Recombinant antithrombin attenuates acute kidney injury associated with rhabdomyolysis: an in vivo animal study.

BACKGROUND: Rhabdomyolysis is characterized by the destruction and necrosis of skeletal muscle tissue, resulting in acute kidney injury (AKI). Recombinant antithrombin (rAT) has DNA repair and vascular endothelial-protection properties. Herein, we investigated whether rAT therapy has beneficial effects against rhabdomyolysis-induced AKI. Ten-week-old male B6 mice were injected with 5 mL/kg of 50% glycerol intramuscularly in the left thigh after 24 h of fasting to create a rhabdomyolysis mouse model. Further, 750 IU/kg rAT was injected intraperitoneally at 24 and 72 h after the rhabdomyolysis model was established. The mice were euthanized after 96 h for histological analysis. Saline was administered to mice in the control group. RESULTS: Blood tests show elevated serum creatinine, urea nitrogen, and neutrophil gelatinase-associated lipocalin levels in rhabdomyolysis. Loss of tubular epithelial cell nuclei and destruction of the tubular luminal surface structure was observed in the untreated group, which improved with rAT treatment. Immunostaining for Ki-67 showed increased Ki-67-positive nuclei in the tubular epithelial cells in the rAT group, suggesting that rAT may promote tubular epithelial cell regeneration. The microvilli of the brush border of the renal tubules were shed during rhabdomyolysis, and rAT treatment reduced this injury. The vascular endothelial glycocalyx, which is usually impaired by rhabdomyolysis, became functional following rAT treatment. CONCLUSIONS: Treatment with rAT suppressed rhabdomyolysis-induced AKI, suggesting that rAT therapy may be a novel therapeutic approach.

Leriche syndrome diagnosed due to polytrauma: a case report.

BACKGROUND: Leriche syndrome is caused by atherosclerosis and is often characterized by symptoms such as intermittent claudication and numbness and coldness of the lower limbs. Its exact prevalence and incidence are unknown because it is a rare disease. We report a case of Leriche syndrome diagnosed incidentally on trauma pan-scan computed tomography (CT). CASE PRESENTATION: A 61-year-old Asian male was driving a passenger car and had a head-on collision with a dump truck that required an emergency call. The patient was transported to our hospital in a doctor's helicopter. Physical examination revealed the following vital signs: respiratory rate, 23 breaths per min; SpO2, 98% under a 10-L administration mask; pulse rate, 133 beats per min; blood pressure, 142/128 mmHg; Focused Assessment with Sonography for Trauma, positive; Glasgow Coma Scale assessment, E3V5M6; and body temperature, 35.9 °C. Trauma pan-scan CT showed bilateral mandibular fractures, bilateral multiple rib fractures, bilateral pneumothorax, sternal fractures, hematoma around thoracic spine, small bowel perforation, mesenteric injury, right clavicle fracture, right ankle debridement injury, and thrombotic occlusion from just above the abdominal aortic bifurcation to the bilateral common iliac arteries. Although thrombotic occlusion needed to be differentiated from traumatic aortic injury, the presence of collateral blood vessels led to the diagnosis of Leriche syndrome, and conservative treatment was performed. Damage control surgery was required for the small bowel injuries. From the second day of admission, the patient was treated with continuous intravenous heparin and prostaglandin preparations. However, impaired blood flow and reperfusion injury in the right lower extremity progressed. On the fifth day of admission, right thigh amputation was performed. The patient required renal replacement therapy for 2 weeks starting from the third day of admission. CONCLUSIONS: In this case, conservative therapy was initially chosen for Leriche syndrome. However, the complex factors in the acute phase of trauma led to development of hemorrhagic necrosis, requiring amputation of the lower extremity. Our findings indicate the need to carefully consider the unique factors affecting Leriche syndrome patients when considering treatment indications and choices for trauma.

Diffuse midline glioma in the spinal cord with rapid respiratory deterioration.

