High dietary intake of branched-chain amino acids is associated with an increased risk of insulin resistance in adults

Transcription

1 Journal of Diabetes 10 (2018), ORIGINAL ARTICLE High dietary intake of branched-chain amino acids is associated with an increased risk of insulin resistance in adults Highlights Higher intake of dietary total branched-chain amino acids (BCAAs), leucine and valine in particular, may increase the incidence of insulin resistance by more than 60% in adults and play an important role in the development of diabetes. No significant association of was found between the intake of total BCAAs or isoleucine, leucine, and valine individually and the risk of hyperinsulinemia, β-cell dysfunction, or insulin insensitivity in adults. Golaleh ASGHARI, 1 Hossein FARHADNEJAD, 1 Farshad TEYMOORI, 1 Parvin MIRMIRAN, 2 Maryam TOHIDI 3 and Fereidoun AZIZI 4 1 Nutrition and Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran, 2 Department of Clinical Nutrition and Dietetics, Faculty of Nutrition Sciences and Food Technology, National Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, Tehran, Iran, 3 Prevention of Metabolic Disorders Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran, and 4 Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran Correspondence Parvin Mirmiran, Department of Clinical Nutrition and Dietetics, Faculty of Nutrition Sciences and Food Technology, National Nutrition and Food Technology Research Institute, Shahid Beheshti University of Medical Sciences, PO Box , Tehran, Iran. Tel: Fax: mirmiran@endocrine.ac.ir Received 25 July 2017; revised 29 November 2017; accepted 22 December doi: / Abstract Background: The aim of this study was to investigate the association between branched-chain amino acid (BCAA) intake and markers of insulin metabolism in adults. Methods: This cohort study was conducted within the framework of the Tehran Lipid and Glucose Study on 1205 subjects, aged 20 years, who were followed-up for a mean of 2.3 years. Dietary intake of BCAAs, including valine, leucine, and isoleucine, was determined using a valid and reliable food frequency questionnaire. Hyperinsulinemia, β-cell dysfunction, insulin resistance (IR), and insulin insensitivity were determined according to optimal cut-off values. Logistic regression was to estimate the occurrence of IR across tertiles of BCAA intake. Results: The mean ( SD) age and BCAA intake of participants (43% male) at baseline were years and g/day, respectively. The incidence of hyperinsulinemia, β-cell dysfunction, insulin insensitivity, and IR was 19.5%, 24.0%, 28.0%, and 12.5%, respectively. After adjustment for confounding variables, subjects in the highest tertile for total BCAAs (odds ratio [OR] 1.67; 95% confidence interval [CI] ), leucine (OR 1.75; 95% CI ), and valine (OR 1.61; 95% CI ) intake had a greater risk of incident IR than subjects in the lowest tertile. A higher intake of isoleucine was not associated with risk of incident IR. There was no association of total BCAAs, leucine, isoleucine, and valine intake with the risk of hyperinsulinemia, insulin insensitivity, or β-cell dysfunction. Conclusion: The findings of this study support the hypothesis that higher intakes of BCAAs may have adverse effects on the development of IR. Keywords: branched-chain amino acid intake, hyperinsulinemia, insulin insensitivity, insulin resistance, β-cell dysfunction Ruijin Hospital, Shanghai Jiaotong University School of Medicine and John Wiley & Sons Australia, Ltd 357

