"iDoctor – Medical Blog"

Functional genetic variants of glutathione S-transferase protect against serum ascorbic acid deficiency.

Am J Clin Nutr. 2009 Aug 26;

Authors: Cahill LE, Fontaine-Bisson B, El-Sohemy A

BACKGROUND: Glutathione S-transferases (GSTs) are detoxifying enzymes that contribute to the glutathione-ascorbic acid (vitamin C) antioxidant cycle. OBJECTIVE: The objective was to determine whether GST genotypes modify the association between dietary vitamin C and serum ascorbic acid. DESIGN: Nonsmoking men and women (n = 905) between 20 and 29 y of age were participants in the Toronto Nutrigenomics and Health Study. Overnight fasting blood samples were collected to determine serum ascorbic acid concentrations by HPLC and to genotype for deletion polymorphisms in GSTM1 and GSTT1 and an Ile105Val substitution in GSTP1. A 196-item food-frequency questionnaire was used to estimate vitamin C intake. RESULTS: A gene-diet interaction on serum ascorbic acid was observed for GSTM1 (P = 0.04) and GSTT1 (P = 0.01) but not for GSTP1 (P = 0.83). The odds ratio (95% CI) for serum ascorbic acid deficiency (<11 mumol/L) was 3.20 (1.88, 5.44) for subjects who did not meet the Recommended Dietary Allowance of vitamin C compared with those who did. The corresponding odds ratios (95% CIs) were 2.17 (1.10, 4.28) and 12.28 (4.26, 33.42), respectively, for individuals with the GSTT1*1/*1 +*1/*0 (functional) and GSTT1*0/*0 (null) genotypes and 2.29 (0.96, 5.45) and 4.03 (2.01, 8.09), respectively, for the GSTM1*1/*1+GSTM1*1/*0 and GSTM1*0/*0 genotypes. CONCLUSIONS: The recommended intake of vitamin C protects against serum ascorbic acid deficiency, regardless of genotype. Individuals with GST null genotypes had an increased risk of deficiency if they did not meet the Recommended Dietary Allowance for vitamin C, which suggests that the GST enzymes protect against serum ascorbic acid deficiency when dietary vitamin C is insufficient.

PMID: 19710200 [PubMed - as supplied by publisher]

High protein intake reduces intrahepatocellular lipid deposition in humans.

Am J Clin Nutr. 2009 Aug 26;

Authors: Bortolotti M, Kreis R, Debard C, Cariou B, Faeh D, Chetiveaux M, Ith M, Vermathen P, Stefanoni N, Lê KA, Schneiter P, Krempf M, Vidal H, Boesch C, Tappy L

BACKGROUND: High sugar and fat intakes are known to increase intrahepatocellular lipids (IHCLs) and to cause insulin resistance. High protein intake may facilitate weight loss and improve glucose homeostasis in insulin-resistant patients, but its effects on IHCLs remain unknown. OBJECTIVE: The aim was to assess the effect of high protein intake on high-fat diet-induced IHCL accumulation and insulin sensitivity in healthy young men. DESIGN: Ten volunteers were studied in a crossover design after 4 d of either a hypercaloric high-fat (HF) diet; a hypercaloric high-fat, high-protein (HFHP) diet; or a control, isocaloric (control) diet. IHCLs were measured by (1)H-magnetic resonance spectroscopy, fasting metabolism was measured by indirect calorimetry, insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp, and plasma concentrations were measured by enzyme-linked immunosorbent assay and gas chromatography-mass spectrometry; expression of key lipogenic genes was assessed in subcutaneous adipose tissue biopsy specimens. RESULTS: The HF diet increased IHCLs by 90 +/- 26% and plasma tissue-type plasminogen activator inhibitor-1 (tPAI-1) by 54 +/- 11% (P < 0.02 for both) and inhibited plasma free fatty acids by 26 +/- 11% and beta-hydroxybutyrate by 61 +/- 27% (P < 0.05 for both). The HFHP diet blunted the increase in IHCLs and normalized plasma beta-hydroxybutyrate and tPAI-1 concentrations. Insulin sensitivity was not altered, whereas the expression of sterol regulatory element-binding protein-1c and key lipogenic genes increased with the HF and HFHP diets (P < 0.02). Bile acid concentrations remained unchanged after the HF diet but increased by 50 +/- 24% after the HFHP diet (P = 0.14). CONCLUSIONS: Protein intake significantly blunts the effects of an HF diet on IHCLs and tPAI-1 through effects presumably exerted at the level of the liver. Protein-induced increases in BA concentrations may be involved. This trial was registered at www.clinicaltrials.gov as NCT00523562.

