Results of energy-loss measurements on passenger car tires operating in the free-rolling and braking/traction modes. Final report.

Transportation Systems Center, Cambridge, Mass.

Adjusting Body Cell Mass for Size in Women of Differing Nutritional Status

Background: Body cell mass (BCM) may be estimated in clinical practice to assess functional nutritional status, eg, in patients with anorexia nervosa. Interpretation of the data, especially in younger patients who are still growing, requires appropriate adjustment for size. Previous investigations of this general issue have addressed chemical rather than functional components of body composition and have not considered patients at the extremes of nutritional status, in whom the ability to make longitudinal comparisons is of particular importance. Objective: Our objective was to determine the power by which height should be raised to adjust BCM for height in women of differing nutritional status. Design: BCM was estimated by K-40 counting in 58 healthy women, 33 healthy female adolescents, and 75 female adolescents with anorexia nervosa. The relation between BCM and height was explored in each group by using log-log regression analysis. Results: The powers by which height should be raised to adjust BCM,A,ere 1.73. 1.73, and 2.07 in the women, healthy female adolescents, and anorexic female adolescents, respectively. A simplified version of the index, BCM/height(2), was appropriate for all 3 categories and was negligibly correlated with height. Conclusions: In normal-weight women, the relation between height and BCM is consistent with that reported previously between height and fat-free mass. Although the consistency of the relation between BCM and fat-free mass decreases with increasing weight loss, the relation between height and BCM is not significantly different between normal-weight and underweight women. The index BCM/height(2) is easy to calculate and applicable to both healthy and underweight women. This information may be helpful in interpreting body-composition data in clinical practice.

Body-mass management of Australian lightweight rowers prior to and during competition

Purpose: Although the body-mass management strategies of athletes in high-participation weight-category sports such as wrestling have been thoroughly investigated, little is known about such practices among lightweight rowers. This study examined the body-mass management practices of lightweight rowers before competition and compared these with current guidelines of the International Federation of Rowing Association (FISA). Quantification of nutrient intake in the 1-2 h between weigh-in and racing was also sought. Methods: Lightweight rowers (N = 100) competing in a national regatta completed a questionnaire that assessed body-mass management practices during the 4 wk before and throughout a regatta plus recovery strategies after weigh-in. Biochemical data were collected immediately after weigh-in to validate questionnaire responses. Responses were categorized according to gender and age category (Senior B or younger than 23 yr old, i.e., U23, Senior A or OPEN, i.e., open age limit) for competition. Results: Most athletes (male U23 76.5%, OPEN 92.3%; female U23 84.0%, OPEN 94.1%) decreased their body mass in the weeks before the regatta at rates compliant with FISA guidelines. Gradual dieting, fluid restriction, and increased training load were the most popular methods of body-mass management. Although the importance of recovery after weigh-in was recognized by athletes, nutrient intake and especially sodium (male U23 5.3 ± 4.9, OPEN 7.7 ± 5.9; female U23 5.7 ± 6.8, OPEN 10.2 ± 5.4 mg-kg(-1)) and fluid intake (male U23 12.1 ± 7.1, OPEN 13.5 ± 8.1; female U23 9.4 ± 7.4, OPEN 14.8 ± 6.9 mL.kg(-1)) were below current sports nutrition recommendations. Conclusion: Few rowers were natural lightweights; the majority reduced their body mass in the weeks before a regatta. Nutritional recovery strategies implemented by lightweight rowers after weigh-in were not consistent with current guidelines.

Bone loss in Crohn's disease: Exercise as a potential countermeasure

Crohn's disease (CD) is associated with a number of secondary conditions including osteoporosis, which increases the risk of bone fracture. The cause of metabolic bone disease in this Population is believed to be multifactorial and may include the disease itself and associated inflammation, high-close corticosteroid use, weight loss and malabsorption, a lack of exercise and physical activity, and all underlying genetic predisposition to bone loss. Reduced bone mineral density has been reported in between 5% to 80% of CD sufferers, although it is generally believed that approximately 40% of patients suffer from osteopenia and 15% from osteoporosis. Recent studies Suggest a small but significantly increased risk of fracture compared with healthy controls and, perhaps, sufferers of other gastrointestinal disorders Such as ulcerative colitis. The role of physical activity and exercise in the prevention and treatment of CD-related bone loss has received little attention, despite the benefits of specific exercises being well documented in healthy populations. This article reviews the prevalence of and risk factors for low bone mass in CD patients and examines various treatments for osteoporosis in these patients, with a particular focus on physical activity.

