Relationship between plasma leptin and zinc levels and the effect of insulin and oxidative stress on leptin levels in obese diabetic patients

Leptin is thought to be a lipostatic signal that contributes to body weight regulation. Zinc plays an important role in appetite regulation also. Our aim is to evaluate the relationship between leptin and zinc in obese and nonobese type 2 diabetic patients and its relationship with oxidative stress and insulin. We studied 25 nonobese nondiabetic women (controls); 35 nonobese diabetic women; and 45 obese diabetic women. Plasma leptin concentration was determined by immunoradiometric assay. Thiobarbituric acid reactive substances (TBARS), markers of oxidative stress, were assayed by the spectrofotometric method. Plasma levels of zinc and insulin were measured by atomic absorption spectrophotometer and electrochemiluminescence methods, respectively. We found that nonobese diabetic patients had significantly lower zinc and higher TBARS levels than control subjects (P<0.01). There was no difference in plasma leptin levels between nonobese diabetic subjects and controls. Obese diabetic subjects had significantly higher plasma leptin, TBARS, and insulin levels and significantly lower plasma zinc levels than nonobese diabetic subjects (for each comparison; P<0.01). The univariate and multivariate analyses demonstrated a significant positive correlation between leptin and body mass index (P<0.01) and insulin (P<0.01), and a significant negative correlation between leptin and zinc in obese subjects. Additionally, TBARS levels was positive correlated with insulin and negative correlated with zinc in obese diabetic subjects. We conclude that zinc may be a mediator of the effects of leptin, although the detailed mechanism is still unknown and requires further investigation. Free radical induced mechanism(s) may be involved in this process.     

Skeletal muscle contraction stimulates capillary recruitment and glucose uptake in insulin-resistant obese Zucker rats

Exercise and insulin increase muscle glucose uptake by different mechanisms and also increase capillary recruitment, which is proposed to facilitate access for hormones and nutrients. The genetically obese Zucker rat shows impaired insulin- but not contraction-mediated glucose uptake in muscle. Recently, we have shown the genetically obese Zucker rats to have impaired insulin-mediated capillary recruitment and proposed that this contributes to the insulin resistance of muscle in vivo. Because this might imply a general loss of recruitable capillaries, we now assess responses to contraction in muscles of 18 +/- 3-wk-old lean and obese Zucker rats in vivo. Field stimulation (2 Hz, 0.1 ms) was conducted for 1 h on one leg of anesthetized instrumented rats, and measurements were made of femoral blood flow (FBF), heart rate (HR), blood pressure (BP), hindleg metabolism of 1-methylxanthine (a measure of capillary recruitment), hindleg glucose uptake (HGU), and lower leg muscle glucose uptake by 2-deoxyglucose (R'g). Lean animals (311 +/- 9 g) developed tension at 219 +/- 27 g/g muscle with no change in BP but with significant increases in HR, FBF, HGU, 1-MX metabolism, and R'g (P < 0.05), compared with nonstimulated control leans. Obese animals (469 +/- 7 g) developed tension at 265 +/- 31 g/g muscle with no change in HR or BP but with significant increases in FBF, HGU, 1-MX metabolism, and R'g (P < 0.05) compared with nonstimulated control obese rats. Muscle contraction of lean animals led to a greater increase in lower leg R'g, similar responses in HGU and 1-MX, and a smaller increase in FBF than in obese animals. A tight correlation between FBF and capillary recruitment was noted for all data (P < 0.001). It is concluded that contraction-mediated muscle capillary recruitment and glucose uptake are essentially normal in the obese Zucker rat and that control of FBF and capillary recruitment in exercise is closely linked.     

TNF-alpha acutely inhibits vascular effects of physiological but not high insulin or contraction

