Mechanisms of antihyperglycemic effects of moxonidine in the obese spontaneously hypertensive Koletsky rat (SHROB).

Increased activity of the sympathetic nervous system may be a critical factor in the development of impaired insulin secretion and insulin resistance. We studied the chronic effects of sympathetic inhibition with moxonidine on glucose metabolism in the spontaneously hypertensive genetically obese rat (SHROB). This unique animal model closely resembles human syndrome X, expressing insulin resistance, genetic obesity, spontaneous hypertension, and hyperlipoproteinemia. Moxonidine, a selective imidazoline receptor agonist, was administered to lean spontaneous hypertensive rats (SHR) and SHROBs for 90 days in food at 8 mg/kg/day and significantly reduced mean blood pressure. Moxonidine treatment reduced fasting insulin levels by 71% in SHROB and lowered plasma free fatty acids by 25%. In SHR, moxonidine treatment decreased free fatty acids by 17% compared with controls. During an oral glucose tolerance test, blood glucose levels in moxonidine-treated SHROB were reduced relative to untreated controls from 60 min onwards. Insulin secretion was facilitated at 30 min (83% greater) and 60 min (67% greater) postchallenge compared with control SHROB. In skeletal muscle, moxonidine treatment increased the expression of the insulin receptor beta subunit by 19% in SHROB but was without effect in SHR. The level of insulin receptor substrate-1 (IRS-1) protein was decreased by 60% in control SHROB compared with lean SHR. Moxonidine treatment enhanced the expression and insulin-stimulated phosphorylation of IRS-1 protein in skeletal muscle in SHROB by 74 and 27%, respectively, and in SHR by 40 and 56%, respectively. Moxonidine increased the levels of expression of IRS-1 protein in liver in SHR by 275% and in SHROB by 260%. These findings indicate that chronic inhibition of sympathetic activity with moxonidine therapy can lower free fatty acids and significantly improve insulin secretion, glucose disposal, and expression of key insulin signaling intermediates in an animal model of obese hypertension.

Anti-hyperglycemic activity of moxonidine: metabolic and molecular effects in obese spontaneously hypertensive rats.

Hypertension and insulin resistance are often part of a complex set of abnormalities including obesity, hyperlipidemia, and glucose intolerance, described as syndrome X. Besides a common genetic basis, insulin resistance and hypertension might be linked by excessive activity of the sympathetic nervous system. We studied the effects of chronic inhibition of sympathetic activity with the antihypertensive agent moxonidine on glucose metabolism in the genetically obese SHR Koletsky rat (SHROB), a unique animal model which closely resembles human syndrome X, expressing genetic obesity, hypertension, and hyperlipidemia. Moxonidine, a selective I1-imidazoline receptor agonist, was administered to SHROB and SHR for 90 days in food at 8 mg/kg/day. Moxonidine not only lowered blood pressure, but also reduced fasting insulin levels by 49% in SHROB, and reduced plasma free fatty acids by 30%. In lean SHR, moxonidine treatment decreased circulating free fatty acids by 33% compared to controls. During oral glucose tolerance tests, blood glucose levels in moxonidine-treated SHROB were reduced from 60 min onwards, and there was a sharply higher insulin secretion post-challenge compared to control SHROB. Western blot analysis of insulin signaling proteins showed that IRS-1 was decreased 42% in control SHROB compared with SHR. Moxonidine treatment enhanced the expression of IRS-1 protein in skeletal muscle by 74% in SHROB and 40% in SHR. Moxonidine increased expression of IRS-1 protein in liver by 245% in SHROB and 268% in SHR. Long-term inhibition of sympathetic activity with moxonidine therapy lowered free fatty acids and significantly improved insulin secretion, glucose disposal, and expression of key insulin signaling intermediates. Thus, moxonidine should be considered for the treatment of multiple metabolic and cardiovascular abnormalities associated with syndrome X.

Reduced insulin receptor signaling in the obese spontaneously hypertensive Koletsky rat.

