Defects in insulin secretion and insulin action in non-insulin-dependent diabetes mellitus are inherited. Metabolic studies on offspring of diabetic probands

Investigating family history of diabetes as a predictor of fasting insulin and fasting glucose activity in a sample of healthy weight adults

AIMS

Type 2 diabetes is a major public health problem for the global community. Having a family history of diabetes significantly increases risk for diabetes development and understanding how family history contributes to diabetes risk could lead to more effective prevention efforts for at-risk individuals. In a previous study, we showed family history of diabetes is a significant predictor of fasting insulin in healthy weight children. The present study aimed to use the National Health and Nutrition Examination Survey (NHANES 2017) to apply similar multiple regression models to a population of healthy weight adults to determine if family history is a significant predictor of fasting glucose and fasting insulin.

METHODS

Fasting glucose (mg/dL) and fasting insulin (pmol/L) were used as dependent variables in each model, respectively, with family history of diabetes as the independent variable. Covariates for each model included age, gender, race/ethnicity, waist circumference, and macronutrient intake.

RESULTS

The model significantly predicted the variance of fasting glucose [(F(11,364) = 34.80, p < 0.001, R² = 0.2342] and fasting insulin [F(11,343) = 17.58, p < 0.001, R² = 0.1162]. After adjusting for covariates, family history was a significant predicator of fasting glucose (p = 0.0193) as well as age, gender, non-Hispanic black ethnicity, waist circumference, and fat intake. Significant predictors of fasting insulin included gender and waist circumference, but not family history (p = 0.8264). In addition, fasting glucose was higher in individuals with a family history of diabetes (p = 0.033).

CONCLUSIONS

These results add to the understanding of how family history influences the biomarkers that contribute to diabetes development. Knowledge of how family history of diabetes relates to fasting insulin and fasting glucose activity in healthy weight individuals can be used to design personalized screening and early prevention strategies.

iPSCs derived from insulin resistant offspring of type 2 diabetic patients show increased oxidative stress and lactate secretion

Background

The genetic factors associated with insulin resistance (IR) are not well understood. Clinical studies on first-degree relatives of type 2 diabetic (T2D) patients, which have the highest genetic predisposition to T2D, have given insights into the role of IR in T2D pathogenesis. Induced pluripotent stem cells (iPSCs) are excellent tools for disease modeling as they can retain the genetic imprint of the disease. Therefore, in this study, we aimed to investigate the genetic perturbations associated with insulin resistance (IR) in the offspring of T2D parents using patient-specific iPSCs.

Methods

We generated iPSCs from IR individuals (IR-iPSCs) that were offspring of T2D parents as well as from insulin-sensitive (IS-iPSCs) individuals. We then performed transcriptomics to identify key dysregulated gene networks in the IR-iPSCs in comparison to IS-iPSCs and functionally validated them.

Results

Transcriptomics on IR-iPSCs revealed dysregulated gene networks and biological processes indicating that they carry the genetic defects associated with IR that may lead to T2D. The IR-iPSCs had increased lactate secretion and a higher phosphorylation of AKT upon stimulation with insulin. IR-iPSCs have increased cellular oxidative stress indicated by a high production of reactive oxygen species and higher susceptibility to H2O2 -induced apoptosis.

Conclusions

IR-iPSCs generated from offspring of diabetic patients confirm that oxidative stress and increased lactate secretion, associated with IR, are inherited in this population, and may place them at a high risk of T2D. Overall, our IR-iPSC model can be employed for T2D modeling and drug screening studies that target genetic perturbations associated with IR in individuals with a high risk for T2D.

Prohormone convertase 1/3 deficiency causes obesity due to impaired proinsulin processing

Defective insulin processing is associated with obesity and diabetes. Prohormone convertase 1/3 (PC1/3) is an endopeptidase required for the processing of neurotransmitters and hormones. PC1/3 deficiency and genome-wide association studies relate PC1/3 with early onset obesity. Here, we find that deletion of PC1/3 in obesity-related neuronal cells expressing proopiomelanocortin mildly and transiently change body weight and fail to produce a phenotype when targeted to Agouti-related peptide- or nestin-expressing tissues. In contrast, pancreatic β cell-specific PC1/3 ablation induces hyperphagia with consecutive obesity despite uncontrolled diabetes with glucosuria. Obesity develops not due to impaired pro-islet amyloid polypeptide processing but due to impaired insulin maturation. Proinsulin crosses the blood-brain-barrier but does not induce central satiety. Accordingly, insulin therapy prevents hyperphagia. Further, islet PC1/3 expression levels negatively correlate with body mass index in humans. In this work, we show that impaired PC1/3-mediated proinsulin processing, as observed in human prediabetes, promotes hyperphagic obesity.

Defective insulin secretion is observed early in the development of diabetes. Here the authors report that β cell-specific deficiency of the insulin prohormone convertase 1/3 (PC1/3) leads not only to hyperglycemia, but also to hyperphagic obesity in mice.

Severity of the metabolic syndrome as a predictor of prediabetes and type 2 diabetes in first degree relatives of type 2 diabetic patients: A 15-year prospective cohort study

BACKGROUND

Type 2 diabetes mellitus (T2DM) has high morbidity and mortality worldwide, therefore there is of paramount importance to identify the risk factors in the populations at risk early in the course of illness. A strong correlation between severity of metabolic syndrome (MetS) and HbA1c, fasting insulin and insulin resistance has been reported. Accordingly, the MetS severity score (or MestS Z-score) can potentially be used to predict the risk of T2DM progression over time.

AIM

To evaluate the association the of MestS Z-score in first degree relatives (FDRs) of T2DM with the risk of prediabetes and type 2 diabetes in future.

METHODS

A prospective open cohort study was conducted between 2003-2018. At baseline, the sample comprised of 1766 FDRs of patients with T2DM who had a normal glucose tolerance test. Relative risk (RR) and 95% confidence interval were calculated based on logistic regression. The receiver-operator characteristic analysis and area under the curve based on MetS Z-score were used to evaluate the risk of prediabetes and diabetes among the FDR population.

RESULTS

Baseline MetS Z-scores were associated with the its latest values (P < 0.0001). Compared with individuals who were T2DM free at the end of follow up, those who developed T2DM had higher MetS Z-score at baseline (P < 0.001). In multivariable logistic regression analyses for every unit elevation in MetS Z-score at the baseline, the RR for developing future T2DM and prediabetes was (RR = 1.94, RR = 3.84), (RR = 1.5, RR = 2.17) in total population and female group, respectively (P < 0.05). The associations remained significant after adjusting the potential confounding variables. A cut off value of 0.97 and 0.94 was defined in the receiver-operator characteristic curve based on the MetS Z-score for differentiating female patients with diabetes and prediabetes from the normal population, respectively.

CONCLUSION

The MetS Z-score was associated with an increased risk of future T2DM. Appropriate interventions at earlier stages for preventing and attenuating MetS effects may be considered as an effective strategy for FDR as at-risk population.

Family history of diabetes in both parents is strongly associated with impaired residual β-cell function in Japanese type 2 diabetes patients

AIMS/INTRODUCTION

The objective of the present study was to clarify the association of the type and number of first-degree family history of diabetes (FHD) with the clinical characteristics, especially with residual β-cell function, in type 2 diabetes patients.

MATERIALS AND METHODS

A total of 1,131 type 2 diabetes patients were recruited and divided into four groups according to FHD information as follows: (i) patients without FHD (FHD-); (ii) those with at least one sibling who had diabetes without parental diabetes (FHD+); (iii) those with one parent (FHD++); or (iv) those with both parents (FHD+++) who had diabetes with or without a sibling with diabetes.

RESULTS

The percentages of the FHD-, FHD+, FHD++ and FHD+++ groups were 49.4%, 13.4%, 34.0% and 3.2%, respectively. Patients in the FHD++ and FHD+++ groups were significantly younger at the time of diabetes diagnosis (P < 0.001) than those in the FHD- and FHD+ groups, even after adjusting for confounding factors. In addition, the levels of insulin secretion were significantly lower in the patients in the FHD+, FHD++ and FHD+++ groups than those in the FHD- group (P < 0.05) after adjusting for confounding factors, and the patients in the FHD+++ group presented with the lowest levels of insulin secretion among the four groups.

CONCLUSIONS

Our results showed that in type 2 diabetes patients, the degree of the associations between FHD and clinical characteristics differs according to the number and the type of FHD. In particular, FHD in both parents is most strongly associated with impaired residual β-cell function.

PI4KIIα regulates insulin secretion and glucose homeostasis via a PKD-dependent pathway

Insulin release by pancreatic β cells plays a key role in regulating blood glucose levels in humans, and to understand the mechanism for insulin secretion may reveal therapeutic strategies for diabetes. We found that PI4KIIα transgenic (TG) mice have abnormal glucose tolerance and higher serum glucose levels than wild-type mice. Glucose-stimulated insulin secretion was significantly reduced in both PI4KIIα TG mice and PI4KIIα-overexpressing pancreatic β cell lines. A proximity-based biotin labeling technique, BioID, was used to identify proteins that interact with PI4KIIα, and the results revealed that PI4KIIα interacts with PKD and negatively regulates its activity. The effect of PI4KIIα on insulin secretion was completely rescued by altering PKD activity. PI4KIIα overexpression also worsened glucose tolerance in streptozotocin/high-fat diet-induced diabetic mice by impairing insulin secretion. Our study has shed new light on PI4KIIα function and mechanism in diabetes and identified PI4KIIα as an important regulator of insulin secretion.