TNF-alpha is elevated in many states of insulin resistance, and acutely administered TNF-alpha in vivo inhibits insulin-mediated hemodynamic effects and glucose uptake in muscle. In this study, we assess whether the inhibitory effects of TNF-alpha are affected by insulin dose or muscle contraction. Whole body glucose infusion rate (GIR), femoral blood flow (FBF), hindleg vascular resistance, hindleg glucose uptake (HGU), 2-deoxyglucose uptake into muscles of the lower leg (R'g) and hindleg metabolism of infused 1-methylxanthine (1-MX), a measure of capillary recruitment, were determined. Three groups were studied with and without infusion of TNF-alpha: euglycemic insulin-clamped, one-leg field-stimulated (2 Hz, 0.1 ms at 30 V), and saline-infused control anesthetized rats. Insulin infusions were 3, 10, or 30 mU x kg-1 x min-1 for 2 h x 1-MX metabolism was maximally increased by all three doses of insulin. GIR, HGU, and R'g were maximal at 10 mU and FBF was maximal at 30 mU of insulin. Contraction increased FBF, HGU, and 1-MX. TNF-alpha (0.5 microg x kg-1 x h-1) totally blocked the 3 and 10 mU insulin-mediated increases in FBF and 1-MX, and partly blocked GIR, HGU, and R'g. None of the increases due to twitch contraction was affected by TNF-alpha, and only the increase in FBF due to 30 mU of insulin was partly affected. We conclude that muscle capillary recruitment and glucose uptake due to high levels of insulin or muscle contraction under twitch stimuli at 2 Hz are resistant to TNF-alpha. These findings may have implications for ameliorating muscle insulin resistance resulting from increased plasma TNF-alpha and for the differing mechanisms by which contraction and insulin recruit capillary flow in muscle.     

Hinokitiol, a metal chelator derived from natural plants, suppresses cell growth and disrupts androgen receptor signaling in prostate carcinoma cell lines

Diabetic patients are often treated with a lipid lowering statin and an ACE inhibitor or angiotensin receptor antagonist against hypertension or albuminuria. These drugs may also improve glucose tolerance, but the mechanism for this remains elusive. We now studied whether these drugs and the fatty acid palmitate influence insulin secretion in vivo in rats through effects on islet blood perfusion. Whole pancreatic blood flow was markedly increased by captopril and irbesartan, and decreased by palmitate. Islet blood flow was significantly and preferentially enhanced by captopril, irbesartan, and pravastatin, and suppressed by palmitate. Both captopril and irbesartan raised serum insulin concentrations significantly. However, glycemia was not affected in any group. In conclusion, the present study suggests that a local pancreatic RAS and pravastatin may be selectively controlling pancreatic islet blood flow and thereby influencing insulin secretion. The antidiabetic actions of statins and RAS inhibitors might in part occur through the beneficial direct islet effects shown here. Conversely, free fatty acids that are elevated in type 2 diabetic patients may contribute to an impaired nutritive islet blood flow and thereby further aggravate the diabetic state by limiting the supply of insulin needed to curb hyperglycemia.     

Seven days of aerobic exercise training improves conduit artery blood flow following glucose ingestion in patients with type 2 diabetes

The vasodilatory effects of insulin account for up to 40% of insulin-mediated glucose disposal; however, insulin-stimulated vasodilation is impaired in individuals with type 2 diabetes, limiting perfusion and delivery of glucose and insulin to target tissues. To determine whether exercise training improves conduit artery blood flow following glucose ingestion, a stimulus for increasing circulating insulin, we assessed femoral blood flow (FBF; Doppler ultrasound) during an oral glucose tolerance test (OGTT; 75 g glucose) in 11 overweight or obese (body mass index, 34 ± 1 kg/m2), sedentary (peak oxygen consumption, 23 ± 1 ml·kg?1·min?1) individuals (53 ± 2 yr) with non-insulin-dependent type 2 diabetes (HbA1c, 6.63 ± 0.18%) before and after 7 days of supervised treadmill and cycling exercise (60 min/day, 60-75% heart rate reserve). Fasting glucose, insulin, and FBF were not significantly different after 7 days of exercise, nor were glucose or insulin responses to the OGTT. However, estimates of whole body insulin sensitivity (Matsuda insulin sensitivity index) increased (P < 0.05). Before exercise training, FBF did not change significantly during the OGTT (1 ± 7, -7 ± 5, 0 ± 6, and 0 ± 5% of fasting FBF at 75, 90, 105, and 120 min, respectively). In contrast, after exercise training, FBF increased by 33 ± 9, 39 ± 14, 34 ± 7, and 48 ± 18% above fasting levels at 75, 90, 105, and 120 min, respectively (P < 0.05 vs. corresponding preexercise time points). Additionally, postprandial glucose responses to a standardized breakfast meal consumed under "free-living" conditions decreased during the final 3 days of exercise (P < 0.05). In conclusion, 7 days of aerobic exercise training improves conduit artery blood flow during an OGTT in individuals with type 2 diabetes.     

