High visceral and low abdominal subcutaneous fat stores in the obese adolescent: a determinant of an adverse metabolic phenotype.

OBJECTIVE: To explore whether an imbalance between the visceral and subcutaneous fat depots and a corresponding dysregulation of the adipokine milieu is associated with excessive accumulation of fat in the liver and muscle and ultimately with insulin resistance and the metabolic syndrome. RESEARCH DESIGN AND METHODS: We stratified our multi-ethnic cohort of 118 obese adolescents into tertiles based on the proportion of abdominal fat in the visceral depot. Abdominal and liver fat were measured by magnetic resonance imaging and muscle lipid (intramyocellular lipid) by proton magnetic resonance spectroscopy. RESULTS: There were no differences in age, BMI Z score, or fat-free mass across tertiles. However, as the proportion of visceral fat increased across tertiles, BMI and percentage of fat and subcutaneous fat decreased, while hepatic fat increased. In addition, there was an increase in 2-h glucose, insulin, c-peptide, triglyceride levels, and insulin resistance. Notably, both leptin and total adiponectin were significantly lower in tertile 3 than 1, while C-reactive protein and interleukin-6 were not different across tertiles. There was a significant increase in the odds ratio for the metabolic syndrome, with subjects in tertile 3 5.2 times more likely to have the metabolic syndrome than those in tertile 1. CONCLUSIONS: Obese adolescents with a high proportion of visceral fat and relatively low abdominal subcutaneous fat have a phenotype reminiscent of partial lipodystrophy. These adolescents are not necessarily the most severely obese, yet they suffer from severe metabolic complications and are at a high risk of having the metabolic syndrome.

Adiponectin in childhood and adolescent obesity and its association with inflammatory markers and components of the metabolic syndrome.

CONTEXT: Adiponectin levels are lower in obese children and adolescents, whereas markers of inflammation and proinflammatory cytokines are higher. Hypoadiponectinemia may contribute to the low-grade systemic chronic inflammatory state associated with childhood obesity. OBJECTIVE: We investigated whether C-reactive protein (CRP), the prototype of inflammation, is related to adiponectin levels independently of insulin resistance and adiposity. DESIGN, SETTING, PARTICIPANTS, AND MAIN OUTCOME MEASURES: In a multiethnic cohort of 589 obese children and adolescents, we administered a standard oral glucose tolerance test and obtained baseline measurements for adiponectin, plasma lipid profile, CRP, IL-6, and leptin. RESULTS: Stratifying the cohort into quartiles of adiponectin levels and adjusting for potential confounding variables, such as age, gender, ethnicity, body mass index z-score, pubertal status, and insulin sensitivity, the present study revealed that low levels of adiponectin are associated not only with higher CRP levels, but also with components of the metabolic syndrome, such as low high-density lipoprotein cholesterol and a high triglyceride-to-high-density-lipoprotein ratio. CONCLUSIONS: The link between adiponectin levels and a strong marker of inflammation, CRP, is independent of insulin resistance and adiposity in obese children and adolescents. Adiponectin may be one of the signals linking inflammation and obesity. Thus, adiponectin may function as a biomarker of the metabolic syndrome in childhood obesity.

Alanine aminotransferase levels and fatty liver in childhood obesity: associations with insulin resistance, adiponectin, and visceral fat.

BACKGROUND: Concurrent with the rise in obesity, nonalcoholic fatty liver disease is recognized as the leading cause of serum aminotransferase elevations in obese youth. Nevertheless, the complete metabolic phenotype associated with abnormalities in biomarkers of liver injury and intrahepatic fat accumulation remains to be established. METHODS: In a multiethnic cohort of 392 obese adolescents, alanine aminotransferase (ALT) levels were related with parameters of insulin sensitivity, glucose, and lipid metabolism as well as adipocytokines and biomarkers of inflammation. A subset of 72 adolescents had determination of abdominal fat partitioning and intrahepatic fat accumulation using magnetic resonance imaging. FINDINGS: Elevated ALT (> 35 U/liter) was found in 14% of adolescents, with a predominance of male gender and white/Hispanic race/ethnicity. After adjusting for potential confounders, rising ALT was associated with reduced insulin sensitivity and glucose tolerance as well as rising free fatty acids and triglycerides. Worsening of glucose and lipid metabolism was already evident as ALT levels rose into the upper half of the normal range (18-35 U/liter). When hepatic fat fraction was assessed using fast magnetic resonance imaging, 32% of subjects had an increased hepatic fat fraction, which was associated with decreased insulin sensitivity and adiponectin, and increased triglycerides, visceral fat, and deep to superficial sc fat ratio. The prevalence of the metabolic syndrome was significantly greater in those with fatty liver. INTERPRETATION: Deterioration in glucose and lipid metabolism is associated even with modest ALT elevations. Hepatic fat accumulation in childhood obesity is strongly associated with the triad of insulin resistance, increased visceral fat, and hypoadiponectinemia. Hence, hepatic steatosis may be a core feature of the metabolic syndrome.

