Divergent Survival Outcomes Associated with Elevated Branched-Chain Amino Acid Levels among Older Adults with or without Hypertension and Diabetes: A Validated, Prospective, Longitudinal Follow-Up Study.

Branched-chain amino acids are critical metabolic intermediates that can indicate increased risk of cardiometabolic disease when levels are elevated or, alternatively, suggest sufficient mitochondrial energy metabolism and reserve in old age. The interpretation of BCAA levels can be context-dependent, and it remains unclear whether abnormal levels can inform prognosis. This prospective longitudinal study aimed to determine the interrelationship between mortality hazard and fasting serum BCAA levels among older men and women aged ≥65 years with or without hypertension and diabetes mellitus. At baseline (0Y), fasting serum BCAA concentration in 2997 community-living older men and women were measured. Approximately 14 years later (14Y), 860 study participants returned for repeat measurements. Deaths were analysed and classified into cardiovascular and non-cardiovascular causes using International Classification of Diseases codes. Survival analysis and multivariable Cox regression were performed. During a median follow-up of 17Y, 971 (78.6%) non-cardiovascular and 263 (21.4%) cardiovascular deaths occurred among 1235 (41.2%) deceased (median age, 85.8 years [IQR 81.7-89.7]). From 0Y to 14Y, BCAA levels declined in both sexes, whereas serum creatinine concentration increased (both p < 0.0001). In older adults without hypertension or diabetes mellitus, the relationship between mortality hazard and BCAA level was linear and above-median BCAA levels were associated with improved survival, whereas in the presence of cardiometabolic disease the relationship was U-shaped. Overall, adjusted Cox regression determined that each 10% increment in BCAA concentration was associated with a 7% (p = 0.0002) and 16% (p = 0.0057) reduction in mortality hazard estimated at 0Y and 14Y, respectively. Our findings suggested that abnormally high or low (dyshomeostatic) BCAA levels among older adults with hypertension and/or diabetes mellitus were associated with increased mortality, whereas in those with neither disease, increased BCAA levels was associated with improved survival, particularly in the oldest-old.

The Associations of Habitual Intake of Sulfur Amino Acids, Proteins and Diet Quality with Plasma Sulfur Amino Acid Concentrations: The Maastricht Study.

BACKGROUND: Plasma sulfur amino acids (SAAs), i.e., methionine, total cysteine (tCys), total homocysteine (tHcy), cystathionine, total glutathione (tGSH), and taurine, are potential risk factors for obesity and cardiometabolic disorders. However, except for plasma tHcy, little is known about how dietary intake modifies plasma SAA concentrations. OBJECTIVE: To investigate whether the intake of SAAs and proteins or diet quality is associated with plasma SAAs. METHODS: Data from a cross-sectional subset of The Maastricht Study (n = 1145, 50.5% men, 61 interquartile range: [55, 66] y, 22.5% with prediabetes and 34.3% with type 2 diabetes) were investigated. Dietary intake was assessed using a validated food frequency questionnaire. The intake of SAAs (total, methionine, and cysteine) and proteins (total, animal, and plant) was estimated from the Dutch and Danish food composition tables. Diet quality was assessed using the Dutch Healthy Diet Index, the Mediterranean Diet Score, and the Dietary Approaches to Stop Hypertension score. Fasting plasma SAAs were measured by liquid chromatography (LC) tandem mass spectrometry (MS) (LC/MS-MS). Associations were investigated with multiple linear regressions with tertiles of dietary intake measures (main exposures) and z-standardized plasma SAAs (outcomes). RESULTS: Intake of total SAAs and total proteins was positively associated with plasma tCys and cystathionine. Associations were stronger in women and in those with normal body weight. Higher intake of cysteine and plant proteins was associated with lower plasma tHcy and higher cystathionine. Higher methionine intake was associated with lower plasma tGSH, whereas cysteine intake was positively associated with tGSH. Higher intake of methionine and animal proteins was associated with higher plasma taurine. Better diet quality was consistently related to lower plasma tHcy concentrations, but it was not associated with the other SAAs. CONCLUSION: Targeted dietary modifications might be effective in modifying plasma concentrations of tCys, tHcy, and cystathionine, which have been associated with obesity and cardiometabolic disorders.

