Search

The aim of this study was to estimate genetic parameters for pork intramuscular fatty acid (FA) composition and indices for desaturase and elongase activities involved in n-3 and n-6 PUFA metabolism. The LM of 437 slaughter pigs was analyzed for FA composition (expressed as g/100 g of FA). Indices for enzyme activities were calculated from product to precursor FA ratios. Genetic parameters were estimated with single-and multi-trait animal models. The total FA content, reflecting the intramuscular fat content, was either included or not in the model. Results from the models without total FA content showed relatively high heritability estimates, generally above 0.50, for the proportion of the most important MUFA and PUFA, compared with much smaller values for the SFA. When total FA content was included in the models, heritability values decreased (P < 0.001) for most individual FA and for all sums of FA groups, except for C18:0, C18:3n-6, and C18:3n-3. Heritability estimates for the ratios C20:4n-6/C18:2n-6 and C22:6n-3/C18:3n-3, reflecting the overall conversion in the n-6 and n-3 PUFA pathway, respectively, were 0.29 and 0.35, respectively, with total FA content in the model and increased to 0.38 and 0.49, respectively, if total FA content was not in the model. Heritabilities for other more specific indices were of the same order. Genetic correlations between PUFA proportions and indices for enzyme activities with ADG were mostly negative, whereas the correlations with carcass lean meat percentage were mostly positive. It was concluded that there is meaningful genetic variation for long-chain PUFA metabolism that is only partly dependent on the carcass and muscle fat content. This may allow selection for improved FA composition of pork. Key words: fatty acid, genetic correlation, heritability, intramuscular fat, pig, polyunsaturated fatty acid doi: 10.2527/jas.2009-2355

Sirtuins are [NAD.sup.+]-dependent protein deacetylases. They mediate adaptive responses to a variety of stresses, including calorie restriction and metabolic stress. Sirtuin 3 (SIRT3) is localized in the mitochondrial matrix, where it regulates the acetylation levels of metabolic enzymes, including acetyl coenzyme A synthetase 2 (refs 1, 2). Mice lacking both Sirt3 alleles appear phenotypically normal under basal conditions, but show marked hyperacetylation of several mitochondrial proteins (3). Here we report that SIRT3 expression is upregulated during fasting in liver and brown adipose tissues. During fasting, livers from mice lacking SIRT3 had higher levels of fatty-acid oxidation intermediate products and triglycerides, associated with decreased levels of fatty-acid oxidation, compared to livers from wild-type mice. Mass spectrometry of mitochondrial proteins shows that long-chain acyl coenzyme A dehydrogenase (LCAD) is hyperacetylated at lysine 42 in the absence of SIRT3. LCAD is deacetylated in wild-type mice under fasted conditions and by SIRT3 in vitro and in vivo; and hyperacetylation of LCAD reduces its enzymatic activity. Mice lacking SIRT3 exhibit hallmarks of fatty-acid oxidation disorders during fasting, including reduced ATP levels and intolerance to cold exposure. These findings identify acetylation as a novel regulatory mechanism for mitochondrial fatty-acid oxidation and demonstrate that SIRT3 modulates mitochondrial intermediary metabolism and fatty-acid use during fasting., Proteomic analysis of mitochondrial proteins revealed the acetylation levels of numerous mitochondrial proteins change during fasting (4). The dependence of SIRT3 enzymatic activity on [NAD.sup.+] suggests that SIRT3 serves as [...]

Exposure to high vs. low glycemic index (GI) diets increases fat mass and insulin resistance in obesity-prone C57BL/6J mice. However, the longer-term effects and potentially involved mechanisms are largely unknown. We exposed four groups of male C57BL/6J mice (n = l0 per group) to long-term (20 wk) or short-term (6 wk) isoenergetic and macronutrient matched diets only differing in starch type and as such GI. Body composition, liver fat, molecular factors of lipid metabolism, and markers of insulin sensitivity and metabolic flexibility were investigated in all four groups of mice. Mice fed the high GI diet showed a rapid-onset (from week 5) marked increase in body fat mass and liver fat, a gene expression profile in liver consistent with elevated lipogenesis, and, after long-term exposure, significantly reduced glucose clearance following a glucose load. The long-term high-GI diet also led to a delayed switch to both carbohydrate and fat oxidation in the postprandial state, indicating reduced metabolic flexibility. In contrast, no difference in carbohydrate oxidation was observed after short-term high- vs. low-GI exposure. However, fatty acid oxidation was significantly blunted as early as 3 wk after beginning of the high-GI intervention, at a time where most measured phenotypic markers including body fat mass were comparable between groups. Thus long-term high-GI feeding resulted in an obese, insulin-resistant, and metabolically inflexible phenotype in obesity-prone C57BL/6J mice. Early onset and significantly impaired fatty acid oxidation preceded these changes, thereby indicating a potentially causal involvement. glycemic index; fat metabolism; body fat; insulin resistance; liver fat; metabolic flexibility; insulin resistance doi: 10.1152/ajpendo.00515.2009

Weight loss is accompanied by several metabolic adaptations that work together to promote rapid, efficient regain. We employed a rodent model of regain to examine the effects of a regular bout of treadmill exercise on these adaptations. Obesity was induced in obesity-prone rats with 16 wk of high-fat feeding and limited physical activity. Obese rats were then weight reduced (~14% of body wt) with a calorie-restricted, low-fat diet and maintained at that reduced weight for 8 wk by providing limited provisions of the diet with (EX) or without (SED) a daily bout of treadmill exercise (15 m/min, 30 min/day, 6 days/wk). Weight regain, energy balance, fuel utilization, adipocyte cellularity, and humoral signals of adiposity were monitored during eight subsequent weeks of ad libitum feeding while the rats maintained their respective regimens of physical activity. Regular exercise decreased the rate of regain early in relapse and lowered the defended body weight. During weight maintenance, regular exercise reduced the biological drive to eat so that it came closer to matching the suppressed level of energy expenditure. The diurnal extremes in fuel preference observed in weight-reduced rats were blunted, since exercise promoted the oxidation of fat during periods of feeding (dark cycle) and promoted the oxidation of carbohydrate (CHO) later in the day during periods of deprivation (light cycle). At the end of relapse, exercise reestablished the homeostatic steady state between intake and expenditure to defend a lower body weight. Compared with SED rats, relapsed EX rats exhibited a reduced turnover of energy, a lower 24-h oxidation of CHO, fewer adipocytes in abdominal fat pads, and peripheral signals that overestimated their adiposity. These observations indicate that regimented exercise altered several metabolic adaptations to weight reduction in a manner that would coordinately attenuate the propensity to regain lost weight. fat oxidation; energy balance; indirect calorimetry; postobese; adipocyte cellularity

Objective: To determine whether a series of new computed tomography (CT)-derived indices are better diagnostic criteria than the classical CT-derived measurements. A second objective is to propose specific or sensitive threshold values of the most accurate criteria for the occurrence of metabolic disturbances. Subjects/Methods: Anthropometric measurements and CT scans were performed in 74 obese subjects. Fat thicknesses, diameters, diagonals and areas were determined. Plasma lipids, insulin, glucose and fat cell size were analyzed. A multivariate regression analysis was performed to determine the most accurate predictor index for metabolic alterations explaining the highest percentage of variance. Results: All the new indices were highly correlated with body mass index, percentage of fat and fat cell size. Subcutaneous thicknesses were greater in women, while internal-coronal and sagittal diameters, visceral adipose tissue (VAT) and internal circumference area were greater in men (P Conclusion: For the first time, we have described SSAT and the SSAT/VAT ratio as important indices in obesity-related disturbances. doi:10.1038/ejcn.2008.47; published online 29 October 2008 Keywords: abdominal fat distribution; superficial subcutaneous adipose tissue; visceral adipose tissue; cardiovascular risk; HOMA index, Introduction The distribution of body fat has a singular impact on the development of obesity-related alterations, and abdominal fat accumulation represents a risk factor per se. Thus, both localization and [...]

Consuming low-glycemic index (LGI) carbohydrates (CHO) before endurance exercise results in increased fat oxidation during exercise in trained men and women. It is not known if this phenomenon occurs during low intensity exercise and in untrained participants. We examined the effects of breakfasts containing high-GI (HGI) or LGI foods on substrate utilization during rest and walking exercise in sedentary women. The metabolic and appetite responses to a standard lunch consumed after exercise were also investigated. Eight healthy sedentary women completed 2 trials. On each occasion, participants were provided with a HGI or LGI breakfast 3 h before walking for 60 min. Following exercise, participants were provided with lunch and remained in the laboratory for a further 2 h. Plasma glucose and serum insulin responses (area under the curve) were higher following the HGI breakfast than following the LGI breakfast (P < 0.05). During the 3-h postprandial period, fat oxidation was suppressed following both breakfasts but remained higher in the LGI trial (P < 0.05). During exercise, total fat oxidation was also greater in the LGI trial (P < 0.001). There were no differences in the metabolic responses to lunch. Participants reported feeling fuller following lunch in the LGI trial (P < 0.05). Consuming a LGI breakfast increases fat oxidation during subsequent exercise and improves satiety during recovery in sedentary females.

