Effects of diacylglycerol on glucose, lipid metabolism, and plasma serotonin levels in lean Japanese

OBJECTIVE

Diacylglycerol (DAG)-rich oil has been suggested to suppress postprandial hyperlipidemia and promote negative caloric balance by increasing energy expenditure (EE), due to small intestine physiochemical dynamics that differ from triacylglycerol (TAG). We studied the effect of DAG on postprandial glucose/insulin metabolism by loading of carbohydrate with oil. Further, to reveal the mechanism for increased EE by DAG, we measured plasma serotonin, which is mostly present in the small intestine and mediates peripheral sympathetic thermogenesis.

METHODS AND PROCEDURES

Randomized crossover study with 2-week wash-out interval between differing fat ingestion. Seven male, lean, Japanese students ingested DAG or TAG oil with 40 g of carbohydrate. Measurements of metabolic parameters were performed before and at 2, 4, and 6 h after fat ingestion. Plasma serotonin levels and cholesterol concentration in each lipoprotein were measured using high-performance liquid chromatography (HPLC).

RESULTS

The substitution of DAG for TAG decreased very-low-density lipoprotein-cholesterol (VLDL-C) by 45.6% at 2 h, and decreased serum insulin by 41.3% at 4 h after ingestion. The incremental area under the curve (IAUC) for VLDL-C was positively correlated with the IAUC for insulin. Concurrently, DAG elevated plasma serotonin levels by 47.3% at 2 h, while TAG did not influence.

DISCUSSION

This study indicates that the substitution of DAG for TAG suppresses the postprandial increase in serum VLDL-C and insulin. This study also demonstrates that DAG ingestion increases plasma serotonin, proposing a possible mechanism for a postprandial increase in EE by DAG.

Constitutional thinness: unusual human phenotype of low bone quality

CONTEXT

Low fat mass and hormonal or nutritional deficiencies are often incriminated in bone loss related to thinness. Constitutional thinness has been described in young women with low body mass index (BMI) but close-to-normal body composition, physiological menstruation, no hormonal abnormalities, and no anorexia nervosa (AN) psychological profile.

OBJECTIVE

Our objective was to determine whether constitutional thinness is associated with impaired bone quality.

DESIGN, SETTING, AND PARTICIPANTS

This was an observational, cross-sectional study on 25 constitutionally thin and 44 AN young women with similar low BMI (<16.5 kg/m2) and 28 age-matched controls.

MAIN OUTCOME MEASURES

Femoral and lumbar spine bone mineral density by dual-energy x-ray absorptiometry, distal tibia and radius bone architecture and breaking strength by three-dimensional peripheral quantitative computed tomography, and bone turnover markers were determined.

RESULTS

Constitutionally thin subjects displayed a higher percentage of fat mass than AN subjects but had similar lumbar and femoral bone mineral density, which were significantly lower than in controls (P < 0.001). Constitutionally thin subjects displayed more markedly impaired trabecular and cortical bone parameters in the distal tibia than in the radius. AN bone structure was impaired only in subjects with a long history of disease. Calculated breaking strength was decreased in constitutional thinness and long-standing AN in both the radius and the tibia. Bone markers in constitutionally thin subjects were similar to those of controls. Osteoprotegerin to receptor activator of nuclear factor kappa B ligand ratio was higher in constitutionally thin subjects than in controls or AN women.

CONCLUSIONS

Young women with constitutional thinness present an unexpectedly high prevalence of low bone mass (44%) associated with small bone size, overall diminished breaking strength, but normal bone turnover. Mechanisms related to insufficient skeletal load and/or genetics are proposed to explain this new phenotype of impaired bone quality.

Energy expenditure and energy intake in 10-12 years obese and non-obese Chinese children in a Guangzhou boarding school

OBJECTIVE

The objective of this study was to observe the variation of energy intake and energy expenditure in the obese Chinese children.

METHODS

Basic metabolic rate was measured by using open-circuit indirect calorimetry in 54 obese children and 60 non-obese children aged 10-12 years in a full- time boarding school in Guangzhou suburb, China. Total energy expenditure was estimated by using a factorial method. Dietary intake was surveyed by the weighed inventory method. Physical activity was determined using a 2-day activity diary.

RESULTS

Univariate analysis showed that basic metabolic rate was significantly higher (p<0.05) in obese children than in non-obese ones, but the significant difference disappeared after controlling for fat free mass and fat mass. Energy intake and total energy expenditure were significantly higher (p<0.05) in obese than in non-obese children. Obese children spent more time in sleeping and light physical activity, but less time in moderate physical activity and vigorous physical activity than non-obese children (p<0.05).

