[Hyperglycemia in critically ill]. / Therapie der Hyperglykämie bei erwachsenen, kritisch kranken PatientInnen (Update 2023).

In critical illness hyperglycemia is associated with increased mortality. Based on the currently available evidence, an intravenous insulin therapy should be initiated when blood glucose is above 180 mg/dl. After initiation of insulin therapy blood glucose should be maintained between 140 and 180 mg/dl.

Changes in the prognostic values of modern cardiovascular biomarkers in relation to duration of diabetes mellitus.

BACKGROUND: Based on the complex pathophysiology of type 2 diabetes and atherosclerosis we hypothesized a dynamic change in prognostic value of cardiovascular biomarkers over time. METHODS: In this prospective study 746 patients with type 2 diabetes mellitus, being followed up for 60 months were analysed. The primary endpoint was defined as unplanned hospitalization for cardiovascular disease or death. Beside others, especially the prognostic performance of the biomarkers of interest (GDF-15, NT-proBNP, hs-TnT) was evaluated in relation to quartiles of diabetes duration. RESULTS: In patients having a diabetes duration below 7 years lnGDF-15 (HR 2.84; p < 0.01) and lnhs-TnT (HR 2.96; p < 0.01) were significant predictors of the primary endpoint. LnAge (HR 40.01; p < 0.01) and lnNT-proBNP (HR 1.56; p = 0.03) were significant predictors in patients with a diabetes duration between 7 and 12 years. In the third quartile (diabetes duration 12-22 years) lnurinary albumin to creatinine ratio (HR 1.25; p = 0.005) and lnNT-proBNP (HR 2.13, p < 0.001) predicted the endpoint. In patients with a diabetes duration above 22 years, lnAge (HR 75.35; p = 0.001) and lnNT-proBNP (HR 2.0; p < 0.01) were the only significant predictors of the endpoint. CONCLUSION: Prognostic power of cardiovascular biomarkers changes dynamically in relation to duration of type 2 diabetes mellitus. In patients with shorter duration of the disease markers of subclinical cardiovascular dysfunction and inflammation perform better than markers of systemic advanced organ dysfunction and cardiovascular disease.

GDF15 reflects beta cell function in obese patients independently of the grade of impairment of glucose metabolism.

BACKGROUND AND AIMS: Growth differentiation factor 15 (GDF15) is a strong predictor of cardiovascular morbidity and mortality found to be both marker and target of impaired glucose metabolism. GDF15 increases following glucose administration and is up-regulated in obesity and diabetes. We investigate here the relationship between GDF15 and beta cell function. METHODS AND RESULTS: In this cross-sectional study we evaluated GDF15 concentrations in 160 obese subjects (BMI 35-63 kg/m2, age 39.4 ± 18.6 years, m/f 38/122) who underwent a 75 g oral glucose tolerance test (OGTT). Based on the OGTT results, the cohort was divided into two groups: 1) normal fasting glucose and normal glucose tolerance (n = 80), 2) impaired fasting glucose, impaired glucose tolerance or type 2 diabetes (n = 80). The relationship of GDF15 to fasting and OGTT-based dynamic insulin sensitivity and insulin secretion parameters was evaluated. GDF15 was higher in the prediabetes and diabetes groups and correlated with HbA1c, glucose, insulin as well as baseline and dynamic indices of insulin sensitivity and estimated beta cell function. Multiple regression analysis revealed that age, waist-to-height ratio, glomerular filtration rate and prehepatic beta cell function, but not the grade of impairment of glucose metabolism, were independent predictors of GDF15. Subgroup analysis showed that of all parameters of glucose metabolism only C-peptide, fasting prehepatic beta cell function and insulinogenic index remained significantly related to GDF15 in both groups. CONCLUSION: We conclude that in patients with severe obesity, GDF15 strongly relates to beta cell function and should be further investigated as a potential therapeutic target and biomarker guiding treatment options.

