Beta-cell failure in the pathogenesis of type 2 diabetes mellitus

Use of continuous glucose monitoring in insulin-treated older adults with type 2 diabetes

BACKGROUND

Few studies have reported the adherence to and efficacy of continuous glucose monitoring (CGM) for improving diabetes management in insulin-treated older adults with type 2 diabetes mellitus (T2DM).

METHODS

Prospective observational cohort study using FreeStyle Libre Flash CGM in insulin-treated adults > 65 years with T2DM and HbA1c between 7% and 9%. The participants wore the CGM during the 6-weeks study period. The primary outcome was time in range (TIR) between 70 and 180 mg/dL. Secondary outcomes included time below range (TBR), glycemic variability (GV), adherence, and use of glucose data for self-insulin adjustment. Linear regressions with random effects verified the changes in TBR, TIR, time above range (TAR), GV, and GMI across the three visits using CGM (baseline, 4 weeks and 6 weeks), controlled for sex, age, educational level, and health system (private or public).

RESULTS

A total of 66 participants completed the six weeks of CGM (age 72·8 ± 5·3 years; BMI 27·8 ± 3·6 kg/m2), HbA1c: 8·0 ± 0·6%, with an overall sensor utilization of 93·1 ± 6·0%. We observed a stability in TIR (baseline: 63.5 ± 18.9% vs. endpoint: 65.5 ± 18.8%; β = 1,0, p = 0.190). Despite the low TBR at the baseline, we observed statistically significant reduction over the study period (baseline: 5.8 ± 7.0% vs. endpoint: 3.8 ± 4.7%; (β=-1.00, p = 0.008). Glucose variability also reduced from the baseline (34.9 ± 7.2%) to the endpoint (33.0 ± 6.8%) (β=-0.99, p = < 0.001).

CONCLUSION

FreeStyle Libre Flash CGM is well accepted by older adults with T2DM and allows participants to make therapeutic decisions to reduce TBR and glycemic variability.

Time Elapsed For Switching From Oral Antidiabetic Therapy to Insulin Therapy in Type 2 Diabetic Patients and Evaluation of The Factors Affecting This Period

Background We aimed to determine the time elapsed for switching from oral antidiabetic therapy to insulin therapy in patients with type 2 diabetes mellitus and the factors that affect this period. Material and Methods Three hundred fifteen patients with type 2 diabetes mellitus who were followed up in the diabetes outpatient clinic were included in the study. The gender, education level, age of onset of diabetes, presence of hypertension, smoking and body mass index of the patients were examined, and the effects of these variables on time elapsed for switching to insulin therapy were analyzed in three phases. Results Three hundred fifteen patients (117 males, 198 females) were enrolled in the study. The mean time elapsed for switching from oral antidiabetic therapy to insulin therapy was 9.93±6.67 years. The effects of education level, age at the onset of diabetes, presence of hypertension, and body mass index on time elapsed for switching to insulin therapy were found to be statistically significant (p0.05). The time elapsed for switching to insulin therapy shortened as the education level, the age at the onset of diabetes, and body mass index level increased. It was found that hypertension in patients with type 2 diabetes mellitus prolongs the time elapsed for switching to insulin therapy. Conclusion The body mass index level, presence of hypertension, education level and age at the onset of diabetes were the significant factors affecting the time elapsed for switching to insulin therapy.

Function of Nr4a Orphan Nuclear Receptors in Proliferation, Apoptosis and Fuel Utilization Across Tissues

The Nr4a family of nuclear hormone receptors is composed of three members-Nr4a1/Nur77, Nr4a2/Nurr1 and Nr4a3/Nor1. While currently defined as ligandless, these transcription factors have been shown to regulate varied processes across a host of tissues. Of particular interest, the Nr4a family impinge, in a tissue dependent fashion, on cellular proliferation, apoptosis and fuel utilization. The regulation of these processes occurs through both nuclear and non-genomic pathways. The purpose of this review is to provide a balanced perspective of the tissue specific and Nr4a family member specific, effects on cellular proliferation, apoptosis and fuel utilization.

Prolonged Exposure to Insulin Inactivates Akt and Erk1/2 and Increases Pancreatic Islet and INS1E β-Cell Apoptosis