Acute weight loss followed by an aggressive nutritional recovery strategy has little impact on on-water rowing performance

Objectives: To assess the influence of moderate, acute weight loss on on-water rowing performance when aggressive nutritional recovery strategies were used in the two hours between weigh in and racing. Methods: Competitive rowers (n=17) undertook three on-water 1800 m time trials under cool conditions ( mean (SD) temperature 8.4 (2.0)degrees C), each separated by 48 hours. No weight limit was imposed for the first time trial-that is, unrestricted body mass (UNR1). However, one of the remaining two trials followed a 4% loss in body mass in the previous 24 hours (WT-4%). No weight limit was imposed for the other trial (UNR2). Aggressive nutritional recovery strategies (WT-4%, 2.3 g/kg carbohydrate, 34 mg/kg Na+, and 28.4 ml/kg fluid; UNR, ad libitum) were used in the first 90 minutes of the two hours between weigh in and performance trials. Results: WT-4% had only a small and statistically non-significant effect on the on-water time trial performance ( mean 1.0 second, 95% confidence interval (CI) 20.9 to 2.8; p=0.29) compared with UNR. This was despite a significant decrease in plasma volume at the time of weigh in for WT-4% compared with UNR (-9.2%, 95% CI -12.8% to -5.6%; p

Conditional deletion of hypothalamic Y2 receptors reverts gonadectomy-induced bone loss in adult mice

Reduction in levels of sex hormones at menopause in women is associated with two common, major outcomes, the accumulation of white adipose tissue, and the progressive loss of bone because of excess osteoclastic bone resorption exceeding osteoblastic bone formation. Current antiresorptive therapies can reduce osteoclastic activity but have only limited capacity to stimulate osteoblastic bone formation and restore lost skeletal mass. Likewise, the availability of effective pharmacological weight loss treatments is currently limited. Here we demonstrate that conditional deletion of hypothalamic neuropeptide Y2 receptors can prevent ongoing bone loss in sex hormone-deficient adult male and female mice. This benefit is attributable solely to activation of an anabolic osteoblastic bone formation response that counterbalances persistent elevation of bone resorption, suggesting the Y2-mediated anabolic pathway to be independent of sex hormones. Furthermore, the increase in fat mass that typically occurs after ovariectomy is prevented by germ line deletion of Y2 receptors, whereas in male mice body weight and fat mass were consistently lower than wild-type regardless of sex hormone status. Therefore, this study indicates a role for Y2 receptors in the accumulation of adipose tissue in the hypogonadal state and demonstrates that hypothalamic Y2 receptors constitutively restrain osteoblastic activity even in the absence of sex hormones. The increase in bone formation after release of this tonic inhibition suggests a promising new avenue for osteoporosis treatment.

Identification of oxidized phospholipids by electrospray ionization mass spectrometry and LC-MS using a QQLIT instrument

Phospholipids are complex and varied biomolecules that are susceptible to lipid peroxidation after attack by free radicals or electrophilic oxidants and can yield a large number of different oxidation products. There are many available methods for detecting phospholipid oxidation products, but also various limitations and problems. Electrospray ionization mass spectrometry allows the simultaneous but specific analysis of multiple species with good sensitivity and has a further advantage that it can be coupled to liquid chromatography for separation of oxidation products. Here, we explain the principles of oxidized phospholipid analysis by electrospray mass spectrometry and describe fragmentation routines for surveying the structural properties of the analytes, in particular precursor ion and neutral loss scanning. These allow targeted detection of phospholipid headgroups and identification of phospholipids containing hydroperoxides and chlorine, as well as the detection of some individual oxidation products by their specific fragmentation patterns. We describe instrument protocols for carrying out these survey routines on a QTrap5500 mass spectrometer and also for interfacing with reverse-phase liquid chromatography. The article highlights critical aspects of the analysis as well as some limitations of the methodology.

