Insulin and C-peptide secretion in non-obese patients with polycystic ovarian disease

Plasma glucose, immunoreactive insulin (IRI) and C-peptide responses during an oral glucose tolerance test (oGTT) were assessed in 11 non-obese patients with polycystic ovarian disease (PCOD) and 11 reference subjects matched for age, height and weight. Also, 6 patients with PCOD and 6 normal women were subjected to intravenous glucose tolerance testing (ivGTT) On oGTT, all subjects exhibited normal glucose tolerance; however, PCOD patients had significantly higher mean plasma glucose levels at 30, 60, 90 and 120 min and higher mean incremental glucose areas. In addition the patients with polycystic ovaries showed higher mean basal IRI and C-peptide levels, higher mean glucose stimulated IRI and C-peptide levels and higher mean incremental IRI and C-peptide values. The molar ratios of C-peptide/IRI were significantly lower in the PCOD group at all time intervals after glucose stimulation when compared to the normal women. During ivGTT, there were significantly higher mean glucose levels at 5, 40, 50 and 60 min in the PCOD group when compared to the reference group. The IRI response to intravenous glucose in the PCOD women was similar to the reference group. The findings on oGTT suggest that non-obese patients with PCOD have increased pancreatic IRI secretion as well as impaired hepatic extraction of the hormone.     

Hyperinsulinemia of chronic active hepatitis: impaired insulin removal rather than pancreatic hypersecretion

Exaggerated insulin response to oral glucose was demonstrated in peripheral blood of patients with chronic hepatic diseases. High peripheral insulin levels may be the result of pancreatic hypersecretion or decreased hepatic removal of insulin. The simultaneous assay of insulin and C-Peptide concentrations in peripheral blood enables the determination of both beta-cell activity and hepatic fractional insulin extraction. We have measured peripheral insulin and C-Peptide levels during OGTT in a group of subjects with chronic active hepatitis (CAH). These subjects showed glucose levels and incremental areas significantly higher than controls, but still in the upper range of normality. Insulin response to oral glucose was significantly greater in CAH patients than in controls, whereas C-Peptide levels and areas were quite similar in the two groups. The C-Peptide to insulin molar ratios before and after glucose, and the relations between C-Peptide and insulin incremental areas were lower in CAH patients than in controls. We conclude that the peripheral hyperinsulinemia observed in subjects with CAH is due to diminished insulin removal by the diseased liver rather than pancreatic hypersecretion.     

Plasma insulin and C-peptide responses to oral glucose load after physical exercise in men with normal and impaired glucose tolerance

Blood glucose, plasma insulin and C-peptide responses to oral glucose tolerance test (OGTT) were studied under basal conditions and immediately after 90-min exercise (60% VO2 max) in nondiabetic subjects with normal or impaired glucose tolerance. During the postexercise recovery blood glucose response to OGTT was increased in normal subjects and markedly decreased in those with impaired glucose tolerance, while insulin and C-peptide responses were diminished in both subgroups. The ratio of blood glucose to insulin was similarly elevated in all subjects. Comparing with basal conditions no significant changes were found in C-peptide to insulin ratio in response to OGTT after exercise, although a tendency towards an elevation of this ratio was noted in the subjects with impaired glucose tolerance. The data indicate that the reduced insulin response to OGTT during postexercise recovery in healthy subjects is due to diminished insulin secretion without any substantial changes in the hormone removal from blood, whereas in the glucose intolerant men the latter process may be enhanced.     

Leptin levels in type 2 diabetes: associations with measures of insulin resistance and insulin secretion.

Interactions between leptin and insulin have been shown previously, in vitro and in vivo. In this study, we evaluate the associations of leptin levels with insulin secretion and insulin sensitivity in type 2 diabetes. Fasting leptin levels, HbA 1c, glucose, insulin, C-peptide, intact and des-31,32-proinsulin were measured in 100 non-insulin-treated type 2 diabetic patients. Glucose, insulin and C-peptide were measured 2 hours after an oral glucose load. Insulin resistance and beta-cell function were calculated using HOMA. Leptin levels were found to be associated with all measures of beta-cell secretion: with fasting and 2 hours insulin and C-peptide, with intact and des-31,32-proinsulin concentrations, and with beta-cell secretion estimated with HOMA. This association was independent of age and body fat in women, but in men, associations with insulin and C-peptide weakened after controlling for fat mass, whereas those with intact and des-31,32-proinsulin disappeared. Fasting insulin and C-peptide levels were also significant in multiple regression analyses, besides gender and fat mass. Insulin resistance, as assessed by HOMA, was strongly correlated with leptin, also after correction for age and fat mass in both genders. We conclude that, besides fat mass and gender - the main determinants for leptin levels in type 2 diabetic subjects as in healthy subjects - insulin secretion and the degree of insulin resistance also seem to contribute significantly to leptin levels.     

