Ingestion of whey protein and β-conglycinin exerts opposite effects on intestinal FGF15 and serotonin secretion in mice

Farnesoid X receptor (FXR) and Takeda G protein-coupled Receptor 5 (TGR5), the intestinal bile acid (BA) receptors, regulate the gut-derived hormones including fibroblast growth factor 15/19 (FGF15/19) and serotonin (5-hydrooxytryptamine, 5-HT). Here we show that ingestion of whey protein isolate, a milk protein, significantly decreased expression of heteromeric organic solute transporter Ostα and Ostβ, which is the basolateral BA transporter in the enterocyte, and increased the expression of FXR and FGF15 in C57BL6J mouse ileum and plasma FGF15 levels. In addition, the ingestion of whey protein isolate significantly suppressed expression of hepatic cholesterol-7α hydroxylase (CYP7A1), which induces the primary BA synthesis, bile salt export pump (BSEP) and sodium-taurocholate cotransporting polypeptide (NTCP), which are the key transporters for the BA excretion and uptake in the liver, and genes involved in gluconeogenesis, and decreased the primary BAs including cholic acid, taurocholic acid, glycocholic acid, and taurochenodeoxycholic acid in the liver compared with controls. Moreover, ingestion of whey protein isolate significantly decreased the expression of TGR5, glucagon-like peptide 1 (GLP-1), and tryptophan hydroxylase1 (Tph1) in the small intestine, leading to decreases in plasma 5-HT and insulin levels. On the other hand, ingestion of the soy protein β-conglycinin significantly increased the expression of Ostα and Ostβ, and decreased the expression of FGF15 in the ileum and plasma FGF15 levels, leading to the increases in expression of hepatic CYP7A1, BSEP, NTCP, and genes involved in gluconeogenesis, and the primary BAs in the liver. Moreover, ingestion of β-conglycinin significantly increased the expression of intestinal TGR5, GLP-1, and Tph1, leading to increases in plasma 5-HT and insulin levels. These findings suggest that whey protein and β-conglycinin have opposite effects on intestinal FGF15 and 5-HT secretion in mice.

The Regulatory Role of the Central and Peripheral Serotonin Network on Feeding Signals in Metabolic Diseases

Central and peripheral serotonin (5-hydroxytryptamine, 5-HT) regulate feeding signals for energy metabolism. Disruption of central 5-HT signaling via 5-HT2C receptors (5-HT2CRs) induces leptin-independent hyperphagia in mice, leading to late-onset obesity, insulin resistance, and impaired glucose tolerance. 5-HT2CR mutant mice are more responsive than wild-type mice to a high-fat diet, exhibiting earlier-onset obesity and type 2 diabetes. High-fat and high-carbohydrate diets increase plasma 5-HT and fibroblast growth factor-21 (FGF21) levels. Plasma 5-HT and FGF21 levels are increased in rodents and humans with obesity, type 2 diabetes, and non-alcohol fatty liver diseases (NAFLD). The increases in plasma FGF21 and hepatic FGF21 expression precede hyperinsulinemia, insulin resistance, hyperglycemia, and weight gain in mice fed a high-fat diet. Nutritional, pharmacologic, or genetic inhibition of peripheral 5-HT synthesis via tryptophan hydroxylase 1 (Tph1) decreases hepatic FGF21 expression and plasma FGF21 levels in mice. Thus, perturbing central 5-HT signaling via 5-HT2CRs alters feeding behavior. Increased energy intake via a high-fat diet and/or high-carbohydrate diet can upregulate gut-derived 5-HT synthesis via Tph1. Peripheral 5-HT upregulates hepatic FGF21 expression and plasma FGF21 levels, leading to metabolic diseases such as obesity, insulin resistance, type 2 diabetes, and NAFLD. The 5-HT network in the brain–gut–liver axis regulates feeding signals and may be involved in the development and/or prevention of metabolic diseases.

Pharmacologic inhibition of serotonin htr2b ameliorates hyperglycemia and the altered expression of hepatic FGF21, Sdf2l1, and htr2a in db/db mice and KKAy mice

Plasma fibroblast growth factor 21 (FGF21) levels and hepatic FGF21, serotonin 2a receptor (htr2a), and stromal cell-derived factor 2 like 1 (Sdf2l1) expression are increased in insulin-resistant C57BL6J mice fed a high-fat diet. Here we show that plasma FGF21 levels and hepatic FGF21, Sdf2l1, and htr2a expression were decreased in 6-week-old db/db mice compared with C57BL6J mice, whereas they were increased in 6-week-old KKA^y mice compared with KK mice. Expression of hepatic htr2b was increased in db/db mice and KKA^y mice compared with controls. Treatment with the selective htr2b antagonist SB204741 suppressed the hyperglycemia in either db/db mice or KKA^y mice. Treatment with SB20471 reversed the decreases in plasma FGF21 levels and hepatic FGF21, Sdf2l1, and htr2a expression in db/db mice, whereas it suppressed the increases in plasma FGF21 levels and hepatic FGF21, Sdf2l1, and htr2a expression in KKA^y mice. Moreover, treatment with SB204741 increased plasma FGF21 levels and expression of hepatic FGF21, htr2a, and Sdf2l1 in C57BL6J mice, whereas it decreased plasma FGF21 levels and hepatic FGF21 expression in KK mice. These findings suggest that pharmacologic inhibition of htr2b ameliorates the hyperglycemia and altered expression of hepatic FGF21, Sdf2l1 and htr2a in obese and diabetic db/db and KKA^y mice.

Low-frequency and low-intensity ultrasound increases cardiac parasympathetic neural activity and decreases clinic hypertension in elderly hypertensive subjects with type 2 diabetes

Background

The aims of the present study were to determine the effects of an ultrasound irradiation on clinic hypertension and the heart rate variability in elderly hypertensive subjects with type 2 diabetes.

Methods

We examined the effects of ultrasound (800 kHz, 25 mW/cm²) applied to the forearm for 10 min on the autonomic nerve activity and the difference between BP at home and at a clinic visit in Japanese subjects with type 2 diabetes and hypertension.

Results

In 108 subjects who displayed systolic BP (SBP) >140 mm Hg at a clinic visit, 75 subjects (69%) had a mean SBP <135 mm Hg at home and 33 subjects (31%) had a mean SBP >135 mm Hg at home in the morning for 14 days. SBP, pulse rate, and pulse pressure in the ultrasound treatment group were significantly lower than the baseline values in these hypertensive subjects with type 2 diabetes, and lower than those of placebo controls independently of SBP at home. In 31 subjects who displayed systolic BP >140 mm Hg at a clinic, standard deviation of all RR intervals and the root mean square of successive differences were significantly higher in the ultrasound treatment group than the baseline values in these hypertensive subjects with type 2 diabetes, and lower than those of placebo controls.

Conclusions

The ultrasound treatment increases the cardiac parasympathetic neural activity and decreases the differences between SBP at home and at a clinic visit in elderly hypertensive subjects with type 2 diabetes.

