Malfunction of Vascular Control in Lifestyle-Related Diseases: Mechanisms Underlying Endothelial Dysfunction in the Insulin-Resistant State

Brain Dopamine-Clock Interactions Regulate Cardiometabolic Physiology: Mechanisms of the Observed Cardioprotective Effects of Circadian-Timed Bromocriptine-QR Therapy in Type 2 Diabetes Subjects

Despite enormous global efforts within clinical research and medical practice to reduce cardiovascular disease(s) (CVD), it still remains the leading cause of death worldwide. While genetic factors clearly contribute to CVD etiology, the preponderance of epidemiological data indicate that a major common denominator among diverse ethnic populations from around the world contributing to CVD is the composite of Western lifestyle cofactors, particularly Western diets (high saturated fat/simple sugar [particularly high fructose and sucrose and to a lesser extent glucose] diets), psychosocial stress, depression, and altered sleep/wake architecture. Such Western lifestyle cofactors are potent drivers for the increased risk of metabolic syndrome and its attendant downstream CVD. The central nervous system (CNS) evolved to respond to and anticipate changes in the external (and internal) environment to adapt survival mechanisms to perceived stresses (challenges to normal biological function), including the aforementioned Western lifestyle cofactors. Within the CNS of vertebrates in the wild, the biological clock circuitry surveils the environment and has evolved mechanisms for the induction of the obese, insulin-resistant state as a survival mechanism against an anticipated ensuing season of low/no food availability. The peripheral tissues utilize fat as an energy source under muscle insulin resistance, while increased hepatic insulin resistance more readily supplies glucose to the brain. This neural clock function also orchestrates the reversal of the obese, insulin-resistant condition when the low food availability season ends. The circadian neural network that produces these seasonal shifts in metabolism is also responsive to Western lifestyle stressors that drive the CNS clock into survival mode. A major component of this natural or Western lifestyle stressor-induced CNS clock neurophysiological shift potentiating the obese, insulin-resistant state is a diminution of the circadian peak of dopaminergic input activity to the pacemaker clock center, suprachiasmatic nucleus. Pharmacologically preventing this loss of circadian peak dopaminergic activity both prevents and reverses existing metabolic syndrome in a wide variety of animal models of the disorder, including high fat-fed animals. Clinically, across a variety of different study designs, circadian-timed bromocriptine-QR (quick release) (a unique formulation of micronized bromocriptine-a dopamine D2 receptor agonist) therapy of type 2 diabetes subjects improved hyperglycemia, hyperlipidemia, hypertension, immune sterile inflammation, and/or adverse cardiovascular event rate. The present review details the seminal circadian science investigations delineating important roles for CNS circadian peak dopaminergic activity in the regulation of peripheral fuel metabolism and cardiovascular biology and also summarizes the clinical study findings of bromocriptine-QR therapy on cardiometabolic outcomes in type 2 diabetes subjects.

Bromocriptine-QR Therapy Reduces Sympathetic Tone and Ameliorates a Pro-Oxidative/Pro-Inflammatory Phenotype in Peripheral Blood Mononuclear Cells and Plasma of Type 2 Diabetes Subjects