2 BCAA and insulin resistance Introduction Insulin resistance (IR) is defined as decreased secretion of insulin from pancreatic β-cells or an insufficient response of peripheral tissues, including adipose tissue and skeletal muscle, to insulin secretion. 1 Insulin resistance, as well as β-cell dysfunction, not only contribute to the progression of type 2 diabetes, 2 but are also important precursors of some chronic diseases, including hypertension, metabolic syndrome, dyslipidemia, and cardiovascular disease (CVD). 3 5 Insulin resistance has recently received considerable attention, and data reveal that nutritional factors, including food patterns, macronutrients, dietary fiber, and some micronutrients, may be associated with the development of IR. 6 8 Branched-chain amino acids (BCAAs), including leucine, isoleucine, and valine, are essential amino acids 9 frequently found in dietary protein, accounting for up to 15% 20% of protein intake, that have direct and indirect metabolic effects (e.g. regulation of body weight, muscle protein synthesis, energy homeostasis, food intake control, and glucose homeostasis) Studies on circulating serum concentrations of BCAAs and insulin metabolism or IR have shown controversial findings; some studies indicate impaired BCAA metabolism and increased plasma levels to be associated with a higher risk of IR or type 2 diabetes and preceding hyperglycemia, 9,13,14 whereas other studies indicate that increased plasma BCAA concentrations have no effect on insulin sensitivity. 15,16 Similarly, the limited studies available assessing the association between BCAA intake from the diet and the risk of diabetes have yielded inconsistent results, with one study indicating that a higher intake of these amino acids was associated with a decreased risk of diabetes 17 and the other study reporting that high consumption of BCAAs increases the risk of diabetes. 18 Nevertheless, to date, no population-based cohort study has investigated the association of dietary BCAA intake with the risk of IR and β-cell dysfunction. Thus, the aim of the present study was to assess the association between dietary intake of BCAAs and markers of insulin metabolism among Iranian adults. Methods Study population The present study was conducted within the framework of the Tehran Lipid and Glucose Study (TLGS), an ongoing community-based prospective study aimed at preventing non-communicable diseases (NCD) by developing programs promoting healthy lifestyles and reducing NCD risk factors. 19 The TLGS was conducted on a sample of residents from District No. 13 of Tehran, the capital city of Iran. The baseline survey was a cross-sectional study conducted from 1999 to 2001, and Surveys II ( ), III ( ), and IV ( ) were prospective follow-up surveys. In the third survey of the TLGS ( ), of participants, 3462 were randomly selected for dietary assessment. For the present study, 1348 men and women aged 20 years, with complete information on insulin, were selected. Subjects with a history of myocardial infarction or stroke (n = 28), those who reported daily energy intakes outside the range of kcal/ day (n = 63), those on specific diets (n = 52), and pregnant and lactating women (n = 25) were excluded; some individuals fell into more than one exclusion category. Finally, 1205 participants were followed until Survey IV ( ), with a median follow-up period of 2.3 years (interquartile range [IQR] years). The Ethics Committee of the Research Institute for Endocrine Sciences of Shahid Beheshti University of Medical Sciences approved the study protocol, and written informed consent was obtained from all participants. Measurements G. ASGHARI et al. Dietary intake was assessed by expert interviewers, using a food frequency questionnaire (FFQ), 19 the reliability and validity of which have been reported previously. 20 Trained dietitians asked participants in face-to-face interviews to designate their consumption frequency for each food item consumed during the previous year on a daily, weekly, or monthly basis. Portion sizes of consumed foods, reported in household measures, were then converted to grams. Because the Iranian Food Composition Table 21 (FCT) is incomplete, the USDA FCT 22 was used. For national foods not listed in the USDA FCT, the Iranian FCT was the alternative. Amino acid intake was calculated using the USDA FCT (USDA National Nutrient Database for Standard Reference, Release 28, 2015; accessed 15 December 2015), which is based on the chemical analysis of amino acid composition. We assigned values for BCAAs, including leucine, isoleucine, and valine, to each of the FFQ food items. Then, BCAA intake was calculated as the frequency of consumption of each food item multiplied by the leucine, isoleucine, and valine content of the food. Physical activity was determined using the Modifiable Activity Questionnaire (MAQ) to calculate metabolic equivalent task (MET) minutes per week, which has Ruijin Hospital, Shanghai Jiaotong University School of Medicine and John Wiley & Sons Australia, Ltd

