Acute and chronic regulation of ob mRNA levels by beta3-adrenoceptor agonists in obese Yellow KK mice

The inhibitory effect of beta3-adrenoceptor agonists on the ob gene in brown adipose tissue (BAT) and white adipose tissue (WAT) is now well documented both in vivo in lean animals and in vitro, but the reported effects of beta3-adrenoceptor agonists on ob gene expression in obese animals remain controversial. We investigated whether ob gene expression in BAT and WAT is reduced by acute and chronic administrations of a beta3-adrenoceptor agonist, CL316,243 (CL). The ob gene mRNA levels in BAT, perimetric and inguinal WAT of obese Yellow KK mice were about 4-fold higher than those of lean controls. Acute exposure (6 h) to CL decreased ob gene mRNA levels in three fat depots in both animals. Chronic exposure (10 days) to CL also decreased ob gene mRNA levels in BAT, perimetric, and inguinal WAT in both animals. We concluded that acute and chronic regulation by a beta3-adrenoceptor agonist suppressed ob gene expression in obese Yellow KK mice and lean controls.

beta 3-Adrenergic agonist induces a functionally active uncoupling protein in fat and slow-twitch muscle fibers

The mitochondrial uncoupling protein (UCP) has usually been found only in brown adipose tissue. We recently observed that a chronic administration of the beta 3-adrenergic agonist CL-316,243 (CL) induced the ectopic expression of UCP in white fat and skeletal muscle in genetic obese yellow KK mice. The aim of the present study was to examine whether UCP could be induced in nongenetic obese animals produced by neonatal injections of monosodium L-glutamate (MSG). The daily subcutaneous injection of CL (0.1 mg/kg) to MSG-induced obese mice for 2 wk caused significant reductions of body weight (15%) and white fat pad weight (58%). Northern and Western blot analyses showed that CL induced significant expressions of UCP in the white fat and muscle, as well as in brown fat. Immunohistochemical observations revealed that the UCP stains in white fat were localized on multilocular cells and that those in muscle were localized on slow-twitch fibers rich in mitochondria. Immunoelectron microscopy confirmed the mitochondrial localization of UCP in the myocytes. The guanosine 5'-diphosphate (GDP) binding to mitochondria in brown fat doubled after the CL treatment. Moreover, significant GDP binding was detected in the white fat and muscle of the CL-treated mice, at about one-fourth and one-thirteenth the activity of brown fat, respectively, suggesting that ectopically expressed UCP is functionally active. We concluded that the beta 3-adrenergic agonist CL can induce functionally active UCP in white fat and slow-twitch muscle fibers of obese mice.

Effects of Trp64Arg mutation in the beta 3-adrenergic receptor gene on weight loss, body fat distribution, glycemic control, and insulin resistance in obese type 2 diabetic patients

OBJECTIVE

To investigate the effects of Trp64Arg mutation in the beta 3-adrenergic receptor gene on weight loss, body fat distribution, glycemic control, and insulin resistance in obese type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

We measured body weight, waist-to-hip ratio (WHR), adjusted resting metabolic rate, fasting blood glucose, fasting serum insulin levels, insulin resistance index (fasting glucose x fasting insulin/22.5), and HbA1c levels before and after 12 weeks of obesity treatment in 61 obese women with type 2 diabetes. The MvaI polymorphism of the beta 3-adrenergic receptor gene was determined by polymerase chain reaction-restriction fragment length polymorphism analysis.

RESULTS

Of obese type 2 diabetic patients, those with the mutation (n = 24) had a higher WHR (P < 0.001), a lower adjusted metabolic rate, and higher blood glucose levels, serum insulin levels, insulin resistance index (P < 0.001), and HbA1c levels (P = 0.016). Furthermore, patients with the mutation had smaller decreases in body weight, WHR, insulin resistance index, and HbA1c levels after the weight-loss program compared with patients without the mutation (n = 37), even though food intake, exercise, and serum thyroid hormone levels were similar in both groups.

CONCLUSIONS

These present findings show that the Trp64Arg allele of the beta 3-adrenergic receptor gene may predict difficulty in losing body weight, lowering WHR, and improving glycemic control and insulin resistance in obese patients with type 2 diabetes.

