Low- and high-frequency insulin secretion pulses in normal subjects and pancreas transplant recipients: role of extrinsic innervation.

Low-frequency ultradian and high-frequency insulin secretion pulses were studied in normal subjects and in metabolically stable pancreas transplant recipients. Insulin secretion pulsatility was evaluated after deconvoluting the pulsatile plasma C peptide concentrations with its kinetic coefficients. In normal subjects, ultradian insulin secretion pulses with periodicities of 75-115 min were consistently observed during the 24-h secretory cycle. Pulse period and relative amplitude during the overnight rest (95 +/- 4 min and 27.6 +/- 2.4%) were similar to those during the steady state of continuous enteral feeding (93 +/- 5 min and 32.6 +/- 3.3%). Sampling at 2-min intervals revealed the presence of high-frequency insulin secretion pulses with periodicities of 14-20 min and an average amplitude of 46.6 +/- 5.4%. Pancreas transplant recipients had normal fasting and fed insulin secretion rates. Both low- and high-frequency insulin secretion pulses were present. The high-frequency pulse characteristics were identical to normal. Low-frequency ultradian pulse periodicity was normal but pulse amplitude was increased. Thus, ultradian insulin secretory pulsatility is a consistent feature in normal subjects. The low- and high-frequency secretion pulsatilities are generated independent of extrinsic innervation. Autonomic innervation might modulate low-frequency ultradian pulse amplitude exerting a dampening effect.

Skeletal muscle glycolysis, oxidation, and storage of an oral glucose load.

Although muscle is considered to be the most important site for postprandial glucose disposal, the metabolic fate of oral glucose taken up by muscle remains unclear. We, therefore, employed the dual isotope technique (intravenous, [6-3H]-glucose; oral, [1-14C]glucose), indirect calorimetry, and forearm balance measurements of glucose, lactate, alanine, pyruvate, O2, and CO2 in nine normal volunteers to determine the relative importance of muscle glycogenic, glycolytic, and oxidative pathways in disposal of an oral glucose load. During the 5 h after glucose ingestion (1 g/kg), 37 +/- 3% (24.9 +/- 2.3 g) of the load was oxidized and 63 +/- 3% (42.8 +/- 2.7 g) was stored. At least 29% (19.4 +/- 1.3 g) was taken up by splanchnic tissues. Muscle took up 26% (17.9 +/- 2.9 g) of the oral glucose coincident with a 50% reduction in its oxidation of fat. 15% of the oral glucose taken up by muscle (2.5 +/- 0.9 g) was released as lactate, alanine, or pyruvate; 50% (8.9 +/- 1.4 g) was oxidized, and 35% (6.4 +/- 2.3 g) was available for storage. We conclude that muscle and splanchnic tissues take up a comparable percentage of an oral glucose load and that oxidation is the predominant fate of glucose taken up by muscle, with storage in muscle accounting for less than 10% of the oral load. Thus, contrary to the prevailing view, muscle is neither the major site of storage nor the predominant site of disposal of an oral glucose load.

Cross-protective mucosal immunity mediated by memory Th17 cells against Streptococcus pneumoniae lung infection.

Pneumonia caused by Streptococcus pneumoniae (Sp) remains a leading cause of serious illness and death worldwide. Immunization with conjugated pneumococcal vaccine has lowered the colonization rate and consequently invasive diseases by inducing serotype-specific antibodies. However, many of the current pneumonia cases result from infection by serotype strains not included in the vaccine. In this study, we asked if cross-protection against lung infection by heterologous strains can be induced, and investigated the underlying immune mechanism. We found that immune mice recovered from a prior infection were protected against heterologous Sp strains in the pneumonia challenge model, as evident by accelerated bacterial clearance, reduced pathology, and apoptosis of lung epithelial cells. Sp infection in the lung induced strong T-helper type 17 (Th17) responses at the lung mucosal site. Transfer of CD4+ T cells from immune mice provided heterologous protection against pneumonia, and this protection was abrogated by interleukin-17A (IL-17A) blockade. Transfer of memory CD4+ T cells from IL-17A-knockout mice failed to provide protection. These results indicate that memory Th17 cells had a key role in providing protection against pneumonia in a serotype-independent manner and suggest the feasibility of developing a broadly protective vaccine against bacterial pneumonia by targeting mucosal Th17 T cells.

