Racial and etiopathologic dichotomies in insulin hypersecretion and resistance in obese children

Aging and "Age-Related" Diseases - What Is the Relation?

The study explores the intricate relationship between aging and the development of noncommunicable diseases [NCDs], focusing on whether these diseases are inevitable consequences of aging or primarily driven by lifestyle factors. By examining epidemiological data, particularly from hunter-gatherer societies, the study highlights that many NCDs prevalent in modern populations are rare in these societies, suggesting a significant influence of lifestyle choices. It delves into the mechanisms through which poor diet, smoking, and other lifestyle factors contribute to systemic physiological imbalances, characterized by oxidative stress, insulin resistance and hyperinsulinemia, and dysregulation of the sympathetic nervous system, the renin-angiotensin-aldosterone system, and the immune system. The interplay between this pattern and individual factors such as genetic susceptibility, biological variability, epigenetic changes and the microbiome is proposed to play a crucial role in the development of a range of age-related NCDs. Modified biomolecules such as oxysterols and advanced glycation end products also contribute to their development. Specific diseases such as benign prostatic hyperplasia, Parkinson's disease, glaucoma and osteoarthritis are analyzed to illustrate these mechanisms. The study concludes that while aging contributes to the risk of NCDs, lifestyle factors play a crucial role, offering potential avenues for prevention and intervention through healthier living practices. One possible approach could be to try to restore the physiological balance, e.g. through dietary measures [e.g. Mediterranean diet, Okinawan diet or Paleolithic diet] in conjunction with [a combination of] pharmacological interventions and other lifestyle changes.

Hyperinsulinemia and Its Pivotal Role in Aging, Obesity, Type 2 Diabetes, Cardiovascular Disease and Cancer

For many years, the dogma has been that insulin resistance precedes the development of hyperinsulinemia. However, recent data suggest a reverse order and place hyperinsulinemia mechanistically upstream of insulin resistance. Genetic background, consumption of the “modern” Western diet and over-nutrition may increase insulin secretion, decrease insulin pulses and/or reduce hepatic insulin clearance, thereby causing hyperinsulinemia. Hyperinsulinemia disturbs the balance of the insulin–GH–IGF axis and shifts the insulin : GH ratio towards insulin and away from GH. This insulin–GH shift promotes energy storage and lipid synthesis and hinders lipid breakdown, resulting in obesity due to higher fat accumulation and lower energy expenditure. Hyperinsulinemia is an important etiological factor in the development of metabolic syndrome, type 2 diabetes, cardiovascular disease, cancer and premature mortality. It has been further hypothesized that nutritionally driven insulin exposure controls the rate of mammalian aging. Interventions that normalize/reduce plasma insulin concentrations might play a key role in the prevention and treatment of age-related decline, obesity, type 2 diabetes, cardiovascular disease and cancer. Caloric restriction, increasing hepatic insulin clearance and maximizing insulin sensitivity are at present the three main strategies available for managing hyperinsulinemia. This may slow down age-related physiological decline and prevent age-related diseases. Drugs that reduce insulin (hyper) secretion, normalize pulsatile insulin secretion and/or increase hepatic insulin clearance may also have the potential to prevent or delay the progression of hyperinsulinemia-mediated diseases. Future research should focus on new strategies to minimize hyperinsulinemia at an early stage, aiming at successfully preventing and treating hyperinsulinemia-mediated diseases.

Development of Obesity: The Driver and the Passenger

Obesity has reached epidemic proportions and is one of the greatest challenges for public health in the twenty-first century. The macronutrient composition of diets, in particular the amount and ratio of carbohydrates, fat and protein, have received considerable attention in recent decades due to its potential relevance to the development of obesity and weight loss. The effects of various macronutrients on body weight regulation are still under debate. High-carbohydrate diets, and particularly high-fat diets, have been blamed for the increase in the prevalence of obesity. This paper shows that neither fat nor carbohydrates are fattening per se. Mixed diets with substantial amounts of fat and high-glycemic carbohydrates, like current WDs, are required to promote weight gain and obesity. High-glycemic carbohydrates are the active partner (the "driver"), which promotes fat storage through its insulinogenic effect, while fat is the passive partner (the "passenger") on the way to obesity. Elevated insulin levels (postprandial, but more importantly due to hypersecretion and hyperinsulinemia) promote fat storage and play a key role in obesogenesis and the obesity epidemic. Furthermore, mixed diets high in high-glycemic carbohydrates and fat promote fetal programming, with long-term adverse impacts on the offspring, including insulin hypersecretion, (childhood) obesity and metabolic diseases. Maternal obesity and high weight gain during pregnancy have also been linked to deleterious effects on fetal programming. As the global obesity epidemic increasingly affects women of reproductive age, a significant percentage of fetuses will experience fetal programming with a tendency towards obesity - a self-reinforcing process that further fuels the epidemic. A change in lifestyle and diet composition is needed to prevent or limit the development of obesity and related diseases.