CONCLUSIONS

Compared to non-obese children, both energy intake and expenditure were higher in obese Chinese children. It appears that an area for preventive strategies may be to encourage increased physical activity expenditure in this age group.

Mitochondrial gene expression and increased oxidative metabolism: role in increased lifespan of fat-specific insulin receptor knock-out mice

Caloric restriction, leanness and decreased activity of insulin/insulin-like growth factor 1 (IGF-1) receptor signaling are associated with increased longevity in a wide range of organisms from Caenorhabditis elegans to humans. Fat-specific insulin receptor knock-out (FIRKO) mice represent an interesting dichotomy, with leanness and increased lifespan, despite normal or increased food intake. To determine the mechanisms by which a lack of insulin signaling in adipose tissue might exert this effect, we performed physiological and gene expression studies in FIRKO and control mice as they aged. At the whole body level, FIRKO mice demonstrated an increase in basal metabolic rate and respiratory exchange ratio. Analysis of gene expression in white adipose tissue (WAT) of FIRKO mice from 6 to 36 months of age revealed persistently high expression of the nuclear-encoded mitochondrial genes involved in glycolysis, tricarboxylic acid cycle, beta-oxidation and oxidative phosphorylation as compared to expression of the same genes in WAT from controls that showed a tendency to decline in expression with age. These changes in gene expression were correlated with increased cytochrome c and cytochrome c oxidase subunit IV at the protein level, increased citrate synthase activity, increased expression of peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha) and PGC-1beta, and an increase in mitochondrial DNA in WAT of FIRKO mice. Together, these data suggest that maintenance of mitochondrial activity and metabolic rates in adipose tissue may be important contributors to the increased lifespan of the FIRKO mouse.

Effects of subcutaneous leptin injections on hypothalamic gene profiles in lean and ob/ob mice

OBJECTIVE

Leptin-deficient ob/ob mice are more sensitive to exogenous leptin than lean mice and leptin treatment normalizes many of the phenotypic characteristics of ob/ob mice. The primary objective of this experiment was to investigate whether this altered leptin sensitivity in ob/ob mice was reflected in the hypothalamic mRNA profile.

RESEARCH METHODS AND PROCEDURES

Fifteen-week-old female ob/ob and lean mice were treated with 14 days of subcutaneous (sc) infusion of phosphate-buffered saline (PBS) or leptin (10 mug/d) using osmotic pumps. Real-time Taqman reverse transcription polymerase chain reaction (RT-PCR) (ABI Microfluidic cards) was used to quantitatively compare the mRNA levels of selected hypothalamic genes in these groups.

RESULTS

Hypothalamic mRNA levels for ob/ob control mice were higher for agouti-related protein (AGRP), neuropeptide Y (NPY), and arginine vasopressin (AVP), and lower for cocaine- and amphetamine-regulated transcript (CART), cAMP response element binding protein (CREB)-1, proopiomelanocortin (POMC)-1, and urocortin (UCN)-3 compared with lean controls. In leptin-treated ob/ob mice, hypothalamic mRNA levels were reduced for NPY, AGRP, AVP, and increased for suppressor of cytokine signaling 3 (SOCS3) compared with ob/ob controls. Leptin treatment dramatically up-regulated hypothalamic mRNA level of POMC1 in both lean and ob/ob mice. Strong correlations were observed between hypothalamic Janus kinase 2 (JAK2) and CREB1, STAT3 and CREB1, JAK2 and STAT3, NPY and AVP in all samples.

DISCUSSION

ob/ob and lean mice have different hypothalamic mRNA expression patterns (particularly those of feeding-related genes), and selected genes in ob/ob mice are more sensitive to exogenous leptin stimulation compared with lean mice.

Ideal weight better predicts resting energy expenditure than does actual weight in patients with short bowel syndrome

OBJECTIVE

The objective of the present study was to compare measured energy expenditure with predicted energy expenditure in patients with short bowel syndrome.

METHODS

Thirteen patients with short bowel syndrome underwent anthropometric measurements and indirect calorimetry for the determination of resting energy expenditure. Energy expenditure was also estimated by use of the Harris-Benedict equation with current weight and ideal weights.

RESULTS

The difference between measured energy expenditure and energy expenditure estimated by use of current weight was statistically significant, whereas the difference between measured energy expenditure and energy expenditure estimated by use of ideal weight was not significant.

CONCLUSION

The energy expenditure of patients with short bowel syndrome can be estimated by use of the Harris-Benedict equation and patients' ideal weight.

