Inhibition of polyamine biosynthesis preserves β cell function in type 1 diabetes

In preclinical models, α-difluoromethylornithine (DFMO), an ornithine decarboxylase (ODC) inhibitor, delays the onset of type 1 diabetes (T1D) by reducing β cell stress. However, the mechanism of DFMO action and its human tolerability remain unclear. In this study, we show that mice with β cell ODC deletion are protected against toxin-induced diabetes, suggesting a cell-autonomous role of ODC during β cell stress. In a randomized controlled trial (ClinicalTrials.gov: NCT02384889) involving 41 recent-onset T1D subjects (3:1 drug:placebo) over a 3-month treatment period with a 3-month follow-up, DFMO (125-1,000 mg/m2) is shown to meet its primary outcome of safety and tolerability. DFMO dose-dependently reduces urinary putrescine levels and, at higher doses, preserves C-peptide area under the curve without apparent immunomodulation. Transcriptomics and proteomics of DFMO-treated human islets exposed to cytokine stress reveal alterations in mRNA translation, nascent protein transport, and protein secretion. These findings suggest that DFMO may preserve β cell function in T1D through islet cell-autonomous effects.

Genetic Correlates as a Predictor of Bariatric Surgery Outcomes after 1 Year

This study analyzed genetic risk assessments in patients undergoing bariatric surgery to serve as a predictive factor for weight loss parameters 1 year after the operation. Thirty (30) patients were assessed for Genetic Addiction Risk Severity (GARS), which analyzes neurogenetic polymorphisms involved in addiction and reward deficiency. Genetic and psychosocial data collected before the operation were correlated with weight loss data, including changes in weight, body mass index (BMI), and percent of expected weight loss (%EWL). Results examined correlations between individual gene risk alleles, 1-year body weight data, and psychosocial trait scores. Spearman's correlations revealed that the OPRM1 (rs1799971) gene polymorphism had significant negative correlation with 1-year weight (rs = -0.4477, p < 0.01) and BMI (rs = -0.4477, p < 0.05). In addition, the DRD2 risk allele (rs1800497) was correlated negatively with BMI at 1 year (rs = -0.4927, p < 0.05), indicating that one risk allele copy was associated with lower BMI. However, this allele was positively correlated with both ∆Weight (rs = 0.4077, p < 0.05) and %EWL (rs = 0.5521, p < 0.05) at 1 year post-surgery. Moreover, the overall GARS score was correlated with %EWL (rs = 0.4236, p < 0.05), ∆Weight (rs = 0.3971, p < 0.05) and ∆BMI (rs = 0.3778, p < 0.05). Lastly, Food Cravings Questionnaire (FCQ) scores were negatively correlated with %EWL (rs = -0.4320, p < 0.05) and ∆Weight at 1 year post-surgery (rs = -0.4294, p < 0.05). This suggests that individuals with a higher genetic addiction risk are more responsive to weight loss treatment, especially in the case of the DRD2 polymorphism. These results should translate clinically to improve positivity and attitude related to weight management by those individuals born with the risk alleles (rs1800497; rs1799971).

The First Exploratory Personalized Medicine Approach to Improve Bariatric Surgery Outcomes Utilizing Psychosocial and Genetic Risk Assessments: Encouraging Clinical Research

It is predicted that by 2030, globally, an estimated 2.16 billion adults will be overweight, and 1.12 billion will be obese. This study examined genetic data regarding Reward Deficiency Syndrome (RDS) to evaluate their usefulness in counselling patients undergoing bariatric surgery and gathered preliminary data on the potential use in predicting short term (6-month) weight loss outcomes. Methods: Patients undergoing bariatric surgery (n = 34) were examined for Genetic Addiction Risk Severity (GARS) [measures the presence of risk alleles associated with RDS]; as well as their psychosocial traits (questionnaires). BMI changes and sociodemographic data were abstracted from Electronic Health Records. Results: Subjects showed ∆BMI (M = 10.0 ± 1.05 kg/m2) and a mean % excess weight loss (56 ± 13.8%). In addition, 76% of subjects had GARS scores above seven. The homozygote risk alleles for MAO (rs768062321) and DRD1 (rs4532) showed a 38% and 47% prevalence among the subjects. Of the 11 risk alleles identified by GARS, the DRD4 risk allele (rs1800955), was significantly correlated with change in weight and BMI six months post-surgery. We identified correlations with individual risk alleles and psychosocial trait scores. The COMT risk allele (rs4680) showed a negative correlation with EEI scores (r = -0.4983, p < 0.05) and PSQI scores (r = -0.5482, p < 0.05). The GABRB3 risk allele (rs764926719) correlated positively with EEI (r = 0.6161, p < 0.01) and FCQ scores (r = 0.6373, p < 0.01). The OPRM1 risk allele showed a positive correlation with the DERS score (r = 0.5228, p < 0.05). We also identified correlations between DERS and BMI change (r = 0.61; p < 0.01). Conclusions: These data support the potential benefit of a personalized medicinal approach inclusive of genetic testing and psychosocial trait questionnaires when counselling patients with obesity considering bariatric surgery. Future research will explore epigenetic factors that contribute to outcomes of bariatric surgery.

Type 1 diabetes

Type 1 diabetes is a chronic disease caused by autoimmune destruction of pancreatic β cells. Individuals with type 1 diabetes are reliant on insulin for survival. Despite enhanced knowledge related to the pathophysiology of the disease, including interactions between genetic, immune, and environmental contributions, and major strides in treatment and management, disease burden remains high. Studies aimed at blocking the immune attack on β cells in people at risk or individuals with very early onset type 1 diabetes show promise in preserving endogenous insulin production. This Seminar will review the field of type 1 diabetes, highlighting recent progress within the past 5 years, challenges to clinical care, and future directions in research, including strategies to prevent, manage, and cure the disease.

Role of Dual-Contingency Management in Family-Based Obesity Therapy and the Effects of Weight Loss on Liver Transient Elastography Parameters in Youth: A Pilot Study

The pilot study evaluated contingency management (CM) for family-based obesity therapy (FBT). The secondary outcome assessed the association of the hepatic transient electrography (TE) parameters, including the controlled attenuation parameter (CAP) and liver stiffness (LSM), and changes in liver function blood tests and BMI changes in youth involved in intensive FBT. It included youth-parent dyads from an urban pediatric center randomized to weekly behavioral therapy (BT, n= 4) who received fixed financial compensation for attendance, or BT+CM (n= 5) who received an escalating monetary reward for weight loss. At week 30, all youth and parents had weight-loss trends without significant differences between groups. While the TE measures and blood tests were normal in the youth at baseline and week 30, the CAP changes correlated with BMI changes (R²= 0.86, P< 0.001) and LSM changes with alanine aminotransferase changes (R²= 0.79, P=0.005). In conclusion, BT+CM did not significantly add to the BMI improvement seen with BT alone in youth and their parents. However, in youth with obesity and normal liver blood tests, TE may be useful for monitoring changes in fatty liver disease.

