Role of Metalloproteinases in Diabetes-associated Mild Cognitive Impairment.

Diabetes has been linked to an increased risk of mild cognitive impairment (MCI), a condition characterized by a subtle cognitive decline that may precede the development of dementia. The underlying mechanisms connecting diabetes and MCI involve complex interactions between metabolic dysregulation, inflammation, and neurodegeneration. A critical mechanism implicated in diabetes and MCI is the activation of inflammatory pathways. Chronic low-grade inflammation, as observed in diabetes, can lead to the production of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-1 beta (IL-1ß), and interferon-gamma (IFNγ), each of which can exacerbate neuroinflammation and contribute to cognitive decline. A crucial enzyme involved in regulating inflammation is ADAM17, a disintegrin, and metalloproteinase, which can cleave and release TNF-α from its membrane-bound precursor and cause it to become activated. These processes, in turn, activate additional inflammation-related pathways, such as AKT, NF-κB, NLP3, MAPK, and JAK-STAT pathways. Recent research has provided novel insights into the role of ADAM17 in diabetes and neurodegenerative diseases. ADAM17 is upregulated in both diabetes and Alzheimer's disease, suggesting a shared mechanism and implicating inflammation as a possible contributor to much broader forms of pathology and pointing to a possible link between inflammation and the emergence of MCI. This review provides an overview of the different roles of ADAM17 in diabetes-associated mild cognitive impairment diseases. It identifies mechanistic connections through which ADAM17 and associated pathways may influence the emergence of mild cognitive impairment.

Targeting Mitochondrial ATP-Synthase: Evolving Role of Chromium as a Regulator of Carbohydrate and Fat Metabolism.

The micronutrient trivalent chromium, 3 + (Cr(III)), is postulated to play a role in carbohydrate, lipid, and protein metabolism. Although the mechanisms by which chromium mediates its actions are largely unknown, previous studies have suggested that pharmacological doses of chromium improve cardiometabolic symptoms by augmenting carbohydrate and lipid metabolism. Activation of AMP-activated protein kinase (AMPK) was among the many mechanisms proposed to explain the salutary actions of chromium on carbohydrate metabolism. However, the molecular pathways leading to the activation of AMPK by chromium remained elusive. In an elegant series of studies, Sun and coworkers recently demonstrated that chromium augments AMPK activation by binding to the beta-subunit of ATP synthase and inhibiting its enzymatic activity. This mini-review attempts to trace the evolving understanding of the molecular mechanisms of chromium leading to the hitherto novel pathway unraveled by Sun and coworkers and its potential implication to our understanding of the biological actions of chromium.

Role of cathepsin K in the expression of mechanical hypersensitivity following intra-plantar inflammation.

Persistent/chronic inflammatory pain involves multiple pathophysiological mechanisms and is far more complex than acute/momentary pain. Current therapeutics for chronic inflammatory pain are often not effective because the etiology responsible for the pain is not addressed by traditional pharmacological treatments. Cathepsin K is a cysteine protease that has mostly been studied in the context of bone and joint disorders. Previous work by others has shown that inhibition of cathepsin K activity reduces osteoarthritis-associated nociception in joints. However, the role of cathepsin K in cutaneous inflammation is understudied. We assessed the effectiveness of genetic deletion or pharmacological inhibition of cathepsin K in male mice on the expression of nocifensive behaviors after formalin injection or mechanical and thermal hypersensitivity after injection of complete Freund's adjuvant (CFA) into the mouse hind paw. Our data demonstrate that cathepsin K knockout mice (Ctsk-/-) have a reduction in nocifensive behaviors in the formalin test. In addition, Ctsk-/- do not develop mechanical hypersensitivity after CFA injection for up to 7 days. Moreover, we found that inhibition of cathepsin K reduced mechanical hypersensitivity after CFA injection and mRNA levels, protein levels, and cathepsin K activity levels were elevated after CFA injection. Based upon our data, cathepsin K is indicated to play a role in the expression of chemically-induced cutaneous hypersensitivity, as Ctsk-/- mice do not develop mechanical hypersensitivity and show a reduction in nocifensive behaviors. Further research is needed to determine whether attenuating cathepsin K activity may generate a clinically relevant therapeutic.