Associations between plasma sulfur amino acids and specific fat depots in two independent cohorts: CODAM and The Maastricht Study.

PURPOSE: Sulfur amino acids (SAAs) have been associated with obesity and obesity-related metabolic diseases. We investigated whether plasma SAAs (methionine, total cysteine (tCys), total homocysteine, cystathionine and total glutathione) are related to specific fat depots. METHODS: We examined cross-sectional subsets from the CODAM cohort (n = 470, 61.3% men, median [IQR]: 67 [61, 71] years) and The Maastricht Study (DMS; n = 371, 53.4% men, 63 [55, 68] years), enriched with (pre)diabetic individuals. SAAs were measured in fasting EDTA plasma with LC-MS/MS. Outcomes comprised BMI, skinfolds, waist circumference (WC), dual-energy X-ray absorptiometry (DXA, DMS), body composition, abdominal subcutaneous and visceral adipose tissues (CODAM: ultrasound, DMS: MRI) and liver fat (estimated, in CODAM, or MRI-derived, in DMS, liver fat percentage and fatty liver disease). Associations were examined with linear or logistic regressions adjusted for relevant confounders with z-standardized primary exposures and outcomes. RESULTS: Methionine was associated with all measures of liver fat, e.g., fatty liver disease [CODAM: OR = 1.49 (95% CI 1.19, 1.88); DMS: OR = 1.51 (1.09, 2.14)], but not with other fat depots. tCys was associated with overall obesity, e.g., BMI [CODAM: ß = 0.19 (0.09, 0.28); DMS: ß = 0.24 (0.14, 0.34)]; peripheral adiposity, e.g., biceps and triceps skinfolds [CODAM: ß = 0.15 (0.08, 0.23); DMS: ß = 0.20 (0.12, 0.29)]; and central adiposity, e.g., WC [CODAM: ß = 0.16 (0.08, 0.25); DMS: ß = 0.17 (0.08, 0.27)]. Associations of tCys with VAT and liver fat were inconsistent. Other SAAs were not associated with body fat. CONCLUSION: Plasma concentrations of methionine and tCys showed distinct associations with different fat depots, with similar strengths in the two cohorts.

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.

Blood pressure measurement protocol determines hypertension phenotypes in a Middle Eastern population.

Clinic blood pressure (BP) measurement remains a crucial step in managing hypertension. While the number of measures recorded in different settings varies, with typically 1-3 measures, there has been no prior justification for the actual number of measures required. We investigated the pattern of BP variability over 5 consecutive automated readings (R1-R5) and the influence of patient characteristics on this pattern to identify the phenotype of hypertension in a Middle Eastern population. There were 1389 outpatients (51% men, 49% women), age range (18-87 y) who had 5 unattended automated consecutive BP measurements with one-minute intervals using the validated Datascope Mindray Passport V Monitor with the patient blinded from the results. Mean (±SEM) SBP for R1 (136.0 ± 2 mm Hg) was similar to R2 (136.2 ± 2 mm Hg). Thereafter SBP progressively declined till R5 by total of 5.5 mm Hg. The SBP decline was less (4.2 mm Hg) in older (>50 years) vs younger participants (8.1 mm Hg; P < .001) and was blunted in diabetic and hypertensive participants. Overall, 43% of participants had R2 > R1, and 24% additionally had R5 > R1. Age was a strong independent predictor of having both R2 > R1 and R5 > R1, as well as diabetes. Diastolic blood pressure (DBP) decreased by average 2.8 mm Hg from R1 to R5. Females had a 5-fold greater total decline in DBP vs males (P < .001). Using the mean of 5 BP measures resulted in fewer participants being classified as hypertensive (36% of the population) compared to using one measurement (46%), or established BP guidelines which use different combinations of R1-R3 (37%-42%). Our findings in a Middle Eastern population highlight the importance of the BP measurement protocol in combination with patient characteristics in determining whether a patient is diagnosed with hypertension. Protocols that rely on different combinations of only 3 measures (R1-3) will classify more participants as hypertensive, compared to using 5 measures or disregarding a high R2.

Body mass index determines the response of plasma sulfur amino acids to methionine loading.

