Presurgery health influences outcomes following vertical sleeve gastrectomy in adolescents.

OBJECTIVE: Weight loss following vertical sleeve gastrectomy (VSG) in youth can range from 10% to 50%. We examined whether there are differences in demographic or metabolic parameters before VSG in youth who achieve above-average weight loss (AAWL) versus below-average weight loss (BAWL) at 1 year post VSG and if youth with BAWL still achieve metabolic health improvements at 1 year post VSG. METHODS: Demographic, anthropometric, and clinical lab data were collected before VSG and at 1, 3, 6, and 12 months after VSG. RESULTS: Forty-three youth with a mean age of 16.9 (SD 1.7) years before VSG were studied; 70% were female, 19% non-Hispanic Black, 58% non-Hispanic White, and 23% mixed/other race. Mean baseline BMI was 51.1 (SD 10.5) kg/m2. Average weight loss was 25.8%. The AAWL group lost 18.6 kg/m2 (35.3%) versus the BAWL group, who lost 8.8 kg/m2 (17.5%). BMI, age, race, sex, and socioeconomic status at baseline were similar between AAWL and BAWL groups; however, the BAWL group had a higher frequency of pre-VSG dysglycemia, steatotic liver disease, and dyslipidemia. At 1 year post VSG, fewer youth in the BAWL group achieved ideal health parameters, and they had less resolution of comorbidities. CONCLUSIONS: The presence of comorbidities before VSG is associated with less weight loss and reduced resolution of metabolic conditions at 1 year post VSG.

Decline in case rates of youth onset type 2 diabetes in year three of the COVID-19 pandemic.

OBJECTIVES: To determine changes in case rates of youth onset type 2 diabetes in the three years following the COVID-19 pandemic. METHODS: A single-center, retrospective medical record review was conducted for patients newly diagnosed with T2D between 3/1/18 and 2/28/23 at a pediatric tertiary care center. The number of patients referred to CHLA with a T2D diagnosis date between 3/1/2020 and 2/28/2023 was compared to historical rates between 3/1/2018 and 2/29/2020. χ2 or Fisher's exact test was used to compare categorical variables between each year and 2019. RESULTS: Compared to prepandemic baseline (3/1/19-2/29/20, 11.8±3.7 cases/month), there was a significant increase in new T2D monthly case rates in pandemic year 1 (3/1/20-2/28/21, 20.1±6.0 cases/month, 171 %, p=0.005) and pandemic year 2 (3/1/21-2/28/22, 25.9±8.9 cases/month, 221 %, p=0.002). Case rates declined in pandemic year 3 to 14.5±4.1 cases/month (3/1/22-2/28/23, p=0.43). Compared to prepandemic year 1, the frequency of DKA at diagnosis was higher in pandemic year 1 (13.3 vs. 5.0 %, p=0.009). The DKA rate in pandemic years 2 (6.8 %) and 3 (3.4 %) were comparable to prepandemic year 1 (p=0.53 and 0.58, respectively). CONCLUSIONS: Youth onset type 2 diabetes cases and DKA rates in year 3 of the pandemic have returned to prepandemic level.

Addressing Obesity Care in Children With Chronic Health Conditions.

Obesity care in pediatric populations has entered a new era. The recent discovery of molecular genetic causes for abnormal weight gain, development of antiobesity medications, mounting data on the robust efficacy and favorable safety profile of bariatric surgery, and implementation of clinical guidelines fill a long-standing gap in the care of children affected by obesity, one of the most challenging pediatric diseases. However, these novel clinical approaches do not appear to have reached every individual who is in need, particularly children with chronic health conditions (CHCs), raising important questions for equitable medical care. In this study, we discuss specific etiologies, challenges, and ideas for future directions in diagnosing and managing obesity in children with CHCs. Although this article is not intended to be utilized as clinical guidelines, it underscores potential practical solutions for the current issues.

A Narrative Review: Phentermine and Topiramate for the Treatment of Pediatric Obesity.

