GPR40/GPR120 Agonist GW9508 Improves Metabolic Syndrome-Exacerbated Periodontitis in Mice.

G protein-coupled receptor (GPR)40 and GPR120 are receptors for medium- and long-chain free fatty acids. It has been well documented that GPR40 and GPR120 activation improves metabolic syndrome (MetS) and exerts anti-inflammatory effects. Since chronic periodontitis is a common oral inflammatory disease initiated by periodontal pathogens and exacerbated by MetS, we determined if GPR40 and GPR120 activation with agonists improves MetS-associated periodontitis in animal models in this study. We induced MetS and periodontitis by high-fat diet feeding and periodontal injection of lipopolysaccharide, respectively, and treated mice with GW9508, a synthetic GPR40 and GPR120 dual agonist. We determined alveolar bone loss, osteoclast formation, and periodontal inflammation using micro-computed tomography, osteoclast staining, and histology. To understand the underlying mechanisms, we further performed studies to determine the effects of GW9508 on osteoclastogenesis and proinflammatory gene expression in vitro. Results showed that GW9508 improved metabolic parameters, including glucose, lipids, and insulin resistance. Results also showed that GW9508 improves periodontitis by reducing alveolar bone loss, osteoclastogenesis, and periodontal inflammation. Finally, in vitro studies showed that GW9508 inhibited osteoclast formation and proinflammatory gene secretion from macrophages. In conclusion, this study demonstrated for the first time that GPR40/GPR120 agonist GW9508 reduced alveolar bone loss and alleviated periodontal inflammation in mice with MetS-exacerbated periodontitis, suggesting that activating GPR40/GPR120 with agonist GW9508 is a potential anti-inflammatory approach for the treatment of MetS-associated periodontitis.

Circulating Lipoprotein Sphingolipids in Chronic Kidney Disease with and without Diabetes.

Abnormalities of sphingolipid metabolism play an important role in diabetes. We compared sphingolipid levels in plasma and in isolated lipoproteins between healthy control subjects and two groups of patients, one with chronic kidney disease without diabetes (ND-CKD), and the other with type 2 diabetes and macroalbuminuria (D-MA). Ceramides, sphingomyelins, and sphingoid bases and their phosphates in LDL were higher in ND-CKD and in D-MA patients compared to controls. However, ceramides and sphingoid bases in HDL2 and HDL3 were lower in ND-CKD and in D-MA patients than in controls. Sphingomyelins in HDL2 and HDL3 were lower in D-MA patients than in controls but were normal in ND-CKD patients. Compared to controls, lactosylceramides in LDL and VLDL were higher in ND-CKD patients but not in D-MA patients. However, lactosylceramides in HDL2 and HDL3 were lower in both ND-CKD and D-MA patients than in controls. Plasma hexosylceramides in ND-CKD patients were increased and sphingoid bases decreased in both ND-CKD and D-MA patients. However, hexosylceramides in LDL, HDL2, and HDL3 were higher in ND-CKD patients than in controls. In D-MA patients, only C16:0 hexosylceramide in LDL was higher than in controls. The data suggest that sphingolipid measurement in lipoproteins, rather than in whole plasma, is crucial to decipher the role of sphingolipids in kidney disease.

Circulating Sphingolipids in Insulin Resistance, Diabetes and Associated Complications.

Sphingolipids play an important role in the development of diabetes, both type 1 and type 2 diabetes, as well as in the development of both micro- and macro-vascular complications. Several reviews have been published concerning the role of sphingolipids in diabetes but most of the emphasis has been on the possible mechanisms by which sphingolipids, mainly ceramides, contribute to the development of diabetes. Research on circulating levels of the different classes of sphingolipids in serum and in lipoproteins and their importance as biomarkers to predict not only the development of diabetes but also of its complications has only recently emerged and it is still in its infancy. This review summarizes the previously published literature concerning sphingolipid-mediated mechanisms involved in the development of diabetes and its complications, focusing on how circulating plasma sphingolipid levels and the relative content carried by the different lipoproteins may impact their role as possible biomarkers both in the development of diabetes and mainly in the development of diabetic complications. Further studies in this field may open new therapeutic avenues to prevent or arrest/reduce both the development of diabetes and progression of its complications.