[Palliative care consultation in the ICU : Descriptive analysis of internal medicine intensive care using a mixed model over 12 months]. / Palliative Care auf der Intensivstation : Deskriptive Analyse der Ergebnisse eines Mischmodells an einer internistischen Intensivstation über einen Zeitraum von 12 Monaten.

We retrospectively analyzed the data of 56 of 669 critically ill patients admitted to an internal medicine intensive care unit (ICU) with palliative care provided by a palliative care team over the period of 12 months. For delivering palliative care, we used a mixed model-consisting of both integrative and consultative elements. SAPS III severity score in patients with palliative care was 63 ± 15 compared to 50 ± 15 in all critically ill patients. Hospital mortality was 62.5 vs. 16%. After 3 months, 19.6% of patients with palliative care provided by the palliative care team were still alive. In 15 patients curative therapies were discontinued, while there was no further escalation of the therapy in 30 patients. In 47 patients, special help to the relatives was offered. In 13 cases, there was a disagreement between relatives and the ICU team; in 5 cases a family conference was implemented. Two patients wanted extensive intensive care therapy, despite unfavorable prognosis; one patient wished to die. One patient had an advanced directive.

Targeted multiple biomarker approach in predicting cardiovascular events in patients with diabetes.

OBJECTIVE: We hypothesised that biomarkers representing different pathophysiological pathways of atherosclerosis namely growth differentiation factor 15 (GDF-15), N-terminal pro B-type natriuretic peptide (NT-proBNP) and high-sensitive troponin T (hs-TnT) could enhance cardiovascular risk prediction in patients with type 2 diabetes mellitus. METHODS: This is a prospective study in 746 patients with type 2 diabetes mellitus, who were followed up for 60 months. The primary endpoint was defined as unplanned hospitalisation for cardiovascular disease or death. The prognostic performance of the biomarkers of interest (GDF-15 in comparison with NT-proBNP and hs-TnT) was evaluated in univariate as well as in stepwise Cox regression models. HRs are presented per standard unit increase. RESULTS: The primary endpoint was registered in 171 patients (22.9%). In univariate Cox regression models, GDF-15 as well as hs-TnT provided significant prognostic information. Even after adjusting for established cardiovascular risk factors, GDF-15, hs-TnT and NT-proBNP remained strong independent predictors of the endpoint (logGDF-15: HR 1.37, p<0.01, CI 1.12 to 1.68; loghs-TnT: HR 1.43, p<0.01, CI 1.13 to 1.1.82; logNT-proBNP: HR 1.45, p<0.01, CI 1.26 to 1.66). The number of elevated markers showed a strong complementarity to predict future long-term risk. Adding hs-TnT and GDF-15 to a zero model already including NT-proBNP led to a net reclassification improvement (NRI) of 33.6% (CI 16.0% to 50.8%, NRI for patients with event: 11.1% CI -4.7% to 26.6%, for patients without event: 22.5% CI 13.6% to 30.5%). CONCLUSIONS: GDF-15 and hs-TnT are strong independent cardiovascular biomarkers augmenting the predictive value of NT-proBNP in patients with diabetes.

Effects of B-type natriuretic peptide on cardiovascular biomarkers in healthy volunteers.

Cardiovascular biomarkers provide independent prognostic information in the assessment of mortality and cardiovascular complications. However, little is known about possible interactions between these biomarkers. In the present study, we evaluated the influence of B-type natriuretic peptide (BNP) on midregional-proadrenomedullin (MR-proADM), C-terminal-proendothelin-1 (CT-proET-1), growth differentiation factor-15 (GDF-15), midregional-proatrial natriuretic peptide (MR-proANP), copeptin, and procalcitonin in healthy volunteers. Ten healthy male subjects (mean age 24 yr) participating in a randomized, placebo-controlled, single-blinded crossover study received placebo or 3.0 pmol·kg(-1)·min(-1) human BNP 32 during a continuous infusion lasting for 4 h. Effects of BNP on other cardiovascular biomarkers were assessed. BNP did not change concentrations of MR-proADM, copeptin, CT-proET1, GDF-15, or procalcitonin. In contrast, MR-proANP was significantly decreased during BNP infusion. BNP as an established cardiovascular biomarker did not affect plasma concentrations of other cardiovascular biomarkers in a model of healthy volunteers.