Liraglutide, a GLP-1 Receptor Agonist, Which Decreases Hypothalamic 5-HT2A Receptor Expression, Reduces Appetite and Body Weight Independently of Serotonin Synthesis in Mice

A recent report suggested that brain-derived serotonin (5-HT) is critical for maintaining weight loss induced by glucagon-like peptide-1 (GLP-1) receptor activation in rats and that 5-HT2A receptors mediate the feeding suppression and weight loss induced by GLP-1 receptor activation. Here, we show that changes in daily food intake and body weight induced by intraperitoneal administration of liraglutide, a GLP-1 receptor agonist, over 4 days did not differ between mice treated with the tryptophan hydroxylase (Tph) inhibitor p-chlorophenylalanine (PCPA) for 3 days and mice without PCPA treatment. Treatment with PCPA did not affect hypothalamic 5-HT2A receptor expression. Despite the anorexic effect of liraglutide disappearing after the first day of treatment, the body weight loss induced by liraglutide persisted for 4 days in mice treated with or without PCPA. Intraperitoneal administration of liraglutide significantly decreased the gene expression of hypothalamic 5-HT2A receptors 1 h after injection. Moreover, the acute anorexic effects of liraglutide were blunted in mice treated with the high-affinity 5-HT2A agonist (4-bromo-3,6-dimethoxybenzocyclobuten-1-yl) methylamine hydrobromide 14 h or 24 h before liraglutide injection. These findings suggest that liraglutide reduces appetite and body weight independently of 5-HT synthesis in mice, whereas GLP-1 receptor activation downregulates the gene expression of hypothalamic 5-HT2A receptors.

Low-frequency and low-intensity ultrasound irradiation to the forearm improves an index of arterial stiffness in subjects with type 2 diabetes and hypertension

Objectives

The arterial pressure-volume index (API) is a non-invasive assessment of arterial stiffness, and is suggested as a useful predictor of future cardiovascular events. The aim of the present study was to determine the effects of low-frequency and low-intensity ultrasound applied to the forearm for 10 min on the API in Japanese subjects with type 2 diabetes and hypertension.

Methods

We examined the effects of low-frequency and low-intensity ultrasound (800 kHz, 25 mW/cm²) applied to the forearm for 10 min on the API, blood pressure (BP) and pulse rate in 40 Japanese subjects (13 men and 27 women; mean age ± SE, 70 ± 2 years) with type 2 diabetes and hypertension, who had the API > 30 and systolic BP > 140 mmHg at a clinic visit. We also examined the effects of the ultrasound irradiation for 10 min on the API, BP and pulse rate in 33 Japanese subjects (11 men and 22 women; mean age ± SE, 65 ± 2 years) with type 2 diabetes and hypertension, who had the API > 30 and systolic BP (SBP) < 140 mmHg.

Results

The API, systolic BP and pulse rate in the ultrasound treatment group was significantly lower than the baseline values in the subjects who had the API > 30 and either the baseline of systolic BP > 140 mmHg or systolic BP < 140 mmHg.

Conclusions

The low-frequency and low-intensity ultrasound irradiation to the forearm for 10 min might be useful as a preventive application for arterial stiffness in subjects with type 2 diabetes and hypertension.

The acute anorexic effect of liraglutide, a GLP-1 receptor agonist, does not require functional leptin receptor, serotonin, and hypothalamic POMC and CART activities in mice

The acute anorexic effect of liraglutide, a GLP-1 receptor agonist, did not require functional leptin receptor, serotonin, and hypothalamic proopiomelanocortin and cocaine amphetamine regulated transcript activities in mice, although decrease in functional hypothalamic orexin activity might be involved in the acute anorexic effect of liraglutide.

Low-frequency and very low-intensity ultrasound decreases blood pressure in hypertensive subjects with type 2 diabetes

BACKGROUND

Despite lifestyle interventions and various types of anti-hypertension agents, hypertension remains difficult to control in some patients with type 2 diabetes. As a noninvasive device-based approach for the treatment of clinic hypertension, we examined the effects of low-frequency and low-intensity ultrasound (500 or 800kHz, 25mW/cm(2)) applied to the forearm on blood pressure (BP) and pulse rate in Japanese subjects with type 2 diabetes and hypertension.

METHODS

We examined the effects of low-frequency and low-intensity ultrasound (500 or 800kHz, 25mW/cm(2)) applied to the forearm on BP, pulse rate, and pulse pressure in 212 Japanese subjects (82 men and 130 women; mean age±SE, 65±1years) with type 2 diabetes and hypertension (systolic BP>140mmHg). The subjects were treated with anti-hypertension agents.

RESULTS

Systolic and diastolic BP, pulse rate, pulse pressure in the 800-kHz ultrasound treatment group were significantly lower than the baseline values in hypertensive subjects with type 2 diabetes, and lower than those of placebo controls. In addition, systolic and diastolic BP, pulse rate, and pulse pressure in the 500-kHz ultrasound treatment group were significantly lower than the baseline values in hypertensive subjects with type 2 diabetes, and systolic BP, pulse rate, and pulse pressure were significantly lower than those of placebo controls.

CONCLUSIONS

Low-frequency (800kHz or 500kHz) and low-intensity (25mW/cm(2)) ultrasound irradiation to the forearm might have potential usefulness as a therapeutic application for clinic hypertension in subjects with type 2 diabetes.

Pharmacologic stimulation of central GLP-1 receptors has opposite effects on the alterations of plasma FGF21 levels induced by feeding and fasting

Fibroblast growth factor 21 (FGF21) functions as an endocrine hormone to regulate energy metabolism. Circulating FGF21 is derived from the liver and is produced in response to alterations of nutritional status. Here we show the effects of liraglutide, a human glucagon-like-peptide-1 (GLP-1) receptor agonist, injected into the third cerebral ventricle on body weight and plasma FGF21 levels in free-feeding mice, food-deprived mice, and mice provided 1g after the injection. In free-feeding mice, liraglutide (5-100μg/kg) injected into the third cerebral ventricle suppressed food intake and body weight after 24h in a dose-dependent manner. Liraglutide (50 and 100μg/kg) significantly increased plasma FGF21 levels and hepatic FGF21 expression, whereas smaller doses (5 and 10μg/kg) had no effect. In food-deprived mice, body weight did not differ significantly between the saline control and liraglutide-treated groups, but liraglutide (100μg/kg) significantly decreased plasma FGF21 levels at 24h compared with the saline control. In mice provided 1g food, body weight did not differ significantly between the saline control and liraglutide-treated groups, but liraglutide (50μg/kg) significantly decreased plasma FGF21 levels at 24h compared with the saline control. These findings suggest that intracerebral injection of liraglutide decreases body weight by inhibiting food intake and increases plasma FGF21 levels in free-feeding mice, whereas it suppresses the elevations of plasma FGF21 levels induced by fasting or the restricted feeding. Thus, pharmacologic stimulation of central GLP-1 receptors has opposite effects on the alterations of plasma FGF21 levels induced by feeding and fasting.

