Unlikely partners in weight loss?

The classic role of bile acids is as a key component of cholesterol homeostasis. New evidence recently published in Nature (Watanabe et al., 2006), however, describes a bile acid signaling pathway that controls energy expenditure through induction of thyroid hormone signaling pathways. This work may point to new approaches to tissue-specific metabolic regulation.     

Future research in weight bias: What next?

The 2015 Canadian Weight Bias Summit disseminated the newest research advances and brought together 40 experts, stakeholders, and policy makers in various disciplines in health, education, and public policy to identify future research directions in weight bias. In this paper we aim to share the results of the Summit as well as encourage international and interdisciplinary research collaborations in weight bias reduction. Consensus emerged on six research areas that warrant further investigation in weight bias: costs, causes, measurement, qualitative research and lived experience, interventions, and learning from other models of discrimination. These discussions highlighted three key lessons that were informed by the Summit, namely: language matters, the voices of people living with obesity should be incorporated, and interdisciplinary stakeholders should be included.     

Molecular weight of a germination-enhancing compound in smoke†

The active compound(s) in smoke responsible for promoting seed germination of a number of plant species has so far remained unknown. A germination-promoting fraction containing approximately ten compounds has been obtained from cellulose-derived smoke. Furthermore, activity has been associated with one of the compounds in this fraction. The UV absorbance maximum and molecular weight of the active compound has been established and the molecular formula has been tentatively assigned as C₈H₆O₃.     

The effect of rider weight and additional weight in Icelandic horses in tölt: part I. Physiological responses

This study examined the effect of increasing BW ratio (BWR) between rider and horse, in the BWR range common for Icelandic horses (20% to 35%), on heart rate (HR), plasma lactate concentration (Lac), BWR at Lac 4 mmol/l (W₄), breathing frequency (BF), rectal temperature (RT) and hematocrit (Hct) in Icelandic horses. In total, eight experienced school-horses were used in an incremental exercise test performed outdoors on an oval riding track and one rider rode all horses. The exercise test consisted of five phases (each 642 m) in tölt, a four-beat symmetrical gait, at a speed of 5.4±0.1 m/s (mean±SD), where BWR between rider (including saddle) and horse started at 20% (BWR₂₀), was increased to 25% (BWR₂₅), 30% (BWR₃₀), and 35% (BWR₃₅) and finally decreased to 20% (BWR_20b). Between phases, the horses were stopped (~5.5 min) to add lead weights to specially adjusted saddle bags and a vest on the rider. Heart rate was measured during warm-up, the exercise test and after 5, 15 and 30 min of recovery and blood samples were taken and BF recorded at rest, and at end of each of these aforementioned occasions. Rectal temperature was measured at rest, at end of the exercise test and after a 30-min recovery period. Body size and body condition score (BCS) were registered and a clinical examination performed on the day before the test and for 2 days after. Heart rate and BF increased linearly (P<0.05) and Lac exponentially (P<0.05) with increasing BWR. The W₄ was 22.7±4.3% (individual range 17.0% to 27.5%). There was a positive correlation between back BCS and W₄ (r=0.75; P=0.032), but no other correlations between body measurements and W₄ were found. Hematocrit was not affected by BWR (P>0.05), but negative correlations (P<0.05) existed between body size measurements and Hct. While HR, Hct and BF recovered to values at rest within 30 min, Lac and RT did not. All horses had no clinical remarks on palpation and at walk 1 and 2 days after the test. In conclusion, increasing BWR from 20% to 35% resulted in increased HR, Lac, RT and BF responses in the test group of experienced adult Icelandic riding horses. The horses mainly worked aerobically until BWR reached 22.7%, but considerable individual differences (17.0% to 27.5%) existed that were not linked to horse size, but to back BCS.     

Does smoking affect body weight and obesity in China?

