A post-mortem stereological study of striatal cell number in human obesity

OBJECTIVE

Neuroimaging studies have revealed abnormalities in brain structure, including the striatum, in obese people. In this study, the cellular and parenchymal basis for these findings in post-mortem brain tissue was investigated.

METHODS

Design-based (unbiased) stereology combined with histochemical and immunocytochemical staining was used to quantify total number of neurons and astrocytes in post-mortem striatal brain samples from nine obese (BMI 40.2 ± 6.1 kg/m(2) ) and eight lean (BMI 24.4 ± 1.0 kg/m(2) ) donors. Total numbers of Nissl-stained neurons and glial fibrillary acidic protein-immunopositive astrocytes were counted in 10 systematic-random sections starting from the frontal pole of the striatum.

RESULTS

There were no differences in mean total numbers of neurons (obese: 7.60 E+06; SD 2.50 E+06; lean: 7.85 E+06; SD 8.26 E+05; P < 0.78) or astrocytes (obese: 7.42 E+06; SD 2.27 E+06; lean: 7.43 E+06; SD 2.50 E+06; P < 0.99). A higher variance was found for number of neurons (P < 0.007) but not astrocytes (P < 0.72) in the obese group. Neuron/glia ratios were similar in both groups (obese: 1.07, SD 0.39; lean: 1.15, SD 0.37; P < 0.70) with an overall striatal neuron/glia ratio of 1.11 (SD 0.37) across the entire study population (n = 17).

CONCLUSIONS

No difference was found in the average numbers of neurons and astrocytes in the anterior striatum between lean and obese people. The morphological basis for structural brain changes in obesity requires further investigation.

Pharmacology of manipulating lean body mass

Dysfunction and wasting of skeletal muscle as a consequence of illness decreases the length and quality of life. Currently, there are few, if any, effective treatments available to address these conditions. Hence, the existence of this unmet medical need has fuelled large scientific efforts. Fortunately, these efforts have shown many of the underlying mechanisms adversely affecting skeletal muscle health. With increased understanding have come breakthrough disease-specific and broad spectrum interventions, some progressing through clinical development. The present review focuses its attention on the role of the antagonistic process regulating skeletal muscle mass before branching into prospective promising therapeutic targets and interventions. Special attention is given to therapies in development against cancer cachexia and Duchenne muscular dystrophy before closing remarks on design and conceptualization of future therapies are presented to the reader.

Impact of maternal under nutrition on obstetric outcomes

Maternal malnutrition, ranging from under nutrition to over dietary intake before and in the pregnant state, is worldwide problem with significant consequences, not only for survival and increased risk for acute and chronic diseases both in mother and child, but also for economic productivity of individuals in the societies and additional costs on health system. Inter alia, pre-pregnancy underweight and insufficient gestational weight gain are considered as individual risk factors for the occurrence of spontaneous interruption, preterm birth, fetal growth restriction, and hypertensive disorders, strongly associated with poorer perinatal outcome. In a portion of this population, major eating disorders (anorexia and bulimia nervosa), once thought to be rare, but nowadays enlarged due to cultural pressure on the drive for thinness, have been identified as the etiology of an abnormal nutritional condition in developed countries, in contrast to long standing food deprivation in developing countries. Actually, even if without a complete weight management guidance for these selected pregnant women, an appropriate weight gain is recommended during pregnancy. Mainly, therapeutic approach is prevention using specific programs of improving weight before pregnant status. In this article, a review of the literature on selected obstetrical risks associated with maternal underweight has been performed and both the target prevention and management strategies have been described.

Cross-sectional and Longitudinal Analyses of Factors Contributing to the Progressive Loss of the β-cell Function in Type 2 Diabetes

OBJECTIVE

Type 2 diabetes is a progressive disease characterized by insulin resistance and insulin secretory dysfunction. In this study, we assessed the factors contributing to an insulin secretory defect in type 2 diabetes patients.

METHODS

The subjects consisted of 382 patients with type 2 diabetes, aged 57±13 years. We estimated the β-cell function using 6-min post-glucagon increments in C-peptide (ΔCPR).

RESULTS

A significant inverse correlation was observed between the time since the diagnosis of diabetes and ΔCPR. A simple liner regression analysis showed that ΔCPR decreases at a rate of 0.056 ng/mL/year. According to a multiple regression model, body mass index (BMI) and log (triglyceride) were positively correlated with ΔCPR. Time since the diagnosis of diabetes, diabetes in 1st degree relatives, the presence of diabetic retinopathy, and HbA1c were inversely correlated with ΔCPR. In 50 patients who underwent the glucagon stimulation test twice, the ΔCPR decreased from 2.27±1.47 to 1.72±1.08 ng/mL over a period of 6.5±0.9 years. A multiple regression analysis revealed the BMI and fasting plasma glucose level to be significant contributing factors to the decline in ΔCPR.

