High dietary methionine intake increases the risk of acute coronary events in middle-aged men

NMR based Serum metabolomics revealed metabolic signatures associated with oxidative stress and mitochondrial damage in brain stroke

Brain stroke (BS, also known as a cerebrovascular accident), represents a serious global health crisis. It has been a leading cause of permanent disability and unfortunately, frequent fatalities due to lack of timely medical intervention. While progress has been made in prevention and management, the complexities and consequences of stroke continue to pose significant challenges, especially, its impact on patient's quality of life and independence. During stroke, there is a substantial decrease in oxygen supply to the brain leading to alteration of cellular metabolic pathways, including those involved in mitochondrial-damage, leading to mitochondrial-dysfunction. The present proof-of-the-concept metabolomics study has been performed to gain insights into the metabolic pathways altered following a brain stroke and discover new potential targets for timely interventions to mitigate the effects of cellular and mitochondrial damage in BS. The serum metabolic profiles of 108 BS-patients were measured using 800 MHz NMR spectroscopy and compared with 60 age and sex matched normal control (NC) subjects. Compared to NC, the serum levels of glutamate, TCA-cycle intermediates (such as citrate, succinate, etc.), and membrane metabolites (betaine, choline, etc.) were found to be decreased BS patients, whereas those of methionine, mannose, mannitol, phenylalanine, urea, creatine and organic acids (such as 3-hydroxybutyrate and acetone) were found to be elevated in BS patients. These metabolic changes hinted towards hypoxia mediated mitochondrial dysfunction in BS-patients. Further, the area under receiver operating characteristic curve (ROC) values for five metabolic features (methionine, mannitol, phenylalanine, mannose and urea) found to be more than 0.9 suggesting their high sensitivity and specificity for differentiating BS from NC subjects.

[Diet as a source of hydrogen sulfide and its effects on health and disease]

Introduction

Initially known for its deleterious health effects, hydrogen sulfide (H2S) has recently been recognized as a biologically important gas carrier, like nitric oxide and carbon monoxide. H2S is produced endogenously in mammalian cells by enzymatic and non-enzymatic pathways. When it is produced by the enzymatic pathway, its synthesis is carried out from the amino acid L-cysteine through the transsulfuration pathway. It can also be produced endogenously from exogenous compounds that function as H2S donors as, for example, the naturally occurring organic donors found in some plants. Currently, the role of S2H is well known as brain and cardiac protector, and its research as a therapeutic adjuvant in metabolic diseases such as obesity and type-2 diabetes is becoming increasingly important. The objective of this review is to examine how the contribution of donors and precursors of hydrogen sulfide by the diet impacts health and disease.

Modulation of DNA methylation by one-carbon metabolism: a milestone for healthy aging

Healthy aging can be defined as an extended lifespan and health span. Nutrition has been regarded as an important factor in healthy aging, because nutrients, bioactive food components, and diets have demonstrated beneficial effects on aging hallmarks such as oxidative stress, mitochondrial function, apoptosis and autophagy, genomic stability, and immune function. Nutrition also plays a role in epigenetic regulation of gene expression, and DNA methylation is the most extensively investigated epigenetic phenomenon in aging. Interestingly, age-associated DNA methylation can be modulated by one-carbon metabolism or inhibition of DNA methyltransferases. One-carbon metabolism ultimately controls the balance between the universal methyl donor S-adenosylmethionine and the methyltransferase inhibitor S-adenosylhomocysteine. Water-soluble B-vitamins such as folate, vitamin B6, and vitamin B12 serve as coenzymes for multiple steps in one-carbon metabolism, whereas methionine, choline, betaine, and serine act as methyl donors. Thus, these one-carbon nutrients can modify age-associated DNA methylation and subsequently alter the age-associated physiologic and pathologic processes. We cannot elude aging per se but we may at least change age-associated DNA methylation, which could mitigate age-associated diseases and disorders.

Dietary Methionine via Dose-Dependent Inhibition of Short-Chain Fatty Acid Production Capacity Contributed to a Potential Risk of Cognitive Dysfunction in Mice

High-methionine diets induce impaired learning and memory function, dementia-like neurodegeneration, and Alzheimer's disease, while low-methionine diets improve learning and memory function. We speculated that variations in intestinal microbiota may mediate these diametrically opposed effects; thus, this study aimed to verify this hypothesis. The ICR mice were fed either a low-methionine diet (LM, 0.17% methionine), normal methionine diet (NM, 0.86% methionine), or high-methionine diet (HM, 2.58% methionine) for 11 weeks. We found that HM diets damaged nonspatial recognition memory, working memory, and hippocampus-dependent spatial memory and induced anxiety-like behaviors in mice. LM diets improved nonspatial recognition memory and hippocampus-dependent spatial memory and ameliorated anxiety-like behavior, but the differences did not reach a significant level. Moreover, HM diets significantly decreased the abundance of putative short-chain fatty acid (SCFA)-producing bacteria (Roseburia, Blautia, Faecalibaculum, and Bifidobacterium) and serotonin-producing bacteria (Turicibacter) and significantly increased the abundance of proinflammatory bacteria Escherichia-Shigella. Of note, LM diets reversed the results. Consequently, the SCFA and serotonin levels were significantly decreased with HM diets and significantly increased with LM diets. Furthermore, HM diets induced hippocampal oxidative stress and inflammation and selectively downregulated the hippocampus-dependent memory-related gene expression, whereas LM diets selectively upregulated the hippocampus-dependent memory-related gene expression. In conclusion, dietary methionine via dose-dependent inhibition of SCFA production capacity contributed to a potential risk of cognitive dysfunction in mice.

The association of serum sulfur amino acids and related metabolites with incident diabetes: a prospective cohort study

AIM

Plasma total cysteine (tCys) is associated with fat mass and insulin resistance, whereas taurine is inversely related to diabetes risk. We investigated the association of serum sulfur amino acids (SAAs) and related amino acids (AAs) with incident diabetes.

METHODS

Serum AAs were measured at baseline in 2997 subjects aged ≥ 65 years. Diabetes was recorded at baseline and after 4 years. Logistic regression evaluated the association of SAAs [methionine, total homocysteine (tHcy), cystathionine, tCys, and taurine] and related metabolites [serine, total glutathione (tGSH), glutamine, and glutamic acid] with diabetes risk.

RESULTS

Among 2564 subjects without diabetes at baseline, 4.6% developed diabetes. Each SD increment in serum tCys was associated with a 68% higher risk (95% CI 1.27, 2.23) of diabetes [OR for upper vs. lower quartile 2.87 (1.39, 5.91)], after full adjustments (age, sex, other AAs, adiposity, eGFR, physical activity, blood pressure, diet and medication); equivalent ORs for cystathionine were 1.33 (1.08, 1.64) and 1.68 (0.85, 3.29). Subjects who were simultaneously in the upper tertiles of both cystathionine and tCys had a fivefold risk [OR = 5.04 (1.55, 16.32)] of diabetes compared with those in the lowest tertiles. Higher serine was independently associated with a lower risk of developing diabetes [fully adjusted OR per SD = 0.68 (0.54, 0.86)]. Glutamic acid and glutamine showed positive and negative associations, respectively, with incident diabetes in age- and sex-adjusted analysis, but only the glutamic acid association was independent of other confounders [fully adjusted OR per SD = 1.95 (1.19, 3.21); for upper quartile = 7.94 (3.04, 20.75)]. tGSH was inversely related to diabetes after adjusting for age and sex, but not other confounders. No consistent associations were observed for methionine, tHcy or taurine.