An inverse relationship between smoking and body weight has been documented in the medical literature, but the effect of cigarette smoking on obesity remains inconclusive. In addition, the evidence is mixed on whether rising obesity rates are an unintended consequence of successful anti-smoking policies. This study re-examines these relationships using data from China, the largest consumer and manufacturer of tobacco in the world that is also experiencing a steady rise in obesity rates. We focus on the impact of the total number of cigarettes smoked per day on individuals’ body mass index (BMI) and on the likelihood of being overweight and obese. Instrumental variables estimation is used to correct for the endogeneity of cigarette smoking. We find a moderate negative and significant relationship between cigarette smoking and BMI. Smoking is also negatively related to being overweight and obese, but the marginal effects are small and statistically insignificant for being obese. Quantile regression analyses reveal that the association between smoking and BMI is quite weak among subjects whose BMIs are at the high end of the distribution but are considerably stronger among subjects in the healthy weight range. Ordered probit regression analyses also confirm these findings. Our results thus reconcile an inverse average effect of smoking on body weight with the absence of any significant effect on obesity. From a policy perspective these findings suggest that, while smoking cessation may lead to moderate weight gain among subjects of healthy weight, the effects on obese subjects are modest and should not be expected to lead to a large increase in obesity prevalence rates.     

Why weight?

Whether phylogenetic data should be differentially or equally weighted is currently debated. Further, if differential weighting is to be explored, there is no consensus among investigators as to which weighting scheme is most appropriate. Mitochondrial genome data offer a powerful tool in assessment of differential weighting schemes because taxa can be selected from which a highly corroborated phylogeny is available (so that accuracy can be assessed), and it can be assumed that different data partitions share the same history (so that gene-sorting issues are not so problematic). Using mitochondrial data from 17 mammalian genomes, we evaluated the most commonly used weighting schemes, such as successive weighting, transversion weighting, codon-based weighting, and amino acid coding, and compared them to more complex weighting schemes including a 6-parameter weighting, pseudoreplicate reweighting, and tri-level weighting. We found that the most commonly used weighting schemes perform the worst with these data. Some of the more complex schemes perform well, however, none of them is consistently superior. These results support ones biases; if one has a predilection to avoid differential weighting, these data support equally weighted parsimony and maximum likelihood. Others might be encouraged by these results to try weighting as a form of data exploration.     

Is density-dependent growth in young-of-the-year fishes a question of critical weight?

We develop a conceptual argument thatdensity-dependent growth via reductions in preyresources are most likely to occur in the late-larvalor juvenile stage in both marine and freshwaterfishes. We use results from a suite ofindividual-based models and literature examples of avariety of marine, estuarine and freshwater species toprovide evidence of the effects of age-0 fish on theirprey. We conclude that larval-stage survival relatedto food-limited growth contributes significantly torecruitment variability. However, density-dependentregulation of cohort biomass via feedbacks derivedfrom reductions in prey resources is most likely tooccur at a ``critical-weight' during the late-larval orjuvenile stage. This occurs when fish densitiesremain relatively high, and population consumption ishighest relative to prey density and replenishmentrate. We compare our critical weight concept toHoude's (1997) critical size hypothesis.     

Changes in the association of low birth weight with socioeconomic status in Hawaii: 1970–1990

Abstract

This study examines rates of low birth weight (LBW) in the state of Hawaii and changes in the association of LBW with socioeconomic status from 1970 to 1990. The analysis is based on aggregate data for census tracts. Rates of low birth weight were calculated for each census tract. Relative socioeconomic scores were calculated from average household income and years of education. The results show that (1) there was a decrease in the rate of low birth weight infants in Hawaii; and (2) that the correlation between socioeconomic status and low birth weight was substantially reduced, though a significant correlation remains. The paper suggests likely ceiling effects, but that the progressive public health policies and expansion of access to primary health care in Hawaii during this period played a major role in reducing the rate of low birth weight infants and in decreasing socioeconomic inequality on this important health indicator.     

Rheological and microstructural investigation of oat β-glucan isolates varying in molecular weight