CONCLUSION

The duration of diabetes, a low BMI, genetic factors, and the presence of microangiopathy may be associated with β-cell dysfunction in diabetic patients. The observations in this study suggest that obese subjects showed a rapid decline in the β-cell function despite an initial high CPR response. Environmental factors causing insulin resistance and glucotoxicity may therefore be involved in progressive β-cell failure.

MAP kinase phosphatase DUSP1 is overexpressed in obese humans and modulated by physical exercise

Chronic low-grade inflammation and dysregulation of the stress defense system are cardinal features of obesity, a major risk factor for the development of insulin resistance and diabetes. Dual-specificity protein phosphatase 1 (DUSP1), known also as MAP kinase phosphatase 1 (MKP1), is implicated in metabolism and energy expenditure. Mice lacking DUSP1 are resistant to high-fat diet-induced obesity. However, the expression of DUSP1 has not been investigated in human obesity. In the current study, we compared the expression pattern of DUSP1 between lean and obese nondiabetic human subjects using subcutaneous adipose tissue (SAT) and peripheral blood mononuclear cells (PBMCs). The levels of DUSP1 mRNA and protein were significantly increased in obese subjects with concomitant decrease in the phosphorylation of p38 MAPK (p-p38 MAPK) and PGC-1α and an increase in the levels of phospho-JNK (p-JNK) and phospho-ERK (p-ERK). Moreover, obese subjects had higher levels of circulating DUSP1 protein that correlated positively with various obesity indicators, triglycerides, glucagon, insulin, leptin, and PAI-1 (P < 0.05) but negatively with V̇O(2max) and high-density lipoprotein (P < 0.05). The observation that DUSP1 was overexpressed in obese subjects prompted us to investigate whether physical exercise could reduce its expression. In this study, we report for the first time that physical exercise significantly attenuated the expression of DUSP1 in both the SAT and PBMCs, with a parallel increase in the expression of PGC-1α and a reduction in the levels of p-JNK and p-ERK along with attenuated inflammatory response. Collectively, our data suggest that DUSP1 upregulation is strongly linked to adiposity and that physical exercise modulates its expression. This gives further evidence that exercise might be useful as a strategy for managing obesity and preventing its associated complications.

Healthy obese versus unhealthy lean: the obesity paradox

Overweight and obesity have reached epidemic proportions in the USA and most of the rest of the world. Particularly concerning is the very high prevalence of class III obesity (BMI ≥40 kg/m(2)), which has reached ∼3% in the USA. In the past few years, controversy has surrounded the idea that some individuals with obesity can be considered healthy with regards to their metabolic and cardiorespiratory fitness, which has been termed the 'obesity paradox'. These controversies are reviewed in detail here, including discussion of the very favourable prognosis in patients with obesity who have no notable metabolic abnormalities and who have preserved fitness. The article also discusses the suggestion that greater emphasis should be placed on improving fitness rather than weight loss per se in the primary and secondary prevention of cardiovascular diseases, at least in patients with overweight and class I obesity (BMI 30-35 kg/m(2)).

Evidence for greater production of colonic short-chain fatty acids in overweight than lean humans

BACKGROUND

Short-chain fatty acids (SCFA) are produced by colonic microbiota from dietary carbohydrates and proteins that reach the colon. It has been suggested that SCFA may promote obesity via increased colonic energy availability. Recent studies suggest obese humans have higher faecal SCFA than lean, but it is unclear whether this difference is due to increased SCFA production or reduced absorption.

OBJECTIVES

To compare rectal SCFA absorption, dietary intake and faecal microbial profile in lean (LN) versus overweight and obese (OWO) individuals.

DESIGN

Eleven LN and eleven OWO individuals completed a 3-day diet record, provided a fresh faecal sample and had SCFA absorption measured using the rectal dialysis bag method. The procedures were repeated after 2 weeks.

RESULTS

Age-adjusted faecal SCFA concentration was significantly higher in OWO than LN individuals (81.3±7.4 vs 64.1±10.4 mmol kg(-1), P=0.023). SCFA absorption (24.4±0.8% vs 24.7±1.2%, respectively, P=0.787) and dietary intakes were similar between the groups, except for a higher fat intake in OWO individuals. However, fat intake did not correlate with SCFAs or bacterial abundance. OWO individuals had higher relative Firmicutes abundance (83.1±4.1 vs 69.5±5.8%, respectively, P=0.008) and a higher Firmicutes:Bacteriodetes ratio (P=0.023) than LN individuals. There was a positive correlation between Firmicutes and faecal SCFA within the whole group (r=0.507, P=0.044), with a stronger correlation after adjusting for available carbohydrate (r=0.615, P=0.005).

