[Key updates and interpretation of the ninth version of AJCC staging system for neuroendocrine tumors of the stomach].

The cancer staging system of the American Joint Committee on Cancer (AJCC) is the most widely used clinical basis for tumor staging. In October 2023, AJCC released the staging system (ninth version) for the neuroendocrine tumors of stomach (NET), which has been implemented in January 2024. The ninth version of NET staging system mainly updated the histopathologic classification, diagnosis and staging methods, clinical and pathological staging, prognosis grade, tumor and non-tumor prognostic features. The update and implementation of the staging system provide a more detailed reference for the accurate diagnosis, staging and precise treatment of gastric neuroendocrine tumors. Moreover, it is convenient for clinicians to carry out clinical practice. The purpose of our article is to provide a high-level overview of the major changes in AJCC staging system (version 9) for gastric NET based on the latest evidence-based medical research.

[Computer-vision-based artificial intelligence for detection and recognition of instruments and organs during radical laparoscopic gastrectomy for gastric cancer: a multicenter study].

Objective: To investigate the feasibility and accuracy of computer vision-based artificial intelligence technology in detecting and recognizing instruments and organs in the scenario of radical laparoscopic gastrectomy for gastric cancer. Methods: Eight complete laparoscopic distal radical gastrectomy surgery videos were collected from four large tertiary hospitals in China (First Medical Center of Chinese PLA General Hospital [three cases], Liaoning Cancer Hospital [two cases], Liyang Branch of Jiangsu Province People's Hospital [two cases], and Fudan University Shanghai Cancer Center [one case]). PR software was used to extract frames every 5-10 seconds and convert them into image frames. To ensure quality, deduplication was performed manually to remove obvious duplication and blurred image frames. After conversion and deduplication, there were 3369 frame images with a resolution of 1,920×1,080 PPI. LabelMe was used for instance segmentation of the images into the following 23 categories: veins, arteries, sutures, needle holders, ultrasonic knives, suction devices, bleeding, colon, forceps, gallbladder, small gauze, Hem-o-lok, Hem-o-lok appliers, electrocautery hooks, small intestine, hepatogastric ligaments, liver, omentum, pancreas, spleen, surgical staplers, stomach, and trocars. The frame images were randomly allocated to training and validation sets in a 9:1 ratio. The YOLOv8 deep learning framework was used for model training and validation. Precision, recall, average precision (AP), and mean average precision (mAP) were used to evaluate detection and recognition accuracy. Results: The training set contained 3032 frame images comprising 30 895 instance segmentation counts across 23 categories. The validation set contained 337 frame images comprising 3407 instance segmentation counts. The YOLOv8m model was used for training. The loss curve of the training set showed a smooth gradual decrease in loss value as the number of iteration calculations increased. In the training set, the AP values of all 23 categories were above 0.90, with a mAP of 0.99, whereas in the validation set, the mAP of the 23 categories was 0.82. As to individual categories, the AP values for ultrasonic knives, needle holders, forceps, gallbladders, small pieces of gauze, and surgical staplers were 0.96, 0.94, 0.91, 0.91, 0.91, and 0.91, respectively. The model successfully inferred and applied to a 5-minutes video segment of laparoscopic gastroenterostomy suturing. Conclusion: The primary finding of this multicenter study is that computer vision can efficiently, accurately, and in real-time detect organs and instruments in various scenarios of radical laparoscopic gastrectomy for gastric cancer.

[A nomogram for predicting lymph node metastasis in early gastric cancer].