β cell function and insulin resistance in lean cases with polycystic ovary syndrome

Obesity is a major factor in development of insulin resistance (IR) and metabolic features in polycystic ovary syndrome (PCOS) patients. Nearly two-thirds patients with PCOS (30 of 37 confirmed cases of PCOS) in our previous community based study were lean, in contrast to Caucasians. Metabolic parameters including IR and β cell function have not been characterized well in this group of lean PCOS. To study the metabolic features including IR and β cell function in lean PCOS patients, 53 patients with BMI, <23 kg/m² were compared with 71 obese PCOS and 45 age and body mass index matched controls. Lean patients had similar β cell function and IR as compared to controls and obese patients, though the latter group had more metabolic abnormality. Fasting c-peptide and its ratio to glucose were significantly higher in lean patients compared to controls. In subset of subjects with five point OGTT, disposition index and Matsuda index (MI) showed significant negative correlation with BMI and blood pressure. MI also negatively correlated with waist, WHR, and HOMAB. High fasting C-peptide is probably a class effect as is seen in both lean and obese PCOS.

Impact of Perturbed Pancreatic β-Cell Cholesterol Homeostasis on Adipose Tissue and Skeletal Muscle Metabolism

Elevated pancreatic β-cell cholesterol levels impair insulin secretion and reduce plasma insulin levels. This study establishes that low plasma insulin levels have a detrimental effect on two major insulin target tissues: adipose tissue and skeletal muscle. Mice with increased β-cell cholesterol levels were generated by conditional deletion of the ATP-binding cassette transporters, ABCA1 and ABCG1, in β-cells (β-DKO mice). Insulin secretion was impaired in these mice under basal and high-glucose conditions, and glucose disposal was shifted from skeletal muscle to adipose tissue. The β-DKO mice also had increased body fat and adipose tissue macrophage content, elevated plasma interleukin-6 and MCP-1 levels, and decreased skeletal muscle mass. They were not, however, insulin resistant. The adipose tissue expansion and reduced skeletal muscle mass, but not the systemic inflammation or increased adipose tissue macrophage content, were reversed when plasma insulin levels were normalized by insulin supplementation. These studies identify a mechanism by which perturbation of β-cell cholesterol homeostasis and impaired insulin secretion increase adiposity, reduce skeletal muscle mass, and cause systemic inflammation. They further identify β-cell dysfunction as a potential therapeutic target in people at increased risk of developing type 2 diabetes.

Type 2 diabetes and atherosclerotic cardiovascular disease: do they share common antecedents?

It has been suggested that the association between type 2 diabetes and atherosclerotic cardiovascular disease might result from a shared antecedent — the `common soil' hypothesis. The antecedent could provide a fundamental link between type 2 diabetes and atherosclerosis via the metabolic (or insulin resistance) syndrome. The relative contributions of genes, fetal nutrition and environmental factors to this syndrome remain unclear. Although most patients with type 2 diabetes have insulin resistance, it is uncertain whether the insulin resistance-hyperinsulinaemia complex directly promotes atherogenesis, and whether type 2 diabetes and atheroma are connected via a common mediator such as central obesity, vascular endothelial dysfunction, or disordered lipid metabolism. Insulin sensitivity and cardiovascular risk may be influenced by adipocytokines (e.g. leptin and adiponectin), by excess fatty acids liberated from visceral fat, and inflammatory processes. Disturbances of the neuro-endocrine system, possibly mediated via visceral obesity, are also under investigation. Other putative links between type 2 diabetes and atheroma include polymorphisms in the genes for tumour necrosis factor-α,insulin-like growth factor-1 promoter, and lamin A/C. Trials with certain cardioprotective agents including inhibitors of the renin-angiotensin-aldosterone system and statins can improve cardiovascular outcomes and protect against the development of type 2 diabetes, lending support to the common soil hypothesis.

Effect of Different Insulin Response Patterns During Oral Glucose Tolerance Test on Glycemia in Individuals with Normal Glucose Tolerance

BACKGROUND

Research is still going on for detecting the earliest glucose homeostasis derangements in individuals, which is crucial for the prevention of glucose intolerance. This cross-sectional study analyzes different insulin response patterns during the oral glucose tolerance test (OGTT) and their implications on glycemia in normoglycemic individuals.

SUBJECTS AND METHODS

The sample frame was the "Offspring of Individuals with Diabetes Study" database. All participants underwent OGTT. Blood samples were collected at 0, 30, 60, and 120 min for measurement of insulin, C-peptide, and proinsulin levels. Normal glucose tolerant individuals were selected for analysis.

RESULTS

Four hundred fifty subjects (mean age, 25 years) were included and divided into two groups according to timing of plasma insulin peaking during OGTT: Group 1, peaking at 30 min; and Group 2, peaking at 60 or 120 min. Body mass index (BMI) and insulin resistance were comparable between the groups; however, Group 2 showed a significantly higher 60- and 120-min glucose level and lower disposition index. Based on the magnitude of the insulin levels, Group 1 was subdivided into Group N (normal pattern) and Group E (exaggerated pattern) with a 30-min insulin cutoff of 74 μU/mL (Group E, ≥74 μU/mL). Group 2 was subdivided into Group DL (delayed and limited pattern; 60-min insulin <73.0 μU/mL and 120-min insulin <80.0 μU/mL) and Group DE (delayed and exaggerated pattern; 60-min insulin ≥73.0 μU/mL or 120-min insulin ≥80.0 μU/mL). Group DE showed a significantly higher area under the curve (AUC) of glucose compared with the other groups and had a lower disposition index and high-density lipoprotein levels. Group DL had significantly lower insulin resistance and BMI compared with Group E but showed a similar AUC of glucose.

CONCLUSIONS

A delayed insulin pattern was associated with higher postprandial glucose levels. Individuals with delayed and exaggerated insulin secretion may have a higher risk for glucose intolerance.

The potential impact of family history of metabolic syndrome and risk of type 2 diabetes mellitus: In a highly endogamous population

AIM

This study aims to determine the potential impact of positive family history of Metabolic Syndrome (MetS) among two generations, on developing Type 2 Diabetes Mellitus (T2DM) and the potential relation of consanguineous marriage among patients with MetS to the risk of developing T2DM among a sample of Qataris.

DESIGN

A cross-sectional study.

SETTING

Primary healthcare (PHC) centers.

MATERIALS AND METHODS

The survey and measurement were conducted from April 2011 to December 2012 among Qatari nationals above 20 years of age. Of the 2,182 subjects, who were approached to participate in the study, 1,552 (71%) gave their consent. Face-to-face interviews were conducted using a structured questionnaire followed by anthropometric measurements and laboratory tests. Metabolic syndrome was defined using the National Cholesterol Education Program-Third Adult Treatment Panel (ATP III) as well as International Diabetes Federation (IDF).

RESULTS

Overall, the prevalence of MetS was 26.2% according to ATP III and 36.9% according to IDF (P < 0.0001). The mean age of MetS patients with T2DM was significantly higher than those without T2DM (Mean 48 ± 9.9 vs. 42.5 ± 9.2; P < 0.001). The proportion of females was higher among MetS patients with T2DM as compared to those without T2DM (61% vs. 51%; P = 0.053). In addition, there were significant differences between MetS patients with and without DM in terms of co-morbidities of hypertension, coronary heart disease, and high cholesterol. The proportion of MetS patients with positive family history for MetS was significantly higher in MetS patients with T2DM as compared to those without T2DM (46.7% vs. 33.8%; P = 0.009). The proportion of positive family history of MetS among fathers (35% vs. 21.9%; P = 0.005), mothers (30.5% vs. 18.8%; P = 0.008), maternal aunt (18.3% vs. 11.2%; P = 0.055), and maternal grand father (19.5% vs. 10%; P = 0.010) were significantly higher in MetS patients with T2DM as compared to the counterpart. The proportion of consanguineous marriages was almost two times higher among MetS patients with T2DM as compared to those without T2DM (80.9% vs. 41.9%; P < 0.001). The proportion of MetS patients with T2DM was lower than MetS patients without DM below 45 years, but after 45 years, the proportion of MetS patients with T2DM remained higher than their counterparts.

CONCLUSION

Family history of MetS among parents, maternal aunt, maternal grandfather, and consanguineous marriages among patients of MetS are significantly associated with the development of T2DM in Qatar. These results support the necessity of earlier screening for T2DM among MetS patients with positive family history of MetS.