Beta 3-adrenoreceptor gene polymorphism: a newly identified risk factor for proliferative retinopathy in NIDDM patients

Proliferative diabetic retinopathy is an important cause of visual impairment. We investigated whether the polymorphism of the beta 3-adrenoreceptor (beta 3-AR) gene, which is associated with insulin resistance and an earlier onset of NIDDM, was associated with proliferative diabetic retinopathy (PDR) in 215 Japanese NIDDM patients with a duration of diabetes of > or = 10 years. The polymorphism of the beta 3-AR gene was determined by polymerase chain reaction-restriction fragment length polymorphism analysis. The Trp64Arg allele of the beta 3-AR gene was significantly more frequent in the NIDDM patients with PDR (P = 0.002), but not in those with non-PDR (P = 0.151), than in NIDDM patients without diabetic retinopathy. Those with the mutation had an earlier onset of diabetes, a longer duration of diabetes, and higher current and maximal BMI values, compared with those without the mutation. Moreover, this mutation was also associated with higher serum triglyceride and decreased HDL-cholesterol levels. When adjustment was made for age, age at diagnosis, duration of diabetes, current BMI, systolic blood pressure, HbA1e, and serum lipids in a multiple regression analysis, a significant association was found between the Trp64Arg allele and diabetic retinopathy (P = 0.039). The Arg/Arg or Arg/Trp genotype was significantly associated with PDR, compared with the Trp/Trp genotype, with an odds ratio of 2.55 (95% CI 1.25-5.16). We concluded that the beta 3-AR gene polymorphism is a newly identified risk factor for PDR.

Anti-obesity and anti-diabetic effects of CL316,243, a highly specific beta 3-adrenoceptor agonist, in Otsuka Long-Evans Tokushima Fatty rats: induction of uncoupling protein and activation of glucose transporter 4 in white fat

The anti-obesity and anti-diabetic effects of a highly specific beta 3-adrenoceptor agonist, CL316,243 (CL; beta 1: beta 2: beta 3 = 0:1:100,000), were investigated in Otsuka Long-Evans Tokushima Fatty (fatty) and Long-Evans Tokushima Otsuka (control) rats. Daily injection of CL (0.1 mg/kg, s.c.) to these rats (10 weeks old) for 14 weeks caused a significant reduction in body weight (fatty, 27%; control, 15%), associated with a marked decrease in fat pad weight (inguinal: fatty, 60%; control, 36%; retroperitoneal: fatty, 75%; control, 77%) without affecting food intake. The levels of uncoupling protein mRNA and protein levels of uncoupling protein (UCP), as well as guanosine 5'-diphosphate-binding (a reliable index of thermogenesis) in brown adipose tissue, were lower in the fatty than in the control rats. However, after CL treatment, these parameters in brown adipose tissue increased significantly 2- to 3-fold in both groups. Furthermore, uncoupling protein was induced in white adipose tissue as well as in brown adipose tissue. The fatty rats showed hyperglycemia and hyperinsulinemia during the glucose tolerance test, but CL ameliorated these parameters. These findings suggest that decreased thermogenesis in brown adipose tissue may be one of the causes of obesity in the fatty rats and that administration of CL prevents obesity by decreasing white fat mass, by activating brown adipose tissue thermogenesis, and by inducing uncoupling protein in white adipose tissue. Furthermore, CL treatment may inhibit diabetes mellitus by ameliorating obesity and by activating glucose transporter 4 in white adipose tissue and brown adipose tissue.

Octreotide and bromocriptine suppress thyroid hormone levels and thyroid nodule in an acromegalic patient with nontoxic autonomous goiter

An acromegalic patient with nontoxic autonomous goiter was sequentially treated with octreotide and bromocriptine. Before therapy, serum GH, PRL and insulin-like growth factor-I (IGF-I) levels were increased. Free T3 and free T4 were within the normal range with suppressed TSH levels, whereas 123Iodine-uptake of thyroid was 5.6% after 24 h. During treatment with octreotide and bromocriptine, serum GH, PRL, and IGF-I became normal and free T3 and free T4 were slightly but significantly decreased, but TSH levels remained very low. After thyroidectomy, thyroglobulin, free T3 and free T4 were further decreased, and the TSH levels were recovered to normal. These findings suggested that octreotide and bromocriptine inhibit the release of thyroid hormones from the autonomous thyroid gland directly or indirectly through the decline in IGF-I.

