Potential contributors to variation in weight-loss response to liraglutide

Obesity treatment requires a chronic state of negative energy balance. Obesity medications can help with this, increasing long-term dietary compliance by promoting satiety or reducing hunger. However, efficacy and safety of obesity medications vary for individuals. Early identification of non-responders to obesity medications may limit drug exposure while optimizing benefits for responders. This review summarizes factors that impact weight-loss response to liraglutide. Factors linked to greater weight loss on liraglutide include being female, not having diabetes, having relatively high baseline weight, and losing at least 4% of initial weight after 16 weeks of treatment. Other covariates that may predict treatment response but require further confirmation include central effects, nausea, gastric emptying of solids, and genotype. Baseline body mass index, race, and age seem less relevant for predicting weight-loss response to liraglutide. Lesser known and harder-to-measure factors such as cerebral blood flow, food cue reactivity, gut hormone levels, and dietary adherence possibly impact variability of response to liraglutide. This information should assist healthcare providers with establishing realistic weight-loss probability for individual patients. Future research should improve the ability to identify responders to liraglutide. Importantly, this review may provide a framework to identify responders to other obesity medications.

Biobehavioural approaches to prevention and treatment: A call for implementation science in obesity research

Much progress has been made in the last 30 years in understanding the causes and mechanisms that contribute to obesity, yet widely available and successful strategies for prevention and treatment remain elusive at population levels. This paper discusses the biobehavioural framework and provides suggestions for applying it to enable greater progress in the science of obesity prevention and treatment, including an increased focus on implementation of science strategies. The objective is to promote a re-evaluation of current views about preventing and treating obesity within a unified biobehavioural framework. Further integration of research exploring how both behavioural and biological components interact is a critical step forward.

A randomized cross-over trial to determine the effect of a protein vs. carbohydrate preload on energy balance in ad libitum settings

BACKGROUND

Although high protein diets have been tested in controlled environments for applications to weight management, it is not understood if adding high protein foods to the diet would impact ad libitum energy balance in the absence of other lifestyle changes.

METHODS

This double-blinded randomized crossover trial compared the effects of a protein shake (PS) to a carbohydrate shake (CS), consumed prior to each major meal to equate to 20% of total energy needs over the course of the day, on energy balance over two 5-day treatment periods in healthy adults with BMI 20-30 kg/m2. Tri-axial accelerometers estimated physical activity energy expenditure. Ad libitum energy intake was measured in a laboratory kitchen.

RESULTS

Energy balance was positive during both treatment periods but was not different between periods. There were no interactions between treatment and preload caloric dose or treatment and BMI status on energy balance. Satiety ratings did not differ for any pairwise comparisons between treatment and caloric dose. Controlling for gender and basal metabolic rate, thermic effect of food was greater for PS than CS.

CONCLUSIONS

Preload periods significantly altered the macronutrient composition of the overall diet. This study found limited evidence that carbohydrate or protein preloads have differential effects on energy balance in short-term ad libitum settings.

TRIAL REGISTRATION

This trial was pre-registered on clinicaltrials.gov as NCT02613065 on 11/30/2015.

Subjective social status is associated with compensation for large meals - A prospective pilot study

OBJECTIVES

Subjective social status (SSS) is known to be inversely associated with obesity. Our objective was to determine if SSS is associated with eating behaviors that would predispose to weight gain, specifically, with inadequate compensation for excess energy consumed during a single large meal. Therefore, we conducted a pilot study to determine the association of SSS with 24-h energy balance, 24-h and post-lunch energy intake, changes in body composition and changes in adjusted resting energy expenditure on days when a high-energy lunch was consumed in free-living human subjects.

METHOD

Female participants (7 normal weight and 10 overweight) consumed 60% of' estimated 24-h energy requirements as a lunchtime meal in the laboratory for 14 days. Subjective social status was measured at baseline using the MacArthur Scale. Remote Food Photography Method was used to record food intake outside of the lab on days 1-2, 7-8, and 12-13. Associations of 24-h energy balance, 24-h and post-lunch energy intake, changes in adjusted resting energy expenditure and changes in percent body fat (measured by dual x-ray absorptiometry) with SSS were studied.

RESULTS

Mean (standard deviation) age and BMI were 36.29 (8.25) years and 26.43 (2.32) kg/m², respectively. Lower SSS was significantly associated with positive energy balance (p for trend 0.002), and higher post-lunch energy intake (p = 0.02) when controlled for age and initial body mass index.

