Control of Eating Attributes and Weight Loss Outcomes over One Year After Sleeve Gastrectomy

PURPOSE

Sleeve gastrectomy (SG) is a commonly performed metabolic-bariatric surgery, but its effectiveness is variable and difficult to predict. Our study aimed to compare control of eating (CoE) attributes pre- and post-SG depending on the achievement of optimal weight loss target at 1 year post-SG.

MATERIALS AND METHODS

A prospective longitudinal cohort study using the CoE Questionnaire, pre-SG, and postoperatively at 3, 6, and 12 months was conducted. Total weight loss (TWL) ≥ 25% at 12 months post-SG was set as an optimal weight loss target.

RESULTS

Forty-one patients (80.5% females, mean age 41.7 ± 10.6) were included. Sex, age, baseline weight, BMI, and smoking status were all comparable. At 3 months post-SG, "difficulty to control eating" score became significantly different between ≥ 25%TWL and < 25%TWL groups (7 [0-50] vs. 17 [5-63], p = 0.042). At 6 months, it was followed by "feeling of fullness," "frequency of food cravings," and "difficulty to resist cravings" demonstrating significant differences between ≥ 25%TWL and < 25%TWL groups. At 12 months, significant differences between groups were observed in "feeling hungry," "difficulty to resist cravings," "eating in response to cravings," and difficulty to control eating scores.

CONCLUSION

Individuals with obesity who achieved a target of ≥ 25%TWL at 1 year post-SG have an early improvement in overall eating control at 3 months that steadily persists at 6 and 12 months. Improvements in other aspects tend to follow later, at 6 and 12 months. These findings may assist in identifying individuals with inadequate response to help attain optimal weight loss targets and developing a prognostic model to identify predictors of successful weight loss.

Bite by byte: can fitness wearables help bariatric patients lose more weight after surgery?

BACKGROUND

Multidisciplinary approaches to weight loss have been shown to improve outcomes in bariatric patients. Few studies have been performed assessing the utility and compliance of fitness tracking devices after bariatric surgery. We aim to determine whether use of an activity tracking device assists bariatric patients in improving postoperative weight loss behaviors.

METHODS

A fitness wearable was offered to patients undergoing bariatric surgery from 2019 to 2022. A telephone survey was conducted to elucidate the impact of the device on the patient's postoperative weight loss efforts 6 to 12 months after surgery. Weight loss outcomes of sleeve gastrectomy (SG) patients receiving the fitness wearable (FW) were compared to those of a group of SG patients who did not receive one (non-FW).

RESULTS

Thirty-seven patients were given a fitness wearable, 20 of whom responded to our telephone survey. Five patients reported not using the device and were excluded. 88.2% reported that using the device had a positive impact on their overall lifestyle. Patients felt that using the fitness wearable to keeping track of their progress helped them both to achieve short-term fitness goals and sustain them in the long run. From the patients that utilized the device, 44.4% of those that discontinued felt like it helped them build a routine that they maintained even after they were no longer using it. Demographic data between FW and non-FW groups (age, sex, CCI, initial BMI, and surgery BMI) did not differ significantly. The FW group trended towards greater %EWL at 1 year post-operation (65.2% versus 52.4%, p = 0.066) and had significantly greater %TWL at 1 year post-operation (30.3% versus 22.3%, p = 0.02).

CONCLUSION

The use of an activity tracking device enhances a patient's post-bariatric surgery experience, serving to keep patients informed and motivated, and leading to improved activity that may translate to better weight loss outcomes.

Mesenteric fat cryolipolysis attenuates insulin resistance in the Ossabaw swine model of the metabolic syndrome

BACKGROUND

The rising prevalence of insulin resistance (IR), metabolic syndrome, and type 2 diabetes are associated with increases in abdominal mesenteric fat. Adipocytes are sensitive to low temperatures, making cryolipolysis of mesenteric fat an attractive treatment modality to potentially reduce IR.

OBJECTIVES

We aimed to determine whether (1) cryolipolysis is safe in reducing the volume of the mesenteric fat and (2) reduction in mesenteric fat volume reduces indices of IR and glycemic dysfunction.

SETTING

Indiana University School of Medicine.

