Trp64Arg polymorphism of the beta 3-adrenergic receptor gene is associated with increased plasma leptin levels in obese Chinese women

BACKGROUND

beta 3-Adrenergic receptors are predominantly expressed in the fat cells of visceral adipose tissue in humans. They mediate catecholamine-induced lipolysis and thermogenesis of adipose tissue, which are important for the regulation of energy expenditure and, therefore, body weight. Recently, a Trp64Arg polymorphism of the beta 3-adrenergic receptor gene was reported to be associated with obesity and obesity-related metabolic complications in some ethnic populations. Leptin, a protein secreted by adipocytes, is proposed as a signal linkage between the central nervous system and peripheral fat storage. It has been shown in rodents that leptin may activate the sympathetic nervous system and, thus, beta 3-adrenergic receptors in adipose tissue. However, little is known about the relationship between the Trp64Arg polymorphism and plasma leptin in humans.

METHODS

To determine the effects of the beta 3-adrenergic receptor gene Trp64Arg mutation on anthropometric measures, metabolic parameters and plasma leptin levels, 188 premenopausal Chinese women (mean age +/- standard deviation, 32 +/- 10 years) with body mass index (BMI) between 16.1 and 59.8 kg/m2 were investigated. Trp64Arg polymorphism was determined by DNA analysis, body fat mass by bioelectric impedance analysis and plasma leptin by radioimmunoassay.

RESULTS

Trp64Arg allele frequency was 15% in this population and there was no homozygous Arg64Arg mutant. When the subjects were divided into three groups based on BMI values (BMI < 22.2, n = 60; 22.2 < or = BMI < or = 29.5, n = 63; BMI > 29.5 kg/m2, n = 65), there was no difference in Trp64Arg allele frequency (16% vs 11% vs 18%, p = 0.149). Across the three groups, plasma leptin correlated positively with BMI (r = 0.843, p < 0.0001) and total fat mass (r = 0.824, p < 0.0001). Within each BMI tertile, the waist to hip ratio, fat mass, plasma lipids, glucose and insulin were relatively similar between Trp64Trp homozygotes and Trp64Arg heterozygotes. However, Trp64Arg heterozygotes had higher plasma leptin levels than Trp64Trp homozygotes (35.9 +/- 11.0 vs 30.0 +/- 12.8 ng/ml, p = 0.0023) in those with BMI above 29.5 kg/m2, a difference which remained after adjustment for body fat mass (p = 0.024).

CONCLUSIONS

Trp64Arg polymorphism of the beta 3-adrenergic receptor gene is not associated with obesity in Chinese women. Plasma leptin concentrations correlate well with BMI and total fat mass. For obese Chinese women, the Trp64Arg genotype of the beta 3-adrenergic receptor gene may contribute to an increased plasma leptin level.

Short stature in a 46,XX male adolescent

We describe a patient with a 46,XX karyotype who was assessed because of short stature and a subnormal rate of linear growth. The patient had normal male external genitalia. Endocrinologic analysis revealed elevated levels of luteinizing hormone and follicle-stimulating hormone but an exaggerated gonadotropin response to luteinizing hormone-releasing hormone stimulation. The growth hormone response to insulin-induced hypoglycemia was also exaggerated. All sequences examined on the sex-determining region Y gene were present. The diagnosis was 46,XX male with the major manifestation of short stature.

Plasma leptin concentrations are related to body fat mass and gender but not to thyroid dysfunction

