Greater Increase In Plasma Levels Research Articles

Evolocumab on top of empagliflozin improves endothelial function of individuals with diabetes: randomized active-controlled trial

BackgroundSodium-glucose cotransporter 2 inhibitors (SGLT2i) improve endothelial dysfunction and reduce cardiovascular events in individuals with type 2 diabetes (T2D). Proprotein convertase subtilisin/kexin 9 (PCSK9i) inhibitors reduce cardiovascular events in high-risk patients. Whether the addition of PCSK9i to SGLT2i treatment adds benefits is not known.ObjectivesTo assess the PCSK9-i effect on the endothelial function of T2D individuals under treatment with SGLT2-i.MethodsIndividuals with T2D were randomized in a 1:1 ratio to a 16-week treatment with either empagliflozin (E) or empagliflozin plus evolocumab (EE). The primary endpoint was post-treatment change from baseline in flow-mediated dilation (FMD) at 1-min. Secondary outcomes included changes in plasma levels of nitric oxide metabolites and isoprostane.ResultsA total of 110 patients were enrolled, the mean age was 58 years, and 71% were men. The median post-treatment change in FMD at 1-min was 2.7% (interquartile range [IQR]: 0.9%) and 0.4% (IQR: 0.9%) in the EE and E groups, respectively (p < 0.001). There was a greater increase in plasma levels of nitrate [5.9 (16.5) vs. 2.6 (11.8); p = 0.001] and nitrite [0.14 (0.72) vs. 0.02 (0.74); p = 0.025] in the EE group than in the E group, respectively. Isoprostane reduction was more pronounced in the EE group when compared to the E group [−1.7 (5.9) vs. −1.1 (5.3); p < 0.001).ConclusionsIn individuals with T2D, the addition of evolocumab on top of empagliflozin improves endothelial function.

Receptor-Mediated Bioassay Reflects Dynamic Change of Glucose-Dependent Insulinotropic Polypeptide by Dipeptidyl Peptidase 4 Inhibitor Treatment in Subjects With Type 2 Diabetes.

Objective: We recently observed a greater increase in plasma levels of bioactive glucose-dependent insulinotropic polypeptide (GIP) than glucagon-like peptide 1 (GLP-1) using the receptor-mediated bioassays in the subjects with normal glycemic tolerance (NGT) treated with dipeptidyl peptidase 4 (DPP-4) inhibitors, which may be unappreciated using conventional enzyme-linked immunosorbent assays (ELISAs) during oral glucose tolerance test. Thus, we determined incretin levels in addition to glucagon level using the bioassays in type 2 diabetes mellitus (T2DM) subjects with or without treatment of DPP-4 inhibitor, to evaluate whether these assays can accurately measure bioactivity of these peptides.Methods: We performed single meal tolerance test (MTT) by using a cookie meal (carbohydrate 75.0 g, protein 8.0 g, fat 28.5 g) in the subjects with NGT (n = 9), the subjects with T2DM treated without DPP-4 inhibitor (n = 7) and the subjects with T2DM treated with DPP-4 inhibitor (n = 10). All subjects fasted for 10–12 h before the MTT, and blood samples were collected at 0, 30, 60, and 120 min. We used the cell lines stably cotransfected with human-form GIP, GLP-1 or glucagon receptor, and a cyclic adenosine monophosphate–inducible luciferase expression construct for the bioassays. We measured active GIP, active GLP-1, and glucagon by the bioassays. To evaluate the efficacy of bioassay, we measured identical samples via ELISA kits.Results: During the single MTT study, postprandial active GIP bioassay levels of T2DM with DPP-4 inhibitor treatment were drastically higher than those of NGT and T2DM without DPP-4 inhibitor, although the DPP-4 inhibitor-treated group showed moderate increase of active GIPELISA and active GLP-1bioassay, while active GLP-1bioassay levels of T2DM subjects without DPP-4 inhibitor were comparable to those of NGT subjects. During the serial MTT, administration of DPP-4 inhibitor significantly increased active GIPbioassay levels, but not active GLP-1bioassay.Conclusions: In comparison to conventional ELISA, receptor-mediated bioassay reflects dynamic change of GIP polypeptide by DPP-4 inhibitor treatment in subjects with type 2 diabetes.