Chromium (D-phenylalanine)3 improves obesity-induced cardiac contractile defect in ob/ob mice

OBJECTIVE

Low-molecular weight chromium compounds, such as chromium picolinate [Cr(pic)(3)], improve insulin sensitivity, although toxicity is a concern. We synthesized a novel chromium complex, chromium (d-phenylalanine)(3) [Cr(d-phe)(3)], in an attempt to improve insulin sensitivity with reduced toxicity. The aim of this study was to compare the two chromium compounds on cardiac contractile function in ob/ob obese mice.

RESEARCH METHODS AND PROCEDURES

C57BL lean and ob/ob obese mice were randomly divided into three groups: H(2)O, Cr(d-phe)(3), or Cr(pic)(3) (45 mug/kg per day orally for 6 months).

RESULTS

The glucose tolerance test displayed improved glucose clearance by Cr(d-phe)(3) but not Cr(pic)(3). Myocytes from ob/ob mice exhibited depressed peak shortening (PS) and maximal velocity of shortening/relengthening (+/-dL/dt), prolonged time-to-PS and time-to-90% relengthening (TR90), reduced electrically stimulated rise in intracellular Ca(2+) (Deltafura-2 fluorescence intensity), and slowed intracellular Ca(2+) decay. Although a 3-month Cr(d-phe)(3) treatment for a separate group of ob/ob and lean 2-month-old mice only rectified reduced +/-dL/dt in ob/ob mice, all mechanical and intracellular Ca(2+) abnormalities were significantly attenuated or ablated by 6 months of Cr(d-phe)(3) but not Cr(pic)(3) treatment (except TR90). Sarco(endo)plasmic reticulum Ca(2+) ATPase activity and Na(+)-Ca(2+) exchanger expression were depressed in ob/ob mice, which were reversed by both Cr(d-phe)(3) and Cr(pic)(3), with a more pronounced effect from Cr(d-phe)(3). Cr(d-phe)(3) corrected reduced insulin-stimulated glucose uptake and improved basal phosphorylation of Akt and insulin receptor, as well as insulin-stimulated phosphorylation of Akt and insulin receptor in ob/ob myocytes. Heart homogenates from ob/ob mice had enhanced oxidative stress and protein carbonyl formation compared with the lean group, which were attenuated by both Cr(d-phe)(3) and Cr(pic)(3).

DISCUSSION

Our data suggest that the new Cr(d-phe)(3) compound possesses better cardio-protective and insulin-sensitizing properties against obesity.

Changes in gene expression in skeletal muscle in response to fat overfeeding in lean men

OBJECTIVE

The adaptive mechanisms in response to excess energy supply are still poorly known in humans. Our aims were to define metabolic responses and changes in gene expression in skeletal muscle of healthy volunteers during fat overfeeding.

RESEARCH METHODS AND PROCEDURES

Eight lean young healthy men were given a diet rich in saturated fat with an excess of approximately 550 kcal/d for 4 weeks. Using oligonucleotide microarrays, gene expression changes in skeletal muscle were analyzed at Day 0, Day 14, and Day 28.

RESULTS

Fat overfeeding led to an increase in body weight (1.0 +/- 0.3 kg) and waist circumference (2.2 +/- 0.5 cm, p = 0.005) and a significant decrease in fasting non-esterified fatty acid plasma levels (-29 +/- 5%, p = 0.028). Respiratory quotient was significantly increased (0.84 +/- 0.01 to 0.88 +/- 0.02, p = 0.034) and lipid oxidation rate tended to decrease. The expression of 55 genes was modified in skeletal muscle. The main pathways indicated a coordinated stimulation of triacylglycerol synthesis, inhibition of lipolysis, reduction of fatty acid oxidation, and development of adipocytes. Promoter analysis of the regulated genes suggests that sterol regulatory element binding proteins might be important players of the short-term adaptation to fat overfeeding in human skeletal muscle.

DISCUSSION

This combined metabolic and genomic investigation shows that fat overfeeding for 28 days promotes the storage of the excess energy in lean men and demonstrates the usefulness of a transcriptomic approach to a better understanding of the metabolic adaptation to changes in nutritional behavior in human.