CONCLUSIONS

Our pilot data show that lower SSS is associated with higher post-lunch energy intake, which is indicative of poor energy compensation following a large meal. Over a longer time period, this could result in fat mass gain. Studies that are of longer duration and well-powered are warranted to confirm our findings.

Body Mass Index and Subjective Social Status: The Coronary Artery Risk Development in Young Adults Study

OBJECTIVE

Subjective social status (SSS), or perceived social status, may explain, in part, the relationship between socioeconomic status (SES) and obesity. The objective of this study was to test whether SSS mediates the relationship between two indicators of SES (income and education) and body mass index (BMI).

METHODS

A cross-sectional, structural equation path analysis was applied to the Coronary Artery Risk Development in Young Adults (CARDIA) study (n = 2,624). The analysis tested whether SSS (MacArthur scale), education, and income were associated with BMI at the year 20 examination (adjusting for sex, age, and race), and it was hypothesized that the associations of education and income with BMI would be at least partly mediated by SSS.

RESULTS

SSS had a significant direct effect on BMI (-0.21, P = 0.018). Education had a significant direct relationship with SSS (0.11, P < 0.001) and a small but significant indirect relationship with BMI through SSS (-0.02, P = 0.022). Although income did not have a significant direct relationship with BMI, it did have a significant indirect relationship through SSS (b = -0.05, P = 0.019).

CONCLUSIONS

Results are consistent with the hypothesized model in which SSS partially mediates the relationship between SES indicators and BMI.

Exercise following Mental Work Prevented Overeating

Mental work may promote caloric intake, whereas exercise may offset positive energy balance by decreasing energy intake and increasing energy expenditure.

PURPOSE

This study aimed to replicate previous findings that mental work increases caloric intake compared with a rest condition and assess whether exercise after mental work can offset this effect.

METHODS

Thirty-eight male and female university students were randomly assigned to mental work + rest (MW + R) or mental work + exercise (MW + E). Participants also completed a baseline rest (BR) visit consisting of no mental work or exercise. Visit order was counterbalanced. During the MW + R or MW + E visit, participants completed a 20-min mental task and either a 15-min rest (MW + R) or a 15-min interval exercise (MW + E). Each visit ended with an ad libitum pizza lunch. A two-way repeated-measures ANOVA was used to compare eating behavior between groups.

RESULTS

Participants in the MW + R condition consumed an average of 100 more kilocalories compared with BR (633.3 ± 72.9 and 533.9 ± 67.7, respectively, P = 0.02), and participants in MW + E consumed an average of 25 kcal less compared with BR (432.3 ± 69.2 and 456.5 ± 64.2, respectively, P > 0.05). When including the estimated energy expenditure of exercise in the MW + E conditions, participants were in negative energy balance by an average of 98.5 ± 41.5 kcal, resulting in a significant difference in energy balance between the two groups (P = 0.001).

CONCLUSION

An acute bout of interval exercise after mental work resulted in significantly decreased food consumption compared with a nonexercise condition. These results suggest that an acute bout of exercise may be used to offset positive energy balance induced by mental tasks.

True, true, unrelated? A review of recent evidence for a causal influence of breakfast on obesity

PURPOSE OF REVIEW

It has long been known that breakfast skipping is associated with obesity; however, well controlled clinical trials have only recently been conducted to determine a causative relationship.

RECENT FINDINGS

Skipping breakfast is likely to be detrimental for insulin sensitivity; however, randomized trials suggest that it does not play a large role in weight gain or weight loss. Specific breakfast strategies such as certain types of breakfast, and consuming more calories in the morning relative to the evening, however, may produce greater weight loss.

SUMMARY

The act of eating breakfast, compared to skipping it, does not appear to have a large impact on body weight. More specific strategies regarding the size and type of breakfast may be required for a substantial effect on weight loss, and improving glycemic regulation may be an important reason to consume breakfast rather than skipping it.

Regarding Obesity as a Disease: Evolving Policies and Their Implications

In 2013, the American Medical Association recognized obesity as a complex, chronic disease requiring medical attention. Defining obesity as a disease is a very public process, largely driven by expectation of costs and benefits. Although the public has been slow to embrace this definition, evidence is emerging for broader awareness of influencing factors beyond personal choice. This decision seems to be working with other factors to bring more access to care, less blame for people with the condition, and more favorable conditions for research to identify effective strategies for prevention and clinical care to reduce the impact.

The food-insecurity obesity paradox: A resource scarcity hypothesis

Food insecurity is paradoxically associated with obesity in the United States. Current hypotheses to explain this phenomenon are descriptive regarding the low food security population's dietary and physical activity habits, but are not mechanistic. Herein it is proposed that a resource scarcity hypothesis may explain this paradox, such that fattening is a physiologically regulated response to threatened food supply that occurs specifically in low social status individuals. Evidence that this may be occurring, the implications for addressing the food insecurity-obesity paradox, and future areas of research, are reviewed and discussed.