Beta 3-adrenergic-receptor polymorphism: a genetic marker for visceral fat obesity and the insulin resistance syndrome

We investigated whether the polymorphism of the beta 3-adrenergic receptor (beta 3-AR) gene, which is associated with insulin resistance in non-diabetic subjects and an earlier onset of non-insulin-dependent diabetes mellitus in Pima Indians, was associated with visceral fat obesity and features of the insulin resistance syndrome in Japanese premenopausal obese women. There was no difference between 131 obese women and 256 control subjects (0.23 vs 0.17, p = 0.112) in the frequency of the Arg64 allele. The visceral fat area measured by computerised tomography scan was greater in homozygous Arg64Arg (172 +/- 17 cm2, n = 6) and heterozygous Trp64Arg (178 +/- 47 cm2, n = 48) women than in women homozygous for the Trp64Trp (121 +/- 46 cm2, n = 77) genotype (p < 0.01). This was also reflected by increased total body fat but not by increased body mass index. The association between the Trp64 allele and visceral fat mass by multiple regression analysis, was independent of age, body mass index and total fat mass (p < 0.004). Moreover, homozygous carriers of the Arg64 allele had higher systolic blood pressure, higher fasting and post-load glucose and insulin concentrations, higher cholesterol, and triglyceride and lower HDL-cholesterol concentrations than homozygous carriers of the Trp64 allele. Some of these differences were also observed between heterozygous Trp64Arg and homozygous Trp64Trp genotypes (glucose tolerance, insulin and cholesterol concentration). We conclude that in obese women the beta 3-AR polymorphism may be used as a genetic marker for visceral fat obesity and the insulin resistance syndrome.

Effect of CL316,243, a highly specific beta(3)-adrenoceptor agonist, on lipolysis of epididymal, mesenteric and subcutaneous adipocytes in rats

To clarify whether a beta(3)-adrenoceptor agonist is more lipolytic in the visceral adipocytes than in the subcutaneous adipocytes, the lipolysis induced by CL316,243, a highly specific beta(3)-adrenoceptor agonist (relative selectivities of 0, 1 and 10,000 for beta(1)-, beta(2)- and beta(3)-receptors, respectively) was investigated in adipose tissue from rats. White adipocytes were prepared from the subcutaneous, mesenteric, and epididymal white adipose tissues of male Wistar rats (weighing about 150 g). Our findings showed that lipolysis of white adipocytes was stimulated both by the non-specific beta-adrenoceptor agonist, isoproterenol, and by the beta(3)-specific adrenoceptor agonist, CL316,243, but the lipolytic sensitivity to CL316,243 was about 10 times greater than that to isoproterenol in these three adipose tissues. Both isoproterenol and CL316,243 induced more noticeable lipolysis in the epididymal and mesenteric than in the subcutaneous adipose cells in terms of the pD2 value [-log mol l-1 for EC50 (the concentration of an agonist giving half of its own maximum stimulation)]. These findings show that CL316,243 is more lipolytic in the visceral adipose cells than in the subcutaneous adipose cells, although epididymal adipose cells showed a high lipolytic response close to those observed in visceral adipose cells. CL316,243 may therefore be especially useful for the treatment of visceral fat type obesity related to various diseases.

A case of Sheehan's syndrome with delirium

A 53 year old woman was brought to a psychiatric clinic because of delirium. Upon immediate examination, severe hyponatremia (105 mEq/L) was detected. She was suspected of having internal diseases and referred to our university hospital. When she reached our hospital she was delirious and showed excitement and agitation. Her electroencephalogram showed low voltage theta waves (20 microV) in all leads. She was hospitalized and diagnosed with acute tonsillar abscess and panhypopituitarism based on various endocrine tests. Her past history suggested that Sheehan's syndrome had developed after child-bearing at age 31, resulting in panhypopituitarism. After administration of antibiotics, the fever and tonsillar abscess gradually recovered, and the correction of electrolytes improved the level of consciousness, suggesting that the hyponatremia had been closely related to the clouding of consciousness. As the subsequent administration of cortisol kept the patient's serum sodium levels within the normal range, a decrease in plasma cortisol seemed to be the major cause of the hyponatremia. Psychological symptoms of panhypopituitarism often included abulia, apathy and occasionally coma. However, it is rare for a patient with panhypopituitarism to be misdiagnosed as having a psychiatric disease with delirium. This rare case is presented.