The prevalence of pediatric obesity has increased exponentially over the past four decades. The American Academy of Pediatrics recently released updated clinical practice guidelines highlighting the importance of identifying pediatric obesity as a chronic disease. The guidelines support consideration of concurrent treatment with intensive lifestyle interventions, obesity pharmacotherapy, and bariatric surgery. The dramatic rise in pediatric obesity has spurred interest in utilizing obesity pharmacotherapy to support sustained weight reduction in pediatric cohorts, in the hopes of preventing the emergence of later-appearing, significant co-morbidities. Despite the enormous demand, the obstacles posed by performance of needed clinical trials in the pediatric population markedly limits available pharmacotherapy for the treatment of obesity in pediatrics. Currently, there are five medications approved by the Food and Drug Administration for use in youth with obesity. In 2022, the phentermine/topiramate (PHEN/TPM), once-daily, controlled-release, combination product received FDA approval, for the indication of chronic weight management, in youth with obesity, ages 12 years and older. The objectives of this narrative review are to: (1) Review the mechanism of action of phentermine and topiramate, (2) Summarize the safety and efficacy data of topiramate and phentermine use as both monotherapies and in combination, and (3) Discuss clinical practice guidelines and clinical implications, for the use of these agents in youths with obesity.

Impact of 8-hour time-limited eating on sleep in adolescents with obesity.

STUDY OBJECTIVES: The relationship between time-limited eating (TLE) and sleep quality is a topic of growing interest in the field of chronobiology. Data in adult cohorts shows that TLE may improve sleep quality, but this has not been evaluated in adolescents. The aim of this secondary analysis was to (1) examine the impact of 8-hour TLE on sleep parameters in youth with obesity and (2) explore if there was any association between sleep patterns and glycemic profiles. METHODS: Adolescents with obesity were randomized into one of three groups: 8-hour TLE (participants self-selected their eating window) + real-time continuous glucose monitor, 8-hour TLE + blinded continuous glucose monitor, or a prolonged eating window. In the primary analysis, it was found that participants in the real-time continuous glucose monitor group + 8-hour TLE group did not access their continuous glucose monitor data and thus for this analysis the two TLE groups were combined and only completers who had available Pittsburgh Sleep Quality Index (PSQI) data at all three time points were included. Participants completed the PSQI at baseline, week 4, and week 12. Mixed-effects generalized linear regression models were utilized to examine the change in PSQI score and assess association between glycemic variability and PSQI total score overtime by intervention arm. RESULTS: The median PSQI total score for the TLE groups (n = 27) was 6 at week 0 (interquartile range = 5 to 10) and 5 at week 12 (interquartile range = 2 to 7). There was no significant difference in the change in total PSQI score or sleep latency between TLE and control over the study period (P > .05). There was no association between PSQI score and change in weight or glycemic profile between groups (all P values > 0.05). CONCLUSIONS: These results suggest that in adolescents with obesity, an 8-hour TLE approach did not negatively impact sleep quality or efficiency when compared to a prolonged eating window. The potential effects of TLE on sleep should be further investigated in larger randomized trials. CITATION: Jayakumr A, Gillett ES, Wee CP, Kim A, Vidmar AP. Impact of 8-hour time-limited eating on sleep in adolescents with obesity. J Clin Sleep Med. 2023;19(11):1941-1949.

Two Case Reports of Newly Diagnosed Crohn's Disease after COVID-19 in Pediatric Patients.

Since the coronavirus disease 2019 (COVID-19) outbreak caused by the severe acute respiratory syndrome-coronavirus-2 virus (SARS-CoV-2), various complications have been reported. Although most COVID-19 cases exhibited flu-like symptoms, COVID-19 may dysregulate the immune response and promote overwhelming levels of inflammation in some patients. Inflammatory bowel disease (IBD) is caused by dysregulated or inappropriate immune responses to environmental factors in a genetically susceptible host, and a SARS-CoV-2 infection may act as a possible cause of IBD. This paper describes two pediatric patients who developed Crohn's disease following a SARS-CoV-2 infection. They were previously healthy before the SARS-CoV-2 infection. On the other hand, they started to develop fever and gastrointestinal symptoms several weeks after recovery from the infection. They were diagnosed with Crohn's disease by imaging and endoscopic studies, and their symptoms improved after treatment with steroids and azathioprine. This paper suggests that a SARS-CoV-2 infection may trigger IBD in predisposed patients.

Increased anxiety symptoms in pediatric type 1 diabetes during the acute phase of COVID-19 lockdown.