(1)H nuclear magnetic resonance metabolomic analysis of mammary tumors from lean and obese Zucker rats exposed to 7,12-dimethylbenz[a]anthracene

Obesity increases mammary tumor development in Zucker rats following a single administration of the procarcinogen 7,12-dimenthylbenz(a)anthracene (DMBA). Fifty-day-old obese and lean female Zucker rats were orally gavaged with 65 mg/kg DMBA and sacrificed 139 days post DMBA treatment. At the end of the experiment, mammary tumors were detected in 68% of the obese rats compared to 32% of the lean group (P<0.001). 1H nuclear magnetic resonance (1H-NMR) spectra obtained for hydrophilic and lipophilic extracts from excised tumors illustrated fundamental differences in metabolic profiles between the two groups. Differences were observed for key choline compounds, namely phosphocholine and glycerophosphocholine, both markers of malignancy and apoptosis. In addition, levels of lactate, creatine, myo-inositol, alpha-glucose, alanine, leucine, glutamate, glutamine, tyrosine, phenylalanine, and NADH varied between the lean and obese groups. Principal component analysis indicated class separation between tumors from lean and obese rats based on their metabolic profiles, illustrating the potential for using 1H-NMR metabolomic methods for identifying altered metabolic pathways. Our results suggest that obesity enhances the risk for DMBA-induced mammary tumor development in rats. However, the mechanism for this increase in risk is currently unknown and will require further studies for elucidation.

Visfatin, TNF-alpha and IL-6 mRNA expression is increased in mononuclear cells from type 2 diabetic women

Visfatin, is a new adipokine, highly expressed in the visceral fat of both mice and humans. To examine whether visfatin is expressed in human peripheral monocyte-enriched mononuclear cells and whether its expression is altered in type 2 diabetes (DM2), we compared 24 DM2 women [17 overweight (BMI >25) and 7 lean (BMI<25)] to 26 healthy women (14 overweight and 12 lean), all premenopausal. Relative visfatin mRNA levels were significantly higher (approximately 3-fold) in DM2 compared to healthy control women (p<0.02), independently of the presence of overweight/obesity. Mononuclear TNF-alpha and IL-6 mRNA expression was also elevated in DM2 compared to control women (p=0.001 and p=0.004, respectively), an increase observed in both lean and overweight DM2 women. By contrast, circulating visfatin, TNF-alpha, and IL-6 levels showed no difference between DM2 and control women, while adiponectin plasma levels were significantly decreased in the DM2 women (p<0.001). Circulating visfatin and TNF-alpha levels did not differ either between the lean and the overweight subgroups of DM2 and control women, while IL-6 plasma levels were significantly higher in both overweight subgroups compared to their lean counterparts. In conclusion, visfatin, TNF-alpha, and IL-6 mRNA expressions are increased in peripheral mononuclear-monocytic cells from women with type 2 diabetes, independent of their BMI, which may enhance the effects of their adipose-derived levels and may contribute to the increased insulin resistance and atherogenic risk of these patients.

Interleukin-18 in plasma and adipose tissue: effects of obesity, insulin resistance, and weight loss

OBJECTIVE

Interleukin (IL)-18 is associated with obesity, insulin resistance, and cardiovascular disease. The present study compared 1) IL-18 in adipocytes versus stromal vascular (SV) cells, 2) IL-18 in plasma and adipose tissue (AT) in obese versus lean subjects, and 3) IL-18 in plasma, AT, and skeletal muscle (SM) in obese subjects after weight loss.

SUBJECTS AND METHODS

At baseline, plasma and AT IL-18 in 23 obese subjects were compared with that in 12 lean subjects. The obese subjects were submitted to a 15-week life-style intervention (hypocaloric diet and daily exercise) after which plasma samples, AT, and SM biopsies were obtained. Analyses were performed by ELISA and RT-PCR respectively.

RESULTS

IL-18 expression in isolated adipocytes was approximately 2% of that in SV cells. Plasma IL-18 was higher in obese subjects (P < 0.001) and associated with insulin resistance (HOMA; P < 0.001). AT expression of IL-18, CD14, and CD68 was higher in obese (P < 0.01). The intervention reduced body weight (P < 0.001), plasma IL-18 (P < 0.001), and increased insulin sensitivity (HOMA; P < 0.05). AT and SM expression of IL-18 remained unchanged after the intervention. Changes in plasma IL-18 were associated with changes in insulin sensitivity (P < 0.05) but not with BMI or AT expression of IL-18.

CONCLUSION

Plasma IL-18 is associated with changes in insulin resistance and reduced after weight loss. AT expression of IL-18 is increased in obesity but not affected by weight loss, indicating that changes in plasma IL-18 are related to insulin resistance rather than changes in obesity per se.