3 G. ASGHARI et al. BCAA and insulin resistance previously been shown to have high reliability and moderate validity for the Persian translation of the MAQ. 23 Levels of physical activity were categorized as light (MET <600 min/week), moderate (MET min/ week), and vigorous (MET 1500 min/week). Weight, height, waist circumference, systolic blood pressure (SBP), and diastolic blood pressure (DBP) were recorded according to standard protocols, 19 and body mass index (BMI) was calculated as weight (kg) divided by height squared (m 2 ). Blood samples were taken from all participants after an overnight fast of h to measure fasting plasma glucose (FPG), 2-h plasma glucose (2-hPG; equivalent to 75 g anhydrous glucose; Cerestar EP, Barcelona, Spain), and fasting serum insulin, as described previously. 19 Hyperinsulinaemia was defined as fasting insulin and 9.16 μu/ml in women and men, respectively. 24 The homeostatic model assessment of insulin resistance (HOMA-IR) was calculated as follows: HOMA IR = ðfins FPGÞ=22:5 where FINS is fasting insulin (μu/ml) and FPG is fasting plasma glucose (mmol/l). Subjects with HOMA-IR >3.2 were considered to be insulin resistant. β-cell function was evaluated using the homeostatic model assessment of β-cell function (HOMA-B), calculated as follows: HOMA B= ð20 FINS Þ= ðfpg 3:5Þ Values of HOMA-B 86.2 and 67.1 for women and men, respectively, were considered to indicate β-cell dysfunction. Insulin sensitivity was evaluated using the homeostasis model assessment of insulin sensitivity (HOMA-S), calculated as follows: HOMA S = 1=HOMA IR 100: Values of HOMA-S 54.1 and 46.1 for women and men, respectively, were considered to indicate insulin insensitivity. 24,25 Statistical analysis The present study was a prospective study; information on diet was collected at baseline ( ) and serum insulin was measured at baseline and after 3 years of follow-up. Branched-chain amino acids were categorized into tertiles using cut-off points (<2.22%, %, and >2.64% of energy). Continuous variables are reported as the mean SD or as the median (IQR), whereas categorical variables are reported as percentages. Tests of trend for continuous and categorical variables across BCAA tertiles (using the median value in each tertile) were conducted using linear regression and the Chi-squared test, respectively. To examine the association of incident hyperinsulinemia, IR, β-cell dysfunction, and insulin insensitivity in each BCAA tertile, multivariable logistic regression models were used and odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. The lowest BCAA tertile (T1) served as the reference group. Model 1 was adjusted for age and sex, and Model 2 was further adjusted for BMI, physical activity, smoking, a family history of diabetes and CVD, hypertension, glycemic load, and daily intakes of energy, saturated fat, and dietary fiber. To calculate the trend of ORs across increasing BCAA categories, we considered the tertile categories as continuous variables. In addition, the ORs of incident hyperinsulinemia, IR, β-cell dysfunction, and insulin insensitivity were estimated across tertiles of leucine, isoleucine, and valine intake using multivariable logistic regression models. All data were analyzed using SPSS version 15.0 (SPSS Inc., Chicago, IL, USA). Two-sided P < 0.05 was considered significant. Results At baseline, the mean ( SD) age of participants (43% male) was years and the mean BCAA intake was g/day. The incidence of hyperinsulinemia, β-cell dysfunction, insulin