METHODS

A novel cooling device and method delivered cryolipolysis in a controlled manner to avoid tissue ablative temperatures. Ossabaw pigs (n = 8) were fed a high-fat diet for 9 months to develop visceral obesity, IR, and metabolic syndrome. Following laparotomy, mesenteric fat cryolipolysis (MFC) was performed in 5 pigs, while 3 served as sham surgery controls. The volume of the mesenteric fat was measured by computed tomography and compared with indices of glucose intolerance before and at 3 and 6 months postprocedure.

RESULTS

MFC safely reduced mesenteric fat volume by ∼30% at 3 months, which was maintained at 6 months. Body weight did not change in either the MFC or sham surgery control groups. Measure of glycemic control, insulin sensitivity, and blood pressure significantly improved after MFC compared with sham controls.

CONCLUSION

MFC reduces the volume of mesenteric fat and improves glycemic control in obese, IR Ossabaw pigs, without adverse effects.

Weight loss outcomes are not compromised in bariatric patients using cannabis

BACKGROUND

The legalization of cannabis in several states has led to increased documented use in the population. Bariatric surgery patients are no exception with estimates of anywhere from 6 to 8%. Cannabis is known to be associated with increased appetite, mood disorders, hyperphagia, and rarely, hyperemesis, which can potentially affect post-surgical weight loss. We aim to study the differences in bariatric surgery outcomes between cannabis users and non-users.

METHODS

A retrospective review identified patients undergoing bariatric surgery. Patients were divided into two groups, cannabis users (CU) and non-cannabis users (non-CU). Cannabis users (defined as using at least once weekly) and a group of non-users were called to obtain additional information. Primary outcome was weight loss. Secondary outcomes included incidence of post-operative nausea and vomiting (PONV), length of stay (LOS), readmission, and need for additional intervention.

RESULTS

A cohort of 364 sleeve gastrectomy patients met inclusion criteria, 31 (8.5%) CU and 333 (91.5%) non-CU. There was no difference in EWL between CU and non-CU at 1 week, 1 month, 3 months, 6 months, 9 months, 1 year, and 2 years. However, the CU group trended towards greater EWL at 3 years (52.9% vs. 38.1%, p = 0.094) and at 5 years (49.8% vs. 32.7%, p = 0.068). There were no significant differences between CU and non-CU with respect to either incidence or severity of PONV at one year after surgery or longer follow-up.

CONCLUSION

Cannabis users did not experience inferior weight loss after bariatric surgery despite common assumptions that appetite stimulation can lead to suboptimal weight loss outcomes. Our findings add to other work challenging this dogma. Larger, long-term, multicenter studies are warranted.

Exploring the Effect of Adding an Interactive Lecture to a Standardized Patient Curriculum on the Attitudes of Third-Year Medical Students About Patients With Obesity: A Quasi-Experimental Study

OBJECTIVES

Anti-obesity bias is pervasive among medical professionals, students, and trainees. Stigmatization of patients leads to suboptimal care and clinical outcomes. Educational strategies in medical training are needed to reverse these attitudes. The aim of this study was to evaluate the effect of an innovative didactic intervention and a standardized patient (SP) exercise on attitudes towards patients with obesity among medical students.

METHODS

In 2016, a quasi-experimental study design was used at a US medical school. The class was divided into 2 groups according to a pre-determined protocol based on their clinical schedule, one assessed after exposure to a SP group and the other after exposure to the SP and an interactive lecture (IL + SP group) with real patients. The Attitudes about Treating Patients with Obesity and The Perceived Causes of Obesity questionnaires measured changes in several domains. A generalized estimating equations model was used to estimate the effect of the interventions both within and between groups.

RESULTS

Both groups showed improvements in negative and positive attitudes, although the reduction in scores for the negative attitude domain did not reach statistical significance in the IL + SP group (for the SP group, P = .01 and  < .001, respectively; for the IL + SP group, P = .15 and .01, respectively). For perceived causes of obesity, there were no statistically significant changes for pre-post survey measures within each group, except for the physiologic causes domain in the SP group (P = .03). The addition of an IL to a SP curriculum did not result in any changes for any domain in between-group analyses.

CONCLUSIONS

Although adding a novel intervention utilizing real patients to a SP curriculum failed to show an additional educational benefit, our study showed that it is possible to influence attitudes of medical students regarding patients with obesity.

AGA Clinical Practice Guideline on Pharmacological Interventions for Adults With Obesity

BACKGROUND & AIMS

Pharmacological management of obesity improves outcomes and decreases the risk of obesity-related complications. This American Gastroenterological Association guideline is intended to support practitioners in decisions about pharmacological interventions for overweight and obesity.