Sex Differences in Cardiac AMP-Activated Protein Kinase Following Exhaustive Exercise.

Ischemic heart disease presents with significant differences between sexes. Endurance exercise protects the heart against ischemic disease and also distinctly impacts male and female patients through unidentified mechanisms, though some evidence implicates 5'-AMP-activated protein kinase (AMPK). The purpose of this investigation was to assess the impact of training and sex on cardiac AMPK activation following exhaustive exercise. AMPK activation was measured in trained and sedentary mice of both sexes. Trained mice ran on a treadmill at progressively increasing speeds and duration for 12 weeks. Trained and sedentary mice of both sexes were euthanized immediately following exhaustive exercise and compared to sedentary controls. Endurance training elicited adaptations indicative of aerobic adaptation including higher max running velocities and cardiac hypertrophy with no differences between males and females. AMPK activity was higher in male compared to females, and trained exhibited higher AMPK activity compared to sedentary mice. In response to training, male mice activated AMPK more robustly than female mice. Chronic exercise training increases the ability to activate cardiac AMPK in response to exhaustive exercise in a sex-specific manner. Understanding the interaction between exercise and sex is vital for use of exercise as medicine for heart disease in both men and women.

Correction: Cardiomyocyte-specific disruption of Cathepsin K protects against doxorubicin-induced cardiotoxicity.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Safety and Efficacy of N-SORB®, a Proprietary KD120 MEC Metabolically Activated Enzyme Formulation: A Randomized, Double-Blind, Placebo-Controlled Study.

Background: Enzymes are crucial for all aspects of metabolic function. Digestive enzymes from natural sources have been credited with beneficial effects in the digestion and absorption of food. N-SORB is a novel KD120 multienzyme complex (MEC) of metabolically activated enzymes composed of proteases, amylases, lipases, alpha-galactosidase, and glucoamylase from natural sources. These enzymes are encapsulated in a SK713 SLP (non-GMO soy lecithin phospholipid) absorption technology (Prodosome®). Objective: This randomized, double-blind placebo-controlled investigation assessed the safety and efficacy of N-SORB KD120 MEC in healthy male and female volunteers on various parameters of the blood, immunity, body composition, physical health, and quality of life following a 90-day intervention. Methods: Forty-six male and female (mean age: 25.8 ± 12.1 years) healthy volunteers were randomly assigned to receive either N-SORB (1 mL, twice daily) or placebo for 90 consecutive days. Complete blood count, as well as blood glucose, liver enzymes, and lipid profile were assessed pre- and post-intervention. Serum cytokine levels were determined by using a Bio-Plex Pro Human Cytokine 8-plex assay and enzyme linked immunosorbent assay (ELISA). Whole body composition analysis was performed by dual-energy x-ray absorptiometry (DEXA) to determine body fat mass, lean mass, and android and gynoid fat. Body weight, blood pressure, and physical health were assessed. Changes in quality of life were examined using the World Health Organization Quality of Life-abbreviated version and sleep quality was assessed using the 24-item Pittsburgh Sleep Quality Index (PSQI) questionnaire. Adverse events were monitored before, during, and after completion of the study. Results: Of the 46 subjects enrolled, a total of 40 subjects successfully completed the study. Compared to placebo, changes in blood cell counts including hematocrit, hemoglobin, mean corpuscular volume, platelets, and lymphocytes provide evidence of some improvement. Quality of life (QOL) parameters showed a small but significant improvement in the N-SORB group. A significant increase was observed in aspartate aminotransferase level in the placebo group at the end of 90 days of treatment; however, no increase was observed in the N-SORB group. No significant changes in blood urea nitrogen, serum creatinine, alkaline phosphatase, alanine aminotransferase, and lipid profile were observed between the placebo and treatment groups before and following intervention. No adverse effects were reported. Conclusions: This randomized, double blind, placebo-controlled clinical study demonstrates that short-term intervention with N-SORB improves the QOL and PSQI in healthy volunteers and did not significantly alter cardiometabolic parameters, lipid profile, or body composition.

Effect of Curcumin and α-Lipoic Acid in Attenuating Weight Gain and Adiposity.