B-type natriuretic peptide (BNP) affects the initial response to intravenous glucose: a randomised placebo-controlled cross-over study in healthy men.

AIMS/HYPOTHESIS: B-type natriuretic peptide (BNP) is a hormone released from cardiomyocytes in response to cell stretching and elevated in heart failure. Recent observations indicate a distinct connection between chronic heart failure and diabetes mellitus. This study investigated the role of BNP on glucose metabolism. METHODS: Ten healthy volunteers (25 ± 1 years; BMI 23 ± 1 kg/m(2); fasting glucose 4.6 ± 0.1 mmol/l) were recruited to a participant-blinded investigator-open placebo-controlled cross-over study, performed at a university medical centre. They were randomly assigned (sequentially numbered opaque sealed envelopes) to receive either placebo or 3 pmol kg(-1) min(-1) BNP-32 intravenously during 4 h on study day 1 or 2. One hour after beginning the BNP/placebo infusion, a 3 h intravenous glucose tolerance test (0.33 g/kg glucose + 0.03 U/kg insulin at 20 min) was performed. Plasma glucose, insulin and C-peptide were frequently measured. RESULTS: Ten volunteers per group were analysed. BNP increased the initial glucose distribution volume (13 ± 1% body weight vs 11 ± 1%, p < 0.002), leading to an overall reduction in glucose concentration (p < 0.001), particularly during the initial 20 min of the test (p = 0.001), accompanied by a reduction in the initial C-peptide levels (1.42 ± 0.13 vs 1.62 ± 0.10 nmol/l, p = 0.015). BNP had no impact on beta cell function, insulin clearance or insulin sensitivity and induced no adverse effects. CONCLUSIONS/INTERPRETATION: Intravenous administration of BNP increases glucose initial distribution volume and lowers plasma glucose concentrations following a glucose load, without affecting beta cell function or insulin sensitivity. These data support the theory that BNP has no diabetogenic properties, but improves metabolic status in men, and suggest new questions regarding BNP-induced differences in glucose availability and signalling in various organs/tissues. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01324739 FUNDING: The study was funded by Jubilée Fonds of the Austrian National Bank (OeNB-Fonds).

Serum uric acid is related to cardiovascular events and correlates with N-terminal pro-B-type natriuretic peptide and albuminuria in patients with diabetes mellitus.

BACKGROUND: Hyperuricemia is a risk factor for cardiovascular events and renal insufficiency. It correlates to intima-media thickness and microalbuminuria. In this study we evaluated uric acid as an independent marker for cardiac events in patients with diabetes. METHODS: In a prospective observational study we recruited 494 patients with diabetes. Patients were then followed for 12.8 months (mean follow-up) and hospitalizations as a result of cardiac events (ischaemic heart disease, arrhythmias, heart failure) were recorded. RESULTS: The median duration of diabetes was 11 ± 10.35 years. Patients were in the mean 60 ± 13 years old and mean HbA(1c) was 62 ± 13 mmol/mol (7.8 ± 3.3%). At baseline, mean uric acid was 321.2 ± 101.1 µmol/l (range 101.1-743.5 µmol/l), median N-terminal pro-B-type natriuretic peptide was 92 ± 412 pg/ml and median urinary albumin to creatinine ratio was 8 ± 361 mg/g; Uric acid significantly correlated to N-terminal pro-B-type natriuretic peptide (r = 0.237, P < 0.001) and urinary albumin:creatinine ratio (r = 0.198, P < 0.001). In a Cox regression model, including age, estimated glomerular filtration rate, gender, systolic blood pressure, smoking and alcohol consumption, uric acid was the best predictor of cardiac events (hazard ratio 1.331, confidence interval 1.095-1.616, P = 0.04). However, uric acid lost its prognostic value when the natural logarithm of N-terminal pro-B-type natriuretic peptide was added to the model. CONCLUSION: Serum uric acid is a predictor of cardiac events and correlates to N-terminal pro-B-type natriuretic peptide and albuminuria, underscoring the importance of uric acid as a cardiovascular risk marker in patients with diabetes.