CONCLUSIONS

The higher faecal SCFA in OWO individuals is not because of differences in SCFA absorption or diet. Our results are consistent with the hypothesis that OWO individuals produce more colonic SCFA than LN individuals because of differences in colonic microbiota. However, further studies are needed to prove this.

Metabolite profile deviations in an oral glucose tolerance test-a comparison between lean and obese individuals

OBJECTIVE

While impaired glucose tolerance diagnosed by the oral glucose tolerance test (OGTT) is a common trait in obese individuals, less is known about changes in levels of other metabolites. The aim was to reveal the complex alterations in metabolite levels provoked by an OGTT and its perturbation in obese individuals.

METHODS

Gas chromatography/mass spectrometry was used to profile metabolite levels in serum from 14 obese participants (body mass index [BMI] of 43.6 ± 1.5 kg m(-2) [mean ± SEM]) at 0, 30, and 120 min during a standard 2-h 75 g OGTT. Metabolite profiles from six lean individuals (BMI of 22.4 ± 2.4 kg m(-2) ), collected from a previous study, were included for comparison.

RESULTS

In the obese group, 59 metabolite profiles were determined. Among these, 16 deviated from profiles in the lean group. Deviating metabolites were categorized into three groups. Delayed reduction in levels of five fatty acids. Increased levels at 30 min of five amino acids, including isoleucine and leucine. A blunted increase at 30 min of six metabolites.

CONCLUSIONS

Metabolomics analysis revealed distinct differences in alterations of metabolite levels during an OGTT in obese and lean subjects. To this end, our data suggests a disrupted regulation of ketogenesis, lipolysis and proteolysis in obese individuals.

Divergent effects of oxytocin treatment of obese diabetic mice on adiposity and diabetes

Oxytocin has been suggested as a novel therapeutic against obesity, because it induces weight loss and improves glucose tolerance in diet-induced obese rodents. A recent clinical pilot study confirmed the oxytocin-induced weight-reducing effect in obese nondiabetic subjects. Nevertheless, the mechanisms involved and the impact on the main comorbidity associated with obesity, type 2 diabetes, are unknown. Lean and ob/ob mice (model of obesity, hyperinsulinemia, and diabetes) were treated for 2 weeks with different doses of oxytocin, analogues with longer half-life (carbetocin) or higher oxytocin receptor specificity ([Thr4,Gly7]-oxytocin). Food and water intake, body weight, and glycemia were measured daily. Glucose, insulin, and pyruvate tolerance, body composition, several hormones, metabolites, gene expression, as well as enzyme activities were determined. Although no effect of oxytocin on the main parameters was observed in lean mice, the treatment dose-dependently reduced food intake and body weight gain in ob/ob animals. Carbetocin behaved similarly to oxytocin, whereas [Thr4,Gly7]-oxytocin (TGOT) and a low oxytocin dose decreased body weight gain without affecting food intake. The body weight gain-reducing effect was limited to the fat mass only, with decreased lipid uptake, lipogenesis, and inflammation, combined with increased futile cycling in abdominal adipose tissue. Surprisingly, oxytocin treatment of ob/ob mice was accompanied by a worsening of basal glycemia and glucose tolerance, likely due to increased corticosterone levels and stimulation of hepatic gluconeogenesis. These results impose careful selection of the conditions in which oxytocin treatment should be beneficial for obesity and its comorbidities, and their relevance for human pathology needs to be determined.

Association of obesity with leukocyte count in obese individuals without metabolic syndrome

AIMS

Inflammation in obesity is associated to insulin resistance (IR), hyperglycemia, hypertension and hyperlipidemia. Leukocytes play an important role in obesity associated inflammation. The initial factors that generate the inflammatory events in the obesity remain unclear. Therefore, the aim of this study was to determine the association of circulating leukocytes with clinical and biochemical parameters in obese individuals with clinical and biochemical parameters in normal range and with or without IR.

METHODS

Nineteen obese non-diabetic and 9 lean subjects were studied for serum levels of insulin, lipids, glycated hemoglobin, glycemia, for clinical parameters as HOMA-IR, arterial pressure and anthropometric parameters, and for leukocyte counts. Neutrophil/lymphocyte ratio (N/L) was calculated using the loge of leukocyte counts. Association between leukocytes and studied parameters was determined by Pearson's correlation.