Chronic hyperinsulinemia, in vivo, increases the resistance of peripheral tissues to insulin by desensitizing insulin signaling. Insulin, in a heterologous manner, can also cause IGF-1 resistance. The aim of the current study was to investigate whether insulin-mediated insulin and IGF-1 resistance develops in pancreatic β-cells and whether this resistance results in β-cell decompensation. Chronic exposure of rat islets or INS1E β-cells to increasing concentrations of insulin decreased Akt^S473 phosphorylation in response to subsequent acute stimulation with 10 nM insulin or IGF-1. Prolonged exposure to high insulin levels not only inhibited Akt^S473 phosphorylation, but it also resulted in a significant inhibition of the phosphorylation of P70S6 kinase and Erk_1/2 phosphorylation in response to the acute stimulation by glucose, insulin, or IGF-1. Decreased activation of Akt, P70S6K, and Erk_1/2 was associated with decreased insulin receptor substrate 2 tyrosine phosphorylation and insulin receptor β-subunit abundance; neither IGF receptor β-subunit content nor its phosphorylation were affected. These signaling impairments were associated with decreased SERCA2 expression, perturbed plasma membrane calcium current and intracellular calcium handling, increased endoplasmic reticulum stress markers such as eIF2α^S51 phosphorylation and Bip (GRP78) expression, and increased islet and β-cell apoptosis. We demonstrate that prolonged exposure to high insulin levels induces not only insulin resistance, but in a heterologous manner causes resistance to IGF-1 in rat islets and insulinoma cells resulting in decreased cell survival. These findings suggest the possibility that chronic exposure to hyperinsulinemia may negatively affect β-cell mass by increasing β-cell apoptosis.

The stress-response molecule NR4A1 resists ROS-induced pancreatic β-cells apoptosis via WT1

Pancreatic β-cells often face endoplasmic reticulum stress and/or ROS-associated oxidative stress under adverse conditions. Our previous work has verified that NR4A1 protects pancreatic β-cells from ER-stress induced apoptosis. However, It remains unknown whether NR4A1 is able to protect pancreatic β-cells against ROS-associated oxidative stress. In the present study, our data showed that NR4A1 protein expression rapidly increased in MIN6 cells upon H₂O₂ treatment, and overexpression of NR4A1 in MIN6 cells conferred resistance to cell apoptosis induced by H₂O₂. These results were further substantiated in isolated islets from mice infected with an adenovirus overexpressing NR4A1. 8-hydroxy-2'-deoxyguanosine (8-OHdG) was used as a biomarker for oxidative stress or a marker for ROS damage. We found that the 8-OHdG level in the islets from NR4A1 knockout mice fed with high-fat diet was much higher than that in the islets from parental control mice; and higher apoptotic rate was observed in the islets from NR4A1 KO mice compared to control mice. Further investigation of underlying mechanisms of NR4A1's protective effects showed that NR4A1 overexpression in MIN6 cells reduced Caspase 3 activation caused by H₂O₂, and increased expression of WT1 and SOD1. There is a putative NR4A1 binding site (-1118bp to -1111bp) in WT1 promoter; our data demonstrated that NR4A1 protein physically associates with the WT1 promoter, and enhanced WT1 promoter transactivation and knockdown of WT1 in MIN6 cells induced apoptosis. These findings suggest that NR4A1 protects pancreatic β-cells against H₂O₂ mediated apoptosis by up-regulating WT1 expression.

A 3-year follow-up study of β-cell function in patients with early-onset type 2 diabetes

Insulin resistance and reduced β-cell glucose sensitivity are present in patients with type 2 diabetes. In the present study, we investigated the changes in β-cell function in patients with type 2 diabetes during a 3-year follow-up study. A total of 48 patients with early-onset type 2 diabetes (EOD) and 55 patients with late-onset type 2 diabetes (LOD) were enrolled. Weight, height, waist circumference, hip circumference, blood pressure and plasma levels of lipids, glucose, fasting serum C-peptide (CPR0) and serum C-peptide 6 min after glucagon stimulation (CPR6) were measured. In addition, islet β-cell secretory activity was detected. Subjects with EOD had lower Systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), fasting CPR0, CPR6 and greater glycated hemoglobin A1c (HbA1c), triglyceride (TG) compared with subjects with LOD. CPR0, CPR6 and TG were decreased in both EOD and LOD groups 3 years later. The ratio of β-cell function failure was 29.17 and 10.91% in the EOD and LOD groups, respectively, and there was significant difference between the two groups. A positive correlation was identified between the CPR0 and waist-hip ratio, HbA1c in the EOD group. A similar positive correlation was observed between CPR0 and BMI in the LOD group. Collectively, islet β-cell function has declined in patients with EOD, and this change may be more evident when compared with those with LOD.

Observational Registry of Basal Insulin Treatment (ORBIT) in Patients with Type 2 Diabetes Uncontrolled by Oral Hypoglycemic Agents in China--Study Design and Baseline Characteristics

BACKGROUND

Efficacy of basal insulin (BI) has been well studied by randomized controlled trials, but the impact of BI on glycemic control in the real world has not been well documented. The Observational Registry for BI Treatment (ORBIT) study is designed to evaluate the real-life outcomes of BI in China.

MATERIALS AND METHODS

Participants with type 2 diabetes (n=19,894), from December 2011 to June 2013, inadequately controlled on oral hypoglycemic agents (OHAs) were initiated on BI treatment from 209 hospitals in all the eight regions in Mainland China. Data for each patient on use of OHAs and insulin (type and dose), glycemic control, hypoglycemic episodes, body weight, quality of life, and costs were collected at baseline and 3 and 6 months.