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.

High-fat diet-induced metabolic syndrome increases ligature-induced alveolar bone loss in mice.

BACKGROUND: It has been well documented that metabolic syndrome (MetS) increases severity of periodontitis. In this study, we determined the effect of high-fat diet (HFD)-induced MetS on alveolar bone loss in a mouse model with ligature-induced periodontitis. To understand how MetS increases bone loss, we tested our hypothesis that palmitic acid (PA), a most abundant saturated fatty acid in the HFD, interacts with lipopolysaccharide (LPS) to promote osteoclastogenesis. METHODS: We induced MetS by feeding mice HFD for 18 weeks and induced periodontitis with ligature placement. After treatments, we assessed alveolar bone loss using micro-computed tomography and determined osteoclastogenesis using tartrate-resistant acid phosphatase (TRAP) staining. To explore the mechanisms, we treated macrophages with PA, LPS or both and analyzed the osteoclast formation and cytokine expression in macrophages. RESULTS: While ligature robustly induced periodontitis in mice with or without MetS, the mice with MetS had more bone loss than those without MetS. PA and LPS cooperatively induced osteoclast formation and stimulated the expression of inflammatory cytokines involved in osteoclastogenesis potentially via a FAT/CD36-dependent mechanism in macrophages. CONCLUSIONS: HFD-induced MetS increases alveolar bone loss in mice with ligature-induced periodontitis, and PA and LPS cooperatively stimulate osteoclast formation and proinflammatory gene expression in macrophages.

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.

Plasma apoM Levels and Progression to Kidney Dysfunction in Patients With Type 1 Diabetes.

Apolipoprotein M (apoM), primarily carried by HDL, has been associated with several conditions, including cardiovascular disease and diabetic nephropathy. This study proposes to examine whether plasma apoM levels are associated with the development of diabetic kidney disease, assessed as progression to macroalbuminuria (MA) and chronic kidney disease (CKD). Plasma apoM was measured using an enzyme immunoassay in 386 subjects from the Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications (EDIC) cohort at DCCT entry and closeout and the concentrations used to determine the association with risk of progression to kidney dysfunction from the time of measurement through 18 years of EDIC follow-up. apoM levels, at DCCT baseline, were higher in patients who developed CKD than in those who retained normal renal function. At DCCT closeout, participants who progressed to MA, CKD, or both MA and CKD also had significantly higher apoM levels than those who remained normal, and increased levels of apoM were associated with increased risk of progression to both MA (risk ratio [RR] 1.30 [95% CI 1.01, 1.66]) and CKD (RR 1.69 [95% CI 1.18, 2.44]). Our results strongly suggest that alterations in apoM and therefore in the composition and function of HDL in type 1 diabetes are present early in the disease process and are associated with the development of nephropathy.

Diabetes and kidney dysfunction markedly alter the content of sphingolipids carried by circulating lipoproteins.

BACKGROUND: We have previously shown that very long ceramides/lactosylceramides predicted the development of macroalbuminuria (MA) in type 1 diabetes and expanded our studies into type 2 diabetes. OBJECTIVE: This study proposes comparing the levels of plasma sphingolipids and their distribution in circulating lipoproteins (VLDL/IDL, LDL, HDL2 and HDL3) between a healthy control group and two groups of subjects with type 2 diabetes, one with and other without MA. METHODS: Plasma and lipoprotein sphingolipids/glycosphingolipids were measured using HPLC-MS/MS in 114 subjects (40 controls; 74 type 2 diabetes, 40 without MA; and 34 with MA) and the levels were compared between controls and the two groups of diabetes. Group effect sizes were calculated using Cohen's d. RESULTS: Sphingomyelin species carried by LDL are significantly higher in diabetic patients with MA than in those with normal albumin excretion rate (AER). Compared to controls, significant decreases in the levels of sphingolipids carried by HDL in patients with diabetes with normal AER or MA were observed for all sphingolipid classes except for hexosylceramide, which was normal in diabetic patients without MA. Although lower than in controls, the levels of lactosylceramides carried by HDL2/HDL3 were significantly higher in diabetes with MA. CONCLUSIONS: Considering the critical role sphingolipids play in major cell biological responses and cell signaling pathways, the consequences for disease development of changes in the distribution of sphingolipids/glycosphingolipids carried by lipoproteins could be considerable. Our work is just a first step to address a considerable gap in our present knowledge in this important field.