The objective was to examine pathways of androgen metabolism in abdominal adipose tissue in women. Abdominal subcutaneous (SC) and omental (OM) adipose tissue samples were surgically obtained in women. Total RNA was isolated from whole adipose tissue samples and from primary preadipocyte cultures before and after induction of differentiation. Expression levels of several steroid-converting enzyme transcripts were examined by real-time RT-PCR. Androgen conversion rates were also measured. We found higher expression levels in SC compared with OM adipose tissue for type 1 3[beta]-hydroxysteroid dehydrogenase (3[beta]-HSD-1; P < 0.05), for aldo-keto reductase 1C3 (AKR1C3; P < 0.0001), for AKR1C2 (P < 0.0001), and for the androgen receptor (P < 0.0001). 17[beta]-HSD-2 mRNA levels were lower in SC adipose tissue (P < 0.05). Induction of adipocyte differentiation led to significantly increased expression levels in SC cultures for AKR1C3 (4.7-fold, P < 0.01), 11-cis-retinol dehydrogenase (6.9-fold, P < 0.02), AKR1C2 (5.6-fold, P < 0.004), P-450 aromatase (5.7-fold, P < 0.02), steroid sulfatase (3.1-fold, P < 0.02), estrogen receptor-[beta] (11.8-fold, P < 0.01), and the androgen receptor (4.0-fold, P < 0.0005). Generally similar but nonsignificant trends were obtained in OM cultures. DHT inactivation rates increased with differentiation, this effect being mediated by dexamethasone alone, through a glucocorticoid receptor-dependent mechanism. In conclusion, higher mRNA levels of enzymes synthesizing and inactivating androgens are found in differentiated adipocytes, consistent with higher androgen-processing rates in these cells. Glucocorticoidinduced androgen inactivation may locally modulate the exposure of adipose cells to active androgens. aldo-keto reductases; short-chain dehydrogenases; adipocyte differentiation; omental visceral fat; estrogen

A dual-tracer approach (dietary [sup.14]C-palmitate and intraperitoneal [sup.3]H-[H.sub.2]O) was used to assess the trafficking of dietary fat and net retention of carbon in triglyceride depots during the first 24 h of weight regain. Obesity-prone male Wistar rats were allowed to mature under obesogenic conditions for 16 wk. One group was switched to ad libitum feeding of a low-fat diet for 10 wk (Obese group). The remaining rats were switched to an energy-restricted, low-fat diet for 10 wk that reduced body weight by 14% and were then assessed in energy balance (Reduced group), with free access to the low-fat diet (Relapse-Dayl group), or with a provision that induced a minor imbalance (+ 10 kcal) equivalent to that observed in obese rats (Gap-Matched group). Fat oxidation remained at a high, steady rate throughout the day in Obese rats, but was suppressed in Reduced, Gap-Matched, and Relapse-Dayl rats though 9, 18, and 24 h, respectively. The same caloric excess in Obese and Gap-Matched rats led to less fat oxidation over the day and greater trafficking of dietary fat to visceral depots in the latter. In addition to trafficking nutrients to storage, Relapse-Dayl rats had more small, presumably new, adipocytes at the end of 24 h. Dietary fat oxidation at 24 h was related to the phospborylation of skeletal muscle acetyl-CoA carboxylase and fatty acid availability. These observations provide evidence of adaptations in the oxidation and trafficking of dietary fat that extend beyond the energy imbalance, which facilitate rapid, efficient regain during the relapse to obesity. acetyl-CoA carboxylase; metabolic inflexibility; postobese; adipocyte cellularity

Obesity is associated with a decrement in the ability of skeletal muscle to oxidize lipid. The purpose of this investigation was to determine whether clinical interventions (weight loss, exercise training) could reverse the impairment in fatty acid oxidation (FAO) evident in extremely obese individuals. FAO was assessed by incubating skeletal muscle homogenates with [1-[sup.14]C]palmitate and measuring [sup.14]C[O.sub.2] production. Weight loss was studied using both cross-sectional and longitudinal designs. Muscle FAO in extremely obese women who had lost weight (decrease in body mass of--50 kg) was compared with extremely obese and lean individuals (BMI of 22.8 [+ or -] 1.2, 50.7 [+ or -] 3.9, and 36.5 [+ or -] 3.5 kg/[m.sup.2] for lean, obese, and obese after weight loss, respectively). There was no difference in muscle FAO between the extremely obese and weight loss groups, and FAO was depressed (-45%; P [less than or equal to] 0.05) compared with the lean subjects. Muscle FAO also did not change in extremely obese women (n = 8) before and 1 yr after a 55-kg weight loss. In contrast, 10 consecutive days of exercise training increased (P [less than or equal to] 0.05) FAO in the skeletal muscle of lean (+ 1.7-fold), obese (+ 1.8-fold), and previously extremely obese subjects after weight loss (+2.6-fold). mRNA content for PDK4, CPT I, and PGC-l[alpha] corresponded with FAO in that there were no changes with weight loss and an increase with physical activity. These data indicate that a defect in the ability to oxidize lipid in skeletal muscle is evident with obesity, which is corrected with exercise training but persists after weight loss. extreme obesity; fat oxidation; gastric bypass surgery; mitochondria; physical activity

When using [sup.13]C tracer to measure plasma fat oxidation, an acetate recovery factor should be determined in every subject to correct for label sequestration. Less is known regarding the acetate recovery factor for dietary fatty acid oxidation. We compiled data from six studies to investigate the determinants of the dietary acetate recovery factor (dARF) at rest and after physical activity interventions and compared the effects of different methods of dARF calculation on both the fat oxidation and its variability. In healthy lean subjects, DARF was 50.6 [+ or -] 5.4% dose (n = 56) with an interindividual coefficient of variation of 10.6% at rest and 9.2% after physical activity modifications. The physical activity interventions did not impact dARF, and the intraindividual coefficient of variation was 4.6%. No major anthropological or physiological determinants were detected except for resting metabolic rate, which explains 7.4% of the dARF variability. Applying an individual or an average group dARF did not affect the mean and the variability of the derived dietary lipid oxidation at rest or after physical activity interventions. Using a mean dARF for a group leads to over- or underestimation of fat oxidation of less than 10% in individual subjects. Moreover, the use of a group or individual correction did not affect the significant relationship found between fasting respiratory exchange ratio and dietary fat oxidation. These data indicate that an average dARF can be applied for longitudinal and cross-sectional studies investigating dietary lipid metabolism. exogenous fatty acid oxidation; stable isotopes; mass spectrometry

There is evidence from studies in animals that the effects of both fat and CCK on gastrointestinal function and energy intake are attenuated by consumption of a high-fat diet. In humans, the effects of exogenous CCK-8 on antropyloroduodenal motility, plasma CCK, peptide YY (PYY), and ghrelin concentrations, appetite, and energy intake are attenuated by a high-fat diet. Ten healthy lean males consumed isocaloric diets (~15,400 kJ per day), containing either 44% (high-fat, HF) or 9% (low-fat, LF) fat, for 21 days in single-blind, randomized, crossover fashion. Immediately following each diet (i.e., on day 22), subjects received a 45-min intravenous infusion of CCK-8 (2 ng x [kg.sup.-1] x [min.sup.-1]), and effects on antropyloroduodenal motility, plasma CCK, PYY, ghrelin concentrations, hunger, and fullness were determined. Thirty minutes after commencement of the infusion, subjects were offered a buffet-style meal, from which energy intake (in kilojoules) was quantified. Body weight was unaffected by the diets. Fasting CCK (P < 0.05), but not PYY and ghrelin, concentrations were greater following the HF, compared with the LF, diet. Infusion of CCK-8 stimulated pyloric pressures (P < 0.01) and suppressed antral and duodenal pressures (P < 0.05), with no difference between the diets. Energy intake also did not differ between the diets. Short-term consumption of a HF diet increases fasting plasma CCK concentrations but does not affect upper gut motility, PYY and ghrelin, or energy intake during CCK-8 infusion, in a dose of 2 ng x [kg.sup.-1] x [min.sup.-1], in healthy males. antropyloroduodenal motility; appetite; gut hormones; healthy subjects