CONCLUSION

Specific SAAs and related metabolites show strong and independent associations with incident diabetes. This suggests that perturbations in the SAA metabolic pathway may be an early marker for diabetes risk.

Metabolomics Deciphering the Potential Biomarkers of Hengqing I Prescription against Vascular Dementia

With the aging of population, vascular dementia (VaD) seriously threatens people's health and quality of life. It is of great significance to explore biomarkers of VaD from the perspective of metabolomics and traditional Chinese medicine (TCM). Therefore, VaD was divided into kidney deficiency and blood stasis syndrome (KDBS) and non-KDBS according to TCM. Then, some patients received the treatment of Hengqing I (HQI) prescription. The urine of six groups (VaD group, normal group, KDBS group, non-KDBS group, HQI group, and control group) was detected on LC-MS/MS. Multivariate statistical analysis showed that the metabolic profiles of the three comparisons were significantly different. The top analysis-ready molecules of downregulated histamine and upregulated biotin, methionine, pantothenic acid, SAH, histidine, and kaempferol may be the most related metabolites. These putative biomarkers play an important role in the regulation of key metabolic processes linked to VaD. Additionally, pathway analysis showed aminoacyl-tRNA biosynthesis, and amino acids metabolic pathways were highly correlated with the occurrence of VaD. In this present paper, vitamins, amino acids, and their derivatives were selected as the basis for VaD diagnosis and treatment monitoring, and the significance of TCM classification and Hengqing I prescription in the treatment of VaD was discussed.

Methionine adenosyltransferase 1a antisense oligonucleotides activate the liver-brown adipose tissue axis preventing obesity and associated hepatosteatosis

Altered methionine metabolism is associated with weight gain in obesity. The methionine adenosyltransferase (MAT), catalyzing the first reaction of the methionine cycle, plays an important role regulating lipid metabolism. However, its role in obesity, when a plethora of metabolic diseases occurs, is still unknown. By using antisense oligonucleotides (ASO) and genetic depletion of Mat1a, here, we demonstrate that Mat1a deficiency in diet-induce obese or genetically obese mice prevented and reversed obesity and obesity-associated insulin resistance and hepatosteatosis by increasing energy expenditure in a hepatocyte FGF21 dependent fashion. The increased NRF2-mediated FGF21 secretion induced by targeting Mat1a, mobilized plasma lipids towards the BAT to be catabolized, induced thermogenesis and reduced body weight, inhibiting hepatic de novo lipogenesis. The beneficial effects of Mat1a ASO were abolished following FGF21 depletion in hepatocytes. Thus, targeting Mat1a activates the liver-BAT axis by increasing NRF2-mediated FGF21 secretion, which prevents obesity, insulin resistance and hepatosteatosis.

Dietary protein and amino acid restriction: Roles in metabolic health and aging-related diseases

The prevalence of obesity is a worldwide phenomenon in all age groups and is associated with aging-related diseases such as type 2 diabetes, as well metabolic and cardiovascular diseases. The use of dietary restriction (DR) while avoiding malnutrition has many profound beneficial effects on aging and metabolic health, and dietary protein or specific amino acid (AA) restrictions, rather than overall calorie intake, are considered to play key roles in the effects of DR on host health. Whereas comprehensive reviews of the underlying mechanisms are limited, protein restriction and methionine (Met) restriction improve metabolic health and aging-related neurodegenerative diseases, and may be associated with FGF21, mTOR and autophagy, improved mitochondrial function and oxidative stress. Circulating branched-chain amino acids (BCAAs) are inversely correlated with metabolic health, and BCAAs and leucine (Leu) restriction promote metabolic homeostasis in rodents. Although tryptophan (Trp) restriction extends the lifespan of rodents, the Trp-restricted diet is reported to increase inflammation in aged mice, while severe Trp restriction has side effects such as anorexia. Furthermore, inadequate protein intake in the elderly increases the risk of muscle-centric health. Therefore, the restriction of specific AAs may be an effective and executable dietary manipulation for metabolic and aging-related health in humans, which warrants further investigation to elucidate the underlying mechanisms.

Extracellular cystine influences human preadipocyte differentiation and correlates with fat mass in healthy adults

Plasma cysteine is associated with human obesity, but it is unknown whether this is mediated by reduced, disulfide (cystine and mixed-disulfides) or protein-bound (bCys) fractions. We investigated which cysteine fractions are associated with adiposity in vivo and if a relevant fraction influences human adipogenesis in vitro. In the current study, plasma cysteine fractions were correlated with body fat mass in 35 adults. Strong positive correlations with fat mass were observed for cystine and mixed disulfides (r ≥ 0.61, P < 0.001), but not the quantitatively major form, bCys. Primary human preadipocytes were differentiated in media containing cystine concentrations varying from 10-50 μM, a range similar to that in plasma. Increasing extracellular cystine (10-50 μM) enhanced mRNA expression of PPARG2 (to sixfold), PPARG1, PLIN1, SCD1 and CDO1 (P = 0.042- < 0.001). Adipocyte lipid accumulation and lipid-droplet size showed dose-dependent increases from lowest to highest cystine concentrations (P < 0.001), and the malonedialdehyde/total antioxidant capacity increased, suggesting increased oxidative stress. In conclusion, increased cystine concentrations, within the physiological range, are positively associated with both fat mass in healthy adults and human adipogenic differentiation in vitro. The potential role of cystine as a modifiable factor regulating human adipocyte turnover and metabolism deserves further study.

Association of dietary sulfur amino acid intake with mortality from diabetes and other causes

PURPOSE

Sulfur amino acid (SAA) consumption in Western countries is far greater than recommended levels. In preclinical studies, reduced SAA intake enhanced longevity and reduced risk for numerous chronic diseases. The current objective was to examine for associations between the intake of total SAA, including methionine (Met) and cysteine (Cys), and all-cause and disease-specific mortality US adults.

METHODS

This prospective analysis included 15,083 US adult participants (mean age = 46.7 years) from the Third National Examination and Nutritional Health Survey (NHANES III, 1988-1994) with available mortality status (National Death Registry, 1988-2011). Dietary SAA intake was obtained from 24-h recall data. Associations between quintile (Q) of SAA intake (expressed as absolute intake or protein density) and mortality were assessed using Cox proportional hazard models and expressed as hazard ratio (HR).

RESULTS

During follow-up (mean = 16.9 years), 4636 deaths occurred. After multivariable adjustment (including demographics and traditional risk factors, such as fat and other micronutrients intake), diabetes-caused mortality rates were nearly threefold higher in the highest compared to lowest SAA intake quintiles [HR_Q5-Q1 total SAA_, 2.68 (1.46-4.90); HR_Q5-Q1 methionine, 2.45 (1.37-4.38); HR_Q5-Q1 cysteine, 2.91 (1.57-5.37)] (P < 0.01)]. Higher total SAA protein density was also associated with diabetes-caused mortality [HR_Q5-Q1 1.75 (1.31-2.35)]. Associations between SAA intake and all-cause mortality, and mortality caused by other major diseases were not detected.

CONCLUSION

Results suggest that high-SAA diets are associated with increased risk for diabetes mortality and that lowering intake towards to Recommended Dietary Allowance levels could lead to reductions in lifetime risk.

