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K Rett

Publications and source records attributed to K Rett.

At least 19 recordsLinked to original sources
PubMed1998

Antihypertensive therapy and insulin sensitivity: do we have to redefine the role of beta-blocking agents?

Essential hypertension is, at least in many subjects, associated with a decrease in insulin sensitivity, whereas glycemic control is (still) normal. Metaanalyses of hypertension intervention studies revealed different efficacy of treatment on cerebral (cerebrovascular accidents [CVA]) and cardiac (coronary heart disease [CHD]) morbidity and mortality. Although CVA were reduced to an extent similar to that anticipated, the decrease in CHD was less than expected. These differences are likely to be caused by the different impact of concomitant cardiovascular risk factors, such as dyslipidemia, impaired glucose tolerance, and non-insulin-dependent diabetes mellitus on CHD and CVA. Frequently these cardiovascular risk factors are ineffectively controlled in hypertensive patients, and moreover, some of the widely used antihypertensive agents have unfavorable side effects and further deteriorate these particular metabolic risk factors. Therefore, the metabolic side effects of antihypertensive treatment have received more attention. During the past few years, studies demonstrated that most antihypertensive agents modify insulin sensitivity in parallel with alterations in the atherogenic lipid profile. Alpha1-blockers and angiotensin converting enzyme inhibitors were shown to either have no impact on or even improve insulin resistance and the profile of atherogenic lipids, whereas most of the calcium channel blockers were found to be metabolically inert. The diuretics and beta-adrenoreceptor antagonists further decrease insulin sensitivity and worsen dyslipidemia. The mechanisms by which beta-adrenoreceptor antagonist treatment exert its disadvantageous effects are not fully understood, but several possibilities exist: significant body weight gain, reduction in enzyme activities (muscle lipoprotein lipase and lecithin cholesterol acyltransferase), alterations in insulin clearance and insulin secretion, and, probably most important, reduced peripheral blood flow due to increase in total peripheral vascular resistance. Recent metabolic studies found beneficial effects of the newer vasodilating beta-blockers, such as dilevalol, carvedilol and celiprolol, on insulin sensitivity and the atherogenic risk factors. In many hypertensive patients, elevated sympathetic nerve activity and insulin resistance are a deleterious combination. Although conventional beta-blocker treatment was able to take care of the former, the latter got worse; the newer vasodilating beta-blocker generation seems to be capable of successfully treating both of them.

Adrenergic beta-Antagonists↗
PubMed1997

Perfusion-independent effect of bradykinin and fosinoprilate on glucose transport in Langendorff rat hearts.

Angiotensin-converting enzyme (ACE) inhibitor-stimulated glucose metabolism and perfusion in muscle tissue seem to be, at least in part, mediated by kinins. However, the relative contribution of direct metabolic or secondary hemodynamically induced effects is unclear. It was the aim of this study to characterize the effects of ACE inhibition and bradykinin on glucose transport while changes in cardiocoronary function that might influence glucose transport were minimized. Hearts from Wistar rats were perfused by a Langendorff preparation and a set of functional parameters were simultaneously measured. Bradykinin (10[-11] M) and fosinoprilate (10[-7] M) were administered at concentrations that did not affect coronary flow. Insulin was employed as reference at half-maximal concentration. The nonmetabolizable glucose analog 3-O-[14C]methyl-D-glucose and the nontransportable tracer L-[3H]glucose were coperfused for the calculation of glucose transport. Using a 2-compartment mathematical model we found that the glucose transport rate, which was doubled with insulin, was increased almost 3-fold by either bradykinin or fosinoprilate. In the presence of the B2 bradykinin receptor antagonist HOE 140 (D-Arg[Hyp3,Thi5,D-Tic7,Oic8]-bradykinin; icatibant), the effect of both agents was completely abolished. Both agents also induced minor changes in contractility/relaxation parameters that again were completely neutralized with icatibant. A perfusion-independent but B2-kinin receptor-dependent stimulating effect on glucose transport by either bradykinin or fosinoprilate is concluded. This effect could, in analogy to insulin be due to increased glucose transporter translocation, increased endothelium-derived nitric oxide formation, or--despite constant coronary flow conditions--secondary to altered cardiac function.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

[Newly manifested type IIb diabetes presents with significant hyperinsulinemia].