insensitivity, and IR was 19.5%, 24.0%, 28.0%, and 12.5%, respectively. Characteristics of individuals according to BCAA tertile are given in Table 1. From Table 1, it can be seen that, across BCAA tertiles, intake of protein and saturated fat increased (P < 0.001), whereas energy, fiber, polyunsaturated fat, and glycemic load decreased (P < 0.001). There was no significant differences in age, sex, BMI, family history of diabetes, family history of CVD, hypertension, physical activity, smoking, FPG, insulin, HOMA-IR, HOMA-B, and HOMA-S across tertiles of BCAA intake (P trend > 0.05 for all). In addition, at the end of the median 2.3-year follow-up period, these characteristics did not differ across tertiles of BCAA intake. The association between BCAA intake and risk of insulin resistance, hyperinsulinemia, β-cell dysfunction, and insulin insensitivity is given in Table 2. In the crude model, participants with a higher BCAA intake were 59% more likely to have a risk of insulin resistance 2017 Ruijin Hospital, Shanghai Jiaotong University School of Medicine and John Wiley & Sons Australia, Ltd 359

4 BCAA and insulin resistance G. ASGHARI et al. Table 1 Characteristics of the study population across tertiles of dietary branched-chain amino acids Dietary BCAA tertiles (n = 1205) T1 (n = 403) T2 (n = 405) T3 (n = 397) P trend * Baseline Median % of energy 1.99 [ ] 2.43 [ ] 2.94 [ ] g/day Age (years) Men (%) BMI (kg/m 2 ) Family history of diabetes (%) Family history of CVD (%) Hypertension (%) Physical activity (METh/week) 24.3 [ ] 25.3 [ ] 26.2 [ ] Current smoker (%) FBG (mg/dl) FINS (mu/ml) HOMA-IR 1.70 [ ] 1.71 [ ] 1.74 [ ] HOMA-B HOMA-S 58.5 [ ] 58.3 [ ] 57.4 [ ] Year follow-up BMI (kg/m 2 ) Physical activity (METh/week) 35.0 [ ] 51.6 [ ] 40.2 [ ] Current smoker (%) FBG (mg/dl) FINS (mu/ml) HOMA-IR 1.98 [ ] 1.91 [ ] 2.02 [ ] HOMA-B HOMA-S 50.3 [ ] 52.3 [ ] 49.3 [ ] Baseline dietary intake Energy (kcal) <0.001 Glycemic load <0.001 Protein (% of energy) <0.001 Saturated fat (% of energy) <0.001 Polyunsaturated fat (% of energy) <0.001 Fiber (g/1000 kcal) <0.001 Data are presented as the mean SD or as the median (interquartile range) for continuous variables and as percentages for categorical variables. *P trend was calculated using general linear models for continuous variables or Chi-square tests for categorical variables. BCAA, Branched-chain amino acids; BMI, body mass index; CVD, cardiovascular disease; FBG, fasting blood glucose; FINS, fasting serum insulin; HOMA-B, homeostatic model assessment of β-cell function; HOMA-IR, homeostasis model assessment of insulin resistance; HOMA- S, homeostasis model assessment of insulin sensitivity. (OR 1.59, 95% CI ), than those with the lowest intake (P trend = 0.032). However, there was no significant association between the dietary intake of BCAAs and the risk of hyperinsulinemia (OR 0.74, 95% CI ), β-cell dysfunction (OR 0.82, 95% CI ), or insulin insensitivity (OR 0.8, 95% CI ). In the final model, after adjusting for all potential confounding variables, subjects in the highest tertile of BCAA intake had a greater risk of developing IR (OR 1.67, 95% CI ) compared with those in the lowest tertile (P trend = 0.034). However, a higher intake of BCAAs was not significantly associated with hyperinsulinemia (OR 0.74, 95% CI ), β-cell dysfunction (OR 0.86, 95% CI ), or insulin insensitivity (OR 0.85, 95% CI ). Multivariable-adjusted ORs for insulin resistance, hyperinsulinemia, β-cell dysfunction, and insulin insensitivity across tertiles of leucine, isoleucine, and valine intake are shown in Fig. 1. Subjects with the highest intake of leucine (OR 1.61, 95% CI ) and valine (OR 1.75, 95% CI ) had higher odds of incident IR than those with the lowest intake after adjusting for potential confounding factors (P trend < 0.05). However, a higher intake of isoleucine (OR 1.57, 95% CI ) was not significantly associated with the risk of incident insulin resistance (Fig. 1a). In addition, higher intake of leucine, isoleucine, and valine was not significantly related to the incidence of hyperinsulinemia (Fig. 1b), β-cell dysfunction (Fig. 1c), or insulin insensitivity (Fig. 1d) Ruijin Hospital, Shanghai Jiaotong University School of Medicine and John Wiley & Sons Australia, Ltd

