Serum Proinsulin Research Articles

CE SE AFLĂ DINCOLO DE GENETICA DIABETULUI ZAHARAT?

The modern era of diabetes, which began in the early nineteenth century, continues until now, despite the hopes that the genetic revolution will bring major clarifications, both in terms of defining diabetes, the classification of its different phenotypes, the pathogenetic mechanisms and especially the finding of effective therapeutic solutions or even their prevention. Despite the useful information brought by genetic revolution, which refers primarily to identify structural or functional molecules associated with the various phenotypes, most of them expresed in pancreatic β-cell, the pancreatic genetic risk score, failed to improve prediction of diabetes. In the authors’ concept, the primary cause of diabetes, regardless of phenotype analyzed can be identified in β-cell secretory dysfunction, in turn, secondary to pancreatic β-cell inability to produce mature secretory vesicles, the only one able to respond promptly and efficiently to its physiological stimuli. The authors propose as indicator for the β-cell dysfunction, the increas of serum proinsulin, or better yet the ratio proinsulin / adiponectin.

Serum Proinsulin in Bangladeshi Subjects with Impaired Glucose Tolerance

Hyperproinsulinemia is commonly present in subjects with impaired glucose tolerance. The present study was undertaken to investigate the proinsulin level in Bangladeshi IGT subjects and to explore its association with insulin resistance. This observational study was conducted under a case-control design with IGT subjects (n=50) and controls (n=44). IGT was diagnosed following the WHO Study Group Criteria. Serum glucose was measured by glucose-oxidase method, serum lipid profile by enzymatic method and serum insulin and serum proinsulin were measured by ELISA method. Insulin secretory capacity (HOMA%B) and insulin sensitivity (HOMA%S) were calculated from fasting serum glucose and fasting serum insulin by homeostasis model assessment. The study subjects were age- and BMI- matched. Mean (±SD) age (yrs) of the control and IGT subjects were 40±6 and 40±5 respectively (p=0.853). Mean (±SD) BMI of the control and IGT subjects were 23±3 and 22±2 respectively (p=0.123). Fasting glucose was not significantly higher in IGT subjects, but serum glucose 2 hours after 75 gm glucose load was significantly higher in IGT subjects. Median (Range) value of fasting serum glucose (mmol/l) of control and IGT subjects were 5.3 (3.8-6) and 5.2 (4-12) respectively; (p=0.297). Median (Range) value of serum glucose (mmol/l) 2 hours after 75 gm glucose load of control and IGT subjects were 6.1 (3-7.8) and 7.9 (5- 21) respectively; (p=0.001). Fasting TG was significantly higher in IGT subjects and LDL-c was significantly lower in IGT subjects. Serum Total cholesterol and HDL-c were not significantly different between the IGT and control subjects. Median (Range) value of fasting serum TG (mg/dl) of control and IGT subjects were 119 (51-474) and 178 (82-540) respectively; (p=0.001). Median (Range) value of fasting serum T chol (mg/dl) of control and IGT subjects were 180 (65-272) and 186 (140-400) respectively; (p=0.191). Median (Range) value of fasting serum HDL-C (mg/dl) of control and IGT subjects were 29 (19-45) and 31 (15-78) respectively; (p=0.914). Median (Range) value of fasting serum LDL-C (mg/dl) of control and IGT subjects were 117(29-201) and 111(41- 320) respectively; (p=0.001). Fasting serum proinsulin was significantly higher in IGT subjects. Median (Range) value of fasting serum proinsulin (pmol/l) of control and IGT subjects were 9.2(1.8-156) and 17(3-51) respectively; (p=0.001). Insulin secretory capacity (HOMA%B) was higher but insulin sensitivity (HOMA%S) was significantly lower in case of IGT subjects. Median (Range) value of HOMA%B of control and IGT subjects were 97(46-498) and 164(17-300) respectively; (p=0.001). Median (Range) value of HOMA%S of control and IGT subjects were 68(19-270) and 39(15-110) respectively (p=0.001). In multiple regression analysis a significant negative association was found between fasting proinsulin and insulin sensitivity (p=0.037). The data led to the following conclusions: a) Insulin resistance is the predominant defect in Bangladeshi IGT subjects. b) Basal proinsulin level is significantly increased in IGT subjects. c) Insulin resistance is negatively associated with serum proinsulin in IGT subjects. DOI: http://dx.doi.org/10.3329/bjmb.v7i2.22411 Bangladesh J Med Biochem 2014; 7(2): 41-46

