Decreased circulating IPA levels identify subjects with metabolic comorbidities: A multi-omics study

In recent years several experimental observations demonstrated that the gut microbiome plays a role in regulating positively or negatively metabolic homeostasis. Indole-3-propionic acid (IPA), a Tryptophan catabolic product mainly produced by C. Sporogenes, has been recently shown to exert either favorable or unfavorable effects in the context of metabolic and cardiovascular diseases. We performed a study to delineate clinical and multiomics characteristics of human subjects characterized by low and high IPA levels. Subjects with low IPA blood levels showed insulin resistance, overweight, low-grade inflammation, and features of metabolic syndrome compared to those with high IPA. Metabolomics analysis revealed that IPA was negatively correlated with leucine, isoleucine, and valine metabolism. Transcriptomics analysis in colon tissue revealed the enrichment of several signaling, regulatory, and metabolic processes. Metagenomics revealed several OTU of ruminococcus, alistipes, blautia, butyrivibrio and akkermansia were significantly enriched in highIPA group while in lowIPA group Escherichia-Shigella, megasphera, and Desulfovibrio genus were more abundant. Next, we tested the hypothesis that treatment with IPA in a mouse model may recapitulate the observations of human subjects, at least in part. We found that a short treatment with IPA (4 days at 20/mg/kg) improved glucose tolerance and Akt phosphorylation in the skeletal muscle level, while regulating blood BCAA levels and gene expression in colon tissue, all consistent with results observed in human subjects stratified for IPA levels. Our results suggest that treatment with IPA may be considered a potential strategy to improve insulin resistance in subjects with dysbiosis.

TIMP3 overexpression in myeloid lineage alleviates pancreatic damage and confers resistance to the development of type 1 diabetes in the MLDS -induced model

Introduction

Type 1 diabetes mellitus (T1DM) development involves a complex interplay of genetic, environmental, and immunological factors. By modulating the activity of proteases and receptors, the protein tissue inhibitor of metalloproteinase 3 (TIMP3) plays a role in limiting the expression and function of pro-inflammatory cytokines, which have been implicated in the advancement of T1DM. This study was aimed at examining the effect of TIMP3 overexpression in myeloid cells on the development of T1DM.

Methods and results

Twelve weeks after multiple low doses of streptozotocin (MLDS) treatment, diabetic mice overexpressing TIMP3 specifically in myeloid cells under the CD68 promoter (MacT3 mice) showed improved insulin secretion, islet morphology and vascularization, antioxidant defense system, and regulatory factors of mitochondrial biosynthesis and function. To get mechanistic insights into the origin of this protection, the severity of insulitis and inflammatory parameters were evaluated in pancreatic tissues 11 days after MLSD treatment, showing significantly reduced insulitis and levels of the pro-inflammatory cytokine tumor necrosis factor-α, interleukin -1β, and interferon -γ in MacT3 mice.

Discussion

The results indicate that TIMP3 is involved in maintaining islet architecture and functions, at least in part, through modulation of pro-inflammatory cytokine production associated with insulitis and may represent a novel therapeutic strategy for T1DM.

GLP-1RAs and cardiovascular disease: is the endothelium a relevant platform?

Hyperglycemia strongly affects endothelial function and activation, which in turn increases the risk of atherosclerotic cardiovascular disease. Among pharmacotherapies aimed at lowering blood glucose levels, glucagon-like peptide 1 receptor agonists (GLP-1RA) represent a class of drugs involved in the improvement of the endothelium damage and the progression of cardiovascular diseases. They show antihypertensive and antiatherosclerotic actions due at least in part to direct favorable actions on the coronary vascular endothelium, such as oxidative stress reduction and nitric oxide increase. However, cumulative peripheral indirect actions could also contribute to the antiatherosclerotic functions of GLP-1/GLP-1R agonists, including metabolism and gut microbiome regulation. Therefore, further research is necessary to clarify the specific role of this drug class in the management of cardiovascular disease and to identify specific cellular targets involved in the protective signal transduction. In the present review, we provide an overview of the effects of GLP-1RAs treatment on cardiovascular disease with particular attention on potential molecular mechanisms involving endothelium function on formation and progression of atherosclerotic plaque.

ITCH E3 Ubiquitin Ligase downregulation compromises hepatic degradation of branched-chain amino acids

Objective

Metabolic syndrome, obesity, and steatosis are characterized by a range of dysregulations including defects in ubiquitin ligase tagging proteins for degradation. The identification of novel hepatic genes associated with fatty liver disease and metabolic dysregulation may be relevant to unravelling new mechanisms involved in liver disease progression

Methods

Through integrative analysis of liver transcriptomic and metabolomic obtained from obese subjects with steatosis, we identified itchy E ubiquitin protein ligase (ITCH) as a gene downregulated in human hepatic tissue in relation to steatosis grade. Wild-type or ITCH knockout mouse models of non-alcoholic fatty liver disease (NAFLD) and obesity-related hepatocellular carcinoma were analyzed to dissect the causal role of ITCH in steatosis

Results

We show that ITCH regulation of branched-chain amino acids (BCAAs) degradation enzymes is impaired in obese women with grade 3 compared with grade 0 steatosis, and that ITCH acts as a gatekeeper whose loss results in elevation of circulating BCAAs associated with hepatic steatosis. When ITCH expression was specifically restored in the liver of ITCH knockout mice, ACADSB mRNA and protein are restored, and BCAA levels are normalized both in liver and plasma

Conclusions

Our data support a novel functional role for ITCH in the hepatic regulation of BCAA metabolism and suggest that targeting ITCH in a liver-specific manner might help delay the progression of metabolic hepatic diseases and insulin resistance.