Fat depot sizes peak in middle age but decrease by advanced old age. This phenomenon is associated with ectopic fat deposition, decreased adipocyte size, impaired differentiation of preadipocytes into fat cells, decreased adipogenic transcription factor expression, and increased fat tissue inflammatory cytokine generation. To define the mechanisms contributing to impaired adipogenesis with aging, we examined the release of TNF[alpha], which inhibits adipogeneszs, and the expression of CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP), which blocks activity of adipogenic C/EBP family members, in preadipocytes cultured from young, middle-aged, and old rats. Medium conditioned by fat tissue, as well as preadipocytes, from old rats impeded lipid accumulation by preadipocytes from young animals. More TNF[alpha] was released by preadipocytes from old than young rats. Differences in TNF[alpha]-converting enzyme, TNF[alpha] degradation, or the presence of macrophages in cultures were not responsible. TNF[alpha] induced rat preadipocyte CHOP expression. CHOP was higher in undifferentiated preadipocytes from old than younger animals. Over-expression of CHOP in young rat preadipocytes inhibited lipid accumulation. TNF[alpha] short interference RNA reduced CHOP and partially restored lipid accumulation in old rat preadipocytes. CHOP normally increases during late differentiation, potentially modulating the process. This late increase in CHOP was not affected substantially by aging: CHOP was similar in differentiating preadipocytes and fat tissue from old and young animals. Hypoglycemia, which normally causes an adaptive increase in CHOP, was less effective in inducing CHOP in preadipocytes from old than younger animals. Thus increased TNF[alpha] release by undifferentiated preadipocytes with elevated basal CHOP contributes to impaired adipogenesis with aging. adipocytes; CCAAT/enhancer-binding protein-[zeta]; growth arrest and DNA damage 153; differentiation; stress response; hypoglycemia

The inability to maintain body weight within prescribed ranges occurs in a significant portion of the human spinal cord injury (SCI) population. Using a rodent model of long-term high thoracic (spinal level T3) spinal cord transection (TX), we aimed to identify derangements in body weight, body composition, plasma insulin, glucose tolerance, and metabolic function, as measured by uncoupling protein 1 (UCP1) expression in interscapular brown adipose tissue (IBAT). Sixteen weeks after SCI, body weights of injured female rats stabilized and were significantly lower than surgical control animals. At the same time point, SCI rats had a significantly lower whole body fat:lean tissue mass ratio than controls, as measured indirectly by NMR. Despite lower body weight and fat mass, the cumulative consumption of standard laboratory chow (4.0 kcal/g) and mean energy intake (kcal*[day.sup.-1]*100 g body [wt.sup.-1]) of chronic SCI rats was significantly more than controls. Glucose tolerance tests indicated a significant enhancement in glucose handling in 16-wk SCI rats, which were coupled with lower serum insulin levels. The post mortem weight of gonadal and retroperitoneal fat pads was significantly reduced after SCI and IBAT displayed significantly lower real-time PCR expression of UCP1 mRNA. The reduced fat mass and IBAT UCP1 mRNA expression are contraindicative of the cumulative caloric intake by the SCI rats. The prolonged postinjury loss of body weight, including fat mass, is not due to hypophagia but possibly to permanent changes in gastrointestinal transit and absorption, as well as whole body homeostatic mechanisms. metabolic syndrome; fat mass; lean body mass; weight loss; energy balance

The recruitment process induced by acclimation of mammals to cold includes a marked alteration in the acyl composition of the phospholipids of mitochondria from brown adipose tissue: increases in 18:0, 18:2(n-6), and 20:4(n-6) and decreases in 16:0, 16:1, 18:1, and 22:6(n-3). A basic question is whether these alterations are caused by changes in the concentration of uncoupling protein-1 (UCP1) or the thermogenesis it mediates--implying that they are secondary effects--or whether they are an integrated, independent part of the recruitment process. This question was addressed here using wild-type and UCP1-ablated C57BL/6 mice acclimated to 24[degrees]C or 4[degrees]C. In wild-type mice, the phospholipid fatty acyl composition of mitochondria from brown adipose tissue showed the changes in response to cold that were expected from observations in other species and strains. The changes were specific, as different changes occurred in skeletal muscle mitochondria. In UCP1-ablated mice, cold acclimation induced acyl alterations in brown adipose tissue that were qualitatively identical and quantitatively similar to those in wild-type mice. Therefore, neither the increased content of UCP1 nor mitochondrial uncoupling altered the effect of cold on acyl composition. Cold acclimation in wild-type mice had little effect on phospholipid acyl composition in muscle mitochondria, but cold-acclimation in UCP1-ablated mice caused significant alterations, probably due to sustained shivering. Thus, the alterations in brown adipose tissue phospholipid acyl composition are revealed to be an independent part of the recruitment process, and their functional significance for thermogenesis should be elucidated. knockout mice; adaptive thermogenesis; skeletal muscle

Epidemiological and animal studies suggest that the alteration of hormonal and metabolic environment during fetal and neonatal development can contribute to development of metabolic syndrome in adulthood. In this paper, we investigated the impact of maternal high-fat (HF) diet on hypothalamic leptin sensitivity and body weight gain of offspring. Adult Wistar female rats received a HF or a control normal-fat (C) diet for 6 wk before gestation until the end of the suckling period. After weaning, pups received either C or HF diet during 6 wk. Body weight gain and metabolic and endocrine parameters were measured in the eight groups of rats formed according to a postweaning diet, maternal diet, and gender. To evaluate hypothalamic leptin sensitivity in each group, STAT-3 phosphorylation was measured in response to leptin or saline intraperitoneal bolus. Pups exhibited similar body weights at birth, but at weaning, those born to HF dams weighed significantly less (-12%) than those born to C dams. When given the HF diet, males and females born to HF dams exhibited smaller body weight and feed efficiency than those born to C dams, suggesting increased energy expenditure programmed by the maternal HF diet. Thus, maternal HF feeding could be protective against adverse effects of the HF diet as observed in male offspring of control dams: overweight (+ 17%) with hyperleptinemia and hyper-insulinemia. Furthermore, offspring of HF dams fed either C or HF diet exhibited an alteration in hypothalamic leptin-dependent STAT-3 phosphorylation. We conclude that maternal high-fat diet programs a hypothalamic leptin resistance in offspring, which, however, fails to increase the body weight gain until adulthood. leptin resistance; hypothalamus; high-fat diet

We previously reported that oxytocin knockout (OT KO) mice display markedly enhanced intake of sweet and nonsweet carbohydrate solutions compared with intake by wild-type (WT) mice of the same background strain. The present study was conducted to determine whether OT KO mice demonstrate enhanced intake of Intralipid, a palatable lipid emulsion. Male or female mice of both genotypes that were naive to the test solution were given continuous two-bottle access to Intralipid and water with food available ad libitum for 3 days. Throughout the experiment, mice of both genotypes showed a marked preference for Intralipid over water. On the 1st day, OT KO mice displayed twofold greater preference and consumed nearly twice as much Intralipid compared with WT cohorts. However, on subsequent days of exposure, Intralipid preference and intake did not differ between genotypes over a range of lipid concentrations presented in descending or ascending order. Daily and hourly measures of lipid vs. sucrose intake confirmed that OT KO mice consumed more sucrose solution, but not lipid emulsion, than WT mice. During ad libitum access to Intralipid, both genotypes consumed significantly more calories from the emulsion as concentration increased. Both genotypes maintained consistent total daily caloric intake (lipid plus chow) and compensated by decreasing chow intake over the course of the study. These findings, coupled with prior reports from our laboratory, support the view that OT signaling pathways participate in limiting intake of palatable carbohydrate-containing solutions, but do not appear to play a role in limiting intake of Intralipid. ingestive behavior; hypothalamus; neurohypophysis

We previously reported an exaggerated endocrine and weight loss response to stress in rats fed a high-fat (HF) diet for 5 days. Others report blunted stress-induced anxiety in rats made obese on a HF diet. Experiments described here tested whether sensitivity to stress-related peptides was changed in obese and nonobese HF-fed rats. Third ventricle infusion of corticotropin-releasing factor (CRF) in rats made obese on HF diet (40% kcal fat) produced an exaggerated hypophagia, which is thought to be mediated by CR[F.sub.2] receptors. Obese rats responded to a lower dose of CRF for a longer time than rats fed a low-fat (LF) diet (12% kcal fat). CRF-induced release of corticosterone, which is thought to be mediated by CR[F.sub.1] receptors, was not exaggerated in obese HF-fed rats. In contrast, rats fed HF diet for 5 days showed the same food intake and corticosterone response to CRF as LF-fed rats. CRF mRNA expression in the paraventricular nucleus of the hypothalamus was stimulated by mild stress (ip saline injection and placement in a novel cage) in LF-fed rats but not in rats fed HF diet for 5 days because of a nonsignificant increase in expression in nonstressed HF-fed rats. In addition, nonstressed levels of urocortin (UCN) I mRNA expression in the Edinger-Westphal nucleus were significantly inhibited in HF-fed rats. These data suggest that rats that have become obese on a HF diet show a change in responsiveness to stress peptides, whereas the increased stress response in nonobese HF-fed rats may he associated with changes in basal CRF and UCN I mRNA expression. rats; food intake; corticosterone; corticotropin-releasing factor mRNA; urocortin I mRNA

