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Targeted stool metabolomics suggests exploratory catecholamine- and tryptophan-linked metabolic features in autism spectrum disorder.

Code ↔ Paper

4 matches between paragraphs of the paper and lines of its authors' code, computed by the harvester (lexical-v1). Click a colored paragraph or line to see its counterpart.

The 4 matches
  1. [1] § Materials and methods › Statistical analysis › Machine learning ↔ statistical_analysis.Rmd, lines 953–1036 · score 0.77 · Brier score, predicted probabilities, positive class, Calibration, LOESS, smoothed
  2. [2] § Results › Discriminative performance of metabolite features in classifying ASD ↔ statistical_analysis.Rmd, lines 491–587 · score 0.62 · cross validated, positive class, random forest, predicting ASD, ROC, AUC
  3. [3] § Results › Model calibration performance ↔ statistical_analysis.Rmd, lines 953–1036 · score 0.62 · Brier score, predicted probabilities, calibration, LOESS, smoothed, curves
  4. [4] § Materials and methods › Statistical analysis › Machine learning ↔ statistical_analysis.Rmd, lines 491–587 · score 0.60 · Random forest classifiers, cross validation, seed, trees, workflow, fold

Paper

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The authors' code

R Markdown · 1,040 lines · 30 KB · MIT · 4 matches

  1. ---
  2. title: "Targeted ASD Stool Metabolomics Analysis"
  3. author: "Kevin Liu"
  4. date: "`r Sys.Date()`"
  5. output:
  6. pdf_document:
  7. toc: true
  8. keep_tex: true
  9. ---
  10. ```{r setup, include=FALSE, message=FALSE}
  11. knitr::opts_chunk$set(echo = TRUE)
  12. options(scipen = 999)
  13. library(tidyverse)
  14. library(egg)
  15. library(rstatix)
  16. library(tidymodels)
  17. library(yardstick)
  18. library(ranger)
  19. library(pROC)
  20. library(patchwork)
  21. library(scales)
  22. library(broom)
  23. library(ggpubr)
  24. theme_set(theme_article() +
  25. theme(aspect.ratio = 1))
  26. ```
  27. ```{r read_data, message=FALSE}
  28. clin_data = read_csv("data/clin_data.csv")
  29. avg_data = read_csv("data/data_averaged.csv") %>%
  30. left_join(clin_data, by = "subject_id") %>%
  31. relocate(subject_id, group, sex, age) %>%
  32. mutate(group = factor(group, levels = c("NAC", "ASD")),
  33. sex = factor(sex, levels = c("Female", "Male")))
  34. norm_data = read_csv("data/data_normalized.csv") %>%
  35. left_join(clin_data, by = "subject_id") %>%
  36. relocate(subject_id, group, sex, age) %>%
  37. mutate(group = factor(group, levels = c("NAC", "ASD")),
  38. sex = factor(sex, levels = c("Female", "Male")))
  39. name_map = read_csv("data/name_map.csv", na = c("", "NaN"))
  40. levels(avg_data$group)
  41. levels(norm_data$group)
  42. ```
  43. ```{r descriptive_stats}
  44. # Figure S1
  45. avg_data %>%
  46. ggplot(aes(x = age, fill = group)) +
  47. geom_histogram(data = subset(avg_data, group == "NAC"),
  48. aes(y = after_stat(count)), binwidth = 1, boundary = 0, closed = "left") +
  49. geom_histogram(data = subset(avg_data, group == "ASD"),
  50. aes(y = -after_stat(count)), binwidth = 1, boundary = 0, closed = "left") +
  51. scale_y_continuous(labels = abs, limits = c(-10, 10)) +
  52. scale_fill_manual(values = c("NAC" = "#21918c", "ASD" = "#fde725")) +
  53. labs(x = "Age (years)", y = "Number of Subjects", fill = "Group") +
  54. theme(legend.position = "bottom") +
  55. geom_hline(yintercept = 0, linewidth = 0.25) +
  56. coord_flip()
  57. age_tbl = avg_data %>%
  58. group_by(group) %>%
  59. summarise(
  60. value = sprintf(
  61. "%.2f ± %.2f, [%.2f, %.2f]",
  62. mean(age, na.rm = TRUE),
  63. sd(age, na.rm = TRUE),
  64. min(age, na.rm = TRUE),
  65. max(age, na.rm = TRUE)
  66. ),
  67. .groups = "drop"
  68. ) %>%
  69. pivot_wider(names_from = group, values_from = value) %>%
  70. mutate(
  71. Characteristic = "Age (mean ± SD, [min, max])")
  72. sex_tbl = avg_data %>%
  73. count(group, sex) %>%
  74. group_by(group) %>%
  75. mutate(value = sprintf("%d (%.1f%%)", n, 100 * n / sum(n))) %>%
  76. ungroup() %>%
  77. select(group, sex, value) %>%
  78. pivot_wider(names_from = group, values_from = value) %>%
  79. mutate(Characteristic = as.character(sex)) %>%
  80. select(-sex)
  81. wilcox.test(age ~ group, data = avg_data)
  82. fisher.test(table(avg_data$group, avg_data$sex))
  83. # Table 1
  84. bind_rows(age_tbl, sex_tbl) %>%
  85. select(Characteristic, NAC, ASD) %>%
  86. write.csv("output_data/1_demographics.csv")
  87. ```
  88. ```{r get_mol_summary}
  89. num_cols = avg_data %>%
  90. select(where(is.numeric), -subject_id, -age) %>%
  91. names()
  92. # Table 2
  93. avg_data %>%
  94. select(group, all_of(num_cols)) %>%
  95. pivot_longer(
  96. cols = -group,
  97. names_to = "variable",
  98. values_to = "value"
  99. ) %>%
  100. group_by(group, variable) %>%
  101. summarise(
  102. n = n(),
  103. n_zero = sum(value == 0, na.rm = TRUE),
  104. pct_zero = n_zero / n * 100,
  105. n_nonzero = sum(value != 0 & !is.na(value)),
  106. # stats excluding zeros
  107. mean = mean(if_else(value == 0, NA_real_, value), na.rm = TRUE),
  108. sd = sd(if_else(value == 0, NA_real_, value), na.rm = TRUE),
  109. min = min(if_else(value == 0, NA_real_, value), na.rm = TRUE),
  110. max = max(if_else(value == 0, NA_real_, value), na.rm = TRUE),
  111. median = median(if_else(value == 0, NA_real_, value), na.rm = TRUE),
  112. .groups = "drop"
  113. ) %>%
  114. ungroup() %>%
  115. mutate(across(where(is.numeric), \(x) round(x, 2))) %>%
  116. mutate(range = str_c("[", min, ", ", max, "]"),
  117. mean_sd = str_c(mean, " (", sd, ")"),
  118. zeros = str_c(n_zero, "/", n, " (", pct_zero, "%)")) %>%
  119. select(group, variable, mean_sd, range, median, zeros) %>%
  120. write_csv("output_data/2_mol_summary.csv")
  121. ```
  122. ```{r viz_data, fig.dpi=300, fig.width=8}
  123. # Figure 1
  124. avg_data %>%