BACKGROUND: Neurogenic acute respiratory failure is usually caused by either infection or vascular insufficiency. We report the case of a patient who developed acute respiratory failure secondary to a spinal tumor. CASE PRESENTATION: A 32-year-old man, presenting with numbness and muscle weakness in his legs for 2 weeks, was transferred to our hospital with worsening quadriplegia and development of respiratory symptoms. We carried out emergent spinal decompression and initiated steroid pulse therapy, with no resolution of symptoms; a tumor incision biopsy after contrast cervical magnetic resonance imaging revealed an intraspinal tumor with a pathological diagnosis of World Health Organization grade IV glioma. The patient developed bradycardia, severe sepsis, status epilepticus, and cardiopulmonary arrest due to hypoxemia and was treated with chemoradiotherapy under mechanical ventilation. He was later transferred to another hospital for subacute care. CONCLUSION: Acute respiratory failure caused by spinal tumors is uncommon. However, acute care practitioners should be mindful of neoplastic lesions as a potential cause.

Increased SLC38A4 Amino Acid Transporter Expression in Human Pancreatic α-Cells After Glucagon Receptor Inhibition.

Plasma amino acids and their transporters constitute an important part of the feedback loop between the liver and pancreatic α-cell function, and glucagon regulates hepatic amino acid turnover. Disruption of hepatic glucagon receptor action activates the loop and results in high plasma amino acids and hypersecretion of glucagon associated with α-cell hyperplasia. In the present study, we report a technique to rescue implanted human pancreatic islets from the mouse kidney capsule. Using this model, we have demonstrated that expression of the amino acid transporter SLC38A4 increases in α-cells after administration of a glucagon receptor blocking antibody. The increase in SLC38A4 expression and associated α-cell proliferation was dependent on mechanistic target of rapamycin pathway. We confirmed increased α-cell proliferation and expression of SLC38A4 in pancreas sections from patients with glucagon cell hyperplasia and neoplasia (GCHN) with loss-of-function mutations in the glucagon receptor. Collectively, using a technique to rescue implanted human islets from the kidney capsule in mice and pancreas sections from patients with GCHN, we found that expression of SLC38A4 was increased under conditions of disrupted glucagon receptor signaling. These data provide support for the existence of a liver-human α-cell endocrine feedback loop.

RNA-sequencing reveals altered skeletal muscle contraction, E3 ligases, autophagy, apoptosis, and chaperone expression in patients with critical illness myopathy.

BACKGROUND: Critical illness myopathy (CIM) is associated with severe skeletal muscle wasting and impaired function in intensive care unit (ICU) patients. The mechanisms underlying CIM remain incompletely understood. To elucidate the biological activities occurring at the transcriptional level in the skeletal muscle of ICU patients with CIM, the gene expression profiles, potential upstream regulators, and enrichment pathways were characterized using RNA sequencing (RNA-seq). We also compared the skeletal muscle gene signatures in ICU patients with CIM and genes perturbed by mechanical loading in one leg of the ICU patients, with an aim of reducing the loss of muscle function. METHODS: RNA-seq was used to assess gene expression changes in tibialis anterior skeletal muscle samples from seven critically ill, immobilized, and mechanically ventilated ICU patients with CIM and matched control subjects. We also examined skeletal muscle gene expression for both legs of six ICU patients with CIM, where one leg was mechanically loaded for 10 h/day for an average of 9 days. RESULTS: In total, 6257 of 17,221 detected genes were differentially expressed (84% upregulated; p < 0.05 and fold change ≥ 1.5) in skeletal muscle from ICU patients with CIM when compared to control subjects. The differentially expressed genes were highly associated with gene changes identified in patients with myopathy, sepsis, long-term inactivity, polymyositis, tumor, and repeat exercise resistance. Upstream regulator analysis revealed that the CIM signature could be a result of the activation of MYOD1, p38 MAPK, or treatment with dexamethasone. Passive mechanical loading only reversed expression of 0.74% of the affected genes (46 of 6257 genes). CONCLUSIONS: RNA-seq analysis revealed that the marked muscle atrophy and weakness observed in ICU patients with CIM were associated with the altered expression of genes involved in muscle contraction, newly identified E3 ligases, autophagy and calpain systems, apoptosis, and chaperone expression. In addition, MYOD1, p38 MAPK, and dexamethasone were identified as potential upstream regulators of skeletal muscle gene expression in ICU patients with CIM. Mechanical loading only marginally affected the skeletal muscle transcriptome profiling of ICU patients diagnosed with CIM.

Effect of high-flow high-volume-intermittent hemodiafiltration on metformin-associated lactic acidosis with circulatory failure: a case report.