Food intake is stimulated following administration of orexin-A into the perifornical region of the lateral hypothalamus (LH/PFA). Orexin neurons originating in the LH/PFA interact with a number of hypothalamic systems known to influence food intake, including glutamatergic neurons. Glutamatergic systems in the LH/PFA were demonstrated to initiate feeding through N-methyl-D-aspartic acid (NMDA) receptors. Male SpragueDawley rats fitted with brain guide cannulas to the LH/PFA were used in two experiments. In the first experiment, a combination microdialysis/microinjection probe was used to deliver artificial cerebrospinal fluid (aCSF) or 500 pmol of orexin-A into the LH/PFA. Orexin-A increased interstitial glutamate to 143 [+ or -] 12% of baseline (P < 0.05), which remained elevated over the 120-rain collection period. In the second experiment, the NMDA receptor antagonist D-2-amino-5phosphonopentanoic acid (D-AP5; 10 nmol) was administered before orexin-A. The orexin-induced increase in food intake (from 1.1 [+ or -] 0.4 to 3.2 [+ or -] 0.5 g, P < 0.05) during the first hour was absent in rats receiving D-AP5 + orexin-A (1.2 [+ or -] 0.5 g). There was no effect of D-AP5 alone on food intake. These data support glutamatergic systems in the LH/PFA mediating the feeding response to orexin-A through NMDA receptors. food intake regulation; hypocretin; microdialysis

The Wnt family of secreted glycoproteins had previously been shown to regulate diverse processes during early development. Wnt signaling also plays a key role in the homeostasis of adult tissues maintaining stem cell pluripotency and determining differentiating cell fate. The age-related decrease in Wnt signaling may contribute to increased muscle adiposity and diminished bone strength. In the current study, we investigated the long-term metabolic consequences of the upregulated Wnt/[beta]-catenin signaling in skeletal muscles of adult diet-induced obese (DIO) rats. To this end, we generated a recombinant adeno-associated virus (rAAV) vector encoding murine Wnt10b cDNA. The long-term expression of rAAV1-Wnt10b was tested after intramuscular injection in the female DIO rat. Animals fed high-fat diet and treated with rAAV1-Wnt10b showed a sustained reduction in body weight compared with controls, and expression of Wnt10b was accompanied by a reduction in hyperinsulinemia and triglyceride plasma levels as well as improved glucose homeostasis. Nuclear magnetic resonance methods revealed that ectopic expression of Wnt10b resulted in a decrease in both global and muscular fat deposits in DIO rats. The long-range effect of locally expressed Wnt10b was also manifested through the increased bone mineral density. The detailed analysis of molecular markers revealed fibroblast growth factor-4 and vascular endothelial growth factor as possible mediators of the systemic effect of Wnt10b transgene expression. Our data demonstrate that altering Wnt/[beta]-catenin signaling in the skeletal muscle of an adult animal invokes moderate responses with favorable metabolic profile, bringing the notion of alternative therapeutic modality in the treatment of obesity, diabetes, and osteoporosis. Wnt10b; gene therapy; obesity: diabetes

Central-omental obesity plays a causative role in the pathogenesis of the metabolic syndrome. Adipokines are involved in the pathogenesis of this syndrome. However, adipokines secreted by omental adipose tissue (OAT) are still poorly characterized in human obesity. Therefore, we searched for novel adipokines abnormally secreted by OAT in obesity and examined their relationships with some features of metabolic syndrome and the respective contribution of adipocytes vs. stromal-vascular cells. OAT from obese and nonobese men was fractionated into adipocytes and SV cells, which were then cultured. Medium was screened by medium-scale protein arrays and ELISAs. Adipokine mRNA levels were measured by real-time RT-qPCR. We detected 16 cytokines secreted by each cellular fraction of lean and obese subjects. Of the 16 cytokines, six adipokines were newly identified as secretory products of OAT, which were dysregulated in obesity: three chemokines (growth-related oncogen factor, RANTES, macrophage inflammatory protein-l[beta]), one interleukin (IL-7), one tissue inhibitor of metalloproteinases (TIMP-1), and one growth factor (thrombopoietin). Their secretion and expression were enhanced in obesity, with a relatively similar contribution of the two fractions. The higher proportion of macrophages and endothelial cells in obesity may contribute to this enhanced production as well as changes in intrinsic properties of hypertrophied adipocytes. Accordingly, mRNA concentrations of most of these adipokines increased during adipocyte differentiation. Eventually, expression of the investigated adipokines did correlate with several features of the metabolic syndrome. In conclusion, six adipokines were newly identified as oversecreted by OAT in obesity. These adipokines may link obesity to its cardiovascular or metabolic comorbidities. obesity; adipocytes; stromal-vascular cells; inflammation; metabolic syndrome

The aim was to investigate the effects of intestinal electrical stimulation (IES) on food intake, body weight, and gastric emptying in rats. An experiment on food intake and weight change was performed in 22 rats on a control diet and 10 diet-induced obese (DIO) rats for 4 wk with IES or sham IES. The effect of IES on gastric emptying was performed in another 20 rats in the control group. We found that 1) in control rats, 4-wk IES resulted in a reduction of 18.2% in the total amount of food intake compared with sham-IES (P = 0.02); the rats treated with IES had a weight change of -1 [+ or -] 7.8g (P = 0.03), which was equivalent to a weight loss of 6.2% due to IES when adjusted for normal growing. 2) Acute IES delayed gastric emptying by 20% in the control rats (P < 0.01). 3) In the DIO rats, 1-wk IES with the same parameters as those used in the control rats resulted in a significant reduction in the total amount of food intake (126.6 [+ or -] 6.3 g vs. 116.9 [+ or -] 3.2 g, P < 0.01). More reduction in food intake was noted, and a significant weight change was also observed when stimulation energy was increased. 4) No adverse events were observed in any of the experiments. In conclusion, IES delays gastric emptying, reduces food intake, and decreases weight gain in control growing rats. These data suggest that it is worthy to explore therapeutic potentials of IES for obesity. gastrointestinal motility; obesity; diet-induced obese rats; stimulation parameter; mechanism doi:10.1152/ajpregu.00318.2006

Adiponectin, a physiologically active polypeptide secreted by adipocytes, shows insulin-sensitizing, anti-inflammatory, and antiatherogenic properties in rodents and humans. To assess the effects of chronic hyperadiponectinemia on metabolic phenotypes, we established three lines of transgenic mice expressing human adiponectin in the liver. When maintained on a high-fat/high-sucrose diet, mice of two lines that had persistent hyperadiponectinemia exhibited significantly decreased weight gain associated with less fat accumulation and smaller adipocytes in both visceral and subcutaneous adipose tissues. Macrophage infiltration in adipose tissue was markedly suppressed in the transgenic mice. Expression levels of adiponectin receptors were not altered in skeletal muscle or liver. Circulating levels of endogenous adiponectin were elevated, whereas fasting glucose, insulin, and leptin levels were reduced compared with control mice. In the hyperadiponectinemic mice daily food intake was not altered, but oxygen consumption was significantly greater, suggesting increased energy expenditure. Moreover, high-calorie diet-induced premature death was almost completely prevented in the hyperadiponectinemic mice in association with attenuated oxidative DNA damage. The transgenic mice also showed longer life span on a conventional low-fat chow. In conclusion, transgenic expression of human adiponectin blocked the excessive fat accumulation and reduced the morbidity and mortality in mice fed a high-calorie diet. These observations may provide new insights into the prevention and therapy of metabolic syndrome in humans. adipocyte; macrophage; life span; 8-hyroxy-2-deoxyguanosine doi:10.1152/ajpendo.00645.2006

To determine whether long-term melanocortinergic activation can attenuate the metabolic effects of a high fat diet, mice overexpressing an NH2-terminal POMC transgene that includes [alpha]- and [[gamma].sub.3]-MSH were studied on either a 10% low-fat diet (LFD) or 45% high-fat diet (HFD). Weight gain was modestly reduced in transgenic (Tg-MSH) male and female mice vs. wild type (WT) on HFD (P < 0.05) but not LFD. Substantial reductions in body fat percentage were found in both male and female Tg-MSH mice on LFD (P < 0.05) and were more pronounced on HFD (P < 0.001). These changes occurred in the absence of significant feeding differences in most groups, consistent with effects of Tg-MSH on energy expenditure and partitioning. This is supported by indirect calorimetry studies demonstrating higher resting oxygen consumption and lower RQ in Tg-MSH mice on the HFD. Tg-MSH mice had lower fasting insulin levels and improved glucose tolerance on both diets. Histological and biochemical analyses revealed that hepatic fat accumulation was markedly reduced in Tg-MSH mice on the HFD. Tg-MSH also attenuated the increase in corticosterone induced by the HFD. Higher levels of Agrp mRNA, which might counteract effects of the transgene, were measured in Tg-MSH mice on LFD (P = 0.02) but not HFD. These data show that long-term melanocortin activation reduces body weight, adiposity, and hepatic fat accumulation and improves glucose metabolism, particularly in the setting of diet-induced obesity. Our results suggest that long-term melanocortinergic activation could serve as a potential strategy for the treatment of obesity and its deleterious metabolic consequences. melanocyte-stimulating hormone; melanocortins; proopiomelanocortin; obesity; hepatic steatosis; diabetes doi:10.1152/ajpendo.00555.2006.