Parental history of type 2 diabetes, TCF7L2 variant and lower insulin secretion are associated with incident hypertension. Data from the DESIR and RISC cohorts

AIMS/HYPOTHESIS

The relationship between insulin secretion and the incidence of hypertension has not been well characterised. We hypothesised that both a parental history of diabetes and TCF7L2 rs7903146 polymorphism, which increases susceptibility to diabetes because of impaired beta cell function, are associated with incident hypertension. In a separate cohort, we assessed whether low insulin secretion is related to incident hypertension.

METHODS

Nine year incident hypertension was studied in 2,391 normotensive participants from the Data from an Epidemiological Study on the Insulin Resistance Syndrome (DESIR) cohort. The relationship between insulin secretion and 3 year incident hypertension was investigated in 1,047 non-diabetic, normotensive individuals from the Relationship between Insulin Sensitivity and Cardiovascular Disease (RISC) cohort. Insulin secretion during OGTT was expressed in relation to the degree of insulin resistance, as assessed by a hyperinsulinaemic-euglycaemic clamp.

RESULTS

In the DESIR cohort, a parental history of diabetes and the TCF7L2 at-risk variant were both associated with hypertension incidence at year 9, independently of waist circumference, BP, fasting glucose, insulin levels and HOMA-IR at inclusion (p = 0.02 for parental history, p = 0.006 for TCF7L2). In the RISC cohort, a lower insulin secretion rate during the OGTT at baseline was associated with both higher BP and a greater risk of hypertension at year 3. This inverse correlation between the insulin secretion rate and incident hypertension persisted after controlling for baseline insulin resistance, glycaemia and BP (p = 0.007).

CONCLUSIONS/INTERPRETATION

Parental history of diabetes, TCF7L2 rs7903146 polymorphism and a reduced insulin secretion rate were consistently associated with incident hypertension. A low insulin secretion rate might be a new risk factor for incident hypertension, beyond insulin resistance.

The antioxidant effect of the Malaysian Gelam honey on pancreatic hamster cells cultured under hyperglycemic conditions

Type 2 diabetes consists of progressive hyperglycemia, insulin resistance, and pancreatic β-cell failure which could result from glucose toxicity, inflammatory cytokines, and oxidative stress. In the present study, we investigate the effect of pretreatment with Gelam honey (Melaleuca spp.) and the individual flavonoid components chrysin, luteolin, and quercetin, on the production of reactive oxygen species (ROS), cell viability, lipid peroxidation, and insulin content in hamster pancreatic cells (HIT-T15 cells), cultured under normal and hyperglycemic conditions. Phenolic extracts from a local Malaysian species of Gelam honey (Melaleuca spp.) were prepared using the standard extraction methods. HIT-T15 cells were cultured in 5 % CO2 and then preincubated with Gelam honey extracts (20, 40, 60, and 80 μg/ml) as well as some of its flavonoid components chrysin, luteolin, and quercetin (20, 40, 60, and 80 μM), prior to stimulation by 20 and 50 mM of glucose. The antioxidative effects were measured in these cultured cells at different concentrations and time point by DCFH-DA assay. Pretreatment of cells with Gelam honey extract or the flavonoid components prior to culturing in 20 or 50 mM glucose showed a significant decrease in the production of ROS, glucose-induced lipid peroxidation, and a significant increase in insulin content and the viability of cells cultured under hyperglycemic condition. Our results show the in vitro antioxidative property of the Gelam honey and the flavonoids on the β-cells from hamsters and its cytoprotective effect against hyperglycemia.

Adipose tissue TCF7L2 splicing is regulated by weight loss and associates with glucose and fatty acid metabolism

We investigated the effects of obesity surgery-induced weight loss on transcription factor 7-like 2 gene (TCF7L2) alternative splicing in adipose tissue and liver. Furthermore, we determined the association of TCF7L2 splicing with the levels of plasma glucose and serum free fatty acids (FFAs) in three independent studies (n = 216). Expression of the short mRNA variant, lacking exons 12, 13, and 13a, decreased after weight loss in subcutaneous fat (n = 46) and liver (n = 11) and was more common in subcutaneous fat of subjects with type 2 diabetes than in subjects with normal glucose tolerance in obese individuals (n = 54) and a population-based sample (n = 49). Additionally, there was a positive correlation between this variant and the level of fasting glucose in nondiabetic individuals (n = 113). This association between TCF7L2 splicing and plasma glucose was independent of the TCF7L2 genotype. Finally, this variant was associated with high levels of serum FFAs during hyperinsulinemia, suggesting impaired insulin action in adipose tissue, whereas no association with insulin secretion or insulin-stimulated whole-body glucose uptake was observed. Our study shows that the short TCF7L2 mRNA variant in subcutaneous fat is regulated by weight loss and is associated with hyperglycemia and impaired insulin action in adipose tissue.

Impact of family history of diabetes on β-cell function and insulin resistance among Chinese with normal glucose tolerance

OBJECTIVE

This study investigated the impact of family history of diabetes (FHD) on β-cell function among Chinese with normal glucose tolerance.

RESEARCH DESIGN AND METHODS

A multistage, stratified, cluster random sampling method was used to select a provincially representative sample from Fujian Province. Eventually, a total of 1,183 subjects were entered into the analysis. Several indexes were used to assess the function of β cells, including homeostasis model assessment (HOMA) of insulin resistance (IR), HOMA of β cells, insulinogenic index (IGI), and disposition index.

RESULTS

Overweight, increased body mass index, higher low-density lipoprotein cholesterol, and higher total cholesterol (TC) were the dominant features of positive FHD (FHD(+)). The FHD(+) subjects had lower insulin sensitivity (P<0.05). FHD(+) subjects showed higher risk of IR after adjusting for other risk factors (odds ratio 1.523 [1.272-2.009]). However, there was no significant difference in insulin secretion between the two groups. With the use of the multiple linear regression model, waist circumference (WC) and triglycerides (TGs) were found to be independent risk factors of the decline of insulin sensitivity in FHD(+) subjects, and insulin sensitivity declined significantly (P<0.05) with the increase of WC and TGs. In addition, the offspring of fathers with diabetes (PT2D) were much older and had higher TC than those of mothers with diabetes (MT2D). After adjusting for gender of the parents, there was no difference between MT2D and PT2D on insulin sensitivity.

CONCLUSIONS

Inheritance if diabetes is associated with the decline of insulin sensitivity. In addition, insulin sensitivity declined with increasing WC and TG in FHD(+) subjects.

Interaction of barley β-glucan and tea polyphenols on glucose metabolism in streptozotocin-induced diabetic rats

Soluble dietary fiber and antioxidants have received much attention as most important components of functional foods. However, few data are available on the effects of the combination of tea polyphenols (TP) and β-glucan (BG) on blood glucose in a diabetic rat. The effects of administration of barley BG and TP or their combination (TP + BG) on blood glucose, lipid profiles, and antioxidant parameters on streptozotocin-induced diabetic rats were investigated. Significant improvements on the blood glucose level, serum lipid parameters (decreases in triglyceride, total cholesterol, LDL-C, and increase in HDL-C), lipid peroxidation (decrease in malondiadehyde content), and serum antioxidant status (increases in superoxide dismutase, glutathione peroxidase, and total antioxidant capacity) resulted in diabetic rats after administering TP + BG. This study, therefore, demonstrated that the intake of TP + BG has beneficial effects on glucose tolerance, lipid metabolism, and serum antioxidant status. It also revealed that TP + BG is better than TP or BG alone in improving glucose metabolism and antioxidant status in diabetic rats. Practically, the present study suggested that polyphenols-rich cereal foods are help for type 2 diabetes.

PRACTICAL APPLICATION

Although TP or BG was definitely helpful in the treatment and management of diabetes mellitus, synthetic anti-hyperglycemic effects were found between TP and BG. The fortification of a BG-rich cereal diet with TP could be used as a strategy to maintain health of diabetic subjects.

Insulin clearance is different in men and women

Insulin is often infused based upon total body weight (TBW) or fat-free mass (FFM) for glucose clamp protocols. We observed greater insulin concentrations in men than women using this approach and examined whether splanchnic insulin extraction accounts for the differences. Whole-body insulin clearance was measured during a pancreatic clamp study (somatostatin to inhibit islet hormone secretion) including 13 adults (6 men); and whole-body insulin clearance was measured during a euglycemic, hyperinsulinemic clamp study including 27 adults (13 men). Femoral artery and hepatic vein blood samples were collected to measure splanchnic insulin balance. For the pancreatic clamp study, insulin was infused at rates of 0.5, 1.0, and 2.0 mU/kg of TBW per minute; and for the euglycemic, hyperinsulinemic clamp study, insulin was infused at 2.5 mU/kg of FFM per minute. Significantly greater arterial insulin concentrations were found in men than women. Splanchnic plasma flow was similar in men and women in both protocols. Splanchnic insulin extraction and the fraction of infused insulin removed by splanchnic bed were significantly greater in men than in women. However, whole-body insulin clearance was greater in women than men. Infusing insulin per body weight or FFM results in higher plasma insulin concentrations in men than women. Splanchnic insulin extraction is greater in men, indicating that greater peripheral insulin clearance in women accounts for the sex differences we observed. This finding has implications for insulin clamp study design and raises the question of which tissues take up more insulin in women.