Methionine Diet Evoked Hyperhomocysteinemia Causes Hippocampal Alterations, Metabolomics Plasma Changes and Behavioral Pattern in Wild Type Rats

L-methionine, an essential amino acid, plays a critical role in cell physiology. High intake and/or dysregulation in methionine (Met) metabolism results in accumulation of its intermediate(s) or breakdown products in plasma, including homocysteine (Hcy). High level of Hcy in plasma, hyperhomocysteinemia (hHcy), is considered to be an independent risk factor for cerebrovascular diseases, stroke and dementias. To evoke a mild hHcy in adult male Wistar rats we used an enriched Met diet at a dose of 2 g/kg of animal weight/day in duration of 4 weeks. The study contributes to the exploration of the impact of Met enriched diet inducing mild hHcy on nervous tissue by detecting the histo-morphological, metabolomic and behavioural alterations. We found an altered plasma metabolomic profile, modified spatial and learning memory acquisition as well as remarkable histo-morphological changes such as a decrease in neurons' vitality, alterations in the morphology of neurons in the selective vulnerable hippocampal CA 1 area of animals treated with Met enriched diet. Results of these approaches suggest that the mild hHcy alters plasma metabolome and behavioural and histo-morphological patterns in rats, likely due to the potential Met induced changes in "methylation index" of hippocampal brain area, which eventually aggravates the noxious effect of high methionine intake.

Effect of Methionine Restriction on Aging: Its Relationship to Oxidative Stress

Enhanced oxidative stress is closely related to aging and impaired metabolic health and is influenced by diet-derived nutrients and energy. Recent studies have shown that methionine restriction (MetR) is related to longevity and metabolic health in organisms from yeast to rodents. The effect of MetR on lifespan extension and metabolic health is mediated partially through a reduction in oxidative stress. Methionine metabolism is involved in the supply of methyl donors such as S-adenosyl-methionine (SAM), glutathione synthesis and polyamine metabolism. SAM, a methionine metabolite, activates mechanistic target of rapamycin complex 1 and suppresses autophagy; therefore, MetR can induce autophagy. In the process of glutathione synthesis in methionine metabolism, hydrogen sulfide (H₂S) is produced through cystathionine-β-synthase and cystathionine-γ-lyase; however, MetR can induce increased H₂S production through this pathway. Similarly, MetR can increase the production of polyamines such as spermidine, which are involved in autophagy. In addition, MetR decreases oxidative stress by inhibiting reactive oxygen species production in mitochondria. Thus, MetR can attenuate oxidative stress through multiple mechanisms, consequently associating with lifespan extension and metabolic health. In this review, we summarize the current understanding of the effects of MetR on lifespan extension and metabolic health, focusing on the reduction in oxidative stress.

Animal Protein Intake Is Positively Associated with Metabolic Syndrome Risk Factors in Middle-Aged Korean Men

Few studies have examined the relationship of protein intake by food source with metabolic syndrome in Korean adults, even though animal food intake has increased. This study examined the association between plant and animal protein intake and metabolic syndrome among middle-aged Korean adults. A total of 13,485 subjects aged 30-64 years were selected from the 2013-2018 Korea National Health and Nutrition Examination Survey. Protein intake was assessed using 24-h dietary recall data and divided into quintiles. Men had a higher percentage of energy intake from animal protein (7.4%) than plant protein (6.9%). Men in the highest quintile group of animal protein intake had a higher prevalence of abdominal obesity (OR: 1.30, 95% CI: 1.00-1.70), reduced high-density lipoprotein cholesterol (HDL-C) (OR: 1.43, 95% CI: 1.07-1.90), and elevated fasting glucose (OR: 1.32, 95% CI: 1.01-1.74), after adjusting for covariates. Furthermore, stronger associations of animal protein intake with abdominal obesity were shown in men who consumed less than estimated energy requirements (OR: 1.60, 95% CI: 1.11-2.31). Plant protein intake was negatively associated with increased blood pressure in men. Neither animal nor plant protein intakes were significantly associated with any of the metabolic syndrome risk factors in women. The results imply that lower animal protein intake may be a beneficial factor for metabolic syndrome management in middle-aged Korean men.

S-methyl-L-cysteine Protects against Antimycin A-induced Mitochondrial Dysfunction in Neural Cells via Mimicking Endogenous Methionine-centered Redox Cycle

Mitochondrial superoxide overproduction is believed to be responsible for the neurotoxicity associated with neurodegeneration. Mitochondria-targeted antioxidants, such as MitoQ, have emerged as potentially effective antioxidant therapies. Methionine sulfoxide reductase A (MsrA) is a key mitochondrial-localized endogenous antioxidative enzyme and it can scavenge oxidizing species by catalyzing the methionine (Met)-centered redox cycle (MCRC). In this study, we observed that the natural L-Met acted as a good scavenger for antimycin A-induced mitochondrial superoxide overproduction in PC12 cells. This antioxidation was largely dependent on the Met oxidase activity of MsrA. S-methyl-L-cysteine (SMLC), a natural analogue of Met that is abundantly found in garlic and cabbage, could activate the Met oxidase activity of MsrA to scavenge free radicals. Furthermore, SMLC protected against antimycin A-induced mitochondrial membrane depolarization and alleviated 1-methyl-4-phenylpyridinium (MPP⁺)-induced neurotoxicity. Thus, our data highlighted the possibility for SMLC supplement in the detoxication of mitochondrial damage by activating the Met oxidase activity of MsrA.

The association of animal and plant protein with successful ageing: a combined analysis of MEDIS and ATTICA epidemiological studies

OBJECTIVE

The aim of the present study was to investigate the differences between the consumption of plant-based v. animal-based protein-rich diets on successful ageing, as well as to identify the optimal combination of dietary protein intake for facilitating successful ageing in people aged >50 years.

DESIGN

A combined analysis was conducted in older adults of the ATTICA and MEDIS population-based cross-sectional studies. Anthropometrical, clinical and sociodemographic characteristics, lifestyle parameters, dietary habits and level of protein intake were derived through standard procedures. Successful ageing was evaluated using the validated Successful Aging Index (SAI) composed of ten health-related social, lifestyle and clinical characteristics.

SETTING

Athens area and twenty Greek islands.

PARTICIPANTS

A total of 3349 Greek women and men over 50 years old.

RESULTS

Participants with high consumption of plant proteins were more likely to be male, physically active, with higher daily energy intake, higher adherence to the Mediterranean diet and higher level of SAI (P < 0·001). Participants with 'Low animal & High plant' and 'High animal & High plant' protein consumption had a 6 and 7 % higher SAI score, respectively, compared with the other participants (P < 0·001). In contrast, 'Low animal & Low plant' and 'High animal & Low plant' protein intake was negatively associated with SAI as compared to the combination of all other consumption categories (P < 0·02).

CONCLUSIONS

The consumption of a plant-based protein-rich diet seems to be a beneficial nutritional choice that should be promoted and encouraged to older people since it may benefit both individual's health and prolong successful ageing.

Effects of dietary methionine and cysteine restriction on plasma biomarkers, serum fibroblast growth factor 21, and adipose tissue gene expression in women with overweight or obesity: a double-blind randomized controlled pilot study

Background

Dietary restriction of methionine and cysteine is a well-described model that improves metabolic health in rodents. To investigate the translational potential in humans, we evaluated the effects of dietary methionine and cysteine restriction on cardiometabolic risk factors, plasma and urinary amino acid profile, serum fibroblast growth factor 21 (FGF21), and subcutaneous adipose tissue gene expression in women with overweight and obesity in a double-blind randomized controlled pilot study.

Methods

Twenty women with overweight or obesity were allocated to a diet low (Met/Cys_-low, n = 7), medium (Met/Cys_-medium, n = 7) or high (Met/Cys_-high, n = 6) in methionine and cysteine for 7 days. The diets differed only by methionine and cysteine content. Blood and urine were collected at day 0, 1, 3 and 7 and subcutaneous adipose tissue biopsies were taken at day 0 and 7.