β-Cell function in obese children and adolescents with metabolic syndrome compared to isolated obesity

OBJECTIVE

To evaluate β-cell function in obese children and adolescents meeting clinical criteria for isolated obesity (iOB), isolated components of dysmetabolism (cMD), or metabolic syndrome (MS), and in obese children and adolescents with normal glucose tolerance (NGT), impaired glucose regulation (IGR), or type 2 diabetes (T2DM).

STUDY DESIGN

We undertook a prospective study of Han Chinese children and adolescents aged 8-16 years (median 11 ± 1.4) seen in an obesity clinic between May 2013 and 2018. Patients were classified as iOB (53), cMD (139), and MS (139) groups based on clinical criteria. The same patients were also classified as NGT (212), IGR (111), or T2DM (8) based on results of an oral glucose tolerance test (OGTT). The MS patients were classified as NGT [MS](59) and IGR [MS](72) for the further study. All participants also completed a mixed-meal tolerance test (MMTT).

RESULTS

Compared with the iOB group, the MS group had significantly higher area under the curve of C-peptide up to the 2 hours (AUC CP) (P = .03) and peak C-peptide (P = .03), adjusted for BMI, age and Tanner stage, on MMTT. However, there was no difference in the insulinogenic index (ΔI30/ΔG30) or oral disposition index (oDI) derived from the OGTT among the three groups. However, 52% of participants with MS had IGR, compared to 28% in the cMD group. Compared with the NGT group, the individuals with IGR had significantly lower ΔI30/ΔG30 (P = .001) and oDI (P < .001). Compared with the iOB group, the NGT[MS] had significantly higher AUC CP (P = .004), peak C-peptide (P = .004) and ΔI30/ΔG30 (P = .007) adjusted for age, but no difference in oDI. Compared with the NGT[MS], the IGR[MS] had significantly lower ΔI30/ΔG30 (P = .005) and oDI (P < .001), but the AUC CP and peak C-peptide had no difference.

CONCLUSION

Although the MS youth have β-cell hyperfunction as a whole, β-cell dysfunction is present in the early stages of dysmetabolism in obese youth with cMD or MS and worsened across the spectrum from iOB to cMD and MS, contributing to development of T2DM.

How Western Diet And Lifestyle Drive The Pandemic Of Obesity And Civilization Diseases

Westernized populations are plagued by a plethora of chronic non-infectious degenerative diseases, termed as "civilization diseases", like obesity, diabetes, cardiovascular diseases, cancer, autoimmune diseases, Alzheimer's disease and many more, diseases which are rare or virtually absent in hunter-gatherers and other non-westernized populations. There is a growing awareness that the cause of this amazing discrepancy lies in the profound changes in diet and lifestyle during recent human history. This paper shows that the transition from Paleolithic nutrition to Western diets, along with lack of corresponding genetic adaptations, cause significant distortions of the fine-tuned metabolism that has evolved over millions of years of human evolution in adaptation to Paleolithic diets. With the increasing spread of Western diet and lifestyle worldwide, overweight and civilization diseases are also rapidly increasing in developing countries. It is suggested that the diet-related key changes in the developmental process include an increased production of reactive oxygen species and oxidative stress, development of hyperinsulinemia and insulin resistance, low-grade inflammation and an abnormal activation of the sympathetic nervous system and the renin-angiotensin system, all of which play pivotal roles in the development of diseases of civilization. In addition, diet-related epigenetic changes and fetal programming play an important role. The suggested pathomechanism is also able to explain the well-known but not completely understood close relationship between obesity and the wide range of comorbidities, like type 2 diabetes mellitus, cardiovascular disease, etc., as diseases of the same etiopathology. Changing our lifestyle in accordance with our genetic makeup, including diet and physical activity, may help prevent or limit the development of these diseases.

The incretin effect in obese adolescents with and without type 2 diabetes: impaired or intact?