  125. pivot_longer(cols = starts_with("mol_"), names_to = "molecule") %>%
  126. left_join(name_map %>% select(mol_name, compound_acronym), by = c("molecule" = "mol_name")) %>%
  127. mutate(molecule = compound_acronym) %>%
  128. select(-compound_acronym) %>%
  129. ggplot(aes(x = group, y = value, fill = group)) +
  130. geom_violin() +
  131. geom_jitter(width = 0.2, alpha = 0.5) +
  132. facet_wrap(~ molecule, scales = "free_y", ncol = 6) +
  133. labs(x = "", y = "Concentration (nM)",
  134. fill = "Group") +
  135. theme(legend.position = "bottom", aspect.ratio = 1,
  136. strip.text = element_text(size = 6)) +
  137. scale_fill_manual(values = c("#21918c", "#fde725"))
  138. ```
  139. ```{r corr_matrix, fig.width=10}
  140. num_vars = c("age", grep("^mol_", names(avg_data), value = TRUE))
  141. name_lookup = setNames(c(name_map$compound_acronym, "Age"),
  142. c(name_map$mol_name, "age"))
  143. axis_levels = num_vars
  144. corr_lower_by_group = function(df_group, group_label) {
  145. mat = df_group %>%
  146. select(all_of(num_vars)) %>%
  147. as.matrix()
  148. rc = Hmisc::rcorr(mat, type = "spearman")
  149. R = rc$r
  150. P = rc$P
  151. vars = colnames(R)
  152. idx = which(lower.tri(R), arr.ind = TRUE)
  153. tibble(
  154. Group = group_label,
  155. Var1 = vars[idx[,1]],
  156. Var2 = vars[idx[,2]],
  157. r = as.numeric(R[idx]),
  158. p = as.numeric(P[idx])
  159. )
  160. }
  161. cor_df = bind_rows(
  162. corr_lower_by_group(filter(avg_data, group == "ASD"), "ASD"),
  163. corr_lower_by_group(filter(avg_data, group == "NAC"), "NAC")
  164. ) %>%
  165. group_by(Group) %>%
  166. mutate(
  167. p_adj = p.adjust(p, method = "fdr"), # FDR within each group
  168. p_cap = pmax(p_adj, 1e-300), # avoid -Inf for -log10
  169. Var1 = factor(Var1, levels = axis_levels),
  170. Var2 = factor(Var2, levels = axis_levels),
  171. Significant = !is.na(p_adj) & p_adj < 0.05
  172. ) %>%
  173. ungroup() %>%
  174. mutate(
  175. Var1_label = recode(Var1, !!!name_lookup),
  176. Var2_label = recode(Var2, !!!name_lookup)
  177. )
  178. # Figure 5
  179. cor_df %>%
  180. ggplot(aes(x = Var1_label, y = Var2_label)) +
  181. geom_point(aes(fill = r, size = -log10(p_cap)),
  182. shape = 21, color = "grey60", stroke = 0.1, na.rm = TRUE) +
  183. geom_point(data = filter(cor_df, Significant),
  184. aes(size = -log10(p_cap)),
  185. shape = 21, fill = NA, color = "black", stroke = 0.5, na.rm = TRUE) +
  186. scale_fill_gradient2(low = "blue", mid = "white", high = "red",
  187. midpoint = 0, limits = c(-1, 1),
  188. oob = scales::squish, name = "Spearman r") +
  189. scale_size(range = c(1.5, 6), name = NULL, guide = "none") +
  190. coord_fixed() +
  191. facet_wrap(~ Group, ncol = 2) +
  192. theme_light() +
  193. theme(
  194. axis.text.x = element_text(angle = 45, hjust = 1, vjust = 1),
  195. legend.position = "right"
  196. ) +
  197. labs(x = NULL, y = NULL)
  198. # Table S5
  199. cor_df %>%
  200. filter(p_adj < 0.05) %>%
  201. select(Group, Var1_label, Var2_label, r, p, p_adj) %>%
  202. mutate(
  203. r = signif(r, 3),
  204. p = formatC(p, format = "e", digits = 2),
  205. p_adj = formatC(p_adj, format = "e", digits = 2)
  206. ) %>%
  207. write_csv("output_data/s5_groupwise_sigif_corr.csv")
  208. ```
  209. ```{r corr_scatterplots_all_significant_patchwork, fig.dpi=300, fig.width=10, fig.height=12}
  210. # Supplementary Figure 2
  211. # Scatterplots for all FDR-significant within-group correlations
  212. cor_df_labeled = cor_df %>%
  213. select(-any_of(c("Var1_label", "Var2_label"))) %>%
  214. left_join(
  215. name_map %>% select(mol_name, compound_acronym),
  216. by = c("Var1" = "mol_name")
  217. ) %>%
  218. rename(Var1_label = compound_acronym) %>%
  219. left_join(
  220. name_map %>% select(mol_name, compound_acronym),
  221. by = c("Var2" = "mol_name")
  222. ) %>%
  223. rename(Var2_label = compound_acronym) %>%
  224. mutate(
  225. Var1 = as.character(Var1),
  226. Var2 = as.character(Var2),
  227. Var1_label = if_else(Var1 == "age", "Age", Var1_label),
  228. Var2_label = if_else(Var2 == "age", "Age", Var2_label)
  229. )
  230. panel_order = tribble(
  231. ~Group, ~Var1, ~Var2, ~order,
  232. "ASD", "mol_trp", "mol_niacin", 1,
  233. "NAC", "mol_trp", "mol_kyn", 2,
  234. "ASD", "mol_trp", "mol_gaba", 3,
  235. "ASD", "mol_trp", "mol_ne", 4,
  236. "ASD", "mol_trp", "mol_aea", 5,
  237. "NAC", "mol_trp", "mol_aea", 6,
  238. "ASD", "mol_ne", "mol_aea", 7,
  239. "ASD", "mol_niacin", "mol_gaba", 8,
  240. "ASD", "mol_3nt", "mol_ua", 9,
  241. "ASD", "mol_lca", "mol_dca", 10,
  242. "NAC", "mol_lca", "mol_dca", 11
  243. )
  244. sig_corr_stats = cor_df_labeled %>%
  245. filter(Significant == TRUE) %>%
  246. inner_join(panel_order, by = c("Group", "Var1", "Var2")) %>%
  247. arrange(order) %>%
  248. mutate(
  249. q_label = case_when(
  250. p_adj < 0.001 ~ "q < 0.001",
  251. TRUE ~ str_c("q = ", sprintf("%.3f", p_adj))
  252. ),
  253. stat_label = str_c(
  254. "Spearman r = ", sprintf("%.2f", r),
  255. "\nFDR ", q_label
  256. ),
  257. panel_title = str_c(Group, ": ", Var2_label, " vs ", Var1_label)
  258. )
  259. plot_sig_corr_pair = function(group_label, var1, var2, var1_label, var2_label,
  260. stat_label, panel_title) {
  261. plot_df = avg_data %>%
  262. filter(group == group_label) %>%
  263. transmute(
  264. Group = group,
  265. x = .data[[var2]],
  266. y = .data[[var1]]
  267. ) %>%
  268. filter(x > 0, y > 0)
  269. label_df = plot_df %>%
  270. summarise(
  271. x = 10^(min(log10(x), na.rm = TRUE) + 0.05 * diff(range(log10(x), na.rm = TRUE))),
  272. y = 10^(max(log10(y), na.rm = TRUE) - 0.05 * diff(range(log10(y), na.rm = TRUE)))
  273. ) %>%
  274. mutate(label = stat_label)
  275. ggplot(plot_df, aes(x = x, y = y)) +
  276. geom_point(
  277. aes(fill = Group),
  278. shape = 21,
  279. color = "black",
  280. stroke = 0.2,