Expression of uncoupling protein in skeletal muscle and white fat of obese mice treated with thermogenic beta 3-adrenergic agonist

The mitochondrial uncoupling protein (UCP) is usually expressed only in brown adipose tissue (BAT) and a key molecule for metabolic thermogenesis. The effects of a highly selective beta 3-adrenergic agonist, CL316,243 (CL), on UCP expression in skeletal muscle and adipose tissues were examined in mice. Daily injection of CL (0.1 mg/kg, sc) to obese yellow KK mice for two weeks caused a significant reduction of body weight, associated with a marked decrease of white fat pad weight and hypertrophy of the interscapular BAT with a sixfold increase in UCP content. Clear signals of UCP protein and mRNA were detected by Western and Northern blot analyses in inguinal, mesenteric and retroperitoneal white fat pads, and also in gastrocnemius and quadriceps muscles, whereas no signal in saline-treated mice. The presence of UCP mRNA in muscle tissues was also confirmed by reverse transcription-PCR analysis. Weaker UCP signals were also detected in control C57BL mice treated with CL, but only in inguinal and retroperitoneal fat pads. Immunohistochemical examinations revealed that UCP stains in the white fat pads were localized on multilocular cells quite similar to typical brown adipocyte, and those in the muscle tissues on myocytes. The mitochondrial localization of UCP in myocytes was confirmed by immunoelectron microscopy. In addition to UCP protein, UCP mRNA was also detected in myocytes by in situ hybridization analysis. Thus, chronic stimulation of the beta 3-adrenergic receptor induces ectopic expression of UCP in adipose tissues conventionally considered as white fat and even in skeletal muscle, which probably contributes to the potent anti-obesity effect of the beta 3-adrenergic agonist.

Effect of CL316,243, a highly specific beta3-adrenoceptor agonist, on sympathetic nervous system activity in mice

To examine whether long-term administration of a beta3-adrenoceptor agonist influences sympathetic nervous system (SNS) activity, norepinephrine (NE) turnover, a reliable indicator of SNS activity, in the interscapular brown adipose tissue (IBAT), the heart, and the spleen, as well as urinary excretion of NE, were measured using mice treated with CL316,243 (CL), a highly specific beta3-adrenoceptor agonist, at a dose that stimulated thermogenesis and reduced body weight. CL significantly decreased NE turnover in the IBAT, heart, and spleen and decreased urinary excretion of NE without affecting food intake over 1 to 4 weeks of treatment. These findings show that long-term administration of the beta3-adrenoceptor agonist decreases SNS activity and urinary excretion of NE.

Anti-obesity and anti-diabetic effects of mazindol in yellow KK mice: its activating effect on brown adipose tissue thermogenesis

1. The anti-obesity and anti-diabetic effects of mazindol were evaluated in obese diabetic yellow KK mice and C57Bl control mice. 2. The study compound was fed through a gastric tube at a rate of 1 or 2 mg/kg per day (0.01 mol/L HCl as control) for 2 weeks. The following parameters were compared in treated and control animals: bodyweight, food intake, white adipose tissue (WAT) weight, brown adipose tissue (BAT) weight and its thermogenesis, noradrenaline (NA) turnover, blood glucose and serum insulin levels and glucose transporter 4 (GLUT4). 3. Furthermore, bodyweight loss of mice pair-fed the same amount of food as the mazindol-treated mice for 2 weeks was measured. 4. Mazindol significantly decreased food intake and significantly increased guanosine-5'-diphosphate-binding in BAT mitochondria and NA turnover in BAT in both yellow KK and C57Bl groups. The amounts of WAT in subcutaneous, mesenteric and retroperitoneal regions and bodyweights were significantly decreased in both groups. Bodyweight loss in mice pair fed with the mazindol-treated groups was approximately 70% compared with that in the mazindol-treated groups. Furthermore, mazindol decreased the levels of blood glucose and serum insulin during the glucose overloading test in yellow KK mice, but it did not influence the GLUT4 protein concentration in WAT and muscle. 5. These observations suggest that mazindol possesses both an anti-obesity action, due to the inhibition of appetite as well as the activation of BAT thermogenesis via increased NA turnover in BAT, and an anti-diabetic action. Consequently, mazindol may be useful for the treatment of obesity as well as non-insulin-dependent diabetes mellitus in obese persons.