Congenital Hypothyroidism: Screening and Management

ABSTRACT

Untreated congenital hypothyroidism (CH) leads to intellectual disabilities. Prompt diagnosis by newborn screening (NBS) leading to early and adequate treatment results in grossly normal neurocognitive outcomes in adulthood. However, NBS for hypothyroidism is not yet established in all countries globally. Seventy percent of neonates worldwide do not undergo NBS.The initial treatment of CH is levothyroxine, 10 to 15 mcg/kg daily. The goals of treatment are to maintain consistent euthyroidism with normal thyroid-stimulating hormone and free thyroxine in the upper half of the age-specific reference range during the first 3 years of life. Controversy remains regarding detection of thyroid dysfunction and optimal management of special populations, including preterm or low-birth weight infants and infants with transient or mild CH, trisomy 21, or central hypothyroidism.Newborn screening alone is not sufficient to prevent adverse outcomes from CH in a pediatric population. In addition to NBS, the management of CH requires timely confirmation of the diagnosis, accurate interpretation of thyroid function testing, effective treatment, and consistent follow-up. Physicians need to consider hypothyroidism in the face of clinical symptoms, even if NBS thyroid test results are normal. When clinical symptoms and signs of hypothyroidism are present (such as large posterior fontanelle, large tongue, umbilical hernia, prolonged jaundice, constipation, lethargy, and/or hypothermia), measurement of serum thyroid-stimulating hormone and free thyroxine is indicated, regardless of NBS results.

Congenital Hypothyroidism: Screening and Management

Untreated congenital hypothyroidism (CH) leads to intellectual disabilities. Newborn screening (NBS) for CH should be performed in all infants. Prompt diagnosis by NBS leading to early and adequate treatment results in grossly normal neurocognitive outcomes in adulthood. However, NBS for hypothyroidism is not yet practiced in all countries globally. Seventy percent of neonates worldwide do not undergo NBS. The recommended initial treatment of CH is levothyroxine, 10 to 15 mcg/kg daily. The goals of treatment are to maintain consistent euthyroidism with normal thyroid-stimulating hormone and with free thyroxine in the upper half of the age-specific reference range during the first 3 years of life. Controversy remains regarding the detection of thyroid dysfunction and optimal management of special populations, including preterm or low-birth-weight infants and infants with transient or mild CH, trisomy 21, or central hypothyroidism. NBS alone is not sufficient to prevent adverse outcomes from CH in a pediatric population. In addition to NBS, the management of CH requires timely confirmation of the diagnosis, accurate interpretation of thyroid function testing, effective treatment, and consistent follow-up. Physicians need to consider hypothyroidism in the face of clinical symptoms, even if NBS thyroid test results are normal. When clinical symptoms and signs of hypothyroidism are present (such as large posterior fontanelle, large tongue, umbilical hernia, prolonged jaundice, constipation, lethargy, and/or hypothermia), measurement of serum thyroid-stimulating hormone and free thyroxine is indicated, regardless of NBS results.

Once-Weekly Semaglutide in Adolescents with Obesity

BACKGROUND

A once-weekly, 2.4-mg dose of subcutaneous semaglutide, a glucagon-like peptide-1 receptor agonist, is used to treat obesity in adults, but assessment of the drug in adolescents has been lacking.

METHODS

In this double-blind, parallel-group, randomized, placebo-controlled trial, we enrolled adolescents (12 to <18 years of age) with obesity (a body-mass index [BMI] in the 95th percentile or higher) or with overweight (a BMI in the 85th percentile or higher) and at least one weight-related coexisting condition. Participants were randomly assigned in a 2:1 ratio to receive once-weekly subcutaneous semaglutide (at a dose of 2.4 mg) or placebo for 68 weeks, plus lifestyle intervention. The primary end point was the percentage change in BMI from baseline to week 68; the secondary confirmatory end point was weight loss of at least 5% at week 68.

RESULTS

A total of 201 participants underwent randomization, and 180 (90%) completed treatment. All but one of the participants had obesity. The mean change in BMI from baseline to week 68 was -16.1% with semaglutide and 0.6% with placebo (estimated difference, -16.7 percentage points; 95% confidence interval [CI], -20.3 to -13.2; P<0.001). At week 68, a total of 95 of 131 participants (73%) in the semaglutide group had weight loss of 5% or more, as compared with 11 of 62 participants (18%) in the placebo group (estimated odds ratio, 14.0; 95% CI, 6.3 to 31.0; P<0.001). Reductions in body weight and improvement with respect to cardiometabolic risk factors (waist circumference and levels of glycated hemoglobin, lipids [except high-density lipoprotein cholesterol], and alanine aminotransferase) were greater with semaglutide than with placebo. The incidence of gastrointestinal adverse events was greater with semaglutide than with placebo (62% vs. 42%). Five participants (4%) in the semaglutide group and no participants in the placebo group had cholelithiasis. Serious adverse events were reported in 15 of 133 participants (11%) in the semaglutide group and in 6 of 67 participants (9%) in the placebo group.

CONCLUSIONS

Among adolescents with obesity, once-weekly treatment with a 2.4-mg dose of semaglutide plus lifestyle intervention resulted in a greater reduction in BMI than lifestyle intervention alone. (Funded by Novo Nordisk; STEP TEENS ClinicalTrials.gov number, NCT04102189.).

Preventing type 1 diabetes development and preserving beta-cell function

PURPOSE OF REVIEW

Type 1 diabetes (T1D) is the most common chronic disease of childhood presenting a significant burden, both in terms of day-to-day medical management and lifelong care. Studies aligned with diverse strategies to prevent or modify the course of T1D are reviewed.

RECENT FINDINGS

The diagnosis of T1D precedes the classic clinical presentation when insulin dependence develops. With an increased understanding of the pathophysiology of the autoimmune process leading to T1D, treatment strategies to prevent the development of autoimmunity and/or modify the immune response have been trialed in persons at risk for developing the disease. Interventions prior to insulin dependence or very early after clinical diagnosis show some promise both in preventing disease onset and prolonging beta-cell insulin production.

SUMMARY

Significant progress has been made in the treatment of T1D. However, suboptimal glycemic control remains a challenge impacting overall health and quality of life for patients with this chronic disease. Although physicians and basic sciences investigators continue to pursue the prevention of the autoimmune process, the advent of disease-modifying agents is a promising strategy. Further studies are needed to ensure that insulin preservation can be achieved longer term.

Youth with type 2 diabetes have a high rate of treatment failure after discontinuation of insulin: A Pediatric Diabetes Consortium study

Insulin is commonly used to reverse gluco-toxicity in youth with newly diagnosed type 2 diabetes (T2D), but many are subsequently weaned off insulin. We analyzed Pediatric Diabetes Consortium (PDC) data to determine how long glycemic control is maintained after termination of initial insulin treatment. Youth with T2D who had previously been on insulin but were on either an intensive lifestyle intervention alone or metformin alone upon enrollment in the PDC T2D Registry were studied (N = 183). The primary outcome was time to treatment failure, defined by need to restart insulin or metformin or another diabetes medication. Data were analyzed using logistic regression to assess risk factors for treatment failure. Of the 183 participants studied (mean age 15 years, diabetes duration 1.7 years), 54% experienced treatment failure (median follow-up time 1.7 years). In the subgroup on metformin monotherapy (N = 140), 45% subsequently required restart of insulin. Moreover, of participants in the subgroup treated with an intensive lifestyle intervention alone (N = 43), 81% restarted insulin or were treated with metformin or other diabetes medication. In both groups, median time to treatment failure was 1.2 years. Higher HbA1c at enrollment was significantly associated with treatment failure (p < 0.001). Youth with T2D who are initially treated with insulin have a high rate of treatment failure when switched to intensive lifestyle alone or metformin alone. Our data highlight the severe and progressive nature of youth onset T2D, hence patients should be monitored closely for deteriorating glycemic control after being weaned off insulin.