Leptin, a newly defined protein synthesized and secreted from fat cells in both animals and humans, has gained wide attention. Many studies have been conducted on its roles in the regulation of body fat storage, energy expenditure and body weight changes. Thyroid dysfunction is known to have influences on the above changes in humans and these changes may in turn lead to a variation in circulating leptin levels. In addition, a sex dimorphism of plasma leptin levels has been a constant finding in many studies. However, the relationship between body fat mass and gender to plasma leptin levels in patients with various thyroid dysfunction has been rarely discussed together. A total of 134 patients with various thyroid function status were included in this study (hyperthyroidism: n = 50, hypothyroidism: n = 24, and euthyroidism: n = 60). Plasma leptin concentrations were compared between different thyroid function groups, and compared with body fat mass and body mass index (kg/m2) to check if these two parameters affect the circulating leptin levels. There were no significant differences between plasma leptin concentrations in the different thyroid function groups (Mean +/- SD: hyperthyroidism: 8.5 +/- 5.4 ng/ml, range: 1.5-25.8; hypothyroidism: 8.4 +/- 4.7 ng/ml, range: 1.8-20.1, and euthyroidism: 7.3 +/- 4.5 ng/ml, range: 0.6-20.9). Rather, a significant gender difference was found, with female subjects having two-fold higher levels than males when all study subjects were encompassed (female: 8.8 +/- 4.9 ng/ml, range: 11.7-25.8 vs male: 4.1 +/- 2.1 ng/ml, range 0.6-8.1, p < 0.001) or when thyroid function status was analyzed separately (hyperthyroidism: female: 9.7 +/- 5.5 ng/ml vs male: 4.3 +/- 2.1 ng/ml, p < 0.001; hypothyroidism: female: 9.7 +/- 4.6 ng/ml vs male: 4.4 +/- 2.4 ng/ml, p = 0.015; and euthyroidism: female: 7.9 +/- 4.5 ng/ml vs male: 3.6 +/- 1.9 ng/ml, p = 0.013). Plasma leptin concentrations had strong correlation with body fat mass in both females (r = 0.47, p < 0.001) and males (r = 0.71, p < 0.001). Good correlation was also observed between plasma leptin concentrations and body mass index in females (r = 0.51, p < 0.001) and males (r = 0.78, p < 0.001). Plasma leptin concentrations were not different in thyroid dysfunction. A significant gender difference existed and a positive correlation between body fat mass and BMI to plasma leptin was observed.

Family aggregation and maternal inheritance of Chinese type 2 diabetes mellitus in Taiwan

BACKGROUND

Type 2 diabetes mellitus (DM) is a well-known familial disease, although the genetics of this complex condition remains unclear. Recent evidence suggests the significance of maternal inheritance. However, the pattern of family aggregation and the influence of other family relatives on the mode of transmission in Chinese patients with diabetes are lacking.

METHODS

We interviewed 449 patients (151 men and 298 women) with type 2 DM who were aged between 35 and 74 years with a mean age of 58 +/- 1 years in a referral hospital in central Taiwan. We recorded a detailed family history of diabetes for each patient.

RESULTS

Overall, 60% of diabetic patients had at least one diabetic family member. Among these index patients, 22.5% had a diabetic mother compared with 12.0% who had a diabetic father (p < 0.001). Approximately 29% of diabetic patients had at least one diabetic sister compared with 24% who had at least one diabetic brother (p = 0.13). A total of 27% of diabetic men had a diabetic mother, compared with 20% of diabetic women. Women with diabetes had more diabetic sisters than did diabetic men. In contrast, diabetic men had a significantly increased percentage of diabetic family members on the maternal side or paternal uncles or aunts than did diabetic women. The percentage of diabetic patients who had a diabetic mother decreased as their age increased. The maternal effect disappeared in the diabetic patients who were over 65 years old. Statistical differences between diabetic fathers and mothers were observed when DM was diagnosed in patients under 65 years of age.

CONCLUSIONS

We documented the presence of family aggregation and significant maternal inheritance in Chinese patients with type 2 DM in Taiwan. Further prospective study is needed to monitor the offspring of diabetic parents and other relatives in order to clarify the true mode of family aggregation and maternal transmission of type 2 DM.

Mixed medullary-follicular carcinoma and papillary carcinoma of the same thyroid

We report a rare case of mixed medullary-follicular carcinoma and papillary carcinoma of the same thyroid. A 27-year-old Chinese female complained of a single thyroid nodule for 2-3 months. Needle aspiration revealed suspicious papillary carcinoma and thyroidectomy performed later showed mixed medullary-follicular carcinoma and papillary carcinoma of the same thyroid which was extremely rare. Whether neoplastic transformation is due to tumorigenic stimulus or just due to the collision phenomenon is still controversial for its etiology.

Regulation of NAD+ glycohydrolase activity by NAD(+)-dependent auto-ADP-ribosylation

NAD+ glycohydrolase (NADase; EC 3.2.2.5) is an enzyme that catalyses hydrolysis of NAD+ to produce ADP-ribose and nicotinamide. Its physiological role and the regulation of its enzymic activity have not been fully elucidated. In the present study, the mechanism of self-inactivation of NADase by its substrate, NAD+, was investigated by using intact rabbit erythrocytes and purified NADase. Our results suggest that inactivation of NADase was due an auto-ADP-ribosylation reaction. ADP-ribosylated NADase of rabbit erythrocytes was deADP-ribosylated when incubated without NAD+, and thus enzyme activity was simultaneously restored. These findings suggest that reversible auto-ADP-ribosylation of NADase might regulate the enzyme's activity in vivo.

