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Biomedical subjects

P E Jennings

Publications and source records attributed to P E Jennings.

At least 19 recordsLinked to original sources
PubMed2004

Orlistat is as beneficial as metformin in the treatment of polycystic ovarian syndrome.

The objective of this study was to evaluate and compare the effect of treatment with orlistat vs. metformin on the hormonal and biochemical features of patients with polycystic ovarian syndrome (PCOS). Twenty-one Caucasian women with PCOS [mean (+/-SEM) age 27 +/- 0.9 yr and body mass index 36.7 +/- 3.3 kg/m(2)] participated in this prospective, randomized, open-labeled study. All subjects had an 8-wk run-in period of dietary modification and then randomized to receive either metformin (500 mg three times daily) or orlistat (120 mg three times daily) for 3 months. Weight, blood pressure, and fasting blood samples were taken at screening, randomization, and on completion. Insulin resistance (IR) was calculated using the homeostasis model of assessment (HOMA)-IR method [HOMA-IR = (insulin x glucose)/22.5]. The results are expressed as mean +/- SEM. When compared with baseline, treatment with both orlistat [93.5 +/- 11.5 ng/dl (3.24 +/- 0.4 nmol/liter) vs. 114.5 +/- 11.5 ng/dl (3.97 +/- 0.4 nmol/liter), P = 0.039] and metformin [97.2 +/- 11.5 ng/dl (3.37 +/- 0.4 nmol/liter) vs. 120.0 +/- 8.7 ng/dl (4.16 +/- 0.3 nmol/liter), P = 0.048] produced a significant reduction in total testosterone. Treatment with orlistat produced a 4.69% reduction in weight (99.0 +/- 6.0 vs. 94.6 +/- 6.1 kg, P = 0.002), and this reduction was more significant than the reduction produced by metformin (4.69 vs. 1.02%, P = 0.006). There was no significant reduction seen after either treatment group for fasting insulin, HOMA-IR, SHBG, or any of the lipid parameters studied. In this study, orlistat produced a significant reduction in weight and total testosterone. The reduction in total testosterone was similar to that seen after treatment with metformin. Therefore, orlistat may prove to be a useful adjunct in the treatment of PCOS.

Adult↗
PubMed2003

The biological variation of testosterone and sex hormone-binding globulin (SHBG) in polycystic ovarian syndrome: implications for SHBG as a surrogate marker of insulin resistance.

This study was designed to assess the biological variability of total testosterone and SHBG in polycystic ovarian syndrome (PCOS) and to determine the use of SHBG as a surrogate marker of insulin resistance in PCOS. Fasting blood samples were collected at 4-d intervals on 10 consecutive occasions from 12 PCOS patients and 11 age- and weight-matched controls. Duplicate samples were analyzed for SHBG, testosterone, and insulin in a single batch, and insulin resistance was calculated by the homeostasis model assessment method (HOMA-IR). The PCOS group had higher testosterone (mean +/- SD, 3.9 +/- 0.8 vs. 3.2 +/- 1.3 nmol/liter; P = 0.001), lower SHBG (28.6 +/- 17.1 vs. 57.6 +/- 30.2 nmol/liter; P = 0.001), and greater HOMA-IR (5.85 +/- 5.3 vs. 1.67 +/- 0.63 U; P = 0.001) than the controls. In contrast to HOMA-IR (1.09 vs. 0.48 U; P = 0.001), the intraindividual variation in SHBG was lower in the PCOS group (mean, 3.4 vs. 6.3 nmol/liter; P = 0.041). The index of individuality for SHBG and testosterone in PCOS was 0.49 and 0.69, respectively. This study shows that for patients with PCOS, SHBG is an integrated marker of insulin resistance that may be of use to identify insulin-resistant individuals for targeted treatment with insulin-sensitizing agents. However, SHBG and testosterone concentrations measured in isolation are inherently unsuitable for use as tests to detect hyperandrogenemia.

Adult↗
PubMed2002

The biological variation of insulin resistance in polycystic ovarian syndrome.