Evidence from human, animal and cellular studies suggests that high plasma total cysteine (tCys) is causally linked to human obesity, but determinants of population tCys variability are unknown. We hypothesized that tCys elevation in obesity may be mediated by an altered tCys response to intake of its precursor, methionine. We investigated whether BMI influences the change in plasma tCys, total homocysteine (tHcy) and total cysteinylglycine (tCysGly) 6h following a 100 mg/kg oral methionine load in 800 healthy subjects and 750 cardiovascular disease (CVD) cases. Methionine loading decreased tCys from mean 275 (95% CI, 273, 277) µmol/L to 253 (251,255) µmol/L. The decline in tCys was less in overweight (-8%) and obese (-6%) compared to normal weight (-9%) subjects, adjusting for age, gender and CVD (P-ANOVA = 0.006). Compared to normal weight subjects, individuals with obesity had a 2.8-fold likelihood (95% CI, 1.52, 5.01) of experiencing a rise (rather than decline), in tCys postload, after multiple adjustments. tCysGly also decreased postload, and the decline was similarly smaller in overweight (-18%) and obese (-15%) compared to normal weight (-21%) individuals (P-ANOVA <0.001). The tHcy response was modified by CVD status, with an increase in tHcy postload being BMI-dependent in controls (P-ANOVA<0.001) but not in CVD cases (P-interaction = 0.07). Although the methionine dose used was supraphysiologic, these data suggest that an altered tCys response to ingested methionine occurs in obesity, whereby tCys might rise in response to dietary methionine. This may contribute to explaining why human obesity is consistently associated with elevated tCys.

Food Overconsumption in Healthy Adults Triggers Early and Sustained Increases in Serum Branched-Chain Amino Acids and Changes in Cysteine Linked to Fat Gain.

Background: Plasma concentrations of branched-chain amino acids (BCAAs) and the sulfur-containing amino acid cysteine are associated with obesity and insulin resistance. BCAAs predict future diabetes. Objective: We investigated amino acid changes during food overconsumption. Methods: Forty healthy men and women with a body mass index (mean ± SEM) of 25.6 ± 0.6 were overfed by 1250 kcal/d for 28 d, increasing consumption of all macronutrients. Insulin sensitivity and body composition were assessed at baseline (day 0) and day 28. Fasting serum amino acids were measured at days 0, 3, and 28. Linear mixed-effects models evaluated the effect of time in the total group and separately in those with low and high body fat gain (below compared with at or above median fat gain, 1.95 kg). At days 0 and 28, insulin-induced suppression of serum amino acids during a hyperinsulinemic-euglycemic clamp test and, in a subset (n = 20), adipose tissue mRNA expression of selected amino acid metabolizing enzymes were assessed. Results: Weight increased by 2.8 kg. High fat gainers gained 2.6 kg fat mass compared with 1.1 kg in low fat gainers. Valine and isoleucine increased at day 3 (+17% and +22%, respectively; P ≤ 0.002) and remained elevated at day 28, despite a decline in valine (P = 0.019) from day 3 values. Methionine, cystathionine, and taurine were unaffected. Serum total cysteine (tCys) transiently increased at day 3 (+11%; P = 0.022) only in high fat gainers (P-interaction = 0.043), in whom the cysteine catabolic enzyme cysteine dioxygenase (CDO1) was induced (+26%; P = 0.025) in adipose tissue (P-interaction = 0.045). Overconsumption did not alter adipose tissue mRNA expression of the BCAA-metabolizing enzymes branched-chain keto acid dehydrogenase E1α polypeptide (BCKDHA) or branched-chain amino transferase 1 (BCAT1). In the total population at day 0, insulin infusion decreased all serum amino acids (-11% to -47%; P < 0.01), except for homocysteine and tCys, which were unchanged, and glutathione, which was increased by 54%. At day 28, insulin increased tCys (+8%), and the insulin-induced suppression of taurine and phenylalanine observed at day 0, but not that of BCAAs, was significantly impaired. Conclusions: These findings highlight the role of nutrient oversupply in increasing fasting BCAA concentrations in healthy adults. The link between cysteine availability, CDO1 expression, and fat gain deserves investigation. This trial was registered at www.clinicaltrials.gov as NCT00562393.

The relation of CUN-BAE index and BMI with body fat, cardiovascular events and diabetes during a 6-year follow-up: the Hordaland Health Study.