Objective: To explore the independent risk factors of lymph node metastasis (LNM) in early gastric cancer, and to use nomogram to construct a prediction model for above LNM. Methods: A retrospective cohort study was conducted. Inclusion criteria: (1) primary early gastric cancer as stage pT1 confirmed by postoperative pathology; (2) complete clinicopathological data. Exclusion criteria: (1) patients with advanced gastric cancer, stump gastric cancer or history of gastrectomy; (2) early gastric cancer patients confirmed by pathology after neoadjuvant chemotherapy; (3) other types of gastric tumors, such as lymphoma, neuroendocrine tumor, stromal tumor, etc.; (4) primary tumors of other organs with gastric metastasis. According to the above criteria, 1633 patients with early gastric cancer who underwent radical gastrectomy at the Department of General Surgery of the Chinese PLA General Hospital First Medical Center from December 2005 to December 2020 were enrolled as training set, meanwhile 239 patients with early gastric cancer who underwent gastrectomy at the Department of General Surgery of the Chinese PLA General Hospital Fourth Medical Center from December 2015 to December 2020 were enrolled as external validation set. Risk factors of LNM in early gastric cancer were identified by using univariate and multivariate logistic regression analyses. A nomogram prediction model was established with significant factors screened by multivariate analysis. Area under the receiver operating characteristic curve (AUC) was used for assessing the predictive value of the model. Calibration curve was drawn for external validation. Results: Among 1633 patients in training set, the mean number of retrieved lymph nodes was 20 (13-28), and 209 patients (12.8%) had lymph node metastasis. Univariate analysis showed that gender, resection range, tumor location, tumor morphology, lymph node clearance, vascular invasion, lymphatic cancer thrombus, tumor length, tumor differentiation, microscopic presence of signet ring cells and depth of tumor invasion were associated with LNM (all P<0.05). Multivariate analysis revealed that females, tumor morphology as ulcer type, vascular invasion, lymphatic cancer thrombus, tumor length≥3 cm, deeper invasion of mucosa, and poor differentiation were independent risk factors for LNM in early gastric cancers (all P<0.05). Receiver operating characteristic curve indicated that AUC of training set was 0.818 (95%CI: 0.790-0.847) and AUC of external validation set was 0.765 (95%CI: 0.688-0.843). The calibration curve showed that the LNM probability predicted by nomogram was consistent with the actual situation (C-index: 0.818 in training set and 0.765 in external validation set). Conclusions: Females, tumor morphology as ulcer type, vascular invasion, lymphatic cancer thrombus, tumor length≥3 cm, deeper invasion of mucosa and poor differentiation are independent risk factors for LNM of early gastric cancer. The establishment of a nomogram prediction model for LNM in early gastric cancer has great diagnostic value and can provide reference for treatment selection.

[Risk factors of postoperative complication after total gastrectomy in advanced gastric cancer patients receiving neoadjuvant chemotherapy].

Objective: At present, there are few studies focusing on the factors short-term complications after total gastrectomy in patients with advanced gastric cancer receiving neoadjuvant chemotherapy (NACT). The purpose of this study is to provide a reference for clinical prevention of complications in these patients. Methods: A retrospective case-control study was conducted. Case inclusion criteria: (1) clinical stage II-III gastric cancer diagnosed by preoperative gastroscopy, pathology, abdominal CT, EUS or PET-CT; (2) evaluated suitable for NACT by MDT discussion; (3) no previous history of other malignant tumors and no concurrent tumor; (4) undergoing total gastrectomy+ D2 lymphadenectomy after NACT. Exclusion criteria: (1) age <18 or >80 years old; (2) severe concurrent diseases, and ASA classification>grade III; (3) stump gastric cancer or history of gastric surgery; (4) incomplete clinicopathological data. According to the above criteria, clinicopathological data of 140 advanced gastric cancer patients who underwent total gastrectomy after NACT in Chinese PLA General Hospital between June 2012 and June 2019 were collected, including 109 males and 31 females with mean age of (56.9±11.4) years and body mass indey (BMI) of (23.3±3.1) kg/m(2). Logistic analysis was used to analyze the relationship between postoperative complication and clinicopathological data. Factors in univariate analysis with P<0.05 were included in the multivariate analysis. Results: Postoperative complications (Clavien-Dindo classification ≥ II) occurred in 35 cases (25.0%) and severe complications (Clavien-Dindo classification ≥ IIIa) occurred in 4 cases (2.9%), including 1 case of esophago-jejunal anastomotic leakage, 1 case of vena cava thrombosis, 1 case of pleural effusion, 1 case of septic shock during perioperative days resulting in death. Univariate analysis showed that BMI (P=0.011), cycle of NACT (P=0.027), tumor diameter (P=0.021), and vascular invasion (P=0.033) were associated with postoperative complication within 30 days, while open/laparoscopic total gastrectomy were not associated with postoperative complication (P=0.926). Multivariate analysis revealed that BMI ≥ 25 kg/m(2) (OR=3.294, 95% CI: 1.343-8.079, P=0.009) and < 4 cycles of NACT (OR=2.922, 95% CI: 1.217-7.016, P=0.016) were independent risk factors for postoperative complication. The 3-year overall survival rates of patients with or without complication were 54.4% and 64.0%, respectively (P=0.395), and 3-year disease-free survival rates were 47.4% and 52.9%, respectively (P=0.587). Conclusions: Higher BMI and fewer cycles of NACT are independent risk factors of postoperative complication in advanced gastric cancer patients undergoing total gastrectomy after NACT. No obvious association is found between postoperative complication and surgical approaches.