Increased insulin resistance (IR) is a cardinal feature of overweight patients with polycystic ovarian syndrome (PCOS). However, there are no data on the variability of IR for subjects with PCOS. The biological variation of IR (homeostasis model assessment model) was assessed by measuring IR at 4-d intervals on 10 consecutive occasions in 12 overweight PCOS patients (median age, 28 yr; range, 18-31 yr) and 11 weight-matched control women having regular menses and without PCOS (median age, 30 yr; range, 19-33 yr). The distribution of IR was log Gaussian in PCOS and Gaussian distribution in the control group. The IR in PCOS subjects was significantly greater than in the controls [mean (range), 5.85 U (1-42.1) vs. 1.67 U (0.48-3.49); P = 0.001]. After accounting for analytical variation, the mean intraindividual variance was also substantially greater in PCOS patients than in controls (mean, 1.19 vs. 0.23). As a consequence, at any level of IR, a subsequent sample must rise by more than 322% or fall by more than 31% to be considered significantly different from the first. IR, measured using the homeostasis model assessment model, is significantly greater and more variable for overweight patients with PCOS. Therefore, this inherent variability needs to be accounted for in studies of IR in PCOS.

Adult↗
PubMed2001

[Free radical scavenging activity of sulfonylureas: a clinical assessment of the effectiveness of gliclazide].

In long-term clinical studies the beneficial effects of gliclazide on platelets have been related to a reduction in oxidative stress. This property is because of gliclazide's free radical scavenging ability that relates to the unique amino azabicyclo-octane ring, which is grafted on to the sulfonylurea. During a blinded clinical trial, the possible effects of gliclazide were assessed in 30 non-insulin-dependent diabetic patients. All patients had been treated for diabetes for more than 2 years (mean 8 years) and had been established on glibenclamide for over 2 years with or without adjunctive metformin therapy. Patients were studied for 6 months and randomized to continue either their present dose of glibenclamide or to be converted to an equipotent dose of gliclazide. Measurements were taken of hemostatic variables, the oxidative status of the plasma, and the redox status, both extracellularly as plasma albuminthiols (PSH) and lipid peroxides, and intracellularly as red blood cell superoxide dismutase activity (SOD). At 3 months, diabetic control was unaltered, but there were significant improvements in the oxidative status of the gliclazide-treated patients. Lipid peroxides decreased (8.3 +/- 1.1 to 7.0 +/- 0.06 mumol/l, P < 0.01) and red blood cell SOD increased (135 +/- 21 to 152 +/- 36 micrograms/ml, P < 0.05). PSH levels were unaltered at 453 +/- 38 mumol/l, whereas they had decreased significantly in the glibenclamide patients (414 +/- 34 mumol/l, P < 0.05), resulting in a significant difference between the 2 treatment groups (P < 0.004). Platelet reactivity to collagen also improved in the gliclazide-treated patients, decreasing from 65.1% +/- 14% to 50.8 +/- 24% (p < 0.01). The reactivity of the platelets remained unaltered in the glibenclamide patients. At 6 months, the significant differences between the 2 treatment groups remained. Hence, gliclazide was shown in a clinical study to have free radical scavenging activity independent of glycemic control.

Adult↗
PubMed2000

Free radical scavenging activity of sulfonylureas: a clinical assessment of the effect of gliclazide.

In long-term clinical studies the beneficial effects of gliclazide on platelets have been related to a reduction in oxidative stress. This property is because of gliclazide's free radical scavenging ability that relates to the unique amino azabicyclo-octare ring, which is grafted on to the sulfonylurea. During a blinded clinical trial, the possible effects of gliclazide were assessed in 30 non-insulin-dependent diabetic patients. All patients had been treated for diabetes for more than 2 years (mean 8 years) and had been established on glibenclamide for over 2 years with or without adjunctive metformin therapy. Patients were studied for 6 months and randomized to continue either their present dose of glibenclamide or to be converted to an equipotent dose of gliclazide. Measurements were taken of hemostatic variables, the oxidative status of the plasma, and the redox status, both extracellularly as plasma albumin-thiols (PSH) and lipid peroxides, and intracellularly as red blood cell superoxide dismutase activity (SOD). At 3 months, diabetic control was unaltered, but there were significant improvements in the oxidative status of the gliclazide-treated patients. Lipid peroxides decreased (8.3 +/- 1.1 to 7.0 +/- .06 micromol/L, P < .01) and red blood cell SOD increased (135 +/- 21 to 152 +/- 36 microg/mL, P < .05). PSH levels were unaltered at 458 +/- 38 micromol/L, whereas they had decreased significantly in the glibenclamide patients (414 +/- 34 micromol/L, P < .05), resulting in a significant difference between the 2 treatment groups (P < .004). Platelet reactivity to collagen also improved in the gliclazide-treated patients, decreasing from 65.1% +/- 14% to 50.8% +/- 24% (P < .01). The reactivity of the platelets remained unaltered in the glibenclamide patients. At 6 months, the significant differences between the 2 treatment groups remained. Hence, gliclazide was shown in a clinical study to have free radical scavenging activity independent of glycemic control.