RESULTS

Two groups of obese individuals were observed: with high levels of insulin (with IR) and with normal levels (without IR). Positive correlations were observed between leukocyte and lymphocyte counts with body mass index and HOMA-IR and negative correlation with decreased HDL levels. Lymphocytes correlated with increased levels of insulin. Leukocytes and neutrophils correlated positively with increased visceral fat and liver steatosis. These associations were absent in the obese group without IR. N/L ratio did not show correlations with studied parameters. The leukocyte associations were mainly observed in obese individuals with IR.

CONCLUSIONS

These data may represent initial leukocyte associations with morbidity features and define two different obese individuals that may evolve to the chronic inflammation observed in the obesity.

IRF4 is a key thermogenic transcriptional partner of PGC-1α

Brown fat can reduce obesity through the dissipation of calories as heat. Control of thermogenic gene expression occurs via the induction of various coactivators, most notably PGC-1α. In contrast, the transcription factor partner(s) of these cofactors are poorly described. Here, we identify interferon regulatory factor 4 (IRF4) as a dominant transcriptional effector of thermogenesis. IRF4 is induced by cold and cAMP in adipocytes and is sufficient to promote increased thermogenic gene expression, energy expenditure, and cold tolerance. Conversely, knockout of IRF4 in UCP1(+) cells causes reduced thermogenic gene expression and energy expenditure, obesity, and cold intolerance. IRF4 also induces the expression of PGC-1α and PRDM16 and interacts with PGC-1α, driving Ucp1 expression. Finally, cold, β-agonists, or forced expression of PGC-1α are unable to cause thermogenic gene expression in the absence of IRF4. These studies establish IRF4 as a transcriptional driver of a program of thermogenic gene expression and energy expenditure.

Activation of noncanonical Wnt signaling through WNT5A in visceral adipose tissue of obese subjects is related to inflammation

CONTEXT

Wingless-type mouse mammary tumor virus integration site family (WNT)-5A is a glycoprotein involved in the regulation of the inflammatory response by activating the noncanonical Wnt signaling pathway. Secreted frizzled-related protein (SFRP)-5 acts as a decoy receptor that binds and sequesters WNT5A, preventing activation of frizzled receptors and attenuating the noncanonical Wnt signaling.

OBJECTIVE

The aim of the study was to evaluate the involvement of WNT5A and SFRP5 in obesity and obesity-related comorbidities as well as to explore their effect in visceral adipose tissue inflammation.

PATIENTS AND METHODS

Samples obtained from 90 subjects were used. Circulating and gene expression levels of WNT5A and SFRP5 were analyzed in different metabolic tissues. The effect of TNF-α and lipopolysaccharide on the transcript levels of WNT5A and SFRP5 in adipocytes was explored. We also investigated whether WNT5A itself can activate an inflammatory response.

RESULTS

Increased circulating levels of WNT5A in obese patients (P < .05) were decreased (P < .001) after gastric bypass. In this line, WNT5A mRNA in visceral adipose tissue was increased (P < .05) in obese patients with gene expression levels of SFRP5 being down-regulated (P < .05). WNT5A mRNA expression was significantly enhanced (P < .01) by lipopolysaccharide and TNF-α treatment, whereas no effects were found in SFRP5 gene expression levels. Furthermore, exogenous WNT5A induced (P < .05) IL-6, IL1B, MMP2, MMP9, and SSP1 mRNA expression in human adipocyte cultures.

CONCLUSIONS

Activation of noncanonical Wnt signaling through the up-regulation of WNT5A and down-regulation of SFRP5 may promote a proinflammatory state in visceral adipose tissue contributing to the development of obesity-associated comorbidities.

Increased interaction with insulin receptor substrate 1, a novel abnormality in insulin resistance and type 2 diabetes

Insulin receptor substrate 1 (IRS1) is a key mediator of insulin signal transduction. Perturbations involving IRS1 complexes may lead to the development of insulin resistance and type 2 diabetes (T2D). Surprisingly little is known about the proteins that interact with IRS1 in humans under health and disease conditions. We used a proteomic approach to assess IRS1 interaction partners in skeletal muscle from lean healthy control subjects (LCs), obese insulin-resistant nondiabetic control subjects (OCs), and participants with T2D before and after insulin infusion. We identified 113 novel endogenous IRS1 interaction partners, which represents the largest IRS1 interactome in humans and provides new targets for studies of IRS1 complexes in various diseases. Furthermore, we generated the first global picture of IRS1 interaction partners in LCs, and how they differ in OCs and T2D patients. Interestingly, dozens of proteins in OCs and/or T2D patients exhibited increased associations with IRS1 compared with LCs under the basal and/or insulin-stimulated conditions, revealing multiple new dysfunctional IRS1 pathways in OCs and T2D patients. This novel abnormality, increased interaction of multiple proteins with IRS1 in obesity and T2D in humans, provides new insights into the molecular mechanism of insulin resistance and identifies new targets for T2D drug development.