Multi-step ahead predictive model for blood glucose concentrations of type-1 diabetic patients

Continuous monitoring of blood glucose (BG) levels is a key aspect of diabetes management. Patients with Type-1 diabetes (T1D) require an effective tool to monitor these levels in order to make appropriate decisions regarding insulin administration and food intake to keep BG levels in target range. Effectively and accurately predicting future BG levels at multi-time steps ahead benefits a patient with diabetes by helping them decrease the risks of extremes in BG including hypo- and hyperglycemia. In this study, we present a novel multi-component deep learning model BG-Predict that predicts the BG levels in a multi-step look ahead fashion. The model is evaluated both quantitatively and qualitatively on actual blood glucose data for 97 patients. For the prediction horizon (PH) of 30 mins, the average values for root mean squared error (RMSE), mean absolute error (MAE), mean absolute percentage error (MAPE), and normalized mean squared error (NRMSE) are [Formula: see text] mg/dL, 16.77 ± 4.87 mg/dL, [Formula: see text] and [Formula: see text] respectively. When Clarke and Parkes error grid analyses were performed comparing predicted BG with actual BG, the results showed average percentage of points in Zone A of [Formula: see text] and [Formula: see text] respectively. We offer this tool as a mechanism to enhance the predictive capabilities of algorithms for patients with T1D.

Liraglutide pharmacokinetics and exposure-response in adolescents with obesity

BACKGROUND

Obesity in adolescence presents a major public health challenge, often leading to obesity in adulthood with associated chronic disease.

OBJECTIVES

This study aimed to perform a population pharmacokinetic and exposure-response analysis of liraglutide by meta-analysis of data from trials conducted in children, adolescents and adults with obesity.

METHODS

The population pharmacokinetic analysis investigated the effect of covariates body weight, age group (children, adolescents and adults) and sex on liraglutide exposure in adolescents compared with previous results in adults. The exposure-response relationship of liraglutide for the change from baseline in body mass index standard deviation score (BMI SDS) was evaluated in adolescents and compared to that in adults.

RESULTS

Body weight was the main covariate affecting liraglutide exposure, with lower exposures at higher body weights, whereas age group was of no importance and sex was of little importance. An exposure-response relationship was demonstrated for liraglutide in both adolescents and adults as the decrease in BMI SDS from baseline increased in an exposure-dependent manner with increasing liraglutide exposure.

CONCLUSIONS

The population pharmacokinetic analysis supported similar liraglutide exposures in adolescents and adults; body weight was the most important covariate affecting exposure. An exposure-response relationship was established for liraglutide.

Evidence of Early Diabetic Nephropathy in Pediatric Type 1 Diabetes

BACKGROUND

Diabetic nephropathy (DN) is one of the most common microvascular complications in type 1 diabetes Mellitus (T1D). Urinary markers of renal damage or oxidative stress may signal early stages of DN. The association of these markers with blood pressure (BP) patterns and glycemic variability (GV) in children is yet to be explored.

METHODS

Subjects between the ages of 10 and 21 years with T1D were enrolled. Continuous glucose monitoring (CGM) and ambulatory blood pressure monitoring (ABPM) were performed on each subject. Urine samples were collected and analyzed for albumin, creatinine, neutrophil gelatinase-associated lipocalin (NGAL) and pentosidine.

RESULTS

The study included 21 subjects (62% female) with median age of 16.8 (IQR: 14.5, 18.9). Median HbA1C was 8.4 (IQR: 7.5, 9.3). While microalbuminuria was negative in all but one case (4.8%), urinary NGAL/Cr and pentosidine/Cr ratios were significantly elevated (P<0.001) in diabetic patients despite having normal microalbuminuria, and they correlated significantly with level of microalbumin/Cr (r=0.56 [CI: 0.17, 0.8] and r=0.79 [CI: 0.54, 0.91], respectively). Using ABPM, none had hypertension, however, poor nocturnal systolic BP dipping was found in 48% of cases (95% CI: 28-68%). Urinary NGAL/Cr negatively correlated with nocturnal SBP dipping (r=-0.47, CI: -0.76, -0.03). Urine NGAL/Cr also showed a significant negative correlation with HbA1c measurements, mean blood glucose, and high blood glucose index (r=-0.51 [CI: -0.78, -0.09], r=-0.45 [CI: -0.74, -0.03], and r=-0.51 [CI: -0.77, -0.1], respectively). Median urinary NGAL/Cr and pentosidine/Cr ratios were higher in the high GV group but were not significantly different.

DISCUSSION

This pilot study explores the role of ABPM and urinary markers of tubular health and oxidative stress in early detection of diabetic nephropathy. GV may play a role in the process of this diabetic complication.

Delay Discounting, Glycemic Regulation and Health Behaviors in Adults with Prediabetes

The majority of people with prediabetes transition to type 2 diabetes. Research has suggested that persons with type 2 diabetes are likely to discount the future and focus on immediate rewards. This study was designed to assess whether this process of delay discounting (DD) is associated with glycemic regulation, medication adherence and eating and exercise behaviors in adults with prediabetes. Participants included 81 adults with prediabetes who were also prescribed hypertension or dyslipidemia drugs, which is common for people with prediabetes. Participants completed adjusting amount DD $100 and $1000 tasks, as well assessments of glycemic control (Hemoglobin (Hb) A1c), medication adherence, diet quality, and objectively measured physical activity. Relationships between DD and these variables were assessed. Results showed higher rates of DD were related to higher HbA1c; as well as poorer medication adherence, lower diet quality and lower physical activity. Hierarchical regression showed that the association between minority status, a known risk factor for type 2 diabetes, was moderated by DD, as minorities with higher DD had greater HbA1c values. Delay discounting may represent a novel target to prevent progression from prediabetes to type 2 diabetes.

Characteristics of adult- compared to childhood-onset type 1 diabetes

AIMS

To compare diagnosis characteristics, diabetes management and comorbidities in a population diagnosed with type 1 diabetes in childhood with those in a similar population diagnosed in adulthood to identify disease differences related to the age of diabetes onset.

METHODS

This analysis was performed using the T1D Exchange Clinic Registry, a cross-sectional survivor cohort. Retrospectively collected characteristics were compared across the following age-at-diagnosis groups: <10, 10-17, 18-24, 25-39 and ≥40 years.

RESULTS

The entire cohort included 20 660 participants [51% female, median (interquartile range) age 18 (14-36) years, 82% non-Hispanic white]. Diabetic ketoacidosis at diagnosis was more common among those with onset in childhood. Participants diagnosed as adults were more likely to be overweight/obese at diagnosis and to have used oral agents preceding type 1 diabetes diagnosis (57%). Current insulin pump use was less frequent in participants diagnosed at older ages. Current glycaemic control, measured by HbA_1c , insulin requirements and use of a continuous glucose monitor were not different by age at diagnosis. Coeliac disease was the only comorbidity that was observed to have a different frequency by age at diagnosis, being more common in the participants diagnosed at a younger age.