[Effects of aspirin and nifedipine alone or in combination on mesenteric microcirculation of rats]

AIM

To study the effects of the combination of aspirin (Asp) and nifedipine (Nif) on mesenteric microcirculation of rats.

METHODS

Acute microcirculation disturbance (AMD) was produced by high molecular weight dextran (M(r) 480,000, 360 mg.kg-1 i.v.). Arteriole and venule blood flow velocity and diameter (ABFV, VBFV, AD, VD) and blood flow state (BFS) were observed by intravital microcirculation method.

RESULTS

Asp 2.5, 5 mg.kg-1, Nif 0.05, 0.1 mg.kg-1, Asp + Nif (1 + 0.025), (2.5 + 0.05) mg.kg-1, i.v. had the significant increase of 11.1%, 31.3%, 18.5%, 19.3%, 30.5%, 39.8% of ABFV and 12.5%, 25.7%, 12.6%, 15.2%, 29.6%, 36.1% of VBFV respectively, the marked improvement of BFS, and the distinctive increase of 4.3%, 17.9%, 35.9%, 39.7%, 15.2%, 42.8% of AD and 2.2%, 4.2%, 26.2%, 27.4%, 3.4%, 28.9% of VD separately, and got a raise in the number of capillaries. Asp + Nif (1 + 0.025), 2.5 + 0.05) mg.kg-1 i.v. could reverse AMD.

CONCLUSION

Asp was superior to Nif in the increase of BFV, but Nif was superior to Asp in expansion of blood vessel. Asp in combination with Nif produced marked synergistic action and protection againist AMD.

[Effects of aspirin and nifedipine alone or in combination on hemodynamics in anesthetized dogs]

AIM

To study the effects of the combination of aspirin (Asp) and nifedipine (Nif) on hemodynamics in 8 anesthetized dogs.

METHODS

Tension time index (TTI), left ventricular work index (LVWI), mean arterial pressure (MAP), and total peripheral vascular resistance (TPVR), femoral artery blood flow (FBF), ventricular systolic pressure (LVSP), maximum of its first derivative (dp/dt(max)), left ventricular end diastolic pressure (LVEDP) and heart rate (HR) were recorded on polygraph and electromagnetic flowmeter.

RESULTS

Asp 5, 10 mg.kg-1, i.v. exerted a significant effect on the hemodynamic indices, wheras Nif 15 micrograms.kg-1, i.v. decreased TTI, LVWI, MAP, and TRVR, increased FBF distinctively, and slightly affected LVSP, dp/dt(max), LVEDP, and HR. The effects of Asp in combination with Nif on hemodynamics were similar to those of Nif alone.

CONCLUSION

The improvement of cardiovascular function caused by Nif was not affected by the presence of Asp.

Role of basal insulin in maintenance of intracellular glucose metabolic pathways in non-insulin-dependent diabetes mellitus

Impairments of both basal and insulin-stimulated oxidative (Gox) and nonoxidative (Nox) glucose metabolism are documented to exist in non-insulin-dependent diabetes mellitus (NIDDM). Although these defects have been well characterized during insulin stimulation, little is known about the effects of basal insulin or its deficiency on intracellular glucose metabolism in NIDDM. To determine the physiological significance of basal insulin in the maintenance of glucose metabolism in NIDDM, we studied nine subjects with NIDDM in the basal and insulin-deficient state produced by 3 hours of somatostatin (SRIF) infusion (0.08 pmol/kg/min). Glucose turnover rates were quantified by [3-3H]glucose turnover, and substrate oxidation was assessed by a combination of indirect calorimetry and urinary nitrogen measurements. Skeletal muscle glycogen synthase (GS) and pyruvate dehydrogenase (PDH) activities were also measured in the basal state and during SRIF infusion. Basal glucose levels were maintained during SRIF infusion by exogenous glucose infusion (12.5 +/- 0.9 mmol/L in the basal state v 12.8 +/- 0.8 during SRIF infusion, P = NS). During the last hour of SRIF infusion, plasma C-peptide levels declined by 88% from 0.73 +/- 0.11 to 0.09 +/- 0.02 nmol/L (P < .001), and serum insulin concentrations were undetectable (< 14 pmol/L). During insulinopenic conditions, rates of glucose uptake (GU) were decreased by 12% from basal level of 2.26 +/- 0.13 to 1.99 +/- 0.12 mg/kg/min (P < .05), and were entirely accounted for by reduced rates of Gox (1.01 +/- 0.10 to 0.65 +/- 0.14 mg/kg/min, P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of caffeine on the levels of brain serotonin and catecholamine in the genetically obese mice