Clustering of insulin resistance, total and central abdominal fat: same genes or same environment?

Obesity, insulin resistance and disturbed glucose metabolism cluster within the Insulin Resistance Syndrome (IRS). Whether this reflects shared genetic or environmental factors detectable in ‘normal’ populations (not selected for IRS features) is unknown. This study estimated (i) genetic influences on IRS traits and (ii) shared and specific genetic and environmental factors on the relationships between these traits in healthy female twins. Fasting insulin, glucose, total and central fat were measured in 59 monozygotic (MZ) and 51 dizygotic (DZ) female twin pairs aged ( ± SD) 52 ± 13 years. Body fat was measured by dual-energy X-ray absorptiometry, insulin resistance and secretion by a modified homeostasis model assessment. Using intraclass correlation coefficients and univariate model-fitting analyses, genetic influences were found in total fat, central fat, insulin resistance, fasting glucose and insulin secretion, with genetic factors explaining 64, 57, 59, 75 and 68% of their variance, respectively, using the latter technique. In matched analysis intra-pair differences in total and central fat related to intra-pair differences in insulin resistance (r2 = 0.19, P < 0.001). Multivariate model-fitting showed a close genetic relationship between total and central fat (r = 0.88). The genetic correlation between IR and central fat (0.41) was significantly greater than that for total fat (0.24), suggesting that central fat is not only a predictor of, but shares considerable genetic influence with, insulin resistance. In Cholesky analysis, these genetic influences were separate from those shared between central and total fat. In conclusion, both shared and specific genetic factors regulate components of the IRS in healthy females. However, there were discrete genetic influences on -cell insulin secretion, not shared with other IRS components, suggesting that a separate genetic propensity exists for Type2 diabetes. These findings suggest we may understand the genetic and environmental influences on IRS from the study of the normal population.

Glucose tolerance, insulin sensitivity and insulin release in European non-diabetic carriers of a polymorphism upstream of CDKN2A and CDKN2B

AIMS/HYPOTHESIS

The aim of this study was to investigate the association of the rs10811661 polymorphism near the CDKN2B/CDKN2A genes with glucose tolerance, insulin sensitivity and insulin release in three samples of white people with European ancestry.

METHODS

Sample 1 comprised 845 non-diabetic offspring of type 2 diabetes patients recruited in five European centres participating in the EUGENE2 study. Samples 2 and 3 comprised, respectively, 864 and 524 Italian non-diabetic participants. All individuals underwent an OGTT. Screening for the rs10811661 polymorphism was performed using a TaqMan allelic discrimination assay.

RESULTS

The rs10811661 polymorphism did not show a significant association with age, BMI and insulin sensitivity. Participants carrying the TT genotype showed a significant reduction in insulin release, measured by an OGTT-derived index, compared with carriers of the C allele, in the three samples. When these results were pooled with those of three published studies, and meta-analysed with a random-effects model, the T allele was significantly associated with reduced insulin secretion (-35.09 [95% CI 14.68-55.52], p = 0.0008 for CC+CT vs TT; and -29.45 [95% CI 9.51-49.38], p = 0.0038, for the additive model). In addition, in our three samples, participants carrying the TT genotype exhibited an increased risk for impaired glucose tolerance (IGT) compared with carriers of the C allele (OR 1.55 [95% CI 1.20-1.95] for the meta-analysis of the three samples).

CONCLUSIONS/INTERPRETATION

Our data, together with the meta-analysis of previously published studies, show that the rs10811661 polymorphism is associated with impaired insulin release and IGT, suggesting that this variant may contribute to type 2 diabetes by affecting beta cell function.

Liver and pancreatic fat content and metabolism in healthy monozygotic twins with discordant physical activity

BACKGROUND & AIMS

Ectopic fat in muscle and liver is linked to obesity and type 2 diabetes. Recently, pancreatic lipid accumulation has also been associated with β-cell dysfunction and reduced insulin production, leading to the development of type 2 diabetes. Physical exercise training has been shown to attenuate β-cell dysfunction in patients, but little is known about its effects on pancreatic and hepatic fat accumulation. In this study, we validated in-vivo proton magnetic resonance spectroscopy ((1)H MRS) in pancreatic fat measurement with biochemical measurements in a pig model. Thereafter, the effects of increased physical activity on the amounts of pancreatic and liver fat were studied in eight monozygotic twin pairs who have discordant physical activity and fitness.

METHODS

Pancreatic fat content was studied in 15 pigs using (1)H MRS and/or biochemical analyses. In addition, liver and pancreatic fat were assessed using (1)H MRS in eight monozygotic male twin pairs with 18% mean difference in VO(2max) between the twin brothers.

RESULTS

Twins with higher physical fitness had 23% less liver fat (1.3±1.3% vs. 2.1±2.6%, p=0.022) but no such difference was observed in the pancreatic fat (8.2±9.3% vs. 9.8±8.5%, respectively, p=0.3). Hepatic fat content was inversely associated with VO(2max). A positive association was found between pancreatic and liver fat contents (β=5.18, p=0.012). Pancreatic fat content was also associated with insulin sensitivity indexes and plasma adiponectin and glutamyltransferase concentrations.

CONCLUSIONS

Pancreatic fat content is associated with insulin resistance and hepatic fat content. An active lifestyle seems to beneficially influence hepatic fat metabolism.

Clinical Characteristics of Type 2 Diabetes Patients according to Family History of Diabetes

Background

Type 2 diabetes mellitus (T2DM) has a strong genetic component, and its prevalence is notably increased in the family members of T2DM patients. However, there are few studies about the family history of T2DM. We carried out this study to assess the influences of family history on clinical characteristics in T2DM patients.

Methods

This is a cross-sectional study involving 651 T2DM patients. Patient history and physical examination were performed and fasting blood was taken. If any first degree relative was diabetic, a family history of diabetes was considered to exist.

Results

Among the total 621 patients, 38.4% had a family history of diabetes. Patients with a family history had a younger age, higher weight, younger age at diagnosis and higher triglyceride level than did those without a family history. Dyslipidemia medication and metabolic syndrome were more prevalent in familial diabetes. Sex, blood pressure, previous treatment for diabetes, HbA1c, C-peptide, total cholesterol, high density lipoprotein cholesterol, and low density lipoprotein cholesterol were not different between familial and non-familial diabetes. Upon multiple linear regression analysis, the family history of diabetes remained significantly associated with serum triglyceride level.

Conclusion

In T2DM patients with a family history of diabetes, the disease tended to develop earlier. Metabolic syndrome and cardiovascular risk factors are more prevalent in familial T2DM than they were in non-familial T2DM. These results support the necessity of earlier screening for diabetes in family members of T2DM patients and more active prevention against cardiovascular disease in T2DM patients with a family history.

Effect of physical training on insulin secretion and action in skeletal muscle and adipose tissue of first-degree relatives of type 2 diabetic patients

Physical training affects insulin secretion and action, but there is a paucity of data on the direct effects in skeletal muscle and adipose tissue and on the effect of training in first-degree relatives (FDR) of patients with type 2 diabetes. We studied insulin action at the whole body level and peripherally in skeletal muscle and adipose tissue as well as insulin-secretory capacity in seven FDR and eight control (CON) subjects before and after 12 wk of endurance training. Training improved physical fitness. Insulin-mediated glucose uptake (GU) increased (whole body and leg; P < 0.05) after training in CON but not in FDR, whereas glucose-mediated GU increased (P < 0.05) in both groups. Adipose tissue GU was not affected by training, but it was higher (abdominal, P < 0.05; femoral, P = 0.09) in FDR compared with CON. Training increased skeletal muscle lipolysis (P < 0.05), and it was markedly higher (P < 0.05) in subcutaneous abdominal than in femoral adipose tissue and quadriceps muscle with no difference between FDR and CON. Glucose-stimulated insulin secretion was lower in FDR compared with CON, but no effect of training was seen. Glucagon-like peptide-1 stimulated insulin secretion five- to sevenfold. We conclude that insulin-secretory capacity is lower in FDR than in CON and that there is dissociation between training-induced changes in insulin secretion and insulin-mediated GU. Maximal GU rates are similar between groups and increases with physical training.