Integrated genomic and BMI analysis for type 2 diabetes risk assessment

Type 2 Diabetes (T2D) is a chronic disease arising from the development of insulin absence or resistance within the body, and a complex interplay of environmental and genetic factors. The incidence of T2D has increased throughout the last few decades, together with the occurrence of the obesity epidemic. The consideration of variants identified by Genome Wide Association Studies (GWAS) into risk assessment models for T2D could aid in the identification of at-risk patients who could benefit from preventive medicine. In this study, we build several risk assessment models, evaluated with two different classification approaches (Logistic Regression and Neural Networks), to measure the effect of including genetic information in the prediction of T2D. We used data from to the Original and the Offspring cohorts of the Framingham Heart Study, which provides phenotypic and genetic information for 5245 subjects (4306 controls and 939 cases). Models were built by using several covariates: gender, exposure time, cohort, body mass index (BMI), and 65 SNPs associated to T2D. We fitted Logistic Regressions and Bayesian Regularized Neural Networks and then assessed their predictive ability by using a ten-fold cross validation. We found that the inclusion of genetic information into the risk assessment models increased the predictive ability by 2%, when compared to the baseline model. Furthermore, the models that included BMI at the onset of diabetes as a possible effector, gave an improvement of 6% in the area under the curve derived from the ROC analysis. The highest AUC achieved (0.75) belonged to the model that included BMI, and a genetic score based on the 65 established T2D-associated SNPs. Finally, the inclusion of SNPs and BMI raised predictive ability in all models as expected; however, results from the AUC in Neural Networks and Logistic Regression did not differ significantly in their prediction accuracy.

Hope thinking and past trauma mediate the relationships of body mass index with perceived mental health treatment need and mental health treatment use

Greater body mass is associated with a greater risk of mental health conditions and more frequent mental health treatment use. However, factors that might influence perceived mental health treatment need and mental health treatment use among those of greater weight, including hope thinking, trauma history and perceived mental health treatment stigma, are not well understood.

OBJECTIVE

The objective of this study was to determine if hope thinking, trauma history and/or perceived mental health treatment stigma mediate the relationships of body mass index [BMI] with perceived mental health treatment need and mental health treatment use.

METHOD

Primary care clinic patients in the Midwest United States (N = 196; BMI range = 18.5 to 47.0, mean = 29.26 ± 6.61, median = 27.90) were recruited to complete a battery of self-report measures that assessed perceived mental health treatment need, mental health treatment use, hope thinking (Trait Hope Scale), trauma history (a single-item traumatic event history screen from the posttraumatic stress disorder module of the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition), and perceived mental health treatment stigma (Stigma Scale for Receiving Psychological Help).

RESULTS

Reduced hope thinking and a greater incidence of past trauma accounted for greater perceived mental health treatment need and greater mental health treatment use among those of greater BMI. BMI was not related to perceived unmet mental health treatment need.

CONCLUSION

Increased perceived mental health treatment need and mental health treatment use among those of greater BMI may be explained by lower hope thinking and a greater incidence of trauma in this population. Heavier patients may benefit from interventions designed to augment hope and address traumatic histories.

Even modest prediction accuracy of genomic models can have large clinical utility

Whole Genome Prediction (WGP) jointly fits thousands of SNPs into a regression model to yield estimates for the contribution of markers to the overall variance of a particular trait, and for their associations with that trait. To date, WGP has offered only modest prediction accuracy, but in some cases even modest prediction accuracy may be useful. We provide an illustration of this using a theoretical simulation that used WGP to predict weight loss after bariatric surgery with moderate accuracy (R² = 0.07) to assess the clinical utility of WGP despite these limitations. Prevention of Type 2 Diabetes (T2DM) post-surgery was considered the major outcome. Treating only patients above predefined threshold of predicted weight loss in our simulation, in the realistic context of finite resources for the surgery, significantly reduced lifetime risk of T2DM in the treatable population by selecting those most likely to succeed. Thus, our example illustrates how WGP may be clinically useful in some situations, and even with moderate accuracy, may provide a clear path for turning personalized medicine from theory to reality.

Predicting adult weight change in the real world: a systematic review and meta-analysis accounting for compensatory changes in energy intake or expenditure

BACKGROUND

Public health and clinical interventions for obesity in free-living adults may be diminished by individual compensation for the intervention. Approaches to predict weight outcomes do not account for all mechanisms of compensation, so they are not well suited to predict outcomes in free-living adults. Our objective was to quantify the range of compensation in energy intake or expenditure observed in human randomized controlled trials (RCTs).

