Effects of saxagliptin on adipose tissue inflammation and vascular function in overweight and obese people: a placebo-controlled study.

AIMS: To test the effect of the dipeptidyl peptidase-4 inhibitor saxagliptin on adipose tissue inflammation and microvascular function, and whole-body postprandial endothelial function. METHODS: A randomized, double-blind, placebo-controlled, parallel study was conducted between June 2013 and November 2016 in 44 overweight or obese people without diabetes (saxagliptin, n=28; placebo, n=16). Subcutaneous abdominal adipose tissue biopsies, a 4-h fat-enriched meal test and peripheral arterial tonometry for measurement of endothelial function were performed at baseline and after 6 weeks of treatment with saxagliptin (5 mg/day) or matching placebo. RESULTS: Forty participants were analysed (saxagliptin, n=26; placebo, n=14). Secretion of interleukin-8 from adipose tissue explants was reduced after saxagliptin (median fold-change from baseline: 0.8 saxagliptin vs 3.3 placebo; P=0.02). Adipose tissue expression of thioredoxin-inhibitory protein (TxNIP) was lower after saxagliptin (0.75 vs 1.0; P=0.02), while there were no significant differences in adipose tissue secretion of interleukin-1b, interleukin-6 or macrophage chemoattractant protein 1 (MCP-1), adipose tissue macrophage content, adipose tissue mRNA levels of mcp1, cd36, cd68, il6, il8, txnip and adpq, and activation of adipose tissue inflammatory pathways [extracellular signal-regulated kinase, c-Jun N-terminal kinase (JNK) and nuclear factor-κB (NF- κB)] or insulin-induced vasodilation of adipose tissue arterioles. Postprandial plasma glucose was slightly lower (by an estimated 0.3 mmol/l; P=0.01), while postprandial insulin, triglyceride levels and endothelial function were unchanged after saxagliptin. CONCLUSIONS: The effect of saxagliptin on adipose tissue inflammation was relatively modest, with many inflammatory markers unchanged. We also found no evidence that saxagliptin therapy improved adipose tissue arteriole vasodilation or postprandial endothelial function.

Salsalate has no effect on insulin secretion but decreases insulin clearance: a randomized, placebo-controlled trial in subjects without diabetes.

To elucidate whether increased insulin concentration after salsalate treatment (3 g/day for 7 days) is attributable to an increased insulin secretion rate (ISR) or to reduced metabolic clearance of endogenous insulin (MCI) during stepped glucose infusion (SGI). The analysis was performed in obese subjects who participated in a randomized double-blind, parallel, placebo-controlled clinical trial. A total of 27 participants (16 on salsalate, 11 on placebo) completed baseline and follow-up SGI. During SGI in the salsalate group, C-peptide concentrations were reduced by 11%, while plasma insulin concentrations were increased by 30%, corresponding to a 30% reduction in MCI (p < 0.0001). At molar increments of glucose, insulin concentrations were increased by 27% (p = 0.02), but ISR was unchanged. Salsalate did not alter insulin secretion, but lowered MCI, indicating that a reduction in insulin clearance is the principal mechanism for increased insulin levels after salsalate administration.

A randomised trial of salsalate for insulin resistance and cardiovascular risk factors in persons with abnormal glucose tolerance.