OBJECTIVE: We compared Clínica Universidad de Navarra-Body Adiposity Estimator (CUN-BAE) and body mass index (BMI) as correlates of body fat percent (BF%) and the association with future risk of cardiovascular disease (CVD) and type 2 diabetes in a Caucasian population. METHODS: We used data from 6796 individuals (born 1925-27 and 1950-52) from the Hordaland Health Study, a prospective cohort study in Norway. The study was conducted in 1992-1993 and 1997-1999. Cross-sectional analyses were conducted with data from 1997/99, including BF% measured by dual-energy X-ray absorptiometry. Longitudinal analyses included BMI and CUN-BAE calculated in 1992/93, and self-reported information on CVD events and diabetes in 1997/99. RESULTS: The correlation between CUN-BAE and BF% (r=0.88) was stronger than between BMI and BF% (r=0.56). In sex-stratified analyses, CUN-BAE and BMI correlated similarly with BF% in men (r=0.77 and r=0.76, respectively) and women (r=0.82 and r=0.81, respectively). In longitudinal analyses, the odds ratio (per 1 SD increase) of CVD and type 2 diabetes was higher for BMI (ORCVD =1.23 [95% CI: 1.11-1.36]; ORdiabetes =2.11 [1.82-2.45]) than for CUN-BAE (ORCVD =1.15 [1.04-1.27]; ORdiabetes =2.06 [1.72-2.47]) in the total population. In sex-stratified analyses, CUN-BAE showed higher CVD and diabetes risk than BMI: in men BMI ORCVD =1.22 (1.04-1.44), ORdiabetes =2.13 (1.64-2.83); CUN-BAE ORCVD =1.93 (1.54-2.43), ORdiabetes =4.33 (2.80-6.71); and in women BMI ORCVD =1.22 (1.07-1.39), ORdiabetes =2.11 (1.76-2.53); CUN-BAE ORCVD =2.06 (1.69-2.51), ORdiabetes =5.45 (3.87-7.67). CONCLUSION: CUN-BAE is more strongly associated with future risk of type 2 diabetes and CVD compared with BMI in analysis stratified by sex. As a measure of adiposity in men and women separately, CUN-BAE has no advantage over BMI, except when the value of estimated BF% itself is of interest.

Perturbed adipose tissue hydrogen peroxide metabolism in centrally obese men: Association with insulin resistance.

OBJECTIVE: Although adipose tissue hydrogen peroxide (H2O2) and its metabolizing enzymes have been linked to obesity and insulin resistance in animal studies, this relation remains to be evaluated in humans. METHODS: Non-diabetic men (N = 43, median age, 49 (37, 54 y)) undergoing abdominal surgeries were studied. Participants were classified by body mass index (BMI) into normal-weight (N = 19), or overweight/obese (Ow/Ob; BMI ≥25; N = 24). Centrally obese men were identified by waist-height ratio ≥0.5. H2O2 and activities of superoxide dismutase, catalase and glutathione peroxidase enzymes were assayed in subcutaneous fat samples, and visceral fat (available from N = 33), and their associations with anthropometric parameters, fasting serum lipids, and the homeostasis model of insulin resistance (HOMA-IR) were tested using correlations and multivariate linear regression. RESULTS: H2O2 concentrations and catalase activity were increased in visceral fat from Ow/Ob men, compared to normal-weight subjects (+32%, P = 0.038 and +51%, P = 0.043 respectively). Centrally obese subjects had >2-fold higher superoxide dismutase activity (P = 0.005), 46% higher H2O2 (P = 0.028), and 89% higher catalase activity (P = 0.009) in visceral fat, compared to lean subjects. Central obesity did not alter these markers in subcutaneous fat, apart from a 50% increase in catalase, and did not affect glutathione peroxidase in either fat depot. H2O2 in visceral fat positively correlated with insulin resistance (r = 0.40, P = 0.032). Catalase activity in visceral fat was an independent determinant of HOMA-IR, explaining ~18% of the variance (ß = 0.42, P = 0.016), after adjustment for age and BMI. CONCLUSION: These findings suggest that adipose tissue catalase shows compensatory up-regulation in response to obesity-induced H2O2 accumulation, and that perturbed H2O2 metabolism in visceral fat is linked to insulin resistance in obese humans.