BACKGROUND: Data concerning the insulin status in the early phase of NIDDM are controversial. PATIENTS AND METHOD: Since this has therapeutical implications, ten patients were identified with new-onset type 2 diabetes, defined by fasting blood glucose concentrations below 120 mg/dl, no previous history of diabetes and venous blood glucose concentrations at 120 min of an oral glucose tolerance test above 200 mg/dl (x 262 +/- 15 mg/dl) ("diabetic glucose tolerance"). Ten subjects with normal glucose tolerance and no familial history of NIDDM, who were matched for gender, age (n: 56 +/- 2 years, D: 61 +/- 5) and BMI (n: 28 +/- 1, D: 28 +/- 1), served as control group. Serum insulin was measured using a double-antibody sandwich-test (no cross-reaction with proinsulin and C-peptide) at 0, 30 and 120 min of an oGTT. RESULT: In the diabetic group, basal insulin levels were found to be elevated 1.7-fold (n: 7.9 +/- 1.4 uU/ml, D: 13.3 +/- 1.4, p = 0.03), 30 min values were the same in both groups and the 120 min value was 4.6-fold higher in the diabetic group (n: 33.9 +/- 8.7, D: 156.2 +/- 27.4, p = 0.0008). CONCLUSION: Thus, in new-onset diabetes, in the early phase of an oGTT (30 min) both insulin secretion and action are reduced, in the second phase (120 min) severe insulin resistance predominates at maximally stimulated secretion. These findings underline the therapeutical strategy in these patients, to reduce postprandial blood glucose increments and improve insulin resistance by diet and, if necessary, pharmacologically.

Blood Glucose↗
PubMed1996

Circulating TNF-alpha and leptin levels in offspring of NIDDM patients do not correlate to individual insulin sensitivity.

Obesity plays a central role in the development of skeletal muscle insulin resistance. The molecular mechanism causing skeletal muscle insulin resistance in obese people is still poorly understood. It has been speculated that circulating factors derived from adipose tissue impair insulin signalling in the skeletal muscle cell. TNF-alpha and leptin, which are overproduced in fat tissue of obese insulin resistant animal models and in obese humans, might mediate such an inhibitory effect on insulin signalling in skeletal muscle. The aim of the present study was to evaluate whether circulating TNF-alpha and leptin correlates to the individual skeletal muscle insulin sensitivity in individuals with different degrees of obesity and insulin resistance. We measured circulating TNF-alpha and leptin values in non diabetic offsprings of NIDDM patients. 36 German and 47 Finnish subjects participated in the study. The GDR of each participant was determined by the euglycemic hyperinsulinemic clamp technique, a range between 1.37 to 14.01 mg/kg LBM x min was observed. Percent of desirable body weight (PDW) covered also a wide range (87.58% to 197.06%). Although linear regression analysis suggested a dependence between TNF-alpha and GDR (Germany group: r = -0.37, p < 0.05, Finnish group: r = -0.32, p < 0.05) and a dependence between TNF and PDW (German group: r = 0.46, p < 0.05, Finnish group: r = 0.38, p < 0.05), in multiple linear regression analysis only the correlation with PDW was significant. Leptin levels were measured from 29 German and 36 Finnish subjects and a strong association was found between leptin and PDW (German group: r = 0.55, p < 0.05, Finnish group: r = 0.73, p < 0.05). In contrast, leptin levels did not correlate with GDR and TNF-alpha. In summary, even though, in a few insulin resistant subjects, higher circulating TNF-alpha or leptin levels with the individual insulin sensitivity can be demonstrated, the data suggest that the circulating pool of TNF-alpha and leptin in blood is unlikely to be a major contributing factor for obesity induced insulin resistance in the vast majority of individuals at high risk to develop NIDDM.