OBJECTIVES: The prevalence of mental health issues has increased at an alarming rate during the COVID-19 pandemic. Furthermore, an exacerbated psychosocial burden in populations with chronic disease is observed. This cross-sectional study evaluated the psychosocial factors of pediatric type 1 diabetes (T1D) during the COVID-19 pandemic. METHODS: During April 2020, 15 min phone interviews were performed for pediatric T1D group (n=100) and healthy comparison group (n=93) to assess psychosocial functioning during the acute lockdown phase of the pandemic. The patient health questionnaire-4 was utilized to assess anxiety and depressive symptoms. An additional questionnaire to assess specific concerns related to T1D and COVID-19 was administered to the T1D group to explore potential causes for increased psychosocial burden. RESULTS: T1D was associated with a five-times higher risk of anxiety symptoms. Increased anxiety symptoms in T1D group appear to be, at least in part, due to fear of higher risk of severe COVID-19 infection and uncertainty regarding access to diabetes supplies. CONCLUSIONS: This study provides a snapshot of mental well-being in a diverse population of patients with T1D in the acute phase of a crisis and underscores the need for timely, accurate medical information and distribution of medical resources for pediatric T1D population.

Factors Associated With Achieving Target A1C in Children and Adolescents With Type 1 Diabetes: Findings From the T1D Exchange Quality Improvement Collaborative.

The optimal care of type 1 diabetes involves consistent glycemic management to avoid short- and long-term complications. However, despite advancements in diabetes technology and standards, achieving adequate glycemic levels in children and adolescents remains a challenge. This study aimed to identify factors associated with achieving the recommended A1C target of <7% from the United States-based multicenter T1D Exchange Quality Improvement Collaborative cohort, including 25,383 children and adolescents living with type 1 diabetes.

Hepatic Ago2 Regulates PPARα for Oxidative Metabolism Linked to Glycemic Control in Obesity and Post Bariatric Surgery.

Argonaute 2 (Ago2) is the main component of the RNA-induced silencing complex. We recently showed that liver-specific Ago2-deficiency in mice (L-Ago2 knockout [KO] mice) enhances mitochondrial oxidation and alleviates obesity-associated pathophysiology. However, the precise mechanisms behind the role of hepatic Ago2 in regulating the mitochondrial oxidation associated with glucose metabolism are still unclear. Here, we show that hepatic Ago2 regulates the function of peroxisome proliferator-activated receptor α (PPARα) for oxidative metabolism. In both genetically and diet-induced severe obese conditions, L-Ago2 KO mice developed obesity and hepatic steatosis but exhibited improved glucose metabolism accompanied by lowered expression levels of pathologic microRNAs (miRNAs), including miR-802, miR-103/107, and miR-152, and enhanced expression of PPARα and its target genes regulating oxidative metabolism in the liver. We then investigated the role of hepatic Ago2 in the outcomes of vertical sleeve gastrectomy (VSG) in which PPARα plays a crucial role in a drastic transcription reprogram associated with improved glycemia post VSG. Whereas VSG reduced body weight and improved fatty liver in wild-type mice, these effects were not observed in hepatic Ago2-deficient mice. Conversely, glucose metabolism was improved in a hepatic Ago2-dependent manner post VSG. Treating Ago2-deficient primary hepatocytes with WY-14643, a PPARα agonist, showed that Ago2-deficiency enhances sensitivity to WY-14643 and increases expression of PPARα target genes and mitochondrial oxidation. Our findings suggest that hepatic Ago2 function is intrinsically associated with PPARα that links Ago2-mediated RNA silencing with mitochondrial functions for oxidation and obesity-associated pathophysiology.

Treatment-Induced Neuropathy of Diabetes in Youth: Case Series of a Heterogeneous and Challenging Complication.

Treatment-induced neuropathy of diabetes (TIND) is a small fiber neuropathy precipitated by rapid correction of hyperglycemia. Literature on TIND in pediatric diabetes is scarce. We present 7 cases of TIND in children and young adults, increasing awareness of this condition in pediatric diabetes and broadening the scope of published knowledge.

XY Gonadal Dysgenesis in a Phenotypic Female Identified by Direct-to-Consumer Genetic Testing.

We report a 16-year-old phenotypic female with 46,XY complete gonadal dysgenesis and metastatic dysgerminoma, unexpectedly discovered through direct-to-consumer (DTC) commercial genetic testing. This case underscores the importance of timely interdisciplinary care, including psychosocial intervention and consideration of gonadectomy, to optimize outcomes for individuals with differences of sex development. Her unique presentation highlights the implications of DTC genetic testing in a new diagnostic era and informs general pediatricians as well as specialists of nongenetic services about the value, capabilities, and limitations of DTC testing.