[Comparison of short-term efficacy between robotic and 3D laparoscopic-assisted D2 radical distal gastrectomy for gastric cancer].

Objective: To compare short-term efficacy of robotic versus 3D laparoscopic-assisted D2 radical distal gastrectomy in gastric cancerpatients and those with different body mass index (BMI). Method: A retrospective cohort study was performed. Inclusion criteria:(1) gastric cancer proved by preoperative pathological results and tumor location was suitable for D2 radical distal gastrectomy; (2) no distal metastases such as in liver, kidney or abdominal cavity, and no direct invasion to the pancreas or colon on preoperative imaging; (3) postoperative pTNM stage ranged from I to III; (4) no conversion to open surgery or change of surgical procedure during operation; (5) complete clinicopathological data. Patients with severe chronic diseases, other malignant tumors, tumor invasion of other organs or distant metastases, benign gastric tumors, gastrointestinal stromal tumors and recurrent gastric cancer were excluded. According to the above criteria, 531 patients who underwent robotic or 3D laparoscopic-assisted distal gastrectomy at the General Surgery Department of Chinese PLA General Hospital from January 2016 to December 2019 were enrolled. Among them, 344 patients underwent 3D laparoscopic-assisted distal gastrectomy (3D-LADG group), including 250 males, 94 females, 66 cases (19.2%) with a BMI ≥ 25 kg/m(2), and 278 cases (80.8%) with a BMI < 25 kg/m(2), and 187 patients underwent robotic-assisted distal gastrectomy (RADG group), including 122 males, 65 females, 69 cases (36.9%) with a BMI≥25 kg/m(2) and 118 cases (63.1%) with a BMI < 25kg/m(2). There were no significant differences in baseline characteristics between the two groups (all P > 0.05). Operative indicators, postoperative recovery, pathological characteristics and complication rate were compared between the two groups. Subgroup analysis stratified BMI was also performed. Results: Compared with RADG group, 3D-LADG group presented more harvested lymph nodes (29.1±12.4 vs. 25.2±9.0, t=4.238, P<0.001), shorter postoperative hospital stay [8.0 (7.0 to 10.0) days vs. 10.0 (9.0 to 11.0) days, Z=-6.205, P<0.001], less operative cost [(3.6×10(4)±1.1×10(4)) yuan vs. (6.2×10(4)±3.5×10(4)) yuan, t=-9.727, P<0.001], less cost of hospitalization [8.6×10(4)(7.5×10(4) to 10.0×10(4)) yuan vs. 12.8×10(4)(11.7×10(4) to 14.1×10(4)) yuan, Z=-15.997, P<0.001] and longer first flatus time [(3.9±1.0) days vs. (3.4±1.2) days, t=4.271, P<0.001], whose differences were all statistically significant (all P<0.05). While there were no statistically significant differences in operation time, intraoperative blood loss, overall complication rate [10.8%(37/344) vs. 12.8%(24/187), χ(2)=0.515, P=0.473] and severe complications rate [2.0%(7/344) vs. 3.2%(6/187), χ(2)=0.294, P=0.588] between 3D-LADG group and RADG group (all P>0.05). In BMI<25 kg/m(2) group, propensity score matching (PSM) was used to reduce bias of baseline characteristics. After PSM, 3D-LADG group presented higher proportion of intraoperative blood loss <50 ml [26.7% (31/116) vs. 8.6% (10/116), χ(2)=13.065, P<0.001], more harvested lymph nodes [30.3±12.2 vs. 25.3±9.5, t=-3.192, P=0.002] and shorter postoperative hospital stay [9.0 (7.0 to 10.0) days vs. 10.0 (9.0 to 11.0) days, Z=-4.275, P<0.001] compared with RADG group, while other perioperative indicators showed no statistically significant differences between the two groups (all P>0.05). In BMI≥25 kg/m(2) group, 3D-LADG group presented higher proportion of intraoperative blood loss >200 ml [18.2% (12/66) vs. 1.4% (1/69), χ(2)=10.853, P=0.001] and shorter postoperative hospital stay [8.0 (6.0 to 10.0) days vs. 9.0 (8.0 to 10.5) days, Z=-3.039, P=0.002] compared with RADG group, while other perioperative indicators also showed no statistically significant differences between the two groups (all P>0.05). Conclusion: It is safe and feasible to perform 3D-LADG and RADG for patients with gastric cancer. The short-term efficacy of both is similar.