Interactions of glucose metabolism and chronic heart failure.

BACKGROUND: We evaluated insulin sensitivity and beta cell function in patients with chronic heart failure (CHF), and investigated a possible correlation of these metabolic parameters with specific biomarkers of heart failure. Additionally, we investigated the effects of two angiotensin receptor blockers (ARBs), namely telmisartan and candesartan, that were administered over a 5 month treatment period, as additional therapy to standard care. METHODS AND RESULTS: The study group consisted of 94 CHF patients. Insulin sensitivity (OGIS index) and insulin secretion parameters were investigated by frequently sampled oral glucose tolerance tests and consecutive mathematical modelling. In total, 94.6 % of patients had clinically overt diabetes, impaired glucose tolerance or insulin resistance at the time of enrolment HbA1c was found to correlate to NT-proBNP, MR-proADM, CT-proET-1, and MR-proANP, but not to Copeptin. NT-proBNP correlated inversely to OGIS. None of the metabolic parameters were altered significantly after candesartan or telmisartan treatment in either the patient or standard care group. CONCLUSION: Insulin sensitivity and insulin secretion are impaired in CHF and biomarkers of heart failure and atherosclerotic disease correlate to glucose metabolism.

Pituitary function in patients with newly diagnosed untreated systemic lupus erythematosus.

OBJECTIVES: To determine whether hormonal dysfunction involving the hypothalamic-pituitary-adrenal (HPA) axis, prolactin (PRL) secretion, and sex hormone status contribute to development of systemic lupus erythematosus (SLE). METHODS: 11 patients with SLE and 9 healthy controls were tested for their total anterior pituitary gland reserve by simultaneous injection of corticotropin-, growth hormone- (GH), thyrotropin-, and gonadotropin-releasing hormone (GnRH). Serum concentrations of adrenocorticotropin (ACTH), cortisol, GH, thyroid stimulating hormone (TSH), PRL, luteinising hormone (LH), and follicle stimulating hormone (FSH) were measured at baseline and after injection. Baseline values of oestradiol, testosterone, and thyroxine were determined. RESULTS: Basal and stimulated serum concentrations of ACTH, cortisol, GH, and PRL were similar in both groups. In contrast, despite similar basal thyroxine levels the TSH response to TRH was significantly higher in patients than in controls. LH and FSH levels in premenopausal female patients of both groups were identical. In contrast, two of the three male patients were hypogonadal without compensatory increases of basal LH and FSH levels, but they retained excessive stimulatory capacity in response to GnRH. CONCLUSION: No significant alteration of the HPA axis was found in patients with SLE, which is inadequate in view of the continuing inflammation. GH and PRL secretion were normal. The pituitary-thyroid and pituitary-gonadal axes were affected in patients with newly diagnosed, untreated SLE.

Inverse relation between amylin and glucagon secretion in healthy and diabetic human subjects.

BACKGROUND: The role of amylin, which is cosecreted together with insulin by the pancreatic B-cells, in the pathogenesis of type-2 diabetes is still unclear. To elucidate a possible relation between amylin and glucagon we directly evaluated the respective prehepatic secretions following administration of a 75-g oral glucose load (OGL) in humans. MATERIALS AND METHODS: We studied six healthy controls (C), six obese, insulin resistant subjects (O) and six patients with type 2 diabetes (D). Catheters were placed in the femoral artery and hepatic vein according to the hepatic vein catheterization technique. Splanchnic blood flow was assessed by infusion of indocyanine-green dye. The measured variables were analyzed by a general circulatory model for calculation of prehepatic secretion. RESULTS: The total amount of released glucagon was not different between the respective groups (20.5 +/- 2.3 in C, 27.7 +/- 5.1 in O and 27.9 +/- 5.4 micro g/4 h in D). When considered as the difference from the fasting profile, however, glucagon secretion was reduced by 3.5 +/- 14% in C, 25 +/- 12% in O and increased by 36 +/- 21% in D (P = 0.051, D vs. C). Amylin secretion was increased in O (1.10 +/- 0.15) vs. C (0.63 +/- 0.05, P < 0.05) and D (0.24 +/- 0.10 nmol, P < 0.01). Following glucose administration, glucagon secretion significantly inversely correlated with secretion of amylin (r = -0.6, P < 0.01), but not with that of insulin (r =-0.23, P = 0.36). CONCLUSIONS: The inverse correlation between amylin and glucagon secretion suggests that amylin modulates glucagon secretion following oral glucose administration. This study proves for the first time a role of endogenous amylin in the regulation of glucose homeostasis.

