Upregulation of free fatty acid receptors in periodontal tissues of patients with metabolic syndrome and periodontitis

Lipotoxicity: The missing link between diabetes and periodontitis?

Lipotoxicity refers to the accumulation of lipids in tissues other than adipose tissue (body fat). It is one of the major pathophysiological mechanisms responsible for the progression of diabetes complications such as non-alcoholic fatty liver disease and diabetic nephropathy. Accumulating evidence indicates that lipotoxicity also contributes significantly to the toxic effects of diabetes on periodontitis. Therefore, we reviewed the current in vivo, in vitro, and clinical evidence of the detrimental effects of lipotoxicity on periodontitis, focusing on its molecular mechanisms, especially oxidative and endoplasmic reticulum stress, inflammation, ceramides, adipokines, and programmed cell death pathways. By elucidating potential therapeutic strategies targeting lipotoxicity and describing their associated mechanisms and clinical outcomes, including metformin, statins, liraglutide, adiponectin, and omega-3 PUFA, this review seeks to provide a more comprehensive and effective treatment framework against diabetes-associated periodontitis. Furthermore, the challenges and future research directions are proposed, aiming to contribute to a more profound understanding of the impact of lipotoxicity on periodontitis.

Sports Diet and Oral Health in Athletes: A Comprehensive Review

Food and fluid supply is fundamental for optimal athletic performance but can also be a risk factor for caries, dental erosion, and periodontal diseases, which in turn can impair athletic performance. Many studies have reported a high prevalence of oral diseases in elite athletes, notably dental caries 20-84%, dental erosion 42-59%, gingivitis 58-77%, and periodontal disease 15-41%, caused by frequent consumption of sugars/carbohydrates, polyunsaturated fats, or deficient protein intake. There are three possible major reasons for poor oral health in athletes which are addressed in this review: oxidative stress, sports diet, and oral hygiene. This update particularly summarizes potential sports nutritional effects on athletes' dental health. Overall, sports diet appropriately applied to deliver benefits for performance associated with oral hygiene requirements is necessary to ensure athletes' health. The overall aim is to help athletes, dentists, and nutritionists understand the tangled connections between sports diet, oral health, and oral healthcare to develop mitigation strategies to reduce the risk of dental diseases due to nutrition.

Effects of probiotics in rats with experimental metabolic syndrome and periodontitis: An investigation of the intestine-adipose tissue axis

BACKGROUND

This study evaluated the systemic (intestine and adipose tissue) and local (periodontal tissues) impact of probiotic therapy in rats with metabolic syndrome (MS) associated or not with periodontitis (PE).

METHODS

Forty-eight rats received a high-fat diet for induction of MS for 16 weeks. They were subdivided into groups with (+) and without (-) PE, receiving (*) or not (**) receiving probiotics (PROB): MS (-**), MSP (-*), MSPE (+**), and MSPEP (+*). PROB administration (Bifidobacterium animalis subsp. lactis HN019) started on the 8th week of the study and PE was induced on the 14th week by placing ligature on the animals' lower first molars. Euthanasia occurred in the 16th week. Biomolecular, immunoenzymatic assays, and histomorphometric analyses were performed. The data obtained were statistically analyzed (ANOVA, Tukey, p < 0.05).

RESULTS

The MSPEP group exhibited reduced alveolar bone loss when compared with the MSPE group, as well as lower levels of hepatic steatosis and proteinuria (p < 0.05). In the intestinal environment, the MSPE group exhibited significantly lower villus height and crypt depth, as well as a greater increase in Bacillota when compared with the MSPEP group (p < 0.05). The MSPEP group showed lower adipokine gene expression (LEPR, NAMPT, and FABP4) in adipose tissue than the MSPE group (p < 0.05).

CONCLUSION

The probiotic B. lactis HN019 reduced the severity of experimental periodontitis and modulated the expression of lipogenic genes and intestinal morphological and microbiological parameters in rats with MS.