BACKGROUND: Metformin-associated lactic acidosis is a well-known life-threatening complication of metformin. We here report the case of a patient who developed metformin-associated lactic acidosis without organ manifestations, due to the simultaneous ingestion of an overdose of metformin and alcohol, and who recovered with high-flow high-volume intermittent hemodiafiltration. CASE PRESENTATION: A 44-year-old Asian woman with type 2 diabetes attempted suicide by ingesting 10 tablets of metformin 500 mg and drinking approximately 600 mL of Japanese sake containing 15% alcohol. She was transferred to our emergency department because of disturbed consciousness. Continuous intravenous administration of noradrenalin (0.13 µg/kg per minute) was given because she was in shock. Laboratory findings included a lactate level of 119 mg/dL (13.2 mmol/L), bicarbonate of 14.5 mmol/L, and serum metformin concentration of 1138 ng/mL. She was diagnosed as having metformin-associated lactic acidosis worsened by alcohol. After 4560 mL of bicarbonate ringer (Na+ 135 mEq/L, K+ 4 mEq/L, Cl- 113 mEq/L, HCO3- 25 mEq/L) was administered, high-flow high-volume intermittent hemodiafiltration. (dialysate flow rate: 500 mL/min, substitution flow rate: 3.6 L/h) was carried out for 6 h to treat metabolic acidosis and remove lactic acid and metformin. Consequently, serum metformin concentration decreased to 136 ng/mL and noradrenalin administration became unnecessary to maintain normal vital signs. On hospital day 12, she was moved to the psychiatry ward. CONCLUSIONS: HFHV-iHDF may be able to remove metformin and lactic acid efficiently and may improve the condition of hemodynamically unstable patients with metformin-associated lactic acidosis.

Alpha7 nicotinic acetylcholine receptor-specific agonist DMXBA (GTS-21) attenuates Aß accumulation through suppression of neuronal γ-secretase activity and promotion of microglial amyloid-ß phagocytosis and ameliorates cognitive impairment in a mouse model of Alzheimer's disease.

We previously demonstrated that stimulation of nicotinic acetylcholine receptors (nAChRs) increases amyloid-ß (Aß) phagocytosis in rat microglia and is closely associated with the decrease of brain Aß and amelioration of memory dysfunction in a transgenic mouse model of Alzheimer's disease (AD). Here, we examined the subtypes of nAChRs involved in these beneficial effects. In primary cultures of rat microglia, the α7 nAChR selective agonist 3-[(2,4-dimethoxy)benzylidene]-anabaseine dihydrochloride (DMXBA) promoted Aß and fluorescent latex bead phagocytosis, whereas selective α7 nAChR antagonists suppressed the enhanced Aß phagocytosis. In a transgenic mouse model of AD, administration of DMXBA attenuated brain Aß burden and memory dysfunction. Moreover, DMXBA suppressed γ-secretase activity in solubilized fractions of human neuroblastoma cells and transgenic mouse brain. These results suggested that selective activation of α7 nAChRs promoted microglial Aß phagocytosis and suppressed neuronal γ-secretase activity to contribute to the attenuation of the brain Aß burden and cognitive impairment. Thus, we propose neuronal and microglial α7 nAChRs as new therapeutic targets in the treatment of AD.

Thyrotoxic and pheochromocytoma multisystem crisis: a case report.