Surgery Versus Snacking as Treatment of Insulinoma

From the Department of Internal Medicine, University of Oklahoma, Tulsa. A 19-year-old man presented with a generalized tonic-clonic seizure and serum glucose of 19 mg/dL. The seizure was aborted with dextrose and resolution of hypoglycemia. The patient had begun experiencing episodes of lightheadedness, fatigue, and seizures at age 16. Physicians in Mexico attributed his symptoms to poor nutritional intake and instructed him to increase his meal frequency and intake of soda and candy. He remained symptomatic for 3 years despite consuming 8 to 12 sodas daily supplemented by candy bars. Laboratory testing showed elevated serum insulin (200.8 mlU/mL), C-peptide (13.7 ng/ mL), proinsulin (296 pmol/L), and betahydroxybutyrate (0.3 mg/dL) levels. The sulfonylurea panel results were negative, and the serum calcium, intact parathyroid hormone, corticotropin, thyrotropin, and cortisol levels were within the normal range. A 72-hour fast revealed a glucose level of 30 mg/dL at 5 hours without neuroglycopenic or adrenergic symptoms. Computed tomography of the abdomen

The proinsulin/insulin (PI/I) ratio is reduced by postprandial targeting therapy in type 2 diabetes mellitus: a small-scale clinical study

BackgroundAn elevated PI/I ratio is attributable to increased secretory demand on β-cells. However, the effect of postprandial targeting therapy on proinsulin level is unknown. We evaluated the metabolic effect of glinide and sulfonylurea (SU) using the meal tolerance test (MTT).MethodsMTT was applied to previously untreated Type 2 Diabetes Mellitus (T2DM) subjects. Twenty-two participants were given a test meal (450 kcal). Plasma glucose and insulin were measured at 0 (fasting), 30, 60, 120, and 180 min. Serum proinsulin and C-peptide immunoreactivity (CPR) were measured at 0 and 120 min. Postprandial profile was assessed at baseline and following 3 months treatment with either mitiglinide or glimepiride.ResultsPlasma glucose level at 30, 60, 120, and 180 min was significantly improved by mitiglinide. Whereas, glimepiride showed a significant improve plasma glucose at 0, 180 min. Peak IRI shifted from 120 to 30 min by mitiglinide treatment. The pattern of insulin secretion was not changed by glimepiride treatment. Whereas mitiglinide did not affect the PI/I ratio, glimepiride tended to increase the PI/I ratio. Moreover, although mitiglinide did not affect PI/I ratio as a whole, marked reduction was noted in some patients treated by mitiglinide. PI/I ratio was reduced significantly in the responder group. The responder subgroup exhibited less insulin resistance and higher insulinogenic index at baseline than non-responders. Moreover, the triglyceride level of responders was significantly lower than that of non-responders.ConclusionsMitiglinide improved postprandial insulin secretion pattern and thereby suppressed postprandial glucose spike. In T2DM patients with low insulin resistance and low triglyceride, mitiglinide recovered impaired β-cell function from the viewpoint of the PI/I ratio.Trial registrationUMIN-CTR: UMIN000010467

Low serum adiponectin concentrations are associated with insulin sensitivity independent of obesity in Sudanese subjects with type 2 diabetes mellitus.

AimsPrevalence of Type 2 diabetes mellitus among Sudanese population was found to be 3.4% and associated with high rates of complications and obesity. Different adipocytokines are secreted from adipose tissues, among them adiponectin, which was shown to have insulins ensitizing properties and anti-inflammatory, anti-atherogenic effect. The aim of this study was to characterize type 2 diabetes in Sudanese diabetic subjects and controls in respect to hormones influencing or influenced by glucose metabolism.Methods104 type 2 diabetic patients (45 men and 59 women), and 75 matched control subjects (34 men and 41 women) were studied. Fasting serum samples were used to measure adiponectin, leptin, insulin, proinsulin, ghrelin and glucose. Body mass index, insulin/proinsulin ratio and (HOMA) insulin resistance and beta cell function were also calculated.ResultsAdiponectin serum concentrations were significantly lower in subjects with type 2 diabetes compared with controls subjects (P = 0.002), comparison between males and females did not reach significant levels in both diabetic (P = 0.06) or controls (P = 0.16) groups. In the diabetic group adiponectin correlated positively with serum glucose, negatively with serum proinsulin and HOMA beta cell function (P = 0.03) respectively and serum ghrelin (P = 0.003), but not with BMI, HOMA insulin resistance, insulin or leptin. In controls serum adiponectin correlated negatively with BMI (P = 0.002) but not with other variables.ConclusionsThe findings of this study suggest that, adiponectin concentrations independent on BMI as a measure of adiposity, were mostly linked to insulin sensitivity and not to insulin resistance in Sudanese type 2 diabetic subjects, where race specific regulation mechanisms or different type 2 diabetes phenotype suggested being a major contributory factor in clarification the findings of this study.

