Asghar Ghasemi

Although the insulin secretion deficit in hypothyroid male rats has been documented, the underling mechanisms of the effect of hypothyroidism on insulin secretion are not clear. Isolated islets of the PTU-induced hypothyroid and control rats were exposed to glibenclamide, acetylcholine, and nifedipine in the presence of glucose concentrations of 2.8 or 8.3 and 16.7 mmol/L. Glucokinase and hexokinase specific activity, glucokinase content, and glucose transporter 2 protein expression were also determined in the isolated islets. Isolated islets from the hypothyroid rats showed a defect in insulin secretion in response to high glucose. In the presence of glibenclamide or acetylcholine, the isolated islets from the hypothyroid and control rats stimulated by glucose concentration of 16.7 mmol/L secreted similar amounts of insulin. In the presence of glucose concentrations of 8.3 mmol/L and 16.7 mmol/L, nifedipine was able to diminish insulin secretion from isolated islets of both groups,...

Objective. Gamma-amino butyric acid (GABA) is an inhibitory neurotransmitter found widely in the central nervous system and some peripheral tissues such as the islets of pancreas. The aim of this study was to determine the time depend-ency of the effect of GABA on glucose-stimulated insulin secretion in isolated islets of rats. Materials and Methods. The collagenase digestion technique was used to isolate the islets from pancreata of male Wistar rats (200 – 250 g). Insulin secre-tion was assessed in islets exposed to different concentrations of glucose (8.3 and 16.7 mM), in the presence or absence of GABA (50 μ M), for different incubation times and also pre-incubation of islets with GABA, 30 and 45 min before 8.3 mM glucose stimulation. Furthermore insulin secretion with different concentrations of glucose (8.3 and 16.7 mM), and in the presence or absence of different concentrations of baclofen, a GABA B agonist and of saclofen, a GABA B antagonist during 1 h of incubation was asse...

Menopausal status could increase cardiovascular disease (CVD) risk. Nitric oxide plays a role in protection against CVD onset and progression but has not been studied around the menopause. We investigated associations between serum nitric-oxide metabolite (NOx) concentrations and menopausal status. Comparative case-control cross-sectional study. Tehran-lipid and glucose-study, university center. Sub-groups from a cohort of 2137 women, of whom 213 met enrolment criteria. We studied four sub-groups in a 1:2 ratio: 1) post-menopausal women (n=29) with natural amenorrhea for 13-24 months, 2) age- and BMI-matched controls (n=58) with regular menstrual cycles; 3) peri-menopausal women (n=42) with natural amenorrhea for 1-12 months, and 4) age- and BMI-matched women as controls for these latter women (n=84). Serum nitric oxide concentrations. Medians (inter-quartile ranges) of NOx in post-menopausal women and their controls were 31 (21.7-40.2) and 23.5 (17.2-31) μmol/L, respectively (p = 0...

The potential effects of inorganic nitrate/nitrite on global health are a much debated issue. In addition to possible methemoglobinemia and carcinogenic properties, anti-thyroid effects of nitrate/nitrite have been suggested. Considering the growing significance of nitrate/nitrite and since there is no comprehensive review in data available, clarifying the effect of nitrate/nitrite on thyroid disorder outcomes is essential. Therefore, we conducted this systematic review of experimental and clinical studies, and a meta-analysis of relevant cohort and cross-sectional studies investigating the association of nitrate/nitrite exposure and thyroid function was conducted. Most animal studies show that high exposure (~10-600 times of acceptable daily intake) to nitrate/nitrite induces anti-thyroid effects, including decreased serum level of thyroid hormones and histomorphological changes in thyroid gland; however no similar observations have been documented in humans. Based on our meta-analysis, no significant association was observed between nitrate exposure and the risk of thyroid cancer, hyper- and hypothyroidism; findings from three cohort studies however showed a significant association between higher exposure to nitrite and the risk of hypothyroidism (risk=1.48, 95% confidence interval=1.09-2.02, P=0.012). Additional research is needed to clarify the association between nitrate/nitrite exposures and both thyroid function and cancer.

Thyroid hormones play an essential role in fetal growth and maternal hypo-thyroidism which leads to cardiovascular deficiency in their offspring. Considering this, we intended to investigate the impact of gestational hypothyroidism on offspring vascular contractibility and possible underlying mechanisms. Hypothyroidism was induced in female rats by administration of 6-n-propyl-2-thiouracil in drinking water (0.02%) till delivery. The offspring aorta smooth muscle (without endothelium) contractile response to KCl (10-100 mM), KCl in the presence of nifedipine (10(-4)-10(-1) µM), phenylephrine (10(-9)-10(-6) M) and finally, phenylephrine and caffeine 100 mM in Ca(2+)-free Krebs were measured. KCl and phenylephrine-induced contractions were considerably lower in gestational hypothyroid (GH) than euthyroid offspring. GH responded to nifedipine with less sensitivity than control. The GH and control groups produced almost equal contraction in respond to phenylephrine and caffeine in Ca(2+...