Intramyocellular triacylglycerol (IMTG) has been suggested to represent an important substrate source during exercise. In the present study, IMTG utilization during exercise is assessed through the use of various methodologies. In addition, we identified differences in the use of intramyocellular lipids deposited in the immediate subsarcolemmal (SS) area and those stored in the more central region of the fiber. Contemporary stable isotope technology was applied in combination with muscle tissue sampling before and immediately after 3 h of moderate-intensity cycling exercise (62 [+ or -] 2% V[O.sub.2max]) in eight well-trained male cyclists. Continuous infusions with [U-[sup.13]C]palmitate and [6,6-[sup.2][H.sub.2]]glucose were applied to quantify plasma free fatty acid (FFA) and glucose oxidation rates and to estimate whole body IMTG and glycogen use. Both immunohisto-chemical analyses of oil red O (ORO)-stained muscle cross sections and biochemical triacylglycerol (TG) extraction were performed to assess muscle lipid content. During exercise, plasma FFA, muscle (and/or lipoprotein)-derived TG, plasma glucose, and muscle glycogen oxidation contributed 24 [+ or -] 2, 22 [+ or -] 3, 11 [+ or -] 1, and 43 [+ or -] 3% to total energy expenditure, respectively. In accordance, a significant net decline in muscle lipid content was observed following exercise as assessed by ORO staining (67 [+ or -] 8%) and biochemical TG extraction (49 [+ or -] 8%), and a positive correlation was observed between methods (r = 0.56; P < 0.05). Lipid depots located in the SS area were utilized to a greater extent than the more centrally located depots. This is the first study to show significant use of IMTG as a substrate source during exercise in healthy males via the concurrent implementation of three major methodologies. In addition, this study shows differences in resting subcellular intramyocellular lipid deposit distribution and in the subsequent net use of these deposits during exercise. fat metabolism; intramyocellular triacylglycerol; skeletal muscle; cycling; substrate utilization doi:10.1152/ajpendo.00678.2006.

We have recently reported that inhibition of transforming growth factor (TGF)-[beta] in the brain reduced fat-related energy substrates concentrations in response to exercise. We investigated the relevance between the mobilization of fat-related energy substrates (nonesterified fatty acid and ketone bodies) during exercise and the effects of TGF-[beta] in the brain. Low-intensity exercise was simulated by contraction of the hindlimbs, induced by electrical stimulation at 2 Hz in anesthetized rats (Sim-Ex). As with actual exercise, it was confirmed that mobilization of carbohydrate-related energy substrates (glucose and lactic acid) occurred immediately after the onset of Sim-Ex, and mobilization of fat-related energy substrates followed thereafter. The timing of mobilization of fat-related substrates corresponded to that of the increase in TGF-[3 in cerebrospinal fluid (CSF) in Sim-Ex. The level of TGF-[beta] in CSF significantly increased after 10 min of Sim-Ex and remained elevated until 30 min of Sim-Ex. Intracisternal administration of TGF-[beta] caused rapid mobilization of fat-related energy substrates. Meanwhile, there were no effects on the changes in carbohydrate-related substrates. The levels of catecholamines were slightly elevated after TGF-[beta] administration, and, although not significantly in statistical terms, we consider that at least a part of TGF-[beta] signal was transducted via the sympathetic nervous system because of these increases. These data indicate that TGF-[beta] in the brain is closely related to the mobilization of fat-related energy substrates during low-intensity exercise. We hypothesized that the central nervous system plays a role in the regulation of energy metabolism during low-intensity exercise and this may be mediated by TGF-[beta]. central nervous system; energy metabolism; flux; ketone bodies; nonesterifed fatty acid doi:10.1152/ajpregu.00632.2006

Intestinal alkaline phosphatase (IAP) is involved in the process of fat absorption, a conclusion confirmed by an altered lipid transport and a faster body weight gain from 10 to 30 wk in both male and female mice with a homozygous null mutation of the IAP coding gene (Akp[3.sup.-/-] mice). This study was aimed to delineate morphologically and quantitatively the accelerated lipid absorption in male Akp[3.sup.-/-] mice. Feeding a corn oil bolus produced an earlier peak of triacylglycerol in serum (2 vs. 4 h for Akp[3.sup.-/-] and wild-type mice, respectively) and an approximately twofold increase in serum triacylglycerol concentration in Akp[3.sup.-/-] mice injected with a lipolysis inhibitor, Triton WR-1339. A corn oil load induced the threefold enlargement of the Golgi vacuoles in male wild-type mice but not in Akp[3.sup.-/-] mice, indicating that absorbed lipids rarely reached the Golgi complex and that the transcytosis of lipid droplets does not follow the normal pathway in male Akp[3.sup.-/-] mice. Force feeding an exaggerated fat intake by a 30% fat chow for 10 wk induced obesity in both male Akp[3.sup.-/-] and wild-type mice, and therefore no phenotypic difference was observed between the two. On the other hand, the forced high-fat chow induced an 18% greater body weight gain, hepatic steatosis, and visceral fat accumulation in female Akp[3.sup.-/-] mice but not in female wild-type controls. These results provide further evidence that IAP is involved in the regulation of the lipid absorption process and that its absence leads to progressive metabolic abnormalities in certain fat-forced conditions. fat absorption; metabolic abnormality; obesity; small intestine doi:10.1152/ajpgi.00331.2006.

This study describes the previously uncharacterized ontogeny and regulation of truncal adipose reserves in the profoundly GH-deficient dwarf (dw/dw) rat. We show that, despite normal proportionate food intake, dw/dw rats develop abdominal leanness and hypoleptinemia (circulating leptin halved in dw/dw males, P < 0.05) during puberty. This contrasts with the hyperleptinemia seen in moderately GH-deficient Tgr rats (circulating leptin doubled at 6 wk of age, P < 0.05) and in GH receptor-binding protein (GHR/BP)-null mice (circulating leptin doubled; P < 0.05). This lean/hypoleptinemic phenotype was not completely normalized by GH treatment, but dw/dw rats developed abdominal obesity in response to neonatal MSG treatment or maintenance on a high-fat diet. Unlike Tgr rats, dw/dw rats did not become obese with age; plasma leptin levels and fat pad weights became similar to those in wild-type rats. In contrast with truncal leanness, tibial marrow adiposity was normal in male and doubled in female dwarves (P < 0.01), this increase being attributable to increased adipocyte number (P < 0.01). Neonatal MSG treatment and high-fat feeding elevated marrow adiposity in dw/dw rats by inducing adipocyte enlargement (P < 0.05). These results demonstrate that, despite lipolytic influence of GH, severe GH deficiency in dw/dw rats is accompanied by a paradoxical leanness. This lean/hypoleptinemic phenotype is not solely attributable to reduced GH signaling and does not appear to result from a reduction in nutrient intake or the ability of dw/dw adipocytes to accumulate lipid. Disruption of preadipocyte differentiation or adipocyte proliferation in the dw/dw rat may lead to the development of this unusually lean/hypoleptinemic phenotype. adipose tissue; bone marrow fat; leptin; dwarfism doi:10.1152/ajpendo.00417.2006

Adipose tissue inflammation has recently been linked to the pathogenesis of obesity and insulin resistance. C1 complex comprising three distinct proteins, C1q, C1r, and C1s, involves the key initial activation of the classic pathway of complement and plays an important role in the initiation of inflammatory process. In this study, we investigated adipose expression and regulation of C1 complement subcomponents and C1 activation regulator decorin in obesity and insulin resistance. Expression of C1q in epididymal adipose tissue was increased consistently in ob/ob mice, Zucker obese rats, and high fat-diet-induced obese (HF-DIO) mice. Decorin was found to increase in expression in Zucker obese rats and HF-DIO mice but decrease in ob/ob mice. After TZD administration, C1q and decorin expression was reversed in Zucker obese rats and HF-DIO mice. Increased expression of C1 complement and decorin was observed in both primary adipose and stromal vascular cells isolated from Zucker obese rats. Upregulation of C1r and C1s expression was also perceived in adipose cells from insulin-resistant humans. Furthermore, expression of C1 complement and decorin is dysregulated in TNF-[alpha]-induced insulin resistance in 3T3-L1 adipocytes and cultured rat adipose cells as they become insulin resistant after 24-h culture. These data suggests that both adipose and immune cells are the sources for abnormal adipose tissue production of C1 complement and decorin in obesity. Our findings also demonstrate that excessive activation of the classic pathway of complement commonly occurs in obesity, suggesting its possible role in adipose tissue inflammation and insulin resistance. C1 complement; gene expression doi:10.1152/ajpendo.00664.2006