AIMS/HYPOTHESIS: Chronic sub-acute inflammation contributes to the pathogenesis of type 2 diabetes mellitus and cardiovascular disease. High doses of salicylate reduce inflammation, glucose and triacylglycerols, and may improve insulin sensitivity, suggesting therapeutic potential in impaired fasting glucose and/or impaired glucose tolerance. This trial aimed to evaluate the effect of salsalate vs placebo on insulin resistance and glycaemia in impaired fasting glucose and/or impaired glucose tolerance. METHODS: We conducted a 12 week, two-centre, randomised, placebo-controlled study to evaluate the effect of salsalate (up to 4 g/day) vs placebo on systemic glucose disposal. Secondary objectives included treatment effects on glycaemia, inflammation and cardiovascular risk factors. Seventy-eight participants with impaired fasting glucose and/or impaired glucose tolerance from two VA healthcare systems were enrolled. Randomisation assignment was provided by the coordinating center directly to site pharmacists, and participants and research staff were blinded to treatment assignment. RESULTS: Seventy-one individuals were randomised to placebo (n = 36) or salsalate (n = 35). Glucose disposal did not change in either group (salsalate 1% [95% CI -39%, 56%]; placebo 6% [95% CI -20%, 61%], p = 0.3 for placebo vs salsalate). Fasting glucose was reduced by 6% during the study by salsalate (p = 0.006) but did not change with placebo. Declines in glucose were accompanied by declines in fasting C-peptide with salsalate. Insulin clearance was reduced with salsalate. In the salsalate group, triacylglycerol levels were lower by 25% (p = 0.01) and adiponectin increased by 53% (p = 0.02) at the end of the study. Blood pressure, endothelial function and other inflammation markers did not differ between groups. Adipose tissue nuclear factor κB (NF-κB) activity declined in the salsalate group compared with placebo (-16% vs 42%, p = 0.005), but was not correlated with metabolic improvements. The frequency of tinnitus was low but tended to be higher with salsalate therapy (n = 4 vs n = 2). CONCLUSIONS/INTERPRETATION: In summary, salsalate therapy was well tolerated, lowered fasting glucose, increased adiponectin and reduced adipose tissue NF-κB activity. These changes were not related to changes in peripheral insulin sensitivity, suggesting additional mechanisms for metabolic improvement. TRIAL REGISTRATION: ClinicalTrials.gov NCT00330733. FUNDING: Office of Research and Development, Medical Research Service, Department of Veterans Affairs and NIH K24 DK63214.

High prevalence of prediabetes and diabetes in a population exposed to high levels of an organochlorine cocktail.

AIMS/HYPOTHESIS: A heavily polluted area of Eastern Slovakia was targeted by the PCBRISK cross-sectional survey to search for possible links between environmental pollution and both prediabetes and diabetes. METHODS: Associations of serum levels of five persistent organic pollutants (POPs), namely polychlorinated biphenyls (PCBs), 2,2'-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), 2,2'-bis(4-chlorophenyl)-1,1,1-trichloro-ethane (p,p'-DDT), hexachlorobenzene (HCB) and beta-hexachlorocyclohexane (beta-HCH), with prediabetes and diabetes were investigated in 2,047 adults. Diabetes and prediabetes were diagnosed by fasting plasma glucose in all participants and by OGTT in 1,220 compliant participants. RESULTS: Our population was stratified in terms of individual POPs quintiles and associations between environmental pollution, prediabetes and diabetes were investigated. Prevalence of prediabetes and diabetes increased in a dose-dependent manner, with individuals in upper quintiles of individual POPs showing striking increases in prevalence of prediabetes as shown by OR and 95% CI for PCBs (2.74; 1.92-3.90), DDE (1.86; 1.17-2.95), DDT (2.48; 1.77-3.48), HCB (1.86; 1.7-2.95) and beta-HCH (1.97; 1.28-3.04). Interestingly, unlike PCBs, DDT and DDE, increased levels of HCB and beta-HCH seemed not to be associated with increased prevalence of diabetes. Nevertheless, individuals in the 5th quintile of the variable expressing the cumulative effect of all five POPs (sum of orders) had a more than tripled prevalence of prediabetes and more than six times higher prevalence of diabetes when compared with the 1st referent quintile. CONCLUSIONS/INTERPRETATION: Increasing serum concentrations of individual POPs considerably increased prevalence of prediabetes and diabetes in a dose-dependent manner. Interaction of industrial and agricultural pollutants in increasing prevalence of prediabetes or diabetes is likely.

The effect of salsalate on insulin action and glucose tolerance in obese non-diabetic patients: results of a randomised double-blind placebo-controlled study.