Mosapride, a selective serotonin 5-HT4 receptor agonist, and alogliptin, a selective dipeptidyl peptidase-4 inhibitor, exert synergic effects on plasma active GLP-1 levels and glucose tolerance in mice

Pharmacologic stimulation of serotonin 5-HT4 receptors increased plasma active glucagon-like-peptide-1 (GLP-1) levels independent of feeding, and that pharmacologic stimulation of 5-HT4 receptors and pharmacologic inhibition of dipeptidyl peptidase-4 exerted synergic effects on plasma active GLP-1 levels and glucose tolerance in mice.

Pharmacological stimulation of serotonin 5-HT1B receptors enhances increases in plasma active glucagon-like peptide-1 levels induced by dipeptidyl peptidase-4 inhibition independently of feeding in mice

AIM

Glucagon-like peptide-1 (GLP-1), an incretin hormone, is released from intestinal L cells in response to nutrient ingestion. Dipeptidyl peptidase-4 (DPP-4) rapidly degrades the active form of GLP-1 to an inactive form in the bloodstream. The present study aimed to investigate the role of serotonin (5-HT)1B receptors in the regulation of plasma active GLP-1 levels and glucose tolerance under DPP-4 inhibition.

METHODS

C57BL6J mice treated with or without alogliptin, a highly selective DPP-4 inhibitor, for 4 days were intraperitoneally injected with either saline, the 5-HT1B/2C receptor agonist meta-chlorophenylpiperazine (mCPP) at 2.5mg/kg and 5mg/kg or the selective 5-HT1B receptor agonist CP94253 at 2.5mg/kg and 5mg/kg, and food-deprived after treatment. An hour later, plasma active GLP-1 levels were determined. Also, a glucose tolerance test was done by injecting D-glucose (2g/kg) following the injection of saline or CP94253 (5mg/kg) in mice treated with alogliptin.

RESULTS

Intraperitoneal injection of mCPP (2.5 and 5mg/kg) or CP94253 (2.5 and 5mg/kg) in mice treated with alogliptin for 4 days significantly increased plasma active GLP-1 levels compared with saline controls in mice that were food-deprived after the injections. While intraperitoneal injection of either mCPP or CP94253 alone had no significant effect on plasma active GLP-1 levels, the injection of CP94253 improved glucose tolerance in mice treated with alogliptin compared with saline.

CONCLUSION

These findings suggest that pharmacological stimulation of 5-HT1B receptors enhances the increases in plasma active GLP-1 induced by DPP-4 inhibition independently of feeding and also improves glucose tolerance in mice.

Ingestion of eicosapentaenoic acid in the early stage of social isolation reduces a fibroblast growth factor 21 resistant state independently of body weight in KKA(y) mice

Fibroblast growth factor (FGF) 21 is a mediator of glucose and lipid metabolism. Although exogenous administration of FGF21 exerts beneficial effects on glucose and lipid metabolism, circulating FGF21 levels are elevated in ob/ob and db/db mice, diet-induced obese mice and obese human. Here we show that ingestion of eicosapentaenoic acid (EPA) for 6 days after individually-housing significantly suppressed the hyperglycemia and hypertriglyceridemia associated with decreases in plasma insulin and FGF21 levels in KKA(y) mice while having no effects on food intake, body weight or plasma active GLP-1 levels. The ingestion of EPA had no significant effects on the expression of FGF21 in the liver, epididymal white adipose tissue and skeletal muscle. Moreover, the ingestion of EPA significantly decreased the expression of hepatic peroxisome sterol regulatory element-binding protein (SREBP1c), carbohydrate response element-binding protein (ChREBP), stearoyl-CoA deaturase and periostin, which are involved in hepatic lipogenesis and hepatosteaotosis, in KKA(y) mice. On the other hand, the ingestion of EPA had no significant effects on expression of hepatic gp78, Notch, forkhead box protein O1 or glucose-6-phosphatase. These findings suggest that EPA ingestion in the early stage of social isolation suppresses hyperglycemia and hypertriglyceridemia associated with reduced FGF21 and insulin resistance without altering food intake and body weight, and that the EPA ingestion suppresses hepatic lipogenesis by suppressing Notch- and gp78-independent SEREBP1c and ChREBP pathways in KKA(y) mice.

Role of homeobox genes in the hypothalamic development and energy balance

Homeobox genes contribute to the regionalization, patterning and cell differentiation during embryogenesis and organ development. During mammalian embryonic development, homeobox genes, including orthopedia (Otp), a brain-specific homeobox transcription factor (Bsx) and a thyroid transcription factor-1 (TTF-1), are expressed in the hypothalamus. The genetic ablation of these genes indicated that Otp and TTF-1 are essential for the normal morphological development of the hypothalamus, including the arcuate nucleus (ARC), whereas Bsx is not required. In the adult stage, Bsx and TTF-1 continue to be expressed in the hypothalamus, including the ARC, and serve as transcription factors of neuropeptide Y and agouti-related protein. The expression of hypothalamic Bsx and TTF-1 can be altered by the feeding state and appetite regulatory hormones such as ghrelin and leptin. Although Bsx and TTF-1 are essential for normal feeding behavior in adult mice, they exert different effects on the expression of hypothalamic pro-opiomelanocortin (POMC) and body weight homeostasis. Thus, the hypothalamic homeobox genes may contribute to the dissociation of food intake and body weight via AgRP-POMC neurons.

Serotonin conflict in sleep-feeding

Short sleep duration has been suggested to be a risk factor for weight gain and adiposity. Serotonin (5-HT) substantially contributes to the regulation of sleep and feeding behavior. Although 5-HT predominately promotes waking and satiety, the effects of 5-HT depend on 5-HT receptor function. The 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2C, 5-HT6, and 5-HT7 receptors reportedly contribute to sleep-waking regulation, whereas the 5-HT1B and 5-HT2C receptors contribute to the regulation of satiety. The 5-HT1B and 2C receptors may therefore be involved in the regulation of sleep-feeding. In genetic studies, 5-HT1B receptor mutant mice display greater amounts of rapid eye movement sleep (REMS) than wild-type mice, while displaying no effects on waking or slow wave sleep (SWS). On the other hand, 5-HT2C receptor mutant mice exhibit increased wakefulness and decreased SWS, without any effect on REMS. Moreover, the 5-HT2C receptor mutants display leptin-independent hyperphagia, leading to a middle-aged onset of obesity, whereas 5-HT1B receptor mutants do not display any effect on food intake. Thus, the genetic deletion of 5-HT2C receptors results in sleep loss-associated hyperphagia, leading to the late onset of obesity. This is a quite different pattern of sleep-feeding behavior than is observed in disturbed leptin signaling, which displays an increase in sleep-associated hyperphagia. In pharmacologic studies, 5-HT1B and 5-HT2C receptors upregulate wakefulness and downregulate SWS, REMS, and food intake. These findings suggest that 5-HT1B/2C receptor stimulation induces sleep loss-associated anorexia. Thus, the central 5-HT regulation of sleep-feeding can be dissociated. Functional hypothalamic proopiomelanocortin and orexin activities may contribute to the dissociated 5-HT regulation.