5 G. ASGHARI et al. BCAA and insulin resistance Table 2 intake Odds ratios (95% confidence intervals) of incident diabetes and insulin resistance across tertiles of branched-chain amino acid Dietary BCAA tertiles T1 T2 T3 P trend Hyperinsulinemia No. cases/total 56/279 59/269 41/252 Model (Reference) 1.08 ( ) 0.74 ( ) Model (Reference) 1.12 ( ) 0.74 ( ) Insulin resistance No. cases/total 38/354 39/355 54/332 Model (Reference) 1.00 ( ) 1.59 ( ) Model (Reference) 1.05 ( ) 1.67 ( ) β-cell dysfunction No. cases/total 71/289 79/298 60/285 Model (Reference) 1.16 ( ) 0.82 ( ) Model (Reference) 1.07 ( ) 0.86 ( ) Insulin insensitivity No. cases/total 65/219 65/226 55/214 Model (Reference) 0.96 ( ) 0.82 ( ) Model (Reference) 0.98 ( ) 0.85 ( ) Model 1 was adjusted for age and sex. Model 2 was further adjusted for body mass index, physical activity, smoking, a family history of diabetes and cardiovascular disease, hypertension, glycemic load, and daily intakes of energy, saturated fat, and dietary fiber. Discussion In the present study we investigated the association between dietary BCAA intake and the risk of IR, β-cell dysfunction, and hyperinsulinemia in 1205 men and women after a 2.3-year follow-up, independent of confounding factors. The findings indicate that a high intake of BCAAs is related to increased risk of IR. However, no significant association was found between dietary BCAA intake and the development of β-cell dysfunction and hyperinsulinemia. In addition, of the BCAAs, a higher intake of leucine and valine was significantly associated with a higher risk of incident IR. Because 80% of serum BCAAs concentrations are determined by the consumption of protein or BCAAs from the diet or supplements and the remaining 20% is related to the catabolism of BCAA metabolites, 26,27 it can be said that the findings of the present study are comparable with studies showing the association of serum concentrations of circulating BCAAs and IR; 9,13 16 some studies indicated that high BCAA concentrations are related to hyperglycemia, development of IR, and diabetes, 9,13,14 although others found no significant associations between serum concentrations of these amino acids and insulin metabolism. 15,16 To the best of our knowledge, no previous population-based cohort study has investigated the relationship between dietary BCAA intake and the risk of developing IR; only limited epidemiological studies have investigated the association between BCAA intake and the risk of diabetes, and unfortunately the reported results are inconsistent. 17,18 In the study of Zheng et al., 18 high dietary BCAA intakes in terms of absolute intake increased the risk of diabetes by nearly 13%. Similarly, in the present study we found a 67% higher risk of IR based on high BCAA intake in terms of the percentage of total energy. However, in another study of a Japanese community, high BCAA intake was associated with a decreased risk of incident diabetes, 17 findings that contrast the findings of the present study. This could be explained by differences in the major food sources contributing to total BCAA intake between the Iranian and Japanese populations. The main sources of BCAAs in the Japanese diet are cereals, potatoes, and starches (23% 25%), fish and shellfish (21% 23%), and meats (14 15%); 17 in Iranian populations, dairy products (38%), cereals (26%), and poultry (12%) are the main sources of dietary BCAAs. As indicated by these two different dietary patterns, there may be nutritional factors contributing to the differences between these two studies. In addition, in the Takayama study population, 17 the range of BCAA intake across tertiles was narrow compared with that in the present study (1 2 difference according to BCAA tertiles vs 4 5 g, respectively), indicating that in the present study there was a considerable difference in BCAA intake between T1 and T3, consequently enabling us to clearly distinguish differences in dietary patterns compared with the Japanese study. 17 Other factors, such as duration of follow-up, confounding factors, and partial differences in the type of outcome assessment (IR vs diabetes), should also be considered when comparing study 2017 Ruijin Hospital, Shanghai Jiaotong University School of Medicine and John Wiley & Sons Australia, Ltd 361