RESULTS

For the 18,995 participants who were eligible for baseline analysis, mean±SD age was 55.4±10.4 years, with 52.5% males. The mean duration of diabetes was 6.4±5.3 years and was positively associated with the economic level of eight regions. Before initiation of BI, patients had a mean hemoglobin A1c level of 9.6±2.0% with a fasting plasma glucose level of 11.7±4.0 mmol/L. Of the patients, 35.5% had some diabetes complications. Metformin, sulfonylureas, and α-glycosidase inhibitors were the most commonly used OHAs. The proportions of patients using one, two, or more than two OHAs before BI initiation were 48.4%, 42.7%, and 8.9%, respectively.

CONCLUSIONS

To the best of our knowledge, the ORBIT study is the largest registry study to evaluate glycemic outcomes and safety of BI in real-world China. Baseline data indicate delays in initiation of BI in the majority of patients with type 2 diabetes in China.

Evaluation of Saptarangyadi Ghanavati in the management of Apathyanimittaja Prameha w.s.r. to type-2 diabetes mellitus

Type-2 diabetes mellitus is a persistent health problem that requires innovative strategies to improve health and needs a multifactorial approach for the treatment. Saptarangyadi Ghanavati, a new formulated Ayurvedic compound consists of herbs with anti-diabetic potential, in addition to a folklore herb Saptarangi (Salacia chinensis) has been evaluated. In a total of 67 patients, 36 patients were of newly detected type-2 diabetes mellitus and 31 patients were of chronic type-2 diabetes mellitus and they were divided into group A and group B, respectively. Group A consisted newly detected subjects of type-2 diabetes and were not taking any regular medication and group B consisted of chronic cases of type-2 diabetes mellitus, who were taking modern ant-diabetic medication, but their blood-glucose level was not controlled to desired level. Patients in group A were administered Saptarangyadi Ghanavati each of 200 mg, 5 Vatis, 3-times a day-after breakfast, lunch, and dinner. Patients in group B were administered Saptarangyadi Ghanavati, in the same dose in addition to the concomitant anti-diabetic (Allopathic) medication. Serum insulin investigation, both fasting and post-prandial levels were evaluated in six patients of group B, showed a highly significant increase in first-phase insulin response. Glycosylated hemoglobin (serum HbA1c) evaluated in six patients of group A showed statistically significant reduction. There was also statistically significant reduction in the fasting blood sugar (FBS) and post prandial blood sugar (PPBS) parameters, both in newly detected cases as well as chronic cases of type-2 diabetes mellitus.

Can targeting SIRT-1 to treat type 2 diabetes be a good strategy? A review

INTRODUCTION

Dysregulation of metabolic pathways, caused by imbalances in energy homeostasis, leads to type 2 diabetes characterized by high glucose concentration in the blood due to insulin resistance which is a major disorder in developed countries.

AREAS COVERED

One of the recent treatment strategies is using activators of SIRT1, which has been in clinical trials. Many of the cellular processes including insulin secretion, cell cycle, and apoptosis are imperatively regulated by a family of mediators called sirtuins. First known mammalian sirtuin, SIRT1 is a positive regulator of insulin secretion, which triggers glucose uptake and utilization. Since the past decade, a major outstanding question is whether SIRT1 activation is a safe therapy for human diseases such as type 2 diabetes? This review summarizes and discusses the advances of the past decade and the challenges that will brazen out perplexity about homeostasis and metabolic pathways linked to SIRT1 and type 2 diabetes. Furthermore, we described the interlink between SIRT1 metabolic pathways of various tissues such as pancreas, skeletal muscle, adipose tissue and liver.

EXPERT OPINION

However be the complexity of the pathways involved, T2DM regulated by SIRT1 affected metabolism is dropping down progressively due to profound research. In the context of interlinking all the SIRT1 pathways in T2DM we found various crucial intermediaries in metabolic tissues, which can also be targeted for future prospects.

Mediation of glucolipotoxicity in INS-1 rat insulinoma cells by small heterodimer partner interacting leucine zipper protein (SMILE)

Sustained elevations of glucose and free fatty acid concentration have deleterious effects on pancreatic beta cell function. One of the hallmarks of such glucolipotoxicity is a reduction in insulin gene expression, resulting from decreased insulin promoter activity. Sterol regulatory element binding protein-1c (SREBP-1c), a lipogenic transcription factor, is related to the development of beta cell dysfunction caused by elevated concentrations of glucose and free fatty acid. Small heterodimer partner (SHP) interacting leucine zipper protein (SMILE), also known as Zhangfei, is a novel protein which interacts with SHP that mediates glucotoxicity in INS-1 rat insulinoma cells. Treatment of INS-1 cells with high concentrations of glucose and palmitate increased SREBP-1c and SMILE expression, and decreased insulin gene expression. Adenovirus-mediated overexpression of SREBP-1c in INS-1 cells induced SMILE expression. Moreover, adenovirus-mediated overexpression of SMILE (Ad-SMILE) in INS-1 cells impaired glucose-stimulated insulin secretion as well as insulin gene expression. Ad-SMILE overexpression also inhibited the expression of beta-cell enriched transcription factors including pancreatic duodenal homeobox factor-1, beta cell E box transactivator 2 and RIPE3b1/MafA, in INS-1 cells. Finally, in COS-1 cells, expression of SMILE inhibited the insulin promoter activity induced by these same beta-cell enriched transcription factors. These results collectively suggest that SMILE plays an important role in the development of beta cell dysfunction induced by glucolipotoxicity.