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ITCH expression is reduced in liver during NAFLD.

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Transcriptomics analysis of liver in obese women highlighted the interplay between ITCH and genes involved in BCAA degradation.

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Modulation of ITCH in models of metabolic hepatic diseases supported the association between ITCH and BCAA metabolism.

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Targeting ITCH in a liver specific manner might help to delay the progression of metabolic hepatic diseases and insulin resistance.

TIMP3 involvement and potentiality in the diagnosis, prognosis and treatment of diabetic nephropathy

Diabetic kidney disease, one of the most severe complications associated with diabetes, is characterized by albuminuria, glomerulosclerosis and progressive loss of renal function. Loss of TIMP3, an Extracellular matrix-bound protein, is a hallmark of diabetic nephropathy in human and mouse models, suggesting its pivotal role in renal diseases associated to diabetes. There is currently no specific therapy for diabetic nephropathy, and the ability to restore high TIMP3 activity specifically in the kidney may represent a potential therapeutic strategy for the amelioration of renal injury under conditions in which its reduction is directly related to the disease. Increasing evidence shows that diabetic nephropathy is also regulated by epigenetic mechanisms, including noncoding RNA. This review recapitulates the pathological, diagnostic and therapeutic potential roles of TIMP3 and the noncoding RNA (microRNA, long noncoding RNA) related to its expression, in the progression of diabetic nephropathy.

High Sensitivity C-Reactive Protein Increases the Risk of Carotid Plaque Instability in Male Dyslipidemic Patients

Background: The aim of this study was to evaluate how the high sensitivity C-reactive protein (hs-CRP) values influence the risk of carotid plaque instability in association with other cardiovascular risk factors. Methods: One hundred and fifty-six carotid plaques from both symptomatic and asymptomatic patients requiring surgical carotid endarterectomy were retrospectively collected. According to the modified American Heart Association, atherosclerosis plaques have been histologically distinguished into unstable and stable. The following anamnestic and hematochemical data were also considered: age, gender, hypertension, diabetes mellitus, smoking habit, therapy, low-density lipoprotein (LDL)-C, kidney failure and hs-CRP. Results: The results of our study clearly show that high levels of hs-CRP significantly increase the carotid plaque instability in dyslipidemic patients. Specifically, a 67% increase of the risk of carotid plaque instability was observed in patients with high LDL-C. Therefore, the highest risk was observed in male dyslipidemic patients 2333 (95% CI 0.73–7.48) and in aged female patients 2713 (95% CI 0.14–53.27). Discussion: These data strongly suggest a biological relationship between the hs-CRP values and the alteration of lipidic metabolism mostly in male patients affected by carotid atherosclerosis. The measurement of hs-CRP might be useful as a potential screening tool in the prevention of atheroscletotic disease.

A Serum Resistin and Multicytokine Inflammatory Pathway Is Linked With and Helps Predict All-cause Death in Diabetes

CONTEXT

Type 2 diabetes (T2D) shows a high mortality rate, partly mediated by atherosclerotic plaque instability. Discovering novel biomarkers may help identify high-risk patients who would benefit from more aggressive and specific managements. We recently described a serum resistin and multicytokine inflammatory pathway (REMAP), including resistin, interleukin (IL)-1β, IL-6, IL-8, and TNF-α, that is associated with cardiovascular disease.

OBJECTIVE

We investigated whether REMAP is associated with and improves the prediction of mortality in T2D.

METHODS

A REMAP score was investigated in 3 cohorts comprising 1528 patients with T2D (409 incident deaths) and in 59 patients who underwent carotid endarterectomy (CEA; 24 deaths). Plaques were classified as unstable/stable according to the modified American Heart Association atherosclerosis classification.

RESULTS

REMAP was associated with all-cause mortality in each cohort and in all 1528 individuals (fully adjusted hazard ratio [HR] for 1 SD increase = 1.34, P < .001). In CEA patients, REMAP was associated with mortality (HR = 1.64, P = .04) and a modest change was observed when plaque stability was taken into account (HR = 1.58; P = .07). REMAP improved discrimination and reclassification measures of both Estimation of Mortality Risk in Type 2 Diabetic Patients and Risk Equations for Complications of Type 2 Diabetes, well-established prediction models of mortality in T2D (P < .05-< .001).

CONCLUSION

REMAP is independently associated with and improves predict all-cause mortality in T2D; it can therefore be used to identify high-risk individuals to be targeted with more aggressive management. Whether REMAP can also identify patients who are more responsive to IL-6 and IL-1β monoclonal antibodies that reduce cardiovascular burden and total mortality is an intriguing possibility to be tested.

The feeding behaviour of Amyotrophic Lateral Sclerosis mouse models is modulated by the Ca2+ -activated KCa 3.1 channels

BACKGROUND AND PURPOSE

Amyotrophic lateral sclerosis (ALS) patients exhibit dysfunctional energy metabolism and weight loss, which is negatively correlated with survival, together with neuroinflammation. However, the possible contribution of neuroinflammation to deregulations of feeding behaviour in ALS has not been studied in detail. We here investigated if microglial K_Ca 3.1 is linked to hypothalamic neuroinflammation and affects feeding behaviours in ALS mouse models.

