Creation of an Age-Adjusted, Dual-Energy X-ray Absorptiometry-Derived Trabecular Bone Score Curve for the Lumbar Spine in Non-Hispanic US White Women.

The trabecular bone score (TBS, Med-Imaps, Pessac, France) is an index of bone microarchitecture texture extracted from anteroposterior dual-energy X-ray absorptiometry images of the spine. Previous studies have documented the ability of TBS of the spine to differentiate between women with and without fractures among age- and areal bone mineral density (aBMD)-matched controls, as well as to predict future fractures. In this cross-sectional analysis of data collected from 3 geographically dispersed facilities in the United States, we investigated age-related changes in the microarchitecture of lumbar vertebrae as assessed by TBS in a cohort of non-Hispanic US white American women. All subjects were 30 yr of age and older and had an L1-L4aBMDZ-score within ±2 SD of the population mean. Individuals were excluded if they had fractures, were on any osteoporosis treatment, or had any illness that would be expected to impact bone metabolism. All data were extracted from Prodigy dual-energy X-ray absorptiometry devices (GE-Lunar, Madison, WI). Cross-calibrations between the 3 participating centers were performed for TBS and aBMD. aBMD and TBS were evaluated for spine L1-L4 but also for all other possible vertebral combinations. To validate the cohort, a comparison between the aBMD normative data of our cohort and US non-Hispanic white Lunar data provided by the manufacturer was performed. A database of 619 non-Hispanic US white women, ages 30-90 yr, was created. aBMD normative data obtained from this cohort were not statistically different from the non-Hispanic US white Lunar normative data provided by the manufacturer (p = 0.30). This outcome thereby indirectly validates our cohort. TBS values at L1-L4 were weakly inversely correlated with body mass index (r = -0.17) and weight (r = -0.16) and not correlated with height. TBS values for all lumbar vertebral combinations decreased significantly with age. There was a linear decrease of 16.0% (-2.47 T-score) in TBS at L1-L4 between 45 and 90 yr of age (vs. -2.34 for aBMD). Microarchitectural loss rate increased after age 65 by 50% (-0.004 to -0.006). Similar results were obtained for other combinations of lumbar vertebra. TBS, an index of bone microarchitectural texture, decreases with advancing age in non-Hispanic US white women. Little change in TBS is observed between ages 30 and 45. Thereafter, a progressive decrease is observed with advancing age. The changes we observed in these American women are similar to that previously reported for a French population of white women (r(2) > 0.99). This reference database will facilitate the use of TBS to assess bone microarchitectural deterioration in clinical practice.

Enteral versus parenteral nutrition: comparison of energy metabolism in healthy subjects.

Continuous respiratory exchange measurements were performed on 10 healthy young women for 1 h before, 3 h during, and 3 h after either parenteral (iv) or intragastric (ig) administration of a nutrient mixture (52% glucose, 18% amino acid, and 30% lipid energy) infused at twice the postabsorptive resting energy expenditure (REE). REE rose from 0.98 +/- 0.02 (iv) and 0.99 +/- 0.02 kcal/min (ig) postabsorptively to 1.13 +/- 0.03 (iv) and 1.13 +/- 0.02 kcal/min (ig), resulting in nutrient-induced thermogenesis of 10 +/- 0.6 and 9.3 +/- 0.9%, respectively, when related to the metabolizable energy. The respiratory quotient rose from preinfusion values of 0.81 +/- 0.02 (iv) and 0.80 +/- 0.01 (ig) to 0.86 +/- 0.01 (iv) and 0.85 +/- 0.01 (ig). After nutrient administration the respiratory quotient fell significantly to below the preinfusion values. Plasma glucose and insulin concentrations rose during nutrient administration but were higher during the intravenous route. It is concluded that, although the response time to intragastric administration was delayed, the thermic effects and overall substrate oxidations were comparable during intravenous or intragastric administration, albeit, at lower plasma glucose and insulin concentrations via the intragastric route.

Macronutrients and energy balance in obesity.