Results

Plasma methionine and cystathionine and urinary total cysteine decreased, whereas FGF21 increased in the Met/Cys_-low vs. Met/Cys_-high group. The Met/Cys_-low group had increased mRNA expression of lipogenic genes in adipose tissue including DGAT1. When we excluded one participant with high fasting insulin at baseline, the Met/Cys_-low group showed increased expression of ACAC, DGAT1, and tendencies for increased expression of FASN and SCD1 compared to the Met/Cys_-high group. The participants reported satisfactory compliance and that the diets were moderately easy to follow.

Conclusions

Our data suggest that dietary methionine and cysteine restriction may have beneficial effects on circulating biomarkers, including FGF21, and influence subcutaneous adipose tissue gene expression. These results will aid in the design and implementation of future large-scale dietary interventions with methionine and cysteine restriction.

Trial registration ClinicalTrials.gov Identifier: NCT03629392, registration date: 14/08/2018 https://clinicaltrials.gov/ct2/show/NCT03629392.

NMR-based plasma metabolic profiling in patients with unstable angina

OBJECTIVES

Unstable angina (UA) is a form of the acute coronary syndrome (ACS) that affects more than a third of the population before age 70. Due to the limitations of diagnostic tests, appropriate identification of UA is difficult. In this study, we proceeded to investigate metabolite profiling in UA patients compared with controls to determine potential candidate biomarkers.

MATERIALS AND METHODS

Ninety-four plasma samples from UA and 32 samples from controls were analyzed based on 1H NMR spectroscopy. The raw data were processed, analyzed, and subjected to partial least squares-discrimination analysis (PLS-DA), a supervised classification method with a good separation of control and UA patients was observed. The most important variables (VIP) ≥1 were selected and submitted to MetaboAnalyst pathway enrichment to identify the most important ones.

RESULTS

We identified 17 disturbed metabolites in UA patients in comparison with the controls. These metabolites are involved in various biochemical pathways such as steroid hormone biosynthesis, aminoacyl-tRNA biosynthesis, and lysine degradation. Some of the metabolites were deoxycorticosterone, 17-hydroxyprogesterone, androstenedione, androstanedione, etiocholanolone, estradiol, 2-hydroxyestradiol, 2-hydroxyestrone, 2-methoxyestradiol, and 2-methoxyestrone. In order to determine test applicability in diagnosing UA, a diagnostic model was further created using the receiver operator characteristic (ROC) curve. The areas under the curve (AUC), sensitivity, specificity, and precision were 0.87, 90%, 65%, and 91%, respectively, for diagnosing of UA.

CONCLUSION

These metabolites could not only be useful for the diagnosis of UA patients but also provide more information for further deciphering of the biological processes of UA.

Animal Protein Intake Is Associated with General Adiposity in Adolescents: The Teen Food and Development Study

Protein plays a crucial role in the growth and development of adolescents. However, being a secondary energy source, protein's role in obesity has been sidelined. We examined whether intake of protein (total, animal, plant), branched-chain (BCAAs), and sulfur-containing (SCAAs) amino acids are associated with general body and central obesity and body composition in a cross-sectional study among healthy adolescents. Students aged 12-18 years old (n = 601) in schools near two major Adventist universities in California and Michigan provided dietary data via a validated web-based food frequency questionnaire (FFQ) and anthropometric data during school visits. Intakes of total, animal, and plant proteins, and BCAAs and SCAAs were derived from FFQ data. We defined general body obesity with body-mass-index-for-age (BMIz) z-scores and central obesity with waist-to-height ratios (WHtR). After full adjustment for covariates, multiple regression analyses showed significant positive associations between intakes of total protein (β = 0.101, 95% CI: 0.041, 0.161), animal protein (β = 0.118, 95% CI: 0.057, 0.178), BCAAs (β = 0.056, 95% CI: 0.025, 0.087), and SCAAs (β = 0.025, 95% CI: 0.012, 0.038) with general body adiposity. Animal protein (β = 0.017, 95% CI: 0.001, 0.033) and SCAAs (β = 0.004, 95% CI: 0.000, 0.008) were also associated with central obesity. Total and animal protein and BCAA and SCAA were also significantly associated with fat mass. Our findings suggest that high protein intake may pose a possible detriment to adolescent health. Longitudinal and safety evaluation studies are recommended.

Hypercysteinemia, A Potential Risk Factor for Central Obesity and Related Disorders in Azores, Portugal

In Azores, the standardized mortality rate for coronary artery disease (CAD) is nearly the double when compared to mainland Portugal. The aim of this study was to compare the prevalence of conventional CAD risk factors, as well as the plasma aminothiol profile (and its major determinants), between two groups of healthy subjects from Ponta Delgada (in Azores) and Lisbon (in mainland) cities, searching for precocious biomarker(s) of the disease. The study groups consisted of 101 healthy volunteers from Ponta Delgada (PDL) and 121 from Lisbon, aged 20–69 years. No differences in the prevalence of classical CAD risk factors were found between the study groups, except in physical inactivity and related central obesity, which were both higher in PDL men than in those from Lisbon. Hypercysteinemia, which seems to result from sulfur-rich amino acid diets and/or vitamin B₁₂ malabsorption, revealed to be significantly more prevalent in PDL vs. Lisbon subjects (18% vs. 4%, P=0.001), namely, in male gender. Moreover, plasma Cys levels predicted waist circumference (β coefficient = 0.102, P=0.032) and concomitant central obesity and were also associated with insulin resistance. Nevertheless, hyperhomocysteinemia prevalence was similar in both groups, despite the fact that PDL subjects exhibited a higher rate of vitamin B₁₂ deficiency compared to those from Lisbon (19% vs. 6%, P=0.003). Owing to the nature of this study design, a cause-effect relationship between high plasma Cys levels and central obesity or CAD risk could not be derived, but results strongly suggest that hypercysteinemia is a potential risk factor for metabolic disorders, i.e., obesity and insulin resistance, and CAD in Azores, a hypothesis that asks for confirmation through further large prospective studies.

The impact of dietary protein intake on longevity and metabolic health

Lifespan and metabolic health are influenced by dietary nutrients. Recent studies show that a reduced protein intake or low-protein/high-carbohydrate diet plays a critical role in longevity/metabolic health. Additionally, specific amino acids (AAs), including methionine or branched-chain AAs (BCAAs), are associated with the regulation of lifespan/ageing and metabolism through multiple mechanisms. Therefore, methionine or BCAAs restriction may lead to the benefits on longevity/metabolic health. Moreover, epidemiological studies show that a high intake of animal protein, particularly red meat, which contains high levels of methionine and BCAAs, may be related to the promotion of age-related diseases. Therefore, a low animal protein diet, particularly a diet low in red meat, may provide health benefits. However, malnutrition, including sarcopenia/frailty due to inadequate protein intake, is harmful to longevity/metabolic health. Therefore, further study is necessary to elucidate the specific restriction levels of individual AAs that are most effective for longevity/metabolic health in humans.

The Antisteatotic and Hypolipidemic Effect of Insect Meal in Obese Zucker Rats is Accompanied by Profound Changes in Hepatic Phospholipid and 1-Carbon Metabolism

SCOPE

The hypothesis is tested that insect meal, which has a low methionine content, reduces the hepatic phosphatidylcholine (PC):phosphatidylethanolamine (PE) ratio, which is a critical determinant of hepatic lipid synthesis, by decreasing availability of the methionine metabolite S-adenosylmethionine (SAM).