[Surgical selection and metastatic warning of splenic lymph node dissection in advanced gastric cancer radical surgery: a prospective, single-center, randomized controlled trial].

Objective: To investigate the surgical options for splenic lymph node dissection in patients with advanced gastric cancer undergoing radical total gastrectomy, and to evaluate the sentinel effect of No. 4s lymph node on splenic lymph node metastasis. Methods: A prospective, single-center, randomized and controlled study was carried out (Trial registration, No.NCT02980861). Enrollment criteria: (1) >18 years old and <65 years old; (2) gastric adenocarcinoma locating in the proximal or corpus; (3) preoperative clinical staging as cT2-4aN0-3M0; (4) D2 radical total gastrectomy feasible judged before operation; (5) physical ability score 0 to 1; (6) I to III of ASA classification. Pregnant or lactating women, patients with severe mental illness or previous history of upper abdominal surgery, those suffered from other malignant tumors in the past 5 years, or heart and lung system diseases judged to affect surgery before operation, those receiving preoperative chemotherapy, radiotherapy or targeted therapies, and distant metastases being found during surgery were excluded. According to above criteria, 222 patients at The First Medical Center of Chinese PLA General Hospital from December 2016 to December 2017 were enrolled prospectively and were randomly divided into the laparoscopic splenic hilar lymph node dissection group (laparoscopic group, n=114) and the open splenic hilar lymph node dissection group (open group, n=108). The result of rapid frozen immunohistochemistry of harvested No.4s lymph nodes was used to evaluate the sensitivity and specificity of sentinel effect on splenic hilar lymph node metastasis. The surgical parameters, postoperative recovery parameters, and complication rates were compared between the two groups. Results: There were 80 males and 34 females in the lapascopic group with a mean age of (56.1±10.2) years, and 69 males and 39 females in the open group with a mean age of (58.4±10.9) years. There were no significant differences in baseline data between the two groups (all P>0.05). Total blood loss was less in the laparoscopic group [(96.3±82.4) ml vs. (116.6±101.9) ml, t=1.124, P<0.001], and the amount of bleeding from the splenic hilar lymph nodes dissected was also less than that in the open group [(25.3±17.8) ml vs. (59.5±36.4) ml, t=1.172, P<0.001]. However, the operation time, the time of splenic hilar lymph node, the number of lymph node dissected and number of splenic hilar lymph node dissected were not significantly different between the two groups (all P>0.05). As compared to the open group, the laparoscopic group had shorter time to the first flatus [(1.3±1.2) days vs. (1.6±1.5) days, t=1.665, P=0.021], shorter time to fluid diet [(4.6±1.4) days vs. (4.9 ± 1.6) days, t=1.436, P=0.007], shorter time to remove nasogastric tube [(3.9±2.6) days vs. (4.3±2.4) days, t=0.687, P<0.001] and shorter hospital stay [(10.3±6.6) days vs. (12.1±7.2) days, t=0.697, P<0.001]. Complication rate was 14.0% (16/114) and (12.0%) ((1)3/108) in the laparoscopic group and the open group, respectively, without significant difference (χ(2)=6.723, P=0.331). The sensitivity of the No. 4s lymph node for the prediction of splenic hilar lymph node metastasis reached 89.5%, and the specificity reached 99.6%. Conclusions: Laparoscopic technique is safe and feasible in the treatment of splenic hilar lymph node dissection in advanced gastric cancer. The No.4s lymph node examination has good sentinel effect on predicting the metastasis of splenic hilar lymph nodes.