Splanchnic insulin dynamics and secretion pulsatilities in abdominal obesity.

Insulin secretion, clearance dynamics, and their relationship to peripheral plasma insulin and glucose levels were monitored during three 12-h periods of overnight rest, intake of three meals, and continuous enteral feeding of mixed nutrients. The low-frequency ultradian and the high-frequency insulin secretion pulsatility characteristics during the steady-states of overnight rest and continuous enteral feeding were also examined. In abdominally obese subjects, the insulin secretion rate was consistently higher than normal by 2.3-fold. Peripheral plasma insulin levels were increased by 3.4-fold during the overnight period and by 4- to 5-fold during the two fed states. Endogenous insulin clearance was significantly reduced during feeding. Both low- and high-frequency insulin secretory pulsatilities were detected in the abdominally obese subjects. Pulse periods were within the normal range. Pulse maxima, nadirs, and absolute amplitudes were increased concomitant with the increase in insulin secretion. Ultradian relative pulse amplitudes, however, were blunted. A significantly higher pulse-to-pulse variability was observed in the abdominally obese subjects compared with normal subjects. Furthermore, a significantly higher level of interindividual variability in the nutrient-stimulated insulin secretion and in the ultradian pulse characteristics was observed. Thus in abdominal obesity, the increase in pancreatic insulin output is limited and the secretory pulsatilities are aberrant, suggesting a defect in the insulin secretory process. Diminished insulin clearance contributes to the degree of peripheral hyperinsulinemia compensating for the insulin resistance characteristic of this form of obesity.

Human and porcine regular insulins are equally effective in subcutaneous replacement therapy. Results of a double-blind crossover study in type I diabetic patients with continuous subcutaneous insulin infusion.

Semisynthetic human Actrapid insulin (HAI, Novo, Copenhagen) was tested against porcine Actrapid insulin (PAI, Novo, Copenhagen) in 12 type I diabetic patients treated with continuous subcutaneous insulin infusion (CSII). In a double-blind crossover trial each patient received both types of insulin over a 3-wk period, respectively. No significant differences between HAI and PAI were observed in the following parameters: mean blood glucose levels (MBG) of 3-6 measurements per day (129 +/- 5 versus 125 +/- 4 mg/dl, means +/- SEM), mean maximal excursions of blood glucose during the day (107 +/- 6.6 versus 107 +/- 6.9 mg/dl), total daily insulin requirements (sum of basal and premeal insulin doses, 45.7 +/- 1.4 versus 42.7 +/- 1.4 U/day), and a mean of weekly determined hemoglobin A1c values (7.77 +/- 0.13 versus 7.83 +/- 0.14% of total hemoglobin); the frequency of mild hypoglycemic episodes was similar with the two insulins. Thus, under the controlled conditions of CSII, semisynthetic human and porcine regular insulin preparations are of identical efficacy in type I diabetic patients at near normoglycemia.

Role of glucagon in enhancing ketone body production in ketotic diabetic man.

To assess the role of endogenous glucagon in regulating hepatic ketone body production in ketotic insulin-withdrawn diabetic subjects, ketone body kinetics were determined in two groups of C-peptide-negative diabetics 6 h after interruption of a s.c. insulin infusion. In group 1 (N = 5), glucagon levels were suppressed by infusion of somatostatin (SRIF), whereas in group 2 (N = 6) glucagon was replaced during SRIF by infusing glucagon at 2 ng/kg/min. Ketone body production rates as determined by primed-continuous infusion of [3-14C]acetoacetate declined from 19.5 +/- 0.8 to 16.4 +/- 0.4 mumol/kg/min (P less than 0.01) during 105 min of SRIF-induced glucagon suppression, whereas they remained unchanged (+0.2 +/- 0.4 mumol/kg/min, P less than 0.01 compared with SRIF) during glucagon replacement. Total ketone body concentrations remained unchanged during SRIF infusion but increased from 2.2 +/- 0.3 to 2.9 +/- 0.2 mmol/L (P less than 0.01) during glucagon replacement. The metabolic clearance rate of total ketone bodies declined significantly (P less than 0.01) by 27% and 21% in the two groups. Plasma free fatty acid and glycerol concentrations remained unchanged in both groups whereas plasma glucose decreased by 3.2 +/- 0.5 mmol/L during SRIF (P less than 0.01). Thus, endogenous glucagon contributed significantly to the maintenance of ketone body production rates in ketotic insulin-deficient diabetics. Since ketogenesis was altered in the absence of changes in free fatty acid levels, the results suggested that glucagon enhanced ketogenesis by an intrahepatic effect.