Circulating linoleic acid and alpha-linolenic acid and glucose metabolism: the Hoorn Study.

PURPOSE: Data on the relation between linoleic acid (LA) and alpha-linolenic acid (ALA) and type 2 diabetes mellitus (T2DM) risk are scarce and inconsistent. The aim of this study was to investigate the association of serum LA and ALA with fasting and 2 h post-load plasma glucose and glycated hemoglobin (HbA1c). METHOD: This study included 667 participants from third examination (2000) of the population-based Hoorn study in which individuals with glucose intolerance were overrepresented. Fatty acid profiles in serum total lipids were measured at baseline, in 2000. Diabetes risk markers were measured at baseline and follow-up in 2008. Linear regression models were used in cross-sectional and prospective analyses. RESULTS: In cross-sectional analyses (n = 667), serum LA was inversely associated with plasma glucose, both in fasting conditions (B = -0.024 [-0.045, -0.002]) and 2 h after glucose tolerance test (B = -0.099 [-0.158, -0.039]), but not with HbA1c (B = 0.000 [-0.014, 0.013]), after adjustment for relevant factors. In prospective analyses (n = 257), serum LA was not associated with fasting (B = 0.003 [-0.019, 0.025]) or post-load glucose (B = -0.026 [-0.100, 0.049]). Furthermore, no significant associations were found between serum ALA and glucose metabolism in cross-sectional or prospective analyses. CONCLUSIONS: In this study, serum LA was inversely associated with fasting and post-load glucose in cross-sectional, but not in prospective analyses. Further studies are needed to elucidate the exact role of serum LA and ALA levels and dietary polyunsaturated fatty acids in glucose metabolism.

Exploring the Lean Phenotype of Glutathione-Depleted Mice: Thiol, Amino Acid and Fatty Acid Profiles.

BACKGROUND: Although reduced glutathione (rGSH) is decreased in obese mice and humans, block of GSH synthesis by buthionine sulfoximine (BSO) results in a lean, insulin-sensitive phenotype. Data is lacking about the effect of BSO on GSH precursors, cysteine and glutamate. Plasma total cysteine (tCys) is positively associated with stearoyl-coenzyme A desaturase (SCD) activity and adiposity in humans and animal models. OBJECTIVE: To explore the phenotype, amino acid and fatty acid profiles in BSO-treated mice. DESIGN: Male C3H/HeH mice aged 11 weeks were fed a high-fat diet with or without BSO in drinking water (30 mmol/L) for 8 weeks. Amino acid and fatty acid changes were assessed, as well as food consumption, energy expenditure, locomotor activity, body composition and liver vacuolation (steatosis). RESULTS: Despite higher food intake, BSO decreased particularly fat mass but also lean mass (both P<0.001), and prevented fatty liver vacuolation. Physical activity increased during the dark phase. BSO decreased plasma free fatty acids and enhanced insulin sensitivity. BSO did not alter liver rGSH, but decreased plasma total GSH (tGSH) and rGSH (by ~70%), and liver tGSH (by 82%). Glutamate accumulated in plasma and liver. Urine excretion of cysteine and its precursors was increased by BSO. tCys, rCys and cystine decreased in plasma (by 23-45%, P<0.001 for all), but were maintained in liver, at the expense of decreased taurine. Free and total plasma concentrations of the SCD products, oleic and palmitoleic acids were decreased (by 27-38%, P <0.001 for all). CONCLUSION: Counterintuitively, block of GSH synthesis decreases circulating tCys, raising the question of whether the BSO-induced obesity-resistance is linked to cysteine depletion. Cysteine-supplementation of BSO-treated mice is warranted to dissect the effects of cysteine and GSH depletion on energy metabolism.

Brain atrophy in cognitively impaired elderly: the importance of long-chain ω-3 fatty acids and B vitamin status in a randomized controlled trial.