BACKGROUND: Thyrotoxic crisis and pheochromocytoma multisystem crisis are rare, life-threatening, emergency endocrine diseases with various clinical manifestations. Here we report a case of a patient who simultaneously developed thyrotoxic crisis and pheochromocytoma multisystem crisis and required intensive cardiovascular management. CASE PRESENTATION: A 60-year-old Asian man experienced nausea and vomiting, and subsequently developed dyspnea and cold sweats while farming. His serum free thyroxine, free triiodothyronine, and thyrotropin receptor antibody levels were elevated at 2.9 ng/dL, 7.2 pg/dL, and 4.7 IU/L, respectively. Serum thyrotropin levels were suppressed at less than 0.01 µIU/mL. Thyroid echography demonstrated no thyroid swelling (23 × 43 mm). A whole body computed tomography was performed for systemic evaluation. This revealed exophthalmos and a mass of size 57 × 64 mm in the anterior pararenal space. Based on these findings, we made an initial diagnosis of thyrotoxic crisis secondary to exacerbation of Grave's hyperthyroidism. Treatment was begun with an iodine agent at a dose of 36 mg/day, thiamazole at a dose of 30 mg/day, and hydrocortisone at a dose of 300 mg daily for 3 consecutive days. To control tachycardia, continuous intravenously administered propranolol and diltiazem infusions were given. At the same time, small doses of doxazosin and carvedilol were used for both alpha and beta adrenergic blockade. On hospital day 5, his blood pressure and serum catecholamine concentrations (adrenalin 42,365 pg/mL, dopamine 6409 pg/mL, noradrenalin 72,212 pg/mL) were still high despite higher beta blocker and calcium channel blocker doses. These findings contributed to the diagnosis of pheochromocytoma multisystem crisis with simultaneous thyrotoxic crisis. We increased the doses of doxazosin and carvedilol, which stabilized his hemodynamic status. On hospital day 16, metaiodobenzylguanidine scintigraphy showed high accumulation in the right adrenal gland tumor. After retroperitoneal laparoscopic adrenalectomy on hospital day 33, his condition stabilized. He was discharged on hospital day 58. CONCLUSIONS: Since he required more intensive cardiovascular management for thyrotoxic crisis, beta blockade was increased under intensive care unit monitoring even though initial alpha blockade is recommended in pheochromocytoma. When these crises occur simultaneously, cardiovascular management can be very challenging.

Blunt cardiac injury due to trauma associated with snowboarding: a case report.

BACKGROUND: Cardiac trauma is associated with a much higher mortality rate than injuries to other organ systems, even though cardiac trauma is identified in less than 10% of all trauma admissions. Here we report blunt trauma of the left atrium due to snowboarding trauma. CASE PRESENTATION: A 45-year-old Asian man collided with a tree while he was snowboarding and drinking. He lost consciousness temporarily. An air ambulance was requested and he was transported to an advanced critical care center. On arrival, a pericardial effusion was detected by a focused assessment with sonography for trauma. His presenting electrocardiogram revealed normal sinus rhythm and complete right bundle branch block. Laboratory findings included a white blood cell count of 13.5 × 103/µl, serum creatine kinase level of 459 IU/l, and creatine kinase-myocardial band level of 185 IU/l. Enhanced computed tomography showed a large pericardial effusion and bleeding from his left adrenal gland. There were no pelvic fractures. A diagnosis of cardiac tamponade due to blunt cardiac injury and left adrenal injury due to blunt trauma was made. Subsequently, emergency thoracic surgery and transcatheter arterial embolization of his left adrenal artery were performed simultaneously. A laceration of the left atrial appendage in the lateral wall of his left ventricle was detected intraoperatively and repaired. His postoperative course progressed favorably, although a pericardial effusion was still detected on chest computed tomography on hospital day 35. His electrocardiogram showed normal sinus rhythm and the complete right bundle branch block pattern changed to a narrow QRS wave pattern. He was discharged on hospital day 40. CONCLUSIONS: The present case report illustrates two points: (1) severe injuries resulted from snowboarding, and (2) complete right bundle branch block was caused by blunt cardiac injury. The present report showed blunt trauma of the left atrium with complete right bundle branch block as an electrocardiogram change due to snowboarding trauma. To detect cardiac trauma in snowboarding accidents, an examination of an electrocardiogram is required in all patients who might have a bruised chest.

Glucagon receptor inhibition normalizes blood glucose in severe insulin-resistant mice.

Inactivating mutations in the insulin receptor results in extreme insulin resistance. The resulting hyperglycemia is very difficult to treat, and patients are at risk for early morbidity and mortality from complications of diabetes. We used the insulin receptor antagonist S961 to induce severe insulin resistance, hyperglycemia, and ketonemia in mice. Using this model, we show that glucagon receptor (GCGR) inhibition with a monoclonal antibody normalized blood glucose and ß-hydroxybutyrate levels. Insulin receptor antagonism increased pancreatic ß-cell mass threefold. Normalization of blood glucose levels with GCGR-blocking antibody unexpectedly doubled ß-cell mass relative to that observed with S961 alone and 5.8-fold over control. GCGR antibody blockage expanded α-cell mass 5.7-fold, and S961 had no additional effects. Collectively, these data show that GCGR antibody inhibition represents a potential therapeutic option for treatment of patients with extreme insulin-resistance syndromes.

RNA Sequencing of Single Human Islet Cells Reveals Type 2 Diabetes Genes.