PMID: 19710199 [PubMed - as supplied by publisher]

Contribution of individual organ mass loss to weight loss-associated decline in resting energy expenditure.

Am J Clin Nutr. 2009 Aug 26;

Authors: Bosy-Westphal A, Kossel E, Goele K, Later W, Hitze B, Settler U, Heller M, Glüer CC, Heymsfield SB, Müller MJ

BACKGROUND: Weight loss leads to reduced resting energy expenditure (REE) independent of fat-free mass (FFM) and fat mass (FM) loss, but the effect of changes in FFM composition is unclear. OBJECTIVE: We hypothesized that a decrease in REE adjusted for FFM with weight loss would be partly explained by a disproportionate loss in the high metabolic activity component of FFM. DESIGN: Forty-five overweight and obese women [body mass index (in kg/m(2)): 28.7-46.8] aged 22-46 y followed a low-calorie diet for 12.7 +/- 2.2 wk. Body composition was measured by magnetic resonance imaging, dual-energy X-ray absorptiometry, and a 4-compartment model. REE measured by indirect calorimetry (REEm) was compared with REE calculated from detailed body-composition analysis (REEc) by using specific organ metabolic rates (ie, organ REE/mass). RESULTS: Weight loss was 9.5 +/- 3.4 kg (8.0 +/- 2.9 kg FM and 1.5 +/- 3.1 kg FFM). Decreases in REE (-8%), free triiodothyronine concentrations (-8%), muscle (-3%), heart (-5%), liver (-4%), and kidney mass (-6%) were observed (all P < 0.05). Relative loss in organ mass was significantly higher (P < 0.01) than was the change in low metabolically active FFM components (muscle, bone, and residual mass). After weight loss, REEm – REEc decreased from 0.24 +/- 0.58 to 0.01 +/- 0.44 MJ/d (P = 0.01) and correlated with the decrease in free triiodothyronine concentrations (r = 0.33, P < 0.05). Women with high adaptive thermogenesis (defined as REEm – REEc < -0.17 MJ/d) had less weight loss and conserved FFM, liver, and kidney mass. CONCLUSIONS: After weight loss, almost 50% of the decrease in REEm was explained by losses in FFM and FM. The variability in REEm explained by body composition increased to 60% by also considering the weight of individual organs.

PMID: 19710198 [PubMed - as supplied by publisher]

Modification effects of physical activity and protein intake on heritability of body size and composition.

Am J Clin Nutr. 2009 Aug 26;

Authors: Silventoinen K, Hasselbalch AL, Lallukka T, Bogl L, Pietiläinen KH, Heitmann BL, Schousboe K, Rissanen A, Kyvik KO, Sørensen TI, Kaprio J