BACKGROUND

Most obesities are known low in sympathetic activity, and brain neurotransmitters may play roles in the defective exhibitions of obesity. Caffeine, a stimulant, which can prompt lipolysis, has been applied on the therapy of obesity. Although the interactive combinations between caffeine and certain neurotransmitters has been appreciated recently, but its regulatory mechanisms are still obscure. This study investigated the effect of caffeine on the body fat deposition, and its interactions with brain serotonin and catecholamine in the genetically obese (ob/ob) mice.

METHODS

At 12-week of age, obese mice and their lean counterparts (+/?) were administered with caffeine (4 mg/d) in water for 4 weeks. The brain neurotransmitters levels and body fat content were measured.

RESULTS

The obese mice without caffeine treatment had lower brain norepinephrine and epinephrine levels than the lean controls. And there had no difference between obese and lean mice in brain levels of serotonin, tryptophan, and 5-hydroxyindoleacetic acid. Caffeine treatment showed no effect on the food intake, but decreased the body fat content significantly in obese mice. Mice with caffeine treatment showed increase of the levels of brain neurotransmitters in both phenotypes; this effect was more predominant in obese mice.

CONCLUSIONS

This study indicated that the effect of caffeine to decrease body fat deposition in the obese mice might be associated with the recovered increases of sympathetic activity.

Intracellular glucose metabolism after long term metabolic control with glyburide: improved glucose oxidation with unchanged glycogen synthase activity

To determine whether improved metabolic control with long term glyburide treatment alters intracellular glucose metabolism independent of effects on glucose uptake (GU), we studied eight obese patients with noninsulin-dependent diabetes mellitus before and 7 months after glyburide therapy. Indirect calorimetry and skeletal muscle biopsies were performed in the basal state and during 300 pmol/m2.min insulin infusions, with glucose turnover rates determined by [3-3H]glucose turnover. During the glucose clamps, rates of GU were matched before and after treatment using equivalent hyperinsulinemia and variable levels of hyperglycemia. After glyburide treatment, rates of GU were decreased in the basal state [4.16 +/- 0.57 vs. 3.29 +/- 0.37 mg/kg fat free mass (FFM)/min; P < 0.05], but similar during glucose clamps (11.53 +/- 1.42 vs. 11.93 +/- 1.32 mg/kg FFM.min; P = NS) according to study design. In both the basal state and during glucose clamps after glyburide therapy, rates of glucose oxidative metabolism (Gox) increased by 68-78% [1.21 +/- 0.16 vs. 2.03 +/- 0.31 mg/kg FFM.min (P < 0.05) and 3.13 +/- 0.51 vs. 5.58 +/- 0.55 mg/kg FFM.min (P < 0.05), respectively], and rates of nonoxidative glucose metabolism decreased [2.96 +/- 0.68 vs. 1.25 +/- 0.21 mg/kg FFM.min (P < 0.05) and 8.40 +/- 1.50 to 6.30 +/- 1.40 mg/kg FFM.min (P < 0.01), respectively]. Circulating plasma FFA levels and rates of fat oxidation (Fox) remained unchanged in both the basal state and during clamp studies. Skeletal muscle glycogen synthase (GS) activity, expressed as fractional velocity, was unchanged by glyburide therapy (2.2 +/- 0.8 vs. 2.7 +/- 0.3% in the basal state and 7.3 +/- 1.8 vs. 6.1 +/- 0.9% during clamps; both P = NS). In summary, at both matched (during clamp studies) and unmatched (during basal studies) rates of GU, improved metabolic control with glyburide therapy resulted in marked improvement of Gox independent of the effects on GU. The improvement in Gox was not associated with changes in Fox, circulating FFA, or muscle GS activity. These data indicate that long term metabolic control achieved by glyburide therapy markedly improves Gox, but not skeletal muscle GS activity, in noninsulin-dependent diabetes mellitus independent of GU and Fox.