EXPERIMENTAL APPROACH

hSOD1^G93A and TDP43^A315T mice were treated daily with 120 mg·kg^-1 of TRAM-34 or vehicle by intraperitoneal injection from the presymptomatic until the disease onset phase. Body weight and food intake were measured weekly. The later by weighing food provided minus that left in the cage. RT-PCR and immunofluorescence analysis were used to characterize microglia phenotype and the main populations of melanocortin neurons in the hypothalamus of hSOD1^G93A and age-matched non-tg mice. The cannabinoid-opioid interactions in feeding behaviour of hSOD1^G93A mice were studied using an inverse agonist and an antagonist of the cannabinoid receptor CB₁ (rimonabant) and μ-opioid receptors (naloxone), respectively.

KEY RESULTS

We found that treatment of hSOD1^G93A mice with the K_Ca 3.1 inhibitor TRAM-34 (i), attenuates the pro-inflammatory phenotype of hypothalamic microglia, (ii) increases food intake and promotes weight gain, (iii) increases the number of healthy pro-opiomelanocortin (POMC) neurons and (iv), changes the expression of cannabinoid receptors involved in energy homeostasis.

CONCLUSION AND IMPLICATIONS

Using ALS mouse models, we describe defects in the hypothalamic melanocortin system that affect appetite control. These results reveal a new regulatory role for K_Ca 3.1 to counteract weight loss in ALS.

Inhibition of Lysine 63 Ubiquitination Prevents the Progression of Renal Fibrosis in Diabetic DBA/2J Mice

Diabetic nephropathy (DN) is the most frequent cause of end-stage renal disease. Tubulointerstitial accumulation of lysine 63 (K63)-ubiquitinated (Ub) proteins is involved in the progression of DN fibrosis and correlates with urinary miR-27b-3p downregulation. We explored the renoprotective effect of an inhibitor of K63-Ub (NSC697923), alone or in combination with the ACE-inhibitor ramipril, in vitro and in vivo. Proximal tubular epithelial cells and diabetic DBA/2J mice were treated with NSC697923 and/or ramipril. K63-Ub protein accumulation along with α-SMA, collagen I and III, FSP-1, vimentin, p16^INK4A expression, SA-α Gal staining, Sirius Red, and PAS staining were measured. Finally, we measured the urinary albumin to creatinine ratio (uACR), and urinary miR-27b-3p expression in mice. NSC697923, both alone and in association with ramipril, in vitro and in vivo inhibited hyperglycemia-induced epithelial to mesenchymal transition by significantly reducing K63-Ub proteins, α-SMA, collagen I, vimentin, FSP-1 expression, and collagen III along with tubulointerstitial and glomerular fibrosis. Treated mice also showed recovery of urinary miR-27b-3p and restored expression of p16^INK4A. Moreover, NSC697923 in combination with ramipril demonstrated a trend in the reduction of uACR. In conclusion, we suggest that selective inhibition of K63-Ub, when combined with the conventional treatment with ACE inhibitors, might represent a novel treatment strategy to prevent the progression of fibrosis and proteinuria in diabetic nephropathy and we propose miR-27b-3p as a biomarker of treatment efficacy.

Restoration of renal TIMP3 levels via genetics and pharmacological approach prevents experimental diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN), one of the major complications of diabetes, is characterized by albuminuria, glomerulosclerosis, and progressive loss of renal function. Loss of TIMP3, an Extracellular Matrix bound protein affecting both inflammation and fibrosis, is a hallmark of DN in human subjects and mouse models.

METHODS

This study was designed to provide evidences that the modulation of the system involving TIMP3 and its target A Disintegrin And Metalloproteinase 17 (ADAM17), may rescue kidney pathology in diabetic mice. Mice with cell-targeted overexpression of TIMP3 in myeloid cells (MacT3), podocyte-specific ADAM17 knockout mice (∆PodA17), and DBA/2J mice, were rendered diabetic at 8 weeks of age with a low-dose streptozotocin protocol. DBA/2J mice were administered new peptides based on the human TIMP3 N-terminal domain, specifically conjugated with G3C12, a carrier peptide highly selective and efficient for transport to the kidney. Twelve weeks after Streptozotocin injections, 24-hour albuminuria was determined by ELISA, kidney morphometry was analyzed by periodic acid-shift staining, and Real Time-PCR and western blot analysis were performed on mRNA and protein extracted from kidney cortex.

RESULTS

Our results showed that both genetic modifications and peptides treatment positively affect renal function and structure in diabetic mice, as indicated by a significant and consistent decline in albuminuria along with reduction in glomerular lesions, as indicated by reduced mesangial expansion and glomerular hypertrophy, decreased deposition of extracellular matrix in the mesangium, diminished protein expression of the NADPH oxidases 4 (NOX4), and the improvement of podocyte structural markers such as WT1, nephrin, and podocin. Moreover, the positive effects were exerted through a mechanism independent from glycemic control.

CONCLUSIONS

In diabetic mice the targeting of TIMP3 system improved kidney structure and function, representing a valid approach to develop new avenues to treat this severe complication of diabetes.