Deoxysphingolipids Upregulate MMP-1, Downregulate TIMP-1, and Induce Cytotoxicity in Human Schwann Cells.

Sphingolipids are a heterogeneous class of lipids and essential components of the plasma membrane and plasma lipoproteins. Studies have shown that plasma deoxysphingolipid (DSL), a newly identified sphingolipid class, is increased in diabetic patients and associated with diabetic neuropathy. However, it remains unknown if there is a causal relationship between plasma DSL increase and diabetic neuropathy. Since matrix metalloproteinases (MMPs) play an important role in diabetic neuropathy by degrading extracellular matrix in the peripheral nervous system, we investigated the effect of DSLs on the expression of MMPs and tissue inhibitor of metalloproteinase (TIMPs), and cytotoxicity in human Schwann cells. We quantified protein secretion, gene expression, and collagenase activity, and performed cytotoxicity assays. Results showed that DSLs upregulated MMP-1, downregulated TIMP-1, and induced cytotoxicity in Schwann cells. Furthermore, we quantified DSLs in VLDL, LDL, HDL2, and HDL3 isolated from type 2 diabetes mellitus (T2DM) patients with or without neuropathy. Interestingly, lipidomic analysis showed that only HDL2 isolated from T2DM patients with neuropathy contains significantly higher level of DSLs than that isolated from T2DM patients without neuropathy. Additionally, results showed that HDL2 isolated from T2DM patients with neuropathy was more potent than that isolated from T2DM patients without neuropathy in upregulating MMP-1, downregulating TIMP-1, and stimulating collagenase activity in Schwann cell. Taken together, this study demonstrated for the first time a potential causal relationship between DSLs and diabetic neuropathy and that DSL-containing HDL2 from T2DM patients with neuropathy was more potent than that from T2DM patients without neuropathy in stimulating collagenase activity.

Inhibition of acid sphingomyelinase by imipramine abolishes the synergy between metabolic syndrome and periodontitis on alveolar bone loss.

BACKGROUND AND OBJECTIVE: Clinical studies have shown that metabolic syndrome (MetS) exacerbates periodontitis. However, the underlying mechanisms remain largely unknown. Since our animal study has shown that high-fat diet-induced MetS exacerbates lipopolysaccharide (LPS)-stimulated periodontitis in mouse model and our in vitro study showed that acid sphingomyelinase (aSMase) plays a key role in the amplification of LPS-triggered pro-inflammatory response by palmitic acid (PA) in macrophages, we tested our hypothesis that inhibitor of aSMase attenuates MetS-exacerbated periodontitis in animal model. Furthermore, to explore the potential underlying mechanisms, we tested our hypothesis that aSMase inhibitor downregulates pro-inflammatory and pro-osteoclastogenic gene expression in macrophages in vitro. MATERIAL AND METHODS: We induced MetS and periodontitis in C57BL/6 mice by feeding high-fat diet (HFD) and periodontal injection of A. actinomycetemcomitans LPS, respectively, and treated mice with imipramine, a well-established inhibitor of aSMase. Micro-computed tomography (micro-CT), tartrate-resistant acid phosphatase staining, histological and pathological evaluations as well as cell cultures were performed to evaluate alveolar bone loss, osteoclast formation, periodontal inflammation and pro-inflammatory gene expression. RESULTS: Analysis of metabolic parameter showed that while HFD induced MetS by increasing bodyweight, insulin resistance, cholesterol and free fatty acids, imipramine reduced free fatty acids but had no significant effects on other metabolic parameters. MicroCT showed that either MetS or periodontitis significantly reduced bone volume fraction (BVF) of maxilla and the combination of MetS and periodontitis further reduced BVF. However, imipramine increased BVF in mice with both MetS and periodontitis to a level similar to that in mice with periodontitis alone, suggesting that imipramine abolished the synergy between MetS and periodontitis on alveolar bone loss. Consistently, results showed that imipramine inhibited osteoclast formation and periodontal inflammation in mice with both MetS and periodontitis. To elucidate the mechanisms by which imipramine attenuates MetS-exacerbated periodontitis, we showed that imipramine inhibited the upregulation of pro-inflammatory cytokines and transcription factor c-FOS as well as ceramide production by LPS plus PA in macrophages. CONCLUSION: This study has shown that imipramine as an inhibitor of aSMase abolishes the synergy between MetS and periodontitis on alveolar bone loss in animal model and inhibits pro-inflammatory and pro-osteoclastogenic gene expression in macrophages in vitro. This study provides the first evidence that aSMase is a potential therapeutic target for MetS-exacerbated periodontitis.