Energy balance is the difference between metabolizable energy intake and total energy expenditure. Energy intake is difficult to measure accurately; changes in body weight, for example, are not a good measure of the adequacy of energy intake, because fluctuations in body weight are common even if the overall trend is toward weight loss. It is now customary to assess energy requirements indirectly from total energy expenditure. Total energy expenditure consists of basal metabolism, postprandial thermogenesis, and physical activity. Energy expenditure is related to both body weight and body composition. A reduction in total energy expenditure accompanies weight loss, because basal metabolic rate decreases with the loss of lean tissue mass. Similarly, with weight gain, there is an increase in basal metabolic rate, because lean tissue mass grows to support the increase in fat tissue mass. Excess energy intake over energy expenditure causes weight gain and an accompanying increase in total energy expenditure. Following a period of adaptation, total energy expenditure will match energy intake and body weight will stabilize at a higher level. This same relationship holds for weight loss. Respiratory quotient (measured in steady state) is an indication of the proportion of energy expenditure derived from fat and carbohydrate oxidation. Over long periods of time, fat balance is equivalent to energy balance, as an excess of fat intake over fat oxidation causes fat storage.

On the transition of genetic differentiation from isolation to panmixia: What we can learn from GST and D.

Population genetic differentiation characterizes the repartition of alleles among populations. It is commonly thought that genetic differentiation measures, such as GST and D, should be near zero when allele frequencies are close to their expected value in panmictic populations, and close to one when they are close to their expected value in isolated populations. To analyse those properties, we first derive analytically a reference function f of known parameters that describes how important features of genetic differentiation (e.g. gene diversity, proportion of private alleles, frequency of the most common allele) are close to their expected panmictic and isolation value. We find that the behaviour of function f differs according to three distinct mutation regimes defined by the scaled mutation rate and the number of populations. Then, we compare GST and D to f, and demonstrate that their signal of differentiation strongly depends on the mutation regime. In particular, we show that D captures well the variations of genetic diversity when mutation is weak, otherwise it overestimates it when panmixia is not met. GST detects population differentiation when mutation is intermediate but has a low sensitivity to the variations of genetic diversity when mutation is weak. When mutation is strong the domain of sensitivity of both measures are altered. Finally, we also point out the importance of the number of populations on genetic differentiation measures, and provide recommendations for the use of GST and D.

Social isolation causers mortality by disrupting energy homeostrasis in ants

Social deprivation can have negative effects on the lives of social animals, including humans, yet little is known about the mechanisms by which social withdrawal affects animal health. Here we show that in the carpenter ant Camponotus fellah, socially isolated workers have a greatly reduced life span relative to ants kept in groups of ten individuals. By using a new tracking system, we found that social isolation resulted in important behavioral changes and greatly increased locomotor activity. The higher activity of single ants and their increased propensity to leave the nest to move along the walls suggested that the increased mortality of isolated ants might stem from an imbalance of energy income and expenditure. This view was supported by the finding that while isolated ants ingested the same amount of food as grouped ants, they retained food in the crop, hence preventing its use as an energy source. Moreover, the difference in life span between single and grouped individuals vanished when ants were not fed. This study thus underlines the role of social interactions as key regulators of energy balance, which ultimately affects aging and health in a highly social organism.

The twist, writhe and overall shape of supercoiled DNA change during counterion-induced transition from a loosely to a tightly interwound superhelix. Possible implications for DNA structure in vivo.

A cryo-electron microscopy study of supercoiled DNA molecules freely suspended in cryo-vitrified buffer was combined with Monte Carlo simulations and gel electrophoretic analysis to investigate the role of intersegmental electrostatic repulsion in determining the shape of supercoiled DNA molecules. It is demonstrated here that a decrease of DNA-DNA repulsion by increasing concentrations of counterions causes a higher fraction of the linking number deficit to be partitioned into writhe. When counterions reach concentrations likely to be present under in vivo conditions, naturally supercoiled plasmids adopt a tightly interwound conformation. In these tightly supercoiled DNA molecules the opposing segments of interwound superhelix seem to directly contact each other. This form of supercoiling, where two DNA helices interact laterally, may represent an important functional state of DNA. In the particular case of supercoiled minicircles (178 bp) the delta Lk = -2 topoisomers undergo a sharp structural transition from almost planar circles in low salt buffers to strongly writhed "figure-eight" conformations in buffers containing neutralizing concentrations of counterions. Possible implications of this observed structural transition in DNA are discussed.

Force-induced globule-coil transition in laminin binding protein and its role for viral-cell membrane fusion.