Adult↗
PubMed1996

Potential role of bradykinin in forearm muscle metabolism in humans.

Using the euglycemic-hyperinsulinemic glucose clamp and the human forearm technique, we have demonstrated that the improved glucose disposal rate observed after the administration of an angiotensin-converting enzyme (ACE) inhibitor such as captopril may be primarily due to increased muscle glucose uptake (MGU). These results are not surprising because ACE, which is identical to the bradykinin (BK)-degrading kininase II, is abundantly present in muscle tissue, and its inhibition has been observed to elicit the observed metabolic actions via elevated tissue concentrations of BK and through a BK B2 receptor site in muscle and/or endothelial tissue. These findings are supported by several previous studies. Exogenous BK applied into the brachial artery of the human forearm not only augmented muscle blood flow (MBF) but also enhanced the rate of MGU. In another investigation, during rhythmic voluntary contraction, both MBF and MGU increased in response to the higher energy expenditure, and the release of BK rose in the blood vessel, draining the working muscle tissue. Inhibition of the activity of the BK-generating protease in muscle tissue (kallikrein) with aprotinin significantly diminished these functional responses during contraction. Applying the same kallikrein inhibitor during the infusion of insulin into the brachial artery significantly reduced the effect of insulin on glucose uptake into forearm muscle. This is of interest, because in recent studies insulin has been suggested to elicit its actions on MBF and MGU via the accelerated release of endothelium-derived nitric oxide, the generation of which is also stimulated by BK in a concentration-dependent manner. This new evidence obtained from in vitro and in vivo studies sheds new light on the discussion of whether BK may play a role in energy metabolism of skeletal muscle tissue.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

Insulin-induced glucose transporter (GLUT1 and GLUT4) translocation in cardiac muscle tissue is mimicked by bradykinin.

The effect of bradykinin on glucose transporter translocation in isolated rat heart was compared with the effect of insulin. Hearts from male obese (fa/fa) Zucker rats were perfused under normoxic conditions and constant pressure in a classic Langendorff preparation with 12 mmol/l glucose as substrate, and a set of functional parameters was measured simultaneously. Bradykinin was administered at a concentration (10(-11) mmol/l) that did not increase coronary flow. Insulin was used at a concentration (8 x 10(-8) mmol/l) known to maximally stimulate glucose transport in this model. After 15 min of perfusion with insulin or bradykinin, subcellular membrane fractions of the heart were prepared, and distribution of glucose transporter protein (GLUT1 and GLUT4) in fractions enriched with surface membranes (transverse tubules [TTs] and sarcolemmal membranes [PMs]) and with low-density microsomal membranes (LDMs) were determined by immunoblotting with the respective antibodies. Both glucose transporter isoforms were translocated after stimulation with insulin (increased transporter protein content in the PM+TT-enriched fraction with a concomitant decrease in the LDM-enriched fraction) and, to a smaller extent, also with bradykinin. These data suggest that in hearts of insulin-resistant obese (fa/fa) Zucker rats, bradykinin interacts with or facilitates the translocation process of both GLUT1 and GLUT4.

Animals↗
PubMed1996

Differential effect of chronic treatment with two beta-blocking agents on insulin sensitivity: the carvedilol-metoprolol study.