Bromocriptine-QR is a sympatholytic dopamine D2 agonist for the treatment of type 2 diabetes that has demonstrated rapid (within 1 year) substantial reductions in adverse cardiovascular events in this population by as yet incompletely delineated mechanisms. However, a chronic state of elevated sympathetic nervous system activity and central hypodopaminergic function has been demonstrated to potentiate an immune system pro-oxidative/pro-inflammatory condition and this immune phenotype is known to contribute significantly to the advancement of cardiovascular disease (CVD). Therefore, the possibility exists that bromocriptine-QR therapy may reduce adverse cardiovascular events in type 2 diabetes subjects via attenuation of this underlying chronic pro-oxidative/pro-inflammatory state. The present study was undertaken to assess the impact of bromocriptine-QR on a wide range of immune pro-oxidative/pro-inflammatory biochemical pathways and genes known to be operative in the genesis and progression of CVD. Inflammatory peripheral blood mononuclear cell biology is both a significant contributor to cardiovascular disease and also a marker of the body’s systemic pro-inflammatory status. Therefore, this study investigated the effects of 4-month circadian-timed (within 2 h of waking in the morning) bromocriptine-QR therapy (3.2 mg/day) in type 2 diabetes subjects whose glycemia was not optimally controlled on the glucagon-like peptide 1 receptor agonist on (i) gene expression status (via qPCR) of a wide array of mononuclear cell pro-oxidative/pro-inflammatory genes known to participate in the genesis and progression of CVD (OXR1, NRF2, NQO1, SOD1, SOD2, CAT, GSR, GPX1, GPX4, GCH1, HMOX1, BiP, EIF2α, ATF4, PERK, XBP1, ATF6, CHOP, GSK3β, NFkB, TXNIP, PIN1, BECN1, TLR2, TLR4, TLR10, MAPK8, NLRP3, CCR2, GCR, L-selectin, VCAM1, ICAM1) and (ii) humoral measures of sympathetic tone (norepinephrine and normetanephrine), whole-body oxidative stress (nitrotyrosine, TBARS), and pro-inflammatory factors (IL-1β, IL-6, IL-18, MCP-1, prolactin, C-reactive protein [CRP]). Relative to pre-treatment status, 4 months of bromocriptine-QR therapy resulted in significant reductions of mRNA levels in PBMC endoplasmic reticulum stress-unfolded protein response effectors [GRP78/BiP (34%), EIF2α (32%), ATF4 (29%), XBP1 (25%), PIN1 (14%), BECN1 (23%)], oxidative stress response proteins [OXR1 (31%), NRF2 (32%), NQO1 (39%), SOD1 (52%), CAT (26%), GPX1 (33%), GPX4 (31%), GCH1 (30%), HMOX1 (40%)], mRNA levels of TLR pro-inflammatory pathway proteins [TLR2 (46%), TLR4 (20%), GSK3β (19%), NFkB (33%), TXNIP (18%), NLRP3 (32%), CCR2 (24%), GCR (28%)], mRNA levels of pro-inflammatory cellular receptor proteins CCR2 and GCR by 24% and 28%, and adhesion molecule proteins L-selectin (35%) and VCAM1 (24%). Relative to baseline, bromocriptine-QR therapy also significantly reduced plasma levels of norepinephrine and normetanephrine by 33% and 22%, respectively, plasma pro-oxidative markers nitrotyrosine and TBARS by 13% and 10%, respectively, and pro-inflammatory factors IL-18, MCP1, IL-1β, prolactin, and CRP by 21%,13%, 12%, 42%, and 45%, respectively. These findings suggest a unique role for circadian-timed bromocriptine-QR sympatholytic dopamine agonist therapy in reducing systemic low-grade sterile inflammation to thereby reduce cardiovascular disease risk.

Time-of-Day-Dependent Effects of Bromocriptine to Ameliorate Vascular Pathology and Metabolic Syndrome in SHR Rats Held on High Fat Diet