The contribution of serotonin 5-HT2C and melanocortin-4 receptors to the satiety signaling of glucagon-like peptide 1 and liraglutide, a glucagon-like peptide 1 receptor agonist, in mice

Glucagon-like peptide 1 (GLP-1), an insulinotropic gastrointestinal peptide produced mainly from intestinal endocrine L-cells, and liraglutide, a GLP-1 receptor (GLP-1R) agonist, induce satiety. The serotonin 5-HT2C receptor (5-HT2CR) and melanoroctin-4 receptor (MC4R) are involved in the regulation of food intake. Here we show that systemic administration of GLP-1 (50 and 200μg/kg)-induced anorexia was blunted in mice with a 5HT2CR null mutation, and was attenuated in mice with a heterozygous MC4R mutation. On the other hand, systemic administration of liraglutide (50 and 100μg/kg) suppressed food intake in mice lacking 5-HT2CR, mice with a heterozygous mutation of MC4R and wild-type mice matched for age. Moreover, once-daily consecutive intraperitoneal administration of liraglutide (100μg/kg) over 3days significantly suppressed daily food intake and body weight in mice with a heterozygous mutation of MC4R as well as wild-type mice. These findings suggest that GLP-1 and liraglutide induce anorexia via different central pathways.

Contribution of central SGK-1 to the acute phase responses of mice to social isolation

Ghrelin is a hormone produced mainly by P/D1 cells which line the fundus of the stomach and epsilon cells of the pancreas that stimulate hunger. Ghrelin exists in an endocrinologicaly inactive (des-acyl ghrelin) and active (n-octanoyl-modified ghrelin) forms. The serum- and glucocorticoid-inducible kinase 1 (SGK-1) is a member of the AGC family of serine/threonine protein kinase. In this study, mice were isolated individually or in groups, and deprived from food supply for a period of 24-h. Despite decreases in plasma corticosterone levels and no changes in plasma des-acyl ghrelin, and the expression of hypothalamic neuropeptide Y and proopiomelanocortin, plasma active ghrelin levels and the expression of hypothalamic SGK-1 were increased in the acute-isolated mice. Injection of SGK-1 small interfering RNA (siRNA) oligonucleotide into the third cerebral ventricle suppressed the acute social isolation-induced decreases in body weight and increases in plasma active ghrelin levels. Pretreatment with phentolamine (alpha-adrenergic receptor antagonist) but not alprenolol (beta-adrenergic receptor antagonist), partially but significantly suppressed the decreases in body weight induced by acute isolation stress. These finding suggest that isolation stress is a novel inducer of hypothalamic SGK-1 expression. SGK-1 might contribute to the isolation stress-induced body weight reductions and increases in plasma active ghrelin levels via, at least partly, altered central autonomic outflow in mice.

Fluvoxamine, a selective serotonin reuptake inhibitor, and 5-HT2C receptor inactivation induce appetite-suppressing effects in mice via 5-HT1B receptors

Serotonin (5-hydroxytryptamine; 5-HT) 2C receptors and the downstream melanocortin pathway are suggested to mediate the appetite-suppressing effects of 5-HT drugs such as m-chlorophenylpiperazine (mCPP) and fenfluramine. Here, we report that fluvoxamine (3-30 mg/kg), a selective serotonin reuptake inhibitor (SSRI), in the presence of SB 242084 (1-2 mg/kg), a selective 5-HT2C receptor antagonist, exerts appetite-suppressing effects while fluvoxamine or SB 242084 alone has no effect. The appetite-suppressing effects were attenuated in the presence of SB 224289 (5 mg/kg), a selective 5-HT1B receptor antagonist. Moreover, CP 94253 (5-10 mg/kg), a selective 5-HT1B receptor agonist, exerted appetite-suppressing effects and significantly increased hypothalamic pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) gene expression and decreased hypothalamic orexin gene expression. These results suggest that fluvoxamine and inactivation of 5-HT2C receptors exert feeding suppression through activation of 5-HT1B receptors, and that 5-HT1B receptors up-regulate hypothalamic POMC and CART gene expression and down-regulate hypothalamic orexin gene expression in mice.

Social isolation affects the development of obesity and type 2 diabetes in mice

Social isolation is associated with increased risks of mortality and morbidity. In this study, we show that chronic individual housing accelerated body weight gain and adiposity in KK mice but not C57BL6J mice, and fully developed diabetes in KKA(y) mice. Individually housed KK and KKA(y) mice increased body weight gain over the initial 2 wk without increased daily average food consumption compared with group-housed animals. The individually housed KK and KKA(y) mice then gradually increased food consumption for the next 1 wk. The chronic social isolation-induced obesity (SIO) was associated with hyperleptinemia and lower plasma corticosterone and active ghrelin levels but not hyperinsulinemia. Elevated plasma leptin in the SIO suppressed expression of 5-HT2C receptor in white adipose tissue. The SIO was also associated with decreased expression of beta3-adrenergic receptors in white adipose tissue and hypothalamic leptin receptor, which might be secondary to the enhanced adiposity. Interestingly, social isolation acutely reduced food consumption and body weight gain compared with group-housed obese db/db mice with leptin receptor deficiency. Social isolation-induced hyperglycemia in KKA(y) mice was associated with increased expression of hepatic gluconeogenetic genes independent of insulin. These findings suggest that social isolation promotes obesity due to primary decreased energy expenditure and secondary increased food consumption, which are independent of the disturbed leptin signaling, in KK mice, and develops into insulin-independent diabetes associated with increased expression of hepatic gluconeogenetic genes in KKA(y) mice. Thus, social isolation can be included in the environmental factors that contribute to the development of obesity and type 2 diabetes.

Serotonin activates the hypothalamic-pituitary-adrenal axis via serotonin 2C receptor stimulation

The dynamic interplay between serotonin [5-hydroxytryptamine (5-HT)] neurotransmission and the hypothalamic-pituitary-adrenal (HPA) axis has been extensively studied over the past 30 years, but the underlying mechanism of this interaction has not been defined. A possibility receiving little attention is that 5-HT regulates upstream corticotropin-releasing hormone (CRH) signaling systems via activation of serotonin 2C receptors (5-HT(2C)Rs) in the paraventricular nucleus of the hypothalamus (PVH). Through complementary approaches in wild-type rodents and 5-HT(2C)R-deficient mice, we determined that 5-HT(2C)Rs are necessary for 5-HT-induced HPA axis activation. We used laser-capture PVH microdissection followed by microarray analysis to compare the expression of 13 5-HTRs. Only 5-HT(2C)R and 5-HT(1D)R transcripts were consistently identified as present in the PVH, and of these, the 5-HT(2C)R was expressed at a substantially higher level. The abundant expression of 5-HT(2C)Rs in the PVH was confirmed with in situ hybridization histochemistry. Dual-neurohistochemical labeling revealed that approximately one-half of PVH CRH-containing neurons coexpressed 5-HT(2C)R mRNA. We observed that PVH CRH neurons consistently depolarized in the presence of a high-affinity 5-HT(2C)R agonist, an effect blocked by a 5-HT(2C)R antagonist. Supporting the importance of 5-HT(2C)Rs in CRH neuronal activity, genetic inactivation of 5-HT(2C)Rs produced a downregulation of CRH mRNA and blunted CRH and corticosterone release after 5-HT compound administration. These findings thus provide a mechanistic explanation for the longstanding observation of HPA axis stimulation in response to 5-HT and thereby give insight into the neural circuitry mediating the complex neuroendocrine responses to stress.