GPR40 deficiency worsens metabolic syndrome-associated periodontitis in mice

BACKGROUND AND OBJECTIVE

G protein-coupled receptor 40 (GPR40) is a receptor for medium- and long-chain free fatty acids (FFAs). GPR40 activation improves type 2 diabetes mellitus (T2DM), metabolic syndrome (MetS), and the complications of T2DM and MetS. Periodontitis, a common oral inflammatory disease initiated by periodontal pathogens, is another complication of T2DM and MetS. Since FFAs play a key role in the pathogenesis of MetS which exacerbates periodontal inflammation and GPR40 is a FFA receptor with anti-inflammatory properties, it is important to define the role of GPR40 in MetS-associated periodontitis.

MATERIALS AND METHODS

We induced MetS and periodontitis by high-fat diet and periodontal injection of lipopolysaccharide (LPS), respectively, in wild-type and GPR40-deficient mice and determined alveolar bone loss and periodontal inflammation using micro-computed tomography, histology, and osteoclast staining. We also performed in vitro study to determine the role of GPR40 in the expression of proinflammatory genes.

RESULTS

The primary outcome of the study is that GPR40 deficiency increased alveolar bone loss and enhanced osteoclastogenesis in control mice and the mice with both MetS and periodontitis. GPR40 deficiency also augmented periodontal inflammation in control mice and the mice with both MetS and periodontitis. Furthermore, GPR40 deficiency led to increased plasma lipids and insulin resistance in control mice but had no effect on the metabolic parameters in mice with MetS alone. For mice with both MetS and periodontitis, GPR40 deficiency increased insulin resistance. Finally, in vitro studies with macrophages showed that deficiency or inhibition of GPR40 upregulated proinflammatory genes while activation of GPR40 downregulated proinflammatory gene expression stimulated synergistically by LPS and palmitic acid.

CONCLUSION

GPR40 deficiency worsens alveolar bone loss and periodontal inflammation in mice with both periodontitis and MetS, suggesting that GPR40 plays a favorable role in MetS-associated periodontitis. Furthermore, GPR40 deficiency or inhibition in macrophages further upregulated proinflammatory and pro-osteoclastogenic genes induced by LPS and palmitic acid, suggesting that GPR40 has anti-inflammatory and anti-osteoclastogenic properties.

Oncogenic signaling of the free-fatty acid receptors FFA1 and FFA4 in human breast carcinoma cells

Globally, breast cancer is the most frequent type of cancer in women, and most breast cancer-associated deaths are due to metastasis and recurrence of the disease. Dietary habits, specifically dietary fat intake is a crucial risk factor involved in breast cancer development and progression. Decades of research has revealed that free-fatty acids (FFA) modulate carcinogenic processes through fatty acid metabolism and lipid peroxidation. The ground-breaking discovery of free-fatty acid receptors, which are members of the G-protein coupled receptor (GPCR) superfamily, has led to the realization that FFA can also act via these receptors to modulate carcinogenic effects. The long-chain free-fatty acid receptors FFA1 (previously termed GPR40) and FFA4 (previously termed GPR120) are activated by mono- and polyunsaturated fatty acids including ω-3, 6, and 9 fatty acids. Initial enthusiasm towards the study of these receptors focused on their insulin secretagogue and sensitization effects, and the downstream associated metabolic regulation. However, recent studies have demonstrated that abnormal expression and/or aberrant FFA1/FFA4 signaling are evident in human breast carcinomas, suggesting that FFA receptors could be a promising target in the treatment of breast cancer. The current review discusses the diverse roles of FFA1 and FFA4 in the regulation of cell proliferation, migration, invasion, and chemotherapy resistance in human breast carcinoma cells and tissue.