Restraint stress increases prolactin-mediated phosphorylation of signal transducer and activator of transcription 5 in the hypothalamus and adrenal cortex in the male mouse.

Prolactin is a pleiotropic peptide hormone produced by the lactotrophs in the anterior pituitary. Its rate of secretion is primarily regulated by a negative-feedback mechanism where prolactin stimulates the activity of the tuberoinfundibular dopaminergic (TIDA) neurones, increasing their release of dopamine, which accesses the pituitary via the median eminence to suppress further prolactin secretion. In addition to its well established role in lactation, circulating prolactin is secreted in response to stress, although the mechanism by which this is achieved or its cellular targets remains unknown. In the present study, we show that 15 minutes of restraint stress causes an approximately seven-fold increase in circulating prolactin concentration in male mice. Monitoring prolactin receptor activation, using immunohistochemistry to determine the level and distribution of tyrosine phosphorylated signal transducer and activator of transcription 5 (pSTAT5), we show that this stress-induced increase in prolactin interacts with both central and peripheral targets. Restraint stress for 15 minutes significantly increased pSTAT5 staining in the arcuate nucleus, median eminence and the zona fasciculata of the adrenal cortex. In each case, this response was prevented by pretreating the animals with bromocriptine to block prolactin secretion from the pituitary. Interestingly, in contrast to many cells in the arcuate nucleus, stress reduced pSTAT5 staining of the TIDA neurones (identified by dual-labelling for tyrosine hydroxylase). This suggests that there is reduced prolactin signalling in these cells and thus potentially a decline in their inhibitory influence on prolactin secretion. These results provide evidence that prolactin secreted in response to acute stress is sufficient to activate prolactin receptors in selected target tissues known to be involved in the physiological adaptation to stress.

Effect of ozone on vascular endothelial growth factor (VEGF) and related inflammatory cytokines in rats with diabetic retinopathy.

The aim of this study was to investigate the effect of ozone on inflammatory cytokines in diabetic retinopathy (DR) rats. Male rats (40) weighing 300-360 g were included in this study. Thirty rats were randomly divided into the model and ozone groups after DR was induced by streptozotocin. Ten rats served as the blank group. After the diabetic models were established for one month, the rats in the ozone group were treated with 50 mg/kg ozone coloclysis for one month (three times a week). After the rats were anesthetized by intraperitoneal injection, blood samples from the abdominal aorta were collected, and the supernatant was obtained by centrifugation. Vascular endothelial growth factor (VEGF) and inflammatory cytokine content in the serum was detected by enzyme linked immunosorbent assay. The values of VEGF, intercellular cell adhesion molecule-1, interleukin-1 beta, tumor necrosis factor-a, and IL-6 were significantly different among the three groups (P < 0.05). The cytokine levels in the model group were higher than those in the blank group (P < 0.05). The level of each cytokine in the ozone group was higher than that in the blank group. Compared with the model group, the cytokine levels in the ozone group were significantly reduced (P < 0.05). Ozone had no effect on the blood glucose of diabetic rats. Treatment with ozone coloclysis may effectively reduce the secretion of VEGF and inflammatory cytokines in diabetic retinopathy rats.