Attenuation of proteasome-induced proteolysis in skeletal muscle by beta-hydroxy-beta-methylbutyrate in cancer-induced muscle loss

Loss of skeletal muscle is an important determinant of survival in patients with cancer-induced weight loss. The effect of the leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) on the reduction of body weight loss and protein degradation in the MAC16 model of cancer-induced weight loss has been compared with that of eicosapentaenoic acid (EPA), a recognized inhibitor of protein degradation. HMB was found to attenuate the development of weight loss at a dose greater than 0.125 g/kg accompanied by a small reduction in tumor growth rate. When EPA was used at a suboptimal dose level (0.6 g/kg) the combination with HMB seemed to enhance the anticachectic effect. Both treatments caused an increase in the wet weight of soleus muscle and a reduction in protein degradation, although there did not seem to be a synergistic effect of the combination. Proteasome activity, determined by the "chymotrypsin-like" enzyme activity, was attenuated by both HMB and EPA. Protein expression of the 20S alpha or beta subunits was reduced by at least 50%, as were the ATPase subunits MSS1 and p42 of the 19S proteasome regulatory subunit. This was accompanied by a reduction in the expression of E2(14k) ubiquitin-conjugating enzyme. The combination of EPA and HMB was at least as effective or more effective than either treatment alone. Attenuation of proteasome expression was reflected as a reduction in protein degradation in gastrocnemius muscle of cachectic mice treated with HMB. In addition, HMB produced a significant stimulation of protein synthesis in skeletal muscle. These results suggest that HMB preserves lean body mass and attenuates protein degradation through down-regulation of the increased expression of key regulatory components of the ubiquitin-proteasome proteolytic pathway, together with stimulation of protein synthesis.

Effect of a protein and energy dense n-3 fatty acid enriched oral supplement on loss of weight and lean tissue in cancer cachexia:A randomised double blind trial

Aim: N-3 fatty acids, especially eicosapentaenoic acid (EPA), may possess anticachectic properties. This trial compared a protein and energy dense supplement enriched with n-3 fatty acids and antioxidants (experimental: E) with an isocaloric isonitrogenous control supplement (C) for their effects on weight, lean body mass (LBM), dietary intake, and quality of life in cachectic patients with advanced pancreatic cancer. Methods: A total of 200 patients (95 E; 105 C) were randomised to consume two cans/day of the E or C supplement (480 ml, 620 kcal, 32 g protein ± 2.2 g EPA) for eight weeks in a multicentre, randomised, double blind trial. Results: At enrolment, patients' mean rate of weight loss was 3.3 kg/month. Intake of the supplements (E or C) was below the recommended dose (2 cans/day) and averaged 1.4 cans/day. Over eight weeks, patients in both groups stopped losing weight (Δweight E: -0.25 kg/month versus C: -0.37 kg/month; p=0.74) and LBM (ΔLBM E: +0.27 kg/month versus C: +0.12 kg/month; p=0.88) to an equal degree (change from baseline E and C, p<0.001). In view of evident non-compliance in both E and C groups, correlation analyses were undertaken to examine for potential dose-response relationships. E patients demonstrated significant correlations between their supplement intake and weight gain (r=0.50, p<0.001) and increase in LBM (r=0.33, p=0.036). Such correlations were not statistically significant in C patients. The relationship of supplement intake with change in LBM was significantly different between E and C patients (p=0.043). Increased plasma EPA levels in the E group were associated with weight and LBM gain (r=0.50, p<0.001; r=0.51, p=0.001). Weight gain was associated with improved quality of life (p<0.01) only in the E group. Conclusion: Intention to treat group comparisons indicated that at the mean dose taken, enrichment with n-3 fatty acids did not provide a therapeutic advantage and that both supplements were equally effective in arresting weight loss. Post hoc dose-response analysis suggests that if taken in sufficient quantity, only the n-3 fatty acid enriched energy and protein dense supplement results in net gain of weight, lean tissue, and improved quality of life. Further trials are required to examine the potential role of n-3 enriched supplements in the treatment of cancer cachexia.