Influence of dietary fat intake on the endocannabinoid system in lean and obese subjects

OBJECTIVE

Endocannabinoid system (ECS) activation promotes obesity-associated metabolic disease. Increased dietary fat intake increases blood endocannabinoids and alters adipose and skeletal muscle ECS gene expression in human.

METHODS

Two weeks isocaloric low- (LFD) and high-fat diets (HFD) in obese (n = 12) and normal-weight (n = 17) subjects in a randomized cross-over study were compared. Blood endocannabinoids were measured in the fasting condition and after food intake using mass spectrometry. Adipose and skeletal muscle gene expression was determined using real-time RT-PCR.

RESULTS

Baseline fasting plasma endocannabinoids were similar with both diets. Anandamide decreased similarly with high- or low-fat test meals in both groups. Baseline arachidonoylglycerol plasma concentrations were similar between groups and diets, and unresponsive to eating. In subcutaneous adipose tissue, DAGL-α mRNA was upregulated and fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) mRNAs were down-regulated in obese subjects, but the diets had no influence. In contrast, the HFD produced pronounced reductions in skeletal muscle CB1-R and MAGL mRNA expression, whereas obesity did not affect muscular gene expression.

CONCLUSIONS

Weight-neutral changes in dietary fat intake cannot explain excessive endocannabinoid availability in human obesity. Obesity and dietary fat intake affect ECS gene expression in a tissue-specific manner.

Eszopiclone and dexmedetomidine depress ventilation in obese rats with features of metabolic syndrome

STUDY OBJECTIVES

Obesity alters the therapeutic window of sedative/hypnotic drugs and increases the probability of respiratory complications. The current experiments used an established rodent model of obesity to test the hypothesis that the sedative/hypnotic drugs eszopiclone and dexmedetomidine alter ventilation differentially in obese rats compared with lean/fit rats.

DESIGN

This study used a within-groups/between-groups experimental design.

SETTING

University of Michigan.

PARTICIPANTS

Experiments were conducted using lean/fit rats (n = 21) and obese rats (n = 21) that have features of metabolic syndrome.

INTERVENTIONS

Breathing was measured with whole-body plethysmography after systemic administration of vehicle (control), the nonbenzodiazepine, benzodiazepine site agonist eszopiclone, or the alpha-2 adrenergic receptor agonist dexmedetomidine.

MEASUREMENTS AND RESULTS

Data were analyzed using two-way analysis of variance and appropriate post hoc comparisons. At baseline, the obese/metabolic syndrome rats had increased respiratory rates (21.6%), lower tidal volumes/body weight (-24.1%), and no differences in minute ventilation compared to lean/fit rats. In the obese rats, respiratory rate was decreased by dexmedetomidine (-29%), but not eszopiclone. In the lean and the obese rats, eszopiclone decreased tidal volume (-12%). Both sedative/hypnotic drugs caused a greater decrease in minute ventilation in the obese (-26.3%) than lean (-18%) rats. Inspiratory flow rate (VT / TI) of the obese rats was decreased by dexmedetomidine (-10.6%) and eszopiclone (-18%). Duty cycle (TI / TTOT) in both rat lines was decreased by dexmedetomidine (-16.5%) but not by eszopiclone.

CONCLUSIONS

Dexmedetomidine, in contrast to eszopiclone, decreased minute ventilation in the obese/metabolic syndrome rats by depressing both duty cycle and inspiratory flow rate. The results show for the first time that the obese phenotype differentially modulates the respiratory effects of eszopiclone and dexmedetomidine. These differences in breathing are consistent with previously documented differences in sleep between lean/fit and obese rats. These findings also encourage future studies of obese/metabolic syndrome rats that quantify the effect of sedative/hypnotic drugs on respiratory mechanics as well as hypoxic and hypercapnic ventilatory responses. Continued findings of favorable homology between obese humans and rodents will support the interpretation that these obese rats offer a unique animal model for mechanistic studies.