The rheological properties and microstructure of aqueous oat β-glucan solutions varying in molecular weight were investigated. The structural features and molecular weights (MW) were characterized by ¹³C NMR spectroscopy and high performance size-exclusion chromatography (HPSEC), respectively. The microstructure of the β-glucans dispersions was also examined by atomic force microscopy (AFM). The samples with β-glucan content between 78 and 86% on a dry weight basis had MW, intrinsic viscosity ([η]) and critical concentration (c*) in the range of 142-2800 × 10³ g/mol, 1.7-7.2 dl/g and 0.25-1.10 g/dl, respectively. The flow and viscoelastic behaviour was highly dependent on MW and on the concentration of the β-glucans dispersions. Pseudoplastic behaviour was exhibited at high concentrations and Newtonian behaviour was evident at low concentrations. At the same concentration, the viscosity was higher for higher MW samples. The Cox-Merz rule was applicable for the lower molecular weight samples at higher concentrations whereas the high molecular weight sample deviated at concentrations greater than 1.0%, w/v. The mechanical spectra with variation of both MW and concentration were typical of entangled biopolymer solutions. AFM images revealed the formation of clusters or aggregates linked via individual polymer chains scattered heterogeneously throughout the system. The aggregate size increased with the molecular weight of the samples investigated and has been linked to the rheological behaviour of the samples.     

Evidence for high molecular weight Na−Ca exchange in cardiac sarcolemmal vesicles

Summary Cardiac sarcolemma (SL) vesicles were subjected to irradiation inactivation-target sizing analyses and gel permeation high performance liquid chromatography (HPLC) to ascertain the weight range of native Na–Ca exchange. Frozen SL vesicle preparations were irradiated by electron bombardment and assayed for Na–Ca exchange activity. When applied to classical target sizing theory, the results yielded a minimum molecular weight (M _r) of approximately 226,000±20,000sd (n=6). SL vesicle proteins were solubilized in 6% sodium cholate in the presence of exogenous phospholipid and fractionated by size on a TSK 30XL HPLC column. Eluted proteins were mixed 11 with mobile phase buffer containing 50mg/ml soybean phospholipid and reconstituted by detergent dilution. The resulting proteoliposomes were assayed for Na–Ca exchange activity. Na–Ca exchange activity eluted in early fractions containing larger proteins as revealed by SDS-PAGE. Recovery of total protein and Na–Ca exchange activity were 91±7 and 68±11%, respectively. In the peak fraction, Na–Ca exchange specific activity increased two-to threefold compared to reconstituted controls. Compared to the elution profile of protein standards under identical column conditions, sodium cholate solubilized exchange activity had a minimumM _r of 224,000 Da. Specific⁴⁵Ca²⁺-binding SL proteins withM _r of 234,000, 112,000, and 90,000 Da were detected by autoradiography of proteins transferred electrophoretically to nitrocellulose.These data suggest that native cardiac Na–Ca exchange is approximately 225,000 Da or larger. The exact identification and purification of cardiac Na–Ca exchange protein(s) remains incomplete.     

Birth weight and cognitive development in adolescence: causal relationship or social selection?

Using data from the National Longitudinal Survey of Adolescent Health (Add Health), I investigate the relationship between birth weight and cognitive development among adolescents aged 12-17. Initial OLS regression models reveal a significant, positive relationship between low birth weight and verbal ability. Controlling for demographic, socioeconomic, and other adolescent characteristics modifies, but does not eliminate, this relationship. Additional models that stratify the sample by parental education illustrate the greater importance of other family and adolescent characteristics for cognitive development in adolescence, and a diminished role of birth weight. In the final section of the paper, fixed effects models of non-twin full siblings indicate no significant association between birth weight and verbal ability, suggesting that traditional cross-sectional models overstate the influence of birth weight for cognitive development in adolescence.     

Long-term selection for 8-week body weight in chickens — direct and correlated responses

Summary A bidirectional selection experiment for 8-week body weight in chickens was conducted. In addition to 27 generations of selection, random samples were chosen from each selected line in generations 6, 13, 19 and 26 to initiate lines in which selection was relaxed. Genetic change was evident in the selected high-weight line through the first 75% of the study after which response in the direction opposing selection occurred. Selection for low body weight resulted in considerable reduction in body size, particularly in the last quarter of the study. Correlated responses evaluated were body weight at several ages, conformation, age at onset of lay, various reproductive and egg quality traits and ratio (female: male) of some traits. Data from lines where selection was relaxed indicated that natural selection opposed artificial selection with the effects greater in later generations.     