The proinsulin level in the blood of children with type 1 diabetes mellitus of various duration

Proinsulin content was measured in the serum of 82 children (aged from 3 to 14 years) with type 1 diabetes mellitus of various duration. Three groups of patients characterized by low (54%), normal (42%) and high (4%) levels of this prohormone were recognized. No dependence the proinsulin level on the disease term was found. The serum proinsulin level may be used as a parameter specifying the pathogenesis of type 1 diabetes mellitus.

Relationship between proinsulin and beta cell function in different states of glucose tolerance

To measure proinsulin concentrations in different states of glucose tolerance and examine the relationship between proinsulin and beta cell function. Serum true insulin (TI), proinsulin (PI), immunoreactive insulin (IRI), C peptide (CP) and blood glucose (BG) levels were measured in the fasting state and during an oral glucose tolerance test (OGTT) in 32 individuals with normal glucose tolerance (NGT), 42 individuals with impaired glucose tolerance (IGT), and 54 individuals with newly diagnosed type 2 diabetes mellitus. All participants were also subdivided into nonobese [body mass index (BMI) <25 kg/m2] and obese (BMI ≥25 kg/m2) subgroups. The levels of TI, PI, IRI and CP were higher in obese patients compared with the corresponding NGT subgroup, whereas there was no difference in PI/TI. The levels of IRI, PI and PI/TI were higher in nonobese patients with type 2 diabetes mellitus than in the corresponding NGT subgroup. The levels of PI and TI increased in obese patients with NGT and IGT, whereas PI/TI did not change. In contrast, PI increased but TI did not in subjects with newly diagnosed diabetes mellitus, which led to an increase in PI/TI, and a decrease in beta cell function. Therefore, PI and the PI/TI ratio could offer markers for beta cell dysfunction in DM.

Dual and opposing roles of the unfolded protein response regulated by IRE1α and XBP1 in proinsulin processing and insulin secretion

As a key regulator of the unfolded protein response, the transcription factor XBP1 activates genes in protein secretory pathways and is required for the development of certain secretory cells. To elucidate the function of XBP1 in pancreatic β-cells, we generated β-cell-specific XBP1 mutant mice. Xbp1(f/f);RIP-cre mice displayed modest hyperglycemia and glucose intolerance resulting from decreased insulin secretion from β-cells. Ablation of XBP1 markedly decreased the number of insulin granules in β-cells, impaired proinsulin processing, increased the serum proinsulin:insulin ratio, blunted glucose-stimulated insulin secretion, and inhibited cell proliferation. Notably, XBP1 deficiency not only compromised the endoplasmic reticulum stress response in β-cells but also caused constitutive hyperactivation of its upstream activator, IRE1α, which could degrade a subset of mRNAs encoding proinsulin-processing enzymes. Hence, the combined effects of XBP1 deficiency on the canonical unfolded protein response and its negative feedback activation of IRE1α caused β-cell dysfunction in XBP1 mutant mice. These results demonstrate that IRE1α has dual and opposing roles in β-cells, and that a precisely regulated feedback circuit involving IRE1α and its product XBP1s is required to achieve optimal insulin secretion and glucose control.