Adipocyte triglyceride lipase expression in human obesity

We have investigated the gene and protein expression of adipose triglyceride lipase (ATGL) and triglyceride (TG) lipase activity from subcutaneous and visceral adipose tissue of lean and obese subjects. Visceral and subcutaneous adipose tissue was obtained from 16 age-matched lean and obese subjects during abdominal surgery. Tissues were analyzed for mRNA expression of lipolytic enzymes by real-time quantitative PCR. ATGL protein content was assessed by Western blot and TG lipase activity by radiometric assessment. Subcutaneous and visceral adipose tissue of obese subjects had elevated mRNA expression of PNPLA2 (ATGL) and other lipases including PNPLA3, PNPLA4, CES1, and LYPLAL1 (P < 0.05). Surprisingly, ATGL protein expression and TG lipase activity were reduced in subcutaneous adipose tissue of obese subjects. Immunoprecipitation of ATGL reduced total TG lipase activity in adipose lysates by 70% in obese and 83% in lean subjects. No significant differences in the ATGL activator CGI-58 mRNA levels (ABHD5) were associated with obesity. These data demonstrate that ATGL is important for efficient TG lipase activity in humans. They also demonstrate reduced ATGL protein expression and TG lipase activity despite increased mRNA expression of ATGL and other novel lipolytic enzymes in obesity. The lack of correlation between ATGL protein content and in vitro TG lipase activity indicates that small decrements in ATGL protein expression are not responsible for the reduction in TG lipase activity observed here in obesity, and that posttranslational modifications may be important.

Glucose metabolism during ghrelin infusion in patients with anorexia nervosa

Anorexia nervosa (AN) is an eating disorder characterized by self-induced starvation due to fear of adiposity. Ghrelin, gastric peptide with potent orexigenic, adipogenic, GH-releasing and metabolic properties, is elevated in AN. We have previously shown that intervention with exogenous ghrelin is not effective in terms of inducing neuroendocrine and appetite responses in AN. In this arm of the same study protocol we investigated glucose metabolism responses to 5 h i.v. infusion of active ghrelin in a) 9 severely malnourished AN patients, b) 6 AN patients who partially recovered body weight (PRAN), c) 10 constitutionally thin female subjects with regular menstrual cycles. At baseline, no significant differences were observed in blood glucose, insulin, c-peptide, adiponectin, and homeostasis model assessment index values, between the studied groups. During ghrelin infusions, blood glucose levels significantly increased in all groups although significantly less in low-weight AN; insulin levels were not significantly affected, while c-peptide levels were significantly suppressed only in the constitutionally thin and PRAN subjects. In addition to our previous findings of impaired neuroendocrine and appetite responses in patients with AN, we conclude that metabolic responses to ghrelin are attenuated in these patients, which tend to recover with weight gain.

Effects of fasting on insulin action and glucose kinetics in lean and obese men and women

The development of insulin resistance in the obese individual could impair the ability to appropriately adjust metabolism to perturbations in energy balance. We investigated a 12- vs. 48-h fast on hepatic glucose production (R(a)), peripheral glucose uptake (R(d)), and skeletal muscle insulin signaling in lean and obese subjects. Healthy lean [n = 14; age = 28.0 +/- 1.4 yr; body mass index (BMI) = 22.8 +/- 0.42] and nondiabetic obese (n = 11; age = 34.6 +/- 2.3 yr; BMI = 36.1 +/- 1.5) subjects were studied following a 12- and 48-h fast during 2 h of rest and a 3-h 40 mUxm(-2)xmin(-1) hyperinsulinemic-euglycemic clamp (HEC). Basal glucose R(a) decreased significantly from the 12- to 48-h fast (lean 1.96 +/- 0.23 to 1.63 +/- 0.15; obese 1.23 +/- 0.07 to 1.07 +/- 0.07 mgxkg(-1)xmin(-1); P = 0.004) and was equally suppressed during the HEC after both fasts. The increase in glucose R(d) during the HEC after the 12-h fast was significantly decreased in lean and obese subjects after the 48-h fast (lean 9.03 +/- 1.17 to 4.16 +/- 0.34, obese 6.10 +/- 0.77 to 3.56 +/- 0.30 mgxkg FFM(-1)xmin(-1); P < 0.001). After the 12- but not the 48-h fast, insulin-stimulated AKT Ser(473) phosphorylation was greater in lean than obese subjects. We conclude that 1) 48 h of fasting produces a marked decline in peripheral insulin action, while suppression of hepatic glucose production is maintained in lean and obese men and women; and 2) the magnitude of this decline is greater in lean vs. obese subjects.

The effect of dietary carbohydrate on genes for fatty acid synthase and inflammatory cytokines in adipose tissues from lean and obese subjects

BACKGROUND

Hepatic de novo lipogenesis (DNL) is markedly stimulated in humans by low-fat diets enriched in simple sugars. However, the dietary responsiveness of the key enzyme controlling DNL in human adipose tissue, fatty acid synthase (FAS), is uncertain.