[Corticosteroids in septic shock]. / Kortikosteroide im septischen Schock.

Adequate adrenocortical function is essential to survive critical illness. Most critically ill patients display an elevated plasma Cortisol level, reflecting activation of the pituitary-adrenal axis, which is considered to be a homeostatic adaptation. In the setting of critical illness, the failure of an appropriate neuroendocrine response can lead to the picture of vasopressor-dependent refractory hypotension. In randomised trials with patients in septic shock, a more rapid haemodynamic recovery was obtained with physiological doses of hydrocortisone than with placebo. The observed haemodynamic response following hydrocortisone administration supports the concept of relative adrenal insufficiency. Causes of this relative adrenal insufficiency are a dysfunction of the hypothalamic-pituitary-adrenal axis and/or Cortisol resistance. There is increasing evidence that Cortisol physiology and regulation are substantially altered in the course of septic shock. Several controlled studies have shown that stress doses of hydrocortisone given in patients with septic shock reduce the time to shock reversal and decrease mortality. A multicenter large-scale trial (CORTICUS) is on the way investigating the benefit of stress doses of hydrocortisone on the mortality of septic shock. In this review glucocorticoid physiology and regulation during septic shock and the effects of hydrocortison administration in the course of septic shock are being discussed.

Apoplexy of a pituitary macroadenoma with reversible third, fourth and sixth cranial nerve palsies following administration of hypothalamic releasing hormones: MR features.

Pituitary apoplexy in patients with pituitary macroadenomas can occur either spontaneously or following various interventions. We present a case of a 71-year-old woman who developed third, fourth, and sixth cranial nerve palsies following administration of the four hypothalamic releasing hormones for routine preoperative testing of pituitary function. The MR examination showed interval tumor growth with impression of the floor of the third ventricle. There were also changes in signal intensity characteristics of the mass, suggestive of intratumoral bleeding. A transsphenoidal surgery with subtotal resection of the pituitary adenoma was performed. Microscopical examination revealed large areas of necrosis and blood surrounded by adenomatous tissue. Third, fourth, and sixth cranial nerve palsies completely resolved within 4 months. We conclude that MR imaging is useful in the demonstration of pituitary apoplexy following preoperative stimulation tests, but we suggest that these tests should be abandoned in patients with pituitary macroadenomas.

The increased insulin sensitivity in growth hormone-deficient adults is reduced by growth hormone replacement therapy.