Independent relationships of obesity and insulin resistance with serum proinsulin level in prepubertal children with normal glucose tolerance

We compared the fasting serum proinsulin levels in lean, overweight, and obese prepubertal children with normal glucose tolerance (NGT). We also evaluated the relationship between fasting proinsulin level and indices of insulin resistance (IR). One hundred nine prepubertal children (mean age, 8.6 yr) with NGT were included. The indices of IR included the homeostasis model assessment of IR (HOMA-IR) and adiponectin level. We recorded the presence of one or more of the following metabolic derangements: triglycerides ≥ 150 mg/dL, HDL-cholesterol < 35 mg/dL, and hypertension. Fasting proinsulin levels significantly increased with body mass index (BMI) category from lean (n = 52, 7.22 ± 3.01 pmol/L) to overweight (n = 14, 12.31 ± 2.91 pmol/L) to obese (n = 43, 16.51 ± 7.27 pmol/L) (p < 0.001), after controlling for HOMA-IR. The ratio of the fasting levels of proinsulin to insulin did not differ significantly between the three groups. Both BMI z-score and HOMA-IR were significant independent factors related to the fasting proinsulin level (p < 0.001 for each). A significant inverse association was found between fasting proinsulin level and adiponectin level (r = -0.464, p < 0.001). Children with NGT who had at least one metabolic derangement had higher proinsulin levels than those without metabolic derangement. Obesity itself or obesity-related IR may independently impose β-cell overload on prepubertal children with NGT, leading to hyperproinsulinemia without causing failure to convert proinsulin to insulin when some degree of IR and metabolic derangement appears.

Inhibition of Deoxyhypusine Synthase Enhances Islet β Cell Function and Survival in the Setting of Endoplasmic Reticulum Stress and Type 2 Diabetes

Islet β cell dysfunction resulting from inflammation, ER stress, and oxidative stress is a key determinant in the progression from insulin resistance to type 2 diabetes mellitus. It was recently shown that the enzyme deoxyhypusine synthase (DHS) promotes early cytokine-induced inflammation in the β cell. DHS catalyzes the conversion of lysine to hypusine, an amino acid that is unique to the translational elongation factor eIF5A. Here, we sought to determine whether DHS activity contributes to β cell dysfunction in models of type 2 diabetes in mice and β cell lines. A 2-week treatment of obese diabetic C57BLKS/J-db/db mice with the DHS inhibitor GC7 resulted in improved glucose tolerance, increased insulin release, and enhanced β cell mass. Thapsigargin treatment of β cells in vitro induces a picture of ER stress and apoptosis similar to that seen in db/db mice; in this setting, DHS inhibition led to a block in CHOP (CAAT/enhancer binding protein homologous protein) production despite >30-fold activation of Chop gene transcription. Blockage of CHOP translation resulted in reduction of downstream caspase-3 cleavage and near-complete protection of cells from apoptotic death. DHS inhibition appeared to prevent the cytoplasmic co-localization of eIF5A with the ER, possibly precluding the participation of eIF5A in translational elongation at ER-based ribosomes. We conclude that hypusination by DHS is required for the ongoing production of proteins, particularly CHOP, in response to ER stress in the β cell.

Beta cell function during rapamycin monotherapy in long-term type 1 diabetes

Type 1 diabetes is considered non-reversible at end-stage disease when there is no measurable insulin production. However, there are indications that insulin-producing beta cells could be present or return if autoimmunity could be controlled. We therefore sought to determine whether immunosuppression therapy can reinstate beta cell function in patients with long-term type 1 diabetes. We examined pancreatic beta cell function in 22 patients with long-term type 1 diabetes (median disease duration 27 years), who had been receiving rapamycin monotherapy (0.1 mg/kg; target trough levels 8-10 ng/ml; 26-314 days) as pre-conditioning for islet transplantation. As control, beta cell function was measured in 14 patients (median disease duration 17 years) who were waiting for an islet transplant without rapamycin pre-conditioning. Fasting C-peptide increased from <0.03 nmol/l (0.0066 nmol/l, interquartile range [IQR] 0.0003-0.023) at baseline to 0.039 nmol/l (IQR 0.0066-0.096) at end of rapamycin monotherapy (p < 0.005). In 12 patients, fasting C-peptide increased to >0.076 nmol/l (C-peptide responders). Exogenous insulin requirement decreased from 0.64 U/kg daily (IQR 0.56-0.72) to 0.57 U/kg (IQR 0.45-0.70; p = 0.01), but this reduction was significant only in the 12C-peptide-responsive patients. Rapamycin monotherapy was also associated with a decrease in insulin antibody titre (median decrease 110 to 35.9 U/ml; p < 0.001) and fasting serum proinsulin (median decrease 0.51 to 0.28 pmol/l; p = 0.001). All variables remained unchanged in the 14 control patients. Therapies to reinstate beta cell function may be applicable to patients with long-term C-peptide-negative type 1 diabetes. ClinicalTrial.gov NCT01060605.