Leptin: a significant indicator of total body fat but not of visceral fat and insulin insensitivity in African-American women.

The recently cloned adipose tissue hormone leptin has been proposed to be involved in the neuroendocrine regulation of adiposity and its metabolic sequelae. Visceral fat is known to predict reduced insulin sensitivity and associated adverse metabolic profiles. In this study, we report the first evaluation of the relationships between leptin levels and total body fat, visceral fat, and insulin sensitivity in a cohort of premenopausal African-American women. Thirty-four subjects were analyzed for total fat mass and visceral fat by dual-energy X-ray absorptiometry and computerized axial tomography, respectively. Insulin sensitivity (SI) was assessed using Bergman's minimal model. Results showed that fasting leptin levels strongly correlated with total body fat mass (r = 0.797, P < 0.001). Correlations of leptin with visceral fat (r = 0.54, P < 0.001) and SI (r = -0.419, P = 0.02) were dependent on total body fat. In conclusion, leptin levels reflect total body fat mass, and although visceral fat is known to predict reduced insulin sensitivity independently, leptin did not. Our data thus suggest that diverse mechanisms are responsible for the regulation of total body versus visceral fat distribution, with its metabolic and health risks.

Plasma leptin and insulin levels in weight-reduced obese women with normal body mass index: relationships with body composition and insulin.

Obesity is a complex disease with multiple features that has confounded efforts to unravel its pathophysiology. As a means of distinguishing primary from secondary characteristics, we compared levels of fasting plasma leptin and insulin in a cohort of weight-reduced obese women who have attained and maintained a normal BMI for more than 1 year with the levels in cohorts of never-obese and currently obese women. Weight-reduced obese women showed decreased plasma concentrations of leptin and insulin compared with obese women, but these levels remained significantly higher than those of never-obese women. Plasma leptin levels were highly correlated with plasma insulin levels (r = 0.60, P < 0.001). To further explore relationships with body composition, total body fat was determined by dual-energy X-ray absorptiometry and body fat distribution by computed tomography in subsets of these groups. Weight-reduced obese women had a significantly greater percent body fat and subcutaneous abdominal fat mass than did the never-obese women, and these were highly correlated with plasma leptin (r = 0.90, P < 0.001, and r = 0.52, P < 0.001, respectively). In these weight-reduced obese women, visceral fat mass was similar to that of the never-obese. The insulin sensitivity index and first-phase insulin response were also comparable. These results demonstrate that higher leptin levels in weight-reduced obese women are related to the higher total fat and particularly the subcutaneous fat masses. Normalization of visceral fat mass in the weight-reduced obese was accompanied by normalization of insulin sensitivity index and first-phase insulin response. This study suggests that increases in plasma leptin and insulin in obesity are secondary features of the obese state.

Less expensive, reliable blood glucose self-monitoring.

We examined the reliability of split test strips for blood glucose self-monitoring. One hundred visual readings were performed with each of the following test strips: original Haemoglukotest 20-800 (HGT 1/1; Boehringer-Mannheim, Mannheim, FRG) and Haemoglukotest 20-800 halved either by a splitting device (HGT 1/2 SP) or by a pair of scissors (HGT 1/2 SC). Within the plasma glucose range of 20-360 mg/dl, there was a close correlation between the results of all three test-strip readings and the values obtained by the reference method (Beckman glucose analyzer): HGT 1/1, r = .950; HGT 1/2 SP, r = .966; and HGT 1/2 SC, r = .966. Absolute deviations from the reference values were 17 +/- 2, 17 +/- 1, and 17 +/- 1 mg/dl (mean +/- SE). Analysis of variance did not reveal any significant differences between the values of each of the three procedures compared with the reference method (P = .98). These results indicate that visual reading of split test strips is as reliable as the reading of original test strips. A special splitting device is not necessary. Diabetic patients should be advised to use split test strips for blood glucose self-monitoring to reduce costs.