Loss of GPR40 in LDL receptor-deficient mice exacerbates high-fat diet-induced hyperlipidemia and nonalcoholic steatohepatitis

GPR40, a G protein-coupled receptor for free fatty acids (FFAs), is considered as a therapeutic target for type 2 diabetes mellitus (T2DM) since GPR40 activation in pancreatic beta cells enhances glucose-stimulated insulin secretion. Nonalcoholic fatty liver disease (NAFLD) is a common complication of T2DM or metabolic syndrome (MetS). However, the role of GPR40 in NAFLD associated with T2DM or MetS has not been well established. Given that it is known that cholesterol and FFAs are critically involved in the pathogenesis of nonalcoholic steatohepatitis (NASH) and LDL receptor (LDLR)-deficient mice are a good animal model for human hyperlipidemia including high cholesterol and FFAs, we generated GPR40 and LDLR double knockout (KO) mice in this study to determine the effect of GPR40 KO on hyperlipidemia-promoted NASH. We showed that GPR40 KO increased plasma levels of cholesterol and FFAs in high-fat diet (HFD)-fed LDLR-deficient mice. We also showed that GPR40 KO exacerbated HFD-induced hepatic steatosis, inflammation and fibrosis. Further study demonstrated that GPR40 KO led to upregulation of hepatic CD36 and genes involved in lipogenesis, fatty acid oxidation, fibrosis and inflammation. Finally, our in vitro mechanistic studies showed that while CD36 was involved in upregulation of proinflammatory molecules in macrophages by palmitic acid (PA) and lipopolysaccharide (LPS), GPR40 activation in macrophages exerts anti-inflammatory effects. Taken together, this study demonstrated for the first time that loss of GPR40 in LDLR-deficient mice exacerbated HFD-induced hyperlipidemia, hepatic steatosis, inflammation and fibrosis potentially through a CD36-dependent mechanism, suggesting that GPR40 may play a beneficial role in hyperlipidemia-associated NASH in LDLR-deficient mice.

Obesity, Bone Loss, and Periodontitis: The Interlink

Obesity and periodontitis are both common health concerns that have given rise to considerable economic and societal burden worldwide. There are established negative relationships between bone metabolism and obesity, obesity and diabetes mellitus (DM), and DM and periodontitis, to name a few, with osteoporosis being considered a long-term complication of obesity. In the oral cavity, bone metabolic disorders primarily display as increased risks for periodontitis and alveolar bone loss. Obesity-driven alveolar bone loss and mandibular osteoporosis have been observed in animal models without inoculation of periodontopathogens. Clinical reports have also indicated a possible association between obesity and periodontitis. This review systematically summarizes the clinical periodontium changes, including alveolar bone loss in obese individuals. Relevant laboratory-based reports focusing on biological interlinks in obesity-associated bone remodeling via processes like hyperinflammation, immune dysregulation, and microbial dysbiosis, were reviewed. We also discuss the potential mechanism underlying obesity-enhanced alveolar bone loss from both the systemic and periodontal perspectives, focusing on delineating the practical considerations for managing periodontal disease in obese patients.

Fisetin attenuates periodontitis through FGFR1/TLR4/NLRP3 inflammasome pathway

The purpose of the present study was to investigate the pharmacological effect of Fisetin on experimental periodontitis in rats and explore its potential mechanism. The ligature/LPS method was used to induce periodontitis in rats. LPS was employed to cause inflammation in Human gingival fibroblasts (HGF). The transfections with FGFR1 SiRNA, NLRP3 SiRNA and the selective TLR4 inhibitor TAK242 were used to investigate the mechanism of Fisetin-mediated inflammatory reaction in LPS-induced HGF. As a result, Fisetin reduced the alveolar bone gap, reversed histopathological lesion and inhibited serum inflammatory cytokine concentration in periodontitis rats. Fisetin decreased the inflammatory cytokine contents in the supernatant of LPS-induced HGF. The inhibitory effect of Fisetin might be attributed to FGFR1/TLR4/NLRP3 inflammasome pathway both in vivo and in vitro. The suppressions of FGFR1, TLR4 and NLRP3 proved that FGFR1/TLR4/NLRP3 signaling was involved in the Fisetin-mediated inflammatory response. Fisetin also inhibited NLRP3 priming. The data demonstrated that Fisetin attenuated periodontitis by inhibiting inflammatory reaction via FGFR1/TLR4/NLRP3 inflammasome pathway.

Blockade of fatty acid signalling inhibits lipopolysaccharide-induced macrophage recruitment and progression of apical periodontitis

AIM

To examine the role of palmitic acid in lipopolysaccharide (LPS)-stimulated chemotaxis of macrophages and the potential contribution of saturated fatty acid in signalling during the pathogenesis of apical periodontitis.