Chronic and acute effects of different antihypertensive drugs on femoral artery relaxation of L-NAME hypertensive rats

We aimed to compare the effects of chronic and acute administration of structurally different antihypertensives, diuretics - indapamide and hydrochlorothiazide, ACE inhibitor - captopril and indapamide+captopril combination on endothelium-dependent relaxation of femoral artery isolated from nitric oxide (NO)-deficient rats. In the chronic experiment, femoral artery was isolated from Wistar rats receiving L-NAME (40 mg/kg/day) solely or with indapamide (1 mg/kg/day), hydrochlorothiazide (10 mg/kg/day), captopril (10 mg/kg/day), and indapamide+captopril combination for seven weeks. In the acute in vitro experiment, the incubation medium with femoral artery isolated from L-NAME-hypertensive rats was supplemented with investigated antihypertensives in the same concentration 10(-4) mol/l. Interestingly, chronic L-NAME treatment did not cause a reduction of vasorelaxation. Indapamide+captopril elevated relaxation above the control level and completely prevented blood pressure increase induced by L-NAME. Acute incubation with captopril only or indapamide+captopril improved relaxation of femoral artery isolated from L-NAME-hypertensive rats, while the incubation with all antihypertensives increased vasorelaxation of femoral artery isolated from control Wistar rats. In conclusion, NO might be involved in the indapamide- and hydrochlorothiazide-induced improvement of vasorelaxation, while different vasorelaxing factors (prostacyclin, EDHF) contribute to the captopril-induced improvement of vasorelaxation. During the chronic treatment additive and synergic effects of indapamide and captopril may contribute to the prevention of hypertension and increase of vasorelaxation.     

Changes in feeding level during early pregnancy affect fertility in gilts

Modified feeding combining the benefits of restricted feeding after ovulation and abundant feeding during implantation in autumn was tested. Three groups of eight gilts were housed with individual feeding stalls and fed 40 MJ per day of a commercial ration. Following insemination gilts were fed 27 MJ per day (LLL) or 54 MJ per day (HHH) for 34 days or 27 MJ per day for 10 days, 54 MJ per day for 7 days followed by 27 MJ per day until day 34 (LHL). Blood for progesterone analysis was collected daily during the week of ovulation and then twice a week until the end of the study. For LH assay, blood was collected from five gilts from each group at 15 min interval for 10 h on the day 15 of pregnancy. Gilts were weighed three times at intervals of 4 weeks. The effect of dietary treatment was significant (P<0.05) on body weight gain from days 0 to 30 of pregnancy, 1201, 287 and 438 g per day for groups HHH, LLL and LHL respectively. The pregnancy rate at day 34 was significantly higher (P<0.005) in HHH-group (100%) compared with LLL (25%) and LHL (38%) although HHH group had significantly lower (P<0.05) progesterone concentration on days 9 and 12. The basal LH level was significantly higher (P<0.01) in HHH group compared to LHL group (mean±S.D.) (0.98±0.22 and 0.60±0.08, respectively). Gilts in HHH group had a significantly higher mean LH concentration (1.18±0.24) than those in group LHL (0.7±0.07) (P<0.05), but not in group LLL (0.93±0.15) (P=0.09). There was a tendency (P=0.058) for amplitude to be higher for gilts in HHH group. The LHL feeding strategy did not provide the benefits anticipated. Instead, it was the HHH feeding strategy that provided a disfinct advantage in pregnancy rate. The mechanism mediating supportive effect of high feeding level on the maintenance of early pregnancy is yet to be determined.     

Secretion of inflammatory mediators by isolated rat Kupffer cells: the effect of octreotide

