The role of dietary protein in obesity

Reviews in Endocrine and Metabolic Disorders - Protein-rich diets are surging in popularity for weight loss. An increase in diet-induced thermogenesis, better preservation of fat-free mass, and...     

Effect of zoledronic acid on markers of bone turnover and mineral density in osteoporotic patients with beta-thalassaemia

Osteoporosis has emerged as an important cause of morbidity in patients with thalassemia major. Studies regarding the efficacy of bisphosphonates in thalassemia-induced osteoporosis have yielded conflicting results. We performed this prospective study to evaluate the efficacy of zoledronic acid in osteoporotic patients with thalassemia major. Patients, 29, were given 1 mg zoledronic acid intravenously every 3 months for a total of four doses. Twenty age- and sex-matched healthy blood donors served as controls. Before each infusion and 3 months after the last infusion, we determined serum levels of osteoprotegerin (OPG), N-terminal cross-linking telopeptide of type I collagen (NTX), osteocalcin (OC) and insulin-like growth factor 1 (IGF-1). Bone mineral density (BMD) of the lumbar spine was measured at baseline and after the treatment’s completion. At baseline, OPG did not differ significantly between patients and controls (p=0.2), NTX were higher in patients although not significantly (p=0.139), whereas, OC levels were significantly higher and IGF-1 levels significantly lower in patients than in controls (p<0.001 and p<0.006, respectively). Zoledronic acid administration resulted in a significant decrease in NTX, OC and IGF-1 (p<0.05, p<0.001 and p<0.05, respectively) and in a significant increase in OPG and BMD (p<0.05 for both comparisons). The change in NTX, osteocalcin and IGF-1 became significant as early as 3 months after the first administration of zoledronic acid, while the change in OPG reached significance only after three infusions. Our study supports the effectiveness of bisphosphonates in the treatment of thalassemia-induced osteoporosis.     

Improved insulin sensitivity after a single bout of exercise is curvilinearly related to exercise energy expenditure

A single bout of moderate-intensity exercise increases whole-body insulin sensitivity for 12-48 h post-exercise; however, the relationship between exercise energy expenditure and the improvement in insulin sensitivity is not known. We hypothesized that the exercise-induced increase in whole-body insulin sensitivity, assessed with HOMA(IR) (homoeostasis model assessment of insulin resistance), is directly related to the energy expended during exercise. We studied 30 recreationally active non-obese men (age, 27+/-5 years; body mass index, 24+/-2 kg/m(2)) in the post-absorptive state on two separate occasions: once after exercising at 60% of VO(22peak) (peak oxygen consumption) for 30-120 min on the preceding afternoon (expending a total of 1.28-5.76 MJ) and once after an equivalent period of rest. Blood samples were obtained the following morning. Exercise-induced changes in HOMA(IR) were curvilinearly related to exercise energy expenditure (r=-0.666, P=0.001) with a threshold of approx. 3.77 MJ (900 kcal) for improvements in HOMA(IR) to be manifested. In particular, HOMA(IR) was reduced by 32+/-24% (P=0.003) in subjects who expended more than 3.77 MJ during exercise, but did not change for those who expended fewer than 3.77 MJ (-2+/-21%; P=0.301). Furthermore, the magnitude of change in HOMA(IR) after exercise was directly associated with baseline (i.e. resting) HOMA(IR) (r=-0.508, P=0.004); this relationship persisted in multivariate analysis. We conclude that improved whole-body insulin resistance after a single bout of exercise is curvilinearly related to exercise energy expenditure, and requires unfeasible amounts of exercise for most sedentary individuals.     

Decrease in hepatic very‐low‐density lipoprotein–triglyceride secretion after weight loss is inversely associated with changes in circulating leptin

Aim: Although weight loss usually decreases very‐low‐density lipoprotein–triglyceride (VLDL‐TG) secretion rate, the change in VLDL‐TG kinetics is not directly related to the change in body weight. Circulating leptin also declines with weight loss and can affect hepatic lipid metabolism. The aim of this study was to determine whether circulating leptin is associated with weight loss‐induced changes in VLDL‐TG secretion. Methods: Ten extremely obese subjects were studied. VLDL‐TG secretion rate and the contribution of systemic (derived from lipolysis of subcutaneous adipose tissue TG) and non‐systemic fatty acids (derived primarily from lipolysis of intrahepatic and intraperitoneal TG, and de novo lipogenesis) to VLDL‐TG production were determined by using stable isotopically labelled tracer methods before and 1 year after gastric bypass surgery. Results: Subjects lost 33 ± 12% of body weight, and VLDL‐TG secretion rate decreased by 46 ± 23% (p = 0.001), primarily because of a decrease in the secretion of VLDL‐TG from non‐systemic fatty acids (p = 0.002). Changes in VLDL‐TG secretion rates were not significantly related to reductions in body weight, body mass index, plasma palmitate flux, free fatty acid or insulin concentrations. The change in VLDL‐TG secretion was inversely correlated with the change in plasma leptin concentration (r = ?0.72, p = 0.013), because of a negative association between changes in leptin and VLDL‐TG secretion from non‐systemic fatty acids (r = ?0.95, p < 0.001). Conclusions: Weight loss‐induced changes in plasma leptin concentration are inversely associated with changes in VLDL‐TG secretion rate. Additional studies are needed to determine whether the correlation between circulating leptin and VLDL‐TG secretion represents a cause‐and‐effect relationship.     