We recently showed that diencephalic TRH may mediate the central leptin-induced pressor effect. Here, to study the role of TRH in obesity-induced hypertension (OIH), we used a model of OIH produced by a high-fat diet (HFD, 45 days) in male Wistar rats. After 4 wk, body weight and systolic arterial blood pressure (SABP) increased in HFD animals. Plasma leptin was correlated with peritoneal adipose tissue. Then, we treated OIH animals with an antisense oligodeoxynucleotide and small interfering (si)RNA against the prepro-TRH. Antisense significantly decreased diencephalic TRH content and SABP at 24 and 48 h posttreatment. Similar effects were observed with siRNA against prepro-TRH but for up to 4 wk. Conversely, vehicle, an inverted antisense sequence and siRNA against green fluorescence protein, produced no changes. SABP decrease seems to be owing to an inhibition of the obesity-enhanced sympathetic outflow but not to an alteration in thyroid status. Using a simple OIH model we demonstrated, for the first time, that central TRH participates in the hypertension induced by body weight gain probably through its well-known action on sympathetic activity. Thus the TRH-leptin interaction may contribute to the strong association between hypertension and obesity. thyroliberin; antisense; small interfering ribonucleic acid; blood pressure; leptin doi:10.1152/ajpendo.00234.2006

Peptide YY [(PYY).sub.3-36] has been shown to produce dramatic reductions in energy intake (EI), but no human data exist regarding energy expenditure (EE), glucose and fat metabolism. Nothing is known regarding PYY1-36. To compare effects of PY[Y.sup.1-36] and PY[Y.sub.3-36] on appetite, EI, EE, insulin, glucose and free fatty acids (FFA) concentrations, 12 lean and 12 obese males participated in a blinded, randomized, crossover study with 90-min infusions of saline, 0.8 pmol*[kg.sup.-1]*[min.sup.-1] PY[Y.sub.1-36] and PY[Y.sub.3-36]. Only four participants completed PY[Y.sub.3-36] infusions because of nausea. Subsequently, six lean and eight obese participants completed 0.2 pmol*[kg.sup.-1]*[min.sup.-1] PY[Y.sub.3-36] and 1.6 pmol* [kg.sup.-1]*[min.sup.-1] PY[Y.sub.1-36] infusions. PY[Y.sub.3-36] at 0.8 pmol*[kg.sup.-1]*[min.sup.-1] produced reduced EI, lower ratings of well-being, increases in FFA, postprandial glucose (only 0.8 pmol* [kg.sup.1]*[min.sup.-1] PY[Y.sub.3-36]) and insulin concentrations, as well as heart rate and EE (only 0.8 pmol*[kg.sup.-1]*[min.sup.-1] PY[Y.sup.3-36]). PY[Y.sub.1-36] at 1.6 pmol*[kg.sup.-1]*[min.sup.-1] produced increased heart rate and postprandial insulin response. Ratings of appetite were opposite with infusions of 0.8 and 1.6 pmol*[kg.sup.-1]*[min.sup.-1] PY[Y.sub.1-36] and seemed to depend on subjects being lean or obese. PY[Y.sub.3-36] caused increased thermogenesis, lipolysis, postprandial insulin and glucose responses, suggestive of increased sympathoadrenal activity. PY[Y.sub.1-36] had no effect on EI and no clear effects on appetite but resulted in increased heart rate and postprandial insulin response. However, highest tolerable dose of PY[Y.sub.1-36] was probably not reached in the present study. Peptide YY; free fatty acids; insulin sensitivity; arcuate nucleus; neuropeptide Y receptors

Angus and Wagyu steers consuming high-roughage diets exhibit large differences in adipose tissue fatty acid composition, but there are no differences in terminal measures of stearoyl-CoA desaturase (SCD) activity or gene expression. Also, adipose tissue lipids of cattle fed corn-based diets have greater MUFA:SFA ratios than cattle fed hay-based diets. We hypothesized that any changes in SCD gene expression and activity would precede similar changes in adipose tissue lipogenesis between short- and long-fed end-points. Furthermore, changes in SCD activity and gene expression between production endpoints would differ between corn- and hay-fed steers and between Wagyu and Angus steers. Angus (n = 8) and Wagyu (n = 8) steers were fed a corn-based diet for 8 mo (short-fed; 16 mo of age) or 16 mo (long-fed; 24 mo of age), whereas another group of Angus (n = 8) and Wagyu (n = 8) steers was fed a hay-based diet for 12 mo (short-fed; 20 mo of age) or 20 mo (long-fed; 28 mo of age) to match the end point BW of the corn-fed steers. Acetate incorporation into lipids in vitro was greater (P < 0.01) in corn-fed steers than in hay-fed steers and tended (P = 0.06) to be greater in Wagyu than in Angus s.c. adipose tissue because the rate in Wagyu was twice that of Angus adipose tissue in the corn-fed, short-fed steers. There were diet x end point interactions for lipogenesis in i.m. and s.c. adipose tissues (both P < 0.01) because lipogenesis was 60 to 90% lower in the long-fed cattle than in short-fed cattle fed the corn-based diet. The greatest SCD enzyme activity in Angus s.c. adipose tissue was observed at 24 mo of age (corn-based diet), but activity in Wagyu adipose tissue was greatest at 28 mo of age (hay-based diet; breed x diet x end point interaction, P = 0.08). For short- vs. long-fed endpoints in Angus, s.c. adipose tissue SCD activity was less (hay diet) or the same (corn diet). Conversely, SCD gene expression was greatest in long-fed Wagyu steers fed the hay- or corn-based diets (breed x end point interaction; P < 0.01). Contrary to our hypotheses, SCD activity increased over time, whereas lipogenesis from acetate decreased. However, the developmental pattern of SCD gene expression and activity differed markedly between hay-fed Angus and Wagyu adipose tissues, which may explain the differences in the MUFA:SFA ratios observed in adipose tissues from these cattle. Key words: adipose tissue, bovine, lipogenesis, stearoyl-CoA desaturase

Activin and myostatin are related members of the TGF-[beta] growth factor superfamily. FSTL3 (Follistatin-like 3) is an activin and myostatin antagonist whose physiological role in adults remains to be determined. We found that homozygous FSTL3 knockout adults developed a distinct group of metabolic phenotypes, including increased pancreatic islet number and size, [beta] cell hyperplasia, decreased visceral fat mass, improved glucose tolerance, and enhanced insulin sensitivity, changes that might benefit obese, insulin-resistant patients. The mice also developed hepatic steatosis and mild hypertension but exhibited no alteration of muscle or body weight. This combination of phenotypes appears to arise from increased activin and myostatin bioactivity in specific tissues resulting from the absence of the FSTL3 antagonist. Thus, the enlarged islets and [beta] cell number likely result from increased activin action. Reduced visceral fat is consistent with a role for increased myostatin action in regulating fat deposition, which, in turn, may be partly responsible for the enhanced glucose tolerance and insulin sensitivity. Our results demonstrate that FSTL3 regulation of activin and myostatin is critical for normal adult metabolic homeostasis, suggesting that pharmacological manipulation of FSTL3 activity might simultaneously reduce visceral adiposity, increase [beta] cell mass, and improve insulin sensitivity. activin | diabetes | metabolism | myostatin | [beta] cell

The purpose of this study was to investigate fatty acid (FA) oxidation in isolated mitochondrial vesicles (mit) and its relation to training status, fiber type composition, and whole body FA oxidation. Trained ([Vo.sub.2peak] 60.7 [+ or -] 1.6, n = 8) and untrained subjects (39.5 [+ or -] 2.0 ml * [min.sup.-1] * [kg.sup.-1], n = 5 ) cycled at 40, 80, and 120 W, and whole body relative FA oxidation was assessed from respiratory exchange ratio (RER). Mit were isolated from muscle biopsies, and maximal ADP stimulated respiration was measured with carbohydrate-derived substrate [pyruvate + malate (Pyr)] and FA-derived substrate [palmitoylL-carnitine + malate (PC)]. Fiber type composition was determined from analysis of myosin heavy-chain (MHC) composition. The rate of mit oxidation was lower with PC than with Pyr, and the ratio between PC and Pyr oxidation (MFO) varied greatly between subjects (49-93%). MFO was significantly correlated to muscle fiber type distribution, i.e., %MHC I (r = 0.62, P = 0.03), but was not different between trained (62 [+ or -] 5%) and untrained subjects (72 [+ or -] 2%). MFO was correlated to RER during submaximal exercise at 80 (r = -0.62, P = 0.02) and 120 W (r = -0.71, P = 0.007) and interpolated 35% [Vo.sub.2peak] (r = -0.74, P = 0.004). ADP sensitivity of mit respiration was significantly higher with PC than with Pyr. It is concluded that MFO is influenced by fiber type composition but not by training status. The inverse correlation between PER and MFO implies that intrinsic mit characteristics are of importance for whole body FA oxidation during low-intensity exercise. The higher ADP sensitivity with PC than that with Pyr may influence fuel utilization at low rate of respiration. oxidative phosphorylation; training