Adult↗
PubMed2000

Vascular benefits of gliclazide beyond glycemic control.

Advanced glycolysation end products (AGEs) and the free radicals generated in this process can both be implicated in the accelerated atherosclerosis and vascular and prothrombotic microangiopathic changes typified by diabetes. The rate of formation of free radicals is dependent on the rate of protein glycosylation and therefore the level and duration of hyperglycemia. Glycation and oxidation are inextricably linked. Increased oxidative stress due to excess free radical activity may be central to diabetic vascular disease, since endothelial cell damage, lipoprotein oxidation, and modification of platelet reactivity and the arachidonic acid cascade are all properties of free radicals and their reaction products, lipid peroxides. The importance of the demonstration of the mechanism whereby hyperglycemia contributes to vascular damage opens the possibility of scavenging free radicals, which will have effects independently of improving diabetic control. Over the past 15 years, studies have shown that gliclazide not only lowers blood glucose but also confers beneficial effects on the hemorrheologic abnormalities seen in diabetic vascular disease. Clinically, gliclazide reduces platelet reactivity and stimulates endothelial prostacyclin synthesis; it also increases fibrinolysis by its effects on tissue plasminogen activator. These effects, seen both in vitro and in vivo, are independent of glycemic control and are not seen with other sulfonylureas. In clinical studies, the beneficial effects of gliclazide on platelets have been related to a reduction in oxidative stress. This property is due to gliclazide's free radical scavenging ability that relates to the unique aminoazabicyclo-octane ring grafted onto the sulfonylurea. It is fully maintained by the gliclazide modified-release preparation. In diabetes, therefore, where increased glycation and oxidation are fundamental to the pathogenesis of diabetic vascular disease, agents such as gliclazide with its antioxidant activities may have an enhanced therapeutic role.

Blood Glucose↗
PubMed1997

Oral antihyperglycaemics. Considerations in older patients with non-insulin-dependent diabetes mellitus.

Non-insulin-dependent diabetes mellitus (NIDDM) is increasing in incidence as the population in most countries ages. Multiple pathology is common in the elderly, and cardiovascular disease is usually present at diagnosis. Patients who develop NIDDM at age 65 years may live long enough to develop microvascular complications. Others who are frail and have multiple pathologies may require treatment to prevent both symptomatic hyperglycaemia and dehydration, whilst avoiding hypoglycaemia. The goals in the management of NIDDM in elderly people are the prevention of complications and the relief of symptoms. Treatment must be tailored to the individual's expectations and should be reviewed regularly with the changing circumstances of aging. If dietary measures fail to control glucose levels, antihyperglycaemic sulphonylureas are the most frequently prescribed form of treatment. However, concern over the potential of these drugs to cause hypoglycaemia limits the choice to second generation sulphonylureas, agents that preserve the first phase of insulin release and have non-biologically active metabolites that are promptly eliminated. The biguanide agent metformin is also appropriate in elderly obese patients with NIDDM who do not have renal, liver or cardiac failure. The combination of a sulphonylurea and metformin can be effective in patients in whom insulin would otherwise be required. Novel compounds such as acarbose and the thiazolinediones may also be useful in the treatment of older diabetic patients.

Administration, Oral↗
PubMed1994

The potential of gliclazide, a sulphonylurea to influence the oxidative processes within the pathogenesis of diabetic vascular disease.