BACKGROUND: Increased brain atrophy rates are common in older people with cognitive impairment, particularly in those who eventually convert to Alzheimer disease. Plasma concentrations of omega-3 (ω-3) fatty acids and homocysteine are associated with the development of brain atrophy and dementia. OBJECTIVE: We investigated whether plasma ω-3 fatty acid concentrations (eicosapentaenoic acid and docosahexaenoic acid) modify the treatment effect of homocysteine-lowering B vitamins on brain atrophy rates in a placebo-controlled trial (VITACOG). DESIGN: This retrospective analysis included 168 elderly people (≥70 y) with mild cognitive impairment, randomly assigned either to placebo (n = 83) or to daily high-dose B vitamin supplementation (folic acid, 0.8 mg; vitamin B-6, 20 mg; vitamin B-12, 0.5 mg) (n = 85). The subjects underwent cranial magnetic resonance imaging scans at baseline and 2 y later. The effect of the intervention was analyzed according to tertiles of baseline ω-3 fatty acid concentrations. RESULTS: There was a significant interaction (P = 0.024) between B vitamin treatment and plasma combined ω-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid) on brain atrophy rates. In subjects with high baseline ω-3 fatty acids (>590 µmol/L), B vitamin treatment slowed the mean atrophy rate by 40.0% compared with placebo (P = 0.023). B vitamin treatment had no significant effect on the rate of atrophy among subjects with low baseline ω-3 fatty acids (<390 µmol/L). High baseline ω-3 fatty acids were associated with a slower rate of brain atrophy in the B vitamin group but not in the placebo group. CONCLUSIONS: The beneficial effect of B vitamin treatment on brain atrophy was observed only in subjects with high plasma ω-3 fatty acids. It is also suggested that the beneficial effect of ω-3 fatty acids on brain atrophy may be confined to subjects with good B vitamin status. The results highlight the importance of identifying subgroups likely to benefit in clinical trials. This trial was registered at www.controlled-trials.com as ISRCTN94410159.

Body composition in gene knockouts of sulfur amino acid-metabolizing enzymes.

Plasma concentrations of several amino acids are elevated in human obesity and insulin resistance, but there is no conclusive evidence on whether the amino acid alterations are causal. Dietary restriction of the essential SAA methionine (MR) in rats produces a hypermetabolic phenotype, with an integrated set of transcriptional changes in lipid enzymes in liver and adipose tissue. MR also induces an array of changes in methionine metabolites, including elevated plasma homocysteine and decreased cystathionine, cysteine, glutathione, and taurine. Several knockouts of enzymes acting downstream of methionine recapitulate the phenotypic results of MR, suggesting that the MR phenotype may be driven by changes distal to methionine. Here we review the changes in SAA and body composition in seven relevant knockout mouse models. All seven models feature decreased body weight, which in five of these have been further explored and shown to result from predominantly decreased fat mass. Common to several models is increased energy expenditure, enhanced insulin sensitivity, and protection against dietary obesity, as occurs in MR. A decrease in plasma total cysteine concentrations is also seen in most models. The lean phenotype could often be reversed by dietary supplementation of cysteine or choline, but not taurine, betaine or a H2S donor. Importantly, the plasma concentrations of both cysteine and choline are positively associated with fat mass in large populations studies, while taurine, betaine, and H2S are not. Collectively, the emerging data from dietary and knockout models are in harmony with human epidemiologic data, suggesting that the availability of key nutrients in the SAA pathway regulates fat storage pathways.

The first international mini-symposium on methionine restriction and lifespan.

It has been 20 years since the Orentreich Foundation for the Advancement of Science, under the leadership Dr. Norman Orentreich, first reported that low methionine (Met) ingestion by rats extends lifespan (Orentreich et al., 1993). Since then, several studies have replicated the effects of dietary methionine restricted (MR) in delaying age-related diseases (Richie et al., 1994; Miller et al., 2005; Ables et al., 2012; Sanchez-Roman and Barja, 2013). We report the abstracts from the First International Mini-Symposium on Methionine Restriction and Lifespan held in Tarrytown, NY, September 2013. The goals were (1) to gather researchers with an interest in MR and lifespan, (2) to exchange knowledge, (3) to generate ideas for future investigations, and (4) to strengthen relationships within this community. The presentations highlighted the importance of research on cysteine, growth hormone (GH), and ATF4 in the paradigm of aging. In addition, the effects of dietary restriction or MR in the kidneys, liver, bones, and the adipose tissue were discussed. The symposium also emphasized the value of other species, e.g., the naked mole rat, Brandt's bat, and Drosophila, in aging research. Overall, the symposium consolidated scientists with similar research interests and provided opportunities to conduct future collaborative studies (Figure 3).