METHODS

We searched multiple databases (PubMed, CINAHL, SCOPUS, Cochrane, ProQuest, PsycInfo) up to 1 August 2012 for RCTs evaluating the effect of dietary and/or physical activity interventions on body weight/composition.

INCLUSION CRITERIA

subjects per treatment arm ≥5; ≥1 week intervention; a reported outcome of body weight/body composition; the intervention was either a prescribed amount of over- or underfeeding and/or supervised or monitored physical activity was prescribed; ≥80% compliance; and an objective method was used to verify compliance with the intervention (for example, observation and electronic monitoring). Data were independently extracted and analyzed by multiple reviewers with consensus reached by discussion. We compared observed weight change with predicted weight change using two models that predict weight change accounting only for metabolic compensation.

FINDINGS

Twenty-eight studies met inclusion criteria. Overfeeding studies indicate 96% less weight gain than expected if no compensation occurred. Dietary restriction and exercise studies may result in up to 12-44% and 55-64% less weight loss than expected, respectively, under an assumption of no behavioral compensation.

INTERPRETATION

Compensation is substantial even in high-compliance conditions, resulting in far less weight change than would be expected. The simple algorithm we report allows for more realistic predictions of intervention effects in free-living populations by accounting for the significant compensation that occurs.

The aetiology of obesity beyond eating more and exercising less

Although recent increases in availability of energy dense, processed foods and reductions in institutionally driven physical activity have created an environment that is permissible for obesity to occur, several other factors may contribute to the development of obesity in this context. We review evidence for eleven such factors: endocrine disruptors, intrauterine effects, epigenetics, maternal age, differential fecundity and assortative mating by body mass index, microorganisms, reduction in variability of ambient temperatures, smoking cessation, sleep debt, and pharmaceutical iatrogenesis. Evidence for the role of endocrine disruptors, microorganisms, ambient temperatures, sleep and reproductive factors is accumulating, but additional research is needed to confirm the causative role of these factors in human obesity. However, the role of certain pharmaceuticals and smoking cessation in development of human obesity is clear. Practice points for consideration and future research needed are highlighted for each factor.

The effectiveness of breakfast recommendations on weight loss: a randomized controlled trial

BACKGROUND

Breakfast is associated with lower body weight in observational studies. Public health authorities commonly recommend breakfast consumption to reduce obesity, but the effectiveness of adopting these recommendations for reducing body weight is unknown.

OBJECTIVE

We tested the relative effectiveness of a recommendation to eat or skip breakfast on weight loss in adults trying to lose weight in a free-living setting.

DESIGN

We conducted a multisite, 16-wk, 3-parallel-arm randomized controlled trial in otherwise healthy overweight and obese adults [body mass index (in kg/m²) between 25 and 40] aged 20-65 y. Our primary outcome was weight change. We compared weight change in a control group with weight loss in experimental groups told to eat breakfast or to skip breakfast [no breakfast (NB)]. Randomization was stratified by prerandomization breakfast eating habits. A total of 309 participants were randomly assigned.

RESULTS

A total of 283 of the 309 participants who were randomly assigned completed the intervention. Treatment assignment did not have a significant effect on weight loss, and there was no interaction between initial breakfast eating status and treatment. Among skippers, mean (±SD) baseline weight-, age-, sex-, site-, and race-adjusted weight changes were -0.71 ± 1.16, -0.76 ± 1.26, and -0.61 ± 1.18 kg for the control, breakfast, and NB groups, respectively. Among breakfast consumers, mean (±SD) baseline weight-, age-, sex-, site-, and race-adjusted weight changes were -0.53 ± 1.16, -0.59 ± 1.06, and -0.71 ± 1.17 kg for the control, breakfast, and NB groups, respectively. Self-reported compliance with the recommendation was 93.6% for the breakfast group and 92.4% for the NB group.

CONCLUSIONS

A recommendation to eat or skip breakfast for weight loss was effective at changing self-reported breakfast eating habits, but contrary to widely espoused views this had no discernable effect on weight loss in free-living adults who were attempting to lose weight.