Overexpression of Insig-1 protects β cell against glucolipotoxicity via SREBP-1c

BACKGROUND

High glucose induced lipid synthesis leads to β cell glucolipotoxicity. Sterol regulatory element binding protein-1c (SREBP-1c) is reported to be partially involved in this process. Insulin induced gene-1 (Insig-1) is an important upstream regulator of Insig-1-SREBPs cleavage activating protein (SCAP)-SREBP-1c pathway. Insig-1 effectively blocks the transcription of SREBP-1c, preventing the activation of the genes for lipid biosynthesis. In this study, we aimed to investigate whether Insig-1 protects β cells against glucolipotoxicity.

METHODS

An Insig-1 stable cell line was generated by overexpression of Insig-1 in INS-1 cells. The expression of Insig-1 was evaluated by RT-PCR and Western blotting, then, cells were then treated with standard (11.2 mM) or high (25.0 mM) glucose for 0 h, 24 h and 72 h. Cell viability, apoptosis, glucose stimulated insulin secretion (GSIS), lipid metabolism and mRNA expression of insulin secretion relevant genes such as IRS-2, PDX-1, GLUT-2, Insulin and UCP-2 were evaluated.

RESULTS

We found that Insig-1 suppressed the high glucose induced SREBP-1c mRNA and protein expression. Our results also showed that Insig-1 overexpression protected β cells from ER stress-induced apoptosis by regulating the proteins expressed in the IRE1α pathway, such as p-IRE1α, p-JNK, CHOP and BCL-2. In addition, Insig-1 up-regulated the expression of IRS-2, PDX-1, GLUT-2 and Insulin, down-regulated the expression of UCP-2 and improved glucose stimulated insulin secretion (GSIS). Finally, we found that Insig-1 inhibited the lipid accumulation and free fatty acid (FFA) synthesis in a time-dependent manner.

CONCLUSIONS

There results suggest that Insig-1 may play a critical role in protecting β cells against glucolipotoxicity by regulating the expression of SREBP-1c.

Non-glycemic effects of insulin therapy: a comparison between insulin aspart and regular human insulin during two consecutive meals in patients with type 2 diabetes

OBJECTIVE

To control postprandial hyperglycemia in insulin-treated type 2 diabetic patients, prandial therapy with regular human insulin (HI) or fast acting insulin analogs is used. Postprandial hyperglycemia seems to be reduced more effectively with insulin analogs than with normal insulin, but there are no data concerning the effect on lipolysis or pancreatic insulin and proinsulin secretion of normal insulin in comparison to insulin analogs.

DESIGN AND METHODS

We included 13 patients with type 2 diabetes mellitus (age 62.2±10.3 years) with preexisting insulin therapy in this crossover, prospective, open-labeled, randomized trial comparing regular HI with insulin aspart (IA) in the setting of a standardized breakfast and a standardized lunch 4 h later. Blood samples for determination of glucose, free fatty acids (FFA), triglycerides, C-peptide, and intact proinsulin were drawn during fasting and every 30 min until 4 h after the second test meal. Statistical analysis was performed with ANOVA for repeated measurements and paired Student's t-test.

RESULTS

The mean increase in blood glucose was significantly lower after IA (24.18±16.33 vs 34.92±29.07 mg/dl, P=0.02) compared with HI. Both therapies reduced FFA; however, the mean reduction was significantly higher after IA than after HI (-0.47±0.16 vs -0.35±0.15 μmol/l, P<0.001). The mean increase in intact proinsulin was significantly lower after IA than after HI (10.53±5 vs 15.20±6.83 pmol/l, P<0.001). No differences were observed in the C-peptide levels between the two groups.

CONCLUSION

In the setting of two consecutive meals, IA reduces lipolysis and proinsulin secretion more effectively than HI.

The flavonoid-rich fraction of Coreopsis tinctoria promotes glucose tolerance regain through pancreatic function recovery in streptozotocin-induced glucose-intolerant rats

AIM OF THE STUDY

Infusions of Coreopsis tinctoria Nutt. flowering tops have been used traditionally in Portugal to control hyperglycaemia and a previous study revealed that daily administration of the infusion during a 3-week period promoted the recovery of glucose tolerance by a mechanism different from inhibition of glucose absorption and direct promotion of insulin secretion. We know report the study of the ethyl acetate fraction of Coreopsis tinctoria flowers infusion aiming to confirm flavonoids as bioactive metabolites. To give one step forward into the antihyperglycaemic mechanism of action of this traditionally used plant we also studied the activity of Coreopsis tinctoria flavonoids on the pancreatic function of glucose-intolerant rats. A standard antioxidant, Trolox, was also studied for comparative purposes as the antioxidant mechanism has been frequently purposed as one of the mechanisms mediating antihyperglycaemic effects of flavonoid-rich extracts.