A Nomogram for Predicting Non-Alcoholic Fatty Liver Disease in Obese Children.

PURPOSE: Non-alcoholic fatty liver disease (NAFLD) ranges in severity from simple steatosis to steatohepatitis. Early detection of NAFLD is important for preventing the disease from progressing to become an irreversible end-stage liver disease. We developed a nomogram that allows for non-invasive screening for NAFLD in obese children. METHODS: Anthropometric and laboratory data of 180 patients from our pediatric obesity clinic were collected. Diagnoses of NAFLD were based on abdominal ultrasonographic findings. The nomogram was constructed using predictors from a multivariate analysis of NAFLD risk factors. RESULTS: The subjects were divided into non-NAFLD (n=67) and NAFLD groups (n=113). Factors, including sex, body mass index, abdominal circumference, blood pressure, insulin resistance, and levels of aspartate aminotransferase, alanine aminotransferase (ALT), γ-glutamyl transpeptidase (γGT), uric acid, triglycerides, and insulin, were significantly different between the two groups (all p<0.05) as determined using homeostatis model assessment of insulin resistance (HOMA-IR). In our multivariate logistic regression analysis, elevated serum ALT, γGT, and triglyceride levels were significantly related to NAFLD development. The nomogram was established using γGT, uric acid, triglycerides, HOMA-IR, and ALT as predictors of NAFLD probability. CONCLUSION: The newly developed nomogram may help predict NAFLD risk in obese children. The nomogram may also allow for early NAFLD diagnosis without the need for invasive liver biopsy or expensive liver imaging, and may also allow clinicians to intervene early to prevent the progression of NAFLD to become a more advanced liver disease.

Extracellular Vesicles: A Potential Novel Regulator of Obesity and Its Associated Complications.

Childhood obesity continues to be a major public health concern. Obesity causes various metabolic complications, including insulin resistance, type 2 diabetes mellitus (T2DM), non-alcoholic fatty liver disease (NAFLD), dyslipidemia, and cardiovascular disease. However, currently, we have a limited understanding of the pathophysiology in the development of these processes. Extracellular vesicles (EVs) are nano-sized vesicles secreted by different cell types that travel to various organ systems carrying molecular and genetic information. These vesicles have been proposed as a novel intercellular communication mode in systemic metabolic regulation and in several pathophysiologic processes. In particular, recent studies indicate that EVs play a critical role in the pathogenesis of obesity and its metabolic complications. In this study, we reviewed the current literature that supports the role of EVs in the regulation of metabolic homeostasis and pathogenesis of obesity and its associated metabolic complications, with a short discussion about future directions in the EV research field.

Adrenal Insufficiency, Sex Reversal, and Angelman Syndrome due to Uniparental Disomy Unmasking a Mutation in CYP11A1.

BACKGROUND/AIMS: Cholesterol side-chain cleavage enzyme (P450scc) deficiency is a rare genetic disorder causing primary adrenal insufficiency with or without a 46,XY disorder of sexual development (DSD). Herein, we report a case of the combination of primary adrenal insufficiency, a DSD (testes with female external genitalia in a setting of a 47,XXY karyotype), and Angelman syndrome. METHODS: Comprehensive genetic analyses were performed, including a single nucleotide polymorphism microarray and whole-exome sequencing. In vitro studies were performed to evaluate the pathogenicity of the novel mutation that was identified by whole-exome sequencing. RESULTS: The patient was found to have segmental uniparental disomy (UPD) of chromosome 15 explaining her diagnosis of Angelman syndrome. Whole-exome sequencing further revealed a novel homozygous intronic variant in CYP11A1, the gene encoding P450scc, found within the region of UPD. In vitro studies confirmed that this variant led to decreased efficiency of CYP11A1 splicing. CONCLUSION: We report the first case of the combination of 2 rare genetic disorders, Angelman syndrome, and P450scc deficiency. After 20 years of diagnostic efforts, significant advances in genetic diagnostic technology allowed us to determine that these 2 disorders originate from a unified genetic etiology, segmental UPD unmasking a novel recessive mutation in CYP11A1.

Different Age Distribution between Campylobacteriosis and Nontyphoidal Salmonellosis in Hospitalized Korean Children with Acute Inflammatory Diarrhea.