The incretin effect reflects the actions of enteral stimuli to promote prandial insulin secretion. Impairment of this measure has been proposed as an early marker of β-cell dysfunction and described in T2D, IGT, and even obesity without IGT. We sought to determine the effects of obesity and diabetes on the incretin effect in young subjects with short exposures to metabolic abnormalities and a few other confounding medical conditions. Subjects with T2D (n = 10; 18.0 ± 0.4 yr) or NGT, either obese (n = 11; 17.7 ± 0.4 yr) or lean (n = 8; 26.5 ± 2.3 yr), had OGTT and iso-iv. The incretin effect was calculated as the difference in insulin secretion during these tests and was decreased ∼50% in both the NGT-Ob and T2D subjects relative to the NGT-Ln group. The T2D group had impaired glucose tolerance and insulin secretion during the OGTT, whereas the lean and obese NGT subjects had comparable glucose excursions and β-cell function. During the iso-iv test, the NGT-Ob subjects had significantly greater insulin secretion than the NGT-Ln and T2D groups. These findings demonstrate that in young subjects with early, well-controlled T2D the incretin effect is reduced, similar to what has been described in diabetic adults. The lower incretin effect calculated for the obese subjects with NGT is driven by a disproportionately greater insulin response to iv glucose and does not affect postprandial glucose regulation. These findings confirm that the incretin effect is an early marker of impaired insulin secretion in persons with abnormal glucose tolerance but suggest that in obese subjects with NGT the incretin effect calculation can be confounded by exaggerated insulin secretion to iv glucose.

Hypothalamic obesity after craniopharyngioma: mechanisms, diagnosis, and treatment

Obesity is a common complication after craniopharyngioma therapy, occurring in up to 75% of survivors. Its weight gain is unlike that of normal obesity, in that it occurs even with caloric restriction, and attempts at lifestyle modification are useless to prevent or treat the obesity. The pathogenesis of this condition involves the inability to transduce afferent hormonal signals of adiposity, in effect mimicking a state of CNS starvation. Efferent sympathetic activity drops, resulting in malaise and reduced energy expenditure, and vagal activity increases, resulting in increased insulin secretion and adipogenesis. Lifestyle intervention is essentially useless in this syndrome, termed "hypothalamic obesity." Pharmacologic treatment is also difficult, consisting of adrenergics to mimic sympathetic activity, or suppression of insulin secretion with octreotide, or both. Recently, bariatric surgery (Roux-en-Y gastric bypass, laparoscopic gastric banding, truncal vagotomy) have also been attempted with variable results. Early and intensive management is required to mitigate the obesity and its negative consequences.

Ethnicity, obesity and the metabolic syndrome: implications on assessing risk and targeting intervention

Pediatric obesity threatens the future health of a growing number of children worldwide. An added challenge in identifying the patients at greatest need for intervention due to their elevated risk for future disease is that pediatric obesity and the associated metabolic syndrome manifest differently among different ethnic groups. African-Americans and Hispanics are more likely to exhibit obesity and insulin resistance and are at a higher risk for developing Type 2 diabetes. Nevertheless, using current criteria, African-American adolescents are much less likely to be diagnosed with metabolic syndrome, largely owing to lower rates of dyslipidemia. Further development is needed in ethnicity-inclusive means of risk identification among adolescents to accurately target treatment toward children at highest risk for future disease and to motivate adolescent patients and their families towards lifestyle improvement. Effective targeting and intensive treatment efforts may help in avoiding future sequelae of obesity among all ethnicities.

Population analysis of ethnicity and first-phase insulin release

OBJECTIVE

A mechanistic, physiologically-based pharmacokinetic (PK/PD) model was developed to describe the biphasic insulin release and evaluate the racial effects on the glucose-insulin kinetics in response to intravenous glucose.

METHODS

Fifteen African-American and 18 Caucasian children and adolescents between 8 and 18 years of age were enrolled in the study. Intravenous bolus of glucose (250 mg/kg) was administered and blood samples collected at frequent intervals for three hours following the glucose injection. A nonlinear mixed-effect population kinetic analysis with covariate structure was performed using Monolix.

RESULTS

A significantly higher initial insulin secretion from a readily releasable pool, which is responsible for the first-phase insulin secretion, was detected in African-Americans compared to Caucasians (p<0.05).