Carriers of the TCF7L2 rs7903146 TT genotype have elevated levels of plasma glucose, serum proinsulin and plasma gastric inhibitory polypeptide (GIP) during a meal test

The transcription factor 7-like 2 (TCF7L2) rs7903146 T allele associates with type 2 diabetes in several populations, possibly mediated via decreased incretin secretion and/or action and altered beta and alpha cell function. We aimed to study circulating levels of glucose, proinsulin, insulin, C-peptide, glucagon, glucagon-like peptide-1 (GLP-1), glucagon-like peptide-2 (GLP-2) and gastric inhibitory polypeptide (GIP) among individuals carrying the high-risk rs7903146 TT genotype and low-risk CC genotype following a meal test. A meal challenge was performed in 31 glucose-tolerant men (age 54 ± 7 years and BMI 26 ± 3 kg/m²) with rs7903146 TT genotype and 31 glucose-tolerant age- and BMI-matched men with CC genotype (age 53 ± 6 years and BMI 26 ± 3 kg/m²). Serum proinsulin, insulin, C-peptide and plasma glucose, glucagon, GLP-1, GLP-2 and GIP were obtained 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 180, 210, and 240 min after ingestion of a standardised breakfast meal. An elevated incremental AUC for plasma glucose was observed among TT genotype carriers (CC carriers 21.8 ± 101.9 mmol/l × min vs TT carriers 97.9 ± 89.2 mmol/l × min, p = 0.001). TT carriers also had increased AUCs for proinsulin (CC carriers 6,030 ± 3,001 pmol/l × min vs TT carriers 6,917 ± 4,820 pmol/l × min, p = 0.03), C-peptide (CC carriers 397.6 ± 131.9 nmol/l × min vs TT carriers 417.1 ± 109.3 nmol/l × min, p = 0.04) and GIP (CC carriers 12,310 ± 3,840 pmol/l × min vs TT carriers 14,590 ± 5,910 pmol/l × min, p = 0.004). Middle-aged normoglycaemic individuals carrying the rs7903146 TCF7L2 risk TT genotype show early signs of dysregulated glucose metabolism, decreased processing of proinsulin and elevated GIP secretion following a meal challenge.

Establishment of electrochemiluminescence immunoassay to detect proinsulin levels in human serum

Objective To establish a electrochemilumineecenee immunoaasay (ECLIA) for detecting proinsulin(PI) levels in human serum. Methods PI ECLIA kit contains biotinylated monoclonal insulin-specificantibody, ruthenium labeled monoclonal C-peptide specific antibody, and streptavidin-coated microparticlea. Its method performance, such as sensitivity, specific, accuracy, was evaluated. Then, the levels of PI in clinical samples were detected by ECLIA, including 44 type 2 diabetes and 60 healthy volunteers. Results Average recovery of ECLIA was 103. 8% with a lower detection limit of 0.38 pmol/L and biologic detection limit between 0.25 pmol/L and 0.5 pmol/L, and the function sensitivity was 0.5 pmol/L. The human insulin and human C-peptide did not cross-react at 500 μU/ml recovery of ECLIA was 103.8% with a lower detection limit of 0.38 pmol/L and biologic detection limit between 0.25 pmol/L and 0.5 pmol/L, and the function sensitivity was 0.5 pmoL/L. The human insulin and human C-peptide did not cross-react at 500 μU/ml and 450 ng/ml respectively. The total coefficient of variation of the ECLIA were leas than 5.0%, and the analytical measure range (AMR) was between 2.22 and 169.68 pmol/L. There was a good correlation (r=0.967,P=0.000) between ECLIA and radio immunoassay (RIA). The 95% reference value for human proinsulin was 1.07-15.54 pmol/L. The plasma levels of PI in type 2 diabetes were significantly higher than those in control healthy group[6.72(3.61-11.92) pmol/L vs 5.72(2.65-8.74) pmol/L, Z=-2.023, P<0.05]. Conclusions The monoclonal-based ECLIA is a sensitive, specific, and rapid method and no radiocontamination. It can be used to detect hanum serum proinsulin in type 2 diabetes. Key words: Proinsulin; Electrochemistry; Luminescence; Immunoassay

Alterations in Proinsulin and Insulin Dynamics, HDL Cholesterol and ALT After Gastric Bypass Surgery. A 42-Months Follow-up Study