Dipeptidyl peptidase-4 inhibitor treatment induces a greater increase in plasma levels of bioactive GIP than GLP-1 in non-diabetic subjects

ObjectiveGlucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) possess multiple bioactive isoforms that are rendered non-insulinotropic by the enzyme dipeptidyl peptidase-4 (DPP-4). Recently, some ELISA kits have been developed to specifically measure “active” GIP and GLP-1, but it is unclear if these kits can accurately quantify all bioactive forms. Therefore, it remains uncertain to what extent treatment with a DPP-4 inhibitor boosts levels of biologically active GIP and GLP-1. Thus, we evaluated our novel receptor-mediated incretin bioassays in comparison to commercially available ELISA kits using plasma samples from healthy subjects before and after DPP-4 inhibitor administration. MethodsWe utilized cell lines stably co-transfected with human GIP or GLP-1 receptors and a cAMP-inducible luciferase expression construct for the bioassays and commercially available ELISA kits. Assays were tested with synthetic GIP and GLP-1 receptor agonists and plasma samples collected from subjects during a 75 g oral glucose tolerance test (OGTT) performed before or following 3-day administration of a DPP-4 inhibitor. ResultsA GIP isoform GIP(1–30)NH2 increased luciferase activity similarly to GIP(1–42) in the GIP bioassay but was not detectable by either a total or active GIP ELISA kit. During an OGTT, total GIP levels measured by ELISA rapidly increased from 0 min to 15 min, subsequently reaching a peak of 59.2 ± 8.3 pmol/l at 120 min. In contrast, active GIP levels measured by the bioassay peaked at 15 min (43.4 ± 6.4 pmol/l) and then progressively diminished at all subsequent time points. Strikingly, at 15 min, active GIP levels as determined by the bioassay reached levels approximately 20-fold higher after the DPP-4 inhibitor treatment, while total and active GIP levels determined by ELISA were increased just 1.5 and 2.1-fold, respectively. In the absence of DPP-4 inhibition, total GLP-1 levels measured by ELISA gradually increased up to 90 min, reaching 23.5 ± 2.4 pmol/l, and active GLP-1 levels determined by the bioassay did not show any apparent peak. Following administration of a DPP-4 inhibitor there was an observable peak of active GLP-1 levels as determined by the bioassay at 15 min after oral glucose load, reaching 11.0 ± 0.62 pmol/l, 1.4-fold greater than levels obtained without DPP-4 inhibitor treatment. In contrast, total GLP-1 levels determined by ELISA were decreased after DPP-4 inhibitor treatment. ConclusionOur results using bioassays indicate that there is a greater increase in plasma levels of bioactive GIP than GLP-1 in subjects treated with DPP-4 inhibitors, which may be unappreciated using conventional ELISAs.

Cognitive correlates of white matter growth and stress hormones in female squirrel monkey adults.

Neurobiological studies of stress and cognitive aging seldom consider white matter despite indications that complex brain processes depend on networks and white matter interconnections. Frontal and temporal lobe white matter volumes increase throughout midlife adulthood in humans, and this aspect of aging is thought to enhance distributed brain functions. Here, we examine spatial learning and memory, neuroendocrine responses to psychological stress, and regional volumes of gray and white matter determined by magnetic resonance imaging in 31 female squirrel monkeys between the ages of 5 and 17 years. This period of lifespan development corresponds to the years 18-60 in humans. Older adults responded to stress with greater increases in plasma levels of adrenocorticotropic hormone and modest reductions in glucocorticoid feedback sensitivity relative to young adults. Learning and memory did not differ with age during the initial cognitive test sessions, but older adults more often failed to inhibit the initial learned response after subsequent spatial reversals. Impaired cognitive response inhibition correlated with the expansion of white matter volume statistically controlling for age, stress hormones, gray matter, and CSF volumes. These results indicate that instead of enhancing cognitive control during midlife adulthood, white matter volume expansion contributes to aspects of cognitive decline. Cellular and molecular research combined with brain imaging is needed to determine the basis of white matter growth in adults, elucidate its functions during lifespan development, and provide potential new targets for therapies aimed at maintaining in humans cognitive vitality with aging.