The treatment of type 2 diabetes patients with bromocriptine-QR, a unique, quick release micronized formulation of bromocriptine, improves glycemic control and reduces adverse cardiovascular events. While the improvement of glycemic control is largely the result of improved postprandial hepatic glucose metabolism and insulin action, the mechanisms underlying the drug's cardioprotective effects are less well defined. Bromocriptine is a sympatholytic dopamine agonist and reduces the elevated sympathetic tone, characteristic of metabolic syndrome and type 2 diabetes, which potentiates elevations of vascular oxidative/nitrosative stress, known to precipitate cardiovascular disease. Therefore, this study investigated the impact of bromocriptine treatment upon biomarkers of vascular oxidative/nitrosative stress (including the pro-oxidative/nitrosative stress enzymes of NADPH oxidase 4, inducible nitric oxide (iNOS), uncoupled endothelial nitric oxide synthase (eNOS), the pro-inflammatory/pro-oxidative marker GTP cyclohydrolase 1 (GTPCH 1), and the pro-vascular health enzyme, soluble guanylate cyclase (sGC) as well as the plasma level of thiobarbituric acid reactive substances (TBARS), a circulating marker of systemic oxidative stress), in hypertensive SHR rats held on a high fat diet to induce metabolic syndrome. Inasmuch as the central nervous system (CNS) dopaminergic activities both regulate and are regulated by CNS circadian pacemaker circuitry, this study also investigated the time-of-day-dependent effects of bromocriptine treatment (10 mg/kg/day at either 13 or 19 h after the onset of light (at the natural waking time or late during the activity period, respectively) among animals held on 14 h daily photoperiods for 16 days upon such vascular biomarkers of vascular redox state, several metabolic syndrome parameters, and mediobasal hypothalamic (MBH) mRNA expression levels of neuropeptides neuropeptide Y (NPY) and agouti-related protein (AgRP) which regulate the peripheral fuel metabolism and of mRNA expression of other MBH glial and neuronal cell genes that support such metabolism regulating neurons in this model system. Such bromocriptine treatment at ZT 13 improved (reduced) biomarkers of vascular oxidative/nitrosative stress including plasma TBARS level, aortic NADPH oxidase 4, iNOS and GTPCH 1 levels, and improved other markers of coupled eNOS function, including increased sGC protein level, relative to controls. However, bromocriptine treatment at ZT 19 produced no improvement in either coupled eNOS function or sGC protein level. Moreover, such ZT 13 bromocriptine treatment reduced several metabolic syndrome parameters including fasting insulin and leptin levels, as well as elevated systolic and diastolic blood pressure, insulin resistance, body fat store levels and liver fat content, however, such effects of ZT 19 bromocriptine treatment were largely absent versus control. Finally, ZT 13 bromocriptine treatment reduced MBH NPY and AgRP mRNA levels and mRNA levels of several MBH glial cell/neuronal genes that code for neuronal support/plasticity proteins (suggesting a shift in neuronal structure/function to a new metabolic control state) while ZT 19 treatment reduced only AgRP, not NPY, and was with very little effect on such MBH glial cell genes expression. These findings indicate that circadian-timed bromocriptine administration at the natural circadian peak of CNS dopaminergic activity (that is diminished in insulin resistant states), but not outside this daily time window when such CNS dopaminergic activity is naturally low, produces widespread improvements in biomarkers of vascular oxidative stress that are associated with the amelioration of metabolic syndrome and reductions in MBH neuropeptides and gene expressions known to facilitate metabolic syndrome. These results of such circadian-timed bromocriptine treatment upon vascular pathology provide potential mechanisms for the observed marked reductions in adverse cardiovascular events with circadian-timed bromocriptine-QR therapy (similarly timed to the onset of daily waking as in this study) of type 2 diabetes subjects and warrant further investigations into related mechanisms and the potential application of such intervention to prediabetes and metabolic syndrome patients as well.

Reduced Graphene Oxide Modified the Interdigitated Chain Electrode for an Insulin Sensor

Insulin is a key regulator in glucose homeostasis and its deficiency or alternations in the human body causes various types of diabetic disorders. In this paper, we present the development of a reduced graphene oxide (rGO) modified interdigitated chain electrode (ICE) for direct capacitive detection of insulin. The impedance properties of rGO-ICE were characterized by equivalent circuit modeling. After an electrochemical deposition of rGO on ICE, the electrode was modified with self-assembled monolayers and insulin antibodies in order to achieve insulin binding reactions. The impedance spectra and capacitances were measured with respect to the concentrations of insulin and the capacitance change (ΔC) was analyzed to quantify insulin concentration. The antibody immobilized electrode showed an increment of ΔC according to the insulin concentration in human serum ranging from 1 ng/mL to 10 µg/mL. The proposed sensor is feasible for label-free and real-time measuring of the biomarker and for point-of-care diagnosis.

Δ9-tetrahydrocannabinol treatment improved endothelium-dependent relaxation on streptozotocin/nicotinamide-induced diabetic rat aorta

OBJECTIVE

In this study, we investigated the possible effect of Δ(9)-tetrahydrocannabinol (THC), a peroxisome proliferator-activated receptor gamma (PPARγ) agonist, on metabolic control and vascular complications of diabetes in streptozotocin/nicotinamide (STZ/NIC) induced type 2 diabetes mellitus.