AIM/HYPOTHESIS: Low-grade inflammation may contribute to obesity-related insulin resistance and has been associated with increased risk of type 2 diabetes mellitus. The present study evaluated whether treatment with salsalate, a traditional anti-inflammatory medication, would improve insulin action in obese non-diabetic individuals. METHODS: The study was a randomised, double-blind, placebo-controlled, parallel trial conducted at the inpatient clinical research unit of the NIDKK (Phoenix, AZ, USA). Participants were 54 adults (18 to 45 years of age) with BMI >or= 30 kg/m(2). The intervention was salsalate (3 g/day, n = 28) or identical placebo (n = 26) for 7 days. The allocation was kept concealed by giving the investigator only a number corresponding to a vial of placebo or salsalate sequentially randomised in blocks by sex. Main outcomes were changes in insulin action assessed as rate of glucose disposal (R (d)) by euglycaemic-hyperinsulinaemic clamp (insulin infusion rate 40 mU m(-2) min(-1)) and glucose tolerance by 75 g OGTT. RESULTS: The study was completed by 47 participants, of which 40 were analysed (salsalate n = 22, placebo n = 18). Salsalate treatment resulted in decreased fasting plasma glucose concentration (mean [SD]; 4.83 [0.28] vs 5.11 [0.33] mmol/l, p = 0.001) and glucose AUC during the OGTT (p = 0.01), and in increased R (d) (20 [8] vs 18 [6] micromol [kg estimated metabolic body size](-1) min(-1), p = 0.002), while there was no significant change in these variables with placebo (p > 0.3 for all). The effect of salsalate on R (d) disappeared (p = 0.9) after normalising to increased insulin concentrations (701 [285] vs 535 [201] pmol/l, p < 0.0001) measured during the clamp. No side effects of salsalate were observed during the study. CONCLUSIONS/INTERPRETATION: The glucose-lowering potential of salicylates appears to be due to effects on insulin concentration rather than improved insulin action. Salicylate-based compounds may be useful for the treatment and prevention of type 2 diabetes.

mRNA concentrations of MIF in subcutaneous abdominal adipose cells are associated with adipocyte size and insulin action.

OBJECTIVE: To determine whether the mRNA concentrations of inflammation response genes in isolated adipocytes and in cultured preadipocytes are related to adipocyte size and in vivo insulin action in obese individuals. DESIGN: Cross-sectional inpatient study. SUBJECTS: Obese Pima Indians with normal glucose tolerance. MEASUREMENTS: Adipocyte diameter (by microscope technique; n=29), expression of candidate genes (by quantitative real-time PCR) in freshly isolated adipocytes (monocyte chemoattractant protein (MCP) 1 and MCP2, macrophage inflammatory protein (MIP) 1alpha, MIP1beta and MIP2, macrophage migration inhibitory factor (MIF), tumor necrosis factor alpha, interleukin (IL) 6 and IL8; n=22) and cultured preadipocytes (MCP1, MIP1alpha, MIF, IL6 and matrix metalloproteinase 2; n=33) from subcutaneous abdominal adipose tissue (by aspiration biopsy, n=34), body fat by dual-energy X-ray absorptiometry, glucose tolerance by 75 g oral glucose tolerance test and insulin action by euglycemic-hyperinsulinemic clamp (insulin infusion rate 40 mU m(-2) min(-1)) (all n=34). RESULTS: MIF was the only gene whose expression in both freshly isolated adipocytes and cultured preadipocytes was positively associated with adipocytes diameter and negatively associated with peripheral and hepatic insulin action (all P<0.05). In multivariate analysis, the association between adipocyte MIF mRNA concentrations and adipocytes diameter was independent of the percentage of body fat (P=0.03), whereas adipocyte MIF mRNA concentrations, but not adipocyte diameter, independently predicted peripheral insulin action. The mRNA expression concentrations of the MIF gene in adipocytes were not associated with plasma concentrations of MIF, but were negatively associated with plasma adiponectin concentrations (P=0.004). In multivariate analysis, adipocyte MIF RNA concentrations (P=0.03) but not plasma adiponectin concentrations (P=0.4) remained a significant predictor of insulin action. CONCLUSIONS: Increased expression of MIF gene in adipose cells may be an important link between obesity characterized by enlarged adipocytes and insulin resistance in normal glucose tolerant people.