CONCLUSIONS

These results show differences and similarities between type 1 diabetes diagnosed in childhood vs adulthood; notably, there was a tendency for there was a higher frequency of diabetic ketoacidosis at onset in children and a higher frequency of use of oral antidiabetes agents in adults. The data indicate that there is little distinction between the clinical characteristics and outcomes of type 1 diabetes diagnosed in childhood vs adulthood. Optimizing glycaemic control remains a challenge in all age groups, with lower use of insulin pumps impacting those diagnosed as adults.

Bleak present, bright future: II. Combined effects of episodic future thinking and scarcity on delay discounting in adults at risk for type 2 diabetes

The present study sought to determine if episodic future thinking (EFT) can decrease delay discounting (DD) and demand for fast food under simulations of economic scarcity in adults at risk for diabetes (i.e., overweight/obese and with hemoglobin A1c values in, or approaching, the prediabetic range). Across two sessions, participants completed assessments of DD and food demand at baseline and while prompted to: (1) engage in either EFT or control episodic recent thinking, and (2) while reading a brief narrative describing either economic scarcity or neutral income conditions. Results showed that EFT significantly reduced DD, whereas the economic scarcity narrative significantly increased DD; no significant interaction between EFT and scarcity was observed. No significant effect of either EFT or scarcity was observed on food demand. We conclude that EFT decreases DD even when challenged by simulated economic scarcity in adults at risk for diabetes. The absence of a significant interaction between EFT and scarcity suggests that these variables operate independently to influence DD in opposing directions. Effects of EFT and economic scarcity on food demand require further study. The present study was registered on clinicaltrials.gov (NCT03664726).

A Randomized, Controlled Trial of Liraglutide for Adolescents with Obesity

BACKGROUND

Obesity is a chronic disease with limited treatment options in pediatric patients. Liraglutide may be useful for weight management in adolescents with obesity.

METHODS

In this randomized, double-blind trial, which consisted of a 56-week treatment period and a 26-week follow-up period, we enrolled adolescents (12 to <18 years of age) with obesity and a poor response to lifestyle therapy alone. Participants were randomly assigned (1:1) to receive either liraglutide (3.0 mg) or placebo subcutaneously once daily, in addition to lifestyle therapy. The primary end point was the change from baseline in the body-mass index (BMI; the weight in kilograms divided by the square of the height in meters) standard-deviation score at week 56.

RESULTS

A total of 125 participants were assigned to the liraglutide group and 126 to the placebo group. Liraglutide was superior to placebo with regard to the change from baseline in the BMI standard-deviation score at week 56 (estimated difference, -0.22; 95% confidence interval [CI], -0.37 to -0.08; P = 0.002). A reduction in BMI of at least 5% was observed in 51 of 113 participants in the liraglutide group and in 20 of 105 participants in the placebo group (estimated percentage, 43.3% vs. 18.7%), and a reduction in BMI of at least 10% was observed in 33 and 9, respectively (estimated percentage, 26.1% vs. 8.1%). A greater reduction was observed with liraglutide than with placebo for BMI (estimated difference, -4.64 percentage points) and for body weight (estimated difference, -4.50 kg [for absolute change] and -5.01 percentage points [for relative change]). After discontinuation, a greater increase in the BMI standard-deviation score was observed with liraglutide than with placebo (estimated difference, 0.15; 95% CI, 0.07 to 0.23). More participants in the liraglutide group than in the placebo group had gastrointestinal adverse events (81 of 125 [64.8%] vs. 46 of 126 [36.5%]) and adverse events that led to discontinuation of the trial treatment (13 [10.4%] vs. 0). Few participants in either group had serious adverse events (3 [2.4%] vs. 5 [4.0%]). One suicide, which occurred in the liraglutide group, was assessed by the investigator as unlikely to be related to the trial treatment.

CONCLUSIONS

In adolescents with obesity, the use of liraglutide (3.0 mg) plus lifestyle therapy led to a significantly greater reduction in the BMI standard-deviation score than placebo plus lifestyle therapy. (Funded by Novo Nordisk; NN8022-4180 ClinicalTrials.gov number, NCT02918279.).

OR33-01 Liraglutide for Weight Management in Pubertal Adolescents with Obesity: A Randomized Controlled Trial

Background: Pediatric obesity is a chronic disease with rising prevalence and limited treatment options; first-line intervention is lifestyle therapy, which is typically unsuccessful.¹ Liraglutide (3.0 mg) as an adjunct to lifestyle therapy has provided weight loss and improved cardiometabolic risk factors in adults.² Here we report the results of liraglutide 3.0 mg in adolescents with obesity who failed to respond to lifestyle therapy.

Methods: A multinational, randomized, double-blind trial (NCT02918279) with a 12-wk run-in of lifestyle therapy, 4-8-wk dose escalation, 52-wk maintenance period and 26-wk follow-up off trial drug. Adolescents aged 12-<18 years with obesity, stable weight and suboptimal response to lifestyle therapy alone were randomized 1:1 to once-daily subcutaneous liraglutide 3.0 mg (or maximum tolerated dose) or placebo (PBO), both as an adjunct to lifestyle therapy. Randomization was stratified by pubertal and glycemic (normal vs prediabetes/type 2 diabetes) status. Primary endpoint was change in BMI standard deviation score (SDS)³ from wk 0 to 56.

Results: Of 125 adolescents randomized to liraglutide 3.0 mg and 126 to PBO, 101 and 100 completed treatment at wk 56, respectively; 99 in each arm completed the trial at wk 82. 40.6% were male; mean age 14.5 years; mean BMI 35.6 kg/m²; mean BMI SDS 3.17. Liraglutide 3.0 mg was superior to PBO for change in BMI SDS at wk 56 (estimated treatment difference [ETD] -0.22; 95% CI -0.37, -0.08; p=0.0022). In the liraglutide 3.0 mg vs PBO arm, 43.25% vs 18.73% (p=0.0002) and 26.08% vs 8.11% (p=0.0006) of adolescents had ≥5% and ≥10% reduction in baseline BMI at wk 56, respectively. A significant difference in change in BMI was seen for liraglutide 3.0 mg vs PBO: ETD -4.64%; 95% CI -7.14, -2.14; p=0.0003. A significant reduction in waist circumference with liraglutide 3.0 mg was shown at wk 56 (p=0.0126). Greater weight regain/rebound in BMI SDS at wk 82 was seen for liraglutide 3.0 mg vs PBO after drug discontinuation (ETD 0.15; 95% CI 0.07, 0.23; p=0.0002). There were no significant differences in blood pressure, fasting lipids, fasting plasma glucose or HbA1c at wk 56. No unexpected safety concerns and no severe hypoglycemia were reported. During treatment (0–56 wks), more adolescents in the liraglutide 3.0 mg (64.8%) vs PBO arm (36.5%) reported gastrointestinal adverse events (AEs), and 3 vs 5 adolescents, respectively, reported serious AEs. Mental health questionnaire results were similar in both arms at wk 56. No effect on growth or pubertal development was found.