6 BCAA and insulin resistance G. ASGHARI et al. Figure 1 Odds ratios and 95% confidence intervals (CIs) of the risk of incident (a) insulin resistance, (b) hyperinsulinemia, (c) β-cell dysfunction, and (d) insulin insensitivity across tertiles (T1 T3) of leucine, isoleucine, and valine intake. results. Another interesting point in the present study was that the average BMI of participants was in the overweight range, so some of the increase in IR may be due to obesity. However, the mean BMI did not differ significantly between BCAA tertiles and in both Models 1 and 2 there was a significant increase in the incidence of IR across BCAA tertiles. Furthermore, BMI was adjusted for in the regression models; therefore, some of the increased risk of developing IR can be attributed to dietary BCAAs in the present study. Recently, several studies assessing the potential therapeutic effects of BCAA supplementation, in particular leucine, on certain metabolic abnormalities (e.g. IR, hyperglycemia, diabetes, and body weight gain) have reported controversial result Some experimental studies indicated that leucine supplementation improved glucose metabolism and reduced diet-induced IR, especially in high-fat diet-fed mice, by reducing glucose-6- phosphatase gene expression and plasma glucagon levels. 28,30,31 However, others reported that high BCAA Ruijin Hospital, Shanghai Jiaotong University School of Medicine and John Wiley & Sons Australia, Ltd

7 G. ASGHARI et al. BCAA and insulin resistance intake along with a high-protein diet contributes to the development of IR by increasing plasma glucose concentrations and interfering with the intracellular insulin signaling pathway. 29,32 Therefore, taking these apparently contradictory results into consideration, further studies are needed to explore the role of dietary BCCA intake or supplementation on the risk of IR and the pathogenesis of metabolic abnormalities, such as metabolic syndrome, obesity, and type 2 diabetes. Although the mechanisms underlying the role of dietary BCAAs on the risk of IR are not yet fully understood, the following mechanisms have been suggested. High serum concentrations of BCAAs persistently activate the mammalian target of rapamycin complex 1 (mtorc1) signaling pathway, leading to inhibition of glucose transport in insulin-sensitive tissues, including muscle and fat tissues, and IR with serine phosphorylation of insulin receptor substrate 1 (IRS-1), a condition that occurs in response to persistent hyperinsulinemia or aminoacidemia. 12,29 This pathway has an important role in critical cellular and developmental processes, such as cell growth, differentiation, cell survival, and metabolism; 33 in fact, activation of mtorc1 signaling by excess dietary BCAAs and activation of ribosomal S6 kinase 1 (S6K1) phosphorylate IRS-1, block insulin intracellular signaling, and increase IR. 12,14,34 Of the BCAAs, leucine apparently has greater effects in mediating mtorc1 activity and is more important in the insulin signaling pathway than the other two BCAAs. 12 In addition, other studies have suggested that accumulation of mitotoxic metabolites resulting from the metabolism of BCAAs can increase β-cell mitochondrial dysfunction and stimulate stress kinase signaling and β-cell apoptosis. 12,35,36 It is possible that these cell disorders may be associated with IR and the risk of incident diabetes. 