Insertion/deletion polymorphism on ACE gene is associated with endothelial dysfunction in young patients with hypertension.

Endothelial dysfunction, insulin resistance (IR) and genetic predispositions are important risk factors of hypertension. Aim of our study was to test the hypothesis, whether insertion/deletion (I/D) polymorphism on the angiotensin converting enzyme (ACE) gene and M235T polymorphism on angiotesinogen gene (AGT) correlates with parameters of insulin sensitivity and plasminogen activator inhibitor (PAI-1) levels in newly diagnosed hypertensive patients as compared with normotensive controls. Blood pressure (BP), fasting plasma glucose, insulin, epinephrine, norepinephrine and PAI-1 concentrations were determined in 30 male patients with hypertension grade 1 (HT) and in 31 matched healthy subjects (NT). Insulin resistance was estimated using IR HOMA formula. Patients with HT had increased levels of PAI-1, norepinephrine, fasting plasma insulin levels, IR HOMA (p<0.001) compared to controls. Subjects (HT and NT) with DD and ID genotype had a significantly higher systolic BP (p<0.05) and PAI-1 compared to those with II genotype. Homozygous subjects 235T had a higher systolic BP and higher levels of epinephrine and norepinephrine than heterozygous or homozygous M235 (p<0.05). In conclusion, no association was found between M235T polymorphism and insulin resistance or PAI-1 levels, but results indicate relationship between I/D polymorphism of the ACE gene and plasma PAI-1 levels in the early stage of hypertension.

Decreased pituitary response to insulin-induced hypoglycaemia in young lean male patients with essential hypertension.

Essential hypertension is associated with changes in central catecholaminergic pathways which might also be reflected in the pituitary response to stress stimuli. The aim of this study was to determine whether the response of pituitary hormones, cortisol, plasma renin activity, aldosterone and catecholamines to insulin-induced hypoglycaemia is changed in hypertension. We studied 22 young lean male patients with newly diagnosed untreated essential hypertension and 19 healthy normotensive, age- and body mass index (BMI)-matched controls. All subjects underwent an insulin tolerance test (0.1 IU insulin/kg body weight intravenously) with blood sampling before and 15, 30, 45, 60 and 90 min after insulin administration. Increased baseline levels of norepinephrine (P<0.05), increased response of norepinephrine (P<0.001) and decreased response of growth hormone (P<0.001), prolactin (P<0.001), adrenocorticotropic hormone (P<0.05) and cortisol (P<0.001) were found in hypertensive patients when compared to normotensive controls. Increased norepinephrine levels and a decreased pituitary response to metabolic stress stimuli may represent another manifestation of chronically increased sympathetic tone in early hypertension.

Insulin sensitivity indices: a proposal of cut-off points for simple identification of insulin-resistant subjects.

Demanding measurement of insulin sensitivity using clamp methods does not simplify the identification of insulin resistant subjects in the general population. Other approaches such as fasting- or oral glucose tolerance test-derived insulin sensitivity indices were proposed and validated with the euglycemic clamp. Nevertheless, a lack of reference values for these indices prevents their wider use in epidemiological studies and clinical practice. The aim of our study was therefore to define the cut-off points of insulin resistance indices as well as the ranges of the most frequently obtained values for selected indices. A standard 75 g oral glucose tolerance test was carried out in 1156 subjects from a Caucasian rural population with no previous evidence of diabetes or other dysglycemias. Insulin resistance/sensitivity indices (HOMA-IR, HOMA-IR2, ISI Cederholm, and ISI Matsuda) were calculated. The 75th percentile value as the cut-off point to define IR corresponded with a HOMA-IR of 2.29, a HOMA-IR2 of 1.21, a 25th percentile for ISI Cederholm, and ISI Matsuda of 57 and 5.0, respectively. For the first time, the cut-off points for selected indices and their most frequently obtained values were established for groups of subjects as defined by glucose homeostasis and BMI. Thus, insulin-resistant subjects can be identified using this simple approach.