Nicotinamide N-methyltransferase knockdown protects against diet-induced obesity

In obesity and type 2 diabetes, Glut4 glucose transporter expression is decreased selectively in adipocytes. Adipose-specific knockout or overexpression of Glut4 alters systemic insulin sensitivity. Here we show, using DNA array analyses, that nicotinamide N-methyltransferase (Nnmt) is the most strongly reciprocally regulated gene when comparing gene expression in white adipose tissue (WAT) from adipose-specific Glut4-knockout or adipose-specific Glut4-overexpressing mice with their respective controls. NNMT methylates nicotinamide (vitamin B3) using S-adenosylmethionine (SAM) as a methyl donor. Nicotinamide is a precursor of NAD(+), an important cofactor linking cellular redox states with energy metabolism. SAM provides propylamine for polyamine biosynthesis and donates a methyl group for histone methylation. Polyamine flux including synthesis, catabolism and excretion, is controlled by the rate-limiting enzymes ornithine decarboxylase (ODC) and spermidine-spermine N(1)-acetyltransferase (SSAT; encoded by Sat1) and by polyamine oxidase (PAO), and has a major role in energy metabolism. We report that NNMT expression is increased in WAT and liver of obese and diabetic mice. Nnmt knockdown in WAT and liver protects against diet-induced obesity by augmenting cellular energy expenditure. NNMT inhibition increases adipose SAM and NAD(+) levels and upregulates ODC and SSAT activity as well as expression, owing to the effects of NNMT on histone H3 lysine 4 methylation in adipose tissue. Direct evidence for increased polyamine flux resulting from NNMT inhibition includes elevated urinary excretion and adipocyte secretion of diacetylspermine, a product of polyamine metabolism. NNMT inhibition in adipocytes increases oxygen consumption in an ODC-, SSAT- and PAO-dependent manner. Thus, NNMT is a novel regulator of histone methylation, polyamine flux and NAD(+)-dependent SIRT1 signalling, and is a unique and attractive target for treating obesity and type 2 diabetes.

Leanness and heightened nonresting energy expenditure: role of skeletal muscle activity thermogenesis

A high-calorie diet accompanied by low levels of physical activity (PA) accounts for the widespread prevalence of obesity today, and yet some people remain lean even in this obesogenic environment. Here, we investigate the cause for this exception. A key trait that predicts high PA in both humans and laboratory rodents is intrinsic aerobic capacity. Rats artificially selected as high-capacity runners (HCR) are lean and consistently more physically active than their low-capacity runner (LCR) counterparts; this applies to both males and females. Here, we demonstrate that HCR show heightened total energy expenditure (TEE) and hypothesize that this is due to higher nonresting energy expenditure (NREE; includes activity EE). After matching for body weight and lean mass, female HCR consistently had heightened nonresting EE, but not resting EE, compared with female LCR. Because of the dominant role of skeletal muscle in nonresting EE, we examined muscle energy use. We found that lean female HCR had higher muscle heat dissipation during activity, explaining their low economy of activity and high activity EE. This may be due to the amplified skeletal muscle expression levels of proteins involved in EE and reduced expression levels of proteins involved in energy conservation in HCR relative to LCR. This is also associated with an increased sympathetic drive to skeletal muscle in HCR compared with LCR. We find little support for the hypothesis that resting metabolic rate is correlated with maximal aerobic capacity if body size and composition are fully considered; rather, the critical factor appears to be activity thermogenesis.

[Hepatic steatosis, visceral fat and metabolic alterations in apparently healthy overweight/obese individuals]

Clinical observation indicates that many obese individuals do not display important metabolic alterations. Consequently, the objective of this study was to establish whether simple obesity, non concurrent with other important risk factors, was associated with metabolic alterations; or if the phenomenon known as "obesity paradox" was present. A clinical history, measurements of anthropometric and metabolic parameters and estimation of hepatic steatosis and visceral fat, were determined in 30, apparently healthy, individuals from Maracaibo, Venezuela, between 20 and 59 years of age and a body mass index (BMI) above 25 kg/m2, and compared to a lean control group of 11 individuals with BMI less than 25 kg/m2. The study demonstrated that only one third of overweight/obese individuals (OW/OB), with high body mass index (BMI) and waist circumference (WC), presented elevated values of insulin, HOMA-IR and triglycerides. Nevertheless, the presence of hepatic steatosis was elevated in the OW/OB group (91%) vs. 9% in the control group. The visceral fat in the lean control group was associated with both, WC and glycemia; however, it was not related to the BMI or insulin, HOMA-IR and HDLc. The visceral fat in the OW/OB group, although elevated in relation to the lean group, revealed a loss of these associations. In the OW/OB it was the BMI that was associated with insulin and HOMA-IR. The results emphasize the importance of investigating for the presence of hepatic steatosis, rather than visceral fat, in individuals with OW/OB, to identify subjects with high cardiometabolic risk.

The effect of exercise intensity on endothelial function in physically inactive lean and obese adults

Purpose

To examine the effects of exercise intensity on acute changes in endothelial function in lean and obese adults.