Frataxin deficiency induces lipid accumulation and affects thermogenesis in brown adipose tissue

Decreased expression of mitochondrial frataxin (FXN) causes Friedreich's ataxia (FRDA), a neurodegenerative disease with type 2 diabetes (T2D) as severe comorbidity. Brown adipose tissue (BAT) is a mitochondria-enriched and anti-diabetic tissue that turns excess energy into heat to maintain metabolic homeostasis. Here we report that the FXN knock-in/knock-out (KIKO) mouse shows hyperlipidemia, reduced energy expenditure and insulin sensitivity, and elevated plasma leptin, recapitulating T2D-like signatures. FXN deficiency leads to disrupted mitochondrial ultrastructure and oxygen consumption as well as lipid accumulation in BAT. Transcriptomic data highlights cold intolerance in association with iron-mediated cell death (ferroptosis). Impaired PKA-mediated lipolysis and expression of genes controlling mitochondrial metabolism, lipid catabolism and adipogenesis were observed in BAT of KIKO mice as well as in FXN-deficient T37i brown and primary adipocytes. Significant susceptibility to ferroptosis was observed in adipocyte precursors that showed increased lipid peroxidation and decreased glutathione peroxidase 4. Collectively our data point to BAT dysfunction in FRDA and suggest BAT as promising therapeutic target to overcome T2D in FRDA.

Timp3 deficiency affects the progression of DEN-related hepatocellular carcinoma during diet-induced obesity in mice

AIM

Obesity and low-grade inflammation are associated with an increased risk of hepatocellular carcinoma (HCC), a leading cause of cancer-related death worldwide. The tissue inhibitor of metalloproteinase (TIMP) 3, an endogenous inhibitor of protease activity that represents a key mediator of inflammation, is reduced in inflammatory metabolic disorders and cancer. In contrast, Timp3-deficient mice (Timp3^-/-) are highly resistant to developing HCC in response to a diethylnitrosamine (DEN); therefore, we aimed to elucidate the biological role of genetic loss of Timp3 in obesity-related hepatocarcinogenesis.

METHODS

Fourteen-day-old male wild-type (wt) and Timp3^-/- mice were injected with 25 mg/kg DEN or an equal volume of saline. After 4 weeks, mice were randomized into two dietary groups and fed either normal or high-fat diet and allowed to grow until 32 weeks of age. Liver histological features were analyzed, and differentially expressed genes in the liver were quantified.

RESULTS

In Timp3^-/- mice fed with the obesogenic diet, despite the increase in liver steatosis and inflammation, both the number of tumors and the total tumor size are significantly reduced 30 weeks post-DEN injection, compared to control mice. Moreover, Timp3 deletion in hepatocarcinogenesis during obesity is associated with a reduction in FoxM1 transcriptional activity through H19/miR-675/p53 pathway.

CONCLUSIONS

This study suggests that Timp3 ablation leads to cell cycle perturbation, at least in part by repressing FoxM1 transcriptional activity through H19/miR-675/p53 pathway.

Soluble ST2 is a biomarker for cardiovascular mortality related to abnormal glucose metabolism in high-risk subjects

AIMS

Inflammation plays a role in the development and progression of type 2 diabetes macroangiopathy. Interleukin 33 (IL-33) drives production of Th2-associated cytokines. The soluble form of suppression of tumorigenicity 2 (sST2) acting as a decoy receptor blocks IL-33 and tones down Th2 inflammatory response. We investigated the role of sST2 as a predictor of CV and all-cause mortality in a cohort of patients affected by established atherosclerotic disease.

METHODS

399 patients with atherosclerotic disease from the Tor Vergata Atherosclerosis Registry performed follow-up every year by phone interview. The primary endpoint was cardiovascular death and the secondary endpoint was death for any other disease.

RESULTS

sST2 plasma levels were significantly increased from normal glucose-tolerant patients to patients with history of type 2 diabetes (p < 0.00001). Levels of sST2 were significantly correlated with fasting plasma glucose (R = 0.16, p = 0.002), HbA1c (R = 0.17, p = 0.002), and HOMA (R = 0.16, p = 0.004). Dividing patients in tertiles of sST2 levels, those belonging to the highest tertile showed an increased rate of all-cause and cardiovascular mortality, (all-cause mortality p = 0.045 and CVD mortality p = 0.02). A multivariate Cox analysis revealed that sST2 increased the risk in cardiovascular mortality per SD by hazard ratio 1.050 (95% CI 1.006-1.097, p = 0.025) after adjustment for age and hs-CRP while it did not significantly change the risk for all-cause mortality.

CONCLUSIONS

High circulating level of sST2 is associated to increased CVD mortality and markers of metabolic dysfunction in subjects with atherosclerotic disease.

2-hydroxycaproate predicts cardiovascular mortality in patients with atherosclerotic disease

BACKGROUND AND AIMS

We aimed to identify novel biomarkers for cardiovascular mortality through a non-targeted metabolomics approach in patients with established atherosclerotic disease from the Tor Vergata Atherosclerosis Registry (TVAR).

METHODS

We compared the serum baseline metabolome of 19 patients with atherosclerosis suffering from cardiovascular death during follow-up with the baseline serum metabolome of 20 control patients matched for age, gender, body mass index (BMI) and atherosclerotic disease status, who survived during the observation period.

RESULTS

Three metabolites were significantly different in the cardiovascular mortality (CVM) group compared to controls: 2-hydroxycaproate, gluconate and sorbitol. 2-hydroxycaproate (otherwise known as alpha hydroxy caproate) was also significantly correlated with time to death. The metabolites performed better when combined together rather than singularly on the identification of CVM status.

CONCLUSIONS

Our analysis led to identify few metabolites potentially amenable of translation into the clinical practice as biomarkers for specific metabolic changes in the cardiovascular system in patients with established atherosclerotic disease.

