The physiological mechanisms through which nutrition mediates its effects in controlling reproduction are not well characterized. Both neural and endocrine components have been implicated in the communication of nutritional status to the central nervous system. Leptin, a hormone synthesized and secreted mainly by adipocytes, is heavily involved in this communication network. The objectives of studies reported herein were 1) to determine the effects of short-term restriction of nutrients on circulating leptin, leptin gene expression in adipose tissue, and leptin receptor (LR) gene expression in the adenohypophysis of ovariectomized cows; and 2) to investigate the responsiveness of the hypothalamic-adenohypophyseal (AP) axis of fasted and non-fasted cattle to leptin. Studies demonstrated that circulating concentrations of leptin and leptin gene expression in subcutaneous adipose tissue are decreased by fasting. Although 2 to 3 days of fasting did not affect patterns of release of luteinizing hormone (LH), cerebroventricular infusions of leptin increased mean circulating concentrations of LH in fasted, but not normal-fed cows, without affecting frequency or amplitude of pulses of LH. In vitro studies were conducted to determine whether the in vivo effects of leptin could be accounted for at the hypothalamic and/or AP levels. Leptin did not affect the release of gonadotropin-releasing hormone (GnRH) from hypothalamic-infundibular explants from either normal-fed or fasted cattle. Moreover, leptin did not affect the basal release of LH from bovine AP cells or AP explants from normal-fed cows. However, leptin induced a higher basal release of LH from AP explants of fasted cows and increased GnRH-stimulated release of LH from AP explants of normal-fed cows. Results demonstrate that leptin acts directly at the AP level to modulate the secretion of LH, and its effects are dependent upon nutritional status. Cellular mechanisms associated with the increased responsiveness of gonadotropes to leptin in fasted cows were investigated. Expression of LR and suppressor of cytokine signaling-3 (SOCS-3) in the adenohypophysis did not account for the increased responsiveness of fasted cows to leptin. Therefore, although leptin clearly stimulates the hypothalamic-gonadotropic axis in nutrient-restricted cattle, it is unclear why cattle maintained under neutral or positive energy balance are resistant to leptin.

Metabolic homeostasis is orchestrated by the hypothalamus through the neuroendocrine and the autonomic nervous systems. The hypothalamic nuclei respond to the peptide leptin secreted from adipose tissue to suppress feeding and increase energy expenditure by promoting fat metabolism via sympathetic activity. Another important, but perhaps less appreciated function of central leptin signaling is to elevate peripheral insulin sensitivity. Environmental and genetic risk factors that affect hypothalamic leptin signaling can lead to obesity and type 2 diabetes mellitus (T2DM). Here, we discovered that LIM domain only 4, LMO4, is a novel protein participating in central leptin signaling. In a process strikingly similar to T2DM in humans, CaMKIIα-Cre;LMO4flox/flox mice, which have LMO4 knocked out in the postnatal brain including the hypothalamus, develop visceral adiposity, reduced insulin sensitivity, obesity and diabetes when fed with regular chow. Central leptin signaling was significantly lost in key hypothalamic nuclei of mutant mice. Caloric restriction prevents obesity but not insulin resistance in these mice. Taken together, our results suggest that LMO4 function in the brain is required for central leptin signaling to control fat metabolism and peripheral insulin sensitivity.

<p>Olanzapine is an atypical antipsychotic drug exhibiting a low incidence of extrapyramidal side effects. It is not only effective in treating positive symptoms of schizophrenia, but also more efficacious against negative and depressive symptoms than classical antipsychotics. Olanzapine has been recommended as the first-line drug for the treatment of schizophrenia. Unfortunately, a common side effect of olanzapine, namely weight gain, has also been observed. A comprehensive literature analysis revealed that olanzapine induced higher weight gain than most other antipsychotics, only second to clozapine. The incidence of olanzapine-induced weight gain and related diseases, such as diabetes and cardiovascular diseases, is higher than that of the general population. These unwanted side effects have decreased the adherence to treatment. Many clinical observations and preliminary animal studies have attempted to elucidate the possible mechanism involved. To date, the mechanism for olanzapine-induced weight gain remains unclear.</p><p>This research project utilizes an animal model to investigate the possible mechanism of olanzapine-induced weight gain. The specific research objectives include: 1) does olanzapine affect feeding behavior; 2) can olanzapine influence the levels of glucose and triglyceride; 3) are cytokines, such as insulin, leptin, and TNF-Ñ involved in olanzapine-induced weight gain; 4) how does olanzapine affect adipose tissue?</p><p> An olanzapine-induced weight gain animal model has been established in the present investigation. An increase in food and water intake and increase in fat deposition accompanied with weight gain after treatment were observed. No significant increase in levels of glucose and triglyceride was detected. The changes of insulin and leptin levels in blood suggest that olanzapine may affect the endocrine system. A dramatic morphological alteration of adipose tissue by olanzapine was serendipitously observed. Immunohistochemical staining revealed that olanzapine stimulated collagen VI expression and deposition in the extracellular matrix suggesting that adipocyte differentiation may be enhanced. The effect of olanzapine on fat deposition might play a critical role in olanzapine-induced weight gain. The data from adipose tissue have provided a new clue on future research in understanding the mechanism of olanzapine-induced weight gain. Due to limitation of small number of animals and relatively short term of treatment, a large variation in groups diminished the power of analysis regarding the effects of olanzapine related to weigh gain.