HYPOTHESIS

Adipose tissue mRNA for FAS is increased in lean and obese subjects when hepatic DNL is elevated by a eucaloric, low-fat, high-sugar diet.

DESIGN

Twelve lean and seven obese volunteers were given two eucaloric diets (10% vs. 30% fat; 75% vs. 55% carbohydrate; sugar/starch 60/40) each for 2 weeks by a random-order cross-over design. FAS mRNA in abdominal and gluteal adipose tissues was compared to hepatic DNL measured in serum by isotopic and nonisotopic methods. Adipose tissue mRNA for tumor necrosis factor-alpha and IL-6, which are inflammatory cytokines that modulate DNL, was also assayed.

RESULTS

The low-fat high-sugar diet induced a 4-fold increase in maximum hepatic DNL (P<.001) but only a 1.3-fold increase in adipose tissue FAS mRNA (P=.029) and no change in cytokine mRNA. There was a borderline significant positive correlation between changes in FAS mRNA and hepatic DNL (P=.039). Compared to lean subjects, obese subjects had lower levels of FAS mRNA and higher levels of cytokine mRNA (P<.001).

CONCLUSIONS

The results suggest that key elements of human adipose tissue DNL are less responsive to dietary carbohydrate than is hepatic DNL and may be regulated by diet-independent factors. Irrespective of diet, there is reduced expression of the FAS gene and increased expression of cytokine genes in adipose tissues of obese subjects.

BMR variability in women of different weight

BACKGROUND & AIMS

Non-exercise activity thermogenesis (NEAT) and substrate oxidation are significant components of Energy Balance; their regulation may be modulated according to nutritional status and their impairment has been advocated as a factor facilitating the development of excess body fat.

METHODS

In this study body composition, resting metabolic rate (RMR), fidgeting as a component of NEAT and respiratory quotient (RQ), an index of preferential substrate oxidation, have been evaluated in 80 young women: 20 restrictive anorexia nervosa (rAN: BMI 15.1+/-1.6 kg/m(2)); 20 constitutional leanness (CL: BMI 17.2+/-1.0); 20 obese patients (Ob: BMI 43.8+/-10.0) and 20 controls (CTR: BMI 21.7+/-2.4).

RESULTS

Fat free mass, fat mass and RMR progressively increased from rAN to Ob (p < 0.05). Fidgeting was higher in CL (67.2+/-27.2 kcal; p < 0.05) than in the other groups. Lipid oxidation, evaluated with RQ showed a negative correlation with fidgeting in CL (r=-0.433; p<0.05) and positive in Ob (r=0.572; p<0.05) and in rAN (r=0.434; p<0.05).

CONCLUSION

Our findings support the regulatory function of NEAT, its protective role to prevent excess body fat accumulation and its positive relation with fat oxidation in CL.

Relationship between the change in overweight status from childhood to adolescence and metabolic syndrome phenotypes: a 9-year retrospective study

OBJECTIVE

To evaluate how the changes in overweight status from childhood to adolescence are related to metabolic syndrome phenotypes in adolescents.

SUBJECTS AND METHODS

A total 375 adolescents aged 16 years. The overweight status from childhood to adolescence (from 7 years of age to 16 years) was determined by body mass index (BMI, kg/m(2)) calculated from records of the School Physical Examination data. The change in body weight was classified into four groups: normal weight to normal weight (NW-NW); overweight to normal (OW-NW); normal to overweight (NW-OW); overweight to overweight (OW-OW). Metabolic syndrome phenotypes were examined from a cross-sectional survey.

RESULTS

The mean values of all phenotypes except for body fatness (BMI and waist) and the cluster score of phenotypes at 16 years of age were not different between the NW-NW group and the OW-NW group, nor between the NW-OW group and the OW-OW group. However, the score as well as the level of body fatness and blood glucose were significantly different between current overweight and normal adolescents regardless of overweight status during childhood (P<0.05).

CONCLUSION

There was a linear relationship between overweight status during childhood and metabolic syndrome phenotypes in adolescence but current overweight status (adolescence overweight) was more closely related to the adolescent risk of metabolic syndrome than childhood overweight status.