Time-controlled fasting prevents aging-like mitochondrial changes induced by persistent dietary fat overload in skeletal muscle

A large body of evidence suggests that persistent dietary fat overload causes mitochondrial dysfunction and systemic metabolic gridlock. Mitochondrial and lipid metabolism in skeletal muscle (SkM) are severely affected upon persistent high fat diet (HFD) leading to premature tissue aging. Here, we designed weekly cycles of fasting (called as time-controlled fasting, TCF) and showed that they were effective in limiting mitochondrial damage and metabolic disturbances induced by HFD. Specifically, TCF was able to prevent the decline of adipose triglyceride lipase (Atgl), maintain efficient mitochondrial respiration in SkM as well as improve blood glucose and lipid profile. Atgl was found to be the mediator of such preventive effects as its downregulation or up-regulation in C2C12 myotubes triggers mitochondrial alteration or protects against the deleterious effects of high fat levels respectively. In conclusion, TCF could represent an effective strategy to limit mitochondrial impairment and metabolic inflexibility that are typically induced by modern western diets or during aging.

Proteomic and metabolomic characterization of streptozotocin-induced diabetic nephropathy in TIMP3-deficient mice

AIMS

The tissue inhibitor of metalloproteinase TIMP3 is a stromal protein that restrains the activity of both protease and receptor in the extracellular matrix and has been found to be down-regulated in diabetic nephropathy (DN), the leading cause of end-stage renal disease in developed countries.

METHODS

In order to gain deeper insights on the association of loss of TIMP3 and DN, we performed differential proteomic analysis of kidney and blood metabolic profiling of wild-type and Timp3-knockout mice before and after streptozotocin (STZ) treatment, widely used to induce insulin deficiency and hyperglycemia.

RESULTS

Kidney proteomic data and blood metabolic profiles suggest significant alterations of peroxisomal and mitochondrial fatty acids β-oxidation in Timp3-knockout mice compared to wild-type mice under basal condition. These alterations were exacerbated in response to STZ treatment.

CONCLUSIONS

Proteomic and metabolomic approaches showed that loss of TIMP3 alone or in combination with STZ treatment results in significant alterations of kidney lipid metabolism and peripheral acylcarnitine levels, supporting the idea that loss of TIMP3 may generate a phenotype more prone to DN.

A Role for Timp3 in Microbiota-Driven Hepatic Steatosis and Metabolic Dysfunction

The effect of gut microbiota on obesity and insulin resistance is now recognized, but the underlying host-dependent mechanisms remain poorly undefined. We find that tissue inhibitor of metalloproteinase 3 knockout (Timp3(-/-)) mice fed a high-fat diet exhibit gut microbiota dysbiosis, an increase in branched chain and aromatic (BCAA) metabolites, liver steatosis, and an increase in circulating soluble IL-6 receptors (sIL6Rs). sIL6Rs can then activate inflammatory cells, such as CD11c(+) cells, which drive metabolic inflammation. Depleting the microbiota through antibiotic treatment significantly improves glucose tolerance, hepatic steatosis, and systemic inflammation, and neutralizing sIL6R signaling reduces inflammation, but only mildly impacts glucose tolerance. Collectively, our results suggest that gut microbiota is the primary driver of the observed metabolic dysfunction, which is mediated, in part, through IL-6 signaling. Our findings also identify an important role for Timp3 in mediating the effect of the microbiota in metabolic diseases.

TIMP3 interplays with apelin to regulate cardiovascular metabolism in hypercholesterolemic mice

OBJECTIVE

Tissue inhibitor of metalloproteinase 3 (TIMP3) is an extracellular matrix (ECM) bound protein, which has been shown to be downregulated in human subjects and experimental models with cardiometabolic disorders, including type 2 diabetes mellitus, hypertension and atherosclerosis. The aim of this study was to investigate the effects of TIMP3 on cardiac energy homeostasis during increased metabolic stress conditions.

METHODS

ApoE(-/-)TIMP3(-/-) and ApoE(-/-) mice on a C57BL/6 background were subjected to telemetric ECG analysis and experimental myocardial infarction as models of cardiac stress induction. We used Western blot, qRT-PCR, histology, metabolomics, RNA-sequencing and in vivo phenotypical analysis to investigate the molecular mechanisms of altered cardiac energy metabolism.

RESULTS

ApoE(-/-)TIMP3(-/-) revealed decreased lifespan. Telemetric ECG analysis showed increased arrhythmic episodes, and experimental myocardial infarction by left anterior descending artery (LAD) ligation resulted in increased peri-operative mortality together with increased scar formation, ventricular dilatation and a reduction of cardiac function after 4 weeks in the few survivors. Hearts of ApoE(-/-)TIMP3(-/-) exhibited accumulation of neutral lipids when fed a chow diet, which was exacerbated by a high fat, high cholesterol diet. Metabolomics analysis revealed an increase in circulating markers of oxidative stress with a reduction in long chain fatty acids. Using whole heart mRNA sequencing, we identified apelin as a putative modulator of these metabolic defects. Apelin is a regulator of fatty acid oxidation, and we found a reduction in the levels of enzymes involved in fatty acid oxidation in the left ventricle of ApoE(-/-)TIMP3(-/-) mice. Injection of apelin restored the hitherto identified metabolic defects of lipid oxidation.

CONCLUSION

TIMP3 regulates lipid metabolism as well as oxidative stress response via apelin. These findings therefore suggest that TIMP3 maintains metabolic flexibility in the heart, particularly during episodes of increased cardiac stress.