Aims: We studied the production of inflammatory mediators by rat KC and the possible in vitro effect of the somatostatin analogue octreotide. Methods: Primary KC cultures were incubated with LPS added alone or with different concentrations of octreotide. The production of TNF, IL-6, IL-10, IL-12 and IL-13 was assessed in culture supernatants by ELISA and that of nitric oxide (NO) by a modification of the Griess reaction. Results: Isolated KC produced a basal amount of TNF, IL-6, IL-12, IL-13, and NO but not IL-10. LPS-stimulated KC secreted significantly increased amounts of TNF (P<0.001), IL-6 (P<0.01), IL-10 (P<0.001), IL-12 (P<0.01), and NO (P<0.001) whereas IL-13 production remained constant. Octreotide reduced IL-12 (P<0.05) and increased IL-13 (P<0.05) production by unstimulated KC. Furthermore, octreotide suppressed TNF production (P<0.05), without modifying TNF mRNA expression and decreased iNOS expression and NO (P≈0.05) production by LPS-activated KC. These effects were reversed with Wortmannin pre-treatment suggesting that octreotide may act via interference with phosphatidylinositol 3-kinase pathways. Conclusions: These data demonstrate that KC is a source of multiple inflammatory mediators, indicating a critical role in liver inflammatory disorders. Octreotide modulates inflammatory mediator production by isolated KC, suggesting that it might have immunoregulatory and anti-inflammatory effects in liver diseases.     

Postprandial Vascular Reactivity in Obese and Normal Weight Young Adults

As humans spend a significant amount of time in the postprandial state, we examined whether vascular reactivity (a key indicator of cardiovascular health) was different after a high‐fat meal in 11 obese (median BMI 46.4, age 32.1 ± 6.3 years, 7 men) and 11 normal weight (median BMI 22.6) age‐ and sex‐matched controls. At baseline and 1 and 3 h postmeal, blood pressure (BP), heart rate (HR), reactive hyperemia peripheral artery tonometry (RH‐PAT) index, radial augmentation index adjusted for HR (AIx75), brachial pulse wave velocity (PWV_b), glucose, insulin, total and high‐density lipoprotein (HDL) cholesterol, and triglycerides were measured. Brachial flow‐mediated dilatation (FMD) and, by venous plethysmography, resting and hyperemic forearm blood flows (FBFs) were measured at baseline and 3 h. At baseline, obese subjects had higher systolic BP, HR, resting FBF, insulin and equivalent FMD, RH‐PAT, hyperemic FBF, AIx75, PWV_b, glucose, total cholesterol, triglycerides, and lower HDL cholesterol. In obese and lean subjects, FMD at baseline and 3 h was not significantly different (6.2 ± 1.7 to 5.8 ± 4.3% for obese and 4.7 ± 4.1 to 4.3 ± 3.9% for normal weight, P = 0.975 for group × time). The meal did not produce significant changes in RH‐PAT, hyperemic FBF, and PWV_b in either group (P > 0.1 for the effect of time and for group × time interactions). In conclusion, the vascular responses to a high‐fat meal are similar in obese and normal weight young adults. An exaggerated alteration in postprandial vascular reactivity is thus unlikely to contribute importantly to the increased cardiovascular risk of obesity.     

Vitamin C prevents hyperoxia-mediated vasoconstriction and impairment of endothelium-dependent vasodilation

High arterial blood oxygen tension increases vascular resistance, possibly related to an interaction between reactive oxygen species and endothelium-derived vasoactive factors. Vitamin C is a potent antioxidant capable of reversing endothelial dysfunction due to increased oxidant stress. We tested the hypotheses that hyperoxic vasoconstriction would be prevented by vitamin C, and that acetylcholine-mediated vasodilation would be blunted by hyperoxia and restored by vitamin C. Venous occlusion strain gauge plethysmography was used to measure forearm blood flow (FBF) in 11 healthy subjects and 15 congestive heart failure (CHF) patients, a population characterized by endothelial dysfunction and oxidative stress. The effect of hyperoxia on FBF and derived forearm vascular resistance (FVR) at rest and in response to intra-arterial acetylcholine was recorded. In both healthy subjects and CHF patients, hyperoxia-mediated increases in basal FVR were prevented by the coinfusion of vitamin C. In healthy subjects, hyperoxia impaired the acetylcholine-mediated increase in FBF, an effect also prevented by vitamin C. In contrast, hyperoxia had no effect on verapamil-mediated increases in FBF. In CHF patients, hyperoxia did not affect FBF responses to acetylcholine or verapamil. The addition of vitamin C during hyperoxia augmented FBF responses to acetylcholine. These results suggest that hyperoxic vasoconstriction is mediated by oxidative stress. Moreover, hyperoxia impairs acetylcholine-mediated vasodilation in the setting of intact endothelial function. These effects of hyperoxia are prevented by vitamin C, providing evidence that hyperoxia-derived free radicals impair the activity of endothelium-derived vasoactive factors.     