Methods

Sixteen lean (BMI <25, age 23±3 yr) and 10 obese (BMI >30, age 26±6 yr) physically inactive adults were studied during 3 randomized admissions [control (C, no exercise), moderate-intensity exercise (M, @ lactate threshold (LT)) and high-intensity exercise (H, midway between LT and VO₂peak) (30 min)]. Endothelial function was assessed by flow-mediated dilation (FMD) at baseline and 1, 2, and 4 h post-exercise.

Results

RM ANCOVA revealed significant main effects for group, time, and group x condition interaction (p<0.05). A diurnal increase in FMD was observed in lean but not obese subjects. Lean subjects exhibited greater increases in FMD than obese subjects (p = 0.0005). In the obese group a trend was observed for increases in FMD at 2- and 4-hr after M (p = 0.08). For lean subjects, FMD was significantly elevated at all time points after H. The increase in FMD after H in lean subjects (3.2±0.5%) was greater than after both C (1.7±0.4%, p = 0.015) and M (1.4±0.4%, p = 0.002). FMD responses of lean and obese subjects significantly differed after C and H, but not after M.

Conclusion

In lean young adults, high-intensity exercise acutely enhances endothelial function, while moderate-intensity exercise has no significant effect above that seen in the absence of exercise. The FMD response of obese adults is blunted compared to lean adults. Diurnal variation should be considered when examining the effects of acute exercise on FMD.

Obesity and heterozygous endothelial overexpression of prepro-endothelin-1 modulate responsiveness of mouse main and segmental renal arteries to vasoconstrictor agents

AIMS

Levels of the endothelium-derived peptide endothelin-1 (ET-1) are elevated in obese humans, and ET-1 mediated vascular tone is increased. Renal arterial smooth muscle is highly responsive to ET-1. Whether or not endothelium-derived ET-1 affects contractions of the renal artery under normal conditions or in obesity is unknown. The present study was designed to investigate whether or not overexpression of endogenous ET-1 in the endothelium affects the responsiveness of the main and segmental renal arteries differently in obesity.

MAIN METHODS

Mice with tie-1 promoter-driven endothelium-restricted heterozygous overexpression of preproendothelin-1 were used (TET(het)). Obesity was induced in TET(het) mice and wild-type (WT) littermates by feeding a high fat diet for 30 weeks; lean controls were kept on standard chow. The renal arteries were studied in wire myographs testing contractions (in the presence of l-NAME) to ET-1, serotonin, and U46619.

KEY FINDINGS

Contractions to ET-1 were comparable between groups in main renal arteries, but augmented in segmental preparations from obese mice. Serotonin-induced responses were enhanced in obese TET(het) mice renal arteries compared to lean controls. Concentration-contraction curves to U46619 were shifted significantly to the left in main renal arteries of obese animals, and the maximal response was significantly increased between lean and obese TET(het) mice.

SIGNIFICANCE

These results indicate an augmented responsiveness of main renal arteries in obesity particularly to TP receptor activation. When combined with endothelial ET-1 overexpression this effect is even more pronounced, which may help to gain further insights into the mechanisms of hypertension in obesity.

[Characteristics of gonadotropic function in patients with pubertal uterine bleeding in the modern society]

The character of gonadotropin changes, which have been studied in patients with pubertal uterine bleeding, enable the authors to establish that its nature depends on the body weight value against the background of uterine bleeding. The study provides evidence that only half of all patients with bleeding has normal hormone levels. Disorders in gonadotropin levels have been registered in one third of our patients. The authors have also revealed that bleeding in patients with body weight excess significantly more often is accompanied by the increased LH and PRL morning levels and LH/FSH ratio, which occurs against the background of hypothalamic-pituitary function activation. Positive effect of insulin level on the LH production has been found in patients of the above group.

Glucose-stimulated oxidative stress in mononuclear cells is related to pancreatic β-cell dysfunction in polycystic ovary syndrome

CONTEXT

Oxidative stress induced by reactive oxygen species (ROS) is involved in the development of pancreatic β-cell dysfunction.

OBJECTIVE

We determined the relationship between mononuclear cell (MNC)-derived ROS generation and p47phox protein content in response to glucose ingestion and β-cell function in women with polycystic ovary syndrome (PCOS).

DESIGN

This was a cross-sectional study.

SETTING

This study was conducted at an academic medical center.

PARTICIPANTS

Twenty-nine normoglycemic women with PCOS (13 lean, 16 obese) and 25 ovulatory controls (16 lean, 9 obese) underwent a 3-h 75-g oral glucose tolerance test (OGTT).