Insulin resistance is associated with both obesity and hypertension. However, the cellular mechanisms of insulin resistance in genetic models of obese-hypertension have not been identified. The objective of the present study was to investigate the effects of genetic obesity on a background of inherited hypertension on initial components of the insulin signal transduction pathway and glucose transport in skeletal muscle and liver. Oral glucose tolerance testing in SHROB demonstrated a sustained postchallenge elevation in plasma glucose at 180 and 240 min compared with lean spontaneously hypertensive rat (SHR) littermates, which is suggestive of glucose intolerance. Fasting plasma insulin levels were elevated 18-fold in SHROB. The rate of insulin-stimulated 3-O-methylglucose transport was reduced 68% in isolated epitrochlearis muscles from the SHROB compared with SHR. Insulin-stimulated tyrosine phosphorylation of the insulin receptor beta-subunit and insulin receptor substrate-1 (IRS-1) in intact skeletal muscle of SHROB was reduced by 36 and 23%, respectively, compared with SHR, due primarily to 32 and 60% decreases in insulin receptor and IRS-1 protein expression, respectively. The amounts of p85 alpha regulatory subunit of phosphatidylinositol-3-kinase and GLUT-4 protein were reduced by 28 and 25% in SHROB muscle compared with SHR. In the liver of SHROB, the effect of insulin on tyrosine phosphorylation of IRS-1 was not changed, but insulin receptor phosphorylation was decreased by 41%, compared with SHR, due to a 30% reduction in insulin receptor levels. Our observations suggest that the leptin receptor mutation fak imposed on a hypertensive background results in extreme hyperinsulinemia, glucose intolerance, and decreased expression of postreceptor insulin signaling proteins in skeletal muscle. Despite these changes, hypertension is not exacerbated in SHROB compared with SHR, suggesting these metabolic abnormalities may not contribute to hypertension in this model of Syndrome X.

Phosphoenolpyruvate carboxykinase (GTP) gene transcription and hyperglycemia are regulated by glucocorticoids in genetically obese db/db transgenic mice.

The molecular mechanisms underlying increased hepatic phosphoenolpyruvate carboxykinase (PEPCK) gene transcription and gluconeogenesis in type II diabetes are largely unknown. To examine the involvement of glucocorticoids and the cis-acting insulin response sequence (IRS, -416/-407) in the genetically obese db/db mouse model, we generated crosses between C57BL/KsJ-db/+ mice and transgenic mice that express -460 or -2000 base pairs of the rat PEPCK gene promoter containing an intact or mutated IRS, linked to a reporter gene. Transgenic mice expressing the intact PEPCK(460)-CRP (C-reactive protein) transgene bred to near homozygosity at the db locus were obese, hyperinsulinemic, and developed fasting hyperglycemia (389 +/- 26 mg/100 ml) between 4 and 10 weeks of age. Levels of CRP reporter gene expression were increased 2-fold despite severe hyperinsulinemia compared with non-diabetic non-obese transgenic mice. Reporter gene expression was also increased 2-fold in transgenic obese diabetic db/db mice bearing a mutation in the IRS, -2000(IRS)-hGx, compared with non-obese non-diabetic transgenic 2000(IRS)-hGx mice. Treatment of obese diabetic db/db transgenic mice with the glucocorticoid receptor blocker RU 486 decreased plasma glucose by 50% and reduced PEPCK, GLUT2, glucose-6-phosphatase, tyrosine aminotransferase, CRP, and hGx reporter gene expression to levels similar to those of non-obese normoglycemic transgenic mice. Taken together, these results establish that -460 bp of 5'-flanking sequence is sufficient to mediate the induction of PEPCK gene transcription in genetically obese db/db mice during the development of hyperglycemia. The results further demonstrate that the mechanism underlying increased expression of gluconeogenic enzymes in the db/db mouse requires the action of glucocorticoids and occurs independently of factors acting through the PEPCK IRS (-416/-407) promoter binding site.