BACKGROUND: Hypertensive patients frequently show resistance to insulin-stimulated glucose uptake and hyperinsulinemia. Diuretics and beta-adrenoceptor blocking agents have been found to decrease insulin sensitivity, whereas alpha 1-blockers and angiotensin converting enzyme inhibitors seem to improve it. OBJECTIVE: To compare the effects of a 3 months' antihypertensive treatment with carvedilol, a non-selective beta-adrenoceptor blocker with alpha 1-blocking properties, with the beta 1-selective receptor blocker metoprolol on insulin sensitivity in non-diabetic hypertensive patients. DESIGN: A multicenter double-blind randomized study. SUBJECTS AND METHODS: Seventy-two non-diabetic hypertensive patients were randomly assigned to treatment with either carvedilol or metoprolol. An isoglycemic, hyperinsulinemic glucose clamp was conducted before and after 12 weeks of treatment; the metabolic clearance rate for glucose was taken as an indicator of insulin sensitivity. RESULTS: The two groups did not differ in age, sex, body mass index, blood pressure or lipids, and treatment effectively lowered blood pressure. In both groups, insulin sensitivity was impaired at baseline. After metoprolol treatment, insulin sensitivity further decreased significantly by about 14%, whereas it increased after carvedilol. There was also a decrease in high-density lipoprotein and an increase in triglycerides levels in patients in the metoprolol-treated group, whereas these parameters remained unchanged in patients in the carvedilol-treated group. CONCLUSION: This study confirms previous findings of a reduction in insulin sensitivity after chronic metoprolol treatment. Carvedilol treatment, however, resulted in a small amelioration of insulin resistance and a better lipid profile [corrected]. We thus demonstrate that a beta-blocker with alpha 1-blocking properties has favorable effects on glucose metabolism, suggesting a potentially important role of peripheral blood flow in regulating glucose uptake. These findings imply that beta-blocker treatment, when combined with alpha 1-blocking activity has advantageous effects on insulin sensitivity and lipids and could therefore be suitable for patients with the metabolic syndrome.

Adrenergic beta-Antagonists↗
PubMed1995

Hypertension in the non-insulin-dependent diabetes mellitus syndrome: a critical review of therapeutic intervention.

BACKGROUND: Since it is not yet clear whether and to what degree treatment of mild hypertension will decrease cardiovascular morbidity and mortality in non-insulin-dependent diabetes (NIDDM), decisions concerning the treatment of hypertension diabetics are at present based on data from the non-diabetic population. RECENT RESEARCH ON CAUSES OF DIABETES: A large body of recent work on the sequence of events leading from the prediabetic to the hyperglycemic stages of the NIDDM syndrome has suggested that elevated blood pressure and other cardiovascular risk factors may precede NIDDM by many years and that after the onset of NIDDM intervention might be too late to be beneficial. PROSPECTIVE INTERVENTION STUDY IN PROGRESS: It is not possible to draw firm conclusions that can be applied to the treatment of hypertensive diabetics before the results of the United Kingdom Prospective Diabetes Study/Hypertension in Diabetes Study are published later this decade. Unfortunately, this study does not consider different stages within the NIDDM syndrome. Moreover, World Health Organization criteria are not used for the diagnosis of either NIDDM or hypertension, so that the study subjects are insufficiently characterized. Finally, confounding variables such as racial, ethnic and sex differences and the individual stage of the NIDDM syndrome (and consequent variation in antidiabetic treatment) have been either not considered or not completely ruled out. These shortcomings seriously threaten the significance of this otherwise important study. CONCLUSIONS: As long as there are no diabetes-specific data from adequately sized intervention studies, recommendations for antihypertensive treatment in NIDDM will be based on strategies accepted for the non-diabetic population. These recommendations involve symptom-based diagnostic and therapeutic concepts of both NIDDM and hypertension and ignore recent pathogenetic concepts which could lead to an interdisciplinary and integrated approach to cardiovascular risk management, and possibly to the prevention of end-stage NIDDM syndrome with its advanced macrovascular complications.

Antihypertensive Agents↗
PubMed1995

Influence of ACE inhibition on glucose tolerance in patients with stable chronic renal failure.