Combined treatment with immunotherapy and chemotherapy using endoscopic ultrasonography guided injection for locally advanced pancreatic carcinoma

13503

Background: Dendritic cells (DCs) play a pivotal role in T cell-mediated immunity. Usually, mature DCs were cultured using resected tumor tissue, but for inoperable cases, this method is impractical. The injection of immature DCs into the tumor after appropriate chemotherapy is reasonable, if DCs come to maturity capturing the specific cancer antigen . The aim of this study is to assess the toxicity and efficacy of combined treatment with immunotherapy and chemotherapy for locally advanced pancreatic carcinoma. Methods: Five patients with pathologically confirmed pancreatic ductal carcinoma using EUS-FNA were enrolled, median age 56 years (range, 46–70 years). All cases without distant metastasis were diagnosed as surgically unresectable . Patients underwent leukapheresis, immature DCs were prepared from peripheral blood by a culture with granulocyte macrophage colony-stimulating factor and interleukin 4. Lymphokine-activated killer (LAK) were also prepared from peripheral blood. Immature DCs were injected biweekly in the mass by endoscopic ultrasound-guided fine needle injection (EUS-FNI), LAK were administered intravenously. Patients received the treatment of gemcitabine 1000 mg / m2 by intravenous injection 3 days before the immunotherapy. One course with 6 times combined therapy was continued until the judgment of progressive diseases (PD) was given. The toxicity and efficacy of this treatment were assessed. We also assessed whether tumor associated antigen (TAA)-specific IFN-?producing cells increase after treatment. Results: Hematological toxicity occurred in one case, leucopenia of grade 2. No severe toxicities of grade 3 to 4 occurred. One had a partial response (PR), stable disease (SD) was observed in 2 patients for more than 6 months (long-term SD). PR patient could undergo curative operation after this therapy. The number of TAA-specific IFN-?producing cells in PR patient increased 12-fold higher than that seen before treatments. Conclusions: These results support the safety and efficacy of combined treatment with immunotherapy and chemotherapy for locally advanced pancreatic ductal carcinoma. This treatment may be a useful for the treatment of pancreatic ductal carcinoma.

No significant financial relationships to disclose.

Milnacipran, a serotonin and norepinephrine reuptake inhibitor, induces appetite-suppressing effects without inducing hypothalamic stress responses in mice

Milnacipran, a selective serotonin (5-HT) and norepinephrine (NE) reuptake inhibitor, increases extracellular 5-HT and NA levels equally in the central nervous system. Here, we report that systemic administration of milnacipran (20–60 mg/kg) significantly suppressed food intake after fasting in C57BL6J mice. The appetite-suppressing effects of milnacipran were sustained for 5 h. Neither SB242084, a selective 5-HT2C receptor antagonist, nor SB224289, a selective 5-HT1B receptor antagonist, reversed the appetite-suppressing effects of milnacipran. Milnacipran suppressed food intake and body weight in wild-type mice and in Ay mice, which have ectopic expression of the agouti protein. Moreover, milnacipran significantly increased hypothalamic proopiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) mRNA levels, while having no effect on hypothalamic neuropeptide Y, ghrelin, corticotropin-releasing hormone (CRH), and suppressor of cytokine signaling-3 mRNA levels. Interestingly, milnacipran did not increase plasma corticosterone and blood glucose levels, whereas fenfluramine, which inhibits 5-HT reuptake and stimulates 5-HT release, significantly increased plasma corticosterone and blood glucose levels in association with increased hypothalamic CRH mRNA levels. The appetite-suppressing effects of milnacipran had no effects on food intake in food-restricted, wild-type mice and Ay mice. On the other hand, fenfluramine suppressed food intake in food-restricted wild-type mice, but it had no effects in food-restricted Ay mice. These results suggest that inhibition of 5-HT and NA reuptake induces appetite-suppressing effects independent of 5-HT2C and 5-HT1B receptors, and increases hypothalamic POMC and CART gene expression without increasing plasma corticosterone and blood glucose levels in mice.

Ghrelin and feedback systems

Ghrelin is produced primarily in the stomach in response to hunger, and circulates in the blood. Plasma ghrelin levels increase during fasting and decrease after ingesting glucose and lipid, but not protein. The efferent vagus nerve contributes to the fasting-induced increase in ghrelin secretion. Ghrelin secreted by the stomach stimulates the afferent vagus nerve and promotes food intake. Ghrelin also stimulates pituitary gland secretion of growth hormone (GH) via the afferent vagus nerve. GH inhibits stomach ghrelin secretion. These findings indicate that the vagal circuit between the central nervous system and stomach has a crucial role in regulating plasma ghrelin levels. Moreover, body mass index modulates plasma ghrelin levels. In a lean state and anorexia nervosa, plasma ghrelin levels are increased, whereas in obesity, except in Prader-Willi syndrome, plasma ghrelin levels are decreased and the feeding- and sleeping-induced decline in plasma ghrelin levels is disrupted. There are two forms of ghrelin: active n-octanoyl-modified ghrelin and des-acyl ghrelin. Fasting increases both ghrelin types compared with the fed state. Hyperphagia and obesity are likely to decrease plasma des-acyl ghrelin, but not n-octanoyl-modified ghrelin levels. Hypothalamic serum and glucocorticoid-inducible kinase-1 and serotonin 5-HT2C/1B receptor gene expression levels are likely to be proportional to plasma des-acyl ghrelin levels during fasting, whereas they are likely to be inversely proportional to plasma des-acyl ghrelin levels in an increased energy storage state such as obesity. Thus, a dysfunction of the ghrelin feedback systems might contribute to the pathophysiology of obesity and eating disorders.

Increased hypothalamic 5-HT2A receptor gene expression and effects of pharmacologic 5-HT2A receptor inactivation in obese Ay mice

Serotonin (5-hydroxytryptamine; 5-HT) 2A receptors contribute to the effects of 5-HT on platelet aggregation and vascular smooth muscle cell proliferation, and are reportedly involved in decreases in plasma levels of adiponectin, an adipokine, in diabetic subjects. Here, we report that systemic administration of sarpogrelate, a 5-HT2A receptor antagonist, suppressed appetite and increased hypothalamic pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript, corticotropin releasing hormone, 5-HT2C, and 5-HT1B receptor gene expression. A(y) mice, which have ectopic expression of the agouti protein, significantly increased hypothalamic 5-HT2A receptor gene expression in association with obesity compared with wild-type mice matched for age. Systemic administration of sarpogrelate suppressed overfeeding, body weight gain, and hyperglycemia in obese A(y) mice, whereas it did not increase plasma adiponectin levels. These results suggest that obesity increases hypothalamic 5-HT2A receptor gene expression, and pharmacologic inactivation of 5-HT2A receptors inhibits overfeeding and obesity in A(y) mice, but did not increase plasma adiponectin levels.