The first and second phase of insulin secretion in naive Chinese type 2 diabetes mellitus

Impaired insulin secretion (ISEC) has been recognized as one of the most important pathophysiologies of type 2 diabetes mellitus. There are 2 phases of ISEC: the first phase (first ISEC) and second phase (second ISEC). This study aimed to evaluate the 2 phases of ISEC in newly diagnosed type 2 diabetes mellitus patients. Fifty-two drug-naive type 2 diabetes mellitus patients were given 2 tests: a modified low-dose graded glucose infusion (M-LDGGI) and frequent sample intravenous glucose tolerance test. The M-LDGGI is a simplified version of the Polonsky method. Two stages of intravenous infusion of glucose with different rates were given, starting from 2 mg/(kg min) and then followed by 6 mg/(kg min). Each stage was maintained for 80 minutes. The results were interpreted as the slope of the changes of plasma insulin against the glucose levels. The slope of these curves was regarded as the second ISEC and used as the criterion for grouping-the responders and nonresponders. The responders are older and had higher body mass index and log (homeostasis model assessment of beta-cell function) (log HOMA-beta) but lower fasting plasma glucose and hemoglobin A(1c) (HbA(1c)) than the nonresponders. Significant correlations were only noted between the second ISEC and first ISEC (r = 0.278, P = .046) and between the second ISEC and log HOMA-beta (r = 0.533, P = .000). Correlation between different parameters and HbA(1c) was also evaluated. Only second ISEC and log HOMA-beta were correlated significantly with HbA(1c) (r = -0.388, P = .015 and r = -0.357, P = .026, respectively). In type 2 diabetes mellitus, subjects with higher second ISEC are older and have higher body mass index. At the same time, second ISEC is the most important factor for determining glucose levels in naive Chinese type 2 diabetes mellitus patients. The first and second ISECs were only modestly correlated, which indicated that the deterioration of these 2 phases was not synchronized. Finally, we also recommend using the M-LDGGI for quantifying second ISEC. This practical method could be done in many centers without difficulty.

Higher free fatty acid uptake in visceral than in abdominal subcutaneous fat tissue in men

Visceral adipose tissue has been shown to have high lipolytic activity. The aim of this study was to examine whether free fatty acid (FFA) uptake into visceral adipose tissue is enhanced compared to abdominal subcutaneous tissue in vivo. Abdominal adipose tissue FFA uptake was measured using positron emission tomography (PET) and [(18)F]-labeled 6-thia-hepta-decanoic acid ([(18)F]FTHA) and fat masses using magnetic resonance imaging (MRI) in 18 healthy young adult males. We found that FFA uptake was 30% higher in visceral compared to subcutaneous adipose tissue (0.0025 +/- 0.0018 vs. 0.0020 +/- 0.0016 micromol/g/min, P = 0.005). Visceral and subcutaneous adipose tissue FFA uptakes were strongly associated with each other (P < 0.001). When tissue FFA uptake per gram of fat was multiplied by the total tissue mass, total FFA uptake was almost 1.5 times higher in abdominal subcutaneous than in visceral adipose tissue. In conclusion, we observed enhanced FFA uptake in visceral compared to abdominal subcutaneous adipose tissue and, simultaneously, these metabolic rates were strongly associated with each other. The higher total tissue FFA uptake in subcutaneous than in visceral adipose tissue indicates that although visceral fat is active in extracting FFA, its overall contribution to systemic metabolism is limited in healthy lean males. Our results indicate that subcutaneous, rather than visceral fat storage plays a more direct role in systemic FFA availability. The recognized relationship between abdominal visceral fat mass and metabolic complications may be explained by direct effects of visceral fat on the liver.

Changes in cytokine levels during acute hyperinsulinemia in offspring of type 2 diabetic subjects

OBJECTIVE

To investigate the changes in the levels of cytokines and adhesion molecules in response to acute hyperinsulinemia in the offspring of type 2 diabetic subjects.

METHODS

Forty healthy offspring of type 2 diabetic subjects and 19 control offspring of healthy parents were included in the study. Twenty offspring had normal glucose tolerance (NGT) and twenty offspring impaired glucose tolerance (IGT). Insulin sensitivity was determined by the hyperinsulinemic euglycemic clamp and insulin secretion with the intravenous glucose tolerance test. The levels of cytokines and adhesion molecules were measured before and at the end of the clamp.

RESULTS

Acute hyperinsulinemia induced by the euglycemic hyperinsulinemic clamp reduced the levels of TNF-alpha, IL-8, IL-10 and IL-18 in healthy controls but not in the offspring of type 2 diabetic subjects having NGT or IGT. In response to insulin, levels of hs-CRP decreased and levels of IL-6 increased significantly in all study groups. The levels of adhesion molecules (ICAM-1, VCAM-1, E-Selectin) remained unchanged in response to hyperinsulinemia.

CONCLUSIONS

The suppression of cytokine levels (particularly proinflammatory cytokines) during acute hyperinsulinemia observed in healthy controls was not present in offspring of type 2 diabetic patients. This emphasizes the crucial role of low-grade inflammation in insulin resistance in subjects with high risk of developing diabetes.

Beta cell (dys)function in non-diabetic offspring of diabetic patients

AIMS/HYPOTHESIS

The first-degree offspring of patients with type 2 diabetes are prone to develop type 2 diabetes, and have both insulin resistance and beta cell impairment. However, it is still unclear whether both pathophysiological features are inseparably combined and which is the outstanding determinant in the offspring.

METHODS

Glucose metabolism, insulin sensitivity (calculated as M value divided by insulin [M/I]) and beta cell function were studied in the offspring of individuals with type 2 diabetes (n = 187; 57% females; age 43.8 +/- 8.1 years; BMI 26.8 +/- 4.5 kg/m(2)) and in individuals without a family history of type 2 diabetes (controls, n = 519, 55% females; age 43.4 +/- 8.2 years; BMI 26.4 +/- 3.7 kg/m(2), no significant differences between the groups for any characteristic) by performance of 75 g OGTT and 2 h hyperinsulinaemic (40 mU min(-1) m(-2))-isoglycaemic clamp tests. Beta cell function was evaluated by calculating insulinogenic index (IGI) from C-peptide AUC:glucose AUC ratios from the first hour of OGTT (IGI[60 min]) and from the total OGTT (IGI[120 min]).

RESULTS

During the OGTT, the offspring of individuals with type 2 diabetes showed 4-14% higher plasma glucose from 30 to 120 min (p < 0.05) and 20-29% higher serum insulin from 90 to 120 min, but decreased IGI(60 min) and IGI(120 min) (p < 0.05). M/I was 11% lower in the offspring of affected individuals than in controls (p < 0.01). To study the offspring of patients with type 2 diabetes with insulin sensitivity similar to that of the control group, the offspring of affected patients were divided into M/I quartiles. Those in the third M/I quartile showed M/I values and major anthropometric characteristics similar to those of the controls, but insulin AUC and C-peptide AUC values were lower in the first hour and the total OGTT (p < 0.05). The third M/I quartile had lower IGI values at 60 min and 120 min: 11% and 14% lower, respectively (p < 0.02).

CONCLUSIONS/INTERPRETATION

The first-degree offspring of type 2 diabetic patients show insulin resistance and beta cell dysfunction in response to oral glucose challenge. Beta cell impairment exists in insulin-sensitive offspring of patients with type 2 diabetes, suggesting beta cell dysfunction to be a major defect determining diabetes development in diabetic offspring.

Uncoupling protein 2 Ala55Val polymorphism is associated with a higher acute insulin response to glucose

Recent evidence suggests that mitochondrial uncoupling protein 2 (UCP2) in pancreatic beta-cells plays a crucial role in insulin production and secretion. We hypothesized that 2 UCP2 polymorphisms, a -55C/T (Ala55Val) substitution in exon 4 and an exon 8 insertion, would alter the acute insulin response to glucose (AIRg). Subjects were 155 African American (AA) and European American (EA) women. Body composition was determined by dual-energy x-ray absorptiometry. Insulin sensitivity and AIRg were measured with an intravenous glucose tolerance test and minimal modeling. To account for the confounding effects of population stratification, estimates of African admixture were obtained from approximately 35 ancestry-informative markers. Uncoupling protein 2 genotyping was conducted with gel electrophoresis. Information was analyzed using mixed linear models. A positive association between the -55C/T homozygous mutation and AIRg was identified in the total sample (P < .01) and independently in EA women (P = .02) but not AA women. The exon 8 insertion did not significantly affect AIRg. No interaction effects of the 2 polymorphisms on AIRg were noted. These results indicate that AIRg is associated with the -55C/T UCP2 homozygous mutation and that the presence of this mutation could alter postchallenge insulin concentration.

Twenty-four hour insulin secretion and beta cell NEFA oxidation in type 2 diabetic, morbidly obese patients before and after bariatric surgery

AIMS/HYPOTHESIS

We have previously demonstrated that type 2 diabetes resolves after bariatric surgery. To study the role of NEFA in the prompt normalisation of beta cell glucose sensitivity, insulin secretion and beta cell glucose and lipid metabolism were investigated by a model of nutrient-stimulated insulin secretion using a multiple-meal test.

METHODS

Hourly glucose, C-peptide and NEFA were measured in nine morbidly obese, type 2 diabetic patients before and 1 week after bariatric surgery and in six matched healthy volunteers over 24 h. A mathematical model of glucose-NEFA comodulation of insulin secretion rate (ISR) was used to compute ISR and beta-oxidation. Insulin sensitivity was measured by an OGTT minimal model.

RESULTS

Beta cell sensitivity to glucose and NEFA was doubled after surgery, while the 24 h insulin secretion decreased from 277.1 +/- 144.4 to 198.0 +/- 107.6 nmol/m(2) (p < 0.02). Insulin sensitivity was restored. The beta-oxidation rate of beta cells was completely normalised (from 0.032 +/- 0.012 x 10(-12) to 0.103 +/- 0.031 x 10(-12) mmol/min per cell, p < 0.005). The best predictor of beta cell function improvement was the duration of diabetes.