MATERIAL AND METHODS

Thirteen compounds, mainly of flavanone and chalcone flavonoidal type, have been identified in this fraction by HPLC-DAD-ESI-MS/MS, and the major one (marein) quantified by HPLC-UV. The fraction (125 mg containing 20 mg of marein/kg b.w.) and Trolox (50 mg/kg b.w.) were administered daily by oral gavage to normal and STZ (40 mg/kg b.w.)-induced glucose-intolerant Wistar rats for 3 weeks. Blood glucose levels were measured weekly by Oral Glucose Tolerance Test. Pancreatic function was evaluated by plasma lipase of treated and non-treated glucose-tolerant and- intolerant rats after the 3-week treatment period.

RESULTS

After 2 weeks oral treatment with Coreopsis tinctoria AcOEt fraction the animals were no longer glucose-intolerant, an effect maintained over the remaining experimental period. Additionally, plasma lipase values of glucose-intolerant animals treated with the AcOEt fraction (13.5 ± 0.84 U/L) showed a clear reduction when compared with the glucose-intolerant group (34.60 ± 1.76 U/L; P<0.001) and normoglycaemic control (8.35 ± 0.69 U/L) demonstrating recovery of pancreatic function. On the other hand, treatment with standard antioxidant Trolox had no effect on glucose homeostasis of glucose-intolerant rats. The oral treatment with Coreopsis tinctoria fraction caused no hepatotoxicity, as determined by blood alanine and aspartate transaminases, and had also no effect on glucose homeostasis and pancreatic function of normal rats.

CONCLUSIONS

AcOEt fraction, containing the same amount of marein as the infusion, promoted glucose tolerance regain in the rats more quickly, which means that the bioactivity is probably due to the several flavonoids present in Coreopsis tinctoria extracts and not to marein alone. The results also strongly suggest that these compounds act by promoting pancreatic cell function recovery from STZ-induced injury, possibly through a mechanism of action other than merely antioxidant mediated.

Diabetes and breast cancer among women with BRCA1 and BRCA2 mutations

BACKGROUND

Hyperinsulinemia and the metabolic syndrome are both risk factors for breast cancer. It is not clear if diabetes is associated with the risk of breast cancer in women with a BRCA1 or BRCA2 mutation.

METHODS

The authors reviewed the medical histories of 6052 women with a BRCA1 or BRCA2 mutation, half of whom had been diagnosed with breast cancer. They estimated the odds ratio for breast cancer, given a self-report of diabetes. They then estimated the hazard ratio for a new diagnosis of diabetes associated with a history of breast cancer.

RESULTS

There was no excess of diabetes in the period before the diagnosis of breast cancer, compared with controls with no diagnosis of breast cancer. The risk of diabetes was doubled among BRCA carriers in the 15-year period after the diagnosis of breast cancer (relative risk, 2.0; 95% confidence interval [CI], 1.4-2.8; P = .0001), compared with carriers without cancer. The risk was particularly high for women with a body mass index (BMI) >25.0 kg/m(2) (odds ratio, 5.8; 95% CI, 4.0-8.6; P = .0001).

CONCLUSIONS

After a diagnosis of breast cancer, women with a BRCA1 or BRCA2 mutation face a 2-fold increase in the risk of diabetes, which is exacerbated by a high BMI.

Insulin therapy in type 2 diabetes: insulin analogue mix 50, a potential role in reducing postprandial hyperglycaemia and cardiovascular disease

IMPORTANCE OF THE FIELD

Postprandial hyperglycaemia is becoming topical, with studies suggesting a link to cardiovascular disease. Recently, a number of new therapies for the treatment of type 2 diabetes have become available.

AREAS COVERED IN THIS REVIEW

This review looks at the evidence for the potential role of insulin analogue mix 50 to reduce postprandial hyperglycaemia and cardiovascular disease.

SEARCH STRATEGY

Medline and Embase databases were searched using the MeSH terms to identify relevant studies from 1980 to 2009. Both original articles and reviews were extracted. Published reference lists were also examined. MeSH terms used for literature searching: human insulins, insulin analogues, insulin analogue mix 50, glycaemia, postprandial glucose, fasting glucose, type 2 diabetes, type 1 diabetes, cardiovascular disease.

WHAT THE READER WILL GAIN

The reader is presented with evidence discussing the importance of postprandial hyperglycaemia and studies comparing different insulin regimes and in particular insulin analogue mix 50 and its potential to reduce postprandial glucose surges and reduce cardiovascular disease.

TAKE-HOME MESSAGE

Insulin analogue mix 50 is a viable therapeutic option in a sub-group of patients with type 2 diabetes.