MAIN OUTCOME VARIABLES

Pancreatic β-cell function was calculated as glucose-stimulated insulin secretion (insulin/glucose area under the curve0-30 min; GSIS)×Matsuda index-derived insulin sensitivity (ISOGTT). ROS generation was measured by chemiluminescence, and p47phox protein was quantified by Western blotting in MNC isolated from blood samples obtained at 0 and 2 hours of the OGTT.

RESULTS

Compared with controls, women with PCOS exhibited a higher percent change from baseline in ROS generation and p47phox protein in conjunction with greater GSIS and a tendency toward lower β-cell function. Lean women with PCOS exhibited a greater percent change from baseline in ROS generation and p47phox protein yet had similar GSIS responses compared with lean controls despite having lower ISOGTT. For the combined groups, β-cell function was inversely related to ROS generation and p47phox protein. GSIS was directly related to body mass index, central obesity, and circulating androgens.

CONCLUSION

In normoglycemic women, obesity plays a role in exaggerating GSIS. However, MNC-derived oxidative stress is independent of obesity and may contribute to the decline in β-cell function in women with PCOS.

Plasma apolipoprotein B-48 transport in obese men: a new tracer kinetic study in the postprandial state

CONTEXT

The mechanisms responsible for impaired chylomicron metabolism have not been adequately investigated in obese subjects.

OBJECTIVE

We aimed to compare apolipoprotein (apo) B-48 kinetics in obese and lean men by developing a new model to describe the kinetics of apoB-48 particles in the postprandial state.

DESIGN, SETTING, AND PATIENTS

Seven obese and 13 age-matched lean men were given an oral fat load. apoB-48 tracer to tracee ratios were measured after intravenous d3-leucine administration using gas chromatography-mass spectrometry. Kinetic parameters were derived using a multicompartmental model.

OUTCOMES MEASURES

Plasma total and incremental apoB-48 0-10 hour areas under the curve as well as apoB-48 secretion and fractional catabolic rate.

RESULTS

Compared with lean men, fasting plasma triglyceride (+148%) and apoB-48 (+110%) concentrations as well as plasma total and incremental triglycerides (+184% and +185%, respectively) and apoB-48 (+182% and 224%, respectively) areas under the curve were significantly higher in obese men (P<.05 for all). The obese men also had significantly (P<.05 for all) higher secretion rates of apoB-48 in the fasted state (+145%) as well as at 3 hours (+70%), 4 hours (+82%), 5 hours (+82%), 6 hours (+76%), and 8 hours (+61%) in response to the fat load. This was associated with a greater number of apoB-48-containing particles secreted over the 10-hour study period in the obese men, compared with lean men (+125%, P<.01). The fractional catabolic rate of apoB-48 was significantly lower in the obese men compared with the lean men (-33%, P<.05) CONCLUSION: We demonstrate that postprandial hypertriglyceridemia in central obesity relates to an overproduction and impaired catabolism of apoB-48-containing lipoproteins. These findings are based on a new, physiologically relevant, kinetic model, which describes the non-steady-state postprandial metabolism of apoB-48.

Association between lean mass, fat mass, and bone mineral density: a meta-analysis

CONTEXT

Body weight is the most important anthropometric determinant of bone mineral density (BMD). Body weight is mainly made up of lean mass (LM) and fat mass (FM), and which component is more important to BMD has been a controversial issue.

OBJECTIVE

This study sought to compare the magnitude of association between LM, FM, and BMD by using a meta-analytic approach.

DATA SOURCE

Using an electronic and manual search, we identified 44 studies that had examined the correlation between LM, FM, and BMD between 1989 and 2013. These studies involved 20,226 men and women (4966 men and 15,260 women) aged between 18 and 92 years. We extracted the correlations between LM, FM, and BMD at the lumbar spine, femoral neck, and whole body. The synthesis of correlation coefficients was done by the random-effects meta-analysis model.

RESULTS

The overall correlation between LM and femoral neck BMD (FNBMD) was 0.39 (95% confidence interval, 0.34 to 0.43), which was significantly higher than the correlation between FM and FNBMD (0.28; 95% confidence interval, 0.22 to 0.33). The effect of LM on FNBMD in men (r=0.43) was greater than that in women (r=0.38). In premenopausal women, the effect of LM on BMD was greater than the effect of FM (r=0.45 vs r=0.30); however, in postmenopausal women, the effects of LM and FM on BMD were comparable (r=0.33 vs r=0.31).

CONCLUSION

LM exerts a greater effect on BMD than FM in men and women combined. This finding underlines the concept that physical activity is an important component in the prevention of bone loss and osteoporosis in the population.