Absorption kinetics of semisynthetic human insulin and biosynthetic (recombinant DNA) human insulin.

Absorption kinetics of subcutaneously injected human insulin (recombinant DNA) and semisynthetic human regular insulin were investigated and compared to the respective porcine insulin preparations in normal volunteers. The absorption of all regular human insulin preparations tested was accelerated as compared to porcine insulins. The clinical relevance of these findings in regard to the treatment of diabetes mellitus appears to be doubtful. As for mixtures of porcine regular and intermediate-acting insulin preparations, the absorption of human regular insulin is not altered when mixed with intermediate-acting human insulin.

Subcutaneous use of regular human insulin (Novo): pharmacokinetics and continuous insulin infusion therapy.

The absorption kinetics of human insulin (Novo) were studied and compared with those of purified porcine insulin preparations in seven healthy men. The absorption of insulin after subcutaneous injection of human insulin (Actrapid, Novo) was significantly accelerated and its hypoglycemic effect significantly stronger when compared with porcine insulin (Actrapid). No differences in the absorption kinetics were observed using human insulin (Monotard, Novo) and porcine insulin (Monotard) preparations, respectively. A clinical trial was designed to determine whether the pharmacokinetic differences were relevant for the clinical use of regular human insulin. The efficacy of human and porcine insulin (Actrapid) was tested in a double-blind crossover protocol in 12 type I diabetic patients treated with continuous subcutaneous insulin infusion. Near-normoglycemia was achieved with both types of insulin. Diurnal blood glucose values and excursions, insulin requirements, the frequency of mild hypoglycemic episodes, and the carbohydrate content of the diet were essentially identical. Thus, the differences between the absorption of human insulin and porcine regular insulin from a subcutaneous depot as observed in the pharmacokinetic studies in normal man do not appear to be relevant in the clinical practice of the subcutaneous insulin replacement therapy in type I diabetes mellitus at near-normoglycemia.

Acute cutaneous complications and catheter needle colonization during insulin-pump treatment.

Forty unselected type I (insulin-dependent) diabetic patients with insulin pumps were examined three times for cutaneous complications and bacterial colonization of their subcutaneous catheter needles. Fifty-eight of the 120 needles were contaminated, 42 of them with Staphylococcus epidermis. Cutaneous complications, i.e, erythema of greater than or equal to 1-mm diam at the needle-insertion site, were seen with similar frequency. Significantly fewer (P less than .001) cutaneous complications and contaminated needles were found when a disinfectant was sprayed on the skin before insertion of the needle. The results indicate that infection along the indwelling subcutaneous needle contributes substantially to cutaneous complications during continuous subcutaneous insulin infusion and that these complications can successfully be prevented by appropriate antiseptic measures.

Incidence and management of severe hypoglycemia in 434 adults with insulin-dependent diabetes mellitus.

The risk of severe hypoglycemia associated with the particular therapeutic approach of two University hospitals was assessed in 96% of all patients with insulin-dependent diabetes mellitus (IDDM) who had been admitted during a period of almost 3 yr to the diabetic wards of two hospitals and who participated in a structured teaching and treatment program. During a mean follow-up period of 18 mo, 10% of the conventionally treated patients (N = 384; age 30 +/- 13 yr; duration of diabetes 12 +/- 9 yr) and 9% of the CSII-treated patients (N = 50, age 28 +/- 7 yr, duration of diabetes 13 +/- 7 yr, total follow-up period 1093 patient-mo) experienced at least one severe hypoglycemic episode per year, and a total of 123 severe hypoglycemic episodes occurred. In a subgroup of 169 conventionally treated patients, mean glycosylated hemoglobin values decreased from 10.5 +/- 1.9% before participation in the program to 9.2 +/- 2.0% (P less than 0.001) 18 +/- 4 mo thereafter. For the CSII-treated patients, glycosylated hemoglobin values were 9.7 +/- 1.9% before initiation of pump therapy and remained at the upper normal range from 3 mo thereafter throughout the study. There was no relationship between glycosylated hemoglobin levels and the occurrence of severe hypoglycemic episodes. Fifty-three severe hypoglycemic episodes were treated with glucagon injections by the patients' relatives (all but one effectively), 30 were managed by assisting physicians, and 44 led to hospitalization. Thus, successful attempts to improve glycosylated hemoglobin values in an unselected group of patients with IDDM were not associated with an unduly high risk of severe hypoglycemia when compared with the scarce data from the literature.