Statistical errors are common in scientific literature and about 50% of the published articles have at least one error. The assumption of normality needs to be checked for many statistical procedures, namely parametric tests, because their validity depends on it. The aim of this commentary is to overview checking for normality in statistical analysis using SPSS.

Nitric oxide (NO) plays numerous important roles in many biological systems and, therefore, research in this field, which impacts all aspects of biology and medicine, especially NO measurement, is steadily increasing. Nitric oxide has a short biological half-life, making its direct determination in vivo difficult. Therefore, currently assessment of nitrite and nitrate (NOx) in biological fluids seems to be the most suitable method to assess NO synthesis in vivo. The most frequently used method of NOx analysis is based on the Griess reaction. Although measurement of NOx by the Griess assay is simple and cheap, the accurate determination of plasma/serum concentrations of nitrate/ nitrite using the Griess assay is prone to interferences and can be influenced by several factors. The aim of this study was to overview preanalytical and analytical considerations for measuring NOx in serum or plasma using the Griess assay.

Nitric oxide (NO) is a simple ubiquitous signaling molecule and plays important roles in almost every biological system. Recent evidences suggest that NO may act as an endocrine molecule. The aim of this review is considering available literature on endocrine roles of NO and/or its metabolites, i.e. nitrite and nitrate. Existing data suggest the idea that NO is a hormone that after production in tissues, it is stabilized and transported as nitrite and/or S-nitrosothiols in the blood to target cells.

Impaired fasting glucose and diabetes are prevalent in Iran; however the definition of high fasting glucose is inconsistent and has not been reported in this population. This study aims at determining the reference values for fasting serum glucose in Iranian adults. Serum glucose concentrations were measured in 10368 adult subjects who participated in the Tehran Lipid and Glucose Study (TLGS). After excluding those with disease or risk factors, 962 apparently healthy nonsmoking participants (404 men and 558 women), aged 20 to 78 years, remained for analysis. The International Federation of Clinical Chemistry guidelines (non-parametric method) and robust methods were used for determining reference values. Overall, 95% reference values for fasting serum glucose concentrations were 4.0 to 5.7, 3.8 to 5.6, and 3.9 to 5.7 mmol/L in men, women, and total population, respectively. In addition, there is a significant increase for medians of fasting serum glucose with increasing age (p < ...

Endothelial dysfunction and impaired release of endothelial nitric oxide occurs in hypertension. The aim of this study was to determine the relation between nitric oxide metabolites (NOx) concentrations and blood pressure levels in a general population. In a cross-sectional study, NO(x)was measured in 2,968 adult subjects, randomly selected from a population-based study, using the Griess method. Subjects were classified into normal, prehypertension, stage 1 hypertension and stage two hypertension groups, according to the seventh report of the Joint National Committee on prevention, detection, evaluation, and treatment of high blood pressure. Serum NO(x)values were negatively correlated with systolic blood pressure ≥160 mm Hg in men (r=-0.523, P=0.002). Serum NOx was higher in men with stage 1 hypertension while those with stage 2 hypertension had significantly lower NO(x) levels. In men, medication increased serum NO(x) concentration in both stages of hypertension but in women, a si...

The effect of propylthiouracil (PTU) administration to pregnant and lactating rats on isolated aorta contractility of their adult offspring was investigated. Three groups of female rats were selected; in the fetal group (FG), PTU was added to their drinking water during gestation; in the neonatal group (NG), PTU was added to the mothers' drinking water for 25 days after delivery; untreated rats were controls (CG). Thyroid hormone concentrations were measured in the sera of the mothers and their adult offspring. Aortic contractility of the offspring was measured with an isometric transducer in the presence of different concentrations of potassium chloride (KCl) and phenylephrine. The mothers were hypothyroid at the time of PTU cessation. Thyroid hormone levels in offspring were not significantly different from those of controls except for TSH, which was significantly (p<0.05) higher in the FG offspring. Recorded tension in FG offspring with 5, 10, 20, 40, and 60 mmol/l KCl wer...