Effect of Deletion of Ghrelin-O-Acyltransferase on the Pulsatile Release of Growth Hormone in Mice.

Ghrelin, a gut hormone originating from the post-translational cleavage of preproghrelin, is the endogenous ligand of growth hormone secretagogue receptor 1a (GHS-R1a). Within the growth hormone (GH) axis, the biological activity of ghrelin requires octanoylation by ghrelin-O-acyltransferase (GOAT), conferring selective binding to the GHS-R1a receptor via acylated ghrelin. Complete loss of preproghrelin-derived signalling (through deletion of the Ghrl gene) contributes to a decline in peak GH release; however, the selective contribution of endogenous acyl-ghrelin to pulsatile GH release remains to be established. We assessed the pulsatile release of GH in ad lib. fed male germline goat(-/-) mice, extending measures to include mRNA for key hypothalamic regulators of GH release, and peripheral factors that are modulated relative to GH release. The amount of GH released was reduced in young goat(-/-) mice compared to age-matched wild-type mice, whereas pulse frequency and irregularity increased. Altered GH release did not coincide with alterations in hypothalamic Ghrh, Srif, Npy or Ghsr mRNA expression, or pituitary GH content, suggesting that loss of Goat does not compromise canonical mechanisms that contribute to pituitary GH production and release. Although loss of Goat resulted in an irregular pattern of GH release (characterised by an increase in the number of GH pulses observed during extended secretory events), this did not contribute to a change in the expression of sexually dimorphic GH-dependent liver genes. Of interest, circulating levels of insulin-like growth factor (IGF)-1 were elevated in goat(-/-) mice. This rise in circulating levels of IGF-1 was correlated with an increase in GH pulse frequency, suggesting that sustained or increased IGF-1 release in goat(-/-) mice may occur in response to altered GH release patterning. Our observations demonstrate that germline loss of Goat alters GH release and patterning. Although the biological relevance of altered GH secretory patterning remains unclear, we propose that this may contribute to sustained IGF-1 release and growth in goat(-/-) mice.

Increased adiposity and insulin correlates with the progressive suppression of pulsatile GH secretion during weight gain.

Pathological changes associated with obesity are thought to contribute to GH deficiency. However, recent observations suggest that impaired GH secretion relative to excess calorie consumption contributes to progressive weight gain and thus may contribute to the development of obesity. To clarify this association between adiposity and GH secretion, we investigated the relationship between pulsatile GH secretion and body weight; epididymal fat mass; and circulating levels of leptin, insulin, non-esterified free fatty acids (NEFAs), and glucose. Data were obtained from male mice maintained on a standard or high-fat diet. We confirm the suppression of pulsatile GH secretion following dietary-induced weight gain. Correlation analyses reveal an inverse relationship between measures of pulsatile GH secretion, body weight, and epididymal fat mass. Moreover, we demonstrate an inverse relationship between measures of pulsatile GH secretion and circulating levels of leptin and insulin. The secretion of GH did not change relative to circulating levels of NEFAs or glucose. We conclude that impaired pulsatile GH secretion in the mouse occurs alongside progressive weight gain and thus precedes the development of obesity. Moreover, data illustrate key interactions between GH secretion and circulating levels of insulin and reflect the potential physiological role of GH in modulation of insulin-induced lipogenesis throughout positive energy balance.

The decline in pulsatile GH secretion throughout early adulthood in mice is exacerbated by dietary-induced weight gain.