The bone response to non-weight-bearing exercise is sport-, site-, and sex-specific.

OBJECTIVE: To examine whether skeletal adaptations to chronic non-weight-bearing exercise depend on the type of aquatic exercise (swimming or water polo) as well as on sex (men or women). DESIGN, SETTING, AND PARTICIPANTS: This was a cross-sectional study at the Laboratory of Nutrition and Clinical Dietetics, Department of Nutrition and Dietetics, Harokopio University, Athens, Greece. A total of 43 water polo players, 26 swimmers, and 30 sedentary individuals, aged 17 to 34 years, were recruited (52 men, 47 women). MAIN OUTCOME MEASURES: Bone mineral content (BMC) and areal bone mineral density (aBMD) of the total body and of various subregions. RESULTS:: Compared with controls, swimmers had lower leg and total aBMD (P < 0.05), whereas water polo players had lower leg but higher arm and trunk aBMD (all P < 0.05). Swimmers and water polo athletes differed at the arms (men only), trunk, and total body (all higher in water polo players, at P < 0.05). Bone adaptations to water polo playing were unaffected by sex. Female swimmers, but not male swimmers, had 13% higher arm BMC than controls (P < 0.05), whereas male swimmers, but not female swimmers, had 12% lower leg BMC than controls (P < 0.05). CONCLUSIONS: Athletes participating in long-term water polo playing and swimming have substantially different total and regional aBMD. The effect is not mediated by sex in water polo players; however, sex may mediate the differences between swimmers and controls. Whether the observed differences between athlete groups and sexes arise from different bone adaptations to activity or from other factors cannot be answered by the current data. CLINICAL RELEVANCE: Water polo playing may be preferable over swimming for maintaining bone health; both types of aquatic exercise at the elite level of participation, however, have unfavorable effects on the lower limb bones.     

Water polo is associated with an apparent redistribution of bone mass and density from the lower to the upper limbs

The bone response to exercise is site-specific and load-dependent. Recent evidence suggests that an inverse relationship may exist between loaded and unloaded sites, such that the former may benefit at the expense of the latter. The present study examined this possibility in 48 males (21 water polo players, 12 handball players, and 15 sedentary controls). Water polo and handball are alike with respect to the active loading of the upper limbs during overhead throwing; however, the weight-supporting environment of water polo removes the weight-bearing effect from the lower limbs. Bone mineral content (BMC), bone projected area (Ap), and areal bone mineral density (aBMD) of the total body and of various subregions were determined by dual-energy X-ray absorptiometry. After adjusting for age, height, and weight, water polo players had higher arms BMC, Ap, and aBMD (by 22.2, 11.1, and 10.5%, respectively; P < 0.05), but lower legs aBMD (−6.3%; P < 0.05) relative to controls. On the contrary, compared to controls, handball players had higher BMC (from 11.8 to 24.3%), Ap (from 5.2 to 11.7%), and aBMD (from 6.4 to 11.9%) for the total body at all sites. Water polo athletes had increased arms and decreased legs aBMD ratios (regional-to-total) than either handball players or sedentary subjects (P < 0.001). Water polo is associated with an apparent redistribution of bone mass and density from the lower to the upper limbs, with no major effects on the rest of the body.     

Neuroendocrine tumors and fibrosis: An unsolved mystery?

Neuroendocrine tumors are a heterogeneous group of slow‐growing neoplasms arising mainly from the enterochromaffin cells of the digestive and respiratory tract. Although they are relatively rare, their incidence is rising. It has long been observed that they often are associated with the development of fibrosis, both local and distant. Fibrotic complications, such as carcinoid heart disease and mesenteric desmoplasia, may lead to considerable morbidity or even affect prognosis. The elucidation of the pathophysiology of fibrosis would be of critical importance for the development of targeted therapeutic strategies. In this article, the authors review the available evidence regarding the biological basis of fibrosis in neuroendocrine tumors. They explore the role of the tumor microenvironment and the interplay between tumor cells and fibroblasts as a key factor in fibrogenesis and tumor development/progression. They also review the role of serotonin, growth factors, and other peptides in the development of carcinoid‐related fibrotic reactions. Cancer 2017;123:4770‐90 . © 2017 American Cancer Society.     

Identifying nutritionally vulnerable groups in case of emergencies: experience from the Athens 1999 earthquake

During emergency situations in developing countries, young children have been identified as the most nutritionally vulnerable group. Comparatively less is known regarding nutritional risk of individuals in well-nourished societies hit by a major disaster. The aim of the present study, therefore, was to assess the nutritional status of Greek people who were left homeless after the Athens 1999 earthquake. A total of 225 volunteers from two camps were surveyed for dietary intake information and surrogate measures of nutritional status. Energy consumption and anthropometric indices of the children and adolescents revealed no sign of undernourishment. On the other hand, adults and the elderly consumed considerably less energy than that required for long-term preservation of health. Short-term energy and protein deficits, however, did not jeopardise their nutritional status as it might have expected, on the basis of high body mass indexes and normal haematological and biochemical profiles that were documented. In conclusion, the results of the present study indicate that nutritional risk in the acute phase after a major emergency in a previously well-nourished population is rather low. This is especially true for younger individuals, probably due to increased provision from the family and the community. Nevertheless, older persons may face increased risk as the situation is prolonged.