Roux-en-Y gastric bypass (RYGBP) powerfully reduces type 2 diabetes (T2DM) incidence. Proinsulin predicts development of T2DM. Adjustable gastric banding is associated with lowered proinsulin but after RYGBP information is scant. Twenty-one non-diabetic morbidly obese patients who underwent RYGBP surgery were evaluated before (baseline), at 12 months (first follow-up), and at 42 months, range 36-50 (second follow-up), after surgery and compared to a control group, matched at baseline regarding fasting glucose, insulin, proinsulin, alanine aminotransferase (ALT), high-density lipoprotein (HDL) cholesterol, and body mass index (BMI). In the RYGBP group, fasting serum proinsulin concentrations were markedly lowered from 13.5 to 3.5 pmol/l at first follow-up and to 4.9 pmol/l at second follow-up (p < 0.001, respectively). Fasting insulin concentrations were reduced from 83.4 to 24.6 pmol/l at first follow-up (p < 0.001) and to 36.4 pmol/l at second follow-up (p < 0.01). ALT was lowered from 0.62 to 0.34 mukatal/l at first follow-up and continued to lower to 0.24 mukatal/l at second follow-up (p < 0.001, respectively). The further decrease between first and second follow-up was also significant (p = 0.002). HDL cholesterol increased from 1.16 to 1.45 mmol/l at the first follow-up and continued to increase at second follow-up to 1.58 mmol/l (p < 0.001, respectively). The further increase between first and second follow-up was also significant (p = 0.006). The differences between groups at first follow-up were significant for BMI, proinsulin, insulin, ALT, and HDL cholesterol (p = 0.04-0.001). RYGBP surgery in morbidly obese patients is not only characterized by markedly and sustained lowered BMI but also lowered concentrations of proinsulin, insulin, and ALT and increased HDL cholesterol.

IL-12 serum levels in patients with type 2 diabetes treated with sulphonylureas

Interleukin-12 (IL-12) has been identified as a pro-inflammatory cytokine which is thought to contribute to the development of atherosclerosis. However, to date, the various associations between factors related to the course of type 2 diabetes, like metabolic compensation, beta cell secretory dysfunction, insulin resistance and IL-12 serum levels, remain unclear. Our study involved 41 patients with type 2 diabetes, 19 patients with coronary artery disease (CAD), and 19 healthy controls. We measured serum levels of fasting glucose, HbA 1c, 1,5-anhydro- d-glucitol, and lipids. In addition, serum levels of C-peptide, insulin, proinsulin and IL-12 were assayed. HOMA IR score was calculated. The serum concentrations of IL-12 were higher in diabetics than in either patients with CAD or healthy controls, and were correlated with BMI, C-peptide, insulin, HOMA IR, proinsulin and HDL serum levels. Multiple regression analysis revealed that the IL-12 serum level in type 2 diabetics primarily is dependent upon fasting proinsulin concentration. Our results demonstrate that elevated IL-12 serum levels in type 2 diabetics treated with sulphonylureas are induced especially by peripheral insulin resistance and beta cells dysfunction, as expressed by fasting serum proinsulin levels. This finding gives us hope that treatment to decrease peripheral insulin resistance and to avoid excessive proinsulin secretion might be successful in the prevention of IL-12-induced atherosclerosis.

Metabolic Risk Factors for Stroke and Transient Ischemic Attacks in Middle-Aged Men

The impact of lipometabolic and glucometabolic disturbances on stroke incidence remains to be characterized in detail. We investigated relations of a comprehensive panel of baseline lipometabolic and glucometabolic variables to incident fatal and nonfatal stroke or transient ischemic attack (TIA), and stroke subtypes. A community-based prospective study of 2313 middle-aged men invited to a health survey at age 50. During a follow-up of up to 32 years, 421 developed stroke or TIA. In Cox proportional hazards analyses adjusting for treatment with cardiovascular drugs at baseline, 1-standard deviation increases in body mass index, systolic and diastolic blood pressures, serum proinsulin, and lipoprotein(a) were associated with 11 to 35% increased risk for subsequent stroke/TIA. Electrocardiographic left ventricular hypertrophy and smoking were also associated with a higher risk for stroke/TIA. Essentially the same variables were related to brain infarction/TIA. Higher proportions of palmitic (16:0), palmitoleic (16:1), and oleic acid (18:1) in cholesterol esters were associated with an increased risk, whereas a higher proportion of linoleic acid (18:2 n-6) was protective against stroke/TIA. Further adjusting all models also for hypertension, diabetes, the metabolic syndrome, serum cholesterol, atrial fibrillation, cardiovascular disease, smoking, and physical activity, essentially the same pattern was observed. Indices of an unhealthy dietary fat intake and a high serum lipoprotein (a) level predicted fatal and nonfatal stroke/TIA independently of established risk factors in a community-based sample of middle-aged men followed for 32 years.