METHODS

A multidisciplinary panel of content experts and guideline methodologists used the Grading of Recommendations Assessment, Development and Evaluation framework to prioritize clinical questions, identify patient-centered outcomes, and conduct an evidence synthesis of the following agents: semaglutide 2.4 mg, liraglutide 3.0 mg, phentermine-topiramate extended-release (ER), naltrexone-bupropion ER, orlistat, phentermine, diethylpropion, and Gelesis100 oral superabsorbent hydrogel. The guideline panel used the evidence-to-decision framework to develop recommendations for the pharmacological management of obesity and provided implementation considerations for clinical practice.

RESULTS

The guideline panel made 9 recommendations. The panel strongly recommended the use of pharmacotherapy in addition to lifestyle intervention in adults with overweight and obesity (body mass index ≥30 kg/m2, or ≥27 kg/m2 with weight-related complications) who have an inadequate response to lifestyle interventions. The panel suggested the use of semaglutide 2.4 mg, liraglutide 3.0 mg, phentermine-topiramate ER, and naltrexone-bupropion ER (based on moderate certainty evidence), and phentermine and diethylpropion (based on low certainty evidence), for long-term management of overweight and obesity. The guideline panel suggested against the use of orlistat. The panel identified the use of Gelesis100 oral superabsorbent hydrogel as a knowledge gap.

CONCLUSIONS

In adults with overweight and obesity who have an inadequate response to lifestyle interventions alone, long-term pharmacological therapy is recommended, with multiple effective and safe treatment options.

Effect of Obesity on Risk of Hospitalization, Surgery, and Serious Infection in Biologic-Treated Patients With Inflammatory Bowel Diseases: A CA-IBD Cohort Study

INTRODUCTION

Obesity is variably associated with treatment response in biologic-treated patients with inflammatory bowel diseases (IBD). We evaluated the association between obesity and risk of hospitalization, surgery, or serious infections in patients with IBD in new users of biologic agents in a large, multicenter, electronic health record (EHR)-based cohort (CA-IBD).

METHODS

We created an EHR-based cohort of adult patients with IBD who were new users of biologic agents (tumor necrosis factor [TNF-α] antagonists, ustekinumab, and vedolizumab) between January 1, 2010, and June 30, 2017, from 5 health systems in California. Patients were classified as those with normal body mass index (BMI), overweight, or obese based on the World Health Organization classification. We compared the risk of all-cause hospitalization, IBD-related surgery, or serious infections among patients with obesity vs those overweight vs those with normal BMI, using Cox proportional hazard analyses, adjusting for baseline demographic, disease, and treatment characteristics.

RESULTS

Of 3,038 biologic-treated patients with IBD (69% with Crohn's disease and 76% on TNF-α antagonists), 28.2% (n = 858) were overweight, and 13.7% (n = 416) were obese. On a follow-up after biologic initiation, obesity was not associated with an increased risk of hospitalization (adjusted hazard ratio [aHR] vs normal BMI, 0.90; [95% confidence interval, 0.72-1.13]); IBD-related surgery (aHR, 0.62 [0.31-1.22]); or serious infection (aHR, 1.11 [0.73-1.71]). Similar results were observed on stratified analysis by disease phenotype (Crohn's disease vs ulcerative colitis) and index biologic therapy (TNF-α antagonists vs non-TNF-α antagonists).

DISCUSSION

In a multicenter, EHR-based cohort of biologic-treated patients with IBD, obesity was not associated with hospitalization, surgery, or serious infections. Further studies examining the effect of visceral obesity on patient-reported and endoscopic outcomes are needed.

Point-of-care magnetic resonance technology to measure liver fat: Phantom and first-in-human pilot study

PURPOSE

To assess feasibility and accuracy of point-of-care (POC) NMR-proton density fat fraction (PDFF) in phantoms and in a human pilot study in a POC setting.

METHODS

POC NMR (LiverScope, Livivos, San Diego CA) PDFF measurements were obtained of certified phantoms with known PDFF values (0%-40%). In an institutional review board-approved, Health Insurance Portability and Accountability Act-compliant prospective human study, a convenience sample of participants from an obesity clinic was enrolled (November 2020 to June 2021). The inclusion criteria required body mass index (BMI) = 27-40 kg/m² and willingness to undergo POC NMR and MRI-PDFF measurements. Liver PDFF was measured by POC NMR and, within 35 days after, by a confounder corrected CSE MRI PDFF acquisition and reconstruction method. The adverse events were documented and linear regression analyses were performed.