Weight loss in tumour-bearing mice is not associated with changes in resistin gene expression in white adipose tissue

Resistin, a product of white adipose tissue, is postulated to induce insulin resistance in obesity and regulate adipocyte differentiation. The aim of this study was to examine resistin gene expression in adipose tissue from mice bearing the MAC16 adenocarcinoma, which induces cancer cachexia with marked wasting of adipose tissue and skeletal muscle mass. MAC16-bearing mice lost weight progressively over the period following tumour transplantation, while the weight of control mice remained stable. Leptin mRNA in gonadal fat was 50% lower in MAC16 mice than in controls (p<0.05). Plasma insulin concentrations were also significantly lower in the MAC16 group (p<0.05). However, resistin mRNA level in gonadal fat in MAC16 mice was similar to controls (94% of controls). Thus, despite severe weight loss and significant falls in leptin expression and insulin concentration, resistin gene expression appears unchanged in white adipose tissue of mice with MAC16 tumour. Maintenance of resistin production may help inhibit the formation of new adipocytes in cancer cachexia.

Loss of skeletal muscle in cancer: biochemical mechanisms

Patients with cancer often undergo a specific loss of skeletal muscle mass, while the visceral protein reserves are preserved. This condition known as cachexia reduces the quality of life and eventually results in death through erosion of the respiratory muscles. Nutritional supplementation or appetite stimulants are unable to restore the loss of lean body mass, since protein catabolism is increased mainly as a result of the activation of the ATP-ubiquitin-dependent proteolytic pathway. Several mediators have been proposed. An enhanced protein degradation is seen in skeletal muscle of mice administered tumour necrosis factor (TNF), which appears to be mediated by oxidative stress. There is some evidence that this may be a direct effect and is associated with an increase in total cellular-ubiquitin-conjugated muscle proteins. Another cytokine, interleukin-6 (IL-6), may play a role in muscle wasting in certain animal tumours, possibly through both lysosomal (cathepsin) and non-lysosomal (proteasome) pathways. A tumour product, proteolysis-inducing factor (PIF) is produced by cachexia-inducing murine and human tumours and initiates muscle protein degradation directly through activation of the proteasome pathway. The action of PIF is blocked by eicosapentaenoic acid (EPA), which has been shown to attenuate the development of cachexia in pancreatic cancer patients. When combined with nutritional supplementation EPA leads to accumulation of lean body mass and prolongs survival. Further knowledge on the biochemical mechanisms of muscle protein catabolism will aid the development of effective therapy for cachexia.

Mass spectrometric analysis of HOCl- and free-radical-induced damage to lipids and proteins

In inflammatory diseases, release of oxidants leads to oxidative damage to biomolecules. HOCl (hypochlorous acid), released by the myeloperoxidase/H2O2/Cl- system, can cause formation of phospholipid chlorohydrins, or alpha-chloro-fatty aldehydes from plasmalogens. It can attack several amino acid residues in proteins, causing post-translational oxidative modifications of proteins, but the formation of 3-chlorotyrosine is one of the most stable markers of HOCl-induced damage. Soft-ionization MS has proved invaluable for detecting the occurrence of oxidative modifications to both phospholipids and proteins, and characterizing the products generated by HOCl-induced attack. For both phospholipids and proteins, the application of advanced mass spectrometric methods such as product or precursor ion scanning and neutral loss analysis can yield information both about the specific nature of the oxidative modification and the biomolecule modified. The ideal is to be able to apply these methods to complex biological or clinical samples, to determine the site-specific modifications of particular cellular components. This is important for understanding disease mechanisms and offers potential for development of novel biomarkers of inflammatory diseases. In the present paper, we review some of the progress that has been made towards this goal.

Protein oxidation:role in signalling and detection by mass spectrometry

Proteins can undergo a wide variety of oxidative post-translational modifications (oxPTM); while reversible modifications are thought to be relevant in physiological processes, non-reversible oxPTM may contribute to pathological situations and disease. The oxidant is also important in determining the type of oxPTM, such as oxidation, chlorination or nitration. The best characterized oxPTMs involved in signalling modulation are partial oxidations of cysteine to disulfide, glutathionylated or sulfenic acid forms that can be reversed by thiol reductants. Proline hydroxylation in HIF signalling is also quite well characterized, and there is increasing evidence that specific oxidations of methionine and tyrosine may have some biological roles. For some proteins regulated by cysteine oxidation, the residues and molecular mechanism involved have been extensively studied and are well understood, such as the protein tyrosine phosphatase PTP1B and MAP3 kinase ASK1, as well as transcription factor complex Keap1-Nrf2. The advances in understanding of the role oxPTMs in signalling have been facilitated by advances in analytical technology, in particular tandem mass spectrometry techniques. Combinations of peptide sequencing by collisionally induced dissociation and precursor ion scanning or neutral loss to select for specific oxPTMs have proved very useful for identifying oxidatively modified proteins and mapping the sites of oxidation. The development of specific labelling and enrichment procedures for S-nitrosylation or disulfide formation has proved invaluable, and there is ongoing work to establish analogous methods for detection of nitrotyrosine and other modifications.