Efficacy and safety of the dipeptidyl peptidase-4 inhibitor sitagliptin added to ongoing pioglitazone therapy in patients with type 2 diabetes: A 24-week, multicenter, randomized, double-blind, placebo-controlled, parallel-group study

Objective: The efficacy and tolerability of the dipeptidyl peptidase-4 inhibitor sitagliptin added to ongoing pioglitazone therapy were assessed in patients with type 2 diabetes and inadequate glycemic control (glycosylated hemoglobin [HbA 1c] ≥7% and ≤10%) while receiving a stable dose of pioglitazone. Methods: This was a 24-week, multicenter, ran domized, double-blind, placebo-controlled, parallel group study in patients aged ≥18 years (ClinicalTrials. gov NCT00086502). At screening, all patients began a diet/exercise program that continued throughout the study period. Patients taking antihyperglycemic therapy other than pioglitazone underwent a washout of this therapy and entered an 8- to 14-week open-label pioglitazone dose-titration/stabilization period. Patients with an HbA 1c ≥7% and ≤10% at the end of this period entered a 2-week, single-blind, placebo run-in period (total duration of run-in period, up to 21 weeks). Patients who had been receiving pioglitazone monotherapy (30 or 45 mg/d) and had an HbA 1c ≥7% and ≤10% entered the 2-week, single-blind, placebo run-in period directly. Thus, at the time of randomization, all patients were receiving ongoing pioglitazone (30 or 45 mg/d). Patients were randomized in a 1:1 ratio to receive sitagliptin 100 mg once daily or placebo for 24 weeks. The primary efficacy end point was the change from baseline in HbA 1c at week 24. Secondary efficacy end points included the change from baseline in fasting plasma glucose (FPG), insulin, and proinsulin; the Homeostasis Model Assessment β-cell function and insulin-resistance indexes; the proinsulin/ insulin ratio; the Quantitative Insulin Sensitivity Check Index; the percent changes from baseline in selected lipid parameters; the proportion of patients meeting the American Diabetes Association HbA 1c, goal of <7.0%; the proportion of patients requiring metformin rescue therapy; and the time to the initiation of rescue therapy. Results: One hundred seventy-five patients were randomized to receive sitagliptin, and 178 were randomized to receive placebo. The mean (SD) baseline HbAlc value was 8.1% (0.8) in the sitagliptin group and 8.0% (0.8) in the placebo group. After 24 weeks, sitagliptin added to pioglitazone therapy was associated with significant reductions compared with placebo in HbA 1c (between-treatment difference in least squares [LS] mean change from baseline. −0.70 %; 95 % CI, −0.85 to −0.54; P < 0.001) and FPG (−17.7 mg/dL; 95% CI, −24.3 to -11.0; P < 0.001). Mean HbA 1c values at end point were 7.2% (0.9) and 7.8% (1.1) in the respective treatment groups, and the proportions of patients reaching a target HbA 1c of <7.0% were 45.4% and 23.0% ( P < 0.001). Significant reductions in fasting serum proinsulin levels and the proinsulin/insulin ratio were seen with sitagliptin treatment compared with placebo (both, P < 0.01). Sitagliptin was generally well tolerated, with no increased risk of hypoglycemia compared with placebo (2 vs 0 patients, respectively).