Methodological framework: discovering foods or nutrients with a causative influence on body weight in free-living settings

A significant increase in food availability has been implicated in the worldwide obesity epidemic, and there is significant interest in understanding if specific foods may contribute to weight gain or aid in weight loss. Many foods have been studied in controlled laboratory studies or short-term studies, and these findings are often the basis for food-based public health recommendations to reduce or prevent obesity. Unfortunately, often these findings are not applicable to free-living settings where many interacting factors influence energy balance and body weight. Therefore, a proposed set of evidence criteria for making a food-based public health recommendation to reduce or prevent obesity is outlined and discussed herein, to serve as a basis for future committee or panel discussion and formalization. Using these criteria as a basis for making strong evidence-based recommendations will improve the state of science and policy in this area.

Propagation of obesity across generations: the roles of differential realized fertility and assortative mating by body mass index

BACKGROUND/AIMS

To quantify the extent to which the increase in obesity observed across recent generations of the American population is associated with the individual or combined effects of assortative mating (AM) for body mass index (BMI) and differential realized fertility by BMI.

METHODS

A Monte Carlo framework is formed and informed using data collected from the National Longitudinal Survey of Youth (NLSY). The model has 2 portions: one that generates childbirth events on an annual basis and another that produces a BMI for each child. Once the model is informed using the data, a reference distribution of offspring BMIs is simulated. We quantify the effects of our factors of interest by removing them from the model and comparing the resulting offspring BMI distributions with that of the baseline scenario.

RESULTS

An association between maternal BMI and number of offspring is evidenced in the NLSY data as well as the presence of AM. These 2 factors combined are associated with an increased mean BMI (+0.067, 95% CI: 0.056; 0.078), an increased BMI variance (+0.578, 95% CI: 0.418; 0.736) and an increased prevalence of obesity (RR 1.032, 95% CI: 1.023; 1.041) and BMIs >40 (RR 1.083, 95% CI: 1.053; 1.118) among offspring.

CONCLUSION

Our investigation suggests that both differential realized fertility and AM by BMI appear to play a role in the increasing prevalence of obesity in America.

Genome-wide meta-analysis of observational studies shows common genetic variants associated with macronutrient intake

BACKGROUND

Macronutrient intake varies substantially between individuals, and there is evidence that this variation is partly accounted for by genetic variants.

OBJECTIVE

The objective of the study was to identify common genetic variants that are associated with macronutrient intake.

DESIGN

We performed 2-stage genome-wide association (GWA) meta-analysis of macronutrient intake in populations of European descent. Macronutrients were assessed by using food-frequency questionnaires and analyzed as percentages of total energy consumption from total fat, protein, and carbohydrate. From the discovery GWA (n = 38,360), 35 independent loci associated with macronutrient intake at P < 5 × 10(-6) were identified and taken forward to replication in 3 additional cohorts (n = 33,533) from the DietGen Consortium. For one locus, fat mass obesity-associated protein (FTO), cohorts with Illumina MetaboChip genotype data (n = 7724) provided additional replication data.

RESULTS

A variant in the chromosome 19 locus (rs838145) was associated with higher carbohydrate (β ± SE: 0.25 ± 0.04%; P = 1.68 × 10(-8)) and lower fat (β ± SE: -0.21 ± 0.04%; P = 1.57 × 10(-9)) consumption. A candidate gene in this region, fibroblast growth factor 21 (FGF21), encodes a fibroblast growth factor involved in glucose and lipid metabolism. The variants in this locus were associated with circulating FGF21 protein concentrations (P < 0.05) but not mRNA concentrations in blood or brain. The body mass index (BMI)-increasing allele of the FTO variant (rs1421085) was associated with higher protein intake (β ± SE: 0.10 ± 0.02%; P = 9.96 × 10(-10)), independent of BMI (after adjustment for BMI, β ± SE: 0.08 ± 0.02%; P = 3.15 × 10(-7)).

CONCLUSION

Our results indicate that variants in genes involved in nutrient metabolism and obesity are associated with macronutrient consumption in humans. Trials related to this study were registered at clinicaltrials.gov as NCT00005131 (Atherosclerosis Risk in Communities), NCT00005133 (Cardiovascular Health Study), NCT00005136 (Family Heart Study), NCT00005121 (Framingham Heart Study), NCT00083369 (Genetic and Environmental Determinants of Triglycerides), NCT01331512 (InCHIANTI Study), and NCT00005487 (Multi-Ethnic Study of Atherosclerosis).