Conclusions: This trial demonstrates clinically meaningful⁴ weight loss in adolescents with obesity treated with liraglutide 3.0 mg as an adjunct to lifestyle therapy. The safety profile was similar to that observed in adults.

References

1. Ryder et al Obesity 2018;26:951

2. Pi-Sunyer et al N Engl J Med 2015;373:11

3. EMA doc. ref. EMEA/402888/2008

4. Grossman et al JAMA 2017;317:2417

Liraglutide effects in a paediatric (7-11 y) population with obesity: A randomized, double-blind, placebo-controlled, short-term trial to assess safety, tolerability, pharmacokinetics, and pharmacodynamics

BACKGROUND

Childhood obesity is a major public health concern with limited treatment options.

OBJECTIVE

The aim of this study was to assess safety, tolerability, pharmacokinetics, and pharmacodynamics during short-term treatment with liraglutide in children (7-11 y) with obesity.

METHODS

In this randomized, double-blind, placebo-controlled trial, 24 children received at least one dose of once-daily subcutaneous liraglutide (n = 16) or placebo (n = 8) starting at 0.3 mg with weekly dose escalations up to 3.0 mg or maximum tolerated dose, and 20 children completed the trial (14 in the liraglutide group and six in the placebo group). The primary endpoint was the number of adverse events.

RESULTS

Baseline characteristics (mean ± standard deviation) included the following: age 9.9 ± 1.1 years, weight 71.5 ± 15.4 kg, and 62.5% male. Thirty-seven adverse events were reported in nine liraglutide-treated participants (56.3%) versus 12 events in five placebo-treated participants (62.5%). Most adverse events were mild in severity, three were of moderate severity, and none were severe. Gastrointestinal disorders were the most frequently reported events occurring in 37.5% of liraglutide-treated participants compared with placebo (12.5%). Six asymptomatic hypoglycaemic episodes occurred in five participants of whom four were liraglutide treated. Liraglutide exposure was consistent with dose proportionality. Body weight was the only covariate to significantly impact exposure. A significant reduction in body mass index (BMI) Z score from baseline to end of treatment (estimated treatment difference: -0.28; P = 0.0062) was observed.

CONCLUSION

Short-term treatment with liraglutide in children with obesity revealed a safety and tolerability profile similar to trials in adults and adolescents with obesity, with no new safety issues.

Hematuria as an adverse outcome following provocative growth hormone stimulation testing in children

BACKGROUND

Provocative growth hormone (GH) stimulation testing is used to evaluate short stature and growth failure in children. Agents commonly used for testing include clonidine, arginine and glucagon. While stimulation testing is generally considered safe, gross hematuria has been described as a rare idiopathic complication of GH stimulation testing. This study was designed to estimate the incidence of both microscopic and macroscopic hematuria following GH testing with different provocative agents.

METHODS

Subjects undergoing GH stimulation testing were invited to participate in the study. Prior to testing, vital signs were measured and baseline point-of-care (POC) urinalysis was done. The subjects performed urine testing at home on days 1, 2, 3 and 7 following GH stimulation studies. Families notified the study team with any positive findings and returned the data collection tool by mail.

RESULTS

In total, 34 subjects aged 11.14±2.71 years (91.2% male) completed the study. Agents used in provocative testing included arginine (73.5%), clonidine (94.1%) and glucagon (32.4%). Three subjects developed hematuria after GH stimulation testing (clonidine/arginine). The hematuria resolved by 7 days after testing. Additional adverse effects included nausea, vomiting and hypotension.

CONCLUSIONS

In this study of children undergoing GH testing, hematuria was identified in three subjects. This study demonstrates that side effects to agents used for GH testing are self-limited, yet not rare, and should be discussed with patients and families prior to stimulation testing.

Salivary inflammatory markers and microbiome in normoglycemic lean and obese children compared to obese children with type 2 diabetes

BACKGROUND

There is emerging evidence linking diabetes with periodontal disease. Diabetes is a well-recognized risk factor for periodontal disease. Conversely, pro-inflammatory molecules released by periodontally-diseased tissues may enter the circulation to induce insulin resistance. While this association has been demonstrated in adults, there is little information regarding periodontal status in obese children with and without type 2 diabetes (T2D). We hypothesized that children with T2D have higher rates of gingivitis, elevated salivary inflammatory markers, and an altered salivary microbiome compared to children without T2D.

METHODS

Three pediatric cohorts ages 10-19 years were studied: lean (normal weight-C), obese (Ob), and obese with T2D (T2D). Each subject completed an oral health survey, received a clinical oral examination, and provided unstimulated saliva for measurement of inflammatory markers and microbiome analysis.

RESULTS

The diabetes group was less likely to have had a dental visit within the last six months. Body mass index (BMI) Z-scores and waist circumference/height ratios were similar between Ob and T2D cohorts. The number of carious lesions and fillings were similar for all three groups. The gingival index was greater in the T2D group compared to the Ob and C groups. Although salivary microbial diversity was minimal between groups, a few differences in bacterial genus composition were noted.

CONCLUSIONS

Obese children with T2D show a trend toward poorer oral health compared to normal weight and obese children without T2D. This study characterizes the salivary microbiome of children with and without obesity and T2D. This study supports a modest link between T2D and periodontal inflammation in the pediatric population.

Evaluation of Pump Discontinuation and Associated Factors in the T1D Exchange Clinic Registry

BACKGROUND

The objectives of this study were to examine factors associated with insulin pump discontinuation among children and adults followed longitudinally for 1 year in the multicenter T1D Exchange clinic registry, and to provide participant-reported reasons for stopping pump therapy.

METHODS

We longitudinally followed 8935 participants of all ages using an insulin pump at the time of registry enrollment. Logistic regressions were used to identify demographic and clinical factors associated with pump discontinuation. Pump discontinuation was self-reported by participants on a first annual follow-up survey.

RESULTS

The overall frequency of pump discontinuation was 3%. Discontinuation was higher in adolescents (4%) and young adults (4%) than in younger children (3%) or older adults (1%). In multivariate analysis of children between 6 and <13 and 13 and <18 years, participants who discontinued pump use were more likely to have higher HbA1c levels at baseline (adjusted P < .001 for both). The top participant-reported reasons for discontinuing the pump included problems with wearability (57%), disliking the pump or feeling anxious (44%), and problems with glycemic control (30%).

CONCLUSIONS

In T1D Exchange registry participants, insulin pump discontinuation is uncommon, but more prevalent among adolescents and young adults, and youth with poor glycemic control. Given the known benefits of pump therapy, these populations should be targeted for support and education on troubleshooting pump use. Common reasons for discontinuation should also be considered in future device design and technological improvement.

Testicular failure following severe diabetic ketoacidosis complicated by hypotensive shock

The stalling or regression of pubertal development may be the first sign of hypergonadotropic hypogonadism in adolescent males. We report here a case of pediatric hypergonadotropic hypogonadism that likely developed secondary to ischemic injury during severe diabetic ketoacidosis (DKA). This case highlights the importance of performing genital exams during all evaluations of pediatric patients.