CONCLUSIONS/INTERPRETATION

Bariatric surgery in type 2 diabetes restores beta-oxidation in beta cells, doubles glucose-NEFA sensitivity and reverses diabetes. It is likely that ISR is reduced to match insulin-sensitivity normalisation, in spite of no significant reduction in NEFA levels. We hypothesise that insulin sensitivity normalisation might appear as a consequence of nutrient exclusion from proximal intestinal transit, and that secondarily the need for insulin secretion diminishes. The insulin sensitivity increase is much higher than usually obtained by insulin-sensitising agents and is independent of weight changes.

A review of islet of Langerhans degeneration in rodent models of type 2 diabetes

Type 2 diabetes mellitus (TTDM) is characterized by progressive loss of glucose control through multifactorial mechanisms. The search for an understanding of TTDM has relied on animal models since the realization of the importance of the pancreas in controlling plasma glucose concentration. Rodent models of TTDM are developed to express hyperglycemia and not islet degeneration per se. Degeneration of the islets of Langerhans with beta-cell loss is secondary to insulin resistance and is regarded as the more important lesion. Despite this, differences between models are seen in the development and progression of islet degeneration. Assessing the differences between the models is important to appreciate the various aspects of TTDM and understand their advantages as well as their deficiencies. Relevant animal models of TTDM provide opportunities to investigate important physiological and cell biological processes that may ultimately lead to development of targeted therapies. This article reviews the importance, advantages, and limitations of rodent models of TTDM in relation to the histopathological changes that characterize islet degeneration. Pathophysiological mechanisms that contribute to islet degeneration are also discussed and are placed into the context of changes in islet histological appearances.

Markers of endothelial dysfunction and low-grade inflammation are associated in the offspring of type 2 diabetic subjects

The offspring of type 2 diabetic patients are at elevated risk for type 2 diabetes and cardiovascular disease. The aim of our study was to characterize the role of various biomarkers of endothelial activation in a cohort of offspring of type 2 diabetic subjects and to assess the association of adhesion molecules with inflammatory markers and metabolic parameters. Cytokine and adhesion molecule levels were measured in 19 healthy subjects and in 129 offspring of patients with type 2 diabetes (109 with normal glucose tolerance and 20 with impaired glucose tolerance). Insulin sensitivity was determined with the hyperinsulinemic-euglycemic clamp, insulin secretion with the intravenous glucose tolerance test, and abdominal fat distribution with computed tomography. The levels of vascular cell adhesion molecule-1, intercellular adhesion molecule-1, E-Selectin and vascular adhesion protein-1 were not increased in offspring of type 2 diabetic subjects, but they correlated with inflammatory markers (C-reactive protein, tumor necrosis-alpha, interleukin-6, interleukin-1 beta, interleukin-1 receptor antagonist, interleukin-8, interleukin-10 and interleukin-18). In conclusion, the levels of adhesion molecules were not elevated in the prediabetic state. Inflammatory markers and adhesion molecules were correlated suggesting that low-grade inflammation may precede the elevation of levels of adhesion molecules.

Impaired glucose-stimulated insulin secretion is coupled with exocrine pancreatic lesions in the Cohen diabetic rat

OBJECTIVE

The Cohen diabetes-sensitive rat develops postprandial hyperglycemia when fed a high-sucrose, copper-poor diet, whereas the Cohen diabetes-resistant rat maintains normoglycemia. The pathophysiological basis of diabetes was studied in the Cohen diabetic rat centering on the interplay between the exocrine and endocrine compartments of the pancreas.

RESEARCH DESIGN AND METHODS

Studies used male Cohen diabetes-sensitive and Cohen diabetes-resistant rats fed 1-month high-sucrose, copper-poor diet. Serum insulin and glucose levels were measured during glucose and insulin tolerance tests. The pancreas was evaluated for weight, insulin content, macrophage, and fat infiltration. Glucose-stimulated insulin secretion (GSIS) was determined in isolated perfused pancreas and in islets.

RESULTS

Hyperglycemic Cohen diabetes-sensitive rats exhibited reduced pancreatic weight with lipid deposits and interleukin-1beta-positive macrophage infiltration in the exocrine pancreas. Islet morphology was preserved, and total pancreatic insulin content did not differ from that of Cohen diabetes-resistant rats. Lipids did not accumulate in skeletal muscle, nor was insulin resistance observed in hyperglycemic Cohen diabetes-sensitive rats. Intravenous glucose-tolerance test revealed markedly elevated glucose levels associated with diminished insulin output. Insulin release was induced in vivo by the non-nutrient secretagogues arginine and tolbutamide, suggesting a selective unresponsiveness to glucose. Decreased GSIS was observed in the isolated perfused pancreas of the hyperglycemic Cohen diabetes-sensitive rat, whereas islets isolated from these rats exhibited glucose-dependent insulin secretion and proinsulin biosynthesis.

CONCLUSIONS

The association of the in vivo insulin secretory defect with lipid accumulation and activated macrophage infiltration in the exocrine pancreas suggests that changes in the islet microenvironment are the culprit in the insulin secretory malfunction observed in vivo.

Protection of pancreatic beta-cells: is it feasible?

Hyperglycemia, which is the biochemical hallmark of type 2 diabetes, mainly results from insulin resistance and beta-cell dysfunction. However, the latter is crucial in the development of the disease because diabetes cannot occur without an impairment of insulin secretion. Beta-cell failure is also responsible for progressive loss of metabolic control in type 2 diabetic patients and the eventual need for insulin treatment. An impairment of beta-cell function can be detected in several ways and can be observed already in pre-diabetic individuals. Histopathology studies documented that beta-cell volume is reduced in pre-diabetes and, to a greater extent, in type 2 diabetes mainly because the apoptotic rate of beta-cells is increased whereas neogenesis is intact. All anti-diabetic agents can improve, directly or indirectly, beta-cell function. However, only PPAR-gamma agonists and incretin-mimetic agents seem to have favorable effects on beta-cell morphology and volume. Many trials showed that type 2 diabetes can be prevented but few of them directly addressed the issue of beta-cell protection by the intervention used in the study. It is reasonable to conclude that in these trials diabetes prevention, which was based on the use of lifestyle changes (diet and/or exercise) or different drugs (tolbutamide, acarbose, metformin, glitazones, bezafibrate, orlistat, angiotensin converting enzyme inhibitors, angiotensin II receptor blockers or pravastatin), depended also, or mainly, on a protection of the beta-cells but in most studies data on insulin secretion are not available or are insufficient to draw firm conclusions. The mechanisms of beta-cell protection in these trials, if any, remain unknown. They could be various and likely included reduced glucotoxicity, lipotoxicity, insulin resistance, inflammation, oxidant stress and/or apoptosis, an amelioration of islet blood flow and/or favorable changes in cation balance within the islets. Contrasting the decline and the eventual failure of beta-cells is crucial in preventing type 2 diabetes as well as in changing the natural history of the disease, when it occurs. The protection can be achieved in several ways but any strategy should include a change in lifestyle in order to generate a healthier islet milieu. Among anti-diabetic drugs, PPAR-gamma agonists and incretin-mimetic agents are the most promising in the protection. Among other drugs, inhibitors of the renin-angiotensin system might play a significant role. The increased worldwide diffusion of type 2 diabetes and the progressive loss of metabolic control in affected patients are clear demonstrations that the strategies to protect the beta-cells implemented so far, if any, were largely inadequate. Anti-diabetic agents targeting the intimate mechanisms of beta-cell damage might change the scenario in the near future.

Impact of metabolic syndrome risk factors in first-degree relatives of type 2 diabetic patients

OBJECTIVE

Family members of patients with an established diagnosis of type 2 diabetes mellitus (T2DM) are theoretically at risk of having the metabolic syndrome (MetS). A sample of these family members was studied from a population in a small township in Argentina, which has a high prevalence of T2DM.

METHODS

We examined the clinical and metabolic characteristics of 132 first-degree relatives of T2DM patients (FDR) and 112 age-matched controls. The subjects were categorized according to the International Diabetes Federation (IDF) and National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATPIII) criteria for MetS.

RESULTS

The prevalence of MetS in the FDR group was 34.8 (IDF) and 26.5% (NCEP-ATPIII) respectively, which was significantly different to the prevalence in controls (p < 0.025). According to IDF criteria, the most prevalent factors among FDR subjects with MetS were low HDL-cholesterol (87%) followed by hypertriglyceridemia (69.5%). In the MetS group, which ranged between 20-29 years old (36%), the major risk factor in women was a low HDL-cholesterol serum level. In the MetS group, which ranged between 30-39 years old (44.4%), the most important risk factor in men was hypertriglyceridemia.

CONCLUSION

This study revealed that the prevalence of MetS is high in young FDR adults, who need urgent preventive treatment, including lifestyle changes. The risk of developing T2DM is five times higher in non-diabetic people with MetS than in those without the syndrome.