BACKGROUND: The development of obesity is still a poorly understood process that is dependent on both genetic and environmental factors. OBJECTIVE: The objective was to examine how physical activity and the proportion of energy as protein in the diet modify the genetic variation of body mass index (BMI), waist circumference, and percentage body fat. DESIGN: Twins from Denmark (756 complete pairs) and Finland (278 complete pairs) aged 18-67 and 21-24 y, respectively, participated. The proportion of energy as protein in the diet was estimated by using food-frequency questionnaires. The participants reported the frequency and intensity of their leisure time physical activity. Waist circumference and BMI were measured. Percentage body fat was assessed in Denmark by using a bioelectrical impedance method. The data were analyzed by using gene-environment interaction models for twin data with the Mx statistical package (Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA). RESULTS: High physical activity was associated with lower mean values, and a high proportion of protein in the diet was associated with higher mean BMI, waist circumference, and percentage body fat and a reduction in genetic and environmental variances. Genetic modification by physical activity was statistically significant for BMI (-0.18; 95% CI: -0.31, -0.05) and waist circumference (-0.14; 95% CI: -0.22, -0.05) in the merged data. A high proportion of protein in the diet reduced genetic and environmental variances in BMI and waist circumference in Danish men but not in women or in Finnish men. CONCLUSIONS: Our results suggest that, in physically active individuals, the genetic variation in weight is reduced, which possibly suggests that physical activity is able to modify the action of the genes responsible for predisposition to obesity, whereas the protein content of the diet has no appreciable effect.

PMID: 19710197 [PubMed - as supplied by publisher]

Food insulin index: physiologic basis for predicting insulin demand evoked by composite meals.

Am J Clin Nutr. 2009 Aug 26;

Authors: Bao J, de Jong V, Atkinson F, Petocz P, Brand-Miller JC

BACKGROUND: Diets that provoke less insulin secretion may be helpful in the prevention and management of diabetes. A physiologic basis for ranking foods according to insulin “demand” could therefore assist further research. OBJECTIVE: We assessed the utility of a food insulin index (FII) that was based on testing isoenergetic portions of single foods (1000 kJ) in predicting the insulin demand evoked by composite meals. DESIGN: Healthy subjects (n = 10 or 11 for each meal) consumed 13 different isoenergetic (2000 kJ) mixed meals of varying macronutrient content. Insulin demand predicted by the FII of the component foods or by carbohydrate counting and glycemic load was compared with observed insulin responses. RESULTS: Observed insulin responses (area under the curve relative to white bread: 100) varied over a 3-fold range (from 35 +/- 5 to 116 +/- 26) and were strongly correlated with insulin demand predicted by the FII of the component foods (r = 0.78, P = 0.0016). The calculated glycemic load (r = 0.68, P = 0.01) but not the carbohydrate content of the meals (r = 0.53, P = 0.064) also predicted insulin demand. CONCLUSIONS: The relative insulin demand evoked by mixed meals is best predicted by a physiologic index based on actual insulin responses to isoenergetic portions of single foods. In the context of composite meals of similar energy value, but varying macronutrient content, carbohydrate counting was of limited value.

PMID: 19710196 [PubMed - as supplied by publisher]

Dairy products and metabolic effects in overweight men and women: results from a 6-mo intervention study.

Am J Clin Nutr. 2009 Aug 26;

Authors: Wennersberg MH, Smedman A, Turpeinen AM, Retterstøl K, Tengblad S, Lipre E, Aro A, Mutanen P, Seljeflot I, Basu S, Pedersen JI, Mutanen M, Vessby B

BACKGROUND: Some epidemiologic studies have suggested inverse relations between intake of dairy products and components of the metabolic syndrome. OBJECTIVE: The objective was to investigate the effects of an increased intake of dairy products in persons with a habitually low intake on body composition and factors related to the metabolic syndrome. DESIGN: Middle-aged overweight subjects (n = 121) with traits of the metabolic syndrome were recruited in Finland, Norway, and Sweden and randomly assigned into milk or control groups. The milk group was instructed to consume 3-5 portions of dairy products daily. The control group maintained their habitual diet. Clinical investigations were conducted on admission and after 6 mo. RESULTS: There were no significant differences between changes in body weight or body composition, blood pressure, markers of inflammation, endothelial function, adiponectin, or oxidative stress in the milk and the control groups. There was a modest unfavorable increase in serum cholesterol concentrations in the milk group (P = 0.043). Among participants with a low calcium intake at baseline (<700 mg/d), there was a significant treatment effect for waist circumference (P = 0.003) and sagittal abdominal diameter (P = 0.034). When the sexes were analyzed separately, leptin increased (P = 0.045) and vascular cell adhesion molecule-1 decreased (P = 0.001) in women in the milk group. CONCLUSIONS: This study gives no clear support to the hypothesis that a moderately increased intake of dairy products beneficially affects aspects of the metabolic syndrome. The apparently positive effects on waist circumference and sagittal abdominal diameter in subjects with a low calcium intake suggest a possible threshold in relation to effects on body composition.