Attenuated insulin response and normal insulin sensitivity in lean patients with ankylosing spondylitis.

Chronic low-grade inflammation is associated with insulin resistance. The aim of this study was to determine insulin response to intravenous glucose load and insulin sensitivity in patients with ankylosing spondylitis (AS). Fourteen nonobese male patients with AS and 14 matched healthy controls underwent frequent-sampling intravenous glucose tolerance test (FSIVGTT). Insulin secretion and insulin sensitivity were calculated using the computer-minimal and homeostasis-model assessment 2 (HOMA2) models. Fasting glucose, insulin, cholesterol, high-density lipoprotein and low-density lipoprotein cholesterol, triglyceride levels, HOMA2, glucose effectiveness, insulin sensitivity and insulin response to FSIVGTT did not differ between patients and controls. Tumor necrosis factor-alpha and interleukin (IL)-6 concentrations tended to be higher in AS patients than in controls. Second-phase beta-cell responsiveness was 37% lower (p = 0.05) in AS patients than in controls. A negative correlation was found between the percentage of beta-cell secretion and IL-6 in all subjects (r = -0.54, p = 0.006). We found normal insulin sensitivity but attenuated glucose utilization in the second phase of FSIVGTT in AS patients. Our results indicate that elevated IL-6 levels may play a pathophysiological role in attenuating beta-cell responsiveness, which may explain the association between elevated IL-6 levels and increased risk for type 2 diabetes.

Malondialdehyde, lipofuscin and activity of antioxidant enzymes during physical exercise in patients with essential hypertension.

DESIGN: To clarify the role of oxidative damage in essential hypertension, levels of lipid peroxidation products (malondialdehyde and lipofuscin) and activity of antioxidant enzymes (superoxide dismutase and glutathione peroxidase) were examined during a short period of physical exercise. PATIENTS AND METHODS: We studied 11 male patients with mild to moderate essential hypertension in World Health Organization classes I or II and 10 healthy male controls. Physical exercise was performed on a bicycle ergometer at graded intensities of 1.0, 1.5 and 2.0 W/kg body weight Plasma concentrations of lipofuscin, malondialdehyde, epinephrine, norepinephrine, insulin, free fatty acids and glucose were determined. Superoxide dismutase activity was analysed in erythrocytes and glutathione peroxidase activity in whole blood. RESULTS: Concentrations of lipofuscin and malondialdehyde were significantly elevated in hypertensive patients. Superoxide dismutase activity was not different between groups, while glutathione peroxidase activity was significantly decreased in hypertensive subjects. During exercise, the concentration of malondialdehyde and antioxidant enzyme activities increased significantly in both groups. No differences were found in absolute increases between the normotensive and hypertensive subjects. The levels of glucose, insulin and free fatty acids were similar in both groups. Basal concentrations of catecholamines and also the exercise-induced increases were lower in hypertensive patients. CONCLUSIONS: Our results indicate increased oxidative damage in patients with essential hypertension, which might be caused by a decrease in the activity of glutathione peroxidase. The ability of superoxide dismutase and glutathione peroxidase to respond to increased production of reactive oxygen species during a short period of physical exercise was not impaired in hypertensive subjects.

Does orthostatic stress influence the neuroendocrine response to subsequent hypoglycemia in humans?