MATERIAL AND METHODS

Type 2 diabetes was induced with 65 mg/kg STZ, 15 minute later 85 mg/kg NIC was given intraperitoneally (i.p.) to rats. Three days after diabetes induction, THC (3 mg/kg/day, i.p.) was given for 7 days to diabetic rats. Body weight and plasma glucose levels of rats were measured in all groups before and at the end of 3 weeks after diabetes induction. Acetylcholine (Ach) and sodium nitroprusside (SNP) potency and maximum relaxant effects were calculated on aortic rings pre-contracted with noradrenaline (NA).

RESULTS

At the end of 3 weeks, blood glucose levels of diabetic group significantly increased in comparison with the control group. Increased plasma glucose levels were significantly decreased by the treatment of THC. Ach induced relaxation was impaired whereas endothelium-independent relaxation to SNP was unaffected on isolated diabetic rat aorta. THC treatment enhanced Ach induced relaxation on diabetic rat aortas.

DISCUSSION

These results suggested that THC improved endothelium-dependent relaxation in STZ/NIC induced diabetic rat aorta and that these effects were mediated at least in part, by control of hyperglycemia and enhanced endothelial nitric oxide bioavailability.

Rapid clearance of supplemented tetrahydrobiopterin is driven by high-capacity transporters in the kidney

Tetrahydrobiopterin (BH(4)) is an essential cofactor of aromatic amino acid hydroxylases and NO synthase. Supplementation of BH(4) potentially targets cardiovascular dysfunction as well as inherited BH(4) deficiencies and BH(4)-responsive phenylketonuria. However, the high cost/effect ratio of the recommended daily dose of BH(4) supplementation acts against further popularization of this therapy. The aim of this study was to attenuate urinary excretion with the intention of improving efficacy of BH(4) supplementation. The rapid excretion of BH(4) in the urine was confirmed to be the major route of supplemented BH(4) loss. In addition to glomerular filtration into the urine, a dominant rapid exclusion by renal secretion was observed in rats (T((1/2))=16 min) when the plasma BH(4) was higher than about 1 nmol/mL (more than 10 times higher than normal), due to BH(4) supplementation. The rapidity of the process was slowed by prior administration of cyclosporin A, a representative anti-excretory drug, and the excretion decelerated to a moderate rate (T((1/2))=53 min). By the combined administration of BH(4) plus cyclosporin A, the blood BH(4) levels were dramatically elevated. It was hypothesized that the drug interfered with kidney excretion of BH(4) rather than by attenuating organ tissue distribution by inhibiting biopterin uptake from the plasma. Consistent with this hypothesis, biopterin levels after BH(4) administration were elevated in major organs in the presence of anti-excretory drugs without notable change in their BH(4) fraction which was consistently 95% or higher regardless of combined administration with the drugs. Targeting these putative transporters would be a promising approach for improving the efficiency of BH(4) supplementation therapy.

Alpha lipoic acid treatment improved endothelium-dependent relaxation in diabetic rat aorta

The aim of this study was to ascertain the effects of α-lipoic acid (ALA) treatment on relaxant responses of acetylcholine (ACh) and isoprenaline (ISO) in aortic rings precontracted with serotonin (5-HT, 10(-6) M) obtained from streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in the rats by 50 mg/kg streptozotocin (STZ) via an intraperitoneal injection. Rat body and aorta weights were measured. The isometric tension to ACh (10(-9)-3×10(-6) M) and ISO (10(-9)-10(-4) M) of 5-HT-precontracted diabetic and non-diabetic rat (control), diabetic-ALA-treated, and ALA-treated aortas, in organ baths were recorded. Six weeks after STZ treatment blood glucose was elevated compared to control rats. In aortic rings from diabetic rats ACh and ISO-induced relaxations were impaired whereas endothelium-independent relaxation to sodium nitroprusside (SNP) was unaffected. ALA (100 mg/kg/day) treatment for 5 weeks enhanced ACh and ISO-induced relaxation in diabetic aortas. This recovering effect was via NO because prevented by incubating the vessels with N(G)-nitro-L-arginine methyl ester (L-NAME, a NOS inhibitor). It may be assumed that ALA treatment in vivo, can protect against impaired vascular responsiveness in STZ-induced diabetic rats.