PMID: 19710195 [PubMed - as supplied by publisher]

&lt;table border=&quot;0&quot; width=&quot;100%&quot;&gt;&lt;tr&gt;&lt;td align=&quot;left&quot;/&gt;&lt;td align=&quot;right&quot;&gt;&lt;a href=&quot;http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&amp;amp;cmd=Display&amp;amp;dopt=PubMed_PubMed&amp;amp;from_uid=19710194&quot;&gt;Related Articles&lt;/a&gt;&lt;/td&gt;&lt;/tr&gt;&lt;/table&gt;<br> &lt;p&gt;&lt;b&gt;Experimentally observed vitamin D requirements are higher than extrapolated ones.&lt;/b&gt;&lt;/p&gt;<br> &lt;p&gt;Am J Clin Nutr. 2009 Aug 26;&lt;/p&gt;<br> &lt;p&gt;Authors: Vieth R&lt;/p&gt;<br> &lt;p&gt;&lt;/p&gt;<br> &lt;p&gt;PMID: 19710194 [PubMed - as supplied by publisher]&lt;/p&gt;

Generalizability of dietary patterns associated with incidence of type 2 diabetes mellitus.

Am J Clin Nutr. 2009 Aug 26;

Authors: Imamura F, Lichtenstein AH, Dallal GE, Meigs JB, Jacques PF

BACKGROUND: Reduced rank regression (RRR) has been used to derive dietary pattern scores that predict linear combinations of disease biomarkers. The generalizability of these patterns to independent populations remains unknown. OBJECTIVE: The goal was to examine the generalizability of dietary patterns from prior studies using RRR to predict type 2 diabetes mellitus (T2DM): the Nurses’ Health Study (NHS), European Prospective Investigation into Cancer and Nutrition Germany (EPIC), and Whitehall II Study (WS). DESIGN: The relative weights of food groups of each dietary pattern were used to generate each dietary pattern score in the Framingham Offspring Study (n = 2879). Each of the external scores (confirmatory scores) was examined to determine whether it could predict incident T2DM during 7 y of follow-up as well as scores developed internally in the Framingham Offspring Study using a Cox-proportional hazard model adjusted for T2DM risk factors. RESULTS: Consumption of meat products, refined grains, and soft drinks (caloric and noncaloric) was found to be common predictive components of all confirmatory scores, but fried foods, eggs, and alcoholic beverages were predictive in some, but not in all, confirmatory scores. On the basis of a continuous increase in the score by 1 SD, the NHS-based confirmatory score predicted T2DM risk (hazard ratio: 1.44; 95% CI: 1.25, 1.66). However, T2DM risk was only weakly predicted by the EPIC-based score (hazard ratio: 1.14; 95% CI: 0.99, 1.32) and the WS-based score (hazard ratio: 1.16; 95% CI: 1.00, 1.35). CONCLUSIONS: The study suggested that dietary patterns that predict T2DM risk in different populations may not be generalizable to different populations. Additional dietary pattern studies should be conducted with regard to generalizability.

PMID: 19710193 [PubMed - as supplied by publisher]

Overweight children have a greater proportion of fat mass relative to muscle mass in the upper limbs than in the lower limbs: implications for bone strength at the distal forearm.