  281. size = 1.8,
  282. alpha = 0.8
  283. ) +
  284. geom_smooth(
  285. method = "loess",
  286. se = FALSE,
  287. linewidth = 0.5,
  288. color = "black") +
  289. geom_text(
  290. data = label_df,
  291. aes(x = x, y = y, label = label),
  292. inherit.aes = FALSE,
  293. hjust = 0,
  294. vjust = 1,
  295. size = 2.5,
  296. lineheight = 0.95
  297. ) +
  298. scale_x_log10() +
  299. scale_y_log10() +
  300. scale_fill_manual(values = c("NAC" = "#21918c", "ASD" = "#fde725")) +
  301. labs(
  302. title = panel_title,
  303. x = str_c(var2_label, " (nM, log10)"),
  304. y = str_c(var1_label, " (nM, log10)"),
  305. fill = "Group"
  306. ) +
  307. theme(
  308. plot.title = element_text(size = 8),
  309. axis.title = element_text(size = 7),
  310. axis.text = element_text(size = 6),
  311. aspect.ratio = 1
  312. )
  313. }
  314. sig_corr_plots = pmap(
  315. sig_corr_stats %>%
  316. select(
  317. group_label = Group,
  318. var1 = Var1,
  319. var2 = Var2,
  320. var1_label = Var1_label,
  321. var2_label = Var2_label,
  322. stat_label,
  323. panel_title
  324. ),
  325. plot_sig_corr_pair
  326. )
  327. wrap_plots(sig_corr_plots, ncol = 3, guides = "collect") &
  328. theme(
  329. legend.position = "bottom",
  330. legend.title = element_text(size = 9),
  331. legend.text = element_text(size = 9)
  332. )
  333. ```
  334. ```{r univar_tests}
  335. # norm_data %>%
  336. # pivot_longer(cols = starts_with("mol_"), names_to = "metabolite") %>%
  337. # group_by(metabolite) %>%
  338. # wilcox_test(value ~ group) %>%
  339. # adjust_pvalue(method = "fdr") %>%
  340. # arrange(p) %>%
  341. # left_join(name_map %>% select(mol_name, compound_name), by = c("metabolite" = "mol_name"))
  342. ```
  343. ```{r adj_univar_tests}
  344. adj_univar_lm = norm_data %>%
  345. pivot_longer(cols = starts_with("mol_"), names_to = "molecule", values_to = "value") %>%
  346. group_by(molecule) %>%
  347. do(tidy(lm(value ~ group + age + sex, data = .))) %>%
  348. ungroup() %>%
  349. filter(term == "groupASD") %>%
  350. mutate(p_adj = p.adjust(p.value, method = "fdr")) %>%
  351. arrange(p.value) %>%
  352. select(molecule, estimate, std.error, statistic, p.value, p_adj) %>%
  353. left_join(name_map %>% select(mol_name, compound_acronym), by = c("molecule" = "mol_name")) %>%
  354. mutate(molecule = compound_acronym) %>%
  355. select(-compound_acronym)
  356. ```
  357. ```{r log2fc, fig.dpi=300}
  358. log2fc_result = norm_data %>%
  359. pivot_longer(cols = starts_with("mol_"), names_to = "molecule", values_to = "value") %>%
  360. group_by(group, molecule) %>%
  361. summarise(mean_value = mean(value, na.rm = TRUE), .groups = "drop") %>%
  362. pivot_wider(names_from = group, values_from = mean_value) %>%
  363. mutate(
  364. log2_fc = (ASD - NAC) * log2(10) # Convert log10 difference to log2 scale
  365. ) %>%
  366. arrange(desc(log2_fc)) %>%
  367. left_join(name_map %>% select(mol_name, compound_acronym), by = c("molecule" = "mol_name")) %>%
  368. mutate(molecule = compound_acronym) %>%
  369. select(-compound_acronym)
  370. # Figure 2
  371. log2fc_result %>%
  372. mutate(molecule = fct_rev(fct_inorder(molecule))) %>%
  373. ggplot(aes(x = molecule, y = log2_fc, fill = log2_fc > 0)) +
  374. geom_col() +
  375. coord_flip() +
  376. scale_fill_manual(values = c("TRUE" = "#fde725", "FALSE" = "#21918c"),
  377. labels = c("NAC > ASD", "ASD > NAC")) +
  378. labs(
  379. title = "Log2 Fold Change (ASD vs. NAC)",
  380. x = NULL,
  381. y = "Log2 Fold Change",
  382. fill = "Direction"
  383. ) +
  384. ylim(-2.25, 2.25) +
  385. theme(legend.position = "bottom") +
  386. geom_hline(yintercept = 1, linetype = "dashed", color = "gray") +
  387. geom_hline(yintercept = -1, linetype = "dashed", color = "gray")
  388. # Table S2
  389. log2fc_result %>%
  390. left_join(adj_univar_lm, by = "molecule") %>%
  391. mutate(across(where(is.numeric), \(x) round(x, 4))) %>%
  392. arrange(p.value) %>%
  393. left_join(name_map %>% select(compound_acronym, compound_name), by = c("molecule" = "compound_acronym")) %>%
  394. mutate(molecule = str_c(compound_name, " (", molecule, ")")) %>%
  395. select(-compound_name) %>%
  396. write_csv("output_data/s2_log2fc_adj_univar.csv")
  397. ```
  398. ```{r ne_sensitivity, message=FALSE, fig.width=5, fig.height=4}
  399. # NE sensitivity check
  400. # # NE distribution by group
  401. # ggplot(avg_data, aes(x = group, y = mol_ne, color = group)) +
  402. # geom_boxplot(outlier.shape = NA) +
  403. # geom_jitter(width = 0.1, alpha = 0.7, size = 2) +
  404. # labs(x = NULL, y = "Norepinephrine (nM)")
  405. # Top NE values
  406. ne_top = avg_data %>%
  407. arrange(desc(mol_ne)) %>%
  408. select(subject_id, group, sex, age, mol_ne) %>%
  409. slice_head(n = 10)
  410. ne_top
  411. # IQR-based outlier threshold
  412. Q1_ne = quantile(avg_data$mol_ne, 0.25, na.rm = TRUE)
  413. Q3_ne = quantile(avg_data$mol_ne, 0.75, na.rm = TRUE)
  414. IQR_ne = Q3_ne - Q1_ne
  415. upper_bound_ne = Q3_ne + 1.5 * IQR_ne
  416. upper_bound_ne
  417. avg_data_ne = avg_data %>%
  418. mutate(ne_outlier = mol_ne > upper_bound_ne)
  419. # Full-data test
  420. wilcox.test(mol_ne ~ group, data = avg_data_ne)
  421. # Outlier-removed test
  422. avg_data_ne_no_outliers = avg_data_ne %>%
  423. filter(!ne_outlier)
  424. wilcox.test(mol_ne ~ group, data = avg_data_ne_no_outliers)
  425. # Mean and median by group
  426. avg_data_ne %>%
  427. group_by(group) %>%
  428. summarise(
  429. mean_ne = mean(mol_ne, na.rm = TRUE),
  430. median_ne = median(mol_ne, na.rm = TRUE),
  431. min_ne = min(mol_ne, na.rm = TRUE),
  432. max_ne = max(mol_ne, na.rm = TRUE),
  433. .groups = "drop"
  434. )
  435. ```
  436. ```{r univar_rf}
  437. rf_base_data = avg_data %>%
  438. mutate(group = factor(group, levels = c("NAC", "ASD"))) # ASD is the positive class
  439. set.seed(123)