CONCLUSIONS

The proposed kinetic model is able to describe the glucose-stimulated insulin response, account for the first-phase insulin release and identify a racially-based pharmacokinetic difference in insulin's biphasic secretion behavior. It is hypothesized that the first-phase insulin component may play an important role in the development of type 2 diabetes. The proposed mechanistic model provides a quantitative analysis of the biphasic insulin release that may be useful in the early detection of diabetes.

Intraperitoneal fat and insulin resistance in obese adolescents

Obesity is epidemic among adolescents in the United States. We sought to analyze the anthropometric measures of adiposity and fasting indices of insulin resistance, including insulin-like growth factor-binding protein-1 (IGFBP-1), and to provide a clinical estimate of intraperitoneal (IP) fat in obese adolescents (BMI > or =95th percentile), between ages 13 and 17 years. Subjects had baseline testing to determine eligibility for a subsequent randomized, placebo-controlled trial of metformin XR therapy. Anthropometry and dual-energy X-ray absorptiometry (DXA) were used to quantify total body fat while abdominal computed tomography (CT) was used to measure IP (CT-IP) and subcutaneous (CT-SQ) fat. Using anthropometry and fasting laboratory data, we constructed regression models for both CT-IP and CT-SQ. A total of 92 subjects, 33 males, were evaluated. Of the 92 subjects, 19 were black. Fasting insulin concentrations were highly associated with other measures of insulin resistance. Median percent body fat across all subjects, as measured by DXA, was 41%. Using CT measures, 67% of abdominal cross-sectional area was fat, 14% of which was IP fat. In multiple regression analysis, waist circumference (WC) and BMI, jointly and independently, were strongly associated with both CT-IP and CT-SQ fat. BMI and WC explained 62% of variance of CT-SQ fat, but only 26% of variance of CT-IP fat. Adding triglyceride:high-density lipoprotein (TG:HDL) ratio and IGFBP-1 (among nonblacks) to the regression model increased the explained variance for estimating CT-IP fat to 45%. When evaluating the metabolic morbidity of an obese adolescent, a model using fasting IGFBP-1, TG:HDL, BMI, and WC may be worthwhile as an estimate of IP fat.

A clinic-based lifestyle intervention for pediatric obesity: efficacy and behavioral and biochemical predictors of response

AIM

To examine efficacy and predictors of response to a lifestyle intervention for obese youth.

METHODS

Retrospective chart review of 214 children and adolescents aged 8-19 years. Linear regression identified baseline predictors of response (delta BMI z-score) at first and ultimate follow-up visits.

RESULTS

Mean delta BMI z-score from baseline was -0.04 (p < 0.001) at first follow-up and -0.09 (p < 0.001) at ultimate follow-up (median time 10 mo) among 156 children and adolescents. Higher baseline BMI z-score predicted poor response at first and ultimate follow-up, explaining 10% of variance in response. Fasting insulin explained 6% of response variance at first follow-up. delta BMI z-score at the first visit along with baseline BMI z-score explained up to 50% of variance in response at ultimate visit.

CONCLUSION

Clinic-based interventions improve weight status. Baseline variables predict only a small proportion of response; response at the first visit is a more meaningful tool to guide clinical decisions.

Use of somatostatin analogues in obesity

Obesity is a condition that results from dysregulation of energy balance. Insulin, a component of the efferent pathway of the energy-regulatory circuit, promotes storage of energy substrates in adipose tissue and is, therefore, a potential target for pharmacotherapy. Somatostatin and its analogues (octreotide and lanreotide) bind to somatostatin subtype 5 receptors on the beta-cell membrane, which limits insulin release and, consequently, may decrease adipogenesis. Somatostatin and its analogues have been used in trials in patients with paediatric hypothalamic obesity. These children have hypothalamic dysfunction, mainly due to brain tumours such as craniopharyngiomas, which are thought to generate increased vagal output, leading to hyperinsulinaemia and weight gain. Two small trials, each of 6 months' duration, in children with paediatric hypothalamic obesity showed either a minimal weight loss or stabilization of bodyweight. In children with Prader-Willi syndrome, the most common genetic hypothalamic disorder associated with hyperphagia, hyperghrelinaemia, massive obesity and other endocrine disturbances, somatostatin failed to control hyperphagia and weight gain in a small number of patients, although it lowered the levels of the anorexigenic hormone ghrelin. Long-acting release octreotide was recently used in hyperinsulinaemic obese adults without cranial pathology. Insulin suppression was associated with small decreases in the body mass indexes of obese subjects receiving the higher dosages of the drug, with an acceptable safety profile, similar to that in previous studies. In conclusion, somatostatin and its analogues, by suppressing beta-cell insulin secretion, can retard weight gain in children with hypothalamic obesity and induce a small amount of weight loss in some adults with hyperinsulinaemic obesity.