Pancreatic islet cells are critical for maintaining normal blood glucose levels, and their malfunction underlies diabetes development and progression. We used single-cell RNA sequencing to determine the transcriptomes of 1,492 human pancreatic α, ß, δ, and PP cells from non-diabetic and type 2 diabetes organ donors. We identified cell-type-specific genes and pathways as well as 245 genes with disturbed expression in type 2 diabetes. Importantly, 92% of the genes have not previously been associated with islet cell function or growth. Comparison of gene profiles in mouse and human α and ß cells revealed species-specific expression. All data are available for online browsing and download and will hopefully serve as a resource for the islet research community.

Use of the Fluidigm C1 platform for RNA sequencing of single mouse pancreatic islet cells.

This study provides an assessment of the Fluidigm C1 platform for RNA sequencing of single mouse pancreatic islet cells. The system combines microfluidic technology and nanoliter-scale reactions. We sequenced 622 cells, allowing identification of 341 islet cells with high-quality gene expression profiles. The cells clustered into populations of α-cells (5%), ß-cells (92%), δ-cells (1%), and pancreatic polypeptide cells (2%). We identified cell-type-specific transcription factors and pathways primarily involved in nutrient sensing and oxidation and cell signaling. Unexpectedly, 281 cells had to be removed from the analysis due to low viability, low sequencing quality, or contamination resulting in the detection of more than one islet hormone. Collectively, we provide a resource for identification of high-quality gene expression datasets to help expand insights into genes and pathways characterizing islet cell types. We reveal limitations in the C1 Fluidigm cell capture process resulting in contaminated cells with altered gene expression patterns. This calls for caution when interpreting single-cell transcriptomics data using the C1 Fluidigm system.

Loss of SFRP4 Alters Body Size, Food Intake, and Energy Expenditure in Diet-Induced Obese Male Mice.

Secreted frizzled-related protein 4 (SFRP4) is an extracellular regulator of the wingless-type mouse mammary tumor virus integration site family (WNT) pathway. SFRP4 has been implicated in adipocyte dysfunction, obesity, insulin resistance, and impaired insulin secretion in patients with type 2 diabetes. However, the exact role of SFRP4 in regulating whole-body metabolism and glucose homeostasis is unknown. We show here that male Sfrp4(-/-) mice have increased spine length and gain more weight when fed a high-fat diet. The body composition and body mass per spine length of diet-induced obese Sfrp4(-/-) mice is similar to wild-type littermates, suggesting that the increase in body weight can be accounted for by their longer body size. The diet-induced obese Sfrp4(-/-) mice have reduced energy expenditure, food intake, and bone mineral density. Sfrp4(-/-) mice have normal glucose and insulin tolerance and ß-cell mass. Diet-induced obese Sfrp4(-/-) and control mice show similar impairments of glucose tolerance and a 5-fold compensatory expansion of their ß-cell mass. In summary, our data suggest that loss of SFRP4 alters body length and bone mineral density as well as energy expenditure and food intake. However, SFRP4 does not control glucose homeostasis and ß-cell mass in mice.

Development of PEGylated serum albumin with multiple reduced thiols as a long-circulating scavenger of reactive oxygen species for the treatment of fulminant hepatic failure in mice.

Reactive oxygen species (ROS) are involved in the pathophysiology of fulminant hepatic failure. Therefore, we developed polyethylene glycol-conjugated bovine serum albumin with multiple reduced thiols (PEG-BSA-SH) for the treatment of fulminant hepatic failure. As a long-circulating ROS scavenger, PEG-BSA-SH effectively scavenged highly reactive oxygen species and hydrogen peroxide in buffer solution. PEG-BSA-SH showed a long circulation time in the plasma after intravenous injection into mice. Fulminant hepatic failure was induced by intraperitoneal injection of lipopolysaccharide and D-galactosamine (LPS/D-GalN) into mice. The LPS/D-GalN-induced elevation of plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels was significantly inhibited by a bolus intravenous injection of PEG-BSA-SH. Furthermore, the changes in hepatic lipid peroxide and hepatic blood flow were effectively suppressed by PEG-BSA-SH. In contrast, L-cysteine, glutathione, and dithiothreitol, three traditional reduced thiols, had no statistically significant effects on the serum levels of ALT or AST. These findings indicate that PEG-BSA-SH is a promising ROS scavenger and useful in the treatment of fulminant hepatic failure.