Serum urate and cardiovascular events in the DCCT/EDIC study.

In type 2 diabetes, hyperuricemia is associated with cardiovascular disease (CVD) and the metabolic syndrome (MetS), but associations in type 1 diabetes (T1D) have not been well-defined. This study examined the relationships between serum urate (SU) concentrations, clinical and biochemical factors, and subsequent cardiovascular events in a well-characterized cohort of adults with T1D. In 973 participants with T1D in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study (DCCT/EDIC), associations were defined between SU, measured once in blood collected 1997-2000, and (a) concurrent MetS and (b) incident 'any CVD' and major adverse cardiovascular events (MACE) through 2013. SU was higher in men than women [mean (SD): 4.47 (0.99) vs. 3.39 (0.97) mg/dl, respectively, p < 0.0001], and was associated with MetS features in both (men: p = 0.0016; women: p < 0.0001). During follow-up, 110 participants (11%) experienced "any CVD", and 53 (5%) a MACE. Analyzed by quartiles, SU was not associated with subsequent CVD or MACE. In women, SU as a continuous variable was associated with MACE (unadjusted HR: 1.52; 95% CI 1.07-2.16; p = 0.0211) even after adjustment for age and HbA1c (HR: 1.47; 95% CI 1.01-2.14; p = 0.0467). Predominantly normal range serum urate concentrations in T1D were higher in men than women and were associated with features of the MetS. In some analyses of women only, SU was associated with subsequent MACE. Routine measurement of SU to assess cardiovascular risk in T1D is not merited.Trial registration clinicaltrials.gov NCT00360815 and NCT00360893.

LPS and palmitic acid Co-upregulate microglia activation and neuroinflammatory response.

Growing evidence indicates that disturbances in the inflammatory response system can have deleterious effects on neuronal function and mental health. While the correlation between elevated peripheral inflammatory markers and psychiatric disorders are well documented, the exact molecular and neuronal mechanism underlying the connection between activated inflammation and neuropsychiatric behaviour remain elusive. Microglia activation is the key interface between neuro-inflammation and manifestation of psychiatric symptoms. Microglia are immunocompetent cells in the central nervous system (CNS) which are primarily involved in the response to inflammatory stimulation and are widely used to study neuroinflammation and test anti-inflammatory chemicals. In the brain, activated microglia play very important roles during neuroinflammation and neurodegeneration. Both stress-related disorders such as Depression and PTSD, and medical conditions such as metabolic syndrome (Mets) and type 2 diabetes (TD2) are associated with increased levels of both saturated fatty acids (SFAs) and lipopolysaccharide (LPS) in circulation. This work was aimed at determining whether SFA interacts with LPS to activate microglia, thus up-regulating neuroinflammatory processes and, if so which pathways were involved in this process. Our results showed that low-dose LPS and palmitic acid (PA) robustly stimulated the expression of proinflammatory cytokines, and the combination of PA and LPS further upregulated proinflammatory cytokines through MAPK, NFκB and AP-1 signaling pathways in the HMC3-human microglial cell line. In addition, PA stimulated ceramide production via de novo synthesis and sphingomyelin hydrolysis, and the combination of LPS and PA further increased ceramide production. HMC3 co-cultured with macrophage and lymphocyte enhanced LPS and PA induced-inflammatory response more than that in HMC3 alone. These results indicate that LPS interacts with PA to activated microglia; induced neuroinflammatory responses, upregulate proinflammatory cytokine expression via MAPK, NFκB, and AP-1 signaling pathways, and induced sphingolipid metabolism in HMC3. These observations suggest that inhibiting microglia activation and reducing LPS and PA-induced inflammatory response may be useful in the treatment of neuronal inflammatory diseases.