Neuroendocrine response to stress stimuli is influenced by previous stimuli of different nature. The aim of the study was to test whether antecedent orthostatic stress may affect the neuroendocrine response to subsequent hypoglycemia. A group of 12 (6 men, 6 women) nonobese, healthy volunteers aged 19 to 27 y (mean 24 +/- 0.8) participated in the study in two sessions: controlled insulin-induced hypoglycemia to 2.7 mmol/L for 15 min either with or without antecedent orthostatic stress (30 min of 60 degrees head-up tilt before insulin administration). Orthostatic stress caused a significant decrease in plasma volume (-9.6%; P < 0.001) and a significant increase in plasma renin activity, aldosterone, norepinephrine (P < 0.01), and adrenocorticotropic hormone (ACTH) concentrations (P < 0.05) in all subjects. Growth hormone response to hypoglycemia was diminished in women (P < 0.01). The epinephrine response to hypoglycemia was diminished in women in comparison to men (P < 0.001), but was unaffected by antecedent orthostatic stress. Hypoglycemia failed to induce the ACTH release after its elevation during orthostatic stress. ACTH response to moderate hypoglycemia without previous orthostatic stress was evident only in men in comparison to women (P < 0.05). We conclude that the epinephrine, growth hormone, and ACTH responses to hypoglycemia were diminished in women. Except ACTH, the neuroendocrine response to mild hypoglycemia was not affected by previous orthostatic stress in healthy subjects. In the case of ACTH, the first stress stimulus is consequential for the subsequent response of this hormone, probably due to short-loop negative feedback effects.

Correlation of M235T DNA polymorphism with cardiovascular and endocrine responses during physical exercise in healthy subjects.

In our experiments, we evaluated the possible effect of M235T molecular variant of the angiotensinogen gene on the response to a physical workload. A group of volunteers was composed of healthy male subjects, approximately of the same weight and height, same age and not actively trained. None of these subjects was under any medication. Blood sampling was carried out via an indwelling catheter. Besides blood pressure and heart rate, angiotensin I, angiotensin II, epinephrine and norepinephrine concentrations were measured in the blood. Our results suggest that only the response of diastolic blood pressure during submaximal exercise corresponded to the presence of M235T molecular variant. In all other parameters we found no significant correlation of the response with the M235T molecular variant.

Effect of head-down bed rest on the neuroendocrine response to orthostatic stress in physically fit men.

The role of neuroendocrine responsiveness in the development of orthostatic intolerance after bed rest was studied in physically fit subjects. Head-down bed-rest (HDBR, -6 degrees, 4 days) was performed in 15 men after 6 weeks of aerobic training. The standing test was performed before, after training and on day 4 of the HDBR. Orthostatic intolerance was observed in one subject before and after training. The blood pressure response after training was enhanced (mean BP increments 18+/-2 vs. 13+/- 2 mm Hg, p<0.05, means +/- S.E.M.), although noradrenaline response was diminished (1.38+/-0.18 vs. 2.76+/-0.25 mol.l(-1), p<0.01). Orthostatic intolerance after HDBR was observed in 10 subjects, the BP response was blunted, and noradrenaline as well as plasma renin activity (PRA) responses were augmented (NA 3.10+/-0.33 mol.l(-1), p<0.001; PRA 2.98+/-1.12 vs. 0.85+/-0.15 ng.ml(-1), p<0.05). Plasma noradrenaline, adrenaline and aldosterone responses in orthostatic intolerant subjects were similar to the tolerant group. We conclude that six weeks of training attenuated the sympathetic response to standing and had no effect on the orthostatic tolerance. In orthostatic intolerance the BP response induced by subsequent HDBR was absent despite an enhanced sympathetic response.

Insulin, catecholamines, glucose and antioxidant enzymes in oxidative damage during different loads in healthy humans.