Oral glucose decreases hepatic extraction of insulin.

Peripheral venous (plasma) insulin and C-peptide concentrations were measured in eight normal subjects given oral or intravenous glucose sufficient to produce similar plasma glucose concentrations. The expected increased insulin response to oral as compared with intravenous glucose was not matched by a comparable increase in C-peptide concentration. The ratio of insulin to C-peptide concentrations doubled 30 minutes after oral glucose was given; no comparable rise was seen with intravenous glucose (p = 0.01). This finding is interpreted as evidence for decreased hepatic extraction of insulin after administration of oral glucose. Such a decrease could account for at least half of the well known difference in peripheral insulin concentrations after administration of oral as compared with intravenous glucose.     

Secretion of incretin hormones (GIP and GLP-1) and incretin effect after oral glucose in first-degree relatives of patients with type 2 diabetes

AIMS/HYPOTHESIS: Since insulin secretion in response to exogenous gastric inhibitory polypeptide (GIP) is diminished not only in patients with type 2 diabetes, but also in their normal glucose-tolerant first-degree relatives, it was the aim to investigate the integrity of the entero-insular axis in such subjects. METHODS: Sixteen first-degree relatives of patients with type 2 diabetes (4 male, 12 female, age 50+/-12 years, BMI 26.1+/-3.8 kg/m(2)) and 10 matched healthy controls (negative family history, 6 male, 4 female, 45+/-13 years, 26.1+/-4.2 kg/m(2)) were examined with an oral glucose load (75 g) and an "isoglycaemic" intravenous glucose infusion. Blood was drawn over 240 min for plasma glucose (glucose oxidase), insulin, C-peptide, GIP and glucagon-like peptide 1 (GLP-1; specific immunoassays). RESULTS: The pattern of glucose concentrations could precisely be copied by the intravenous glucose infusion (p=0.99). Insulin secretion was stimulated significantly more by oral as compared to intravenous glucose in both groups (p<0.0001). The percent contribution of the incretin effect was similar in both groups (C-peptide: 61.9+/-5.4 vs. 64.4+/-5.8%; p=0.77; insulin: 74.2+/-3.3 vs. 75.8+/-4.9; p=0.97; in first-degree relatives and controls, respectively). The individual responses of GIP and GLP-1 secretion were significantly correlated with each other (p=0.0003). The individual secretion of both GIP and GLP-1 was identified as a strong predictor of the integrated incremental insulin secretory responses as well as of the incretin effect. CONCLUSION/INTERPRETATION: Despite a lower insulin secretory response to exogenous GIP, incretin effects are similar in first-degree relatives of patients with type 2 diabetes and control subjects. This may be the result of a B cell secretory defect that affects stimulation by oral and intravenous glucose to a similar degree. Nevertheless, endogenous secretion of GIP and GLP-1 is a major determinant of insulin secretion after oral glucose.     

Insulin and C-peptide secretion and kinetics in humans: direct and model-based measurements during OGTT

To directly evaluate prehepatic secretion of pancreatic hormones during a 3-h oral glucose tolerance test (OGTT), we measured insulin and C-peptide in six healthy control, six obese, and six type 2 diabetic subjects in the femoral artery and hepatic vein by means of the hepatic catheterization technique. Hypersecretion in obesity was confirmed (309 +/- 66 nmol in obese vs. 117 +/- 22 in control and 79 +/- 13 in diabetic subjects, P 0.3, r(2) = 0.93), whereas estimation of hepatic insulin extraction and insulin clearance needs further investigation for improvement.     