  440. folds = vfold_cv(rf_base_data, v = 5, strata = group)
  441. mol_names = names(rf_base_data)[str_starts(names(rf_base_data), "mol_")]
  442. get_cv_rf_auc = function(mol) {
  443. df = rf_base_data %>% select(group, !!sym(mol))
  444. rec = recipe(group ~ ., data = df) %>%
  445. step_zv(all_predictors()) # Remove zero-variance predictors (just in case)
  446. rf_spec = rand_forest(trees = 500) %>%
  447. set_mode("classification") %>%
  448. set_engine("ranger", importance = "none")
  449. wf = workflow() %>%
  450. add_recipe(rec) %>%
  451. add_model(rf_spec)
  452. res = fit_resamples(
  453. wf,
  454. resamples = folds,
  455. metrics = metric_set(roc_auc),
  456. control = control_resamples(save_pred = TRUE, verbose = FALSE)
  457. )
  458. auc_val = collect_metrics(res) %>%
  459. filter(.metric == "roc_auc") %>%
  460. pull(mean)
  461. tibble(molecule = mol, auc = auc_val)
  462. }
  463. rf_auc_all = map_dfr(mol_names, get_cv_rf_auc) %>%
  464. arrange(desc(auc))
  465. # rf_auc_all %>%
  466. # mutate(molecule = fct_reorder(molecule, auc)) %>%
  467. # ggplot(aes(x = molecule, y = auc)) +
  468. # geom_col(fill = "#21918c") +
  469. # coord_flip() +
  470. # labs(
  471. # title = "Random Forest Classification Performance by Molecule",
  472. # y = "Cross-Validated AUC",
  473. # x = NULL
  474. # ) +
  475. # geom_hline(yintercept = 0.5, linetype = "dashed", color = "gray")
  476. ind_auc_results = map_dfr(mol_names, function(mol) {
  477. df = avg_data %>% select(group, !!sym(mol))
  478. rec = recipe(group ~ ., data = df) %>%
  479. step_zv(all_predictors())
  480. wf = workflow() %>%
  481. add_recipe(rec) %>%
  482. add_model(rand_forest(trees = 500) %>%
  483. set_mode("classification") %>%
  484. set_engine("ranger"))
  485. res = fit_resamples(
  486. wf, resamples = folds,
  487. metrics = metric_set(roc_auc),
  488. control = control_resamples(save_pred = TRUE)
  489. )
  490. preds = collect_predictions(res)
  491. roc_obj = roc(response = preds$group, predictor = preds$.pred_ASD,
  492. levels = c("NAC", "ASD"), direction = "<", ci = TRUE, boot.n = 2000)
  493. tibble(
  494. metabolite = mol,
  495. auc = as.numeric(auc(roc_obj)),
  496. ci_low = as.numeric(ci.auc(roc_obj)[1]),
  497. ci_high = as.numeric(ci.auc(roc_obj)[3])
  498. )
  499. }) %>%
  500. arrange(desc(auc)) %>%
  501. mutate(
  502. auc_ci = sprintf("%.3f [%.3f-%.3f]", auc, ci_low, ci_high)
  503. ) %>%
  504. select(metabolite, auc_ci) %>%
  505. left_join(name_map %>% select(mol_name, compound_name), by = c("metabolite" = "mol_name")) %>%
  506. mutate(metabolite = compound_name) %>%
  507. select(-compound_name)
  508. # Table S3
  509. ind_auc_results %>%
  510. left_join(name_map %>% select(compound_acronym, compound_name), by = c("metabolite" = "compound_name")) %>%
  511. mutate(metabolite = str_c(metabolite, " (", compound_acronym, ")")) %>%
  512. select(-compound_acronym) %>%
  513. write_csv("output_data/s3_univar_rf_auc.csv")
  514. ```
  515. ```{r univar_roc}
  516. top_molecule = rf_auc_all %>%
  517. slice_max(auc, n = 3) %>%
  518. pull(molecule)
  519. rf_top_data = avg_data %>%
  520. mutate(group = factor(group, levels = c("NAC", "ASD"))) %>%
  521. select(group, all_of(top_molecule))
  522. rec = recipe(group ~ ., data = rf_top_data) %>%
  523. step_zv(all_predictors())
  524. rf_spec = rand_forest(trees = 500) %>%
  525. set_mode("classification") %>%
  526. set_engine("ranger")
  527. wf = workflow() %>%
  528. add_recipe(rec) %>%
  529. add_model(rf_spec)
  530. set.seed(123)
  531. folds = vfold_cv(rf_top_data, v = 5, strata = group)
  532. res = fit_resamples(
  533. wf,
  534. resamples = folds,
  535. metrics = metric_set(roc_auc),
  536. control = control_resamples(save_pred = TRUE)
  537. )
  538. preds = collect_predictions(res)
  539. roc_obj = roc(
  540. response = preds$group,
  541. predictor = preds$.pred_ASD,
  542. levels = c("NAC", "ASD"),
  543. direction = "<",
  544. ci = TRUE,
  545. ci.alpha = 0.95,
  546. boot.n = 2000,
  547. stratified = FALSE
  548. )
  549. roc_df = tibble(
  550. specificity = rev(roc_obj$specificities),
  551. sensitivity = rev(roc_obj$sensitivities)
  552. )
  553. auc_val = auc(roc_obj)
  554. ci_vals = ci.auc(roc_obj)
  555. # ggplot(roc_df, aes(x = 1 - specificity, y = sensitivity)) +
  556. # geom_line(color = "#21918c", linewidth = 1.2) +
  557. # geom_abline(linetype = "dashed", color = "gray") +
  558. # annotate(
  559. # "text",
  560. # x = 0.25,
  561. # y = 0.25,
  562. # label = sprintf("AUC = %.3f [%.3f–%.3f]", auc_val, ci_vals[1], ci_vals[3]),
  563. # hjust = 0,
  564. # size = 5
  565. # ) +
  566. # labs(
  567. # title = paste0("ROC Curve with 95% CI for ", paste0(top_molecule, collapse = ", ")),
  568. # x = "1 - Specificity",
  569. # y = "Sensitivity"
  570. # )
  571. ```
  572. ```{r multivar_rf_all, fig.dpi=300, fig.height=10}
  573. set.seed(123)
  574. folds = vfold_cv(avg_data, v = 5, strata = group)
  575. top_mols = rf_auc_all %>%
  576. slice_max(auc, n = 3) %>%
  577. pull(molecule)
  578. model_definitions = tribble(
  579. ~model_name, ~formula, ~panel_group, ~color,
  580. "Age", group ~ age, "Demographics", "#21908CFF",
  581. "Sex", group ~ sex, "Demographics", "#440154FF",
  582. "Age + Sex", group ~ age + sex, "Demographics", "#FDE725FF",
  583. "BH4", group ~ mol_bh4, "Metabolites", "#35B779FF",
  584. "KYN", group ~ mol_kyn, "Metabolites", "#31688EFF",
  585. "GABA", group ~ mol_gaba, "Metabolites", "#440154FF",
  586. "BH4 + KYN + GABA", reformulate(top_mols, response = "group"), "Metabolites", "#26828EFF",
  587. "Age + BH4 + KYN + GABA", reformulate(c("age", top_mols), response = "group"), "Combined", "#5DC863FF",
  588. "Sex + BH4 + KYN + GABA", reformulate(c("sex", top_mols), response = "group"), "Combined", "#3B528BFF",
  589. "Age + Sex + BH4 + KYN + GABA", reformulate(c("age", "sex", top_mols), response = "group"), "Combined", "#481567FF"