The specific interactions of the pairs laminin binding protein (LBP)-purified tick-borne encephalitis viral surface protein E and certain recombinant fragments of this protein, as well as West Nile viral surface protein E and certain recombinant fragments of that protein, are studied by combined methods of single-molecule dynamic force spectroscopy (SMDFS), enzyme immunoassay and optical surface waves-based biosensor measurements. The experiments were performed at neutral pH (7.4) and acid pH (5.3) conditions. The data obtained confirm the role of LBP as a cell receptor for two typical viral species of the Flavivirus genus. A comparison of these data with similar data obtained for another cell receptor of this family, namely human αVβ3 integrin, reveals that both these receptors are very important. Studying the specific interaction between the cell receptors in question and specially prepared monoclonal antibodies against them, we could show that both interaction sites involved in the process of virus-cell interaction remain intact at pH 5.3. At the same time, for these acid conditions characteristic for an endosome during flavivirus-cell membrane fusion, SMDFS data reveal the existence of a force-induced (effective already for forces as small as 30-70 pN) sharp globule-coil transition for LBP and LBP-fragments of protein E complexes. We argue that this conformational transformation, being an analog of abrupt first-order phase transition and having similarity with the famous Rayleigh hydrodynamic instability, might be indispensable for the flavivirus-cell membrane fusion process. Copyright © 2014 John Wiley & Sons, Ltd.

Nutrition transition in a middle-income country: 22-year trends in the Seychelles.

BACKGROUND/OBJECTIVES: There is little objective information regarding nutrition transition in African countries. We assessed trends in nutrition patterns in the Seychelles between 1989 and 2011. SUBJECTS/METHODS: Population-based samples were obtained in 1989, 1994 and 2011 and participants aged 25-44 are considered in this study (n=493, 599 and 471, respectively). Similar, although not identical, food frequency questionnaires (FFQs) were used in each survey and the variables were collapsed into homogenous categories for the purpose of this study. RESULTS: Between 1989 and 2011, consumption frequency of fish (5+/week) decreased from 93 to 74%, whereas the following increased: meat (5+/week) 25 to 51%, fruits (1+/week) 48 to 94%, salty snacks (1+/week) 22 to 64% and sweet snacks (1+/week) 38 to 67% (P<0.001 for all). Consumption frequency decreased for home-brewed alcoholic drinks (1+/week) 16 to 1%, but increased for wine (1+/week) 5 to 33% (both P<0.001). Between 2004 and 2011, consumption frequency decreased for rice (2/day) 62 to 57% and tea (1+/day) 72 to 68%, increased for poultry (1+/week) 86 to 96% (all P<0.01), and did not change for vegetables (70.3 to 69.8%, P=0.65). CONCLUSIONS: Seychelles is experiencing nutrition transition characterized by a decreased consumption frequency of traditional staple foods (fish, polished rice), beverages (tea) and of inexpensive home brews, and increased consumption frequency of meat, poultry and snacks. Food patterns also became more varied along with a broader availability of products in the 22-year interval. The health impact of these changes should be further studied.

Effects of a glucose meal on energy metabolism in patients with cirrhosis before and after liver transplantation.

HYPOTHESIS: Liver transplantation results in hepatic denervation. This may produce alterations of liver energy and substrate metabolism, which may contribute to weight gain after liver transplantation. DESIGN: Prospective clinical study. SETTING: Liver transplantation clinics in a university hospital. PATIENTS: Seven nondiabetic patients with cirrhosis were recruited while on a waiting list for liver transplantation. Seven healthy subjects were recruited as controls. INTERVENTION: Orthotopic liver transplantation. MAIN OUTCOME MEASURES: Evaluation of energy and substrate metabolism after ingestion of a glucose load with indirect calorimetry was performed before, 2 to 6 weeks after, and 5 to 19 months after transplantation. Whole-body glucose oxidation and storage and glucose-induced thermogenesis were calculated. RESULTS: Patients with cirrhosis had modestly elevated resting energy expenditure and normal glucose-induced thermogenesis and postprandial glucose oxidation and storage. These measures remained unchanged after liver transplantation despite a significant increase in postprandial glycemia. Patients, however, gained an average of 3 kg of body weight after 5 to 19 months compared with their weight before transplantation. CONCLUSION: Liver denervation secondary to transplantation does not lead to alterations of energy metabolism after ingestion of a glucose load.