Monosodium glutamate neurotoxicity increases beta amyloid in the rat hippocampus: a potential role for cyclic AMP protein kinase.

BACKGROUND: Glutamate excitotoxicity and cyclic AMP-activated protein kinase (AMPK) are both recognized as important mediators in neurodegenerative disorders including Alzheimer's disease (AD). OBJECTIVES: To investigate whether oral or subcutaneous monosodium glutamate (MSG) neurotoxicity mimics some features of AD and whether these can be reversed by the AMPK activator Pioglitazone. METHODS: Male Wistar rats aged 5 weeks were administered oral or subcutaneous MSG for 10 days with or without daily oral Pioglitazone. Two additional groups given only saline orally or subcutaneously acted as controls. At age 10 weeks the rats were subjected to neurobehavioral testing, then sacrificed for measurement of AMPK, ß-amyloid and Fas ligand in the hippocampus. RESULTS: Oral and subcutaneous MSG both induced a lowering of hippocampal AMPK by 43% and 31% respectively (P<0.05 for both) and >2-fold increase in hippocampal Fas ligand, a mediator of apoptosis (P<0.001 for both). MSG treatment also induced a significant increase in ß-amyloid in the hippocampus by >4-fold and >5-fold in the oral and subcutaneous groups. This was associated with increased latency before crossing to the white half in the black-white alley and before the first rear in the holeboard test, suggesting increased anxiety. Pioglitazone decreased hippocampal ß-amyloid accumulation and Fas ligand, but did not ameliorate the neurobehavioural deficits induced by MSG. CONCLUSIONS: MSG treatment enhances ß-amyloid accumulation in the rat hippocampus. Our results suggest a role for AMPK reduction in mediating the neurotoxic effects of glutamate, including ß-amyloid accumulation.

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.

Associations between plasma polyunsaturated fatty acids, plasma stearoyl-CoA desaturase indices and body fat.

OBJECTIVE: Stearoyl-CoA desaturase (SCD)-1 deficient mice are resistant to obesity and plasma SCD indices are related to obesity in humans. Both n-3 and n-6 polyunsaturated fatty acids (PUFA) regulate expression of the SCD enzymes. Whether higher plasma PUFA were associated with lower SCD indices in humans was examined. DESIGN AND METHODS: Population-based study of 2,021 elderly subjects from the Hordaland Health Study. Using multivariate linear regression, the cross-sectional associations among plasma PUFA, estimated SCD indices (from fatty acid profiles in plasma total lipids), and fat mass measured by dual-energy X-ray absorptiometry were explored. Two plasma SCD indices were used: SCD-16 (16:1n-7/16:0) and SCD-18 (18:1n-9/18:0). RESULTS: Plasma total, n-6 and n-3 PUFA were inversely associated with both SCD indices (P < 0.001 for all). Among the individual PUFA, 18:2n-6 showed the strongest association with SCD-16 (partial r = -0.59, P < 0.001) followed by 20:5n-3 (partial r = -0.13; P < 0.001). Plasma total, n-6 and n-3 PUFA were inversely associated with body fat (P < 0.001 for all); the associations were markedly attenuated following adjustment for SCD-16. CONCLUSIONS: The epidemiological data are in line with animal studies and suggest that PUFA may decrease SCD1 activity in humans, with possible reduction in body fat.

Evaluation of the body adiposity index in a Caucasian population: the Hordaland health study.

In this study, we compared the relationships of body mass index (BMI) and body adiposity index (BAI) with body fat percentage (BF%) in a Caucasian, European population. BF% was measured by dual-energy x-ray absorptiometry in a population-based cross-sectional study of 5,193 middle-aged (47-49 years) and elderly (71-74 years) men and women from the Hordaland Health Study in western Norway from 1997 to 1999. In the total population, the correlation between BAI and BF% was stronger (r = 0.78) than the correlation between BMI and BF% (r = 0.56) with similar results in the middle-aged and elderly groups. However, in men and women separately, BMI was a better correlate of BF% (for men, r = 0.76; for women, r = 0.81) than was BAI (for men, r = 0.57; for women, r = 0.72). BMI was also a better correlate of BF% than was BAI assessed by partial correlations adjusted for sex (for BMI-BF%, r = 0.79; for BAI-BF%, r = 0.67). Bland-Altman plots and BF%-stratified analyses showed that BAI tended to overestimate BF% in lean subjects and to underestimate it in those with higher proportions of body fat, but that it predicted BF% well for those whose BMI was in a normal range. At the individual level and in population studies adjusted for sex, BMI outperforms BAI as a predictor of BF%.