The transition between puberty and adulthood is accompanied by a slowing in linear growth. Although GH is a key factor that drives somatic development into adulthood, early adulthood coincides with a reduction in circulating levels of GH. To this extent, a pathological decline in postpubertal GH secretion is detrimental to attainment of peak lean muscle mass and bone mass and promotes adiposity and increases susceptibility to the development of obesity in adulthood. Here we characterized pulsatile GH secretion in C57BL/6J mice at 12 and 16 wk of age. Deconvolution analysis of these measures reveals a reduction in pulsatile GH secretion between 12 and 16 wk of age. Dietary intervention with high-fat feeding at 8 wk of age results in a significant increase in adiposity, the development of glucose intolerance, and hyperinsulinemia. We show the exacerbation of the age-associated decline in pulsatile GH secretion in high-fat-fed mice after 4 wk of dietary intervention (at 12 wk of age), and a further suppression of pulsatile GH secretion by 8 wk of dietary intervention (at 16 wk of age). Suppressed pulsatile secretion of GH did not coincide with an elevation in circulating free fatty acids. Rather, we observed increased hepatic triglyceride content and an eventual decrease in circulating levels of IGF-I. Given the established role of GH in maintaining healthy aging, we anticipate that an advancing of the age-associated decline in pulsatile GH secretion as a consequence of dietary-induced weight gain may have long-term ramifications on adult health.

GH does not modulate the early fasting-induced release of free fatty acids in mice.

Fasting results in the mobilization of adipose stores and the elevation of levels of free fatty acids (FFA). In humans, this process is driven by a release in GH. Little is known regarding the role of GH in modulating this process during early stages of fasting in the mouse. Confirmation of the role of GH in modulating FFA release in the fasting mouse is of particular importance given the frequent use of mouse models to study metabolic mechanisms. Here, we correlate the initial release of FFA throughout fasting in mice with pulsatile GH secretion. Observations illustrate the rapid release of FFA in response to food withdrawal. This does not correlate with a rise in GH secretion. Rather, we observed a striking loss in pulsatile secretion of GH throughout the first 6 h of fasting, suggesting that GH does not modulate the initial release of FFA in the mouse in response to fasting. This was confirmed in GH receptor knockout mice, in which we observed a robust fasting-induced rise in FFA. We further illustrate the dynamic relationship between the orexigenic and anorexigenic hormones ghrelin and leptin during fasting in the mouse. Our findings show an initial suppression of leptin and the eventual rise in circulating levels of acyl-ghrelin with fasting. However, altered acyl-ghrelin and leptin secretion occurs well after the rise in FFA and the suppression of GH secretion. Consequently, we conclude that although acyl-ghrelin and leptin may modulate the physiological response to drive food intake, these changes do not contribute to the initial loss of pulsatile GH secretion. Rather, it appears that the suppression of GH secretion in fasting may occur in response to an elevation in fasting levels of FFA or physiological stress. Observations highlight a divergent role for GH in modulating FFA release between man and mouse.

Development of a method for the determination of pulsatile growth hormone secretion in mice.

Measures of pulsatile GH secretion require frequent collection and analysis of blood samples at regular intervals. Due to blood volume constraints, repeat measures of circulating levels of GH in mice remain challenging. Consequently, few observations exist in which the pulsatile pattern of GH secretion in mice have been characterized. To address this, we developed a technique for the collection and analysis of circulating levels of GH at regular and frequent intervals in freely moving mice. This was achieved through the development of a sensitive assay for the detection of GH in small (2 µl) quantities of whole blood. The specificity and accuracy of this assay was validated following guidelines established for single-laboratory validation as specified by the International Union of Pure and Applied Chemistry. We incorporated an established method for tail-clip blood sample collection to determine circulating levels of GH secretion in 36 whole blood samples collected consecutively over a period of 6 h. Resulting measures were characterized by peak secretion periods and interpulse stable baseline secretion periods. Periods characterized by elevated whole blood GH levels consisted of multicomponent peaks. Deconvolution analysis of resulting measures confirmed key parameters associated with pulsatile GH secretion. We show a striking decrease in pulsatile GH secretion in mice after 12-18 h of fasting. This model is necessary to characterize the pulsatile profile of GH secretion in mice and will significantly contribute to current attempts to clarify mechanisms that contribute to the regulation of GH secretion.