Diet liberalization and metabolic control in type I diabetic outpatients treated by continuous subcutaneous insulin infusion.

In 10 type I diabetic outpatients treated by continuous subcutaneous insulin infusion (CSII), dietary habits and metabolic control were investigated. Under conditions of a conventional diabetes diet (including 5-6 meals per day and a strictly planned meal intake) as well as under a "less restricted diabetes diet" (e.g., free choice of number, timing, and amount of carbohydrate intake) near normoglycemia could be achieved. Mean daily blood glucose levels did not change significantly when the patients' nutrition was alternated between both diets. During the "less restricted diabetes diet," the patients opted for a rather high fat intake (51 +/- 5% fat, 34 +/- 5% carbohydrate, and 15 +/- 2% protein). Despite this unintended dietary behavior, serum lipids and body weight remained normal after an observation period of 4-6 mo. It is concluded that during permanent near normoglycemia achieved by CSII a partial liberalization of the diabetes diet does not introduce any short-term or long-term metabolic risk factors for cardiovascular diseases.

Evidence for an augmented glucagon dependence of hepatic glucose production in cirrhosis of the liver.

The role of endogenous glucagon in maintaining hepatic glucose production after an overnight fast in patients with cirrhosis of the liver was studied with arterial-hepatic-venous catheterization and using somatostatin to suppress glucagon secretion. Arterial glucagon levels were elevated in eight cirrhotics to 290 +/- 90 pg/ml (SEM) compared to 100 +/- 10 pg/ml (P less than 0.02) in five normal controls, and they were lowered during administration of somatostatin (SRIF; 250 microgram/h) by a mean of 154 pg/ml and 39 pg/ml in cirrhotics and controls, respectively. Basal net splanchnic glucose production (NSGP) was similar in patients with and without cirrhosis (approximately 100 mg/min) but declined more markedly during 30 min of SRIF in cirrhotics to a net splanchnic uptake of glucose of 30 +/- 20 ml/min, as opposed to a fall of NSGP by 44 +/- 2 mg/min in controls (P less than 0.01). To assure that NSGP declined during SRIF infusion due to the fall of glucagon levels, SRIF was combined with a glucagon infusion at 150 ng/m2 . min in four cirrhotics and in five control subjects. Arterial glucagon levels were elevated to a mean of 650 pg/ml and 559 pg/ml in cirrhotics and controls, respectively. NSGP increased after 40 min of SRIF and glucagon replacement to 179 +/- 33 mg/min in cirrhotics and significantly more, to 412 +/- 68 mg/min, in controls (P less than 0.01). Thus, hepatic glucose production during basal and elevated glucagon levels suggested hepatic resistance to glucagon in cirrhosis. Nevertheless, endogenous glucagon played an augmented stimulatory role in maintaining glucose production in the normal range since there was an exaggerated fall of hepatic glucose output during glucagon suppression.

Plasma leptin concentrations during extended fasting and graded glucose infusions: relationships with changes in glucose, insulin, and FFA.

Despite numerous studies, the in vivo regulation of plasma leptin levels in response to nutritional factors continues to remain unclear. We investigated temporal and dose-response relationships of plasma leptin in response to physiological changes in insulin/glucose. After an overnight fast of 10 h, lean, healthy subjects were investigated for an additional 16 h of either extended fasting or one of three levels of glycemia/insulinemia induced by stepwise increasing iv glucose infusions. During extended fasting, plasma leptin values declined steadily and significantly. Plasma leptin levels remained constant at glucose concentrations between 5.8-6.5 mmol/liter, which maintained normoinsulinemia at 41.5-45.4 pmol/liter and FFA at 106-123 mg/liter, but leptin concentrations were increased at higher rates of glucose infusion (with plasma glucose rising to 8.7 mmol/liter). Concentrations of serum leptin were inversely related to FFA levels during extended fasting and at all levels of glycemia. Our data indicate that in lean healthy subjects, physiological changes in glycemia and insulinemia significantly alter plasma FFA and leptin concentrations. The increases in leptin concentrations demonstrate dose-dependent relationships that appear to relate to changes in FFA levels as well as to changes in glycemia/insulinemia.