BACKGROUND: Growth hormone deficiency is associated with increased morbidity and mortality from cardiovascular diseases, which might be related to changes in glucose and lipid metabolism. DESIGN: To assess the influence of long-term growth hormone replacement therapy (GHRT) on glucose metabolism we examined eight growth hormone-deficient (GHD) adults (seven female/one male; age, 46 +/- 3 years; body mass index, 31 +/- 2 kg m-2) over a period of 18 months in comparison to an adequate control group consisting of eight obese subjects matched for age, sex, and body mass index. We performed frequently sampled intravenous glucose tolerance tests (FSIGT) with minimal model analysis before the study, and after 12 and 18 months. RESULTS: Following GHRT, insulin-like growth factor-1 (IGF-1) increased significantly from a basal level of 75.9 +/- 18.9 to 200.8 +/- 31.0 microg L-1 after 12 months of therapy and remained stable, thereafter. GHRT did not affect fasting blood glucose, basal insulin, cholesterol, blood pressure and body weight. However, at 12 months, HbA1c (6.0 +/- 0.1 vs. 5.6 +/- 0.1% at basal, P < 0.05) and triglyceride (2.3 +/- 0.4 vs. 1.4 +/- 0.3 mmol L-1) significantly increased but returned to pretreatment values at 18 months. Insulin sensitivity was higher in GHD (8.2 +/- 3.1) compared to controls (3. 6 +/- 0.53 x 10-4 min-1/(microU mL-1), P = 0.06) and decreased significantly after 18 months of GHRT to 5.1 +/- 2.6, P < 0.05. Basal insulin secretion was similar to that in the control group and increased significantly after 12 and 18 months, total insulin secretion only after 12 months. SG (glucose effectiveness)was lower in GHD patients (0.0095 +/- 0.001 min-1) compared to controls (0.020 +/- 0.003 min-1, P < 0.05) and increased significantly after 12 and 18 months of GHRT (0.016 +/- 0.002, and 0.015 +/- 0.001 min-1, P < 0. 05), respectively. Hepatic insulin extraction rate was similar in both groups and remained unchanged following GHRT. CONCLUSION: We conclude that long-term GHRT induces a significant decrease of the increased insulin sensitivity in GHD patients to levels observed in body mass index-matched control subjects. This is accompanied by an increase in basal and total insulin secretion as well as in glucose effectiveness as a possible compensatory mechanism.

Relative hypoleptinemia in patients with type 1 and type 2 diabetes mellitus.

OBJECTIVE: To determine the relation between plasma leptin concentrations and metabolic control in human diabetes mellitus. DESIGN AND SUBJECTS: Cross sectional study consisting of 156 patients with diabetes mellitus type 1 (n=42), type 2 (n=114), and non-diabetic subjects (n=74). RESULTS: Plasma leptin concentrations were lower (P<0.05) in type 1 (8.3+/-1.7 ng/ml) and type 2 diabetic (14.9+/-1.8 ng/ml) than in non-diabetic humans (18.3+/-1.9 ng/ml). Only female type 1 and type 2 diabetic subjects also had decreased leptin/BMI ratios (P<0.05 vs non-diabetic females). The log rank test identified age-adjusted correlation of plasma leptin concentration with sex (P<0.0004) and body mass index (P<0.0218), but not with glycosylated haemoglobin A1c (P>0.5) in all groups. Plasma leptin was correlated with age (P<0.0058) and serum triglycerides (P<0.0199) in type 1 diabetic patients, and with serum cholesterol (P<0.0059) and LDL (P<0.0013) in type 2 diabetic patients. CONCLUSIONS: Defective leptin production and/or secretion might be present independently of metabolic control in female patients with type 1 or type 2 diabetes mellitus.

Urinary apo(a) excretion is not altered by changes in glomerular filtration rate and renal plasma flow in healthy males.

Lipoprotein(a) (Lp(a)) is an independent risk factor for atherosclerotic disease. However, information concerning the site of Lp(a) catabolism and breakdown is scarce. Several studies have shown that, in renal insufficiency, plasma Lp(a) levels are elevated, and that after normalisation of kidney function they return to normal. We have recently shown that fragments of apo(a) are found in the urine of healthy individuals. Despite this evidence that apo (a) is excreted into the urine, the mode of excretion of apo(a) remains unclear. Since it has been reported that intravenous infusion of somatostatin can reduce glomerular filtration rate (GFR) and renal plasma flow (RPF), we analysed urinary apo(a) excretion in ten healthy volunteers receiving somatostatin infusions. The infusion of somatostatin led to reversible changes in GFR and RPF. Apo(a) excretion was constant in all 10 individuals over the entire time course when normalised for creatinine. There was a highly significant correlation between plasma Lp(a) levels and urinary apo(a) values. Changes in renal plasma flow and glomerular filtration rate did not alter urinary apo(a) excretion. We conclude that a constant amount of apo(a) is excreted into urine, depending on plasma Lp(a) levels, and that urinary apo(a) excretion is not altered by changes in GFR and RPF in healthy males.