METHODS AND RESULTS

Obese rats (n = 24) are randomly divided into two groups (Obese Casein and Obese Insect) of 12 rats each. In addition, lean rats (n = 12) are used as control group (LC). Groups LC and OC receive a control diet with casein as protein source, whereas in the OI group, casein is replaced isonitrogenously by insect meal, which is found to be less digestible (-12% units). Plasma and liver concentrations of lipids and hepatic expression of lipid synthesizing genes are reduced in the OI group compared to the OC group. Plasma and liver concentration of PC and the PC:PE ratio are decreased in the OI group compared to the OC group, while hepatic concentration of SAM and the hepatic SAM:S-adenosylhomocysteine (SAH) ratio is lower in the OI group than in the OC group.

CONCLUSION

The decrease of the hepatic PC:PE ratio is probably a key mechanism explaining the pronounced antisteatotic and hypolipidemic action of insect meal in obese rats.

Dietary Sulfur-Containing Amino Acids Are Associated with Higher Prevalence of Overweight/Obesity in Northern Chinese Adults, an Internet-Based Cross-Sectional Study

BACKGROUND/AIMS

Elevation of plasma sulfur-containing amino acids (SAAs) is generally associated with higher body mass index (BMI) and unfavorable lipid profiles. It is not known how dietary SAAs relate to these associations in humans.

METHODS

A convenient tool named internet-based dietary questionnaire for Chinese (IDQC) was used to estimate dietary SAAs intake. A total of 936 participants were randomly recruited and asked to complete the IDQC. Furthermore, 90 subjects were randomly selected to perform a subgroup study. The associations between dietary SAAs and prevalence of obesity, lipid profiles, and status of insulin resistance (IR), inflammation and oxidative stress were assessed.

RESULTS

Dietary total SAAs and cysteine of overweight/obese participants were significantly higher. Dietary total SAAs and cysteine were positively associated with BMI and waist circumference. Higher dietary total SAAs were associated with higher prevalence of overweight/obesity. Higher dietary total SAAs and cysteine also associated with higher serum triglyceride (total cholesterol), low density lipoprotein, fasting blood glucose, 2 h-postprandial glucose, and homeostasis model assessment of IR. In the subgroup study, positive associations between dietary SAAs and inflammation biomarkers were also observed.

CONCLUSIONS

Dietary SAAs are associated with higher prevalence of overweight/obesity, unfavorable lipid profiles and status of IR, and inflammation.

Dimethyl sulfide protects against oxidative stress and extends lifespan via a methionine sulfoxide reductase A-dependent catalytic mechanism

Methionine (Met) sulfoxide reductase A (MsrA) is a key endogenous antioxidative enzyme with longevity benefits in animals. Only very few approaches have been reported to enhance MsrA function. Recent reports have indicated that the antioxidant capability of MsrA may involve a Met oxidase activity that facilities the reaction of Met with reactive oxygen species (ROS). Herein, we used a homology modeling approach to search the substrates for the oxidase activity of MsrA. We found that dimethyl sulfide (DMS), a main metabolite that produced by marine algae, emerged as a good substrate for MsrA‐catalytic antioxidation. MsrA bounds to DMS and promoted its antioxidant capacity via facilitating the reaction of DMS with ROS through a sulfonium intermediate at residues Cys72, Tyr103, and Glu115, followed by the release of dimethyl sulfoxide (DMSO). DMS reduced the antimycin A‐induced ROS generation in cultured PC12 cells and alleviated oxidative stress. Supplement of DMS exhibited cytoprotection and extended longevity in both Caenorhabditis elegans and Drosophila. MsrA knockdown abolished the cytoprotective effect and the longevity benefits of DMS. Furthermore, we found that the level of physiologic DMS was at the low micromolar range in different tissues of mammals and its level decreased after aging. This study opened a new window to elucidate the biological role of DMS and other low‐molecular sulfides in the cytoprotection and aging.

Validity and reliability of a self-administered food frequency questionnaire for the JPHC study: The assessment of amino acid intake

Background

The Japanese database of food amino acid composition was revised in 2010 after a 24-year interval. To examine the impact of the 2010 revision compared with that of the 1986 revision, we evaluated the validity and reliability of amino acid intakes assessed using a food frequency questionnaire (FFQ).

Methods

A FFQ including 138 food items was compared with 7-day dietary records, completed during each distinct season, to assess validity and administered twice at approximately a 1-year interval, to assess reliability. We calculated amino acid intakes using a database that compensated for missing food items via the substitution method. Subjects were a subsample of two cohorts of the Japan Public Health Center-based prospective study. A total of 102 men and 113 women in Cohort I and 174 men and 176 women in Cohort II provided complete dietary records and the FFQ, of whom 101 men and 108 women of Cohort I and 143 men and 146 women of Cohort II completed the FFQ twice.

Results

In the comparison of the FFQ with dietary records, the medians (ranges) of energy-adjusted correlation coefficients for validity were 0.35 (0.25–0.43) among men and 0.29 (0.19–0.40) among women in Cohort I, and 0.37 (0.21–0.52) and 0.38 (0.24–0.59), respectively, in Cohort II. Values for reliability were 0.47 (0.42–0.52) among men and 0.43 (0.38–0.50) among women in Cohort I, and 0.59 (0.52–0.70) and 0.54 (0.45–0.61), respectively, in Cohort II.

Conclusions

The FFQ used in our prospective cohort study is a suitable tool for estimating amino acid intakes.

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The Japanese database for food amino acid compositions was revised in 2010.

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We evaluated the validity and reliability of amino acid intakes assessed via a FFQ.

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The estimation via a new database had better validity than via the former database.

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The estimation using the new database indicated good reliability.

Contribution of Drosophila TRPA1 to Metabolism

Transient receptor potential (TRP) cation channels are highly conserved in humans and insects. Some of these channels are expressed in internal organs and their functions remain incompletely understood. By direct knock-in of the GAL4 gene into the trpA1 locus in Drosophila, we identified the expression of this gene in the subesophageal ganglion (SOGs) region. In addition, the neurites present in the dorsal posterior region as well as the drosophila insulin-like peptide 2 (dILP2)-positive neurons send signals to the SOGs. The signal is sent to the crop, which is an enlarged organ of the esophagus and functions as a storage place for food in the digestive system. To systematically investigate the role of TRPA1 in metabolism, we applied non-targeted metabolite profiling analysis together with gas-chromatography/time-of-flight mass spectrometry, with an aim to identify a wide range of primary metabolites. We effectively captured distinctive metabolomic phenotypes and identified specific metabolic dysregulation triggered by TRPA1 mutation based on reconstructed metabolic network analysis. Primarily, the network analysis pinpointed the simultaneous down-regulation of intermediates in the methionine salvation pathway, in contrast to the synchronized up-regulation of a range of free fatty acids. The gene dosage-dependent dynamics of metabolite levels among wild-type, hetero- and homozygous mutants, and their coordinated metabolic modulation under multiple gene settings across five different genotypes confirmed the direct linkages of TRPA1 to metabolism.

Serum S-adenosylmethionine, but not methionine, increases in response to overfeeding in humans

BACKGROUND

Plasma concentration of the methyl donor S-adenosylmethionine (SAM) is linearly associated with body mass index (BMI) and fat mass. As SAM is a high-energy compound and a sensor of cellular nutrient status, we hypothesized that SAM would increase with overfeeding.

METHODS

Forty normal to overweight men and women were overfed by 1250 kcal per day for 28 days.