<p>Single nucleotide polymorphisms (SNP) in leptin (LEP) and pro-opiomelanocortin (POMC) have been associated with beef carcass quality and yield respectively. Both hormones also play a role in immune performance. Since both of these genes are pleiotrophic, it was important to determine whether selection based on these SNPs would negatively affect immune cell numbers. A SNP in each of these hormones was assessed for effects on immune cell counts and antibody titres in twenty-seven beef cattle herds (n = 556). A commercial rabies vaccine was administered to these animals. Prior to being vaccinated, the types of lymphocytes evaluated included B cells, gamma delta cells, regular and activated CD4 and CD8 cells and numbers of lymphocytes as well as baseline serum antibody titres. On day 21, antibody titres were measured and a booster vaccine was administered. Finally on day 42, antibody titres and lymphocyte types were again counted. Several cell types were significantly associated with the LEP genotype however, no consistent pattern of correlation was observed between LEP genotype (TT, CT or CC) and peripheral blood lymphocyte populations. The number of different lymphocytes significantly associated with LEP genotype increased from two on day 0 to four on day 42. Animals with CT and CC genotypes had significantly higher increased rabies antibody titres in the first 21 days after vaccination than those with TT genotypes. The POMC SNP also did not show a clear pattern of association between lymphocyte subtypes and genotype. There was no difference in response to the rabies vaccination associated with the POMC genotype. Our results suggested that selection at either of the SNPs examined in this research would not detrimentally impact immune function in beef cattle.</p>

Metabolic homeostasis is orchestrated by the hypothalamus through the neuroendocrine and the autonomic nervous systems. The hypothalamic nuclei respond to the peptide leptin secreted from adipose tissue to suppress feeding and increase energy expenditure by promoting fat metabolism via sympathetic activity. Another important, but perhaps less appreciated function of central leptin signaling is to elevate peripheral insulin sensitivity. Environmental and genetic risk factors that affect hypothalamic leptin signaling can lead to obesity and type 2 diabetes mellitus (T2DM). Here, we discovered that LIM domain only 4, LMO4, is a novel protein participating in central leptin signaling. In a process strikingly similar to T2DM in humans, CaMKIIα-Cre;LMO4flox/flox mice, which have LMO4 knocked out in the postnatal brain including the hypothalamus, develop visceral adiposity, reduced insulin sensitivity, obesity and diabetes when fed with regular chow. Central leptin signaling was significantly lost in key hypothalamic nuclei of mutant mice. Caloric restriction prevents obesity but not insulin resistance in these mice. Taken together, our results suggest that LMO4 function in the brain is required for central leptin signaling to control fat metabolism and peripheral insulin sensitivity.