Genetic variation at the adipsin locus and response to long-term overfeeding.

The role of adipsin and adipsin Hinc II polymorphisms on the metabolic and body composition changes in response to overfeeding was studied. A total of 12 pairs of male monozygotic twins ate a 4.2 MJ/day energy surplus, 6 days a week, during a period of 100 days. The preoverfeeding plasma adipsin concentration correlated positively with the change in CT-measured abdominal total and subcutaneous (P<0.05) fat. The changes in abdominal total fat and abdominal subcutaneous fat correlated negatively with changes in plasma adipsin concentrations (P<0.005). Overfeeding induced greater increases in body weight, fat mass, abdominal total and subcutaneous fat (P<0.05) in 6.1 kb noncarriers (n=10) than in 6.1 kb carriers (n=14) of the adipsin Hinc II polymorphism. The 6.1 kb noncarriers had a greater increase in plasma leptin levels (P<0.01). Also the total (P<0.01) and very-low-density lipoprotein (VLDL)-triglycerides (P<0.05), apolipoprotein B (P<0.05) and VLDL-cholesterol (P<0.05) levels increased more in the 6.1 kb noncarriers than in the 6.1 kb carriers. Adipsin plasma level could be a predictor of the changes in abdominal subcutaneous fat during times of increased energy intake. However, a greater increase in the abdominal subcutaneous fat was related to a lower increase in the plasma adipsin level. The adipsin Hinc II 6.1 kb allele noncarriers gained more abdominal subcutaneous fat and had a greater increase in plasma levels of leptin- and triglyceride-rich lipoproteins when exposed to a long-term positive energy balance. These findings provide new information on the role of adipsin on individual differences in response to chronically elevated food intake.

Effect of short-term hormone therapy on oxidative stress and endothelial function in African American and Caucasian postmenopausal women

Objective In postmenopausal women (PMW), the effect of a short-term course of estrogen/progestin HT on free radical oxidative stress was evaluated. In addition, HT’s effect on plasma nitric oxide (NO) activity was determined as a measure of vascular endothelial function. We investigated the relationship of these markers and HT across race and the cardiovascular risk factors of smoking, diabetes and hypertension. Design A prospective, observational study comparing preintervention and postintervention. Setting Academic research center. Patient(s) Twenty-seven (14 African American and 13 Caucasian) PMW volunteers. Intervention(s) Six weeks of continuous, combined estrogen/progestin HT. Main outcome measure(s) Plasma concentrations of free 8-epi-prostaglandin F 2α (8-isoprostane) before and after HT were compared as a measure of oxidative stress. Nitrite, the stable oxidation metabolite of NO, was measured by the Greiss reaction after nitrate reduction to nitrite with cadmium. Results Plasma levels of free 8-isoprostane decreased significantly after 6 weeks of HT. Although almost all subjects benefited from the reduction in free 8-isoprostane, PMW with at least one cardiovascular risk factor (n = 19) demonstrated higher free 8-isoprostane than did subjects with no risk factors. Plasma levels of nitrite increased after 6 weeks of HT, but the difference was not statistically significant. Caucasian PMW demonstrated a greater increase in plasma levels of nitrite after 6 weeks of HT as compared with African American subjects, who exhibited almost no change. Conclusion(s) Short-term administration of HT significantly reduces oxidative stress in PMW and is consistent across race. However, there was an observed racial difference in endothelial NO response to HT between African American and Caucasian PMW.