Methylphenidate decreases fat and carbohydrate intake in obese teenagers

OBJECTIVE

Dopamine is a neurotransmitter that mediates the reward value of food. Methylphenidate (MPH) selectively binds and inhibits the dopamine transporter, thus increasing brain dopamine levels shortly after oral administration. This investigation studied whether a single dose of MPH decreases energy intake (EI) in obese teenagers compared to placebo (P).

METHODS

This study used a single-blind, placebo-controlled, within subject design. Teenagers with body mass index (BMI) ≥95th percentile underwent two identical meal tests (P or MPH) after a 10 h fast in random order. Food was weighed before and after the meals, and EI was calculated as energy content/gram of consumed foods. Total and macronutrient EI (mean ± SD) were analyzed by Mann-Whitney U and Wilcoxon tests.

RESULTS

Twenty-two subjects (15 females, 7 males) completed the study. Participants were 13.4 ± 2.2 years old and had BMI 34.9 ± 10.7 kg/m². EI from fat (167 vs. 203 kcal, P = 0.03) and carbohydrates (311 vs. 389 kcal, P = 0.04) was decreased for MPH compared to P meals, with a trend in decreased total EI (545 vs. 663 kcal, P = 0.06).

CONCLUSION

A single dose of MPH decreases EI from fat and carbohydrates in obese adolescents. This effect underscores the importance of central dopamine signaling on eating behavior.

Serum sphingolipids and inflammatory mediators in adolescents at risk for metabolic syndrome

The purpose of this study was to determine low-grade inflammation associated with obesity that is mediated partially by TNF-α, an adipocytokine which stimulates sphingomyelinase activity in adipocytes. Circulating ceramide (Cer) and sphingosine 1-phosphate (S1P) are elevated in genetically obese (ob/ob) mice. We aimed to determine whether serum sphingolipid concentrations correlate with measures of obesity, insulin resistance, and lipid profiles in overweight versus lean adolescents. This cross-sectional study recruited 30 healthy overweight (body mass index, BMI ≥ 85%) and 15 lean (BMI 10-84%) adolescents. Anthropometric measurements and fasting blood samples were collected at one clinic visit. Serum glucose, insulin, and fasting lipid profiles were measured. Serum adipocytokine concentrations were measured by ELISA or colorimetric assay and sphingolipids were measured by HPLC-mass spectrometry. Between group differences in serum sphingolipid concentrations were assessed. Correlations between sphingolipid concentrations and (i) body mass index, (ii) calculated homeostasis model assessment of insulin resistance (HOMA-IR), (iii) adipocytokines, and (iv) lipoproteins were determined. The results showed that significant differences in HOMA-IR (4.5 ± 3.2 vs. 1.2 ± 0.7), free fatty acids (0.8 ± 0.3 mmol/l vs. 0.4 ± 0.3 mmol/l), and adiponectin (6.4 ± 3.8 vs. 12.6 ± 9.9 μg/ml) were seen between groups (overweight vs. lean). There were significant correlations between Cer and TNF-α (r = 0.429), S1P and TNF-α (r = 0.288), Cer and adiponectin (r = 0.321), Cer:S1P and adiponectin (r = 0.324), Cer and HOMA-IR (r = 0.307), and Cer:S1P and LDL cholesterol (r = 0.453); these associations persisted after adjustment for BMI Z-score, sex, and Tanner stage. We concluded that elevated sphingolipid concentrations correlate with TNF-α, adiponectin, lipoprotein profiles, and HOMA-IR. Ceramide is associated with atherogenic lipid profiles and the development of insulin resistance in obese adolescents, similar to adults.

Managing diabetes with inhaled insulin

The incidence of diabetes is increasing world-wide. Many individuals with diabetes require insulin to control their blood sugar and prevent both microvascular and macrovascular complications associated with this chronic disease. Current regimens involve delivery of subcutaneous insulin by injection or continuous insulin infusion. One area of research to advance diabetes care is aimed at developing alternate routes of insulin administration that will make daily management less invasive for patients. This review will focus on inhaled insulin, a novel formulation which takes advantage of drug delivery through the pulmonary system. The pharmacology, efficacy, and safety of inhaled insulin will be discussed. In addition, the status of inhaled insulin as a potential therapy for individuals with diabetes will be reviewed.

Sphingosine kinase 1 knockdown reduces insulin synthesis and secretion in a rat insulinoma cell line

To evaluate the role of sphingosine kinase 1 (SphK1) in insulin secretion, we used stable transfection to knock down the expression of the Sphk1 gene in the rat insulinoma INS-1 832/13 cell line. Cell lines with lowered Sphk1 mRNA expression and SphK1 enzyme activity (SK11 and SK14) exhibited lowered glucose- and 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH) plus glutamine-stimulated insulin release and low insulin content associated with decreases in the mRNA of the insulin 1 gene. Overexpression of the rat or human Sphk1 cDNA restored insulin secretion and total insulin content in the SK11 cell line, but not in the SK14 cell line. The Sphk1 cDNA-transfected SK14 cell line expressed significantly less SphK1 activity than the Sphk1 cDNA-transfected SK11 cells suggesting that the shRNA targeting SK14 was more effective in silencing the exogenous rat Sphk1 mRNA. The results indicate that SphK1 activity is important for insulin synthesis and secretion.

ATP-independent glucose stimulation of sphingosine kinase in rat pancreatic islets

Sphingosine kinase (SPHK) catalyzes sphingosine 1-phosphate production, promoting cell survival and reducing apoptosis in isolated rat pancreatic islets. Glucose, the primary islet beta-cell growth factor and insulin secretagogue, increased islet SPHK activity by 3- to 5-fold following acute (1 h) or prolonged (7 days) stimulation. Prolonged stimulation of islets with glucose induced SPHK1a and SPHK2 mRNA levels; there were no changes in SPHK protein expression. To isolate the metabolic effects of glucose on SPHK activation, islets were stimulated with glucose analogs or metabolites. 2-deoxy-D-glucose (2-DG), an analog phosphorylated by glucokinase but not an effective energy source, activated SPHK similarly to glucose. In contrast, 3-o-methylglucose (3-oMeG), which is transported but neither phosphorylated nor metabolized, did not increase islet SPHK activity. Glyceraldehyde and alpha-ketoisocaproic acid (KIC), metabolites that stimulate glycolysis and the citric acid cycle, respectively, did not activate islet SPHK. Moreover, inorganic phosphate blocked glucose-induced SPHK activation. A role for SPHK activity in beta-cell growth was confirmed when small interfering (si)SPHK2 RNA transfection reduced rat insulinoma INS-1e cell SPHK levels and activity and cell growth. Glucose induced an early and sustained increase in islet SPHK activity that was dependent on glucose phosphorylation, but independent of ATP generation or new protein biosynthesis. Glucose-supported beta-cell growth appears to be in part mediated by SPHK activity.

Does the dopamine transporter protein allele predict growth hormone testing results or response to growth hormone therapy?