RESULTS

POC NMR-PDFF measurements agreed with known phantom PDFF values (R²  = 0.99). Fourteen participants were enrolled in the pilot human study. MRI-PDFF could not be obtained in 4 participants (claustrophobia reaction, n = 3, exceeded size of MR scanner bore, n = 1). POC NMR was unevaluable in 2 participants (insufficient signal penetration depth, n = 1, failure to comply with instructions, n = 1). Technical success was 11 of 13 (85%) for POC NMR PDFF. In 7 participants (4 female; 31-74 years old; median BMI 35 kg/m² ), MRI-PDFF (range, 2.8%-18.1%), and POC NMR-PDFF (range, 3%-25.2%), agreed with R²  = 0.94. POC NMR had no adverse events.

CONCLUSION

POC NMR measures PDFF accurately in phantoms and, in a first-in-human pilot study, is feasible and accurate in adults with obesity. Further testing to determine precision and accuracy across larger and more diverse cohorts is needed.

Obesity Hypoventilation Syndrome and Postsurgical Outcomes in a Bariatric Surgery Cohort

Purpose

Patients with obesity and elevated serum bicarbonate suggesting obesity hypoventilation syndrome (OHS) undergoing bariatric surgery may represent a unique subgroup. Information regarding surgical outcomes in this population remains limited. We sought to test the hypothesis that an elevated bicarbonate would be an important predictor of perioperative complications (i.e., length of hospital stay) and postsurgical outcomes (i.e., weight loss at 1 year).

Materials and Methods

Consecutive patients undergoing bariatric surgery between January 2015 and December 2018 were included. Patients with a preoperative serum bicarbonate ≥ 27 mEq/L were classified as suspected OHS.

Results

Of 297 patients, the prevalence of suspected OHS based on an elevated bicarbonate was 19.5% (95% CI: 15.3 to 24.6%). Length of hospital stay was similar in the suspected OHS and non-OHS control group (1.50 vs 1.49 days, P = 0.98). The achieved weight loss from peak preoperative weight to 1 year post-surgery was less in the suspected OHS vs the control group (4.2% [95% CI 1.6 to 6.8]; P = 0.002).

Conclusion

Patients with serum bicarbonate ≥ 27 mEq/L as a surrogate marker for OHS experienced weight loss that was significantly less than their normal serum bicarbonate counterparts, but still achieved weight loss deemed clinically important by current guidelines. We observed no significant difference in length of hospital stay at time of surgery.

Graphical abstract

Phentermine-topiramate extended release for the dual treatment of obesity and sleep-related eating disorder: a case report

Background

Obesity and eating disorders can present together, and pose diagnostic and therapeutic challenges to the clinician. Generally, lifestyle interventions alone for the treatment of obesity have modest long-term effectiveness. Phentermine–topiramate extended release is a relatively new medication approved for weight reduction. Sleep-related eating disorder is a rare condition that is often underdiagnosed. Both conditions are chronic and require long-term management. There is no definitive treatment for sleep-related eating disorder, and therapeutic options are based on case reports.

Case presentation

A 35-year-old Caucasian male with a body mass index of 41.7 kg/m² presented for obesity treatment. History revealed nocturnal episodes of hyperphagia associated with amnesia of overeating and other features of sleep-related eating disorder. Treatment was initiated with phentermine–topiramate extended release. Five months later he lost 5% of his body weight and demonstrated resolution of sleep-related eating disorder behaviors. He reported no adverse side effects. Upon self-discontinuation of the medication, his eating disorder recurred.

Conclusions

Clinicians intending to help patients reduce body weight should screen for nocturnal eating and other eating disorders. Sleep-related eating disorder can be associated with significant morbidity and excess weight. Patients report adverse effects on quality of life as a result. Phentermine–topiramate extended release may be a good therapeutic option for patients presenting with comorbid obesity and sleep-related eating disorder. More research is needed to explore the efficacy and safety in this patient population.