Resting energy expenditure and nutritional status in patients undergoing transthoracic esophagectomy for esophageal cancer.

This study was to assess the resting energy expenditure of patients with esophageal cancer using indirect calorimetry. Eight male patients with esophageal cancer and eight male healthy controls were enrolled in this study. All patients underwent transthoracic esophagectomy with lymph nodes dissections. The resting energy expenditure was measured preoperatively, and on postoperative day 7 and 14 using indirect calorimetry. Preoperatively, the measured resting energy expenditure/body weight in these patients was significantly higher than that of the controls (23.3 ± 2.1 kcal/kg/day vs 20.4 ± 1.6 kcal/kg/day), whereas the measured/predicted energy expenditure from the Harris-Benedict equation ratio was 1.01 ± 0.09, which did not differ significantly from the control values. The measured resting energy expenditure/body weight was 27.3 ± 3.5 kcal/kg/day on postoperative day 7, and 23.7 ± 5.07 kcal/kg/day on postoperative day 14. Significant increases in the measured resting energy expenditure were observed on postoperative day 7, and the measured/predicted energy expenditure ratio was 1.17 ± 0.15. In conclusion, patients with operable esophageal cancers were almost normometabolic before surgery. On the other hand, the patients showed a hyper-metabolic status after esophagectomy. We recommended that nutritional management based on 33 kcal/body weight/day (calculated by the measured resting energy expenditure × active factor 1.2-1.3) may be optimal for patients undergoing esophagectomy.

Resting energy expenditure in patients undergoing pylorus preserving pancreatoduodenectomies for bile duct cancer or pancreatic tumors.

We measured the energy expenditure weekly in patients undergoing a pylorus preserving pancreatoduodenectomy for bile duct cancer or pancreatic tumors. Twelve patients (5 women and 7 men; mean age 70.1 years) were enrolled in this study, and their resting energy expenditure levels were determined by indirect calorimetry. In these patients, a significant correlation was observed between the measured resting energy expenditures and the predicted resting energy expenditures calculated by the Harris-Benedict equation. The resting energy expenditures measured before surgery were almost the same as the predicted resting energy expenditures (measured resting energy expenditure: 22.4 ± 3.9 kcal/kg/day vs predicted resting energy expenditure: 21.7 ± 2.0 kcal/kg/day). The measured resting energy expenditure/predicted resting energy expenditure ratio, which reflects the stress factor, was 1.02 ± 0.10. After the pylorus preserving pancreatoduodenectomy, a significant increase in energy expenditure was observed, and the measured resting energy expenditure was 25.7 ± 3.5 kcal/kg/day on postoperative day 7 and 25.4 ± 4.9 kcal/kg/day on postoperative day 14. The measured resting energy expenditure/predicted resting energy expenditure ratio was 1.16 ± 0.14 on postoperative day 7, and 1.16 ± 0.18 on postoperative day 14 respectively. In conclusion, patients undergoing a pylorus preserving pancreatoduodenectomy showed a hyper-metabolic status as evaluated by their measured resting energy expenditure/predicted resting energy expenditure ratio. From our observations, we recommend that nutritional management based on 30 kcal/body weight/day (calculated by the measured resting energy expenditure×activity factor 1.2-1.3) may be optimal for patients undergoing a pylorus preserving pancreatoduodenectomy.

Peptide YY regulates bone turnover in rodents.

BACKGROUND & AIMS: Peptide YY (PYY) and pancreatic polypeptide (PPY) are members of the neuropeptide Y peptide family. The neuropeptide Y receptor signaling pathway has been implicated in a number of physiologic processes, including the regulation of energy balance and bone mass. To investigate the contribution of endogenous PYY and PPY to these processes, we generated both Pyy- and Ppy-deficient mice. METHODS: Pyy(-/-) and Ppy(-/-) mice and their respective wild-type littermates were studied from 8 weeks to 9 months of age. Food intake, metabolic parameters, and locomotor activity were monitored using indirect calorimetry. Body composition and bone parameters were analyzed using dual energy x-ray absorptiometry, histomorphometry, and vertebral compression testing. RESULTS: Studies in these mice showed an osteopenic phenotype specific to the Pyy-deficient line, which included a reduction in trabecular bone mass and a functional deficit in bone strength. Furthermore, female Pyy(-/-) mice showed a greater sensitivity to ovariectomy-induced bone loss compared with wild-type littermates. No food intake or metabolic phenotype was apparent in male or female Pyy(-/-) mice on standard chow. However, female Pyy(-/-) mice on a high-fat diet showed a greater propensity to gain body weight and adiposity. No metabolic or osteopenic phenotype was observed in Ppy-deficient mice. CONCLUSIONS: These results indicate that endogenous PYY plays a critical role in regulating bone mass. In comparison, its role in regulating body weight is minor and is confined to situations of high-fat feeding.