Animal studies have shown dopamine transporter protein (DAT1) knock out mice are growth retarded and hyperactive. DAT1 has been researched in several human psychiatric studies with varying results regarding phenotype and DAT1 alleles. However, the relationship between DAT1 and short stature in humans has not been explored. Buccal swabs were collected from patients receiving growth hormone (GH) therapy and were genotyped for variable number tandem repeat (VNTR) by polymerase chain reaction. Forty subjects were included; twenty-three patients had the 10/10 DAT1 genotype and thirteen had the 9/10 genotype. Fifteen of the patients with the 10/10 genotype tested GH deficient. Seven patients with the 9/10 genotype tested GH sufficient. The linear growth rate during the first year of GH therapy was equivalent in both genotypes. In conclusion, polymorphisms in the DAT1 40 base pair (bp) VNTR genotype do not predict GH deficiency or response to GH therapy in short children.

Inhaled insulin: overview of a novel route of insulin administration

Diabetes is a chronic disease characterized by inadequate insulin secretion with resulting hyperglycemia. Diabetes complications include both microvascular and macrovascular disease, both of which are affected by optimal diabetes control. Many individuals with diabetes rely on subcutaneous insulin administration by injection or continuous infusion to control glucose levels. Novel routes of insulin administration are an area of interest in the diabetes field, given that insulin injection therapy is burdensome for many patients. This review will discuss pulmonary delivery of insulin via inhalation. The safety of inhaled insulin as well as the efficacy in comparison to subcutaneous insulin in the various populations with diabetes are covered. In addition, the experience and pitfalls that face the development and marketing of inhaled insulin are discussed.

Young women with type 1 diabetes have lower bone mineral density that persists over time

OBJECTIVE

Individuals with type 1 diabetes have decreased bone mineral density (BMD), yet the natural history and pathogenesis of osteopenia are unclear. We have previously shown that women with type 1 diabetes (aged 13-35 years) have lower BMD than community age-matched nondiabetic control subjects. We here report 2-year follow-up BMD data in this cohort to determine the natural history of BMD in young women with and without diabetes.

RESEARCH DESIGN AND METHODS

BMD was measured by dual-energy X-ray absorptiometry at baseline and 2 years later in 63 women with type 1 diabetes and in 85 age-matched community control subjects. A1C, IGF-1, IGF binding protein-3, serum osteocalcin, and urine N-teleopeptide were measured at follow-up.

RESULTS

After adjusting for age, BMI, and oral contraceptive use, BMD at year 2 continued to be lower in women >or=20 years of age with type 1 diabetes compared with control subjects at the total hip, femoral neck, and whole body. Lower BMD values were observed in cases <20 years of age compared with control subjects; however, the differences were not statistically significant. Lower BMD did not correlate with diabetes control, growth factors, or metabolic bone markers.

CONCLUSIONS

This study confirms our previous findings that young women with type 1 diabetes have lower BMD than control subjects and that these differences persist over time, particularly in women >or=20 years of age. Persistence of low BMD as well as failure to accrue bone density after age 20 years may contribute to the increased incidence of osteoporotic hip fractures seen in postmenopausal women with type 1 diabetes.

Bisphosphonate Treatment of Tumor-Induced Hypercalcemia in a Toddler: Case Report and Review of Related Literature

OBJECTIVE

To describe the initial manifestations and treatment of parathyroid hormone-related peptide (PTH-rP)-induced hypercalcemia in a toddler with a malignant rhabdoid tumor.

METHODS

We report a case of a 2-year-old boy presenting with poor appetite, lethargy, and a 1.5-kg weight loss during a 2-week period. On examination, the child was found to have a right upper quadrant abdominal mass. Laboratory studies revealed severe hypercalcemia. We review the patients' clinical course and management of hypercalcemia.

RESULTS

Initial evaluation revealed no cardiovascular instability. An abdominal mass was identified on physical examination. Initial laboratory studies revealed elevated levels of total and ionized calcium, low phosphorus, microcytic anemia, and elevated erythrocyte sedimentation rate. Saline diuresis with furosemide was begun. Abdominal ultrasonography revealed a large right renal tumor. Because of refractory hypercalcemia, intravenously administered bisphosphonate was used. Within 12 hours after bisphosphonate infusion, the serum calcium level declined from 14.9 mg/dL to 10.9 mg/dL. The furosemide dose was decreased and finally discontinued 2 days after bisphosphonate administration. Because of development of a femoral thrombosis, definitive surgical intervention was delayed. During that time, serum calcium levels again increased and necessitated administration of a second bisphosphonate dose. At surgical treatment, a right renal tumor was identified, and frozen section pathology revealed a rhabdoid tumor. After tumor resection, calcium levels were stable. Other laboratory studies performed at admission revealed suppressed PTH, normal vitamin D and calcitonin levels, and elevated PTH-rP.

CONCLUSION

Hypercalcemia in a toddler is a rare event and can be attributable to humoral factors released by malignant tumors. Hypercalcemia in the pediatric population can be treated effectively with bisphosphonates when conservative measures fail.

Clinical evaluation of inhaled insulin

Diabetes affects over 18.2 million individuals in the United States alone. Current therapy to treat type 1 diabetes relies on subcutaneous insulin administration either by injection or continuous infusion. In addition, patients with type 2 diabetes who fail lifestyle intervention and oral therapy require subcutaneous insulin. Optimal injection protocols to achieve tight metabolic control often prove burdensome to patients. Thus, development of pulmonary insulin delivery to supplement and/or replace subcutaneous insulin injections may be an effective alternative, allowing patients to achieve intensive diabetes management. This review will discuss the devices in development for the delivery of inhaled insulin. In addition, the efficacy of inhaled insulin in both type 1 and type 2 diabetic populations will be discussed. Finally, the available safety data with respect to the unique pulmonary effects of inhaled insulin will be covered.

Sphingosine 1-phosphate affects cytokine-induced apoptosis in rat pancreatic islet beta-cells

Cytokines mediate pancreatic islet beta-cell apoptosis and necrosis, leading to loss of insulin secretory capacity and type 1 diabetes mellitus. The cytokines, IL-1beta and interferon-gamma, induced terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) staining of rat islet cells within 48 h by about 25-30%, indicative of apoptosis and/or necrosis. Sphingosine 1-phosphate (S1P) at nanomolar concentrations significantly reduced islet cell cytokine-induced TUNEL staining. Similar effects were observed in INS-1 cells. The dihydro analog of S1P also reduced the percentage of TUNEL stained islet and INS-1 cells, whereas the S1P receptor antagonist BML-241 blocked the protective effects. Pertussis toxin did not affect the S1P protective response. In the presence of a phospholipase C antagonist, U73122, there was significant inhibition of the S1P protective effects against apoptosis/necrosis. S1P stimulated INS-1 cell protein kinase C activity. Carbamylcholine chloride acting through muscarinic receptors also inhibited cytokine-induced TUNEL staining in pancreatic islet cells. S1P and/or dihydro-S1P also antagonized cytokine-induced increases in cytochrome c release from mitochondria and caspase-3 activity in INS-1 cells, which are indicative of cell apoptosis vs. necrosis. S1P failed to affect nitric oxide synthase activity after 48 h. Thus, the evidence suggests that S1P acting on S1P receptors coupled to G(q) mediates protective effects on islet beta-cells against cytokine-induced apoptosis.