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.

ASSOCIATIONS BETWEEN ACCELERATED ATHEROSCLEROSIS, OXIDIZED LDL IMMUNE COMPLEXES, AND IN VITRO ENDOTHELIAL DYSFUNCTION IN SYSTEMIC LUPUS ERYTHEMATOSUS.

Systemic lupus erythematosus (SLE) is an independent risk factor for atherosclerosis. This study was designed to determine the association between atherosclerosis, oxidized LDL immune complexes (oxLDL-IC), and endothelial dysfunction in SLE. SLE patients were recruited, and carotid atherosclerotic total plaque area (TPA) was determined by ultrasound. Levels of oxLDL-IC were measured. In vitro endothelial function was measured by aortic endothelial nitric oxide (NO) production after culture of human aortic endothelial cells (HAEC) with SLE serum. Levels of oxLDL-IC are associated significantly with TPA. In vitro HAEC NO production after culture with SLE serum was positively correlated with serum complement. HAEC NO production was increased with sepiapterin to couple eNOS. To our knowledge, this is the first study to demonstrate an association between subclinical accelerated atherosclerosis and oxLDL-IC in SLE. This is also the first study to demonstrate the effect of sepiapterin on improving in vitro aortic endothelial cell function in SLE.

Acid sphingomyelinase deficiency exacerbates LPS-induced experimental periodontitis.

BACKGROUND: Mutation of the gene for acid sphingomyelinase (ASMase) causes Niemann-Pick disease. However, the effect of ASMase deficiency on periodontal health is unknown. Periodontal disease is a disease resulting from infection and inflammation of periodontal tissue and alveolar bone that support the teeth. The goal of this study was to determine the role of ASMase deficiency in periodontal inflammation and alveolar bone loss. METHODS: We induced periodontitis in wild-type and ASMase-deficient (ASMase-/- ) mice with periodontal lipopolysaccharide (LPS) injection and compared the alveolar bone loss and periodontal inflammation between these mice. RESULTS: Results showed that ASMase deficiency did not significantly change metabolic parameters, but exacerbated LPS-induced alveolar bone loss, osteoclastogenesis, and periodontal tissue inflammation. To understand the mechanisms by which ASMase deficiency aggravates LPS-induced periodontitis, we analyzed sphingolipids in periodontal tissues. Results showed that ASMase deficiency led to increases in not only sphingomyelin, but also ceramide (CER), a bioactive sphingolipid known to promote inflammation. Results further showed that ASMase deficiency increased CER de novo synthesis. CONCLUSION: ASMase deficiency exacerbated LPS-induced alveolar bone loss and periodontal inflammation. ASMase deficiency leads to an unexpected CER increase by stimulating de novo synthesis CER, which is likely to be involved in the ASMase deficiency-exacerbated periodontitis.

Amitriptyline inhibits nonalcoholic steatohepatitis and atherosclerosis induced by high-fat diet and LPS through modulation of sphingolipid metabolism.