ACE inhibitors improve glucose tolerance and insulin sensitivity in hypertensive patients with normal renal function. Hypertensive patients with renal failure are a high-risk group who are particularly glucose intolerant and insulin resistant. We have therefore studied whether ACE inhibition improve glucose tolerance in this group as well. In a double-blind placebo-controlled crossover study 10 patients with stable moderate chronic renal failure (mean endogenous creatinine clearance 40 +/- 16 ml/min/1.73 m2) were examined. Patients were randomly allocated to receive either placebo or the ACE inhibitor perindopril (2 mg/day per os) for 14 days. After 7 days of wash-out they received the alternative medications in random order for another 14 days. Before and after each of the two treatment periods (day 1 and day 15) an intravenous glucose tolerance test (i.v. GTT) with concomitant determination of insulin levels was performed. The glucose disappearance rate (K value) was calculated to express changes in glucose tolerance. An i.v. GTT was also performed in a group of healthy volunteers. The mean K value was significantly (P < 0.05) lower, i.e. glucose tolerance was impaired, in patients compared with healthy controls. In addition, baseline and peak insulin levels after the i.v. GTT were significantly higher (P < 0.05) in patients than in healthy subjects. The K values in patients before and after placebo treatment (1.33 +/- 0.31 and 1.41 +/- 0.45 respectively) were not significantly different from the values with perindopril treatment (1.35 +/- 0.37 and 1.41 +/- 0.48 respectively). Furthermore, no significant differences between placebo and perindopril treatment were found with respect to the insulin response to the glucose load. The peak (5 min) insulin concentrations after the i.v. glucose load were 49.0 +/- 19.2 microU/ml (day 1) and 50.0 +/- 24.9 (day 15) with placebo and 49.2 +/- 19.3 (day 1) and 46.8 +/- 17.9 (day 15) with perindopril.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[How can primary prevention of coronary heart disease be improved in general practice?].

BACKGROUND: The basic issue of primary prevention strategies of coronary heart disease is an individually adapted cardiovascular risk factor management. However, transformation of these strategies by health care professionals is still insufficient, as was demonstrated by three studies performed in private practice. METHODS AND RESULTS: In oral glucose tolerance tests performed in 234 patients with essential hypertension who were under regular medical control, 25.6% turned out to have previously unknown diabetes and 41.4% had impaired glucose tolerance. In the remaining 33.3% with normal glucose tolerance, mean total serum cholesterol was 260 mg/dl. 82 patients with essential hypertension and known diabetes had a mean total serum cholesterol of 276 mg/dl. Neither cohort was under lipid lowering drugs. Out of 290 unselected patients treated for type II-diabetes in private practice, 62% were hypertensive. Of those, hypertension was not known untreated or not sufficiently treated in 78.2%. CONCLUSION: As a consequence, in patients at high cardiovascular risk, not only the "leading" disease (i.e. diabetes, hypertension, hyperlipidaemia), but also the concomitant constellation deserves attention and early intervention.

Adult↗
PubMed1994

Insulin-induced translocation of GLUT 4 in skeletal muscle of insulin-resistant Zucker rats.

The genetically obese Zucker rat (fa/fa) is an animal model with severe insulin resistance of the skeletal muscle. We investigated whether a defect of insulin-dependent glucose transporter (GLUT 4) translocation might contribute to the pathogenesis of the insulin-resistant state. fa/fa rats, lean controls (Fa/Fa) as well as normal Wistar rats were injected intraperitoneally with insulin and were killed after 2 or 20 min, respectively. Subcellular fractions were prepared from hind-limb skeletal muscle and were characterized by determination of marker-enzyme activities and immunoblotting applying antibodies against alpha 1 Na+/K+ ATPase. The relative amounts of GLUT 1 and GLUT 4 were determined in the fractions by immunoblotting with the respective antibodies. Insulin induced an approximately two-fold increase of GLUT 4 in a plasma membrane and transverse tubule enriched fraction and a decrease in the low density enriched membrane fraction in all three groups of rats. There was a high individual variation in GLUT 4 translocation efficiency within the groups. However, no statistically significant difference was noted between the groups. No effect of insulin was detectable on the distribution of GLUT 1 or alpha 1 Na+K+ ATPase. The data suggest that skeletal muscle insulin resistance of obese Zucker rats is not associated with a lack of GLUT 4 translocation.

Animals↗
PubMed1994

New aspects of insulin resistance in hypertension.