Insulin resistance as the underlying cause for the metabolic syndrome

Classically, the metabolic syndrome is characterized as group of pathologies including visceral obesity, hypertension, dyslipidemia, and impaired glucose tolerance. It is now realized that insulin resistance plays a principal role in initiating and perpetuating the pathologic manifestations of the metabolic syndrome. A more in-depth understanding of the basic pathophysiologic mechanisms underlying insulin resistance may aid clinicians in treating and possibly delaying or even preventing the onset of the metabolic syndrome and its complications. This article outlines how abnormal insulin signaling and secretion, impaired glucose disposal, lipotoxicity, and proinflammatory cytokines exacerbate insulin resistance and result in the perturbations of the metabolic syndrome.

Is family history a useful tool for detecting children at risk for diabetes and cardiovascular diseases? A public health perspective

Several studies indicate that the risk for type 2 diabetes or cardiovascular disease is detectable in childhood, although these disorders may not emerge until adulthood. In addition, type 2 diabetes and cardiovascular disease seem to share risk factors, including obesity and dyslipidemia, and might even share etiology, which has important implications for screening and prevention strategies for both diseases. Primary prevention, in particular, has gained importance because the results of major randomized, controlled trials strongly suggest that, at least in high-risk adult groups, type 2 diabetes can be prevented or delayed. Furthermore, some intervention studies indicate that the risk factors for diabetes and cardiovascular disease can be reduced in children. A simple way to detect risk for either diabetes or cardiovascular disease is to examine the family history. Numerous studies have shown that adults who have 1 or more first- or second-degree relatives affected with diabetes or cardiovascular disease are at high risk of having or developing these diseases. Currently, there are no overall screening strategies recommended for either diabetes or cardiovascular disease among children and adolescents. The evidence is strong, however, that youth with a positive family history already show signs of increased risk for these conditions. Family history can be part of the approach to screening for children at risk of diabetes and cardiovascular disease and should be part of prevention campaigns aimed at reducing the burden of these diseases and their risk factors in children.

Effects on insulin secretion and insulin action of a 48-h reduction of plasma free fatty acids with acipimox in nondiabetic subjects genetically predisposed to type 2 diabetes

Elevated plasma FFA cause beta-cell lipotoxicity and impair insulin secretion in nondiabetic subjects predisposed to type 2 diabetes mellitus [T2DM; i.e., with a strong family history of T2DM (FH+)] but not in nondiabetic subjects without a family history of T2DM. To determine whether lowering plasma FFA with acipimox, an antilipolytic nicotinic acid derivative, may enhance insulin secretion, nine FH+ volunteers were admitted twice and received in random order either acipimox or placebo (double-blind) for 48 h. Plasma glucose/insulin/C-peptide concentrations were measured from 0800 to 2400. On day 3, insulin secretion rates (ISRs) were assessed during a +125 mg/dl hyperglycemic clamp. Acipimox reduced 48-h plasma FFA by 36% (P < 0.001) and increased the plasma C-peptide relative to the plasma glucose concentration or DeltaC-peptide/Deltaglucose AUC (+177%, P = 0.02), an index of improved beta-cell function. Acipimox improved insulin sensitivity (M/I) 26.1 +/- 5% (P < 0.04). First- (+19 +/- 6%, P = 0.1) and second-phase (+31 +/- 6%, P = 0.05) ISRs during the hyperglycemic clamp also improved. This was particularly evident when examined relative to the prevailing insulin resistance [1/(M/I)], as both first- and second-phase ISR markedly increased by 29 +/- 7 (P < 0.05) and 41 +/- 8% (P = 0.02). There was an inverse correlation between fasting FFA and first-phase ISR (r2 = 0.31, P < 0.02) and acute (2-4 min) glucose-induced insulin release after acipimox (r2 =0.52, P < 0.04). In this proof-of-concept study in FH+ individuals predisposed to T2DM, a 48-h reduction of plasma FFA improves day-long meal and glucose-stimulated insulin secretion. These results provide additional evidence for the important role that plasma FFA play regarding insulin secretion in FH+ subjects predisposed to T2DM.

Variants of transcription factor 7-like 2 (TCF7L2) gene predict conversion to type 2 diabetes in the Finnish Diabetes Prevention Study and are associated with impaired glucose regulation and impaired insulin secretion

AIMS/HYPOTHESIS

We investigated the association of variants of the transcription factor 7-like 2 (TCF7L2) gene with: (1) incident diabetes in the Finnish Diabetes Prevention Study (DPS, Study I); (2) type 2 diabetes and impaired glucose regulation (i.e. IGT or IFG) in a cross-sectional study (Study II); and (3) insulin secretion, insulin sensitivity and adipose tissue expression of TCF7L2 in offspring of type 2 diabetic probands (III).

SUBJECTS AND METHODS

Study I (the DPS) included 507 individuals with IGT who were randomly allocated to control and intervention groups and followed for an average of 3.9 years to monitor for progression to diabetes. Study II was a population-based cross-sectional study of 1,766 men, aged 50-70 years, randomly selected from the population of Kuopio, eastern Finland. Study III included 238 non-diabetic offspring of patients with type 2 diabetes. Genotyping of rs12255372 and rs7903146 of TCF7L2 was carried out.

RESULTS

In the DPS, the TT genotype of rs12255372 was significantly associated with an adjusted 2.85-fold risk (95% CI 1.17-6.95, p = 0.021) of incident diabetes in the control group, but not in the intervention group. In Study II, the adjusted odds ratio in subjects with the TT genotype was 3.40 (1.45-7.97, p = 0.005) for the comparison of diabetic subjects with normoglycaemic subjects. The T allele of rs12255372 was significantly associated with decreased insulin secretion (Studies II, III). Expression of TCF7L2 in adipose tissue tended to be lower in subjects with the TT risk genotypes of rs12255372 and rs7903146.

CONCLUSIONS/INTERPRETATION

The variant of rs12255372 of TCF7L2 was associated with incident type 2 diabetes in the DPS and in a separate population-based cross-sectional study. Impaired insulin secretion is likely to be the main cause for our findings.

The effect of exercise, training, and inactivity on insulin sensitivity in diabetics and their relatives: what is new?

Insulin resistance is a hallmark characteristic of type 2 diabetes. However, in healthy first-degree relatives of type 2 diabetics, insulin resistance is often present years before glucose intolerance or diabetes becomes clinically manifest. The mechanisms of insulin resistance involve conditions leading to an increased supply of fatty acids (e.g., high energy intake, obesity) and conditions in which the degradation/oxidation of muscular fatty acids is impaired. Several large-scale studies have documented the fact that increased physical activity can reduce or at least postpone the development of type 2 diabetes, and low physical fitness is a clear independent risk factor for the development of type 2 diabetes. The mechanisms responsible for the improvement in insulin sensitivity after exercise training have been studied extensively, but are not fully understood. This review focuses on insulin resistance in skeletal muscle and, in particular, its relation to changes in aerobic fitness in type 2 diabetics and their first-degree relatives.

Increased physical activity decreases hepatic free fatty acid uptake: a study in human monozygotic twins

Exercise is considered to be beneficial for free fatty acid (FFA) metabolism, although reports of the effects of increased physical activity on FFA uptake and oxidation in different tissues in vivo in humans have been inconsistent. To investigate the heredity-independent effects of physical activity and fitness on FFA uptake in skeletal muscle, the myocardium, and liver we used positron emission tomography (PET) in nine healthy young male monozygotic twin pairs discordant for physical activity and fitness. The cotwins with higher physical activity constituting the more active group had a similar body mass index but less body fat and 18 +/- 10% higher (P < 0.001) compared to the less active brothers with lower physical activity. Low-intensity knee-extension exercise increased skeletal muscle FFA and oxygen uptake six to 10 times compared to resting values but no differences were observed between the groups at rest or during exercise. At rest the more active group had lower hepatic FFA uptake compared to the less active group (5.5 +/- 4.3 versus 9.0 +/- 6.1 micromol (100 ml)(-1) min(-1), P = 0.04). Hepatic FFA uptake associated significantly with body fat percentage (P = 0.05). Myocardial FFA uptake was similar between the groups. In conclusion, in the absence of the confounding effects of genetic factors, moderately increased physical activity and aerobic fitness decrease body adiposity even in normal-weighted healthy young adult men. Further, increased physical activity together with decreased intra-abdominal adiposity seems to decrease hepatic FFA uptake but has no effects on skeletal muscle or myocardial FFA uptake.

Common polymorphisms of calpain-10 are associated with abdominal obesity in subjects at high risk of type 2 diabetes

AIMS/HYPOTHESIS

The mechanisms by which the calpain-10 gene (CAPN10) affects the risk of type 2 diabetes are unclear. Therefore, we investigated the effects of four polymorphisms in CAPN10 (single nucleotide polymorphism [SNP]-43, SNP-44, Insertion/Deletion [Indel]-19 and SNP-63) on insulin secretion, insulin action and abdominal fat distribution in offspring of patients with type 2 diabetes.

SUBJECTS AND METHODS

Insulin secretion was determined by an IVGTT, insulin action by the hyperinsulinaemic-euglycaemic clamp and abdominal fat distribution by computed tomography in 158 non-diabetic offspring (age 34.9+/-6.3 years [mean+/-SD], BMI 26.2+/-4.9 kg/m(2)) of type 2 diabetic patients.