Peptide YY release in anorectic patients after liquid meal

Fasting and postprandial levels of human peptide YY (PYY) were recently found to be lower in obesity. To investigate whether PYY levels are correspondingly high in patients with anorexia nervosa, PYY concentrations were analyzed under basal conditions and in response to a liquid meal. We investigated PYY plasma levels in 16 female anorectic (BMI 15.2+/-0.3 kg/m2) and seven lean subjects (BMI 21.3+/-0.6 kg/m2) before and after ingestion of a liquid meal (250 kcal; 15% protein, 55% carbohydrates, and 30% fat). PYY levels were analyzed using PYY ELISA (DSL, USA). Values are given as mean+/-SEM. Basal PYY levels in anorectic patients (89.0+/-14.4 pg/mL) were not significantly different from lean subjects (64.1+/-12.1 pg/mL). Postprandial PYY levels in healthy volunteers increased significantly after 20 and 60 min (80.4+/-12.7 and 96.0+/-19.9 pg/mL, respectively). In anorectic women PYY was increased at 20 min (137.9+/-19.5 pg/mL) and at 60 min (151.3+/-19.2 pg/mL). No difference was found between both groups. We conclude that basal and postprandial PYY levels in normal weight women are not different from anorectic patients. We could not confirm the recently published blunted postprandial PYY response in anorexia, a finding that merits further study.

Drive for thinness score is a proxy indicator of energy deficiency in exercising women

The purpose of this study was to determine the association between drive for thinness (DT) and adaptations to energy deficiency in exercising women. This observational study evaluated psychometric and metabolic factors in sedentary (n=9, 27.9+/-2.0 yr) and exercising women (n=43, 24.0+/-1.1 yr). Volunteers were retrospectively grouped according to exercise status (sedentary or exercising) and a DT score of normal (sedentary or exercising) or high (exercising only). Resting energy expenditure (REE) and metabolic hormones (triiodothyronine, (TT3), ghrelin, leptin, insulin) were measured repeatedly over a 2-3 month period. The DT subscale successfully discriminated the groups based on energy status. Although the groups did not differ in body weight, the high DT group exhibited adaptations to chronic energy deficiency, including a REE below 90% of their predicted REE (86+/-3.0%), significantly lower TT3 levels and significantly higher ghrelin levels than the normal DT groups. Since energy deficiency plays a causal role in the Female Athlete Triad, DT may serve as a proxy indicator of underlying energy deficiency and may be useful for identifying individuals at risk for Triad disorders prior to the development of serious clinical sequelae.

Alterations in soleus muscle gene expression associated with a metabolic endpoint following exercise training by lean and obese Zucker rats

Exercise training decreases insulin resistance and increases glucose tolerance in conditions of prediabetes and overt Type 2 diabetes. However, the adaptive responses in skeletal muscle at the molecular and genetic level for these effects of exercise training have not been clearly established in an animal model of prediabetes. The present study identifies alterations in muscle gene expression that occur with exercise training in prediabetic, insulin-resistant obese Zucker rats and insulin-sensitive lean Zucker rats and are associated with a well-defined metabolic outcome. Treadmill running for up to 4 wk caused significant enhancements of glucose tolerance as assessed by the integrated area under the curve for glucose (AUCg) during an oral glucose tolerance test. Using microarray analysis, we identified a set of only 12 genes as both significantly altered by exercise training (>1.5-fold change; P < 0.05) and significantly correlated ( P < 0.05) with the AUCg. Two genes, peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) and protein kinase C-ζ (PKC-ζ), are involved in the regulation of muscle glucose transport, and we provide the first evidence that PKC-ζ gene expression is enhanced by exercise training in insulin-resistant muscle. Protein expression of PGC-1α and PKC-ζ were positively correlated with the mRNA expression for these two genes. Overall, we have identified a limited number of genes in soleus muscle of lean and obese Zucker rats that are associated with both decreased insulin resistance and increased glucose tolerance following endurance exercise training. These findings could guide the development of pharmaceutical “exercise mimetics” in the treatment of insulin-resistant, prediabetic, or Type 2 diabetic individuals.

Mice lacking inhibitory leptin receptor signals are lean with normal endocrine function

The adipose-derived hormone, leptin, acts via its receptor (LRb) to convey the status of body energy stores to the brain, decreasing feeding and potentiating neuroendocrine energy expenditure. The failure of high levels of leptin in most obese individuals to promote weight loss defines a state of diminished responsiveness to increased leptin, termed leptin resistance. Leptin stimulates the phosphorylation of several tyrosine residues on LRb to mediate leptin action. We homologously replaced LRb in mice with a receptor with a mutation in one of these sites (Tyr985) in order to examine its role in leptin action and signal attenuation in vivo. Mice homozygous for this mutation are neuroendocrinologically normal, but females demonstrate decreased feeding, decreased expression of orexigenic neuropeptides, protection from high-fat diet-induced obesity, and increased leptin sensitivity in a sex-biased manner. Thus, leptin activates autoinhibitory signals via LRb Tyr985 to attenuate the anti-adiposity effects of leptin, especially in females, potentially contributing to leptin insensitivity in obesity.