Primary hypertension is a frequent polygenic disease with strong genetic and environmental components. During the last decade, evidence has been increasing that insulin resistance as a marker of increased risk for Type 2 diabetes and cardiovascular atherosclerotic disease is present not only in individuals with obesity, Type 2 diabetes and impaired glucose tolerance, but also in the majority of the hypertensive population. Insulin resistance describes a tissue- and pathway-specific defect of glucose metabolism present in the so called 'metabolic syndrome'. Hyperinsulinaemia compensates for insulin resistance, leading to a cluster of undesirable processes predisposing to diabetes, atheroma and, directly or indirectly, hypertension. Candidate mechanisms whereby this metabolic syndrome might lead to hypertension include renal sodium retention, vascular hyperresponsiveness, arteriolar smooth muscle cell proliferation, altered cellular electrolyte transport and composition, stimulation of sympatho-adrenergic activity and growth promoting effects. Insulin per se does not appear to be the cause of elevated blood pressure as frequently seen in insulin-resistant states, but it may act with other factors to promote hypertension and atherosclerotic cardiovascular disease.

Animals↗
PubMed1994

Possible synergistic effect of ACE inhibition and calcium-channel blockade on insulin sensitivity in insulin-resistant type II diabetic hypertensive patients.

So-called insulin resistance is a frequent phenomenon and a marker of increased risk for both type II diabetes mellitus and atherosclerosis. Today, insulin resistance is widely understood as a tissue- and pathway-specific defect of insulin-stimulated glucose uptake into skeletal muscle that is compensated for by hyperinsulinemia, leading to a cluster of undesirable hypertensiogenic, diabetogenic, and atherogenic processes. Additional defects of insulin-stimulated muscle blood flow and cellular kation balance are presently attracting increasing awareness. Clinical and experimental evidence suggests that angiotensin-converting enzyme (ACE) inhibition ameliorates both insulin-stimulated skeletal-muscle glucose uptake and blood flow in insulin-resistant states by a direct stimulation of cellular glucose uptake, which appears to be kinin-mediated. This improvement of insulin sensitivity could mean not only improvement of glucose metabolism, but also reduction of chronically elevated serum insulin and the ensuing atherogenic consequences (hyper- and dyslipidemia, sympathetic overactivity, growth of vascular smooth-muscle cells, hypertension, etc.). Ca(2+)-channel blockers that do not increase heart rate appear to exert direct antiatherogenic effects while being metabolically neutral. Thus, the combination of Ca(2+)-channel blockade by sustained release verapamil and ACE inhibition by trandolapril in insulin-resistant type II diabetic patients with essential hypertension appears to be promising in terms of possible synergistic effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1994

[The metabolic syndrome. Pathophysiologic causes, diagnosis, therapy].

The individual components of the metabolic syndrome such as central obesity, dyslipidemia with increased triglycerides and decreased HDL-cholesterol, hyperuricemia, hypertension and progressive glucose intolerance are markers for an increased risk of atheroma and type 2 (non-insulin-dependent) diabetes. All components, with the exception of hyperuricemia, are associated with skeletal muscle insulin resistance, leading to compensatory chronic hyperinsulinemia. Insulin resistance/hyperinsulinemia, in turn, is associated with a series of hypertensiogenic and atherogenic side effects, aggravating the individual components of the metabolic syndrome. From a more pathophysiologically orientated point of view, early identification of individuals obviously at risk for atheroma and type 2 diabetes, as well as early intervention aimed at the improvement of reduced insulin action may play a central role in an integrated life-style approach of primary prevention of atherosclerosis and type 2 diabetes.

Arteriosclerosis↗
PubMed1992

[Hypertension in metabolic syndrome. Etiology and consequences].

Essential hypertension in patients with the metabolic syndrome is regularly associated with other metabolic disorders. Thus, most hypertensives are overweight and have a glucose intolerance, while many have concomitant hyperproteinemia and dyslipoproteinemia. Up until fairly recently, it was not known that so-called insulin resistance is a common denominator both of metabolic risk factors and hypertension. In recent years, our knowledge about insulin resistance has spawned an equally convincing and fascinating multidimensional concept which reveals and plausibly explains complex relationships between metabolism, hypertension and the coronary risk.

Blood Glucose↗