Insulin secretion and sensitivity in acromegaly

To examine the effect of excess growth hormones on carbohydrate metabolism, we studied glucose-stimulated insulin secretion and glucose utilization in 6 patients with acromegaly and 6 age-, sex- and weight-matched normal subjects. The levels of plasma glucose and serum insulin were determined during fasting and every 30 min up to 180 min after 75 g of oral glucose loading. In addition, plasma glucose, serum insulin and serum C-peptide were measured during euglycemic glucose clamp with insulin infusion of 40 mU/m2,min-1. The acromegalic patients had significantly higher mean levels of fasting plasma glucose (p less than 0.05) and insulin (p less than 0.01). After glucose loading for 3 h, the acromegalic patients also had a higher incremental area under the curve of plasma glucose (p less than 0.05) and serum insulin (p less than 0.05). However, no significant difference in the fasting molar ratio of C-peptide/IRI was noted between these two groups. During euglycemic clamp studies, the steady-state serum insulin levels were identical between the two groups. The glucose disposal rate was lower in acromegalics than in normal subjects (p less than 0.01). The results demonstrated that glucose intolerance, hyperinsulinemia and insulin resistance are present in acromegalic patients.     

Metabolic Effects of 2 Days of Strict Bed Rest

ObjectiveTo examine the possibility of whether 2 days of strict hospitalized bed rest would alter the metabolic profile (including insulin resistance as calculated by the quantitative insulin sensitivity check index or QUIC- KI) in both normal subjects and patients with type 2 diabetes in comparison with 2 days of normal activity.MethodsThe design of this pilot study was a randomized, crossover protocol that evaluated the effects of strict bed rest versus normal activity in 5 healthy normal subjects and 5 healthy patients with type 2 diabetes. All study participants completed a screening visit for assessment of baseline health.ResultsAll 10 study subjects completed the protocol without adverse events. Fasting plasma glucose, insulin, and C-peptide levels as well as several known risk factors for atherosclerosis were unchanged in both the subjects without diabetes and the patients with type 2 diabetes after 2 days of hospitalized bed rest. Insulin resistance demonstrated no significant change during the 48 hours of bed rest when compared with the mean value at baseline.ConclusionThis study demonstrates that 48 hours of bed rest has no significant effect on insulin resistance or standard metabolic variables in normal subjects and patients with type 2 diabetes. Therefore, achieving good glucose control in patients hospitalized for a period of 2 days or less does not necessitate early ambulation to prevent an increase in insulin resistance. (Endocr Pract. 2008;14:564-569)     

Residual beta-cell function in type II diabetes and evaluation of the hepatic insulin extraction

Insulin and C-peptide (free insulin and C-peptide in insulin-treated patients) were measured after glucose stimulation in nine Type II diabetics on chlorpropamide, eleven insulin-treated maturity-onset diabetics and in 8 normal controls. Dissociation between C-peptide and insulin response to glucose was observed in several diabetics. The relation between incremental molar areas under C-peptide and insulin curves, after glucose challenge (delta CPR - delta IRI/delta CPR) were used to evaluate the hepatic insulin extraction in all but the insulin-treated diabetics. The lower insulin requirements and better control of the short-duration insulin-treated maturity-onset diabetics in relation to the long-term ones could not be explained either by the residual insulin secretion or by the level of "insulin antibodies". The chlorpropamide-responsive patients presented higher insulin levels after the glucose challenge and a lower hepatic insulin extraction than the non-responsive ones.     

Study of insulin response to oral glucose load after acute and chronic glycemic control in type 2 diabetic subjects

To investigate whether correction of fasting hyperglycemia per se improves the insulin secretion in type 2 diabetic subjects, plasma insulin response to 75 g oral glucose load has been studied after acute and chronic normalization of fasting plasma glucose levels in 7 overt type 2 diabetic subjects. For the acute normalization of elevated fasting plasma glucose levels, an artificial endocrine pancreas was employed. Although fasting plasma glucose concentrations were normalized before the oral glucose challenge, insulin response to oral glucose was not improved compared to those without normalization of fasting plasma glucose levels. After 1-3 month control of hyperglycemia, the insulin response to glucose in the subjects was significantly improved compared to those without treatments. Results indicate that chronic metabolic control is essential for the improvement of insulin response to glucose in type 2 diabetic subjects, and also suggest that the impaired insulin secretion in type 2 diabetes is not due to hyperglycemia per se, but due to the metabolic derangements which lead to chronic hyperglycemia.     