12,35,36 The present study has some limitations. First, we did not have serum BCAA concentration data for further investigation of the effects of the dietary intake of the different BCAAs on their serum concentrations. Second, although we attempted to adjust for major confounders in the present study, the effects of unknown factors and residual confounding cannot be ruled out. Despite these limitations, the present study has several strengths, including using a valid and reliable FFQ for estimation of dietary BCAAs and other nutrient intake, a long enough follow-up period to detect new cases of IR, and its population-based prospective design. Conclusion The present study revealed that high consumption of dietary BCAAs may increase the risk of incident IR and can precede the development of metabolic abnormalities, such as metabolic syndrome and diabetes. However, there was no significant association of dietary BCAA intake with β-cell dysfunction and hyperinsulinemia in adults. Acknowledgements The authors express their appreciation to the participants in the Tehran Lipid and Glucose Study for their enthusiastic support and to the staff of the Research Institute for Endocrine Sciences, Tehran Lipid and Glucose Study Unit, for their valuable help. The authors also acknowledge Ms N. Shiva (Research Institute for Endocrine Sciences of Shahid Beheshti University of Medical Sciences) for the English language editing of this manuscript. This work was funded by a grant No from the Shahid Beheshti University of Medical Sciences. Disclosure The authors declare no conflicts of interest. References 1. Abdul-Ghani MA, Tripathy D, DeFronzo RA. Contributions of beta-cell dysfunction and insulin resistance to the pathogenesis of impaired glucose tolerance and impaired fasting glucose. Diabetes Care. 2006; 29: Lillioja S, Mott DM, Spraul M et al. Insulin resistance and insulin secretory dysfunction as precursors of noninsulin-dependent diabetes mellitus. Prospective studies of Pima Indians. N Engl J Med. 1993; 329: Facchini FS, Hua N, Abbasi F, Reaven GM. Insulin resistance as a predictor of age-related diseases. J Clin Endocrinol Metab. 2001; 86: Jeppesen J, Hansen TW, Rasmussen S, Ibsen H, Torp- Pedersen C, Madsbad S. Insulin resistance, the metabolic syndrome, and risk of incident cardiovascular disease: A population-based study. J Am Coll Cardiol. 2007; 49: Yang P, Hu W, Fu Z et al. The positive association of branched-chain amino acids and metabolic dyslipidemia in Chinese Han population. Lipids Health Dis. 2016; 15: Lau C, Faerch K, Glumer C et al. Dietary glycemic index, glycemic load, fiber, simple sugars, and insulin resistance: The Inter99 study. Diabetes Care. 2005; 28: Garcia OP, Ronquillo D, del Carmen Caamano M et al. Zinc, iron and vitamins A, C and E are associated with obesity, inflammation, lipid profile and insulin 2017 Ruijin Hospital, Shanghai Jiaotong University School of Medicine and John Wiley & Sons Australia, Ltd 363

8 BCAA and insulin resistance resistance in Mexican school-aged children. Forum Nutr. 2013; 5: Mahalle N, Kulkarni MV, Naik SS, Garg MK. Association of dietary factors with insulin resistance and inflammatory markers in subjects with diabetes mellitus and coronary artery disease in Indian population. J Diabetes Complications. 2014; 28: Lee CC, Watkins SM, Lorenzo C et al. Branched-chain amino acids and insulin metabolism: The Insulin Resistance Atherosclerosis Study (IRAS). Diabetes Care. 2016; 39: Layman DK, Walker DA. Potential importance of leucine in treatment of obesity and the metabolic syndrome. J Nutr. 2006; 136(Suppl.): 319S NaN. 11. Potier M, Darcel N, Tome D. Protein, amino acids and the control of food intake. Curr Opin Clin Nutr Metab Care. 2009; 12: Lynch CJ, Adams SH. Branched-chain amino acids in metabolic signalling and insulin resistance. Nat Rev Endocrinol. 