Hunger in the absence of caloric restriction improves cognition and attenuates Alzheimer's disease pathology in a mouse model

It has been shown that caloric restriction (CR) delays aging and possibly delays the development of Alzheimer's disease (AD). We conjecture that the mechanism may involve interoceptive cues, rather than reduced energy intake per se. We determined that hunger alone, induced by a ghrelin agonist, reduces AD pathology and improves cognition in the APP-SwDI mouse model of AD. Long-term treatment with a ghrelin agonist was sufficient to improve the performance in the water maze. The treatment also reduced levels of amyloid beta (Aβ) and inflammation (microglial activation) at 6 months of age compared to the control group, similar to the effect of CR. Thus, a hunger-inducing drug attenuates AD pathology, in the absence of CR, and the neuroendocrine aspects of hunger also prevent age-related cognitive decline.

Doxycycline-regulated 3T3-L1 preadipocyte cell line with inducible, stable expression of adenoviral E4orf1 gene: a cell model to study insulin-independent glucose disposal

Impaired glycemic control and excessive adiposity are major risk factors for Type 2 Diabetes mellitus. In rodent models, Ad36, a human adenovirus, improves glycemic control, independent of dietary fat intake or adiposity. It is impractical to use Ad36 for therapeutic action. Instead, we identified that E4orf1 protein of Ad36, mediates its anti-hyperglycemic action independent of insulin signaling. To further evaluate the therapeutic potential of E4orf1 to improve glycemic control, we established a stable 3T3-L1 cell system in which E4orf1 expression can be regulated. The development and characterization of this cell line is described here. Full-length adenoviral-36 E4orf1 cDNA obtained by PCR was cloned into a tetracycline responsive element containing vector (pTRE-Tight-E4orf1). Upon screening dozens of pTRE-Tight-E4orf1 clones, we identified the one with the highest expression of E4orf1 in response to doxycycline treatment. Furthermore, using this inducible system we characterized the ability of E4orf1 to improve glucose disposal in a time dependent manner. This stable cell line offers a valuable resource to carefully study the novel signaling pathways E4orf1 uses to enhance cellular glucose disposal independent of insulin.

E4orf1 improves lipid and glucose metabolism in hepatocytes: a template to improve steatosis & hyperglycemia

Hepatic steatosis often accompanies obesity and insulin resistance. The cornerstones of steatosis treatment include reducing body weight and dietary fat intake, which are marginally successful over the long term. Ad36, a human adenovirus, may offer a template to overcome these limitations. In vitro and in vivo studies collectively indicate that via its E4orf1 protein, Ad36 improves hyperglycemia, and attenuates hepatic steatosis, despite a high fat diet and without weight loss. Considering that hepatic insulin sensitivity, or the synthesis, oxidation, or export of fatty acid by hepatocytes are the key determinant of hepatic lipid storage, we determined the role of E4orf1 protein in modulating these physiological pathways. For this study, HepG2 cells, or mouse primary hepatocytes were transfected with E4orf1 or the null vector. Glucose output by hepatocytes was determined under gluconeogenic conditions (cAMP and dexamethasone, or glucagon exposure). Also, de-novo lipogenesis, palmitate oxidation, and lipid export as determined by apoB secretion were measured 48 h post transfection. Results show that compared to null vector transfected cells, E4orf1 significantly reduced glucose output in basal and gluconeogenic conditions. E4orf1 reduced de-novo lipogenesis by about 35%, increased complete fatty acid oxidation 2-fold (p<0.0001), and apoB secretion 1.5 fold(p<0.003). Response of key signaling molecules to E4orf1 transfection was in agreement with these findings. Thus, E4orf1 offers a valuable template to exogenously modulate hepatic glucose and lipid metabolism. Elucidating the underlying molecular mechanism may help develop therapeutic approaches for treating diabetes or non-alcoholic fatty liver disease(NAFLD).

Submitted for your consideration: potential advantages of a novel clinical trial design and initial patient reaction

In many circumstances, individuals do not respond identically to the same treatment. This phenomenon, which is called treatment response heterogeneity (TRH), appears to be present in treatments for many conditions, including obesity. Estimating the total amount of TRH, predicting an individual's response, and identifying the mediators of TRH are of interest to biomedical researchers. Clinical investigators and physicians commonly postulate that some of these mediators could be genetic. Current designs can estimate TRH as a function of specific, measurable observed factors; however, they cannot estimate the total amount of TRH, nor provide reliable estimates of individual persons' responses. We propose a new repeated randomizations design (RRD), which can be conceived as a generalization of the Balaam design, that would allow estimates of that variability and facilitate estimation of the total amount of TRH, prediction of an individual's response, and identification of the mediators of TRH. In a pilot study, we asked 118 subjects entering a weight loss trial for their opinion of the RRD, and they stated a preference for the RRD over the conventional two-arm parallel groups design. Research is needed as to how the RRD will work in practice and its relative statistical properties, and we invite dialog about it.