METHODOLOGY

J774, a mouse macrophage cell line, was used in the experiments. After treatment with LPS, proteolytic maturation of sterol regulatory element-binding protein-1c (SREBP-1c) and expression of fatty acid synthase (FASN) were examined by Western analysis. Levels of palmitic acid were measured by reverse phase-high performance liquid chromatography-mass spectrometry. Knockdown of SREBP-1c and FASN was accomplished by small interfering RNA technology. Secretion of CC-chemokine ligand 2 (CCL2) and cellular chemotaxis were assessed by enzyme-linked immunosorbent assay and transwell migration assay, respectively. Sulfo-N-succinimidyl oleate (SSO) treatment was used to inhibit fatty acid signalling in vitro and also in a rat model of apical periodontitis. All data were first subjected to Levene's test. In vitro data were then analysed using ANOVA followed by Tukey's multiple comparison test. Data from animal experiments were analysed by independent t-tests. The significant level was set at 0.05.

RESULTS

LPS stimulated proteolytic maturation of SREBP-1c and FASN expression in macrophages and significantly enhanced palmitic acid synthesis (P < 0.05). Knockdown of SREBP-1c attenuated LPS-enhanced FASN expression. Knockdown of FASN significantly suppressed LPS-enhanced palmitic acid synthesis (P < 0.05). LPS and exogenous palmitic acid significantly enhanced CCL2 secretion and macrophage chemotaxis (all P < 0.05). Inhibition of FASN expression significantly alleviated LPS-augmented CCL2 secretion (P < 0.05). SSO significantly suppressed CCL2 secretion and macrophage chemotaxis augmented by LPS and palmitic acid (all P < 0.05). In a rat model of induced apical periodontitis, SSO treatment significantly attenuated progression of apical periodontitis and macrophage recruitment (all P < 0.05).

CONCLUSIONS

LPS/SREBP-1c/FASN/palmitic acid signalling contributed to tissue destruction caused by bacterial infection. Modulation of lipid metabolism and signalling may be helpful for the management of apical periodontitis.

GPR40 deficiency is associated with hepatic FAT/CD36 upregulation, steatosis, inflammation, and cell injury in C57BL/6 mice

G-protein-coupled receptor 40 (GPR40) is highly expressed in pancreatic islets, and its activation increases glucose-stimulated insulin secretion from pancreas. Therefore, GPR40 is considered as a target for type 2 diabetes mellitus (T2DM). Since nonalcoholic fatty liver disease (NAFLD) is associated with T2DM and GPR40 is also expressed by hepatocytes and macrophages, it is important to understand the role of GPR40 in NAFLD. However, the role of GPR40 in NAFLD in animal models has not been well defined. In this study, we fed wild-type or GPR40 knockout C57BL/6 mice a high-fat diet (HFD) for 20 wk and then assessed the effect of GPR40 deficiency on HFD-induced NAFLD. Assays on metabolic parameters showed that an HFD increased body weight, glucose, insulin, insulin resistance, cholesterol, and alanine aminotransferase (ALT), and GPR40 deficiency did not mitigate the HFD-induced metabolic abnormalities. In contrast, we found that GPR40 deficiency was associated with increased body weight, insulin, insulin resistance, cholesterol, and ALT in control mice fed a low-fat diet (LFD). Surprisingly, histology and Oil Red O staining showed that GPR40 deficiency in LFD-fed mice was associated with steatosis. Immunohistochemical analysis showed that GPR40 deficiency also increased F4/80, a macrophage biomarker, in LFD-fed mice. Furthermore, results showed that GPR40 deficiency led to a robust upregulation of hepatic fatty acid translocase (FAT)/CD36 expression. Finally, our in vitro studies showed that GPR40 knockdown by siRNA or a GPR40 antagonist increased palmitic acid-induced FAT/CD36 mRNA in hepatocytes. Taken together, this study indicates that GPR40 plays an important role in homeostasis of hepatic metabolism and inflammation and inhibits nonalcoholic steatohepatitis by possible modulation of FAT/CD36 expression.