2014; 10: Wurtz P, Tiainen M, Makinen VP et al. Circulating metabolite predictors of glycemia in middle-aged men and women. Diabetes Care. 2012; 35: Yoon M-S. The emerging role of branched-chain amino acids in insulin resistance and metabolism. Forum Nutr. 2016; 8: Everman S, Mandarino LJ, Carroll CC, Katsanos CS. Effects of acute exposure to increased plasma branchedchain amino acid concentrations on insulin-mediated plasma glucose turnover in healthy young subjects. PLoS One. 2015; 10: e Takeshita Y, Takamura T, Kita Y et al. Beneficial effect of branched-chain amino acid supplementation on glycemic control in chronic hepatitis C patients with insulin resistance: Implications for type 2 diabetes. Metabolism. 2012; 61: Nagata C, Nakamura K, Wada K, Tsuji M, Tamai Y, Kawachi T. Branched-chain amino acid intake and the risk of diabetes in a Japanese community: The Takayama study. Am J Epidemiol. 2013; 178: Zheng Y, Li Y, Qi Q et al. Cumulative consumption of branched-chain amino acids and incidence of type 2 diabetes. Int J Epidemiol. 2016; 45: Azizi F, Ghanbarian A, Momenan AA et al. Prevention of non-communicable disease in a population in nutrition transition: Tehran lipid and glucose study phase II. Trials. 2009; 10: Mirmiran P, Esfahani FH, Mehrabi Y, Hedayati M, Azizi F. Reliability and relative validity of an FFQ for nutrients in the Tehran lipid and glucose study. Public Health Nutr. 2010; 13: Azar M, Sarkisian E. Food Composition Table of Iran: National Nutrition and Food Research Institute. Shaheed Beheshti University, Tehran, United States Department of Agriculture Agricultural Research Service, USDA Food Composition Databases Available from: (Accessed 27 April 2009). G. ASGHARI et al. 23. Momenan AA, Delshad M, Sarbazi N, Rezaei Ghaleh N, Ghanbarian A, Azizi F. Reliability and validity of the Modifiable Activity Questionnaire (MAQ) in an Iranian urban adult population. Arch Iran Med. 2012; 15: Ghasemi A, Tohidi M, Derakhshan A, Hasheminia M, Azizi F, Hadaegh F. Cut-off points of homeostasis model assessment of insulin resistance, beta-cell function, and fasting serum insulin to identify future type 2 diabetes: Tehran lipid and glucose study. Acta Diabetol. 2015; 52: Tohidi M, Ghasemi A, Hadaegh F, Derakhshan A, Chary A, Azizi F. Age- and sex-specific reference values for fasting serum insulin levels and insulin resistance/sensitivity indices in healthy Iranian adults: Tehran lipid and glucose study. Clin Biochem. 2014; 47: Rietman A, Schwarz J, Tome D, Kok FJ, Mensink M. High dietary protein intake, reducing or eliciting insulin resistance? Eur J Clin Nutr. 2014; 68: Newgard CB. Interplay between lipids and branchedchain amino acids in development of insulin resistance. Cell Metab. 2012; 15: Binder E, Bermudez-Silva FJ, Andre C et al. Leucine supplementation protects from insulin resistance by regulating adiposity levels. PLoS One. 2013; 8: e Newgard CB, An J, Bain JR et al. A branched-chain amino acid-related metabolic signature that differentiates obese and lean humans and contributes to insulin resistance. Cell Metab. 2009; 9: Zhang Y, Guo K, LeBlanc RE, Loh D, Schwartz GJ, Yu YH. Increasing dietary leucine intake reduces dietinduced obesity and improves glucose and cholesterol metabolism in mice via multimechanisms. Diabetes. 2007; 56: Eller LK, Saha DC, Shearer J, Reimer RA. Dietary leucine improves whole-body insulin sensitivity independent of body fat in diet-induced obese Sprague-Dawley rats. J Nutr Biochem. 2013; 24: Tremblay F, Krebs M, Dombrowski L et al. Overactivation of S6 kinase 1 as a cause of human insulin resistance during increased amino acid availability. Diabetes. 2005; 54: Zoncu R, Efeyan A, Sabatini DM. mtor: From growth signal integration to cancer, diabetes and ageing. Nat Rev Mol Cell Biol. 2011; 12: Um SH, D Alessio D, Thomas G. Nutrient overload, insulin resistance, and ribosomal protein S6 kinase 1, S6K1. Cell Metab. 2006; 3: Olson KC, Chen G, Xu Y, Hajnal A, Lynch CJ. Alloisoleucine differentiates the branched-chain aminoacidemia of Zucker and dietary obese rats. Obesity (Silver Spring). 2014; 22: Adams SH. Emerging perspectives on essential amino acid metabolism in obesity and the insulin-resistant state. Adv Nutr. 2011; 2: Ruijin Hospital, Shanghai Jiaotong University School of Medicine and John Wiley & Sons Australia, Ltd