Involvement of transcription factor C/EBP-beta in stimulation of PEPCK gene expression during exercise.

Prolonged exercise increases gluconeogenesis and activates transcription of the hepatic phosphoenol pyruvate carboxykinase (PEPCK) gene. The mechanisms that regulate the transcriptional control of gene expression depend on the interaction of nuclear proteins with distinct DNA sequences. To determine the involvement with the liver-enriched transcription factor CCAAT/enhancer binding protein beta (C/EMP-beta) in the induction of PEPCK gene transcription during prolonged exercise or adenosine 3',5'-cyclic monophosphate (cAMP) treatment, we examined C/EBP-beta mRNA and nuclear protein concentrations, as well as C/EBP-beta binding to the PEPCK promoter at the cAMP response element (CRE)(-87/-74) and P3I (-248/-230) binding sites. The requirement of these DNA elements for exercise-induced stimulation of PEPCK gene expression was established in transgenic mice carrying -460 +/- 73 of the PEPCK promoter with a mutation in either the CRE or P3I binding domain linked to a bovine growth hormone (bGH) reporter gene. In mice carrying the intact promoter, prolonged exercise increased the concentration of liver bGH mRNA by 510% compared with an increase of only 270% in mice with a mutation in either the CRE or P3I site. Exercise or cAMP injection induced a 7.5- and 13-fold increase in nuclear C/EBP-beta protein, respectively. In electrophoretic mobility shift assays (EMSA), the total quantity of nuclear proteins bound to either oligomer was not altered by treatment. However, addition of C/EBP-beta antisera in the EMSA in a supershift assay indicated that liver nuclear extracts from exercised or cAMP-treated mice demonstrated significantly greater DNA binding due to C/EBP-beta (CRE: control 44.4 +/- 2.3%, exercise 56.7% +/- 2.2%, cAMP 54.5 +/- 3.6% of total binding, P < 0.001; P3I: control 35.8 +/- 2.5%, exercise 64.9 +/- 1.9%, cAMP 57.3 +/- 2.5% of total binding, P < 0.001). Taken together, these results suggest that exercise and cAMP treatment induce a transient increase in C/EBP-beta that may contribute to the molecular mechanism for signaling PEPCK gene transcription and increasing gluconeogenesis during exercise.

A metropolitan experience with infrainguinal revascularization. Operative risk and late results in northeastern Ohio.

Despite being of fundamental importance, the late results of major arterial reconstruction rarely have been documented throughout a large metropolitan area. In this study of 932 patients entered into the computer registry of the Cleveland Vascular Society, 19 surgeons representing 13 community hospitals and referral centers in Cleveland and Akron report the intermediate-term outcome during a mean interval of 35 months after infrainguinal lower extremity revascularization performed in northeastern Ohio from 1978 through 1982. Operative risk (5%), the early amputation rate (7%), and actuarial 5-year survival (48% to 55%) for patients with rest pain or tissue necrosis were significantly worse (p less than 0.05) than comparable figures (0.6%, 0%, and 77%, respectively) for others who underwent procedures for disabling claudication. Although both materials had similar success above the knee, the cumulative 3-year patency rate of autogenous vein bypass to the distal popliteal (69% to 88%; p less than 0.05) and tibioperoneal arteries (43%; 0.05 less than p less than 0.1) was superior to the results of polytetrafluoroethylene grafts (32% to 50% and 19%, respectively). Moreover, polytetrafluoroethylene grafts required reoperations at three times the rate of vein grafts to maintain limb salvage.

The early results of vascular surgery in patients 75 years of age and older: an analysis of 3259 cases.