Comparison of mechanisms involved in impaired vascular reactivity between high sucrose and high fat diets in rats

BACKGROUND

To determine the effects of high sucrose diets on vascular reactivity. We hypothesized that similar to high fat diets (HFD), HSD feeding would lead to increased adiposity resulting in inflammation and oxidative stress-mediated impairment of vasodilation.

METHODS

Male Sprague-Dawley rats were fed control chow (Chow), HSD or HFD diets for 6 weeks. The role of inflammation and oxidative stress on impaired vasodilation were assessed in isolated mesenteric arterioles.

RESULTS

HSD and HFD induced increased adiposity, oxidative stress and inflammation. HFD rats developed fasting hyperglycemia. Both HSD and HFD rats developed impaired glucose tolerance and hyperleptinemia. Nitric oxide (NO)-mediated vasodilation was significantly attenuated in both HSD and HFD rats but was normalized by treatment with antioxidants or anti-inflammatory drugs. Endothelial NO synthase (eNOS) protein expression was not affected by diet. Sensitivity to NO was reduced since NOS inhibition attenuated vasodilation in Chow rats but did not further impair vasodilation in HSD or HFD rats. Likewise, responsiveness to a NO donor was attenuated in both experimental groups.

CONCLUSIONS

Oxidative stress diminishes vasodilatory responsiveness in HSD and HFD rats through ROS-mediated scavenging of NO and decreased smooth muscle sensitivity to NO. Inflammation also plays a significant role in the impaired vasodilation.

Losartan normalizes endothelium-derived hyperpolarizing factor-mediated relaxation by activating Ca2+-activated K+ channels in mesenteric artery from type 2 diabetic GK rat

Ca(2+)-activated K(+) (K(Ca)) channels are important for endothelium-derived hyperpolarizing factor (EDHF) signaling. Since treatment with angiotensin II receptor blockers (ARBs) improves vasculopathies in type 2 diabetic patients, we asked whether the EDHF-type relaxation and its associated K(Ca) channels [small (SK(Ca))-, intermediate (IK(Ca))-, and large (BK(Ca))-conductance channels] are abnormal in mesenteric arteries isolated from Goto-Kakizaki (GK) rats at the chronic stage of type 2 diabetes (34 - 38 weeks) and whether an ARBs (losartan, 25 mg . kg(-1) . day(-1) for 2 weeks) might correct these abnormalities. Although the acetylcholine chloride-induced EDHF-type relaxation in mesenteric arteries from GK rats was reduced versus the Wistar controls, it was significantly restored by losartan treatment. The SK(Ca)-blocker apamin or the IK(Ca)-blocker 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34) inhibited such relaxations in the losartan-treated or -untreated Wistar groups and in the losartan-treated GK group, but not in the losartan-untreated GK group. The BK(Ca)-blocker iberiotoxin had a significant inhibitory effect in only one of these groups, the losartan-treated GK. The relaxations induced by the SK(Ca)/IK(Ca) activator NS309 and the BK(Ca) activator NS1619, which were impaired in GK rats, were normalized by losartan treatment. We conclude that losartan improves EDHF-type relaxation in GK rats at least partly by normalizing SK(Ca)/IK(Ca) activities and increasing BK(Ca) activity.

Pyrrolidine dithiocarbamate reduces vascular prostanoid-induced responses in aged type 2 diabetic rat model

It has been shown that enhancement of vasoconstrictor prostanoids plays an important role in the development of cardiovascular diseases. The aim of the present study was to examine the effects of pyrrolidine dithiocarbamate (PDTC), a low-molecular-weight thiol antioxidant and a potent inhibitor of nuclear factor-kappaB (NF-kappaB), on both the response to and production of prostanoids in arterial vessels isolated from rats at the chronic stage of type 2 diabetes. Using aortas from type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats, control Long-Evans Tokushima Otsuka (LETO) rats, and LETO and OLETF rats treated with PDTC (30 mg/kg, s.c., daily, for 1 week), we measured the production of prostanoids and NF-kappaB activity. The arachidonic acid-induced contraction and the acetylcholine-induced endothelium-derived contracting factor (EDCF)-mediated contraction in mesenteric arteries were also compared among these groups. OLETF rats exhibited (vs. age-matched LETO rats) the following: increased responses to both arachidonic acid and EDCF and greater productions of PGE(2) and TXA(2). Treatment with PDTC resulted in the following: 1) reduced arachidonic acid- and EDCF-mediated contractions, 2) suppressed the production of prostanoids, and 3) normalized NF-kappaB activity. These results suggest that PDTC has beneficial effects against the abnormal vasoconstrictor prostanoid signaling present in rats at the chronic stage of type 2 diabetes.