The Role of Lumbar Sympathetic Nerves in Regulation of Blood Flow to Skeletal Muscle during Anaphylactic Hypotension in Anesthetized Rats

During hypovolemic shock, skeletal muscle blood flow could be redistributed to vital organs via vasoconstriction in part evoked by activation of the innervating sympathetic nerve activity. However, it is not well known whether this mechanism operates during anaphylactic shock. We determined the femoral artery blood flow (FBF) and lumbar sympathetic nerve activity (LSNA) mainly regulating the hindquater muscle blood flow during anaphylactic hypotension in anesthetized rats. Anesthetized Sprague-Dawley rats were randomly allocated to the following groups (n = 7/group): (1) non-sensitized, (2) anaphylaxis, (3) anaphylaxis-lumbar sympathectomy (LS) and (4) anaphylaxis-sinoaortic denervation (SAD) groups. Anaphylaxis was induced by an intravenous injection of the ovalbumin antigen to the sensitized rats. The systemic arterial pressure (SAP), heart rate (HR), central venous pressure (CVP), FBF and LSNA were continuously measured. In the anaphylaxis group, LSNA and HR increased, while SAP and FBF decreased after antigen injection. In the anaphylaxis-SAD group, LSNA did not significantly change during the early phase, but the responses of SAP and FBF were similar to those in the anaphylaxis group. In the anaphylaxis-LS group, both FBF and SAP decreased similarly to the anaphylaxis group during anaphylactic hypotension. These results indicated that LSNA increased via baroreceptor reflex, but this sympathoexcitation or LS did not affect antigen-induced decreases in FBF or SAP. Lumbar sympathetic nerves are not involved in regulation of the blood flow to the hindlimb or systemic blood pressure during anaphylactic hypotension in anesthetized rats.     

Sucking behaviour of dairy calves fed milk ad libitum by bucket or teat

The milk intake and sucking behaviour of Dutch and Holstein-Friesian crossbred calves fed milk replacer ad libitum by either the bucket method (n=8) or an artificial teat (n=6) were compared. The animals were observed for 3 weeks from the age of 2 weeks, penned individually and all provided with a “dummy” (artificial) teat near the milk source within the pen.

The teat-fed calves ingested significantly more milk than the bucket-fed calves (11.9 vs. 8.0 kg/day; P<0.05), and this intake took much longer (44.2 vs. 17.7 min/day; P<0.05). In both treatment groups, milk intake was organized in “meals”. The meal criterion, separating the withinmeal and between-meal non-feeding intervals, was set at 5 min. Frequency of meals and daily total meal duration did not differ significantly. Meals occurred rather randomly throughout a 24-h period.

On average, the dummy teat was used for 13 min per day by bucket-fed calves, but for only 1 min by teat-fed calves (P<0.05). Sucking of the dummy teat was largely clustered within the meal periods.

It is concluded that in the young calf a need for sucking exists independently of milk satiation. However, the level of satiation depends on whether the calf drinks or sucks the milk. Nutritive sucking is clearly more reinforcing than non-nutritive sucking.     

Coincident increases in oxytocin receptor expression and EMG responsiveness to oxytocin in the ovine cervix at oestrus

This study has localised oxytocin receptor (OTR) mRNA expression within the cervix of non-pregnant ewes and related this to changes in the sensitivity of the cervical musculature to administered oxytocin (OT) during the oestrous cycle by recording electromyographic (EMG) activity. Cervices were collected from 34 ewes at specified time points throughout the cycle. OTR mRNA expression was localised by in situ hybridisation and results were expressed as optical density measurements from autoradiographs in each of four different cervical regions. EMG recordings were made for up to 8 h per day from four non-pregnant ewes undergoing seasonal oestrous cycles between Days −3 and +3 relative to oestrus (Day 0). The highest concentrations of OTR mRNA were detectable within the luminal epithelium (LE) of the cervix, with values increasing from Day 15 of the cycle, peaking during the follicular phase (P<0.001, compared to the mid-luteal phase) and returning to basal by Day 2. There was a small but significant increase in OTR mRNA hybridisation (above basal/luteal phase values) within the stromal cells (STR) adjacent to the lumen (P<0.05) during the same time period, but no differences from basal values were detectable in the dense collagenous annular ring or in tissue superficial to this. Analysis of pooled EMG activity recorded daily from the cervix indicated that endogenous contractile activity was higher on Day 0 than on the Days +1 (P<0.05), −2, +2 and +3 (P<0.001). The response to bolus intravenous (i.v.) injections of 25 mU OT (25 mU) varied with day of the cycle. This dose produced a measurable and significant response on Days 0 (P<0.001) and +1 (P<0.001), but not on any of the other days, indicating that the sensitivity of the cervical musculature to OT peaked on these days. These data show that the cervix is highly responsive to OT at oestrus. This coincides with an increase in OTR mRNA expression in the luminal epithelial cells, suggesting the likely production of an intermediary messenger between the epithelial and smooth muscle cells.     