The population in the United States older than 75 years of age will double by the year 2000. The computerized registry of The Cleveland Vascular Society includes 19,990 vascular procedures, which have been divided into two groups. Group A consists of 16,731 operations performed on patients younger than 75 years of age and group B consists of 3259 procedures performed on patients older than 75 years of age. The overall operative mortality rate in group A was 4.4% (736 of 16,731). In subsets of group B the mortality rates were: age 75 to 79 years, 11.3% (210 of 1862), age 80 to 84 years, 13.4% (125 of 932), age 85 to 89 years, 18.0% (68 of 376), and age 90 to 98 years, 28.1% (25 of 89). In carotid endarterectomy there were no significant differences in the stroke and operative mortality rates when groups A and B were compared. Group A stroke rate was 1.8% (94 of 5220), operative mortality rate was 1.5% (77 of 5220); group B stroke rate was 2.2% (17 of 782) and the mortality rate was 2.3% (18 of 782). For aortic reconstructions group A mortality rate was 7.1% (276 of 3905); group B operative mortality rate was 24.1% (148 of 615) (p less than 0.001). In femoropopliteal reconstructions group A operative mortality rate was 2.2% (55 of 2377) and group B mortality rate was 6.7% (38 of 571) (p less than 0.0001). For lower extremity thromboembolectomy group A operative mortality rate was 14.3% (113 of 789) and the mortality rate for group B was 28.4% (196 of 689) (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis of naturally occurring Fasciola hepatica infections in cattle with an enzyme-linked immunosorbent assay.

Sera from 100 herds of cattle located in the state of Washington were examined with an enzyme-linked immunosorbent assay for antibody to Fasciola hepatica in a screening procedure that included 5 to 10 samples/herd. Twenty-eight herds contained infected cattle and F hepatica was most prevalent in 3 distinct geographic areas. Subsequent retesting of all sera available from 14 herds (mean of 109 samples/herd) revealed that the screening procedure correctly detected 7 of 7 operations in which greater than 40% of samples were positive or suspect and 3 of 3 operations in which 12% to 13% of the samples were positive or suspect. One of 3 herds considered negative after screening was found to contain a few (7%) positive samples and 1 herd considered possibly infected was negative on retest. These results were compared with those obtained by fecal examination for F hepatica eggs in 9 of the 14 herds. A good correlation (5 of 5) was found in which a high percentage (48% to 85%) of sera were positive or suspect. Fasciola eggs were not found in samples from 2 herds with few (7% to 12%) positive or suspect sera or in 2 herds that were negative by an enzyme-linked immunosorbent assay.

The risk of vascular surgery in a metropolitan community. With observations on surgeon experience and hospital size.

From 1978 through 1981 complete perioperative information concerning a total of 10,189 peripheral vascular procedures performed in northeastern Ohio was recorded in the computer registry of The Cleveland Vascular Society. This report is an analysis of mortality and morbidity rates for all 5686 operations involving carotid endarterectomy (N = 2646), lower extremity revascularization (N = 1987), and abdominal aortic aneurysm resection (N = 1053). The operative mortality rate was 1.2% for carotid reconstruction, 2.8% for femoropopliteal or distal bypass, 3.5% for aortofemoral revascularization, and 11.9% for aortic aneurysm resection (elective operations 6.5%; emergency operations 32.9%). Postoperative strokes occurred after endarterectomy in 2.7% of patients having preoperative neurologic symptoms and in 2.0% of those with asymptomatic carotid stenosis. Lower extremity amputation was unavoidable in 1.5% of patients after aortofemoral reconstruction and in 6.0% after femoropopliteal or distal bypass. Statistical testing indicated that the operative mortality rate was not related to the respective size of the 27 hospitals involved in the survey. The relative annual experience of the 29 participating surgeons significantly influenced only the mortality rate of elective aneurysm resection and the amputation rate after femoropopliteal or distal revascularization. This study suggests that the results of major arterial reconstruction in metropolitan areas may be expected to be comparable to those of published series if the responsible surgeons are specifically trained and maintain an active interest in the field of vascular surgery.

Experimentally induced Fasciola hepatica infection in young calves.