Treatment of cycling female rats with fluoxetine induces desensitization of hypothalamic 5-HT 1A receptors with no change in 5-HT 2A receptors

Although women constitute the majority of patients who receive treatment with selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine, most animal studies of SSRIs are conducted on males. The present study investigated whether long-term treatment of cycling female rats with fluoxetine alters their estrous cycle and the sensitivity of hypothalamic serotonin (5-HT) 5-HT 1A and 5-HT 2A receptor systems. Adult female rats received daily injections of fluoxetine (10 mg/kg, i.p.) for three consecutive estrous cycles (15.2±0.2 days) with the first injection beginning on metestrus (when circulating estrogen levels are low and stable). Fluoxetine did not alter basal plasma estradiol levels at metestrus, nor did it alter the pattern of estrous cyclicity. Rats treated with fluoxetine showed a loss in body weight. On the morning of metestrus of the fourth cycle (18 h after the last fluoxetine injection), the rats were injected with a sub-maximal dose of the 5-HT 1A agonist (±)-8-hydroxy-2-dipropylaminotetralin (8-OH-DPAT, 50 μg/kg, s.c.) or a maximal dose of the 5-HT 2A agonist [(±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl] (DOI). Plasma levels of oxytocin, ACTH and corticosterone were measured as peripheral indicators of hypothalamic 5-HT 1A and 5-HT 2A receptor sensitivity. Injecting 8-OH-DPAT to saline pretreated rats produced a significant increase in plasma oxytocin (299%), ACTH (1456%) and corticosterone (170%) levels but not in plasma prolactin or renin concentrations. Greater increases in plasma levels of these hormones were observed after injecting DOI. Fluoxetine treatment completely blocked the oxytocin, ACTH and corticosterone responses to 8-OH-DPAT, but did not inhibit the effect of DOI on any hormone, thus confirming that fluoxetine treatment did not produce a deficit in the functioning of corticotropin releasing hormone or oxytocin containing neurons. These results indicate that in cycling female rats, fluoxetine treatment desensitizes hypothalamic post-synaptic 5-HT 1A receptor signaling. Understanding the pharmacological effects of fluoxetine in females may lead to more effective treatment of women with mood disorders.

Leptin receptor Gln223Arg variant is associated with a cluster of metabolic abnormalities in response to long-term overfeeding.

The role of the leptin receptor (LEPR) gene Gln223Arg polymorphism on the metabolic and body composition changes in response to overfeeding was studied. Twelve pairs of male monozygotic twins ate a 4.2 MJ day-1 energy surplus, 6 days week-1, during a period of 100 days. Overfeeding induced a significantly greater increase in glucose (P = 0.001 for percentage change) and insulin (P = 0.038) areas under the curve during oral glucose tolerance tests (OGTTs) in the GlnGln (n = 10) than in the GlnArg/ArgArg (n = 14) subjects. In addition, the GlnGln genotype was associated with a greater increase in plasma levels of leptin (P = 0.037) and total triglycerides (P = 0.003), as well as a greater decrease in high-density lipoprotein cholesterol (P = 0.010), than for the combined GlnArg/ArgArg genotypes. Body composition changes were not different between the genotypes. We conclude that the GlnGln subjects of the LEPR gene polymorphism are more susceptible to metabolic abnormalities when they are exposed to long-term positive energy balance. These findings provide new information on the genetic basis of individual differences in response to chronically elevated food intake.

Cardiovascular, neuroendocrine, and monoaminergic responses to psychological stressors: Possible differences between remitted panic disorder patients and healthy controls

Both clinical symptomatology and stress research suggest that panic attacks might be partially attributable to exaggerated psychophysiological responses to environmental stressors. In the present study, we aimed to explicitly test this idea by measuring the physiological responses to a mild psychological stressor in both healthy controls (n = 8) and fully remitted, medication-free panic disorder patients (n = 8). One hour before the stressor, former patients, compared to healthy controls, exhibited higher diastolic blood pressure. From a blood sample taken 30 min before the stressor, patients, compared to controls, had lower paroxetine platelet binding site densities. During the stressor, patients, compared to controls, had greater increases in plasma levels of cortisol. These preliminary findings suggest that remitted panic disorder patients might have disturbed physiological responses to mild psychological stressors. These disturbances might be related to the development of future episodes.

Interleukin 6 modulates interleukin-1-and stress-induced activation of the hypothalamic-pituitary-adrenal axis in male rats.