Baseline correlates of insulin resistance in inner city high-BMI African-American children

To characterize the influence of diet-, physical activity-, and self-esteem-related factors on insulin resistance in 8- 10-year-old African-American (AA) children with BMI greater than the 85th percentile who were screened to participate in a community-based type 2 diabetes mellitus (T2DM) prevention trial. In 165 subjects, fasting glucose- and insulin-derived values for homeostasis model assessment of insulin resistance (HOMA-IR) assessed insulin resistance. Body fatness was calculated following bioelectrical impedance analysis, and fitness was measured using laps from a 20-m shuttle run. Child questionnaires assessed physical activity, dietary habits, and self-esteem. Pubertal staging was assessed using serum levels of sex hormones. Parent questionnaires assessed family demographics, family health, and family food and physical activity habits. Girls had significantly higher percent body fat but similar anthropometric measures compared with boys, whereas boys spent more time in high-intensity activities than girls. Scores for self-perceived behavior were higher for girls than for boys; and girls desired a more slender body. Girls had significantly higher insulin resistance (HOMA-IR), compared with boys (P < 0.01). Adjusting for age, sex, pubertal stage, socioeconomic index (SE index), and family history of diabetes, multivariate regression analysis showed that children with higher waist circumference (WC) (P < 0.001) and lower Harter's scholastic competence (SC) scale (P = 0.044) had higher insulin resistance. WC and selected self-esteem parameters predicted insulin resistance in high-BMI AA children. The risk of T2DM may be reduced in these children by targeting these factors.

Impaired endothelial function in healthy African-American adolescents compared with Caucasians

OBJECTIVE

To determine whether African-American adolescents have endothelial dysfunction compared with Caucasians and whether differences are a result of differences in insulin sensitivity calculated from total glucose (S(I)) or secretion.

STUDY DESIGN

Thirty-three Caucasian (13.6 +/- 2.6 years of age; body mass index [BMI] 21.6 +/- 4.4 kg/m2 mean +/- SD) and 25 African-American (13.3 +/- 2.9 years of age; BMI 24.0 +/- 4.4 kg/m2) adolescents were studied. Forearm blood flow (FBF; plethysmography) was measured before and after 5 minutes of arterial occlusion. S(I) and acute insulin response to glucose (AIRG) were measured using intravenous glucose tolerance tests and minimal modeling.

RESULTS

Baseline FBF did not differ between races. Postocclusion FBF was lower in African-Americans (17.2 +/- 1.2 vs 22.6 +/- 1.2 mL/dL/minute, P = .006). AIRG was higher in African-Americans (6050 +/- 940 vs 2410 +/- 30 microU minute/mL, P = .001). Pubertal stage had no effect. S(I) did not differ by race or pubertal stage. In African-Americans, percent fall in FVR following arterial occlusion correlated (r = 0.67, P = .001) with log AIRG. No relationships were found between percent fall in FVR and S(I) in either race.

CONCLUSION

African-American adolescents have decreased endothelial function. This may be a result of increased insulin secretion. Endothelial dysfunction in African-American adolescents may predispose to cardiovascular and type II diabetes.

The 'skinny' on childhood obesity: how our western environment starves kids' brains