We reported previously that increased acid sphingomyelinase (ASMase)-catalyzed hydrolysis of sphingomyelin, which leads to increases in ceramide and sphingosine 1 phosphate (S1P), played a key role in the synergistic upregulation of proinflammatory cytokines by palmitic acid (PA), a major saturated fatty acid, and lipopolysaccharide (LPS) in macrophages. Since macrophages are vital players in nonalcoholic steatohepatitis (NASH) and atherosclerosis, we assessed the effect of ASMase inhibition on NASH and atherosclerosis cooperatively induced by high-PA-containing high-fat diet (HP-HFD) and LPS in LDL receptor-deficient (LDLR-/-) mice. LDLR-/- mice were fed HP-HFD, injected with low dose of LPS and treated with or without the ASMase inhibitor amitriptyline. The neutral sphingomyelinase inhibitor GW4869 was used as control. Metabolic study showed that both amitriptyline and GW4869 reduced glucose, lipids, and insulin resistance. Histological analysis and Oil Red O staining showed that amitriptyline robustly reduced hepatic steatosis while GW4869 had modest effects. Interestingly, immunohistochemical study showed that amitriptyline, but not GW4869, strongly reduced hepatic inflammation. Furthermore, results showed that both amitriptyline and GW4869 attenuated atherosclerosis. To elucidate the underlying mechanisms whereby amitriptyline inhibited both NASH and atherosclerosis, but GW4869 only inhibited atherosclerosis, we found that amitriptyline, but not GW4869, downregulated proinflammatory cytokines in macrophages. Finally, we found that inhibition of sphingosine 1 phosphate production is a potential mechanism whereby amitriptyline inhibited proinflammatory cytokines. Collectively, this study showed that amitriptyline inhibited NASH and atherosclerosis through modulation of sphingolipid metabolism in LDLR-/- mice, indicating that sphingolipid metabolism in macrophages plays a crucial role in the linkage of NASH and atherosclerosis.

Serum pigment epithelium-derived factor: Relationships with cardiovascular events, renal dysfunction, and mortality in the Veterans Affairs Diabetes Trial (VADT) cohort.

BACKGROUND: To determine if serum pigment epithelium-derived factor (PEDF) levels predict cardiovascular events, renal dysfunction and mortality in the Veterans Affairs Diabetes Study (VADT). METHODS: PEDF was evaluated in relation to subsequent cardiovascular outcomes, mortality, and renal dysfunction (defined as urinary albumin creatinine ratio (ACR) ≥300 mg/g), or chronic kidney disease (CKD) stages 3 (eGFR<60 ml/min) or 4 (eGFR<60 and <30 ml/min respectively). PEDF was measured by ELISA on sera from 881 participants collected a median (range) of 1.7 (0-5.0) years post-baseline, and later, from 832 participants 4.0 (1.5-6.9) years post-baseline. RESULTS: In 743 participants, PEDF was measured at both time-points. PEDF increased over time from (mean ±â€¯SD) 10.5 ±â€¯4.03 to 11.0 ±â€¯4.86 ng/ml (paired t-test p = 0.0092). Lower eGFR (p < 0.01), higher serum creatinine (p < 0.01) and urinary ACR (p < 0.01) were associated with increasing PEDF. Multivariate event time models included either one or two follow-up windows (i.e., between first and second PEDF measures; and, when available, from second PEDF measure until study-end). PEDF tertiles were not associated with cardiovascular events, but were significantly associated with all-cause mortality [HR = 2.00 (1.03, 3.89) comparing first to third tertile] in models adjusted for age, minority status, VADT treatment arm and prior cardiovascular event status. Higher PEDF levels also associated with development of kidney dysfunction with adjusted HRs (95% CI comparing third to first PEDF tertiles: 2.74 (1.71, 4.39) for stage 3 CKD; and 3.84 (95% CI: 1.17, 12.5) for stage 4 CKD. CONCLUSIONS: Over 2-years, higher serum PEDF levels predicted advanced nephropathy in patients with type 2 diabetes.

Immune Complexes and the Risk of CVD in Type 1 Diabetes.

We investigated whether the composition of modified forms of LDL in circulating immune complexes (LDL-ICs) was associated with cardiovascular disease (CVD) outcomes, including any CVD, major adverse cardiac and cerebrovascular events (MACCE), myocardial infarction (MI), and coronary artery disease, in type 1 diabetes (T1D). Our results demonstrate that the baseline levels of oxidized LDL (oxLDL), MDA-modified LDL (MDA-LDL), and advanced glycosylation-modified LDL (AGE-LDL) in circulating ICs were associated with the four CVD outcomes in unadjusted models, and adjustment by age and mean HbA1c only resulted in minimal reduction of these associations. After adjustments were made for other cardiovascular risk factors, particularly LDL cholesterol, oxLDL-IC and MDA-LDL-IC remained independently associated with the risk of CVD, and oxLDL-IC was independently associated with the risk of MACCE and MI. In the majority of cases, the baseline levels of modified LDL-IC (measured many years before the occurrence of any CVD event) were associated with the risk of CVD over a 25-year period even after adjustment for other risk factors (including LDL cholesterol). Therefore, modified LDL biomarkers may help identify patients with T1D at high risk for MACCE and CVD events very early in the evolution of the disease, before other signals of disease are apparent.

