMI, 25.24 ± 4.20 kg/m2) with fasting plasma glucose (FPG) < 5.6 mmol/L. Based on 2hPPG, the participants were divided into three groups: NGT1 (2hPPG < 6.67 mmol/L), NGT2 (6.67 ≤ 2hPPG < 7.78 mmol/L), and IGT (7.78 ≤ 2hPPG<11.1 mmol/L). We analyzed the association of GSIS and GSPS with commonly used indexes of β-cell function, insulin resistance and family history of diabetes.

RESULTS

Although not diagnosed with prediabetes, the individuals with NGT2 have clinical characteristics and high diabetes risk factors similar to those of the IGT group. However, unlike individuals with IGT, NGT2 participants did not exhibit a delayed GSIS. Instead, GSPS was impaired in NGT2 groups but not in NGT1 group.

CONCLUSIONS

This study suggests that impaired GSPS, but not impaired GSIS, may serve as an early biomarker to identify a subpopulation of NGT with a high risk of diabetes.

Beta cell stress in a 4-year follow-up of patients with type 2 diabetes: A longitudinal analysis of the BetaDecline Study

BACKGROUND

Type 2 diabetes mellitus (T2DM) is associated with a progressive deterioration in beta cell function and loss of glycaemic control. Clinical predictors of beta cell failure are needed to guide appropriate therapy.

METHODS

A prospective evaluation of a large set of potential predictors of beta cell stress, measured as change in the proinsulin/insulin (PI/I) ratio, was conducted in a cohort of 235 outpatients with T2DM on stable treatment with oral hypoglycaemic agents or diet followed up for ~4 years (median value 3.9 years; interquartile range 3.8-4.1 years).

RESULTS

Overall, metabolic control deteriorated over time, with a significant increase in glycated haemoglobin (HbA1c; P < .0001), proinsulin (P < .0001), and PI/I ratio (P = .001), without significant changes in the homeostatic model assessment of insulin resistance. Multivariate regression analysis showed that for each 1% (10.9 mmol/mol) increase from baseline in HbA1c, the risk of beta cell stress increased by 3.8 times; for each 1% (10.9 mmol/mol) incremental increase in HbA1c during the study, risk of beta cell stress increased by 2.25 times that at baseline. By contrast, baseline anthropometric and clinical variables, lipid profile, inflammatory markers (PCR, IL-6), non-esterified fatty acids, and current therapies did not independently influence PI/I ratio variation during follow-up.

CONCLUSIONS

In this cohort of patients with T2DM, beta cell function progressively deteriorated despite current therapies. Among a large set of clinical and biochemical predictors, only baseline HbA1c levels and their deterioration overtime were associated with higher beta cell stress over time.

Human EndoC-βH1 β-cells form pseudoislets with improved glucose sensitivity and enhanced GLP-1 signaling in the presence of islet-derived endothelial cells

Three-dimensional (3D) pseudoislets (PIs) can be used for the study of insulin-producing β-cells in free-floating islet-like structures similar to that of primary islets. Previously, we demonstrated the ability of islet-derived endothelial cells (iECs) to induce PIs using murine insulinomas, where PI formation enhanced insulin production and glucose responsiveness. In this report, we examined the ability of iECs to spontaneously induce the formation of free-floating 3D PIs using the EndoC-βH1 human β-cell line murine MS1 iEC. Within 14 days, the coculturing of both cell types produced fully humanized EndoC-βH1 PIs with little to no contaminating murine iECs. The size and shape of these PIs were similar to primary human islets. iEC-induced PIs demonstrated reduced dysregulated insulin release under low glucose levels and higher insulin secretion in response to high glucose and exendin-4 [a glucagon-like peptide-1 (GLP-1) analog] compared with monolayer cells cultured alone. Interestingly, iEC-PIs were also better at glucose sensing in the presence of extendin-4 compared with PIs generated on a low-adhesion surface plate in the absence of iECs and showed an overall improvement in cell viability. iEC-induced PIs exhibited increased expression of key genes involved in glucose transport, glucose sensing, β-cell differentiation, and insulin processing, with a concomitant decrease in glucagon mRNA expression. The enhanced responsiveness to exendin-4 was associated with increased protein expression of GLP-1 receptor and phosphokinase A. This rapid coculture system provides an unlimited number of human PIs with improved insulin secretion and GLP-1 responsiveness for the study of β-cell biology.

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.

Association of serum pancreatic derived factor (PANDER) with beta-cell dysfunction in type 2 diabetes mellitus

AIM

Beta-cell dysfunction is the critical determinant for type 2 diabetes. The novel PANcreatic DERived factor (PANDER) has been identified as interesting islet-secreted cytokine that might be involved in beta-cell dysfunction, a role that has n"ot been clinically elucidated yet. Therefore, this study was designed to study the potential clinical association of this cytokine with beta-cell dysfunction in type 2 diabetes.

METHODS

Anthropometric parameters, routine biochemical markers and serum levels of PANDER were measured in 63 diabetic subjects including; recently diagnosed type 2 diabetic patients with duration of diabetes ≤6months and long-standing type 2 diabetic patients with duration of diabetes ≥5years then compared to 16 healthy control volunteers. Proinsulin, C-peptide, insulin and PANDER were measured by ELISA. Beta-cell dysfunction was assessed by HOMA2-%β, proinsulin, proinsulin-to-insulin (PI/I) ratio and proinsulin-to-C-peptide (PI/C-pep) ratio. Relations among various parameters were studied using simple and multiple linear regressions.

RESULTS

Serum PANDER levels were found to be significantly elevated in long-standing diabetics as compared to recently diagnosed diabetics and controls. In addition, PANDER was found to be significantly correlated negatively to HOMA2-%β, as well as positively to proinsulin, PI/I and PI/C-pep ratios.

CONCLUSION

PANDER is associated with beta-cell dysfunction in diabetic patients.

Abdominal subcutaneous and visceral adipose tissue and insulin resistance in the Framingham heart study

Insulin resistance is associated with central obesity and an increased risk of cardiovascular disease. Our objective is to examine the association between abdominal subcutaneous (SAT) and visceral adipose tissue (VAT) and insulin resistance, to determine which fat depot is a stronger correlate of insulin resistance, and to assess whether there was an interaction between SAT, VAT, and age, sex, or BMI. Participants without diabetes from the Framingham Heart Study (FHS), who underwent multidetector computed tomography to assess SAT and VAT (n = 3,093; 48% women; mean age 50.4 years; mean BMI 27.6 kg/m(2)), were evaluated. Insulin resistance was measured using the homeostasis model and defined as HOMA(IR) ≥75th percentile. Logistic regression models, adjusted for age, sex, smoking, alcohol, menopausal status, and hormone replacement therapy use, were used to assess the association between fat measures and insulin resistance. The odds ratio (OR) for insulin resistance per standard deviation increase in SAT was 2.5 (95% confidence interval (CI): 2.2-2.7; P < 0.0001), whereas the OR for insulin resistance per standard deviation increase in VAT was 3.5 (95% CI: 3.1-3.9; P < 0.0001). Overall, VAT was a stronger correlate of insulin resistance than SAT (P < 0.0001 for SAT vs. VAT comparison). After adjustment for BMI, the OR of insulin resistance for VAT was 2.2 (95% CI: 1.9-2.5; P < 0.0001). We observed an interaction between VAT and BMI for insulin (P interaction = 0.0004), proinsulin (P interaction = 0.003), and HOMA(IR) (P interaction = 0.003), where VAT had a stronger association in obese individuals. In conclusion, SAT and VAT are both correlates of insulin resistance; however, VAT is a stronger correlate of insulin resistance than SAT.