Objective: Obesity is growing at epidemic proportions worldwide. Natural compounds curcumin and α-lipoic acid have been shown to reduce body-weight gain in both preclinical and clinical studies. This study examined the effect of a combination of curcumin and α-lipoic acid on weight gain and adiposity in high-fat-diet (HFD)-fed mice. Methods: C57BL6 mice (7 weeks old) were randomly assigned to receive either HFD (60% fat) or a normal diet (ND, 10% fat) for a 12-week period, following which the mice receiving HFD were further assigned to supplemental curcumin (0.07%), α-lipoic acid (0.2%), or a combination of curcumin and α-lipoic acid formulated into the HFD for a further 12 weeks. Food intake and body mass were determined on a weekly basis. Body fat composition was determined by dual energy X-ray absorptiometry. Results: Treatment with both curcumin and α-lipoic acid significantly reduced body weight gain in HFD-treated mice, and the combination was more effective in attenuating body weight compared to the individual agents. Food intake and caloric intake were significantly lower in the mice that received α-lipoic acid. Percentage body fat and fat mass and lean body mass, which were increased following HFD feeding, were attenuated in the mice receiving curcumin and the combination. Lean mass was also elevated in the mice that were subjected to an HFD, which was unaltered by curcumin or the combination. Conclusions: Taken together, the combination of curcumin and α-lipoic acid exhibits an additive effect in reducing weight gain and adiposity in response to high-fat feeding.

Cardiomyocyte-specific knockout of endothelin receptor a attenuates obesity cardiomyopathy.

Endothelin (ET)-1 is implicated in the pathophysiology of cardiovascular diseases although its role in obesity anomalies has not been fully elucidated. This study was designed to examine the impact of ET-1 receptor A (ETA) ablation on obesity-induced changes in cardiac geometry and contractile function, as well as the mechanisms involved with a focus on autophagy. Cardiomyocyte-specific ETA receptor knockout (ETAKO) and WT mice were fed either low-fat (10% calorie from fat) or high-fat (45% calorie from fat) diet for 24 weeks. Glucose tolerance test was examined to confirm insulin resistance. High-fat diet intake compromised myocardial geometry (enlarged left ventricular diameters in systole and diastole), morphology (cardiac hypertrophy, increased wall thickness and interstitial fibrosis), contractile function (reduced fractional shortening, ejection fraction and cardiomyocyte shortening) and intracellular Ca2+ handling, the effect of which was significantly attenuated by ETAKO. TUNEL staining revealed overt apoptosis in high-fat-fed group, the effect was reverted by ETAKO. Western blot analysis noted that high-fat intake downregulated leptin receptor and PPARγ, insulin signaling (elevated basal/dampened insulin-stimulated phosphorylation of Akt and IRS1), phosphorylation of AMPK, ACC, upregulated GATA-4, ANP, NFATc3, PPARα, m-TOR/p70s6k signaling, which were attenuated by ETAKO with the exception of AMPK/ACC. Furthermore, high-fat intake suppressed cardiac autophagy, which was abrogated by ETAKO. In cultured murine cardiomyocytes, palmitic acid challenged mimicked high-fat diet-induced hypertrophic and autophagic responses, the effect of which were abolished by the ETA receptor antagonist BQ123 or mTOR inhibitor rapamycin. These results suggest that inhibition of ETA rescues high-fat intake-induced cardiac anomalies possibly through autophagy regulation.

Cardiomyocyte-specific disruption of Cathepsin K protects against doxorubicin-induced cardiotoxicity.