Am J Clin Nutr. 2009 Aug 26;

Authors: Ducher G, Bass SL, Naughton GA, Eser P, Telford RD, Daly RM

BACKGROUND: The influence of adiposity on upper-limb bone strength has rarely been studied in children, despite the high incidence of forearm fractures in this population. OBJECTIVE: The objective was to compare the influence of muscle and fat tissues on bone strength between the upper and lower limbs in prepubertal children. DESIGN: Bone mineral content, total bone cross-sectional area, cortical bone area (CoA), cortical thickness (CoTh) at the radius and tibia (4% and 66%, respectively), trabecular density (TrD), bone strength index (BSI; 4% sites), cortical density (CoD), stress-strain index (SSIpol), and muscle and fat areas (66% sites) were measured by using peripheral quantitative computed tomography in 427 children (206 boys) aged 7-10 y. RESULTS: Overweight children (n = 93) had greater values for bone variables (0.3-1.3 SD; P < 0.0001) than did their normal-weight peers, except for CoD 66% and CoTh 4%. The between-group differences were 21-87% greater at the tibia than at the radius. After adjustment for muscle cross-sectional area, TrD 4%, bone mineral content, CoA, and CoTh 66% at the tibia remained greater in overweight children, whereas at the distal radius total bone cross-sectional area and CoTh were smaller in overweight children (P < 0.05). Overweight children had a greater fat-muscle ratio than did normal-weight children, particularly in the forearm (92 +/- 28% compared with 57 +/- 17%). Fat-muscle ratio correlated negatively with all bone variables, except for TrD and CoD, after adjustment for body weight (r = -0.17 to -0.54; P < 0.0001). CONCLUSIONS: Overweight children had stronger bones than did their normal-weight peers, largely because of greater muscle size. However, the overweight children had a high proportion of fat relative to muscle in the forearm, which is associated with reduced bone strength.

PMID: 19710192 [PubMed - as supplied by publisher]

Role of depressive symptoms in explaining socioeconomic status disparities in dietary quality and central adiposity among US adults: a structural equation modeling approach.

Am J Clin Nutr. 2009 Aug 26;

Authors: Beydoun MA, Kuczmarski MT, Mason MA, Ling SM, Evans MK, Zonderman AB

BACKGROUND: The link between socioeconomic status (SES), depression, dietary quality, and central adiposity remains unclear. OBJECTIVE: Pathways linking SES to dietary quality and central adiposity through depressive symptoms were examined across sex-ethnicity groups. DESIGN: Extensive data on US adults aged 30-64 y from the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study were used in multiple linear logistic regression models and structural equation models to test pathway associations. Measures included Center for Epidemiologic Studies-Depression (CES-D) scores, 2005 Healthy Eating Index (HEI) values, and dual-energy X-ray absorptiometry. Sample sizes for most analyses ranged between 1789 for anthropometric outcomes and 1227 for trunk fat outcomes. RESULTS: The CES-D score was associated with lower HEI scores in all sex-ethnicity groups, except in African American men, and with higher waist-to-hip ratios (WHRs) among African American women. A CES-D score >/=16 was positively associated with waist circumference (WC) and with trunk fat among white women and men, respectively. SES was positively related to central adiposity among African American men (central obesity and WC) and African American women (central obesity and percentage trunk fat) but was inversely related to central adiposity among white women. Among whites only, the total positive effect of SES on HEI was significantly mediated by CES-D score. Among white women, the total inverse effect of SES on WC and WHR was significantly explained by the CES-D score and HEI, whereas the CES-D score was positively associated with WHR among African American women, independently of SES. CONCLUSION: Future mental health interventions targeted at reducing SES disparities in dietary quality and central adiposity may have different effects across sex-ethnicity groups.

PMID: 19710191 [PubMed - as supplied by publisher]