[PYY.sub.3-36] is a gut-derived hormone acting on hypothalamic nuclei to inhibit food intake. We recently showed that [PYY.sub.3-36] acutely reinforces insulin action on glucose disposal in mice. We aimed to evaluate effects of [PYY.sub.3-36] on energy metabolism and the impact of chronic [PYY.sub.3-36] treatment on insulin sensitivity. Mice received a single injection of [PYY.sub.3-36] or were injected once daily for 7 days, and energy metabolism was subsequently measured in a metabolic cage. Furthermore, the effects of chronic [PYY.sub.3-36] administration (continuous and intermittent) on glucose turnover were determined during a hyperinsulinemic-euglycemic clamp. [PYY.sub.3-36] inhibited cumulative food intake for 30 min of refeeding after an overnight fast (0.29 [+ or -] 0.04 vs. 0.56 [PYY.sub.3-36] 0.12 g, P = 0.036) in an acute setting, but not after 7 days of daily dosing. Body weight, total energy expenditure, and physical activity were not affected by [PYY.sub.3-36]. However, it significantly decreased the respiratory quotient. Both continuous and intermittent [PYY.sub.3-36] treatment significantly enhanced insulin-mediated whole body glucose disposal compared with vehicle treatment (81.2 [+ or -] 6.2 vs. 77.1 [+ or -] 5.2 vs. 63.4 [+ or -] 5.5 [micro]mol * [min.sup.-1] * [kg.sup.-1], respectively). In particular, [PYY.sub.3-36] treatment increased glucose uptake in adipose tissue, whereas its impact on glucose disposal in muscle did not attain statistical significance. [PYY.sub.3-36] treatment shifts the balance of fuel use in favor of fatty acids and enhances insulin sensitivity in mice, where it particularly promotes insulin-mediated glucose disposal. Notably, these metabolic effects of [PYY.sub.3-36] remain unabated after chronic administration, in contrast to its anorexic effects. diabetes; brain; metabolism; gut hormone

Using data from the Third National Health and Nutrition Examination Survey (NHANES III), conducted from 1988-1994, we investigated the effect of reproduction on the distribution of body fat in well-nourished American women. While women tend to gain weight and fat with succeeding pregnancies, if age and body mass index are controlled, increasing parity is associated with a decrease in hip and thigh circumferences, suprailiac and thigh skinfolds, and body fat estimated from skinfolds, while waist circumference increases, resulting in a relative decrease in lower-body fat. The mobilization of fat stores in the lower body during late pregnancy and lactation may help to meet the special needs of the developing brain for essential fatty acids and energy during the time of peak growth. When fat is regained after the postpartum period, relatively more is stored in central vs. peripheral depots, resulting in a patterned change in body shape with parity. KEY WORDS fat metabolism; pregnancy; lactation; brain development

Five days of a high-fat diet while training, followed by 1 day of carbohydrate (CHO) restoration, increases rates of whole body fat oxidation and decreases CHO oxidation during aerobic cycling. The mechanisms responsible for these shifts in fuel oxidation are unknown but involve up- and downregulation of key regulatory enzymes in the pathways of skeletal muscle fat and CHO metabolism, respectively. This study measured muscle PDH and HSL activities before and after 20 min of cycling at 70% V[O.sub.2 peak] and 1 min of sprinting at 150% peak power output (PPO). Estimations of muscle glycogenolysis were made during the initial minute of exercise at 70% V[O.sub.2 peak] and during the 1-min sprint. Seven male cyclists undertook this exercise protocol on two occasions. For 5 days, subjects consumed in random order either a high-CHO (HCHO) diet (10.3 g*[kg.sup.-1]*[day.sup.-1] CHO, or ~70% of total energy intake) or an isoenergetic high-fat (FAT-adapt) diet (4.6 g*[kg.sup.-]*[day.sup.-1] FAT, or 67% of total energy) while undertaking supervised aerobic endurance training. On day 6 for both treatments, subjects ingested an HCHO diet and rested before their experimental trials on day 7. This CHO restoration resulted in similar resting glycogen contents (FAT-adapt 873 [+ or -] 121 vs. HCHO 868 [+ or -] 120 [micro]mol glucosyl units/g dry wt). However, the respiratory exchange ratio was lower during cycling at 70% V[O.sub.2 peak] in the FAT-adapt trial, which resulted in an ~45% increase and an ~30% decrease in fat and CHO oxidation, respectively. PDH activity was lower at rest and throughout exercise at 70% V[O.sub.2 peak] (1.69 [+ or -] 0.25 vs. 2.39 [+ or -] 0.19 mmol*kg wet [wt.sup.-1]*[min.sup.-1]) and the 1-min sprint in the FAT-adapt vs. the HCHO trial. Estimates of glycogenolysis during the 1st min of exercise at 70% V[O.sub.2 peak] and the 1-min sprint were also lower after FAT-adapt (9.1 [+ or -] 1.1 vs. 13.4 [+ or -] 2.1 and 37.3 [+ or -] 5.1 vs. 50.5 [+ or -] 2.7 glucosyl units*kg dry [wt.sup.-l]*[min.sup.-1]). HSL activity was ~20% higher (P = 0.12) during exercise at 70% V[O.sub.2 peak] after FAT-adapt. Results indicate that previously reported decreases in whole body CHO oxidation and increases in fat oxidation after the FAT-adapt protocol are a function of metabolic changes within skeletal muscle. The metabolic signals responsible for the shift in muscle substrate use during cycling at 70% V[O.sub.2 peak] remain unclear, but lower accumulation of free ADP and AMP after the FAT-adapt trial may be responsible for the decreased glycogenolysis and PDH activation during sprinting. skeletal muscle metabolism; pyruvate dehydrogenase; substrate phosphorylation; fat oxidation; carbohydrate oxidation

Bacterial butyryl-CoA CoA-transferase activity plays a key role in butyrate formation in the human colon, but the enzyme and corresponding gene responsible for this activity have not previously been identified. A novel CoA-transferase gene is described from the colonic bacterium Roseburia sp. A2-183, with similarity to acetyl-CoA hydrolase as well as 4-hydroxybutyrate CoA-transferase sequences. The gene product, overexpressed in an Escherichia coli lysate, showed activity with butyryl-CoA and to a lesser degree propionyl-CoA in the presence of acetate. Butyrate, propionate, isobutyrate and valerate competed with acetate as the co-substrate. Despite the sequence similarity to 4-hydroxybutyrate CoA-transferases, 4-hydroxybutyrate did not compete with acetate as the co-substrate. Thus the CoA-transferase preferentially uses butyryl-CoA as substrate. Similar genes were identified in other butyrate-producing human gut bacteria from clostridial clusters IV and XIVa, while other candidate CoA-transferases for butyrate formation could not be detected in Roseburia sp. A2-183. This suggests strongly that the newly identified group of CoA-transferases described here plays a key role in butyrate formation in the human colon.

Stimulation of cholecystokinin and glucagon-like peptide-1 secretion by fat is mediated by the products of fat digestion. Ghrelin, peptide YY (PYY), and pancreatic polypeptide (PP) appear to play an important role in appetite regulation, and their release is modulated by food ingestion, including fat. It is unknown whether fat digestion is a prerequisite for their suppression (ghrelin) or release (PYY, PP). Moreover, it is not known whether small intestinal exposure to fat is sufficient to suppress ghrelin secretion. Our study aimed to resolve these issues. Sixteen healthy young males received, on two separate occasions, 120-min intraduodenal infusions of a long-chain triglyceride emulsion (2.8 kcal/min) 1) without (condition FAT) or 2) with (FAT-THL) 120 mg of tetrahydrolipstatin (THL, lipase inhibitor), followed by a standard buffet-style meal. Blood samples for ghrelin, PYY, and PP were taken throughout. FAT infusion was associated with a marked, and progressive, suppression of plasma ghrelin from t = 60 min (P < 0.001) and stimulation of PYY from t = 30 min (P < 0.01). FAT infusion also stimulated plasma PP (P [less than or equal to] 0.01), and the release was immediate. FAT-THL completely abolished the FAT-induced changes in ghrelin, PYY, and PP. In response to the meal, plasma ghrelin was further suppressed, and PYY and PP stimulated, during both FAT and FAT-THL infusions. In conclusion, in healthy humans, 1) the presence of fat in the small intestine suppresses ghrelin secretion, and 2) fat-induced suppression of ghrelin and stimulation of PYY and PP is dependent on fat digestion. lipase inhibition; gut hormone secretion