Exercise, insulin-induced hypoglycemia and oral glucose loads (50 g and 100 g) were used to compare the production of malondialdehyde and the activity of antioxidant enzymes in healthy subjects. Twenty male volunteers participated in the study. Exercise consisted of three consecutive work loads on a bicycle ergometer of graded intensity (1.5, 2.0, and 2.5 W/kg, 6 min each). Hypoglycemia was induced by insulin (Actrapid MC Novo, 0.1 IU/kg, i.v.). Oral administration of 50 g and 100 g of glucose was given to elevate plasma glucose. The activity of superoxide dismutase (SOD) was determined in red blood cells, whereas glutathione peroxidase (GSH-Px) activity was measured in whole blood. The concentration of malondialdehyde (MDA) was determined by HPLC, catecholamines were assessed radioenzymatically and glucose was measured by the glucose-oxidase method. Exercise increased MDA concentrations, GSH-Px and SOD activities as well as plasma noradrenaline and adrenaline levels. Insulin hypoglycemia increased plasma adrenaline levels, but the concentrations of MDA and the activities of GSH-Px and SOD were decreased. Hyperglycemia increased plasma MDA concentrations, but the activities of GSH-Px and SOD were significantly higher after a larger dose of glucose only. Plasma catecholamines were unchanged. These results indicate that the transient increase of plasma catecholamine and insulin concentrations did not induce oxidative damage, while glucose already in the low dose was an important triggering factor for oxidative stress.

Effect of hyperthermic water bath on parameters of cellular immunity.

Effects of hyperthermic water bath on selected immune parameters (lymphocyte subpopulations, natural killer (NK) cell counts and their activity) were studied in a group of 10 volunteers. Application of hyperthermic water bath (both topical and whole-body) was followed by a significant reduction of relative B lymphocyte counts. Whole-body hyperthermic water bath reduced relative total T lymphocyte counts, increased relative CD8+ T lymphocyte and NK cell counts and increased NK activity. Whole-body hyperthermic bath increased somatotropic hormone (STH) activity in eight out of 10 volunteers; higher relative counts of CD8+ lymphocytes and NK cells were observed compared with the group of volunteers not responding to hyperthermic water bath by STH secretion. In five volunteers STH was released in response to local hyperthermic water bath and the NK activity of lymphocytes also increased but their relative counts did not. The results suggest that these increases in CD8+ lymphocyte and NK cell counts are probably dependent on increased STH production.

Body position and the neuroendocrine response to insulin-induced hypoglycemia in healthy subjects.

Changes in body fluid distribution are known to influence neuroendocrine function. The aim of the present study was to test the hypothesis that changes in plasma volume affect the counterregulatory neuroendocrine response to hypoglycemia. The tests were performed in 12 subjects in two situations: 'head-up' (+60 degrees head-up tilt standing for 30 min and hypoglycemia in sitting position afterwards) and 'leg-up' (leg-up position for 30 min and hypoglycemia in leg-up position afterwards) in a random order. Insulin-induced hypoglycemia was adjusted to 2.7 mmol/l for 15 min by glucose infusion. Plasma volume was greater by 2.2% (p < 0.001) in leg-up and lower by 9.6% (p < 0.001) in head-up position compared to the basal value in sitting position. Head-up position was associated with increases in ACTH, aldosterone, norepinephrine levels and plasma renin activity (p < 0.01). Leg-up position resulted in decreases in plasma growth hormone and epinephrine concentrations (p < 0.05). Except epinephrine, the neuroendocrine response to hypoglycemia, if any, was mild. Hypoglycemia failed to activate ACTH release after head-up position. Body fluid redistribution did not modify hormonal changes during insulin hypoglycemia. In conclusion, we suggest that body position and accompanying plasma volume changes do not appear to affect neuroendocrine and counterregulatory responses to moderate, short duration hypoglycemia in healthy subjects.

The response of endocrine system to stress loads during space flight in human subject.