The lysosomal cysteine protease Cathepsin K is elevated in humans and animal models of heart failure. Our recent studies show that whole-body deletion of Cathepsin K protects mice against cardiac dysfunction. Whether this is attributable to a direct effect on cardiomyocytes or is a consequence of the global metabolic alterations associated with Cathepsin K deletion is unknown. To determine the role of Cathepsin K in cardiomyocytes, we developed a cardiomyocyte-specific Cathepsin K-deficient mouse model and tested the hypothesis that ablation of Cathepsin K in cardiomyocytes would ameliorate the cardiotoxic side-effects of the anticancer drug doxorubicin. We used an α-myosin heavy chain promoter to drive expression of Cre, which resulted in over 80% reduction in protein and mRNA levels of cardiac Cathepsin K at baseline. Four-month-old control (Myh-Cre-; Ctsk fl/fl) and Cathepsin K knockout (Myh-Cre+; Ctsk fl/fl) mice received intraperitoneal injections of doxorubicin or vehicle, 1 week following which, body and tissue weight, echocardiographic properties, cardiomyocyte contractile function and Ca2+-handling were evaluated. Control mice treated with doxorubicin exhibited a marked increase in cardiac Cathepsin K, which was associated with an impairment in cardiac structure and function, evidenced as an increase in end-systolic and end-diastolic diameters, decreased fractional shortening and wall thickness, disruption in cardiac sarcomere and microfilaments and impaired intracellular Ca2+ homeostasis. In contrast, the aforementioned cardiotoxic effects of doxorubicin were attenuated or reversed in mice lacking cardiac Cathepsin K. Mechanistically, Cathepsin K-deficiency reconciled the disturbance in cardiac energy homeostasis and attenuated NF-κB signaling and apoptosis to ameliorate doxorubicin-induced cardiotoxicity. Cathepsin K may represent a viable drug target to treat cardiac disease.

Deletion of protein tyrosine phosphatase 1B obliterates endoplasmic reticulum stress-induced myocardial dysfunction through regulation of autophagy.

Endoplasmic reticulum (ER) stress has been demonstrated to prompt various cardiovascular risks although the underlying mechanism remains elusive. Protein tyrosine phosphatase-1B (PTP1B) serves as an essential negative regulator for insulin signaling. This study examined the role of PTP1B in ER stress-induced myocardial anomalies and underlying mechanism involved with a focus on autophagy. WT and PTP1B knockout mice were subjected to the ER stress inducer tunicamycin (1mg/kg). Cardiac function was evaluated with echocardiography and an Ion-Optix MyoCam system. Western blot analysis was used to monitor the levels of ER stress, autophagy and insulin signaling including insulin receptor substrate (IRS), tribbles homolog 3 (TRIB3), Atg5/7, p62 and LC3-II. Our results showed that ER stress resulted in compromised echocardiographic and cardiomyocyte contractile function, intracellular Ca2+ mishandling, ER stress, O2- production, apoptosis, the effects of which (with the exception of ER stress) were significantly attenuated or negated by PTP1B ablation. Levels of serine phosphorylation of IRS-1, TRIB3, Atg5/7, LC3B and the autophagy adaptor p62 were significantly upregulated while IRS-1 tyrosine phosphorylation was reduced by tunicamycin, the effect of which were obliterated by PTP1B ablation. In vitro study revealed that the autophagy inducer rapamycin and TRIB3 overexpression cancelled PTP1B ablation-offered beneficial effects on cardiomyocyte function or O2- production in murine cardiomyocytes or H9C2 myoblasts. Antioxidant or gene silencing of TRIB3 mimicked PTP1B ablation-induced protective effects. These findings collectively suggested that PTP1B ablation protects against ER stress-induced cardiac anomalies through regulation of autophagy.

Cathepsin K knockout protects against cardiac dysfunction in diabetic mice.

Diabetes is a major risk factor for cardiovascular disease and the lysosomal cysteine protease cathepsin K plays a critical role in cardiac pathophysiology. To expand upon our previous findings, we tested the hypothesis that, knockout of cathepsin K protects against diabetes-associated cardiac anomalies. Wild-type and cathepsin K knockout mice were rendered diabetic by streptozotocin (STZ) injections. Body weight, organ mass, fasting blood glucose, energy expenditure, cardiac geometry and function, cardiac histomorphology, glutathione levels and protein levels of cathepsin K and those associated with Ca2+ handling, calcineurin/NFAT signaling, insulin signaling, cardiac apoptosis and fibrosis were determined. STZ-induced diabetic mice exhibited distinct cardiac dysfunction, dampened intracellular calcium handling, alterations in cardiac morphology, and elevated cardiomyocyte apoptosis, which were mitigated in the cathepsin K knockout mice. Additionally, cathepsin K knockout mice attenuated cardiac oxidative stress and calcineurin/NFAT signaling in diabetic mice. In cultured H9c2 myoblasts, pharmacological inhibition of cathepsin K, or treatment with calcineurin inhibitor rescued cells from high-glucose triggered oxidative stress and apoptosis. Therefore, cathepsin K may represent a potential target in treating diabetes-associated cardiac dysfunction.