Defining the role of basal and prandial insulin for optimal glycemic control

Type 2 diabetes mellitus is a progressive disease characterized by early impairment of beta-cell function and ultimately loss of beta-cell mass. Hence, a single daily injection of a long-acting insulin is commonly initiated after intensification of oral antihyperglycemic therapy. Hemoglobin A1C should be measured every 3 months and therapy adjusted if the target is not met. As beta-cell function continues to decline, it is often necessary to add exogenous bolus insulin therapy, using short-acting insulin analogs or regular insulin. Alternatively, the use of pre-mixed insulin preparations, combining both long-acting and short-acting insulins, may be used.

Primary defects in beta-cell function further exacerbated by worsening of insulin resistance mark the development of impaired glucose tolerance in obese adolescents

OBJECTIVE

Impaired glucose tolerance (IGT) is a pre-diabetic state of increasing prevalence among obese adolescents. The purpose of this study was to determine the natural history of progression from normal glucose tolerance (NGT) to IGT in obese adolescents.

RESEARCH DESIGN AND METHODS

We determined the evolution of beta-cell function, insulin sensitivity (S(I)), and glucose tolerance in a multiethnic group of 60 obese adolescents over the course of approximately 30 months. Each subject underwent three serial 3-h oral glucose tolerance tests. Dynamic, static, and total beta-cell responsivity (Phi(d), Phi(s), and Phi(tot), respectively) and S(i) were assessed by oral C-peptide and glucose minimal models. The disposition index (DI), which adjusts insulin secretion for S(i), was calculated.

RESULTS

At baseline, all 60 subjects had NGT. Seventy-seven percent (46 subjects) maintained NGT over the three testing periods (nonprogressors), whereas 23% (14 subjects) developed IGT over time (progressors). At baseline, percent fat and BMI Z score were comparable between the groups. Fasting plasma glucose, 2-h glucose, glucose area under the curve at 180 min, and Phi(d) were significantly different between the two groups at baseline, whereas S(i) was comparable between the two groups. Over time, although S(i) remained unchanged in nonprogressors, it steadily worsened by approximately 45% (P > 0.04) in progressors. beta-Cell responsivity decreased by 20% in progressors, whereas it remained stable in nonprogressors. The DI showed a progressive decline in progressors compared with a modest improvement in nonprogressors (P = 0.02).

CONCLUSIONS

Obese adolescents who progress to IGT may manifest primary defects in beta-cell function. In addition, progressive decline in S(i) further aggravates beta-cell function, contributing to the worsening of glucose intolerance.

Initiation of insulin glargine therapy in type 2 diabetes subjects suboptimally controlled on oral antidiabetic agents: results from the AT.LANTUS trial

OBJECTIVE

For many patients with type 2 diabetes, oral antidiabetic agents (OADs) do not provide optimal glycaemic control, necessitating insulin therapy. Fear of hypoglycaemia is a major barrier to initiating insulin therapy. The AT.LANTUS study investigated optimal methods to initiate and maintain insulin glargine (LANTUS, glargine, Sanofi-aventis, Paris, France) therapy using two treatment algorithms. This subgroup analysis investigated the initiation of once-daily glargine therapy in patients suboptimally controlled on multiple OADs.

RESEARCH DESIGN AND METHODS

This study was a 24-week, multinational (59 countries), multicenter (611), randomized study. Algorithm 1 was a clinic-driven titration and algorithm 2 was a patient-driven titration. Titration was based on target fasting blood glucose < or =100 mg/dl (< or =5.5 mmol/l). Algorithms were compared for incidence of severe hypoglycaemia [requiring assistance and blood glucose <50 mg/dl (<2.8 mmol/l)] and baseline to end-point change in haemoglobin A(1c) (HbA(1c)).

RESULTS

Of the 4961 patients enrolled in the study, 865 were included in this subgroup analysis: 340 received glargine plus 1 OAD and 525 received glargine plus >1 OAD. Incidence of severe hypoglycaemia was <1%. HbA(1c) decreased significantly between baseline and end-point for patients receiving glargine plus 1 OAD (-1.4%, p < 0.001; algorithm 1 -1.3% vs. algorithm 2 -1.5%; p = 0.03) and glargine plus >1 OAD (-1.7%, p < 0.001; algorithm 1 -1.5% vs. algorithm 2 -1.8%; p = 0.001).

CONCLUSIONS

This study shows that initiation of once-daily glargine with OADs results in significant reduction of HbA(1c) with a low risk of hypoglycaemia. The greater reduction in HbA(1c) was seen in patients randomized to the patient-driven algorithm (algorithm 2) on 1 or >1 OAD.

Does garlic have a role as an antidiabetic agent?