RESULTS

SNP-43 (p=0.009 over the three genotypes, adjusted for age, sex, BMI and family relationship) and haplotypes carrying the A allele of SNP-43 were associated with intra-abdominal fat area. The A allele of SNP-43 was associated with intra-abdominal fat area in men (p=0.014) but not in women. SNP-44, InDel-19 and SNP-63 were not associated with intra-abdominal fat area or insulin action. Furthermore, we demonstrated in a separate sample of middle-aged men (n=234) who had a history of type 2 diabetes in first-degree relatives that the A allele of SNP-43 was associated with a large waist circumference, and high insulin levels in an OGTT.

CONCLUSIONS/INTERPRETATION

SNP-43 of CAPN10 may contribute to the risk of diabetes by regulating abdominal obesity in subjects with high risk of type 2 diabetes.

Contributions of beta-cell dysfunction and insulin resistance to the pathogenesis of impaired glucose tolerance and impaired fasting glucose

Impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) are intermediate states in glucose metabolism that exist between normal glucose tolerance and overt diabetes. Epidemiological studies demonstrate that the two categories describe distinct populations with only partial overlap, suggesting that different metabolic abnormalities characterize IGT and IFG. Insulin resistance and impaired beta-cell function, the primary defects observed in type 2 diabetes, both can be detected in subjects with IGT and IFG. However, clinical studies suggest that the site of insulin resistance varies between the two disorders. While subjects with IGT have marked muscle insulin resistance with only mild hepatic insulin resistance, subjects with IFG have severe hepatic insulin resistance with normal or near-normal muscle insulin sensitivity. Both IFG and IGT are characterized by a reduction in early-phase insulin secretion, while subjects with IGT also have impaired late-phase insulin secretion. The distinct metabolic features present in subjects with IFG and IGT may require different therapeutic interventions to prevent their progression to type 2 diabetes.

Feline Models of Type 2 Diabetes Mellitus

Feline diabetes mellitus (FDM) closely resembles human type 2 diabetes mellitus (T2DM) in many respects including clinical, physiological, and pathological features of the disease. These features include age of onset of FDM in middle age, association with obesity, residual but declining insulin secretion, development of islet amyloid deposits, loss of approximately 50% of beta-cell mass, and development of complications in several organ systems including peripheral polyneuropathy and retinopathy. Many of the pathological aspects of the disease are also experimentally inducible, facilitating study of the pathogenesis of these lesions. Physiological aspects of FDM and obesity are also well studied in the cat and provide an excellent basis for comparative studies of human T2DM. The relatively short generation time of cats along with breed predispositions to development of FDM may allow for more rapid screening and identification of genetic markers for diabetes susceptibility. FDM, in both spontaneous and inducible forms, therefore provides a good animal model of human T2DM and may provide additional insights into the pathogenesis of this important condition.

The emerging functions of UCP2 in health, disease, and therapeutics

The uncoupling proteins (UCPs) are attracting an increased interest as potential therapeutic targets in a number of important diseases. UCP2 is expressed in several tissues, but its physiological functions as well as potential therapeutic applications are still unclear. Unlike UCP1, UCP2 does not seem to be important to thermogenesis or weight control, but appears to have an important role in the regulation of production of reactive oxygen species, inhibition of inflammation, and inhibition of cell death. These are central features in, for example, neurodegenerative and cardiovascular disease, and experimental evidence suggests that an increased expression and activity of UCP2 in models of these diseases has a beneficial effect on disease progression, implicating a potential therapeutic role for UCP2. UCP2 has an important role in the pathogenesis of type 2 diabetes by inhibiting insulin secretion in islet beta cells. At the same time, type 2 diabetes is associated with increased risk of cardiovascular disease and atherosclerosis where an increased expression of UCP2 appears to be beneficial. This illustrates that therapeutic applications involving UCP2 likely will have to regulate expression and activity in a tissue-specific manner.

Metallothionein alleviates cardiac contractile dysfunction induced by insulin resistance: role of Akt phosphorylation, PTB1B, PPARgamma and c-Jun

AIMS/HYPOTHESIS

Insulin resistance is concomitant with metabolic syndrome, oxidative stress and cardiac contractile dysfunction. However, the causal relationship between oxidative stress and cardiac dysfunction is unknown. This study was designed to determine the impact of overexpression of the cardiac antioxidant metallothionein on cardiac dysfunction induced by insulin resistance in mice.

METHODS

Whole-body insulin resistance was generated in wild-type FVB and metallothionein transgenic mice by feeding them with sucrose for 12 weeks. Contractile and intracellular Ca(2+) properties were evaluated in ventricular myocytes using an IonOptix system. The contractile indices analysed included: peak shortening (PS), time to 90% PS (TPS(90)), time to 90% relengthening (TR(90)), half-width duration, maximal velocity of shortening (+dL/dt) and relengthening (-dL/dt), fura-fluorescence intensity change (DeltaFFI) and decay rate (tau).

RESULTS

The sucrose-fed mice displayed glucose intolerance, enhanced oxidative stress, hyperinsulinaemia, hypertriglyceridaemia and normal body weight. Compared with myocytes in starch-fed mice, those from sucrose-fed mice exhibited depressed PS, +dL/dt, -dL/dt, prolonged TR(90) and decay rate, and reduced DeltaFFI associated with normal TPS(90) and half-width duration. Western blot analysis revealed enhanced basal, but blunted insulin (15 mU/g)-stimulated Akt phosphorylation. It also showed elevated expression of insulin receptor beta, insulin receptor tyrosine phosphorylation, peroxisome proliferator-activated receptor gamma, protein tyrosine phosphatase 1B and phosphorylation of the transcription factor c-Jun, associated with a reduced fold increase of insulin-stimulated insulin receptor tyrosine phosphorylation in sucrose-fed mice. All western blot findings may be attenuated or ablated by metallothionein.

CONCLUSIONS/INTERPRETATION

These data indicate that oxidative stress may play an important role in cardiac contractile dysfunction associated with glucose intolerance and possibly related to alteration in insulin signalling at the receptor and post-receptor levels.

Genetic and nongenetic regulation of CAPN10 mRNA expression in skeletal muscle

The gene encoding calpain-10 (CAPN10) has been identified as a candidate gene for type 2 diabetes. Our aim was to study the impact of genetic (heritability and polymorphisms) and nongenetic (insulin, free fatty acids, and age) factors on CAPN10 mRNA expression in skeletal muscle using two different study designs. Muscle biopsies were obtained before and after hyperinsulinemic-euglycemic clamps from 166 young and elderly monozygotic and dizygotic twins as well as from 15 subjects with normal (NGT) or impaired glucose tolerance (IGT) exposed to an Intralipid infusion. We found hereditary effects on both basal and insulin-exposed CAPN10 mRNA expression. Carriers of the type 2 diabetes-associated single nucleotide polymorphism (SNP)-43 G/G genotype had reduced CAPN10 mRNA levels compared with subjects carrying the SNP-43 A-allele. Age had no significant influence on CAPN10 mRNA levels. Insulin had no significant effect on CAPN10 mRNA levels, neither in the twins nor in the basal state of the Intralipid study. However, after a 24-h infusion of Intralipid, we noted a significant increase in CAPN10 mRNA in response to insulin in subjects with NGT but not in subjects with IGT. In conclusion, we provide evidence that mRNA expression of CAPN10 in skeletal muscle is under genetic control. Glucose-tolerant but not glucose-intolerant individuals upregulate their CAPN10 mRNA levels in response to prolonged exposure to fat.

A 100-kDa urinary protein is associated with insulin resistance in offspring of type 2 diabetic patients

AIMS/HYPOTHESIS

One-third of normoalbuminuric type 1 diabetic patients show immunoreactive nephrin in urine. Offspring of type 2 diabetic patients are insulin-resistant and susceptible to the development of diabetes. We investigated whether the offspring of type 2 diabetic patients show nephrin in urine and whether possible nephrinuria is associated with insulin resistance.

METHODS

Urinary proteins from timed overnight urine collections from 128 offspring of type 2 diabetic patients and 9 control subjects were analysed by western blotting using an antibody against nephrin. Glucose metabolism was assessed by OGTT and IVGTT and the euglycaemic-hyperinsulinaemic clamp technique.

RESULTS

Of the offspring, 12.5% were strongly and 14.1% weakly positive for a 100-kDa urinary protein. All controls were negative. During the first 10 min of an IVGTT, the offspring strongly positive for the urinary protein had a higher insulin response than the offspring without the protein (3,700 vs 2,306 pmol l(-1)min(-1), p=0.007). Insulin sensitivity (the rate of whole-body glucose uptake divided by the steady-state insulin level x 100) was lower among the offspring strongly positive for the urinary protein than among the offspring negative for the protein (11.3 vs 15.8 micromol kg(-1)min(-1)pmol(-1)l(-1), p=0.008).

CONCLUSIONS/INTERPRETATION

A 100-kDa urinary protein detectable with a nephrin antibody is associated with insulin resistance in offspring of type 2 diabetic patients.