Serum apolipoproteins and apolipoprotein-defined lipoprotein subclasses: a hypothesis-generating prospective study of cardiovascular events in T1D.

APOB, APOC3, and APOE and apolipoprotein-defined lipoprotein subclasses (ADLSs; based on qualitative apolipoprotein complement) have been associated with dyslipidemia and CVD. Our main objective was to define associations of serum apolipoproteins and ADLSs with "any CVD" and "major atherosclerotic cardiovascular events" (MACEs) in a prospective study of T1D. Serum apolipoproteins and ADLSs (14 biomarkers in total) were measured in sera (obtained between 1997 and 2000) from a subset (n = 465) of the Epidemiology of Diabetes Interventions and Complications cohort. Prospective associations of "any CVD" (myocardial infarction, stroke, confirmed angina, silent myocardial infarction, revascularization, or congestive heart failure) and MACEs (fatal or nonfatal myocardial infarction or stroke), over 5,943 and 6,180 patient-years follow-up, respectively, were investigated using Cox proportional hazards models that were unadjusted and adjusted for risk factors. During 15 years of follow-up, 50 "any CVD" events and 24 MACEs occurred. Nominally significant positive univariate associations with "any CVD" were APOB, APOC3 and its subfractions [heparin precipitate, heparin-soluble (HS)], and ADLS-defined Lp-B. In adjusted analyses, APOC3-HS remained nominally significant. Nominally significant positive univariate associations with MACEs were APOC3 and its subfractions and Lp-B:C; those with total APOC3 and APOC3-HS persisted in adjusted analyses. However, these associations did not reach significance after adjusting for multiple testing. There were no significant associations of APOA1, APOA2, APOE, or other ADLSs with either "any CVD" or MACEs. These hypothesis-generating data suggest that total serum APOC3 and APOC3 in HDL are potentially important predictive biomarkers for any CVD and MACEs in adults with T1D.

Glycosylated sphingolipids and progression to kidney dysfunction in type 1 diabetes.

BACKGROUND: Glycosphingolipids are important components of cell membranes, modulators of cell-cell interactions and cell recognition, and have recently emerged as bioactive molecules and important players in nearly all cell biological processes. We previously have shown that decreased plasma levels of long and very long species of ceramides were able to predict the development of macroalbuminuria (MA) in type 1 diabetes. OBJECTIVE: This study proposed to examine whether plasma glycosphingolipids could predict development of diabetic nephropathy, assessed as MA or chronic kidney disease (CKD). METHODS: Measurement of plasma hexosylceramides (H) and lactosylceramides (L) were conducted in the Lipidomics Core Facility of our Institution in a subcohort of 432 patients from the DCCT/Epidemiology of Diabetes Interventions and Complications cohort in plasma collected at entry into the study. Inverse probability weighted Cox proportional hazards regression models were used to assess the effect of glycosphingolipids levels on the risk of developing MA (albumin excretion rate ≥300 mg/24 hours) or CKD (glomerular filtration rate <60 mL/min) over a period of 21 to 28 years. RESULTS: Decreases of several long and very long chain lactosylceramides were significantly associated with increased risk of progression to MA but not CKD. Among the hexosylceramides, the only significant association observed was between one of its minor species C18:1-H and CKD. CONCLUSION: Our findings showed that decreased levels of long and very long lactosylceramides were able to predict the development of MA in type 1 diabetes. This finding is similar to previous findings showing that low levels of long and very long ceramides were also able to predict development of MA in the same cohort. Further studies are needed to determine the changes in sphingolipid metabolism leading to the development of complications.