RESULTS

Serum SAM increased from 106 to 130 nmol/l (P=0.006). In stratified analysis, only those with weight gain above the median (high-weight gainers; average weight gain 3.9±0.3 kg) had increased SAM (+42%, P=0.001), whereas low-weight gainers (weight gain 1.5±0.2 kg) did not (Pinteraction=0.018). Overfeeding did not alter serum concentrations of the SAM precursor, methionine or the products, S-adenosyl-homocysteine and homocysteine. The SAM/SAH (S-adenosylhomocysteine) ratio was unchanged in the total population, but increased in high-weight gainers (+52%, P=0.006, Pinteraction =0.005). Change in SAM correlated positively with change in weight (r=0.33, P=0.041) and fat mass (r=0.44, P=0.009), but not with change in protein intake or plasma methionine, glucose, insulin or low-density lipoprotein (LDL)-cholesterol.

CONCLUSION

Overfeeding raised serum SAM in proportion to the fat mass gained. The increase in SAM may help stabilize methionine levels, and denotes a responsiveness of SAM to nutrient state in humans. The role of SAM in human energy metabolism deserves further attention.

S-adenosylmethionine is associated with fat mass and truncal adiposity in older adults

S-adenosylmethionine (SAM) is synthesized from methionine, which is abundant in animal-derived protein, in an energy-consuming reaction. SAM and S-adenosylhomocysteine (SAH) correlate with body mass index (BMI). Plasma total concentration of the SAM-associated product cysteine (tCys) correlates with fat mass in humans and cysteine promotes adiposity in animals. In a cross-sectional study of 610 participants, we investigated whether SAM and SAH are associated with BMI via lean mass or fat mass and dietary protein sources as determinants of SAM and tCys concentrations. Plasma SAM was not associated with lean mass, but mean adjusted fat mass increased from 24 kg (95% CI: 22.6, 25.1) to 30 kg (95% CI: 28.7, 31.3) across SAM quartiles (P < 0.001) and trunk fat:total fat ratio increased from 0.48 to 0.52 (P < 0.001). Erythrocyte SAM was also positively associated with fat mass and trunk fat:total fat ratio. The association of SAM with fat mass was not weakened by adjustment for serum tCys, lipids, creatinine, or dietary or lifestyle confounders. Concentrations of the SAM precursor, methionine, and the SAM product, SAH, were not independently associated with adiposity. Intake of animal-derived protein was not related to serum methionine but was positively associated with plasma SAM (partial r = 0.11) and serum tCys (partial r = 0.13; P < 0.05 for both after adjustment for age, gender, and total energy intake). In conclusion, plasma SAM, but not methionine, is independently associated with fat mass and truncal adiposity, suggesting increased conversion of methionine to SAM in obese individuals. Prospective studies are needed to investigate the interactions among dietary energy and animal protein content, SAM concentrations, and change in body weight and cardiometabolic risk.

Macronutrient composition of the diet and prospective weight change in participants of the EPIC-PANACEA study

BACKGROUND

The effect of the macronutrient composition of the usual diet on long term weight maintenance remains controversial.

METHODS

373,803 subjects aged 25-70 years were recruited in 10 European countries (1992-2000) in the PANACEA project of the EPIC cohort. Diet was assessed at baseline using country-specific validated questionnaires and weight and height were measured at baseline and self-reported at follow-up in most centers. The association between weight change after 5 years of follow-up and the iso-energetic replacement of 5% of energy from one macronutrient by 5% of energy from another macronutrient was assessed using multivariate linear mixed-models. The risk of becoming overweight or obese after 5 years was investigated using multivariate Poisson regressions stratified according to initial Body Mass Index.

RESULTS

A higher proportion of energy from fat at the expense of carbohydrates was not significantly associated with weight change after 5 years. However, a higher proportion of energy from protein at the expense of fat was positively associated with weight gain. A higher proportion of energy from protein at the expense of carbohydrates was also positively associated with weight gain, especially when carbohydrates were rich in fibre. The association between percentage of energy from protein and weight change was slightly stronger in overweight participants, former smokers, participants ≥60 years old, participants underreporting their energy intake and participants with a prudent dietary pattern. Compared to diets with no more than 14% of energy from protein, diets with more than 22% of energy from protein were associated with a 23-24% higher risk of becoming overweight or obese in normal weight and overweight subjects at baseline.

CONCLUSION

Our results show that participants consuming an amount of protein above the protein intake recommended by the American Diabetes Association may experience a higher risk of becoming overweight or obese during adult life.

The association of fasting plasma sulfur-containing compounds with BMI, serum lipids and apolipoproteins

BACKGROUND AND AIM

Sulfur amino acids are recognized as potent modulators of lipid metabolism. Plasma total cysteine (tCys) is associated with fat mass, obesity and serum LDL-cholesterol and apolipoprotein (Apo)-B in large population studies. It is not known how fasting plasma concentrations of cysteine precursors and products relate to these associations in humans, given that sulfur-containing compounds (SCC) influence rodent weight gain and serum lipids.

METHODS AND RESULTS

We investigated the cross-sectional associations of fasting plasma SCC (methionine, total homocysteine, cystathionine, tCys, taurine and total glutathione) with BMI and fasting serum lipids and apolipoproteins in 854 men and women with and without cardiovascular disease (CVD). In multiple linear regression analysis adjusted for age, gender, CVD and other SCC, neither methionine, taurine, nor total glutathione was associated with BMI. Plasma taurine was, however, inversely related to HDL-cholesterol (partial r = -0.12, p = 0.004) and its associated apoA1 (partial r = -0.18, p < 0.001). Plasma cystathionine correlated positively with triglycerides and BMI, while tCys positively correlated with total cholesterol, LDL-cholesterol (partial r = 0.20, p < 0.001) and its associated apoB. The associations of SCC with serum lipids were independent of BMI. tCys was also independently associated with BMI (partial r = 0.20, p < 0.001) after adjustment for other SCC, glucose, lipids and apolipoproteins.

CONCLUSIONS

Fasting tCys is associated with BMI independently of metabolically related SCC. Elevation of plasma SCC is generally associated with an unfavorable lipid profile. The negative relations of plasma taurine with HDL-C and apoA1 deserve further investigation.

Relationship between paraoxonase and homocysteine: crossroads of oxidative diseases

Homocysteine (Hcy) is an accepted independent risk factor for several major pathologies including cardiovascular disease, birth defects, osteoporosis, Alzheimer's disease, and renal failure. Interestingly, many of the pathologies associated with homocysteine are also linked to oxidative stress. The enzyme paraoxonase (PON1) - so named because of its ability to hydrolyse the toxic metabolite of parathion, paraoxon - was also shown early after its identification to manifest arylesterase activity. Although the preferred endogenous substrate of PON1 remains unknown, lactones comprise one possible candidate class. Homocysteine-thiolactone can be disposed of by enzymatic hydrolysis by the serum Hcy-thiolactonase/paraoxonase carried on high-density lipoprotein (HDL). In this review, Hcy and the PON1 enzyme family were scrutinized from different points of view in the literature and the recent articles on these subjects were examined to determine whether these two molecular groups are related to each other like a coin with two different sides, so close and yet so different and so opposite.

Cysteine and obesity: consistency of the evidence across epidemiologic, animal and cellular studies

PURPOSE OF REVIEW

The concentrations of several plasma amino acids increase in obesity. Notably, plasma total concentrations of the sulphur amino acid cysteine (tCys) are linearly associated with fat mass in large population studies. Animal and cellular experiments support the concept that cysteine may be obesogenic. Here we review experimental and epidemiologic findings linking cysteine and related compounds with fat regulation and obesity.