Neuropsychological deficits in nonsmokers with schizophrenia: effects of a nicotinic antagonist.

BACKGROUND: Biochemical, physiological and genetic evidence suggests dysregulation of central nicotinic acetylcholine receptor (nAChR) systems in schizophrenia, which may contribute to neuropsychological dysfunction and the high rates of smoking in this disorder. To evaluate the effects of nAChR blockade on neuropsychological performance in schizophrenia without the confounding effects of cigarette smoking, we compared neuropsychological performance in schizophrenia and healthy control nonsmokers after pre-treatment with the centrally-acting nAChR antagonist mecamylamine (MEC). METHODS: Using a within-subjects, counterbalanced design, schizophrenia (n = 14) and control (n = 15) nonsmokers were pre-treated for 3 days with MEC (0.0, 5.0, and 10.0 mg/day). Subjects performed repeated neuropsychological assessments including visuospatial working memory (VSWM), Continuous Performance Test (CPT), Wisconsin Card Sorting Test (WCST), Word Serial Position Test (WSPT) and Stroop Color Word Test (SCWT) during three sequential test sessions per week over three test weeks. RESULTS: We found significant main effects of schizophrenia diagnosis on: VSWM 30 and 60 delays (p's < 0.01), CPT (% Hit Rate, Reaction Time, Variability Index; p < 0.01 for all outcomes), WCST (p < 0.01 for all outcomes) and Word Serial Position Test (p < 0.01). However, there were no main effects of repeated test administration (Session) or MEC dose on any of these outcomes, and no significant 3-way (DiagnosisxSessionxMEC dose) interactions. CONCLUSIONS: Our results suggest that there are a broad range of neuropsychological deficits in nonsmokers with schizophrenia. Furthermore, pretreatment with a centrally-acting nAChR antagonist did not alter neuropsychological performance in either nonsmoking patients with schizophrenia or controls.

Smoking cue reactivity in schizophrenia: effects of a nicotinic receptor antagonist.

BACKGROUND: Rates of cigarette smoking in schizophrenia are higher than in the general population. To investigate differences in sensitivity to smoking cues between schizophrenia and control subjects, we compared smoking cue reactivity (CR) in schizophrenia versus control smokers with and without pretreatment with the nicotinic acetylcholine receptor (nAChR) antagonist mecamylamine (MEC). METHODS: Smoking CR in schizophrenia (n = 22) and nonpsychiatric control (n = 20) smokers was determined using exposure to smoking pictures. Three doses of MEC (0, 5, and 10 mg/day) were administered during the 3 test weeks to determine the role of nAChRs in mediating the smoking CR response. RESULTS: Eleven of 22 (50%) schizophrenia and 10 of 20 (50%) control smokers displayed smoking CR. Smoking CR was not significantly different between schizophrenia and control smokers in the placebo (0 mg/day) condition. However, MEC pretreatment produced a dose-dependent reduction of CR in schizophrenia smokers compared with placebo. There was no significant effect of MEC on CR in control smokers. CONCLUSIONS: Our findings suggest that blockade of CR by MEC may be more robust in schizophrenia versus control smokers, possibly due to reduced nAChR levels in the brains of patients with schizophrenia.

Neuropsychological deficits are associated with smoking cessation treatment failure in patients with schizophrenia.

Schizophrenics have deficits in neuropsychological performance, some of which are modified by cigarette smoking. These patients also have high rates of smoking and resistance to smoking cessation interventions. We examined whether the presence of neuropsychological deficits prior to smoking cessation treatment was associated with smoking cessation treatment failure in schizophrenic as compared to non-psychiatric control smokers. Neuropsychological assessments were performed prior to treatment with pharmacological agents during the course of placebo-controlled trials in schizophrenic and non-psychiatric control smokers, and included the Wisconsin Card Sorting Test (WCST), a Visuospatial Working Memory (VSWM) task, the Stroop Color Word Test (SCWT) and the Continuous Performance Test (CPT). In schizophrenics (n=32), subjects who had greater deficits in VSWM and WCST performance were significantly less likely to quit smoking, but this association was not observed in controls (n=40). Differences between quitters and non-quitters were not likely related to atypical antipsychotic treatment or differences in depressive symptoms. No associations between baseline performance on CPT or SCWT and quit status were found in either group. These preliminary data suggest that in schizophrenics, neuropsychological deficits are associated with smoking cessation treatment failure.