Effects of training and weight support on muscle activation in Parkinson’s disease

The aim of this study was to investigate the effect of high-intensity locomotor training on knee extensor and flexor muscle activation and adaptability to increased body-weight (BW) support during walking in patients with Parkinson’s disease (PD). Thirteen male patients with idiopathic PD and eight healthy participants were included. The PD patients completed an 8-week training program on a lower-body, positive-pressure treadmill. Knee extensor and flexor muscles activation during steady treadmill walking (3 km/h) were measured before, at the mid-point, and after training. Increasing BW support decreased knee extensor muscle activation (normalization) and increased knee flexor muscle activation (abnormal) in PD patients when compared to healthy participants. Training improved flexor peak muscle activation adaptability to increased (BW) support during walking in PD patients. During walking without BW support shorter knee extensor muscle off-activation time and increased relative peak muscle activation was observed in PD patients and did not improve with 8 weeks of training. In conclusion, patients with PD walked with excessive activation of the knee extensor and flexor muscles when compared to healthy participants. Specialized locomotor training may facilitate adaptive processes related to motor control of walking in PD patients.     

Urinary F₂-isoprostanes, obesity, and weight gain in the IRAS cohort

Obesity has been associated with increased F(2)-isoprostane (F(2)-IsoP) levels cross-sectionally. However, the prospective association may be inverse, based on our earlier finding that elevated urinary F(2)-IsoP levels predict lower risk of diabetes. This earlier finding led us to hypothesize that urinary F(2)-IsoPs reflect the intensity of oxidative metabolism and as such predict lower risk of both diabetes and weight gain. We examined cross-sectional relationships with obesity and prospective relationships with weight gain using the data from 299 participants of the Insulin Resistance Atherosclerosis Study (IRAS), all of whom were free of diabetes at baseline. Four urinary F(2)-IsoPs were assayed in stored baseline urine samples using liquid chromatography with tandem mass spectrometry: iPF(2α)-III, 2,3-dinor-iPF(2α)-III, iPF(2α)-VI, and 8,12-iso-iPF(2α)-VI (F(2)-IsoP 1-4, respectively). Baseline F(2)-IsoPs were positively associated with baseline measures of obesity; the strongest associations were found with two F(2)-IsoPs: odds ratios (95% confidence intervals) for overall and abdominal obesity were 1.74 (1.26-2.40) and 1.63 (1.18-2.24) for F(2)-IsoP2 and 1.47 (1.12-1.94) and 1.64 (1.22-2.20) for F(2)-IsoP4. F(2)-IsoP2 showed the strongest and significant inverse association with weight gain during the 5-year follow-up period: increase in F(2)-IsoP2 equal to 1 s.d. was associated with 0.90 kg lower weight gain (P = 0.02) and the odds ratios for relative (≥5%) and absolute (≥5 kg) weight gain were 0.67 (0.47-0.96) and 0.57 (0.37-0.87), respectively. The other three F(2)-IsoPs were consistently inversely associated with weight gain, although not significantly, suggesting that different F(2)-IsoPs vary in their ability to detect the association with weight gain.     

Parents’ education and child body weight in France: The trajectory of the gradient in the early years

This paper explores the relationship between parental education and offspring body weight in France. Using two large datasets spanning the 1991–2010 period, we examine the existence of inequalities in maternal and paternal education and reported child body weight measures, as well as their evolution across childhood. Our empirical specification is flexible and allows this evolution to be non-monotonic. Significant inequalities are observed for both parents’ education – maternal (respectively paternal) high education is associated with a 7.20 (resp. 7.10) percentage points decrease in the probability that the child is reported to be overweight or obese, on average for children of all ages. The gradient with respect to parents’ education follows an inverted U-shape across childhood, meaning that the association between parental education and child body weight widens from birth to age 8, and narrows afterward. Specifically, maternal high education is correlated with a 5.30 percentage points decrease in the probability that the child is reported to be overweight or obese at age 2, but a 9.62 percentage points decrease at age 8, and a 1.25 percentage point decrease at age 17. The figures for paternal high education are respectively 5.87, 9.11, and 4.52. This pattern seems robust, since it is found in the two datasets, when alternative variables for parental education and reported child body weight are employed, and when controls for potential confounding factors are included. The findings for the trajectory of the income gradient corroborate those of the education gradient. The results may be explained by an equalization in actual body weight across socioeconomic groups during youth, or by changes in reporting styles of height and weight.