The clinical studies have demonstrated that patients showed significant improvements in their oxidative status after 3 months treatment. This improvement in oxidative status which was associated with a reduction in platelet reactivity, remained constant for the rest of the study period. The effect was independent of glycaemic control. The demonstration of a benefit to clinical vascular disease has proved difficult to achieve in all studies of non-insulin dependent diabetes. This is due to the multifactorial nature of complications and the long duration of disease required before microvascular complications such as retinopathy became apparent. The Japanese Diabetic Retinopathy Program24 studied the progression of retinopathy over a 5 year period comparing Gliclazide with other sulphonylureas and with placebo. The study suggested that with equivalent metabolic control there was a trend towards a lower rate of deterioration of retinopathy and a significantly lower incidence of pre-proliferative retinopathy in the group receiving Gliclazide compared with patients receiving other sulphonylureas or placebo. There is little comparative evidence on the effect of specific sulphonylureas on large vessel disease. Although improvement in parameters of hyperglycaemia is associated with an improvement in morbidity from large vessel disease. In Type II diabetes atherosclerosis coexists in the majority of patients and often predates the clinical diagnosis of diabetes. The presence of atherosclerosis which often determines the ultimate fate of the patient, further increases the level of lipid peroxidation of oxidative stress, amplifying the effects of hyperglycaemia and potentiating vascular damage. In diabetes, therefore where increased glycation and oxidation are fundamental in the pathogenesis of diabetic vascular disease agents such as Gliclazide with anti-oxidant activities may have an enhanced therapeutic role.

Adult↗
PubMed1992

Effects of gliclazide on platelet reactivity and free radicals in type II diabetic patients: clinical assessment.

In vitro studies have demonstrated that gliclazide has free radical scavenging and antiplatelet activities. To assess this clinically, we studied gliclazide in a blinded, randomized, glibenclamide-controlled trial in 30 type II diabetic patients with retinopathy. All patients had been taking glibenclamide for more than 12 months before being randomized to receive either an equipotent dose of gliclazide or to continue on glibenclamide. Diabetic control was not modified. The patients were well matched at randomization (mean age, 58 years; duration of diabetes, 8 years; 20 males; mean hemoglobin A1 [HbA1], 8.6%) and their degree of diabetic control was not altered during the trial. Free radical activity was assessed as oxidative status by plasma thiols (PSH), lipid peroxides (MDA-LM), and red blood cell superoxide dismutase activity (SOD). Platelet aggregation in whole blood to collagen (Plt-ag) was used as the measure of platelet reactivity. There were no differences between these measurements at baseline. At 3 months, the oxidative status and platelet aggregation in the gliclazide group had improved significantly compared with baseline and had also showed significant differences in all parameters when compared with the glibenclamide group. Therefore, comparing gliclazide with glibenclamide-treated patients at 3 months, we found: PSH, 458 +/- 38 versus 414 +/- 34 mumol/L, P less than .004; MDA-LM, 7.0 +/- 0.6 versus 8.3 +/- 0.8 mumol/L, P less than .0002; SOD, 152 +/- 36 versus 123 +/- 15 micrograms/mL, P less than .016; Plt-ag, 50.8 +/- 24 versus 72.3% +/- 15%, P less than .006. These changes were maintained at 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Detection of microvascular impairment in type I diabetics by laser Doppler flowmetry.

The use of a laser Doppler flowmeter to detect microcirculatory impairment and abnormalities in sympathetic neural control of blood flow in the hands and feet was evaluated. Measurements were carried out in 15 insulin dependent diabetic patients with retinopathy, 14 uncomplicated diabetics and 15 normal subjects. Three tests were assessed (1) the hyperaemic response of the skin microcirculation to local heating at 44 degrees C; (2) the reactive hyperaemic response of the skin microcirculation to 2 min arterial occlusion; and (3) the peripheral vasoconstrictor reflexes to cold challenge and inspiratory gasp. Tests (1) and (2) were applied to the dorsum of the hand and foot and test (3) to the pulp of the fingertip and toe. All tests were carried out with the subjects peripherally vasodilated by indirect heating. At the hand no differences were found between the groups for any of the measures. The hyperaemic response to local heating at the dorsum of the foot showed that the maximum flow in complicated diabetics was significantly lower than that in uncomplicated patients (P less than 0.01) and in normal subjects (P less than 0.002). A new measure, the time for flow to increase to 3 times basal flow, was longer in the complicated group compared with the uncomplicated (P less than 0.02) and the normal groups (P less than 0.001). This test also showed that the response in the uncomplicated group was slower than in the normal group (P less than 0.01). The post-occlusive hyperaemic response did not differ between groups. Measurement of vasoconstrictor reflexes showed that the complicated group had a poorer response to cold challenge at the big toe than the uncomplicated group (P less than 0.02) and the complicated group generally tended to have poorer responses than the other two groups. In conclusion, we have found that the hyperaemic response to local heating can detect microvascular impairment in diabetes before other complications become apparent and that the vasoconstriction test may be able to identify individuals with peripheral sympathetic neuropathy.