The present study was designed as a randomized, double-blind placebo (Plc)-controlled study to determine the effect of 2 wk of growth hormone administration (GH-adm.) on energy expenditure (EE) and substrate oxidation in healthy humans. Sixteen young healthy men were divided into two groups. The study consisted of two 24-h measurements (indirect calorimetry), separated by 2 wk of either Plc or GH injections (6 IU/day). At baseline, no significant differences were observed between the two groups in any of the measured anthropometric, hormonal, or metabolic parameters, neither did the parameters change over time in the Plc group. GH-adm. resulted in a 4.4% increase in 24-h EE (P < 0.05) and an increase in fat oxidation by 29% (P < 0.05). However, a decrease in the respiratory quotient was only observed in the postabsorptive phase after an overnight fast (0.84 [+ or -] 0.1 to 0.79 [+ or -] 0.1, P < 0.05). Furthermore, lean body mass (LBM) was increased by GH-adm. only [62.8 [+ or -] 2.5 kg (baseline) vs. 64.7 [+ or -] 2.4 kg (after), P < 0.001]. In conclusion, GH-adm. increases 24-h EE, which may be partly explained by increased LBM. Furthermore, GH-adm. stimulates fat combustion, especially in the postabsorptive state. energy expenditure; fat oxidation; growth hormone; insulin-like growth factor 1; metabolism

Appropriate response to nutritional stress is critical for animal survival and metabolic health. To better understand regulatory networks that sense and respond to nutritional availability, we developed a quantitative RT-PCR strategy to monitor changes in metabolic gene expression resulting from short-term food deprivation (fasting) in Caenorhabditis elegans. Examining 97 fat and glucose metabolism genes in fed and fasted animals, we identified 18 genes significantly influenced by food withdrawal in all developmental stages. Fasting response genes fell into multiple kinetic classes, with some genes showing significant activation or repression just 1 h after food was removed. As expected, fasting stimulated the expression of genes involved in mobilizing fats for energy production, including mitochondrial [beta]-oxidation genes. Surprisingly, however, we found that other mitochondrial [beta]-oxidation genes were repressed by food deprivation. Fasting also affected genes involved in mono- and polyunsaturated fatty acid synthesis: four desaturases were induced, and one stearoyl-CoA desaturase (SCD) was strongly repressed. Accordingly, fasted animals displayed considerable changes in fatty acid composition. Finally, nuclear receptor nhr-49 played a key role in nutritional response, enabling induction of [beta]-oxidation genes upon food deprivation and facilitating activation of SCD in fed animals. Our characterization of a fasting response system and our finding that nhr-49 regulates a sector within this system provide insight into the mechanisms by which animals respond to nutritional signals. fasting | fat metabolism | HNF4 | stearoyl-CoA desaturase

This study investigates the consequences of inhibition of adipose tissue lipolysis on skeletal muscle substrate use. Ten subjects were studied at rest and during exercise and subsequent recovery under normal, fasting conditions (control trial, CON) and following administration of a nicotinic acid analog (low plasma free fatty acid trial, LFA). Continuous [U-[sup.13]C]palmitate and [6,6-[sup.2][H.sub.2]]glucose infusions were applied to quantify plasma free fatty acid (FFA) and glucose oxidation rates and to estimate intramuscular triacylglycerol (IMTG) and glycogen use. Muscle biopsies were collected to measure 1) fiber type-specific IMTG content; 2) allosteric regulators of hormone-sensitive lipase (HSL), glycogen phosphorylase, and pyruvate dehydrogenase; and 3) the phosphorylation status of HSL at [Ser.sup.563] and [Ser.sup.565]. Administration of a nicotinic acid analog (acipimox) substantially reduced plasma FFA rate of appearance and subsequent plasma FFA concentrations (P < 0.0001). At rest, this substantially reduced plasma FFA oxidation rates, which was compensated by an increase in the estimated IMTG use (P < 0.05). During exercise, the progressive increase in FFA rate of appearance, uptake, and oxidation was prevented in the LFA trial and matched by greater IMTG and glycogen use. Differential phosphorylation of HSL or relief of its allosteric inhibition by long-chain fatty acyl-CoA could not explain the increase in muscle TG use, but there was evidence to support the contention that regulation may reside at the level of the glucose-fatty acid cycle. This study confirms the hypothesis that plasma FFA availability regulates both intramuscular lipid and glycogen use in vivo in humans. muscle metabolism; intramyocellular triacylglycerol; fat oxidation; insulin resistance

Leptin is a multifunctional hormone, produced predominantly in adipocytes. It regulates energy balance through its impact on appetite and fat metabolism, and its concentration indicates the size of body fat reserves. Leptin also plays a vital role in stretch-induced surfactant production during alveolar development in the fetus. The structure, expression pattern, and role of leptin have not previously been explored in marine mammals. Phocid seals undergo cyclical changes in body composition as a result of prolonged fasting and intensive foraging bouts and experience rapid, dramatic, and repeated changes in lung volume during diving. Here, we report the tissue-specific expression pattern of leptin in these animals. This is the first demonstration of leptin expression in the lung tissue of a mature mammal, in addition to its expression in the blubber and bone marrow, in common with other animals. We propose a role for leptin in seal pulmonary surfactant production, in addition to its likely role in long-term energy balance. We identify substitutions in the phocine leptin sequence in regions normally highly conserved between widely distinct vertebrate groups, and, using a purified seal leptin antiserum, we confirm the presence of the leptin protein in gray seal lung and serum fractions. Finally, we report the substantial inadequacies of using heterologous antibodies to measure leptin in unextracted gray seal serum. surfactant production; fat metabolism; parathyroid hormone-related protein; leptin antibody

Obesity and its attendant disorders, such as type 2 diabetes, are global health problems. We previously reported that C75, an inhibitor of fatty acid synthase (FAS) and stimulator of carnitine palmitoyltransferase I (CPT I), caused anorexia and profound weight loss in lean and genetically obese mice. To approximate human obesity, we utilized a chronic C75 treatment model for diet-induced obese (DIO) mice. Chronic C75 treatment decreased food consumption and increased energy expenditure due to increased fatty acid oxidation in both DIO and lean mice. There was a substantial loss of adipose tissue and resolution of hepatic steatosis in C75-treated DIO mice. Analysis of changes in the expression of hypothalamic neuropeptides demonstrated that the reduced food consumption in C75-treated DIO mice was accompanied by an increase in cocaine and amphetamine-related transcript expression but not by changes in neuropeptide Y such as seen with acute C75 treatment of lean mice. Inhibition of FAS and stimulation of CPT I provide a means to achieve stable, sustained weight loss in DIO mice. fatty acid synthase; carnitine palmitoyltransferase I; neuropeptide Y

Byline: Wolfgang Geisser (1), Josef Vogt (1), Ulrich Wachter (1), Hannes Hofbauer (1), Michael Georgieff (1), Hermann Ensinger (1) Keywords: Glucose metabolism; Adrenergic agonist; Dopexamine; Fenoterol; Protein; Stable isotopes Abstract: Objective In critically ill patients adrenergic agonists are used to treat haemodynamic disorders. Their metabolic actions should be considered in controlling metabolic homeostasis. Dopexamine has assumed effects on carbohydrate, fat and protein metabolism. The aim of this study was to define its metabolic actions and compare these with those of fenoterol by using a stable isotope dilution technique. Design Prospective, randomized experimental study. Setting Experimental section of a university anaesthesiology department. Participants Twenty-seven healthy male volunteers in three groups with nine participants each. Interventions Participants received a 4-h infusion of dopexamine (2.25 Aug/kg per min), fenoterol (at least 0.025 Aug/kg per min) or saline. Measurements and results Before and every 80 min during drug infusion, we measured endogenous glucose production and the plasma appearance rates for leucine and urea. In addition, we measured plasma concentrations of glucose, lactate, free fatty acids (FFAs), noradrenaline, adrenaline, insulin, glucagon and potassium. Endogenous glucose production did not differ among the groups. Glucose plasma concentration and glucose clearance remained constant during the dopexamine infusion. Fenoterol increased glucose plasma concentration and decreased glucose clearance. Lactate, FFAs, insulin and noradrenaline plasma concentrations were increased and the rate of leucine appearance was decreased by both drugs. The rate of urea appearance did not differ from the control group. Conclusions Dopexamine has no or only weak effects on carbohydrate metabolism, its effects on fat and protein metabolism are comparable to those of fenoterol. This metabolic profile may be advantageous in increasing cardiac output in patients with impaired glucose tolerance. Author Affiliation: (1) University Clinic of Anaesthesiology, University Clinics Ulm, Steinhoevelstrasse 9, 89075 , Ulm, Germany Article History: Registration Date: 05/12/2003 Received Date: 10/04/2003 Accepted Date: 01/12/2003 Online Date: 24/02/2004