Insulin receptor-independent upregulation of cellular glucose uptake

BACKGROUND

Cellular glucose uptake can be enhanced by up-regulating Ras signaling in either insulin dependent or independent manner. In presence of insulin and intact insulin signaling, Ras plays a negligible role in glucose uptake. Conversely, when insulin signaling is impaired in obesity or diabetes, the insulin-independent Ras pathway may be valuable for enhancing glucose disposal. We previously reported that Ad36, a human adenovirus, enhances cellular glucose uptake by up-regulating the Ras/Glut4 pathway. Here, we investigated if Ad36-up-regulated Ras via the insulin-independent pathway, to enhance glucose uptake. Furthermore, uncontrolled up-regulation of Ras is linked with oncogenic cell transformation, if the tumor suppressor gene p53 is also down regulated. Hence, we determined if up-regulation of Ras by Ad36 would induce oncogenic cell transformation. Finally, we determined the relevance of Ad36 to insulin resistance in humans.

METHODS

Insulin receptor (IR) was knocked down with siRNA in 3T3-L1 adipocytes, to determine if Ad36 increases the Ras/Glut4 pathway and glucose uptake without IR-signaling. Next, the effects of Ad36 on cell transformation and p53 abundance were determined. Finally, overweight or obese women were screened for seropositivty to Ad36, as an indicator of natural Ad36 infection. Associations of Ad36 infection with adiposity and C-Reactive proteins (CRP) –two key markers of insulin resistance, and with glucose disposal, were determined.

RESULTS

Unaffected by IR knock-down, Ad36 significantly increased the Ras pathway, Glut4 translocation, and glucose uptake in 3T3-L1 adipocytes. Despite Ras up-regulation, Ad36 did not transform 3T3-L1 cells. This may be because Ad36 significantly increased p53 protein in 3T3-L1 cells or mice adipose tissue. Ad36 seropositivity was associated with greater adiposity and CRP levels, yet a significantly higher systemic glucose disposal rate.

CONCLUSIONS

Overall, the study offers Ras/Glut4 pathway as an alternate to enhance glucose disposal when insulin signaling is impaired, and, importantly, provides Ad36 as a tool to understand the modulation of that pathway.

Recent advances in understanding and mitigating adipogenic and metabolic effects of antipsychotic drugs

Although offering many benefits for several psychiatric disorders, antipsychotic drugs (APDs) as a class have a major liability in their tendency to promote adiposity, obesity, and metabolic dysregulation in an already metabolically vulnerable population. The past decade has witnessed substantial research aimed at investigating the mechanisms of these adverse effects and mitigating them. On July 11 and 12, 2011, with support from 2 NIH institutes, leading experts convened to discuss current research findings and to consider future research strategies. Five areas where significant advances are being made emerged from the conference: (1) methodological issues in the study of APD effects; (2) unique characteristics and needs of pediatric patients; (3) genetic components underlying susceptibility to APD-induced metabolic effects; (4) APD effects on weight gain and adiposity in relation to their acute effects on glucose regulation and diabetes risk; and (5) the utility of behavioral, dietary, and pharmacological interventions in mitigating APD-induced metabolic side effects. This paper summarizes the major conclusions and important supporting data from the meeting.

PPARgamma-independent increase in glucose uptake and adiponectin abundance in fat cells

Although thiazolidinediones (TZD) effectively improve hyperglycemia and increase adiponectin, a proinsulin-sensitizing adipokine, they also increase adipogenesis via peroxisome proliferator-activated receptor (PPAR)γ induction, which may be undesirable. Recent safety concerns about some TZD have prompted the search for next generation agents that can enhance glycemic control and adiponectin independent of PPARγ or adipogenesis. Reminiscent of TZD action, a human adenovirus, adenovirus 36 (Ad36), up-regulates PPARγ, induces adipogenesis, and improves systemic glycemic control in vivo. We determined whether this effect of Ad36 requires PPARγ and/or adipogenesis. Glucose uptake and relevant cell signaling were determined in mock-infected or human adenoviruses Ad36 or Ad2-infected cell types under the following conditions: 1) undifferentiated human-adipose-tissue-derived stem cells (hASC), 2) hASC differentiated as adipocytes, 3) hASC in presence or absence of a PPARγ inhibitor, 4) NIH/3T3 that have impaired PPARγ expression, and 5) PPARγ-knockout mouse embryonic fibroblasts. Mouse embryonic fibroblasts with intact PPARγ served as a positive control. Additionally, to determine natural Ad36 infection, human sera were screened for Ad36 antibodies. In undifferentiated or differentiated hASC, or despite the inhibition, down-regulation, or the absence of PPARγ, Ad36 significantly enhanced glucose uptake and PPARγ, adiponectin, glucose transporter 4, and glucose transporter 1 protein abundance, compared with mock or Ad2-infected cells. This indicated that Ad36 up-regulates glucose uptake and adiponectin secretion independent of adipogenesis or without recruiting PPARγ. In humans, natural Ad36 infection predicted greater adiponectin levels, suggesting a human relevance of these effects. In conclusion, Ad36 provides a novel template to metabolically remodel human adipose tissue to enhance glycemic control without the concomitant increase in adiposity or PPARγ induction associated with TZD actions.