The responses of endocrine system to the exposure to stress-work load and hormonal changes during oral glucose tolerance tests were studied in the Slovak astronaut before (three weeks before flight), during (on the 4th and the 6th days of space flight), and after space flight (1-3 days and 15-17 days after space flight) on board of space station MIR. Blood samples during the tests were collected via cannula inserted into cubital vein, centrifuged in the special appliance Plasma-03, frozen in Kryogem-03, and at the end of the 8-day space flight transferred to Earth in special container for hormonal analysis. Preflight workload produced an increase of plasma norepinephrine and a moderate elevation of epinephrine levels. Plasma levels of insulin, growth hormone, prolactin and cortisol were not markedly changed immediately or 10 min after the end of work load. The higher increases of plasma growth hormone, prolactin and catecholamine levels were noted after workload during space flight as compared to preflight response. The higher plasma glucose and insulin levels were noted during the oral glucose tolerance test in space flight and also in the post flight period. Plasma epinephrine levels were slightly decreasing during glucose tolerance test; however, plasma norepinephrine levels were not changed. The similar patterns of catecholamine levels during glucose tolerance test were found when compared the preflight, in-flight and post flight values. These data demonstrate the changes of the dynamic responses of endocrine system to stress-work and metabolic loads during space flight in human subject.

Plasma cytokine concentration and the cytokine producing ability of whole blood cell cultures from healthy females with pharmacologically induced hyperprolactinemia.

We investigated the in vitro effect of domperidone-induced hyperprolactinemia on plasma cytokine concentration and blood leukocyte cytokine production in healthy female volunteers. No changes were found in the plasma concentration of interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, interleukin (IL)-4, IL-10, IL-6 and IL-13 during hyperprolactinemia when compared with control values. Using unseparated blood leukocytes, we found that the spontaneous production of IL-6 (4-8 h) and transforming growth factor (TGF)-beta 1 (2-4 h) was significantly decreased and that the in vitro stimulated production of IFN-gamma (2-8 h) and TNF (4 h) was significantly increased compared with control. Our data concerning the increased IFN-gamma and TNF producing capacity of unseparated leukocytes during pharmacologically induced hyperprolactinemia strongly support the possibility that the lymphocyte production of these cytokines can be rapidly amplified by prolactin via a priming mechanism.

Hyperprolactinemia does not influence hypothalamic-pituitary-adrenocortical function during hypoglycemia in women.

Elevated plasma prolactin and mild hypocortisolemia have been observed in patients with rheumatic disorders. This study was designed to assess the potential inhibitory effect of hyperprolactinemia on hypothalamic-pituitary-adrenocortical function. Hypoglycemia was induced by intravenous insulin injection (0.1 IU/kg) in 10 female volunteers of fertile age during their follicular phase twice: 60 min after either domperidone (10 mg orally) or placebo administration. Blood samples were collected from an indwelling catheter inserted into the cubital vein at -60, 0, 30, 45, 60 and 90 min. The concentrations of prolactin, adrenocorticotropic hormone (ACTH), cortisol, epinephrine, norepinephrine and glucose were measured in plasma. Domperidone administration significantly increased plasma prolactin concentrations (71 +/- 11 ng/ml vs. 14 +/- 6 ng/ml; p <0.001), while basal plasma concentrations of ACTH, cortisol, norepinephrine and epinephrine were unaffected. Insulin-induced hypoglycemia resulted in a significant rise in the mean plasma ACTH levels from 10 +/- 1 pg/ml (domperidone) and 11 +/- 1 pg/ml (controls) to 148 +/- 19 pg/ml (domperidone) and 139 +/- 12 pg/ml (controls) at 45 min (p < 0.001), in plasma cortisol from 407 +/- 62 nmol/l (domperidone) and 391 +/- 42 nmol/l (controls) to 925 +/- 60 nmol/l (domperidone) and 810 +/- 52 nmol/l (controls) at 60 min (p < 0.001), and in plasma epinephrine from 40 +/- 26 pg/ml (domperidone) and 16 +/- 3 pg/ml (controls) to 274 +/- 55 pg/ml (domperidone) and 352 +/- 61 pg/ml (controls) at 30 min; (p < 0.001). The significant increase in ACTH, cortisol and epinephrine responses to hypoglycemia was similar in both groups. We observed mild norepinephrine response to hypoglycemia but this was irrespective of the medication. In conclusion, pharmacologically-induced hyperprolactinemia did not induce significant changes of hypothalamic-pituitary-adrenocortical function and did not influence sympathoadrenal activity in healthy young women.