Plasma stearoyl-CoA desaturase indices: association with lifestyle, diet, and body composition.

OBJECTIVE: Stearoyl-coenzyme A desaturase-1 (SCD1) is a key enzyme in fatty acid and energy metabolism. Increased hepatic SCD1 activity is associated with obesity and obesity-related diseases. We examined the relations of two plasma SCD activity indices (16:1n-7/16:0, 18:1n-9/18:0) with body composition, and the association of lifestyle and dietary variables with the plasma SCD indices. DESIGN AND METHODS: This population-based, cross-sectional study of 2021 elderly (71-74 y) men and women from the Hordaland Health Study in Western Norway was conducted using a validated food frequency questionnaire, body composition measurements by dual-energy X-ray absorptiometry and determination of the plasma fatty acid profile. RESULTS: In multivariate regression analyses, plasma SCD indices were positively associated with BMI and body fat (P < 0.001 for both). From the 2.5th to 97.5th percentiles of plasma SCD-16 and SCD-18 indices, fat mass differed by about 8 kg and 5 kg, respectively. Intake of polyunsaturated fatty acids were negatively associated with SCD-16 (partial r = -0.30) and SCD-18 (partial r = -0.24) (P < 0.001 for both). Alcohol intake was positively associated with SCD-16 (partial r = 0.26) and SCD-18 (partial r = 0.16) (P < 0.001 for both), whereas coffee consumption and physical activity were inversely associated with SCD-16 (P = 0.026 and P = 0.006, respectively) and SCD-18 (P = 0.001 and P = 0.022, respectively). CONCLUSIONS: In this elderly population, plasma markers of SCD1 activity are associated with increased adiposity. Furthermore, modifiable dietary habits and lifestyle are associated with plasma SCD indices. These results suggest that SCD1 activity may be a promising target for weight control.

Effect of taurine and N-acetylcysteine on methionine restriction-mediated adiposity resistance.

OBJECTIVES: Methionine-restricted (MR) rats, which are lean and insulin sensitive, have low serum total cysteine (tCys) and taurine and decreased hepatic expression and activity indices of stearoyl-coenzyme A desaturase-1 (SCD1). These effects are partly or completely reversed by cysteine supplementation. We investigated whether reversal of MR phenotypes can be achieved by other sulfur compounds, namely taurine or N-acetylcysteine (NAC). METHODS: MR and control-fed (CF) rats were supplemented with taurine (0.5%) or NAC (0.5%) for 12weeks. Adiposity, serum sulfur amino acids (SAA), Scd1 gene expression in liver and white adipose tissue, and SCD1 activity indices (calculated from serum fatty acid profile) were monitored. RESULTS: Taurine supplementation of MR rats did not restore weight gain or hepatic Scd1 expression or indices to CF levels, but further decreased adiposity. Taurine supplementation of CF rats did not affect adiposity, but lowered triglyceridemia. NAC supplementation in MR rats raised tCys and partly or completely reversed MR effects on weight, fat %, Scd1 expression in liver and white adipose tissue, and estimated SCD1 activity. In CF rats, NAC decreased body fat % and lowered SCD1-18 activity index (P<0.001). Serum triglycerides and leptin were over 40% lower in CF+NAC relative to CF rats (P≤0.003 for both). In all groups, change in tCys correlated with change in SCD1-16 index (partial r=0.60, P<0.001) independent of other SAA. CONCLUSION: The results rule out taurine as a mediator of increased adiposity produced by cysteine in MR, and show that NAC, similar to L-cysteine, blocks anti-obesity effects of MR. Our data show that dietary SAA can influence adiposity in part through mechanisms that converge on SCD1 function. This may have implications for understanding and preventing human obesity.