Characterization of Insulin Secretion in Valproate‐treated Patients with Epilepsy

Valproate (VPA) treatment has been reported to be associated with obesity and high fasting serum insulin concentrations in parallel with an unfavorable serum lipid profile and hyperandrogenism and polycystic ovaries in women. The pathogenetic mechanism underlying these changes has remained unknown, although several mechanisms have been implicated. Fifty-one patients receiving monotherapy (31 male and 20 female patients) were included in this study, with 45 (23 male and 22 female) healthy control subjects. These participants were interviewed, clinically examined, and blood samples for fasting plasma glucose, serum insulin, proinsulin, and C-peptide concentrations were taken after an overnight fast. The valproate-treated patients had fasting hyperinsulinemia (11.30 +/- 6.23 pM vs. 6.28 +/- 4.66 pM in the control subjects; p < 0.001), although the fasting serum proinsulin and C-peptide concentrations were not significantly higher in the patients than in the control subjects. In addition, proinsulin/insulin (0.30 +/- 0.14) and C-peptide/insulin ratios (35.48 +/- 24.09) were lower (p < 0.001) in the VPA-treated patients when compared with the control subjects (0.53 +/- 0.36 and 94.27 +/- 61.85, respectively), and they also had lower fasting plasma glucose concentrations (4.72 +/- 0.35 mM) than the control subjects (5.12 +/- 0.58 mM; p < 0.01). This study suggests that valproate does not induce insulin secretion but might interfere with the insulin metabolism in the liver, resulting in higher insulin concentrations in the peripheral circulation. These changes are seen irrespective of concomitant weight gain, suggesting that increased insulin concentrations induce weight gain and not vice versa.

Association of Serum Proinsulin With Hormone Replacement Therapy in Nondiabetic Older Women

One putative benefit of hormone replacement therapy (HRT) is a reduced risk of diabetes or reduced fasting glucose level. We report here the association of HRT with proinsulin, insulin, and fasting and postchallenge glucose levels in older adults. Current HRT use was validated and cross-sectionally compared with diabetes-related variables in 785 women without diabetes by history or glucose tolerance test. Median age was 72 years (range 50-97); median value of fasting plasma glucose, postchallenge plasma glucose, and proinsulin was 5.08 mmol/l, 6.93 mmol/l, and 9.3 pmol/l, respectively. In age-adjusted comparisons, current HRT use was associated with significantly lower fasting plasma glucose and higher postchallenge plasma glucose compared with never/previous HRT use, as well as with lower LDL and higher HDL cholesterol and higher triglycerides. Fasting and postchallenge intact insulin did not differ by HRT group, but proinsulin was significantly lower in current HRT users than in previous and never HRT users. The significant association between proinsulin and HRT status persisted after adjustment for age, waist-to-hip ratio, pulse pressure, LDL-to-HDL cholesterol ratio, triglycerides, fasting and postchallenge glucose, and intact insulin. Reduced fasting and increased 2-h glucose replicate findings in a randomized clinical trial. The proinsulin effect has not been previously reported. Decreased fasting glucose and proinsulin levels in current HRT use suggest a potential antidiabetes effect of HRT. Increased postchallenge glucose in HRT, however, suggests insulin resistance and would be expected to increase the risk of heart disease.

Indices of insulin sensitivity, beta cell function and serum proinsulin levels in the polycystic ovary syndrome

Background The study aim was to investigate the relationship between insulin resistance (IR), β-cell function (βF), hyperandrogenism and proinsulin levels during an oral glucose tolerance test (OGTT) in women with polycystic ovary syndrome (PCOS). Methods One hundred and twenty-six selected women were classified as follows: PCOS, BMI > 25 kg/m 2 ( n = 39); PCOS, BMI < 25 kg/m 2 ( n = 54); controls, BMI > 25 kg/m 2 ( n = 14); controls, BMI < 25 kg/m 2 ( n = 19). Blood samples were collected between the third and sixth day of a spontaneous menstrual cycle, at 9:00 a.m., after an overnight fast. Serum levels of FSH, LH, PRL, 17α-OH-progesterone, SHBG, testosterone, Δ 4-androstenedione, insulin, proinsulin and glucose were measured. A 75 g OGTT was performed, and concentrations of glucose, insulin and proinsulin were also measured at t = 30, 60, 90, and 120 min. Results The markers of insulin secretion and the AUC for proinsulin were higher in obese and overweight women and in women with PCOS, respectively. The AUC for proinsulin was positively correlated with markers of IR, βF and androgen levels. An inverse relationship between PI/I values and indices of IR and βF was observed. Conclusions Increased proinsulin levels reflect, most probably, insulin resistance, which is the key disorder in PCOS-associated metabolic abnormalities. β-Cell function, pre-proinsulin mRNA processing and proinsulin conversion to insulin could be initially increased as a result of IR. An interaction between circulating proinsulin and androgen biosynthesis or action might also exist.