Hyperphagia alters expression of hypothalamic 5-HT2C and 5-HT1B receptor genes and plasma des-acyl ghrelin levels in Ay mice

The central melanocortin (MC) pathway is suggested to mediate satiety signaling downstream of serotonin (5-HT)2C receptors. 5-HT2C receptor mutant mice consume more food, which leads to late-onset obesity and impaired glucose tolerance. Ay mice with ectopic expression of the agouti peptide, which leads to a perturbation of the central MC pathway, develop obesity and diabetes, associated with low levels of plasma total ghrelin. Here, we report that 5-wk-old Ay mice consumed more food in association with decreases in levels of plasma des-acyl ghrelin, but not active ghrelin, and increases in hypothalamic 5-HT2C and 5-HT1B receptor gene expression compared with wild-type mice matched for age and body weight. These alterations were also observed in 8-wk-old obese Ay mice. Restricted feeding significantly decreased hypothalamic 5-HT2C and 5-HT1B receptor gene expression in association with a reversal of the decreases in plasma des-acyl ghrelin levels in 5-wk-old Ay mice. Moreover, restricted feeding reduced body weight, hyperinsulinemia, and hyperglycemia in association with increases in plasma des-acyl ghrelin levels in 8-wk-old obese Ay mice. Administration of m-chlorophenylpiperazine and fenfluramine, both of which induce anorexic effects via 5-HT2C receptors and/or 5-HT1B receptors, suppressed food intake in 5- and 8-wk-old Ay mice, whereas the anorexic effects were attenuated in food-restricted Ay mice. These findings suggest that the agouti peptide down-regulates hypothalamic 5-HT2C and 5-HT1B receptor gene expression under restricted feeding conditions, whereas chronic hyperphagia increases the expression of these genes and decreases plasma des-acyl ghrelin levels in Ay mice.

Induction of hypothalamic serum- and glucocorticoid-induced protein kinase-1 gene expression and its relation to plasma des-acyl ghrelin in energy homeostasis in mice

Serum- and glucocorticoid-induced protein kinase (SGK) is a serine/threonine-specific protein kinase that is transcriptionally regulated by serum, glucocorticoids, and mineral corticoids. Here, we report that fasting or obesity with hyperphagia increased hypothalamic SGK-1 gene expression. Hypothalamic SGK-1 mRNA levels were proportional to daily food intake and body weights in C57BL6J mice, KK mice, and KKA(y) mice matched for age. Plasma des-acyl ghrelin, but not active ghrelin, levels were inversely proportional to daily food intake and body weights among these animals. The increases in hypothalamic SGK-1 gene expression in these animals were not accompanied by increases in plasma corticosterone levels. Under conditions of increased energy usage such as fasting, hypothalamic SGK-1 gene expression and plasma des-acyl ghrelin levels were positively correlated while during conditions of increased energy storage, they were negatively correlated. These results suggest that hypothalamic SGK-1 gene is a novel candidate gene involving in energy homeostasis in mice.

A negative feedback system between brain serotonin systems and plasma active ghrelin levels in mice

Brain serotonin (5-hydroxytryptamine; 5-HT) systems contribute to regulate eating behavior and energy homeostasis. 5-HT2C receptors and 5-HT1B receptors have been shown to mediate anorexic effects of 5-HT drugs such as d-fenfluramine, which stimulates 5-HT release and inhibits 5-HT reuptake, and m-chlorophenylpiperazine (mCPP), a 5-HT2C receptor agonist. Here, we report that 24-h fasting increased the expression of hypothalamic 5-HT2C receptor and 5-HT1B receptor genes in association with increases in plasma active ghrelin levels compared with fed state in mice. Treatment with mCPP or fenfluramine significantly inhibited the increases in plasma active ghrelin levels. mCPP or fenfluramine significantly increased the expression of hypothalamic pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript genes while having no significant effects on the expression of hypothalamic neuropeptide Y, agouti- related protein, and ghrelin genes. These results suggest that there is a negative feedback system between brain 5-HT systems and plasma active ghrelin levels in energy homeostasis in mice.

Hyperactivity and reduced energy cost of physical activity in serotonin 5-HT(2C) receptor mutant mice

We have observed late-onset obesity in mutant mice lacking the serotonin 5-HT(2C) receptor. Despite chronically elevated food intake, young adult mutants exhibit neither elevated adiposity nor altered glucose or fat homeostasis. However, obesity subsequently develops after 6 months of age without increases in their level of hyperphagia. In this study, we investigated determinants of energy expenditure in 5-HT(2C) receptor mutant mice. Young adult mutants displayed patterns of elevated activity levels that were enhanced by fasting and tightly associated with repeated visits to a food source. Surprisingly, subsequent obesity development occurred despite persisting locomotor hyperactivity and without age-related declines in resting metabolic rate. Rather, substantial reductions in the energy cost of locomotor activity (LA) were observed in 5-HT(2C) receptor mutant mice. Moreover, both mutant and wild-type mice displayed age-related declines in the energy cost of LA, indicating that this process may be regulated by both aging and serotonergic signaling. These results indicate that a mutation of the 5-HT(2C) receptor gene (htr2c) increases LA, which contributes to the maintenance of normal body composition in young adult mutants despite their hyperphagia. Moreover, age-dependent reductions in the energy cost of physical activity could contribute to the subsequent development of late-onset obesity in 5-HT(2C) receptor mutant mice.

Altered gene expressions involved in energy expenditure in 5-HT(2C) receptor mutant mice

Mice with a targeted null mutation of the serotonin 5-HT(2C) receptor gene exhibit hyperphagia that leads to a late-onset obesity. Here we show that oxygen consumption was decreased in fed and fasted obese mutants. No phenotypic differences were observed in uncoupling protein-1 (UCP-1) mRNA levels in brown adipose tissues and UCP-3 mRNA in skeletal muscle. UCP-2 mRNA levels were significantly increased in white adipose tissue (4-fold) and skeletal muscle (47%) in older obese mutant mice, whereas UCP-2 mRNA in liver are significantly increased in both young lean (54% increase) and older obese (52% increase) mutant mice. In contrast, 5-HT(2C) receptor mutants displayed age-dependent decreases in beta 3-adrenergic receptor (beta 3-AR) mRNA levels in white adipose tissue, however, no such changes were observed in brown adipose tissue. These results indicate that a mutation of 5-HT(2C) receptor gene leads to a secondary decrease in beta 3-AR gene expression that is related to enhanced adiposity.