We investigated recent epidemiologic trends regarding campylobacteriosis vs. nontyphoidal salmonellosis (NTS), a previously known leading cause of bacterial enterocolitis in Korean children. Among 363 hospitalized children with acute inflammatory diarrhea, Campylobacter (18.7%) was the most frequently detected pathogen using multiplex polymerase chain reaction tests followed by Salmonella (15.4%). Children with campylobacteriosis were older than children with NTS (112.6 months [interquartile range (IQR) 66.0-160.1] vs. 53 months [IQR 31.0-124.0], P < 0.001) and had higher prevalences of abdominal cramping and stool hemoglobin. Campylobacteriosis may be suspected as a primary cause of acute inflammatory diarrhea in hospitalized school-aged Korean children and adolescents.

Epidemiology and Factors Related to Clinical Severity of Acute Gastroenteritis in Hospitalized Children after the Introduction of Rotavirus Vaccination.

We aimed to investigate epidemiology and host- and pathogen-related factors associated with clinical severity of acute gastroenteritis (AGE) in children after rotavirus vaccination introduction. Factors assessed included age, co-infection with more than 2 viruses, and virus-toxigenic Clostridium difficile co-detection. Fecal samples and clinical information, including modified Vesikari scores, were collected from hospitalized children with AGE. The presence of enteric viruses and bacteria, including toxigenic C. difficile, was detected by polymerase chain reaction (PCR). Among the 415 children included, virus was detected in stool of 282 (68.0%) children. Co-infection with more than 2 viruses and toxigenic C. difficile were found in 24 (8.5%) and 26 (9.2%) children with viral AGE, respectively. Norovirus (n = 130) infection, including norovirus-associated co-infection, was the most frequent infection, especially in children aged < 24 months (P < 0.001). In the severity-related analysis, age < 24 months was associated with greater diarrheal severity (P < 0.001) and modified Vesikari score (P = 0.001), after adjustment for other severity-related factors including rotavirus status. Although the age at infection with rotavirus was higher than that for other viruses (P = 0.001), rotavirus detection was the most significant risk factor for all severity parameters, including modified Vesikari score (P < 0.001). Viral co-infection and toxigenic C. difficile co-detection were not associated with any severity-related parameter. This information will be helpful in the management of childhood AGE in this era of rotavirus vaccination and availability of molecular diagnostic tests, which often lead to the simultaneous detection of multiple pathogens.

Diencephalic syndrome: a frequently neglected cause of failure to thrive in infants.

PURPOSE: Diencephalic syndrome is an uncommon cause of failure to thrive in early childhood that is associated with central nervous system neoplasms in the hypothalamic-optic chiasmatic region. It is characterized by complex signs and symptoms related to hypothalamic dysfunction; such nonspecific clinical features may delay diagnosis of the brain tumor. In this study, we analyzed a series of cases in order to define characteristic features of diencephalic syndrome. METHODS: We performed a retrospective study of 8 patients with diencephalic syndrome (age, 5-38 months). All cases had presented to Seoul National University Children's Hospital between 1995 and 2013, with the chief complaint of poor weight gain. RESULTS: Diencephalic syndrome with central nervous system (CNS) neoplasm was identified in 8 patients. The mean age at which symptoms were noted was 18±10.5 months, and diagnosis after symptom onset was made at the mean age of 11±9.7 months. The mean z score was -3.15±1.14 for weight, -0.12±1.05 for height, 1.01±1.58 for head circumference, and -1.76±1.97 for weight-for-height. Clinical features included failure to thrive (n=8), hydrocephalus (n=5), recurrent vomiting (n=5), strabismus (n=2), developmental delay (n=2), hyperactivity (n=1), nystagmus (n=1), and diarrhea (n=1). On follow-up evaluation, 3 patients showed improvement and remained in stable remission, 2 patients were still receiving chemotherapy, and 3 patients were discharged for palliative care. CONCLUSION: Diencephalic syndrome is a rare cause of failure to thrive, and diagnosis is frequently delayed. Thus, it is important to consider the possibility of a CNS neoplasm as a cause of failure to thrive and to ensure early diagnosis.

Clinical Manifestations and Treatment Outcomes of Eosinophilic Gastroenteritis in Children.