An ACVR1R375P pathogenic variant in two families with mild fibrodysplasia ossificans progressiva

Genetic variants are vital in informing clinical phenotypes, aiding physical diagnosis, guiding genetic counseling, understanding the molecular basis of disease, and potentially stimulating drug development. Here we describe two families with an ultrarare ACVR1 gain-of-function pathogenic variant (codon 375, Arginine > Proline; ACVR1^R375P ) responsible for a mild nonclassic fibrodysplasia ossificans progressiva (FOP) phenotype. Both families include people with the ultrarare ACVR1^R375P variant who exhibit features of FOP while other individuals currently do not express any clinical signs of FOP. Thus, the mild ACVR1^R375P variant greatly expands the scope and understanding of this rare disorder.

Screening for Obstructive Sleep Apnea in a Diverse Bariatric Surgery Population

OBJECTIVE

Obstructive sleep apnea (OSA) is common among bariatric surgery patients and is associated with perioperative risk. Preoperative screening is recommended, but some screening tools lack validation, and their relative performance is unclear in this population. The study objective was to compare the ability of four existing tools (STOP-BANG, NO-OSAS, No-Apnea, and the Epworth Sleepiness Scale [ESS]) to screen for moderate to severe OSA in a diverse bariatric cohort.

METHODS

Data from patients presenting for first-time bariatric surgery who underwent a sleep study within 1 year of the initial encounter were retrospectively reviewed. Performance of the four tools for detecting moderate to severe OSA was compared based on the area under the receiver operating characteristic curves (AUC).

RESULTS

Of the included 214 patients (83.2% female, median age 39 years), 45.3% had moderate to severe OSA. Based on AUC, STOP-BANG (0.75 [95% CI: 0.68-0.81], N = 185), NO-OSAS (0.76 [95% CI: 0.69-0.82], N = 185), and No-Apnea (0.69 [95% CI: 0.62-0.76], N = 190) had similar performance (P > 0.16). Compared with STOP-BANG and NO-OSAS, ESS (0.61 [95% CI: 0.54-0.68], N = 198) had a significantly lower AUC (P < 0.01). Hispanic/Latino self-identification, sex, or obesity class did not significantly modify test performance.

CONCLUSIONS

STOP-BANG and NO-OSAS may be preferable to No-Apnea and ESS when screening bariatric surgery patients for moderate to severe OSA. Efforts to screen bariatric patients for OSA are recommended.

0611 Screening for Obstructive Sleep Apnea in the Bariatric Surgery Population

Introduction

Obstructive sleep apnea (OSA) is prevalent in the bariatric surgery population and has been associated with increased perioperative risk, especially if OSA is moderate-severe (apnea-hypopnea index ≥ 15/h). Consequently, screening for OSA is recommended as part of the preoperative evaluation. Several screening tools for OSA have been developed; however, some tools lack validation and their relative performance is unclear. The purpose of this study was to compare four existing screening tools (Epworth Sleepiness Scale (ESS), STOP-BANG, NO-OSAS, and No-Apnea) with regards to the ability to identify patients with moderate-severe OSA among bariatric surgery patients.

Methods

We retrospectively reviewed data from Jan 2015 to Mar 2019 for adult patients presenting consecutively to UC San Diego for first-time bariatric surgery who had undergone a home or in-lab sleep study (within one year of the initial encounter for bariatric surgery), which is our standard of care. We compared the accuracy of the four screening tools for detecting moderate-severe OSA based on the area under the receiver operating characteristic curves (AUC). Subgroup analyses were explored based on sex, BMI, and ethnicity (Hispanic/Latino vs non-Hispanic/Latino).

Results

Of the 214 patients (83.2% female, median age 39 years) included in the study, 45.4% had moderate-severe OSA. STOP-BANG (AUC 0.75 [95%CI: 0.68 to 0.81]) and NO-OSAS (AUC 0.76 [95%CI: 0.69 to 0.82]) had similar performance (p 0.62); both performed significantly better than the ESS (AUC 0.61 [95%CI: 0.54 to 0.68]; p 0.02 for both). STOP-BANG and NO-OSAS tended to perform better in the female vs male subgroup, but this finding did not reach statistical significance.

Conclusion

STOP-BANG and NO-OSAS are superior to the ESS when screening bariatric surgery patients for moderate-severe OSA. In future analyses we will further explore if adjustments of standard cut-offs improve test characteristics (i.e. sensitivity/specificity) when screening bariatric surgery patients (analyses ongoing).

Support

None.