Diabetes affects a large segment of the population worldwide, and the prevalence of this disease is rapidly increasing. Despite the availability of medication for diabetes, traditional remedies are desirable and are currently being investigated. Garlic (Allium sativum), which is a common cooking spice and has a long history as a folk remedy, has been reported to have antidiabetic activity. However, there is no general agreement on the use of garlic for antidiabetic purposes, primarily because of a lack of scientific evidence from human studies and inconsistent data from animal studies. The validity of data from previous studies of the hypoglycemic effect of garlic in diabetic animals and the preventive effects of garlic on diabetes complications are discussed in this review. The role of garlic as both an insulin secretagogue and as an insulin sensitizer is reviewed. Evidence suggests that garlic's antioxidative, antiinflammatory, and antiglycative properties are responsible for garlic's role in preventing diabetes progression and the development of diabetes-related complications. Large-scale clinical studies with diabetic patients are warranted to confirm the usefulness of garlic in the treatment and prevention of diabetes.

Variants in the FFAR1 gene are associated with beta cell function

Background

The FFAR1 receptor is expressed mainly in pancreatic beta cells and is activated by medium to long chain free fatty acids (FFAs), as well as by thiazolidinediones, resulting in elevated Ca²⁺ concentrations and promotion of insulin secretion. These properties suggest that FFAR1 could be a mediator of lipotoxicity and a potential candidate gene for Type 2 diabetes (T2D). We therefore investigated whether variations at the FFAR1 locus are associated with T2D and beta cell function.

Methodology/Principal Findings

We re-sequenced the FFAR1 region in 96 subjects (48 healthy and 48 T2D individuals) and found 13 single nucleotide polymorphisms (SNPs) 8 of which were not previously described. Two SNPs located in the upstream region of the FFAR1 gene (rs1978013 and rs1978014) were chosen and genotyped in 1929 patients with T2D and 1405 healthy control subjects. We observed an association of rs1978013 and rs1978014 with insulinogenic index in males (p = 0.024) and females (p = 0.032), respectively. After Bonferroni corrections, no association with T2D was found in the case-control material, however a haplotype consisting of the T-G alleles conferred protection against T2D (p = 0.0010).

Conclusions/Significance

Variation in the FFAR1 gene may contribute to impaired beta cell function in T2D.

Sterol regulatory element-binding protein-1c and pancreatic beta-cell dysfunction

It has long been known that excess intracellular fatty acids cause impaired insulin secretion, referred to as beta-cell lipotoxicity. Sterol regulatory element-binding protein (SREBP)-1c is a transcription factor that controls hepatic fatty acid synthesis. Activation of SREBP-1c by overnutrition also inhibits insulin receptor substrate-2 (IRS-2) and induces insulin resistance in the liver. As SREBP-1c is also expressed in beta cells, we hypothesized that activation of SREBP-1c could be a part of the mechanism by which saturated fatty acids induce beta-cell lipotoxicity. We found that nuclear SREBP-1c has a negative impact on both glucose- and potassium-stimulated insulin secretion as determined in islets from beta-cell-specific SREBP-1c transgenic mice as well as SREBP-1c knockout mice. This effect of SREBP-1c involves multiple functional pathways required for insulin secretion from beta cells: (i) decreased ATP caused by energy consumption through lipogenesis and uncoupling protein-2 (UCP-2) activation; (ii) repressed IRS-2 and pancreas duodenum homeobox 1 (PDX1) expression, leading to impaired beta-cell mass; and (iii) impaired post-ATP membrane voltage-dependent steps of the insulin secretion pathway caused by upregulated granuphilin and other ion channel proteins. Saturated fatty acids, such as palmitic acid (PA), impair insulin secretion through SREBP-1c activation, whereas polyunsaturated fatty acids including eicosapentaenoic acid (EPA) restore PA-suppressed insulin secretion through suppression of SREBP-1c. These data implicate a therapeutic potential of EPA against insulin secretion defects caused by lipotoxicity.

Leptin decreases apoptosis and alters BCL-2 : Bax ratio in clonal rodent pancreatic beta-cells

AIMS/HYPOTHESIS

The adipocyte derived peptide hormone leptin is known to regulate apoptosis and cell viability in several cells and tissues, as well as having several pancreatic islet beta-cell specific effects such as inhibition of glucose-stimulated insulin secretion. This study investigated the effects of leptin upon apoptosis induced by serum depletion and on expression of the apoptotic regulators B-cell leukaemia 2 gene product (BCL-2) and BCL2-associated X protein (Bax) in the glucose-responsive BRIN-BD11 beta-cell line.

METHODS

BRIN-BD11 cells were cultured in RPMI 1640 and subsequently serum depleted +/- leptin (10 and 50 ng/mL) for 24 h. Cell viability and apoptosis were measured using a modified MTS assay and TUNEL/YO-PRO-1 assays, respectively. BCL-2 and Bax expression were measured by real-time PCR and Western blotting.

RESULTS

Leptin caused a reduction in serum-depleted apoptosis, although it failed to have any effect on the overall cell viability, causing a 68% shift from apoptosis to necrosis. Leptin significantly increased the level of BCL-2 mRNA expression (150% compared to serum depletion alone), without altering Bax mRNA expression. At the protein level, leptin increased BCL-2 and decreased Bax, altering the BCL-2 : Bax ratio.