E4orf1: a novel ligand that improves glucose disposal in cell culture

Reducing dietary fat intake and excess adiposity, the cornerstones of behavioral treatment of insulin resistance (IR), are marginally successful over the long term. Ad36, a human adenovirus, offers a template to improve IR, independent of dietary fat intake or adiposity. Ad36 increases cellular glucose uptake via a Ras-mediated activation of phosphatidyl inositol 3-kinase(PI3K), and improves hyperglycemia in mice, despite a high-fat diet and without reducing adiposity. Ex-vivo studies suggest that Ad36 improves hyperglycemia in mice by increasing glucose uptake by adipose tissue and skeletal muscle, and by reducing hepatic glucose output. It is impractical to use Ad36 for therapeutic action. Instead, we investigated if the E4orf1 protein of Ad36, mediates its anti-hyperglycemic action. Such a candidate protein may offer an attractive template for therapeutic development. Experiment-1 determined that Ad36 'requires' E4orf1 protein to up-regulate cellular glucose uptake. Ad36 significantly increased glucose uptake in 3T3-L1 preadipocytes, which was abrogated by knocking down E4orf1 with siRNA. Experiment-2 identified E4orf1 as 'sufficient' to up-regulate glucose uptake. 3T3-L1 cells that inducibly express E4orf1, increased glucose uptake in an induction-dependent manner, compared to null vector control cells. E4orf1 up-regulated PI3K pathway and increased abundance of Ras--the obligatory molecule in Ad36-induced glucose uptake. Experiment-3: Signaling studies of cells transiently transfected with E4orf1 or a null vector, revealed that E4orf1 may activate Ras/PI3K pathway by binding to Drosophila discs-large (Dlg1) protein. E4orf1 activated total Ras and, particularly the H-Ras isoform. By mutating the PDZ domain binding motif (PBM) of E4orf1, Experiment-4 showed that E4orf1 requires its PBM to increase Ras activation or glucose uptake. Experiment-5: In-vitro, a transient transfection by E4orf1 significantly increased glucose uptake in preadipocytes, adipocytes, or myoblasts, and reduced glucose output by hepatocytes. Thus, the highly attractive anti-hyperglycemic effect of Ad36 is mirrored by E4orf1 protein, which may offer a novel ligand to develop anti-hyperglycemic drugs.

Template to improve glycemic control without reducing adiposity or dietary fat

Drugs that improve chronic hyperglycemia independently of insulin signaling or reduction of adiposity or dietary fat intake may be highly desirable. Ad36, a human adenovirus, promotes glucose uptake in vitro independently of adiposity or proximal insulin signaling. We tested the ability of Ad36 to improve glycemic control in vivo and determined if the natural Ad36 infection in humans is associated with better glycemic control. C57BL/6J mice fed a chow diet or made diabetic with a high-fat (HF) diet were mock infected or infected with Ad36 or adenovirus Ad2 as a control for infection. Postinfection (pi), systemic glycemic control, hepatic lipid content, and cell signaling in tissues pertinent to glucose metabolism were determined. Next, sera of 1,507 adults and children were screened for Ad36 antibodies as an indicator of past natural infection. In chow-fed mice, Ad36 significantly improved glycemic control for 12 wk pi. In HF-fed mice, Ad36 improved glycemic control and hepatic steatosis up to 20 wk pi. In adipose tissue (AT), skeletal muscle (SM), and liver, Ad36 upregulated distal insulin signaling without recruiting the proximal insulin signaling. Cell signaling suggested that Ad36 increases AT and SM glucose uptake and reduces hepatic glucose release. In humans, Ad36 infection predicted better glycemic control and lower hepatic lipid content independently of age, sex, or adiposity. We conclude that Ad36 offers a novel tool to understand the pathways to improve hyperglycemia and hepatic steatosis independently of proximal insulin signaling, and despite a HF diet. This metabolic engineering by Ad36 appears relevant to humans for developing more practical and effective antidiabetic approaches.