Hypoglycemia After Gastric Bypass Successfully Treated With Calcium Channel Blockers: Two Case Reports

Postprandial hyperinsulinemic hypoglycemia is an uncommon yet well-established complication of Roux-en-Y gastric bypass (RYGB) that can result in serious morbidity and adversely affect quality of life. It is often unrecognized and may be difficult to diagnose. Management is challenging. As the number of bariatric procedures increases in parallel with the obesity epidemic, clinicians will be tasked to offer effective medical therapies for this complication. Two patients presented several years after RYGB with severe postprandial hypoglycemia. In one of the patients, we were able to document simultaneous postprandial hypoglycemia and hyperinsulinemia. Conventional treatment approaches, including medical nutrition therapy, acarbose, diazoxide, and octreotide, were either ineffective or limited by poor tolerance. Nifedipine and verapamil were used adjunctively with dietary modification, resulting in resolution of symptomatic hypoglycemic episodes. These agents are therapeutic options that can be used for some patients refractory to more traditional treatments. They should be tried before surgical procedures are considered for affected patients. These two cases demonstrate that calcium channel blockers may be efficacious and appropriate for select patients refractory to dietary interventions alone.

Effect of Obesogenic Medications on Weight-Loss Outcomes in a Behavioral Weight-Management Program

OBJECTIVE

This study aimed to evaluate a possible association between the use of obesogenic medications and inadequate weight loss in a behavioral weight-management program.

METHODS

This is a case-control, single-center study of 666 adult patients within a Veterans Health Administration health system who participated in the MOVE! behavioral weight-loss program. The cohort was divided into responders (n = 150), patients who achieved ≥ 5% total weight loss by the end of the MOVE! program, and nonresponders (n = 516), those who achieved < 5% total weight loss. We reviewed each patient's medical records for exposure to obesogenic medication during the time of treatment.

RESULTS

Approximately 62% (n = 411) of patients entering MOVE! had a prescription for obesogenic medications. Obesogenic medication use was associated with worse weight-loss outcomes, and participants were 37% less likely to achieve a clinically meaningful (≥ 5% total weight loss) outcome at the end of the MOVE! program (odds ratio, 0.633; 95% CI: 0.427-0.937; adjusted P = 0.022). Patients who received three or more medications (n = 72) had the greatest difficulty achieving 5% weight loss compared with the control group (odds ratio, 0.265; 95% CI: 0.108-0.646; adjusted P = 0.003).

CONCLUSIONS

The use of provider-prescribed obesogenic medications was associated with worse weight-loss outcomes in a behavioral weight-loss program. Closer scrutiny of patient medications is necessary to help improve outcomes of weight-loss treatments.

In the absence of endogenous IFN-gamma, mice develop unimpaired IL-12 responses to Toxoplasma gondii while failing to control acute infection

The relationship between IFN-gamma and IL-12 in generating innate immune responses and resistance to acute Toxoplasma gondii infection was assessed in T. gondii-exposed IFN-gamma knockout (gko) mice. Gko mice, in contrast to wild-type (wt) animals, rapidly succumbed to infection with either the avirulent ME49 strain or, surprisingly, an attenuated temperature-sensitive mutant strain, ts4. Microscopic examination of peritoneal exudates from infected gko mice demonstrated that mortality is associated with unchecked tachyzoite replication. Nevertheless, both wt and gko animals developed a peritoneal inflammatory response that in gko animals was greater due to a 5- to 10-fold increase in the number of granulocytes recruited to the site of infection. In addition, IL-12 production in gko mice was both unimpaired and functional since a significant, albeit lower than wt, IL-12-dependent NK cell response developed in these animals. Regardless, no evidence for an IFN-gamma-independent protective function for IL-12 or NK cells was apparent since in vivo treatment of gko mice with an IL-12-neutralizing mAb ablated the NK cell response, but did not decrease survival. Together, these data identify distinct functions for IL-12 and IFN-gamma in host resistance to T. gondii: IL-12 precedes and initiates synthesis of IFN-gamma, while the latter lymphokine directly controls parasite growth and diminishes the contribution of IL-4- and IL-5-producing T cell subsets.