  590. )
  591. get_rf_roc = function(formula, model_label) {
  592. rec = recipe(formula, data = avg_data) %>%
  593. step_zv(all_predictors()) %>%
  594. step_dummy(all_nominal_predictors())
  595. wf = workflow() %>%
  596. add_model(rand_forest(trees = 500, mode = "classification") %>%
  597. set_engine("ranger")) %>%
  598. add_recipe(rec)
  599. res = fit_resamples(
  600. wf, resamples = folds,
  601. metrics = metric_set(roc_auc),
  602. control = control_resamples(save_pred = TRUE)
  603. )
  604. preds = collect_predictions(res)
  605. roc_obj = roc(
  606. response = preds$group,
  607. predictor = preds$.pred_ASD,
  608. levels = c("NAC", "ASD"),
  609. direction = "<",
  610. ci = TRUE, boot.n = 2000
  611. )
  612. tibble(
  613. model_name = model_label,
  614. specificity = rev(roc_obj$specificities),
  615. sensitivity = rev(roc_obj$sensitivities),
  616. auc = as.numeric(auc(roc_obj)),
  617. ci_low = as.numeric(ci.auc(roc_obj)[1]),
  618. ci_high = as.numeric(ci.auc(roc_obj)[3])
  619. )
  620. }
  621. roc_results = model_definitions %>%
  622. mutate(roc = map2(formula, model_name, get_rf_roc)) %>%
  623. unnest(roc, names_sep = "_") %>%
  624. rename(
  625. specificity = roc_specificity,
  626. sensitivity = roc_sensitivity,
  627. auc = roc_auc,
  628. ci_low = roc_ci_low,
  629. ci_high = roc_ci_high
  630. )
  631. roc_labeled = roc_results %>%
  632. group_by(model_name) %>%
  633. mutate(
  634. label = sprintf("%s\nAUC = %.3f [%.3f-%.3f]", model_name, first(auc), first(ci_low), first(ci_high))
  635. ) %>%
  636. ungroup()
  637. label_order = roc_labeled %>%
  638. distinct(model_name, label) %>%
  639. arrange(factor(model_name, levels = model_definitions$model_name)) %>%
  640. pull(label)
  641. roc_labeled = roc_labeled %>%
  642. mutate(label = factor(label, levels = label_order))
  643. plot_roc_group = function(data, panel) {
  644. df = filter(data, panel_group == panel)
  645. ggplot(df, aes(x = 1 - specificity, y = sensitivity, color = label)) +
  646. geom_line(linewidth = 1) +
  647. geom_abline(linetype = "dashed", color = "gray") +
  648. scale_color_manual(values = setNames(df$color, df$label)) +
  649. labs(
  650. x = "1-Specificity",
  651. y = "Sensitivity",
  652. color = NULL
  653. ) +
  654. coord_equal()
  655. }
  656. p_demo = plot_roc_group(roc_labeled, "Demographics")
  657. p_metab = plot_roc_group(roc_labeled, "Metabolites")
  658. p_combined = plot_roc_group(roc_labeled, "Combined")
  659. # Figure 3
  660. p_demo / p_metab / p_combined +
  661. plot_annotation(tag_levels = "A", tag_prefix = "(", tag_suffix = ")")
  662. ```
  663. ```{r multivar_rf_metrics}
  664. set.seed(123)
  665. folds = vfold_cv(avg_data, v = 5, strata = group)
  666. compute_model_metrics = function(formula, label) {
  667. rec = recipe(formula, data = avg_data) %>%
  668. step_zv(all_predictors()) %>%
  669. step_dummy(all_nominal_predictors())
  670. rf_spec = rand_forest(trees = 500) %>%
  671. set_mode("classification") %>%
  672. set_engine("ranger")
  673. wf = workflow() %>%
  674. add_model(rf_spec) %>%
  675. add_recipe(rec)
  676. res = fit_resamples(
  677. wf,
  678. resamples = folds,
  679. metrics = metric_set(roc_auc, accuracy, sens, spec, precision, recall, f_meas),
  680. control = control_resamples(save_pred = TRUE)
  681. )
  682. preds = collect_predictions(res)
  683. roc_obj = roc(
  684. response = preds$group,
  685. predictor = preds$.pred_ASD,
  686. levels = c("NAC", "ASD"),
  687. direction = "<",
  688. ci = TRUE,
  689. boot.n = 2000
  690. )
  691. auc_val = as.numeric(auc(roc_obj))
  692. ci_vals = as.numeric(ci.auc(roc_obj))
  693. metric_vals = preds %>%
  694. summarise(
  695. accuracy = accuracy_vec(group, .pred_class),
  696. sens = sens_vec(group, .pred_class, event_level = "second"),
  697. spec = spec_vec(group, .pred_class, event_level = "second"),
  698. precision = precision_vec(group, .pred_class, event_level = "second"),
  699. recall = recall_vec(group, .pred_class, event_level = "second"),
  700. f_meas = f_meas_vec(group, .pred_class, event_level = "second")
  701. )
  702. tibble(
  703. model = label,
  704. auc = auc_val,
  705. auc_ci_low = ci_vals[1],
  706. auc_ci_high = ci_vals[3]
  707. ) %>%
  708. bind_cols(metric_vals)
  709. }
  710. formulas = list(
  711. "Age" = group ~ age,
  712. "Sex" = group ~ sex,
  713. "Age + Sex" = group ~ age + sex,
  714. "BH4" = group ~ mol_bh4,
  715. "KYN" = group ~ mol_kyn,
  716. "GABA" = group ~ mol_gaba,
  717. "BH4 + KYN + GABA" = reformulate(top_mols, response = "group"),
  718. "Sex + BH4 + KYN + GABA" = reformulate(c("sex", top_mols), response = "group"),
  719. "Age + BH4 + KYN + GABA" = reformulate(c("age", top_mols), response = "group"),
  720. "Age + Sex + BH4 + KYN + GABA" = reformulate(c("age", "sex", top_mols), response = "group")
  721. )
  722. metrics_all = imap_dfr(formulas, compute_model_metrics) %>%
  723. mutate(across(where(is.numeric), ~ round(.x, 3)),
  724. auc = paste0(auc, " [", auc_ci_low, "-", auc_ci_high, "]")) %>%
  725. select(-auc_ci_low, -auc_ci_high)
  726. ```
  727. ```{r rf_model_comparison}
  728. # Model comparison to assess whether adding more metabolites
  729. # improves classification performance beyond the top 3 features.
  730. set.seed(123)
  731. folds = vfold_cv(avg_data, v = 5, strata = group)
  732. # Select metabolite sets
  733. top3_mols = rf_auc_all %>%
  734. slice_max(auc, n = 3, with_ties = FALSE) %>%
  735. pull(molecule)
  736. top5_mols = rf_auc_all %>%
  737. slice_max(auc, n = 5, with_ties = FALSE) %>%
  738. pull(molecule)
  739. all_mols = names(avg_data)[str_starts(names(avg_data), "mol_")]
  740. feature_labels = list(
  741. "Top 3 metabolites" = str_c(top3_mols, collapse = ", "),
  742. "Top 3 + Trp" = str_c(c(top3_mols, "mol_trp"), collapse = ", "),