Growth hormone replacement therapy is not associated with retinal changes.

GH and/or growth factors are thought to play a role in the pathogenesis of diabetic retinopathy. In addition, the occurence of retinal changes mimicking diabetic retinopathy in two GH-deficient (GHD) patients receiving GH replacement therapy (GHRT) has recently been reported. The present study was performed to evaluate whether this was a coincidence or whether GHRT might regularly induce retinal changes. Sixty-one GHD patients on GHRT with a mean age of 42.5 +/-17.3 yr were examined by one ophthalmologist (AR). The mean duration of GHRT was 8.4 +/- 3.7 yr in childhood onset and 3.5 +/- 2.1yr in adult onset patients. Plasma insulin-like growth factor I concentrations were 76.4 +/- 49.6 ng/mL before GHRT and 244.3 +/- 119.2 ng/mL while receiving GHRT with a dose of 1.7 +/- 0.7 IU/day. After pupil dilatation with tropicamide, fundus examinations of both eyes were performed using a Volk 90 diopter fundus lens with a slit lamp (Haag Streit, Bern, Switzerland). In none of the patients were vascular or retinal changes like macular edema, microaneurysms, hemorrhages, hard exsudates, cotton wool spots, preproliferative signs, or proliferations found. The optic discs were also normal in all patients. We conclude, therefore, that long-term GHRT can be administered safely in GHD patients without an increased risk of retinal changes.

G alpha-q/11 protein plays a key role in insulin-induced glucose transport in 3T3-L1 adipocytes.

We evaluated the role of the G alpha-q (Galphaq) subunit of heterotrimeric G proteins in the insulin signaling pathway leading to GLUT4 translocation. We inhibited endogenous Galphaq function by single cell microinjection of anti-Galphaq/11 antibody or RGS2 protein (a GAP protein for Galphaq), followed by immunostaining to assess GLUT4 translocation in 3T3-L1 adipocytes. Galphaq/11 antibody and RGS2 inhibited insulin-induced GLUT4 translocation by 60 or 75%, respectively, indicating that activated Galphaq is important for insulin-induced glucose transport. We then assessed the effect of overexpressing wild-type Galphaq (WT-Galphaq) or a constitutively active Galphaq mutant (Q209L-Galphaq) by using an adenovirus expression vector. In the basal state, Q209L-Galphaq expression stimulated 2-deoxy-D-glucose uptake and GLUT4 translocation to 70% of the maximal insulin effect. This effect of Q209L-Galphaq was inhibited by wortmannin, suggesting that it is phosphatidylinositol 3-kinase (PI3-kinase) dependent. We further show that Q209L-Galphaq stimulates PI3-kinase activity in p110alpha and p110gamma immunoprecipitates by 3- and 8-fold, respectively, whereas insulin stimulates this activity mostly in p110alpha by 10-fold. Nevertheless, only microinjection of anti-p110alpha (and not p110gamma) antibody inhibited both insulin- and Q209L-Galphaq-induced GLUT4 translocation, suggesting that the metabolic effects induced by Q209L-Galphaq are dependent on the p110alpha subunit of PI3-kinase. In summary, (i) Galphaq appears to play a necessary role in insulin-stimulated glucose transport, (ii) Galphaq action in the insulin signaling pathway is upstream of and dependent upon PI3-kinase, and (iii) Galphaq can transmit signals from the insulin receptor to the p110alpha subunit of PI3-kinase, which leads to GLUT4 translocation.

Urinary excretion of apolipoprotein(a) fragments in type 1 diabetes mellitus patients.