In the absence of endogenous IFN-gamma, mice develop unimpaired IL-12 responses to Toxoplasma gondii while failing to control acute infection

The relationship between IFN-gamma and IL-12 in generating innate immune responses and resistance to acute Toxoplasma gondii infection was assessed in T. gondii-exposed IFN-gamma knockout (gko) mice. Gko mice, in contrast to wild-type (wt) animals, rapidly succumbed to infection with either the avirulent ME49 strain or, surprisingly, an attenuated temperature-sensitive mutant strain, ts4. Microscopic examination of peritoneal exudates from infected gko mice demonstrated that mortality is associated with unchecked tachyzoite replication. Nevertheless, both wt and gko animals developed a peritoneal inflammatory response that in gko animals was greater due to a 5- to 10-fold increase in the number of granulocytes recruited to the site of infection. In addition, IL-12 production in gko mice was both unimpaired and functional since a significant, albeit lower than wt, IL-12-dependent NK cell response developed in these animals. Regardless, no evidence for an IFN-gamma-independent protective function for IL-12 or NK cells was apparent since in vivo treatment of gko mice with an IL-12-neutralizing mAb ablated the NK cell response, but did not decrease survival. Together, these data identify distinct functions for IL-12 and IFN-gamma in host resistance to T. gondii: IL-12 precedes and initiates synthesis of IFN-gamma, while the latter lymphokine directly controls parasite growth and diminishes the contribution of IL-4- and IL-5-producing T cell subsets.

Biochemical characterization and protein kinase C dependency of monokine-inducing activities of Toxoplasma gondii

Previous reports have indicated that the early induction of interleukin-12 (IL-12), tumor necrosis factor alpha (TNF-alpha), IL-1beta, and IL-10 is crucial for the establishment and regulation of host cell-mediated immunity to the intracellular protozoan parasite Toxoplasma gondii. In this study, we demonstrate that a soluble tachyzoite extract (soluble tachyzoite antigen) can trigger the expression of these four monokines by murine inflammatory macrophages. Further characterization revealed that the parasite molecules in soluble tachyzoite antigen responsible for monokine induction are heat stable at 100 degree C but differ in sensitivity to protease digestion. Thus, the tachyzoite factors that stimulate TNF-alpha and IL-to expression were found to be more resistant to treatment with proteinase K than those responsible for IL-12 and IL-10 induction. Similarly, while the factors responsible for the induction of all four monokines were found to be sensitive to periodate oxidation, the TNF-alpha-stimulating activity was partially resistant to treatment with the compound at a low concentration (1 mM). A further dichotomy in monokine induction signals was inferred from experiments with isoquinoline sulfonamide protein kinase inhibitors. The latter work suggested that the pathways for TNF-alpha and IL-1beta are protein kinase C dependent, while expression of IL-12 and expression of IL-10 share distinct signal transduction mechanisms involving other kinases. Together, these data argue that monokine induction by T. gondii is mediated by glycoproteins that may belong to distinct groups in terms of their biochemical properties and intracellular signaling pathways.

Transfected leukocyte integrin CD11b/CD18 (Mac-1) mediates phorbol ester-activated, homotypic cell:cell adherence in the K562 cell line

The CD11b/CD18 leukocyte integrin molecule mediates diverse neutrophil adherence-related functions, including cell:cell and cell:extracellular matrix attachments. To study the individual role of this leukocyte integrin in cell adherence in hematopoietic cells, we expressed the CD11b/CD18 complex on the surface of K562 cells, a cell line derived from an individual with chronic myelogenous leukemia in blast crisis. We used an amphotrophic retroviral vector designated LCD18SN, harboring the complete coding sequence for the CD18 subunit, to transfer the CD18 cDNA into K562 cells and select stable cell lines. The CD11b subunit in the expression plasmid pREP4 was transfected into these K562/CD18 cells by electroporation and stable cell clones were selected. These K562 cells possessed RNA and intracellular protein for each subunit, and they expressed the CD11b/CD18 heterodimer on the cell surface. When CD11b/CD18 expressing K562 cells were stimulated with phorbol myristate acetate (50 ng/mL) for 24 to 48 hours, these K562 cells formed dense cell:cell aggregates. This homotypic aggregation required both activation of the CD11b/CD18 complex and the induction of the counter-receptor for CD11b/CD18 on the conjugate cell. This cell line will (1) enable the structure-function relationships between cell activation and homotypic adherence to be assessed, (2) provide the opportunity to identify accessory molecules required for activation of the CD11b/CD18 complex, and (3) facilitate the identification of novel ligands for the CD11b/CD18 complex.