  743. "Top 5 metabolites" = str_c(top5_mols, collapse = ", "),
  744. "All 18 metabolites" = "All metabolites"
  745. )
  746. # Reuse the same modeling framework as in Table S4
  747. compute_model_metrics_compare = function(formula, label) {
  748. rec = recipe(formula, data = avg_data) %>%
  749. step_zv(all_predictors()) %>%
  750. step_dummy(all_nominal_predictors())
  751. rf_spec = rand_forest(trees = 500) %>%
  752. set_mode("classification") %>%
  753. set_engine("ranger")
  754. wf = workflow() %>%
  755. add_model(rf_spec) %>%
  756. add_recipe(rec)
  757. res = fit_resamples(
  758. wf,
  759. resamples = folds,
  760. metrics = metric_set(roc_auc),
  761. control = control_resamples(save_pred = TRUE)
  762. )
  763. preds = collect_predictions(res) %>%
  764. mutate(
  765. .pred_class = factor(
  766. if_else(.pred_ASD >= 0.5, "ASD", "NAC"),
  767. levels = c("NAC", "ASD")
  768. )
  769. )
  770. roc_obj = roc(
  771. response = preds$group,
  772. predictor = preds$.pred_ASD,
  773. levels = c("NAC", "ASD"),
  774. direction = "<",
  775. ci = TRUE,
  776. boot.n = 2000
  777. )
  778. auc_val = as.numeric(auc(roc_obj))
  779. ci_vals = as.numeric(ci.auc(roc_obj))
  780. metric_vals = preds %>%
  781. summarise(
  782. accuracy = accuracy_vec(group, .pred_class),
  783. sens = sens_vec(group, .pred_class, event_level = "second"),
  784. spec = spec_vec(group, .pred_class, event_level = "second"),
  785. precision = precision_vec(group, .pred_class, event_level = "second"),
  786. f_meas = f_meas_vec(group, .pred_class, event_level = "second")
  787. )
  788. tibble(
  789. model = label,
  790. auc = auc_val,
  791. auc_ci_low = ci_vals[1],
  792. auc_ci_high = ci_vals[3]
  793. ) %>%
  794. bind_cols(metric_vals)
  795. }
  796. # Define comparison models
  797. compare_formulas = list(
  798. "Top 3 metabolites" = reformulate(top3_mols, response = "group"),
  799. "Top 3 + Trp" = reformulate(c(top3_mols, "mol_trp"), response = "group"),
  800. "Top 5 metabolites" = reformulate(top5_mols, response = "group"),
  801. "All 18 metabolites" = reformulate(all_mols, response = "group")
  802. )
  803. # Run comparison
  804. rf_model_compare = imap_dfr(compare_formulas, compute_model_metrics_compare) %>%
  805. mutate(
  806. features = feature_labels[model] %>% unlist()
  807. ) %>%
  808. mutate(
  809. across(where(is.numeric), \(x) round(x, 3)),
  810. auc = paste0(auc, " [", auc_ci_low, "-", auc_ci_high, "]")
  811. ) %>%
  812. select(model, features, everything(), -auc_ci_low, -auc_ci_high)
  813. rf_model_compare
  814. # Optional export for supplement
  815. rf_model_compare %>%
  816. write_csv("output_data/s6_rf_model_comparison.csv")
  817. ```
  818. ```{r multivar_rf_calibration, fig.dpi=300, fig.height=10}
  819. get_calibration_metrics = function(formula, model_label) {
  820. rec = recipe(formula, data = avg_data) %>%
  821. step_zv(all_predictors()) %>%
  822. step_dummy(all_nominal_predictors())
  823. wf = workflow() %>%
  824. add_model(rand_forest(trees = 500, mode = "classification") %>% set_engine("ranger")) %>%
  825. add_recipe(rec)
  826. res = fit_resamples(
  827. wf, resamples = folds,
  828. control = control_resamples(save_pred = TRUE)
  829. )
  830. preds = collect_predictions(res) %>%
  831. mutate(group = factor(group, levels = c("NAC", "ASD"))) # ASD = positive class
  832. brier = mean((if_else(preds$group == "ASD", 1, 0) - preds$.pred_ASD)^2)
  833. cal_curve_raw = preds %>%
  834. transmute(
  835. pred = .pred_ASD,
  836. obs = as.integer(group == "ASD"),
  837. model_name = model_label
  838. )
  839. list(
  840. brier = tibble(model_name = model_label, brier_score = brier),
  841. curve_raw = cal_curve_raw
  842. )
  843. }
  844. set.seed(123)
  845. cal_results = model_definitions %>%
  846. mutate(cal = map2(formula, model_name, get_calibration_metrics))
  847. brier_all = map_dfr(cal_results$cal, "brier")
  848. curve_all_raw = map_dfr(cal_results$cal, "curve_raw")
  849. curve_all_annotated = curve_all_raw %>%
  850. left_join(model_definitions %>% select(model_name, panel_group, color), by = "model_name") %>%
  851. left_join(brier_all, by = "model_name") %>%
  852. mutate(
  853. label = sprintf("%s\nBrier = %.3f", model_name, brier_score)
  854. )
  855. label_order_brier = model_definitions %>%
  856. left_join(brier_all, by = "model_name") %>%
  857. mutate(label = sprintf("%s\nBrier = %.3f", model_name, brier_score)) %>%
  858. pull(label)
  859. curve_all_annotated = curve_all_annotated %>%
  860. mutate(label = factor(label, levels = label_order_brier))
  861. plot_calibration_panel = function(data, panel_name) {
  862. df = filter(data, panel_group == panel_name)
  863. ggplot(df, aes(x = pred, y = obs, color = label)) +
  864. geom_smooth(method = "loess", formula = y ~ x, se = FALSE, span = 1, linewidth = 1) +
  865. geom_abline(slope = 1, intercept = 0, linetype = "dashed", color = "gray50") +
  866. scale_color_manual(values = setNames(df$color, df$label)) +
  867. labs(
  868. x = "Predicted Probability (ASD)",
  869. y = "Observed Proportion (ASD)",
  870. color = NULL
  871. ) +
  872. coord_fixed(xlim = c(0, 1), ylim = c(0, 1))
  873. }
  874. p_cal_demo = plot_calibration_panel(curve_all_annotated, "Demographics")
  875. p_cal_metab = plot_calibration_panel(curve_all_annotated, "Metabolites")
  876. p_cal_combined = plot_calibration_panel(curve_all_annotated, "Combined")
  877. # Figure 4
  878. p_cal_demo / p_cal_metab / p_cal_combined +
  879. plot_annotation(tag_levels = "A", tag_prefix = "(", tag_suffix = ")")
  880. # Table S4
  881. metrics_all %>%
  882. left_join(brier_all %>% mutate(brier_score = signif(brier_score, 3)), by = c("model" = "model_name")) %>%
  883. write_csv("output_data/s4_multivar_rf_perf_brier_scores.csv")
  884. ```
  885. ```{r session-info}
  886. sessionInfo()
  887. ```