ITCH modulates SIRT6 and SREBP2 to influence lipid metabolism and atherosclerosis in ApoE null mice

Atherosclerosis is a chronic inflammatory disease characterized by the infiltration of pro-inflammatory macrophages into a lipid-laden plaque. ITCH is an E3 ubiquitin ligase that has been shown to polarize macrophages to an anti-inflammatory phenotype. We therefore investigated the effect of ITCH deficiency on the development of atherosclerosis. ApoE-/-ITCH-/- mice fed a western diet for 12 weeks showed increased circulating M2 macrophages together with a reduction in plaque formation. Bone marrow transplantation recreated the haemopoietic phenotype of increased circulating M2 macrophages but failed to affect plaque development. Intriguingly, the loss of ITCH lead to a reduction in circulating cholesterol levels through interference with nuclear SREBP2 clearance. This resulted in increased LDL reuptake through upregulation of LDL receptor expression. Furthermore, ApoE-/-ITCH-/- mice exhibit reduced hepatic steatosis, increased mitochondrial oxidative capacity and an increased reliance on fatty acids as energy source. We found that ITCH ubiquitinates SIRT6, leading to its breakdown, and thus promoting hepatic lipid infiltration through reduced fatty acid oxidation. The E3 Ubiquitin Ligase ITCH modulates lipid metabolism impacting on atherosclerosis progression independently from effects on myeloid cells polarization through control of SIRT6 and SREBP2 ubiquitination. Thus, modulation of ITCH may provide a target for the treatment of hypercholesterolemia and hyperlipidemia.

IL-21 is a major negative regulator of IRF4-dependent lipolysis affecting Tregs in adipose tissue and systemic insulin sensitivity

Obesity elicits immune cell infiltration of adipose tissue provoking chronic low-grade inflammation. Regulatory T cells (Tregs) are specifically reduced in adipose tissue of obese animals. Since interleukin (IL)-21 plays an important role in inducing and maintaining immune-mediated chronic inflammatory processes and negatively regulates Treg differentiation/activity, we hypothesized that it could play a role in obesity-induced insulin resistance. We found IL-21 and IL-21R mRNA expression upregulated in adipose tissue of high-fat diet (HFD) wild-type (WT) mice and in stromal vascular fraction from human obese subjects in parallel to macrophage and inflammatory markers. Interestingly, a larger infiltration of Treg cells was seen in the adipose tissue of IL-21 knockout (KO) mice compared with WT animals fed both normal diet and HFD. In a context of diet-induced obesity, IL-21 KO mice, compared with WT animals, exhibited lower body weight, improved insulin sensitivity, and decreased adipose and hepatic inflammation. This metabolic phenotype is accompanied by a higher induction of interferon regulatory factor 4 (IRF4), a transcriptional regulator of fasting lipolysis in adipose tissue. Our data suggest that IL-21 exerts negative regulation on IRF4 and Treg activity, developing and maintaining adipose tissue inflammation in the obesity state.

ITCH deficiency protects from diet-induced obesity

Classically activated macrophages (M1) secrete proinflammatory cytokine and are predominant in obese adipose tissue. M2 macrophages, prevalent in lean adipose tissue, are induced by IL-13 and IL-4, mainly secreted by Th2 lymphocytes, and produce the anti-inflammatory cytokine IL-10. ITCH is a ubiquitously expressed E3 ubiquitin ligase involved in T-cell differentiation and in a wide range of inflammatory pathways. ITCH downregulation in lymphocytes causes aberrant Th2 differentiation. To investigate the role of Th2/M2 polarization in obesity-related inflammation and insulin resistance, we compared wild-type and Itch(-/-) mice in a context of diet-induced obesity (high-fat diet [HFD]). When subjected to HFD, Itch(-/-) mice did not show an increase in body weight or insulin resistance; calorimetric analysis suggested an accelerated metabolism. The molecular analysis of metabolically active tissue revealed increased levels of M2 markers and genes involved in fatty acid oxidation. Histological examination of livers from Itch(-/-) mice suggested that ITCH deficiency protects mice from obesity-related nonalcoholic fatty liver disease. We also found a negative correlation between ITCH and M2 marker expression in human adipose tissues. Taken together, our data indicate that ITCH E3 ubiquitin ligase deficiency protects from the metabolic disorder caused by obesity.

MiR-216a: a link between endothelial dysfunction and autophagy

Endothelial dysfunction and impaired autophagic activity have a crucial role in aging-related diseases such as cardiovascular dysfunction and atherosclerosis. We have identified miR-216a as a microRNA that is induced during endothelial aging and, according to the computational analysis, among its targets includes two autophagy-related genes, Beclin1 (BECN1) and ATG5. Therefore, we have evaluated the role of miR-216a as a molecular component involved in the loss of autophagic function during endothelial aging. The inverse correlation between miR-216a and autophagic genes was conserved during human umbilical vein endothelial cells (HUVECs) aging and in vivo models of human atherosclerosis and heart failure. Luciferase experiments indicated BECN1, but not ATG5 as a direct target of miR-216a. HUVECs were transfected in order to modulate miR-216a expression and stimulated with 100 μg/ml oxidized low-density lipoprotein (ox-LDL) to induce a stress repairing autophagic process. We found that in young HUVECs, miR-216a overexpression repressed BECN1 and ATG5 expression and the ox-LDL induced autophagy, as evaluated by microtubule-associated protein 1 light chain 3 (LC3B) analysis and cytofluorimetric assay. Moreover, miR-216a stimulated ox-LDL accumulation and monocyte adhesion in HUVECs. Conversely, inhibition of miR-216a in old HUVECs rescued the ability to induce a protective autophagy in response to ox-LDL stimulus. In conclusion, mir-216a controls ox-LDL induced autophagy in HUVECs by regulating intracellular levels of BECN1 and may have a relevant role in the pathogenesis of cardiovascular disorders and atherosclerosis.