The reduction in hepatic insulin clearance after oral glucose is not mediated by gastric inhibitory polypeptide (GIP)

Since the C-peptide/insulin ratio is reduced after oral glucose ingestion, the incretin hormone gastric inhibitory polypeptide (GIP) has been assumed to decrease hepatic insulin extraction. It was the aim of the present study to evaluate the effects of GIP on insulin extraction. Seventy-eight healthy subjects (27 male, 51 female, 43+/-11 years) were subjected to (a). an oral glucose tolerance test and (b). an intravenous injection of 20 pmol GIP/kg body weight, with capillary and venous blood samples collected over 30 min for insulin, C-peptide and GIP (specific immunoassays). Following GIP administration, plasma concentrations of total and intact GIP reached to peak levels of 80+/-7 and 54+/-5 pmol/l, respectively (p<0.0001). The rise in insulin after oral glucose and after intravenous GIP administration significantly exceeded the rise in C-peptide (p<0.0001). Estimating insulin extraction from the total integrated insulin and C-peptide concentrations (AUCs), only the oral glucose load (p<0.0001), but not the intravenous GIP administration (p=0.18) significantly reduced insulin clearance. Therefore, insulin clearance is reduced after an oral glucose load. This effect does not appear to be mediated by GIP.     

Insulin-sparing effect of hydroxychloroquine in diabetic rats is concentration dependent.

To study the effect of hydroxychloroquine (HCQ) on glucose and insulin homeostasis, healthy rats were dosed with 160 mg x kg (-1) x day(-1) of HCQ orally, and streptozocin-induced diabetic rats received 80, 120, and 160 mg x kg(-1) x day(-1) of HCQ, while controls received normal saline. Ten days after treatment with HCQ, healthy animals were challenged intravenously with insulin or glucose, while diabetic rats were given only an i.v. injection of insulin. In healthy rats, the areas within and under the glucose concentration - time curve following insulin and glucose challenge were estimated. In diabetic animals, the areas under the curve for both the percent change in serum glucose from baseline (AUG) and the percent change in serum insulin from baseline (AUI) were used as pharmacodynamic end points. In healthy rats, HCQ did not influence fasting serum glucose concentrations or glycemic profiles following i.v. administration of glucose or insulin. In diabetic rats, AUG and AUI were increased dependent on blood HCQ concentrations. The normal homeostatic mechanisms responsible for insulin-glucose regulation may compensate for possible HCQ-induced reduction of insulin metabolism in healthy rats. The HCQ dose- or concentration-effect relationships for glucose and insulin were linear over the range of HCQ concentrations tested. It is concluded that HCQ significantly elevated insulin blood concentration resulting in reduced glucose levels in a concentration-dependent fashion in diabetic rats. HCQ may have therapeutic potential in the treatment of type I and type II diabetes.     

Effect of cyproheptadine administration on insulin secretion in acromegalic, diabetic and normal subjects.

The effect of cyproheptadine (Cypro) and Placebo administration on insulin secretion and glucose utilization following i.v. glucose (IVGTT) was evaluated in 8 normal, 7 diabetic and 8 acromegalic subjects. Five of the diabetic subjects had overt diabetes and two of the diabetic subjects had "chemical" diabetes (oral GTT). One of the acromegalic subjects had overt diabetes, while one had borderline glucose tolerance and six had normal glucose tolerance (oral GTT). Cypro increased insulin secretion in the acromegalic but not in the diabetic or normal subjects. Methysergide (Methyl) increased insulin secretion in acromegalic and diabetic subjects but not in normal subjects. Methy and Cypro both increased insulin secretion in the same acromegalic subjects. None of the three groups of subjects had a modification in insulin secretion following Placebo administration. Neither Placebo, Cypro or Methy altered the glucose utilization rate contant (KG). There was no change in insulin half life or tissue sensitivity to insulin from Cypro (normal and acromegalic subjects) or Methy (normal subjects) administration. Despite their increase in insulin secretion in response to serotonin antagonists, acromegalic subjects have normal urinary 5-hydroxyindoleacetic acid excretion and normal serum serotonin concentrations. Their response cannot therefore be attributed to a generalized overproduction of serotonin.     