Up-regulation of peroxisome proliferator-activated receptors (PPAR-alpha) and PPAR-gamma messenger ribonucleic acid expression in the liver in murine obesity: troglitazone induces expression of PPAR-gamma-responsive adipose tissue-specific genes in the liver of obese diabetic mice

Peroxisome proliferator-activated receptors (PPARs) are transcription factors that play an important role in the regulation of genes involved in lipid utilization and storage, lipoprotein metabolism, adipocyte differentiation, and insulin action. The three isoforms of the PPAR family, i.e. alpha, delta, and gamma, have distinct tissue distribution patterns. PPAR-alpha is predominantly present in the liver, and PPAR-gamma in adipose tissue, whereas PPAR-delta is ubiquitously expressed. A recent study reported increased PPAR-gamma messenger RNA (mRNA) expression in the liver in ob/ob mice; however, it is not known whether increased PPAR-gamma expression in the liver has any functional consequences. The expression of PPAR-alpha and -delta in the liver in obesity has not been determined. We have now examined the mRNA levels of PPAR-alpha, -delta, and -gamma in three murine models of obesity, namely, ob/ob (leptin-deficient), db/db (leptin-receptor deficient), and serotonin 5-HT2c receptor (5-HT2cR) mutant mice. 5-HT2cR mutant mice develop a late-onset obesity that is associated with higher plasma leptin levels. Our results show that PPAR-alpha mRNA levels in the liver are increased by 2- to 3-fold in all three obese models, whereas hepatic PPAR-gamma mRNA levels are increased by 7- to 9-fold in ob/ob and db/db mice and by 2-fold in obese 5-HT2cR mutant mice. PPAR-delta mRNA expression is not altered in ob/ob or db/db mice. To determine whether increased PPAR-gamma expression in the liver has any functional consequences, we examined the effect of troglitazone treatment on the hepatic mRNA levels of several PPAR-gamma-responsive adipose tissue-specific genes that have either no detectable or very low basal expression in the liver. The treatment of lean control mice with troglitazone significantly increased the expression of adipocyte fatty acid-binding protein (aP2) and fatty acid translocase (FAT/CD36) in the liver. This troglitazone-induced increase in the expression of aP2 and FAT/CD36 was markedly enhanced in the liver in ob/ob mice. Troglitazone also induced a pronounced increase in the expression of uncoupling protein-2 in the liver in ob/ob mice. In contrast to the liver, troglitazone did not increase the expression of aP2, FAT/CD36, and uncoupling protein-2 in adipose tissue in lean or ob/ob mice. Taken together, our results suggest that the effects of PPAR-gamma activators on lipid metabolism and energy homeostasis in obesity and type 2 diabetes may be partly mediated through their effects on PPAR-gamma in the liver.

New insights into sympathetic regulation of glucose and fat metabolism

The autonomic nervous system modulates glucose and fat metabolism through both direct neural effects and hormonal effects. This review presents recent concepts on the sympathetic regulation of glucose and fat metabolism. Focally released norepinephrine from sympathetic nerves is likely to increase glucose uptake in skeletal muscle and adipose tissues independent of insulin but norepinephrine does not contribute so much as epinephrine to hepatic glucose production. Epinephrine increases hepatic glucose production and inhibits insulin secretion and the glucose uptake by tissues that is induced by insulin. Additionally, catecholamines can increase thermogenesis and lipolysis, leading to increased energy expenditure and decreased fat stores. It is likely that beta-(beta3)-adrenergic receptors mediate these responses. Alterations of central neurotransmission and environmental factors can change the relative contribution of sympathetic outflow to the pancreas, liver, adrenal medulla and adipose tissues, leading to the modulation of glucose and fat metabolism. Recent studies have proposed that leptin, an adipocyte hormone, affects the central nervous system to increase sympathetic outflow independent of feeding. The effects of leptin on glucose and fat metabolism could be in part mediated by the sympathetic nervous system. Studies using mice with a genetic disruption of serotonin 5-HT2c receptor indicate that central neural mechanisms in the regulation of sympathetic outflow and satiety could be dissociated. Abnormalities of sympathetic effects, including disturbances of leptin and beta3-adrenergic receptor signalling, are likely to cause obesity and impaired glucose tolerance in rodents and humans. These findings indicate that dysfunction of the sympathetic nervous system could predispose to obesity and Type II (non-insulin-dependent) diabetes mellitus.

Leptin-independent hyperphagia and type 2 diabetes in mice with a mutated serotonin 5-HT2C receptor gene

Brain serotonin and leptin signaling contribute substantially to the regulation of feeding and energy expenditure. Here we show that young adult mice with a targeted mutation of the serotonin 5-HT2C receptor gene consume more food despite normal responses to exogenous leptin administration. Chronic hyperphagia leads to a 'middle-aged'-onset obesity associated with a partial leptin resistance of late onset. In addition, older mice develop insulin resistance and impaired glucose tolerance. Mutant mice also responded more to high-fat feeding, leading to hyperglycemia without hyperlipidemia. These findings demonstrate a dissociation of serotonin and leptin signaling in the regulation of feeding and indicate that a perturbation of brain serotonin systems can predispose to type 2 diabetes.

Stress, acute hyperglycemia, and hyperlipidemia role of the autonomic nervous system and cytokines

Stress is accompanied by metabolic alterations that could contribute to the etiology of diabetes mellitus, arteriosclerosis, and cardiovascular diseases; however, the mechanisms by which stress affects glucose and lipid metabolism remain to be resolved. Stress-induced effects on neurotransmission and interleukin-1 (IL-1) signaling rapidly produce hyperglycemia by increasing sympathetic outflow. Activation of the sympathetic nervous system can also rapidly stimulate lipolysis and hepatic triglyceride secretion. Furthermore, stress increases serum interleukin-6 (IL-6) and nerve growth factor (NGF) levels by activating neuroendocrine systems. IL-6 and NGF can rapidly increase lipolysis and hepatic triglyceride secretion without inducing hyperglycemia. The sympathetic nervous system does not mediate cytokine-induced hypertriglyceridemia. Thus, the central nervous system plays an important role in regulation of hepatic glucose and lipid metabolism via the sympathetic nervous system and cytokines. (Trends Endocrinol Metab 1997;8:192-197). (c) 1997, Elsevier Science Inc.

Role of central neural mechanisms in the regulation of hepatic glucose metabolism

Central monoamine neurotransmitters affect blood glucose homeostasis. Activation of central cholinergic, noradrenergic histaminergic, and serotonergic neurons rapidly increase hepatic glucose output via the sympathetic nervous system. Acute hyperglycemia is mediated by three distinct pathways: the action of epinephrine on the liver, the action of glucagon on the liver, and the direct innervation of the liver. The relative contribution of these factors to hyperglycemia can be altered by diet and the kinds of neurotransmitters evoked in the central nervous system, but the magnitude of epinephrine secretion is closely related to the magnitude of hyperglycemia. On the other hand, neuropharmacological stimulation of central cholinergic muscarinic receptors, histaminergic H1 receptors, and serotonergic 5-HT2 receptors increases hypothalamic noradrenergic neuronal activity, which is associated with hyperglycemia. In contrast, central GABAA receptors play an inhibitory role in the regulation of hepatic glucose metabolism. Thus, central monoaminergic neurons could be linked together, and play a homeostatic role in the regulation of hepatic glucose metabolism.

