Toll-like receptors (TLR) mediate infection-induced inflammation and sterile inflammation by endogenous molecules. Among the TLR family, TLR4 is the best understood. However, while its downstream signaling pathways have been well defined, not all ligands of TLR4 are currently known. Current evidence suggests that saturated fatty acids (SFA) act as non-microbial TLR4 agonists, and trigger its inflammatory response. Thus, our present review provides a new perspective on the potential mechanism by which SFAs could modulate TLR4-induced inflammatory responses: (1) SFAs can be recognized by CD14-TLR4-MD2 complex and trigger inflammatory pathways, similar to lipopolysaccharide (LPS). (2) SFAs lead to modification of gut microbiota with an overproduction of LPS after a high-fat intake, enhancing this natural TLR4 ligand. (3) In addition, this metabolic endotoxemia leads to an oxidative stress thereby producing atherogenic lipids - oxLDL and oxidized phospholipids - which trigger CD36-TLR4-TLR6 inflammatory response. (4) Also, the high SFA consumption increases the lipemia and the mmLDL and oxLDL formation through oxidative modifications of LDL. The mmLDL, unlike oxLDL, is involved in activation of the CD14-TLR4-MD2 inflammatory pathway. Those molecules can induce TLR4 inflammatory response by MyD88-dependent and/or MyD88-independent pathways that, in turn, promotes the expression of proinflammatory transcript factors such as factor nuclear kappa B (NF-κB), which plays a crucial role in the induction of inflammatory mediators (cytokines, chemokines, or costimulatory molecules) implicated in the development and progression of many chronic diseases.

Dietary fat strongly affects human health by modulating gut microbiota composition and low-grade systemic inflammation. High-fat diets have been implicated in reduced gut microbiota richness, increased Firmicutes to Bacteroidetes ratio, and several changes at family, genus and species levels. Saturated (SFA), monounsaturated (MUFA), polyunsaturated (PUFA) and conjugated linolenic fatty acids share important pathways of immune system activation/inhibition with gut microbes, modulating obesogenic and proinflammatory profiles. Mechanisms that link dietary fat, gut microbiota and obesity are mediated by increased intestinal permeability, systemic endotoxemia, and the activity of the endocannabinoid system. Although the probiotic therapy could be a complementary strategy to improve gut microbiota composition, it did not show permanent effects to treat fat-induced dysbiosis. Based upon evidence to date, we believe that high-fat diets and SFA consumption should be avoided, and MUFA and omega-3 PUFA intake should be encouraged in order to regulate gut microbiota and inflammation, promoting body weight/fat control.