Interrelation between glucose, insulin, C-peptide and 3-hydroxybutyrate in plasma and amniotic fluid in last trimester diabetic women without residual betacell function

The relationship between maternal plasma and amniotic fluid (AF) concentrations of glucose, insulin, C-peptide and 3-hydroxybutyrate (3-HB) was analysed between 45 to 140 minutes after a standardized breakfast in 8 type I diabetic women without residual betacell function and in 13 nondiabetic control women during the last trimester of gestation. AF levels of both glucose and C-peptide were slightly and AF insulin levels significantly (P less than 0.05) elevated above normal in the diabetic women. 3-HB levels in plasma and in AF were significantly (P less than 0.05) elevated in the diabetic group between 45 to 65 minutes after breakfast. AF insulin and glucose was significantly correlated in the diabetic group (r = 0.96, P less than 0.05). During the 2 hour study period AF levels of glucose, insulin and C-peptide remained essentially unchanged in both groups of women. Changes in maternal plasma 3-HB concentrations seemed to be more rapidly reflected in AF.     

短期速效胰岛素联合长效胰岛素强化治疗对初诊2型糖尿病患者胰岛功能及氧化应激的影响

目的：探讨短期速效胰岛素联合长效胰岛素强化治疗方案对初诊2型糖尿病患者胰岛功能及氧化应激的影响。方法：选择30例初诊2型糖尿病患者,在一般治疗的基础上,应用短期速效胰岛素联合长效胰岛素强化治疗方案进行治疗,检测并比较患者治疗前后一般血清指标包括空腹血糖（FBG）、餐后2小时血糖（2h PPG）、糖化血红蛋白（HbA1c）、血清C肽（FCP）,胰岛细胞功能指标包括胰岛素曲线下面积（AUG）、β细胞功能稳态模型评估（HOMA-B）、I30/G30、胰岛素抵抗指数（HOMA-IR）、胰岛素及C肽水平,以及氧化应激指标包括丙二醛（MDA）及超氧化物岐化酶（SOD）。结果：（1）与治疗前相比,患者治疗后FPG、2h PPG、HbA1c、AUG、HomaB、HomaIR及I30/G30水平均显著改善,差异均有统计学意义（P均〈0.05）;患者口服糖耐量试验0h、1h及2h胰岛素水平及C肽水平均显著回升,差异有统计学差异（P〈0.05）。（2）治疗后,患者MDA水平显著降低,SOD水平显著升高,其差异有统计学意义（P〈0.05）。结论：短期速效胰岛素联合长效胰岛素强化治疗方案可以明显改善初诊2型糖尿病患者胰岛功能,降低患者体内的氧化应激水平。     

Use of an artificial beta cell in surgery.

Using a Biostator glucose-controlled insulin infusion system to monitor blood glucose during surgery, we have shown that both nondiabetic and diabetic patients have a tendency towards hyperglycemia during surgery. This appears to be due to suppression of endogenous insulin secretion as measured by serum C-peptide levels. Some diabetic patients maintained relatively normal glucose values during surgery when infused with saline alone and not given glucose or insulin, but 2 of 5 were not well controlled by this means. Hyperglycemia in both diabetic and non-diabetic patients was related to the rate of infusion of exogenous glucose. The biostator glucose-controlled insulin infusion system could be used in feedback mode as an apparently safe and effective means of controlling blood glucose during surgery on diabetic patients.     