CONCLUSIONS

We conclude that leptin reduces apoptosis in beta-cells at physiological concentrations, possibly via its ability to up-regulate BCL-2 and Bax expression.

Physiological and behavioral aspects of glycemic control and hypoglycemia in diabetes

Homeostatic mechanisms that maintain blood glucose concentration within a narrow physiologic range are complex and redundant. Elaborate feedback loops involving insulin, glucagon, sympathoadrenal mediators, growth hormone, amylin, and incretins normally operate synchronously to keep blood glucose within a narrow set point. Individuals with diabetes have defects in glucose homeostatic pathways, including the counterregulatory pathways that oppose hypoglycemia and ensure sufficient glucose is available to serve the brain's metabolic needs. Because available interventions to manage hyperglycemia do not precisely mimic physiologic insulin secretion patterns, hypoglycemia can occur any time dosing exceeds demand. Focusing on the practical implications, we review the endocrinological principles underlying normal glucose homeostasis and the defects in regulation and counterregulation, including hypoglycemia unawareness, that occur with diabetes. Iatrogenic and behavioral factors that contribute to hypoglycemia risk and nocturnal hypoglycemia are discussed. A companion manuscript reviews the clinical symptoms and fundamentals of hypoglycemia prevention, recognition, and management.

Diabetes mellitus and breast cancer: a retrospective population-based cohort study

PURPOSE

Evidence suggests that women with type 2 diabetes may be at increased risk of breast cancer, possibly due to chronic exposure to insulin resistance and/or hyperinsulinemia. The purpose of this study was to compare the incidence of breast cancer in postmenopausal women with and without diabetes.

METHODS

Using population-based validated health databases from Ontario, Canada, this retrospective cohort study compared breast cancer incidence between women, aged 55-79 years, with newly diagnosed diabetes (n=73,796) to women without diabetes (n=391,714).

RESULTS

Women with diabetes were slightly older, were more likely to reside in a lower income neighborhood, had greater comorbidity, and had more annual physician visits than women without diabetes. After 2.2 million person-years of follow-up from 1994 to 2002, breast cancer incidence was 2.97/1000 person-years in the diabetes group and 2.75/1000 person-years in the non-diabetes group. After adjustment for age and income, there was a significant increase in breast cancer among women with diabetes (hazard ratio, HR, 1.08, 95% confidence interval, CI, 1.01-1.16, p=0.021).

CONCLUSION

This study found a small but significant increase in incident breast cancer in a predominantly postmenopausal population of women with diabetes, when compared to women without diabetes. These results support the possibility that insulin resistance or some other aspect of type 2 diabetes may promote breast cancer, and may further direct treatment and prevention strategies.

The pancreatic beta-cell in human Type 2 diabetes

AIM

There is growing evidence that the beta-cell is central to the development of Type 2 diabetes. In this brief review we discuss the factors predisposing to beta-cell dysfunction and some characteristics of islet cells in Type 2 diabetes.

DATA SYNTHESIS

Several genes have been associated with islet cell dysfunction in Type 2 diabetes, including those encoding for transcription factors, glucose metabolism proteins, molecules of the insulin signaling pathways, and several others. On the other hand, many environmental factors can directly or indirectly affect pancreatic islet cells, and possibly contribute to the development and/or progression of Type 2 diabetes. In this regard, the role of prolonged exposure to high glucose (glucotoxicity) and high fatty acid (lipotoxicity) concentrations seems to be of particular relevance. More recently, it has been possible to directly evaluate some properties of pancreatic islets prepared from Type 2 diabetic donors. Consistently, a marked decrease in insulin secretion during glucose stimulation has been found, although the secretory response to amino acids or sulphonylurea is usually less severely affected. In addition, increased beta-cell apoptosis in Type 2 diabetes islets has been reported. Interestingly, experimental data show that in vitro manipulation of human Type 2 diabetes islets by agents that are able to reduce oxidative stress can improve beta-cell function and survival.

CONCLUSION

Available data are consistent with the concept that the defect of the beta-cell is of primary importance in Type 2 diabetes; the evidence that some alterations in Type 2 diabetes beta-cells can be reverted, at least in vitro, may open new perspectives in the treatment of this disease.

An immune origin of type 2 diabetes?

Subclinical, low-grade systemic inflammation has been observed in patients with type 2 diabetes and in those at increased risk of the disease. This may be more than an epiphenomenon. Alleles of genes encoding immune/inflammatory mediators are associated with the disease, and the two major environmental factors the contribute to the risk of type 2 diabetes-diet and physical activity-have a direct impact on levels of systemic immune mediators. In animal models, targeting of immune genes enhanced or suppressed the development of obesity or diabetes. Obesity is associated with the infiltration and proinflammatory activity of macrophages in adipose tissue, and immune mediators may be important regulators of insulin resistance, mitochondrial function, ectopic lipid storage and beta cell dysfunction or death. Intervention studies targeting these pathways would help to determine the contribution of an activated innate immune system to the development of type 2 diabetes.