RECENT FINDINGS

tCys, and to a lesser extent cystathionine, are the only plasma sulphur amino acids consistently associated with human obesity, whereas glutathione is inversely associated with BMI. Supplementing cyste(i)ne in rodents decreases energy expenditure and promotes adiposity, whereas defects of cysteine-synthesizing enzymes decrease body weight. In adipocytes, cysteine inhibits lipolysis and promotes lipogenesis via H2O2 production. Unlike most plasma amino acids, tCys levels do not decrease with gastric bypass-induced weight loss, further supporting the concept that elevated cysteine may be a cause, not a consequence of obesity. Although cysteine products (glutathione, taurine and H2S) are altered in obesity, they do not appear to explain cysteine's effects on body weight.

SUMMARY

Cellular, animal and epidemiologic data are consistent with the view that cysteine is obesogenic. Targeted research linking in-vitro and in-vivo findings is needed to elucidate mechanisms involved.

A diet with 35% of energy from protein leads to kidney damage in female Sprague-Dawley rats

High-protein (HP) diets for weight loss remain popular despite questions surrounding overall safety. In a recent study using the pig model, we showed that long-term intakes from whole proteins at 35 % energy (en %) cause moderate renal histological damage. To examine whether this observation may be species specific or more generalisable, the effect of this diet in rats was examined. Using plant and animal whole proteins, 70-d-old female Sprague-Dawley rats were randomised to either a normal-protein (NP; 15 en %) or a HP (35 en %) diet for 4, 8, 12 and 17 months. Renal function was assessed by creatinine clearance and urinary protein levels, and pathology was assessed by examination of glomerular hypertrophy, glomerulosclerosis and tubulointerstitial fibrosis. Rats consuming the HP diet had 17 % higher kidney weights (P < 0·0001), three times higher proteinuria (P < 0·0001) and 27 % higher creatinine clearance (P = 0·0012) compared with those consuming the NP diet. Consistent with this, HP-fed rats had larger glomeruli (P < 0·0001) and more glomerulosclerosis (P = 0·0003) compared with NP-fed rats. The HP diet also resulted in altered levels of free monocyte chemoattractant protein-1 (P < 0·0001). The histological changes are consistent with those observed in the pig model. In contrast to the pig model, the elevated proteinuria and creatinine clearance observed in the rat model are also usually observed with HP consumption in human subjects. These results indicate that the rat is a useful model for HP effects on the kidney and, along with previous results using the pig model, suggest that long-term intake of high levels of protein may be detrimental to renal health.

Dietary cystine level affects metabolic rate and glycaemic control in adult mice

Plasma total cysteine (tCys) is strongly and independently associated with obesity in large human cohorts, but whether the association is causal is unknown. Dietary cyst(e)ine increases weight gain in some rodent models. We investigated the body composition, metabolic rate and metabolic phenotype of mature C3H/HeH mice assigned to low-cystine (LC) or high-cystine (HC) diets for 12 weeks.

Compared to LC mice, HC mice gained more weight (P=.004 for 12-week weight gain %), with increased fat mass and lean mass, and lowered O₂ consumption and CO₂ production by calorimetry. The HC mice had 30% increase in intestinal fat/body weight % (P=.003) and ∼twofold elevated hepatic triglycerides (P=.046), with increased expression of hepatic lipogenic factors, peroxisome proliferator-activated receptor-γ and sterol regulatory element binding protein-1. Gene expression of both basal and catecholamine-stimulated lipolytic enzymes, adipose triglyceride lipase and hormone-sensitive lipase was inhibited in HC mice adipose tissue. The HC mice also had elevated fasting glucose (7.0 vs. 4.5 mmol/L, P<.001) and a greater area under the curve (P<.001) in intraperitoneal glucose tolerance tests, with enhanced expression of the negative regulator of insulin signaling, protein tyrosine phosphatase-1B, in liver and adipose tissue.

Overall, high cystine intake promotes adiposity and an adverse metabolic phenotype in mice, indicating that the positive association of plasma tCys with obesity in humans may be causal.

Cysteine/cystine redox signaling in cardiovascular disease

Extracellular thiol/disulfide redox environments are highly regulated in healthy individuals. The major thiol/disulfide redox couple in human plasma is cysteine (Cys) and its disulfide form, cystine (CySS). Oxidation of this redox couple, measured as a more positive steady-state redox potential (E(h)), is associated with risk factors for cardiovascular disease (CVD), including aging, smoking, obesity, and alcohol abuse. Rodent and vascular cell studies show that the extracellular redox state of Cys/CySS (E(h)CySS) can play a vital role in controlling CVD through proinflammatory signaling. This inflammatory signaling is regulated by cell-surface protein redox state and involves mitochondrial oxidation, nuclear factor-κB activation, and elevated expression of genes for monocyte recruitment to endothelial cells. Gene array and proteomics studies reveal the global nature of redox effects, and different cell types, e.g., endothelial cells, monocytes, fibroblasts, and epithelial cells, show cell-specific redox responses with different phenotypic traits, e.g., proliferation and apoptosis, which can contribute to CVD. The critical nature of the proinflammatory redox signaling and cell biology associated with E(h)CySS supports the use of plasma levels of Cys, CySS, and E(h)CySS as key indicators of vascular health. Plasma redox-state-based pharmacologic interventions to control or improve E(h)CySS may be effective in preventing CVD onset or progression.

Dietary protein and risk of ischemic heart disease in middle-aged men

BACKGROUND

Prospective studies in US women have suggested an inverse relation between dietary protein and risk of ischemic heart disease (IHD). However, no large-scale prospective studies have been conducted in US men.

OBJECTIVE

The objective was to examine the association between dietary protein and risk of IHD in a prospective study of US men.

DESIGN

Intakes of protein and other nutrients were assessed by using a validated food-frequency questionnaire at 4 time points during follow-up of 43,960 men participating in the Health Professionals Follow-Up Study. Cox proportional hazards models were used to calculate multivariable-adjusted relative risks (RRs) and 95% CIs.

RESULTS

During 18 y of follow-up, we documented 2959 incident cases of IHD. The RR of IHD was 1.08 (95% CI: 0.95, 1.23; P for trend = 0.30) comparing the top with the bottom quintile of percentage of energy from total protein. RRs for animal and vegetable protein were 1.11 (95% CI: 0.97, 1.28; P for trend = 0.18) and 0.93 (95% CI: 0.78, 1.12; P for trend = 0.49), respectively. When the population was restricted to "healthy" men (those free of hypertension, hypercholesterolemia, and diabetes at baseline), the RR of IHD was 1.21 (95% CI: 1.01, 1.44; P for trend = 0.02) for total protein, 1.25 (95% CI: 1.04, 1.51; P for trend = 0.02) for animal protein, and 0.93 (95% CI: 0.72, 1.19; P for trend = 0.65) for vegetable protein.

CONCLUSIONS

We observed no association between dietary protein and risk of total IHD in this group of men aged 40-75 y. However, higher intake of animal protein may be associated with an increased risk of IHD in "healthy" men.

Cysteine supplementation reverses methionine restriction effects on rat adiposity: significance of stearoyl-coenzyme A desaturase

Stearoyl-CoA desaturase-1 (SCD1) is a key enzyme in fatty acid and energy metabolism, but little is known about its nutritional regulation. Dietary methionine restriction in rats decreases hepatic Scd1 mRNA and protein, increases energy expenditure, and decreases fat-pad mass/body-weight% (FM/BW%). In humans, plasma concentrations of the methionine product, cysteine, are associated with obesity. To determine which consequences of methionine-restriction are mediated by decreased cysteine availability, we monitored obesity-related variables in 4 dietary groups for 12 weeks: control-fed (CF), methionine-restricted (MR), MR supplemented with 0.5% l-cysteine (MR+Cys) and CF+Cys rats. MR lowered weight gain and FM/BW% despite higher food intake/weight than CF, and lowered serum cysteine. Hepatic Scd1 expression was decreased, with decreased serum SCD1 activity indices (calculated from serum fatty acid profile), decreased serum insulin, leptin and triglycerides, and higher adiponectin. Cysteine supplementation (MR+Cys) essentially reversed all these phenotypes and raised serum cysteine but not methionine to CF levels. Adding extra cysteine to control diet (CF+Cys) increased serum taurine but did not affect serum cysteine, lipids, proteins, or total weight gain. FM/BW% and serum leptin were modestly decreased. Our results indicate that anti-obesity effects of MR are caused by low cysteine and that dietary sulfur amino acid composition contributes to SCD1 regulation.