Chronic production of peroxynitrite in the vascular wall impairs vasorelaxation function in SHR/NDmcr-cp rats, an animal model of metabolic syndrome

We have previously reported that peroxynitrite is involved in dysfunction of nitric oxide (NO)-mediated vasorelaxation in SHR/NDmcr-cp rats (SHR-cp), which display typical symptoms of metabolic syndrome. This study investigated whether peroxynitrite is actually generated in the vascular wall with angiotensin II-induced NADPH-oxidase activation, thus contributing to the dysfunction. In isolated mesenteric arteries of male 18-week-old SHR-cp, relaxations in response to acetylcholine and sodium nitroprusside were impaired compared with that in Wistar-Kyoto rats. This impaired relaxation was not restored by treatment with apocynin, an NADPH-oxidase inhibitor. Protein expression of endothelial NO synthase increased while that of soluble guanylyl cyclase (sGC) decreased in the artery. We observed increased production of superoxide anions and peroxynitrite from the artery and their inhibition by apocynin, and also increased contents of nitrotyrosine, a biomarker of peroxynitrite, in mesenteric arteries and angiotensin II in aortas. Long-term (8 weeks) administration of telmisartan, an angiotensin II type 1-receptor antagonist, prevented the impaired vasorelaxation, decreased sGC expression and increased nitrotyrosine content in mesenteric arteries. These findings suggest that in the vascular wall of SHR-cp, peroxynitrite is continually produced by the reaction of NO with NADPH oxidase-derived superoxide via angiotensin II and gradually denatures sGC protein, leading to vasorelaxation dysfunction.

Endothelial dysfunction: from molecular mechanisms to measurement, clinical implications, and therapeutic opportunities

Endothelial dysfunction has been implicated as a key factor in the development of a wide range of cardiovascular diseases, but its definition and mechanisms vary greatly between different disease processes. This review combines evidence from cell-culture experiments, in vitro and in vivo animal models, and clinical studies to identify the variety of mechanisms involved in endothelial dysfunction in its broadest sense. Several prominent disease states, including hypertension, heart failure, and atherosclerosis, are used to illustrate the different manifestations of endothelial dysfunction and to establish its clinical implications in the context of the range of mechanisms involved in its development. The size of the literature relating to this subject precludes a comprehensive survey; this review aims to cover the key elements of endothelial dysfunction in cardiovascular disease and to highlight the importance of the process across many different conditions.

Peroxynitrite is Involved in the dysfunction of vasorelaxation in SHR/NDmcr-cp rats, spontaneously hypertensive obese rats

SHR/NDmcr-cp (SHR-cp) rats display typical symptoms and features of the metabolic syndrome. We previously reported that endothelium-dependent relaxation decreases in the thoracic aortas of SHR-cp rats, despite increased nitric oxide (NO) production from the endothelium. In the present study, to search for the reasons for this contradiction, we investigated whether vascular abnormality could be reduced by treatment of SHR-cp rats with antihypertensive drugs; a calcium channel blocker (amlodipine), an alpha 2 and imidazoline receptor agonist (moxonidine), and an angiotensin II type 1 (AT1) receptor antagonist (telmisartan). Telmisartan but not amlodipine and moxonidine ameliorated the impairment of relaxation in response to acetylcholine and the increased protein expression of endothelium NO synthase in thoracic aortas. All three drugs significantly lowered the blood pressure. Telmisartan decreased the serum levels of lipid peroxide and 8-hydroxy-2'-deoxyguanosine, oxidative stress markers, and also the aortic levels of the protein expression of gp91, a component of NADPH oxidase, and 3-nitrotyrosine, a biomarker of peroxynitrite. These findings suggest that NADPH oxidase-derived superoxide, probably produced due to stimulation of AT1 receptors, reacts with NO to form peroxynitrite, and consequently decreases active NO, leading to attenuation of endothelium-dependent relaxation. Angiotensin receptor antagonists may be effective for preventing endothelial dysfunction in metabolic syndrome.