Twenty-four calves between 1 and 66 days of age (allotted to 3 age groups) were each inoculated with 100 Fasciola hepatica metacercariae to determine their susceptibility to fluke infection. Studies included measuring the immune response, as determined by enzyme-linked immunosorbent assay, fecal egg counts (to evaluate the length of the life cycle between times of metacercariae ingestion and fluke maturation), and the numbers of flukes in the liver of the calves at slaughter. Fasciola hepatica ova started appearing in the feces of calves, all ages, at 60 days after inoculations were done and reached average maximal number by 80 to 90 days. The enzyme-linked immunosorbent assay results indicated that the oldest group of calves had significantly (P less than 0.01) greater antibody concentration from 6 weeks until the 18th to 20th week after inoculation than did the 2 younger groups. At slaughter, calves in the 52- to 66-day age group had mean fluke numbers significantly (P less than 0.01) greater than did calves in the 1- to 27-day and 35- to 44-day age groups.

An enzyme-linked immunosorbent assay for diagnosis of Fasciola hepatica infection in cattle.

An enzyme-linked immunosorbent assay (ELISA) was investigated for the diagnosis of Fasciola hepatica infection in cattle. Studies included examination of 4 antigen preparations: freshly collected fluke antigen (FFA), dead fluke antigen (DFA), lyophilized fluke antigen (LFA), and partially purified antigen (PPA) for activity and use of an ELISA with FFA and LFA for diagnosis of experimentally and naturally occurring fascioliasis in cattle. The ELISA, using FFA, detected F hepatica antibody in calves as early as 4 weeks after exposure to this parasite. The DFA exhibited slightly less activity, and LFA did not have diagnostic value until 9 to 10 weeks after exposure. The PPA produced high background readings with noninfected control sera and was not considered sufficiently specific for further use. The long incubation and short incubation ELISA procedures can be used for diagnostic work. Both were equally sensitive, with optical density readings of known positive sera routinely 2.5 times those of sera from normal controls. The repeatability of these tests was also excellent, and only slight variation in optical density was observed in ELISA was performed on representative known positive and negative sera with similar reagents in replicate tests.

Efficacy of avermectin B1a for treatment of experimentally induced nematode infections in cattle.

Two formulations of avermectin B1a, C-076 and MK-933, were examined for anthelmintic activity in two trials, each using 20 calves with experimentally produced nematode infections. In one trial, C-076 was given orally, and in the other trial, MK-933 was given by injection at dosages of 50, 100, and 200 micrograms/kg of body weight. Treated calves were held for 7 to 8 days and then, together with nontreated controls, were euthanatized and were examined for nematodes in their gastrointestinal tracts and lungs. Efficacy of C-076 approached 100% for Dictyocaulus viviparus, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, and Oesophagostomum radiatum at 50 micrograms/kg. A dosage level of 100 micrograms/kg was required to achieve 97% efficacy against Cooperia punctata. Efficacy of MK-933 at 50 micrograms/kg was variable, but at 100 micrograms/kg, it approached 100% for D viviparus, O ostertagi, Haemonchus placei, T axei, and T longispicularis. Activity against C oncophora was less, reaching 80% efficacy at 200 micrograms/kg.

Efficacy of albendazole for treatment of naturally acquired nematode infections in Washington cattle.

Albendazole, methyl 5-propylthio-1H-benzimidazol-2-yl carbamate, was given as a bolus (7.68 to 8.18 mg/kg of body weight) to cattle naturally infected with gastrointestinal nematodes and lungworms in a controlled trial. Over 99% of adult Ostertagia ostertagi, Trichostrongylus longispicularis, Cooperia oncophora, Nematodirus helvetianus, and Dictyocaulus viviparus were removed by the treatment. Efficacy against immature O ostertagi, early fourth-stage O ostertagi, and Oesophagostomum radiatum was 95.2%, 86.6%, and 96.7%, respectively. In a field trial, the same compound administered in a paste formulation (at approximately 7.5 mg/kg) eliminated over 99% of strongylin and Moniezia eggs from feces of treated cattle.