Adult↗
PubMed1992

Microangiopathy as a prognostic indicator in diabetic patients suffering from acute myocardial infarction.

Diabetic patients have an increased mortality following myocardial infarction (MI) due to left ventricular failure rather than larger infarcts or dysrhythmias. As this may be due to diabetic microangiopathy affecting the myocardium, we have examined the case records of diabetic clinic patients admitted to the Coronary Care Unit (CCU) with proven MI and compared the hospital outcome of those with and without retinopathy or nephropathy, i.e. markers for generalised microangiopathy. Sixty four consecutive records were traced, for the period when diabetic treatment policy was standardised in CCU, 24 patients had retinopathy (7 proteinuria). When compared to non-retinopathy patients they had similar ages 67 +/- 12 yr [+/- SD] v 63 +/- 9yr) but were of longer duration of diabetes p less than 0.05). There were no differences between the groups in size or site of infarct, previous infarct or hypertension history, blood glucose on admission or diabetic treatment before or after admission. Death occurred in 29% of retinopathy patients compared to 3% of non-retinopathy patients (p less than 0.01). Cardiac failure complicated 75% of retinopathy patients and 25% of non-retinopathy patients (p less than 0.001). Dysrhythmia occurred in 50% and 33% of patients respectively (P = NS). Nine patients had clinical peripheral vascular disease and five of these died. This study, of a selected group of diabetic clinic attenders admitted to CCU with acute MI, demonstrates that microangiopathy and peripheral vascular disease are important prognostic factors in determining hospital outcome as these patients are at increased risk of cardiac failure and death.

Aged↗
PubMed1991

Gliclazide: a general free radical scavenger.

Free radical mechanisms have been implicated in diabetic microangiopathy. Agents that scavenge free radicals may be beneficial. We assessed the scavenging ability of two sulphonylureas, gliclazide and glibenclamide, in vitro. The assay which employs o-dianisidine sensitised by riboflavin can be used to distinguish between superoxide scavengers and general scavengers. The former species lead to an augmentation while the latter has an inhibitory effect. The drugs were added in final concentrations of 0.5, 1.0, 2.5 and 5.0 micrograms/ml. The percentage inhibition (mean +/- S.D.) for each concentration of gliclazide respectively was 11.0 +/- 2.5%, 20.8 +/- 2.9%, 31.4 +/- 2.2% and 47.2 +/- 0.8%. Glibenclamide had no scavenging effects. The results demonstrate that gliclazide is a powerful general free radical scavenger in vitro. We postulate that this scavenging quality of gliclazide may be important in diabetes.

Dianisidine↗
PubMed1991

Oxidative effects of laser photocoagulation.

Diabetic proliferative retinopathy is a common and sight-threatening condition. Oxidative stress is an integral and possibly causative part of the pathogenesis. Although laser photocoagulation is usually a beneficial treatment it remains unclear how it works. The possibility that it induces a sudden, temporary increase in free radical activity either by direct thermal damage or by oxygen reperfusion is explored in this clinical study by measuring the oxidative status in the peripheral blood of 13 patients undergoing panretinal photocoagulation. There were significant increases at one hour in malondialdehyde-like material (MDA-LM), 8.1 (6.9-9.6) nmol/mL, to 9.1 (7.6-9.8) nmol/mL, (less than 0.005); plasma thiols (PSH), 423 (352-457) microns/L, to 444 (382-478) microns/L, (p less than 0.005) and red cell reduced glutathione (GSH), 1357 (1295-1655) microns/L, to 1480 (1305-1760) microns/L, (p less than 0.01). Diene conjugates rose over the first hour 0.55 (0.36-0.79) od/mL, to 0.58 (0.34-0.85) od/mL falling to 0.56 (0.36-0.79) od/mL at 2 h but these changes were not significant. At 2 h, MDA-LM 8.4 (6.7-9.6) nmol/mL and PSH 404 (379-462) microns/L had returned to baseline but GSH remained significantly elevated 1500 (1325-1675) microns/L, (p less than 0.005 compared to baseline). This is a new observation and in some circumstances such generation of free radicals could explain the mechanism behind the complications of photocoagulation by direct or indirect damage to vascular endothelium leading to increased vascular permeability manifest as macular oedema or choroidal effusions.