Association of insulin resistance and nocturnal fall of blood pressure in GH-deficient adults during GH replacement

The GH deficiency syndrome in adults is characterized by changes in body composition, metabolic, cardiovascular and psychological profile. Such alterations fit the metabolic syndrome. Changes of blood pressure (BP) levels related to the presence of insulin resistance (IR) may be present in the GH-deficient adult prior to or after therapy with recombinant GH (hGH). The purpose of the study was to assess the relationship between BP and IR in GH-deficient adults after 24 months of replacement with hGH. Thirteen GH-deficient adults were studied [7 men and 6 women, with an average age of 38.6+/-14.14 yr body mass index (BMI) 25.83+/-2.26 kg/m2]. The BP was assessed by means of ambulatory monitoring of BP (AMBP), prior to the treatment and 12 and 24 months after replacement with hGH. Glucose metabolism was assessed by the homeostatic model assessment (HOMA), during the same periods. The average dosage of hGH utilized was 0.67+/-0.15 mg/day. In the analysis of BP levels, we observed a decrease of the diurnal systolic BP (SB P) (p=0.043) and a reduction of the diurnal systolic (p=0.002) and diastolic pressure loads (p=0.038). During the night there were no changes in BP levels. We observed an increase in the percentage of patients with a non-physiological nocturnal fall (non dippers) after replacement with hGH (61.53%). The mean HOMA, insulin and glucose in the fasting state did not present any statistically significant changes. Although the patients within the nondipper group had higher HOMA and insulin levels throughout the study, there were no changes in any of these parameters after GH replacement. All patients with HOMA >2.5 were within the non-dipper group, whereas all dippers had HOMA <2.5. In conclusion, 24 months of therapy with hGH do not seem to have affected glucose homeostasis, and since there is no relationship with the increase of the percentage of non-physiological nocturnal fall, we will need a longer observation time to discover the effects of this finding.

[Influence of orlistat therapy on serum insulin level and morphological and functional parameters of peripheral arterial circulation in obese patients]

BACKGROUND/AIM

Insulin resistance is related to accelerated atherosclerosis, whereas weight loss is associated with the increasing insulin sensitivity, the improvement of functional and the morphological parameters of arterial circulation, and the reduction of cardiovascular morbidity and mortality. The aim of our study was to evaluate the influence of orlistat treatment on serum insulin level and functional and morphologic parameters of peripheral arterial circulation.

METHODS

We conducted a prospective, randomized, double - blind, placebo - controlled study. Thirty patients with body mass index over 30 kg/m2 normotensive, nonsmokers, without clinically manifested cardiovascular disease or diabetes were randomly assigned either orlistat (120 mg, 3 times daily; n = 20) or placebo (n = 10) in a double - blind manner. All of the patients were on individually calculated hypocaloric diet. The follow-up period was 24 weeks. Arterial pressure, fasting serum glucose and insulin level, triglycerides, total cholesterol and low density lipoprotein-cholesterol were determined at the beginning, following 3 and 6 months. Also, the intima - media thickness of right superficial femoral artery and the mean blood flow velocity were determined with ultrasonography.

RESULTS

Inside the period of 3 and 6 months, there were the greater reductions of body mass index, arterial pressure, fasting glucose and insulin level, total cholesterol, low density lipoproteins, as well as the greater reductions of mean velocity blood flow and peripheral pulse pressure in the orlistat group vs the placebo group (p < 0.01). Greater reductions in the waist circumference and intima - media thickness were registered following 6 months in the orlistat vs the placebo group (p < 0.01).

CONCLUSION

In the group of obese patients orlistat therapy reduced risk factors, serum insulin level and improved early arterial functional changes as assessed with the reductions of the mean velocity blood flow and peripheral pulse pressure following 3 months. The regression of morphological changes, as assessed with the reduction in intima - media thickness, was feasible over the six - month period.