<p>Olanzapine is an atypical antipsychotic drug exhibiting a low incidence of extrapyramidal side effects. It is not only effective in treating positive symptoms of schizophrenia, but also more efficacious against negative and depressive symptoms than classical antipsychotics. Olanzapine has been recommended as the first-line drug for the treatment of schizophrenia. Unfortunately, a common side effect of olanzapine, namely weight gain, has also been observed. A comprehensive literature analysis revealed that olanzapine induced higher weight gain than most other antipsychotics, only second to clozapine. The incidence of olanzapine-induced weight gain and related diseases, such as diabetes and cardiovascular diseases, is higher than that of the general population. These unwanted side effects have decreased the adherence to treatment. Many clinical observations and preliminary animal studies have attempted to elucidate the possible mechanism involved. To date, the mechanism for olanzapine-induced weight gain remains unclear.</p><p>This research project utilizes an animal model to investigate the possible mechanism of olanzapine-induced weight gain. The specific research objectives include: 1) does olanzapine affect feeding behavior; 2) can olanzapine influence the levels of glucose and triglyceride; 3) are cytokines, such as insulin, leptin, and TNF-Ñ involved in olanzapine-induced weight gain; 4) how does olanzapine affect adipose tissue?</p><p> An olanzapine-induced weight gain animal model has been established in the present investigation. An increase in food and water intake and increase in fat deposition accompanied with weight gain after treatment were observed. No significant increase in levels of glucose and triglyceride was detected. The changes of insulin and leptin levels in blood suggest that olanzapine may affect the endocrine system. A dramatic morphological alteration of adipose tissue by olanzapine was serendipitously observed. Immunohistochemical staining revealed that olanzapine stimulated collagen VI expression and deposition in the extracellular matrix suggesting that adipocyte differentiation may be enhanced. The effect of olanzapine on fat deposition might play a critical role in olanzapine-induced weight gain. The data from adipose tissue have provided a new clue on future research in understanding the mechanism of olanzapine-induced weight gain. Due to limitation of small number of animals and relatively short term of treatment, a large variation in groups diminished the power of analysis regarding the effects of olanzapine related to weigh gain.

<p>Single nucleotide polymorphisms (SNP) in leptin (LEP) and pro-opiomelanocortin (POMC) have been associated with beef carcass quality and yield respectively. Both hormones also play a role in immune performance. Since both of these genes are pleiotrophic, it was important to determine whether selection based on these SNPs would negatively affect immune cell numbers. A SNP in each of these hormones was assessed for effects on immune cell counts and antibody titres in twenty-seven beef cattle herds (n = 556). A commercial rabies vaccine was administered to these animals. Prior to being vaccinated, the types of lymphocytes evaluated included B cells, gamma delta cells, regular and activated CD4 and CD8 cells and numbers of lymphocytes as well as baseline serum antibody titres. On day 21, antibody titres were measured and a booster vaccine was administered. Finally on day 42, antibody titres and lymphocyte types were again counted. Several cell types were significantly associated with the LEP genotype however, no consistent pattern of correlation was observed between LEP genotype (TT, CT or CC) and peripheral blood lymphocyte populations. The number of different lymphocytes significantly associated with LEP genotype increased from two on day 0 to four on day 42. Animals with CT and CC genotypes had significantly higher increased rabies antibody titres in the first 21 days after vaccination than those with TT genotypes. The POMC SNP also did not show a clear pattern of association between lymphocyte subtypes and genotype. There was no difference in response to the rabies vaccination associated with the POMC genotype. Our results suggested that selection at either of the SNPs examined in this research would not detrimentally impact immune function in beef cattle.</p>

Mechanical unloading and food restriction (FR) are leading causes of bone loss, which increase the risk of fracture later in life. Leptin, a 16kDa cytokine like hormone principally produced by white adipocytes, may be involved in bone metabolism with physiological or mechanical changes causing bone loss. The hypotheses of the first study were aimed at determining if serum leptin is reduced by unloading or FR. The serum leptin level reduced by unloading or by global FR, is associated with the decline in bone formation rate. It was conjectured that decreased serum leptin may be due to reduced adipocyte number/size and/or sympathetic nervous system (SNS) activation of betaadrenoreceptors with unloading or FR, inhibiting the release of leptin from adipocytes. In the second experiment, we tested whether leptin or beta-adrenoreceptor blockade attenuates bone loss during unloading and whether such an effect due to beta blockade is associated with changes in serum leptin level. Beta-blockade mitigated unloading induced reduction in serum leptin and also beta blockade was as effective as leptin administration in mitigating a reduction in cancellous bone mineral density with unloading through both stimulation of bone formation and suppression of resorption. It was previously demonstrated that energy restriction (ER) is a major contributor to the bone loss during global FR. In the third study, we tested whether beta- blockade attenuates bone loss during ER and whether such an effect is associated with changes in serum leptin level and leptin localization in bone tissues. Beta blockade attenuated the ER induced reduction in serum leptin level, cancellous bone mineral density and bone formation rate, and also abolished the ER induced increase in bone resorption. Reduction in leptin expression in bone marrow adipocytes observed with ER was attenuated by beta-blockade. Reduction in the number of cells (bone lining cells, osteocytes and chondrocytes in cartilage) which are stained positive for leptin was also attenuated by beta-blockade. Collectively, these data identify circulating leptin effects on preventing bone loss during mechanical unloading or energy restriction. Also beta blockade is associated with mitigating reduction in serum leptin and subsequently with mitigating reduction in bone mass with unloading or ER.