LIF and CNTF, which share the gp130 transduction system, stimulate hepatic lipid metabolism in rats

We determined the effects of leukemia inhibitory factor (LIF) and ciliary neurotrophic factor (CNTF) on lipid metabolism in intact rats. Administration of LIF and CNTF increased serum triglycerides in a dose-dependent manner with peak values at 2 h. The effects of LIF and CNTF on serum cholesterol were very small, and serum glucose was unaffected. Both LIF and CNTF stimulated hepatic triglyceride secretion, hepatic de novo fatty acid synthesis, and lipolysis. Pretreatment with phenylisopropyl adenosine, which inhibits lipolysis, partially inhibited LIF- and CNTF-induced hypertriglyceridemia. Interleukin-4, which inhibits cytokine-induced hepatic fatty acid synthesis, also partially inhibited LIF- and CNTF-induced hypertriglyceridemia. These results indicate that both lipolysis and de novo fatty acid synthesis play a role in providing fatty acids for the increase in hepatic triglyceride secretion. Neither indomethacin nor adrenergic receptor antagonists affected the hypertriglyceridemia. The combination of LIF plus CNTF showed no additive effects consistent with the action of both cytokines through the gp130 transduction system. Thus LIF and CNTF have similar effects on lipid metabolism; they join a growing list of cytokines that stimulate hepatic triglyceride secretion and may mediate the changes in lipid metabolism that accompany the acute phase response.

Beta-nerve growth factor as a mediator of the acute phase response in vivo

Nerve growth factor (NGF) is increased during inflammation and stress. Stress-induced increases in specific serum proteins, such as serum amyloid A (SAA) and serum triglyceride (TG) levels, are part of the acute phase response which is mediated by cytokines. We now report the effect of systemic administration of beta-NGF on levels of serum lipids and SAA. Beta-NGF induced a rapid and sustained increase in serum TG and free fatty acid (FFA) in a dose dependent manner, while decreasing serum cholesterol levels in rats. Additionally, beta-NGF increased hepatic mRNA levels and serum concentrations of SAA at 16 hours in mice. Thus, beta-NGF joins the list of cytokines and growth factors that can mediate the acute phase response.

Increase in insulin release from rat pancreatic islets by quinolone antibiotics

1. The present study was undertaken to elucidate the mechanism(s) of hypoglycaemia caused by quinolone antibiotics. We investigated the effects of various quinolone antibiotics on insulin release in rat pancreatic islets. 2. At a non-stimulatory concentration of 3 mM glucose, lomefloxacin (LFLX) or sparfloxacin at 1 mM and pipemidic acid (0.1-1 mM) induced slight insulin release but tosufloxacin or enoxacin up to 100 microM did not. 3. At the stimulatory concentration of 10 mM glucose, all quinolones augmented insulin release in a dose-dependent manner. LFLX (100 microM) shifted the dose-response curve of glucose-induced insulin release to the left without altering the maximal response. 4. At 10 mM glucose, LFLX (100 microM) increased insulin release augmented by forskolin (5 microM) or 12-O-tetradecanoyl phorbol-13-acetate (100 nM) but not by raising the K+ concentration from 6 to 25 mM. 5. Verapamil (50 microM) or diazoxide (50-400 microM) antagonized the insulinotropic effect of LFLX. 6. These data suggest that quinolone antibiotics may cause hypoglycaemia by increasing insulin release via blockade of ATP-sensitive K+ channels.

Keratinocyte growth factor increases fatty acid mobilization and hepatic triglyceride secretion in rats

Keratinocyte growth factor (KGF) is a member of the fibroblast growth factor family that was originally identified as a keratinocyte mitogen after isolation from a lung fibroblast cell line. In this study, we demonstrate that administration of KGF to mice and rats elevates serum lipid levels. In rats, 1 h after KGF administration, serum triglyceride and FFA levels were increased, with peak values at 2 h (1.9-fold increase). The increase in serum triglyceride levels was sustained for at least 16 h. Serum cholesterol levels were also increased, but the effect was delayed beginning at 4 h, with peak values at 16 h (1.27-fold increase). KGF did not decrease the clearance of triglyceride-rich lipoproteins, but increased hepatic triglyceride secretion. KGF stimulated lipolysis, but not hepatic de novo fatty acid synthesis, and the increased delivery of FFA to the liver plays a crucial role in the KGF-induced hypertriglyceridemia. Neither alpha- nor beta-adrenergic receptor antagonists affected the hypertriglyceridemia induced by KGF, indicating that endogenous catecholamines are not involved in mediating KGF-induced hypertriglyceridemia. These results demonstrate that KGF induces hypertriglyceridemia by increasing hepatic triglyceride secretion, with the fatty acids provided by lipolysis making a major contribution. Thus, KGF could modulate lipid metabolism in vivo.

Lipoteichoic acid stimulates lipolysis and hepatic triglyceride secretion in rats in vivo

The host response to infection is frequently accompanied by changes in lipid metabolism. Previous studies have shown that endotoxin (LPS), a component of the cell wall of gram-negative bacteria, increases serum lipid levels. In this study, we demonstrate that lipoteichoic acid (LTA), a component of the cell membrane of gram-positive bacteria, also increases serum lipid levels in rats in a dose-dependent manner (0.1-300 micrograms/200 g body weight). Serum triglyceride levels increased within 2 h after LTA administration with peak values at 4 h (2-fold increase). Serum cholesterol levels also increased but the effect was delayed occurring at 16 h and was relatively small (1.2-fold increase). LTA (10 micrograms/200 g BW) did not decrease adipose tissue lipoprotein lipase activity or the clearance of triglyceride-rich lipoproteins. Rather, the LTA-induced hypertriglyceridemia is due to an increase in hepatic triglyceride secretion. LTA stimulates both hepatic de novo fatty acid synthesis and lipolysis. The increased delivery of free fatty acids to the liver plays a major role in the LTA-induced hypertriglyceridemia. Pretreatment with phentolamine, an alpha-adrenergic receptor antagonist, and alprenolol, a beta-adrenergic receptor antagonist, or phentolamine alone significantly suppressed the hypertriglyceridemia induced by LTA. These adrenergic inhibitors had no significant effect on the increase in lipolysis. These results indicate that catecholamines are involved in mediating the LTA-induced increase in hepatic triglyceride secretion via alpha-adrenergic receptors. These changes in lipid metabolism may play an important role in the organism's response to gram-positive infection.

Neuropeptide Y inhibits in vivo specific antibody production in rats

The sympathetic neurotransmitter neuropeptide-Y (NPY) is hypothesized to play a role in the in vivo modulation of immune responses. This study examined the effects of intraperitoneal administration of NPY on specific antibody responses to keyhole limpet hemocyanin (KLH) in rats. Antibody levels were repeatedly measured by enzyme-linked immunosorbent assay before and after intraperitoneal immunization with KLH. NPY induced a dose-dependent inhibition of IgM and IgG antibody responses following immunization with either physiologic or supraphysiologic doses of antigen. These in vivo results suggests that NPY may be involved in endogenous modulation of immune responses.