Analysis of oxidized and chlorinated lipids by mass spectrometry and relevance to signalling

Oxidized and chlorinated phospholipids are generated under inflammatory conditions and are increasingly understood to play important roles in diseases involving oxidative stress. MS is a sensitive and informative technique for monitoring phospholipid oxidation that can provide structural information and simultaneously detect a wide variety of oxidation products, including chain-shortened and -chlorinated phospholipids. MSn technologies involve fragmentation of the compounds to yield diagnostic fragment ions and thus assist in identification. Advanced methods such as neutral loss and precursor ion scanning can facilitate the analysis of specific oxidation products in complex biological samples. This is essential for determining the contributions of different phospholipid oxidation products in disease. While many pro-inflammatory signalling effects of oxPLs (oxidized phospholipids) have been reported, it has more recently become clear that they can also have anti-inflammatory effects in conditions such as infection and endotoxaemia. In contrast with free radical-generated oxPLs, the signalling effects of chlorinated lipids are much less well understood, but they appear to demonstrate mainly pro-inflammatory effects. Specific analysis of oxidized and chlorinated lipids and the determination of their molecular effects are crucial to understanding their role in disease pathology.

Editorial : which weight loss diet?

Full editorial: A recent study evaluating the long-term (2 yr) weight reducing efficacy of different types of diets – high or low in carbohydrates (CHOs), protein or fat - confirmed that it is calorie deficit not dietary composition that determines the loss and maintenance of body weight.1 Is there any advantage in following a specific weight loss diet? Short-term use of nutritionally complete commercially available (very) low calorie diets has benefited people with diabetes when  supported by education programmes.2 Initial weight loss has been encouraging with some fad diets eg the Atkins and the South Beach diets, but these diets are difficult to maintain and there are safety issues regarding their short- and long-term use – especially in people with diabetes.3 The types of macronutrients consumed can have a considerable impact on glycaemic control and energy metabolism. Although a low CHO diet additionally enhances initial weight loss by reducing cellular water content, if fat is not proportionally reduced the diet may not benefit the lipid profile for vascular disease risk. High fat and high protein diets – which are simultaneously low in CHOs – increase vulnerability to hypoglycaemia in people taking insulin secretagogues or on insulin therapy, and may promote excess fat metabolism and ketogenesis, particularly in people vulnerable to lack of insulin. Very low protein diets are not recommended as lean body mass tends to be reduced in diabetes. Altering the macronutrient balance has implications for the micronutrient mix: deficiencies are higher if more foods are excluded and conversely specific micronutrient excess can occur with some fad diets. The altered nutrient mix affects intestinal fauna and flora, and gut motility and glycaemic control are influenced by the quantity and type of fibre consumed. Support programmes help individuals achieve long term weight loss and there is mounting evidence that community schemes which educate and promote lifestyle changes may stem the rising tide of obesity and consequent type 2 diabetes.4 Consuming smaller portions of a balanced diet (and adjusting antidiabetic medications accordingly) will create an energy deficit to promote healthy weight loss. Increased movement/exercise will enhance this energy deficit. Knowledge (eg 1g fat has 2.25 times more energy than 1g CHO) allows sensible food choices and compensation for inclusion of small volumes of  ‘naughty but nice’ foods. Ultimately weight control requires self control. References 1. Sacks FM, Bray GA, Carey VJ et al. Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates. N Engl J Med 2009;360:859–73. 2. Bennett P. Obesity, diabetes and VLCD. Br J Diabetes Vasc Dis 2004;4:328–30. 3. Baldwin EJ. Fad diets in diabetes. Br J Diabetes Vasc DIs 2004;4:333–7. 4. Romon M, Lommoz A, Tafflet M et al. Downward trends in the prevalence of childhood overweight in the setting of 12-year school- and community-based programmes. Public Health Nutr 2008; Dec 28, 1–8 [Epub ahead of print].