The objective of this study was to more clearly define the relationship between body condition, plasma leptin and insulin-like growth factor-I (IGF-I) in stallions and geldings in moderate (5.0-5.5) versus fleshy (7.0-7.5) body condition. Data analyses of physical measurements showed that there was a difference for BCS (P<0.001) even though the fat group only achieved a mean BCS of 6.3 + 0.2 as compared with a mean BCS of 5.3 + 0.1 for the moderate group. Differences also existed for rump fat (P<0.05) and percent body fat (P<0.05) between BCS groups. Analysis of physical measurements revealed that there was no sex effect as geldings and stallions within each group were not significantly different. Analysis of plasma leptin concurred with previous reports as a difference (P<0.001) existed between the BCS groups. Mean leptin concentrations were 2.13 + 0.1 ng/ml for the fat group and 1.44 + 0.1 ng/ml for the moderate group. After normalization of the data, changes in leptin concentrations still revealed a significant difference (P<0.05) between BCS groups, yet no difference in leptin concentrations between stallions and geldings was seen. Dexamethasone (DEX) treatment on d 0 caused a subsequent 24 h rise in plasma leptin in both groups. Analysis of plasma IGF-I revealed no difference in IGF-I concentrations between BCS groups. Mean plasma IGF-I was 347.2 + 11.4 ng/ml for the fat group and 344.3 + 10.0 ng/ml for the moderate group. There was however a difference (P<0.05) between geldings and stallions. Geldings exhibited an overall mean plasma IGF-I concentration of 360.6 + 9.1 ng/ml with stallions exhibiting a mean IGF-I concentration of 329.1 + 12.1 ng/ml. The post DEX challenge rise seen with leptin was not evident when analyzing the change in plasma IGF-I concentrations. In conclusion, the data presented herein have provided a more accurate profile of circulating concentrations of leptin and IGF-I in stallions and geldings of moderate and fleshy body condition.

Developmental changes within the hypothalamus are necessary for maturation of the reproductive neuroendocrine axis. Recent reports have implicated several neuronal networks in this process, but genes involved in their regulation have not been elucidated. Using a well-established model for nutritional induction of precocious puberty, objectives were to 1) use microarray technology to examine changes in gene expression within the arcuate nucleus (ARC) of the hypothalamus in pre-pubertal heifers fed high or low-concentrate diets, and 2) determine if high-concentrate diets are required for nutritional induction of precocious puberty. In Experiment 1, early-weaned, cross-bred heifers were fed either a high-forage/low-gain (HF/LG; 0.45 kg/d) or a highconcentrate/ high-gain (HC/HG; 0.91 kg/d) diet for 91 d. Analysis of microarray data indicated that 346 genes were differentially expressed (P < 0.05) between HC/HG and HF/LG heifers. Expression of three key metabolic genes [neuropeptide Y (NPY), agoutirelated protein (AGRP), and growth hormone receptor (GHR)] observed to be differentially expressed in the microarray analysis was investigated further by quantitative PCR. Real-time RT-PCR indicated that expression of NPY, AGRP and GHR was lower (P < 0.05) in HC/HG compared to HF/LG heifers. In contrast, concentrations of insulin (P < 0.05), IGF-1 (P < 0.002) and leptin (P = 0.1) were greater in HC/HG compared to HF/LG. For Experiment 2, 48 heifers were used in 2 replicates (24 heifers/replicate) in a 2 x 2 factorial design to examine the roles of diet type (HF vs HC) and rate of gain (LG, 0.45 kg/d vs HG, 0.91 kg/d) on age at puberty. Heifers were fed HC/HG, HC/LG, HF/HG or HF/LG (n = 12/group) for 14 wk, and then switched to a common growth diet (0.68 kg/d) until puberty. Heifers in both HG groups reached puberty at a younger age (54.5 ± 1.8 wk) than heifers in both LG groups (60.2 ± 1.9 wk; P < 0.04). A marked increase (P < 0.01) in serum concentrations of leptin occurred in HC/HG heifers between 24 and 30 wk of age. This increase in circulating leptin was not observed in other groups. Overall, results indicate that nutritional regulation of reproductive neuroendocrine development involves the control of NPY, AGRP and GHR expression. The abrupt increase noted for circulating leptin in heifers fed HC/HG diets, if timed and sustained appropriately, could represent an important temporal cue for activation of the neuroendocrine system and the onset of puberty.