Role of microRNA in diabetic cardiomyopathy: From mechanism to intervention.

Diabetic cardiomyopathy is a chronic and irreversible heart complication in diabetic patients, and is characterized by complex pathophysiologic events including early diastolic dysfunction, cardiac hypertrophy, ventricular dilation and systolic dysfunction, eventually resulting in heart failure. Despite these characteristics, the underlying mechanisms leading to diabetic cardiomyopathy are still elusive. Recent studies have implicated microRNA, a small and highly conserved non-coding RNA molecule, in the etiology of diabetes and its complications, suggesting a potentially novel approach for the diagnosis and treatment of diabetic cardiomyopathy. This brief review aims at capturing recent studies related to the role of microRNA in diabetic cardiomyopathy. This article is part of a Special Issue entitled: Genetic and epigenetic control of heart failure - edited by Jun Ren & Megan Yingmei Zhang.

Targeting Apelinergic System in Cardiometabolic Disease.

BACKGROUND: Global burden of cardiometabolic disease warrants development of newer treatment strategies. Apelin is ubiquitously expressed endogenous peptide which is a ligand for the apelinergic (APJ) receptor. Apelin/APJ receptors regulate a variety of biological functions and have been implicated in cardiovascular and metabolic homeostasis. Consequently, the apelinergic pathway represents an attractive target to treat conditions associated with cardiometabolic syndrome. OBJECTIVE: This review highlights the important regulatory role played by apelin in energy metabolism and cardiovascular function, and potential avenues that could be harnessed for therapeutic benefit. CONCLUSION: Apelin/APJ system is a druggable target to treat or prevent a variety of cardiometabolic diseases.

CARD9 as a potential target in cardiovascular disease.

Systemic inflammation and localized macrophage infiltration have been implicated in cardiovascular pathologies, including coronary artery disease, carotid atherosclerosis, heart failure, obesity-associated heart dysfunction, and cardiac fibrosis. Inflammation induces macrophage infiltration and activation and release of cytokines and chemokines, causing tissue dysfunction by instigating a positive feedback loop that further propagates inflammation. Cytosolic adaptor caspase recruitment domain family, member 9 (CARD9) is a protein expressed primarily by dendritic cells, neutrophils, and macrophages, in which it mediates cytokine secretion. The purpose of this review is to highlight the role of CARD9 as a potential target in inflammation-related cardiovascular pathologies.

CARD9 knockout ameliorates myocardial dysfunction associated with high fat diet-induced obesity.

Obesity is associated with chronic inflammation which plays a critical role in the development of cardiovascular dysfunction. Because the adaptor protein caspase recruitment domain-containing protein 9 (CARD9) in macrophages regulates innate immune responses via activation of pro-inflammatory cytokines, we hypothesize that CARD9 mediates the pro-inflammatory signaling associated with obesity en route to myocardial dysfunction. C57BL/6 wild-type (WT) and CARD9(-/-) mice were fed normal diet (ND, 12% fat) or a high fat diet (HFD, 45% fat) for 5months. At the end of 5-month HFD feeding, cardiac function was evaluated using echocardiography. Cardiomyocytes were isolated and contractile properties were measured. Immunofluorescence was performed to detect macrophage infiltration in the heart. Heart tissue homogenates, plasma, and supernatants from isolated macrophages were collected to measure the concentrations of pro-inflammatory cytokines using ELISA kits. Western immunoblotting analyses were performed on heart tissue homogenates and isolated macrophages to explore the underlying signaling mechanism(s). CARD9 knockout alleviated HFD-induced insulin resistance and glucose intolerance, prevented myocardial dysfunction with preserved cardiac fractional shortening and cardiomyocyte contractile properties. CARD9 knockout also significantly decreased the number of infiltrated macrophages in the heart with reduced myocardium-, plasma-, and macrophage-derived cytokines including IL-6, IL-1ß and TNFα. Finally, CARD9 knockout abrogated the increase of p38 MAPK phosphorylation, the decrease of LC3BII/LC3BI ratio and the up-regulation of p62 expression in the heart induced by HFD feeding and restored cardiac autophagy signaling. In conclusion, CARD9 knockout ameliorates myocardial dysfunction associated with HFD-induced obesity, potentially through reduction of macrophage infiltration, suppression of p38 MAPK phosphorylation, and preservation of autophagy in the heart.