Long-term high intake of whole proteins results in renal damage in pigs

Despite evidence of potential antiobesity effects of high-protein (HP) diets, the impact of consuming diets with protein levels at the upper limit of the acceptable macronutrient distribution range (AMDR) on kidney health is unknown. To test whether HP diets affect renal health, whole plant and animal proteins in proportions that mimicked human diets were given to pigs, because their kidneys have a similar anatomy and function to those of humans. Adult female pigs received either normal-protein (NP) or HP (15 or 35% of energy from protein, respectively) isocaloric diets for either 4 or 8 mo. The higher protein in the HP diet was achieved by increasing egg and dairy proteins. Although there were initial differences in body weight and composition, after 8 mo these were similar in pigs consuming the NP and HP diets. The HP compared with NP diet, however, resulted in enlarged kidneys at both 4 and 8 mo. Renal and glomerular volumes were 60-70% higher by the end of the study. These enlarged kidneys had greater evidence of histological damage, with 55% more fibrosis and 30% more glomerulosclerosis. Renal monocyte chemoattractant protein-1 levels also were 22% higher in pigs given the HP diet. Plasma homocysteine levels were higher in the HP pigs at 4 mo and continued to be elevated by 35% at 8 mo of feeding. These findings suggest that long-term intakes of protein at the upper limit of the AMDR from whole protein sources may compromise renal health.

Biochemical risk indices, including plasma homocysteine, that prospectively predict mortality in older British people: the National Diet and Nutrition Survey of People Aged 65 Years and Over

Predictive power, for total and vascular mortality, of selected indices measured at baseline in the British National Diet and Nutrition Survey (community-living subset) of People Aged 65 Years and Over was tested. Mortality status and its primary and underlying causes were recorded for 1100 (mean age 76.7 (sd 7.5) years, 50.2% females) respondents from the baseline survey in 1994-5 until September 2008. Follow-up data analyses focussed especially on known predictors of vascular disease risk, together with intakes and status indices of selected nutrients known to affect, or to be affected by, these predictors. Total mortality was significantly predicted by hazard ratios of baseline plasma concentrations (per sd) of total homocysteine (tHcy) (95% CI) 1.19 (1.11, 1.27), pyridoxal phosphate 0.90 (0.81, 1.00), pyridoxic acid 1.10 (1.03, 1.19), alpha1-antichymotrypsin 1.21 (1.13, 1.29), fibrinogen 1.14 (1.05, 1.23), creatinine 1.20 (1.10, 1.31) and glycosylated Hb 1.23 (1.14, 1.32), and by dietary intakes of energy 0.87 (0.80, 0.96) and protein 0.86 (0.77, 0.97). Prediction patterns and significance were similar for primary-cause vascular mortality. The traditional risk predictors plasma total and HDL cholesterol were not significant mortality predictors in this age group, nor were the known tHcy-regulating nutrients, folate and vitamin B12 (intakes and status indices). Model adjustment for known risk predictors resulted in the loss of significance for some of the afore-mentioned indices; however, tHcy 1.34 (1.04, 1.73) remained a significant predictor for vascular mortality. Thus, total and primary vascular mortality is predicted by energy and protein intakes, and by biochemical indices including tHcy, independent of serum folate or vitamin B12.

Study of molecular targets influencing homocysteine and cholesterol metabolism in growing rats by manipulation of dietary selenium and methionine concentrations

Inconsistent results exist from human and animal studies for Se and methionine (Met) regarding their influence on homocysteine (HCys) and cholesterol (Chol) metabolism. To elucidate these contradictions, sixty-four weanling albino rats were divided into eight groups of 8, and were fed diets containing four different Se levels (15, 50, 150 and 450 microg/kg) either in combination with the recommended Met level of 3 g/kg (C15, C50, C150 and C450) or with an increased Met concentration of 15 g/kg (M15, M50, M150 and M450) for 8 weeks. Plasma HCys was twofold higher in the Se-supplemented C groups than in group C15. Met addition also doubled plasma HCys compared with the respective C groups. In contrast, the expression of the key enzymes of glutathione biosynthesis in the liver was significantly lowered by Se and in particular by Met. Liver Chol concentration was significantly higher in all the Se-supplemented C and M groups than in groups C15 and M15. Plasma Chol was, however, lowered. The uninfluenced expression of sterol-regulatory element-binding protein 2 and of hydroxymethyl-glutaryl-CoA reductase, the increased LDL receptor expression and the reduced expression of the hepatobiliary Chol exporter ATP-binding-cassette-transporter 8 (ABCG8) by Se and/or Met explain these findings. We conclude that the elevation of plasma HCys in rats by Se and Met results from a higher export into plasma. The fact that Se in particular combined with Met increases liver Chol but reduces plasma Chol should be addressed in future investigations focussing on the regulation of ABCG8, which is also selectively involved in the reverse transport of phytosterols in the small intestine.

Nutrients: the environmental regulation of cardiovascular gene expression

The complexity of nutrient-gene interactions has led to the development of a new branch in the nutrition sciences, the nutrigenomics. The individual susceptibility to nutrients based on environment --> genotype --> phenotype interplay makes this new research field extremely promising although complex. In this review, we highlight and examine recent findings and the most relevant hypotheses on the role of the diet in the onset and progression of cardiovascular diseases. The effect of unbalanced diets on the cardiovascular system is considered one of the most important risk factors both for ischemic and degenerative myocardial pathologies. The concept that nutrigenomics could help in improving public and personal health is becoming tangible indicating future directions for basic and applied research in the pathophysiology of cardiovascular disease.

Testosterone regulation of renal cystathionine β-synthase: implications for sex-dependent differences in plasma homocysteine levels

Elevated plasma total homocysteine (tHcy) is an independent risk factor for ischemic heart disease and stroke. Epidemiological studies reveal that men have higher tHcy levels than women, but the mechanism underlying this sex-dependent difference is unknown. One route for intracellular disposal of homocysteine is catalyzed by cystathionine β-synthase (CBS). Renal function is known to be an important determinant of tHcy, and, in this study, we demonstrate that renal CBS expression and activity in mice diminished approximately twofold after castration, whereas ovariectomization was without effect. The higher renal CBS activity in males (22.7 ± 3.1 mmol cystathionine·h−1·kg kidney−1) vs. females (8.4 ± 3.4 mmol cystathionine·h−1·kg kidney−1, P ≤ 10−6) in C57Bl/6J mice was associated with lower plasma tHcy levels in males vs. females, and this difference was exacerbated in Cbs+/− mice (7.7 ± 1.9 μmol/l in males vs. 13.8 ± 6.4 μmol/l in females, P = 0.005). Surprisingly, mammals exhibit a diversity of regulatory patterns for kidney CBS, with females exhibiting lower CBS activity in mice, higher in rats and humans, and being indistinguishable from males in rabbit, hamster, and guinea pig. Our data suggest that testosterone-dependent regulation of human CBS in kidney may contribute to sex-dependent differences in homocysteine transsulfuration.