statistical_analysis.Rmd at commit f07a3a4, under MIT · at the source

Overview

Authors: Kevin Liu1, Huixi Li2, Shaohan Zhang3, Muya Xi1, Junru Zhu2,4, Jonathan Chen3, William Xu3, Alexander Xie1, Alexandros Makriyannis2, Jason J. Guo2,4, Xue-Jun Kong1,3,5
  1. Fetal-Neonatal Neuroimaging and Developmental Science Center, Division of Newborn Medicine, Boston Children’s Hospital, Boston, MA, United States
  2. Department of Pharmaceutical Sciences, Center for Drug Discovery, Northeastern University, Boston, MA, United States
  3. Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States
  4. Department of Chemistry and Chemical Biology, Barnett Institute for Chemical and Biological Analysis, Northeastern University, Boston, MA, United States
  5. Department of Medicine and Psychiatry, Beth Israel Deaconess Medical Center, Boston, MA, United States
Journal: Frontiers in neuroscience, volume 20, article 1858005
Dates: received 16 April 2026; accepted 22 June 2026; published online 3 July 2026
Type: Research article · Language: English
License: CC BY
Identifiers: DOI 10.3389/fnins.2026.1858005 · PMID 42490967 · PMCID PMC13375968 · OpenAlex W7167221654
Open access: gold, a free copy (OpenAlex)
Status: code verified
Categories: genetics / omics (modality), autism (population), clinical / translational (subfield)
Methods: Connectivity, Statistics, Machine learning
Keywords: autism spectrum disorder, biomarkers, catecholamines, gut-brain axis, machine learning, microbiome, stool metabolomics, tryptophan metabolism
Topic: Autism Spectrum Disorder Research (Cognitive Neuroscience, Neuroscience), according to OpenAlex
Citations: not cited yet (Europe PMC); 62 references in the paper

Abstract

Background: Gut-brain axis dysregulation and microbiome-linked metabolic alterations have been implicated in autism spectrum disorder (ASD), but the contribution of gut-derived neuroactive metabolites remains incompletely characterized.

