The obesity pandemic has been strongly associated with the Western diet, characterized by the consumption of ultra-processed foods. The Western lifestyle causes gut dysbiosis leading to impaired fatty acid metabolism. Therefore, this study aimed to evaluate shifts in gut microbiota and correlate these with serum fatty acid profiles in male Wistar rats fed a cafeteria diet. Ten male rats were fed with standard diet (CTL, n = 5) and cafeteria diet (CAF, n = 5) for fifteen weeks. Body weight and food intake were recorded once and three times per week, respectively. At the end of the study, fresh fecal samples were collected, tissues were removed, and serum samples were obtained for further analyses. Gut microbiota was analyzed by sequencing the V3-V4 region of 16S rRNA gene. Serum fatty acid profiles were fractioned and quantified via gas chromatography. The CAF diet induced an obese phenotype accompanied by impaired serum fatty acids, finding significantly higher proportions of total saturated fatty acids (SFAs) and C20:3 n-6, and lower C18:1 n-7 and C18:3 n-3 in the phospholipid (PL) fraction. Furthermore, circulating C10:0, total n-3 and n-7 decreased and total monounsaturated fatty acids (MUFAs), including oleic acid C18:1 n-9, increased in the cholesterol ester (CE) fraction. The obesity metabotype may be mediated by gut dysbiosis caused by a cafeteria diet rich in C16:0, C18:0, C18:1 n-9 and C18:2 n-6 fatty acids resulting in a 34:1 omega-6/omega-3 ratio. Therefore, circulating C10:0 was associated with several genera bacteria such as Prevotella (positive) and Anaerotruncus (negative). Two classes of Firmicutes, Bacilli and Erysipelotrichi, were positively correlated with PL- C20:3 n-6 and CE- 18:1 n-9, respectively. TM7 and Bacteroidetes were inversely correlated with PL-SFAs and CE- 18:2 n-6, respectively.

Type 2 diabetes mellitus (T2DM) and metabolic syndrome (MetS) in children and adolescents are characterized by altered lipid metabolism and gut microbiota. Prior untargeted (nonquantitative) lipidomics of the present T2DM and MetS pediatric cohort revealed alterations in plasma lipids. Fatty acids (FAs) bonded to plasma phospholipids (PLs) and cholesterol esters (CEs) reflect endogenous metabolism and exogenous sources. The present study focused on targeted quantification of FAs esterified to plasma PLs and CEs in children and adolescents with T2DM and MetS and healthy controls ( n = 60, ages 7 to 17). Regression models and Spearman correlations assessed associations of esterified FA with the disease, metabolic risk factors, pro-inflammatory cytokines, and gut microbiota composition. T2DM and MetS groups featured higher concentrations of saturated FAs esterified to PLs (C17:0) and CEs (C10:0, C12:0, and C24:0) than healthy controls. Also, both groups had higher omega-6 FA levels, including dihomo-γ-linolenic acid (C20:3n-6) in both plasma fractions (PLs and CEs), C22:5n-6 in PLs, and C18:2n-6 and C20:4n-6 in CEs. These FAs were inversely correlated with high-density lipoprotein cholesterol and directly correlated with obesity, triglycerides, and insulin resistance. Also, MetS had a high CE-omega-6/omega-3 ratio. Gut microbial taxa associated with T2DM and MetS after Tanner, sex, and body mass index percentile adjustment were Agathobacter , Dorea , Fusicatenibacter , and Gemmiger , with higher abundances than those in healthy controls, and the genus Faecalimonas at lower abundances. This work contributes to the current knowledge of lipid metabolism and the role of gut microbiota in T2DM and MetS in children and adolescents.