The genetic basis of plasma variation in adiponectin, a global endophenotype for obesity and the metabolic syndrome.

Here we present the first genetic analysis of adiponectin levels, a newly identified adipocyte-derived protein. Recent work has suggested that adiponectin may play a role in mediating the effects of body weight as a risk factor for coronary artery disease. For this analysis we assayed serum levels of adiponectin in 1100 adults of predominantly northern European ancestry distributed across 170 families. Quantitative genetic analysis of adiponectin levels detected an additive genetic heritability of 46%. The maximum LOD score detected in a genome wide scan for adiponectin levels was 4.06 (P = 7.7 x 10(-6)), 35 cM from pter on chromosome 5. The second largest LOD score (LOD = 3.2; P = 6.2 x 10(-5)) was detected on chromosome 14, 29 cM from pter. The detection of a significant linkage with a quantitative trait locus on chromosome 5 provides strong evidence for a replication of a previously reported quantitative trait locus for obesity-related phenotypes. In addition, several secondary signals offer potential evidence of replications for additional previously reported obesity-related quantitative trait loci on chromosomes 2 and 10. Not only do these results identify quantitative trait loci with significant effects on a newly described, and potentially very important, adipocyte-derived protein, they also reveal the emergence of a consistent pattern of linkage results for obesity-related traits across a number of human populations.

Sampling of arterialized heated-hand venous blood as a noninvasive technique for the study of ketone body kinetics in man.

To determine if sampling of arterialized-hand venous (HV) blood is a suitable alternative for arterial (A) blood to study ketone body metabolism, concentrations of unlabeled and labeled ketone bodies were measured during continuous infusion of 3-14C-acetoacetate in simultaneously drawn samples from A and HV blood in normal subjects. The mean difference of acetoacetate between A and HV blood was in the basal state 1.5% and that of beta-hydroxybutyrate 6% (n.s.). Similarly, the 14C-content of ketone bodies and their calculated rates of production of metabolic clearance were not significantly different between A and HV blood. Following induction of ketosis by acetoacetate loading infusions, the difference of concentrations and 14C-content of total ketone bodies between HV and A blood remained insignificant (average 3%), and ketone body kinetics calculated from A and HV blood were similar. Furthermore, concentrations of glucose, lactate and pCO2 did nit differ significantly between the two sampling sites. In contrast, concentrations of ketone bodies, glucose and pO2 were significantly lower, and the metabolic clearance rate of ketone bodies and pCO2 higher in antecubital venous blood compared to heated-hand venous blood. Thus, the similarity of heated-hand venous and arterial blood suggests that the noninvasive technique is suited for kinetic analyses using tracer methods and for arteriovenous balance studies of ketone bodies.

Effects of the glycaemic index of dietary carbohydrates on prandial glycaemia and insulin therapy in type I diabetes mellitus.

Four carbohydrate diets with different glycaemic index were fed to 10 type I diabetic patients on continuous subcutaneous insulin infusion (CSII). Every diet consisted of 4 meals with identical carbohydrate content, being consumed during one day each at 8.00, 12.00, 16.00 and 18.00 h. CSII was conducted according to the patients' experiences, aiming at plasma glucose values between 70 and 160 mg/dl. From 8.00 to 20.00 h, plasma glucose was measured every 2 h. Plasma glucose profiles were near-normal with all of the diets; differences between the diets were statistically insignificant. The premeal insulin dosages, as delivered by the patients, varied significantly in relation to the time of the day, and to the premeal plasma glucose concentration. The patients varied their prandial insulin doses also in relation to the 4 diets, indicating that the glycaemic index was helpful for the prediction of their prandial insulin requirements. It is concluded that near-normoglycaemia can be achieved in type I diabetic subjects on CSII irrespective of the glycaemic index of their diet, if the prandial insulin requirements are met adequately.