Modifications in the aggressive and ingestive behavior of the neonatal piglet as a result of prenatal elevation of cortisol in the dam

Ninety-eight piglets from 10 sows were used to study their neonatal agonistic and ingestive behavior after stimulation of the preparturient sow with adrenocorticotrophic hormone (ACTH). The sows were randomly assigned to either an ACTH or a control group on the 104th day of gestation. Sows in the ACTH group were catheterized and infused with 1IU porcine ACTH kg⁻¹ day⁻¹ in 1 l of saline. Control sows were similarly catheterized and infused with the same volume of saline, both treatments being maintained until parturition. A blood sample was collected daily from all sows. At birth piglets were weighed, bled and freed in the rear of the farrowing crate. They were then observed for the first 6 h of life to record their birth to suckle (BTS) interval. At the same time all instigator and victim interactions were recorded. Three subsequent blood samples were then collected from the piglets at 2, 4 and 6 h of life, and analyzed for glucose and cortisol. In both groups the concentration of plasma cortisol proved to be decreased (P<0.05) after birth while glucose increased within 2 h. The total number of instigations observed was higher (P<0.05) in pigs born to control sows than in those born to ACTH-treated sows. When values were expressed as instigations per pig or number of instigations relative to the total number of possible interactions within the litter, piglets of the ACTH group also exhibited less (P<0.05) aggressive instigations than those born to the control sows. Victimizations were not influenced either by treatment or sex. ACTH pigs had slightly shorter BTS intervals (P<0.05) than those in the control group. Females were lighter (P<0.05) than males at birth but they took less time to suckle than males. Accordingly it is concluded that the prenatal treatment of the sows with ACTH reduces the rate of agonistic interactions and tends to reduce the time required for first-time successful suckling.     

Gemfibrozil treatment is associated with elevated adrenal androgen, androstanediol glucuronide and cortisol levels in dyslipidemic men

We have investigated the role of steroid hormones as coronary risk factors in Helsinki Heart Study population of dyslipidemic middle-aged men. We compare here the effects of gemfibrozil and placebo on the serum levels of dehydroepiandrosterone (DHEA), its sulfate (DHEAS), their metabolite androstanediol glucuronide (3-AdiolG), androstenedione, cortisol, testosterone, and sex-hormone binding globulin (SHBG) in non-smokers. We also examined the associations between steroid and lipoprotein levels in both treatment groups. Compared with placebo gemfibrozil treatment was associated with significant elevations of the mean levels of DHEA 10.2 vs 8.0 nmol/1; P<0.005, of DHEAS 8.0 vs 5.8 μmol/1; P<0.001, of 3AdiolG 18.3 vs 8.4 nmol/1; P<0.001, of androstenedione 5.7 vs 5.1 nmol/1; P<0.02, and of cortisol 426 vs 358 nmol/1; P<0.001. The mean SHBG levels decreased from 46.4 to 41.7 nmol/1; P=0.03 with gemfibrozil treatment. No difference was found in testosterone levels 17.7 vs 18.8 nmol/1; P=0.11, or the ratio of testosterone/SHBG 0.45 vs 0.43; P=0.23. Positive correlations were found between high density lipoprotein-cholesterol and DHEAS (r=0.267; P<0.01) and DHEA (r=0.282; P<0.01) levels and negative correlations between low density lipoprotein-cholesterol and 3-AdiolG (r=−0.400; P<0.001) and cortisol (r=−0.281; P<0.01) levels in the gemfibozil group. Our results indicate that gemfibrozil treatment increases the production and turnover of adrenal androgens and cortisol, and suggest that activation of the adrenocorticol function and increased metabolism of androgens are related to the improved lipoprotein pattern during gemfibrozil treatment.     