Spectroscopic and biological activity studies of the chromium-binding peptide EEEEGDD.

While trivalent chromium has been shown at high doses to have pharmacological effects improving insulin resistance in rodent models of insulin resistance, the mechanism of action of chromium at a molecular level is not known. The chromium-binding and transport agent low-molecular-weight chromium-binding substance (LMWCr) has been proposed to be the biologically active form of chromium. LMWCr has recently been shown to be comprised of a heptapeptide of the sequence EEEEDGG. The binding of Cr(3+) to this heptapeptide has been examined. Mass spectrometric and a variety of spectroscopic studies have shown that multiple chromic ions bind to the peptide in an octahedral fashion through carboxylate groups and potentially small anionic ligands such as oxide and hydroxide. A complex of Cr and the peptide when administered intravenously to mice is able to decrease area under the curve in intravenous glucose tolerance tests. It can also restore insulin-stimulated glucose uptake in myotubes rendered insulin resistant by treating them with a high-glucose media.

Furostanolic saponins from Trigonella foenum-graecum alleviate diet-induced glucose intolerance and hepatic fat accumulation.

SCOPE: The objective of this study was to evaluate the effect of fenugreek furostanolic saponins (Fenfuro(TM) ) either alone or in combination with chlorogenic acid (GCB-70(TM) ) on insulin resistance in mice. METHODS AND RESULTS: Male C57BL/6J mice were subjected to a normal or high-fat diet (HFD) and were randomly assigned to receive Fenfuro(TM) , GCB-70(TM) , or their combination for 24 wk. Metabolic parameters, glucose tolerance, serum triglycerides, cardiac function, and hepatic insulin signaling were evaluated using indirect open-circuit calorimetry, intraperitoneal glucose tolerance test, oil red O staining, echocardiography, and Western blotting, respectively. Intraperitoneal glucose tolerance test revealed glucose intolerance in the mice receiving HFD, which was attenuated by Fenfuro(TM) . Serum triglyceride that was elevated following an HFD was reconciled by both Fenfuro(TM) and the combination. HFD compromised myocardial contractile function, which was unaffected by the treatment. Insulin-stimulated phosphorylation of Protein kinase B (AKT) in the liver was attenuated in mice receiving HFD, which was partially rescued by GCB-70(TM) . Neither treatment altered metabolic parameters or energy expenditure. CONCLUSION: Collectively, our data suggest that fenugreek furostanolic saponins and green coffee bean extract may have potential benefits in treating insulin resistance and related conditions.

Removal of Trace Elements by Cupric Oxide Nanoparticles from Uranium In Situ Recovery Bleed Water and Its Effect on Cell Viability.

In situ recovery (ISR) is the predominant method of uranium extraction in the United States. During ISR, uranium is leached from an ore body and extracted through ion exchange. The resultant production bleed water (PBW) contains contaminants such as arsenic and other heavy metals. Samples of PBW from an active ISR uranium facility were treated with cupric oxide nanoparticles (CuO-NPs). CuO-NP treatment of PBW reduced priority contaminants, including arsenic, selenium, uranium, and vanadium. Untreated and CuO-NP treated PBW was used as the liquid component of the cell growth media and changes in viability were determined by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay in human embryonic kidney (HEK 293) and human hepatocellular carcinoma (Hep G2) cells. CuO-NP treatment was associated with improved HEK and HEP cell viability. Limitations of this method include dilution of the PBW by growth media components and during osmolality adjustment as well as necessary pH adjustment. This method is limited in its wider context due to dilution effects and changes in the pH of the PBW which is traditionally slightly acidic however; this method could have a broader use assessing CuO-NP treatment in more neutral waters.