Expression of tissue inhibitor of metalloprotease 3 is reduced in ischemic but not neuropathic ulcers from patients with type 2 diabetes mellitus

Diabetic foot ulceration remains one of the most common and most serious consequences of diabetes. Persistently high levels of matrix metalloproteases (MMPs) contribute to wound chronicity. Our aim was to assess the concentrations of MMPs and tissue inhibitors of metalloproteinases (TIMPs) in neuropathic and ischemic diabetic foot ulcers by analyzing biopsy samples. In this study, biopsies were taken from 35 diabetic foot ulcers of type 2 diabetes mellitus patients and distinguished in neuropathic (n = 14) or ischemic (n = 21). Zymography assay was utilized for the analysis of MMP-2 and MMP-9 activity. TACE activity was evaluated by a specific fluorimetric assay. mRNA levels of MMPs as well as TIMPs were detected using quantitative real-time polymerase chain reaction. The activity of MMP9 and A Disintegrin and A MetalloProtease Domain 17/TNF-Alpha Converting Enzyme (ADAM17/TACE) was significantly increased in ischemic compared to neuropathic biopsies. No differences were detected between both groups for the mRNA levels of MMPs as well as of ADAMs. However, TIMP3 mRNA expression was decreased in ischemic samples. The combination of increased activity of MMP9 and ADAM17/TACE with decreased concentrations of TIMP-3 mRNA expression in ischemic diabetic foot ulcers compared to neuropathic samples suggests that the increased proteolytic environment may represent a causative factor in the ulcer progression. New treatment strategies for healing diabetic foot ulcers could be directed toward increasing levels of TIMP3.

Loss of TIMP3 underlies diabetic nephropathy via FoxO1/STAT1 interplay

ADAM17 and its inhibitor TIMP3 are involved in nephropathy, but their role in diabetic kidney disease (DKD) is unclear. Diabetic Timp3^−/− mice showed increased albuminuria, increased membrane thickness and mesangial expansion. Microarray profiling uncovered a significant reduction of Foxo1 expression in diabetic Timp3^−/− mice compared to WT, along with FoxO1 target genes involved in autophagy, while STAT1, a repressor of FoxO1 transcription, was increased. Re-expression of Timp3 in Timp3^−/− mesangial cells rescued the expression of Foxo1 and its targets, and decreased STAT1 expression to control levels; abolishing STAT1 expression led to a rescue of FoxO1, evoking a role of STAT1 in linking Timp3 deficiency to FoxO1. Studies on kidney biopsies from patients with diabetic nephropathy confirmed a significant reduction in TIMP3, FoxO1 and FoxO1 target genes involved in autophagy compared to controls, while STAT1 expression was strongly increased.

Our study suggests that loss of TIMP3 is a hallmark of DKD in human and mouse models and designates TIMP3 as a new possible therapeutic target for diabetic nephropathy.

The role of ADAM17 in metabolic inflammation

The TNF-alpha Converting Enzyme (TACE), also called ADAM17 (A Disintegrin and A Metalloproteinase 17) is a type I transmembrane metalloproteinase involved in the shedding of the extracellular domain of several transmembrane proteins such as cytokines, growth factors, receptors and adhesion molecules. Some of these proteolytic events are part of cleavage cascades known as Regulated Intramembrane Proteolysis and lead to intracellular signaling. Evidence is provided that ADAM17 plays a role in atherosclerosis, in adipose tissue metabolism, insulin resistance and diabetes. The multitude of substrates cleaved by ADAM17 makes this enzyme an attractive candidate to study its role in inflammatory disorders. This review is focused on effects of ADAM17 in major metabolic tissues.

Tissue inhibitor of metalloproteinase-3 regulates inflammation in human and mouse intestine

BACKGROUND & AIMS

Tissue inhibitor of metalloproteinases (TIMP)-3 is an inhibitor of matrix metalloproteinases, which regulates tissue inflammation, damage, and repair. We investigated the role of TIMP-3 in intestinal inflammation in human beings and mice.

METHODS

We used real-time polymerase chain reaction and flow cytometry to measure levels of TIMP-3 in intestine samples from patients with Crohn's disease (CD) and those without (controls). We also analyzed TIMP-3 levels in lamina propria mononuclear cells (LPMCs) collected from biopsy samples of individuals with or without CD (controls) and then stimulated with transforming growth factor (TGF)-β1, as well as in biopsy samples collected from patients with CD and then incubated with a Smad7 anti-sense oligonucleotide (knock down). LPMCs and biopsy samples from patients with CD were cultured with exogenous TIMP-3 and levels of inflammatory cytokines were measured. We evaluated the susceptibility of wild-type, TIMP-3-knockout (TIMP-3-KO), and transgenic (TIMP-3-Tg) mice to induction of colitis with 2, 4, 6-trinitrobenzene-sulfonic-acid (TNBS), and the course of colitis in recombinase-activating gene-1-null mice after transfer of wild-type or TIMP-3-KO T cells.