This study examined the interaction between interleukin 6 (IL-6) and IL-1 and between IL-6 and stress on the activation of the hypothalamic-pituitary-adrenal (HPA) axis. Coadministration of IL-6 (100 ng/rat) with IL-1 (20 or 100 mg/ rat) resulted in synergistic stimulation of the HPA axis, as determined by increased plasma levels of ACTH and corticosterone (CORT) which were greater in rats that received both cytokines than in rats receiving either cytokine alone. Concomitant administration of IL-6 (100 ng/rat) with exposure to a novelty stressor also synergistically stimulated the activation of the HPA axis, as IL-6-treated rats subjected to novelty stress had greater increases in plasma levels of ACTH and CORT than vehicle-treated rats exposed to novelty stress or rats receiving IL-6 alone. However, concomitant administration of IL-6 (100 ng/rat) did not significantly affect restraint stress induced elevation of plasma levels of ACTH and CORT, although IL-6 tended to prolong restraint stress induced elevation of plasma levels of CORT. These findings indicate a modulatory role for IL-6 stimulated HPA axis activity in response to IL-1 or a novelty psychological stressor, but not for restraint stress.

Protective role of dietary vitamin E on oxidative stress in aging

Free radical reactions and the peroxidation of membrane lipids have been implicated in the mechanism of aging and age-associated degenerative conditions. Vitamin E appears to play a critical role in protecting the cell membrane from free radical reactions and peroxidation of polyunsaturated fatty acids (PUFA). In a series of human studies, the protective role of vitamin E supplementation against oxidative stress was investigated in young and older volunteers. Muscle biopsies taken from young ( 55 y) supplemented with vitamin E for 48 d excreted a lower level of lipid peroxidation products in urine compared to placebo control following eccentric exercise. In conditions where the composition of membrane fatty acids changes to more PUFA, older subjects may be at a greater risk of oxidative damage. In a study of 15 young ( 51 y) women receiving fish oil capsules for 3 months, older women showed a greater increase in plasma levels of eicosapentaenoic (EPA) (p<0.001) and docosahexaenoic (DHA) (p<0.5) acids compared to young subjects. By substituting membrane fatty acids with potentially unstable (n-3) fatty acids of fish oil, older subjects were found to be at a greater risk of oxidative stress than young subjects. This was indicated by decreased E/EPA+DHA (4.9 fold in older and 3.6 fold in young women) and a higher increase (p<0.05) in lipid peroxides (63.1% in older vs. 29.4% in young women) in their plasma. These findings indicate that vitamin E plays an important protective antioxidant role in older subjects, particularly in conditions where oxidative stress and free radicals are potentiated.

Comparison of the effects of oral and transdermal oestradiol administration on oestrogen metabolism, protein synthesis, gonadotrophin release, bone turnover and climacteric symptoms in postmenopausal women : Clin. Endocrinol.; 30/3 (241–249)/1989/

We compared the effect of administering oestradiol via the transdermal or oral routes in six and eight postmenopausal women respectively. Although both treatments achieved similar plasma levels of oestradiol, oral administration led to much greater increases in plasma levels of oestrone and the sulphates and glucuronides of oestradiol, oestrone and oestriol than transdermal treatment (P less than 0.001). Both treatments reduced plasma FSH; from 42 +/- 10 (SE) IU/l to 30 +/- 2 IU/l with oral and from 46 +/- 7 IU/l to 28 +/- 6 IU/l with transdermal treatment. Urine calcium excretion fell from 0.41 +/- 0.06 (molar ratio to creatinine) to 0.17 +/- 0.02 with oral and from 0.25 +/- 0.06 to 0.13 +/- 0.02 with transdermal treatment. Patients' symptoms were improved by both treatments. These changes were related to the plasma oestradiol concentration but not to that of oestrone. Oral, but not transdermal, treatment stimulated hepatic protein synthesis as shown by increased plasma levels of both vitamin-D-binding globulin and sex-hormone-binding globulin. We conclude that although both oral and transdermal oestradiol reduce postmenopausal bone loss, gonadotrophin secretion and symptoms, oral treatment also leads to hepatic stimulation and extensive metabolism of oestradiol, both of which may increase side-effects without conferring additional benefit.