PURPOSE: The aim of the present study was to investigate the clinical features and outcome of eosinophilic gastroenteritis (EGE) in children. METHODS: Our study enrolled 24 children who were diagnosed with EGE from 1993 to 2014 at the Department of Pediatrics, Seoul National University Children's Hospital. The patients' clinical manifestations, treatments, and outcomes were reviewed from the medical records. RESULTS: The mean age at diagnosis was 5.3 years. Most patients had gastrointestinal symptoms including diarrhea (54.2%) and abdominal pain (45.8%). Peripheral eosinophilia was present in 91.7% of the patients. Thirteen patients (54.2%) showed anemia, and 15 patients (62.5%) had hypoalbuminemia. EGE was classified as mucosal, subserosal, or muscular in 75.0%, 20.8%, and 4.2% of cases, respectively. Three patients showed gastroduodenal ulcers upon endoscopic analysis. A history of allergy was reported in 13 patients, including atopic dermatitis, allergic rhinitis, and asthma. Five patients (20.8%) improved with food restrictions. Among the 19 patients treated with steroids, 11 (57.9%) discontinued steroid treatment without subsequent relapse, 4 (21.1%) relapsed after ceasing steroid treatment, and 4 (21.1%) showed no response to steroids. Two patients who were resistant to steroids underwent therapeutic surgery. The presence of gastroduodenal ulcers was significantly associated with relapse and steroid resistance. CONCLUSION: A high suspicion of EGE is warranted when children have nonspecific gastrointestinal symptoms and peripheral eosinophilia. Most patients improved with food restrictions or steroid treatment, although one-third of patients showed a relapse or steroid resistance.

Epstein-barr virus infection with acute acalculous cholecystitis.

Acute acalculous cholecystitis (AAC) is an inflammation of the gallbladder in the absence of demonstrated stones. AAC is frequently associated with severe systemic inflammation. However, the exact etiology and pathogenesis of AAC still remain unclear. Acute infection with Epstein Barr virus (EBV) in childhood is usually aymptomatic, whereas it often presents as typical infectious mononucleosis symptoms such as fever, cervical lymphadenopathy, and hepatosplenomegaly. AAC may occur during the course of acute EBV infection, which is rarely encountered in the pediatric population. AAC complicating the course of a primary EBV infection is usually associated with a favorable outcome. Most of the patients recover without any surgical treatment. Therefore, the detection of EBV in AAC would be important for prediction of better prognosis. We describe the case of a 10-year-old child who presented with AAC during the course of primary EBV infection, the first in Korea, and review the relevant literature.

Vesicular sorting controls the polarity of expanding membranes in the C. elegans intestine.

Biological tubes consist of polarized epithelial cells with apical membranes building the central lumen and basolateral membranes contacting adjacent cells or the extracellular matrix. Cellular polarity requires distinct inputs from outside the cell, e.g., the matrix, inside the cell, e.g., vesicular trafficking and the plasma membrane and its junctions.(1) Many highly conserved polarity cues have been identified, but their integration during the complex process of polarized tissue and organ morphogenesis is not well understood. It is assumed that plasma-membrane-associated polarity determinants, such as the partitioning-defective (PAR) complex, define plasma membrane domain identities, whereas vesicular trafficking delivers membrane components to these domains, but lacks the ability to define them. In vitro studies on lumenal membrane biogenesis in mammalian cell lines now indicate that trafficking could contribute to defining membrane domains by targeting the polarity determinants, e.g., the PARs, themselves.(2) This possibility suggests a mechanism for PARs' asymmetric distribution on membranes and places vesicle-associated polarity cues upstream of membrane-associated polarity determinants. In such an upstream position, trafficking might even direct multiple membrane components, not only polarity determinants, an original concept of polarized plasma membrane biogenesis(3) (,) (4)that was largely abandoned due to the failure to identify a molecularly defined intrinsic vesicular sorting mechanism. Our two recent studies on C. elegans intestinal tubulogenesis reveal that glycosphingolipids (GSLs) and the well-recognized vesicle components clathrin and its AP-1 adaptor are required for targeting multiple apical molecules, including polarity regulators, to the expanding apical/lumenal membrane.(5) (,) (6) These findings support GSLs' long-proposed role in in vivo polarized epithelial membrane biogenesis and development and identify a novel function in apical polarity for classical post-Golgi vesicle components. They are also compatible with a vesicle-intrinsic sorting mechanism during membrane biogenesis and suggest a model for how vesicles could acquire apical directionality during the assembly of the functionally critical polarized lumenal surfaces of epithelial tubes.