Methods: We conducted a cross-sectional case-control study of 59 participants (32 ASD, 27 controls) and quantified 18 stool metabolites related to catecholamine synthesis, inhibitory neurotransmission, and tryptophan-linked NAD+-precursor metabolism using targeted liquid chromatography-tandem mass spectrometry. Group differences were assessed using fold-change analysis and linear models adjusted for age and sex. Random forest models evaluated classification performance, and within-group Spearman correlations were used to examine metabolic relationships.

Results: Norepinephrine showed the largest increase in ASD, whereas dopamine and tetrahydrobiopterin exhibited nominal group differences that did not remain significant after correction for multiple testing. A three-metabolite panel comprising tetrahydrobiopterin, γ-aminobutyric acid, and kynurenine showed exploratory discrimination between groups (area under the receiver operating characteristic curve = 0.750, 95% confidence interval 0.622–0.878), but this performance requires external validation. Correlation analysis revealed conserved bile acid coupling in both groups. In controls, tryptophan was positively associated with kynurenine, whereas this relationship was not observed in ASD. Instead, ASD samples showed broader associations between tryptophan and metabolites linked to neurotransmission and NAD+-precursor metabolism.

Conclusion: Stool metabolite profiling revealed altered organization of tryptophan- and catecholamine-linked metabolic associations in ASD and identified a small metabolite panel with exploratory discriminative potential. These findings provide a foundation for future studies examining gut-derived neuroactive metabolites in ASD and their relationship to gut-brain axis biology.

Reproduced under the paper's license (CC BY), from the paper cited above.

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kevinliu-bmb/targeted-asd-stool-metabolomics

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  • 4 matches between paragraphs of the paper and lines of the code (method lexical-v1);
  • neither the text of the paper nor the code itself.

Its JSON (tracing-map.json) is deposited on Zenodo with its DOI once the map is validated.

Data

No dataset and no data link were found in the paper.

Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Reproduced under the paper's license (CC BY), from the paper cited above.

Versions

The history of this record: each version stored by the harvester or made by a correction of its authors or of the maintainers of its code, and what changed in its facts. The texts of the paper (its abstract, its availability statements) are not part of it; versions that changed only those are not listed.

Version 1, 27 September 2026: the first record

Recorded: type, language, journal, volume, pages, dates, 11 authors, 8 keywords, 2 funders, 61 references.

Cite

This paper

Liu, K., Li, H., Zhang, S., Xi, M., Zhu, J., Chen, J., Xu, W., Xie, A., Makriyannis, A., Guo, J. J., & Kong, X.-J. (2026). Targeted stool metabolomics suggests exploratory catecholamine- and tryptophan-linked metabolic features in autism spectrum disorder. Frontiers in neuroscience, 20, 1858005. https://doi.org/10.3389/fnins.2026.1858005

BibTeX

@article{liu2026targeted,
author = {Liu, Kevin and Li, Huixi and Zhang, Shaohan and Xi, Muya and Zhu, Junru and Chen, Jonathan and Xu, William and Xie, Alexander and Makriyannis, Alexandros and Guo, Jason J. and Kong, Xue-Jun},
title = {{Targeted stool metabolomics suggests exploratory catecholamine- and tryptophan-linked metabolic features in autism spectrum disorder}},
journal = {Frontiers in neuroscience},
year = {2026},
month = jul,
volume = {20},
pages = {1858005},
publisher = {Frontiers Media SA},
issn = {1662-4548},
doi = {10.3389/fnins.2026.1858005},
url = {https://doi.org/10.3389/fnins.2026.1858005},
pmid = {42490967},
pmcid = {PMC13375968}
}

RIS

TY - JOUR
AU - Liu, Kevin
AU - Li, Huixi
AU - Zhang, Shaohan
AU - Xi, Muya
AU - Zhu, Junru
AU - Chen, Jonathan
AU - Xu, William
AU - Xie, Alexander
AU - Makriyannis, Alexandros
AU - Guo, Jason J.
AU - Kong, Xue-Jun
TI - Targeted stool metabolomics suggests exploratory catecholamine- and tryptophan-linked metabolic features in autism spectrum disorder
T2 - Frontiers in neuroscience
J2 - Front Neurosci
PY - 2026
DA - 2026/07/03
VL - 20
SP - 1858005
SN - 1662-4548
PB - Frontiers Media SA
DO - 10.3389/fnins.2026.1858005
UR - https://doi.org/10.3389/fnins.2026.1858005
LA - en
ER -

CSL-JSON

{
"id": "10.3389/fnins.2026.1858005",
"type": "article-journal",
"title": "Targeted stool metabolomics suggests exploratory catecholamine- and tryptophan-linked metabolic features in autism spectrum disorder",
"container-title": "Frontiers in neuroscience",
"author": [
{
"family": "Liu",
"given": "Kevin"
},
{
"family": "Li",
"given": "Huixi"
},
{
"family": "Zhang",
"given": "Shaohan"
},
{
"family": "Xi",
"given": "Muya"
},
{
"family": "Zhu",
"given": "Junru"
},
{
"family": "Chen",
"given": "Jonathan"
},
{
"family": "Xu",
"given": "William"
},
{
"family": "Xie",
"given": "Alexander"
},
{
"family": "Makriyannis",
"given": "Alexandros"
},
{
"family": "Guo",
"given": "Jason J."
},
{
"family": "Kong",
"given": "Xue-Jun"
}
],
"container-title-short": "Front Neurosci",
"volume": "20",
"page": "1858005",
"DOI": "10.3389/fnins.2026.1858005",
"PMID": "42490967",
"PMCID": "PMC13375968",
"ISSN": "1662-4548",
"publisher": "Frontiers Media SA",
"URL": "https://doi.org/10.3389/fnins.2026.1858005",
"language": "en",
"issued": {
"date-parts": [
[
2026,
7,
3
]
]
}
}

The tracing map gets a citation of its own once an author has validated it and it has a DOI.

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