High levels of plasma lipoprotein(a) [Lp(a)] represent an independent risk factor for cardiovascular morbidity; however, Lp(a) has not yet been identified as a risk factor for type 1 diabetic patients. Results from the limited number of available studies on plasma Lp(a) levels in relation to renal function in type 1 diabetes mellitus are inconclusive. We hypothesized that only type 1 diabetes mellitus patients with impaired renal function show increased plasma Lp(a) levels, due to decreased urinary apolipoprotein(a) [apo(a)] excretion. We therefore measured urinary apo(a) levels in 52 type 1 diabetes mellitus patients and 52 matched controls, and related the urinary apo(a) concentration to the plasma Lp(a) level, kidney function, and metabolic control. Our findings indicate that patients with incipient diabetic nephropathy as evidenced by microalbuminuria (20 to 200 microg/min) exhibit significantly higher plasma Lp(a) levels (median, 15.6 mg/dL) in comparison to normoalbuminuric patients (median, 10.3 mg/dL) and healthy controls (median, 12.0 mg/dL). Urinary apo(a) normalized to creatinine excretion was significantly elevated in both normoalbuminuric (median, 22.3 microg/dL) and microalbuminuric type 1 diabetic patients (median, 29.1 microg/dL) compared with healthy subjects (median, 16.0 microg/dL) and correlated significantly with Lp(a) plasma levels in both patient and control groups (P < .003). No correlation existed between the Lp(a) plasma level or urinary apo(a) concentration and metabolic control in type 1 diabetes mellitus patients. From these studies, we conclude that urinary apo(a) excretion is significantly increased in type 1 diabetic patients and correlates with plasma Lp(a) levels, and only type 1 diabetic patients with microalbuminuria have higher plasma levels of Lp(a) compared with patients with normoalbuminuria and healthy controls.

An SH2 domain-containing 5' inositolphosphatase inhibits insulin-induced GLUT4 translocation and growth factor-induced actin filament rearrangement.

Tyrosine kinase receptors lead to rapid activation of phosphatidylinositol 3-kinase (PI3 kinase) and the subsequent formation of phosphatidylinositides (PtdIns) 3,4-P2 and PtdIns 3,4, 5-P3, which are thought to be involved in signaling for glucose transporter GLUT4 translocation, cytoskeletal rearrangement, and DNA synthesis. However, the specific role of each of these PtdIns in insulin and growth factor signaling is still mainly unknown. Therefore, we assessed, in the current study, the effect of SH2-containing inositol phosphatase (SHIP) expression on these biological effects. SHIP is a 5' phosphatase that decreases the intracellular levels of PtdIns 3,4,5-P3. Expression of SHIP after nuclear microinjection in 3T3-L1 adipocytes inhibited insulin-induced GLUT4 translocation by 100 +/- 21% (mean +/- the standard error) at submaximal (3 ng/ml) and 64 +/- 5% at maximal (10 ng/ml) insulin concentrations (P < 0.05 and P < 0.001, respectively). A catalytically inactive mutant of SHIP had no effect on insulin-induced GLUT4 translocation. Furthermore, SHIP also abolished GLUT4 translocation induced by a membrane-targeted catalytic subunit of PI3 kinase. In addition, insulin-, insulin-like growth factor I (IGF-I)-, and platelet-derived growth factor-induced cytoskeletal rearrangement, i.e., membrane ruffling, was significantly inhibited (78 +/- 10, 64 +/- 3, and 62 +/- 5%, respectively; P < 0.05 for all) in 3T3-L1 adipocytes. In a rat fibroblast cell line overexpressing the human insulin receptor (HIRc-B), SHIP inhibited membrane ruffling induced by insulin and IGF-I by 76 +/- 3% (P < 0.001) and 68 +/- 5% (P < 0.005), respectively. However, growth factor-induced stress fiber breakdown was not affected by SHIP expression. Finally, SHIP decreased significantly growth factor-induced mitogen-activated protein kinase activation and DNA synthesis. Expression of the catalytically inactive mutant had no effect on these cellular responses. In summary, our results show that expression of SHIP inhibits insulin-induced GLUT4 translocation, growth factor-induced membrane ruffling, and DNA synthesis, indicating that PtdIns 3,4,5-P3 is the key phospholipid product mediating these biological actions.