Enhanced endothelin-1 system activity with overweight and obesity

Endothelin (ET)-1-mediated vasoconstrictor tone contributes to the development and progression of several adiposity-related conditions, including hypertension and atherosclerotic vascular disease. The aims of the present study were to determine 1) whether endogenous ET-1 vasoconstrictor activity is elevated in overweight and obese adults, and, if so, 2) whether increased ET-1-mediated vasoconstriction contributes to the adiposity-related impairment in endothelium-dependent vasodilation. Seventy-nine adults were studied: 34 normal weight [body mass index (BMI) < 25 kg/m(2)], 22 overweight (BMI ≥ 25 and < 30 kg/m(2)), and 23 obese (BMI ≥ 30 kg/m(2)). Forearm blood flow (FBF) responses to intra-arterial infusion of ET-1 (5 pmol/min for 20 min) and selective ET-1 receptor blockade (BQ-123, 100 nmol/min for 60 min) were determined. In a subset of the study population, FBF responses to ACh (4.0, 8.0, and 16.0 μg·100 ml tissue(-1)·min(-1)) were measured in the absence and presence of selective ET-1 receptor blockade. The vasoconstrictor response to ET-1 was significantly blunted in overweight and obese adults (～ 70%) compared with normal weight adults. Selective ET-1 receptor blockade elicited a significant vasodilator response (～ 20%) in overweight and obese adults but did not alter FBF in normal weight adults. Coinfusion of BQ-123 did not affect FBF responses to ACh in normal weight adults but resulted in an ～ 20% increase (P < 0.05) in ACh-induced vasodilation in overweight and obese adults. These results demonstrate that overweight and obesity are associated with enhanced ET-1-mediated vasoconstriction that contributes to endothelial vasodilator dysfunction and may play a role in the increased prevalence of hypertension with increased adiposity.     

A method to reduce the invasiveness of fetal catheterization in the cow

Surgical intervention in general anesthesia (GA) of the cow in late gestation is a stressful condition for both mother and fetus, potentially leading to premature delivery or fetal death. The present study hypothesized that fetal catheterization at days 246–253 (90% of gestation) is done with less physical and metabolic stress for the mother and fetus, when the surgery is performed on a standing cow and local anesthesia (LA) rather than on a recumbent cow in general anesthesia. Fetal and uterine maternal intra-vascular catheters were implanted during general anesthesia (GA, n=24) or local analgesia (LA, n=7). Blood gases and metabolite levels in the fetal calves and their mothers were measured during surgery and for 5 days post-operatively. During surgery, venous blood pH was higher (7.44±0.01 versus 7.39±0.01, P<0.05) and hemoglobin and oxygen contents lower in LA cows compared with GA cows (9.3±0.3 mg/dl versus 11.8±0.2 mg/dl, P<0.001 and 10.1±0.3 ml/dl versus 12.6±0.6 ml/dl, P<0.05). The differences between the two groups of fetuses reflected those of their dams in that LA fetuses showed lower arterial oxygen pressure (18.3±1.4 mmHg versus 24.8±1.4 mmHg, P<0.05) and hemoglobin (7.81±0.30 mg/dl versus 9.22±0.21 mg/dl P<0.01) and furthermore, they also showed higher blood glucose (2.4±0.2 mM versus 1.4±0.1 mM, P<0.01). During the 5 days post-surgery, 10 GA fetuses (42%) and 1 LA fetus (14%) died in utero. Bacterial contamination was implicated in six of the GA deaths and in the one LA death. In the dams with surviving calves, differences in hemoglobin (9.49±0.21 mg/dl versus 11.17±0.23 mg/dl P<0.001) and O₂ct (10.9±0.3 ml/dl versus 12.5±0.5 ml/dl, P<0.05) were still present, and in addition, blood glucose was higher in LA versus GA cows (4.3±0.2 mM versus 3.8±0.1 mM, P<0.05). The choice of surgical method did not affect post-surgery blood chemistry in the surviving fetuses, except that the higher blood glucose in the LA fetuses at surgery tended to be maintained also post-operatively (2.0±0.2 mM versus 1.5±0.1 mM, P=0.07). The observed differences in blood chemistry parameters between the two methods of surgery and possibly in the fetal death may be explained by differences in catheterization method and the associated differences in physical and metabolic stress during and after surgery. Thus, surgery upon a standing cow in local anesthesia should be considered as an alternative to surgery in universal anesthesia for fetal catheterization in the cow in late gestation.     