CONTEXT AND OBJECTIVE: Diet is an important modifiable factor involved in obesity-induced inflammation. We reviewed clinical trials that assessed the effect of consumption of different fatty acids on the expression of inflammation-related genes, such as cytokines, adipokines, chemokines and transcription factors. DESIGN AND SETTING: Narrative review study conducted at a research center. METHODS:This was a review on the effect of fat intake on inflammatory gene expression in humans. RESULTS: Consumption of saturated fatty acids (SFAs) was related to postprandial upregulation of genes associated with pro-inflammatory pathways in peripheral blood mononuclear cells (PBMCs), in comparison with monounsaturated fatty acid (MUFA) or polyunsaturated fatty acid (PUFA) intake. In addition, acute intake of a high-SFA meal also induced a postprandial pro-inflammatory response for several inflammatory genes in subcutaneous adipose tissue. Both high-MUFA and high-PUFA diets showed anti-inflammatory profiles, or at least a less pronounced pro-inflammatory response than did SFA consumption. However, the results concerning the best substitute for SFAs were divergent because of the large variability in doses of MUFA (20% to 72% of energy intake) and n3 PUFA (0.4 g to 23.7% of energy intake) used in interventions. CONCLUSIONS: The lipid profile of the diet can modulate the genes relating to postprandial and longterm inflammation in PBMCs and adipose tissue. Identifying the optimal fat profile for inflammatory control may be a promising approach for treating chronic diseases such as obesity. RESUMO CONTEXTO E OBJETIVO:A dieta é um importante fator modificável envolvido na inflamação induzida pela obesidade. Nós revisamos ensaios clínicos que avaliaram o efeito do consumo de diferentes ácidos graxos sobre a expressão de genes relacionados com a inflamação, tais como citocinas, adipocitocinas, quimiocinas e fatores de transcrição. TIPO DE ESTUDO E LOCAL: Estudo de revisão narrativa realizado em um centro de pesquisa. MÉTODOS: Revisão do efeito da ingestão de gordura sobre a expressão de genes envolvidos com inflamação em seres humanos. RESULTADOS: O consumo do ácido graxo saturado (AGS) foi relacionado com a regulação favorável pós--prandial de genes associados com vias pró-inflamatórias nas células mononucleares de sangue periféri-co (CMSP), em comparação com a ingestão do ácido graxo monoinsaturado (AGMI) ou do ácido graxo poli-insaturado (AGPI). Além disso, o consumo agudo de uma dieta com alto conteúdo de AGS também induziu uma resposta pró-inflamatória pós-prandial para vários genes da inflamação no tecido adiposo subcutâneo. Ambas as dietas com alto conteúdo de AGMI e AGPI apresentaram perfil anti-inflamatório ou, pelo menos, menor resposta pró-inflamatória em relação ao consumo de AGS. Contudo, os resultados são controversos acerca do melhor substituto para o AGS, devido à grande variabilidade na dose de AGMI (20% a 72% da ingestão energética) e AGPI n3 (0,4 g para 23,7% da ingestão energética) utilizados nos estudos de...

There is a growing mortality related to co-morbidities associated with diabetes mellitus. Intake of polyunsaturated fatty acids (PUFA) has been associated with low cardiometabolic risk and reduction of inflammatory process. The objective of this paper is to review the impact of PUFA intake on glycemic control in diabetic patients as well as to elucidate the possible mechanisms involved. Medline/PubMed electronic database was searched to identify studies published within last five years regarding the effect of PUFA intake on glucose metabolism in type 2 diabetics. The search terms used were "polyunsaturated fatty acid(s)," "PUFA," and "diabetes." We included only interventional studies that assessed the effects of PUFA intake on glucose metabolism - fasting glucose, serum insulin, HbA1c, and HOMA-IR assessment- in type 2 diabetics. Initially, 48 articles were identified, of which one was not available and 41 did not match the inclusion criteria. Within the selected studies, three articles showed an improvement in fasting blood glucose, two showed an increase in fasting glycemia, and there was no effect of intervention in one article only. Based on the analyzed clinical interventional studies, supplementation of 0.42-5.2-g PUFA/day for at least eight weeks may become an alternative treatment for type 2 diabetes mellitus, particularly in Asian subjects.

The metabolic effects of cranberry and blueberry consumption on glycemic control have been evaluated in vitro and in animal models as well as in human studies, although findings have not been systematically reviewed yet. Therefore, a systematic review was carried out of relevant randomized clinical trials (RCTs) in order to assess the effect of berries (blueberry and cranberry) consumption on type 2 diabetes (T2DM) glycemic control. Some evidences were also discussed on the anti-diabetic mechanisms exerted by berries polyphenols. Studies were identified by searching electronic databases: LILACS, PubMed/MEDLINE, Scopus, The Cochrane Library and Web of Science. Three authors independently searched and extracted RCTs in which the effect of berries (cranberry or blueberry) consumption on T2DM glycemic control was assessed. A total of 7 RCTs, involving 270 adults with type 2 diabetes were included. Despite the heterogeneity of the administration forms (in natura, dried, extract, preparations - juice), dosage, duration of the intervention and type of population of the studies involving these two berries some studies highlight the potential benefit of berries, especially of blueberry, on glucose metabolism in T2DM subjects. Daily cranberry juice (240 mL) consumption for 12 weeks and blueberry extract or powder supplementation (9.1 to 9.8 mg of anthocyanins, respectively) for 8 to 12 weeks showed a beneficial effect on glucose control in T2DM subjects. Those results indicate a promising use of these berries in T2DM management; although more studies are required to better understand the mechanisms involved.