RESULTS

Levels of TIMP-3 were reduced in intestine samples from patients with CD compared with controls. Incubation of control LPMCs with TGF-β1 up-regulated TIMP-3; knockdown of Smad7, an inhibitor of TGF-β1, in biopsy samples from patients with CD increased levels of TIMP-3. Exogenous TIMP-3 reduced levels of inflammatory cytokines in CD LPMCs and biopsy samples. TIMP-3-KO mice developed severe colitis after administration of TNBS, whereas TIMP-3-Tg mice were resistant to TNBS-induced colitis. Reconstitution of recombinase-activating gene-1-null mice with T cells from TIMP-3-KO mice increased the severity of colitis, compared with reconstitution with wild-type T cells.

CONCLUSIONS

TIMP-3 is down-regulated in inflamed intestine of patients with CD. Its expression is regulated by TGF-β1, and knock-down of Smad7 in intestinal tissues from patient with CD up-regulates TIMP-3. Loss or reduction of TIMP-3 in mice promotes development of colitis.

TIMP3 overexpression in macrophages protects from insulin resistance, adipose inflammation, and nonalcoholic fatty liver disease in mice

The tissue inhibitor of metalloproteinase (TIMP)3, a stromal protein that restrains the activity of proteases and receptors, is reduced in inflammatory metabolic disorders such as type 2 diabetes mellitus (T2DM) and atherosclerosis. We overexpressed Timp3 in mouse macrophages (MacT3) to analyze its potential antidiabetic and antiatherosclerotic effects. Transgenic mice with myeloid cells targeting overexpression of TIMP3 were generated and fed a high-fat diet for 20 weeks. Physical and metabolic phenotypes were determined. Inflammatory markers, lipid accumulation, and insulin sensitivity were measured in white adipose tissue (WAT), liver, and skeletal muscle. In a model of insulin resistance, MacT3 mice were more glucose tolerant and insulin sensitive than wild-type mice in both in vitro and in vivo tests. Molecular and biochemical analyses revealed that increased expression of TIMP3 restrained metabolic inflammation and stress-related pathways, including Jun NH2-terminal kinase and p38 kinase activation, in WAT and liver. TIMP3 overexpression in macrophages resulted in reduced activation of oxidative stress signals related to lipid peroxidation, protein carbonylation, and nitration in WAT and liver. Our data show that macrophage-specific overexpression of TIMP3 protects from metabolic inflammation and related metabolic disorders such as insulin resistance, glucose intolerance, and nonalcoholic steatohepatitis.

TIMP3 is reduced in atherosclerotic plaques from subjects with type 2 diabetes and increased by SirT1

OBJECTIVE

Atherosclerosis is accelerated in subjects with type 2 diabetes by unknown mechanisms. We identified tissue inhibitor of metalloproteinase 3 (TIMP3), the endogenous inhibitor of A disintegrin and metalloprotease domain 17 (ADAM17) and other matrix metalloproteinases (MMPs), as a gene modifier for insulin resistance and vascular inflammation in mice. We tested its association with atherosclerosis in subjects with type 2 diabetes and identified Sirtuin 1 (SirT1) as a major regulator of TIMP3 expression.

RESEARCH DESIGN AND METHODS

We investigated ADAM10, ADAM17, MMP9, TIMP1, TIMP2, TIMP3, and TIMP4 expression levels in human carotid atherosclerotic plaques (n = 60) from subjects with and without diabetes. Human vascular smooth muscle cells exposed to several metabolic stimuli were used to identify regulators of TIMP3 expression. SirT1 small interference RNA, cDNA, and TIMP3 promoter gene reporter were used to study SirT1-dependent regulation of TIMP3.

RESULTS

Here, we show that in human carotid atherosclerotic plaques, TIMP3 was significantly reduced in subjects with type 2 diabetes, leading to ADAM17 and MMP9 overactivity. Reduced expression of TIMP3 was associated in vivo with SirT1 levels. In smooth muscle cells, inhibition of SirT1 activity and levels reduced TIMP3 expression, whereas SirT1 overexpression increased TIMP3 promoter activity.

CONCLUSIONS

In atherosclerotic plaques from subjects with type 2 diabetes, the deregulation of ADAM17 and MMP9 activities is related to inadequate expression of TIMP3 via SirT1. Studies in vascular cells confirmed the role of SirT1 in tuning TIMP3 expression.

MicroRNA 217 modulates endothelial cell senescence via silent information regulator 1

BACKGROUND

Aging is a major risk factor for the development of atherosclerosis and coronary artery disease. Through a microarray approach, we have identified a microRNA (miR-217) that is progressively expressed in endothelial cells with aging. miR-217 regulates the expression of silent information regulator 1 (SirT1), a major regulator of longevity and metabolic disorders that is progressively reduced in multiple tissues during aging.

METHODS AND RESULTS

miR-217 inhibits SirT1 expression through a miR-217-binding site within the 3'-UTR of SirT1. In young human umbilical vein endothelial cells, human aortic endothelial cells, and human coronary artery endothelial cells, miR-217 induces a premature senescence-like phenotype and leads to an impairment in angiogenesis via inhibition of SirT1 and modulation of FoxO1 (forkhead box O1) and endothelial nitric oxide synthase acetylation. Conversely, inhibition of miR-217 in old endothelial cells ultimately reduces senescence and increases angiogenic activity via an increase in SirT1. miR-217 is expressed in human atherosclerotic lesions and is negatively correlated with SirT1 expression and with FoxO1 acetylation status.

CONCLUSIONS

Our data pinpoint miR-217 as an endogenous inhibitor of SirT1, which promotes endothelial senescence and is potentially amenable to therapeutic manipulation for prevention of endothelial dysfunction in metabolic disorders.