In this review, the mechanism of our "toxic environment's" effects on insulin and weight gain in the genesis of obesity is elaborated. The composition of our diet is highly insulinogenic. The insulin drives energy into fat, and interferes with leptin signaling in the VMH. This results in weight gain and the sense of starvation, which results in decreased SNS activity, reducing energy expenditure and physical activity; and increased vagal activity, which promotes yet further insulin release and energy storage. Thus, hyperinsulinemia turns the leptin negative feedback system into a "vicious cycle" of obesity (see Figure 3, page 905). Externally, this appears as "gluttony and sloth" but it is biochemically driven. How does this work? A thin, insulin-sensitive, 13-year-old boy might consume a daily allotment of 2,000 kcal, and burn 2,000 kcal daily (or 50 kcal/kg fat-free mass) in order to remain weight-stable, with a stable leptin level. However, if that same 13-year-old became hyperinsulinemic and/or insulin resistant, perhaps as many as 250 kcal of the daily allotment would be shunted to storage in adipose tissue, promoting a persistent obligate weight gain. Due to the obligate energy storage, he now only has 1,750 kcal per day to burn. The hyperinsulinemia also results in a lower level of leptin signal transduction, conveying a CNS signal of energy insufficiency. The remaining calories available are lower than his energy expenditure; the CNS would sense starvation. Through decreased SNS tone, he would reduce his physical activity, resulting in decreased quality of life; and through increased vagal tone, he would increase caloric intake and insulin secretion, but now at a much higher level. Thus, the vicious cycle of gluttony, sloth, and obesity is promulgated. Is this personal responsibility, when a kid's brain thinks it's starving? Is it personal responsibility when the American Academy of Pediatrics still recommends juice for toddlers? Is it personal responsibility when the Women, Infant and Children program subsidizes fruit juice but not fruit? Is it personal responsibility when the first ingredient in the barbecue sauce is high-fructose corn syrup? Is it personal responsibility when high-fiber fresh produce is unavailable in poor neighborhoods? Is it personal responsibility when the local fast food restaurant is the only neighborhood venue that is clean and air-conditioned? Is it personal responsibility when in order to meet the criteria for No Child Left Behind, the school does away with physical education class? Is it personal responsibility when children are not allowed out of the house to play for fear of crime? We must get the insulin down. Fixing the "toxic environment" by altering the food supply and promoting physical activity for all children can't be done by government, and won't be done by Big Food. This will require a grassroots, bottom-up effort on the part of parents and community leaders. We as pediatricians must lead the way.

A multicenter, randomized, double-blind, placebo-controlled, dose-finding trial of a long-acting formulation of octreotide in promoting weight loss in obese adults with insulin hypersecretion

OBJECTIVE

To compare changes in weight in obese patients who received long-acting octreotide (octreotide LAR) at one of three dose levels (20, 40, or 60 mg) or placebo over 6 months and to identify the lowest dose of octreotide LAR that safely achieved optimal weight loss.

DESIGN

Randomized, double-blind, placebo-controlled trial of octreotide LAR at three dose levels.

PATIENTS

A total of 172 adults (28 men and 144 women) with at least moderate obesity (body mass index (BMI) range 30-65 kg/m2) and evidence of insulin hypersecretion were enrolled. Patients were predominantly either Caucasian (50.0%) or African American (45.3%). The mean age (38 +/- 11 year), weight (110.7 +/- 23 kg), and BMI (39.8 +/- 6.5 kg/m2) were similar across the four treatment groups.

MEASUREMENTS

Efficacy measures included weight, BMI, fasting serum glucose; triglycerides; percentage of total body fat and abdominal fat as measured by dual-energy X-ray absorptiometry; skin fold thickness; waist-to-hip circumference; leptin; percentage of carbohydrates, fat, and protein ingested; nutritional evaluation (including dietary analysis--3-day food record); quality of life (QoL; using the Impact of Weight on Quality of Life-Lite); Beck Depression Inventory; and Carbohydrate Craving Questionnaire. Safety measures included medical history, vital signs, physical examinations, hematology, blood chemistries, thyroid function tests, hemoglobin A1c, gallbladder ultrasound, electrocardiograms, and adverse events.

RESULTS

After 6 months of treatment, patients receiving 40 or 60 mg of octreotide LAR experienced statistically significant weight loss compared to baseline, with mean differences from placebo in percent weight change of -1.98 and -1.87%, respectively. This finding was accompanied by statistically significant mean decreases in BMI compared to baseline, that is, a mean decrease of 0.73 and 0.79 kg/m2 for the 40 and 60 mg treatment arms, respectively. The observed weight loss was progressive during the 6-month treatment in the two higher dose groups. The lowest dose to reach statistical significance in weight loss after 6 months' treatment was 40 mg. Post hoc analysis revealed a 3.5-3.8% weight loss at month 6 in the two higher dose groups among Caucasian patients having insulin secretion greater than the median of the cohort, defined as CIR(gp) (corrected insulin response at the glucose peak) > or = 1.43. There were no statistically significant changes in QoL scores, body fat, leptin concentration, Beck Depression Inventory, or macronutrient intake. Mean changes of blood glucose AUC(0-180 min) during an oral glucose tolerance test in patients taking octreotide LAR were 39-40 mg/dl h higher than those on placebo. A total of 7-21% of the patients taking octreotide LAR reached a 5% or greater decrease in body weight from Baseline, compared to 11% for the placebo group. This was not statistically significant. The most common adverse events included diarrhea, headache, cholelithiasis, nausea, and abdominal pain.