Sphingosine kinase activity and sphingosine-1 phosphate production in rat pancreatic islets and INS-1 cells: response to cytokines

Sphingosine-1 phosphate (S1P) is a bioactive sphingolipid with the potential to mobilize Ca2+, to inhibit apoptosis, and to promote mitogenesis. Sphingosine kinase (SPHK) and S1P were characterized in INS-1 insulinoma cells and isolated rat islets of Langerhans. SPHK activity increased in INS-1 cell homogenates treated with interleukin-1beta (IL-1beta) or tumor necrosis factor-alpha (TNF-alpha), and responses were additive. IL-1beta or TNF-alpha increased islet SPHK activity within 15 min to 1 h; activity remained elevated after 8 h. SPHK2 was the predominant active isoform in INS-1 cells; little or no SPHK1 activity was detected. Cytokines increased endogenous S1P biosynthesis in 32P(i)-prelabeled INS-1 cells, and cycloheximide inhibited the response after 8 h, suggesting that protein synthesis mediated the response. There was no [32P]S1P release from cells. Compared with basal values, IL-1beta and TNF-alpha induced increases in SPHK1a mRNA levels relative to 18S ribosomal RNA in INS-1 cells within 1 h; relative SPHK2 mRNA levels were unchanged after cytokine treatment. IL-1beta, but not TNF-alpha, induced relative SPHK1a mRNA expression levels within 1 h in islets, whereas SPHK2 mRNA levels were unchanged. Thus, IL-1beta and TNF-alpha induced an early and sustained increase in SPHK activity in INS-1 cells and isolated islets, suggesting that S1P plays a role in the pathological response of pancreatic beta-cells to cytokines.

E2/E3-mediated assembly of lysine 29-linked polyubiquitin chains

Polyubiquitin (Ub) chains linked through Lys-48-Gly-76 isopeptide bonds represent the principal signal by which substrates of the Ub-dependent protein degradation pathway are targeted to the 26 S proteasome, but the mechanism(s) whereby these chains are assembled on substrate proteins is poorly understood. Nor have assembly mechanisms or definitive functions been assigned to polyubiquitin chains linked through several other lysine residues of ubiquitin. We show that rabbit reticulocyte lysate harbors enzymatic components that catalyze the assembly of unanchored Lys-29-linked polyubiquitin chains. This reaction can be reconstituted using the ubiquitin-conjugating enzyme (E2) known as UbcH5A, a 120-kDa protein(s) that behaves as a ubiquitin-protein ligase (E3), and ubiquitin-activating enzyme (E1). The same partially purified E3 preparation also catalyzes the assembly of unanchored chains linked through Lys-48. Kinetic studies revealed a K(m) of approximately 9 microM for the acceptor ubiquitin in the synthesis of diubiquitin; this value is similar to the concentration of free ubiquitin in most cells. Similar kinetic behavior was observed for conjugation to Lys-48 versus Lys-29 and for conjugation to tetraubiquitin versus monoubiquitin. The properties of these enzymes suggest that there may be distinct pathways for ubiquitin-ubiquitin ligation versus substrate-ubiquitin ligation in vivo.

Core domain mutation (S86Y) selectively inactivates polyubiquitin chain synthesis catalyzed by E2-25K

The mammalian ubiquitin conjugating enzyme known as E2-25K catalyzes the synthesis of polyubiquitin chains linked exclusively through K48-G76 isopeptide bonds. The properties of truncated and chimeric forms of E2-25K suggest that the polyubiquitin chain synthesis activity of this E2 depends on specific interactions between its conserved 150-residue core domain and its unique 50-residue tail domain [Haldeman, M. T., Xia, G., Kasperek, E. M., and Pickart, C. M. (1997) Biochemistry 36, 10526-10537]. In the present study, we provide strong support for this model by showing that a point mutation in the core domain (S86Y) mimics the effect of deleting the entire tail domain: the ability to form an E2 approximately ubiquitin thiol ester is intact, while conjugation activity is severely inhibited (>/=100-fold reduction in kcat/Km). The properties of E2-25K enzymes carrying the S86Y mutation indicate that this mutation strengthens the interaction between the core and tail domains: both free and ubiquitin-bound forms of S86Y-25K are completely resistant to tryptic cleavage at K164 in the tail domain, whereas wild-type enzyme is rapidly cleaved at this site. Other properties of S86Y-26K suggest that the active site of this mutant enzyme is more occluded than the active site of the wild-type enzyme. (1) Free S86Y-25K is alkylated by iodoacetamide 2-fold more slowly than the wild-type enzyme. (2) In assays of E2 approximately ubiquitin thiol ester formation, S86Y-25K shows a 4-fold reduced affinity for E1. (3) The ubiquitin thiol ester adduct of S86Y-25K undergoes (uncatalyzed) reaction with dithiothreitol 3-fold more slowly than the wild-type thiol ester adduct. One model to accommodate these findings postulates that an enhanced interaction between the core and tail domains, induced by the S86Y mutation, causes a steric blockade at the active site which prevents access of the incoming ubiquitin acceptor to the thiol ester bond. Consistent with this model, the S86Y mutation inhibits ubiquitin transfer to macromolecular acceptors (ubiquitin and polylysine) more strongly than transfer to small-molecule acceptors (free lysine and short peptides). These results suggest that unique residues proximal to E2 active sites may influence specific function by mediating intramolecular interactions.

Induction of ubiquitin-conjugating enzymes during terminal erythroid differentiation

A global cellular reorganization occurs during the reticulocyte stage of erythroid differentiation. This reorganization is accomplished partly through programmed protein degradation. The selection of proteins for degradation can be mediated by covalent attachment of ubiquitin. We have cloned cDNAs encoding two ubiquitin-conjugating (E2) enzymes, E2-20K and E2-230K, and found their genes to be strongly induced during the differentiation of erythroblasts into reticulocytes. Induction of the E2-20K and E2-230K genes is specific, as transcript levels for at least two other ubiquitinating enzymes fall during erythroblast differentiation. In contrast to most proteins induced in reticulocytes, E2-20K and E2-230K enzymes are present at strongly reduced levels in erythrocytes and thus decline in abundance as reticulocyte maturation is completed. This result suggests that both enzymes function during the reticulocyte stage, when enhanced protein degradation has been observed. These data implicate regulated components of the ubiquitin conjugation machinery in erythroid differentiation.

Information-theoretical entropy as a measure of sequence variability

We propose the use of the information-theoretical entrophy, S = -sigman pi log2 pi, as a measure of variability at a given position in a set of aligned sequences. pi stands for the fraction of times the i-th type appears at a position. For protein sequences, the sum has up to 20 terms, for nucleotide sequences, up to 4 terms, and for codon sequences, up to 61 terms. We compare S and Vs, a related measure, in detail with Vk, the traditional measure of immunoglobulin sequence variability, both in the abstract and as applied to the immunoglobulins. We conclude that S has desirable mathematical properties that Vk lacks and has intuitive and statistical meanings that accord well with the notion of variability. We find that Vk and the S-based measures are highly correlated for the immunoglobulins. We show by analysis of sequence data and by means of a mathematical model that this correlation is due to a strong tendency for the frequency of occurrence of amino acid types at a given position to be log-linear. It is not known whether the immunoglobulins are typical or atypical of protein families in this regard, nor is the origin of the observed rank-frequency distribution obvious, although we discuss several possible etiologies.