Adult↗
PubMed1991

The relationship of oxidative stress to thrombotic tendency in type 1 diabetic patients with retinopathy.

Increased free radical activity may contribute to thrombosis via effects on platelet aggregation and the prostanoid balance. To investigate this further we studied 15 Type 1 diabetic patients with retinopathy, matched with uncomplicated Type 1 patients for age, duration of diabetes and HbA1, together with matched healthy non-diabetic control subjects. The oxidative effects of free radicals as total diene conjugates and lipid peroxides were measured, together with redox status extracellularly as plasma albumin-thiols and intracellularly as erythrocyte superoxide dismutase activity. Platelet count, aggregation of platelets in whole blood to collagen, thromboxane B2, and prostacyclin stimulating factor (PGI2SF) were also assessed. Free radicals measured as lipid peroxides were significantly higher (9.6 (8.1-11.6) mumol l-1 (median and interquartile range) in diabetic patients with retinopathy than in control subjects (8.1 (7.4-9.2) mumol l-1; p less than 0.05). There were also significant reductions in redox status both extracellularly as plasma albumin thiols (408 (383-473) vs 490 (456-517) mumol l-1, p less than 0.001) and intracellularly as erythrocyte superoxide dismutase activity (34 (27-41) vs 44 (36-51) g l-1, p less than 0.05) between patients with retinopathy and control subjects. Platelet counts were increased in diabetic patients with retinopathy (p less than 0.05), as was collagen-induced platelet aggregation (p less than 0.01). Prostacyclin stimulating factor was reduced in patients with retinopathy (p less than 0.05) and correlated within the plasma with lipid peroxides (r = -0.53, p less than 0.04) and albumin thiols (r = 0.64, p less than 0.01). The results suggest that diabetic patients, particularly with retinopathy, are under oxidative stress and have an increased thrombotic tendency with increased platelet reactivity and a reduction in prostacyclin stimulating factor.

Adult↗
PubMed1990

Prolonged aldose reductase inhibition in chronic peripheral diabetic neuropathy: effects on microangiopathy.

A 2-year randomized placebo-controlled double-blind trial of 250 mg day-1 of the aldose reductase inhibitor Sorbinil in severe symptomatic chronic peripheral neuropathy was performed in 21 diabetic patients. Due to adverse reactions 8 patients completed the trial on Sorbinil and 6 patients on placebo. Despite differences in baseline neurophysiological parameters, duration of diabetes, and presence of retinopathy between the placebo and treatment groups, there were no initial differences in in vitro platelet aggregation, albumin excretion rate (AER) or muscle capillary basement membrane thickness. After 2 years the median deterioration in AER in the placebo group was 18.4 micrograms min-1 (range 2.6-64.8 micrograms min-1). This deterioration was significant (p less than 0.03). The change in AER in the Sorbinil group was +1.25 (-10.7 to +20.4) micrograms min-1, an insignificant change. In vitro platelet responsiveness to collagen and adenosine diphosphate (ADP) increased in the placebo group (median change max% collagen + 8 (+2 to +30)%; ADP +4.5 (0 to +20)% compared with a fall in the Sorbinil treated patients (median change; collagen -17.5 (-2 to -40)%, p less than 0.05; ADP, -4 (0 to -25)%, p less than 0.05). Muscle capillary basement membrane thickness was measured in only 3 patients in each group and did not alter significantly during the trial. All 12 neurophysiological measurements showed no significant changes between the treatment and placebo groups. The data suggest that aldose reductase inhibition has effects on platelet reactivity and microalbuminuria.

Aldehyde Reductase↗