COMPARISON OF THE EFFECTS OF ORAL AND TRANSDERMAL OESTRADIOL ADMINISTRATION ON OESTROGEN METABOLISM, PROTEIN SYNTHESIS, GONADOTROPHIN RELEASE, BONE TURNOVER AND CLIMACTERIC SYMPTOMS IN POSTMENOPAUSAL WOMEN

We compared the effect of administering oestradiol via the transdermal or oral routes in six and eight postmenopausal women respectively. Although both treatments achieved similar plasma levels of oestradiol, oral administration led to much greater increases in plasma levels of oestrone and the sulphates and glucuronides of oestradiol, oestrone and oestriol than transdermal treatment (P less than 0.001). Both treatments reduced plasma FSH; from 42 +/- 10 (SE) IU/l to 30 +/- 2 IU/l with oral and from 46 +/- 7 IU/l to 28 +/- 6 IU/l with transdermal treatment. Urine calcium excretion fell from 0.41 +/- 0.06 (molar ratio to creatinine) to 0.17 +/- 0.02 with oral and from 0.25 +/- 0.06 to 0.13 +/- 0.02 with transdermal treatment. Patients' symptoms were improved by both treatments. These changes were related to the plasma oestradiol concentration but not to that of oestrone. Oral, but not transdermal, treatment stimulated hepatic protein synthesis as shown by increased plasma levels of both vitamin-D-binding globulin and sex-hormone-binding globulin. We conclude that although both oral and transdermal oestradiol reduce postmenopausal bone loss, gonadotrophin secretion and symptoms, oral treatment also leads to hepatic stimulation and extensive metabolism of oestradiol, both of which may increase side-effects without conferring additional benefit.

Plasma metabolites and food intake reduction following heparinoid injection in rats

Behavioral and physiological consequences of heparinoid injections, which increase plasma levels of nonesterified fatty acids (NEFA) by releasing lipoproteinlipase into the circulation, were studied in rats, because, according to the lipostatic hypothesis of food intake control, changes in plasma metabolite levels should influence food intake. Subcutaneously injected 55 mg/kg body wt. of the heparinoid Na-pentosanpolysulfate (PPS) significantly reduced feeding in rats with ad lib access to either a high carbohydrate (HC) or a high fat (HF) diet. However, the reduction of food intake in HF-rats exceeded that in HC-rats. Moreover, the food intake reduction following PPS-injections was associated with greater increases in plasma levels of NEFA and free glycerol in HF-rats, whereas PPS increased plasma levels of D-(−)-3-hydroxybutyrate only in HF-rats, and did not alter blood glucose concentrations. Although PPS inhibited blood coagulation, it did not affect the hematocrit. Furthermore, PPS-injections that reduced feeding, failed to produce a conditioned taste aversion in a two bottle preference test. The data therefore strongly suggest that elevated levels of plasma NEFA and/or free plasma glycerol decrease food intake in rats. These metabolites might contribute to a lipostatic mechanism of feeding control.

Alterations in plasma catecholamines and behavior during acute stress in spontaneously hypertensive and Wistar-Kyoto normotensive rats

The responsiveness of the sympathoadrenal system to stress was assessed in spontaneously hypertensive (SHR) and Wistar-Kyoto normotensive (WKY) rats at 6, 18, and 48 weeks of age. Two days after insertion of a tail arterial catheter, each rat was transferred from its home cage to a shock chamber, and after 5 min received 60 footshocks over a 5 min interval. Blood samples were taken from undisturbed rats when in the home cage, 3–5 min after transfer to the shock chamber, and at the end of shock. An additional group of naive SHR and WKY rats was exposed to footshock and behavioral responses were recorded. There were no strain differences in levels of norepinephrine (NE) or epinephrine (EPI) while rats were undisturbed in their home cages. Transfer to the shock chamber resulted in a greater increase in plasma levels of both catecholamines in SHRs of each age. A similar pattern was evident after footshock; SHR rats had significantly higher post-shock levels of plasma NE and EPI than age-matched WKY rats. During shock, SHR rats were more active and jumped and reared more frequently than WKYs. These results demonstrate that the sympathoadrenal system of SHR rats is more responsive than normotensive rats to stressful stimuli and that this hyper-responsitivity is independent of increases in blood pressure. The excessive discharge of NE and EPI into plasma during stress may contribute to the development and maintenance of high blood pressure in SHR rats.