The Impact of Diet, Nutrition and Nutraceuticals on Oral and Periodontal Health

Oral and periodontal diseases can determine severe functional, phonatory and aesthetic impairments and are the main cause of adult tooth loss. They are caused by some specific bacteria that provoke an intense local inflammatory response and affect-with particular gravity-susceptible subjects, because of reasons related to genetics and lifestyles (e.g., smoking and home oral hygiene habits). They are more frequent in the disadvantaged segments of society and, in particular, in subjects who have difficulty accessing preventive services and dental care. Some systemic diseases, such as uncontrolled diabetes, can increase their risk of development and progression. Recently, in addition to the obvious considerations of severe alterations and impairments for oral health and well-being, it has been noted that periodontitis can cause changes in the whole organism. Numerous clinical and experimental studies have highlighted the presence of a strong association between periodontitis and some systemic diseases, in particular, cardiovascular diseases, diabetes, lung diseases and complications of pregnancy. The purpose of this editorial is to provide a current and thoughtful perspective on the relationship of diet and natural agents on oral, periodontal diseases, and chewing disorder preventions which may reflect good systemic conditions and related quality of life or to analyze indirect effects through the contribution of diet and nutrition to systemic health in order to obtain a modern diagnostic-therapeutic approach.

Palmitate induces apoptosis and inhibits osteogenic differentiation of human periodontal ligament stem cells

OBJECTIVE

The aim of the present study was to investigate the effect of palmitate on human periodontal ligament stem cells (PDLSCs).

DESIGN

PDLSCs were isolated from the third molars of healthy adult donors, and cultured in normal or osteogenic medium supplemented with palmitate (0, 100, or 250 μM) for 21 days. Cell proliferation was evaluated by measuring the amount of formazan at 6, 24, 48, and 72 h. Apoptosis was detected by ELISA and terminal deoxynucleotidyl transferase dUTP nick end labeling assay at days 3 and 7. Osteogenic differentiation was evaluated by measuring the alkaline phosphatase (ALP) activity, production of procollagen type I C-peptide and osteocalcin, mineralization, and mRNA expression of Runx2 at days 3, 7, 14, and 21. In addition, mRNA expression of IL-6 and IL-8 was measured at day 3.

RESULTS

Palmitate inhibited the proliferation, ALP activity, production of procollagen type I C-peptide and osteocalcin, mineralization, and mRNA expression of Runx2 in the cultured PDLSCs. Palmitate also induced apoptosis and mRNA expression of IL-6 and IL-8 in the PDLSCs.

CONCLUSIONS

The results of the present study demonstrate that palmitate induces apoptosis and inhibits osteogenic differentiation of PDLSCs. These findings may help clarify the relationship between palmitate and periodontal tissue regeneration.

Protective Effects of Omega-3 Fatty Acids in Cancer-Related Complications

Omega-3 polyunsaturated fatty acids (PUFAs) are considered immunonutrients and are commonly used in the nutritional therapy of cancer patients due to their ample biological effects. Omega-3 PUFAs play essential roles in cell signaling and in the cell structure and fluidity of membranes. They participate in the resolution of inflammation and have anti-inflammatory and antinociceptive effects. Additionally, they can act as agonists of G protein-coupled receptors, namely, GPR40/FFA1 and GPR120/FFA4. Cancer patients undergo complications, such as anorexia-cachexia syndrome, pain, depression, and paraneoplastic syndromes. Interestingly, the 2017 European Society for Clinical Nutrition and Metabolism (ESPEN) guidelines for cancer patients only discuss the use of omega-3 PUFAs for cancer-cachexia treatment, leaving aside other cancer-related complications that could potentially be managed by omega-3 PUFA supplementation. This critical review aimed to discuss the effects and the possible underlying mechanisms of omega-3 PUFA supplementation in cancer-related complications. Data compilation in this critical review indicates that further investigation is still required to assess the factual benefits of omega-3 PUFA supplementation in cancer-associated illnesses. Nevertheless, preclinical evidence reveals that omega-3 PUFAs and their metabolites might modulate pivotal pathways underlying complications secondary to cancer, indicating that this is a promising field of knowledge to be explored.