Different transcription profiles of SOCS-3, ob and IGF-I genes and their possible correlations in obese and lean pigs

Pig breeds have significant differences in fat deposition and muscle development ability. However, the molecular mechanism behind these differences is still unknown. In this study, the expression patterns of three candidate genes, suppressor of cytokine signaling 3 (SOCS-3), obesity (ob) and insulin-like growth factor I (IGF-I), which are involved in adipose metabolism or muscle development, were analyzed. Total RNA was extracted from dorsal subcutaneous adipose tissue and longissimus of 8-month-old Bamei and Largewhite pigs. Semiquantitative reverse transcription-polymerase chain reaction was used to determine the expression levels of the SOCS-3 and ob genes in adipose tissue, and SOCS-3 and IGF-I genes in muscle tissue. The results showed that in adipose tissue the expression level of SOCS-3 was significantly higher in Bamei (obese) pigs than that in Largewhite (lean) pigs (P<0.01). However, in muscle tissue it was significantly lower in Bamei than that in Largewhite pigs (P<0.01). Furthermore, the expression of SOCS-3 was positively correlated to that of ob in adipose tissue and that of IGF-I in muscle tissue. These findings suggest that the difference in SOCS-3 gene expression levels in adipose and muscle tissues, the relationship between SOCS-3 and ob in adipose tissue, and that between SOCS-3 and IGF-I in muscle tissue, might contribute to the different fat deposition and muscle development ability between obese and lean pigs.

Endothelin limits insulin action in obese/insulin-resistant humans

The normal action of insulin to vasodilate and redistribute blood flow in support of skeletal muscle metabolism is impaired in insulin-resistant states. Increased endogenous endothelin contributes to endothelial dysfunction in obesity and diabetes. Here, we test the hypothesis that increased endogenous endothelin action also contributes to skeletal muscle insulin resistance via impairments in insulin-stimulated vasodilation. We studied nine lean and seven obese humans, measuring the metabolic and hemodynamic effects of insulin (300 mU . m(-2) . min(-1)) alone and during femoral artery infusion of BQ123 (an antagonist of type A endothelin receptors, 1 micromol/min). Endothelin antagonism augmented skeletal muscle responses to insulin in obese subjects through changes in both leg blood flow (LBF) and glucose extraction. Insulin-stimulated LBF was significantly increased in obese subjects only. These changes, combined with differential effects on glucose extraction, resulted in augmented insulin-stimulated leg glucose uptake in obese subjects (54.7 +/- 5.7 vs. 107.4 +/- 18.9 mg/min with BQ123), with no change in lean subjects (103.7 +/- 11.4 vs. 88.9 +/- 16.3, P = 0.04 comparing BQ123 across groups). BQ123 allowed augmented leg glucose extraction in obese subjects even in the face of NOS antagonism. These findings suggest that increased endogenous endothelin action contributes to insulin resistance in skeletal muscle of obese humans, likely through both vascular and tissue effects.

Regulation of adiponutrin expression by feeding conditions in rats is altered in the obese state

OBJECTIVE

To characterize the effect of feeding conditions on the expression behavior of adiponutrin, a non-secreted adipose-specific protein proposed to be involved in energy homeostasis maintenance, and its relation with leptin expression in different rat adipose tissue depots under normal and obese conditions.

RESEARCH METHODS AND PROCEDURES

Two rat models were used, Wistar (lean and overweight) and Zucker (lean and obese), submitted to fasting/refeeding. Adiponutrin and leptin expression was determined in different white adipose tissue depots (epididymal, inguinal, mesenteric, and retroperitoneal) and in interscapular brown adipose tissue by reverse transcription-polymerase chain reaction.

RESULTS

We have found site-specific differences in adiponutrin expression in different adipose depots, being the expression pattern close to that of leptin in white adipose tissue. The depot-specific adiponutrin expression is similar in lean and obese animals, except in the inguinal depot, where adiponutrin is overexpressed in obese Zucker. Independently of the degree of expression in the tissue, adiponutrin is an acute sensor of feeding conditions compared with other diet-regulated adipokines, as is leptin. In lean rats, 14-hour fasting greatly decreases adiponutrin mRNA levels in all of the depots studied, whereas 3-hour refeeding allows the recovery of the levels found in control animals. In both overweight Wistar and obese Zucker rats, the decreased mRNA expression observed after fasting in lean rats is not as evident; moreover, in the obese Zucker, there is no recovery after refeeding.

DISCUSSION

Adiponutrin expression is highly regulated by feeding conditions in the different adipose tissue depots, but this regulation is impaired in obese rats.