Effect of superovulation on maternal serum progesterone concentration, uterine and fetal weights at weeks 7 and 15 of pregnancy in Javanese Thin-Tail ewes

Twenty-one pregnant ewe lambs (nine superovulated and 12 non-superovulated) were used to study the effects of superovulation (injecting 700 IU PMSG at the end of diestrus) on maternal serum progesterone concentrations, uterine and fetal weights at weeks 7 and 15 of pregnancy. In the ewes sacrificed at week 7 of pregnancy, superovulation increased the mean number of corpora lutea (P<0.01), fetuses (P<0.01), maternal mean serum progesterone concentration (P<0.01), mean uterine weight (P<0.05), total fetal weight (P<0.01), and average fetal weight (P<0.01) by 133%, 69%, 354%, 66%, 150% and 40%, respectively, when compared to non-superovulated ewes. In the ewes sacrificed at week 15 of pregnancy, superovulation increased the number of corpora lutea (P<0.01), fetuses (P<0.05), maternal serum progesterone concentration (P<0.01), uterine weight (P<0.05), total fetal weight (P>0.05), and average fetal weight (P<0.05) by 207%, 20%, 84%, 37%, 29% and 24%, respectively, compared to those non-superovulated ewes. It was concluded that the increased number of corpora lutea and, therefore, their hormonal secretions by superovulation could increase uterine and fetal growth and development.     

Evaluation of muscle metaboreflex function through graded reduction in forearm blood flow during rhythmic handgrip exercise in humans

Hypoperfusion of active skeletal muscle elicits a reflex pressor response termed the muscle metaboreflex. Our aim was to determine the muscle metaboreflex threshold and gain in humans by creating an open-loop relationship between active muscle blood flow and hemodynamic responses during a rhythmic handgrip exercise. Eleven healthy subjects performed the exercise at 5 or 15% of maximal voluntary contraction (MVC) in random order. During the exercise, forearm blood flow (FBF), which was continuously measured using Doppler ultrasound, was reduced in five steps by manipulating the inner pressure of an occlusion cuff on the upper arm. The FBF at each level was maintained for 3 min. The initial reductions in FBF elicited no hemodynamic changes, but once FBF fell below a threshold, mean arterial blood pressure (MAP) and heart rate (HR) increased and total vascular conductance (TVC) decreased in a linear manner. The threshold FBF during the 15% MVC trial was significantly higher than during the 5% MVC trial. The gain was then estimated as the slope of the relationship between the hemodynamic responses and FBFs below the threshold. The gains for the MAP and TVC responses did not differ between workloads, but the gain for the HR response was greater in the 15% MVC trial. Our findings thus indicate that increasing the workload shifts the threshold for the muscle metaboreflex to higher blood flows without changing the gain of the reflex for the MAP and TVC responses, whereas it enhances the gain for the HR response.     

Postexercise responses of muscle sympathetic nerve activity and blood flow to hyperinsulinemia in humans.

Although insulin and exercise cause dramatic changes in physiological parameters, the impact of exercise on neural and hemodynamic responses to insulin administration has not been described. In a study of the effects of a single bout of exercise on blood pressure (BP), muscle sympathetic nerve activity (MSNA), and forearm blood flow (FBF) responses to insulin infusion during the postexercise period, 11 healthy men underwent, in a random order, two hyperinsulinemic euglycemic clamps performed after 45 min of 1) bicycle exercise (50% peak O(2) uptake, Exercise session) and 2) seated rest (Control session). Data were analyzed during baseline and steady-state periods. Although insulin levels and insulin sensitivity were similar, baseline plasma glucose levels were significantly lower in the Exercise than in the Control session. Mean BP was significantly lower (3%) and FBF was higher (27%) in the Exercise session. Exercise increased insulin-induced MSNA enhancement (84%) without changing FBF and BP responses to hyperinsulinemia. In conclusion, a single bout of exercise that does not alter insulin sensitivity exacerbates insulin-induced increase in MSNA without changing FBF and BP responses to hyperinsulinemia.