Genetic deletion of Trb3, the mammalian Drosophila tribbles homolog, displays normal hepatic insulin signaling and glucose homeostasis.

Trb3, a mammalian homolog of Drosophila tribbles, was proposed as a suppressor of Akt activity, predominantly in conditions of fasting and diabetes. Given these prior studies, we sought to determine whether Trb3 plays a major role in modulating hepatic insulin sensitivity. To answer this question, we produced mice in which a lacZ reporter was knocked into the locus containing the gene Trib3, resulting in a Trib3 null animal. Trib3 expression analyses demonstrated that the Trib3 is expressed in liver, adipose tissues, heart, kidney, lung, skin, small intestine, stomach, and denervated, but not normal, skeletal muscle. Trib3(-/-) mice are essentially identical to their wild-type littermates in overall appearance and body composition. Phenotypic analysis of Trib3(-/-) mice did not detect any alteration in serum glucose, insulin, or lipid levels; glucose or insulin tolerance; or energy metabolism. Studies in Trib3(-/-) hepatocytes revealed normal Akt and glycogen synthase kinase- 3beta phosphorylation patterns, glycogen levels, and expressions of key regulatory gluconeogenic and glycolytic genes. These data demonstrate that deletion of Trib3 has minimal effect on insulin-induced Akt activation in hepatic tissue, and, as such, they question any nonredundant role for Trb3 in the maintenance of glucose and energy homeostasis in mice.

Role of the forkhead protein FoxO1 in beta cell compensation to insulin resistance.

Diabetes is associated with defective beta cell function and altered beta cell mass. The mechanisms regulating beta cell mass and its adaptation to insulin resistance are unknown. It is unclear whether compensatory beta cell hyperplasia is achieved via proliferation of existing beta cells or neogenesis from progenitor cells embedded in duct epithelia. We have used transgenic mice expressing a mutant form of the forkhead-O1 transcription factor (FoxO1) in both pancreatic ductal and endocrine beta cells to assess the contribution of these 2 compartments to islet expansion. We show that the mutant FoxO1 transgene prevents beta cell replication in 2 models of beta cell hyperplasia, 1 due to peripheral insulin resistance (Insulin receptor transgenic knockouts) and 1 due to ectopic local expression of IGF2 (Elastase-IGF2 transgenics), without affecting insulin secretion. In contrast, we failed to detect a specific effect of the FoxO1 transgene on the number of periductal beta cells. We propose that beta cell compensation to insulin resistance is a proliferative response of existing beta cells to growth factor signaling and requires FoxO1 nuclear exclusion.

Increased CD36 protein as a response to defective insulin signaling in macrophages.

Accelerated atherosclerosis is a major cause of morbidity and death in insulin-resistant states such as obesity and the metabolic syndrome, but the underlying mechanisms are poorly understood. We show that macrophages from obese (ob/ob) mice have increased binding and uptake of oxidized LDL, in part due to a post-transcriptional increase in CD36 protein. Macrophages from ob/ob mice are also insulin resistant, as shown by reduced expression and signaling of insulin receptors. Three lines of evidence indicate that the increase in CD36 is caused by defective insulin signaling: (a) Treatment of wild-type macrophages with LY294002, an inhibitor of insulin signaling via PI3K, results in an increase in CD36; (b) insulin receptor knockout macrophages show a post-transcriptional increase in CD36 protein; and (c) administration of thiazolidinediones to intact ob/ob mice and ob/ob, LDL receptor-deficient mice results in a reversal of macrophage insulin receptor defects and decreases CD36 protein. The last finding contrasts with the increase in CD36 that results from treatment of macrophages with these drugs ex vivo. The results suggest that defective macrophage insulin signaling predisposes to foam cell formation and atherosclerosis in insulin-resistant states and that this is reversed in vivo by treatment with PPAR-gamma activators.