To determine the prevalence of the metabolic syndrome (MS) in an Iranian elderly population and show its association with coronary heart disease (CHD). This is a cross-sectional study on 720 Iranian men and women aged > or = 65 years who participated in the Tehran Lipid and Glucose Study (TLGS). Logistic regression analysis was used to estimate the odds ratio (OR) of developing CHD in model 1, an age-adjusted model; model 2, adjusted for age, smoking status, premature history of CHD and low-density lipoprotein (LDL) cholesterol; and model 3, adjusted for mentioned variables plus the MS components. The prevalence of MS was 50.8%, 41.8% and 41.9% based on the Adult Treatment Panel (ATPIII), the World Health Organisation (WHO), and the International Diabetes Federation (IDF) definitions, respectively. The IDF definition showed high agreement with the ATPIII definition. Age-adjusted OR (95% CI) of the MS for CHD was 1.6 (1.2 to 2.2) by both the ATPIII and WHO definitions and 1.4 (1.0...

To determine whether triglyceride/high-density lipoprotein cholesterol ratio (TG/HDL-C), which has been shown to be an indicator of the metabolic syndrome (MetS) and insulin resistance, can predict coronary heart disease (CHD) independently of total cholesterol (TC) and other risk factors in an Iranian population with a high prevalence of MetS and low HDL-C. Between February 1999 and August 2001, 1824 men > or =40 years old, free of clinical cardiovascular diseases at baseline, were followed. Baseline measurements included serum level of TC, HDL-C, TG and risk factors for CHD including age, systolic and diastolic blood pressure, body mass index, waist circumference, diabetes, smoking and a family history of premature cardiovascular diseases. During a median follow up of 6.5 years until March 2007 (11,316 person-years at risk), a total of 163 new CHD events (27 fatal and 136 nonfatal) occurred. The prevalence of MetS in subjects with TG/HDL-C > or =6.9 (top quartile) reached 63...

To determine cut-off points of homeostasis model assessment of insulin resistance (HOMA-IR), β-cell function (HOMA-B), insulin sensitivity (HOMA-S), and fasting insulin for identifying the subjects with type 2 diabetes mellitus (T2DM) in Iranian adults using data from a prospective population-based study. From participants of Tehran Lipid and Glucose Study, 4942 Iranian subjects, aged 20-86 years, were followed for incident T2DM. Fasting serum insulin was determined by the electrochemiluminescence immunoasaay. The associations between HOMA-IR, HOMA-B, HOMA-S, and fasting insulin and incident T2DM were evaluated using Cox proportional hazards models. The receiver operator characteristic curve analysis was used to determine the cut-off points of HOMA-IR, HOMA-B, HOMA-S, and fasting insulin. After 9.2 year follow-up, 346 (7.0 %) incident cases of T2DM were identified; the risk-factor-adjusted hazard ratios for HOMA1-IR, HOMA2-IR, HOMA1-B, HOMA2-B, HOMA1-S, HOMA2-S, and insulin were 1.15, 1.70, 0.732, 0.997, 0.974, 0.986, and 1.01 in women and 1.37, 1.67, 0.588, 0.993, 0.986, 0.991, and 1.06 in men, respectively (all p < 0.05 except for HOMA2-B in women). Optimal cut-off points for HOMA1-IR, HOMA2-IR, HOMA1-B, HOMA2-B, HOMA1-S, HOMA2-S, and insulin were 1.85, 1.41, 86.2, 72.5, 54.1, 63.7, and 11.13 µU/ml in women and 2.17, 1.18, 67.1, 74.6, 46.1, 74.1, and 9.16 µU/ml in men, respectively. HOMA-IR, HOMA-B (except for HOMA2-B in women), HOMA-S, and fasting insulin were independent predictors of T2DM. Optimal cut-off points of HOMA-IR, HOMA-B, HOMA-S, and fasting serum insulin were determined from a population-based study for identifying incident T2DM.

Evidence exists for reciprocal effects of insulin and desacyl-ghrelin (DAG) concentration, but the association between different fatty acid saturation in high fat diet (HFD) and these hormones remain to be established. To evaluate the impact of different sources of dietary fat and the level of fatty acid saturation on plasma insulin and DAG levels and also the association of DAG with insulin action this study was carried out. Male weaning Wistar rats were randomly divided into four groups of HFDs, high fat butter (HF-B), high fat soy (HF-S), high fat olive (HF-O), high fat fish (HF-F), and a group of standard diet (SD). Blood samples were collected after 8 weeks and after they were fasted for 24 h. Body weight, food intake, plasma glucose, insulin, DAG and insulin resistance (HOMA-IR) were measured. Plasma insulin levels at fed and fasted status, were significantly higher in rats on HF-B compared to those on SD, HF-F and HF-O diets (P<0.05). Insulin concentration in rats on HF-S ...