CONCLUSION

Octreotide LAR given at 40 or 60 mg resulted in statistically significant weight loss. A post hoc analysis stratifying patients by race and CIR(gp) indicated that Caucasian patients with the greater degree of insulin hypersecretion appeared to derive the most benefit from treatment. The observed safety profile was consistent with the known effects of octreotide from previous studies.

Childhood obesity: behavioral aberration or biochemical drive? Reinterpreting the First Law of Thermodynamics

Childhood obesity has become epidemic over the past 30 years. The First Law of Thermodynamics is routinely interpreted to imply that weight gain is secondary to increased caloric intake and/or decreased energy expenditure, two behaviors that have been documented during this interval; nonetheless, lifestyle interventions are notoriously ineffective at promoting weight loss. Obesity is characterized by hyperinsulinemia. Although hyperinsulinemia is usually thought to be secondary to obesity, it can instead be primary, due to autonomic dysfunction. Obesity is also a state of leptin resistance, in which defective leptin signal transduction promotes excess energy intake, to maintain normal energy expenditure. Insulin and leptin share a common central signaling pathway, and it seems that insulin functions as an endogenous leptin antagonist. Suppressing insulin ameliorates leptin resistance, with ensuing reduction of caloric intake, increased spontaneous activity, and improved quality of life. Hyperinsulinemia also interferes with dopamine clearance in the ventral tegmental area and nucleus accumbens, promoting increased food reward. Accordingly, the First Law of Thermodynamics can be reinterpreted, such that the behaviors of increased caloric intake and decreased energy expenditure are secondary to obligate weight gain. This weight gain is driven by the hyperinsulinemic state, through three mechanisms: energy partitioning into adipose tissue; interference with leptin signal transduction; and interference with extinction of the hedonic response to food.

Insulin dynamics predict body mass index and z-score response to insulin suppression or sensitization pharmacotherapy in obese children

OBJECTIVE

To assess the use of oral glucose tolerance testing (OGTT) to predict efficacy of insulin sensitization (metformin) or suppression (octreotide) because insulin resistance and insulin hypersecretion may impact pharmacotherapeutic efficacy in obese children.

STUDY DESIGN

Forty-three and 24 obese children, with and without central nervous system (CNS) insult, underwent OGTT. Insulin sensitivity was expressed as composite insulin sensitivity index (CISI), and secretion as corrected insulin response (CIRgp). Those without CNS insult received metformin (weight-based dosing) for 6 to 16 months. Those with CNS insult received octreotide SQ 15 microg/kg/d for 6 months. Body mass index (BMI) and z-score responses were modeled using CIRgp and CISI.

RESULTS

Metformin: With CIRgp and CISI = 1, BMI z-score in white children declined by 0.23 over the first 4 months (P < .001), and by 0.14 over the next year (P = .33). Each 2-fold increase in CIRgp or CISI attenuated BMI z-score reduction, but with wide uncertainty (P = .24). Black children exhibited little response. Octreotide: With CIRgp and CISI = 1, BMI z-score decreased by 0.23 in the first 4 months (P = .052). Efficacy was dependent on an interaction between CIRgp and CISI (P = .051).

CONCLUSIONS

Efficacy of metformin was predicted by pretreatment insulin resistance. Efficacy of octreotide was predicted by insulin hypersecretion and sensitivity.

Fast Food, Central Nervous System Insulin Resistance, and Obesity

Rates of obesity and insulin resistance have climbed sharply over the past 30 years. These epidemics are temporally related to a dramatic rise in consumption of fast food; until recently, it was not known whether the fast food was driving the obesity, or vice versa. We review the unique properties of fast food that make it the ideal obesigenic foodstuff, and elucidate the mechanisms by which fast food intake contributes to obesity, emphasizing its effects on energy metabolism and on the central regulation of appetite. After examining the epidemiology of fast food consumption, obesity, and insulin resistance, we review insulin’s role in the central nervous system’s (CNS) regulation of energy balance, and demonstrate the role of CNS insulin resistance as a cause of leptin resistance and in the promotion of the pleasurable or “hedonic” responses to food. Finally, we analyze the characteristics of fast food, including high-energy density, high fat, high fructose, low fiber, and low dairy intake, which favor the development of CNS insulin resistance and obesity.