Development of hyperinsulinemia and insulin resistance during the early stage of weight gain

Obesity is associated with insulin resistance and hyperinsulinemia, which is considered to be a core component in the pathophysiology of obesity-related comorbidities. As yet it is unknown whether insulin resistance and hyperinsulinemia already develop during weight gain within the normal range. In 10 healthy male subjects the effect of intentional weight gain by 2 BMI points was examined on insulin. C-peptide and glucose levels following a meal, 75 g of glucose, and a two-step hyperglycemic clamp increased plasma glucose by 1.38 and 2.75 mmol/l, respectively. Baseline insulin, C-peptide, and glucose concentrations were significantly higher after weight gain from 21.8 to 23.8 kg/m(2) BMI within 4(1/2) mo. Calculations of insulin secretion and clearance indicate that reduced insulin clearance contributes more to post-weight gain basal hyperinsulinemia than insulin secretion. Following oral or intravenous stimulation insulin concentrations were significantly higher post-weight gain during all three test conditions, whereas C-peptide and glucose levels did not differ. Calculations of insulin secretion and clearance demonstrated that higher stimulated insulin concentrations are entirely due to clearance but not secretion. Despite significantly higher insulin levels, the rate of intravenous glucose required to maintain the defined elevation of glucose levels was either identical (1.38 mmol/l) or even significantly lower (2.75 mmol/l) following weight gain. The present study demonstrates for the first time that insulin resistance already develops during weight gain within the normal range of body weight. The associated basal and stimulated hyperinsulinemia is the result of differentiated changes of insulin secretion and clearance, respectively.     

Sustained normoglycemia and remission phase in newly diagnosed type I diabetic subjects. Comparison between continuous subcutaneous insulin infusion and conventional therapy during a one year follow-up

After onset of type I diabetes 7 diabetics were randomized to subcutaneous insulin pump treatment (CSII) (age 12 to 29 years, mean: 21 years) and 7 diabetics to conventional insulin treatment (CI) (age 14 to 28 years, mean: 21 years). HbA1, glycosylated serum proteins and mean blood glucose (MBG) as parameters of metabolic control were determined monthly. After 2 months both groups showed HbA1 values in the normal range. Mean MBG values were (mean +/- SD) 116 +/- 7 mg/dl for CSII and 118 +/- 14 mg/dl for CI. Residual insulin secretion was determined monthly by fasting C-peptide. After 14 days, 5, 7, 8 months fasting C-peptide values were significantly (P less than 0.05) higher in CI. After one year fasting C-peptide was comparable in both groups (CSII and CI mean: 0.06 nmol/l). The administered insulin dose was comparable in both groups with a 55% reduction of insulin dose after 5 months in CSII (0.35 +/- 0.15 U/kg/24 h) and in CI after 7 months (0.31 +/- 0.28 U/kg/24 h). After 12 months of insulin therapy about 60% of the initial insulin dose was injected in both groups. 1 patient on CSII (12 years) and 2 patients on CI (15, 28 years) showed a complete remission (for 3-9 months) with no exogenous insulin and normal HbA1 values. 50% of the patients had episodes where they did need less than 0.2 U/kg/24 h insulin to maintain optimal diabetic control (3 CSII, 4 CI). During the first year of insulin treatment in type I diabetes with CSII as well as with CI a comparable near normalisation of diabetic control could be achieved.     

Positive correlation of galanin with glucose in healthy volunteers during an oral glucose tolerance test.

Galanin has been found in increased amounts in subjects with type 2 diabetes. The purpose of the present study was to determine the levels of galanin in healthy volunteers during an oral glucose tolerance test (OGTT). We enrolled 11 healthy volunteers, 4 males aged 48+/-3.56 years with BMI 27+/-0.5 kg/m (2) and 7 females aged 41.3+/-3.05 years with BMI 27.6+/-0.9 kg/m (2). All were in good health without cardiac, hepatic, renal or other chronic disease. None were taking any medication affecting glucose tolerance (beta-blockers, thiazide diuretics, and corticoids) and none had a first degree relative with type 2 diabetes. Glucose tolerance was determined by using the International Expert Committee criteria. Blood samples were collected at 0, 30, 60, 90, 120 and 180 minutes for the measurement of plasma glucose, insulin, C-peptide and human galanin (hGal). During the OGTT, hGal exhibited a significant increase from time 0 to 90 minutes (p < 0.001) and returned to the basal values at 180 minutes, while a positive correlation of blood glucose with hGal was observed during the time scale of OGTT. A significant increase was detected both in insulin and C-peptide from the early beginning of the test at 30 minutes, which remained steady until 90 minutes, and returned gradually to the basal values at 180 minutes. No relationship was found either between hGal and serum insulin, or between hGal and serum C-peptide among the healthy subjects, during the OGTT.