Abnormal thyroid hormone levels in critical nonthyroidal illness

Low levels of thyroid hormone in the absence of clinical hypothyroidism often happen to patients with critical non-thyroidal illnesses (NTI). Low thyroid hormone concentrations in serum do not necessarily mean hypofunction of the thyroid gland; rather it is a helpful adaptation of the human body to the underlying diseases. We collected 133 hospitalized cases of critical NTI and analyzed the incidence of this phenomenon. Fifty-three per cent of the patients had T3 level lower than 60 ng/dl (normal:85-165 ng/dl) and 60% had T4 level lower than 6 ug/dl (normal:6-12 ug/dl). The lowest levels were observed in patients who had sepsis, were aged over 70 or died in this admission. Free T4 and TSH levels were within normal range in most cases. There is a strong negative correlation between the prognosis and the level of T4 in these patients. Those patients with markedly low levels of T3 and T4 should be treated more sophisticatedly.

Serotonin (5-HT1c) receptors in pig choroid plexus

It is very important to find suitable reaction conditions to attain a high specific binding (specific/total binding) in the receptor binding study. Membrane homogenates of pig choroid plexus are known to have exclusively serotonin (5-hydroxytryptamine, 5-HT) receptor of the subtype 5-HT1c. In this study, we used the membrane preparation of pig choroid plexus tissue and the specific binding of [3H]5-HT was 72-84% to serotonin receptor subtype 5-HT1c, as defined by the inhibition of 1 uM 5-HT, when a radioligand concentration of 0.5 nM of [3H]5-HT was used in the assay. Analysis of the properties of specific [3H]5-HT binding in pig choroid plexus tissue membrane preparation revealed linear Scatchard plots. In Tris-HCl buffer without CaCl2, pargyline or ascorbic acid, high average of affinity dissociation constant (Kd) of 1.3 +/- 0.2 nM (SEM, n = 4) and also a high average of receptor density (Bmax) of 284 +/- 12 fmol/mg of protein were found. Pig choroid plexus proves to be a good material for 5-HT1c receptor binding study.

Modulation of glycine receptor chloride channels by cAMP-dependent protein kinase in spinal trigeminal neurons

Glycine is an important inhibitory transmitter in the brainstem and spinal cord. In the trigeminal subnucleus caudalis (medullary dorsal horn) and in the spinal dorsal horn (the relaying centres for processing pain and sensory information), glycine inhibits the glutamate-evoked depolarization and depresses firing of neurons. The binding of glycine to its receptor produces a large increase in Cl- conductance, which causes membrane hyperpolarization. The selectivity and gating properties of glycine receptor channels have been well characterized; the glycine receptor molecules have also been purified. The amino-acid sequence, deduced from complementary DNA clones encoding one of the peptides (the 48K subunit), shows significant homology with gamma-aminobutyric acid A (GABAA) and nicotinic acetylcholine receptor subunits, suggesting that glycine receptors may belong to a superfamily of chemically gated channel proteins. However, very little is known about the modulation of glycine receptor channels. We have investigated the regulation of strychnine-sensitive glycine receptor channels by cyclic AMP-dependent protein kinase in neurons isolated from spinal trigeminal nucleus of rat and report here that the protein kinase A dramatically increased the glycine-induced Cl- currents by increasing the probability of the channel openings. GS protein, which is sensitive to cholera toxin, was involved in the modulation.

[Gemfibrozil in the treatment of hyperlipidemia]

An elevated serum cholesterol level is a well known major risk factor for developing atherosclerosis in general, and for coronary heart disease in particular. There are many lipid lowering agents currently available. We used gemfibrozil in twenty hyperlipidemic cases who failed to response to diet control for three months. They were thirteen males and seven females with their ages ranging from thirty to eighty-one year-old. They included ten diabetes, one nephrotic syndrome and nine pure hyperlipidemic patients. All cases received gemfibrozil 600mg twice daily for 4-12 weeks. Gemfibrozil caused an increase in HDL cholesterol. The reductions in serum level of total cholesterol, total cholesterol/HDL cholesterol, and triglyceride were found. Only one case developed mild gastrointestinal side effect. There was no other major side effects.

The effect of upstream sequences to initiator on the expression of gene coding for hepatitis B core antigen

The nucleotide sequences of cloned adw hepatitis B core antigens (HBcAg) which have different levels of expression have been determined by dideoxy chain-terminating method. The results indicate that the different levels of gene expression is primarily due to the different structures of upstream sequences before the initiator of HBcAg genes. The hepatitis B core gene in the low-expressed clone forms a secondary structure before the initiator. This secondary structure has been removed by Bal-31 exonuclease in the high-expressed clone and half of the structure removed in the mid-expressed clone. It is apparent that the transcription/translation of the hepatitis B core gene is somehow blocked because of the secondary structure. Therefore, the amount of HBcAg synthesized in E. coli is dramatically reduced.